CBRS sharing system to be tweaked, enable more uninterrupted spectrum access

The changes would expand access by changing up the aggregate interference model used to determine sharing

Changes are coming to the shared Citizens Broadband Radio Service band at 3.5 GHz, with proposed tweaks to the aggregate interference model that is used to determine spectrum access for non-governmental users, with the aim of shrinking protection zones in which CBRS users can be bumped out of the band to make way for naval incumbents.

The Federal Communications Commission estimates that the changes will enable CBRS Spectrum Access System administrators to provide “uninterrupted access” to approximately 72 million more people than they do now.

The National Telecommunications and Information Administration formally put in a request to change the aggregate interference model for CBRS access on Tuesday of this week, after consultation with the U.S. Navy. The executive agency said in a letter to the FCC that the changes to the interference model include the addition of Time Division Duplex (TDD) and loading factors, accounting for clutter loss and using a 50% confidence factor and 50% reliability factor for propagation loss calculations.

Those changes, the agency added, reduce the Dynamic Protection Areas (DPAs) where access to the spectrum can be suspended for non-incumbents, decrease the number of grants for Citizens Broadband Radio Service Devices (CBSDs) that have to be suspended when a DPA is activated and enable more accurate propagation modeling “due to higher confidence through experience.”

An NTIA report in January 2023 said at the time that 45% of the total number of CBSDs were deployed in counties that are part of DPAs. According to NTIA, the changes to the interference model will have the greatest impact in Texas (with CBRS access expanded for more than 9.2 million POPs), Pennsylvania (an increase for 8.1 million POPs), North Carolina (8 million) and Georgia (7.9 million).

The FCC has since issued a public notice in support of the interference model changes and asked SAS operators to submit demonstrations that they can implement the new protection criteria. NTIA had requested that SAS administrators only be allowed to apply the new changes after conducting testing, including testing in a non-operational environment, to demonstrate that they could put the changes into practice effectively.

“The innovative approach of the Citizens Broadband Radio Service is a win-win: The Department of Defense has the airwaves it needs to carry out crucial missions while providing greater access for commercial 5G and high-speed Internet deployment,” said Assistant Secretary of Commerce for Communications and Information and NTIA Administrator Alan Davidson in a press statement. “The changes outlined in NTIA’s letter will expand Internet access to more people across the country. They could not have been implemented without the collaboration of the Navy and our ongoing coordination with the FCC.”

“The CBRS dynamic spectrum sharing framework is already fertile ground for wireless innovation, and through collaboration with Department of Defense, NTIA, and stakeholders, we are expanding opportunities for reliable spectrum access while also ensuring that federal incumbents remain protected,” FCC Chairwoman Jessica Rosenworcel said, adding, “This is creative spectrum policy at work.”

“The Department of the Navy is committed to developing a Dynamic Spectrum Sharing capability with our industry partners to appropriately balance national economic and defense priorities,” said DON Chief Information Officer Jane Overslaugh Rathbun. “Agile spectrum access is critical to preserving the DON’s maritime warfighting competitive advantage and we are actively pursuing the development of innovative wireless solutions that will increase the quality life for Sailors and Marines.”

In its letter, NTIA also added: “The successful ongoing evolution of CBRS spectrum-sharing demonstrates how a collaborative partnership among government and industry stakeholders can facilitate meaningful spectrum-sharing and critical spectrum access while protecting key government systems vital for national security and other public services.”