Trellis-Coded MPSK with Reference Phase Errors

With trellis-coded MPSK schemes, reference phase errors have a major impact on the system performance. This paper analyzes the interrelation among the coded-modulation format, the reference phase tracker, and the carrier phase noise. A tight upper bound to the error probability of a maximum likelihood decoder is introduced. This bound reveals eight new distance-type functions which, along with the wellknown minimum Euclidean distance, characterize the coded-modulation scheme. Relationships between the new distance-type functions and the various system parameters as well as the irreducible probability of error are pointed out. Numerical results for uncoded QPSK and three Ungerboeck encoded 8-PSK schemes showy that excessive smoothing of the reference phase in presence of carder phase noise can degrade the performance of coded 8-PSK modulation considerably.