Differential scheme for reconfigurable intelligent surface-based spatial modulation system

In this paper, a differential scheme is proposed for reconfigurable intelligent surface (RIS) assisted spatial modulation, which is referred to as RIS-DSM, to eliminate the need for channel state information (CSI) at the receiver. The proposed scheme is an improvement over the current differential modulation scheme used in RIS-based systems, as it avoids the high-order matrix calculation and improves the spectral efficiency. A mathematical framework is developed to determine the theoretical average bit error probability (ABEP) of the system using RIS-DSM. The detection complexity of the proposed RIS-DSM scheme is extremely low through the simplification. Finally, simulations results demonstrate that the proposed RIS-DSM scheme can deliver satisfactory error performance even in low signal-to-noise ratio environments.