Emergency Service Routing Proxy for IMS Emergency Call Trunk Reduction
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Solution Overview
Problem
The existing IMS-based emergency call routing systems require setting up thousands of direct trunks to legacy SRs, which is expensive and inefficient, especially before all PSAPs are compatible with IP networks.
Innovation Solution
The system routes IMS-based emergency calls to either legacy PSAPs or IP PSAPs based on their capabilities, using a conversion of legacy MSCs to TrFO MSCs that enable emergency calls to be routed without dedicated trunks, thereby reducing the need for direct trunks and lowering maintenance costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If direct trunks are set up from IMS media gateways to legacy SRs to support emergency calls, then emergency call routing reliability is improved, but device complexity and installation cost increase significantly
Solution Approach 1:
The patent introduces an ESRP (Emergency Service Routing Proxy) as an intermediary component that receives emergency call requests from the IMS network and routes them to legacy PSAPs. This mediator eliminates the need for direct trunks between IMS media gateways and legacy SRs, reducing complexity while maintaining routing reliability. The ESRP acts as a bridge between the IP-based IMS network and the legacy telephony network.
2Adaptability or versatility
If thousands of direct trunks are installed to support IMS-based emergency calls to legacy SRs, then emergency service coverage is improved, but maintenance cost and operational expense increase
Solution Approach 1:
The ESRP is designed as a universal routing platform that can handle multiple emergency call routing scenarios: routing to legacy PSAPs via SIP trunking, routing to IP-based PSAPs, and interfacing with location services. This multi-functional design allows a single system to replace thousands of dedicated direct trunks, reducing maintenance costs while maintaining comprehensive emergency service coverage.
3Reliability
If direct trunks are used to connect IMS media gateways to legacy SRs, then emergency call delivery is improved, but installation cost and setup time increase
Solution Approach 1:
The patent replaces the physical mechanical infrastructure of direct trunks (copper wires, dedicated physical connections) with an IP-based signaling system. The ESRP uses SIP (Session Initiation Protocol) over IP networks to establish and manage emergency call routes, substituting physical direct connections with virtual IP-based routing, thereby reducing installation cost and complexity while maintaining delivery reliability.
Data Source
AI summary
A device receives an emergency call invite generated by a user device associated with an Internet protocol (IP) multimedia subsystem (IMS) media gateway, and forwards the emergency call invite to a location resource function/route determination function (LRF/RDF) device for determining public safety answering point (PSAP) routing information. The device receives, from the LRF/RDF device, the PSAP routing information based on the emergency call invite, and routes the emergency call invite to a particular PSAP based on the PSAP routing information. If the emergency call invite is routed to a legacy PSAP, the emergency call is routed to the legacy PSAP via legacy mobile switching center (MSC) direct trunks. If the emergency call invite is routed to an IP PSAP, the emergency call is routed to the IP PSAP via an IP connection.