Cellular networks such as LightSquared's transmit at much higher power than do satellite-based systems -- as much as 1 billion times as high, according to some critics. In tests, the LTE network overwhelmed GPS receivers, such as in-car navigation systems, that were trying to lock on to weaker signals coming from GPS satellites. At a Congressional hearing last week, federal officials and GPS industry representatives said interference with GPS could endanger critical systems and a thriving industry. GPS device sales total $20 billion per year, and about $3 trillion worth of commerce each year relies on the U.S.-built system, said Roy Kienitz, under secretary for policy at the U.S. Department of Transportation.
One initiative that would be endangered by LightSquared is NextGen, a new air traffic control system designed to improve safety that relies on GPS, Kienitz said. The Federal Aviation Administration and airline industry have already invested $8 billion in NextGen, he said.
Given what's at stake, it's not surprising that a debate over technology has turned political. Last week, the House Appropriations Committee approved an amendment to a spending bill that would block any funding for the FCC to help LightSquared's plans move forward until all interference issues had been resolved. This effort to control the FCC through its purse strings is on its way to the full House for consideration along with the spending bill. The FCC already requires a solution to the interference problem before it will let LightSquared go forward.
"It's really just Congress reinforcing, through the appropriations process, what the FCC has already stated is their plan," said Steve Gilleland, a legislative assistant to Rep. Steve Austria, an Ohio Republican who co-sponsored the amendment.
In response to attacks from the GPS industry, LightSquared has pointed its finger in the other direction. The problem is not its LTE gear transmitting over the line into GPS spectrum, but GPS receivers going into LightSquared's frequencies when they look for satellite signals, according to a report by the wireless consultancy The Brattle Group, which was sponsored by LightSquared. Those devices should have been equipped with better filters to keep them within the GPS band, the report said.
GPS vendors and users defend their gear as government-approved and said filters could degrade GPS performance and are too expensive.
"Even if the development of filtering equipment proves technically feasible, the U.S. airline industry simply cannot afford to purchase and install it in approximately 6,600 aircraft, which would cost billions of dollars," said Thomas Hendricks, senior vice president of safety, security and operations at the Air Transport Association of America.
LightSquared's alternative plan has its own potential problems. In it, the company wants to leave aside the upper portion of its spectrum, which is closest to the GPS band, and initially launch its service in a lower set of frequencies. After a few years of testing and developing solutions to interference, it would look to expand into the upper band. Less than 1 percent of all GPS receivers use the lower band, so most would not face interference there, LightSquared said.
However, opponents question whether the lower band would be free from interference, and given what has happened so far, lawmakers and others are cautious.
"The impacts of LightSquared's revised plans should be independently and thoroughly tested to ensure the FCC does not approve plans that would introduce unacceptable risk into the aviation system, or leave aviation GPS users with new, costly burdens," said Rep. Tom Petri, Republican of Wisconsin, who co-chaired a hearing on the issue last week.
A moratorium on using the upper frequency band would probably have to be permanent, said analyst Tim Farrar of TMF Associates.
"It would be enormously expensive and disruptive for LightSquared to use the upper part," Farrar said. Losing half of its spectrum could eventually force the carrier to offer a lesser service than it hoped for, he said.
"Perhaps LightSquared thought this would be confined to a purely technical discussion. The reality is, you take on something like this, where the GPS people have enormous politically influential constituencies on their side, and you're going to end up in a nightmare situation," Farrar said.