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Detection Method of Same Spreading Code Signals by multimodulus algorithm

IEICE TRANSACTIONS ON COMMUNICATIONS 2014年第4期E97B卷 807-816页

作者： Umebayashi, Kenta Murata, Genichiro Suzuki, Yasuo Tokyo Univ Agr & Technol Grad Sch Engn Koganei Tokyo 1848588 Japan

This paper investigates a signal detection method with a RAKE combiner for the case wherein the receiving signals use the same spreading code. In the case where multiple user interference with the same spreading code (MUI-SC) occurs, blind channel estimation is difficult and as far as we know has not been investigated. To tackle the issue of MUI-SC, we propose two blind channel estimation methods based on the multi-modulus algorithm (MMA), i.e., MMA-IQ and MMA-I methods. When a one dimensional modulation scheme, such as differential binary phase-shift keying (DBPSK), is used, the output of the MMA-IQ channel estimation method can, under MUI-SC, have two states. The first state is that the channel estimate corresponds to a channel response for one of the received signals, and the second state is that the channel estimate corresponds to combined channel responses for two of the received signals. This is because the MMA-IQ uses two degrees of freedom (both axes in the IQ-plane), however one DBPSK signal uses only one degree of freedom. In the case of the second state, it is possible to detect two signals/packets at once. However, in the MMA-IQ, the receiver has to recognize the state of the channel estimate before the signal detection, thus we also propose a state recognition method. In the MMA-I channel estimation method, only the I-axis is used thus the channel estimate always corresponds the case with one signal. Numerical results show that the average number of detected packets of the MMA-IQ is more than that of the MMA-I in high signal-to-noise power ratio case. In addition, several aspects of the MMA-1 and MMA-IQ based RAKE signal detection methods are shown.

关键词： CDMA RAKE combiner multiple user interference multimodulus algorithm

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Hybrid time-frequency domain equalization based on sign-sign joint decision multimodulus algorithm for 6 x 6 mode division multiplexing system

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OPTICS COMMUNICATIONS 2018年 409卷 123-130页

作者： Li, Jiao Hu, Guijun Gong, Caili Li, Li Jilin Univ Coll Commun Engn 5372 Nanhu Rd Changchun 130012 Jilin Peoples R China

In this paper, we propose a hybrid time-frequency domain sign-sign joint decision multimodulus algorithm (Hybrid-SJDMMA) for mode-demultiplexing in a 6 x 6 mode division multiplexing (MDM) system with highorder QAM modulation. The equalization performance of Hybrid-SJDMMA was evaluated and compared with the frequency domain multimodulus algorithm (FD-MMA) and the hybrid time-frequency domain signsign multimodulus algorithm (Hybrid-SMMA). Simulation results revealed that Hybrid-SJDMMA exhibits a significantly lower computational complexity than FD-MMA, and its convergence speed is similar to that of FD-MMA. Additionally, the bit-error-rate performance of Hybrid-SJDMMA was obviously better than FD-MMA and Hybrid-SMMA for 16 QAM and 64 QAM. (C) 2017 Elsevier B.V. All rights reserved.

关键词： Mode division multiplexing Hybrid time-frequency domain equalization Sign-sign error Decision-directed multimodulus algorithm

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A momentum fractional order multimodulus blind equalization algorithm

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DIGITAL SIGNAL PROCESSING 2022年第0期126卷

作者： Yang, Jiali Zhang, Qiang Luo, Yongjiang Jiang, Kaiyu Xidian Univ Sch Mechanoelect Engn 2 South Taibai Rd Xian 710071 Shaanxi Peoples R China Xidian Univ Sch Elect Engn 2 South Taibai Rd Xian 710071 Shaanxi Peoples R China

The multimodulus algorithm (MMA) is widely used to suppress inter-symbols interference (ISI) in communication systems because of its advantages that it can complete blind equalization and carrier phase recovery simultaneously. However, the slow convergence speed of MMA causes the equalizer to be unable to eliminate ISI effectively, which deteriorate the communication quality of the system. For that, we first present a momentum fractional order MMA (MFOMMA) to improve the performance of MMA for blind equalization in this paper. By optimizing MMA with the momentum term and the fractional order gradient information of the cost function, the proposed algorithm can get better ISI suppression performance. Then, the convergence performance of MFOMMA is analyzed to reveal the relationship between algorithm parameters and equalization ability. Moreover, in order to further enhance the ISI elimination capability of MFOMMA, we develop a variable fractional order scheme, which guarantee that the algorithm not only obtains a faster convergence speed but also a lower residual ISI. Finally, the effectiveness and superiorities of the proposed algorithm are demonstrated by some simulation experiments. (C) 2022 Elsevier Inc. All rights reserved.

