UE Network Selection Using RAN Assistance and ANDSF Policies
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Solution Overview
Problem
In the context of 3GPP LTE/SAE technology, there is a challenge in network selection and traffic routing when a user equipment (UE) roams between different public land mobile networks (PLMNs), as it is unclear which policy information to preferentially use from the home ANDSF and visited ANDSF, leading to confusion in applying RAN assistance information and ANDSF policies for network selection and traffic routing.
Innovation Solution
A method where the UE determines its roaming state and applies either the RAN assistance information or ANDSF policy based on flags indicating preference, with specific configurations for home and visited networks to prioritize either RAN rules or ANDSF policies, ensuring consistent network selection and traffic routing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the UE receives RAN assistance information from both home PLMN and visited PLMN, then the UE has multiple policy options for network selection, but it becomes unclear which policy information to preferentially use
Solution Approach 1:
The patent applies local quality by making the policy application behavior context-dependent on the roaming state. When the UE is in its home PLMN, it applies RAN assistance information from home; when roaming in a visited PLMN, it applies RAN assistance information from the visited network. This localized approach resolves the contradiction by providing clear, context-specific policy application rules rather than requiring complex global decision-making logic.
Solution Approach 2:
The patent inverts the traditional approach by using the roaming state determination as the primary decision criterion rather than trying to prioritize between multiple policy sources. Instead of asking 'which policy should I prefer?', the system asks 'am I roaming or at home?', and the answer automatically determines which policy source to use, simplifying the decision logic.
2Adaptability or versatility
If the UE applies RAN assistance information without clear preference rules, then network selection can be flexible, but traffic routing becomes ambiguous during roaming
Solution Approach 1:
The patent applies preliminary action by determining the roaming state before applying RAN assistance information for traffic routing. The UE proactively checks whether it is in home or visited PLMN and stores this state information, which then guides the subsequent policy application. This preliminary determination ensures that the correct RAN assistance information is applied, eliminating ambiguity in traffic routing while maintaining flexibility in network selection.
3Adaptability or versatility
If the UE uses multiple policy sources simultaneously, then more network options are available, but the policy application process becomes confused
Solution Approach 1:
The patent extracts the roaming state determination as a separate, independent function that precedes policy application. By taking out the context determination step and making it the foundation for subsequent decisions, the system maintains access to multiple network options through different policy sources while simplifying the actual policy application process to a straightforward lookup based on the pre-determined roaming state.
Data Source
AI summary
A method is provided for performing network selection and traffic routing. A user equipment (UE) receives an Access Network Discovery and Selection Function (ANDSF) rule including an Inter-System Routing Policy (ISRP) rule or an Inter-Access Point Name (Inter-APN) Routing Policy (IARP) rule. The UE receives, from a base station, radio access network (RAN) assistance information. The RAN assistance information received from the base station is used to evaluate the ISRP rule or the IARP rule of the ANDSF rule. The UE evaluates whether the ISRP rule or the IARP rule of the ANDSF rule is valid or not by using the RAN assistance information. The UE selects one of the RAN assistance information and the ANDSF rule including the ISRP rule or the IARP rule.