Asynchronous SNR estimation of PSK/QAM modulated signals in flat-fading channels

The majority of prior work in signal-to-noise ratio estimation makes fairly strong assumptions concerning a priori knowledge of the channel state and signal. For instance, many of these estimators assume knowledge of the modulation scheme of the signal, or even complete knowledge of the transmitted set of modulated data symbols (typically through the use of training sequences). Even more universally, perfect time synchronization between the transmitter and receiver is assumed. The purpose of this paper is to remove some of these commonly stated assumptions through the presentation of a novel asynchronous, noncoherent, and non-data-aided method-of-moments based signal-to-noise ratio estimator for PSK/QAM modulated signals in flat-fading channels. This estimator requires no a priori knowledge of the channel gain, phase, and delay, nor the specific modulation scheme (PSK or QAM) and modulation order used.