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blind OFDM symbol synchronization in ISI channels

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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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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blind INTERFERENCE CANCELING EQUALIZER FOR MOBILE RADIO-COMMUNICATIONS

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IEICE TRANSACTIONS ON COMMUNICATIONS 1994年第5期E77B卷 580-588页

作者： FUKAWA, K SUZUKI, H NTT Mobile Communications Network Inc Yokosuka-shi Japan

This paper proposes a new adaptive Interference Cancelling Equalizer (ICE) with a blind algorithm. From a received signal, ICE not only eliminates inter-symbol interference, but also cancels co-channel interference. blind ICE can operate well even if training signals for the interference are unknown. First, training signal conditions for applying blind ICE are considered. Next, a theoretical derivation for blind ICE is developed in detail by applying the maximum likelihood estimation theory. It is shown that RLS-MLSE with diversity, which is derived for mobile radio equalizers, is also effective for blind ICE. Computer simulations demonstrate the 40 kb/s QDPSK transmission performance of blind ICE as a blind canceller with two branch diversity reception under Rayleigh fading in a single interference environment. The simulations assume synchronous training;the canceller is trained for the desired signal but not for the interference signals. blind ICE can be successfully achieved at more than - 10 dB CIR values when average Eb/No is 15 dB and a maximum Doppler frequency is 40 Hz.

关键词： COCHANNNEL INTERFERENCE INTERFERENCE CANCELER blind algorithm MAXIMUM LIKELIHOOD ESTIMATION MOBILE COMMUNICATIONS

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blind adaptive carrier phase recovery for QAM systems

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DIGITAL SIGNAL PROCESSING 2016年 49卷 65-85页

作者： Abrar, Shafayat Zerguine, Azzedine Nandi, Asoke K. COMSATS Inst Informat Technol Islamabad 44000 Pakistan King Fahd Univ Petr & Minerals Dhahran 31261 Saudi Arabia Brunel Univ London Uxbridge UB8 3PH Middx England Tongji Univ Shanghai 200092 Peoples R China

This paper provides a study of adaptive phase recovery in quadrature amplitude modulation (QAM) based communication systems. Here, we modify the traditional fourth-power phase recovery algorithm (FP-PRA) to propose three improved algorithms, and analyze their performances in the presence of additive white Gaussian noise, phase noise, frequency-offset, and inter-symbol interference. We demonstrate that it is possible to obtain the optimal values of step-sizes (or loop-gains) in closed-form in the presence of phase noise and/or frequency-offset. In particular, we discuss two methods to improve FP-PRA. The first method involves utilizing the idea of partitioning the QAM constellation into QPSK-like and not-QPSK-like annular regions. The phase synchronizer is allowed to update only when a derotated QAM symbol lies in QPSK-like region;otherwise, the update process is stopped. The second method exploits an evolving idea of QAM-to-QPSK transformation, and uses transformed symbols to estimate phase mismatch. We provide a new interpretation of this transformation method and relate it to the quadrant-wise centroid of the rotated constellation. Furthermore, we discuss the feasibility of this method for both square and cross-QAM, and, identify and verify numerically the existence of false-locks in the case of cross-QAM. To the best of our knowledge, the ideas of constellation partitioning and constellation transformation have not appeared earlier in the context of adaptive phase recovery. We discuss adaptive blind estimation of optimal step-sizes in the presence of phase noise and frequency-offset. Finally, we discuss the modification of the proposed stochastic gradient methods to transform them into batch processing algorithms so as to make them more suitable for higher data rate systems. Numerical experiments indicate that the proposed algorithms can outperform the traditional FP-PRA algorithm for a number of practical QAM sizes under different mismatch conditions, and that o

关键词： Adaptive receiver design blind algorithm Carrier phase recovery Quadrature amplitude modulation Quadrature phase shift keying Mean square deviation

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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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ADAPTIVE SIGNAL-PROCESSING FOR OPTIMAL TRANSMISSION IN MOBILE RADIO-COMMUNICATIONS

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IEICE TRANSACTIONS ON COMMUNICATIONS 1994年第5期E77B卷 535-544页

作者： SUZUKI, H NTT Mobile Communications Network Inc Yokosuka-shi Japan

This paper reviews recent progress in adaptive signal processing techniques for digital mobile radio communications. In Radio Signal Processing (RSP), digital signal processing is becoming more important because it makes it relatively easy to develop sophisticated adaptive processing techniques. Adaptive signal processing is especially important for carrier signal processing in RSP. Its main objective is to realize optimal or near-optimal radio signal transmission. Application environments of adaptive signal processing in mobile radio are clarified. Adaptive equalization is discussed in detail with the focus on adaptive MLSE based on the blind algorithm. Demodulation performance examples obtained by simulations and experiments are introduced, which demonstrates the recent advances in this field. Next, new trends in adaptive array processing, interference cancelling, and orthogonalization processing are reviewed. Finally, the three automatic calibration techniques that are based on adaptive signal processing are described for realizing high precision transmission devices.

