Section: 16.15.2 Awareness
Content: XR-Awareness relies on QoS flows, PDU Sets, Data Bursts and traffic assistance information (see TS 23.501[ System architecture for the 5G System (5GS) ]  [3]). The following PDU Set QoS Parameters may be provided by the SMF to the gNB as part of the QoS profile of the QoS flow, and to enable PDU Set based QoS handling at least one of them shall be provided: - PDU Set Delay Budget (PSDB): as defined in TS 23.501[ System architecture for the 5G System (5GS) ]  [3], upper bound for the duration between the reception time of the first PDU (at the UPF for DL, at the UE for UL) and the time when all PDUs of a PDU Set have been successfully received (at the UE in DL, at the UPF in UL). A QoS Flow is associated with only one PSDB, and when available, it applies to both DL and UL and supersedes the PDB of the QoS flow. - PDU Set Error Rate (PSER): as defined in TS 23.501[ System architecture for the 5G System (5GS) ]  [3], upper bound for a rate of non-congestion related PDU Set losses between RAN and the UE. A QoS Flow is associated with only one PSER, and when available, it applies to both DL and UL and supersedes the PER of the QoS flow. NOTE 1: In this release, a PDU set is considered as successfully delivered only when all PDUs of a PDU Set are delivered successfully. - PDU Set Integrated Handling Information (PSIHI): indicates whether all PDUs of the PDU Set are needed for the usage of PDU Set by application layer, as defined in TS 23.501[ System architecture for the 5G System (5GS) ]  [3]. NOTE 2: The PDU Set QoS parameters are common for all PDU Sets within a QoS flow. During the Xn-handover preparation procedure, the source gNB sends the stored PDU Set QoS Parameters as part of the QoS profile to the target NG-RAN node. In addition, the UPF can identify PDUs that belong to PDU Sets, and may indicate to the gNB the following PDU Set Information in the GTP-U header: - PDU Set Sequence Number; - Indication of End PDU of the PDU Set; - PDU Sequence Number within a PDU Set; - PDU Set Size in bytes; - PDU Set Importance (PSI), which identifies the relative importance of a PDU Set compared to other PDU Sets within the same QoS Flow. 5GC may provide XR traffic assistance information to gNB through NG AP TSC Assistance Information (TSCAI) as specified in clause 5.37.8 of TS 23.501[ System architecture for the 5G System (5GS) ] [3] (for both GBR and non-GBR QoS flows): - UL and/or DL Periodicity; - N6 Jitter Information (i.e. between UPF and Data Network) associated with the DL Periodicity. This assistance information can be used by the gNB to configure DRX to enable better UE power saving. In addition, 5GC may provide the following information through NG-U as specified in clause 5.37.5.2 of TS 23.501[ System architecture for the 5G System (5GS) ] [3]: - Indication of End of Data Burst in the GTP-U header of the last PDU in downlink. This information can be used by the gNB to push the UE back to sleep when possible. In the uplink, the UE needs to be able to identify PDU Sets and Data Bursts dynamically, including PSI. How this is done is left up to UE implementation but when possible for a QoS flow, this is indicated to the gNB via UE Assistance Information.