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full Contents for  TS 23.288  Word version:   16.3.0

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6.2  Procedures for Data CollectionWord-p. 13
6.2.1  General
The Data Collection feature permits NWDAF to retrieve data from various sources (e.g. NF such as AMF, SMF, PCF, 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.
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)
The NWDAF shall obtain the proper information to perform data collection for a UE or group of UEs:
  • 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 or group of UEs, optionally 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_EventSubscribe services to collect data from the determined NF instance(s), and/or triggers the procedure in clause 6.2.3.2 to subscribe to OAM services to collect the OAM measurement.
The NWDAF performs data collection from an AF directly as defined in clause 6.2.2.2 or via NEF as defined in clause 6.2.2.3.
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 probability assertion 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 of the analytics" 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 requested 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 statistics from NFs/OAM, the NWDAF, upon operator configuration, may collect data on its own initiative, e.g. on samples of UEs (e.g. mobility), and retain the data collected in the data storage.
  • The volume and maximum duration of data storage is also subject of 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.
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.
NOTE:
NWDAF can skip data collection phase for some specific input data per the requested analytics e.g. when some of the data is already available at NWDAF for the requested analytics, or when NWDAF considers that some of the data is not needed at all to provide the requested analytics as per the analytics consumer request (e.g. based on preferred level of accuracy or based on the time when analytics are needed).
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6.2.2  Data Collection from NFsWord-p. 14
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 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).
Service producer
Service
Reference in TS 23.502

AMF
Namf_EventExposure
SMF
Nsmf_EventExposure
PCF
Npcf_EventExposure (for a group of UEs or any UE)
Npcf_PolicyAuthorization_Subscribe (for a specific UE)
UDM
Nudm_EventExposure
NEF
Nnef_EventExposure
AF
Naf_EventExposure
NRF
Nnrf_NFDiscovery
Nnrf_NFManagement

NOTE 1:
The present document specifies that NWDAF can collect some UPF input data for deriving analytics, but how NWDAF collects these UPF input data is not defined in this Release of the specification.
To retrieve data related to a specific UE, 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.
Type of NF instance (serving the UE) to determine
NF to be contacted by NWDAF
Service
Reference in TS 23.502

UDM
NRF
Nnrf_NFDiscovery
AMF
UDM
Nudm_UECM
SMF
UDM
Nudm_UECM
BSF
NRF
Nnrf_NFDiscovery
PCF
BSF
Nbsf_Management
NEF
NRF
Nnrf_NFDiscovery

