ePDG Selection for Emergency Call Routing via Untrusted WLAN
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Solution Overview
Problem
Conventional ePDG selection methods are inadequate for ensuring emergency calls can be routed to the correct public safety answering point (PSAP) when a user equipment (UE) is roaming, as they often rely on cellular network coverage and fail to prioritize access to PLMNs that do not provide cellular service at the UE's location, leading to potential call failures.
Innovation Solution
A method where the UE is configured with a prioritized list of PLMNs and associated ePDG selection conditions, allowing it to select an appropriate ePDG based on criteria such as country matching, cellular visibility, and attachment status, ensuring emergency calls can be routed correctly even without cellular coverage, by using a DNS query to obtain the ePDG's IP address and establishing a secure connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ePDG selection methods rely on cellular network coverage, then cellular network access is maintained, but emergency call routing fails when cellular coverage is unavailable at the UE's location
Solution Approach 1:
The ePDG selection mechanism dynamically adapts between cellular and WLAN access methods based on real-time network availability. The system transitions from static cellular-only selection to dynamic multi-access selection, enabling the UE to choose WLAN-based ePDG access when cellular coverage is unavailable, thus maintaining emergency call reliability while improving adaptability to different network conditions
Solution Approach 2:
The patent introduces WLAN as an intermediary access path to reach the ePDG when direct cellular access is unavailable. The UE can establish a WLAN connection to the ePDG through untrusted WLAN access points, using the ePDG as a mediator to provide packet transport and authentication, enabling emergency calls to be routed correctly even without cellular coverage
2Reliability
If the UE prioritizes access to PLMNs providing cellular service, then cellular connectivity is maintained, but access to PLMNs without cellular coverage is delayed or failed
Solution Approach 1:
The system performs preliminary evaluation of multiple PLMNs and their associated access methods (cellular and WLAN) before actual access is needed. The UE pre-configures a list of PLMNs with both cellular and WLAN access capabilities, and pre-establishes selection criteria that prioritize based on both cellular availability and WLAN accessibility, enabling rapid access when emergency calls are initiated without requiring real-time exploration of access options
3Adaptability or versatility
If the UE uses WLAN access to reach ePDG when cellular coverage is unavailable, then access to cellular network services is enabled, but the complexity of selection criteria increases
Solution Approach 1:
The patent segments the ePDG selection process into distinct evaluation stages: first evaluating cellular availability for each PLMN, then evaluating WLAN accessibility as an alternative path, and finally applying selection criteria to choose the optimal PLMN-access method combination. This segmented approach breaks down the complex multi-factor selection into manageable sequential steps, reducing overall system complexity while maintaining comprehensive evaluation of all access options
Data Source
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AI summary
In aspects of the disclosure, a method, an apparatus, and a computer program product for wireless communication by a user equipment (UE) are provided. In one aspect, the UE associates with an access point of a wireless local area network which may be untrusted, obtains a list comprising a plurality of public land mobile network (PLMN) entries and one or more selection conditions associated with each one of the plurality of PLMN entries, and selects a PLMN from the list when the one or more selection conditions associated with the PLMN are satisfied. The UE may further discover an evolved packet data gateway (ePDG) for the selected PLMN using one or more fully qualified domain name (FQDN) rules for the selected PLMN. The UE may then attach to the selected PLMN using the discovered ePDG.