Optical/IP Networks

When Will WLAN Get Its Wings?

Your plane has reached its cruising altitude; as cabin staff bring 'round drinks, you turn on your laptop and download that morning's email wirelessly via an 802.11 network inside the aircraft. Sound like a dream? Well, it is possible with today's technology. However, it could be years before aviation authorities around the world approve the use of wireless LAN technology in the air.

Apparently this is not a deterrent for companies like Cisco Systems Inc. or Tenzing Communications Inc., which are working with airlines, Lufthansa AG and SAS AB respectively. The companies plan to develop and test in-cabin wireless LAN systems that can allow passengers to access email or surf the Web.

Cisco is working with the German airline to begin tests of its Aironet 350 wireless LAN equipment aboard a Boeing 747-400 jet this November. Lufthansa says that it hopes to deploy the service over the next two years on its 80 aircraft flying intercontinental routes from Europe to North America and Asia. The companies say that one of the reasons for deploying a wireless LAN system is that it will be lighter than providing wired connections to each of the 380 seats on a typical Lufthansa 747.

The Lufthansa plane is already equipped with the kit necessary for it to link to the satellite-powered Internet service provided by Boeing subsidiary Connexion . The satellite data link between the plane and the ground promises data rates of up to 5 Mbit/s downstream and 750 kbit/s upstream. Although it will be interesting to see what kind of data transfer speeds customers will actually get while in their seat.

Scandinavian airline SAS is planning to test an in-flight system this fall that connects a WLAN network to a server from Seattle-based Tenzing that links the system to ground-to-air communications. The problem with such a system is its slow data transfer speed. Tenzing says its next-generation products will link to the inmarsat satellite system and offer rates of around 64 kbit/s.

However, there is one big problem that could keep in-flight wireless LAN systems for passengers waiting at the gate: Aviation authorities have not approved their use. As Cisco's own FAQ on wireless LAN networking says:

"The use of wireless devices on an aircraft with the door closed, whether it is sitting at the gate, taxiing, or in flight, is prohibited by the FAA [Federal Aviation Authority] and other Civil Aviation Agencies worldwide. Wireless devices used on the aircraft (when the door is open at the gate) must meet the requirements of the local country agency or have been granted a waiver by the agency or airport authority."

The networking giant couldn't find anyone who could give Unstrung any further information about the regulatory status of in-flight WLAN systems by press time. Tenzing was unable to shed much light on the subject, and calls to the FAA bore no fruit either.

The lack of regulatory approval seems to be a very gray area for vendors and airlines testing these systems. They are talking about starting to install commercial systems in planes next year, yet they still have to be approved by some of toughest regulatory bodies in the world.

Vendors that have tested 802.11b systems running over the 2.4GHz band in planes say that the technology does not interfere with the smooth running of the aircraft's essential systems. This was no doubt under ideal test conditions. The concern for regulatory authorities must be how such systems operate under normal flying conditions, with a plane load of business travelers eager to get to their email.

As we seen have before, commercial 802.11b cards tend to have quite varied performance specs (see Symbol Talks Up Voice Over 802.11). This could be a hassle for regulatory bodies as they test WLAN services in the air. Will they have to check each card to see if it is safe?

The situation is only going to get more difficult as devices get more complex. Soon enough, smartphones and other devices that support Bluetooth and 802.11b as well as wide-area cellular communications could be widely available. Even if regulatory bodies approve short-range wireless links, they are unlikely to approve cell phone calls on planes any time soon. So how are the poor cabin staff meant to know what capabilities a device has just by looking?

Incidentally, an unscientific survey here at the Unstrung offices established that the average globe-trotting hack loves the idea of getting his or her email wirelessly piped direct to their seat (right back in cattle class, near the toilets, since you're asking). But they like the idea of a few extra inches of legroom more.

— Dan Jones, Senior Editor, Unstrung

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