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Content for  TS 23.503  Word version:  18.4.0

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6  Functional descriptionp. 28

6.1  Overall descriptionp. 28

6.1.1  Generalp. 28

6.1.1.1  PCF Discovery and Selectionp. 28

The procedures for PCF Discovery and Selection by the AMF and by the SMF are described in TS 23.501.
The procedure to ensure that a consumer NF (e.g. an AF, NEF or PCF for a UE) reaches the PCF selected for a PDU Session is described in clause 6.1.1.2.
The procedure to ensure that a consumer NF (e.g. an AF) reaches the PCF selected for a UE is described in clause 6.1.1.2a.
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6.1.1.2  Binding an AF request targeting an UE address to the relevant PCFp. 28

6.1.1.2.1  Generalp. 28
When multiple and separately addressable PCFs have been deployed, a network functionality is required in order to ensure that a consumer NF (e.g. AF) needing to send policies about UE traffic identified by an UE address can reach over N5 the PCF holding the corresponding PDU Session information. This network functionality has the following characteristics:
  • It has information about the user identity, the DNN, the UE (IP or MAC) address(es), the S-NSSAI and the selected PCF address for a certain PDU Session.
    • For IP PDU Session type, it shall receive information when an IP address is allocated or released for a PDU Session.
    • If integration with TSN applies (see clause 5.28 of TS 23.501), it shall receive the DS-TT port MAC address.
    • For Ethernet PDU Sessions supporting binding of AF request based on MAC address, it shall receive information when a MAC address is detected as being used by the UE over the PDU Session (this detection takes place at the UPF under control of SMF and is defined in clause 5.8.2 of TS 23.501). In addition, it receives the DS-TT port MAC address in the case of support of time sensitive communication and time synchronization (as described in clause 5.28.3.2 of TS 23.501).
  • The functionality determines the PCF address and if available the associated PCF instance ID and PCF set ID, selected by the PCF discovery and selection function described in TS 23.501.
A private IPv4 address may be allocated to different PDU Sessions, e.g.:
  • The same UE IPv4 address is allocated to different PDU Sessions to the same DNN and different S-NSSAI;
  • The same UE IPv4 address is allocated to different PDU Sessions to the same S-NSSAI and different DNN.
In the case of private IPv4 address being used for the UE, the AF or the NEF may send DNN S-NSSAI, in addition, in Npcf_PolicyAuthorization_Create request and Nbsf_Management_Discovery request. The DNN and S-NSSAI can be used by the PCF for session binding, and they can be also used to help selecting the correct PCF.
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6.1.1.2.2  The Binding Support Function (BSF)p. 28
The BSF has the following characteristics:
  • The BSF stores internally information about the corresponding selected PCF:
    • For a certain PDU Session, the BSF stores internally information about the user identity, the DNN, the UE (IP or MAC) address(es), the S-NSSAI, the selected PCF address and if available the associated PCF instance ID, PCF set ID and the level of binding (see clause 6.3.1.0 of TS 23.501).
    • For a certain UE, the BSF stores internally information about the user identity, the selected PCF address and if available the associated PCF instance ID, PCF set ID and the level of binding (see clause 6.3.1.0 of TS 23.501).
  • The PCF registers, updates and removes the stored information in the BSF using the Nbsf management service operations defined in TS 23.502:
    • For a PDU Session, the PCF ensures that it is updated each time an IP address is allocated or de-allocated to the PDU Session or, for Ethernet PDU Sessions supporting binding of AF request based on MAC address, each time it has been detected that a MAC address is used or no more used by the UE in the PDU Session.
    • For a UE, the PCF ensures that it is updated each time the AMF selects a new PCF.
    • Based on operator's policies and configuration, the PCF determines whether the same PCF shall be selected for the SM Policy Associations to the same UE ID and S-NSSAI combination in the non-roaming or home-routed scenario.
  • Based on operator's policies and configuration, the PCF determines whether the same PCF shall be selected for the SM Policy Associations to the same UE ID and S-NSSAI combination in the non-roaming or home-routed scenario.
