Method and apparatus for supporting network slice changes in a wireless communication system

Abstract

The present invention provides an apparatus and method for supporting higher data transmission rates for applications in 5G or 6G communication systems. [Solution] The method performed by an access mobility and management function (AMF) node in a mobile communication system of the present invention includes the steps of receiving a notification message including information about an unavailable slice from a slice availability check function (SACF) node, receiving information about a protocol data unit (PDU) session from a network data analysis function (NWDAF) node, determining a target slice and at least one PDU session that requires a slice change based on the notification message and the information about the PDU session, and transmitting a request message to a session management function (SMF) node to change the slice of the determined at least one PDU session to the target slice.

Description

[Technical field]

[0001] The present invention relates to a method and apparatus for supporting network slice changes in a wireless communication system, and more particularly, to a method and apparatus for determining a target slice in a wireless communication system and moving a PDU session belonging to a specific slice to the target slice. [Background technology]

[0002] 5G mobile communication technology defines a wide frequency band to enable high transmission speeds and new services, and can be implemented not only in the sub-6GHz band such as 3.5 gigahertz (3.5GHz), but also in the ultra-high frequency band known as mmWave (Above 6GHz) such as 28GHz and 39GHz. In addition, in the case of 6G mobile communication technology, known as the Beyond 5G system, implementation in the terahertz band (for example, 95GHz to 3THz band) is being considered to achieve transmission speeds 50 times faster than 5G mobile communication technology and ultra-low latency times that are reduced to one-tenth of those of 5G mobile communication technology.

[0003] In the early stage of 5G mobile communication technology, the service support and performance requirements for enhanced Mobile Broadband (eMBB), Ultra-Reliable Low-Latency Communications (URLLC), and Massive Machine-Type Communications (mMTC) are being addressed. To this end, the following technologies have been developed: Beamforming and Massive MIMO to mitigate the path loss of radio waves in the ultra-high frequency band and increase the transmission distance of radio waves; various numerology support (e.g., operation of multiple subcarrier intervals) and dynamic operation of slot formats for efficient use of ultra-high frequency resources; initial access technology to support multiple beam transmission and wideband; definition and operation of BWP (Band-Width Part); new channel coding methods such as LDPC (Low Density Parity Check) code for large-volume data transmission and Polar Code for reliable transmission of control information; L2 pre-processing (L2 Standardization has progressed in areas such as network pre-processing, and network slicing, which provides dedicated networks specialized for specific services.

[0004] Currently, discussions are underway to improve and enhance the performance of the initial 5G mobile communications technology in consideration of the services that 5G mobile communications technology was intended to support. Physical layer standardization is underway for technologies such as Vehicle-to-Everything (V2X), which assists autonomous vehicles in making driving decisions based on their own position and status information transmitted by the vehicle to increase user convenience, New Radio Unlicensed (NR-U), which aims to operate systems in unlicensed spectrum in accordance with various regulatory requirements, technology to reduce power consumption of NR terminals (UE Power Saving), Non-Terrestrial Network (NTN), which is direct communication between terminals and satellites to ensure coverage in areas where communication with terrestrial networks is not possible, and positioning.

[0005] In addition, standardization is underway in the areas of radio interface architecture / protocol for technologies such as the Industrial Internet of Things (IIoT) to support new services through collaboration and convergence with other industries, Integrated Access and Backhaul (IAB) to provide nodes for expanding network service areas by integrating wireless backhaul links and access links, mobility enhancement technologies including Conditional Handover and Dual Active Protocol Stack (DAPS) handover, and 2-step random access (2-step RACH for NR) to simplify random access procedures. Standardization is also underway in the areas of system architecture / service for 5G baseline architecture (e.g., Service based Architecture, Service based Interface) for combining Network Functions Virtualization (NFV) and Software-Defined Networking (SDN) technologies, and Mobile Edge Computing (MEC) to provide services based on the location of the terminal.

[0006] When such 5G mobile communication systems are commercialized, it is expected that the number of connected devices, which is increasing explosively, will be connected to the communication network, and it is expected that it will be necessary to enhance the functions and performance of the 5G mobile communication system and to integrate the operation of connected devices.To this end, new research will be conducted on improving 5G performance and reducing complexity by using extended reality (XR) to efficiently support augmented reality (AR), virtual reality (VR), mixed reality (MR), artificial intelligence (AI), and machine learning (ML), AI service support, metaverse service support, drone communication, etc.

[0007] In addition, the development of such 5G mobile communication systems will be the basis for the development of multiple antenna transmission technologies such as new waveforms to ensure coverage in the terahertz band of 6G mobile communication technology, full dimensional MIMO (FD-MIMO), array antennas, and large scale antennas, metamaterial-based lenses and antennas to improve the coverage of terahertz band signals, high-dimensional spatial multiplexing technology using orbital angular momentum (OAM), and reconfigurable intelligent surface (RIS) technology, as well as full duplex technology to improve the frequency efficiency of 6G mobile communication technology and improve system networks, AI-based communication technology that utilizes satellites and artificial intelligence (AI) from the design stage and incorporates end-to-end AI support functions to optimize the system, and next-generation distributed computing technology that utilizes ultra-high performance communication and computing resources to realize services of a complexity that exceeds the limits of terminal computing capabilities.

[0008] As described above, with the development of wireless communication systems, when congestion occurs between various 5G network entities belonging to a network slice for each protocol data unit (PDU) session, or when it is necessary to temporarily or permanently suspend use of a specific slice for operational reasons, a method for providing smooth efficiency of an application is required. In particular, when a situation in which the performance of an application is degraded is found and it is necessary to temporarily or permanently suspend use of the corresponding slice, a method for determining a target slice and a method for moving a PDU session belonging to a specific slice to the target slice are required. Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention has been made in view of the above-mentioned prior art, and an object of the present disclosure is to provide an apparatus and method for providing smooth efficiency of applications in a wireless communication system. [Means for solving the problem]

[0010] In order to achieve the above object, a method performed by an access mobility and management function (AMF) node in a mobile communication system according to one aspect of the present invention includes the steps of receiving a notification message including information regarding an unavailable slice from a slice availability check function (SACF) node, receiving information regarding a protocol data unit (PDU) session from a network data analysis function (NWDAF) node, determining a target slice and at least one PDU session that requires a slice change based on the notification message and the information regarding the PDU session, and transmitting a request message to a session management function (SMF) node to change the slice of the determined at least one PDU session to the target slice.

[0011] A method performed by a session management function (SMF) node in a mobile communication system according to another aspect of the present invention, which has been made to achieve the above-mentioned object, includes the steps of receiving a request message from an access mobility and management function (AMF) node to change a slice of at least one protocol data unit (PDU) session to a target slice, and transmitting information regarding the change of the at least one PDU session based on the request message to the AMF node, wherein the request message includes information regarding the target slice and an indicator indicating a change method of the at least one PDU session, and the change method includes at least one of a first method of modifying a context of the at least one PDU session, a second method of setting up one or more PDU sessions after releasing the at least one PDU session, or a third method of releasing the at least one PDU session after setting up the one or more PDU sessions.

[0012] In order to achieve the above-mentioned object, an access mobility and management function (AMF) node in a mobile communication system according to one aspect of the present invention comprises at least one controller, and the at least one controller is configured to receive a notification message including information regarding an unavailable slice from a slice availability check function (SACF) node, receive information regarding a protocol data unit (PDU) session from a network data analysis function (NWDAF) node, determine a target slice and at least one PDU session that requires a slice change based on the notification message and the information regarding the PDU session, and transmit a request message to a session management function (SMF) node to change the slice of the determined at least one PDU session to the target slice.

[0013] According to one embodiment of the present invention, a session management function (SMF) node in a mobile communication system includes at least one controller, and the at least one controller is configured to receive a request message from an access mobility and management function (AMF) node to change a slice of at least one protocol data unit (PDU) session to a target slice, and to transmit information regarding the change of the at least one PDU session to the AMF node based on the request message, wherein the request message includes information regarding the target slice and an indicator indicating a change method of the at least one PDU session, and the change method includes at least one of a first method of modifying a context of the at least one PDU session, a second method of setting up one or more PDU sessions after releasing the at least one PDU session, or a third method of releasing the at least one PDU session after setting up the one or more PDU sessions. Effect of the Invention

[0014] According to the present invention, it is possible to effectively provide services in a wireless communication system, and when a situation in which the performance of an application in a wireless communication system deteriorates is discovered and it is necessary to temporarily or permanently suspend use of the corresponding slice, a target slice is determined, and a PDU (protocol data unit) session belonging to a specific slice can be moved to the target slice.

[0015] The effects obtained by the present invention are not limited to those mentioned in the various embodiments, and other effects not mentioned will be clearly understood by those having ordinary skill in the art to which the present invention pertains from the following description. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 illustrates a communication network including a core network entity in a wireless communication system according to various embodiments of the present invention. [Figure 2A] FIG. 1 illustrates a wireless environment including a core network in a wireless communication system according to various embodiments of the present invention. [Figure 2B] A diagram showing the configuration of a core network entity in a wireless communication system according to various embodiments of the present invention. [Figure 2C] FIG. 2 is a diagram illustrating the configuration of a terminal in a wireless communication system according to various embodiments of the present invention. [Diagram 3] FIG. 13 illustrates a signal flow for requesting slice movement according to various embodiments of the present invention. [Figure 4] A flowchart illustrating the operational flow of AMF for requesting slice movement according to various embodiments of the present invention. [Diagram 5] FIG. 2 illustrates a signal flow diagram for moving slices relative to a session in accordance with various embodiments of the present invention. [Figure 6] A flowchart illustrating the operational flow of AMF for moving slices for a session according to various embodiments of the present invention. [Figure 7] 11 is a flowchart illustrating the operational flow of an SMF for moving slices for a session in accordance with various embodiments of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific examples of the present invention will be described in detail with reference to the drawings, in which the same reference numerals indicate the same parts.

[0018] Before understanding the detailed description that follows, it is advantageous to clarify the definitions of certain words and phrases used throughout the specification. The terms "include" and "comprise" and their derivatives mean "including" without limitation, the term "or" means inclusive "and / or", and the phrases "associated with" and "associated therewith" and their derivatives mean including, containing, interconnected, including in inclusion, connected, coupled, capable of communicating, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, and the like. The term "controller" refers to any device, system, or part thereof that controls at least one operation, whether such device is implemented in hardware, firmware, or software, or a combination of at least two or more thereof. It should be noted that the functionality associated with a particular controller may be centralized or distributed, whether locally or remotely.

