Content for  TS 37.483  Word version:  18.2.0

The purpose of the BC Bearer Context Setup procedure is to allow the gNB-CU-CP to establish MBS session resources for a broadcast MBS session in the gNB-CU-UP. The procedure uses MBS-associated signalling.

The gNB-CU-CP initiates the procedure by sending the BC BEARER CONTEXT SETUP REQUEST message to the gNB-CU-UP. If the gNB-CU-UP succeeds to establish the requested MBS session resources, it replies to the gNB-CU-CP with the BC BEARER CONTEXT SETUP RESPONSE message. The gNB-CU-UP shall report to the gNB-CU-CP, in the BC BEARER CONTEXT SETUP RESPONSE message, the result of all the requested resources in the following way:

• A list of BC MRBs which are successfully established shall be included in the BC MRB Setup Response List IE;
• A list of BC MRBs which failed to be established shall be included in the BC MRB Failed List IE;
• For each established BC MRB, a list of MBS QoS Flows which are successfully established shall be included in the MBS QoS Flow Setup List IE;
• For each established BC MRB, a list of MBS QoS Flows which failed to be established shall be included in the MBS QoS Flow Failed List IE;
• For each newly established BC MRB, if the F1-U TNL Info to Add List IE was included for an MRB within the BC MRB Setup Configuration IE, the gNB-CU-UP shall establish multiple F1-U resources which have one to one mapping with F1-U context referred by the Broadcast F1-U Context ReferenceE1 IE and include the F1-U TNL Info Added List IE in the BC MRB Setup Response List IE;

When the gNB-CU-UP reports the unsuccessful establishment of a BC MRB or MBS QoS Flow the cause value should be precise enough to enable the gNB-CU-CP to know the reason for the unsuccessful establishment. If the Requested Action for Available Shared NG-U Termination IE in the BC Bearer Context To Setup IE in the BC BEARER CONTEXT SETUP REQUEST message is set to

• "apply available configuration" and an appropriate Shared NG-U Termination is available, the gNB-CU-UP shall apply the radio bearer configuration of the Shared NG-U Termination, and indicate in the BC BEARER CONTEXT SETUP RESPONSE message within the Available BC MRB Configuration IE in the BC Bearer Context To Setup Response IE the radio bearer configuration of the Shared NG-U Termination, if the radio bearer configuration of the Shared NG-U Termination is different than the one requested by the gNB-CU-CP.
• "apply requested configuration" the gNB-CU-UP shall make use of an available appropriate Shared NG-U Termination if the radio bearer configuration of the Shared NG-U Termination, is the same as the one requested by the gNB-CU-CP, otherwise allocate separate resources as requested by the gNB-CU-CP and indicate in the BC BEARER CONTEXT SETUP RESPONSE message within the Available BC MRB Configuration IE in the BC Bearer Context To Setup Response IE the radio bearer configuration of the Shared NG-U Termination.
• "apply available configuration if same as requested" the gNB-CU-UP shall make use of an available appropriate Shared NG-U Termination only if the radio bearer configuration of the Shared NG-U Termination is the same as the one requested by the gNB-CU-CP and reply with BC BEARER CONTEXT SETUP RESPONSE message.

If the Associated Session ID IE is contained in the BC BEARER CONTEXT SETUP REQUEST message, the gNB-CU-UP shall, if supported, take this information into account to determine the appropriate resources, as specified in TS 38.401. If the MBS Service Area IE is contained in the BC BEARER CONTEXT SETUP REQUEST message, the gNB-CU-UP shall, if supported, take this information into account to determine the appropriate resources, as specified in TS 38.401.

If the gNB-CU-UP cannot establish the requested resources for the MBS session, it shall consider the procedure as failed and respond with the BC BEARER CONTEXT SETUP FAILURE message and an appropriate cause value. If the Requested Action for Available Shared NG-U Termination IE in the BC Bearer Context To Setup IE in the BC BEARER CONTEXT SETUP REQUEST message is set to "apply available configuration if same as requested" and the requested configuration does not match the available shared NG-U termination, the gNB-CU UP shall reply with BC BEARER CONTEXT SETUP FAILURE message.

void.

The purpose of the gNB-CU-CP initiated BC Bearer Context Modification procedure is to allow the gNB-CU-CP to modify MBS session resources for a broadcast MBS session. The procedure uses MBS-associated signalling.

