Space-time chip equalization for space-time coded downlink CDMA

In downlink CDMA, frequency-selectivity destroys the orthogonality of the user signals and introduces multi-user interference (MUI). A space-time chip equalizer is an attractive tool to restore the orthogonality of the user signals and suppress MUI. Recently, efficient pilot-based methods have been developed to design such a space-time chip equalizer. In this paper, we show how these pilot-based methods can be generalized to space-time coded downlink CDMA. As space-time coded downlink CDMA transmission scheme, we consider the conventional single-antenna downlink CDMA transmission scheme followed by a space-time block code for single-carrier block transmissions that exploits the maximum achievable diversity in a frequency-selective fading channel. Simulation results show improved performance over a pilot-based space-time RAKE-type receiver applied to the space-time coded downlink CDMA transmission schemes that were proposed for the UMTS and IS-2000 W-CDMA standards