Section: 5.7.2.4.1b Notification control with Alternative QoS Profiles
Content: If, for a given GBR QoS Flow, Notification control is enabled and the NG-RAN has received a list of Alternative QoS Profile(s) for this QoS Flow and supports the Alternative QoS Profile handling, the following shall apply: 1) If the NG-RAN determines that the GFBR, the PDB or the PER of the QoS profile cannot be fulfilled, NG-RAN shall send a notification towards SMF that the "GFBR can no longer be guaranteed". Before sending a notification that the "GFBR can no longer be guaranteed" towards the SMF, the NG-RAN shall check whether the GFBR, the PDB and the PER that the NG-RAN currently fulfils match any of the Alternative QoS Profile(s) in the indicated priority order. If there is a match, the NG-RAN shall indicate the reference to the matching Alternative QoS Profile with the highest priority together with the notification to the SMF. If there is no match, the NG-RAN shall send a notification that the "GFBR can no longer be guaranteed" towards the SMF indicating that the lowest Alternative QoS Profile cannot be fulfilled (unless specific conditions at the NG-RAN require the release of the NG-RAN resources for this GBR QoS Flow, e.g. due to Radio link failure or RAN internal congestion). 2) If a notification that the "GFBR can no longer be guaranteed" has been sent to the SMF and the NG-RAN determines that the currently fulfilled GFBR, PDB or PER are different (better or worse) from the situation indicated in the last notification, the NG-RAN shall send a notification (i.e. "GFBR can no longer be guaranteed" or "GFBR can be guaranteed again") to the SMF and indicate the current situation (unless specific conditions at the NG-RAN require the release of the NG-RAN resources for this GBR QoS Flow, e.g. due to Radio link failure or RAN internal congestion). NOTE 1: The current situation is either that the QoS Profile can be fulfilled (which is implicitly indicated by the "GFBR can be guaranteed again" notification itself), that a different Alternative QoS Profile can be fulfilled, or that the lowest priority Alternative QoS Profile cannot be fulfilled. 3)- The NG-RAN should always try to fulfil the QoS profile and, if this is not possible, any Alternative QoS Profile that has higher priority. NOTE 2: In order to avoid a too frequent signalling to the SMF, it is assumed that NG-RAN implementation can apply hysteresis (e.g. via a configurable time interval) before notifying the SMF that the currently fulfilled values match the QoS Profile or a different Alternative QoS Profile of higher priority. It is also assumed that the PCF has ensured that the QoS values within the different Alternative QoS Profile(s) are not too close to each other. 4) Upon receiving a notification from the NG-RAN, the SMF may inform the PCF. If it does so, the SMF shall indicate the currently fulfilled situation to the PCF. See TS 23.503[ Policy and charging control framework for the 5G System (5GS); Stage 2 ]  [45]. 5) If the PCF has not indicated differently, the SMF uses NAS signalling (that is sent transparently through the RAN) to inform the UE about changes in the QoS parameters (i.e. 5QI, GFBR, MFBR) that the NG-RAN is currently fulfilling for the QoS Flow after Notification control has occurred.