Leaky Waveguide for Train-to-Wayside Communication-Based Train Control

Abstract

In guided urban automated transportation systems, the maintenance of a high-quality broadband train-to-wayside communication at all locations along the track poses a major problem. Several techniques are currently used. However, to achieve sufficient rates, a communication frequency range of 2-6 GHz is widely in use. At these frequencies, the natural propagation in tunnels usually works efficiently, but the communication through a leaky waveguide that is continuously laid along the track has several advantages. Over the required communication ranges of several hundred meters, between stations, such waveguides provide low longitudinal attenuation and remain of reasonable size. They also provide predictable communication ranges that could offer significant advantages over the natural propagation approach. This paper will theoretically and experimentally describe such a technical solution. Using ray-optical modeling of the radio propagation in a railway-type tunnel, the radiation characteristics of such a system will be evaluated. At the same operating frequencies, it will be compared with a conventional base solution using antennas separated a few hundred meters apart. An example of a recently operational implemented system will be presented.