Method and apparatus for supporting network slice changes in wireless communication systems

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 Art

[0002] 5G mobile communication technology defines a wide frequency band to enable rapid transmission speeds and new services, and can be implemented not only in frequency bands below 6 GHz such as 3.5 gigahertz (3.5 GHz) ("Sub 6 GHz"), but also in extremely high frequency bands called millimeter waves (mmWave) such as 28 GHz and 39 GHz ("Above 6 GHz"). Also, in the case of 6G mobile communication technology, which is called a system after 5G communication (Beyond 5G), implementation in the terahertz (THz) band (for example, the band from 95 GHz to 3 terahertz (3 THz)) is considered to achieve a transmission speed 50 times faster and an ultra-low (Ultra Low) latency time reduced to one-tenth compared to 5G mobile communication technology.

[0003] In the early stages of 5G mobile communication technology, the goal was to meet the service support and performance requirements for enhanced Mobile Broadband (eMBB), Ultra-Reliable Low-Latency Communications (URLLC), and massive Machine-Type Communications (mMTC). This included beamforming and Massive MIMO to mitigate path loss and increase transmission distance in the ultra-high frequency band, dynamic operation of various numerology support (such as operation of multiple subcarrier spacings) and slot formats for efficient utilization of ultra-high frequency resources, multiplex beam transmission, and initial access technologies to support broadband, definition and operation of Band-Width Parts (BWP), new channel coding methods such as Low Density Parity Check (LDPC) codes for high-capacity data transmission and Polar Code for reliable transmission of control information, and L2 pre-processing (L2 Standardization efforts were made for pre-processing and network slicing, which provides dedicated networks for specific services.

[0004] Currently, discussions are underway to improve and enhance the performance of early 5G mobile communication technologies, taking into account the services that 5G mobile communication technologies were intended to support. Physical layer standardization is progressing for technologies such as V2X (Vehicle-to-Everything), which assists autonomous vehicles in making driving decisions based on their own location and status information transmitted by the vehicle and increases user convenience; NR-U (New Radio Unlicensed), which aims for system operation that complies with various regulatory requirements on the unlicensed spectrum; NR terminal power saving technology (UE Power Saving); Non-Terrestrial Network (NTN), which is direct terminal-satellite communication to ensure coverage in areas where communication with terrestrial networks is impossible; and positioning.

[0005] Furthermore, standardization is underway in the field of wireless interface architecture / protocols for technologies such as Industrial Internet of Things (IIoT) to support new services through collaboration and convergence with other industries, Integrated Access and Backhaul (IAB) which provides nodes for network service area expansion by integrating support for wireless backhaul links and access links, Mobility Enhancement including Conditional Handover and Dual Active Protocol Stack (DAPS) handover, and 2-step RACH for NR which simplifies random access procedures. Standardization is also underway in the field of system architecture / services for 5G baseline architectures (e.g., Service-based Architecture, Service-based Interface) for the combination of Network Functions Virtualization (NFV) and Software-Defined Networking (SDN) technologies, and Mobile Edge Computing (MEC) which provides services based on the location of the terminal.

[0006] With the commercialization of such 5G mobile communication systems, it is expected that the explosively increasing number of connected devices will be connected to the communication network. Consequently, it is anticipated that enhancements to the functionality and performance of 5G mobile communication systems and the integrated operation of connected devices will be necessary. To this end, new research is planned on improving 5G performance and reducing complexity using Extended Reality (XR), Artificial Intelligence (AI), and Machine Learning (ML) to efficiently support Augmented Reality (AR), Virtual Reality (VR), and Mixed Reality (MR), as well as AI service support, metaverse service support, and drone communication.

[0007] Furthermore, the development of such 5G mobile communication systems could serve as the basis for the development of new technologies for 6G mobile communication, including new waveforms to guarantee terahertz band coverage, multiplex antenna transmission technologies such as Full Dimensional MIMO (FD-MIMO), array antennas, and large-scale antennas, metamaterial-based lenses and antennas to improve terahertz band signal coverage, high-dimensional spatial multiplexing technologies using Orbital Angular Momentum (OAM), and Reconfigurable Intelligent Surface (RIS) technologies, as well as full duplex technologies to improve the frequency efficiency and system network of 6G mobile communication technologies, satellites, AI (artificial intelligence) from the design stage, AI-based communication technologies that integrate end-to-end AI support functions to optimize the system, and next-generation distributed computing technologies that realize services of a complexity exceeding the limits of terminal computing power by utilizing ultra-high-performance communication and computing resources.

[0008] As described above, with the development of wireless communication systems, congestion may occur among various 5G network entities belonging to a network slice for each PDU (protocol data unit) session, or it may be necessary to temporarily or permanently suspend access to a specific slice for operational reasons. In particular, there is a need for a method to determine a target slice when a situation is detected where application performance is degrading and it is necessary to temporarily or permanently suspend access to that slice, and a method to move PDU sessions belonging to a specific slice to the target slice. [Overview of the Initiative] [Problems that the invention aims to solve]

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

[0010] To achieve the above objective, a method performed by an AMF (access mobility and management function) node in a mobile communication system according to one aspect of the present invention includes the steps of: receiving a notification message from a SACF (slice availability check function) node containing information about an unavailable slice; receiving information about a PDU (protocol data unit) session from an NWDAF (network data analysis function) 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 an SMF (session management function) node to change the slice of the determined at least one PDU session to the target slice.

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

[0012] To achieve the above objective, an AMF (access mobility and management function) node in a mobile communication system according to one aspect of the present invention comprises at least one controller, the at least one controller receiving notification messages from a SACF (slice availability check function) node containing information about unavailable slices, receiving information about PDU (protocol data unit) sessions from an NWDAF (network data analysis function) node, determining a target slice and at least one PDU session that requires a slice change based on the notification messages and the information about the PDU sessions, and transmitting a request message to an SMF (session management function) 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, an SMF (session management function) node in a mobile communication system comprises at least one controller, the at least one controller is configured to receive a request message from an AMF (access mobility and management function) node to change a slice of at least one PDU (protocol data unit) session to a target slice, and to transmit to the AMF node information regarding the change of the at least one PDU session based on the request message, the request message comprising information regarding the target slice and an indicator indicating a method for changing the at least one PDU session, the change method comprising at least one of a first method for modifying the context of the at least one PDU session, a second method for setting up one or more PDU sessions after releasing the at least one PDU session, or a third method for releasing the at least one PDU session after setting up one or more PDU sessions. [Effects of the Invention]

[0014] According to the present invention, services in a wireless communication system can be effectively provided, and when a situation is detected in which the performance of an application in the wireless communication system deteriorates and it is necessary to temporarily or permanently suspend use of the affected slice, a target slice can be determined, and PDU (protocol data unit) sessions 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 can be clearly understood by a person with ordinary skill in the art to which the present invention pertains from the following description. [Brief explanation of the drawing]

[0016] [Figure 1] This figure shows a communication network including a core network entity in a wireless communication system according to various embodiments of the present invention. [Figure 2A] This figure shows a wireless environment, including a core network, in a wireless communication system according to various embodiments of the present invention. [Figure 2B] This figure shows the configuration of the core network entity in a wireless communication system according to various embodiments of the present invention. [Figure 2C] This figure shows the configuration of a terminal in a wireless communication system according to various embodiments of the present invention. [Figure 3] This figure shows the signal flow for requesting slice movement according to various embodiments of the present invention. [Figure 4] This flowchart shows the operation flow of the AMF for requesting slice movement according to various embodiments of the present invention. [Figure 5] This figure shows the signal flow for moving slices to a session according to various embodiments of the present invention. [Figure 6] This flowchart shows the operation flow of the AMF for moving slices to a session according to various embodiments of the present invention. [Figure 7] This flowchart shows the flow of SMF operation for moving slices to a session according to various embodiments of the present invention. [Modes for carrying out the invention]

[0017] Hereinafter, specific examples of embodiments for carrying out the present invention will be described in detail with reference to the drawings. Here, the same reference numerals indicate the same parts.

