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A novel constant modulus array for multiuser detection

Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2005年第1期6卷 38-42页

作者：张继东郑宝玉傅洪亮 Department of Electronic Engineering Shanghai Jiaotong University Shanghai 200030 China Bureau of Telecom Transmission Jiangsu Nanjing 210003 China Institute of Signal and Information Processing Nanjing University of Posts and Telecommunications Nanjing 210003 China Department of Communication Engineering Nanjing University of Posts and Telecommunications Nanjing 210003 China

This paper proposes a new multitarget constant modulus array structure for code division multiple access (CDMA) systems. The new algorithm for the structure is called pre-despreading and wavelet denoising constant modulus algorithm (D-WD-CMA). In the new algorithm, the pre-despreading is applied to multitarget arrays to remove some multiple access inter- ferences. After that the received signal is subjected to wavelet de-noising to reduce some noise, and used in CMA adaptive iteration for signal separation. Simulation results showed that the proposed algorithm performed better than the traditional CMA algorithm.

关键词： constant modulus algorithm Adaptive array Wavelet de-noising Multiuser detection CDMA

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A new blind equalization method based on negentropy minimization for constant modulus signals

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IEICE TRANSACTIONS ON COMMUNICATIONS 2008年第4期E91B卷 1207-1210页

作者： Choi, Sooyong Chung, Jong-Moon Jeong, Wun-Cheol Yonsei Univ Sch Elect & Elect Engn Seoul 120749 South Korea ETRI Taejon South Korea

A new blind adaptive equalization method for constant modulus signals based on minimizing the approximate negentropy of the estimation error for a finite-length equalizer is presented. We consider the approximate negentropy using nonpolynomial expansions of the estimation error as a new performance criterion to improve the performance of a linear equalizer using the conventional constant modulus algorithm (CMA). Negentropy includes higher order statistical information and its minimization provides improved convergence, performance, and accuracy compared to traditional methods, such as the CMA, in terms of the bit error rate (BER). Also, the proposed equalizer shows faster convergence characteristics than the CMA equalizer and is more robust to nonlinear distortion than the CMA equalizer.

关键词： blind equalization negentropy information theoretic learning constant modulus algorithm

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Fast converging approach for blind constant modulus interference suppression

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JOURNAL OF THE CHINESE INSTITUTE OF ENGINEERS 2004年第2期27卷 275-279页

作者： Chang, AC Huang, ZF Natl Def Univ Chung Cheng Inst Technol Dept Elect Engn Taoyuan 335 Taiwan

The convergence behavior of the constant modulus algorithm (CMA) is examined in the proper initialization condition of locking onto the desired signal. An improved CMA converging approach is proposed that has the advantage of suppressing multiple access interference without explicit knowledge of interference parameters for synchronous DS-CDMA systems. Simulation results demonstrate that the method overcomes the slower convergence of the CMA in the sudden birth of the number of users and outperforms the CMA detector and matched filter.

关键词： CDMA constant modulus algorithm speed of convergence blind adaptive interference suppression

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Fractionally Nyquist Sample Spaced ARMA Blind Equalizer for Direct Signal Recovery in Passive Bistatic Radar

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Chinese Journal of Electronics 2017年第3期27卷 658-666页

作者： WANG Feng SHEN Wei JIANG Defu WEI Shuang Array and Information Processing Laboratory College of Computer and Information Hohai University Nanjing Research Institute of Electronics Technology

This paper proposes a modified signal processing structure based on the fractionally Nyquist sample spaced structure for passive bistatic *** recover the direct signal from the multipath clutter,an equalizer of the Auto regressive moving average(ARMA)type is proposed based on the fractionally Nyquist sample spaced constant modulus *** with the conventional Nyquist sample spaced equalizer,the equalizer of the fractionally Nyquist sample spaced ARMA structure is more effective in dealing with deep fading multipath channels with zeros near the unit *** simulations and real data tests indicate that the proposed approach outperforms the conventional processing structure in terms of both clutter residual and mean square error.

