L1/L2 Inter-Cell Mobility Management for Lower-Latency Handover
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Solution Overview
Problem
Current inter-cell mobility management methods in wireless communication systems, such as L3-based handover and RRM measurements, incur delays and interruptions due to the need for Layer 3-based methods that require UE synchronization and system information acquisition from target cells, leading to suboptimal user experience.
Innovation Solution
Implementing Layer 1 (L1) and Layer 2 (L2) based inter-cell mobility management using radio resource control (RRC) signaling to facilitate direct synchronization and system information acquisition from neighbor cells, reducing latency through simplified cell search processes and uplink transmission mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If L3-based handover and RRM measurements are used for inter-cell mobility management, then the UE can maintain connectivity during cell transitions, but delays and interruptions occur due to the need for UE synchronization and system information acquisition from target cells
Solution Approach 1:
The patent applies preliminary action by having the UE acquire system information and perform synchronization with the target cell before the actual handover is triggered. The network configures the UE with RRM measurement opportunities on target cells, allowing the UE to pre-synchronize and pre-acquire system information, thereby reducing handover latency when the handover is actually executed.
Solution Approach 2:
The patent segments the handover process into distinct phases: measurement configuration phase, synchronization and system information acquisition phase, and actual handover execution phase. This segmentation allows the UE to perform preparatory actions independently and efficiently, reducing the critical path delay during the actual handover transition.
2Adaptability or versatility
If L3-based RRM measurements and handover commands are used, then inter-cell mobility management can be performed, but the process complexity increases due to multiple synchronization and information acquisition steps
Solution Approach 1:
The patent extracts the synchronization and system information acquisition steps from the critical handover path and performs them independently in advance. By taking out these preparatory actions and executing them during measurement periods before handover is triggered, the complexity of the main handover process is reduced while maintaining full inter-cell mobility management capability.
3Reliability
If the UE synchronizes with target cell and acquires system information before handover, then seamless connectivity is maintained, but the handover latency increases due to these preparatory steps
Solution Approach 1:
The patent maintains continuity of useful action by having the UE perform synchronization and system information acquisition during regular measurement opportunities that occur continuously as the UE moves between cells. Rather than performing these actions only when handover is triggered, the UE continuously maintains updated synchronization and system information, making the handover execution faster while preserving seamless connectivity.
Data Source
Figure 1A~1C
Figure 1D
Figure 2
AI summary
Aspects of the present disclosure pertain to mobility management processes for cells directly at Layer 1 (L1) or Layer 2 (L2), in a manner that reduces latency of inter-cell mobility methods and enhances user experience under mobility (i.e. handover). To address some of the limitations of existing inter-cell mobility methods, embodiments of the disclosure aid in enabling system information acquisition from neighbor cells for inter-cell mobility, system information update for neighbor cells for inter-cell mobility, radio link monitoring (RLM) for inter-cell mobility and using an uplink transmission mechanism for inter-cell mobility to acknowledge receipt of a handover message for inter-cell mobility.