Spectrum management in the United States is a hydra-headed challenge — there are technical, policy, political and financial dimensions to the ongoing process of identifying spectrum bands where spectrum can be reallocated or where existing users, both licensed and unlicensed, can coexist with new and different spectrum uses. While over time, technology can allow government and commercial interests to utilize spectrum that had been thought to be unusable, that tends to be a gradual process. In the meantime, the amount of spectrum that is available for reallocation or sharing is reasonably finite, and not all spectrum is usable for all potential applications. As a result, there is hard but necessary spectrum management and policy work undertaken at the Federal Communications Commission (FCC), the agency that handles commercial spectrum licensing and management and at the National Telecommunications and Information Administration (NTIA), the entity within the Department of Commerce that handles spectrum licensing for the federal government.
Radio equipment manufacturers, engineers and radio system developers have been aware of an issue that the FCC recently decided to surface for public comment (Notice of Inquiry); that of whether and under what circumstances the FCC should regulate the technical specifications for radio receivers as they already routinely do for radio transmitters. While this proposed change in approach would likely be prospective if the proceeding moves forward to the adoption of rules, it is conceivable that over time those using radio receivers in any number of situations might be required to upgrade or replace them if their particular receiver equipment fails to filter adjacent frequencies or effectively reject harmful interference. This could pit incumbent users facing unexpected new receiver replacement or upgrade costs against new industries or licensees and operators eager to deploy new services and new technologies.
This FCC Notice of Inquiry on receiver technical standards comes on the heels of a very public dispute regarding whether the initiation of 5G deployment in formerly fixed satellite spectrum, known as the C-band, would wreak havoc on U.S. domestic aviation. This dispute came to a head well after the FCC conducted a years-long rulemaking proceeding that included a study of how new 5G services could be used in the reallocated spectrum band without adversely affecting adjacent frequency use and after the wireless industry had paid the U.S. Treasury over $80 billion dollars collectively in a public spectrum auction for licenses to operate in the C-band. While the FCC was aware of spectrum use of frequencies adjacent to the C-band by airline GPS receivers known as altimeters, and it had been advised by stakeholders in the aviation industry that some older altimeters installed in airplanes were insufficiently robust so as to reject adjacent frequency interference. The FCC stated its expectation in its 2020 order that the Federal Aviation Administration (FAA) would make the aviation industry aware of the need to upgrade or replace older GPS equipment prior to 5G deployment.
While it is not obvious that this message was effectively delivered, the aviation industry became alarmed and very active when 5G deployment actually began. Through very public efforts at the White House, Congress, the Department of Transportation (DoT), the FCC and the FAA, a “voluntary” compact emerged between the airlines, the DoT and the deploying wireless carriers to operate 5G facilities temporarily at lower power than authorized near designated U.S. airports and to not operate using the new frequencies, at least temporarily, at others. This unfortunate incident appears to have been the catalyst for the FCC’s unanimous vote to start a proceeding to build a record on setting technical standards for receivers. In 2003, the FCC instituted a similar proceeding to review whether it should exercise its authority to prescribe technical operations for receivers as well as transmitters, but that proceeding was never completed.
The FCC now believes it is appropriate to consider within the scope of its spectrum management portfolio all elements of a radio network ecosystem. While a transmitter plainly emits radio energy and is already subject to FCC technical rules, a receiver is a passive device. But if a receiver is designed in a way that it cannot effectively reject undesired signals, then claims of harmful interference of established operations can affect the deployment of new spectrum uses. This is well illustrated by the DoT dust-up with the FCC and wireless carriers anxious to deploy 5G. While it may be more expensive to design and produce a more resilient receiver that does not receive adjacent frequencies or that has advanced filtering features, the continuing lack either of comprehensive voluntary or mandatory rules that apply generally to radio receivers has, as the Notice of Inquiry reflects, precluded or substantially delayed the introduction of new services and use cases.
There are a range of issues for the FCC to consider if the agency moves forward, including whether the FCC should establish a “harm claim” threshold for establishing receiver parameters, whether the FCC should prescribe technical requirements for receivers in some cases, as well as how to best incentivize manufacturers to invest in better quality receivers. It is notable that every FCC Commissioner was strongly in favor of initiating this important inquiry. Comments on the Notice of Inquiry will be due 45 days after it is published in the Federal Register, with any reply comments due 75 days following Federal Register publication.