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 or the group identity. 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.
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, NEF/AF, etc. NWDAF may first discover the instances of the required 5GC NFs deployed in the network, e.g. by querying NRF.
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 the instances in the network by using the Nnrf_NFDiscovery service.
NOTE 2:
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 TS 23.502, clause 4.15.3.2.3.
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.
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6.2.2.2  Procedure for Data Collection from NFsWord-p. 16
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.
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Step 1.
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.
Step 2.
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.
NOTE 2:
The NWDAF can use the immediate reporting flag as defined in Table 4.15.1-1 of TS 23.502 to meet the request-response model for data collection from NFs.
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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)).
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Step 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).
Step 1b.
NRF stores the received NEF registration information including available data to be collected from AF.
Step 1c.
NRF sends Nnrf_NFManagement_NFUpdate_response message to NEF.
Step 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.
Step 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.
Step 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.
Step 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.
Step 4.
If the NEF subscribes to data in AF, the AF notifies the NEF with the data by invoking Naf_EventExposure_Notify service operation.
Step 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.
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6.2.2.4  Procedure for Data Collection from NRFWord-p. 18
The NWDAF may use NRF services and Network Function service framework procedures as defined in TS 23.502, clause 5.2.7 and clause 4.17:
  • NF/NF service discovery procedures (in TS 23.502, clause 4.17.4) and Nnrf_NFDiscovery service (in TS 23.502, clause 5.2.7.3) 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 TS 23.502, clause 4.17.7) and Nnrf_NFManagement service (in TS 23.502, clause 5.2.7.2) 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 operations are the NFProfile and the NFService. Such information can be used to set-up and maintain a consistent network map for data collection and also, depending on use cases, in order to perform estimations:
  • NF profile: NF capacity, NF load information, NF status, NF recovery time, NF locality;
  • NF service: service capacity, service load information, service status, service recovery time.
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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 TS 23.502, clause 4.15. This framework supports the possibility for the NWDAF to indicate / request:
  • Events-ID: one or multiple Event ID(s) defined in TS 23.502, clause 4.15.1
  • 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.
  • Event Reporting Information described in TS 23.502 Table 4.15.1-1.
  • Expiry time as defined in TS 23.502, clause 4.15.1.
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.
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6.2.3  Data Collection from OAMWord-p. 19
6.2.3.1  General
The NWDAF may collect relevant management data from the services in the OAM as configured by the PLMN operator.
  • NG RAN or 5GC performance measurements as defined in TS 28.552.
  • 5G End to end KPIs as defined in TS 28.554.
NWDAF shall use the following services to have access to the information provided by OAM:
  • Generic performance assurance and fault supervision management services as defined in TS 28.532.
  • PM (Performance Management) services as defined in TS 28.550.
  • FS (Fault Supervision) services defined in TS 28.545.
NWDAF can be configured to invoke the existing OAM services to retrieve the management data that are relevant for analytics generation, which may include NF resources usage information (e.g. usage of virtual resources assigned to NF) and NF resource configuration information (e.g. life cycle changes of NF resource configurations).
OAM perform the required configuration in order to provide the information requested by NWDAF subscription and perform the tasks, e.g. data collection, data processing, associated with the subscribed request from NWDAF.
Another usage of OAM services is when the target of data collection is a specific UE, via MDT based retrieval of information:
  • Measurement collection for MDT as defined in TS 37.320.
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6.2.3.2  Procedure for data collection from OAM
The interactions between NWDAF and OAM for data collection are illustrated in Figure 6.2.3.2-1. The data collected depends on the use cases. This figure is an abstraction of the OAM performance data file report management service that is defined TS 28.532. The actual OAM services and reporting mechanisms that NWDAF may use are specified in TS 28.532, TS 28.550 or TS 28.545.
The flow below assumes the NWDAF is configured on how to subscribe to the relevant OAM services.
OAM shall setup the required mechanisms to guarantee the continuous data collection requested by NWDAF.
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Step 1.
(Clause 7.1.1.3.2 of TS 28.532), Subscribe (Input): NWDAF subscribes to the notification(s) related to the services provided by the management service producer.
Step 2.
(Clause 7.1.1.3.3 of TS 28.532), Subscribe (Output): management service producer responses to NWDAF if the subscription is success or not.
Step 3.
Data processing: management service producer prepares the data.
Step 4.
(Clause 7.1.1.1 of TS 28.532), Notification (notifyFileReady): management service producer notifies the data file is ready.
As the final step, NWDAF fetches data by using FTP (not specified in 3GPP, based on vendor implementation).
NOTE:
The call flow in Figure 6.2.3.2-1 only shows a subscribe/notify model for the simplicity, however both request-response and subscription-notification models are supported.
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6.2.4  Correlation between network data and service dataWord-p. 20
The Correlation information in each NF input data which helps NWDAF correlate data from different NFs is defined in Table 6.2.4-1, which is subject to all the network data analytics.
NOTE:
For simplicity, the correlation information is not listed in the input data per network data analytics.
Correlation Information
Description

Timestamp, IP address 5-tuple
To correlate the data from AF and from UPF.
Timestamp, AN Tunnel Info (Clause 9.3.2.2 of TS 38.413)
To correlate the UPF data and OAM data which are reported by the RAN (e.g. Reference Signal Received Power or Reference Signal Received Quality as defined in Table 6.4.2-3).
Timestamp, UE IP address
To correlate the data from UPF and SMF.
Timestamp, SUPI
To correlate data from SMF and AMF.
Timestamp, SUPI, DNN, S-NSSAI or UE IP address
To correlate data from SMF and PCF.
Timestamp, RAN UE NGAP ID (Clause 9.3.3.2 of TS 38.413) and Global RAN Node ID
To correlate the AMF data and OAM data reported by the RAN (e.g. Reference Signal Received Power or Reference Signal Received Quality as defined in Table 6.4.2-3).
Timestamp, Application ID, IP filter information
To correlate data from SMF and AF.

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