Method and device for supporting slice replacement in consideration of mobility in wireless communication system

Abstract

The present disclosure relates to a method performed by a first access and mobility management function (AMF) of a communication system, the method comprising the steps of: transmitting, to a second AMF, a first message including information indicating whether network slice replacement (NSR) is supported; when the first AMF does not support the NSR, receiving, from the second AMF, a second message for the first AMF that does not support the NSR; and transmitting, to a terminal, a third message including information about network slice selection assistance information (NSSAI), wherein, when the first AMF does not support the NSR, information related to the NSR is excluded from the second message and the third message.

Description

Method and device for supporting slice replacement considering mobility in a wireless communication system

[0001] The present disclosure relates to a method or device for providing a service by considering whether a network slice replacement function is supported according to the location of a terminal in a wireless communication system.

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

[0003] In the early stages of 5G mobile communication technology, the goal is to support services and satisfy performance requirements for enhanced Mobile Broadband (eMBB), Ultra-Reliable Low-Latency Communications (URLLC), and massive Machine-Type Communications (mMTC). These include beamforming and massive MIMO to mitigate path loss of radio waves in ultra-high frequency bands and increase the transmission distance of radio waves, support for various numerologies (such as operation of multiple subcarrier intervals) and dynamic operation of slot formats for efficient use of ultra-high frequency resources, initial access technology to support multi-beam transmission and wideband, definition and operation of BWP (Bidth Part), new channel coding methods such as LDPC (Low Density Parity Check) codes for large-capacity data transmission and Polar Code for reliable transmission of control information, and L2 pre-processing (L2). Standardization has been made for network slicing, which provides dedicated networks specialized for specific services, and pre-processing.

[0004] Currently, discussions are underway to improve and enhance the initial 5G mobile communication technology in consideration of the services that 5G mobile communication technology was intended to support, and physical layer standardization is in progress for technologies such as V2X (Vehicle-to-Everything) to help autonomous vehicles make driving decisions and increase user convenience based on their own location and status information transmitted by vehicles, NR-U (New Radio Unlicensed) for the purpose of system operation that complies with various regulatory requirements in unlicensed bands, NR terminal low power consumption technology (UE Power Saving), Non-Terrestrial Network (NTN), which is direct terminal-satellite communication to secure coverage in areas where communication with terrestrial networks is impossible, and Positioning.

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

[0006] Once these 5G mobile communication systems are commercialized, an explosive increase in connected devices will be connected to the communication network, necessitating enhanced functionality and performance of 5G mobile communication systems and integrated operation of these connected devices. To this end, new research will be conducted on improving 5G performance and reducing complexity, supporting AI services, supporting metaverse services, and drone communications by utilizing eXtended Reality (XR), Artificial Intelligence (AI), and Machine Learning (ML) to efficiently support Augmented Reality (AR), Virtual Reality (VR), and Mixed Reality (MR).

[0007] In addition, the development of these 5G mobile communication systems includes new waveforms to ensure coverage in the terahertz band of 6G mobile communication technology, multi-antenna transmission technologies such as Full Dimensional MIMO (FD-MIMO), Array Antenna, and Large Scale Antenna, metamaterial-based lenses and antennas to improve the coverage of terahertz band signals, high-dimensional spatial multiplexing technology using Orbital Angular Momentum (OAM), Reconfigurable Intelligent Surface (RIS) technology, as well as full duplex technology to improve the frequency efficiency and system network of 6G mobile communication technology, satellite, AI (Artificial Intelligence) from the design stage and AI-based communication technology that realizes system optimization by internalizing end-to-end AI support functions, and ultra-high-performance communication and computing resources to provide services with complexity that exceeds the limits of terminal computing capabilities. It can serve as a basis for the development of next-generation distributed computing technologies that can be realized by utilizing them.

[0008] There may be instances where one or all of a network slice's protocol data unit (PDU) sessions need to be moved to another network slice. For example, congestion may occur among various 5G network entities within a network slice, a particular slice may need to be temporarily or permanently discontinued for operational reasons (e.g., equipment replacement or upgrade), or the performance of a network slice carrying application traffic may degrade, requiring the traffic to be moved to another slice.

[0009] In such cases, a network slice replacement function may be provided to provide service continuity by performing data transmission and reception through an alternative network slice instead of the existing network slice. In one embodiment, this network slice replacement function may be supported by terminals and network devices (e.g., AMF, SMF, etc.).

[0010] In an embodiment, in an environment where only some network devices support the network slice replacement feature, the network slice replacement feature may be provided only in areas covered by network devices that support the feature. Depending on whether the network slice replacement feature is supported based on the location of the terminal, a method may be required to update terminal configuration information related to how to handle related sessions (e.g., replaced PDU sessions, or PDU sessions associated with the replaced network slice along with the replacement network slice).

[0011] In some embodiments, if the network equipment does not support NSR, a method may be required to release a replaced PDU session or update terminal configuration information.

[0012] The technical problems to be achieved in the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by a person having ordinary skill in the technical field to which the present invention belongs from the description below.

[0013] Based on the discussion as described above, the present disclosure relates to a method performed by a first AMF (access and mobility management function) of a communication system,

[0014] The method comprises the steps of: transmitting a first message including information indicating whether network slice replacement (NSR) is supported to a second AMF; receiving, from the second AMF, a second message for the first AMF that does not support the NSR when the first AMF does not support the NSR; and transmitting, to a terminal, a third message including information on network slice selection assistance information (NSSAI), wherein, when the first AMF does not support the NSR, information related to the NSR is excluded from the second message and the third message.

[0015] In addition, when the first AMF supports the NSR, the second message and the third message are characterized in that they include the information related to the NSR.

[0016] In addition, the information related to the NSR is characterized in that it includes at least one of information about a replaced PDU (protocol data unit) session, information about a replaced S-NSSAI (single network slice selection assistance information), information about a replacement S-NSSAI, or information about a mapping related to the replaced S-NSSAI.

[0017] In addition, if the first AMF does not support the NSR, the information related to the NSR is deleted by the terminal.

[0018] According to one embodiment, a method performed by a terminal of a communication system,

[0019] A method comprising: receiving, from a first AMF (access and mobility management function), a third message including information on network slice selection assistance information (NSSAI), wherein a first message including information indicating whether network slice replacement (NSR) is supported is transmitted from the first AMF to a second AMF, and when the first AMF does not support the NSR, a second message for the first AMF not supporting the NSR is received by the first AMF from the second AMF, and when the first AMF does not support the NSR, information related to the NSR is excluded from the second message and the third message.

[0020] According to one embodiment, a first AMF (access and mobility management function) of a communication system comprises: a transceiver; and a control unit connected to the transceiver and configured to transmit a first message including information indicating whether network slice replacement (NSR) is supported to a second AMF, and if the first AMF does not support the NSR, to receive a second message for the first AMF not supporting the NSR from the second AMF, and to transmit a third message including information on network slice selection assistance information (NSSAI) to a terminal, wherein if the first AMF does not support the NSR, information related to the NSR is excluded from the second message and the third message.

[0021] According to one embodiment, a terminal of a communication system comprises: a transceiver; and a control unit connected to the transceiver and configured to receive, from a first AMF (access and mobility management function), a third message including information on NSSAI (network slice selection assistance information), wherein a first message including information indicating whether NSR (network slice replacement) is supported is transmitted from the first AMF to a second AMF, and when the first AMF does not support the NSR, a second message for the first AMF not supporting the NSR is received by the first AMF from the second AMF, and when the first AMF does not support the NSR, information related to the NSR is excluded from the second message and the third message.

