DOCSLIB.ORG

Multipath Interference Characterization in Wireless Communication Systems

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Multipath Interference Characterization in Wireless Communication Systems Multipath Interference Characterization in Wireless Communication Systems Michael Rice BYU Wireless Communications Lab 9/29/00 BYU Wireless Communications 1 166 Multipath Propagation • Multiple paths between transmitter and receiver • Constructive/destructive interference • Dramatic changes in received signal amplitude and phase as a result of small changes (λ/2) in the spatial separation between a receiver and transmitter. • For Mobile radio (cellular, PCS, etc) the channel is time-variant because motion between the transmitter and receiver results in propagation path changes. • Terms: Rayleigh Fading, Rice Fading, Flat Fading, Frequency Selective Fading, Slow Fading, Fast Fading …. • What do all these mean? 9/29/00 BYU Wireless Communications 2 167 LTI System Model N −1 θ = j k δ ()−τ h(t) ∑ ak e t k = s(t) r(t) k 0 h(t) N −1 θ = δ ()+ j k δ (−τ ) a0 t ∑ ak e t k k =1 line-of-sight multipath propagation propagation N −1 θ = + j k ()−τ r(t) a0s(t) ∑ ak e s t k k =1 line-of-sight multipath component component 9/29/00 BYU Wireless Communications 3 168 Some Important Special Cases τ ≈ All the delays are so small and we approximate k 0 for all k N −1 θ = + j k ()−τ r(t) a0s(t) ∑ ak e s t k k=1 N −1 θ ≈ + j k () a0s(t) ∑ ak e s t k=1 N −1 θ = + j k a0 ∑ ak e s(t) • sum of complex random numbers (random amplitudes = k 1 and phases) α • if N is large enough, this sum is well approximated by complex Gaussian pdf N −1 θ α = α + α m = E{}α = E a e j k R j I a ∑ k k =1 2 α ()σ N −1 R ~ N ma , a θ = ∑ E{}a E{}e j k 2 k α ~ N()m ,σ k =1 I a a = θ []−π π 0 when k ~ U , 9/29/00 BYU Wireless Communications 4 169 Some Important Special Cases τ ≈ All the delays are so small and we approximate k 0 for all k 2 2 φ N −1 = ()()+α + α j θ r(t) a0 R I e s(t) = + j k ()−τ r(t) a0s(t) ∑ ak e s t k 2 2 jφ k=1 = + X1 X 2 e s(t) N −1 θ ≈ + j k () a0s(t) ∑ ak e s t k=1 N −1 ()σ 2 ()σ 2 θ X1 ~ N a0 , a X 2 ~ N 0, a = + j k a0 ∑ ak e s(t) k =1 = []+α a0 s(t) = []+α + α a0 R j I s(t) = ()()+α 2 + α 2 jφ a0 R I e s(t) 9/29/00 BYU Wireless Communications 5 170 Important PDF’s ()σ 2 X1 ~ N a0 , a ()σ 2 X1 ~ N 0, a ()σ 2 X 2 ~ N 0, a ()σ 2 X 2 ~ N 0, a = 2 + 2 W X1 X 2 = 2 + 2 W X1 X 2 2 + − a0 w 2 w 1 2σ a0 Non-central − = a 1 2σ 2 pW (w) 2 e I0 w 2 = a Chi-square pdf σ σ pW (w) e 2 a a Chi-square pdf σ 2 2 a 2 2 = + 2 2 U X1 X 2 = + U X1 X 2 a2 +u 2 − 0 u2 u σ 2 ua − 2 a 0 σ 2 ()= Rice pdf u 2 a pU u 2 e I0 2 ()= σ σ pU u 2 e Rayleigh pdf a a σ a 9/29/00 BYU Wireless Communications 6 171 Back to Some Important Special Cases τ ≈ All the delays are so small and we approximate k 0 for all k > = a0 0 a0 0 N −1 N −1 θ θ = + j k ()−τ = j k ()−τ r(t) a0s(t) ∑ak e s t k r(t) ∑ ak e s t k k=1 k=1 N −1 N −1 θ θ ≈ + j k () ≈ j k () a0s(t) ∑ak e s t ∑ ak e s t k=1 k=1 = ()()+α 2 + α 2 jφ = ()()α 2 + α 2 jφ a0 R I e s(t) R I e s(t) Rice pdf Rayleigh pdf “Ricean fading” “Rayleigh fading” 9/29/00 BYU Wireless Communications 7 172 Some Important Special Cases τ ≈τ All the delays are small and we approximate k for all k > = a0 0 a0 0 N −1 N −1 θ θ = + j k ()−τ = j k ()−τ r(t) a0s(t) ∑ ak e s t k r(t) ∑ak e s t k k=1 k=1 N −1 N −1 θ θ ≈ + j k ()−τ ≈ j k ()−τ a0s(t) ∑ ak e s t ∑ak e s t k=1 k=1 = + ()()α 2 + α 2 jφ ()−τ = ()()α 2 + α 2 jφ ()−τ a0s(t) R I e s t R I e s t Rayleigh pdf Rayleigh pdf “Line-of-sight with Rayleigh Fading” “Rayleigh fading” 9/29/00 BYU Wireless Communications 8 173 Multiplicative Fading In the past two examples, the received signal was of the form r(t) = Fe jφ s(t) The fading takes the form of a random attenuation: the transmitted signal is multiplied by a random value whose envelope is described by the Rice or Rayleigh pdf. This is sometimes called multiplicative fading for the obvious reason. It is also called flat fading since all spectral components in s(t) are attenuated by the same value. 