  • The selected PCF (if needed) downloads the user profile from the UDR as described in clause 4.16.4 step 2 of TS 23.502. If usage monitoring is enabled for the user, and based on operator's policies, the PCF checks if the BSF has already existing PCF serving the combination of SUPI, S-NSSAI and DNN:
    • If no such PCF is found the PCF shall register itself to the BSF as described above in this clause.
    • Else if an existing PCF is found for the above combination, the PCF shall return to the SMF the available information about the existing PCF and a redirection indication.
  • The BSF verifies whether to provide the address of a PCF for a PDU Session or a PCF for a UE according to the information provided by the consumer NF (e.g. the AF, the NEF, or the PCF for a UE). If the consumer NF provides the user identity and neither a UE address nor a (DNN, S-NSSAI) tuple, the BSF shall provide the address of the PCF for a UE. If the consumer NF (e.g. the PCF for a UE) provides the user identity (e.g. SUPI or GPSI) and the tuple (DNN, S-NSSAI), the BSF shall provide the address of a PCF for a PDU Session for this UE. If the consumer NF (e.g. the AF or the NEF) provides the UE address, the BSF shall provide the address of a PCF for a PDU Session.
  • For retrieval binding information, any NF, such as NEF or AF, that needs to discover the selected PCF address(es), and if available, the associated PCF instance ID, PCF set ID and level of binding (see clause 6.3.1.0 of TS 23.501) for the tuple (UE address, DNN, S-NSSAI, SUPI, GPSI) (or for a subset of this Tuple) uses the Nbsf management service discovery service operation defined in TS 23.502.
  • The NF may discover the BSF via NRF or based on local configuration. When registering the NF profile in NRF, the Range(s) of UE IPv4 addresses, Range(s) of UE IPv6 prefixes supported by the BSF and optionally, the DNN list, S-NSSAI(s) or IP domain list as described in TS 29.510, may be provided to NRF.
  • If the NF received a PCF set ID or a PCF instance ID with an indication of level of binding as result of the Nbsf management service discovery service operation, it should use that information as NF set level or NF instance level Binding Indication to route requests to the PCF as defined in clause 6.3.1.0 of TS 23.501 and according to the following provisions:
    • For the NF set level of binding, the NF will receive a PCF set ID but no PCF instance ID. If an NF is not able to reach the received PCF address(es) and applies direct discovery, it should query the NRF for PCF instances within the PCF set and select another instance.
    • For the NF instance level of binding, the NF will receive a PCF set ID and a PCF instance ID. If an NF is not able to reach the received PCF address(es) and applies direct discovery, it should query the NRF for PCF service instances within the PCF and select another instance.
    • The NF should provide a Routing Binding Indication based on the received PCF set ID, level of binding and possible PCF instance ID in requests it sends to the PCF.
  • For an ongoing NF service session, the PCF may provide Binding indication to the NF (see clause 6.3.1.0 of TS 23.501). This Binding indication shall then be used instead of any PCF information received from the BSF.
  • If a new PCF instance is selected, the new PCF should invoke Nbsf_Management_Update service operation to update the binding information in BSF.
The BSF may be deployed standalone or may be collocated with other network functions, such as PCF, UDR, NRF and SMF.
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6.1.1.2a  Binding an NF request targeting a UE to the relevant PCF for a UE |R17|p. 30

When multiple and separately addressable PCFs have been deployed, a network functionality is required in order to ensure that a consumer NF (e.g. AF, 5G DDNMF) reaches the PCF serving the UE. This network functionality is provided by the BSF (described in clause 6.1.1.2.2) and has the following characteristics:
  • It has information about the user identity, and the selected PCF address for a certain UE.
  • The functionality determines the PCF address and if available the associated PCF instance ID and PCF set ID, selected by the PCF discovery and selection function described in TS 23.501.
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6.1.1.3  Policy decisions based on network analyticsp. 30

Policy decisions based on network analytics allow PCF to perform policy decisions taking into account analytics information defined for Analytics IDs listed in TS 23.288. The analytics information may be provided by NWDAF directly or via DCCF, depending on the deployment of NWDAF or DCCF. Local configuration in the PCF indicates if one or multiple or all Analytics ID(s) are retrieved either from NWDAF directly or using DCCF. The PCF uses the DCCF services and DCCF service operations to fetch, subscribe and unsubscribe to the Analytics IDs as described in clause 6.1.4 and clause 8 in TS 23.288.
