Autonomous UE Measurement Window Adjustment for NTN Handover
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Solution Overview
Problem
In non-terrestrial networks (NTNs) like 5G NR with moving satellites, the frequent handover events due to satellite movement cause challenges in reliable neighbor cell measurements, as conventional terrestrial network techniques do not account for the movement of satellite-based gNBs, leading to misaligned measurement windows and increased signaling overhead.
Innovation Solution
User equipment (UE) autonomously adjusts the measurement window parameters, such as the synchronization signal block (SSB) measurement timing configuration (SMTC), by aligning the temporal position and duration based on timing thresholds and reference information, without continuous signaling or location updates, to facilitate accurate neighbor cell measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional terrestrial network measurement techniques are used in NTN, then measurement procedures remain simple, but measurement accuracy deteriorates due to misaligned measurement windows caused by satellite movement
Solution Approach 1:
The measurement window parameters are made dynamic by allowing the UE to autonomously adjust the SMTC window timing based on detected SSB timing variations. The UE monitors the actual timing of neighbor cell SSBs and adapts the measurement window accordingly, transforming a static measurement configuration into a dynamic one that compensates for satellite movement effects.
Solution Approach 2:
The UE performs self-adjustment of the measurement window without requiring continuous network control or location updates. By autonomously detecting SSB timing and independently modifying SMTC parameters, the UE serves itself in maintaining accurate measurements, eliminating the need for complex network-coordinated adjustment mechanisms.
2Reliability
If frequent handover events are supported due to satellite movement, then network connectivity is maintained, but control signaling overhead increases
Solution Approach 1:
The UE performs preliminary adjustment of measurement window parameters before handover decisions are made. By proactively aligning the SMTC window with actual SSB timing, the UE ensures that measurement reports contain accurate neighbor cell information, enabling reliable handover decisions without requiring additional signaling for measurement coordination.
Solution Approach 2:
The UE uses feedback from detecting actual SSB timing to adjust measurement window parameters. This feedback loop allows the UE to continuously optimize measurement accuracy based on real-time satellite movement effects, ensuring reliable handover decisions while minimizing the need for additional control signaling from the network.
3Measurement precision
If measurement window parameters are adjusted continuously to maintain accuracy, then measurement precision improves, but power consumption increases
Solution Approach 1:
The UE adjusts measurement window parameters periodically based on detected SSB timing variations rather than continuously. By monitoring timing changes and applying adjustments only when necessary, the UE maintains measurement precision while reducing power consumption compared to continuous adjustment mechanisms.
Data Source
AI summary
A method of operating a user equipment (UE) having a serving cell and a neighbor cell included in a wireless communications system, includes receiving (S410), by the UE, parameters defining a measurement window; receiving, by the UE, one or more timing thresholds; performing a measurement operation with respect to the neighbor cell by measuring (S415) reference information of the neighbor cell in accordance with the measurement window; determining, by the UE, whether to adjust one or more of the parameters of the measurement window based on a temporal position of the reference information and the one or more timing thresholds; and adjusting one or more of the parameters of the measurement window based on the determining.