UE redirection based on energy

Abstract

A method for energy saving in a communication network. Based on energy information associated with a first network node it is determined that the capacity of the node should be reduced, 101. A second

Description

BACKGROUND Field Certain examples of the present disclosure provide one or more techniques for redirecting a User Equipment (UE) based on energy, for example in a 3rd Generation Partnership Project (3GPP) 5th Generation (5G) New Radio (NR) network. Description of the Related Art Various acronyms, abbreviations and definitions used in the present disclosure are defined at the end of this description. The following documents may be referenced in the present disclosure: [1] 3GPP SP-231192: New SID on 5GS Enhancement for Energy Efficiency and Energy Saving [2] 3GPP TS 24.501 V18.4.0 Study on Energy Efficiency 3GPP SA2 is currently performing a study on energy efficiency for which the scope and objectives are defined in [1], The following work task (WT) is from [1] and it describes some of the objectives of the study. - I / VT #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 TR 22.882 by SA1 EnergyServ. As can be seen from the above, one of the aspects that will be studied is related to energy savings. 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 illustrates an exemplary method for energy saving in a network; and Figure 2 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 order and / or combination. Certain examples of the present disclosure provide one or more techniques for redirecting UEs based on energy, for example in 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. 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. There are no current solutions which have been proposed for redirecting the UE to a target network, or a target Network Function (NF), when a source network or a source NF wants to reduce its capacity due to energy. Certain examples of the present disclosure provide one or more techniques for redirecting UEs based on energy. Certain examples of the present disclosure provide a method for energy saving in a network, the method comprising: determining, based on energy information associated with a first network node, that the capacity of the first network node should be reduced; based on the determining, selecting a second network node; and redirecting a UE from the first network node to the second network node. In certain examples, the energy information may comprise information based on an energy usage level of the first network node. In certain examples, the determining is based on a comparison between the energy usage level and a threshold. In certain examples: the first network node may be a first Access and Mobility Management Function (AMF), and the second network node may be a second AMF different from the first AMF; the first network node may be a first Session Management Function (SMF), and the second network node may be a second SMF different from the first SMF; or the first network node may be a first User Plane Function (UPF), and the second network node may be a second UPF different from the first UPF. In certain examples, the first network node may be a node of a first Core Network (CN), and the second network node is a node of a second CN different from the first CN. In certain examples, the determining, selecting and / or redirecting may be performed by one or more of: the first network node; a third network node different from the first and second network nodes; a Radio Access Network (RAN) node; a Mobility Management Entity (MME); an Access and Mobility Management Function (AMF); and a Session Management Function (SMF). In certain examples, the redirecting may be performed based on Non Access Stratum (NAS) messages. In certain examples, the redirected UE may be selected based on UE subscription information. In certain examples, the selecting may be performed based on energy information associated with the second network node. In certain examples, the method may further comprise receiving, from the UE, an indication that the UE supports redirection based on energy. In certain examples, the method may further comprise transmitting, to the UE, an indication that the network supports redirection based on energy. Certain examples of the present disclosure provide a network node 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 network node according to any example, aspect, embodiment and / or claim 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. Various examples will now be described in more detail. In the following sections are described (1) actions to redirect UEs across AMFs using NAS messages, (2) actions to redirect UEs across AMFs via interactions with the RAN, (3) actions to redirect UEs across CN due to energy, (4) actions to redirect UEs across SMFs due to energy, and (5) RAN selection of AMF / MME considering energy. The skilled person will appreciate that the techniques described in these sections may be used in any suitable order and / or combination. The following section describes the network behaviour when it determines to reduce the capacity on certain NFs and how it can do so by moving UEs to other NFs or target networks for the purpose of reducing capacity and hence energy. As such, the actions for the NFs are due to energy constraints. 