9/29/00 BYU Wireless Communications 9 174 An Example θ 2 h(t) = δ ()t + ae j δ (t −τ ) H ( f ) H ()f =1+ ae j(θ −2πfτ ) 2 H ()f 2 =1+ a2 + 2a cos()2πfτ −θ ()1+ a ()1− a 2 f s(t) h(t) r(t) θ 1 τ S()f R()f H ( f ) 2 (dB) ()+ 2 10log10 1 a S()f R()f ? ? ? ? ()− 2 ? ? 10log10 1 a ? ? f f f −W W −W W θ 1 τ 9/29/00 BYU Wireless Communications 10 175 Example (continued) attenuation is even across the s(t) h(t) r(t) signal band (i.e. channel transfer function is “flat” in the () () τ is very small S f R f signal band) 2 S()f H ( f ) R()f f f f −W W −W W attenuation is uneven across the signal band -- this causes τ is very large “frequency selective fading” 2 S()f H ( f ) R()f f f f −W W −W W 9/29/00 BYU Wireless Communications 11 176 Another important special case τ <τ < <τ The delays are all different: 1 2 L N −1 N −1 θ = + j k ()−τ r(t) a0s(t) ∑ ak e s t k k=1 intersymbol interference if the delays are “long enough”, the multipath reflections are resolvable. 9/29/00 BYU Wireless Communications 12 177 Two common models for non-multiplicative fading s(t) ∆ ∆ L ∆ Taped delay-line with α × α × α × α × α × random weights 1 2 3 N −2 N −1 + + + + r(t) central limit theorem: approximately a Gaussian RP Additive complex N −1 Gaussian random process θ = + j k ()−τ r(t) a0s(t) ∑ ak e s t k k=1 ≈ +ξ a0s(t) (t) 9/29/00 BYU Wireless Communications 13 178 Multipath Intensity Profile The characterization of multipath fading as either flat (multiplicative) or frequency selective (non-multiplicative) is governed by the delays: small delays ⇒ flat fading (multiplicative fading) large delays ⇒ frequency selective fading (non-multiplicative fading) The values of the delay are quantified by the multipath intensity profile S(τ) 1. “maximum excess delay” or “multipath spread” ()τ τ = {}* ()()τ τ Rhh 1, 2 E h 1 h 2 T =τ − = S()(τ δ τ −τ ) m N 1 uncorrelated 1 1 2 scattering (US) 2. average delay N −1 τ assumption − ∑ ak k 2 1 N 1 S()τ = E{}h ()τ τ = ∑τ or τ = k =1 − k N −1 N 1 k =1 ∑ ak S()τ = 3. delay spread k 1 N −1 2 2 − ∑ a τ 1 N 1 k k σ = τ 2 −τ 2 σ = k =1 −τ 2 power τ ∑ or − k τ N −1 τ N 1 k =1 2 τ τ τ ∑ ak 1 2 N −1 k =1 9/29/00 BYU Wireless Communications 14 179 Characterization using the multipath intensity profile S()τ Compare multipath spread Tm with symbol Compare multipath spread Tm with symbol power time Ts: τ time Ts: τ τ τ 1 2 N −1 ⇒ Tm < Ts ⇒ flat fading (frequency non- Tm < Ts flat fading (frequency non- selectiveselective fading) fading) 1. “maximum excess delay” or “multipath spread” ⇒ =τ Tm > Ts ⇒ frequency selective fading Tm N −1 Tm > Ts frequency selective fading 2. average delay N −1 ∑ a τ 1 N −1 k k τ = ∑τ or τ = k =1 − k N −1 N 1 k =1 ∑ ak = 3. delay spread k 1 N −1 2τ 2 N −1 ∑ ak k 1 2 2 k =1 2 σ τ = ∑τ −τ or σ = −τ − k τ N −1 N 1 k =1 2 ∑ ak k =1 9/29/00 BYU Wireless Communications 15 180 Spaced Frequency Correlation Function S()τ R()∆f Fourier Xform power τ f τ τ τ 1 2 N −1 f0 R(∆f) is the “correlation between the channel response to two signals as a function of the Compare coherence bandwidth f0 with frequency difference between the two signals.” Compare coherence bandwidth f0 with transmittedtransmitted signal signal bandwidth bandwidth W W: : “What is the correlation between received ⇒ f0 > W ⇒ flat fading (frequency non- signals that are spaced in frequency ∆f = f -f ?” f0 > W flat fading (frequency non- 1 2 selectiveselective fading) fading) Coherence bandwidth f = a statistical measure ⇒ 0 f0 < W ⇒ frequency selective fading of the range of frequencies over which the f0 < W frequency selective fading channel passes all spectral components with approximately equal gain and linear phase.
