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Performance improvement of bandwidth-limited coherent OCDMA system

PHOTONIC NETWORK COMMUNICATIONS 2008年第2期16卷 149-154页

作者： Chen, Xiaogang Chen, Deyi Wang, Zonglong China Three Gorges Univ Coll Sci Yichang 443002 Hubei Peoples R China

The performance of an optical code division multiplexing access (OCDMA) system employing the differential phase shift keying (DPSK) data format and turbo code is investigated and simulated. A bandwidth-limited coherent time spreading (TS) OCDMA system is considered. Theoretical results show that performance degradation due to bandwidth limitation could be effectively restrained by the application of the DPSK data format in a coherent OCDMA system, and further performance improvement could be achieved by incorporating turbo coding into the OCDMA system.

关键词： optical code division multiplexing access (OCDMA) bandwidth limitation differential phase shift keying (DPSK) turbo coding

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Multimedia Transmission Over Cognitive Radio Channels Under Sensing Uncertainty

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IEEE TRANSACTIONS ON SIGNAL PROCESSING 2016年第3期64卷 726-741页

作者： Ye, Chuang Ozcan, Gozde Gursoy, M. Cenk Velipasalar, Senem Syracuse Univ Dept Elect Engn & Comp Sci Syracuse NY 13244 USA

This paper studies the performance of hierarchical modulation-based multimedia transmission in cognitive radio (CR) systems with imperfect channel sensing results under constraints on both transmit and interference power levels. Unequal error protection (UEP) of data transmission using hierarchical quadrature amplitude modulation (HQAM) is considered in which high priority (HP) data is protected more than low priority (LP) data. In this setting, closed-form bit error rate (BER) expressions for HP data and LP data are derived in Nakagami-fading channels in the presence of sensing errors. Subsequently, the optimal power control that minimizes weighted sum of average BERs of HP bits and LP bits or its upper bound subject to peak/average transmit power and average interference power constraints is derived and a low-complexity power control algorithm is proposed. Power levels are determined in three different scenarios, depending on the availability of perfect channel side information (CSI) of the transmission and interference links, statistical CSI of both links, or perfect CSI of the transmission link and imperfect CSI of the interference link. The impact of imperfect channel sensing decisions on the error rate performance of cognitive transmissions is also evaluated. In addition, tradeoffs between the number of retransmissions, the severity of fading, and peak signal-to-noise ratio (PSNR) quality are analyzed numerically. Moreover, performance comparisons of multimedia transmission with conventional quadrature amplitude modulation (QAM) and HQAM, and the proposed power control strategies are carried out in terms of the received data quality and number of retransmissions.

关键词： Bit error probability cognitive radio H.264/MPEG-4 HQAM imperfect channel sensing JPEG2000 power control PSNR turbo coding unequal error protection

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Reduced-Complexity Iterative-Detection-Aided Generalized Space-Time Shift Keying

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2012年第8期61卷 3656-3664页

作者： Sugiura, Shinya Xu, Chao Ng, Soon Xin Hanzo, Lajos Toyota Cent Res & Dev Labs Inc Nagakute Aichi 4801192 Japan Univ Southampton Sch Elect & Comp Sci Southampton SO17 1BJ Hants England

A novel reduced-complexity soft decision (SoD)-aided detector is proposed for the recent concept of space-time shift keying (STSK), where the detector's achievable performance is capable of closely approaching that of the optimal maximum a posteriori (MAP) detector. More specifically, we exploit a hybrid combination of the modified matched filtering concept and of reduced-complexity exhaustive search for the sake of reducing the MAP detector's decoding complexity. Furthermore, we extended this detector to support the class of generalized STSK (GSTSK) scheme that subsumes diverse multiple-input-multiple-output (MIMO) arrangements. The proposed reduced-complexity SoD-aided GSTSK detector also attains significantly lower complexity than the MAP detector while imposing only marginal performance degradation, which is in the range of 1-2 dB. As an optional means of further reducing complexity, the Markov Chain Monte Carlo (MCMC) algorithm is invoked for the proposed GSTSK detector. Our EXtrinsic Information Transfer (EXIT) chart analysis reveals that the proposed STSK detector is capable of closely approaching the optimal performance, whereas the GSTSK detector advocated exhibits a modest performance gap with respect to the max-log MAP detector.

