METHOD AND APPARATUS FOR IMPROVING SERVICE STABILITY IN A WIRELESS COMMUNICATION

Abstract

To provide a method and an apparatus therefor for improving service reliability in a wireless communication system.SOLUTION: A method, performed by a first SMF (session management function), for providing a continuous service to a terminal includes the steps of: identifying, by the first SMF, triggering of an SMF change operation; transmitting, to an AMF (access and mobility management function), a message indicating a change in a status of a PDU (packet data unit) session related to the terminal so as to request a procedure of changing an SMF; receiving a context request message requesting a context of the terminal from a second SMF that is a target SMF; and transmitting a context request response message to the second SMF.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a method for managing a context in a mobile communication system. [Background technology]

[0002] 4G(4 th Since the commercialization of the 5G (5G) communication system, improved 5G (5G) has been developed to meet the increasing demand for wireless data traffic. th Efforts are underway to develop 5G (5th generation) or pre-5G communication systems. For this reason, 5G or pre-5G communication systems are also referred to as beyond 4G network communication systems or post-LTE (long term evolution) systems.

[0003] To achieve high data transmission rates, 5G communication systems are being considered for implementation in ultra-high frequency (mmWave) bands (e.g., 60 GHz bands). To mitigate radio wave propagation path loss and extend the radio wave propagation distance in the ultra-high frequency bands, technologies such as beamforming, massive multiple-input multiple-output (MIMO), full-dimensional multiple-input multiple-output (FD-MIMO), array antennas, analog beamforming, and large-scale antennas are being discussed for 5G communication systems.

[0004] In addition, to improve the system's network, technologies such as advanced small cells, cloud radio access networks (cloud RAN), ultra-dense networks, device to device communication (D2D), wireless backhaul, moving networks, cooperative communication, coordinated multi-points (CoMP), and interference cancellation are being developed in 5G communication systems.

[0005] In addition, advanced coding modulation (ACM) methods such as hybrid frequency shift keying and quadrature amplitude modulation (FQAM) and sliding window superposition coding (SWSC) as well as advanced access technologies such as filter bank multicarrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) are being developed for 5G systems.

[0006] The 5G system is expected to support a wider variety of services than the existing 4G system. For example, the most representative services may include enhanced mobile broadband (eMBB), ultra-reliable and low latency communication (URLLC), massive machine-type communication (mMTC), and evolved multimedia broadcast / multicast service (eMBMS). A system providing the URLLC service may be referred to as a URLLC system, and a system providing the eMBB service may be referred to as an eMBB system. The terms "service" and "system" may be used interchangeably.

[0007] Among them, URLLC service is a new service being considered for the 5G system, unlike the existing 4G system, and it has ultra-high reliability (for example, a packet error rate of approximately 10 -5 ) and low latency (e.g., about 0.5 msec). To meet such strict requirements, URLLC services must apply a shorter transmission time interval (TTI) than eMBB services, and various operation methods that take advantage of this are being considered.

[0008] Meanwhile, the Internet, a human-centered network where people generate and consume information, is evolving into an Internet of Things (IoT) network that exchanges and processes information between distributed components like things. IoE (Internet of Everything) technology, which combines IoT technology with big data processing technology through connections to cloud servers, has also been proposed. To realize IoT, technological elements such as sensing technology, wired and wireless communication and network infrastructure, service interface technology, and security technology are required, and recent research has focused on technologies such as sensor networks for connecting things, machine-to-machine (M2M) communication, and machine-type communication (MTC).

[0009] In the IoT environment, intelligent IT (internet technology) services can be provided that collect and analyze data generated by connected things and create new value in human life. The IoT is also applied to fields such as smart homes, smart buildings, smart cities, smart cars or connected cars, smart grids, healthcare, smart home appliances, and advanced medical services through the fusion and integration of existing IT (information technology) with various industries.

[0010] To this end, various attempts are being made to apply 5G communication systems to IoT networks. For example, technologies such as sensor networks, machine-to-machine (M2M) communication, and MTC are being implemented using 5G communication techniques such as beamforming, MIMO, and array antennas. The application of cloud radio access networks (cloud RAN), the aforementioned big data processing technology, can also be considered an example of the fusion of 5G and IoT technologies.

[0011] Meanwhile, with the development of various IT technologies, network equipment is evolving into virtualized network functions (NFs) by applying virtualization technology. The virtualized NFs are free from physical constraints and can be implemented in software form and installed / operated in various types of clouds and data centers (DCs). In particular, the NFs can be freely scaled and initiated / terminated according to service requirements, system capacity, and network load. Summary of the Invention [Means for solving the problem]

[0012] According to one aspect of the exemplary embodiment, a method of communication in a wireless communication system is provided. [Effects of the Invention]

[0013] The disclosed embodiments provide an apparatus and method that can effectively support services in a wireless communication system. [Brief explanation of the drawings]

[0014] Having described the embodiments of the present disclosure, other aspects, features, and advantages will become apparent from the following written description taken in conjunction with the drawings. [Figure 1] FIG. 1 is a diagram illustrating a 5G system structure based on a service-based architecture (SBA) according to an embodiment of the present disclosure. [Figure 2] FIG. 1 illustrates a network function (NF) configuration and context management structure according to one embodiment of the present disclosure. [Figure 3] A diagram illustrating an example of the operation of a 5G system including a terminal, a base station, and a core according to one embodiment of the present disclosure. [Figure 4]FIG. 10 is a diagram illustrating a method for processing without collision while maintaining service when an NF change is required during service according to an embodiment of the present disclosure. [Figure 5] FIG. 10 is a diagram illustrating a method for processing without collision while maintaining service when an NF change is required during service according to an embodiment of the present disclosure. [Figure 6] FIG. 10 is a diagram illustrating a method for selecting an NF in consideration of network conditions according to an embodiment of the present disclosure. [Figure 7] FIG. 10 is a diagram illustrating a method for shortening the time required to change the state of a terminal and moving the context of an NF according to an embodiment of the present disclosure. [Figure 8] FIG. 10 is a diagram illustrating a method for triggering a state change of a terminal and changing an NF according to an embodiment of the present disclosure. [Figure 9] FIG. 10 is a diagram illustrating a method for exchanging information related to an NF that plays a backup role for an NF according to one embodiment of the present disclosure. [Figure 10] FIG. 2 illustrates a configuration of a network entity according to one embodiment of the present disclosure. [Figure 11] FIG. 2 is a diagram illustrating a configuration of a terminal according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0015] The disclosed embodiments are based on 5G (5 th In order to increase communication efficiency and improve customer service quality in the network-generation system, we propose a structure and communication method that allows NFs (network functions) to exchange or store user data (context) they process.

[0016] Additional aspects will be set forth in part in the description that follows, and in part will be obvious from the description, or may be learned by practice of presented embodiments of the present disclosure.

[0017] According to one embodiment of the present disclosure, a method performed by a first session management function (SMF) to provide continuous services to a user equipment (UE) includes: identifying triggering of an SMF change operation by the first SMF; transmitting a message indicating a change in the state of a protocol data unit (PDU) session of the UE to an access and mobility management function (AMF) to request an SMF change procedure; receiving a context request message requesting a context of the UE from a second SMF, which is a target SMF; and transmitting a context request response message to the second SMF.

[0018] The SMF change operation is triggered in response to a request by an OAM (operations, administration and maintenance), the OAM request also including identification information of the second SMF.

[0019] The method may further include transmitting a message to the AMF requesting notification of information related to a state change of the UE, and receiving a notification message from the AMF indicating the state change of the UE.

[0020] The message instructing a change in the state of the PDU session associated with the UE may include at least one of identification information of the second SMF, a context ID (identification), or ID information of the UE.

[0021] The context request response message also includes information regarding the UE's context requested by the second SMF and a user plane function (UPF) selected by the second SMF.

[0022] According to one embodiment of the present disclosure, a method performed by an access and mobility management function (AMF) to provide continuous services to a user equipment (UE) includes receiving a message from a first session management function (SMF) indicating a change in the state of a protocol data unit (PDU) session of the UE to request a procedure for changing an SMF, selecting a second SMF as a target SMF, transmitting a request message to the second SMF requesting the creation of a new session, and receiving a response message related to the request message requesting the creation of the new session from the second SMF.

