QAM signal amplitude and snr estimation using em algorithm. generalization for constellations, containing zero value amplitude level
Closed-form expressions for EM algorithm iteration phases are obtained for QAM signal amplitude and SNR estimation in presence of AWGN. High SNR approximation of likelihood function is applied. Constellations containing zero amplitude level are considered. Simulation results show that the proposed estimation is close to the Cramer-Rao lower bound