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Fast blind adaptive beamforming algorithm with interference suppression

IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2008年第3期57卷 1985-1988页

作者： Xie, Ning Zhou, Yuanping Xia, Minghua Tang, Wenming Shenzhen Univ Coll Informat Engn Shenzhen 518060 Peoples R China Sichuan Univ Sch Elect & Informat Engn Chengdu 6160064 Peoples R China ETRI Beijing R&D Ctr Beijing 100027 Peoples R China Sun Yat Sen Univ Dept Elect & Commun Engn Guangzhou 510275 Guangdong Peoples R China

A fast blind adaptive beamforming algorithm is proposed in code-division multiple-access wireless systems based on an array pattern synthesis approach. By incorporating an interference suppression mechanism in the iterative procedure, the proposed algorithm outperforms conventional blind algorithms. Two practical adaptive beamforming algorithms are further presented, which provide fast convergence speed with low complexity. The simulation results demonstrate the effectiveness of the proposed adaptive beamforming algorithms in various signal environments.

关键词： adaptive beamforming blind algorithm fast convergence low complexity

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A blind SNR ESTIMATOR FOR DIGITAL BANDPASS SIGNALS

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Journal of Electronics(China) 2008年第1期25卷 7-13页

作者： Sui Dan Ge Lindong Institute of Information Engineering Information Engineering University Zhengzhou 450002 China

A subspace-based blind Signal-to-Noise Ratio (SNR) estimation algorithm for digital bandpass signals in Additive White Gaussian Noise (AWGN) channel is discussed. The lower bounds of the mean and variance of the estimation are derived, and simulations are performed for the commonly used digital bandpass signals, such as MPSK (M=2, 4, 8), MFSK (M=2, 4) and MQAM (M=16, 64, 128, 256) signals. Theoretical analyses and simulation results indicate that the proposed algorithm is ef- fective even when the SNR is below 0dB. Furthermore, the algorithm can provide a blind estimator in that it needs neither the parameters of the received signals, such as the carrier frequency, symbol rate and modulation scheme, nor the synchronization of the system.

关键词： Signal-to-Noise Ratio （SNR） estimation blind algorithm Performance analysis Bandpass signals Subspace projection

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blind algorithm for RIBI mitigation in OFDM systems

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ELECTRONICS LETTERS 2002年第22期38卷 1382-1383页

作者： Chen, SP Yao, TR Huazhong Univ Sci & Technol Dept Elect & Informat Engn Wuhan 430074 Hubei Peoples R China

A novel blind algorithm is developed to mitigate the residual inter-block interference (RIBI) for orthogonal frequency division multiplexing (OFDM) systems. The algorithm is based on the RIBI cancellation and cyclic structure recovery. Simulation shows that the proposed algorithm can effectively mitigate RIBI and has a low computation complexity.

关键词： interference suppression orthogonal frequency division multiplexing blind algorithm Electromagnetic compatibility and interference OFDM systems RIBI mitigation residual interblock interference cyclic structure recovery intersymbol interference computational complexity low computation complexity RIBI cancellation Modulation and coding methods ISI channels OFDM modulation

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blind adaptive equalizer based on CMA and LMS algorithm

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IEICE TRANSACTIONS ON COMMUNICATIONS 2004年第4期E87B卷 1012-1015页

作者： Okello, J Ueda, K Ochi, H NEC Corp Ltd Multimedia Res Labs Kawasaki Kanagawa Japan Kyushu Inst Technol Fac Comp & Elect Engn Iizuka Fukuoka 8208502 Japan

In this letter we verify that a blind adaptive algorithm operating at a low intermediate frequency (Low-IF) can be applied to a system where carrier phase synchronization has not been achieved. We consider a quadrature amplitude shift keyed (QPSK) signal as the transmitted signal and assume that the orthogonal low intermediate sinusoidal frequency used to generate the transmitted signal is well known. The proposed algorithm combines two algorithms: Namely, the least mean square (LMS) algorithm which has a cost function with unique minimum, and the constant modulus algorithm (CMA), which was first proposed by Godard. By doing this and operating the equalizer at a rate greater than the symbol rate, we take advantage of the variable amplitude of the sub-carriers and the fast convergence of LMS algorithm, so as to achieve a faster convergence speed. When the computer simulation results of the proposed algorithm are compared with the constant modulus algorithm (CMA) and the modified CMA (MCMA), we observed that the proposed algorithm exhibited a faster convergence speed.

关键词： equalizer blind algorithm CMA LMS

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blind adaptive beamformer for cyclostationary sources with application to CDMA systems

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IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES 2004年第5期E87A卷 1258-1269页

作者： Miyajima, T Ibaraki Univ Dept Syst Engn Hitachi Ibaraki 3168511 Japan

In this paper, a simple blind algorithm for a beamforming antenna is proposed. This algorithm exploits the property of cyclostationary signals whose cyclic autocorrelation function depends on delay as well as frequency. The cost function is the mean square error between the delay product of the beamformer output and a complex exponential. Exploiting the delay greatly reduces the possibility of capturing undesired signals. Through analysis of the minima of the non-quadratic cost function, conditions to extract a single signal are derived. Application of this algorithm to code-division multiple-access systems is considered, and it is shown through simulation that the desired signal can be extracted by appropriately choosing the delay as well as the frequency.

