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 Large System Performance of Linear Interference Suppression for DS CDMA written by Weimin Xiao and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The performance of linear filtering is studied for the suppression of multiple access interference in a Direct-Sequence Code-Division Multiple Access (DS-CDMA) system with random spreading sequences. Both full-rank and reduced-rank filters are investigated. The emphasis of our study is on large system performance analysis.
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 An Experimental Approach to CDMA and Interference Mitigation written by Luca Fanucci and published by Springer Science & Business Media. This book was released on 2007-05-08 with total page 284 pages. Available in PDF, EPUB and Kindle. Book excerpt: An Experimental Approach to CDMA and Interference Mitigation was written with the admittedly ambitious intent of filling the gap between communication theory and VLSI implementation, and thus to provide a more general/theoretical approach to the design, development, and testing of a CDMA receiver. As a consequence, the concepts and techniques that are presented turn out to be applicable to a more general kind of digital wireless modems in terms of receiver architecture design and implementation. As the reader will easily find out, the subject of digital modem design and implementation is addressed in the book starting from a theoretical approach (supported by proper bibliographic references), and is followed by application issues, with reference to an ESA experiment assumed as a case study. A complete design flow, from specification to implementation, including testing and final verification is then presented. This leads the reader step-by-step to a thorough understanding of CDMA transmission and detection, and constitutes a practical guidance for the design of VLSI wireless mobile terminals.
Download or read book SNR Maximizing Linear Filters with Interference Suppression Capabilities for DS CDMA written by Young C. Yoon and published by . This book was released on 1998 with total page 226 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Interference Suppression Techniques for Multicarrier DS CDMA written by Weiping Xu and published by . This book was released on 1998 with total page 254 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Interference Suppression for DS CDMA Systems in Non Gaussian Impulsive Channels written by Seoyoung Lee and published by . This book was released on 1998 with total page 238 pages. Available in PDF, EPUB and Kindle. Book excerpt: Simulation results show that the proposed detector provides remarkable performance improvements over the adaptive MD detector in a wide range of near-far situations. The proposed detector has much better near-far resistance than the adaptive MD detector. Finally, fuzzy hybrid detector combines the adaptive MD detector and the hard-limiting matched filter (HLMF) detector. The HLMF detector performs well when the additive impulsive noise significantly dominates over MAI. Simulation results indicate significant performance improvements over the adaptive MD detector alone in impulsive noise-limited environments. When MAI dominates, the fuzzy hybrid detector nearly has the same performance as the adaptive MD detector.
Download or read book Structures and algorithms for multiuser detection and interference supression in ds cdma systems written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Esta tese apresenta novas estruturas e algoritmos para detecção multiusuário e supressão de interferência em sistemas DS-CDMA. São investigadas estruturas baseadas em redes neurais recorrentes para projeto de receptores com decisão realimentada e desenvolvidos algoritmos adaptativospara combater a interferência de múltiplo acesso e a interferência entre símbolos. Novos algoritmos baseados na minimização da taxa de erro de bits são examinados e generalizados para esquemas de detecção com cancelamento de interferência. Para situações onde uma seqüência de treinamento não é disponibilizada, é considerado um novo critério de projeto às cegas de receptores com restrições lineares baseado na função custo módulo constante. Algoritmos adaptativos às cegas baseados neste novo critério são usados para estimar os parâmetros de um receptor linear e do canal decomunicações. São também desenvolvidos novos mecanismos às cegas de ajuste do passo para algoritmos do tipo gradiente estocástico em receptores lineares com base no critério de mínima variância com restrições. Com base nos critérios de mínima variância e módulo constante com restrições, sãodesenvolvidos critérios de projeto às cegas para receptores com decisão realimentada e propostos algoritmos adaptativos para essas estruturas. Um novo esquema de cancelamento sucessivo de interferência baseado no conceito de arbitragem é proposto e incorporado a uma estrutura de recepção com decisão realimentada para o enlace reverso. Em seguida, o novo esquema decancelamento de interferência é combinado com uma estrutura iterativa queemprega múltiplos estágios, resultando em melhores estimativas do receptore um desempenho uniforme para os usuários. Finalmente, são apresentadasnovas estruturas de recepção com posto reduzido, baseadas em filtros FIRinterpolados e interpoladores variantes no tempo, e desenvolvidos algoritmosadaptativos às cegas e supervisionados para o novo esquema.
