RIS-Assisted Railway Communications in Tunnels Using Cloudrt Simulator for Wideband Systems

Tunnels are one of the most challenging environments for wireless communications in millimeter waves due to the high risk of signal attenuation and blockage with trains, particularly in narrow tunnels. In this context, reconfigurable intelligent surfaces (RISs) play a significant role by making communications controllable. Raytracer is an excellent tool for realistically modeling and studying the propagation and behavior of channels in these environments. This paper focuses on extending the CloudRT raytracer simulator to work with RIS for wideband systems and evaluating the feasibility of deploying RIS in railway tunnel scenarios. We compare the effectiveness of RIS in two types of tunnels: a rectangular single-track tunnel and a rectangular double-track tunnel. Simulation results show that RIS is particularly beneficial in narrow single-track tunnels, especially when a train obstructs the direct Tx-Rx path.