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On the equivalence between the Godard and Shalvi-Weinstein schemes of blind equalization

SIGNAL PROCESSING 1999年第1-2期73卷 185-190页

作者： Regalia, PA Inst Natl Telecommun Dept Signal & Image F-91011 Evry France

Certain equivalences between the Godard and Shalvi-Weinstein schemes have been previously noted under special circumstances. We present here a simple proof for real signals that an equivalence can be established assuming little more than stationarity to fourth order of the equalizer input;the exact nature of the input sequence proves otherwise irrelevant to the validity of the equivalence. The equivalence also carries over to complex signals, but subject to more restrictive circularity conditions. In a communication context, the equivalence implies that many performance issues, such as susceptibility to local minima, the ability (or lack there of) to open the eye, or mean performance degradations due to channel noise and/or source correlation properties, are common to the two, even when applied with nonlinear channels. Our equivalence also indicates a simple modification to the Godard algorithm to render it applicable to leptokurtic sources. (C) 1999 Elsevier Science B.V. All rights reserved.

关键词： Godard algorithm Shalvi-Weinstein algorithm blind equalization constant modulus algorithm

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Concurrent Blind Channel Equalization in Impulsive Noise Environments

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CHINESE JOURNAL OF ELECTRONICS 2013年第4期22卷 741-746页

作者： Li Sen Wang Yan Lin Bin Dalian Maritime Univ Coll Informat Sci & Technol Dalian 116026 Peoples R China

In some communication systems the transmitted signal is contaminated by impulsive noise with a non-Gaussian distribution. Non-Gaussian noise caused significant performance degradation to communication receivers. The new constant modulus blind equalizer based on Fractional lower-order statistics of the equalizer input, which is defined as FLOS_CMA, is able to mitigate impulsive channel noise while restoring the constant modulus character of the transmitted communication signal. However, like the constant modulus algorithm (CMA), the steady-state Mean square error (MSE) of the FLOS_CMA algorithm may not be sufficient low for the system to obtain adequate performance. This paper proposes a concurrent equalizer, in which a Decision-directed least mean p norm (DD_LMP) equalizer operates cooperatively with a FLOS_CMA equalizer, controlled through a non-linear link. Simulation results using M-QAM and 8-PSK signaling have shown that besides the capability of compensating the phase offset, the proposed concurrent FLOS_CMA and DD_LMP blind equalizer has faster convergence rate and lower steady-state MSE than the FLOS_CMA approach.

关键词： Alpha-stable distribution Fractional lower-order statistics Least mean p norm constant modulus algorithm Concurrent equalizer

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Capacity Bounds Under Imperfect Polarization Tracking

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IEEE TRANSACTIONS ON COMMUNICATIONS 2022年第11期70卷 7240-7249页

作者： Farsi, Mohammad Karlsson, Magnus Agrell, Erik Chalmers Univ Technol Dept Elect Engn S-41296 Gothenburg Sweden Chalmers Univ Technol Dept Microtechnol & Nanosci S-41296 Gothenburg Sweden

In optical fiber communication, due to the random variation of the environment, the state of polarization (SOP) fluctuates randomly with time leading to distortion and performance degradation. The memory-less SOP fluctuations can be regarded as a two-by-two random unitary matrix. In this paper, for what we believe to be the first time, the capacity of the polarization drift channel under an average power constraint with imperfect channel knowledge is characterized. An achievable information rate (AIR) is derived when imperfect channel knowledge is available and is shown to be highly dependent on the channel estimation technique. It is also shown that a tighter lower bound can be achieved when a unitary estimation of the channel is available. However, the conventional estimation algorithms do not guarantee a unitary channel estimation. Therefore, by considering the unitary constraint of the channel, a data-aided channel estimator based on the Kabsch algorithm is proposed, and its performance is numerically evaluated in terms of AIR. Monte Carlo simulations show that Kabsch outperforms the least-square error algorithm. In particular, with complex, Gaussian inputs and eight pilot symbols per block, Kabsch improves the AIR by 0.20 to 0.30 bits/symbol throughout the range of studied signal-to-noise ratios.