[0019] In addition, the various functions described below are implemented or supported by one or more computer programs, each of which is formed of computer-readable program code and implemented in a computer-readable recording 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 adapted to be implemented in suitable computer-readable program code. The phrase "computer-readable program code" includes any type of computer code, including source code, object code, and executable code. The phrase "computer-readable recording medium" includes any type of recording medium accessible by a computer, such as read-only memory (ROM), random access memory (RAM), hard disk drive, compact disk (CD), digital video disk (DVD), or any other type of memory. A "non-transitory" computer-readable recording medium excludes wired, wireless, optical, or other communication links that transmit temporary electrical or other signals. A non-transitory computer-readable recording medium includes media that permanently store data, and media that store data and can be rewritten later, such as a re-recordable optical disk or a removable memory device.

[0020] Throughout this specification definitions are provided for particular words or phrases, and those of skill in the art should understand that in many, if not most, instances such definitions also apply to prior or future uses of the word or phrase so defined.

[0021] 1-7 described below and various embodiments used herein to explain the principles of the present invention are merely examples and should not be construed in a manner that limits the scope of the present invention. Those skilled in the art will understand that the principles of the present invention may be implemented in any appropriately arranged system or device.

[0022] The terms used in this specification are merely used to describe a particular embodiment and are not intended to limit the scope of other embodiments. A singular expression includes a plural expression unless the context clearly indicates a different meaning. Terms used herein, including technical or scientific terms, have the same meaning as commonly understood by a person having ordinary skill in the technical field described herein. Terms defined in a general dictionary among the terms used in this specification are interpreted as meanings that are the same as or similar to the meanings in the context of the related art, and are not interpreted as ideal or overly formal meanings unless clearly defined in this specification. In some cases, even terms defined in this specification cannot be interpreted to exclude embodiments of the present invention.

[0023] In the various embodiments of the present invention described below, a hardware approach is described as an example, but the various embodiments of the present invention do not exclude a software-based approach, since the various embodiments of the present invention include techniques that use both hardware and software.

[0024] The present invention relates to an apparatus and method for changing a slice for a session in a wireless communication system. In particular, the present invention describes a technique for determining a target slice in a wireless communication system and moving a protocol data unit (PDU) session belonging to a specific slice to the target slice.

[0025] Various embodiments of the present invention enable an access and mobility management function (AMF) in a 5G system to receive information about a specific slice that requires mobility and perform appropriate processing for the slice. In addition, the AMF sets an optimal target slice in consideration of requirements for a protocol data unit (PDU) session and slice status information.

[0026] In addition, the apparatus and method according to various embodiments of the present invention enable the AMF to determine a slice movement method taking into account the requirements for the PDU session and the reason for the need to move the slice, thereby ensuring user experience and network control efficiency. Various embodiments of the present invention enable the SMF to move the PDU session to a target slice while maintaining session continuity.

[0027] In the following description, the terms referring to signals, channels, control information, network entities, and device components are provided as examples for the sake of convenience. Therefore, the present invention is not limited to the terms described below, and other terms having equivalent technical meanings may be used.

[0028] Although the present invention will be described in various embodiments using terminology used in some communication standards (e.g., 3GPP (registered trademark) (3rd Generation Partnership Project)), this is merely an example for the purpose of explanation. Various embodiments of the present invention can be easily modified and applied to other communication systems.

[0029] FIG. 1 illustrates a communication network including a core network entity in a wireless communication system according to various embodiments of the present invention.

[0030] The 5G mobile communication network 100 includes a 5G UE (user equipment) 110, a 5G RAN (radio access network) 120, and a 5G core network.

[0031] The 5G core network is composed of network functions such as an access and mobility management function (AMF) 150 that provides UE mobility management functions, a session management function (SMF) 160 that provides session management functions, a user plane function (UPF) 170 that performs the role of data transmission, a policy control function (PCF) 180 that provides policy control functions, a unified data management (UDM) 153 that provides data management functions such as subscriber data and policy control data, and a unified data repository (UDR) that stores data for various network functions.

[0032] Referring to FIG. 1, a user equipment (UE) 110 communicates with a base station (e.g., eNB, gNB) through a radio channel, i.e., an access network. In some embodiments, the terminal 110 is a device used by a user and configured to provide a user interface (UI). As an example, the UE 110 is a terminal mounted on a vehicle for driving. In some other embodiments, the terminal 110 is a device that performs machine type communication (MTC) operated without user involvement, or is an autonomous vehicle. In addition to electronic devices, the UE may be referred to as a "terminal," "vehicle terminal," "user equipment (UE)," "mobile station," "subscriber station," "remote terminal," "wireless terminal," or "user device," or other terms having equivalent technical meanings. In addition to UE, customer-premises equipment (CPE) or dongle-type terminals are also used as terminals. CPE is connected to the NG-RAN node in the same way as UE, and provides a network to other communication devices (e.g., laptops).

[0033] 1, the AMF 150 provides a function for connection and mobility management for each terminal 110, and one terminal 110 is basically connected to one AMF 150. Specifically, the AMF 150 performs at least one function of signaling between core network nodes for mobility between 3GPP (registered trademark) access networks, an interface (N2 interface) between radio access networks (e.g., 5G RAN) 120, NAS signaling with the terminal 110, identification of the SMF 160, and transmission of session management (SM) messages between the terminal 110 and the SMF 160. A part or the entire function of the AMF 150 is supported within a single instance of one AMF 150.

[0034] Referring to FIG. 1, the SMF 160 provides a session management function, and when the terminal 110 has multiple sessions, each session is managed by a different SMF 160. Specifically, the SMF 160 performs at least one of the following functions: session management (e.g., session establishment, modification, and release, including tunnel maintenance between the UPF 170 and an access network node), selection and control of user plane (UP) functions, traffic steering setting for routing traffic to an appropriate destination in the UPF 170, termination of the SM part of the NAS message, downlink data notification (DDN), and initiator of AN-specific SM information (e.g., transmission to the access network via the N2 interface via the AMF 150). Some or all of the functions of the SMF 160 are supported within a single instance of one SMF 160.

[0035] In the 3GPP (registered trademark) system, a conceptual link connecting NFs in a 5G system may be referred to as a reference point. A reference point may also be referred to as an interface. The following illustrates reference points included in the 5G system architecture illustrated in Figures 1 to 5.

[0036] -N1: Reference point between UE 110 and AMF 150 -N2: Reference point between (R)AN120 and AMF150 -N3: Reference point between (R)AN120 and UPF170 -N4: Reference point between SMF160 and UPF170 -N5: Reference point between PCF180 and AF130 -N6: Reference point between UPF170 and DN140 -N7: Reference point between SMF160 and PCF180 -N8: Reference point between UDM153 and AMF150 -N9: Reference point between two core UPF170 -N10: Reference point between UDM153 and SMF160 -N11: Reference point between AMF150 and SMF160 -N12: Reference point between the AMF 150 and the authentication server function (AUSF) 151 -N13: Reference point between UDM 153 and authentication server function 151 -N14: Reference point between the two AMF150s -N15: Reference point between PCF180 and AMF150 in a non-roaming scenario, and reference point between PCF180 and AMF150 in a visited network in a roaming scenario

[0037] FIG. 2A illustrates a wireless environment including a core network 200 in a wireless communication system in accordance with various embodiments of the present invention.

[0038] Referring to FIG. 2A, the wireless communication system includes a radio access network (RAN) 120 and a core network (CN) 200.

[0039] The wireless access network 120 is a network directly connected to a user device, for example, a terminal 110, and is an infrastructure that provides wireless access to the terminal 110. The wireless access network 120 includes a set of base stations including a base station 125, and the base stations communicate with each other through interfaces formed therewith. At least a part of the interfaces between the base stations is wired or wireless. The base station 125 has a structure separated into a central unit (CU) and a distributed unit (DU). In this case, one CU controls multiple DUs. The base station 125 is also called an "access point (AP)", "gNB (next generation node B)", "5G node (5th generation node)", "wireless point", "transmission / reception point (TRP)", or other terms having equivalent technical meanings, in addition to a base station. The terminal 110 connects to the wireless access network 120 and communicates with the base station 125 through a wireless channel. The terminal 110 may be referred to as a "user equipment (UE)," a "mobile station," a "subscriber station," a "remote terminal," a "wireless terminal," or a "user device," or other terms having equivalent technical meanings.

[0040] The core network 200 is a network that manages the entire system, controls the radio access network 120, and processes data and control signals for the terminal 110 transmitted and received through the radio access network 120. The core network 200 performs various functions such as controlling a user plane and a control plane, processing mobility, managing subscriber information, charging, and interworking with other types of systems (e.g., long term evolution (LTE) system). In order to perform the various functions described above, the core network 200 includes a number of functionally separated entities each having a different network function (NF). For example, the core network 200 includes an access and mobility management function (AMF) 150, a session management function (SMF) 160, a user plane function (UPF) 170, a policy and charging function (PCF) 180, a network repository function (NRF) 159, a user data management (UDM) 153, a network exposure function (NEF) 155, and a unified data repository (UDR) 157.

[0041] The terminal 110 is connected to the radio access network 120 and is connected to the AMF 150 which performs a mobility management function of the core network 200. The AMF 150 is a function or device which is responsible for all of the connection of the radio access network 120 and the mobility management of the terminal 110. The SMF 160 is an NF which manages sessions. The AMF 150 is connected to the SMF 160 and the AMF 150 routes session-related messages for the terminal 110 to the SMF 160. The SMF 160 is connected to the UPF 170 to allocate user plane resources to be provided to the terminal 110 and establish a tunnel for transmitting data between the base station 125 and the UPF 170. The PCF 180 controls information related to policies and charging for sessions used by the terminal 110. The NRF 159 performs a function of retaining information about NFs installed in the mobile communication operator network and notifying the retained information. The NRF 159 is connected to all NFs. When each NF starts operating in a carrier network, it registers with the NRF 159 to inform the NRF 159 that the corresponding NF is operating in the network. The UDM 153 is an NF that performs a role similar to a home subscriber server (HSS) in a 4G network, and holds subscription information of the terminal 110 or a context that the terminal 110 uses in the network.

