Download or read book Interference Suppression for DS CDMA with Space and Time Diversity written by Wayne G. Phoel and published by . This book was released on 2000 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Finally, we consider transmitter diversity for the forward link of a DS-CDMA system. Orthogonal designs, which avoid self-interference from the multiple transmitters, are compared with space-time coding, which enables a lower code rate but introduces self-interference. The receiver uses a linear MMSE filter followed by a parallel Decision-Feedback Detector to cancel self-interference. In frequency-selective fading, space-time coding can provide a significant gain over orthogonal designs.

Download or read book Signal Processing for DS CDMA and OFDM CDMA Systems Interference Suppression Timing Recovery and Space Time Processing written by and published by . This book was released on 2006 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Space time Spreading and Transmit Diversity for DS CDMA Systems Over Fading Channels written by Mohamed Aljerjawi and published by . This book was released on 2006 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: The application of space-time coding in wireless communication systems has shown to improve the quality of the received signal at the mobile user by placing the spatial diversity at the base station. In this thesis, we propose a simple space-time spreading scheme for code-division multiple-access (CDMA) systems over fast-fading channels. The proposed transmit diversity scheme is based on two transmit and M receive antennas and is suitable for Rayleigh fast-fading channels. In this we employ orthogonal spreading codes to exploit the time diversity introduced by the channel, and hence a two-fold of the diversity order obtained using existing spacetime spreading schemes is achieved. Nevertheless, for slowly-fading channels, we show that the proposed coding scheme reduces to existing schemes introduced in the literature with no performance degradation. Then, we examine the effect of using nonorthogonal spreading codes on the receiver performance. Our results show that using a simple adaptive decoder, based on the minimum mean-squared error (MMSE) criterion, the diversity order is still maintained and only a small loss in the signal-to noise ratio (SNR) is incurred relative to the ideal case with orthogonal codes.

Download or read book Space time Equalizers for Interference Suppression in DS CDMA Systems written by Pham Van Dong and published by . This book was released on 1999 with total page 328 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Adaptive Signal Processing in Wireless Communications written by Mohamed Ibnkahla and published by CRC Press. This book was released on 2017-12-19 with total page 520 pages. Available in PDF, EPUB and Kindle. Book excerpt: Adaptive techniques play a key role in modern wireless communication systems. The concept of adaptation is emphasized in the Adaptation in Wireless Communications Series through a unified framework across all layers of the wireless protocol stack ranging from the physical layer to the application layer, and from cellular systems to next-generation wireless networks. This specific volume, Adaptive Signal Processing in Wireless Communications is devoted to adaptation in the physical layer. It gives an in-depth survey of adaptive signal processing techniques used in current and future generations of wireless communication systems. Featuring the work of leading international experts, it covers adaptive channel modeling, identification and equalization, adaptive modulation and coding, adaptive multiple-input-multiple-output (MIMO) systems, and cooperative diversity. It also addresses other important aspects of adaptation in wireless communications such as hardware implementation, reconfigurable processing, and cognitive radio. A second volume in the series, Adaptation and Cross-layer Design in Wireless Networks(cat no.46039) is devoted to adaptation in the data link, network, and application layers.

Download or read book Interference Suppression Techniques for Multi rate CDMA Communication Systems written by Tao Luo and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis is concerned with interference suppression in multi-rate Code-division multiple-access (CDMA) communication systems. Specifically, the following problems within the area of CDMA communication systems have been addressed: interference suppression through chip waveform design, interference reduction through new diversity techniques for users having low mobility by exploiting inherent channel diversity and joint spatial-temporal interference suppression; all with the ultimate goal to increase the system capacity. First, we examine interference issues in the multi-rate CDMA communication systems. We minimize the interference by designing different chip waveforms for different data rate users. A general chip waveform design framework is formulated. It is shown that it is better to separate different data rate users in spectrum if their quality of service requirements are quite different. Next, we propose a new receiver structure targeting those users having low mobility but whose channels have small dispersion in frequency. We show that even a very small delay spread can be exploited to achieve significant gain in terms of the signal-to-noise ratio. Then we consider joint spatial and temporal interference suppression through an adaptive antenna array. We show that adaptive spatial and temporal correlation control between different users can give us higher system capacity. Sub-optimal algorithms with low complexity are proposed and analyzed. We show that the proposed algorithms reduce the transmit power significantly, therefore, greatly increase the system capacity. Finally, we examine the role of the adaptive antenna array in the multi-rate CDMA communication systems. We show that if we perform beamforming for different data rate users, most of the achieved gain is due to the high data rate users if the total power of the high data rate users is much higher than that of the low rate users. Thus, significant computational savings can be achieved but with near optimum transmit power.

