VPLMN Selection via S-NSSAI Steering of Roaming
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Solution Overview
Problem
Existing systems fail to effectively provide network slice-based Visited Public Land Mobile Network (VPLMN) selection and reselection for wireless transmit receive units (WTRUs) while roaming, as they lack information on available network slices in neighboring cells, leading to inefficient service access and potential rejection of essential network slices.
Innovation Solution
Implementing a Steering of Roaming (SoR) procedure to convey Single Network Slice Selection Assistance Information (S-NSSAI) associated with VPLMNs and access technologies, allowing WTRUs to determine unavailable slices and request alternative VPLMNs through deregistration procedures, utilizing the SOR-AF to generate slice-aware information for informed reselection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a WTRU roams to a VPLMN without network slice availability information, then the WTRU can access the visited network, but the WTRU cannot identify unavailable network slices and may fail to access essential services
Solution Approach 1:
The system performs preliminary actions by obtaining network slice availability information (S-NSSAI) for VPLMNs before the WTRU actually needs to access them. The AMF retrieves and stores this information in advance, so when the WTRU needs to roam or access services, the slice availability data is already prepared and can be immediately provided to the WTRU through registration accept messages or system information broadcasts, preventing service access failures.
Solution Approach 2:
The AMF acts as an intermediary between the NSSF (which has network slice information) and the WTRU (which needs slice information). The AMF obtains S-NSSAI information from the NSSF and then provides it to the WTRU during registration or through system information, mediating the information flow so that WTRUs can access slice availability data without directly interfacing with the NSSF.
2Adaptability or versatility
If the WTRU requests network slice information during roaming, then the WTRU can make informed VPLMN selection, but additional signaling overhead and processing time are required
Solution Approach 1:
The system performs preliminary actions by obtaining network slice availability information (S-NSSAI) for VPLMNs before the WTRU actually needs to access them. The AMF retrieves and stores this information in advance, so when the WTRU needs to roam or access services, the slice availability data is already prepared and can be immediately provided to the WTRU through registration accept messages or system information broadcasts, preventing service access failures.
Solution Approach 2:
The network slice availability information mechanism serves multiple functions: it enables informed VPLMN selection, supports network slice-based cell reselection, provides steering of roaming information, and facilitates service continuity. By creating a universal information framework that serves multiple purposes, the system reduces the need for separate information exchange procedures for each function.
3Measurement precision
If the system provides detailed S-NSSAI information for multiple VPLMNs, then the WTRU can accurately select appropriate networks, but the information complexity and message size increase
Solution Approach 1:
The system segments network slice information by organizing S-NSSAIs according to specific VPLMNs rather than providing a single unified list. Each VPLMN's supported slices are identified separately, allowing the WTRU to process information in manageable segments corresponding to individual networks, reducing overall processing complexity while maintaining selection accuracy.
Solution Approach 2:
The system applies local quality by providing differentiated S-NSSAI information tailored to each specific VPLMN rather than uniform information for all networks. Each VPLMN receives or is associated with the specific slice information relevant to it, allowing the WTRU to make precise local decisions about which VPLMN to select based on its specific service requirements.
Data Source
AI summary
In an embodiment, a wireless transmit receive unit (WTRU) includes a processor configured to receive configuration information that includes information related to S-NSSAI support for each visited public land mobile network (VPLMN) of a plurality of VPLMNs, to receive a message indicating that an S-NSSAI is not available on a current VPLMN, and to send a request message including an indication that the S-NSSAI is not available in the current VPLMN, the request message being one of a deregistration message and a registration request message based on the configuration information.