Energy related aspects in charging mechanism in network

Abstract

A method of a network function (NF), the NF having functionality relating to energy information, wherein the method comprises: providing an event exposure service for energy information to a consumer

Description

BACKGROUND Field Certain examples of the present disclosure provide one or more techniques relating to energy related aspects in a charging mechanism in a network, for example a 3rd Generation Partnership Project (3GPP) 5th Generation (5G) New Radio (NR) network. Description of the Related Art Various acronyms and abbreviations used in the present disclosure may be interpreted, for example, according to the 3GPP 5G specification. General description of energy usage / consumption and energy efficiency of 3GPP system Currently, there are more than 110 countries committed to a net zero emissions target by 2050. What the Paris Agreement attempts to uphold is making sure global temperatures stay within 2C by 2100, but preferably closer to 1.5C. The motivation of reducing the energy emissions and increase the energy efficiency of the telecoms sector is more urgent than before. Also considering the price of energy are going up and the increasing traffic load of the telecoms system, mobile network operators are keen to optimize the costs of ongoing operations (opex). Energy-saving measures in network operations are necessary for NR radio equipment and other components of telecommunications systems. Compared to the previous generations, the 5G New Radio (NR) offers a significant energyefficiency improvement in its first release (3GPP Rel-15), i.e. cell activation / deactivation over Xn / X2 / F1 interface via coordination between peer eNB / gNBs, sparser RS and SS signals, URLLC, CU / DU architecture and MR-DC, etc. However, based on the GSMA report ‘5G energy efficiencies: Green is the new black’ (https: / / data.gsmaintelligence.com / api-web / v2 / research-file-download?id=54165956&file=241120-5G-energy.pdf) published in 2020, Network opex tends to account for around 25% of Verizon’s cost base, or 10% of revenue. In addition, over 90% of network costs are spent on energy, consisting mostly of fuel and electricity consumption. To further reduce energy consumption and improve the efficiency of the 3GPP system, in the releases later than Rel-15, some of the working groups (WGs) in RAN, SA and CT have completed or are developing mechanisms to increase energy saving or energy efficiency. To reduce the energy consumption of RAN part, in Rei-18, RAN WG started to study and specify the techniques on network energy savings (RAN WID in RP-223540 / RP-230566 Sept. 2023), and RAN will further work on network energy saving improvement in Rel-19 (RP-234065) on supporting on-demand SSB SCell operation for UEs in connected mode, on-demand SIB1 for UEs in idle / inactive mode, and adaptation of common signal / channel transmissions. SA5 started their work on Energy efficiency of the 5G system in Rel-16. In Rel-17 (3GPP TR 28.813 - Study on new aspects of Energy Efficiency (EE) for 5G) and Rel-18 (3GPP TR 28.913), SA5 extended its scope from RAN only to the whole 5G system. The specified techniques are documented in 3GPP TS 28.310 ‘Management and orchestration; Energy efficiency of 5G’ and the corresponding KPIs and measurements related to Energy efficiency (EE) are documented in 3GPP TS 28.552 ‘Management and orchestration; 5G performance measurements’ and 3GPP TS 28.554 ‘Management and orchestration; 5G end to end Key Performance Indicators (KPI)’. In Rel-19, SA5 will keep working on energy efficiency and energy saving aspects of 5G networks and services according to the SID approved in SP-231723 in Dec 2023. SA1 is currently working on the potential requirements and solutions on Rel-19 Energy Efficiency as a service criteria (acronym: EnergyServ). This topic will be 100% completed by TSG 102 (Dec, 2023). The outcome of the study phase is documented in TR 22.882 - Study on Energy Efficiency as service criteria). And some of the specified SA1 stage 1 requirements, e.g. the max. energy credit, might be down streamed to SA2 for further stage 2 work. Overview of Existing and ongoing work in 3GPP SA1 working groups In the previous releases of NR (earlier than Rel-19), the studies concentrated more on how to satisfy user experience and try to achieve energy efficiency at the same time. The use cases and solutions basically concern enhancements within the 3GPP network. For example, requirements for energy efficiency have been introduced by SA1 to clause 6.15 of 3GPP TS 22.261 as a fundamental 5G system requirement. However, those requirements more focused on the optimization of UEs battery life based on network configuration and control, including the UEs using small rechargeable and single coin cell batteries. But the verticals (diverse industry sectors' service providers) and customers have no approach to enhance or improve the energy efficiency for the whole system. SA1 is completed a study on energy efficiency as a service in Rel-19 (3GPP TR 22.882), which enables the users to select energy efficiency criteria based on request and some of the network performance parameters is needed. Therefore, in some scenarios, e.g. satellite and terrestrial convenience scenario, the users or operators could choose / request the best way in satisfying both user experience and energy efficiency. At the same time, the network could also deploy the more efficient strategies, i.e. energy-efficient network resource allocation and scheduling. The SA1 work on Energy Efficiency as a service criteria mainly focuses on: • Define and support energy efficiency criteria as part of communication service to user and application services. • Provide information exposure on systematic energy consumption or level of energy efficiency to vertical customers. The conclusions of this study have been captured in the 5G system requirements specification, 3GPP TS 22.261. These requirements might be addressed by SA2, the system architecture group. SA2 is studying potential solutions to accomplish or satisfy the corresponding SA1 requirements. The consolidated conclusions include but are not limited to the following (in clause 6 of 3GPP TR 22.882 and clause 6.15a of 3GPP TS 22.261): • Subject to operator’s policy, the 5G system shall support subscription policies and means to enforce the policy that define a maximum energy consumption rate for services without QoS criteria; • The 5G network shall support a means to define maximum energy consumption rate with specific granularities (which include subscriber granularity, network slice granularity). • Subject to operator’s policy, the 5G system shall support subscription policies that define a maximum energy credit limit for services. The maximum energy credit limit could be used to control the services. • Charging related requirements, i.e. subject to operator’s policy, the 5G system shall support a means to associate energy consumption with charging information based on subscription policies. • The 5G system shall support different energy states of network elements and network functions and dynamic switch between different energy states. • For Monitoring and measurement related to energy efficiency purposes, the 5G network shall support energy consumption monitoring at per network slice and per subscriber granularity, 5G system shall be able to acquire energy consumption information of the network functions serving this 3rd party, 5G system shall be able to acquire the ratio of renewable energy used to provide dedicated communication service to this 3rd party on periodic basis, , the 5G system shall be able to acquire the energy efficiency information (e.g., including the estimated carbon emissions) related to a subscriber based on the subscriber’s data volume over a specific period of time, the operator’s network energy consumption, and the carbon intensity of operator’s network. Overview of Existing and ongoing work in 3GPP RAN working groups To improve the energy saving / efficiency and reduce the operation expense of NR system, in R15 and later release, RAN3 introduced energy saving for intra- and inter-system, as described in clause 15.4 of 3GPP TS 38.300. This function allows the deployment of capacity boosters which provides extra capability on top of the basic coverage. Different from the cell that provides basic coverage, the capacity booster cells could be turned on and off by the NR-RAN node or the O&M autonomously, i.e. based on the load of the cell. The activation status or request of the capacity booster cell will be interacted over Xn interface between the corresponding NG-RAN nodes. The O&M-involved energy saving was specified by SA5 and documented in clause 5.1.3.3 of 3GPP TS 28.310. In Rel-18, considering the significant operational cost in the radio part, RAN approved the topic - ‘Network energy savings for NR’ in order to optimize the energy consumption and energy efficiency of the radio part. The objectives of RAN WGs include but not limited to the following: • Specify SSB-less SCell operation for inter-band CA for FR1 and co-located cells. • Specify enhancement on cell DTX / DRX mechanism including the alignment of cell DTX / DRX and UE DRX in RRC_CONNECTED mode, and inter-node information exchange on cell DTX / DRX. • Improve energy efficiency or reduce energy consumption via spatial and power domains optimization, i.e. enhancements on CSI and beam management related procedures. • Specify mechanism(s) to prevent legacy UEs camping on cells adopting the Rel-18 NES techniques, if necessary • Specify CHO procedure enhancement(s) in case source / target cell is in NES mode • Specify inter-node beam activation and enhancements on restricting paging in a limited area • Specify the corresponding RRM / RF core requirements, if necessary, for the above features For the above RAN works, 5GC are not involved into either the decision making on energy saving and energy efficiency enhancement or the capacity booster cell activation and deactivation or configuration in the currently standards. Overview of Existing and ongoing work in 3GPP SA5 working groups 3GPP SA5 started the work on ‘Energy efficiency of 5G’ since Rel-16. In Rel-16, SA5 focused on the Energy Efficiency (EE) and Energy saving (ES) of mobile networks. In Rel-17, the SA5 extended the scope from RAN part only to the whole 5G system. EE Key Performance Indicators (KPI) have been defined for the 5G core network, network slices etc. SA5 work focuses on OA&M, i.e. define mechanisms to collect measurements from the 5G Network Functions via OA&M standardized APIs. Performance of network slices has been defined per type of network slice, namely for enhanced Mobile Broadband (eMBB), Ultra-Reliable and Low Latency Communication (URLLC) and massive Internet of Things (MIoT), whereas user plane traffic volumes have been considered to define the performance of the 5GC. How to measure the energy consumption (EC) of Physical Network Functions (PNF) has been defined by ETSI EE, however to measure the EC of Virtualized Network Functions (VNF) was blank. In Rel-17, SA5 has defined a method to estimate it, based on the estimated energy consumption of the underlying virtual compute resource instance(s), i.e. Virtual Machine(s) (VM). Currently, SA5 is still working on Rel-18 energy efficiency of 5G. On top of Rel-17, in Rel-18, SA5 is working on more accurate virtual CPU usage measurements from ETSI NFV MANO which could be used to estimate the Energy Consumption of virtual machines, new use cases for Energy Saving in the whole 3GPP system, considerations on digital sobriety etc. In the future releases, some of the parameters and measurement technique / metrics may be further enhanced by SA2 WG to support the system level energy saving and the efficient operation. SA5 also introduced the MDA (Management Data Analytics) assisted Energy Saving in clause 7.2.4 and clause 8.4.4 of 3GPP TS 28.104. The MDA assisted energy saving is achieved by activating the energy saving mode of the NR capacity booster cell or 5GC NFs (e.g. UPF etc.). With considering the energy saving policies setup by the operators, the Management Data Analytics Service (MDAS) producer is able to provide energy saving recommendations to the service consumer to assist with the energy saving decision-making. For example, the MDAS procedure may provide the output to indicate where the energy efficiency issues (e.g. high-energy consumption, low energy efficiency) exist in the system and the cause of the energy efficiency issues based on the request of the consumer. Overview of Consideration of energy saving and enhancement of energy efficiency in SA2 Considering the energy cost is one of the most significant sources of operations costs for Mobile Network Operators (MNOs), there has been increasing work in 