Comparison of Several SNR Estimators for QPSK Modulations

The performances of several signal-to-noise ratio (SNR) estimation techniques reported in the literature are compared to identify the "best" estimator. The SNR estimators are investigated by the computer simulation of quartenary phase-shift keying (QPSK) signals in complex additive white Gaussian noise (AWGN).The mean square error is used as a measure of performance. In addition to comparing the relative performances, the absolute levels of performance are also established, the simulated performances are compared for complex AWGN that is derived here. Computer simulations verify the performance of the \´Phase-lock\´ method is the best estimator for the high SNR range (around higher than 15dB). The \´improved\´ method is the best estimator for SNR lower than 15dB and higher than 10 dB. for the low SNR range, the \´M2M4\´ method performs better than the other method.