[0022] One embodiment of the present disclosure determines in advance whether network equipment (e.g., AMF and / or SMF) in charge of a terminal (User Equipment, UE) supports a network slice replacement function (NSR), and accordingly efficiently processes replaced PDU sessions (e.g., PDU sessions associated with Alternative S-NSSAI and S-NSSAI being replaced, etc.) and updates UE configuration information.

[0023] The effects that can be obtained from the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by a person having ordinary skill in the art to which the present disclosure pertains from the description below.

[0024] FIG. 1 illustrates a communication network including core network entities in a wireless communication system according to various embodiments of the present disclosure.

[0025] FIG. 2 is a diagram illustrating a method for processing associated PDU sessions and providing terminal configuration information depending on whether AMF supports NSR in a registration procedure.

[0026] FIG. 3 is a diagram illustrating a method for processing associated PDU sessions and providing terminal configuration information depending on whether NSR is supported in a handover procedure.

[0027] FIG. 4 is a drawing showing an example of a terminal structure according to an embodiment of the present disclosure.

[0028] FIG. 5 is a drawing showing an example of the structure of a base station according to one embodiment of the present disclosure.

[0029] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the attached drawings.

[0030] In describing the embodiments, descriptions of technical contents that are well known in the technical field to which the present disclosure belongs and are not directly related to the present disclosure are omitted.

[0031] This is to convey the gist of the present disclosure more clearly without obscuring it by omitting unnecessary explanations.

[0032] For the same reason, some components in the attached drawings are exaggerated, omitted, or schematically depicted. Furthermore, the dimensions of each component do not entirely reflect the actual size. Identical or corresponding components in each drawing are assigned the same reference numbers.

[0033] The advantages and features of the present disclosure and the methods for achieving them will become apparent with reference to the embodiments described in detail below together with the accompanying drawings.

[0034] However, the present disclosure is not limited to the embodiments disclosed below and may be implemented in various different forms. These embodiments are provided only to complete the composition of the present disclosure and to fully inform those skilled in the art of the disclosure of the scope of the disclosure, and the present disclosure is defined only by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

[0035] At this time, it will be understood that each block of the processing flow diagrams and combinations of the flow diagrams can be performed by computer program instructions. These computer program instructions can be installed in a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing equipment, so that the instructions executed by the processor of the computer or other programmable data processing equipment create a means for performing the functions described in the flow diagram block(s). These computer program instructions can also be stored in a computer-available or computer-readable memory that can be directed to a computer or other programmable data processing equipment for implementation in a specific manner, so that the instructions stored in the computer-available or computer-readable memory can also produce a manufactured item that includes an instruction means for performing the functions described in the flow diagram block(s). Since the computer program instructions can also be installed on a computer or other programmable data processing device, a series of operational steps can be performed on the computer or other programmable data processing device to create a computer-executable process, and the instructions that cause the computer or other programmable data processing device to perform the steps for performing the functions described in the flowchart block(s) can also provide steps for performing the functions described in the flowchart block(s).

[0036] Additionally, each block may represent a module, segment, or portion of code that contains one or more executable instructions for performing a specific logical function(s). It should also be noted that in some alternative implementation examples, the functions described in the blocks may occur out of order. For example, two blocks depicted in succession may actually be executed substantially concurrently, or the blocks may sometimes be executed in reverse order, depending on their respective functions.

[0037] Here, the term '~ unit' used in the present embodiment means software or hardware components such as FPGA (field programmable gate array) or ASIC (application-specific integrated circuit), and the '~ unit' performs certain roles. However, the '~ unit' is not limited to software or hardware. The '~ unit' may be configured to be on an addressable storage medium, and may be configured to play one or more processors. Accordingly, as an example, the '~ unit' includes components such as software components, object-oriented software components, class components, and task components, processes, functions, properties, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and variables. The functions provided within the components and '~ units' may be combined into a smaller number of components and '~ units', or further separated into additional components and '~ units'. Additionally, the components and '~parts' may be implemented to play one or more central processing units (CPUs) within the device or secure multimedia card.

[0038] For the convenience of the following description, some terms and names defined in the 3rd generation partnership project (3GPP) standards (standards for 5G, NR, LTE, or similar systems) may be used. In addition, terms and names newly defined in next-generation communication systems (e.g., 6G, Beyond 5G systems) to which the present disclosure may be applied, or terms and names used in existing communication systems may be used. The use of such terms is not limited to the terms and names of the present disclosure, and may be equally applied to systems conforming to other standards, and may be modified into other forms without departing from the technical spirit of the present disclosure. Embodiments of the present disclosure may be easily modified and applied to other communication systems.

[0039] Additionally, it will be understood that singular expressions such as “a” and “the above” include plural expressions unless they clearly indicate otherwise in one embodiment of the present disclosure.

[0040] Additionally, in one embodiment of the present disclosure, terms including ordinal numbers, such as first, second, etc., may be used to describe various components, but the components are not limited by these terms. These terms are used solely to distinguish one component from another. For example, without departing from the scope of the present disclosure, a first component could be referred to as a second component, and similarly, a second component could also be referred to as a first component.

[0041] Additionally, in one embodiment of the present disclosure, the term “and / or” includes a combination of a plurality of related described items or any one of a plurality of related described items.

[0042] In addition, the terms used in the embodiments of the present disclosure are only used to describe specific embodiments and are not intended to limit the present disclosure. The singular expression includes the plural expression unless the context clearly indicates otherwise. In this specification, it should be understood that the terms "comprise" or "have" are intended to specify the presence of a feature, number, step, operation, component, part, or combination thereof described in the specification, but do not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0043] Additionally, the terms “associated with” and “associated therewith” and their derivatives used in one embodiment of the present disclosure may mean include, be included within, interconnect with, contain, be contained within, connect to or with, couple to or with, be communicated with, cooperate with, interleave, juxtapose, be proximate to, be bound to or with, have, have a property of, and the like.

[0044] Additionally, in the present disclosure, expressions such as "more than" and "less than" are used to determine whether a specific condition is satisfied or fulfilled. However, this is merely a description to express an example and does not exclude descriptions of more than or less than. Conditions described as "more than" may be replaced with "more than," conditions described as "less than" may be replaced with "less than," and conditions described as "more than and less than" may be replaced with "more than and less than."

[0045] Additionally, although the present disclosure describes embodiments using terms used in certain communication standards (e.g., long term evolution (LTE) and new radio (NR) defined by the 3rd generation partnership project (3GPP)), these are merely examples for illustrative purposes. The embodiments of the present disclosure can be easily modified and applied to other communication systems.

[0046] Before delving into the detailed description of this disclosure, examples of possible interpretations of some terms used herein are provided. However, it should be noted that the interpretations provided below are not limited to these examples.

