A code-assisted carrier synchronization algorithm based on Expectation-Maximum algorithm

The performance of the LDPC decoder suffers from deterioration when receiving a signal with residual carrier bias. To address this problem, a carrier synchronization algorithm assisted by LDPC code is proposed. The proposed algorithms include rough carrier estimation and carrier fine estimation based on Expectation-Maximum (EM) algorithm. To reduce the problem of high resource consumption, a cost function that is only related to residual frequency bias is proposed in this article. An iterative carrier fine estimation algorithm using posteriori probability obtained by the LDPC decoder is proposed based on EM algorithm, and the analytic solution of the algorithm is derived in this article. The simulation results validated that the proposed algorithm has a large estimation range, and realizes effective carrier synchronization at a low signal-to-noise ratio (SNR).