1. Actions to redirect UEs across Access and Mobility Management functions (AMFs) using Non Access Stratum (NAS) messages In certain examples, the AMF may determine to reduce its capacity (or reduce the number of UEs that it serves) due to energy constraints. For example, the AMF may make this determination based on local energy usage levels (e.g. exceeding a certain threshold) and / or based on operation and maintenance procedures, and / or based on an explicit indication from another NF. When this occurs, the AMF may be configured to redirect at least one UE to another AMF, where the determination of which UE to redirect may be based on subscription information. As such, new subscription information may be defined such that it indicates if a UE may be subject to redirection based on energy levels in the current NF that serves the UE, where this NF may be an AMF, Session Management Function (SMF), or any other suitable NFs. As such, the subscription information may be sent to at least the AMF, SMF, or any other suitable NFs. Once an AMF determines that a UE should be redirected, for example based on any of techniques disclosed herein, the AMF may use any suitable redirection mechanism towards the UE, for example as follows: • The AMF sends the Configuration Update Command (CUC) message and includes the necessary parameters which will lead to the UE to register again from idle mode and not include the 5G-Globally Unique Temporary Identifier (GUTI) during the registration procedure, which will then lead to not selecting this same AMF as there is not temporary ID (i.e. 5G-GUTI) to point to this particular AMF. o For example, the AMF should shall indicate "registration requested" in the Registration requested bit of the Configuration update indication Information Element (IE) which is in the CUC message. In certain examples, the message should not contain any other parameter. o When the UE performs a registration again, the UE NAS shall not provide the lower layers with the 5G-Short (S)-Temporary Mobile Subscriber Identity (TMSI) or the registered Globally Unique AMF ID (GUAMI). • In certain examples, the AMF should reject a NAS message from the UE and include a suitable cause value that indicates the need to re-register due to energy constraints in the network. o The UE should then register again the UE NAS shall not provide the lower layers with the 5G-S-TMSI or the registered GUAMI. The skilled person will appreciate that the techniques described herein can be applied to UEs that are in connected mode, and / or that are sending a NAS message either from connected mode or from idle mode, and / or from 5G Mobile Management (5GMM)-CONNECTED mode with Radio Resource Control (RRC) inactive indication. 2. Actions to redirect UEs across AMFs via interactions with the RAN In certain examples, the AMF may determine to reduce its capacity (and / or reduce the number of UEs that it serves) due to energy constraints. For example, the AMF may do this determination based on local energy usage levels (e.g. exceeding a certain threshold) and / or based on operation and maintenance procedures, and / or based on an explicit indication form another NF. When this occurs, the AMF may be configured to redirect at least one UE to another AMF, where the determination of which UE to redirect may be based on subscription information. As such, new subscription information may be defined such that it indicates if a UE may be subject to redirection based on energy levels in the current NF that serves the UE, where this NF may be an AMF, SMF, or any other suitable NFs. As such, the subscription information may be sent to at least the AMF, SMF, or any other suitable NFs. Once an AMF determines that a UE should be redirected, for example based on any of the techniques disclosed herein, the AMF may use any suitable redirection mechanism towards the UE, for example as follows: • The AMF should trigger the re-route procedure on the NG-AP interface (see 3GPP TS 38.413) by sending the REROUTE NAS REQUEST to the NG-RAN. The AMF should include the NAS message which was received from the UE. The AMF may indicate that the reason is due to energy constraints. • The NG-RAN should then select another AMF and route the NAS message to the new AMF, optionally based on the indication of energy constraints from the source AMF. • When re-routing the NAS message to another AMF, the NG-RAN may indicate that this is a due to a re-route as a result of energy constraints in a source AMF. The skilled person will appreciate that the techniques described herein can be applied to S1 mode, i.e. to Evolved Packet System (EPS). For example, the same reroute mechanism can be used by Mobility Management Entity (MME) based on a similar S1 Application Protocol (S1AP) message which is defined in 3GPP TS 36.413. As such, the MME may also reroute a NAS message to a target MME due to energy constraints. Therefore, various techniques disclosed herein can also be applied to EPS where similar or equivalent messages and / or lEs can be used. 3. Actions to redirect UEs across CN due to energy In certain examples, the AMF may determine to reduce its capacity (and / or reduce the number of UEs that it serves) due to energy constraints. For example, the AMF may make this determination based on local energy usage levels (e.g. exceeding a certain threshold) and / or based on operation and maintenance procedures, and / or based on an explicit indication form anther NF. When this occurs, the AMF may be configured to redirect at least one UE to another core network, for example to Evolved Packet Core (EPC). The AMF may use any suitable mechanism to redirect the UE to EPC, where the trigger to do so may be based on energy usage levels in 5GS, and the AMF being configured to redirect the UE to EPC where the AMF may be aware that the EPC’s energy level usage is acceptable. How the AMF makes this determination may be out of scope. In certain examples, the AMF may redirect a UE to EPC based on indication that the UE supports energy efficiency or based on the UE supporting Cellular Internet of Things (CloT) optimizations. The UE may indicate in an existing IE or a new IE that it supports energy efficiency or it supports redirection to a target CN based on energy efficiency. The network may also inform the UE that it supports redirecting UEs to target CN based on energy efficiency. The network may do so for UEs for which there is subscription information to redirect the UEs based on energy considerations. As such, any suitable subscription information may be defined for this purpose, where this may be provided for example to the AMF, for example from the Unified Data Management (UDM), and for example based on which the AMF may determine which UE to redirect to EPC. In certain examples, to perform the actual redirection, the AMF may behave as follows: • When the UE sends any NAS message, the AMF may respond with a NAS reject message and include the 5GMM cause value #31 Redirection to EPC required, or a new IE may be used to indicate