Communication method and device for use of network slice in wireless communication system

Abstract

The present disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. According to an embodiment of the present disclosure, a method performed by a first core node in a wireless communication system may be provided, the method comprising the steps of: receiving a packet data network (PDN) connectivity generation request including a packet data unit (PDU) session ID and single-network slice selection assistance information (S-NSSAI) which are provided from a terminal; obtaining subscribed S-NSSAI for the terminal from a unified data management (UDM); determining S-NSSAI associated with PDN connectivity on the basis of the S-NSSAI provided from the terminal, the subscribed S-NSSAI, and at least one piece of S-NSSAI supported by the first core node; and transmitting a response message including the determined S-NSSAI to the terminal.

Description

Communication method and device for utilizing network slices in wireless communication systems

[0001] The present disclosure relates generally to wireless communication systems, and more particularly to a communication device and method for providing network slicing in a wireless communication system or a mobile communication system.

[0002] The present disclosure relates to a method and apparatus for providing a terminal policy (UE Policy) in a wireless communication system or a mobile communication system, and more particularly, to a method and apparatus for providing a terminal policy in a composite mobile communication system having different communication protocols.

[0003] 5G (5th generation) 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 band (for example, 3 terahertz (3THz) 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.

[0004] 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.

[0005] 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.

[0006] 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.

[0007] 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).

[0008] In addition, the development of these 5G mobile communication systems includes new waveforms to ensure coverage in the terahertz band of 6G mobile communication technology, multi-antenna transmission technologies such as Full Dimensional MIMO (FD-MIMO), Array Antenna, and Large Scale Antenna, metamaterial-based lenses and antennas to improve the coverage of terahertz band signals, high-dimensional spatial multiplexing technology using Orbital Angular Momentum (OAM), Reconfigurable Intelligent Surface (RIS) technology, as well as full duplex technology to improve the frequency efficiency and system network of 6G mobile communication technology, satellite, AI (Artificial Intelligence) from the design stage and AI-based communication technology that realizes system optimization by internalizing end-to-end AI support functions, and ultra-high-performance communication and computing resources to provide services with complexity that exceeds the limits of terminal computing capabilities. It can serve as a basis for the development of next-generation distributed computing technologies that can be realized by utilizing them.

[0009] To meet the growing demand for wireless data traffic following the commercialization of 4G communication systems, efforts are being made to develop improved 5G or pre-5G communication systems. For this reason, 5G or pre-5G communication systems are also referred to as "Beyond 4G Network" or "Post-LTE" systems. The 5G communication system specified by 3GPP is called the New Radio (NR) system.

[0010] To achieve high data rates, 5G communication systems are being considered for implementation in ultra-high frequency (mmWave) bands (e.g., the 60 GHz band). To mitigate radio path loss and increase the transmission range of radio waves in ultra-high frequency bands, beamforming, massive MIMO (massive MIMO), full-dimensional MIMO (FD-MIMO), array antennas, analog beamforming, and large-scale antenna technologies have been discussed and applied to NR systems in 5G communication systems.

[0011] Additionally, to improve the network of the system, technologies such as evolved small cells, advanced small cells, cloud radio access networks (cloud RAN), ultra-dense networks, device-to-device communication (D2D), wireless backhaul, moving networks, cooperative communication, CoMP (Coordinated Multi-Points), and interference cancellation are being developed in 5G communication systems.

[0012] In addition, advanced coding modulation (ACM) methods such as FQAM (Hybrid FSK and QAM Modulation) and SWSC (Sliding Window Superposition Coding), as well as advanced access technologies such as FBMC (Filter Bank Multi Carrier), NOMA (non-orthogonal multiple access), and SCMA (sparse code multiple access) are being developed in 5G systems.

[0013] Meanwhile, the Internet is evolving from a human-centric network where humans create and consume information to an Internet of Things (IoT) network where information is exchanged and processed between distributed components, such as objects. The Internet of Everything (IoE) is also emerging, combining IoT technologies with big data processing technologies, such as those connected to cloud servers. To implement the IoT, technological elements such as sensing technologies, wireless and wired communication and network infrastructure, service interface technologies, and security technologies are required. Recently, research is being conducted on technologies such as sensor networks, Machine-to-Machine (M2M), and Machine-Type Communication (MTC) for connecting objects. In the IoT environment, intelligent IT (Internet Technology) services can be provided that collect and analyze data generated from connected objects to create new value for human life. IoT can be applied to areas such as smart homes, smart buildings, smart cities, smart or connected cars, smart grids, healthcare, smart appliances, and advanced medical services through the convergence and integration of existing IT (Information Technology) technologies with various industries.

