[DMM] Emergency 911 Services over Wi-Fi

[David Lake <[e-mail]>]

Sri

Thank you for the interesting presentation.

I think we have two problems:


  1.  Network attachment
  2.  E911 calling via the inbuilt dialler

Taking each of these in turn:


  1.  Network attachment.   The solution with a roaming WiFi partner is good but we should also consider the ability to extend the concept of an ‘Emergency Attach’ to LTE/5GNR without the need for credentials (or with well-known credentials). This is made much more complex in the case of incoming roamers where 2G/3G has sunset – for example, if I visit the US now, I can be in a position where I get LTE/5G data service through a roaming partner but no IMS access.   Many international carriers also limit ‘home’ ePDG (‘WiFi Calling’) access.


  1.  No matter how I attach to an IP network, I should be able to access the upper-layer application (which is essentially a SIP dialler) and make a 911 call.   I can’t because the dialler currently relies on IMS registration which then takes me straight back to the issues with IMS access, IMS-to-IMS roaming, non-availability of VoWiFi (via ePDG), etc.  Location SHOULD be available via GPS from the end device or from the IP path of the packets (knowing the location of the attached AP/gNB).


I see 2) as the major issue to solve but I think this is a subset of the wider issue of relying on the 3GPP architecture for a voice applications.   If I use a non-IMS voice application (e.g. WhatsApp, iMessage, second-number services such as Swytch, etc), then as long as I have IP connectivity, I have the ability to make an E911 call (or in fact any other call).   So surely the answer is to decouple the application from the network in some manner such that it doesn’t have to make an IMS registration specifically for E911/112/999 calls but instead uses generic SIP (maybe with default/well-known credentials)?

Best

David Lake

Tel: [phone]
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5G & 6G Innovation Centres
Institute for Communication Systems (ICS)
University of Surrey
Guildford
GU2 7XH