4G networks - a good thing, right? A super-fast data connection, access to anything, anywhere. But maybe not so great, says GPS manufacturer Garmin, if you want to know exactly where you are.
Garmin says that LightSquared's proposed new 4G network is a disaster for GPS, jamming signals for miles around its transmitters. And it's not just geographically-challenged consumers that will suffer, but 911 systems, air traffic control and the military.
"The proposed LightSquared plan to add 40,000 high-powered transmitters in the band adjacent to GPS will result in widespread, severe jamming," says Garmin. "This will deny GPS service over vast areas of the United States."
LightSquared is planning to complete its network in the next four years, offering download speeds of up to 10Mbps. But, says Garmin,the fact that LightSquared is using a band right next to that used for GPS - and with a stronger signal level - will mean that GPS systems get drowned out.
Garmin engineers tested a portable GPS device and an FAA-certified aviation receiver along with a signal generator that mimicked LightSquared transmitters.
They found that the GPS device started to experience interference at just 5.8km away, losing the signal altogether when it got within 1.1km. The aviation receiver fared similarly, with interference starting 22.1km away, and signal loss occurring at 0.9km. And because of FAA receiver specifications, it takes 90 seconds to regain a fix once it's lost - with potentially disastrous consequences.
Garmin's expressed its concerns to the Federal Communications Commission, which says it will investigate, and the Department of Defense is also looking into the matter. LightSquared is shortly to give the FCC a report into how it plans to deal with the problem.