Long-term accuracy of LEO satellite clocks for NR-NTN positioning

Determine the long-term stability and accuracy of clocks onboard Low-Earth Orbit (LEO) satellites in NR-NTN systems and specify mechanisms to communicate any satellite clock offsets to user equipment (UE) to ensure accurate downlink positioning using positioning reference signals (PRS).

Background

Accurate positioning in NR-NTN requires tight synchronization across satellites, including alignment of downlink frame boundaries. The study assumes perfect synchronization for evaluation, but the practical feasibility depends on the stability of onboard satellite clocks over time.

Network-level synchronization could impose operational overhead on satellite network operators (SNOs). If satellite clock inaccuracies arise, clock offsets must be communicated to UEs to avoid degrading positioning accuracy, making the characterization of clock stability and offset handling a critical unresolved question.

References

It remains uncertain how accurate LEO satellite clocks will remain over time, and if inaccuracies occur, clock offsets must be communicated to the UE.

— LEO-based Positioning: Foundations, Signal Design, and Receiver Enhancements for 6G NTN  (2410.18301 - Dureppagari et al., 2024) in Concluding Remarks and Future Work – Handling Satellite Clock Drift and Synchronization