Figure 7.7.1-1 illustrates a high level call flow for an interworking scenario between a UE and a PSAP supporting NG-eCall. This scenario occurs, when the UE detects that the NG-eCall is supported by the IP-CAN.

Figure 7.7.2-1 illustrates a high level call flow for an interworking scenario between a UE and a PSAP via the CS domain. This scenario may occur in the case, when PS access is available, but the UE does not detect that the NG-eCall is supported by the IP-CAN and there is no CS access available. In this case, the UE shall establish a regular IMS emergency call. A similar scenario may occur in the case, when the UE detects that the IP_C AN supports NG-eCall and initiates an NG eCall but the session is handled by a PSAP not supporting NG-eCall. The only exception would be step 2 and where the SIP INVITE shall contain the initial MSD and the eCall type of emergency service indicator (automatic, manual).

Figure 7.7.3-1 illustrates a high level call flow for transfer of an updated MSD in the case that the emergency centre or PSAP is accessed via the PS domain. The call flow is applicable following establishment of an emergency services session for eCall as described in clause 7.1.1 in which the initial MSD is transferred in the INVITE and prior to release of the emergency services session.