On error probability for CPM with Viterbi detection in interference and Gaussian noise

An upper bound on the symbol error probability is given for a Viterbi detector for continuous phase modulation (CPM), when the desired signal is received in multiple interfering signals and white Gaussian noise. Coherent detection and perfect timing in the detector are assumed. It is found that the smoothed binary and all quaternary modulations sustain much larger interference power in adjacent channel interference than minimum-shift keying does. In cochannel interference, on the other hand, the difference in error performance between the schemes is relatively small.<>