Load more

Recommended publications
  • Protection of Data Transmission Systems from the Influence of Intersymbol Interference of Signals
    59 Protection of data transmission systems from the influence of intersymbol interference of signals © Volodymyr Yartsev 1 and © Dmitry Gololobov 2 1 State University of Telecommunications, Kyiv, Ukraine 2 Taras Shevchenko National University of Kyiv, Ukraine [email protected], [email protected] Abstract. The problems of creating a regenerator of an optical system for trans- mitting discrete messages with the aim of protecting against the influence of in- tersymbol interference of signals using the methods of statistical theory for a mixture of probability distributions are considered. A demodulator adaptation model that calculates the weighted sum of 4 samples of the input signal and com- pares the resulting sum with a threshold value has been created and studied. The main operations for adaptation of the regenerator during demodulation of signals distorted by intersymbol interference are assigned under certain transmission conditions, which are formulated as the task of evaluating some parameters of the probability distribution of the mixture. A block diagram of a regenerating optical signal in which an algorithm for digital processing of a mixture is imple- mented is proposed. The analysis is carried out and the requirements for the pa- rameters of the analog-to-digital converter used in the regenerator are deter- mined. The results of modeling digital processing of a discrete test message to verify the process of adaptation of the device to the influence of intersymbol dis- tortions of signals are presented. The block diagram of a digital processing device is substantiated, in which high-speed nodes that perform real-time processing are combined with a microprocessor, which implements an algorithm for adapting the regenerator to specific message transmission conditions.
    [Show full text]
  • VHF and UHF Signal Characteristics Observed on a Long Knife-Edge Diffraction Path A
    JOURNAL OF RESEARCH of the National Bureau of Standards- D. Radio Propagatior. Vol. 65D, No. 5, September- Odober 1961 VHF and UHF Signal Characteristics Observed on a Long Knife-Edge Diffraction Path A. P. Barsis and R. S. Kirby (R eceived April 6, 1961) Contribution from Central Radio Propagation Laboratory, National Bureau of Standards, Boulder, Colo. During 1959 and 1960 long-term transmission loss measurements were performed over a 223 kilom eter path in Eastern Colorado using frequencies of 100 and 751 megacycles per second. This path intersects P ikes P eak which forms a knife-edge type obstacle visible from both terminals. The transmission loss measurements have been analyzed in terms of diurnal a nd seaso nal variations in hourly medians and in instan taneous levels. As expected, results show t hat the long-term fading range is substantially less t han expected for t ropospheric seatter paths of comparable length. T ransmission loss levels were in general agreem ent wi t h predicted k ni fe-edge d iffraction propagation when a ll owance is made for rounding of t he knife edge. A technique for est imatin g long-term fading ra nges is presented a nd t he res ults are in good agreement with observations. Short-term variations in some case resemble t he space-wave fadeo uts commonly observed on within- the-horizon paths, a lthough other phe­ nomena may contribute to t he fadin g. Since t he foreground telTain was rough there was no evidence of direct a nd grou nd-refl ected lobe structure.