关键词： MOBILE COMMUNICATIONS DIGITAL SIGNAL PROCESSING ADAPTIVE SIGNAL PROCESSING blind algorithm RADIO SIGNAL PROCESSING DEMODULATION AUTOMATIC CALIBRATION

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Fast-Converging Constant Modulus algorithm with Variable Step Size for Multibeam Massive MIMO

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IEICE TRANSACTIONS ON COMMUNICATIONS 2022年第10期E105B卷 1154-1161页

作者： Nishimori, Kentaro Maruta, Kazuki Hiraguri, Takefumi Shiomi, Hidehisa Niigata Univ Fac Engn Niigata 9502102 Japan Tokyo Univ Sci Dept Elect Engn Tokyo 1258585 Japan Nippon Inst Technol Fac Engn Saitamaken 3458501 Japan Osaka Univ Ctr Quantum Informat & Quantum Biol Toyonaka 5600043 Japan

Multibeam massive multiple-input multiple-output (MIMO) configuration has been proposed that selects high-power beams in an analog part and uses a blind algorithm, such as the constant-modulus algorithm (CMA), in the digital part. The CMA does not require channel state information. However, when least-squares CMA (LS-CMA) is applied to a quadrature amplitude modulation signal whose amplitude changes, the interference cancellation effect decreases as the modulation order increases. In this paper, a variable-step-size-based CMA (VS-CMA), which modifies the step size of the steepest-descent CMA, is proposed as a blind adaptive algorithm to replace LS-CMA. The basic performance of VS-CMA, its success in cancelling interference, and its effectiveness in multibeam massive MIMO transmission are verified via simulation and compared with other blind algorithms such as independent component analysis, particularly when the data smoothing size is small.

关键词： constant modulus blind algorithm variable step size multi-beam massive MIMO QAM

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Two blind algorithms of MMSE Filter Based on Second-Order Statistics in MIMO Systems with Multiple Interferences

Two Blind Algorithms of MMSE Filter Based on Second-Order St...

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2011年无线通信与信号处理国际会议(WCSP 2011)

作者： Bo Hu Xu Wang Tao Yang Fan He Rueywen Liu E.E. Dept. of Fudan University Shanghai 200433 China University of Notre Dame Notre Dame IN USA

In this paper, we consider an MIMO system with multiple interferences. The minimum mean-square error (MMSE) criterion is the best trade off between the rejection of interference and the preservation of user signal in terms of bit error rate (BER). The solution of MMSE filter is known but it requires channel state information which is to be estimated by pilot signals. The estimation tends to be inaccurate or time consuming when the interferences are large. As such, an accurate blind algorithm under heavy interferences would be an attractive alternative approach. In this paper two blind algorithms are presented, one for strong signal and one for strong interferences. The deviation of the mean-square error (MSE) between the ideal MMSE filter and the estimated MMSE filter by the blind algorithms are shown by simulation to be within 0.001.

关键词： Autocorrelation function MMSE filter blind algorithm Linear MIMO system

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Joint blind Compensation of Inter-Block Interference and Frequency-Dependent IQ Imbalance

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IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES 2016年第1期E99A卷 196-198页

作者： Zhang, Xi Miyajima, Teruyuki Ibaraki Univ Grad Sch Sci & Engn Hitachi Ibaraki 3168511 Japan Ibaraki Univ Coll Engn Hitachi Ibaraki 3168511 Japan Toppan Printing Co Ltd Tokyo Japan

In this letter, we propose a blind adaptive algorithm for joint compensation of inter-block interference (IBI) and frequency-dependent IQ imbalance using a single time-domain equalizer. We combine the MERRY algorithm for IBI suppression with the differential constant modulus algorithm to compensate for IQ imbalance. The effectiveness of the proposed algorithm is shown through computer simulations.

关键词： blind algorithm inter-block interference IQ imbalance time-domain equalization

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blind Interference Suppression Scheme by Eigenvector Beamspace CMA Adaptive Array with Subcarrier Transmission Power Assignment for Spectrum Superposing

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IEICE TRANSACTIONS ON COMMUNICATIONS 2015年第6期E98B卷 1050-1057页

作者： Maruta, Kazuki Mashino, Jun Sugiyama, Takatoshi NTT Corp NTT Access Network Serv Syst Labs Yokosuka Kanagawa 2390847 Japan NTT Corp NTT Network Innovat Labs Yokosuka Kanagawa 2390847 Japan Kogakuin Univ Tokyo 1638677 Japan

This paper proposes a novel blind adaptive array scheme with subcarrier transmission power assignment (STPA) for spectrum superposing in cognitive radio networks. The Eigenvector Beamspace Adaptive Array (EBAA) is known to be one of the blind adaptive array algorithms that can suppress inter-system interference without any channel state information (CSI). However, EBAA has difficulty in suppressing interference signals whose Signal to Interference power Ratio (SIR) values at the receiver are around 0 dB. With the proposed scheme, the ST intentionally provides a level difference between subcarriers. At the receiver side, the 1st eigenvector of EBAA is applied to the received signals of the subcarrier assigned higher power and the 2nd eigenvector is applied to those assigned lower power. In order to improve interference suppression performance, we incorporate Beamspace Constant Modulus algorithm (BSCMA) into EBAA (E-BSCMA). Additionally, STPA is effective in reducing the interference experienced by the primary system. Computer simulation results show that the proposed scheme can suppress interference signals received with SIR values of around 0 dB while improving operational SIR for the primary system. It can enhance the co-existing region of 2 systems that share a spectrum.

关键词： adaptive array Subcarrier Transmission Power Assignment (STPA) blind algorithm Eigenvector Beamspace Adaptive Array (EBAA) Constant Modulus algorithm (CMA) spectrum superposing

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