The Federal Communications Commission (FCC) said today that it will not approve LightSquared's proposal to build a national 4G-LTE network, after testing showed that the network would interfere with most existing GPS devices.

The decision came swiftly after the National Telecommunications and Information Administration (NTIA) today warned the FCC that "LightSquared's proposed mobile broadband network will impact GPS services and that there is no practical way to mitigate the potential interference at this time." The FCC responded by indefinitely suspending LightSquared's conditional waiver to operate the network, the Washington Post and others are reporting. The FCC will also issue a public notice on Wednesday seeking comment on the NTIA's conclusions. The conditional waiver had been issued in January 2011.

LightSquared proposed to build an open-access, wholesale wireless broadband network integrating satellite and terrestrial technology, but government testing showed that the network would harm performance of 75 percent of GPS devices. GPS makers and the airline industry (which is building a GPS-based navigation system) were among numerous groups objecting to the plan, raising pressure on the FCC to block it. LightSquared can still fight on, but the NTIA recommendation and subsequent FCC decision dramatically reduce its chances of final success.

LightSquared controls spectrum originally intended for satellite communication, and wants approval to use it for terrestrial broadband service. The spectrum is adjacent to that used by GPS, and GPS makers complain the LightSquared signals will be so powerful they would cause widespread jamming of GPS devices. LightSquared has long insisted that the problem lies with the GPS community, which should have to redesign its receivers.

LightSquared has renewed its bitter complaints that the GPS industry has become "too big to fail" and is being protected by government even though its receivers often don't filter frequencies properly and "listen" on adjacent spectrum, including that now held by LightSquared.

"You can get a cell phone for free with a two-year contract that is more resilient to GPS interference than what’s being installed in today’s commercial airliners," the company said, though it pledged to keep working on a solution.

"This proceeding has revealed challenges to maximizing the opportunities of mobile broadband for our economy," the FCC said in a statement. "In particular, it has revealed challenges to removing regulatory barriers on spectrum that restrict use of that spectrum for mobile broadband. This includes receivers that pick up signals from spectrum uses in neighboring bands. There are very substantial costs to our economy and to consumers of preventing the use of this and other spectrum for mobile broadband. Congress, the FCC, other federal agencies, and private sector stakeholders must work together in a concerted effort to reduce regulatory barriers and free up spectrum for mobile broadband. Part of this effort should address receiver performance to help ensure the most efficient use of all spectrum to drive our economy and best serve American consumers."