6.2.2 Data Collection from NFs
23.2883GPPArchitecture enhancements for 5G System (5GS) to support network data analytics servicesRelease 18TS
6.2.2.1 General
The Data Collection from NFs is used by NWDAF to subscribe/unsubscribe at any 5GC NF to be notified for data on a set of events.
The Data Collection from NFs is based on the services of AMF, SMF, UDM, PCF, NRF, NSACF and AF (possibly via NEF):
– Event Exposure Service offered by each NF as defined in clause 4.15 and clause 5.2 of TS 23.502 [3].
– other NF services (e.g. Nnrf_NFDiscovery and Nnrf_NFManagement in NRF as defined in clause 4.17 of TS 23.502 [3])
This data collection service is used directly in order to retrieve behaviour data for individual UEs or groups of UEs (e.g. UE reachability) and also to retrieve global UE information (e.g. Number of UEs present in a geographical area).
Table 6.2.2.1-1: NF Services consumed by NWDAF for data collection
|
Service producer |
Service |
Reference in TS 23.502 [3] |
|
AMF |
Namf_EventExposure (NOTE 3) |
5.2.2.3 5.2.3.5 |
|
SMF |
Nsmf_EventExposure (NOTE 3) |
5.2.8.3 5.2.3.5 |
|
PCF |
Npcf_EventExposure (for a group of UEs or any UE) Npcf_PolicyAuthorization_Subscribe (for a specific UE) |
5.2.5.7 |
|
UDM |
Nudm_EventExposure |
5.2.3.5 |
|
NEF |
Nnef_EventExposure |
5.2.6.2 |
|
AF |
Naf_EventExposure |
5.2.19.2 |
|
NRF |
Nnrf_NFDiscovery |
5.2.7.3 |
|
Nnrf_NFManagement |
5.2.7.2 |
|
|
NSACF |
Nnsacf_SliceEventExposure |
5.2.21.4 |
NOTE 1: The present document specifies that NWDAF can collect some UPF input data for deriving analytics, how NWDAF collects these UPF input data via the SMF is defined in clause 4.15.11 of TS 23.502 [3].
NOTE 2: There is no data collected from the PCF by the NWDAF defined in this Release of the specification.
NOTE 3: The Nudm_EventExposure can be used when NWDAF uses the procedures specified in clause 4.15.4.4 of TS 23.502 [3] to subscribe to AMF or SMF via UDM.
To retrieve data related to a specific UE, there are two cases:
– If no Area of interest is indicated by the consumer, the NWDAF shall first determine which NF instances are serving this UE as stated in table 6.2.2.1-2 unless the NWDAF has already obtained this information due to recent operations related to this UE.
– If an Area of interest is indicated, the NWDAF can:
– First determine the AMF serving the UE and subscribe UE location from the AMF. Once the UE is in or moves into the Area of interest, the NWDAF determines which NF instances are serving this UE as stated in table 6.2.2.1-2 unless the NWDAF has already obtained this information due to recent operations related to this UE; or
– Determine the NF instances of a given type of network function serving the Area of interest by querying NRF unless the NWDAF has already obtained this information due to recent operations related to this UE.
Table 6.2.2.1-2: NF Services consumed by NWDAF to determine which NF instances are serving a UE
|
Type of NF instance (serving the UE) to determine |
NF to be contacted by NWDAF |
Service |
Reference in TS 23.502 [3] |
|---|---|---|---|
|
UDM |
NRF |
Nnrf_NFDiscovery |
5.2.7.3 |
|
AMF |
UDM |
Nudm_UECM |
5.2.3.2 |
|
SMF |
UDM |
Nudm_UECM |
5.2.3.2 |
|
BSF |
NRF |
Nnrf_NFDiscovery |
5.2.7.3 |
|
PCF |
BSF |
Nbsf_Management |
5.2.13.2 |
|
NEF |
NRF |
Nnrf_NFDiscovery |
5.2.7.3 |
|
NWDAF |
NRF UDM |
Nnrf_NFDiscovery Nudm_UECM |
5.2.7.3 5.2.3.2 |
|
NSACF |
NRF |
Nnrf_NFDiscovery |
5.2.7.3 |
The UDM instance should be determined using NRF as described in clause 4.17.4 of TS 23.502 [3] and factors to determine as described in clause 6.3.8 of TS 23.501 [2].
