I’m curious about how this works, can you link me someplace where I can read more about it? I tried searching for “cellular over wifi” but wasn’t about to find anything promising.
EDIT: I searched harder and found “VoWiFi”. It looks like this can support SMS and is supported by iOS. TIL.
For someone more curious, I tried to learn more about this tech, and this [1] is the best resource I found about someone explaining how it works.
Essentially VoWifi connects to your ISP via a IPSec VPN using secrets derived using your sim card as a smart card, then connects to a internal SIP server and voila.
I spent a lot of time trying to connect to the IPSec server from a computer, but couldn't figure out how to get the challenge solved by my sim. Gosh I wish I could make normal calls from my computer.
EDIT: I searched harder and found “VoWiFi”. It looks like this can support SMS and is supported by iOS. TIL.