[Federal Register Volume 86, Number 101 (Thursday, May 27, 2021)]
[Proposed Rules]
[Pages 28522-28523]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-10536]


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FEDERAL COMMUNICATIONS COMMISSION

47 CFR Parts 2 and 30

[ET Docket No. 21-186; GN Docket No. 14-177; DA 21-482; FRS 27278]


Emission Limits for the 24.25-27.5 GHz Band

AGENCY: Federal Communications Commission (FCC).

ACTION: Requests for comments.

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SUMMARY: In this document, The Office of Engineering and Technology 
(OET) and the Wireless Telecommunications Bureau (WTB) seek comment on 
implementing certain of the decisions of the World Radiocommunication 
Conference held by the International Telecommunication Union (ITU) in 
2019 (WRC-19) regarding the 24.25-27.5 GHz band. Specifically, OET and 
WTB seek comment on aligning the FCC's rules with the unwanted 
emissions limits into the passive 23.6-24.0 GHz band that were adopted 
at WRC-19.

DATES: Comments are due on or before June 28, 2021, and reply comments 
are due on or before July 26, 2021.

ADDRESSES: Federal Communications Commission, 45 L Street NE, 
Washington, DC 20554.

FOR FURTHER INFORMATION CONTACT: Nicholas Oros, Office of Engineering 
and Technology, 202-418-0636, [email protected] or John Schauble of 
the Wireless Telecommunications Bureau, at (202) 418-0797, or 
[email protected].

SUPPLEMENTARY INFORMATION: This is a summary of the Commission's 
document, Public Notice, DA 21-482, ET Docket No. 21-186, GN Docket No. 
14-177, released April 26, 2021. The full text of this document is 
available for public inspection and can be downloaded at: https://www.fcc.gov/document/oet-wtb-seek-comment-emission-limits-2425-275-ghz-band or by using the search function for ET Docket No. 21-186 on the 
Commission's ECFS web page at www.fcc.gov/ecfs.

Synopsis

    1. In 2017, the Commission established service rules for fixed and 
mobile operation in the 24.25-24.45 GHz and 24.75-25.25 GHz bands 
(collectively, 24 GHz band) under the Upper Microwave Flexible Use 
Service (UMFUS). The Commission applied the UMFUS rules, including the 
technical rules, to the 24 GHz band. The UMFUS rules specify that 
emissions outside of a licensee's assigned frequency block must be 
limited to -13 dBm/MHz. With respect to the passive systems operating 
in the 23.6-24 GHz band, the Commission noted that ongoing 
international studies include analyses to determine International 
Mobile Telecommunications (IMT) out-of-band emission limits necessary 
to protect passive sensors onboard weather satellites in that band, and 
it acknowledged that the Commission's UMFUS rules might be revisited 
once these international studies have been completed.
    2. WRC-19 allocated 24.25-25.25 GHz to mobile (except aeronautical) 
on a primary basis in Regions 1 and 2, globally identified the 24.25-
27.5 GHz band for IMT, and established limits of unwanted emissions 
that apply to IMT in the 24.25-27.5 GHz band to protect Earth 
Exploration-Satellite Service (EESS) passive systems in the 23.6-24.0 
GHz band from harmful interference. To protect EESS passive systems, 
WRC-19 modified a footnote to the International Table of Allocations to 
specify that Resolution 750 (Rev. WRC-19) applies to the 24.25-27.5 GHz 
band. Resolution 750 specifies unwanted emission limits as the amount 
of power that may be radiated into any 200 megahertz of the 23.6-24.0 
GHz passive band by IMT base stations and IMT mobile stations operating 
in the 24.25-27.5 GHz band. Resolution 750 specifies unwanted emission 
limits in terms of Total Radiated Power (TRP) that currently apply to 
IMT stations and stricter emission limits that are effective for IMT 
stations brought into use after September 1, 2027. These unwanted 
emission limits are shown in Table 1.