[0018] Before understanding the following detailed description, it is advantageous to clarify the definitions of certain words and phrases used throughout this specification. The terms "include" and "comprise" and their derivatives mean "including" without limitation, the term "or" is inclusive and means "and / or", and the phrases "associated with" and "associated therewith" and their derivatives mean including, encompassing, interconnected, included within, connected, combined, communicable, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, etc. The term "controller" means all devices, systems, or parts thereof that control at least one operation, and such devices are implemented in hardware, firmware, software, or a combination of at least two of them. It should be noted that the functions associated with a particular controller may be centralized or decentralized 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 on a computer-readable recording medium. The terms "application" and "program" refer to one or more computer programs, software components, sets of instructions, procedures, functions, objects, classes, instances, related data, or portions thereof adapted to be implemented by appropriate 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 disc (CD), digital video disc (DVD), or any other type of memory. The "non-transitory" computer-readable recording medium excludes wired, wireless, optical, or other communication links that transmit transient electrical or other signals. Non-transitory computer-readable recording media include media that permanently store data and media that store data and can be rewritten later, such as rewritable optical discs or erasable memory devices.

[0020] Throughout this specification, definitions are provided for specific words or phrases, and those skilled in the art should understand that such definitions, in most cases if not all, are also applicable to the previous or future use of the words and phrases so defined.

[0021] The figures 1 to 7 described below and the various embodiments used to explain the principles of the present invention in this specification 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 be able to understand that the principles of the present invention can be implemented in a system or device appropriately arranged.

[0022] The terms used herein are used solely to describe specific embodiments and are not intended to limit the scope of other embodiments. Singular expressions include plural expressions unless the context clearly indicates a different meaning. Terms used herein, including technical or scientific terms, have the same meaning as those generally understood by a person of ordinary skill in the art described herein. Terms used herein that are defined in a general dictionary are to be interpreted as having the same or similar meaning as their meaning in the context of the relevant art, and not as ideal or overly formal unless explicitly defined herein. In some cases, even terms defined herein cannot be construed as excluding embodiments of the present invention.

[0023] In the various embodiments of the present invention described below, hardware approaches are described as examples. However, since the various embodiments of the present invention include techniques that use both hardware and software, the various embodiments of the present invention do not exclude software-based approaches.

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

[0025] Various embodiments of the present invention enable the AMF (access and mobility management function) in a 5G system to receive information about a specific slice that needs to be moved and to perform appropriate processing on that slice. The AMF also sets the optimal target slice by considering requirements for the PDU (protocol data unit) session and slice status information.

[0026] Furthermore, the apparatus and methods according to various embodiments of the present invention enable the AMF to determine the slice movement method by considering the requirements for the PDU session and the reasons why slice movement is necessary, 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] The terms used in the following description to refer to signals, channels, control information, network entities, and device components are illustrative examples for the sake of clarity. Therefore, the present invention is not limited to the terms described below, and other terms with equivalent technical meanings may be used.

[0028] Although this invention describes various embodiments using terminology used in certain communication standards (e.g., 3GPP® (3rd Generation Partnership Project)), these are merely illustrative examples. Various embodiments of this invention can be easily modified and applied to other communication systems.

[0029] Figure 1 shows 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 comprises a 5G UE (user equipment) 110, a 5G RAN (radio access network) 120, and a 5G core network.

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

[0032] Referring to Figure 1, the user equipment (UE) 110 communicates via a radio channel, i.e., an access network, formed with a base station (e.g., eNB, gNB). In some embodiments, the terminal 110 is a device used by a user and configured to provide a user interface (UI). For example, the UE 110 is an equipment terminal mounted on a vehicle for driving. In other embodiments, the terminal 110 is a device that performs machine-type communication (MTC) without user involvement, or an autonomous vehicle. In addition to being an electronic device, the UE is also referred to as "terminal," "vehicle terminal," "user equipment (UE)," "mobile station," "subscriber station," "remote terminal," "wireless terminal," or "user device," or other terms with equivalent technical meaning. In addition to UEs, customer-premises equipment (CPE) or dongle-type terminals can also be used as terminals. Customer-premises equipment, like UEs, is connected to NG-RAN nodes and also provides networking to other communication equipment (e.g., laptops).

[0033] Referring to Figure 1, the AMF150 provides connectivity and mobility management functions on a per-terminal 110 basis, with essentially one AMF150 connected to each terminal 110. Specifically, the AMF150 performs at least one of the following functions: core network node signaling for mobility between 3GPP® access networks, inter-wireless access network (e.g., 5G RAN) interface (N2 interface), NAS signaling with terminal 110, SMF160 identification, and providing transmission of session management (SM) messages between terminal 110 and SMF160. Some or all of the functions of the AMF150 are supported within a single instance of one AMF150.

[0034] Referring to Figure 1, the SMF160 provides session management functionality, and if terminal 110 has multiple sessions, each session is managed by a different SMF160. Specifically, the SMF160 performs at least one of the following functions: session management (e.g., session establishment, modification, and termination, including maintaining the tunnel between UPF170 and the access network node), selection and control of UP (user plane) functionality, traffic steering configuration for routing traffic to the appropriate destination on UPF170, termination of the SM portion of NAS messages, downlink data notification (DDN), and initiator of AN-specific SM information (e.g., transmission to the access network via the N2 interface through AMF150). Some or all of the functions of the SMF160 are supported within a single instance of one SMF160.

[0035] In 3GPP® systems, conceptual links connecting NFs within a 5G system are sometimes referred to as reference points. Reference points are also sometimes referred to as interfaces. The following are examples of reference points included in the 5G system architecture shown in Figures 1 to 5.

[0036] -N1: Reference point between UE110 and AMF150 -N2:(R)Reference point between AN120 and AMF150 -N3:(R)Reference point between 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 UPF170s -N10: Reference point between UDM153 and SMF160 -N11: Reference point between AMF150 and SMF160 -N12: Reference point between AMF150 and authentication server function (AUSF)151 -N13: Reference point between UDM153 and authentication server function 151 -N14: Reference point between two AMF150s -N15: Reference point between PCF180 and AMF150 in non-roaming scenarios, and reference point between PCF180 and AMF150 within the visited network in roaming scenarios.

[0037] Figure 2A shows a wireless environment including a core network 200 in a wireless communication system according to various embodiments of the present invention.

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

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

[0040] The core network 200 is a network that manages the entire system, controlling the wireless connectivity network 120 and processing data and control signals for terminals 110 transmitted and received via the wireless connectivity network 120. The core network 200 performs various functions such as user plane and control plane control, mobility processing, subscriber information management, billing, and coordination with other types of systems (e.g., LTE (Long Term Evolution) system). 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 function (UDM) 153, a network exposure function (NEF) 155, and a unified data repository (UDR) 157.

