Content for TS 23.288 Word version: 18.4.0

1… 4… 5… 5A… 6… 6.1.3 6.1.4… 6.1.4.4… 6.1.5… 6.1A… 6.1B… 6.1B.2.3… 6.1C 6.2… 6.2.3… 6.2.6… 6.2.6.2 6.2.6.3… 6.2.6.3.3 6.2.6.3.4 6.2.6.3.5 6.2.6.3.6… 6.2.7… 6.2.8… 6.2.9… 6.2.13… 6.2A… 6.2B… 6.2B.3 6.2B.4… 6.2C… 6.2D… 6.2E… 6.2F… 6.3… 6.4… 6.5… 6.6… 6.7… 6.7.3… 6.7.4… 6.7.5… 6.8… 6.9… 6.10… 6.11… 6.12… 6.13… 6.14… 6.16… 6.17… 6.18… 6.19… 6.20… 6.21… 7… 7.4… 7.7… 7.9… 8… 9… 10…

6.1B Transfer of analytics context and analytics subscription 6.1B.1 General 6.1B.2 Analytics Transfer Procedures 6.1B.2.1 Analytics context transfer initiated by target NWDAF selected by the NWDAF service consumer 6.1B.2.2 Analytics Subscription Transfer initiated by source NWDAF
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6.1B Transfer of analytics context and analytics subscription |R17| p. 58

6.1B.1 General p. 58

In a multiple NWDAFs deployment scenario, procedures for transfer of analytics context and analytics subscription can be used to support the target NWDAF to produce the needed analytics.

When the analytics consumer provides the target NWDAF with information on the subscription that could be transferred from the source NWDAF, the target NWDAF may initiate the transfer of analytics context. The analytics consumer provides the information via Nnwdaf_AnalyticsSubscription_Subscribe service operation. When the analytics consumer is an AMF, the old subscription information (if related to a UE) may be provided by the source AMF to the target AMF using a UE context transfer procedure as specified in TS 23.502.

An analytics subscription transfer to the target NWDAF may be initiated by the source NWDAF, followed by an analytics context transfer initiated by the target NWDAF. An NWDAF may transfer one or more of its analytics subscriptions to another NWDAF instance due to internal (e.g. load balancing, graceful shutdown) or external triggers (e.g. UE mobility). For external triggers, the NWDAF may subscribe to NF(s) to be notified about the corresponding events. As for UE mobility, upon the UE location change event notified by the AMF subscribed by the NWDAF, the NWDAF determines whether it can continue to provide the analytics service. If the NWDAF cannot continue to serve the consumer, it should either select a target NWDAF and initiate analytics subscription transfer, or notify the analytics consumer that it cannot provide the service anymore, so that the analytics consumer can select a new NWDAF.

Procedures for analytics subscription transfer allow one NWDAF instance to transfer its ongoing analytics subscriptions to another NWDAF instance. The transfer can be done for all subscriptions or just a selected subset of subscriptions related to specific area(s), specific Analytics ID(s), specific NF(s) and/or specific UE(s).

The procedure for prepared analytics subscription transfer can be used if the source NWDAF instance anticipates that it will soon not be able to continue its current analytics tasks.

6.1B.2 Analytics Transfer Procedures p. 59

6.1B.2.1 Analytics context transfer initiated by target NWDAF selected by the NWDAF service consumer p. 59

The procedure in Figure 6.1B.2.1-1 is used when an NF decides to select a new NWDAF instance due to internal or external triggers, e.g. the NF starts serving a UE with analytics subscription information received upon UE context transfer procedure as described in TS 23.502, or the NF starts to request NF related analytics, or the NF receives a "Termination Request" for an existing analytics subscription from an NWDAF. The NF sends to the target NWDAF information about the NWDAF previously used for analytics subscription, if available, in Nnwdaf_AnalyticsSubscription_Subscribe service operation. The target NWDAF may initiate the transfer of the analytics context, using the Nnwdaf_AnalyticsInfo_ContextTransfer or Nnf_DataManagement_Subscribe service operation.

The procedure in Figure 6.1B.2.1-1 is also used when an Aggregator NWDAF decides to select a new NWDAF to request output analytics for analytics aggregation. For example, upon receiving a Termination Request from one of the NWDAFs that are collectively serving a request for analytics subscription as specified in clause 6.1A, the Aggregator NWDAF queries the NRF or UDM to select a target NWDAF as specified in clause 6.1A.3 using information e.g. the UE location, the 5GC NFs (identified by their NF Set IDs or NF types) serving the UE or to be contacted for data collection (if Area of Interest is not provisioned for the requested analytics), or the subset of AoI (if Area of Interest is provisioned for the requested analytics). Then, the Aggregator NWDAF sends information about the NWDAF previously used for analytics subscription, if available, in Nnwdaf_AnalyticsSubscription_Subscribe service operation towards the selected target NWDAF.

