nnected. node. The mobile has a temporary The NG-RAN node knows identity created by the core the RNA location area on network. which the mobile is camped No UE context is stored on The mobile radio context is stored at the mobile side and the the NG-RAN node. NG-RAN node side. The core network and the NG-RAN node exchange information through NG-C and NG-U interfaces. Table 1.1. RRC mobile states 1.4. Scheduling and QoS 1.4.1. Scheduling Scheduling enables us to share radio resources among all connected users. A scheduling task is performed in real time to share radio resources among all mobiles. Scheduling attribution is calculated based on: - the quality of the radio link for each mobile; - requirements in terms of the quality of service expected by each mobile; - the state of the mobile buffer. The scheduler is performed at the MAC layer of the NG-RAN node and defines the scheduling for downlink and uplink transmissions. The quality of the radio link is used to define the modulation and coding scheme (MCS) for a given mobile, as well as the transmission power. The MCS is dynamically adjusted according to the HARQ (Hybrid Automatic Repeat Request) retransmission rate. To meet mobile requirements, several strategies can be defined at the scheduler level: - fairness, a strategy for which each mobile receives the same resource allocation regardless of the modulation scheme; NG-RAN and 5G-NR - proportional fairness which allocates more frequency resources for mobiles with less efficient MCS; - round-robin, a strategy which consists of allocating equal resources to all mobiles; - max-CQI, a strategy that aims to maximize cell capacity by prioritizing the allocation of radio resources to mobiles which have the best radio quality. The scheduler is based on measurement reports: - the state of the buffer BSR (Buffer Status Report); - the quality of the radio link (CSI-RS); - the rising power margin PHR (Power Headroom Reports); - Inter-Cell Interference Coordination (ICIC) between NG-RAN nodes. From this information, the