[0041] Terminal 110 is connected to the wireless connection network 120 and to the AMF150, which performs the mobility management function of the core network 200. The AMF150 is a function or device that is responsible for all aspects of the wireless connection network 120 connection and the mobility management of terminal 110. The SMF160 is an NF that manages sessions. The AMF150 is connected to the SMF160, and the AMF150 routes session-related messages to terminal 110 to the SMF160. The SMF160 is connected to the UPF170 to allocate user plane resources provided to terminal 110 and establish a tunnel for data transfer between base station 125 and UPF170. The PCF180 controls information related to the policy and charging for the session used by terminal 110. The NRF159 holds information about NFs installed in the mobile carrier network and performs the function of informing about the held information. The NRF159 is connected to all NFs. When each NF starts operating on the carrier network, it registers with the NRF159 to inform the NRF159 that the NF is operating within the network. The UDM153 is an NF that performs a role similar to the HSS (home subscriber server) of a 4G network, and holds the subscription information of terminal 110 or the context used by terminal 110 within the network.

[0042] NEF155 plays the role of connecting third-party servers with NFs within the 5G mobile communication system. It also plays the role of providing, updating, or obtaining data from UDR157. UDR157 performs functions such as holding subscriber information of terminal 120, holding policy information, holding data that is exposed externally, and holding information necessary for third-party applications. UDR157 also plays the role of providing the held data to other NFs.

[0043] Figure 2B shows the configuration of the core network entity in a wireless communication system according to various embodiments of the present invention.

[0044] The configuration 200 illustrated in Figure 2B is understood as a device configuration having at least one of the functions of 150, 153, 155, 157, 160, 170, 180, and 190 in Figure 1. The terms "...part," "...device," etc., used below refer to a unit that processes at least one function or operation, which may be implemented in hardware, software, or a combination of hardware and software.

[0045] Referring to Figure 2B, the core network entity is comprised of 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. Specifically, the communication unit 210 converts bit sequences transmitted from the core network entity to other devices into physical signals and converts physical signals received from other devices into bit sequences. In other words, the communication unit 210 transmits and receives signals. Therefore, the communication unit 210 is referred to as a modem, transmitter, receiver, or transceiver. In this context, the communication unit 210 enables the core network entity to communicate with other devices or systems via a backhaul connection (e.g., wired backhaul or wireless backhaul) or through the 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 composed of volatile memory, non-volatile memory, or a combination of volatile and non-volatile memory. The storage unit 230 then provides the stored data in response to requests from the control unit 220.

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

[0049] Figure 2C shows the configuration of a terminal in a wireless communication system according to various embodiments of the present invention.

[0050] The configuration illustrated in Figure 2C is understood to be the configuration of terminal 110. The terms "...part" and "...device" used below refer to a unit that processes at least one function or operation, which is implemented in hardware, software, or a combination of hardware and software.

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

[0052] The communication unit 240 performs functions for transmitting and receiving signals via a wireless channel. For example, the communication unit 240 performs a conversion function between a baseband signal and a bit sequence in accordance with the system's physical layer specifications. For example, when transmitting data, the communication unit 240 generates a complex symbol by encoding and modulating the transmitted bit sequence. When receiving data, the communication unit 240 restores the received bit sequence by demodulating and decoding the baseband signal. The communication unit 240 also upconverts the baseband signal to an RF band signal and transmits it via the antenna, and downconverts the RF band signal received via the antenna back to a baseband signal. For example, the communication unit 240 includes a transmit filter, a receive filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, and so on.

[0053] Furthermore, the communication unit 240 includes numerous transmit and receive paths. In addition, the communication unit 240 includes at least one antenna array composed of numerous antenna elements. From a hardware perspective, the communication unit 240 consists of digital and analog circuits (e.g., RFIC (radio frequency integrated circuit)). Here, the digital and analog circuits can be implemented as a single package. The communication unit 240 also includes numerous 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 the "transmitting unit," the "receiving unit," or the "transmitting / receiving unit." In the following explanation, transmission and reception via the wireless channel are used to mean that the communication unit 240 performs the processing described above.

[0055] The storage unit 250 stores data such as basic programs for terminal operation, application programs, and configuration information. The storage unit 250 is composed of volatile memory, non-volatile memory, or a combination of volatile and non-volatile memory. The storage unit 250 then provides the stored data in response to requests 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 from the storage unit 250. Furthermore, the control unit 260 performs the functions of the protocol stack required by the communication standard. To this end, the control unit 260 includes at least one processor or microprocessor, or is part of a processor. Also, part of the communication unit 240 and the control unit 260 are referred to as the CP (communication processor). 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 later.

[0057] The terms used in the following description to identify connected nodes, network entities, messages, inter-network entity interfaces, and various identification information are illustrative examples for illustrative purposes only. Therefore, this specification does not limit itself to the terms described below, but uses other terms with equivalent technical meanings.

[0058] For the sake of clarity, this specification uses terms and names defined in the 5GS (5G system) and NR (new radio) standards, which are the most recent standards defined by the 3GPP® organization among 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 under other standards. In particular, the present invention applies to 3GPP® fifth-generation mobile communication standards (e.g., 5GS and NR).

[0059] In 5G systems, there is a technology called Session and Service Continuity (SSC) Mode that supports session continuity with the aim of improving the user's QoE (quality of experience) or supporting Mission Critical services. SSC consists of three modes. Of these, SSC mode 3 is called Make-Before-Break. When network 200 determines that it is necessary to terminate the SSC mode 3 PDU session that terminal 110 is using, it establishes a new PDU session to replace the PDU session in question. Network 200 also supports session continuity by terminating the existing PDU session. Terminal 110 maintains session continuity by transferring the traffic flow that was being sent and received through the existing PDU session to the new PDU session before the existing PDU session is terminated.

[0060] Network slicing in 5G systems refers to a technology and structure that enables access to several virtualized, independent logical networks within a single physical network. Network operators configure virtual end-to-end networks called network slices to provide services that meet the specific requirements of services / applications. Network slices are distinguished by an identifier called S-NSSAI (single-network slice selection assistance information). Network operators provide network slices to terminals to enable them to receive services.

[0061] Specifically, in a 5G system, when terminal 110 registers with the network, it transmits identifier information for the network slice it wishes to request (e.g., Requested S-NSSAIs) to the AMF 150. Upon receiving the identifier information, the AMF 150 provides terminal 110 with information about the network slices that terminal 110 can use (e.g., Allowed NSSAIs), taking into account the Requested S-NSSAIs and subscriber information. Even if terminal 110 does not provide information about the slice it requests, the AMF 150 can still provide Allowed NSSAIs to terminal 110. In this case, Allowed NSSAIs include information about the basic configured slice (e.g., Default Configured NSSAI) and information about the default configured slices among the subscriber slices included in the terminal subscriber information (e.g., Default Subscribed S-NSSAIs).

[0062] If no slices are included in Allowed NSSAI (for example, if Default Configured NSSAI and Default Subscribed S-NSSAIs do not exist or are unavailable), AMF150 transmits a network registration rejection message to terminal 110 along with a cause code indicating that registration is rejected due to the absence of available slices.

