Performance evaluation of trellis-coded 8-PSK with phase offset

The authors present a detailed analysis of the bit error probability for trellis-coded M-PSK systems with and without carrier phase offset. An equivalent distance measure is used for studying the effect of phase offset on specific error events. Methods to calculate the error event probability and distance spectrum (the number of error events having a certain distance or probability) and an upper bound on the bit error probability are given. A modified state diagram is used to arrive at these results. Numerical results are given for the rate-2/3 trellis-coded 8-PSK system with memory 2. It is observed that the distance spectrum changes from distinct discrete values for phase offset zero to almost a continuous function with many different and typically much smaller and closer values for large phase-offset values