EPS to 5G Handover Without Using N26 Interface
This section describes the call flow for the EPS to 5G handover procedure without using the N26 interface.

Step | Description |
---|---|
1 | The UE initiates a registration request to the NG-RAN. |
2 | The NG-RAN selects an AMF. |
3 | The NG-RAN forwards the Registration Request with the N2 message parameters to the new AMF. |
4 | Refer to the General Registration procedure in TS 23.502. |
5 |
The new AMF registers with the UDM using Nudm_UECM_Registration for the access to be registered. |
6 | Refer to the General Registration procedure in TS 23.502. |
7 |
The new AMF sends the Registration Accept message to the UE. The AMF includes an "Interworking without N26" indicator to the UE. |
8 |
The UE responds with a Registration Complete message to the new AMF. |
9 | The UE initiates a PDU Session establishment procedure. |
10 | The PGW-C+SMF performs release of the resources in EPC for the PDN connections(s) transferred to 5GS by performing the PDN GW initiated bearer deactivation procedure. |