中文摘要：

正交频分复用（Orthogonal Frequency Division Multiplexing,OFDM）技术由于具有频谱利用率高、抗多径能力强等优点,成为当前水声通信的研究重点和热点,但较高的峰均功率比（Peak-to-Average Power Ratio,PAPR）严重影响了水声OFDM通信系统的性能。采用重复累积码（Repeat Accumulate,RA）作为信道编码方案,并用线性反馈移位寄存器（Linear Feedback Shift Registers,LFSR）代替原RA码结构中的累加器,再通过选择映射（Selective Mapping,SLM）方法降低系统的峰均功率比。计算机仿真和水池实验结果表明,采用改进结构的RA码结合SLM技术能有效降低水声OFDM系统的PAPR,提高系统的性能,具有很好的应用前景。

英文摘要：

Orthogonal frequency division multiplexing （OFDM） technology has become the research focus and hotspot of underwater acoustic communications owing to its advantages such as high spectrum efficiency and robustness to multipath fading, but it possesses high peak-to-average power ratio （PAPR） which severely degrades the performance of Underwater Acoustic OFDM Communication System. In this paper, repeat accumulate （RA） code is adopted as the channel coding scheme, and linear feedback shift registers （LFSR） is used to replace the accumulator of original RA code structure, then selective mapping （SLM） method is also adopted to reduce the PAPR of system. Computer simulation and experimental results show that modified RA code and SLM can effectively reduce the PAPR and improve the per- formance of underwater acoustic OFDM communication system, which have a very good application prospect.