Joint frequency-domain equalization and despreading for DS-CDMA cyclic delay transmit diversity

Cyclic delay transmit diversity (CDTD) using frequency-domain equalization (FDE) based on the minimum mean square error (MMSE) criterion is a powerful technique to improve the bit error rate (BER) performance of direct sequence code division multiple access (DS-CDMA) signal transmission in a frequency-selective fading channel. CDTD simultaneously transmits the same signal from different antennas after adding different cyclic delays to increase the number of equivalent propagation paths and hence achieves the larger frequency diversity gain. However, the BER performance of DS-CDMA with CDTD using MMSE-FDE is limited by the residual inter-chip interference (ICI) after FDE. In this paper, we propose a new joint FDE and despreading suitable for CDTD, which can simultaneously perform equalization and despreading in the frequency-domain. We evaluate the achievable BER performance by computer simulation.