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Code-constrained blind detection of CDMA signals in multipath channels

IEEE SIGNAL PROCESSING LETTERS 2002年第12期9卷 389-392页

作者： Xu, ZY Liu, P Univ Calif Riverside Dept Elect Engn Riverside CA 92521 USA

In this letter, a constant-modulus-algorithm-based multiuser detection scheme is proposed for a communication system under multipath propagation. To mitigate channel distortion and multiuser interference, we integrate multiple constraints into the optimization criterion. According to our analysis, the ability of the detector to remove all interference is ensured in the absence of noise when the constraints are properly preselected. However, in the presence of noise, the constraints highly affect the performance of the receiver. In order to optimally combine signals from different paths to achieve performance gains, those constraints can also be treated as variables and jointly optimized with the receiver, as verified by numerical examples.

关键词： constant modulus algorithm constrained optimization multiuser detection

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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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Variable Step-Size Multi-modulus algorithm with Quantized Error Method

Variable Step-Size Multi-Modulus Algorithm with Quantized Er...

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International Conference on Graphic and Image Processing (ICGIP)

作者： Zhou, Jun Liu, Peng Cao, Suzhi Zhang, Shancong Chinese Acad Sci Grad Univ Acad Optoelect Beijing Peoples R China Beijing Trans Univ Space Technol Co Ltd Chinese Acad Sci Acad Optoelect Beijing Peoples R China

ISBN: (纸本)9780819489326

In this paper, we propose a variable step-size multi-modulus algorithm with quantized-error method (QE-VSSMMA), which benefits from a nonlinear quantized error method as well as the variable step-size method and thus holds reduced computational complexity and improved convergence rate compared to conventional multi-modulus algorithm (MMA). Simulation shows that the new algorithm has the characteristics of faster convergence, lower implementation cost while preserves the robustness property and the phase recovery functionality of MMA. The new algorithm is suitable for resource-limited environment.

关键词： blind equalization constant modulus algorithm multi-modulus algorithm variable step-size quantized error method

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Equalizer Optimization using Flower Pollination algorithm 1

Equalizer Optimization using Flower Pollination Algorithm

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1st IEEE International Conference on Power Electronics, Intelligent Control, and Energy Systems (ICPEICES)

作者： Banerjee, Subhabrata Chattopadhyay, Sudipta Future Inst Engn & Management Dept Elect & Commun Engn Kolkata India Jadavpur Univ Dept Elect & Telecommun Engn Kolkata India

ISBN: (纸本)9781467385879

Transmission of information from the source to the receiver involves automatic inclusion of random errors to the signal due to noise, interference or other system imperfections. Equalizers can be fruitfully utilized to minimize this error. Since the channel condition is always dynamic, the coefficients of the equalizer have to be set in an adaptive manner. This leads to the necessity of using Adaptive Equalizer (AE) in the communication system. Efficient optimization techniques add up an extra dimension to it. In this regard, a novel Flower Pollination algorithm (FPA) based Adaptive Equalizer (AE) has been proposed in this paper to minimize the channel errors with minimum number of iterations. The convergence behavior of the adaptive algorithm has been studied to establish the effectiveness of our proposition. Moreover, the Bit Error Rate (BER) performance of the proposed adaptive equalizer has been studied which shows considerable improvement over the entire range of SNR. Finally, the superiority of the proposed FPA optimized Adaptive Equalizer has been established over the existing techniques like Least-Mean-Square (LMS) and constant modulus algorithm (CMA) based Adaptive Equalizer in terms of convergence as well as BER performance.

关键词： Adaptive Equalizer BER constant modulus algorithm Flower Pollination algorithm Least-Mean-Square algorithm

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Blind Equalization Based on a Cascade of a New algorithm and Multi-Step Prediction error Filter 4

Blind Equalization Based on a Cascade of a New Algorithm and...

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4th International Japan-Egypt Conference on Electronics, Communications and Computers (JEC-ECC)

作者： Badran, Mohammad S. T. Al Obour Acad Engn & Technol Elect & Commun Dept Cairo Egypt

ISBN: (纸本)9781467389372

Adaptive channel equalization accomplished without a training sequence is known as blind equalization. Blind equalizers may be implemented with linear prediction error filters (LPEF) but the delay (D) cannot be controlled with one-step predictors to minimize the mean square error (MSE). Consequently, multi-step prediction error filters (MSPEF) has been suggested as a solution to the problem. But the slowness of the convergence process will remain a problem, so we propose a new technique to fast the convergence rate. In this paper, a blind equalizer composed of a modified algorithm (MA) cascaded with MSPEF is proposed (MA_MSPEF). Simulation results show comparable improvements of the proposed equalizer relative to the LPEF or the MSPEF equalizers and compared also with CMA_MSPEF for symmetric constellation QAM.

