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LDPC编码系统中接收端通常将译码和同步联合进行,传统的基于分组的译码联合同步算法一般要求对频偏和相差进行充分预估计,以保证迭代算法的收敛。但是这样带来了两个问题,首先预估计算法存在一定概率不满足收敛条件,从而对系统性能带来了一定的恶化;其次,即便在收敛的范围之内,残留的频偏和相差仍然会对译码性能产生一定量的恶化。基于以上两个问题,提出了一种适合于MF-TDMA卫星通信系统的迭代同步方案,并通过文献[6]中的迭代译码联合载波同步算法对方案进行了验证。经过论证,文中提出的方案可以在不对迭代算法进行任何修改的前提下,提高系统的误码性能,而且不仅仅局限于载波同步,可应用于其他任何迭代同步算法中。
The receiving end of LDPC coding system usually combines decoding and synchronization. The traditional packet-based decoding joint synchronization algorithm generally requires that the frequency offset and phase difference be fully estimated to ensure the convergence of the iterative algorithm. However, this brings about two problems. First, it is estimated that there is a certain probability that the algorithm does not satisfy the convergence condition, which brings some deterioration to the system performance. Second, even within the range of convergence, the residual frequency deviation and the difference are still Decoding performance will have a certain amount of deterioration. Based on the above two problems, an iterative synchronization scheme suitable for the MF-TDMA satellite communication system is proposed, and the scheme is verified by the iterative decoding combined with carrier synchronization algorithm in [6]. After the demonstration, the proposed scheme can improve the BER of the system without any modification to the iterative algorithm, and it is not limited to carrier synchronization and can be applied to any other iterative synchronization algorithm.