[0023] The step of selecting the second SMF may be performed by the AMF or via a service communication proxy (SCP).

[0024] The method also includes the steps of receiving a change message request for information related to a state change of the UE from the first SMF, monitoring the state change of the UE, and transmitting a notification message to the first SMF instructing the state change of the UE based on the monitoring result.

[0025] The message indicating a change in the state of the PDU session associated with the UE may include at least one of identification information of the second SMF, a context ID, or ID information of the UE, and the identification information of the second SMF may include SMF set identification information. The second SMF is also registered by a unified data management (UDM).

[0026] According to an embodiment of the present disclosure, a first session management function (SMF) for providing continuous services to a user equipment (UE) may include a transceiver unit and a processor coupled to the transceiver unit. The processor may identify triggering of an SMF change operation via the first SMF, transmit a message indicating a change in a protocol data unit (PDU) session state of the UE to request an access and mobility management function (AMF) to change the SMF, receive a context request message requesting a context of the UE from a second SMF that is a target SMF, and transmit a context request response message to the second SMF.

[0027] The SMF change operation may be triggered in response to a request by an OAM (operations, administration and maintenance), and the OAM request may include identification information of the second SMF.

[0028] The processor may transmit a message to the AMF requesting notification of information related to a state change of the UE, and may receive a notification message from the AMF indicating a state change of the UE.

[0029] The message indicating a change in the state of the PDU session associated with the UE may include at least one of identification information of the second SMF, a context ID, or ID information of the UE.

[0030] The context request response message may include information regarding the UE's context requested by the second AMF and a user plane function (UPF) selected by the second SMF.

[0031] According to an embodiment of the present disclosure, an access and mobility management function (AMF) for providing continuous services to a user equipment (UE) may include a transceiver unit and a processor coupled to the transceiver unit. The processor may receive a message indicating a change in a protocol data unit (PDU) session state of the UE to request a procedure for changing an SMF from a first session management function (SMF), select a second SMF as a target SMF, transmit a request message requesting creation of a new session to the second SMF, and receive a response message related to the request message requesting creation of the new session from the second SMF.

[0032] The step of selecting the second SMF may be performed by the AMF or via a service communication proxy (SCP).

[0033] The processor can receive a message request change of information related to a state change of the UE from the first SMF, monitor the state change of the UE, and transmit a notification message to the first SMF instructing a state change of the UE based on the monitoring result.

[0034] The message instructing a state change of the PDU session related to the UE may include at least one of identification information of the second SMF, a context ID, or ID information of the UE, and the identification information of the second SMF may also include SMF set identification information.

[0035] The second SMF is also registered with a unified data management (UDM).

[0036] Before embarking on the detailed description below, it will be advantageous to refer to definitions of certain words and phrases used throughout this patent document. The terms "comprise" and "include," as well as their derivatives, refer to an open-ended inclusion. The term "or" is inclusive and means "and / or." The term "pertaining to," as well as its derivatives, refers to "including," "contained within," "interconnected with," "incorporating," "incorporated within," "connected to or with," "coupled to or with," "capable of communicating with," "cooperating with," "interleaving," "juxtaposing," "adjacent to," "connected to or with," "having," "having characteristics of," and "relating to or with." The term "controller" refers to any device, system, or portion thereof that controls at least one operation. Such a controller may also be embodied in hardware or a combination of hardware and / or software and / or firmware. The functionality associated with any particular control unit may be local or remote, centralized or distributed.

[0037] Moreover, various functions described below may be embodied or supported by one or more computer programs, each of which is formed from computer-readable program code and embodied in a computer-readable medium. The terms "application" and "program" refer to one or more computer programs, software components, instruction sets, procedures, functions, objects, classes, instances, associated data, or portions thereof suitable for implementation in suitable computer-readable program code. The term "computer-readable program code" includes any type of computer code, including source code, object code, and executable code. The term "computer-readable medium" includes any type of medium that can be accessed by a computer, such as read-only memory (ROM), random access memory (RAM), hard disk drive, compact disc (CD), digital video disc (DVD), or any other type of memory. "Non-transitory" computer-readable medium excludes wired, wireless, optical, or other communication links that transmit transient electrical or other signals. Non-transitory computer-readable media include media on which data can be stored permanently and later overwritten, such as rewritable optical disks or erasable memory devices.

[0038] Definitions for other specific words and phrases are provided throughout this patent document, and those skilled in the art should understand that in many, if not most, cases, such definitions may apply to prior and future uses of the words and phrases so defined.

[0039] 1-11 discussed below, and the various embodiments used to illustrate the principles of the present disclosure in this patent document, are merely exemplary and are not to be construed as limiting the scope of the present disclosure in any way. Those skilled in the art will understand that the principles of the present disclosure may be embodied in any suitably arranged system or device. The operating principles of the present disclosure will be described in further detail with reference to the accompanying drawings. In the description of the present disclosure, detailed descriptions of related well-known functions and configurations may be omitted if it is determined that such descriptions may unnecessarily obscure the gist of the present disclosure. Furthermore, the terms used below are defined in consideration of the functions in the present disclosure and may have other meanings depending on the intentions, practices, etc. of users or operators. These terms are also defined based on the description of the entire specification.

[0040] For the same reason, in the accompanying drawings, some components are exaggerated or omitted for schematic illustration, and the size of each component does not fully reflect the actual size. In each drawing, the same reference numerals are used to denote the same or corresponding components.

[0041] The advantages, features, and methods for achieving the same of the present disclosure will become clearer with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present disclosure is not limited to the embodiments disclosed below, and may be embodied in various different forms. However, the present embodiments are provided to complete the disclosure and fully convey the scope of the disclosure to those skilled in the art to which the disclosure pertains, and the present disclosure is defined only by the scope of the claims. The same reference numerals refer to the same elements throughout the specification.

[0042] It will be understood that each block of the process flowchart diagrams, and combinations of blocks in the flowchart diagrams, can be implemented by computer program instructions. These computer program instructions can be loaded into a processor in a general-purpose computer, special-purpose computer, or other programmable data processing device, such that the instructions, executed by the processor in the computer or other programmable data processing device, create means for performing the functions described in the flowchart blocks. These computer program instructions can also be stored in computer-usable or computer-readable memory that can direct the computer or other programmable data processing device to implement the functions in a particular way, such that the instructions stored in the computer-usable or computer-readable memory can produce an article of manufacture containing instruction means for performing the functions described in the flowchart blocks. The computer program instructions may be embodied on a computer or other programmable data processing device such that a series of operational steps are performed on the computer or other programmable data processing device to create a computer-implemented process, and the instructions that cause the computer or other programmable data processing device to provide steps for performing the functions described in the flowchart blocks.

[0043] Also, each block may represent a module, segment, or portion of code that includes one or more executable instructions for performing the specified logical function. Also, it should be noted that in some alternative implementations, the functions noted in the blocks may occur out of order. For example, two blocks shown in succession may actually be performed substantially simultaneously, or the blocks may sometimes be performed in reverse order depending on the function.

[0044] In this embodiment, the term "module" refers to a software component or a hardware component such as an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit), and the "module" performs a certain function. However, the "module" is not limited to software or hardware. The "module" may be configured to reside on an addressable recording medium and to execute one or more processors. Thus, as an example, the "module" includes components such as software components, object-oriented software components, class components, and task components, as well as processes, functions, attributes, procedures, subroutines, program code segments, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and variables. The functions provided by the components and "modules" may be combined into fewer components and "modules" or further separated into additional components and "modules." Furthermore, the components and "modules" may be embodied to execute one or more central processing units (CPUs) in a device or a secure multimedia card. In this embodiment, the "unit" may include one or more processors.

[0045] In particular, the present disclosure relates to 3GPP (registered trademark) rdGeneration Partnership Project) NR (new radio) (5th generation (5G:5 th The present disclosure can be applied to 5G (5G generation) mobile communication standards. In addition, the present disclosure can also be applied to intelligent services (e.g., smart homes, smart buildings, smart cities, smart cars or connected cars, healthcare, digital education, retail, security-related and safety-related services, etc.) based on 5G communication technology and IoT (Internet of Things)-related technology. In this disclosure, eNB is also used interchangeably with gNB for convenience of explanation. That is, a base station described as eNB can refer to a gNB. In addition, the term terminal can refer to not only a mobile phone, an NB-IoT device, and a sensor, but also other wireless communication devices.

