采用反馈滤波器组的单载波迭代均衡接收机

A Single Carrier Iterative Equalizer Receiver with Feedback Filter Bank

针对宽带无线通信中信道的多径效应问题,提出了一种采用反馈滤波器组的单载波迭代均衡接收机。首先,利用多径时延带来的信号分集,设计接收机的反馈滤波器组和前馈滤波器,反馈滤波器组的主要作用是尽可能消除不同时延信号间的符号间干扰,前馈滤波器的主要作用是将经过干扰消除后的多路信号进行分集合并;然后,利用最小均方误差准则,联合优化滤波器系数,得到最优解,实现多径信号的最佳分离和分集合并效果;最后,估计滤波器系数中的相关系数,并对均衡信号循环前缀部分进行最大比合并,增大信号信噪比。仿真结果表明:与现有的单载波迭代均衡接收机相比,该接收机在信道长度不超过循环前缀长度的情况下,当误比特率为10-5时,第一次迭代后性能改善0.5 dB,且随着迭代次数的增加性能更快逼近匹配滤波界;在信道长度超过循环前缀长度的超大时延扩展的情况下,能有效消除误比特率及误帧率的平台效应,且当误比特率为10-5时,两次迭代后的性能改善为4 dB,逼近匹配滤波界。

A single carrier iterative equalizer receiver with feedback filter bank is proposed to solve the multipath effect in broadband wireless communication.Firstly,a feedback filter bank and a feedforward filter are designed by exploiting signal diversity brought by multipath delay.The main function of the feedback filter bank in the equalizer is to eliminate intersymbol interference between different delay signals as much as possible,and the main function of the feedforward filter is to combine the multipath components after the interference elimination.Then,by exploiting the minimum mean square error criterion,the feedforward coefficient and the feedback filter bank coefficient are optimized jointly to obtain the optimal solutions of the coefficients,and the optimal separation and diversity combination of multipath components are realized.Finally,the correlation coefficients in the filter coefficients are estimated,and the maximum ratio combination is carried out for the cyclic prefix part of the balanced signal to increase the signal to noise ratio.Simulation results and a comparison with the existing single carrier iterative equalizer receivers show that in the case that the length of the multipath channel does not exceed the length of the cyclic prefix,when the bit error rate is 10-5,the performance of the receiver improves by 0.5 dB after the first iteration,and approximates the matched filter boundary faster with the increase of iteration times;In the case that the length of the multipath channel exceeds the length of the cyclic prefix,the“platform effect”of bit error rate and frame error rate are eliminated effectively,and when the bit error rate is 10-5,the performance is improved by 4 dB after two iterations to approximate the matched filter boundary.