Method and equipment for supporting network slice change in consideration of network slice quota

Abstract

A method performed by an access and mobility management function (AMF) entity in a wireless communication system is provided. A protocol data unit (PDU) session with respect to a terminal is established via a first network slice. And determining whether the first network slice needs to be replaced. And when replacement is needed, providing information about the second network slice to the terminal. A session management (SM) context update message including information about the second network slice is provided to a session management function (SMF) entity corresponding to the PDU session. An SM context update response message is received from the SMF entity including information about whether the new PDU session is assignable to the second network slice. Based on the SM context update response message, replacement with the second network slice is attempted, replacement with another network slice is performed, or replacement is stopped.

Description

Technical Field

[0001] The present disclosure relates to the operation of a terminal and a base station in a wireless communication system. In particular, the present disclosure relates to a method and apparatus for supporting network slice changes in consideration of network slice quotas in a wireless communication system. Background Art

[0002] Fifth-generation (5G) mobile communication technology defines a wide frequency band, enabling high transmission rates and new services, and can be implemented not only in "sub-6 gigahertz (GHz)" frequency bands such as 3.5 GHz, but also in "above 6 GHz" frequency bands, known as millimeter waves (mmWave), including 28 GHz and 39 GHz. Furthermore, consideration has been given to implementing sixth-generation (6G) mobile communication technology (referred to as a "super 5G system") in terahertz (THz) frequency bands (e.g., 95 GHz to 3 THz bands) in order to achieve transmission rates fifty times faster than 5G mobile communication technology and ultra-low latency one-tenth that of 5G mobile communication technology.

[0003] Since the start of the development of 5G mobile communication technology, in order to support services and meet performance requirements related to enhanced mobile broadband (eMBB), ultra-reliable low-latency communications (URLLC) and massive machine-type communications (mMTC), there has been ongoing standardization on the following: beamforming and massive multiple-input multiple-output (MIMO) for mitigating radio wave path loss in millimeter waves and increasing radio wave transmission range, dynamic operation of parameter sets (e.g., operating multiple subcarrier spacings) and time slot formats to support efficient utilization of millimeter wave resources, initial access technology to support multi-beam transmission and wideband, definition and operation of bandwidth parts (BWPs), new channel coding methods such as low-density parity-check (LDPC) codes for large-scale data transmission and polar codes for highly reliable transmission of control information, L2 preprocessing, and network slicing for providing dedicated networks customized for specific services.

[0004] Currently, there are ongoing discussions on improvements and performance enhancements to initial 5G mobile communication technologies in view of the services to be supported by 5G mobile communication technologies, and there has been standardization of physical layers on technologies such as Vehicle-to-Everything (V2X) for assisting driving decisions of autonomous vehicles based on information on the position and status of vehicles transmitted by the vehicles and for enhancing user convenience, New Radio for Unlicensed (NR-U) for system operation designed to comply with various regulatory requirements within unlicensed frequency bands, New Radio (NR) user equipment (UE) energy saving, Non-Terrestrial Network (NTN) as UE-satellite direct communication for providing coverage in areas where communication with terrestrial networks is not possible, and positioning.

[0005] In addition, in the air interface architecture / protocol area, standardization is already underway on technologies such as the Industrial Internet of Things (IIoT), which supports new services through interconnection and integration with other industries; Integrated Access and Backhaul (IAB), which provides nodes for network service area expansion by supporting wireless backhaul links and access links in an integrated manner; mobility enhancements including conditional handover and dual-active protocol stack (DAPS) handover; and two-step random access (two-step random access channel (RACH) for NR) to simplify the random access process. In terms of system architecture / services, standardization is also underway on a 5G baseline architecture (e.g., a service-based architecture or service-based interface) for incorporating network function virtualization (NFV) and software-defined networking (SDN) technologies; and mobile edge computing (MEC) for receiving services based on UE location.

[0006] With the commercialization of 5G mobile communication systems, the already exponentially growing number of connected devices will be connected to communication networks, and it is expected that enhanced functionality and performance of 5G mobile communication systems and the integrated operation of connected devices will become necessary. To this end, new research is being planned on extended reality (XR) for effectively supporting augmented reality (AR), virtual reality (VR), mixed reality (MR), etc., 5G performance improvements and complexity reduction through the use of artificial intelligence (AI) and machine learning (ML), AI service support, metaverse service support, and drone communications.

[0007] Furthermore, such development of 5G mobile communication systems will serve as the foundation for the development of not only new waveforms for providing terahertz band coverage for 6G mobile communication technology, multi-antenna transmission technologies such as full-dimensional MIMO (FD-MIMO), array antennas, and massive antennas, metamaterial-based lenses and antennas for improving terahertz band signal coverage, high-dimensional spatial multiplexing technologies using orbital angular momentum (OAM), and reconfigurable smart surfaces (RIS), but also full-duplex technologies for improving the frequency efficiency of 6G mobile communication technology and improving system networks, AI-based communication technologies for leveraging satellites and AI to achieve system optimization and internalize end-to-end AI support functions from the design stage, and next-generation distributed computing technologies for implementing services at a complexity level that exceeds the operational capabilities of UEs by utilizing ultra-high-performance communication and computing resources.

[0008] The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with respect to the present disclosure. Summary of the Invention

[0009] Solution to the problem

[0010] The embodiment provides an apparatus and method capable of efficiently providing services in a wireless communication system.

[0011] According to an embodiment, a method performed by an access and mobility management function (AMF) entity in a wireless communication system may include: establishing a protocol data unit (PDU) session about a terminal via a first network slice; determining whether the first network slice needs to be replaced; when replacement is required, providing information about a second network slice to the terminal; sending a session management (SM) context update message including information about the second network slice to a session management function (SMF) entity corresponding to the PDU session; receiving an SM context update response message from the SMF entity, the SM context update response message including information about whether the new PDU session can be allocated to the second network slice; and based on the received SM context update response message, attempting to replace with the second network slice, performing replacement with another network slice, or stopping replacement.

[0012] Attempting to replace with a second network slice, performing replacement with another network slice, or stopping replacement may include: when the SM context update response message includes information indicating that the number of PDU sessions of the second network slice is a maximum number, attempting to replace with a second network slice, performing replacement with another network slice, or stopping replacement.

[0013] Attempting to replace with a second network slice, performing replacement with another network slice, or stopping replacement may include: based on a predetermined timer value, attempting to replace with the second network slice, or sending a NAS message to the terminal for deleting information about the second network slice in order to stop replacement.

[0014] The method may also include obtaining load information about multiple network slices and determining a second network slice based on the load information.

[0015] The second network slice may be a network slice that replaces the first network slice.

[0016] According to an embodiment, a method performed by an SMF entity in a wireless communication system may include: receiving an SM context update message from an AMF entity, the SM context update message being used to request replacing a first network slice for establishing a PDU session with a terminal with a second network slice; determining whether a new PDU session needs to be generated for the second network slice based on the received SM context update message; identifying whether the first network slice and the second network slice are subject to network slice admission control (NSAC) based on a result of the determination; sending a message to a network slice admission control function (NSACF) entity requesting to reduce the number of PDU sessions of the first network slice and requesting to increase the number of PDU sessions of the second network slice based on a result of the identification; and sending an SM context update response message to the AMF entity, the SM context update response message including information about whether the new PDU session can be allocated to the second network slice.

[0017] The method may further include requesting information from the NSACF or the Network Data Analysis Function (NWDAF) about whether a new PDU session allocation to the second network slice is possible; and receiving information from the NSACF or the NWDAF about whether a new PDU session allocation to the second network slice is possible.

[0018] The information about whether a new PDU session allocation is possible may include information about whether the number of PDU sessions of the second network slice has reached a maximum value.

[0019] The method may also include receiving information from the NSACF regarding whether the request to reduce the number of PDU sessions of the first network slice and the request to increase the number of PDU sessions of the second network slice are successful.

[0020] In the method, based on the result of the identification, a message for requesting to reduce the number of PDU sessions of the first network slice and a message for requesting to increase the number of PDU sessions of the second network slice are sent via a single message.

[0021] According to an embodiment, an AMF entity in a wireless communication system may include a transceiver, and at least one processor coupled to the transceiver, wherein the at least one processor is configured to: establish a PDU session regarding a terminal via a first network slice; determine whether the first network slice needs to be replaced; when replacement is required, provide information about a second network slice to the terminal; send an SM context update message including information about the second network slice to an SMF entity corresponding to the PDU session; receive an SM context update response message from the SMF entity, the SM context update response message including information about whether the new PDU session can be allocated to the second network slice; and based on the received SM context update response message, attempt to replace with the second network slice, perform replacement with another network slice, or stop replacement.

[0022] At least one processor may be configured to, when the SM context update response message includes information indicating that the number of PDU sessions of the second network slice is a maximum number, attempt to replace with the second network slice, perform replacement with another network slice, or stop replacement.

[0023] At least one processor may be configured to attempt replacement with a second network slice based on a predetermined timer value, or to send a NAS message to the terminal for deleting information about the second network slice in order to stop the replacement.