[0014] Accordingly, various attempts are being made to apply 5G communication systems to IoT networks. For example, 5G communication such as sensor networks, machine-to-machine (M2M), and machine-type communication (MTC) are being implemented using techniques such as beamforming, MIMO, and array antennas. The application of cloud radio access networks (cloud RAN), a big data processing technology described above, can also be considered an example of the convergence of 5G and IoT technologies.

[0015] The present disclosure provides a method for providing network slicing in a wireless communication system.

[0016] Additionally, the present disclosure provides a method for providing a terminal policy in a wireless communication system.

[0017] According to one embodiment of the present disclosure, a method performed by a first core node of a wireless communication system is provided, comprising: receiving a packet data network (PDN) connection creation request including a packet data unit (PDU) session ID and single-network slice selection assistance information (S-NSSAI) provided from a terminal; obtaining a subscribed S-NSSAI for the terminal from a unified data management (UDM); determining an S-NSSAI associated with the PDN connection based on the S-NSSAI provided from the terminal, the subscribed S-NSSAI, and at least one S-NSSAI supported by the first core node; and transmitting a response message including the determined S-NSSAI to the terminal.

[0018] According to another embodiment of the present disclosure, a method performed by a terminal of a wireless communication system is provided, comprising: transmitting a packet data network (PDN) connection creation request including a packet data unit (PDU) session ID and single-network slice selection assistance information (S-NSSAI) to a first core node; and receiving a response message including an S-NSSAI determined in association with the PDN connection from the first core node, wherein the determined S-NSSAI is determined based on an S-NSSAI provided from the terminal, a subscribed S-NSSAI for the terminal obtained from a unified data management (UDM), and at least one S-NSSAI supported by the first core node.

[0019] According to another embodiment of the present disclosure, a first core node of a wireless communication system is provided, comprising: at least one transceiver; at least one processor communicatively connected to the at least one transceiver; and a memory communicatively connected to the at least one processor and configured to store instructions that cause the first core node to perform the steps of: receiving a packet data network (PDN) connection creation request including a packet data unit (PDU) session ID and single-network slice selection assistance information (S-NSSAI) provided from a terminal; obtaining a subscribed S-NSSAI for the terminal from a unified data management (UDM); determining an S-NSSAI associated with the PDN connection based on the S-NSSAI provided from the terminal, the subscribed S-NSSAI, and at least one S-NSSAI supported by the first core node; and transmitting a response message including the determined S-NSSAI to the terminal.

[0020] According to another embodiment of the present disclosure, a terminal of a wireless communication system is provided, comprising: at least one transceiver; at least one processor communicatively connected to the at least one transceiver; and a memory communicatively connected to the at least one processor and storing instructions executable individually or in any combination of the at least one processor, the instructions causing the terminal to perform the steps of transmitting a packet data network (PDN) connection creation request including a packet data unit (PDU) session ID and single-network slice selection assistance information (S-NSSAI) to a first core node, and receiving a response message including an S-NSSAI determined in association with the PDN connection from the first core node, wherein the determined S-NSSAI is determined based on an S-NSSAI provided from the terminal, a subscribed S-NSSAI for the terminal obtained from a unified data management (UDM), and at least one S-NSSAI supported by the first core node.

[0021] The various embodiments of the present disclosure described above are only some of the preferred embodiments of the present disclosure, and various embodiments reflecting the technical features of the various embodiments of the present disclosure can be derived and understood by a person having ordinary skill in the art based on the detailed description to be described below.

[0022] According to one embodiment of the present disclosure, communication efficiency in a wireless communication system can be improved.

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

[0024] FIG. 1 is a diagram illustrating a network structure and interface of a 5G system according to one embodiment of the present disclosure.