3GPP on improving energy efficiency (EE), energy saving (ES) and reducing the energy consumption (EC) of 5GS. In the above sections, the existing work related to EE, ES and EC in other 3GPP WGs is reviewed. From the network perspective, the previous solutions studied how to optimize energy consumption by adapting the network itself, e.g. activating and deactivating parts of the network including cells, network functions (NFs), etc. Such change to the topology and components of the network could be either transparent to the network architecture or have implications with the architecture, e.g. reselection of proper network functions. The previous work is more from the perceptive of network management, including the OAM and Ran node / cell management; or from the UE perspective. Previous work does not study how to improve and enhance the energy saving and energy efficiency from the system level, i.e. considering the end-to-end energy saving and energy efficiency of a service or UE etc. before R19, standardization work on Enhancement for Energy Efficiency and Energy Saving as Service Criteria for NR system has not been introduced to SA2 before Rel-19. As mentioned above under the heading “Existing and ongoing work in 3GPP SA1 working groups”, stage 1 requirements for energy as a service criteria have been identified by SA1 in the FS_EnergyServ study. Some of the SA1 requirements need to be addressed by SA2, i.e. by introducing new functionalities and machismos by SA2. The goal of the SA1 energy efficiency is to provide the same services in a more efficient manner, i.e. the services could be provided in an energy-aware manner with considering the energy use control as service criteria, functional requirements include the ability to control energy use based on operator policies such as 'energy credit limits' and 'maximum energy usage rate' applying to services provided to a UE or group of UEs. Also, SA plenary has issued a 3GPP-wide recommendation on considering Energy efficiency as an important design criterion for the technical solutions 3GPP defines in their specifications (see SP-211621). Therefore, SA2 decided to investigate options for improved system behaviour aimed at energy saving and energy efficiency in Re-19. The SID of SA2 work has been approved in the plenary meeting in SP-231192 (September 2023), including: • WT #1. Study potential framework for network energy consumption exposure. This will include whether and what information is exposed, how it is exposed (e.g., charging) and at what granularity, e.g., at RAN level, Core Network level, network slice level, UE level, PDU session level, and / or QoS flow level. Additionally, whether and how renewable energy or carbon emission information for such granularities can be exposed by an MNO will be studied. • WT #2. Study enhancement for subscription and policy control to enable network energy savings as service criteria. • WT #3. Study 5GS enhancements (e.g., energy usage adjustment for NF from CN aspect, energy saving related decision making, NF selection leveraging NF energy states) for network energy saving including 5GC(NFs) and NG-RAN interactions, analytics, etc. Impacts on the UE are not ruled out e. g., for scenarios specified in 3GPP TR 22.882 by SA1 EnergyServ. In order to support the above objectives, SA2 study is being carried out between Nov. 2023 to May 2024. For WT#2, the Key Issue (KI) descriptions have been approved in S2-2313823 in SA2 160 meeting in Nov. 2023 and documented in clause 5.2 of 3GPP TR 23.700-66: 5.2 Key Issue #2: Subscription and policy control to support energy efficiency and energy saving as service criteria 5.2.1 Description Energy related information as service criteria allows delivering services based on e.g., energy related subscriptions and policies to achieve the goal of energy saving. The following aspects will be studied for this key issue: Whether and how to enhance the existing subscription and policy control framework to support energy related information as service criteria, including: Whether and what new energy related UE subscription information are to be defined, and whether and how to use the energy related UE subscription information. Whether and what new energy related policies are to be defined, and how to perform energy related policy control, e.g. to determine, provision and enforce energy related policies. - At what granularity (e.g., network slice, UE, NF, PDU Session, QoS flow, application ID, etc.) the energy related policy control can be performed. What network energy related information is required for subscription and policy control and how it is obtained. Whether and how the above enhancements on subscription and policy control will impact charging. NOTE 1: Charging enhancement aspects, if any, are to be addressed in coordination with SA WG5. NOTE 2: The study will address use cases corresponding to the identified requirements as described in clause 6.15a.2 ofTS 22.261 [8], The possible enhancements on subscription and policy control depend on the use case. Solutions should identify related use cases which will be addressed. NOTE 3: The potential impact of the enhancements will be evaluated to ensure not to consume more energy than expected to save. 5 Overview of Existing subscription and policy control framework The NR policy and charging framework is mainly documented in 3GPP TS 23.503. The existing policy control could be dived into non-session management related policy control and session management related policy control. The non-session management related policy control mainly include: Access and mobility 10 related policy control, UE policy control, Management of packet flow descriptions, SMF selection management related policy control, etc. The non-session management related network capability could be exposed to the AF from the NEF. Session management related policy control is more referred to PCC (Polices and Charging Control) rules. The basic requirements for the session management related policy control include (in clause 4.3.1 of 3GPP TS 23.503) but not limited to: • It shall be possible for the PCC framework to base decisions upon subscription information, Access Type and the RAT Type. • A PCC rule may be predefined or dynamically provisioned at establishment and during the lifetime of a PDU Session. The latter is referred to as a dynamic PCC rule. • It shall be possible to take a PCC rule into service, and out of service, at a specific time of day, without any PCC interaction at that point in time. • It shall be possible with the PCC framework, in real-time, to monitor the overall amount of resources that are consumed by a user and to control usage independently from charging mechanisms, the so-called usage monitoring control. • The PCC framework shall support making policy decisions based on subscriber spending limits. • The PCC framework shall support making policy decisions for N6 traffic steering. The requirements of Session management related policy control include many different aspects, i.e. Gating control requirements, QoS control requirements at different levels (i.e. service data flow level, PDU session level, QoS flow level), Subscriber spending limits requirements (enforce policies based on subscriber spending limits based on information requested by PCF from Charging Function, CHF), Usage monitoring control requirements (i.e. for PCF (Policy Control Function) to make / modify decisions of PCC rules), Application detection and control requirements. As mentioned in clause 4.3.6 of 3GPP TS 23.503, Support for network capability exposure enables an AF (e.g. an external ASP) to request the following session management related policy control functionality from the NEF: - Set or change a chargeable party at AF session setup (see clause 4.15.6.4 and 4.15.6.5 of 3GPP TS 23.502 [3]); - Set up an AF session with required QoS (see clause 6.1.3.22 and clause 4.15.6.6 of 3GPP TS 23.502 [3]); - Request QoS, traffic characteristics provisioning and performance monitoring for an individual UE or a group of UEs (see clause 4.15.6.14 of 3GPP TS 23.502 [3]); - Transfer of traffic characteristics of Time Sensitive Communication from the TSN AF (see clause 6.1.3.23) or from theTSCTSF (see clause 6.1.3.23a). - Set up a time synchronization service from the TSCTSF (see clauses 5.27.1.8 and 6.1.3.23a of 3GPP TS 23.501 [2] and clause 4.15.9 of 3GPP TS 23.502 [3]). The CHF maintains policy counter(s) to track spending for a subscription. The PCF may request information regarding the subscriber's spending from the CHF for PDU Session or for UE or both., to be used as input for dynamic policy decisions for the subscriber, using subscriptions to spending limit reports. The CHF makes information regarding the subscriber's spending available to the PCF using spending limit reports. The PCF uses the information relating to subscriber spending available in the CHF as input for policy decisions related to e.g. QoS control, gating or charging conditions. • The PCF may interact with the CHF to make session management policy decisions, UE policy decisions and Access and Mobility related policy decisions based on spending limits. • The PCF may also retrieve the status of additional policy counters available at the CHF or to unsubscribe from spending limit reporting, • PCF may cancel the subscriptions to status changes for the policy counters available at the CHF. The Nchf enables the PCF to access policy counter status information relating to subscriber spending from CHF and support the following functionality: • Request for reporting of policy counter status information from PCF to CHF and subscribe to or unsubscribe from spending limit reports (i.e. notifications of policy counter status changes); • Report of policy counter status information upon a PCF request from CHF to PCF; • Notification of spending limit reports from CHF to PCF; • Cancellation of spending limit reporting from PCF to CHF. The SMF and CHF may also interact between each other to enable online and offline charging, or the differentiated PDU Session resource usage information (measured at the UPF), etc. Overview of Existing charging mechanism within 5GS In the existing 5GS, policies, e.g. PCC rules, can be determined and enforced based on subscriber spending limits. For example, the 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 maintains policy counter(s) to track spending for a subscription, if the policy counters are available in the CHF prior to their use over the N28 interface. The PCF shall request information regarding the subscriber's spending from the CHF, to be used as input for dynamic policy decisions for the subscriber, using subscriptions to spending limit reports. The CHF shall make information regarding the subscriber's spending available to the PCF using spending limit reports. In 5GS, the charging related issues are handled by Charging Function (CHF) based on interaction with other NFs, e.g. SMF, PCF, AMF, etc. Within the service based architecture, the service-based interface exhibited by CHF is Nchf in 3GPP specifications, as defined in 3GPP TS 32.290. The CHF has interface with several network functions, e.g. N28 between PCF and CHF, N40 between SMF and CHF, N41 and N42 between AMF and CHF in HPLMN and VPLMN respectively. Overall non-roaming reference architecture of policy and charging control framework for the 5G System (service based representation) and Overall non-roaming reference architecture of policy and charging control framework for the 5G System (reference point representation) are shown below. As specified in clause 4.3.4 of 3GPP TS 23.503, the PCF that uses usage monitoring for making dynamic policy decisions shall set and send the applicable thresholds to the SMF for monitoring. The usage monitoring thresholds shall be based either on time, or on volume. The PCF may send both thresholds to the SMF. The SMF shall notify the PCF when a threshold is reached and report the accumulated usage since the last report for usage monitoring. If both time and volume thresholds were provided to the SMF, the accumulated usage since last report shall be reported when either the time or the volume thresholds are reached. The PCF may determine, modify, revoke the polices (e.g. AM, SM policies) based on the charging credit, reporting of resource usage, network conditions, etc. to enforce the charging related requirement and policies, e.g. based on the requirements of operators. For example, the PCF may use Spending Limits information from the CHF to decide whether to install, update or delete LIRSP rules, As documented in clause 5.8.2.6 of 3GPP TS 23.501, upon receiving the request from PCF, the SMF activates the usage reporting in UPF: The SMF shall request the report of the relevant usage information for Usage Monitoring, based on Monitoring Keys and triggers which are specified in TS 23.503