The AMF, SMF instances should be determined using a request to UDM providing the SUPI. To determine the SMF serving a PDU session, the NWDAF should in addition provide the DNN and S-NSSAI of this PDU Session; otherwise the NWDAF will obtain a list of possibly multiple SMFs (e.g. one per PDU session).
The BSF instance should be discovered using NRF thanks to optional request parameters (e.g. DNN list, IP domain list, IPv4 address range, IPv6 prefix range) as stated in clause 4.17.4 of TS 23.502 [3] or based on local configuration at the NWDAF.
The PCF instance serving UE PDU Session(s) should be determined using a request to BSF with the allocated UE address, DNN and S-NSSAI.
To collect data (e.g. current number of UEs registered in a network slice or current number of PDU Sessions established in a network slice) from NSACF, the NSACF instance should be discovered using NRF as specified in clause 6.3.22 of TS 23.501 [2] or based on local configuration at the NWDAF.
When NWDAF receives a request addressed to an Internal Group ID from a consumer, NWDAF may need to initiate data collection from several 5GC NFs, such as AMF, SMF, UDM, PCF, AF (e.g. via NEF), etc. If an Area of interest is indicated by the consumer, NWDAF may first discover the instances of the required 5GC NFs deployed in the network, e.g. by querying NRF, otherwise:
– For discovering the UDM, NWDAF can query the NRF with the Internal Group ID as the target of the query.
– For discovering AMF, SMF, PCF, NEF and AF, NWDAF may need to discover all instances in the network by using the Nnrf_NFDiscovery service.
NOTE 4: It is assumed that all members of an Internal Group ID belong to the same UDM Group ID. NWDAF can select a UDM instance supporting the UDM Group ID of the Internal Group ID.
Then, if data needs to be collected from AMF, SMF, UDM and PCF, NWDAF may initiate the data collection with the Internal Group ID as the target, e.g. subscribing to the event exposure in all the instances of a given type of network function. This subscription to all the instances of required source of event exposure handles, e.g. mobility of UEs across AMFs, or initiation of new PDU sessions with different allocated SMFs.
For collecting data from AMF and SMF, NWDAF may collect the data directly from AMF and/or SMF, or indirectly via UDM, according to clause 4.15.4.4 of TS 23.502 [3]. The indirect method may be required if the event exposure subscription from NWDAF, for a UE or group of UEs, needs to survive the removal of UE context in the AMF including event exposure subscriptions, or upon the creation of new UE context in AMF or SMF serving the UE or group of UEs. In this case the UDM is responsible for (re)creating event exposure subscriptions in AMF and SMF, as specified in clause 4.15.4.4 of TS 23.502 [3].
The NWDAF determines to collect data from a trusted AF supporting specific Event ID(s) and serving specific application(s) based on internal configuration.
The NEF instance that is serving a specific network slices and/or applications of a UE should be determined using NRF using optional request parameters as defined in clause 6.3.14 of TS 23.501 [2]
If NWDAF needs to collect data from an AF deployed outside the operator’s domain, the NWDAF shall contact NEF with a SUPI or Internal Group ID as the target of the data collection. NEF is responsible for translation of SUPI to GPSI, or internal to external group identifiers, by querying UDM, prior to contacting the AF.
NOTE 5: It is assumed that an AF is provisioned with the list of UE IDs (GPSIs or SUPIs) belonging to an External or Internal Group ID.
