featuretrack focus
Clive Kessell reports...
GSM-R is an acronym increasingly
familiar to most railway people. It means
Global System for Mobile – Railway. So
what is this system and how did it come
about? Track to train radio has existed for
many years in the countries of Europe,
although the UK was always slow to systems incorporating group and The GSM-R Constituent Parts
develop and use radio. By the 1970s, the broadcast calling and priority call A GSM-R system has five main
number of different technologies across facilities components:
Europe was too great - each country • a bearer for the European Train Control MSC (Mobile Switching Centre). This is
having 'invented' its own specification, System (part of ERTMS) between signal the 'intelligence' of the system where all
backed by national radio suppliers. control centres and trains. the call routing, the data processing, the
The UIC attempted to standardise things functional numbering register and call
with Leaflet 751-3 but this was only Developing the specification management is done, including the
'Advisory' and could not be mandated. In The European Telecommunications priority and pre-emption to meet specific
any case, the UIC specification called for a Standards Institute (ETSI) was directed to rail operational requirements. Railway call
four frequency channel in the UHF band, develop the specification and work rates are much lower than in public GSM,
which was both wasteful and unlicensable started in 1993. Radio suppliers were so only one MSC is normally required per
in some countries, the UK being one. coaxed on board and a test programme rail network.
Britain developed the Cab Secure Radio (Project EIRENE) was commenced. GSM-R In practice most countries provide two,
and also the lower specification add-on to was underway. so as to provide a back up in the event of
the National Radio Network as an An important element was to get a failure. From the MSC, connections are
alternative to this. standard allocation of frequency made to the Radio Block Centre if ETCS is
bandwidth across Europe. This was being used, to the Signallers' Control
The need for a Single eventually achieved with a 4 MHz Uplink Consoles, to external telephone networks
International Standard (Train to Ground, 876 – 880 MHz ) and a and to an Operational Management
By the early 1990s, these forerunner Downlink (Ground to Train, 921 – 925 Centre for maintenance and system
systems needed to be replaced and a MHz). Not all countries including the UK control.
decision to develop a new specification could release these frequencies BSC (Base Station Controller). These are
was taken, which would be mandatory immediately, but it was a major step connected to both the main and standby
within the EC. The two choices of forward. The MORANE trials as part of MSC and are the focal point for
technology identified were: EIRENE started in 1995 in Germany, Italy distributing and routing radio signals to
GSM – the then new standard for the and France. Some initial problems were and from the lineside transmitting points.
public mobile networks found but the basic concept of using GSM Each BSC can support up to 250 BTSs.
TETRA (Trans European Trunked Radio technology for track to train TRAU (Transcoder Rate Adaption Unit).
Application) – driven by the need for a communication was proven. This sits between the MSC and the BSCs
unified system for the emergency
services.
Advocates of both technologies
campaigned vigorously for the perceived
rail business. A contract to compare the
two systems was let by the UIC to Smiths
Systems Engineering of Guildford, UK.
Trials were conducted which concluded
that both GSM and Tetra could be used for
railway application but some adaptation
of the specs would be necessary.
The decision to go GSM was made
because it was by then an established
technology and many firms were making
equipment. TETRA was still a bit of an
unknown at that time with a commercial
future far from being assured. The
implementation costs for the two systems
were similar.
The railway requirements were two fold:
• a replacement for existing voice radio
36 | the rail engineer | october 2008
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