LETTER ISSN 1687-1421, Volume 17, Number 2, June 2006

EURASIP NEWS LETTER ISSN 1687-1421, Volume 17, Number 2, June 2006

European Association for Signal, Speech, and Image Processing

Newsletter, Volume 17, Number 2, June 2006

Contents

EURASIP MESSAGES President’sMessage ...... 1

AWARDS 2005 Nokia Foundation Recognition Award ...... 3

SHORT TUTORIALS A Tutorial on Relevance Vector Machines for Regression and ClassiﬁcationwithApplications ...... 4

EURASIP (CO-)SPONSORED EVENTS Report on the 2006 Second International Symposium on Communications, Control and Signal Processing (ISCCSP 2006) ...... 24 Report on the 7th International Workshop on Image Analysis for Multimedia InteractiveServices(WIAMIS) ...... 25 CalendarofEvents ...... 27 CallforPapers:AdvancedConceptsforIntelligentVisionSystems ...... 28 Call for Papers: Fifth International Symposium on Communication Systems, NetworksandDigitalSignalProcessing(CSNDSP’06) ...... 29 CallforPapers:eNTERFACE’06 ...... 30 Call for Papers: 14th European Signal Processing Conference (EUSIPCO 2006) ...... 32 Call for Papers: 15th European Signal Processing Conference (EUSIPCO 2007) ...... 33 Call for Papers: International Symposium on Signal Processing and its Applications (ISSPA 2007) ...... 34 Call for Papers: 13th International Conference on Systems, Signals & Image Processing (IWSSIP ’06) ...... 35 Call for Papers: International Workshop on Multimedia Content Representation, ClassiﬁcationandSecurity(IWMRCS) ...... 36 Call for Papers: An ISCA Tutorial and Research Workshop on Non-Linear SpeechProcessing(NOLISP’07) ...... 37 Call for Papers: 26th Picture Coding Symposium (PCS 2007) ...... 38 Call for Papers: 1st International Conference on Semantic and Digital Media Technologies (Samt 2006) ...... 39 Call for Papers: 4th International Workshop on Total Least Squares and Errors-in-VariablesModeling ...... 40 Call for Papers: 2006 International Workshop on Acoustic Echo and Noise Control (IWAENC 2006) ...... 41 Call for Papers: International Conference on Artiﬁcial Neural Network(ICANN’06) ...... 42

EURASIP JOURNALS EURASIPJournalonAppliedSignalProcessing ...... 43 EURASIPJournalonAudio,Speech,andMusicProcessing ...... 45 EURASIPJournalonBioinformaticsandSystemsBiology ...... 46 EURASIPJournalonEmbeddedSystems ...... 48 EURASIP Journal on Wireless Communications and Networking ...... 49 SignalProcessing ...... 50 SignalProcessing:ImageCommunication ...... 51 SpeechCommunication ...... 52

EURASIP Journal on Embedded Systems EURASIPJESCallforPapers ...... 54

EURASIP Journal on Applied Signal Processing Abstracts of EURASIP JASP, Volume 2006, Regular Issue ...... 58 Abstracts of EURASIP JASP, Volume 2006, Special Issue on ImplementationAspectsandTestbedsforMIMOSystems ...... 74 Abstracts of EURASIP JASP, Volume 2006, Special Issue on Video Analysis and Coding for Robust Transmission ...... 83 Abstracts of EURASIP JASP, Volume 2006, Special Issue on AdvancedSignalProcessingforDigitalSubscriberLines ...... 93 Abstracts of EURASIP JASP, Volume 2006, Special Issue on Frames and Overcomplete Representations in Signal Processing, Communications,andInformationTheory ...... 103 Abstracts of EURASIP JASP, Volume 2006, Special Issue on RadarSpace-TimeAdaptiveProcessing ...... 114 Abstracts of EURASIP JASP, Volume 2006, Special Issue on Super-ResolutionImaging:Analysis,Algorithms,andApplications ...... 121 Abstracts of EURASIP JASP, Volume 2006, Special Issue on InverseSyntheticApertureRadar ...... 130 EURASIPJASPCallforPapers ...... 137 EURASIP Journal on Wireless Communications and Networking Abstracts of EURASIP JWCN, Volume 2006, Regular Issue ...... 145 Abstracts of EURASIP JWCN, Volume 2006, Special Issue on QualityofServiceinMobileAdHocNetworks ...... 151 EURASIPJWCNCallforPapers ...... 158

EURASIP Journal on Audio, Speech, and Music Processing ...... 168 EURASIP Journal on Bioinformatics and Systems Biology ...... 169 EURASIP Journal on Embedded Systems ...... 170 International Journal of Biomedical Imaging ...... 171 EURASIP Journal on Information Security ...... 172

EURASIP Book Series on Signal Processing and Communications EURASIPBookSeriesonSignalProcessingandCommunications ...... 173 SignalProcessingfortheAcousticHuman-MachineInterface ...... 174 AdvancesonNonlinearSignalandImageProcessing ...... 175 GeneticandEvolutionaryComputationforImageProcessingandAnalysis ...... 176 AdvancesinSignalTransforms:TheoryandApplications ...... 177

How to Become a EURASIP Member ...... 178 EURASIP Membership Application ...... 180

EURASIP MESSAGES

President’s Message

As human societies continuously evolve to something new, either towards the positive or towards the negative, it seems that there are some values that retain the same significance throughout the centuries. As long as history goes back, there is proof that societies tend to value citizens that show an outstanding performance in an area that significantly contributes to the welfare of the society as a whole. EURASIP,everyyear,offers a small number of prestigious awards to scientists, from all over the world, whose major contributions left a distinct “stamp” on the Signal Processing community and research. For each award, a committee of experts, who are recognized internationally, is formed that finally decides to offer the award to one among a number of strong candidates. This year’s EURASIP Awards recipients are: • Meritorious Service Award: Giovanni Sicuranza, “For Fundamental Activities in Non- linear Signal and Image Processing and for Continuous Commitment with EURASIP in the Last Ten Years.” • Individual Technical Achievement Award: Pierre Comon, “For Contributions in the Field of Blind Signal Processing and the Independent Component Analysis Method- ology.” • European Group Technical Achievement Award: Alfonso Farina, “For Development and Application of Adaptive Signal Processing Techniques in Radar Systems.” • Best Paper Award published in Signal Processing: R. Schober, W. H. Gerstacker, L. Lampe, for their paper: “On suboptimum receivers for DSCDMA with BPSK modulation,” Vol. 85(6), pp. 1149–1163, 2005. • Best Paper Award published in Image Communications: N. Bozinovic, J. Konrad, for their paper: “Motion analysis in 3D DCT domain and its application to video coding,” Vol. 20(6), pp. 510–528, 2005. • Best Paper Award published in Journal of Applied Signal Processing: G . Pasrija, Y. Chen, B. Farhang-Boroujeny, S. Blair, for their paper: “DSP approach to the design of nonlinear optical devices,” Vol. 5(10), pp. 1485–1497, 2005. • Best Paper Award published in Journal on Wireless Communications and Networking: H. Li, H.V.Poor, for their paper: “Impact of channel estimation errors on multiuser detection via the replica method,” Issue 2, pp. 175–186, 2005.

I would like to congratulate all the above colleagues for their achievements. Nomination will take place during EUSIPCO-06 in Florence. 2 EURASIP Messages

This year, the EURASIP adcom has decided to establish the “Athanasios Papoulis” award, named after the great scientist and educator. The award will not be given regularly, but only on demand, i.e., every time an exceptional candidate, with significant contributions in Education in the areas of Signal Processing and related technologies, is nominated. The award will be offered for the first time next year. See all of you in Florence to enjoy another EUSIPCO and have discussions on all aspects of Signal Processing research and education.

Sergios Theodoridis President EURASIP AWARDS

Awards

2005 Nokia Foundation Recognition Award

Prof. Moncef Gabbouj The Award recognizes Professor Gabbouj’s achievements in the development of an international educational network and graduate engineering studies in Finland. Nokia Foundation has granted its 2005 Recognition Award to Professor Moncef Gab- bouj, Tampere University of Technology, Finland for his merits in the development of an international educational network and graduate engineering studies in Finland since 1990. Dr. Gabbouj is a world-renowned expert who has progressively broadened international cooperation in the teaching of information technology and signal processing. With the Recognition Award, Nokia Foundation wants to emphasize the importance of international education and networking in Finland. The internationalization of research and attracting international experts to Finland is vitally important to maintaining competitiveness. Professor Gabbouj has participated in establishing Finland’s first international master’s degree program in the field of signal processing, and he has been involved in planning the graduate engineering educational program in signal processing. He has also led the efforts to expand the international university program to cover the master and doctorate programs at Tampere University of Technology’s IT department. Professor Gabbouj is a long-time res- ident of Finland and a distinguished researcher in the fields of signal and image processing and multimedia data analysis, indexing and retrieval. Nokia Foundation was formed in 1995. The Foundation supports the scientific development of information and telecommunications technologies and promotes education of the sector in Finland. SHORT TUTORIALS

A Tutorial on Relevance Vector Machines for Regression and Classiﬁcation with Applications

Dimitris G. Tzikas Department of Computer Science, University of Ioannina, Ioannina 45110, Greece

Liyang Wei Department of Electrical and Computer Engineering, Illinois Institute of Technology, Chicago, IL 60616, USA

Aristidis Likas Department of Computer Science, University of Ioannina, Ioannina 45110, Greece

Yongyi Yang Department of Electrical and Computer Engineering, Illinois Institute of Technology, Chicago, IL 60616, USA

Nikolas P.Galatsanos Department of Computer Science, University of Ioannina, Ioannina 45110, Greece

Relevance vector machines (RVM) have recently attracted much interest in the research community because they provide a number of advantages. They are based on a Bayesian formulation of a linear model with an appropriate prior that results in a sparse representation. As a consequence, they can generalize well and provide inferences at low computational cost. In this tutorial we first present the basic theory of RVM for regression and classification, followed by two examples illustrating the application of RVM for object detection and classification. The first example is target detection in images and RVM is used in a regression context. The second example is detection and classification of microcalcifications from mammograms and RVM is used in a classification framework. Both examples illustrate the application of the RVM methodology and demonstrate its advantages.

1. Introduction Linear models are commonly used in a variety of regression problems, where the value t∗ = y(x∗)ofafunctiony(x) needs to be predicted at some arbitrary point x∗,givenaset of (typically noisy) measurements of the function t ={t1,...,tN } at some training points X ={x1,...,xN }: ti = y xi + εi, (1) A Tutorial on Relevance Vector Machines for Regression and Classiﬁcation with Applications 5 where εi is the noise component of the measurement. Under a linear model assumption, the unknown function y(x) is a linear combination of some known basis functions φi(x), that is,

M y(x) = wiφi(x), (2) i=1 where w = (w1,...,wM) is a vector consisting of the linear combination weights. Equation (1) can then be written in vector form as

t = Φw + ε, (3) where Φ is an N × M design matrix, whose ith column is formed with the values of basis function φi(x) at all the training points, and ε = (ε1,...,εN ) is the noise vector. Assuming independent, zero-mean, Gaussian distribution for the noise term, that is, 2 εi ∼ N(0,σ ), the maximum-likelihood estimate for w = (w1,...,wM)isgivenby 2 T −1 T wOLS = arg min t − Φw = Φ Φ Φ t, (4) w which is also known as the ordinary least-square (OLS) estimate. In many applications, the matrix ΦT Φ is often ill-conditioned, and the OLS estimate suffers from over-fitting, which is typical with maximum-likelihood estimates. In order to overcome this problem, constraints are commonly introduced on the parameters w = (w1,...,wM), which are used to imply specific desired properties of the estimated function. The Bayesian methodology provides an elegant approach to define such constraints by treating the parameters as random variables, to which suitable prior distributions are introduced. For example, preference for smaller weight values, which can lead to desirable smooth function estimates, can be specified by assigning a zero-mean, Gaussian distribution to the weights

p(w) = N(w | 0,λI). (5)

Here, the variance parameter λ is adjusted according to the learning problem in order to achieve good results. Another desirable property of the unknown function, developed more recently, is sparseness, in which the least number of basis functions are desired in the function representation, while all the other basis functions are pruned by setting their corresponding weight parameters to zero. Sparseness property is useful for several reasons. First, sparse models can generalize well and are fast to compute. Second, they also provide a feature selection mechanism which can be useful in some applications. There exist different methodologies for sparse linear regression, including least absolute shrinkage and selection operator (LASSO) [1, 2] and support vector machines (SVM) [3]. In a Bayesian approach such as RVM, sparseness is achieved by assuming a sparse distribution on the weights in a regression model. Specifically, RVM is based on a hierarchical prior, where an independent Gaussian prior is defined on the weight parameters in the first level, 6 Short Tutorials and an independent Gamma hyperprior is used for the variance parameters in the second level. This results in an overall Student t prior on the weight parameters, which leads to model sparseness. A similar Bayesian methodology to achieve sparseness is to use a Lapla- cian prior [4], which can also be considered as a two-level hierarchical prior, consisting of an independent Gaussian prior on the weights and an independent exponential hyperprior on their variances.

2. RVM theory 2.1. Multikernel relevance vector machine Relevance vector machine (RVM) is a special case of a sparse linear model, where the basis functions are formed by a kernel function φ centred at the different training points: N y(x) = wiφ x − xi . (6) i=1 While this model is similar in form to the support vector machines (SVM), the kernel function here does not need to satisfy the Mercer’s condition, which requires φ to be a continuous symmetric kernel of a positive integral operator. Multikernel RVM is an extension of the simple RVM model. It consists of several different types of kernels φm given by M N y(x) = wmiφm x − xi . (7) m=1 i=1 The sparseness property enables automatic selection of the proper kernel at each location by pruning all irrelevant kernels, though it is possible that two different kernels remain on the same location. 2.2. Sparse Bayesian prior A sparse weight prior distribution can be obtained by modifying the commonly used Gaus- sian prior in (5), such that a different variance parameter is assigned for each weight: M −1 p(w | α) = N wi | 0,αi , (8) i=1 where α = (α1,...,αM) is a vector consisting of M hyperparameters, which are treated as independent random variables. A Gamma prior distribution is assigned on these hyperparameters: p αi = Gamma(a, b), (9) where a and b are constants and are usually set to zero, which results in a flat Gamma distribution. By integrating over the hyperparameters, we can obtain the “true” weight prior p(w) = p(w | a)p(a)da. The above integral gives a Student t prior, which is known to enforce sparse representations, owing to the fact that its mass is mostly concentrated near the origin and the axes of definition. A Tutorial on Relevance Vector Machines for Regression and Classification with Applications 7

2.3. Bayesian inference Assuming independent, zero-mean, Gaussian noise with variance β−1, that is, ε ∼ N 0,β−1I , (10) we have the likelihood of the observed data as p(t | w,α,β) = N t | Φw,β−1I , (11) where Φ is either an N × N or an N × (N ∗ M) “design” matrix for the single and multikernel cases, respectively. This matrix is formed by all the basis functions evaluated at all T the training points, that is, Φ = [φ(x1),...,φ(xN )] with φ(xi) = [φ1(xi − x1),...,φ1(xi − T xN ),...,φM(xi − xN )] . In order to make predictions using the Bayesian model, the parameter posterior distribution p(w,α | t) needs to be computed. Unfortunately, it cannot be computed analytically owing to its complexity, and approximations have to be made. Following the procedure described in [5], we decompose the parameter posterior as

p(w,α,β | t) = p(w | t,α,β)p(α, β | t). (12)

Then, the posterior distribution of the weights can be computed as p(t | w,β)p(w | α) p(w | t,α,β) = ∼ N(w | μ, Σ), (13) p(t | α, β) where − Σ = βΦT Φ + A 1, (14) μ = βΣΦT t, and A = diag(α1,...,αM). The posterior of the hyperparameters p(α, β | t) cannot be computed analytically and is approximated by a delta function at its mode: p(α, β | t) ≈ δ αMP,βMP . (15)

We can ﬁnd αMP and βMP by maximizing p(α, β | t) ∝ p(t | α, β)p(α)p(β)as αMP = arg max p(t | α, β)p(α) , (16) α βMP = arg max p(t | α, β)p(β) . (17) β

An alternative approach is to follow the variational Bayesian methodology to obtain an approximation to the posterior parameter distribution p(w,α | t). This is demonstrated in [4], but it is concluded that the method achieves only slightly improved results at signiﬁcant additional computations.

2.4. Marginal likelihood optimization The optimization problem in (16)forαMP cannot be solved analytically and an iterative method has to be used. Instead of maximizing the hyperparameter posterior, it is equivalent, and more convenient, to minimize its negative log likelihood [5] which for the multikernel case is M N 1 T − L(α) =− log |C| + t C 1t + a log αmi − bαmi + c log β − dβ, (20) 2 m=1 i=1 where C = βI + ΦA−1ΦT . This equation when M = 1 gives the single kernel case. Setting the derivative of L(α) to zero gives the following iterative formula: a αnew = 1+2 , mi 2 (21) μmi + Σ(mi)(mi) +2b where μmi is the mith element of the posterior mean weight and Σ(mi)(mi) is the mith diagonal element of the posterior weight covariance. At each iteration, both μmi and Σ(mi)(mi) are evaluated from (14) using the current estimate of αMP. Similarly, the following formula can be obtained for the variance parameter:

M N N − m= i= 1 − αmiΣ mi mi +2c β = 1 1 ( )( ) . (22) t − Φμ2 +2d

Computation of Σ requires O((NM)3) computations, which can be very demanding for models with many basis functions. During the training process, basis functions whose corresponding weights are estimated to be zero may be pruned. This will make matrix Σ smaller after a few iterations, and its inversion will be easier. However, there are M basis functions initially at each point, and computation of Σ is time consuming. It is interesting to note that the iterative updates for the hyperparameters in (21)and (22) can also be derived using an expectation-maximization (EM) algorithm by treating the weights w as hidden variables and the observations t and the hyperparameters α and β as observed variables.

2.5. Incremental optimization Amoreefficient approach is the incremental algorithm proposed in [6]. The model is initially assumed to contain only one basis function, and basis functions are incrementally A Tutorial on Relevance Vector Machines for Regression and Classification with Applications 9 added or deleted subsequently. For the case of a flat prior on hyperparameter a, maximization of the marginal likelihood is equivalent to maximizing 1 L(α) = log p(t | α) =− N log 2π +log|C| + tT C−1t . (23) 2

Given a single hyperparameter αi we can decompose L(α) into two terms: φT C−1t 2 L α =−1 N π C tT C t − α α φT C−1φ − i −i ( ) log 2 +log i + i log i +log i + i −i i T −1 2 αi + φi C−i φi = L α−i + l αi , (24) where L(α−i) is independent of αi and 2 1 qi l αi = log αi − log αi + si + (25) 2 αi + si

T −1 T −1 with si = φi C−i φi, qi = φi C−i t, while C−i is matrix C with the contribution of basis −1 T function φi removed, that is, C−i = C − αi φiφi . Analysis of l(αi) shows that L(α)hasa unique maximum with respect to αi:

s2 α = i q2 >s, i 2 if i i qi − si (26) 2 αi =∞ if qi ≤ si.

Thus, we can ﬁnd aMP by iteratively 2 (i) adding a basis function φi with qi >si, (ii) reestimating a hyperparameter αi for a basis function already in the model, or 2 (iii) deleting a basis function φi with qi ≤ si.

When adding a basis function or reestimating the value of its hyperparameter, we set 2 2 αi = si /(qi − si), which maximizes L(α). Thus at each step the marginal likelihood increases. Vectors s and q are calculated using an iterative algorithm that utilizes their value from the previous iteration, details of these calculations can be found in [6]. This incremental algorithm successfully overcomes the major difficulty of inverting the full matrix Σ. However, since at each iteration only one basis function can be modified, significantly more iterations are required to reach convergence. Convergence could be faster by choosing at each step to modify the basis function that leads to the largest increase of the marginal likelihood. However, this requires evaluating the marginal likelihood increase for all the basis functions at each step and is computationally expensive. Overall, the incremental algorithm is a major improvement over the initial nonincremental algorithm. However, it is still computationally demanding for very large data sets. 10 Short Tutorials

2.6. RVM for classification Similar to regression, RVM has also been used for classification. Consider a two-class problem with training points X ={x1,...,xN } and corresponding class labels t ={t1,...,tN } with ti ∈{0, 1}. Based on the Bernoulli distribution, the likelihood (the target conditional distribution) is expressed as N ti 1−ti p(t | w) = σ y xi 1 − σ y xi , (27) i=1 where σ(y) is the logistic sigmoid function 1 σ y x = . (28) 1+exp −y(x) Unlike the regression case, however, the marginal likelihood p(t | α) can no longer be obtained analytically by integrating the weights from (27), and an iterative procedure has to be used. ∗ Let αi denote the maximum a posteriori (MAP) estimate of the hyperparameter αi.The MAP estimate for the weights, denoted by wMAP, can be obtained by maximizing the posterior distribution of the class labels given the input vectors. This is equivalent to maximizing the following objective function: N N ∗ J w1,w2,...,wN = log p ti | wi + log p wi | αi , (29) i=1 i=1 where the first summation term corresponds to the likelihood of the class labels, and the second term corresponds to the prior on the parameters wi. In the resulting solution, only those samples associated with nonzero coefficients wi (called relevance vectors) will contribute to the decision function. The gradient of the objective function J with respect to w is ∇J =−A∗w − ΦT ( f − t), (30) T where f = [σ(y(x1)) ···σ(y(xN ))] ,matrixΦ has elements φi,j = K(xi,xj ). The Hessian of J is H =∇2(J) =− ΦT BΦ + A∗ , (31) where B = diag(β1,...,βN ) is a diagonal matrix with βi = σ(y(xi))[1 − σ(y(xi))]. The posterior is approximated around wMAP by a Gaussian approximation with covariance Σ =− H| −1 wMAP (32) and mean μ = ΣΦT Bt. (33)

These results are identical to the regression case (14) and the hyperparameters αi are updated iteratively in the same manner as for the regression case. A Tutorial on Relevance Vector Machines for Regression and Classiﬁcation with Applications 11

2.7. Comparison to SVM learning SVM is another methodology for regression and classification that has attracted considerable interest [3]. It is a constructive learning procedure rooted in statistical learning theory [3], which is based on the principle of structural risk minimization. It aims at minimizing the bound on the generalization error (i.e., the error made by the learning machine on data unseen during training) rather than minimizing the empirical error such as the mean- square error over the data set [3]. This results in good generalization capability and an SVM tends to perform well when applied to data outside the training set. In the context of classification, an SVM classifier in concept first maps an input data vector x into a higher dimensional space Ᏼ through an underlying nonlinear mapping Φ(x), then applies linear classification in this mapped space. Introducing a kernel function T K(x, y) ≡ Φ(x) Φ(y), we can write an SVM classifier fSVM(x) as follows:

Ns fSVM(x) = αiK x, si + b, (34) i=1 where si, i = 1, 2,...,Ns, are a subset of the training samples {xi,i= 1, 2,...,N} (called support vectors). The SVM classifier in (34) resembles in form the RVM classifier in (6), yet the two classifiers are derived from different principles. As will be demonstrated later by the application results (Section 3.3), for SVM the support vectors are typically formed by “borderline,” difficult-to-classify samples in the training set, which are located near the decision boundary of the classifier; in contrast, for RVM the relevance vectors are formed by samples appearing to be more representative of the two classes, which are located away from the decision boundary of the classifier. Compared to SVM, RVM is found to be advantageous on several aspects including (1) the RVM decision function can be much sparser than the SVM classifier, that is, the number of relevance vectors can be much smaller than that of support vectors; (2) RVM does not need the tuning of a regularization parameter (C) as in SVM during the training phase. As a drawback, however, the training phase of RVM typically involves a highly nonlinear optimization process.

3. Applications The relevance vector machine (RVM) technique has been applied in many different areas of pattern recognition, including communication channel equalization [7], head model retrieval [8], feature optimization [9], functional neuroimages analysis [10], and facial expressions recognition [11]. In this paper we describe two applications: the first concerns the application of large scale multikernel RVM for object detection in large scale images, while the second deals with computer-aided diagnosis of microcalcifications in digitized mammograms. 3.1. RVM for images: optimization in the Fourier domain As previously noted, one of the main difficulties of RVM when applied to large data sets (such as images) is that the computations required for the posterior statistics in equation 12 Short Tutorials

(14) can be prohibitive. In what follows we ﬁrst introduce a methodology to ameliorate this problem. When the training points are uniform samples of a signal (e.g., the pixels of an image) and the kernel is symmetric, the RVM for the single kernel case can be written using a convolution as

y = w ∗ φ, (35) where ϕ = (K(x1,x1),K(x2,x1),...,K(x1,xN )) is the kernel vector, containing the kernel function centred at x1, evaluating each training point. This convolution can be expressed in matrix form as

y = Φw, (36) where Φ is a circulant matrix whose ﬁrst row is vector φ. Such convolution can be easily computed using DFT as

Υk = WkΨk, (37) where Υk is the kth DFT coefficient of y, Wk is the kth DFT coefficient of w,andΨk is the kth DFT coefficient of φ. This observation allows very efficient computation of the output of an RVM model. More importantly, the same idea can be utilized to compute the posterior statistics of the weights μ and Σ. Starting from (14), we can compute these quantities by solving the following linear system: βΦT Φ + A μ = βΦT t. (38)

T −1 The solution involves inversion of the matrix Φ Cn Φ + A, which is computationally expensive. Instead, we can employ an optimization method, such as conjugate gradient, to solve this linear system by solving the following optimization problem:

T μ = arg min wT βΦT Φ + A w − βΦT t w , (39) w which is equivalent, since the derivative of the minimized quantity will be zero at the minimum. The quantities wT (βΦT Φ)w and (βΦT t)T w can be efficiently computed in the DFT domain, since the matrix Φ is circulant, while computation of wT Aw is straightforward since A is diagonal. Assuming we could perform arithmetic operations with infinite precision, the conjugate gradient algorithm is guaranteed to converge after a finite number of iterations. In practice, a very good estimate can be obtained after only a few iterations. However, in order to compute the posterior weight covariance we have to invert the T −1 matrix Φ Cn Φ + A, which is computationally demanding. Instead, observe that we only need to compute the diagonal of Σ, which can be approximated by assuming ΦT Φ to be diagonal as T Σii = 1/ βΦ Φ + A ii. (40) A Tutorial on Relevance Vector Machines for Regression and Classification with Applications 13

Although this approximation is not generally valid, it has been proven effective in experiments, because the matrix A has commonly very large values and is the dominant term in the expression βΦT Φ + A. This approach can be extended easily for the multikernel case; in such case instead of y = M Φ w Φ w equation (36)wehave m=1 m m,where m and m are the circulant matrix and m weights, respectively, that correspond to the th kernel. Thus we can write in the DFT Y = M Ψmwm Υ k ffi Wm k domain k m=1 k k ,where k is the th DFT coe cient of y, k is the th DFT m coefficient of wm,andΨk is the kth DFT coefficient of φm. 3.2. Object detection In an object detection problem, the goal is to determine the locations of a given “target” image in an “observed” image in the presence of noise. The “target” may appear significantly different in the observed image, as a result of being scaled, rotated, occluded by other objects, of different illumination conditions, and so forth. A commonly used approach to object detection is matched filter and its variants, such as the phase-only [12] and the symmetric phase-only [13] matched filters. These are based on computing the correlation image between the “observed” and “target” images, which is thresholded to determine the locations where the “target” object is present. Alternatively, the problem can be formulated as image restoration, where the image to be restored is considered as an impulse function at the location of the “target” object. This technique allows explicit modeling of the background to be incorporated in the detection process, such as autoregressive models, and has been shown to be superior to the different versions of the “matched filter” [14]. Below we describe a methodology for object detection based on training a multikernel DFT-RVM model on the “observation” image. This RVM model consists of two sets of basis functions: basis functions that are used to model the “target” image and basis functions that are used to model the background. After training the model, each “target” basis function that survives in the model can be considered as a detected “target” object. However, if the background basis functions are not flexible enough, “target” functions may also be used to model areas of the background. Thus, we should consider only “target” basis functions whose corresponding weight is larger than a specified threshold. Let t = (t1,...,tN ) be a vector consisting of the intensity values of the pixels of the “observed” image. We model this image using the RVM model, as

N N t = wtiφt x − xi + wbiφb x − xi + ε, (41) i=1 i=1 where φt is the “target” basis function which is a vector consisting of the intensity values of the pixels of the “target” image, and φb is the background basis function which we choose to be a Gaussian function. After training the RVM model, we obtain the vectors μt and μb which are the posterior mean weights for the kernel and background, respectively. Ideally, “target” kernel functions would only be used to model occurrences of the “target” object. However, because the background basis functions are often not flexible enough to model the background accurately, some “target” basis functions have been used to model 14 Short Tutorials the background as well. In order to decide which “target” basis functions actually correspond to “target” occurrences, the posterior “target” weight mean values are thresholded, and only those that exceed a specified threshold are considered significant:

target exists at location i ⇐⇒ μti >T. (42) Choosing a low threshold may generate false alarms, indicating that the object is present in locations where it actually does not exist. On the other hand, choosing a high threshold may result in failing to detect an existing object. There is no universal optimal value for the threshold, but instead it should be chosen depending on the characteristics of each application. 3.2.1 Numerical experiments In this section we present experiments that demonstrate the improved performance of the DFT-RVM algorithm compared to autoregressive impulse restoration (ARIR), which is found to be superior to most existing object detection methods [14]. We first demonstrate an example in which the “observed” image is constructed by adding the “target” object to a background image and then adding white Gaussian noise. An image consisting of the values of the target kernel weights computed with the DFT-RVM algorithm is shown in Figure 1. Note that because of the RVM sparseness property, only few weights have nonzero values. The “target” object is the tank located at pixel (10 050), where the bright white spot on the kernel weight image exists. When evaluating a detection algorithm it is important to consider the detection probability PD, which is the probability that an existing “target” is detected and the probability of false alarm PFA, which is the probability that a “target” is incorrectly detected. Any of these probabilities can be set to an arbitrary value by selecting an appropriate value for the threshold T. A receiver operating characteristics (ROC) curve is a plot of the probability of detection PD versus the probability of false alarm PFA, which provides a comprehensive way to demonstrate the performance of a detection algorithm. However, an ROC curve is not suitable for evaluating object detection algorithms because it only considers if an algorithm has detected an object or not; it does not consider if the object was detected in the correct location. Instead, we can use the localized ROC (LROC) curve, which is a plot of the probability of detection and correct localization PDL versus the probability of false alarm and considers also the location where a “target” has been detected. In order to evaluate the performance of the algorithm, we created 50 “observed” images by adding a “target” image to a random location of a background image, and another 50 “observed” images without the “target” object. White Gaussian noise was then added to each “observed” image. The DFT-RVM algorithm was then used to estimate the parameters of an RVM model with a “target” kernel and a Gaussian background kernel for each “observed” image, generating 100 kernel weight images. These kernel weight images were then thresholded for many different threshold values, and estimates of the probabilities PDL and PFA were computed for each threshold value. Similar experiments were performed for the ARIR algorithm also. An LROC curve was then plotted for each algorithm, see Figure 2. The area under the LROC curve, which is a common measure of the performance of a detection algorithm, is significantly larger for the DFT-RVM algorithm. It is important that A Tutorial on Relevance Vector Machines for Regression and Classification with Applications 15

(a) (b) (c)

Figure 1: Object detection example. The “target” image is a tank located at pixel (10 050). (a) The noisy “observed” image. (b) Area around target of the result of the ARIR algorithm. (c) Area around target of the result of the DFT-RVM algorithm.

the LROC curve is high for small values of PFA, since usually the threshold is chosen so that only a small fraction of false detections are allowed [14].

3.3. Applications on computer-aided diagnosis 3.3.1 Background Breast cancer is a common form of cancer diagnosed in women. One of the important early signs of breast cancer in mammograms is the appearance of microcalcification (MC) clusters, which appear in 30–50 % of mammographically diagnosed cases [15]. MCs are calcium deposits of very small dimension and appear as a group of granular bright spots in a mammogram. As an example, Figure 3 shows a mammogram image with a cluster of MCs. Individual MCs are sometimes difficult to detect because of the surrounding breast tissue, their variation in shape, and small dimension. Because of its importance in breast cancer diagnosis, accurate detection and classification of MC clusters are very important problems.

3.3.2 Automatic detection of microcalcification clusters In recent years, there has been a great deal of research in the development of computerized methods for automatic and accurate detection of MC clusters, which could potentially assist radiologists in diagnosis of breast cancer. A thorough review of various methods for MC detection reported in the literature can be found in [16]. In [17], we developed a support vector machine (SVM) approach for the detection of clustered MCs in mammograms, and demonstrated that such an approach could outperform several well-known methods in the literature. While the SVM approach achieves the best detection performance, the computational complexity of the SVM classifier may prove to be burdensome in real-time or near real- time applications. In an SVM classifier, the decision function is determined by a subset of training samples (called support vectors); the computational complexity of the decision function is linearly proportional to the number of support vectors. As a consequence, too many a support vector can lead to a classifier (SVM) that is computationally expensive. This issue is especially important for MC detection, as modern digital mammography scanners 16 Short Tutorials

0.4 1 0.9 0.35 0.8 0.3 0.7 0.25 0.6

0.2 0.5 . 0.15 0 4 0.3 0.1 0.2 . 0 05 0.1

0 0 00.20.40.60.8100.20.40.60.81

(a) (b)

Figure 2: LROC curves for the ARIR (a) and DFT-RVM (b) algorithms.

(a) (b)

Figure 3: (a) Mammogram in craniocaudal view. (b) Expanded view showing MCs. can produce images at high resolutions, which may require significant computation time to process. To address this issue, in [18] we proposed to improve the computational efficiency of our previously developed SVM detection by using an alternative—relevance vector machine (RVM)—for MC detection. The advantage is that the RVM classifier can yield a decision function that is much sparser than the SVM while maintaining its detection accuracy. This can lead to significant reduction in the computational complexity of the decision function, thereby making it more suitable for real-time applications. Here MC detection is formulated as a binary classification problem. Specifically, at each location of a mammogram image, we apply an RVM classifier to determine whether an MC object is present or not. That is, for a given mammogram image, the MC detection process A Tutorial on Relevance Vector Machines for Regression and Classification with Applications 17 consists of the following two steps: (1) at each pixel location in the image, extract an input vector x to describe its surrounding image feature; (2) apply the RVM classifier fRVM(x)to decide whether x belongs to “MC present” class or “MC absent” class. We define the input vector x to the RVM classifier to be formed by a small window of M × M pixels centered at the location of interest in a mammogram image. The choice of M should be large enough to cover an MC and yet small enough to avoid any interference from neighboring MCs. In the data set used in this study, the mammograms were digitized at 0.05 mm/pixel, and M=15 was chosen empirically in our experiments. To suppress the background and thereby restrict the intraclass variations among the input samples, a high-pass filter with a narrow stop band was applied to each mammogram image. The high-pass filter was designed to be a finite impulse response (FIR) filter with cutoff frequency wc = 0.05 cycles/pixel and length 10. In summary, the input vector x is obtained at each pixel location as follows: x = W[Hf], (43) where f denotes the entire mammogram image, H denotes the filtering operator, and W is the windowing operator. Note that for M = 15, the dimension of x is 225. The training of the RVM classifier function consists of the following two steps: (1) col- lect training samples {(xi,di),i= 1, 2,...,N} from the existing mammograms, (2) optimize the model parameters of the RVM classifier for best performance. To demonstrate the RVM classifier, we used a set of 141 mammograms from 66 clinical cases collected by the Department of Radiology at the University of Chicago. Each mammogram had one or more clusters of MCs which were histologically proven. These mammograms were digitized with a spatial resolution of 0.05 mm/pixel and 10-bit grayscale with a dimension of 3000 × 5000 pixels. The MCs in each mammogram were manually identified by a group of experienced radiologists. To save computation time, a section of 900 × 1000 pixels, containing all the identified MCs, was cropped from each mammogram such that it was free of nontissue areas. These section images were used in our subsequent experiments. In our study, we divided the data set in a random fashion into two separate subsets, each containing 33 cases. Subsequently, mammograms in one subset were used for training the classifiers, and mammograms in the other subset were used exclusively for testing the classifiers. Thus, mammograms from the same case were used either for training or testing, but never for both. The mammograms in the training subset were found to have a total of 1291 individual MCs. For each of these MCs, a window of M × M image pixels centered at its center was extracted; the vector formed by this window of pixels, denoted by xi, was then treated as an input pattern to the classifier for the “MC present” class (di = +1). This yielded a total of 1291 samples for the “MC present” class. Similarly, nearly twice as many (2232, to be exact) “MC absent” samples were collected (di =−1), except that their locations were selected randomly from the set of all “MC absent” locations in the training mammograms. In this procedure no sample window was allowed to overlap with any other sample window. For demonstration purpose, we show in Figure 4 some examples of sample image windows for “MC present” and “MC absent” classes in the resulting training data set. 18 Short Tutorials

“MC present” samples “MC absent” samples

(a) (b)

Figure 4: Examples of 15 × 15 image windows of training samples from the “MC present” and “MC absent” classes. These are randomly selected from the training set.

To determine the fine-tuning parameters of the RVM classifier model for optimal performance, we apply a ten-fold cross validation in the training set. The best error level (4.89 %) was obtained by an order-2 polynomial kernel. For the RVM classifier, the number of relevance vectors (produced during training) was found to be 65 (1.85 % of the number of training samples). For comparison, we also trained an SVM classifier using the same data set. The number of support vectors was found to be 521 (14.79 % of the number of training samples). Indeed, the RVM classifier is much sparser than the SVM. Togain further insight on the RVM classifier, we show in Figure 5 the corresponding image windows for some relevance vectors from both “MC present” and “MC absent” classes; for comparison, we show in Figure 6 the image windows for some support vectors of the SVM classifier. As can be seen, for the RVM, the relevance vectors from the two classes are distinctly different. The “MC present” relevance vectors consist of MCs that are clearly visible, and the “MC absent” relevance vectors consist of image windows that do not show MC-like features at all. In a sense, the relevance vectors are formed by “easy-to-classify” samples from both classes. In contrast, for the SVM, the support vectors from the two classes do not seem to be distinctly different, that is, the “MC present” support vectors could be mistaken for “MC absent” image regions, and vice versa. These support vectors are samples that appear to be “borderline,” “difficult-to-classify.” These results demonstrate that the two classifiers are quite different from each other. The performance of the RVM classifier for detection of clustered MCs is summarized using free-response receiver operating characteristic (FROC) curves. An FROC curve [19] plots the correct detection rate (i.e., true positive fraction (TPF)) versus the average number of false-positives (FPs) per image varied over the continuum of the decision threshold. It provides a comprehensive summary of the tradeoff between detection sensitivity and speci- ficity. The trained classifiers were evaluated using all the mammograms in the test subset. The test results are summarized using FROC curves in Figure 7. In particular, the RVM A Tutorial on Relevance Vector Machines for Regression and Classification with Applications 19

“MC present” relevance vectors “MC absent” relevance vectors

(a) (b)

Figure 5: Examples of 15 × 15 image windows of the relevance vectors (RVs) from the “MC present” and “MC absent” classes. All the 19 “MC present” RVs are shown and only 25 of the 46 “MC absent” RVs are shown.

“MC present” support vectors “MC absent” support vectors

(a) (b)

Figure 6: Examples of 15 × 15 image windows of the support vectors (SVs) from the “MC present” and “MC absent” classes. achieved a sensitivity of approximately 90 % when the false positive rate is at one FP cluster on average per image. Interestingly, this sensitivity level is also similar to that achieved by the SVM. Compared to SVM, the RVM classifier has reduced the detection time from nearly 250 s to about 30 s per image, nearly an order of magnitude reduction. Experimental results showed that the RVM technique could greatly reduce the computational complexity of the SVM while maintaining its detection accuracy. This makes RVM more feasible for real-time processing of MC clusters in mammograms. 3.3.3 Classification of microcalcification clusters Once MCs are detected, another issue is how to classify them. Since these lesions appear in benign breast tissues as well as in malignant ones, they are often very difficult to diagnose 20 Short Tutorials

0.95

0.9

0.85 TP fraction 0.8

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0 012345 Average number of FP clusters

RVM SVM

Figure 7: FROC curves of the different methods. accurately. It is reported that among those with radiographically suspicious, nonpalpable lesions who are sent for biopsy, only 15 % to 34 % are found to actually have malignan- cies [20, 21]. There has been a great deal of research in recent years to develop computerized methods that potentially could assist radiologists to differentiate benign from malignant MCs. In particular, Jiang et al. [22] developed an automated computer scheme that was demonstrated to classify clustered MCs more accurately than radiologists. This scheme made use of a feedforward artificial neural network (FFNN), which was trained to predict the likelihood of malignancy based on quantitative image features automatically extracted from the clustered MCs. It was subsequently demonstrated in [23] that when used as a di- agnostic aid, this scheme could also lead to significant improvement in radiologists’ performance in distinguishing between malignant and benign clustered MCs. In [24]weinvesti- gated several state-of-the-art machine-learning methods including RVM, SVM, and kernel Fisher’s discriminant for automated classification of clustered microcalcifications (MCs). In our study, classification of malignant from benign clustered MCs is treated as a two- class pattern classification problem, that is, a microcalcification cluster (MCC) under consideration is either malignant or benign. The different classifier models were developed and tested using a data set collected by the Department of Radiology at the University of Chicago. This data set consisted of 697 mammograms from 386 clinical cases, of which all had lesions containing clustered microcalcifications which were histologically proven. Among them 75 were malignant, and the rest (311) were benign. Furthermore, most of these cases have two standard-view mammograms: mediolateral oblique (ML) and craniocaudal (CC) views. The clustered MCs were identified by a group of experienced researchers. For computer analysis, all the mammograms in the data set were digitized with a A Tutorial on Relevance Vector Machines for Regression and Classification with Applications 21

Table 1: Classification results obtained with different classifier models. SVM KFD RVM FFNN Az 0.8545 0.8303 0.8421 0.8007 Std. dev. 0.0259 0.0254 0.0243 0.0266 3layers, Order-2 Order-2 Order-2 6 hidden Parameters polynomial polynomial polynomial neurons, kernel, C=700 kernel kernel 100 seeds spatial resolution of 0.1 mm/pixel and 10-bit grayscale. The data set includes a wide spectrum of cases that are judged to be difficult to classify by radiologists. For automated classification, the following eight features [22, 23], all computed from the mammogram images, were used to characterize an MCC: (1) the number of MCs in the cluster, (2) the mean effective volume (area times effective thickness) of individual MCs, (3) the area of the cluster, (4) the circularity of the cluster, (5) the relative standard deviation of the effective thickness, (6) the relative standard deviation of the effective volume, (7) the mean area of MCs, and (8) the second highest microcalcification-shape-irregularity measure. The numerical values of all these features were normalized to be within the range of 0 and 1. These features were selected to have intuitive meanings that correlate qualita- tively to features used by radiologists [22]. This provides an important common ground for the computer scheme to achieve high classification performance and for radiologists to interpret the computer results. For preparation of training and testing samples for the classifier models, the eight features are extracted for each MCC in the mammogram data set; the vector formed by the eight feature values, denoted by xi, is then treated as an input pattern, and is labeled as yi = +1 for a malignant case, and as yi =−1 otherwise. Together, (xi,yi) forms an input- output pair. There are in total 697 such pairs obtained from the whole mammogram data set. These pairs are subsequently used for training and testing of the classifier models. To determine the fine-tuning parameters for each classifier model, we apply a leave- one-out cross validation procedure. To evaluate the performance of a classifier, we use the so-called receiver operating characteristic (ROC) analysis, which is now used routinely for many classification tasks. We list in Table 1 the estimate of Az and its standard deviation, obtained using the ROCKIT program [25], and the parametric settings resulting from the training procedure for the different classifier models. These results demonstrate that the kernel methods (RVM, SVM, and KFD) are similar in performance (in terms of Az), significantly outperforming a well-established, clinically-proven CADx approach that is based on neural network.

4. Conclusions The relevance vector machine (RVM) constitutes a powerful methodology for regression and classification tasks. It achieves very good generalization performance and yields sparse 22 Short Tutorials models that provide inference at moderate computational cost. However, during the training phase the inversion of a large matrix is required. This makes this methodology inappro- priate for large data sets. This problem can be partially overcome by a modified learning algorithm, based on building the desired model incrementally. For image data where a pe- riodically sampled training set is available, a methodology based on computations in the DFT domain has been described which can bypass these difficulties. Since RVM can be also used for classification tasks we present a successful example of RVM for microcalcification detection and classification. This example clearly demonstrates the advantages of RVM and illustrates its differences from SVM.

References [1] V. Roth, “The generalized LASSO,” IEEE Transactions on Neural Networks,vol.15,no.1,pp. 16–28, 2004. [2] R. Tibshirani, “Regression shrinkage and selection via the LASSO,” Journal of the Royal Statistical Society: Series B, vol. 58, no. 1, pp. 267–288, 1996. [3] V. Vapnik, Statistical Learning Theory, John Wiley & Sons, New York, NY, USA, 1998. [4] M. A. T. Figueiredo and A. K. Jain, “Bayesian learning of sparse classifiers,” in Proceedings of the IEEE Computer Society Conference on Computer Vision and Pattern Recognition (CVPR ’01), vol. 1, pp. 35–41, Kauai, Hawaii, USA, December 2001. [5] M. E. Tipping, “Sparse Bayesian learning and the relevance vector machine,” Journal of Machine Learning Research, vol. 1, no. 3, pp. 211–244, 2001. [6] M. E. Tipping and A. Faul, “Fast marginal likelihood maximisation for sparse Bayesian models,” in Proceedings of the 9th International Workshop on Artificial Intelligence and Statistics (AI & Statistics ’03), Key West, Fla, USA, January 2003. [7] S. Chen, S. R. Gunn, and C. J. Harris, “The relevance vector machine technique for channel equalization application,” IEEE Transactions on Neural Networks, vol. 12, no. 6, pp. 1529–1532, 2001. [8] P. F. Yeung, H. S. Wong, B. Ma, and H. H.-S. Ip, “Relevance vector machine for content-based retrieval of 3D head models,” in Proceedings of International Conference on Information Visuali- sation (IV ’05), pp. 425–429, London, UK, July 2005. [9] L. Carin and G. Dobeck, “Relevance vector machine feature selection and classification for un- derwater targets,” in Proceedings of OCEANS, vol. 2, p. 1110, San Diego, Calif, USA, September 2003. [10] D. G. Tzikas, A. Likas, N. P. Galatsanos, A. S. Lukic, and M. N. Wernick, “Relevance vector machine analysis of functional neuroimages,” in Proceedings of 2nd IEEE International Symposium on Biomedical Imaging: Macro to Nano, vol. 1, pp. 1004–1007, Arlington, Va, USA, April 2004. [11] D. Datcu and L. J. M. Rothkrantz, “Facial expression recognition with relevance vector machines,” in Proceedings of International Conference on Multimedia and Expo (ICME ’05),pp. 193–196, Amsterdam, The Netherlands, July 2005. [12] J. L. Horner and P. D. Gianino, “Phase-only matched filtering,” Applied Optics,vol.23,no.6,pp. 812–816, 1984. [13] Q.-S. Chen, M. Defrise, and F. Deconinck, “Symmetric phase-only matched filtering of Fourier- Mellin transforms for image registration and recognition,” IEEE Transactions on Pattern Analysis and Machine Intelligence, vol. 16, no. 12, pp. 1156–1168, 1994. [14] A. Abu-Naser, N. P. Galatsanos, M. N. Wernick, and D. Schonfeld, “Object recognition based on impulse restoration with use of the expectation-maximization algorithm,” Journal of the Optical Society of America, vol. 15, no. 9, pp. 2327–2340, 1998. [15] Cancer Facts and Figures 1998. Atlanta, Ga, USA: American Cancer Society, 1998. A Tutorial on Relevance Vector Machines for Regression and Classification with Applications 23

[16] R. M. Nishikawa, “Detection of microcalcifications,” in Image-Processing Techniques for Tumor Detection, R. N. Strickland, Ed., Marcel Dekker, New York, NY, USA, 2002. [17] I. El-Naqa, Y. Yang, M. N. Wernick, N. P. Galatsanos, and R. M. Nishikawa, “A support vector machine approach for detection of microcalcifications,” IEEE Transactions on Medical Imaging, vol. 21, no. 12, pp. 1552–1563, 2002. [18] L. Wei, Y. Yang, R. M. Nishikawa, M. N. Wernick, and A. Edwards, “Relevance vector machine for automatic detection of clustered microcalcifications,” IEEE Transactions on Medical Imaging, vol. 24, no. 10, pp. 1278–1285, 2005. [19] P. C. Bunch, J. F. Hamilton, G. K. Sanderson, and A. H. Simmons, “A free-response approach to the measurement and characterization of radiographic-observer performance,” Journal of Applied Photographic Engineering, vol. 4, no. 4, pp. 166–171, 1978. [20] A. M. Knutzen and J. J. Gisvold, “Likelihood of malignant disease for various categories of mammographically detected, nonpalpable breast lesions,” Mayo Clinic Proceedings,vol.68,no.5,pp. 454–460, 1993. [21] D. B. Kopans, “The positive predictive value of mammography,” American Journal of Roentgenol- ogy, vol. 158, no. 3, pp. 521–526, 1992. [22] Y. Jiang, R. M. Nishikawa, D. E. Wolverton, et al., “Malignant and benign clustered microcalcifications: automated feature analysis and classification,” Radiology, vol. 198, no. 3, pp. 671–678, 1996. [23] Y. Jiang, R. M. Nishikawa, R. A. Schmidt, C. E. Metz, M. L. Giger, and K. Doi, “Improving breast cancer diagnosis with computer-aided diagnosis,” Academic Radiology, vol. 6, no. 1, pp. 22–33, 1999. [24] L. Wei, Y. Yang, R. M. Nishikawa, and Y. Jiang, “A study on several machine-learning methods for classification of malignant and benign clustered microcalcifications,” IEEE Transactions on Medical Imaging, vol. 24, no. 3, pp. 371–380, 2005. [25] C. E. Metz, B. A. Herman, and C. A. Roe, “Statistical comparison of two ROC-curve estimates obtained from partially-paired datasets,” Medical Decision Making, vol. 18, no. 1, pp. 110–121, 1998. EURASIP (CO-)SPONSORED EVENTS

Report on the 2006 Second International Symposium on Communications, Control and Signal Processing (ISCCSP2006)

ISCCSP2006 was sponsored by the IEEE organisation, the European Society for Signal Pro- cessing (EURASIP) and the Moroccan Information Technology Network of excellence (Pole de competences STIC). During these 3 days, 7 plenary lectures have been given by world- renowned scholars in addition to 15 special sessions that included 73 invited papers and 27 sessions composed of 224 contributed papers from 42 countries. We had a large attendance; more than 300 participants were present at the symposium. The feedback so far has been very positive. The Symposium provided a convenient space and forum where researchers from three fields i.e., signal/image processing, communications, control and computer sciences can interact and hopefully benefit from these interactions. The participants enjoyed during the banquet traditional performances from different regions of Morocco including the fantasia and the classical Moroccan foods: Harira, tagines, mechoui and couscous paired with Moroccan wines. We are looking forward to meeting you at the symposium next March 2008.

