5G QoS (Quality of Service) Architecture

  • To exchange data stream between the 5G device and DN (Data Network), a logical connection called PDU session is established between the device and PSA UPF (PDU Session Anchor User Plane Function) by SMF(Session Management Function).

  • In Downlink direction:

    • The IP flows created by application layers and received from DN are mapped to SDFs (Service Data Flow) and then then to QoS flows using e.g. the PDRs (Packet Detection Rules).
    • The QoS flows are carried through N3 GPRS tunnels using GTPv1-U protocol.
    • The QoS flows received from N3 tunnels are then mapped by the SDAP layer in the gNB to the DRBs using the QoS profiles prepared by the SMF as well as the parameters configured by the operator.
  • In UL direction:

    • To map IP flows received from the application layer to QoS flows, QoS rules are prepared by SMF.
    • To map the QoS flows to the DRBs, the 5G device is configured through RRC Reconfiguration or by using SDAP header in the case of Reflective QOS.

Here I try to depict how QoS flows are exchanged in the 5GS (5G System):

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