The authentication model is based on Radius with EAP, the main point is that anything after and including 3G does mutual authentication and in 4G/5G this is bas

The authentication model is based on Radius with EAP, the main point is that anything after and including 3G does mutual authentication and in 4G/5G this is based on IETF protocols, in theory, you can associate with 4G network with whatever authentication supplier that works with WPA-Enterprise (and in theory that even works the other way around). The idea there is that 4G/5G is simply an physical layer for Ethernet2 frames with some kind of access control and QoS layer. And quite obviously the frames are encrypted and authenticated on L2. And as the whole thing is IP, some carriers just tunnel the whole thing in additional layer of IPSec tunnels.