Effect of Co-Channel Interference on CPSK Carriers

This paper investigates the problem of estimating the effects of interference to a coherent phase-shift-keyed (CPSK) digital carrier. Paralleling Saltzberg [1], the principal tool utilized is the CramérChernoff bounding technique. The interference effects can be characterized by equating the larger interferers to an equivalent coherent canceling sine wave and the remaining interferers to an equivalent incoherent source of thermal noise. Subject to an envelope constraint, any allocation of the interferers between a canceling sine wave and thermal noise is allowed. Conditions are developed for the case: 1) when all the interference should be allocated to thermal noise; and 2) when as much as possible of the interference should be allocated to a canceling sine wave. This provides insight into the formal procedure of equating interference as additional thermal noise.