[0047] In the present disclosure, a terminal (or communication terminal) is an entity that communicates with a base station or another terminal, and may be referred to as a node, UE (user equipment), NG UE (next generation UE), MS (mobile station), device, or terminal. In addition, the terminal may include at least one of a smartphone, a tablet PC, a mobile phone, a video phone, an e-book reader, a desktop PC, a laptop PC, a netbook computer, a PDA, a PMP (portable multimedia player), an MP3 player, a medical device, a camera, or a wearable device. In addition, the terminal may include at least one of a television, a DVD (digital video disk) player, an audio player, a refrigerator, an air conditioner, a vacuum cleaner, an oven, a microwave oven, a washing machine, an air purifier, a set-top box, a home automation control panel, a security control panel, a media box, a game console, an electronic dictionary, an electronic key, a camcorder, or an electronic picture frame.In addition, the terminal may include at least one of various medical devices (e.g., various portable medical measuring devices (such as blood glucose meters, heart rate monitors, blood pressure monitors, or body temperature monitors), magnetic resonance angiography (MRA), magnetic resonance imaging (MRI), computed tomography (CT), cameras, or ultrasound machines), navigation devices, global navigation satellite systems (GNSS), event data recorders (EDR), flight data recorders (FDR), automotive infotainment devices, electronic equipment for ships (e.g., navigation devices for ships, gyrocompasses, etc.), avionics, security devices, head units for vehicles, industrial or home robots, drones, ATMs for financial institutions, POSs (points of sales) for stores, or Internet of Things devices (e.g., light bulbs, various sensors, sprinkler devices, fire alarms, thermostats, streetlights, toasters, exercise equipment, hot water tanks, heaters, boilers, etc.). Additionally, the terminal may include various types of multimedia systems capable of performing communication functions. Meanwhile, the present disclosure is not limited to the above description, and the terminal may also be referred to by terms having the same or similar meaning.

[0048] In addition, in the present disclosure, the base station is an entity that communicates with a terminal and performs resource allocation of the terminal, and may have various forms and may be referred to as a BS (base station), a NodeB (NB), an NG RAN (next generation radio access network), an AP (access point), a TRP (transmission reception point), a wireless access unit, a base station controller, or a node on a network. Alternatively, it may be referred to as a CU (central unit) or a DU (distributed unit) depending on functional separation. Meanwhile, the present disclosure is not limited thereto, and the base station may be referred to by a term having the same or similar meaning.

[0049] Additionally, in the present disclosure, an RRC (radio resource control) message may be referred to as a higher level information, a higher level message, a higher level signal, a higher level signaling, a higher layer signaling, or a higher layer signaling, and the present disclosure is not limited thereto and may also be referred to by terms having the same or similar meaning.

[0050] Additionally, in the present disclosure, data may be referred to as user data, user plane (UP) data, or application data, or may be referred to by terms having the same or similar meaning as signals transmitted and received via a data radio bearer (DRB).

[0051] Additionally, in the present disclosure, the direction of data transmitted from a terminal may be referred to as uplink (UL), and the direction of data transmitted to the terminal may be referred to as downlink (DL). Accordingly, in the case of uplink transmission, the transmitter may refer to the terminal, and the receiver may refer to a base station or a specific network entity of the communication system. Alternatively, in the case of downlink transmission, the transmitter may refer to a base station or a specific network entity of the communication system, and the receiver may refer to the terminal.

[0052] FIG. 1 illustrates a communication network including core network entities in a wireless communication system according to embodiments of the present disclosure. A 5G mobile communication network may be configured to include a 5G user equipment (UE) (110), a 5G radio access network (RAN) (120), and a 5G core network.

[0053] The 5G core network may be configured to include network functions such as an access and mobility management function (AMF) (150) that provides a mobility management function of UE, a session management function (SMF) (160) that provides a session management function, a user plane function (UPF) (170) that performs a data transfer role, a policy control function (PCF) (180) that provides a policy control function, a unified data management (UDM) (153) that provides a data management function such as subscriber data and policy control data, or a unified data repository (UDR) that stores data of various network functions.

[0054] Referring to FIG. 1, a user equipment (UE) (110) may communicate via a wireless channel formed with a base station (e.g., an eNB or gNB), i.e., an access network. In some embodiments, the UE (110) may be a device used by a user and configured to provide a user interface (UI). As an example, the UE (110) may be a terminal mounted (equipment) on a vehicle for driving. In some other embodiments, the UE (110) may be a device that performs machine type communication (MTC) that operates without user intervention, or may be an autonomous vehicle. UE may be referred to as a 'terminal', 'vehicle terminal', 'user equipment (UE)', 'mobile station', 'subscriber station', 'remote terminal', 'wireless terminal', or 'user device' or other terms having equivalent technical meanings, other than electronic devices. As the terminal, in addition to the UE, a customer-premises equipment (CPE) or a dongle-type terminal may be used. The CPE, while connected to the NG-RAN node like the UE, may also provide a network to other communication devices (e.g., a laptop).

[0055] Referring to FIG. 1, the AMF (150) provides a function for connection and mobility management per terminal (110), and basically, one AMF (150) can be connected to one terminal (110). Specifically, the AMF (150) can perform at least one of signaling between core network nodes for mobility between 3GPP access networks, an interface (N2 interface) between wireless access networks (e.g., 5G RAN) (120), NAS signaling with the terminal (110), identification of the SMF (160), and provision of transmission of session management (SM) messages between the terminal (110) and the SMF (160). Some or all of the functions of the AMF (150) can be supported within a single instance of one AMF (150).

[0056] Referring to FIG. 1, the SMF (160) provides a session management function, and when the terminal (110) has multiple sessions, each session can be managed by a different SMF (160). Specifically, the SMF (160) can perform at least one of the following functions: session management (e.g., session establishment, modification, and release, including tunnel maintenance between the UPF (170) and the access network node), selection and control of UP (user plane) functions, traffic steering setup for routing traffic to an appropriate destination in the UPF (170), termination of the SM portion of NAS messages, downlink data notification (DDN), and initiation of AN-specific SM information (e.g., delivery to the access network via the N2 interface via the AMF (150)). Some or all of the functions of the SMF (160) can be supported within a single instance of one SMF (160).

[0057] In the 3GPP system, conceptual links connecting NFs within a 5G system may be referred to as reference points. Reference points may also be referred to as interfaces. The following exemplifies reference points (hereinafter, interchangeably referred to as interfaces) included in the 5G system architecture represented across various embodiments of the present disclosure.

[0058] - N1: Reference point between UE (110) and AMF (150)

[0059] - N2: Reference point between (R)AN(120) and AMF(150)

[0060] - N3: Reference point between (R)AN(120) and UPF(170)

[0061] - N4: Reference point between SMF (160) and UPF (170)

[0062] - N5: Reference point between PCF (180) and AF (130)

[0063] - N6: Reference point between UPF (170) and DN (140)

[0064] - N7: Reference point between SMF (160) and PCF (180)

[0065] - N8: Reference point between UDM (153) and AMF (150)

[0066] - N9: Reference point between two core UPFs (170)

[0067] - N10: Reference point between UDM (153) and SMF (160)

[0068] - N11: Reference point between AMF (150) and SMF (160)

[0069] - N12: Reference point between AMF (150) and authentication server function (AUSF) (151)

[0070] - N13: Reference point between UDM (153) and authentication server function (151)

[0071] - N14: Reference point between two AMFs (150)

[0072] - N15: For non-roaming scenarios, reference point between PCF (180) and AMF (150), for roaming scenarios, reference point between PCF (180) and AMF (150) within the visited network.

[0073] In 5G systems, network slicing technology can refer to a technology and architecture that enables multiple virtualized, independent, logical networks within a single physical network. Network operators can provide services by configuring virtual end-to-end networks called network slices to meet the specialized requirements of services / applications. At this time, network slices can be identified by an identifier called single-network slice selection assistance information (S-NSSAI). During the UE registration procedure (e.g., UE registration procedure), the network transmits a set of allowed slices (e.g., allowed NSSAI(s)) to the UE, and the UE can transmit and receive application data through a protocol data unit (PDU) session created through one of these S-NSSAIs (i.e., network slices).

