In July of 2015, NASA held its first UAS Traffic Management conference. I nervously stood in front of a massive aviation crowd and said that I feared that agreeing upon suitable spectrum/communications solutions for uncrewed aviation and drones would be the long pole in the tent for enabling widespread use of uncrewed aircraft systems. The Federal Communications Commission (FCC) works on its own time schedule apart from the Federal Aviation Administration (FAA). There are, of course, many important FAA issues to resolve for uncrewed aviation. But there are also fundamental questions the FCC must resolve in consultation with the FAA:
- How are we going to communicate with uncrewed aircraft?
- How will uncrewed aircraft communicate with each other and crewed aviation?
- How will uncrewed aircraft communicate with UAS traffic management (UTM) and air traffic management (ATM)?
- How do we, as industry, coordinate the work of the FCC and FAA around emerging aviation?
If we cannot answer these fundamental questions about the communications architecture, the UAS industry will not have a viable and scalable ecosystem for the future. When we raised these issues at the first UTM conference, 10 years ago, my team had already been working on UAS spectrum issues for two years—from the moment Jeff Bezos appeared on 60 Minutes in 2013 and talked about Amazon drone delivery.
Cover image: UAS-NAS ACAS Xu FT2 Flight. Ikhana flies a UAS Integration in the NAS mission. Image by Carla Thomas, courtesy of NASA.
Twelve years later, the FCC released a long-awaited Report and Order for UAS-dedicated spectrum in the 5030-5091 MHz band (the UAS Spectrum Order). The Order reflects the same “crawl, walk, run” philosophy that generally applies to adoption of UAS regulations in the United States, and it is clear we are in the “crawl” phase. The UAS Spectrum Order adopts a limited set of rules to temporarily enable use of a small portion of the spectrum from the 5030-5091 MHz band. This limited UAS Spectrum Order was issued 12 years after the International Telecommunications Union recommended allocation of the 5030-5091 MHz band for UAS.
The UAS Spectrum Order for 5030-5091 MHz.
The UAS Spectrum Order adopts a near-term approach that is substantially more limited than the proposals contained in the Notice of Proposed Rulemaking (NPRM). In the NPRM, the smart FCC lawyers and engineers working on the item set forth a comprehensive and thoughtful set of issues and proposals for the communications architecture, including use of the 5030-5091 MHz band for both networked and non-networked UAS access to the spectrum. The FCC also raised whether other bands should be authorized for use of UAS, including the cellular and satellite bands. Sadly, the UAS Spectrum Order puts these issues off to future rulemakings. At this time, the FCC is taking just one temporary step to enable non-networked access (NNA) to a small portion of the 5030-5091 MHz band.
As some of you may recall, this same scenario played out when the FAA adopted rules for remote identification of UAS. The FAA proposed both direct broadcast (non-networked) solutions for remote ID, and a comprehensive networked solution that would utilize wireless networks and the Internet to coordinate nationwide remote ID. Just before finalizing the rule, the FAA changed course and adopted only the direct broadcast solution—a binary, non-networked solution that is not future-proofed. Networked systems for remote ID, spectrum and UTM are all necessary in order for any country to have a viable advanced aviation ecosystem.
To be clear, the FCC pledges in the UAS Spectrum Order to conduct further rulemakings and take a phased approach to enabling use of the 5030-5091 MHz band over time. This entire process, however, will take many, many additional years to complete.
Initial Plan for Use of 5040-5060 MHz.
For now, the FCC has adopted temporary rules for “immediate” access to 20 MHz of the 61 MHz available in the band—the spectrum from 5040-5060 MHz. This spectrum resides in the middle of the band, ensuring no interference with nearby bands. The FCC offers immediate access to this spectrum while it works with other agencies to make a Dynamic Frequency Management System (DFMS) operational (described more below). The interim access mechanism (IAM) for the 5040-5060 MHz spectrum will enable access to the band for non-networked operations while the DFMS framework is developed. Additional things that must happen as part of the IAM are as follows:
- Certification of transmission equipment to be used in the band as compliant with the new Part 88 rules for UAS spectrum. This equipment also must comply with restrictions against authorizing equipment to companies on the FCC’s Covered List.
- The FCC will release a public notice setting forth the FCC registration process for people and entities wanting access to the spectrum.
- Prospective users must submit a request to the FAA for approval/authorization to use the spectrum.
- Prospective users also must submit a registration form to the FCC providing information and certifying that:
- They complied with the FAA authorization process.
- They have/will comply with the Commission’s NNA rules and technical requirements.
