VoLTE and VoNR are just SIP over a cell carrier prioritized data channel (Google LTE QCI). T-Mobile has a beta for latency sensitive applications to access the

VoLTE and VoNR are just SIP over a cell carrier prioritized data channel (Google LTE QCI). T-Mobile has a beta for latency sensitive applications to access the 5G equivalent of this, it's called Network Slicing. UMTS an similar 2G and 3G protocols could do neat things like have multiple towers compare the signals received from your phone to enable more reliable calling, but this functionality did not survive to make it into cellular's LTE or 5G New Radio (NR) standards.