Novel RIS-Aided Receive Spatial Modulation via Joint Active and Passive Beamforming

Existing reconfigurable intelligent surface-aided receive spatial modulation (RIS-RSM) suffers from severe performance degradation in Rician fading channels. To solve this problem, we propose a novel RIS-RSM scheme in this letter for multi-input-multi-output communications. In contrast to the existing RIS-RSM that uses passive beamforming only to maximize the received power at a targeted receive antenna, our advanced RIS-RSM employs joint active and passive beamforming (JAPB) to minimize the error probability of antenna index detection. The active and passive beamforming vectors are optimized alternately. It is shown that the active beamforming vector is the eigenvector associated with the largest eigenvalue of a matrix, and the passive beamforming vector can be obtained in closed-form in each iteration via a majorization-minimization method. Simulation results reveal the effectiveness of RIS-RSM-JAPB by comparing with the existing RSM and RIS-RSM schemes in terms of bit error rate and detection complexity.