[45] , Each Usage Reporting Rule requested for usage monitoring control is associated with the PDR(s) whose traffic is to be accounted under this rule. The SMF shall generate the Usage Reporting Rule for each Monitoring-key within the active PCC Rule(s), either preconfigured or received from the PCF and also shall keep the mapping between them. Multiple Usage Reporting Rules may be associated with the same PDR. The SMF shall request the report of the relevant usage information for offline and online charging, based on Charging keys and additional triggers which are specified in TS 32.255. Each Usage Reporting Rule requested for offline or online charging is associated with the PDR(s) whose traffic is to be accounted under this rule. The SMF shall generate the Usage Reporting Rule for each Charging key and Sponsor Identity (if applicable) within the active PCC Rule(s), either preconfigured or received from the PCF, and also shall keep the mapping between them. Multiple Usage Reporting Rules may be associated with the same PDR. The SMF function shall also provide reporting trigger events to the UPF for when to report usage information. The reporting trigger events (e.g. triggers, threshold information etc.) shall be supported for the PDU Session level reporting as well as on Rule level basis as determined by the SMF. The triggers may be provided as a volume, time or event to cater for the different charging / usage monitoring models supported by the TS 23.503 for usage monitoring and by TS 32.255 for converged offline and online charging. The SMF shall decide on the thresholds value(s) based on allowance received from PCF, CHF or based on local configuration In some cases, the same Usage Reporting Rule can be used for different purposes (for both usage monitoring and charging), e.g. in the case that the same set of PDR(s), measurement method, trigger event, threshold, etc. apply. Similarly a reported measurement can be used for different purposes by the SMF. The UPF shall support reporting of usage information to the SMF based on the requests / indication / triggers from SMF The SMF may also need to combine the report information with session and subscriber related information which is available at SMF, based on the mapping between Charging Key, Sponsor Identity (if applicable) and PCC rules that are stored at SMF, e.g. for offline and online charging reporting over corresponding charging interfaces. Charging information shall be reported based on the result from the service data flow detection and measurement on a per PDU Session basis from the SMF to CHF. In detail, for the functionality of Policy decisions based on spending limits, as specified in clause 6.1.1.4 of 3GPP TS 23.503, it is applicable to session management (SM) related policy control, access and mobility (AM) management related policy control and UE policy control. 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. In order to understand the status of policy counters in the CHF, the PCF may invoke Initial or Intermediate Spending Limit Report Retrieval Procedure to retrieve the spending limit or subscribe to the CHF. For retrieval procedures, 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. For the subscription, 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 LIRSP rule (e.g. remove or add an RSD that allows the UE to use a dedicated S-NSSAI and DNN). If an operator policy indicates that a policy counter and its status should be available for a policy decision before the PCF retrieves the status of the policy counter from the CHF, the PCF stores the policy counter and its status in the UDR at termination of the respective UE Policy Association, AM Policy Association or SM Policy Association. As specified in clause 4.3.2.2 of 3GPP TS 23.503, the PCC charging may support the following charging models for charging performed by SMF: Volume based charging; Time based charging; Volume and time based charging; Event based charging; No charging. Different charging rate could be applied in different scenarios, e.g. different rates and charging models depending on a UE's roaming status. different rates based on the location of a UE. different rates for specific part of a service, e.g. allow the UE to download a certain volume for one rate, and after this volume has been reached continue with a different rate. different rates based on the time of day. enforce per service data flow, identified by PCC Rule, usage limits on a per UE basis. different rates depending on the access used to carry a Service Data Flow apply an online charging action upon Application Start / Stop events. It shall be possible to indicate to the SMF that interactions with the CHF are not required for a PCC rule, i.e. to not perform accounting, credit control or recording of usage for the service data flow, in this case no charging information is generated. For charging, the SMSF (Short Message Service Function) may interact with CHF and AMF to send SMS messages to UE(s). The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present invention. SUMMARY It is an aim of certain examples of the present disclosure to address, solve and / or mitigate, at least partly, at least one of the problems and / or disadvantages associated with the related art, for example at least one of the problems and / or disadvantages described herein. It is an aim of certain examples of the present disclosure to provide at least one advantage over the related art, for example at least one of the advantages described herein. The present invention is defined in the independent claims. Advantageous features are defined in the dependent claims. Embodiments or examples disclosed in the description and / or figures falling outside the scope of the claims are to be understood as examples useful for understanding the present invention. Other aspects, advantages and salient features of the invention will become apparent to those skilled in the art from the following detailed description taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a reproduction of Figure 4.16.8.2.1 in 3GPP TS 23.502: Initial Spending Limit Report Retrieval; Figure 2 is a reproduction of Figure 5.2.1-1 of 3GPP TS 23.503: Overall non-roaming reference architecture of policy and charging control framework for the 5G System (service based representation); Figure 3 is a reproduction of Figure 5.2.1-1a of 3GPP TS 23.503: Overall non-roaming reference architecture of policy and charging control framework for the 5G System (reference point representation); Figure 4 illustrates an exemplary procedure for charging with considering energy aspects; Figure 5 illustrates an exemplary procedure for charging considering energy aspects; Figure 6 illustrates an exemplary method according to examples of the present disclosure; Figure 7 illustrates an exemplary method according to examples of the present disclosure; Figure 8 illustrates an exemplary method according to examples of the present disclosure; Figure 9 illustrates an exemplary method according to examples of the present disclosure; Figure 10 illustrates an exemplary method according to examples of the present disclosure; and Figure 11 is a block diagram of an exemplary network entity that may be used in certain examples of the present disclosure. DETAILED DESCRIPTION The following description of examples of the present disclosure, with reference to the accompanying drawings, is provided to assist in a comprehensive understanding of the present invention, as defined by the claims. The description includes various specific details to assist in that understanding but these are to be regarded as merely exemplary. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the examples described herein can be made without departing from the scope of the invention. The same or similar components may be designated by the same or similar reference numerals, although they may be illustrated in different drawings. Detailed descriptions of techniques, structures, functions, operations or processes known in the art may be omitted for clarity and conciseness, and to avoid obscuring the subject matter of the present invention. The terms and words used herein are not limited to the bibliographical or standard meanings, but, are merely used to enable a clear and consistent understanding of the invention. Throughout the description and claims of this specification, the words “comprise”, “include” and “contain” and variations of the words, for example “comprising” and “comprises”, means “including but not limited to”, and is not intended to (and does not) exclude other features, elements, components, integers, steps, processes, operations, functions, characteristics, properties and / or groups thereof. Throughout the description and claims of this specification, the singular form, for example “a”, “an” and “the”, encompasses the plural unless the context otherwise requires. For example, reference to “an object” includes reference to one or more of such objects. Throughout the description and claims of this specification, language in the general form of “X for Y” (where Y is some action, process, operation, function, activity or step and X is some means for carrying out that action, process, operation, function, activity or step) encompasses means X adapted, configured or arranged specifically, but not necessarily exclusively, to do Y. Features, elements, components, integers, steps, processes, operations, functions, characteristics, properties and / or groups thereof described or disclosed in conjunction with a particular aspect, embodiment, example or claim are to be understood to be applicable to any other aspect, embodiment, example or claim described herein unless incompatible therewith. The skilled person will appreciate that the techniques described herein may be used in any suitable combination. Certain examples of the present disclosure provide one or more techniques relating to energy related aspects in a charging mechanism in a network, for example a 3GPP 5G NR network. However, the skilled person will appreciate that the present invention is not limited to these examples, and may be applied in any suitable system or standard, for example one or more existing and / or future generation wireless communication systems or standards, including any existing or future releases of the same standards specification, for example 3GPP 5G, 5G-advanced or 6th Generation (6G). The functionality of the various network entities and other features disclosed herein may be applied to corresponding or equivalent entities or features in the same or any other suitable communication systems or standards. Corresponding or equivalent entities or features may be regarded as entities or features that perform the same or similar role, function or purpose within the network. For example, the functionality of a base station or the like (e.g. eNB, gNB, NB, RAN node, access point, wireless point, transmission / reception point, central unit, distributed unit, radio unit, remote radio head, etc.) in the examples below may be applied to any other suitable type of entity performing RAN functions, and the functionality of a UE or the like (e.g. electronic device, user device, mobile station, subscriber station, customer premises equipment, terminal, remote terminal, wireless terminal, vehicle terminal, etc.) in the examples below may be applied to any other suitable type of device. A particular network entity may be implemented as a network element on a dedicated hardware, as a software instance running on a dedicated hardware, and / or as a virtualised function instantiated on an appropriate platform, e.g. on a cloud infrastructure. The skilled person will appreciate that the present invention is not limited to the specific examples disclosed herein. For example: • The techniques disclosed herein are not limited to 3GPP 5G. • One or more entities in the examples disclosed herein may be replaced with one or more alternative entities performing equivalent or corresponding functions, processes or operations. • One or more of the messages in the examples disclosed herein may be replaced with one or more alternative messages, signals or other type of information carriers that communicate equivalent or corresponding information. • One or more further elements or entities may be added to the examples disclosed herein. • One or more non-essential elements or entities may be omitted in certain examples. • The functions, processes or operations of a particular entity in one example may be divided between two or more separate entities in an alternative example. • The functions, processes or operations of two or more separate entities in one example may be performed by a single entity in an alternative example. • Information carried by a particular message in one example may be carried by two or