Space time block coded transmit antenna diversity scheme for WCDMA

Abstract

In this paper we present a new space time block code as an antenna diversity scheme for transmit antenna diversity. The space-time-transmit-diversity (STTD) method is an open loop transmit diversity scheme, i.e. it does not require any knowledge of the channel at the transmitter. Simulations have shown that the STTD scheme significantly outperforms the case where no antenna diversity is used. In fact, it even outperforms the non-diversity (ND) case even when soft handoff is used. STTD exploits the extra path diversity afforded by the second antennas and therefore outperforms two other open loop transmit antenna diversity techniques, viz. the orthogonal transmit diversity (OTD) and the time switched time diversity (TSTD). These techniques use multiple transmit antennas to provide some interleaver time diversity against fading, particularly at low Doppler rates and when the mobile receiver does not have enough paths at the RAKE receiver. STTD has the added advantages of being a power amplifier (PA) balanced technique, is easily backward compatible with ND systems and does not need careful interleaver design.