Signal detection for orthogonal/quasi-orthogonal space-frequency block coded OFDM transmit diversity schemes

The combination of space-time block coding (STBC) and orthogonal frequency division multiplexing (OFDM) has drawn much attention in recent years. However, the application of conventional STBC decoding for OFDM renders poor performance due to high channel gain variation across the STBC codeword. In this paper, we propose a square root and division free recursive QR (SDRQR) decomposition based detector for STBC coded OFDM systems that utilize four transmit antennas. The proposed detection scheme is applied to both orthogonal and quasi-orthogonal STBCs. Performance of the proposed detector is evaluated semi-analytically and compared with results obtained from exact link simulations. Our analyses show an excellent performance gain attained by SDRQR compared to previously proposed solutions. It is also shown that the relative computational complexity of the proposed detector is justified by the performance gain it attains over the previous solutions