DOCSLIB.ORG

Transmit/Receive-Antenna Diversity Techniques for OFDM Systems

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Transmit/Receive-Antenna Diversity Techniques for OFDM Systems Multi-Carrier Spread-Spectrum and Related Topics Transmit/Receive-Antenna Diversity Techniques for OFDM Systems ARMIN DAMMANN,STEFAN KAISER Institute of Communications and Navigation, German Aerospace Center (DLR), P.O.Box 1116, D-82230 Wessling, Germany {Armin.Dammann, Stefan.Kaiser}@DLR.de Abstract. In this paper, we investigate different antenna diversity concepts, which can be easily applied to orthogonal frequency division multiplexing (OFDM) systems. The focus is on standard compatibility, i.e. these schemes can be implemented to already existing OFDM systems without changing the standards. The introduced diversity techniques are applied exemplarily to the DVB-T system. Bit error performance investigations were done by simulation for different DVB-T and diversity parameter sets. 1 INTRODUCTION multipath environments, it is necessary for wireless com- munications systems to use techniques like interleaving and Future mobile wireless systems are required to pro- channel coding in addition to OFDM. These techniques vide high data rate services in a spectral efficient man- add redundancy and diversity in time and frequency di- ner due to the high costs of bandwidth resources, e.g. rection. For many scattering environments, spatial diver- ≈ 400, 000, 000 e/MHz for UMTS in Germany. In terms sity is another effective way to improve the error perfor- of power efficiency - especially for mobiles - and electro- mance of wireless radio systems. In [6, 7] space-time- magnetic pollution it is required to keep the isotropic radi- coding is proposed in order to get the benefits of chan- ated power as low as possible. Particularly the electromag- nel coding in combination with spatial (antenna) diver- netic radiation charge becomes more and more important sity. Unfortunately space-time-coding is not suitable for for the acceptance of wireless systems in society. Wireless extending existing systems, because this would make non systems have to operate in different environments. So a standard conformable modifications necessary. Therefore mobile is expected to work reliably in scenarios like rural, for standardized systems additional spatial diversity tech- urban, indoor, outdoor, etc. niques can only be implemented, if this modifications keep Mobile communication systems mainly suffer from the systems standard compatible. In [8] such techniques for time-varying multipath fading with extremely different the transmitter side are proposed. multipath intensity profiles [1]. For systems, which have to work in multipath environments, an improvement in er- In this paper we will investigate standard conformable ror performance may become very difficult. Already a antenna diversity techniques, which are well suited for the slight improvement in the bit error rate can necessitate a extension of existing standardized OFDM systems. Sec- huge amount of additional transmitter power, which con- tion 2 introduces diversity techniques for both transmitter tradicts the aforementioned item of an economically use of and receiver. At this, the main idea is to increase the fre- transmission power. It is an enormous challenge to design quency selectivity of the resulting channel transfer function wireless communication systems, which are capable to deal by specific cyclic delays at the transmitter and/or receiver with these varying scenarios. antennas. The transmitter sided delay diversity is also in- Orthogonal frequency division multiplexing (OFDM) vestigated in combination with receiver sided maximum ra- [2] is a suitable technique for broadband transmission in tio combining. It is shown in Section 3 how the mentioned multipath fading environments and is implemented in new diversity techniques are applicable to the DVB-T system broadcast standards like digital audio broadcasting (DAB) in order to improve the bit error performance in multipath [3] or terrestrial digital video broadcasting (DVB-T) [4] as environments. In Section 4 the DVB-T system and trans- well as wireless local area network (WLAN) standards [5] mission parameters as well as the used channel models are such as HIPERLAN/2 or IEEE 802.11a. described. Finally, simulation results for the bit error rates Because of the poor error performance of OFDM in are presented for various DVB-T system parameter sets in Vol. 13, No. 5 September-October 2002 531 A. Dammann, S. Kaiser 1,...,M − 1. After the superposition from these signals is built, the guard interval section is removed and the re- sulting signal is finally transformed into frequency domain (IOFDM). To avoid intersymbol interference (ISI) the time delays δn, δm must hold the condition δ , δ ≤ τ − τ , n = 1,...,N − 1, n m g max (1) m = 1,...,M − 1, Figure 1: OFDM transmitter with DD where τg is the guard interval length and τmax denotes the multipath channel delay spread. For tight dimensioned guard intervals, where τg is only slightly larger than τmax, Eq. 1 strongly restricts the choice of the time delays δn, δm. In the next section cyclic delay diversity is introduced, which overcomes this problem. 