LightSquared says that GPS industry’s failure to comply with filtering standards is the root cause of potential interference issues involving it's proposed LTE network.

Refering to DoD’s GPS Standard Positioning Service Performance Standard, issued in September 2008, LightSquared  said that the DOD standard grants GPS a 4 MHz “guard band.” Now, however, the GPS manufacturers are rejecting LightSquared’s offer of a 23 MHz guard band that would be created by LightSquared’s decision to begin its terrestrial operations in the lower half of the downlink band. Instead, the GPS industry unreasonably insists on a 34 MHz guard band – 8.5 times as wide as the DoD recommendation.

“Had the GPS industry complied with DoD’s recommended filtering standards for GPS receivers, there would be no issue with LightSquared’s operations in the lower portion of its downlink band,” said LightSquared Executive Vice President Jeffrey Carlisle in the FCC filing.

Making it's case LightSquared further argues that ITU has cautioned that “a more stringent pre-correlator filter may be needed to protect [GPS] receiver operations from adjacent band RF emissions and asked GPS industry to use its licensed spectrum in accordance with international and federal government standards

Earlier this year,  company has submitted spectrum plan to the FCC and proposed a comprehensive solution to the GPS interference issue. At that time LightSquared has said that GPS device test results show that the interference is caused by the GPS device manufacturer's decision over the last eight years to design products that depend on using spectrum assigned to other FCC licensees.