Transmit diversity based on space-time block codes in frequency selective Rayleigh fading DS-CDMA systems

Exploring the temporal and spatial domains both at the receiver and transmitter offers important means for considerably improving the system performance in cellular networks. In this paper, the impact of using open-loop transmit diversity based on space-time block codes in a multi-user DS-CDMA system operating in a frequency selective fading environment is explored. A non-joint linear multi-user detection and space-time decoding approach is proposed. It is shown that by introducing a simple constraint with respect to the spatio-temporal cross-correlation properties of the space-time code-corresponding to introducing interleaving-any space-time block code can be used as the base for the transmit diversity scheme. Simulation results using the complex (2,2,2) space-time block code known as Alamouti's (see IEEE Trans. on Select Areas in Communications, vol.16, p.1451-58, 1998) code, indicates that large diversity gains are achievable and that the amount of overhead originating from training data can be reduced considerably using the proposed approach.