Download or read book Iterative Multiuser Receivers for Coded DS CDMA Systems written by José Martín Luna Rivera and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The introduction of cellular wireless systems in the 1980s has resulted in a continuous and growing demand for personal communication services. This demand has made larger capacity systems necessary. With the interest from both the research community and industry in wireless code-division multiple-access (CDMA) systems, the application of multiuser detection (MUD) techniques to wireless systems is becoming increasingly important. MUD is an important area of interest to help obtain the significant increase in capacity needed for future wireless services. The standardisation of direct-sequence CDMA (DS-CDMA) systems in the third generation of mobile communication systems has raised even more interest in exploiting the capabilities and capacity of this type of technology. However, the conventional DS-CDMA system has the major problem of multiple-access interference (MAI). The MAI is unavoidable because receivers deal with information which is transmitted not by a single source but by several uncoordinated and geographically separated sources. As a result, the capacity of these systems is inherently interference limited by other users. To overcome these limitations, MUD emerges as a promising approach to increase the system capacity. This thesis addresses the problem of improving the downlink capacity of a coded DS-CDMA system with the use of MUD techniques at the mobile terminal receiver. The optimum multiuser receiver scheme is far too computational intensive for practical use. Therefore, the aim of this thesis is to investigate sub-optimal multiuser receiver schemes that can exploit the advantages of MUD but also simplify its implementation. The attention is primarily focused on iterative MUD receiver schemes which apply the turbo multiuser detection principle. Essentially this principle consists of an iterative exchange of extrinsic information among the receiver modules to achieve improved performance. In this thesis, the implementation of an iterative receiver based on a linear MUD technique and a cancellation scheme over an additive white Gaussian noise (AWGN) channel is first proposed and analysed. The interference analysis shows that good performance is achieved using a lowcomplexity receiver structure. In more realistic mobile channels, however, this type of receiver suffers from the presence of higher levels of interference resulting in poor receiver performance. The reason for this is that in such scenarios the desired signals are no longer linearly separable. Therefore, non-linear detection techniques are required to provide better performance. With this purpose, a hybrid iterative multiuser receiver is investigated for the case of a stationary multipath channel. The incorporation of antenna arrays is an effective and practical technique to provide a significant capacity gain over conventional single-antenna systems. In this context, a novel space-time iterative multiuser receiver is proposed which achieves a large improvement in spectral efficiency and performance over multipath fading channels. In addition, it is shown that this architecture can be implemented without a prohibitive complexity cost. The exploitation of the iterative principle can be used to approach the capacity bounds of a coded DS-CDMA system. Using the Shannon's sphere packing bound, a comparison is presented to illustrate how closely a practical system can approach the theoretical limits of system performance.

Download or read book Iterative Multi user Turbo code Receiver for DS CDMA written by Amir K. (Amir Keyvan) Khandani and published by Department of Electrical and Computer Engineering, University of Waterloo. This book was released on 2000 with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Frequency Domain Multiuser Detection for CDMA Systems written by Paulo Silva and published by CRC Press. This book was released on 2022-09-01 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt: Future broadband wireless communication systems are expected to be able to offer new and powerful services enabling fast transmission rates of several tens of Mbit/s. This is an ambitious challenge especially for mobile communication systems since these systems should be able to cope with severely time dispersive channels, associated to the signal multipath propagation. Moreover, these systems should have high spectral and power efficiencies, as well as high capacity and flexibility. Spread spectrum techniques, particularly coded division multiple access (CDMA) techniques allow high capacity and flexibility, continuous transmission requiring low-peak power requirements for the amplifiers, as well as some robustness against fading and time-dispersion effects associated with the multipath propagation. When employed in prefix assisted (PA) block transmission schemes combined with frequency-domain receiver implementations they become especially interesting for broadband wireless systems. In Frequency-Domain Multiuser Detection for CDMA Systems the use of PA block transmission is considered in the context of both DS (Direct Sequence) and MC (Multicarrier) CDMA schemes. The main goal is the study of frequency-domain multiuser detection techniques with iterative signal detection/decoding techniques, also in combination with estimation and cancelation of nonlinear distortion effects. The receiver structures are suitable to scenarios with high interference levels and strongly time-dispersive channels.

