Emergency Call PLMN Selection for Caller Number Retrieval
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Solution Overview
Problem
Emergency call centers struggle to obtain the phone number of a user when the user's SIM card is not from their home network or an equivalent network, leading to hindered rescue operations.
Innovation Solution
The user terminal determines if the available PLMNs include the home PLMN or equivalent PLMNs and prioritizes these networks for emergency calls, ensuring the core network has subscription information to facilitate successful phone number retrieval by the emergency call center.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the user terminal selects a communication path through a PLMN that is not the home network or equivalent network, then the emergency call can be made through any available network, but the emergency call center cannot obtain the user's phone number
Solution Approach 1:
The user terminal performs preliminary identification of the home PLMN or equivalent PLMN before making the emergency call. By checking the PLMN list against stored home PLMN information in advance, the terminal ensures that the call is routed through a network that has the user's subscription information, thereby preventing loss of phone number data while still allowing emergency calls through any available network.
Solution Approach 2:
The patent introduces an intermediary mechanism where the user terminal acts as a mediator between the emergency caller and the emergency call center. The terminal identifies and selects the appropriate PLMN (home or equivalent) as an intermediary network that possesses the user's subscription information, ensuring that the emergency call center can obtain the phone number while still utilizing available network infrastructure.
2Loss of information
If the user terminal always selects the home PLMN for emergency calls, then the emergency call center can obtain the user's phone number, but the emergency call may fail when the home network is unavailable
Solution Approach 1:
The patent implements a dynamic PLMN selection mechanism where the user terminal adaptively chooses between home PLMN, equivalent PLMN, and other available PLMNs based on real-time network availability. The terminal first attempts to use home or equivalent PLMN to ensure phone number transmission, but dynamically switches to other available PLMNs if the home network is unavailable, thereby maintaining both information integrity and call availability.
Solution Approach 2:
The user terminal performs preliminary identification of equivalent PLMNs and their hierarchy before emergency calls. By pre-storing home PLMN and equivalent PLMN information, the terminal can quickly determine the optimal call path when emergency calls are initiated, ensuring both phone number transmission and call success based on current network conditions.
3Loss of information
If the user terminal searches for and identifies home PLMN or equivalent PLMN before emergency calls, then the emergency call center can successfully obtain the user's phone number, but the call setup time increases
Solution Approach 1:
The user terminal performs the PLMN identification and selection process in advance, storing home PLMN and equivalent PLMN information before emergency calls are needed. When an emergency call is initiated, the terminal can immediately select from pre-identified suitable networks without performing time-consuming searches during the critical emergency call setup phase, thereby minimizing call setup time while ensuring phone number transmission.
Data Source
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AI summary
Embodiments of the present invention disclose an emergency call method and a user terminal. The method includes: obtaining an HPLMN and an EHPLMN from a subscriber identification module SIM card of a user terminal; receiving an emergency call operation of a user; receiving, in response to the emergency call operation of the user, a public land mobile network PLMN list that is broadcast by an access network device, where the access network device is an access network device in a multi-operator core network MOCN, and the PLMN list includes a plurality of PLMNs that share the access network device; when the PLMN list includes the HPLMN or the EHPLMN, determining that the HPLMN or the EHPLMN in the PLMN list is an optimal PLMN; and making an emergency call through a core network of the optimal PLMN. According to the method described in the first aspect, an emergency call center can successfully obtain a phone number of the user terminal.