GPS industry and LightSquared spar over responsibility for interference issue

The GPS industry and the wireless broadband company LightSquared joined forces to test whether the nationwide broadband network that LightSquared plans to build would cause interference for the GPS system. But as preliminary reports indicate that the network could, in fact, render GPS devices useless, the partnership is ending fast amid a growing debate over whose job it is to prevent the interference.

LightSquared is scheduled to provide initial interference test results and assessments to the Federal Communications Commission on June 15, but other, independent test results are rolling. Last month the Radio Technical Commission for Aeronautics, which advises the Federal Aviation Administration, said tests showed that LightSquared's transmissions caused a "complete loss of GPS receiver function."

According to a publicly released summary, the RTCA report concluded that "the current LightSquared terrestrial authorization would be incompatible with the current aviation use of GPS, however modifications could be made to allow the LightSquared system to co-exist with aviation use of GPS."

And therein lies the problem. Who should have to modify their systems?

Jeff Carlisle, LightSquared executive vice president for regulatory affairs and public policy, says the planned network of ground towers and a satellite are perfectly compatible with the system of GPS satellites and their transmissions. The problem, he says, is that GPS devices, whether in a cell phone or million-dollar airplane, "look" into a wide range of spectrum and therefore receive transmissions made on LightSquared's bandwidth.

Carlisle said LightSquared is waiting for the results of all the tests before determining what the best fix is, but added that the interference problem stems from GPS devices. LightSquared has developed filters to prevent its transmissions from bleeding into GPS bands, he said, while suggesting filters for GPS devices could be part of a solution. An April report by technology company Qualcomm, which is a vendor for LightSquared and also supplies GPS chips, found that GPS units in cell phones could possibly be modified to avoid interference for as little as 5 cents apiece.

Not so fast, said Jim Kirkland, Carlisle's GPS-industry counterpart on the Washington-lobbying circuit. He argues that there is no known fix for many types of GPS receivers, and it is still not clear whether filters would work on even limited receivers like cell phones.

"It's just the laws of physics," said Kirkland, vice president and general counsel for GPS manufacturer Trimble. In a recent letter to Rep. Anna Eshoo, D-Calif., a top lawmaker on telecom issues, he argued that the FCC and LightSquared want to change the rules the GPS industry has used for decades.

"The commission and LightSquared cannot now rewrite the rules to shift the burden of eliminating interference to GPS providers," Kirkland wrote. "That burden remains squarely with LightSquared. If LightSquared cannot demonstrate that it will not cause - or that it alone will ameliorate - harmful interference to GPS operations, it must not be permitted to initiate service."

Carlisle could not confirm whether LightSquared could operate as planned without the spectrum nearest the GPS band. Virginia-based LightSquared will begin rolling out its national 4G broadband network later this year, putting it in a category occupied by only AT&T, Verizon, and Clearwire.