关键词： Blind equalization multimodulus algorithm Fractional order gradient Momentum Variable fractional order

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Steady-state performance of multimodulus blind equalizers

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SIGNAL PROCESSING 2015年 108卷 509-520页

作者： Azim, Ali W. Abrar, Shafayat Zerguine, Azzedine Nandi, Asoke K. Inst Polytech Grenoble St Martin Heres F-38400 Grenoble France COMSATS Inst Informat Technol Islamabad 44000 Pakistan King Fahd Univ Petr & Minerals Dhahran 31261 Saudi Arabia Brunel Univ Uxbridge UB8 3PH Middx England

multimodulus algorithms (MMA) based adaptive blind equalizers mitigate inter-symbol interference in a digital communication system by minimizing dispersion in the quadrature components of the equalized sequence in a decoupled manner, i.e., the in-phase and quadrature components of the equalized sequence are used to minimize dispersion in the respective components of the received signal. These unsupervised equalizers are mostly incorporated in bandwidth-efficient digital receivers (wired, wireless or optical) which rely on quadrature amplitude modulation based signaling. These equalizers are equipped with nonlinear error-functions in their update expressions which makes it a challenging task to evaluate analytically their steady-state performance. However, exploiting variance relation theorem, researchers have recently been able to report approximate expressions for steady-state excess mean square error (EMSE) of such equalizers for noiseless but interfering environment. In this work, in contrast to existing results, we present exact steady-state tracking analysis of two multimodulus equalizers in a non-stationary environment. Specifically, we evaluate expressions for steady-state EMSE of two equalizers, namely the MMA2-2 and the beta MMA. The accuracy of the derived analytical results is validated using different set experiments and found in close agreement. (C) 2014 Elsevier B.V. All rights reserved.

关键词： Blind equalization multimodulus algorithm Mean square error Tracking performance Steady-state analysis Quadrature amplitude modulation Energy conservation theorem Variance relation

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Stabilised blind interference suppression of constant modulus-based adaptive array over Rayleigh fading channels by initial antenna selection

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IET MICROWAVES ANTENNAS & PROPAGATION 2019年第11期13卷 1876-1882页

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

This article proposes an initial antenna selection for constant modulus-based blind interference suppression algorithms to stabilise their prominent interference suppression performance. Constant modulus algorithm (CMA) is a well-known blind adaptive array scheme, but it cannot suppress the interference when signal-to-interference power ratio (SIR) is <0 dB. It faces strong limits on their applicable region over Rayleigh fading channels where instantaneous channel gain fluctuates over 10 dB range. Even if the expected desired signal strength is larger than interference, CMA may still miscapture the interference and incorrectly suppress the desired signal. The authors' proposal is simplified approach to select the antenna element whose reception power is maximal. Certain antenna element can be expected to capture the desired signal precisely under the condition where SIR is statistically positive, so that the CMA processor can utilise it as an initial input. This condition will be ensured by increasing antenna element number, supported by the trends that base station antenna elements are going massive. Computer simulations verifies improved interference suppression performance provided by the proposed scheme. This article also verified applicability for multi-modulus algorithm to accommodate M-ary quadrature amplitude modulation (QAM) use.

