USSD-Based E911 Test Call Redirecting
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Solution Overview
Problem
Testing enhanced 911 (E911) calls on mobile devices diverts resources away from actual emergencies, as real PSAPs handle false test calls, potentially blocking or delaying assistance to true emergencies.
Innovation Solution
Implementing a system that uses custom unstructured supplementary service data (USSD) codes to redirect E911 test calls to an answering system instead of a public safety access point (PSAP), ensuring mobile devices are correctly tested without occupying emergency dispatch resources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If test E911 calls are connected to real PSAPs, then E911 functionality can be tested, but PSAP resources are diverted and emergency response is delayed
Solution Approach 1:
The patent introduces a redirect server as an intermediary component that sits between the mobile device and the PSAP. When a test E911 call is detected (through USSD codes or other identifiers), the redirect server intercepts the call and redirects it to an answering system instead of allowing it to reach the PSAP. This mediator approach enables testing to occur while preventing test calls from consuming PSAP resources, thus resolving the contradiction between testing reliability and emergency response time.
2Productivity
If test E911 calls are redirected to an answering system, then PSAP resources are preserved, but testing verification becomes more complex
Solution Approach 1:
The patent segments the E911 call handling system into distinct functional components: the redirect server that intercepts and redirects calls, the answering system that handles test calls, and the PSAP that handles real emergencies. This segmentation allows each component to have a specialized function, simplifying the overall system architecture despite the added redirection capability. The redirect server uses simple identification mechanisms (USSD codes) to determine whether to redirect, keeping the decision logic straightforward.
3Extent of automation
If USSD codes are used to identify test calls, then automatic redirection is enabled, but risk of false redirection increases
Solution Approach 1:
The patent applies local quality by making the redirection behavior specific to certain call types and identifiers rather than applying it universally. The redirect server examines specific characteristics of incoming E911 calls (such as presence of particular USSD codes or identifier patterns) and applies redirection only to those matching test call criteria. This localized approach to redirection based on specific call properties ensures that only test calls are redirected while real emergencies maintain their normal routing path, thus preserving routing accuracy.
Data Source
AI summary
To reduce the likelihood that test E911 calls will be improperly connected to a public safety access point (PSAP), while ensuring that mobile devices sold to consumers are correctly routed to a PSAP in an emergency, a system for automatically redirecting test E911 calls to an answering system is disclosed. An unstructured supplementary service data (USSD) node receives a first USSD message from a mobile device during E911 testing procedure at the mobile device. In response to identifying a first code in the first USSD message, the USSD node retrieves an identifier associated with the mobile device. The USSD node sends an instruction to a gateway mobile location center (GMLC) system to redirect E911 calls from the mobile device based on the retrieved identifier such that a subsequent E911 call placed by the mobile device is automatically rerouted by the GMLC to an answering line instead of a PSAP.