Ligado Asks Officials to Disregard GPS Testing Report

Ligado Networks LLC has asked the FCC and the Defense and Transportation departments to reject a recent report by the Space-Based Positioning Navigation & Timing National Systems Engineering Forum (NPEF) assessing whether there are gaps in testing of adjacent-band interference to the Global Positioning System L1 band (TR Daily, March 20).

The NPEF was tasked with doing the assessment by the National Executive Committee for Space-Based PNT, an intergovernmental agency body. The analysis evaluated tests done by an FCC-mandated technical working group, the NPEF, the Department of Transportation, Roberson and Associates LLC for Ligado, and the National Advanced Spectrum and Communications Test Network (NASCTN).

The NPEF report faulted the Roberson and NASCTN tests for not using a 1 dB increase in the noise floor as the threshold for assessing harmful interference to GPS receivers, as the other tests did. It said that the other tests “included sufficient scope and methodology in compliance with the PNTAB’s [Space-Based PNT Advisory Board] set of recommendations, namely the DOT ABC, NPEF, and FCC TWG tests.”

But in a letter Monday to Patrick M. Shanahan and Jeffrey A. Rosen, the deputy secretaries of the Defense and Transportation departments who chair the National PNT Committee, Ligado President and Chief Executive Officer Doug Smith said there were “fundamental flaws” in the NPEF report.

He said that the report failed to mention that major GPS equipment manufacturers have signed agreements with Ligado stating they will not oppose the company’s planned LTE network deployment as long as certain technical parameters are met.

Mr. Smith also said that the NPEF’s report “is flawed because it is based on criteria that simply have no basis in spectrum regulation.” In particular, he complained that it “concludes that the only testing that matters is the testing for a change of 1 dB in the noise floor caused by operations in adjacent bands, and it gives no value to almost 1,500 hours of testing done by” the NASCTN.

Mr. Smith added, “The metric of a 1 dB change in the noise floor is appropriately used by regulators to govern users who share a band, sometimes referred to as a ‘co-channel interference.’ While Ligado’s operations and GPS are near each other (but not exactly ‘adjacent’ given the 23-megahertz guard band), the truth is that under all spectrum regulations GPS and Ligado do not share a band. That is a fact that some GPS advocates seem unwilling to accept.”

GPS equipment makers Garmin International, Inc., Deere & Co., Trimble Navigation Ltd., TopCon Positioning Systems, Inc., and NovAtel, Inc., have reached agreements with Ligado under which they will not oppose Ligado’s network, but those agreements don’t cover use of the 1 dB threshold, which most of the companies support.

Mr. Smith’s letter was attached to an ex parte Ligado filing with the FCC yesterday in IB docket 11-109 that also criticized the NPEF report.

“We encourage the Commission, as the expert spectrum agency in consultation with NTIA, to consider the full record before it, which shows that Ligado can both protect GPS devices and enable the use of prime mid-band spectrum to enhance American competitiveness and security, invest in American infrastructure, and create thousands of new jobs,” Ligado said.- Paul Kirby,

Courtesy TRDaily