[0046] In the following description, terms for identifying connection nodes, terms for indicating network entities or NFs, terms for indicating messages, terms for indicating interfaces between network objects, terms for indicating various identification information, etc. are provided for convenience of explanation. Therefore, the present invention is not limited to the terms described below, and other terms for indicating objects having equivalent technical meanings may be used. In addition, an NF is also a network entity.

[0047] For ease of explanation, the present invention will use terms and names defined in the 3GPP LTE (long term evolution) standard and 5G standard. However, the present invention is not limited to the above terms and names and may be equally applied to systems according to other standards.

[0048] Meanwhile, in describing the embodiments of the present disclosure, the main subject is the terminal information (UE context) processed / managed by the NF. The terminal information (UE context) may include, but is not limited to, the above examples, a mobility management (MM) context related to terminal mobility, an access management (AM) context related to wireless connection, and a session management (SM) context related to the session. It may include all types of information necessary to be stored / processed / generated to provide services in a communication network.

[0049] Meanwhile, in this disclosure, the term "service" is used to refer to a request made by a specific communication device (or NF) to another communication device (or NF), i.e., an NF service, and when specifically referring to a service delivered to an actual user (end-user), it is distinguished from the term "customer service."

[0050] According to an embodiment of the present disclosure, a structure and a communication method are provided in which NFs can exchange or store user data (context) processed by each other in order to increase communication efficiency and improve customer service quality in a system. Furthermore, according to an embodiment of the present disclosure, a method is proposed to prevent service processing collisions (transaction collisions or race conditions) between NFs that may occur when a structure for exchanging and storing user data processed by NFs is introduced. Furthermore, according to an embodiment of the present disclosure, a method is proposed to increase the speed at which data is exchanged and processed between NFs, thereby improving service quality and network operation efficiency.

[0051] Here, it goes without saying that the technical problems to be solved by the present disclosure are not limited to the technical problems mentioned above, and other unmentioned technical problems will be clearly understood by those skilled in the art to which the present invention pertains from the following description.

[0052] Although the following describes embodiments of the present disclosure using LTE, LTE-A (LTE-Advanced), LTE Pro, or 5G (or NR (Next Generation Mobile Communications)) systems as examples, the embodiments of the present disclosure may also be applied to other communication systems having similar technical backgrounds or channel configurations. Furthermore, the embodiments of the present disclosure may be applied to other communication systems with some modifications at the discretion of a person skilled in the art, without departing significantly from the scope of the present disclosure.

[0053] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0054] FIG. 1 is a diagram illustrating a 5G system architecture based on a service-based architecture (SBA) according to one embodiment of the present disclosure.

[0055] To support the diverse services of 5G, new system architectures and protocols are required, and 3GPP has decided to introduce a new technology called the Service Infrastructure Architecture (SBA). The main feature of the service infrastructure is that, taking into account the introduction of virtualization technology, cloud environments, and the expansion of web-based services, the functionalities of the NFs defined in the 3GPP standard are divided into service units, and the HTTP / 2 protocol is used to implement those services. However, it goes without saying that the main features of the service infrastructure are not limited to the above examples.

[0056] Referring to FIG. 1, the AMF is an NF that manages wireless network access and mobility for a terminal (UE). The SMF is an NF that manages sessions related to a terminal, and the session information includes QoS information, charging information, and information related to packet processing. The UPF is an NF that processes user plane traffic and is controlled by the SMF. Although not shown in FIG. 1, the 5G system includes an unstructured data storage network function (UDSF), which is an NF that stores unstructured data and can store and retrieve any type of data at the request of the NF. 1, RAN (radio access network) refers to a wireless access network, and may refer to a wireless network between a terminal and a base station or the base station itself. DN (data network) refers to a data network, and the DN may deliver PDUs (packet data units) to be transmitted to the terminal to the UPF, and may receive PDUs transmitted by the terminal via the UPF.

[0057] In addition, the PCF (policy control function) is an NF that determines policies related to billing, the AF (application function) is an NF that provides information related to packet flow to guarantee QoS, the AUSF (authentication server function) is an NF that stores information for user terminal authentication, and the UDM (unified data management) is an NF that stores information related to users.

[0058] Further referring to FIG. 1, the NSSF (network slice selection function) is also an NF that selects a network slice corresponding to a user terminal, and the NEF (network exposure function) is also an NF that provides means for securely exposing services and capabilities provided by 3GPP network functions, such as third parties, internal exposure / re-exposure, application functions, and edge computing.

[0059] An NRF (network repository function) is an NF that supports service discovery functions and maintains available NF instances and the services they support, and an SCP (service control point) is an NF that controls services in the network.

[0060] According to an embodiment of the present disclosure, each NF can communicate using a predetermined interface. For example, the AMF and UE can communicate using the N1 interface, and the UPF and SMF can communicate using the N4 interface. Other NFs can also communicate with each other using predetermined interfaces as shown in FIG. 1. This is obvious to those skilled in the art, so detailed description will be omitted.

[0061] Furthermore, the 5G system of Figure 1 may be configured by excluding at least one of the illustrated NFs, and is not limited to the above example.

[0062] FIG. 2 is a diagram illustrating an NF configuration and context management structure according to one embodiment of the present disclosure.

[0063] 2, UE context, which is data within an NF, is exchanged / shared between NFs, and a set of NFs that can share and use data within an NF is referred to as an NF set 200. Depending on the implementation environment, a specific NF is operated / managed in the form of an NF instance, and the embodiments of the present disclosure are applicable to any operation and management environment of an NF or an NF instance.

[0064] Furthermore, according to one embodiment of the present disclosure, when an NF service unit operates rather than realizing / constructing an NF unit, an NF may also be replaced by an NF service. Therefore, the term NF in the present disclosure may include an NF instance, an NF service, and an NF service instance.

[0065] Furthermore, according to one embodiment of the present disclosure, if multiple NF sets coexist, the NF sets are assigned mutually distinguishable identifiers or names to distinguish them, and even if the NFs within the NF set operate in a shared context, each NF may receive a different identifier / name from the others in the management / operation dimension.

[0066] FIG. 3 is a diagram illustrating an example of a 5G system operation including a terminal, a base station, and a core according to one embodiment of the present disclosure.

[0067] 3, SMF #1 301 and SMF #2 302 are SMF instances included in the same SMF set, and the two SMFs 301 and 302 are connected to the same UPF 303 to provide services.

[0068] If SMF #1 301 is providing a service to a specific UE 304 and it becomes difficult to provide the service to SMF #1 301 any further, it provides the UE context (more specifically, the SM context in this embodiment) that SMF #1 301 has to SMF #2 302 and links to the same UPF 303, thereby enabling the service to continue to be provided to the specific terminal 304. At this time, processing must be performed so that no collision occurs during UE context transmission between SMF #1 301 and SMF #2 302, or a race condition or UE context change occurs.

[0069] In the present disclosure, it is considered that the following embodiments of the present disclosure are applied to continue providing services when the terminal is in an idle state or an inactive state so that errors such as collisions, race conditions, and changes in UE context during transmission do not occur. However, it goes without saying that the present disclosure is not limited to the above examples, and the embodiments of the present disclosure may be applied to only one of the two states depending on the network settings and operator preferences.

[0070] FIG. 4 is a diagram illustrating a method for processing without conflict while maintaining a service when an SMF change is required during service provision according to an embodiment of the present disclosure.

[0071] In step 401, SMF #1 430 indicates the SMF (old SMF) that provided the service to the terminal (UE) 410. In step 401, a condition for forwarding the service to the terminal 410 to another SMF may be satisfied in SMF #1 430. The SMF change operation may be initiated by a command from an operator or a request from an OAM (operation and management) system. In this case, the command or request to change the SMF may include designation of a specific terminal (or subscriber), a specific session, or a specific DNN / APN / slice, and may also include designation of a target SMF (SMF #2 440 in this embodiment) that will take over the service from the SMF.