more separate messages in an alternative example. • Information carried by two or more separate messages in one example may be carried by a single message in an alternative example. • The order in which operations are performed and / or the order in which messages are transmitted may be modified, if possible, in alternative examples. Certain examples of the present disclosure may be provided in the form of an apparatus / device / network entity configured to perform one or more defined network functions and / or a method therefor. Certain examples of the present disclosure may be provided in the form of a system (e.g. network or wireless communication system) comprising one or more such apparatuses / devices / network entities, and / or a method therefor. At least the following problem exists in the related art. Based on the previous work, energy related aspects are not considered in charging mechanism. Considering the ‘Green service’ requirements of operators, service providers, government etc., energy consumption, energy efficiency and usage of renewable energy should be considered into the charging mechanism. In order to support the 5G charging with considering energy related aspects, and policy determination and modification considering energy related charging aspects, the end-to-end procedures are proposed. To determine the energy related cost / bill / credit, the status of the energy related charging key and policy counter, etc. the CHF will collected information from the network function that supports energy related functionality (e.g. EECF) and other assistance information (e.g. data volume, data rate, QoS, time window etc. from SMF, UPF, AF, OAM) etc. Different charging rates could be applied to different energy states. Based on the collection information or notification, the CHF is able to determine the energy related cost / bill / credit, the status of the energy related charging key and policy counter, whether the energy related credit reaches the thresholds, etc. The CHF may send notification to the PCF, if the energy related charging key and policy counter subscribed by PCF is changed. Based on the CHF notification, the PCF may modify the AM, SM, UE polices. The network may also notify the UE about the (status of) energy related credit / bill, e.g. via NAS, RRC signalling or SMS messages. In order to expose the energy related information to the CHF, the corresponding energy information exposure events and services are also specified. Various examples of the present disclosure will now be described in more detail. Overall call flow The CHF may take the energy related information into account for the 5GS charging issues, e.g. for the credit management, bill / credit / usage reporting. 1. The PCF determines to retrieve / subscribe the status of the energy related policy counters / spending limit available at CHF, e.g. to determine or modify the policies / PCC rules, including AM, SM and UE policies. - The details of the energy related policy counters / spending limit are described below under the heading “UE subscription information related to energy”. If the PCF subscribes to the status change of the energy related policy counter, once the status is changed, the CHF will notify the PCF. 2. In order to determine the bill and whether the usage / credit reaches the limits / thresholds, the CHF and / or PCF needs to collect / monitor the usage information and the energy related information from different data sources, e.g. 5GC NFs, AF, GAM, NG-RAN, UE, etc. 2a. - 2c. The usage monitoring and reporting from the SMF might be based on QoS monitoring. Therefore, to activate the usage monitoring and reporting, the PCF will generate PCC rules and sends to the SMF. The SMF will activate the UPF to implement monitoring of the parameters based on PCC rules. The UPF will reporting the monitoring to SMF via N4 based on SMF requirements. 2d. [Conditional] if the monitoring and reporting is not activated by PCF, the CHF activate the usage monitoring and reporting and SMF and UPF (via SMF). 2d. the CHF may require / subscribe to the reporting / notification of usage monitoring from SMF or directly from UPF. 3. The CHF may request or subscribe to the energy related information from EECF (if any) or the 5GC NFs that hosts energy monitoring, calculation, exposure or EECF functionalities. If the energy related information monitoring, calculation, exposure is not activated at EECF or the 5GC NFs that hosts the EECF functionalities, the request from CHF will activate the energy related information monitoring, calculation, exposure. The EECF or the 5GC NFs that hosts the EECF functionalities will collect information to determine / calculate the energy related information based on CHF request / subscription. The EECF may send the direct energy related information, e.g. EE / EC / ES / carbon emission; or the EECF may convert the direction energy related information into / send the indirect energy related information, e.g. traffic volume (DV) (transmitted using renewable and / or non-renewable energy), time window, data rate etc. or the indirect energy related information can be collected from SMF or UPF by the CHF. The CHF may also indicate the threshold of the energy related credit (of energy or bill / cost, allowed EE / EC, allowed DV associated to EE / EC requirement) to the EECF or the 5GC NFs that hosts the EECF functionalities. Once the thresholds is reached, the EECF or the 5GC NFs that hosts the EECF functionalities will send notification includes (the measurements / amount of) the corresponding energy related information / to the CHF. - The energy related information includes energy consumption / usage, energy efficiency, amount of the generated carbon dioxide, ratio of renewable energy, energy (saving / efficiency) states, energy saving / consumption / efficiency class / band, etc. or the billing related to energy usage / type, etc. - The above energy related information / energy aspects might be accumulated / averaged / calculated within a time window / period of time / between start and stop time / during the activation of the policy counter or charging rules etc.), which is applicable to the entire embodiment. - The above energy related information / energy aspects might be at different granularities, e.g. the energy related information of a subscriber, UE, PDU session, qos flow, service flow, service, 5GC NF, slice, NG-RAN node, PLMN etc., which is applicable to the entire embodiment. - The EECF or the 5GC NF hosts the EECF functionality may need to collect information from UPF and SMF to calculate the energy related information. To activate the monitoring and reporting in UPF and SMF, the EECF or the 5GC NF hosts the EECF functionality may trigger the monitoring towards the SMF or UPF; alternatively, the EECF or the 5GC NF hosts the EECF functionality may send request for data monitoring to PCF, the PCF will modify the PCC rules to trigger the monitoring and reporting of SMF and UPF. 4. The CHF may request or subscribe to the energy related analytics from NWDAF. Based on the request of the CHF, the NWDAF collects data and generates the required the analytics related to energy. The NWDAF report / notifies the analytics to CHF. As described below under the heading “Energy related events and service operations”, the CHF may require the statistics and / or prediction of the bill / cost / expense / credit (related energy aspects) from the NWDAF. The bill / cost / expense / credit might be associated to different energy supply mode (e.g. the ratio of renewable energy), carbon emission, traffic volume, time window, different charging rates, different energy states of the subscribers, etc. The CHF may use the analytics to determine the credit, charging rates, charging policy, charging threshold of different charging rates, etc., along with the available credit / budget of the subscriber. 5. The CHF may require information from AMF, AF, NG-RAN, UE. e.g. CHF require location information, registration information, access type, etc. of the subscriber from AMF. The information can be used to apply different charging rates to determine the cost. 6. Based on the information collected by CHF, the CHF determines whether the status is changed for a subscribed energy related policy counter, whether the energy-related credit limit / threshold is reached, whether the energy credit / bill / budget is used up etc., based on the events subscribed by PCF. 7. The CHF send notification to PCF of the status changes of the energy related policy counter, energy-related credit limit / threshold is reached, whether the energy credit / bill / budget is used up. 8. The PCF may determine to update the policy towards 5GC NFs (AMF, SMF, UPF, CHF, NEF etc.), AF, GAM, UE, NG-RAN node, etc. [Note] in this embodiment, the EECF can be replace by any (5GC) NF that is able to calculate, monitor and expose the energy related information, e.g. the amount of carbon dioxide / energy related information. Simplified procedures Procedures for charging considering energy aspects 1. The PCF determines to retrieve / subscribe the status of the energy related policy counters / spending limit available at CHF, e.g. to determine or modify the policies / PCC rules, including AM, SM and UE policies. 2. In order to determine energy aspects related bill / credit or whether the energy credit reaches the limits, the CHF will monitor the usage information and the energy related information from SMF and UPF. 2a. - 2b. Based on policy from PCF, the usage monitoring and reporting at UPF is triggered by SMF. 2c. The SMF will report the usage information for charging and for the energy related charging key value. 3. In order to determine energy aspects related bill / credit or whether the energy credit reaches the limits, the CHF will request or subscribe to the energy related information from EECF (if any). 3a. The CHF may request the energy efficiency and ratio of renewable energy to apply the different charging rates, and the amount of energy consumption and carbon emission of the subscriber to determine the energy cost or the used credit. 3b. Based on the request of CHF, the EECF will collect information from other sources to determine the energy efficiency, ratio of renewable energy, energy consumption, carbon emission etc. 3c. The EECF send the required energy related information to CHF. 4. [Optional] The CHF may also request or subscribe to the energy related information from other 5GC NFs, OAM, AF, etc. to determine the energy related bill or credit usage. The CHF may require the statistics and / or prediction of energy related bill or credit usage from the NWDAF. CHF may require the EC at NF or slice level and NF energy state from the OAM. The CHF may require the RAN resource usage or energy saving mode the RAN node. Different energy related charging rates might be applied to different scenarios, e.g. different level of energy consumption, energy supply type (e.g. renewable or non-renewable). 