Hello Experts.
In Outdoor FWA CPE use case, how does a voice call will be supported?
Does it work as Vo-WiFi? I don’t think so, as the backhaul will be NR only not fiber nw.
I think Vo-Wifi is configured on Core side & of course UE capability.
So no matter the transport is 4G, 5G, or Optic, Vo-Wifi still can running on.
But which part of Core?
May be core expert may explain better 
Vo-Wifi works over Internet.
If UE has internet connection over WiFi.
A secure tunnel is setup between EPDG and UE over internet
There is a separate NE deployed for it, called EPDG.
That is anchor between WiFi and IMS.
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Really?
Has a different NE to be deployed?
I thought it will have same principle as VoLTE and VoNR.
EPDG is for voWIFI
Let me show you with a flow:
This one will better help you understand…
Switch between voWIFI anf VoLTE.
Nodes after (right side of) PGW remain the same.
Nodes on left side are changed.
It all depends on whether your network that you are connected to (irrespective of whether it is wireless or fixed network), if it has accessibility till ePDG, it will work on ViWIFI.
If you go into details , if you have VoWIFi switch enabled, an FQDN will be sent to your connected network DNS. If that DNS or the Global DNS has routing for that FQDN, accessibility till ePDG will be there and you can establish a call based on service subscription
Thank you all, nice discussion.
Ahhhaa… understand now! Great!
Yes, true.
We do require a separate node ePDG for VoWiFi and IMS interconnected.
Because one is non 3Gpp network (WiFI) and another is 3GPP standard (NR).
So the authentication is done with the help of SIM and the Voice will support over the WiFi network.
Therefore for authencation AAA node was standardised for voWiFi solution.
Yes.
Now if we check the FWA CPE connection at indoor the mobile handset is connected through WiFI.
But the network is ultimately remain 3GPP standard.
Hence I don’t think VoWiFi will be a requirement in this case…
Does someone have end to end trace from UE to ePDG?
UE and ePDG create ipsec tunnel which goes through two phases of ike.
You will need traces and keys which you can import in Wireshark to check traces.