Driss Aboutajdine Sanjit K. Mitra Mohamed Najim EURASIP (CO-)SPONSORED EVENTS

Report on the 7th International Workshop on Image Analysis for Multimedia Interactive Services (WIAMIS)

At the Welcome Reception.

The 7th International Workshop on Image Analysis for Multimedia Interactive Services (WIAMIS) was held at the Hyatt Regency Hotel, Incheon, Korea, ﬁrst time outside of European countries. One of the contributions of WIAMIS2006 is to encourage Asian researchers to actively participate in the interactive media research forum. Second contribution is to link researchers from both continents and exchange their ideas and information. During three-day workshop (19–21 April, 2006), 64 regular papers and 19 special session papers were presented. The workshop program included three excellent invited lectures by Professor Ebroul Izquierdo (Queen Mary University of London, UK) on “The semantic gap in visual information retrieval,” by Dr. Paola Hobson (Motorola Labs, UK) on “Commercial realisation of research visions: Practical applications development in the aceMedia project,” and Dr. Chieteuk Ahn (ETRI, Korea) on “DMB: Current status and future developments.” Professor Hyoung Joong Kim (Kangwon National Uni- versity, Korea) and Professor Izquierdo, Program Chairs, hosted around 100 participants warmly, especially with welcome reception and banquet with Korean traditional food and performances. Detail information and photos are available at www.wiamis.net.WIAMIS 2007 will be held on 6–8 June, 2007 at Santorini, Greece. Call for Papers are available at http://mkg.iti.gr/wiamis2007/index.html. 26 EURASIP (Co-)Sponsored Events

Prof. Hyoung Joong Kim (Kangwon National University), Dr. Chieteuk Ahn (ETRI), Dr. Paola Hobson (Motorola Labs), Prof. Ebroul Izquiedo (Queen Mary University of London), Prof. Munchul Kim (ICU, Korea), and Mr. Christian Timmerer (Klagenfurt University) from the left.

Other photos are available at http://www.wiamis.net/photo.html. EURASIP (CO-)SPONSORED EVENTS

Calendar of Events

EURASIP Chairperson/Information Year Date Event Location Involvement 2006 July 5th International Symposium on Com- Patras, Cooperation Z. Ghassemlooy 19–21 munication Systems, Networks and Dig- Greece http://www.wcl.ee.upatras.gr/ ital Signal Processing (CSNDSP) csndsp/ July 17– eNTERFACE, The Similar NoE Summer Dubrovnik, Cooperation Igor Pandzic August 11 Workshop on Multimodal Interfaces Croatia http://www.enterface.net August 4th International Workshop on Leuven, Cooperation SabineVanHuffel, Ivan Markovsky 21–23 Total Least Squares and Belgium http://www.esat.kuleuven.be/ Errors-in-Variables Modeling ∼imarkovs/workshop.html September 14th European Signal Processing Florence, Sponsor Marco Luise 4–8 Conference (EUSIPCO 2006) Italy http://www.eusipco2006.org/ September International Conference on Artificial Athens, Cooperation Stefanos Kollias 10–14 Neural Networks (ICANN ’06) Greece http://www.icann2006.org/ September Multimedia Content Representation, Istanbul, Cooperation Bilge Gunsel, Anil Jain 11–13 Classification and Security (MRCS) Turkey http://www.ehb.itu.edu.tr/∼mrcs/ September Numerical Linear Algebra in Signals and Monopoli, Cooperation Nicola Mastronardi 11–15 Systems Italy http://www.cs.kuleuven.be/∼raf/ bari2006/ September International Workshop on Acoustic Echo Paris, France Cooperation Yves Grenier 12–14 and Noise Control (IWAENC 2006) http://www.iwaenc06.enst.fr/ September Advanced Concepts for Intelligent Vision Antwerp, Cooperation Jacques Blanc-Talon 18–21 Systems (ACIVS 2006) Belgium http://acivs.org/acivs2006 September The 13th International Conference on Budapest, Cooperation Kalman Fazekas, Jan Turan 21–23 Systems, Signals and Image Processing Hungary http://cyberspace.mht.bme.hu/ (IWSSIP 2006) iwssip06/ December 1st International Conference on Semantic Athens, Cooperation Yannis Avrithis 6–8 and Digital Media Technologies (SAMT) Greece http://www.samt2006.org/ 2007 February International Symposium on Signal Pro- Sharjah, Cooperation B.Boashash 12–15 cessing and its Applications, ISSPA 2007 U.A.E http://www.isspa.info/ May Nonlinear Speech processing (Nolisp07) Paris, France Cooperation Mohamed Chetouani 20–25 http://www.congres.upmc.fr/ nolisp2007/ June 6th EURASIP Conference on Speech and Maribor, Cooperation Zarkoˇ F. Cuˇ cejˇ 26–30 Image Processing, Multimedia Commu- Slovenia http://ec2007.feri.uni-mb.si/ nications and Services (ECSIPM 2007) members.htm September 15th European Signal Processing Poznan, Sponsor Marek Domanski 3–7 Conference (EUSIPCO 2007) Poland http://www.eusipco2007.org September 26th Picture Coding Symposium Lisboa, Cooperation Fernando Pereira 7–9 (PCS2007) Portugal http://www.pcs2007.org/ 2008 August 16th European Signal Processing Lausanne, Sponsor Jean Philip Thiran 26–29 Conference (EUSIPCO 2008) Switzerland http://www.eusipco2008.org/

Markus Rupp; Workshops/Confs Coordinator EURASIP ADVANCED CONCEPTS FOR INTELLIGENT VISION SYSTEMS September 18-21, 2006 University of Antwerp, Antwerp, Belgium http://acivs.org/acivs2006 STEERING COMMITTEE I th Jacques BLANC-TALON AC VS 2006 is the 8 of a series of conferences focusing on techniques for building adaptive, MRIS, France intelligent, safe and secure imaging systems. ACIVS 2006 will consist of 4 days of lecture Wilfried PHILIPS Ghent University, Belgium sessions, both regular (25 mn) and invited presentations, and poster sessions. Dan POPESCU ACIVS 2006 will also feature a conference dinner and other social activities. CSIRO, Australia Paul SCHEUNDERS The conference fee includes the social program (conference dinner, coffee breaks, snacks and Atwerp University, Belgium cultural activities) and a hard copy of the LNCS proceedings. Students, IEEE and EURASIP members can register at a reduced fee.

PROGRAM COMMITTEE TOPICS INCLUDE (BUT ARE NOT LIMITED TO): Fritz ALBREGTSEN, University of Oslo, Norway Attila BASKURT, LIRIS, UCB Lyon 1, France − Image and Video Processing (linear/non-linear filtering and enhancement, restoration, Laure BLANC-FERAUD, INRIA/ARIANA, France segmentation, wavelets & multiresolution, Markovian techniques, color processing, modeling, Philippe BOLON, ESIA, France analysis, interpolation and spatial transforms, fractals-multifractals, structure from motion) Nikolaos BOURBAKIS, Wright State University, − Pattern Analysis (shape analysis, data and image fusion, pattern matching, neural nets, learning, USA grammatical techniques) and Content-Based Image Retrieval Salah BOURENNANE, EGIM, France − Remote Sensing (techniques for filtering, enhancing, compressing, displaying and analyzing Patrick BOUTHEMY, IRISA/INRIA, France Jocelyn CHANUSSOT, INPG-ENSIEG, France optical, infrared, radar, multi-hyperspectral airborne and spaceborne images) David CLAUSI, University of Waterloo, Canada − Still Image and Video Transmission (still image/video coding, model-based coding, Pamela COSMAN, University of California, USA synthetic/natural hybrid coding, quality metrics, image watermarking, image and video databases, Jennifer DAVIDSON, Iowa State University, USA image search and sorting, video indexing, multimedia applications) Ricardo de QUEIROZ, Univ. de Brasilia, Brazil − System Architecture and Performance Evaluation (implementation of algorithms, benchmarking, Christine FERNANDEZ-MALOIGNE, SP2MI/SIC, evaluation criteria, algorithmic evaluation) France Jan FLUSSER, IITA, Czech Republic Both classical research papers and application papers are welcome. Don FRASER, ADFA, Australia Sidharta GAUTAMA, Ghent University, Belgium VENUE Jérôme GILLES, CEP, Arcueil, France Georgy GIMEL'FARB, Auckland University, New I Zealand AC VS 2006 will take place in the Middelheim campus of the university of Antwerp which can be easily Daniele GIUSTO, University of Cagliari, Italy reached from Antwerp airport or by train from Brussels main airport. John ILLINGWORTH, University of Surrey, UK Pieter JONKER, Delft University of Technology, PAPER SUBMISSION AND REVIEW PROCESS The Netherlands Prospective authors should prepare a full paper and submit it electronically. The paper should consist of 8- Frédéric JURIE, INRIA/GRAVIR, France Andrzej KASINSKI, Poznan University of 12 pages in A4 format and should conform to the style guidelines outlines on the ACIVS 2006 Technology, Poland website. LaTex style sheets, MSWord templates and more detailed information on the submission process Ashraf KASSIM, National University of Singapore can be found on the conference website: http://acivs.org/acivs2006 Richard KLEIHORST, Philips Research, The Netherlands All submissions will be reviewed by at least 2 members of the PC; extra reviewers may be consulted if Murat KUNT, EPFL, Switzerland needed. Submissions should provide sufficient background information and should clearly indicate the Hideo KURODA, Nagasaki University, Japan original contribution; they should state and discuss the main results and provide adequate references. Kenneth LAM, The Hong Kong Polytechnic Paper submission implies that one of the authors will present the paper if it is accepted. University, China Bruce LITOW, James Cook University, Australia ONFERENCE PROCEEDINGS Jesus MALO, Universitat de Valencia, Spain C Gérard MEDIONI, USC/IRIS, USA Fabrice MÉRIAUDEAU, Le2i Le Creusot, France Ali MOHAMMAD-DJAFARI, SUPELEC/LSS, France The proceedings of Acivs 2006 will be published by Springer-Verlag in the Lecture Rafael MOLINA, Universidad de Granada, Spain Vittorio MURINO, Universita` degli Studi di Notes in Computer Science series. LNCS is published, in parallel to the printed books, in full-text Verona, Italy electronic form via Springer-Verlag’s internet platform http://www.springerlink.com Stanley OSHER, UCLA, Los Angeles, USA Marcin PAPRZYCKI, SWPS, Warsaw, Poland IMPORTANT DATES Jussi PARKKINEN, Lappeenranta University, Finland Full paper submission April 9, 2006 Early registration July 14, 2006 Fernando PEREIRA, IST, Lisboa, Portugal Notification of acceptance May 22, 2006 Late registration August 21, 2006 Béatrice PESQUET-POPESCU, ENST Paris, France Final papers + author registration June 16, 2006 Sep 18-21, 2006 Matti PIETIKÄINEN, Oulu University, Finland ACIVS 2006 Aleksandra PIZURICA, Ghent University, Belgium Gianni RAMPONI, Trieste University, Italy Luis Salgado A. de SOTOMAYOR, Universidad Politécnica de Madrid, Spain Frederic TRUCHETET, Le2i Le Creusot, France Benelux Signal Dimitri VAN DE VILLE, EPFL, Switzerland Processing Chapter Peter VEELAERT, Hogeschool Ghent, Belgium

Fifth International Symposium on

COMMUNICATION SYSTEMS, NETWORKS AND DIGITAL SIGNAL PROCESSING (CSNDSP’06) 19-21 July 2006, Patras Univ. Conference Centre, Greece. http://www.wcl.ee.upatras.gr/csndsp/ Hosted by: Department of Electrical & Computer Engineering, University of Patras, Greece. Sponsored by: IEE, IEEE Greece Section, Patras Univ.

The Mediterranean Journals: - Computer & Networks - Electronics & Communications

Second Call for Papers

Steering Committee: Following the success of the last event, and after 8 years from the first event, the Prof. Z Ghassemlooy (Univ. of Northumbria, UK) – steering committee of CSNDSP decided to hold the next event at the University of Chairman Patras, in Patras/Greece, the 2006 Cultural Capital of Europe. CSNDSP has now Prof. A C Boucouvalas (Bournemouth Univ. UK) – been recognised as a forum for the exchange of ideas among engineers, scientists Symp. Secr. and young researchers from all over the world on advances in communication Prof. R A Carrasco (Newcastle Univ. UK) Dr M Logothetis (Patras Univ. Greece) – Local Organiser systems, communications networks, digital signal processing and other related areas and as a means to provide a focus for future research and developments. Local Organising Committee: Once again the organising committee invites you to submit original high quality T. Antonakopoulos (Associate Professor) papers addressing research topics of interest for presentation at the conference N. Fakotakis (Professor) and inclusion in the symposium proceedings. G. Kokkinakis (Professor) S. Kotsopoulos (Associate Professor) Papers are solicited from, but not limited to the following topics: M. Koukias (Assistant Professor) Adaptive signal processing Optical fibre transmission M. Logothetis (Associate Professor, Chairman) ATM systems and networks technology V. Makios (Professor) Optical communication systems J. Mourjopoulos (Associate Professor) Communication theory V. Stylianakis (Lecturer) Coding and error control Optical switching and networks Communication protocols Optical MEMS for lightwave National/International Technical Committee: DSP algorithms and applications networks Prof. M Al-Akaidi (De Montfort Univ. UK) E-commerce and e-learning Optical wireless communications Dr M. Ali (Oxford Brookes Univ. UK) (indoor and outdoors) Dr G. Anastassopoulos (Democritus Univ. of Thrace, applications Greece) Intelligent systems/networks Quality of service, reliability and Prof. P. Ball (Oxford Brookes Univ. UK) Internet communications performance modelling Prof. J. L Bihan (Ecole Nation. d'Ingen. de Brest, France) High performance networks Radio, satellite and space Dr K.E. Brown (Heriot-Watt Univ. UK) Low rate image transmission communications Prof. R. A Carrasco (Newcastle Univ. UK) Mobile communication systems & Speech technology Dr J. B Carruthers (Boston University, USA) Signal processing for storage Prof. F. Castanie (INPT, France) networks Dr L. Chao (Nanyang Tech. Univ. Singapore) Mobile computing for e- Teletraffic models and traffic Prof. R. J Clarke (Heriot-Watt Univ. UK) commerce engineering Dr M. Connelly (Univ. of Limerick, Ireland) Mobility management VLSI for communications and Prof. A. Constantinides (Imperial College, UK) Modulation and synchronisation DSP Dr D Dimitrov (Tech. Univ. of Sofia, Bulgaria) Modelling and simulation Wireless LANs and ad hoc Dr S. Dlay (Newcastle Univ. UK) networks Dr Mircea Giurgiu (Univ. of Cluj-Napoca, Romania) techniques Wireless Sensor Networks Dr A. Gonzalez (Univ. of Valencia, Spain) Multimedia communications and Dr Akiya Inoue (NTT, Japan) broadband services 3G/4G network evolution Prof. L. Izzo (Univ. of Napoli, Italy) Microwave Communications Any other related topics Dr G. K Karagiannidis (Aristotle Univ. of Thessaloniki, Network management & Greece) operation Prof. K. Kawashima (Tokyo Univ. TUAT, Japan) Papers may be presented in the following forms: Prof. Charles Knutson (Brigham Young Univ., USA) Prof. K. Liu (Reading Univ. UK) Oral presentation Poster Dr M. D Logothetis (Univ. of Patras, Greece) Contributions by MPhil/PhD research students are particularly encouraged. Dr. W. P Ng (Northumbria University, UK) All the papers will be refereed. Dr T. Ohtsuki (Tokyo Univ. of Sci., Japan) Prof. R. Penty (Cambridge Univ. UK) Submission Dates: Dr H.R. Rabiee (Sharif Univ. of Techn. Iran) • Full Paper due: 27th Jan. 2006 Prof. J. A Robinson (Univ. of York, UK) st Dr D. Roviras (INPT, France) • Notification of acceptance by: 1 April 2006 Dr S. Shioda (Chiba Univ. Japan) • Camera ready paper due: 5th May 2006 Dr J. Sodha (Univ. of West Indies, Barbados, W.Indies) Dr I. Soto (Santiago Univ. Chile) Electronic submission by e-mail to: [email protected] Dr U. Speidel (Univ. of Auckland, Newzeland) All papers will be incorporated into a bound volume of proceeding, which will Prof. M. Stasiak (Poznan Univ. Poland) be available on arrival at the symposium. Selected papers will be published Dr L. Stergioulas (Brunel Uni. UK) to The Mediterranean Journals of Computers and Networks and The Prof. E. Sykas (Nation. Tech. Univ. Athens, Greece) Mediterranean Journals of Electronics and Communications. Prof. M. Theologou (Nation. Tech. Univ. Athens, Greece)

Prof. R. T Valadas (Univ. of Aveiro, Portugal) Dr C. Vassilopoulos (OTE, Greece) Fees: 300.00 Euro per person (Group Delegates of 3 persons: 700.00 Euro) Prof. I. S Venieris (Nation. Tech. Univ. Athens, Greece) Includes: Dr I. Viniotis (N.Caroline State Univ.USA) - A copy of the Symposium Proceedings, Dr V. Vitsas (TEI of Thessaloniki, Greece) - Lunches, Prof. M. N. Zervas (Southampton Univ. UK) - Symposium Dinner on the 20th July.

CSNDSP’06 General Information Contact: Dr Michael Logothetis - Local Organising Committee Chair Wire Communications Laboratory, Department of Electrical & Computer Engineering, University of Patras, 265 00 Patras, Greece. Tel. +30 2610 996433, Fax. +30 2610 991855, URL: http://www.wcl.ee.upatras.gr/m-logo, E-mail: [email protected] Or: [email protected]

Call for Participation The eNTERFACE summer workshops, organized by the SIMILAR European FP6 Network of Excellence (www.similar.cc), aim at establishing a tradition of collaborative, localized research and development work by gathering, in a single place, a team of senior project leaders in multimodal interfaces, researchers, and (undergraduate) students, to work on a pre-specified list of challenges, for 4 weeks. Participants are organized in teams, attached to specific projects, working on free software. Tutorial state-of-the art surveys of aspects of multimodal interfaces design will be given every week by invited senior researchers. Plenary sessions with progress presentations by all teams shall be organized to stimulate exchange of ideas. The eNTERFACE'06 committee now invites candidate participants to apply for a summer workshop on multimodal interfaces, to be held in Dubrovnik, Croatia, from July 17th to August 11th, 2006. eNTERFACE'06 will welcome approx. 50 students, researchers, and seniors, working in teams on the following projects (selected from the proposals received in the Call for Projects): 1. An Agent Based Multicultural User Interface in a Customer Service Application (Coordinator: Hung-Hsuan Huang, Kyoto University, Japan; Advisors: Prof. Toyoaki Nishida, Kyoto University, Japan, Prof. Yukiko Nakano, Tokyo University of Agriculture and Technology, Japan, Prof. Igor Pandzic, University of Zagreb, Croatia). To improve communication of embodied conversational agent (ECA) systems with their human users, the importance of their capability to cover the cultural differences emerged. This project aims to explore the possibility of rapidly building multicultural ECA interfaces for customer service applications with a common framework connecting their functional blocks.

2. Multimodal tools and interfaces for the intercommunication between visually impaired and “deaf and mute” people (Coordinator: Prof. Dimitrios Tzovaras, Informatics and Telematics Institute (ITI-CERTH), Greece). The main objective of the project is to build a multimodal interface that combines visual, aural and haptic interaction with gesture-speech recognition, speech synthesis and sign language recognition and synthesis, in order to enable the communication of people exhibiting different kinds of disabilities.

3. Sign Language Tutoring Tool (Coordinators: Prof. Alice Caplier, l'Institut National Polytechnique de Grenoble, France, Prof. Lale Akarun, Boğaziçi University of Istanbul, Turkey). The goal of this project is the development of a real time sign language tutoring tool related to a limited number of well defined gestures which associate hand gestures and head motion and facial expressions. This will exhibit the feasibility of such a system which requires the fusion of three sources of information.

4. Multimodal Character Morphing (Coordinators: Prof. Thierry Dutoit, Faculté Polytechnique de Mons, Belgium, Prof. Ioannis Stylianou, University of Crete, Greece, Prof. Antonio Bonafonte, Universitat Politècnica de Catalunya, Spain). This project aims at performing high quality transformation on the multimodal recordings (audiovisual files) of a source speaker A. Using both voice conversion and video morphing, the result will be a set of audiovisual files with a target speaker B speaking with his/her own voice and acting like A does.

5. Introducing Network-Awareness for Networked Multimedia and Multi-modal Applications (Coordinator: Miran Mosmondor, Ericsson Nikola Tesla R&D, Croatia; Advisors: Prof. Maja Matijasevic, University of Zagreb, Croatia, Dr. Sasa Desic, Ericsson Nikola Tesla R&D, Croatia) The project objective is to create an application programming interface (API) which will enable multimodal application developers to create networked services for heterogeneous end-user devices, capable of requesting and adapting to network quality of service (QoS), but without the need to know the signalling protocol specifics.

6. An instrument of sound and visual creation driven by biological signals (Coordinator: Prof. Benoit Macq, UCL Louvain La Neuve, Belgium) Pursuing this first eNTERFACE workshop, this project aims to use biophysical signals (EEG, EMG, ECG, EOG, etc…) analysis to drive digital musical instruments, enhanced with a rich visual feedback, and playable in real-time. This year, we will try to improve the interaction musician- instrument by expanding the mapping between biological signals and synthesis parameters.

7. Emotion Detection in the Loop from Brain Signals and Facial Images (Coordinators: Bulent Sankur, Boğaziçi University, Turkey, Prof. Magnus Borga, Linköping University, Sweden (TO BE CONFIRMED), Prof. Alice Caplier, Université de Grenoble, France (TO BE CONFIRMED)). In this project, we intend to develop techniques for multimodal emotion detection, one modality being brain signals via fNIRS, the other modality being face video and the third modality being the scalp EEG signals.

8. Realtime and Accurate Control of Expression in Singing Synthesis (Coordinators: Prof. Christophe d'Alessandro, LIMSI-CNRS, Orsay, France, Nicolas d'Alessandro, Faculté Polytechnique de Mons, Belgium) The main purpose of this project is to develop a full computer-based system musical instrument allowing real-time synthesis of expressive singing voice. The expression will result from the continuous action of an interpreter through a gesture controlled interface. Those gesture parameters will influence the voice characteristics thanks to a particular mapping strategy.

9. Multimodal Driving Simulator (Coordinators: Dr. Laurent Bonnaud and Dr. Alice Caplier, Institut National Polytechnique de Grenoble, France, Prof. Laurence Nigay, Université Joseph Fourier, Grenoble, France, Dr. Dimitrios Tzovaras, Informatics and Telematics Institute, Greece) Facing the sophisticated sensing and interaction technology available in modern cars, this project aims at designing and developing a multimodal driving simulator that is based on both multimodal driver's focus of attention detection and driver's state detection (i.e., stress and fatigue) as well as multimodal interaction for enhancing a driving task.

People (seniors, PhD students, undergraduate students) interested in participating to the workshop should send us an application by email, before February 15th 2006, in form of a document containing the following information: • A short CV (1 page max.) • A list of skills to offer for these projects • A list of 3 preferred projects to work on • Possibility to bring a laptop? 1 No funding will be provided for researchers, but no registration fees will be asked for. Researchers will therefore have to pay for their travel, lodging, and catering expenses. Lodging will be available at or near the workshop venue, at minimal rates (between €25 and €45 per person, per night, depending on type of accommodation). See eNTERFACE06 website for more information. Seven undergraduate students will be selected, whose travel and lodging expenses will be paid by the workshop organizers.

Important • February 15th, 2006: Call for Participation closes dates: • February 20th, 2006: Notification of Acceptance; Team Building begins • July 17th-August 11th: eNTERFACE Workshop

http://www.enterface.net/enterface06 Correspondence: [email protected]

The eNTERFACE’06 Scientific Committee Niels Ole Bernsen, University of Southern Denmark - Odense, Denmark Thierry Dutoit, Faculté Polytechnique de Mons, Belgium Christine Guillemot, IRISA, Rennes, France Richard Kitney, University College of London, United Kingdom Benoît Macq, Université Catholique de Louvain, Louvain-la-Neuve, Belgium Cornelius Malerczyk, Zentrum für Graphische Datenverarbeitung e.V, Germany Ferran Marques, Univertat Politécnica de Catalunya PC, Spain Laurence Nigay, Université Joseph Fourier, Grenoble, France Dimitrios Tzovaras, Informatics and Telematics Institute, Greece Jean-Philippe Thiran, Swiss Federal Institute of Technology Lausanne (EPFL), Switzerland Jean Vanderdonckt, Université Catholique de Louvain, Louvain-la-Neuve, Belgium

1 Workshop organizers can not provide computers. Some project coordinators may be able to provide them, but this is not guaranteed. Therefore the impossibility to bring your own computer may limit the choice of possible projects. 14th European Signal Processing Conference EUSIPCO 2006 European Association September 4-8, 2006, Florence, Italy for Signal, Speech and Image Processing

General Chairman CALL FOR PAPERS Marco Luise University of Pisa, Italy The 2006 European Signal Processing Conference (EUSIPCO-2006) is the four- [email protected]

teenth in a series of conferences promoted by EURASIP, the European Associa- Technical Program Chairman tion for Signal, Speech, and Image Processing (www.eurasip.org). Formerly bian- Fulvio Gini nual, this conference turns for the second time into a yearly event. This edition will University of Pisa, Italy be organized by the University of Pisa in the Palazzo dei Congressi, at the very [email protected]

heart of Florence, the capital of Italian Renaissance. Special Sessions and EUSIPCO-2006 will focus on the key aspects of signal processing theory and ap- Plenary Talks plications as listed below. Exploration of new avenues and methodologies of signal Giovanni Sicuranza processing will also be encouraged. Accepted papers will be published in the Pro- University of Trieste, Italy [email protected] ceedings of EUSIPCO-2006. Acceptance will be based on quality, relevance and originality. Proposals for special sessions and tutorials are also invited. Helmut Bölcksei ETH Zürich, Switzerland [email protected]

Areas of Interest Tutorials Ercan E. Kuruoğlu • Audio and Electroacoustics • Speech Processing CNR, Pisa, Italy [email protected] • Design and Implementation • Education in Signal Processing of Signal Processing Systems • Nonlinear Signal Processing Publications • Image and Multidimensional Sig- • Medical Imaging and Image Maria S. Greco nal Processing Analysis University of Pisa, Italy [email protected] • Multimedia Signal Processing • Signal Processing Applications • Signal Detection and Estimation (Biology, Geophysics, Seismic, Luca Fanucci CNR, Pisa, Italy • Sensor Array and Multichannel Radar, Sonar, Remote Sensing, [email protected] Processing Astronomy, Bio-informatics, • Signal Processing for Communi- Positioning etc.) Local Arrangements cations • Emerging Technologies Filippo Giannetti University of Pisa, Italy [email protected]

Arianna Morelli University of Pisa, Italy Best Student Paper Awards [email protected]

There will be a student paper contest. Student Publicity authors who appear as first authors in a paper may G. Tong Zhou enter the student paper contest. Georgia Tech, USA [email protected]

Romano Fantacci University of Florence, Italy Submission [email protected]

Procedures to submit a paper, proposals for special sessions/tutorials, can be US Liason found at www.eusipco2006.org. Submitted papers must be camera-ready, Georgios B. Giannakis final, no more than four pages long all inclusive and conforming to the format University of Minnesota, USA specified on the EUSIPCO web-site above. [email protected]

Exhibits & Awards Fabrizio Berizzi University of Pisa, Italy Important Dates [email protected]

Proposals for Special Sessions and Tutorials: December 02, 2005 Secretariat and Registration Submission of Full papers: January 20, 2006 D.G.M.P. srl [email protected] Notification of Acceptance: April 07, 2006 tel. +39 050 879740 fax +39 050 879812 Submission of Camera-Ready Papers and Registration: May 05, 2006

www.eusipco2006.org

ISSPA 2007

International Symposium on Signal Processing and its Applications in conjunction with the International Conference on Information Sciences, Signal Processing and their Applications

12 – 15 February 2007, Sharjah, U.A.E.

ISSPA General Chair & Steering Committee Chair B. Boashash University of Sharjah, UAE The University of Queensland, Australia

Conference Chair M. Bettayeb University of Sharjah, UAE First Call For Papers Conference Vice-Chair S. Al-Araji ISSPA 2007 marks the 20th anniversary of launching the first ISSPA in 1987 in Brisbane, Etisalat University College, UAE Australia. Since its inception, ISSPA has provided, through a series of 8 symposia, Technical Program a high quality forum for engineers and scientists engaged in research and development of K. Assaleh, Chair Signal and Image Processing theory and applications. Effective 2007, ISSPA will extend its American University of Sharjah, UAE M. IbnKahla, Co-Chair scope to add the new track of information sciences. Hence, the intention that the previous Queens University, Canada full name of ISSPA is replaced after 2007 by the following new full name: I. Tabus, Co - C ha i r Tampere University of Technology, Finland International Conference on Information Sciences, Signal Processing and their Applications. ISSPA is an IEEE indexed conference. Plenary Sessions S. Mitra University of California, Santa Barbara, USA ISSPA 2007 will be organized by three prominent institutions located in Sharjah in the United Arab Emirates: University of Sharjah, American University of Sharjah, and Etisalat University College. Special Sessions M. Barkat American University of Sharjah, UAE The regular technical program will run for three days along with an exhibition of signal M. Cheriet University of Quebec, Canada processing and information sciences products. In addition, tutorial sessions will be held on the L. Karam first day of the symposium. Papers are invited in, but not limited to, the following topics: Arizona State University, USA

Tutorials 1.Filter Design Theory and Methods 11. Multimedia Signal Processing 21.Signal Processing for Bioinformatics M. El-Tarhuni 2. Multirate Filtering & Wavelets 12. Nonlinear signal processing 22. Signal Processing for Geoinformatics American University of Sharjah, UAE 3.Adaptive Signal Processing 13.Biomedical Signal and Image 23.Biometric Systems and Security Processing Publications 4.Time-Frequency/Time-Scale Analysis 14.Image and Video Processing 24.Machine Vision M. Al-Qutayri 5.Statistical Signal & Array Processing 15.Image Segmentation and Scene 25.Data visualization Etisalat University College, UAE Analysis

6.Radar & Sonar Processing 16. VLSI for Signal and Image 26. Data mining Publicity Processing M. Al-Mualla 7.Speech Processing & Recognition 17.Cryptology, Steganography, and 27. Sensor Networks and Sensor Fusion Etisalat University College, UAE Digital Watermarking 8.Fractals and Chaos Signal Processing 18. Image indexing & retrieval 28.Signal Processing and Information Sponsorship & Exhibits Sciences Education K. Al-Midfa Etisalat University College, UAE 9.Signal Processing in 19.Soft Computing & Pattern 29.Others Communications Recognition Student Sessions 10.Signal processing in Networking 20. Natural Language Processing A. Elwakil University of Sharjah, UAE Perspective authors are invited to submit full length (four pages) papers for presentation in any of

Finance & Registration the areas listed above (indicate area in your submission). We also encourage the submission of C. B. Yahya proposal for student session, tutorial and sessions on special topics. All articles submitted to University of Sharjah, UAE ISSPA 2007 will be peer-reviewed using a blind review process.

Local Arrangements I. Kamel For more details see University of Sharjah, UAE

Social Events w w w . i s s p a . i n f o / A. Al-Ali American University of Sharjah, UAE

Web and IT B. Soudan Important Deadlines: Conference Secretary University of Sharjah, UAE Full Paper Submission: A-K. Hamid

June 30, 2006 University of Sharjah, UAE IEEE Liaison Tutorials/Special Sessions Proposals: (TBA) May 30,2006 Tel : +971 6 5050932 Industry Liaison Notification of Paper Acce ptance : Fax :+971 6 5050872 (TBA) October 15, 2006 E-mail: [email protected] Final Accepted Paper Submission: International Liaisons November, 15, 2006 S. Anderson, Australia DSTO, Australia T. Fukuda, Asia and Pacific Nagoya University, Japan M . Gabbouj, Europe Tampere University of Technology, Finland M. Jaidane, Africa ENIT, Tunisia Y. Zhang, America Villanova University, USA

ORGANIZING COMMITTEE

General Co-Chair Fazekas K., Hungary Turán J., Slovak Republic

Publicity Chair Panos Liatsis, UK IWSSIP'06

Tutorials Chair th Zovko-Cihlar B., Croatia 13 International Conference on Systems, Signals &Image Processing September 21-23, 2006 - Budapest, Hungary Special Sessions Chair Mislav Grgic, Croatia CALL FOR PAPERS The 13th International Conference on Systems, Signals and Image Processing, IWSSIP'06 is co-organised by the BUTE Organizing Committee Enyedi B., Hungary of Budapest, Hungary and TUKE of Košice, Slovak Republic, in co-operation with IEEE, IEE, IEEE Region 8, IEEE Konyha L., Hungary Hungarian Section and EURASIP. IWSSIP'06 is an International Conference on the theoretical, experimental and Szombathy Cs., Hungary applied signal and image processing techniques and systems which brings together researchers and developers from Tran S. M., Hungary both academia and industry to report on the latest scientific and theoretical advances, to discuss and debate major issues Ovseník L., Slovak Republic and to demonstrate state of-the-art systems. The IWSSIP'06 program will also include a variety of special sessions and tutorials devoted to recent and important developments in the field.

INTERNATIONAL PROGRAM COMMITTEE SCOPE Ansorge M., Switzerland 1. Signal Processing: General techniques and algorithms. Adaptive DSP algorithms; Filter Bank Theory; Spectrum Bojkovic Z., Serbia Estimation and Processing; Non-linear Systems; Digital Transforms; Multidimensional Signal Processing; Pattern Chariglione L., Italy Recognition. Cristea P., Romania 2. Technologies: Neural Networks; Fuzzy Systems; Expert Systems; Genetic Algorithms; Data Fusion. Cucej Z., Slovenia 3. Multimedia Content Processing: Speech Processing and Recognition, Audio Enhancement, Restoration and Domanski M., Poland Analysis, Image Representation and Modelling, Image Restoration and Enhancement; Colour Vision, 3D Vision, Image Doshi B., USA and Video Analysis; Pattern Recognition; Watermarking, New Media. Ebrahimi T., Switzerland 4. Multimedia Data Compression: Speech and Audio Compression, Image and Video Coding, Scalable Techniques, Fazekas K., Hungary Standards. Grgic M., Croatia 5. Multimedia Systems: Human Factors, Multimodal Interfaces, Networked Multimedia, Seamless Audiovisual Grgic S., Croatia Networks, Multimedia Services; Multimedia Servers; Multimedia Streaming, Wireless and Mobile Multimedia, Heute U., Germany Universal Multimedia Access, Right Protection and Management. Izguierdo E., UK 6. Content Description: Metadata and Media Abstracts, Audiovisual Databases. Katsaggelos A. K., USA 7. Implementations: Analog and Digital Circuits and Systems for Audio, Image and Video Processing; Architectures Kazakos D., USA and VLSI Hardware; Programmable Signal Processors; Real-time Software. Kocur D., Slovak Republic 8. Applications: Bioinformatics; Broadcasting; Control; Communications; Digital Production; Medical; Opto- Levický,D., Slovak Republic mechatronics; Remote Sensing; Robotics; Speech; Television; Telepresence; e-learning; Virtual Reality; Remote Liatsis P., UK Sensing. Lukáč R., Canada Marchevský S., Slovak Republic SUBMISSION PROCEDURE Mertzios B., Greece Prospective authors are invited to submit original research papers in any of the technical areas listed above. They should Pereira F., Portugal submit their full paper in English, including the summary of the accomplishments and the significance of the Pitas I., Greece contribution. Submission should include in a separate sheet the author(s) name(s) and affiliation(s); the contact author Planinsic P., Slovenia should be identified by providing his/her mail and e-mail address, telephone and fax numbers. All papers will be fully Podhradský P., Slovak Republic peer reviewed. Hardcopy and electronic submission, along with www uploading are available. For more information Rao K.R., USA please visit the official IWSSIP’06 Site: http://cyberspace.mht.bme.hu/iwssip06/ Accepted papers will be published Rozinaj G., Slovak Republic in the IWSSIP’06 Proceedings. At least one author of each accepted paper must register for the conference and present Schaefer R., Germany the contribution. After further peer reviewing, selected papers will be proposed for publication in special issues of Sonka M., USA scientific journals. Šimák B., Czech Republic Stamatis V., GREECE SCHEDULE Stasinski R., Poland Deadline for submission of full papers May 22, 2006 Tasic J., Slovenia Notification of acceptance mailed out by June 30, 2006 Tekalp M., USA Early Registration deadline July 10, 2006 Turán J., Slovak Republic Deadline for submission of camera-ready papers July 14, 2006 Vlaicu A., Romania Registration deadline August 14, 2006 Wajda K., Poland Conference September 21, 2006 Zahariadis T., GREECE Zervos N., Greece CONFERENCE SITE Zorzi M., Italy IWSSIP’06 will be held at Flamenco Hotel, Tasvezér utca 7., Budapest, Hungary Zovko-Cihlar B., Croatia Information: http://cyberspace.mht.bme.hu/iwssip06 and [email protected] (will be available after December 1, 2005.)

Budapest University of Technology and Economics

General Chairs

Bilge Gunsel Istanbul Technical Univ.,Turkey

Anil K. Jain

Michigan State University, USA CALL FOR PAPERS Technical Program Chair Workshop on Multimedia Content Representation, Classification and Security Murat Tekalp (MRCS) is being organized with the objective of bringing together researchers, Koc University, Turkey developers and practitioners from academia and industry working in related areas of multimedia systems. MRCS aims to serve as a forum for the dissemination of Publicity Chair state-of-the-art research, development, and implementations of multimedia content

extraction and classification, multimedia security technologies, and innovative Kivanc Mihcak Microsoft Research, USA applications. IMRCS is co-sponsored by IAPR, EURASIP, TUBITAK, ITU, and IEEE Turkey Chapter. Financial Chair

Gozde Bozdagi-Akar The areas of interest include but are not limited to: Middle East Tech. Univ.,Turkey - Feature extraction, multimedia content representation and classification techniques Local Arrangements - Multimedia signal processing Sima Etaner-Uyar - Authentication, content protection and digital rights management Istanbul Technical Univ.,Turkey - Audio/Video/Image Watermarking/Fingerprinting - Information hiding, steganography, steganalysis Program Committee - Audio/Video/Image hashing and clustering techniques - Evolutionary algorithms in content based multimedia data representation, A. Akansu, NJIT, USA indexing and retrieval A. Alatan, METU, Turkey - Transform domain representations M. Barni, Univ. of Sienna, Italy P. Bouthemy, IRISA, France - Multimedia mining R.Civanlar, Koc Univ., Turkey - Benchmarking and comparative studies E. Delp, Purdeu University, USA - Multimedia applications (broadcasting, medical, biometrics, content aware J. Dittmann, Otto-von-Guericke networks, CBIR.) Univ., Germany C. Dorai, IBM T.J. Watson, USA Prospective authors are invited to submit extended summaries of not more than six A. Ercil, Sabanci Univ., Turkey (6) pages including results, figures and references. Submitted papers will be A. Fred, IST Lisbon, Portuqal reviewed by at least two members of the program committee. Conference M.Gokmen, ITU, Turkey A. Hanjalic, Tech. Univ. Delft, Proceedings will be available on site. Please check the website Netherlands http://www.ehb.itu.edu.tr/~mrcs for further information. H. Ip, City University, Hong Kong D. Kundur, Texas A&M , USA I. Lagendijk, Tech. Univ. Delft, Important Dates Netherlands K.J.R. Liu, Univ. of Maryland,USA Special Sessions (contact the technical program chair): March 10, 2006 J. Luo, Eastman Kodak, USA B. Macq, UCL, Belgium Submission of Extended Summary: April 10, 2006 B. Manjunath, Univ. of CA, USA Notificatin of Acceptance: June 10, 2006 V. Monga, Xerox Labs, USA Camera-ready Paper Submission Due: July 10, 2006 P. Moulin, Univ. of Illinois, USA L. Onural, Bilkent Univ., Turkey Contact F. Gonzalez, Univ. of Vigo, Spain B. Sankur, Bogazici Univ., Turkey J. Smith, IBM T.J. Watson, USA Istanbul Technical University, Electrical-Electronics Eng. Faculty, 34469 Maslak S. Voloshynovskiy, Univ. of Istanbul, Turkey. Attn: Dr. Sima Etaner-Uyar Geneva, Switzerland Phone: (90) 212 285 6471 Fax: (90) 212 285 3679 R. Venkatesan, Microsoft E-mail: [email protected] Web:http://www.ehb.itu.edu.tr/~mrcs Research, USA H-J. Zhang, Microsoft China

FIRST CALL February 2006 NOLISP’07 AN ISCA TUTORIAL AND RESEARCH WORKSHOP ON NON-LINEAR SPEECH PROCESSING

After the success of NOLISP’03 held in Le Croisic, and NOLISP’05 held in Barcelona, we are pleased to present NOLISP’07

22-25 May 2007, Paris, France

Local Organizers : University Pierre and Marie Curie (UPMC)

AIMS OF THE WORKSHOP SCIENTIFIC COMMITTEE Many specifics of the speech signal are not well Frédéric BIMBOT, IRISA, Rennes (France) addressed by the conventional models currently used in Mohamed CHETOUANI, UPMC, Paris (France) the field of speech processing. The purpose of the Gérard CHOLLET, ENST, Paris (France) workshop is to present and discuss novel ideas, work Tariq DURRANI, University of Strathclyde, Glasgow (UK) and results related to alternative techniques for speech Marcos FAÚNDEZ-ZANUY, EUPMt, Barcelona (Spain) processing, which depart from mainstream approaches. Bruno GAS, UPMC, Paris (France) Hynek HERMANSKY, OGI, Portland (USA) FOCUS OF THE WORKSHOP Amir HUSSAIN, University of Stirling, Scotland (UK) Eric KELLER, University of Lausanne (Switzerland) Contributions are expected in the following domains Bastiaan KLEIJN, KTH, Stockholm (Sweden) (non-limited list): Gernot KUBIN, TUG, Graz (Austria) I. Non-Linear Approximation and Estimation Petros MARAGOS, Nat. Tech. Univ. of Athens (Greece) II. Non-Linear Oscillators and Predictors Stephen Mc LAUGHLIN, University of Edimburgh (UK) III. Higher-Order Statistics Maurice MILGRAM, UPMC, Paris (France) IV. Independent Component Analysis Kuldip PALIWAL, University of Brisbane (Australia) V. Nearest Neighbours Bojan PETEK, University of Ljubljana (Slovenia) VI. Neural Networks Jean ROUAT, University of Sherbrooke (Canada). VII. Decision Trees Jean SCHOENTGEN, Univ. Libre Bruxelles (Belgium) VIII. Non-Parametric Models Isabel TRANCOSO, INESC (Portugal) IX. Dynamics of Non-Linear Systems X. Fractal Methods SUBMISSION XI. Chaos Modeling Prospective authors are invited to submit a 3 to 4-page XII. Non-Linear Differential Equations paper proposal in English, which will be evaluated by the XIII. Others Scientific Committee. Final papers will be due 1 month

after the workshop, for inclusion in the CD-ROM All fields of speech processing are targeted by the proceedings. workshop, namely : 1. Speech Production KEY DATES 2. Speech Analysis and Modeling Submission (full paper): 15 January 2007 3. Speech Coding Notification of acceptance: 23 February 2007 4. Speech Synthesis Workshop: 22-25 May 2007 5. Speech Recognition Final (revised) paper: 25 June 2007 6. Speaker Identification/ Verification 7. Speech Enhancement / Separation 8. Speech Perception 9. Others

ORGANISING COMMITTEE : Mohamed CHETOUANI (UPMC), Bruno GAS (UPMC), Amir HUSSAIN (Stirling), Maurice MILGRAM (UPMC), Jean-Luc ZARADER (UPMC).

CONTACT : [email protected] WEB SITE : http://www.congres.upmc.fr/nolisp2007/

PCS 2007 th 26 Picture Coding Symposium

(www.pcs2007.org)

November 7-9, 2007, Lisbon, Portugal

Call for Papers

Picture Coding Symposium (PCS) is an international forum devoted specifically to advancements in visual data coding. Since 1969, PCS has provided the meeting place for the visual coding community: industry, research, academia and users. The 26th PCS will be held in Lisbon, Portugal, on 7-9 November 2007, just before the 16th International Packet Video Workshop that will be held in Lausanne, Switzerland, on 12-13 November 2007.

Topics Organization

Topics of interest include, but are not limited to: General Chair • Coding of still and moving pictures Fernando Pereira • Content-based and object-based coding IST-IT, Lisbon, Portugal • Scalable video coding Program Chair • Coding of multiview video and 3D graphics • Modeling and synthetic coding Paulo Lobato Correia • Virtual/augmented reality and telepresence IST-IT, Lisbon, Portugal • Coding for mobile, IP and sensor networks Special Sessions Chair • High fidelity visual data processing and coding Luis Ducla Soares • Analysis for coding and adaptation ISCTE-IT, Lisbon, Portugal • Transcoding and transmoding • Joint audio and visual processing and coding Deadlines • Subjective and objective quality assessment metrics and methods Submission of special sessions • Error robustness, resilience and concealment June 1, 2007 • Coding and indexing for database applications • Protection and integrity of visual data Submission of extended summaries • Persistent association of information to visual data June 10, 2007 • Joint source and channel coding Notification of acceptance • Implementation architectures and VLSI • New applications and techniques for visual data coding September 3, 2007 • Standards for visual data coding Submission of camera-ready papers September 21, 2007

Paper Submission Prospective authors are invited to submit extended summaries of no more than four (4) pages, in English, with font size 11, including results, figures and references. Submissions will be accepted only in PDF format and should be made using the on-line submission system available at www.pcs2007.org. Special Sessions Submission Proposals for special sessions must include a title, rationale, session outline, session chair, a list of authors who have agree to present a paper, and a tentative title and abstract of each paper. Proposals should be sent to the Special Session Chair at [email protected] before June 1, 2007.

