A cool article on Technology Review (MIT) shows that the U.S. is a bit behind on Location Based Services: AT&T Wireless offers the hottest location-aware service, a friend finder, but only to a few hundred thousand of its 21.2 million subscribers.
Some say that the number of American businesses and consumers using location-aware computing will grow from 150,000 in 2002 to 42 million in 2005, with the market growing from US$6 million to US$828 million. Worldwide, Gartner estimates the market will exceed $26 billion by 2007. By then, or soon after, it’s likely that devices will be able to locate people anywhere—at least outdoors—bringing the era of ubiquitous computing a giant step closer.
Two of the most promising means for outdoor tracking are the Global Positioning System and existing mobile networks.
The GPS accuracy is now routinely within five to 20 meters, but because GPS requires a line of sight to the satellites, it doesn’t work well in large cities. To get around this shortfall, some wireless carriers employ a technology known as assisted GPS. Here, the existing cellular network augments GPS receivers, which can take a few minutes to locate satellites. The network speeds up this search-and-find process and helps GPS work in areas where it might not otherwise, identifying the nearest positioning satellites and acting as a sort of “You Are Here” sign. Korean and Japanese carriers have widely adopted assisted GPS, and as a result, Qualcomm has sold millions of GPS-enabled cell phones to Asian customers.
But any variety of GPS requires that consumers purchase compatible handsets, meaning it could take years to build up a critical mass, at least in the United States. So some wireless carriers have developed ingenious ways to use their existing networks alone to pinpoint customers’ locations. Because wireless-phone networks are broken up into individual cells that hand off calls to each other, which cell a caller is using gives a rough indication of his or her location. The accuracy, however, is poor—a Gartner report puts it at between 30 and 150 kilometers, depending on conditions.
A method called “time difference of arrival” can narrow things down. Similar to GPS triangulation, this approach plots location by measuring the exact time it takes for a signal from a cell phone to travel to three or more cellular base stations and calculating the differences. If only two cell sites are present, which is often the case in rural areas, then the angles of the arriving signals can provide the additional position information instead.
But while cellular location technologies don’t require customers to buy new equipment, they still aren’t as accurate as GPS—with resolutions of only about 120 meters.
The rest of the article keeps us informed on new technologies being developed by HP Labs and other companies.