itu-r Series-SF: Frequency Sharing Between Fixed-Satellite and Fixed Services
Coordination and interference mitigation standards for spectrum sharing between satellite and terrestrial systems — the regulatory framework for protecting satellite-dependent communications from jamming and co-channel interference.
Official Scope
Study Group: SG4 (Satellite services) & SG5 (Terrestrial services)
Active Status: Ongoing
Defines methodologies and limits for frequency sharing and coordination between Fixed-Satellite Service (FSS) earth stations and Fixed Service (FS) terrestrial radio links in shared frequency bands. Covers coordination distance calculations, interference assessment methodologies, and protection criteria for both systems.
Tactical Security Significance
- Relevance: 🟡 Medium — Co-channel Interference Mitigation, Satellite Link Protection, HAPS Coordination
- Key Security Concepts: Coordination Distance Calculation, Co-channel Interference Modeling, Guard-Band Management, Cross-Border Interference Disputes
- Attack Surface: Interference attacks exploiting shared band ambiguity; rogue terrestrial transmitters in coordination zones that degrade satellite links
Key Recommendations
| ITU Rec | Title | Security Domain | Cross-Reference |
|---|---|---|---|
| SF.355 | Sharing between the FSS and the fixed service using the same frequency bands | FSS / FS Interference Baseline | ITU-R F.1245 |
| SF.1006 | Determination of the coordination area around an Earth station | Coordination Zone Calculation | ITU RR Article 9 |
| SF.1481 | Sharing between HAPS and GSO FSS at 47/48 GHz | HAPS-to-Satellite Coordination | ITU-R F.2086 |
| SF.1486 | Sharing between Fixed Wireless Access and VSAT in 3.4–3.7 GHz | 5G / VSAT Band Coexistence | 3GPP TS 38.101-1 |
| SF.1649 | Protection of geostationary satellite networks from high-density FS systems | VSAT/HTS Protection from FWA Interference | ITU-R S.1711 |
Security Mapping
5G / VSAT Coexistence — SF.1486 and C-Band Conflicts
The C-band (3.4–4.2 GHz) is used simultaneously by VSAT satellite networks and 5G terrestrial deployments (NR Band n77/n78). SF.1486 defines the coordination distances and power limits to prevent 5G base station interference from degrading VSAT satellite downlinks.
- Threat: An improperly coordinated 5G base station deployed within the SF.1486 coordination zone of a VSAT earth station can generate interference levels that degrade satellite link availability — effectively a regulatory-compliant DoS
- Mitigation: Validate coordination compliance before 5G base station commissioning in C-band; apply the SF.1006 coordination zone methodology; coordinate with affected VSAT operators through national spectrum authorities per ITU RR Article 9
HAPS-to-Satellite Interference (SF.1481)
High-Altitude Platform Stations (HAPS) operating in shared bands with GSO FSS satellites create a unique interference geometry: HAPS transmissions can illuminate satellite earth station receivers with near-constant elevation angles, degrading link quality.
- Threat: A HAPS system operator fails to comply with SF.1481 power flux density limits → persistent interference to VSAT earth stations in the coverage area
- Detection: Satellite operators should monitor for interference events correlated with known HAPS operational hours and positions; report to national spectrum authority for coordination under SF.1481
Coordination Zone Exploitation
SF.1006 defines how coordination zones are calculated for FSS earth stations. An attacker who understands these calculations could deliberately place a high-EIRP terrestrial transmitter just outside the formal coordination zone while still generating harmful interference.
- Threat: Rogue transmitter placed just outside the nominal SF.1006 coordination boundary exploits calculation margin to generate interference while avoiding regulatory action
- Mitigation: Earth station operators should use more conservative guard margins than the minimum SF.1006 calculation; deploy spectrum monitoring at the earth station to detect and geolocate interferers
Operational Audit
- Frequency Sharing Audit Checklist: Guidance on calculating coordination areas, assessing interference margins, and validating SF.1006/SF.1486 compliance.
!NOTE This series is part of the master Series Tracker.