Emergency Call Routing in Roaming IMS Networks
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Solution Overview
Problem
In the IP Multimedia Subsystem (IMS), emergency calls made while roaming may not be routed to the appropriate public safety communications systems in a timely manner, leading to delays and high call drop rates due to non-detection of emergency calls.
Innovation Solution
A communications apparatus and method that transmit a normal call-establishment signal with a remote identifier to a network, record the identifier as an emergency call when indicated, and subsequently initiate an emergency call when the same identifier is recognized as an emergency call address, ensuring proper routing of emergency calls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a user equipment transmits a normal call-establishment signal when roaming, then the call can be initiated, but the emergency call may not be routed to the appropriate public safety system in a timely manner
Solution Approach 1:
The user equipment performs preliminary detection of whether the current network supports emergency calls before initiating the call setup. This preliminary action allows the device to prepare the appropriate call-establishment signal (normal or emergency) in advance, ensuring that when an emergency call is made, the correct routing procedure is already in place, thus resolving the contradiction between reliable routing and fast setup time
Solution Approach 2:
The system implements feedback mechanisms where the network responds to call-establishment signals with indication messages that confirm whether the call is being routed as a normal or emergency call. This feedback loop allows the user equipment to detect and correct routing issues in real-time, ensuring that emergency calls are properly routed while maintaining efficient call setup procedures
2Reliability
If the user equipment detects emergency calls correctly, then emergency calls are routed accurately, but the complexity of call processing increases
Solution Approach 1:
The detection and processing mechanisms are applied selectively based on local conditions - specifically, the user equipment only performs enhanced emergency call detection and uses different call-establishment signals when roaming in networks where emergency call support is uncertain. In networks where emergency call support is confirmed, the device uses normal call processing procedures. This localized application of complex detection logic reduces overall system complexity while maintaining high detection accuracy where needed
Solution Approach 2:
The system changes processing parameters dynamically based on the calling context. The key parameter change is the selection between normal call-establishment signals and emergency call-establishment signals, along with corresponding detection enablement. By changing these parameters based on whether the device is roaming and the detected network capabilities, the system achieves accurate emergency call detection without permanently increasing processing complexity for all calls
Data Source
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AI summary
A communications apparatus includes a baseband signal processing device, an RF signal processing device, a memory device, and a processor. The processor transmits a normal call-establishment signal with a remote identifier to a network to originate a normal call in response to a first call-origination request with the remote identifier, receives an indication message indicating that the normal call is routed as an emergency call from the network, records the remote identifier in the memory device, and when receiving a second call-origination request with the remote identifier, transmits an emergency call-establishment signal with the remote identifier to the network to originate an emergency call in response to the second call-origination request.