The PCF performs discovery and selection of NWDAF and DCCF as defined in TS 23.501 and subscribes/unsubscribes to Analytics information as defined in TS 23.288. In addition, the AMF and/or SMF may include, in the AM/SM Policy Association establishment or modification procedures, the list of NWDAF instance IDs used for the UE or the PDU Session and their associated Analytics ID(s) consumed by the AMF or SMF respectively. The PCF may select those NWDAF instances as the ones to subscribe for their associated Analytics ID(s) for the UE for which those AM/SM Policy Associations are related to or may perform NWDAF discovery if the NWDAF for an Analytics ID not provided by the AMF or SMF is needed.
The following Analytics IDs are relevant for Policy decisions: "Load level information", "Service Experience", "Network Performance", "Abnormal behaviour", "UE Mobility", "UE Communication", "User Data Congestion", "Data Dispersion", "Session Management Congestion Control Experience", "DN Performance", "WLAN performance" and "Redundant Transmission Experience". The PCF may subscribe to NWDAF as described below or alternatively, the PCF may use Ndccf_DataManagement_Subscribe including the "Analytics Specification" with the same information as provided in the Nnwdaf_AnalyticsSubscription_Subscribe, and optionally the PCF may include the NWDAF ID, e.g. if provided by AMF or SMF:
  • The PCF may subscribe to notifications of network analytics related to "Service Experience" using the Nnwdaf_AnalyticsSubscription_Subscribe service operation including the Analytics ID "Service Experience", the Target of Analytics Reporting "SUPI", "Internal Group Id" or "any UE", the Analytics Filter including one or more Application Identifier(s), one or more or "any" RAT Type(s) or Frequency value(s), one or more list(s) of combination of (S-NSSAI, DNN, PDU Session type and SSC Mode) optionally per Access Type and the Analytics Reporting Information set to service experience threshold value(s) for the RAT Type(s) and/or Frequency value(s). The PCF is notified on the Service Experience statistics or predictions including, for each Application Identifier, the list of SUPIs for which Service Experience is provided and the list of RAT Types and/or Frequency values for which the Service Experience applies. In addition, the list of SUPIs for which Service Experience is provided is also added when the Target of Analytics Reporting is "Internal Group Id" or "any UE". Both spatial and time validity may be provided as well as the confidence of the prediction.
    The NWDAF service to retrieve the Load Level Information is described in clause 6.3 of TS 23.288.
  • The PCF may subscribe to notifications of network analytics related to "Service Experience" using the Nnwdaf_AnalyticsSubscription_Subscribe service operation including the Analytics ID "Service Experience", the Target of Analytics Reporting "SUPI", "Internal Group Id" or "any UE", the Analytics Filter including one or more Application Identifier(s), one or more or "any" RAT Type(s) or Frequency value(s), one or more value(s) of each RSC (e.g. S-NSSAI, DNN, PDU Session type, SSC Mode, Access Type), one or more combination(s) of RSCs and the Analytics Reporting Information set to service experience threshold value(s) for the RAT Type(s) and/or Frequency value(s). The PCF is notified on the Service Experience statistics or predictions including, for each Application Identifier, the list of SUPIs for which Service Experience is provided and the list of RAT Types and/or Frequency values for which the Service Experience applies. In addition, both spatial and time validity may be provided as well as the confidence of the prediction.
    The NWDAF service to retrieve the service experience (i.e. the average observed Service MoS) is described in clause 6.4 of TS 23.288.
  • The PCF may subscribe to notifications of network analytics related to "Network Performance" using the Nnwdaf_AnalyticsSubscription_Subscribe service operation including the Analytics ID "Network Performance", the Target of Analytics Reporting "Internal Group Id" and the Analytics Filter including the Area of Interest. The PCF is notified on the Network Performance statistics or predictions including the Area of Interest. In addition, the confidence of the prediction may be provided.
    The NWDAF services to retrieve "Network Performance" as described in clause 6.6 of TS 23.288.