[0072] When transferring a service for a specific terminal (or subscriber) to another SMF, SMF #1 430 waits for a state in which no traffic transmission or transaction occurs for the terminal to prevent errors such as the above-mentioned collision or race condition from occurring. If SMF #1 430 knows that the PDU (protocol data unit) session for the terminal 410 is idle or inactive, it can proceed directly to step 406.

[0073] In step 402, the SMF #1 430 can transmit a subscription to the AMF 420 to receive an alarm when the state of the terminal 410 changes to idle or inactive, in order to know that the PDU session of the terminal 410 has become idle or inactive. The subscription message includes, but is not limited to, the identifier of the target terminal (subscriber) and the identifier of the target PDU session.

[0074] In step 403, the AMF 420 may monitor the terminal 410 for state changes.

[0075] In step 404, the AMF 420 can perform step 405 if the state of the PDU session of the terminal 410 requested by the SMF #1 430 in step 402 is satisfied (e.g., idle or inactive).

[0076] In step 405, the AMF 420 may notify the SMF #1 430 that the state of the PDU session of the terminal 410 has changed.

[0077] In step 406, SMF #1 430 determines that the state of the terminal 410 is suitable for performing an operation to transfer the SMF, and can perform an operation to transmit the context related to a specific PDU session to the target SMF.

[0078] According to an embodiment of the present disclosure, SMF #1 430 can request the Nsmf_PDUSession_ContextPush service from SMF #2 440. The Nsmf_PDUSession_ContextPush service request can include a UE context related to the PDU session. In addition to the transmission related to the context, the Nsmf_PDUSession_ContextPush service request can also include an explicit request (SMF reallocation / change indication) indicating that the SMF related to the PDU session should be changed afterwards and that the terminal 410 should continue to be provided with services related to the PDU session.

[0079] In step 407, SMF #2 440 determines whether the request can be processed based on the received context. If it is determined that the SMF can be modified, it searches for UPF(PGW-U) 450 using the PGW-U tunnel information included in the received context and performs a process to change the N4 path to the modified SMF. In this case, SMF #2 440 can update the SMF information using an N4 session modification procedure. Although not shown in the drawing, SMF #2 440 can alternatively perform a process of releasing and then establishing an N4 session.

[0080] In step 408, SMF #2 440 may receive a response from UPF 450.

[0081] In step 409-1, SMF #2 440 can notify SMF #1 430 of the result of the request. If the request fails, SMF #2 440 can additionally include the cause of the failure when notifying SMF #1 430 of the result of the request, and each failure reason can also be replaced with a pre-agreed number. Cause #1: Insufficient resources, if SMF #2 lacks resources Cause #2: Failure in N4 session, failure to change / create session with UPF Cause #3: Authentication, SMF #1 request cannot be honored Cause #4: Semantic error. An error occurs while processing the received context. If the process fails, the entire procedure ends. If the request is successful, in step 409-2, SMF #2 440 may perform an operation to change the SMF to send and receive SM messages and process with AMF 420. To find AMF 420, SMF #2 440 may use AMF information (e.g., AMF identifier) ​​in the received UE context to request an update for N2, and the update request may include the target terminal (subscriber), PDU session ID, and SMF identifier / address.

[0082] In step 410, the AMF 420 transmits a response to the process for updating the SMF information to the SMF #2 440.

[0083] In step 411, SMF #2 440 performs any remaining procedures that must be processed due to the changes to the SMF, which may include registering with the UDM, establishing a PCF and PCC session, etc. It goes without saying that the above examples are not limiting.

[0084] FIG. 5 is a diagram illustrating a method for processing without collision while maintaining service when an SMF change is required during service according to one embodiment of the present disclosure.

[0085] In step 501, SMF #1 430 indicates the SMF (old SMF) that provided the service to the terminal (UE) 410. In step 501, the SMF #1 430 may satisfy the conditions for forwarding the service to the terminal 410 to another SMF. The SMF change operation is initiated by a command from an operator or a request from an OAM (operation and management) system. In this case, the command or request to change the SMF may include designation of a specific terminal (or subscriber), a specific session, or a specific DNN / APN / slice, and may also include designation of a target SMF (SMF #2 440 in this embodiment) that will take over the service from the SMF.

[0086] When SMF #1 430 transfers services for a specific terminal (or subscriber) to another SMF, it waits for a state in which no traffic transmissions or transactions are occurring for the terminal to prevent errors such as the aforementioned collisions or race conditions from occurring.

[0087] In step 502, if the PDU session of the terminal 410 becomes idle or inactive, the SMF #1 430 can transmit a notification notifying the status change of the PDU session related to the terminal to request the AMF 420 to perform an operation to change the SMF. Before performing step 502, the AMF 420 performs a subscription procedure to the SMF #1 430 to receive notification when the status of a specific PDU session changes.

[0088] When notifying of a change in the status of a PDU session, if SMF #1 430 can distinguish the target context using a separate identifier, it can transmit the notification notifying of the change in the status of the PDU session including the context ID, type, and ID of the SMF to be changed, and if the context ID cannot be identified, it can transmit the ID of the target UE (subscriber), the PDU session ID, the context type, and the ID of the SMF to be changed.

[0089] In step 503, the AMF 420 can monitor the terminal for state changes.

[0090] In step 504, the AMF 420 can perform step 505 if the state of the PDU session of the terminal 410 requested by the SMF #1 430 in step 502 is satisfied (e.g., idle or inactive).

[0091] In step 505, the AMF 420 notifies the SMF #1 430 that the state of the PDU session of the terminal 410 has changed to be suitable for performing an operation to transfer the SMF, and therefore the AMF 420 can perform an operation to change the SMF. The AMF 420 can receive the context related to the PDU session using the ID of the SMF #2 440 received in step 502 and transmit a request to provide a service to the SMF #2 440. The message that the AMF 420 requests the SMF #2 440 may include the ID of the SMF (SMF #1 430) that provided the service to the terminal 410, the ID and type of the target context, or the ID of the target terminal, the ID of the PDU session, and the type of the context.

[0092] In step 506, SMF #2 440 may receive the context from SMF #1 430 and transmit a context request to provide the service.

[0093] According to an embodiment of the present disclosure, SMF #2 440, acting as a consumer, can request a context transmission using the Nsmf_PDUSession_ContextRequest service. For example, if a context ID is received, SMF #2 440 can request a context transmission from SMF #1 430 using the context ID and context type. Otherwise, SMF #2 440 can request a context transmission using the ID of the target terminal (subscriber), the PDU session ID, and the context type.

[0094] If SMF #2 440 is unable to continue providing the service, SMF #2 440 can reject the request. When SMF #2 440 rejects the request, it can transmit a failure reason, and each failure reason can be replaced by a pre-promised number. Cause #1: Insufficient resources, if SMF #2 lacks resources Cause #2: Failure in N4 session, unable to change / create session with UPF Cause #3: Authenticated, unable to accept SMF #1 request Cause #4: Semantic error, when an error occurs while processing the context If the process fails, the entire procedure ends.

[0095] In step 507, SMF #1 430 determines whether it can process the context transmission request, and if so, performs a process to release the N4 session. Although not shown in the drawing, this process may also be replaced by a process to change the N4 session with the UPF from SMF #1 430 to SMF #2 440.

[0096] In step 508, SMF #1 430 can respond by placing the context requested by SMF #2 440 in a container in step 506. If the request fails, SMF #1 430 can additionally transmit the cause of the failure when responding, and each failure reason can also be replaced with a pre-agreed number. Cause #2: Failure in N4, failure to modify / create a session with UPF Cause #3: Inability to accept SMF #2 request, which is authenticated Cause #4: Semantic error. An error occurs while processing the received context. If the process fails, the entire procedure ends.

[0097] If the N4 release procedure is applied in step 507 and step 508 is successful, SMF #2 440 can perform a procedure to create an N4 session (between the SMF and the UPF) with UPF 450 in step 509. In this case, SMF #2 440 can use the PGW-U tunnel information in the received context to know which UPF and N4 session should be created with, and if the UPF needs to be changed in the N4 configuration, can perform a UPF selection procedure.

