Finite Resolution RIS-Aided MIMO Downlink Communications Based on SZFDPC

A novel design of reconfigurable intelligent surfaces (RIS)-aided MIMO downlink communications is proposed in this paper. The new design employs successive zero-forcing dirty paper coding at base station and allows users to have multiple antennas for receiving, making it much more realistic for modern wireless communications. Furthermore, the new design uses RIS elements with finite and low resolution of phases and is highly practical for implementation. Simulation results show that the proposed design significantly improves the performance of RIS-aided downlink communications. In particular, for the classical scenario of single-antenna users, the design using only QPSK phases for RIS elements increases by more than 35–347% the energy efficiency of several existing works that require an infinite phase resolution for RIS elements. When applying to the MIMO scenario, the design can further double the energy efficiency.