LightSquared has stalled the release of a key report disclosing the full extent of the interference its network causes to GPS systems as it works to find possible solutions for the problem, which threatens to delay the launch of its hybrid satellite-terrestrial LTE network.

The venture-backed company was required to submit the report to the FCC yesterday but asked for a two-week extension after it was unable to come up with a fix for the GPS interference issue.

"Among the main reasons for the slight delay has been that based on preliminary test results, LightSquared determined that additional testing, beyond what had been planned initially, including alternative frequency plans to support its network roll-out, was necessary to permit a proper evaluation of various mitigation options for addressing the GPS receiver overload issue," LightSquared spokesman Jeff Carlisle wrote in a document to the FCC.

The FCC granted LightSquared's request, pushing the deadline out to July 1.

The U.S. GPS Industry Council asked the FCC to deny LightSquared's request for an extension.

"The submission of the Working Group Report should not be delayed simply to accommodate additional information that can be submitted at a later date," said Michael Swiek, executive director of the U.S. GPS Industry Council, in a letter to the FCC.

Swiek said the council had "devoted countless hours to testing devices against overload and desensitization and preparing reports describing their findings" and argued that the reports were ready to be submitted to the agency.

LightSquared will not be able to launch its network until it can prove to the FCC its network will not harm GPS systems under the terms of a waiver allowing the company to use its satellite spectrum for land-based cellular service.

LightSquared said last week it "has not taken any options for mitigation off the table," including the possibility that it may need to deploy its network in spectrum further away from GPS bands. LightSquared had said filters installed on its transmitters and on GPS receivers would mitigate the problem, but yesterday's delay suggests those methods will not be enough to stop its network from blacking out GPS service.

A recent report from the National Space-Based PNT Advisory Board showed LightSquared's network would knock out GPS receivers used by the Federal Aviation Administration (FAA), John Deere, U.S. Coast Guard, NASA and Garmin if allowed to go live.

The board was unable to come up with a "universal mitigation approach" and suggested LightSquared deploy its network in different spectrum.

LightSquared's spectrum, which is directly adjacent to airwaves used by GPS, had been reserved for mobile satellite service before the FCC granted the company a waiver for terrestrial-only service in January.