[0024] At least one processor may be configured to obtain load information about a plurality of network slices and determine a second network slice based on the load information of the plurality of network slices.

[0025] The second network slice may include a network slice for replacing the first network slice.

[0026] According to an embodiment, an SMF entity in a wireless communication system may include a transceiver and at least one processor coupled to the transceiver, wherein the at least one processor is configured to: receive an SM context update message from an AMF entity, the SM context update message being used to request replacing a first network slice for establishing a PDU session with a terminal with a second network slice; determine whether a new PDU session needs to be generated for the second network slice based on the received SM context update message; identify whether the first network slice and the second network slice are subject to NSAC based on a result of the determination; send a message to the NSACF entity requesting to reduce the number of PDU sessions of the first network slice and requesting to increase the number of PDU sessions of the second network slice based on the result of the identification; and send an SM context update response message to the AMF entity, the SM context update response message including information about whether the new PDU session can be allocated to the second network slice.

[0027] At least one processor may be configured to request information from the NSACF or NWDAF regarding whether a new PDU session allocation to the second network slice is possible, and to receive information from the NSACF or NWDAF regarding whether a new PDU session allocation to the second network slice is possible.

[0028] The information about whether a new PDU session allocation is possible may include information about whether the number of PDU sessions of the second network slice has reached a maximum value.

[0029] At least one processor may be configured to receive information from the NSACF regarding whether a request to reduce the number of PDU sessions of the first network slice and a request to increase the number of PDU sessions of the second network slice are successful.

[0030] Based on the identification result, a message for requesting to reduce the number of PDU sessions of the first network slice and a message for requesting to increase the number of PDU sessions of the second network slice can be sent to the NSACF entity via a single message.

[0031] The present disclosure provides an apparatus and method capable of efficiently providing services in a wireless communication system. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The above and other aspects, features and advantages of the embodiments of the present disclosure will become more apparent through the following description in conjunction with the accompanying drawings, in which:

[0033] Figure 1 is a diagram illustrating a communication network including a core network (CN) entity in a wireless communication system according to an embodiment;

[0034] Figure 2 is a diagram showing a wireless environment including a CN in a wireless communication system according to an embodiment;

[0035] Figure 3 2 is a diagram illustrating a process of changing a PDU session network slice based on AMF according to an embodiment;

[0036] Figure 4 is a diagram showing a structure of a terminal according to an embodiment;

[0037] Figure 5 is a diagram showing a structure of a base station according to an embodiment; and

[0038] Figure 6 is a diagram showing a structure of a network entity according to an embodiment. DETAILED DESCRIPTION

[0039] Hereinafter, the operating principle of the present disclosure will be described in detail with reference to the accompanying drawings. In the following description of the present disclosure, a detailed description of known functions or configurations incorporated herein will be omitted when it is determined that the description may make the subject matter of the present disclosure unnecessarily unclear. The terms described below are defined in consideration of the functions in the present disclosure and may vary depending on the user, the user's intention, or custom. Therefore, the definition of terms should be based on the content throughout the specification.

[0040] For the same reason, in the accompanying drawings, some elements may be exaggerated, omitted or schematically shown. In addition, the size of each element does not fully reflect the actual size. In the accompanying drawings, the same or corresponding elements are provided with the same reference numerals.

[0041] The advantages and features of the present disclosure and the manner in which they are achieved will be apparent with reference to the embodiments described in detail below in conjunction with the accompanying drawings. However, the present disclosure is not limited to the embodiments set forth below, but may be implemented in a variety of different forms. The following embodiments are provided solely to fully disclose the present disclosure and to inform those skilled in the art of the scope of the present disclosure, and the present disclosure is limited only by the scope of the appended claims. Throughout the specification, identical or similar reference numerals represent identical or similar elements.

[0042] In this article, each block of the flowchart diagram and the combination of blocks in the flowchart diagram can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device create a device for implementing the function specified in one or more flowchart blocks. These computer program instructions can also be stored in a computer-usable or computer-readable memory, which can instruct the computer or other programmable data processing device to act in a particular manner, so that the instructions stored in the computer-usable or computer-readable memory produce an article of manufacture comprising an instruction device that implements the function specified in one or more flowchart blocks. The computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are performed on the computer or other programmable device to produce a computer-implemented process so that the instructions executed on the computer or other programmable device provide steps for implementing the function specified in one or more flowchart blocks.

[0043] In addition, each block of the flowchart diagram can represent a module, fragment or portion of code, which includes one or more executable instructions for implementing the specified logical function. In some alternative embodiments, the functions marked in the blocks can occur out of sequence. For example, two blocks shown in succession can actually be executed substantially simultaneously, or these blocks can sometimes be executed in reverse order, depending on the functions involved.

[0044] As used herein, the term "unit" refers to a software element or hardware element, such as a field programmable gate array (FPGA) or an application-specific integrated circuit (ASIC), that performs a predetermined function. However, the term "unit" is not always limited to software or hardware. A unit can be configured to be stored in an addressable storage medium or to execute one or more processors. Thus, a unit includes, for example, a software element, an object-oriented software element, a class element, or a task element, a process, a function, a property, a procedure, a subroutine, a program code segment, a driver, firmware, microcode, circuits, data, a database, a data structure, a table, an array, and parameters. The elements and functions provided by a unit can be combined into a smaller number of elements or units, or divided into a larger number of elements or units. Furthermore, elements and units can be implemented as one or more CPUs within a reproduction device or a secure multimedia card. Furthermore, a unit can include one or more processors.

[0045] A detailed description of known functions or configurations incorporated herein will be omitted when it is determined that the description may make the subject matter of the present disclosure unnecessarily unclear. Hereinafter, embodiments are described with reference to the accompanying drawings.

[0046] In this document, for the convenience of description, terms referring to network entities or network functions and edge computing system entities, terms referring to messages, terms referring to identification information, etc. are illustratively used. Therefore, the present disclosure is not limited to the terms used below, and other terms referring to subjects with equivalent technical meanings may be used.

[0047] For convenience, the present disclosure is described using terms and names defined in the LTE and NR standards, which are the latest of the existing communication standards specified by the Third Generation Partnership Project (3GPP) group. However, the present disclosure is not limited by these terms and names and can be applied in the same manner to systems conforming to other standards. Specifically, the present disclosure can be applied to 3GPP 5GS / NR (fifth-generation mobile communication standards). In addition, the embodiments of the present disclosure can be applied to other communication systems with similar technical backgrounds or channel types. Moreover, based on the determination of those skilled in the art, the embodiments of the present disclosure can be applied to other communication systems with some modifications without significantly departing from the scope of the present disclosure.

[0048] A 5G mobile communication network may include a 5G UE, a 5G radio access network (RAN), and a 5G CN. The 5G CN includes NFs such as an AMF that provides a mobility management function for the UE, an SMF that provides a session management function, a user plane function (UPF) for transmitting data, a policy control function (PCF) that provides a policy control function, a unified data management (UDM) that provides a function for managing data such as subscriber data and policy control data, and a unified data repository (UDR) that stores data of various NFs such as the UDM.

[0049] In 5G systems, network slicing technology refers to the architecture and technology that enables the virtualization of multiple independent logical networks within a single physical network. To meet the specialized requirements of services and applications, network operators provide services by configuring virtual end-to-end networks called network slices. Network slices are distinguished by an identifier called Single Network Slice Selection Assistance Information (S-NSSAI), and network operators provide network slices to terminals to receive services.

[0050] Specifically, in the 5G system, when registering with the network, the terminal sends the identifier information of the network slice to be requested by the terminal (i.e., the requested S-NSSAI) to the AMF, and the AMF provides the terminal with information about the network slices available to the terminal in consideration of the requested S-NSSAI, subscriber information, etc. Even if the information about the slice requested by the terminal is not provided, the AMF may provide the terminal with the allowed NSSAI. In this case, the allowed NSSAI may include information about the slice configured by default (default-configured NSSAI) and information about the slice configured by default among the subscribed slices included in the terminal subscriber information (i.e., default-subscribed S-NSSAI).

[0051] If the allowed NSSAI cannot include any slices (e.g., the default configured NSSAI and the default subscribed S-NSSAI are missing or unavailable), the AMF sends a Network Registration Reject message including a reason code to the terminal indicating that the registration is rejected due to no available slices.

[0052] When attempting to include any slice in the allowed NSSAI of a terminal, admission control (NSAC) and authentication (Network Slice Specific Authentication and Authorization (NSSAA)) may be performed for the corresponding slice.

[0053] In the NSAC, whether to allow a slice (i.e., whether to include the slice in the allowed NSSAI) is determined based on the number of terminals currently registered with a specific slice and the maximum number of registered terminals allowed for the slice. Specifically, the NSACF may monitor the number of registered terminals and the number of established PDU sessions for each slice for network slices subject to the NSAC, and may perform control so that the number of registered terminals and the number of established PDU sessions for each slice remain less than the maximum number of registered terminals and the maximum number of PDU sessions, respectively.