Download or read book Adaptation in Wireless Communications 2 Volume Set written by Mohamed Ibnkahla and published by CRC Press. This book was released on 2018-10-08 with total page 1048 pages. Available in PDF, EPUB and Kindle. Book excerpt: The widespread use of adaptation techniques has helped to meet the increased demand for new applications. From adaptive signal processing to cross layer design, Adaptation in Wireless Communications covers all aspects of adaptation in wireless communications in a two-volume set. Each volume provides a unified framework for understanding adaptation and relates various specializations through common terminologies. In addition to simplified state-of-the-art cross layer design approaches, they also describe advanced techniques, such as adaptive resource management, 4G communications, and energy and mobility aware MAC protocols.

Download or read book Advanced Wireless Communications and Internet written by Savo G. Glisic and published by John Wiley & Sons. This book was released on 2011-05-03 with total page 1025 pages. Available in PDF, EPUB and Kindle. Book excerpt: ADVANCED WIRELESS COMMUNICATIONS AND INTERNET THIRD EDITION ADVANCED WIRELESS COMMUNICATIONS AND INTERNET Future Evolving Technologies The new edition of Advanced Wireless Communications: 4G Cognitive and Cooperative Broadband Technology, 2nd Edition, including the latest developments In the evolution of wireless communications, the dominant challenges are in the areas of networking and their integration with the Future Internet. Even the classical concept of cellular networks is changing and new technologies are evolving to replace it. To reflect these new trends, Advanced Wireless Communications & INTERNET builds upon the previous volumes, enhancing the existing chapters, and including a number of new topics. Systematically guiding readers from the fundamentals through to advanced areas, each chapter begins with an introductory explanation of the basic problems and solutions followed with an analytical treatment in greater detail. The most important aspects of new emerging technologies in wireless communications are comprehensively covered including: next generation Internet; cloud computing and network virtualization; economics of utility computing and wireless grids and clouds. This gives readers an essential understanding of the overall environment in which future wireless networks will be operating. Furthermore, a number of methodologies for maintaining the network connectivity, by using tools ranging from genetic algorithms to stochastic geometry and random graphs theory, and a discussion on percolation and connectivity, are also offered. The book includes a chapter on network formation games, covering the general models, knowledge based network formation games, and coalition games in wireless ad hoc networks. Illustrates points throughout using real-life case studies drawn from the author’s extensive international experience in the field of telecommunications Fully updated to include the latest developments, key topics covered include: advanced routing and network coding; network stability control; relay-assisted Wireless Networks; multicommodity flow optimization problems, flow optimization in heterogeneous networks, and dynamic resource allocation in computing clouds Methodically guides readers through each topic from basic to advanced areas Focuses on system elements that provide adaptability and re-configurability, and discusses how these features can improve wireless communications system performance Enjoyed this book? Why not tell others about it and write a review on your favourite online bookseller.