2.2 CYCLIC DELAY DIVERSITY Fig. 3 illustrates the difference between DD and CDD in the time domain and shows the transmission of 2 con- secutive OFDM symbols with their cyclic prefixes as guard Figure 2: OFDM receiver with DD intervals. For clarity, the 1st subcarrier is plotted as a sine wave. The reference signal is undelayed and transmitted indoor and outdoor environments. (resp. received) for both DD and CDD. In the case of DD it can be seen, that the DD signal is a simple copy of the reference signal, but delayed by δ. It’s also observable, that OFDM symbols of the DD signal partly overlap the guard 2 SPATIAL ANTENNA DIVERSITY WITH interval of the subsequent OFDM symbol in the reference OFDM signal at δ. The result is the above mentioned restriction in the choice of δ (see Eq. 1). In the case of CDD one In this section we will introduce Delay Diversity (DD), can see, that there is no overlapping of CDD OFDM sym- Cyclic Delay Diversity (CDD), Phase Diversity (PD) and bols with the reference signal OFDM symbols, whereas Maximum Ratio Combining (MRC), which can easily be the time signals of DD and CDD in the time section used applied to existing OFDM system standards with little ef- for OFDM demodulation are totally equal. This makes the forts. A combination of this diversity techniques is eas- performance of CDD equal to DD while there is no ISI in ily possible. Thus, we can even with hindsight improve case of DD, i.e. Eq. 1 holds. Concurrently, no ISI can oc- OFDM systems and find an optimal tradeoff between com- cur with CDD due to a too large dimensioned cyclic delay. plexity and performance. The OFDM symbols of the CDD signal can be generated from the reference signal OFDM symbols just by applying cy 2.1 DELAY DIVERSITY a cyclic time shift of δ to the reference signals’ OFDM symbols and subsequent insertion of the cyclic prefix. This section will briefly introduce delay diversity (DD), Fig. 4 shows the block diagram of an N-transmitter- which was described in [8]. Fig. 1 shows the block dia- antenna OFDM system with CDD. The OFDM modulated gram of an N-transmitter-antenna OFDM system with DD. The OFDM modulated signal is transmitted over N anten- t max Time Section for nas, whereas the particular signals only differ in an antenna OFDM Demodulation specific delay. Before shifting, an additional cyclic prefix cyclic Reference Signal extension OFDM-Symbol as guard interval may be inserted. The functional block t g ISI ”UC” stands for upconversion from the baseband into the cyclic DD Signal OFDM-Symbol RF-band. Note, that in case of DD δn, n = 1,...,N − 1, extension denote simple time shifts. d Because of linearity, it is also possible to implement cyclic CDD Signal extension OFDM-Symbol DD at the receiver side. The appropriate block diagram of d cy a M-antenna receiver with DD is shown in Fig. 2. The Time received signals are downconverted (”DC”) into the base- band and shifted in time direction according to δm, m = Figure 3: Time signals for OFDM transmitters with DD and CDD 532 ETT Transmit/Receive-Antenna Diversity Techniques for OFDM Systems 10 0 −10 −20 −30 Channel Gain [dB] −40 −50 Figure 4: OFDM transmitter with CDD 500 400 200 300 150 200 100 100 50 # Subcarrier # OFDM Symbol Figure 6: Indoor channel snapshot for a single antenna system frequency and the complex-valued signals in time- and frequency-domain respectively with `, k = 0 ...K − 1. As it can be seen from Eq. 2, a cyclic delay δcy in the time −j 2π kδcy domain corresponds to a phase factor of e K in the Figure 5: OFDM receiver with CDD frequency domain. PD is not only restricted to linearly in- cremented phases. It’s also possible to choose phase factors signal is transmitted over N antennas, whereas the partic- ejφ(k), where φ(k) is an arbitrary function of the discrete ular signals only differ in an antenna specific cyclic shift. frequency k. Eq. 2 also shows that the operation for PD After cyclic shifting, the guard interval is inserted. Again, has to be done before OFDM modulation. So for an M- the functional block ”UC” performs upconversion of the antenna PD system, M OFDM transformations have to be signals from the baseband into RF-band. Again because of calculated. Therefore the implementation of PD is more linearity CDD can be implemented at the receiver. Fig. 5 complex compared to CDD. shows the principle block diagram of a CDD receiver. CDD and PD are independent of the existence of a Because of simple time shifts for DD resp. cyclic time cyclic prefix (guard interval) and are capable to increase shifts for CDD, these techniques are implementable with the channel frequency selectivity without increasing the only slight additional complexity as long as the delays δn overall channel delay spread because these operations are cy and δn are multiples of the system sampling time.
