DA 24-553 DPA Interference Model

Federal Communications Commission
45 L Street NE
Washington, DC 20554

News Media Information 202-418-0500
Internet: <www.fcc.gov>
TTY: 888-835-5322

DA 24-553

Released: June 12, 2024

WIRELESS TELECOMMUNICATIONS BUREAU AND OFFICE OF ENGINEERING AND TECHNOLOGY ANNOUNCE MODIFIED AGGREGATE INTERFERENCE MODEL USED BY SPECTRUM ACCESS SYSTEM ADMINISTRATORS

GN Docket Nos. 17-258 and 15-319

With this Public Notice, the Wireless Telecommunications Bureau (WTB) and the Office of Engineering and Technology (OET) of the Federal Communications Commission (Commission or FCC) notify certified Spectrum Access System (SAS) administrators¹ that they will be permitted to implement changes to the existing aggregate interference model used to protect federal operations in the 3.55-3.7 GHz (3.5 GHz) band from Citizens Broadband Radio Service operations.² Specifically, as described in NTIA's June 11, 2024 letter, WTB and OET permit certified SAS administrators "to modify the existing aggregate interference model by adding Time Division Duplex (TDD) and loading factors, accounting for clutter loss, and using a 50% confidence factor and 50% reliability factor for the propagation loss calculations."³ SAS administrators will be permitted to apply the changes to the aggregate interference model used to protect federal operations in the band only after demonstration—including testing in a nonoperational environment—of their ability to effectively implement these changes and subsequent approval by WTB and OET.

Once implemented, the modified aggregate interference model is intended to: (1) decrease the size of the Category B Citizens Broadband Radio Service Device (CBSD) Dynamic Protection Area (DPA) neighborhood areas along the coastlines and around federal facilities;⁴ (2) decrease the number of CBSD grants that are suspended when a DPA is activated; and (3) increase the fidelity of the propagation modeling.⁵ SAS administrators that successfully implement these changes should be able to authorize service to approximately 72 million more people (for a total of approximately 240 million) nationwide including millions of people in major metro areas like Atlanta, Phoenix, Las Vegas, San Antonio, and Pittsburgh—without periodic service adjustments to protect federal operations.⁶

Consistent with NTIA's recommendations, our established coordination procedures for the 3.5 GHz band, and the Commission's rules, WTB and OET will allow SAS administrators to apply the following specific changes to the aggregate interference model used to protect federal operations in the 3.5 GHz band, subject to the successful demonstration of their ability to do so:

• The SAS administrators may assume an 80% TDD activity factor and 20% network loading factor for each CBSD in the aggregate interference calculation. The total impact will reduce, by 8 dB, the equivalent isotopically radiated power (EIRP) used in the aggregate interference calculations for each CBSD.⁷
• The SAS administrators may use median Irregular Terrain Model (ITM) terrain dependent propagation loss (in dB)—using reliability and confidence factors of 0.5—to calculate the aggregate received power levels within a DPA.⁸
• The SAS administrators may apply median clutter loss—calculated using the methodology described in Recommendation ITU-R P.2108,⁹ section 3.2 —for any CBSD with an antenna height Above Ground Level (AGL) of less than or equal to six meters, that is operating at a distance of at least 250 meters from a DPA boundary.¹⁰

Accordingly, we invite all certified SAS administrators to submit a demonstration of their ability to implement these new testing parameters in GN Docket No. 15-319, including testing in a non-operational environment.¹¹ WTB/OET will review these submissions in close collaboration with NTIA and DoD. SAS administrators will be permitted to apply the revised parameters only after final approval by WTB and OET.

By the Chief, Wireless Telecommunications Bureau, and the Chief, Office of Engineering and Technology.

