A pretty nice system unveiled by Fujitsu at the "Fujitsu Forum 2005" incorporates a technique called "Time Difference of Arrival" to calculate the position of objects in a closed environment. So, you'll be able to pinpoint the location of a wireless LAN card (and thus computer, and thus person) with an accuracy of 1 to 4 meters. This is o­n par with similar triangulation systems offered by GPS and PHS.

On display at the show was a demonstration of a position information management system that uses wireless LAN. By taking three different TDOA (Time Difference of Arrival) measurements from different locations, the position of an object can be pinpointed within an error of 1 to 4 meters, allowing for an indoor usage resolution o­n par with that of GPS and PHS.

On the client side of things, if the unit has a wireless LAN function, there is no need for special software to receive position information. However, for controlling purposes, the units need to have a MAC addess pre-registered. Though IEEE 802.11b and g are currently supported, the company also said IEEE 802.11a is also "technically" supported.

The location of each user can be confirmed, and this data will be displayed in a list setup. Furthermore, making calls to users from this same screen is also possible, using either a software phone o­n the PC or an IP phone call o­n a wireless LAN supporting handset through a server.

Although Hitachi Manufacturing currently a wireless LAN position information system through TDOA in their "Hitachi AirLocation," the staff at the booth explained that "AirLocation requires integration of the access point and receiver, though Fujitsu's setup requires o­nly a receiver." This means that this system can be introduced into places where a wireless LAN has already been established, by o­nly introducing a receiver unit; this makes arrangements quite flexible.

Inspired by:
http://bb.watch.impress.co.jp/cda/event/10352.html

Fujitsu Forum 2005:
http://forum.fujitsu.com/