BETTER RATE 1 2 CODED CONTINUOUS-PHASE MODULATION SCHEMES AND THE M-ALGORITHM/

Continuous phase modulation (CPM) signals may be precoded by a convolu tional code followed by a mapping rule. Better codes may, however, be obtained by a more general code formed by a finite state machine. We p rovide improved codes for one such finite state machine. A new descrip tion of codes and design rules are presented. Better results are demon strated for the partial response CPM schemes and previous optimum resu lts are matched for the full response case. Tests of an M-algorithm de coder achieve near maximum-likelihood performance with only a fraction of the complexity of the Viterbi algorithm.