Accepted papers will be published in the Workshop CD Proceedings.

samt 1st International Conference on Semantic and Digital Media Technologies 2006 December 6-8, 2006 Athens, Greece

C a l l F o r P a p e r s

General Chairs Yannis Avrithis National Technical University of Athens, Greece Yiannis Kompatsiaris The first international conference on Semantics And digital Media Technology (SAMT) targets to Informatics and Telematics Institute, Greece narrow the large disparity between the lowlevel descriptors that can be computed automatically from multimedia content and the richness and subjectivity of semantics in user queries and human Technical Programme Chairs interpretations of audiovisual media - The Semantic Gap. Noel O’Connor Dublin City University, Ireland Steffen Staab SAMT started out as two workshops, EWIMT 2004 and EWIMT 2005, that quickly achieved University of Koblenz-Landau, Germany enormous success in attracting high-quality papers and over 100 participants from across Europe Special Sessions and beyond. This year EWIMT has turned into the full-fledged conference SAMT, addressing Jose Martinez integrative research on new knowledge-based forms of digital media systems. It brings together Universidad Autónoma de Madrid, Spain those forums, projects, institutions and individuals investigating the integration of knowledge, semantics and low-level multimedia processing, and links them with industrial research and Tutorials & Workshops Raphael Troncy development engineers who exploit the underlying emerging technology. CWI, The Netherlands Vassilis Tzouvaras National Technical University of Athens In cooperation with the European Commission DG Information Society, the third day of the conference is dedicated to featuring the launch of the 7th Framework ICT Research programme EU Liaison and keynote talks from EC representatives. Paola Hobson Motorola Labs, UK

Technical Programme Committee (to be extended) Prospective contributors are invited to submit their papers on-line according to Wolf-Tilo Balke, Univ Hannover, Germany Jenny Benois-Pineau, University of Bordeaux, France the guidelines at http://www.samt2006.org Patrick Bouthemy, IRISA, France Andrea Cavallaro, Queen Mary University of London, UK Fabio Ciravegna, University of Sheffield, UK Thierry Declerck, DFKI, Germany Anastasios Delopoulos, Aristotle Univ. of Thessaloniki, Greece Edward Delp, Purdue University, US Touradj Ebrahimi, Swiss Federal Institute of Technology, CH Topics of interest include, but are not limited to: Borko Furht, Florida Atlantic University, US Moncef Gabbouj, Tampere University of Technology, Finland Werner Haas, Joanneum Research, Austria lIntegration of multimedia processing and Semantic Web technologies Siegfried Handschuh, DERI Galway, Ireland lMultimedia ontologies and infrastructures Alan Hanjalic, TU Delft, The Netherlands Lynda Hardman, CWI, The Netherlands lKnowledge assisted multimedia data mining Andreas Hotho, Univ Kassel, Germany lKnowledge based inference for semi-automatic semantic media annotation Ebroul Izquierdo, Queen Mary University of London, UK Franciska de Jong, University of Twente, The Netherlands lIntegration of content-based image/video analysis with natural language and speech processing Joemon Jose, University of Glasgow, UK l Hyoung Joong Kim, Kangwon National University, Korea Multimodal techniques, high dimensionality reduction and low-level feature fusion Joachim Kohler, Fraunhofer IMK, Germany lRelevance feedback for finding semantics Stefanos Kollias, National Technical Univ. of Athens, Greece l Paul Lewis, University of Southampton, UK Semantic-driven multimedia indexing and retrieval Petros Maragos, National Technical Univ. of Athens, Greece lMetadata management for multimedia Ferran Marques, Technical University of Catalonia, Spain Adrian Matellanes, Motorola Labs, UK lBrowsing large multimedia archives Dietrich Paulus, Uni Koblenz, Germany lScalable, semantic-driven multimedia content adaptation and summarization Dennis Quan, IBM Keith Van Rijsbergen, University of Glasgow, UK lInterfaces and personalization for interaction with large multimedia repositories Mark Sandler, Queen Mary, University of London l Simone Santini, Univ. of California, San Diego, US Semantics-driven multimedia presentation generation Guus Schreiber, Free Univ. Amsterdam, The Netherlands lContent, user,network and semantics-aware media engineering Sergej Sizov, Uni Koblenz, Germany l Alan Smeaton, Dublin City University, Ireland Standards bridging the multimedia and knowledge domains Fred S Stentiford, University College London, UK Michael Strintzis, ITI, Greece Rudi Studer, Univ Karlsruhe, Germany Vojtech Svatek, UEP, Czech Republic Murat Tekalp, Univ. Rochester, US Paulo Villegas, Telefonica I+D, Spain 01 May 2006 Special Sessions Gerhard Widmer, Univ. Linz, Austria Li-Qun Xu, British Telecom, UK 22 May 2006 Tutorials & Workshops 16 June 2006 Regular Paper Submission 11 August 2006 Notification of Acceptance 11 September 2006 Submission of camera-ready papers

IVML Information Society 4th International Workshop on Total Least Squares and Errors-in-Variables Modeling August 21–23, 2006 Arenberg castle, Leuven, Belgium Announcement and Call for Papers

Conference Committee This interdisciplinary workshop is a continuation of 3 previous workshops which were held in Leuven, Belgium, August 1991, 1996, and 2001 and aims to bring Chairpersons together numerical analysts, statisticians, engineers, economists, chemists, etc. in order to discuss recent advances in Total Least Squares (TLS) techniques and Sabine Van Huffel and errors-in-variables (EIV) modeling. Ivan Markovsky Katholieke Universiteit Leuven, BE Papers are solicited for technical sessions on the following and related topics : Members Concepts and Properties : structured and weighted TLS, other norms, mis- fit versus latency errors, nonlinear measurement error models, dynamic Bart De Moor errors-in-variables, hypersurface fitting, statistical, numerical, robustness Katholieke Universiteit Leuven, BE and optimization aspects Yasuo Amemiya Algorithms : real-time, adaptive, recursive, neural, iterative algorithms, based IBM Research Center, USA on SVD or related matrix/tensor decompositions, architectures, complexity, Gene Golub accuracy, regularization, convergence, lower rank approximations Stanford University, USA Applications : array signal and image processing, filtering, system identifi- Björn Ottersten cation, computer vision, document retrieval, spectral analysis, harmonic re- Royal Institute of Technology, SE trieval, direction finding, geology, chemistry, biomedicine G.W. Stewart In particular, overview papers describing recent advances on any of the above- University of Maryland, USA mentioned topics are invited. Other topics related to total least squares, errors- Rik Pintelon in-variables modeling, and their applications are also welcome. Vrije Universiteit Brussel, BE Authors are invited to submit (electronically and via ordinary mail) an extended Paul Van Dooren summary (2 pages) to the workshop secretariat for review. Fax number and email UniversitéCatholique de Louvain, BE should be provided if possible. Overview papers will be presented as lecture, the other ones in poster form. Authors of accepted contributions will be asked to Nicola Mastronardi prepare a version for publication in the conference proceedings to be published as CNR Bari, IT special issues of numerical linear algebra and applied statistics journals. Richard Vaccaro University of Rhode Island, USA Authors’ Schedule

Chi-Lun Cheng Submission of summary: March 1, 2006 Academia Sinica, Taiwan Notification of Acceptance: April 1, 2006 Submission of camera-ready paper: October 1, 2006 Alexander Kukush University of Kiev, Ukraine Workshop Secretariat Lieven De Lathauwer CNRS–ETIS, FR Ida Tassens Chris Paige Dept. of Electrical Engineering, ESAT-SCD (SISTA) McGill University, CA Katholieke Universiteit Leuven Kasteelpark Arenberg 10 Shalabh B–3001 Leuven–Heverlee, Belgium Indian Institute of Technology Kanpur, IN tel : 32/16/32.17.09 fax : 32/16/32.19.70 Helmut Küchenhoff email : [email protected] University of Munich, Germany web : www.esat.kuleuven.be/∼imarkovs/workshop.html 2006 INTERNATIONAL W ORKSH OP ON ACOUSTIC ECH O AND NOISE CONTROL IW AENC2006

Télécom Paris (ENST), Paris, France Se pte m be r 12 (Tue ) - 14 (Th u), 2006 h ttp://w w w .iw ae nc06.e nst.fr/

CALL FOR PAPERS Th e 10th Inte rnational W ork sh op on Acoustic Ech o and Noise Control w ill be h e ld in Paris, France , Se pte m be r 12-14, 2006. Starting form 2006, th is w ork sh op w ill be h e ld on e ve n ye ars (since th e cre ation in 19 89 , th e nine pre vious e ditions h ad be e n h e ld on odd ye ars). Th e w ork sh op w ill focus on th e topics of signal proce ssing for acoustic e ch o and noise control. Applications are , am ong oth e rs, te le ph ony, confe re ncing syste m s and voice control syste m s. Th e th re e day Organis ation com m itte e program include s poste r pre se ntations of re ce nt w ork and late st re sults, k e ynote talk s and de m onstrations. Yve s Gre nie r, Télécom Paris, France TECH NICAL SCOPE Gaë l Rich ard, Th e te ch nical scope of th e w ork sh op include s signal proce ssing for spe e ch e nh ance m e nt lik e Télécom Paris, France Cath e rine Vazza, th rough th e control of acoustic e ch o and th e re duction of noise . Th e se are as of signal proce ssing Télécom Paris, France h ave be e n of w ide acade m ic inte re st for m any ye ars and h ave , m ore re ce ntly, se e n a substantial Dom iniq ue Asse line au, grow th in industrial applications such as h ands-fre e m obile te le ph one s and vide o-confe re ncing Télécom Paris, France syste m s. Th e re le vant topics for th e w ork sh op include : Te ch nical Com m itte e - Adaptive filte ring algorith m s and - Syste m s for ste re oph onic e ch o and noise Jacob Be ne sty, structure s for e ch o and noise control control Univ. Que be c, Canada - Noise re duction te ch niq ue s - Microph one arrays and array signal Albe rto Carini, - Active noise control, sound re production proce ssing Univ. Urbino, Italy and h e aring aids - Sound e nh ance m e nt and sound se paration Tom as Gae nsle r, - Transduce rs and acoustic front-e nds - Te m poral se gm e ntation of signals Age re , USA - H ardw are and re al-tim e issue s - Voice activity de te ction and double -talk Sh aron Gannot - Spe e ch -database s and softw are tools de te ction Bar-Llan Univ., Israe l - Multirate filte r bank s and subband syste m s - Noise and acoustic e nvironm e nts and Andre Gilloire , ch aracte ristics FT R& D, France Ste ve n Grant, Univ. Missouri-Rolla, USA Yve s Gre nie r, DEMONSTRATIONS Télécom Paris, France Ebe rh ard H ae nsle r, You are strongly e ncourage d to give a re le vant de m onstration of your w ork Darm stadt Univ. of Te ch ., PROCEDURES Ge rm any Yoich i H ane da, Auth ors are invite d to propose pape rs in any of th e te ch nical are as re le vant to th e w ork sh op. NTT SP Labs, Japan Th e te ch nical com m itte e w ill se le ct pape rs for poste r-pre se ntation. A copy of e ach pape r w ill be Ke e s Janse publish e d on line at th e tim e of th e w ork sh op. Ph ilips Re se arch , Eindh ove n, To subm it a proposal: Th e Ne th e rlands Pre pare 2 page pape r sum m ary or 4 page pape r. Th e subm ission sh ould be m ade th rough on-line . W alte r Ke lle rm ann, If a de m onstration of th e w ork is planne d, include a brie f de scription of th e de m onstration in th e Univ. of Erlange n, Ge rm any pape r sum m ary. Ple ase use our LaTe X style file and h ave a look at a sam ple pape r in both te x and Sh oji Mak ino, pdf for th e de sign of your pape r. NTT CS Labs, Japan Raine r Martin, SCH EDULE Rurh Univ., Ge rm any Subm ission of 2 page pape r sum m ary or 4 page pape r by: April 21, 2006 Marc Moone n, Notification of acce ptance by: June 20, 2006 Kath olie k e Unive rsite it, Subm ission of 4 page final pape r (as pdf-file only, at m ax. 10 MB !) by: July 31, 2006 Le uve n, Be lgium Patrick Naylor, BEST PAPER AW ARD Im pe rial Colle ge , London, UK Pie t Som m e n, Th e IW AENC Te ch nical Com m itte e w ill aw ard a prize for th e be st stude nt pape r. Th e se le ction of Eindh ove n Univ., Th e th e be st pape r w ill be base d on originality, scie ntific m e rit of th e re se arch , and th e q uality of Ne th e rlands th e subm itte d pape r. Pe te r Vary CONTACT ADDRESS FOR SUBMISSIONS AND MORE INFORMATION RW TH Aach e n, Ge rm any iw ae nc2006@ e nst.fr

General -Chair Stefanos Kollias, Preliminary Call for Papers National Technical University of Athens (NTUA), Greece Co-Chair International Conference on Artificial Neural Andreas Stafylopatis, Network (ICANN 06) NTUA, Greece Program Chair Wlodzislaw Duch, Torum, PL & Singapore; ENNS President-elect Erkki Oja, Helsinki, Fi; ENNS President Honorary Chair John G. Taylor, Kings College, London, 10-14 September 2006 UK; ENNS Past President Holiday Inn Hotel, Athens, Greece International Program Committee • Peter Andreas, U. Newcastle, UK Conference Framework • Panos Antsaklis, U. N. Dame, USA The 16th International Conference on Artificial Neural Networks, ICANN 2006, will be held • Nikolaos Bourbakis, Wright State from September 10 to September 14, 2006, at the Holiday Inn Hotel, Athens Greece. ICANN Univ., USA is an annual conference organized by the European Neural Network Society in cooperation • Peter Erdi, Univ. Budapest, HU & with the International Neural Network Society, Japanese Neural Network Society, and the Kalamazoo IEEE Computational Intelligence Society, and is a premier European event in all topics related • Georg Dorffner, Univ. Wien, AT to neural networks. • Erol Gelenbe, Imperial College ICANN 2006 (www.icann2006.org) welcomes contributions on the theory, algorithms, London, UK applications and implementations in the following broad areas: • Stan Gielen, Univ. Nijmegen, NL • Computational neuroscience; • Nikola Kasabov, Kedri, AUT, NZ • Connectionist cognitive science; • Janusz Kacprzyk, Warsaw, PL • Data analysis and pattern recognition; • Chris Koutsougeras, Tulane • Graphical networks models, Bayesian networks; University, USA • Hardware implementations and embedded systems; • Thomas Martinetz, Luebeck, DE • Neural and hybrid architectures and learning algorithms; • Evangelia Micheli-Tzanakou, • Neural control, reinforcement learning and robotics applications; Rutgers University, USA • Neuroinformatics; • Lars Niklasson, Skövde SE • Neural dynamics and complex systems; • Marios Polycarpou, Univ. of • Real world applications; Cyprus • Robotics, control, planning; • Demetris Psaltis, Caltech, USA • Signal and time series processing; • Olli Simula, Espoo, FI • Self-organization; • Alessandro Sperduti, U.Padova, IT • Vision and image processing; • Lefteris Tsoukalas, Purdue • Web semantics; University, USA • Intelligent Multimedia and the Semantic Web.

• , Michel Verleysen Louvain-la- Ideas and nominations for interesting tutorials, special sessions, workshops and experts willing

Neuve, BE to organize various session tracks are called for. Most active experts will be included in the • Alessandro Villa, U. Grenoble, FR scientific committee of the conference. Local Organizing Committee Proceedings of ICANN will be published in Springer's "Lecture Notes in Computer Science". Paper length is restricted to a maximum of 10 pages, including figures. • Yannis Avrithis, NTUA • Christos Douligeris, Piraeus Univ Deadlines and Conference dates • George Dounias, Aegean Univ • Kostas Karpouzis, ICCS-NTUA 06.01 Submission page opens • Aris Likas, Univ. of Ioannina 14.03 End of submission of papers (abstract+full paper) to regular sessions • Konstantinos Margaritis, Univ. of 30.03 End of submission of papers to special sessions Macedonia 30.04 Acceptance/rejection notification • Stavros Perantonis, NCSR 15.06 Deadline for camera ready papers Demokritos, Athens 01.07 Deadline for early registration • Yannis Pitas, AUTH, Salonica 10.09 Tutorials - first day of the conference • Kostas Pattichis, Univ. of Cyprus 11-13.09 Main part of the conference 14.09 Workshops • Apostolos Paul Refenes, Athens University Economics & Business For further information and/or contacts, send inquiries to • Christos Schizas, Univ. of Cyprus Prof. Stefanos Kollias ([email protected])

• Giorgos Stamou, ICCS-NTUA Prof Andreas Stafylopatis ([email protected]) • Sergios Theodoridis, UoA School of Electrical & Computer Engineering • Spyros Tzafestas, NTUA National Technical University of Athens • Mihalis Zervakis, TUC, Crete 9, Heroon Polytechniou str., 157 80 Zografou, Athens, Greece.

EURASIP JOURNALS

EURASIP JOURNAL ON APPLIED SIGNAL PROCESSING

Scope The overall aim of EURASIP Journal on Applied Signal Processing (EURASIP JASP) is to bring science and applications together with emphasis on practical aspects of signal processing in new and emerging technologies. It is directed as much at the practicing engineers as at the academic researchers. EURASIP JASP will highlight the diverse applications of signal processing and encourage a cross fertilization of techniques. All papers should attempt to bring theory to life with practical simulations and examples. Tutorial articles on topics of interest are also welcomed. EURASIP JASP employs paperless, electronic review process to foster fast and speedy turnaround in review process. There are two diﬀerent issues: regular issues and special issues. The regular issues publish collections of papers without special solicitation. The special issues have speciﬁcally aimed and targeted topics of interest contributed by authors responding to a particular Call-for- Papers or by invitation, edited by invited guest editor(s). Regular papers can be submitted at any time, while special issue papers can be submitted only based on planned schedules and submission guidelines of the Call-for-Papers. Proposals for special issues can be submitted directly to the Editor-in-Chief.

Subjects Subject areas include, but are by no means limited to: • Signal processing theory, algorithm, architecture, design, and implementation • Speech processing, coding, compression, and recognition • Audio signal processing, coding, and compression • Image/video processing, coding, compression, restoration, analysis and understanding, and communications • Multimedia signal processing and technology • Signal processing for communications and networking • Statistical and adaptive signal processing • Nonlinear signal processing techniques • Signal processing design tools • Signal processing for security, authentication, and cryptography • Analog signal processing • Signal processing for smart sensor and systems 44 EURASIP Journals

Application areas include, but not limited to: communications; networking; sensors and actuators; radar and sonar; medical imaging; biomedical applications; remote sensing; consumer electronics; computer vision; pattern recognition; robotics; ﬁber optic sensing/transducers; industrial automation; transportation; stock market and ﬁnancial analysis; seismography; avionics.

Indexed/Abstracted In The articles of the EURASIP JASP are reviewed/indexed in Acoustics Abstracts; Computer and Communications Security Abstracts (CCSA); CompuMath Citation Index; Current Contents: Engineering, Computing & Technology; CSA Engineering Research Database; CSA High Technology Research Database with Aerospace; CSA High Technology Research Database with Metadex; Engineering Information databases including (Compendex and Paperchem); INIST-CNRS (Pascal Database); INSPEC; JournalSeek Database; Mathemat- ical Reviews; Science Citation Index Expanded; Scopus; Technology and Management (TEMA); and Zentralblatt fur¨ Mathematik.

Editor-in-Chief Ali H. Sayed, Electrical Engineering Dept., University of California, Los Angeles, CA 90095, USA EURASIP JOURNALS

EURASIP JOURNAL ON AUDIO, SPEECH, AND MUSIC PROCESSING

Scope The aim of “EURASIP Journal on Audio, Speech, and Music Processing” (EURASIP JASMP) is to bring together researchers and engineers working on the theory and applications of EURASIP Journal on Audio, Speech, and Music Processing. EURASIP JASMP will be an interdisciplinary journal for the dissemination of all basic and applied aspects of speech communication and audio processes. Its primary objectives are: • To publish papers on the advancement of both human speech communication science and automatic speech and audio systems • To allow rapid and wide diﬀusion of excellent contributions in these areas • To provide world-wide, barrier-free access to the full text of research articles • To conduct a rapid but thorough review process in order to assure high quality papers • To provide immediate web access once a paper is editorially approved The journal will be dedicated to having original research work, but will also allow tutorial and review articles. Articles will deal with both theoretical and practical aspects of EURASIP Journal on Audio, Speech, and Music Processing.

Subjects Subject areas include (but are not limited to): • Speech and audio technology, as well as related science and engineering methods • Speech analysis, synthesis, coding, recognition, speaker veriﬁcation, language modeling and recognition, human speech production and perception, speech enhancement • Room acoustics, human audition, analysis, synthesis, and coding of music and other audio, transducers, active sound and noise control • Speech and audio separation, computational auditory scene analysis and independent component analysis

Editor-in-Chief Douglas O’Shaughnessy, INRS-EMT (Place Bonaventure), 800 de la Gauchetiere west, suite 6900, Montreal, Quebec, Canada H5A 1K6 EURASIP JOURNALS

EURASIP JOURNAL ON BIOINFORMATICS AND SYSTEMS BIOLOGY

Scope The overall aim of “EURASIP Journal on Bioinformatics and Systems Biology” (EURASIP JBSB) is to publish research results related to signal processing and bioinformatics theories and techniques relevant to a wide area of applications into the core new disciplines of genomics, proteomics, and systems biology. The journal is intended to offer a common platform for scientists from several areas including signal processing, bioinformatics, statistics, biology and medicine, who are interested in the development of algorithmic, mathematical, statistical, modeling, simulation, data mining, and computational techniques, as demanded by various applications in genomics, proteomics, system biology, and more general in health and medicine. Papers should emphasize original results related to the theoretical and algorithmic aspects of signal processing and bioinformatics, in close connection with the applications to genomics, proteomics, systems biology and medicine. Tutorial papers, especially those emphasizing strong components of signal processing or bioinformatics in multidisciplinary views of genomics, proteomics and systems biology are also welcome. The journal will embrace a wide range of topics, and will accommodate different exposition styles, to help scientists with various backgrounds, e.g., engineering, bioinformatics, or biology, to interact effortlessly and to facilitate the exchange of information across the multidisciplinary areas involved. EURASIP JBSB employs a paperless, electronic submission and evaluation system to promote a rapid turnaround in the peer review process. The journal publishes two types of issues: regular issues and special issues. Regular issues publish collections of papers without special solicitation. The special issues feature specifically aimed and targeted topics of interest contributed by authors responding to a particular Call-for-Papers or by invitation, edited by invited guest editor(s). Regular papers can be submitted at any time, while special issue papers can be submitted only based on planned schedules and submission guidelines of the Call-for-Papers. Proposals for special issues can be submitted directly to the Editor-in-Chief.

Subjects Subject areas include (but are by no means limited to): • Reverse engineering of biological circuits • Data mining methods for genomics and proteomics • Signal Processing theory and techniques for systems biology • Modeling and simulation of biological networks • Nanotechnology in genomics and proteomics • Signal processing methods in sequence analysis EURASIP Journal on Bioinformatics and Systems Biology 47

• Information theoretic approaches to genomics and proteomics • Microarray image and data analysis • Noise models in high-throughput technologies • Integration of heterogeneous data

Editor-in-Chief Ioan Tabus, Room TF414 (Tietotalo), Institute of Signal Processing Tampere University of Techology, Korkeakoulunkatu 1, P.O. Box 553, FIN-33101, Tampere, Finland EURASIP JOURNALS

EURASIP JOURNAL ON EMBEDDED SYSTEMS

Scope “EURASIP Journal on Embedded Systems” is an international journal that serves the large community of researchers and professional engineers who deal with the theory and practice of embedded systems, particularly encompassing all practical aspects of theory and methods used in designing homogeneous as well as heterogeneous embedded systems that combine data-driven and control-driven behaviors. There are two diﬀerent issues: regular issues and special issues. The regular issues publish collections of papers without special solicitation. The special issues have speciﬁcally aimed and targeted topics of interest contributed by authors responding to a particular Call-for- Papers or by invitation, edited by invited guest editor(s). Regular papers can submitted at any time, while special issue papers can be submitted only based on planned schedules and submission guidelines of the Call-for-Papers. Proposals for special issues can be submitted directly to Editor-in-Chief.

Subjects Original full and short papers, correspondence and reviews on design and development of embedded systems, methodologies applied for their specification, modeling and design, and adaptation of algorithms for real-time execution are encouraged for submission. The coverage includes complex homogeneous and heterogeneous embedded systems, specification languages and tools for embedded systems, modeling and verification techniques, hardware/software trade-offs and co-design, new design flows, design methodologies and synthesis methods, platform-based design, component-based design, adaptation of signal processing algorithms to limited implementation resources, rapid prototyping, computing structures and architectures for complex embedded systems, real-time operating systems, methods and techniques for the design of low-power systems, interfacing with the real world, novel application case studies and experiences, and does not exclude other interesting related and emerging topics like software defined radio. Example applications include wireless and data communication systems, speech processing, image and video-processing, digital signal processing applications as well as control and instrumentation.

Editor-in-Chief Zoran Salcic, University of Auckland, Department of Electrical and Computer Engineering, Science Centre (Building 303, level 2, room 242), Private Bag 92019, 38 Princess Street, Auckland, New Zealand EURASIP JOURNALS

EURASIP JOURNAL ON WIRELESS COMMUNICATIONS AND NETWORKING

Scope The overall aim of EURASIP Journal on Wireless Communications and Networking (EURASIP JWCN) is to bring science and applications together on wireless communications and networking technologies with emphasis on signal processing techniques and tools. It is directed at both practicing engineers and academic researchers. EURASIP JWCN high- lights the continued growth and new challenges in wireless technology, both for application development and basic research. Papers should emphasize original results relating to the theory and/or applications of wireless communications and networking. Tutorial papers, especially those emphasizing multidisciplinary views of communications and networking, are also welcomed. EURASIP JWCN employs a paperless, electronic submission and evaluation system to promote a rapid turnaround in the peer review process. The journal publishes two types of issues: regular issues and special issues. Regular issues publish collections of papers without special solicitation. The special issues feature speciﬁ- cally aimed and targeted topics of interest contributed by authors responding to a particular Call-for-Papers or by invitation, edited by invited guest editor(s). Regular papers can be submitted at any time, while special issue papers can be submitted only based on planned schedules and submission guidelines of the Call-for-Papers. Proposals for special issues can be submitted directly to the Editor-in-Chief.

Subjects Subject areas include, but are by no means limited to: Ad hoc networks; Channel modeling and propagation; Detection, estimation, and synchronization; Diversity and space- time techniques; End-to-end design techniques; Error control coding; Iterative techniques for joint optimization; Modulation techniques (CDMA, OFDM, multicarrier, spread- spectrum, etc.); Multiuser, MIMO channels, and multiple access schemes; Network performance, reliability, and quality of service; Resource allocation over wireless networks; Security, authentication, and cryptography; Signal processing techniques and tools; Ultra wideband systems; Wireless network services and medium access control.

Editor-in-Chief Phillip Regalia, Institut National des Tel´ ecommunications,´ 9 rue Charles Fourier, F-91011 Evry Cedex, France EURASIP JOURNALS

SIGNAL PROCESSING

Editorial Policy Signal Processing is an interdisciplinary journal presenting the theory and practice of signal processing. Its primary objectives are the following: • dissemination of research results and of engineering developments to all signal processing groups and individuals; • presentation of practical solutions to current signal processing problems in engineering and science. The editorial policy and the technical content of the journal are the responsibility of the Editor-in-Chief and the Editorial Board. The journal is self-supporting from the subscription income and contains a minimum amount of advertisements. Advertisements are subject to the prior approval of the Editor-in-Chief. The journal welcomes contributions from every country in the world.

Scope Signal Processing incorporates all aspects of the theory and practice of signal processing (analogue and digital). It features original research work, tutorial and review articles, and accounts of practical developments. It is intended for a rapid dissemination of knowledge and experience to engineers and scientists working on signal processing research, development, or practical application.

Subjects Subject areas covered by the journal include: Signal Theory; Stochastic Processes; Detection and Estimation; Spectral Analysis; Filtering; Communication Signal Processing; Biomedical Signal Processing; Geophysical and Astrophysical Signal Processing; Earth Resources Signal Processing; Acoustic and Vibration Signal Processing; Signal Processing Systems; Software Developments; Image Processing; Pattern Recognition; Optical Signal Processing; Multidi- mensional Signal Processing; Data Processing; Remote Sensing; Signal Processing Technol- ogy; Speech Processing; Radar Signal Processing; Sonar Signal Processing; Special Signal Processing; Industrial Applications; New Applications.

Editor-in-Chief B. Ottersten, Royal Institute of Technology, Stockholm, Sweden EURASIP JOURNALS

SIGNAL PROCESSING: IMAGE COMMUNICATION

Editorial Policy Signal Processing: Image Communication is an international journal for the development of the theory and practice of image communication. Its primary objectives are the following: • to present a forum for the advancement of the theory and practice of image communication; • to simulate cross fertilization between areas similar in nature which have traditionally been separated, for example, various aspects of visual communications and information systems; • to contribute to a rapid information exchange between the industrial and academic environments. The editorial policy and the technical content of the journal are the responsibility of the Editor-in-Chief and the Editorial Board. The journal is self-supporting from the subscription income and contains a minimum amount of advertisements. Advertisements are subject to the prior approval of the Editor-in-Chief. The journal welcomes contributions from every country in the world.

Scope Signal Processing: Image Communication publishes articles relating to aspects of design, implementation, and use of image communication systems. Signal Processing: Image Com- munication features original research work, tutorial and review articles, and accounts of practical developments.

Subjects Subject areas covered by the journal include: TV, HDTV, and 3DTV systems; Visual Sci- ence; Image; TV and Advanced TV; Broadcasting; Image Storage and Retrieval; Graphic Arts; Electronic Printing; Image Transmission; Interactive Image Coding Communication; Imaging Technology; Display Technology; VLSI Processors for Image Communications.

Editor-in-Chief M. Tekalp, Koc¸ University, College of Engineering, Rumelifeneri Yolu, 34450 Sariyer, Istan- bul, Turkey EURASIP JOURNALS

SPEECH COMMUNICATION

Editorial Policy The journal’s primary objectives are the following: • to present a forum for the advancement of human and human-machine speech communication science; • to stimulate cross fertilization between different fields of this domain; • to contribute towards the rapid and wide diffusion of scientifically sound contributions in this domain. Speech Communication is an interdisciplinary journal whose primary objective is to fulfill the need for the rapid dissemination and thorough discussion of basic and applied research results. In order to establish frameworks of inter-relate results from the various areas of the field, emphasis will be placed on viewpoints and topics of a transdisciplinary nature. The editorial policy and the technical content of the journal are the responsibility of the Editors and the Institutional Representatives. The Institutional Representatives assist the Editors in the definition and the control of editorial policy as well as in maintaining connections with scientific associations, international congresses, and regional events. The Editorial Board contributes towards the gathering of material for publication and assists the Editors in the editorial process.

Scope Speech Communication is an interdisciplinary journal for the development and dissemination of all basic and applied aspects of speech communication processes. Speech Com- munication features original research work, tutorial and review articles dealing with the theoretical, empirical, and practical aspects of this scientiﬁc ﬁeld.

Subject Coverage Subject areas covered in this journal include: • Basics of oral communication and dialogue: modelling of production and perception processes; phonetics and phonology; syntax; semantics of speech communication; cognitive aspects. • Models and tools for language learning: functional organisation and developmen- tal models of human language capabilities; acquisition and rehabilitation of spoken language; speech and hearing defects and aids. • Speech signal processing: analysis; coding; transmission; enhancement, robustness to noise. • Models for automatic speech communication: speech recognition; language identiﬁ- cation; speaker recognition; speech synthesis; oral dialogue. Speech Communication 53

• Development and evaluation tools: monolingual and multilingual databases; assessment methodologies; specialised hardware and software packages; ﬁeld experiments; market development. • Multimodal human-computer interface: using speech I/O in combination with modalities, for example, gesture and handwriting.

Editors-in-Chief J.-L. Gauvain, Universite´ Paris-Sud, LIMSI-CNRS, Orsay Cedex, France J. Hirschberg, Columbia University, Department of Computer Science, 1214 Amsterdam Ave., M/C 0401, 450 CS Building, New York, NY 10027, USA K. Paliwal, Griﬃth University, School of Microelectronic Engineering, Brisbane, QLD 4111, Australia EURASIP JOURNAL ON EMBEDDED SYSTEMS

Special Issue on Embedded Digital Signal Processing Systems

CALL FOR PAPERS With continuing progress in VLSI and ASIC technologies, digital signal processing (DSP) algorithms have continued to find great use in increasingly wide application areas. DSP has gained popularity also in embedded systems although these systems set challenging constraints for implementations. Embedded systems contain limited resources, thus embedded DSP systems must balance trade-offs between the requirements on computational power and computational resources. Energy efficiency has been important in battery-powered devices but nowadays also the limited heat dissipation in small devices calls for low-power consumption. Successful implementation of DSP applications in embedded systems requires tailoring, which in turn sets challenges for design methodologies. This special issue aims to present state-of-the-art embedded DSP systems. Contribu- tions in design methodologies, energy-efficient realizations, advances in computation, and real-world applications are strongly encouraged. Topics of interest include (but are not limited to): • Design methodologies and tools for DSP • Hardware/software codesign • Hardware/software interfaces • Models of computation • Integration of control and dataflow • Real-time scheduling • DSP implementations • Parallel systems • Multiprocessor systems • Low-power systems • Programmable processors for DSP • Application-specific instruction-set processors • Domain-specific processors • Compiler technology and software synthesis • Novel applications Authors should follow the EURASIP JES manuscript format described at the journal site http://www.hindawi.com/journals/es/. Prospective authors should submit an electronic copy of their complete manuscript through the EURASIP JES manuscript tracking system at http://www.mstracking.com/mts, according to the following timetable:

Manuscript Due July 1, 2006 Acceptance Notiﬁcation November 1, 2006 Final Manuscript Due February 1, 2007 Publication Date 2nd Quarter, 2007

GUEST EDITORS: Jarmo Takala, Tampere University of Technology, P.O. Box 553, 33101 Tampere, Finland; jarmo.takala@tut.ﬁ Shuvra Bhattacharyya, University of Maryland, College Park, MD 20742, USA 076, India; [email protected] Gang Qu, University of Maryland, College Park, MD 20742, USA; [email protected]

http://www.hindawi.com EURASIP JOURNAL ON EMBEDDED SYSTEMS

Special Issue on Embedded Systems for Intelligent Vehicles

CALL FOR PAPERS The transport sector is seeking new technology to improve safety, driver comfort, and efficient use of infrastructures. Computer vision, range sensors, adaptive control, and networking, among the others, target problems like traffic flow control, pedestrian protection, lane-departure monitoring, smart parking facilities, and driver assistance in general. Em- bedded systems are sought after to implement technologically advanced solutions in smart vehicles. The automotive industry addresses mass markets in which embedded systems have a dramatic impact on the final consumer market price. From the point of view of academic research, intelligent vehicles represent a complete and sufficiently complex benchmark for integrating sensors, actuators, and control to test prototypes of autonomous systems. Ad- ditionally, intelligent vehicles are a challenging environment with a direct applicative aspect for research on autonomous systems, intended as systems reacting in a closed loop with the environment. Topics of interest include smart sensors, sensor fusion, embedded vehicle controls, autonomous vehicles, centralized and local traffic control, GSM and ad hoc networking, Blue- tooth and IEEE 802.15.4 technologies, driver-computer interface, signal processing for embedded environments, autonomous components, and intelligent control. This special issue focuses on new results of research work in the field of embedded systems for intelligent vehicles. Several main keywords are: • Intelligent vehicles • Autonomous vehicles • Embeddedsystemsversusautonomoussystems • Computer vision in embedded systems • Laser/radar range sensors • Multiple sensor embedded architectures • Sensor networks for automotive applications • Vehicle networking • Obstacle detection and tracking • GPS-based navigation • Design methodologies • FPGA for embedded systems with application to intelligent vehicles Authors should follow the EURASIP JES manuscript format described at the journal site http://www.hindawi.com/journals/es/. Prospective authors should submit an electronic copy of their complete manuscript through the EURASIP JES manuscript tracking system at http://www.hindawi.com/mts/, according to the following timetable:

Manuscript Due October 15, 2006 Acceptance Notiﬁcation February 15, 2007 Final Manuscript Due May 15, 2007 Publication Date 3rd Quarter, 2007

GUEST EDITORS: Samir Bouaziz, Institut d’Electronique Fondamentale, Universite´ Paris-Sud XI, Bat.ˆ 220, 91405 Orsay Cedex, France; [email protected] Paolo Lombardi, Institute for the Protection and Security of the Citizen, European Commission Joint Research Centre, TP210, Via Fermi1, 21020 Ispra, Italy; [email protected] Roger Reynaud, Institut d’Electronique Fondamentale, Universite´ Paris-Sud XI, Bat.ˆ 220, 91405 Orsay Cedex, France; [email protected] Gunasekaran S. Seetharaman, Department of Electrical and Computer Engineering, Air Force Institute of Technology, Dayton, OH, 45433, USA; [email protected]

Volume 2006 Contents and Abstracts

Computationally Efficient Direction-of-Arrival Estimation Based on Partial A Priori Knowledge of Signal Sources Lei Huang, Shunjun Wu, Dazheng Feng, and Linrang Zhang DOI: 10.1155/ASP/2006/19514 A computationally efficient method is proposed for estimating the directions-of-arrival (DOAs) of signals impinging on a uniform linear array (ULA), based on partial a priori knowledge of signal sources. Unlike the classical MUSIC algorithm, the proposed method merely needs the forward recursion of the multistage Wiener filter (MSWF) to find the noise subspace and does not involve an estimate of the array covariance matrix as well as its eigendecomposition. Thereby, the proposed method is computationally efficient. Numerical results are given to illustrate the performance of the proposed method.

Information Theory for Gabor Feature Selection for Face Recognition Linlin Shen and Li Bai DOI: 10.1155/ASP/2006/30274 A discriminative and robust feature–kernel enhanced informative Gabor feature–is proposed in this paper for face recognition. Mutual information is applied to select a set of informative and nonredundant Gabor features, which are then further enhanced by kernel methods for recognition. Compared with one of the top performing methods in the 2004 Face Verification Competition (FVC2004), our methods demonstrate a clear advantage over existing methods in accuracy, computation efficiency, and memory cost. The proposed method has been fully tested on the FERET database using the FERET evaluation protocol. Significant improvements on three of the test data sets are observed. Compared with the classical Gabor wavelet-based approaches using a huge number of features, our method requires less than 4 milliseconds to re- trieve a few hundreds of features. Due to the substantially reduced feature dimension, only 4 seconds are required to recognize 200 face images. The paper also unified different Gabor filter definitions and proposed a training sample generation algorithm to reduce the effects caused by unbalanced number of samples available in different classes. Regular Issue, Vol. 2006 59

Arrhythmic Pulses Detection Using Lempel-Ziv Complexity Analysis Lisheng Xu, David Zhang, Kuanquan Wang, and Lu Wang DOI: 10.1155/ASP/2006/18268 Computerized pulse analysis based on traditional Chinese medicine (TCM) is relatively new in the field of automatic physiological signal analysis and diagnosis. Considerable re- searches have been done on the automatic classification of pulse patterns according to their features of position and shape, but because arrhythmic pulses are difficult to identify, until now none has been done to automatically identify pulses by their rhythms. This paper proposes a novel approach to the detection of arrhythmic pulses using the Lempel-Ziv complexity analysis. Four parameters, one lemma, and two rules, which are the results of heuristic approach, are presented. This approach is applied on 140 clinic pulses for detecting seven pulse patterns, not only achieving a recognition accuracy of 97.1% as assessed by experts in TCM, but also correctly extracting the periodical unit of the intermittent pulse.

The Optimal Design of Weighted Order Statistics Filters by Using Support Vector Machines Chih-Chia Yao and Pao-Ta Yu DOI: 10.1155/ASP/2006/24185 Support vector machines (SVMs), a classification algorithm for the machine learning community, have been shown to provide higher performance than traditional learning machines. In this paper, the technique of SVMs is introduced into the design of weighted order statistics (WOS) filters. WOS filters are highly effective, in processing digital signals, because they have a simple window structure. However, due to threshold decomposition and stacking property, the development of WOS filters cannot significantly improve both the design complexity and estimation error. This paper proposes a new designing technique which can improve the learning speed and reduce the complexity of designing WOS filters. This technique uses a dichotomous approach to reduce the Boolean functions from 255 levels to two levels, which are separated by an optimal hyperplane. Furthermore, the optimal hyperplane is gotten by using the technique of SVMs. Our proposed method approx- imates the optimal weighted order statistics filters more rapidly than the adaptive neural filters.

Concept of Complex-Valued Parametric Open Access Pulse Models Klaus Pourvoyeur, Andreas Stelzer, and Gerald Oßberger DOI: 10.1155/ASP/2006/74145 In pulse-based radar systems, the knowledge of certain parameters of the received radar pulse is of great importance. We introduce a complex-valued parametric pulse model by 60 Regular Issue, Vol. 2006 extending a real-valued pulse signal into the complex plane. A modulation angle parameter unique to the complex representation gives an additional degree of freedom and can be used to model the basic shape of the pulse, thus lifting the conventional restriction to ﬁxed pulse shapes in real-valued correlation techniques. As physical signals are real valued, the imaginary part of the complex signal is calculated by using the Hilbert transformation. Parameter estimation is based on the complex-valued continuous wavelet transform. The main advantages of this concept are demonstrated on synthetic data and veriﬁed on ultra- wideband pulse radar measurements.

An Automated Acoustic System to Monitor and Open Access Classify Birds C.Kwan,K.C.Ho,G.Mei,Y.Li,Z.Ren,R.Xu,Y.Zhang,D.Lao, M. Stevenson, V. Stanford, and C. Rochet DOI: 10.1155/ASP/2006/96706 This paper presents a novel bird monitoring and recognition system in noisy environments. The project objective is to avoid bird strikes to aircraft. First, a cost-effective microphone dish concept (microphone array with many concentric rings) is presented that can provide directional and accurate acquisition of bird sounds and can simultaneously pick up bird sounds from different directions. Second, direction-of-arrival (DOA) and beamforming algorithms have been developed for the circular array. Third, an efficient recognition algorithm is proposed which uses Gaussian mixture models (GMMs). The overall system is suitable for monitoring and recognition for a large number of birds. Fourth, a hardware prototype has been built and initial experiments demonstrated that the array can acquire and classify birds accurately.

Differential Space-Time Coding Scheme Using Star Quadrature Amplitude Modulation Method Xiangbin Yu, DaZhuan Xu, and Guangguo Bi DOI: 10.1155/ASP/2006/89849 Differential space-time coding (DSTC) has received much interest as it obviates the requirement of the channel state information at the receiver while maintaining the desired properties of space-time coding techniques. In this paper, by introducing star quadrature amplitude modulation (star QAM) method, two kinds of multiple amplitudes DSTC schemes are proposed. One is based on differential unitary space-time coding (DUSTC) scheme, and the other is based on differential orthogonal space-time coding (DOSTC) scheme. Corresponding bit-error-rate (BER) performance and coding-gain analysis are given, respectively. The proposed schemes can avoid the performance loss of conventional DSTC schemes based on phase-shift keying (PSK) modulation in high spectrum efficiency via multiple amplitudes modulation. Compared with conventional PSK-based DSTC schemes, the developed schemes have higher spectrum efficiency via carrying information not only on phases but also on amplitudes, and have higher coding gain. Moreover, the first scheme can implement low-complexity differential modulation and different code rates and be Regular Issue, Vol. 2006 61 applied to any number of transmit antennas; while the second scheme has simple decoder and high code rate in the case of 3 and 4 antennas. The simulation results show that our schemes have lower BER when compared with conventional DUSTC and DOSTC schemes.

Efficient Implementation of Complex Modulated Filter Banks Using Cosine and Sine Modulated Open Access Filter Banks Ari Viholainen, Juuso Alhava, and Markku Renfors DOI: 10.1155/ASP/2006/58564 The recently introduced exponentially modulated filter bank (EMFB) is a 2M-channel uniform, orthogonal, critically sampled, and frequency-selective complex modulated filter bank that satisfies the perfect reconstruction (PR) property if the prototype filter of an M-channel PR cosine modulated filter bank (CMFB) is used. The purpose of this paper is to present various implementation structures for the EMFBs in a unified framework. The key idea is to use cosine and sine modulated filter banks as building blocks and, therefore, polyphase, lattice, and extended lapped transform (ELT) type of implementation solutions are studied. The ELT-based EMFBs are observed to be very competitive with the existing modified discrete Fourier transform filter banks (MDFT-FBs) when comparing the number of multiplications/additions and the structural simplicity. In addition, EMFB provides an alternative channel stacking arrangement that could be more natural in certain subband processing applications and data transmission systems.

Nonmyopic Sensor Scheduling and its Efficient Implementation for Target Tracking Applications Amit S. Chhetri, Darryl Morrell, and Antonia Papandreou-Suppappola DOI: 10.1155/ASP/2006/31520 We propose two nonmyopic sensor scheduling algorithms for target tracking applications. We consider a scenario where a bearing-only sensor is constrained to move in a finite number of directions to track a target in a two-dimensional plane. Both algorithms provide the best sensor sequence by minimizing a predicted expected scheduler cost over a finite time-horizon. The first algorithm approximately computes the scheduler costs based on the predicted covariance matrix of the tracker error. The second algorithm uses the unscented transform in conjunction with a particle filter to approximate covariance-based costs or information-theoretic costs. We also propose the use of two branch-and-bound-based optimal pruning algorithms for efficient implementation of the scheduling algorithms. We design the first pruning algorithm by combining branch-and-bound with a breadth-first search and a greedy-search; the second pruning algorithm combines branch-and-bound with a uniform-cost search. Simulation results demonstrate the advantage of nonmyopic scheduling over myopic scheduling and the significant savings in computational and memory resources when using the pruning algorithms. 62 Regular Issue, Vol. 2006

A Posterior Union Model with Applications to Robust Speech and Speaker Recognition Ji Ming, Jie Lin, and F. Jack Smith DOI: 10.1155/ASP/2006/75390 This paper investigates speech and speaker recognition involving partial feature corruption, assuming unknown, time-varying noise characteristics. The probabilistic union model is extended from a conditional-probability formulation to a posterior-probability formulation as an improved solution to the problem. The new formulation allows the order of the model to be optimized for every single frame, thereby enhancing the capability of the model for dealing with nonstationary noise corruption. The new formulation also allows the model to be readily incorporated into a Gaussian mixture model (GMM) for speaker recognition. Experiments have been conducted on two databases: TIDIGITS and SPIDRE, for speech recognition and speaker identiﬁcation. Both databases are subject to unknown, time-varying band-selective corruption. The results have demonstrated the improved robustness for the new model.

