FT) for both downlink and uplink, while the higher part hosted in the en-gNB-CU contains other functions; - variant 7.2: the lower part hosted in the en-gNB-DU adds the mapping function to the resource elements for both downlink and uplink; NG-RAN Network - Protocol Architecture - variant 7.3: channel coding is performed at the gNB-CU level and lower functionalities are implemented at the gNB-DU level. Channel Coding Rate Matching Scrambling Modulation Precoding Resource Allocation IFFT CP Figure 2.9. Functions of the physical layer 2.1.3.1. Control plane function F1-C F1-C control functions support: - management functions of the F1 interface: configuration or update of the gNB-CU, configuration or update of the gNB-DU, synchronization, error detection and restarting of the gNB unit; - coordination of radio resource sharing (RAN Sharing); - exchanges of broadcast information messages. NR-MIB and SIB1 messages are the responsibility of the gNB-DU and the other messages are handled by the gNB-CU; - management of user contexts. This function is responsible for establishing or modifying a user context for data exchange (DRB) or signaling (SRB). The establishment of the F1 UE context is initiated by the gNB-CU. The gNB-DU can accept or decline the establishment request depending on the resources available (gNB-DU admission criteria). Modification of the F1 UE context can be initiated either by the gNB-CU or by the gNB-DU; - exchanges of RRC messages between gNB-DUs and gNB-CUs. The gNB-DU is responsible for scheduling and broadcasting information messages. NG-RAN and 5G-NR The scheduling is based on context UE parameters which are provided from the gNB-CU to the gNB-DU during the procedure of creation of context (UE Context Setup Procedure) or during the procedure of modification of context (UE Context Modification Procedure). The user context contains the QoS rules for the radio bearer and the S-NSSAI (Single Network Slice Assistance Indicator) for the network slice. The gNB-CU performs the mapping between the PDU se