Interference suppression in single- and multi-carrier CDMA systems
Interference suppression in single- and multi-carrier CDMA systems
In this dissertation we aimed for investigating numerous interference suppressing techniques designed for CDMA communications systems, which include chip-waveform optimization, spreading code optimization, and multiuser detection. We investigated the achievable performance in conjunction with the various time-limited and band-limited chip-waveforms. In the context of spreading code optimization, we comparatively studied LAS-CDMA and traditional DS-CDMA systems communicating over a Nakagami-m fading channel. The employment of LAS spreading codes is capable of suppressing both the multiple access interference (MAI) and multi-path interference (MPI), hence LAS-CDMA exhibited a significantly better performance than that of the traditional random code based DS-CDMA system in a quasi-synchronous channel. Considering the receiver optimization techniques, we investigated several multiuser detectors, which include iterative multiuser detectors, genetic algorithm (GA) aided multiuser detectors, M-algorithm (MA) assisted multiuser detectors, blind multiuser detectors, as well as combined GA and Radial Basis Function (GA-RBF) assisted multiuser detectors. Following the philosophy of turbo equalization, the iterative multiuser detector investigated utilized the soft outputs of the channel decoder for soft interference cancellation. This specific detector was capable of significantly improving the achievable performance. We comparatively investigated both GA aided and M-algorithm assisted multiuser detectors designed for DS-CDMA systems. The GA-RBF assisted MUD exhibited a significantly lower complexity than that of the conventional RBF network based multiuser detector. We also proposed GA assisted multiuser detectors designed for MC-CDMA systems, which constitute a low-complexity suboptimal MUD technique applicable to both synchronous and asynchronous MC-CDMA systems communicating over frequency selective fading channels. Finally, we studied joint time- and frequency-domain spreading assisted MC DS-CDMA.
University of Southampton
Wei, Hua
9551b623-22ca-4aed-b566-305dfceafdb1
2005
Wei, Hua
9551b623-22ca-4aed-b566-305dfceafdb1
Wei, Hua
(2005)
Interference suppression in single- and multi-carrier CDMA systems.
University of Southampton, Doctoral Thesis.
Record type:
Thesis
(Doctoral)
Abstract
In this dissertation we aimed for investigating numerous interference suppressing techniques designed for CDMA communications systems, which include chip-waveform optimization, spreading code optimization, and multiuser detection. We investigated the achievable performance in conjunction with the various time-limited and band-limited chip-waveforms. In the context of spreading code optimization, we comparatively studied LAS-CDMA and traditional DS-CDMA systems communicating over a Nakagami-m fading channel. The employment of LAS spreading codes is capable of suppressing both the multiple access interference (MAI) and multi-path interference (MPI), hence LAS-CDMA exhibited a significantly better performance than that of the traditional random code based DS-CDMA system in a quasi-synchronous channel. Considering the receiver optimization techniques, we investigated several multiuser detectors, which include iterative multiuser detectors, genetic algorithm (GA) aided multiuser detectors, M-algorithm (MA) assisted multiuser detectors, blind multiuser detectors, as well as combined GA and Radial Basis Function (GA-RBF) assisted multiuser detectors. Following the philosophy of turbo equalization, the iterative multiuser detector investigated utilized the soft outputs of the channel decoder for soft interference cancellation. This specific detector was capable of significantly improving the achievable performance. We comparatively investigated both GA aided and M-algorithm assisted multiuser detectors designed for DS-CDMA systems. The GA-RBF assisted MUD exhibited a significantly lower complexity than that of the conventional RBF network based multiuser detector. We also proposed GA assisted multiuser detectors designed for MC-CDMA systems, which constitute a low-complexity suboptimal MUD technique applicable to both synchronous and asynchronous MC-CDMA systems communicating over frequency selective fading channels. Finally, we studied joint time- and frequency-domain spreading assisted MC DS-CDMA.
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Published date: 2005
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Local EPrints ID: 465668
URI: http://eprints.soton.ac.uk/id/eprint/465668
PURE UUID: cf503045-0d38-4981-903b-d962ff29bb7d
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Date deposited: 05 Jul 2022 02:30
Last modified: 16 Mar 2024 20:18
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Author:
Hua Wei
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