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Just to clarify: WiFi calling uses an 802.11 connection nearby, instead of a cell tower, and sends UDP packets over the WiFi network. (I don't know how far the
by NoZebra120vClip 3y ago
Just to clarify:
WiFi calling uses an 802.11 connection nearby, instead of a cell tower, and sends UDP packets over the WiFi network. (I don't know how far they transit the Internet; I assumed that they went to your mobile provider and entered the PSTN there.)
https://en.wikipedia.org/wiki/Generic_Access_Network https://en.wikipedia.org/wiki/Generic_Access_Network
In this scenario, your "home country SIM" is providing you a phone number and provider's authorization to activate and use WiFi calling, but your voice calls aren't actually using the SIM or a cell tower.
Neither is your "holiday SIM" using data for this call: you're free to use that data allowance for browsing, streaming, general Internet use; it won't be taken up by phone calls.
- fatfingerd 3y agoIt's not really just WIFI calling. A data network and a WiFi network are all the same to a UDP packet and your phone can have settings to prefer one or the other so that you can use the data plan you want as if the WIFI were setup.
- hx833001 3y agoYeah, an iPhone will use a secondary esim data connection to route “wifi” calls while abroad.