A Real-Time SNR Estimator for D-MPSK over Frequency-Flat Slow Fading AWGN Channels

We present a channel SNR (signal-to-noise ratio) estimator for D-MPSK (differential M-ary phase shift keying) in AWGN (additive white Gaussian noise). The estimator is shown to have the following advantages: (1) the estimator has a compact fixed-point hardware implementation; (2) it requires only 1 sample/symbol; (3) accurate estimates can be generated in real-time; (4) the estimator is resistant to imperfections in the AGC (automatic gain control) circuit. We investigate the proposed estimator theoretically and through simulations. General formulas are developed for SNR estimation in the presence of frequency-flat slow fading, and specific results are presented for Nakagami-m fading. The proposed estimator is then compared to other SNR estimators, and it is shown that the proposed method requires less hardware resources while at the same time providing superior performance. Finally, we briefly consider application of the proposed SNR estimator to SNR estimation in coherent M-PSK receivers when carrier synchronization has not been achieved.