On November 24 Google filed an application with the FCC for a two-year experimental license to conduct nationwide testing in the 71-76 and 81-86 GHz millimeter-wave bands. The application consists of a form and supporting exhibit. As is usual with Google, the version of the exhibit made available to the public is redacted, but there’s enough there to infer that that this involves high-altitude airborne testing – perhaps connected to Project Loon or to solar-powered drones emerging from Google’s Titan Aerospace acquisition.
The exhibit says the application is related to two previous experimental authorizations assigned call signs WH9XYD and WH2XUP. WH9XYD covered two sequential periods of special temporary authorization running from October 2014 to October 2015. It covered a narrower frequency range, near 75 and 85 GHz. The area of operation was limited to the vicinity of Winnemucca, Nevada. The WH9XYD authorization alludes to interference concerns to the National Science Foundation’s Very Long Baseline Array from “high flying aircraft.”
WH2XUP, is a longer-term two-year experimental license running from June 2015 to June 2017. Compared to WH9XYD, the same frequency bands and Winnemucca location appear. Added is coverage in California, Idaho, Oregon, and Utah. More coverage is added in Nevada. The application form states as one mobile operation parameter “airborne max altitude 75,500 ft. AGL.” That’s consistent with operation by Project Loon balloons or Titan-Aerospace-type drones.
Back to the November 24 application, it resembles the others but now the proposal is for operation nationwide. The frequency range is greatly increased, but the bandwidth specified in all applications is the same — variable from 60 to 580 MHz. There’s no explicit mention of aircraft this time, but it’s tied to the WH2XUP application that specified airborne operation. The exhibit references “continued development” and says the operation “builds on testing conducted” under the previous call signs. Also, looking at power levels and antenna gains on all these applications, they’re generally consistent.
From WH9XYD to WH2XUP to the current application, the scale of testing has grown. It’s ramped up from Nevada, to several states, to nationwide in less than a year. The FCC is leery of experimental operations morphing into services, and it may probe Google why it needs to go nationwide over a much larger frequency range, and why it can’t make do with it’s present experimental authority.