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 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 Multi user Detection for Multi rate DS CDMA Systems written by Jinwen Ma and published by . This book was released on 2000 with total page 190 pages. Available in PDF, EPUB and Kindle. Book excerpt: Wireless cellular communication is witnessing a rapid growth in market, technology and range of services. Current and future demands for wireless communication services motivate the need for handling multi-media traffic types. In a multimedia communication system, users with different and even time-varying rates and quality of services (QoS) requirements, such as voice, image and data, must be accommodated. The use of Spread Spectrum modulation with Code Division Multiple Access (CDMA) technology is an attractive approach for economical spectrally efficient and high quality cellular and personal communication services. This dissertation explores the technologies of applying different interference cancellation techniques to multi-rate CDMA systems that serve users with different QoS. Multiple Access Interference (MAI) and multipath propagation are the major issues in wireless communication systems. It is also true for multi-rate CDMA systems. Multi-user detection has been shown to be effective in combating the near-far problem and providing superior performance over conventional detection method. In this dissertation, we combine both linear minimum mean squared error (LMMSE) detector, nonlinear decision feedback detector, with other signal processing techniques, such as array processing and multipath combining, to create effective near-far resistant detectors for multi-rate CDMA systems. Firstly, we propose MMSE receivers for synchronous multi-rate CDMA system and compare the performance with the corresponding multi-rate decorrelating detectors. The multi-rate decorrelating detector is optimally near-far resistant and easy to implement. The proposed linear MMSE multi-rate receiver can be adaptively implemented only with the knowledge of the desired user. Due to the fact that MMSE detector offers best trade-off between the MAI cancellation and noise variance enhancement, it is shown that multi-rate MMSE receiver can offer better performance than the multi-rate decorrelator when the interfering users' Signal to Noise Ratio (SNR) is relatively low comparing to the desired user's SNR. Secondly, the asynchronous multi-rate CDMA system, we propose multi-rate multi-shoot decorrelating detectors and multi-rate multi-shot MMSE detectors. The performance of multi-shot detectors can be improved monotonically with increasing the number of stacked bits, but a great computational complexity is going to be introduced in order to get better performance. A debiasing method is introduced to multi-rate multi-shot linear detectors. Debiasing method optimizes multi-rate detectors based on the multi-rate multi-shot model. Debiasing multi-shot MMSE detector for multi-rate signals can offer performance than the corresponding debiasing multi-shot decorrelating detector. Thirdly, we propose linear space-time receivers for multi-rate CDMA systems. The minimum mean-squared error criteria is used. We perform a comparative study on the multi-rate receiver which uses either multipath (temporal) processing or array (spatial) processing, and the one which uses both array and multipath (space-time) processing. The space-time receiver for the multi-rate CDMA signals give us the potential of improving the capacity of multi-rate systems. The space-time processing combined with multiuser detection have the advantages of combating multipath fading through temporal processing, reducing MAI through MMSE method and provide antenna or diversity gain through spatial processing and increasing the capacity of the multi-rate CDMA systems. Lastly, the group-wise interference cancellation methods are proposed for multi-rate CDMA signals. The non-linear decision feedback detection (DFD) schemes are used in the proposed receivers. The proposed interference cancellation schemes benefit from the nature of the unequal received amplitudes for multi-rate CDMA signals. Users with same data rate are grouped together. Users with the highest data-rate are detected first. Interference between the groups is cancelled in a successive order. The results show that the group-wise MMSE DFD yields better performance than multi-rate linear MMSE detector and multi-rate decorrelating detector, especially for highly loaded 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 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 On the Capacity of Asynchronous CDMA Systems with Tractable Multiuser Detection written by S. Boztaş and published by . This book was released on 1999 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Multiuser receivers with optimal group detection for code division multiple access channels written by and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: As técnicas de múltiplo acesso mais cogitadas nas propostas para padrões de 3 geração de sistemas celulares envolvem alguma forma de CDMA (Code Division Multiple Access)na qual os usuários podem transmitir simultaneamente na mesma faixa de freqüência sendo separáveis no receptor pela ortogonalidade, ou quase ortogonalidade, entre os sinais utilizados pelos diferentes usuários para transmissão de informação. Os receptores multiusuário, propostos para uso na 3 geração de sistemas celulares, realizam a detecção do sinal do usuário desejado conjuntamente com os sinais interferentes, resultando em um ganho de desempenho em relação aos receptores CDMA convencionais, que tratam os sinais interferentes como um simples ruído de fundo. Este trabalho tem por objetivo estudar a viabilidade de um receptor CDMA multiusuário hpibrido síncrono, que combina a eficiência do recepor Decorrelator no combate a interferência de múltiplo acesso (IMA) e sua simpicidade de implementação com a robustez e alto desempenho do receptor ótimo. Para evitar a complexidade inerente a estrutura de detecção ótima é sugerido que o conjunto de sinais na saída do estágio Decorrelator seja particionado em grupos e detectados de forma paralela e ótima. Esta técnica é conhecida como detecção ótima por grupos. Também é proposto e explorada a utilização de uma métrica para a formação dos grupos, baseada na minimização da probabilidade de erro de bit do usuário com pior desenpenho no sistema. Ao longo deste trabalho são exibidos resultados analíticos e de simulação, que comprovam a utilidade e exelente relação entre desempenho e complexidade da estrutura proposta em canais AWGN. Por fim, a estrutura proposta é avaliada para um canal com desvanecimento de Rayleigh plano.

