Performance evaluation of trellis-coded modulation on imperfect coherent detection

For the same signal-to-noise ratio (SNR) of a phase reference, the sensitivity to the phase offset for an 8-phase-shift keying (8-PSK) scheme is greater than for uncoded quaternary phase-shift keying (QPSK). The effect of imperfect coherent detection is evaluated. The authors introduce the concept of equivalent distance on the basis of the conventional distance metric. By using the equivalent distances, the corresponding upper bound can be approached. Simulation results for the event error probability are presented