NTN Measurement Triggering for Satellite Handover
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Solution Overview
Problem
Non-Terrestrial Networks (NTNs) face challenges such as moving cells, long propagation delays, and large Doppler shifts, which complicate handover processes and measurement reporting in satellite-based communication systems, leading to potential service interruptions and radio link failures.
Innovation Solution
Implementing measurement report triggering mechanisms based on timing advance values, satellite node proximity, expected service times, elevation angles, and configured points in time to enhance measurement reporting accuracy and timeliness, thereby improving handover robustness and reducing service disruptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If measurement reporting is triggered based on traditional terrestrial network criteria, then handover processes in NTN systems experience service interruptions and radio link failures due to moving cells, long propagation delays, and large Doppler shifts
Solution Approach 1:
The patent modifies measurement triggering parameters specifically for NTN environments by introducing timing advance value thresholds, elevation angle thresholds, and satellite proximity conditions. These parameter changes adapt the measurement reporting mechanism to account for NTN characteristics such as long propagation delays, moving cells, and Doppler shifts, thereby improving handover reliability without requiring complete system redesign
Solution Approach 2:
The patent implements preliminary assessment of NTN-specific conditions (timing advance values, elevation angles, satellite proximity) before triggering measurement reporting. By evaluating these parameters in advance, the system prepares handover procedures proactively, reducing service interruptions and radio link failures that would occur with traditional reactive triggering mechanisms
2Loss of time
If measurement reporting is triggered frequently to capture rapid satellite movement, then handover timing accuracy improves, but network signaling overhead and UE power consumption increase
Solution Approach 1:
The patent implements dynamic measurement triggering that adapts to satellite movement characteristics. By using elevation angle thresholds and timing advance value changes as triggers, the system dynamically adjusts when measurement reporting occurs based on actual NTN conditions rather than using fixed periodic intervals. This dynamic approach captures critical handover moments while avoiding unnecessary reporting during stable periods, reducing UE power consumption while maintaining timing accuracy
Solution Approach 2:
The patent applies preliminary anti-action by setting thresholds for timing advance value changes and elevation angle changes that prevent premature or unnecessary measurement reporting. These thresholds act as pre-filtering mechanisms that block spurious triggers caused by normal satellite motion, allowing reporting only when significant handover-related changes occur, thus reducing power consumption while preserving timing accuracy
3Measurement precision
If multiple NTN-specific parameters are monitored for measurement triggering, then measurement reporting accuracy improves, but processing complexity and signaling overhead increase
Solution Approach 1:
The patent segments the measurement triggering process into distinct evaluation stages: first evaluating timing advance value changes, then elevation angle changes, then satellite proximity conditions. This segmentation allows the UE to process parameters in a structured sequence, improving measurement reporting accuracy through comprehensive parameter monitoring while managing processing complexity through organized modular evaluation of each parameter type
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed solution enhances measurement report triggering in NTN systems, ensuring timely and accurate handover processes, reducing service interruptions, and improving overall network performance by addressing the unique challenges of satellite-based communication.
Implementation Method 1
The satellites are moving with a very high velocity. This leads to a Doppler shift of the carrier frequency on the service link of up to 24 ppm for a LEO satellite at 600 km altitude.
Implementation Method 2
Non-Terrestrial Networks (NTNs) face challenges such as moving cells, long propagation delays, and large Doppler shifts
Data Source
AI summary
A method by a wireless device includes determining whether one or more conditions for triggering measurement reporting have occurred and triggering the measurement reporting based on the occurrence of the one or more conditions. The one or more conditions for triggering the measurement reporting are based on at least one of: a timing advance value in a source cell; the wireless device being within a pre-determined distance of a satellite node serving the source cell and/or a candidate target cell of the wireless device; an expected time for the wireless device to be served in the source cell and/or in the candidate target cell; an elevation angle of the satellite node serving the source cell and/or the candidate target cell; a point in time configured by the network is reached; detection of an identifier associated with a specific cell.