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针对深衰落稀疏多径信道下多进制相移键控(Multiple Phase Shift Keying,MPSK)信号的盲均衡问题,提出了一种l0-范数约束的分数间隔稀疏自适应双模式盲均衡算法.该算法借鉴传统的分数间隔双模式盲均衡算法思想,结合稀疏自适应滤波理论,首先利用l0-范数对均衡器抽头系数进行稀疏性约束,构造出一种l0-范数约束的分数间隔双模式最小均方误差代价函数,然后依据梯度下降法推导出盲均衡器抽头系数更新公式,并对迭代步长进行归一化和比例系数化.理论分析和仿真实验表明,与基于门限稀疏化的盲均衡算法、基于分数阶范数的盲均衡算法及分数间隔双模式盲均衡算法相比,本文所提算法在保证较快收敛速度的前提下,能有效降低剩余符号间干扰.本文设计的盲均衡算法为水声通信系统中接收方恢复出发送信号,提供了一种快速有效的方法. 相似文献
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针对稀疏多径信道下MPSK信号的快速盲均衡问题,提出了一种l0-范数约束的递归最小二乘常模盲均衡算法.该算法借鉴传统的递归最小二乘常模盲均衡算法思想,结合稀疏自适应滤波理论,首先利用l0-范数对均衡器抽头系数进行稀疏性约束,构造出一种l0-范数约束的加权最小二乘误差代价函数,然后依据递归最小二乘算法推导出均衡器抽头系数更新公式.该算法发挥递归最小二乘常模算法收敛速度快的优势,并对幅度极小系数附加零点吸引调整,从而实现不同幅度抽头系数的快速收敛.理论分析与仿真结果表明,与现有算法相比,该算法在保证较低剩余符号间干扰的前提下,能有效提高均衡器的收敛速度. 相似文献
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针对较低信噪比下的深衰落稀疏多径信道,提出了一种基于信道缩短的自适应稀疏均衡改进算法。该算法采用前置分数间隔信道缩短均衡器与后置自适应稀疏均衡器级联的均衡器结构,其中,首先利用短训练序列设计基于最小均方误差准则的前置均衡器,前置均衡器与稀疏多径信道级联后得到能量集中于较短时间区域且分布稀疏的等效信道,使得原始信道的深衰落畸变得到部分有效补偿;然后采用能实现稀疏信号重构的随机梯度追踪算法调整后置自适应均衡器的抽头系数,后置均衡器用于消除等效信道的剩余符号间干扰。仿真结果表明,与传统的单级分数间隔自适应均衡器相比,该算法具有收敛速度快和运算复杂度低的优点。 相似文献
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There are serious intersymbol interference (ISI) and signal attenuation in wireless ultraviolet communication system.Aiming at this problem,an improved constant modulus fractionally spaced equalizer (CMA-FSE) based on signal-to-noise (SNR) estimation was proposed.The algorithm combined the fractionally spaced equalizer (FSE) and constant modulus algorithm (CMA) for blind equalization of wireless ultraviolet channels.The input SNR was measured by the mean square value of the received signal,and it was used to determine the best iterative step to ensure the convergence of the equalization algorithm.Simulation results show that the improved CMA-FSE algorithm can converge rapidly under various SNR,and it can effectively suppress ISI and improve the BER performance of the system.Compared with the existing algorithms,the improved algorithm is more useful in channel tracking and noise suppression. 相似文献
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基于复指数基扩展模型(Complex exponential basis expansion model, CE-BEM),利用信道的稀疏特性和发送信号的常模特性(Constant Modulus, CM),提出水声稀疏时变(Time-variant, TV)SIMO信道盲均衡算法。首先采用l0-范数约束的比例系数归一化最小均方误差常模算法对等效信道矩阵的稀疏时不变部分进行均衡,然后采用基频率估计算法估计基频率并对多普勒频移进行补偿,最后对恢复信号中存在的相偏进行估计补偿。仿真实验结果表明,本文算法提高了均衡器的收敛速度,降低了剩余码间干扰。 相似文献
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稀疏水声信道判决反馈盲均衡算法研究 总被引:2,自引:0,他引:2
针对高速水声通信中信道的稀疏特性,提出了一种基于常数模准则的稀疏水声信道判决反馈盲均衡算法。该算法将改进的常数模算法与一种变化的判决反馈均衡器结构(部分反馈均衡器)有机结合,利用水声信道的稀疏特性,不但很好地实现了稀疏水声信道的盲均衡,而且简化了计算,易于算法的硬件实现。用典型稀疏水声信道进行了计算机仿真。结果表明,该算法性能稳定,计算量小,稳态均方误差低,整体性能与基于自适应LMS的稀疏迭代算法接近。该研究为高速水声通信中稀疏信道的均衡提供了一种可实现的方法。 相似文献
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Monika Pinchas 《Signal, Image and Video Processing》2013,7(1):67-74
In this paper, I propose for the noisy, real, and two independent quadrature carrier case, an approximated closed-form expression for the achievable minimum mean square error (MSE) performance obtained by blind equalizers where the error that is fed into the adaptive mechanism which updates the equalizer’s taps can be expressed as a polynomial function of the equalized output of order three like in Godard’s algorithm. The proposed closed-form expression for the achievable MSE is based on the step-size parameter, on the equalizer’s tap length, on the channel power, on the signal to noise ratio (SNR), on the nature of the chosen equalizer, and on the input signal statistics. Since the channel power is measurable or can be calculated if the channel coefficients are given, there is no need anymore to carry out any simulation with various step-size parameters, different values for the signal to noise ratio (SNR) and equalizer’s tap length for a given equalization method, and input signal statistics in order to find the MSE performance in the convergence state. 相似文献
