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Adaptive set membership constant modulus algorithm with a generalized sidelobe canceler based on dynamic bounds for beamforming

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SIGNAL PROCESSING 2014年 104卷 94-104页

作者： Cai, Yunlong de Lamare, Rodrigo C. Zhao, Minjian Zhejiang Univ Dept Informat Sci & Elect Engn Hangzhou 310027 Zhejiang Peoples R China Univ York Dept Elect Commun Res Grp York YO10 5DD N Yorkshire England CETUC PUC Rio BR-22453900 Rio De Janeiro Brazil

In this study, we propose an adaptive set membership constant modulus (SM-CM) algorithm with a generalized sidelobe canceler (GSC) structure for blind beamforming. We develop a stochastic gradient (SG) type algorithm based on the concept of SM filtering to facilitate an adaptive implementation. The filter weights are updated only if the constraint cannot be satisfied. In addition, we also propose an extension of two schemes of time-varying bounds for beamforming with a GSC structure where we incorporate parameter and interference dependency to characterize the environment, which improves the tracking performance of the proposed algorithm in dynamic scenarios. A convergence analysis of the proposed adaptive SM filtering technique was performed. The simulation results showed that the proposed adaptive SM-CM-GSC algorithm with dynamic bounds delivered superior performance compared with previously reported methods and at a reduced update rate. (C) 2014 Elsevier B.V. All rights reserved.

关键词： Adaptive beamforming constant modulus algorithm Generalized sidelobe canceler Interference suppression Set-membership filtering

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PAPR reduction using constant modulus algorithm and IDCT in MIMO-OFDM Networks 3

PAPR reduction using Constant Modulus Algorithm and IDCT in ...

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3rd International Conference on Eco-Friendly Computing and Communication Systems (ICECCS)

作者： Sujatha, S. Dananjayan, P. Pondicherry Engn Coll Dept ECE Pondicherry India

ISBN: (纸本)9781479970025

In MIMO-OFDM networks, the main drawback includes the large peak-to-average power ratio (PAPR) of the transmitter's output signal on different antennas. In order to overcome this issue, PAPR is reduced using IDCT in this paper. In this technique, Inverse Discrete Cosine Transform (IDCT) along with constant modulus algorithm is used to reduce the PAPR in MIMO-OFDM networks. It involves two methods, first the time domain signal from the Resource Block is combined linearly using pre-coding weights which is transparent to the receiver side. Then the precoding weights are modified to decrease the modulus variations of the resulting signal, which leads to the reduction of PAPR in MIMO OFDM. By simulation results, it is observed that the proposed technique reduces PAPR.

关键词： MIMO-OFDM PAPR constant modulus algorithm IDCT

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A class of widely linear quaternion blind equalisation algorithms

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SIGNAL PROCESSING 2025年 230卷

作者： Zhang, Min Xiang, Min Zheng, Zhi Talebi, Sayed Pouria Mandic, Danilo P. Beihang Univ Sch Instrumentat & Optoelect Engn Beijing Peoples R China Beihang Univ Hangzhou Innovat Inst Hangzhou Peoples R China Natl Inst Extremely Weak Magnet Field Infrastruct Hangzhou Peoples R China Univ Elect Sci & Technol China Sch Informat & Commun Engn Chengdu Peoples R China Univ Roehampton Comp Sci Dept London England Imperial Coll London Dept Elect & Elect Engn London England

Quaternion adaptive filters have been applied extensively to model three- and four-dimensional phenomena in signal processing, but most of them require a known reference signal. In this paper, a class of widely linear quaternion-valued Godard (WL-QGodard) algorithms is derived, which include the widely linear quaternionvalued constant modulus algorithm (WL-QCMA) as a special case. The derived filter allows for signal recovery operations in the absence of reference signals to be performed directly in the quaternion domain, eliminating the need for transformation to real-valued vector algebras and preserving the advantages of the quaternion division algebra. Compared to state-of-the-art quaternion blind equalisation algorithms, the proposed algorithm models the signal transmission channel using the widely linear quaternion framework, which has more extensive applicability and can better represent real-world scenarios. Furthermore, aided by GHR calculus, for the first time, we present a performance analysis framework for the QGodard algorithm and WL-QGodard algorithms, which depicts the dynamic and their static convergence behaviours, overcoming the challenges posed by the noncommutative quaternion algebra and non-isomorphism between the quaternion equalisers and real-valued equalisers. Finally, simulation results over physically meaningful wireless communication signals indicate the effectiveness and superiority of the proposed WL-QCMA, and the validity of the theoretical performance analysis.