To retrieve required data for any UE, the NWDAF may subscribe to events from the AMF and/or SMF instances it has determined, setting the target of event reporting to "any UE" and the event filter(s) according to the Analytics Filter Information. Alternatively, if the required data is communication related and for any UE within an Area of interest, the NWDAF can obtain from the AMF instances it has determined a list of UEs located within the Area of Interest. Based on the obtained UE list, for each UE in the list, the NWDAF retrieves the SMF serving the UE and the NWDAF subscribes to data from the relevant SMF per each specific UE. The indirect event exposure subscription to AMF or SMF via UDM is not available for "any UE" or "any UE within an Area of interest". If the required data is collected from UE via AF as described in clause 6.2.8 and the Target of Analytics Reporting received from consumer is "any UE", the NWDAF may either set the target of event reporting to "any UE" in the data collection request to the AF, or may determine a list of UEs from AMF and/or SMF based on the Analytics Filter Information and send the data collection request to the AF for the determined list of UEs.
NOTE 6: If NWDAF requires collecting data from either AMF or SMF for "any UE" or "any UE within an Area of Interest", NWDAF can use the direct Event Exposure subscription to AMF or SMF, since subscriptions to "any UE" or "any UE within an Area of Interest" are persistent by nature in AMF or SMF, due to not being linked to a UE context.
To retrieve data related to "any UE" based on Analytics Filter Information, the NWDAF shall first determine which NF instances are matching the Analytics Filter Information (see clause 6.7.5.1) as stated in table 6.2.2.1-3 unless the NWDAF has already obtained this information due to recent operations related to this Analytics Filter Information.
Table 6.2.2.1-3: NF Services consumed by NWDAF to determine which NF instances are matching analytics filters
|
Type of NF instance (matching analytics filters) to determine |
NF to be contacted by NWDAF |
Service |
Reference in TS 23.502 [3] |
|---|---|---|---|
|
AMF, SMF |
NRF |
Nnrf_NFDiscovery |
5.2.7.3 |
To retrieve data related to Analytics IDs for "any UE" with Analytics Filter Information defining an area of interest in terms of TA or Cells and/or with specific S-NSSAIs, NWDAF requires the network slice association information to properly determine the AMFs to collect data from as well as the proper queries to OAM for data collection.
NOTE 7: Examples of Analytics ID requiring NWDAF to use network slice association information for data retrieval are: network performance clause 6.6.1; user data congestion clause 6.8.1; QoS Sustainability clause 6.9; Dispersion Analytics clause 6.10.1; observed service experience for a Network Slice clause 6.4.1; and slice load analytics clause 6.3.
The network slice association information comprises the TAs associated with each AMF and for each TAI its associated access type, cells and list of supported S-NSSAIs (including indication of S-NSSAIs restricted by AMF). Additionally, the mapping of cells per TAI and supported S-NSSAIs (including indication of S-NSSAIs restricted by AMF) for TAI for each AMF can change and NWDAF shall obtain this accurate information in order to properly retrieve data for analytics generation.
In order to derive the network slice association information, NWDAF may be configured with the mapping of cells per TAI and the S-NSSAIs per TAI. NWDAF may subscribe to the "S-NSSAIs per TAI mapping" event exposed by AMF. The NWDAF may use the configured information (when the analytics subscription or request is at cell granularity) and the area of interest in the analytics subscription or request to retrieve from AMF the list of supported S-NSSAIs (including indication of S-NSSAIs restricted by AMF) per TAI and access types per TAI for each AMF in the required area of interest. NWDAF consumes the "S-NSSAIs per TAI mapping" event exposed by AMF using, as target of event reporting, the list of TAIs based on the area of interest received in the Analytics Filter Information or identified by the mapping of the Cells per TAI matching to the Cell granularity included in the Analytics Filter Information. The AMF "S-NSSAIs per TAI mapping" event output contains, for each of the TAIs requested by NWDAF, its associated access type and the list of supported S-NSSAIs (including indication of S-NSSAIs restricted by AMF).