[0098] In step 510, SMF #2 440 may transmit a response at the request of AMF 420 that the SMF has been changed.

[0099] In step 511, SMF #2 440 performs the remaining procedures that must be processed due to the changes to the SMF, which may include registering with the UDM, establishing a PCF and PCC session, etc. It goes without saying that the above examples are not limiting.

[0100] On the other hand, if several NFs (or NF instances) belong to an NF set and the state of the NF changes dynamically, it would be more effective to select the target NF according to the situation at the time the context actually moves, rather than specifying the old NF (SMF #1 430) as the target NF.

[0101] FIG. 6 is a diagram illustrating a method for selecting an NF in consideration of network conditions according to an embodiment of the present disclosure.

[0102] In yet another embodiment of the present invention, when an NF change is required, rather than selecting and specifying the target NF at the time of the request, a method is proposed in which an NF is selected taking into account the network conditions at the time when actual context transmission is possible.

[0103] In step 601, SMF #1 430 indicates the SMF (old SMF) that originally provided services to the terminal (UE) 410. In step 601, conditions for forwarding services for the terminal 410 from SMF #1 430 to another SMF may be satisfied. The SMF change operation is initiated by a command from an operator or a request from an OAM (operation and management) system. In this case, the command or request to change the SMF may include designation of a specific terminal (or subscriber), a specific session, or a specific DNN / APN / slice, or the target SMF to be changed (target SMF) may not be specified and may be dynamically selected in the same SMF set as the current SMF.

[0104] In step 602, when SMF #1 430 transfers the service for the terminal 410 (or subscriber) to another SMF, it waits for a state in which no traffic transmission or transaction for the terminal occurs to prevent errors such as the above-mentioned collision or race condition from occurring. If the PDU session of the terminal 410 becomes idle or inactive, SMF #1 430 can transmit a notification notifying the status change of the PDU session related to the terminal to request the AMF 420 to perform an operation to change the SMF. Before performing step 602, the AMF 420 performs a subscription procedure to the SMF #1 430 to receive notification when the status of a specific PDU session changes.

[0105] When notifying a change in the status of a PDU session, if SMF #1 430 can distinguish the target context by a separate identifier, it can transmit the notification notifying the change in the status of the PDU session including the context ID and type, and a set ID including the SMF to be changed, and if the context ID cannot be identified, it can transmit the notification including the ID of the target UE (subscriber), the PDU session ID, the context type, and a set ID including the SMF to be changed.

[0106] In step 603, the AMF 420 may monitor the terminal for state changes.

[0107] In step 604, the AMF 420 can perform step 605-1 or step 605-2 if the state of the PDU session of the terminal requested by the SMF #1 430 in step 602 is satisfied (e.g., idle or inactive).

[0108] In step 605-1, the AMF 420 performs an operation to change the SMF since the UE PDU session state has been established with SMF #1 430. The AMF 420 can select the target SMF, SMF #2 440, using the set ID of the SMF received in step 602. If the set includes information for selecting an SMF (capacity, current load status, and operator preference of each SMF), the AMF 420 can select the target SMF using the information for selecting an SMF.

[0109] Otherwise, in step 605-2, the AMF 420 may perform a discovery and selection process to select an SMF with the NRF or SCP 660. In this case, the AMF 420 may use the set ID of the SMF received in step 602 to transmit a message including information indicating that this is a selection process for an SMF change. If one SMF is pre-configured for the SMF change operation, this SMF may be explicitly selected. The selected SMF is then referred to as SMF #2 440. In step 606, the AMF 420 may receive the context related to the PDU session using the ID of the SMF selected in step 602 and transmit a request to provide the service to the SMF #2 440. The message that the AMF 420 requests the SMF #2 440 may include the ID of the SMF (SMF #1 430) that provided the service to the terminal 410, the ID and type of the target context, or the ID of the target terminal 410, the ID of the PDU session, and the type of the context.

[0110] In step 607, SMF #2 440 may receive a context from SMF #1 430 and transmit a context request to provide a service.

[0111] According to an embodiment of the present disclosure, SMF #2 440, acting as a consumer, can request a context transmission using the Nsmf_PDUSession_ContextRequest service. For example, if a context ID is received, SMF #2 440 can request a context transmission from SMF #1 430 using the context ID and context type. Otherwise, SMF #2 440 can request a context transmission using the ID of the target terminal (subscriber), the PDU session ID, and the context type.

[0112] If SMF #2 440 is unable to continue providing the service, SMF #2 440 can reject the request. When SMF #2 440 rejects the request, it can transmit a failure reason, and each failure reason can be replaced by a pre-promised number. Cause #1: Insufficient resources, if SMF #2 lacks resources Cause #2: Failure in N4 session, unable to change / create session with UPF Cause #3: Authenticated, unable to accept SMF #1 request Cause #4: Semantic error, when an error occurs while processing the context If the process fails, the entire procedure ends.

[0113] In step 608, SMF #1 430 determines whether it can process the context transmission request, and if so, performs a process to release the N4 session. Although not shown in the drawing, this process may also be replaced by a process to change the N4 session with the UPF from SMF #1 430 to SMF #2 440.

[0114] In step 609, SMF #1 430 can respond by placing the context requested by SMF #2 440 in a container in step 606. If the request fails, SMF #1 430 can additionally transmit the cause of the failure, and each failure cause can also be replaced by a pre-agreed number. Cause #2: Failure in N4 session, failure to change / create session with UPF Cause #3: Inability to accept SMF #2 request, which is authenticated Cause #4: Semantic error. An error occurs while processing the received context. If the process fails, the entire procedure ends.

[0115] If the N4 release procedure is applied in step 608 and step 609 is successful, SMF #2 440 can perform a procedure to create an N4 session (between the SMF and the UPF) with UPF 450 in step 610. In this case, SMF #2 440 can use the PGW-U tunnel information in the received context to know which UPF and N4 session should be created with, and if the UPF needs to be changed in the N4 configuration, can perform a UPF selection procedure.

[0116] In step 611, SMF #2 440 may transmit a response at the request of AMF 420 that the SMF has been changed.

[0117] In step 612, SMF #2 440 performs any remaining procedures that must be processed due to the changes to the SMF, which may include registering with the UDM, establishing a PCF and PCC session, etc. It goes without saying that the above examples are not limiting.

[0118] In the above embodiment, with reference to Figure 5, the AMF 420 directly requests the target SMF #2 440 to create a context. However, the NF selection performed when the state of the terminal (subscriber) changes can also be applied to the embodiment of Figure 4. In this case, the SMF (SMF #1) can select the target SMF (SMF #2). When the SMF (SMF #1) selects the target SMF (SMF #2), the above-mentioned step 607 is also changed as follows, but the other steps remain the same.

[0119] In step 607, SMF #1 430 determines that the terminal status is suitable for performing an operation to transfer the SMF and can perform an operation to select the target SMF. If SMF #1 430 has information for selecting an SMF for the set (capacity, current load status, and operator preference of each SMF), SMF #1 430 can select the target SMF using the information for selecting an SMF.

[0120] Otherwise, SMF #1 430 may perform a discovery and selection process to select an SMF with the NRF or SCP 660. In this case, AMF 420 may use the set ID of the SMF received in step 602 to transmit a message including information indicating that this is a selection process for an SMF change. If one SMF is pre-configured for the SMF change operation, that SMF may be explicitly selected. The selected SMF is then referred to as SMF #2 440.

[0121] In the above-described embodiment relating to the operation of changing an NF, in order to prevent collisions or race conditions related to transactions / procedures, context exchange is performed between NFs after a terminal session becomes idle or inactive. However, when applied to many terminals (subscribers), if the connection state is maintained for a long time due to a traffic transmission pattern, it takes a long time for an NF to transfer a terminal (subscriber) it is serving to another NF. Therefore, a method of changing an NF while shortening the time for changing a terminal to an idle or inactive state will be described below with reference to FIG. 7.

[0122] FIG. 7 is a diagram illustrating a method for shortening the time it takes for a terminal (subscriber) state to be changed to idle or deactivated and for more quickly moving the context of an NF, taking into account the service type and operator settings, according to one embodiment of the present disclosure.

