NOAA Sees Notable Interference, Data User Issues To Be Tackled in Ligado Proposal for 1675-1680 MHz
Ligado's plans for commercial access to the 1675-1680 MHz band for its terrestrial broadband network could face a hurdle in the form of downlinks from the National Oceanic and Atmospheric Administration Geostationary Operational Environmental Series satellite-R (GOES-R) set to launch in October. The company previously named LightSquared is pushing the FCC to open up that NOAA-used band for commercial sharing and auction (see 1512310016), and hopes to see that auction in federal FY 2017 (see 1602090067). But NOAA said a variety of issues -- chief among them interference with its downlinks -- need to be addressed first.
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“It's a tractable problem, to identify use cases and missions affected and develop technical workarounds if protection zones are not an option," Zach Goldstein, NOAA chief information officer, told us. "That's work that hasn't been done but we have faith could be done.”
NOAA uses the spectrum for radiosonde operations, with the transmitters carried aloft by weather balloons around the U.S., Goldstein said. Those radiosondes are to be relocated to a different spectrum to make way for GOES-R downlinks carrying various earth observation data, as well as serve as a communications platform for thousands of sensors around the country in everything from stream gauges to wind sensors in forests, he said.
Challenges with sharing 1675-1680 MHz include that NOAA has no idea who uses the agency's Data Collection System. "The sensors and the information they provide are for anybody's use," Goldstein said. "There are emergency management organizations and dam operators and fill in the blank ... that can get this data off the satellite because it's broadcast. The dilemma we have is we know public safety organizations across this country use this data. The thing we don't want to do is cut it off or let it be jammed.”
Interference seems highly possible, Goldstein said, pointing to interference issues NOAA has seen between its operations in 1670-1675 MHz and Ligado terrestrial operations licensed to operate in that spectrum. "Every now and then, it causes interference with our downlink," Goldstein said. While Ligado will then shut off the transmitter temporarily, Goldstein said, "that's not a sustainable solution. At that point, we've already had a problem with our imagery." Goldstein said NOAA and Ligado are "working very cooperatively" on devising means of identifying interference before it causes downlink damage.
NOAA and the company are hopeful joint efforts between the two to be tested later this year in the 1670-1675 MHz band could also apply to the 1675-1680 MHz band, Ligado counsel Gerard Waldron of Covington & Burling told us Tuesday: “Both sides are optimistic this will do the trick.” Ligado-commissioned reports by Alion in 2014 also said "shared use of that band by a commercial terrestrial wireless operator is feasible while still protecting NOAA earth stations" (see 1404160030).
Ligado has taken some steps of identifying nonfederal users of NOAA services that could be affected by interference. The company also has repeatedly pushed the FCC to issue a public notice seeking comment on a proposed 1675-1680 MHz auction and on Ligado's related license modification request (see 1602120052). It's a step Waldron said would help identify at least all the typical public use cases, if not every single user. The FCC as a condition on the auction winner then could put in requirements for dealing with those use cases, he said.
Ligado also is pushing the idea of alternative delivery of NOAA-generated data to non-NOAA users, such as establishing a cloud-hosted private content delivery network maintained by an independent, nonprofit body, potentially as a license condition on the auction winner, it said in a filing earlier this month in docket 12-340.
NOAA had used the 1695-1710 MHz band for previous GOES satellite downlinks, though the agency moved GOES-R to allow sale of that spectrum in the AWS-3 auction, said Jim Mentzer, NOAA director-radio frequency management division. Changing the downlink frequency for GOES-R to accommodate Ligado is not feasible due to both costs and the delays it would entail, Goldstein said. "Even if we could switch, I don't know where we could," Mentzer said. "Finding another suitable band would be very difficult.”
President Barack Obama's FY 2017 budget proposal calls for flexible use of 1675-1680 MHz, subject to sharing with federal weather satellites, by 2020 (see 1602090067). "We can read the president's budget as well as the next person," Goldstein said. "We're moving as expeditiously as possible.”