5. Based on the information collected in step 2-4, the CHF determines whether the status of energy related policy counter is changed for a subscribed, whether the energy-related credit limit / threshold is reached, or whether the energy credit is used up etc. 6. If the on the events subscribed by PCF is triggered, the CHF send notification to PCF 5 7. The PCF may determine to update the policy towards 5GC NFs, NG-RAN, or UE. Energy related events and service operations Energy related events The 5GC NFs, AF, GAM, RAN-node, UE may need to request or subscribe to the energy related information from EECF or the (5GC) NF that is able to calculate, monitor and expose 10 the energy related information. E.g. the CHF needs to request or subscribe the energy related information from EECF to calculate the bill, monitor the usage, and send notification to consumers (e.g. PCF ) if the energy credit related threshold is reached etc. New service operations are needed to enable an NF to subscribe and be notified about the energy related Event ID. New EECF event ID(s) are also needed. The different granularity of 15 the monitoring parameters / measurements / estimation / output analytics might be determined, e.g. by EECF, based on the consumer’s request. The events in Table 1 List of events for monitoring, exposure, notification, reporting capability might be also supported by other 5GC NFs, e.g. SMF, UPF, NRF, NEF, PCF, UDM, etc., or 0AM, AF. Table 1 List of events for monitoring, exposure, notification, reporting capability Event (ID) Description Detection criteria Additional information Energy consumption The energy consumed by a subscriber / at different granularities, e.g. at RAN level, Core Network level, network slice level, UE level, PDU session level, and / or QoS flow level / service / area (AOI) The EC within a period. the notification to consumer will be triggered based on configured thresholds, if the EECF detects / determines the EC exceeds the configured thresholds / band The Energy consumption determined by EECF / OAM based on information consumer’s request. To determine the EC, the EECF may need to collect information from 5GC NFs (SMF / UPF for data volume, data rate, etc.), AF, QAM, etc. Energy efficiency The energy efficiency of a subscriber / RAN, Core Network, network slice level, UE, PDU session, NF, and / or QoS flow / service / area (AOI) Average, minimum, maximum, variance values. The notification to consumer will be triggered based on configured thresholds, e.g. if EECF detects / determines the EE is lower / high than the configured thresholds The Energy efficiency determined by EECF / OAM based on information consumer’s request. To determine the EE, the EECF may need to collect information from 5GC NFs (SMF / UPF for data volume, data rate, etc.), AF, QAM, etc. Carbon emission / generation Carbon emission / generation by a subscriber / at different granularities, e.g. at RAN level, Core Network level, network slice level, UE level, PDU session level, and / or QoS flow level / service / area (AOI), within a period. The notification to consumer will be triggered based on configured thresholds, e.g. If the EECF detects / determines the Carbon emission / generation exceeds the configured thresholds The Carbon emission / generation determined by EECF / OAM based on information consumer’s request. To determine the EE, the EECF may need to collect information from 5GC NFs (SMF / UPF for data volume, data rate, etc.), AF, OAM, etc. Aggregated EC / EE / carbon emission Aggregated value of, e.g. the EC / EE / carbon emission of multiple subscribers / UEs / slices / NFs / PDU sessions / QoS flows, e.g. of a service The notification to consumer will be triggered based on configured thresholds, e.g. If the EECF detects / determines the EC / EE / carbon emission exceeds / higher than / lower than the configured thresholds This event can also be an SMF / UPF / OAM / NWDAF event. Or the EECF requires the information related to Aggregated EC / EE / carbon emission from SMF / UPF / OAM / NWDAF to expose the information to the EECF consumer, if the event is triggered. Energy supply type / state The type of the energy supply of a subscriber / RAN, Core Network, network slice level, UE, PDU session, NF, and / or QoS flow / service / area (AOI) e.g. renewable energy, nonrenewable energy, mixed of both, different types of renewable energy The notification to consumer will be triggered if the type of the energy supply cannot / can meet the requirement / threshold of the consumer. This event can also be an OAM / AF event. Or the EECF requires the information related to Energy supply type / state from OAM / AF to expose the information to the EECF consumer, if the event is triggered. Ratio of renewable energy Ratio of renewable energy within the overall energy supply. Could be the ratio of renewable energy of a subscriber / RAN, Core Network, network slice level, UE, PDU session, NF, and / or QoS flow / service / area (AOI) The notification to consumer will be triggered based on configured thresholds, e.g. If the EECF detects / determines the Ratio of renewable energy is lower / higher than the configured thresholds. This event can also be an OAM / AF event. Or the EECF requires the information related to Ratio of renewable energy from OAM to expose the information to the EECF consumer, if the event is triggered. Energy related state / class / band change e.g. the Energy saving (ES) / efficiency / consumption state of RAN, Core Network, network slice level, UE, PDU session, NF, and / or QoS flow / service / area (AOI) e.g. the state is on / off, the high- / medium- / low-EE / EC / ES band / class If the energy state is changed, the notification to consume will be triggered. If the energy state is switched to the required state by the consumer, the notification to consume will be triggered. This event can also be an QAM / NRF / UDM event. Or the EECF requires the information related to Energy related state / class / band change (of NF / slice etc.) to expose the information to the EECF consumer, if the event is triggered. Energy credit status Available / remaining / No energy credit of a subscriber / RAN, Core Network, network slice level, UE, PDU session, NF, and / or QoS flow / service / area (AOI). The credit could be energy related bill / cost, amount of energy can be consumed, data volume can be transferred, etc. The notification to consumer will be triggered based on configured thresholds / states. e.g. If the EECF detects / determines the Available / remaining is lower / higher than the configured thresholds ,or there is no Energy credit left. This event can also be CHF event. State of subscriber / RAN, Core Network, network slice level, UE, PDU session, NF, and / or QoS flow / service due to energy related reasons e.g. UE’s request was rejected, UE loss of connectivity due to energy aspects (e.g. EC / EE / ES) e.g. PDU session, QoS flow / service suspended / released due to energy aspects (e.g. EC / EE / ES) e.g. NF is ON / OFF due to consideration of EC / EE / ES. Existing events might be enhanced by considering energy related aspects as event triggers The notification to consumer may also include the type of energy related aspect that triggered the event / procedure (as a cause value), and the amount / level of the energy related aspects. This event can also be an AMF / SMF / UPF / OAM / NRF / UDM event. Or the EECF requires State of subscriber / RAN, Core Network, network slice level, UE, PDU session, NF, and / or QoS flow / service due to energy related reasons from AMF / SMF / UPF / OAM / NRF / UDM to expose the information to the EECF consumer, if the event is triggered. Failed / succeed to meet energy related requirement The required energy related requirements could be / not be met by the network, e.g. • the required ES / EE cannot / can be achieved • the required QoS / alternative QoS cannot / can be enforced / supported • the required energy state can / cannot be enforce by the network • the required type of energy supply (renewable / non renewable) can / cannot be met • the required service cannot / can be provided by using the (available) energy consumption credit • failed / succeed to meet all of the energy related events / requirements in this table. For the ‘succeed to meet energy related requirement’ events, it might be triggered in the scenario: the network failed to meet the requirement for some reasons, the network take actions to enforce / improve the performance and requirements, in the end the requirements can be met again. This event can also be an AMF / SMF / UPF / OAM / NRF / UDM event. Or the EECF the results of whether the energy requirements are met or policy can be enforced from AMF / SMF / PCF, then expose the information to the EECF consumer. Service operations for energy information exposure The EventExposure service for energy information supported by EECF enables an NF to subscribe and get notified about energy related Event ID (as described below). [Note] in this embodiment, the EECF can be replace by any (5GC) NF that is able to calculate, monitor and expose the energy related information, e.g. the amount of carbon dioxide / energy related information. Table 2 energy information exposure related Services Service Name Service Operations Operation Semantic Consumer(s) Neecf_EventExposure Subscribe Subscri be / Notify NEF, SMF, UDM, NWDAF, LMF, GMLC, TSCTSF, OAM, AMF, UPF, CHF, AF, 0AM, PCF Unsubscribe Subscri be / Notify NEF, SMF, UDM, NWDAF, LMF, GMLC, TSCTSF, OAM, AMF, UPF, CHF, AF, OAM, PCF Notify Subscri be / Notify NEF, SMF, UDM, NWDAF, LMF, GMLC, TSCTSF, OAM, AMF, UPF, CHF, AF, OAM, PCF 1. Neecf_EventExposure_Subscribe service operation Service operation name: Neecf_EventExposure_Subscribe. Description: The consumer NF uses this service operation to subscribe to or modify event reporting for one / a group of / any subscriber / RAN, Core Network, network slice level, UE, PDU session, NF, and / or QoS flow / service / area (AOI) etc. Input, Required: - NFID, e.g. the ID of EECF - Target of Event Reporting: ID of subscriber / RAN, Core Network, network slice level, UE, PDU session, NF, and / or QoS flow / service / area (AOI); ((set of) Energy related Event ID(s) (as described below) Notification Target Address (+ Notification Correlation ID))s, Event Reporting Information Input, Optional: (Event Filter (s) associated with each energy related Event ID; Output, Required: When the subscription is accepted: Subscription Correlation ID (required for management of this subscription), Expiry time (required if the subscription can be expired based on the operator's policy). Output, Optional: First corresponding event report is included, if available (see clause 4.15.1 of 3GPP TS 23.502). 2. Neecf_EventExposure_UnSubscribe service operation Service operation name: Neecf_EventExposure_UnSubscribe. Description: The NF consumer uses this service operation to unsubscribe for one / a group of / any subscriber / RAN, Core Network, network slice level, UE, PDU session, NF, and / or QoS flow / service / area (AOI) etc. Input, Required: Subscription Correlation ID. Input, Optional: None. Output, Required: Operation execution result indication. Output, Optional: None. The NF consumer unsubscribes the event notification by invoking Neecf_EventExposure_Unsubscribe (Subscription Correlation ID) to the EECF. 3. Neecf_EventExposure_Notify service operation Service operation name: Neecf_EventExposure_Notify. Service operation description: Provides the previously subscribed event information to the NF Consumer which has subscribed to that event before. Input, Required: EECF ID, Notification Correlation Information, Event ID, corresponding ID of subscriber / RAN, Core Network, network slice level, UE, PDU session, NF, and / or QoS flow I service / area (AOI); time stamp. Input, Optional: Event specific parameter list. Output, Required: None. Output, Optional: None. Other service operations for energy related information exposure This service enables the exposure of energy related status (any events in Table 1 List of events for monitoring, exposure, notification, reporting capability) from the service provider to the consumer. e.g. the SMF / EECF exposes the energy consumption band / class of a PUD session / QoS flow, the NRF / EECF exposes the energy state of a NF etc. Table 3 energy information exposure related Services Service Name Service Operations Operation Semantic Consumer(s) Nnrf_ EnergyStatusExposure (NRF is an example, can be replaced any 5GC NF, e.g. EECF, UDR, SMF, UPF, AMF.etc.) Energy status Subscribe Subscri be / Notify Request / Response NEF, SMF, UDM, NWDAF, LMF, GMLC, TSCTSF, GAM, AMF, UPF, CHF, AF, 0AM, PCF Energy status Unsubscribe NEF, SMF, UDM, NWDAF, LMF, GMLC, TSCTSF, 0AM, AMF, UPF, CHF, AF, 0AM, PCF Energy status Notify NEF, SMF, UDM, NWDAF, LMF, GMLC, TSCTSF, 0AM, AMF, UPF, CHF, AF, 0AM, PCF 1. Nnrf_ EnergyStatusExposureSubscribe service operation Service Operation name: Nnrf_ EnergyStatusExposureSubscribe Description: Consumer can subscribe to be notified of the following: - energy state, e.g. o ON / OFF / configuration / status of Energy saving (ES) / efficiency / consumption state o high- / medium- / low-EE / EC / ES band / class. Configuration of charging rates The CHF may request or subscribes to the energy related information from the EECF or the 5GC NF that hosts the functionality of EECF. Different charging rates might be applied to the scenarios with different energy consumption status of the subscriber, e.g. different charging rates are applicable depending on the amount of the energy has been consumed, the energy efficiency level, the ratio of the renewable energy in the entire energy supply, the amount of carbon emission generated, etc. As specified in clause 4.3.2.3 of 3GPP TS 23.503, different charging rate could be applied in different scenarios, e.g. UE ‘s roaming status, location, etc. Energy related information should be considered into to apply the different charging rates, e.g. based on the energy saving / efficiency mode, type of energy consumed, energy (saving / consumption) band / class of the subscriber / UE / PDU session / Qos flow / service flow etc. In detail, • Different charging rates of different energy status of the subscriber / UE / PDU session / Qos flow / service flow, e.g. Different charging rates in high / medium / low energy consumption (EC) band / class / status, in different energy saving / efficiency mode and non- different energy saving / efficiency mode, in different types of energy saving / efficiency mode (e.g. high- / medium- / low- / non- energy saving / efficiency mode). • Different charging rates of the subscriber / UE / PDU session in different