Improved decoder schemes for QOSTBCs based on single-symbol decoding

It has been shown that a quasi-orthogonal space-time block code (QOSTBC) provides full transmission rate for four transmit antennas [3]-[5]. However, one of the QOSTBC's main disadvantages is high decoder complexity due to the channel interference terms in detection matrix. In this paper, we propose two improved decoder schemes to reduce complexity at the decoder. Our decoder schemes can fully eliminate channel interference parameters in detection matrix. As a result, only diagonal components remain, and we can detect the transmitted symbols easily with single-symbol maximum-likelihood (ML) detector. The proposed schemes can be used for all known QOSTBCs in four transmit antennas systems and can be extended for systems with number of transmit antennas greater than four.