Optimum asymptotic multiuser efficiency of randomly spread CDMA

Abstract

This correspondence analyzes the high signal-to-noise ratio (SNR) performance of optimum multiuser detectors for synchronous direct-sequence spread spectrum with random spreading in an additive white Gaussian noise channel. Under very general conditions on the received powers, we show that the optimum asymptotic efficiency of a -user system with spreading gain converges to 1 almost surely as , and is kept equal to an arbitrary nonzero constant. Therefore, the asymptotic behavior of the minimum bit error rate is equivalent to that of a single-user system.Index Terms-Asymptotic efficiency, CDMA, multiuser detection, optimum multiuser detection, spread spectrum.