Load more

Recommended publications
  • MULTIPLE ANTENNA TECHNIQUES in Wimax
    MEE10:05 MULTIPLE ANTENNA TECHNIQUES IN WiMAX Waseem Hussain Sandhu Muhammad Awais This thesis is presented as part of Degree of Master of Science in Electrical Engineering Blekinge Institute of Technology February 2010 Blekinge Institute of Technology School of Engineering Department of Signal Processing Supervisor: Dr. Benny Lövström Examiner: Dr. Benny Lövström 1 Acknowledgements All praises to ALLAH, the cherisher and the sustainer of the universe, the most gracious and the most merciful, who bestowed us with health and abilities to complete this project successfully. We are extremely grateful to our project supervisor Benny Lövström who guided us in the best possible way in our project. He is always a source of inspiration for us. His encouragement and support never faltered. We are especially thankful to the Faculty and Staff of School of Engineering at Blekinge Institute of Technology (BTH) Karlskrona, Sweden, who have always been a source of motivation for us and supported us tremendously during this research. Our special gratitude and acknowledgments are there for our parents for their everlasting moral support and encouragements. Without their support, prayers, love and encouragement, we wouldn’t be able to achieve our Goals. Waseem Hussain Sandhu & Muhammad Awais Karlskrona, February 2010. 2 Abstract Now-a-days wireless networks such as cellular communication have deeply affected human lives and became an essential part of it. The demand to buy high capacity and better performance devices and cellular services has been rapidly increased. There are more than two hundred different countries and almost three billion users all over the world which are using cellular services provided by Global System for Mobile (GSM), Universal Mobile Telecommunication System (UMTS), Wireless Local Area Network (WLAN) and Worldwide Interoperability for Microwave Access (WiMAX).
    [Show full text]
  • Multiple Antenna Technologies
    Multiple Antenna Technologies Manar Mohaisen | YuPeng Wang | KyungHi Chang The Graduate School of Information Technology and Telecommunications INHA University ABSTRACT the receiver. Alamouti code is considered as the simplest transmit diversity scheme while the receive diversity includes maximum ratio, equal gain and selection combining Multiple antenna technologies have methods. Recently, cooperative received high attention in the last few communication was deeply investigated as a decades for their capabilities to improve the mean of increasing the communication overall system performance. Multiple-input reliability by not only considering the multiple-output systems include a variety of mobile station as user but also as a base techniques capable of not only increase the station (or relay station). The idea behind reliability of the communication but also multiple antenna diversity is to supply the impressively boost the channel capacity. In receiver by multiple versions of the same addition, smart antenna systems can increase signal transmitted via independent channels. the link quality and lead to appreciable On the other hand, multiple antenna interference reduction. systems can tremendously increase the channel capacity by sending independent signals from different transmit antennas. I. Introduction BLAST spatial multiplexing schemes are a good example of such category of multiple Multiple antennas technologies proposed antenna technologies that boost the channel for communications systems have gained capacity. much attention in the last few years because In addition, smart antenna technique can of the huge gain they can introduce in the significantly increase the data rate and communication reliability and the channel improve the quality of wireless transmission, capacity levels. Furthermore, multiple which is limited by interference, local antenna systems can have a big contribution scattering and multipath propagation.
