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I used to live in an old apartment block with thick concrete walls, and away from a cellular base station. VoWifi was really helpful if I wanted to make calls from my home. I guess I could use WhatsApp/Facetime/Signal, but the insurance agent won't call me on WhatsApp from her landline phone :)

And it is not handled by an app on your phone, because of legacy reasons. I believe that, before LTE was introduced, 2G and 3G had a distinction between IP and voice traffic, so the baseband handled the voice transmission. Then they thought that LTE should be IP only and voice should be sent as VOIP over it, but it still had to be handled by the baseband for backwards compatibility with 2G and 3G. And then they came up with the idea that the VOIP traffic could also be piped over Wi-Fi (through the main processor of the phone), and so VoWi-Fi was created.

I think it was lots of parallel development - some mid-to-late 3G phones had carrier hand-rolled Wi-Fi calling, some had femtocell support instead, LTE was to be just faster packet-only Internet mode for 3G, became its own thing too late which necessitated CSFB, and then Wi-Fi calling became reimplemented as part of standard, etc.

> I guess I could use WhatsApp/Facetime/Signal, but the insurance agent won't call me on WhatsApp from her landline phone

Huh. I would expect that it's more common for the insurance agent to have WhatsApp (or equivalent) as the only option than it is for them to refuse to use it in favor of the telephone network.

WhatsApp, FaceTime, etc. all require both endpoints of a call to use that app. VoWiFi lets you receive calls to your regular phone number from any normal phone. The fact that the last mile of the call is being carried over WiFi becomes an invisible implementation detail.

The phones could just use the SIP protocol for voice. You don't need an accompanying chat app. The huge disadvantage of that is that the customer could then use any VOIP supplier for their phone calls. ... or none at all for SIP to SIP calls. That would create a competitive market in voice. A competitive market is the last thing any cell phone provider wants. They need to maintain their monopoly on the last mile connection.

This might be an interesting idea for a government interested in improving this particular market. Forbid the provision of anything but reasonable latency data by a last mile provider. Establish standards.

I note that jmp.chat, a provider of SMS and voice over internet connections, is toying with the idea of providing, pay as you go, data only plans as a complement to their primary service.

VoLTE is literally SIP + IPSec + auth with SIM card (+ some pretty usual SIP optional extensions marked as required)

I think your concerns are misplaced.

Things like TCP/IP and DNS are child’s play compared to the complexity of cellular baseband firmware — even for just a single 2G/3G/4G standard.

The SIM card layer is also another nightmare in itself.

VoWifi is neither US centric nor purely about efficiency - it allows you to make calls with your phone to another phone via a third party network when you don’t have cellular connectivity.

For example if you have poor cell coverage at your home or office, you can still make and receive calls via a wifi connection using your phone number instead of forcing everyone to sign up for some third party service.

Well, this sort of reinforces the point - there are about zero places in Europe where you have Wifi but do not have cheap almost-unlimited 4G/LTE. In fact it's wifi that's dying out here, the only thing that keeps it alive is that in a cafe setting it's still somewhat faster, and it eats a bit less battery.

I’m not sure we are talking about the same thing - just because you have cheap unlimited 4G doesn’t mean you get that 4G signal in a basement. VoWifi lets you still call someone with your phone number when the signal is bad but you have wifi access…

I was never into insisting to only talk on the phone from the basement of my medieval castle. The view from the battlements is much better.

We're not all jamesbondesque supervillains here.

Like I said above, for like $8/mo you have in fact unlimited 4G at decent speeds here. Or for idk maybe $15 you can get a gpon, unlimited traffic, 30+Mbit to the house, depending on local laziness of course. And that is for a rural place in Balkans, not something in more civilized places.

Yes, and VoWifi lets your cell phone make a call over that fiber when your wireless coverage isn’t great. Not really sure where castles and battlements come to play here - there are plenty of completely normal places people visit with connectivity issues.

Maybe it is your experience in the rural balkans, where cellular congestion and significant building density aren’t factors, and your assumption it must be better in “civilized” places that is confusing the issue…

I just got back from a week in Paris where I frequently had limited cell service indoors on a major provider. Even with antennas all over there’s just a lot of masonry for signals to get through.

I’ve been really happy on many occasions to have Wifi calling, both where I live in NYC (where service sometimes behaves similarly to Paris) and the rural places I visit frequently (where having the cellular modem off while at home saves tons of battery vs constantly having no service).

I do love how, seemingly to counteract the US-centric nature of many discussions, some Europeans act as though Europe is this one homogeneous block where everything works the same everywhere.

I guarantee you there are quite a few people in various countries in Europe where they don't have great cellular coverage, whether because of their location, or because of the building materials used in whatever house or office building they spend a lot of time in.

Regardless, I don't really get the hate toward VoWifi. Like... it's an added option. In some cases it might be redundant (or worse than the normal VoLTE option), but... it's an added option, that you don't have to use, that can be a great fallback in some cases.

Europe is approximately 7% of the land surface area of the world. We don't all live in small, densely populated places :)

And US is 6.1% Your point?

Would you describe the entirety of the US as “densely populated”?

My point is exactly what I said. There are lots of parts of the world where mobile service is not good (or available at all) because it's not economically sensible to build out coverage where populations are very low.

You wrote "there are about zero places in Europe where you have Wifi but do not have cheap almost-unlimited 4G/LTE" on a site with a global audience.

And even where the connectivity is there, the "cheap almost-unlimited" bit might not necessarily be true – that, too, significantly varies from country to country.

That's not quite true. There are older buildings with brick walls that have bad cellular reception.

Conversely, some high rises have a too _good_ reception and the radio spectrum can get congested.

Where it does matter they put a femtocell which is about as complicated as a wifi AP.

I live in the UK and pretty much rely on VoWifi to make/receive calls when at home. I can also think of a few places within an hours drive where my reception drops to “No Service”.

You are completely wrong in your assertions.

> Not to take away from your excellent work, but what the hell is the point of VoWifi ?

The point is that your phone should continue to work even if you are deep inside a building without coverage. Or that you should have connectivity if you for some other reason have good wifi coverage but bad cellular.

Now, the protocol choices I won't defend, it is layers upon layers of complexity that I don't know enough to understand what is motivated or what is bad.

I can make "regular" phone calls when on a different continent and on WiFi without paying any roaming fees.