redirection to EPC due to energy constraints. • The NAS message from the UE may be any suitable NAS message, for example Registration Request, Service Request, or Control Plane Service Request. o In EPC, the UE may use Attach Request, Tracking Area Update Request message, Service Request, or Control Plane Service Request. • The AMF may redirect the UE, due to energy constraints, by using Registration Reject or Service Reject, and by including the 5GMM cause value #31 Redirection to EPC required, or a new cause value. o In EPC, the MME may use Attach Reject, Tracking Area Update Reject, or Service Reject. • The AMF may also send a Deregistration Request message to the UE and include the 5GMM cause value #31 Redirection to EPC required, or a new cause value. o In EPC, the MME may use Detach Request for the same purpose. Although some of the messages above are re-used, the trigger for doing so is now energy related. As such, the AMF may behave as described above when it needs to reduce energy in the network (or the AMF). The skilled person will appreciate that the techniques described herein can be applied to EPS in which the MME may use similar methods (with appropriate or corresponding or equivalent NAS messages) in order to redirect a UE to 5GC. The same technique can also be used for a new system, for example for 6G such that a 6G NF can redirect the UE to 5G or 4th Generation (4G). 4. Actions to redirect UEs across SMFs due to energy Redirecting a UE from one SMF may also mean that the SMF will stop serving the UE. The SMF may determine to reduce its capacity (and / or reduce the number of UEs that it serves) due to energy constraints. For example, the SMF may make this determination based on local energy usage levels (e.g. exceeding a certain threshold) and / or based on operation and maintenance procedures, and / or based on an explicit indication form anther NF. The UE may indicate in an existing IE or a new IE that it supports energy efficiency or it supports redirection to a target CN based on energy efficiency. The network may also inform the UE that it supports redirecting UEs to target CN based on energy efficiency. The network may do so for UEs for which there is subscription information to redirect the UEs based on energy considerations. As such, any suitable subscription information may be defined for this purpose, where this may be provided for example to the SMF, for example from the UDM, for example based on which the SMF may determine which UE to stop serving. When this occurs, the SMF may be configured to redirect at least one UE to another SMF, and / or may determine to stop serving the UE in question, for which the SMF may behave for example as follows: • The SMF may release the Protocol Data Unit (PDU) session (and send PDU Session Release Command message) and indicate any existing 5G Session Management (5GSM) cause value, or a new value may be defined to indicate that the reason is due to energy. • The SMF may send the PDU Session Modification Command message and indicate a new 5GSM cause value to indicate that the reason is due to energy, or the SMF may use an existing #39- Reactivation requested. In certain examples, when the UE receives any of the messages listed above, the UE may behave as follows: • The UE may attempt to establish another PDU session and indicate that the establishment is due to energy, i.e. that the session is being used to replace another session as a result of energy constraints. The UE may provide this indication in the NAS message that is a mobility management message (e.g. the Uplink (UL) NAS TRANSPORT message), and / or any session management message (e.g. PDU Session Establishment Request message), and / or any suitable IE may be used to provide this indication from the UE. The SMF may inform the AMF that it needs to reduce capacity due to energy. The AMF may be configured to reduce the number of UEs which use a particular SMF, for example based on local policies, and / or based on indication from the SMF, and / or based on Operations, Administration and Maintenance (0AM). In certain examples, to reduce the number of UEs which use an SMF, the AMF should update the allowed Network Slice Selection Assistance Information (NSSAI) for each and every UE that was provided with a Single NSSAI (S-NSSAI) that is served by the SMF in question. The AMF may send a new allowed NSSAI (e.g. using any NAS message) such that the S-NSSAI which corresponds to the SMF (that is constrained with energy) is not part of the updated (or new) allowed NSSAI. The AMF may indicate that the S-NSSAI is rejected or simply not include the S-NSSAI in the allowed NSSAI. The AMF may indicate that a slice is not available (e.g. temporarily) due to energy constraints. In certain examples, the AMF may do so for particular UEs that support this, for example based on capabilities which may be exchanged between the UE and the network as described above. In certain examples, the AMF may do so for UE that are subject to this, for example based on subscription information as described above. In certain examples, if the SMF determines that a User Plane Function (UPF) is having energy constraints (e.g. the UPF cannot serve more UEs and / or existing UEs), the SMF may take the following actions: • The SMF may release the PDU session for at least one UE where the PDU session is being served by the UPF in question. • The SMF may indicate that resources are not available in the UPF. In certain examples, the AMF may reject a request for user plane establishment towards a UPF (e.g. based on indication from the SMF to the AMF) due to energy constraints. The AMF may indicate that resources are not available, where a new cause value may be used or existing cause values may be used e.g. #67- Insufficient resources for specific slice and Data Network (DN), or #92 - Insufficient user-plane resources for the PDU session, or any other suitable cause value. The AMF or SMF may use the new cause value, or existing cause values, in any NAS message. The NAS message may be new or existing. 