NOMA-based precoded quadrature spatial modulation in multiuser MIMO downlink transmission over correlated channel

In this paper, a non-orthogonal multiple access (NOMA)-based precoded quadrature spatial modulation (PQSM) technique (NOMA-PQSM) has been proposed for the downlink scenario. In NOMA-PQSM, two intended receiving antennas are activated at any time instant. One antenna is activated for the in-phase component of the transmitted signal, and another one is activated for the quadrature phase component, on the basis of data bits. NOMA-PQSM provides benefits like improved spatial diversity and spectral efficiency in comparison with spatial modulation. This work uses zero forcing (ZF) precoding over downlink flat fading Rayleigh multiple input multiple output (MIMO) channels, to limit the channel's deteriorating effect on transmitted signal, assuming perfect channel state information (CSI) at the transmitter. A low complexity receiver based on the successive interference cancellation is used. An expression for the upper bound of average bit error probability is derived. Moreover, the expressions for the sum mutual information of users and its lower bound are also derived. The proposed scheme is compared with the preprocessing aided spatial modulation (PSM)-based counterpart. Monte Carlo simulations reveal that the NOMA-PQSM scheme outperforms its orthogonal counterpart and the PSM scheme.