An important system requirement was to concurrently support all four tunnel communications systems. At the heart of the system is the 900MHz Global System for Mobile Communications-Railway (GSM-R). Emergency services use a separate terrestrial trunked radio (TETRA) system operating at 380MHz, with the London Fire Brigade operating an additional 462MHz system. Communications to the locomotive is presently via cab-secure radio (CSR) operating at 448MHz.
According to Moxsom, the GSM-R system will ultimately replace the CSR and also the trackside signalling. All signal and control information will be transmitted directly to the locomotive, and the familiar sight of railway signals alongside the track will be a thing of the past.
Reliability and redundancy
In such systems, a fail-safe mechanism stops the train if the GSM-R communications are lost for more than three seconds. For built-in system redundancy, every component of the CTRL Section 2 communications system has been duplicated. The RFS RADIAFLEX cable was the only exception, as in single-cable format it exceeded the ‘mean-time-between-failure’ (MTBF) reliability specifications.
This was achieved, not only because of the quality of the cable, but also by careful system design: the dual-redundant communications signals are fed simultaneously into the cable, from opposite ends of the tunnel. In the event of accidental cable damage, communications can continue on both sides of the break.
The emerging use of GSM-R for train control in CTRL Section 2 and other links opens the way for harmonized communications systems throughout the entire pan-European rail network. GSM-R is also gaining acceptance elsewhere, with plans for its implementation in India, China, the USA and Australia. This standard—coupled with premium infrastructure such as the ClearFill solution set—stands ready for a key role in enabling trains to move freely across national borders and continents around the world.