L1/L2 Mobility Enhancements for 5G NR Serving Cell Change Latency
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Solution Overview
Problem
Current 5G new radio (NR) systems experience longer latency and higher overhead during serving cell changes due to complete L1 and L2 resets, which is more significant than beam switch mobility.
Innovation Solution
Implementing L1/L2 mobility enhancements that allow serving cell changes via L1/L2 signaling, incorporating some L1/L2 configuration of non-serving cells in current RRC configurations before handover conditions are triggered, to reduce latency and interruption time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If serving cell change is performed through complete L1 and L2 resets with RRC signaling, then reliability of cell change is improved, but latency and interruption time increase
Solution Approach 1:
The patent applies preliminary action by pre-configuring L1/L2 parameters and candidate target cell information in RRC configurations before handover conditions are triggered. This allows the UE to have measurement and reporting capabilities ready in advance, so when handover is needed, the transition can occur faster without requiring complete L1/L2 reset and RRC reconfiguration, thus reducing latency while maintaining reliability
Solution Approach 2:
The patent segments the handover process by separating the configuration phase (where L1/L2 parameters are pre-configured) from the execution phase (where actual cell change occurs). This segmentation allows partial L1/L2 configuration to be maintained during handover, avoiding complete reset and reducing interruption time while ensuring reliable cell change through controlled L1/L2-based mobility
2Productivity
If L1/L2-based mobility is implemented to reduce latency, then productivity of cell change is improved, but measurement precision and reporting accuracy may be affected
Solution Approach 1:
The patent implements dynamics by allowing flexible switching between L3 measurement-based handover and L1/L2 measurement-based mobility depending on conditions. The system can dynamically adjust the measurement and reporting mechanisms, using L1 measurements with pre-configured parameters when speed is critical, while maintaining the ability to use traditional L3 measurements when higher precision is required, thus achieving both productivity improvement and measurement accuracy
Solution Approach 2:
The patent applies parameter changes by modifying L1 measurement parameters and reporting configurations dynamically based on mobility conditions. Pre-configured L1/L2 parameters allow the system to adjust measurement thresholds, reporting frequencies, and candidate cell lists according to current network conditions, enabling fast handover when appropriate while maintaining measurement precision through configurable parameters
Data Source
AI summary
A method and an apparatus are provided in which it is detected that a condition for triggering a layer-1 (L1) measurement report transmission is satisfied based on a layer-3 (L3) measurement. It is determined whether the condition is detected over a first duration based on an L1 measurement, in response to detecting that the condition is satisfied based on the L3 measurement, and the measurement report is transmitted in case that the condition is detected over the first duration.