Application of cyclic delay transmit diversity to uplink 2-dimensional block spread CDMA with frequency-domain equalization

Abstract

The presence of the multi-access interference (MAI) limits the uplink performance of code division multiple access (CDMA). 2-dimensional (2D) block spread CDMA makes it possible to achieve MAI free uplink transmission while obtaining the frequency diversity gain by using low-complexity single-user frequency-domain equalization (FDE). To further improve the uplink transmission performance, the transmit diversity technique can be used. Cyclic delay transmit diversity (CDTD) can strengthen the frequency-selectivity of the channel. In this paper, we apply CDTD to 2D block spread CDMA with MMSE-FDE. The achievable uplink BER performance is evaluated by computer simulation for both direct sequence CDMA and multi-carrier CDMA. It is shown that CDTD can offer improved uplink BER performance in a frequency-selective uplink channel.