MMSE frequency-domain equalization combined with space-time transmit diversity and antenna receive diversity for DS-CDMA

DS-CDMA transmission performance can be improved with minimum mean square error frequency-domain equalization (MMSE-FDE) compared to the use of coherent rake combining. In this paper, to achieve a further performance improvement, combined use of space-time transmit diversity (STTD) and antenna receive diversity is applied. The bit error rate (BER) performances of DS-CDMA downlink and uplink are evaluated by computer simulation. It is confirmed that the use of STTD and antenna receive diversity combined with MMSE-FDE is very effective to improve the BER performance. When STTD/receive diversity is used at both base and mobile stations, both uplink and downlink have almost the same BER performance for small number U of users. As U increases, the uplink performance degrades and exhibits BER floors due to large multiuser interference (MUI). However, the uplink BER floor When U=16 can be reduced to around 2×10^-3 when the spreading factor of SF=64 is used.