A decision-directed SNR estimator for QAM signals over time-varying SIMO channels

The problem of signal-to-noise ratio (SNR) estimation over time-varying flat fading single-input multiple-output (SIMO) channels, for non constant envelope signals, is addressed in this article when the signal is corrupted by complex additive white Gaussian noise (AWGN). It is based on the use of periodically transmitted pilot symbols to facilitate the estimation process. It relies also on the detection of the remaining symbols, and is therefore a decision directed (DD) procedure. The normalized root mean square error (NRMSE) is used as a measure of performance by Monte Carlo simulations that validate our approach and its performance over a wide SNR range.