GPS backers told to protect turf

Users of the Global Positioning System must remain vigilant about potential systems and devices that could interfere with GPS, government and industry officials advised last week.

From its 27 satellites, GPS broadcasts low-power signals that are used for determining precise location and time. Spectrum protection is vital because GPS is used in public safety services such as emergency 911 and aircraft navigation and landing, said Sally Frodge, radio-navigation policy analyst at the Transportation Department.

"There's only so much energy that can go in a band," Frodge told attendees at the Institute of Navigation GPS 2000 meeting Sept. 19 in Salt Lake City. "At what point did you want your navigation systems on your aircraft that you were flying in to be interfered with?"

A 158-member U.S. delegation defeated proposals for mobile satellite communications services to share GPS spectrum. That victory for GPS spectrum protection occurred in May at the International Telecommunication Union's World Radiocommunication Conference 2000 in Istanbul.

But there was little time to celebrate, as the Federal Communications Commission considered a proposal for an emerging technology called ultra-wideband (UWB) to transmit its pulses across spectrum in and near radio frequency bands reserved for GPS.

Although there are interesting synergies between GPS and UWB, such as using UWB for positioning where GPS signals are obscured by buildings or other structures, "if it's done stupidly, then we're in for a world of hurt," said Scott Pace, defense policy analyst at the government-sponsored Rand Science and Technology Policy Institute.

Nearly 350 comments that included those from DOT and many technology firms were submitted to the FCC by Sept. 12 in response to the proposed UWB rulemaking. Meanwhile, interference tests are being conducted by the UWB industry, GPS users and the government.

Test results are due Oct. 30, when the FCC will decide whether to grant UWB companies permission to operate those devices on an unlicensed basis, similar to hair dryers.

But there are five differences between a hair dryer and a UWB device, said Charles Trimble, chairman of the U.S. GPS Industry Council. "A hairdryer is not on all the time. A hairdryer is usually not portable. A hair dryer has no antenna. Hairdryers are not connected in networks. And you can't convert a hair dryer into a GPS jammer," he said.

"I'm worried that the political pressure to allow new technology to come to the marketplace is obscuring the need to protect national information infrastructure," Trimble said.Ultra-wideband devices produce short radio frequency pulses spread over thousands of megahertz. Global Positioning System satellites use about 20 megahertz of spectrum in bands restricted for radionavigation.

The technologies could potentially be blended to make better use of spectrum for applications such as non-destructive ground-penetrating radar used for roadwork. But UWB signals may also be strong enough to block GPS signals used for critical air communications and synchronizing telecommunications systems.

More information on the Federal Communications Commission's notice of proposed rulemaking can be found at www.fcc.gov/e-file/ecfs.html, ET Docket No. 98-153.