Download or read book Multiuser Receivers for Coded Transmit Diversity Direct Spread code Division Multiple Access Systems written by Thirukkumaran Sivahumaran and published by . This book was released on 2006 with total page 260 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book THE CODING SPREADING TRADEOFF PROBLEM IN FINITE SIZED SYNCHRONOUS DS CDMA SYSTEMS written by and published by . This book was released on 2005 with total page 268 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation provides a comprehensive analysis of the coding-spreading tradeoff problem in finite-sized synchronous DS-CDMA systems. In contrast to the large system which has a large number of users, the finite-sized system refers to a system with a small number of users. Much work has been performed in the past on the analysis of the spectral efficiency of synchronous DS-CDMA systems and the associated coding-spreading tradeoff problem. However, most of the analysis is based on the large-system assumptions. In this dissertation, we focused on finite-sized systems with the help of numerical methods and Monte-Carlo simulations. Binary-input achievable information rates for finite-sized synchronous DS-CDMA systems with different detection/decoding schemes on AWGN channel are numerically calculated for various coding/spreading apportionments. We use these results to determine the existence and value of an optimal code rate for a number of different multiuser receivers, where optimality is in the sense of minimizing the SNR required for reliable multiuser communication. Our results are consistent with the well-known fact that all coding (no spreading) is optimal for the maximum a posteriori receiver. Simulations of the LDPC-coded synchronous DS-CDMA systems with iterative multiuser detection/decoding and MMSE multiuser detection/single-user decoding are also presented to show that the binary-input capacities can be closely approached with practical schemes. The coding-spreading tradeoff is examined using these LDPC code simulation results, where agreement with the information-theoretic results is demonstrated. We extend our work to the DS-CDMA systems on two idealized Rayleigh flat-fading channels: the chip-level flat-fading (CLFF) and the (code) symbol-level flat-fading (SLFF). These models represent ideal fast fading and slow fading channels, respectively. Both information-theoretic results and LDPC code simulation results are presented to show the effects of channel fading on system performance and the coding-spreading tradeoff. It is shown that fast fading can be beneficial to system performance under the condition of perfect channel state information at receiver, but slow fading is very harmful. Slow fading also increases the importance of coding greatly, compared to the AWGN and fast fading. Finally, we present some comparisons with large-system results on AWGN and CLFF channels, which show both consistencies and discrepancies.

Download or read book Multiuser Receivers for Coded CDMA Systems written by Thomas R. Giallorenzi and published by . This book was released on 1994 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this dissertation, the asynchronous direct sequence code division multiple access (CDMA) communication system is described and a number of multiuser detection approaches are proposed that improve upon the performance of the conventional base station. Both coded and uncoded systems are studied for nondispersive, additive white Gaussian noise (AWGN) channels. For the uncoded system case, the multiuser detection techniques that have already been proposed are first reviewed. Then, two decision feedback equalizers (DFE's) that have been proposed are combined to form a new hybrid DFE which outperforms the others in situations where the multiuser interference in the system is high. Next, the case where each user in the system employs a convolutional code to improve its performance is studied. First, the optimal multiuser sequence estimator is formulated, and it is shown that this receiver may be implemented using a Viterbi algorithm which operates on a time varying trellis with a number of states which is exponential in the product of the number of users in the system and the constraint length of the codes used (for the rate 1/2 code case). Because this optimal receiver has a very high complexity, a variety of suboptimum receivers are proposed which have a performance level near that of the optimal receiver's but have a more manageable complexity. All of the approaches are compared on the basis of their performance (through analysis and simulation), their complexity and their decoding delay.

Download or read book CDMA Techniques for Third Generation Mobile Systems written by Francis Swarts and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 324 pages. Available in PDF, EPUB and Kindle. Book excerpt: CDMA Techniques for Third Generation Mobile Systems presents advanced techniques for analyzing and developing third generation mobile telecommunication systems. Coverage includes analysis of CDMA-based systems, multi-user receivers, Turbo coding for mobile radio applications, spatial and temporal processing techniques as well as software radio techniques. Special emphasis has been given to recent advances in coding techniques, smart antenna systems, spatial filtering, and software implementation issues. Internationally recognized specialists contributed to this volume, and each chapter has been reviewed and edited for uniformity. CDMA Techniques for Third Generation Mobile Systems is an invaluable reference work for engineers and researchers involved in the development of specific CDMA systems.

Download or read book Multiuser Receivers for Coded CDMA Systems written by Thomas R. Giallorenzi and published by . This book was released on 1994 with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this dissertation, the asynchronous direct sequence code division multiple access (CDMA) communication system is described and a number of multiuser detection approaches are proposed that improve upon the performance of the conventional base station. Both coded and uncoded systems are studied for nondispersive, additive white Gaussian noise (AWGN) channels. For the uncoded system case, the multiuser detection techniques that have already been proposed are first reviewed. Then, two decision feedback equalizers (DFE's) that have been proposed are combined to form a new hybrid DFE which outperforms the others in situations where the multiuser interference in the system is high. Next, the case where each user in the system employs a convolutional code to improve its performance is studied. First, the optimal multiuser sequence estimator is formulated, and it is shown that this receiver may be implemented using a Viterbi algorithm which operates on a time varying trellis with a number of states which is exponential in the product of the number of users in the system and the constraint length of the codes used (for the rate 1/2 code case). Because this optimal receiver has a very high complexity, a variety of suboptimum receivers are proposed which have a performance level near that of the optimal receiver's but have a more manageable complexity. All of the approaches are compared on the basis of their performance (through analysis and simulation), their complexity and their decoding delay.

