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2011 3rd International Conference on Environmental Science and Information Application Technology(ESIAT 2011)

作者： Wei Rao Nanchang Institute of Technology

In the digital transmission system, constant modulus algorithm(CMA) is a famous blind equalization to overcome the inter-symbol interference without the aid of training sequences. But for the non-constant modulus signals such as higher-order PAM signals, the CMA just achieve moderate steady-state mean square error(MSE) which may not be sufficient for the system to obtain adequate performance. By studying the amplitude relationship between different constellations of PAM signals, a new amplitude transformation method is proposed. According to such method the non-constant modulus signals can be changed to be constant modulus, and then using it to the CMA the zero steadystate MSE can be obtained. The efficiency of the proposed method is proved by computer simulations.

关键词： blind equalization amplitude transformation constant modulus algorithm PAM

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Amplitude Transformation-Based Blind Equalization Part II:Suitable for High-Order QAM Signals

Amplitude Transformation-Based Blind Equalization Part II:Su...

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2011 3rd International Conference on Environmental Science and Information Application Technology(ESIAT 2011)

作者： Wei Rao Nanchang Institute of Technology

In the digital transmission system, constant modulus algorithm(CMA) is a famous blind equalization to overcome the inter-symbol interference without the aid of training sequences. But for the non-constant modulus signals such as higher-order QAM signals, the CMA just achieve moderate steady-state mean square error(MSE) which may not be sufficient for the system to obtain adequate performance. By studying the amplitude relationship between different constellations of QAM signals, a new amplitude transformation method is proposed. According to such method the non-constant modulus signals can be changed to be constant modulus, and then using it to the CMA the zero steadystate MSE can be obtained. The efficiency of the proposed method is proved by computer simulations.

关键词： blind equalization amplitude transformation constant modulus algorithm QAM

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Semi-blind fast equalization of QAM channels using concurrent gradient-Newton CMA and soft decision-directed scheme

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INTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING 2010年第6期24卷 467-476页

作者： Chen, S. Univ Southampton Sch Elect & Comp Sci Southampton SO17 1BJ Hants England

This contribution considers semi-blind adaptive equalization for communication systems that employ high-throughput quadrature amplitude modulation signalling. A minimum number of training symbols, approximately equal to the dimension of the equalizer, are first utilized to provide a rough initial least-squares estimate of the equalizer's weight vector. A novel gradient-Newton concurrent constant modulus algorithm and soft decision-directed scheme are then applied to adapt the equalizer. The proposed semi-blind adaptive algorithm is capable of converging fast and accurately to the optimal minimum mean-square error equalization solution. Simulation results obtained demonstrate that the convergence speed of this semi-blind adaptive algorithm is close to that of the training-based recursive least-square algorithm. Copyright (C) 2009 John Wiley & Sons, Ltd.

关键词： channel equalization quadrature amplitude modulation semi-blind adaptive algorithm constant modulus algorithm soft decision-directed adaptation stochastic-gradient algorithm gradient-Newton algorithm minimum mean-square error

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Blind Multiuser Detection in Frequency Domain for MC-CDMA Systems Using Particle Swarm Optimization

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WIRELESS PERSONAL COMMUNICATIONS 2010年第3期54卷 447-466页

作者： Wen, Jyh-Hrong Chang, Chuan-Wang Hung, Ho-Lung Chien Kuo Technol Univ Dept Elect Engn Changhua Taiwan Natl Chung Cheng Univ Dept Elect Engn Chiayi Taiwan Tunghai Univ Dept Elect Engn Taichung 40704 Taiwan

In digital communication systems, the constant modulus algorithm (CMA) for blind multiuser detector has some disadvantage such as slow convergence speed and weight phase rotation. In this paper, we put forward a novel receiver, which combines CMA blind adaptive multiuser detection and particle swarm optimization (PSO) technique in frequency domain for multi-carrier direct sequence code division multiple access (MC DS-CDMA) systems. By this approach we present an adaptive multistage structure based on PSO technique. In this structure, the weights are obtained by PSO technique between the received signal and its estimate through a CMA. The resulting weights contain reliability information for the hard decisions made in the previous stage. The simulation results show that BER performance of the PSO-based CMA blind multiuser detector is superior to that of steepest decreasing constant modulus algorithm (SDCMA), linearly constrained constant modulus algorithm (LCCMA), CMA based multiuser detection and is worthy due to its significant detection performance to achieve desirable improvement in convergence speed and tractability.