[0025] FIG. 2 is a diagram illustrating a network structure and interface of an evolved packet system (EPS) / 5th generation system (5GS) interworking system according to one embodiment of the present disclosure.

[0026] FIG. 3 illustrates an example of a method for determining establishment of a PDN connection by evaluating a URSP Rule in an EPS in consideration of the connection relationship between an APN, a DNN, and an S-NSSAI in a communication system supporting 5GS-EPS interworking according to one embodiment of the present disclosure.

[0027] FIG. 4 illustrates an example of a method for selecting an appropriate S-NSSAI when using a PDN connection through a 4G system (EPS) when a terminal is connected to a 5G core and then moves to a 4G core and / or when the terminal is connected to a 4G core, in a communication system supporting 5GS-EPS interworking according to one embodiment of the present disclosure.

[0028] FIG. 5 illustrates an example of a method for selecting an appropriate S-NSSAI when using a PDN connection through a 4G system (EPS) when a terminal is connected to a 5G core and then moves to a 4G core and / or when the terminal is connected to a 4G core, in a communication system supporting 5GS-EPS interworking according to one embodiment of the present disclosure.

[0029] FIG. 6a illustrates an example of a procedure in which an SMF+PGW-C obtains UE Context information registered as SMF data in subscriber information of a UE through an HSS+UDM according to an embodiment of the present disclosure.

[0030] FIG. 6b illustrates an example of a procedure in which an SMF+PGW-C obtains UE Context information registered as SMF data in subscriber information of a UE through an HSS+UDM according to an embodiment of the present disclosure.

[0031] FIG. 7 illustrates a method for causing an MME to reselect SMF+PGW-C when an S-NSSAI requested by a UE and / or an S-NSSAI corresponding to a PDU Session ID requested by the UE is an S-NSSAI that cannot be supported by SMF+PGW-C according to one embodiment of the present disclosure.

[0032] FIG. 8A illustrates an example of a method for selecting an appropriate S-NSSAI when using a PDN connection through a 4G system (EPS) when a terminal is connected to a 5G core and then moves to a 4G core and / or when the terminal is connected to a 4G core, in a communication system supporting 5GS-EPS interworking according to one embodiment of the present disclosure.

[0033] FIG. 8b illustrates an example of a method for selecting an appropriate S-NSSAI when using a PDN connection through a 4G system (EPS) when a terminal is connected to a 5G core and then moves to a 4G core and / or when the terminal is connected to a 4G core, in a communication system supporting 5GS-EPS interworking according to one embodiment of the present disclosure.

[0034] FIG. 9 is a diagram for explaining a method for determining establishment of a PDN connection by evaluating a URSP Rule in EPS in consideration of the connection relationship between an APN, a DNN, an S-NSSAI, and an Application in a communication system supporting 5GS-EPS interworking according to one embodiment of the present disclosure.

[0035] FIG. 10 illustrates an example of a method for selecting an appropriate S-NSSAI when using a PDU Session via 5GS when a terminal is connected to a 4G core and then moves to a 5G core and / or when the terminal is connected to a 5G core in a communication system supporting 5GS-EPS interworking according to one embodiment of the present disclosure.

[0036] FIG. 11 illustrates an example of a method for selecting an appropriate S-NSSAI when using a PDU Session via 5GS when a terminal is connected to a 4G core and then moves to a 5G core and / or when the terminal is connected to a 5G core in a communication system supporting 5GS-EPS interworking according to one embodiment of the present disclosure.

[0037] FIG. 12A illustrates an example of a method for selecting an appropriate S-NSSAI when using a PDN connection through a 4G system (EPS) when a terminal is connected to a 5G core and then moves to a 4G core and / or when the terminal is connected to a 4G core, in a communication system supporting 5GS-EPS interworking according to one embodiment of the present disclosure.

[0038] FIG. 12b illustrates an example of a method for selecting an appropriate S-NSSAI when using a PDN connection through a 4G system (EPS) when a terminal is connected to a 5G core and then moves to a 4G core and / or when the terminal is connected to a 4G core, in a communication system supporting 5GS-EPS interworking according to one embodiment of the present disclosure.

