5A CBCF Functionality

23.0413GPPRelease 18Technical realization of Cell Broadcast Service (CBS)TS

In 3GPP the CBCF is a network function in the 5G core network.

The CBCF may be connected to several AMFs. The CBCF may be connected to several CBEs. The CBCF shall be responsible for the management of CBS messages including:

– allocation of serial numbers;

– modifying or deleting CBS messages held by the NG-RAN node;

– initiating broadcast by sending fixed length CBS messages to a NG-RAN node for each language provided by the cell, and where necessary padding the pages to a length of 82 octets (see 3GPP TS 23.038 [3]);

– determining the set of cells to which a CBS message should be broadcast, and indicating within the Serial Number the geographical scope of each CBS message;

– determining the time at which a CBS message should commence being broadcast;

– determining the time at which a CBS message should cease being broadcast and subsequently instructing each NG-RAN node to cease broadcast of the CBS message;

– determining the period at which broadcast of the CBS message should be repeated;

– when CBS transmits emergency messages, allocation of "emergency indication" to differentiate it from normal CBS messages, including the "Cell ID/Service Area ID list", "warning type", "warning message". If "warning type" is of ‘test’, only UEs which are specially designed for testing purposes may display warning message.

The CBCF supports service based interface. The CBCF uses AMF communication services to forward warning messages to the NG-RAN and to subscribe to receive warning delivery related notifications.