Generalized spatial modulation for downlink multiuser MIMO systems with multicast

We propose a further generalization of spatial modulation (SM) in a downlink multiuser MIMO system with multicast in order to improve the system's spectral and energy efficiencies. A base station equipped with multiple antennas sends three types of information to several users who are also equipped with multiple antennas. The individual information to each user is conveyed in the form of receive SM as well as through conventional QAM modulation. On top of that, common transmit SM information is conveyed to all users. To this end, specific preprocessing and postprocessing are obtained based upon the singular value decomposition technique. A simple additional processing based on phase shifts is proposed to improve detectability. Computer simulation results reveal that the proposed scheme has improved average bit-error rate (BER) over a reference scheme under the same spectral efficiency.