Ephemeris Data for Reliable Conditional Handover in NTN
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Solution Overview
Problem
Existing wireless communication systems face challenges in managing handovers in non-terrestrial networks, particularly in satellite communications, due to long propagation delays and variable channel conditions, which can lead to errors and interruptions during handover processes.
Innovation Solution
The use of ephemeris data to assist User Equipment (UE) in determining satellite positions and velocities, enabling accurate timing and frequency adjustments for seamless handovers in Non-Terrestrial Networks (NTN), combined with Conditional Handover (CHO) mechanisms to autonomously trigger handovers based on predefined conditions, reducing errors and interruptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional handover mechanisms are used in NTN, then network control is maintained, but long propagation delays cause handover errors and interruptions
Solution Approach 1:
The patent applies preliminary action by pre-configuring multiple candidate target cells with their ephemeris data and handover parameters before the actual handover is needed. The UE stores this configuration information in advance, enabling it to execute handover autonomously when conditions are met, thus eliminating the need for real-time network signaling during the critical handover moment and reducing propagation delay impacts.
Solution Approach 2:
The patent implements self-service by enabling the UE to autonomously monitor handover conditions and execute handover decisions based on pre-configured ephemeris data without continuous network control. The UE independently evaluates whether handover conditions are satisfied using stored satellite position and velocity information, making the handover process self-driven and reducing dependency on real-time network signaling.
2Reliability
If network-controlled handover is used, then connectivity is maintained, but service interruptions occur during handover execution
Solution Approach 1:
The patent applies preliminary action by preparing multiple candidate target cells with complete handover configurations including ephemeris data, timing information, and frequency parameters in advance. When handover is triggered, the UE can immediately execute the pre-configured handover to a ready target cell, eliminating the need for real-time configuration exchange and significantly reducing handover interruption duration.
Solution Approach 2:
The patent implements dynamics by enabling the UE to flexibly select from multiple pre-configured candidate target cells based on real-time condition monitoring. The UE dynamically evaluates which candidate cell satisfies the handover conditions best and executes handover to that specific cell, making the handover process adaptive and responsive to current network conditions while maintaining continuity.
3Measurement precision
If ephemeris data is provided for candidate target cells, then timing and frequency adjustments are enabled, but signaling overhead increases
Solution Approach 1:
The patent applies preliminary action by providing complete ephemeris data, timing information, and frequency parameters for multiple candidate target cells in advance during the handover preparation phase. This pre-provisioning of all necessary timing and frequency adjustment parameters eliminates the need for additional signaling during the actual handover execution, as the UE already possesses the required data to perform accurate timing and frequency adjustments.
Solution Approach 2:
The patent implements universality by designing the handover configuration to serve multiple functions simultaneously. The pre-provided ephemeris data and timing parameters not only enable timing adjustments but also support frequency calculations, satellite position determination, and handover decision-making. This multi-functional use of the pre-configured data reduces the need for separate signaling messages for each function.
Data Source
AI summary
According to certain embodiments, a method by a UE during a handover of the UE from a source cell associated with a source node to a candidate target cell associated with a candidate target node is provided. The method includes receiving, from the source node, a message including a handover command associated with the candidate target node associated with the candidate target cell. The handover command includes ephemeris data and at least one common TA parameter associated with the candidate target cell.