    [Show full text]
  • Rayleigh Fading Multi-Antenna Channels
    EURASIP Journal on Applied Signal Processing 2002:3, 316–329 c 2002 Hindawi Publishing Corporation Rayleigh Fading Multi-Antenna Channels Alex Grant Institute for Telecommunications Research, University of South Australia, Mawson Lakes Boulevard, Mawson Lakes, SA 5095, Australia Email: [email protected] Received 29 May 2001 Information theoretic properties of flat fading channels with multiple antennas are investigated. Perfect channel knowledge at the receiver is assumed. Expressions for maximum information rates and outage probabilities are derived. The advantages of transmitter channel knowledge are determined and a critical threshold is found beyond which such channel knowledge gains very little. Asymptotic expressions for the error exponent are found. For the case of transmit diversity closed form expressions for the error exponent and cutoff rate are given. The use of orthogonal modulating signals is shown to be asymptotically optimal in terms of information rate. Keywords and phrases: space-time channels, transmit diversity, information theory, error exponents. 1. INTRODUCTION receivers such as the decorrelator and MMSE filter [10]; (b) mitigation of fading effects by averaging over the spatial Wireless access to data networks such as the Internet is ex- properties of the fading process. This is a dual of interleav- pected to be an area of rapid growth for mobile communi- ing techniques which average over the temporal properties cations. High user densities will require very high speed low of the fading process; (c) increased link margins by simply delay links in order to support emerging Internet applica- collecting more of the transmitted energy at the receiver. tions such as voice and video.
    [Show full text]
  • Pulse Shape Filtering in Wireless Communication-A Critical Analysis
    (IJACSA) International Journal of Advanced Computer Science and Applications, Vol. 2, No.3, March 2011 Pulse Shape Filtering in Wireless Communication-A Critical Analysis A. S Kang Vishal Sharma Assistant Professor, Deptt of Electronics and Assistant Professor, Deptt of Electronics and Communication Engg Communication Engg SSG Panjab University Regional Centre University Institute of Engineering and Technology Hoshiarpur, Punjab, INDIA Panjab University Chandigarh - 160014, INDIA [email protected] [email protected] Abstract—The goal for the Third Generation (3G) of mobile networks. The standard that has emerged is based on ETSI's communications system is to seamlessly integrate a wide variety Universal Mobile Telecommunication System (UMTS) and is of communication services. The rapidly increasing popularity of commonly known as UMTS Terrestrial Radio Access (UTRA) mobile radio services has created a series of technological [1]. The access scheme for UTRA is Direct Sequence Code challenges. One of this is the need for power and spectrally Division Multiple Access (DSCDMA). The information is efficient modulation schemes to meet the spectral requirements of spread over a band of approximately 5 MHz. This wide mobile communications. Pulse shaping plays a crucial role in bandwidth has given rise to the name Wideband CDMA or spectral shaping in the modern wireless communication to reduce WCDMA.[8-9] the spectral bandwidth. Pulse shaping is a spectral processing technique by which fractional out of band power is reduced for The future mobile systems should support multimedia low cost, reliable , power and spectrally efficient mobile radio services. WCDMA systems have higher capacity, better communication systems. It is clear that the pulse shaping filter properties for combating multipath fading, and greater not only reduces inter-symbol interference (ISI), but it also flexibility in providing multimedia services with defferent reduces adjacent channel interference.