关键词： Multi-carrier direct sequence code division multiple access constant modulus algorithm Particle swarm optimization Blind multiuser detector

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A Class of Channels Resulting in Ill-Convergence for CMA in Decision Feedback Equalizers

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IEEE TRANSACTIONS ON SIGNAL PROCESSING 2010年第11期58卷 5736-5743页

作者： Neves, Aline Panazio, Cristiano Univ Fed ABC Ctr Engn Modelagem & Ciencias Sociais Aplicadas BR-09210170 Sao Paulo Brazil Univ Sao Paulo Escola Politecn BR-05508900 Sao Paulo Brazil

This paper analyzes the convergence of the constant modulus algorithm (CMA) in a decision feedback equalizer using only a feedback filter. Several works had already observed that the CMA presented a better performance than decision directed algorithm in the adaptation of the decision feedback equalizer, but theoretical analysis always showed to be difficult specially due to the analytical difficulties presented by the constant modulus criterion. In this paper, we surmount such obstacle by using a recent result concerning the CM analysis, first obtained in a linear finite impulse response context with the objective of comparing its solutions to the ones obtained through the Wiener criterion. The theoretical analysis presented here confirms the robustness of the CMA when applied to the adaptation of the decision feedback equalizer and also defines a class of channels for which the algorithm will suffer from ill-convergence when initialized at the origin.

关键词： Blind equalization constant modulus algorithm decision directed algorithm decision feedback equalization ill-convergence

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Optimal Polarization Demultiplexing for Coherent Optical Communications Systems

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JOURNAL OF LIGHTWAVE TECHNOLOGY 2010年第7期28卷 1121-1134页

作者： Roudas, Ioannis Vgenis, Athanasios Petrou, constantinos S. Toumpakaris, Dimitris Hurley, Jason Sauer, Michel Downie, John Mauro, Yihong Raghavan, Srikanth Univ Patras Dept Elect & Comp Engn Rion 26500 Greece Corning Inc Corning NY 14831 USA

Spectrally-efficient optical communications systems employ polarization division multiplexing (PDM) as a practical solution, in order to double the capacity of a fiber link. Polarization demultiplexing can be performed electronically, using polarization-diversity coherent optical receivers. The primary goal of this paper is the optimal design, using the maximum-likelihood criterion, of polarization-diversity coherent optical receivers for polarization-multiplexed optical signals, in the absence of polarization mode dispersion (PMD). It is shown that simultaneous joint estimation of the symbols, over the two received states of polarization, yields optimal performance, in the absence of phase noise and intermediate frequency offset. In contrast, the commonly used zero-forcing polarization demultiplexer, followed by individual demodulation of the polarization-multiplexed tributaries, exhibits inferior performance, and becomes optimal only if the channel transfer matrix is unitary, e. g., in the absence of polarization dependent loss (PDL), and if the noise components at the polarization diversity branches have equal variances. In this special case, the zero-forcing polarization demultiplexer can be implemented by a 2 2 lattice adaptive filter, which is controlled by only two independent real parameters. These parameters can be computed recursively using the constant modulus algorithm (CMA). We evaluate, by simulation, the performance of the aforementioned zero-forcing polarization demultiplexer in coherent optical communication systems using PDM quadrature phase shift keying (QPSK) signals. We show that it is, by far, superior, in terms of convergence accuracy and speed, compared to conventional CMA-based polarization demultiplexers. Finally, we experimentally test the robustness of the proposed constrained CMA polarization demultiplexer to realistic imperfections of polarization-diversity coherent optical receivers. The PMD and PDL tolerance of the proposed demultiple

关键词： Coherent communications polarization demultiplexing constant modulus algorithm

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Adaptive Minimum Entropy Equalization algorithm

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IEEE COMMUNICATIONS LETTERS 2010年第10期14卷 966-968页

作者： Abrar, Shafayat Nandi, Asoke K. Dept Elect Engn & Elect Liverpool L69 3GJ Merseyside England

We employ minimum entropy deconvolution principle for blind equalization of complex digital signals. In essence, we maximize the output energy, constrain the equalizer output not to exceed certain level and obtain an adaptive solution capable of opening a closed-eye with the recovery of true energy of signal. We provide evidence of good performance in comparison to existing adaptive methods, like CMA and its variants, through simulations.