[0042] The NEF 155 serves to connect a third party server with NFs in the 5G mobile communication system. It also serves to provide data to the UDR 157, update data, or obtain data. The UDR 157 serves to hold subscription information of the terminal 120, hold policy information, hold data exposed to the outside, or hold information required for a third party application. The UDR 157 also serves to provide the held data to other NFs.

[0043] FIG. 2B is a diagram illustrating a configuration of core network entities in a wireless communication system according to various embodiments of the present invention.

[0044] The configuration 200 illustrated in Fig. 2B is understood as a configuration of an apparatus having at least one function of 150, 153, 155, 157, 160, 170, 180, and 190 in Fig. 1. Terms such as "unit" and "device" used below refer to a unit that processes at least one function or operation, and is implemented by hardware or software, or a combination of hardware and software.

[0045] Referring to FIG. 2B, the core network entity includes a communication unit 210, a storage unit 230, and a control unit 220.

[0046] The communication unit 210 provides an interface for communicating with other devices in the network. That is, the communication unit 210 converts bit strings transmitted from the core network entity to other devices into physical signals, and converts physical signals received from other devices into bit strings. That is, the communication unit 210 transmits and receives signals. Thus, the communication unit 210 may be referred to as a modem, a transmitter, a receiver, or a transceiver. In this regard, the communication unit 210 enables the core network entity to communicate with other devices or systems via a backhaul connection (e.g., a wired backhaul or a wireless backhaul) or via a network.

[0047] The storage unit 230 stores data such as basic programs, application programs, and configuration information for the operation of the core network entity. The storage unit 230 is configured with a volatile memory, a non-volatile memory, or a combination of a volatile memory and a non-volatile memory. The storage unit 230 provides the stored data in response to a request from the control unit 220.

[0048] The controller 220 controls the overall operation of the core network entity. For example, the controller 220 transmits and receives signals via the communication unit 210. The controller 220 also records and reads data in the memory unit 230. To this end, the controller 220 includes at least one processor. According to various embodiments of the present invention, the controller 220 controls synchronization with a wireless communication network. For example, the controller 220 controls the core network entity to perform operations according to various embodiments described below.

[0049] FIG. 2C is a diagram illustrating a configuration of a terminal in a wireless communication system according to various embodiments of the present invention.

[0050] 2C is understood as the configuration of the terminal 110. In the following, the terms "unit" and "device" refer to a unit that processes at least one function or operation, and is implemented in hardware or software, or a combination of hardware and software.

[0051] Referring to FIG. 2C, the terminal includes a communication unit 240, a storage unit 250, and a control unit 260.

[0052] The communication unit 240 performs a function for transmitting and receiving signals through a wireless channel. For example, the communication unit 240 performs a conversion function between a baseband signal and a bit string according to a physical layer standard of the system. For example, when transmitting data, the communication unit 240 generates complex symbols by encoding and modulating a transmission bit string. Also, when receiving data, the communication unit 240 restores a received bit string by demodulating and decoding a baseband signal. Also, the communication unit 240 up-converts a baseband signal to an RF band signal and transmits the RF band signal through an antenna, and down-converts an RF band signal received through the antenna to a baseband signal. For example, the communication unit 240 includes a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, and the like.

[0053] The communication unit 240 also includes multiple transmission and reception paths. Furthermore, the communication unit 240 includes at least one antenna array configured with multiple antenna elements. From the hardware perspective, the communication unit 240 is configured with a digital circuit and an analog circuit (e.g., an RFIC (radio frequency integrated circuit)). Here, the digital circuit and the analog circuit can be implemented as one package. The communication unit 240 also includes multiple RF chains. Furthermore, the communication unit 240 performs beamforming.

[0054] The communication unit 240 transmits and receives signals as described above. Therefore, all or part of the communication unit 240 is referred to as a "transmitter," a "receiver," or a "transmitter / receiver." In the following description, transmission and reception via a wireless channel are used to mean that the above-mentioned processing is performed by the communication unit 240.

[0055] The storage unit 250 stores data such as basic programs, application programs, and setting information for the operation of the terminal. The storage unit 250 is configured with a volatile memory, a non-volatile memory, or a combination of a volatile memory and a non-volatile memory. The storage unit 250 provides the stored data in response to a request from the control unit 260.

[0056] The control unit 260 controls the overall operation of the terminal. For example, the control unit 260 transmits and receives signals via the communication unit 240. The control unit 260 also records and reads data in the memory unit 250. The control unit 260 also performs the functions of a protocol stack required by a communication standard. To this end, the control unit 260 includes at least one processor or microprocessor, or is a part of a processor. Also, a part of the communication unit 240 and the control unit 260 are referred to as a communication processor (CP). According to various embodiments of the present invention, the control unit 260 controls the terminal to perform synchronization using a wireless communication network. For example, the control unit 260 controls the terminal to perform operations according to various embodiments described below.

[0057] The terms for identifying connection nodes, network entities, messages, interfaces between network entities, and various identification information used in the following description are provided as examples for the sake of convenience. Therefore, the present specification is not limited to the terms described below, and other terms having equivalent technical meanings may be used.

[0058] For the sake of convenience, the present specification uses the terms and names defined in the 5GS (5G system) and NR (new radio) standards, which are the latest standards defined by the 3GPP (registered trademark) organization among the existing communication standards. However, the present invention is not limited to the above terms and names and may be similarly applied to wireless communication networks according to other standards. In particular, the present invention is applied to the 3GPP (registered trademark) 5th generation mobile communication standards (e.g., 5GS and NR).

[0059] In the 5G system, there is a technology called Session and service continuity (SSC) Mode that supports session continuity for the purpose of improving the user's quality-of-experience (QoE) or supporting Mission Critical services. SSC consists of three modes. Among them, SSC mode 3 is called Make-Before-Break. When the network 200 determines that it is necessary to release the SSC mode 3 PDU session that is being used by the terminal 110, it establishes a new PDU session to replace the corresponding PDU session. In addition, the network 200 supports session continuity by releasing the existing PDU session. Before the existing PDU session is released, the terminal 110 maintains session continuity by transferring the traffic flow that was being transmitted and received via the existing PDU session to the new PDU session.

[0060] Network slicing in the 5G system refers to the technology and structure that enables access to several independent logical networks that are virtualized on one physical network. Network operators provide services by configuring virtual end-to-end networks called network slices to meet the specialized requirements of services / applications. Network slices are distinguished by an identifier called S-NSSAI (single-network slice selection assistance information). Network operators provide network slice(s) to terminals to receive services.

[0061] Specifically, in a 5G system, the terminal 110 transmits identifier information (e.g., Requested S-NSSAIs) for a network slice to be requested when registering with a network to the AMF 150. The AMF 150 that receives the identifier information provides the terminal 110 with information (e.g., Allowed NSSAI) on a network slice that the terminal 110 can use, taking into consideration the Requested S-NSSAIs and subscriber information. Even if the terminal 110 does not provide information on a slice requested by the terminal 110, the AMF 150 can provide the Allowed NSSAI to the terminal 110. In this case, the Allowed NSSAI includes information on a default configured slice (e.g., Default Configured NSSAI) and information on a slice configured by default among subscriber slices included in the terminal subscriber information (e.g., Default Subscribed S-NSSAIs).

[0062] If the Allowed NSSAI does not include any slices (e.g., if the Default Configured NSSAI and Default Subscribed S-NSSAIs do not exist or are unavailable), AMF 150 transmits a network registration rejection message to terminal 110 with a cause code indicating that the registration rejection is due to the absence of an available slice.

[0063] On the other hand, when an arbitrary slice is to be included in the Allowed NSSAI of the terminal 110, a network slice admission control (NSAC) procedure and a network slice-specific authentication and authorization (NSSAA) procedure for the corresponding slice are performed. In the NSAC procedure, it is determined whether or not to admit the corresponding slice based on the number of terminals currently registered in a specific slice and the maximum number of terminals allowed to be registered in the corresponding slice (for example, it is determined whether or not to include the corresponding slice in the Allowed NSSAI). In the NSSAA procedure, an authentication procedure is performed with an authentication authorization and accounting-server (AAA-S), which is a server that performs authentication for the corresponding slice through an NSSAAF (for example, an NSSAA Function), based on the terminal's credential information for the corresponding slice. At this time, it is determined whether or not to admit the corresponding slice in consideration of the authentication result (for example, it is determined whether or not to include the corresponding slice in the Allowed NSSAI).

[0064] Meanwhile, the terminal 110 selects one of the allowed slices for transmitting and receiving data to a specific data network (DN) 140 via the allowed slices (Allowed NSSAIs). The terminal 110 also requests the corresponding slice to generate a packet data unit (PDU) session to a specific data network name (DNN), and transmits and receives data through the generated PDU session. The PDU session is composed of several traffic flows, and the traffic flows are composed of two types: guaranteed bitrate quality-of-service flow (GBR QoS flow) and non-GBR QoS flow.

[0065] Meanwhile, in the 5G system, a congestion situation may occur for a slice, or an operational reason (e.g., OAM (operations, administration and maintenance)) may occur for a particular slice. Due to the congestion situation or operational reason, a situation may occur in which some slices in which the terminal 110 has already established a PDU session and is in use are unavailable or performance degradation occurs even if they are used. In this case, the 5G system needs a method for moving an existing PDU session belonging to the corresponding slice to another slice (e.g., a target slice). In this case, the slice(s) to be moved and the target slice(s) need to be adaptively determined for each terminal, and the continuity of the session needs to be guaranteed.

[0066] According to various embodiments of the present invention, in a 5G system, when congestion occurs between various 5G network entities belonging to a network slice for each PDU session (e.g., a network slice congestion situation), or when it is necessary to temporarily or permanently suspend use of a particular slice(s) for operational reasons (e.g., in the case of OAM), a method for detecting a situation in which the performance of an application or service is degraded is proposed. Also, a method for determining a target slice when it is necessary to temporarily or permanently suspend use of the slice(s) and a method for moving all or part of the PDU sessions belonging to the particular slice(s) to the target slice are proposed.

[0067] According to various embodiments of the present invention, when the availability of a slice(s) needs to be temporarily or permanently suspended, a slice availability check network function (SACNF) 310 determines such a situation. The SACNF 310 informs the AMF 150 about the slice(s) that needs to be moved, and the AMF 150 determines the PDU session(s) that needs to be moved and the target slice(s).

