Wireless Train Backbone (WLTB) Communications: simulation of antenna propagation between two vehicles

5 April 2022

One of the objectives of Safe4RAIL-3 Work Package 2 is to simulate the wireless propagation between two vehicles of a train, in order to replace the currently-wired train data backbone by a Wireless Train Backbone (WLTB), using antennas located on the roof of the vehicles. In this context, it is important to study the effect of the different elements located on the roof as well as the surrounding environment. Some examples of elements located on the roof are auxiliary boxes, fairings or pantographs. Regarding the environmental elements, the most important ones are tunnels and the railway curvature. There are also other elements that can affect the system in a minor way, such as the catenary, posts along the railway track, bridges or train stations.
In order to tackle this challenge, a fully-parametrized simulation model has been built in order to be able to simulate any kind of scenarios and to study the impact on the wireless propagation. This approach allows to define the best positions for the antennas or to suggest modifications on the roof configuration, in order to improve signal strength and reliability. However, a model of two train vehicles is too large for classical finite element methods, as the simulator requires an excessive amount of computer resources to simulate the full model. A way to overcome this is the use of asymptotic simulators based on Shooting and Bouncing Rays (SBR) techniques, where the simulator treats the electromagnetic propagation as optical rays. When the ray reaches a surface, the simulator considers the reflectiveness of the surface and calculates the bouncing ray on the surface. The result is an image with the launched rays and their propagation paths throughout the model.
In Safe4RAIL-3 WP2, this approach, followed for the WLTB, will also be extended to optimize the location of antennas inside the train for a Wireless Consist Network (WLCN), made by connecting end devices such as sensors or cameras to train control units. This simulation approach will also be applied to optimize the location of the antennas on the roof for Train-to-Ground (T2G) links.