Scope
Since 3G, mobile networking standards are being standardised by 3GPP, enabling true world-wide interoperability. Currently, 3GPP is finalising the 5G standard – “5G Advanced” (5GA) – and started to develop the 6G standard. Energy efficiency is increasingly becoming a topic within 3GPP. This summary discusses energy efficiency related efforts within the scope of 5GA (R19-20) and 6G (R20-21). Some of this is still work-in-progress.
Summary
Up to Release 18, 3GPP was internally focused with regards to energy efficiency, that is its goal was to satisfy user experience (i.e. to provide optimal network performance), while at the same time achieving energy efficiency within the network e.g., to reduce network operators’ operational expenditure.
Release 19 (5GA)
Starting from Release 19, energy efficiency is also being considered as service criteria. This means that customers (i.e., end users and verticals / authorised 3rd parties), can include energy efficiency as criteria for consuming services, next to other, more traditional, network performance parameters. Consequently, the mobile network may play a role in end-to-end energy optimisation scenarios as targeted by EXIGENCE.
As usual, within 3GPP, this work started by defining use cases and requirements within 3GPP SA1, as part of a dedicated study item. The outcome of this work has been documented in a technical report, TR 22.882. Subsequently, the (consolidated) requirements of this effort have been included in Section 6.15a of TS 22.261. The complete specification document TS 22.261 includes all service requirements for the 5G system (in this case for Release 19), and requirements for energy efficiency as service criteria are now included.
Subsequently, this work was picked up by 3GPP SA2, by starting a study. The goal of that study, as documented in TR 23.700-66, was to identify the key technical issues to be solved and to propose solutions to solve them. Subsequently, the work progressed into the so-called normative phase, amongst others by adding a new network function “Energy Information Function” (EIF), and additional procedures to the core 5G specifications (i.e., TS 23.501, 23.502, and 23.503).
The requirements stated in Section 6.15a of TS 22.261 address the following topics:
- Subscription policies that define a maximum energy credit limit for services without QoS criteria (i.e., best-effort services), including associating energy consumption information with charging information.
- Selection of an application server from a set, based on energy-related information.
- Modifying a communication service based on energy-related information based on subscription policies.
- Operating (part) of the network according to energy consumption requirements based on subscription policies or requested by an authorised 3rd party.
- Support for different energy states of network elements and functions, which may change dynamically, and involve different charging mechanisms.
- Monitoring of energy consumption, and associated network performance statistics, per network slice and per subscriber, as well as per service consumed by that subscriber. Specifically, the 5GS may provide monitoring for serving a 3rd party, subject to an agreement with such 3rd party. Note, that energy monitoring is done by means of averaging or applying a statistical model and does not imply some form of ‘real time monitoring’.
- Exposing such energy consumption, prediction on energy consumption, and associated network performance statistics to a 3rd party, and enabling authorised 3rd parties to obtain information related to above mentioned credit limit and to configure which information should be exposed. Also, the 3rd party shall be able to provide current or predicted energy consumption information (note, that the ratio of renewable energy and carbon emission information are also in scope).
- Internal network optimisation, taking energy and network load information into account, for a specific area and timeframe. In particular, this is about inter-MNO (inter-PLMN and/or also involving NPN) optimisation, where one MNO can provide service for others at times of low usage. Similarly, regulators could ask for such coordination in case of temporal energy shortage.
The SA2 study report TR 23700-66 proposed solutions to the following key issues:
- Network energy-related information exposure. This is about whether and what information can be exposed and at what granularity, how this information can be exposed, and what information must be obtained from various network entities to achieve that.
- Subscription and policy control to support energy efficiency and energy saving as service criteria. This is about whether and how to enhance the existing subscription and policy control framework, and whether and how these enhancements will impact charging.
- 5GS enhancements for network energy saving and efficiency. This is about whether and how to enhance the existing operations and procedures, whether and how to enhance NF (re)selection, whether and how to enhance network analytics and what, if any, energy-related information (e.g., per QoS flow/PDU session/UE/NF) is required and how it is collected.
Release 20 (5GA)
Within the scope of Release 20, 3GPP SA1 conducted another study, “energy service as service criteria, phase 2”, extending the abovementioned Release 19 efforts. This study item was initially proposed by China Mobile and supported and adjusted by TNO and Telefonica on behalf of EXIGENCE, in order to create sufficient maneuvering room for submitting use cases and requirements derived from EXIGENCE work.
