Experimental Assessment of 5 GHz WiFi Coverage Expansion in Underground Mine Using Reconfigurable Intelligent Surface

This paper explores the application of Reconfigurable Intelligent Surfaces (RIS) to expand 5 GHz WiFi coverage in underground mining environments, where traditional RF networks face significant challenges due to complex propagation conditions and Non-Line-of-Sight (NLOS) scenarios. Using RIS with transmitarray-like behavior, we demonstrate the ability to dynamically redirect electromagnetic waves into orthogonal tunnels, overcoming sharp angles and confined spaces. Our experimental study, conducted in a decommissioned underground mine, shows that a daisy chain of RIS can improve signal strength by up to 30 dB and extend coverage to more than 90% of previously unreachable areas. The LATYS FOCUS RIS prototypes used in this work exhibit high directivity, enabling efficient signal bending without degradation of the already covered areas. To complement the experimental findings, we propose a simulation methodology integrating RIS models into a standard RF planning tool. By accurately modeling the propagation behavior in tunnels with sharp angles, the simulations align closely with real-world measurements, validating the feasibility of using RIS for RF network planning. These results highlight the transformative potential of RIS technology in underground mining, offering a scalable, cost-effective alternative to traditional deployments involving extensive cabling and multiple access points.