User Equipment Conditional Handover Paths for Mobility Robustness
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Solution Overview
Problem
Existing cellular networks face challenges in ensuring mobility robustness during handovers, particularly in non-terrestrial networks with moving base stations, leading to radio link failures due to late measurement reports or failed handover commands.
Innovation Solution
The implementation of conditional handovers (CHO) with configuration data that includes trigger conditions for multiple target cells along a predicted mobility path, allowing UEs to execute handovers proactively and maintaining configuration data for sequential handovers without immediate network updates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conditional handover configuration is provided for multiple target cells along mobility path, then mobility robustness is improved, but device complexity increases
Solution Approach 1:
The network provides conditional handover configuration data for multiple target cells in advance, before the UE actually needs to handover. This preliminary configuration includes trigger conditions and handover parameters for multiple potential target cells along the predicted mobility path, allowing the UE to execute handover quickly when conditions are met without needing real-time network coordination for each target cell selection.
Solution Approach 2:
The UE autonomously monitors trigger conditions for multiple target cells and independently decides which handover to execute based on the pre-configured conditions. The UE self-manages the configuration data, storing it locally and using it to make handover decisions without continuous network intervention, thereby improving mobility robustness while managing complexity through autonomous operation.
2Duration of action of stationary object
If configuration data for multiple sequential handovers is maintained, then service continuity is improved, but loss of information increases due to signaling overhead
Solution Approach 1:
The network sends conditional handover configuration data for multiple sequential target cells in advance, including all necessary handover parameters and trigger conditions. This preliminary action ensures that when the UE needs to handover, the configuration is already available locally, eliminating the need for repeated signaling exchanges during the handover process and reducing overall signaling overhead while maintaining service continuity.
Solution Approach 2:
The UE maintains configuration data for multiple sequential handovers in continuous readiness state. As the UE moves along the predicted mobility path, it continuously monitors trigger conditions for each configured target cell and can immediately execute handover when conditions are met, ensuring uninterrupted service continuity without requiring additional signaling for configuration updates during the handover sequence.
3Reliability
If conditional handover is executed proactively, then radio link failure is reduced, but loss of time increases due to configuration processing
Solution Approach 1:
The network provides conditional handover configuration data in advance, including pre-configured handover parameters, target cell information, and trigger conditions. This preliminary configuration allows the UE to execute handover immediately when trigger conditions are met, without needing to process configuration requests or wait for network commands during the handover event, thereby reducing radio link failures while minimizing handover execution time.
Solution Approach 2:
The UE autonomously monitors trigger conditions and independently executes handover decisions based on pre-configured parameters. This self-service approach eliminates the need for real-time network coordination during handover execution, allowing the UE to quickly switch to the appropriate target cell when conditions are met, thus reducing both radio link failures and handover execution time.
Data Source
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AI summary
An embodiment of a user equipment supports conditional handovers to one or more cells of a cellular network. The user equipment is configured to receive configuration data from the cellular network. The configuration data indicates for a plurality of target cells of the cellular network, conditions to trigger a conditional handover to any of the target cells. The user equipment is further configured to check the conditions with respect to appliance, and, in case of appliance, trigger the conditional handover.