Content for  TS 23.288  Word version:  19.0.0

The NWDAF provides slice load level information to a consumer NF on a Network Slice level or a Network Slice instance level or both. The NWDAF is not required to be aware of the current subscribers using the slice. The NWDAF notifies slice specific network status analytics information to the consumer NF that is subscribed to it. A consumer NF may collect directly slice specific network status analytics information from NWDAF. This information is not subscriber specific. The NWDAF services as defined in the clause 7.2 and clause 7.3 are used to expose slice load level analytics from the NWDAF to the consumer NF (e.g. PCF, NSSF, AMF or AF, possibly via NEF). The consumer of these analytics shall indicate in the request or subscription:

• Analytics ID = "Load level information";
• Analytics Filter Information:
  • S-NSSAI and NSI ID;
  • optionally, the list of analytics subsets that are requested among those specified in clause 6.3.3A;
  • optionally, for analytics exposure in roaming case (see clause 6.1.5), the PLMN ID identifying the target PLMN (i.e. PLMN of which the roaming analytics is requested); and
  • optionally, for analytics exposure in roaming case (see clause 6.1.5), mapped S-NSSAI of the HPLMN if the consumer NF is in the VPLMN.
• an optional Area of Interest (i.e. list of TAs or cells);
• an optional list of NF types;
• optionally, Load Level Threshold value;
• optionally, "maximum number of objects" indicating the maximum number of Network Slice instances expected in output, when the Analytics Filter Information does not indicate an NSI ID; and
• an Analytics target period indicating the time period over which the statistics or predictions are requested.

The detailed information collected by the NWDAF is listed in Table 6.3.2A-1 and Table 6.3.2A-2.

NWDAF collects input data on the number of UEs registered in a S-NSSAI or S-NSSAI and NSI combination using one of the following options:

• Total number of UE registered to a S-NSSAI or to a S-NSSAI and NSI ID from each AMF(s) and/or from NSCAF serving the slice:
  • Namf_EventExposure_Subscribe (Target for Event Reporting = "any UE", Event ID = "Number of UEs served by the AMF and located in "Area of Interest"", Event Filter information = S-NSSAI(s) or one or more of the tuple (S-NSSAI, NSI ID), Event reporting mode = periodic along with periodicity) as defined in clause 5.2.2.3.1 of TS 23.502; or
  • Nnsacf_SliceEventExposure_Subscribe (EventID = "Number of UE registered", EventFilter = "S-NSSAI", Event reporting mode = periodic along with periodicity) as defined in clause 5.2.21.4.2 of TS 23.502.
• Individual UE registration/deregistration to a S-NSSAI or to a S-NSSAI and NSI ID reported by AMF(s):
  • Namf_EventExposure_Subscribe (Target for Event Reporting = "any UE", Event ID = "UE moving in or out of a subscribed "Area of Interest"", Event Filter information = S-NSSAI(s) or one or more of the tuples (S-NSSAI, NSI ID), Event reporting mode = reporting to a maximum number or a maximum duration) as defined in clause 5.2.2.3.1 of TS 23.502.

NWDAF collects input data on the number of PDU Sessions established in a S-NSSAI using one of the following options:

• Total number of PDU Sessions established in a S-NSSAI from each NSACF serving the slice:
  • Nnsacf_SliceEventExposure_Subscribe (EventID = "Number of PDU sessions established", EventFilter = "S-NSSAI(s)", Event reporting mode = periodic along with periodicity) as defined in clause 5.2.21.4.2 of TS 23.502.
• Individual PDU Session Established or PDU Session Released in a S-NSSAI from SMF:
  • Nsmf_EventExposure_Subscribe (Target for Event Reporting = "any UE", Event ID = "PDU Session Establishment and/or PDU Session Release", Event Filter information = S-NSSAI(s), Event reporting mode = reporting to a maximum number or a maximum duration) as defined in clause 5.2.8.3.1 of TS 23.502.

The NWDAF services as defined in the clause 7.2 and clause 7.3 are used to expose the following analytics:

• Network Slice instance load statistics information as defined in Table 6.3.3A-1.
• Network Slice load statistics information as defined in Table 6.3.3A-2.
• Network Slice instance load predictions information as defined in Table 6.3.3A-3.
• Network Slice load predictions information as defined in Table 6.3.3A-4.

The predictions are provided with a Validity Period, as defined in clause 6.1.3. The Network Slice Load statistics and predictions may be exposed to the AF by NEF under the conditions defined in clause 5.9.2.3 of TS 33.501 NEF security requirements.

Figure 6.3.4-1 shows the procedure for NWDAF to derive slice load analytics. The steps are described as follows: