NTIA identified in 2019 an additional military site for protection, which was a small coordination zone around Edwards Air Force Base (AFB) to the south of Federal facilities in China Lake, California.¹³ In addition, NTIA sought the conversion into a single area of four overlapping coordination zones listed in the Table of Allocations under the China Lake site. The intent was to protect DoD’s operations in the China Lake coordination area and nearby Edwards AFB, without impacting Upper 37 GHz licensees’ access to relevant population centers in California. NTIA recommended that coordination with the Federal operations be conducted via the IRAC process.

In 2006, NTIA sent a follow-up letter to the FCC, reiterating the need to protect NASA, NSF, and military operations from non-Federal terrestrial and FSS operations in 37-38 band.¹⁵ NTIA recommended that because of potential interference from airborne systems, the aeronautical mobile service allocation should be deleted from the 37-38 GHz band.

2014: By 2014, the state of wireless technology had evolved. The FCC launched a regulatory proceeding to examine the potential provision of mobile radio services in the mmW spectrum.¹⁶ In a 2014 Notice of Inquiry (NOI), the FCC noted that until then, the prevailing assumption was that mobile service in spectrum at higher frequencies was infeasible “because radio waves at those frequencies travel in straight lines and could provide only line-of-sight service. Also, the propagation and atmospheric absorption characteristics of higher frequency bands significantly reduce the coverage of individual base stations and require a very expensive network to achieve a reasonable extent of aggregate coverage.”¹⁷ Leading wireless equipment manufacturers began developing ways to provide non-line-of-sight services in higher spectrum bands with increased range.

The NOI sought comment on the suitability of the 37 GHz and 42 GHz bands for advanced mobile services, noting that the FCC and NTIA would work together to ensure that in the 37 GHz range “federal operations are protected” while maximizing the use of the band for commercial operations.¹⁸

2016: In 2016, the FCC, in coordination with NTIA, took further steps to promote technological advances in the mmW bands, including the creation of a “new paradigm for Federal and non-Federal sharing in the 37 GHz band.” The First Spectrum Frontiers Report and Order (First R&O) concluded that non-Federal fixed and mobile operations can share the 37-38.6 GHz band with DoD operations.¹⁹ The FCC made the Lower 37 GHz band available for coordinated co-primary sharing between Federal and non-Federal fixed and mobile users, determining both sets of operators would access the band by registering individual sites through a coordination mechanism to be developed through government and industry collaboration. (Of note: The FCC made the Upper 37 GHz band, 37.6-38.6 GHz, available on a licensed geographic basis, with protected Federal sites, via an auction which concluded in 2020.)

In the Lower 37 GHz band, the First R&O designated non-Federal users as authorized by rule with Federal and non-Federal users accessing the band through a coordination mechanism. The FCC explained that it “envision[ed] this segment serving as a proving ground for Federal and non-Federal sharing in the mmW bands, as a way to facilitate expanded Federal use in the band, an opportunity to facilitate lower-cost access to mmW bands, and a means for all providers to gain additional capacity where and when it is needed.”²⁰ For the entire 37-38.6 GHz range, the Order designated coordination zones for the Federal sites identified by NTIA.²¹

2018: In 2018, the FCC affirmed the co-primary sharing framework for the Lower 37 GHz band and sought comment on the details of that approach, including a third-party coordinator or a coordination model similar to that used in Part 101 point-to-point bands.²² A Third Further Notice of Proposed Rulemaking (Third FNPRM), which accompanied the Spectrum Frontiers Third Report and Order, recognized the importance of the Lower 37 GHz band to future Federal operations, stating the FCC would “work in partnership with NTIA, DoD, and other Federal agencies to develop a sharing approach that allows for robust Federal and non-Federal use in this band.”²³ The FCC sought comment on accommodating coordination zones for future Federal operations at a limited number of additional sites.²⁴ The Spectrum Frontiers Fourth Report and Order (Fourth R&O) set a course for the auction of the Upper 37 GHz band, among other bands.²⁵

2019: To continue efforts to make access to millimeter wave spectrum available, the FCC adopted a coordination process in 2019 for the Upper 37 GHz band (37.6-38.6 GHz) to accommodate future military use beyond protected DoD sites when access to the Lower 37 GHz band cannot be accommodated.²⁶ The Spectrum Frontiers Fifth Report and Order (Fifth R&O) addressed protection of specific Federal sites in the Upper 37 GHz band, with the sharing framework for the Lower 37 GHz band to be determined at a later date.²⁷ FCC rules require equipment in these bands be capable of operating across the 37-40 GHz range, which is expected to drive equipment availability with respect to the overall technological ecosystem for the 37 GHz and 39 GHz bands. Licensees in the Upper 37 GHz band must demonstrate buildout at license renewal; licenses have 10-year terms (i.e., 2030 timeframe.)²⁸

The Fifth R&O established a process to allow DoD to access the Upper 37 GHz band to accommodate the military’s needs while protecting the interests of non-Federal licensees in the Upper 37 GHz spectrum band. DoD may submit requests for access to the Upper 37 GHz band “for specific additional military bases and ranges, for the purpose of defense applications or national security. Such requests must include a justification regarding why the proposed operations could not be accommodated in the Lower 37 GHz band.”²⁹

When such requests are made, FCC staff will review them, in consultation with affected licensees, NTIA and DoD, to determine whether “the request for access can be accommodated without creating a significant risk of harmful interference to current or planned deployments by potentially affected non-Federal licensees.”³⁰ The FCC based this decision on several factors, including an expectation that DoD requests are likely to be relatively rare, since the Commission anticipated that most such operations can be accommodated in the Lower 37 GHz band.³¹ Further, military use, when it cannot be accommodated in the Lower 37 GHz band, is likely to be limited to military bases and ranges, for the purpose of defense applications or national security. The technical characteristics of systems in this spectrum are marked by high path losses and use of advanced antennas and adaptive power control, which can be utilized to mitigate impact on licensees’ operations.