[0068] According to one embodiment, the AMF 150 requests the SMF 160 to move some or all of the sessions established through the unavailable slice to the target slice. The move request can be of three types:

[0069] In one embodiment using an existing session (e.g., context modification method), only the context of the session is updated (e.g., only slice information is changed to the target slice). A session context update procedure in the AMF 150, SMF 160, RAN 120, UE 110, and UPF 170 is performed.

[0070] According to this embodiment, method 1) supports continuity by using existing sessions as is.

[0071] In one embodiment of creating a new session after releasing an existing session (eg, break-before-make), the existing session is released and a new PDU session is created in the target slice.

[0072] According to this embodiment, continuity is supported since the traffic flow that was sent over the existing session is sent over the new PDU session.

[0073] In one embodiment where the existing session is released after the new session is created (e.g., make-before-break), a new PDU session is created in the target slice and the traffic flow that was sent to the existing session is sent over the new PDU session, thereby supporting continuity.

[0074] In one embodiment, after the new session is established, the existing session is torn down.

[0075] FIG. 3 is a diagram illustrating a signal flow for requesting slice movement according to various embodiments of the present invention.

[0076] Specifically, Fig. 3 shows a procedure in which the AMF 150 receives unavailable slice-related information via a Slice Availability Check Function (SACF) 310 and requests determination of a target slice for a session and movement to the target slice. Referring to Fig. 3, the SACF 310 is also referred to as a slice availability check network function (SACNF).

[0077] According to one embodiment, the SACF 310 is located in (e.g., includes at least one entity) of at least one of the following entities: the AMF 150, the Application Function (AF) 130, the Radio Access Network (RAN) 120, the Network Slice Selection Function (NSSF) 190, the Network Data Analytics Function (NWDAF) (not shown), the OAM (not shown), the PCF 180, or the UDM 153. The OAM is one of the entities that manages network resources (e.g., resource monitoring and resource allocation for NFs, NF life cycle management, etc.) (e.g., a network slice management function (NSMF), a communication service management function (CSMF), or a network function virtualization orchestrator (NFVO) belonging to operation support systems / business support systems (OSS / BSS)). However, according to various embodiments of the present invention, without being limited thereto, the SACF 310 may exist in the network as a separate entity.

[0078] In step S305, AMF 150 receives a notification message (e.g., a notification message) from SACF 310.

[0079] Referring to step S315, the AMF 150 determines the slice(s) that are unavailable due to OAM or congestion based on information provided by a network administrator or configuration information, or based on a notification message received from the SACF 310.

[0080] According to one embodiment, the notification message received from the Slice Availability Check NF 310 includes the following information:

[0081] "Unavailable slice(s)", "list of TA(tracking area)(s)", "cause=congestion or OAM or performance issue", "slice change required information".

[0082] However, according to various embodiments of the present invention, the notification message received by AMF 150 is not limited to this and may include information other than the information described above.

[0083] "Unavailable slice(s)" includes identifier information for unavailable slice(s) (or slice(s) that need to be moved). "List of Tracking Areas (TAs)" includes information indicating the area in which the unavailable slice(s) are unavailable. "Cause" includes information about the reason why the slice(s) are unavailable (e.g., congestion or OAM, etc.).

[0084] In one embodiment, the "slice change required information" includes at least one of an indicator indicating a slice change for the unavailable slice(s) or target slice information for each slice belonging to the unavailable slice(s).

[0085] Also, referring to step S315, when the "cause" of the message received from the SACF 310 is Congestion among the PDU sessions belonging to the determined unavailable slice(s), the AMF 150 receives experience data by congestion control for each terminal or slice (e.g., S-NSSAI) and DNN (data network name) for the PDU sessions belonging to the determined unavailable slice(s) from the Network Data Analytics Function (NWDAF). The AMF 150 determines the PDU sessions to be moved to another slice based on the received experience data.

[0086] Referring to step S325, when AMF 150 receives a message from SACF 310 in step S315, it initiates a procedure to move all or part of the PDU sessions (e.g., the sessions determined in step S315) belonging to the unavailable slice(s) to the target slice(s).

[0087] In one embodiment, AMF 150 releases an existing session established in the unavailable slice, and requests the creation of a new PDU session to the target slice to replace the released session (e.g., change the PDU session ID).

[0088] According to one embodiment, the AMF 150 does not release the existing session, but requests that only information regarding the slice of the corresponding session be modified to the target slice through a modification to the existing session.

[0089] According to one embodiment, when determining a target slice, AMF 150 takes into account slice information and Allowed NSSAI supported by SMF 160 managing the corresponding session.

[0090] According to one embodiment, when AMF 150 determines a target slice, it requests and receives the following information from the corresponding NF, and then takes this into consideration when determining the target slice.

[0091] "Load information per slice from NWDAF," "Number of registered terminals per slice requested / received from Network Slice Admission Control Function (NSACF)," "Number of PDU sessions per slice," "slice change required information received from SACF," etc.

[0092] Referring to step S335, the AMF 150 transmits a request message to the SMF 160 to move the PDU session for which slice movement was determined in step S315 to the target slice determined in step S325. The request message transmitted by the AMF 150 is referred to as an update session management request message. At least one of "Nsmf_PDUSession_UpdateSMContext Request", "Nsmf_PDUSession_ReleaseSMContext Request", "Nsmf_PDUSession_UpdateSMContext Request", or "Nsmf_PDUSession_ContextPushRequest" is used as the message format of the request message transmitted by the AMF 150.

[0093] According to one embodiment, the request message transmitted by the AMF 150 includes at least one of the following information:

[0094] "SM Context ID or PDU session ID", "indication", "Cause=OAM or congestion", "target slice information".

[0095] However, according to various embodiments of the present invention, the request message transmitted by AMF 150 is not limited thereto and may include information other than the information described above.

[0096] "SM Context ID" is an identifier that indicates information for each session. "Indication" is set to at least one of the following three: "context modification", "release with make-before-break", and "session release with break-before-make".

[0097] According to one embodiment, AMF 150 sets 'indication' to 'context modification' when making a request to modify only information regarding the slice of the corresponding session to the target slice through modification to the existing session without releasing the existing session.

[0098] According to one embodiment, if the PDU session corresponding to the SM Context ID or PDU Session ID is an SSC (session and service continuity) mode 1 PDU session, the AMF 150 sets the “Indication” included in the message transmitted to the SMF 160 to “context modification”.

[0099] In one embodiment, when AMF150 requests to release an existing session established on an unavailable slice and generate a new PDU session to a target slice to replace the session, it sets "indication" to "indication session release with break-before-make" (or "session release with break-before-make").

[0100] In one embodiment, AMF150 sets "indication" to "indication session release with make-before-break" (or "session release with make-before-break") when requesting that a new PDU session be generated and then released to a target slice to replace an existing session established in an unavailable slice before releasing the session.

[0101] Referring to step S345, in one embodiment, when the "indication" of the message received in step S335 is "context modification", the SMF160 that receives the request message from the AMF initiates a procedure to modify information regarding the slice to which the corresponding session is currently established, among the context information for the PDU session corresponding to the "SM Context ID" or "PDU session ID" of the message received in step S335 stored in the 5G system (e.g., SMF160, AMF150, UPF170, UE110), to the target slice.

[0102] According to one embodiment, if the "indication" of the message received in step S335 is "release with break-before-make", SMF160 releases the PDU session corresponding to the "SM Context ID" or "PDU session ID" of the message received in step S335, and then performs a procedure to generate a new PDU session to the target slice to replace the corresponding session.

[0103] According to one embodiment, when the "indication" of the message received in step S335 is "release with make-before-break", before releasing the PDU session corresponding to the "SM Context ID" or "PDU session ID" of the message received in step S335, SMF160 performs a procedure to generate and then release a new PDU session to the target slice to replace the corresponding session.

[0104] According to various embodiments of the present invention, the SMF 160 that performed the procedure notifies the AMF 150 of the processing result.

[0105] FIG. 4 is a flow chart of the operation of AMF 150 to request slice movement in accordance with various embodiments of the present invention.

[0106] Specifically, the operation flow of the AMF 150 shown in FIG. 4 operates based on the signal flow shown in FIG.

[0107] In step 405, the AMF 150 receives a notification message from the SACF 310.

[0108] In one embodiment, the SACF 310 is referred to as a SACNF 310.

[0109] According to one embodiment, the SACF 310 is located in at least one of the following entities: the AMF 150, the Application Function (AF) 130, the Radio Access Network (RAN) 120, the Network Slice Selection Function (NSSF) 190, the Network Data Analytics Function (NWDAF) (not shown), the operations, administration and maintenance (OAM) (not shown), the PCF 180, or the UDM 153. However, according to various embodiments of the present invention, without being limited thereto, the SACF 310 may be formed as an entity other than those illustrated above.

[0110] In one embodiment, the notification message received from the SACN 310 includes the following information:

[0111] "Unavailable slice(s)", "list of TA(tracking area)(s)", "cause=congestion or OAM or performance issue", "slice change required information".

[0112] However, according to various embodiments of the present invention, the notification message received by AMF 150 is not limited to this and may include information other than the information described above.

[0113] "Unavailable slice(s)" includes identifier information for unavailable slice(s) (or slice(s) that need to be moved). "List of Tracking Areas (TAs)" includes information indicating the area in which the unavailable slice(s) are unavailable. "Cause" includes information about the reason why the slice(s) are unavailable (e.g., congestion or OAM, etc.).

[0114] In one embodiment, the "slice change required information" includes at least one of an indicator indicating a slice change for the unavailable slice(s) or target slice information for each slice belonging to the unavailable slice(s).

[0115] In step 415, AMF 150 determines the unavailable slices and the PDU sessions to be modified based on the received notification message.

[0116] In one embodiment, the AMF 150 determines the slice(s) that are unavailable due to OAM or congestion based on information provided by a network administrator or configuration information, or based on a notification message received from the SACF 310.

[0117] According to one embodiment, when the "cause" of the message received from the SACF 310 is Congestion, the AMF 150 receives experience data by congestion control for each terminal or slice (e.g., S-NSSAI) and DNN (data network name) for the PDU sessions belonging to the determined unavailable slice(s) from the Network Data Analytics Function (NWDAF). The AMF 150 determines the PDU sessions to be moved to another slice based on the received experience data.