Download or read book Advanced Wireless Communications written by Savo G. Glisic and published by John Wiley & Sons. This book was released on 2005-12-13 with total page 878 pages. Available in PDF, EPUB and Kindle. Book excerpt: The wireless community is on the verge of the standardization of fourth generation (4G) systems. Research has generated a number of solutions for significant improvement of system performance. The development of enabling technologies such as adaptive coding and modulation, iterative (turbo) decoding algorithms and space-time coding, means that industry can now implement these solutions. Advanced Wireless Communications: 4G Technologies focuses on the system elements that provide adaptability and reconfigurability and discusses how these features can improve 4G system performance. There are several different systems comprising 4G, including adaptive WCDMA (Wideband Code Division Multiple Access), ATDMA (Adaptive Time Division Multiple Access), Multicarrier (OFDMA) and Ultra Wide Band (UWB) receiver elements. This book provides a comparative study of these technologies and focuses on their future co-existence. Topics covered include: Space Time Coding, including discussions on diversity gain, the encoding and transmission sequence, the combining s cheme and ML decision rule for two-branch transmit diversity scheme with one and M receivers. Ultra Wide Band Radio, UWB multiple access in Gaussian channels, the UWB channel, UWB system with M-ary modulation, M-ary PPM UWB multiple access, coded UWB schemes, multi-user detection in UWB radio, UWB with space time processing and beam forming for UWB radio. Antenna array signal processing with focus on Space-Time receivers for CDMA communications, MUSIC and ESPRIT DOA estimation, joint array combining and MLSE receivers, joint combiner and channel response estimation and complexity reduction in the wide-band beam forming Channel modeling and measurement, adaptive MAC, adaptive routing and TCP layer are also addressed. This book will supply the reader with a comprehensive understanding of the relationship between the systems performance, its complexity/reliability and cost-effectiveness. It gives an insight into the impact of existing and new technologies on the receiver structure and provides an understanding of current approaches and evolving directions for personal and indoor communication.

Download or read book 2002 IEEE 7th International Symposium on Spread Spectrum Techniques and Applications written by and published by IEEE Computer Society Press. This book was released on 2002 with total page 378 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Time windowed Multiuser Decorrelating Receivers for Asynchronous Code Division Multiple Access Communication Channels written by Michael Stephen Feeney and published by . This book was released on 1994 with total page 294 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Subspace Multiuser Detection in DS CDMA Communication Systems and Its Applications written by Yong-Suk Moon and published by . This book was released on 1999 with total page 284 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 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 Transmitter Based Multiple Access Interference Rejection and Diversity Techniques for Code Division Multiple Access Systems written by Jia Liu and published by . This book was released on 2005 with total page 121 pages. Available in PDF, EPUB and Kindle. Book excerpt: Keywords: transmit diversity, multiuser detection, CDMA, multiple access interference, multiuser precoding.

Download or read book Azienda segni distintivi concorrenza written by and published by . This book was released on 1973 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Dissertation Abstracts International written by and published by . This book was released on 1998 with total page 716 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book IEEE International Symposium on Information Theory written by and published by . This book was released on 2000 with total page 550 pages. Available in PDF, EPUB and Kindle. Book excerpt: