Improved Statistical Interference Suppression Techniques in Single and Multi-rate Direct Sequence Spread Spectrum Code Division Multiple Access Systems PDF Download
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Author: Beibei Wang
Publisher:
ISBN: 9789072151094
Category :
Languages : en
Pages : 280
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Book Description
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.
Author: Beibei Wang
Publisher:
ISBN: 9789072151094
Category :
Languages : en
Pages : 280
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Book Description
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.
Author: Matthew G. Glen
Publisher:
ISBN: 9781423519928
Category : Coding theory
Languages : en
Pages : 78
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Book Description
This research characterizes MAI effects on DS/SSMA system performance through simulation in Matlab , and explores the impact of multiple access code selection, chip waveform shaping, and multiple access code length on BER for both synchronous and asynchronous multiple access networks. In addition, the simulated DS/SSMA model permits rapid research into the effects of additional factors on BER. Prior to experimental testing, model validation is conducted through single user trials and by comparison with existing research for similar system designs. For synchronous and asynchronous networks, Gold coding improves BER by 7.5 and 4.0 dB, respectively, relative to aperiodic random spreading codes. Synchronous network results show that chip waveform shaping provides no significant BER improvement for the Blackman or Lanczos shapes. However, asynchronous network results show a potential BER improvement for Blackman and Lanczos shapes. Increasing code length from 31 to 511 resulted in a 7.5 dB BER improvement. Collectively, these results directly relate changes in BER to waveform cross-correlation statistics.
Author: Mingxi Fan
Publisher:
ISBN:
Category :
Languages : en
Pages : 184
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Book Description
In this thesis we investigate efficient modulation and detection techniques for the uplink (i.e. transmission from mobile to base station) of a DS-CDMA network. Specifically, the thesis contains three parts. In the first part, we focus on the mobile transmitter. In particular, we evaluate and compare the spectral efficiency of two promising variable rate DS-CDMA transmission techniques, multicode (MCD) and variable-spreading-gain (VSG), under the presence of multiple-access (user-to-user) interferences (MAI) and multipath interferences. The uniqueness of our study is that in bit-error-rate evaluation, instead of approximating the interference as Gaussian noise (which has been done in most of the previous studies), we incorporate both power and distribution of interferences into consideration. We show where the Gaussian assumption may give misleading answers and how our results in these cases are different from those obtained in the past. In part two and three of the thesis, we focus on the base station receiver. Specifically, we present effective joint detection techniques that have good performance-complexity tradeoff. Part two of the thesis introduces a class of novel multistage parallel interference cancellation algorithms based on stage-by-stage minimum mean-squared error (MMSE) optimization. We show that this scheme is capable of achieving significantly better performance than other algorithms with similar complexity. Part three of the thesis presents a low-complexity dual-mode multiuser detector that dynamically switches its detection mode between the matched-filter receiver and the decorrelator. We show that this detector is capable of achieving the performance of a decorrelator but with significant savings in processing power and complexity.
Author: John Doherty
Publisher:
ISBN:
Category :
Languages : en
Pages : 56
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Book Description
This report presents research results focused on the mitigation of both narrowband and multiple access interference in direct sequence spread spectrum communication systems. Both linear and nonlinear adaptive algorithmic approaches are developed and reported. Specific attention has been paid to making the algorithmic practicable. In addition to the algorithmic development, a software simulation for a code division multiple access system is developed using a commercially available programming environment.
Author:
Publisher:
ISBN:
Category : Electrical engineering
Languages : en
Pages : 2240
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Book Description
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 80
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Book Description
This report presents a comprehensive summary of a number of methods used in filtering narrowband jammers and interference out of direct sequence spread spectrum communication systems. The basic concept is presented first followed by a discussion of several analog techniques for interference suppression. Most of the emphasis is on digital adaptive methods, which rely on adaptive filtering algorithms. Many of these algorithms are highlighted. This is followed by a discussion on the research which has been conducted in digital excision over the past several years. Two cases based on the author's work are also presented. The first details the performance one can expect from the recursive least squares algorithm when the interferer is a stable tone. An analytical model, which predicts the bit error rate performance for the recursive algorithm under certain conditions, is derived. This model is compared to results obtained from computer simulation, the tracking and filtering capabilities of hte block and recursive least square algorithms when the interference is of the FM-type, i.e., a swept tone having a bandwidth which is approximately 20% of the chip rate. (Author).
Author: Hossein Bidgoli
Publisher: John Wiley & Sons
ISBN: 0471689971
Category : Business & Economics
Languages : en
Pages : 979
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Book Description
The Internet Encyclopedia in a 3-volume reference work on the internet as a business tool, IT platform, and communications and commerce medium.
Author: Hossein Bidgoli
Publisher: John Wiley and Sons
ISBN: 0470051191
Category : Business & Economics
Languages : en
Pages : 1122
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Book Description
The Handbook of Information Security is a definitive 3-volume handbook that offers coverage of both established and cutting-edge theories and developments on information and computer security. The text contains 180 articles from over 200 leading experts, providing the benchmark resource for information security, network security, information privacy, and information warfare.
Author: Wan Shi Chen
Publisher:
ISBN:
Category :
Languages : en
Pages : 114
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Author: Katherine Jauregui Lovette
Publisher:
ISBN:
Category :
Languages : en
Pages : 108
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Book Description