To retrieve data from SMFs for Analytics IDs subscription or requests for "any UE" including Analytics Filter Information with specific Applications, DNNs, DNAIs and area of interest per TA granularity, NWDAF shall first discover the SMF serving the area of interest via NRF.
NOTE 8: Examples of Analytics ID requiring NWDAF to collect data related to PDU sessions associated with an AoI with TA granularity are: network performance clause 6.6.1; user data congestion clause 6.8.1, QoS Sustainability clause 6.9.
NWDAF may directly consume events from the discovered SMF using the event target set to "any PDU session" and event filters with the same parameters of the Analytics Filter Information, i.e. list of Application IDs and/or DNNs and/or DNAI and the area of interest related to the requested Analytics ID.
1. When SMF supports the exchange of UE Location parameter when SMF interacts with AMF via Nsmf_PDUSession_Create/Update/CreateSMContext/UpdateSMContext due to session establishment, modification, or release, service request, or handover procedures (as defined in clause 5.2.8.2 of TS 23.502 [3]), SMF can directly map the PDU sessions to an AoI with TA granularity.
If there are any changes in PDU sessions in the area of interest, for the Application ID and/or DNN and/or DNAI subscribed by NWDAF, SMF notifies the detected changes to NWDAF via Nsmf_EventExposure_Notify service operation, enabling NWDAF to keep an updated map of SMF and PDU sessions associated with the Analytics Filter Information in an area of interest.
2. When SMF does not support the exchange of UE Location parameter when SMF interacts with AMF but supports the mapping of PDU sessions per TA (as defined in clause 5.6.11 of TS 23.501 [2]), SMF may subscribe to UE mobility event notifications of AMF as described in clause 5.3.4.4 of TS 23.501 [2] using event ID "UE moving in or out of Area of Interest" and Event Filters as described in Table 5.2.2.3.1-1 from TS 23.502 [3] to retrieve the list of SUPIs (and GPSIs if available) in the area of interest. Based on the retrieved list of SUPIs in the area of interest, SMF identifies the PDU sessions in the area of interest.
3. When SMF does not support the exchange of UE Location parameter when SMF interacts with SMF nor supports the mapping of PDU sessions per TA (as defined in clause 5.6.11 of TS 23.501 [2]), SMF rejects the request from NWDAF. Upon the reject, NWDAF identifies the need to create the mapping of PDU sessions per TA. NWDAF subscribes to UE mobility event notifications of AMF as described in clause 5.3.4.4 of TS 23.501 [2] using event ID "UE moving in or out of Area of Interest" and Event Filters as described in Table 5.2.2.3.1-1 from TS 23.502 [3] to retrieve the list of SUPIs (and GPSIs if available) in the area of interest. Based on the retrieved list of SUPIs in the area of interest, NWDAF subscribes to the SMFs serving the UEs in the area of interest and derives the mapping of PDU sessions per TA.
An NWDAF may require to discover and select other NWDAFs for UE related analytics. In this case, the NWDAF may discover from UDM if an NWDAF is already collecting data related to the UE, as specified in clauses 5.2 and 6.1C.
6.2.2.2 Procedure for Data Collection from NFs
The procedure in Figure 6.2.2.2-1 is used by NWDAF to subscribe/unsubscribe at NFs in order to be notified for data collection on a related event (s), using Event Exposure Services as listed in Table 6.2.2.1-1. Depending on local regulation requirements, user consent for UE related data collection and usage of collected data may be required. User consent is defined for a specific purpose such as, e.g. analytics or model training. NWDAF checks user consent taking the purpose for data collection and usage of these data into account.
Figure 6.2.2.2-1: Event Exposure Subscribe/unsubscribe for NFs
1. The NWDAF checks if data is to be collected for a user, i.e. SUPI or GPSI, then, depending on local policy and regulations, the NWDAF checks the user consent by retrieving the user consent information from UDM using Nudm_SDM_Get including data type "User consent". If user consent is not granted, NWDAF does not subscribe to event exposure for events related to this user and the data collection for this SUPI or GPSI stops here.
