OCNWDAF Services

5.1 Analytics Subscription Service

The Analytics Subscription Service handles the subscription and notification functions in the OCNWDAF. The NF service consumers can subscribe or unsubscribe to the notification for different analytics information from the OCNWDAF through this service. The service is implemented as per 3GPP TS 29.520(v16.11).

The consumer NFs use the APIs for subscribing or unsubscribing and updating the existing subscription for OCNWDAF analytics events. The consumers are notified of the observed events as per the subscription request, and the notification can be:

A single notification: Analytics Subscription Service sends only a single notification and purges the subscription.
A periodic notification: Analytics Subscription Service receives the periodic analytics generated from the Analytics Generation Service as per the notification period specified in the subscription request. A notification is generated for the received analytics data. On receiving this notification, subscriptionId and Notification URI mapping is fetched, notification data is prepared, and a REST call is made to the Notification URI.
A specific event notification: The Analytics Subscription Service processes the subscription request, validates the subscription information, generates the subscriptionID, and stores the subscription request in the subscription database. The Data Collection Service waits for the notification data corresponding to the observed events (such as configured thresholds breached) from the Analytics Generation Service and is invoked by using REST APIs.

The subscription can be for descriptive (KPIs and statistics) and predictive analytics (future event prediction). The subscription data is validated, and requests are stored in the subscription database.

Based on the subscription data, the Analytics Subscription Service intimates the Data Collection Service to gather data corresponding to the subscribed events from one or more NF functions.

The probable consumers of the Nnwdaf_EventsSubscription service are listed below:

Policy Control Function (PCF)
Network Slice Selection Function (NSSF)
Access and Mobility Management Function (AMF)
Session Management Function (SMF)
Network Exposure Function (NEF)
Application Function (AF)
Operations, Administration, and Maintenance (OAM)

The Nnwdaf interface is used for communication between the 5G consumers and OCNWDAF in the Nnwdaf_EventsSubscription service.

5.2 Analytics Information Service

The Analytics Information Service enables the consumer NFs to request and get specific analytics from the OCNWDAF. The nwdaf-analyticsinfo service manages the functions related to the Analytics Information Service. The service is implemented according to 3GPP TS 29.520(v16.0). Analytics Information Service is a REST API based service.

Note:

This service handles only HTTP2 requests.

The Analytics Information Service provides the following kinds of analytics information:

Descriptive Analytics: If the parameters startTime and endTime specify a past time, then the request is for the statistics reports.
Predictive Analytics: If the parameters startTime and endTime specify a future time, then the request is for the predictive analytics.

The Analytics Information Service provides analytics information corresponding to the Analytics ID in the consumer request.

The probable consumers of the Nnwdaf_AnalyticsInfo service are listed below:

Policy Control Function (PCF)
Network Slice Selection Function (NSSF)
Access and Mobility Management Function (AMF)
Session Management Function (SMF)
Network Exposure Function (NEF)
Application Function (AF)
Operation, Administration, and Maintenance (OAM)

5.3 Data Collection Service

This service collects data from the sources listed below for different types of analytics:

Global management data configured by the CSP.
NFs data available in the 5G network.
Data available in the individual NFs (for example, UE or UE group information).

The data collected is used as the basis for computing the analytics information. The data collection service handles the NF instance identification for the UEs and raises subscription requests to various NFs for NF data. It also receives notifications from the NFs for the subscribed events. This service enables the OCNWDAF to efficiently obtain appropriate data with the proper granularity. The operator can configure the OCNWDAF to collect analytics information from the NFs for future analytics requests. The operator defines the volume and maximum data storage. If the OCNWDAF has collected sufficient data to provide the requested information, it can skip the data collection procedure. The OCNWDAF can send an error response to the analytics consumer if the requested analytics are not available with the OCNWDAF. The data collection service retrieves behavior data for individual UEs or groups of UEs and global UE information.

The collected data helps in computing predictive and descriptive analytics based on the AnalyticsID. Following AnalyticsIDs are supported:

UE Mobility
Slice Load Level
Abnormal behavior (unexpected UE location)
NF Load

Data Collection Procedure from NFs:

The following call flow depicts the data collection procedure from various NFs:

Figure 5-1 Data Collection from NFs

The Data Collection Service enables the OCNWDAF to subscribe or unsubscribe to an Event ID (or a set of Event ID(s)) by invoking the Nnf_EventExposure_Subscribeor Nnf_EventExposure_Unsubscribe service operation.
The NFs notify the OCNWDAF of requested analytics (for example, event report) by invoking the Nnf_EventExposure_Notify service operation.