关键词： Rayleigh channels radiofrequency interference quadrature amplitude modulation interference suppression adaptive antenna arrays radio reception initial antenna selection constant modulus-based blind interference suppression algorithms constant modulus algorithm CMA signal-to-interference power ratio Rayleigh fading channels base station antenna elements multimodulus algorithm stabilised blind interference suppression interference suppression performance instantaneous channel gain fluctuation constant modulus-based adaptive array scheme SIR M-ary quadrature amplitude modulation QAM

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Blind Source Separation algorithms Using Hyperbolic and Givens Rotations for High-Order QAM Constellations

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IEEE TRANSACTIONS ON SIGNAL PROCESSING 2018年第7期66卷 1802-1816页

作者： Shah, Syed Awais Wahab Abed-Meraim, Karim Al-Naffouri, Tareq Y. King Fahd Univ Petr & Minerals Dept Elect Engn Dhahran 34463 Saudi Arabia Qatar Univ Dept Elect Engn Doha 2713 Qatar Univ Orleans PRISME Lab F-45100 Orleans France King Abdullah Univ Sci & Technol Dept Elect Engn Thuwal 23955 Saudi Arabia

This paper addresses the problem of blind demixing of instantaneous mixtures in a multiple-input multiple-output communication system. The main objective is to present efficient blind source separation (BSS) algorithms dedicated to moderate or high-order quadratic-amplitude modulation (QAM) constellations. Four new iterative batch, BSS algorithms are presented dealing with the multimodulus (MM) and alphabet matched (AM) criteria. For the optimization of these cost functions, iterative methods of Givens and hyperbolic rotations are used. A prewhitening operation is also utilized to reduce the complexity of design problem. It is noticed that the designed algorithms using Givens rotations give satisfactory performance only for a large number of samples. However, for a small number of samples, the algorithms designed by combining both Givens and hyperbolic rotations compensate for the ill-whitening that occurs in this case and thus improves the performance. Two algorithms dealing with the MM criterion are presented for moderate-order QAM signals such as 16-QAM. The other two dealing with the AM criterion are presented for high-order QAM signals. These methods are finally compared with the state-of-the-art batch BSS algorithms in terms of signal-to-interference and noise ratio, symbol error rate, and convergence rate. Simulation results show that the proposed methods outperform the contemporary batch BSS algorithms.

关键词： Alphabet matched algorithm blind source separation constant modulus algorithm constellation matched error Givens and hyperbolic rotations multimodulus algorithm

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Space-Time Semi-Blind Equalizer for Dispersive QAM MIMO System Based on Modified Newton Method

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2014年第6期13卷 3244-3256页

作者： Li, Jin Feng, Da-Zheng Zheng, Wei Xing Xidian Univ Natl Lab Radar Signal Proc Xian 710071 Peoples R China Univ Western Sydney Sch Comp Engn & Math Penrith NSW 2751 Australia

This paper proposes a space-time semi-blind equalizer (ST-SBE) for dispersive multiple-input multiple-output (MIMO) communication systems that employ high throughput quadrature amplitude modulation (QAM) signals. A novel cost function (CF) that integrates multimodulus algorithm (MMA) with soft decision-directed (SDD) scheme is established to efficiently obtain the weight vector associated with the ST-SBE. In the ST-SBE, a very short training sequence is used to provide a rough initial least squares estimate of the weight vector. An efficient modified Newton method (MNM) for minimizing the established cost function is proposed to fast search the optimal weight vector. Very interestingly, we prove that the proposed MNM has the same quadratic order of convergence as Newton methods. In addition, the proposed MNM has much lower computational complexity than Newton methods. Simulation results are provided to demonstrate that the ST-SBE has better performances than the gradient-Newton (GN)-based concurrent constant modulus algorithm (CMA) with SDD scheme (GN-CMA+SDD).

关键词： Space-time semi-blind equalizer modified Newton method constant modulus algorithm multimodulus algorithm soft decision-directed scheme

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SVR Based Blind Signal Recovery for Convolutive MIMO Systems With High-Order QAM Signals

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IEEE ACCESS 2019年 7卷 23249-23260页

作者： Sun, Chao Yang, Ling Chen, Li Zhang, Jiliang Lanzhou Univ Sch Informat Sci & Engn Lanzhou 730000 Gansu Peoples R China

This paper addresses the blind signal recovery for convolutive multiple-input multiple-output systems with high-order quadrature amplitude modulation (QAM) signals. First, a family of batch blind recovery algorithms is proposed. Concretely, they introduce the error function of multimodulus algorithm and the cross-correlation among different equalizer output vectors into the penalty term of the support vector regression (SVR) framework to recover all sources simultaneously. Then, the corresponding dual-mode blind recovery schemes are constructed to further decrease the interference. The new blind formulation through iterative re-weighted least square achieves low complexity optimization. The SVR framework, in essence, determines that the proposals perform better than the conventional methods in terms of data block size, total interference, and symbol error rate. Moreover, the excellent initialization provided by the first mode and the accurate error expression in the second mode ensure that the SVR-based dual-mode schemes work well with the high-order QAM signals. Finally, the efficiency of the proposals over the classical approaches is evaluated by simulations.