  • The PCF may subscribe to notifications of network analytics related to "Abnormal behaviour" using the Nnwdaf_AnalyticsSubscription_Subscribe service operation including the Analytics ID "Abnormal behaviour", the Target of Analytics Reporting "SUPI", "Internal Group Id" or "any UE" and the Analytics Filter including the expected analytics type or the list of Exceptions IDs and per each Exception Id a possible threshold and other Analytics Filter Information if needed. The list of Exception IDs is specified in TS 23.288.
    The NWDAF services to retrieve "Abnormal behaviour" analytics are described in clause 6.7.5 of TS 23.288.
  • The PCF may subscribe to notifications of network analytics related to "UE Mobility" using NWDAF_AnalyticsSubscription_Subscribe service operation including the Analytics ID "UE Mobility", the Target of Analytics Reporting "SUPI", "Internal Group Id" and the Analytics Filter may include one or more "Area(s) of Interest". The PCF is notified on the UE Mobility statistics or predictions as defined clause 6.7.2 of TS 23.288.
    The NWDAF services to retrieve "UE Mobility" analytics are described in clause 6.7.2 of TS 23.288.
  • The PCF may subscribe to notifications of network analytics related to "UE Communication" using NWDAF_AnalyticsSubscription_Subscribe service operation including the Analytics ID "UE communication", the Target of Analytics Reporting "SUPI", "Internal Group Id" and the Analytics Filter may include one or more "Application Identifier(s)". The PCF is notified on the UE communication statistics or predictions including list of application(s) in use and corresponding characteristics, e.g. start time and duration time. In addition, the confidence of the prediction may be provided.
    The NWDAF services to retrieve "UE Communication" analytics are described in clause 6.7.3 of TS 23.288.
  • The PCF may subscribe to notifications of network analytics related to "User Data Congestion" using NWDAF_AnalyticsSubscription_Subscribe service operation including the Analytics ID "User Data Congestion", the Target of Analytics Reporting containing a SUPI, indication requesting the identifiers of the applications that contribute the most to the traffic and the Analytics Filter may include Area of Interest, reporting threshold and maximum number of applications to be reported. The PCF is notified when the congestion level reaches the threshold. The notification can include the identifiers of the applications that contribute the most to the traffic.
    The NWDAF services to retrieve "User Data Congestion" analytics are described in clause 6.8 of TS 23.288.
  • The PCF may subscribe to notifications of network analytics related to "Data Dispersion" using NWDAF_AnalyticsSubscription_Subscribe service operation including the Analytics ID "UE Dispersion Analytics" and the dispersion analytic (DA) type, i.e. Data or Transactions. The Target of Analytics Reporting containing "SUPI", "Internal Group Id" or "any UE", and the Analytics Filter may include a list of TA(s) or an Area of Interest, or a list of Cells, or an S-NSSAI or top heavy users. With the Data Volume Dispersion Analytics type, the PCF may calculate the average data rate in the network slice by subscribing to notifications of network analytics related to Data Volume Dispersion in the network slice for a duration of interest when it sets the Target of Analytics Reporting as "any UE" and the Analytics Filter as the S-NSSAI.
    The NWDAF services to retrieve "Data Dispersion" analytics are described in clause 6.10 of TS 23.288.
  • The PCF may subscribe to notifications of network analytics related to "WLAN performance" using the Nnwdaf_AnalyticsSubscription_Subscribe service operation including the Analytics ID "WLAN performance", the Target of Analytics Reporting "SUPI", "Internal Group Id" or "any UE" and the Analytics Filter including the Area of Interest, SSID(s), or BSSID(s). The PCF is notified on the WLAN performance statistics or predictions. In addition, the confidence of the prediction may be provided.
    The NWDAF services to retrieve "WLAN performance" analytics are described in clause 6.11 of TS 23.288.
  • The PCF may subscribe to notifications of network analytics related to "Session Management Congestion Control Experience" using the Nnwdaf_AnalyticsSubscription_Subscribe service operation including the Analytics ID "Session Management Congestion Control Experience", the Target of Analytics Reporting containing "SUPI" and the Analytics Filter may include DNN and/or S-NSSAI. The PCF is notified on the Session Management Congestion Control Experience statistics including the DNN and/or S-NSSAI.
