LightSquared, which plans to build a wholesale nationwide LTE network in the L-band satellite spectrum, has proposed to use just a 10-megahertz swathe of its spectrum to avoid interference with GPS signals, but the GPS community is already shooting holes through the idea.
LightSquared's plan calls for the company to avoid launching service in the upper band, where interference has been discovered. It said it would use the 1526-1536 MHz band rather than the full 59 megahertz of spectrum it owns in the 1525-1559 MHz band. As part of this revised plan, LightSquared said it would modify its FCC license to reduce the maximum authorized power of its base-station transmitters by over 50 percent. This action will limit LightSquared to the power it was authorized to use in 2005, which will provide additional protection to GPS, the company said.
In January, the FCC granted LightSquared a waiver that would allow it to provide terrestrial-only service in its L-band spectrum, which was previously allocated for hybrid satellite/terrestrial use. The spectrum sits adjacent to frequencies used by GPS receivers. The FCC directed LightSquared to work with the GPS community to research interference problems. A final report on the matter was due June 15, but the FCC granted LightSquared an extension to file the report on July 1.
"Test results show this lower block of frequencies is largely free of interference issues with the exception of a limited number of high precision GPS receivers that are specifically designed to rely on LightSquared's spectrum," LightSquared said in a statement.
The Coalition to Save Our GPS, which includes GPS vendors such as Garmin, Magellan and Trimble, as well as big industries that rely on GPS, disagrees.
"Confining its operation to the lower MSS band still interferes with many critical GPS receivers in addition to the precision receivers that even LightSquared concedes will be affected," the group said in a statement attributed to Jim Kirkland, vice president and general counsel of Trimble. "It is time for LightSquared to move out of the MSS band."
LightSquared is also paying Inmarsat to transition parts of its spectrum so that LightSquared has a contiguous block of spectrum. In its announcement, LightSquared said it entered negotiations with Inmarsat, the satellite company that controls the alternative block of spectrum in the L Band, to accelerate the schedule for LightSquared to begin using the frequencies.
According to the original plan, LightSquared was expected to get access to two more 5 MHz channels no later than November 2012, depending on how fast Inmarsat can clear the band. Two more 10 MHz channels were to be available for LightSquared's use by the end of 2013.
Tim Farrar, principal analyst with TMF Associates, said in an interview that the plan still may not enable LightSquared to launch on time. The original testing directed by the FCC did not focus on the upper band where LTE signals still might interfere with highly sensitive GPS receivers such as those used by the Department of Defense and industries such as agriculture and aeronautical industries.
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