Emails Show Federal Disagreements on Protection Standard for GPS
Emails between the Office of the DOD Chief Information Officer and the Positioning, Navigation and Timing (PNT) office within the Department of Transportation raise new questions about the government’s stance on what some consider an overly conservative emissions standard to protect GPS -- 1 dB. In emails from 2015 we obtained, DOD officials discussed whether that standard is necessary.
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The FCC recently sent an order addressing Ligado's licensing applications to NTIA for the Interdepartment Radio Advisory Committee (IRAC) to scope (see 1910300050). The Ligado applications have been before the FCC for nearly four years. Ligado maintained in various filings at the FCC that 1 dB is not a "standard" and the FCC and NTIA never used the 1 dB metric in the context of adjacent band emissions. Officials said the only power levels that would satisfy the criterion are at an extremely low Bluetooth-level.
Ligado and rules to protect GPS have long been an issue. If the Pentagon ultimately insists on a 1 dB standard it could potentially render some bands unusable for commercial operations, particularly 1.3 GHz, targeted for reallocation by NTIA, industry officials say (see 1812110057). DOD and DOT didn’t comment.
A senior official from the DOD CIO’s office was “very concerned that bunkering down with this criteria as the only thing we are willing to explore or verify is a losing proposition, especially since we have both NTIA and FCC not supporting,” said a key email from the CIO’s office to PNT. “We have to do our due diligence and explore other options and if we ultimately come back to this criteria as the best way to protect GPS then so be it,” the email said. “But to say we will not explore other options because in the past it was supported is not good strategy.” The email argues DOD must be “much more strategic in how we go about doing this.”
A PNT official urged a “firm” federal line, in an email to DOD from the same time period. The 1 dB limit is the “standard protection criteria for GPS used internationally, and that NTIA and FCC supported in the past,” the PNT official said. “Lots of IRAC activity and DoD spectrum work galvanized the federal community on this and there are no valid technical or policy reasons I can think of to warrant a change now.”
A second set of emails indicates that in 2013 an official working for DOD's CIO told key Hill staff the department had no objections to the uplink bands and the upper downlink being used by Ligado.
"GPSIA and its members continue to recognize that spectrum management should employ the internationally established criteria of a 1 dB decrease in Carrier-to-Noise Ratio as an interference protection criterion,” emailed David Grossman, executive director of the GPS Innovation Alliance: “The 1 dB standard provides the most readily identifiable and predictable metric that will ensure a harmful interference level is prevented in the first place, so that systems operating in the same or adjacent bands do not interfere with one another."
In a report last week, New Street noted the Ligado order is now apparently before IRAC. “After a decade of being sidelined due to complaints from the GPS community, the industry would no doubt welcome seeing this spectrum repurposed,” New Street told investors: “Moreover, it could be released for terrestrial use at an interesting time; Ligado has been testing use cases in which the spectrum is paired with higher frequency bands to improve their propagation.”