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 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 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 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 Multistage Decision Feedback and Trellis Based Multiuser Receivers for Convoluntionally Coded CDMA Systems written by T. Giallorenzi and published by . This book was released on 1993 with total page 47 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this report, multistage decision feedback and trellis-based multiuser receivers are studied for convolutionally coded CDMA links. Some of the receiver structures proposed combine the functions of equalization and decoding while some consider the operations separately. A variety of decision feedback approaches are proposed, and through simulations, it is shown that these approaches are able to significantly outperform the conventional basestation architecture. Two trellis-based approaches are also proposed. The first is a partitioned structure which attacks the MUI equalization and decoding operations separately. The second approach is the maximum likelihood sequence estimator for this problem which is a combined equalizer and decoder. This decoder is formulated and its complexity is seen to depend exponentially on the number of users in the system, the number of states in the individual users' encoders and the number of input information bits per interval.

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 Performance Analysis and Power Control for Multiuser Receivers in Code Division Multiple Access CDMA Systems written by Yong Liu and published by . This book was released on 2002 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Pseudo decorrelating Multiuser Receivers for Asynchronous Code Division Multiple Access CDMA Systems written by Joong Hoo Park and published by . This book was released on 1997 with total page 98 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 264 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 Coded Modulation Systems written by John B. Anderson and published by Springer Science & Business Media. This book was released on 2006-04-11 with total page 494 pages. Available in PDF, EPUB and Kindle. Book excerpt: Coded Modulation Systems is an introduction to the subject of coded modulation in digital communication. It is designed for classroom use and for anyone wanting to learn the ideas behind this modern kind of coding. Coded modulation is signal encoding that takes into account the nature of the channel over which it is used. Traditional error correcting codes work with bits and add redundant bits in order to correct transmission errors. In coded modulation, continuous time signals and their phases and amplitudes play the major role. The coding can be seen as a patterning of these quantities. The object is still to correct errors, but more fundamentally, it is to conserve signal energy and bandwidth at a given error performance. The book divides coded modulation into three major parts. Trellis coded modulation (TCM) schemes encode the points of QAM constellations; lattice coding and set-partition techniques play major roles here. Continuous-phase modulation (CPM) codes encode the signal phase, and create constant envelope RF signals. The partial-response signaling (PRS) field includes intersymbol interference problems, signals generated by real convolution, and signals created by lowpass filtering. In addition to these topics, the book covers coding techniques of several kinds for fading channels, spread spectrum and repeat-request systems. The history of the subject is fully traced back to the formative work of Shannon in 1949. Full explanation of the basics and complete homework problems make the book ideal for self-study or classroom use.

Download or read book Multiuser Receivers for Future CDMA Mobile Radio Systems written by Homoud M. I. Alkussayer and published by . This book was released on 1997 with total page 180 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis a group of simplified multiuser receivers for a CDMA system are presented and evaluated. The problem of multiuser detection in a synchronous channel is considered where a class of new simplified sub-optimum bear multiuser detectors are suggested, for both the decorrelating and the MMSE detectors. It is shown that by using Gold code as the spreading sequence the complexity of the two new multiuser detectors is independent of the number of users. For an asynchronous CDMA system a one-shot linear decorrelating detector is investigated. A novel improved one-shot detector which outperforms Verdu's one-shot detector with much reduced complexity is proposed. A second new detector using non-orthogonal matching which reduces the complexity even further, with small reduction in performance, is also suggested. A third is the matched filter slicing detector which is a more simplified detector for a special system. For the same channel, a novel CDMA system using dual-signalling with multiuser detection is presented. Using a replicated spreading sequence at the transmitters and halved correlation period plus linear combining at the central station, a one-shot detection is achieved. Two decorrelating algorithms, the direct method and the recursive method, are presented. Theoretical and simulation results showed that this scheme significantly outperforms the conventional detector and its performance approaches that of the single user. Finally, the multiuser detection in a frequency non-selective Rayleigh fading channel is studied. Two novel detectors are proposed.The first uses dual-signalling without interleaving, which results in a greatly simplified near-far resistant detector. The second uses dual-signalling with interleaving which results in a slightly more complex detector. The performance of both detectors is however superior to the conventional detector, and they can outperform the original LDD detector which is far too complex.

