The procedure for changing the UE state from RRC-connected to RRC-inactive is shown in Figure 220.127.116.11-1
The gNB-CU-CP sends BEARER CONTEXT SETUP REQUEST message with UE/PDU session/DRB level inactivity timer.
The gNB-CU-UP sends BEARER CONTEXT SETUP RESPONSE message.
The gNB-CU-UP sends BEARER CONTEXT INACTIVITY NOTIFICATION message with inactivity monitoring results.
The gNB-CU-CP determines that the UE should enter RRC-inactive (e.g., after receiving Bearer Context Inactivity Notification procedure).
The gNB-CU-CP sends BEARER CONTEXT MODIFICATION REQUEST message with a Bearer Context Status Change to the gNB-CU-UP, which indicates that the UE is entering RRC-inactive state. The gNB-CU-CP keeps the F1 UL TEIDs.
The gNB-CU-UP sends the BEARER CONTEXT MODIFICATION RESPONSE message including the PDCP UL and DL status that may be needed for e.g., data volume reporting. The gNB-CU-UP keeps the Bearer Context, the UE-associated logical E1-connection, the NG-U related resource (e.g., NG-U DL TEIDs) and the F1 UL TEIDs.
The gNB-CU-CP sends the UE CONTEXT RELEASE COMMAND message to the gNB-DU serving the UE, together with the RRCRelease message to be sent to the UE.
The gNB-DU sends the RRCRelease message to the UE.
The gNB-DU sends the UE CONTEXT RELEASE COMPLETE message to the gNB-CU-CP.
The procedure for changing the UE state from RRC-inactive to RRC-connected is shown in Figure 18.104.22.168-1
The gNB-CU-UP receives DL data on NG-U interface.
The gNB-CU-UP sends DL DATA NOTIFICATION message to the gNB-CU-CP.
The gNB-CU-CP sends PAGING message to the gNB-DU.
The gNB-DU sends the Paging message to the UE.
The UE sends RRCResumeRequest message either upon RAN paging or UL data arrival.
The gNB-DU sends the INITIAL UL RRC MESSAGE TRANSFER message to the gNB-CU-CP.
The gNB-CU-CP sends UE CONTEXT SETUP REQUEST message including the stored F1 UL TEIDs to create the UE context in the gNB-DU.
The gNB-DU responds with the UE CONTEXT SETUP RESPONSE message including the F1 DL TEIDs allocated for the DRBs.
The gNB-CU-CP and the UE perform the RRC-Resume procedure via the gNB-DU.
The gNB-CU-CP sends BEARER CONTEXT MODIFICATION REQUEST message with a RRC Resume indication, which indicates that the UE is resuming from RRC-inactive state. The gNB-CU-CP also includes the F1 DL TEIDs received from the gNB-DU in step 7.
The gNB-CU-UP responds with theBEARER CONTEXT MODIFICATION RESPONSE message.