[0123] In step 701, SMF #1 430 indicates the SMF (old SMF) that provided the service to the terminal (UE) 410. In step 701, a condition for forwarding the service for the terminal 410 from SMF #1 430 to another SMF may be satisfied. The SMF change operation may be initiated by a command from an operator or by a request from an OAM (operation and management) system. In this case, the command or request for changing the SMF may include designation of a specific terminal (or subscriber), a specific session, or a specific DNN / APN / slice. In addition, the waiting time for a terminal (subscriber) session to be changed to idle or inactive may be explicitly specified depending on the service type or operator settings.

[0124] In step 702, when transferring a service for the terminal 410 (or subscriber) to another SMF, the SMF #1 430 waits for a state in which no traffic transmission or transaction for the terminal occurs to prevent errors such as the above-mentioned collision or race condition from occurring. If the PDU session of the terminal becomes idle or inactive, the SMF #1 430 can transmit a notification notifying the status change of the PDU session related to the terminal to request the AMF 420 to perform an operation to change the SMF. Before performing step 702, the AMF 420 performs a subscription procedure to the SMF #1 430 to receive notification when the status of a specific PDU session changes.

[0125] When notifying a PDU session state change, if the target context can be distinguished by a separate identifier, the SMF #1 430 may transmit the notification of the PDU session state change including the context ID and type, and the SMF ID or SMF set ID to be changed, or if the context ID cannot be identified, the notification of the PDU session state change may include the target UE (subscriber) ID, PDU session ID, context type, and the SMF ID or SMF set ID to be changed. In addition, the notification of the PDU session state change may include the expected activity period for the UE (subscriber) session to be changed to idle or inactive.

[0126] That is, the waiting time until a terminal (subscriber) session is changed to idle or inactive is also a parameter that transitions the terminal to an idle or inactive state if no traffic (user data) or signaling is sent or received from the terminal for a predetermined time. SMF #1 430 sets the waiting time until a terminal (subscriber) session is changed to idle or inactive for a terminal (subscriber) to which an SMF change must be applied to be shorter (e.g., 1 second) than the time used to transition a terminal to an idle state in general cases, so that the terminal (subscriber) can be transitioned to an idle or inactive state as quickly as possible.

[0127] In step 703, the AMF 420 updates the waiting time until a terminal (subscriber) session related to the terminal is changed to idle or inactivated using the received information, and in step 704, the AMF 420 can transmit the waiting time until a terminal (subscriber) session related to the terminal is changed to idle or inactivated to the base station (RAN) 760 via an NG-AP message. Specifically, the AMF 420 can insert the waiting time until a terminal (subscriber) session is changed to idle or inactivated into the UE activity operation expected in the core network assistance information in a UE context modification request message and transmit it to the base station 760.

[0128] In step 705, the base station 760 stores the received core network assistance information, transmits a response thereto to the AMF 420, and can adjust the connection status for the terminal 410 using the time it waits until the terminal (subscriber) session is changed to idle or inactive.

[0129] In step 706, the AMF 420 can perform step 707 if the state of the PDU session of the terminal 410 requested by the SMF #1 430 in step 702 is satisfied (e.g., idle or inactive).

[0130] In step 707, the AMF 420 can perform an operation to change the SMF because the state of the UE's PDU session has changed to be suitable for performing an operation to transfer the SMF to the SMF #1 430. The AMF 420 can select the target SMF using the set ID of the SMF received in step 702.

[0131] If there is information for selecting an SMF for the set (each SMF's capacity, current load status, and operator preference), the AMF 420 selects the target SMF using the information for selecting an SMF. Otherwise, the AMF 420 can perform a discovery and selection process to select an SMF with the NRF or SCP. In this case, the AMF 420 can transmit a message including information indicating that this is a selection process for an SMF change using the set ID of the SMF received in step 602. If one SMF is pre-configured for the SMF change operation, that SMF can be explicitly selected. Thereafter, the selected SMF is referred to as SMF #2 440.

[0132] The AMF 420 can receive the context related to the PDU session using the ID of the SMF selected in step 702 and transmit a request to provide the service to the SMF #2 440. In this case, the message that the AMF 420 requests the SMF #2 440 may include the ID of the SMF (SMF #1) that provided the service to the terminal 410, the ID and type of the target context, or the ID of the target terminal, the ID of the PDU session, and the type of the context.

[0133] In step 708, SMF #2 440 may receive the context from SMF #1 430 and transmit a context request to provide the service.

[0134] According to an embodiment of the present disclosure, SMF #2 440, acting as a consumer, can request a context transmission using the Nsmf_PDUSession_ContextRequest service. For example, if a context ID is received, SMF #2 440 can request a context transmission from SMF #1 430 using the context ID and context type. Otherwise, SMF #2 440 can request a context transmission using the ID of the target terminal (subscriber), the PDU session ID, and the context type.

[0135] If SMF #2 440 is unable to continue providing the service, SMF #2 440 can reject the request. When SMF #2 440 rejects the request, it may include a cause of failure, and each cause of failure is also replaced by a pre-promised number. Cause #1: Insufficient resources, if SMF #2 lacks resources Cause #2: Failure in N4 session, UPF and session modification / creation not possible Cause #3: Authenticated, unable to accept SMF #1 request Cause #4: Semantic error, when an error occurs while processing the context If the process fails, the entire procedure ends.

[0136] In step 709-1, SMF #1 430 determines whether it can process the context transmission request, and if so, performs a process to release the N4 session. Although not shown in the drawing, this process may also be replaced by a process to change the N4 session with the UPF from SMF #1 430 to SMF #2 440.

[0137] In step 710, SMF #1 responds by placing the context requested by SMF #2 440 in a container in step 706. If the request fails, SMF #1 430 can send a response that includes an additional cause of failure, and each failure cause is also replaced by a pre-agreed number. Cause #2: Failure in N4 session, UPF and session change / creation failure Cause #3: Inability to accept SMF #2 request, which is authenticated Cause #4: Semantic error. An error occurs while processing the received context. If the process fails, the entire procedure ends.

[0138] If the N4 release procedure is applied in step 709-1 and step 708 is successful, SMF #2 440 can perform a procedure to create an N4 session (between the SMF and the UPF) with the UPF in step 709-2. In this case, SMF #2 440 can use the PGW-U tunnel information in the received context to determine which UPF and N4 session should be created with, and if the UPF needs to be changed in the N4 configuration, can perform a UPF selection procedure. In step 711, SMF #2 440 may transmit a response at the request of AMF 420 that the SMF has been changed.

[0139] In step 712, SMF #2 440 performs any remaining procedures that must be processed due to the changes to the SMF, which may include registering with the UDM, establishing a PCF and PCC session, etc. It goes without saying that the above examples are not limiting.

[0140] The embodiment of FIG. 7 may also be modified to an embodiment in which a terminal state change is explicitly triggered to perform an SMF change if the terminal does not enter an idle state or an inactive state for a specific time. A method for changing the NF via a method for explicitly triggering a terminal state change will be described in more detail below with reference to FIG. 8.

[0141] FIG. 8 is a diagram illustrating a method for triggering a state change of a terminal and changing an NF according to one embodiment of the present disclosure.

[0142] In step 801, SMF #1 430 indicates the SMF (old SMF) that provided the service to the terminal (UE) 410. In step 801, a condition for forwarding the service for the terminal 410 from SMF #1 430 to another SMF may be satisfied. The SMF change operation may be initiated by a command from an operator or by a request from an OAM (operation and management) system. In this case, the command or request for changing the SMF may include designation of a specific terminal (or subscriber), a specific session, or a specific DNN / APN / slice. In addition, the waiting time for a terminal (subscriber) session to be changed to idle or inactive may be explicitly specified depending on the service type or operator settings.

[0143] In step 802, when transferring a service for the terminal 410 (or subscriber) to another SMF, the SMF #1 430 waits for a state in which no traffic transmission or transaction for the terminal occurs to prevent errors such as the above-mentioned collision or race condition from occurring. If the PDU session of the terminal becomes idle or inactive, the SMF #1 430 can transmit a notification notifying the status change of the PDU session related to the terminal to request the AMF 420 to perform an operation to change the SMF. Before performing step 802, the AMF 420 performs a subscription procedure to the SMF #1 430 to receive notification when the status of a specific PDU session changes.