-FCC-

¹ On January 27, 2020, WTB and OET approved four SAS administrators for full scale commercial deployment in the 3.5 GHz band. See WTB And OET Approve Four Spectrum Access System Administrators For Full Scale Commercial Deployment In The 3.5 GHz Band And Emphasize Licensee Compliance Obligations In The 3650-3700 MHz Band Under Part 96, GN Docket No. 15-319, Public Notice, 35 FCC Rcd 117 (WTB/OET 2020). WTB and OET subsequently approved three more SAS administrators for commercial operations. See Wireless Telecommunications Bureau and Office of Engineering and Technology Approve Spectrum Access Administrator Amdocs for Full Scale Commercial Deployment in the 3.5 GHz Band, GN Docket No. 15-319, Public Notice, 35 FCC Rcd 3687 (WTB/OET 2020); Wireless Telecommunications Bureau and Office of Engineering and Technology Approve Key Bridge Wireless for Full Scale Commercial Deployment in the 3.5 GHz Band, GN Docket No. 15-319, Public Notice, 36 FCC Rcd 4880 (WTB/OET 2021); Wireless Telecommunications Bureau and Office of Engineering and Technology Approve Spectrum Access System Administrator Red Technologies for Full Scale Commercial Deployment in the 3.5 GHz Band, to Support Spectrum Manager Leasing, and to Use Key Bridge Wireless LLC's Environmental Sensing Capability, GN Docket No. 15-319, Public Notice, DA 23-893, 2023 WL 6263552 (WTB/OET 2023).

² See Letter from Paige R. Atkins, Assoc. Admin., Office of Spectrum Mgt., NTIA, to Julius P. Knapp, Chief, Office of Eng. and Tech. and Donald K. Stockdale, Jr., Chief, Wireless Telecom. Bureau, FCC (May 17, 2018) (NTIA 2018 Letter), https://www.fcc.gov/ecfs/document/10530233711963/1.

³ See Letter from Charles Cooper, Associate Administrator, Office of Spectrum Management, NTIA, to Ronald T. Repasi, Chief, OET, FCC, and Joel Taubenblatt, Chief, Wireless Telecommunications Bureau, FCC (June 11, 2024), https://www.fcc.gov/ecfs/document/1061155768162/1 (NTIA June 2024 Letter) (footnotes excluded).

⁴ DPAs are pre-defined protection areas that extend beyond the coastline or that enclose a protected terrestrial radar facility, which may be activated or deactivated as necessary to protect DoD radar systems. In general, when a DPA is activated, SASs may direct CBSDs in a DPA neighborhood to cease operations, reduce transmit power, or relocate to a non-interfering frequency in order to protect federal operations in the band. See Promoting Investment in the 3550-3700 MHz band, GN Docket No. 17-258, Order, 33 FCC Rcd 4987 (WTB/OET 2018) (DPA Waiver Order); see also Letter from Paige R. Atkins, Assoc. Admin., Office of Spectrum Mgt., NTIA, to Julius P. Knapp, Chief, OET, FCC, and Donald Stockdale, Chief, WTB, FCC, (May 17, 2018) (depicting the DPAs in Attachment A). This NTIA letter and the specific coordinates for the DPAs and DPA neighborhood areas are available at https://www.ntia.doc.gov/fcc-filing/2015/ntia-letter-fcc-commercial-operations-3550-3650-mhz-band.

⁵ NTIA June 2024 Letter at 1.

⁶ As NTIA notes in its June 2024 letter, these changes do not supersede the obligation for Citizens Broadband Radio Service users to comply with the Commission's rules, including 47 CFR § 96.15(a)(1) ("CBSDs and End User Devices must not cause harmful interference to and must accept interference from federal Incumbent Users authorized to operate in the 3550-3700 MHz band and below 3550 MHz."). In addition, Citizens Broadband Radio Service users' CBSDs operated outside of DPA neighborhoods would still be subject to pre-emption pursuant to the War Powers clause of the Communications Act. See 47 U.S.C. § 606; 47 CFR § 96.15(a)(4) ("[i]f the President of the United States (or another designated Federal Government entity) issues instructions to discontinue use of CBSDs pursuant to 47 U.S.C. 606, SAS Administrators must instruct CBSDs to cease operations as soon as technically possible."). NTIA June 2024 Letter, note 8.

⁷ NTIA June 2024 Letter at 2.

⁸ Id.

⁹ Id.; ITU, Recommendations, Rec. P.2108, "Prediction of Clutter Loss" (Sept. 2021), https://www.itu.int/rec/R-REC-P.2108/en.

¹⁰ NTIA June 2024 Letter at 2.

¹¹ See id. at 2-3.