关键词： Passive bistatic radar constant modulus algorithm Direct signal recovery Multipath clutter cancellation Fractionally spaced equalizer

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Learning strategies for adaptive equalizers using the constant modulus error criterion

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INTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING 1998年第2期12卷 97-116页

作者： Soni, RA Schirtzinger, TA Jenkins, WK Univ Illinois Dept Elect & Comp Engn Urbana IL 61801 USA Univ Illinois Coordinated Sci Lab Urbana IL 61801 USA

In communication systems, data are often corrupted during transmission due to imperfect communication channels. Since channel characteristics may be time varying or unknown prior to data transmission, adaptive equalizers are typically incorporated into the receiver to reduce the ill effects of the imperfect channel. Conventional equalizers utilize a training signal to achieve the proper correction. Blind equalization schemes do not require the use of a training signal, but instead attempt restoration based upon some known property of the transmitted signal. The constant modulus algorithm (CMA) is a blind equalization technique that may be used to equalize certain communication signals (e.g. BPSK, QPSK, and FM). This paper investigates three new techniques for adaptive equalization based on the constant modulus error criterion: (i) the fast quasi-Newton CMA, (ii) the conjugate gradient quasi-Newton CMA, (iii) the conjugate gradient CMA. These three methods are formulated analytically and evaluated experimentally on several typical communication channel models. (C) 1998 John Wiley & Sons, Ltd.

关键词： adaptive channel equalization blind equalization conjugate gradient algorithm constant modulus algorithm fast quasi-Newton CMA algorithm LMS algorithm

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Least squares approach to fractionally spaced blind channel equalisation

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SIGNAL PROCESSING 1997年第1期58卷 63-78页

作者： Dogancay, K Kennedy, RA Department of Electrical and Electronic Engineering The University of Melbourne Parkville Victoria 3052 Australia Telecommunications Engineering Group Research School of Information Sciences and Engineering The Australian National University Canberra ACT 0200 Australia

A new approach to fractionally spaced blind equalisation of finite-duration impulse response (FIR) channels is proposed based on the method of least squares (LS) and the constant modulus algorithm (CMA). A nonlinear transformation of the equaliser parameters is formulated and solved for, so as to avoid the potential problems associated with fractionally spaced CMA (FS-CMA) when the channel input is correlated. The new algorithm has a fast convergence rate in comparison with FS-CMA and the resulting equaliser setting is invariant to channel input correlation so long as all finite-length subsequences of the channel input sequence occur with nonzero probability. Although the algorithm is based on the assumption of constant modulus channel inputs, its application to nonconstant modulus constellations such as M-ary quadrature amplitude modulation (QAM) is also illustrated. The issue of channel noise enhancement is studied in connection with subchannel zeros, and a method for reducing inflated equaliser norms is proposed by way of reduced rank matrix approximation. A modified recursive least squares implementation of the algorithm is simulated to demonstrate its superior performance vis-a-vis FS-CMA. (C) 1997 Elsevier Science B.V.

关键词： blind channel equalisation fractionally spaced channel equalisation least squares constant modulus algorithm reduced rank matrix approximation

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Blind decision feedback equalisers, how to avoid degenerative solutions

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SIGNAL PROCESSING 2002年第11期82卷 1675-1693页

作者： Szczecinski, LL Gei, A INRS Energy Mat & Telecommun Montreal PQ H5A 1C6 Canada Univ Chile Dept Elect Engn Santiago Chile

Decision feedback equalisers offer a good compromise between complexity and performance for channels with strong intersymbol interference. However, their blind or decision-directed adaptation may converge to degenerative solutions for which signal at the equaliser's output is independent of its input. The known algorithms proposed to solve this problem, are evaluated in this paper. It is shown that their main defect is a lack of well-defined criteria allowing the detection of degenerative solutions, so this paper introduces a criterion proved to be sufficient for reliable detection of such solutions. Using the new criterion, an algorithm of blind decision feedback equalisation, based on constrained optimisation, is proposed. The new algorithm does not admit degenerative solutions therefore should be preferred among the analysed algorithms. Also, the problem of false phase lock, characteristic of some modulations, is addressed and a solution to it is proposed. The results of the study are presented using the experimental data and simulation. (C) 2002 Elsevier Science B.V. All rights reserved.