[0074] A 5G mobile communication network can be composed of 5G User Equipment (UE), 5G Radio Access Network (RAN), and 5G core network. The 5G core network can be composed of NFs such as Access and Mobility Management Function (AMF) that provides UE mobility management function, Session Management Function (SMF) that provides session management function, User Plane Function (UPF) that performs data transfer role, Policy Control Function (PCF) that provides policy control function, Unified Data Management (UDM) that provides data management function such as subscriber data and policy control data, and Unified Data Repository (UDR) that stores data of various network functions (NFs) such as UDM.

[0075] In 5G systems, network slicing technology can represent a technology and architecture that enables multiple virtualized, independent logical networks within a single physical network. Network operators can provide services by configuring virtual end-to-end networks called network slices to meet the specialized requirements of services and applications. Network slices are identified by an identifier called Single-Network Slice Selection Assistance Information (S-NSSAI), and network operators can provide network slice(s) to terminals to enable them to receive services.

[0076] Specifically, in a 5G system, when a terminal registers a network, the terminal transmits identifier information for network slices it wishes to request (e.g., Requested S-NSSAIs) to the AMF, and the AMF can provide the terminal with information about network slices that the terminal can use (e.g., Allowed NSSAI) by considering the Requested S-NSSAIs and subscriber information. Even if the terminal does not provide information about slices requested by the terminal, the AMF can provide Allowed NSSAI to the terminal, and at this time, Allowed NSSAI can include information about default configured slices (e.g., Default Configured NSSAI) and information about slices set as default among subscription slices included in the terminal subscriber information (e.g., Default Subscribed S-NSSAIs).

[0077] If the Allowed NSSAI cannot contain any slices (e.g., if the Default Configured NSSAI and Default Subscribed S-NSSAIs are missing or unavailable), the AMF may send the UE a Network Registration Reject message containing a cause code indicating that the registration rejection is due to no available slices.

[0078] Meanwhile, when a user wants to include an arbitrary slice in the Allowed NSSAI of a terminal, an admission control (Network Slice Admission Control, NSAC) procedure and an authentication (Network Slice-Specific Authentication and Authorization, NSSAA) procedure for the corresponding slice may be performed. In the NSAC procedure, whether to allow the corresponding slice may be determined based on the number of terminals currently registered in the specific slice and the maximum number of registered terminals allowed in the corresponding slice (for example, determining whether to include the corresponding slice in the Allowed NSSAI). As a specific example, the Network Slice Admission Control Function (NSACF) may monitor the number of registered terminals and the number of established PDU sessions for each slice for network slices that are the target of NSAC, and may perform control so that the number of registered terminals and the number of established PDU sessions for each slice are maintained to be less than the maximum number of registered terminals and the maximum number of PDU sessions, respectively.

[0079] At this time, AMF can send an update request message to notify NSACF when a new terminal is registered in a slice that is the target of NSAC or when an existing registered terminal is deregistered.

[0080] Additionally, according to one embodiment, the SMF may send an update request message to notify the NSACF when a new PDU session is created or an existing PDU session is released in a slice that is the target of the NSAC.

[0081] In one embodiment, when the NSAC receives a message notifying registration of a new terminal in a slice or a message notifying creation of a new PDU session, the NSAC may determine whether to allow the message based on the maximum number of terminals and the maximum number of PDU sessions for the slice, and may include the determination of whether to allow the message in each response message.

[0082] Meanwhile, the terminal selects one of the allowed slices (Allowed NSSAIs) to transmit and receive data to a specific data network (DN) through the allowed NSSAIs, requests the creation of a PDU (Packet Data Unit) session to a specific DNN (Data Network Name) in the selected slice, and transmits and receives data through the created PDU session. The PDU session consists of multiple traffic flows, and the traffic flows can be composed of two types: GBR QoS Flow (Guaranteed Bitrate Quality-of-Service Flow) and non-GBR QoS Flow.

[0083] Meanwhile, situations may arise where a network slice becomes unavailable (e.g., congestion occurs among various 5G network entities belonging to a network slice, or a particular slice must be temporarily or permanently unavailable for operational reasons (e.g., equipment replacement and upgrades), or the performance of the network slice carrying application traffic degrades and the traffic must be moved to another slice), and there may be a capability to provide services through an alternate network slice for service continuity.

[0084] Specifically, the network may transmit information (e.g., Mapping of Alternative S-NSSAI) indicating to the terminal that it will use Alternative S-NSSAI instead of S-NSSAI, in order to replace the S-NSSAI being used by the terminal (e.g., S-NSSAI being replaced) with Alternative S-NSSAI (e.g., alternative network slice).

[0085] The PDU session(s) associated with the S-NSSAI being replaced of the terminal are moved to the Alternative S-NSSAI, and the network (e.g., AMF and / or SMF) may store the S-NSSAI being replaced together with the Alternative S-NSSAI as the associated network slice information for the moved PDU session(s).

[0086] When new traffic that the terminal must transmit with S-NSSAI being replaced occurs, if the terminal stores information indicating that it will use Alternative S-NSSAI instead of the corresponding S-NSSAI (e.g., Mapping of Alternative S-NSSAI), it can transmit the PDU session establishment request message including Alternative S-NSSAI and S-NSSAI being replaced.

[0087] In one embodiment, this network slice replacement functionality may be supported by terminals and network devices (e.g., AMF, SMF, etc.).

[0088] Meanwhile, in environments where only some network devices support the network slice replacement feature, the network slice replacement feature may only be available in areas covered by network devices that support the feature. Depending on whether the network slice replacement feature is supported by the terminal's location, a method may be required to update terminal configuration information related to handling related sessions (e.g., replaced PDU sessions, or PDU sessions associated with the replaced network slice along with the replacement network slice).

[0089] For example, at this time, if the terminal newly selects network equipment (e.g., AMF and / or SMF) that does not support the network slice replacement function (e.g., Network Slice Replacement, NSR) due to movement, etc. (e.g., when receiving service through network equipment that does not support NSR), the following problems may occur.

[0090] - Unable to process sessions involving non-NSR-supporting network equipment (e.g., AMF or SMF) (e.g., replaced PDU sessions or PDU sessions associated with replaced network slices with replaced network slices, etc.).

[0091] - Network equipment that does not support NSR (e.g., AMF or SMF) cannot process NSR-related terminal configuration information (e.g., Mapping of Alternative S-NSSAI).

[0092] - When a terminal sends a PDU Session establishment request related to NSR (e.g., a PDU Session establishment request message containing Alternative S-NSSAI and S-NSSAI being replaced) to a network device that does not support NSR, it cannot be processed.

[0093] In some embodiments, if the network equipment does not support NSR, a method may be required to release a replaced PDU session or update terminal configuration information.

[0094] FIG. 2 is a diagram illustrating a method for processing associated PDU sessions and providing terminal configuration information depending on whether AMF supports NSR in a registration procedure.

