Vo5G/NR will naturally help with the most crucial service used to communicate, Voice, with ultra high-quality, delivering an unmatched service experience.
Similar to the VoLTE implementation process, the industry needed several years to design to test, develop, and then commercialize new voice services. The same will happen with VoNR. Since 4G is the core technology of 5G’s NR implementations, it is not doubt that VoLTE will remain the 5G Voice solution for a long time to come.
5G is taking mainly 3 Stages for Voice Solutions:
1. 5G NSA phase:
When 5G services are launched, operators should, by default, enable VoLTE services for 5G NSA subscribers.
2. 5G SA Initial Phase:
As per 3GPP R-15/R16, CS fallback from 5G to 2G/3G isn’t allowed. This means that in the initial phase of voice call establishment 5G SA networks must use Evolved Packet System Fallback (EPS FB) technology to allow voice fallback back to the LTE network, which will complete the connection using VoLTE.
3. 5G SA maturation phase:
Support for terminals to 5G SA will need to become a mainstream and their default configuration needs to be changed to VoNR (set on by default). If the user is outside of the 5G coverage area during a conversation, Packet Switched Handover (PSHO) technology is used to seamlessly switch the call from the NR to LTE network, allowing VoLTE to handle the voice service. (This is similar to SRVCC with 4G however the concepts are different).
So before 5G SA coverage will be fully accessible all over the world and across different geographic regions,having full 4G Coverage with IMS technologie for VoLTE is very important.
Knowing that VoNR call takes place purely in the IMS environment, incase if 5G coverage become unavailable, the call is transferred to LTE and than it can go to 2G/3G depending on coverage scenario
You can find more details about Voice over NR training at this link if you are interested.