On hybrid trellis-coded 8/4-PSK modulation systems

The authors discuss how a more robust performance can be achieved by using rate 2/3 trellis-coded 8-phase-shift-keying (PSK) signals and 4-PSK signals in a time-varying manner. It is assumed that the data are transmitted in blocks (packets) with a unique word in the packet header. Simulation results of bit error rate (BER) and performance of the recovery loop (S-curve) are presented. Several options are presented for designing the decision-directed carrier recovery and for shaping the S-curve. The cycle slip rate of the conventional system at 7.5° RMS jitter is about 25% but less than 0.1% in the new schemes. This is achieved with almost no penalty in bandwidth or in BER in blocks received without cycle slips