A reduced-complexity formulation for DS-SSMA performance evaluation via the characteristic function method

A significant body of literature has been devoted to the evaluation of error probabilities for direct sequence spread spectrum multiple access (DS-SSMA) systems. This paper presents a reduced-complexity formulation for such a performance evaluation via the characteristic function method which is a powerful tool for accurate evaluation of DS-SSMA performance and does not require a large number of moments of the decision statistic. In the previous version of this technique, the characteristic function of the multiple access interference (MAI) component of the decision statistic (for a correlation receiver) was expressed in terms of a double integral over the distributions of phase and delay. The new formulation generates a more compact expression for the characteristic function of the MAI, eliminates the need for numerical integration over the phase distribution (thus improving the accuracy) and yields a computational complexity reduction proportional to the product of the spreading gain and the number of terms required to integrate over the phase distribution. This renders the characteristic function method more attractive for application to future wideband CDMA systems and by extension, to more complex transceiver structures and time-varying channels