Three parties seek service rules or waivers for the 102-109.5 GHz band.

The FCC’s licensing and service rules presently provide for use of spectrum up to 95 GHz, an extremely high frequency. Now the FCC is considering requests to go even higher: to open the 102-109.5 GHz band for fixed microwave applications.

Radio waves in this part of the spectrum behave differently from those used for, say, cell phones or broadcasting. These signals travel in short, straight lines. The transmit and receive antennas must be in sight of each other. The signals are easily blocked by building walls, terrain, and other obstacles, and are attenuated or blocked by rain or snow. So-called “space attenuation” is high at these frequencies, which limits the useful range even in clear air. Because the wavelength is very short, less than three millimeters, designing circuits is a major challenge. A device’s internal components typically have dimensions comparable to this wavelength; without appropriate precautions, they act like little antennas transmitting and receiving to each other within the device, and that impairs performance.

Still, this part of the spectrum offers important advantages. Uniquely in the spectrum, there is enough radio bandwidth here to permit data capacities similar to those of fiber-optic cable. A compact antenna just a few inches across can provide a highly directional beam. The same frequencies can be reused nearby. And, unlike nearly all other useful radio frequencies, these are practically empty.

By international agreement, the 102-109.5 GHz band has been set aside, or “allocated”, for fixed service use on a co-primary basis with mobile, radio astronomy and, above 105 GHz, passive space research. But despite that allocation, the band cannot be used domestically until the FCC establishes service rules for it.

Back in February, 2014, Battelle Memorial Institute asked the FCC to adopt service rules for 102-109.5 GHz. Battelle proposed that the FCC carry over the same “light licensing” rules as presently apply to the bands at 71-76, 81-86, and 92-95 GHz: each user first obtains a non-exclusive, nationwide license, and then coordinates individual links using an automated system.

Reaction to the Battelle request was almost entirely supportive. The only dissent came from the radio astronomy community, which split: the National Research Council’s Committee on Radio Frequencies does not object so long as astronomy sites observing at these frequencies are protected, while the National Radio Astronomy Observatory wants the rules to protect radio astronomy frequencies everywhere. After soliciting comments, the FCC has taken no further action.

A few months ago, ZenFi Networks requested a waiver on essentially the same terms as the Battelle proposal. It wants to use the 102-109.5 GHz band for backhaul – i.e., carrying network signals to and from cell sites. Shortly thereafter, McKay Brothers asked the FCC either to move forward on the Battelle rulemaking, with small modifications, or else to grant McKay Brothers a waiver similar to that requested by ZenFi. Both proposals were “accepted” by the FCC last week and it has now asked for public comment on both the ZenFi and McKay Brothers submissions.

Meanwhile, hovering in the background, is a two-year-old pending petition from the Institute of Electrical and Electronics Engineers (IEEE) asking that any request related to technologies or services using frequencies above 95 GHz be classed as “a new technology or service” under Section 7 of the Communications Act. This would impose two requirements:

  1. Anyone opposing the request would have the burden of showing that the proposed use is not in the public interest. This reverses the usual presumption, which places the burden on the party seeking a waiver or rule change.
  2. The FCC would have to decide whether the request is in the public interest within one year of its being filed.

The FCC solicited comments on the IEEE petition but has not ruled on it. Although the FCC often cites Section 7 as authority for its actions, we are not aware of a case where it has explicitly followed the section’s mandates. It has already missed the one-year deadline for the Battelle request (assuming Section 7 applies). We agree with IEEE that applications over 95 GHz can legitimately be deemed new technologies, which makes the ZenFi and McKay Brothers requests a good place to start applying Section 7.

Comments on these requests are due on November 12, 2015 and reply comments on November 30 (the Monday after the U.S. Thanksgiving weekend). Submit your filing at this link; use proceeding number 15-245.

(FHH represents an industry group that filed in support of the Battelle request.)