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Performance of multi-relay coded cooperative diversity in asynchronous code-division multiple-access over fading channels

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IET COMMUNICATIONS 2011年第5期5卷 683-692页

作者： Eid, A. Hamouda, W. Dayoub, I. Concordia Univ Dept Elect & Comp Engn Montreal PQ H3G 1M8 Canada Univ Valenciennes IEMN DOAE F-59313 Le Mt Houy Valenciennes France

In this study, multi-relay decode-and forward (DAF) cooperative networks employing convolutional coding are studied for asynchronous direct-sequence code-division multiple-access (DS-CDMA) systems over frequency-selective slow fading channels. The authors show that the full benefits of coded cooperative diversity cannot be achieved if no multi-user interference suppression is employed at the cooperative end. The authors consider two scenarios;perfect and imperfect inter-user channels. In that, the bit-error-rate performance of the cooperative system is investigated for an uplink transmission where a decorrelator detector is used at both the relay and base station receivers. Both simulation and analytical results are presented to demonstrate the diversity gains of the convolutionally coded cooperative network.

关键词： Direct-sequence code-division multiple access relay Code division multiple access convolutional coding Asynchronous Fading channels

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Switchable-rate quasi-cyclic low-density parity-check codes for internet protocol over high-frequency systems

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IET COMMUNICATIONS 2011年第4期5卷 505-511页

作者： Heravi, B. M. Kariyawasam, S. R. Vongas, G. Honary, B. Univ Lancaster Dept Commun Syst Lancaster LA1 4WA England Def Sci & Technol Lab Fareham PO17 6AD Hants England

A switchable-rate quasi-cyclic low-density parity-check (QC-LDPC) coding scheme has been proposed for integration within the legacy and next-generation high-frequency internet protocol (HF-IP) systems. The novelty in this work is based upon using a class of switchable-rate short-block-length (<1500 bits) QC-LDPC codes for the HF fading channel modelled by the ITU-R F. 1487 for all latitudes and conditions. The QC-LDPC codes are constructed using a switchable-rate approach based on finite fields which provides the ability to switch among three rates to combat varying channel conditions using a single encoder/decoder structure. The proposed structure enables low-complexity implementation of the low-density parity-check encoder/decoder for use within the existing data link (DL) layer of the standardisation agreement (STANAG) 5066 profile. The performance of the proposed scheme has been evaluated comprehensively for all the HF channel conditions and latitudes. A comparison between the proposed and the current coding scheme in HF-IP systems (based on convolutional coding) shows an improvement in error-rate performance.

关键词： encoder structure ITU-R F.1487 parity check codes Protocols switchable-rate quasi-cyclic low-density parity-check codes convolutional codes Codes fading channels encoding cyclic codes IP networks Computer communications decoding high-frequency Internet protocol system finite field high-frequency fading channel Other computer networks decoder structure Internet protocols standardisation agreement 5066 profile Radio links and equipment convolutional coding

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Performance of Rate 1/2 convolutional Encoder with Adaptive Feedback-Controlled on Hyperchaotic-Chaotic States

Performance of Rate 1/2 Convolutional Encoder with Adaptive ...

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Conference of the Complex Adaptive Systems on Responding to Continuous Global Change in Systems Needs

作者： Arasteh, Davoud So Univ & A&M Coll Dept Elect Engn Technol Baton Rouge LA USA

In this paper we have studied the performance of rate. 1/2 convolutional encoders with adaptive states developed in chaotic and hyperchaotic regions. These states are generated by varying the control parameters in a feedback. controlled system. Several sets of closed. loop simulations are performed to demonstrate the benefit of information. based chaos system. In particular, it is demonstrated that two varieties of an information. based systems provide improved performance over all the encoder choices when hyperchaos states are utilized. Special attention was paid to the algorithmic complexity of the systems for an entire class of rate. 1/2 encoders. The decoder is able to recover the encrypted data and is able to reasonably estimate the bit error rate for different signal strengths under a noisy AWGN channel. This indicates that the encoder can update the information map in real time to compensate for changing data for both chaotic and hyperchaotic states. This is the evidence that occasional changes in the data stream can be handled by the decoder in a real time application. Numerical evidence indicates algorithmic complexity associated with the hyperchaotic. encrypted and convolutionally-encoded data, provide better security along with the increase in the error correcting capacity of the decoder. (C) 2010 Published by Elsevier B.V.