Speech/Non-Speech Segmentation Based on Open Access Phoneme Recognition Features

Janez Zibert,ˇ Nikola Pavesiˇ c,´ and France Mihelicˇ DOI: 10.1155/ASP/2006/90495 This work assesses different approaches for speech and non-speech segmentation of audio data and proposes a new, high-level representation of audio signals based on phoneme recognition features suitable for speech/non-speech discrimination tasks. Unlike previous model-based approaches, where speech and non-speech classes were usually modeled by several models, we develop a representation where just one model per class is used in the segmentation process. For this purpose, four measures based on consonant- vowel pairs obtained from different phoneme speech recognizers are introduced and applied in two different segmentation-classification frameworks. The segmentation systems were evaluated on different broadcast news databases. The evaluation results indicate that the proposed phoneme recognition features are better than the standard mel- frequency cepstral coefficients and posterior probability-based features (entropy and dy- namism). The proposed features proved to be more robust and less sensitive to different training and unforeseen conditions. Additional experiments with fusion models based on cepstral and the proposed phoneme recognition features produced the highest scores overall, which indicates that the most suitable method for speech/non-speech segmentation is a combination of low-level acoustic features and high-level recognition features. Regular Issue, Vol. 2006 63

A Systematic Approach to Modiﬁed BCJR MAP Open Access Algorithms for Convolutional Codes

Sichun Wang and François Patenaude DOI: 10.1155/ASP/2006/95360 Since Berrou, Glavieux and Thitimajshima published their landmark paper in 1993, different modified BCJR MAP algorithms have appeared in the literature. The existence of a relatively large number of similar but different modified BCJR MAP algorithms, derived using the Markov chain properties of convolutional codes, naturally leads to the following questions. What is the relationship among the different modified BCJR MAP algorithms? What are their relative performance, computational complexities, and memory requirements? In this paper, we answer these questions. We derive systematically four major modified BCJR MAP algorithms from the BCJR MAP algorithm using simple mathematical transformations. The connections between the original and the four modified BCJR MAP algorithms are established. A detailed analysis of the different modified BCJR MAP algorithms shows that they have identical computational complexities and memory requirements. Computer simulations demonstrate that the four modified BCJR MAP algorithms all have identical performance to the BCJR MAP algorithm.

Subband-Adaptive Shrinkage for Denoising of ECG Signals S. Poornachandra and N. Kumaravel DOI: 10.1155/ASP/2006/81236 This paper describes subband dependent adaptive shrinkage function that generalizes hard and soft shrinkages proposed by Donoho and Johnstone (1994). The proposed new class of shrinkage function has continuous derivative, which has been simulated and tested with normal and abnormal ECG signals with added standard Gaussian noise using MATLAB. The recovered signal is visually pleasant compared with other existing shrinkage functions. The implication of the proposed shrinkage function in denoising and data compression is discussed.

Efficient and Secure Fingerprint Verification for Open Access Embedded Devices Shenglin Yang, Kazuo Sakiyama, and Ingrid Verbauwhede DOI: 10.1155/ASP/2006/58263 This paper describes a secure and memory-efficient embedded fingerprint verification system. It shows how a fingerprint verification module originally developed to run on a work- station can be transformed and optimized in a systematic way to run real-time on an embedded device with limited memory and computation power. A complete fingerprint recognition module is a complex application that requires in the order of 1000 M unop- timized floating-point instruction cycles. The goal is to run both the minutiae extraction 64 Regular Issue, Vol. 2006 and the matching engines on a small embedded processor, in our case a 50 MHz LEON-2 softcore. It does require optimization and acceleration techniques at each design step. In order to speed up the fingerprint signal processing phase, we propose acceleration techniques at the algorithm level, at the software level to reduce the execution cycle number, and at the hardware level to distribute the system work load. Thirdly, a memory trace map- based memory reduction strategy is used for lowering the system memory requirement. Lastly, at the hardware level, it requires the development of specialized coprocessors. As results of these optimizations, we achieve a 65% reduction on the execution time and a 67% reduction on the memory storage requirement for the minutiae extraction process, compared against the reference implementation. The complete operation, that is, fingerprint capture, feature extraction, and matching, can be done in real-time of less than 4 seconds.

A Systematic Approach to Modiﬁed BCJR MAP Algorithms for Convolutional Codes C. Kwan, B. Li, R. Xu, X. Li, T. Tran, and T. Nguyen DOI: 10.1155/ASP/2006/10968 A complete system was built for high-performance image compression based on overlapped block transform. Extensive simulations and comparative studies were carried out for still image compression including benchmark images (Lena and Barbara), synthetic aperture radar (SAR) images, and color images. We have achieved consistently better results than three commercial products in the market (a Summus wavelet codec, a baseline JPEG codec, and a JPEG-2000 codec) for most images that we used in this study. Included in the system are two post-processing techniques based on morphological and median ﬁlters for enhancing the perceptual quality of the reconstructed images. The proposed system also supports the enhancement of a small region of interest within an image, which is of interest in various applications such as target recognition and medical diagnosis.

From Matched Spatial Filtering towards the Fused Statistical Descriptive Regularization Method for Enhanced Radar Imaging Yuriy Shkvarko DOI: 10.1155/ASP/2006/39657 We address a new approach to solve the ill-posed nonlinear inverse problem of high- resolution numerical reconstruction of the spatial spectrum pattern (SSP) of the backscattered wavefield sources distributed over the remotely sensed scene. An array or synthesized array radar (SAR) that employs digital data signal processing is considered. By exploiting the idea of combining the statistical minimum risk estimation paradigm with numerical descriptive regularization techniques, we address a new fused statistical descriptive regularization (SDR) strategy for enhanced radar imaging. Pursuing such an approach, we establish a family of the SDR-related SSP estimators, that encompass a manifold of existing beamforming techniques ranging from traditional matched filter to robust and adaptive spatial filtering, and minimum variance methods. Regular Issue, Vol. 2006 65

FPGA Prototyping of RNN Decoder for Convolutional Codes Zoran Salcic, Stevan Berber, and Paul Secker DOI: 10.1155/ASP/2006/15640 This paper presents prototyping of a recurrent type neural network (RNN) convolutional decoder using system-level design specification and design flow that enables easy mapping to the target FPGA architecture. Implementation and the performance measurement results have shown that an RNN decoder for hard-decision decoding coupled with a simple hard-limiting neuron activation function results in a very low complexity, which easily fits into standard Altera FPGA. Moreover, the design methodology allowed modeling of complete testbed for prototyping RNN decoders in simulation and real-time environment (same FPGA), thus enabling evaluation of BER performance characteristics of the decoder for various conditions of communication channel in real time.

A Human Body Analysis System Vincent Girondel, Laurent Bonnaud, and Alice Caplier DOI: 10.1155/ASP/2006/61927 This paper describes a system for human body analysis (segmentation, tracking, face/hands localisation, posture recognition) from a single view that is fast and completely automatic. The system first extracts low-level data and uses part of the data for high-level interpretation. It can detect and track several persons even if they merge or are completely occluded by another person from the camera’s point of view. For the high-level interpretation step, static posture recognition is performed using a belief theory-based classifier. The belief theory is considered here as a new approach for performing posture recognition and classification using imprecise and/or conflicting data. Four different static postures are considered: standing, sitting, squatting, and lying. The aim of this paper is to give a global view and an evaluation of the performances of the entire system and to describe in detail each of its processing steps, whereas our previous publications focused on a single part of the system. The efficiency and the limits of the system have been highlighted on a database of more than fifty video sequences where a dozen different individuals appear. This system allows real- time processing and aims at monitoring elderly people in video surveillance applications or at the mixing of real and virtual worlds in ambient intelligence systems.

An FIR Notch Filter for Adaptive Filtering of a Sinusoid in Correlated Noise Osman Kukrer and Aykut Hocanin DOI: 10.1155/ASP/2006/38190 A novel adaptive FIR filter for the estimation of a single-tone sinusoid corrupted by additive noise is described. The filter is based on an offline optimization procedure which, for a given notch frequency, computes the filter coefficients such that the frequency response is unity at that frequency and a weighted noise gain is minimized. A set of such coefficients is obtained for notch frequencies chosen at regular intervals in a given range. The filter coefficients corresponding to any frequency in the range are computed using an interpolation scheme. 66 Regular Issue, Vol. 2006

An adaptation algorithm is developed so that the filter tracks the sinusoid of unknown frequency. The algorithm first estimates the frequency of the sinusoid and then updates the filter coefficients using this estimate. An application of the algorithm to beamforming is included for angle-of-arrival estimation. Simulation results are presented for a sinusoid in correlated noise, and compared with those for the adaptive IIR notch filter.

Efficient Realization of Sigma-Delta (Σ-Δ) Kalman Lowpass Filter in Hardware Using FPGA Saman S. Abeysekera and Charayaphan Charoensak DOI: 10.1155/ASP/2006/52736 Sigma-delta (Σ-Δ) modulation techniques have moved into mainstream applications in signal processing and have found many practical uses in areas such as high-resolution A/D, D/A conversions, voice communication, and software radio. Σ-Δ modulators produce a single, or few bits output resulting in hardware saving and thus making them suitable for implementation in very large scale integration (VLSI) circuits. To reduce quantization noise produced, higher-order modulators such as multiloop and multistage architectures are commonly used. The quantization noise behavior of higher-order Σ-Δ modulators is well understood. Based on these quantization noise characteristics, various demodulator architectures, such as sinc filter, optimal FIR filter, and Laguerre filter are reported in literature. In this paper, theory and design of an efficient Kalman recursive demodulator filter is shown. Hardware implementation of Kalman lowpass filter, using field programmable gate array (FPGA), is explained. The FPGA synthesis results from Kalman filter design are compared with previous designs for sinc filter, optimum FIR filter, and Laguerre filter.

An Exact FFT Recovery Theory: A Nonsubtractive Dither Quantization Approach with Applications L. Cheded and S. Akhtar DOI: 10.1155/ASP/2006/34838 Fourier transform is undoubtedly one of the cornerstones of digital signal processing (DSP). The introduction of the now famous FFT algorithm has not only breathed a new lease of life into an otherwise latent classical DFT algorithm, but also led to an explosion in applications that have now far transcended the confines of the DSP field. For a good accuracy, the digital implementation of the FFT requires that the input and/or the 2 basis functions be finely quantized. This paper exploits the use of coarse quantization of the FFT signals with a view to further improving the FFT computational efficiency while preserving its computational accuracy and simplifying its architecture. In order to resolve this apparent conflict between preserving an excellent computational accuracy while using a quantization scheme as coarse as can be desired, this paper advances new theoretical results which form the basis for two new and practically attractive FFT estimators that rely on the principle of 1 bit nonsubtractive dithered quantization (NSDQ). The proposed theory is very well substantiated by the extensive simulation work carried out in both noise-free and noisy environments. This makes the prospect of implementing the 2 proposed 1 bit FFT estimators on a chip both practically attractive and rewarding and certainly worthy of a further pursuit. Regular Issue, Vol. 2006 67

Shape-from-Shading for Oblique Lighting with Accuracy Enhancement by Light Direction Optimization Osamu Ikeda DOI: 10.1155/ASP/2006/92456 We present a shape-from-shading approach for oblique lighting with accuracy enhancement by light direction optimization. Based on an application of the Jacobi iterative method to the consistency between the reflectance map and image, four surface normal approximations are introduced and the resulting four iterative relations are combined as constraints to get an iterative relation. The matrix that converts the shading information to the depth is modified so as to be uniform over the whole image region, making the iteration stable and, as a result, the resulting shape more accurate. Then, to enhance the accuracy, the light direction is optimized for slant angle using two criteria based on the initial boundary value and the rank of the converting matrix. The method is examined using synthetic and real images to show that it is superior to the current state-of-the-art methods and that it is effective for oblique light direction whose slant angle ranges from 55 to 75 degrees.

Time-Frequency Signal Synthesis and Its Application in Multimedia Watermark Detection Lam Le and Sridhar Krishnan DOI: 10.1155/ASP/2006/86712 We propose a novel approach to detect the watermark message embedded in images under the form of a linear frequency modulated chirp. Localization of several time-frequency distributions (TFDs) is studied for diﬀerent frequency modulated signals under various noise conditions. Smoothed pseudo-Wigner-Ville distribution (SPWVD) is chosen and applied to detect and recover the corrupted image watermark bits at the receiver. The synthesized watermark message is compared with the referenced one at the transmitter as a detection evaluation scheme. The correlation coeﬃcient between the synthesized and the referenced chirps reaches 0.9oraboveforamaximumbiterrorrateof15%underintentionaland nonintentional attacks. The method provides satisfactory result for detection of image watermark messages modulated as chirp signal and could be a potential tool in multimedia security applications.

Performance Analysis of the Blind Minimum Output Variance Estimator for Carrier Frequency Offset in OFDM Systems Feng Yang, Kwok H. Li, and Kah C. Teh DOI: 10.1155/ASP/2006/49257 Carrier frequency offset (CFO) is a serious drawback in orthogonal frequency division multiplexing (OFDM) systems. It must be estimated and compensated before demodu- lation to guarantee the system performance. In this paper, we examine the performance 68 Regular Issue, Vol. 2006 of a blind minimum output variance (MOV) estimator. Based on the derived probability density function (PDF) of the output magnitude, its mean and variance are obtained and it is observed that the variance reaches the minimum when there is no frequency offset. This observation motivates the development of the proposed MOV estimator. The theoretical mean-square error (MSE) of the MOV estimator over an AWGN channel is obtained. The analytical results are in good agreement with the simulation results. The performance evaluation of the MOV estimator is extended to a frequency-selective fading channel and the maximal-ratio combining (MRC) technique is applied to enhance the MOV estimator’s performance. Simulation results show that the MRC technique significantly improves the accuracy of the MOV estimator.

Contour Estimation by Array Processing Methods Salah Bourennane and Julien Marot DOI: 10.1155/ASP/2006/95634 This work is devoted to the estimation of rectilinear and distorted contours in images by high-resolution methods. In the case of rectilinear contours, it has been shown that it is possible to transpose this image processing problem to an array processing problem. The existing straight line characterization method called subspace-based line detection (SLIDE) leads to models with orientations and offsets of straight lines as the desired parameters. Firstly, a high-resolution method of array processing leads to the orientation of the lines. Secondly, their offset can be estimated by either the well-known method of extension of the Hough transform or another method, namely, the variable speed propagation scheme, that belongs to the array processing applications field. We associate it with the method called “modified forward-backward linear prediction” (MFBLP). The signal generation process devoted to straight lines retrieval is retained for the case of distorted contours estimation. This issue is handled for the first time thanks to an inverse problem formulation and a phase model determination. The proposed method is initialized by means of the SLIDE algorithm.

Global Motion Model for Stereovision-Based Motion Analysis Jia Wang, Zhencheng Hu, Keiichi Uchimura, and Hanqing Lu DOI: 10.1155/ASP/2006/53691 An advantage of stereovision-based motion analysis is that the depth information is available, thus motion can be estimated more precisely in 2.5D stereo coordinate system (SCS) constructed by the depth and the image coordinates. In this paper, stereo global motion in SCS, which is induced by 3D camera motion in real-world coordinate system (WCS), is parameterized by a five-parameter global motion model (GMM). Based on such model, global motion can be estimated and identified directly in SCS without knowing the physical parameters about camera motion and camera setup in WCS. The reconstructed global motion field accords with the spatial structure of the scene much better. Experiments on both synthetic data and real-world images illustrate its promising performance. Regular Issue, Vol. 2006 69

A Novel Efficient Cluster-Based MLSE Equalizer for Satellite Communication Channels with M-QAM Signaling Eleftherios Kofidis, Vassilis Dalakas, Yannis Kopsinis, and Sergios Theodoridis DOI: 10.1155/ASP/2006/34343 In satellites, nonlinear amplifiers used near saturation severely distort the transmitted signal and cause difficulties in its reception. Nevertheless, the nonlinearities introduced by memoryless bandpass amplifiers preserve the symmetries of the M-ary quadrature amplitude modulation (M-QAM) constellation. In this paper, a cluster-based sequence equalizer (CBSE) that takes advantage of these symmetries is presented. The proposed equalizer exhibits enhanced performance compared to other techniques, including the conventional linear transversal equalizer, Volterra equalizers, and RBF network equalizers. Moreover, this gain in performance is obtained at a substantially lower computational cost.

Generalized Sampling Theorem for Bandpass Signals Ales Prokes DOI: 10.1155/ASP/2006/59587 The reconstruction of an unknown continuously defined function f (t) from the samples of the responses of m linear time-invariant (LTI) systems sampled by the 1/mth Nyquist rate is the aim of the generalized sampling. Papoulis (1977) provided an elegant solution for the case where f (t) is a band-limited function with finite energy and the sampling rate is equal to 2/m times cutoff frequency. In this paper, the scope of the Papoulis theory is extended to the case of bandpass signals. In the first part, a generalized sampling theorem (GST) for bandpass signals is presented. The second part deals with utilizing this theorem for signal recovery from nonuniform samples, and an efficient way of computing images of reconstructing functions for signal recovery is discussed.

Analysis of Effort Constraint Algorithm in Active Noise Control Systems F. Taringoo, J. Poshtan, and M. H. Kahaei DOI: 10.1155/ASP/2006/54649 In ANC systems, in case of loudspeakers saturation, the adaptive algorithm may diverge due to nonlinearity. The most common algorithm used in ANC systems is the FXLMS which is especially used for feed-forward ANC systems. According to its mathematical representation, its cost function is conventionally chosen independent of control signal magnitude, and hence the control signal may increase unlimitedly. In this paper, a modiﬁed cost function is proposed that takes into account the control signal power. Choosing an appropriate weight can prevent the system from becoming nonlinear. A region for this weight is obtained and the mean weight behavior of the algorithm using this cost function is achieved. 70 Regular Issue, Vol. 2006

In addition to the previous paper results, the linear range for the effort coefficient variation is obtained. Simulation and experimental results follow for confirmation.

Source Depth Estimation Using a Horizontal Array by Matched-Mode Processing in the Frequency-Wavenumber Domain Barbara Nicolas, Jer´ omeˆ I. Mars, and Jean-Louis Lacoume DOI: 10.1155/ASP/2006/65901 In shallow water environments, matched-field processing (MFP) and matched-mode processing (MMP) are proven techniques for doing source localization. In these environments, the acoustic field propagates at long range as depth-dependent modes. Given a knowledge of the modes, it is possible to estimate source depth. In MMP, the pressure field is typically sampled over depth with a vertical line array (VLA) in order to extract the mode amplitudes. In this paper, we focus on horizontal line arrays (HLA) as they are generally more practical for at sea applications. Considering an impulsive low-frequency source (1– 100 Hz) in a shallow water environment (100–400 m), we propose an efficient method to estimate source depth by modal decomposition of the pressure field recorded on an HLA of sensors. Mode amplitudes are estimated using the frequency-wavenumber transform, which is the 2D Fourier transform of a time-distance section. We first study the robustness of the presented method against noise and against environmental mismatches on simulated data. Then, the method is applied both to at sea and laboratory data. We also show that the source depth estimation is drastically improved by incorporating the sign of the mode amplitudes.

A Secure Watermarking Scheme for Buyer-Seller Identification and Copyright Protection Fawad Ahmed, Farook Sattar, Mohammed Yakoob Siyal, and Dan Yu DOI: 10.1155/ASP/2006/56904 We propose a secure watermarking scheme that integrates watermarking with cryptography for addressing some important issues in copyright protection. We address three copyright protection issues—buyer-seller identification, copyright infringement, and ownership verification. By buyer-seller identification, we mean that a successful watermark extraction at the buyer’s end will reveal the identities of the buyer and seller of the watermarked image. For copyright infringement, our proposed scheme enables the seller to identify the specific buyer from whom an illegal copy of the watermarked image has originated, and further prove this fact to a third party. For multiple ownership claims, our scheme enables a legal seller to claim his/her ownership in the court of law. We will show that the combination of cryptography with watermarking not only increases the security of the overall scheme, but it also enables to associate identities of buyer/seller with their respective watermarked images. Regular Issue, Vol. 2006 71

On the Channel Capacity of Multiantenna Systems Open Access with Nakagami Fading

Feng Zheng and Thomas Kaiser DOI: 10.1155/ASP/2006/39436 We discuss the channel capacity of multiantenna systems with the Nakagami fading channel. Analytic expressions for the ergodic channel capacity or its lower bound are given for SISO, SIMO, and MISO cases. Formulae for the outage probability of the capacity are presented. It is shown that the channel capacity could be increased logarithmically with the number of receive antennas for SIMO case; while employing 3–5 transmit antennas (irrespective of all other parameters considered herein) can approach the best advantage of the multiple transmit antenna systems as far as channel capacity is concerned for MISO case. We have shown that for a given SNR, the outage probability decreases considerably with the number of receive antennas for SIMO case, while for MISO case, the upper bound of the outage probability decreases with the number of transmit antennas when the transmission rate is lower than some value, but increases instead when the transmission rate is higher than another value. A critical transmission rate is identiﬁed.

Partial Equalization of Non-Minimum-Phase Impulse Responses Ahfir Maamar, Izzet Kale, Artur Krukowski, and Berkani Daoud DOI: 10.1155/ASP/2006/67467 We propose a modified version of the standard homomorphic method to design a minimum-phase inverse filter for non-minimum-phase impulse responses equalization. In the proposed approach some of the dominant poles of the filter transfer function are replaced by new ones before carrying out the inverse DFT. This method is useful when partial magnitude equalization is intended. Results for an impulse response measured in the car interior show that by using the modified version we can control the sound quality more precisely than when using the standard method.

Fast Registration of Remotely Sensed Images for Earthquake Damage Estimation Arash Abadpour, Shohreh Kasaei, and S. Mohsen Amiri DOI: 10.1155/ASP/2006/76462 Analysis of the multispectral remotely sensed images of the areas destroyed by an earthquake is proved to be a helpful tool for destruction assessments. The performance of such methods is highly dependant on the preprocess that registers the two shots before and after an event. In this paper, we propose a new fast and reliable change detection method for remotely sensed images and analyze its performance. The experimental results show the eﬃciency of the proposed algorithm. 72 Regular Issue, Vol. 2006

High Efﬁciency EBCOT with Parallel Coding Open Access Architecture for JPEG2000 Jen-Shiun Chiang, Chun-Hau Chang, Chang-Yo Hsieh, and Chih-Hsien Hsia DOI: 10.1155/ASP/2006/42568 This work presents a parallel context-modeling coding architecture and a matching arithmetic coder (MQ-coder) for the embedded block coding (EBCOT) unit of the JPEG2000 encoder. Tier-1 of the EBCOT consumes most of the computation time in a JPEG2000 encoding system. The proposed parallel architecture can increase the throughput rate of the context modeling. To match the high throughput rate of the parallel context-modeling architecture, an eﬃcient pipelined architecture for context-based adaptive arithmetic encoder is proposed. This encoder of JPEG2000 can work at 180 MHz to encode one symbol each cycle. Compared with the previous context-modeling architectures, our parallel architectures can improve the throughput rate up to 25%.

Frequency and 2D Angle Estimation Based on a Sparse Uniform Array of Electromagnetic Vector Sensors Fei Ji and Sam Kwong DOI: 10.1155/ASP/2006/80720 We present an ESPRIT-based algorithm that yields extended-aperture two-dimensional (2D) arrival angle and carrier frequency estimates with a sparse uniform array of electromagnetic vector sensors. The ESPRIT-based frequency estimates are first achieved by using the temporal invariance structure out of the two time-delayed sets of data collected from vector sensor array. Each incident source’s coarse direction of arrival (DOA) estimation is then obtained through the Poynting vector estimates (using a vector cross-product estimator). The frequency and coarse angle estimate results are used jointly to disambiguate the cyclic phase ambiguities in ESPRIT’s eigenvalues when the intervector sensor spacing exceeds a half wavelength. Monte Carlo simulation results verified the effectiveness of the proposed method.

Erratum to “A New Class of Particle Filters for Random Dynamic Systems with Unknown Statistics” Joaqu´ın M´ıguez, Monica´ F. Bugallo, and Petar M. Djuric´ DOI: 10.1155/ASP/2006/78708 We have found an error in the proof of Lemma presented in our paper “A New Class of Particle Filters for Random Dynamic Systems with Unknown Statistics” (EURASIP Journal on Applied Signal Processing, 2004). In the sequel, we provide a restatement of the lemma and a corrected (and simpler) proof. We emphasize that the original result in the said paper still holds true. The only diﬀerence with the new statement is the relaxation of condition (3), which becomes less restrictive. Regular Issue, Vol. 2006 73

Aspects of Radar Imaging Using Frequency-Stepped Chirp Signals Qun Zhang and Ya-Qiu Jin DOI: 10.1155/ASP/2006/85823 The high-resolution, frequency-stepped chirp signal can be applied to radar systems employing narrow-bandwidth chirp pulses, in order to enhance the range resolution, and to implement SAR/ISAR imaging capabilities. This paper analyzes the effect of moving targets on the synthetic high-resolution range profile obtained using this signal waveform. Some constraints are presented for compensation of the radial motion from shift and amplitude depression of the synthetic range profile. By transmitting two chirp pulses with the same carrier frequency in a pulse-set, a method of ground clutter cancellation is designed with respect to this signal format. Finally, our simulation data demonstrate the effectiveness of the proposed method.

2D Four-Channel Perfect Reconstruction Filter Bank Realized with the 2D Lattice Filter Structure S. Sezen and A. Ertuz¨ un¨ DOI: 10.1155/ASP/2006/42672 A novel orthogonal 2D lattice structure is incorporated into the design of a nonseparable 2D four-channel perfect reconstruction filter bank. The proposed filter bank is obtained by using the polyphase decomposition technique which requires the design of an orthogonal 2D lattice filter. Due to constraint of perfect reconstruction, each stage of this lattice filter bank is simply parameterized by two coefficients. The perfect reconstruction property is satisfied regardless of the actual values of these parameters and of the number of the lattice stages. It is also shown that a separable 2D four-channel perfect reconstruction lattice filter bank can be constructed from the 1D lattice filter and that this is a special case of the proposed 2D lattice filter bank under certain conditions. The perfect reconstruction property of the proposed 2D lattice filter approach is verified by computer simulations.

Image Quality Assessment Using the Joint Spatial/Spatial-Frequency Representation Azeddine Beghdadi and Razvan˘ Iordache DOI: 10.1155/ASP/2006/80537 This paper demonstrates the usefulness of spatial/spatial-frequency representations in image quality assessment by introducing a new image dissimilarity measure based on 2D Wigner-Ville distribution (WVD). The properties of 2D WVD are shortly reviewed, and the important issue of choosing the analytic image is emphasized. The WVD-based measure is shown to be correlated with subjective human evaluation, which is the premise towards an image quality assessor developed on this principle. EURASIP Journal on Applied Signal Processing, Volume 2006 © 2006 Hindawi Publishing Corporation

Special Issue on Implementation Aspects and Testbeds for MIMO Systems

Thomas Kaiser Department of Communication Systems, Faculty of Engineering, University of Duisburg-Essen, 47048 Duisburg, Germany

Andre´ Bourdoux IMEC vzw, DESICS Division, Kapeldreef 75, 3001 Leuven, Belgium

Markus Rupp Institute of Communications and RF Engineering, TU Wien, Gusshausstrasse 25/389, 1040 Wien, Austria

Ulrich Heute Institute for Circuits and Systems Theory, Faculty of Engineering, Christian-Albrechts-University Kiel, Kaiserstraße 2, 24143 Kiel-Gaarden, Germany

The MIMO (multiple-input multiple-output) systems have emerged as a key technology for wireless local area networks (WLANs), wireless metropolitan area networks (WMANs), and cellular mobile communication systems (3G, 4G) because they promise greater coverage, higher data rates, and improved link robustness by adding a spatial dimension to the time, the frequency, and the code dimensions. Recent progress in standardization and in first MIMO prototype chipsets has forced manufacturers worldwide to pay more attention to MIMO implementation aspects. Moreover, MIMO testbeds have become more and more attractive to universities and to research institutes as has been observed in the past few years. The aim of this special issue is to reflect the current state-of-the-art MIMO testbeds and to examine the several MIMO implementation challenges for current and for future wireless communication standards. We classified the accepted thirteen submissions into four major categories: (1) hardware-oriented prototypes, (2) flexible testbeds, (3) analog issues, and (4) fast algorithms.

Hardware-oriented prototypes In the first paper, Guo et al. present an efficient circulant approximation-based MIMO equalizer architecture for the CDMA downlink, reducing the direct matrix inverse (DMI) Special Issue on Implementation Aspects and Testbeds for MIMO Systems 75 to some FFT operations. Further parallel and pipelined VLSI architectures with Hermi- tian optimization and reduced-state FFT reduce the complexity even more. A comparative study of both the conjugate-gradient and the DMI algorithms shows very promising performance/complexity tradeoff. VLSI design space in terms of area/time efficiency is explored extensively for layered parallelism and pipelining with a Catapult C high-level synthesis methodology. In the next paper, Dowle et al. describe the development of the STAR (space- time array research) platform, an FPGA-based research unit operating at 2.45 GHz and capable of having a maximum of twelve 20 MHz bandwidth channels of real-time, space-time, and MIMO processing. The design method starts with Matlab/Octave. With manual refinement steps, VHDL code for FPGAs is obtained and verified via ModelSim with the original design. Various pitfalls associated with the implementation of MIMO algorithms in real time are highlighted, and finally the development requirements are given to aid comparison with traditional DSP development. The paper by Goud et al. describes a portable 4 × 4 MIMO test-bed operating in an ISM band around 900 MHz. Details of channel measurements and capacity analysis of unusual indoor and outdoor locations obtained with the test-bed are also included. The next paper by Haustein et al. presents a reconfigurable hardware test-bed suitable for real-time mobile communication with multiple antennas. Sup- ported are four transmit and five receive antennas operating at 5.2 GHz with a maximum bandwidth of 100 MHz. Efficient implementation of MIMO signal processing using FPGAs and DSPs is described. An experimental verification of several real-time MIMO transmission schemes at high data rates in a typical office scenario is presented, and results on the achieved BER and throughput performance are given. Spectral efficiencies of more than 20 bps/Hz and a throughput of more than 150 Mbps was shown with a single-carrier transmission. The experimental results clearly show the feasibility of real-time high-data-rate MIMO techniques with state-of-the-art hardware and that more sophisticated baseband signal processing will be an essential part of future communication systems. Weijers et al. propose a systematic way from a transmission-system model, as often underlying a Matlab simulation, to a real-time prototype realized on a predefined hardware platform, avoiding inconsistencies of adhoc procedures. The suggested design flow is partly manual, but always systematic and assisted by tools suitable for the individual steps. Flexible testbeds The next five papers of the issue cover flexible testbeds, where the flexibility is usually achieved by higher-level programming languages. Xiang et al. describe a 4 × 4MIMO- OFDM test-bed mainly based on laboratory test equipment and offline processing. Chan- nel measurements and antenna selection techniques are presented. The paper also assesses the degradation due to carrier frequency offset and imperfect channel estimation. The next paper by Borkowski et al. presents a real-time MIMO test-bed for both single-carrier and OFDM transmission. A specific SIMD processor implemented on FPGAs is described, as well as the specific analog hardware at 10 GHz that is supported by offline and online calibration. The influence of polarization on the channel capacity is also addressed. In the paper by Caban et al., the focus is on the comfortable use of a flexible DSP/FPGA and RF hardware setup. Real-time tests with four transmit and receive channels each are possible at a data rate of 2.45 GHz. All pre- and postprocessing is done within Matlab, while the real-time requirements are fulfilled by burst-data transmission through the hardware. Multiuser abilities are also provided. In the contribution by Samuelsson et al., a test-bed for spatial multiplexing is proposed that relies on off-the-shelf radio hardware only. A comparison of SISO with 76 EURASIP Journal on Applied Signal Processing, Vol. 2006

MIMO reveals that even with rather low-cost hardware the remarkable spectral eﬃciency improvement and the associated multiplexing gain of MIMO can be demonstrated. The paper by Fabregas` et al. presents the complete design methodology of a MIMO-OFDM test-bed for WLAN applications. The design steps include a characterization of the indoor MIMO channel and the speciﬁc baseband and RF hardware at 5 GHz. The mapping and validation of the algorithms using Matlab, C++, and VHDL is detailed, and measurements are described.

Analog issues The contribution by Liu et al. addresses a specific problem in the popular transmit-antenna diversity scheme termed “transmit MRC.” While symmetries are usually assumed for the up- and downlink channels as well as between the antennas, in reality mismatches are found. A novel statistical analysis provides a deeper understanding and especially leads to a novel calibration scheme, which is finally implemented on a real-time prototyping platform. The paper by Piechocki et al. presents an extension of analogue turbo decoder concepts to MIMO detection. The first analogue implementation results show reductions of a few orders of magnitude in the number of required transistors, consumed energy, and the same order of improvement in processing speed. LDPC is used as a test case for the analysis.

Fast algorithms Safar et al. propose an eﬃcient detection of space-frequency block codes by means of the sphere decoding technique formulated in the complex domain. Three approaches are detailed: one approach is modulation independent, whereas the two others are speciﬁc for QAM and QPSK, respectively. The complexity analysis of these techniques is assessed.

Acknowledgments We thank the authors, the reviewers, the publisher, and the Editor-in-Chief for their efforts. We also hope that this special issue will stimulate subsequent contributions on MIMO testbeds so as to widely spread the required technical knowledge and to validate in further detail the realistic performance gain of multiantenna systems.

Thomas Kaiser Andr´e Bourdoux Markus Rupp Ulrich Heute Special Issue on Implementation Aspects and Testbeds for MIMO Systems 77 Volume 2006, No. 4 Contents and Abstracts

From MIMO-OFDM Algorithms to a Real-Time Wireless Prototype: A Systematic Matlab-to-Hardware Design Flow Jan-Willem Weijers, Veerle Derudder, Sven Janssens, Frederik Petre,´ and Andre´ Bourdoux DOI: 10.1155/ASP/2006/39297 To assess the performance of forthcoming 4th generation wireless local area networks, the algorithmic functionality is usually modelled using a high-level mathematical software package, for instance, Matlab. In order to validate the modelling assumptions against the real physical world, the high-level functional model needs to be translated into a prototype. A systematic system design methodology proves very valuable, since it avoids, or, at least reduces, numerous design iterations. In this paper, we propose a novel Matlab-to-hardware design flow, which allows to map the algorithmic functionality onto the target prototyping platform in a systematic and reproducible way. The proposed design flow is partly manual and partly tool assisted. It is shown that the proposed design flow allows to use the same testbench throughout the whole design flow and avoids time-consuming and error-prone intermediate translation steps.

An Efficient Circulant MIMO Equalizer for CDMA Downlink: Algorithm and VLSI Architecture Yuanbin Guo, Jianzhong(Charlie) Zhang, Dennis McCain, and Joseph R. Cavallaro DOI: 10.1155/ASP/2006/57134 We present an efficient circulant approximation-based MIMO equalizer architecture for the CDMA downlink. This reduces the direct matrix inverse (DMI) of size (NF × NF) ᏻ NF 3 ᏻ NF F with (( ) ) complexity to some FFT operations with ( log2( )) complexity and the inverse of some (N × N) submatrices. We then propose parallel and pipelined VLSI architectures with Hermitian optimization and reduced-state FFT for further complexity optimization. Generic VLSI architectures are derived for the (4 × 4) high-order receiver from partitioned (2 × 2) submatrices. This leads to more parallel VLSI design with 3× further complexity reduction. Comparative study with both the conjugate-gradient and DMI algorithms shows very promising performance/complexity tradeoff. VLSI design space in terms of area/time efficiency is explored extensively for layered parallelism and pipelining with a Catapult C high-level-synthesis methodology. 78 EURASIP Journal on Applied Signal Processing, Vol. 2006

Realization of a Spatially Multiplexed MIMO System Open Access David Samuelsson, Joakim Jalden,´ Per Zetterberg, and Bjorn¨ Ottersten DOI: 10.1155/ASP/2006/78349 Multi-antenna systems can provide improvements in wireless systems increasing spectral efficiency, reliability, range, and system capacity. Herein we show how some of the poten- tials of MIMO systems can be realized on a simple radio hardware platform by utilizing advanced real-time signal processing and coding. We present a real-time implementation of a 2 by 2 MIMO system employing spatial multiplexing to achieve high spectral efficiency in an indoor non-line-of-sight environment operating in the 1800 MHz range. Well-known processing and coding techniques are employed and our contributions lie in: discussing implementational aspects and solutions often overlooked but critical for high-performance operation; demonstrating the degree to which the simple baseband AWGN model can be used to accurately model/predict the MIMO system on the current hardware; and demonstrating the feasibility of real-time spatial multiplexing achieving up to 15 bps/Hz on a 2 by 2 system in a realistic indoor environment with off-the-shelf radio hardware.

Vienna MIMO Testbed Open Access Sebastian Caban, Christian Mehlfuhrer,¨ Robert Langwieser, Arpad L. Scholtz, and Markus Rupp DOI: 10.1155/ASP/2006/54868 While the field of MIMO transmission has been explored over the past decade mainly theoretically, relatively few results exist on how these transmissions perform over realistic, imperfect channels. The reason for this is that measurement equipment is expensive, difficult to obtain, and often inflexible when a multitude of transmission parameters are of interest. This paper presents a flexible testbed developed to examine MIMO algorithms and channel models described in literature by transmitting data at 2.45 GHz through real, physical channels, supporting simultaneously four transmit and four receive antennas. Operation is performed directly from Matlab allowing for a cornucopia of real-world experiments with minimum effort. Examples measuring bit error rates on space-time block codes are provided in the paper.

An FPGA-Based MIMO and Space-Time Processing Platform J. Dowle, S. H. Kuo, K. Mehrotra, and I. V. McLoughlin DOI: 10.1155/ASP/2006/34653 Faced with the need to develop a research unit capable of up to twelve 20 MHz bandwidth channels of real-time, space-time, and MIMO processing, the authors developed the STAR (space-time array research) platform. Analysis indicated that the possible degree of processing complexity required in the platform was beyond that available from contemporary digital signal processors, and thus a novel approach was required toward the provision of baseband signal processing. This paper follows the analysis and the consequential development Special Issue on Implementation Aspects and Testbeds for MIMO Systems 79 of a ﬂexible FPGA-based processing system. It describes the STAR platform and its use through several novel implementations performed with it. Various pitfalls associated with the implementation of MIMO algorithms in real time are highlighted, and ﬁnally, the development requirements for this FPGA-based solution are given to aid comparison with traditional DSP development.

Impact and Mitigation of Multiantenna Analog Front-End Mismatch in Transmit Maximum Ratio Combining Jian Liu, Nadia Khaled, Frederik Petre,´ Andre´ Bourdoux, and Alain Barel DOI: 10.1155/ASP/2006/86931 Transmit maximum ratio combining (MRC) allows to extend the range of wireless local area networks (WLANs) by exploiting spatial diversity and array gains. These gains, however, depend on the availability of the channel state information (CSI). In this perspective, an open-loop approach in time-division-duplex (TDD) systems relies on channel reciprocity between up- and downlink to acquire the CSI. Although the propagation channel can be assumed to be reciprocal, the radio-frequency (RF) transceivers may exhibit amplitude and phase mismatches between the up- and downlink. In this contribution, we present a statistical analysis to assess the impact of these mismatches on the performance of transmit-MRC. Furthermore, we propose a novel mixed-signal calibration scheme to mitigate these mismatches, which allows to reduce the implementation loss to as little as a few tenths of a dB. Finally, we also demonstrate the feasibility of the proposed calibration scheme in a real-time wireless MIMO-OFDM prototyping platform.

A High-Speed Four-Transmitter Four-Receiver MIMO OFDM Testbed: Experimental Results and Analyses Weidong Xiang, Paul Richardson, Brett Walkenhorst, Xudong Wang, and Thomas Pratt DOI: 10.1155/ASP/2006/45401 By adopting multiple-input multiple-output (MIMO) and orthogonal frequency-division multiplexing (OFDM) technologies, indoor wireless systems could reach data rates up to several hundreds of Mbits/s and achieve spectral efficiencies of several tens of bits/Hz/s, which are unattainable for conventional single-input single-output systems. The enhancements of data rate and spectral efficiency come from the fact that MIMO and OFDM schemes are indeed parallel transmission technologies in the space and frequency domains, respectively. To validate the functionality and feasibility of MIMO and OFDM technologies, we set up a four-transmitter four-receiver OFDM testbed in a typical indoor environment, which achieves a peak data rate of 525 Mbits/s and a spectral efficiency of 19.2 bits/Hz/s. The performances including MIMO channel characteristics, bit-error rate against signal- to-noise ratio curves, the impairments of carrier frequency offset and channel estimation inaccuracy, and an asymmetric MIMO scheme are reported and analyzed in this paper. 80 EURASIP Journal on Applied Signal Processing, Vol. 2006

A MIMO-OFDM Testbed for Wireless Local Open Access Area Networks Albert Guillen´ i Fabregas,` Maxime Guillaud, Dirk T. M. Slock, Giuseppe Caire, Karine Gosse, Stephanie´ Rouquette, Alexandre Ribeiro Dias, Philippe Bernardin, Xavier Miet, Jean-Marc Conrat, Yann Toutain, Alain Peden, and Zaiqing Li DOI: 10.1155/ASP/2006/18083 We describe the design steps and final implementation of a MIMO OFDM prototype platform developed to enhance the performance of wireless LAN standards such as HiperLAN/2 and 802.11, using multiple transmit and multiple receive antennas. We first describe the channel measurement campaign used to characterize the indoor operational propagation environment, and analyze the influence of the channel on code design through a ray-tracing channel simulator. We also comment on some antenna and RF issues which are of importance for the final realization of the testbed. Multiple coding, decoding, and channel estimation strategies are discussed and their respective performance-complexity trade-offs are evaluated over the realistic channel obtained from the propagation studies. Finally, we present the design methodology, including cross-validation of the Matlab, C++, and VHDL components, and the final demonstrator architecture. We highlight the increased measured performance of the MIMO testbed over the single-antenna system.

Analogue MIMO Detection Robert J. Piechocki, Jose Soler-Garrido, Darren McNamara, and Joe McGeehan DOI: 10.1155/ASP/2006/41898 In this contribution we propose an analogue receiver that can perform turbo detection in MIMO systems. We present the case for a receiver that is built from nonlinear analogue devices, which perform detection in a “free-ﬂow” network (no notion of iterations). This contribution can be viewed as an extension of analogue turbo decoder concepts to include MIMO detection. These ﬁrst analogue implementations report reductions of few orders of magnitude in the number of required transistors and in consumed energy, and the same order of improvement in processing speed. It is anticipated that such analogue MIMO decoder could bring about the same advantages, when compared to traditional digital implementations.

A Portable MIMO Testbed and Selected Channel Measurements Paul Goud Jr., Robert Hang, Dmitri Truhachev, and Christian Schlegel DOI: 10.1155/ASP/2006/51490 Aportable4×4 multiple-input multiple-output (MIMO) testbed that is based on field programmable gate arrays (FPGAs) and which operates in the 902–928 MHz industrial, scientific, and medical (ISM) band has been developed by the High Capacity Digital Commu- nications (HCDC) Laboratory at the University of Alberta. We present a description of the HCDC testbed along with MIMO channel capacities that were derived from measurements taken with the HCDC testbed for three special locations: a narrow corridor, an athletics field that is surrounded by a metal fence, and a parkade. These locations are special because Special Issue on Implementation Aspects and Testbeds for MIMO Systems 81 the channel capacities are different from what is expected for a typical indoor or outdoor channel. For two of the cases, a ray-tracing analysis has been performed and the simulated channel capacity values closely match the values calculated from the measured data. A ray- tracing analysis, however, requires accurate geometrical measurements and sophisticated modeling for each specific location. A MIMO testbed is ideal for quickly obtaining accurate channel capacity information.

Real-Time Signal Processing for Multiantenna Systems: Algorithms, Optimization, and Implementation on an Experimental Test-Bed Thomas Haustein, Andreas Forck, Holger Gabler,¨ Volker Jungnickel, and Stefan Schiffermuller¨ DOI: 10.1155/ASP/2006/27573 A recently realized concept of a reconfigurable hardware test-bed suitable for real-time mobile communication with multiple antennas is presented in this paper. We discuss the reasons and prerequisites for real-time capable MIMO transmission systems which may allow channel adaptive transmission to increase link stability and data throughput. We describe a concept of an efficient implementation of MIMO signal processing using FPGAs and DSPs. We focus on some basic linear and nonlinear MIMO detection and precoding algorithms and their optimization for a DSP target, and a few principal steps for computational performance enhancement are outlined. An experimental verification of several real-time MIMO transmission schemes at high data rates in a typical office scenario is presented and results on the achieved BER and throughput performance are given. The different transmission schemes used either channel state information at both sides of the link or at one side only (transmitter or receiver). Spectral efficiencies of more than 20 bits/s/Hz and a throughput of more than 150 Mbps were shown with a single-carrier transmission. The experimental results clearly show the feasibility of real-time high data rate MIMO techniques with state- of-the-art hardware and that more sophisticated baseband signal processing will be an essential part of future communication systems. A discussion on implementation challenges towards future wireless communication systems supporting higher data rates (1 Gbps and beyond) or high mobility concludes the paper.

A Fast Sphere Decoding Algorithm for Space-Frequency Block Codes Zoltan Safar, Weifeng Su, and K. J. Ray Liu DOI: 10.1155/ASP/2006/97676 The recently proposed space-frequency-coded MIMO-OFDM systems have promised considerable performance improvement over single-antenna systems. However, in order to make multiantenna OFDM systems an attractive choice for practical applications, implementation issues such as decoding complexity must be addressed successfully. In this paper, we propose a computationally efficient decoding algorithm for space-frequency block codes. The central part of the algorithm is a modulation-independent sphere decoding framework formulated in the complex domain. We develop three decoding approaches: a modulation-independent approach applicable to any memoryless modulation method, a QAM-specific and a PSK-specific fast decoding algorithm performing nearest-neighbor 82 EURASIP Journal on Applied Signal Processing, Vol. 2006 signal point search. The computational complexity of the algorithms is investigated via both analysis and simulation. The simulation results demonstrate that the proposed algorithm can significantly reduce the decoding complexity. We observe up to 75% reduction in the required FLOP count per code block compared to previously existing methods without no- ticeable performance degradation.

