Part of the 37 GHz band was auctioned in 2019; another part is being explored for federal/non-federal spectrum sharing
The 37 GHz band represents a new opportunity to develop a spectrum-sharing model for federal and non-federal uses, according to a new report from the National Telecommunications and Information Administration (NTIA).
The 37 GHz band is one of the sections of spectrum that were identified in the National Spectrum Strategy (and the subsequent implementation plan, released earlier this year) as a pipeline of spectrum to study with an eye toward opening up additional spectrum for various uses.
The Biden administration’s National Spectrum Strategy (NSS) identified five candidate bands for near-term study and development, totaling 2,786 megahertz with an emphasis on midband spectrum and bolstering technology for dynamic sharing of spectrum. The candidate bands ranged from 3.1 GHz to 37.6 GHz, with all but one of them under 20 GHz, and were a mix of federal bands and shared federal/non-federal bands, to be studied not only for terrestrial wireless use but for space-based services and aerial drones.
The NSS also declared that “Evolving to a ‘designed to share whenever feasible’ mindset will accelerate efficient and effective use of spectrum for all users” and said that NTIA would pursue “development of an enduring, scalable mechanism to manage shared spectrum access, including through the development of a common spectrum management platform.”
The first assessment of NSS-identified bands has focused on the 37 GHz spectrum. In NTIA’s report, it said that because there are limited incumbent uses of 37 GHz, “the band presents a ‘clean slate’ for developing a new model for co-primary Federal and non-Federal access. Specifically, this spectrum supports the creation of very narrow, directed beams and limited propagation for ground communications, making robust forms of sharing possible.”
Some history, here: Back in 2016, the Federal Communications Commission’s order on the 37 GHz band “concluded that non-Federal fixed and mobile applications can share 37-38.6 GHz with DoD operations.” The lower 37 GHz band was made available for “co-primary sharing,” via a coordination mechanism that would require registering of sites. There are a number of protected federal sites already identified, including 15 military sites, five National Aeronautics and Space Administration receiving earth station operations and two National Science Foundation sites.
The upper 37 GHz band, at 37.6-38.6 GHz, was part of the millimeter-wave spectrum that was auctioned by the FCC in 2019 as part of its Spectrum Frontiers auction. That band was divided for auction into 10 blocks of 100 megahertz in each Partial Economic Area (PEA) geographic designation.
According to the NTIA report, the agency, along with the FCC and DoD, have been having discussions about a coordination mechanism in the lower 37 GHz band since 2020, including a 2024 public notice from the FCC gathering more input on potential sharing issues and accommodations of use cases.
37 GHz: Potential uses and access methods
Here are some key takeaways from the NTIA spectrum sharing report for 37 GHz:
-The report focuses on federal/non-federal sharing, as opposed to exploring how sharing might work between multiple non-federal users.
-The report outlined a number of potential use cases for the 37 GHz spectrum. Wireless operators could use the mmWave spectrum to provide additional bandwidth in capacity-constrained environments like large indoor venues, or for offloading from other bands. It’s also a candidate for Fixed Wireless Access, high-capacity backhaul, and mobile or private networks to support industrial IoT or other high-bandwidth, indoor scenarios.
Federal uses are likely to be similar and overlap with commercial uses, with additional hardening of systems for federal use. DoD is also looking at the potential of using 37 GHz for unmanned aerial systems and wireless power transfer, according to the report.
-The report outlines two methods of access to the lower 37 GHz band: A “priority access” section of 200 megahertz of spectrum from 37.0-37.2 GHz, which non-federal users could access with the understanding that they could be preempted by DoD operations; and a section of “co-equal access” at 37.2-37.6 GHz.
-The report provides a general outline of a coordination framework for federal and non-federal users. This would be a two-phased approach. The first phase would look at simple propagation models and let operations proceed as long as there is no anticipated overlap between them—which is a less risky proposition at mmWave frequencies than in lower bands, given propagation constraints.
The second phase would come into play in the event that there is potential conflict between an existing, registered site and a new one and would require both parties to work together, exchange more information and try to coordinate—and because of federal tech development and procurement timelines, federal users may arrive in the band later than commercial users, NTIA noted. “We expect the second phase of coordination will proceed quickly; if there is a dispute between the parties, the matter would be referred to NTIA and the FCC for resolution,” NTIA said.
-Site-based coordination would also represent a technological “floor” for sharing, NTIA noted, adding that it “support the potential evolution … to more dynamic mechanisms based on demonstrated need and available technology.”
-Challenges in the band include adjacent-band protection of satellite systems. The earth-observing, environmental satellites that use the 36-37 GHz band provide information about things like water and precipitation, and DoD leverages them “extensively,” according to the NTIA report. The report also noted that there was a resolution at the World Radiocommunications Conference of 2019 on addressing interference risk of passive, space-based sensors between 37 GHz that could accompany expansion of fixed and mobile wireless deployments above 37 Ghz.