- The equipment utilized in NNA operations meets the equipment certification requirements.
- The user understands that their authorization to use the IAM assignment in the 5030-5091 MHz band terminates immediately in the event a DFMS becomes operational.
Once the DFMS is viable, as discussed below, the 20 MHz assigned for the IAM will reduce to 10 MHz.
DFMS – A Spectrum Access System for the Sky.
The most innovative development contained in the UAS Spectrum Order, which we have evangelized for many years, is the creation and reliance on DFMS administrators to assign frequencies for UAS use. Once the DFMS is available, aviators looking to use the 5030-5091 MHz spectrum will register with a Commission-approved DFMS administrator, and that DFMS administrator will assign, for each flight, the spectrum, location and time period for use. DFMS administrators will ensure proper FAA authorization for users prior to assigning spectrum, and they will coordinate to prevent interference and confliction.
Multiple DFMS administrators will coordinate their efforts, and the system is expected to be very similar to the spectrum access systems (SAS) that are authorized by the FCC today to manage the Citizens Broadband Radio Service (CBRS) band. Our team has worked from the beginning of the CBRS rulemakings with Federated Wireless and the FCC to establish the regulatory framework and rules for SAS administrators. We are gratified that the FCC decided to use the CBRS model for DFMS.
Similar to the CBRS band and the WInnForum, the UAS Spectrum Order also anticipates the formation of an “informal multi-stakeholder group” that will work jointly on DFMS requirements, processes and standards that will facilitate UAS operations in the band.
Spectrum Used by UAS Today.
To date, UAS in the United States have relied upon either unlicensed wireless bands (Wi-Fi and Bluetooth), licensed cellular bands or satellite to accomplish communications functions for UAS. These communications functions include command and control, tracking, payload communications, etc. Other bands are either utilized or are under evaluation for detect and avoid technologies. It is important to know that although commercial wireless bands are apparently used for UAS communications functions today, the FCC has not confirmed this use.
The FCC made clear in its Section 374 Report to Congress that even though many flexible use wireless bands do not have explicit restrictions on aeronautical use, there are technical and regulatory issues that must be resolved before these bands can host aeronautical operations. The technical rules for these bands contemplated only terrestrial use, not airborne use. The FCC said that “[b]ecause aeronautical operations were not contemplated when the rules were adopted for these bands,” there are issues that warrant further Commission study before aeronautical operations can take place in these bands, including the potential for harmful interference for other communications. This determination by the FCC has not changed. It is critical, therefore, that in the further rulemakings contemplated in the UAS Spectrum Order, the Commission considers and confirms the use of flexible-use spectrum and existing commercial wireless networks as platforms for UAS operations.
National Spectrum Strategy.
The National Spectrum Strategy, which the National Telecommunications and Information Administration (NTIA) released in November of 2023, imposes a study requirement on the 5030-5091 MHz band, which will take time. After the FCC, NTIA and FAA facilitate the limited deployment of a small amount of the 5030-5091 MHz band discussed above, “this 61 megahertz of spectrum will be studied so that the FCC can optimize UAS spectrum access across the band while avoiding harmful interference to other protected in-band and adjacent-band operations.” At a recent conference at NASA Glenn in which we participated, the FAA indicated that its required study for the 5030-5091 MHz band will begin in January of 2025 and will continue for one year.
Conclusion.
When the FCC released the UAS Spectrum Order, Chairwoman Jessica Rosenworcel hit an optimistic note: “We are already starting to live in the future we’ve long imagined: uncrewed aircraft systems are fighting wildfires, supporting news gathering, delivering packages, and supporting national security. The FCC is working hard to meet the spectrum needs of remote-piloted aircraft activity. We will continue to work with our public and private partners to support the best outcomes for public safety, wireless services, consumers, and our economy.” The UAS industry is no doubt grateful for the UAS Spectrum Order and it is grateful for the FCC’s co-leadership of the infrastructure working group as part of the Department of Transportation’s Advanced Air Mobility initiative.
We also appreciate the Rubik’s cube of issues that must be addressed by government and industry in order to create a comprehensive communications architecture that will support uncrewed aircraft and advanced aviation. It is critical, though, that our government agencies responsible for spectrum continue to press forward with urgency. Decisions must be made for a comprehensive communications architecture that will include the 5030-5091 MHz band, commercial wireless and satellite spectrum. Given how foundational a communications architecture is for uncrewed aircraft and advanced aviation, we must begin “walking and running” with spectrum solutions for UAS so that a ready and scalable UAS ecosystem is enabled.