2. If the user consent is granted, the NWDAF subscribes to UDM to notifications of changes on subscription data type "User consent" for this user using Nudm_SDM_Subscribe.
3. The NWDAF subscribes to or cancels subscription for a (set of) Event ID(s) by invoking the Nnf_EventExposure_Subscribe/Nnf_EventExposure_Unsubscribe service operation.
NOTE 1: The Event ID(s) are defined in TS 23.502 [3].
4. If NWDAF subscribes to a (set of) Event ID(s), the NFs notify the NWDAF (e.g. with the event report) by invoking Nnf_EventExposure_Notify service operation according to Event Reporting Information in the subscription.
When the Reporting type is provided at step 1, the NWDAF determines that the events are disappeared, if the same events are included in the notification compared to the previous notification. Otherwise, NWDAF determines the events are newly appeared or changed. Also, the NWDAF restores the events that are not included in the notification, but included in the previous notification.
If the Granularity of dynamics is applied to the subscription, the NWDAF shall infer the events in the NF from the events in the previous notification with the applied Granularity of dynamics.
NOTE 2: The Event Reporting Information are defined in TS 23.502 [3].
NOTE 3: The NWDAF can use the immediate reporting flag as defined in Table 4.15.1-1 of TS 23.502 [3] to meet the request-response model for data collection from NFs.
NOTE 4: This procedure is also used when the NWDAF subscribes for data from a trusted AF.
5. The UDM may notify the NWDAF on changes of user consent at any time after step 2.
6-7. If user consent is no longer granted for a user for which data has been collected, the NWDAF shall unsubscribe to any Event ID to collect data for that SUPI or GPSI. The NWDAF may unsubscribe to be notified of user consent updates from UDM for each SUPI for which data consent has been revoked.
6.2.2.3 Procedure for Data Collection from AF via NEF
The procedure in Figure 6.2.2.3-1 is used by NWDAF to collect information from AFs via the NEF.
NOTE 1: In this release, AF registers its available data to NWDAF via OAM configuration at NEF.
The AF collectable data information includes: AF identification, AF service identification (e.g. endpoint information of Naf_EventExposure), available data to be collected per application (e.g. identified by Event ID(s)).
Figure 6.2.2.3-1: Data Collection from AF via NEF
1a. After the registration of AF available data at the NEF, NEF generates an event exposure with new EventID to be associated with available data to be collected from AF. NEF invokes Nnrf_NFManagement_NFUpdate_request service operation to update its registration information (i.e. NEF Profile) including the generated Event IDs and associated AF identification, Application ID(s) (i.e. internal application ID or Application ID known in the core network).
1b. NRF stores the received NEF registration information including available data to be collected from AF.
1c. NRF sends Nnrf_NFManagement_NFUpdate_response message to NEF.
1d. When NWDAF needs to discovery the available data from AFs and the appropriated NEF to collect this data, NWDAF invokes Nnrf_NFDiscovery_Request_request service operation using as parameter the NEF NF Type, a list of Event ID(s) and optionally AF identification, application ID.
1e. NRF matches the requested query for available data in AFs with the registered NEF Profiles and sends this information via Nnrf_NFDiscovery_Request_response message to NWDAF.
NOTE 2: After the registration and discovery procedure described in step 1, NWDAF identifies the available data per AF per application and the proper NEF to collect such data.
2. The NWDAF subscribes to or cancels subscription to data in AF via NEF by invoking the Nnef_EventExposure_Subscribe or Nnef_EventExposure_Unsubscribe service operation. If the event subscription is authorized by the NEF, the NEF records the association of the event trigger and the NWDAF identity.
NOTE 3: User consent for retrieving user data in AF via NEF is not specified in this Release.