[0118] In step 425, AMF 150 determines the target slice(s) for the PDU session to be modified.

[0119] In one embodiment, when AMF 150 receives a message from SACF 310, it initiates a procedure to move all or some of the PDU sessions (e.g., the sessions determined in step 415) belonging to the unavailable slice(s) to the target slice(s).

[0120] In one embodiment, AMF 150 releases an existing session established in an unavailable slice. AMF 150 requests the creation of a new PDU session to the target slice to replace the released session (e.g., PDU session ID change). In one embodiment, AMF 150 does not release the existing session, but requests the target slice to modify only information about the slice of the corresponding session through modification of the existing session.

[0121] According to one embodiment, when AMF 150 determines a target slice, it takes into account slice information and Allowed NSSAI supported by SMF 160 that manages the corresponding session.

[0122] According to one embodiment, when determining a target slice, the AMF 150 requests and receives the following information from the corresponding NF, and then takes this into consideration when determining the target slice.

[0123] "Load information per slice from NWDAF," "Number of registered terminals per slice requested / received from Network Slice Admission Control Function (NSACF)," and "Number of PDU sessions per slice," etc.

[0124] Referring to step 435, AMF 150 transmits an update session management request message to SMF 160.

[0125] According to one embodiment, AMF 150 transmits a request message to SMF 160 to move the PDU session for which slice movement was determined in step 415 to the target slice determined in step 425.

[0126] According to an embodiment, the request message transmitted by the AMF 150 is referred to as an update session management request message. The message format of the request message transmitted by the AMF 150 uses at least one of "Nsmf_PDUSession_UpdateSMContext Request", "Nsmf_PDUSession_ReleaseSMContext Request", "Nsmf_PDUSession_UpdateSMContext Request", or "Nsmf_PDUSession_ContextPushRequest". According to an embodiment, the request message transmitted by the AMF 150 includes at least one of the following information:

[0127] "SM Context ID or PDU session ID", "indication", "Cause=OAM or congestion", "target slice information".

[0128] However, according to various embodiments of the present invention, the request message transmitted by AMF 150 is not limited thereto and may include information other than the information described above.

[0129] "SM Context ID" is an identifier that indicates information for each session. "Indication" is set to at least one of the following three: "context modification", "release with make-before-break", or "session release with break-before-make".

[0130] According to one embodiment, AMF 150 sets 'indication' to 'context modification' when making a request to modify only information regarding the slice of the corresponding session to the target slice through a modification to the existing session without releasing the existing session.

[0131] According to one embodiment, if the PDU session corresponding to the SM Context ID or PDU Session ID is an SSC (session and service continuity) mode 1 PDU session, the AMF 150 sets the “Indication” included in the message transmitted to the SMF 160 to “context modification”.

[0132] In one embodiment, AMF 150 sets 'indication' to 'indication session release with break-before-make' when requesting to release an existing session established in an unavailable slice and generate a new PDU session to a target slice to replace the session.

[0133] In one embodiment, AMF150 sets 'indication' to 'indication session release with make-before-break' when requesting that a new PDU session be generated and then released to a target slice to replace an existing session established on an unavailable slice before releasing the session.

[0134] FIG. 5 is a diagram illustrating signal flows for moving slices relative to a session according to various embodiments of the present invention.

[0135] Specifically, FIG. 5 shows a procedure in which, when the SMF 160 receives a slice movement request for a session from the AMF 150, the SMF 160 moves a slice for the session according to the received movement method.

[0136] In step S515, the AMF 150 transmits a request message to the SMF 160 to request a slice move for the PDU session. At least one of "Nsmf_PDUSession_UpdateSMContext Request", "Nsmf_PDUSession_ReleaseSMContext Request", "Nsmf_PDUSession_UpdateSMContext Request", and "Nsmf_PDUSession_ContextPushRequest" is used as the message format of the request message transmitted by the AMF 150. According to an embodiment, the request message transmitted by the AMF 150 includes at least one of the following information:

[0137] "SM Context ID or "PDU session ID", "indication", "Cause=OAM or congestion, target slice information".

[0138] According to one embodiment, the SM Context ID is an identifier for a connection established between the SMF 160 and the AMF 150 for each PDU session. The 'Target slice information' includes target slice (e.g., a newly determined slice for a PDU session) identifier information (e.g., S-NSSAI). In this case, if the PDU session corresponding to the SM Context ID or PDU session ID is a home-routed PDU session, the AMF 150 transmits the 'target slice information' including the V-PLMN (visited public land mobile network) S-NSSAI and the H-PLMN (home public land mobile network) S-NSSAI for the target slice (e.g., a newly determined slice). When deriving the H-PLMN S-NSSAI, the AMF 150 utilizes slice mapping information between the H-PLMN and the V-PLMN. The above content is similarly applied to various embodiments of FIG. 6 and FIG. 7.

[0139] According to an embodiment, if the PDU session corresponding to the information included in the message received by the SMF 160 from the AMF 150 is a Home-routed PDU session (e.g., a PDU session established via an H-SMF and an H-UPF located in a home network) or if the message received from the AMF 150 includes an H-PLMN S-NSSAI, the SMF 160 transmits an Nsmf_PDUSession_Update request message to the H-SMF (not shown). The Nsmf_PDUSession_Update request message transmitted by the SMF 160 to the H-SMF includes at least one of information on the SM Context ID in the H-SMF, "indication", "Cause=OAM or congestion, target slice information", and target slice information including the H-PLMN S-NSSAI information for the PDU session. If the UE is roaming and the PDU session is a home-routed PDU session, the H-SMF (not shown) performs the role of SMF 160 in the following procedure, and the SMF 160 transmits the message received from the H-SMF (not shown) to the AMF 150. The above content is also applicable to the various embodiments of FIG. 6 and FIG. 7.

[0140] However, according to various embodiments of the present invention, the request message transmitted by AMF 150 is not limited thereto and may include information other than the information described above.

[0141] As described in Figure 3, "SM Context ID" is an identifier that indicates information for each session. "Indication" is set to at least one of the following three: "context modification", "release with make-before-break", and "session release with break-before-make".

[0142] According to one embodiment, AMF 150 sets 'indication' to 'context modification' when making a request to modify only information regarding the slice of the corresponding session to the target slice through modification to the existing session without releasing the existing session.

[0143] According to one embodiment, if the PDU session corresponding to the SM Context ID or PDU Session ID is an SSC (session and service continuity) mode 1 PDU session, the AMF 150 sets the “Indication” included in the message transmitted to the SMF 160 to “context modification”.

[0144] In one embodiment, AMF 150 sets 'indication' to 'session release with break-before-make' when requesting to release an existing session established in an unavailable slice and generate a new PDU session to a target slice to replace the session.

[0145] In one embodiment, AMF 150 sets 'indication' to 'session release with make-before-break' when requesting that a new PDU session be generated and then released to a target slice to replace an existing session established in an unavailable slice before releasing the session.

[0146] Referring to step S525, SMF 160 transmits a response message to AMF 150 based on the request message received from AMF 150.

[0147] Referring to step S525, if only the target slice is present in the received message received from AMF 150 in step S515, SMF 160 sets "indication" taking into consideration the SSC mode for the PDU session, whether it is an MPS session, configuration information, terminal subscriber information, etc.

[0148] According to one embodiment, if the PDU session corresponding to the SM Context ID or PDU Session ID included in the message received from AMF 150 is an SSC mode 1 PDU session (e.g., a PDU session requesting that no UPF changes be made to the PDU session), SMF 160 sets "indication" to "context modification".

[0149] According to one embodiment, when SMF 160 sets "indication" to "context modification", AMF 150 decides not to release the existing session, but to only change information regarding the slices of the session through modification to the existing session.

[0150] According to one embodiment, if the PDU session corresponding to the SM Context ID or PDU Session ID included in the message received from the AMF 150 is SSC mode 2 or SSC mode 3, the SMF 160 sets the 'indication' to 'context modification'.

[0151] According to one embodiment, if the PDU session corresponding to the SM Context ID or PDU Session ID included in the message received from AMF 150 is an SSC mode 1 PDU session, SMF 160 does not set "indication" to "session release with make-before-break" or "session release with break-before-make".

[0152] If the target slice is not present in the received message received from AMF 150 in step S515, SMF 160 determines the target slice via configuration information or interaction with AMF 150.

[0153] According to one embodiment, if the SMF 160 decides to move to the target slice, it transmits a response message to the AMF 150. The response message transmitted by the SMF 160 includes information about the target slice. The response message transmitted by the SMF 160 is referred to as an update session management response message.

[0154] Referring to step S525, if the 'indication' of the request message received from AMF 150 is 'context modification', the response message transmitted to AMF 150 includes the following information:

[0155] "SM Context ID or PDU session ID", "target slice", "N2 SM container("SM Context ID or PDU session ID", "target slice", "cause=OAM or congestion", "N1 SM Container")".

[0156] The "N1 SM container" contains the following information:

[0157] "PDU Session Modification Command("PDU Session ID", "target slice")".

[0158] For example, according to one embodiment, if the PDU session corresponding to the "SM Context ID" or "PDU Session ID" included in the message received by SMF 160 from AMF 150 is an SSC mode 1 PDU session, the message transmitted by SMF 160 to UE 110 includes information instructing to change the S-NSSAI (slice identifier) ​​for the PDU session.

[0159] In one embodiment, the N1 SM container message includes other information identifying the PDU session in addition to the "PDU Session ID."

[0160] However, according to various embodiments of the present invention, the response message transmitted by SMF 160 is not limited thereto and may include information other than that described above.

[0161] Referring to step S525, if the 'indication' of the request message received from AMF 150 is 'session release with break-before-make' or 'session release with make-before-break', the message transmitted to AMF 150 includes the following information:

[0162] "SM Context ID or PDU session ID", "N2 SM container("SM Context ID or PDU session ID", "target slice", "cause=OAM or congestion", "N1 SM Container")".

[0163] In one embodiment, if the "indication" of the message received by SMF 160 is "session release with break-before-make", the "N1 SM container" contains the following information:

[0164] "PDU Session Release Command" ("PDU Session ID", "target slice", "session re-establishment request to the same DN", "target slice indication").

