Time-Based Handover in Non-Terrestrial Networks

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Solution Overview

Problem

The challenge in Non-Terrestrial Networks (NTNs) is the frequent and unavoidable handovers due to satellite cell switches, leading to significant control plane overheads, service interruptions, and increased inter-node signaling, particularly in quasi-earth-fixed cell scenarios, where traditional signal strength-based handover methods are inadequate.

Innovation Solution

Implementing a time-based trigger condition for Conditional Handover (CHO) in NTNs, where the source network node informs the target network node of a time window during which the UE should perform handover, allowing for more efficient resource management and reduced inter-node signaling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional signal strength-based handover methods are used in NTNs, then handover decisions can be made based on current radio conditions, but frequent handovers occur due to satellite cell switches causing significant control plane overheads and service interruptions

Engineering Contradiction:

Improvehandover reliabilityVSAvoidservice continuity

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent applies preliminary action by configuring Conditional Handover (CHO) with predetermined execution conditions before the handover is actually needed. The UE is pre-configured with target cell information and handover execution conditions (such as signal strength thresholds or time-based triggers), allowing the handover to be executed automatically when conditions are met, thereby reducing control plane overhead and preventing service interruptions during satellite cell switches

Inventive Principle:

Principle #10Preliminary action

2Reliability

If frequent handovers are performed to maintain connectivity in NTNs, then service continuity is maintained, but control plane overheads and inter-node signaling increase significantly

Engineering Contradiction:

Improveconnectivity maintenanceVSAvoidsignaling overhead

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

The patent applies self-service by enabling the UE to autonomously execute handovers based on pre-configured conditions without requiring continuous network intervention. The UE monitors handover execution conditions (signal strength, time window) and independently triggers handovers, eliminating the need for frequent cancel messages and reducing inter-node signaling overhead while maintaining connectivity

Inventive Principle:

Principle #25Self-service

3Loss of information

If time-based trigger condition is implemented for Conditional Handover, then inter-node signaling is reduced and resource usage is optimized, but handover execution must be precisely timed

Engineering Contradiction:

Improvesignaling overheadVSAvoidhandover timing precision

Core Design Contradiction:

Loss of informationVSManufacturing precision

Solution Approach 1:

The patent applies parameter changes by introducing time-based trigger conditions as an additional handover execution criterion. The handover execution is triggered when the current time falls within a predefined time window, providing a precise and objective trigger mechanism that reduces signaling overhead while ensuring accurate timing through configurable time parameters

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS20250113277A1Systems and methods for time-based handover in non-terrestrial networks

Publication Date: 2025.04.03 TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

AI summary

A method (700) by a source network node (110A) for handover of a wireless device (112) in a Non-Terrestrial Network (NTN) to a target network node (110B) includes transmitting (702), to the target network node, time information for performing, by the wireless device, the handover to a target cell associated with the target network node.