[0144] When notifying a PDU session state change, if the target context can be distinguished by a separate identifier, the SMF #1 430 may transmit the notification of the PDU session state change including the context ID and type, and the SMF ID or SMF set ID to be changed, or if the context ID cannot be identified, the notification of the PDU session state change may include the target UE (subscriber) ID, PDU session ID, context type, and the SMF ID or SMF set ID to be changed. In addition, the notification of the PDU session state change may include the maximum waiting time that the UE (subscriber) session can wait until it is changed to idle or inactive.

[0145] In step 803, the AMF 420 runs a timer based on the received information, and if the terminal does not enter an idle or inactive state within that time, it transmits a UE context release request to the base station 760 to change the terminal to an idle state.

[0146] In steps 804 to 806, the base station 760 may perform an operation to change the terminal to an idle state at the request of the AMF 420.

[0147] Steps 807 to 813 correspond to those described above, and therefore detailed description thereof will be omitted.

[0148] Furthermore, according to one embodiment of the present disclosure, when an inactive (more specifically, RRC inactive) state is applied to the terminal 410, traffic is transmitted between the terminal 410 and the base station 760, but the core network (such as the AMF 420, the SMF 430, or 430) cannot know such a state. In this situation, if an SMF change is triggered, it may affect the quality of service. Therefore, the RRC inactive state may be configured not to be applied to a terminal (subscriber) for which an SMF change is required.

[0149] That is, if an RRC deactivation state is applicable to the terminal 410 and RRC deactivation assistance information has already been delivered to the base station (NG-RAN) 760, the AMF 420 can delete the RRC deactivation assistance information through a UE context modification procedure. If RRC deactivation assistance information has not yet been delivered to the base station 760 (NG-RAN) for the terminal 410, the AMF 420 should not include the RRC deactivation assistance information in the UE context that it subsequently transmits to the base station 760 for the terminal 410.

[0150] Furthermore, according to one embodiment of the present disclosure, as described above, NFs including SMFs can exchange context with each other to provide services. Such a structure can be used to continue providing services to UEs that have already received services when a specific NF fails or is removed due to capacity reduction, or when the configuration of a specific NF needs to be changed or updated. As in the above embodiment, the selection of an NF to take over the services provided by a specific NF can be specified by OAM or by taking into account dynamic network conditions. However, the selection can also be specified in advance to back up a specific NF using a network redundancy method. Such a method has the advantage of reducing the time required to create a new NF to take over the service or to search for an NF, especially in an emergency situation such as a failure.

[0151] According to one embodiment of the present disclosure, NFs used for backup purposes can be freely configured, such as by designating one or more NFs within a specific NF set as backup purposes, or by designating one NF to serve as a backup for each NF.

[0152] FIG. 9 is a diagram illustrating a method for exchanging information related to an NF that serves as a backup for an NF according to one embodiment of the present disclosure.

[0153] In step 901, NF#1 910 receives or sets information related to NFs that will serve as its backups. The list of NFs that will serve as backups may include identifiers of NFs used in the backups, and the list may be divided into backups for failures, backups for planned removals, backups for operational matters, etc.

[0154] In step 902, NF #2 940 can register or update its information with the NRF or SCP 930. At that time, NF #2 940 can transmit its NF profile. The NF profile includes a list of NFs that operate as backups, and the list of NFs that operate as backups can include identifiers of NFs used as backups. The list can also be divided into different categories, such as backups for failures, backups for planned removals, and backups for work items.

[0155] In step 903, the NRF / SCP 930 stores the received NF profile, which may include a list of NFs that operate as backups. The list includes identifiers of NFs used as backups, and the list is also set up by purpose, i.e., backup for failure, backup for planned removal, backup for work items, etc.

[0156] In step 904, if another NF (referred to as NF#2 940) uses the services provided by NF#1 920 or transmits a request (NF discovery) to the NRF or SCP 930 to receive information about NF#1 920.

[0157] In step 905, the NRF or SCP 930 may transmit an NF profile while responding to the NF discovery in step 904. The NF profile may include a list of NFs that act as backups, where the list includes identifiers of NFs used as backups, and the list may also be configured by use, i.e., backup for failures, backup for planned removal, backup for work items, etc.

[0158] In step 906, NF#2 940 can store the received NF profile. If a service is provided in conjunction with NF#1 920, but a NF (referred to as NF#3) must be selected to replace NF#1 920 due to a failure or other reason, NF#2 940 can provide the service using an NF belonging to the backup list of NF#1 920.

[0159] NF#2 940 may find out that NF#1 920 is no longer providing service and that a change to another NF is necessary by directly informing NF#2 940 that NF#1 920 is no longer providing service (NF status change notification), or NF#1 920 may inform NRF / SCP 930 of the status change, and NRF / SCP 930 may then inform NF#2 940 of the status regarding NF#1 920, thereby finding out that NF#1 920 is no longer providing service and that a change to another NF is necessary.

[0160] Also, if NF#2 940 requests a specific service or sends a message to NF#1 920 but does not receive a response, NF#1 920 can understand that it will no longer provide the service and that a change to another NF is necessary. Meanwhile, in the above embodiment, the method by which NF#1 920 notifies other NFs of its backup NF information has been described as transmitting the information via the NRF / SCP 930, but it can also be transmitted directly during message exchange between NFs. That is, if NF#1 920 cooperates with other NFs to provide a specific service (when establishing registration or association, or transmitting NF status), NF#1 920 can directly transmit its backup NF information (the same information as described in the above embodiment of FIG. 9) to the other NFs. The receiving NFs use this information in the same way as in the above embodiment.

[0161] 10 is a diagram showing the configuration of a network entity according to the present invention. The network entity according to the present invention is a concept including NFs (Network Functions) depending on the system implementation.

[0162] As shown in FIG. 10, the network entity of the present disclosure may include a transceiver 1000, a memory 1010, and a processor 1020. The processor 1020, the transceiver 1000, and the memory 1010 of the network entity may operate according to the above-described network entity communication method. However, the components of the network entity are not limited to the above-described examples. For example, the network entity may include more or fewer components than those described above. Furthermore, the processor 1020, the transceiver 1000, and the memory 1010 may be embodied in the form of a single chip. Furthermore, the processor 1020 may include at least one processor.

[0163] The transceiver unit 1000 collectively refers to the receiver unit of the network entity and the transmitter unit of the network entity, and can transmit and receive signals to and from a base station. The signals transmitted and received to and from the base station may include control information and data. To this end, the transceiver unit 1000 also includes an RF (radio frequency) transmitter that up-converts and amplifies the frequency of a transmitted signal, and an RF receiver that low-noise amplifies and down-converts the frequency of a received signal. However, this is only one embodiment of the transceiver unit 1000, and the components of the transceiver unit 1000 are not limited to the RF transmitter and RF receiver. The transceiver unit 1000 can also transmit and receive signals to and from other network entities. Furthermore, the transceiver 1000 can receive signals via a wireless channel, output the signals to the processor 1020, and transmit the signals output from the processor 10200 via a wireless channel.

[0164] The memory 1010 can store programs and data necessary for the operation of the network entity. The memory 1010 can also store control information or data included in signals acquired by the network entity. The memory 1010 can be configured by a ROM, a RAM, a hard disk, a recording medium such as a CD-ROM (compact disc read only memory) or a DVD (digital versatile disc), or a combination of recording media.

[0165] The processor 1020 can control a series of processes so that the network entity operates according to the above-described embodiments of the present disclosure. For example, the processor 1020 can receive control signals and data signals via the transceiver unit 1000, process the received control signals and data signals, and transmit the processed control signals and data signals via the transceiver unit 1000.

[0166] The transceiver 1000, memory 1010, and processor 1020 may be electrically connected to each other. For example, the controller 910 may be a circuit, an application-specific circuit, or at least one processor. The operation of the network entity may be implemented by providing a memory device storing the program code in any component within the network entity. The network entity may be any one of a base station (RAN), AMF, SMF, UPF, NF, NEF, NRF, CF, NSSF, UDM, AF, AUSF, SCP, UDSF, context storage, OAM, EMS, configuration server, and ID management server, but needless to say, the network entity is not limited to the above examples.

