Layer 2 Mobility Timing Advance Adjustment for 5G Handover
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Solution Overview
Problem
Current 5G mobile communication systems experience significant latency and overhead during cell handovers due to L3-triggered serving cell changes, which involve complete L2 and L1 resets, leading to increased interruption time and overhead.
Innovation Solution
The proposed solution involves receiving RRCReconfiguration messages from the base station to manage layer 2 mobility by determining Timing Advance between downlink and uplink based on specific fields and subcarrier spacing, allowing for smoother transitions between mobility groups without full resets, thereby reducing interruption time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If L3-triggered serving cell change is performed with complete L2 and L1 resets, then reliability of cell handover is improved, but interruption time and overhead increase
Solution Approach 1:
The patent segments the handover process into two distinct types: L3-triggered handover (with complete L2/L1 resets for reliability) and L2-triggered handover (with partial resets for reduced interruption). By dividing the unified handover procedure into separate pathways with different reset scopes, the system can select the appropriate handover type based on service requirements, thus resolving the contradiction between reliability and interruption time.
Solution Approach 2:
The patent introduces dynamic handover triggering mechanisms where the handover type (L3 or L2) can be flexibly selected based on real-time service requirements, UE capabilities, and network conditions. The L2 mobility feature allows dynamic switching between full-reset and partial-reset handover modes, enabling the system to adaptively balance reliability and interruption time.
2Reliability
If L3-triggered serving cell change is performed with complete L2 and L1 resets, then reliability of cell handover is improved, but overhead increases
Solution Approach 1:
The patent segments the handover procedure into different types with varying overhead requirements. L2-triggered handover with partial resets generates less signaling overhead compared to L3-triggered handover with complete resets. This segmentation allows the system to reduce overhead by selecting the appropriate handover type while maintaining necessary reliability through the dual-handover architecture.
Solution Approach 2:
The patent changes the reset scope parameter from complete L2/L1 resets to selective partial resets in L2-triggered handover. By modifying this parameter, the system reduces the quantity of signaling messages and processing operations required during handover, thereby reducing overhead while maintaining sufficient reliability for the service.
3Loss of time
If beam switch mobility is used instead of L3-triggered handover, then interruption time is reduced, but reliability and service requirements may not be met
Solution Approach 1:
The patent introduces dynamic handover triggering where the system can switch between L3-triggered (high reliability) and L2-triggered (low interruption) modes based on real-time service requirements. This dynamic adaptation allows beam switch mobility to be enhanced with selective L2-triggered handovers that maintain low interruption time while meeting diverse service reliability requirements through capability-based selection.
Solution Approach 2:
The patent changes the handover triggering parameter from solely L3-based to a flexible mechanism supporting both L3 and L2 triggering. This parameter change enables the system to adjust the handover behavior dynamically, allowing beam switch mobility to achieve low interruption time while meeting service requirements through selective L2-triggered handovers based on UE capability and service type.
Data Source
AI summary
A method and apparatus for layer 2 mobility is provided. Method for lower layer mobility includes receiving a RRCReconfigruation from the base station, receiving a TAC MAC CE in a first cell and determining Timing advance between downlink and uplink (TTA). If the type1 TAC MAC CE is received, the terminal determining Timing advance between downlink and uplink (TTA) of a second TAG of a first mobility group based on the first field (TAC) and the second field (TAG ID) and a first subcarrier spacing. If the type2 TAC MAC CE is received, the terminal determining Timing advance between downlink and uplink (TTA) of a second TAG of a second mobility group based on the first field (TAC) and the second field (TAG ID) and a third field (CMG ID field) and a second subcarrier spacing.