5.7.2.4.2 Usage of Notification control with Alternative QoS Profiles at handover

During handover, the prioritized list of Alternative QoS Profile(s) (if available) is provided to the Target NG-RAN per QoS Flow in addition to the QoS profile. If the Target NG-RAN is not able to guarantee the GFBR, the PDB and the PER included in the QoS profile and if Alternative QoS Profiles are provided to the Target NG-RAN and the Target NG-RAN supports Alternative QoS Profiles, the Target NG-RAN checks whether the GFBR, the PDB and the PER values that it can fulfil match any of the Alternative QoS Profile(s) taking the priority order into account. If there is a match between one of the Alternative QoS Profiles and the GFBR, the PDB and the PER values that Target NG-RAN can fulfil, the Target NG-RAN shall accept the QoS Flow and indicate the reference to that Alternative QoS Profile to the Source NG-RAN.

If there is no match to any Alternative QoS Profile, the Target NG-RAN rejects QoS Flows for which the Target NG-RAN is not able to guarantee the GFBR, the PDB and the PER included in the QoS profile.

After the handover is completed and a QoS Flow has been accepted by the Target NG-RAN based on an Alternative QoS Profile, the Target NG-RAN shall treat this QoS Flow in the same way as if it had sent a notification that the "GFBR can no longer be guaranteed" with a reference to that Alternative QoS Profile to the SMF (as described in clause 5.7.2.4.1b).

If a QoS Flow has been accepted by the Target NG-RAN based on an Alternative QoS Profile, the reference to the matching Alternative QoS Profile is provided from the Target NG-RAN to the AMF (which forwards the message to the SMF) during the Xn and N2 based handover procedures as described in TS 23.502 [3]. After the handover is completed successfully, the SMF shall send a notification to the PCF that the "GFBR can no longer be guaranteed" for a QoS Flow (see TS 23.503 [45] for details) if the SMF has received a reference to an Alternative QoS Profile and this reference indicates a change in the previously notified state of this QoS Flow. If the PCF has not indicated differently, the SMF shall also use NAS signalling (that is sent transparently through the RAN) to inform the UE about the QoS parameters (i.e. 5QI, GFBR, MFBR) corresponding to the new state of the QoS Flow.

NOTE: A state change for the QoS Flow comprises a change from QoS profile fulfilled to Alternative QoS Profile fulfilled as well as the state change between fulfilled Alternative QoS Profiles.

If a QoS Flow has been accepted by the Target NG-RAN based on the QoS Profile, the SMF shall interpret the fact that a QoS Flow is listed as transferred QoS Flow in the message received from the AMF as a notification that "GFBR can again be guaranteed" for this QoS Flow. After the handover is successfully completed, the Target NG-RAN performs as described in clause 5.7.2.4.1b. If the SMF has previously notified the PCF that the "GFBR can no longer be guaranteed" and the SMF does not receive an explicit notification that the "GFBR can no longer be guaranteed" for that QoS Flow from the Target NG-RAN within a configured time, the SMF shall notify the PCF that the "GFBR can again be guaranteed".

If a QoS Flow has been accepted by the Target NG-RAN and SMF did not receive from the Target NG-RAN a reference to any Alternative QoS Profile and the SMF has previously informed the UE about QoS parameters corresponding to any of the Alternative QoS Profile(s), the SMF shall use NAS signalling to inform the UE about the QoS parameters corresponding to the QoS Profile.