关键词： Achievable information rate constant modulus algorithm capacity channel estimation decision-directed least mean square Kabsch algorithm lower bound least square error mutual information multimode fiber multicore fiber polarization-mode dispersion state of polarization space-division multiplexing

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Pilot decontamination for multi-cell massive MIMO systems using asynchronous pilot design and data-aided channel estimation

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PHYSICAL COMMUNICATION 2018年 30卷 76-85页

作者： Huy-Dung Han Dang-An Nguyen Van-Duc Nguyen Tien-Hoa Nguyen Zia, Muhammad Hanoi Univ Sci & Technol Sch Elect & Telecommun Hanoi Vietnam Quaid I Azam Univ Dept Elect Islamabad Pakistan

In this work, we investigate the pilot contamination problem in multi-cell massive multi-input multi-output (MIMO) systems. The conventional approaches to address pilot contamination for multi-cell MIMO systems impose orthogonal pilots constraint across multiple users and cells, which leads to bandwidth inefficiency under large number of active users. We propose an uplink (UL) transmission protocol in which the pilot segments of users partially overlap across cells and even overlap with data from other cells, which provides more freedom in system designing. We also apply semi-blind algorithms at base station (BS) in order to separate the data streams of each user. Our analysis shows that semi-blind receiver removes pilot contamination effectively under large UL data length. The simulation results demonstrate that the performance of the proposed protocol with semi-blind receiver employing constant modulus algorithm (CMA) is superior as compared to the existing schemes. (C) 2018 Elsevier B.V. All rights reserved.

关键词： Massive MIMO Pilot contamination Least square estimation constant modulus algorithm

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Efficient parallel architecture for implementation of the CMA adaptive antenna

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IETE TECHNICAL REVIEW 2013年第4期30卷 303-312页

作者： Boonpoonga, Akkarat Sirisuk, Phaophak Krairiksh, Monai King Mongkuts Univ Technol North Bangkok Fac Engn Dept Elect & Comp Engn Bangkok 10800 Thailand King Mongkuts Inst Technol Ladkrabang Int Coll Bangkok Thailand King Mongkuts Inst Technol Ladkrabang Fac Engn Bangkok Thailand

This paper presents an efficient parallel architecture for implementation of a constant modulus algorithm (CMA) adaptive array antenna. By inserting delay units into the original CMA, a novel delayed CMA (DCMA) that can significantly reduce the associated critical path is derived. Consequently, a pipelining architecture that supports parallel processing is introduced for implementation of the DCMA. In addition to the pipelining technique, a power-of-two multiplier is proposed for the DCMA leading to the efficient FPGA implementation. The effects of delays and finite word-length on the convergence property of CMA are investigated via simulations. Moreover, the synthesized results demonstrate that FPGA implementation of the proposed architecture using power-of-two arithmetic achieves 26.9% resource reduction in comparison with that of fixed-point arithmetic and operating clock frequency higher than 65 MHz. The implemented FPGA was tested to confirm that the designed architecture operates well for CMA.

关键词： Adaptive antenna constant modulus algorithm Field programmable gate array Pipelining

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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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Algebraic methods for deterministic blind beamforming

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PROCEEDINGS OF THE IEEE 1998年第10期86卷 1987-2008页

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

Deterministic blind beamforming algorithms try to separate superpositions of soul ce signals impinging on a phased antenna array by using deterministic properties of the signals or the channels such as their constant modulus or directions-of-arrival. Progress in this area has been abundant over the past ten years and has resulted in several powerful algorithms. Unlike optimal or adaptive methods, the algebraic methods discussed in this review act on a fixed block of data and give closed-form expressions for beamformers by focusing on algebraic structures. This typically leads to subspace estimation and generalized eigenvalue problems. After introducing a simple and widely used multipath channel model, the paper provides an anthology of properties that are available, as well as generic algorithms that exploit them.