关键词： constant modulus algorithm blind equalization, multi-step prediction error filters

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Space-Time Blind Decision Feedback Equalizer

Space-Time Blind Decision Feedback Equalizer

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2006 International Telecommunications Symposium (ITS)

作者： Mendes Filho, Joao Silva, Magno T. M. Miranda, Maria D. Univ Presbiteriana Mackenzie Programa Posgrad Engn Eletr BR-01302907 Sao Paulo Brazil

ISBN: (纸本)9781424436446

We address the problem of signal separation using space-time blind decision feedback equalizer. Assuming correct decisions and absence of noise, the perfect equalization conditions are obtained. We present an extension of the blind algorithm which avoids degenerated solutions in the single-input single output case. The proposed algorithm jointly adapts the feedforward and feedback filters of DFE, avoids degenerated solutions, and has capability of simultaneously recovering all sources.

关键词： Decision Feedback Equalizer constant modulus algorithm Space-time equalization

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Blind Equalization of Multilevel Signals via Support Vector Regression 10

Blind Equalization of Multilevel Signals via Support Vector ...

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10th International Conference on Advanced Computational Intelligence (ICACI)

作者： Sun, Chao Yang, Ling Chen, Li Zhang, Jiliang Yang, Rong Lanzhou Univ Sch Informat Sci & Engn Lanzhou Gansu Peoples R China

ISBN: (纸本)9781538643624

In this paper, two families of batch algorithms are constructed in the support vector regression (SVR) framework for blind equalization of multilevel signals. Specifically, the error functions of constant modulus algorithm CMA(p, 2) and multimodulus algorithm MMA(p,2) are contained in the penalty term of the SVR. Simulation results show that the proposed MMA(p,2)-based algorithms perform better than the CMA(p,2)based ones, which exhibit lower residual intersymbol interference (ISI) and higher probability of convergence. With respect to conventional dual-mode scheme, the MMA(p,2)-based algorithms show better performance in the case of higher noise or smaller data block, therefore they are robust and more suitable for multilevel signals. In addition, they avoid tedious switching mechanism of dual-mode scheme and overcome phase rotation.

关键词： blind equalization batch algorithm support vector regression constant modulus algorithm multimodulus algorithm

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A Variable Step Size Blind Equalization algorithm Based on Gamma Distribution

A Variable Step Size Blind Equalization Algorithm Based on G...

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International Conference on Advanced Materials and Engineering Materials (ICAMEM 2011)

作者： Zhao Xiang Sun Jinyong Tan Hanhong Guilin Univ Elect Technol Sch Informat & Commun Guilin 541004 Guangxi Peoples R China Guangdong Univ Sci & Technol Dept Mech & Elect Dongguan 523083 Guangdong Peoples R China

ISBN: (纸本)9783037853559

a variable step size constant modulus algorithm (CMA) based on the gamma distribution is implemented as solutions to optimize the problem of blind equalization. The factor of step size in blind equalization algorithm is varied with gamma variable, in terms of the characteristics of which, the algorithm can search for the globe optimal equalizer weight vector. Simulation results indicate that the convergence rate and the steady Mean Square Errors (MSE) performances of the algorithm proposed are much better than conventional CMA and modified CMA blind equalization algorithms.

关键词： variable step size gamma distribution constant modulus algorithm blind equalization

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Blind Equalization algorithm for Underwater Acoustic Channel Based on Support Vector Regression 11

Blind Equalization Algorithm for Underwater Acoustic Channel...

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11th International Conference on Intelligent Human-Machine Systems and Cybernetics (IHMSC)

作者： Zhang, Guolong Yang, Ling Chen, Liang Zhao, Bin Li, Yuan Wei, Wanjun Lanzhou Univ Sch Informat Sci & Engn Lanzhou Peoples R China 91388 Army Unit 93 Zhanjiang Guangdong Peoples R China

ISBN: (纸本)9781728118598

In order to overcome the inter-symbol interference generated by multipath effect and improve the frequency band utilization ratio in the underwater acoustic communication system, the blind equalization problem of the underwater acoustic channel is expressed as the support vector regression problem. The error function of constant modulus algorithm (CMA) and multi-modulus algorithm (MMA) are included in the penalty term of the SVR, and the iterative reweighted least squares (IRWLS) method is used to find the optimal equalizer coefficients, thus two batch blind equalization algorithms are proposed in this paper. The simulation experiments show that the proposed two batch algorithms can effectively realize the blind equalization of underwater acoustic channel, compared with the traditional online blind algorithm, they achieves fast convergence with small samples and have excellent blind equalization performance.

关键词： blind equalization Support Vector Regression constant modulus algorithm Multi-modulus algorithm

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A FAMILY OF algorithmS FOR BLIND EQUALIZATION OF QAM SIGNALS

A FAMILY OF ALGORITHMS FOR BLIND EQUALIZATION OF QAM SIGNALS

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IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP)

作者： Mendes Filho, Joao Silva, Magno T. M. Miranda, Maria D. Univ Sao Paulo Escola Politecn Sao Paulo Brazil

ISBN: (纸本)9781457705397

We propose blind equalization algorithms that perform similarly to supervised ones, independently of the QAM order. They converge approximately to the Wiener solution, which generally provides a relatively low misadjustment. Besides presenting strategies to speed up their convergences, we provide sufficient conditions for the stability of the symbol-based decision algorithm, which is an extension of the decision-directed algorithm. Their behaviors are illustrated through simulation results.

关键词： Blind equalization adaptive equalizers QAM constant modulus algorithm decision-directed equalizer

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