Download or read book Space time Diversity for CDMA Systems Over Frequency selective Fading Channels written by Ayman M. Assra and published by . This book was released on 2010 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Supporting the expected high data rates required by wireless Internet and high-speed multimedia services is one of the basic requirements in broadband mobile wireless systems. However, the achievable capacity and data rate of wireless communication systems are limited by the time-varying nature of the channel. Efficient techniques for combating the time-varying effects of wireless channels can be achieved by utilizing different forms of diversity. In recent years, transmit diversity based on space-time coding (STC) has received more attention as an effective technique for combating fading. On the other hand, most existing space-time diversity techniques have been developed for flat-fading channels. Given the fact that wireless channels are generally frequency-selective, in this thesis, we aim to investigate the performance of space-time diversity schemes for wideband code-division multiple-access (WCDMA) systems over frequency-selective fading channels. The proposed receiver in this case is a rake-type receiver, which exploits the path diversity inherent to multipath propagation. Then, a decorrelator detector is used to mitigate the multiple access interference (MAI) and the known near-far problem. We derive the bit error rate (BER) expression over frequency-selective fading channels considering both the fast and slow fading cases. Finally, we show that our proposed receiver achieves the full system diversity through simulation and analytical results. Most of the work conducted in this area considers perfect knowledge of the channel at the receiver. Hence, channel identification brings significant challenges to multiple-input multiple-output (MIMO) CDMA systems. In light of this, we propose a channel estimation and data detection scheme based on the superimposed training-based approach. The proposed scheme enhances the performance by eliminating the MAI from both the channel and data estimates by employing two decorrelators; channel and data decorrelators. The performance of the proposed estimation technique is investigated over frequency-selective slow fading channels where we derived a closed-form expression for the BER as a function of the number of users, K, the number resolvable paths, L, and the number of receive antennas, V . Finally, our proposed scheme is shown to be more robust to channel estimation errors. Furthermore, both the analytical and simulation results indicate that the full system diversity is achieved. Considering that training estimation techniques suffer either from low spectral efficiency (i.e., conventional training approach) or from high pilot power consumption (i.e., superimposed training-based approach), in the last part of the thesis, we present an iterative joint detection and estimation (JDE) using the expectation-maximization (EM) algorithm for MIMO CDMA systems over frequency-selective fading channels. We also derive a closed-form expression for the optimized weight coefficients of the EM algorithm, which was shown to provide significant performance enhancement relative to the conventional equal-weight EM-based signal decomposition. Finally, our simulation results illustrate that the proposed receiver achieves near-optimum performance with modest complexity using very few training symbols.

Download or read book Coded Transmit Diversity in CDMA Over Nakagami m Fading Channels written by Ariel Sacramento and published by . This book was released on 2008 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: With applications such as video conferencing, extensive web browsing and live video streaming, future wireless systems become extremely demanding in terms of high data rates and improved signal quality. In this thesis the performance of a space-time spreading transmit diversity scheme is examined over a frequency-flat Nakagami- m fading channel. The Nakagami- m channel model is considered as it is well known for modeling signal fading conditions ranging from severe to moderate, to light fading or no fading, through its parameter m. We also propose in this thesis a coded transmit diversity scheme which is based on a combination of a convolutional code with a space-time transmit diversity scheme that uses direct-sequence code division multiple access (DS-CDMA) for multiuser access. Our focus will be on the uplink of the communication system. The space-time scheme employs N = 2 and N r antennas at the mobile station (MS) side and at the base station (BS) side respectively. DS-CDMA is used to support many users and a linear decorrelator detector is used to combat the effect of multiuser interference. We study the performance of both the uncoded and coded transmit diversity schemes over slow fading and fast fading channels. In all cases, the investigations start by determining the probability density function (PDF) of the signal to interference and noise ratio at the output of the space-time combiner at the BS receiver side. Using this PDF we derive a closed-form (or an approximation) expression for the bit error rate (BER) of the system under consideration. The accuracy of the PDF and BER expressions are verified when compared to simulation results for different values of the fading figure m and for different combinations of transmit and receive antennas. In the case of the coded space-time transmit diversity scheme, the pairwise error probability and the corresponding BER upper bounds are obtained for fast and slow fading channels. The derived error bounds, when compared to system simulations, are shown to be tight at high signal-to-noise ratios. Furthermore, our analytical results explicitly show the achieved system diversity in terms of the number of transmit and receive antennas and the fading figure m. When the coded space-time scheme is considered, its diversity is shown to be a function of the minimum free distance d free of the convolutional code used. Furthermore we show that the diversity of the different schemes considered is always independent of the system load.