    The NWDAF services to retrieve "Session Management Congestion Control Experience" analytics are described in clause 6.12 of TS 23.288.
  • The PCF may subscribe to notifications of network analytics related to "DN Performance" using the Nnwdaf_AnalyticsSubscription_Subscribe service operation including the Analytics ID "DN Performance", the Target of Analytics Reporting containing "SUPI", "Internal Group Id" or "any UE", and the Analytics Filter may include Application ID(s). The PCF is notified on the DN Performance statistics or predictions including Application ID(s). In addition, the confidence of the prediction may be provided.
    The NWDAF services to retrieve "DN Performance" analytics are described in clause 6.14 of TS 23.288.
  • The PCF may subscribe to notifications of network analytics related to "Redundant Transmission Experience" using the Nnwdaf_AnalyticsSubscription_Subscribe service operation including the Analytics ID "Redundant Transmission Experience", the Target of Analytics Reporting "SUPI", "Internal Group Id" or "any UE" and the Analytics Filter including the Area of Interest, DNN, or S-NSSAI. The PCF is notified on the Redundant Transmission Experience statistics or predictions.
    The NWDAF services to retrieve "Redundant Transmission Experience" analytics are described in clause 6.13 of TS 23.288.
In the Analytic filter information of Analytics ID = "Service Experience" in Table 6.4.1-1 of TS 23.288, some of the information is equal to the RSCs in URSP rules, for example, DNN, S-NSSAI, PDU session type, Access type and S-NSSAI. So, the PCF can request the analytic of different combinations of RSC values to NWDAF, and these RSC values can be listed in Analytics Filter Information of Analytics request/subscribe towards NWDAF. And the NWDAF can provide the analytic of these combinations of RSCs to PCF. For example, if the PCF subscribes the Analytics ID = "Service Experience" with analytic filter {DNN1, SSC mode 1}, the NWDAF can provide the analytic of RSC combination of DNN1 + SSC mode 1 to PCF. The PCF can know the performance of each of the RSC combination.
Possible triggers for the PCF to subscribe to analytics information from the NWDAF may include:
  • Requests from AF/NEF;
  • AM Policy Association establishment or modification request from the AMF;
  • UE Policy Association establishment or modification;
  • SM Policy Association establishment or modification request from the SMF;
  • Notifications received from UDR or CHF on UE subscription change;
  • Analytics information received.
The trigger conditions may depend on operator and implementation policy in the PCF. When a trigger condition happens, the PCF may check local configuration or evaluate operator policy to decide if any analytics information is needed and if so, initiate a subscription to the analytics information from the NWDAF directly or via DCCF, if deployed.
The PCF may, upon a request from AF/NEF for negotiation for future background data transfer, subscribe to the network analytics related to "Network Performance" from the NWDAF directly or via DCCF, if deployed to assist in determination of BDT policies as described in clause 6.1.2.4.
The PCF shall, upon a request from AF/NEF for negotiation for Planned Data Transfer with QoS requirements (PDTQ), subscribe to the network analytics related to "Network Performance" or "DN Performance" from the NWDAF directly or via DCCF, if deployed to assist in determination of PDTQ policies as described in clause 6.1.2.7.
The PCF may, upon AM or UE or SM Policy Association establishment or modification request from the AMF or SMF, or based on notifications received from UDR or CHF on UE subscription change, decide that network analytics related to "Abnormal behaviour", "UE Mobility" or "UE Communication" of the UE, "Session Management Congestion Control Experience", "DN Performance", "User Data Congestion" is needed for policy decision and therefore subscribe to notifications of those network analytics from the NWDAF.
The PCF may, upon reception of analytics information, subscribe to other analytics information from the NWDAF directly or via DCCF, if deployed.
The PCF may use the network analytics information as input to its policy decision to apply operator defined actions for session management related policy control (as described in clauses 6.1.3), non-session management related policy control (as described in clause 6.1.2) and network slice related policy control (as described in clause 6.1.4.
