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- Create Date June 14, 2024
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In the context of 5G networks, Voice over New Radio (VoNR) is the technology designed to carry voice services. However, there are scenarios where VoNR might need to fallback to GSM or other legacy networks. Here are some possible scenarios where this could happen:
1. Insufficient 5G Coverage: If a user moves out of the 5G coverage area while on a VoNR call, the call may fallback to GSM to maintain the connection.
2. Network Congestion: During peak times or in crowded areas, if the 5G network cannot handle the traffic, calls might be transferred to GSM to ensure service continuity.
3. Technical Issues with 5G SA Core: If there are technical issues or maintenance activities in the 5G Standalone (SA) core network, which is required for VoNR, the network might temporarily route calls through GSM.
4. Device Compatibility: Some devices may not support VoNR or may have compatibility issues with the 5G network, prompting a fallback to GSM for voice services.
5. EPS Fallback (EPS-FB): This is an early introduction step to VoNR until sufficient NR low-band or low mid-band coverage has been deployed.It allows devices to use LTE or 2G/3G voice networks when outside the coverage of a 5G standalone network.
6. VoNR Failure: In case of a VoNR call setup failure, for example, receiving a SIP 503 error, the call might fallback to GSM as part of the Continuity of Service (CSFB) procedure.
These fallback mechanisms ensure that voice services remain available even when 5G VoNR cannot be supported, providing a seamless experience for users.