Guard Timer for NAS Signaling Connection Release in MUSIM UEs
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Solution Overview
Problem
User equipment (UE) supporting multiple universal subscriber identity modules (MUSIM) faces challenges in releasing NAS signaling connections efficiently, leading to prolonged occupation of radio resources when switching between USIMs, especially when more important activities require resource allocation on a second USIM.
Innovation Solution
Implementing a guard timer mechanism that allows the UE to locally release the NAS signaling connection upon expiry after receiving a confirmation message from the network, ensuring timely release of resources and enabling smoother switching between USIMs for more critical activities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE waits for network confirmation to release NAS signaling connection, then connection release reliability is improved, but resource occupation time increases
Solution Approach 1:
The UE performs preliminary action by starting a guard timer upon receiving the accept message, preparing for potential connection release before the network's explicit release indication arrives. This preliminary timer mechanism ensures that the UE proactively manages resource release timing rather than passively waiting for network confirmation.
Solution Approach 2:
The guard timer acts as an intermediary mechanism between the network's accept message and the actual connection release. It mediates the timing discrepancy by providing a structured waiting period with automatic expiry handling, bridging the gap between network resource allocation confirmation and actual resource release execution.
2Loss of time
If the UE releases radio resources immediately upon sending release request, then resource occupation time is reduced, but connection release reliability deteriorates
Solution Approach 1:
The UE sends the release request message as a preliminary action to initiate the release process, but does not immediately release resources. Instead, it starts a guard timer to wait for network confirmation or timeout, ensuring that resource release only occurs after proper protocol sequencing is completed or the network fails to respond.
Solution Approach 2:
The guard timer provides a cushioning mechanism that prevents premature resource release. It creates a protective waiting period that cushions against potential network issues or protocol sequencing problems, ensuring reliable connection release while still enabling timely resource recovery if the network responds normally.
3Reliability
If the UE maintains NAS signaling connection for extended period, then connection reliability is improved, but hardware resource availability for second USIM deteriorates
Solution Approach 1:
The connection management becomes dynamic through the guard timer mechanism. The UE can adaptively release the NAS signaling connection after a predetermined time period, allowing the system to transition from a static maintained connection state to a dynamic state where resources can be reallocated to the second USIM when needed, while still maintaining connection reliability during the active period.
Solution Approach 2:
The guard timer introduces a periodic time-based action for connection management. The UE periodically evaluates whether to maintain or release the connection based on timer expiry, enabling rhythmic resource allocation patterns that balance connection reliability with hardware resource availability for multiple USIMs.
Data Source
AI summary
A method of handling NAS signaling connection release using guard timers for UE supporting MUSIM in an EPS/5GS network is proposed. When a UE establishes a NAS signaling connection over a first USIM, the UE may need to switch a second USIM due to more important activities on the second USIM. If both the UE and the network support the feature of releasing the NAS signalling connection or rejection of paging, the UE can set a Request type to “NAS Signaling connection release” or “Rejection of paging” in a request message. In order to guarantee the release of the NAS signaling connection over the first USIM, the UE can start a guard timer upon receiving an accept message from the network. The UE can locally release the NAS signaling connection upon timer expiry to improve service on the second USIM.