Network Slice Registration via Back-Off Timer
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Solution Overview
Problem
In the context of 5G network slicing, it is unclear how to effectively communicate network slice congestion to user equipment (UE) that does not support extended rejected S-NSSAI, and how to estimate a suitable back-off timer for when congested network slices will be accessible, leading to potential unnecessary signaling and registration denials.
Innovation Solution
The introduction of the Extended Rejected Network Slice Selection Assistance Information (ER-NSSAI) with a back-off timer allows the network to inform UE when congested network slices will be available for registration, enabling UE to retry connections once the congestion is resolved, and the use of a 5GMM capability IE to indicate support for ER-NSSAI.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the network sends registration rejection messages to UE without providing back-off timer information, then simple rejection is achieved, but unnecessary signaling and registration attempts occur
Solution Approach 1:
The network performs preliminary action by estimating the back-off timer duration before sending the rejection message. The AMF calculates an estimated time when the congested network slice will be available and includes this information in the rejection message, allowing the UE to wait appropriately rather than attempting immediate reconnection.
Solution Approach 2:
The estimated back-off timer acts as an intermediary information element that mediates between the network's congestion state and the UE's registration behavior. This intermediate information allows the UE to make informed decisions about when to retry registration without continuous network signaling.
2Measurement precision
If the network provides detailed congestion information to all UE, then accurate back-off timing is achieved, but device complexity increases for UE that do not support extended rejected S-NSSAI
Solution Approach 1:
The solution applies local quality by providing detailed congestion information (estimated back-off timer) only to UE that support extended rejected S-NSSAI, while maintaining simple rejection for legacy UE. The network identifies UE capability and tailors the rejection message content accordingly, avoiding unnecessary complexity for devices that don't require detailed information.
Solution Approach 2:
The network changes the parameter of rejection message content based on UE capability. For advanced UE, the message includes estimated back-off timer and slice availability information; for legacy UE, it contains only basic rejection. This parameter adaptation resolves the contradiction between providing accurate information and maintaining device simplicity.
Data Source
AI summary
Apparatuses, methods, and systems are disclosed for registering to a congested network slice. One method includes receiving a registration request from a communication device to register to a network slice subject to NSAC and determining that registration to the network slice is rejected for NSAC. The method includes initiating a timer in response to determining that the registration to the network slice is rejected and sending, to the communication device, an update message in response to expiry of the timer, the update message including an indication that the communication device is permitted to register to the network slice.