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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
111

New channel estimation and multiuser detection algorithms for multicarrier(MC)-CDMA communications systems

Cheng, Hui, 成慧 January 2005 (has links)
published_or_final_version / abstract / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy
112

Multicarrier CDMA overlay for ultra-wideband wireless communications

Wong, Tat-tung., 黃達東. January 2003 (has links)
published_or_final_version / abstract / toc / Electrical and Electronic Engineering / Master / Master of Philosophy
113

A multiple access interference rejection technique using weighted despreading functions for direct-sequence code division multipleaccess communications

黃耀進, Huang, Yuejin. January 1998 (has links)
published_or_final_version / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy
114

Multiuser detection employing recurrent neural networks for DS-CDMA systems.

January 2006 (has links)
Over the last decade, access to personal wireless communication networks has evolved to a point of necessity. Attached to the phenomenal growth of the telecommunications industry in recent times is an escalating demand for higher data rates and efficient spectrum utilization. This demand is fuelling the advancement of third generation (3G), as well as future, wireless networks. Current 3G technologies are adding a dimension of mobility to services that have become an integral part of modem everyday life. Wideband code division multiple access (WCDMA) is the standardized multiple access scheme for 3G Universal Mobile Telecommunication System (UMTS). As an air interface solution, CDMA has received considerable interest over the past two decades and a great deal of current research is concerned with improving the application of CDMA in 3G systems. A factoring component of CDMA is multiuser detection (MUD), which is aimed at enhancing system capacity and performance, by optimally demodulating multiple interfering signals that overlap in time and frequency. This is a major research problem in multipoint-to-point communications. Due to the complexity associated with optimal maximum likelihood detection, many different sub-optimal solutions have been proposed. This focus of this dissertation is the application of neural networks for MUD, in a direct sequence CDMA (DS-CDMA) system. Specifically, it explores how the Hopfield recurrent neural network (RNN) can be employed to give yet another suboptimal solution to the optimization problem of MUD. There is great scope for neural networks in fields encompassing communications. This is primarily attributed to their non-linearity, adaptivity and key function as data classifiers. In the context of optimum multiuser detection, neural networks have been successfully employed to solve similar combinatorial optimization problems. The concepts of CDMA and MUD are discussed. The use of a vector-valued transmission model for DS-CDMA is illustrated, and common linear sub-optimal MUD schemes, as well as the maximum likelihood criterion, are reviewed. The performance of these sub-optimal MUD schemes is demonstrated. The Hopfield neural network (HNN) for combinatorial optimization is discussed. Basic concepts and techniques related to the field of statistical mechanics are introduced and it is shown how they may be employed to analyze neural classification. Stochastic techniques are considered in the context of improving the performance of the HNN. A neural-based receiver, which employs a stochastic HNN and a simulated annealing technique, is proposed. Its performance is analyzed in a communication channel that is affected by additive white Gaussian noise (AWGN) by way of simulation. The performance of the proposed scheme is compared to that of the single-user matched filter, linear decorrelating and minimum mean-square error detectors, as well as the classical HNN and the stochastic Hopfield network (SHN) detectors. Concluding, the feasibility of neural networks (in this case the HNN) for MUD in a DS-CDMA system is explored by quantifying the relative performance of the proposed model using simulation results and in view of implementation issues. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2006.
115

Effect of amplifier non-linearity on the performance of CDMA communication systems in a Rayleigh fading environment

31 August 2010 (has links)
The effect of amplifier non-linearity on the performance of a CDMA communications system / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2009.
116

Performance of turbo-coded DS-CDMA systems in fading and burst channels.

Nkouatchah, Telex Magloire Ngatched. January 2001 (has links)
Turbo codes are a class of forward error correction (FEC) codes that offer energy efficiencies close to the limits predicted by information theory. The features of turbo codes include parallel code concatenation, recursive convolutional encoding, nonuniform interleaving, and an associated iterative decoding algorithm. The excellent performance of turbo codes explains why much of the current research is focused on applying turbo codes to different systems. This dissertation first outlines a new simple criterion for stopping the iterative process of the turbo decoder for each individual frame immediately after the bits are correctly estimated and thus prevents unnecessary computations and decoding delay. The dissertation then considers the performance of turbo coded DS-CDMA systems. The performance analysis begins with simulation results for turbo coded DS-CDMA over a multi-path Rayleigh fading channel. The channel is then modeled using the Gilbert-Elliott channel model and analytical expressions for the performance of the system are derived. The influence of various parameters such as the Doppler frequency, the signal-to-noise ratio threshold on the system performance are analyzed and investigated. / Thesis (M.Sc.Eng)-University of Natal, Durban, 2001.
117

Extensions of the constant modulus algorithm and the phase-locked loop for blind multiuser detection

Batra, Anuj 05 1900 (has links)
No description available.
118

Multiple coding and space-time multi-user detection in multiple antenna systems

Liu, Jianhan, 1974 January 2005 (has links)
Thesis (Ph. D.)--University of Hawaii at Manoa, 2005. / Includes bibliographical references (leaves 84-89). / Also available by subscription via World Wide Web / xi, 89 leaves, bound ill. 29 cm
119

Feasibility of a narrow band DS-CDMA overlay on a TDMA system /

Sahota, Raminder Singh. Unknown Date (has links)
Thesis (MEng)--University of South Australia, 1996
120

Coding for reduced spectral regrowth on nonlinear channels /

Morrison, Ian Stuart. Unknown Date (has links)
Thesis (PhD)--University of South Australia, 1996

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