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.

Call Flow for the EPS to 5G Handover Without Using the N26 Interface
Call Flow Description for the EPS to 5G Handover 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.