CMAS Subscription, Message Delivery, and Notification Call Flow

This section describes the CMAS Subscription, Message Delivery, and Notification call flow.

CMAS Subscription, Message Delivery, and Notification Call Flow
CMAS Subscription, Message Delivery, and Notification Call Flow Description

Step

Description

1

The Cell Broadcast Center (CBC) creates and sends a NonUeN2InfoSubscribe to the AMF to be notified by the NG-RANs for the UE coverage of warning messages sent. The message type is the subscription parameter. The Cell Broadcase Entity (CBE) cannot subscribe a subset of warning messages.

2

The AMF creates a subscription and returns the location of the subscription to the CBE. The CBCF uses this location if it needs to modify or cancel the subscription.

3

The CBCF creates a Write Replace Warning Request NG-RAN message containing the warning message to broadcast. The message contains the following:

  • Message Identifier

  • Serial Number

  • List of NG-RAN TAIs

  • Warning Area List NG-RAN

  • OMC ID

  • CWM Indicator

  • Send Write-Replace-Warning-Indication

  • Global RAN Node ID

  • Warning Area Coordinates

This becomes a binary part to a Non-UE Message Transfer request to the AMF. The CBCF also optionally sends a list of TAI or a list of gNBs to AMF that need to receive this message.

4

The AMF responds to the CBCF that sending of warning messages to the gNodeB has started.

5

The AMF determines the set of gNB that need the message to send. This could be a list of gNB (if the CBCF sends the list), all gNB in a list of TAI, or all the gNB that are connected to the AMF. The AMF doesn't interpret the binary information that is part of the request. The AMF then sends a Write Replace warning request to the gNB.

6

The gNB responds to the warning message after broadcasting it.

7

If the CBCF has registered for notifications, the AMF notifies the CBCF. Each message that is sent by the gNB becomes an individual notification, as multiple binary payloads are not allowed in a single message.

8

The CBCF responds to the notification from the AMF.