A Code-Aided Soft Frame Synchronization Algorithm for Quasi-Cyclic LDPC Coded System

A LDPC code-aided frame synchronization algorithm based on maximum-likelihood rule is proposed. Firstly the probability presenting the satisfaction of all check restrictions in the quasi-cyclic LDPC parity-check matrix for soft information vectors with different frame offsets are computed respectively, and then the point corresponding to the maximum value is chosen as the final frame synchronization point. Because of the cyclic nature of quasi-cyclic LDPC codes, a PN sequence is used to overcome the inherent ramp of the probability computed in synchronization search process. Compared to other code-aided frame synchronization algorithms, simulation results show favorable synchronization performance of the new code-aided frame synchronization algorithm based on soft information.