Method and apparatus for continuously providing user plane function service while user plane function is relocated in wireless communication system

Abstract

The present disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate, and an operation method of a first session management function (SMF) entity (104-1) in a wireless communication system, according to an embodiment of the present disclosure, may comprise the operations of: determining to relocate a first user plane function (UPF) entity (105-1) connected to a terminal (102) through a first PDU session; transmitting, to an access and mobility management function (AMF) entity (103), a request message comprising information indicating the relocation of the first UPF entity (105-1); and transmitting, to an application function (AF) entity (114) through a network exposure function (NEF) entity (108), a PDU session release notification message notifying release of a first PDU session.

Description

Method and device for continuously providing user plane function services while user plane functions are changed in a wireless communication system

[0001] The present disclosure relates to the operation of a terminal and a base station in a wireless communication system. More specifically, the present disclosure relates to a method and device for notifying NFs that have subscribed to a service for a data session that is being released when a data session is released or a UPF is changed due to the movement of a terminal in a wireless communication system, thereby releasing an existing data session and creating a new data session, and further providing the subscribed service continuously through the newly created data session.

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

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

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

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

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

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

[0008] Based on the discussion described above, the present disclosure aims to provide a method and device that can continuously provide a service subscribed to a data session in a wireless communication system even when the data session is changed.

[0009] The technical problems to be achieved in the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by a person having ordinary skill in the technical field to which the present invention belongs from the description below.

[0010] According to one embodiment of the present disclosure, a method performed by a user plane function (UPF) of a wireless communication system is provided. The method comprises the steps of: receiving, from a consumer network function (NF), an event exposure subscribe message including an indicator requesting the UPF to notify the consumer NF when a protocol data unit (PDU) session is released; identifying that the PDU session has been released; and transmitting, to the consumer NF, an event exposure notify message for notifying that the PDU session has been released.

[0011] According to one embodiment of the present disclosure, a method performed by a consumer network function (NF) of a wireless communication system is provided. The method comprises the steps of: transmitting, to a user plane function (UPF), an event exposure subscribe message including an indicator requesting the UPF to notify the consumer NF when a protocol data unit (PDU) session is released; and, when the PDU session is released, receiving, from the UPF, an event exposure notify message for notifying that the PDU session has been released.

[0012] According to one embodiment of the present disclosure, a user plane function (UPF) of a wireless communication system is provided. The UPF includes: at least one transceiver; at least one processor communicatively coupled to the at least one transceiver; and a memory communicatively coupled to the at least one processor and executable individually or by any combination of the at least one processor, the memory storing instructions that cause the UPF to receive, from a consumer network function (NF), an event exposure subscribe message including an indicator requesting the UPF to notify the consumer NF when a protocol data unit (PDU) session is released, identify that the PDU session has been released, and transmit, to the consumer NF, an event exposure notify message for notifying that the PDU session has been released.

[0013] According to one embodiment of the present disclosure, a consumer network function (NF) of a wireless communication system is provided. The consumer NF includes: at least one transceiver; at least one processor communicatively coupled to the at least one transceiver; and a memory communicatively coupled to the at least one processor and executable individually or by any combination of the at least one processor, the memory storing instructions that cause the consumer NF to transmit, to a user plane function (UPF), an event exposure subscribe message including an indicator requesting the UPF to notify the consumer NF when a protocol data unit (PDU) session is released, and, when the PDU session is released, to receive, from the UPF, an event exposure notify message for notifying that the PDU session has been released.

[0014] In a wireless communication system according to an embodiment of the present disclosure, a method of operating a first SMF (session management function) entity (104-1) may include: an operation of determining to relocate a first UPF (user plane function) entity (105-1) connected to a terminal (102) through a first PDU session; an operation of transmitting a request message including information instructing an AMF (access and mobility management function) entity (103) to change the first UPF entity (105-1); and an operation of transmitting a PDU session release notification message notifying release of the first PDU session to an AF (application function) entity (114) through a NEF (network exposure function) entity (108).

[0015] The above request message may include information indicating a change to the first SMF entity (104-1) if a change to the first SMF entity (104-1) is required.

[0016] The above operating method may further include an operation of transmitting a PDU session release request message requesting release of the first PDU session with the terminal (102) to the first UPF entity (105-1).

[0017] The above operating method may further include an operation of transmitting a PDU session establishment request message requesting the second UPF entity (105-2) to establish a second PDU session with the terminal (102).

[0018] The above method of operation may further include an operation of transmitting UPF service subscription information of the AF (114) related to the first UPF entity (105-1) to the second UPF (105-2) entity.

[0019] The above UPF service subscription information can be transmitted via an N4 session modification message or an event exposure subscribe request message.

[0020] The above method of operation may further include an operation of transmitting the UPF service subscription information to the second SMF entity (104-2).

[0021] An N4 session modification message or event exposure subscription request message including the above UPF service subscription information may be transmitted to the second UPF (105-2) entity via the second SMF entity (104-2).

[0022] In a wireless communication system according to an embodiment of the present disclosure, a method of operating a first user plane function (UPF) entity (105-1) may include the steps of: receiving a PDU session release request message requesting release of a first PDU session connected to a terminal (102) from a first session management function (SMF) entity (104-1); and transmitting a PDU session release notification message notifying release of the first PDU session to an application function (AF) entity (114) through a network exposure function (NEF) entity (108).

[0023] The above method of operation may further include an operation of transmitting UPF service subscription information of an AF (114) related to the first UPF entity (105-1) to the first SMF entity (104-1).

[0024] The above UPF service subscription information can be transmitted via an N4 session modification message or an event exposure subscribe request message.

[0025] The above operating method may further include an operation of receiving a PDU session establishment request message requesting establishment of a second PDU session with the terminal (102) from the first SMF entity (104-1).

[0026] In a wireless communication system according to an embodiment of the present disclosure, a first SMF (session management function) entity (104-1) may include a transceiver (1601); a memory (1602) electrically coupled to the transceiver (1601) and storing various commands for controlling the first SMF entity (104-1); and a processor (1603) electrically coupled to the transceiver (1601) and the memory (1602). The processor (1603) may be configured to perform an operation of determining to relocate a first UPF (user plane function) entity (105-1) connected to a terminal (102) through a first PDU session; an operation of transmitting a request message including information instructing an AMF (access and mobility management function) entity (103) to change the first UPF entity (105-1); And an operation of transmitting a PDU session release notification message notifying the release of the first PDU session to the AF (application function) entity (114) through the NEF (network exposure function) entity (108) can be performed.

[0027] The above request message may include information indicating a change to the first SMF entity (104-1) if a change to the first SMF entity (104-1) is required.

[0028] The processor (1603) may further perform an operation of transmitting a PDU session release request message requesting release of the first PDU session with the terminal (102) to the first UPF entity (105-1).

[0029] The processor (1603) may further perform an operation of transmitting a PDU session establishment request message requesting the second UPF entity (105-2) to establish a second PDU session with the terminal (102).

[0030] The above processor (1603) may further perform an operation of transmitting UPF service subscription information of the AF (114) related to the first UPF entity (105-1) to the second UPF (105-2) entity.

[0031] The above UPF service subscription information can be transmitted via an N4 session modification message or an event exposure subscribe request message.

[0032] The above processor (1603) may further perform an operation of transmitting the UPF service subscription information to the second SMF entity (104-2).

[0033] An N4 session modification message or event exposure subscription request message including the above UPF service subscription information may be transmitted to the second UPF (105-2) entity via the second SMF entity (104-2).

[0034] One embodiment of the present invention provides a device and method capable of effectively providing a service in a wireless communication system.

[0035] The effects that can be obtained from the present invention are not limited to the effects mentioned above, and other effects not mentioned can be clearly understood by a person having ordinary skill in the art to which the present disclosure pertains from the description below.

[0036] FIG. 1 illustrates the structure of a wireless communication system according to various embodiments of the present disclosure.

[0037] FIG. 2 is a conceptual diagram illustrating an operation for subscribing to a UPF service (e.g., UPF event exposure service) according to an embodiment of the present disclosure.

[0038] FIG. 3 is a flowchart illustrating a procedure for subscribing to a UPF service (e.g., UPF event exposure service) according to an embodiment of the present disclosure.

[0039] FIG. 4 is a conceptual diagram illustrating an SSC (Session and Service Continuity) mode that determines whether a PSA (PDU Session Anchor) UPF is changed due to movement of a terminal according to an embodiment of the present disclosure.

[0040] FIG. 5 is a flowchart illustrating an indirect subscription procedure in which a Consumer NF indirectly subscribes to a UPF service through an SMF according to an embodiment of the present disclosure.

[0041] FIG. 6 is a flowchart illustrating a procedure for a terminal to move and change (relocate) a PSA UPF according to SSC 2 mode according to an embodiment of the present disclosure.

[0042] FIG. 7 is a flowchart illustrating a procedure for a terminal to move and change (relocate) a PSA UPF according to SSC 2 mode according to an embodiment of the present disclosure.

[0043] FIG. 8 is a flowchart illustrating a procedure for a terminal to move and change (relocate) a PSA UPF according to SSC 2 mode according to an embodiment of the present disclosure.

[0044] FIG. 9 is a flowchart illustrating a direct subscription procedure in which a Consumer NF directly subscribes to a UPF service with a UPF according to an embodiment of the present disclosure.

[0045] FIG. 10 is a flowchart illustrating a procedure for changing a PSA UPF according to SSC 2 mode when a terminal moves according to an embodiment of the present disclosure.

[0046] FIG. 11 is a flowchart illustrating a procedure for changing a PSA UPF in SSC 2 mode by moving a terminal according to an embodiment of the present disclosure.

[0047] FIG. 12 is a flowchart illustrating a procedure for changing a PSA UPF in SSC 2 mode when a terminal moves according to an embodiment of the present disclosure.

[0048] FIG. 13 is a flowchart illustrating a procedure for changing a PSA UPF in SSC 2 mode when a terminal moves according to an embodiment of the present disclosure.

[0049] FIG. 14 is a block diagram illustrating the configuration of a terminal according to embodiments of the present disclosure.

[0050] FIG. 15 is a block diagram illustrating a configuration of a base station according to embodiments of the present disclosure.

[0051] FIG. 16 is a block diagram illustrating a configuration of a network entity according to embodiments of the present disclosure.

[0052] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. It should be noted that, where possible, identical components are represented by identical reference numerals throughout the drawings. Furthermore, detailed descriptions of well-known functions and configurations that may obscure the gist of the present invention will be omitted.

[0053] In describing the embodiments herein, descriptions of technical details that are well known in the technical field to which the present disclosure pertains and are not directly related to the present invention will be omitted. This is to avoid obscuring the gist of the present disclosure by omitting unnecessary explanations and to convey the gist more clearly.

[0054] For the same reason, some components in the attached drawings are exaggerated, omitted, or schematically depicted. Furthermore, the dimensions of each component do not entirely reflect its actual size. Identical or corresponding components in each drawing are assigned the same reference numbers.

[0055] The advantages and features of the present disclosure, and the methods for achieving them, will become clearer with reference to the embodiments described in detail below together with the accompanying drawings. However, the present disclosure is not limited to the embodiments disclosed below and may be implemented in various different forms. These embodiments are provided only to ensure that the disclosure of the present disclosure is complete and to fully inform those skilled in the art of the scope of the disclosure, and the present disclosure is defined only by the scope of the claims. Like reference numerals refer to like elements throughout the specification.

[0056] Furthermore, when describing the present disclosure, detailed descriptions of related functions or configurations will be omitted if they are deemed to unnecessarily obscure the gist of the present disclosure. Furthermore, the terms described below are defined based on the functions of the present disclosure and may vary depending on the intent or custom of the user or operator. Therefore, their definitions should be based on the content throughout this specification.