[0095] In addition, FIG. 2 may correspond to a registration procedure related to an embodiment in IDLE mode of a terminal. According to FIG. 2, in step 210, a terminal (UE (201)) may transmit an AN (access network) message (e.g., AN parameter, registration request) to a base station (RAN). At this time, the registration request message may include at least one of a UE identifier (e.g., a subscription concealed identifier (SUCI), a 5G-globally unique temporary identity (5G-GUTI), or a permanent equipment identifier (PEI)), a registration type, a requested NSSAI, a UE MM (mobility management) core network capability, a List Of PDU Sessions To Be Activated, a PDU Session Status, etc.

[0096] When UE (201) provides the Network Slice Replacement function, UE (201) may include information indicating that it supports the function in a message transmitted to a base station, etc. For example, information indicating that it supports the Network Slice Replacement function may be included in the UE (201) MM core network capability of the registration request message.

[0097] When UE (201) connects to a new base station, it can determine that the Network Slice Replacement function is not supported by the base station based on the configuration information received in the previous registration procedure (e.g., whether NSR is supported is included in the registration accept message transmitted by AMF) or information received from the connected base station. In this case, UE (201) can internally release (e.g., local release) the replaced PDU session (e.g., PDU session associated with Alternative S-NSSAI and S-NSSAI being replaced, or PDU session associated with two S-NSSAIs, etc.) and include the PDU Session Status excluding the corresponding PDU sessions in the Registration request message, etc. The release of the replaced PDU session can be performed after transmitting the Registration request message to AMF.

[0098] According to one embodiment, the UE (201) may internally delete terminal configuration information (e.g., information expressed as Mapping of Alternative S-NSSAI or Mapping of S-NSSAI to Alternative S-NSSAI) indicating that it will use Alternative S-NSSAI instead of S-NSSAI being replaced.

[0099] According to FIG. 2, at step 220, the RAN may select an AMF based on information in the AN message received from the UE (201).

[0100] At step 230, the RAN may transmit an N2 message (N2 parameters, registration request) to the AMF. The N2 parameters may include a selected PLMN ID, UE (201) location information (e.g., Location Information and Cell ID associated with the cell where the UE (201) is camping (e.g., NG-RAN CGI), etc.), or a UE context request.

[0101] Additionally, the N2 message may include RAN ID, etc.

[0102] In one embodiment, if the previous AMF of the UE (201) does not exist (e.g., if the registration request is an Initial Registration request, etc.) or if the AMF has not changed, steps 240 and 250 below may be omitted.

[0103] Additionally, in the following steps, Old AMF (203) and New AMF (202) may be referred to as the first AMF and the second AMF.

[0104] In step 240, if the AMF has changed, the New AMF (202) can identify the Old AMF (203) for the UE (201) based on the 5G-GUTI, etc. included in the information received in step 230. The New AMF (202) can transmit a message (e.g., Namf_Communication_UEContextTransfer Request, etc.) including the Access Type of the UE (201), the identifier of the UE (e.g., 5G-GUTI or SUPI), and the supported features to the Old AMF (203). The Supported features may include information on the functions supported by the NF (e.g., the New AMF (202)). If the New AMF (202) supports the Network Slice Replacement function, the information may be included in the Supported features, and if it does not support the function, the information may not be included in the Supported features. According to one embodiment, the Old AMF (203) can determine whether the New AMF (202) supports Network Slice Replacement. The Old AMF (203) can determine based on information (e.g., supported features) included in a message received from the New AMF (202). For example, if the supported features do not include information indicating that Network Slice Replacement is supported, the Old AMF (203) can determine that the New AMF (202) does not support Network Slice Replacement. Specifically, an indicator indicating that Network Slice Replacement is supported may be included in the supported features, and a message including the indicator may be transmitted to the base station or the AMF.Additionally, transmissions can be sent via non-access stratum (NAS) messages.

[0105] According to one embodiment, when Old AMF (203) receives a message (e.g., Namf_Communication_UEContextTransfer Request) from New AMF (202), it can determine whether New AMF (202) supports the NSR function. First, if the supported features of the message from New AMF (202) do not include information indicating that Network Slice Replacement is supported, Old AMF (203) can determine that New AMF (202) does not support Network Slice Replacement.

[0106] Alternatively, the Old AMF (203) can determine whether the New AMF (202) supports NSR based on information about the New AMF (202) received from the Network Repository Function (NRF). For example, if the Old AMF (203) transmits an NF discovery message to the NRF, and the NRF transmits a response message thereto, and if the NF Profile for the New AMF (202) in the response message does not include information indicating that Network Slice Replacement is supported, the Old AMF (203) can determine that the New AMF (202) does not support Network Slice Replacement.

[0107] In step 250, when the Old AMF (203) receives the UE Context request message from the New AMF (202) in step 240, it may include information including the UE Context in a response message (e.g., Namf_Communication_UEContextTransfer response) transmitted to the New AMF (202). For example, if the Old AMF (203) determines in step 240 that the New AMF (202) does not support Network Slice Replacement, the Old AMF (203) may include the UE Context, excluding information related to Network Slice Replacement, in the message transmitted to the New AMF (202). Information associated with Network Slice Replacement may include, for example, context information (e.g., PDU Session ID, S-NSSAI, Alternative S-NSSAI, Access Type, RAT Type, SMF ID, PCF ID, etc.) for a replaced PDU session (e.g., a PDU session associated with an Alternative S-NSSAI and an S-NSSAI being replaced, or a PDU session associated with two S-NSSAIs, etc.). In addition, there may be terminal configuration information indicating that the Alternative S-NSSAI is to be used instead of the S-NSSAI being replaced (e.g., information expressed as Mapping of Alternative S-NSSAI or Mapping of S-NSSAI to Alternative S-NSSAI).

[0108] Additionally, according to one embodiment, if the Old AMF (203) determines that the New AMF (202) does not support Network Slice Replacement in step 240, the Old AMF (203) may remove the replaced S-NSSAI and the corresponding Alternative S-NSSAI from the Allowed NSSAI included in the UE Context transmitted to the New AMF (202).

[0109] According to one embodiment, if the Old AMF (203) determines that the New AMF (202) does not support Network Slice Replacement in step 240, the Old AMF (203) may remove the Alternative S-NSSAI corresponding to the replaced S-NSSAI from the Configured NSSAI included in the UE Context transmitted to the New AMF (202).

[0110] Additionally, according to one embodiment, the message or information (e.g., UE context information, etc.) sent to the New AMF (202) may be configured to be transmitted excluding information associated with Network Slice Replacement.

[0111] In step 260, if the Old AMF (203) includes context information (e.g., PDU Session ID, S-NSSAI, Alternative S-NSSAI, Access Type, RAT Type, SMF ID, PCF ID, etc.) for a replaced PDU session in the UE Context (e.g., a PDU session associated with an Alternative S-NSSAI and an S-NSSAI being replaced, or a PDU session associated with two S-NSSAIs), and if the New AMF (202) determines in step 240 that it does not support the Network Slice Replacement function or if it transmits the UE Context excluding the context information for the replaced PDU session to the New AMF (202) in step 250 (e.g., if it does not transmit the context information for the replaced PDU session to the New AMF (202)), it may transmit a PDU Session Release Request message to the SMF (204)(s) in charge of the corresponding PDU session(s). Specifically, Old AMF (203) can send a message (e.g., Nsmf_ReleaseSMContext request) including the SM Context ID of the PDU session to the SMF (204) responsible for each PDU session to release the corresponding PDU session(s).

