混合采用被动时反及RAKE接收的扩频水声通信方案

Underwater Acoustic Spread Communication Scheme by Hybridly Adopting Passive Time Reversal and RAKE Receiving

在多径水声信道条件下,时间反转和RAKE接收机技术是直接序列扩频通信系统利用多径能量提高通信性能的2种常用方法,但在实际环境中信道多径结构、信噪比等因素影响着时间反转技术和RAKE接收机技术的性能.针对这个问题,分析了时间反转技术和RAKE接收机抑制多径干扰的不同机制,并提出一种通过混合使用被动时反与RAKE接收来结合两者优点的扩频水声通信新方案.该方案在不同信道结构及信噪比条件下可优化选择合适的多径抑制手段从而提高系统稳健性.湖试实验表明:在高信噪比下,时间反转可利用高质量的探针信息对多径进行聚焦,在低信噪比下则通过RAKE接收机重组多径能量,从而更好地抑制多径,克服码间干扰,提高通信系统的稳健性.

Direct sequence spread spectrum（DSSS）offers an effective way for underwater acoustic（UWA）communication due to its spread spectrum processing gain and its capability to discriminate multipath components.For DSSS underwater acoustic communication systems,the time reversal strategy as well as the RAKE receiver technique is recognized as potential candidates for mitigating the multipath interference.However,performances of time reversal and RAKE receiver is subject to factors such as multipath patterns and SNRs（signal noise ratios）.In this paper,based on the theoretical analysis of different multipath mitigation mechanisms of time reversal and RAKE receiver,a novel hybrid multipath mitigation scheme is proposed,switching between the time reversal and the RAKE mode according to the SNR.Finally,experimental results show that time reversal focuses the multipath by using high quality probe under high SNR,and under low SNR,RAKE receiver restructures the multipath.In these ways,the proposed scheme suppresses the multipath better and eliminates the code interference.Experimental results are provided to validate the effectiveness of the proposed method.