关键词： EXtrinsic Information Transfer (EXIT) chart Markov chain Monte Carlo (MCMC) multiple-antenna array soft decision space-time shift keying (STSK) turbo coding

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MIMO-OFDM-based DVB-H systems: A hardware design for a PAPR reduction technique

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IEEE TRANSACTIONS ON CONSUMER ELECTRONICS 2006年第4期52卷 1201-1206页

作者： Al-Akaidi, Marwan M. Daoud, Omar R. Gow, John A. De Montfort Univ Sch Engn & Technol Wireless & Multimediai Res Grp Leicester LE1 9BH Leics England

Digital Video Broadcasting Handheld (DVB-H) is the technology driving mobile TV, which uses Orthogonal Frequency Division Multiplexing (OFDM) systems with Multiple-Input Multiple-Output technology (MIMO). These mobile communication systems have a promising future of supporting high data rate transmissions for both video and data. However, since the OFDM systems are sensitive to the peak-to-average power ratio (PAPR) problem, this work proposes a new technique (Novel Technique to Reduce the PAPR based on turbo coding (NTRPT)), based on the turbo encoding technology, to reduce the PAPR effects for MIMO-OFDM-based DVB-H systems. This technique has been implemented and validated in different types of modulation and hardware. It can support offers better results in reducing the coding techniques, and of PAPR than the conventional techniques currently proposed for this purpose, such as the clipping technique and the Partial Transmit Sequence (PTS) technique, presented here using computer simulations(1).

关键词： MIMO OFDM PAPR turbo coding

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MIMO-Aided Near-Capacity turbo Transceivers: Taxonomy and Performance versus Complexity

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IEEE COMMUNICATIONS SURVEYS AND TUTORIALS 2012年第2期14卷 421-442页

作者： Sugiura, Shinya Chen, Sheng Hanzo, Lajos Toyota Cent Res & Dev Labs Inc Nagakute Aichi 4801192 Japan Univ Southampton Sch Elect & Comp Sci Southampton SO17 1BJ Hants England

In this treatise, we firstly review the associated Multiple-Input Multiple-Output (MIMO) system theory and review the family of hard-decision and soft-decision based detection algorithms in the context of Spatial Division Multiplexing (SDM) systems. Our discussions culminate in the introduction of a range of powerful novel MIMO detectors, such as for example Markov Chain assisted Minimum Bit-Error Rate (MC-MBER) detectors, which are capable of reliably operating in the challenging high-importance rank-deficient scenarios, where there are more transmitters than receivers and hence the resultant channel-matrix becomes non-invertible. As a result, conventional detectors would exhibit a high residual error floor. We then invoke the Soft-Input Soft-Output (SISO) MIMO detectors for creating turbo-detected two-or three-stage concatenated SDM schemes and investigate their attainable performance in the light of their computational complexity. Finally, we introduce the powerful design tools of EXtrinsic Information Transfer (EXIT)-charts and characterize the achievable performance of the diverse near-capacity SISO detectors with the aid of EXIT charts.

关键词： EXIT chart iterative detection MIMO multiuser detection turbo coding wireless communication

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An iterative receiver for turbo-coded pilot-assisted modulation in fading channels

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IEEE COMMUNICATIONS LETTERS 2001年第4期5卷 145-147页

作者： Li, QH Georghiades, CN Wang, XD Texas A&M Univ Dept Elect Engn College Stn TX 77843 USA

In this letter, we introduce an iterative joint channel and data estimation receiver that exploits both the power of pilot-symbol assisted modulation (PSAM) and turbo coding for fading channels. The key innovation is a low-complexity soft channel estimator which divides a processing block into overlapped cells and performs maximum a posteriori (MAP) sequence estimation and MMSE filtering based on the received signal and extrinsic information delivered by the soft channel decoder. Simulation results show that for turbo-coded PSAM systems under time-variant fading the proposed receiver offers significant performance gains over a noniterative receiver and two other cancellation schemes.