EC / EE status / amount / thresholds / class / band, e.g. the EC / EE (accumulated within a period of time) of subscriber / UE / PDU session / Qos flow / service flow is low than threshold A, the charging rate is a; if that is between threshold A and B, the charging rate is b, etc. • Different charging rates of different type of energy consumed by the subscriber / UE / PDU session / Qos flow / service flow, e.g. rate 1 for renewable energy, other rates for conventional / non-renewal / fossil fuels etc. For renewable energy, it is also possible to apply different charging rates for the different types of renewable energy, e.g. solar, wind energy, geothermal energy, hydropower, ocean energy, bioenergy, etc. [Note] in this disclosure, the renewable energy includes but not limited to solar, wind energy, geothermal energy, hydropower, ocean energy, bioenergy, etc. The above charging rates can be merged into / work in conjunction with the existing charging requirements. E.g. it would be possible to apply different rates based on the location of a UE / UE's roaming status / specific part of service / time of the day / access type etc. and the energy related information (EE / EC / renewable energy / energy saving / efficiency mode etc.). To determine the bill for charging / whether the credit threshold is reached, the CHF may need to request the information related to energy information from / subscribe to SMF, UPF, NWDAF, QAM, AMF, Energy Efficiency Control Function (EECF) (if any), or the NF that hosts the functionality of energy information collection calculation, exposure. The energy information may include: • Energy efficiency (EE) and / or EC of overall energy / of renewable energy / of nonrenewable energy • The ratio of renewable energy within the overall energy • The type of the renewable energy, e.g. solar, wind energy, geothermal energy, hydropower, ocean energy, bioenergy, etc. • The energy state of the subscriber / UE / PDU session / qos flow / service low, e.g. whether the subscriber / UE / PDU session / qos flow / service low is operating in energy saving / efficiency mode or not, the type of energy saving / efficiency mode (e.g. high- / medium- / low- / non- energy saving / efficiency mode). UE subscription information related to energy Energy related threshold / requirements / capability might be included in the UE subscription data. The UE subscription data is stored in UDM / UDR. The Energy related threshold / requirements / capability related UE subscription information might be reported by the UE, e.g. during (initial) registration, (re-)registration update, etc.; or provisioned by other 5GC AF or AF; or reported by NG-RAN node. The energy related UE subscription information may include: • UE billing credit / threshold / limit of a service / PDU session / QoS flow / service flow or any other granularities related to energy. UE billing credit / threshold / limit might be applied / accumulated within a period of time / time window / between a start time and stop time, hourly, daily, monthly, yearly, etc. The UE billing credit / threshold / limit might be related to energy consumption, energy efficiency, energy saving, and the above of the renewable energy, etc. Configuration of policy counters and spending limit The policy counter is a mechanism within the CHF to track spending applicable to a subscriber. For each policy counter there is a policy counter identifier which is a reference to a policy counter in the CHF for a subscriber. In order to convey information relating to subscriber spending from CHF to PCF. Specific labels are configured jointly in CHF and PCF, Policy counter status is identified which is a label whose values are not standardized and that is associated with a policy counter's value relative to the spending limit(s) (the number of possible policy counter status values for a policy counter is one greater than the number of thresholds associated with that policy counter, i.e. policy counter status values describe the status around the thresholds). In order to consider the energy related aspects into the charging mechanism, policy counter related to energy information can be introduced. E.g. policy counter considers (the thresholds / limits of) the bill of (renewable and / or non-renewable) energy consumption with a period of time, (the thresholds / limits of) the amount of (renewable and / or non-renewable) energy consumption, the (footprint of / amount of) the carbon dioxide within a period of time / of a service, etc. the period of time could be an hour / hourly, a day / daily, a month / monthly, a year / yearly, etc. The PCF may subscribe to the CHF of the energy related policy counters. If the status of the energy related policy counter changes, e.g. the energy credit / bill threshold is reached, the energy credit / bill is used up / the energy related events are triggered, the CHF will notify PCF of the change. The PCF may take the notification into account to modify the AM and SM policies of the associated UE / subscriber / PDU session etc. The spending limit could be related the spend / cost of energy consumption, e.g. cost of the (renewable and / or non-renewable) energy consumption / generation of carbon dioxide on top of the exiting specified spending limit (e.g. considering traffic volume, time, UE location, etc.) , or the overall spending limit include the cost of the energy and any other aspects. Energy related events and service operations The amount of carbon dioxide reported / exposed by EECF (or the 5GC NF that is able to calculate, monitor and expose the amount of carbon dioxide / energy related information) to other 5GC NFs, AF, NG-RAN, UE, GAM, etc. Enhancements to analytics In order to assist with the 5GC charging, the NWDAF analytic could be enhanced to provide the predictions and statics of the energy related bill credit. The energy related bill credit may associated to different sets of the energy (supply) strategies (e.g. the ratio of renewable energy), service operation strategies (e.g. different QoS or requirements, energy saving / efficiency mode), different charging policies or charging rates as described herein, etc. The consumer of the NWDAF analytics could be any 5GC NF (e.g. CHF, PCF, SMF, NEF), AF, 0AM, etc. The consumer, e.g. the PCF, CHF, NEF, may use credit / bill / cost related to energy to determine / modify the policies, service operation strategies, etc. The credit limit / requirements of the UE or the subscriber might be also considered, e.g. the credit limit / requirements within the UE subscription information stored in UDM. Table 3 Data collected by NWDAF for energy related analytics from OAM, 5GC NFs, AF etc. Information Source Description energy saving / efficiency mode OAM, EECF or the 5GC hosts EECF, energy saving / efficiency mode of a UE, subscriber, PDU session, QoS flow, service flow etc. Charging policies or rates CHF, UDR / UDM, PCF Charging policies or rates at different scenarios, e.g. different rates associated to different energy related supply mode, energy states, energy consumption amount / levels, carbon emission amount / levels, time windows, etc. renewable energy related information OAM, EECF or the 5GC hosts EECF One or more of the following: Ratio of renewable energy, carbon emission, etc. of a UE, subscriber, PDU session, QoS flow, service flow etc. Traffic volume AF, SMF, UPF Traffic volume of the a UE, subscriber, PDU session, QoS flow, service flow Table 4 Statistics and / or predictions of the output analytics Information Description (list of) Credit / bill / cost The Statistics and / or predictions of credit / bill / cost of a UE, subscriber, PDU session, QoS flow, service flow etc. The credit / bill / cost may be related to energy aspects. The credit / bill / cost might be associated to a time window (stop and start time) / a period of time (e.g. an hour, a day, a month, a year) etc. The consumer, e.g. the PCF, CHF, NEF, may use the output analytics, and optional the UE credit limit / requirement of billing (in UE subscription information), to determine or modify the policy; and therefore, to provide the service in the manner to satisfy the service quality, UE requirements of credits or billing, operator policy etc. e.g. the PCF / consumer may determine the SM or AM policy based on the prediction of the (list of) credit / bill / cost and available credit / budget of the subscriber. If the subscriber has low (energy) credit / budget, the PCF may provide relax Qos requirements, allow higher packet error rates etc. to cooperate with available budget of the subscriber, based on the charging rates. E.g. CHF / consumer may determine / update / renewthecredit / threshold for charging based on the statistics and prediction of the (energy-related) bill. energy saving / efficiency mode The energy saving / efficiency mode of a UE, subscriber, PDU session, QoS flow, service flow etc. associated to the credit / bill / cost. Traffic volume Traffic volume can be transmitted associated the credit / bill / cost. The Annex to this description discloses one or more further techniques according to the present disclosure. The skilled person will appreciate that the techniques disclosed in the 5 Annex may be used together with the techniques disclosed herein in any suitable combination. Figure 6 illustrates an exemplary method according to examples of the present disclosure. The method is a method of a NF, the NF having functionality relating to energy information. In step 602, the method comprises providing an event exposure service for energy information to a consumer NF (e.g. NEF, AF). Providing the event exposure service to the consumer NF 10 comprises providing energy consumption information to the consumer NF. Figure 7 illustrates an exemplary method according to examples of the present disclosure. The method is a method of a NF, the NF having functionality relating to energy information. In step 702, the method comprises receiving, from a consumer NF (e.g. NEF, AF), a subscription request, the subscription request including an energy consumption event ID. In step 704, the method further comprises, in response to receiving the subscription request including the energy consumption event ID, providing energy consumption information to the consumer NF when an energy consumption event is triggered. Figure 8 illustrates an exemplary method according to examples of the present disclosure. The method is a method of a consumer NF (e.g. NEF, AF). In step 802, the method comprises transmitting, to a NF having functionality relating to energy information, a subscription request, the subscription request including an energy consumption event ID. In step 804, the method further comprises receiving energy consumption information from the NF when an energy consumption event is triggered. Figure 9 illustrates an exemplary method according to examples of the present disclosure. The method is a method of a first NF (e.g. PCF). In step 902, the method comprises subscribing, or requesting, from a second network function (e.g. CHF), energy related information (e.g. energy related policy information, energy related charging information). In step 904, the method further comprises receiving, from a second network function, energy related information. In step 906, the method further comprises determining, or modifying, a policy based on the received energy related information. Figure 10 illustrates an exemplary method according to examples of the present disclosure. The method is a method of a second NF (e.g. CHF). In step 1002, the method comprises receiving, from a first NF (e.g. PCF), a request for, or subscription to, energy related information (e.g. energy related policy information, energy related charging information). In step 1004, the method further comprises collecting energy related information from at least one data source. In step 1006, the method further comprises providing, to the first NF based on the request or subscription, the energy related information. Figure 11 is a block diagram of an exemplary network entity that may be used in examples of the present disclosure. For example, a UE / network entity (e.g. CHF, PCF, SMF, UPF, EECF, NWDAF, CAM, AMF, NF, AF) I base station (e.g. eNB, gNB, NG-RAN) in the examples of Figures 1-10 may comprise an entity of Figure 11. The skilled person will appreciate that a network entity may be implemented, for example, as a network element on a dedicated hardware, as a software instance running on a dedicated hardware, and / or as a virtualised function instantiated on an appropriate platform, e.g. on a cloud infrastructure. The entity 1100 comprises a processor (or controller) 1101, a transmitter 1103 and a receiver 1105. The receiver 1105 is configured for receiving one or more messages from one or more other network entities, for example as described above. The