Roaming Steering via UDM Policy Decisions for Clear PLMN Selection
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Solution Overview
Problem
Existing 5G telecommunication networks prevent third-party providers from offering Roaming Value Added Services (RVAS) due to encrypted signaling, and standardized 5GS SOR mechanisms lack clarity in procedures and messaging, leading to unclear PLMN selection and potential no-service scenarios for roaming UEs.
Innovation Solution
A Unified Data Management (UDM) node in the Home PLMN obtains SOR information from a Network Exposure Function (NEF) to determine whether to accept or reject a UE's registration attempt, providing guidance with rejection causes and retention timers to steer the UE to suitable VPLMNs, compatible with both 4G and legacy SOR mechanisms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If HPLMN uses encrypted signaling via H-SEPP and V-SEPP in 5G networks, then network security is improved, but third-party providers cannot offer Roaming Value Added Services (RVAS) because signaling interception is prevented
Solution Approach 1:
The patent introduces an intermediary mechanism where the HPLMN provides SOR information to the UE through standardized 3GPP interfaces (N1 NAS signaling via UDM). This intermediary approach allows the HPLMN to maintain encrypted signaling security while still enabling roaming control capabilities that third-party providers can utilize through authorized access to SOR information, thus resolving the contradiction between security and service versatility.
2Reliability
If 3GPP standardized 5GS SOR mechanism is implemented, then roaming control is improved, but procedures and messaging remain unclear leading to potential no-service scenarios
Solution Approach 1:
The patent applies preliminary action by having the HPLMN pre-determine and provide SOR information to the UE before the UE attempts registration with a VPLMN. The UDM generates rejection causes and SOR information in advance based on roaming agreements and network policies, enabling the UE to make informed PLMN selection decisions without encountering unclear procedures or no-service scenarios during actual roaming attempts.
Solution Approach 2:
The patent implements feedback mechanisms where the HPLMN monitors UE roaming status and provides updated SOR information when conditions change. The UDM can update the UE with new SOR information or rejection causes based on current network conditions, roaming agreements, and policy changes, ensuring the UE always has accurate guidance for PLMN selection and preventing no-service scenarios through continuous feedback.
3Reliability
If HPLMN provides SOR information to steer UE to different VPLMN, then roaming service quality is improved, but messaging procedures between PLMN and SOR-AF remain unclear
Solution Approach 1:
The patent applies universality by designing the SOR information delivery mechanism to work across multiple scenarios and interfaces through standardized 3GPP procedures. The UDM can provide SOR information through various messaging paths (registration accept/reject, periodic updates, event-triggered notifications) using common NAS signaling interfaces, eliminating the need for complex proprietary messaging procedures between PLMN and SOR-AF while maintaining versatile roaming service quality.
Data Source
AI summary
A node in a core network (CN) of a Public Land Mobile Network (PLMN) supports steering of roaming (SOR). The node receives (220) an indication of a registration attempt by a roaming UE for which the PLMN operates as a home PLMN (HPLMN), the registration attempt occurring at a visitor PLMN (VPLMN). The node obtains (242, 232), from an entity configured to provide SOR information of the CN, SOR information related to the registration attempt; determines (250), based at least on the received response and an operator policy related to the UE and the VPLMN, whether to accept or reject the registration attempt; and provides (260), to the VPLMN, a result of the determining.