STTD Decoding Combined with MMSE Equalization and Diversity Reception for MC-CDMA in the Presence of Multiple Users

In this paper, the space time transmit diversity (STTD) decoding combined with minimum mean square error (MMSE) equalization and antenna diversity reception is presented for MC-CDMA downlink and uplink in the presence of multiple users. The equalization weights that minimize the mean square error (MSE) for each subcarrier are used. From computer simulation, it was found that the downlink BER performance of STTD decoding combined with MMSE equalization and Mr-antenna diversity reception using the weights derived in this paper provides the same diversity order as 2Mr-antenna receive diversity with MMSE equalization but with 3dB performance penalty. The uplink BER performance can also be improved with STTD, but the error floor still exists. However, with 2-receive antennas in addition to 2-antenna STTD, the BER floor can be reduced to around 10 even for uplink MC-CDMA.