基于IDMA的水声通信自适应Turbo迭代接收机技术研究

Research on the adaptive iterative receiver for IDMA-based underwater acoustic communication

有效的多用户多址接入方式一直是水声通信网络研究的重点与难点;在十分有限的水声可用带宽条件下常规的基于频分技术的多址接入方式并不适用;而基于CDMA的码分多址接入方式则又存在着严重的难以克服的远近效应问题,且水声信道的多途效应使接收信号产生严重的码间窜扰(ISI)。针对以上问题,本文提出了基于交织分多址接入(IDMA)的自适应Turbo迭代接收机技术的研究。接收机采用联合均衡过程和译码过程的Turbo迭代接收机,通过迭代的方式获得反馈的外信息从而提高系统性能。针对未知参数的信道,采用递归最小二乘(RLS)自适应均衡算法对信道参数迭代估计,从而指导均衡器消除码间窜扰(ISI)。RLS算法利用每次迭代译码器反馈的外信息再次估计信道参数,直接的增加了除训练序列外的可利用数据长度,从而提高估计精度。通过仿真得出在未知信道条件下接收机的性能比已知信道系统接收机的性能降低0.4 d B。

Effective multi user multi address access method is always the emphasis and difficulty of the research on underwater acoustic communication network; in very limited underwater acoustic available bandwidth condition, conventional multi-access based on frequency division technology does not apply; then there is a serious problem in division multiple access method based on CDMA code, which is difficult to overcome and the multipath of underwater acoustic channel make receive signals serious intersymbol interference. Aiming at those question, the paper carries out the research on self-adaptive Turbo iterative receiver based on Interleave-Division Multiple-Access(IDMA). The receiver which adopts joint iterative equalization and decoding can obtain external feedback to help with performance improvement. For channels with unknown parameters, Recursive Least Square(RLS) Adaptive Equalization Algorithm is used to iteratively estimate parameters of channel, which guides equalizers to reduce the Inter Symbol Interference(ISI). RLS estimates channel parameters repeatedly according to the information fed back by decoders. That directly increases the length of available data except training sequence to improve estimation accuracy According to simulation, the performance of receivers without known channel conditions is 0.4 d B less than the one with known channel conditions.