FCC debates UWB deployment

Interference with other wireless signals could restrict usage

A powerful, little-known wireless technology called ultrawideband could be unleashed on the market if the FCC decides that the technology does not interfere too much with other radio signals.

Ultrawideband, or UWB, technology holds potential for a variety of communications and radar applications, from indoor wireless networks to the detection of people buried in earthquake rubble. So far, its use has been confined to military and other government systems.

Devices based on the technology can't be sold commercially because their regulatory status is unclear. The FCC in June 1999 allowed three companies - Time Domain, US Radar and Zircon - to sell limited numbers of devices, but nothing has hit the market yet.

UWB developers hope to move from prototypes to products early next year, assuming a positive outcome of government-sponsored tests now under way and a green light from the FCC.

"There needs to be some hope this technology can get to market," said Jeff Ross, Time Domain's vice president of corporate development and strategy. The Huntsville, Ala., company is developing UWB systems, which can image people and objects located behind walls and under debris, to be used by public safety personnel.

Unlike conventional wireless devices, which emit continuous digital signals in a limited bandwidth, UWB technology works by transmitting very short - a few billionths of a second or less) - on-and-off pulses that operate across a wide swath of spectrum, from a few megahertz up to several gigahertz. The FCC is looking at UWB devices operating in the 1 to 4 GHz band, part of which are used for public safety.

UWB also transmits very low power signals - 50 millionths of a watt is typical - so devices can operate extremely efficiently, advocates say. That level is about one-ten thousandth the power of a cell phone, according to Time Domain.

The FCC has taken a favorable but cautious stance toward UWB. On one hand, it wants to encourage advanced technologies and efficient spectrum use. On the other hand, it must protect the radio spectrum, especially the portions involved in public safety.

"We believe that UWB devices may offer significant benefits for public safety, businesses and consumers," the FCC said in a proposed rule issued in May. "At the same time, we recognize that any new rule... must ensure that radio services are protected against interference."

The key technical question is whether or not UWB devices interfere harmfully with navigation, cellular, TV GPS and other signals, experts said. The U.S. Department of Transportation, for example, is concerned that devices could interfere with the GPS-based navigation systems that guide airplane landings.

The transportation department hired Stanford University to conduct tests to determine potential interference of UWB signals with GPS. "Although the test program is incomplete, the results to date demonstrate a potential for such interference under a variety of conditions," the department wrote in comments submitted to the FCC last month. It urged the FCC to "exercise caution."

The National Telecommunications Information Administration, which manages government-owned portions of the spectrum, is conducting two sets of interference tests, one for GPS receivers and one for non-GPS receivers, at its laboratories in Boulder, Colo., a spokesman said. Non-GPS results are expected by mid-January and GPS results in late February.

"We are confident tests will show UWB will not show harmful interference. If [interference] is shown, we will take steps to mitigate that," Ross said. Time Domain paid the University of Texas Applied Research Laboratories more than $500,000 to collect interference data. It has hired the Johns Hopkins Applied Physics Laboratory to analyze that data.

Although the FCC could give UWB the go-ahead without waiting for results of the various tests, "they'll wait to hear from the NTIA," Ross said.

Assuming positive test results, UWB advocates hope that the FCC will revise its "Part 15" rules to let UWB devices operate in the same category as the 8 billion or so garage door openers, laptop computers, Palm Pilots and other wireless devices that emit low levels of energy, Ross said. Part 15 allows certain devices to operate without a license as long as they don't interfere with TV broadcast and restricted frequency bands such as those used by law enforcement and the military.

UWB-based public safety systems have generated support from police, fire and rescue operations, but the technology has its detractors, too. "Everybody's going to be coming in making their cases," an FCC official said. The agency received 158 comments on its proposed UWB rule.

The U.S. GPS Industry Council, American Airlines and United Airlines tried unsuccessfully to block the Part 15 waivers granted to three UWB developers, arguing that the FCC should prohibit any UWB emissions in GPS frequency bands. TV broadcasters, wireless spectrum buyers and government users also are concerned, the FCC official said.

Even some UWB promoters think their devices should not be allowed to operate across the spectrum. Multispectral Solutions, a Germantown, Md., company that builds UWB systems for the government, recommended to the FCC that UWB devices be allowed only at 3.1 GHz or above, said Robert J. Fontana, company president.

"It would allow the FCC to give legs to the [UWB] industry while still protecting other industries," said Jay Knight, Multi-spectral Solutions director of strategy and finance.

At 3.1 GHz and above, UWB devices pose little risk of interference and much less than at bands of 2 GHz and below, in which GPS and other sensitive signals operate, Fontana said. In addition, restricting the technology to higher frequencies also would avoid a political battle between small UWB players and the giants of government and the aviation, wireless and broadcasting industries, he added.