[0057] Hereinafter, the base station is an entity that performs resource allocation of a terminal, and may be at least one of a gNode B (gNB), an eNode B (eNB), a Node B, a BS (Base Station), a wireless access unit, a base station controller, or a node on a network. The terminal may include a UE (User Equipment), an MS (Mobile Station), a cellular phone, a smartphone, a computer, or a multimedia system capable of performing a communication function. In the present disclosure, downlink (DL) refers to a wireless transmission path of a signal transmitted from a base station to a terminal, and uplink (UL) refers to a wireless transmission path of a signal transmitted from a terminal to a base station. In addition, although the LTE (long-term evolution), LTE-A (LTE-advanced), or 5G (5th generation) system may be described below as an example, embodiments of the present disclosure may also be applied to other communication systems having similar technical backgrounds or channel types. For example, this may include the fifth-generation mobile communication technology (5G, new radio (NR)) developed after LTE-A. The term "5G" below may also encompass existing LTE, LTE-A, and other similar services. Furthermore, the present disclosure may be applied to other communication systems with some modifications, as determined by a person skilled in the art, without significantly departing from the scope of the present disclosure.

[0058] At this time, it will be understood that each block of the processing flow diagrams and combinations of the flow diagrams can be performed by computer program instructions. These computer program instructions can be installed in a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing equipment, so that the instructions executed by the processor of the computer or other programmable data processing equipment create a means for performing the functions described in the flow diagram block(s). These computer program instructions can also be stored in a computer-available or computer-readable memory that can direct a computer or other programmable data processing equipment to implement the functions in a specific manner, so that the instructions stored in the computer-available or computer-readable memory can also produce a manufactured item that includes an instruction means for performing the functions described in the flow diagram block(s). Since the computer program instructions may be installed on a computer or other programmable data processing device, a series of operational steps may be performed on the computer or other programmable data processing device to create a computer-executable process, and the instructions that cause the computer or other programmable data processing device to perform the steps for performing the functions described in the flowchart block(s) may also provide steps for performing the functions described in the flowchart block(s).

[0059] Additionally, each block may represent a module, segment, or portion of code that contains one or more executable instructions for performing a specific logical function(s). It should also be noted that in some alternative implementation examples, the functions described in the blocks may occur out of order. For example, two blocks depicted in succession may actually be executed substantially concurrently, or the blocks may sometimes be executed in reverse order, depending on their respective functions.

[0060] Here, the term '~ unit' used in the present embodiments means a software or hardware component such as an FPGA or ASIC, and the '~ unit' performs certain roles. However, the '~ unit' is not limited to software or hardware. The '~ unit' may be configured to be on an addressable storage medium and may be configured to reproduce one or more processors. Thus, as an example, the '~ unit' includes components such as software components, object-oriented software components, class components, and task components, processes, functions, properties, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and variables. The functions provided within the components and '~ units' may be combined into a smaller number of components and '~ units' or further separated into additional components and '~ units'. In addition, the components and '~ units' may be implemented to reproduce one or more CPUs within a device or a secure multimedia card. Additionally, in the embodiment, '~bu' may include one or more processors.

[0061] Wireless communication systems have evolved from providing voice-oriented services in the early days to broadband wireless communication systems that provide high-speed, high-quality packet data services, such as communication standards such as 3GPP's HSPA (High Speed ​​Packet Access), LTE (or E-UTRA (Evolved Universal Terrestrial Radio Access)), LTE-Advanced (LTE-A), LTE-Pro, 3GPP2's HRPD (High Rate Packet Data), UMB (Ultra Mobile Broadband), and IEEE's 802.16e.

[0062] As a representative example of a broadband wireless communication system, the LTE system uses the OFDM (Orthogonal Frequency Division Multiplexing) method in the downlink and the SC-FDMA (Single Carrier Frequency Division Multiple Access) method in the uplink. The uplink refers to a wireless link in which a terminal (User Equipment (UE) or Mobile Station (MS)) transmits data or control signals to a base station (eNode B, gNode B, or base station (BS)), and the downlink refers to a wireless link in which a base station transmits data or control signals to a terminal. The above-described multiple access method can distinguish the data or control information of each user by allocating and operating the time-frequency resources to be transmitted, including data or control information, so that they do not overlap with each other (i.e., so that orthogonality is established).

[0063] As a future communication system beyond LTE, 5G communication systems must be able to freely reflect the diverse needs of users and service providers. Therefore, they must support services that simultaneously satisfy these diverse requirements. Services being considered for 5G communication systems include enhanced Mobile Broadband (eMBB), massive Machine Type Communication (mMTC), and Ultra-Reliable Low Latency Communication (URLLC).

[0064] eMBB aims to provide data transmission rates that are significantly higher than those supported by existing LTE, LTE-A, or LTE-Pro. For example, in a 5G communication system, eMBB must be able to support a peak data rate of 20 Gbps in the downlink and a peak data rate of 10 Gbps in the uplink from a single base station. Furthermore, 5G communication systems must simultaneously provide the peak data rate and an increased user-perceived data rate for terminals. To meet these requirements, improvements in various transmission and reception technologies, including improved multi-input, multi-output (MIMO) transmission technology, are required. Furthermore, while LTE transmits signals using a maximum 20 MHz transmission bandwidth in the 2 GHz band, 5G communication systems can meet the data transmission rates required by 5G communication systems by utilizing a wider frequency bandwidth than 20 MHz in the 3-6 GHz or higher 6 GHz bands.

[0065] At the same time, massive Machine Type Communications (mMTC) is being considered to support application services such as the Internet of Things (IoT) in 5G communication systems. To efficiently provide the IoT, mMTC requires supporting a large number of terminals within a cell, improving terminal coverage, extending battery life, and reducing terminal costs. The IoT requires the ability to support a large number of terminals (e.g., 1,000,000 terminals / km^2) within a cell, as it provides communication capabilities through the attachment of various sensors and devices. Furthermore, terminals supporting mMTC are likely to be located in shadow areas, such as basements, beyond cell coverage due to the nature of the service, and thus may require wider coverage than other services provided by 5G communication systems. Terminals supporting mMTC must be inexpensive, and because frequent battery replacement is difficult, they may require extremely long battery lifespans, such as 10 to 15 years.

[0066] Finally, URLLC refers to a cellular-based wireless communication service used for a specific purpose (mission-critical). Examples include remote control of robots or machinery, industrial automation, unmanned aerial vehicles (UAVs), remote health care, and emergency alerts. Therefore, URLLC communications must provide extremely low latency and high reliability. For example, services supporting URLLC must meet air interface latency requirements of less than 0.5 milliseconds and a packet error rate (PER) of less than 10^-5. Therefore, for services supporting URLLC, 5G systems must provide a shorter transmission time interval (TTI) than other services, and design requirements may require the allocation of extensive resources in the frequency band to ensure communication link reliability.

[0067] The three 5G services—eMBB, URLLC, and mMTC—can be multiplexed and transmitted within a single system. To meet the differing requirements of each service, different transmission and reception techniques and parameters can be used. Of course, 5G is not limited to the three services described above.

[0068] According to various embodiments of the present disclosure, phrases such as “A and / or B,” “A or B,” “at least one of A and B,” “at least one of A or B,” “A, B, or C,” “at least one of A, B, and C,” and “at least one of A, B, or C” can each include any one of the items listed together in that phrase, or all possible combinations thereof. Terms such as “first,” “second,” or “first” or “second” may be used simply to distinguish the corresponding element from other corresponding elements and do not limit the corresponding elements in any other respect (e.g., importance or order).

[0069] Hereinafter, the base station is an entity that performs resource allocation of a terminal, and may be at least one of a Node B, a BS (Base Station), an eNB (eNode B), a gNB (gNode B), a wireless access unit, a base station controller, or a node on a network. The terminal may include a UE (User Equipment), an MS (Mobile Station), a cellular phone, a smartphone, a computer, or a multimedia system capable of performing a communication function. In addition, the embodiments of the present disclosure may be applied to other communication systems having a similar technical background or channel form to the embodiments of the present disclosure described below. In addition, the embodiments of the present disclosure may be applied to other communication systems through some modifications without significantly departing from the scope of the present disclosure at the discretion of a person having skilled technical knowledge.

[0070] In the present disclosure, network technology may refer to standard specifications defined by the International Telecommunication Union (ITU) or 3GPP (e.g., TS 23.501, TS 23.502, TS 23.503, etc.), and components included in the network structure of FIG. 1 may each mean a physical entity, or may mean software performing an individual function, or hardware combined with software. Reference symbols shown as Nx, such as N1, N2, N3, ..., in the drawings represent known interfaces between NFs (network functions) in a 5G core network (CN), and since a related description may refer to a standard specification (e.g., TS 23.501), a detailed description will be omitted.

[0071] In the following description, terms used to identify connection nodes, terms referring to network entities (NEs) or network functions (NFs), terms referring to messages, terms referring to interfaces between network objects, terms referring to various identification information, etc. are examples provided for convenience of explanation. Therefore, the present disclosure is not limited to the terms described below, and other terms referring to objects having equivalent technical meanings may be used.

[0072] For convenience of explanation, some terms and names defined in the 3rd generation partnership project long-term evolution (3GPP) standards may be used. However, the present disclosure is not limited to these terms and names, and can be equally applied to systems conforming to other standards.

[0073] FIG. 1 is a conceptual diagram illustrating the structure of a wireless communication system according to various embodiments of the present disclosure.

[0074] Referring to Figure 1, an example of a 5G system configuration is illustrated. The 5G network may include at least one of the network entities (NEs) or network functions (NFs) described below.

[0075] According to one embodiment, the (R)AN ((Radio) Access Network) (101) is an entity that performs radio resource allocation of the terminal (102), and may include at least one of an eNode B, a Node B, a BS (Base Station), an NG-RAN (Next Generation Radio Access Network), a 5G-AN (5G Access Network), a 5G NR (5G New Radio), a radio access unit, a base station controller, or a node on the network.

[0076] According to one embodiment, the terminal (102) may include a UE (User Equipment), an NG UE (Next Generation UE), an MS (Mobile Station), a cellular phone, a smartphone, a computer, an IoT (Internet of Things) device, or a multimedia system capable of performing a communication function.

[0077] Furthermore, while the embodiments of the present disclosure are described below using a 5G system as an example, the embodiments of the present disclosure can also be applied to other communication systems with similar technical backgrounds. Furthermore, the embodiments of the present disclosure can be applied to other communication systems with some modifications, as determined by a person skilled in the art, without significantly departing from the scope of the present disclosure.

[0078] As wireless communication systems evolve from 4G to 5G, a new core network (CN) called the Next Generation Core (NG Core) or 5GC (5G Core Network) is defined. This new core network can virtualize all existing network entities (NEs) into network functions (NFs). According to one embodiment of the present disclosure, a network function may refer to a network entity, a network component, or a network resource.

[0079] According to one embodiment of the present disclosure, 5GC may include one or more NFs illustrated in FIG. 1. Of course, the present invention is not limited to the example illustrated in FIG. 1, and 5GC may include more or fewer NFs than the NFs illustrated in FIG. 1.

[0080] According to one embodiment, the Access and Mobility Management Function (AMF) (103) may be a network function that manages access and mobility of a terminal (UE) (102). For example, the AMF (103) may perform network functions such as registration, connection, reachability, mobility management, access verification, authentication, and mobility event generation of the terminal (102).

[0081] According to one embodiment, a Session Management Function (SMF) (104) may be a network function that manages a Packet Data Network (PDN) connection provided to a User Equipment (UE) (102). The PDN connection may be referred to as a Protocol Data Unit (PDU) Session. For example, the SMF (104) may perform network functions such as session management through establishing, modifying, and releasing sessions and maintaining a tunnel between a User Plane Function (UPF) (105) and a RAN (101) required therefor, selecting and controlling a User Plane (UPF), controlling traffic processing in the UPF (105), and controlling collection of charging data.

[0082] According to one embodiment, the Policy Control Function (PCF) (106) may be a network function that applies a mobile communication operator's service policy, charging policy, and policy for PDU Session to the terminal (102).

[0083] In one embodiment, Unified Data Management (UDM) (107) may be a network function that stores information about subscribers. For example, UDM (107) may perform functions such as generating authentication information for 3GPP security, processing user identifiers (User IDs), managing a list of network functions supporting UE (101), and managing subscription information.

[0084] In one embodiment, the Network Exposure Function (NEF) (108) may be a function that provides information about the terminal (102) to a server outside the 5G network. In addition, the NEF (108) may provide a function that provides information necessary for services to the 5G network and stores the information in a Unified Data Repository (UDR) (not shown).

