Space-Time Quadrature Spatial Modulation

In this paper, a new multiple-input multiple-output (MIMO) transmission technique, which is called space-time quadrature spatial modulation (ST-QSM), is proposed. The ST-QSM scheme aims to provide a diversity gain for quadrature spatial modulation (QSM) by combining it with the Alamouti or ABBA space-time block codes (STBCs). In the ST-QSM scheme, the transmit antennas are subdivided into two groups and the information is conveyed with the indices of the antennas in these groups, in addition to the two complex modulated symbols. These two complex symbols are decomposed into their in-phase and quadrature components and independently transmitted through their corresponding active transmit antennas, whose indices are determined from the first and the second groups. Then, the Alamouti's STBC or ABBA STBC principle is applied to each group depending on the number of antennas in them. The superior error performance of the proposed ST-QSM scheme is shown by computer simulations compared to QSM, Alamouti's STBC and space-time block coded spatial modulation (STBC-SM) schemes. In addition, the pairwise error probability (PEP) of ST-QSM is derived and the average bit error probability (ADEP) over uncorrelated Rayleigh fading channels is obtained for different MIMO configurations.