FCC Grants Licence For 40,000 Watt Transmitters On Adjacent Frequencies

The FCC has granted a license to a company called LightSquared, which plans to offer 4G wireless broadband services nationwide. But studies show the service may severely interfere with GPS navigation, according to one GPS industry source.

A report on the GPS World website indicated that the GPS industry offered data to the FCC showing that LightSquared's operations could cause GPS receivers to "cease to operate" in areas near the the 40,000 watt transmitters the company plans to erect. GPS manufacturers Garmin and Trimble both contributed to the report "Experimental Evidence Of Wide Area GPS Jamming" which was presented to the FCC.

The manufacturers found that a Garmin GNS 430W lost its fix in open sky more than five statute miles from one of the transmitters, and interference was detected at nearly 14 SM. The testing was conducted using simulated GPS signals representing a constellation of 31 satellites, and the Lightsquared transmission was simulated to actual technical specifications, according to the report.

The FCC decided to waive its own rules and permit Lightsquared to broadcast in the L Band despite potential interference. In its final ruling, the FCC does admit that interference with GPS is a "significant concern," and that the interference issues "must be addressed" before LightSquared could light up its wireless network. But since the interference would stem from transmissions in the authorized spectrum, rather than the GPS band, the FCC "expects the GPS industry to work expeditiously and in good faith with LightSquared to ameliorate the interference concerns."

Lightsquared has said it will "work with the GPS industry" to determine which GPS receivers would require "filtering so that they don't look into our band." There is no mention as to what those filters might entail, or at what cost to those who own the equipment.

LightSquared hopes to have its 4G wireless network up and operating by June 15th of this year.

FMI: www.fcc.gov, Jamming Report , www.lightsquared.com