Joint Estimation of Carrier Frequency and Symbol Rate of MQAM signal Based on Fractional Lower Order Moments under Impulsive Noise

In view of the poor performance and even failure of the traditional MQAM signal carrier frequency and symbol rate estimation algorithm under impulse noise. By combining the fractional lower order moment(FLOM) and covariant theory, he fractional lower order cyclic spectral density function of the MQAM is derived in this paper, and the characteristics of signal cyclic spectrum under raised cosine pulse shaping are analyzed. Then, a joint carrier frequency and symbol rate estimation algorithm of MQAM based on FLOM is proposed by introducing the FLOM into discrete frequency domain smoothing method(DFSM). And the method of averaging by adjacent spectral section is used here to avoid the estimation error caused by the lack of resolution. The simulation results show that compared with the second-order DFSM cyclic spectrum estimation algorithm, the proposed algorithm can not only suppress the impulse noise, but also can effectively estimate the carrier frequency and symbol rate of the MQAM signal in the harsh noise conditions, and have better anti-interference ability and application. It is suitable for MQAM signals with different modulation orders.