RIS-Assisted Precoding Spatial Modulation: Optimal Design and Performance Analysis

Reconfigurable intelligent surface (RIS) is a vital enabler of paradigm-shifting transmission technologies for next-generation wireless. In this paper, we propose a RIS-assisted transmitter precoding spatial modulation (RIS-PSM), such that the transmission reliability of the PSM-modulated multiple-input multiple-output systems can be remarkably enhanced. To fulfill our novel design, a two-phase decision process (TPDP) based optimization algorithm is propounded, such that the optimal transmitter precoding vector and the RIS reflection matrix can be jointly achieved in terms of closed-form. In addition, we design two receive detection algorithms, namely the optimal co-detection (OCD) and the sub-optimal detached detection, by which the indices of the designated receive antenna and the baseband modulated signal can be reliably detected with different levels of computational complexity. Eventually, the achievable error performance is evaluated analytically for the RIS-PSM proposal with the detection of OCD. Simulation and numerical results are depicted to demonstrate the superiorities of the proposed system, as well as to substantiate the accuracy of the performance analysis.