Layer 2 Uplink Mobility Across Cells Using MAC CE Switching
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Solution Overview
Problem
Current mobility mechanisms in 5G systems, such as L3 mobility, involve significant latency, overhead, and interruption time during cell changes, which are not suitable for meeting the stringent requirements of future mobile communication systems.
Innovation Solution
Implementing layer 2 mobility by receiving RRC messages and MAC CEs to perform uplink transmissions based on specific PDCP and BSR configurations, reducing the need for complete L2 resets and minimizing interruption time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If L3 mobility with complete L2 resets is used for serving cell change, then reliability of cell transition is improved, but latency and interruption time increase
Solution Approach 1:
The patent segments the mobility process into two distinct types: L3 mobility with complete L2 resets for robust cell changes, and L2 mobility without complete resets for faster beam switching. This segmentation allows the system to choose the appropriate mobility type based on specific transition requirements, thereby reducing unnecessary latency while maintaining reliability when needed.
Solution Approach 2:
The patent introduces dynamic mobility mechanisms where the UE can switch between L3 and L2 mobility modes based on current conditions. The dynamic nature allows the system to perform quick L2 beam switches when conditions permit, reducing interruption time, while falling back to L3 mobility with complete resets when higher reliability is required.
2Reliability
If L3 mobility with complete L2 resets is performed, then cell transition robustness is improved, but overhead increases
Solution Approach 1:
The patent divides mobility overhead into two categories: full L2 reset overhead for L3 mobility, and reduced overhead for L2 mobility without complete resets. By segmenting the mobility types, the system can perform lightweight L2 beam switches that require minimal overhead, reserving the heavier L3 mobility protocol only when robustness is absolutely necessary.
Solution Approach 2:
The patent changes the mobility parameters by introducing L2 mobility mode where complete L2 resets are not performed. This parameter change reduces the overhead associated with cell transitions while maintaining adequate robustness through alternative mechanisms such as MAC CE-based beam switching and selective configuration updates.
3Loss of time
If L2 mobility without complete L2 resets is used, then interruption time is reduced, but configuration management complexity increases
Solution Approach 1:
The patent introduces dynamic configuration management for L2 mobility where the UE maintains existing L2 configurations during beam switches but updates specific parameters as needed. This dynamic approach allows rapid switching without complete resets, reducing interruption time while managing complexity through selective configuration updates rather than full reconfiguration.
Solution Approach 2:
The patent implements feedback mechanisms where the UE reports its capability to support L2 mobility without complete L2 resets to the network. This feedback enables the network to appropriately manage configurations and provide suitable L2 mobility configurations, thereby reducing the burden on the UE while maintaining reduced interruption time.
4Adaptability or versatility
If L2 mobility is implemented with multiple MAC CE types, then uplink transmission flexibility is improved, but MAC layer complexity increases
Solution Approach 1:
The patent segments MAC CE functionality into multiple specialized types: first MAC CEs for triggering uplink transmissions with first BSR/PHR configurations, and second MAC CEs for triggering uplink transmissions with second BSR/PHR configurations. This segmentation provides uplink transmission flexibility by handling different scenarios with specialized CEs while managing MAC layer complexity through clear functional separation.
Solution Approach 2:
The patent creates a universal MAC CE framework where different types of MAC CEs serve multiple uplink transmission scenarios. The first and second MAC CEs are designed to handle various uplink transmission needs by triggering different BSR and PHR configurations, providing multi-functionality that enhances flexibility while avoiding the need for entirely separate mechanisms for each scenario.
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 MAC CE, and performing an uplink transmission. The uplink transmission is performed based on the first PDCP configuration and the first BSR configuration and the first PHR configuration if the MAC CE is a first MAC CE. The uplink transmission is performed based on the first PDCP configuration and the second BSR configuration and the second PHR configuration if the MAC CE is a second MAC CE.