非规则QC-LDPC码联合自适应均衡技术在浅海水声信道研究

Abstract

浅海水声信道具有长时延、多途强、起伏快等特点,为提高数据传输可靠性,采用纠错能力强、编译码复杂度低的非规则准循环低密度奇偶校验(QC-ldPC)码作为信道纠错码方案,并联合自适应判决反馈均衡器(dfE)作为接收机结构以消除码间干扰(ISI).综合考虑非规则QC-ldPC码编译码参数选择、自适应均衡器中的最小均方差(lMS)、可变步长lMS(SVSlMS)和递归最小二乘(rlS)等3种算法的性能与复杂度权衡问题,结合福建泉港浅海域实测水声信道特性,研究了该接收机的性能.仿真结果表明:非规则QC-ldPC码的性能优于随机构造的规则ldPC码;联合自适应均衡的非规则QC-ldPC码可显著提高浅海水声通信系统性能,在较高信噪比(Snr)下,选用rlS算法时,误码率(bEr)可降为0(15db),选用低复杂度的SVSlMS算法bEr可达到10-4(18db).

Shallow water acoustic channel is characterized by long transmission delay,strong multipath interference,and large fluctuation.To improve reliability of underwater acoustic data transmission,this paper use irregular quasi-cyclic low density parity check(QC-LDPC)codes as an error-correcting coding scheme,which have strong error correction capability and low coding and decoding complexity,joint adaptive equalization as a receiver structure for eliminating inter-symbol interference caused by strong multipath effect.This paper makes comprehensive considerations of optimal design problem,such as the choices of coding and decoding parameters for irregular QC-LDPC codes,the balances of performance and complexity for least mean square,recursive least squares and sigmoid variable step-size least mean square algorithms in adaptive decision feedback equalizer;combining the measurement shallow water acoustic channel of characteristics Fujian quangang Xiaocuo harbour to analyses the performance of the receiver.Simulation results show that the irregular QC-LDPC codes perform better than random structure regular LDPC codes;irregular QC-LDPC coding joint adaptive equalization can significantly improve the performance of shallow water acoustic communication system.At high SNR,when select RLS algorithm,bit error rate can be reduced to 0;when select SVSLMS algorithm with low complexity,error rate can reach 10-4.