RIS-Assisted SSK With Dual-Mode Reflection Phase Modulation

In this letter, a new reconfigurable intelligent surface (RIS)-assisted space shift keying (SSK) and dual-mode (DM) reflection phase modulation (RPM) scheme named RIS-SSK-DM-RPM is proposed, where RIS performs two tasks: 1) reflecting the incident signal from the transmitter, and 2) being divided into multiple groups each modulated by one of two distinguishable modes. RIS transmits its own information bits not only by reflection phase shift but also implicitly by the mode pattern index. Thus, the proposed scheme significantly improves the spectral efficiency. Furthermore, a low-complexity tree-search-based decoding algorithm is proposed. Simulations and theoretical analysis show that the RIS-SSK-DM-RPM scheme achieves remarkably better bit error rate (BER) performance than the existing RIS-SSK-RPM scheme.