[0039] FIG. 13A illustrates an example of a method for selecting an appropriate S-NSSAI when using a PDN connection through a 4G system (EPS) when a terminal is connected to a 5G core and then moves to a 4G core and / or when the terminal is connected to a 4G core, in a communication system supporting 5GS-EPS interworking according to one embodiment of the present disclosure.

[0040] FIG. 13b illustrates an example of a method for selecting an appropriate S-NSSAI when using a PDN connection through a 4G system (EPS) when a terminal is connected to a 5G core and then moves to a 4G core and / or when the terminal is connected to a 4G core, in a communication system supporting 5GS-EPS interworking according to one embodiment of the present disclosure.

[0041] FIG. 14 is a block diagram of a network entity and / or terminal according to an embodiment of the present disclosure.

[0042] Hereinafter, embodiments of the present disclosure 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 in the attached drawings. In addition, it should be noted that the attached drawings of the present disclosure are provided to aid in understanding the present disclosure, and the scope of the present disclosure is not limited to the forms or arrangements illustrated in the drawings. In addition, detailed descriptions of well-known functions and configurations that may obscure the gist of the present disclosure will be omitted. It should be noted that in the following description, only the parts necessary for understanding the operation according to various embodiments of the present disclosure will be described, and the description of other parts will be omitted so as not to distract from the gist of the present disclosure.

[0043] Additionally, while this disclosure describes various embodiments using terminology used in certain communication standards (e.g., 3rd Generation Partnership Project (3GPP)), these are merely illustrative examples. The various embodiments of this disclosure can be easily modified and applied to other communication systems.

[0044] FIG. 1 is a diagram illustrating a network structure and interface of a 5G system according to one embodiment of the present disclosure.

[0045] A network entity included in the network structure of the 5G system of Fig. 1 may include a network function (NF) depending on the system implementation.

[0046] Referring to FIG. 1, the network structure of a 5G system (100) may include various network entities. For example, the 5G system (100) includes an authentication server function (AUSF) (108), an access and mobility management function (AMF) (103), a session management function (SMF) (105), a policy control function (PCF) (106), an application function (AF) (107), a unified data management (UDM) (109), a data network (DN) (110), a network exposure function (NEF) (113), a network slicing selection function (NSSF) (114), a network repository function (NRF) (115), a user plane function (UPF) (104), a (radio) access network (R)AN) (102), and a terminal, i.e., a user It may include a device (user equipment: UE) (or terminal) (101). In addition, the 5G system (100) may also include an edge application service domain repository (EDR) (not shown) and an edge application server (EAS, not shown).

[0047] Each NF of the 5G system (100) supports the following functions.

[0048] AUSF (108) processes and stores data for authentication of UE (101).

[0049] AMF (103) provides functions for access and mobility management per UE, and one UE can be connected to one AMF by default. Specifically, the AMF (103) provides signaling between CN nodes for mobility between 3GPP access networks, termination of a radio access network (RAN) CP interface (i.e., N2 interface), termination of non-access stratum (NAS) signaling (N1), NAS signaling security (NAS ciphering and integrity protection), AS security control, registration management (registration area management), connection management, idle mode UE reachability (including control and performance of paging retransmission), mobility management control (subscription and policy), intra-system mobility and inter-system mobility support, support for network slicing, SMF selection, lawful intercept (for AMF events and interfaces to the LI system), provision of forwarding of session management (SM) messages between UE and SMF, transparent proxy for SM message routing, access authentication, access authorization including roaming authorization check. It supports functions such as authorization, provision of SMS message transmission between UE and SMSF, security anchor function (SAF) and / or security context management (SCM). Some or all of the functions of AMF (103) may be supported within a single instance of AMF.

[0050] DN (110) refers to, for example, an operator service, Internet access, or a third-party service. DN (110) transmits a downlink protocol data unit (PDU) to UPF (104) or receives a PDU transmitted from UE (101) from UPF (104).

[0051] PCF (106) receives information about packet flows from the application server and provides a function to determine policies such as mobility management and session management. Specifically, PCF (106) supports functions such as supporting a unified policy framework for controlling network operations, providing policy rules so that control plane functions (e.g., AMF, SMF, etc.) can enforce the policy rules, and implementing a front end for accessing related subscription information for policy determination within a user data repository (UDR).

