Wireless Local Area Network Positioning - Ambient Intelligence for Scientific Discovery - page 247

Wireless Local Area Network Positioning

Ophir Tanz and Jeremy Shaffer

Carnegie Mellon University, USA
[e-mail] , [e-mail]

1 Introduction

The ability to determine the location of a mobile device is a challenge that has
persistently evaded technologists. Although solutions to this problem have been
extensively developed, none provide the accuracy, range, or cost-effectiveness to
serve as a solution over a large urban area. The Global Positioning System (GPS)
does not work well indoors or in urban environments. Infrared based systems
require line-of-site, are costly to install and do not perform well in direct sunlight
[1]. Cellular network-based positioning systems are limited by cell size and also
do not work well indoors [23]. The list goes on. With the rise of Wireless Internet,
or WiFi as it is commonly dubbed, the best infrastructure for location awareness
to date has been created. WiFi is standardized, inexpensive to deploy, easy to
install and a default component in a wide-range of consumer devices. These
characteristics are the drivers behind WiFi's most significant trait: increasing
ubiquity. By developing within the existing 802.11 infrastructure, developers
can leverage WiFi to create wide-spread context-aware services.
Location is significant because location suggests context. In addition to deliv-
ering information about a user's physical setting, a valuable piece of information
in its own right, location implies an individual's current tasks and goals. We are
living in a period of information overload where there is simply too much in-
formation to retrieve and intelligibly digest. Context-aware services address the
problem of information overload for both information vendors and receivers by
delivering content when it is most appropriate. Ambient intelligent applications
are, in fact, considered intelligent precisely because they can respond to an indi-
vidual in relation to his or her context. Examples of location-aware applications
that have recently, or will soon emerge include: tracking equipment, personnel
and patients in hospitals, notifying friends when they are in close proximity to
each other, providing on-the-fly directories and advertisements to mall visitors
and providing guided tours of facilities such as a college campus [16] or museum.
The ability to locate a device in a wireless network was not inherently built
into the 802.11 protocol. A real-time Wireless Local Area Network (WLAN)
positioning system addresses this problem. A WLAN positioning system is a
software system that aggregates the location data of all wireless devices within a
network 1 . Through the clever utilization and processing of available information

1 Often, to enhance and make better sense of the location data, statistical analysis is
performed on it and a WLAN map is created that displays the data visually.