Last summer, I wrote here a couple of times about a controversy surrounding a proposed new broadband wireless Internet service, to be provided by a company called LightSquared. The central issue was the possibility that the new system would cause interference problems with the Global Positioning System [GPS]. The new service was planned to use a slice of the frequency spectrum, originally intended for satellite telephone service, that is just below the frequencies used by GPS. When the spectrum licenses were originally acquired by SkyTerra Communications, a predecessor company to LightSquared, the plan was to make connections primarily with satellite links, with some small ground stations to fill in holes in the coverage. The controversy has come about because LightSquared persuaded the Federal Communications Commission[FCC] to amend its license to allow a service based almost entirely on a network of 40,000 ground transmitters.
As I noted in my earlier posts, there have been a variety of studies proposed and carried out to asses the potential for interference. The results have suggested that the interference problem is real, and might have a significant adverse effect on GPS users. Now, according to articles at Ars Technica and the New York Times, the FCC has indefinitely suspended its provisional approval of the LightSquared system, following the release of a final report from the National Telecommunications and Information Administration, part of the Department of Commerce.
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.”
LightSquared claims that the interference is primarily due to the poor design of existing GPS equipment, which does not adequately reject signals on nearby frequencies. There probably is at least some truth in this; originally, the spectrum LightSquared proposed using was slated to be used for satellite-based services. Like the signals from GPS satellites, these would have been relatively weak. But the ground stations LightSquared proposed as part of its system would have produced signals about a billion times as strong as the GPS signals, making adequate filtering very difficult.
The company says that it still hopes to reach a mutually acceptable solution with the FCC, which has issued a request for comments on the NTIA letter. I hope that they succeed, because the new broadband capacity would be valuable, but messing up the GPS, which is used for so many purposes, is a price too high.