A fundamental lower bound to the performance of phase estimators over Rician-fading channels

We present a fundamental lower bound to the mean-square error of estimators of the phase of a sine wave passed through a Rician-fading channel. Explicit expressions for the bound with Gaussian and Rayleigh channels are provided. The bound is derived by analyzing the performance of the Bayes minimum mean-square error phase estimator, and therefore represents the best performance attainable by physically realizable phase estimators over a Rician channel