IMS Emergency SMS to PSAPs Through Media-Free SIP Dialogues
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Solution Overview
Problem
Current solutions for sending SMS messages from a UE to a PSAP are not always reliable, may not support UEs in limited service state, have long delays, and are susceptible to spoofing, especially for in-bound roamers.
Innovation Solution
Establish a Session Initiation Protocol (SIP) dialogue with no active SIP media for emergency calls, utilizing the Internet Protocol (IP) Multimedia Subsystem (IMS) for reliable emergency SMS messaging, including IMS Emergency Registration and subsequent voice bearer addition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional SMS transfer methods are used to support legacy mobile devices, then device compatibility is improved, but SMS transfer reliability and PSAP response reliability deteriorate
Solution Approach 1:
The solution segments the emergency communication process into two distinct paths: traditional SMS transfer for legacy devices and SIP dialogue-based messaging for advanced devices. This segmentation allows each path to be optimized independently, with the SIP-based path providing higher reliability for capable devices while maintaining backward compatibility through the traditional path for legacy devices.
Solution Approach 2:
The system implements a universal emergency messaging framework that can handle both traditional SMS and SIP dialogue-based messaging. The PSAP and network infrastructure are designed to support multiple messaging paradigms simultaneously, allowing the system to serve both legacy and advanced devices through a unified architecture that adapts to the capabilities of each device.
2Adaptability or versatility
If traditional SMS transfer methods are used, then legacy device support is maintained, but SMS transfer delay increases
Solution Approach 1:
The system dynamically selects the appropriate messaging path based on device capabilities. Devices that support SIP dialogues utilize this faster path, while legacy devices automatically fall back to the traditional SMS path. This dynamic adaptation allows the system to minimize delay for capable devices without compromising support for legacy devices.
3Device complexity
If traditional SMS transfer methods are used, then network infrastructure requirements are reduced, but support for roaming and limited service state devices deteriorates
Solution Approach 1:
The system performs preliminary capability assessment during the emergency call setup phase. Before attempting SMS transfer, the system determines whether the device supports SIP dialogues and whether the PSAP supports the emergency SMS over IMS feature. This preliminary action allows the system to select the appropriate messaging path in advance, ensuring optimal performance for roaming and limited service state devices without requiring complex real-time decisions.
Data Source
AI summary
Techniques are described for sending an emergency related Short Message Service message (SM) from a user equipment (UE) to a Public Safety Answering Point (PSAP) with higher reliability and security and lower delay than with previous techniques. Following detection of a user input emergency SM, a UE establishes a Session Initiation Protocol (SIP) dialogue with a PSAP, where the SIP dialogue has no active SIP media, which can be compliant with SIP protocol rules. The emergency SM is sent to the PSAP in association with the SIP dialogue, as are any subsequent SMs, and PSAP SM replies are similarly returned to the UE. Media such as voice may be added and previous restrictions on support of UEs that are roaming or in limited service state can be overcome.