    [Show full text]
  • Capacity of Flat and Freq.-Selective Fading Channels Linear Digital Modulation Review
    Lecture 8 - EE 359: Wireless Communications - Winter 2020 Capacity of Flat and Freq.-Selective Fading Channels Linear Digital Modulation Review Lecture Outline • Channel Inversion with Fixed Rate Transmission • Comparison of Fading Channel Capacity under Different Schemes • Capacity of Frequency Selective Fading Channels • Review of Linear Digital Modulation • Performance of Linear Modulation in AWGN 1. Channel Inversion with Fixed Rate Transmission • Suboptimal transmission strategy where fading is inverted to maintain constant re- ceived SNR. • Simplifies system design and is used in CDMA systems for power control. • Capacity with channel inversion greatly reduced over that with optimal adaptation (capacity equals zero in Rayleigh fading). • Truncated inversion: performance greatly improved by inverting above a cutoff γ0. 2. Comparison of Fading Channel Capacity under Different Schemes: • Fading generally decreases channel capacity. • Rate/power adaptation have similar capacity as rate adaptation alone. • Rate adaptation alone has same capacity as no adaptation (RX CSI only) but rate adaptation is more practical due to complexity of ML decoding over long blocklengths that experience all fading values. This ML decoding is necesssary to achieve capacity in the RX CSI only case. • Truncated channel inversion is more practical than rate adaptation, with significant capacity gain over full channel inversion, which has zero capacity in Rayleigh fading. 3. Capacity of Frequency Selective Fading Channels • Capacity for time-invariant frequency-selective fading channels is a \water-filling” of power over frequency. • For time-varying ISI channels, capacity is unknown in general. Approximate by di- viding up the bandwidth subbands of width equal to the coherence bandwidth (same premise as multicarrier modulation) with independent fading in each subband.
    [Show full text]
  • Fading Channels: Capacity, BER and Diversity
    Fading Channels: Capacity, BER and Diversity Master Universitario en Ingenier´ıade Telecomunicaci´on I. Santamar´ıa Universidad de Cantabria Introduction Capacity BER Diversity Conclusions Contents Introduction Capacity BER Diversity Conclusions Fading Channels: Capacity, BER and Diversity 0/48 Introduction Capacity BER Diversity Conclusions Introduction I We have seen that the randomness of signal attenuation (fading) is the main challenge of wireless communication systems I In this lecture, we will discuss how fading affects 1. The capacity of the channel 2. The Bit Error Rate (BER) I We will also study how this channel randomness can be used or exploited to improve performance diversity ! Fading Channels: Capacity, BER and Diversity 1/48 Introduction Capacity BER Diversity Conclusions General communication system model sˆ[n] bˆ[n] b[n] s[n] Channel Channel Source Modulator Channel ⊕ Demod. Encoder Decoder Noise I The channel encoder (FEC, convolutional, turbo, LDPC ...) adds redundancy to protect the source against errors introduced by the channel I The capacity depends on the fading model of the channel (constant channel, ergodic/block fading), as well as on the channel state information (CSI) available at the Tx/Rx Let us start reviewing the Additive White Gaussian Noise (AWGN) channel: no fading Fading Channels: Capacity, BER and Diversity 2/48 Introduction Capacity BER Diversity Conclusions AWGN Channel I Let us consider a discrete-time AWGN channel y[n] = hs[n] + r[n] where r[n] is the additive white Gaussian noise, s[n] is the
    [Show full text]
  • 2 the Wireless Channel
    CHAPTER 2 The wireless channel A good understanding of the wireless channel, its key physical parameters and the modeling issues, lays the foundation for the rest of the book. This is the goal of this chapter. A defining characteristic of the mobile wireless channel is the variations of the channel strength over time and over frequency. The variations can be roughly divided into two types (Figure 2.1): • Large-scale fading, due to path loss of signal as a function of distance and shadowing by large objects such as buildings and hills. This occurs as the mobile moves through a distance of the order of the cell size, and is typically frequency independent. • Small-scale fading, due to the constructive and destructive interference of the multiple signal paths between the transmitter and receiver. This occurs at the spatialscaleoftheorderofthecarrierwavelength,andisfrequencydependent. We will talk about both types of fading in this chapter, but with more emphasis on the latter. Large-scale fading is more relevant to issues such as cell-site planning. Small-scale multipath fading is more relevant to the design of reliable and efficient communication systems – the focus of this book. We start with the physical modeling of the wireless channel in terms of elec- tromagnetic waves. We then derive an input/output linear time-varying model for the channel, and define some important physical parameters. Finally, we introduce a few statistical models of the channel variation over time and over frequency. 2.1 Physical modeling for wireless channels Wireless channels operate through electromagnetic radiation from the trans- mitter to the receiver.
