ome of these procedures can be illustrated by the handover example. The procedure is shown in Figure 3.3.5 in a simplified form, where interactions inside the 5GC are hidden. 3 5G System Overview Source gNB Target gNB 1.Measurement Control and Reports 2. Handover Decision HANDOVER REQUIRED 4. HANDOVER REQUEST 5. Admission control and Resource setup 6. HANDOVER REQUEST ACKNOWLEDGE HANDOVER COMMAND 8. HANDOVER COMMAND 9. Detach from old cell Synchronize to new cell UPLINK RAN STATUS TRANSFER 11. DOWNLINK RAN STATUS TRANSFER 12. HANDOVER CONFIRM 13. HANDOVER NOTIFY UE CONTEXT RELEASE COMMAND UE CONTEXT RELEASE COMPLETE Figure 3.3.5 NG handover. (Source: Reproduced by permission of © 3GPP). dover execution. Generally, a handover procedure is divided into two steps: handover preparation and han- 1. The source gNB configures the UE measurement procedures and the UE reports the measurements according to the configuration. gNB decides to hand over the UE. Based on measurement report and potentially other information (e.g. load), the source 3. The ries source gNB sends the Handover Required message to the AMF. The a the source-to-target transparent RRC container with necessary information message to car- The information, and optionally the direct forwarding path availability indication. pare handover at the target side, the list of established PDU sessions with associated pre- 4. the AMF sends the Handover Request message to the target gNB. The carries from source-to-target the transparent RRC container and the list of PDU sessions, message received imum source gNB, along with various other parameters, such as UE Aggregate Max- Bitrate, UE Security Capabilities, Allowed NSSAI, and others. 3.3 NG Radio Access Network 5. The target gNB allocates the resources for the UE. 6. If the target gNB decides to admit the handover, it sends the Handover Request Acknowledge message to the AMF. The message carries the lists of admitted and not admitted PDU sessions, along with the target-to-source transparent RRC container to be sent t