5G • 5G-Advanced (Rel-18)
Satellite Doppler Pre-Compensation
Orbital Velocity Doppler Shift and Delay Compensation
Pre-shifts carrier frequencies and timing advance commands to cancel out massive Doppler shifts caused by LEO satellites moving at 27,000 km/h.
Technical Explanation
Low Earth Orbit (LEO) satellites orbit at 7.5 km/s, producing continuous Doppler frequency shifts up to ±50 kHz and rapid propagation delay shifts. In Rel-18, the satellite broadcast orbital ephemeris data (position and velocity vectors); the UE calculates its relative geometric trajectory and pre-shifts its uplink transmission frequency, arriving at the satellite with zero frequency error.
Key Functions
- Cancels out up to ±50 kHz Doppler frequency shifts caused by orbital satellite velocity
- Broadcasts high-precision orbital ephemeris parameters in System Information Blocks (SIB19)
- Calculates terminal-side autonomous frequency pre-compensation using GNSS coordinates
- Maintains orthogonal subcarrier spacing and prevents inter-carrier interference in orbit
Specifications
3GPP TS 38.211, TS 38.331 (Rel-18)
Interfaces
Uu (SIB19)
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