iPhone 7/Plus iPhone 7 GSM (A1778) chipset questions - why doesn't it support VoLTE only for VZ?

[acadiel]

I tried posting this arch/engineering question over on Reddit /r/apple and it got removed as a 'tech support' question. (Tech support is asking for help - this is asking for datasheets, chipset, and other engineering answers.)

So anyway, from my understanding, what makes the A1778 model different than the A1660 is that it used an Intel XMM7360 modem, not a Qualcomm modem. The only thing is lack of CDMA. The LTE bands are similiar.

So, if this both Qualcomm and Intel XMM7360 7's support VoLTE and support the LTE bands of carriers like Verizon, Visible, etc, what are the limitations keeping it the Intel one from using VoLTE only on those networks? (Just like a lot of Verizon's new phone are VoLTE only.) Is it a technical limitation of the Intel XMM7360 that doesn't like Verizon's equipment? Or is it Verizon just refuses to allow the Intel chipset on its network? Just curious what the limitation is and the technical details on why. (The reason I'm bringing this up is that Verizon allows the CDMAless iPhone 8 - which, IMO, is equivalent to a CDMAless iPhone 7.)

For those that have tried - what happens if you actually try a Verizon SIM in a GSM iPhone 7 - will it get service and do VoLTE? There's so much vagueness around this online - so I wanted to see if there were any engineers here who knew the technical "Why" on this.

Thanks!

 

[rui no onna]

For those that have tried - what happens if you actually try a Verizon SIM in a GSM iPhone 7 - will it get service and do VoLTE? There's so much vagueness around this online - so I wanted to see if there were any engineers here who knew the technical "Why" on this.

Tried it a couple months ago and as far as I recall, it simply doesn't work at all (not even data, iirc).

 

[kevink2]

Speculation is that there is some firmware missing to support Verizon, and no one is willing to pay to add this support. Either pay Verizon for certification, or pay Apple to implement the support.

The Intel modem in the 8 and X also doesn't support CDMA, but it supports LTE/VoLTE on Verizon as long as the account is configured correctly.