General techniques for analyzing DS/SSMA interference illustrated by evaluating a noncoherent system

A conditional probability density function of the multiple-access interference (MAI) in direct sequence/spectrum-spreading multiple access (DS/SSMA) systems with complex modulation (e.g., M-ary and continuous phase) is derived from a geometric viewpoint. A method to efficiently calculate the two-dimensional (2-D) convolutions of a number of circularly symmetric densities is presented. The utility of these methods is then illustrated by evaluating a noncoherent DS/SSMA system.