5G registration is crucial because it’s the process that allows a device to securely connect to the network, authenticate itself, and establish the initial trust relationship with the core. Without registration, the UE cannot access mobility, security, or service features. It’s the foundation step that ensures seamless connectivity and enables advanced services like PDU session establishment for data transfer.
This procedure outlines the coordination between the Source/Target gNB-CUs and DUs to maintain service continuity during UE mobility.
The objective is to verify that the target node can support the UE's requirements before the move is executed.
Step 1: Handover Request (XnAP): The Source gNB-CU sends the Handover Request to the Target gNB-CU over the Xn interface, providing the UE's context and QoS requirements.
Step 1a & 1b: UE Context Setup (F1AP): The Target gNB-CU initiates a UE Context Setup Request to the Target gNB-DU. The DU reserves the necessary radio resources and responds with the UE Context Setup Response.
Step 2: Handover Request Acknowledge (XnAP): The Target CU confirms the successful preparation to the Source CU.