一种适用于BICM-ID系统的迭代载波同步算法

摘要

在比特交织编码调制迭代译码(BICM-ID)系统中,针对低信噪比条件下传统的同步算法对频偏和相差估计精度较低的问题,提出了一种码辅助的迭代载波同步算法.该算法基于最大期望(EM)算法,并在此基础上加以改进,利用译码器输出的软信息,迭代的在载波同步和译码之间相互交换信息,实现同步和译码的联合处理.仿真结果表明,在译码器收敛的允许范围之内,提出的算法能够大幅提高同步参数的估计精度,在迭代次数达到8次时,BICM-ID系统的误比特率性能基本接近理想同步条件下的译码性能.%In the system of bit-interleaved coded modulation with iterative decoding (BICM-ID),considering that the traditional carrier synchronization algorithm performs big inaccuracy for frequency and phase estimation,a code-aided iterative carrier synchronization algorithm is proposed.It is based on the expectation-maximization (EM) algorithm,as well as some improved methods are proposed.The new algorithm makes use of the soft information provided by the decoder and gets good estimate of synchronization by iteratively exchanging information between the synchronizer and the decoder.Simulations show that as long as meeting the decoder convergence condition,the estimation precision will be improved,and the system bit error rate performance can approach optimality in ideal synchronization when the iterative number reaches eight.