    [Show full text]
  • Performance Analysis of Diversity Techniques for Wireless Communication System
    1 Performance Analysis of Diversity Techniques for Wireless Communication System Md. Jaherul Islam [email protected] This Thesis is a part (30 ECTS) of Master of Science degree (120 ECTS) in Electrical Engineering emphasis on Telecommunication Blekinge Institute of Technology February 12 Blekinge Institute of Technology School of Engineering Department of Telecommunication Supervisor: Magnus G Nilsson Examiner: Magnus G Nilsson Contact: [email protected] 2 Abstract Different diversity techniques such as Maximal-Ratio Combining (MRC), Equal-Gain Combining (EGC) and Selection Combining (SC) are described and analyzed. Two branches (N=2) diversity systems that are used for pre-detection combining have been investigated and computed. The statistics of carrier to noise ratio (CNR) and carrier to interference ratio (CIR) without diversity assuming Rayleigh fading model have been examined and then measured for diversity systems. The probability of error ( ) vs CNR and ( ) versus CIR have also been obtained. The fading dynamic range of the instantaneous CNR and CIR is reduced remarkably when diversity systems are used [1]. For a certain average probability of error, a higher valued average CNR and CIR is in need for non-diversity systems [1]. But a smaller valued of CNR and CIR are compared to diversity systems. The overall conclusion is that maximal-ratio combining (MRC) achieves the best performance improvement compared to other combining methods. Diversity techniques are very useful to improve the performance of high speed wireless channel to transmit data and information. The problems which considered in this thesis are not new but I have tried to organize, prove and analyze in new ways.
    [Show full text]
  • Great Expectations: the Value of Spatial Diversity in Wireless Networks
    Great Expectations: The Value of Spatial Diversity in Wireless Networks SUHAS N. DIGGAVI, MEMBER, IEEE, NAOFAL AL-DHAHIR, SENIOR MEMBER, IEEE, A. STAMOULIS, MEMBER, IEEE, AND A. R. CALDERBANK, FELLOW, IEEE Invited Paper In this paper, the effect of spatial diversity on the throughput The challenge here is that Moore’s Law does not seem to and reliability of wireless networks is examined. Spatial diversity apply to rechargeable battery capacity, and though the den- is realized through multiple independently fading transmit/re- sity of transistors on a chip has consistently doubled every ceive antenna paths in single-user communication and through independently fading links in multiuser communication. Adopting 18 mo, the energy density of batteries only seems to double spatial diversity as a central theme, we start by studying its every 10 years. This need to conserve energy (see [2] and ref- information-theoretic foundations, then we illustrate its benefits erences therein) leads us to focus on what is possible when across the physical (signal transmission/coding and receiver signal signal processing at the terminal is limited. Throughout this processing) and networking (resource allocation, routing, and paper, we use the cost and complexity of the receiver to applications) layers. Throughout the paper, we discuss engineering intuition and tradeoffs, emphasizing the strong interactions be- bound the resources available for signal processing. Wireless tween the various network functionalities. spectrum itself is a valuable resource that also needs to be conserved given the economic imperative of return on multi- Keywords—Ad hoc networks, channel estimation, diversity, fading channels, hybrid networks, information theory for wireless billion-dollar investments by wireless carriers [1].
