WLAN Emergency Call Number Interworking via Pre-Association Query
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Solution Overview
Problem
Users of wireless local access networks (WLANs) face challenges in accessing emergency call numbers, as these numbers vary by country and local area, making it impractical to store all numbers in terminals or user memory, especially when roaming, and existing solutions require base stations to query external networks for this information.
Innovation Solution
A method where a terminal can request and receive emergency call numbers from a base station before association, with the base station providing pre-configured emergency call numbers without needing to communicate with an external network's distribution system or server, using a specific message format and protocol within the IEEE 802.11 interworking architecture.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If emergency call numbers are stored in terminals or user memory, then immediate emergency calls can be made, but it becomes impractical due to the large number of different call numbers across countries and local areas
Solution Approach 1:
The patent extracts the emergency call number storage function from the terminal device and relocates it to the base station. The terminal only needs to request and receive the call number from the base station when needed, rather than storing all possible call numbers locally. This resolves the contradiction by maintaining emergency call availability while eliminating the need to store large quantities of call numbers in the terminal.
Solution Approach 2:
The base station acts as an intermediary between the terminal and the emergency service information. Instead of the terminal directly storing and managing multiple call numbers, it requests the appropriate call number from the base station, which provides the correct information based on the current network location. This mediator approach resolves the contradiction by providing on-demand access to call numbers without requiring terminal storage.
2Loss of information
If base stations query external networks for emergency call numbers, then accurate local call numbers can be provided, but it increases system complexity and requires external network communication
Solution Approach 1:
The patent applies preliminary action by pre-configuring emergency call numbers in the base station before they are needed. The base station stores emergency call number information in advance, organized by network identifiers, so that when a terminal requests a call number, the base station can immediately provide the correct information without querying external networks. This resolves the contradiction by maintaining information accuracy while reducing system complexity and eliminating the need for real-time external communication.
3Loss of time
If terminals request emergency call numbers before association, then users can obtain call numbers immediately upon connecting to WLAN, but it requires the base station to process requests before association is complete
Solution Approach 1:
The patent enables terminals to request emergency call numbers before association is complete, applying preliminary action by allowing the base station to process and respond to these requests during the association procedure. The base station is designed to handle these pre-association requests by extracting the terminal's identifier from the request frame and providing the appropriate call number before formal association occurs. This resolves the contradiction by eliminating time loss while the base station's ability to process these requests becomes part of its standard operation.
Data Source
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Figure 5~8
AI summary
Provided are an interworking procedure with an external network in a WLAN, a station supporting the interworking procedure, and a message format for the interworking procedure. In the interworking procedure, a non-AP station transmits a request message which includes an advertisement protocol ID set to a value indicating native query protocol and a native query information ID set to a value indicating emergency call number information. And the non-AP station receives from an access point (AP) a response message including zero or more emergency call numbers in response to the request message.