3. Based on the request from the NWDAF, the NEF subscribes to or cancels subscription to data in AF by invoking the Naf_EventExposure_Subscribe/ Naf_EventExposure_Unsubscribe service operation.
4. If the NEF subscribes to data in AF, the AF notifies the NEF with the data by invoking Naf_EventExposure_Notify service operation according to Event Reporting Information in the subscription.
5. If the NEF receives the notification from the AF, the NEF notifies the NWDAF with the data by invoking Nnef_EventExposure_Notify service operation.
When the Reporting type is provided at step 2, the NWDAF determines that the events are disappeared, if the same events are included in the notification compared to the previous notification. Otherwise, NWDAF determines the events are newly appeared or changed. Also, the NWDAF restores the events that are not included in the notification, but included in the previous notification.
If the Granularity of dynamics is applied to the subscription, the NWDAF shall infer the events in the AF from the events in the previous notification and the applied Granularity of dynamics.
6.2.2.4 Procedure for Data Collection from NRF
The NWDAF may use NRF services and Network Function service framework procedures as defined in clause 5.2.7 and clause 4.17 of TS 23.502 [3]:
– NF/NF service discovery procedures (in clause 4.17.4 of TS 23.502 [3]) and Nnrf_NFDiscovery service (in clause 5.2.7.3 of TS 23.502 [3]) in order to dynamically discover the NF instances and services of the 5GC. Such discovery may be performed on a periodic basis, or under specific circumstances.
– NF/NF service status subscribe/notify procedures (in clause 4.17.7 of TS 23.502 [3]) and Nnrf_NFManagement service (in clause 5.2.7.2 of TS 23.502 [3]) in order to be notified about the change of status of an NF. The service operations for obtaining status information are NFStatusSubscribe and NFStatusNotify, from the Nnrf_NFManagement service.
The information provided by the NRF to the NWDAF with the Nnrf_NFDiscovery_Request and the Nnrf_NFManagement_NFStatusNotify service operations are the NF Profiles and the NF services as defined in clause 5.2.7 of TS 23.502 [3]. Such information can be used to set-up and maintain a consistent network map for data collection and also, depending on use cases, to perform analytics (e.g. NF load analytics as defined in clause 6.5).
If the NWDAF needs to keep a consistent network map for data collection from AMFs and SMFs associated with a list of TAs, the subscription to NFStatusSubscribe for such type of NFs may include the list of TAs target.
6.2.2.5 Usage of Exposure framework by the NWDAF for Data Collection
The NWDAF shall subscribe (and unsubscribe) to the Event exposure service from NF(s) reusing the framework defined in clause 4.15 of TS 23.502 [3]. This framework supports the possibility for the NWDAF to indicate/request:
– Events-ID: one or multiple Event ID(s) defined in clause 4.15.1 of TS 23.502 [3].
– Target of Event Reporting defined in clause 4.15.1 of TS 23.502 [3]: the objects targeted by the Events. Within a subscription, all Event ID(s) are associated with the same target of event reporting. In the case of NWDAF, the objects can be UE(s), UE group(s), any UE.
– Event Filter Information defined in clause 4.15.1 of TS 23.502 [3]. This provides Event Parameter Types and Event Parameter Value(s) to be matched against.
– A Notification Target Address and a Notification Correlation ID as defined in clause 4.15.1 of TS 23.502 [3], allowing the NWDAF to correlate notifications received from the NF with this subscription.
– Event Reporting Information described in TS 23.502 [3] Table 4.15.1-1 and the muted stored events exposure as described in clause 6.2.7.
– Expiry time as defined in clause 4.15.1 of TS 23.502 [3].
The notifications from NFs/AFs contain on top of the Event being reported (and of dedicated information being reported for this event):
– the Notification Correlation Information provided by the NWDAF in its request;
– (when applicable to the event) the Target Id e.g. UE ID (SUPI and if available GPSI); and
– a time stamp.