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

Abstract

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.

Radio Communication for Communications-Based Train Control (CBTC): A Tutorial and Survey

“…Leaky waveguide involves very limited open-air communication, which takes place over a very short distance-normally in the range of 0.3 to 0.6 meters-between the leaky cable and the receiver antenna on the train. Thus, leaky waveguide guarantees a more predictable propagation loss and is less susceptible to interference [47], [62]- [64].…”

“…While radio communication is used in tunnels, leaky waveguide is used in open-air locations where interference is significantly higher, or in the critical locations where radio communication is exceedingly problematic [62]- [64]. An example is stations in tunnels, where several standing trains could obstruct the line-of-sight (LOS) path to the nearest AP.…”

“…A waveguide is a device, usually a hollow metal tube, which transports radio waves from one point to another with minimum propagation loss, a phenomenon known as "the waveguide effect" [61], [62], [97], [106], [107].…”

An experimental study of rectangular leaky waveguide in CBTC

“…Heddebaout [1] has done the field test for the leaky waveguide. But the test method in his paper is not specific; the experimental result is not so intuitive.…”

Modeling of Communication-Based Train Control (CBTC) Radio Channel With Leaky Waveguide

“…Due to the specificity of the CBTC application, there are only a few research works about leaky waveguide in CBTC systems. The author of [4] gives a description of leaky waveguide used in CBTC systems, and the advantages of leaky waveguide are demonstrated by comparisons to natural propagation.…”