[0167] FIG. 11 is a diagram showing the configuration of a terminal (UE) according to the present invention.

[0168] As shown in FIG. 11, the terminal of the present disclosure may include a transceiver 1100, a memory 1110, and a processor 1120. The processor 1120, transceiver 1100, and memory 1110 of the terminal may operate according to the terminal communication method described above. However, the components of the terminal are not limited to the above example. For example, the terminal may include more or fewer components than those described above. Furthermore, the processor 1120, transceiver 1100, and memory 1110 may be embodied in the form of a single chip. Furthermore, the processor 1120 may include at least one processor.

[0169] The transceiver 1100 collectively refers to the receiver and transmitter of the terminal, and can transmit and receive signals to and from a base station. The signals transmitted and received to and from the base station may include control information and data. To this end, the transceiver 1100 also includes an RF transmitter that up-converts and amplifies the frequency of a transmitted signal, and an RF receiver that low-noise amplifies and down-converts the frequency of a received signal. However, this is merely one embodiment of the transceiver 1100, and the components of the transceiver 1100 are not limited to the RF transmitter and RF receiver.

[0170] Furthermore, the transceiver 1100 can receive a signal via a wireless channel, output the signal to the processor 1120, and transmit the signal output from the processor 1120 via a wireless channel.

[0171] The memory 1110 may store programs and data necessary for the operation of the terminal. The memory 1110 may also store control information or data included in signals acquired by the terminal. The memory 1110 may be configured as a recording medium such as a ROM, a RAM, a hard disk, a CD-ROM, or a DVD, or a combination of recording media. The processor 1120 may control a series of processes so that the terminal operates according to the above-described embodiment of the present disclosure. For example, the processor 1120 may receive control signals and data signals via the transceiver 1100, process the received control signals and data signals, and transmit the processed control signals and data signals via the transceiver 1100.

[0172] It should be noted that the configuration diagrams, control / data signal transmission method diagrams, and operation procedure diagrams illustrated in the above-mentioned Figures 1 to 11 are not intended to limit the scope of the present disclosure. In other words, all components, entities, or operation steps illustrated in Figures 1 to 11 should not be construed as essential components for implementing the disclosure, and the disclosure may be embodied by including only some components within a scope that does not detract from the essence of the disclosure.

[0173] The methods according to the claims of the present disclosure or the embodiments described in the specification may be implemented in hardware, software, or a combination of hardware and software.

[0174] In the case of a software implementation, a computer-readable recording medium or computer program product may be provided that stores one or more programs (software modules). The one or more programs stored on the computer-readable recording medium or computer program product may be configured for execution by one or more processors in an electronic device. The one or more programs include instructions that cause the electronic device to perform a method according to the embodiments described in the claims or specification of the present disclosure.

[0175] Such programs (software modules, software) may be stored in RAM, non-volatile memory including flash memory, ROM, electrically erasable programmable read-only memory (EEPROM), magnetic disk storage device, CD-ROM, DVD, other forms of optical storage device, or magnetic cassette, or in memory configured as a combination of some or all of these. Also, each type of memory may be included in multiple instances.

[0176] The program may also be stored in an attachable storage device accessible via a communication network such as the Internet, an intranet, a local area network (LAN), a wide local area network (WLAN), or a storage area network (SAN), or a combination thereof. Such a storage device may be connected to a device that performs an embodiment of the present disclosure via an external port. Alternatively, a separate storage device on the communication network may be connected to a device that performs an embodiment of the present disclosure.

[0177] In the specific embodiments of the present disclosure described above, the components included in the present disclosure are expressed in the singular or plural form according to the specific embodiments presented. However, the expressions in the singular or plural form are selected to suit the presented circumstances for the convenience of explanation, and the present disclosure is not limited to the singular or plural components, and even if a component is expressed in the plural, it may be composed of the singular, or even if a component is expressed in the singular, it may be composed of the plural.

[0178] Meanwhile, the embodiments disclosed in this specification and drawings are presented as specific examples to facilitate the description of the present disclosure and to aid in the understanding of the present disclosure, and are not intended to limit the scope of the present disclosure. In other words, it is obvious to those skilled in the art that other modifications based on the technical concept of the present disclosure are possible. Furthermore, the respective embodiments can be combined with each other as necessary. For example, parts of one embodiment different from one embodiment of the present disclosure can be combined with each other. Furthermore, one embodiment may be implemented in other systems, such as an LTE system, a 5G system, or an NR system, with other modifications based on the technical concept of the above-described embodiment. [Explanation of symbols]

[0179] 200 NF set 301 SMF #1 302 SMF #2 303 UPF 304 UE 1000 Transmitter / Receiver 1010 memory 1020 processor

Claims

1. A method performed by a first SMF (session management function), Identifying a triggering of an SMF change operation; performing a subscription procedure related to an event in which the state of the terminal becomes idle or inactive with an access and mobility management function (AMF); receiving a notification message from the AMF reporting the event when the state of the terminal becomes the idle or the deactivated state; transmitting a message indicating a change in a state of a protocol data unit (PDU) session to the AMF to request an SMF change procedure, the message indicating the change in the state of the PDU session including a context identification (ID); transmitting a push service context request to a second SMF based on the triggering of the SMF modification operation; receiving a PUSH service context response indicating a result of the SMF modification operation from the second SMF in response to the PUSH service context request.

2. The method of claim 1, wherein the PUSH service context request indicates whether the SMF modification operation is successful or unsuccessful.

3. The method of claim 1 , wherein the second SMF is registered with a unified data management (UDM).

4. The SMF change operation is triggered in response to a request by OAM (Operations, Administration and Maintenance), The method of claim 1 , wherein the request by the OAM includes identifier information of the second SMF.

5. A method performed by a second SMF (session management function), receiving a push service context request from the first SMF when an SMF modification operation is triggered in the first SMF; transmitting a PUSH service context response indicating a result of the SMF modification operation to the first SMF in response to the PUSH service context request; The service context request performs a subscription procedure with an access and mobility management function (AMF) related to an event in which the state of the terminal, which is the first SMF, becomes idle or inactive, and when the state of the terminal becomes idle or inactive, receives a notification message reporting the event from the AMF and transmits a message instructing a state change of a protocol data unit (PDU) session to the AMF to request an SMF change procedure, wherein the message instructing the state change of the PDU session is received from the first SMF by including a context identification (ID).

6. The method of claim 5, wherein the PUSH service context request indicates whether the SMF modification operation is successful or unsuccessful.

7. The method of claim 5 , wherein the second SMF is registered with a unified data management (UDM).

8. In a first SMF (session management function), the first SMF comprises: A transmitter / receiver, at least one processor coupled to the transceiver, The at least one processor identifies triggering of an SMF change operation; The subscription procedure related to the event when the terminal state becomes idle or inactive is performed with the access and mobility management function (AMF), When the state of the terminal becomes the idle or the deactivated state, receiving a notification message from the AMF reporting the event; To request an SMF change procedure, a message indicating a change in the state of a protocol data unit (PDU) session is transmitted to the AMF, and the message indicating the change in the state of the PDU session includes a context ID (identification), Sending a push service context request to a second SMF based on the triggering of the SMF modification operation; The first SMF receives a PUSH service context response indicating the result of the SMF modification operation from the second SMF in response to the PUSH service context request.

9. In a second SMF (session management function), the second SMF comprises: A transmitter / receiver, at least one processor coupled to the transceiver, The at least one processor receives a push service context request from the first SMF when an SMF change operation is triggered in the first SMF; In response to the PUSH service context request, transmit a PUSH service context response to the first SMF indicating a result of the SMF modification operation; The service context request performs a subscription procedure with an access and mobility management function (AMF) related to an event in which the state of the terminal, which is the first SMF, becomes idle or inactive. When the state of the terminal becomes idle or inactive, the service context request receives a notification message reporting the event from the AMF and transmits a message instructing a state change of a protocol data unit (PDU) session to the AMF to request an SMF change procedure. The message instructing the state change of the PDU session is received from the first SMF by including a context identification (ID). 2nd SMF.

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