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

[0064] On the other hand, terminal 110 selects one of the allowed slices (Allowed NSSAIs) to send and receive data to a specific data network (DN) 140 via the allowed slices. Terminal 110 also requests the creation of a PDU (packet data unit) session to the specific DNN (data network name) on the selected slice and sends and receives data via the created PDU session. The PDU session consists of several traffic flows, which are composed of two types: GBR QoS Flow (guaranteed bitrate quality-of-service flow) and non-GBR QoS Flow.

[0065] On the other hand, in a 5G system, congestion may occur on a slice, or operational reasons (e.g., OAM (operations, administration, and maintenance)) may occur on a particular slice. Due to congestion or operational reasons, some slices that terminal 110 has already established and is using with PDU sessions may become unusable or experience performance degradation even if they are used. In this case, a 5G system requires a method to move existing PDU sessions belonging to the affected slice to another slice (e.g., a target slice). At this time, the slice(s) to be moved and the target slice(s) must be determined adaptively for each terminal, and the continuity of the session must be guaranteed.

[0066] According to various embodiments of the present invention, a method is proposed for detecting situations in a 5G system where congestion has occurred between various 5G network entities belonging to a network slice for each PDU session (e.g., network slice congestion), or where it is necessary to temporarily or permanently suspend access to a specific slice for operational reasons (e.g., in the case of OAM), resulting in a decrease in the performance of an application or service. Furthermore, a method is proposed for determining a target slice when it is necessary to temporarily or permanently suspend access to the relevant slice, and for moving all or part of the PDU sessions belonging to a specific slice to the target slice.

[0067] According to various embodiments of the present invention, if it is necessary to temporarily or permanently interrupt the use of a slice(s), the SACNF (slice availability check network function) 310 determines such a situation. The SACNF 310 informs the AMF 150 of the information regarding the slice(s) that need to be moved, and the AMF 150 determines the PDU session and target slice(s) that need to be moved.

[0068] According to one embodiment, the AMF150 requests the SMF160 to move some or all of the sessions established through unusable slices to a target slice. The request for movement can be made in three types:

[0069] In one embodiment using an existing session (for example, a context modification method), only the context of the session in question is updated (e.g., only the slice information is changed to the target slice). Session context update procedures are performed in AMF150, SMF160, RAN120, UE110, and UPF170.

[0070] According to this embodiment, continuity is supported by using an existing session as is through method 1).

[0071] In one embodiment (e.g., break-before-make) where a new session is generated after an existing session is released, the existing session is released and a new PDU session is generated on the target slice.

[0072] According to this embodiment, traffic flow that was previously sent to an existing session is now sent through a new PDU session, thus supporting continuity.

[0073] In one embodiment where an existing session is released after a 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 going to the existing session is sent through the new PDU session, thus supporting continuity.

[0074] According to one embodiment, after a new session is established, the existing session is terminated.

[0075] Figure 3 shows the signal flow for requesting slice movement according to various embodiments of the present invention.

[0076] Specifically, Figure 3 illustrates the procedure by which the AMF150 receives information related to unavailable slices via the Slice Availability Check Function (SACF)310, and requests the determination of a target slice for the session and a move to the target slice. Referring to Figure 3, SACF310 is also referred to as SACNF (slice availability check network function).

[0077] According to one embodiment, SACF310 is located in at least one entity from among AMF150, Application Function (AF)130, Radio Access Network (RAN)120, Network Slice Selection Function (NSSF)190, Network Data Analytics Function (NWDAF) (not shown), OAM (not shown), PCF180, or UDM153 (for example, including at least one entity). OAM is one of the entities that manage network resources (e.g., resource monitoring and resource allocation for NF, NF life cycle management, etc.) (for example, network slice management function (NSMF), communication service management function (CSMF) belonging to operation support systems / business support systems (OSS / BSS), or network function virtualization orchestrator (NFVO) belonging to management and orchestration (MANO)). However, according to various embodiments of the present invention, SACF310 may exist in the network as a separate entity.

[0078] In step S305, the AMF150 receives a notification message (for example, a notification message) from the SACF310.

[0079] Referring to step S315, the AMF150 determines which slices are unavailable due to OAM or congestion based on information or configuration information provided by the network administrator, or based on notification messages received from the SACF310.

[0080] According to one embodiment, the notification message received from the Slice Availability Check NF310 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 the AMF150 is not limited to this and may include information other than that described above.

[0083] "Unavailable slice(s)" contains identifier information for the unavailable (or moving) slice(s). "List of Tracking Areas (TAs)" contains information indicating the region where the unavailable slice(s) are unavailable. "Cause" contains information about the reason why the slice(s) are unavailable (e.g., congestion or OAM).

[0084] According to one embodiment, the "slice change required information" (for example, information necessary for slice changes) includes at least one of the following: an indicator that instructs a slice change for unavailable slice(s), or target slice information for each slice belonging to the unavailable slice(s).

[0085] Referring to step S315, if the "cause" of the message received from SACF310 for PDU sessions belonging to the determined unavailable slice(s) is Congestion, AMF150 receives congestion control experience data for each terminal or slice (e.g., S-NSSAI) and DNN (data network name) for the PDU sessions belonging to the Unavailable slice(s) determined by the Network Data Analytics Function (NWDAF). Based on the received experience data, AMF150 determines which PDU sessions should be moved to another slice.

[0086] Referring to step S325, if AMF150 receives a message from SACF310 in step S315, it initiates a procedure to move all or part of the PDU sessions belonging to the unavailable slice(s) (for example, the sessions determined in step S315) to the target slice(s).

[0087] According to one embodiment, the AMF150 releases an existing session established on an unavailable slice. The AMF150 requests the creation of a new PDU session to the target slice to replace the released session (e.g., by changing the PDU session ID).

[0088] According to one embodiment, the AMF150 requests that the target slice be modified only with information about the slice of the existing session, without canceling the existing session.

[0089] According to one embodiment, when determining a target slice, the AMF150 takes into account the slice information and Allowed NSSAI supported by the SMF160 managing the session.

[0090] According to one embodiment, when the AMF150 determines a target slice, it requests and receives the following information from the relevant NF, and then considers this information when determining the target slice.

[0091] This includes "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," and "slice change required information received from SACF."

[0092] Referring to step S335, AMF150 transmits a request message to SMF160 to move the PDU session whose slice move was determined in step S315 to the target slice determined in step S325. The request message transmitted by AMF150 is called an update session management request message. The message format of the request message transmitted by AMF150 uses at least one of the following: "Nsmf_PDUSession_UpdateSMContext Request", "Nsmf_PDUSession_ReleaseSMContext Request", "Nsmf_PDUSession_UpdateSMContext Request", or "Nsmf_PDUSession_ContextPushRequest".

[0093] According to one embodiment, the request message transmitted by the AMF150 includes at least one of the following pieces of 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 the AMF150 is not limited to this and may include information other than that described above.

[0096] The "SM Context ID" is an identifier that shows information specific to each session. The "Indication" (for example, a directive) is set to at least one of three options: "context modification", "release with make-before-break", or "session release with break-before-make".

[0097] According to one embodiment, when the AMF150 requests to modify only the slice information of the session in question to the target slice via modification of the existing session, without releasing the existing session, it sets "indication" to "context modification".

[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 AMF150 sets the "Indication" included in the message transmitted to the SMF160 to "context modification".

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

[0100] According to one embodiment, when the AMF150 requests to generate a new PDU session to a target slice to replace an existing session established on an unavailable slice before releasing the existing session, it sets "indication" to "indication session release with make-before-break" (or "session release with make-before-break").