关键词： cyclostationarity DS/CDMA adaptive array antenna blind algorithm higher-order statistics

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MMSE equalization of downlink CDMA channel utilizing unused orthogonal spreading sequences

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IEEE TRANSACTIONS ON SIGNAL PROCESSING 2003年第5期51卷 1390-1402页

作者： Choi, J Univ New S Wales Sch Elect Engn & Telecommun Sydney NSW Australia

For the code division multiple access (CDMA) downlink channel, the chip-level equalization has been considered in this paper. There is no interference after despreading if all spreading codes are orthogonal, as in IS-95. However, it cannot be true for a frequency-selective fading channel. In this case, the chip-level equalization can be applied to restore the orthogonality. We investigate the chip-level equalization using finite impulse response (FIR) equalizers for the mobile station with multiple receive antennas. A blind approach and the minimum mean square error (MMSE) approach with cod.e-multiplexed pilot are considered. A generalized MMSE equalization, which combines the MMSE and blind approaches together, is also investigated;It is shown that the generalized MMSE equalizer can effectively increase the number of samples to track the variation of channel and thereby performs better when the coherence time is small. In addition, we derive closed-form solutions of the blind, MMSE, and generalized MMSE equalizers for given channels.

关键词： adaptive algorithm blind algorithm CDMA chip-level equalizer IS-95 time-variant frequency-selective fading

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blind OFDM symbol synchronization in ISI channels

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IEEE TRANSACTIONS ON COMMUNICATIONS 2002年第9期50卷 1525-1534页

作者： Negi, R Cioffi, JM Carnegie Mellon Univ Dept Elect & Comp Engn Pittsburgh PA 15213 USA Stanford Univ Dept Elect Engn Stanford CA 94305 USA

We present a new algorithm for blind symbol synchronization in orthogonal frequency division multiplexing (OFDM) systems. The new algorithm declares symbol synchronization when a certain autocorrelation matrix, constructed from the received signal, achieves minimum rank. Unlike previously proposed blind algorithms, the new, rank method guarantees correct symbol synchronization, even in the presence of intersymbol interference. Also, it does not assume that the OFDM time samples are i.i.d.. In particular, the rank method works even with OFDM systems that employ pulse shaping. The increased complexity of the algorithm would be acceptable for systems, such as fixed-receiver broadcast systems, that require guaranteed synchronization under all conditions.

关键词： blind algorithm intersymbol interference orthogonal frequency division multiplexing symbol synchronization

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A semi-blind approach for MMSE equalization in downlink CDMA channel 8

A semi-blind approach for MMSE equalization in downlink CDMA...

引用

8th International Conference on Communication Systems

作者： Choi, JH Univ New S Wales Sch Elect Engn & Telecommun Sydney NSW 2052 Australia

ISBN: (纸本)0780375106

We investigate the chip-level equalization using finite impulse response (FIR) equalizers for the mobile station of code division multiple access (CDMA) systems with single and multiple receive antennas. As a semi-blind method, a generalized minimum mean square error (MMSE) equalization, which combines the MMSE and blind approaches together, is investigated. It is shown that the generalized MMSE equalizer can effectively increase the number of samples to track the variation of channel and thereby performs better when the coherence time is small. In addition, we derive a closed-form solution of the. MMSE and generalized MMSE equalizers for given channels.

关键词： CDMA IS-95 chip-level equalizer blind algorithm adaptive algorithm time-variant frequency-selective fading

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Performance and configuration of M-CMA (modified constant modulus algorithm) adaptive array using polyphase filters

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ELECTRONICS AND COMMUNICATIONS IN JAPAN PART I-COMMUNICATIONS 2002年第12期85卷 53-64页

作者： Denno, S Ohira, T ATR Adapt Commun Res Labs Kyoto 6190288 Japan

As a way to realize an adaptive array of small size, low cost, and low power consumption, there exists a configuration method combining analog signal processing and digital signal processing. M-CMA has been proposed as a control algorithm for such an approach. However, when this approach is applied to an actual communication system, there arises the problem that the narrow-band filter in the receiver prevents M-CMA from converging to the desired solution. In this paper, in order to effectively operate an M-CMA adaptive array in the presence of a narrow-band filter, a configuration is proposed in which polyphase filters are used as narrow-band filters. Its superior interference suppression capability is confirmed by a theoretical analysis and computer simulation. (C) 2002 Wiley Periodicals, Inc.

关键词： adaptive array blind algorithm perturbation polyphase filter

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blind array channel division multiple access (AChDMA) for mobile communications

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IEEE TRANSACTIONS ON SIGNAL PROCESSING 1998年第3期46卷 737-752页

作者： Barroso, VAN Moura, JMF Xavier, J Inst Sistemas & Robot Inst Super Tecn Lisbon Portugal Carnegie Mellon Univ Dept Elect & Comp Engn Pittsburgh PA 15213 USA

The paper introduces;array channel division multiple access (AChDMA), which is a new blind algorithm for advanced SDMA in mobile communications systems, As an SDMA technique, AChDMA increases the system capacity by improving its time and frequency reuse, Being a blind algorithm, it requires no training sequences, previously known directions of arrival, or user codes, AChDMA separates the moving sources by tracking their multipath configuration and resolving their distinct generalized steering vectors, It maximizes a finite mixture log-likelihood function, combining an efficient initialization procedure with an EM-based algorithm that provides fast convergence to the global maximum. AChDMA reconstructs the mobile data sequences using only internal variables of the EM algorithm, These characteristics and its parallel structure make AChDMA suitable for real-time mobile communications. We test AChDMA with synthetic data in a number of different scenarios, illustrating the ability of the blind algorithm to separate and track in time the moving sources, and showing its good performance in a variety of practical situations.

关键词： .Multiple Access EM algorithm log-likelihood SDMA initialization procedure blind Array AChDMA blind algorithm generalized steering fast convergence

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