关键词： Convolutive MIMO systems high-order QAM signals blind equalization blind source separation support vector regression multimodulus algorithm

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Space-Time Blind Equalization of Dispersive MIMO Systems Driven by QAM Signals

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2018年第5期67卷 4136-4148页

作者： Li, Jin Feng, Da-Zheng Li, Bingbing Xidian Univ State Key Lab Integrated Serv Networks Xian 710071 Shaanxi Peoples R China Xidian Univ Natl Lab Radar Signal Proc Xian 710071 Shaanxi Peoples R China

This paper investigates space-time blind equalization (BE) of dispersive multiple-input multiple-output communication systems driven by high throughput quadrature amplitude modulation signals. Multistage processing is adopted to overcome the severe local convergence problem in BE. First, a good initial value for the equalizer is obtained by forcing one of the system inputs with desired delay to be recovered. Then, the fast multimodulus algorithm (MMA) is used to roughly equalize the communication system. After that, an improved MMA (IMMA) is developed to effectively search for a fine equalizer for the system. Moreover, the novel modified Newton method (MNM) proposed in our previous work is employed to fast optimize the MMA and IMMA cost functions, which significantly reduces the computational load. Furthermore, the proposed algorithm has an additional benefit that once a signal is recovered, its corresponding single-input multiple-output channel impulse response is estimated by the classical least squares methods. Then, the influence of the recovered signal to the original received signals is removed to avoid extracting this recovered signal repeatedly. The quadratic rate of convergence of the MNM is theoretically analyzed, and the good equalization performance of the IMMA is explained. Finally, simulation results are provided to illustrate the effectiveness of the proposed algorithm.

关键词： Blind equalization blind identification multimodulus algorithm modified Newton method QAM

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Performance analysis of a family of adaptive blind equalization algorithms for square-QAM

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DIGITAL SIGNAL PROCESSING 2016年 48卷 163-177页

作者： Azim, Ali W. Abrar, Shafayat Zerguine, Azzedine Nandi, Asoke K. Inst Natl Polytech Grenoble F-38400 St Martin Dheres France COMSATS Inst Informat Technol Wah Cantt 47040 Pakistan COMSATS Inst Informat Technol Islamabad 44000 Pakistan King Fahd Univ Petr & Minerals Dhahran 31261 Saudi Arabia Brunel Univ London Uxbridge UB8 3PH Middx England

multimodulus algorithms (MMA) based adaptive blind equalizers mitigate inter-symbol interference and recover carrier-phase in communication systems by minimizing dispersion in the in-phase and quadrature components of the received signal using the respective components of the equalized sequence in a decoupled manner. These equalizers are mostly incorporated in bandwidth-efficient digital receivers which rely on quadrature amplitude modulation (QAM) signaling. The nonlinearities in the update equations of these equalizers tend to lead to difficulties in the study of their steady-state performance. This paper presents originally the steady-state excess mean-square-error (EMSE) analysis of different members of multimodulus equalizers MMAp-q in a non-stationary environment using energy conservation arguments, and thus bypassing the need for working directly with the weight error covariance matrix. In doing so, the exact and approximate expressions for the steady-state mean-square-error of several MMA based blind equalization algorithms are derived, including MMA2-2, MMA2-1, MMA1-2, and MMA1-1. The accuracy of the derived analytical results is validated using Monte-Carlo experiments and found to be in close agreement. (C) 2015 The Authors. Published by Elsevier Inc.

关键词： multimodulus algorithm Blind equalization Adaptive equalizers Steady-state analysis Receiver design Convergence analysis

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