关键词： channel estimation data detection iterative decoding MMSE filtering turbo coding

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Joint Frequency Selective Channel Estimation and turbo Decoding in Space Time Systems

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2008年第12期7卷 4813-4817页

作者： Ronen, Sefi (Yosef) Duman, Tolga M. Arizona State Univ Dept Elect Engn Tempe AZ 85287 USA

A non-coherent multiple input multiple output (MIMO) coded communication system over a frequency selective (FS) block fading channel is considered. A theoretical limit for the channel estimation error is established via a closed form derivation of the modified Cramer-Rao bound (MCRB) (more precisely, a tight lower bound to it) for the underlying channel model and equi-power signal constellations. Furthermore, it is shown that, for a practical coded MIMO system that employs turbo coding and an appropriate iterative decoding, the resulting mean squared error (MSE) in channel estimation approaches very closely to the derived theoretical limit.

关键词： Space-time coding frequency-selective fading Rayleigh fading channel estimation Cramer-Rao bound modified Cramer-Rao bound turbo coding

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Capacity approaching codes design and implementation

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IEE PROCEEDINGS-COMMUNICATIONS 2005年第6期152卷 1060-1061页

作者： Farrell, PG Honary, B Univ Lancaster Dept Commun Syst Lancaster LA1 4YW England

No abstract available

关键词： Gallager low-density parity-check codes turbo codes codes implementation communications services codes design capacity approaching codes error-control systems Codes parity check codes error correction codes LDPQ codes General electrical engineering topics turbo coding

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On the better protection of short-frame turbo codes

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IEEE TRANSACTIONS ON COMMUNICATIONS 2004年第9期52卷 1435-1439页

作者： Chi, ZP Wang, ZF Parhi, KK Marvell Semicond Inc Sunnyvale CA 94089 USA Oregon State Univ Dept Elect Engn Corvallis OR 97331 USA Univ Minnesota Dept Elect & Comp Engn Minneapolis MN 55455 USA

Protecting short data frames by turbo coding is a challenging task because of the small interleaver size and the need for transmission efficiency. In this letter, turbo-decoding-metrics aided short cyclic redundancy check codes are applied to novel tailbiting encoded trellis codes with a twofold purpose: to stop the iterative decoding processes to achieve low-power design and to reduce fractional coding-rate loss. Significant coding gains can be achieved by actually increasing the transmission rate with a negligible increase in power consumption. Performance improvement is demonstrated over additive white Gaussian noise channels. The savings is up to 21.4% for the transmission throughput and 21.5% for the energy consumption of the turbo decoder when frame size 49 is used.

关键词： cyclic redundancy check (CRC) error detection low-power turbo decoder stopping criterion tailbiting trellis termination turbo coding

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Effect of PAPR Reduction Techniques on the Performance of MB-OFDM UWB in Wireless Communications

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IETE JOURNAL OF RESEARCH 2010年第1期56卷 62-68页

作者： Murthy, T. S. N. Rao, K. Deergha Osmania Univ Res & Training Unit Nav Elect Hyderabad 500007 Andhra Pradesh India

Multiband orthogonal frequency division multiplexing (MB-OFDM) is an efficient approach for ultra-wideband (UWB) wireless communication applications. One major difficulty of MB-OFDM UWB signal is its large peak-to-average power Ratio (PAPR). The high PAPR limits its capacity due to the distortion caused by the nonlinear characteristics of both the analog-to-digital converter (ADC) and high-power amplifier (HPA). Hence, it is necessary to reduce the PAPR of MB-OFDM UWB signals. Several techniques have been reported in the literature for PAPR reduction in OFDM. These techniques can also be extended for PAPR reduction in MB-OFDM UWB signals. However, comparative performance evaluation of these techniques for PAPR reduction in MB-OFDM UWB signals is lacking in the literature. Hence, in this paper, four techniques, namely, filtering after clipping, turbo coding of clipped signals, tunable predistorter, and active constellation extension are extended for PAPR reduction of MB-OFDM UWB signals and their performance is evaluated and compared through computer simulations. In this evaluation, the bit-error rate (BER) is used as the performance measure.

关键词： Active constellation extension MB-OFDM UWB Peak-to-average power ratio Predistorter turbo coding

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