SABA: A Testbed for a Real-Time MIMO System Daniel Borkowski, Lars Bruhl,¨ Christoph Degen, Wilhem Keusgen, Gholamreza Alirezaei, Frank Geschewski, Christos Oikonomopoulos, and Bernhard Rembold DOI: 10.1155/ASP/2006/56061 The growing demand for high data rates for wireless communication systems leads to the development of new technologies to increase the channel capacity thus increasing the data rate. MIMO (multiple-input multiple-output) systems are best qualiﬁed for these applications. In this paper, we present a MIMO test environment for high data rate transmissions in frequency-selective environments. An overview of the testbed is given, including the analyzed algorithms, the digital signal processing with a new highly parallel processor to perform the algorithms in real time, as well as the analog front-ends. A brief overview of the inﬂuence of polarization on the channel capacity is given as well. EURASIP Journal on Applied Signal Processing, Volume 2006 © 2006 Hindawi Publishing Corporation

Special Issue on Video Analysis and Coding for Robust Transmission

Beatrice Pesquet-Popescu Ecole Nationale Superieure des Telecommunications, Paris 75634, France

Adriana Dumitras Apple Computer Inc., Cupertino, California, CA 95014, USA

Benoit Macq Universite Catolique de Louvain, 1348 Louvain la Neuve, Belgium

Increasing heterogeneity of networks and diversity of user capabilities have determined and sustained a strong interest in robust coding of visual content and flexible adaptation of the bitstreams to network and user conditions. As a result, several methods for robust coding and transmission have been proposed that include multiple description coding, motion- compensated subband video coding, joint source-channel coding, integrated compression and error control, and adaptation/transcoding solutions. These typically increase transmission robustness and network and user awareness by using scalability, error resilience, and adaptivity at little or sometimes no extra cost in coding efficiency. However, the performance of these methods is affected by the diversity of, and complex interactions within, the visual content. Analysis methods can improve the performance of robust methods for coding and transmission by providing solutions to account for vastly different characteristics of the visual content and complex interactions among data components, to achieve optimal or near-optimal robust solutions. Among several benefits, the application of visual analysis methods within robust coding and transmission frameworks such as those mentioned earlier yields content-aware error resilient solutions and improves prioritization of the visual content for coding and transmission. This special issue focuses on the seamless integration of visual analysis methods in, or joint design with, robust compression and transmission solutions. The special issue consists of three sections that address robust video coding architectures and configurations, robust entropy coding methods, and quality issues related to robust coding, respectively: (a) robust video coding paradigms (multiple description coding, motion-compensated subband coding, distributed coding, and cross-layer designs), (b) robust entropy coding by variable length codes, and (c) quality issues in robust coding (error resilience, error concealment, and quality evaluation). 84 EURASIP Journal on Applied Signal Processing, Vol. 2006

In the first set of nine papers, the first three address multiple description coding methods. The paper “End-to-end rate-distortion optimized MD mode selection for multiple description video coding” by B. A. Heng et al. discusses an adaptive approach to multiple description coding by a rate-distortion optimized selection of the most appropriate multiple description mode, depending on the network conditions and video features. The proposed method is an H.264-compatible video streaming solution over bursty channels and is based on an encoder-side estimation of the end-to-end distortion. The paper “Multi- ple description wavelet coding of layered video using optimal redundancy allocation” by N. V. Boulgouris et al. presents a wavelet-based, predictive, multiple description scheme with drift-free reconstruction. In this work, the redundancy allocation problem is tackled as a maximization of the average quality under a total target bitrate constraint. The paper “Unbalanced quantized multistate video coding” by S. E. Flierl et al. discusses a multiple description coding method that uses multistate video coding (or subsequence splitting). Unbalanced quantized descriptions are designed in this work using a rate-distortion optimization model based on network and video characteristics. Within the same section of robust video coding paradigms, the fourth and fifth papers address motion-compensated subband techniques. The paper “Temporal scalability through adaptive M-band filter banks for robust H.264/MPEG-4 AVC video coding” by C. Bergeron et al. proposes several temporal scalability schemes obtained by frame shuffling that increase robustness in an H.264-compatible framework. This work discusses open-loop and closed- loop architectures in an adaptive M-band hierarchical filter bank framework, and analyzes the sender-side error propagation. The paper “Motion estimation and signaling techniques for 2D + t scalable video coding” by M. Tagliasacchi et al. presents a 2D + t (in-band) video coding method with fast motion estimation in the wavelet domain and an adaptive in-band version of the update lifting step. The distributed source coding paradigm is the focus of the sixth and seventh papers on robust video coding architectures and paradigms. The paper “Distributed coding of highly correlated image sequences with motion-compensated temporal wavelets” by M. Flierl and P. Vandergheynst makes use of motion-compensated temporal filtering subband codecs in a multiple camera distributed video coding system. The paper investigates the relationship between multiview side information and temporal de-correlation, and proposes an optimal motion-compensated spatiotemporal transform at high bitrates. The work in “A framework for adaptive scalable video coding using Wyner-Ziv techniques” by H. Wang et al. presents a practical, low-complexity distributed coding framework, which exploits a multilayer Wyner-Ziv prediction “link” that connects the same bitplane level between successive planes. Such a link is created by exploiting the high quality reconstruction of the previous frame in the enhancement layer coding of the current frame, and provides improved temporal prediction as compared to MPEG-4 FGS, while maintaining a reasonable complexity on the encoder side. The eighth and ninth papers of the robust video coding paradigms provide useful guidelines for the cross-layer design of wireless video systems. The paper “Robust system and cross-layer design for H.264/AVC-based wireless video applications” by T. Stockhammer focuses on the feature selection for an H.264 codec, and the transport and network parameters for real-time applications. The paper “Source-adaptation-based wireless video transport: A cross-layer approach” by Q. Qu et al. proposes a forward error correction/unequal error protection method, which adapts the H.264 source coding to the motion information. This Special Issue on Video Analysis and Coding for Robust Transmission 85 solution allows the system to better cope with bursty packet losses in real-time transmission over wireless networks. The second set of papers tackles robust data representation by progressive and robust variable-length coding. The paper “Progressive and error-resilient transmission strategies for VLC encoded signals over noisy channels” by H. Jegou and C. Guillemot performs a statistical analysis in order to select the most appropriate binarization code. The paper also discusses soft-input-soft-output and turbo decoding methods, with possible applications to EBCOT and CABAC. The third set of four papers in this special issue addresses quality issues in robust video coding systems: error resilience, error concealment, and video quality evaluation. In the first two works on error resilience, the paper “RD optimized, adaptive, error-resilient transmission of MJPEG2000 coded video over multiple time-varying channels” by S. Bezan and S. Shirani proposes a data partitioning technique across multiple channels. This method makes use of rate-distortion optimized channel protection by RCPC codes and adaptive error correction that depends on the bandwidth and error characteristics of the channels. A different point of view is introduced in the paper “Adaptive UEP and packet size assignment for scalable video transmission over burst error channels” by C.-W. Lee et al., which focuses on achieving error resilience by prioritization for coding and transmission over limited- bandwidth bursty channels. This work presents the design of an MPEG-4 FGS streaming system using an analytic model for the evaluation of video quality. The model takes into account the bit-error rate and packet-error rate, which can face varying channel conditions due to an unequal error protection scheme combined with adaptive packet sizes. In the same set, the third paper “Classification-based spatial error concealment for visual communications” by M. Chen et al. proposes an adaptive selection of the error concealment algorithm by classification. This joint sender-receiver system design is discussed in three scenarios: a receiver-side classification, a sender-based classification, and a sender- side that embeds the classification side information. Thefourthandfinalpaperofthissection,“Aframeworkforadvancedvideotraces: Evaluating visual quality for video transmission over lossy networks” by O. A. Lotfallah et al., makes use of video traces for quality evaluation. This work addresses the problem of video quality evaluation in lossy transport schemes without accessing the video content. The proposed solution exploits video content descriptors and perceptual quality metrics in order to predict the quality of the reconstructed video accurately. For this special issue to come to life, significant effort from the contributing authors and reviewers was required. We express our thanks to all. It is our hope that the papers included in this special issue will help researchers and practitioners alike by providing focus and clear understanding of the status and challenges in the area of robust analysis and coding for video transmission. Beatrice Pesquet-Popescu Adriana Dumitras Benoit Macq 86 EURASIP Journal on Applied Signal Processing, Vol. 2006 Volume 2006, No. 5 Contents and Abstracts

Adaptive UEP and Packet Size Assignment for Scalable Video Transmission over Burst-Error Channels Chen-Wei Lee, Chu-Sing Yang, and Yih-Ching Su DOI: 10.1155/ASP/2006/10131 This work proposes an adaptive unequal error protection (UEP) and packet size assignment scheme for scalable video transmission over a burst-error channel. An analytic model is developed to evaluate the impact of channel bit error rate on the quality of streaming scalable video. A video transmission scheme, which combines the adaptive assignment of packet size with unequal error protection to increase the end-to-end video quality, is proposed. Several distinct scalable video transmission schemes over burst-error channel have been compared, and the simulation results reveal that the proposed transmission schemes can react to varying channel conditions with less and smoother quality degradation.

Source-Adaptation-Based Wireless Video Transport: A Cross-Layer Approach Qi Qu, Yong Pei, James W. Modestino, and Xusheng Tian DOI: 10.1155/ASP/2006/28919 Real-time packet video transmission over wireless networks is expected to experience bursty packet losses that can cause substantial degradation to the transmitted video quality. In wireless networks, channel state information is hard to obtain in a reliable and timely manner due to the rapid change of wireless environments. However, the source motion information is always available and can be obtained easily and accurately from video sequences. Therefore, in this paper, we propose a novel cross-layer framework that exploits only the motion information inherent in video sequences and eﬃciently combines a packetization scheme, a cross-layer forward error correction (FEC)-based unequal error protection (UEP) scheme, an intracoding rate selection scheme as well as a novel intraframe interleaving scheme. Our objective and subjective results demonstrate that the proposed approach is very eﬀective in dealing with the bursty packet losses occurring on wireless networks without incurring any additional implementation complexity or delay. Thus, the simplicity of our proposed system has important implications for the implementation of a practical real- time video transmission system.

End-to-End Rate-Distortion Optimized MD Mode Open Access Selection for Multiple Description Video Coding Brian A. Heng, John G. Apostolopoulos, and Jae S. Lim DOI: 10.1155/ASP/2006/32592 Multiple description (MD) video coding can be used to reduce the detrimental effects caused by transmission over lossy packet networks. A number of approaches have been Special Issue on Video Analysis and Coding for Robust Transmission 87 proposed for MD coding, where each provides a different tradeoff between compression efficiency and error resilience. How effectively each method achieves this tradeoff depends on the network conditions as well as on the characteristics of the video itself. This paper proposes an adaptive MD coding approach which adapts to these conditions through the use of adaptive MD mode selection. The encoder in this system is able to accurately estimate the expected end-to-end distortion, accounting for both compression and packet loss-induced distortions, as well as for the bursty nature of channel losses and the effective use of multiple transmission paths. With this model of the expected end-to-end distortion, the encoder selects between MD coding modes in a rate-distortion (R-D) optimized manner to most effectively tradeoff compression efficiency for error resilience. We show how this approach adapts to both the local characteristics of the video and network conditions and demonstrates the resulting gains in performance using an H.264-based adaptive MD video coder.

Distributed Coding of Highly Correlated Image Sequences with Motion-Compensated Temporal Wavelets Markus Flierl and Pierre Vandergheynst DOI: 10.1155/ASP/2006/46747 This paper discusses robust coding of visual content for a distributed multimedia system. The system encodes independently two correlated video signals and reconstructs them jointly at a central decoder. The video signals are captured from a dynamic scene, where each signal is robustly coded by a motion-compensated Haar wavelet. The efficiency of the decoder is improved by a disparity analysis of the first image pair of the sequences, followed by disparity compensation of the remaining images of one sequence. We investigate how this scene analysis at the decoder can improve the coding efficiency. At the decoder, one video signal is used as side information to decode efficiently the second video signal. Additional bitrate savings can be obtained with disparity compensation at the decoder. Fur- ther, we address the theoretical problem of distributed coding of video signals in the presence of correlated video side information. We utilize a motion-compensated spatiotemporal transform to decorrelate each video signal. For certain assumptions, the optimal motion- compensated spatiotemporal transform for video coding with video side information at high rates is derived. It is shown that the motion-compensated Haar wavelet belongs to this class of transforms. Given the correlation of the video side information, the theoretical bitrate reduction for the distributed coding scheme is investigated. Interestingly, the efficiency of multiview side information is dependent on the level of temporal decorrelation: for a given correlation SNR of the side information, bitrate savings due to side information are decreasing with improved temporal decorrelation.

Classification-Based Spatial Error Concealment for Visual Communications Meng Chen, Yefeng Zheng, and Min Wu DOI: 10.1155/ASP/2006/13438 In an error-prone transmission environment, error concealment is an effective technique to reconstruct the damaged visual content. Due to large variations of image characteristics, 88 EURASIP Journal on Applied Signal Processing, Vol. 2006 different concealment approaches are necessary to accommodate the different nature of the lost image content. In this paper, we address this issue and propose using classification to integrate the state-of-the-art error concealment techniques. The proposed approach takes advantage of multiple concealment algorithms and adaptively selects the suitable algorithm for each damaged image area. With growing awareness that the design of sender and receiver systems should be jointly considered for efficient and reliable multimedia communications, we proposed a set of classification-based block concealment schemes, including receiver-side classification, sender-side attachment, and sender-side embedding. Our experimental results provide extensive performance comparisons and demonstrate that the proposed classification-based error concealment approaches outperform the conventional approaches.

Unbalanced Quantized Multiple State Video Coding Sila Ekmekci Flierl, Thomas Sikora, and Pascal Frossard DOI: 10.1155/ASP/2006/14694 Multiple state video coding (MSVC) is a multiple description scheme based on frame-wise splitting of the video sequence into two or more subsequences. Each subsequence is encoded separately to generate descriptions which can be decoded independently. Due to subsequence splitting, the prediction gain decreases. But since reconstruction capabilities improve, error resilience of the system increases. Our focus is on multiple state video coding with unbalanced quantized descriptions, which is particularly interesting for video streaming applications over heterogeneous networks where path diversity is used and transmission channels have varying transmission characteristics. The total bitrate is kept constant, while the subsequences are quantized with different stepsizes depending on the sequence as well as on the transmission conditions. Our goal is to figure out under which transmission conditions unbalanced bitstreams lead to good system performance in terms of the average reconstructed PSNR. Besides, we investigate the effects of intra-coding on the error resilience of the system and show that the sequence characteristics, and in particular the degree of motion in the sequence, have an important impact on the decoding performance. Finally, we propose a distortion model that is the core of an optimized rate allocation strategy, which is dependent on the network characteristics and status as well as on the video sequence characteristics.

Multiple Description Wavelet Coding of Layered Video Using Optimal Redundancy Allocation Nikolaos V. Boulgouris, Konstantinos E. Zachariadis, Angelos Kanlis, and Michael G. Strintzis DOI: 10.1155/ASP/2006/83542 We present a wavelet-based framework for the encoding of video in multiple descriptions. Using the proposed methodology, the generation of multiple descriptions is performed so that drift is eliminated at the decoder regardless of the number of received descriptions. Moreover, the proposed framework is ﬂexible in the sense that it allows the encoding of Special Issue on Video Analysis and Coding for Robust Transmission 89 video into an arbitrary number of descriptions. We also present a thorough analysis of rate allocation issues and propose three algorithms for the optimal allocation of redundancy. Experimental results for the transmission of video using two descriptions demonstrate the eﬃciency of the proposed method.

M Temporal Scalability through Adaptive -Band Open Access Filter Banks for Robust H.264/MPEG-4 AVC Video Coding

C. Bergeron, C. Lamy-Bergot, G. Pau, and B. Pesquet-Popescu DOI: 10.1155/ASP/2006/21930 This paper presents different structures that use adaptive M-band hierarchical filter banks for temporal scalability. Open-loop and closed-loop configurations are introduced and illustrated using existing video codecs. In particular, it is shown that the H.264/MPEG-4 AVC codec allows us to introduce scalability by frame shuffling operations, thus keeping backward compatibility with the standard. The large set of shuffling patterns introduced here can be exploited to adapt the encoding process to the video content features, as well as to the user equipment and transmission channel characteristics. Furthermore, simulation results show that this scalability is obtained with no degradation in terms of subjective and objective quality in error-free environments, while in error-prone channels the scalable versions provide increased robustness.

A Framework for Adaptive Scalable Video Coding Using Wyner-Ziv Techniques Huisheng Wang, Ngai-Man Cheung, and Antonio Ortega DOI: 10.1155/ASP/2006/60971 This paper proposes a practical video coding framework based on distributed source coding principles, with the goal to achieve efficient and low-complexity scalable coding. Starting from a standard predictive coder as base layer (such as MPEG-4 baseline video coder in our implementation), the proposed Wyner-Ziv scalable (WZS) coder can achieve higher coding efficiency, by selectively exploiting the high quality reconstruction of the previous frame in the enhancement layer coding of the current frame. This creates a multi-layer Wyner-Ziv prediction “link,” connecting the same bitplane level between successive frames, thus providing improved temporal prediction as compared to MPEG-4 FGS, while keeping complexity reasonable at the encoder. Since the temporal correlation varies in time and space, a block-based adaptive mode selection algorithm is designed for each bitplane, so that it is possible to switch between different coding modes. Experimental results show improvements in coding efficiency of 3–4.5 dB over MPEG-4 FGS for video sequences with high temporal correlation. 90 EURASIP Journal on Applied Signal Processing, Vol. 2006

A Framework for Advanced Video Traces: Open Access Evaluating Visual Quality for Video Transmission Over Lossy Networks

Osama A. Lotfallah, Martin Reisslein, and Sethuraman Panchanathan DOI:10.1155/ASP/2006/42083 Conventional video traces (which characterize the video encoding frame sizes in bits and frame quality in PSNR) are limited to evaluating loss-free video transmission. To evaluate robust video transmission schemes for lossy network transport, generally experiments with actual video are required. To circumvent the need for experiments with actual videos, we propose in this paper an advanced video trace framework. The two main components of this framework are (i) advanced video traces which combine the conventional video traces with a parsimonious set of visual content descriptors, and (ii) quality prediction schemes that based on the visual content descriptors provide an accurate prediction of the quality of the reconstructed video after lossy network transport. We conduct extensive evaluations using a perceptual video quality metric as well as the PSNR in which we compare the visual quality predicted based on the advanced video traces with the visual quality determined from experiments with actual video. We ﬁnd that the advanced video trace methodology accurately predicts the quality of the reconstructed video after frame losses.

Progressive and Error-Resilient Transmission Strategies for VLC Encoded Signals over Noisy Channels HerveJ´ egou´ and Christine Guillemot DOI: 10.1155/ASP/2006/37164 This paper addresses the issue of robust and progressive transmission of signals (e.g., images, video) encoded with variable length codes (VLCs) over error-prone channels. This paper first describes bitstream construction methods offering good properties in terms of error resilience and progressivity. In contrast with related algorithms described in the literature, all proposed methods have a linear complexity as the sequence length increases. The applicability of soft-input soft-output (SISO) and turbo decoding principles to resulting bitstream structures is investigated. In addition to error resilience, the amenability of the bitstream construction methods to progressive decoding is considered. The problem of code design for achieving good performance in terms of error resilience and progressive decoding with these transmission strategies is then addressed. The VLC code has to be such that the symbol energy is mainly concentrated on the first bits of the symbol representation (i.e., on the first transitions of the corresponding codetree). Simulation results reveal high performance in terms of symbol error rate (SER) and mean-square reconstruction error (MSE). These error-resilience and progressivity properties are obtained without any penalty in compression efficiency. Codes with such properties are of strong interest for the binarization of M-ary sources in state-of-the-art image, and video coding systems making use of, for example, the EBCOT or CABAC algorithms. A prior statistical analysis of the signal allows the construction of the appropriate binarization code. Special Issue on Video Analysis and Coding for Robust Transmission 91

RD Optimized, Adaptive, Error-Resilient Transmission of MJPEG2000-Coded Video over Multiple Time-Varying Channels Scott Bezan and Shahram Shirani DOI: 10.1155/ASP/2006/79769 To reliably transmit video over error-prone channels, the data should be both source and channel coded. When multiple channels are available for transmission, the problem extends to that of partitioning the data across these channels. The condition of transmission channels, however, varies with time. Therefore, the error protection added to the data at one instant of time may not be optimal at the next. In this paper, we propose a method for adaptively adding error correction code in a rate-distortion (RD) optimized manner using rate-compatible punctured convolutional codes to an MJPEG2000 constant rate-coded frame of video. We perform an analysis on the rate-distortion tradeoﬀ of each of the coding units (tiles and packets) in each frame and adapt the error correction code assigned to the unit taking into account the bandwidth and error characteristics of the channels. This method is applied to both single and multiple time-varying channel environments. We compare our method with a basic protection method in which data is either not transmitted, transmitted with no protection, or transmitted with a ﬁxed amount of protection. Simulation results show promising performance for our proposed method.

Motion Estimation and Signaling Techniques for 2D+t Scalable Video Coding M. Tagliasacchi, D. Maestroni, S. Tubaro, and A. Sarti DOI: 10.1155/ASP/2006/57308 We describe a fully scalable wavelet-based 2D+t (in-band) video coding architecture. We propose new coding tools specifically designed for this framework aimed at two goals: reduce the computational complexity at the encoder without sacrificing compression; improve the coding efficiency, especially at low bitrates. To this end, we focus our attention on motion estimation and motion vector encoding. We propose a fast motion estimation algorithm that works in the wavelet domain and exploits the geometrical properties of the wavelet subbands. We show that the computational complexity grows linearly with the size of the search window, yet approaching the performance of a full search strategy. We extend the proposed motion estimation algorithm to work with blocks of variable sizes, in order to better capture local motion characteristics, thus improving in terms of rate-distortion behavior. Given this motion field representation, we propose a motion vector coding algorithm that allows to adaptively scale the motion bit budget according to the target bitrate, improving the coding efficiency at low bitrates. Finally, we show how to optimally scale the motion field when the sequence is decoded at reduced spatial resolution. Experimental results illustrate the advantages of each individual coding tool presented in this paper. Based on these simulations, we define the best configuration of coding parameters and we compare the proposed codec with MC-EZBC, a widely used reference codec implementing the t+2D framework. 92 EURASIP Journal on Applied Signal Processing, Vol. 2006

Robust System and Cross-Layer Design for H.264/AVC-Based Wireless Video Applications Thomas Stockhammer DOI: 10.1155/ASP/2006/89371 H.264/AVC is an essential component in emerging wireless video applications, thanks to its excellent compression efficiency and network-friendly design. However, a video coding standard itself is only a single component within a complex system. Its effectiveness strongly depends on the appropriate configuration of encoders, decoders, as well as transport and network features. The applicability of different features depends on application constraints, the availability and quality of feedback and cross-layer information, and the accessible quality-of-service (QoS) tools in modern wireless networks. We discuss robust integration of H.264/AVC in wireless real-time video applications. Specifically, the use of different coding and transport-related features for different application types is elaborated. Guidelines for the selection of appropriate coding tools, encoder and decoder settings, as well as transport and network parameters are provided and justified. Selected simulation results show the superiority of lower layer error control over application layer error control and video error resilience features. EURASIP Journal on Applied Signal Processing, Volume 2006 © 2006 Hindawi Publishing Corporation

Special Issue on Advanced Signal Processing for Digital Subscriber Lines

Raphael Cendrillon Marvell Hong Kong Ltd., Hong Kong

Iain Collings CSIRO Information Communication Technologies Center, Australia

Tomas Nordstrom¨ Telecommunications Research Center Vienna (ftw.), Donau-City-StraBe 1, 1220 Vienna, Austria

Frank Sjoberg¨ Division of Signal Processing, Lulea˚ University of Technology, and Upzide Labs, Lulea,˚ Sweden

Michail Tsatsanis Aktino Inc., Irvine, California, USA

Wei Yu Electrical and Computer Engineering Department, University of Toronto, 10 King’s College Road, Toronto, ON Canada, M5S 3G4

The recent deployment of digital subscriber line (DSL) technology around the world is rapidly making broadband access for the mass consumer market a reality. The ever-growing customer demand for higher data rates has been fueled by the popularity of applications like peer-to-peer (P2P) ﬁle-sharing networks and video-streaming and high-deﬁnition television (HDTV). DSL technology allows telephone operators to get maximum leverage out of their existing infrastructure by delivering broadband access over existing twisted-pair telephone lines. At the heart of DSL lies a plethora of signal processing techniques which enable such high-speed transmission to be achieved over a medium originally designed with only voice-band transmission in mind. These advanced signal processing techniques address many challenges that exist in DSL networks today, such as the near-end and far-end crosstalk (NEXT/FEXT), impulse noise, peak-to-average-power ratio (PAR), intersymbol and intercarrier interference (ISI/ICI), radio-frequency interference (RFI), and so forth. The goal of this special issue is to discuss the state-of-the-art and recent advances in signal processing techniques for DSL. 94 EURASIP Journal on Applied Signal Processing, Vol. 2006

The special issue consists of fifteen papers on a range of topics. The first set of papers focuses on the area of dynamic spectrum management (DSM). In a conventional DSL deployment, the transmit spectrum for all modems in a bundle are fixed to a predeter- mined level. As DSL deployment becomes increasingly heterogeneous, crosstalk produced by modems under a fixed spectrum can be a source of significant interference. Dynamic spectrum management aims to improve the data rates and reaches of conventional DSL systems by adaptively varying transmit power-spectral density according to geographic locations and the crosstalk channel characteristics of the subscribers in each bundle. This issue contains six papers on DSM. In “The worst-case interference in DSL systems employing dynamic spectral management,” Brady and Cioffi answer the question of what the worst-case crosstalk interference is for a given DSL line. They characterize the performance of the system under the worst-case noise using a game theory technique. In “Joint multiuser detection and optimal spectrum balancing for digital subscriber lines,” Chan and Yu study the optimal spectrum management technique for a scenario in which crosstalk may also be partially cancelled using advanced crosstalk cancellation techniques. In the next three papers, practical spectrum management techniques are investigated. In “Spectrally compatible iterative water-filling,” Verlinden et al. study a system in which spectral allocation scheme is constrained by additional spectrum compatibility requirements and propose a new scheme based on an earlier algorithm called iterative water- filling. In “The normalized-rate iterative algorithm: a practical dynamic spectrum management method for DSL,” Statovci et al. propose a new low-complexity technique for spectrum balancing and frequency partition in a DSL bundle. In “ADSL transceivers applying DSM and their nonstationary noise robustness,” Van den Bogaert et al. report the performance of practical transceivers implementing dynamic spectrum management and study their robustness against nonstationary noise. Finally, from a theoretical perspective, the paper “Analysis of iterative water-filling algorithm for multiuser power control in digital subscriber lines,” by Luo and Pang, takes a new look at the iterative water-filling algorithm and gives a novel interpretation of the algorithm based on optimization theory. The next paper in the special issue deals with crosstalk cancellation. In a DSL deployment, when coordination among the transmit- or receive-modems is possible, further data improvement may be obtained via crosstalk cancellation. In the paper “Alien crosstalk cancellation for multipair digital subscriber line systems,” Ginis and Peng give an overview of this area and propose a new crosstalk cancellation technique that takes advantage of the noise correlation among the multiple receivers. The practical success of dynamic spectrum management and crosstalk cancellation depends very much on how accurately crosstalk channels may be modeled and identified in practice. Two papers of this special issue address this area. In “Crosstalk models for short VDSL2 lines from measured 30 MHz data,” Karipidis et al. propose measurement-based crosstalk models for VDSL. In “Error sign feedback as an alternative to pilots for the tracking of FEXT transfer functions in downstream VDSL,” Louveaux and Van der Veen propose new ways of identifying the crosstalk channel using a novel feedback scheme. Equalization and coding continue to be important research topics in DSL. In the area of time-domain equalization (TEQ), the paper “Iterative refinement methods for time- domain equalizer design” by Arslan et al. proposes a new method to reduce the implementation complexity of the TEQ. In the area of error-correcting coding for the DSL system, the paper “Near capacity coding for discrete multitone (DMT) systems with impulse noise” Special Issue on Advanced Signal Processing for Digital Subscriber Lines 95 by Ardakani et al. proposes a methodology for the design of the newly emerged low-density parity-check (LDPC) codes for a DMT system, while addressing the practical DSL deployment issue of impulse noise. In “Fine-granularity loading schemes using adaptive Reed- Solomon coding for xDSL-DMT systems,” Panigrahi and Le-Ngoc propose a joint design of bit-loading and error-correcting code, and characterize the performance gain made possible by fractional bit-loading. The final set of three papers in this special issue deals with the area of modulation and transmitter design. The design of transmit window to minimize egress is studied in the paper by Cuypers et al. “Intra-symbol windowing for egress reduction in DMT transmitters.” The peak-to-average-power ratio is another important transmitter design issue for DMT systems. This is taken up in the paper “Designing tone reservation PAR reduction” by Andgart et al. DMT is not the only possible multicarrier modulation scheme for DSL. An alternative is proposed and studied in the paper “Cosine modulated multitone for very high-speed digital subscriber lines” by Lin and Farhang-Boroujeny. The continued growth of digital subscriber line technology worldwide is in part fueled by rapid advances in signal processing techniques. We hope that the readers will enjoy the collection of papers on this timely topic. Finally, we wish to take this opportunity to acknowledge and to thank all anonymous reviewers, without whom the success of this special issue would not have been possible.

Raphael Cendrillon Iain Collings Tomas Nordstrom¨ Frank Sjoberg¨ Michail Tsatsanis Wei Yu 96 EURASIP Journal on Applied Signal Processing, Vol. 2006 Volume 2006, No. 6 Contents and Abstracts

The Worst-Case Interference in DSL Systems Open Access Employing Dynamic Spectrum Management Mark H. Brady and John M. Cioffi DOI: 10.1155/ASP/2006/78524 Dynamic spectrum management (DSM) has been proposed to achieve next-generation rates on digital subscriber lines (DSL). Because the copper twisted-pair plant is an interference-constrained environment, the multiuser performance and spectral compatibility of DSM schemes are of primary concern in such systems. While the analysis of multiuser interference has been standardized for current static spectrum-management (SSM) techniques, at present no corresponding standard DSM analysis has been established. This paper examines a multiuser spectrum-allocation problem and formulates a lower bound to the achievable rate of a DSL modem that is tight in the presence of the worst-case interference. A game-theoretic analysis shows that the rate-maximizing strategy under the worst-case interference (WCI) in the DSM setting corresponds to a Nash equilibrium in pure strategies of a certain strictly competitive game. A Nash equilibrium is shown to exist under very mild conditions, and the rate-adaptive waterfilling algorithm is demonstrated to give the optimal strategy in response to the WCI under a frequency-division (FDM) condition. Numerical results are presented for two important scenarios: an upstream VDSL deployment exhibiting the near-far effect, and an ADSL RT deployment with long CO lines. The results show that the performance improvement of DSM over SSM techniques in these channels can be preserved by appropriate distributed power control, even in worst-case interference environments.

Joint Multiuser Detection and Optimal Spectrum Balancing for Digital Subscriber Lines Vincent M. K. Chan and Wei Yu DOI: 10.1155/ASP/2006/80941 In a digital subscriber line (DSL) system with strong crosstalk, the detection and cancellation of interference signals have the potential to improve the overall data rate performance. However, as DSL crosstalk channels are highly frequency selective and multiuser detection is suitable only when crosstalk is strong, the set of frequency tones in which multiuser detection may be used must be carefully chosen. Further, this problem of tone selection is highly coupled with the transmit power spectra of both direct and interfering signals, so the optimal solution requires the tone selection problem to be solved jointly with the multiuser spectrum optimization problem. The main idea of this paper is that the above joint optimization may be done eﬃciently using a dual decomposition technique similar to that of the optimal spectrum balancing algorithm. Simulations show that multiuser detection can increase the bit rate performance in a remotely deployed ADSL environment. Special Issue on Advanced Signal Processing for Digital Subscriber Lines 97

Rate improvement is also observed when near-end crosstalk is estimated and cancelled in a VDSL environment with overlapping upstream and downstream frequency bands.

Spectrally Compatible Iterative Water Filling Jan Verlinden, Etienne Van den Bogaert, Tom Bostoen, Francesca Zanier, Marco Luise, Raphael Cendrillon, and Marc Moonen DOI: 10.1155/ASP/2006/58380 Until now static spectrum management has ensured that DSL lines in the same cable are spectrally compatible under worst-case crosstalk conditions. Recently dynamic spectrum management (DSM) has been proposed aiming at an increased capacity utilization by adaptation of the transmit spectra of DSL lines to the actual crosstalk interference. In this paper, a new DSM method for downstream ADSL is derived from the well-known iterative water- filling (IWF) algorithm. The amount of boosting of this new DSM method is limited, such that it is spectrally compatible with ADSL. Hence it is referred to as spectrally compatible iterative water filling (SC-IWF). This paper focuses on the performance gains of SC-IWF. This method is an autonomous DSM method (DSM level 1) and it will be investigated together with two other DSM level-1 algorithms, under various noise conditions, namely, iterative water-filling algorithm, and flat power back-off (flat PBO).

The Normalized-Rate Iterative Algorithm: Open Access A Practical Dynamic Spectrum Management Method for DSL Driton Statovci, Tomas Nordstrom,¨ and Rickard Nilsson DOI: 10.1155/ASP/2006/95175 We present a practical solution for dynamic spectrum management (DSM) in digital subscriber line systems: the normalized-rate iterative algorithm (NRIA). Supported by a novel optimization problem formulation, the NRIA is the only DSM algorithm that jointly addresses spectrum balancing for frequency division duplexing systems and power allocation for the users sharing a common cable bundle. With a focus on being implementable rather than obtaining the highest possible theoretical performance, the NRIA is designed to efficiently solve the DSM optimization problem with the operators’ business models in mind. This is achieved with the help of two types of parameters: the desired network asymmetry and the desired user priorities. The NRIA is a centralized DSM algorithm based on the iterative water-filling algorithm (IWFA) for finding efficient power allocations, but extends the IWFA by finding the achievable bitrates and by optimizing the bandplan. It is compared with three other DSM proposals: the IWFA, the optimal spectrum balancing algorithm (OSBA), and the bidirectional IWFA (bi-IWFA). We show that the NRIA achieves better bitrate performance than the IWFA and the bi-IWFA. It can even achieve performance almost as good as the OSBA, but with dramatically lower requirements on complexity. Addi- tionally, the NRIA can achieve bitrate combinations that cannot be supported by any other DSM algorithm. 98 EURASIP Journal on Applied Signal Processing, Vol. 2006

ADSL Transceivers Applying DSM and Their Nonstationary Noise Robustness Etienne Van den Bogaert, Tom Bostoen, Jan Verlinden, Raphael Cendrillon, and Marc Moonen DOI: 10.1155/ASP/2006/67686 Dynamic spectrum management (DSM) comprises a new set of techniques for multiuser power allocation and/or detection in digital subscriber line (DSL) networks. At the Alcatel Research and Innovation Labs, we have recently developed a DSM test bed, which allows the performance of DSM algorithms to be evaluated in practice. With this test bed, we have evaluated the performance of a DSM level-1 algorithm known as iterative water-filling in an ADSL scenario. This paper describes the results of, on the one hand, the performance gains achieved with iterative water-filling, and, on the other hand, the nonstationary noise robustness of DSM-enabled ADSL modems. It will be shown that DSM trades off nonstationary noise robustness for performance improvements. A new bit swap procedure is then introduced to increase the noise robustness when applying DSM.

Analysis of Iterative Waterfilling Algorithm for Multiuser Power Control in Digital Subscriber Lines Zhi-Quan Luo and Jong-Shi Pang DOI: 10.1155/ASP/2006/24012 We present an equivalent linear complementarity problem (LCP) formulation of the non- cooperative Nash game resulting from the DSL power control problem. Based on this LCP reformulation, we establish the linear convergence of the popular distributed iterative waterfilling algorithm (IWFA) for arbitrary symmetric interference environment and for certain asymmetric channel conditions with any number of users. In the case of symmetric interference crosstalk coefficients, we show that the users of IWFA in fact, unknowingly but willingly, cooperate to minimize a common quadratic cost function whose gradient measures the received signal power from all users. This is surprising since the DSL users in the IWFA have no intention to cooperate as each maximizes its own rate to reach a Nash equilibrium. In the case of asymmetric coefficients, the convergence of the IWFA is due to a contraction property of the iterates. In addition, the LCP reformulation enables us to solve the DSL power control problem under no restrictions on the interference coefficients using existing LCP algorithms, for example, Lemke’s method. Indeed, we use the latter method to benchmark the empirical performance of IWFA in the presence of strong crosstalk interference.

Alien Crosstalk Cancellation for Multipair Digital Subscriber Line Systems George Ginis and Chia-Ning Peng DOI: 10.1155/ASP/2006/16828 An overview of alien crosstalk cancellation for DSL systems with multiple pairs is here presented. It is shown that when a common crosstalk source affects the receivers of multiple Special Issue on Advanced Signal Processing for Digital Subscriber Lines 99 pairs, the noise exhibits a certain correlation among the pairs. In a DMT system, the frequency-domain noise samples are most strongly correlated between pairs when they correspond to the same tone. Thus, noise decorrelation algorithms applied independently for each tone can provide significant performance enhancements. Three possible methods are described for noise decorrelation, one is suitable for two-sided coordination and two are suited for receiver coordination among the pairs. It is theoretically proven that the data- rate performance of these three methods is identical from the perspective of the sum rate over all pairs. Simulation results corresponding to an ADSL2+ two-pair system with a T1 disturber are presented to illustrate the noise correlation property and to indicate the potential performance benefits.

Crosstalk Models for Short VDSL2 Lines from Measured 30 MHz Data E. Karipidis, N. Sidiropoulos, A. Leshem, Li Youming, R. Tarafi, and M. Ouzzif DOI: 10.1155/ASP/2006/85859 In recent years, there has been a growing interest in hybrid fiber-copper access solutions, as in fiber to the basement (FTTB) and fiber to the curb/cabinet (FTTC). The twisted pair segment in these architectures is in the range of a few hundred meters, thus supporting transmission over tens of MHz. This paper provides crosstalk models derived from measured data for quad cable, lengths between 75 and 590 meters, and frequencies up to 30 MHz. The results indicate that the log-normal statistical model (with a simple parametric law for the frequency-dependent mean) fits well up to 30 MHz for both FEXT and NEXT. This extends earlier log-normal statistical modeling and validation results for NEXT over bandwidths in the order of a few MHz. The fitted crosstalk power spectra are useful for modem design and simulation. Insertion loss, phase, and impulse response duration characteristics of the direct channels are also provided.

Error Sign Feedback as an Alternative to Pilots for the Tracking of FEXT Transfer Functions in Downstream VDSL J. Louveaux and A.-J van der Veen DOI: 10.1155/ASP/2006/94105 With increasing bandwidths and decreasing loop lengths, crosstalk becomes the main im- pairment in VDSL systems. For downstream communication, crosstalk precompensation techniques have been designed to cope with this issue by using the collocation of the transmitters. These techniques naturally need an accurate estimation of the crosstalk channel impulse responses. We investigate the issue of tracking these channels. Due to the lack of coordination between the receivers, and because the amplitude levels of the remaining interference from crosstalk after precompensation are very low, blind estimation schemes are inefficient in this case. So some part of the upstream or downstream bit rate needs to be used to help the estimation. In this paper, we design a new algorithm to try to limit the bandwidth used for the estimation purpose by exploiting the collocation at the transmitter side. The principle is to use feedback from the receiver to the transmitter instead of using pilots in the downstream signal. It is justified by computing the Cramer-Rao lower bound on the estimation error variance and showing that, for the levels of power in consideration, 100 EURASIP Journal on Applied Signal Processing, Vol. 2006 and for a given bit rate used to help the estimation, this bound is effectively lower for the proposed scheme. A simple algorithm based on the maximum likelihood is proposed. Its performance is analyzed in detail and is compared to a classical scheme using pilot symbols. Finally, an improved but more complex version is proposed to approach the performance bound.

Iterative Refinement Methods for Time-Domain Open Access Equalizer Design Guner¨ Arslan, Biao Lu, Lloyd D. Clark, and Brian L. Evans DOI: 10.1155/ASP/2006/43154 Commonly used time domain equalizer (TEQ) design methods have been recently unified as an optimization problem involving an objective function in the form of a Rayleigh quotient. The direct generalized eigenvalue solution relies on matrix decompositions. To reduce implementation complexity, we propose an iterative refinement approach in which the TEQ length starts at two taps and increases by one tap at each iteration. Each iteration involves matrix-vector multiplications and vector additions with 2 × 2 matrices and two-element vectors. At each iteration, the optimization of the objective function either improves or the approach terminates. The iterative refinement approach provides a range of communication performance versus implementation complexity tradeoffs for any TEQ method that fits the Rayleigh quotient framework. We apply the proposed approach to three such TEQ design methods: maximum shortening signal-to-noise ratio, minimum intersymbol interference, and minimum delay spread.

Near-Capacity Coding for Discrete Multitone Systems with Impulse Noise Masoud Ardakani, Frank R. Kschischang, and Wei Yu DOI: 10.1155/ASP/2006/98738 We consider the design of near-capacity-achieving error-correcting codes for a discrete multitone (DMT) system in the presence of both additive white Gaussian noise and impulse noise. Impulse noise is one of the main channel impairments for digital subscriber lines (DSL). One way to combat impulse noise is to detect the presence of the impulses and to declare an erasure when an impulse occurs. In this paper, we propose a coding system based on low-density parity-check (LDPC) codes and bit-interleaved coded modulation that is capable of taking advantage of the knowledge of erasures. We show that by carefully choosing the degree distribution of an irregular LDPC code, both the additive noise and the erasures can be handled by a single code, thus eliminating the need for an outer code. Such a system can perform close to the capacity of the channel and for the same redundancy is signiﬁcantly more immune to the impulse noise than existing methods based on an outer Reed-Solomon (RS) code. The proposed method has a lower implementation complexity than the concatenated coding approach. Special Issue on Advanced Signal Processing for Digital Subscriber Lines 101

Fine-Granularity Loading Schemes Using Adaptive Reed-Solomon Coding for xDSL-DMT Systems Saswat Panigrahi and Tho Le-Ngoc DOI: 10.1155/ASP/2006/65716 While most existing loading algorithms for xDSL-DMT systems strive for the optimal energy distribution to maximize their rate, the amounts of bits loaded to subcarriers are constrained to be integers and the associated granularity losses can represent a significant per- centage of the achievable data rate, especially in the presence of the peak-power constraint. To recover these losses, we propose a fine-granularity loading scheme using joint optimization of adaptive modulation and flexible coding parameters based on programmable Reed- Solomon (RS) codes and bit-error probability criterion. Illustrative examples of applications to VDSL-DMT systems indicate that the proposed scheme can offer a rate increase of about 20% in most cases as compared to various existing integer-bit-loading algorithms. This improvement is in good agreement with the theoretical estimates developed to quantify the granularity loss.

Intra-Symbol Windowing for Egress Reduction in Open Access DMT Transmitters Gert Cuypers, Koen Vanbleu, Geert Ysebaert, and Marc Moonen DOI: 10.1155/ASP/2006/70387 Discrete multitone (DMT) uses an inverse discrete Fourier transform (IDFT) to modulate data on the carriers. The high sidelobes of the IDFT ﬁlter bank used can lead to spurious emissions (egress) in unauthorized frequency bands. Applying a window function within the DMT symbol can alleviate this. However, window functions either require additional redundancy or will introduce distortions that are generally not easy to compensate for. In this paper, a special class of window functions is constructed that corresponds to a precoding at the transmitter. These do not require any additional redundancy and need only a modest amount of additional processing at the receiver. The results can be used to increase the spectral containment of DMT-based wired communications such as ADSL and VDSL (i.e., asymmetric, resp., very-high-bitrate digital subscriber loop).

Designing Tone Reservation PAR Reduction Open Access Niklas Andgart, Per Odling,¨ Albin Johansson, and Per Ola Borjesson¨ DOI: 10.1155/ASP/2006/48789 Tone reservation peak-to-average (PAR) ratio reduction is an established area when it comes to bringing down signal peaks in multicarrier (DMT or OFDM) systems. When designing such a system, some questions often arise about PAR reduction. Is it worth the eﬀort? How much can it give? How much does it give depending on the parameter choices? With this paper, we attempt to answer these questions without resolving to extensive simulations for every system and every parameter choice. From a speciﬁcation of the allowed spectrum, for instance prescribed by a standard, including a PSD-mask and a number of tones, we 102 EURASIP Journal on Applied Signal Processing, Vol. 2006 analytically predict achievable PAR levels, and thus implicitly suggest parameter choices. We use the ADSL2 and ADSL2+ systems as design examples.

Cosine-Modulated Multitone for Very-High-Speed Digital Subscriber Lines Lekun Lin and Behrouz Farhang-Boroujeny DOI: 10.1155/ASP/2006/19329 In this paper, the use of cosine-modulated filter banks (CMFBs) for multicarrier modulation in the application of very-high-speed digital subscriber lines (VDSLs) is studied. We refer to this modulation technique as cosine-modulated multitone (CMT). CMT has the same transmitter structure as discrete wavelet multitone (DWMT). However, the receiver structure in CMT is different from its DWMT counterpart. DWMT uses linear combiner equalizers, which typically have more than 20 taps per subcarrier. CMT, on the other hand, adopts a receiver structure that uses only two taps per subcarrier for equalization. This paper has the following contributions. (i) A modification that reduces the computational complexity of the receiver structure of CMT is proposed. (ii) Although traditionally CMFBs are designed to satisfy perfect-reconstruction (PR) property, in transmultiplexing applications, the presence of channel destroys the PR property of the filter bank, and thus other criteria of filter design should be adopted. We propose one such method. (iii) Through extensive computer simulations, we compare CMT with zipper discrete multitone (z-DMT) and filtered multitone (FMT), the two modulation techniques that have been included in the VDSL draft standard. Comparisons are made in terms of computational complexity, transmission latency, achievable bit rate, and resistance to radio ingress noise. EURASIP Journal on Applied Signal Processing, Volume 2006 © 2006 Hindawi Publishing Corporation

Special Issue on Frames and Overcomplete Representations in Signal Processing, Communications, and Information Theory

Radu V. Balan Siemens Corporate Research, 755 College Road East, Princeton, NJ 08540, USA

Yonina C. Eldar Department of Electrical Engineering, Technion–Israel Institute of Technology, Haifa 32000, Israel

Thomas Strohmer Department of Mathematics, University of California, 1 Shields Avenue, Davis, CA 95616-8633, USA

Many problems in signal processing, communications, and information theory deal with linear signal expansions. The corresponding basis functions are typically orthogonal (nonredundant) signal sets. It is well known that the use of redundancy in engineering systems improves robustness and numerical stability. Motivated by this observation, redundant linear signal expansions (also known as “frames”) have found widespread use in many different engineering disciplines. Recent examples include sampling theory, A/D conversion, oversampled filter banks, pattern classification, multiple description source coding, wavelet-based and frame-based denoising, and space-time coding for wireless communications. This special issue of EURASIP JASP brings together researchers from areas as diverse as harmonic analysis, image processing, and wireless communications by combining invited papers with regular contributions related to these topics. The papers in this issue are broadly classified into four main areas: (1) frame theory, (2) sparse representations, (3) filter banks and sampling, (4) applications. Each area is represented by several papers that sometimes span overlapping territories. The first paper in the category of frame theory, by J. J. Benedetto and J. D. Kolestar, develops methods for constructing Grassmannian frames in 2 and 3 dimensions and reviews many of the prior results on this problem. The existence and properties of chirps over finite groups is the focus of the work of P. G. Casazza and M. C. Fickus. In the next 104 EURASIP Journal on Applied Signal Processing, Vol. 2006 paper, Y. C. Eldar and O. Christensen develop an alternative parametrization of all dual frame sets of a given frame and specialize this description to shift-invariant frames. A. Feuer et al. construct a unified transform to analyze linear time-invariant systems from the viewpoint of frame theory. The paper by S. D. Howard et al. investigates the finite Heisen- berg-Weyl group and its ubiquitous role in radar, communications, and the theory of error- correcting codes. In the final paper in this category, J.-B. Martens surveys the Hermite transform, which can be used for overcomplete representation of signals, treating both theory and applications. The next two papers focus on sparse representations, a topic of intense current research efforts. M. Elad presents uniqueness results regarding sparse signal decompositions in a probabilistic framework. The paper by A. K. Fletcher et al. addresses the problem of denoising by sparse approximation and develops bounds on the mean-squared approximation error, for both deterministic and random dictionaries. Filter banks and sampling theory are the topic of the third group of papers. The first paper in this series, by P. T. Boufounos and A. V. Oppenheim, explores the use of projections onto synthesis frame vectors and the issue of frame-vector ordering. The next paper, by B. Dumitrescu et al., presents an efficient algorithm for designing oversampled modulated filter banks. The paper by H. Johansson and P. Lowenborg¨ studies the problem of reconstruction of band-limited signals from uniform samples and introduces a reconstruction method based on time-varying finite-length discrete-time filters. S. Marinkovic and C. Guillemot consider joint source-channel coding via an oversampled filter bank code and apply their method to a wavelet-based image coding system. C. Siclet et al. present a theoretical analysis of oversampled DFT modulated transmultiplexers and analyze associated design criteria. Finally, the paper by S. Weiss et al. proposes an oversampled filter bank design algorithm for channels with known noise covariance that minimizes the output noise power subject to a normalization constraint. We conclude this special issue by a series of papers focusing on applications of frame theory. The paper by R. Bernardini et al. considers an application of frame expansions to multiple description video coding exploiting the error recovery capabilities of frame expansions. M. M. Hartmann et al. introduce the concept of multipulse multicarrier modulation, a wireless communication scheme that has its roots in multiwindow Gabor systems. The next article by F. Jin et al. proposes a new denoising method in which motion estimation and compensation, as well as temporal and spatial filtering, are all done in the wavelet domain. Another interesting application area is psychoacoustic analysis. In this context, the paper by R. B. Reilly proposes a tone-frequency linear representation of acoustic data designed specifically to accommodate the nonlinear phenomenon of beats. The next two papers by K. Skretting and J. H. Husøy and by J. E. Vila-Forcen´ et al. make use of overcomplete dictionaries to select an optimum representation: the texture classifier in the first paper uses sparse linear representations in a supervised learning fashion, whereas the facial image encoder in the second paper uses the edge process model to achieve higher compression rates. In the final paper of this special issue, Y. Sriraja and T. Karp propose a SPIHT algorithm which incorporates a new interpolation scheme able to partially recover lost data.

Acknowledgments We would like to thank all our colleagues who have contributed to this special issue, including the authors of submitted papers. We also thank the reviewers for their quality work, Dr. Special Issue on Frames and Overcomplete Representations in Signal Processing, . . . 105

Helmut Bolcskei¨ for inviting us to edit this special issue, and ﬁnally Dr. Marc Moonen and the Editorial Board; without their support this special issue would not have been possible.