[0054] In this case, when a new terminal registers with a slice subject to NSAC or an existing registered terminal is deregistered, the AMF can send an update request message to notify the NSACF of the update. When a new PDU session is generated in a slice subject to NSAC or an existing PDU session is released, the SMF can send an update request message to notify the NSACF of the update. When receiving a message notifying the registration of a new terminal to a slice or a message notifying the generation of a new PDU session in a slice, the NSAC can determine whether to allow the slice for the new terminal or PDU session based on the maximum number of terminals and the maximum number of PDU sessions, and then include whether the slice is allowed in each response message.

[0055] For data transmission to or reception from a specific data network (DN) via an allowed slice (allowed NSSAI), the terminal can select one of the allowed slices, generate a PDU session to the specific data network name (DNN) from the slice request, and transmit or receive data via the generated PDU session. The PDU session includes multiple service flows, and the service flows include two types of guaranteed bit rate quality of service flows (GBR QoS flows) and non-GBR QoS flows.

[0056] Depending on the embodiment, it may be necessary to move one or all PDU sessions included in a certain network slice to another network slice. For example, if congestion has occurred in various 5G network entities belonging to the network slice, or if it is necessary to temporarily or permanently stop using a specific slice due to operational reasons (for example, replacing and upgrading equipment, etc.), or if it is necessary to move the corresponding service to another slice due to performance degradation of the network slice that has already sent the application service, it may be necessary to move one or all PDU sessions included in the network slice to another network slice.

[0057] In this case, the network slice of the PDU session that needs to be changed (or replaced) needs to be changed to an alternative network slice. In a 5G network, the number of registered terminals and the number of established PDU sessions for each slice with respect to some slices may be monitored, and control may be performed so that the number of registered terminals and the number of established PDU sessions for each slice may be maintained less than the maximum number of registered terminals and the maximum number of PDU sessions, respectively.

[0058] When an alternative network slice is determined to be a slice that has reached the maximum number of sessions, the generation of a PDU session to the alternative network slice to replace the existing PDU session slice is rejected, so that the continuity of the application service is not guaranteed. Therefore, a method to solve this problem may be needed.

[0059] The present disclosure provides a method for determining another S-NSSAI for an alternative network slice and retrying when the NSAC for an alternative network slice that replaces an existing network slice fails during a network slice change for a PDU session. In addition, when the result of slice quota-based admission control for the alternative network slice for the PDU session fails, the continuity of the existing PDU session can be better guaranteed through a process that can handle the failure (i.e., attempting to generate a PDU session to a new alternative network slice).

[0060] Figure 1 is a diagram illustrating a communication network including a CN entity in a wireless communication system according to an embodiment.

[0061] The 5G mobile communication network includes 5G UE (terminal), 5G RAN, base stations (5G nodeB (gNB), evolved nodeB (eNB), etc.), and 5G CN. The 5G CN includes network functions such as the AMF 150 that provides UE mobility management functions, the SMF 160 that provides session management functions, the UPF 170 for transmitting data, the PCF 180 that provides policy control functions, the UDM 153 that provides functions for managing data such as subscriber data and policy control data, and the UDR that stores data for various network functions.

[0062] refer to Figure 1In the LTE-A network, a terminal (UE) 110 can communicate via a wireless channel (i.e., access network) established with a base station (e.g., an eNB or gNB). In some embodiments, terminal 110 is a device used by a user and may be configured to provide a user interface (UI). For example, UE 110 may be a terminal installed in a vehicle for driving. In other embodiments, terminal 110 may be a device that performs machine-type communication (MTC) without user interaction, or may be an autonomous vehicle. Besides being an electronic device, UE may also be referred to as a terminal, vehicle terminal, mobile station, subscriber station, remote terminal, wireless terminal, user equipment, or other technically equivalent terms. Besides UE, customer premises equipment (CPE) or dongle-type terminals may also be used as terminals. Similar to UEs, CPEs can connect to NG-RAN nodes while providing network access to other communication devices (e.g., laptops).

[0063] refer to Figure 1 , the AMF 150 may provide functions for access and mobility management on a per-terminal 110 basis, and one terminal 110 may be substantially connected to one AMF 150. Specifically, the AMF 150 may perform at least one function of signaling between CN nodes for mobility between 3GPP access networks, an interface (N2 interface) between the radio access network (e.g., 5G RAN) 120, NAS signaling with the terminal 110, identification of the SMF 160, and transmission and provision of SM messages between the terminal 110 and the SMF 160. Some or all functions of the AMF 150 may be supported within a single instance of one AMF 150.

[0064] refer to Figure 1 SMF 160 may provide session management functionality, and when terminal 110 has multiple sessions, each session may be managed by a different SMF 160. Specifically, SMF 160 may perform at least one of session management (e.g., session establishment, modification, and release, including maintaining a tunnel between UPF 170 and an access network node), UPF selection and control, configuration of traffic steering for routing traffic to an appropriate destination by UPF 170, termination of the SM portion of NAS messages, and initiation of Downlink Data Notification (DDN) and AN-specific SM information (e.g., transmitted to the access network via AMF 150 over the N2 interface). Some or all of the functions of SMF 160 may be supported within a single instance of SMF 160.

[0065] In 3GPP systems, the conceptual links connecting NFs in a 5G system can be referred to as reference points. Reference points can also be referred to as interfaces. The following illustrates reference points (hereinafter, used interchangeably with interfaces) included in the 5G system architecture, as presented in various embodiments of the present disclosure.

[0066] -N1: Reference point between UE 110 and AMF 150

[0067] -N2: Reference point between (R)AN 120 and AMF 150

[0068] -N3: Reference point between (R)AN 120 and UPF 170

[0069] -N4: Reference point between SMF 160 and UPF 170

[0070] -N5: Reference point between PCF 180 and AF 130

[0071] -N6: Reference point between UPF 170 and DN 140

[0072] -N7: Reference point between SMF 160 and PCF 180

[0073] -N8: Reference point between UDM 153 and AMF 150

[0074] -N9: Reference point between the two cores UPF 170

[0075] -N10: Reference point between UDM 153 and SMF 160

[0076] -N11: Reference point between AMF 150 and SMF 160

[0077] -N12: Reference point between AMF 150 and Authentication Server Function (AUSF) 151

[0078] -N13: Reference point between UDM 153 and authentication server function 151

[0079] -N14: Reference point between two AMF 150

[0080] -N15: A reference point between the AMF 150 and the PCF 180 for non-roaming scenarios, and a reference point between the AMF 150 and the PCF 180 within a visited network for roaming scenarios. In 5G systems, network slicing refers to a structure and technology that enables the virtualization of multiple independent logical networks in one physical network. To meet the specialized requirements of services / applications, network operators provide services by configuring virtual end-to-end networks called network slices. In this case, network slices are distinguished by an identifier called S-NSSAI. The network sends a set of allowed slices (e.g., allowed NSSAIs) to the terminal during terminal registration (e.g., UE registration process), and the terminal sends or receives application data via a PDU session generated via one S-NSSAI (i.e., network slice).

[0081] In an embodiment, when the alternative network slice selected to replace the network slice of the existing PDU session is determined to be a slice that has reached the maximum number of sessions, the generation of a PDU session to the alternative network slice is rejected to replace the existing PDU session slice, so that the continuity of the application service is not guaranteed. Therefore, the present disclosure proposes a method for solving this problem.

[0082] Figure 2 1 is a diagram showing a wireless environment including a CN in a wireless communication system according to an embodiment. Figure 2 , the wireless communication system includes RAN 120 and CN.

[0083] Radio access network 120 is a network directly connected to user equipment (e.g., terminal 110) and is the infrastructure that provides radio access to terminal 110. Radio access network 120 may include a collection of multiple base stations (including base station 125), and the multiple base stations may communicate via interfaces established between them. At least some of the interfaces between the multiple base stations may be wired or wireless. Base station 125 may have a structure with a separate central unit (CU) and distributed units (DU). In this case, a single CU may control multiple DUs. In addition to base stations, base stations 125 may also be referred to as access points (APs), gNBs, 5G nodes, radio points, transmission / reception points (TRPs), or other technically equivalent terms. Terminal 110 may access radio access network 120 and communicate with base stations 125 via wireless channels. In addition to terminals, terminal 110 may also be referred to as UE, mobile station, subscriber station, remote terminal, wireless terminal, user equipment, or other technically equivalent terms.

[0084] The CN is the network that manages the entire system. It controls the radio access network 120 and processes data and control signals for the terminal 110 sent or received via the radio access network 120. The CN performs various functions, such as controlling the user plane and the control plane, handling mobility, managing subscriber information, billing, and interworking with other types of systems (e.g., Long Term Evolution (LTE) systems). To perform the various functions described, the CN may include multiple functionally separate entities with different NFs. For example, the CN 200 may include the AMF 150, SMF 160, UPF 170, PCF 180, Network Repository Function (NRF) 159, UDM 153, Network Exposure Function (NEF) 155, and UDR 157.

