New Activation Pattern Designs for RIS-SM Systems

In this paper, we address the transmission of local data on the uplink of wireless systems aided by reconfigurable intelligent surface (RIS) arrays using the concept of spatial modulation (SM), and we introduce new activation pattern designs for RIS-SM. First, we describe a simple design that transmits only one bit of local data per user symbol period, but achieves the maximum possible value of the minimum distance, which dictates asymptotic performance. Then, 3 new designs are introduced for increasing the local data rate while preserving the minimum distance. Two of these designs are based on 4-dimensional (4-D) signaling, and both offer higher data rates while preserving the minimum distance of the benchmark pattern design. Using 16-element and 64-element RIS arrays, the bit error rate performance of the proposed designs was confirmed by computer simulations.