Transmissive Reconfigurable Intelligent Surface Enabled Spatial Modulation for MIMO Systems

The authors propose a novel transmissive reconfigurable intelligent surface (TRIS) transmitter-enabled spatial modulation (SM) multiple-input multiple-output (MIMO) system, which activates specific column elements of the TRIS panel per time slot. The receiver employs maximum likelihood detection to retrieve the transmitted signals. The authors derive closed-form expressions for the upper bounds of the average bit error probability (ABEP) using both vector-based and element-based approaches. They also provide asymptotic ABEP expressions and diversity gain analysis. To improve the performance, the authors optimize the ABEP with a fixed data rate constraint and propose a simplified improved TRIS-SM scheme to reduce computational complexity.