NTIA’s 3.45-3.55 GHz Report Shines Spotlight on Spectrum Sharing, But Further Studies Still To Come

The National Telecommunications and Information Administration’s (NTIA) long-awaited Sharing Report on the technical feasibility of sharing in the 3450-3550 MHz (3.45 GHz band) is finally here.  Although the Report concludes that spectrum sharing in the 3.45 GHz band may be “possible,” it ultimately recommends further study and analysis to determine whether sharing mechanisms would be feasible.

NTIA first identified the 3.45 GHz band as potentially suitable to repurpose for commercial use in February 2018.  Thereafter, it convened a joint working group with participants from the Department of Defense (DoD) and the Federal Communications Commission (FCC) to evaluate the technical feasibility of allowing commercial wireless services to share spectrum with incumbent federal systems in the band.  The release of NTIA’s Sharing Report represents the culmination of those efforts and signals that spectrum sharing will be a hot topic with policymakers in 2020.    

Incumbent operations in the 3.45 GHz band include shipborne radars, several types of airborne systems, and ground-based radars.  The Report indicates that while some federal incumbent systems operate only intermittently and in portions of the band at a time, the spectrum may be used at dynamic and unpredictable times, depending on mission requirements.  In addition, DoD continues to deploy additional systems in the band at new locations and anticipates continuing to do so in the future.  Some aspects of these incumbent systems are classified, which, as the Report acknowledges, makes full transparency difficult. 

Despite these variables, the Sharing Report concludes that, although commercial operations would impact incumbent federal systems, “sharing that provides both sufficient protection to incumbent operations and an attractive commercial business case may be possible.”  In particular, the Sharing Report found that frequency- and geographic-based sharing would not be feasible because such approaches would “result in significant restrictions on commercial services, in terms of emitter power limits and exclusion zones, making sufficient access for viable commercial applications unlikely.”  Instead, NTIA concludes that a dynamic, time-based sharing mechanism may present an “attractive” approach to protecting federal operations while also enabling viable commercial operations.  Such a time-based sharing regime would make spectrum available to commercial operations depending on the frequency, time, and location of federal system operations.

Although the Sharing Report acknowledges that the 3.45-3.55 GHz band may be suitable for sharing, it also calls for additional studies.  Further analysis is needed, the Report concludes, to “reach a more definitive conclusion” about whether a sharing mechanism could facilitate shared commercial access without causing harmful interference to incumbent systems.  Specifically, the Report recommends focusing on the development of a time-based sharing mechanism that could facilitate sharing in the 3.45 GHz band.  The Sharing Report further notes that a “more detailed assessment” of incumbent federal systems and the “mission impact of introducing sharing” is warranted.  Additional detail about current and future DoD system needs will also be necessary to establish sharing conditions, NTIA said.

The wireless industry has long considered the 3.45 GHz band as attractive for commercial operations.  Directly below the newly-launched 3.5 GHz citizens broadband radio service (CBRS) spectrum, the 3.45 GHz band offers 100 megahertz of mid-band spectrum that could be used to bolster 5G deployments.  Mid-band spectrum will be a critical building block for 5G due to its ability to both travel far distances and offer high capacity for mobile traffic.     

While the Sharing Report represents another important step toward potentially repurposing the 3.45 GHz band for commercial use, it also signals that much more work is to be done and that sharing options may be limited.  The additional studies called for will likely be time consuming and resource intensive.  Moreover, the focus on developing time-based sharing regimes may be complex and could ultimately impair the commercial uses of the spectrum.  Nevertheless, we expect NTIA to continue its work studying the 3.45 GHz band as potentially suitable for sharing.    

For its part, the FCC has also signaled that it hopes to enable 5G deployments in the 3.45 GHz band.  In December 2019, the FCC released a notice of proposed rulemaking (NPRM) proposing to delete the existing non-federal secondary allocations from the 3.3-3.55 GHz band.  In doing so, the FCC indicated that it intended to prepare the band for possible future shared use between commercial wireless services and federal incumbents, pending the results of NTIA’s sharing feasibility analysis.  NTIA, however, has not issued any further studies on the 3.3-3.45 GHz band since it conducted the Quantitative Assessments of Spectrum Usage in 2016.  NTIA stated in its 2019 Annual Report on the Status of Spectrum Repurposing that “[c]onsideration will be given to extending the detailed studies to the remainder of the band (i.e., 3100-3450 MHz) upon completion of” its report.  Comments on the FCC’s NPRM will be due February 21, 2019.      


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