关键词： Quaternion blind equalisation Godard algorithm constant modulus algorithm Static convergence behaviour Dynamic convergence behaviour Widely linear model

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Modified constant modulus algorithm With Polarization Demultiplexing in Stokes Space in Optical Coherent Receiver

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JOURNAL OF LIGHTWAVE TECHNOLOGY 2013年第19期31卷 3203-3209页

作者： Yu, Zhenming Yi, Xingwen Zhang, Jing Deng, Mingliang Zhang, Hongbo Qiu, Kun Univ Elect Sci & Technol China Key Lab Opt Fiber Sensing & Commun Minist Educ Chengdu 611731 Peoples R China

We propose a modified method of constant modulus algorithm (CMA) based on polarization demultiplexing in Stokes space for polarization demultiplexing (SS-PDM) in optical coherent receivers. SS-PDM can tolerate chromatic dispersion (CD) and polarization-dependent loss (PDL), but is sensitive to PMD. On the other hand, the CMA with high-order FIR filters could compensate for polarization-mode-dispersion (PMD) effectively, but suffers from the singularity problem which results from PDL. Therefore, we use the polarization rotation matrix estimated by SS-PDM to set the initial center taps of the CMA. The singularity problem of the CMA is avoided effectively in a much wider range of PDL and its convergence speed is also improved. We demonstrate this modified CMA in a simulation of 100-Gbit/s PDM-QPSK with PDL of 1, 3, and 5 dB, respectively. PDL is emulated by attenuating one polarization tributary before polarization multiplexing and the interaction between PDL and PMD is ignored. The singularity problem disappears as expected. Because the tolerance of PDL is affected by DGD, we further investigate the PDL tolerance under different DGD. Finally, we conduct the simulation of 100-Gbit/s PDM-QPSK with PDL of 3 dB over 3000 km SSMF and 4000 km SSMF separately. The convergence speed accelerates indeed compared with that of the conventional CMA.

关键词： Coherent detection constant modulus algorithm polarization demultiplexing polarization-dependent loss polarization-mode-dispersion Stokes space

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Wireless sensing network transmission system with improved constant modulus algorithm

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EURASIP JOURNAL ON WIRELESS COMMUNICATIONS AND NETWORKING 2013年第1期2013卷 1-8页

作者： Sung, Wen-Tsai Natl Chin Yi Univ Technol Dept Elect Engn Taichung 41170 Taiwan

To solve the instant signal convergence of wireless sensing network transmission system, this study proposes an improved constant modulus algorithm. The improved constant modulus algorithm can quickly find the convergent direction by adding error functions and learning rates based on the reserved original cost functions. After processed by a matched filter, the received consecutive time signal can be sampled in accordance with symbol interval or fraction interval, so that signal channels can be estimated or balanced. At last, this study verifies the raised method with quadrature amplitude modulation on wireless sensing network transmission system and improved constant modulus algorithm experiments which show that the learning rates and the performances of balancers are improved.

关键词： Wireless sensor network Transmission system constant modulus algorithm 4QAM

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Polarization demultiplexing by recursive least squares constant modulus algorithm based on QR decomposition

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OPTICS AND LASER TECHNOLOGY 2013年 49卷 251-255页

作者： Zhao Ling Wang Yeling Hu Guijun Cui Yunpeng Shi Jian Li Li Jilin Univ Dept Opt Commun Coll Commun Engn Changchun 130012 Peoples R China Jilin Univ Hosp 1 Changchun 130021 Peoples R China

Recursive least squares constant modulus algorithm based on QR decomposition (QR-RLS-CMA) is first proposed as the polarization demultiplexing method. We compare its performance with the stochastic gradient descent constant modulus algorithm (SGD-CMA) and the recursive least squares constant modulus algorithm (RLS-CMA) in a polarization-division-multiplexing system with coherent detection. It is demonstrated that QR-RLS-CMA is an efficient demultiplexing algorithm which can avoid the problem of step-length choice in SGD-CMA. Meanwhile, it also has better symbol error rate (SER) performance and more stable convergence property. (C) 2013 Elsevier Ltd. All rights reserved.

