5.45.6 Available bitrate monitoring

The QoS Monitoring for available bitrate allows the measurement and reporting of the UL and/or DL available bitrate for a GBR QoS Flow without Alternative QoS Profiles by the NG-RAN. The available bitrate refers to the bitrate that NG-RAN is able to provide in the respective direction for a QoS Flow within a duration. The duration is based on RAN implementation.

NOTE 1: How the NG-RAN measures the available bitrate is NG-RAN implementation specific.

NOTE 2: The available bitrate can be larger than the GFBR but can never exceed the MFBR. The available bitrate can also be smaller than the GFBR for a QoS Flow with QoS Notification Control enabled without Alternative QoS Profiles.

For the reporting of the available bitrate, periodic reporting is not applied and only event triggered reporting applies. Based on the PCC rule containing available bitrate as QoS monitoring parameter and Reporting threshold(s) per direction in the QoS Monitoring policy (as described in clause 6.1.3.27.1 of TS 23.503 [45]), the SMF configures the NG-RAN to measure and report the available bitrate by sending QoS monitoring request including the threshold(s). Based on the QoS monitoring request, if the bitrate that NG-RAN is able to provide changes and matches or exceeds indicated threshold(s), the NG-RAN reports the UL and/or DL available bitrate information of the highest fulfilled threshold(s) for the UL and/or DL direction to the PSA UPF via the GTP-U header of UL packets (or dummy UL packets). The NG-RAN shall only send a report when the available bitrate information is different from the previously reported value(s) for at least one direction. If thresholds exist for both directions, the NG-RAN shall always indicate the available bitrate information for both directions when sending a report.

NOTE 3: The NG-RAN is expected to immediately report the UL and/or DL available bitrate when it matches or exceeds a lower threshold value and report the UL and/or DL available bitrate when it matches or exceeds a higher threshold value with some hysteresis.

The SMF may configure the PSA UPF to perform QoS monitoring for available bitrate as described in clause 5.8.2.18. For the reporting of the available bitrate via the PSA UPF, only event-based reporting applies in the PSA UPF. Reporting by the UPF is performed as described in clause 4.15.12 of TS 23.502 [3]. The Reporting threshold(s) in the PCC rule are not sent to UPF. In the UPF, the event for the reporting is the reception of available bitrate information from NG-RAN. According to the QoS Monitoring request for the available bitrate from the SMF, the PSA UPF monitors and exposes the available bitrate information reported from NG-RAN to the target NF as instructed.

During handover, the QoS Monitoring configuration is provided to the Target NG-RAN per QoS Flow in the QoS Monitoring configuration. If the Target NG-RAN supports QoS Monitoring for available bitrate it shall report it for the UL and/or DL direction after the handover according to the QoS Monitoring configuration.

NOTE 4: The AF can subscribe to reporting for the change in support for QoS monitoring as described in clause 5.45.1 to receive notifications when support of Available Bitrate monitoring changes in the Target NG-RAN.