UHF and SHF Fading Analysis Using Wavelets in Tunnel Environments

The propagation of electromagnetic waves in tunnel- like environments differs from other scenarios, basically because tunnels can act as a waveguide, allowing the communication range to be extended. Nevertheless, phenomena such as strong fadings appear. In this context, our research group has been performing multi-robot navigation under communication constraints in this kind of environments. It is clear that fadings greatly affect communication among robots, and an in-depth study of these phenomena is required. In this paper, we present the results of a measuring campaign carried out in the Somport tunnel (in Spain) at 433 MHz, 868 MHz, 2.4 GHz and 5.2 GHz. Slow and fast fadings, as well as near and far sectors are analyzed using wavelets, a tool never used before to study propagation in tunnels. Results obtained from the wavelets and from classic filtering techniques are compared, showing that the former have the advantage of condensing most of the useful and valid information in a single graph.