Emergency Fallback Call Flow
This section describes the Emergency Fallback call flow.

Step |
Description |
---|---|
1 |
The UE camps in the 5G network. |
2 |
The UE starts an emergency session. |
3 |
The UE sends a Service Request to the AMF. For more information, see Service Request Procedure Call Flow in this chapter. |
4 |
The AMF sends a N2 Request for emergency fallback to the NG-RAN. For more information, see Service Request Procedure Call Flow in this chapter. |
5a |
The Inter-RAT handover or RRC is redirected to the 5GC-connected E-UTRA. |
5b |
The intersystem handover or RRC is redirect to EPS. |
6 |
The IMS procedure is started to establish the IMS Emergency Session. |