On the outage probability of quasi-orthogonal space-time codes

Recently, a quasi-orthogonal space-time block code (QSTBC) capable of achieving a significant fraction of the outage mutual information of a multiple-input-multiple output (MIMO) wireless communication system for the case of four transmit and one receive antennas was proposed. We generalize these results to 2 n transmit and an arbitrary number of receive antennas. Furthermore, we derive an an-alytical lower bound for the fraction of outage probability achieved with QSTBC and show that this bound is tight for low signal-to-noise-ratios (SNR) values and also for increas-ing number of receive antennas. We present also an upper bound, which is tight for high SNR values and derive analyt-ical expressions for the case of four transmit antennas. Fur-thermore, by utilizing the special structure of the QSTBC we propose a new transmit strategy, which decouples the signals transmitted from different antennas in order to detect the symbols separately with a linear ML-detector rather than joint detection, an up to now only known advantage of or-thogonal space-time codes (OSTBC).