Iterative Carrier Phase Recovery for MPSK Systems Based on Simplified EM Algorithm

This letter deals with the problem of carrier phase recovery for low-density parity-check (LDPC) coded MPSK systems at low signal-to-noise ratios (SNR). By utilizing Taylor series expansion and the constant-envelope characteristic of PSK signals, we greatly simplify the expectation maximization (EM) algorithm to recover the carrier phase. The proposed method works with simple operations of phase subtraction and accumulation instead of complex multiplication and accumulation in the EM algorithm. Apart from its low complexity, the simulation results for the case of 8-PSK system with a (1944; 972) irregular LDPC code show that the performance loss compared to the EM algorithm is negligible.