Performance Analysis of Space-Time Diversity in Multiuser CDMA Systems over Fading Channels

In this work we examine the probability of error performance for a multiuser DS-CDMA system that exploits spatial and temporal diversities over fast-fading Rayleigh channels using a space-time block coding scheme. We commence the analysis by finding the probability density function (pdf) for the signal to interference ratio (SIR). Then, using this pdf, a closed form expression for the probability of error using the decorrelator multiuser detector is obtained. We verify the accuracy of this expression by comparison with simulations for different number of users. Both theoretical and simulation results show that the diversity order is maintained irrespective of the system load.