关键词： Adaptive equalizers blind equalization minimum entropy deconvolution constant modulus algorithm

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Semi-blind Adaptive Beamforming for High-throughput Quadrature Amplitude Modulation Systems

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International Journal of Automation and computing 2010年第4期7卷 565-570页

作者： Lajos Hanzo School of Electronics and Computer Science University of Southampton

A semi-blind adaptive beamforming scheme is proposed for wireless systems that employ high-throughput quadrature amplitude modulation signalling. A minimum number of training symbols, equal to the number of receiver antenna arrayts elements, are first utilised to provide a rough initial least squares estimate of the beamformer＇s weight vector. A concurrent constant modulus algorithm and soft decision-directed scheme is then applied to adapt the beamformer. This semi-blind adaptive beamforming scheme is capable of converging fast to the minimum mean-square-error beamforming solution, as demonstrated in our simulation study.

关键词： Beamforming minimum mean square error quadrature amplitude modulation semi-blind adaptive algorithm constant modulus algorithm soft decision-directed scheme.

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Blind Deconvolution of Natural Images using Segmentation Based CMA

Blind Deconvolution of Natural Images using Segmentation Bas...

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4th International Conference on Signal Processing and Communication Systems (ICSPCS)/12th International Symposium on DSP and Communication Systems (DSPCS)/9th Workshop on the Internet, Telecommunications and Signal Processing (WTSP)

作者： Samarasinghe, Pradeepa D. Kennedy, Rodney A. Australian Natl Univ Coll Eng & Comp Sci Sch Engn Canberra ACT 0200 Australia

ISBN: (纸本)9781424479078

In this paper, we analyze the applicability of constant modulus algorithm (CMA), one of the most widely used and tested blind equalization technique to blind image deconvolution. With a detailed mathematical analysis, we show that the strong correlation between the neighboring spatial locations found in natural images becomes a major constraint on the convergence of CMA. In order to overcome this constraint, we introduce a novel image pixel correlation model in relation with natural image statistics. Based on this model, a segmented blind image deconvolution through CMA is proposed. The robustness of the proposed algorithm with natural images is discussed in terms of efficiency and effectiveness.

关键词： Equalization blind image deconvolution constant modulus algorithm image correlation stationary points kurtosis natural image statistics whitening Meso-Kurtic

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Invasive Weed Optimization Method Based Blind Multiuser Detection for MC-CDMA Interference Suppression over Multipath Fading Channel

Invasive Weed Optimization Method Based Blind Multiuser Dete...

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IEEE International Conference on Systems, Man and Cybernetics

作者： Hung, Ho-Lung Chao, Chien-Chi Cheng, Chia-Hsin Huang, Yung-Fa Department of Electrical Engineering Chien-Kuo Technology University Changhua County Taiwan Department of Electrical Engineering National Formosa University Yunlin County Taiwan Department of Information and Communication Engineering Chaoyang University of Technology Township Taichung County Taiwan

ISBN: (纸本)9781424465880

The paper presents a novel constrained constant modulus (CMA) approach for the blind suppression of multiuser interference in multi-carrier code division multiple access (MC-CDMA) systems. In this paper, we put forward a novel receiver, which combines CMA blind adaptive multiuser detection with Invasive weed optimization (IWO) for MC-CDMA interference suppression over multipath fading channel. To work around potentially computational intractability, the proposed scheme exploits heuristics in consideration of both global and local exploration the step size of the CMA. The computer simulation results show that compared with the various CMA developed previously, the proposed IWO method obtains the most desirable bit error rate performance with low computational complexity.

关键词： Invasive weed optimization constant modulus algorithm Blind Multiuser Detection Multi-carrier Code Division Multiple Access component formatting

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