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

[0102] According to one embodiment, if the "indication" of the message received in step S335 is "release with break-before-make", the 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 said session.

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

[0104] According to various embodiments of the present invention, the SMF160 that has performed the relevant procedure informs the AMF150 of the processing result.

[0105] Figure 4 is a flowchart of the operation of the AMF150 for requesting slice movement according to various embodiments of the present invention.

[0106] Specifically, the operation flow of the AMF150 shown in Figure 4 operates based on the signal flow shown in Figure 3.

[0107] In step 405, the AMF150 receives a notification message from the SACF310.

[0108] According to one embodiment, SACF310 is referred to as SACNF310.

[0109] According to one embodiment, SACF310 is located in at least one entity from among AMF150, Application Function (AF)130, Radio Access Network (RAN)120, Network Slice Selection Function (NSSF)190, Network Data Analytics Function (NWDAF) (not shown), OAM (operations, administration and maintenance) (not shown), PCF180, or UDM153. However, according to various embodiments of the present invention, SACF310 may be formed as an entity other than those exemplified above, without limitation.

[0110] According to one embodiment, the notification message received from SACN310 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 the AMF150 is not limited to this and may include information other than that described above.

[0113] "Unavailable slice(s)" contains identifier information for the unavailable (or moving) slice(s). "List of Tracking Areas (TAs)" contains information indicating the region where the unavailable slice(s) are unavailable. "Cause" contains information about the reason why the slice(s) are unavailable (e.g., congestion or OAM).

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

[0115] In step 415, the AMF150 determines which slices are unavailable and which PDU sessions to modify based on the received notification messages.

[0116] According to one embodiment, the AMF150 determines slices that are unavailable due to OAM or congestion based on information or configuration information provided by the network administrator, or based on notification messages received from the SACF310.

[0117] According to one embodiment, if the "cause" of a message received from SACF310 for a PDU session belonging to a determined unavailable slice(s) is Congestion, AMF150 receives congestion control experience data for each terminal, or for each slice (e.g., S-NSSAI) and DNN (data network name) for the PDU session belonging to the determined unavailable slice(s). Based on the received experience data, AMF150 determines which PDU sessions should be moved to another slice.

[0118] In step 425, the AMF150 determines the target slice(s) of the PDU session to be modified.

[0119] According to one embodiment, when the AMF150 receives a message from the SACF310, it initiates a procedure to move all or part of the PDU sessions belonging to the unavailable slice(s) (for example, the sessions determined in step 415) to the target slice(s).

[0120] According to one embodiment, the AMF150 releases an existing session established on an unavailable slice. The AMF150 requests the creation of a new PDU session on the target slice to replace the released session (e.g., by changing the PDU session ID). According to another embodiment, the AMF150 does not release the existing session, but requests that only the slice information of the session be modified on the target slice via a modification of the existing session.

[0121] According to one embodiment, when the AMF150 determines the target slice, it takes into account the slice information and Allowed NSSAI supported by the SMF160 that manages the session in question.

[0122] According to one embodiment, when determining the target slice, the AMF150 requests and receives the following information from the relevant NF, and then considers this information when determining the target slice.

[0123] This includes "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, the AMF150 transmits an update session management request message to the SMF160.

[0125] According to one embodiment, the AMF150 transmits a request message to the SMF160 to move the PDU session whose slice movement was determined in step 415 to the target slice determined in step 425.

[0126] According to one embodiment, the request message transmitted by the AMF150 is referred to as an update session management request message. The message format of the request message transmitted by the AMF150 uses at least one of the following: "Nsmf_PDUSession_UpdateSMContext Request", "Nsmf_PDUSession_ReleaseSMContext Request", "Nsmf_PDUSession_UpdateSMContext Request", or "Nsmf_PDUSession_ContextPushRequest". According to one embodiment, the request message transmitted by the AMF150 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 the AMF150 is not limited to this and may include information other than that described above.

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

[0130] According to one embodiment, when the AMF150 requests to modify only the slice information of the session in question to the target slice via modification of the existing session, without releasing the existing session, it sets "indication" to "context modification".

[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 AMF150 sets the "Indication" included in the message transmitted to the SMF160 to "context modification".

[0132] According to one embodiment, when the AMF150 requests to break an existing session established on an unavailable slice and generate a new PDU session on a target slice to replace that session, it sets "indication" to "indication session release with break-before-make".

[0133] According to one embodiment, when the AMF150 requests to generate a new PDU session to a target slice to replace an existing session established on an unavailable slice before releasing the existing session, it sets "indication" to "indication session release with make-before-break".

[0134] Figure 5 shows the signal flow for moving slices to a session according to various embodiments of the present invention.

[0135] Specifically, Figure 5 shows the procedure by which SMF160 moves the slice to a session according to the received move method when it receives a slice move request for a session from AMF150.

[0136] In step S515, the AMF150 transmits a request message to the SMF160 to request a slice move for the PDU session. The message format of the request message transmitted by the AMF150 is at least one of the following: "Nsmf_PDUSession_UpdateSMContext Request", "Nsmf_PDUSession_ReleaseSMContext Request", "Nsmf_PDUSession_UpdateSMContext Request", and "Nsmf_PDUSession_ContextPushRequest". According to one embodiment, the request message transmitted by the AMF150 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 the connection established between the SMF160 and AMF150 for each PDU session. "Target slice information" includes target slice identifier information (e.g., S-NSSAI) for the target slice (e.g., a newly determined slice for the PDU session). In this case, if the PDU session corresponding to the SM Context ID or PDU session ID is a home-routed PDU session, the AMF150 transmits the V-PLMN (visited public land mobile network) S-NSSAI and H-PLMN (home public land mobile network) S-NSSAI for the target slice (e.g., a newly determined slice) in the "target slice information". When deriving the H-PLMN S-NSSAI, the AMF150 utilizes slice mapping information between the H-PLMN and V-PLMN. The above description also applies to the various embodiments shown in Figures 6 and 7.

[0139] According to one embodiment, if the PDU session corresponding to the information contained in the message received by SMF160 from AMF150 is a Home-routed PDU session (for example, a PDU session established via H-SMF and H-UPF located on the home network), or if the message received from AMF150 contains H-PLMN S-NSSAI, SMF160 transmits an Nsmf_PDUSession_Update request message to H-SMF (not shown). The Nsmf_PDUSession_Update request message transmitted by SMF160 to H-SMF contains information about at least one of the following in H-SMF: the SM Context ID, "indication", "Cause=OAM or congestion, target slice information", and target slice information which includes H-PLMN S-NSSAI information for the PDU session. If the terminal is roaming and the PDU session is a home-routed PDU session, in the following steps, the H-SMF (not shown) performs the role of SMF160, and the SMF160 transmits messages received from the H-SMF (not shown) to the AMF150. The above description also applies to the various embodiments shown in Figures 6 and 7.

[0140] However, according to various embodiments of the present invention, the request message transmitted by the AMF150 is not limited to this and may include information other than that described above.

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

[0142] According to one embodiment, when the AMF150 requests to modify only the slice information of the session in question to the target slice via modification of the existing session, without releasing the existing session, it sets "indication" to "context modification".

[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 AMF150 sets the "Indication" included in the message transmitted to the SMF160 to "context modification".

[0144] According to one embodiment, when the AMF150 requests to break an existing session established on an unavailable slice and generate a new PDU session on a target slice to replace that session, it sets "indication" to "session release with break-before-make".