    [Show full text]
  • Performance Evaluation of Wi-Fi Comparison with Wimax Networks
    International Journal of Distributed and Parallel Systems (IJDPS) Vol.3, No.1, January 2012 Performance Evaluation of Wi-Fi comparison with WiMAX Networks 1M.Sreerama Murty, 2 D.Veeraiah, 3A.Srinivas Rao 1Department of Computer Science and Engineering Sai Spurthi Institute of Technology,Khammam,Andhra Pradesh,India [email protected] 2Department of Computer Science and Engineering Sai Spurthi Institute of Technology,Khamamm,Andhra Pradesh,India [email protected] 3Department of Computer Science and Engineering Sai Spurthi Institute of Technology,Khamamm,Andhra Pradesh,India [email protected] Abstract Wireless networking has become an important area of research in academic and industry. The main objectives of this paper is to gain in-depth knowledge about the Wi-Fi- WiMAX technology and how it works and understand the problems about the WiFi- WiMAX technology in maintaining and deployment. The challenges in wireless networks include issues like security, seamless handover, location and emergency services, cooperation, and QoS.The performance of the WiMAX is better than the Wi-Fi and also it provide the good response in the access. It’s evaluated the Quality of Service (Qos) in Wi-Fi compare with WiMAX and provides the various kinds of security Mechanisms. Authentication to verify the identity of the authorized communicating client stations. Confidentiality (Privacy) to secure that the wirelessly conveyed information will remain private and protected. Take necessary actions and configurations that are needed in order to deploy Wi-Fi -WiMAX with increased levels of security and privacy Keywords Wifi ,Wimax,Qos,Security,Privacy,seamless 1. Introduction Recently wireless networking has become an important area of research in academia and industry.
    [Show full text]
  • Diversity Diversity Macrodiversity Microdiversity
    Ch13. Diversity Instructor: • Mohammed Taha O. El Astal LOGO 13.1 Introduction AWGN channels Rayleigh Fading In AWGN, it may that a 10-dB SNR leads to BERs on the order of 10−4. but in fading channels, we need an SNR on the order of 40 dB in order to achieve a 10−4 BER, which is clearly unpractical. CONT. deep fading (very low SNR) The reason ??? is the fading of the channel; since the fading cause to have an attenuation being large, and thus of the instantaneous SNR being low, so the BER be high. CONT. The Solution!!!! Make sure that the SNR at Rx. has a smaller probability of being low. =make sure that the signal has a smaller probability to have a large attenuation 13.1.1 Principle of Diversity The principle of diversity is to ensure that the same information reaches the receiver (RX) on statistically independent channels. Example: SNR BER-DFSK If Pnoise is 50 pW. Consider the following two cases : 0dB 0.5 An AWGN channel with Psig,avg is 1 nW. A fading channel where during 90% of the time the ....... …... received power is 1.11 nW, while for the remainder, it is …… …… zero. 13dB 10−9 1. Compute BER for the case of AWGN channel. 13.5dB 10−10 2. Compute avg. BER with assuming it is selection diversity in the following cases: a. one received antenna. b. two received antenna. c. three received antenna 13.1.2 Definition of the Correlation Coefficient Any correlation between the fading of the channels decreases the effectiveness of diversity, why?? The most important one is the correlation coefficient of signal envelopes x and y: For two statistically independent signals E{xy} = E{x}E{y} ρxy=0 Signals are often said to be “effectively” decorrelated if ρ is below a certain threshold (typically 0.5 or 0.7).
    [Show full text]
  • High Capacity CDMA and Collaborative Techniques
    High Capacity CDMA and Collaborative Techniques By Indu Lal Shakya A Thesis submitted for the degree of Doctor of Philosophy School of Science and Technology University of Sussex April 2008 Declarations I, Indu Lal Shakya hereby certify that the materials presented in this thesis are my own work, except where indicated. Any information or materials that are not my own creations are indicated explicitly as references including their origins, publication dates. I also declare that this thesis has not been submitted, either in the same or different form to this or any other university for a degree. Indu Lal Shakya, Brighton, UK i University of Sussex Indu Lal Shakya Thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy High Capacity CDMA and Collaborative Techniques Summary The thesis investigates new approaches to increase the user capacity and improve the error performance of Code Division Multiple Access (CDMA) by employing adaptive interference can- cellation and collaborative spreading and space diversity techniques. Collaborative Coding Multi- ple Access (CCMA) is also investigated as a separate technique and combined with CDMA. The advantages and shortcomings of CDMA and CCMA are analysed and new techniques for both the uplink and downlink are proposed and evaluated. Multiple access interference (MAI) problem in the uplink of CDMA is investigated first. The practical issues of multiuser detection (MUD) techniques are reviewed and a novel blind adaptive approach to interference cancellation (IC) is proposed. It exploits the constant modulus (CM) property of digital signals to blindly suppress interference during the despreading process and ob- tain amplitude estimation with minimum mean squared error for use in cancellation stages.
