基于组合代价函数的双模式盲均衡新算法

以常数模和判决引导准则设计的双模式盲均衡算法可显著提高均衡性能,目前已有双模式盲均衡算法均需设置切换参数且切换参数选择和设定缺乏理论依据.为解决双模式盲均衡算法中切换参数难以确定的问题,提出来一种组合代价函数的双模式盲均衡新算法.利用常数模和判决引导准则通过加权设计代价函数,在盲均衡器更新过程中自适应调节权值实现算法由常数模算法向判决引导算法的切换,避免了在双模式算法中设计切换参数,提高了算法的泛化性能.为克服常数模算法相位盲的缺点,在虚实分开改进的常数模算法基础上优化组合代价函数以及盲均衡器更新算法的设计,进一步提高了算法收敛性能.仿真结果证明,组合代价函数双模式盲均衡新算法可充分发挥常数模算法和判决引导算法的优点,具有更快的收敛速度和更小的稳态剩余误差.     

用于高阶QAM系统的ASSDD盲均衡算法

本文给出了一种基于无监督高斯簇模型的自适应变步长软判决引导（ＡＳＳＤＤ）盲均衡算法。为了保证算法收敛,由一种Ｇｏｄａｒｄ 类算法来控制均衡算法,使之运行在“Ｓｔｏｐ－ａｎｄ－Ｇｏ”模式。为了获得较快的收敛速度,当均衡算法处于“Ｓｔｏｐ”状态时,使之切换到一种Ｇｏｄａｒｄ 类算法。采用自适应变步长来达到有效地跟踪均衡器输出的卷积噪声的方差的目的。仿真结果表明,这种算法针对高阶ＱＡＭ 信号是非常有效的     

几种适用于水声信道的常模类盲均衡算法研究

对比研究了3种常模类盲均衡算法在水声信道均衡中的收敛性能，这些算法包括传统的常数模算法、归一化常数模算法和解相关常数模算法。通过仿真对各算法性能进行了分析。仿真结果表明，在算法剩余均方误差非常接近的情况下，解相关常数模算法和归一化常数模算法快于传统的常数模算法。     

一种基于切换步长的加权多模盲均衡算法

研究了常数模算法、多模算法、加权多模算法,并分析了各个算法的优缺点。针对加权多模盲均衡算法稳态误差小,但收敛速度慢的缺点,提出了一种基于切换步长的加权多模算法,最后对各算法在复信道环境下进行了仿真。结果表明,改进算法不受相位偏移的影响,而且在稳态误差基本不变的情况下,加快收敛速度。     

基于正交小波变换的变步长盲均衡算法研究

针对常数模算法(CMA)剩余误差大与收敛速度慢的问题,将变步长思想和正交小波变换引入到常数模盲均衡算法中,提出了基于正交小波变换的指数型变步长常数模盲均衡算法(WT-VCMA)。水声信道仿真结果表明:与基于剩余误差的指数型变步长常数模盲均衡算法(VCMA)及常规常数模算法(CMA)相比,新算法具有更快的收敛速度和更小的剩余误差。     

一种基于CMA和DDLMS算法的双模式盲均衡算法

为进一步改进盲均衡算法收敛速度慢、稳态误差大、计算复杂度高等问题,提出一种切换模式和加权模式联合CMA(Constant Modulus Algorithm)+DDLMS(Direct Decision Least Mean Square)双模式盲均衡算法.综合切换双模式盲均衡算法和加权双模式盲均衡算法的优缺点,对切换、加权模式联合的CMA+DDLMS双模式盲均衡算法进行仿真.在不同信噪比条件下,对CMA算法、MCMA(Modified CMA)算法、DDLMS算法和CMA+DDLMS双模式盲均衡算法进行仿真,结果表明,所提算法收敛速度快,约为600个符号;稳态误差小,约为0.1;误码率小,在信噪比为25 dB时,误码率约为10-6.该算法可广泛应用于无线通信、光通信、声呐和雷达等众多领域.     

变步长常数模盲均衡算法研究

为了进一步提高CMA盲均衡算法的收敛速度和均衡性能,研究了一种变步长常数模盲均衡算法.常数模盲均衡算法中,步长参数直接影响算法的收敛速度和均衡性能,合理的选择步长参数不仅能够避免算法发散或收敛过慢,并且适时调整步长参数可以避免算法陷入局部极小值.高阶均方误差直接反映算法的收敛状态,所以可以利用高阶均方误差作为步长参数的调整因子.计算机仿真表明以高阶均方误差作为步长参数调整因子使常数模盲均衡算法具有了更快的收敛速度和更好的均衡效果.     

