Joint frame, carrier and clock synchronization scheme

Abstract

The present invention provides a method to achieve frame synchronization from a received data sequence before the carrier phase and frequency offset recovery for any MPSK modulated signals on the basis of maximum likelihood theory. Two overhead configurations are considered in developing the frame synchronization algorithms. One overhead configuration consists of a unique word followed by a preamble, and the other consists of unique word only. For the first overhead, the frame synchronization can be decoupled from carrier recovery because the preamble following the unique word is a known sequence pattern. In this case, the maximum-likelihood frame synchronization rule is simply a complex correlation. In second overhead, the unique word is immediately followed by random traffic data and thus the coupling effects are generated between frame synchronization and carrier recovery. These coupling effects are not dominant, however, and may be neglected in actual practice. After the frame synchronization is achieved, the time position is already known. The data-aided algorithms for carrier phase and frequency-offset estimation are derived using maximum likelihood theory.