Ligado Assails PNT Systems Engineering Forum Tests
The National Space-Based Positioning, Navigation and Timing (PNT) Systems Engineering Forum testing of the effects on GPS receivers of adjacent band operations ignores Ligado's agreement with major GPS manufacturers and improperly disregards cutting-edge government testing over "outdated tests with erroneous…
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criteria and other problems," Ligado said in docket 11-109 filing Friday. It said the PNT Forum's report runs contrary to what major GPS manufacturers believe, and said the Forum report insistence on using 1 dB change in noise floor as an interference protection criteria is fatally flawed. Ligado said the 1 dB metric isn't applicable to adjacent band emissions since it's been applied only to emissions in the same band, and that it's not accurate or reliable since testing has shown a 1 dB change doesn't correlate to actual degraded performance of a GPS device. Using the 1 dB metric shows "basic misunderstanding of spectrum policy and well-established law" by the Forum, Ligado said, saying the Forum is "effectively grant[ing] a form of 'adverse possession' to all GPS devices ... over nearby bands." Ligado said the Forum has no spectrum management expertise or authority. The filing included a letter sent to the National Executive Committee for Space-Based PNT also criticizing the Forum report. The PNT National Coordination Office didn't comment. The Forum report, issued in March, said National Advanced Spectrum and Communications Test Network (see 1702160056) and others did significant testing of Ligado's proposed LTE network and compatibility with Global Navigation Satellite System spectrum, but its own analysis found that testing scope and framework insufficient. It said other test data from such sources as the FCC, Transportation Department and the Forum are sufficient for determining the maximum aggregate power level of transmissions in GPS adjacent bands.