The following event exposure services enable OCNWDAF data collection:

Table 5-1 Exposure Services

Service producer	Service
AMF	Namf_EventExposure
SMF	Nsmf_EventExposure
UDM	Nudm_EventExposure
NEF	Nnef_EventExposure
NRF	Nnrf_NFDiscovery Nnrf_NFManagement

Data Collection by NRF

The OCNWDAF uses the NRF NF discovery service (Nnrf_NFDiscovery) to dynamically discover NF instances and their services in the 5G Core (5GC). This activity can be periodic or based on any specific event in the network. The OCNWDAF also utilizes the NRF MF Management Service (Nnrf_NFManagement), NFStatusSubscribe (NFStatusSubscribe), and NFStatusNotify services to obtain information about change in NF status. The information collected by these NRF services is used for obtaining NF Load analytics and maintaining a network map for data collection.

Note:

The Nnrf_NFDiscovery service is invoked only after NFStatusSubscribe service to eliminate race conditions of NF status change after the NRF discovery but before the NRFStatusSubscribe service.

NRF NFStatusSubscribe Service

The NFStatusSubscribe service is used to create an OCNWDAF subscription to the NRF. The OCNWDAF gets notified by the NRF when a specific NF instance profile or set of NF instance profiles are modified or deregistered in the NRF.

Figure 5-2 NF Status Subscribe

The OCNWDAF invokes the NFStatusSubscribe service to receive notifications about events (such as registration, deregistration, profile change) related to the Target NF located in the same PLMN by a POST request to the NRF.
The NRF authorizes or rejects the subscription request based on the validity of attributes in the POST request.
If the request is successful, a subscription is created and a HTTP response code "201 Created" is returned to the OCNWDAF.
If the request fails an appropriate HTTP response code is returned (4xx, 5xx or 3xx) indicating the reason for the failure.

NRF NFStatusNotify Service

This service operation notifies the OCNWDAF subscribed to NRF about registration (or deregistration) and profile changes of target NF (or NF instances).

Figure 5-3 NF Status Notify

The NRF invokes the NFStatusNotify service POST request to the subscribed OCNWDAF to indicate any registration or profile changes in the target NF (or NF instances).
If the request is successful, the OCNWDAF responds with a "204 No content" HTTP response code.
If the request fails an appropriate HTTP response code is returned (4xx, 5xx or 3xx) indicating the reason for the failure.

NRF NFDiscover Service

This service is used to obtain a set of NF instances (represented by their NF profile) that are currently registered with the NRF based on the input query parameters. The results are obtained in the SearchResult format. The information obtained is stored for further processing to obtain NF load analytics.

Figure 5-4 NF Discovery Service

The OCNWDAF invokes the NFDiscover service GET request with query parameter "nf-instances" to the NRF.
If the request is successful, the NRF responds with a "200 OK" HTTP code with the response body containing the requested NF profile information based on the request query.
If the request fails an appropriate HTTP response code is returned (4xx, 5xx or 3xx) indicating the reason for the failure.

5.4 Analytics Generation Service

The Analytics Generation service facilitates the generation of descriptive and predictive analytics provided by OCNWDAF. The service interfaces with the Data Collection service to obtain the raw data reports collected from different NFs and uses Analytics Engine (CAP4C) for the analytics processing.

In addition, the Analytics Generation service notifies the Analytics Subscription service about the generated analytics and obtains the generated analytics from either DBtier or Time Series Database. The service forms the core of OCNWDAF along with Data Collection and Analytics DB services. It is also responsible for interfacing with CAP4C to provision and fetch the trained ML models from the running Machine Learning Operations (MLOPs) service pipeline.

Also, the Analytics Generation service is responsible for performing features, such as managing subscription level aggregations, unrolling the raw data reports into a simple format, formatting the generated analytics into the OCNWDAF event notification format. In the case of complex descriptive analytics and predictions, the Analytics Generation service uses the backend Analytics Engine (CAP4C) data pipeline.

5.5 Analytics Database Service

The Analytics Database (DB) service communicates with the Analytics Information, Analytics Subscription, Data Collection, and Analytics Generation services for performing the following database operations:

Storing or updating the analytics data into the analytics database
Finding and deleting records from the analytics database