GPS industry and new cellular carrier spar over interference issue

The GPS industry and a new cellular phone carrier continue to battle over development of a new wireless broadband system, which the industry says will cause widespread jamming of sensitive Global Positioning System signals used for everything from smart maps in cars to aircraft navigation.

LightSquared of Reston, Va., plans to develop a nationwide cellular network that uses satellites and up to 40,000 high-powered land-based transmitters. The company intends to market its service to rural areas that do not currently have broadband service, a key reason the Federal Communications Commission approved LightSquared's hybrid satellite/terrestrial network on Jan. 26.

FCC directed the company to work with the GPS industry to determine the potential effect its terrestrial transmitters, which operate in the 1525-1559 MHz and 1626.5-1660.5 MHz bands, would have on GPS systems that operate in the nearby 1559-1610 MHz bands.

Late last month, LightSquared and the U.S. GPS Industry Council filed a plan for this joint working group, which will deliver its first technical report to the FCC on March 15.

At the same time, both the council and Lockheed Martin Corp. asked the FCC to overturn its order allowing LightSquared to operate. Lockheed Martin operates the communications satellites used by the Federal Aviation Administration's GPS-based Wide Area Augmentation System to support precision navigation across the country. WAAS uses a network of 38 reference receivers to correct for errors in GPS caused by the ionosphere.

The council, in a filing with the FCC on Feb. 25, reiterated its position that the LightSquared system will threaten the operation of millions of GPS receivers. It also said the FCC exceeded its authority by allowing LightSquared to operate its cell towers under rules governing the ancillary use of such transmitters in conjunction with a satellite system.

Only the full commission, in a rule-making proceeding, can change those rules, the council argued.

In a separate Feb. 25 filing, Lockheed Martin asked the FCC to determine that "unresolved and serious issues" remain regarding the potential for the LightSquared system to interfere with its WAAS satellites, which transmit reference signals on the GPS band with a horizontal accuracy of 4 feet, compared to 65 feet for uncorrected GPS signals.

Lockkeed Martin told the FCC that its satellite ground stations have sensitive receivers that control the uplink signal, and interference could cause these receivers to transmit bad data. If enough interference is present, the receiver will shut down, Lockheed said, preventing transmission.

Jeff Carlisle, executive vice president for regulatory affairs at LightSquared, said the company will address the specifics of the Lockheed Martin and council complaints in a filing it plans to make with the FCC next week.

He said interference tests that showed the company's towers jammed GPS signals were flawed. The findings from the tests, which were done by the council and receiver manufacturer Garmin International, were included in a report filed with the FCC in January. Carlisle said GPS receivers used in those tests did not incorporate filters that LightSquared developed to mitigate interference from the company's cellular network.

Carlisle said interference is not caused by the LightSquared system, but by sensitive GPS receivers that "see" into the frequency band used by LightSquared. Not all GPS receivers do that, Carlisle said, and one possible mitigation strategy is to replace GPS receivers that pick up the LightSquared signal.

This is a high-stakes battle. LightSquared has spent $1 billion to build and launch a powerful broadband satellite and industry officials estimate it will cost between $6 billion and $9 billion to build a national terrestrial broadband cellular network. In addition, LightSquared has spent $100 million on chipset technology for dual satellite/terrestrial handsets and data cards, Carlisle said.

According to the council, GPS represents a $22 billion investment by the federal government, in addition to the "orders of magnitude" more invested by end users to develop applications that serve defense, public safety and homeland security needs, as well as a wide range of industries.