Download or read book Interference Suppression in DS CDMA Systems Over Frequency selective Fading Channels written by Stefano Buzzi (ingegnere.) and published by . This book was released on 1999 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Interference Cancellation Algorithms for Detecting DS CDMA Signals and Separating Combined Heart rate Signals written by Kuei-Chiang Lai and published by . This book was released on 2001 with total page 326 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Multiuser detection for DS CDMA systems using optimization methods written by Xianmin Wang (Ph. D.) and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Several new multiuser detectors are developed for different direct-sequence codedivision multiple-access (DS-CDMA) application environments. The first detector is based on a semidefinite-programming (SDP) relaxation technique. In this detector, maximum likelihood (ML) detection is achieved by 'relaxing' the associated combinatorial problem into an SDP problem, which leads to a detector of polynomial complexity. It is shown that the SDP-relaxation (SDPR) based detector can be obtained by solving a dual SDP problem which leads to improved efficiency. Computer simulations demonstrate that the SDPR detector offers near-optimal performance with much reduced computational complexity compared with that of the ML detector proposed by Verdu for both synchronous and asynchronous DS-CDMA systems. The second detector is based on a recursive convex programming (RCP) approach. In this detector, ML detection is carried out in two steps: first, the combinatorial problem associated with ML detection is relaxed to a convex programming problem, and then a recursive approach is used to obtain an approximate solution for ML detection. Efficient unconstrained relaxation approach is proposed for the proposed detector to reduce the involved computational complexity. Computer simulations demonstrate that the proposed detectors offer near-optimal detection performance which is superior to that offered by many other suboptimal detectors including the SDPR detector. However, the computational complexity involved in the proposed detectors is much lower relative to that involved in Verdu's ML detector as well as our SDPR detector. The third detector entails a subspace estimation-based constrained optimization approach for channel estimation in DS-CDMA systems with multipath propagation channels. The proposed approach offers an improved approximation for the noise iii subspace compared with that offered by several existing algorithms. Computer simulations show that the performance of the proposed detector offers nearly the same performance as that of existing subspace detectors but leads to a significant reduction in the amount of computation. Relative to some existing constrained optimization methods, the proposed detector offers a significantly improved performance while requiring a comparable amount of computation. The fourth detector is proposed based on a vector constant-modulus (VCM) approach. This detector is designed for DS-CDMA systems with multipath propagation channels where the effective signatures observed at receiver are distorted by multipath propagation and aliasing concurrently. In this detector, detection is carried out by solving a linear constrained optimization problem whose objective function is formulated based on the VCM criterion. Two adaptation algorithms, namely, the constrained stochastic gradient algorithm and the recursive vector constant-modulus algorithm, are developed. Analysis are presented to investigate the performance of the proposed detector. Computer simulations show that the proposed detectors are able to suppress multiuser interference and inter-symbol interference effectively. More importantly, they offer robust detection performance against the effective signature distortion caused by aliasing at the receiver.
Download or read book Semi blind Strategies for Interference Suppression in DS CDMA Systems written by Ryan A. Pacheco and published by . This book was released on 2000 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: QAM modulation of OFDM signals (OFDM-QAM) is a popular modulation scheme for linear communication systems because it achieves good spectral efficiency while simplifying the equalization process. This comes at the cost of requiring accurate synchronization methods in the receiver, highly stable oscillators (low phase-noise); and power inefficient transmission. This work addresses issues in these three areas. First, a new frame synchronization method is developed based on Bayesian changepoint principles. It has higher accuracy then current popular methods, can be implemented recursively, and has been tested with success on experimental data collected in a WLAN testbed. Second, phase-noise resistant communication is investigated by performing an accurate statistical analysis of self-heterodyne communication systems. The analysis can be used to accurately predict the bit error probability of such systems. Third, power efficient transmission using phase-modulation (OFDM-PM) is analyzed. The bandwidth, equivalent baseband model, and symbol error probability are investigated. We can now predict the performance of OFDM-PM systems; for a given spectral efficiency, when operating well into the threshold region of angle-demodulators., The semi-blind algorithms presented in this work attempt to improve interference suppression for a given number of training and information symbols by combining training-based and blind estimation techniques. We first derive the minimum number of training symbols the training-based least squares (LS) estimator requires for complete suppression of interference (in the noiseless case). This provides a benchmark which the semi-blind algorithms are compared against. Next, a framework for semi-blind iterative interference suppression is developed which is then used to enhance the LS estimator by adding the constant modulus and cyclostationary properties used in blind algorithms. Finally, a decision-aided (multistage) semi-blind algorithm that jointly processes the signals from all intra-cell users is presented. Simulation results indicate a significant improvement over training-based and blind estimation techniques. Application of this work is in the reverse-link of third generation short-burst asynchronous DS-CDMA systems subject to both ISI and MAI.
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 Semi blind Strategies for Interference Suppression in DS CDMA Systems written by and published by . This book was released on 2000 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Adaptive Interference Suppression for Frequency Acquisition in Direct Sequence CDMA Systems written by Brian Scott Johnson and published by . This book was released on 2000 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt:
