Performance of Multiphase CPSK Systems with Intersymbol Interference

An upper bound on the probability of error for multiphase coherent phase-shift-keying (CPSK) systems with intersymbol interference and additive Gaussian noise is presented. The bound is derived through the Chernoff bounding technique and is given by a simple closed-form expression. To demonstrate its applicability the bound is computed for quaternary and octonary CPSK systems with various "typical" pulse responses. Graphical comparisons with other measures of the probability of error show the relative efficacy of the bound.