Content for  TS 38.473  Word version:  18.2.0

The purpose of the UE Context Modification Required procedure is to modify the established UE Context, e.g., modifying and releasing radio bearer resources, or sidelink radio bearer resources or candidate cells in conditional handover or conditional PSCell addition or conditional PSCell change. The procedure uses UE-associated signalling.

The F1AP UE CONTEXT MODIFICATION REQUIRED message is initiated by the gNB-DU. The gNB-CU reports the successful update of the UE context in the UE CONTEXT MODIFICATION CONFIRM message. For a given bearer for which PDCP CA duplication was already configured, if two DL UP TNL Information IEs are included in UE CONTEXT MODIFICATION REQUIRED message for a DRB, the gNB-CU shall include two UL UP TNL Information IEs in UE CONTEXT MODIFICATION CONFIRM message. The gNB-CU and gNB-DU use the UL UP TNL Information IEs and DL UP TNL Information IEs to support packet duplication for intra-gNB-DU CA as defined in TS 38.470, and the first UP TNL Information IE is still for the primary path. For a given bearer for which PDCP CA duplication was already configured, if one or two Additional PDCP Duplication UP TNL Information IEs are included in the UE CONTEXT MODIFICATION REQUIRED message for a DRB, the gNB-CU shall, if supported, include one or two Additional PDCP Duplication UP TNL Information IEs in the UE CONTEXT MODIFICATION CONFIRM message. The gNB-CU and gNB-DU use the Additional PDCP Duplication UP TNL Information IEs to support packet duplication for intra-gNB-DU CA as defined in TS 38.470. If the BH Information IE is included in the UL UP TNL Information to be setup List IE or the Additional PDCP Duplication TNL List IE for a DRB, the gNB-DU shall, if supported, use the indicated BAP Routing ID and BH RLC channel for transmission of the corresponding GTP-U packets to the IAB-donor, as specified in TS 38.340. If the Resource Coordination Transfer Container IE is included in the UE CONTEXT MODIFICATION REQUIRED, the gNB-CU shall transparently transfer this information for the purpose of resource coordination as described in TS 36.423, TS 38.423. For EN-DC operation, if the gNB-CU includes the Resource Coordination Transfer Information IE in the UE CONTEXT MODIFICATION CONFIRM message, the gNB-DU shall, if supported, use it for the purpose of resource coordination. If the gNB-CU received the MeNB Resource Coordination Information as defined in TS 36.423, after completion of UE Context Modification Required procedures, the gNB-CU shall transparently transfer it to the gNB-DU via the Resource Coordination Transfer Container IE in the UE CONTEXT MODIFICATION CONFIRM message. The gNB-DU shall use the information received in the Resource Coordination Transfer Container IE for reception of MeNB Resource Coordination Information at the gNB acting as secondary node as described in TS 36.423. If the Resource Coordination E-UTRA Cell Information IE is included in the Resource Coordination Transfer Information IE, the gNB-DU shall store the information replacing previously received information for the same E-UTRA cell, and use the stored information for the purpose of resource coordination. If the Ignore PRACH Configuration IE is present and set to "true" the E-UTRA PRACH Configuration IE in the UE CONTEXT MODIFICATION CONFIRM message shall be ignored. For NGEN-DC or NE-DC operation, if the gNB-CU includes the Resource Coordination Transfer Information IE in the UE CONTEXT MODIFICATION CONFIRM message, the gNB-DU shall, if supported, use it for the purpose of resource coordination. If the gNB-CU received the MR-DC Resource Coordination Information as defined in TS 38.423, after completion of UE Context Modification Required procedures, the gNB-CU shall transparently transfer it to the gNB-DU via the Resource Coordination Transfer Container IE in the UE CONTEXT MODIFICATION CONFIRM message. The gNB-DU shall use the information received in the Resource Coordination Transfer Container IE for reception of MR-DC Resource Coordination Information at the gNB as described in TS 38.423. If the DU to CU RRC Information IE is included in the UE CONTEXT MODIFICATION REQUIRED message, the gNB-CU shall perform RRC Reconfiguration as described in TS 38.331. The CellGroupConfig IE shall transparently be signaled to the UE as specified in TS 38.331. If the UE CONTEXT MODIFICATION CONFIRM message includes the Execute Duplication IE, the gNB-DU shall perform CA based duplication, if configured, for the SRB for the included RRC-Container IE. If the UE CONTEXT MODIFICATION REQUIRED message contains the RLC Status IE, the gNB-CU shall assume that RLC has been reestablished at the gNB-DU and may trigger PDCP data recovery. If the Candidate Cells To Be Cancelled List IE is included in the UE CONTEXT MODIFICATION REQUIRED message, the gNB-CU shall consider that only the resources reserved for the candidate cells identified by the included NR CGIs and associated to the UE-associated signaling identified by the gNB-CU UE F1AP ID IE and the gNB-CU UE F1AP ID IE are about to be released by the gNB-DU. If the PC5 RLC Channel Required to be Modified List IE or the PC5 RLC Channel Required to be Released List IE is included in the UE CONTEXT MODIFICATION REQUIRED message and the F1AP-IDs is associated with a U2N Relay UE, the PC5 RLC Channel Required to be Modified List IE or the PC5 RLC Channel Required to be Released List shall include the Remote UE Local ID and correspondingly, the PC5 RLC Channel Modified Item IEs in the UE CONTEXT MODIFICATION CONFIRM message shall include the Remote UE Local ID IE. If the UE Multicast MRB Required to Be Modified List IE is included in the UE CONTEXT MODIFICATION REQUIRED message

