LDPC编码系统的码辅助载波相位同步算法

深空通信具有传输距离远、信号衰减严重的特点，针对低信噪比条件下深空通信系统中LDPC编码系统载波同步实现困难的问题，提出一种新的具有较低复杂度的码辅助载波同步算法。分析了载波同步误差对译码性能的影响，基于最大似然准则推导了载波相位的迭代同步算法，算法利用LDPC译码器输出的软判决信息来辅助载波相位的估计，将译码器与载波同步器进行联合迭代，从而得到接近最大似然估计性能的载波相位估计，同时对载波相位进行迭代补偿。仿真结果表明，在低信噪比条件下，算法能够有效纠正载波偏差，并能够以较低的系统复杂度获得近似理想同步的LDPC码译码性能。

Code Aided Carrier Phase Synchronization Algorithm for LDPC Coded Systems

Regarding the carrier synchronization difficulty of LDPC coded system at rather low SNRs in deep space communications, a new code aided carrier synchronization algorithm with low complexity is proposed. In this paper, the effect of carrier phase synchronization error on decoding performance is investigated and an iterative carrier synchronization method is proposed based on the maximum likelihood estimation, the soft decisions provided by the LDPC decoder is used to aid carrier phase estimation. The decoder and the synchronizer are used to iterate jointly for reliable estimation and compensation of the carrier phase. Simulation results indicate that the carrier offset can be compensated effectively at low SNRs with lower complexity, and the code aided carrier synchronization could achieve approximate ideal performance of LDPC code systems.