The gNB-CU-CP initiates the procedure by sending the BC BEARER CONTEXT MODIFICATION REQUEST message to the gNB-CU-UP. If the gNB-CU-UP succeeds to perform at least partially the requested modifications it replies to the gNB-CU-CP with the BC BEARER CONTEXT MODIFICATION RESPONSE message. The gNB-CU-UP shall report to the gNB-CU-CP, in the BC BEARER CONTEXT MODIFICATION RESPONSE message, the result of all the requested MBS session resources in the following way:

• A list of BC MRBs which are successfully established or modified shall be included in the BC MRB Setup or Modify Response List IE;
• A list of BC MRBs which failed to be established or modified shall be included in the BC MRB Failed List IE;
• For each newly established or modified BC MRB, a list of MBS QoS Flows which are successfully established or modified shall be included in the MBS QoS Flow Setup List IE;
• For each newly established or modified BC MRB, a list of MBS QoS Flows which failed to be established or modified shall be included in the MBS QoS Flow Failed List IE;
• If the BC Bearer Context F1-U TNL Info at DU IE is included in the F1-U TNL Info to Add or Modify List IE for an MRB indicated in the BC Bearer Context To Modify IE, the gNB-CU-UP shall allocate or update respective F1-U resources for the F1-U context refered by Broadcast F1-U Context ReferenceE1 IE and indicate in the BC Bearer Context To Modify Response IE the BC Bearer Context F1-U TNL Info at CU IE if updated;
• If the F1-U TNL Info to Release List IE is included for an MRB indicated in the BC Bearer Context To Modify IE, the gNB-CU-UP shall release the respective F1-U resources.

When the gNB-CU-UP reports the unsuccessful establishment of a BC MRB or MBS QoS Flow the cause value should be precise enough to enable the gNB-CU-CP to know the reason for the unsuccessful establishment. If the BC Bearer Context NG-U TNL Info at 5GC To Setup or Modify IE is contained in the BC Bearer Context To Modify IE in the BC BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP shall update the previously received BC Bearer Context NG-U TNL Info at 5GC. If the BC Bearer Context NG-U TNL Info at NG-RAN Request IE set to "true" is contained in the BC Bearer Context To Modify IE in the BC BEARER CONTEXT MODIFICATION REQUEST message, the gNB-CU-UP, shall, if supported, consider the shared NG-U resources for the indicated broadcast MBS session being released, and allocate new shared NG-U resources accordingly and include respective information in the BC Bearer Context NG-U TNL Info at NG-RAN IE in the BC Bearer Context To Modify Response IE in the BC BEARER CONTEXT MODIFICATION RESPONSE message.

If the gNB-CU-UP cannot successfully perform any of the requested modifications, it shall respond with a BC BEARER CONTEXT MODIFICATION FAILURE message and an appropriate cause value.

void.

The purpose of the gNB-CU-UP initiated BC Bearer Context Modification Required procedure is to allow the gNB-CU-UP to request the gNB-CU-CP to initiate the modification MBS session resources for a broadcast MBS session and inform the gNB-CU-CP. The procedure uses MBS-associated signalling.

The gNB-CU-UP initiates the procedure by sending the BC BEARER CONTEXT MODIFICATION REQUIRED message to the gNB-CU-CP. The gNB-CU-CP replies to the gNB-CU-UP with the BC BEARER CONTEXT MODIFICATION CONFIRM message.

void.

The purpose of the gNB-CU-CP initiated BC Bearer Context Release procedure is to allow the gNB-CU-CP to command the release of MBS session resources for a broadcast MBS Session. The procedure uses MBS-associated signalling.

The gNB-CU-CP initiates the procedure by sending the BC BEARER CONTEXT RELEASE COMMAND message to the gNB-CU-UP. Upon reception of the BC BEARER CONTEXT RELEASE COMMAND message, the gNB-CU-UP shall release all related signalling and user data transport resources and reply with the BC BEARER CONTEXT RELEASE COMPLETE message.

Not applicable.

The purpose of the BC Bearer Context Release Request procedure is to allow the gNB-CU-UP to request the gNB-CU-CP to trigger the release of MBS session resources for a broadcast MBS Session. The procedure uses MBS-associated signalling.

The gNB-CU-UP initiates the procedure by sending the BC BEARER CONTEXT RELEASE REQUEST message to the gNB-CU-CP. Interactions with gNB-CU-CP initiated BC Bearer Context Release procedure: Upon reception of the BC BEARER CONTEXT RELEASE REQUEST message the gNB-CU-CP should initiate the BC Bearer Context Release procedure.

Not applicable.