NTN Ephemeris Signaling 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 need for frequent updates and high data volume, especially when UEs must search for satellites over a wide area or prepare for handovers, which increases the time required for initial acquisition and cell reselection.

Innovation Solution

Broadcasting coarse ephemeris data with reduced accuracy, such as truncated parameters or position deltas, by network nodes to assist UEs in locating neighbor satellites, supplemented by on-demand requests for full accuracy data using Msg1 or Msg3 based SI requests, thereby reducing data volume and update frequency.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If full accuracy ephemeris data is broadcast to UEs for satellite positioning, then positioning accuracy is improved, but data volume and update frequency requirements increase

Engineering Contradiction:

Improvepositioning accuracyVSAvoiddata volume

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

The ephemeris data is segmented into two types: coarse ephemeris data with reduced accuracy that is broadcast periodically, and full accuracy ephemeris data that is provided on-demand. This segmentation allows the system to reduce overall data volume while maintaining necessary positioning accuracy for different operational scenarios.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Instead of always providing full accuracy ephemeris data, the system applies partial action by broadcasting only coarse ephemeris data with reduced accuracy. This partial provision of data reduces the data volume and update frequency requirements while still enabling basic satellite positioning and synchronization functions.

Inventive Principle:

Principle #16Partial or excessive action

2Measurement precision

If full accuracy ephemeris data is broadcast frequently, then positioning accuracy is improved, but network signaling overhead increases

Engineering Contradiction:

Improvepositioning accuracyVSAvoidsignaling overhead

Core Design Contradiction:

Measurement precisionVSLoss of information

Solution Approach 1:

The system segments ephemeris data provision into periodic coarse data broadcasting and on-demand full accuracy data retrieval. This reduces signaling overhead by eliminating the need for frequent full accuracy data broadcasts while maintaining positioning capability through the coarse data.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Coarse ephemeris data is broadcast periodically at reduced update frequency compared to full accuracy data. This periodic action with lower frequency reduces network signaling overhead while still providing sufficient positioning accuracy for satellite search and cell reselection operations.

Inventive Principle:

Principle #19Periodic action

3Measurement precision

If UEs perform satellite search over wide area without assistance data, then positioning accuracy is improved, but acquisition time increases

Engineering Contradiction:

Improvepositioning accuracyVSAvoidacquisition time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The network performs preliminary action by broadcasting coarse ephemeris data that provides approximate satellite positions and timing information before the UE initiates satellite search. This preliminary provision of positioning information significantly reduces the time required for UEs to acquire satellites and perform cell reselection while maintaining sufficient accuracy for the initial search.

Inventive Principle:

Principle #10Preliminary action

4Quantity of substance

If coarse ephemeris data with reduced accuracy is used, then data volume is reduced, but positioning precision deteriorates

Engineering Contradiction:

Improvedata volumeVSAvoidpositioning accuracy

Core Design Contradiction:

Quantity of substanceVSMeasurement precision

Solution Approach 1:

The system segments the positioning data requirements into two levels: coarse ephemeris data for basic satellite search and cell reselection, and full accuracy ephemeris data for precise positioning and timing advance calculations. This segmentation allows the system to use reduced data volume for routine operations while maintaining the option to access full accuracy data when needed.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different levels of positioning accuracy are applied to different operational scenarios. Coarse ephemeris data with reduced accuracy is sufficient for satellite search and cell reselection, while full accuracy data is reserved for operations requiring precise positioning. This local quality approach optimizes the balance between data volume and positioning precision for each specific function.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS12487366B2Methods and systems for signalling ephemeris data in a non-terrestrial network

Publication Date: 2025.12.02 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

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.