[0165] In one embodiment, if the "indication" of the message received by SMF 160 is "session release with make-before-break", the "N1 SM container" contains the following information:

[0166] PDU Session Modification Command('PDU Session ID', 'target slice', 'session re-establishment request to the same DN', 'target slice indication', '[PDU session release timer]').

[0167] According to one embodiment, the SMF 160 performs steps S535 and S545 after receiving an Ack (acknowledgement) message for the "PDU Session Modification Command" from the terminal in step S575.

[0168] Referring to step S535, when the request message received from the AMF 150 includes a PDU session identifier (or a PDU session context ID) and "indication" set to "context modification", the SMF 160 transmits an N4 session modification request message to the UPF 170 to change the slice information of the N4 session to the target slice. The N4 interface (e.g., the N4 reference point) is an interface formed between the SMF 160 and the UPF 170. The N4 session modification request message transmitted by the SMF 160 to the UPF 170 includes at least one of the N4 session context ID, information on the target slice, an indicator indicating that this is a slice change request, or information indicating the cause of the slice change.

[0169] Referring to step S545, the UPF 170 transmits an N4 session modification response message to the SMF 160 based on the received N4 session modification request message. The N4 session modification response message transmitted by the UPF 170 to the SMF 160 includes at least one of an N4 session context ID or information related to a result. When the SMF 160 receives a response message from the UPF 170 indicating that the slice modification has been successful, the SMF 160 changes the slice information of the N4 session to the target slice.

[0170] According to an embodiment of the present invention, the UPF 170 and the SMF 160 determine whether to change the N4 interface through the processes of steps S535 and S545, and execute the process.

[0171] Referring to step S555, when the message received from the SMF 160 in step S525 includes a target slice, the AMF 150 changes slice information for the session among the information stored for the session corresponding to the "SM Context ID" or "PDU session ID" to the target slice. Also, in step S555, the AMF 150 transmits information included in the N2 SM container to the RAN 120. When the message received from the AMF includes a target slice, the RAN 120 changes slice information for the session among the information stored for the session corresponding to the received "SM Context ID" or "PDU session ID" to the target slice. The RAN 120 transmits the N1 SM container to the UE 110. The above-mentioned series of processes is not limited thereto, and the flow of messages transmitted from the AMF 150 to the UE 110 via the RAN 120 described above is expressed as transmission of PDU session command message information as shown in FIG. 5.

[0172] Referring to step S565, if the message received from RAN 120 in step S555 includes "PDU Session ID" and "target slice", the terminal 110 changes the slice information for the session corresponding to the received "PDU session ID" among the information stored for the session to the target slice.

[0173] Referring to steps S565 and S575, the terminal 110 transmits a message confirming that the session-related information has been changed to the SMF via the RAN 120 and the AMF 150. In the above-mentioned transmission process, the RAN 120 and the AMF 150 each transmit a message including a message confirming that the session-related information has been changed to the SMF 160. The above-mentioned series of processes is not limited thereto, and the flow of a signal transmitted from the UE 110 to the AMF 150 via the RAN 120 is expressed as the transmission of a PDU session release command Ack (acknowledgement) message (or an Ack message for the "PDU Session Modification Command") as shown in FIG. 5. Also, the flow of a signal transmitted from the AMF 150 to the SMF 160 is expressed as the transmission of a PDU session update request Ack (acknowledgement) message as shown in FIG. 5.

[0174] According to one embodiment, the SMF 160 performs steps S535 and S545 after receiving an Ack message for the PDU Session Modification Command from the terminal in step S575.

[0175] Referring to step S585, if the message received from RAN 120 in step S555 includes “PDU Session ID”, “target slice”, “session re-establishment request to the same DN”, or “target slice indication”, the terminal 110 includes the received PDU Session ID in a PDU session release request message and transmits it to SMF 160 via AMF 150, requesting release of the PDU session corresponding to the received PDU session ID.

[0176] According to one embodiment, the terminal 110 requests a new PDU session by including the DNN (data network name) of the PDU session for which the release request was made and the target slice received in step S555 in a PDU session generation request message and transmitting the message to the SMF 160. When a new session is generated in the target slice, the terminal 110 transmits the traffic flow that was being transmitted in the released PDU session through the generated new PDU session.

[0177] Referring to step S595, if the message received from the RAN 120 in step S555 includes "PDU Session ID", "target slice", "session re-establishment request to the same DN", "target slice indication", or "PDU session release timer", the terminal 110 requests a new PDU session by including a DNN (data network name) such as a PDU session corresponding to the received "PDU session ID" and the target slice received in step S555 in a PDU session generation request message and transmitting the message to the SMF 160. If a new session is generated in the target slice, the terminal 110 transmits the traffic flow that was being transmitted in the existing PDU session through the generated new PDU session.

[0178] According to one embodiment, when a new PDU session is generated and a received PDU session release timer expires or according to internal terminal configuration information, the UE 110 transmits the received PDU session ID to the SMF 160 via the AMF 150 in a PDU session release request message. The UE 110 transmits a message to the SMF 160 to request the release of a PDU session corresponding to the received PDU session ID.

[0179] FIG. 6 is a flowchart illustrating the operation of AMF 150 for moving slices for a session in accordance with various embodiments of the present invention.

[0180] Specifically, the operation flow of the AMF 150 shown in FIG. 6 operates based on the signal flow shown in FIG.

[0181] Referring to step 605, the AMF 150 receives an update session management response message from the SMF 160. Specifically, the AMF 150 receives from the SMF 160 a response message generated based on the request message transmitted to the SMF 160.

[0182] In one embodiment, the response message received by AMF 150 includes information regarding the target slice.

[0183] If the “indication” of the request message received by SMF 160 is “context modification”, the response message received by AMF 150 includes the following information:

[0184] "SM Context ID or PDU session ID", "target slice", "N2 SM container("SM Context ID or PDU session ID", "target slice", "cause=OAM or congestion", "N1 SM Container")".

[0185] The "N1 SM container" contains the following information:

[0186] "PDU Session Modification Command("PDU Session ID", "target slice")".

[0187] For example, according to one embodiment, if the PDU session corresponding to the "SM Context ID" or "PDU Session ID" included in the message received by SMF 160 from AMF 150 is an SSC mode 1 PDU session, the message transmitted by SMF 160 to UE 110 includes information instructing to change the S-NSSAI (slice identifier) ​​for the PDU session.

[0188] In one embodiment, the N1 SM container message includes other information identifying the PDU session in addition to the PDU Session ID.

[0189] However, according to various embodiments of the present invention, the response message received by AMF 150 is not limited thereto and may include information other than that described above.

[0190] According to one embodiment, if the "indication" of the request message received by SMF 160 is "session release with break-before-make" or "session release with make-before-break", the message received by AMF 150 includes the following information:

[0191] "SM Context ID or PDU session ID", "N2 SM container("SM Context ID or PDU session ID", "target slice", "cause=OAM or congestion", "N1 SM Container")".

[0192] In one embodiment, if the "indication" of the message received by SMF 160 is "session release with break-before-make", the "N1 SM container" contains the following information:

[0193] "PDU Session Release Command" ("PDU Session ID", "target slice", "session re-establishment request to the same DN", "target slice indication").

[0194] In one embodiment, if the "indication" of the message received by SMF 160 is "session release with make-before-break", the "N1 SM container" contains the following information:

[0195] PDU Session Modification Command('PDU Session ID', 'target slice', 'session re-establishment request to the same DN', 'target slice indication', '[PDU session release timer]').

[0196] Referring to step 615, AMF 150 transmits a message including PDU session command information to UE 110. According to various embodiments of the present invention, the process of AMF 150 transmitting the PDU session command message to UE 110 includes at least one of a process of AMF 150 transmitting information included in an "N2 SM container" to RAN 120 or a process of RAN 120 transmitting information included in an "N1 SM container" to UE 110.

[0197] According to an embodiment, when the response message received from the SMF 160 includes a target slice, the AMF 150 changes slice information for the session among the stored information for the session corresponding to the "SM Context ID" or "PDU session ID" to the target slice. In addition, the AMF 150 transmits information included in the "N2 SM container" to the RAN 120. When the message received from the AMF 150 includes a target slice, the RAN 120 changes slice information for the session among the stored information for the session corresponding to the received "SM Context ID" or "PDU session ID" to the target slice. The RAN 120 transmits the "N1 SM container" to the UE 110. The above-mentioned series of processes is not limited thereto, and the flow of a signal transmitted from the AMF 150 to the UE 110 via the RAN 120 described above is expressed by transmission of a PDU session command message as shown in FIG. 5.

[0198] Referring to step 625, AMF 150 receives a PDU session command Ack (acknowledgment) message from UE 110.

[0199] According to an embodiment, when a message received from the RAN 120 includes "PDU Session ID" and "target slice", the UE 110 changes slice information for the session corresponding to the received "PDU session ID" to the target slice among stored information for the session. The AMF 150 receives a message from the UE 110 via the RAN 120 to confirm that information related to the session has been changed. The above-mentioned series of processes is not limited thereto, and the above-mentioned signal flow transmitted from the UE 110 to the AMF 150 via the RAN 120 may be expressed as transmission of a PDU Session Release Command Ack (acknowledgement) message (or an Ack message for a PDU Session Modification Command) as shown in FIG. 5.

[0200] In one embodiment, when the message received by UE 110 from RAN 120 includes "PDU Session ID", "target slice", "session re-establishment request to the same DN", or "target slice indication", AMF 150 receives a PDU session release request message including the received "PDU Session ID".

[0201] In one embodiment, the AMF 150 receives a PDU session generation request message from the UE 110, which includes a data network name (DNN) such as a PDU session for which the UE 110 has requested release and a target slice that the UE 110 has received from the RAN 120.

[0202] According to one embodiment, when the message received by UE 110 from RAN 120 includes "PDU Session ID", "target slice", "session re-establishment request to the same DN", "target slice indication", or "PDU session release timer", AMF 150 receives a PDU session generation request message including a DNN (data network name) such as a PDU session corresponding to the received PDU session ID and a target slice received by UE 110.

[0203] According to one embodiment, AMF150 receives a PDU session release request message from UE110, the PDU session release request message including the received PDU session ID when a PDU session release timer expires after a new PDU session is generated by UE110 or when the terminal internal setting information determines that the PDU session release timer expires.