Download or read book Singular Value Decomposition Techniques for Multiuser Detection Receivers microform written by Sujit Sen and published by Library and Archives Canada = Bibliothèque et Archives Canada. This book was released on 2004 with total page 324 pages. Available in PDF, EPUB and Kindle. Book excerpt: Designing multiuser detection (MUD) receivers with low complexity and near single-user performance has generated a great deal of interest in code division multiple access (CDMA) systems. This thesis proposes novel approaches, primarily based on the Singular Value Decomposition (SVD), for designing multiuser detection receivers for CDMA systems with and without the use of multiple antennas. A new transmitter precoding scheme is proposed for the uplink of a single-input single-output (SISO) direct spread (DS) CDMA Rayleigh fading channel where non-orthogonal spreading codes are used. This technique is based on the SVD and can be analytically shown to achieve the single user bound. The application of the SVD to a multiple-input multiple-output (MIMO) DS-CDMA Rayleigh fading channel with forward error correction (FEC) codes is subsequently investigated. An iterative (turbo) multiuser detection algorithm is proposed for this MIMO multiple access system. The proposed MUD receiver is of low complexity when compared to the optimal MUD receiver and has near single-user performance in the presence of long-term power control. The salient feature of our iterative MIMO MUD receiver is that it combines SVD filtering, FEC coding and spreading codes. It is demonstrated that the proposed iterative MIMO MUD receiver can also be derived by applying the sum-product algorithm to the corresponding factor graph. The extrinsic information transfer (EXIT) chart analysis is shown to be accurate in studying the convergence behaviour and estimating the coded bit error rate (BER) for the iterative MIMO MUD receiver. A gear-shift MUD receiver is then introduced where the receiver is allowed to iteratively select a particular algorithm from a group of MUD algorithms in order to achieve a target performance level in the least amount of time.

Download or read book Project of an Iterative Multiuser Receiver for CDMA Systems written by Alberto Tarable and published by . This book was released on 2002 with total page 87 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Space Time Coding written by Branka Vucetic and published by John Wiley & Sons. This book was released on 2003-06-02 with total page 340 pages. Available in PDF, EPUB and Kindle. Book excerpt: The capacity of wireless data communications is lagging behind demands due to unsatisfactory performance of the existing wireless networks, such as low data rates, low spectral efficiency and low quality of service. Space-time coding is an effective transmit diversity technique to combat fading in wireless communications. Space-time codes are a highly bandwidth-efficient approach to signalling within wireless communication that takes advantage of the spatial dimension by transmitting a number of data streams using multiple co-located antennas. There are various approaches to the coding structures, including space-time trellis coded modulation, space-time turbo codes and also layered architectures. The central issue in all these various coding structures is the exploitation of multipath effects in order to achieve very high spectral efficiencies. The spectral efficiencies of traditional wireless systems range between 1-5bps/sec/Hz but by using space-time techniques spectral efficiencies of 20-40bps/sec/Hz have been possible. Hence, space-time coding enables an increase in capacity by an order of magnitude. This is the main reason why space-time codes have been included in the standards for the third generation wireless communication systems and ultimately why Space-time Coding will be in great demand by individuals within industry and academia. The comprehensive understanding of space-time coding is essential in the implementation of 3G, and as the only title currently available, Space-Time Coding will be the standard text for Researchers, telecommunication engineers and network planners, academics and undergraduate/postgraduate students, telecommunications managers and consultants.

Download or read book Multiaccess Mobility and Teletraffic written by David Everitt and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 359 pages. Available in PDF, EPUB and Kindle. Book excerpt: Designers of wireless networks face a problem which is multidimensional in nature, where issues of multiaccess, radio propagation, antennas, mobility and teletraffic all need to be understood and simultaneously addressed in order to create a properly functioning system. This book does not merely concentrate on one of these issues but takes a broader view, and presents a mix of papers addressing systems and networking issues. Multiaccess, Mobility and Teletraffic: Advances in Wireless Networks addresses fundamental theoretical issues about future wireless networks, such as capacity improvements theoretically attainable from spread spectrum systems, and practical concerns associated with current networks such as signalling, implementation of GSM and CDMA networks, and implementation of packet data services over wireless networks. As well as the papers looking at specific technologies, this book contains a number of papers discussing more generic problems in mobile networks, such as issues associated with handoff, resource management, frequency reuse, mobility, signalling and wireless packet networks. Multiaccess, Mobility and Teletraffic: Advances in Wireless Networks covers a broad range of issues associated with wireless networks and provides a very interesting snapshot of the current state-of-the-art. It will be of interest to all researchers and practitioners working in the field of wireless communications and networks.

