a VoNR subscriber requires appropriate SIP-based signaling and Real-Time Transport Protocol (RTP)-based voice packet conversion. Voice over New Radio (VoNR) In the rollout of each new technology, there exist some coverage gaps in RANs. So, in these coverage gaps, the subscribers need to hand over to other technologies for connectivity continuity. This is also valid for 5G rollouts. As the 5G networks roll out, there will be some coverage gaps that affect the VoNR subscribers in terms of call continuity. Therefore, some handover techniques from 5G to legacy networks, such as 4G or 3G, are required. Finally, interworking might be required due to the utilization of other radio technologies such as Wi-Fi calling. Interworking with legacy voice networks The communication between legacy subscribers of circuit switched (CS) networks (e.g., 2G, 3G, or the PSTN) and a VoNR subscriber requires an appropriate SIP-based signaling conversion and RTP-based voice packets conversion. This conversion is done with the Media Gateway Control Function (MGCF) and an IP Multimedia Gateway (IM MGW), as outlined in the following diagram: To BGFC in another network Access To IP Network Multimedia Network To Legacy CS IM MGW Network (2G, 3G, PSTN etc.) Figure 8.11 - IMS architecture break-out to other networks The MGCF is responsible for the conversion of SIP signaling to Signaling System No 7 (SS7) or Bearer-Independent Call Control (BICC) messages that are used by the CS domain networks. IM MGW is responsible for converting RTP-based voice packets to Time-Division Multiplexing (TDM) based delivery under the supervision of MGCF. Packet switched handover from 5G to 4G Even if the service providers have ubiquitous 5G coverage, there will still be some coverage gaps due to high band frequency deployments, or there will be some point where the quality of service decreases. In those cases, the VoNR call should be handed over to a different technology, such as 4G or 3G. In this example, 5G to 4G handover will be evaluated. Here, the network nee