Modified Viterbi algorithm for decoding trellis coded signals in AWGN channel with phase jitter

This paper proposes and analyzes a method for decoding trellis coded modulation (TCM) in the presence of carrier phase jitter. Since TCM is very sensitive to phase errors, it is of interest in the development and analysis of a robust algorithm to be used in such channels. The algorithm presented here is a modified Viterbi algorithm in which different carrier phase estimates are associated with each state. Each of these estimates is computed using 2nd order decision directed PLL-like recursive equations based on the surviving sequence associated with the state. A simplified linear analysis of the recursive equations is provided and applied to a carrier phase modeled as a process with non-zero mean independent increments. Optimum parameter design is performed based on this analysis. The performance of the algorithm is compared with other methods described in the literature. Results show that our algorithm achieves better BER and phase error variance performances.