Download or read book Multiuser Detection written by Sergio Verdú and published by Cambridge University Press. This book was released on 1998-08-13 with total page 478 pages. Available in PDF, EPUB and Kindle. Book excerpt: Originally published in 1998, Multiuser Detection provides a comprehensive treatment of the subject of multiuser digital communications.

Download or read book Multiuser Detection in CDMA Mobile Terminals written by Piero Castoldi and published by Artech House. This book was released on 2002 with total page 256 pages. Available in PDF, EPUB and Kindle. Book excerpt: Here's an authoritative, cutting-edge resource that gives you a thorough understanding of CDMA transmission and detection. It offers practical guidance in designing interference-reducing multi-user receivers for mobile radio systems and multi-user adaptive modems for accessing satellite earth stations. The book provides in-depth descriptions of CDMA principles, and of linear and non-linear multi-user detection , and covers the fine details of the realization of a linear multi-user receiver.

Download or read book Computationally Efficient Multiuser Detection for Coded CDMA written by and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Computationally efficient multiuser detection for coded asynchronous CDMA systems is investigated. The particular receiver studied is a near-far resistant multi-user detector known as the projection receiver (PR) [originally developed in [1, 2]]. The PR perfoms multiple access interference resolution for CDMA with error control coding. The output of the front-end of the projection receiver yields a metric for decoding of the coded sequences. This metric allows the use of a standard sequence decoder (e.g., Viterbi algorithm, M-algorithm) for the error control code. The metric computation can be performed adaptively by an extension of the familiar recursive least-squares (RLS) algorithm. The adaptive PR operates on a single sample per chip. In chis paper it is shown that for random spreading codes this algorithm simplifies and can be executed an order of magnitude faster by exploiting the average cross-correlation of the spreading sequences. The performance of boll1 algorithms are studied for CDMA with random spreading sequences aid compared to theorctical performance bounds.

Download or read book Code Division Multiple Access CDMA written by R. Michael and published by Springer Nature. This book was released on 2022-05-31 with total page 182 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book covers the basic aspects of Code Division Multiple Access or CDMA. It begins with an introduction to the basic ideas behind fixed and random access systems in order to demonstrate the difference between CDMA and the more widely understood TDMA, FDMA or CSMA. Secondly, a review of basic spread spectrum techniques are presented which are used in CDMA systems including direct sequence, frequency-hopping and time-hopping approaches. The basic concept of CDMA is presented, followed by the four basic principles of CDMA systems that impact their performance: interference averaging, universal frequency reuse, soft handoff, and statistical multiplexing. The focus of the discussion will then shift to applications. The most common application of CDMA currently is cellular systems. A detailed discussion on cellular voice systems based on CDMA, specifically IS-95, is presented. The capacity of such systems will be examined as well as performance enhancement techniques such as coding and spatial filtering. Also discussed are Third Generation CDMA cellular systems and how they differ from Second Generation systems. A second application of CDMA that is covered is spread spectrum packet radio networks. Finally, there is an examination of multi-user detection and interference cancellation and how such techniques impact CDMA networks. This book should be of interest and value to engineers, advanced students, and researchers in communications.

Download or read book Multistage Linear Multiuser Receivers written by Mohsen Ghotbi and published by . This book was released on 2005 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis introduces an analytical method for large-system design and analysis of multistage linear multiuser (MLMU) receivers for direct-sequence (DS- ) code division multiple access (CDMA) systems. The figure of merit to evaluate performance is the signal to interference plus noise ratio (SINR) that is calculated for a case where the number of active users and the processing gain tend towards infinity, while their ratio remains finite. The large-system performance will be a function of the number of the interference cancellation stages, the moments of the eigenvalues of the covariance matrix, the system load and the SNR. Compared to other recently-proposed methods, our proposed method offers a more efficient approach to finding the large-system performance by introducing a new expression for the covariance matrix of the interference term. A simplified multistage scheme to estimate the multipath channel gains is also introduced. It will be shown that by applying this new method for data detection and channel estimation, the performance of the MLMU receiver will converge to that of the minimum mean-squared error (MMSE) receiver.

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.