GPS Interference

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LightSquared Tests Reveal Potential Interference with GPS

June 6, 2011

Industry representatives report that trials underway throughout the southwestern United States show that new 4G wireless broadband communications technologies, used by LightSquared, a cellular provider, may interfere with Global Positioning System (GPS) signals, which are used commonly in aviation.

The issue concerns mobile satellite spectrum used for wireless communications. As proposed by companies such as LightSquared, such systems would utilize FCC authorized communications frequencies adjacent to the spectrum internationally authorized for GPS systems.

Field Test of LightSquared System

A wide-range field test of the LightSquared system was conducted in late May near Boulder City, NV. A much larger test, centered near Truth or Consequences, NM, and expanding to a radius of as much as 320 miles, began May 23 and extends through July 1. A Federal Aviation Administration (FAA) advisory cautioned that "the GPS signal may be unreliable or unavailable" at the time of the tests.

While acknowledging that such technologies are likely here to stay, the very real potential exists for those signals to interfere with the integrity of satellite transmissions to hundreds of millions GPS receivers if the currently proposed spectrum is utilized, according to Alan Cameron, Editor-in-Chief of GPS World magazine, who says the fight for bandwidth is a battle over availability: "There is just tremendous and constantly increasing demand," for bandwidth space for digital devices, he says.

Industry Reaction to Possible Interference

Olathe, KS-based electronics manufacturer Garmin International has been at the forefront of this issue for some time, because so many of the company’s GPS systems are used in the transportation industry.

In a January 2011 position paper, Garmin software engineers Scott Burgett and Bronson Hokuf cautioned of the likely impact of LightSquared’s planned use of its technology. "…Widespread, severe GPS jamming will occur," the paper states, adding two of the company's commercial GPS receivers experienced "significant jamming within a radius of several miles from a simulated LightSquared transmitter" in company tests. Review the full paper, including testing details.

Earlier this year, NBAA joined the Coalition to Save Our GPS, which now has more than 200 members and is committed to resolving the threat to GPS and preserving its benefits for industries, government and citizens. But until the matter with LightSquared can be resolved, the FAA has asked for industry’s help in determining the severity of the problem created when LightSquared’s technology threatens to overlap GPS signals. "Pilots are strongly encouraged to report anomalies during testing to the appropriate ARTCC to assist in the determination of the extent of GPS degradation during tests," the agency says.

For additional information, contact NBAA’s Operations Service Group at info@nbaa.org.