N2 Handover Cancel Call Flow
This section describes the N2 Handover cancel call flow.
The source NG-RAN sends Handover Cancel Request to the source AMF, prior to sending the Handover command to UE. It sends this request when it observes the following:
-
Timer expiry
-
Internal failure within the source NG-RAN
-
UE return to source cell
Handover Cancel Request releases the handover reserved resources in the target system.

Step |
Description |
---|---|
1 |
The S-gNB (source gNB) sends the Handover Cancel to the S-AMF (source AMF). |
2 |
S-AMF sends the Namf_Comm_ReleaseReq to the T-AMF (target AMF). |
3, 4 |
T-AMF sends the UE Context Release Command to the T-gNB (target gNB) and receives the UE Context Release Complete. |
5 |
T-AMF sends the Relocation Cancel Indication (Nsmf_Update_Req) to the SMF. |
6 |
SMFsends Nsmf_update_Rsp to T-AMF. |
7 |
S-AMF receives Namf_Comm_ReleaseRsp from the T-AMF. |
8 |
S-AMF sends Handover Cancel ACK to the S-gNB. |