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Will LightSquared’s LTE network block GPS?

LightSquared logo

Lightsquared is getting ready to roll out 4G LTE mobile broadband service linked with satellite coverage over sizable portions of the United States. Although LightSquared doesn’t plan to sell service directly to consumers, it will offer wholesale mobile broadband services to enterprises and businesses—the company has already inked a deal with Best Buy, and may be in talks with Sprint. However, there’s now growing concern that LightSquared’s system might interfere with GPS satellite receptions, which could have profound implications not just for in-vehicle systems but for everything from aircraft to emergency responders. And some are calling for LightSquared to retool its network to shift its broadcast away from GPS frequencies.

Standard GPS devices operate by locking onto comparatively weak signals from GPS satellites in orbit around the earth, then calculating the unit’s position on the planet. However, some federal agencies—including the National Telecommunications and Information Administration, the U.S. Air Force Space Command, and the Department of Homeland Security have raised concerns that satellite-to-terrestrial component of LightSquared’s network could interfere with GPS reception and other technologies used by federal agencies. LightSquared and the FCC insist there’s no risk of the technology interfering with GPS, and the FCC granted LightSquared a waiver to broadcast in L-Band frequencies typically reserved for space systems and RNSS (Radio Navigation Satellite Services).

Through partnerships with other L-Band Mobile Satellite Service (MSS) providers, LightSquared now has access to a nearly-contiguous range of 20 MHZ in the L-band frequencies. As LightSquared’s network service plans have expanded, the company may be operating as many as 40,000 base stations that transmit on the satellite-to-earth portion of the L-Band range closest to the GPS spectrum—and they will do so with high-power signals that could, in theory, completely overwhelm the low-power signals from GPS satellites. GPS receivers have never been designed with filtering to compensate for signal loss, and most don’t have active antennas and preamplifiers to boost the strength of received signals.

LightSquared has worked with the NTIA and the GPS industry to ensure its technology will not interfere with GPS, and tests with GPS devices and GPS-enabled phones conducted in 2009 showed almost no interference from LightSquared technology; however, GPS maker Garmin claimed almost the opposite, that LightSquared’s service could render GPS’s inoperable. LightSquared has agreed to operate within tight technical requirements and will only offer commercial service if the FCC is satisfied the company’s technology will not interfere with GPS and other services. The FCC has been banking on the forthcoming availability of services like LightSquared to increase competition in the mobile broadband market—and hopefully bring broadband service to areas of the United States poorly served by traditional ISPs and broadband operators.

LightSquared already has systems in space: the company’s SkyTerra 1 satellite was launched from Kazakhstan in November of 2010, and is one of the largest commercial satellites ever put into orbit.

LightSquared SkyTerra 1

[Image of SkyTerra 1 courtesy of Boeing]

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