Inter-eNodeB Handover on the S1 Interface
1. The UE sends a measurement report to the eNodeB to trigger the eNodeB to initiate a handover.
2. The source eNodeB sends a Handover Required message to the EPC.
3. Upon receiving the Handover Required message, the EPC sends a Handover Request message to the target eNodeB.
4. Upon receiving the Handover Request message, the target eNodeB makes an admission decision and sends a Handover Request Acknowledge message to the EPC, allowing the handover.
5. Upon receiving the Handover Request Acknowledge message, the EPC sends a Handover Command message to request the source eNodeB to start a handover.
6. Upon receiving the Handover Command message, the source eNodeB sends it to the UE.
7. The UE accesses the target cell based on the information in the command. After successfully accessing the target cell, the UE sends an RRC Connection Reconfiguration Complete message to the target eNodeB.
8. Upon receiving the RRC Connection Reconfiguration Complete message, the target eNodeB sends a Handover Notify message to the EPC to indicate that the handover succeeds.
9. Upon receiving the Handover Notify message, the EPC sends a UE Conext Relese Command with the cause of Successful Handover to the source eNodeB, indicating that the handover is successful and the UE can be released on the source eNodeB. After receiving the UE Conext Release Command message, the source eNodeB waits until local data transmission is complete and then releases the UE.
Signaling tracing over the Uu interface on the UE side
Signaling tracing over the Uu interface on the source eNodeB side
Signaling tracing over the S1 interface on the source eNodeB side
Signaling tracing over the Uu interface on the target eNodeB side
Signaling tracing over the S1 interface on the target eNodeB side
