Voice over LTE

VoLTE - Voice over LTE - is the protocol for using the 4G network for phone calls.

2G and 3G networks were primarily phone networks with data added on. So when making a phone call the connection is switched to the PSDN, the nornal phone network.

4G is an IP only network, a data only network, and will deliver the phone call over the data network using VoLTE. There is no switching from data to voice, everything is data. VoLTE is deisgned for the LTE network and makes an efficient use of it, it does work over WiFi or any other data connection. Although VoLTE can switch to VoWiFi if it needs to to keep the call alive.

In the early days of 4G, VoLTE was not available in all areas so the phone would switch back to 2G. This led to the comments that 'I cannot make phone calls' which was because of the lack of a suitable 2G network. The same fallback works today if necessary. Also if a phone with 4G calls a phone with only 2G, the call will revert to the old 2G network. The quality of the call over 4G - VoLTE - is noticably better than over the 2G network. Primarily, but not limited to, the fact that the input sound wave is sampled at twice the rate in 2G.

Another advantage of VoLTE for a heavy mobile user is that data can be uploaded / download in parallel to the phone call making the network very efficient for the user.

Video calls are also possible with VoLTE

VoLTE is not the same as VoIP. VoIP is a more general protocol used by fixed line phones to use the data network rather than a dedicated phone network.