    [Show full text]
  • Distortion Exponent of Parallel Fading Channels
    Distortion Exponent of Parallel Fading Channels Deniz Gunduz, Elza Erkip Department of Electrical and Computer Engineering, Polytechnic University, Brooklyn, NY 11201, USA [email protected], [email protected] Abstract— We consider the end-to-end distortion achieved by the fading process. Lack of channel state information at the transmitting a continuous amplitude source over M parallel, transmitter prevents the design of a channel code that achieves independent quasi-static fading channels. We analyze the high the instantaneous channel capacity and requires a code that SNR expected distortion behavior characterized by the distortion exponent. We first give an upper bound for the distortion performs well on the average. We aim to design a joint source- exponent in terms of the bandwidth ratio between the channel channel code that achieves the minimum expected end-to-end and the source assuming the availability of the channel state distortion. Our main focus is the high SNR behavior of this information at the transmitter. Then we propose joint source- expected distortion (ED). This behavior is characterized by the channel coding schemes based on layered source coding and distortion exponent denoted by ¢ and defined as multiple rate channel coding. We show that the upper bound is tight for large and small bandwidth ratios. For the rest, we log ED provide the best known distortion exponents in the literature. ¢ = ¡ lim : (1) SNR!1 log SNR By suitably scaling the bandwidth ratio, our results would also apply to block fading channels. When we consider digital transmission strategies that first compress the source and then transmit over the channel at I.
    [Show full text]
  • On Routing in Random Rayleigh Fading Networks Martin Haenggi, Senior Member, IEEE
    IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, VOL. 4, NO. 4, JULY 2005 1553 On Routing in Random Rayleigh Fading Networks Martin Haenggi, Senior Member, IEEE Abstract—This paper addresses the routing problem for large loss probabilities increase with the number of hops (unless the wireless networks of randomly distributed nodes with Rayleigh transmit power is adapted). fading channels. First, we establish that the distances between To overcome some of these limitations of the “disk model,” neighboring nodes in a Poisson point process follow a generalized Rayleigh distribution. Based on this result, it is then shown that, we employ a simple Rayleigh fading link model that relates given an end-to-end packet delivery probability (as a quality of transmit power, large-scale path loss, and the success of a service requirement), the energy benefits of routing over many transmission. The end-to-end packet delivery probability over short hops are significantly smaller than for deterministic network a multihop route is the product of the link-level reception models that are based on the geometric disk abstraction. If the probabilities. permissible delay for short-hop routing and long-hop routing is the same, it turns out that routing over fewer but longer hops may While fading has been considered in the context of packet even outperform nearest-neighbor routing, in particular for high networks [16], [17], its impact on the network (and higher) end-to-end delivery probabilities. layers is largely an open problem. This paper attempts to shed Index Terms—Ad hoc networks, communication systems, fading some light on this cross-layer issue by analyzing the perfor- channels, Poisson processes, probability, routing.
    [Show full text]
  • Kahn Communications, Inc. 425 Merrick Avenue Westbury, New York 11590 (516) 2222221
    KAHN COMMUNICATIONS, INC. 425 MERRICK AVENUE WESTBURY, NEW YORK 11590 (516) 2222221 THE "WGAS EFFECT" AND THE FUTURE OF AM RADIO In the history of broadcasting a number of "Effects" have dramatically impacted on broadcasting. For example, the "Capture Effect" and the "Multipath Effect" of FM, and earlier "Radio Luxemburg Effect" helped shape broadcasting history. More recently, "Clicks and Pops", "Platform Motion", and "Rain Noise" have influenced the path of AM Stereo. Remember when the Magnavox system was selected by the FCC as the standard in 1980 and the "Click and Pop" effect was discovered. By 1982 it became clear that this "Click and Pop" problem made it essential that the FCC revisit its decision. There is now a new phenomenon which we propose to name the "WGAS Effect" because it was first described in the "Open Mike" section of the September 7, 1987 issue of "Broadcasting" by Mr. Glenn Mace, President of WGAS, South Gastonia, North Carolina. It is essential that all AM broadcasters carefully read this short letter because the very future of AM radio may depend upon the industries knowledge of its contents. It should be stressed that WGAS does not, and cannot, endorse our stereo system as they have never used it. But, nevertheless, we are most appreciative that Mr. Mace has taken the time and effort to make his observations public on this important matter. More will follow re the "WGAS Effect" and how it impacts on all stations, large and small, which must serve listeners in their 25 my/meter contour and beyond. age.
