5G to Wi-Fi Handover with Alternate RAT Tunnel Creation Call Flow
This section describes the call flow of the 5G to Wi-Fi handover with an alternate RAT tunnel creation.

Step | Description |
---|---|
1 |
ePDG sends the Create Session Request to SMF+PGW-C. This request includes details on S2bC F-TEID and S2bU F-TEID. |
2 |
SMF+PGW-C sends the Policy Update Request to PCF. |
3 |
PCF sends the Policy Update Response to SMF+PGW-C. |
4 |
SMF+PGW-C sends the Charging Update Request to CHF. |
5 |
CHF sends the Charging Update Response to SMF+PGW-C. |
6 |
SMF+PGW-C sends the Create Session Response to ePDG. This response includes details on the stored Wi-Fi UL tunnel. |
7 |
SMF+PGW-C sends the Create Bearer Request to ePDG. This request includes details on the dedicated bearers with UL tunnel. |
8 |
ePDG sends the Create Bearer Response (DL tunnel information) to SMF+PGW-C. |
9 |
SMF+PGW-C sends the N4 Modification Request to UPF. This request includes information on the DL FAR update and Query URR of gNB tunnel. |
10 |
UPF sends the N4 Modification Response to SMF+PGW-C. |
11 |
SMF+PGW-C sends the N1N2Message Transfer, which is the PDU Session Release Command to AMF. |
12 |
AMF sends the 200 OK response to SMF+PGW-C. |
13 |
AMF sends the SMContext Update Request (N2Message) to SMF+PGW-C. |
14 |
SMF+PGW-C sends the SMContext Update Response (204 OK) to AMF. |
15 |
AMF sends the SMContext Update Request (N1Message) to SMF+PGW-C. |
16 |
SMF+PGW-C sends the SMContext Update Response (204 OK) to AMF. |
17 |
SMF+PGW-C sends the SMContext Status Notification to AMF. This notification indicates the resource status as RELEASED. |
18 |
AMF sends the 204 OK response to SMF+PGW-C. Then, on SMF+PGW-C, the policy and charging updates happen. |