 scheduler defined: - the frequency radio resources to be allocated for each mobile; - the number of spatial layers that can be used, depending on the category of the mobile; - the transmission TTI (Time Transmission Interval) instants. The mobile listens to the information transmitted over the PDCCH (Physical Downlink Control Channel) logical control channel and decodes the information channel when it detects its radio identifier C-RNTI. The scheduler makes its decisions at each slot. The duration of the TTI slot depends on the spacing between SCS (SubCarrier Spacing). While the scheduler decision is 1 ms in 4G, it is variable from 1 ms, 500 us or 250 us for 5G on the FR1 (Frequency Range 1) band, and can go down to 125 us or 62.5 us for the FR2 band. Transmission on the downlink direction can be pre-empted for critical communication (low latency). The NG-RAN node informs the mobiles by transmitting the INT-RNTI identifier over the PDCCH control channel. Semi-persistent scheduling allows us to periodically allocate radio resources for a mobile. The periodicity of the messages is transmitted over the RRC layer and the resource allocation is transmitted to the mobile via the CS-RNTI identifier. NG-RAN Network - Functional Architecture 1.4.2. Support for quality of service on radio link The QoS (Quality Of Service) control consists of implementing the maximum quality of service applicable to a data flow. Like the 4G mobile network, only the core network is aware of the service requirements: QoS management is under the control of the core network (AMF). The NG-RAN has no knowledge of the service to be managed. Thus, when establishing a PDU session, the AMF entity establishes QoS rules between the radio node and one or more UPF entities. The PDU session carries IP flows with one or more different qualities of service for all flows. Each flow is associated with a QFI flow profile identifier. The flow profile corresponds to a QoS indicator (5QI: 5G QoS Identifier) and an allocation and retention priority (ARP). The QFI