- Associated Press - Thursday, June 30, 2011

New test results show that a proposed nationwide wireless broadband network would produce significant interference with GPS systems used for everything from aviation to high-precision timing networks to helping drivers find an unfamiliar address.

Changes to the proposal could reduce interference but wouldn’t eliminate it.

The findings, based on extensive tests conducted in Las Vegas, increase pressure on the Federal Communications Commission to block a Reston company called LightSquared from launching the network, which is designed to compete with superfast systems being rolled out by AT&T and Verizon Wireless.

Although the Federal Communications Commission in January gave LightSquared approval to build the system, the agency said it would not let the company turn on the network until GPS interference problems were resolved. The agency required LightSquared, GPS equipment makers and GPS users to establish a working group to study the matter.

That group filed its report with the commission Thursday, with the two sides offering different interpretations of the test results.

LightSquared insisted the interference problems can be corrected.

But GPS equipment makers, and companies and government agencies that rely on GPS technology, warn that the planned network would jam their systems because LightSquared would use airwaves close to those already set aside for GPS.

They say that sensitive satellite receivers - designed to pick up relatively weak signals coming from space - could be overwhelmed when LightSquared starts sending high-powered signals from as many as 40,000 transmitters on the ground. GPS signals, they say, will be hampered the way a radio station can get drowned out by a stronger broadcast from a nearby channel.

“The FCC needs to consider other options for the LightSquared signals where they do not run up against the laws of physics,” said Charles Trimble, co-founder of Trimble Navigation Limited, which makes GPS systems.

With the working-group report complete, the FCC will now seek public comments. The FCC said it will review the report, adding that it has “a long-standing record of resolving interference disputes.”

The working group’s report follows the release of federal test results that also found significant interference with GPS systems used by a broad cross-section of government agencies, including the Coast Guard, the Federal Aviation Administration and NASA.

Faced with increasing GPS industry resistance, LightSquared last week proposed to move some of its operations to a slice of airwaves located farther away from GPS frequencies. It also proposed to transmit signals at lower power levels to ensure that its network would not interfere with most nearby GPS systems.

Most of the testing conducted by the working group was based on the company’s original plan to use airwaves next to the GPS band.

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