Content for  TS 38.473  Word version:  18.2.0

The purpose of Write-Replace Warning procedure is to start or overwrite the broadcasting of warning messages. The procedure uses non UE-associated signalling.

The gNB-CU initiates the procedure by sending a WRITE-REPLACE WARNING REQUEST message to the gNB-DU. Upon receipt of the WRITE-REPLACE WARNING REQUEST message, the gNB-DU shall prioritise its resources to process the warning message. The gNB-DU acknowledges the WRITE-REPLACE WARNING REQUEST message by sending a WRITE-REPLACE WARNING RESPONSE message to the gNB-CU. Upon receipt of the WRITE-REPLACE WARNING REQUEST message, the gNB-DU shall include the Dedicated SI Delivery Needed UE List IE in the WRITE-REPLACE WARNING RESPONSE message for UEs that are unable to receive system information from broadcast. If Dedicated SI Delivery Needed UE List IE is contained in the WRITE-REPLACE WARNING RESPONSE message, the gNB-CU should take it into account when informing the UE of the updated system information via the dedicated RRC message. Upon reception of the Notification Information IE in the PWS System Information IE in the WRITE-REPLACE WARNING REQUEST message, the gNB-DU shall use this information to avoid that duplications trigger new broadcast or replace existing broadcast. If the gNB-DU receives a WRITE-REPLACE WARNING REQUEST message with the Notification Information IE in the PWS System Information IE which are different from those of ongoing broadcast warning messages, and if the SIB Type IE is set to "8", the gNB-DU shall broadcast the received warning message concurrently with other ongoing messages. If the gNB-DU receives a WRITE-REPLACE WARNING REQUEST message with the Notification Information IE in the PWS System Information IE which are different from those of ongoing broadcast warning messages, and if the SIB Type IE is set to the value other than '8' , the gNB-DU shall use the newly received one to replace the ongoing broadcast warning message with the same value of SIB Type IE. If the SIB Type IE in the PWS System Information IE in the WRITE-REPLACE WARNING REQUEST message is set to "8" and if a value "0" is received in the Number of Broadcast Requested IE and if the Repetition Period IE is different from "0", the gNB-DU shall broadcast the received warning message indefinitely. If Additional SIB Message List IE is included in PWS System Information IE, the gNB-DU shall store all SIB message(s) in PWS System Information IE, and consider that the first segment of public warning message is included in SIB message IE, and the remaining segments are listed in Additional SIB Message List IE in segmentation sequence order.

Not applicable.

If the gNB-DU receives a WRITE-REPLACE WARNING REQUEST message which does not include the Notification Information IE in the PWS System Information IE, the gNB-DU shall consider it as a logical error.

The purpose of the PWS Cancel procedure is to cancel an already ongoing broadcast of a warning message. The procedure uses non UE-associated signalling.

The gNB-CU initiates the procedure by sending a PWS CANCEL REQUEST message to the gNB-DU. The gNB-DU shall acknowledge the PWS CANCEL REQUEST message by sending the PWS CANCEL RESPONSE message. If the Cancel-All Warning Messages Indicator IE is present in the PWS CANCEL REQUEST message, then the gNB-DU shall stop broadcasting and discard all warning messages for the area as indicated in the Cell Broadcast To Be Cancelled List IE or in all the cells of the gNB-DU if the Cell Broadcast To Be Cancelled List IE is not included. The gNB-DU shall acknowledge the PWS CANCEL REQUEST message by sending the PWS CANCEL RESPONSE message, and shall, if there is area to report where an ongoing broadcast was stopped successfully, include the Cell Broadcast Cancelled List IE with the Number of Broadcasts IE set to 0. If the Cell Broadcast To Be Cancelled List IE is not included in the PWS CANCEL REQUEST message, the gNB-DU shall stop broadcasting and discard the warning message identified by the Message Identifier IE and the Serial Number IE in the Notification Information IE in all of the cells in the gNB-DU. If the Notification Information IE is included in the PWS CANCEL REQUEST, the gNB-DU shall cancel broadcast of the public warning message identified by the Notification Information IE. If an area included in the Cell Broadcast To Be Cancelled List IE in the PWS CANCEL REQUEST message does not appear in the Cell Broadcast Cancelled List IE in the PWS CANCEL RESPONSE, the gNB-CU shall consider that the gNB-DU had no ongoing broadcast to stop for the public warning message identified, if present, by the Notification Information IE in that area. If the Cell Broadcast Cancelled List IE is not included in the PWS CANCEL RESPONSE message, the gNB-CU shall consider that the gNB-DU had no ongoing broadcast to stop for the public warning message identified, if present, by the Notification Information IE.

If the gNB-DU receives a PWS CANCEL REQUEST message which contains neither the Cancel-all Warning Messages Indicator IE nor the Notification Information IE, the gNB-DU shall consider it as a logical error.

Not applicable.

The purpose of PWS Restart Indication procedure is to inform the gNB-CU that PWS information for some or all cells of the gNB-DU are available for reloading from the CBC if needed. The procedure uses non UE-associated signalling.

The gNB-DU initiates the procedure by sending a PWS RESTART INDICATION message to the gNB-CU.

Not applicable.

The purpose of the PWS Failure Indication procedure is to inform the gNB-CU that ongoing PWS operation for one or more cells of the gNB-DU has failed. The procedure uses non UE-associated signalling.

The gNB-DU initiates the procedure by sending a PWS FAILURE INDICATION message to the gNB-CU.

Not applicable.