• containing for an MRB the MRB type reconfiguration IE set to "true" the gNB-CU shall take the MRB Reconfigured RLC mode IE into account to reconfigure the UE and to decide whether to request a PDCP status report as specified in TS 38.300 and include the MBS PTP Retransmission Tunnel Required IE in the UE Multicast MRB Confirmed to Be Modified Item IEs IE.
• containing for an MRB the Multicast F1-U Context Reference CU IE the gNB-CU shall, if supported, replace previously provided information by the newly received and take it into account when retrieving MRB progress information.

Interaction with the Multicast Distribution Setup procedure: If the UE CONTEXT MODIFICATION CONFIRM message contains for an MRB the MBS PTP Retransmission Tunnel Required IE in the UE Multicast MRB Confirmed to Be Modified Item IEs IE the gNB-DU shall, if supported, trigger the Multicast Distribution Setup procedure to setup requested F1-U resources, if applicable.

In case none of the requested modifications of the UE context can be successfully performed, the gNB-CU shall respond with the UE CONTEXT MODIFICATION REFUSE message with an appropriate cause value.

If one or more candidate cells in the Candidate Cells To Be Cancelled List IE included in the UE CONTEXT MODIFICATION REQUIRED message were not prepared using the same UE-associated signaling connection, the gNB-CU shall ignore those non-associated candidate cells.

This procedure is initiated by the gNB-DU to indicate the UE activity event. The procedure is also used to request the termination of SDT session. The procedure uses UE-associated signalling.

The gNB-DU initiates the procedure by sending the UE INACTIVITY NOTIFICATION message to the gNB-CU. If the DRB ID IE is included in the DRB Activity Item IE in the UE INACTIVITY NOTIFICATION message, the DRB Activity IE shall also be included. If the gNB-CU receives the SDT Termination Request IE in the UE INACTIVITY NOTIFICATION message, the gNB-CU shall, if supported, consider that the termination of the ongoing SDT transaction is requested from the gNB-DU for this UE and act as specified in TS 38.300.

Not applicable.

The purpose of the Notify procedure is to enable the gNB-DU to inform the gNB-CU that the QoS of an already established GBR DRB cannot be fulfilled any longer or that it can be fulfilled again. The procedure uses UE-associated signalling.

The gNB-DU initiates the procedure by sending a NOTIFY message. The NOTIFY message shall contain the list of the GBR DRBs associated with notification control for which the QoS is not fulfilled anymore or for which the QoS is fulfilled again by the gNB-DU. The gNB-DU may also indicate an alternative QoS parameters set which it can currently fulfil in the Current QoS Parameters Set Index IE. Upon reception of the NOTIFY message, the gNB-CU may identify which are the affected PDU sessions and QoS flows. The gNB-CU may inform the 5GC that the QoS for these PDU sessions or QoS flows is not fulfilled any longer or it is fulfilled again.

Not applicable.

The purpose of the Access Success procedure is to enable the gNB-DU to inform the gNB-CU of which cell the UE has successfully accessed during conditional handover or conditional PSCell addition or conditional PSCell change. The procedure uses UE-associated signalling.

The gNB-DU initiates the procedure by sending a ACCESS SUCCESS message. Upon reception of the ACCESS SUCCESS message, the gNB-CU shall consider that the UE successfully accessed the cell indicated by the included NR CGI IE in this gNB-DU and consider all the other CHO preparations or conditional PSCell addition or conditional PSCell change preparations accepted for this UE under the same UE-associated signaling connection in this gNB-DU as cancelled. Interaction with other procedure: The gNB-CU may initiate UE Context Release procedure toward the other signalling connections or other candidate gNB-DUs for this UE, if any.

If the ACCESS SUCCESS message refers to a context that does not exist, the gNB-CU shall ignore the message.