关键词： Chaotic encryption convolutional coding algorithmic complexity Feedback-Controlled Hyperchaotic System

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Performance of Only-Phase Equalization in OFDM with Soft Decoding in Indoor Environment

Performance of Only-Phase Equalization in OFDM with Soft Dec...

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IEEE GLOBECOM Workshops (GC Wkshps)

作者： Obiedat, Esam A. Asir, Bassam R. Khalaf, Loay D. Jordan Univ Sci & Technol Irbid Jordan Univ Jordan Amman Jordan

ISBN: (纸本)9781467300407

In this paper, we investigate the performance of frequency domain equalization in conjunction with Soft Decision (SD) Viterbi decoding in the Orthogonal Frequency Division Multiplexing (OFDM) systems. Specifically, we compare the performance of two frequency domain equalization methods, one using complete phase and magnitude equalization of complex Quadrature Amplitude Modulated (QAM) symbols, while the other using only-phase equalization, or constellation rotation. Our investigation shows that the OFDM system using only-phase equalization in conjunction with soft decision decoding for convolutional codes has a better performance of about 2.5-4 dB in multipath environment than the system implementing complete equalization with the same soft decision decoding at 10(-4) BER level.

关键词： phase equalization Equalization soft-decision decoding Frequency domain equalization indoor environment convolutional coding

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Performance Analysis of Dispersed Spectrum Cognitive Radio Systems

Performance Analysis of Dispersed Spectrum Cognitive Radio S...

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作者： Mohammad, Muneer Texas A&M University

Dispersed spectrum cognitive radio systems represent a promising approach to exploit the utilization of spectral resources to full extent. Therefore, the performance analysis of such systems is conducted in this research. The Average symbol error probability of dispersed spectrum cognitive radio systems is derived for two cases: where each channel realization experiences independent and dependent Nakagami-m fading, respectively. In addition, the derivation is extended to include the effects of modulation type and order by considering M-PSK and M-QAM modulation schemes. We then study the impacts of topology on the effective transport capacity performance of ad hoc dispersed spectrum cognitive radio systems where the nodes assume 3- dimensional (3D) configurations. We derive the effective transport capacity considering a cubic grid distribution. In addition, numerical results are presented to demonstrate the effects of topology on the effective transport capacity of ad hoc dispersed cognitive radio systems.

关键词： Dispersed Spectrum Cognitive Radio Frequency Diversity M-QAM M-PSK convolutional coding Adhoc Effective transport capacity Book Thesis

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Performance of Rate ½ convolutional Encoder with Adaptive Feedback-Controlled on Hyperchaotic-Chaotic States

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Procedia Computer Science 2011年 6卷 130-135页

作者： Davoud Arasteh Department of Electronic Engineering Technology Southern University and A & M College Baton Rouge Louisiana USA

In this paper we have studied the performance of rate-1/2 convolutional encoders with adaptive states developed in chaotic and hyperchaotic regions. These states are generated by varying the control parameters in a feedback-controlled system. Several sets of closed-loop simulations are performed to demonstrate the benefit of information-based chaos system. In particular, it is demonstrated that two varieties of an information-based systems provide improved performance over all the encoder choices when hyperchaos states are utilized. Special attention was paid to the algorithmic complexity of the systems for an entire class of rate-1/2 encoders. The decoder is able to recover the encrypted data and is able to reasonably estimate the bit error rate for different signal strengths under a noisy AWGN channel. This indicates that the encoder can update the information map in real time to compensate for changing data for both chaotic and hyperchaotic states. This is the evidence that occasional changes in the data stream can be handled by the decoder in a real time application. Numerical evidence indicates algorithmic complexity associated with the hyperchaotic-encrypted and convolutionally-encoded data, provide better security along with the increase in the error correcting capacity of the decoder.

关键词： Chaotic encryption convolutional coding algorithmic complexity Feedback-Controlled Hyperchaotic System

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Effective Cooperative ARQ Protocols with the Opportunistic Selective AF Relaying: The Perspectives of Outage versus Packet Error Probabilities

Effective Cooperative ARQ Protocols with the Opportunistic S...