Reproduction of 3GPP TS 23.288, Fig. 6.1B.2.1-1: Analytics context transfer initiated by target NWDAF selected by the NWDAF service consumer

Figure 6.1B.2.1-1: Analytics context transfer initiated by target NWDAF selected by the NWDAF service consumer

Step 1.

The NWDAF service consumer determines to select an NWDAF instance. The consumer discovers and selects the target NWDAF as specified in clause 5.2.

Step 2.

he consumer sends a request for analytics subscription to the target NWDAF using Nnwdaf_AnalyticsSubscription_Subscribe service operation, including information on the previous analytics subscription (i.e. NWDAF ID, Analytics ID(s), SUPIs, Analytics Filter Information for UE-related Analytics, Subscription Correlation ID, the Analytics Accuracy Request information (as defined in clause 6.1.3) when the Target NWDAF supports accuracy checking capability) which relates to the requested analytics subscription, if available. If the target NWDAF accepts the analytics subscription request, it sends Nnwdaf_AnalyticsSubscription_Subscribe response with a Subscription Correlation ID.

If the target NWDAF does not receive information of previous analytics subscription in step 2, for UE related Analytics, the target NWDAF may discover previously used NWDAF in UDM as specified in clause 5.2.

Step 3a.

[Option 1] If the target NWDAF decides to request an analytics context transfer from the previously used NWDAF, it may make use of information sent in step 2 (e.g. the provided Subscription Correlation ID) and use the analytics context transfer procedure as specified in clause 6.1B.3. The target NWDAF may receive an ADRF ID or DCCF ID for collecting the historical data and/or analytics.

If the target NWDAF supports the accuracy checking capability and the request received in step 2 contains the Analytics Accuracy Request information, the target NWDAF may include in the Nnwdaf_AnalyticsInfo_ContextTransfer request the field Requested Analytics Context Type with value set to Analytics accuracy related information and ML Model accuracy related information (both defined in clause 6.1B.4) in order to retrieve the necessary information for starting, respectively, the analytics accuracy information generation as well as the registration as provider of ML Model accuracy information for the ML model.

Step 3b-c.

[Option 2] If the target NWDAF decides to only request historical data and/or analytics, then it may collect the data and/or analytics via Nnf_DataManagement_Subscribe service, where the NFs may be either the ADRF, NWDAF or DCCF, as described in clauses 10.2.6, 7.4.2 and 8.2.2 respectively.

Target NWDAF is now ready to generate analytics information and if applicable, analytics accuracy information, taking into account the information received in step 3. The target NWDAF is also able to perform the registration as a new provider for an existing ML model accuracy information process as defined in clause 6.2E.3.2.

Step 4.

[Optional] Source NWDAF may purge analytics context after completion of step 3a, if performed and if not already done, unsubscribes from the data source(s) and/or model source(s) that are no longer needed for the remaining analytics subscriptions.

Step 5.

[Optional] Target NWDAF may subscribe to relevant data source(s) and/or model source(s), if it is not yet subscribed to the data source(s) and/or model source(s).

6.1B.2.2 Analytics Subscription Transfer initiated by source NWDAF p. 60

The procedure in Figure 6.1B.2.2-1 is used by an NWDAF instance to request the transfer of analytics subscription(s) to another NWDAF instance, using the Nnwdaf_AnalyticsSubscription_Transfer service operation defined in clause 7.2.5.

If the source NWDAF discovers that the analytics consumer may change concurrently to this procedure, the source NWDAF should not perform the procedure. In such a case, the source NWDAF may send a message to indicate to the analytics consumer that it will not serve this subscription anymore.

Reproduction of 3GPP TS 23.288, Fig. 6.1B.2.2-1: Analytics subscription transfer initiated by source NWDAF

Figure 6.1B.2.2-1: Analytics subscription transfer initiated by source NWDAF

Step 0.

The analytics consumer subscribes to analytics from source NWDAF. The analytics consumer may send its NF ID or serving area, enabling NWDAF to determine whether the following analytics subscription transfer procedure is applicable. Optionally the source NWDAF subscribes to UE mobility events.

Step 1.

[Optional] Source NWDAF determines, e.g. triggered by a UE mobility event notification, to prepare an analytics subscription transfer to target NWDAF(s), as specified in the procedure illustrated in clause 6.1B.2.3.

Step 2.

Source NWDAF determines, e.g. based on the UE location information received and the analytics consumer's serving area either directly received in step 0 or indirectly received via NRF, to perform an analytics subscription transfer to target NWDAF(s). Therefore, the source NWDAF determines the analytics subscription(s) to be transferred to a target NWDAF.

Step 3.

