Improved Statistical Interference Suppression Techniques in Single and Multi-rate Direct Sequence Spread Spectrum Code Division Multiple Access Systems

Improved Statistical Interference Suppression Techniques in Single and Multi-rate Direct Sequence Spread Spectrum Code Division Multiple Access Systems

Bibliographic Details
Main Author: Wang, Beibei
Language:English
Published: Ohio University / OhioLINK 2007
Subjects:
DS-CDMA
Interference suppression
Multi-user detectors
Parallel interference cancellation
Statistical PIC
Generalized soft limiter
Online Access:http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1173119961
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spelling ndltd-OhioLink-oai-etd.ohiolink.edu-ohiou11731199612021-08-03T05:43:56Z Improved Statistical Interference Suppression Techniques in Single and Multi-rate Direct Sequence Spread Spectrum Code Division Multiple Access Systems Wang, Beibei DS-CDMA Interference suppression Multi-user detectors Parallel interference cancellation Statistical PIC Generalized soft limiter <p>We first present a statistical parallel interference cancellation (STPIC) technique. Here we propose two different methods: instantaneous STPIC (ISTPIC), in which IC is performed only on the bits whose absolute log likelihood ratio (LLR) is below a pre-selected threshold, and block STPIC (BSTPIC), in which IC is performed only on the blocks whose average signal-to-interference-plus-noise-ratio (SINR) is below a pre-selected threshold. Both LLR and SINR statistics reduce to quantities simple to obtain. It has been shown that both ISTPIC and BSTPIC can achieve performance similar to or better than conventional full PIC (FPIC), but with significantly reduced computational complexity. It is also shown that the proposed ISTPIC has larger performance gain than conventional FPIC in higher loading case where efficient interference cancellation techniques are mostly needed. We also propose a new generalized soft limiter (GSL) that combines the advantage of hard decision and partial soft decision. In GSL, hard decisions are made on “reliable” signals with absolute amplitudes larger than a threshold, whereas partial soft decisions are made on “unreliable” signals with absolute amplitudes less than the threshold. We have shown that PIC using the proposed GSL has performance similar to that using hyperbolic tangent decision, which has been shown to be the optimal decision in the single user case with Gaussian interference and noise, but with easier implementation. Furthermore, we propose new techniques that combine the STPIC with partial PIC or other improved decision techniques, which have shown to be capable of achieving performance similar to or better than original techniques with reduced computational complexity. We also evaluate and compare the performance of different PIC techniques in the presence of imperfect channel estimation and near-far effects. Performance analysis and comparison of different PIC techniques have also been done in multi-rate DS-CDMA systems with different schemes: variable spreading gain, multi-code, and variable chip rate. Finally, we review narrowband interference (NBI) suppression techniques and investigate the performance of a decision feedback scheme aided by the proposed GSL-PIC in the presence of NBI.</p> 2007-04-20 English text Ohio University / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1173119961 http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1173119961 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.
collection NDLTD
language English
sources NDLTD
topic DS-CDMA
Interference suppression
Multi-user detectors
Parallel interference cancellation
Statistical PIC
Generalized soft limiter
spellingShingle DS-CDMA
Interference suppression
Multi-user detectors
Parallel interference cancellation
Statistical PIC
Generalized soft limiter
Wang, Beibei
Improved Statistical Interference Suppression Techniques in Single and Multi-rate Direct Sequence Spread Spectrum Code Division Multiple Access Systems
author Wang, Beibei
author_facet Wang, Beibei
author_sort Wang, Beibei
title Improved Statistical Interference Suppression Techniques in Single and Multi-rate Direct Sequence Spread Spectrum Code Division Multiple Access Systems
title_short Improved Statistical Interference Suppression Techniques in Single and Multi-rate Direct Sequence Spread Spectrum Code Division Multiple Access Systems
title_full Improved Statistical Interference Suppression Techniques in Single and Multi-rate Direct Sequence Spread Spectrum Code Division Multiple Access Systems
title_fullStr Improved Statistical Interference Suppression Techniques in Single and Multi-rate Direct Sequence Spread Spectrum Code Division Multiple Access Systems
title_full_unstemmed Improved Statistical Interference Suppression Techniques in Single and Multi-rate Direct Sequence Spread Spectrum Code Division Multiple Access Systems
title_sort improved statistical interference suppression techniques in single and multi-rate direct sequence spread spectrum code division multiple access systems
publisher Ohio University / OhioLINK
publishDate 2007
url http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1173119961
work_keys_str_mv AT wangbeibei improvedstatisticalinterferencesuppressiontechniquesinsingleandmultiratedirectsequencespreadspectrumcodedivisionmultipleaccesssystems
_version_ 1719424284857729024

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