The gNB-CU decides to move UE into RRC_INACTIVE state.
The gNB-CU-CP decides to configure CG-SDT, it sends UE CONTEXT MODIFICATION REQUEST message including a query indication for CG-SDT related resource configuration associated with the information of SDT Radio Bearer(s).
The gNB-DU sends the UE CONTEXT MODIFICATION RESPONSE message including the CG-SDT related resource configurations for the requested SDT Radio Bearer(s) within the DU to CU RRC Information IE.
The gNB-CU-CP sends the BEARER CONTEXT MODIFICATION REQUEST towards the gNB-CU-UP, with the suspend indication.
The gNB-CU-UP sends the BEARER CONTEXT MODIFICATION RESPONSE towards the gNB-CU-CP.
The gNB-CU-CP sends the UE CONTEXT RELEASE COMMAND message to the gNB-DU including an RRCRelease message to the UE with the CG-SDT information within suspend configuration. The gNB-CU notifies the gNB-DU to keep the SDT RLC config, F1-U tunnels, F1AP UE association, and store the CG resource for SDT when the UE is entering RRC_INACTIVE state with an explicit CG-SDT kept indicator.
The gNB-DU sends the RRCRelease message to UE.
The gNB-DU sends UE CONTEXT RELEASE COMPLETE message. The gNB-DU keeps the SDT RLC config, F1-U tunnels, F1AP UE association, and stores the CG resource for SDT when the UE entering RRC_INACTIVE. The gNB-DU also stores the C-RNTI, CS-RNTI, and which bearers are CG-SDT bearers.
After a period of time of the UE being in RRC_INACTIVE state.
The UE decides to perform CG based SDT procedure, it sends the RRCResumeRequest message together with UL SDT data/UL NAS PDU.
The gNB-DU sends the UL RRC MESSAGE TRANSFER message including the RRCResumeRequest message to indicate the access due to CG-SDT.
The gNB-CU-CP initiates the BEARER CONTEXT MODIFICATION procedure to resume SDT DRBs.
Step 13 - 13a.
The gNB-DU sends the UL SDT data, if any, to the gNB-CU-UP, and/or sends the UL signalling, if any, to the gNB-CU-CP via the UL RRC MESSAGE TRANSFER message, in which any UL NAS PDU is delivered to AMF.