Source NWDAF performs an NWDAF discovery and selects the target NWDAF. NWDAF discovery may be skipped if the target NWDAF had already been discovered as part of a prepared analytics subscription transfer. In the case of aggregated analytics from multiple NWDAFs, the source NWDAF may use the set of NWDAF identifiers related to aggregated analytics (see clause 6.1.3) to preferably select a target NWDAF that is already serving the consumer. If the analytics subscription to be relocated to a target NWDAF also includes the Analytics Accuracy Request information, the source NWDAF selects, if possible, a target NWDAF also with accuracy checking capability. If the source NWDAF does not discover a target NWDAF with accuracy checking capability, the source NWDAF notifies the analytics consumer with Accuracy Information Termination. Therefore, the consumer based on local policy may decide to unsubscribe the analytics ID or to keep using the analytics ID even without receiving the accuracy information.

Step 4.

Source NWDAF requests, using Nnwdaf_AnalyticsSubscription_Transfer Request service operation, a transfer of the analytics subscription(s) determined in step 2 to the target NWDAF. The request contains a callback URI of the analytics consumer. The request may also contain active data source ID(s) and ML model related information, which are related to the analytics subscriptions requested to be transferred, if not already provided as part of the prepared analytics subscription transfer in the preparation procedure (see step 1). The ML model related information contains the ID(s) of NWDAF(s) containing MTLF that provided the trained models and may contain the file address(es) of the trained ML model(s), where the file address(es) of the trained ML model(s) is included only when the source NWDAF itself provides the trained ML model(s) for the analytics subscription(s) being transferred. The request message may also include "analytics context identifier(s)" indicating the availability of analytics context for particular Analytics ID(s).

Step 5.

Target NWDAF accepts the analytics subscription transfer and takes over the analytics generation and if applicable, the analytics accuracy information generation, based on the information received from the source NWDAF.

The target NWDAF may use analytics accuracy request information included in the analytics subscription transfer received in step 4 to start the process of checking and generating analytics accuracy information for the consumer of the transfer analytics subscription.

Target NWDAF may use the ML model related information, if provided in the Nnwdaf_AnalyticsSubscription_Transfer request. If the ID(s) of NWDAF(s) containing MTLF is provided in the Nnwdaf_AnalyticsSubscription_Transfer request and the NWDAF(s) containing MTLF is part of the locally configured set of NWDAFs containing MTLF, target NWDAF may request or subscribe to the ML model(s) from the indicated NWDAF(s) containing MTLF as specified in clause 6.2A and use the ML model(s) for the transferred analytics subscription. If the file address(es) of the trained ML model(s) is provided and if the NWDAF containing MTLF is part of the locally configured set of NWDAFs containing MTLF, the target NWDAF may retrieve the ML model using the file address of the trained ML model. If the provided ID(s) of NWDAF(s) containing MTLF are not part of the locally configured set of ID(s) of NWDAFs containing MTLF, the target NWDAF discovers the NWDAF(s) supporting MTLF that can provide trained ML model(s) for the Analytics ID(s) as described in clause 5.2.

Step 6.

Target NWDAF informs the analytics consumer about the successful analytics subscription transfer using a Nnwdaf_AnalyticsSubscription_Notify message. A new Subscription Correlation ID, which was assigned by the target NWDAF, is provided in the Subscription Correlation ID and the old Subscription Correlation Id, which was allocated by the source NWDAF, is provided in the Subscription Change Notification Correlation ID parameter of this message as specified in clause 7.2.4.

Step 7.

[Conditional] If "analytics context identifier(s)" had been included in the Nnwdaf_AnalyticsSubscription_Transfer Request received in step 4, the target NWDAF requests the "analytics context". The analytics context transfer procedure is specified in clause 6.1B.3.

If the transfer request received by the target NWDAF also includes the Analytics Accuracy Request information, the target NWDAF will include in the Nnwdaf_AnalyticsInfo_ContextTransfer request the field Requested Analytics Context Type with value set to Analytics accuracy related information (as defined in clause 6.1B.4) in order to retrieve the necessary information for generating the analytics accuracy information.

The target NWDAF may also retrieve from source NWDAF containing AnLF the ML model accuracy information for the ML Model when ML Model accuracy related information context type is included in the "analytics context identifier(s)" in the transfer request. Based on the retrieved ML Model accuracy related information, the target NWDAF containing AnLF registers as provider of ML Model accuracy information for the ML model as defined in clause 6.2E.3.2.

Step 8.

[Optional] Target NWDAF subscribes to relevant data source(s), if it is not yet subscribed to the data source(s) for the data required for the Analytics.

Step 9.

Target NWDAF confirms the analytics subscription transfer to the source NWDAF.

Step 10.

[Optional] Source NWDAF unsubscribes with the data source(s) that are no longer needed for the remaining analytics subscriptions. In addition, Source NWDAF unsubscribes with the NWDAF(s) containing MTLF, if exist, which are no longer needed for the remaining analytics subscriptions.

Step 11-12.

Target NWDAF at some point derives new output analytics and analytics accuracy information (if applicable) based on new input data and notifies the analytics consumer about the new analytics and new analytics accuracy information (if applicable) using a Nnwdaf_AnalyticsSubscription_Notify message as specified in clause 6.1.1.