深空通信中的一种级联编码调制及其迭代接收

摘要

在深空通信中,由于通信距离大幅增加,通信信号的自由空间传播损耗很大,提高系统的功率利用效率是深空通信系统设计需要考虑的重要问题之一.提出了基于LDPC码和FQPSK调制的级联编码调制体制,首先提出该编码调制体制的系统模型,通过修改相应的算法给出适合FQPSK的迭代解调解码算法,通过计算机仿真分析了该体制的误码率性能.研究结果表明:该体制利用FQPSK的恒包络特性克服信道非线性问题并使功放工作在饱和区,利用LDPC码实现低信噪比通信,同时在接收端通过迭代解调解码获得增益,从而能够缓解深空通信中由于传输距离过远而带来的极低信噪比通信问题.%The high power efficiency is more important for deep space communication than other communication systems due to the long distance between spacecraft and the Earth station. One novel coded modulation scheme based on FQPSK (Feher's QPSK) and LDPC is proposed to alleviate the challenge of long distance in space communication in this paper. In this approach, the constant envelope property of FQPSK is used to overcome the nonlinear impact of high power amplifier, and the property of LDPC to enable low signal noise ratio communication. At the receiver side, large gain can be attained by iterative demodulation and decoding. The system model of coded modulation and the iterative receive algorithm are proposed. The bit error rate performance of the new scheme is confirmed by computer simulation.