Maximum likelihood estimation for SNR of PSK and QAM

Signal-to-noise ratio (SNR) is an important parameter of channel quality. The performance of adaptive communications in time-varying channels is affected significantly by the SNR estimation accuracy. In this paper, the new methods of SNR estimation for PSK and QAM are proposed. The methods are based on maximum likelihood estimation (MLE) using the probability density function (pdf) of received signal envelope, and are used in unknown signal power conditions without the carrier synchronization. The proposed methods are shown to estimate SNR efficiently by numerical results of normalized mean square error (NMSE) of SNR.