The Impact of Interference Reflection on Reconfigurable Intelligent Surface-Aided Directional Transmissions

As a promising solution to deal with the blockage-sensitivity of millimeter wave band and to reduce the energy consumption caused by network densification, reconfigurable intelligent surface (RIS) shows good potential in improving the network performance. However, deploying large scale RISs leads to non-negligible reflection of interference, which may reduce the performance gain brought by RISs. In this paper, we investigate the coverage, spectrum efficiency and energy efficiency performance of a downlink directional transmission network with the aid of RISs using stochastic geometry. The numerical results show that deploying suitable density of RISs enhances the network performance while overly dense deployment brings performance degradation. We also find that the optimal RIS deployment fraction is a monotonically non-decreasing function of the blockage density and is monotonically non-increasing functions of the base station density and the beamwidth, which indicates that the deployment of RISs should be properly designed according to the network status instead of ‘the more, the better’.