[0204] Referring to step 635, the AMF 150 transmits a PDU session update acknowledgement message to the SMF 160. Also, the signal flow transmitted from the AMF 150 to the SMF 160 is represented by the transmission of a PDU session update request Ack (acknowledgement) message, as shown in FIG.

[0205] According to one embodiment, the AMF 150 transmits the PDU session release request message received from the UE 110 to the SMF 160.

[0206] In one embodiment, the AMF 150 transmits the PDU session generation request message received from the UE 110 to the SMF 160.

[0207] FIG. 7 is a flowchart illustrating the operation of an SMF for moving slices for a session in accordance with various embodiments of the present invention.

[0208] Specifically, the operation flow of the SMF 160 shown in FIG. 7 operates based on the signal flow shown in FIG.

[0209] In step 705, the SMF 160 receives an update session management request message from the AMF 150. The message format of the request message received by the SMF 160 uses at least one of "Nsmf_PDUSession_UpdateSMContext Request", "Nsmf_PDUSession_ReleaseSMContext Request", "Nsmf_PDUSession_UpdateSMContext Request", and "Nsmf_PDUSession_ContextPushRequest".

[0210] According to one embodiment, the request message transmitted by the AMF 150 includes at least one of the following information:

[0211] "SM Context ID" or "PDU session ID", "indication", "Cause=OAM or congestion, target slice information".

[0212] However, according to various embodiments of the present invention, the request message received by SMF 160 is not limited to this and may include information other than that described above.

[0213] As described in Figure 3, "SM Context ID" is an identifier that indicates information for each session. "Indication" is set to at least one of the following three: "context modification", "release with make-before-break", and "session release with break-before-make".

[0214] According to one embodiment, the AMF 150 transmitting the request message sets 'indication' to 'context modification' when requesting to modify only information regarding the slice of the corresponding session to the target slice through modification of the existing session without releasing the existing session.

[0215] According to one embodiment, if the PDU session corresponding to the "SM Context ID" or "PDU Session ID" is an SSC (session and service continuity) mode 1 PDU session, AMF150 sets the "Indication" included in the message transmitted to SMF160 to "context modification".

[0216] According to one embodiment, the AMF 150 transmitting the request message sets 'indication' to 'session release with break-before-make' when requesting to release an existing session established in an unavailable slice and generate a new PDU session to a target slice to replace the corresponding session.

[0217] According to one embodiment, the AMF 150 transmitting the request message sets 'indication' to 'session release with make-before-break' when requesting that a new PDU session be generated and then released to a target slice to replace an existing session established in an unavailable slice before releasing the session.

[0218] In step 715, the SMF 160 transmits an update session management response message to the AMF 150. If only the target slice exists in the received message received from the AMF 150 in step 705, the SMF 160 sets the "indication" taking into account the SSC mode for the PDU session, whether it is an MPS session, configuration information, terminal subscriber information, etc.

[0219] According to one embodiment, if the PDU session corresponding to the "SM Context ID" or "PDU Session ID" included in the message received from AMF 150 is an SSC mode 1 PDU session (e.g., a PDU session requesting that no UPF changes be made to the PDU session), SMF 160 sets "indication" to "context modification".

[0220] According to one embodiment, when SMF 160 sets "indication" to "context modification", AMF 150 decides not to release the existing session, but to only change information regarding the slices of the session through modification to the existing session.

[0221] According to one embodiment, if the PDU session corresponding to the "SM Context ID" or "PDU Session ID" included in the message received from the AMF 150 is SSC mode 2 or SSC mode 3, the SMF 160 sets "indication" to "context modification".

[0222] According to one embodiment, if the PDU session corresponding to the "SM Context ID" or "PDU Session ID" included in the message received from AMF 150 is an SSC mode 1 PDU session, SMF 160 does not set "indication" to "session release with make-before-break" or "session release with break-before-make".

[0223] If the target slice is not present in the received message received from AMF 150 in step 705, SMF 160 determines the target slice via configuration information or interaction with AMF 150.

[0224] According to one embodiment, if the SMF 160 decides to move to the target slice, it transmits a response message to the AMF 150. The response message transmitted by the SMF 160 includes information about the target slice. The response message transmitted by the SMF 160 is referred to as an update session management response message.

[0225] Referring to step 715, if the 'indication' of the request message received from AMF 150 is 'context modification', the response message transmitted to AMF 150 includes the following information:

[0226] "SM Context ID or PDU session ID", "target slice", "N2 SM container("SM Context ID or PDU session ID", "target slice", "cause=OAM or congestion", "N1 SM Container")".

[0227] The "N1 SM container" contains the following information:

[0228] "PDU Session Modification Command("PDU Session ID", "target slice")".

[0229] For example, according to one embodiment, if the PDU session corresponding to the "SM Context ID" or "PDU Session ID" included in the message received by SMF 160 from AMF 150 is an SSC mode 1 PDU session, the message transmitted by SMF 160 to UE 110 includes information instructing to change the S-NSSAI (slice identifier) ​​for the PDU session.

[0230] In one embodiment, the N1 SM Container message includes other information identifying the PDU session in addition to the PDU Session ID.

[0231] However, according to various embodiments of the present invention, the response message transmitted by SMF 160 is not limited thereto and may include information other than that described above.

[0232] Referring to step 715, if the 'indication' of the request message received from AMF 150 is 'session release with break-before-make' or 'session release with make-before-break', the message transmitted to AMF 150 includes the following information:

[0233] "SM Context ID or PDU session ID", "N2 SM container("SM Context ID or PDU session ID", "target slice", "cause=OAM or congestion", "N1 SM Container")".

[0234] In one embodiment, if the "indication" of the message received by SMF 160 is "session release with break-before-make", the "N1 SM container" contains the following information:

[0235] "PDU Session Release Command" ("PDU Session ID", "target slice", "session re-establishment request to the same DN", "target slice indication").

[0236] In one embodiment, if the "indication" of the message received by SMF 160 is "session release with make-before-break", the "N1 SM Container" contains the following information:

[0237] PDU Session Modification Command('PDU Session ID', 'target slice', 'session re-establishment request to the same DN', 'target slice indication', '[PDU session release timer]').

[0238] In step 725, the SMF transmits an N4 session modification request message to the UPF. Referring to step 725, when the request message received from the AMF 150 includes a PDU session identifier (or a PDU session context ID) and "indication" set to "context modification", the SMF 160 transmits the N4 session modification request message to the UPF 170. The N4 interface (e.g., an N4 reference point) is an interface formed between the SMF 160 and the UPF 170. The N4 session modification request message transmitted by the SMF 160 to the UPF 170 includes at least one of the N4 session context ID, information on a target slice, an indicator indicating a slice change request, or information indicating a slice change cause.

[0239] In step 735, the SMF receives an N4 session modify response message from the UPF. Referring to step 735, the UPF 170 transmits an N4 session modify response message to the SMF 160 based on the received N4 session modify request message. The N4 session modify response message transmitted by the UPF 170 to the SMF 160 includes at least one of an N4 session context ID or information related to a result. If the SMF 160 receives a response message from the UPF 170 indicating that the slice modification has been successful, the SMF 160 changes the slice information of the N4 session to the target slice.

[0240] According to an embodiment of the present invention, the UPF 170 and the SMF 160 determine whether to change the N4 interface through the processes of steps S535 and S545, and execute the process.

[0241] According to various embodiments of the present invention, a method performed by an access mobility and management function (AMF) node in a mobile communication system includes the steps of receiving a notification message including information regarding an unavailable slice from a slice availability check function (SACF) node, receiving information regarding a protocol data unit (PDU) session from a network data analysis function (NWDAF) node, determining a target slice and at least one PDU session requiring a slice change based on the notification message and the information regarding the PDU session, and transmitting a request message to a session management function (SMF) node to change the slice of the determined at least one PDU session to the target slice.

[0242] In one embodiment, the request message includes information regarding the target slice and an indicator indicating a modification method of at least one PDU session, the modification method including at least one of a first method of modifying the context of at least one PDU session, a second method of setting up one or more PDU sessions after releasing at least one PDU session, or a third method of releasing at least one PDU session after setting up one or more PDU sessions.

[0243] According to one embodiment, when the modification method is the first method, the method further includes a step of receiving a modification command for at least one PDU session from the SMF node, and a step of transmitting the modification command for the at least one PDU session to the terminal.

[0244] According to one embodiment, when the modification method is a second method, the method further includes a step of receiving a PDU session release command from the SMF node, the PDU session release command including information related to the generation of one or more PDU sessions, and a step of transmitting the PDU session release command to the terminal.

[0245] According to one embodiment, when the modification method is a third method, the method further includes a step of receiving from the SMF node a modification command for at least one PDU session, the modification command including information related to the generation of one or more PDU sessions and a timer for the release of the at least one PDU session, and a step of transmitting the modification command for the at least one PDU session to the terminal.

[0246] In one embodiment, the notification message further includes slice change required information, where the slice change required information includes at least one of an indicator instructing a slice change for an unavailable slice or information regarding a target slice for each unavailable slice.

[0247] According to one embodiment, the first scheme corresponds to session and service continuity (SSC) mode 1, the second scheme corresponds to SSC mode 2, and the third scheme corresponds to SSC mode 3.

[0248] According to one embodiment, if at least one PDU session is a Home-routed PDU session, the method further includes a step of generating an H-PLMN single-network slice selection assistance (S-NSSAI) for the target slice based on mapping information between an H(home)-PLMN (public land mobile network) and a V(visited)-PLMN, and a step of transmitting the generated H-PLMN S-NSSAI to the SMF node.

[0249] According to various embodiments of the present invention, a method performed by a session management function (SMF) node in a mobile communication system includes the steps of receiving a request message from an access mobility and management function (AMF) node for changing a slice of at least one protocol data unit (PDU) session to a target slice, and transmitting information regarding the change of at least one PDU session based on the request message to the AMF node, wherein the request message includes information regarding the target slice and an indicator indicating a change manner of the at least one PDU session, and the change manner includes at least one of a first scheme of modifying a context of the at least one PDU session, a second scheme of setting up one or more PDU sessions after releasing at least one PDU session, or a third scheme of releasing at least one PDU session after setting up one or more PDU sessions.