Radu V. Balan Yonina C. Eldar Thomas Strohmer 106 EURASIP Journal on Applied Signal Processing, Vol. 2006 Volume 2006, No. 7 Contents and Abstracts

Geometric Properties of Grassmannian Frames for R2 and R3 John J. Benedetto and Joseph D. Kolesar DOI: 10.1155/ASP/2006/49850 Grassmannian frames are frames satisfying a min-max correlation criterion. We translate a geometrically intuitive approach for two- and three-dimensional Euclidean space (R2 and R3) into a new analytic method which is used to classify many Grassmannian frames in this setting. The method and associated algorithm decrease the maximum frame correlation, and hence give rise to the construction of speciﬁc examples of Grassmannian frames. Many of the results are known by other techniques, and even more generally, so that this paper can be viewed as tutorial. However, our analytic method is presented with the goal of developing it to address unresovled problems in d-dimensional Hilbert spaces which serve as a setting for spherical codes, erasure channel modeling, and other aspects of communications theory.

Fourier Transforms of Finite Chirps Peter G. Casazza and Matthew Fickus DOI: 10.1155/ASP/2006/70204 Chirps arise in many signal processing applications. While chirps have been extensively studied as functions over both the real line and the integers, less attention has been paid to the study of chirps over finite groups. We study the existence and properties of chirps over finite cyclic groups of integers. In particular, we introduce a new definition of a finite chirp which is slightly more general than those that have been previously used. We explicitly compute the discrete Fourier transforms of these chirps, yielding results that are number- theoretic in nature. As a consequence of these results, we determine the degree to which the elements of certain finite tight frames are well distributed.

Characterization of Oblique Dual Frame Pairs Yonina C. Eldar and Ole Christensen DOI: 10.1155/ASP/2006/92674 Given a frame for a subspace ᐃ of a Hilbert space Ᏼ, we consider all possible families of oblique dual frame vectors on an appropriately chosen subspace ᐂ. In place of the standard description, which involves computing the pseudoinverse of the frame operator, we develop an alternative characterization which in some cases can be computationally more efficient. We first treat the case of a general frame on an arbitrary Hilbert space, and then specialize the results to shift-invariant frames with multiple generators. In particular, we present explicit versions of our general conditions for the case of shift-invariant spaces with a single generator. The theory is also adapted to the standard frame setting in which the original and dual frames are defined on the same space. Special Issue on Frames and Overcomplete Representations in Signal Processing, . . . 107

A Unified Transform for LTI Systems–Presented as a (Generalized) Frame Arie Feuer, Paul M. J. Van den Hof, and Peter S. C. Heuberger DOI: 10.1155/ASP/2006/91604 We present a set of functions in L2([0,∞)) and show it to be a (tight) generalized frame (as presented by G. Kaiser (1994)). The analysis side of the frame operation is called the continuous unified transform. We show that some of the well-known transforms (such as Laplace, Laguerre, Kautz, and Hambo) result by creating different sampling patterns in the transform domain (or, equivalently, choosing a number of subsets of the original frame). Some of these resulting sets turn out to be generalized (tight) frames as well. The work reported here enhances the understanding of the interrelationships between the above-mentioned transforms. Furthermore, the impulse response of every stable finite-dimensional LTI system has a finite representation using the frame we introduce here, with obvious benefits in identification problems.

The Finite Heisenberg-Weyl Groups in Radar and Open Access Communications S. D. Howard, A. R. Calderbank, and W. Moran DOI: 10.1155/ASP/2006/85685 We investigate the theory of the finite Heisenberg-Weyl group in relation to the development of adaptive radar and to the construction of spreading sequences and error-correcting codes in communications. We contend that this group can form the basis for the representation of the radar environment in terms of operators on the space of waveforms. We also demonstrate, following recent developments in the theory of error-correcting codes, that the finite Heisenberg-Weyl groups provide a unified basis for the construction of useful waveforms/sequences for radar, communications, and the theory of error-correcting codes.

The Hermite Transform: A Survey Jean-Bernard Martens DOI: 10.1155/ASP/2006/26145 With this survey on the Hermite transformation we want to pursue the following two goals. First, we want to provide a comprehensive and up-to-date description of the Hermite transformation, its underlying philosophy, and its most important properties and their implications for applications. As so often when publications and development go hand-in-hand, new insights have led to changes in or generalizations of already published results, and not all of these changes have been considered sufficiently substantial to be published separately. As a consequence, the existing publications on the Hermite transformation do not fully reflect our most recent insights, and the current paper intends to remedy this. Second, we also want to share some new results. Two specific new results, that is, partial signal decompositions and intersection curvatures, are therefore treated in more detail than other aspects. 108 EURASIP Journal on Applied Signal Processing, Vol. 2006

Sparse Representations Are Most Likely to Be the Sparsest Possible Michael Elad DOI: 10.1155/ASP/2006/96247 Given a signal S ∈ ᏾N and a full-rank matrix D ∈ ᏾N×L with N

Denoising by Sparse Approximation: Error Bounds Open Access Based on Rate-Distortion Theory Alyson K. Fletcher, Sundeep Rangan, Vivek K. Goyal, and Kannan Ramchandran DOI: 10.1155/ASP/2006/26318 If a signal x is known to have a sparse representation with respect to a frame, it can be estimated from a noise-corrupted observation y by finding the best sparse approximation to y. Removing noise in this manner depends on the frame efficiently representing the signal while it inefficiently represents the noise. The mean-squared error (MSE) of this denoising scheme and the probability that the estimate has the same sparsity pattern as the original signal are analyzed. First an MSE bound that depends on a new bound on ap- proximating a Gaussian signal as a linear combination of elements of an overcomplete dictionary is given. Further analyses are for dictionaries generated randomly according to a spherically-symmetric distribution and signals expressible with single dictionary elements. Easily-computed approximations for the probability of selecting the correct dictionary element and the MSE are given. Asymptotic expressions reveal a critical input signal-to-noise ratio for signal recovery.

Quantization Noise Shaping on Arbitrary Open Access Frame Expansions Petros T. Boufounos and Alan V. Oppenheim DOI: 10.1155/ASP/2006/53807 Quantization noise shaping is commonly used in oversampled A/D and D/A converters with uniform sampling. This paper considers quantization noise shaping for arbitrary finite Special Issue on Frames and Overcomplete Representations in Signal Processing, . . . 109 frame expansions based on generalizing the view of first-order classical oversampled noise shaping as a compensation of the quantization error through projections. Two levels of generalization are developed, one a special case of the other, and two different cost models are proposed to evaluate the quantizer structures. Within our framework, the synthesis frame vectors are assumed given, and the computational complexity is in the initial determination of frame vector ordering, carried out off-line as part of the quantizer design. We consider the extension of the results to infinite shift-invariant frames and consider in particular filtering and oversampled filter banks.

Simplified Design of Low-Delay Oversampled NPR GDFT Filterbanks Bogdan Dumitrescu, Robert Bregovic,´ and Tapio Saramaki¨ DOI: 10.1155/ASP/2006/42961 We propose an efficient algorithm for designing the prototype filters of oversampled, near- perfect reconstruction (NPR), GDFT modulated filterbanks (FB) with arbitrary delay. We describe simplified conditions for imposing NPR, posed on the frequency response of the distortion transfer function and on the stopband attenuation of the prototype filters. Given the analysis prototype, we show that the minimization of the stopband energy of the synthesis prototype, subject to the simplified NPR constraints, can be expressed as a convex optimization problem. Our algorithm consists of initialization with the prototype of a near- orthogonal FB—which can also be designed via convex optimization—and then successive optimization of the synthesis and analysis prototypes. We give design examples, discuss the properties of the obtained FBs, and present synthetic echo control experiments. The presented results show that, for a given delay, our algorithm produces FBs with significantly better properties than the near-orthogonal FBs.

Reconstruction of Nonuniformly Sampled Bandlimited Signals by Means of Time-Varying Discrete-Time FIR Filters Hakan˚ Johansson and Per Lowenborg¨ DOI: 10.1155/ASP/2006/64185 This paper deals with reconstruction of nonuniformly sampled bandlimited continuous- time signals using time-varying discrete-time finite-length impulse response (FIR) filters. The main theme of the paper is to show how a slight oversampling should be utilized for designing the reconstruction filters in a proper manner. Based on a time-frequency function, it is shown that the reconstruction problem can be posed as one that resembles an ordinary filter design problem, both for deterministic signals and random processes. From this fact, an analytic least-square design technique is then derived. Furthermore, for an important special case, corresponding to periodic nonuniform sampling, it is shown that the reconstruction problem alternatively can be posed as a filter bank design problem, thus with requirements on a distortion transfer function and a number of aliasing transfer functions. This eases the design and offers alternative practical design methods as discussed in the paper. Several design examples are included that illustrate the benefits of the proposed design techniques over previously existing techniques. 110 EURASIP Journal on Applied Signal Processing, Vol. 2006

Joint Source-Channel Coding by Means of newline an Oversampled Filter Bank Code Slavica Marinkovic and Christine Guillemot DOI: 10.1155/ASP/2006/82023 Quantized frame expansions based on block transforms and oversampled filter banks (OFBs) have been considered recently as joint source-channel codes (JSCCs) for erasure and error-resilient signal transmission over noisy channels. In this paper, we consider a coding chain involving an OFB-based signal decomposition followed by scalar quantization and a variable-length code (VLC) or a fixed-length code (FLC). This paper first examines the problem of channel error localization and correction in quantized OFB signal expansions. The error localization problem is treated as an M-ary hypothesis testing problem. The likelihood values are derived from the joint pdf of the syndrome vectors under various hypotheses of impulse noise positions, and in a number of consecutive windows of the received samples. The error amplitudes are then estimated by solving the syndrome equations in the least-square sense. The message signal is reconstructed from the corrected received signal by a pseudoinverse receiver. We then improve the error localization procedure by introducing a per-symbol reliability information in the hypothesis testing procedure of the OFB syndrome decoder. The per-symbol reliability information is produced by the soft- input soft-output (SISO) VLC/FLC decoders. This leads to the design of an iterative algorithm for joint decoding of an FLC and an OFB code. The performance of the algorithms developed is evaluated in a wavelet-based image coding system.

Perfect Reconstruction Conditions and Design of Open Access Oversampled DFT-Modulated Transmultiplexers Cyrille Siclet, Pierre Siohan, and Didier Pinchon DOI: 10.1155/ASP/2006/15756 This paper presents a theoretical analysis of oversampled complex modulated transmultiplexers. The perfect reconstruction (PR) conditions are established in the polyphase domain for a pair of biorthogonal prototype filters. A decomposition theorem is proposed that allows it to split the initial system of PR equations, that can be huge, into small independent subsystems of equations. In the orthogonal case, it is shown that these subsystems can be solved thanks to an appropriate angular parametrization. This parametrization is efficiently exploited afterwards, using the compact representation we recently introduced for critically decimated modulated filter banks. Two design criteria, the out-of-band energy minimization and the time-frequency localization maximization, are examined. It is shown, with various design examples, that this approach allows the design of oversampled modulated transmultiplexers, or filter banks with a thousand carriers, or subbands, for rational oversampling ratios corresponding to low redundancies. Some simulation results, obtained for a transmission over a flat fading channel, also show that, compared to the conventional OFDM, these designs may reduce the mean square error. Special Issue on Frames and Overcomplete Representations in Signal Processing, . . . 111

Paraunitary Oversampled Filter Bank Design for Channel Coding Stephan Weiss, Soydan Redif, Tom Cooper, Chunguang Liu, Paul D. Baxter, and John G. McWhirter DOI: 10.1155/ASP/2006/31346 Oversampled filter banks (OSFBs) have been considered for channel coding, since their redundancy can be utilised to permit the detection and correction of channel errors. In this paper, we propose an OSFB-based channel coder for a correlated additive Gaussian noise channel, of which the noise covariance matrix is assumed to be known. Based on a suitable factorisation of this matrix, we develop a design for the decoder’s synthesis filter bank in order to minimise the noise power in the decoded signal, subject to admitting perfect reconstruction through paraunitarity of the filter bank. We demonstrate that this approach can lead to a significant reduction of the noise interference by exploiting both the correlation of the channel and the redundancy of the filter banks. Simulation results providing some insight into these mechanisms are provided.

Frame-Based Multiple-Description Video Coding with Extended Orthogonal Filter Banks R. Bernardini, M. Durigon, R. Rinaldo, A. Vitali, and P.Zontone DOI: 10.1155/ASP/2006/53623 We propose a frame-based multiple-description video coder. The analysis filter bank is the extension of an orthogonal filter bank which computes the spatial polyphase components of the original video frames. The output of the filter bank is a set of video sequences which can be compressed with a standard coder. The filter bank design is carried out by taking into account two important requirements for video coding, namely, the fact that the dual synthesis filter bank is FIR, and that loss recovery does not enhance the quantization error. We give explicit results about the required properties of the redundant channel filter and the reconstruction error bounds in case of packet errors. We show that the proposed scheme hasgooderrorrobustnesstolossesandgoodperformance,bothintermsofobjectiveand visual quality, when compared to single description and other multiple description video coders based on spatial subsampling. PSNR gains of 5 dB or more are typical for packet loss probability as low as 5%.

Wireless Multicarrier Communications via Multipulse Gabor Riesz Bases Manfred M. Hartmann, Gerald Matz, and Dieter Schafhuber DOI: 10.1155/ASP/2006/23818 We introduce multipulse multicarrier (MPMC) modulation, a wireless communication scheme that augments traditional single-pulse multicarrier systems by using multiple pulses at the transmitter and the receiver. The mathematical foundation of MPMC systems is established by the novel concept of multipulse Gabor Riesz bases.WeadaptZak-Fourier domain tools previously developed for multiwindow Gabor frames to analyze and design 112 EURASIP Journal on Applied Signal Processing, Vol. 2006

(bi)orthogonal multipulse Gabor Riesz bases and the corresponding MPMC systems in a computationally efficient manner. Furthermore, explicit expressions for the interference power and the spectral efficiency in MPMC transmissions over time-varying multipath channels are derived. The superiority of MPMC modulation over single-pulse multicarrier systems is finally demonstrated via numerical simulations.

Wavelet Video Denoising with Regularized Open Access Multiresolution Motion Estimation Fu Jin, Paul Fieguth, and Lowell Winger DOI: 10.1155/ASP/2006/72705 This paper develops a new approach to video denoising, in which motion estimation/compensation, temporal filtering, and spatial smoothing are all undertaken in the wavelet domain. The key to making this possible is the use of a shift-invariant, overcomplete wavelet transform, which allows motion between image frames to be manifested as an equivalent motion of coefficients in the wavelet domain. Our focus is on minimizing spatial blurring, restricting to temporal filtering when motion estimates are reliable, and spatially shrinking only insignificant coefficients when the motion is unreliable. Tests on standard video sequences show that our results yield comparable PSNR to the state of the art in the literature, but with considerably improved preservation of fine spatial details.

An Overcomplete Signal Basis Approach to Nonlinear Time-Tone Analysis with Application to Audio and Speech Processing Richard B. Reilly DOI: 10.1155/ASP/2006/65431 Although a beating tone and the two pure tones which give rise to it are linearly dependent, the ear considers them to be independent as tone sensations. A linear time-frequency representation of acoustic data is unable to model these phenomena. A time-tone sensation approach is proposed for inclusion within audio analysis systems. The proposed approach extends linear time-frequency analysis of acoustic data, by accommodating the nonlinear phenomenon of beats. The method replaces the one-dimensional tonotopic axis of linear time-frequency analysis with a two-dimensional tonotopic plane, in which one direction corresponds to tone, and the other to its frequency of modulation. Some applications to audio prostheses are discussed. The proposed method relies on an intuitive criterion of optimal representation which can be applied to any overcomplete signal basis, allowing for many signal processing applications.

Texture Classification Using Sparse Frame-Based Representations Karl Skretting and John Hakon˚ Husøy DOI: 10.1155/ASP/2006/52561 A new method for supervised texture classification, denoted by frame texture classification method (FTCM), is proposed. The method is based on a deterministic texture model in Special Issue on Frames and Overcomplete Representations in Signal Processing, . . . 113 which a small image block, taken from a texture region, is modeled as a sparse linear combination of frame elements. FTCM has two phases. In the design phase a frame is trained for each texture class based on given texture example images. The design method is an iterative procedure in which the representation error, given a sparseness constraint, is minimized. In the classification phase each pixel in a test image is labeled by analyzing its spatial neighbor- hood. This block is represented by each of the frames designed for the texture classes under consideration, and the frame giving the best representation gives the class. The FTCM is applied to nine test images of natural textures commonly used in other texture classification work, yielding excellent overall performance.

Facial Image Compression Based on Structured Codebooks in Overcomplete Domain J. E. Vila-Forcen,´ S. Voloshynovskiy, O. Koval, and T. Pun DOI: 10.1155/ASP/2006/69042 We advocate facial image compression technique in the scope of distributed source coding framework. The novelty of the proposed approach is twofold: image compression is considered from the position of source coding with side information and, contrarily to the existing scenarios where the side information is given explicitly; the side information is created based on a deterministic approximation of the local image features. We consider an image in the overcomplete transform domain as a realization of a random source with a structured codebook of symbols where each symbol represents a particular edge shape. Due to the partial availability of the side information at both encoder and decoder, we treat our problem as a modiﬁcation of the Berger-Flynn-Gray problem and investigate a possible gain over the solutions when side information is either unavailable or available at the decoder. Finally, the paper presents a practical image compression algorithm for facial images based on our concept that demonstrates the superior performance in the very-low-bit-rate regime.

A Packetized SPIHT Algorithm with Overcomplete Open Access Wavelet Coefficients for Increased Robustness Y. Sriraja and Tanja Karp DOI: 10.1155/ASP/2006/19156 This paper presents a wavelet-based image encoding scheme with error resilience and error concealment suitable for transmission over networks prone to packet losses. The scheme involves partitioning the data into independent descriptions of roughly equal lengths, achieved by a combination of packetization and modifications to the wavelet tree structure without additional redundancy. With a weighted-averaging-based interpolation method, our proposed encoding scheme attains an improvement of about 0.5–1.5 dB in PSNR over other similar methods. We also investigate the use of overcomplete wavelet transform coefficients as side information for our encoding scheme to improve the error resilience when severe packet losses occur. Experiments show that we are able to achieve a high coding performance along with a good perceptual quality for the reconstructed image. EURASIP Journal on Applied Signal Processing, Volume 2006 © 2006 Hindawi Publishing Corporation

Special Issue on Radar Space-Time Adaptive Processing

Fabian D. Lapierre Department of Electrical Engineering, Royal Military Academy, 1000 Brussels, Belgium

Jacques G. Verly Department of Electrical Engineering and Computer Science, University of Li`ege, 4000 Li`ege, Belgium Braham Himed Air Force Research Laboratory, Rome, NY 13441, USA

Richard Klemm FGAN-FFM, 53343 Wachtberg, Germany

Marc Lesturgie ONERA/DEMR, 91761 Palaiseau, France

Space-time adaptive processing (STAP) is a signal processing technique that was originally developed for detecting slow-moving targets using airborne radars. The general principle of STAP is as follows. The radar transmits a train of M coherent pulses. The echoes from potential targets (and clutter) are collected at each of the N elements of an antenna array. Separate receiver chains are attached to each of the array elements. The received signals are sampled at a series of L successive ranges (i.e., distances) also referred to as range gates. STAP processing is applied to the M × N matrix of samples collected at each such range. This matrix is typically called a snapshot. The ensemble of snapshots at all successive ranges is referred to as a data cube and contains all the information available for target detection within a coherent processing interval (CPI). If the radar transmitter and receiver are located on the same platform (airplane or satellite), the configuration is called a monostatic configuration. If not, the term “bistatic” is used. In bistatic configurations, the carrying platforms are not only distinct, but they can also move independently. Although the general principles of STAP have been known since at least the 1980’s, the field has seen a major regain of interest in the 1990’s, mainly as a result of the significant increase in computational power. Much of the 1990’s focused on three major topics of interest. The first is the application of STAP to monostatic radar platforms. The second is the design of computationally efficient adaptive methods (suboptimum methods) to reduce the computational load of the STAP processor. The third is the design of methods to mitigate Special Issue on Radar Space-Time Adaptive Processing 115 barrage jammers. Throughout this period of time, investigators focused almost exclusively on uniform linear arrays (ULAs), where the elements are on a line and uniformly spaced. More recently, much of the attention in STAP has shifted to a new series of issues, which are now briefly described. (1) There is significant interest in bistatic configurations for the simple reason that they allow the receiving platform to remain covert during operation. (2) Researchers are considering arrays that go beyond ULAs, such as arbitrary 3D antenna arrays. One particular case of three-dimensional (3D) array is the conformal antenna array (CAA) that follows the surface of the carrying platform, such as the fuselage of an airplane or the side of a balloon. (3) There is a growing need for STAP to perform well in heterogeneous environments. This problem refers to the lack of (wide-sense) stationarity of the received signals with respect to range. Stationarity tends to disappear in bistatic configurations or when antennas other than ULAs are used. Once the hypothesis of stationarity is no longer verified, conventional covariance estimation methods can no longer be used. Stationarity also tends to disappear when terrain deviates from being flat with uniform reflectivity properties and in the presence of internal clutter motion such as tree leaves moving in the wind. (4) The problems just mentioned have given rise to methods known as knowledge-aided STAP, which attempt to remove as much of the heterogeneity from the snapshots prior to using conventional estimation methods. This is done by using a priori knowledge, typically stored in databases. Knowledge-aided STAP falls in the general domain of knowledge-aided signal processing. (5) Finally, STAP techniques are currently moving into new areas such as sonar and telecommunications, and also in new application areas such as the detection of plastic landmines. The goal of this special issue is to discuss the state of the art in radar STAP techniques (suboptimal, bistatic, etc.) and to explain why STAP techniques are also proving useful in domains that were probably not initially anticipated.

Cancellation of barrage jammers Jamming remains a significant problem in monostatic STAP. This is particularly true of barrage jammers, which emit jamming signals with very wide bandwidths. In monostatic configurations, the receiver is colocated with the transmitter and is thus easily located and jammed. In the present discussion, only a single jammer is considered for simplicity. Classical jammer suppression techniques use spatially adaptive processing to remove the jamming signal from the received signal. In other words, no processing is done along the time dimension, whether fast-time or slow-time. This technique is effective as long as the target and jammer are sufficiently separated in angle and do not both fall within the mainbeam of the receive antenna. In the limit, when the target and jammer are aligned, the spatially adaptive processor cannot cancel the jammer. An emerging class of space-time processing techniques, which may be referred to as space fast-time adaptive processing, can overcome this problem by processing in the fast- time dimension. Fast-time processing differs from more traditional slow-time processing in the following way. If a train of pulses is transmitted, one can process simultaneously the echoes from all these pulses at a particular range. This is slow-time processing. In fast-time 116 EURASIP Journal on Applied Signal Processing, Vol. 2006 processing, one processes simultaneously the echoes corresponding to each particular pulse and to several ranges, typically located in the vicinity of the range being interrogated. The combination of space processing with slow-time or fast-time processing leads to space slow- time processing and to space fast-time processing, respectively. Successful fast-time processing is contingent upon the availability of coherent multipath in the form of terrain-scattered interference (TSI). The paper by Y. Seliktar, D. B. Williams, and E. J. Holder presents a method for space fast-time monopulse processing that can provide better estimation of the jammer’s angle than classical spatially adaptive monopulse can. This method also exploits the presence of TSI. The capabilities of the method are illustrated using the mountaintop data, which contains one jammer as well as TSI. The approach is shown to perform significantly better than conventional monopulse and spatially adaptive monopulse. The paper by D. Madurasinghe and A. P. Shaw addresses the computational complexity of a space fast-time adaptive processor that uses the TSI to cancel barrage jammers. Recall that, in fast-time processing, one piles up a large number of echoes coming from different ranges. Since there is typically a large number of ranges and since the time interval between two consecutive echoes is very short, it becomes virtually impossible to process this large amount of data in real-time. This problem is solved by introducing a preprocessor that allows the STAP processor to select only two desired range returns to form the space fast-time snapshot. The main contribution of the paper is the design of a new space fast-time adaptive processor relying on (eigenvector-based) super-resolution, which also has the feature of being extremely fast.

Knowledge-aided processing In a classical STAP processor, the presence of heterogeneities arising from the use of an arbitrary antenna array and the presence of internal clutter motion (ICM), can lead to severe performance degradation. The goal of the knowledge-aided sensor signal processing and expert reasoning (KASSPER) program, initiated by the Defense Advanced Research Projects Agency (DARPA), is to develop new robust techniques that are able to detect and track targets that are either stationary or moving in the presence of heterogeneities. This is typically achieved by providing auxiliary information, such as digital elevation models (DEMs), clutter reflectivity maps, and GPS positions, to the detection and tracking systems. The paper by J. S. Bergin and P. M. Techau explores signal processing techniques based on a mix of ground moving target indicator (GMTI) processing and synthetic aperture radar (SAR) processing. Whereas STAP aims at detecting slow-moving targets using a short CPI, SAR aims at detecting stationary targets with long CPIs. The authors focus here on STAP implementations using long GMTI CPIs as well as SAR-like processing strategies for detecting targets that move very slowly. SAR data is then used as an aid to improve target detection. The processing technique proposed includes SAR-derived knowledge-aided constraints to improve detection performance in an environment that includes large discrete scatterers, which are responsible for increased false alarm rates. The SAR imagery is, for example, used to locate strong clutter discretes. The paper by D. Page and G. Owirka describes knowledge-aided STAP (KA-STAP) techniques that use data corresponding to several independent CPIs. This can prove useful in surveillance scenarios where the ground may contribute returns extending over multiple CPIs. The paper shows how data coming from multiple CPIs can be used to enhance the Special Issue on Radar Space-Time Adaptive Processing 117 detection performance of the STAP processor. This data is used to enhance the accuracy of the estimated clutter reflectivity maps and, thus, to provide improved knowledge about clutter statistics in nonhomogeneous terrain environments. These maps are estimated using the data recorded over multiple CPIs, DEMs, and geo-registration of the clutter scatterers. This registration is needed since the position of the moving platform varies from one CPI to the next. The reflectivity maps are used to predict the clutter covariance matrices as a function of range. The techniques of covariance tapering, adaptive estimation of gain and phase corrections, knowledge-aided prewhitening, and eigenvalue scaling are also exploited to estimate the space-time filter needed to reject colored interference. This filter cannot handle clutter discretes, but a technique for suppressing large discrete returns is proposed in the paper. Simulation results show that, compared to standard STAP processing, the proposed method leads to more than an order of magnitude in false alarm rate reduction.

Landmine detection One approach for detecting buried plastic landmines is to use quadrupole resonance (QR) based techniques. However, the frequency of the emitted QR signal is located within the AM radio frequency band. The received signal may thus be corrupted by strong radio-frequency interference (RFI). The challenge is to mitigate the RFI in the received signal to be able to extract the very weak signal characterizing the landmine. If the signal is received by an antenna array, the spatial correlation of the signal can be used to improve the rejection of these RFIs. However, just exploiting the spatial correlation does not lead to a good detection probability. At ﬁrst sight, it may come as a surprise that STAP could help in this application, since STAP is typically used to detect slow-moving targets, whereas landmines are typically not moving. The connection is the following. It turns out that the temporal variations of the QR echoes from pulse to pulse is a signature of the chemical present inside the mines, such as trinitrotoluene (TNT) and royal demolition explosive (RDX). The QR echoes are thus both spatially and temporally correlated. Therefore, STAP processing should help reject the RFIs by exploiting these correlations. The paper by G. Liu, Y. Jiang, H. Xiong, J. Li, and G. A. Barrall exploits the spatiotemporal correlation of the RFIs to improve the detection of TNT, which leads to a better landmine detection performance. The authors propose three distinct detection methods, which are later combined. The ﬁrst method exploits only the spatial correlation of the RFIs by using an antenna array. A maximum-likelihood (ML) estimator and a constant false alarm rate (CFAR) detector for TNT detection are also proposed. The second method adopts a multichannel autoregressive (MAR) model to take into account the temporal correlation of the RFIs and leads to a detector based on this model. The third method improves RFI mitigation by using a two-dimensional robust Capon beamformer (RCB) together with an ML estimator. Finally, the three methods are exploited jointly to improve detection performance. Experiments using real data demonstrate the soundness of the proposed RFI mitigation methods and of the combined approach. Fabian D. Lapierre Jacques G. Verly Braham Himed Richard Klemm Marc Lesturgie 118 EURASIP Journal on Applied Signal Processing, Vol. 2006 Volume 2006, No. 8 Contents and Abstracts

A Space/Fast-Time Adaptive Monopulse Technique Yaron Seliktar, Douglas B. Williams, and E. Jeff Holder DOI: 10.1155/ASP/2006/14510 Mainbeam jamming poses a particularly diﬃcult challenge for conventional monopulse radars. In such cases spatially adaptive processing provides some interference suppression when the target and jammer are not exactly coaligned. However, as the target angle approaches that of the jammer, mitigation performance is increasingly hampered and distortions are introduced into the resulting beam pattern. Both of these factors limit the reliability of a spatially adaptive monopulse processor. The presence of coherent multipath in the form of terrain-scattered interference (TSI), although normally considered a nuisance, can be exploited to suppress mainbeam jamming with space/fast-time processing. A method is presented oﬀering space/fast-time monopulse processing with distortionless spatial array patterns that can achieve improved angle estimation over spatially adaptive monopulse. Performance results for the monopulse processor are obtained for mountaintop data containing a jammer and TSI, which demonstrate a dramatic improvement in performance over conventional monopulse and spatially adaptive monopulse.

Mainlobe Jammer Nulling via TSI Finders: Open Access A Space Fast-time Adaptive Processor Dan Madurasinghe and Andrew P.Shaw DOI: 10.1155/ASP/2006/48789 An algorithm based on a space fast-time adaptive processor is presented for nulling the mainlobe jammer when the jammer and the target of interest share the same bearing. The computational load involved in the conventional processor, which blindly looks for the terrain-scattered interference (TSI), is required to stack a large number of consecutive range cell returns to form the space fast-time data snapshot making it almost impossible to implement in real time. This issue is resolved via the introduction of a preprocessor (a TSI ﬁnder which detects the presence of the minute levels of multipath components of the mainlobe jammer and associated time delays) which directs the STAP processor to select only two desired range returns in order to form the space fast-time data snapshot. The end result is a computationally extremely fast processor. Also a new space fast-time adaptive processor based on the super-resolution approach (eigenvector-based) is presented. Special Issue on Radar Space-Time Adaptive Processing 119

Multiresolution Signal Processing Techniques for Ground Moving Target Detection Using Open Access Airborne Radar Jameson S. Bergin and Paul M. Techau DOI: 10.1155/ASP/2006/47534 Synthetic aperture radar (SAR) exploits very high spatial resolution via temporal integration and ownship motion to reduce the background clutter power in a given resolution cell to allow detection of nonmoving targets. Ground moving target indicator (GMTI) radar, on the other hand, employs much lower-resolution processing but exploits relative diﬀerences in the space-time response between moving targets and clutter for detection. Therefore, SAR and GMTI represent two diﬀerent temporal processing resolution scales which have typically been optimized and demonstrated independently to work well for detecting either stationary (in the case of SAR) or exo-clutter (in the case of GMTI) targets. Based on this multiresolution interpretation of airborne radar data processing, there appears to be an opportunity to develop detection techniques that attempt to optimize the signal processing resolution scale (e.g., length of temporal integration) to match the dynamics of a target of interest. This paper investigates signal processing techniques that exploit long CPIs to improve the detection performance of very slow-moving targets.

Knowledge-Aided STAP Processing for Ground Moving Target Indication Radar Using Open Access Multilook Data Douglas Page and Gregory Owirka DOI: 10.1155/ASP/2006/74838 Knowledge-aided space-time adaptive processing (KASTAP) using multiple coherent processing interval (CPI) radar data is described. The approach is based on forming earth- based clutter reﬂectivity maps to provide improved knowledge of clutter statistics in nonhomogeneous terrain environments. The maps are utilized to calculate predicted clutter covariance matrices as a function of range. Using a data set provided under the DARPA knowledge-aided sensor signal processing and expert reasoning (KASSPER) Program, predicted distributed clutter statistics are compared to measured statistics to verify the accuracy of the approach. Robust STAP weight vectors are calculated using a technique that combines covariance tapering, adaptive estimation of gain and phase corrections, knowledge- aided prewhitening, and eigenvalue rescaling. Techniques to suppress large discrete returns, expected in urban areas, are also described. Several performance metrics are presented, including signal-to-interference-plus-noise ratio (SINR) loss, target detections and false alarms, receiver operating characteristic (ROC) curves, and tracking performance. The results show more than an order of magnitude reduction in false alarm density when compared to standard STAP processing. 120 EURASIP Journal on Applied Signal Processing, Vol. 2006

Radio Frequency Interference Suppression for Landmine Detection by Quadrupole Resonance Guoqing Liu, Yi Jiang, Hong Xiong, Jian Li, and Geoffrey A. Barrall DOI: 10.1155/ASP/2006/29890 The quadrupole resonance (QR) technology can be used as a conﬁrming sensor for buried plastic landmine detection by detecting the explosives within the mine. We focus herein on the detection of TNT mines via the QR sensor. Since the frequency of the QR signal is located within the AM radio frequency band, the QR signal can be corrupted by strong radio frequency interferences (RFIs). Hence to detect the very weak QR signal, RFI mitigation is essential. Reference antennas, which receive RFIs only, can be used together with the main antenna, which receives both the QR signal and the RFIs, for RFI mitigation. The RFIs are usually colored both spatially and temporally, and hence exploiting only the spatial diversity of the antenna array may not give the best performance. We exploit herein both the spatial and temporal correlations of the RFIs to improve the TNT detection performance. EURASIP Journal on Applied Signal Processing, Volume 2006 © 2006 Hindawi Publishing Corporation

Special Issue on Super-Resolution Imaging: Analysis, Algorithms, and Applications

Michael Ng Department of Mathematics, Hong Kong Baptist University, Kowloon Tong, Hong Kong

Tony Chan Department of Mathematics, University of California, Los Angeles, CA 90095-1555, USA

Moon Gi Kang Department of Electrical and Electronic Engineering, Yonsei University, Seoul 120-749, Korea

Peyman Milanfar Department of Electrical Engineering, University of California, Santa Cruz, CA 95064, USA

The recent increase in the widespread use of digital imaging technologies in consumer (e.g., digital video) and other markets (e.g., security and military) has brought with it a simultaneous demand for higher-resolution (HR) images. The demand for such images can be partially met by algorithmic advances in super-resolution (SR) technology in addition to hardware development. Such HR images not only give the viewer a more pleasing picture but also oﬀer additional details that are important for subsequent analysis in many applications. The current hardware approach to obtain HR images mainly relies on sensor manufac- turing technology that attempts to increase the number of pixels per unit area by reducing the pixel size. However, the cost for high-precision optics and sensors may be prohibitive for general purpose commercial applications, and there is a limitation to pixel size reduction due to shot noise encountered in the sensor itself. Therefore, a resolution enhancement (SR) approach using computational, mathematical, and statistical techniques has received a great deal of attention recently. The relevant signal processing technology for this SR approach to high-quality imaging is the topic of this special issue. The scope of techniques intended to overcome the above limitations that will be covered in this special issue will include enhancement in spatial resolution for both gray-scale and color images and video, suppression of signal-dependent noise, and various other associated artifacts. Because of the recent emergence of many key-relevant computational, mathematical, and statistical techniques, and the increasing importance of digital imaging technology, a special issue of the EURASIP JASP dedicated to the topic of SR imaging is quite timely. 122 EURASIP Journal on Applied Signal Processing, Vol. 2006

This special issue contains sixteen articles. The ﬁrst seven articles by M. Vega et al., M.-C. Pan, S. Farsiu et al., G. M. Callico et al., B.-W. Jeon et al., N. K. Bose et al., and T. Q. Pham et al.are on the computational, mathematical and statistical techniques for SR imaging. The next three articles by P. Vandewalle et al., M. Trimeche et al., and M. Balci and H. Foroosh are on the subject of subpixel registration of low-resolution images in image reconstruction. The next four articles by C. V. Jiji and S. Chaudhuri, S. Rajaram et al., F. Humblot and A. Mohammad-Djafari, and T. A. Stephenson and T. Chen are on applying diﬀerent learning techniques in the SR image reconstruction. The last part with two articles by S. Zhang and X. Li is about the application of SR reconstruction techniques in optical systems. The Guest Editors thank all the authors who have contributed to this special issue. Spe- cial thanks are also due to the reviewers for their constructive suggestions and comments following their evaluation of the articles. The Guest Editors are indebted to the Editorial Board of EURASIP JASP for providing this opportunity to edit this special issue.

Michael Ng Tony Chan Moon Gi Kang Peyman Milanfar Special Issue on Super-Resolution Imaging: Analysis, Algorithms, and Applications 123 Volume 2006, No. 10 Contents and Abstracts

A Bayesian Super-Resolution Approach to Demosaicing of Blurred Images Miguel Vega, Rafael Molina, and Aggelos K. Katsaggelos DOI: 10.1155/ASP/2006/25072 Most of the available digital color cameras use a single image sensor with a color ﬁlter array (CFA) in acquiring an image. In order to produce a visible color image, a demosaicing process must be applied, which produces undesirable artifacts. An additional problem appears when the observed color image is also blurred. This paper addresses the problem of deconvolving color images observed with a single coupled charged device (CCD) from the super-resolution point of view. Utilizing the Bayesian paradigm, an estimate of the reconstructed image and the model parameters is generated. The proposed method is tested on real images.

Improving a Single Down-Sampled Image Using Probability-Filtering-Based Interpolation and Open Access Improved Poisson Maximum A Posteriori Super-Resolution Min-Cheng Pan DOI: 10.1155/ASP/2006/97492 We present a novel hybrid scheme called “hyper-resolution” that integrates image probability-ﬁltering-based interpolation and improved Poisson maximum a posteriori (MAP) super-resolution to respectively enhance high spatial and spatial-frequency resolutions of a single down-sampled image. A new approach to interpolation is proposed for simultaneous image interpolation and smoothing by exploiting the probability ﬁlter coupled with a pyramidal decomposition and the Poisson MAP super-resolution is improved with the techniques of edge maps and pseudo-blurring. Simulation results demonstrate that this hyper-resolution scheme substantially improves the quality of a single gray-level, color, or noisy image, respectively.

Video-to-Video Dynamic Super-Resolution for Grayscale and Color Sequences Sina Farsiu, Michael Elad, and Peyman Milanfar DOI: 10.1155/ASP/2006/61859 We address the dynamic super-resolution (SR) problem of reconstructing a high-quality set of monochromatic or color super-resolved images from low-quality monochromatic, color, or mosaiced frames. Our approach includes a joint method for simultaneous SR, 124 EURASIP Journal on Applied Signal Processing, Vol. 2006 deblurring, and demosaicing, this way taking into account practical color measurements encountered in video sequences. For the case of translational motion and common space- invariant blur, the proposed method is based on a very fast and memory eﬃcient approximation of the Kalman ﬁlter (KF). Experimental results on both simulated and real data are supplied, demonstrating the presented algorithms, and their strength.

Low-Cost Super-Resolution Algorithms Implementation over a HW/SW Video Compression Platform Gustavo M. Callico,´ Rafael Peset Llopis, Sebastian Lopez,´ JoseFco.L´ opez,´ Antonio Nu´ nez,˜ Ramanathan Sethuraman, and Roberto Sarmiento DOI: 10.1155/ASP/2006/84614 Two approaches are presented in this paper to improve the quality of digital images over the sensor resolution using super-resolution techniques: iterative super-resolution (ISR) and noniterative super-resolution (NISR) algorithms. The results show important improvements in the image quality, assuming that sufficient sample data and a reasonable amount of aliasing are available at the input images. These super-resolution algorithms have been implemented over a codesign video compression platform developed by Philips Research, performing minimal changes on the overall hardware architecture. In this way, a novel and feasible low-cost implementation has been obtained by using the resources encountered in a generic hybrid video encoder. Although a specific video codec platform has been used, the methodology presented in this paper is easily extendable to any other video encoder architectures. Finally a comparison in terms of memory, computational load, and image quality for both algorithms, as well as some general statements about the final impact of the sampling process on the quality of the super-resolved (SR) image, are also presented.

Resolution Enhancement by Prediction of the High-Frequency Image Based on the Laplacian Pyramid Bo-Won Jeon, Rae-Hong Park, and Seungjoon Yang DOI: 10.1155/ASP/2006/72520 According to recent advances in digital image processing techniques, interest in high-quality images has been increased. This paper presents a resolution enhancement (RE) algorithm based on the pyramid structure, in which Laplacian histogram matching is utilized for high-frequency image prediction. The conventional RE algorithms yield blurring near-edge boundaries, degrading image details. In order to overcome this drawback, we estimate an HF image that is needed for RE by utilizing the characteristics of the Laplacian images, in which the normalized histogram of the Laplacian image is ﬁtted to the Laplacian probability density function (pdf), and the parameter of the Laplacian pdf is estimated based on the Laplacian image pyramid. Also, we employ a control function to remove overshoot artifacts in reconstructed images. Experiments with several test images show the eﬀectiveness of the proposed algorithm. Special Issue on Super-Resolution Imaging: Analysis, Algorithms, and Applications 125

A Fast Algorithm for Image Super-Resolution from Blurred Observations Nirmal K. Bose, Michael K. Ng, and Andy C. Yau DOI: 10.1155/ASP/2006/35726 We study the problem of reconstruction of a high-resolution image from several blurred low-resolution image frames. The image frames consist of blurred, decimated, and noisy versions of a high-resolution image. The high-resolution image is modeled as a Markov random field (MRF), and a maximum a posteriori (MAP) estimation technique is used for the restoration. We show that with the periodic boundary condition, a high-resolution image can be restored efficiently by using fast Fourier transforms. We also apply the pre- conditioned conjugate gradient method to restore high-resolution images in the aperiodic boundary condition. Computer simulations are given to illustrate the effectiveness of the proposed approach.

Robust Fusion of Irregularly Sampled Data Using Adaptive Normalized Convolution Tuan Q. Pham, Lucas J. van Vliet, and Klamer Schutte DOI: 10.1155/ASP/2006/83268 We present a novel algorithm for image fusion from irregularly sampled data. The method is based on the framework of normalized convolution (NC), in which the local signal is approximated through a projection onto a subspace. The use of polynomial basis functions in this paper makes NC equivalent to a local Taylor series expansion. Unlike the traditional framework, however, the window function of adaptive NC is adapted to local linear structures. This leads to more samples of the same modality being gathered for the analysis, which in turn improves signal-to-noise ratio and reduces diﬀusion across discontinuities. A robust signal certainty is also adapted to the sample intensities to minimize the inﬂuence of outliers. Excellent fusion capability of adaptive NC is demonstrated through an application of super-resolution image reconstruction.

A Frequency Domain Approach to Registration of Open Access Aliased Images with Application to Super-resolution Patrick Vandewalle, Sabine Susstrunk,¨ and Martin Vetterli DOI: 10.1155/ASP/2006/71459 Super-resolution algorithms reconstruct a high-resolution image from a set of low- resolution images of a scene. Precise alignment of the input images is an essential part of such algorithms. If the low-resolution images are undersampled and have aliasing artifacts, the performance of standard registration algorithms decreases. We propose a frequency domain technique to precisely register a set of aliased images, based on their low-frequency, aliasing-free part. A high-resolution image is then reconstructed using cubic interpolation. Our algorithm is compared to other algorithms in simulations and practical experiments 126 EURASIP Journal on Applied Signal Processing, Vol. 2006 using real aliased images. Both show very good visual results and prove the attractivity of our approach in the case of aliased input images. A possible application is to digital cameras where a set of rapidly acquired images can be used to recover a higher-resolution ﬁnal image.

Adaptive Outlier Rejection in Image Open Access Super-resolution Mejdi Trimeche, Radu Ciprian Bilcu, and Jukka Yrjan¨ ainen¨ DOI: 10.1155/ASP/2006/38052 One critical aspect to achieve efficient implementations of image super-resolution is the need for accurate subpixel registration of the input images. The overall performance of super-resolution algorithms is particularly degraded in the presence of persistent outliers, for which registration has failed. To enhance the robustness of processing against this problem, we propose in this paper an integrated adaptive filtering method to reject the outlier image regions. In the process of combining the gradient images due to each low-resolution image, we use adaptive FIR filtering. The coefficients of the FIR filter are updated using the LMS algorithm, which automatically isolates the outlier image regions by decreasing the corresponding coefficients. The adaptation criterion of the LMS estimator is the error between the median of the samples from the LR images and the output of the FIR filter. Through simulated experiments on synthetic images and on real camera images, we show that the proposed technique performs well in the presence of motion outliers. This relatively simple and fast mechanism enables to add robustness in practical implementations of image super-resolution, while still being effective against Gaussian noise in the image formation model.

Subpixel Registration Directly from the Phase Difference Murat Balci and Hassan Foroosh DOI: 10.1155/ASP/2006/60796 This paper proposes a new approach to subpixel registration, under local/global shifts or rotation, using the phase-difference matrix. We establish the exact relationship between the continuous and the discrete phase difference of two shifted images and show that their discrete phase difference is a 2-dimensional sawtooth signal. As a result, the exact shifts or rota- tions can be determined to subpixel or subangle accuracy by counting the number of cycles of the phase-difference matrix along the frequency axes. The subpixel portion is represented by a fraction of a cycle corresponding to the noninteger part of the shift or rotation. The rotation angle is estimated by applying our method using a polar coordinate system. The problem is formulated as an overdetermined system of equations and is solved by imposing a regularity constraint. The tradeoff for imposing the constraint is determined by exploiting the rank constraint leading to a closed-form expression for the optimal regularization parameter. Special Issue on Super-Resolution Imaging: Analysis, Algorithms, and Applications 127

Single-Frame Image Super-resolution through Contourlet Learning C. V. Jiji and Subhasis Chaudhuri DOI: 10.1155/ASP/2006/73767 We propose a learning-based, single-image super-resolution reconstruction technique using the contourlet transform, which is capable of capturing the smoothness along contours making use of directional decompositions. The contourlet coefficients at finer scales of the unknown high-resolution image are learned locally from a set of high-resolution training images, the inverse contourlet transform of which recovers the super-resolved image. In effect, we learn the high-resolution representation of an oriented edge primitive from the training data. Our experiments show that the proposed approach outperforms standard interpolation techniques as well as a standard (Cartesian) wavelet-based learning both visually and in terms of the PSNR values, especially for images with arbitrarily oriented edges.

Learning-Based Nonparametric Image Super-Resolution Shyamsundar Rajaram, Mithun Das Gupta, Nemanja Petrovic, and Thomas S. Huang DOI: 10.1155/ASP/2006/51306 We present a novel learning-based framework for zooming and recognizing images of digits obtained from vehicle registration plates, which have been blurred using an unknown kernel. We model the image as an undirected graphical model over image patches in which the compatibility functions are represented as nonparametric kernel densities. The crucial feature of this work is an iterative loop that alternates between super-resolution and restoration stages. A machine-learning-based framework has been used for restoration which also models spatial zooming. Image segmentation is done by a column-variance estimation-based “dissection” algorithm. Initially, the compatibility functions are learned by nonparametric kernel density estimation, using random samples from the training data. Next, we solve the inference problem by using an extended version of the nonparametric belief propagation algorithm, in which we introduce the notion of partial messages. Finally, we recognize the super-resolved and restored images. The resulting conﬁdence scores are used to sample from the training set to better learn the compatibility functions.

Super-Resolution Using Hidden Markov Model and Open Access Bayesian Detection Estimation Framework Fabrice Humblot and Ali Mohammad-Djafari DOI: 10.1155/ASP/2006/36971 This paper presents a new method for super-resolution (SR) reconstruction of a high- resolution (HR) image from several low-resolution (LR) images. The HR image is assumed to be composed of homogeneous regions. Thus, the a priori distribution of the pixels is modeled by a finite mixture model (FMM) and a Potts Markov model (PMM) for the labels. The whole a priori model is then a hierarchical Markov model. The LR images are assumed 128 EURASIP Journal on Applied Signal Processing, Vol. 2006 to be obtained from the HR image by lowpass filtering, arbitrarily translation, decimation, and finally corruption by a random noise. The problem is then put in a Bayesian detection and estimation framework, and appropriate algorithms are developed based on Markov chain Monte Carlo (MCMC) Gibbs sampling. At the end, we have not only an estimate of the HR image but also an estimate of the classification labels which leads to a segmentation result.