Download or read book Linear Interference Suppression and Pulse Optimization for DS CDMA written by and published by . This book was released on 1999 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This project is concerned with the applicability of adaptive linear interference suppression for DS-CDMA in a peer-to-peer network. This technique is robust with respect to extreme near-far power variations. The following topics have been studied: (1) performance in the presence of time- and frequency-selective fading, (2) reduced-rank methods for faster convergence and tracking, (3) adaptive transmitter preprocessing for interference avoidance, (4) combined coding and interference suppression, and (5) performance in the presence of mixed rate traffic. Overall, our results indicate that adaptive linear interference suppression can be made robust with respect to time-varying channels and interference. Algorithmic enhancements which improve upon the performance in a dynamically changing environment have been proposed and evaluated.

Download or read book Signal Processing for Wireless Communication Systems written by H. Vincent Poor and published by Springer Science & Business Media. This book was released on 2006-01-19 with total page 299 pages. Available in PDF, EPUB and Kindle. Book excerpt: Signal Processing for Wireless Communication Systems brings together in one place important contributions and up-to-date research results in this fast moving area. The Contributors to this work were selected from leading researchers and practitioners in this field. The book's 18 chapters are divided into three areas: systems, Networks, and Implementation Issues; Channel Estimation and Equalization; and Multiuser Detection. The Work, originally published as Volume 30, Numbers 1-3 of the Journal of VLSI Signal Processing Systems for Signal, Image, and Video Technology, will be valuable to anyone working or researching in the field of wireless communication systems. It serves as an excellent reference, providing insight into some of the most challenging issues being examined today.

Download or read book Interference Suppression in Spread spectrum Networks written by Haichang Sui and published by . This book was released on 2007 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this dissertation, interference suppression techniques and applications will be presented for cellular networks with direct-sequence (DS) CDMA and mobile ad hoc networks with frequency-hopped (FH) CDMA. The first part of the dissertation focuses on three novel finger placement designs that effectively equalize the DS-CDMA multi- path downlink channel to restore code orthogonality and consequently suppress multiple-access interference. For typical multipath channel models, the proposed schemes may significantly outperform the uniformly spaced tapped-delay-line equalizer with much less fingers/taps. In addition, analytic insight into the effect of the finger number and the smoothness of the chip pulse are obtained. The second part of the dissertation considers mobile ad hoc networks with FH-CDMA, where error-correcting codes are employed with differential unitary space-time modulation. The use of multiple transmit antennas in FH-CDMA systems, to the best knowledge of the author, has not been proposed in previous literature. The proposed receiver performs decision-feedback demodulation, decision-aided adaptive estimation, and erasure-insertion decoding jointly to suppress arbitrary unknown interference without channel state information. The third part of the dissertation presents network performance analysis for FH-CDMA networks with the proposed transceiver. Information efficiency and transmission range optimization is investigated under realistic time-varying channel models, which extends previous studies based on static channels and/or simplistic physical layer models. Impacts of various design parameters and channel properties on the network performance are revealed. The results also provide guidance on optimizing the modulation and coding scheme from a network perspective.

Download or read book Spread Spectrum and CDMA written by Valeri P. Ipatov and published by John Wiley & Sons. This book was released on 2005-12-13 with total page 396 pages. Available in PDF, EPUB and Kindle. Book excerpt: Spread spectrum and CDMA are cutting-edge technologies widely used in operational radar, navigation and telecommunication systems and play a pivotal role in the development of the forthcoming generations of systems and networks. This comprehensive resource presents the spread spectrum concept as a product of the advancements in wireless IT, shows how and when the classical problems of signal transmission/processing stimulate the application of spread spectrum, and clarifies the advantages of spread spectrum philosophy. Detailed coverage is provided of the tools and instruments for designing spread spectrum and CDMA signals answering why a designer will prefer one solution over another. The approach adopted is wide-ranging, covering issues that apply to both data transmission and data collection systems such as telecommunications, radar, and navigation. Presents a theory-based analysis complemented by practical examples and real world case studies resulting in a self-sufficient treatment of the subject Contains detailed discussions of new trends in spread spectrum technology such as multi-user reception, multicarrier modulation, OFDM, MIMO and space-time coding Provides advice on designing discrete spread spectrum signals and signal sets for time-frequency measuring, synchronization and multi-user communications Features numerous Matlab-based problems and other exercises to encourage the reader to initiate independent investigations and simulations This valuable text provides timely guidance on the current status and future potential of spread spectrum and CDMA and is an invaluable resource for senior undergraduates and postgraduate students, lecturers and practising engineers and researchers involved in the deployment and development of spread spectrum and CDMA technology. Supported by a Companion website on which instructors and lecturers can find a solutions manual for the problems and Matlab programming, electronic versions of some of the figures and other useful resources such as a list of abbreviations.