[0145] According to one embodiment, when the AMF150 requests to generate a new PDU session to a target slice to replace an existing session established on an unavailable slice before releasing the existing session, it sets "indication" to "session release with make-before-break".

[0146] Referring to step S525, the SMF160 transmits a response message to the AMF150 based on the request message received from the AMF150.

[0147] Referring to step S525, if the received message received from AMF150 in step S515 contains only the target slice, SMF160 sets "indication" considering the SSC mode for the PDU session, whether it is an MPS session or not, 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 AMF150 is an SSC mode 1 PDU session (for example, a PDU session that requests that no UPF changes be made to the PDU session), SMF160 sets "indication" to "context modification".

[0149] According to one embodiment, when SMF160 sets "indication" to "context modification", AMF150 decides not to release the existing session, but to modify only the information regarding the slice of the existing session through modification of 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 AMF150 is in SSC mode 2 or SSC mode 3, SMF160 sets "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 AMF150 is an SSC mode 1 PDU session, SMF160 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 AMF150 in step S515, SMF160 determines the target slice through configuration information or interaction with AMF150.

[0153] According to one embodiment, when the SMF160 decides to move to the target slice, it transmits a response message to the AMF150. The response message transmitted by the SMF160 contains information about the target slice. The response message transmitted by the SMF160 is referred to as an update session management response message.

[0154] Referring to step S525, if the "indication" of the request message received from AMF150 is "context modification", the response message transmitted to AMF150 will include 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 SMF160 from AMF150 is an SSC mode 1 PDU session, the message transmitted by SMF160 to UE110 includes information instructing to change the S-NSSAI (slice identifier) ​​for the PDU session.

[0159] According to one embodiment, the N1 SM container message includes other information that identifies 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 the SMF160 is not limited to this and may include information other than that described above.

[0161] Referring to step S525, if the "indication" of the request message received from AMF150 is "session release with break-before-make" or "session release with make-before-break", the message transmitted to AMF150 will include 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] According to one embodiment, if the "indication" of the message received by SMF160 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] According to one embodiment, if the "indication" of the message received by SMF160 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 SMF160 executes 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, if the request message received from AMF150 contains the PDU session identifier (or PDU session context ID) and the "indication" set in "context modification", SMF160 transmits an N4 session modification request message to UPF170 to change the slice information of the N4 session to the target slice. The N4 interface (e.g., an N4 reference point) is the interface formed between SMF160 and UPF170. The N4 session modification request message transmitted by SMF160 to UPF170 includes at least one of the following: the N4 session context ID, information about the target slice, an indicator that it is a slice modification request, or information indicating the cause of the slice modification.

[0169] Referring to step S545, UPF170 transmits an N4 session modification response message to SMF160 based on the received N4 session modification request message. The N4 session modification response message transmitted by UPF170 to SMF160 includes at least one of the following: the N4 session context ID or information about the result. If SMF160 receives a response message from UPF170 indicating that the slice modification was successful, it changes the slice information of the N4 session to the target slice.

[0170] According to one embodiment of the present invention, the UPF170 and SMF160 decide whether or not to change the N4 interface through the process of steps S535 and S545 and then execute the action.

[0171] Referring to step S555, if the message received from SMF160 in step S525 contains the target slice, AMF150 changes the slice information for the session from the information stored for the session corresponding to the "SM Context ID" or "PDU session ID" to the target slice. Also in step S555, AMF150 transmits the information contained in the N2 SM container to RAN120. If the message received from AMF contains the target slice, RAN120 changes the slice information for the session from the information stored for the session corresponding to the received "SM Context ID" or "PDU session ID" to the target slice. RAN120 transmits the N1 SM container to UE110. The above-described series of processes is not limited to this, and the flow of messages transmitted from AMF150 to UE110 via RAN120 can be represented by the transmission of PDU session command message information, as shown in Figure 5.

[0172] Referring to step S565, if the message received from RAN120 in step S555 contains "PDU Session ID" and "target slice", terminal 110 changes the slice information for the session among the information stored for the session corresponding to the received "PDU session ID" to the target slice.

[0173] Referring to steps S565 and S575, terminal 110 transmits a message to the SMF via RAN120 and AMF150 confirming that a change in session information has been made. In the transmission process described above, RAN120 and AMF150 each transmit a message to SMF160 that includes a message confirming that a change in session information has been made. The above-described series of processes is not limited to this, and the signal flow transmitted from UE110 to AMF150 via RAN120 can be represented by the transmission of a PDU session release command Ack (acknowledgement) message (or an Ack message for "PDU Session Modification Command"), as shown in Figure 5. Also, the signal flow transmitted from AMF150 to SMF160 can be represented by the transmission of a PDU session update request Ack (acknowledgement) message, as shown in Figure 5.

[0174] According to one embodiment, the SMF160 executes steps S535 and S545 after receiving an Ack message for a PDU Session Modification Command from the terminal in step S575.

[0175] Referring to step S585, if the message received from RAN120 in step S555 contains "PDU Session ID", "target slice", "session re-establishment request to the same DN", or "target slice indication", terminal 110 includes the received PDU Session ID in the PDU session release request message and transmits it to SMF160 via AMF150, requesting the release of the PDU session corresponding to the received PDU session ID.

[0176] According to one embodiment, 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 it to SMF 160. If a new session is generated with the target slice, terminal 110 transmits the traffic flow that was being transmitted in the released PDU session through the newly generated PDU session.

[0177] Referring to step S595, if the message received from RAN120 in step S555 contains "PDU Session ID", "target slice", "session re-establishment request to the same DN", "target slice indication", or "PDU session release timer", terminal 110 requests a new PDU session by including the DNN (data network name) corresponding to the received "PDU session ID" and the target slice received in step S555 in a PDU session generation request message and transmitting it to SMF160. If a new session is generated with the target slice, terminal 110 transmits the traffic flow that was being transmitted in the existing PDU session through the newly generated PDU session.

[0178] According to one embodiment, after a new PDU session is created, the terminal 110 transmits the received PDU session ID to the SMF 160 via the AMF 150, including it in a PDU session release request message, when the received PDU session release timer expires or according to the terminal's internal configuration information. The UE 110 requests the release of the PDU session corresponding to the received PDU session ID by transmitting a message to the SMF 160.

[0179] Figure 6 is a flowchart showing the operation of the AMF150 for moving slices to a session according to various embodiments of the present invention.

[0180] Specifically, the operation flow of the AMF150 shown in Figure 6 is based on the signal flow shown in Figure 5.

[0181] Referring to step 605, the AMF150 receives an update session management response message from the SMF160. Specifically, the AMF150 receives a response message from the SMF160 that was generated based on the request message it transmitted to the SMF160.

[0182] According to one embodiment, the response message received by the AMF150 includes information about the target slice.

[0183] If the "indication" of the request message received by SMF160 is "context modification", the response message received by AMF150 will include 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 SMF160 from AMF150 is an SSC mode 1 PDU session, the message transmitted by SMF160 to UE110 includes information instructing to change the S-NSSAI (slice identifier) ​​for the PDU session.

[0188] According to one embodiment, the N1 SM container message includes other information that identifies 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 the AMF150 is not limited to this and may include information other than that described above.