一种快速收敛的水声信道分数间隔盲均衡算法

为了加快常数模盲均衡算法(CMA)的收敛速度并降低剩余均方误差,提出了一种快速收敛的分数间隔常数模算法。新算法采用T/2分数间隔均衡器,针对水声通信中常用的BPSK信号,设计了一个新的误差函数,取代常数模算法中的误差函数。最后,采用浅海水声信道进行了仿真,结果表明,新算法性能稳定;收敛速度高于常数模算法和分数间隔常数模算法;剩余均方误差与分数间隔常数模算法处于同一水平。     

一种适用于水声信道的双模式盲均衡算法

针对常数模算法(CMA)和符号回归常数模算法(SR-CMA)存在的问题,提出了一种基于分数间隔的双模式常数模(DCMA)盲均衡算法。该算法将常规CMA算法和SR-CMA算法相结合,通过判决圆环完成两种算法之间的切换,根据信噪比确定判决圆环的边界。仿真结果表明,DCMA 的计算效率高于CMA,算法稳定性优于SR- CMA,而且可以获得较低的剩余均方误差。     

基于T/4分数间隔采样双模式盲均衡算法的研究

本文针对恒模算法(CMA)收敛速度较慢、收敛后均方误差较大的缺点,提出一种新的双模式盲均衡算法。先采用T/4分数间隔采样的盲均衡算法,由于采用了过采样技术,避免了因欠采样引起的频谱混叠,然后在算法收敛后切换到判决引导(DD-LMS)算法,减少误码率。计算机仿真表明,本文提出的新算法有较快的收敛速度、较小的稳态误差和较低的误码率。     

基于数据重用的集员滤波拟仿射投影盲均衡算法

传统常模盲均衡算法应用广泛但是其收敛速率很慢.为了满足在短突发数据条件下的信道盲均衡,提出一种基于数据重用的集员滤波拟仿射投影盲均衡算法.该算法将仿射投影思想结合到常模算法中,利用多数据向量同时提取信道信息,再附加改进的集员滤波算法有效减小了运算量,并结合数据重用思想重新设计所匹配的数据重用方式.仿真结果证明所提算法具有较快的收敛速率,与同类算法相比能提前700个迭代点收敛,且在信噪比为10 dB以上的信道环境中也有较好的效果,能够在短突发数据信道均衡中有效发挥作用.     

The Linearly Constrained LSCMA for Blind Multi-user Detection

The least square constant modulus algorithm (LSCMA) is a popular constant modulus algorithm (CMA) because of its global convergence and stability. But the performance will degrade when it is affected by the problem of interference capture in the MC-CDMA system that has several constant modulus signals. In order to overcome this shortage, a linearly constrained LSCMA multiuser detection algorithm is proposed by using the spreading code of the desired user to impose linear constraint on the LSCMA. The proposed algorithm ensures the algorithm convergence to the desired user. Thus the performance of the system is improved. The simulation results demonstrate that the proposed algorithm offers faster convergence rate and provides better output signal-to-interference-plus-noise-ratio (SINR) and bit error rate (BER) performance compared with the traditional LSCMA.     

基于模拟退火粒子群优化的恒模算法

传统的固定步长恒模盲均衡算法在收敛速度和稳态剩余误差之间存在着矛盾,影响了恒模算法的均衡性能。为了解决这一缺点,提高恒模算法的性能,本文在介绍恒模盲均衡原理的基础上,提出一种变步长恒模算法,利用粒子群优化算法对均衡器的权向量进行优化,为避免优化过程进入局部极小值引入了模拟退火算法。通过在短波信道中的仿真,证明了该算法不仅加快了收敛速度,并且具有更高的收敛精度。     

Dual-mode type algorithms for blind equalization

Adaptive channel equalization accomplished without resorting to a training sequence is known as blind equalization. The Godard algorithm and the generalized Sato algorithm are two widely referenced algorithms for blind equalization of a QAM system. These algorithms exhibit very slow convergence rates when compared to algorithms employed in conventional data-aided equalization schemes. In order to speed up the convergence process, these algorithms may be switched over to a decision-directed equalization scheme once the error level is reasonably low. The authors present a scheme which is capable of operating in two modes: blind equalization mode and a mode similar to the decision-directed equalization mode. In this proposed scheme, the dominant mode of operation changes from the blind equalization mode at higher error levels to the mode similar to the decision-directed equalization mode at lower error levels. Manual switch-over to the decision-directed mode from the blind equalization mode, or vice-versa, is not necessary since transitions between the two modes take place smoothly and automatically     