transmitter 1103 is configured for transmitting one or more messages to one or more other network entities, for example as described above. The processor 1101 is configured for performing one or more operations, for example according to the operations as described above. The techniques described herein may be implemented using any suitably configured apparatus and / or system. Such an apparatus and / or system may be configured to perform a method according to any aspect, embodiment, example or claim disclosed herein. Such an apparatus may comprise one or more elements, for example one or more of receivers, transmitters, transceivers, processors, controllers, modules, units, and the like, each element configured to perform one or more corresponding processes, operations and / or method steps for implementing the techniques described herein. For example, an operation / function of X may be performed by a module configured to perform X (or an X-module). The one or more elements may be implemented in the form of hardware, software, or any combination of hardware and software. Certain examples of the present disclosure provide a UE / network entity (e.g. CHF, PCF, SMF, UPF, EECF, NWDAF, CAM, AMF, NF, AF) / base station (e.g. eNB, gNB, NG-RAN) configured to perform a method according to any example, aspect, embodiment and / or claim disclosed herein. Certain examples of the present disclosure provide a network (or wireless communication system) comprising a UE / network entity (e.g. CHF, PCF, SMF, UPF, EECF, NWDAF, OAM, AMF, NF, AF) / base station (e.g. eNB, gNB, NG-RAN) according to any examples, aspects, embodiments and / or claims disclosed herein. Certain examples of the present disclosure provide a computer program comprising instructions which, when the program is executed by a computer or processor, cause the computer or processor to carry out a method according to any example, aspect, embodiment and / or claim disclosed herein. Certain examples of the present disclosure provide a computer or processor-readable data carrier having stored thereon a computer program according to any example, aspect, embodiment and / or claim disclosed herein. It will be appreciated that examples of the present disclosure may be implemented in the form of hardware, software or any combination of hardware and software. Any such software may be stored in the form of volatile or non-volatile storage, for example a storage device like a ROM, whether erasable or rewritable or not, or in the form of memory such as, for example, RAM, memory chips, device or integrated circuits or on an optically or magnetically readable medium such as, for example, a CD, DVD, magnetic disk or magnetic tape or the like. It will be appreciated that the storage devices and storage media are embodiments of machine-readable storage that are suitable for storing a program or programs comprising instructions that, when executed, implement certain examples of the present disclosure. Accordingly, certain examples provide a program comprising code for implementing a method, apparatus or system according to any example, embodiment, aspect and / or claim disclosed herein, and / or a machine-readable storage storing such a program. Still further, such programs may be conveyed electronically via any medium, for example a communication signal carried over a wired or wireless connection. While the invention has been shown and described with reference to certain examples, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the scope of the invention, as defined by the appended claims. In a first example, there is provided a method of a network function (NF), the NF having functionality relating to energy information, wherein the method comprises: providing an event exposure service for energy information to a consumer NF (e.g. NEF, AF); wherein providing the event exposure service to the consumer NF comprises providing energy consumption information to the consumer NF. In a second example, there is provided the method of the first example, wherein providing energy consumption information to the consumer NF comprises providing the energy consumption information at a required granularity. In a third example, there is provided the method of the second example, wherein the required granularity comprises at least one of: a UE level, a PDU session level, or a QoS flow level. In a fourth example, there is provided the method of any one of the first to third examples, further comprising monitoring for energy consumption events; wherein providing the event exposure service to the consumer NF comprises notifying the consumer NF when the NF detects an energy consumption event. In a fifth example, there is provided the method of any one of the first to fourth examples, wherein the event exposure service comprises at least one of: a subscribe service operation, an unsubscribe service operation, or a notify service operation. In a sixth example, there is provided the method of the fifth example, wherein the subscribe service operation is used by the consumer NF to subscribe or modify a subscription to receiving the energy information. In a seventh example, there is provided the method of the sixth example, wherein the method further comprises receiving, from the consumer NF, a subscription request, the subscription request including at least one of: consumer NF ID, target of event reporting, at least one event ID, notification target address, notification correlation ID, event reporting information, or at least one event filter associated with each event ID. In an eighth example, there is provided the method of the seventh example, wherein the method further comprises, in response to receiving the subscription request, outputting, to the consumer NF, at least one of: subscription correlation ID, expiry time, first corresponding event report. In a ninth example, there is provided the method of any one of the fifth to eighth examples, wherein the unsubscribe service operation is used by the consumer NF to unsubscribe a subscription to receiving the energy information. In a tenth example, there is provided the method of the ninth example, wherein the method further comprises: receiving, from the consumer NF, an unsubscription request, the unsubscription request including a subscription correlation ID, and in response to receiving the unsubscription request, outputting, to the consumer NF, an operation execution result indication. In an eleventh example, there is provided the method of any one of the fifth to tenth examples, wherein the notify service operation is used to provide the energy consumption information to a subscribed consumer NF. In a twelfth example, there is provided the method of the eleventh example, wherein providing the energy consumption information to the consumer NF comprises providing at least one of: notification correlation information, or time stamp. In a thirteenth example, there is provided a method of a network function (NF), the NF having functionality relating to energy information, wherein the method comprises: receiving, from a consumer NF (e.g. NEF, AF), a subscription request, the subscription request including an energy consumption event ID; and in response to receiving the subscription request including the energy consumption event ID, providing energy consumption information to the consumer NF when an energy consumption event is triggered. In a fourteenth example, there is provided a method of a consumer network function (NF) (e.g. NEF, AF), wherein the method comprises: transmitting, to a NF having functionality relating to energy information, a subscription request, the subscription request including an energy consumption event ID; and receiving energy consumption information from the NF when an energy consumption event is triggered. In a fifteenth example, there is provided a method of a first network function (e.g. PCF), the method comprising: subscribing, or requesting, from a second network function (e.g. CHF), energy related information (e.g. energy related policy information, energy related charging information); receiving, from a second network function, energy related information; and determining, or modifying, a policy based on the received energy related information. In a sixteenth example, there is provided the method of the fifteenth example, wherein the energy related information comprises at least one of: a status of an energy related policy, a status of an energy related usage limit, a status of an energy related credit limit. In a seventeenth example, there is provided a method of a second network function (e.g. CHF), the method comprising: receiving, from a first network function (e.g. PCF), a request for, or subscription to, energy related information (e.g. energy related policy information, energy related charging information); collecting energy related information from at least one data source; providing, to the first network function (NF) based on the request or subscription, the energy related information. In an eighteenth example, there is provided the method of the seventeenth example, wherein the at least one data source comprises at least one of: a third NF having functionality relating to energy information (e.g. a NF configured to perform the method of any of the first to twelfth examples), SMF, UPF, NWDAF, AMF, AF, NG-RAN, or UE. In a nineteenth example, there is provided the method of the eighteenth example, wherein the collected energy related information comprises direct energy related information collected from the third NF having functionality relating to energy information. In a twentieth example, there is provided the method of the nineteenth example, wherein the direct energy related information comprises at least one of: energy efficiency, energy consumption, energy saving, carbon emissions. In a twenty-first example, there is provided the method of any one of the eighteenth to twentieth examples, wherein the collected energy related information comprises indirect energy related information collected from at least one of: the third NF having functionality relating to energy information, SMF, or UPF. In a twenty-second example, there is provided the method of the twenty-first example, wherein the indirect energy related information comprises at least one of: traffic volume (e.g. transmitted using renewable and / or non-renewable energy), time window, data rate. In a twenty-third example, there is provided the method of any one of the seventeenth to twenty-second examples, wherein the collected energy related information comprises energy related analytics collected from NWDAF. In a twenty-fourth example, there is provided the method of any one of the seventeenth to twenty-third examples, wherein providing, to the first NF based on the request or subscription, the energy related information comprises: determining, based on the collected energy related information, at least one of: whether a status is changed for a subscribed energy related policy, whether an energy-related credit limit / threshold is reached, or whether an energy credit / bill / budget is used up, and notifying the first NF of the status changes of the energy related policy, energy-related credit limit / threshold is reached, or whether the energy credit / bill / budget is used up. In a twenty-fifth example, there is provided a first network entity (e.g. NF having functionality relating to energy information, PCF, CHF) configured to operate according to a method of any preceding claim. In a twenty-sixth example, there is provided a second network entity (e.g. NF having functionality relating to energy information, PCF, CHF) configured to cooperate with a first network entity of the twenty-fifth example according to a method of any one of the first to twenty-fourth examples. In a twenty-seventh example, there is provided a network or wireless communication system comprising a first network entity according to the twenty-fifth example and a second network entity according to the twenty-sixth example. In a twenty-eighth example, there is provided a computer program comprising instructions which, when the program is executed by a computer or processor, cause the computer or processor to carry out a method according to any one of the first to twenty-fourth examples. In a twenty-ninth example, there is provided a computer or processor-readable data carrier having stored thereon a computer program according to the twenty-eighth example. Acronyms and Definitions 3GPP 5G 5GC 3rd Generation Partnership Project 5th Generation 5G Core 5 5QI 5G QoS Identifier 5GS 5G System 5GSM 5G System Session Management 5GMM 5G System Mobility Management AF Application Function 10 Al Artificial Intelligence AM Access and Mobility AMBR Aggregated Maximum Bit Rate AMF Access and Mobility Management Function AS Access Stratum 15 ASP Application