Abstract: It is required very low bit-error probabilities in some special underwater acoustic communication systems，and just depending on forward error code cannot satisfy the request of communication quality.Circle Redundancy Check（CRC） is a kind of circle code with good performance，and it is suitable for check error system.The performance of Low Density Parity Check codes（LDPC） is nearly Shannon limit with lower complexity compared with Turbo codes.It is proposed a method that LDPC code and automatic request for repetition can be combined together，added LDPC after CRC.Simulation results indicate that bit-error probabilities can be descended to below 10^-9.

摘要： 在水声通信中，有些情况下系统中要求误码率非常低，仅仅靠信道编码的方法不能满足通信质量要求。循环冗余校验码（CRC）是一种性能良好的循环码，非常适用于检错系统，低密度校验码（LDPC）性能接近香农极限的信道编码之一，其译码复杂度远远小于Turbo码。为了满足低误码率的要求，提出了一种将LDPC码和自动重发请求（ARQ）结合应用的方法，在CRC校验之后进行信道编码，在保证通信质量的前提下尽量减小发送信息的冗余度。仿真结果表明，该方法可以将误码率降低到10^-9以下。