Subsequently, three use cases were submitted on behalf of EXIGENCE. These use cases can be found in Sections 5.3, 5.5, and 5.8 of the study item’s technical report, TR 22.883. Also, Annex A of the report was contributed by EXIGENCE. This annex is effectively a short abstract of this Green ICT DIGEST, to highlight that also other SDOs, next to 3GPP, are addressing the topic of end-to-end energy measurements. Again, the (consolidated) requirements of this effort have been included in Section 6.15a of TS 22.261.
The new R20 requirements stated in Section 6.15a of TS 22.261 address the following topics:
- Exposure of information about network energy-related characteristics (energy consumption and/or carbon emissions), which may either relate to specific UEs over a time period (e.g., month) or to a specific service data flow. Also, energy prediction and exposing information to UEs is covered by these requirements.
- Service adjustments based on energy-related characteristics i.e., service degradation to meet energy rationing constraints, associated subscription policies and means to enable per UE energy savings, means to take the energy mix into account, and even disabling services for a UE.
- Charging-related aspects, when a UE is impacted by abovementioned service degradation.
- Energy-related characteristics as service criteria which enable an authorized 3rd party adjust its own over-the-top service offerings in a way to reduce energy / carbon impact of the mobile network. This includes identifying of a set of target UEs for which to adjust service based on current and predicted energy-related characteristics in the serving network.
- Furthermore, the granularity of the energy-related information has been specified which may be down to minute-level information for each service data flow.
It is interesting to note that the subclause “Monitoring and measurement” explicitly excludes the cross-domain aspects targeted by EXIGENCE, as the energy-related information “only relates to the use of the communication service provided by a telecom operator to its home network subscribers, as a single part of the end-to-end service chain” and as the requirements stated “do not apply to the energy-related information of other providers outside of 3GPP scope potentially involved in the same service chain (e.g. video streaming providers)”. These phrases clearly express the EXIGENCE ideas and the role of a 3GPP domain as one single element therein.
The SA2 study report TR 23.700-67 proposed solutions to the following key issues:
- Enhancements of collection, determination and exposure of Energy-related information. This is about extending these functionalities (i.e., collection, determination, and exposure of energy-related information) beyond the R19 work described above.
- Support of service adjustments for the UE. This is about potentially adjusting traffic handling (e.g., QoS) for the UE, based on energy-related information, as well as related policy control and charging.
- NF (re)selection and/or UP path adjustment based on energy-related information. This is about taking energy-related information into account when (re)selecting NFs and or UP paths i.e., for the internal workings of the 5G network.
Just like for Release 19, this study was followed by the normative work complementing the core 5G specifications (i.e., TS 23.501, 23.502, and 23.503).
The Release 19 efforts only considered best-effort service, with policies to limit energy consumption. In contrast, the Release 20 5GA efforts also investigated services with stringent QoS requirements, in order to determine to which extent they could take into account energy service criteria as well (e.g., user preferences or operator policies) and/or be impacted by energy availability limitations.
Release 20 and 21 (6G)
The 6G Study started in SA1 as part of Release 20. This study collected initial requirements for 6G in a single study report TR 22.870. Note, by the way, that these are additional requirements, as all pre-existing 5G requirements apply to 6G as well. Clause 5.8 of the study report on “Energy-related aspects” contains nine use cases related to energy and carbon optimisations (both internally focused, as well as “as service criteria”). In particular, Clause 5.8.6 “Use case on energy saving for network in industry park” addresses energy-related criteria “as service criteria”. EXIGENCE joined forces with the original submitter of this use case to extend its three requirements to include the aspects of energy prediction and of carbon equivalent emissions. Subsequently, these requirements – along with ten other energy-related requirements – were consolidated as part of Clause 14.1.1.4.
The normative work on 6G is currently ongoing and part of Release 21. The (draft) specification TS 22.270 contains further developed versions of abovementioned thirteen consolidated requirements in its Clause 5.1.5. Again, the first three requirements of this clause were significantly influenced by EXIGENCE. They propose the idea of an energy management system, which is outside of 3GPP system and, amongst others, can collect information like energy mix from an energy supplier in order to compute carbon impact. The information collected enables the 3GPP system to propose different options to deliver 3GPP services i.e., reducing energy / carbon impact by reducing user experience. Also, this information can be exposed to the operator itself and to authorised 3rd parties.
Relevance for EXIGENCE
The use cases and requirements defined by SA1 (TR 22.882, TR 22.883, TS 22.261 Clause 6.15a, TR 22.870 Clauses 5.8 and 14.1.1.4, TS 22.270 Clause 5.1.5) are relevant to requirements and scenarios. The solutions provided by SA2 (TR 23.700-66, TR 23.700-67, and parts of TS 23.501, 23.502, and 23.503) are relevant to energy metrics, energy measurements, data collection, resource interconnectivity, orchestration, and energy optimisation.