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MIMO通信系统中,随着数据率的不断提高,信道呈现出频率选择性,尤其是多径干扰和多用户干扰将会使接收端产生严重的码间干扰,而盲均衡技术能有效消除码间干扰。文中重点研究了基于MIMO通信系统的恒模盲均衡算法,并在此基础上提出了基于Sigmoid函数的变步长CMA均衡算法。该算法与传统方法的不同之处在于,该改进算法中所使用的步长因子能跟随均衡器的收敛情况自适应调整,且计算仿真结果表明,改进后的CMA算法能有效抑制噪声,且收敛速度快。 相似文献
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针对单输入多输出(Single-Input-Multiple-Output, SIMO)模型提出一种完全不需要信道阶数估计的直接盲均衡算法。文章利用接收数据的截短协方差矩阵和信号子空间的关系设计一种零延迟均衡器,并通过信道矩阵和均衡器系数的合响应特性克服了算法相位偏转的问题,最后得到一种对信道阶数估计鲁棒并且没有相位偏转的盲均衡算法。该算法不同于一般子空间类算法,不需要直接对接收信号的协方差矩阵进行信号子空间和噪声子空间的分解,因此对信道阶数估计具有很强的鲁棒性。文章给出了算法的Batch实现过程,同时为更好适应一般时变信道环境和实现实时处理的要求,通过递归迭代得到算法的自适应实现过程。仿真实验表明该算法几乎不受信道阶数过估计或欠估计的影响,同时该算法具有良好的均方误差(Mean Square Error, MSE)和误符号率SER(Symbol Error Rate, SER)性能,并且具有很快的收敛速度。 相似文献
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文章对具有DFE结构的盲均衡算法作了研究,在一种修正常模算法(MCMA)代价函数中引入泄漏因子,并将常模算法(CMA)和直接判决-最小均方误差算法(DD-LMS)同时应用到盲判决反馈均衡器的抽头更新中,得到一种适用范围广?均衡特性好?变步长的DD-LLMS MCMBDFE算法。该算法在均衡的同时能自动补偿由信道引起的相位误差,收敛速度快,收敛后剩余误差小,同时还能克服当均衡器长期没有持续输入激励时,LMS算法产生的抽头系数漂移问题。仿真结果表明DD-LLMS MCMBDFE算法是一种有效的盲判决反馈均衡算法。 相似文献
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Vembu S. Verdu S. Kennedy R.A. Sethares W. 《Signal Processing, IEEE Transactions on》1994,42(8):1952-1960
Existing blind adaptive equalizers that use nonconvex cost functions and stochastic gradient descent suffer from lack of global convergence to an equalizer setup that removes sufficient ISI when an FIR equalizer is used. The authors impose convexity on the cost function and anchoring of the equalizer away from the all-zero setup. They establish that there exists a globally convergent blind equalization strategy for 1D pulse amplitude modulation (PAM) systems with bounded input data (discrete or continuous) even when the equalizer is truncated. The resulting cost function is a constrained l1 norm of the joint impulse response of the channel and the equalizer. The results apply to arbitrary linear channels (provided there are no unit circle zeros) and apply regardless of the initial ISI (that is whether the eye is initially open or closed). They also show a globally convergent stochastic gradient scheme based on an implementable approximation of the l1 cost function 相似文献
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一种用于水声信道的稀疏权超指数迭代盲均衡算法研究 总被引:2,自引:0,他引:2
超指数算法的迭代算法便于跟踪时变信道,但是,其计算量与权长的平方成比例,不利于工程实现.该文利用水声信道的稀疏性,采用超指数算法的部分步骤,估计权向量并进行稀疏处理,初始化超指数迭代算法,不但减小了算法的计算量,而且加快了算法的收敛速度.计算机仿真证明了该方法的有效性. 相似文献
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针对前馈神经网络(FNN)盲均衡算法收敛速度慢、均方误差大的缺点,在分析FNN盲均衡算法和正交小波变换(OWT)理论的基础上,提出了基于正交小波变换的FNN盲均衡算法。该算法利用正交小波变换良好的去相关性,对FNN均衡器输入信号进行预处理后,降低了输入信号的自相关性,从而加快了收敛速度和减小了均方误差。水声信道盲均衡的仿真结果表明,该算法在收敛速度与均方误差方面的性能比FNN盲均衡算法优越。 相似文献
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Monika Pinchas 《Signal, Image and Video Processing》2012,6(2):325-340
In this paper, I propose for the noiseless, real and two independent quadrature carrier case some approximated conditions
on the step-size parameter, on the equalizer’s tap length and on the channel power, related to the nature of the chosen equalizer
and input signal statistics, for which a blind equalizer will not converge anymore. These conditions are valid for type of
blind equalizers where the error that is fed into the adaptive mechanism that updates the equalizer’s taps can be expressed
as a polynomial function of the equalized output of order three like in Godard’s algorithm. Since the channel power is measurable
or can be calculated if the channel coefficients are given, there is no need anymore to carry out any simulation with various
step-size parameters and equalizer’s tap length for a given equalization method and input signal statistics in order to find
the maximum step-size parameter for which the equalizer still converges. 相似文献
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基于严格∪性价值函数的DF结构的盲均衡方案 总被引:1,自引:1,他引:0
本文提出了一种Decision-Feedback.(DF)结构形式的盲均衡价值函数.证明了该价值函数对前向均衡器系数矢量C,反向均衡器系数矢量C和系统传输误差概率Pn,都是严格的∪函数.并且证明了该价值函数保证收敛到全局极小点.分析和计算机模拟结果显示,对于典型16QAM形式的输入信号,本文提出的方案具有低的计算复杂度和快的收敛速度。 相似文献