Train control goes wireless

Radio technology means smoother delivery of advanced signalling

Thales’ SelTrac is the world’s most widely used communications-based train control system. And with Thales’ radio-based transmission system, it’s even easier for metro operators to harness the capacity benefits of SelTrac CBTC.

“There’s a large market shift towards radio-based CBTC” says Dr. Colin Bantin, Chief Engineer, Communications for Rail Signalling Solutions, Thales. “Radio offers higher bandwidth and much greater flexibility for expansion than conventional induction loop communications.”

The solution uses the 802.11 radio protocol, first deployed by Thales in the United States in 2004. It’s an open standard, so there’s no supplier lock-in and components can be purchased off the shelf.

Protecting operations
Security is at the heart of Thales’ offer. “We have implemented a unique solution to support open-standard radio” says Dr. Bantin. “By providing multiple links to each train, the risk of service interruption caused by interference is reduced to the absolute minimum.”

Thales’ radio incorporates authentication protocols to ensure that messages picked up by trains have come from a trusted source. “This goes beyond encryption” emphasises Dr. Bantin. “Thales’ authentication process uses the IPSec open standard with a dynamic key management system that provides maximum security from the train control computer right through to the train itself.”



Resilience and flexibility
As well as offering enhanced security, radio-based CBTC eliminates vulnerabilities associated with conventional train-to-wayside communications.

There’s less lineside equipment and no loop between the rails that can be damaged during maintenance. Thales’ solution is much less susceptible to vandalism and the risk of cable theft is cut, because copper cable is not used.

Radio is comparatively easy to install and maintain. “The system is also readily expandable to include additional lines and can be modified without service disruption, thanks to our overlapping coverage philosophy” adds Dr. Bantin.

The extra bandwidth provided by radio makes it possible to handle audio (voice), video (CCTV) and data (including alarms) while on the move. This opens up the prospect of new onboard services to enhance passenger comfort.

Thales advocates increased interoperability and works with rail industry partners, including the New York City Transit Authority in the United States, and the EU-backed MODURBAN research project in Europe to develop common standards for urban rail.

Service proven
Thales’ radio-based CBTC is trusted around the world and already covers more than 200 km of metro and urban rail routes with implementations in Beijing, Hong Kong, Las Vegas, Shanghai and Washington Dulles International Airport.

Upcoming implementations include Beijing’s new Daxing line and key projects in South Korea, with new lines in Seoul, Busan and Incheon. Thales’ radio solution is also being used in a major retrofit of Line 13 of the Paris Metro.