A Blind Doppler Parameters Estimation Algorithm for High-order QAM Signals

In satellite mobile communication, the received signal may experience time-varying doppler distortion due to the relative motion between the satellite and the ground receiver, which will bring large difficult in carrier synchronization of orthogonal amplitude modulation (QAM) signals. The existing methods usually use the prior information, and they are suitable for the phase-shift keying (PSK) signals. But these methods suppose the doppler frequency is small when estimating the Doppler rate, which is not in accord with the actual situation, and the existing methods can’t estimate large doppler frequency, it is hard to get the prior information in the non-cooperative communication as well. To solve the problems, an algorithm of blind doppler parameters estimation for high-order QAM signals is proposed. After wiping off the modulation information of signals in a blind way, the proposed method can get the doppler rate under large doppler frequency by using the instantaneous frequency estimation function; by detecting one of the cyclic frequencies of signals, which locate at the quartic frequency offset, doppler frequency is effectively estimated. Finally, the initial phase is obtained through the arg handling. All-sided Monte Carlo simulations are employed to analyze the estimation performance. Experimental results indicate that the proposed algorithm can accomplish blind doppler parameters estimation for QAM signals effectively.