And who says you've got to have a complicated electronic gizmo actually on your person to get pegged? Welcome to the secret military technology of Celldar, already hard at work in Orwell's home of England. Consider excerpts from this week's celldar article in Business Week:
Celldar takes a so-called passive approach: It watches and interprets how signals from cell-phone base stations interact with objects such as cars, trucks or planes. The hardware required for this is much simpler than existing radar systems. A Celldar prototype built in 1999 consisted of a PC and the insides of two cell phones, and cost just $3,000, says Peter Lloyd, head of Roke Manor's Celldar program. The flip side is, the signal-processing software is complex: It must allow for the varying travel times for signals between two or more cellular base stations and a Celldar receiver, as well as the times from the different base stations to the target. Lloyd says Roke's clever program is based on "$10 million worth of expertise in writing software" for cellular systems and military radars. One big plus to the military: passive radar systems are invisible to anti-radar weapons because they don't have their own transmitters.
Celldar's implications are exciting -- but also troubling to some. Even though the technology can't be used to identify cell-phone users, since it "sees" only radio waves echoing off hard surfaces, it and similar approaches are evolving quickly. In addition to Celldar, which is sopping up $1.5 million a year for development, a dozen other passive-radar projects are under way in the U.S., Europe, and Asia. As the technology bears fruit, it should give the world's police and homeland security agencies new tools for monitoring shipments of illegal weapons and drug smuggling operations. Highway officials could gain a detailed window on traffic flows, helping them to minimize congestion. But because passive-radar systems could be cheap enough for hobbyists to buy -- or cobble together themselves -- the technology could also become the next fad among people who own police-radio scanners or who enjoy snooping on their neighbors' comings and goings.
Also in late October, radar researchers from around the world will gather in Seattle to discuss recent advances, including passive systems that use FM radio or TV broadcasts instead of cell-phone signals. The invitation-only meeting will be hosted by John D. Sahr, a University of Washington electrical engineer. Since 1997 he has operated a passive-radar system unshrouded by military secrecy. It harnesses an FM station's signals to study particles in the ionosphere -- the top layer of the atmosphere, over 300 miles up. Sahr decided to go with passive radar, he says, "because it's incredibly cheap" -- $20,000 vs. $25 million for a comparable active system. "You could probably do an amateur system for under $5,000," Sahr adds. A system for small airports might cost as little as $15,000. That's important because of the 5,280 public airports in the U.S., only about 300 currently have radar.
Then, of course, there's the privacy implications of the up-and-coming replacement for bar codes called radio frequency identification or RDIF - where a van at the curb of your driveway can read every product barcode in your house in five seconds. But that's another story for another day.
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