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The Ultrawideband Pulse of the Future


It could be the Veg-O-Matic of the wireless world. It chops radio signals into tiny pulses that can zip through the airwaves without interfering with cell-phone conversations or broadcasts. It's called ultrawideband (UWB)--and if its promoters are to be believed, it augurs new applications beyond the abilities of any normal cell phone or radio.

A fireman on a rescue mission could hold up a UWB "flashlight" and peer through walls to locate victims. A camcorder fitted with a UWB chip could beam home movies to a TV set across the room. Home computers on UWB networks could swap data at speeds exceeding anything in today's high-tech offices. And in warehouses, the technology could speed up package location. "UWB doesn't quite make a cup of tea or coffee," says Iain Gillott, president of iGillottResearch Inc., an Austin (Tex.) wireless consulting firm, "but it does all these other things equally well."

Just as impressive, UWB could create--almost from thin air--vast new spectrum space for these and other wireless innovations. "Ultrawideband can open up a huge swath of potential bandwidth that didn't exist before," says John Santhoff, chief technology officer of Pulse-LINK Inc., a UWB startup in San Diego, Calif.

Now, after three years of big-gun opposition, ultrawideband is getting a chance to prove those claims. The Federal Communications Commission approved limited deployment in February, squelching protests from the Pentagon, air-traffic controllers, and telecom companies. Detractors worry that despite the assurances of UWB's boosters, the technology may cause interference with the global positioning system (GPS). Sprint PCS (PCS) and other wireless carriers, which paid a king's ransom for their spectrum rights, also fear interference. But what commercial wireless outfits really dread, UWB backers retort, is low-cost competition, since UWB systems can provide rival services without necessitating fresh purchases of spectrum.

How does the technology create gold out of spectral lead? With a radically different way of encoding signals. Most wireless technologies impart information by changing the shape of radio waves in a specific frequency band, called a carrier. AM radio, for example, uses amplitude modulation--varying the height of the waves--while FM radio alters the frequency of the waves, squeezing some closer together or stretching others out.

But UWB doesn't use carrier waves at all. It sends pulses--as many as a billion zeros and ones per second, rather like superfast Morse code. Moreover, these pulses are scattered across a broad sweep of the spectrum. Distributed this way, within any one frequency band, the UWB pulses are so low-power that they seem to be just background noise. "The odds on it seriously affecting anything are between zero to none," says Edmond J. Thomas, the FCC's chief engineer.

That's also why UWB is inherently secure: Only a receiver that knows the schedule of the transmitter can assemble the apparently random pulses into a coherent message. "It's like sitting in an auditorium, whispering quietly to the person next to you," says Kevin C. Kahn, Intel Corp.'s (INTC) UWB expert. "It doesn't bother the speaker, but your friend can hear you." This has obvious appeal to the Pentagon, which is testing or developing dozens of UWB systems, including eavesdropper-proof battlefield networks--and military brass would prefer to keep the technology out of the hands of potential enemies and terrorists.

For now, the FCC has restricted commercial UWB jobs largely to the 3.1- to 10.6-gigahertz range reserved for satellite transmissions and experimental applications--above the areas where 96% of airwave transmissions are concentrated. That mollified many detractors, but they're still wary that the FCC may expand the spectrum UWB can invade when it reexamines the situation in as little as six months. "You open up the floodgates to use more spectrum," says Ronald L. Swanda, a vice-president at the General Aviation Manufacturers Assn. in Washington, D.C.

Indeed, several high-tech giants are already dipping their toes into UWB's waters, including Sony (SNE), Motorola (MOT), Intel (INTC), and DaimlerChrysler (DCX). They're joining such UWB pioneers as Time Domain Corp. in Huntsville, Ala., and XtremeSpectrum Inc. in Vienna, Va. Commercial ultrawideband services may be three to five years down the road, but the potential is just too good to resist. And while big players like Sony Corp. avoid projections about a technology that is still untested in the marketplace, wireless consultant Andrew M. Seybold says the applications associated with UWB could add up to a $10 billion market--though such demand could take another 10 years to materialize.

One chief focus of the big electronics companies is linking consumer devices at very high data rates. UWB can deliver hundreds of megabits per second--enough to make it perhaps the odds-on favorite for transmitting video and audio streams to PCs, TVs, and other gadgets around the house. For comparison, today's Bluetooth technology has a ceiling of only 700 kilobits per second. That's too little for even one digital TV channel, which needs at least 2 megabits per second, using heavy signal compression. And the next generation of the popular 802.11 wireless network technology will handle just 54 megabits a second.

Because of the limits the FCC has placed on transmitting power, UWB signals can carry for only about 30 feet. "I could probably do some data transfer from my socks to my ears," jokes market researcher Gillott. Bluetooth is even more limited, while 802.11 can reach as far as 100 feet. But even 30 feet could foster a lucrative business in home networking--and conceivably, more powerful UWB systems could rival cell-phone coverage in the future.

So potential applications won't stop with homes. Some analysts believe the killer app may be ultrawideband's location-sensing properties. Its sharply timed pulses can be used to calculate distances within a fraction of an inch--far better than GPS, whose accuracy is measured in feet. That explains why DaimlerChrysler chose UWB for a prototype anticollision device that regulates a car's speed, keeping it from getting too close to a car or slowing it down when another car cuts in front.

Similarly, UWB's radar capabilities could offer a more precise way of locating things behind walls, underground, and inside the body. Motorola, for example, is exploring see-through-the-wall systems for police, firefighters, and other public-safety agencies. Relief agencies, meanwhile, would love to get their hands on tools that could spot buried land mines from helicopters. Some of these new applications could employ a related technology that uses even tinier pulses than UWB--trillions of them per second. Such technology, known as terahertz imaging, is already a hot research topic in the U.S., Europe, and Japan.

If UWB and terahertz imaging make good on such a wealth of applications, "the market is boundless," says wireless consultant Seybold. And from all indications so far, ultrawideband could be the wireless answer to medieval alchemy--a technology for transmuting the limited spectrum into an endless array of new services. By Catherine Yang in Washington


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