Abstract: The invention consists of a communication system that relays a satellite signal inside railway tunnels and relays the signals transmitted inside said tunnels towards the satellite, in such a way as to assure to vehicles transiting inside the tunnels a perfect transmission and reception quality even in the absence of satellite visibility. The system is based on a fixed terminal, for gallery illumination, connected to a fixed satellite station, and on a mobile terminal installed on the vehicle, connected to a mobile satellite terminal. The system automatically effects a switching action between satellite channel and radio channel in the tunnel, and vice versa, to assure the continuity of the vehicle-satellite connection. The system finds elective application for railway vehicles.