基于LDPC码的CPQPSK编码调制方案

Coded continuous phase QPSK modulation scheme based on the low density parity check code

为提高CPQPSK(Continuous Phase QPSK)调制的抗噪声性能,提出了LDPC(Low Density Parity Check)码与CPQPSK的串行级联方案。重点研究了全响应CPQPSK与一种基于有限几何LDPC码的级联,该LDPC码具有高性能的同时,其编译码器都非常简单。CPQPSK信号采用基于PAM(pulse amplitude modulation)的简化接收机,通过改进软输出维特比译码算法(SOVA),解调器直接输出二进制符号的似然信息,用于LDPC码的迭代译码。仿真结果表明,误码率在10-6时编码调制方案可获得6.958dB的编码增益。

A concatenated scheme of the low density parity check （LDPC） code and continuous phase QPSK （CPQPSK） is proposed to protect CPQPSK signal against noise. The focus is laid on the concatenation of the full response CPQPSK and LDPC code, which is based on finite geometry and has high performance against noise and a simple coder and decoder. The soft output Viterbi algorithm （SOVA） is modified for the simplified receiver based on pulse amplitude modulation （PAM）, generating belief message for the LDPC decoder followed. Simulation results show that the CPQPSK-1REC scheme coded by LDPC code has the coding gain of 6.958dB at the bit error rate of 10^-6.