Error probability analysis for continuous phase modulation with Viterbi detection on a Gaussian channel with multiple signal interference

The effects are studied on the symbol error probability of the Viterbi detector for continuous phase modulations with constant amplitude, when the desired signal is received in multiple interfering signals and white Gaussian noise. The detection is assumed to be coherent and, furthermore, perfect timing in the detector is also assumed. An upper bound on the symbol error probability is derived for the Viterbi detector. The bound is based on the union bound technique, and it is shown to be tight for small error probability levels. It is found that the smoothed binary and all quaternary modulations sustain much larger interference power in adjacent channel interference than minimum-shift keying (MSK) does and, thus, the adjacent channels can be spaced closer in frequency for these modulations, In particular, the smoothed quaternary modulations seem to be significantly more efficient than MSK. In cochannel interference the difference in error performance between the schemes is relatively small