Non-Terrestrial UE Cell Selection via Dynamic DU Power Boosting
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Solution Overview
Problem
In non-terrestrial networks with dual-DU satellite configurations, user equipment (UE) randomly selects between DUs connected to different CUs, leading to suboptimal feeder link performance and increased CU change events, which cause signaling overhead and latency due to the UE's inability to determine the optimal CU during initial access or cell reselection.
Innovation Solution
Implementing dynamic downlink transmit power boosting for DUs, either real or virtual, to influence UE measurements, ensuring it connects to the optimal CU-DU pair by adjusting the transmit power levels based on the satellite's trajectory and feeder link quality, thereby minimizing CU changes and latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If UE randomly selects between DUs during initial access or cell reselection, then UE can establish connection quickly, but feeder link performance deteriorates and CU change events increase
Solution Approach 1:
The patent applies parameter changes by modifying the downlink transmit power of DUs dynamically based on satellite trajectory and feeder link quality. The network configures different power levels for DUs connected to different CUs, allowing UEs to measure and select the optimal DU-CU pair. This resolves the contradiction by changing the power parameter to guide UE selection toward optimal connections while maintaining fast access through standardized measurement procedures.
Solution Approach 2:
The patent implements feedback mechanisms where the network monitors satellite position, feeder link quality, and UE connection status, then dynamically adjusts DU transmit power accordingly. The network provides feedback to UEs through measurement configurations and power offset indications, enabling UEs to make informed selection decisions. This feedback loop ensures optimal feeder link performance while maintaining efficient connection establishment.
2Reliability
If UE connects to optimal CU-DU pair through power boosting, then feeder link performance improves, but signaling overhead and latency increase due to additional power adjustment procedures
Solution Approach 1:
The patent applies preliminary action by pre-configuring power boosting parameters and measurement settings in system information before UE access. The network prepares power offset values and measurement configurations in advance, so UEs can perform measurements and selections during initial access without additional signaling delays. This resolves the time loss by performing power adjustment preparations beforehand rather than during connection establishment.
Solution Approach 2:
The patent enables self-service by allowing UEs to autonomously measure downlink power levels and select optimal DUs based on configured parameters without extensive network intervention. The UE independently evaluates measurement results and makes connection decisions, reducing signaling overhead and latency. This self-service approach minimizes the time loss while achieving optimal feeder link performance.
3Reliability
If dynamic power boosting is applied to influence UE measurements, then UE connection optimization improves, but device complexity increases due to dynamic power control mechanisms
Solution Approach 1:
The patent applies segmentation by dividing the power control function into distinct components: network-side power configuration, UE-side measurement and selection, and connection establishment. The network handles high-level power offset configuration based on satellite trajectory, while UEs perform local measurements and selections. This segmentation reduces device complexity by distributing functions appropriately and using standardized measurement procedures.
Solution Approach 2:
The patent applies universality by using existing standardized measurement and selection mechanisms for multiple purposes: initial access, cell reselection, and optimal DU selection. The same measurement framework is reused across different scenarios with minor configuration adjustments, avoiding the need for complex dedicated procedures. This multi-functionality approach minimizes device complexity while achieving UE connection optimization.
Data Source
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AI summary
There is provided an apparatus, said apparatus comprising means for determining which of at least two lower layer radio units (DU1, DU2) co-located at a first location, each lower layer radio unit associated with a higher layer radio unit (CU1-CU3), has the best path to the associated higher layer radio unit and causing the transmit power of the determined one of the at least two lower layer radio units (DU1, DU2) received at a user equipment (UE1, UE2) to be higher relative to the transmit power of any of the other of the at least two lower layer radio units received at the user equipment.