Abstract: An improved iterative expectation-maximization estimator of carrier phase at low SNR is proposed. A new method of parallel initialization is provided, which gives multi-initialization at possible phase space and selects the best result as the new initialization after the first EM iterative process. Thus the EM algorithm can avoid convergence at local maximum and solve the phase ambiguity problem without the aid of a pilot sequence. Simulation results show that the proposed technique performs better than some previous methods, and is convenient to implement with lower complexity and faster convergence.

Key words: low SNR, EM iterative estimation, parallel initialization, phase ambiguity