Reconfigurable Intelligent Surface-Assisted Space Shift Keying: A Channel Signature Constellation Perspective

This work inspects the channel signature (CS) constellations of reconfigurable intelligent surface-assisted space shift keying (RIS-SSK) systems. Investigations show that the optimum CS constellation occurs when the distinctness among CSs is maximized. This can be accomplished by directing all CSs in different directions with equal phase angles between consecutive CSs. Moreover, to operate with the optimal CS constellation, a novel optimum RIS-SSK (O-RIS-SSK) is proposed for an arbitrary number of transmit antennas. Furthermore, analytical expressions for symbol error rate (SER) and average SER for the O-RIS-SSK system are determined and verified by Monte-Carlo simulations. Comparative analysis shows that the proposed O-RIS-SSK system significantly outperforms existing RIS-SSK systems. Moreover, the proposed system is extended to multiple RISs and spatial modulation systems.