GPS backers told to protect turf
- By Paula Shaki Trimble
- Sep 25, 2000
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
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