关键词： constant modulus algorithm blind equalisation decision feedback phase tracking

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A novel high precision adaptive equalizer in digital coherent optical receivers

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OPTICS COMMUNICATIONS 2015年 353卷 63-69页

作者： Ma, Xiurong Xu, Yujun Wang, Xiao Ding, Zhaocai Tianjin Univ Technol Dept Comp & Commun Engn Tianjin 300384 Peoples R China Minist Educ Engn Res Ctr Commun Devices & Technol Tianjin 300384 Peoples R China Tianjin Key Lab Film Elect & Commun Devices Tianjin 300384 Peoples R China

A novel high precision adaptive equalization method is introduced and applied to dynamic equalization for quadrature phase shift keying (QPSK) coherent optical communication system in this paper. A frequency-domain constant modulus algorithm (CMA) method is used to equalize the received signal roughly. Then, some non-ideal output signals will be picked out through the error measurement, and they will be equalized accurately further in a fixed time-domain CMA equalizer. This high precision equalization method can decrease the equalization error, then it can reduce the bit error ratio (BER) of coherent communication system. Simulation results show that there is a 6% decrease for computation complexity by proposed scheme when compared with time-domain CMA. Furthermore, compared with time-domain CMA and frequency-domain CMA, about 2 dB and 2.2 dB in OSNR improvement can be obtained by proposed scheme at the BER value of 1e-3, respectively. (C) 2015 Elsevier B.V. All rights reserved.

关键词： Coherent optical communication system constant modulus algorithm Error measurement

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Blind source separation of convolutive mixtures of non-circular linearly modulated signals with unknown baud rates

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SIGNAL PROCESSING 2012年第3期92卷 715-726页

作者： Florian, E. Chevreuil, A. Loubaton, Ph. Sequans Commun F-92073 Le Parvis De La Def Paris La Defens France Univ Paris Est LIGM CNRS UMR 8049 F-77454 Marne La Vallee 2 France ESIEE Paris F-93162 Noisy Le Grand France

This paper addresses the problem of blind separation of convolutive mixtures of BPSK and circular linearly modulated signals with unknown (and possibly different) baud rates and carrier frequencies. In previous works, we established that the constant modulus algorithm (CMA) is able to extract a source from a convolutive mixture of circular linearly modulated signals. We extend the analysis of the extraction capabilities of the CMA when the mixing also contains BPSK signals. We prove that if the various source signals do not share any non-zero cyclic frequency nor any non-conjugate cyclic frequencies, the local minima of the constant modulus cost function are separating filters. Unfortunately, the minimization of the Godard cost function generally fai s when considering BPSK signals that have the same rates and the same carrier frequencies. This failure is due to the existence of non-separating local minima of the Godard cost function. In order to achieve the separation, we propose a simple modification of the Godard cost function which only requires knowledge of the BPSK sources frequency offsets at the receiver side. We provide various simulations of realistic digital communications scenarios that support our theoretical statements. (C) 2011 Elsevier B.V. AB rights reserved.

关键词： Blind source separation Convolutive mixture constant modulus algorithm Cyclostationarity

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Blind separation of BPSK sources with residual carriers

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SIGNAL PROCESSING 1999年第1-2期73卷 67-79页

作者： van der Veen, AJ Delft Univ Technol Dept Elect Engn NL-2628 CD Delft Netherlands

Blind separation of instantaneous mixtures of binary sources with equal carrier frequencies has been studied before. For independent sources, it may be reasonable to assume that their carrier frequencies are not exactly identical, so that a residual carrier is present after demodulation to baseband. We show how this can be used to separate the sources. If the receiving antenna array is centro-symmetric and there is no multipath, then the performance of the algorithm can be significantly improved. (C) 1999 Elsevier Science B.V. All rights reserved.

关键词： blind source separation constant modulus algorithm residual carrier blind beamforming

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