June 24, 2003 /For most people, Wi-Fi networks are useful for doing work in coffee shops or allowing computers to share an Internet connection at home. But for Iris Junglas and several other researchers, wireless networks are also capable of keeping tabs on wandering computer users.

I want to improve technology that exists and make it a little more intelligent, said Junglas, a computer scientist who recently joined the faculty of the University of Houston. The neat thing is that we have tried to keep it simple and cheap.

Junglas and others are developing Wi-Fi networks that not only track computer users but adjust what the computers are doing to suit the circumstances. By keeping constant track of a technician's whereabouts, a network could increase efficiency by assigning the worker to the nearest job and sending an electronic version of the appropriate repair manual. In a hospital, a network could be used to upload a patient's medical records as a doctor with a wireless laptop approached the bedside.

Most computers are pretty dumb about the user's state, they have no idea what you need, said Asim Smailagic, a professor at Carnegie Mellon University's Institute for Complex Engineered Systems who is also researching wireless networks. But a network's location system, he added, could make the computer become context-aware.

There are, of course, already electronic gadgets that can tell their owners where they are most obvious are Global Positioning System receivers. But their satellite signals do not penetrate office buildings or factories. It is possible to duplicate the network of GPS satellites at cubicle height by placing special transmitters around an office. That is more or less what Smailagic did 10 years ago when he developed a system for tracking mentally ill patients at a hospital. That system involved costly customized electronics. Since then, Wi-Fi networks more formally, 802.11b wireless local area networks have started to blanket some offices with electronic signals. Junglas became interested in adding location-finding capability to standard wireless networks while studying for her doctorate at the University of Georgia's Terry College of Business. Her research involved technologies that could make it possible to buy about anything anywhere using portable computers and wireless networks. As part of the work, Junglas modified a Wi-Fi network that operated in the business school so that each base station had a radius of about 15 feet (4.57 meters). She then created software that logged which computers were using which base station. That database, in turn, produced maps that could be viewed by anyone on the network using a Web browser. To test the system, 117 students were given handheld organizers with wireless cards. In experiments, they were asked to locate specific people.

They found it very, very useful, Junglas said. The system was not without problems. Sometimes a handheld computer would link to the network through a base station that was directly below the room where its user was standing. The database map would show the user on the wrong floor. To solve that problem, the system developed by Smailagic and others takes a different and slightly more complex approach. Rather than mapping the relationship between a computer and a single access point, it compares the strength of the computer's Wi-Fi card signal to that of three base stations. With this information, the system can then use triangulation to calculate and map the computer's location. The next step for Smailagic and fellow researchers will be to test the system which is based on an existing Wi-Fi network that covers the Carnegie Mellon campus in Pittsburgh with a large number of users. Researchers at the University of Maryland's computer science department and the Maryland Information and Networks Dynamics lab, or Mind, have published a paper outlining technologies that could reduce the amount of computing power needed to map a large number of users on a network as well as improve the accuracy of the maps.

Such a system would compensate for the radio interference that occurs when Wi-Fi networks cross signals with office equipment and factory machines. In addition to finding other people within an office, a location- aware Wi-Fi system could make life easier in other ways.

For example, Smailagic said, once a handheld computer discovered that its owner had carried it into the boss's office, it could send out a signal shutting down its owner's cell phone. Alternately, handhelds could remind users about appointments by comparing information stored in their electronic datebooks with their actual locations. Junglas said many people would have concerns about how such networks might be misused. Smailagic and Junglas said that operators of location-sensing networks would have to request permission to track users or risk a backlash. Over all, it's a question of giving up the privacy of where you are, Junglas said, for the sake of someone else being able to locate you very conveniently.

People who allow networks to track them still have a way to move about anonymously. If you don't want to be tracked, Smailagic said, you just turn off your wireless card.