[0085] Terminal 110 can connect to radio access network 120 to access AMF 150, which performs mobility management functions for the CN. AMF 150 is a function or device responsible for access to radio access network 120 and mobility management for terminal 110. SMF 160 is a network function that manages sessions. AMF 150 connects to SMF 160, and AMF 150 routes session-related messages for terminal 110 to SMF 160. SMF 160 connects to UPF 170 to allocate user plane resources to terminal 110 and establish a channel for transmitting data between base station 125 and UPF 170. PCF 180 controls policy and charging information for sessions used by terminal 110.

[0086] The NRF 159 stores information about the NFs installed in the mobile communications operator's network and performs a function of notifying the user of this stored information. The NRF 159 can connect to all NFs. Upon commencing operation in the operator's network, each NF registers with the NRF 159 to notify the NRF 159 that the corresponding NR is operating in the network. The UDM 153 is a NF similar to the Home Subscriber Server (HSS) service in 4G networks and stores the subscription information of the terminal 110 or the context used by the terminal 110 in the network.

[0087] The NEF 155 connects the NFs and third-party servers in the 5G mobile communication system. Furthermore, the NEF 155 provides data to the UDR 157, performs updates, or retrieves data. The UDR 157 stores the terminal 120's subscription information, policy information, externally exposed data, or information required by third-party applications. Furthermore, the UDR 157 provides stored data to another NF.

[0088] Figure 32 is a diagram showing the process of AMF-based PDU session network slice change according to an embodiment.

[0089] At 300, the terminal sends a registration request message to the AMF, and the AMF performs registration and then sends a registration accept message to the terminal. During registration, the terminal may add support for slice remapping (i.e., an indicator indicating that the terminal supports slice remapping) in the registration request message sent to the AMF. The AMF may determine whether the terminal supports the slice remapping function based on whether support for slice remapping is included in the message received from the terminal and store it. After receiving the registration accept message, the terminal may perform PDU session establishment and send or receive application data to the server via the PDU session established for a specific DNN and S-NSSAI.

[0090] At 301, the AMF may determine that a slice change (or replacement) is required when receiving the following information from at least one of Orchestration and Management (OAM), RAN, NWDAF, NSACF, and PCF, or according to the configuration information of the AMF or the AMF's own determination.

[0091] For example, when the AMF receives, in addition to one or more pieces of information among the S-NSSAI, UE ID and PDU session ID, an indicator indicating that the network slice corresponding to the included information is unavailable, an indicator indicating that the network slice corresponding to the included information needs to be changed, etc., or according to the configuration information of the AMF or the AMF's own determination, the AMF may determine that a slice change (or replacement) is required.

[0092] According to an embodiment, when the received information includes a PDU session ID, the AMF may determine a slice change (or replacement) only for the PDU session of the terminal that has provided an indicator indicating support for slice remapping from among the terminals for which the AMF is responsible at 300.

[0093] When the received information includes S-NSSAI and UE ID or only S-NSSAI, the AMF may determine the slice change of the corresponding PDU session only for the terminal among the corresponding UEs that has provided an indicator indicating support for slice remapping from among the terminals for which the AMF is responsible at 300.

[0094] In this document, for ease of description, the S-NSSAI of each PDU session to be changed is referred to as the old S-NSSAI. At 302, the AMF may determine, for each PDU session for which the S-NSSAI change determined at 301 is to be performed, a replacement slice (i.e., a replacement S-NSSAI) as a new S-NSSAI among slices that do not include the existing S-NSSAI of the corresponding PDU session. In this case, when there is an S-NSSAI subject to NSAC among the candidate S-NSSAIs from the replacement S-NSSAI, the AMF may determine the replacement S-NSSAI based on load information of the candidate S-NSSAI. The load information of the S-NSSAI may include at least one of the current number of registered UEs and the maximum number of registered UEs per slice and / or the current number of established PDU sessions and the maximum number of established PDU sessions per slice.

[0095] The AMF may obtain the load information of the S-NSSAI at 302a and 302b. The AMF may obtain the load information of the S-NSSAI via the NWDAF.

[0096] At 302a, the AMF may send a message including the following information to the NSACF (or NWDAF) to obtain information to be referenced for determining the replacement S-NSSAI:

[0097] -Event ID: may include an event ID indicating the number of registered UEs per slice and / or the number of PDU sessions per slice.

[0098] -Event filter: may include S-NSSAI information of slices that may be candidates for replacing S-NSSAI.

[0099] - Event report information: information indicating a report type, wherein the event report information may include an immediate report flag for requesting an immediate response.

[0100] At 302b, the NSACF may, based on the event ID included in the message received from the AMF, add information about the number of registered UEs or the number of established PDU sessions to the response message sent to the AMF for each S-NSSAI included in the event filter of the message received from the AMF. In addition, when the event report information of the message received from the AMF is configured with an immediate report flag, the NSACF may immediately send the response message to the AMF.

[0101] At 303, for the S-NSSAI of the PDU session for which the slice change has been determined at 301, if there is a single PDU session established for the terminal, the AMF may add the following information to the UE Configuration Update message to be sent to the terminal (i.e., UE) via the RAN:

[0102] - Allowed NSSAI: A set of slice identifiers allowed to the terminal, where the existing S-NSSAI (i.e., old S-NSSAI) of the PDU session for which the slice change is to be performed in operation 302 may be excluded from the allowed NSSAI. If the identifier of the alternative slice (i.e., alternative S-NSSAI) determined at 302 is not included in the allowed NSSAI, the AMF may add the alternative S-NSSAI to the allowed NSSAI.

[0103] - Alternative S-NSSAI for the old S-NSSAI: This may include information indicating that an alternative S-NSSAI may be used instead of the old S-NSSAI (i.e., including both the alternative S-NSSAI and the old S-NSSAI information). The alternative S-NSSAI for the old S-NSSAI may be transmitted in the form of a mapping of allowed NSSAIs, where the allowed NSSAI is information indicating which other slice identifier a corresponding identifier replaces for each slice identifier included in the allowed NSSAI, or may be configured and transmitted in a different form (e.g., via an information element (IE) and a separate message format transmitted to the terminal using a non-access stratum (NAS) protocol). The alternative S-NSSAI for the old S-NSSAI may include the alternative slice identifier (i.e., the alternative S-NSSAI) determined at 302, and may include slice identifier information in which the alternative S-NSSAI is used instead of the existing S-NSSAI (i.e., the old S-NSSAI) for the PDU session for which the slice change is to be performed at 302.

[0104] When the terminal receives an allowed NSSAI that does not include an old S-NSSAI, if the alternative S-NSSAI for the old S-NSSAI includes S-NSSAI information used instead of the old S-NSSAI (ie, alternative S-NSSAI), the PDU session established regarding the old S-NSSAI may not be released.

[0105] After receiving the replacement S-NSSAI for the old S-NSSAI, when the terminal needs to send a new PDU session establishment request to the old S-NSSAI according to the UE local configuration stored in the terminal or the UE routing policy (URSP) rule, the NAS message including the PDU session establishment request may include the replacement S-NSSAI and information indicating that the replacement S-NSSAI is a slice identifier that replaces the old S-NSSAI. For example, the terminal configures the S-NSSAI value included in the NAS message including the PDU session establishment request as the replacement S-NSSAI by referring to the replacement S-NSSAI for the old S-NSSAI. In addition, information indicating that the replacement S-NSSAI included in the NAS message including the PDU session establishment request is a value that replaces the old S-NSSAI may be included.

[0106] At 304, when the terminal has a single PDU session established with respect to the old S-NSSAI at 301 and an S-NSSAI change has been determined for the PDU session, the AMF may send an SM context update message to the SMF responsible for the PDU session.

[0107] According to an embodiment, when the terminal has multiple PDU sessions established with respect to the old S-NSSAI at 301, the AMF may determine the S-NSSAI change of some or all of the PDU sessions based on the information received from another NF at 301, and may send an SM context update message for each determined PDU session to the SMF.

[0108] According to an embodiment, the SM context update message sent by the AMF to the SMF may include one of the following information. The present disclosure is not limited to the following examples:

[0109] - Alternative S-NSSAI: May include an alternative S-NSSAI determined by the AMF for the PDU Session.

[0110] - S-NSSAI: may include the existing S-NSSAI of the PDU session.

[0111] -PDU session ID or SM context ID: may include an identifier of a PDU session or an SM context ID for a PDU session.

[0112] At 305 , the SMF may determine whether a new PDU session needs to be generated to replace the PDU session corresponding to the SM context ID or the PDU session ID.

[0113] At 306a, when the alternative S-NSSAI received in operation 304 is subject to NSAC (i.e., it is necessary to determine the accepted slices based on the number of established PDU sessions) and a new PDU session needs to be generated (i.e., when the UE needs to re-request generation of a PDU session based on a new PDU session ID and the alternative S-NSSAI according to information provided by the SMF to the UE), the SMF may send a message (e.g., Nnsacf_SliceEventExposure_Subscribe request) including at least one of the following information to the NSACF (or NWDAF) in order to pre-identify whether session generation via the alternative S-NSSAI is possible:

[0114] -Event ID: may include an event ID indicating the number of registered UEs per slice.

