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(USA: Sub-THz) FCC Publishes Sub-THz Radiated Test Measurement Guidelines (KDB 800303)
On November 20, 2025, the U.S. Federal Communications Commission (FCC) published a new Knowledge Database (KDB) guidance document defining radiated test measurement procedures for equipment operating at frequencies above 95 GHz.
Under this update, the scope of existing millimeter-wave (mmWave) radiated emission testing has been formally extended up to 300 GHz. In addition, a new set of dedicated test guidelines has been introduced for the 300–750 GHz frequency range, commonly referred to as the Sub-THz band, reflecting the unique propagation and environmental characteristics of this spectrum.
In particular, Sub-THz radiated testing now requires explicit consideration of environmental factors that can significantly affect measurement accuracy. These requirements include mitigation of micro-vibration effects, as well as correction for signal attenuation caused by atmospheric conditions such as relative humidity, water vapor, and oxygen absorption. Such measures are essential to ensure reliable and repeatable test results in the Sub-THz frequency range.
For detailed technical requirements and measurement procedures, stakeholders are encouraged to refer to KDB 800303 v01, which provides comprehensive guidance on compliance testing for devices operating in these extended frequency bands.
(USA: 5G NR) FCC Initiates NPRM on Introduction of 5G NR in the Upper C-Band (3.98–4.2 GHz)
On November 21, 2025, the U.S. Federal Communications Commission (FCC) released a Notice of Proposed Rulemaking (NPRM) to explore the introduction of 5G NR services in the Upper C-Band (3.98–4.2 GHz).
Currently, the C-Band spectrum in the United States is allocated across multiple regulatory frameworks:
- 3.45–3.55 GHz under FCC Part 27
- 3.55–3.7 GHz as the CBRS band under Part 96, and
- 3.7–3.98 GHz under Part 27
Through this NPRM, the FCC is considering extending commercial mobile service use into the adjacent 3.98–4.2 GHz band, thereby expanding the overall C-Band spectrum available for 5G deployment.
As part of the proposal, the FCC has outlined a preliminary framework for technical rules, while emphasizing the need to carefully address potential interference with radio altimeters operating in the adjacent 4.2–4.4 GHz band, which are critical for aviation safety. Based on this consideration, the FCC has proposed initial technical parameters, subject to further refinement:
| Item | Base Station | Mobile/Portable |
|---|---|---|
| Max. EIRP/PSD | 1640 / 3280 W/MHz | 1 W |
| PAR (Peak-to-Average Ratio) |
13 dB | 13 dB |
| OOBE (Out-of-band Emissions) |
-13 dBm/MHz (subject to further tightening) |
-13 dBm/MHz |
The FCC has identified interference risk at the 4.2 GHz band edge, adjacent to the radio altimeter band, as a key technical concern. In particular, the Commission highlighted the potential need for more stringent band-edge and OOBE limits for base stations to mitigate interference. However, specific limit values have not yet been finalized and will be determined following additional technical evaluations and interference studies.
Further discussions and refinements are expected as the rulemaking process progresses.
(USA: Covered List) FCC Expands “Covered Equipment” Definition to Explicitly Include Modular Transmitters
On November 25, 2025, the U.S. Federal Communications Commission (FCC) adopted amendments to its Covered List regulations, explicitly extending the definition of Covered Equipment to include Modular Transmitters that may pose risks to U.S. national security.
Key elements of the revised rules include the following:
- Modular Transmitters are explicitly included within the scope of Covered Equipment.
- Modular Transmitters manufactured by entities listed on the Covered List are not eligible for FCC authorization.
- Host devices incorporating such Modular Transmitters are also ineligible for FCC certification, regardless of the host manufacturer.
- Products that have already received FCC authorization will be prohibited from future importation and sale in the United States.
- Permissive Change procedures are no longer allowed for affected products.
- For products manufactured by Covered List entities that are not themselves communications equipment, Supplier’s Declaration of Conformity (SDoC) and certification exemptions are no longer permitted.
- The FCC clarified the interpretation of “produced by”, stating that products manufactured by Covered List entities remain classified as Covered Equipment even if they are re-branded or re-labeled by another party.
These amended rules are scheduled to take effect on December 26, 2025. As a result, the FCC emphasized that supply chain–level security reviews will become increasingly critical, extending beyond end products to include embedded modules and component sourcing decisions.
For the official list of Covered Equipment and manufacturers, please refer to the FCC Covered List
webpage: https://www.fcc.gov/supplychain/coveredlist
(USA: Covered list) FCC Proposes Expansion of “Covered Equipment” Definition to Include Modular Transmitters
On December 4, 2025, the U.S. Federal Communications Commission (FCC) published a notice in the Federal Register proposing amendments to the Covered List framework.
Through this proposal, the FCC aims to further strengthen restrictions on the authorization of covered equipment that may pose risks to U.S. national security, while also clarifying the scope of the applicable rules and their enforcement. In particular, the Commission is seeking public comment on how modular transmitters and component parts should be treated when they are associated with covered equipment.
As part of this proceeding, the FCC has opened a comment period through January 5, 2026, inviting stakeholders to provide input on the relationship between modular transmitters, individual components, and covered equipment under the Equipment Authorization Program.
Stakeholders are encouraged to review the published guidance document for detailed regulatory context and compliance considerations.
(USA: KDB Updates) KDB 986446 D01 v04 Update – Expanded U.S. Agent for Service of Process Requirements
On December 8, 2025, the FCC updated KDB 986446 D01, Covered Equipment Guidance, to Version 04, significantly strengthening the requirements related to the U.S. Agent for Service of Process.
Under this update, effective December 15, 2025, applicants are required to provide complete U.S. Agent for Service of Process information when submitting FCC Form 731. In addition, Telecommunication Certification Bodies (TCBs) are now required to verify this information as a mandatory part of the certification review process.
According to the updated guidance, TCBs must confirm the following key items. For detailed interpretations, applicants should refer directly to the original KDB document.
[Key TCB Verification Criteria]
- 1. Validity of the U.S. Agent’s physical address within the United States
- Addresses such as U.S. postal-only locations, virtual mailboxes, P.O. Boxes, or undeveloped/empty sites are not acceptable.
- 2. Confirmation that the address is a physical location where the U.S. Agent is present
- The address must support the receipt of official legal documents.
- 3. Formal consent from the U.S. Agent to act on behalf of the Grantee
- The consent must explicitly align with the U.S. Agent role identified in the FCC application.
(USA: 5G Upper mmWave) Regulatory Relaxation for the UMFUS Bands
In late October 2025, the Federal Communications Commission (FCC) adopted a Notice of Proposed Rulemaking (NPRM) aimed at expanding the use of the Upper Microwave Flexible Use Service (UMFUS) bands (24.25–24.45 GHz, 24.75–25.25 GHz, 27.5–28.35 GHz, 37–40 GHz, and 47.2–48.2 GHz). The item was published in the Federal Register on 3 December.
Although the UMFUS bands were initially expected to support 5G terrestrial network deployments, actual usage has increasingly been driven by Fixed-Satellite Service (FSS) earth stations, particularly Earth Stations in Motion (ESIMs). In light of these real-world deployment trends, the FCC is seeking public comments on a potential review of the existing regulatory framework, with a comment deadline of 2 January 2026.
The key issues under consideration include:
- A review of the current licensing framework with a view to reducing regulatory burdens
- Reassessment of relevant rules, including 47 CFR §25.136, to rationalize sharing criteria between UMFUS and FSS
- Consideration of potential relaxation of limits on the number and deployment of FSS earth stations