Heathrow Express has claimed a world first for its deployment of wireless broadband on trains that travel underground through 6km of tunnels.
The main challenge for the engineers was to develop and test technology that could be used on moving trains, since most Wi-Fi implementations use fixed points, which can guarantee that connections remain stable.
The mobile network was designed and implemented for Heathrow Express by Nomad Digital and T-Mobile. It allows travellers to use T-Mobile's premium Wi-Fi service to check e-mails and surf the web from their laptops on the 15-minute journey between Paddington Station and Heathrow Airport.
The project, which ran from December 2006 to the end of March, involved refitting 14 trains with antennae and other equipment, and fitting tracks with wireless base stations, said Jay Saw, commercial director at Nomad Digital.
The network uses 802.16 Wimax wireless broadband technology running at 8mbps and T-Mobile's cellular HSDPA technology, which operates at 3.4mbps.
The trains have black box devices that switch seamlessly between the cells by listening out to at least two base stations at any one point, said Saw. This approach meant that a strong network connection could be maintained, he added.
The network design had to meet the approval of several rail bodies, and the deployment had to be scheduled months in advance because trains needed to be held at depots.
Heathrow Express is now exploring the use of wireless CCTV on its trains. "It has huge implications for security," said Saw.
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