Download or read book Electronics and Signal Processing written by Wensong Hu and published by Springer Science & Business Media. This book was released on 2011-06-21 with total page 1015 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume includes extended and revised versions of a set of selected papers from the International Conference on Electric and Electronics (EEIC 2011) , held on June 20-22 , 2011, which is jointly organized by Nanchang University, Springer, and IEEE IAS Nanchang Chapter. The objective of EEIC 2011 Volume 1 is to provide a major interdisciplinary forum for the presentation of new approaches from Electronics and Signal Processing, to foster integration of the latest developments in scientific research. 133 related topic papers were selected into this volume. All the papers were reviewed by 2 program committee members and selected by the volume editor Prof. Wensong Hu. We hope every participant can have a good opportunity to exchange their research ideas and results and to discuss the state of the art in the areas of the Electronics and Signal Processing.

Download or read book Advances in Multiuser Detection written by Michael L. Honig and published by John Wiley & Sons. This book was released on 2009-08-19 with total page 512 pages. Available in PDF, EPUB and Kindle. Book excerpt: A Timely Exploration of Multiuser Detection in Wireless Networks During the past decade, the design and development of current and emerging wireless systems have motivated many important advances in multiuser detection. This book fills an important need by providing a comprehensive overview of crucial recent developments that have occurred in this active research area. Each chapter is contributed by noted experts and is meant to serve as a self-contained treatment of the topic. Coverage includes: Linear and decision feedback methods Iterative multiuser detection and decoding Multiuser detection in the presence of channel impairments Performance analysis with random signatures and channels Joint detection methods for MIMO channels Interference avoidance methods at the transmitter Transmitter precoding methods for the MIMO downlink This book is an ideal entry point for exploring ongoing research in multiuser detection and for learning about the field's existing unsolved problems and issues. It is a valuable resource for researchers, engineers, and graduate students who are involved in the area of digital communications.

Download or read book CDMA Access and Switching written by Diakoumis P. Gerakoulis and published by John Wiley & Sons. This book was released on 2001-03-30 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt: Taking a close look at an integral part of next generation wireless communications, this book presents SS/CDMA system architecture (Satellite Switched Code Division Multiple Access) and its various communications services. TDMA-based satellite communications as well as related satellite systems and services are also examined in detail.

Download or read book Mobile And Wireless Communications Networks Proceedings Of The Fifth Ifip tc6 International Conference With Cd rom written by Cambyse Guy Omidyar and published by World Scientific. This book was released on 2003-10-21 with total page 364 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book covers all areas concerning mobility and wireless communications. Presented papers deal with cellular networks (2G, 3G and 4G), wireless networks (IEEE802.11, Bluetooth and sensor networks), security, quality of service and applications. Accepted papers represent a good selection of research in wireless communications. They offer an overview and also sharp visions of industrial and scientific work.The proceedings have been selected for coverage in:• Index to Scientific & Technical Proceedings (ISTP CDROM version / ISI Proceedings)

Download or read book Coordinated Multiuser Communications written by CHRISTIAN SCHLEGEL and published by Springer Science & Business Media. This book was released on 2006-07-10 with total page 282 pages. Available in PDF, EPUB and Kindle. Book excerpt: Coordinated Multiuser Communications provides for the first time a unified treatment of multiuser detection and multiuser decoding in a single volume. Many communications systems, such as cellular mobile radio and wireless local area networks, are subject to multiple-access interference, caused by a multitude of users sharing a common transmission medium. The performance of receiver systems in such cases can be greatly improved by the application of joint detection and decoding methods. Multiuser detection and decoding not only improve system reliability and capacity, they also simplify the problem of resource allocation. Coordinated Multiuser Communications provides the reader with tools for the design and analysis of joint detection and joint decoding methods. These methods are developed within a unified framework of linear multiple-access channels, which includes code-division multiple-access, multiple antenna channels and orthogonal frequency division multiple access. Emphasis is placed on practical implementation aspects and modern iterative processing techniques for systems both with, and without integrated error control coding. Focusing on the theory and practice of unifying accessing and transmission aspects of communications, this book is a valuable reference for students, researchers and practicing engineers.