[0115] - Event filter: May include alternative S-NSSAI information.

[0116] - Event report information: information indicating a report type, wherein the event report information may include an immediate report flag for requesting an immediate response.

[0117] Alternatively, at 306a, when the alternative S-NSSAI received at 304 is subject to NSAC (i.e., it is necessary to determine the accepted slices based on the number of established PDU sessions) and a new PDU session needs to be generated (i.e., when the UE needs to re-request the generation of a PDU session based on the new PDU session ID and the alternative S-NSSAI according to information provided by the SMF to the UE), the SMF may send a message (e.g., Nnsacf_NSAC_NumOfPDUsUpdate_Request) including at least one of the following information to the NSACF (or NWDAF). The present disclosure is not limited to the following embodiments.

[0118] -PDU session ID or SM context ID: may include an identifier of a PDU session or an SM context ID for a PDU session.

[0119] -UE ID: may include an identifier of the UE (eg, Subscription Permanent Identifier (SUPI)).

[0120] - S-NSSAI: may include the S-NSSAI information of the number of PDU sessions that need to be updated. When the SMF receives both the replacement S-NSSAI (i.e., the S-NSSAI determined by the AMF) and the S-NSSAI (i.e., the existing S-NSSAI) from the AMF at 304, the SMF may include the replacement S-NSSAI.

[0121] - Access Type: may include the access type of the PDU session.

[0122] - Update flag: may include increase and decrease (indicators indicating increase and decrease in the number of PDU sessions of S-NSSAI, respectively).

[0123] At 306b, the NSACF may add information about the number of established PDU sessions to the response message sent to the SMF for each S-NSSAI included in the event filter of the message received from the SMF based on the event ID included in the message received from the SMF. In addition, when the event report information of the message received from the SMF is configured with an immediate report flag, the NSACF may immediately send the response message to the SMF.

[0124] Alternatively, at 306b, upon receiving the Nnsacf_NSAC_NumOfPDUsUpdate_Request message from the SMF, if the update flag in the Nnsacf_NSAC_NumOfPDUsUpdate_Request message is configured as "increase", the NSACF may identify (or determine) whether the current number of PDU sessions has reached a maximum value for one or more of the UE ID, S-NSSAI, and access type included in the nsacf_NSAC_NumOfPDUsUpdate_Request message. If the current number of PDU sessions (e.g., information on the maximum number of PDU sessions per S-NSSAI stored by the NSACF) has not reached the maximum value, the NSACF may increase the number of PDU sessions by 1 and then add information indicating success to the response message sent to the SMF.

[0125] If the current number of PDU sessions (e.g., information about the maximum number of PDU sessions per S-NSSAI stored by the NSACF) has reached the maximum value, the NSACF may add information indicating that the number of PDU sessions has reached the maximum value (e.g., the maximum number of PDU sessions per S-NSSAI has been reached) and / or information indicating failure to the response message sent to the SMF.

[0126] At 307a, when the alternative S-NSSAI received together with the S-NSSAI at 304 is subject to NSAC (i.e., it is necessary to determine the accepted slices based on the number of established PDU sessions) and it is not necessary to generate a new PDU session, or when the SMF determines to retain the existing PDU session (i.e., the SMF provides the PDU session ID of the PDU session for which slice change is to be performed and the slice for change (i.e., the alternative S-NSSAI) to the UE and UPF and RAN responsible for the existing PDU session, and changes the slice of the PDU session to the alternative S-NSSAI), the SMF may send a message including at least one of the following information to the NSACF (or NWDAF) in order to pre-identify whether a session change to the alternative S-NSSAI is possible:

[0127] -PDU Session ID: may include an event ID indicating the number of registered UEs per slice.

[0128] - Event filter: May include alternative S-NSSAI information.

[0129] - Event report information: information indicating a report type, wherein the event report information may include an immediate report flag for requesting an immediate response.

[0130] Alternatively, at 307a, when the alternative S-NSSAI received together with the S-NSSAI at 304 is subject to NSAC (i.e., the accepted slices need to be determined based on the number of established PDU sessions) and a new PDU session does not need to be generated, or when the SMF determines to retain the existing PDU session (i.e., the SMF provides the UE and UPF, RAN responsible for the existing PDU session with the PDU session ID of the PDU session for which slice change is to be performed and the slice to be changed (i.e., the alternative S-NSSAI), and changes the slice of the PDU session to the alternative S-NSSAI), the SMF may send a message (e.g., Nnsacf_NSAC_NumOfPDUsUpdate_Request) including at least one of the following information to the NSACF (or NWDAF) (Case 1). In addition, when the S-NSSAI received together with the replacement S-NSSAI (i.e., the S-NSSAI for the existing PDU session) is subject to NSAC (i.e., it is necessary to determine the accepted slices based on the number of established PDU sessions) and there is no need to generate a new PDU session, or when the SMF determines to retain the existing PDU session (i.e., the SMF provides the UE and UPF and RAN responsible for the existing PDU session with the PDU session ID of the PDU session for which the slice change is to be performed and the slice to be changed (i.e., the replacement S-NSSAI), and changes the slice of the PDU session to the replacement S-NSSAI), the SMF may send a message including at least one of the following information to the NSACF (or NWDAF) (Case 2). The messages sent in the above two cases (Case 1 and Case 2) may be sent in the form of one integrated message (e.g., Nnsacf_NSAC_NumOfPDUsUpdate_Request) or may be sent separately. Of course, the present disclosure is not limited to the following embodiments:

[0131] -PDU session ID or SM context ID: may include an identifier of a PDU session or an SM context ID for a PDU session.

[0132] -UE ID: may include an identifier of the UE (eg, SUPI).

[0133] -S-NSSAI: The S-NSSAI information indicating the number of PDU Sessions that need to be updated may be included. When the SMF has received both the replacement S-NSSAI (i.e., the S-NSSAI determined by the AMF) and the S-NSSAI (i.e., the existing S-NSSAI) from the AMF at 304 and does not need to generate a new PDU Session, or when the SMF determines that the existing PDU Session is to be retained and the replacement S-NSSAI is subject to NSAC, the SMF may include the replacement S-NSSAI and configure the update flag to "increase". Furthermore, when the SMF has received both the replacement S-NSSAI (i.e., the S-NSSAI determined by the AMF) and the S-NSSAI (i.e., the existing S-NSSAI) from the AMF at 304 and does not need to generate a new PDU Session, or when the SMF determines that the existing PDU Session is to be retained and the S-NSSAI (i.e., the existing S-NSSAI) is subject to NSAC, the SMF may include the S-NSSAI and configure the update flag to "decrease".

[0134] Access Type: may include the access type of the PDU session.

[0135] Update flag: may include increase and decrease (indicators indicating increase and decrease in the number of PDU sessions of S-NSSAI, respectively).

[0136] Alternatively, when the SMF has received both the replacement S-NSSAI (i.e., the S-NSSAI determined by the AMF) and the S-NSSAI (i.e., the existing S-NSSAI) from the AMF in operation 304, and the SMF determines to retain the existing PDU session, the SMF may add the UEID, PDU session ID, NF ID, the S-NSSAI configured as the replacement S-NSSAI, the access type, and the update flag configured as "Update" to the message sent to the NSSF (e.g., Nnsacf_NSAC_NumOfPDUsUpdate_Request). When the S-NSSAI for the existing PDU session needs to be replaced with another S-NSSAI (e.g., the replacement S-NSSAI), the SMF may configure the update flag to "Update".

[0137] At 307b, the NSACF may add information about the number of established PDU sessions to the response message sent to the SMF for each S-NSSAI included in the event filter of the message received from the SMF based on the event ID included in the message received from the SMF. In addition, when the event report information of the message received from the SMF is configured with an immediate report flag, the NSACF may immediately send the response message to the SMF.

[0138] Alternatively, at 307b, upon receiving the Nnsacf_NSAC_NumOfPDUsUpdate_Request message from the SMF, if the update flag in the Nnsacf_NSAC_NumOfPDUsUpdate_Request message is configured as "increase", the NSACF may identify (or determine) whether the current number of PDU sessions has reached a maximum value for one or more of the UE ID, S-NSSAI, and access type included in the Nnsacf_NSAC_NumOfPDUsUpdate_Request message. If the current number of PDU sessions (e.g., information on the maximum number of PDU sessions per S-NSSAI stored by the NSACF) has not reached the maximum value, the NSACF may increase the number of PDU sessions by 1 and then add information indicating success to the response message sent to the SMF.

[0139] Alternatively, at 307b, when receiving the Nnsacf_NSAC_NumOfPDUsUpdate_Request message from the SMF, if the update flag in the Nnsacf_NSAC_NumOfPDUsUpdate_Request message is configured as "decrease", the NSACF may reduce the current number of PDU sessions by 1 relative to one or more of the UE ID, S-NSSAI and access type included in the Nnsacf_NSAC_NumOfPDUsUpdate_Request message.

