Emergency Fallback Call Flow

This section describes the Emergency Fallback call flow.

Emergency Fallback Call Flow
Emergency Fallback Call Flow Description

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.