[Poster Presentation]Optimum Number of Transmit Antennas for STTD in MC-CDMA Distributed Antenna Network

Abstract Distributed antenna network (DAN) can mitigate the problems arising from of the propagation path loss and shadowing loss and achieve better transmission performance over the entire cell area compared to centralized antenna network (CAN). Many transmit antennas are spatially distributed in DAN while they are co-located at the same base station in CAN. The use of space time block coded transmit diversity (STTD) can further improve performance. As the multi-access scheme, multicarrier code division multiple access (MC-CDMA) is attractive since it can alleviate a sophisticated resource allocation while achieving the frequency diversity gain. In this paper, the STTD downlink transmission is considered for MC-CDMA DAN. In STTD downlink, higher spatial antenna diversity gain is obtained by increasing the number of transmit antennas. However, the STTD code rate reduces. Furthermore, since the propagation time delays of signals transmitted from some transmit antennas may exceed the cyclic prefix (CP) length of MC-CDMA, the inter-block interference (IBI) is produced. Therefore, there exist the optimum numbers of transmit antennas to be involved in STTD downlink. In this paper, we derive an expression for the received SINR after de-spreading and evaluate, by computer simulation, the STTD downlink capacity to discuss about the optimum number of transmit antennas.