ASSETS, INFRASTRUCTURE & INNOVATION
The switch to GSM-R O
Network Rail’s FTN/GSM-R project has hit the latest in a series of major milestones, and over the next 18 months most of the rest of the country will become operational. Adam Hewitt reports.
n December 31, 2012, the old analogue NRN system (National Radio Network)
was switched off in the south of England, as operators switched over to using GSM-R (Global System for Mobile Communications – Railway).
It will gradually replace the more advanced CSR (Cab Secure Radio) too – GSM-R is much more modern, with digital quality, no interference, and the capability for data communications.
The infrastructure for the new track-to-train radio system is mostly in place already – the underlying FTN (Fixed Telecommunications Network), as well as 2,200 GSM radio masts along the entire network, ranging in height from five metres up to 29.
The project, the total cost of which including FTN, GSM-R and the cross-industry work is £1.839bn, has had a number of drivers. These included meeting European regulations, improving network resilience, the fact that the old NRN system was going to run out of capacity and there was a requirement from Ofcom to release the spectrum in the south of England, and preparing for future communications applications, from ticketing to signalling.
GSM-R addresses the requirements of several recommendations from reports into accidents, including the Cullen Report on Ladbroke Grove, which said there needed to be one unified system of signaller to train driver communications. The overall case has been made in terms of performance, however, with safety benefits being an added plus, for example by lowering the risk of accidents or injury from people getting in and out of cabs to use trackside phones.
GSM-R is only a 2G system, as the specifications have been around so long and the European mandating process was so complex. But it features five key improvements on previous systems (a lot of the extra features are also available on the public mobile phone networks, which use GSM, but just aren’t turned on). These are:
i) Location dependent addressing (this allows the ‘call my signaller’ function, for example, to route it to the right signaller along different parts of the track) ii) Functional addressing iii) Group call
iv) Broadcast calls (similar to group calls, but no-one can respond)
210 | rail technology magazine Apr/May 13
v) Prioritisation and an ‘All Trains Stop’ button (there are five levels, with the highest clearing any other call if the ‘big red button’ is pressed, giving every other train in the area a ‘stop’ message. The equivalent red button process with the previous NRN radios was slower and involved voice communications with the controller.)
Deciding on the protocols around the red button – exactly which services should be stopped, especially when geographically nearby but operationally very different routes might be affected – has been a balancing act. The UK radio equipment also has an extra feature not found in Europe: the yellow button, for less urgent emergencies that don’t require the stopping of the railway.
Resilience
Network Rail’s Trevor Foulkes, formerly the telecoms programme engineering manager and now a senior programme manager, who has had a long career in railway telecoms, said: “We try to make our network resilient. There have been cases in the past where derailments have taken out radio sites, and also cut the cable – [meaning] the very things you’d want to use to stop other trains weren’t actually available.
“So we took quite a lot of effort to ensure that FTN cabling, and the way we ran it and configured it, would be in rings so that the systems would keep running even when we cut cables or had derailments that cut them, or power failures, or cable theft. We’ve had all of that.
“The maintenance people can see any bit of kit in the FTN network or GSM-R, zoom right in and say ‘this card’s failed’, or ‘this input on this card has failed’. They can understand the impacts on operations, and go to the site and take the right card with them. Because we use the same kit everywhere, it’s much easier now.
“We designed it so they don’t have to dash out in the middle of the night – they can go in the day when it’s safer. It also means people aren’t having to fix things absolutely immediately – it can be done when there are no trains running, for example.”
Below: Operational GSM-R and IVRS (interim voice radio system) as of March 2013.
Performance
The performance improvements haven’t necessarily been immediate, however, partly due to staff having to get used to new features. Network Rail’s Dave Palmer, programme sponsor for the FTN/GSM-R project, said it had been a “mixed story”, explaining: “It has had performance impacts, and adverse impact has been felt a few times.
“But predominately the pendulum has swung the other way, with significant improved recovery [times] after incidents, for example.”
The biggest benefit has come for those who had previously used NRN, he explained – those using CSR would see fewer benefits by comparison, as it is already a more modern system.
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