[0140] If the current number of PDU sessions (e.g., information about the maximum number of PDU sessions per S-NSSAI stored by the NSACF) has reached the maximum value, the NSACF may add information indicating that the number of PDU sessions has reached the maximum value (e.g., the maximum number of PDU sessions per S-NSSAI has been reached) and / or information indicating failure to the response message sent to the SMF.

[0141] Alternatively, at 307b, when the NSACF receives the Nnsacf_NSAC_NumOfPDUsUpdate_Request message from the SMF and the update flag in the Nnsacf_NSAC_NumOfPDUsUpdate_Request message is configured as "update", the NSACF may change the already stored S-NSSAI information to the S-NSSAI received from the SMF (i.e., replace the S-NSSAI) with respect to one or more of the UE ID, PDU session ID and access type included in the Nnsacf_NSAC_NumOfPDUsUpdate_Request message, reduce the number of PDU sessions of the already stored S-NSSAI by 1, and increase the number of PDU sessions of the S-NSSAI received from the SMF by 1. For example, when the message received by the NSACF from the SMF includes the UE ID, the PDU session ID, and the S-NSSAI_2, and the NSACF stores S-NSSAI_1 for the UE ID and the PDU session ID, the NSACF may change the S-NSSAI (i.e., S-NSSAI_1) stored for the UE ID and the PDU session ID to S_NSSAI_2, and then reduce the number of PDU sessions of S-NSSAI_1 by 1, and the NSACF may increase the number of PDU sessions of S-NSSAI_2 by 1, if possible. When the current number of PDU sessions has not reached the maximum value of the alternative S-NSSAI included in the Nnsacf_NSAC_NumOfPDUsUpdate_Request message, the NSACF may increase the number of PDU sessions by 1, and then add result information indicating success to the response message sent to the SMF. If the number of current PDU sessions of the alternative S-NSSAI included in the Nnsacf_NSAC_NumOfPDUsUpdate_Request message has reached the maximum value, the NSACF may add a backoff timer for the AMF to the response message sent to the SMF, in addition to the information indicating that the number of PDU sessions has reached the maximum value (e.g., the maximum number of PDU sessions per S-NSSAI has been reached) and / or the information indicating a failure.

[0142] According to an embodiment, depending on whether a new PDU session needs to be generated, only one of 306a, 306b, 307a, and 307b may be performed.

[0143] At 308, the SMF may determine whether a new PDU session can be allocated (or established) for the alternative S-NSSAI included in the message received from the AMF at 305 based on the information included in the message received at 306b (or 307b). For example, when it is identified based on the information included in the message received at 306b (or 307b) that the number of PDU sessions of the alternative S-NSSAI has reached the maximum number of PDU sessions, the SMF may include information indicating that the maximum number of PDU sessions has been reached (e.g., “the maximum number of PDU sessions per S-NSSAI has been reached”) as information corresponding to the cause, in addition to the value indicating the failure result included in the message sent to the AMF.

[0144] If the SMF recognizes that the number of PDU sessions of the alternative S-NSSAI has not reached the maximum number of PDU sessions based on the information included in the message received at 306b (or 307b), the SMF may change the S-NSSAI of the PDU session to the alternative S-NSSAI. Depending on whether a new PDU session is generated as determined at 305, the operation may be performed as follows:

[0145] -When a new PDU session needs to be generated, the SMF may include a replacement S-NSSAI and an existing PDU session ID in a message provided to the UE (terminal). Upon receiving the message, the UE may send a message to the SMF via the RAN and AMF for confirmation. In addition, when the received message includes a PDU session release command, the UE may release the PDU session by sending a PDU session release request message to the network for the PDU session ID included in the message received from the SMF.

[0146] The UE may then generate a new PDU session by including the PDU session ID of the released PDU session, the new PDU session ID, the DNN of the released PDU session, the old S-NSSAI, and the replacement S-NSSAI included in the received message in the PDU session creation request message sent to the AMF. During the generation of the new PDU session, the AMF may include the S-NSSAI received from the UE (i.e., the existing S-NSSAI) and the replacement S-NSSAI (i.e., the S-NSSAI determined by the AMF) in the SM context creation request message sent to the SMF. After the SMF receives the SM context creation request message from the AMF, 306a, 306b, 308, and 309 may be performed.

[0147] When the received message includes a PDU Session Modification Command, the UE may generate a new PDU Session by including the PDU Session ID of the existing PDU Session, the new PDU Session ID, the DNN of the existing PDU Session, the old S-NSSAI, and the replacement S-NSSAI included in the received message in a PDU Session Generation Request message sent to the AMF. During the generation of the new PDU Session, the AMF may include the S-NSSAI received from the UE (i.e., the existing S-NSSAI) and the replacement S-NSSAI (i.e., the S-NSSAI determined by the AMF) in an SM Context Creation Request message sent to the SMF. After the SMF receives the SM Context Creation Request message from the AMF, steps 306a, 306b, 308, and 309 may be performed. When generating a new PDU Session, the UE may release the PDU Session by sending a PDU Session Release Request message to the network for the PDU Session ID of the existing PDU Session.

[0148] -When there is no need to generate a new PDU session, the SMF may change the S-NSSAI of the existing PDU session to the alternative S-NSSAI by including the PDU session ID, the alternative S-NSSAI and the information for requesting a slice change in a message sent to the UE and UPF, RAN responsible for the PDU session corresponding to the PDU session ID or SM context ID received in operation 304.

[0149] At 309, when the message received at 308 includes a result indicating failure (i.e., failure to process the network slice replacement request) (for example, when a cause indicating "maximum number of PDU sessions per S-NSSAI reached" (i.e., SM context update failure) is included), the AMF may perform 302 again. In this case, when determining the new replacement S-NSSAI at 302, the previous replacement S-NSSAI requested at 304 may be excluded. Based on the newly determined replacement S-NSSAI, the AMF may perform 303 (i.e., including the newly determined replacement S-NSSAI in the UE Configuration Update message sent to the terminal) and 304 (i.e., including the newly determined replacement S-NSSAI in the SM Context Update message sent to the SMF).

[0150] Alternatively, when the message received at 309 includes a result indicating failure (i.e., failure to process the network slice replacement request) (for example, when including a cause indicating "reaching the maximum number of PDU sessions per S-NSSAI" (i.e., when the SM context update fails)), the AMF may send a network slice change message back to the SMF after the timer expires based on the backoff timer of the AMF value received from the NSACF at 307b or the timer value stored in the configuration information. In this case, 302 may be performed again for the same alternative S-NSSAI, and when the network slice replacement request fails again at 309, the AMF may double the timer value and then send a network slice replacement request message to the SMF again after the timer expires.

[0151] When a result indicating failure (i.e., failure to process the network slice replacement request) is included in the message received at 309 (e.g., when a cause indicating "maximum number of PDU sessions per S-NSSAI reached" is included (i.e., when the SM context update fails)), the AMF may cancel (or suspend) the network slice change (e.g., network slice replacement) of the UE. When the AMF determines to cancel (or suspend) the network slice replacement after a message including a replacement S-NSSAI for the old S-NSSAI has been sent to the UE, the AMF may send a NAS message to the UE for deleting the allowed S-NSSAI for the old S-NSSAI stored in the UE.

[0152] When the AMF determines to cancel the network slice replacement after a message including the configured NSSAI or the allowed NSSAI including the alternative S-NSSAI has been sent to the UE, the AMF may send a NAS message including the configured NSSAI not including the alternative S-NSSAI and / or the allowed NSSAI not including the alternative S-NSSAI to the UE.

[0153] Alternatively, according to an embodiment, after receiving all response messages from the SMF to the SM context update message sent to the SMF for slice replacement, the AMF may send a 303 message to the UE, which is sent for network slice replacement, only when all the response messages include information indicating success.

[0154] According to an embodiment, a method performed by an AMF entity in a wireless communication system may include: establishing a PDU session regarding a terminal via a first network slice; determining whether the first network slice needs to be replaced; when replacement is required, providing information about a second network slice to the terminal; sending an SM context update message including information about the second network slice to an SMF entity corresponding to the PDU session; receiving an SM context update response message from the SMF entity, the SM context update response message including information about whether the new PDU session can be allocated to the second network slice; and based on the received SM context update response message, attempting to replace with the second network slice, performing replacement with another network slice, or stopping replacement.

[0155] Attempting to replace with a second network slice, performing replacement with another network slice, or stopping replacement may include: when the SM context update response message includes information indicating that the number of PDU sessions of the second network slice is a maximum number, attempting to replace with a second network slice, performing replacement with another network slice, or stopping replacement.

[0156] Attempting to replace with a second network slice, performing replacement with another network slice, or stopping replacement may include: based on a predetermined timer value, attempting to replace with the second network slice, or sending a NAS message to the terminal for deleting information about the second network slice in order to stop replacement.

[0157] The method may also include obtaining load information about multiple network slices, and determining a second network slice based on the load information of the multiple network slices.

[0158] The second network slice may be a network slice that replaces the first network slice.