[0085] According to one embodiment, the User Plane Function (UPF) (105) may be a function that acts as a gateway to transmit user data (e.g., PDU) to a Data Network (DN). More specifically, the UPF (105) may perform a role of processing data so that data transmitted by the terminal (102) can be transmitted to an external network or data received from an external network can be transmitted to the terminal. For example, the UPF (105) may perform network functions such as serving as an anchor between Radio Access Technologies (RATs), packet routing and forwarding, packet inspection, user plane policy application, traffic usage report creation, buffering, etc.

[0086] According to one embodiment, the Network Repository Function (NRF) (109) may store profiles of NFs and perform functions of discovering NFs.

[0087] According to one embodiment, the Authentication Server Function (AUSF) (110) can perform terminal authentication in a 3GPP access network and a non-3GPP access network.

[0088] According to one embodiment, the Network Slice Selection Function (NSSF) (111) may perform a function of selecting a Network Slice Instance provided to the terminal (102).

[0089] In one embodiment, the Network Data Analytics Function (NWDAF) (113) may collect data from multiple NFs (NFs) for the purpose of efficient operation of the 5GC network. In one embodiment, the collected data may be analyzed using a Machine Learning (ML) model, and the analyzed results may be provided back to the NFs to help each NF provide efficient network services.

[0090] According to one embodiment, an Application Function (AF) (114) can communicate with a network operator so that an external server (Application Server) can utilize network services provided by the network operator. The AF (114) can be classified into an internal AF and an external AF depending on the deployment entity. An internal AF deployed by a network operator can directly communicate with NFs within the network operator. An AF (114) deployed by a service provider (3rd Party Service Provider) may have to go through an NEF (108) to communicate with NFs within the network operator.

[0091] According to one embodiment, the DN (Data Network) (115) may be a data network through which the terminal (102) transmits and receives data in order to use a network operator's service or a third party service.

[0092] According to one embodiment, the Network Slice Admission Control Function (NSACF) (116) may limit the number of PDU sessions of registered terminals (102) of each slice, thereby performing a resource management function.

[0093] According to one embodiment, a Network Slice-Specific Authentication and Authorization Function (NSSAAF) (117) may create a slice authentication context for a terminal (102) and perform slice-specific authentication and authorization procedures.

[0094] According to one embodiment, the Edge Application Server Discovery Function (EASDF) (118) may create a domain name system (DNS) context for a PDU session and may perform a function of storing a UE IP (internet protocol) address, DNS message processing rules, etc. in the context.

[0095] According to one embodiment, the SCP (Service Communication Proxy) (119) can perform indirect communication functions such as service search, call response, etc.

[0096] In one embodiment, the terminal may include an IoT device. The IoT device may include a device that does not use battery power or operates with very little power, and such an IoT device may be referred to as an ambient IoT device (or Ambient IoT).

[0097] In the 3GPP system, a conceptual link connecting NFs within a 5G system is defined as a reference point. The following illustrates a reference point included in the 5G system architecture depicted in Figure 1.

[0098] - N1: Reference point between UE (102) and AMF (103)

[0099] - N2: Reference point between (R)AN(101) and AMF(103)

[0100] - N3: Reference point between (R)AN(101) and UPF(105)

[0101] - N4: Reference point between SMF (104) and UPF (105)

[0102] - N6: Reference point between UPF (105) and DN (115)

[0103] - N9: Reference point between two core UPFs (105)

[0104] Additionally, in 3GPP systems, the 5G system architecture may include service-based interfaces such as the following examples.

[0105] - Nnssf: Service-based interface by NSSF(111)

[0106] - Nnssaaf: Service-based interface by NSSAAF (117)

[0107] - Nnef: Service-based interface by NEF(108)

[0108] - Nausf: Service-based interface by AUSF(110)

[0109] - Nnrf: Service-based interface by NRF (109)

[0110] - Namf: Service-based interface by AMF(103)

[0111] - Npcf: Service-based interface by PCF (106)

[0112] - Nsmf: Service-based interface by SMF (104)

[0113] - Nupf: Service-based interface by UPF(105)

[0114] - Nudm: Service-based interface by UDM (107)

[0115] - Naf: Service-based interface by AF(114)

[0116] - Nasaf: Service-based interface by AUSF(110)

[0117] - Neasdf: Service-based interface by EASDF (118)

[0118] - Nnwdaf: Service-based interface by NWDAF (113)

[0119] According to one embodiment of the present disclosure, a Nupf interface is proposed that allows a network device or network function located inside or outside a 5G Core Network to subscribe to and use a UPF service (e.g., UPF event exposure service) provided by a UPF (105). The present disclosure proposes a method for continuously providing subscribed services to NFs subscribed to a UPF service even when the UPF (105) is changed in order to use the UPF service.

[0120] FIG. 2 is a conceptual diagram illustrating an operation for subscribing to a UPF service (e.g., UPF event exposure service) according to an embodiment of the present disclosure.

[0121] Figure 2 illustrates two methods defined for subscribing to a UPF service (e.g., a UPF event exposure service). The UPF event exposure service is an event exposure service of a 5G system defined in 3GPP, and may be a service that allows a UPF (105) to expose related events to service consumers (e.g., NWDAF (113), local NEF (108), AF (114), etc.) who have subscribed to the service when an event occurs. The action performed by a consumer of a specific UPF event service may be referred to as “UPF Event Subscription.”

[0122] A PDU session is a logical connection between a UE and a data network (DN) (e.g., a UE and the Internet), enabling data transfer between services. From the perspective of the UPF, a PDU session can be referred to as an N4 session. An N4 session is a control plane connection between the SMF and the UPF, and can be used by the SMF to manage user plane resources and policies associated with a specific PDU session.

[0123] If a consumer subscribes to a UPF event service for a specific PDU session, this may correspond to an N4 session in the UPF. Therefore, if the N4 session (or PDU session) is released from the UPF, this may correspond to a session release from the UPF perspective, and the UPF may no longer provide UPF event services for the N4 session (or PDU session).

[0124] Fig. 2 illustrates a previously proposed service subscription method for a consumer NF (114 / 113) to use a UPF service provided by a UPF (105). Here, the consumer NF (114 / 113) may be substantially the same as or similar to the AF (114) and / or NWDAF (113) of Fig. 1. The UPF service subscription method may be broadly divided into an indirect subscription method in which a consumer subscribes indirectly through another NF (i.e., SMF (104)), as illustrated in (a) of Fig. 2, and a direct subscription method in which a consumer subscribes directly to the UPF (105), as illustrated in (b) of Fig. 2.

[0125] In addition, the indirect subscription method illustrated in (a) of FIG. 2 may be a method used when subscribing to a service for a specific UPF (105), such as a specific UE (102), a specific IP (internet protocol) flow, or a specific PDU (packet data unit) session. This may be because the only NF that can identify a specific UPF (105) is the SMF (104). Referring to (a) of FIG. 2, the consumer NF (AF (114) / NWDAF (113)) can transmit an Nsmf_EventExposure_Subscribe Request message to the SMF (104). The SMF (104) can transmit an Nupf_EventExposure_Subscribe Request message to a specific UPF (105).

[0126] In addition, the direct subscription method illustrated in (b) of FIG. 2 may refer to a method used when subscribing to a service for a general UPF (105) rather than a specific UPF, such as any UE or any UPF. Referring to (b) of FIG. 2, a consumer NF (AF (114) / NWDAF (113)) may transmit a Nupf_EventExposure_Subscribe Request message to the UPF (105).

[0127] FIG. 3 is a flowchart illustrating a procedure for subscribing to a UPF service (e.g., UPF event exposure service) according to an embodiment of the present disclosure.

[0128] Referring to Fig. 3, a method for subscribing to a UPF service through SMF (104) is illustrated.

[0129] In step 301, the UPF event consumer NF (113) may send a Nudm_UECM_get message to the UDM (107). The UDM (107) may receive the Nudm_UECM_get message from the UPF event consumer (113). The UPF event consumer (113) may be referred to as a UPF service consumer NF (113).

[0130] A UPF service consumer NF (113) can request information on an SMF (104) responsible for a specific UPF (105) from a UDM (107) using a Nudm_UECM_Get message. For example, the Nudm_UECM_Get message may be a message requesting information related to an SMF (104) corresponding to a specific UPF (105). For example, the UPF service consumer NF (113) may be substantially the same as or similar to the NWDAF (113) of FIG. 1. Hereinafter, for convenience, the UPF service consumer NF (113) may be referred to as a consumer NF (113). The Nudm_UECM_Get message may set an SMF (109) to a UE ID, DNN, S-NSSAI managed by the UPF (105) to be found, and an NF type value, which is a type of NF information to be requested. For example, the Nudm_UECM_Get message may include a UE ID, DNN, S-NSSAI, and NF type value indicating the SMF (109) associated with the UPF (105).

[0131] In step 302, the UDM (107) may transmit a Nudm_UECM_Get Response message to the UPF event consumer (113). The UPF event consumer (113) may receive the Nudm_UECM_Get Response message from the UDM (107). The UDM (107) may transmit information related to the SMF (104) to the consumer NF (113) via the Nudm_UECM_Get response message. For example, the Nudm_UECM_Get Response message may include information related to the SMF (104).

[0132] In step 303, the consumer NF (113) may send an Nsmf_EventExposure_Subscribe message to the SMF (104). The SMF (104) may receive the Nsmf_EventExposure_Subscribe message from the consumer NF (113). The consumer NF (113) may send the Nsmf_EventExposure_Subscribe message to the responsible SMF (104) to subscribe to the UPF service. The Nsmf_EventExposure_Subscribe message may include at least one of the following pieces of information:

[0133] - Notification Target Address (UPF event consumer address), Notification Correlation Information.

[0134] - Indication of UPF Event Exposure Service and Target subscription UPF Event Id.

[0135] - Event Filter Information: S-NSSAI, DNN, DNAI, UPF Id, Traffic Description for the target traffic (eg Application Id), Area of ​​Interest, SSID / BSSID.

[0136] - Target of Event Reporting: a UE.

[0137] - Reporting suggestion information.

[0138] - Target Subscription information: Type of Measurement and granularity of the information requested.

[0139] At step 304a, the SMF (104) may send an N4 Session_Modification message to the UPF (105). The N4 Session_Modification message may include information received via the Nsmf_EventExposure_Subscribe message. The UPF (105) may receive the N4 Session_Modification message from the SMF (104).

[0140] Alternatively, at step 304b, the SMF (104) may transmit a Nupf EventExposure_Subscribe message to the UPF (105). The Nupf EventExposure_Subscribe message may include information received via the Nsmf_EventExposure_Subscribe message. The UPF (105) may receive the Nupf EventExposure_Subscribe message from the SMF (104).

[0141] In step 304a / 304b, the SMF (104) can identify a UPF (105) responsible for a specific UE, a specific PDU Session, and a specific IP Flow among the UPFs managed by the SMF (104) based on the Nsmf_EventExposure_Subscribe message. The SMF (104) can include the information received from the consumer NF (113) in an N4_Session_Modification message or a Nupf_EventExposure_Subscribe message and transmit it to the UPF (105) in order to subscribe to the UPF service requested by the consumer NF (113). At this time, which of the above messages is used may vary depending on the type of UPF service requested. SMF (104) can transmit an N4_Session_Modification message or a Nupf_EventExposure_Subscribe message to UPF (105) based on the type of UPF service requested from consumer NF (113).

[0142] In step 305, the UPF (105) may transmit a Nupf_EventExposure_Notify message to the consumer NF (113). The consumer NF (113) may receive the Nupf_EventExposure_Notify message from the UPF (105). When data related to a service requested from the UPF event consumer NF (113) occurs, the UPF (105) may transmit a Nupf_EventExposure_Notify message including the requested service and related data to the consumer NF (113).

[0143] FIG. 4 is a conceptual diagram illustrating an SSC (Session and Service Continuity) mode that determines whether a PSA (PDU Session Anchor) UPF is changed due to movement of a terminal according to an embodiment of the present disclosure.

[0144] Figure 4 (A) illustrates SSC mode 1.

[0145] In the case of SSC mode 1, even if the terminal (102) moves out of the service range of the PSA UPF (105-1) connected to the first base station (101-1), the PSA UPF (105-1) may not be changed. That is, the PDU Session initially established between the terminal (102) and the PSA UPF (105-1) may not be released. In order to continue servicing the terminal (102) that is out of the PSA UPF service range, the SMF (104) may establish an I-UPF (Intermediate UPF) (105-2) connected to the second base station (101-2) and provide a data transmission service to the terminal (102) by retransmitting user data to the I-UPF (105-2).