    [Show full text]
  • BER Analysis of Digital Broadcasting System Through AWGN and Rayleigh Channels
    International Journal of Engineering and Advanced Technology (IJEAT) ISSN: 2249 – 8958, Volume-2 Issue-1, October 2012 BER Analysis of Digital Broadcasting System Through AWGN and Rayleigh Channels P.Ravi Kumar, V.Venkata Rao., M.Srinivasa Rao. transmission system based on Eureka-147 standard [1]. The Abstract — Radio broadcasting technology in this era of design consists of energy dispersal scrambler, QPSK symbol compact disc is expected to deliver high quality audio mapping, convolutional encoder (FEC), D-QPSK modulator programmes in mobile environment. The Eureka-147 Digital with frequency interleaving and OFDM signal generator Audio Broadcasting (DAB) system with coded OFDM (IFFT) in the transmitter side and in the receiver technology accomplish this demand by making receivers highly corresponding inverse operations is carried out along with robust against effects of multipath fading environment. In this fine time synchronization [4] using phase reference symbol. paper, we have analysed the performance of DAB system conforming to the parameters established by the ETSI (EN 300 DAB transmission mode-II is implemented. A frame based 401) using time and frequency interleaving, concatenated processing is used in this work. Bit error rate (BER) has been Bose-Chaudhuri- Hocquenghem coding and convolutional considered as the performance index in all analysis. The coding method in different transmission channels. The results analysis has been carried out with simulation studies under show that concatenated channel coding improves the system MATLAB environment. performance compared to convolutional coding. Following this introduction the remaining part of the paper is organized as follows. Section II introduces the DAB Keywords- DAB, OFDM, Multipath effect, concatenated system standard.
    [Show full text]
  • Iterative Methods for Cancellation of Intercarrier Interference in OFDM Systems
    MITSUBISHI ELECTRIC RESEARCH LABORATORIES http://www.merl.com Iterative Methods for Cancellation of Intercarrier Interference in OFDM Systems Andreas Molisch, Martin Toeltsch, Sameer Vermani TR2007-096 August 2008 Abstract We consider orthogonal frequency-division multiplexing systems with intercarrier interference (ICI) due to insufficient cyclic prefix and/or temporal variations. Intersymbol interference (ISI) and ICI lead to an error floor in conventional receivers. We suggest two techniques for the equalization of ICI. The first, called ”operator-perturbation technique” is an iterative technique for the inversion of a linear system of equations. Alternatively, we show that serial or parallel interference cancellation can be used to drastically reduce the error floor. Simulations show that, depending on the SNR and the origin of the ICI, one of the schemes performs best. In all cases our schemes lead to a drastic reduction of the bit error rate. IEEE Transactions on Vehicular Technology, 2007 This work may not be copied or reproduced in whole or in part for any commercial purpose. Permission to copy in whole or in part without payment of fee is granted for nonprofit educational and research purposes provided that all such whole or partial copies include the following: a notice that such copying is by permission of Mitsubishi Electric Research Laboratories, Inc.; an acknowledgment of the authors and individual contributions to the work; and all applicable portions of the copyright notice. Copying, reproduction, or republishing for any other purpose shall require a license with payment of fee to Mitsubishi Electric Research Laboratories, Inc. All rights reserved. Copyright c Mitsubishi Electric Research Laboratories, Inc., 2008 201 Broadway, Cambridge, Massachusetts 02139 MERLCoverPageSide2 2158 IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, VOL.
    [Show full text]