基于LDPC码的差分空时编码调制的联合优化

Joint Optimization for Coded Differential Space-Time Modulation Based on Irregular LDPC Code

提出一种新的结合低密度校验码(LDPC)和差分空时调制(DSTM)的联合编码调制方案。该方案利用非正则LDPC码中不同度的信息节点具有不同纠错能力的特性,用一个分量码取代传统多级编码(MLC)方案中多个分量码,并通过特定的映射法则,使得系统可以同样逼近联合编码调制的信道容量,并具有更低的编译码复杂度。在分析和阐述了离散概率密度演化理论和多维线性空间极值问题的基础上,给出了适合于该方案的非正则LDPC码的搜索算法和搜索结果。同时仿真比较了不同星座和不同空时编码的选择对系统性能的影响。在准静态MIMO衰落信道下仿真结果表明,该方案能显著提高系统性能。

A new scheme （LDPC-DSTM） combining irregular low-density parity-check （LDPC） code with differential space-time modulation （DSTM） is used for coded modulation （CM）. Different from conventional multilevel code （MLC） schemes using more than one channel coders, the scheme uses only one irregular LDPC code and achieves the capacity of CM with lower decoding complexity. The system can provide different correct abilities to level bit channel by mapping information nodes that have different degrees. By analyzing the discretized density evolution theory and the differential evolution algorithm, a method is proposed to search optimal irregular LDPC code for joint optimization of the system.The performances of LDPC-DSTM are compared with several mapping rules of 16-QAM constellation and two space-time codes. Simulation results in Quasi-stationary fading MIMO channel show that the scheme is very effective。