A characterization of multiple-access interference in generalized quadriphase spread-spectrum communications

A proposition that is useful for studying multiple-access interference (MAI) in generalized quadriphase spread-spectrum systems is established. It provides the conditional density functions, and hence the conditional distributions, of random variables that characterize the MAI given the delays of the interferers. After averaging, it is shown that the characterizing random variables converge in distribution to the true MAI. It provides a method to study the effect of the chip waveform on the performance of the system and provides a means for the design and analysis of spectrally efficient systems. It is also useful for studying systems that send data in packets, since the delays of the interferers are often fixed for the duration of a packet. In addition, the proposition allows the evaluation of the average error probability with arbitrary accuracy without making a Gaussian approximation