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The first passenger train to use Switzerland’s newly constructed Gotthard Base Tunnel has successfully traversed its 35.5 mile length, with passengers able to use their mobile devices as normal throughout the passage, thanks to an underground 4G Long Term Evolution (LTE) network supported by CommScope and Alcatel-Lucent.
At its opening, the Gotthard Base Tunnel is officially the longest and deepest passenger traffic tunnel in the world. It is 4.2 miles longer than the Channel Tunnel, the previous record holder.
It forms part of a massive civil engineering project underway in Switzerland, which is designed to boost freight transport capacity across the mountains and take polluting trucks off Alpine motorway routes.
It also establishes high-speed passenger services between Switzerland and Italy, which will eventually cut transit times from Zürich to Milan by an hour.
The tunnel was first approved by the Swiss in a national referendum in 1992 and construction began in 1996. While mobile technology was well in use in the mid-1990s, the idea of bringing publicly accessible mobile networks into the tunnels was not really considered at first.
However, the tunnel needed network provision for emergency services use. In 2009, Alcatel-Lucent, the supplier responsible for communications provision on the project, enlisted wireless comms specialist CommScope to provision wireless network coverage through the tunnel.
“The main focus was first on public safety, this was the highlight,” said Cem Derdiyok, country manager for Switzerland at CommScope.
Railway operators and emergency personnel will be the primary intended users of the system, with their traffic separated on a different, fully redundant network layer from the publicly accessible signal, a key condition of the contract.
The network infrastructure consists of CommScope’s ION-M multi-band, multi-operator fibre distributed antenna system and Radiax radiating cables through the tunnel. Its deployment was a challenging endeavour for the supplier.
“At a depth of up to three kilometres, this is a harsh environment in terms of temperature and humidity. It made installation a physical and technical challenge,” said Derdiyok.
The main technical challenge was supporting the high-speed handoffs that will be required as passengers move through the tunnel, eventually at speeds of 250kph – meaning they spend approximately 15 minutes underground.
The ION-M system has been specifically designed to eliminate this problem. First, a master unit block is connected to several remote units in the tunnel over fibre. These remote units then transmit the signal along the tunnel by means of a kilometre-long Radiax cable from both ends, with signals from different cells.
This means devices moving through the tunnel at 250kph – roughly 70 metres per second – can pick up and measure the next remote unit early enough to handover without dropping the signal.
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CommScope estimates that at top speed, the time from first detection of the handover candidate to the location where the previously serving remote unit “disappears” is around 14 seconds.
Meanwhile, at the tunnel’s entrances and exits, special cells provide coverage approximately 1km outside the tunnel and 1km inside it. By following the same handover formula, this ensures that passengers can move seamlessly from outdoor to underground coverage.
Phil Sorsky, head of European service providers at CommScope, said the benefits for both rail operators and the Swiss mobile networks would be wide-ranging.
“Mobile users benefit from the ability to work or play on the move and network operators can harness a lucrative revenue stream. Train operators will not only improve the experience of their customers, but can advertise their mobile connectivity as a means of differentiating their network from their competitors,” he said.