Theoretical analysis of a simple transmit diversity scheme

Abstract

The paper presents a theoretical BER analysis of the transmit diversity scheme that was presented by S.M. Alamouti (see IEEE J. on Selected Areas in Commun., vol.16, no.8, 1998). We assume a flat Rayleigh fading channel and pilot-symbol assisted BPSK or QPSK modulation. Alamouti showed that the transmit diversity scheme gives the same diversity order as maximal-ratio receiver combining (MRRC). However, we show that the BER performance for the transmit diversity scheme differs slightly from the MRRC performance in the case where we apply non-ideal channel estimates. In fact, we show that twice as many pilot symbols are needed with transmit diversity to achieve the same diversity gain as with receive diversity.