Performance Analysis of Transmit Diversity in Multiuser DS-CDMA Systems Over Quasi-Static Fading Channels

The performance of space-time spreading transmit diversity designed for fast-fading channels is examined in a multiuser direct-sequence code division multiple access (DS-CDMA) system over quasi-static fading channels. The space-time system employs two transmit antennas and single receive antennas at the user side and base-station receiver, respectively. The receiver employs a decorrelator multiuser detector. In the analysis, we obtain a closed form expression for the bit error probability. It is shown that the performance of the space-time transmit diversity scheme, designed earlier for fast-fading channels, reduces to that of the existing schemes designed for slow-fading channels. Both simulations and analytical results demonstrate that, regardless of the system load, the full system diversity is maintained when a decorrelator detector is used at the receiver side.