UE RRC Connection Recovery via Dynamic Fallback to NAS
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Solution Overview
Problem
In the context of 5G New Radio (NR) access technology, when a Radio Resource Control (RRC) connection failure occurs, user equipment (UE) faces challenges in efficiently recovering the RRC connection through the RRC reestablishment procedure, particularly when the network side lacks UE context information.
Innovation Solution
The proposed solution involves a control method in user equipment (UE) that includes transmitting an RRC connection reestablishment request message to a base station, receiving an RRC connection reestablishment response message, and performing either RRC connection reestablishment or establishing a new RRC connection based on the response message. This method incorporates specific operations such as stopping RRC timers, releasing radio resources, and initiating NAS connection recovery procedures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE attempts RRC connection reestablishment when the network side lacks UE context information, then the UE follows the reestablishment procedure, but the network side cannot complete reestablishment and must establish a new connection, causing procedure inefficiency and extended recovery time
Solution Approach 1:
The network side provides feedback through the RRC connection reestablishment response message to indicate whether reestablishment can be completed or if a new connection should be established. This feedback mechanism allows the UE to adjust its behavior accordingly, avoiding unnecessary reestablishment attempts and reducing recovery time.
Solution Approach 2:
The UE dynamically switches between RRC connection reestablishment mode and new RRC connection establishment mode based on the network's response. This dynamic adaptation allows the system to optimize the recovery procedure based on real-time network conditions and UE context availability.
2Reliability
If the UE performs full RRC connection establishment procedures when reestablishment fails, then a new connection is established, but service interruption time increases due to the complexity of the establishment operations
Solution Approach 1:
The RRC connection establishment operations are segmented into discrete steps (stopping RRC timer, releasing radio resources, indicating fallback to NAS layer, resetting MAC layer, applying configurations, constructing completion message, leaving connected state). This segmentation allows for systematic execution and potential optimization of each individual step.
Solution Approach 2:
The UE prepares for potential new connection establishment by having the RRC layer indicate fallback to the NAS layer before fully committing to the establishment procedure. This preliminary indication allows the NAS layer to initiate recovery procedures in advance, reducing overall recovery time.
3Reliability
If the UE RRC layer indicates fallback to NAS layer for new connection establishment, then the NAS connection recovery procedure is initiated, but the overall recovery process becomes more complex with multiple layer interactions
Solution Approach 1:
The RRC layer acts as an intermediary between the physical layer and the NAS layer during the fallback process. It receives the indication from the network, processes the necessary RRC-level actions (stopping timers, releasing resources, resetting MAC), and then signals the NAS layer to initiate the connection recovery procedure. This structured intermediary role simplifies the overall complexity by providing clear interfaces between layers.
Data Source
AI summary
The present disclosure provides a control method in user equipment and user equipment. The control method in user equipment includes: transmitting, to a base station, a Radio Resource Control (RRC) connection reestablishment request message for requesting RRC connection reestablishment; receiving an RRC connection reestablishment response message transmitted by the base station as a response to the RRC connection reestablishment request message; when the RRC connection reestablishment response message indicates that RRC connection reestablishment is performed, a UE RRC layer performs an RRC connection reestablishment operation; and when the RRC connection reestablishment response message is an RRC connection establishment message used to instruct the UE to establish a new RRC connection, the UE RRC layer performs an RRC connection establishment operation, and a UE NAS layer initiates an NAS connection recovery procedure.