Comment by secondcoming
3 days ago
> Many carriers only permit VoLTE and VoWiFi on devices they sell or have officially tested.
Does this happen even if you are using a carrier's SIM card; it's just because you didn't buy the hardware from them?
It's not just an IMEI-level block so data still works?
No, this is not really tied to whom you purchased the Pixel from. But it is tied to which carriers would sell you a Pixel at all. Meaning they have some sort of an agreement with Google and Google added configuration files whitelisting these features for the carrier in question.
(At least for many EU based carriers.)
VoLTE was an afterthought and carriers don't trust untested vanilla implementations. So they only allow known-good phones.
Ok, but why block VoWiFi?
From what (little) I understand, VoLTE and VoWiFi are quite similar under the hood—VoLTE is more or less SIP, and VoWiFi is that same SIP over IPsec. You see how this would be an interoperability nightmare (not that I’m excusing the telecom people for getting us into this mess). Furthermore, some carriers get testy about you avoiding roaming charges by using VoWiFi (while others actually encourage it).
That still uses their infrastructure at some point, as you are still using your carrier's phone number when you make a VoWiFi call.
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