Transmit diversity by antenna selection in CDMA downlink

We study transmit diversity concepts in DS/CDMA wireless networks with multiple transmit antennas. The previously proposed diversity techniques are reviewed and their performance is compared to a selective transmit diversity (STD) concept, proposed here for CDMA systems. In all the competing concepts the encoded bits are distributed to all transmit antennas, whereas in the proposed concept bit are transmitted only from the best antenna as indicated by a closed loop antenna selection (CL-AS) subchannel from the terminal to the base. We quantify the achievable gains for these transmit diversity concepts with Monte-Carlo simulations.