[0112] In one embodiment, if the Old AMF (203) includes context information (e.g., PDU Session ID, S-NSSAI, Alternative S-NSSAI, Access Type, RAT Type, SMF ID, PCF ID, etc.) for a replaced PDU session (e.g., a PDU session associated with an Alternative S-NSSAI and an S-NSSAI being replaced, or a PDU session associated with two S-NSSAIs, etc.) in the UE Context, or if the New AMF (202) determines in step 240 that it does not support the Network Slice Replacement function or if the UE Context except for the context information for the replaced PDU session is transmitted to the New AMF (202) in step 250 (e.g., if the context information for the replaced PDU session is not transmitted to the New AMF (202)), the Old AMF (203) sends a message (e.g., Nsmf_UpdateSMContext) to the SMF (204) responsible for each PDU session to deactivate the corresponding PDU session(s). You can send a request (e.g. SM Context ID or PDU Session ID, Operation Type (deactivate)).

[0113] In step 265, when the SMF (204) receives the Nsmf_ReleaseSMContext request message exemplified in step 260 from the Old AMF (203), it can perform PDU session release for the SM Context ID included in the received message. The SMF (204) can transmit an N4 message to the UPF (205) to release the PDU session.

[0114] According to one embodiment, when the SMF (204) receives the Nsmf_UpdateSMContext request message illustrated in step 260 from the Old AMF (203), if the Operation type of the received message indicates deactivate, the SMF (204) may perform user plane (UP) deactivation for the SM Context ID or PDU Session ID of the included PDU session. The SMF (204) may send a message (e.g., an N4 message) to the UPF (205) for UP deactivation of the PDU session.

[0115] In step 270, SMF (204) may send a response message to Old AMF (203) including a result indication (e.g., success or failure as a result of processing). In one embodiment, the response message may be Nsmf_ReleaseSMContext response or Nsmf_UpdateSMContext response depending on the message received in step 260.

[0116] In step 280, the New AMF (202) may perform a registration procedure for the UE (201). The New AMF (202) may obtain subscriber information for the UE (201) from the UDM and perform registration for the Access Type to which the UE (201) has accessed in the UDM. In addition, step 280 may include other procedures for registration for the UE (201).

[0117] At step 290, New AMF (202) may transmit a Registration Accept message to UE (201) via RAN.

[0118] According to one embodiment, the New AMF (202) may include PDU session context information, including identifier information for currently established PDU sessions, in the Registration accept message. The New AMF (202) may include updated PDU Session Status, etc. based on the PDU session context information included in the UE Context received in step 250.

[0119] According to one embodiment, the New AMF (202) may include the PDU session ID(s) included in the context information received from the Old AMF (203) in the PDU Session status. For example, if the registration request message received from the UE (201) includes the PDU Session status, the New AMF (202) may include only the PDU session ID(s) included in the PDU Session status received from the UE (201) among the PDU session ID(s) included in the context information received from the Old AMF (203) in the PDU Session Status.

[0120] According to one embodiment, if the New AMF (202) supports the Network Slice Replacement function or if the UE Context received in step 250 includes information indicating to use Alternative S-NSSAI instead of S-NSSAI, the New AMF (202) may include Mapping of Alternative S-NSSAI (e.g., mapping information indicating to use Alternative S-NSSAI instead of S-NSSAI) and Allowed NSSAI (e.g., Allowed NSSAI including the replaced S-NSSAI and the corresponding Alternative S-NSSAI) in the Registration accept message transmitted to the UE (201).

[0121] In one embodiment, if the New AMF (202) does not support the Network Slice Replacement function, the New AMF (202) may remove the replaced S-NSSAI and the corresponding Alternative S-NSSAI from the Allowed NSSAI and include the Allowed NSSAI in the Registration accept message transmitted to the UE (201).

[0122] In one embodiment, if the New AMF (202) does not support the Network Slice Replacement function, the New AMF (202) may remove the Alternative S-NSSAI corresponding to the replaced S-NSSAI from the Configured NSSAI and include the updated Configured NSSAI in the Registration accept message transmitted to the UE (201). In addition, the New AMF (202) may not include the Mapping of Alternative S-NSSAI (e.g., mapping information indicating to use the Alternative S-NSSAI instead of the S-NSSAI) in the Registration accept message transmitted to the UE (201).

[0123] With respect to step 290, a Registration Accept message may be delivered to the UE (201) via the RAN. Additionally, the message may include updated allowed NSSAI information, updated configured NSSAI information, updated PDU session status information, or information related to Network Slice Replacement (e.g., Mapping of Alternative S-NSSAI).

[0124] According to one embodiment, if there is no Mapping of Alternative S-NSSAI in the received Registration Accept message, the UE (201) may delete the stored Mapping of Alternative S-NSSAI and delete the S-NSSAI included in the Mapping of Alternative S-NSSAI and the corresponding Alternative S-NSSAI from the stored Allowed NSSAI.

[0125] According to one embodiment, if there is no Mapping of Alternative S-NSSAI in the received Registration Accept message, the UE (201) may delete the S-NSSAI included in the Mapping of Alternative S-NSSAI and the corresponding Alternative S-NSSAI from the stored Configured NSSAI.

[0126] According to one embodiment, if a PDU session Status exists in a received Registration accept message, the UE (201) may internally release (e.g., local release, etc.) PDU sessions excluding the PDU session ID(s) included in the corresponding PDU session status.

[0127] In one embodiment, when the terminal determines that the AMF cannot support NSR based on a message received from the AMF (e.g., when the message received from the AMF does not include an NSR support indicator of the AMF or a Mapping of Alternative S-NSSAI), the terminal may release stored NSR-related Mapping of Alternative S-NSSAI, etc., release one or more replaced PDU sessions associated with the alternative S-NSSAI, update the PDU session status, and transmit the updated information to the AMF in a registration request message.

[0128] FIG. 3 is a diagram illustrating a method for processing associated PDU sessions and providing terminal configuration information depending on whether NSR is supported in a handover procedure.

[0129] According to one embodiment, FIG. 3 may illustrate the operation of a terminal in Connected mode. According to FIG. 3, at step 310, an N2-based handover procedure may be performed. The S-NG-RAN (source NG-RAN) may transmit a message to the S-AMF (302) (i.e., Old AMF (302)) indicating that a handover is required. The message may include identifier information for PDU Sessions managed by the S-RAN.

[0130] Additionally, according to one embodiment, the message that the S-NG-RAN transmits to the S-AMF (302) may include information about the T-RAN (target RAN), and the S-RAN may determine that the Network Slice Replacement function is not supported in the T-RAN. In this case, the S-RAN may release the replaced PDU sessions (e.g., the PDU sessions associated with the Alternative S-NSSAI and the S-NSSAI being replaced, or the PDU sessions associated with two S-NSSAIs, etc.) and include identifier information for the PDU sessions excluding the corresponding PDU sessions in the message that it transmits to the S-AMF (302) (e.g., the Old AMF (302)). The release of the replaced PDU sessions may be performed after transmitting the handover request message to the S-AMF (302).

[0131] Additionally, according to one embodiment, the UE (301) may transmit a message for release (e.g., a PDU session release message) through the Access in order to release a multi-access (MA) PDU session for a specific Access. Additionally, the AMF may transmit a message including information related to an Access network (AN) type to the SMF (305), and the SMF (305) may determine that the AN type is being released and perform the release.

[0132] At step 320, if the S-AMF (302) is no longer responsible for the UE (301) or at the discretion of the S-AMF (302), the S-AMF (302) may select a new T-AMF (303) (target AMF) (e.g., New AMF (303)).