线性约束差分恒模算法

线性约束恒模算法(LCCM)能解决恒模算法(CMA)中存在的干扰捕获问题,但该算法需要将目标模值σ作为一个参数包含在代价函数中进行优化,因而收敛速度较慢.为克服这一缺点,本文提出了一种线性约束差分恒模算法(LCDCM),它可有效避免对最优σ值的搜索.在单干扰源的情况下,该算法的收敛速度和干扰抑制度均优于σ初始值设置不合适的LCCM算法;存在多个干扰源时,即使对LCCM算法的σ初始值进行最优设置,其对独立干扰源的收敛性能也不如LCDCM算法.     

Fuzzy step size least mean square algorithm tuned linearly constrained constant modulus algorithm for multi‐carrier code division multiple access blind multiuser detector

Adaptive fuzzy logic step size least mean square algorithm (FLCLMS) tuning unit is designed to adjust the step size of the linear constrained constant modulus algorithm for blind multiuser detection (MUD) in multi‐carrier code division multiple access (MC‐CDMA) systems is presented. In wireless communications system, the conventional constant modulus algorithm for blind MUD has some disadvantages such as slow convergence speed and phase rotation. To overcome these shortages, a modified constant modulus algorithm was developed for blind multiuser detector. On the basis of the deterministic behavior of the FLCLMS algorithm, it has also proposed simplification over the cost function calculation, obtaining more efficient algorithm and creating new perspective for the MUD implementation. The proposed algorithm ensures the algorithm convergence to the desired user and suppresses the multiple access interference in this cost function. Thus, the performance of the system is improved. The computational experiments show that the proposed FLCLMS not only can find optimal or closed‐to‐optimal solutions but also can obtain the low computation complexity both better and more robust results than existing algorithm reported recently in the literature. Copyright © 2013 John Wiley & Sons, Ltd.     

Electromagnetism‐like method tuned constant modulus algorithm for blind detector in multicarrier CDMA system

This paper presents an efficient meta‐heuristic algorithm based on electromagnetism‐like method, which has been successfully implemented in multiuser detection problems. The contribution revisits blind multiuser detection for multicarrier code division multiple access systems using a novel combined adaptive step‐size constant modulus algorithm (CMA) and electromagnetism‐like method scheme. To work around potentially computational intractability and improved the capability of suppressing multiple access interference (MAI) for Multicarrier CDMA System, the proposed scheme exploits heuristics in consideration of both global and local exploration of the step size of the CMA. Simulation results obtained confirm that faster convergence and desirable BER performance with low computational complexity can be achieved with electromagnetism‐like method based CMA scheme, compared with the previous step‐size CMA scheme, genetic algorithm, and particle swarm optimization with CMA scheme. Copyright © 2012 John Wiley & Sons, Ltd.     

一种变步长双模式盲均衡算法的研究

在移动通信中,物体的高动态性引起多普勒频移,应用恒模( CMA)算法,不能克服波频率偏移引起的接收信号相位旋转.针对其存在的缺点,给出了一种变步长双模式盲均衡算法,该算法将修正常数模算法(Modify constant modulus algorithm,MCMA)和判决引导(Decision directed,DD)算法有机结合,不仅具有较快的收敛速度,而且能在去除码间干扰的同时有效克服相位旋转和一定范围的载波频率偏移,具有很好的实用性.通过计算机仿真验证了该算法的性能.     

Blind multiuser detection in space division multiple access systems

This paper reviews and proposes blind multiuser detection techniques for space division multiple access systems. In this case, multiple users can be separated due to their spatial position by means of an adaptive antenna array. The constant modulus algorithm is employed in the array weights computation together with the concept of explicit decorrelation, for the sake to recover all users simultaneously. In order to improve the convergence rate and the steady-state error behavior, two new features are introduced. The first contribution is the proposition of a least-squares version of the CMA technique for multiuser detection. Afterwards an adaptive procedure is proposed to provide an improved explicit decorrelation. The performance improvements are confirmed bx some simulation results.