关键词： array signal processing blind source separation constant modulus algorithm delay estimation direction of arrival estimation frequency estimation multipath channels sequence estimation singular value decomposition space division multiplexing

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Ill convergence of minimum output energy infinite impulse response equalizer for digital vestigial sideband signals

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INTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING 2012年第1期26卷 73-83页

作者： Chung, Wonzoo Korea Univ Sch Comp & Commun Engn Seoul South Korea

Minimum output energy (MOE) algorithm is a widely used adaptive algorithm for blind adaptation of infinite impulse response (IIR) filters. In this paper, we show that the MOE algorithm is not suitable for blind adaptation of the complex-valued IIR equalizer for digital vestigial sideband signals, whereas the constant modulus algorithm successfully achieves blind adaptation of the IIR equalizers when MOE fails. Because of the difficulty in analyzing IIR equalizers, the analysis is limited to a simple two-tap channel case. For more general multitap channel cases, the performance of a complex constant modulus algorithm IIR is evaluated through simulation. Copyright (C) 2011 John Wiley & Sons, Ltd.

关键词： minimum output energy algorithm adaptive blind equalizer vestigial sideband IIR filter constant modulus algorithm

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Improving Semi-Blind Uplink Interference Suppression on Multicell Massive MIMO Systems: A Beamspace Approach

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IEICE TRANSACTIONS ON COMMUNICATIONS 2019年第8期E102B卷 1503-1511页

作者： Maruta, Kazuki Ahn, Chang-Jun Chiba Univ Grad Sch Engn Chiba 2638522 Japan

This paper improves our previously proposed semi-blind uplink interference suppression scheme for multicell multiuser massive MIMO systems by incorporating the beamspace approach. The constant modulus algorithm (CMA), a known blind adaptive array scheme, can fully exploit the degree of freedom (DoF) offered by massive antenna arrays to suppress inter-user interference (IUI) and inter-cell interference (ICI). Unfortunately, CMA wastes a lot of the benefit of DoF for null-steering even when the number of incoming signal is fewer than that of receiving antenna elements. Our new proposal introduces the beamspace method which degenerates the number of array input for CMA from element-space to beamspace. It can control DoF expended for subsequent interference suppression by CMA. Optimizing the array beamforming gain and null-steering ability, can further improve the output signal-to-interference and noise power ratio (SINR). Computer simulation confirmed that our new proposal reduced the required number of data symbols by 34.6%. In addition, the 5th percentile SINR was also improved by 14.3 dB.

关键词： massive MIMO multicell pilot contamination adaptive array constant modulus algorithm channel estimation decision feedback beamspace

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A study on blind adaptive receiver for DS-CDMA systems

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IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES 2000年第6期E83A卷 1168-1174页

作者： Woo, DH Yoon, TS Byun, YS Univ Inchon Dept Elect Engn Inchon South Korea

The multiple access causes an interference problem in the direct-sequence code-division multiple process systems. An efficient adaptive algorithm should be used to suppress this interference for the improvement of system performance. In this: paper, the new blind adaptive method is suggested using the constant modulus algorithm for the purpose of interference suppression. Simulation results show that the converged value of signal to interference ratio for the proposed method is approximately 6 [dB] larger than that of a conventional Blind-MOE receiver in the additive white Gaussian noise channel and channel with inter-symbol interference while the signal. to interference ratio improvement is almost 4 [dB] better in the Rayleigh Fading channel. The suggested method is also robust to the new user interference resulting the nearly 3 [dB] improvement of the SIR value comparing with the conventional receiver. Based on these results, it is shown that the BER of the proposed receiver is lower than that of any other conventional receiver. Therefore. using the newly suggested method, the considerable performance improvement can be obtained for the DS-CDMA systems.

关键词： DS-CDMA blind Interference suppression constant modulus algorithm adaptive algorithm

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