Guard Timer Optimizes E911 Call Handling
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Solution Overview
Problem
Current enhanced 911 (e911) systems prevent users from receiving calls while on an emergency call, leading to potential distractions and inefficiencies, such as delayed responses to resolving emergencies, as all calls are automatically rejected or sent to voicemail without notification.
Innovation Solution
Implementing a guard timer system that allows call-waiting for recently dialed numbers during or after an e911 call, using retroactive and proactive timers to differentiate between important and non-essential calls, enabling users to receive critical calls from, for example, public safety answering points or familiar individuals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all calls are automatically rejected during e911 calls, then user distraction is prevented, but important calls from relevant parties cannot be received
Solution Approach 1:
The system applies different call handling rules to different callers based on their relationship to the emergency situation. Calls from recently dialed numbers (potential PSAPs or relevant parties) are treated differently from other calls, allowing selective reception of important calls while maintaining block for unrelated calls
Solution Approach 2:
The system proactively identifies and flags calls from recently dialed numbers before the e911 call begins. By pre-populating a list of potentially important callers based on recent dialing activity, the system prepares to allow these specific calls through while blocking others, resolving the contradiction between reliability and adaptability
2Reliability
If call-waiting is disabled during e911 calls, then emergency service focus is maintained, but response time to resolve emergencies may increase
Solution Approach 1:
The system dynamically changes the call-waiting parameter from completely disabled to selectively enabled based on caller identity. By modifying this parameter conditionally rather than absolutely, the system maintains emergency service focus for most calls while allowing critical updates from PSAPs or relevant parties to through, thereby reducing emergency resolution time without compromising focus
3Reliability
If all incoming calls are sent to voicemail, then user attention remains on emergency call, but critical information may be lost
Solution Approach 1:
The system provides feedback to the user about incoming calls from recently dialed numbers, allowing them to decide whether to answer. This feedback mechanism ensures that critical information from PSAPs or relevant parties is not lost to voicemail, while maintaining emergency call attention by requiring active user decision for non-routine calls
Data Source
AI summary
Systems and methods for optimized call handling during e911 calls. Normally, when a user equipment (UE) is connected to a public safety answering point (PSAP)—e.g., is on a 911 call—all incoming calls are automatically routed to voicemail. In contrast, the systems and methods disclosed herein enable calls that were dialed within a predetermined time window of the 911 call to be sent through to call-waiting to enable the user to accept or reject the call. The system can use a “guard timer” to determine whether a call is within the predetermined time window. The system can include a single guard timer for all incoming calls—e.g., “any call made from the UE within the previous X minutes prior to the 911 call.” The system can also include individual guard timers for each call that expire separately relative to the call's proximity to the 911 call.