The AF invokes the Nnef_BDTPNegotiation_Create (ASP id, Number of UEs, Volume per UE, Desired time window, and optionally External Group Identifier, Network Area Information, Reset request for notification). The Reset request for notification is an indication that BDT warning notification should be sent to the AF.
Based on an AF request, the NEF requests to translate the External Group Identifier into the Internal Group Identifier using Nudm_SDM_Get (Group Identifier Translation, External Group Identifier).
The NEF invokes the Npcf_BDTPolicyControl_Create
(ASP id, Number of UEs, Volume per UE, Desired time window and optionally Internal Group Identifier, the Network Area Information, Reset request for notification) with the H-PCF to authorize the creation of the policy regarding the background data transfer. If the PCF was provided with Reset request for notification, then PCF may send BDT warning notification to the AF as described in clause 220.127.116.11
The H-PCF may request from the UDR the stored transfer policies for all the ASPs using Nudr_DM_Query
(Policy Data, Background Data Transfer) service operation.
If only one PCF is deployed in the PLMN, the transfer policy can be locally stored and no interaction with UDR is required.
The UDR provides all the stored transfer policies and corresponding related information (i.e. volume of data to be transferred per UE, the expected amount of UEs) to the H-PCF.
The H-PCF determines, based on information provided by the AF and other available information one or more transfer policies. The PCF may interact with the NWDAF and request analytics information on the number of UEs and the Load in the area of interest including one or multiple time periods, as defined in TS 23.288
When the External Group Identifier was provided and the Network Area Information was not provided by the AF at step 1, the NWDAF derives the Network Area Information from the Internal Group ID as defined in clause 6.6 of TS 23.288
The maximum aggregated bitrate is not enforced in the network.
The H-PCF send the acknowledge message to the NEF with the acceptable transfer policies and a Background Data Transfer Reference ID.
The NEF sends a Nnef_BDTPNegotiation_Create
response to the AF to provide one or more background data transfer policies and the Background Data Transfer Reference ID to the AF. The AF stores the Background Data Transfer Reference ID for the future interaction with the PCF. If the NEF received only one background data transfer policy from the PCF, steps 8-11 are not executed and the flow proceeds to step 12. Otherwise, the flow proceeds to step 8.
If the NEF receives only one transfer policy, the AF is not required to confirm.
The AF invokes the Nnef_BDTPNegotiation_Update service to provide the NEF with Background Data Transfer Reference ID and the selected background data transfer policy.
The NEF invokes the Npcf_BDTPolicyControl_Update service to provide the H-PCF with the selected background data transfer policy and the associated Background Data Transfer Reference ID.
The H-PCF sends the acknowledge message to the NEF.
The NEF sends the acknowledge message to the AF.
The H-PCF stores the Background Data Transfer Reference ID together with the new transfer policy, the corresponding network area information, optionally the information of request for notification in the UDR by invoking Nudr_DM_Update (BDT Reference id, Policy Data, Background Data Transfer, updated data). This step is not executed, when the PCF decides to locally store the transfer policy.
The UDR sends a response to the H-PCF as its acknowledgement.