[0133] In step 330, the S-AMF (302) may transmit a request message to the NRF (304) for selecting the T-AMF (303). The message may include a target NF Type set to AMF, a Location set to the current UE location, a Consumer NF type set to AMF, and an AMF Capability set by the S-AMF (302). If the S-AMF (302) has a replaced PDU session for the UE (301) or a Mapping of Alternative S-NSSAI exists, the S-AMF (302) may include information indicating that it supports Network Slice Replacement in the AMF Capability. The information indicating the support may correspond to an indicator related to the AMF capability.

[0134] In step 335, NRF (304) may include in a response message to S-AMF (302) an NF Profile for a target NF (e.g., AMF) that satisfies the information included in the request message of step 330. The NF Profile may include whether the NF supports Network Slice Replacement.

[0135] In step 340, the S-AMF (302) can select the T-AMF (303) based on the NF profile included in the message of step 335. In addition, based on the response message, the S-AMF (302) can determine whether the T-AMF (303) supports the NSR function.

[0136] For example, if the supported features included in the message of step 335 do not include information supporting Network Slice Replacement (or include information indicating that it does not support it), the S-AMF (302) may determine that the T-AMF (303) does not support the Network Slice replacement function.

[0137] Alternatively, S-AMF (302) may determine that T-AMF (303) does not support the Network Slice replacement function based on configuration information, etc.

[0138] In step 350, the S-AMF (302) may transmit a UE Context creation message to the T-AMF (303). According to one embodiment, if the S-AMF (302) determines in step 340 that the T-AMF (303) does not support Network Slice Replacement, the S-AMF (302) may include UE Context, excluding information related to Network Slice Replacement, in the message transmitted to the T-AMF (303).

[0139] According to one embodiment, information associated with Network Slice Replacement may include context information (e.g., PDU Session ID, S-NSSAI, Alternative S-NSSAI, Access Type, RAT Type, SMF ID, PCF ID, etc.) for a replaced PDU session (e.g., a PDU session associated with an Alternative S-NSSAI and an S-NSSAI being replaced, or a PDU session associated with two S-NSSAIs), terminal configuration information indicating to use the Alternative S-NSSAI instead of the S-NSSAI being replaced (e.g., information expressed as Mapping of Alternative S-NSSAI or Mapping of S-NSSAI to Alternative S-NSSAI), etc.

[0140] Additionally, if the S-AMF (302) determines in step 340 that the T-AMF (303) does not support Network Slice Replacement, the S-AMF (302) may remove the replaced S-NSSAI and the corresponding Alternative S-NSSAI from the Allowed NSSAI included in the UE Context transmitted to the T-AMF (303).

[0141] Additionally, if the S-AMF (302) determines that the T-AMF (303) does not support Network Slice Replacement in step 340, the S-AMF (302) may remove the Alternative S-NSSAI corresponding to the replaced S-NSSAI from the Configured NSSAI included in the UE Context transmitted to the T-AMF (303).

[0142] At step 360, a handover procedure may be performed. The UE (301) may transmit a handover confirm message to the T-RAN. Upon receiving the handover confirm message for the UE (301), the T-RAN may transmit a handover notify message for the UE (301) to the T-AMF (303).

[0143] At step 365, when the T-AMF (303) receives a handover notify message for the UE (301) from the T-RAN, it can transmit a message indicating that the handover has been performed to the S-AMF (302).

[0144] In step 370, if the S-AMF (302) determines that the T-AMF (303) does not support the Network Slice Replacement function in step 340 or transmits UE Context excluding context information for the replaced PDU session to the T-AMF (303) in step 350 (e.g., if the Context information for the replaced PDU session is not transmitted to the T-AMF (303)), when the S-AMF (302) receives a message from the T-AMF (303) indicating that the handover for the corresponding UE (301) is completed in step 365, the S-AMF (302) may transmit a PDU session release request message to the SMF (305)(s) in charge of the corresponding PDU session(s). Specifically, the S-AMF (302) may transmit a message (e.g., Nsmf_ReleaseSMContext request) including the SM Context ID of the PDU session to the SMF (305) in charge of each PDU session in order to release the corresponding PDU session(s).

[0145] In one embodiment, if the S-AMF (302) determines that the T-AMF (303) does not support the Network Slice Replacement function in step 340 or transmits UE Context excluding context information for the replaced PDU session to the T-AMF (303) in step 350 (e.g., if the Context information for the replaced PDU session is not transmitted to the T-AMF (303)), the S-AMF (302) may transmit a message (e.g., Nsmf_UpdateSMContext request (SM Context ID or PDU Session ID, Operation Type (deactivate)) to the SMF (305) in charge of each PDU session to deactivate the corresponding PDU session(s).

[0146] In step 375, when the SMF (305) receives the Nsmf_ReleaseSMContext request message of step 370 from the S-AMF (302), it can perform PDU session release for the SM Context ID included in the received message. The SMF (305) can transmit a message (e.g., N4 message) to the UPF (306) to release the PDU session.

[0147] According to one embodiment, when the SMF (305) receives the Nsmf_UpdateSMContext request message of step 370 from the S-AMF (302), if the Operation type of the received message indicates deactivate, the SMF (305) may deactivate the user plane (UP) for the SM Context ID or PDU Session ID of the included PDU session. The SMF (305) may send a message (e.g., an N4 message) to the UPF (306) for UP deactivation of the PDU session.

[0148] In step 380, SMF (305) may send a response message to Old AMF (302) including a result indication (e.g., success or failure as a result of processing). The response message may be Nsmf_ReleaseSMContext response or Nsmf_UpdateSMContext response depending on the message received in step 370.

[0149] At step 390, the remaining handover procedures or other additional procedures for handover may be performed. In one embodiment, after the UE (301) is handed over from the S-NG-RAN to the Target NG-RAN (T-NG-RAN), the UE (301) may receive services through the T-NG-RAN and the T-AMF (303).

[0150] Referring to FIG. 4, a terminal (400) according to an embodiment of the present disclosure may be configured to include a control unit (410), a transceiver unit (420), and a memory (430). In the present disclosure, the control unit (410) of the terminal (400) may be defined as a circuit or an application-specific integrated circuit or at least one processor.

[0151] The control unit (410) can control the overall operation of the terminal (400) according to an embodiment proposed in the present disclosure. For example, the control unit (410) can control the signal flow between each block to perform operations according to the drawing (or, flowchart, flow chart) described above.

[0152] The transceiver (420) can transmit and receive signals. The transceiver (420) can transmit signals to a node or base station according to an embodiment of the present disclosure, for example, and receive signals from the node or base station.

[0153] The memory (430) can store at least one of information transmitted and received through the transceiver (420) and information generated through the control unit (410). In addition, the memory (430) can be defined as a storage unit.

[0154] FIG. 5 is a drawing showing an example of the structure of a base station according to one embodiment of the present disclosure.

[0155] Referring to FIG. 5, a base station (500) according to an embodiment of the present disclosure may be configured to include a control unit (510), a transceiver unit (520), and a memory (530). In the present disclosure, the control unit (510) of the base station (500) may be defined as a circuit or an application-specific integrated circuit or at least one processor.

[0156] The control unit (510) can control the overall operation according to an embodiment proposed in the present disclosure. For example, the control unit (510) can control the signal flow between each block to perform the operation according to the drawing (or, flowchart, flow chart) described above.