5. RAN selection of AMF / MME should now consider energy In certain examples, the RAN (e.g. NG-RAN or RAN in Evolved UMTS Terrestrial RAN (E-UTRAN)) may be configured to select a ON node based on energy levels or energy capacity (and / or capacity which may translate to energy) in the CN. The RAN may be configured with the information of each CN node’s energy level or usage. The RAN may receive a NAS message from a UE, for example during RRC establishment procedure, in which the RAN needs to send the NAS message to a selected CN. In certain examples, the selection of a CN node by the RAN should consider the energy levels of a CN node. For example, multiple AMFs and / or multiple MMEs may serve an area and the RAN needs to choose one AMF or one MME. The RAN should make the selection by taking into account the energy levels of the CN. For example, if one AMF or MME is having high energy levels, then the RAN may avoid selecting it and it may select another CN node. The RAN may be configured to select a CN node such that the energy level usage across the CN nodes is (as much as possible) balanced. The RAN may be informed about the energy levels in the CN nodes using any suitable mechanism, for example based on a message from the CN to the RAN (where the message may be new or existing), and / or based on configurations in the RAN, and / or based on operation and maintenance. In certain examples, the RAN may take other factors into account while selecting a CN node, for example load levels, but the RAN should also consider energy levels of the CN nodes as described herein. In certain examples, the RAN may be informed by a CN node (using new and / or existing messages) to stop or to resume selection of the CN node in question for reasons due to energy. In certain examples, the RAN should not select a CN node which has informed the RAN of high energy levels or which have informed the RAN that the CN node should not be selected optionally due to energy constraints. In certain examples, the RAN can select a CN node which has informed the RAN of low energy levels or which have informed the RAN that the CN node can be selected optionally due to energy constraints being acceptable. The skilled person will appreciate that the various techniques disclosed herein may be applied to any suitable system, such as 5G, 4G, 6G, etc. The NAS messages in 5G or 4G may have different names, or the lEs may be named differently, however the proposals may still be applied. Figure 1 illustrates an exemplary method for energy saving in a network. Referring to Figure 1, in a first operation 101, it is determined, based on energy information associated with a first network node (e.g. a first AMF, SMF or UPF, and / or a node of a first CN), that the capacity of the first network node should be reduced. For example, the energy information may comprise information based on an energy usage level of the first network node. In certain examples, the determining may be based on a comparison between the energy usage level and a threshold. In a second operation 102, based on the determining, a second network node (e.g. a second AMF, SMF or UPF, and / or a node of a second CN) is selected. For example, the selecting may be performed based on energy information associated with the second network node. In a third operation 103, a UE is redirected from the first network node to the second network node. For example, the redirected UE may be selected based on UE subscription information. In certain examples, the redirecting may be performed based on NAS messages. The various operations 101, 102,103 may be performed by any suitable nodes and / or entities, for example the first network node and / or another network node / entity (e.g. a third network node, RAN, MME, AMF, SMF). In various examples, the operations 101. 102, 103 may be performed by the same node / entity or different nodes / entities. Although not shown in Figure 1, in certain examples the method may further comprise receiving, from the UE, an indication that the UE supports redirection based on energy, and / or transmitting, to the UE, an indication that the network supports redirection based on energy. Figure 2 is a block diagram of an exemplary network entity that may be used in examples of the present disclosure. 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 200 comprises a processor (or controller) 201, a transmitter 203 and a receiver 205. The receiver 205 is configured for receiving one or more messages from one or more other network entities, for example as described above. The transmitter 203 is configured for transmitting one or more messages to one or more other network entities, for example as described above. The processor 201 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. 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. Acronyms n the present disclosure, the following acronyms / definitions may be used. 3GPP 4G 5G 5G-S-TMSI 6G 5GC 5GMM 5GS 5GSM AMF AP CloT CN cue DN EPC EPS E-UTRAN GUAMI GUTI ID IE MME NAS NF NG NR NSSAI OAM PDU RAN RRC S1 mode 3rd Generation Partnership Project 4th Generation 5th Generation 5G Short TMSI 6th Generation 5G Core 5G Mobility Management 5G System 5G Session Management Access and Mobility Management Function Application Protocol Cellular Internet of Things Core Network Configuration Update Command Data Network Evolved Packet Core Evolved Packet System Evolved UMTS Terrestrial Radio Access Network Globally Unique AMF ID Globally Unique Temporary Identifier Identity / ldentifier Information Element Mobility Management Entity Non Access Stratum Network Function Next Generation New Radio Network Slice Selection Assistance Information Operations, Administration and Maintenance Protocol Data Unit Radio Access Network Radio Resource Control a mode of a UE that operates with a functional division that is in accordance with the use of an S1 interface between the radio access network and the core network S1AP SID SMF S-NSSAI TMSI TR TS UDM UE UL UMTS UPF WT S1 Application Protocol Study Item Description Session Management Function Single Network Slice Selection Assistance Information Temporary Mobile Subscriber Identity Technical Report Technical Specification Unified Data Management User Equipment Uplink Universal Mobile Telecommunications System User Plane Function Work Task