Adaptive Markov Random Fields for Open Access Example-Based Super-resolution of Faces

Todd A. Stephenson and Tsuhan Chen DOI: 10.1155/ASP/2006/31062 Image enhancement of low-resolution images can be done through methods such as interpolation, super-resolution using multiple video frames, and example-based super-resolution. Example-based super-resolution, in particular, is suited to images that have a strong prior (for those frameworks that work on only a single image, it is more like image restoration than traditional, multiframe super-resolution). For example, hallucination and Markov random ﬁeld (MRF) methods use examples drawn from the same domain as the image being enhanced to determine what the missing high-frequency information is likely to be. We propose to use even stronger prior information by extending MRF-based super-resolution to use adaptive observation and transition functions, that is, to make these functions region-dependent. We show with face images how we can adapt the modeling for each image patch so as to improve the resolution.

Application of Super-resolution Image Reconstruction to Digital Holography Shuqun Zhang DOI: 10.1155/ASP/2006/90358 We describe a new application of super-resolution image reconstruction to digital holography which is a technique for three-dimensional information recording and reconstruction. Digital holography has suﬀered from the low resolution of CCD sensors, which signiﬁ- cantly limits the size of objects that can be recorded. The existing solution to this problem is to use optics to bandlimit the object to be recorded, which can cause the loss of details. Here super-resolution image reconstruction is proposed to be applied in enhancing the spatial resolution of digital holograms. By introducing a global camera translation before sampling, a high-resolution hologram can be reconstructed from a set of undersampled hologram images. This permits the recording of larger objects and reduces the distance between the object and the hologram. Practical results from real and simulated holograms are presented to demonstrate the feasibility of the proposed technique. Special Issue on Super-Resolution Imaging: Analysis, Algorithms, and Applications 129

Super-Resolution for Synthetic Zooming Open Access

Xin Li DOI: 10.1155/ASP/2006/58195 Optical zooming is an important feature of imaging systems. In this paper, we investigate a low-cost signal processing alternative to optical zooming—synthetic zooming by super- resolution (SR) techniques. Synthetic zooming is achieved by registering a sequence of low- resolution (LR) images acquired at varying focal lengths and reconstructing the SR image at a larger focal length or increased spatial resolution. Under the assumptions of constant scene depth and zooming speed, we argue that the motion trajectories of all physical points are related to each other by a unique vanishing point and present a robust technique for estimating its 3D coordinate. Such a line-geometry-based registration is the foundation of SR for synthetic zooming. We address the issue of data inconsistency arising from the varying focal length of optical lens during the zooming process. To overcome the difficulty of data inconsistency, we propose a two-stage Delaunay-triangulation-based interpolation for fusing the LR image data. We also present a PDE-based nonlinear deblurring to accommodate the blindness and variation of sensor point spread functions. Simulation results with real-world images have verified the effectiveness of the proposed SR techniques for synthetic zooming. EURASIP Journal on Applied Signal Processing, Volume 2006 © 2006 Hindawi Publishing Corporation

Special Issue on Inverse Synthetic Aperture Radar

Marco Martorella The school of ITEF, The University of Queensland, Brisbane 4072, Australia

John Homer School of Information Technology & Electrical Engineering, University of Queensland, Brisbane 4072, Australia James Palmer Radar Modelling & Analysis Group, Electronic Warfare & Radar Division, Defence Science & Technology Organisation, P.O. Box 1500, Edinburgh 5111, UK Victor Chen Naval Research Laboratory, 4555 Overlook Ave., SW Washington, DC 20375, USA

Fabrizio Berizzi The school of ITEF, The University of Queensland, Brisbane 4072, Australia

Brad Littleton Centre for Quantum Computer Technology, School of Physical Sciences, University of Queensland, Brisbane 4072, Australia Dennis Longstaff The school of ITEF, The University of Queensland, Brisbane 4072, Australia

Inverse synthetic aperture Radar (ISAR) is a powerful signal processing technique that can provide a two-dimensional electromagnetic image of an area or target of interest. Being radar based, this imaging technique can be employed in all weather and day/night conditions. ISAR images are obtained by coherently processing the received radar echoes of transmitted pulses. Commonly, the ISAR image is characterised by high resolution along both the range and cross-range directions. High resolution in the range direction is achieved by means of large bandwidth transmitted pulses, whereas high cross-range resolution is obtained by exploiting a synthetic antenna aperture. In ISAR, the synthetic aperture is generated by motion of the target as well as possibly by motion of the radar platform. In contrast, the related imaging technique of Synthetic aperture radar (SAR) has its synthetic aperture generated by means of radar platform motion only. Special Issue on Inverse Synthetic Aperture Radar 131

Initially, the name ISAR was derived from SAR by simply considering a radar-target dynamic where the radar platform was fixed on the ground and the target was moving around. Today, however, it is understood that the basis of the difference between SAR and ISAR lies in the noncooperation of the ISAR target. Such a subtle difference has led in the last decades to a significant separation of the two areas. The noncooperation of the target introduces the main problem of not knowing the geometry and dynamic of the radar-target system during the coherent integration time. Such a limitation leads to the use of blind radial motion compensation (image autofocusing) and image formation processing that must deal with highly nonstationary signals. The SAR community is very large and the areas of interest within SAR grow steadily each year. The ISAR community is much smaller, in comparison, and it is often difficult to bring together world leaders in this sector. This special issue aims to gather the latest novelties in ISAR in order to provide an updated reference for current and future research in this area. This has involved a comprehensive peer review process to guarantee technical novelty and correctness. As discussed below, the presented papers, six in total, are equally divided amongst the three primary areas of ISAR research, namely: motion compensation (or image autofocusing), image formation,andtarget classification/recognition. Whereas the first two areas are devoted to the reconstruction of the ISAR image, the latter concerns the use of the ISAR image for target recognition—one of the principle motivations for ISAR development.

Motion compensation Motion compensation is the first step in the ISAR image reconstruction chain. Image focus and clarity strongly depend on the accuracy of motion compensation. Often referred to as image focusing or image autofocusing (blind data driven motion compensation), the motion compensation problem has been largely addressed since the beginning of ISAR. Several algorithms have been provided that accomplish motion compensation. Nonparametric algorithms such as prominent point processing (PPP) and phase gradient algorithm (PGA) often, in the past, have been applied in ISAR imaging, largely because they do not need a signal model assumption. More recently, several other nonparametric methods, such as the maximum likelihood- (ML-) based technique and the joint time-frequency analysis (JTFA) technique, have been proposed and are proving to be relatively effective. On the other hand, parametric approaches, such as image-entropy or image contrast-based algorithms, are attracting increased attention due to the potential enhancements they can provide over nonparametric approaches. In this special issue, two papers are presented which address the problem of motion compensation. The first, written by Martorella et al., concerns a general extension of two parametric algorithms, namely, the image contrast based-algorithm (ICBA) and image- entropy-based algorithm (IEBA). A second-order polynomial phase model is often used as the parametric model for motion compensation in algorithms such as the ICBA and the IEBA.Oftensuchamodeldoesnotprovetobeaccurateenough,duetoirregulartarget motions, such as in the cases of fast manoeuvring targets or sea-driven target angular motions in rough sea surface conditions. Motivated by this, researchers, such as those of the Martorella et al. paper, are employing high-order polynomial phase models to achieve accurate image focussing. However, estimation of the required polynomial coefficients (via solving of an optimisation problem) is typically sensitive to the cost function (image contrast 132 EURASIP Journal on Applied Signal Processing, Vol. 2006 or entropy) and the iterative-search technique employed. In particular, solutions provided by classic iterative techniques, such as Newton, quasi-Newton, steepest descent, or gradient, are generally unsuitable due to the multimodal characteristics of the cost function (which become more severe as the number of polynomial coefficients increases). To avoid such convergence problems Martorella et al. consider a genetic-based iterative technique, which they apply to the estimation/optimisation of a third-order polynomial phase model. The second paper, written by Yau et al., also addresses the multimodal-related convergence difficulties associated with many parametric-based motion compensation approaches. This paper proposes to overcome the difficulties by decoupling the estimation of the first- and higher-order polynomial coefficients. This is accomplished via an iterative two-stage approach; first a range-profile cross-correlation step is applied to estimate the first-order coefficient, and then a subspace-based technique, involving eigenvalue decomposition (EVD) or singular value decomposition (SVD), is applied to estimate the higher- order coefficients. The potential benefits of this two-stage approach arise because the optimisation process is implemented over two lower-dimensional spaces, thereby enhancing the likelihood of convergence to a globally optimal solution.

Image formation After motion compensation, the received signal is processed to form the ISAR image. The classic way of forming an ISAR image involves a two-step process. The first step concerns the range compression (or range focussing). Here, either the received time-domain signals are compressed by means of matched filters or the received multifrequency signals are compressed via the inverse Fourier transform—to produce complex range profiles. It is worth pointing out that in some cases the range compression is achieved before the motion compensation. The second step consists of cross-range compression (azimuth compression). The fastest and simplest way of obtaining cross-range compression is by means of a Fourier transform. In ISAR scenarios, where the target is moving smoothly with respect to the radar and when the integration time is short enough, the Fourier transform represents the most effective solution. Nevertheless, in ISAR scenarios with fast manoeuvring targets or sea- driven motioned ships or with the requirement of high resolution, the effectiveness of the Fourier approach is strongly limited. For this reason, several other techniques have been proposed in the last decades, such as the JTFA, the range-instantaneous-Doppler (RID), the enhanced image processing (EIP) techniques, tomography-based techniques and super- resolution techniques, such as the CLEAN technique, and the Capon technique among others. In this special issue, the paper by Djurovic et al. proposes a novel image formation (cross-range compression) technique based on the use of the polynomial Fourier transform (PFT) for enhancing the ISAR image quality in complex reflector geometries at a relatively low computational cost. A model is introduced that describes the received signal as the superposition of contributions from different geometrical areas with given characteristics in terms of signal phases. The local polynomial Fourier transform (LPFT) is then used to match the signal contributions that come from different image areas. The second paper on image formation, by Wong et al., proposes a method of analysis for quantifying the image distortion introduced by the conventional Fourier transform approach. This analysis method involves a numerical model of the time-varying target rotation rate. The analysis implies that severe distortion is often attributed to phase Special Issue on Inverse Synthetic Aperture Radar 133 modulation effects, whereas a time-varying Doppler frequency produces image smearing. Following insights gained from the analysis, the authors also propose a time-frequency processing/analysis based method for deblurring/refocusing conventionally generated ISAR images.

Target classification and identification Radar signatures are often used for target classification and/or identification. The need for classifying a target has led to the development of high-resolution radar. ISAR images can be interpreted as two-dimensional (2D) radar signatures. Therefore, a 2D distribution of the energy backscattered from the target provides a multidimensional way of interpreting the information carried by the radar echo. Several techniques have been proposed for interpreting this ISAR-based information for the purpose of target classification/identification. These fall into two main philosophies: (i) feature matching and (ii) template or point matching, the latter being more oriented towards target identification. In this special issue, two papers deal with the problem of target classification by means of ISAR images. In the paper of Shreyamsha Kumar et al., a full system for target identification is proposed. The authors introduce a wavelet-based approach for ISAR image formation followed by feature extraction and target identification by means of neural networks. The use of the wavelet technique is compared with time-frequency techniques in terms of effectiveness and computational cost. In ISAR imaging it is sometimes difficult to predict the target orientation and often even more difficult to rescale the image along the cross-range coordinate. This problem is avoided in the proposed technique as the features used for target identification are invariant to translation, rotation, and scaling—leading to a robust ISAR image-based identification system. The second paper by Radoi et al. proposes a supervised self-organising feature-based classification technique of super-resolution ISAR images. The super-resolution ISAR images are obtained through a MUSIC-2D method, coupled with phase unwrapping and symmetry enhancement. The proposed feature vector contains Fourier descriptors and moment invariants, which are extracted from the target shape and scattering center distribution of the ISAR image. These features, importantly, are invariant to target position and orientation. The feature-based classification is then carried out via a supervised adaptive resonance theory (SART) approach, which shows improved efficiency over the conventional MLP and fuzzy KNN classifiers.

Marco Martorella John Homer James Palmer Victor Chen Fabrizio Berizzi Brad Littleton Dennis Longstaﬀ 134 EURASIP Journal on Applied Signal Processing, Vol. 2006 Volume 2006, No. 11 Contents and Abstracts

Use of Genetic Algorithms for Contrast and Entropy Optimization in ISAR Autofocusing Marco Martorella, Fabrizio Berizzi, and Silvia Bruscoli DOI: 10.1155/ASP/2006/87298 Image contrast maximization and entropy minimization are two commonly used techniques for ISAR image autofocusing. When the signal phase history due to the target radial motion has to be approximated with high order polynomial models, classic optimization techniques fail when attempting to either maximize the image contrast or minimize the image entropy. In this paper a solution of this problem is proposed by using genetic algorithms. The performances of the new algorithms that make use of genetic algorithms overcome the problem with previous implementations based on deterministic approaches. Tests on real data of airplanes and ships conﬁrm the insight.

Eigenspace-Based Motion Compensation for Open Access ISAR Target Imaging D. Yau, P.E. Berry, and B. Haywood DOI: 10.1155/ASP/2006/90716 A novel motion compensation technique is presented for the purpose of forming focused ISAR images which exhibits the robustness of parametric methods but overcomes their convergence difficulties. Like the most commonly used parametric autofocus techniques in ISAR imaging (the image contrast maximization and entropy minimization methods) this is achieved by estimating a target’s radial motion in order to correct for target scat- terer range cell migration and phase error. Parametric methods generally suffer a major drawback, namely that their optimization algorithms often fail to converge to the optimal solution. This difficulty is overcome in the proposed method by employing a sequential approach to the optimization, estimating the radial motion of the target by means of a range profile cross-correlation, followed by a subspace-based technique involving singular value decomposition (SVD). This two-stage approach greatly simplifies the optimization process by allowing numerical searches to be implemented in solution spaces of reduced dimension.

Adaptive Local Polynomial Fourier Transform in ISAR Igor Djurovic,´ Thayananthan Thayaparan, and Ljubisaˇ Stankovic´ DOI: 10.1155/ASP/2006/36093 The adaptive local polynomial Fourier transform is employed for improvement of the ISAR images in complex reflector geometry cases, as well as in cases of fast maneuvering targets. It has been shown that this simple technique can produce significantly improved results Special Issue on Inverse Synthetic Aperture Radar 135 with a relatively modest calculation burden. Two forms of the adaptive LPFT are proposed. Adaptive parameter in the first form is calculated for each radar chirp. Additional refinement is performed by using information from the adjacent chirps. The second technique is based on determination of the adaptive parameter for different parts of the radar image. Numerical analysis demonstrates accuracy of the proposed techniques.

An Analysis of ISAR Image Distortion Based on the Phase Modulation Effect S. K. Wong, E. Riseborough, and G. Duff DOI: 10.1155/ASP/2006/83727 Distortion in the ISAR image of a target is a result of nonuniform rotational motion of the target during the imaging period. In many of the measured ISAR images from moving targets, such as those from in-flight aircraft, the distortion can be quite severe. Often, the image integration time is only a few seconds in duration and the target’s rotational displacement is only a few degrees. The conventional quadratic phase distortion effect is not adequate in explaining the severe blurring in many of these observations. A numerical model based on a time-varying target rotation rate has been developed to quantify the distortion in the ISAR image. It has successfully modelled the severe distortion observed; the model’s simulated results are validated by experimental data. Results from the analysis indicate that the severe distortion is attributed to the phase modulation effect where a time-varying Doppler frequency provides the smearing mechanism. For target identification applications, an efficient method on refocusing distorted ISAR images based on time-frequency analysis has also been developed based on the insights obtained from the results of the numerical modelling and experimental investigation conducted in this study.

Target Identification Using Harmonic Wavelet Based ISAR Imaging B. K. Shreyamsha Kumar, B. Prabhakar, K. Suryanarayana, V. Thilagavathi, and R. Rajagopal DOI: 10.1155/ASP/2006/86053 A new approach has been proposed to reduce the computations involved in the ISAR imaging, which uses harmonic wavelet-(HW) based time-frequency representation (TFR). Since the HW-based TFR falls into a category of nonparametric time-frequency (T-F) analysis tool, it is computationally efficient compared to parametric T-F analysis tools such as adaptive joint time-frequency transform (AJTFT), adaptive wavelet transform (AWT), and evolutionary AWT (EAWT). Further, the performance of the proposed method of ISAR imaging is compared with the ISAR imaging by other nonparametric T-F analysis tools such as short-time Fourier transform (STFT) and Choi-Williams distribution (CWD). In the ISAR imaging, the use of HW-based TFR provides similar/better results with significant (92%) computational advantage compared to that obtained by CWD. The ISAR images thus obtained are identified using a neural network-based classification scheme with feature set invariant to translation, rotation, and scaling. 136 EURASIP Journal on Applied Signal Processing, Vol. 2006

Supervised Self-Organizing Classification of Open Access Superresolution ISAR Images: An Anechoic Chamber Experiment Emanuel Radoi, Andre´ Quinquis, and Felix Totir DOI: 10.1155/ASP/2006/35043 The problem of the automatic classification of superresolution ISAR images is addressed in the paper. We describe an anechoic chamber experiment involving ten-scale-reduced aircraft models. The radar images of these targets are reconstructed using MUSIC-2D (multiple signal classification) method coupled with two additional processing steps: phase unwrapping and symmetry enhancement. A feature vector is then proposed including Fourier descriptors and moment invariants, which are calculated from the target shape and the scattering center distribution extracted from each reconstructed image. The classification is finally performed by a new self-organizing neural network called SART (supervised ART), which is compared to two standard classifiers, MLP (multilayer perceptron) and fuzzy KNN (K nearest neighbors). While the classification accuracy is similar, SART is shown to outperform the two other classifiers in terms of training speed and classification speed, especially for large databases. It is also easier to use since it does not require any input parameter related to its structure. EURASIP JOURNAL ON APPLIED SIGNAL PROCESSING

Special Issue on Super-resolution Enhancement of Digital Video

CALL FOR PAPERS When designing a system for image acquisition, there is generally a desire for high spatial resolution and a wide field-of-view. To achieve this, a camera system must typically employ small f-number optics. This produces an image with very high spatial-frequency bandwidth at the focal plane. To avoid aliasing caused by undersampling, the corresponding focal plane array (FPA) must be sufficiently dense. However, cost and fabrication complexities may make this impractical. More fundamentally, smaller detectors capture fewer photons, which can lead to potentially severe noise levels in the acquired imagery. Consid- ering these factors, one may choose to accept a certain level of undersampling or to sacrifice some optical resolution and/or field-of-view. In image super-resolution (SR), postprocessing is used to obtain images with resolutions that go beyond the conventional limits of the uncompensated imaging system. In some systems, the primary limiting factor is the optical resolution of the image in the focal plane as defined by the cut-off frequency of the optics. We use the term “optical SR” to refer to SR methods that aim to create an image with valid spatial-frequency content that goes beyond the cut-off frequency of the optics. Such techniques typically must rely on extensive a priori information. In other image acquisition systems, the limiting factor may be the density of the FPA, subsequent postprocessing requirements, or transmission bitrate constraints that require data compression. We refer to the process of overcoming the limitations of the FPA in order to obtain the full resolution afforded by the selected optics as “detector SR.” Note that some methods may seek to perform both optical and detector SR. Detector SR algorithms generally process a set of low-resolution aliased frames from a video sequence to produce a high-resolution frame. When subpixel relative motion is present between the objects in the scene and the detector array, a unique set of scene samples are acquired for each frame. This provides the mechanism for effectively increasing the spatial sampling rate of the imaging system without reducing the physical size of the detectors. With increasing interest in surveillance and the proliferation of digital imaging and video, SR has become a rapidly growing field. Recent advances in SR include innovative algorithms, generalized methods, real-time implementations, and novel applications. The purpose of this special issue is to present leading research and development in the area of super-resolution for digital video. Topics of interest for this special issue include but are not limited to: • Detector and optical SR algorithms for video • Real-time or near-real-time SR implementations • Innovative color SR processing • Novel SR applications such as improved object detection, recognition, and tracking • Super-resolution from compressed video • Subpixel image registration and optical flow

Authors should follow the EURASIP JASP manuscript format described at the journal site http://www.hindawi.com/journals/asp/. Prospective authors should submit an electronic copy of their complete manuscripts through the EURASIP JASP manuscript tracking system at http://www.hindawi.com/mts/, according to the following timetable:

Manuscript Due September 1, 2006 Acceptance Notiﬁcation February 1, 2007 Final Manuscript Due April 15, 2007 Publication Date 3rd Quarter, 2007

GUEST EDITORS: Russell C. Hardie, Department of Electrical and Computer Engineering, University of Dayton, 300 College Park, Dayton, OH 45469-0026, USA; [email protected] Richard R. Schultz, Department of Electrical Engineering, University of North Dakota, Upson II Room 160, P.O. Box 7165, Grand Forks, ND 58202-7165, USA; [email protected] Kenneth E. Barner, Department of Electrical and Computer Engineering, University of Delaware, 140 Evans Hall, Newark, DE 19716-3130, USA; [email protected]

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Special Issue on Transforming Signal Processing Applications into Parallel Implementations

CALL FOR PAPERS There is an increasing need to develop efficient “system-level” models, methods, and tools to support designers to quickly transform signal processing application specification to heterogeneous hardware and software architectures such as arrays of DSPs, heterogeneous platforms involving microprocessors, DSPs and FPGAs, and other evolving multiprocessor SoC architectures. Typically, the design process involves aspects of application and architecture modeling as well as transformations to translate the application models to architecture models for subsequent performance analysis and design space exploration. Accurate predictions are indispensable because next generation signal processing applications, for example, audio, video, and array signal processing impose high throughput, real-time and energy constraints that can no longer be served by a single DSP. There are a number of key issues in transforming application models into parallel implementations that are not addressed in current approaches. These are engineering the application specification, transforming application specification, or representation of the architecture specification as well as communication models such as data transfer and synchronization primitives in both models. The purpose of this call for papers is to address approaches that include application transformations in the performance, analysis, and design space exploration efforts when taking signal processing applications to concurrent and parallel implementations. The Guest Editors are soliciting contributions in joint application and architecture space exploration that outperform the current architecture-only design space exploration methods and tools. Topics of interest for this special issue include but are not limited to: • modeling applications in terms of (abstract) control-dataflow graph, dataflow graph, and process network models of computation (MoC) • transforming application models or algorithmic engineering • transforming application MoCs to architecture MoCs • joint application and architecture space exploration • joint application and architecture performance analysis • extending the concept of algorithmic engineering to architecture engineering • design cases and applications mapped on multiprocessor, homogeneous, or heterogeneous SOCs, showing joint optimization of application and architecture

Authors should follow the EURASIP JASP manuscript format described at the journal site http://www.hindawi.com/journals/asp/. Prospective authors should submit an electronic copy of their complete manuscript through the EURASIP JASP manuscript tracking system at http://www.hindawi.com/mts, according to the following timetable:

Manuscript Due September 1, 2006 Acceptance Notiﬁcation January 1, 2007 Final Manuscript Due April 1, 2007 Publication Date 3rd Quarter 2007

GUEST EDITORS: F. Deprettre, Leiden Embedded Research Center, Leiden University, Niels Bohrweg 1, 2333 CA Leiden, The Netherlands; [email protected] Roger Woods, School of Electrical and Electronic Engineering, Queens University of Belfast, Ashby Building, Stranmillis Road, Belfast, BT9 5AH, UK; [email protected] Ingrid Verbauwhede, Katholieke Universiteit Leuven, ESAT-COSIC, Kasteelpark Arenberg 10, 3001 Leuven, Belgium; [email protected] Erwin de Kock, Philips Research, High Tech Campus 31, 5656 AE Eindhoven, The Netherlands; [email protected]

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Special Issue on Video Adaptation for Heterogeneous Environments

CALL FOR PAPERS The explosive growth of compressed video streams and repositories accessible worldwide, the recent addition of new video-related standards such as H.264/AVC, MPEG-7, and MPEG-21, and the ever-increasing prevalence of heterogeneous, video-enabled terminals such as computer, TV, mobile phones, and personal digital assistants have escalated the need for efficient and effective techniques for adapting compressed videos to better suit the different capabilities, constraints, and requirements of various transmission networks, applications, and end users. For instance, Universal Multimedia Access (UMA) advocates the provision and adaptation of the same multimedia content for different networks, terminals, and user preferences. Video adaptation is an emerging field that offers a rich body of knowledge and techniques for handling the huge variation of resource constraints (e.g., bandwidth, display capability, processing speed, and power consumption) and the large diversity of user tasks in pervasive media applications. Considerable amounts of research and development activities in industry and academia have been devoted to answering the many challenges in making better use of video content across systems and applications of various kinds. Video adaptation may apply to individual or multiple video streams and may call for different means depending on the objectives and requirements of adaptation. Transcod- ing, transmoding (cross-modality transcoding), scalable content representation, content abstraction and summarization are popular means for video adaptation. In addition, video content analysis and understanding, including low-level feature analysis and high-level semantics understanding, play an important role in video adaptation as essential video content can be better preserved. The aim of this special issue is to present state-of-the-art developments in this flour- ishing and important research field. Contributions in theoretical study, architecture design, performance analysis, complexity reduction, and real-world applications are all welcome. Topics of interest include (but are not limited to): • Heterogeneous video transcoding • Scalable video coding • Dynamic bitstream switching for video adaptation • Signal, structural, and semantic-level video adaptation • Content analysis and understanding for video adaptation • Video summarization and abstraction • Copyright protection for video adaptation • Crossmedia techniques for video adaptation • Testing, field trials, and applications of video adaptation services • International standard activities for video adaptation

Authors should follow the EURASIP JASP manuscript format described at the journal site http://www.hindawi.com/journals/asp/. Prospective authors should submit an electronic copy of their complete manuscript through the EURASIP JASP manuscript tracking system at http://www.hindawi.com/mts, according to the following timetable:

Manuscript Due September 1, 2006 Acceptance Notiﬁcation January 1, 2007 Final Manuscript Due April 1, 2007 Publication Date 3rd Quarter 2007

GUEST EDITORS: Chia-Wen Lin, Department of Computer Science and Information Engineering, National Chung Cheng University, Chiayi 621, Taiwan; [email protected] Yap-Peng Tan, School of Electrical and Electronic Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798, Singapore; [email protected] Ming-Ting Sun, Department of Electrical Engineering, University of Washington, Seattle, WA 98195, USA; [email protected] Alex Kot, School of Electrical and Electronic Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798, Singapore; [email protected] Anthony Vetro, Mitsubishi Electric Research Laboratories, 201 Broadway, 8th Floor, Cambridge, MA 02138, USA; [email protected]

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Special Issue on Advanced Signal Processing and Computational Intelligence Techniques for Power Line Communications

CALL FOR PAPERS In recent years, increased demand for fast Internet access and new multimedia services, the development of new and feasible signal processing techniques associated with faster and low-cost digital signal processors, as well as the deregulation of the telecommunications market have placed major emphasis on the value of investigating hostile media, such as powerline (PL) channels for high-rate data transmissions. Nowadays, some companies are offering powerline communications (PLC) modems with mean and peak bit-rates around 100 Mbps and 200 Mbps, respectively. However, advanced broadband powerline communications (BPLC) modems will surpass this performance. For accomplishing it, some special schemes or solutions for coping with the following issues should be addressed: (i) considerable differences between powerline network topologies; (ii) hostile properties of PL channels, such as attenuation proportional to high frequencies and long distances, high-power impulse noise occurrences, time-varying behavior, and strong inter-symbol interference (ISI) effects; (iv) electromagnetic compatibility with other well-established communication systems working in the same spectrum, (v) climatic conditions in different parts of the world; (vii) reliability and QoS guarantee for video and voice transmissions; and (vi) different demands and needs from developed, developing, and poor countries. These issues can lead to exciting research frontiers with very promising results if signal processing, digital communication, and computational intelligence techniques are effectively and efficiently combined. The goal of this special issue is to introduce signal processing, digital communication, and computational intelligence tools either individually or in combined form for advancing reliable and powerful future generations of powerline communication solutions that can be suited with for applications in developed, developing, and poor countries. Topics of interest include (but are not limited to) • Multicarrier, spread spectrum, and single carrier techniques • Channel modeling • Channel coding and equalization techniques • Multiuser detection and multiple access techniques • Synchronization techniques • Impulse noise cancellation techniques • FPGA, ASIC, and DSP implementation issues of PLC modems • Error resilience, error concealment, and Joint source-channel design methods for video transmission through PL channels

Authors should follow the EURASIP JASP manuscript format described at the journal site http://asp.hindawi.com/. Prospective authors should submit an electronic copy of their complete manuscripts through the EURASIP JASP manuscript tracking system at http://www.hindawi.com/mts, according to the following timetable:

Manuscript Due October 1, 2006 Acceptance Notiﬁcation January 1, 2007 Final Manuscript Due April 1, 2007 Publication Date 3rd Quarter, 2007

GUEST EDITORS: Moises´ Vidal Ribeiro, Federal University of Juiz de Fora, Brazil; [email protected] Lutz Lampe, University of British Columbia, Canada; [email protected] Sanjit K. Mitra, University of California, Santa Barbara, USA; [email protected] Klaus Dostert, University of Karlsruhe, Germany; [email protected] Halid Hrasnica, Dresden University of Technology, Germany; [email protected]

Volume 2006 Contents and Abstracts

On the Use of Pade´ Approximation for Open Access Performance Evaluation of Maximal Ratio Combining Diversity over Weibull Fading Channels

Mahmoud H. Ismail and Mustafa M. Matalgah DOI: 10.1155/WCN/2006/58501 We use the Pade´ approximation (PA) technique to obtain closed-form approximate expressions for the moment-generating function (MGF) of the Weibull random variable. Unlike previously obtained closed-form exact expressions for the MGF, which are relatively complicated as being given in terms of the Meijer G-function, PA can be used to obtain simple rational expressions for the MGF, which can be easily used in further computations. We illustrate the accuracy of the PA technique by comparing its results to either the existing exact MGF or to that obtained via Monte Carlo simulations. Using the approximate expressions, we analyze the performance of digital modulation schemes over the single channel and the multichannels employing maximal ratio combining (MRC) under the Weibull fading assumption. Our results show excellent agreement with previously published results as well as with simulations.

A New MAC Protocol with Pseudo-TDMA Open Access Behavior for Supporting Quality of Service in 802.11 Wireless LANs Georgios S. Paschos, Ioannis Papapanagiotou, Stavros A. Kotsopoulos, and George K. Karagiannidis DOI: 10.1155/WCN/2006/65836 A new medium access control (MAC) protocol is proposed for quality-of-service (QoS) support in wireless local area networks (WLAN). The protocol is an alternative to the recent enhancement 802.11e. A new priority policy provides the system with better performance by simulating time division multiple access (TDMA) functionality. Collisions are reduced and starvation of low-priority classes is prevented by a distributed admission control algorithm. The model performance is found analytically extending previous work on this matter. The results show that a better organization of resources is achieved through this scheme. Throughput analysis is veriﬁed with OPNET simulations. 146 Regular Issue, Vol. 2006

Joint Frequency Ambiguity Resolution and Open Access Accurate Timing Estimation in OFDM Systems with Multipath Fading Jun Li, Guisheng Liao, and Shan Ouyang DOI: 10.1155/WCN/2006/62173 A serious disadvantage of orthogonal frequency-division multiplexing (OFDM) is its sensitivity to carrier frequency offset (CFO) and timing offset (TO). For many low-complexity algorithms, the estimation ambiguity exists when the CFO is greater than one or two subcarrier spacing, and the estimated TO is also prone to exceeding the ISI-free interval within the cyclic prefix (CP). This paper presents a method for joint CFO ambiguity resolution and accurate TO estimation in multipath fading. Maximum-likelihood (ML) principle is employed and only one pilot symbol is needed. Frequency ambiguity is resolved and accurate TO can be obtained simultaneously by using the fast Fourier transform (FFT) and one-dimensional (1D) search. Both known and unknown channel order cases are considered. Computer simulations show that the proposed algorithm outperforms some others in the multipath fading channels.

An Implementation of Nonlinear Multiuser Open Access Detection in Rayleigh Fading Channel Wai Yie Leong, John Homer, and Danilo P.Mandic DOI: 10.1155/WCN/2006/45647 A blind nonlinear interference cancellation receiver for code-division multiple-access- (CDMA-) based communication systems operating over Rayleigh ﬂat-fading channels is proposed. The receiver which assumes knowledge of the signature waveforms of all the users is implemented in an asynchronous CDMA environment. Unlike the conventional MMSE receiver, the proposed blind ICA multiuser detector is shown to be robust without training sequences and with only knowledge of the signature waveforms. It has achieved nearly the same performance of the conventional training-based MMSE receiver. Several comparisons and experiments are performed based on examining BER performance in AWGN and Rayleigh fading in order to verify the validity of the proposed blind ICA multiuser detector.

Energy-Efﬁcient Channel Estimation in Open Access MIMO Systems Sarod Yatawatta, Athina P.Petropulu, and Charles J. Graff DOI: 10.1155/WCN/2006/27694 The emergence of MIMO communications systems as practical high-data-rate wireless communications systems has created several technical challenges to be met. On the one hand, there is potential for enhancing system performance in terms of capacity and diversity. On the other hand, the presence of multiple transceivers at both ends has created additional cost in terms of hardware and energy consumption. For coherent detection as well as to do optimization such as water ﬁlling and beamforming, it is essential that the Regular Issue, Vol. 2006 147

MIMO channel is known. However, due to the presence of multiple transceivers at both the transmitter and receiver, the channel estimation problem is more complicated and costly compared to a SISO system. Several solutions have been proposed to minimize the computational cost, and hence the energy spent in channel estimation of MIMO systems. We present a novel method of minimizing the overall energy consumption. Unlike existing methods, we consider the energy spent during the channel estimation phase which includes transmission of training symbols, storage of those symbols at the receiver, and also channel estimation at the receiver. We develop a model that is independent of the hardware or software used for channel estimation, and use a divide-and-conquer strategy to minimize the overall energy consumption.

Differential Detection of Space-Time Spreading Open Access with Two Transmit Antennas Tao Shi and Lei Cao DOI: 10.1155/WCN/2006/70509 Adifferential detection scheme for space-time spreading with two transmit antennas is proposed. The scheme does not require channel state information at either the transmitter or the receiver. With segmentation and preamble symbols padded at the transmitter, the receiver recovers the information using differential detection. Both phase-shift keying (PSK) and quadrature amplitude modulation (QAM) signals are considered. The proposed scheme achieves two-level transmit diversity gain with low complexity and saves the use of channel estimation, while having about 3 dB performance loss as compared to the coherent detection scheme. When multiple receive antennas exist, additional receive diversity gain can be achieved along with the transmit diversity gain. The scheme works fine under block-fading channel as well as slow Rayleigh fading channel, which is a popular scenario for high-rate data communications. The system performance for different segment sizes, channel fading speeds, modulation methods, and numbers of receive antennas is studied through simulations.

Decision-Directed Recursive Least Squares Open Access MIMO Channels Tracking Ebrahim Karami and Mohsen Shiva DOI: 10.1155/WCN/2006/43275 A new approach for joint data estimation and channel tracking for multiple-input multiple- output (MIMO) channels is proposed based on the decision-directed recursive least squares (DD-RLS) algorithm. RLS algorithm is commonly used for equalization and its application in channel estimation is a novel idea. In this paper, after defining the weighted least squares cost function it is minimized and eventually the RLS MIMO channel estimation algorithm is derived. The proposed algorithm combined with the decision-directed algorithm (DDA) is then extended for the blind mode operation. From the computational complexity point of view being O(3) versus the number of transmitter and receiver antennas, the proposed algorithm is very efficient. Through various simulations, the mean square error (MSE) of 148 Regular Issue, Vol. 2006 the tracking of the proposed algorithm for different joint detection algorithms is compared with Kalman filtering approach which is one of the most well-known channel tracking algorithms. It is shown that the performance of the proposed algorithm is very close to Kalman estimator and that in the blind mode operation it presents a better performance with much lower complexity irrespective of the need to know the channel model.

A Multicarrier Multiplexing Method for Very Wide Open Access Bandwidth Transmission Diakoumis Gerakoulis and George Efthymoglou DOI: 10.1155/WCN/2006/64253 The multicarrier orthogonal code division multiplexing (MC-OCDM) introduced here has been designed for very wide bandwidth (VWB) point-to-point and point-to-multipoint transmission. In order to meet VWB transmission requirements, the MC-OCDM design has two components, the basic and the composite. The basic MC-OCDM is a generalized form of the standard orthogonal frequency division multiplexing (OFDM). It has the property of distributing the power of each transmitted symbol into all subcarrier frequencies. Each subcarrier will then carry all transmitted symbols which are distinguished by orthogonal Hadamard sequences. The resulting system is shown to improve the performance of OFDM by introducing frequency and time diversity. As shown, by both analysis and simulation, the basic MC-OCDM combats the effects of narrowband interference (NBI). In particular, the simulation results show that the BER performance of the basic MC-OCDM in the presence of NBI is better than OFDM for both coded and uncoded systems. Further- more, the composite MC-OCDM is a method of orthogonal frequency division multiplexing (OFDM) basic MC-OCDM channels. This allows us to multiplex more than one basic MC-OCDM channel into a VWB transmission system which can have the performance and spectral efficiency required in fixed wireless transmission environments.

On the Geometrical Characteristics of Open Access Three-Dimensional Wireless Ad Hoc Networks and Their Applications Guansheng Li, Pingyi Fan, and Kai Cai DOI: 10.1155/WCN/2006/31467 In a wireless ad hoc network, messages are transmitted, received, and forwarded in a finite geometrical region and the transmission of messages is highly dependent on the locations of the nodes. Therefore the study of geometrical relationship between nodes in wireless ad hoc networks is of fundamental importance in the network architecture design and performance evaluation. However, most previous works concentrated on the networks deployed in the two-dimensional region or in the infinite three-dimensional space, while in many cases wireless ad hoc networks are deployed in the finite three-dimensional space. In this paper, we analyze the geometrical characteristics of the three-dimensional wireless ad hoc network in a finite space in the framework of random graph and deduce an expression to calculate the distance probability distribution between network nodes that are independently and uniformly distributed in a finite cuboid space. Based on the theoretical Regular Issue, Vol. 2006 149 result, we present some meaningful results on the finite three-dimensional network performance, including the node degree and the max-flow capacity. Furthermore, we investigate some approximation properties of the distance probability distribution function derived in the paper.

Equalization of Sparse Intersymbol-Interference Open Access Channels Revisited Jan Mietzner, Sabah Badri-Hoeher, Ingmar Land, and Peter A. Hoeher DOI: 10.1155/WCN/2006/29075 Sparse intersymbol-interference (ISI) channels are encountered in a variety of communication systems, especially in high-data-rate systems. These channels have a large memory length, but only a small number of significant channel coefficients. In this paper, equalization of sparse ISI channels is revisited with focus on trellis-based techniques. Due to the large channel memory length, the complexity of maximum-likelihood sequence estimation by means of the Viterbi algorithm is normally prohibitive. In the first part of the paper, a unified framework based on factor graphs is presented for complexity reduction without loss of optimality. In this new context, two known reduced-complexity trellis-based techniques are recapitulated. In the second part of the paper a simple alternative approach is investigated to tackle general sparse ISI channels. It is shown that the use of a linear filter at the receiver renders the application of standard reduced-state trellis-based equalization techniques feasible without significant loss of optimality.

A Conjugate-Cyclic-Autocorrelation Open Access Projection-Based Algorithm for Signal Parameter Estimation Valentina De Angelis, Luciano Izzo, Antonio Napolitano, and Mario Tanda DOI: 10.1155/WCN/2006/86026 A new algorithm to estimate amplitude, delay, phase, and frequency offset of a received signal is presented. The frequency-offset estimation is performed by maximizing, with respect to the conjugate cycle frequency, the projection of the measured conjugate-cyclic- autocorrelation function of the received signal over the true conjugate second-order cyclic autocorrelation. It is shown that this estimator is mean-square consistent, for moderate values of the data-record length, outperforms a previously proposed frequency-offset estimator, and leads to mean-square consistent estimators of the remaining parameters.

A General Theory for SIR Balancing Open Access Holger Boche and Martin Schubert DOI: 10.1155/WCN/2006/60681 We study the problem of maximizing the minimum signal-to-interference ratio (SIR) in a multiuser system with an adaptive receive strategy. The interference of each user is modelled 150 Regular Issue, Vol. 2006 by an axiomatic framework, which reflects the interaction between the propagation channel, the power allocation, and the receive strategy used for interference mitigation. Assum- ing that there is a one-to-one mapping between the QoS and the signal-to-interference ratio (SIR), the feasible QoS region is completely characterized by the max-min SIR balancing problem. In the first part of the paper, we derive fundamental properties of this problem for the most general case, when interference is modelled with an axiomatic framework. In the second part, we show more specific properties for interference functions based on a nonnegative coupling matrix. The principal aim of this paper is to provide a deeper understanding of the interaction between power allocation and interference mitigation strategies. We show how the proposed axiomatic approach is related to the matrix-based theory.

Voice and Video Telephony Services in Open Access Smartphone Valeria Loscri’,Mauro Tropea, and Salvatore Marano DOI: 10.1155/WCN/2006/84945 Multimedia telephony is a delay-sensitive application. Packet losses, relatively less critical than delay, are allowed up to a certain threshold. They represent the QoS constraints that have to be respected to guarantee the operation of the telephony service and user satis- faction. In this work we introduce a new smartphone architecture characterized by two process levels called application processor (AP) and mobile termination (MT), respectively. Here, they communicate through a serial channel. Moreover, we focus our attention on two very important UMTS services: voice and video telephony. Through a simulation study the impact of voice and video telephony is evaluated on the structure considered using the protocols known at this moment to realize voice and video telephony.

Efficient Low Bit-Rate Low-Latency Open Access Channelization in DECT Rohit Budhiraja and Bhaskar Ramamurthi DOI: 10.1155/WCN/2006/54148 In a TDMA standard such as DECT, low bit-rate transmission is feasible either at the cost of efficiency (shorter slots with fixed overhead per slot) or increased latency (longer frames). This paper proposes a new scheme for low bit-rate low-latency channelization in the DECT standard, in which data can be efficiently transmitted at rates as low as 10 kbps. This could be useful for sending acknowledgments for a high-speed data communication link, or for vocoder/VoIP traffic. The proposed scheme enables efficient low bit-rate transmission by di- viding a DECT channel into four subbands, and by employing a new slot structure wherein TDMA overhead is kept to a minimum. It is shown that the proposed scheme can coexist with the DECT system and can be implemented using existing IMT-2000 DECT hardware with minor modifications. A comparison is also made of the proposed scheme with existing options for low bit-rate channelization in DECT. EURASIP Journal on Wireless Communications and Networking, Volume 2006 © 2006 Hindawi Publishing Corporation

Special Issue on Quality of Service in Mobile Ad Hoc Networks

Wei Li Department of Electrical Engineering and Computer Science, University of Toledo, Toledo, OH 43606, USA Mohsen Guizani Department of Computer Science, Western Michigan University, Kalamazoo, MI 49008, USA

Demetrios Kazakos Department of Electrical and Computer Engineering, University of Idaho, Moscow, ID 83844, USA

Mobile ad hoc networking is a challenging task due to the lack of resources residing in the network as well as the frequent changes in network topology. Although much research has been directed to supporting quality of service (QoS) in the Internet and traditional wireless networks, present results are not suitable for mobile ad hoc network (MANET). QoS support for mobile ad hoc networks remains an open problem, drawing interest from both academia and industry under military and commercial sponsorship. MANETs have certain unique characteristics that pose several difficulties in provisioning QoS, such as dynamically varying network topology, lack of precise state information, lack of central control, error-prone shared radio channels, limited resource availability, hidden terminal problems, and insecure media, and little consensus yet exists on which approaches may be optimal. Future MANETs are likely to be “multimode” or heterogeneous in nature. Thus, the routers comprising a MANET will employ multiple, physical-layer wireless technologies, with each new technology requiring a multiple access (MAC) protocol for supporting QoS. Above the MAC layer, forwarding, routing, signaling, and admission control policies are required, and the best combination of these policies will change as the underlying hardware technology evolves. In response to the above demand for mobile ad hoc networks, this special issue aims at providing a timely and concise reference of the current activities and findings in the relevant technical fields, and focuses as well on the state-of-the-art and up-to-date efforts in design, performance analysis, implementation and experimental results for various QoS issues in MANETs. We believe that all of these papers not only provide novel ideas, new analytical models, simulation and experimental results, and handful experience in this field, but also simulate 152 EURASIP Journal on Wireless Communications and Networking, Vol. 2006 the future research activities in the area of the quality of service for mobile ad hoc networks. Abriefsummaryofeachpaperislistedasfollows. The first paper by Qi He et al. first identifies two critical issues leading to the TCP performance degradation: (1) unreliable broadcast, since broadcast frames are transmitted without the request-to-send and clear-to-send (RTS/CTS) dialog and Data/ACK handshake, so they are vulnerable to the hidden terminal problem; and (2) false link failure which occurs when a node cannot successfully transmit data temporarily due to medium contention. Sec- ondly, the authors propose a scheme to use a narrow-bandwidth, out-of-band busy-tone channel to make reservation for broadcast and link error detection frames only. The proposed scheme is simple and power efficient, because only the sender needs to transmit two short messages in the busy tone channel before sending broadcast or link error detection frames in the data channel. Analytical results show that the proposed scheme can dramatically reduce the collision probability of broadcast and link error detection frames. Exten- sive simulations with different network topologies further demonstrate that the proposed scheme can improve TCP throughput by 23% to 150%, depending on user mobility, and effectively enhance both short-term and long-term fairness among coexisting TCP flows in multi-hop wireless ad hoc networks. The second paper by Deying Li et al. discusses the energy efficient QoS topology control problem for nonhomogeneous ad hoc wireless networks. Given a set of nodes with different energy and bandwidth capacities in a plane, and given the end-to-end traffic demands and delay bounds between node pairs, the problem is to find a network topology that can meet the QoS requirements, and the maximum energy utilization of nodes is minimized. Achieving this objective is vital to the increase of network lifetime. We consider two cases of the problem: (1) the traffic demands are not splittable, and (2) the traffic demands are splittable. For the former case, the problem is formulated as an integer linear programming problem. For the latter case, the problem is formulated as a mixed integer programming problem, and an optimal algorithm has been proposed to solve the problem. The third paper by Hsiao-Hwa Chen et al. proposes autonomous power control MAC protocol (APCMP), which allows mobile nodes dynamically adjusting power level for transmitting DATA/ACK according to the distances between the transmitter and its neighbors. In addition, the power level for transmitting RTS/CTS is also adjustable according to the power level for DATA/ACK packets. In this paper, the performance of APCMP protocol is evaluated by simulation and is compared with that of other protocols. The fourth paper by Yang Yang et al. considers the hybrid problem of the infrastructure and the ad hoc modes in WLAN. They propose in this paper a new coverage improvement scheme that can identify suitable idle MSs in good service zones as trafficagents(TAs)to relay traffic from those out-of-coverage MSs to the AP. The service coverage area of WLAN is then expanded. The QoS requirements (e.g., bandwidth) of those MSs are considered in the selection process of corresponding TAs. Mathematical analysis, verified by computer simulations, shows that the proposed TA scheme can effectively reduce blocking probability when traffic load is light. The fifth paper by S. Ahmed et al. analyzes the performance differentials to compare the commonly used ad hoc network routing protocols. They also analyze the performance over varying loads for each of those protocols using OPNET modeler 10.5. Their findings show that for specific differentials, TORA shows better performance over the two on-demand protocols, that is, dynamic source routing and ad hoc on-demand distance vector routing. Special Issue on Quality of Service in Mobile Ad Hoc Networks 153

Their findings are expected to lead to further performance improvements of various ad hoc networks in the future. The sixth paper by Nagaraja Thanthry et al. analyzes various parameters that affect the performance of TCP in an ad hoc network environment. Congestion and path nonavail- ability are two major factors that affect TCP performance. It was also observed that, in the presence of multiple paths, TCP performance degrades when one of the paths used for forwarding data drops a packet. In the current paper, the authors have proposed establishing multiple connections for every data transfer between the source and the destination. The proposed mechanism would be transparent to the application and session layers; however, it involves the transport layer in multipath routing scheme. The seventh paper by X. Wang et al. develops a modified version that we term CSMA/ CCA (CSMA with copying collision avoidance) in order to mitigate fairness issues arising with CSMA/CA. A station in CSMA/CCA contends for the shared wireless medium by employing a binary exponential backoff similar to CSMA/CA. Different from CSMA/CA, CSMA/CCA copies the contention window (CW) size piggybacked in the MAC header of an overheard data frame within its basic service set (BSS), and updates its backoff counter according to the new CW size. Simulations carried out in several WLAN configurations illustrate that CSMA/CCA improves fairness relative to CSMA/CA and offers considerable advantages for deployment in the 802.11 standard based WLANs.1 The eighth paper by S. Guizani et al. proposes a new technique to compensate the chromatic dispersion optically by applying Talbot effect. Results obtained are inline with what’s proposed. This method is easy to implement and versatile since any type of fiber can be used. Moreover, our technique has the strength to revive a totally deformed signal regardless of the bits transmitted. In closing, we would like to thank the support from the Editor-in-Chief, Phillip Regalia, and the contributions from authors and reviewers, to make this special issue possible.

