Method and apparatus with improved estimation accuracy and robustness for fine frequency offset estimation in coherent receivers

摘要

The present disclosure provides a method and system for fine estimation of a local oscillator frequency offset of a received signal at a coherent receiver, by evaluating the probability mass function (PMF) of the signal phase of output symbols at different frequencies. At frequencies other than the actual frequency offset, the signal phase is uniformly distributed in [−π,π] such that the summation of square of PMF (PMF sum-square) values is minimized. However at the actual frequency offset, the signal phase is no longer uniformly distributed over [−π,π]; in other words the signal phase will take some specific values in [−π,π], therefore a peak PMF sum-square value will result. This peak PMF value provides an indication of the actual offset frequency of the received signal.