    [Show full text]
  • T5 Reed Smartantenna.Pdf
    MOBILE & PORTABLE RADIO RESEARCH GROUP MPRG 1st OMG Software-Based Communications (SBC) Workshop: From Mobile to Agile Communications September 13-16, 2004 - Arlington, VA USA Jeffrey H. Reed and Raqibul Mostafa Mobile and Portable Radio Research Group (MPRG), ECE Department Virginia Virginia Tech Tech [email protected] VIRGINIA POLYTECHNIC INSTITUTE 1 8 7 2 AND STATE UNIVERSITY 1 Outline • Smart Antennas for Software Radios – Fundamentals – Algorithms • Implementation Issues – Hardware – Software • Case Studies • Future Directions 2 Smart Antennas for Software Radio 3 What is a Smart Antenna • Definition – Antenna array system aided by some “smart” algorithm to combine the signals, designed to adapt to different signal environments – The antenna can automatically adjust to a dynamic signal environment • Mechanisms – The gain of the antenna for a given direction of arrival is adjustable – Take advantage of different channels for different antennas • Some antennas are “smarter” than others 4 Smart Antennas in Software Radios • Software radios and smart antennas complement each other • Software radios need to adapt to different protocols, systems and channel environments – Smart antennas aid software radios in attaining this flexibility through the use of signal processing algorithms to combine the received signals in an optimum manner – Smart antennas provide the benefits that motivate the adoption of software radios • Implementation of smart antenna algorithms require flexibility in the infrastructure which is provided by software radios
    [Show full text]
  • Angular Diversity / Antenna Pattern Measurements
    Report WG 16.89.006 APPLICATION FOR ANGULAR DIVERSITY ANTENNA SYSTEMS and DISCUSSION OF ANTENNA PATTERN MEASUREMENTS www.nsma.org 1990 Source: Working Group 16 REPORT Subject: Angular Diversity / Antenna Pattern Measurements Title: Application of Angular Diversity Systems and Discussion of Antenna Pattern Measurements Consideration for the application of Angular Diversity Systems and the possible need to expand characterizing azimuthal and elevational measurements of terrestrial microwave antennas. REPORT WG 16.89.006 1. PURPOSE This paper reports the results of the Working Sub-Group # 16's study to determine the needs for addition measurements to further define the electrical characteristics of Terrestrial Microwave Antennas for improving the evaluation of direct and terrain reflective scatter interference The introduction presents a brief culmination don of inter-dependent conditions contributing to system degradation and general corrective actions In considering direct and reflective terrain scattering interference and the application of Angular Diversity Systems empirical data from 2170 separate cases are analyzed and the results provide a basis concluding that only the vertical angle up to 26° below the m in beam is necessary 2. INTRODUCTION AND EVALUATION during the pest several years, the telecommunications done industry has become more aware of the quality of service and the impact of controlling microwave path propagation and interference The conversion to Digital Transmission has necessary a continuous us evolution of technical
    [Show full text]
  • MIMO Systems and Spatial Diversity
    MIMO systems and Spatial Diversity. Dmitriy Shutin [email protected]. Signal Processing and Speech Communication Laboratory www.spsc.tugraz.at Graz University of Technology MIMO systems andSpatial Diversity. – p.1/36 Content of the talk PART I. Wireless communication and MIMO systems. Wireless channels. Part II. Spatial Diversity MIMO systems andSpatial Diversity. – p.2/36 Outline – PART I. PART I. What is MIMO Multiple antennas in communication Channel and channel models. Channel and signal models. MIMO systems andSpatial Diversity. – p.3/36 PART II. MIMO systems andSpatial Diversity. – p.4/36 Outline – PART II. What is diversity? Diversity schemes. What do we actually win. Implementing diversity – IID channels RX diversity(SIMO). Alamouti scheme and TX diversity (MISO). RX-TX diversity (MIMO). Extended channels. MIMO systems andSpatial Diversity. – p.5/36 What is diversity? Diversity – Multiple independent look at the same transmitted signal. MIMO systems andSpatial Diversity. – p.6/36 What is diversity? Fading impairs wireless link. Use multiple antennas to create alternative transmission branches. −60 1st receiver antenna 2nd receiver antenna −80 −100 −120 Power variations, dB −140 −160 216 218 220 222 224 226 distance, λ MIMO systems andSpatial Diversity. – p.7/36 What is diversity? If p = P (signal is in fade) Having M independent branches results P (all M branches are in fade) = pM p There are Frequency diversity Time diversity Space diversity MIMO systems andSpatial Diversity. – p.8/36 Diversity schemes. Space diversity: RX/TX has multiple antennas, spaced d meters apart such that d > Dc Frequency diversity: signal is transmitted over two carrier frequencies, spaced ∆f, such that 1 ∆f > Bc ∼ RMS delay spread Time diversity: the same signal is re-transmitted with a delay ∆t such that 1 ∆t > Tc = BD MIMO systems andSpatial Diversity.
