A high-ranking federal official and aviation industry leaders called on Wednesday for rules to prevent future interference with GPS, looking beyond a proposal by would-be hybrid mobile operator LightSquared that may be doomed by broad opposition.
LightSquared's proposed cellular data network can't be made compatible with GPS, and the government should set interference standards to prevent future conflicts over companies trying to establish such services, Deputy Transportation Secretary John Porcari told a House Aviation Subcommittee hearing on Wednesday.
Porcari, who co-signed a letter last month that ruled out solving interference issues between the two systems in the coming months or years, repeated that assertion at the hearing and gave more details of the reasoning behind it.
The National Space-Based Positioning, Navigation and Timing Executive Committee (PNT ExComm), which Porcari co-chairs with a deputy secretary of defense, has effectively dismissed LightSquared's proposal. PNT ExComm represents eight federal departments and the Joint Chiefs of Staff. However, the Federal Communications Commission has the ultimate authority to squash the carrier's plan or let it go forward.
LightSquared wants to build an LTE (Long-Term Evolution) network that uses frequencies next to the band assigned to GPS. It would form half of a system that would also include a satellite network, and the company would sell each to carriers at wholesale. The FCC conditionally approved the LTE network plan in January 2011 as part of its push to open up an additional 500MHz of spectrum to mobile broadband. The agency said any interference issues would need to be resolved before LightSquared could launch the network.
Porcari and other speakers, including representatives from GPS vendor Garmin and the industry groups Airlines for America, called for a coordinated effort among government agencies to prevent future interference with GPS by other services. His own proposal calls for the National Telecommunications and Information Administration and PNT ExComm to set standards for what uses would be allowed in adjacent spectrum bands. The proposals would be communicated to all affected parties, including potential new users of spectrum.
"Establishing those standards would give them a good sense of what kind of uses would be compatible and which would not," Porcari said.
In his testimony, Porcari repeated PNT Excom's conclusion that no more tests of LightSquared's system were warranted after the last round, in November, showed that 75 percent of tested general-navigation GPS devices received harmful interference from the LTE transmissions. The federal government spent substantial funds, including US$2 million from the Federal Aviation Administration, on tests of commercial GPS gear such as phones and car navigation devices and on avionics systems, he said.
"Due to the Administration's commitment to increase access to broadband, the investment was merited, but given the results we reviewed, further investment cannot be justified at this time," Porcari wrote.
One critical system that was shown to suffer from interference in the FAA's tests was TAWS (terrain awareness and warning systems), designed to warn pilots of terrain ahead and prevent crashes into mountains, Porcari said. LightSquared proposed to fix interference with TAWS by adjusting the density and operations of its network where necessary. But there are too many variables involved, Porcari said.
"In sum, LightSquared's proposal would require constant, individual monitoring and adjustments to over 40,000 broadcasting sites nationwide, to ensure that they could be, and would remain, consistent with air safety requirements. This is simply not practical," Porcari said. LightSquared said the Transportation Department has refused to discuss the issue directly with the company.
LightSquared has alleged that the November tests were rigged by parties, including PNT ExComm, that are biased toward GPS manufacturers. On Wednesday, Porcari refuted those charges.
"We worked with LightSquared. They were part of developing the testing protocols, they were part of the testing itself," he told the hearing. The test results were independently reviewed by labs with no ties to the GPS industry, he said.
The hearing on Wednesday before the Aviation Subcommittee of the Committee on Transportation and Infrastructure was billed as a general discussion of protecting and improving GPS, but most of the session was focused on the LightSquared controversy. LightSquared slammed the meeting as "a one-sided trial of LightSquared in absentia."
"Despite repeated requests, we were told there was no need to testify because LightSquared was not the subject of the hearing," the company said in a statement. Harbinger Capital Partners, the hedge fund that owns LightSquared, also called the hearing unfair.
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