Layer 2 DRX Mobility for Low-Interruption Cell Handover
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Solution Overview
Problem
Existing mobile communication systems face high latency and overhead during cell handovers due to L3-based serving cell changes, which involve complete L2 and L1 resets, leading to significant interruption times.
Innovation Solution
Implementing layer 2 mobility by receiving RRC messages and MAC CEs to manage DRX operations, allowing seamless transitions between adjacent cells while maintaining layer 2 continuity, thereby reducing interruption times and overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If L3-based serving cell change is performed with complete L2 and L1 resets, then cell handover reliability is improved, but interruption time and latency increase significantly
Solution Approach 1:
The patent segments the handover process into two distinct types: L3 mobility (complete L2/L1 reset for reliability) and L2 mobility (MAC CE-based for speed). By dividing the handover mechanism into these segments, the system can choose the appropriate type based on requirements, resolving the contradiction between reliability and interruption time.
Solution Approach 2:
The patent introduces L2 mobility as an intermediary mechanism between traditional L3 handover and beam switching. This intermediary uses MAC CE commands to enable faster cell changes without complete L2/L1 resets, reducing interruption time while maintaining adequate reliability through RRC message configuration.
2Reliability
If L3-based serving cell change is performed with complete L2 and L1 resets, then cell handover reliability is improved, but signaling overhead increases
Solution Approach 1:
The patent segments handover signaling into L3-based RRC procedures (for reliability-critical scenarios) and L2-based MAC CE procedures (for overhead-reduction scenarios). This segmentation allows the system to use lighter-weight MAC CE signaling when full L3 handover is not necessary, reducing overall signaling overhead while maintaining reliability where needed.
Solution Approach 2:
The patent changes the signaling parameter from full RRC reconfiguration messages to concise MAC CE commands for L2 mobility. This parameter change reduces the size and complexity of signaling messages, thereby reducing overhead while maintaining the essential handover functionality through alternative (MAC layer) procedures.
3Loss of time
If L2 mobility with MAC CE is used for cell transitions, then interruption time is reduced, but DRX configuration management complexity increases
Solution Approach 1:
The patent applies preliminary action by configuring multiple DRX configurations and their associated MAC CE identities in advance through RRC messages. This pre-configuration allows the UE to quickly switch between DRX settings during L2 mobility without real-time configuration complexity, reducing interruption time while managing complexity through ahead-of-time setup.
Solution Approach 2:
The patent enables self-service by allowing the UE to autonomously select and apply the appropriate DRX configuration based on received MAC CE commands. The UE independently manages the switching between different DRX configurations without requiring complex network-controlled real-time reconfiguration, thereby reducing interruption time while keeping management complexity manageable through standardized selection procedures.
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, performing DRX operation based on the first DRX configuration information and the first identifier, receiving from the base station a second MAC CE, and performing DRX operation based on the second DRX configuration information and the second identifier. The first MAC CE comprises an identifier related to a first configuration information. The first configuration information comprises the first identifier and the first DRX configuration information.