GPS community still skeptical of new LightSquared proposal
LightSquared, which is proposing to build a wholesale nationwide LTE network in the L-band satellite spectrum, has proposed to use just a 10-MHz swathe of its spectrum to avoid interference with GPS signals.
In January, the FCC granted LightSquared a waiver that would allow the company to provide terrestrial-only service in its L-band spectrum, which previously was allocated for hybrid satellite/terrestrial use. The spectrum sits adjacent to frequencies used by GPS receivers, and the FCC directed LightSquared to work with the GPS community to research potential interference. A final report on the matter was due June 15, but the FCC granted LightSquared an extension to file the report on July 1.
LightSquared’s plan calls for the company to avoid launching service in the upper band, where interference has been discovered, according to many reports. Instead, it will use the 1526–1536 MHz band. LightSquared owns 59 MHz of spectrum in the 1525–1559 MHz band. As part of this revised plan, LightSquared also would modify its FCC license to reduce the maximum authorized power of its base-station transmitters by more than 50%. 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.
“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.
Also, LightSquared is paying Inmarsat to transition parts of its spectrum, so 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.
Under its original plan with Inmarsat, LightSquared expected to get access to two more 5 MHz channels no later than November 2012, depending on how quickly Inmarsat can clear the band. Two more 10 MHz channels should be available for LightSquared’s use by the end of 2013.
Still, the plan isn’t making the GPS community happy. The Coalition to Save Our GPS — a group that includes GPS vendors such as Garmin, Magellan and Trimble, as well as big industries that rely on GPS — shot arrows at the plan.
“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.”
Tim Farrar, principal analyst with TMF Associates, believes the plan won’t pass muster very smoothly, as the original GPS plans didn’t include testing the upper band.
“What do people from agencies like the FAA say, when they’ve recommended more testing?” Farrar said. “Will the FCC waive this through, if they still have to do more testing?”
Farrar also questioned how quickly Inmarsat can transition off its spectrum, given the fact that it serves marine and other customers, such as the U.S. government, that pay a significant amount for their satellite systems and would have to purchase new equipment.