基于符号的LDPC码在OFDM水声通信仿真

摘要

低密度奇偶校验码(LDPC)具有结构简单、编码增益高、在高斯信道下接近香农限的性能和可并行译码等特点,是当前通信领域研究的热点.水下有限带宽、多径时变和高噪声等特点的信道使信号在传输时,产生的突发和随机错误使系统误码率较高,通信质量难以保证.提出基于符号的LDPC码的OFDM水声通信系统,利用基于符号的迭代编译码算法可有效纠正突发和随机错误,且与高阶调制结合可以提高水下有限频谱利用率.仿真结果表明:基于符号的LDPC码相比传统主流的Turbo码和卷积码,能以更低信噪比达到正交频分复用水声通信系统误码率的要求.%Low density parity check code (LDPC) has the characteristics of simple structure,high coding gain,close to Shannon limit in Gauss channel and parallel decoding.It is currently a hot research topic in the field of communication.Due to the characteristics of underwater acoustic channel multipath time-varying,a serious decline and high noise signal in the transmission,burst and random error generating the bit error rate of communication is higher and the reliability of communication quality is difficult to guarantee.The OFDM underwater acoustic communication system based on symbol LDPC code is proposed,use of symbol based iterative decoding algorithm can effectively correct the burst and random errors,and the combination of high order modulation can improve the utilization of the limited spectrum.The simulation in the shallow sea underwater acoustic channel model is set up,the results show that based on symbols of LDPC code compared with the traditional mainstream of Turbo code and convolution code,which it can achieve lower SNR orthogonal frequency division multiplexing BER index requirements of underwater acoustic communication system.