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IEEE International Conference on Communications Workshops

作者： Chun-Kai Tseng Sau-Hsuan Wu Institute of Communications Engineering National Chiao Tung University

ISBN: (纸本)9781612842325

In contrast to the outage analysis, the packet error rates (PERs) of two types of cooperative automatic retransmission request (ARQ) protocols with opportunistic selective amplified-and-forward (OSAF) relaying are investigated from the perspective of the maximum likelihood sequence detection (MLSD). The results show that PERs with the threshold requirements derived from the outage analysis cannot benefit from the diversity via opportunistic retransmissions. Based on the PER analysis, effective threshold setting methods for the two types of ARQs are developed to avoid the diversity losses during ARQs, and verified via simulations using convolutional codes. In contrast to the ARQ protocols with the typical opportunistic AF relaying, the new threshold setting methods allow the OSAF ARQ protocols to provide for practical systems a spatial and temporal diversity comparable to what predicts with the outage analysis.

关键词： Automatic repeat request Perspective maximum likelihood sequence detection relaying set method protocols convolutional coding Packet

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Performance-complexity tradeoff of convolutional codes for broadband fixed wireless access systems

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IET COMMUNICATIONS 2010年第4期4卷 419-427页

作者： Chatzigeorgiou, I. Demosthenous, A. Rodrigues, M. R. D. Wassell, I. J. Univ Cambridge Comp Lab Digital Technol Grp Cambridge CB3 0FD England UCL Dept Elect & Elect Engn London WC1E 7JE England Univ Porto Dept Comp Sci P-4169007 Oporto Portugal Univ Porto Inst Telecomunicacoes P-4169007 Oporto Portugal

In this study, the authors investigate the performance-complexity tradeoff of convolutional codes for broadband fixed wireless access systems by considering the effects of quantisation and path metric memory in practical Viterbi decoding implementations. They show that in systems with limited antenna diversity, low-memory codes achieve a better error-rate performance compared to that of high-memory codes. Only in systems with considerable antenna diversity, can the performance of a convolutional code be improved by increasing its memory size. Nevertheless, the authors demonstrate that the coding advantage offered by the high-memory codes is not large enough to justify the significant increase in implementation complexity. In particular, memory-2 convolutional codes achieve a coding gain of up to 1.2 dB over their memory-8 counterparts in single-input single-output fixed wireless access systems. The situation is reversed when multiple antennas are used, but the decoder of memory-8 codes occupies at least 130 times more silicon area than that of memory-2 codes.

关键词： tradeoffs Quantization broadband spatial diversity multiple antenna convolutional coding Codes coding gain wireless diversity reception

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Adaptation in convolutionally Coded MIMO-OFDM Wireless Systems Through Supervised Learning and SNR Ordering

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2010年第1期59卷 114-126页

作者： Daniels, Robert C. Caramanis, Constantine M. Heath, Robert W., Jr. Univ Texas Austin Dept Elect & Comp Engn Wireless Networking & Commun Grp Austin TX 78712 USA

Multiple-input-multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) wireless systems use link adaptation to exploit the dynamic nature of wireless environments. Link adaptation maximizes throughput while maintaining target reliability by adaptively selecting the modulation order and coding rate. Link adaptation is extremely challenging, however, due to the difficulty in predicting error rates in OFDM with binary convolutional codes, bit interleaving, MIMO processing, and real channel impairments. This paper proposes a new machine-learning framework that exploits past observations of the error rate and the associated channel-state information to predict the best modulation order and coding rate for new realizations of the channel state without modeling the input-output relationship of the wireless transceiver. Our approach is enabled through our new error-rate expression that is only parameterized by postprocessing signal-to-noise ratios (SNRs), ordered over subcarriers and spatial streams. Using ordered SNRs, we propose a low-dimensional feature set that enables machine learning to increase the accuracy of link adaptation. An IEEE 802.11n simulation study validates the application of this machine-learning framework in real channels and demonstrates the improved performance of SNR ordering as it compares with competing link-quality metrics.

关键词： Adaptive modulation and coding (AMC) convolutional coding IEEE 802.11n machine learning multiple-input multiple-output orthogonal frequency-division multiplexing (MIMO-OFDM) signal-to-noise ratio (SNR) ordering supervised learning

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Serial Turbo Codes with a Low Complexity of Reception Algorithms

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JOURNAL OF COMMUNICATIONS TECHNOLOGY AND ELECTRONICS 2010年第10期55卷 1115-1121页

作者： Nazarov, L. E. Golovkin, I. V.

The results of investigating the developed efficient procedures of iterative reception of serial turbo codes based on a simple convolutional code with two possible states of a code trellis are presented.

关键词： reception Serial Publications BISTABILITY convolutional coding turbo codes

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