The authors apply trellis-coding techniques to continuous phase freque
ncy shift keying (CPFSK). Ring convolutional encoders for trellis-code
d CPFSK are found by optimising the normalised minimum Euclidean dista
nce for a given total number of states in the overall MLSE receiver. C
ode searching results show that several optimum encoders give performa
nces which are better than previous schemes.