NTN Ephemeris Signalling for Faster Satellite Cell Synchronization
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Solution Overview
Problem
In Non-Terrestrial Networks (NTN), providing accurate and efficient ephemeris data to user equipment (UE) for satellite positioning and synchronization is challenging due to the high path loss and frequent satellite movements, leading to increased search times and interference, especially in RRC_IDLE and RRC_INACTIVE states.
Innovation Solution
Broadcasting coarse ephemeris data with reduced accuracy for neighboring satellites, allowing UEs to quickly locate and synchronize with cells, while full accuracy data is provided by the satellites themselves, and utilizing on-demand SI requests for additional details.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If full accuracy ephemeris data is broadcast for all satellites, then positioning precision is improved, but data volume and update frequency increase
Solution Approach 1:
The patent applies local quality by differentiating between serving satellites and non-serving satellites. For serving satellites, full accuracy ephemeris data is provided to ensure precise positioning and synchronization. For non-serving satellites, only coarse ephemeris data is broadcast, reducing data volume while still enabling basic location identification. This selective approach optimizes the balance between positioning precision and data efficiency.
Solution Approach 2:
The ephemeris data is segmented into two distinct types: full accuracy data for serving satellites and coarse data for non-serving satellites. This segmentation allows the system to provide high precision where needed while minimizing overall data transmission requirements. The UE can efficiently process coarse data for multiple satellites and only requires full accuracy data when actively connected to a specific satellite.
2Measurement precision
If full accuracy ephemeris data is broadcast for all satellites, then positioning precision is improved, but network signaling overhead increases
Solution Approach 1:
The patent implements local quality by applying different data accuracy levels to different satellite categories. Serving satellites receive full accuracy ephemeris broadcasts to maintain precise positioning and synchronization, while non-serving satellites receive only coarse ephemeris data. This differentiated approach significantly reduces network signaling overhead compared to broadcasting full accuracy data for all satellites, while still maintaining necessary positioning precision for active connections.
3Quantity of substance
If coarse ephemeris data is used for non-serving satellites, then data volume is reduced, but search accuracy decreases
Solution Approach 1:
The patent applies preliminary action by having the UE first process coarse ephemeris data to quickly identify and locate potential serving satellites before establishing a connection. This preliminary localization using coarse data is sufficient for initial satellite acquisition and beam alignment. Once connected, the UE receives full accuracy ephemeris data from the serving satellite, which then provides precise positioning and synchronization without requiring the UE to perform high-precision measurements on all satellites.
Data Source
AI summary
A method performed by a wireless device includes receiving ephemeris data from a network node associated with a first cell. The ephemeris data is associated with a satellite serving a second cell, and the ephemeris data is coarse ephemeris data comprising less than full accuracy than full ephemeris data. The wireless device uses the coarse ephemeris data to locate a beam associated with the second cell and synchronizes with the second cell.