 Table 1--WRC-19 Resolution 750 Unwanted Emissions Permitted Within Any
              200 Megahertz in the 23.6-24 GHz Passive Band
------------------------------------------------------------------------
                                           Current TRP  TRP limits after
             Type of station                  limits      Sept. 1, 2027
------------------------------------------------------------------------
IMT Base Stations........................      -33 dBW           -39 dBW
IMT Mobile Stations......................      -29 dBW           -35 dBW
------------------------------------------------------------------------

    3. The WRC-19 Final Acts updated the ITU Radio Regulations, 
including Resolution 750. The National Telecommunications and 
Information Administration (NTIA), FCC, and the Department of State 
share responsibility for implementing the WRC Final Acts in the United 
States. The Commission has authority to implement the changes to the 
Radio Regulations through its rulemaking proceedings. Given the 
importance of limiting unwanted emissions into the passive 23.6-24.0 
GHz band, OET and WTB seek to develop a record on implementing the 
changes to the emission limit in Resolution 750 applicable to active 
services in the 24 GHz band.
    4. OET and WTB seek comment broadly on implementing certain of the 
WRC-19 outcomes with respect to the 24.25-27.5 GHz band. Noting that 
the United States is a signatory to the treaty text of the Radio 
Regulations, OET and WTB seek comment on modifying the Commission's 
rules in response to the unwanted emission limits and international 
allocation table footnotes adopted for the 24.25-27.5 GHz band at the 
WRC-19. These rule changes could include, for example, adding footnotes 
to the United States Table of Frequency

[[Page 28523]]

Allocations or aligning the Commission's technical rules.
    5. Appropriate out-of-band emission limits in the 24.25-27.5 GHz 
band are important to protect passive sensing operations in the 23.6-
24.0 GHz band. The limits adopted at WRC-19 are to be measured within a 
200-megahertz bandwidth within the 400-megahertz 23.6-24 GHz passive 
band. For comparison with the Resolution 750 unwanted emission limit, a 
signal at -13 dBm/MHz (conductive or TRP) would result in -20 dBW 
within a 200-megahertz bandwidth. However, OET and WTB note that the -
13 dBm/MHz emission limit applies at the edge of the UMFUS band--i.e., 
24.25 GHz. Given this, OET and WTB seek to understand what level of 
emissions can be expected within the 23.6-24 GHz band from UMFUS 
transmitters, and whether and to what extent harmful interference to 
passive systems operating in the 23.6-24.0 GHz band is expected to 
occur from new 5G deployments at the current UMFUS limit.
    6. Recognizing that the unwanted emission limits in Resolution 750 
and the current out-of-band emission limits in the UMFUS rules are 
specified differently, and further recognizing the two-phased approach 
for the unwanted emissions limits that were adopted in WRC-19, OET and 
WTB seek information on whether and how equipment intended for use 
under the UMFUS rules in the 24.25-24.45 GHz and 24.75-25.25 GHz bands 
can be designed to conform to the Resolution 750 limits--both the 
current limits and the more restrictive limits that apply to new 
equipment brought into use after September 1, 2027. Can licensees meet 
the WRC-19 TRP limits by the relevant deadlines? Is it possible that 
licensees can meet the -39 dBW limit for IMT base stations and the -35 
dBW limit for IMT mobile stations prior to 2027? What steps, if any, 
can the Commission take to help accelerate development and deployment 
of equipment that complies with the post-2027 limits?
    7. OET and WTB note that Resolution 750 specifies TRP as the only 
means of meeting the required emission limits. Are there any 
difficulties in performing over the air TRP measurements at such low 
signal levels in the 24.25-24.45 GHz and 24.75-25.25 GHz bands? 
Consistent with the current UMFUS rules, should a conductive power 
methodology also be included as an alternative means for equipment 
certification?
    8. The UMFUS rules allow licensees flexibility as to the services 
they will deploy and the architecture of their networks. Under these 
rules licensees will be able to deploy mobile services. Licensees will 
also have the freedom to implement point-to-point and point-to-
multipoint systems. The unwanted emission limits of Resolution 750 
apply only to IMT base stations and mobile stations. The Commission's 
rules do not define IMT and do not require that equipment complying 
with a particular technical standard be used in a band licensed under 
the UMFUS rules. If the Commission were to adopt the emission limits in 
Resolution 750 for the 24.25-27.5 GHz band, how should it determine to 
what stations these limits will apply? Should they only apply to 
systems that meet the definition of IMT as specified by the ITU? Should 
the rules apply to point-to-point and point-to-multipoint equipment 
licensed under the UMFUS rules? Should any mobile UMFUS equipment be 
required to comply with these unwanted emission limits regardless of 
the technology used, the application, and the density of deployment?

Federal Communications Commission.
Ronald T. Repasi,
Acting Chief, Office of Engineering and Technology.
[FR Doc. 2021-10536 Filed 5-26-21; 8:45 am]
BILLING CODE 6712-01-P