Enabling Media-Based Modulation for Reconfigurable Intelligent Surface Communications

Reconfigurable intelligent surface (RIS) is highly promising to be applied to enable media-based modulation (MBM) transmissions, which is expected to greatly reduce the hardware cost at the transmitter. In this paper, we propose the two MBM schemes for RIS communications, which are non-differential and differential schemes. In the non-differential scheme, we utilize the phase variations of the RIS to achieve a higher transmission rate compared to the conventional MBM schemes with radio frequency (RF) mirrors. Particularly, in the differential scheme, we decompose the space time block (STB) matrix into a phase state space (PSS) matrix and a selection-permutation (SP) matrix for enhancing the flexibility of differential modulation. The proposed treatment breaks through two inherent design limitations in the traditional differential space time block code (DSTBC). Moreover, the upper bound on the average symbol error rate (SER) of both schemes are derived. Finally, the theory and simulation results show that our proposed schemes can achieve higher transmission rates than the benchmark schemes.