In roaming scenarios, the H-PCF may make policy decisions for the outbound roaming UEs based on network analytics provided by the V-NWDAF. The H-PCF performs discovery and selection of an H-NWDAF with roaming exchange capability (i.e. RE-NWDAF) as defined in TS 23.502 and subscribes/unsubscribes to Analytics information from the V-NWDAF via the H-NWDAF as defined in TS 23.288. The H-PCF may request or subscribe to network analytics related to "Service Experience" or "Load Level Information" of the VPLMN. Based on these analytics, the H-PCF may update the URSP on Network Slice Selection Policy for the UE.
The PCF may, at AM Policy Association establishment or modification, subscribe to network analytics related to "Load Level Congestion" to request load information for the Allowed NSSAI.
Examples of operator policies including network analytics information as inputs for policy decisions included below:
  • Based on the "Load Level Information" statistics or predictions of the Network Slice Instance, the PCF may verify if the RFSP index value needs to be modified for a SUPI for which an AM Policy Association is created; this is based on operator policies in the PCF, as defined in clause 6.1.2.1.
  • Based on the "Service Experience" statistics or predictions, the PCF may check the 5QI values assigned to the Application, and may use this as input to calculate and update the authorized QoS for a service data flow template.
  • The PCF may use the network analytics related to "Network Performance" as input to calculate the background data transfer policies that are negotiated with the ASP, as defined in clause 6.1.2.4.
  • The PCF may use the network analytics related to "Network Performance" or "DN Performance", as input to calculate the planned data transfer with QoS requirements policies that are negotiated with the ASP, as defined in clause 6.1.2.7.
  • Based on the UE mobility statistics or predictions, the PCF may adjust Service Area Restriction as defined in clause 6.1.2.1.
  • The PCF may use the network analytics related to "Unexpected UE location" as input to determine the Service Area Restrictions defined in clause 6.1.2.1, "Suspicion of DDoS attack" or "Too frequent Service Access" to request the SMF to terminate the PDU Session as defined in clause 6.1.3.6, "Wrong destination address" to perform gating of a service data flow as defined in clause 6.1.3.6 and "Unexpected long-live/large rate flows" to perform QoS related policies such as gating or policing as defined in clause 6.2.1.1. Consequently, based on operator policies (that indicate that the PCF should store the subscriber status in the UE/AM/SM context), the PCF may store a Restricted Status for the subscriber in the Data Set "Policy Data" and Data Subset "UE context policy control data" or/and Data Subset "Access and Mobility policy control data" or/and Data Subset "PDU Session policy control data" in the UDR. The Restricted Status contains the reason for that status (i.e. Exception IDs listed in Table 6.7.5.3-3 of TS 23.288) and the time stamp set to the current time.
    Based on operator policies, network conditions and additional reports from NWDAF (e.g. UE moves out of Restricted service area), the PCF may remove the Restricted Status for the subscriber in the UDR for any of the Data Subsets listed above.
  • Based on the WLAN performance statistics or predictions, the PCF may update WLANSP as defined in clause 6.1.2.2.1.
  • Based on the "User Data Congestion" statistics or predictions including the list of applications contributing the most to the traffic the PCF may perform SM Policy Association modifications to update policies in the SMF for the PDU sessions handling traffic from those applications.
  • The PCF may use the network analytics on "Service Experience" for an Application Identifier, "any RAT type" and/or "any Frequency value" to determine the RFSP Index value for running this application, as described in clause 6.1.2.1.
  • The PCF may also use the network analytics as input to its policy decision to apply operator defined actions for example for the UE context(s) or PDU Session(s).
  • Based on the "Load Level Information" statistics or predictions for network slice(s), the PCF may give priority to consider the network slice(s) with lowest load for an application, and the PCF may update URSP on Network Slice Selection Policy.
  • Based on the "Load Level Information" statistics or predictions for network slice(s), the PCF may update the "S-NSSAI availability information" specified in clause 6.5, to indicate that an S-NSSAI is not available and to provide an Alternative S-NSSAI to replace with, this occurs when the Load Level Information reaches a threshold provided by the PCF.
  • Based on the "Load Level Information" statistics or predictions for network slice(s), the PCF may update the "S-NSSAI availability information" specified in clause 6.5, to indicate that an S-NSSAI is available again, and to indicate that replacement with the Alternative S-NSSAI does not apply any longer, this occurs when the Load Level Information goes below a threshold provided by the PCF.
