On 2018-07-29 20:10, James Knott wrote:
On 07/29/2018 01:18 PM, Andrei Borzenkov wrote:
Sigh. The whole point of WiFi calling is that it does not use any mobile data at all.
The whole point of WiFi calling is to be able to use WiFi/Internet to connect to the cell network. Some carriers use this to provide public service beyond their cell networks. Others, to provide a better local connection for those in a poor signal area, such as mine. Either way, calls travel over the VoLTE network, other than that short WiFi hop. As I said, I can start a call on one network and seamlessly transition to the other. That is possible because VoLTE and WiFi calling use exactly the same protocol. Both travel over IP and it does not matter at all which network is used. You could not tell, during a call, without looking at the phone, whether or not WiFi calling is used.
Please bear in mind, I *USE* WiFi calling in the manner I described. I have the same phone number either way. I have verified WiFi calling is encrypted in IPSec, just like VoLTE. I have also done work for 2 Canadian cell carriers at the network level. One thing I can say, with absolute certainty, based on that work experience, is when you're on a cell call, that call is travelling over Ethernet to the carrier, unless you're on one of the older sections of the network that only support 2G calls. Data and VoLTE use IP over that Ethernet. With cell sites, that Ethernet would be over fibre or short haul microwave and not copper cables.
Also I have never said it uses "mobile data" in the context of data plans where you pay for so much data. If you were using a separate VoIP app, that data would be used. It is not with VoLTE, as that is considered part of your voice, not data, package. In the past, with the first digital cell phones, such as GSM, voice was converted to digital and carried in TDM time slots and FDM channels. With UMTS, the exact same digital representation of the voice call was placed in packets and carried that way. We then advanced through 4G etc., with everything, voice, data, video, whatever, carried in IP packets. VoLTE calls, while IP, are billed according to your voice package and and other VoIP apps, such as Skype, Hangouts, etc., are billed under your data package. Those other packages may use standard SIP/RTP or proprietary methods, but they're still considered data. They also have their own phone numbers, independent of your actual cell phone number. Again, VoLTE uses the same phone number, regardless of whether cell or WiFi connection is used. VoLTE uses an industry standard method of VoIP/IPSec/UDP/IP which means it is able to transparently use either the cell network or WiFi for the last hop to the phone. VoLTE is simply a progression in the way cell phone calls have been handled since GSM etc. was introduced.
If you were to call my cell number, your call would travel over the cell network all the way or possibly WiFi for the last hop and you couldn't tell the difference. I could wander back and forth between the two networks and again you couldn't tell, thanks to the seamless transition. The same can't be said for those other VoIP apps. Crossing between networks would likely result in a dropped call.
BTW, because it is VoIP, VoLTE supports other CODECs, including a higher bandwidth one called HD Voice or similar. The basic phone UMTS uses the standard GSM CODEC
https://en.wikipedia.org/wiki/Wideband_audio https://en.wikipedia.org/wiki/Time-division_multiplexing https://en.wikipedia.org/wiki/Frequency-division_multiplexing
There is also CDMA, which uses code division multiplexing, but it's fading fast. https://en.wikipedia.org/wiki/CdmaOne
Interesting. No such thing here though, AFAIK. Confirmed here: https://en.wikipedia.org/wiki/Voice_over_LTE#Deployment https://en.wikipedia.org/wiki/List_of_LTE_networks https://en.wikipedia.org/wiki/List_of_LTE_networks#Europe https://en.wikipedia.org/wiki/List_of_LTE_networks_in_Europe Only one minor provider uses it. -- Cheers / Saludos, Carlos E. R. (from 42.3 x86_64 "Malachite" at Telcontar)