[0146] In the case of SSC mode 1, the IP address of the terminal (102) may not be changed because the PDU session established with the PSA UPF (105-1) is not released. In other words, this may be an SSC mode that can be used to ensure the continuity of the service when using a service that identifies the terminal by the IP address of the terminal (102) among terminal services. The PSA UPF (105-1) and I-UPF (105-2) may be connected to the SMF (104).

[0147] Figures 4 (B) and (C) illustrate SSC mode 2 and SSC mode 3.

[0148] In the case of SSC mode 2 and SSC mode 3, when the terminal (102) goes out of the service range of the PSA UPF (105-1) connected to the first base station (101-1), the SMF (104) may select a new PSA UPF (105-2) through relocation of the UPF and establish a new PDU Session with this new PSA UPF (105-2). In the case of SSC mode 1, when the terminal (102) continues to move and the distance from the initial PSA UPF (105-1) increases, the number of I-UPFs (105-2) connected to the second base station (101-2) may increase. This may ultimately mean that the data transmission path from the PSA UPF (105-1) to the terminal (102) becomes longer. This may result in a longer data transmission time and excessive network resource consumption because the network must use multiple UPFs.

[0149] Accordingly, if the terminal IP address does not need to be maintained, SSC mode 1 may not be used and SSC mode 2 or SSC mode 3 may be used.

[0150] The difference between SSC mode 2 and SSC mode 3 may be whether the PDU Session with the existing PSA UPF (105-1) is released first and a new PDU Session with the new PSA UPF (105-2) is created, or a new PDU Session with the new PSA UPF (105-2) is created and the PDU Session with the existing PSA UPF (105-1) is released. The former may be the case for SSC mode 2, and the latter may be the case for SSC mode 3. The PSA UPF (105-1) and I-UPF (105-2) may be connected to the SMF (104).

[0151] This disclosure explains the two cases separately, because the procedures for indirect and direct subscriptions by Consumer NF when subscribing to UPF services are different.

[0152] FIG. 5 is a flowchart illustrating an indirect subscription procedure in which a Consumer NF indirectly subscribes to a UPF service through an SMF according to an embodiment of the present disclosure.

[0153] Referring to FIG. 5, steps 501 and 502 may be substantially the same as or similar to steps 301 and 302 of FIG. 3.

[0154] In step 503, the consumer NF (113) may transmit an Nsmf_EventExposure_Subscribe message to the SMF (104). The SMF (104) may receive the Nsmf_EventExposure_Subscribe message from the consumer NF (113). The consumer NF (113) may transmit the Nsmf_EventExposure_Subscribe message to the SMF (104) to subscribe to the UPF Event Exposure service. The Nsmf_EventExposure_Subscribe message may include at least one of the following information: Event ID(s), Target of Event Reporting (GPSI, SUPI, UE address information (IP or MAC address)), Event Reporting Information, Notification Target Address, Event Filter, Expiry time, DNN, S-NSSAI.

[0155] If the service requested by Consumer NF (113) is a UPF Event Exposure service or a service related to PDU Session, at least one of the following information may be included: Indication of PDU Session Release, Indication of Subscription Forwarding.

[0156] Indication of PDU Session Release may be information indicating that a notification is requested when the PDU Session related to the requested service is released.

[0157] Indication of Subscription Forwarding may be information indicating that, when the PDU Session related to the requested service is released and a new PSA UPF (105) and PDU Session are established, a request is made to continue to receive the previously subscribed service in the newly established PDU Session.

[0158] That is, when a Consumer NF (113) subscribes to a service regarding a PDU Session, if the PSA UPF and PDU Session are released and a new PSA UPF (105) and PDU Session are established, the Consumer NF (113) can select at least one of the options of receiving a notification for a simple PDU Session Release or requesting continued provision of the previously subscribed service in the newly created PDU Session. The above options can be applied when an Indication of PDU Session Release is received and also when the PDU Session is simply released.

[0159] At step 504a, the SMF (104) may send an N4 Session_Modification message to the UPF (105). The N4 Session_Modification message may include information received via the Nsmf_EventExposure_Subscribe message. The UPF (105) may receive the N4 Session_Modification message from the SMF (104).

[0160] Alternatively, at step 504b, the SMF (104) may transmit a Nupf EventExposure_Subscribe message to the UPF (105). The Nupf EventExposure_Subscribe message may include information received via the Nsmf_EventExposure_Subscribe message. The UPF (105) may receive the Nupf EventExposure_Subscribe message from the SMF (104).

[0161] In step 504a / 504b, the SMF (104) can identify a UPF (105) that manages a specific UE, a specific PDU Session, and a specific IP Flow among the UPFs managed by the SMF (104) based on the Nsmf_EventExposure_Subscribe message. The SMF (104) can transmit an N4_Session_Modification message or a Nupf_EventExposure_Subscribe message, which includes information received from the consumer NF (113), to the UPF (105) for subscribing to the UPF service requested by the consumer NF (113). At this time, which of the above messages is used may vary depending on the type of the requested UPF service. The SMF (104) can transmit an N4_Session_Modification message or a Nupf_EventExposure_Subscribe message to the UPF (105) based on the type of UPF service requested by the consumer NF (113).

[0162] If the service request message received from the Consumer NF (113) in step 503 includes an Indication of PDU Session Release, the SMF (104) can store the Indication together with the Configuration information for the service request.

[0163] If the service request message received from the Consumer NF (113) in step 503 includes an Indication of Subscription Forwarding, the SMF (104) may store the Indication together with the configuration information for the service request. The SMF (104) may transmit the Indication to the UPF (105).

[0164] FIG. 6 is a flowchart illustrating a procedure for a terminal to move and change (relocate) a PSA UPF according to SSC 2 mode according to an embodiment of the present disclosure.

[0165] Referring to FIG. 6, the Consumer NF (114) can indirectly subscribe to the UPF Event Exposure service through SMF 1 (104-1), and the service subscription message can include an Indication of PDU Session Release option. The Consumer NF (114) can be substantially the same as or similar to the AF (114) of FIG. 1. The UE (102) can transmit and receive UL / DL data through UPF 1 (105-1).

[0166] At step 601, SMF 1 (104-1) may decide to relocate to UPF 1 (105-1).

[0167] In step 601a, SMF 1 (104-1) may send an Nsmf_PDUSession_SMContextStatusNotify Request message to AMF (103). AMF (103) may receive the Nsmf_PDUSession_SMContextStatusNotify Request message from SMF 1 (104-1). AMF (103) may send an Nsmf_PDUSession_SMContextStatusNotify Response message to SMF 1 (104-1). SMF 1 (104-1) may receive the Nsmf_PDUSession_SMContextStatusNotify Response message from AMF (103).

[0168] SMF 1 (104-1) can notify AMF (103) of a change to UPF 1 (105-1). The Nsmf_PDUSession_SMContextStatusNotify Request message can include information for notifying a change to UPF 1 (105-1). In addition, in some cases, a change to SMF 1 (104-1) may be required. If a change to SMF 1 (104-1) is required, SMF 1 (104-1) can transmit an Nsmf_PDUSession_SMContextStatusNotify Request message to AMF (103) that includes information indicating that selection of the SMF is required.

[0169] At step 601b, SMF 1 (104-1) may send an Nsmf_EventExposure_Notify message to NEF (108). NEF (108) may receive the Nsmf_EventExposure_Notify message from SMF 1 (104-1). At step 601c, NEF (108) may send an Nnef_EventExposure_Notify message to AF (114). AF (114) may receive the Nnef_EventExposure_Notify message from NEF (108).

[0170] In steps 601b and 601c, SMF 1 (104-1) may send a PDU Session Release Notification message to Consumer NF (114) via NEF (108).

[0171] In step 602, SMF 1 (104-1) may perform an operation for a PDU Session Release procedure via UPF 1 (105-1), AMF (103), (R)AN (101), and UE (102). SMF 1 (104-1) may transmit a message requesting PDU Session Release to UE (102) via at least one of UPF 1 (105-1), AMF (103), and (R)AN (101). UE (102) may receive a message requesting PDU Session Release from SMF 1 (104-1) via at least one of UPF 1 (105-1), AMF (103), and (R)AN (101).

[0172] In step 603, SMF 2 (104-2) may perform an operation for a PDU Session Establishment procedure through at least one of UPF 2 (105-2), AMF (103), (R)AN (101), and UE (102). SMF 2 (104-2) may transmit a message requesting PDU Session Establishment with UPF 2 (105-2), which is a new PSA UPF, to UE (102) through UPF 2 (105-2), AMF (103), and (R)AN (101). UE (102) may receive a message requesting PDU Session Establishment with UPF 2 (105-2), which is a new PSA UPF, from SMF 2 (104-2) through at least one of UPF 2 (105-2), AMF (103), and (R)AN (101). UE (102) can transmit and receive UL / DL data through UPF 2 (105-2).

[0173] FIG. 7 is a flowchart illustrating a procedure for a terminal to move and change (relocate) a PSA UPF according to SSC 2 mode according to an embodiment of the present disclosure.

[0174] Referring to FIG. 7, the Consumer NF (114) can indirectly subscribe to the UPF Event Exposure service through SMF 1 (104-1), and the service subscription message can include an Indication of Subscription Forwarding option. The Consumer NF (114) can be substantially the same as or similar to the AF (114) of FIG. 1. The UE (102) can transmit and receive UL / DL data through UPF 1 (105-1).

[0175] At step 701, SMF 1 (104-1) may decide to make a change to UPF 1 (105-1).

[0176] In step 701a, SMF 1 (104-1) may send an Nsmf_PDUSession_SMContextStatusNotify Request message to AMF (103). AMF (103) may receive the Nsmf_PDUSession_SMContextStatusNotify Request message from SMF 1 (104-1). AMF (103) may send an Nsmf_PDUSession_SMContextStatusNotify Response message to SMF 1 (104-1). SMF 1 (104-1) may receive the Nsmf_PDUSession_SMContextStatusNotify Response message from AMF (103).

[0177] SMF 1 (104-1) can notify AMF (103) of a change to UPF 1 (105-1). The Nsmf_PDUSession_SMContextStatusNotify Request message can include information for notifying a change to UPF 1 (105-1). In addition, in some cases, a change to SMF 1 (104-1) may be required. If a change to SMF 1 (104-1) is required, SMF 1 (104-1) can transmit an Nsmf_PDUSession_SMContextStatusNotify Request message to AMF (103) that includes information indicating that selection of the SMF is required.

[0178] In step 701b, SMF 1 (104-1) may send an Nsmf_EventExposure_Notify message to NEF (108). NEF (108) may receive the Nsmf_EventExposure_Notify message from SMF 1 (104-1). In step 701c, NEF (108) may send an Nnef_EventExposure_Notify message to AF (114). AF (114) may receive the Nnef_EventExposure_Notify message from NEF (108).

[0179] In steps 701b and 701c, SMF 1 (104-1) may send a PDU Session Release Notification message to Consumer NF (113) via NEF (108).

[0180] In step 702, SMF 1 (104-1) may perform an operation for a PDU Session Release procedure through at least one of UPF 1 (105-1), AMF (103), (R)AN (101), and UE (102). SMF 1 (104-1) may transmit a message requesting PDU Session Release to UE (102) through at least one of UPF 1 (105-1), AMF (103), and (R)AN (101). UE (102) may receive a message requesting PDU Session Release from SMF 1 (104-1) through at least one of UPF 1 (105-1), AMF (103), and (R)AN (101).

[0181] At step 703, SMF 2 (104-2) may perform an operation for a PDU Session Establishment procedure through at least one of UPF 2 (105-2), AMF (103), (R)AN (101), and UE (102). SMF 1 (104-1) may transmit a message requesting PDU Session Establishment with UPF 2 (105-2), which is a new PSA UPF, to UE (102) through at least one of UPF 2 (105-2), AMF (103), and (R)AN (101). The UE (102) may receive a message requesting PDU Session Establishment with a new PSA UPF, UPF 2 (105-2), from SMF 2 (104-2) through at least one of UPF 2 (105-2), AMF (103), and (R)AN (101).

