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 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 Multiuser Detection Techniques for CDMA Systems written by Xuechao Du and published by . This book was released on 2002 with total page 110 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 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 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 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 Multi Carrier Spread Spectrum written by Khaled Fazel and published by Springer Science & Business Media. This book was released on 2013-11-11 with total page 515 pages. Available in PDF, EPUB and Kindle. Book excerpt: The benefits and success of multi-carrier (MC) modulation on one side and the flexibility offered by the spread spectrum (SS) technique on the other side have motivated many researchers to investigate the combination of both techniques since 1993. This combination known as multi-carrier spread spectrum (MC-SS) benefits from the advantages of both systems and offers high flexibility, high spectral efficiency, simple detection strategies, narrow-band interference rejection capability, etc. The basic principle of this combination is straightforward: The spreading is performed as direct sequence spread spectrum (DS-SS) but instead of transmitting the chips over a single carrier, several sub-carriers are employed. The MC modulation and demodulation can easily be realized in the digital domain by performing IFFT and FFT operations. The separation of the users' signals can be performed in the code domain. MC-SS systems can perform the spreading in frequency direction, which allows for simple signal detection strategies. Since 1993, MC-SS has been deeply studied and new alternative solutions have been proposed. Meanwhile, deep system analysis and comparison with DS-CDMA have been performed that show the superiority of MC-CDMA.

Download or read book The Newcom Vision Book written by Sergio Benedetto and published by Springer Science & Business Media. This book was released on 2012-04-07 with total page 222 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Book contains the Vision of the researchers of the European Network of Excellence NEWCOM++ (Network of Excellence on Wireless COMmunication) on the present and future status of Wireless Communication Networks. In its content, the community of NEWCOM++ researchers, shaped under the common ground of a mainly academic network of excellence, have distilled their scientific wisdom in a number of areas characterized by the common denominator of wireless communications, by identifying the medium-long term research tendencies/problems, describing the tools to face them and providing a relatively large number of references for the interested reader. The identified areas and the researchers involved in their redaction reflect the intersection of the major topics in wireless communications with those that are deeply investigated in NEWCOM++; they are preceded by an original description of the main trends in user/society needs and the degree of fulfilment that ongoing and future wireless communications standards will more likely help achieving. The appendix of the Book contains a list of "Millenium Problems", seminal problems in the area of wireless communication networks, characterized by being crucial and still unsolved. The problems have been identified by NEWCOM++ researchers and filtered by the editors of the Vision Book.

Download or read book Multistage Decision Feedback and Trellis Based Multiuser Receivers for Convoluntionally Coded CDMA Systems written by and published by . This book was released on 1993 with total page 0 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 Adaptive Rake Multiuser Receiver with Linearly Constrained Sliding Window RLS Algorithm for DS CDMA Systems written by and published by . This book was released on 2003 with total page 102 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book LTE Advanced Air Interface Technology written by Xincheng Zhang and published by CRC Press. This book was released on 2012-09-05 with total page 530 pages. Available in PDF, EPUB and Kindle. Book excerpt: Opportunities are at hand for professionals eager to learn and apply the latest theories and practices in air interface technologies. Written by experienced researchers and professionals, LTE-Advanced Air Interface Technology thoroughly covers the performance targets and technology components studied by 3GPP for LTE-Advanced. Besides being an explanatory text about LTE-Advanced air interface technology, this book exploits the technical details in the 3GPP specification, and explains the motivation and implication behind the specifications. After a general description of wireless cellular technology evolution and the performance targets and major technical features of LTE-Advanced, LTE-Advanced Air Interface Technology discusses various innovative technical features in detail, including Innovative concepts in carrier aggregation techniques Collaborative multipoint (CoMP) theory and performance analysis Enhanced multiantenna solutions or multiple-input, multiple-output (MIMO) technology, in particular, multiuser and multilayer MIMO Relaying issues Self-organizing and heterogeneous networks Interference suppression and enhanced intercell interference coordination (eICIC) technology This book opens the door of LTE-A technology for practitioners in any stage of wireless communications. Beginning with basic communication principles, the book demonstrates how a complete wireless theory is built. Readers can work independently on original case studies and simulation programming examples, with an emphasis on technology and performance. Designed for professionals interested in gaining an upper hand, this book is the ideal educational and informative resource in the emerging field of air interface technology.

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 Single and Multi Carrier DS CDMA written by Lajos L. Hanzo and published by Wiley-IEEE Press. This book was released on 2003-09-26 with total page 1104 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume is dedicated to a range of CDMA and MC-CDMA transmission aspects of systems designed for communicating over fading wireless channels. Currently, a technical in-depth book on this subject, which has a similar detailed exposure of the recent advances in CDMA, M-ary CDMA and MC-CDMA, is unavailable. A further attraction of the joint treatment of these topics is that it allows the reader to view their design trade-offs in a comparative context. Divided into five main parts: Part I: provides a detailed introduction to the subject of CDMA systems designed for employment in various application Part II: deals with the currently hot topic of genetic algorithm assisted multiuser detection Part III: gives a detailed account of new, reduced-complexity M-ary CDMA schemes Part IV: considers a range of novel MC-CDMA schemes which have the potential of supporting numerous design objectives Part V: provides an overview of the 3G wireless system proposals and characterises the expected network capacity gains attained with the aid of adaptive CDMA systems By providing an all-encompassing self-contained treatment this groundbreaking volume will have appeal to researchers, postgraduate students, academics practising research and development engineers working for wireless communications and computer networking companies, as well as senior undergraduate students and technical managers in the field.

Download or read book Distributed Antenna Systems written by Yan Zhang and published by CRC Press. This book was released on 2007-06-27 with total page 480 pages. Available in PDF, EPUB and Kindle. Book excerpt: The rapid growth in mobile communications has led to an increasing demand for wideband high data rate communications services. In recent years, the Distributed Antenna System (DAS) has emerged as a promising candidate beyond 3G and 4G mobile communications. Distributed Antenna Systems: Open Architecture for Future Wireless Communications is

Download or read book Multi user Receiver Design and Performance for High density Synchronous CDMA Systems written by Abdelkader Elmilady and published by . This book was released on 1997 with total page 156 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Combined Multiuser Detection and Adaptive Blind Array Processing for DS CDMA Systems written by Shahrokh Nayeb Nazar and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: