Transmit Antenna Shuffling for Quasi-Orthogonal Space-Time Block Codes With Linear Receivers

Recently, various quasi-orthogonal space-time block codes (QO-STBCs) have been proposed in multi-input and multi-output (MIMO) channels. These codes achieve a full code rate (R=1) at the expense of a loss in the diversity gain. In this paper, we propose a transmit antenna shuffling scheme for QO-STBcs. We show that by adaptively mapping the space-time sequences of the QO-STBC to the appropriate transmit antennas depending on the channel condition, the proposed scheme can improve its transmit diversity with limited feedback information. The performance of the scheme with various numbers of shuffling patterns is analyzed. The bit error probability of the schemes is evaluated by simulations. It is demonstrated that with the linear zero-forcing (M) and the minimum mean squared error (MMSE) receivers, the closed-loop QO-STBC of four transmit antenna shuffling patterns can achieve almost the same performance as the ideal 4-path diversity by using two feedback bits and it is about 4-5 dB better than the open loop schemes.