The Channel Tunnel runs from Shakespeare Cliff in the UK to Sangatte in France and is composed of three tunnels of approximately 20 miles in length. It is operated by Eurotunnel and was completed in 1994, but up until now commercial wireless communications have been unavailable within the tunnels.
There is a northbound and a southbound tunnel for rail traffic, including trains that carry vehicles, passengers and freight, and a central service tunnel that provides maintenance and emergency support. The tunnels carry more than 300 trains, 49,000 people, 5,880 cars and 180 coaches each day.
Although Eurotunnel has had wireless communications in place using GSM-R (the rail industry version of GSM) to run tunnel operations and for public safety for some years, there has, until now, been no commercial communications service available.
That’s partly because the business case for rolling out technology to support consumers on a journey through the tunnel that takes less than 35 minutes has been hard to establish. The tunnel itself is also an unforgiving and hostile environment for wireless communications, while the complexity of bringing together telecoms operators, regulators and infrastructure owners has been insurmountably complex.
Regulating frequencies and transmitting radio signals through fibre optic cables – which present no problem above ground – are transformed into major technical challenges when the same equipment needs to be installed 40 metres below the seabed and has to provide the same level of quality. Adding to the technical challenge is the fact that the Channel Tunnel is also a high-speed rail network, with trains travelling at 160kmph. Although not the fastest rail speed in operation, this increases the difficulty of the task considerably.
Eurotunnel will provide the infrastructure for the transmissions of 2G (GSM 900, DCS 1800) and 3G (UMTS 2100) mobile networks in the railway tunnels of the Channel Tunnel to allow Eurotunnel Shuttle and Eurostar passengers to use their mobile phones.
The unique conditions in the Channel Tunnel make the installation a delicate operation. ‘The first technical challenge was due to the environment,’ says Stéphane Popiolek, sales leader for transportation at Alcatel-Lucent, which is providing and managing the new network on behalf of Eurotunnel.
‘It is a very long tunnel with a specific atmosphere. There’s fog and it’s quite humid so the requirements are stringent. The second technical challenge was that we wanted to mutualise the radio part to bring GSM-R and public UMTS GSM together on the same network with the potential to evolve to LTE.’
That creates problems of its own. ‘If we mutualise the infrastructure, we have a double quality challenge to address,’ explains Popiolek. ‘We had to avoid any interference between GSM-P and GSM-R. Obviously, we can’t afford for there to be any interruption of service between GSM-R users, but equally there is a very high requirement in terms of quality of service for commercial operators in UMTS data [delivery].’
Ian Brown, CEO of Axell Wireless, which has supplied the digital antenna system (DAS) for the project, also identifies the challenging environment. ‘Operating down there is quite challenging,’ he says, ‘but we’re used to that because a lot of our gear is used in metro systems around the world and has to contend with brake dust and extremes of hot and cold temperature. Our gear is very compact which, although not such a big issue in Eurotunnel, is a significant issue in many tunnel deployments.’
Brown also points out the multi-band capability of the Axell equipment being deployed. ‘The system is going to support the three major cellular bands of 900, 1800 and 2100MHz and a combination of 2G and 3G technology. Our equipment is agnostic in that regard.’
Eurotunnel has opted for radio coverage in the railway tunnels using a large band transmitting cable – also called radiating cable – coupled with active elements, the optical repeaters in the cross-passages that link the two tunnels with the service tunnel every 750 metres. An obvious technical limitation is that the tunnels have been designed to enable rail traffic to travel through them, not to accommodate bulky telecommunications equipment.
The commercial operators’ radio equipment will be installed in two buildings constructed near the tunnel entrances. The south tunnel, which will be covered by the French operators, will be the first to offer commercial services following an agreement signed at the French Ministry for the Economy, Finance and Industry on 6 March 2012.
Eurotunnel, the French telecoms operators Orange, SFR, Bouygues Telecom and Free and the equipment provider Alcatel-Lucent signed an agreement to deliver this €14m investment, in the presence of Eric Besson, the French Minister for industry, energy and the digital economy. Since Free is a relatively new operator, it will join the project in 2017.
These operators will finance the €14m GSM-P installation while Eurotunnel will contribute €4m to the costs of the common GSM-R/GSM-P elements. Services in the south tunnel will be operational in time for the London 2012 Olympic Games in July.
The north tunnel, in which traffic runs from the UK to France, will be covered by the UK operators T-Mobile, O2, Orange, Vodafone and Three, with operations starting after the Olympic Games.
Users will not be invoiced a supplementary charge for communications in the tunnel. They will, however, be subject to roaming charges according to whether they are in France - in the south tunnel - or the UK - in the north tunnel - in the same way as they would at the surface when travelling between different countries.
‘Don’t forget this is a fully mutualised network,’ adds Popiolek. ‘It is shared between the GSM-R users and the eight commercial operators so, in the end, the capex for each is smaller. There’s a real business case. The French operators see it as a marketing and communications gain, but all operators also rely to a degree on roaming revenues and tunnel communications have the potential to increase usage, depending on the business model operators choose. For Eurotunnel, the interest is to better serve their customers. Freight transport is the largest Eurotunnel customer and being able to provide access to freight drivers through the tunnel and track lorries will be valuable.’
The regulatory issue
It was essential to create a consensus between the companies involved and the regulatory authorities – Ofcom in the UK and its opposite number ARCEP in France. It is normal practice that telecoms operators stop transmitting at international frontiers, but this notion of territorial sovereignty was uniquely reviewed for the chosen configuration, as the operators did not want the geographical frontier between the United Kingdom and France to act as the limit to the transmission zone.
Therefore, the system is not constructed using the geographic definition of the frontier, but on the understanding that the French networks cover the south tunnel while the UK operators cover the north tunnel.