Time-reversal space-time block coding and transmit delay diversity-separate and combined

Abstract

In this paper we evaluate the performance of what we call here, time-reversal space-time block coding (Lindskog and Paulraj 2000) combined with transmit delay diversity (Wittneben 1991). For comparison we also report on the performance of the two schemes separate, earlier studied in Flore and Lindskog (2000). When combining the two methods we transmit from four antennas and when studying the methods separately we transmit from two antennas. The methods are evaluated in a GSM-like system using test channels from the GSM standard. The time-reversal space-time coding scheme outperforms the transmit delay diversity scheme in two manners. First it achieves a higher SNR gain and second it does not increase memory in the channel and thus does not increase the complexity of the equalizer in the receiver. The combination of the time-reversal space-time coding scheme with the transmit diversity scheme has improved performance as it achieves a higher diversity order. At a BER of 1% the transmit delay diversity and the time-reversal space-lime block coding scheme use separately transmitting from two antennas achieves a gain of 2.5 dB and 3 dB respectively, for an urban scenario and 4.0 and 5.0 dB for a rural scenario, compared to single antenna transmission. When the two methods are combined transmitting from four antennas, a gain of 4.0 dB and 6.0 dB is achieved for the urban and the rural scenarios, respectively.