Claims

1. A method for energy saving in a network, the method comprising:determining, based on energy information associated with a first network node, that the capacity of the first network node should be reduced;based on the determining, selecting a second network node; and redirecting a UE from the first network node to the second network node.

2. A method according to claim 1, wherein the energy information comprises information based on an energy usage level of the first network node.

3. A method according to claim 2, wherein the determining is based on a comparison between the energy usage level and a threshold.

4. A method according to claim 1,2 or 3, wherein:the first network node is a first Access and Mobility Management Function (AMF), and the second network node is a second AMF different from the first AMF;the first network node is a first Session Management Function (SMF), and the second network node is a second SMF different from the first SMF; orthe first network node is a first User Plane Function (UPF), and the second network node is a second UPF different from the first UPF.

5. A method according to any preceding claim, wherein the first network node is a node of a first Core Network (CN), and the second network node is a node of a second CN different from the first CN.

6. A method according to any preceding claim, wherein the determining, selecting and / or redirecting is performed by one or more of:the first network node;a third network node different from the first and second network nodes;a Radio Access Network (RAN) node;a Mobility Management Entity (MME);an Access and Mobility Management Function (AMF); anda Session Management Function (SMF).

7. A method according to any preceding claim, wherein the redirecting is performed based on Non Access Stratum (NAS) messages.

8. A method according to any preceding claim, wherein the redirected UE is selected based on UE subscription information.

9. A method according to any preceding claim, wherein the selecting is performed based on energy information associated with the second network node.

10. A method according to any preceding claim, further comprising receiving, from the UE, an indication that the UE supports redirection based on energy.

11. A method according to any preceding claim, further comprising transmitting, to the UE, an indication that the network supports redirection based on energy.

12. A network node configured to perform a method according to any preceding claim.

13. A network (or wireless communication system) comprising a network node accordingto claim 12.

14. 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 of claims 1 to 11.

15. A computer or processor-readable data carrier having stored thereon a computer program according to claim 14.

Images