Emergency Call Routing via VoIP to E911 Network
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Solution Overview
Problem
Conventional telematics systems face challenges in providing full access to the Enhanced 911 network for emergency calls originating from centralized call centers, as these calls are typically routed through the Public Switched Telephone Network (PSTN) without transmitting callback number and location information to the Public Safety Answering Point (PSAP), leading to inefficiencies and increased costs.
Innovation Solution
Routed emergency calls are converted to Voice Over Internet Protocol (VoIP) and then to Session Initiation Protocol (SIP) packetized IP calls, which are forwarded to an emergency services gateway for conversion back to Time Division Multiplexing (TDM) and routing through a selective router, enabling access to the Enhanced 911 network with accurate caller location and callback number information.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If emergency calls are routed through the PSTN from centralized call centers, then call routing is simplified, but callback number and location information are not transmitted to the PSAP
Solution Approach 1:
A selective router acts as an intermediary device in the PSTN that intercepts emergency calls and injects the necessary callback number and location information into the call stream before forwarding to the PSAP. This mediator resolves the contradiction by enabling full E911 functionality through the PSTN routing path without requiring direct E911 network access from call centers.
2Reliability
If additional PSTN lines are installed to provide E911 access, then callback and location information can be transmitted, but infrastructure costs and system complexity increase
Solution Approach 1:
The selective router is designed to handle multiple functions: it routes emergency calls, injects callback and location information, and interfaces with both the PSTN and E911 networks. This multi-functional device eliminates the need for separate dedicated E911 lines, allowing existing PSTN infrastructure to serve dual purposes while maintaining reliable E911 access.
3Ease of operation
If conventional PSTN routing is used for emergency calls, then call center operations are simplified, but dispatch efficiency and call priority are reduced
Solution Approach 1:
The selective router serves as an intelligent intermediary that enhances PSTN-routed emergency calls by injecting E911 information and prioritizing them appropriately. This allows call centers to maintain simplified operations while the router ensures high-priority handling and efficient dispatch at the network level, resolving the contradiction between operational simplicity and dispatch efficiency.
Data Source
AI summary
An emergency call (e.g., a 911 call, an alarm company call) forwarded by a telematics call center is routed over the switched PSTN to a Voice Over Internet Protocol (VoIP) call server, where the switched call is converted to a session initiating protocol (SIP) packetized IP call for presentation to an emergency services gateway, which reconverts the call to TDM and connects to a selective router via dedicated circuits, gaining full access to the Enhanced 911 network. This provides a PSAP receiving a call from a telematics call center or other call center with all features available in an Enhanced 911 network, e.g., callback number of the 911 caller, and location of the 911 caller. Location of the caller is provided using a VoIP positioning center (VPC).