he Federal Communications Commission (FCC) has adopted new emission limits for the 24 GHz band (24.25–24.45 GHz and 24.75–25.25 GHz), aligning its regulations with international standards established at the 2019 World Radiocommunication Conference (WRC-19). These changes aim to protect the passive 23.6–24.0 GHz spectrum, vital for satellite-based scientific services, such as weather forecasting and climate research.
Background and Significance
The 23.6–24.0 GHz spectrum is a cornerstone for Earth Exploration Satellite Service (EESS) operations. These passive sensors measure natural radio emissions critical for climatology and meteorology. The data supports forecasting severe weather events like hurricanes and facilitates long-term climate monitoring. However, previous emission regulations posed a risk of interference, jeopardizing the accuracy of these services.
Key Updates to the Regulations
Adoption of WRC-19 Resolution 750
The FCC has incorporated Resolution 750 limits into its Part 30 rules for mobile operations. These limits govern out-of-band emissions (OOBE) to prevent interference with the adjacent passive band.
Phased Implementation
Phase 1: Immediate adoption of -33 dBW/200 MHz for base stations and -29 dBW/200 MHz for mobile stations.
Phase 2: Stricter limits (-39 dBW/200 MHz for base stations and -35 dBW/200 MHz for mobile stations) effective for new deployments starting September 1, 2027.
Technical Compliance Methods
Equipment can demonstrate compliance using Total Radiated Power (TRP) or maximum conducted power measurements, providing flexibility for manufacturers while maintaining protection standards.
Regulatory Harmonization
Aligning with global standards ensures interoperability, facilitates technological advancement, and strengthens U.S. leadership in spectrum management.
Impact on Stakeholders
Telecommunication Providers: Must comply with stricter emission standards, potentially requiring updates to existing technologies.
Scientific Community: Enhanced protection of the passive spectrum ensures the accuracy and reliability of critical climate and weather data.
Policy Makers: Harmonized rules promote international collaboration and innovation while safeguarding essential environmental monitoring.
Challenges and Considerations
While some stakeholders advocated for even stricter emission limits, the FCC concluded that the Resolution 750 standards strike the right balance. The Commission noted that adopting more stringent limits could unnecessarily burden telecom operators and diverge from global norms.
Conclusion
The FCC’s revised emission limits for the 24 GHz band represent a significant milestone in balancing technological progress with environmental stewardship. By aligning with WRC-19 standards, the FCC ensures the sustainable use of this critical spectrum, protecting essential satellite-based services that benefit society as a whole.
