码辅助迭代载波同步算法的实现

Code-aided Iteration Carrier Synchronization Algorithm

在低信噪比条件下,载波频偏和相偏会对LDPC编译码系统有明显的影响,需要接收端在译码前对频偏和相偏进行估计。为了解决上述问题,结合LDPC迭代译码输出软信息的统计特性,提出了一种适合于LDPC码的码辅助迭代载波同步技术。其基本思想是利用译码器输出的软信息辅助同步参数的估计,即将译码软信息分别用到基于代价函数的载波粗同步和基于最大似然迭代的载波细同步中,将同步器、解调器与译码器联合迭代,实现较好的载波同步。

At low signal-to-noise ratio,the carrier frequency offset and phase offset will have a significant impact on the LDPC code system,requiring the receiver to estimate the frequency offset and phase offset before decoding.In order to solve the above problems,a code-aided iterative carrier estimation is proposed based on statistics of soft information from LDPC iterative decoder.The basic idea is to use the soft information output by the decoder to assist the estimation of the synchronization parameters,which is to use the soft information for the coarse synchronization of the carrier based on the cost function and the carrier synchronization based on the maximum likelihood iteration respectively.The better carrier synchronization is achieved by conducting the joint iteration of synchronizer,demodulator and decoder.