Non 3GPP Untrusted LTE to WiFi Handover

This section describes the non-3GPP untrusted LTE to WiFi handover call flow.

Non-3GPP Untrusted LTE to WiFi Handover with TFTs more than 4 for a Dedicated Bearer
Non-3GPP Untrusted LTE to WiFi Handover Call Flow Description

Step

Description

1

Session is established in LTE with a default bearer and dedicate bearer with 8 TFTs.

2

LTE to Wi-Fi Handover is triggered, when CSReq is received with hi flag configured from ePDG.

3

After successfully handling CSReq, CSResp is sent back to ePDG, indicating that the default bearer is successfully handed over.

4

For the dedicated bearer which has 8 TFT, since all TFTs cannot be sent in CBReq, the CBReq message is triggered with only 4 TFTs toward ePDG.

5

After successful CBResponse from ePDG, SMF sends the remaining TFTs in the UBReq message.

6

After successful UBResponse from ePDG, SMF continues with completion of establishing the bearer towards UPF.

7

In case of failure in CBResponse or failure in UBResponse at Step 5 or Step 6, the SMF deletes that bearer, and if armed, sends rule report to PCF with corresponding rules information as Inactive.

Important

Steps 4-7 are applicable for LTE to Wi-Fi and NR to Wi-Fi if a dedicate bearer has more than 4 TFTs.