    [Show full text]
  • A Novel Architecture for Antenna Arrangement in Wireless Cellular CDMA Systems
    A Novel Architecture for Antenna Arrangement in Wireless Cellular CDMA Systems Hamed Saghaei, Student Member, IEEE Islamic Azad University, Shahrekord branch, Shahrekord, Iran. Email: [email protected] Abstract— Wise arrangement of antennas is critical in 2. Cellular Architectures wireless cellular systems for both reduction of co-channel The aim of this section is introducing the used and the interference (CCI) and increase the quality of service microzone architectures. In Fig. 1, the used architecture is (QoS). In this paper, a novel architecture for antenna shown that it includes many clusters to cover a big area in arrangement in CDMA wireless cellular systems is which each cluster encompasses 1, 3, 5, or 7 cells [5]. Every presented. In this architecture that we called microzone, cell has a base station (BS) which is located at the center of every cell is divided into three (or more) zones and the cell. Cell sectoring may be used which is a way for information transmission in downlink channel is done by increasing the system capacity while keeping the cell radius an antenna which is placed at the outer region of the constant. It is a process of replacing one omnidirectional related zone. Also, the transmitting signal by the mobile antenna at the BS by several directional antennas. Each of station (MS) in uplink channel is received by all antennas these antennas radiates within a specific sector of the cell. of the related cell. Analytical calculations of the received Directional antennas, therefore, minimize interference for a signal to noise ratio (SIR) and outage probability for given cell by receiving and transmitting with only a fraction both microzone and used architectures show that of available co-channel cells, so the QoS will be increased proposed architecture has better performance in [5].
    [Show full text]
  • Implementation of Antenna Switching Diversity and Its Improvements Over Single-Input Single-Output System
    Implementation of Antenna Switching Diversity and Its Improvements over Single-Input Single-Output System by Oktavius Felix Setya A thesis presented to the University of Waterloo in fulfillment of the thesis requirement for the degree of Master of Applied Science in Electrical and Computer Engineering Waterloo, Ontario, Canada, 2009 © Oktavius Felix Setya 2009 I hereby declare that I am the sole author of this thesis. This is a true copy of the thesis including any required final revisions, as accepted by my examiners. I understand that my thesis may be made electronically available to the public. Oktavius Felix Setya ii Abstract This dissertation study the effectiveness of antenna switching diversity for orthogonal frequency division multiplexing (OFDM) systems such as in IEEE 802.11. One of the ways to exploit the multiple antenna configurations is to use antenna switching diversity. Antenna switching diversity is used in wireless systems to combat the effect of fading, as we can combine multiple independent copies of the same signal into a total signal with high quality. In this work, we implement and compare the performance of two systems, antenna switching diversity system and single-input single-output (SISO) system. We firstly study the performance of the antenna switching diversity system as we increases the number of antennas compared to the performance of signal-to-noise ratio (SNR) or gain of the system. The performance of antenna switching diversity is studied on several difference configurations such as receive diversity where there are multiple receive antennas, and transmit diversity where the there are multiple transmit antennas. The study is performed on eight (8) antenna switching, on either the transmit or receive side.
    [Show full text]