[0159] According to an embodiment, a method performed by an SMF entity in a wireless communication system may include: receiving an SM context update message from an AMF entity, the SM context update message being used to request replacing a first network slice for establishing a PDU session with a terminal with a second network slice; determining whether a new PDU session needs to be generated for the second network slice based on the received SM context update message; identifying whether the first network slice and the second network slice are subject to NSAC based on a result of the determination; sending a message to the NSACF entity requesting to reduce the number of PDU sessions of the first network slice and requesting to increase the number of PDU sessions of the second network slice based on the result of the identification; and sending an SM context update response message to the AMF entity, the SM context update response message including information about whether the new PDU session can be allocated to the second network slice.

[0160] The method may further include requesting information from the NSACF or NWDAF about whether a new PDU session allocation to the second network slice is possible, and receiving information from the NSACF or NWDAF about whether a new PDU session allocation to the second network slice is possible.

[0161] The information about whether a new PDU session allocation is possible may include information about whether the number of PDU sessions of the second network slice has reached a maximum value.

[0162] The method may also include receiving information from the NSACF regarding whether the request to reduce the number of PDU sessions of the first network slice and the request to increase the number of PDU sessions of the second network slice are successful.

[0163] In the method, based on the result of the identification, a message for requesting to reduce the number of PDU sessions of the first network slice and a message for requesting to increase the number of PDU sessions of the second network slice are sent via a single message.

[0164] According to an embodiment, an AMF entity in a wireless communication system may include a transceiver, and at least one processor coupled to the transceiver, wherein the at least one processor is configured to: establish a PDU session regarding a terminal via a first network slice; determine whether the first network slice needs to be replaced; when replacement is required, provide information about a second network slice to the terminal; send an SM context update message including information about the second network slice to an SMF entity corresponding to the PDU session; receive an SM context update response message from the SMF entity, the SM context update response message including information about whether the new PDU session can be allocated to the second network slice; and based on the received SM context update response message, attempt to replace with the second network slice, perform replacement with another network slice, or stop replacement.

[0165] At least one processor may be configured to, when the SM context update response message includes information indicating that the number of PDU sessions of the second network slice is a maximum number, attempt to replace with the second network slice, perform replacement with another network slice, or stop replacement.

[0166] At least one processor may be configured to attempt replacement with a second network slice based on a predetermined timer value, or to send a NAS message to the terminal for deleting information about the second network slice in order to stop the replacement.

[0167] At least one processor may be configured to obtain load information about a plurality of network slices and determine a second network slice based on the load information of the plurality of network slices.

[0168] The second network slice may include a network slice for replacing the first network slice.

[0169] According to an embodiment, an SMF entity in a wireless communication system may include a transceiver and at least one processor coupled to the transceiver, wherein the at least one processor is configured to: receive an SM context update message from an AMF entity, the SM context update message being used to request replacing a first network slice for establishing a PDU session with a terminal with a second network slice; determine whether a new PDU session needs to be generated for the second network slice based on the received SM context update message; identify whether the first network slice and the second network slice are subject to NSAC based on a result of the determination; send a message to the NSACF entity requesting to reduce the number of PDU sessions of the first network slice and requesting to increase the number of PDU sessions of the second network slice based on the result of the identification; and send an SM context update response message to the AMF entity, the SM context update response message including information about whether the new PDU session can be allocated to the second network slice.

[0170] The at least one processor may also be configured to request information from the NSACF or NWDAF about whether a new PDU session allocation to the second network slice is possible, and to receive information from the NSACF or NWDAF about whether a new PDU session allocation to the second network slice is possible.

[0171] The information about whether a new PDU session allocation is possible may include information about whether the number of PDU sessions of the second network slice has reached a maximum value.

[0172] At least one processor may be configured to receive information from the NSACF regarding whether a request to reduce the number of PDU sessions of the first network slice and a request to increase the number of PDU sessions of the second network slice are successful.

[0173] Based on the identification result, a message for requesting to reduce the number of PDU sessions of the first network slice and a message for requesting to increase the number of PDU sessions of the second network slice can be sent to the NSACF entity via a single message.

[0174] Figure 4 is a block diagram showing a structure of a terminal (UE) according to an embodiment.

[0175] like Figure 4 As shown, the terminal of the present disclosure may include a processor 420, a transceiver 400, and a memory 410. However, the elements of the terminal are not limited to the above examples. For example, the terminal may include more or fewer elements than the aforementioned elements. In addition, the processor 420, the transceiver 400, and the memory 410 may be implemented in the form of a single chip.

[0176] Depending on the embodiment, the processor 420 may control a series of processes that enable the terminal to operate according to the aforementioned embodiments of the present disclosure. For example, the processor 420 may control the components of the terminal to execute the method for supporting network slicing changes according to the aforementioned embodiments. The processor 420 may control the components of the terminal to execute the aforementioned embodiments of the present disclosure by executing a program stored in the memory 410. In addition, the processor 420 may be an application processor, a communication processor (CP), a circuit, a dedicated circuit, or at least one processor.

[0177] According to an embodiment, the transceiver 400 can send a signal to a network entity, another terminal or a base station or receive a signal from a network entity, another terminal or a base station. The signal sent to the network entity, another terminal or a base station or received from the network entity, another terminal or a base station may include control information and data. The transceiver 400 may include an RF transmitter configured to perform up-conversion and amplification of the frequency of the transmitted signal, an RF receiver configured to perform low-noise amplification of the received signal and perform down-conversion of the frequency, etc. However, the elements of the transceiver 400 are not limited to the RF transmitter and the RF receiver. In addition, the transceiver 400 can receive a signal via a wireless channel, output the signal to the processor 420, and transmit the signal output from the processor 420 via the wireless channel.

[0178] According to an embodiment, the memory 410 may store programs and data required for the operation of the terminal. In addition, the memory 410 may store control information or data included in the signal sent or received by the terminal. The memory 410 may include a storage medium such as ROM, RAM, hard disk, CD-ROM and DVD, or a combination of storage media. In addition, the memory 410 may be multiple. In addition, the memory 410 may store a program for executing the aforementioned method of supporting network slicing changes.

[0179] Figure 5 is a block diagram showing the structure of a base station according to an embodiment.

[0180] like Figure 5 As shown, the base station of the present disclosure may include a processor 520, a transceiver 500, and a memory 510. However, the elements of the base station are not limited to the above examples. For example, the base station may include more or fewer elements than the aforementioned elements. In addition, the processor 520, the transceiver 500, and the memory 510 may be implemented in the form of a single chip.

[0181] According to an embodiment, the processor 520 may control a series of processes that enable the base station to operate as described above. For example, the processor 520 may control the elements of the base station to perform the method for supporting network slicing changes as described above. The processor 520 may control the elements of the base station to perform the aforementioned embodiments by executing a program stored in the memory 510. In addition, the processor 520 may be an application processor, a CP, a circuit, a dedicated circuit, or at least one processor.

[0182] According to an embodiment, the transceiver 500 may transmit or receive signals to or from a network entity, another base station, or a terminal. The signals transmitted to or received from a network entity, another base station, or a terminal may include control information and data. The transceiver 500 may include an RF transmitter configured to perform up-conversion and amplification of the frequency of the transmitted signal, an RF receiver configured to perform low-noise amplification of the received signal and perform down-conversion of the frequency, etc. However, the components of the transceiver 500 are not limited to RF transmitters and RF receivers. In addition, the transceiver 500 may receive signals via a wireless channel, output the signals to the processor 520, and transmit the signals output from the processor 520 via the wireless channel.

[0183] Depending on the embodiment, the memory 510 may store programs and data required for base station operation. The memory 510 may also store control information or data included in signals transmitted or received by the base station. The memory 510 may include storage media such as read-only memory (ROM), random access memory (RAM), a hard disk, a compact disc ROM (CD-ROM), and a digital versatile disc (DVD), or a combination of these media. Furthermore, there may be multiple memories 510. Furthermore, the memory 510 may store a program for executing the aforementioned method for supporting network slicing changes.

[0184] Figure 6 is a block diagram illustrating a structure of a network entity according to an embodiment.

[0185] like Figure 6 As shown, the network entity of the present disclosure may include a processor 620, a transceiver 600, and a memory 610. However, the elements of the network entity are not limited to the above examples. For example, the network entity may include more or fewer elements than the aforementioned elements. In addition, the processor 620, the transceiver 600, and the memory 610 may be implemented in the form of a single chip. In addition, the network entity may refer to a NF, which may include a RAN, an AMF, a PCF, a UDM, an AF, a NEF, and a UTM.

[0186] According to the embodiment, the processor 620 may control a series of processes that enable the NF to operate as described above. For example, the processor 620 may control the elements of the network entity to perform the method for supporting network slicing changes as described above. The processor 620 may control the elements of the network entity to perform the aforementioned embodiments by executing the program stored in the memory 610. In addition, the processor 620 may be an application processor, a CP, a circuit, a dedicated circuit, or at least one processor.

