Multiuser steered signed quadrature spatial modulation for millimeter-wave massive multiple-input multiple-output with hybrid beamforming

In this article, signed quadrature spatial modulation (SQSM) scheme is intrinsically amalgamated with both fully digital geometric mean decomposition (GMD)-based precoding technique and analog beamforming (ABF) for transmission over millimeter-wave (mmWave) channel. Explicitly, the proposed scheme combines SQSM and GMD-based hybrid beamforming (HBF) in downlink multiuser scenario, where the Frobenius norm-based user selection algorithm is considered. This proposed scheme is denoted as multiuser steered SQSM (MUS-SQSM). The ABF is used to mitigate the severity of the propagation loss in mmWave band by using power amplifiers and phase shifters. The performance of the proposed scheme in terms of both the bit error rate and the average mutual information is assessed in comparison to the conventional SQSM scheme performance. Simulation results show that significant improvements are realized by both the user selection algorithm and the application of ABF technique as the number of antenna array elements increases. It is also demonstrated that MUS-SQSM scheme is robust against the channel estimation errors. Furthermore, the proposed MUS-SQSM scheme with HBF benefits from the multiplexing gain of SQSM, the diversity gain of serving multiple users, and from the beamforming gain. All these gains increase the energy efficiency of the proposed model; thus, the proposed scheme can be considered in 5G wireless systems deployment.