[0182] In step 703a, SMF 1 (104-1) may send an N4_Session_Modification message to PSA UPF 2 (105-2). PSA UPF 2 (105-2) may receive the N4_Session_Modification message from SMF 1 (104-1). The N4_Session_Modification message may include information received from Consumer NF (114). For example, the information received from Consumer NF (113) may be substantially the same as or similar to the information included in the Nsmf_EventExposure_Subscribe message of FIG. 3 or FIG. 5.

[0183] Alternatively, in step 703b, SMF 1 (104-1) may send a Nupf_EventExposure_Subscribe request message to PSA UPF 2 (105-2). PSA UPF 2 (105-2) may receive the Nupf_EventExposure_Subscribe request message from SMF 1 (104-1). The Nupf_EventExposure_Subscribe request message may include information received from Consumer NF (113). For example, the information received from Consumer NF (114) may be substantially the same as or similar to the information included in the Nsmf_EventExposure_Subscribe message of FIG. 3 or FIG. 5.

[0184] In step 703a / 703b, SMF 2 (104-2) may perform an operation for Indication of Subscription Forwarding requested from Consumer NF (114). SMF 1 (104-1) may perform an operation to change the target of UPF service subscription of Consumer NF (114) from existing PSA UPF, UPF 1 (105-1), to new PSA UPF, UPF 2 (105-2). SMF 2 (104-2) may transmit an N4_Session_Modification message or a Nupf_EventExposure_Subscribe message including information received from Consumer NF (114) to UPF 2 (105-2). At this time, which of the above messages is used may vary depending on the type of UPF service requested. SMF 1 (104-1) may transmit an N4_Session_Modification message or a Nupf_EventExposure_Subscribe message to UPF-2 (105-2) based on the type of UPF service requested from the consumer NF (113). UE (102) may transmit and receive UL / DL data via UPF 2 (105-2).

[0185] FIG. 8 is a flowchart illustrating a procedure for a terminal to move and change (relocate) a PSA UPF according to SSC 2 mode according to an embodiment of the present disclosure.

[0186] Referring to FIG. 8, Consumer NF (113) can indirectly subscribe to UPF Event Exposure service through SMF 1 (104-1), and the service subscription message can include an option related to Indication of Subscription Forwarding. Also, referring to FIG. 8, a procedure for changing SMF 1 (104-1) can be performed. Consumer NF (114) can be substantially the same as or similar to AF (114) of FIG. 1. UE (102) can transmit and receive UL / DL data through UPF 1 (105-1).

[0187] At step 801, SMF 1 (104-1) may decide to make a change to UPF 1 (105-1).

[0188] In step 801a, SMF 1 (104-1) may send an Nsmf_PDUSession_SMContextStatusNotify Request message to AMF (103). AMF (103) may receive the Nsmf_PDUSession_SMContextStatusNotify Request message from SMF 1 (104-1). AMF (103) may send an Nsmf_PDUSession_SMContextStatusNotify Response message to SMF 1 (104-1). SMF 1 (104-1) may receive the Nsmf_PDUSession_SMContextStatusNotify Response message from AMF (103).

[0189] SMF 1 (104-1) can notify AMF (103) of a change to UPF 1 (105-1). The Nsmf_PDUSession_SMContextStatusNotify Request message can include information for notifying a change to UPF 1 (105-1). In addition, in some cases, a change to SMF 1 (104-1) may be required. If a change to SMF 1 (104-1) is required, SMF 1 (104-1) can send AMF (103) an Nsmf_PDUSession_SMContextStatusNotify Request message including information indicating that selection of the SMF is required.

[0190] In step 801b, SMF 1 (104-1) may send a Nsmf_EventExposure_Notify message to NEF (108). NEF (108) may receive the Nsmf_EventExposure_Notify message from SMF 1 (104-1). In step 1c, NEF (108) may send a Nnef_EventExposure_Notify message to AF (114). AF (114) may receive the Nnef_EventExposure_Notify message from NEF (108).

[0191] In steps 801b and 801c, SMF 1 (104-1) may send a PDU Session Release Notification message to Consumer NF (114) via NEF (108).

[0192] In step 802, SMF 1 (104-1) may perform an operation for a PDU Session Release procedure through at least one of UPF 1 (105-1), AMF (103), (R)AN (101), and UE (102). SMF 1 (104-1) may transmit a message requesting PDU Session Release to UE (102) through UPF 1 (105-1), AMF (103), and (R)AN (101). UE (102) may receive a message requesting PDU Session Release from SMF 1 (104-1) through at least one of UPF 1 (105-1), AMF (103), and (R)AN (101).

[0193] At step 802a, SMF 1 (104-1) may send an Nsmf_EventExposure_Subscribe request message to SMF 2 (104-2). SMF 2 (104-2) may receive the Nsmf_EventExposure_Subscribe request message from SMF 1 (104-1). SMF 2 (104-2) may send an Nsmf_EventExposure_Subscribe response message to SMF 1 (104-1). SMF 1 (104-1) may receive the Nsmf_EventExposure_Subscribe response message from SMF 2 (104-2).

[0194] SMF 1 (104-1) can transmit to SMF 2 (104-2) the subscription information of the UPF service that Consumer NF (114) subscribed to in the existing PSA UPF 1 (105-1). The Nsmf_EventExposure_Subscribe request message can include the subscription information of Consumer NF (114) related to the UPF service for PSA UPF 1 (105-1).

[0195] In step 803, SMF 2 (104-2) may perform an operation for a PDU Session Establishment procedure through at least one of UPF 2 (105-2), AMF (103), (R)AN (101), and UE (102). SMF 2 (104-2) may transmit a message requesting PDU Session Establishment with UPF 2 (105-2), which is a new PSA UPF, to UE (102) through UPF 2 (105-2), AMF (103), and (R)AN (101). UE (102) may receive a message requesting PDU Session Establishment with UPF 2 (105-2), which is a new PSA UPF, from SMF 2 (104-2) through at least one of UPF 2 (105-2), AMF (103), and (R)AN (101).

[0196] At step 803a, SMF 2 (104-2) may send an N4_Session_Modification message to PSA UPF 2 (105-2). PSA UPF 2 (105-2) may receive the N4_Session_Modification message from SMF 2 (104-2). The N4_Session_Modification message may include information received from Consumer NF (114). For example, the information received from Consumer NF (114) may be substantially the same as or similar to the information included in the Nsmf_EventExposure_Subscribe message of FIG. 3 or FIG. 5.

[0197] Alternatively, in step 803b, SMF 2 (104-2) may send a Nupf_EventExposure_Subscribe request message to PSA UPF 2 (105-2). PSA UPF 2 (105-2) may receive the Nupf_EventExposure_Subscribe request message from SMF 2 (104-2). The Nupf_EventExposure_Subscribe request message may include information received from Consumer NF (114). For example, the information received from Consumer NF (114) may be substantially the same as or similar to the information included in the Nsmf_EventExposure_Subscribe message of FIG. 3 or FIG. 5.

[0198] In steps 803a and 803b, SMF 2 (104-2) may perform an operation for Indication of Subscription Forwarding requested from Consumer NF (113). SMF 2 (104-2) may perform an operation to change the target of UPF service subscription of Consumer NF (114) from existing PSA UPF, UPF 1 (105-1), to new PSA UPF, UPF 2 (105-2). SMF 2 (104-2) may transmit an N4_Session_Modification message or a Nupf_EventExposure_Subscribe message including UPF service subscription information received from SMF 1 (104-1) to UPF 2 (105-2). At this time, which of the above messages is used may vary depending on the type of UPF service requested. SMF 2 (104-2) may transmit an N4_Session_Modification message or a Nupf_EventExposure_Subscribe message to UPF-2 (105-2) based on the type of UPF service requested from the consumer NF (114). UE (102) may transmit and receive UL / DL data through UPF 2 (105-2).

[0199] FIG. 9 is a flowchart illustrating a direct subscription procedure in which a Consumer NF directly subscribes to a UPF service with a UPF according to an embodiment of the present disclosure.

[0200] Referring to FIG. 9, in step 901, the UPF event consumer NF (113) may perform operations related to the analytics consumer subscribe NWDAF service. The UPF event consumer NF (113) may be substantially the same as or similar to the AF (114) of FIG. 1. The UPF event consumer NF (113) may be referred to as a consumer NF (114).

[0201] At step 902, the consumer NF (114) may transmit a message requesting acquisition of a DNAI to the NEF (108). The NEF (108) may be substantially identical to or similar to the NEF (108) of FIG. 1. The NEF (108) may receive a message requesting acquisition of a DNAI from the consumer NF (114).

[0202] At step 903, NEF (108) can transmit DNAI to consumer NF (114). Consumer NF (114) can receive DNAI from NEF (108).

[0203] At step 904, NEF (108) may transmit an Nnrf_NFDiscovery_Request message to NRF (109). NRF (109) may be substantially the same as or similar to NRF (109) of FIG. 1. NRF (109) may receive the Nnrf_NFDiscovery_Request message from NEF (108).

[0204] At step 905, NRF (109) may transmit an Nnrf_NFDiscovery_Response message to NEF (108). NEF (108) may receive the Nnrf_NFDiscovery_Response message from NRF (109).

[0205] At step 906, according to option 1, the consumer NF (114) may perform a procedure for indirect subscription through multiple SMFs including the SMF (104).

[0206] In step 907, according to option 2, the consumer NF (114) may perform a procedure for direct subscription through multiple UPFs including the UPF (105). The consumer NF (114) may transmit a Nupf_EventExposure_Subscribe message to the UPF (105) to subscribe to the UPF Event Exposure service. The UPF (105) may receive the Nupf_EventExposure_Subscribe message from the consumer NF (114). The message may include at least one of the following information: Event ID(s), Target of Event Reporting (GPSI, SUPI, UE address information (IP or MAC address)), Event Reporting Information, Notification Target Address, Event Filter, Expiry time, DNN, S-NSSAI.

[0207] If the service requested by Consumer NF (114) is a PDU Session-related service, it may further include at least one of the following information: Indication of PDU Session Release, Indication of Subscription Forwarding.

[0208] Indication of PDU Session Release may be information indicating that a notification is requested when the PDU Session related to the requested service is released.

[0209] Indication of Subscription Forwarding may be information indicating that, when the PDU Session related to the requested service is released and a new PSA UPF (105) and PDU Session are established, a request is made to continue to receive the previously subscribed service in the newly established PDU Session.

[0210] When a Consumer NF (114) subscribes to a service related to a PDU Session, if a PDU Session with an existing PSA UPF is released and a PDU Session with a new PSA UPF is established, the Consumer NF (114) may simply receive a Notification for PDU Session Release or perform an action to select an option to continue requesting the previously subscribed service in the newly created PDU Session. The UPF (105) may transmit an Indication of PDU Session Release and / or an Indication of Subscription Forwarding received from the Consumer NF (114) to the Serving SMF (104).

[0211] At step 908, UPF (105) may send a Nupf_EventExposure_Notify message to Consumer NF (113). Consumer NF (114) may receive the Nupf_EventExposure_Notify message from UPF (105).

[0212] FIG. 10 is a flowchart illustrating a procedure for changing a PSA UPF according to SSC 2 mode when a terminal moves according to an embodiment of the present disclosure.

[0213] Referring to FIG. 10, Consumer NF (113) can directly subscribe to UPF Event Exposure service through UPF 1 (105-1), and the service subscription message can include an option related to Indication of PDU Session Release.

[0214] At step 1001, SMF 1 (104-1) may decide to make a change to UPF 1 (105-1).

[0215] In step 1001a, SMF 1 (104-1) may send an Nsmf_PDUSession_SMContextStatusNotify Request message to AMF (103). AMF (103) may receive an Nsmf_PDUSession_SMContextStatusNotify Request message from SMF 1 (104-1). AMF (103) may send an Nsmf_PDUSession_SMContextStatusNotify Response message to SMF 1 (104-1). SMF 1 (104-1) may receive an Nsmf_PDUSession_SMContextStatusNotify Response message from AMF (103).

[0216] SMF 1 (104-1) can notify AMF (103) of a change to UPF 1 (105-1). The Nsmf_PDUSession_SMContextStatusNotify Request message can include information for notifying a change to UPF 1 (105-1). In addition, in some cases, a change to SMF 1 (104-1) may be required. If a change to SMF 1 (104-1) is required, SMF 1 (104-1) can send AMF (103) an Nsmf_PDUSession_SMContextStatusNotify Request message including information indicating that selection of the SMF is required.

