Layer 2 Mobility for Low-Latency Serving Cell Changes
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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 serving cell changes, which are not suitable for meeting the stringent requirements of future mobile communication systems.
Innovation Solution
Implementing layer 2 mobility by configuring PDCP and RLC entities, receiving RRC messages, and using MAC CEs to manage mobility between cells, reducing the need for complete L2 resets and maintaining continuous data transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If L3 mobility with complete resets is used for serving cell change, then network can reconfigure radio resources, but latency and interruption time increase significantly
Solution Approach 1:
The patent extracts the reset operation from the mobility procedure by introducing a mobility indication flag that triggers selective re-establishment only when necessary. This allows the network to maintain connection state (avoiding full L3 resets) while still enabling reconfiguration when needed, thus reducing latency while preserving adaptability.
Solution Approach 2:
The patent implements dynamic behavior where the mobility indication flag can be set to different values (first indication value for re-establishment, second indication value for no re-establishment). This dynamic control allows the system to adapt between full reset and selective re-establishment modes based on actual network conditions, optimizing the balance between reconfiguration capability and latency.
2Adaptability or versatility
If L3 mobility with complete resets is used for serving cell change, then radio resources can be reconfigured, but overhead and interruption time increase
Solution Approach 1:
The patent extracts the complex reset operation by introducing a simplified mobility indication mechanism. Instead of always performing complete L3 resets, the system uses a flag to selectively trigger re-establishment only when necessary, reducing procedure complexity while maintaining reconfiguration capability.
Solution Approach 2:
The patent applies partial action by implementing selective re-establishment based on the mobility indication flag. When the flag indicates no re-establishment is needed, the system skips unnecessary reset operations, reducing overhead and complexity while still enabling full reconfiguration when the flag indicates re-establishment is required.
3Loss of time
If layer 2 mobility is implemented to reduce interruption time, then data transmission continuity improves, but MAC and RLC entity management becomes more complex
Solution Approach 1:
The patent applies preliminary action by pre-configuring the mobility indication flag and related parameters before cell change occurs. This allows the MAC and RLC entities to be prepared for selective re-establishment, reducing the complexity of real-time management while enabling continuous data transmission during mobility events.
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, the first RRC message comprises a first configuration information, establishing a PDCP entity and a first RLC entity, performing reception of PDCP SDUs via the PDCP entity and the first RLC entity, receiving from the base station a second RRC message, the second RRC message comprises a second configuration information, establishing a second RLC entities based on a RLC configuration information in the first configuration information and a RLC configuration information in the second configuration information, receiving a first MAC CE, and performing reception of PDCP SDUs via the PDCP entity and the second RLC entity.