Proposed 4G network interferes with GPS signals, test shows

Recent tests of a 4G broadband cellular network found that its signals interfered with Global Positioning System signals operating in an adjacent band of the radio frequency spectrum.

The tests at Holloman Air Force Base, N.M., of LightSquared’s proposed network found that the cellular signals took out GPS receivers of first responders, Bob Brewin writes in NextGov.

New Mexico State Police vehicles and Otero County, N.M., ambulances, which took part in the tests ordered by the Federal Communications Commission, reported outages when they were near LightSquared’s cellular towers, Brewin writes.

LightSquared is a satellite and ground-station network designed to provide Long-Term Evolution 4G service. It could particularly benefit rural areas and other places underserved by cellular networks.

But it operates in the 1525 MHz-to-1559 MHz area of the spectrum, called the L Band, adjacent to the bands used by GPS and the Global Navigation Satellite System, which operate between 1559 MHz and 1610 MHz, Alex Mahrou writes in Directions Magazine.

Mahrou, an engineer, goes into detail about how LightSquared's signal could interfere with GPS and GNSS signals, concluding, "you can't argue with physics."

The Defense and Transportation departments had written a letter to the FCC March 25 expressing concern about the impact LightSquared would have on GPS communications, Ars Technica reported.  


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