[0217] At step 1001b, SMF 1 (104-1) may send a Nsmf_EventExposure_Notify message to NEF (108). NEF (108) may receive the Nsmf_EventExposure_Notify message from SMF 1 (104-1). At step 1001c, NEF (108) may send a Nnef_EventExposure_Notify message to AF (114). AF (114) may receive the Nnef_EventExposure_Notify message from NEF (108).

[0218] In steps 1001b and 1001c, SMF 1 (104-1) may send a PDU Session Release Notification message to Consumer NF (114) via NEF (108).

[0219] In step 1002, SMF 1 (104-1) can perform an operation for a PDU Session Release procedure through at least one of UPF 1 (105-1), AMF (103), (R)AN (101), and UE (102). SMF 1 (104-1) can transmit a message requesting PDU Session Release to UE (102) through at least one of UPF 1 (105-1), AMF (103), and (R)AN (101). UE (102) can receive a message requesting PDU Session Release from SMF 1 (104-1) through at least one of UPF 1 (105-1), AMF (103), and (R)AN (101). In step 1002a, UPF 1 (105-1) may send a Nupf_EventExposure_Notify message to NEF (108) (i.e., the consumer if Nupf_EventExposure_Subscribe operation). NEF (108) may receive the Nupf_EventExposure_Notify message from UPF 1 (105-1). In step 1002b, NEF (108) may send a Nnef_EventExposure_Notify message to AF (114) (i.e., the final consumer). AF (114) may receive the Nnef_EventExposure_Notify message from NEF (108).

[0220] In steps 1002a and 1002b, UPF 1 (105-1) may send a PDU Session Release Notification message to Consumer NF (114) via NEF (108).

[0221] Steps 1001b and 1001c may be performed when UPF 1 (105-1) transmits an Indication of PDU Session Release to SMF 1 (104-1) in the UPF service subscription procedure of Consumer NF (114). Steps 1002a and 1002b may be performed when UPF 1 (105-1) does not transmit an Indication of PDU Session Release to SMF 1 (104-1).

[0222] In step 1003, SMF 2 (104-2) may perform an operation for a PDU Session Establishment procedure through at least one of UPF 2 (105-2), AMF (103), (R)AN (101), and UE (102). SMF 2 (104-2) may transmit a message requesting PDU Session Establishment with UPF 2 (105-2), which is a new PSA UPF, to UE (102) through UPF 2 (105-2), AMF (103), and (R)AN (101). UE (102) may receive a message requesting PDU Session Establishment with UPF 2 (105-2), which is a new PSA UPF, from SMF 2 (104-2) through at least one of UPF 2 (105-2), AMF (103), and (R)AN (101). UE (102) can transmit and receive UL / DL data through UPF 2 (105-2).

[0223] FIG. 11 is a flowchart illustrating a procedure for changing a PSA UPF in SSC 2 mode by moving a terminal according to an embodiment of the present disclosure.

[0224] Referring to FIG. 11, Consumer NF (114) can directly subscribe to UPF Event Exposure service through UPF 1 (105-1), and the service subscription message can include an option related to Indication of Subscription Forwarding.

[0225] At step 1101, SMF 1 (104-1) may decide to make a change to UPF-1 (105-1).

[0226] In step 1101a, SMF 1 (104-1) may send an Nsmf_PDUSession_SMContextStatusNotify Request message to AMF (103). AMF (103) may receive the Nsmf_PDUSession_SMContextStatusNotify Request message from SMF 1 (104-1). AMF (103) may send an Nsmf_PDUSession_SMContextStatusNotify Response message to SMF 1 (104-1). SMF 1 (104-1) may receive the Nsmf_PDUSession_SMContextStatusNotify Response message from AMF (103).

[0227] SMF 1 (104-1) can notify AMF (103) of a change to UPF-1 (105-1). The Nsmf_PDUSession_SMContextStatusNotify Request message can include information for notifying a change to UPF 1 (105-1). In addition, in some cases, a change to SMF 1 (104-1) may be required. If a change to SMF 1 (104-1) is required, SMF 1 (104-1) can send AMF (103) an Nsmf_PDUSession_SMContextStatusNotify Request message including information indicating that selection of the SMF is required.

[0228] In step 1101b, SMF 1 (104-1) may send a Nsmf_EventExposure_Notify message to NEF (108). NEF (108) may receive the Nsmf_EventExposure_Notify message from SMF 1 (104-1). In step 1101c, NEF (108) may send a Nnef_EventExposure_Notify message to AF (114). AF (114) may receive the Nnef_EventExposure_Notify message from NEF (108).

[0229] In steps 1101b and 1101c, SMF 1 (104-1) may send a PDU Session Release Notification message to Consumer NF (114) via NEF (108).

[0230] In step 1102, SMF 1 (104-1) may perform an operation for a PDU Session Release procedure through at least one of UPF 1 (105-1), AMF (103), (R)AN (101), and UE (102). SMF 1 (104-1) may transmit a message requesting PDU Session Release to UE (102) through UPF 1 (105-1), AMF (103), and (R)AN (101). UE (102) may receive a message requesting PDU Session Release from SMF 1 (104-1) through UPF 1 (105-1), AMF (103), and (R)AN (101).

[0231] In step 1102a, UPF 1 (105-1) may send a Nsmf_EventExposure_Notify message to NEF (108). NEF (108) may receive the Nsmf_EventExposure_Notify message from UPF 1 (105-1). In step 1102b, NEF (108) may send a Nnef_EventExposure_Notify message to AF (114). AF (114) may receive the Nnef_EventExposure_Notify message from NEF (108).

[0232] In steps 1102a and 1102b, UPF 1 (105-1) may transmit a PDU Session Release Notification message to Consumer NF (114) via NEF (108). Steps 1101b and 1101c may be steps performed when UPF 1 (105-1) transmits an Indication of Subscription Forwarding to SMF 1 (104-1) in the UPF service subscription procedure of Consumer NF (114). Steps 2a and 2b may be performed when UPF 1 (105-1) does not transmit an Indication of Subscription Forwarding to SMF 1 (104-1).

[0233] In step 1102c, PSA UPF 1 (105-1) may send an N4_Session_Modification message to SMF 1 (104-1). SMF 1 (104-1) may receive the N4_Session_Modification message from PSA UPF 1 (105-1). The N4_Session_Modification message may include information received from Consumer NF (114). For example, the information received from Consumer NF (114) may be substantially the same as or similar to the information included in the Nsmf_EventExposure_Subscribe message of FIG. 3 or FIG. 5.

[0234] Alternatively, in step 1102d, PSA UPF 1 (105-1) may send a Nupf_EventExposure_Subscribe request message to SMF 1 (105-1). SMF 1 (105-1) may receive the Nupf_EventExposure_Subscribe request message from PSA UPF 1 (105-1). The Nupf_EventExposure_Subscribe request message may include information received from Consumer NF (114). For example, the information received from Consumer NF (114) may be substantially the same as or similar to the information included in the Nsmf_EventExposure_Subscribe message of FIG. 3 or FIG. 5.

[0235] In steps 1102c and 1102d, SMF 1 (104-1) may perform an operation for Indication of Subscription Forwarding requested from Consumer NF (114). UPF 1 (105-1), which is an existing PSA UPF, may transmit an N4_Session_Modification message or an Nsmf_EventExposure_Subscribe message including UPF service subscription information of Consumer NF (114) to SMF-1 (104-1). At this time, which of the above messages is used may vary depending on the type of UPF service requested. UPF 1 (105-1) may transmit an N4_Session_Modification message or an Nupf_EventExposure_Subscribe message to SMF-1 (104-1) based on the type of UPF service requested from Consumer NF (114).

[0236] In step 1103, SMF 1 (104-1) may perform an operation for a PDU Session Establishment procedure through at least one of UPF 2 (105-2), AMF (103), (R)AN (101), and UE (102). SMF-1 (104-1) may transmit a message requesting PDU Session Establishment with UPF 2 (105-2), which is a new PSA UPF, to UE (102) through at least one of UPF 2 (105-2), AMF (103), and (R)AN (101). The UE (102) may receive a message requesting PDU Session Establishment with a new PSA UPF, UPF 2 (105-2), from SMF 1 (104-1) through at least one of UPF 2 (105-2), AMF (103), and (R)AN (101).

[0237] In step 1103a, SMF 1 (104-1) may send an N4_Session_Modification message to PSA UPF 2 (105-2). PSA UPF 2 (105-2) may receive the N4_Session_Modification message from SMF 1 (104-1). The N4_Session_Modification message may include information received from Consumer NF (114). For example, the information received from Consumer NF (114) may be substantially the same as or similar to the information included in the Nsmf_EventExposure_Subscribe message of FIG. 3 or FIG. 5.

[0238] Alternatively, in step 1103b, SMF 1 (104-1) may send a Nupf_EventExposure_Subscribe request message to PSA UPF 2 (105-2). PSA UPF 2 (105-2) may receive the Nupf_EventExposure_Subscribe request message from SMF 1 (104-1). The Nupf_EventExposure_Subscribe request message may include information received from Consumer NF (114). For example, the information received from Consumer NF (114) may be substantially the same as or similar to the information included in the Nsmf_EventExposure_Subscribe message of FIG. 3 or FIG. 5.

[0239] In steps 1103a and 1103b, SMF 2 (104-2) may perform an operation for Indication of Subscription Forwarding requested from Consumer NF (114). SMF 2 (104-2) may perform an operation to change the target of UPF service subscription of Consumer NF (133) from existing PSA UPF, UPF 1 (105-1), to new PSA UPF, UPF 2 (105-2). SMF 2 (104-2) may transmit an N4_Session_Modification message or a Nupf_EventExposure_Subscribe message including information received from existing PSA UPF, UPF 1 (105-1), to UPF 2 (105-2). At this time, which of the above messages is used may vary depending on the type of UPF service requested. SMF 2 (104-2) may transmit an N4_Session_Modification message or a Nupf_EventExposure_Subscribe message to UPF-2 (105-2) based on the type of UPF service requested from the consumer NF (114). UE (102) may transmit and receive UL / DL data through UPF 2 (105-2).

[0240] FIG. 12 is a flowchart illustrating a procedure for changing a PSA UPF in SSC 2 mode when a terminal moves according to an embodiment of the present disclosure.

[0241] Referring to FIG. 12, the Consumer NF (114) can directly subscribe to the UPF Event Exposure service through UPF 1 (105-1), and the service subscription message can include an option related to Indication of Subscription Forwarding. Also, referring to FIG. 12, a procedure for changing SMF 1 (104-1) can be performed. The Consumer NF (114) can be substantially the same as or similar to the AF (114) of FIG. 1. The UE (102) can transmit and receive UL / DL data through UPF 1 (105-1).

[0242] At step 1201, SMF 1 (104-1) may decide to make a change to UPF 1 (105-1).

[0243] In step 1201a, SMF 1 (104-1) may send an Nsmf_PDUSession_SMContextStatusNotify Request message to AMF (103). AMF (103) may receive the Nsmf_PDUSession_SMContextStatusNotify Request message from SMF 1 (104-1). AMF (103) may send an Nsmf_PDUSession_SMContextStatusNotify Response message to SMF 1 (104-1). SMF 1 (104-1) may receive the Nsmf_PDUSession_SMContextStatusNotify Response message from AMF (103).

[0244] SMF 1 (104-1) can notify AMF (103) of a change to UPF 1 (105-1). The Nsmf_PDUSession_SMContextStatusNotify Request message can include information for notifying a change to UPF 1 (105-1). In addition, in some cases, a change to SMF 1 (104-1) may be required. If a change to SMF 1 (104-1) is required, SMF 1 (104-1) can send AMF (103) an Nsmf_PDUSession_SMContextStatusNotify Request message including information indicating that selection of the SMF is required.

[0245] At step 1201b, SMF 1 (104-1) may send a Nsmf_EventExposure_Notify message to NEF (108). NEF (108) may receive the Nsmf_EventExposure_Notify message from SMF 1 (104-1). At step 1201c, NEF (108) may send a Nnef_EventExposure_Notify message to AF (114). AF (114) may receive the Nnef_EventExposure_Notify message from NEF (108).