  • Based on the "UE communication" statistics or predictions, the PCF may consider the DNN in Traffic characterization and associated Traffic Volume, Spatial validity and inactivity time, and the PCF may update URSP on DNN Selection Policy for associated UEs.
  • Based on the "Dispersion Analytics" statistics or predictions for Data Volume Dispersion in network slice(s), the PCF may calculate the average data rate in the network slice, and the PCF may update URSP on Network Slice Selection Policy for the associated UEs.
  • Based on the "Session Management Congestion Control Experience" statistics for PDU Session(s) associated with corresponding S-NSSAI(s) or DNN for a UE, PCF may give priority to consider the S-NSSAI or the DNN will be likely to that provide the lowest experience level of Session Management Congestion Control, and then the PCF may update URSP on Network Slice Selection Policy and/or DNN Selection Policy for the UE.
  • Based on the "Network Performance" statistics or predictions on gNB status information, gNB resource usage, communication performance and mobility performance in an Area of Interest, the PCF may consider to offload the traffic to non-3GPP access for the number of UEs that are located in that Area of Interest, and the PCF may update URSP on Non-Seamless Offload Policy for associated UEs.
  • Based on the "User Data Congestion" statistics or predictions including the list of applications contributing the most to the traffic, the PCF may consider to offload the traffic to non-3GPP access for those applications, and the PCF may update URSP on Non-Seamless Offload Policy for those applications.
  • Based on the "DN Performance" statistics or predictions for user plane performance for an application, the PCF may consider the DNN with higher performance, and the PCF may update URSP on DNN Selection Policy for the application.
  • Based on the "Redundant Transmission Experience" statistics or predictions, the PCF may update URSP for redundant PDU Sessions as described in clause 5.33.2.1 of TS 23.501, e.g. by modifying the URSP rule for Network Slice Selection and DNN Selection.
  • Based on the "Service Experience" statistics or predictions, the PCF may select one or a combination of following: the network slice, the DNN, the PDU Session type, the SSC Mode, the Access Type, as one RSC or a combination of RSCs in URSP rule for an application, and the PCF may also adjust the RSD precedence in URSP in terms of statistics or predictions of the whole RSD (a combination of RSCs) and then the PCF may update URSP on one or several of Network Slice Selection Policy, DNN Selection Policy, PDU Session Type Policy, SSC Mode Selection Policy, Access Type preference and the priority of each RSD.
Examples of operator policies including combination of multiple network analytics as inputs for policy decisions are included below:
  • Based on the notification of application(s) in use, provided by "UE Communication" analytics, the PCF may request the "Service Experience" analytics (optionally per RAT Type and/or per Frequency) for each application in use as defined in the list of examples of operator policies that may include network analytics as input for a policy decision.
  • Based on the "User Data Congestion" statistics or predictions, the PCF may further request the NWDAF directly or via DCCF, if deployed, to report the "Data Dispersion Analytics" of either a UE or just the Top Heavy UEs located at the congested area of interest. To mitigate the reported or predicted congestion at the area of interest, the PCF may perform:
    • AM Policy Association modification to update UE-AMBR, RFSP index and/or service area restriction, for those UEs reported as heavy users.
    • SM Policy Association modification to update the policies in the SMF for those UEs reported as heavy users.
    • UE Policy Association establishment/modification: Based on the "Load level information", "Service Experience", "Network Performance", "Abnormal behaviour", "UE Mobility", "UE Communication", "User Data Congestion", "Data Dispersion", "Session Management Congestion Control Experience", "DN Performance", "User Data Congestion" and "WLAN performance" statistics or predictions, the PCF uses analytics results from NWDAF to select proper values of URSP rules provided to UEs.
    • Based on the notification of Spatial validity for application(s) in use, provided by "UE Communication" analytics, the PCF may request the "WLAN performance" analytics for the Area of Interest derived from the Spatial validity of "UE Communication" analytics, and the PCF may update URSP on Non-Seamless Offload Policy for associated UEs.
