A quasi-orthogonal group space-time architecture for higher diversity gains

Multiple-input multiple-output (MIMO) systems can provide two kinds of gain: diversity gain and multiplexing gain. Most existing MIMO schemes, including space-time coding and layered space-time, aim at maximizing either of them. Therefore, it is desirable to design a scheme to get a better tradeoff between the multiplexing gain and diversity gain. In this paper, a novel quasi-orthogonal group space-time (QOGST) architecture is proposed. In QOGST, the transmit stream is divided into several groups and all the groups are encoded via an inter-group space-time block encoder. Group interference suppression is adopted at the receiver. Performance is evaluated in terms of symmetric energy and it is shown that compared to the group layered space-time (GLST) architecture, the proposed QOGST can achieve a higher symmetric energy and a better diversity-multiplexing tradeoff. Simulation results validate our analysis and show that QOGST can achieve at least 3 dB gain over GLST at a FER of 10^-3, for instance.