Blind Carrier Phase Estimation for Non-Equiprobable Constellations

In certain digital communication systems, such as those using Tomlinson-Harashima precoding and signal shaping, the received symbols are not equiprobable; rather, symbols with more energy are less likely. It is shown that in such scenarios the performance of standard carrier phase estimators is severely degraded. Using a discrete Gaussian model for the symbol probability distribution, we present the likelihood function for phase estimation, as well as an approximate maximum likelihood blind phase estimator. Simulation results show that the proposed estimate is much more robust to non-equiprobable symbol distributions than standard ones