水声通信中基于软判决的块迭代判决反馈均衡器

摘要

In single-carrier modulation system with frequency domain equalization, Decision Feedback Equalizer with a Hybrid time-frequency structure (H-DFE) is attractive for its performance; the complexity is also significant, especially for very dispersive channels. Iterative Block Decision Feedback Equalizer with Hard Detection (HD-IBDFE) system performance degrades caused by errors in symbol decision and it needs to calculate the correlation factor of the transmitted and hard detected data. To solve these problems, Iterative Block Decision Feedback Equalizer with Soft Detection (SD-IBDFE) is introduced to improve the system performance. The receiver feedbacks the soft information of the equalizer’s output. The iterative channel estimation is adopted in order to deal with the time-varying underwater acoustic channels. Simulation results show that SD-IBDFE is superior to HD-IBDFE obviously for underwater acoustic channel. One underwater acoustic communication system is designed and tested in the lake. At a distance of 1.8 km with complex channel condition, the useful data rate of around 3000 bps is achieved with uncoded bit error rates310- in lake experiment.%在单载波频域均衡水声通信系统中，混合结构的时-频域判决反馈均衡器(H-DFE)计算复杂度高，不利于实时实现；而基于硬判决的块迭代判决反馈均衡器(HD-IBDFE)存在错误符号判决造成系统性能下降问题，同时需要估计判决符号和发射数据之间的互相关函数。该文对水声通信中基于软判决的块迭代判决反馈均衡(SD-IBDFE)接收机算法进行了研究，通过对均衡器输出信号进行软判决，并将符号软信息进行反馈，提高了系统性能，同时采用迭代信道估计方法来适应水声信道的时变性。通过仿真比较得出，该方法在水声信道条件下明显优于 HD- IBDFE。对湖上试验数据处理结果表明，在浅水1.8 km通信距离下，单通道无编码QPSK调制可实现310-的误码率并达到3000 bps的有效数据率。