[0246] In steps 1201b and 1201c, SMF 1 (104-1) may send a PDU Session Release Notification message to Consumer NF (114) via NEF (108).

[0247] In step 1202, SMF 1 (104-1) can perform an operation for a PDU Session Release procedure via UPF 1 (105-1), AMF (103), (R)AN (101), and UE (102). SMF 1 (104-1) can transmit a message requesting PDU Session Release to UE (102) via at least one of UPF 1 (105-1), AMF (103), and (R)AN (101). UE (102) can receive a message requesting PDU Session Release from SMF 1 (104-1) via at least one of UPF 1 (105-1), AMF (103), and (R)AN (101).

[0248] In step 1202a, UPF 1 (105-1) may send a Nsmf_EventExposure_Notify message to NEF (108). NEF (108) may receive the Nsmf_EventExposure_Notify message from UPF 1 (105-1). In step 1202b, NEF (108) may send a Nnef_EventExposure_Notify message to AF (114). AF (114) may receive the Nnef_EventExposure_Notify message from NEF (108).

[0249] In steps 1202a and 1202b, UPF 1 (105-1) may send a PDU Session Release Notification message to Consumer NF (114) via NEF (108).

[0250] Steps 1201b and 1201c may be performed when UPF 1 (1051-1) transmits an Indication of Subscription Forwarding to SMF 1 (104-1) in the UPF service subscription procedure of Consumer NF (114). Steps 1202a and 1202b may be performed when UPF 1 (105-1) does not transmit an Indication of Subscription Forwarding to SMF 1 (104-1).

[0251] In step 1202c, PSA UPF 1 (105-1) may send an N4_Session_Modification message to SMF 1 (104-1). SMF 1 (104-1) may receive the N4_Session_Modification message from PSA UPF 1 (105-1). The N4_Session_Modification message may include information received from Consumer NF (114). For example, the information received from Consumer NF (114) may be substantially the same as or similar to the information included in the Nsmf_EventExposure_Subscribe message of FIG. 3 or FIG. 5.

[0252] Alternatively, in step 1202d, PSA UPF 1 (105-1) may send an Nsmf_EventExposure_Subscribe request message to SMF 1 (105-1). SMF 1 (105-1) may receive the Nsmf_EventExposure_Subscribe request message from PSA UPF 1 (105-1). The Nsmf_EventExposure_Subscribe request message may include information received from Consumer NF (114). For example, the information received from Consumer NF (114) may be substantially the same as or similar to the information included in the Nsmf_EventExposure_Subscribe message of FIG. 3 or FIG. 5.

[0253] In steps 1202c and 1202d, SMF 1 (104-1) may perform an operation for Indication of Subscription Forwarding requested from Consumer NF (114). UPF 1 (104-1), which is an existing PSA UPF, may transmit an N4_Session_Modification message or an Nsmf_EventExposure_Subscribe message including UPF service subscription information of Consumer NF (114) to SMF 1 (105-1). At this time, which of the above messages is used may vary depending on the type of UPF service requested. UPF 1 (105-1) may transmit an N4_Session_Modification message or an Nupf_EventExposure_Subscribe message to SMF-1 (104-1) based on the type of UPF service requested from Consumer NF (114). In step 3, SMF 1 (104-1) can perform an operation for a PDU Session Establishment procedure through at least one of UPF 2 (105-2), AMF (103), (R)AN (101), and UE (102). SMF 1 (104-1) can transmit a message requesting PDU Session Establishment with UPF 2 (104-2), which is a new PSA UPF, to UE (102) through at least one of UPF 2 (105-2), AMF (103), and (R)AN (101). UE (102) can receive a message requesting PDU Session Establishment with UPF 2 (105-2), which is a new PSA UPF, from SMF 1 (104-1) through at least one of UPF 2 (105-2), AMF (103), and (R)AN (101).

[0254] In step 1203a, SMF 1 (104-1) may send an Nsmf_EventExposure_Subscribe request message to SMF 2 (105-1). SMF 1 (105-1) may receive the Nsmf_EventExposure_Subscribe request message from SMF 2 (105-2). The Nsmf_EventExposure_Subscribe request message may include information received from Consumer NF (114). For example, the information received from Consumer NF (114) may be substantially the same as or similar to the information included in the Nsmf_EventExposure_Subscribe message of FIG. 3 or FIG. 5.

[0255] At step 1203a, SMF 1 (104-1) may transmit UPF service subscription information related to UPF 1 (105-1) of Consumer NF (113) to SMF 2 (104-2).

[0256] In step 1203b, SMF 2 (104-2) may send an N4_Session_Modification message to PSA UPF 2 (105-2). PSA UPF 2 (105-2) may receive the N4_Session_Modification message from SMF 2 (104-2). The N4_Session_Modification message may include information received from Consumer NF (114). For example, the information received from Consumer NF (114) may be substantially the same as or similar to the information included in the Nsmf_EventExposure_Subscribe message of FIG. 3 or FIG. 5.

[0257] Alternatively, in step 1203c, SMF 2 (104-2) may send a Nupf_EventExposure_Subscribe request message to PSA UPF 2 (105-2). PSA UPF 2 (105-2) may receive the Nupf_EventExposure_Subscribe request message from SMF 2 (104-2). The Nupf_EventExposure_Subscribe request message may include information received from Consumer NF (114). For example, the information received from Consumer NF (114) may be substantially the same as or similar to the information included in the Nsmf_EventExposure_Subscribe message of FIG. 3 or FIG. 5.

[0258] In step 1203b, SMF 2 (104-2) may send an N4_Session_Modification message to PSA UPF 2 (105-2). PSA UPF 2 (105-2) may receive the N4_Session_Modification message from SMF 2 (104-2). The N4_Session_Modification message may include information received from Consumer NF (114). For example, the information received from Consumer NF (114) may be substantially the same as or similar to the information included in the Nsmf_EventExposure_Subscribe message of FIG. 3 or FIG. 5.

[0259] Alternatively, in step 1203c, SMF 2 (105-2) may send a Nupf_EventExposure_Subscribe request message to PSA UPF 2 (105-2). PSA UPF 2 (105-2) may receive the Nupf_EventExposure_Subscribe request message from SMF 2 (105-2). The Nupf_EventExposure_Subscribe request message may include information received from Consumer NF (114). For example, the information received from Consumer NF (114) may be substantially the same as or similar to the information included in the Nsmf_EventExposure_Subscribe message of FIG. 3 or FIG. 5.

[0260] In steps 1203b and 1203c, SMF 2 (105-2) may perform an operation for Indication of Subscription Forwarding requested from Consumer NF (114). SMF 2 (104-2) may perform an operation to change the UPF service subscription target of Consumer NF (114) from the existing PSA UPF, UPF 1 (105-1), to the new PSA UPF, UPF 2 (105-2). SMF 2 (104-2) may transmit an N4_Session_Modification message or a Nupf_EventExposure_Subscribe message including the UPF service subscription information received from SMF 1 (104-1) to UPF 2 (104-2). At this time, which of the above messages is used may vary depending on the type of UPF service requested. SMF 2 (105-2) can send an N4_Session_Modification message or a Nupf_EventExposure_Subscribe message to UPF-2 (105-2) based on the type of UPF service requested from consumer NF (114).

[0261] FIG. 13 is a flowchart illustrating a procedure for changing a PSA UPF in SSC 2 mode when a terminal moves according to an embodiment of the present disclosure.

[0262] Referring to FIG. 13, a Consumer NF (114) can subscribe to the UPF Event Exposure service using the UPF Relocation Indication. FIG. 13 illustrates an embodiment of indirect subscription through SMF 1 (104-1) and not changing SMF 1 (104-1) when subscribing to the UPF service; however, the present disclosure is not limited thereto and may include various embodiments, such as an embodiment of directly subscribing to the UPF service and an embodiment of changing SMF 1 (104-1).

[0263] Referring to FIG. 13, Consumer NF (114) can indirectly subscribe to UPF Event Exposure service through SMF 1 (104-1) to UPF 2 (105-2), and the service subscription message can include options related to UPF Relocation Indication.

[0264] At step 1301, SMF 1 (104-1) may decide to make a change to UPF 1 (105-1).

[0265] In step 1301a, SMF 1 (104-1) may send an Nsmf_PDUSession_SMContextStatusNotify Request message to AMF (103). AMF (103) may receive the Nsmf_PDUSession_SMContextStatusNotify Request message from SMF 1 (104-1). AMF (103) may send an Nsmf_PDUSession_SMContextStatusNotify Response message to SMF 1 (104-1). SMF 1 (104-1) may receive the Nsmf_PDUSession_SMContextStatusNotify Response message from AMF (103).

[0266] SMF 1 (104-1) can notify AMF (103) of a change to UPF 1 (105-1). The Nsmf_PDUSession_SMContextStatusNotify Request message can include information for notifying a change to UPF 1 (105-1). In addition, in some cases, a change to SMF 1 (104-1) may be required. If a change to SMF 1 (104-1) is required, SMF 1 (104-1) can send AMF (103) an Nsmf_PDUSession_SMContextStatusNotify Request message including information indicating that selection of the SMF is required.

[0267] At step 1301b, SMF 1 (104-1) may send a Nsmf_EventExposure_Notify message to NEF (108). NEF (108) may receive the Nsmf_EventExposure_Notify message from SMF 1 (104-1). At step 1301c, NEF (108) may send a Nnef_EventExposure_Notify message to AF (114). AF (114) may receive the Nnef_EventExposure_Notify message from NEF (108).

[0268] In steps 1301b and 1301c, SMF 1 (104-1) may send a PDU Session Release Notification message to Consumer NF (114) via NEF (108). For example, the PDU Session Release Notification message may include a cause value, and the cause value may be set to UPF Relocation.

[0269] In step 1302, SMF 1 (104-1) can perform an operation for a PDU Session Release procedure through at least one of UPF 1 (105-1), AMF (103), (R)AN (101), and UE (102). SMF 1 (104-1) can transmit a message requesting PDU Session Release to UE (102) through at least one of UPF 1 (105-1), AMF (103), and (R)AN (101). UE (102) can receive a message requesting PDU Session Release from SMF 1 (104-1) through at least one of UPF 1 (105-1), AMF (103), and (R)AN (101).

[0270] AF (114), which has received a PDU Session Release Notification message and a cause value that can be set to UPF Relocation from SMF 1 (104-1) and / or NEF (108) at step 1302a, can decide whether to continue using the previously subscribed service through PSA UPF 2 (105-2) that is changed from PSA UPF 1 (105-1).

[0271] At step 1303, SMF 1 (104-1) may perform an operation for a PDU Session Establishment procedure through at least one of UPF 2 (105-2), AMF (103), (R)AN (101), and UE (102). SMF 1 (104-1) may transmit a message requesting PDU Session Establishment with UPF 2 (104-2), which is a new PSA UPF, to UE (102) through at least one of UPF 2 (105-2), AMF (103), and (R)AN (101). The UE (102) may receive a message requesting PDU Session Establishment with a new PSA UPF, UPF 2 (105-2), from SMF 1 (104-1) through at least one of UPF 2 (105-2), AMF (103), and (R)AN (101).

[0272] In step 1304, if the AF decides to continue using the previously subscribed service from the newly changed PSA UPF in step 1302a, the AF may send a Configuration Forwarding Indication to the SMF. The SMF, upon receiving the Configuration Forwarding Indication, may forward the existing UPF service subscription information to the new PSA UPF.

[0273] FIG. 14 is a block diagram illustrating the configuration of a terminal according to embodiments of the present disclosure.

[0274] Referring to FIG. 14, the terminal (1400) may be substantially identical to or similar to the terminal (102) of FIGS. 1, 4, 6, and 13. The terminal (1400) according to one embodiment of the present disclosure may include a processor (1403) that controls the overall operation of the terminal, a transceiver (1401) including a transmitter and a receiver, and a memory (1402). Of course, the present invention is not limited to the above-described examples, and the terminal (1400) may include more or fewer components than those illustrated in FIG. 14.

