An Adaptive Multi-User MIMO Scheme for the Millimeter-Wave Downlink

Space-time shift keying (STSK) constitutes a beneficial multiple-input-multiple-output (MIMO) technique that strikes a compelling trade-off between the multiplexing and diversity gains attained. Its close relative, namely layered multi-group STSK (LMG-STSK) combines the concepts of multi-user MIMO, STSK and beamforming for simultaneously conveying information to multiple users. Generalized frequency division multiplexing (GFDM) has been proposed as a promising multicarrier modulation candidate for dispersive wideband channels since it benefits from its time-frequency domain structure when combined with a powerful MIMO scheme. As a further evolution, we propose a novel GFDM-aided adaptive layered multi-group STSK (LMG-STSK) system for the downlink of millimeter wave communications systems. The proposed system tackles the propagation challenges of the high pathloss at millimeter wave frequencies, where multiple users are clustered into groups served by different antenna layers at the transmitter. We propose an adaptive scheme that can adapt both the number of transmit antennas (TAs) per layer based on the number of users in each user group in order to maximize the number of users served and also the STSK codeword in order to maximise the achievable user throughput.