5.45.1 General

QoS monitoring comprises of measurements of QoS monitoring parameters and reports of the measurement result for a QoS Flow and can be enabled based on 3rd party application requests and/or operator policies configured in the PCF. Event Reporting from PCF is specified in clause 6.1.3.18 of TS 23.503 [45] and User Plane QoS Flow related QoS monitoring and reporting in clause 5.8.2.18.

The AF may request measurements for one or more of the following QoS monitoring parameters, which may trigger QoS monitoring for service data flow(s):

• UL packet delay, DL packet delay, round trip packet delay for a service data flow, see clause 5.45.2.
• Congestion, see clause 5.45.3.
• Data Rate, see clause 5.45.4.
• Packet Delay Variation, see clause 5.37.7.
• Round trip packet delay considering UL on a service data flow and DL of another service data flow, see clause 5.37.4.
• Available Bitrate, see clause 5.45.6.

The following AF requested QoS requirements may trigger QoS monitoring for service data flow(s):

• Round-trip latency requirement, see clause 5.37.6.

The PCF may generate the authorized QoS Monitoring policy for a service data flow based on the QoS Monitoring request received from the AF (as described in clause 6.1.3.21 of TS 23.503 [45]) or based on PCF local policy or configuration reasons, such as PCF awareness of dynamic satellite backhaul connection. The PCF includes the authorized QoS Monitoring policy in the PCC rule and provides it to the SMF.

The QoS monitoring parameter(s) that can be measured by means of QoS monitoring are listed below. The QoS monitoring policy in PCC rule (described in clause 6.3.1 of TS 23.503 [45]) may include the following:

• UL packet delay, DL packet delay, round trip packet delay, see clause 5.45.2.
• Congestion, see clause 5.45.3.
• Data Rate, see clause 5.45.4.
• Available Bitrate, see clause 5.45.6.

The SMF configures the UPF to perform QoS monitoring for the QoS Flow and to report the monitoring results as described in clause 5.8.2.18 with parameters determined by the SMF based on the authorized QoS Monitoring policy received from the PCF or local configuration or both.

The SMF may also configure NG RAN to measure the QoS monitoring parameters by sending QoS monitoring request based on the authorized QoS Monitoring policy received from the PCF and/or local configuration. The QoS monitoring request to the NG RAN for different parameters is as defined in clause 5.45.2, 5.45.3 and 5.45.6.

Based on configuration, the AMF may know whether the QoS monitoring feature (i.e. each of Packet delay monitoring and/or Congestion monitoring and/or Available Bitrate monitoring) is supported by all NG RAN nodes in an area. The AMF shall, when configured, inform the SMF about the support of the QoS monitoring feature by sending the parameter NG RAN QoS monitoring capability during PDU Session establishment, PDU Session modification, Service request and UE mobility procedures. The SMF determines whether QoS monitoring is possible or not for the PDU Session based on whether the NG RAN QoS monitoring capability is received (or not) from the AMF and the QoS monitoring capability of the UPF. QoS monitoring is possible if the SMF has received the NG RAN QoS monitoring capability in the last message received from AMF (i.e. Nsmf_PDUSession_CreateSMContext or Nsmf_PDUSession_UpdateSMContext service operation) and the UPF also supports the corresponding QoS monitoring capability. Otherwise, QoS monitoring is not possible for the PDU Session for the respective QoS monitoring parameter(s). The SMF may need to notify the PCF when the support for QoS monitoring has changed as described in clause 6.1.3.5 of TS 23.503 [45] also indicating the affected QoS monitoring parameter(s).

NOTE 1: The AMF is not required to immediately update the SMF about a change of support of the QoS monitoring feature (by all NG RAN nodes in an area) when the change is happening outside of the UE mobility procedures. As AF logic can depend on the QoS monitoring reports, the change from support of QoS monitoring to no support of QoS monitoring is more important to notify than the change in the other direction and is therefore expected to take place in a timely manner.

The following clauses describe the QoS monitoring parameters which can be measured and any specific actions or constraints for their measurement.

NOTE 2: The QoS monitoring parameter which can be measured are parameters which describe the QoS experienced in the 5GS by the application, i.e. they are not restricted to the 5G QoS Parameters defined in clause 5.7.2.