metro networks
generate additional revenues”, he says. “Sensors in carriages and cabs can deliver a broad range of important environmental and performance indicators that in turn can improve efficiencies in the maintenance of both the train and the tracks and tunnels, or in terms of getting non-manual input on conditions in the event of an emergency of some kind. “At the other end of the spectrum, train operators can look
at selling digital advertising space on in-carriage screens, with the content being regularly and automatically refreshed.”
The travel experience Similar points about the potential of TETRA data applications to improve operations are made by Stephen Northcott, senior manager at Motorola Solutions, who also highlights the importance of customer satisfaction. Tis is an especially important issue if the wider population is to be persuaded away from using alternative forms of transport such as cars – especially in cultures unused to mass transit services. “Te user’s whole travelling experience must be enhanced”,
Northcott says. “And TETRA can achieve this in a number of ways, both by collecting real time information from on-board diagnostic systems and trackside sensors and by returning real- time information to the travelling public in the form of digital displays on platforms and in carriages. “Data overheads don’t have to be large and digital displays
can carry libraries of messages that are invoked by remote command as situations change.”
Adding RFID Other wireless technologies also have a role to play here – most notably RFID, which is currently being exploited by companies like Tagmaster to automatically identify and position rolling stock even under the extreme conditions found within underground Metro systems. Already implemented on the London Underground system
in a Motorola project, RFID readers are mounted underneath the train cabs to identify ID tags mounted on sleepers and enable the radio system to automatically change talk group as the train enters a new zone. In another project, this time for the overland Netherlands
railway, a system using Tagmaster technology enables wheel pairs suffering from faults and flats to be identified automatically and accurately, and quickly taken out of service before further damage is done to track or train. Integration of metro TETRA systems with other
communications networks and applications – most significantly those supporting public security and safety – is a recurring theme in longer term plans, and the newer distributed architectures using IP have a key role to play in enabling interconnection.
TETRA – or GSM-R? Two questions, however, remain to be resolved. Firstly there is the issue of how TETRA will coexist alongside GSM-R, the version of GSM developed for the rail sector to handle voice, signalling and telemetry and currently in place in around 30 countries around the world. Debate continues to recur about the viability of GSM-R in the longer term, especially where short-haul travel is involved such as on urban commuter routes. One new TETRA functionality – Expedited Handover – is
particularly relevant to both rail and metro systems because it enhances the ability of radios to hand over to a new cell
Issue 2 February - April 2011 TE TRA TODAY
Passengers on the Beijing Metro system: several of its lines have been equipped with TETRA radio systems by Motorola, including the Airport Express line. Last year, Radio Frequency Systems (RFS), which designed the system for Line 4, announced that it had also been selected as general integrator for a TETRA installation on the Changping Line. This will also use Motorola equipment
quickly as the train moves along. “GSM-R specifies certain parameters for handover, essentially blocking TETRA solutions from that marketplace”, comments Cassidian’s Pesonen. “Important questions exist as to why those particular parameters have been set as they are and what their exact and continuing justification is.”
Finding bandwidth Te second issue – a recurring one as far as the wider, longer term future of TETRA is concerned – concerns bandwidth and the current drivers in the public security and safety sector which naturally interact with the metro market. Sébastien Sabatier, a TETRA expert at Tales, comments:
“Mass transit applications – and especially train and metro applications – are mission-critical, just like public safety. In this context, it’s important to watch what’s happening in the USA with their 4G public safety project and President Obama’s call earlier this year for an investment of $7.5 billion in this area using LTE as an access technology. “We’re currently co-operating with Samsung, developing
LTE and WiMAX on a TETRA core and the size of the US market alone is likely to have a huge impact on the cost and performance of solutions in other mission-critical areas – such as metro solutions.”
‘
One new TETRA functionality – Expedited Handover – is particularly relevant to both rail and metro systems because it enhances the ability of radios to hand over to a new cell
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