关键词： Optical fiber communication Polarization-division-multiplexing constant modulus algorithm

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Blind and Semi-Blind Channel Estimation/Equalization for Poisson Channels in Optical Wireless Scattering Communication Systems

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2022年第8期21卷 5930-5946页

作者： Liu, Beiyuan Gong, Chen Cheng, Julian Xu, Zhengyuan Liu, Jiajia Northwestern Polytech Univ Natl Engn Lab Integrated Aerosp Ground Ocean Big Xian 710072 Shaanxi Peoples R China Univ Sci & Technol China Chinese Acad Sci Key Lab Wireless Opt Commun Hefei 230027 Anhui Peoples R China Univ British Columbia Sch Engn Kelowna BC V1V 1V7 Canada

The communication systems for Poisson channels require long pilot for channel estimation and may result in large percentage of overhead due to the signal-dependent noise of Poisson-distributed signal, i.e., both signal part and noise part experience random processes. In this paper, both blind and semi-blind channel estimation methods are studied to shorten the overhead and increase the transmission efficiency for Poisson channels. First, fractionally spaced equalizers are proposed based on modified constant modulus algorithm (CMA) and subspace (SS). Second, a data-aided iterative channel estimation (ICE) is designed and analyzed in terms of its asymptotic unbiasedness and convergence. The proposed methods are evaluated based on both a constant channel scenario and a varying channel scenario. Numerical simulation results show that the modified CMA has the worst bit-error rate performance but requires the lowest computational complexity. Besides, both SS based channel estimation and ICE have negligible overhead and comparable bit-error rate performances with respect to the conventional periodic pilot based channel estimation having 50% overhead.

关键词： Channel estimation Blind equalizers Estimation Wireless communication Modulation Signal detection Optical scattering Blind channel estimation constant modulus algorithm data-aided iterative channel estimation semi-blind channel estimation subspace based channel estimation poisson channel

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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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Polarization Tracking in the Presence of PDL and Fast Temporal Drift

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JOURNAL OF LIGHTWAVE TECHNOLOGY 2022年第19期40卷 6408-6416页

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

In this paper, we analyze the effectiveness of polarization tracking algorithms in optical transmission systems suffering from fast state of polarization (SOP) rotations and polarization-dependent loss (PDL). While most of the gradient descent (GD)-based algorithms in the literature may require step size adjustment when the channel condition changes, we propose tracking algorithms that can perform similarly or better without parameter tuning. Numerical simulation results show higher robustness of the proposed algorithms to SOP and PDL drift compared to GD-based algorithms, making them promising candidates to be used in aerial fiber links where the SOP can potentially drift rapidly, and therefore becomes challenging to track.

关键词： Signal processing algorithms Channel estimation Symbols Optical fiber dispersion Optical polarization Optical fiber amplifiers Optical fiber couplers constant modulus algorithm hybrid algorithm least square algorithm polarization-dependent loss polarization tracking state of polarization

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Momentum factor constant modulus algorithm And Theory

Momentum factor Constant Modulus Algorithm And Theory

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International Conference on Information Technology and Management Innovation (ICITMI2012)

作者： Yang, Heng Wang, Jing Guan, Jing Lu, Wei Yunnan Univ Sch Informat Sci & Engn Kunming 650091 Yunnan Peoples R China 750 Test Range CSIC Kunming 650032 Yunnan Peoples R China

ISBN: (纸本)9783037855744

The traditional constant modulus algorithm (CMA) has the disadvantage of slow convergence in blind equalization algorithm. This paper studied one improved algorithm based on momentum factor constant modulus algorithm(MCMA) to solve this problem, momentum factor was added to the weight vector iteration formula of CMA to improve the convergence speed. theoretical analysis and simulation showed that: in the case of the same equalization effect, the MCMA converges faster than the traditional constant modulus algorithm, and also different momentum factors have different convergence effects. The larger the momentum factor, the better convergence effect in the defined domain of the momentum factor.

关键词： Blind equalization Momentum factor constant modulus algorithm Error function

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