Distance Event Trigger for Non-Terrestrial Network Mobility
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Solution Overview
Problem
Current wireless communication systems face challenges in managing mobility, particularly in non-terrestrial networks, where handover delays and interruptions are significant due to large propagation distances and cell sizes.
Innovation Solution
The proposed solution involves a user equipment (UE) and base station (BS) configuration that determines whether entering or leaving conditions are met based on distance thresholds and hysteresis parameters, triggering measurement reports and handovers efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If network-controlled handover mechanisms are used to maintain optimal connection quality, then connection reliability is improved, but handover delay and signaling overhead increase
Solution Approach 1:
The network pre-configures the UE with multiple candidate target cells and their corresponding measurement criteria before handover is needed. This allows the UE to have measurement reports ready, eliminating the need for real-time target cell selection during handover execution, thus reducing handover delay while maintaining connection quality.
Solution Approach 2:
The system implements dynamic handover mechanisms where the UE continuously monitors multiple candidate cells and can autonomously trigger handover when predefined conditions are met. This dynamic approach allows faster response to changing channel conditions compared to static network-controlled handover, reducing both delay and signaling overhead.
2Loss of time
If conditional handover and layer 1/layer 2 triggered mobility are introduced to increase handover speed, then handover delay is reduced, but signaling overhead and system complexity increase
Solution Approach 1:
The handover process is segmented into distinct phases: configuration phase (network provides candidate cells and criteria), measurement phase (UE monitors conditions), and execution phase (UE autonomously triggers handover). This segmentation allows each phase to be optimized independently, reducing overall complexity while maintaining fast handover speed.
Solution Approach 2:
The UE is empowered to autonomously evaluate measurement conditions and trigger handover decisions based on pre-configured criteria from the network. This self-service capability eliminates the need for continuous network intervention during handover execution, reducing signaling overhead and system complexity while maintaining fast handover response.
3Measurement precision
If multiple data exchanges between network and UE are conducted during handover, then handover accuracy is improved, but signaling overhead and interruption time increase
Solution Approach 1:
The network pre-configures the UE with measurement objects, reporting configurations, and candidate target cell information before handover is needed. This preliminary action ensures that when handover is triggered, the UE already has accurate measurement data and decision criteria, eliminating the need for additional data exchanges during handover execution and reducing signaling overhead.
Solution Approach 2:
The system implements efficient feedback mechanisms where the UE reports measurements only when predefined triggering conditions are met, rather than continuously. This feedback approach maintains handover accuracy by providing the network with relevant measurement data while minimizing unnecessary signaling overhead and energy consumption.
Data Source
AI summary
A distance event for an earth moving cell is introduced for event-triggered measurement report. The distance event is triggered when a first distance to a configured serving cell reference location is larger than a first threshold and a second distance to a configured neighbor cell reference location is smaller than a second threshold. A user equipment (UE) may determine a real-time reference location based on a reference time (epoch time), a reference location, and ephemeris information associated to a serving cell and neighbor cell. The ephemeris, the reference location, and the reference time for the serving cell are broadcast in SIB19. The ephemeris, the reference location, and the reference time for the neighbor cell are configured in the measurement object configuration.