UE AS Context Validity Handling Across RATs
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Solution Overview
Problem
In the LTE system, there is a need for efficient handling of the user equipment (UE) Access Stratum (AS) context during radio resource control (RRC) connection suspension and resumption across different radio access technologies (RATs), particularly in ensuring the validity and management of the UE AS context when switching between cells of different RANs.
Innovation Solution
The method involves configuring a RRC connection and data radio bearer by a first RAN, suspending the RRC connection upon receiving a suspension message, maintaining the UE AS context, selecting a cell of a second RAN with a different RAT, determining the validity of the UE AS context, and transmitting a RRC connection request message to the first RAN upon reselection, thereby establishing a rule for handling the validity of the UE AS context.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the UE maintains the AS context during RRC suspension to enable quick resumption, then the connection resumption speed is improved, but the risk of context invalidity increases when switching between different RATs
Solution Approach 1:
The UE monitors cell selection events and provides feedback about RAT changes to determine AS context validity. When the UE detects cell selection on a different RAT, it triggers a validity check mechanism that provides feedback to invalidate the AS context, ensuring reliability while maintaining quick resumption when valid
Solution Approach 2:
The AS context validity is made dynamic rather than static. The context can be maintained during suspension for quick resumption, but its validity dynamically changes based on cell selection events and RAT transitions. This allows the system to adapt between speed and reliability based on current conditions
2Reliability
If the UE clears the AS context when selecting a different RAT to ensure validity, then the context reliability is improved, but the connection resumption efficiency deteriorates
Solution Approach 1:
The AS context is treated with different validity qualities based on the local condition of cell selection. When the selected cell is on the same RAT, the context maintains high validity quality for efficient resumption. When a different RAT is selected, the validity quality changes, triggering appropriate handling. This local quality differentiation resolves the contradiction between reliability and efficiency
3Adaptability or versatility
If the UE establishes separate context management rules for different RATs, then the adaptability to multi-RAT environments is improved, but the system complexity increases
Solution Approach 1:
A universal cell selection monitoring mechanism serves multiple functions: it detects RAT changes, triggers AS context validity determination, and initiates appropriate resumption or reestablishment procedures. This single multi-functional mechanism provides adaptability to multi-RAT environments without requiring separate complex management rules for each RAT
Data Source
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AI summary
A communication device for handling a user equipment (UE) Access Stratum (AS) context comprises a storage device for storing instructions and a processing circuit coupled to the storage device. The processing circuit is configured to execute the instructions stored in the storage device. The instructions comprise receiving a first radio resource control (RRC) message via a RRC connection from a first radio access network (RAN) of a first radio access technology (RAT), wherein the RRC message comprises a resume identity and indicates a RRC suspension; suspending the RRC connection in response to the first RRC message; keeping a UE AS context, when the RRC connection is suspended; selecting a cell of a second RAN of a second RAT different from the first RAT; and determining that the UE AS context and the resume identity are invalid in response to the selection.