[0187] According to an embodiment, the transceiver 600 may transmit or receive signals to or from another network entity, base station, or terminal. The signals transmitted to or received from another network entity, base station, or terminal may include control information and data. The transceiver 600 may include an RF transmitter configured to perform up-conversion and amplification of the frequency of the transmitted signal, an RF receiver configured to perform low-noise amplification of the received signal and perform down-conversion of the frequency, etc. However, this is merely an embodiment of the transceiver 600, and the elements of the transceiver 600 are not limited to an RF transmitter and an RF receiver. In addition, the transceiver 600 may receive signals via a wireless channel, output the signals to the processor 620, and transmit the signals output from the processor 620 via the wireless channel.

[0188] Depending on the embodiment, the memory 610 may store programs and data required for the operation of the network entity. The memory 610 may store control information or data included in signals sent or received by the network entity. The memory 610 may include a storage medium such as ROM, RAM, a hard disk, a CD-ROM, and a DVD, or a combination of storage media. In addition, there may be multiple memories 610. In addition, according to the embodiment, the memory 610 may store a program for executing the aforementioned method of supporting network slicing changes.

[0189] It should be noted that Figures 1 to 6 The configuration diagrams, the diagrams illustrating the control / data signal transmission method, and the diagrams illustrating the operation process shown are not intended to limit the scope of protection of the embodiments of the present disclosure. That is, Figures 1 to 6 All constituent elements, entities, or operational steps described in the disclosure should not be construed as being essential to the implementation of the present disclosure, and the present disclosure may be implemented by including only some constituent elements without impairing the essential characteristics of the disclosure.

[0190] The operations in the above embodiments can be implemented by providing a memory device storing corresponding program codes for any unit in the device. That is, the controller in the device can perform the above operations by reading and executing the program codes stored in the memory device with the help of a processor or a central processing unit (CPU).

[0191] The various units or modules of the entity or terminal device described in this disclosure may be operated using hardware circuits such as complementary metal oxide semiconductor-based logic circuits, firmware, or hardware circuits such as software embedded in a machine-readable medium and / or a combination of hardware and firmware and / or software. For example, various electrical structures and methods may be implemented using transistors, logic gates, and circuits such as application-specific integrated circuits.

[0192] The methods according to various embodiments described in the claims or specification of the present disclosure may be implemented by hardware, software, or a combination of hardware and software.

[0193] When the method is implemented via software, a computer-readable storage medium may be provided for storing one or more programs (software modules). The one or more programs stored in the computer-readable storage medium may be configured to be executed by one or more processors within an electronic device. At least one program may include instructions that cause the electronic device to perform the method according to the various embodiments of the present disclosure as defined in the appended claims and / or disclosed herein.

[0194] Programs (software modules or software) can be stored in non-volatile memories, including random access memory and flash memory, ROM, electrically erasable programmable read-only memory (EEPROM), magnetic disk storage devices, CD-ROMs, DVDs or other types of optical storage devices, or magnetic tape cassettes. Alternatively, any combination of some or all of these can form the memory in which the program is stored. Furthermore, multiple such memories may be included in an electronic device.

[0195] In addition, the program can be stored in an attachable storage device that can be accessed by the electronic device via a communication network such as the Internet, an intranet, a local area network (LAN), a wide area LAN (WLAN), and a storage area network (SAN), or a combination thereof. Such a storage device can access the electronic device via an external port. In addition, a separate storage device on a communication network can access the portable electronic device.

[0196] In the above detailed embodiments of the present disclosure, the elements included in the present disclosure are expressed in the singular or plural, depending on the detailed embodiment presented. However, for ease of description, the singular form or plural form is appropriately selected for the situation presented, and the present disclosure is not limited to elements expressed in the singular or plural. Therefore, an element expressed in the plural may also include a single element, or an element expressed in the singular may also include multiple elements.

[0197] Although specific embodiments have been described in the detailed description of the present disclosure, it is apparent that various modifications and changes can be made thereto without departing from the scope of the present disclosure. Therefore, the scope of the present disclosure should not be limited to the embodiments, but should be defined by the appended claims and their equivalents.

Claims

1. A method performed by an access and mobility management function (AMF) entity in a wireless communication system, the method comprising: Establishing a protocol data unit (PDU) session for the terminal via the first network slice; Determining whether the first network slice needs to be replaced; If replacement is required, providing information about the second network slice to the terminal; sending a session management (SM) context update message including information about the second network slice to a session management function (SMF) entity corresponding to the PDU session; receiving an SM context update response message from the SMF entity, the SM context update response message including information about whether a new PDU session can be allocated to the second network slice; as well as Based on the SM context update response message, attempt to replace with the second network slice, perform replacement with another network slice, or stop replacement.

2. The method according to claim 1, wherein Attempting to replace with the second network slice, performing replacement with another network slice, or stopping replacement includes: In a case where the SM context update response message includes information indicating that the number of PDU sessions of the second network slice is the maximum number, attempt to replace with the second network slice, perform replacement with another network slice, or stop replacement.

3. The method according to claim 1, wherein Attempting to replace with the second network slice, performing replacement with another network slice, or stopping replacement includes: Based on a predetermined timer value, attempt to replace with the second network slice, or send a NAS message for deleting information about the second network slice to the terminal to stop the replacement.

4. The method according to claim 1, further comprising: Obtain load information about multiple network slices; as well as Based on the load information, determine the second network slice.

5. The method according to claim 1, wherein The second network slice is a network slice that replaces the first network slice.

6. A method performed by a session management function (SMF) entity in a wireless communication system, the method comprising: receiving an SM context update message from an access and mobility management function (AMF) entity, the SM context update message being used to request replacement of a first network slice for establishing a protocol data unit (PDU) session with the terminal with a second network slice; Determining, based on the received SM context update message, whether a new PDU session needs to be generated for the second network slice; Based on a result of the determining, identifying whether the first network slice and the second network slice are subject to network slice admission control (NSAC); Based on the result of the identification, sending a message to a network slice admission control function (NSACF) entity requesting to reduce the number of PDU sessions of the first network slice and requesting to increase the number of PDU sessions of the second network slice; as well as An SM context update response message is sent to the AMF entity, wherein the SM context update response message includes information about whether a new PDU session can be allocated to the second network slice.

7. The method according to claim 6, further comprising: requesting information from the NSACF or Network Data Analysis Function (NWDAF) as to whether a new PDU session allocation to the second network slice is possible; as well as Receiving information from the NSACF or the NWDAF about whether the new PDU session allocation to the second network slice is possible.

8. The method according to claim 7, wherein: The information about whether the new PDU session allocation is possible includes information about whether the number of PDU sessions of the second network slice has reached a maximum value.

9. The method according to claim 6 also includes receiving information from the NSACF regarding whether the request to reduce the number of PDU sessions of the first network slice and the request to increase the number of PDU sessions of the second network slice are successful.

10. The method according to claim 6, wherein: Based on the result of the identification, a message for requesting to reduce the number of PDU sessions of the first network slice and a message for requesting to increase the number of PDU sessions of the second network slice are sent via a single message.

11. An access and mobility management function (AMF) entity in a wireless communication system, the AMF entity comprising: transceiver; and at least one processor coupled to the transceiver, Wherein, the at least one processor is configured to: Establishing a protocol data unit (PDU) session for the terminal via the first network slice; Determining whether the first network slice needs to be replaced; If replacement is required, providing information about the second network slice to the terminal; sending a session management (SM) context update message including information about the second network slice to a session management function (SMF) entity corresponding to the PDU session; receiving an SM context update response message from the SMF entity, the SM context update response message including information on whether a new PDU session can be allocated to the second network slice; and Based on the SM context update response message, attempt to replace with the second network slice, perform replacement with another network slice, or stop replacement.

12. The AMF entity according to claim 11, wherein: The at least one processor is configured to attempt to replace with the second network slice, replace with another network slice, or stop replacement if the SM context update response message includes information indicating that the number of PDU sessions of the second network slice is a maximum number.

13. The AMF entity according to claim 11, wherein: The at least one processor is configured to attempt to replace with the second network slice based on a predetermined timer value, or to send a NAS message for deleting information about the second network slice to the terminal in order to stop the replacement.

14. The AMF entity according to claim 11, wherein: The at least one processor is configured to: Obtaining load information about multiple network slices; and Based on the load information, determine the second network slice.

15. A session management function (SMF) entity in a wireless communication system, the SMF entity comprising: transceiver; and at least one processor coupled to the transceiver, Wherein, the at least one processor is configured to: receiving an SM context update message from an access and mobility management function (AMF) entity, the SM context update message being used to request replacement of a first network slice for establishing a protocol data unit (PDU) session with the terminal with a second network slice; Determining, based on the received SM context update message, whether a new PDU session needs to be generated for the second network slice; Based on a result of the determining, identifying whether the first network slice and the second network slice are subject to network slice admission control (NSAC); Based on the result of the identification, sending a message to a network slice admission control function (NSACF) entity requesting to reduce the number of PDU sessions of the first network slice and requesting to increase the number of PDU sessions of the second network slice; and An SM context update response message is sent to the AMF entity, wherein the SM context update response message includes information about whether a new PDU session can be allocated to the second network slice.

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