Wi-Fi to LTE Handover Call Flow
This section describes the Wi-Fi to LTE Handover call flow.

Step |
Description |
---|---|
1 |
MME sends create Session Request to SGW. |
2 |
SGW sends Sx Establishment Request to UPF1. |
3 |
SGW receives Sx Establishment Response from SMF. |
4 |
SGW sends Create Session Request to SMF. SMF selects same UPF. |
5 |
SMF sends Sx Establishment Request to UPF1. |
6 |
SMF receives Sx Establishment Response from UPF1. |
7 |
SMF sends Create Session Response to SGW. |
8 |
SGW sends Sx Mod Request to UPF1. |
9, 10 |
SGW receives Sx Mod Response from UPF1 and forwards to MME. |
11 |
Modify Bearer procedure takes place and off-loaded call to Wi-Fi. ePDG sends Create Session Request to SGW. |
12 |
SMF sends Sx Mod Request to UPF1. |
13 |
SMF receives Sx Mod Response from UPF1. |
14 |
ePDG receives Create Session Response from SGW. |
15 |
Call moved to Wi-Fi to clear at SGW. MME sends Delete Session Request to SGW. |
16 |
MME receives Delete Session Response from SGW after performing call clear procedure. |
17 |
MME sends Create Session Request to SGW. |
18 |
SGW sends fetch UPF (UPF1) info request to SMF after checking SMF as same cluster as cnSGW-C. |
19 |
SGW receives UPF (UPF1) Info Response from SMF. |
20 |
SGW sends Sx Establishment Request to UPF1. |
21 |
SGW receives Sx Establishment Response from UPF1. |
22 |
SGW sends Create Session Request with SGWU=UPF1 to UPF1 and performs call setup procedure. |