[0250] According to one embodiment, if the change method is a first method, the method further includes a step of transmitting an N4 session modification request message to a user plane function (UPF) node to change information about a slice of the N4 session to information about the target slice.

[0251] According to various embodiments of the present invention, an access mobility and management function (AMF) node in a mobile communication system comprises at least one controller, and the at least one controller is configured to receive a notification message including information regarding an unavailable slice from a slice availability check function (SACF) node, receive information regarding a protocol data unit (PDU) session from a network data analysis function (NWDAF) node, determine a target slice and at least one PDU session that requires a slice change based on the notification message and the information regarding the PDU session, and transmit a request message to a session management function (SMF) node to change the slice of the determined at least one PDU session to the target slice.

[0252] In one embodiment, the request message includes information regarding the target slice and an indicator indicating a modification method of at least one PDU session, the modification method including at least one of a first method of modifying the context of at least one PDU session, a second method of setting up one or more PDU sessions after releasing at least one PDU session, or a third method of releasing at least one PDU session after setting up one or more PDU sessions.

[0253] According to one embodiment, when the modification method is the first method, the at least one controller is further configured to receive a modification command for at least one PDU session from the SMF node and transmit the modification command for the at least one PDU session to the terminal.

[0254] According to one embodiment, when the modification method is a second method, at least one controller is further configured to receive a PDU session release command from an SMF node, the PDU session release command including information related to the generation of one or more PDU sessions, and to transmit the PDU session release command to a terminal.

[0255] According to one embodiment, when the modification method is a third method, the at least one controller is further configured to receive from the SMF node a modification command for at least one PDU session, the modification command including information related to the generation of one or more PDU sessions and a timer for the release of the at least one PDU session, and to transmit the modification command for the at least one PDU session to the terminal.

[0256] In one embodiment, the notification message further includes slice change required information, where the slice change required information includes at least one of an indicator instructing a slice change for an unavailable slice or information regarding a target slice for each unavailable slice.

[0257] According to one embodiment, the first scheme corresponds to session and service continuity (SSC) mode 1, the second scheme corresponds to SSC mode 2, and the third scheme corresponds to SSC mode 3.

[0258] According to one embodiment, if the at least one PDU session is a Home-routed PDU session, the at least one controller is further configured to generate an H-PLMN single-network slice selection assistance (S-NSSAI) for the target slice based on mapping information between an H(home)-PLMN (public land mobile network) and a V(visited)-PLMN, and transmit the generated H-PLMN S-NSSAI to the SMF node.

[0259] According to various embodiments of the present invention, a session management function (SMF) node in a mobile communication system comprises at least one controller, and the at least one controller is configured to receive a request message from an access mobility and management function (AMF) node for changing a slice of at least one protocol data unit (PDU) session to a target slice, and to transmit information regarding the change of at least one PDU session to the AMF node based on the request message, wherein the request message includes information regarding the target slice and an indicator indicating a change manner of the at least one PDU session, and the change manner includes at least one of a first scheme of modifying a context of the at least one PDU session, a second scheme of setting up one or more PDU sessions after releasing at least one PDU session, or a third scheme of releasing at least one PDU session after setting up one or more PDU sessions.

[0260] According to one embodiment, when the change method is a first method, the at least one controller is further configured to transmit an N4 session modification request message to a user plane function (UPF) node to change information about a slice of the N4 session to information about a target slice.

[0261] The methods according to the embodiments described in the claims or specification of the present invention may be implemented in hardware, software, or a combination of hardware and software.

[0262] When implemented in software, a computer-readable recording medium is provided that stores one or more programs (software modules). The one or more programs stored in the computer-readable recording medium are 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 an embodiment of the invention as claimed or described in the specification.

[0263] Such programs (software modules, software) may be recorded in random access memory, non-volatile memory including flash memory, read only memory (ROM), electrically erasable programmable read only memory (EEPROM), magnetic disc storage device, compact disc-ROM (CD-ROM), digital versatile discs (DVDs), other forms of optical storage, magnetic cassette, or in a memory configured as a combination of some or all of them. Also, each of the constituent memories may include multiple pieces.

[0264] The program may be stored in an attachable storage device that is accessed via a communication network such as the Internet, an Intranet, a local area network (LAN), a wide area network (WAN), or a storage area network (SAN), or a combination thereof. Such a storage device may be accessed by an apparatus that executes an embodiment of the present invention via an external port. Also, a separate storage device on the communication network may be accessed by an apparatus that executes an embodiment of the present invention.

[0265] In the above-mentioned specific embodiments of the present invention, the components included in the present specification are expressed as singular or plural according to the specific embodiments presented. However, the expressions singular or plural are selected to suit the presented situation for the convenience of explanation, and the present invention is not limited to singular or plural components, and even components expressed as plural may be composed of singular and even components expressed as singular may be composed of plural.

[0266] Meanwhile, although the detailed description of the present invention has been given with reference to specific embodiments, it is of course possible to make various modifications without departing from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be determined not only by the claims, but also by equivalents to the claims.

[0267] Although the present invention has been described in conjunction with various embodiments, various changes and modifications will be suggested to those skilled in the art, and it is intended that the present invention encompass all such changes and modifications falling within the scope of the appended claims. [Explanation of symbols]

[0268] 100 Communication Network 110 User Equipment (UE) 120 Radio Access Network (RAN) 125 Base Station 130 AF (Application Function) 140 Data network (DN:data network) 150 AMF(access and mobility management function) 151 Authentication server function (AUSF) 153 UDM(unified data management) 155 NEF(network exposure function) 157 UDR(unified data repository) 159 NRF(network repository function) 160 SMF(session management function) 170 UPF (user plane function) 180 PCF(policy and charging function) 190 NSSF(Network Slice Selection Function) 200 Core Network 210, 240 Communications Department 220, 260 control unit 230, 250 storage section 310 SACF(slice availability check network function)

Claims

1. 1. A method performed by an access mobility and management function (AMF) node in a mobile communication system, comprising: receiving a notification message from a slice availability check function (SACF) node, the notification message including information about unavailable slices; receiving information about a protocol data unit (PDU) session from a network data analysis function (NWDAF) node; Determining at least one PDU session that requires a target slice and a slice change based on the notification message and information about the PDU session; and transmitting a request message to a session management function (SMF) node to change a slice of the determined at least one PDU session to the target slice.

2. The request message includes information about the target slice and an indicator indicating a modification manner of the at least one PDU session; 2. The method according to claim 1, wherein the modification scheme includes at least one of a first scheme of modifying a context of the at least one PDU session, a second scheme of setting up one or more PDU sessions after releasing the at least one PDU session, or a third scheme of releasing the at least one PDU session after setting up the one or more PDU sessions.

3. When the change method is the first method, receiving a modification command for the at least one PDU session from the SMF node; 3. The method of claim 2, further comprising the step of: transmitting to a terminal a modification command for the at least one PDU session.

4. When the change method is the second method, receiving a release command for the PDU session from the SMF node, the release command including information related to the creation of the one or more PDU sessions; 3. The method of claim 2, further comprising: transmitting a release command for the PDU session to a terminal.

5. When the change method is the third method, receiving from the SMF node a modification command for the at least one PDU session, the modification command including information related to the generation of the one or more PDU sessions and a timer for release of the at least one PDU session; 3. The method of claim 2, further comprising the step of: transmitting to a terminal a modification command for the at least one PDU session.

6. The notification message further includes slice change required information, 2. The method of claim 1, wherein the information required for the slice change includes at least one of an indicator instructing a slice change for the unavailable slice or information regarding a target slice for each of the unavailable slices.

7. The first method corresponds to SSC (session and service continuity) mode 1, The second method corresponds to SSC mode 2; The method of claim 2 , wherein the third scheme corresponds to SSC mode 3.

8. If the at least one PDU session is a Home-routed PDU session, the method includes: generating a H-PLMN single-network slice selection assistance (S-NSSAI) for the target slice based on mapping information between a H(home)-PLMN (public land mobile network) and a V(visited)-PLMN; and transmitting the generated H-PLMN S-NSSAI to the SMF node.

9. 1. A method performed by a session management function (SMF) node in a mobile communication system, comprising: Receiving a request message from an access mobility and management function (AMF) node to change a slice of at least one protocol data unit (PDU) session to a target slice; and transmitting information regarding the modification of the at least one PDU session based on the request message to the AMF node; The request message includes information about the target slice and an indicator indicating a modification manner of the at least one PDU session; The method, wherein the change method includes at least one of a first method of modifying a context of the at least one PDU session, a second method of setting up one or more PDU sessions after releasing the at least one PDU session, or a third method of releasing the at least one PDU session after setting up the at least one PDU session.

10. When the change method is the first method, 10. The method of claim 9, further comprising transmitting an N4 session modification request message to a user plane function (UPF) node to change information about a slice of an N4 session to information about the target slice.

11. An access mobility and management function (AMF) node in a mobile communication system, comprising: At least one controller, The at least one controller receiving a notification message from a slice availability check function (SACF) node, the notification message including information about an unavailable slice; Receive information about a protocol data unit (PDU) session from a network data analysis function (NWDAF) node; Determine a target slice and at least one PDU session that requires a slice change based on the notification message and information about the PDU session; The AMF node is configured to transmit a request message to a session management function (SMF) node for changing a slice of the determined at least one PDU session to the target slice.

12. The request message includes information about the target slice and an indicator indicating a modification manner of the at least one PDU session; 12. The AMF node according to claim 11, wherein the modification method includes at least one of a first method of modifying a context of the at least one PDU session, a second method of setting up one or more PDU sessions after releasing the at least one PDU session, or a third method of releasing the at least one PDU session after setting up the at least one PDU session.

13. When the change method is a first method, the at least one controller receiving a modification command for the at least one PDU session from the SMF node; The AMF node of claim 12, further configured to transmit a modification command for the at least one PDU session to a terminal.

14. When the change method is a second method, the at least one controller Receive a release command for the PDU session from the SMF node, the release command including information related to the creation of the one or more PDU sessions; The AMF node of claim 12, further configured to transmit a release command for the PDU session to a terminal.

15. When the change method is a third method, the at least one controller receiving from the SMF node a modification command for the at least one PDU session, the modification command including information related to the generation of the one or more PDU sessions and a timer for release of the at least one PDU session; The AMF node of claim 12, further configured to transmit a modification command for the at least one PDU session to a terminal.

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