[0157] The transceiver (520) can transmit and receive signals. The transceiver (520) can transmit signals to a terminal or node according to an embodiment of the present disclosure, for example, and receive signals from the terminal or node.

[0158] The memory (530) can store at least one of information transmitted and received through the transceiver (520) and information generated through the control unit (510). In addition, the memory (530) can be defined as a storage unit.

[0159] The methods according to the embodiments described in the claims or specification of the present disclosure may be implemented in the form of hardware, software, or a combination of hardware and software.

[0160] When implemented in software, a computer-readable storage medium storing one or more programs (software modules) may be provided. The one or more programs stored in the computer-readable storage medium are configured for execution by one or more processors within an electronic device. The one or more programs include instructions that cause the electronic device to execute methods according to the embodiments described in the claims or specification of the present disclosure.

[0161] These programs (software modules, software) may be stored in random access memory, non-volatile memory including flash memory, read only memory (ROM), electrically erasable programmable read only memory (EEPROM), magnetic disc storage device, compact disc ROM (CD-ROM), digital versatile discs (DVDs) or other forms of optical storage device, magnetic cassette. Or, they may be stored in a memory configured as a combination of some or all of these. In addition, each configuration memory may be included in multiple numbers.

[0162] Additionally, the program may be stored on an attachable storage device that is accessible via a communication network such as the Internet, an intranet, a local area network (LAN), a wide local area network (WLAN), a storage area network (SAN), or a combination thereof. Such a storage device may be connected to a device implementing an embodiment of the present disclosure via an external port.

[0163] Additionally, a separate storage device on a communications network may be connected to a device performing an embodiment of the present disclosure.

[0164] In the specific embodiments of the present disclosure described above, components included in the present disclosure are expressed in the singular or plural form, depending on the specific embodiment presented. However, the singular or plural expressions are selected to suit the presented situation for convenience of explanation, and the present disclosure is not limited to singular or plural components. Components expressed in the plural form may be composed of singular elements, or components expressed in the singular form may be composed of plural elements.

[0165] Meanwhile, the embodiments of the present disclosure disclosed in this specification and drawings are merely specific examples presented to easily explain the technical content of the present disclosure and aid in understanding of the present disclosure, and are not intended to limit the scope of the present disclosure. In other words, it will be apparent to those skilled in the art to which the present disclosure pertains that other modified examples based on the technical concepts of the present disclosure are possible.

[0166] Additionally, each of the above embodiments can be combined and operated as needed.

[0167] Meanwhile, the order of description in the drawings explaining the method of the present disclosure does not necessarily correspond to the order of execution, and the order of precedence may be changed or executed in parallel.

[0168] Alternatively, the drawings illustrating the method of the present disclosure may omit some components and include only some components without detracting from the essence of the present disclosure.

[0169] In addition, the method of the present disclosure may be implemented by combining some or all of the contents included in each embodiment within a scope that does not harm the essence of the present disclosure.

[0170] Meanwhile, the embodiments of the present disclosure disclosed in this specification and drawings are merely specific examples presented to easily explain the technical content of the present disclosure and help understand the present disclosure, and are not intended to limit the scope of the present disclosure. In other words, it will be apparent to those skilled in the art to which the present disclosure pertains that other modified examples based on the technical concept of the present disclosure are possible. In addition, each of the above embodiments can be combined and operated with each other as needed. For example, all of the embodiments of the present disclosure can be operated with parts combined with each other.

Claims

1. A method performed by a first AMF (access and mobility management function) of a communication system, A step of transmitting a first message including information indicating whether network slice replacement (NSR) is supported to a second AMF; If the first AMF does not support the NSR, receiving a second message for the first AMF that does not support the NSR from the second AMF; and A step of transmitting a third message including information about NSSAI (network slice selection assistance information) to the terminal, A method characterized in that if the first AMF does not support the NSR, information related to the NSR is excluded from the second message and the third message.

2. In paragraph 1, A method characterized in that when the first AMF supports the NSR, the second message and the third message include information related to the NSR.

3. In paragraph 1, A method characterized in that the information related to the NSR includes at least one of information about a replaced PDU (protocol data unit) session, information about a replaced S-NSSAI (single network slice selection assistance information), information about a replacement S-NSSAI, or information about a mapping related to the replaced S-NSSAI.

4. In paragraph 1, A method characterized in that if the first AMF does not support the NSR, the information related to the NSR is deleted by the terminal.

5. In a method performed by a terminal of a communication system, A step of receiving a third message including information about network slice selection assistance information (NSSAI) from a first AMF (access and mobility management function), A first message including information indicating whether NSR (network slice replacement) is supported is transmitted from the first AMF to the second AMF, If the first AMF does not support the NSR, a second message for the first AMF that does not support the NSR is received by the first AMF from the second AMF, A method characterized in that if the first AMF does not support the NSR, information related to the NSR is excluded from the second message and the third message.

6. In paragraph 5, A method characterized in that when the first AMF supports the NSR, the second message and the third message include information related to the NSR.

7. In paragraph 5, If the first AMF does not support the NSR, further comprising a step of deleting the information related to the NSR, A method characterized in that the information related to the NSR includes at least one of information about a replaced PDU (protocol data unit) session, information about a replaced S-NSSAI (single network slice selection assistance information), information about a replacement S-NSSAI, or information about a mapping related to the replaced S-NSSAI.

8. In the first AMF (access and mobility management function) of the communication system, Transmitter and receiver; and Connected to the above transceiver, transmits to the second AMF a first message including information indicating whether NSR (network slice replacement) is supported, If the first AMF does not support the NSR, a second message for the first AMF that does not support the NSR is received from the second AMF, A control unit for transmitting a third message including information about NSSAI (network slice selection assistance information) to the terminal, A first AMF, characterized in that if the first AMF does not support the NSR, information related to the NSR is excluded from the second message and the third message.

9. In paragraph 8, A first AMF, characterized in that when the first AMF supports the NSR, the second message and the third message include the information related to the NSR.

10. In paragraph 8, A first AMF, characterized in that the information related to the NSR includes at least one of information about a replaced PDU (protocol data unit) session, information about a replaced S-NSSAI (single network slice selection assistance information), information about a replacement S-NSSAI, or information about a mapping related to the replaced S-NSSAI.

11. In paragraph 8, A first AMF, characterized in that if the first AMF does not support the NSR, the information related to the NSR is deleted by the terminal.

12. At the terminal of the communication system, Transmitter and receiver; and A control unit connected to the above transceiver unit and receiving a third message including information on NSSAI (network slice selection assistance information) from a first AMF (access and mobility management function), A first message including information indicating whether NSR (network slice replacement) is supported is transmitted from the first AMF to the second AMF, If the first AMF does not support the NSR, a second message for the first AMF that does not support the NSR is received by the first AMF from the second AMF, A terminal characterized in that if the first AMF does not support the NSR, information related to the NSR is excluded from the second message and the third message.

13. In paragraph 12, A terminal characterized in that, when the first AMF supports the NSR, the second message and the third message include the information related to the NSR.

14. In paragraph 12, A method characterized in that the information related to the NSR includes at least one of information about a replaced PDU (protocol data unit) session, information about a replaced S-NSSAI (single network slice selection assistance information), information about a replacement S-NSSAI, or information about a mapping related to the replaced S-NSSAI.

15. In paragraph 12, The above control unit is a terminal that deletes the information related to the NSR when the first AMF does not support the NSR.

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