The LAN also covers an area around the terminal - and could be extended across the tarmac in future.

Although the Aruba kit can be used for mesh deployments, Arup stuck with a wired topology. "Inside the building we could get cables where we wanted because it's a new building," says Newbold. If the WLAN is extended further outside the building, that would probably be handled by mesh, he says: "It's a big benefit, making links across an airfield without having to dig the tarmac up."

"The key things Aruba offered were integrated security, a vendor that is really investing in a wireless LAN product set, scalability, decent APs with good radio propagation and integration with a good network management system to prove it is performing as it should," he said.

Each access point can serve up to 25 people, and Newbold hopes to give every user a "broadband experience" including the commercial users in the seating areas.

Will it work?

Despite careful planning, Newbold can't be sure the WLAN will work straight away, because the building has not yet seen a full complement of visitors. "Optimisation is the biggest challenge," he explains. On an average day, the building expects to see 53,000 people, all of whom will have a definite effect on the propagation of radio signals, since they are mostly made of water.

On practice days, the terminal has held up to 2,000 people. To make the planning more tricky, Newbold points out that the usage pattern on day one is likely to be very different, with regular patterns only emerging over the first year or so.

Not every possible application is going onto the WLAN. Heathrow's security demands are too high to run CCTV on the WLAN. By definition, CCTV over wireless isn't exactly CCTV, he points out, because the wireless medium isn't guaranteed, and is not a closed circuit. "Critical monitoring applications need a guaranteed medium, and that means wired," he says. "At any point, someone could make a denial of service attack on a wireless LAN so you can't rely on it for live security."

CCTV images are carried over the IP network, using their own dedicated MPLS "cloud" he explains. However, they might also be exported over the Wi-Fi, to get them to security staff on PDAs so they can monitor special cases around the site.

There's no location tracking and presence awareness yet, either. "We didn't want to open T5 with a whole lot of bells and whistles which no-one had tried," says Newbold. "We needed to get it working first and and then introduce the sophisticated applications."

For BAA, the next step is to take the technology to other locations: moving BA to T5 has emptied Terminal 4, which will get an upgrade involving, among other things, 110 Aruba APs, according to Newbold. There, and elsewhere in BAA's estate, Aruba kit will be put in to replace existing systems from Motorola-owned Symbol.