[0190] According to one embodiment, if the "indication" of the request message received by SMF160 is "session release with break-before-make" or "session release with make-before-break", the message received by AMF150 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] According to one embodiment, if the "indication" of the message received by SMF160 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] According to one embodiment, if the "indication" of the message received by SMF160 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, the AMF150 transmits a message containing PDU session command information to the UE110. In various embodiments of the present invention, the process by which the AMF150 transmits the PDU session command message to the UE110 includes at least one of the following: the process by which the AMF150 transmits information contained in the "N2 SM container" to the RAN120, or the process by which the RAN120 transmits information contained in the "N1 SM container" to the UE110.

[0197] According to one embodiment, if the response message received from the SMF160 contains a target slice, the AMF150 changes the slice information for the session from the information stored for the session corresponding to the "SM Context ID" or "PDU session ID" to the target slice. The AMF150 also transmits the information contained in the "N2 SM container" to the RAN120. If the message received from the AMF150 contains a target slice, the RAN120 changes the slice information for the session from the information stored for the session corresponding to the received "SM Context ID" or "PDU session ID" to the target slice. The RAN120 transmits the "N1 SM container" to the UE110. The above-described series of processes is not limited thereto, and the signal flow transmitted from the AMF150 to the UE110 via the RAN120 can be represented by the transmission of PDU session command messages, as shown in Figure 5.

[0198] Referring to step 625, the AMF150 receives a PDU session command Ack (acknowledgment) message from the UE110.

[0199] According to one embodiment, if the message received by the RAN120 includes a "PDU Session ID" and a "target slice", the UE110 changes the slice information for the session among the information stored for the session corresponding to the received "PDU session ID" to a target slice. The AMF150 receives a message from the UE110 via the RAN120 confirming that the session information has been modified. The above-described series of processes is not limited thereto, and the signal flow transmitted from the UE110 to the AMF150 via the RAN120 can be represented by the transmission of a PDU session release command Ack (acknowledgement) message (or an Ack message for a PDU Session Modification Command), as shown in Figure 5.

[0200] According to one embodiment, if the message received by UE110 from RAN120 includes "PDU Session ID", "target slice", "session re-establishment request to the same DN", or "target slice indication", AMF150 receives a PDU session termination request message that includes the received "PDU Session ID".

[0201] According to one embodiment, the AMF150 receives a PDU session generation request message from the UE110 that includes a DNN (data network name) such as a PDU session for which the UE110 has requested to be released, and a target slice received by the UE110 from the RAN120.

[0202] According to one embodiment, if the message received by UE110 from RAN120 includes "PDU Session ID", "target slice", "session re-establishment request to the same DN", "target slice indication", or "PDU session release timer", AMF150 receives a PDU session generation request message that includes a DNN (data network name) such as a PDU session corresponding to the received PDU session ID and the target slice received by UE110.

[0203] According to one embodiment, the AMF150 receives a PDU session release request message from the UE110, which includes the received PDU session ID, after the UE110 has generated a new PDU session and the received PDU session release timer has expired, or according to the terminal's internal configuration information.

[0204] Referring to step 635, the AMF150 transmits a PDU session update acknowledgment message to the SMF160. The signal flow transmitted from the AMF150 to the SMF160 is represented by the transmission of a PDU session update request Ack (acknowledgement) message, as shown in Figure 5.

[0205] According to one embodiment, the AMF150 transmits the PDU session release request message received from the UE110 to the SMF160.

[0206] According to one embodiment, the AMF150 transmits the PDU session generation request message received from the UE110 to the SMF160.

[0207] Figure 7 is a flowchart showing the operation of the SMF for moving slices to a session according to various embodiments of the present invention.

[0208] Specifically, the operation flow of the SMF160 shown in Figure 7 is based on the signal flow shown in Figure 5.

[0209] In step 705, SMF160 receives an update session management request message from AMF150. The message format of the request message received by SMF160 will be at least one of the following: "Nsmf_PDUSession_UpdateSMContext Request", "Nsmf_PDUSession_ReleaseSMContext Request", "Nsmf_PDUSession_UpdateSMContext Request", or "Nsmf_PDUSession_ContextPushRequest".

[0210] According to one embodiment, the request message transmitted by the AMF150 includes at least one of the following pieces of 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 the SMF160 is not limited to this and may include information other than that described above.

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

[0214] According to one embodiment, when the AMF150 transmitting the request message requests to modify only the slice information of the session in question to the target slice via modification of the existing session, without releasing the existing session, it sets "indication" to "context modification".

[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, the AMF150 sets the "Indication" included in the message transmitted to the SMF160 to "context modification".

[0216] According to one embodiment, when the AMF150 transmitting the request message requests to break an existing session established on an unavailable slice and generate a new PDU session on a target slice to replace that session, it sets "indication" to "session release with break-before-make".

[0217] According to one embodiment, when the AMF150 transmitting a request message requests that a new PDU session be generated on a target slice to replace an existing session established on an unavailable slice before the session is released, the AMF150 sets "indication" to "session release with make-before-break".

[0218] In step 715, SMF160 transmits an update session management response message to AMF150. If the received message received from AMF150 in step 705 contains only the target slice, SMF160 sets the "indication" considering the SSC mode for the PDU session, whether it is an MPS session or not, 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 AMF150 is an SSC mode 1 PDU session (for example, a PDU session that requests that no UPF changes be made to the PDU session), SMF160 sets "indication" to "context modification".

[0220] According to one embodiment, when SMF160 sets "indication" to "context modification", AMF150 decides not to release the existing session, but to modify only the information regarding the slice of the existing session through modification of 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 AMF150 is in SSC mode 2 or SSC mode 3, the SMF160 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 AMF150 is an SSC mode 1 PDU session, SMF160 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 AMF150 in step 705, SMF160 determines the target slice through configuration information or interaction with AMF150.

[0224] According to one embodiment, when the SMF160 decides to move to the target slice, it transmits a response message to the AMF150. The response message transmitted by the SMF160 contains information about the target slice. The response message transmitted by the SMF160 is referred to as an update session management response message.

[0225] Referring to step 715, if the "indication" of the request message received from AMF150 is "context modification", the response message transmitted to AMF150 will include 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 SMF160 from AMF150 is an SSC mode 1 PDU session, the message transmitted by SMF160 to UE110 includes information instructing to change the S-NSSAI (slice identifier) ​​for the PDU session.

[0230] According to one embodiment, the N1 SM Container message includes other information that identifies 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 the SMF160 is not limited to this and may include information other than that described above.

[0232] Referring to step 715, if the "indication" of the request message received from AMF150 is "session release with break-before-make" or "session release with make-before-break", the message transmitted to AMF150 will include 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] According to one embodiment, if the "indication" of the message received by SMF160 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] According to one embodiment, if the "indication" of the message received by SMF160 is "session release with make-before-break", the "N1 SM Container" will contain 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, the SMF160 transmits an N4 session modification request message to the UPF170 if the request message received from the AMF150 contains the PDU session identifier (or PDU session context ID) and the "indication" set in "context modification". The N4 interface (e.g., an N4 reference point) is the interface formed between the SMF160 and the UPF170. The N4 session modification request message transmitted by the SMF160 to the UPF170 includes at least one of the following: the N4 session context ID, information about the target slice, an indicator that it is a slice modification request, or information indicating the cause of the slice modification.

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

[0240] According to one embodiment of the present invention, the UPF170 and SMF160 decide whether or not to change the N4 interface through the process of steps S535 and S545 and then execute the action.

