4 ms·
Wifi calling sends calls (sent and received) over the Internet as UDP packets. So you can call somebody in your home country using your home country SIM, but th
by lozenge 3y ago
Wifi calling sends calls (sent and received) over the Internet as UDP packets. So you can call somebody in your home country using your home country SIM, but the data is actually using your holiday SIM's data allowance. As roaming and "international" rates are crazy.
- NoZebra120vClip 3y agoJust 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.