The PCF may, upon UE Policy Association establishment or modification request from the AMF or based on notifications received from UDR or CHF on UE subscription change, subscribe to the analytics ID(s) listed in Table 6.1.1.3-1 from the NWDAF directly or via DCCF, if deployed, to adjust the fields (i.e. RSCs) and the RSD precedence in URSP rules.
URSP field Analytics ID(s)
Route Selection Components
S-NSSAI "Service Experience", "Load level information", "Dispersion Analytics", "Session Management Congestion Control Experience", "Redundant Transmission Experience".
DNN "Service Experience", "UE Communication", "Session Management Congestion Control Experience", "DN Performance", "Redundant Transmission Experience".
Non-Seamless Offload Indication "UE Communication", "WLAN performance", "Load level information", "Network Performance", "User Data Congestion".
SSC Mode "Service Experience".
PDU Session type "Service Experience".
Access Type Preference "Service Experience", "WLAN Performance".
Route Selection Validation Criteria
Time WindowBased on the validity period and spatial validity provided in the Analytics ID(s) used for RSD generation.
Location CriteriaBased on the validity period and spatial validity provided in the Analytics ID(s) used for RSD generation.
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6.1.1.4  Policy decisions based on spending limits |R18|p. 36

Policy decisions based on spending limits is a functionality that allows PCF taking actions related to the status of policy counters that are maintained in the CHF. The CHF in the non-roaming case or the H-CHF in the Home Routed roaming case provides policy counters for spending limits to the PCF for the PDU Session. The CHF in the non-roaming case provides policy counters for spending limits to the PCF for the UE.
This functionality is applicable to session management related policies, access and mobility management related policies and UE related policies. The PCF determines to enforce SM, UE and/or AM policy based on subscriber spending limits as indicated by Subscriber spending limits control as described in clause 6.2.1.3, respectively.
The PCF uses the CHF selection mechanism defined in TS 23.501 to select the CHF that provides policy counters for spending limits for PDU Session or for UE or both. The PCF for the PDU Session shall also provide the selected CHF address(es) to the SMF in the PDU Session related policy information. The PCF for the UE shall also provide the selected CHF address(es) to the AMF in the access and mobility management related policy information.
The identifiers of the policy counters that are relevant for a policy decision in the PCF may be stored in the PCF or possibly in UDR. The PCF is configured with the actions associated with the policy counter status that is received from CHF.
The PCF may retrieve the status of policy counters in the CHF using the Initial or Intermediate Spending Limit Report Retrieval Procedure. The CHF provides the current status of the policy counters to the PCF. The CHF may in addition provide one or more pending statuses for a policy counter together with the time they have to be applied. The PCF shall immediately apply the current status of a policy counter. A pending status of a policy counter shall autonomously become the current status of a policy counter at the PCF when the indicated corresponding time is reached. Subsequently provided information for pending statuses of a policy counter shall overwrite the previously received information.
The PCF may subscribe to spending limit reporting for policy counters from the CHF using the Initial or Intermediate Spending Limit Report Retrieval procedure. If spending limit reporting for a policy counter is enabled, the CHF shall notify the PCF of changes in the status of this policy counter (e.g. daily spending limit of $2 reached or monthly spending limit of $60 is reached) and optionally pending statuses of this policy counter together with their activation time (e.g. due to a billing period that will expire at midnight). The PCF may cancel spending limit reporting for specific policy counter(s) using the Intermediate Spending Limit Report Retrieval procedure, or for all policy counter(s) using the Final Spending Limit Report Retrieval procedure.
The PCF uses the status of each relevant policy counter, and optional pending policy counter statuses if known, as input to its policy decision to apply operator defined actions, e.g.:
  • change the QoS (e.g. downgrade or upgrade Session-AMBR or UE-AMBR), modify the PCC Rules to apply or remove gating or change charging conditions;
  • change the URSP rule (e.g. remove or add an RSD that allows the UE to use a dedicated S-NSSAI and DNN).
The CHF may report to the PCF the removal of the subscriber from the CHF system, and the PCF shall remove all the policy counters of the subscriber accordingly.
If operator policies indicates that the policy counters and its status should be available for a policy decision before the PCF retrieves the status of the policy counters from the CHF, the PCF stores the policy counters and its status in UDR at termination of the UE or AM or SM Policy Association.
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