LightSquared has stepped up its offensive against the GPS industry as it works to convince the FCC to let it move forward with its plan to launch LTE service in spectrum near GPS bands.

The company has been embroiled in a dispute with manufacturers of GPS receivers over the devices' sensitivity to signals in adjacent bands, and a recent backup plan from the company to deploy in spectrum located farther away from GPS bands has not assuaged concerns from the GPS industry.

LightSquared ratcheted up the rhetoric again yesterday when it sent a letter to the FCC blaming the GPS industry for the interference problems caused by its network.

GPS makers say LightSquared shouldn't be allowed to launch its network because it knocks out GPS service, and LightSquared argues its network wouldn't affect receivers if they were properly designed.

LightSquared claims GPS makers have failed to follow standards set out by the Defense Department that require receivers to filter out transmissions from adjacent spectrum bands, calling it the "root cause" of its network's effect on receivers.

"Had the GPS industry complied with DoD's [Department of Defense] recommended filtering standards for GPS receivers, there would be no issue with LightSquared's operations in the lower portion of its downlink band," LightSquared regulatory affairs executive Jeff Carlisle said in a letter to the FCC.

Carlisle was referring to the company's plan to deploy its network in 10 MHz of spectrum located downstream from GPS bands, instead of using its own spectrum, which is directly adjacent to airwaves used by GPS. LightSquared introduced the plan after testing showed its network would wipe out GPS service if deployed under its original plan.

The GPS industry says it is not possible to filter out signals transmitted by LightSquared's base stations, which are exponentially more powerful than the satellite signals transmitted by GPS satellites.

"There has never been, nor will there ever be, a filter that can block out signals in an immediately adjacent frequency band that are so much more powerful, nor has LightSquared put forward any credible, independent expert opinion or other evidence that this is possible," Dale Leibach, spokesman for the Coalition to Save Our GPS, said in a statement, calling LightSquared's latest missive a "sign of desperation."

The FCC may block LightSquared from deploying its network if the company cannot come up with a fix to the GPS interference issue. Agency Chairman Julius Genachowski said at a press conference this week that the FCC was "not going to do anything that creates problems for GPS safety and services as we explore technical solutions that will both protect GPS and allow a new service to launch."

Last week, the U.S. GPS Industry Council said LightSquared's revised plan to deploy its network in lower spectrum would not fix the GPS interference issue. The council said that even under the new plan, the network would still "cause harmful interference to GPS receivers and GPS-dependent applications."

The FCC is taking comments on LightSquared's new plan until Monday. It is not clear when the agency will make a decision on whether the company will be allowed to move forward with its network.