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 Optical CDMA Networks written by Hooshang Ghafouri-Shiraz and published by John Wiley & Sons. This book was released on 2012-08-07 with total page 434 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book focuses heavily on the principles, analysis and applications of code-division multiple-access (CDMA) techniques in optical communication systems and networks. In this book, the authors intimately discuss modern optical networks and their applications in current and emerging communication technologies, evaluating the quality, speed and number of supported services. In particular, principles and fundamentals of optical CDMA techniques from beginner to advanced levels are heavily covered. Furthermore, the authors concentrate on methods and techniques of various encoding and decoding schemes and their structures, as well as analysis of optical CDMA systems with various transceiver models including advanced multi-level incoherent and coherent modulations with the architecture of access/aggregation networks in mind. Moreover, authors examine intriguing topics of optical CDMA networking, compatibility with IP networks, and implementation of optical multi-rate multi-service CDMA networks. Key features: Expanded coverage of optical CDMA networks, starts from principles and fundamentals Comprehensive mathematical modelling and analysis from signal to system levels Addresses the applications of modern optical networking in the current and emerging communication technologies Greater focus on advanced optical multi-level incoherent and coherent modulations, spreading codes, and transceiver designs Detailed hardware specifications, system-level block diagrams, and network nodes’ functionalities This book appeals to researchers, practicing engineers, and advanced students. It is a practical resource for readers with an interest in optical communications and networks.

Download or read book Estimation of Fading Channel in DS Cdma Multiuser Communications Systems written by Chun-Yu Fung and published by Open Dissertation Press. This book was released on 2017-01-27 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Estimation of Fading Channel in DS-CDMA Multiuser Communications Systems" by Chun-yu, Fung, 馮震宇, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of the Thesis Entitled Estimation of Fading Channel in DS-CDMA Multiuser Communications Systems submitted by Fung Chun Yu for the degree of Master of Philosophy at the University of Hong Kong in December 2002 Multipath fading and multiuser access interference are two major impairments in direct-sequence code-division multiple-access (DS-CDMA) systems. Efficient channel estimation and multiuser detection techniques play important roles in overcoming these deficiencies. This thesis is concerned with the design of a space-time (ST) blind adaptive receiver for DS-CDMA systems and the accompanied channel estimation algorithm. A new space-time decorrelating RAKE (ST-DRAKE) receiver is developed for blind reception of CDMA signals in frequency-selective fading channels. It has the advantage that only the knowledge of the desired user's signature waveform is required and therefore no transmission of training sequence is needed. The ST-DRAKE receiver consists of two parts. The first part is a set of constrained adaptive filters that are designed to suppress interference based on the minimum output energy criterion. These filters are implemented in a structure analogous to the general sidelobe canceller in array processing, which is implemented by a multistage Weiner filter is employed to reduce the complexity of the receiver. The second part of the ST-DRAKE receiver coherently combines the outputs of the constrained adaptive filters and gives an estimate of the transmitted signal. Simulation results show that the ST- DRAKE delivers significant performance improvement by exploiting the spatial diversity of the antenna array. The problem of estimating fast fading channels in the proposed receiver is also addressed. The time-varying channel is modeled as an autoregressive process and the Kalman filter is employed to estimate the time-varying channel coefficients. A robust Kalman filter based on the M-estimate cost function is also developed to suppress impulsive noise present in the received signals. Simulation results show that the Kalman filter provides more accurate channel estimate to the ST-DRAKE than using the decomposition method. Simulation results also show that the coupled receiver has a performance comparable to the optimum minimum mean-squared error receiver with known channel information. DOI: 10.5353/th_b2750902 Subjects: Code division multiple access Wireless communication systems