Design of Multiuser CDMA Systems in Fading Channels

In this paper, the authors examine the effect of channel estimation errors on the performance of Multiple-Input - Multiple-Output (MIMO) systems that employ Code-Division Multiple-Access (CDMA) transmission. Channel estimation based on training techniques has widely been considered throughout the literature. However, employing these training techniques in MIMO-CDMA systems degrades system performance due to multiuser interference. This degradation is clear as the diversity advantage of the MIMO system diminishes with the increased level of interference. As a remedy to this problem, they propose a channel-estimation and data-detection scheme based on the superimposed training technique for space-time spreading systems.