Feature Article

December 13, 2011

LightSquared Disputes Test Results

LightSquared executives are about as mad as AT&T is over “leaked” information, in this case unfavorable test results reported by Bloomberg (AT&T is miffed that the Federal Communications Commission released an analysis of the proposed AT&T purchase of T-Mobile USA).

The latest U.S. government lab test of LightSquared spectrum caused interference to 75 percent of global-positioning system receivers examined, a draft summary of results indicates. It is not immediately clear whether the new tests mean 75 percent of all GPS devices experience interference, or only 75 percent of the class of devices LightSquared itself says will encounter signal interference. 

Nor is it clear how well the laboratory tests would correspond to a real-world deployment. It remains fairly clear that, so long as there are concerns about interference, it will be difficult to impossible for the FCC to approve use of the spectrum as LightSquared proposes. As a rule, licensees proposing to use spectrum must avoid interfering with other licensed users of spectrum.

The results from testing conducted Oct. 31 to Nov. 4 show that “millions of fielded GPS units are not compatible” with the planned nationwide wholesale service, according to the draft seen by Bloomberg News.

LightSquared has argued that its latest spectrum plan causes disruption to about 10 percent of devices.

The laboratory testing was performed for the National Space-Based Positioning, Navigation, and Timing (PNT) Systems Engineering Forum, an executive branch body that helps advise policy makers on issues around GPS. It found that 69 of 92, or 75 percent, of receivers tested “experienced harmful interference” at the equivalent of 100 meters (109 yards) from a LightSquared base station.

“Based on our own review of the test data, we profoundly disagree with that conclusion,” LightSquared says. “That report was based on an incomplete, selective, and slanted analysis of the data of the testing of general location/navigation devices.”

“To achieve that level of threshold of failure, the leaked internal analysis assumes that the power levels of LightSquared networks are 32 times greater than the power levels at which LightSquared will actually operate,” LightSquared says.

Throughout the test process, LightSquared has urged the government agencies involved to analyze the test results based on a measurement of the actual power level of LightSquared’s network that will be experienced by GPS devices and not a theoretical model apparently relied upon by the leaked internal analysis, the firm says.

We submitted a formal proposal of this “power on the ground” standard with the FCC on December 7, 2011. If this “power on the ground” standard is applied to the test data, LightSquared’s own analysis shows that the vast majority of general location and navigation devices will experience no interference from LightSquared’s network, the firm maintains.



Gary Kim is a contributing editor for MobilityTechzone. To read more of Gary’s articles, please visit his columnist page.

Edited by Jennifer Russell


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