The Data Collection feature permits NWDAF to retrieve data from various sources (e.g. NF such as AMF, SMF, PCF, NSACF and AF; OAM), as a basis of the computation of network analytics.
All available data encompass:
OAM global NF data,
Data available in NFs, e.g. behaviour data related to individual UEs or UE groups (e.g. UE reachability), and pre-computed metrics covering UE populations (e.g. number of UEs present in a geographical area), per spatial and temporal dimensions (e.g. per region for a period of time),
NF data available in the 5GC (e.g. NRF),
Data available in AF.
When DCCF, ADRF, MFAF or NWDAF hosting DCCF or ADRF are present in the network, the data collection also follows the principles described in clause 6.2.6.
The NWDAF shall use at least one of the following services:
the Generic management services as defined in TS 28.532, the Performance Management services as defined in TS 28.550 or the Fault Supervision services as defined in TS 28.545, offered by OAM in order to collect OAM global NF data.
the Exposure services offered by NFs in order to retrieve data and other non-OAM pre-computed metrics available in the NFs.
Other NF services in order to collect NF data (e.g. NRF)
DCCF data management service to retrieve data using DCCF.
The NWDAF shall obtain the proper information to perform data collection for a UE, a group of UEs or any UE:
For an Analytics ID, NWDAF is configured with the corresponding NF Type(s) and/or event ID(s) and/or OAM measurement types.
NWDAF shall determine which NF instance(s) of the relevant NF type(s) are serving the UE, the group of UEs or any UE, taking into account the S-NSSAI(s) and area of interest as defined in clause 7.1.3 of TS 23.501.
NWDAF invokes Nnf_EventExposure_Subscribe services to collect data from the determined NF instance(s), and/or triggers the procedure in clause 18.104.22.168 to subscribe to OAM services to collect the OAM measurement.
The NWDAF performs data collection from an AF directly as defined in clause 22.214.171.124 or via NEF as defined in clause 126.96.36.199. According to the data collection request, the AF may further perform data collection from UE (see clause 6.4.2 and clauses 6.5.2 - 6.5.4) as defined in clause 6.2.8.
The NWDAF shall be able to discover the events supported by a NF.
Data collection procedures enables the NWDAF to efficiently obtain the appropriate data with the appropriate granularity.
When a request or subscription for statistics or predictions is received, the NWDAF may not possess the necessary data to perform the service, including:
Data on the monitoring period in the past, which is necessary for the provision of statistics and predictions matching the Analytics target period.
Data on longer monitoring periods in the past, which is necessary for model training.
Therefore, in order to optimize the service quality, the NWDAF may undertake the following actions:
The NWDAF may return a confidence parameter as stated in clause 6.1.3 expressing the confidence in the prediction produced. Prediction may be returned with zero confidence as described below. This confidence is likely to grow in the case of subscriptions.
The value of the confidence depends on the level or urgency expressed by the parameter "preferred level of accuracy" as listed in clause 6.1.3, the parameter "time when analytics information is needed" as listed in clause 6.1.3, and the availability of data. If no sufficient data is collected to provide an estimation for the preferred level of accuracy before the time deadline, the service shall return a zero confidence. Otherwise, the NWDAF may wait until enough data is collected before providing a response or a first notification.
In order to be prepared for future requests on analytics from NFs/OAM, the NWDAF, upon operator configuration, may collect data on its own initiative, e.g. on samples of UEs, and retain the data collected in the data storage.
The volume and maximum duration of data storage is also subject to operator configuration.
The NWDAF may decide to reduce the amount of data collected to reduce signalling load, by either prioritizing requests received from analytics consumers, or reducing the extent (e.g. duration, scope) of data collection, or modifying the sampling ratios. When using sampling ratio, the NWDAF may, depending on the analytics required and based on local configuration, provide additional partitioning criteria to the NFs to allow for a better UEs representation and to request that the NFs first partition the UEs before applying sampling ratio (see Event Reporting Information as specified in TS 23.502). The NWDAF may provide one or multiple partitioning criteria in its request for data collection from NFs.
The NWDAF may skip data collection phase when the NWDAF already has enough information to provide requested analytics.
The data which NWDAF may collect is listed for each analytics in input data clause and is decided by the NWDAF.
Event exposure subscriptions for data collection from the AMF and the SMF may need to survive after the removal of UE context in the AMF including event exposure subscriptions, or upon the creation of new UE context in AMF or SMF. In order for event exposure subscriptions in AMF and SMF to be (re)created in these cases, the NWDAF may subscribe to the events in AMF and/or SMF via UDM for a UE or group of UEs, as specified in TS 23.502, clause 188.8.131.52.
In hierarchical interactions among NWDAFs, without standalone DCCF, or co-located DCCF, the efficiency of data collection can be achieved by inter-NWDAF instance cooperation among NWDAF instances on different levels of the hierarchy. An efficient data collection means that the same data required for the same Analytics ID or different Analytics IDs should not be collected multiple times by the different NWDAFs of the hierarchy.
The Data Collection from NFs is based on the services of AMF, SMF, UDM, PCF, NRF, NSACF and AF (possibly via NEF):
The Data Collection from NFs is based on the services of AMF, SMF, UDM, PCF, NRF and AF (possibly via NEF):
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).
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 184.108.40.206-2 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 220.127.116.11-2 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.
The UDM instance should be determined using NRF as described in clause 4.17.4 of TS 23.502 and factors to determine as described in clause 6.3.8 of TS 23.501.
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 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 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.
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 TS 23.502, clause 18.104.22.168. 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 TS 23.502, clause 22.214.171.124.
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
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.
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.
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 126.96.36.199) as stated in Table 188.8.131.52-3 unless the NWDAF has already obtained this information due to recent operations related to this Analytics Filter Information.
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.
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.
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.
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 the TS 23.502, clause 184.108.40.206), 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.
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 TS 23.501, clause 5.6.11), SMF may subscribe to UE mobility event notifications of AMF as described in clause 220.127.116.11 of TS 23.501 using event ID "UE moving in or out of Area of Interest" and Event Filters as described in Table 18.104.22.168.1-1 from TS 23.502 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.
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 TS 23.501, clause 5.6.11), 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 22.214.171.124 of TS 23.501 using event ID "UE moving in or out of Area of Interest" and Event Filters as described in Table 126.96.36.199.1-1 from TS 23.502 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.
The procedure in Figure 188.8.131.52-1 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 184.108.40.206-1. 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.
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.
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.
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.
The procedure in Figure 220.127.116.11-1 is used by NWDAF to collect information from AFs via the 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)).
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).
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.
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.
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.
NF/NF service discovery procedures (in TS 23.502, clause 4.17.4) and Nnrf_NFDiscovery service (in TS 23.502, clause 18.104.22.168) 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 TS 23.502, clause 4.17.7) and Nnrf_NFManagement service (in TS 23.502, clause 22.214.171.124) 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 TS 23.502, clause 5.2.7. 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.
The NWDAF shall subscribe (and unsubscribe) to the Event exposure service from NF(s) reusing the framework defined in TS 23.502, clause 4.15. This framework supports the possibility for the NWDAF to indicate/request:
Target of Event Reporting defined in TS 23.502, clause 4.15.1: 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 TS 23.502, clause 4.15.1. 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 TS 23.502, clause 4.15.1, allowing the NWDAF to correlate notifications received from the NF with this subscription.