Litchfield, Charan (2006) Single user diversity receivers for frequency selective WCDMA channels. Doctor of Philosophy (PhD) thesis, University of Kent. (doi:10.22024/UniKent/01.02.94487) (KAR id:94487)
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Official URL: https://doi.org/10.22024/UniKent/01.02.94487 |
Abstract
Wideband code division multiple access (WCDMA) forward links are susceptible to performance degradation incurred by multiple access interference (MAI) when the radio channel is frequency selective. This places a tight limit on die channel capacity of die cellular downlink since computationally efficient receiver technologies such as die 2D Rake receiver do not yield significant attenuation of die interference floor for high data rates. The application of optimum spatial processing employing two or more antenna elements is a topic of some interest since an optimum beamformer is one where the desired signal is decoupled into a matched filter while interfering signals are spatially nulled or filtered. However, for realistic radio environments and low number of sensors, array overloading prevents optimum information retrieval (and die required target bit error floor to be met) from a doubly selective spatial radio channel.
The work undertaken in the first part of this thesis investigates adaptive two element array receiver structures to enhance die downlink performance. In addition to per-path adaptive beamforming, oversampling can form several technologies utilizing this basic structure. In particular, an oversampled receiver with additional linger assignment (not necessarily matched to the channel delay spectra) forms die basis of a channel equalizer. This thesis extends upon this criterion by developing adaptive dual antenna interference suppressing receivers that jointly optimize die spatial and temporal multipath channel signatures at chip or symbol level. In particular, a chip-level optimization (forming a 2D chip equalizer) can decorrelate die multipath channel spectra allowing interference suppression with a chip-matched filter. This receiver is a generalized broadband antenna beamformer, where die resultant improvement in performance over die 2D Rake receiver is significant with only moderately increased complexity.
Optimum spatio-temporal diversity receivers require dial die multipath delay spectra are known and the channel phase/attenuation parameters perfectly reproducible with negligible error. However, matched filtering applying estimation of the channel parameters is unlikely to be error free, nor devoid of die effects of quantization. The second part of this diesis investigates the effect of quantization and logarithmic arithmetic on die 2D Rake receiver and 2D Chip equalizer. Logarithmic arithmetic was found to augment many useful properties such as reducing receiver filter inner products into trivial additions by transforming a linear algorithm into die logarithmic domain using the logarithmic number system. This method was found to offer superior error performance even when utilizing very simple codecs. This makes it a promising technique for integrating an adaptive WCDMA receiver onto low power multiplierless programmable hardware devices.
Item Type: | Thesis (Doctor of Philosophy (PhD)) |
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Thesis advisor: | Langley, Richard J. |
DOI/Identification number: | 10.22024/UniKent/01.02.94487 |
Additional information: | This thesis has been digitised by EThOS, the British Library digitisation service, for purposes of preservation and dissemination. It was uploaded to KAR on 25 April 2022 in order to hold its content and record within University of Kent systems. It is available Open Access using a Creative Commons Attribution, Non-commercial, No Derivatives (https://creativecommons.org/licenses/by-nc-nd/4.0/) licence so that the thesis and its author, can benefit from opportunities for increased readership and citation. This was done in line with University of Kent policies (https://www.kent.ac.uk/is/strategy/docs/Kent%20Open%20Access%20policy.pdf). If you feel that your rights are compromised by open access to this thesis, or if you would like more information about its availability, please contact us at ResearchSupport@kent.ac.uk and we will seriously consider your claim under the terms of our Take-Down Policy (https://www.kent.ac.uk/is/regulations/library/kar-take-down-policy.html). |
Subjects: | T Technology |
Divisions: | Divisions > Division of Computing, Engineering and Mathematical Sciences > School of Engineering and Digital Arts |
SWORD Depositor: | SWORD Copy |
Depositing User: | SWORD Copy |
Date Deposited: | 12 Jul 2022 15:50 UTC |
Last Modified: | 17 Jul 2023 09:10 UTC |
Resource URI: | https://kar.kent.ac.uk/id/eprint/94487 (The current URI for this page, for reference purposes) |
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