Service Provider ATG Air-To-Ground AUSF Authentication Server Function CA Carrier Aggregation CDN Content Delivery Network 20 CHF Charging Function CHO Conditional Handover CPU Central Processing Unit CSI Channel State Information CU Central / Centralized Unit 25 DCAF Data Collection Application Function DNAI Data Network Access Identifier DNN Data Network Name DNS Domain Name Server DRB Data Radio Bearer 30 DRX Discontinuous Reception DTX Discontinuous Transmission DU Distributed Unit EC Energy Consumption EE Energy Efficiency 35 EECF Energy Efficiency and Consumption control Function eMBB enhanced Mobile Broadband eNB Evolved Node B EPC Evolved Packet Core ES Energy Saving 40 F1 Interface between CU and DU FEC Forward Error Correction FQDN Fully Qualified Domain Name FR1 Frequency Range 1 GBR Guaranteed Bit Rate 45 GMLC Gateway Mobile Location Centre gNB Next generation Node B GPSI Generic Public Subscription Identifier HPLMN Home PLMN HSS Home Subscriber Service 50 IAB Integrated Access and Backhaul ID Identity / Identifier HoT Industrial Internet of Things IMEI International Mobile Equipment Identities IP Internet Protocol 55 l-SMF Intermediate SMF KPI Key Performance Indicator LADN Local Area Data Network LLSSM Lower Layer SSM LMF Location Management Function 60 MANO Management and Orchestration MBMS Multimedia Broadcast / Multicast Service MBS Multicast / Broadcast Service MBSF Multicast / Broadcast Service Function MBSTF Multicast / Broadcast Service Transport Function 5 MB-SMF Multicast / Broadcast Session Management Function MB-UPF Multicast / Broadcast User Plane Function MCCH Multicast Control Channel MDA Management Data Analytics MDAS Management Data Analytics Service 10 MIoT Massive Internet of Things ML Machine Learning MME Mobility Management Entity MN Master Node MNF Monitoring Network Function 15 MNO Mobile Network Operator MR-DC Multi-RAT Dual Connectivity MT Mobile Termination MTCH Multicast Traffic ChannelN4 Interface between UPF and SMF N6 Interface between the UPF and a Data Network 20 N28 Interface between PCF and CHF N40 Interface between SMF and CHF N41 Interface between AMF and CHF in HPLMN N42 Interface between AMF and CHF in VPLMN NAS Non-Access Stratum 25 Nchf Service-based interface exhibited by Charging Function NEF Network Exposure Function NES Network Energy Savings NF Network Function NFV Network Function Virtualization 30 NR New Radio NRF Network Repository Function NG-RAN Next Generation Radio Access Network NG-eNB Next Generation eNB NGAP Next Generation Application Protocol 35 NSA Non-Standalone NSSF Network Slice Selection Function NTN Non-Terrestrial Networks NW Network NWDAF Network Data Analytics Function 40 O&M Operations and Maintenance OA&M / OAM Operation, Administration, (and) Maintenance opex operating expenses OS Operating System OSAPP OS Application 45 PCC Polices and Charging Control PCF Policy Control Function PCO Protocol Configuration Options PDR Packet Detection Rule PDU Protocol Data Unit 50 PLMN Public Land Mobile Network PNF Physical Network Function PTM Point To Multipoint PTP Point to Point QFI QoS Flow Identifier (ID) 55 QoS Quality of Service RACH Random Access Channel RAN Radio Access Network RAT Radio Access Technology RF Radio Frequency 60 RRC Radio Resource Control RRM Radio Resource Management RS Reference Signal RSD Route Selection Descriptor SA Standalone 5 SCell Secondary Cell SDAP Service Data Adaptation Protocol SDU Service Data Unit SGW Serving Gateway SIB1 System Information Block 1 10 SIM Subscriber Identity Module SLA Service Level Agreement SM Session Management SMF Session Management Function SMS Short Message Service 15 SMSF Short Message Service Function SN Secondary Node S-NSSAI Single Network Slice Selection Assistance Information SS Synchronization Signal SSB Synchronization Signal Block 20 SSM Source Specific IP Multicast address SSC Session and Service Continuity SRB Signaling Radio Bearer SUPI Subscription Permanent Identifier TA Tracking Area 25 TAI Tracking Area Identity TE Terminal Equipment TM Transparent Mode TMGI Temporary Mobile Group Identity TS Technical Specification 30 TSCTSF Time-Sensitive Communication and Time Synchronization Function TSN Time Sensitive Networking UAV Unmanned Aerial Vehicle UDM Unified Data Manager UDR Unified Data Repository 35 UE User Equipment UL Uplink UM Unacknowledged Mode UP User Plane UPF User Plane Function 40 URLLC Ultra-Reliable and Low-Latency Communication URSP UE Route Selection Policy VM Virtual Machine VNF Virtualized Network Function VPLMN Visitor / -ing / -ed PLMN 45 X2 / Xn Interface between 2 base stations Annex to the Description In the following text, changes according to the present disclosure are shown underlined (for additions) or struck-through (for deletions). SA WG2 Meeting #S2-162 S2-2404508 15-19 April, 2024, Changsha, China(Revision of S2-24xxx) Source: Samsung Title: Kl#2, So I #9 Update to resolve EN Document for: Approval Agenda Item: 19.4 Work Item / Release: FS_EnergySys / Rel-19 Abstract of the contribution: This contribution proposes updates to Kl#2 Sol#9. 1. Discussion In the current 5GS charging mechanism, different charging rates are applicable in different scenarios, e.g. UE roaming state, UE location, etc. Considering the requirements of ‘Green service’, different charging rates should be also applicable to the scenarios with different energy consumption status of the subscriber, e.g. different charging rates are applicable depending on the amount of the energy has been consumed, the energy efficiency level, the ratio of the renewable energy in the entire energy supply, the amount of carbon emission generated, etc. In order to determine the energy related bill and credit, the CHF needs to collected energy related information from different 5GC NFs, 0AM, AF, etc. The overall call flow for the 5GS charging with considering energy aspects is also proposed in this solution update to resolve the ENs. 2. Proposal It is proposed to adopt the following changes into Solution #12 in TR 23.700-66. 6.9 Solution #9: Credit limit control according to subscription 6.9.1    Key Issue mapping The solution applies to Key Issue #2. 6.9.2    Functional Description In this solution, CHF controls the available energy credit limit of subscribers, which is enhanced by CHF's Nchf SpendingLimitControl service. CHF is aware of how much credit is used by one single subscriber and whether a credit limit is exceeded. When the credit limit is exceeded, CHF is responsible to notify to the PCF to trigger policy update for the subscribers. The CHF may request or subscribes to the energy related information from the EECF or the 5GC NF that hosts the functionality of EECF, Different charging rates might be applied to the scenarios with different energy consumption status of the subscriber, e.g. different charging rates are applicable depending on the amount of the energy has been consumed, the energy efficiency level, the ratio of the renewable energy in the entire energy supply, the amount of carbon emission generated, etc. For the updated policy, if one subscriber's energy usage is exceeded to the subscribed credit limit, the network may refuse or modify UE's access to application services provided by specific network slices, the PCF will generate new URSP and provided to UE. When the new policy is to change the accessed network slice, e.g. choose a new network slice which has low energy consumption or degraded service experience, the policy update will also cause network slice reselection or AMF re-allocation. Another situation is not to change the accessed network slice, but to change the network performance of the whole application service, this may be achieved by modify the SM policy to update the QoS parameter related to the application service. 6.9.3 Procedures Figure 6.9.3: Procedures 1. According to the subscription of UE, PCF knows policy of the subscriber needs to be decided according to the energy efficiency for example energy usage of the UE, then PCF triggers the reporting / notification of the spending limit of CHF. There may be one or more policy counters for the UE's energy consumption credit limit: - Daily / monthly EE consumption reaches XX J or XX Wh. - Daily / monthly EE expenses / phone bills reached XX dollars. - The current energy efficiency EE is larger than or less than a threshold. Editor's note:--------How the CHF track the spending related to energy credit limit is FFS Editor's note:-------How to enhance policy counters with energy aspects and what are the energy aspects are FFS. NOTEEditor's note: Coordination with SA WG5 is required. 2. PCF requests to subscribe CHF's SpendingLimitControl service. 3. Response from CHF to PCF. 4. When CHF detects that the EE policy counter state has changed, or CHF may detect that the EE policy counter state will change at some point in the future, which means the credit limit exceeds for the subscriber, CHF notify to the PCF. 5. Response from PCF to CHF. 6. PCF decides to update the related policy. Here, the policy maybe UE policy, AM policy and SM policy. 6.9.3.x Procedures for charging considering energy aspects CHF PCF SMF UPF EECF Ws, RAN, -OAJVL J 1. PCF requests or subscribes to the change of policy counters 2a.Trigger usage monitoring arid reporting -,1.-,-- J --------------------5---------►: 2b.Trigger usage 2c. request / subscribe to the usage reporting 3a. CHF activates the parameter monitoring and request / subscribe to the energy related information 3b. Collect info and determine the energy info 3c. CHF activates the parameter monitoring and request / subscribe to the energy related information 4. CHF requires / subscribes to information from other 5G NFs, AF, NG-RAN, etc. 5. CHF determines notification is triggered 6. Notification to PCF 7a. PCF determines to update policy 7b. Policy update Figure 6.9.3.X-1: Procedures for charging considering energy aspects 9. The PCF determines to retrieve / subscribe the status of the energy related policy counters / spending limit available at CHF, e.g. to determine or modify the policies / PCC rules, including AM, SM and UE policies. 10. In order to determine energy aspects related bill / credit or whether the energy credit reaches the limits, the CHF will monitor the usage information and the energy related information from SMF and UPF, 2a. - 2b. Based on policy from PCF, the usage monitoring and reporting at UPF is triggered by SMF, 2c. The SMF will report the usage information for charging and for the energy related charging key value. 11. In order to determine energy aspects related bill / credit or whether the energy credit reaches the limits, the CHF will request or subscribe to the energy related information from EECF (if any), 3a. The CHF may request the energy efficiency and ratio of renewable energy to apply the different charging rates, and the amount of energy consumption and carbon emission of the subscriber to determine the energy cost or the used credit. 3b. Based on the request of CHF, the EECF will collect information from other sources to determine the energy efficiency, ratio of renewable energy, energy consumption, carbon emission etc. 3c. The EECF send the required energy related information to CHF, 12, [Optional] The CHF may also request or subscribe to the energy related information from other 5GC NFs, QAM, AF, etc, to determine the energy related bill or credit usage. The CHF may require the statistics and / or prediction of energy related bill or credit usage from the NWDAF, CHF may require the EC at NF or slice level and NF energy state from the QAM, The CHF may require the RAN resource usage or energy saving mode the RAN node. Different energy related charging rates might be applied to different scenarios, e.g. different level of energy consumption, energy supply type (e.g. renewable or non-renewable). 13, Based on the information collected in step 2-4. the CHF determines whether the status of energy related policy counter is changed for a subscribed, whether the energy-related credit limit / threshold is reached, or whether the energy credit is used up etc. 14, If the on the events subscribed by PCF is triggered, the CHF send notification to PCF 15, The PCF may determine to update the policy towards 5GC NFs. NG-RAN. or UE, 6.9.4 Impacts on existing services, entities and interfaces The following impacts have been identified: CHF: - During spending limit control, when the total energy usage exceeds or approaches the policy counter, CHF report or notify to the PCF. - Support policy counter related to energy efficiency. - Support and apply different charging rates based on the energy related status, e.g. the consumed energy, ratio of renewable energy, energy efficiency, etc. PCF: - Policy decision based on the spending limit control related to energy efficiency.

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