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

[0242] According to one embodiment, a request message includes information about a target slice and an indicator indicating a modification method for at least one PDU session, the modification method including at least one of a first method that modifies the context of at least one PDU session, a second method that sets up one or more PDU sessions after releasing at least one PDU session, or a third method that releases 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 the steps of receiving a modification instruction for at least one PDU session from an SMF node, and transmitting the modification instruction for at least one PDU session to a terminal.

[0244] According to one embodiment, when the modification method is the second method, the method further includes the steps of receiving a PDU session release command from an SMF node, which includes information relating to the creation of one or more PDU sessions, and transmitting the PDU session release command to a terminal.

[0245] According to one embodiment, when the modification method is the third method, the method further includes receiving a modification command for at least one PDU session from an SMF node, which includes information relating to the creation of one or more PDU sessions and a timer for releasing at least one PDU session; and transmitting the modification command for at least one PDU session to a terminal.

[0246] According to one embodiment, the notification message further includes slice change required information, the slice change required information includes at least one of the following: an indicator that instructs a slice change for an unusable slice or information about a target slice for each unusable slice.

[0247] According to one embodiment, the first method corresponds to SSC (session and service continuity) mode 1, the second method corresponds to SSC mode 2, and the third method 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 the steps of generating an H-PLMN S-NSSAI (single-network slice selection assistance) for a target slice based on mapping information between H(home)-PLMN (public land mobile network) and V(visited)-PLMN, and transmitting the generated H-PLMN S-NSSAI to an SMF node.

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

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

[0251] According to various embodiments of the present invention, an AMF (access mobility and management function) node in a mobile communication system comprises at least one controller, the at least one controller receiving notification messages from a SACF (slice availability check function) node containing information about unavailable slices, receiving information about PDU (protocol data unit) sessions from an NWDAF (network data analysis function) node, determining a target slice and at least one PDU session that requires a slice change based on the notification messages and the information about the PDU sessions, and transmitting a request message to an SMF (session management function) node to change the slice of the determined at least one PDU session to a target slice.

[0252] According to one embodiment, a request message includes information about a target slice and an indicator indicating a modification method for at least one PDU session, the modification method including at least one of a first method that modifies the context of at least one PDU session, a second method that sets up one or more PDU sessions after releasing at least one PDU session, or a third method that releases 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, at least one controller is further configured to receive a modification command for at least one PDU session from an SMF node and to transmit the modification command for at least one PDU session to a terminal.

[0254] According to one embodiment, when the modification method is the second method, at least one controller is further configured to receive a PDU session release command from an SMF node, which includes information related to the creation 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 the third method, at least one controller is further configured to receive a modification command for at least one PDU session from an SMF node, which includes information relating to the creation of one or more PDU sessions and a timer for releasing at least one PDU session, and to transmit the modification command for at least one PDU session to a terminal.

[0256] According to one embodiment, the notification message further includes slice change required information, the slice change required information includes at least one of the following: an indicator that instructs a slice change for an unusable slice or information about a target slice for each unusable slice.

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

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

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

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

[0261] The methods according to the embodiments described in the claims or specification of the present invention are implemented in the form of 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 recorded on 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 the embodiments described in the claims or specification of the present invention.

[0263] Such programs (software modules, software) are 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 devices, compact disc-ROMs (CD-ROMs), digital versatile discs (DVDs), or other forms of optical storage devices, magnetic cassettes, or in memory composed of some or all of these. Each constituent memory may also contain multiple instances.

[0264] Furthermore, the program is stored in an attachable storage device that is accessed via a communication network such as the Internet, intranet, LAN (local area network), WAN (wide area network), or SAN (storage area network), or a combination thereof. Such a storage device accesses the device that implements the embodiments of the present invention via an external port. Alternatively, a separate storage device on the communication network can also access the device that implements the embodiments of the present invention.

[0265] In the specific embodiments of the present invention described above, the components included herein are expressed singly or plural by the specific embodiments that presented them. However, the singly or plural expressions are selected to suit the presented circumstances for the sake of explanation, and the present invention is not limited to singly or plural components. Components expressed plural may consist of a singular component, and components expressed singly may consist of a plural component.

[0266] On the other hand, while specific embodiments have been described in the detailed description of the present invention, it goes without saying that various modifications are possible within the limits that do not depart from the scope of the present invention. Therefore, the scope of the present invention should not be limited to the embodiments described, but should be defined not only by the claims, but also by equivalents to the claims.

[0267] Although the present invention has been described with various embodiments, a variety of changes and modifications can be proposed to those skilled in the art. The present invention is intended to include such changes and modifications that fall within the scope of the claims. [Explanation of Symbols]

[0268] 100 Communication Networks 110 terminals (UE: user equipment) 120 Wireless Access Network (RAN) 125 Base Station 130 AF (Application Function) 140 Data Network (DN) 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. An AMF (access mobility and management function) entity in a mobile communication system, Transceiver, The system comprises a controller coupled to the aforementioned transmitting and receiving unit, The aforementioned controller, A notification message is received from the network entity, containing information about the first S-NSSAI (single-network slice selection assistance information) of the first network slice which is unavailable, and information about the second S-NSSAI of the second network slice. Identify the PDU (protocol data unit) session associated with the first S-NSSAI that is transferred to the second S-NSSAI of the second network slice, Based on the notification message, the second S-NSSAI of the second network slice is identified. The SMF (session management function) entity is forwarded a PDU session update request message including the second S-NSSAI, An AMF entity characterized by being configured to receive a PDU session update response message as a response to the PDU session update request message from the SMF entity.

2. The AMF entity according to claim 1, characterized in that the network entity is one of an NSSF (network slice selection function) entity or a PCF (policy control function) entity.

3. If the PDU session is maintained, The AMF entity according to claim 1, characterized in that the PDU session update response message includes a PDU session modification command message including the second S-NSSAI and PDU session ID (identifier).

4. If the aforementioned PDU session is re-established, The PDU session update response message includes a PDU session modification command message or a PDU session release message. The AMF entity according to claim 1, characterized in that the PDU session modification command message or the PDU session release message includes information requesting the second S-NSSAI and the re-establishment of the PDU session on the second S-NSSAI.

5. A method performed by an AMF (access mobility and management function) entity in a mobile communication system, The steps include receiving a notification message from a network entity that includes information about the first S-NSSAI (single-network slice selection assistance information) of an unavailable first network slice and information about the second S-NSSAI of a second network slice, Steps include identifying a PDU (protocol data unit) session associated with the first S-NSSAI that is transferred to the second S-NSSAI of the second network slice, The steps include identifying the second S-NSSAI of the second network slice based on the notification message, The steps include forwarding the PDU session update request message, including the second S-NSSAI, to the SMF (session management function) entity, A method characterized by comprising the step of receiving a PDU session update response message from the SMF entity as a response to the PDU session update request message.

6. The method according to 5, characterized in that the network entity is one of an NSSF (network slice selection function) entity or a PCF (policy control function) entity.

7. If the PDU session is maintained, The method according to 5, characterized in that the PDU session update response message includes a PDU session modification command message including the second S-NSSAI and PDU session ID (identifier).

8. If the aforementioned PDU session is re-established, The PDU session update response message includes a PDU session modification command message or a PDU session release message. The method according to claim 5, characterized in that the PDU session modification command message or the PDU session release message includes information requesting the second S-NSSAI and the re-establishment of the PDU session on the second S-NSSAI.

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