Robust full-diversity full-rate quasi-orthogonal STBC for four transmit antennas

A novel quasi-orthogonal space-time block code (QSTBC) with full-diversity full-rate transmission and double-symbol decoding is proposed for a system with four transmit antennas, which is constructed by linearly combining two optimally power-scaled component Alamouti codes. Compared with the existing QSTBC with optimal constellation rotation, the proposed code provides excellent robustness, in terms of bit error rate performance, against spatially correlated and/or time-selective fading channels.