[0275] According to one embodiment of the present disclosure, the transceiver (1401) can transmit and receive signals with network entities or other terminals. The signals transmitted and received with the network entities may include control information and data. In addition, the transceiver (1401) can receive signals via a wireless channel, output the signals to the processor (1403), and transmit the signals output from the processor (1403) via the wireless channel. The network entities may be substantially the same as or similar to the network entities (101, 103, 104, 105, 106, 107, 108, 109, 110, 111, 113, 114, 115, 116, 117, 118, and 119) of FIG. 1.

[0276] According to one embodiment of the present disclosure, the processor (1403) can control the terminal to perform any one of the operations described above. Meanwhile, the processor (1403), the memory (1402), and the transceiver (1401) do not necessarily have to be implemented as separate modules, and of course, they can be implemented as a single component in the form of a single chip. In addition, the processor (1403) and the transceiver (1401) can be electrically connected. In addition, the processor (1403) can include an application processor (AP), a communication processor (CP), a circuit, an application-specific circuit, a controller, or at least one processor.

[0277] According to one embodiment of the present disclosure, the memory (1402) can store data such as basic programs, application programs, and setting information for the operation of the terminal. In particular, the memory (1402) provides the stored data upon request of the processor (1403). The memory (1402) can be configured as a storage medium or a combination of storage media such as a ROM, a RAM, a hard disk, a CD-ROM, and a DVD. In addition, there can be a plurality of memories (1402). In addition, the processor (1403) can perform the above-described embodiments based on a program for performing the above-described embodiments of the present disclosure stored in the memory (1402).

[0278] FIG. 15 is a block diagram illustrating a configuration of a base station according to embodiments of the present disclosure.

[0279] Referring to FIG. 15, the base station (1500) may be substantially the same as or similar to the (R)AN (101) of FIGS. 1, 4, 6 to 13. The base station (1500) according to one embodiment of the present disclosure may include a processor (1503) that controls the overall operation of the base station (1500), a transceiver (1501) including a transmitter and a receiver, and a memory (1502). Of course, the present invention is not limited to the above-described examples, and the base station (1500) may include more or fewer components than the components illustrated in FIG. 15.

[0280] According to one embodiment of the present disclosure, the transceiver (1501) can transmit and receive signals with at least one of other network entities or terminals (1400). The signals transmitted and received with at least one of other network entities or terminals (1400) can include control information and data. The network entities can be substantially the same as or similar to the network entities (103, 104, 105, 106, 107, 108, 109, 110, 111, 113, 114, 115, 116, 117, 118, 119) of FIG. 1.

[0281] According to one embodiment of the present disclosure, the processor (1503) can control the base station (1500) to perform any one of the operations described above. Meanwhile, the processor (1503), the memory (1502), and the transceiver (1501) do not necessarily have to be implemented as separate modules, and may of course be implemented as a single component in the form of a single chip. In addition, the processor (1503) and the transceiver (1501) may be electrically connected. In addition, the processor (1503) may include an Application Processor (AP), a Communication Processor (CP), a circuit, an application-specific circuit, a controller, or at least one processor.

[0282] According to one embodiment of the present disclosure, the memory (1502) can store data such as basic programs, application programs, and setting information for the operation of the base station (1500). In particular, the memory (1502) provides the stored data upon request of the processor (1503). The memory (1502) can be configured as a storage medium or a combination of storage media such as a ROM, a RAM, a hard disk, a CD-ROM, and a DVD. In addition, there can be a plurality of memories (1502). In addition, the processor (1503) can perform the above-described embodiments based on a program for performing the above-described embodiments of the present disclosure stored in the memory (1502).

[0283] FIG. 16 is a block diagram illustrating a configuration of a network entity according to embodiments of the present disclosure.

[0284] Referring to FIG. 16, a network entity (1600) may be substantially identical to or similar to at least one of the network entities (103, 104, 105, 106, 107, 108, 109, 110, 111, 113, 114, 115, 116, 117, 118, 119) of FIG. 1. A network entity (1600) according to one embodiment of the present disclosure may include a processor (1603) for controlling the overall operation of the network entity, a transceiver (1601) including a transmitter and a receiver, and a memory (1602). Of course, the present invention is not limited to the above-described example, and the network entity (1600) may include more or fewer components than the configuration illustrated in FIG. 16.

[0285] According to one embodiment of the present disclosure, the transceiver (1601) can transmit and receive signals with at least one of other network entities or terminals (1400). The signals transmitted and received with at least one of other network entities or terminals (1400) can include control information and data.

[0286] According to one embodiment of the present disclosure, the processor (1603) can control a network entity to perform any one of the operations described above. Meanwhile, the processor (1603), the memory (1602), and the transceiver (1601) do not necessarily have to be implemented as separate modules, and can of course be implemented as a single component in the form of a single chip. In addition, the processor (1603) and the transceiver (1601) can be electrically connected. In addition, the processor (1603) can include an Application Processor (AP), a Communication Processor (CP), a circuit, an application-specific circuit, a controller, or at least one processor.

[0287] According to one embodiment of the present disclosure, the memory (1602) can store data such as basic programs, application programs, and setting information for the operation of a network entity. In particular, the memory (1602) provides the stored data upon request of the processor (1603). The memory (1602) can be configured as a storage medium or a combination of storage media such as a ROM, a RAM, a hard disk, a CD-ROM, and a DVD. In addition, there can be a plurality of memories (1602). In addition, the processor (1603) can perform the above-described embodiments of the present disclosure based on a program for performing the above-described embodiments stored in the memory (1602).

[0288] It should be noted that the aforementioned configuration diagrams, examples of control / data signal transmission methods, examples of operational procedures, and configuration diagrams are not intended to limit the scope of the present disclosure. That is, not all components, entities, or operational steps described in the embodiments of the present disclosure should be construed as essential components for implementing the disclosure, and implementations may be made without detracting from the essence of the disclosure even if only some components are included. Furthermore, each embodiment may be combined and operated as needed. For example, parts of the methods proposed in the present disclosure may be combined to operate network entities and terminals.

[0289] The operations of the base station or terminal described above can be realized by providing a memory device storing the corresponding program code in any component within the base station or terminal device. That is, the control unit of the base station or terminal device can execute the operations described above by reading and executing the program code stored in the memory device using a processor or CPU (Central Processing Unit).

[0290] The various components and modules of the entity, base station or terminal device described in this specification may be operated using hardware circuits, such as logic circuits based on complementary metal oxide semiconductors, firmware, software and / or hardware and firmware and / or software embedded in a machine-readable medium. For example, various electrical structures and methods may be implemented using electrical circuits such as transistors, logic gates and application-specific semiconductors.

[0291] When implemented in software, a computer-readable storage medium storing one or more programs (software modules) may be provided. The one or more programs stored in the computer-readable storage medium are configured for execution by one or more processors within an electronic device. The one or more programs include instructions that cause the electronic device to execute methods according to embodiments described in the claims or specification of the present disclosure.

[0292] These programs (software modules, software) may be stored in random access memory, non-volatile memory including flash memory, read only memory (ROM), electrically erasable programmable read only memory (EEPROM), magnetic disc storage device, compact disc ROM (CD-ROM), digital versatile discs (DVDs) or other forms of optical storage device, magnetic cassette. Or, they may be stored in a memory configured as a combination of some or all of these. In addition, each configuration memory may be included in multiple numbers.

[0293] Additionally, the program may be stored in an attachable storage device that is accessible via a communication network such as the Internet, an intranet, a local area network (LAN), a wide local area network (WLAN), a storage area network (SAN), or a combination thereof. Such a storage device may be connected to a device performing an embodiment of the present disclosure via an external port. Additionally, a separate storage device on the communication network may be connected to a device performing an embodiment of the present disclosure.

[0294] In the specific embodiments of the present disclosure described above, components included in the disclosure are expressed singularly or plurally, depending on the specific embodiment presented. However, the singular or plural expressions are selected to suit the presented situation for convenience of explanation, and the present disclosure is not limited to singular or plural components. Components expressed in plural may be composed of singular elements, or components expressed in singular may be composed of plural elements.

[0295] While the detailed description of the present disclosure has described specific embodiments, it should be understood that various modifications are possible without departing from the scope of the present disclosure. Therefore, the scope of the present disclosure should not be limited to the described embodiments, but should be determined not only by the scope of the claims described below but also by equivalents thereof. In other words, it will be apparent to those skilled in the art that other modifications based on the technical idea of ​​the present disclosure are possible. In addition, the above-described embodiments can be combined and operated with each other as needed. For example, parts of the methods proposed in the present disclosure can be combined with each other to operate a base station and a terminal. In addition, although the above-described embodiments have been presented based on a 5G, NR system, other modifications based on the technical idea of ​​the above-described embodiments can be implemented with other systems such as LTE, LTE-A, and LTE-A-Pro systems.

Claims

In a method performed by a user plane function (UPF) of a wireless communication system, A step of receiving an event exposure subscribe message from a consumer network function (NF), the event exposure subscribe message including an indicator requesting the UPF to notify the consumer NF when a protocol data unit (PDU) session is released; a step of identifying that the above PDU session has been released; and A method comprising the step of transmitting an event exposure notify message to the consumer NF to notify that the PDU session has been released. In paragraph 1, The above event exposure subscribe message is, Information about the subject of the event report; Event ID (identifier), Information about the address to be notified; Information about event filters, Information about DNN (data network name), and S-NSSAI (single network slice selection assistance information), A method characterized by comprising at least one of: In the second paragraph, A method characterized in that information about the target of the above event report includes information about a UE (user equipment) IP (internet protocol) address. In paragraph 1, A method characterized in that the above event exposure notify message includes a cause value associated with the release of the PDU session. In a method performed by a consumer NF (network function) of a wireless communication system, A step of transmitting an event exposure subscribe message including an indicator requesting the UPF (user plane function) to notify the consumer NF when a PDU (protocol data unit) session is released; and A method comprising the step of receiving an event exposure notify message from the UPF to notify that the PDU session has been released when the PDU session has been released. In paragraph 5, The above event exposure subscribe message is, Information about the subject of the event report; Event ID (identifier), Information about the address to be notified; Information about event filters, Information about DNN (data network name), and S-NSSAI (single network slice selection assistance information), A method characterized by comprising at least one of: In paragraph 6, A method characterized in that information about the target of the above event report includes information about a UE (user equipment) IP (internet protocol) address. In paragraph 5, A method characterized in that the above event exposure notify message includes a cause value associated with the release of the PDU session. In the UPF (user plane function) of a wireless communication system, At least one transceiver; At least one processor communicatively connected to said at least one transceiver; and Communicably connected to at least one processor, and executable individually or in any combination of said at least one processor, wherein said UPF, Receive an event exposure subscribe message from a consumer network function (NF) that includes an indicator requesting the UPF to notify the consumer NF when a protocol data unit (PDU) session is released; Identifies that the above PDU session has been released, A memory storing a command to transmit an event exposure notify message to the consumer NF to notify that the PDU session has been released; UPF including . In paragraph 9, The above event exposure subscribe message is, Information about the subject of the event report; Event ID (identifier), Information about the address to be notified; Information about event filters, Information about DNN (data network name), and S-NSSAI (single network slice selection assistance information), A UPF characterized by including at least one of: In paragraph 10, UPF, characterized in that information on the target of the above event report includes information on the UE (user equipment) IP (internet protocol) address. In paragraph 9, UPF characterized in that the above event exposure notify message includes a cause value associated with the release of the PDU session. In the consumer NF (network function) of a wireless communication system, At least one transceiver; At least one processor communicatively connected to said at least one transceiver; and Communicably connected to at least one processor, and executable individually or in any combination of said at least one processor, wherein said consumer NF, Sending an event exposure subscribe message containing an indicator requesting the UPF (user plane function) to notify the consumer NF when a PDU (protocol data unit) session is released, A memory storing a command to receive an event exposure notify message from the UPF to notify that the PDU session has been released when the PDU session is released; Consumer NF including. In paragraph 13, The above event exposure subscribe message is, Information about the subject of the event report; Event ID (identifier), Information about the address to be notified; Information about event filters, Information about DNN (data network name), and S-NSSAI (single network slice selection assistance information), Contains at least one of, and Information on the target of the above event report is a consumer NF characterized in that it includes information on a UE (user equipment) IP (internet protocol) address. In paragraph 13, A consumer NF characterized in that the above event exposure notify message includes a cause value associated with the release of the PDU session.

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