Wei Li Mohsen Guizani Demetrios Kazakos 154 EURASIP Journal on Wireless Communications and Networking, Vol. 2006 Volume 2006, No. 2 Contents and Abstracts

Improving TCP Performance over Wireless Ad Hoc Open Access Networks with Busy Tone Assisted Scheme

Qi He, Lin Cai, Xuemin (Sherman) Shen, and Pinhan Ho DOI: 10.1155/WCN/2006/51610 It is well known that transmission control protocol (TCP) performance degrades severely in IEEE 802.11-based wireless ad hoc networks. We first identify two critical issues leading to the TCP performance degradation: (1) unreliable broadcast, since broadcast frames are transmitted without the request-to-send and clear-to-send (RTS/CTS) dialog and Data/ACK handshake, so they are vulnerable to the hidden terminal problem; and (2) false link failure which occurs when a node cannot successfully transmit data temporarily due to medium contention. We then propose a scheme to use a narrow- bandwidth, out-of-band busy tone channel to make reservation for broadcast and link error detection frames only. The proposed scheme is simple and power efficient, because only the sender needs to transmit two short messages in the busy tone channel before sending broadcast or link error detection frames in the data channel. Analytical results show that the proposed scheme can dramatically reduce the collision probability of broadcast and link error detection frames. Extensive simulations with different network topologies further demonstrate that the proposed scheme can improve TCP throughput by 23% to 150%, depending on user mobility, and effectively enhance both short-term and long-term fairness among coexisting TCP flows in multihop wireless ad hoc networks.

QoS Topology Control for Nonhomogenous Open Access Ad Hoc Wireless Networks Deying Li, Xiaohua Jia, and Hongwei Du DOI: 10.1155/WCN/2006/82417 This paper discusses the energy-efficient QoS topology control problem for nonhomogenous ad hoc wireless networks. Given a set of nodes with different energy and bandwidth capacities in a plane, and given the end-to-end traffic demands and delay bounds between node-pairs, the problem is to find a network topology that can meet the QoS requirements and the maximum energy utilization of nodes is minimized. Achieving this objective is vital to the increase of network lifetime. We consider two cases of the problem: (1) the trafficde- mands are not splittable, and (2) the traffic demands are splittable. For the former case, the problem is formulated as an integer linear programming problem. For the latter case, the problem is formulated as a mixed integer programming problem, and an optimal algorithm has been proposed to solve the problem. Special Issue on Quality of Service in Mobile Ad Hoc Networks 155

Autonomous Power Control MAC Protocol for Open Access Mobile Ad Hoc Networks Hsiao-Hwa Chen, Zhengying Fan, and Jie Li DOI: 10.1155/WCN/2006/36040 Battery energy limitation has become a performance bottleneck for mobile ad hoc networks. IEEE 802.11 has been adopted as the current standard MAC protocol for ad hoc networks. However, it was developed without considering energy efficiency. To solve this problem, many modifications on IEEE 802.11 to incorporate power control have been proposed in the literature. The main idea of these power control schemes is to use a maximum possible power level for transmitting RTS/CTS and the lowest acceptable power for sending DATA/ACK. However, these schemes may degrade network throughput and reduce the overall energy efficiency of the network. This paper proposes autonomous power control MAC protocol (APCMP), which allows mobile nodes dynamically adjusting power level for transmitting DATA/ACK according to the distances between the transmitter and its neighbors. In addition, the power level for transmitting RTS/CTS is also adjustable according to the power level for DATA/ACK packets. In this paper, the performance of APCMP protocol is evaluated by simulation and is compared with that of other protocols.

Traffic Agents for Improving QoS in Mixed Open Access Infrastructure and Ad Hoc Modes Wireless LAN Yang Yang, Hai-Feng Yuan, Hsiao-Hwa Chen, Wen-Bing Yao, and Yong-Hua Song DOI: 10.1155/WCN/2006/94235 As an important complement to infrastructured wireless networks, mobile ad hoc networks (MANET) are more flexible in providing wireless access services, but more difficult in meeting different quality of service (QoS) requirements for mobile customers. Both infrastructure and ad hoc network structures are supported in wireless local area networks (WLAN), which can offer high data-rate wireless multimedia services to the mobile stations (MSs) in a limited geographical area. For those out-of-coverage MSs, how to effectively connect them to the access point (AP) and provide QoS support is a challenging issue. By mixing the infrastructure and the ad hoc modes in WLAN, we propose in this paper a new coverage improvement scheme that can identify suitable idle MSs in good service zones as traffic agents (TAs) to relay traffic from those out-of-coverage MSs to the AP. The service coverage area of WLAN is then expanded. The QoS requirements (e.g., bandwidth) of those MSs are considered in the selection process of corresponding TAs. Mathematical analysis, verified by computer simulations, shows that the proposed TA scheme can effectively reduce blocking probability when traffic load is light. 156 EURASIP Journal on Wireless Communications and Networking, Vol. 2006

Performance Evaluation of Important Ad Hoc Open Access Network Protocols S. Ahmed and M. S. Alam DOI: 10.1155/WCN/2006/78645 A wireless ad hoc network is a collection of specific infrastructureless mobile nodes forming a temporary network without any centralized administration. A user can move anytime in an ad hoc scenario and, as a result, such a network needs to have routing protocols which can adopt dynamically changing topology. To accomplish this, a number of ad hoc routing protocols have been proposed and implemented, which include dynamic source routing (DSR), ad hoc on-demand distance vector (AODV) routing, and temporally ordered routing algorithm (TORA). Although considerable amount of simulation work has been done to measure the performance of these routing protocols, due to the constant changing nature of these protocols, a new performance evaluation is essential. Accordingly, in this paper, we analyze the performance differentials to compare the above-mentioned commonly used ad hoc network routing protocols. We also analyzed the performance over varying loads for each of these protocols using OPNET Modeler 10.5. Our findings show that for specific differentials, TORA shows better performance over the two on-demand protocols, that is, DSR and AODV. Our findings are expected to lead to further performance improvements of various ad hoc networks in the future.

TCP-M: Multiflow Transmission Control Open Access Protocol for Ad Hoc Networks Nagaraja Thanthry, Anand Kalamkar, and Ravi Pendse DOI: 10.1155/WCN/2006/95149 Recent research has indicated that transmission control protocol (TCP) in its base form does not perform well in an ad hoc environment. The main reason identified for this behavior involves the ad hoc network dynamics. By nature, an ad hoc network does not support any form of quality of service. The reduction in congestion window size during packet drops, a property of the TCP used to ensure guaranteed delivery, further deteriorates the overall performance. While other researchers have proposed modifying congestion window properties to improve TCP performance in an ad hoc environment, the authors of this paper propose using multiple TCP flows per connection. The proposed protocol reduces the influence of packet drops that occurred in any single path on the overall system performance. The analysis carried out by the authors indicates a significant improvement in overall performance.

CSMA/CCA: A Modified CSMA/CA Protocol Open Access Mitigating the Fairness Problem for IEEE 802.11 DCF Xin Wang and Georgios B. Giannakis DOI: 10.1155/WCN/2006/39604 Carrier sense multiple access with collision avoidance (CSMA/CA) has been adopted by the IEEE 802.11 standards for wireless local area networks (WLANs). Using a distributed Special Issue on Quality of Service in Mobile Ad Hoc Networks 157 coordination function (DCF), the CSMA/CA protocol reduces collisions and improves the overall throughput. To mitigate fairness issues arising with CSMA/CA, we develop a modified version that we term CSMA with copying collision avoidance (CSMA/CCA). A station in CSMA/CCA contends for the shared wireless medium by employing a binary exponential backoff similar to CSMA/CA. Different from CSMA/CA, CSMA/CCA copies the contention window (CW) size piggybacked in the MAC header of an overheard data frame within its basic service set (BSS) and updates its backoff counter according to the new CW size. Sim- ulations carried out in several WLAN configurations illustrate that CSMA/CCA improves fairness relative to CSMA/CA and offers considerable advantages for deployment in the 802.11-standard-based WLANs.

Fiber over Wireless Chromatic Dispersion Open Access Compensation for a Better Quality of Service S. Guizani, M. Razzak, H. Hamam, Y. Bouslimani, and A. Cheriti DOI: 10.1155/WCN/2006/85980 “Anywhere” and, in particular, “anyhow”: these are the two best words that can describe an ad hoc wireless network that is due to the increasing demand for connectivity in such an information society. Ad hoc wireless networks can be described as dynamic multihop wireless networks with mobile nodes. However, the mobility condition can be relaxed, and we can consider an ad hoc wireless network as a reconfigurable network where all the nodes are connected to the local environment through wireless links, and where there is not a central or dominant node—as opposed to, for example, the case of cellular wireless networks where a base station is located in each cell. When ad hoc networks are backboned by fibers, distortion of the optical link presents one of the major issues. In this paper, we will be addressing one of the fundamental problems, namely, chromatic dispersion in the fiber optic prior reaching the access points. This will ensure an adequate quality of service (QoS). EURASIP JOURNAL ON WIRELESS COMMUNICATIONS AND NETWORKING

Special Issue on Algorithmic Aspects of Wireless Networks

CALL FOR PAPERS Recent advances in electronic and computer technologies have paved the way for the proliferation of ubiquitous wireless networks. Fast deployment of these communication networks for the users is preferred under many situations. Topics that are related to ad hoc and sensor networking, mobile computing, and wireless and mobile security have been extensively studied recently. Potential applications of these networks include search and rescue, smart homes, battleﬁeld surveillance, environment monitoring and control, and so forth. Common algorithmic issues in wireless networks include location management, topology control and coverage, security and privacy, scalable design, cross-layer design, resource optimization, QoS, to just name a few. Methods used to address these issues include computational geometry, graph theory, combinatorial optimization, linear relaxation, stochastic and probability analysis, and so forth. The goal of this special issue is to publish the most recent results in the development of algorithmic aspects of wireless networks. Researchers and practitioners working in this area are expected to take this opportunity to discuss and express their views on the current trends, challenges, and state-of-the-art solutions addressing various issues in wireless networks. Topics to be covered in this special issue include but are not limited to: • Algorithmic methods and tools • Approximation algorithm design • Localization and tracking • Resource optimization • Quality of service • Topology control and coverage • Energy-eﬃcient routing protocols • Security and privacy • Distributed and localized solutions • Stochastic algorithms • Information processing • Scalability issues • Fault-tolerant issues Authors should follow the EURASIP JWCN manuscript format described at the journal site http://www.hindawi.com/journals/wcn/. Prospective authors should submit an electronic copy of their complete manuscript through the EURASIP JWCN manuscript tracking system at http://www.hindawi.com/mts/, according to the following timetable:

Manuscript Due June 1, 2006 Acceptance Notiﬁcation October 1, 2006 Final Manuscript Due January 1, 2007 Publication Date 2nd Quarter, 2007

GUEST EDITORS: Xiuzhen (Susan) Cheng, Department of Computer Science, The George Washington Uni- versity, Washington, DC 20052, USA; [email protected] Wayne Li, Department of Electrical Engineering and Computer Science, The University of Toledo, Toledo, OH 43606-3390, USA; [email protected] Taieb Znati, Department of Computer Science, University of Pittsburgh, Pittsburgh, PA 15260, USA; [email protected]

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Special Issue on MobileMAN (Mobile Multi-hop Ad Hoc Networks): From Theory to Reality

CALL FOR PAPERS Motivations Ad hoc networking technologies have big potentialities for innovative applications of great impact on our everyday life. To exploit these potentialities, simulation modeling and theoretical analyses have to be complemented by real experiences (e.g., experiences/measurements on real prototypes) which provide both a direct evaluation of ad hoc networks and, at the same time, precious information for a realistic modeling of these systems. The need for more experimental activities stimulated a new community of researchers combining theoretical research on ad hoc networking with experiences/measure-ments obtained by implementing ad hoc network prototypes. This community is growing as witnessed by several workshops organized worldwide. In particular, this special issue is tightly coupled with the REALMAN workshop series, http://www.cl.cam.ac.uk/realman. REAL- MAN workshops constitute a unique forum for presenting and discussing measurement studies and experiences based on real ad hoc networks testbeds and prototypes. Follow- ing the success of the ﬁrst edition (REALMAN 2005), REALMAN 2006 will be the satellite workshop of the most prestigious symposium for mobile ad hoc networks, ACM MobiHoc 2006.

Aims and scope of the Special Issue The aim of this special issue is to present, from an experimental perspective, architectures and protocols for implementing (mobile) ad hoc networks. This special issue constitutes a unique forum to present measurements/experiences/lessons obtained by implementing ad hoc networks testbeds and prototypes. The special issue will investigate the whole protocol stack from enabling technologies to middleware and applications. Original contributions are solicited, related to system and protocol development, measurement, and testing, in all areas related to ad hoc networking. Speciﬁcally, topics of interest include, but are not limited to: • Ad hoc networks applications • System prototypes and experiences • Mobile ad hoc networks • Opportunistic and delay tolerant networks • Sensor networks • Mesh networks • Vehicular networks • Protocol implementation and testing • Middleware platforms for ad hoc networks • Ad hoc networking for pervasive environments • Situated and autonomic communications • Location services • Positioning and tracking technologies and services • Measurement studies • Mobility models based on real data • Enabling technologly Measurements (802.11, 802.15, etc.) • Experiment-based social and/or economic analysis of mobile ad hoc networks

Authors should follow the EURASIP JWCN manuscript format described at the journal site http://www.hindawi.com/journals/wcn/. Prospective authors should submit an electronic copy of their complete manuscript through the EURASIP JWCN manuscript tracking system at http://www.hindawi.com/mts/, according to the following timetable:

Manuscript Due July 1, 2006 Acceptance Notiﬁcation November 1, 2006 Final Manuscript Due February 1, 2007 Publication Date 2nd Quarter, 2007

GUEST EDITORS: Marco Conti, Consiglio Nazionale delle Ricerche (CNR), Sezione Reti Internet, Instituto di Informatica e Telematica (IJI), Via Giuseppe, Moruzzi 1, 56124 Pisa, Italy; [email protected]

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Special Issue on Satellite Communications

CALL FOR PAPERS Aims and scope of the Special Issue Arthur C. Clarke published the concept of the 24-hour orbit communications satellite in his article Extra-Terrestrial Relays, which appeared in Wireless World in 1945. Twenty years on, satellites were first employed to provide telecommunication services in the mid-1960s, when they were used by Intelsat to provide telephony and television services using the Early Bird satellite. Mobile-satellite services followed in the late 1970s and were the subject of significant investment in the 1990s, with the introduction of multi-satellite, low earth orbit systems. After a period of consolidation, the satellite communications industry is once more shaping to address new market opportunities brought about by the growth in services such as broadband wireless Internet access, digital broadcasting to fixed and mobile terminals, mobile communications, integrated communications and navigation, and security and dis- aster relief. The Advanced Satellite Mobile Task Force, the Satellite Network of Excellence (SatNEx), the Integral Satcom Initiative (ISI) represent the European response to the new challenges posed by these opportunities: researchers and industries from all over the world are cooperating to identify roadmaps and find new technical and theoretical breakthroughs in this exciting field. This Special Issue aims to showcase the latest research and development advances in this framework. Original and unpublished work is solicited in all aspects of satellite communications including experimental platforms, heterogeneous networks, market surveys, network protocol design, performance evaluation, practical applications, radio interface solutions, system design, theoretical studies, and trial campaigns.

Topics Covered: Topics of interest include (but are not limited to): • Coding, modulation, and synchronisation • Cross-layer solutions • Delay tolerant networks • Fading and interference mitigation techniques • Mobility management • Heterogeneous network solutions • Interworking with terrestrial networks • Medium access control • Network layer solutions • Networkprotocoldesignandevaluation • Propagation measurements and channel modelling • Resource management

Manuscript Due September 1, 2006 Acceptance Notiﬁcation January 1, 2007 Final Manuscript Due April 1, 2007 Publication Date 2nd Quarter, 2007

GUEST EDITORS: Ray E. Sheriff, School of Engineering, Design and Technology, University of Bradford, Bradford, West Yorkshire, BD7 1DP, UK; r.e.sheriﬀ@bradford.ac.uk Anton Donner, German Aerospace Center (DLR), Institute of Communications and Navigation, Muenchener Street 20, 82234 Wessling/Oberpfaﬀenhofen, Germany; [email protected] Alessandro Vanelli-Coralli, DEIS/ARCES, University of Bologna, Viale Risorgimento, 2-40136 Bologna, Italy; [email protected]

http://www.hindawi.com EURASIP JOURNAL ON WIRELESS COMMUNICATIONS AND NETWORKING

Special Issue on Novel Techniques for Analysis & Design of Cross-Layer Optimized Wireless Sensor Networks

CALL FOR PAPERS Sensor networks have been researched and deployed for decades already; their wireless extension, however, has witnessed a tremendous upsurge in recent years. This is mainly attributed to the unprecedented operating conditions of wireless sensor networks (WSNs), that is, • a potentially enormous amount of sensor nodes, • reliably operating under stringent energy constraints. The wireless sensor networks’ virtually infinite degrees of freedom have ignited feverish research activities, having led to thousands of publications, white papers and patents in less than a decade, with new contributions emerging on a daily basis. The rich mathematical and technical toolboxes already available from the design of wireless cellular and ad hoc systems clearly aided the birth of new ideas tailored to the problems in WSNs. To date, and this may very well change in forthcoming years, the main problem in de- ploying WSNs is their dependence on scarce battery power. A main design criterion is hence to extend the lifetime of the network without jeopardizing reliable and efficient communications between the sensor nodes as well as from the nodes to one or several data sinks. A prominent example of today’s non-optimized WSN deployment experiences is that the start-up alone costs the network half of its battery power. Optimizing every facet of the communication protocols is hence vital and imperative; such stringent design requirements can be met by a plethora of approaches, for example, optimizing each layer of the protocol stack separately (traditional) or jointly (cross-layer), for each node separately (traditional) or for an ensemble of nodes (distributed and cooperative), and so forth. This has led to copious novel distributed signal processing algorithms, energy-efficient medium access control and fault-tolerant routing protocols, self-organizing and self-healing sensor network mechanisms, and so forth. In the light of the above, the main purpose of this special issue is twofold: • to obtain a coherent and concise technical synthesis from the abundance of recently emerged material in the area of WSNs, • to promote novel approaches in analyzing, designing, and optimizing large-scale WSNs, preferably inspired by approaches from other disciplines, such as physics or biology. As for the first one, very few papers are currently available which synthesize the large amount of fairly dispersed technical contributions; a coherent exposure, also touching upon open research issues, will certainly be appreciated by the academic and industrial research community. As for the second one, we believe that novel approaches, potentially inspired by entirely disjoint disciplines, may help considerably in dealing with networks of thousands of nodes.

Topics of Interest Topics of interest in the area of energy-constraint WSNs include (but are not limited to): • Network capacity w/o imperfections • Joint source and channel coding • Cooperative and distributed signal Data fusion and dta aggregation processing • Novel PHY, MAC, and network paradigms • Cross-layer and cross-functionality design • Security, robustness, and reliability • Self-healing, self-stabilization, and self-organization • Applications, architectures, and topologies • (Macroscopic) information ﬂows • Physically and biologically inspired approaches

Authors should follow the EURASIP JWCN manuscript format described at http:// www.hindawi.com/journals/wcn/. Prospective authors should submit an electronic copy of their complete manuscript through the EURASIP JWCN manuscript tracking system at http://www.hindawi.com/mts/, according to the following timetable:

Manuscript Due October 1, 2006 Acceptance Notiﬁcation February 1, 2007 Final Manuscript Due May 1, 2007 Publication Date 3rd Quarter, 2007

GUEST EDITORS: Mischa Dohler, France Telecom R & D, France; [email protected] Taieb Znati, University of Pittsburgh, USA; [email protected] Stavros Toumpis, University of Cyprus, Cyprus; [email protected] Lionel M. Ni, Hong Kong University of Science and Technology, Hong Kong, China; [email protected]

http://www.hindawi.com EURASIP JOURNAL ON WIRELESS COMMUNICATIONS AND NETWORKING

Special Issue on Trust and Digital Rights Management in Wireless Multimedia Networks and Systems

CALL FOR PAPERS With the widespread infusion of digital technologies and the ensuing ease of digital content transport over the Internet, multimedia data distribution is experiencing exponential growth. The use of emerging technologies and systems based on wireless networks has further facilitated the ubiquitous presence of multimedia data. These rapid advances are neither without cost nor without negative impact. With the increasing sophistication and ubiquity of sharing and dissemination of data over a plethora of networks, the complexity and challenges of untrustworthy behavior as well as cyber attacks may grow significantly. Moreover, the emerging unstructured, mobile, and ad hoc nature of today’s heterogeneous network environment is leading to problems such as the exploitation of resources due to selfish and malicious behavior by users and their agents in the networks. Trust and digital rights management (DRM) of data and the underlying systems and networks have therefore become of critical concern. Moreover, satisfying users’ quality of service (QoS) requirements while implementing trust and DRM mechanisms may overbur- den the already resourceconstrained wireless networks. The objective of this solicitation is to encourage cuttingedge research in trust and digital rights management in wireless networks and systems. Dissemination of research results in formulating the trust and DRM issues, and emerging solutions in terms of technologies, protocols, architecture, and models are expected to contribute to the advancement of this field in a significant way. Topics of interests include but are not limited to:

• DRM issues (copyright protection, tracking, tracing, fingerprinting, authentication, concealment, privacy, access control, etc.) in wireless multimedia • Wireless multimedia traffic modeling, analysis, and management • Tradeoff between QoS, security, dependability, and performability requirements • Context, behavior, and reputation specification, modeling, identification, and management • Trust and DRM models, architectures, and protocols • Trust and DRM in applications (telemedicine, ubiquitous commerce, etc.) • Trust and DRM in wireless ad hoc, mesh, sensor and heterogeneous networks • Trust and DRM technologies for wireless multimedia (digital watermarking, encryption, coding, and compression, and their interplay) • Test beds for experimental evaluation of trust and DRM models.

Manuscript Due December 1, 2006 Acceptance Notiﬁcation April 1, 2007 Final Manuscript Due June 1, 2007 Publication Date 4th Quarter, 2007

GUEST EDITORS: Farid Ahmed, Department of Electrical Engineering and Computer Science The Catholic University of America, Washington, DC, 20064, USA; [email protected] Mohamed Eltoweissy, The Bradley Department of Electrical and Computer Engineering, Virginia Tech, Advanced Research Institute, Arlington, VA 22203, USA; [email protected] Kamesh Namuduri, Department of Electrical and Computer Engineering Wichita State University, Wichitan KS 67260, USA; [email protected]

http://www.hindawi.com EURASIP Journal on :: Open Access :: Audio, Speech, and Music Processing

Editor-in-Chief http://www.hindawi.com/journals/asmp/ Douglas O’Shaughnessy Aims and Scope Associate Editors The aim of “EURASIP Journal on Audio, Speech, and Music Processing” Jont Allen (EURASIP JASMP) is to bring together researchers and engineers working on the theory and applications of audio, speech, and music processing. EURASIP Xavier Amatriain JASMP is an interdisciplinary journal for the dissemination of all basic and Gérard Bailly applied aspects of speech communication and audio processes. Its primary Martin Bouchard objectives are: Douglas S. Brungart ► To publish papers on the advancement of both human speech communication science and automatic speech and audio systems Wai-Yip Geoffrey Chan ► To allow rapid and wide diffusion of excellent contributions in these Dan Chazan areas Mark Clements ► To provide worldwide, barrier-free access to the full text of research ar- Roger Dannenberg ticles ► To conduct a rapid but thorough review process in order to assure high- Christophe quality papers d’Alessandro ► To provide immediate web access once a paper is editorially approved Li Deng The journal is dedicated to original research work, but tutorial and review Thomas Eriksson articles will also be accepted. Articles will deal with both theoretical and prac- Horacio Franco tical aspects of audio, speech, and music processing. Qian-Je Fu Subject areas include (but are not limited to): ► Speech and audio technology, as well as related science and engineering James Glass methods Steven Greenberg ► Speech analysis, synthesis, coding, and recognition; speaker verification; Rodrigo Capobianco language modeling and recognition; human speech production and Guido perception; and speech enhancement Richard Heusdens ► Room acoustics, human audition, analysis, synthesis, and coding of music and other audio, transducers, and active sound and noise control James Kates ► Speech and audio separation, computational auditory scene analysis, Tutsuya Kawahara and independent component analysis Yves Laprie ► Music signal analysis, synthesis, and information retrieval Lin-Shan Lee Author Guidelines Dominic Massaro Original articles are invited and should be submitted through the EURASIP Ben Milner JASMP Manuscript Tracking System at http://www.hindawi.com/mts/. Only Climent Nadeu pdf ﬁles are accepted. If, for some reason, submission through the manuscript tracking system is not possible, you can contact [email protected]. Elmar Noeth Open Access Support Hiroshi Okuno The “Open Access” movement is a relatively recent development in academic Joseph Picone publishing. It proposes a new business model for academic publishing that Gerhard Rigoll enables immediate, worldwide, barrier-free, open access to the full text of re- Mark Sandler search articles for the best interests of the scientiﬁc community. All interested Thippur Sreenivas readers can read, download, and/or print any open access article without requiring a subscription to the journal in which these articles are published. Yannis Stylianou Stephen Voran Hindawi Publishing Corporation, 410 Park Avenue, DeLiang Wang 15th Floor, #287 pmb, New York, NY 10022, USA

http://www.hindawi.com/journals/asmp/ EURASIP Journal on :: Open Access :: Bioinformatics and Systems Biology

Editor-in-Chief http://www.hindawi.com/journals/bsb/ Ioan Tabus Finland Aims and Scope The overall aim of “EURASIP Journal on Bioinformatics and Systems Associate Editors Biology” (EURASIP JBSB) is to publish research results related to signal Jaakko Astola processing and bioinformatics theories and techniques relevant to a wide Finland area of applications into the core new disciplines of genomics, proteomics, Junior Barrera and systems biology. Brazil Michael Bittner The journal is intended to offer a common platform for scientists from USA several areas, including signal processing, bioinformatics, statistics, biology, and medicine, who are interested in the development of algorithmic, math- Yidong Chen USA ematical, statistical, modeling, simulation, data mining, and computational techniques, as demanded by various applications in genomics, proteomics, Paul Dan Cristea system biology, and more general in health and medicine. Romania Edward Russell Papers should emphasize original results related to the theoretical and al- Dougherty gorithmic aspects of signal processing and bioinformatics, in close connec- USA tion with the applications to genomics, proteomics, systems biology, and Javier Garcia-Frias medicine. Tutorial papers, especially those emphasizing strong compo- USA nents of signal processing or bioinformatics in multidisciplinary views of Debashis Ghosh genomics, proteomics, and systems biology, are also welcome. The journal USA will embrace a wide range of topics, and will accommodate different exposition styles, to help scientists with various backgrounds, for example, engi- John Goutsias neering, bioinformatics, or biology, to interact effortlessly, and to facilitate USA the exchange of information across the multidisciplinary areas involved. Roderic Guigo EURASIP JBSB employs a paperless, electronic submission and evaluation Spain system to promote a rapid turnaround in the peer review process. Sabine Van Huffel Belgium Author Guidelines Bart De Moor Original articles are invited and should be submitted through the EURASIP Belgium JBSB Manuscript Tracking System at http://www.hindawi.com/mts/. John Quackenbush Only pdf files are accepted. If, for some reason, submission through USA the manuscript tracking system is not possible, author can contact Jorma Rissanen [email protected]. UK Open Access Support Stéphane Robin The “Open Access” movement is a relatively recent development in academic France publishing. It proposes a new business model for academic publishing that Paola Sebastiani enables immediate, worldwide, barrier-free, open access to the full text of USA research articles for the best interests of the scientific community. All in- Ahmed H. Tewfik terested readers can read, download, and/or print any open access article USA without requiring a subscription to the journal in which these articles are Yue Wang published. USA

Z. Jane Wang Hindawi Publishing Corporation, 410 Park Avenue, Canada 15th Floor, #287 pmb, New York, NY 10022, USA

http://www.hindawi.com/journals/bsb/ EURASIP Journal on :: Open Access :: Embedded Systems

Editor-in-Chief http://www.hindawi.com/journals/es/ Zoran Salcic Aims and Scope Associate Editors EURASIP Journal on Embedded Systems is an international journal Sandro Bartolini that serves the large community of researchers and professional engineers who deal with the theory and practice of embedded systems, Neil Bergmann particularly encompassing all practical aspects of theory and methods Shuvra S. used in designing homogeneous as well as heterogeneous embedded Bhattacharyya systems that combine data-driven and control-driven behaviors. Ed Brinksma Original full and short papers, correspondence, and reviews on design Paul Caspi and development of embedded systems, methodologies applied for their Liang-Gee Chen specification, modeling, and design, and adaptation of algorithms for real-time execution are encouraged for submission. Dietmar Dietrich Stephen Edwards The coverage includes complex homogeneous and heterogeneous embedded systems, specification languages and tools for embedded Alain Girault systems, modeling and verification techniques, hardware/software Rajesh Gupta tradeoffs and codesign, new design flows, design methodologies and Susumu Horiguchi synthesis methods, platform-based design, component-based design, adaptation of signal processing algorithms to limited implementation Thomas Kaiser resources, rapid prototyping, computing structures and architectures Bart Kienhuis for complex embedded systems, real-time operating systems, methods Chong-Min Kyung and techniques for the design of low-power systems, interfacing with Miriam Leeser the real world, and novel application case studies and experiences. The coverage, however, does not exclude other interesting related and John McAlister emerging topics like software-defined radio. Example applications Koji Nakano include wireless and data communication systems, speech processing, Antonio Nunez image and video processing, digital signal processing applications, as Sri Parameswaran well as control and instrumentation. Zebo Peng Special Issue Proposals Marco Platzner Proposals for special issues can be submitted directly to the Editor-in- Marc Pouzet Chief or to [email protected]. S. Ramesh Open Access Support Partha Roop The EURASIP JES, as an open access journal, enables immediate, Markus Rupp worldwide, barrier-free online access to the full text of research articles for; reading, downloading, and/or printing any article published in the Asim Smailagic EURASIP JES. Leonel Sousa In this Open Access model, the publication cost should be covered by Jarmo Takala the author’s institution or research funds. Open Access charges, as a re- Jean-Pierre Talpin placement for subscription charges, allow the publishers to make the Juergen Teich published material available for free to all interested online visitors. Dongsheng Wang Hindawi Publishing Corporation Roger Woods 410 Park Avenue, 15th Floor, #287 pmb, New York, NY 10022, USA

http://www.hindawi.com/journals/es/ International Journal of :: Open Access :: Biomedical Imaging

Editor-in-Chief http://www.hindawi.com/journals/ijbi/ Ge Wang Aims and Scope Associate Editors Generally speaking, the scope of biomedical imaging covers data acquisition, Haim Azhari image reconstruction, and image analysis, involving theories, methods, systems, and applications. While tomographic and postprocessing techniques have Kyongtae Bae become increasingly sophisticated, traditional and emerging modalities play Richard Bayford more and more critical roles in anatomical, functional, cellular, and molecular imaging. The overall goal of the International Journal of Biomedical Imaging Freek Beekman (IJBI) is to promote research and development of biomedical imaging by pub- Subhasis Chaudhuri lishing high-quality papers, reviews, and tutorials in this rapidly growing inter- Jyh-Horng Chen disciplinary field. Anne Clough IJBI is operated by a board of editors consisting of internationally known active researchers. IJBI is made available online for free and can also be purchased in Carl Crawford print. IJBI utilizes a web-based review process for speedy turnaround up to high Min Gu standards. In addition to regular issues, special issues will be organized by invited guest editors. Proposals for special issues should be submitted to the Editor-in- Eric Hoffman Chief. Subject areas include (but are not limited to): Jiang Hsieh Digital radiography and tomosynthesis; X-ray computed tomography (CT); Ming Jiang magnetic resonance imaging (MRI); single-photon emission computed tomog- Marc Kachelrie raphy (SPECT); positron emission tomography (PET); ultrasound imaging; diffuse optical tomography, coherence, fluorescence, bioluminescence tomogra- Seung Wook Lee phy and impedance tomography; neutron imaging for biomedical applications; Alfred Louis magnetic and optical spectroscopy and optical biopsy; optical, electron, and scanning tunneling/atomic force microscopy; small animal imaging; function- Erik Meijering al, cellular, and molecular imaging; imaging assays for screening and molecular Vasilis Ntziachristos analysis; microarray image analysis and bioinformatics; emerging biomedical Scott Pohlman imaging techniques; imaging modality fusion; biomedical imaging instrumentation; biomedical image processing, pattern recognition, and analysis; bio- Erik Ritman medical image visualization, compression, transmission, and storage; imaging Jay Rubinstein and modeling related to systems biology and systems biomedicine; applied mathematics, applied physics, and chemistry related to biomedical imaging; Pete Santago grid-enabling technology for biomedical imaging and informatics. Lizhi Sun Special Issue Proposals Jie Tian Proposals for special issues can be submitted directly to the Editor-in-Chief or to Michael Vannier [email protected]. Yue Wang Open Access Support Guowei Wei The “Open Access” movement is a relatively recent development in academic David Wilson publishing. It proposes a new business model for academic publishing that enables immediate, world-wide, barrier-free, open access to the full text of Sunkook Yoo research articles for the best interests of the scientific community. All inter- Habib Zaidi ested readers can read, download, and/or print any open access article without Yantian Zhang requiring a subscription to the journal in which these articles are published. Yibin Zheng Hindawi Publishing Corporation Tiange Zhuang 410 Park Avenue, 15th Floor, #287 pmb, New York, NY 10022, USA

http://www.hindawi.com/journals/ijbi/ EURASIP Journal on :: Open Access :: Information Security

Editor-in-Chief http://www.hindawi.com/journals/is/ Mauro Barni Aims and Scope [email protected] Italy The overall goal of the EURASIP Journal on Information Security (EURASIP JIS), sponsored by the European Association for Signal Associate Editors Processing (EURASIP), is to bring together researchers and prac- Jeffrey A. Bloom titioners dealing with the general field of information security, USA with a particular emphasis on the use of signal processing tools Gwenaël Doërr to enable the security of digital contents. As such, it addresses any UK work whereby security primitives and multimedia signal processing Jean-Luc Dugelay are used together to ensure the secure access to the data. Enabling France technologies include watermarking, data hiding, steganography Teddy Furon and steganalysis, joint signal processing and encryption, percep- France tual hashing, identification, biometrics, fingerprinting, and digital Miroslav Goljan forensics. USA The EURASIP JIS is published using an open access publish- Stefan Katzenbeisser ing model, which makes the full-text of all peer-reviewed papers The Netherlands freely available online with no subscription or registration barriers. Hyoung-Joong Kim EURASIP JIS employs a paperless, electronic submission and eval- Korea uation system to promote a rapid turnaround in the peer-review Darko Kirovski process. Fairness and transparency of the review process are pur- USA sued by traditional and innovative means, including the possibility Deepa Kundur of reviewers of accepted papers to disclose their identity and pub- USA lish a brief commentary together with the article. E. Magli Electronic Submission Italy Manuscripts are invited and should be submitted by one of the au- Fernando Pérez-González thors of the manuscript through the electronic Manuscript Tracking Spain System (MTS) at http://www.hindawi.com/mts/. Regardless of the Alessandro Piva source of the word-processing tool, only electronic PDF files can be Italy submitted through the MTS. Only online submissions are accepted Hans Georg Schaathun to facilitate rapid publication and minimize administrative costs. If UK for some technical reason submission through the MTS is not pos- Martin Steinebach sible, the author can contact [email protected] for support. Germany Open Access Support Qibin Sun Singapore The “Open Access” movement is a relatively recent development in academic publishing. It proposes a new business model for academ- Wade Trappe ic publishing that enables immediate, worldwide, barrier-free, open USA access to the full text of research articles for the best interests of Claus Vielhauer the scientific community. All interested readers can read, download, Germany and/or print any Open Access article without requiring a subscrip- Sviatoslav Voloshynovskiy tion to the journal in which these articles are published. Switzerland

Andreas Westfeld Hindawi Publishing Corporation Germany 410 Park Avenue, 15th Floor, #287 pmb, New York, NY 10022, USA

http://www.hindawi.com/journals/is/ EURASIP BOOK SERIES ON SIGNAL PROCESSING AND COMMUNICATIONS

EURASIP Book Series on Signal Processing and Communications publishes monographs, edited volumes, and textbooks on signal processing and communications. Published Titles • High-Fidelity Multichannel Audio Coding, Dai Tracy Yang, Chris Kyriakakis, and C.-C. Jay Kuo • Genomic Signal Processing and Statistics, Editedby:EdwardR.Dougherty, Ilya Shmulevich, Jie Chen, and Z. Jane Wang • Smart Antennas—State of the Art, Edited by: Thomas Kaiser, Andr´e Bourdoux, Holger Boche, Javier Rodr´ıguez Fonollosa, Jorgen¨ Bach Andersen, and Wolfgang Utschick • Multimedia Fingerprinting Forensics for Traitor Tracing, K. J. Ray Liu, Wade Trappe, Z. Jane Wang, Min Wu, and Hong Zhao • UWB Communication Systems—A Comprehensive Overview, Edited by: Andreas Molisch, Ian Oppermann, Maria Gabriella Di Benedetto, Domenico Porcino, David Bateman, Phillip Rouzet, and Thomas Kaiser

Forthcoming Titles • Signal Processing for the Acoustic Human-Machine Interface, Walter Kellermann and Herbert Buchner • Advances on Nonlinear Signal and Image Processing, Edited by: Stephen Marshall and Giovanni L. Sicuranza • Genetic and Evolutionary Computation for Image Processing and Analysis, Edited by: Stefano Cagnoni, Evelyne Lutton, and Gustavo Olague

Editor-in-Chief Alex Gershman, Darmstadt University of Technology, Germany; [email protected] Editorial Board Zhi Ding, University of California, USA; [email protected] Moncef Gabbouj, Tampere University of Technology, Finland; moncef.gabbouj@tut.ﬁ Peter Grant, University of Edinburgh, UK; [email protected] Ferran Marqu´es, ETSETB Polytechnic University of Catalonia, Spain; [email protected] Marc Moonen, Katholieke Universiteit Leuven, Belgium; [email protected] Hideaki Sakai, Kyoto University, Japan; [email protected] Giovanni Sicuranza, Universita` di Trieste, Italy; [email protected] Bob Stewart, University of Strathclyde, UK; [email protected] Sergios Theodoridis, University of Athens, Greece; [email protected] For more information, please contact [email protected].

http://www.hindawi.com/books/spc/ Forthcoming Volumes in the EURASIP Book Series on Signal Processing and Communications

Signal Processing for the Acoustic Human-Machine Interface

Walter Kellermann and Herbert Buchner; ISBN: 977-5945-16-X

This monograph presents a coherent treatment of the state of the art in acoustic signal processing for speech and audio, especially for ‘natural’ human-machine interfaces, where users are untethered and mobile. This area has attracted many researchers in recent years due to that novel highly advanced signal processing algorithms promise significant practical benefits. For a direct access to the state of the art, this book is designed as a textbook and reference for graduate students, practicing engineers, and researchers with some background in digital signal processing. The book starts with a discussion of the properties of acoustic systems and speech and audio signals involved in the scenario, and then defines the fundamental problems and basic signal processing concepts for both reproduction and acquisition of such signals. For each of these concepts, we start with single-channel algorithms and then strongly emphasize the increasingly important multichannel techniques, which open the door to new solutions by exploiting the spatial domain. The first of these concepts to describe is the extension of acoustic echo cancellation from the single-channel case to multiple loudspeaker channels, to the combination with microphone arrays, and also to nonlinear echo paths. For the enhancement of speech and audio signals as acquired in noisy and reverber- ant environments, we first examine single-channel noise reduction and dereverber- ation schemes. Multichannel schemes are discussed in three chapters on statistical multichannel signal enhancement, classical spatial filtering (supervised beamforming), and blind signal separation for convolutive mixtures, which can be seen as blind beamforming. As an additional building block of natural human-machine interfaces, localization of sources, e.g., as needed for supervised beamforming, is addressed and the current state of the art is reviewed. Finally, the integration of several of the above algorithmic modules into real-world systems is discussed, by way of both general strategies and specific examples.

http://www.hindawi.com/books/spc/

Hindawi Publishing Corporation, 410 Park Avenue, 15th Floor, #287 pmb, INDAWI New York, NY 10022, USA; Fax 1-866-446-3294 (USA, toll-free) Forthcoming Volumes in the EURASIP Book Series on Signal Processing and Communications

Advances on Nonlinear Signal and Image Processing Edited by: Stephen Marshall and Giovanni L. Sicuranza ISBN: 977-5945-21-6

The interest in nonlinear methods in signal processing is steadily increasing, since nowadays the advances in computational capacities make it possible to implement sophisticated nonlinear processing techniques which in turn allow remarkable improvements with respect to standard and well-consolidated linear processing approaches. The aim of the book is to present a review of emerging new areas of interest involving nonlinear signal and image processing theories, techniques, and tools. More than 30 leading researchers have contributed to this book covering the major topics relevant to nonlinear signal processing. These topics include recent theoretical contributions in diﬀerent areas of digital ﬁltering and a number of applications in genomics, speech analysis and synthesis, communication system, active noise control, digital watermarking, feature extraction, texture analysis, and color image processing. The book is intended as a reference for recent advances and new applications of theories, techniques, and tools in the area of nonlinear signal processing. The target audience are graduate students and practitioners working on modern signal processing applications.

http://www.hindawi.com/books/spc/

Genetic and Evolutionary Computation for Image Processing and Analysis

Edited by: Stefano Cagnoni, Evelyne Lutton, and Gustavo Olague ISBN: 977-5945-22-4

Image analysis and processing is steadily gaining relevance within the large number of application fields to which genetic and evolutionary computation (GEC) techniques are applied. Although more and more examples of such applications can be found in literature, they are scattered, apart from a few exceptions, in proceedings and journals dedicated to more general topics. This book is the first attempt to offer a panoramic view on the field, by describing applications of most mainstream GEC techniques to a wide range of problems in image processing and analysis. More than 20 leading researchers in the field have contributed to this book, covering topics ranging from low-level image processing to high-level image analysis in advanced computer vision applications. Although the book is mainly application- oriented, particular care has been given to introducing GEC methods, in each chapter, at a level which makes them accessible to a wide audience. The expected target of the book comprises practitioners and researchers in image analysis and processing who may not be familiar with GEC techniques. At the same time, the book can as well be of interest for researchers in evolutionary computation, since most contributions focus on applications of genetic and evolutionary techniques which are based on nontrivial implementations of such methods. This feature reflects the nature of the contributions which are authored both by researchers for which GEC is the main field of interest and by researchers whose work is mainly focused on image processing and analysis.

http://www.hindawi.com/books/spc/

Advances in Signal Transforms: Theory and Applications

Edited by: J. Astola and L. Yaroslavsky ISBN: 977-5945-11-9

Digital signal transforms are of a fundamental value in digital signal and image processing. Their role is manifold. Transforms selected appropriately enable substantial compressing signals and images for storage and transmission. No signal recovery, image reconstruction and restoration task can be efficiently solved without using digital signal transforms. Transforms are successfully used for logic design and digital data encryption. Fast transforms are the main tools for acceleration of computations in digital signal and image processing. The volume collects in one book most recent developments in the theory and practice of the design and usage of transforms in digital signal and image processing. It emerged from the series of reports published by Tampere International Centre for Signal Processing, Tampere University of Technology. For the volume, all contributions are appropriately updated to represent the state of the art in the field and to cover the most recent developments in different aspects of the theory and applications of transforms. The book consists of two parts that represent two major directions in the field: development of new transforms and development of transform based signal and image processing algorithms. The first part contains four chapters devoted to recent advances in transforms for image compression and switching and logic design and to new fast transforms for digital holography and tomography. In the second part, advanced transform based signal and image algorithms are considered: signal and image local adaptive restoration methods and two complementing families of signal and image re-sampling algorithms, fast transform based discrete sinc- interpolation and spline theory based ones.

http://www.hindawi.com/books/spc/

Hindawi Publishing Corporation, 410 Park Avenue, 15th Floor, #287 pmb, INDAWI New York, NY 10022, USA; Fax 1-866-446-3294 (USA, toll-free) How to Become a EURASIP Member

EURASIP membership is open to all persons and institutions active or interested in signal processing within Europe or outside. Membership benefits include free subscription to EURASIP Newsletter; reduced subscription to the journals “Signal Processing,” “Speech Communication,” “Signal Processing: Image Communication,” “EURASIP Journal on Ap- plied Signal Processing,” and “EURASIP Journal on Wireless Communications and Net- working”; reduced fees for conferences and workshops that are sponsored or cosponsored by the Association; and reduced fees for EURASIP’s short courses. Personal (individual) membership must be paid by personal funds. To validate their category, students should provide an endorsement from school of ricials stating that they are enrolled in regular academic programs. Please send an application letter containing your name, title, position, company/institution, full mailing address, country, phone number, telefax number, and the desired journals to EURASIP, European Association for Signal, Speech, and Image Processing, EPFL-STI-LTS, CH-1015 Lausanne, Switzerland, together with your remittance. Your payments to EURASIP can be made in any of the following methods. In all cases, Euro is the only acceptable currency: 1. Using credit cards: MasterCard, American Express or Visa only. Please fill in your Card No., Expiring date, and signature. 2. Using cheques drawn in Euro mailed to EURASIP. 3. Using international money orders drawn in Euro mailed to EURASIP. 4. Requesting your bank to write transfer funds including your name to EURASIP at the Swiss Credit Bank Lausanne, Switzerland, account no. 322.294-31. 5. Using international postal money transfer to EURASIP postal account no. 10-3279-8 in Lausanne, Switzerland. For membership inquiries contact Fabienne Vionnet at sigpro@epfl.ch Please remember to mention your name and your EURASIP membership number on all payment forms.

2006 Print Only Journal Prices for EURASIP Members (Elsevier journals)

Institutional Individual Signal Processing €2461 €116 Speech Communication €952 €101 Signal Processing: Image Communication €792 €96

2006 Online Only Journal Prices for EURASIP Members (Elsevier Journals)

Institutional Individual Signal Processing – €87 Speech Communication – €87 Signal Processing: Image Communication – €85

All EURASIP members that subscribe to an Elsevier journal have access to its electronic version by the Elsevier Website. How to Become a Member of EURASIP 179

2006 Print Only Journal Prices for EURASIP Members (Hindawi Journals)

Institutional Individual EURASIP JASP €1415 €137

2006 Online Only Journal Prices for EURASIP Members (Hindawi Journals)

Institutional Individual EURASIP JASP €1285 €46 EURASIP JASMP Open Access Open Access EURASIP JBSB Open Access Open Access EURASIP JES Open Access Open Access EURASIP JWCN Open Access Open Access

2006 Print and Online Journal Prices for EURASIP Members (Hindawi Journals)

Institutional Individual EURASIP JASP €1540 €171 Subscribers to the online edition of any journal shall receive perpetual online access to the current volume as well as all back volumes of that journal even if they cancel their subscription in the future. EURASIP MEMBERSHIP APPLICATION

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