Path Loss Modeling for Train-to-Train Communications in Subway Tunnels at 900/2400 MHz

Train-to-train (T2T) communications can improve the capacity and safety of railways. However, to implement these systems, it is necessary to model the propagation in the complex railway environment, where tunnels and stations are very frequent. This letter presents a detailed modeling of path loss for T2T communications, based on a measurement campaign conducted in a Madrid subway in a tunnel scenario, at two frequencies commonly used by railways signaling systems: 900 and 2400 MHz, in straight and curved tunnels and in special situations: a train passing a station or trains passing in different directions. In addition, the fast fading component is statistically analyzed, providing a complete model for T2T communications.