Roaming PLMN Selection Using Stored S-NSSAI Support Lists
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Solution Overview
Problem
When a user equipment (UE) roams away from its home public land mobile network (PLMN), it faces challenges in selecting and registering with a visited PLMN that supports the desired network slice, leading to time- and power-consuming redundant registration attempts due to lack of awareness about which PLMNs support the required S-NSSAI.
Innovation Solution
The UE is provided with an enhanced mechanism to access a stored list of PLMNs that support the desired S-NSSAI through a Home-NSSF maintaining a roaming agreement structure, which includes a validity timer and country-specific PLMN lists, enabling informed selection and reducing redundant registration attempts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE repeatedly attempts registration with different PLMNs to discover slice-supporting networks, then the UE can eventually find a suitable PLMN, but the process becomes time-consuming and power-consuming
Solution Approach 1:
The Home-NSSF maintains a pre-computed roaming agreement structure that identifies which PLMNs support which S-NSSAIs before the UE needs to roam. This preliminary information is stored and can be quickly retrieved when the UE needs to select a PLMN, eliminating the need for repeated trial registrations.
Solution Approach 2:
The roaming agreement structure acts as an intermediary information source between the home network and the UE. It provides the UE with pre-processed knowledge about PLMN-slice compatibility, allowing the UE to make informed selections without direct trial-and-error interactions with multiple PLMNs.
2Reliability
If the UE repeatedly attempts registration with different PLMNs to discover slice-supporting networks, then the UE can eventually find a suitable PLMN, but power consumption increases
Solution Approach 1:
The roaming agreement structure is pre-computed and stored in the UE, containing information about which PLMNs support which S-NSSAIs. When the UE needs to roam, it can quickly query this stored information and select an appropriate PLMN without consuming excessive power on repeated registration attempts.
Solution Approach 2:
The stored roaming agreement structure serves as an intermediary that provides the UE with pre-processed slice-support information. This allows the UE to make informed PLMN selections based on stored data rather than through power-intensive trial registrations with multiple networks.
3Ease of operation
If the UE selects PLMNs without awareness of S-NSSAI support, then PLMN selection is simpler, but redundant registration attempts occur
Solution Approach 1:
The roaming agreement structure pre-identifies which PLMNs support which S-NSSAIs and stores this information in the UE. This allows the UE to select PLMNs with awareness of slice support, improving registration success rate while keeping the selection process relatively simple through structured data lookup.
Solution Approach 2:
The roaming agreement structure acts as an intermediary information layer between the UE and PLMN selection process. It provides structured, pre-processed information about slice support that enables the UE to make informed selections without complex real-time probing, thus improving productivity while maintaining ease of operation.
Data Source
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AI summary
A user equipment (UE) may receive a list of Public Land Mobile Networks (PLMNs) that support a given network slice in a given country, different from a home country of a home PLMN of the UE. When roaming in the given country, UE may access a PLMN of the list if the given network slice is desired. The list may be provided by the home PLMN: while the UE is in the home country; or via a visited PLMN while the UE is in the given country. The list may be received in response to a UE-initiated request, or pushed to the UE by the home PLMN. A validity timer period received with the list may indicate a duration of validity of the list. In an alternative scenario, the UE may receive the list from an entitlement server, e.g., one belonging to a visited PLMN.