NOMA-aided generalized pre-coded quadrature spatial modulation for downlink communication systems

Generalised pre-coding quadrature spatial modulation (GPQSM) is recently proposed to increase the spectral efficiency (SE) of GPSM, which extends the transmitted symbols into in-phase/quadrature domains. In this paper, a novel scheme named non-orthogonal multiple access (NOMA)-aided GPQSM (NOMA-GPQSM), which incorporates the GPQSM scheme into the multi-user communication networks with assist of NOMA, is proposed to further improve the SE and system performance. In NOMA-GPQSM, one base station (BS) is set to serve K users, where user 1 is closest to the BS, and user K is farthest from the BS. In addition, a low-complexity detection method is proposed to reduce the high detection complexity of the maximum-likelihood (ML) detection in successive interference cancellation (SIC) method for all users by NOMA-GPQSM. The theoretical analysis of the BER performance for all users is also derived. Simulation results show that near users achieve relatively good performance, and far users achieve acceptable performance by adjusting power factors for all users in NOMA-GPQSM.