MAC CE Cell Group Switching for Low-Interruption 5G Mobility
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Solution Overview
Problem
Current mobility mechanisms in 5G systems involve L3 measurements and RRC signaling, leading to increased latency, overhead, and interruption time during cell changes, which are not suitable for meeting the stringent requirements of future mobile communication systems.
Innovation Solution
The method involves receiving RRC messages and MAC CEs to apply configuration information at specific points in time based on HARQ feedback, enabling layer 2 mobility with reduced interruption by switching between adjacent cells while maintaining layer 2 continuity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If L3 measurements and RRC signaling are used for cell handover, then cell switching can be performed, but latency and overhead increase leading to longer interruption time
Solution Approach 1:
The patent segments the handover process into two distinct phases: L3 measurement phase (for cell selection and decision-making) and L2 execution phase (for actual configuration switching). This segmentation allows the time-consuming L3 measurements to be performed independently while preparing L2 configurations in advance, thereby reducing the overall interruption time during handover execution.
Solution Approach 2:
The patent implements preliminary action by performing L2 configuration preparation and validation before the actual handover execution. Multiple candidate configurations are pre-configured and validated during the L3 measurement phase, so that when handover is triggered, the execution can proceed immediately with minimal interruption.
2Stability of the object's composition
If complete L2 reset is performed during serving cell change, then configuration consistency is ensured, but overhead and interruption time increase
Solution Approach 1:
The patent applies partial action by performing selective L2 configuration updates rather than complete L2 resets during handover. Only the necessary configuration elements related to the target cell are updated, while other configurations are maintained, thereby reducing overhead and procedure complexity while ensuring configuration consistency for the critical handover parameters.
3Measurement precision
If RRC signaling is used for every cell change, then accurate cell switching control is achieved, but overhead increases significantly
Solution Approach 1:
The patent extracts the cell execution control function from the L3 RRC signaling layer and moves it to the L2 MAC layer. This extraction allows L3 to focus on high-level decision-making while L2 handles the detailed configuration switching, thereby reducing RRC signaling overhead while maintaining precise control through L2 MAC CE commands.
Solution Approach 2:
The patent introduces L2 MAC CE (Medium Access Control Control Element) as an intermediary between L3 RRC signaling and L1 physical layer execution. This intermediary enables compact, efficient configuration commands to be transmitted at the L2 layer, reducing the need for extensive RRC signaling while maintaining accurate control over the handover process.
Data Source
AI summary
A method and apparatus for layer 2 mobility is provided. Method for lower layer mobility includes receiving from a base station a first RRC message and a second RRC message, receiving from the base station a first MAC CE, the first MAC CE comprises an identifier related to the first configuration information, applying the first configuration information at a first point of time, receiving from the base station a second MAC CE, and applying the second configuration information at a second point of time. The first point of time is determined based on a number of a first slot and HARQ feedback transmission for first MAC CE. The second point of time is determined based on a number of a second slot and HARQ feedback transmission for second MAC CE.