[0052] SMF (105) provides a session management function, and when a UE has multiple sessions, each session can be managed by a different SMF. Specifically, the SMF (105) supports functions such as session management (e.g., session establishment, modification, and termination, including tunnel maintenance between UPF (104) and (R)AN (102) nodes), UE IP (internet protocol) address allocation and management (optionally including authentication), selection and control of UPF, traffic steering setup to route traffic from UPF (104) to appropriate destinations, termination of interfaces to policy control functions, enforcement of policy and quality of service (QoS) control portions, lawful intercept (LI) (for SM events and interfaces to LI systems), termination of SM portions of NAS messages, downlink data notification, initiator of AN specific SM information (delivered to (R)AN (102) via N2 via AMF (103)), determination of SSC mode of sessions, roaming functions, etc. Some or all of the functions of SMF (105) may be supported within a single instance of an SMF.

[0053] UDM (109) stores user subscription data, policy data, etc. UDM (109) includes two parts: an application front end (FE) (not shown) and a user data repository (UDR) (not shown).

[0054] The FE includes the UDM FE, which is responsible for location management, subscription management, and credential processing, and the PCF, which is responsible for policy control. The UDR stores the data required for the functions provided by the UDM-FE and the policy profiles required by the PCF. The data stored in the UDR includes user subscription data and policy data, including subscription identifiers, security credentials, access and mobility-related subscription data, and session-related subscription data. The UDM-FE accesses the subscription information stored in the UDR and supports functions such as authentication credential processing, user identification handling, access authentication, registration / mobility management, subscription management, and SMS management.

[0055] UPF (104) transmits a downlink PDU received from DN (110) to UE (101) via (R)AN (102), and transmits an uplink PDU received from UE (101) via (R)AN (102) to DN (110). Specifically, the UPF (104) supports functions such as an anchor point for intra / inter RAT mobility, an external PDU session point for interconnection to the Data Network, a user plane part of packet routing and forwarding, packet inspection and policy rule enforcement, an uplink classifier to support lawful intercept, traffic usage reporting, routing of traffic flows to the Data Network, a branching point to support multi-homed PDU sessions, QoS handling for the user plane (e.g., packet filtering, gating, uplink / downlink rate enforcement), uplink traffic validation (service data flow (SDF) to QoS flow mapping), transport level packet marking in uplink and downlink, downlink packet buffering and downlink data notification triggering. Some or all of the functions of UPF (104) may be supported within a single instance of a UPF.

[0056] AF(107) interacts with the 3GPP core network to provide services (e.g., support for application impact on traffic routing, access to network capability exposure, and interaction with policy frameworks for policy control).

[0057] (R)AN(102) is a general term for a new radio access network that supports both evolved E-UTRA, an evolved version of 4G radio access technology, and new radio (NR) (e.g., gNB).

[0058] The gNB provides functions for radio resource management (i.e., radio bearer control, radio admission control, connection mobility control, dynamic allocation of resources to the UE in uplink / downlink (i.e., scheduling), IP (internet protocol) header compression, encryption and integrity protection of user data streams, selection of an AMF upon attachment of the UE if routing to the AMF is not determined from the information provided to the UE, routing of user plane data to UPF(s), routing of control plane information to the AMF, connection setup and teardown, scheduling and transmission of paging messages (originating from the AMF), scheduling and transmission of system broadcast information (originating from the AMF or operating and maintenance (O&M)), measurement and measurement reporting setup for mobility and scheduling, transport level packet marking in uplink, session management, support for network slicing, and QoS flows. It supports features such as mapping to management and data radio bearers, support for UEs in inactive mode, distribution of NAS messages, NAS node selection, radio access network sharing, dual connectivity, and tight interworking between NR and E-UTRA.

[0059] UE (101) refers to a user equipment. The user equipment may be referred to by terms such as terminal, mobile equipment (ME), or mobile station (MS). Furthermore, the user equipment may be a portable device such as a laptop, mobile phone, personal digital assistant (PDA), smartphone, or multimedia device, or may be a non-portable device such as a personal computer (PC) or vehicle-mounted device.

[0060] The NEF (113) provides a means to securely expose services and capabilities provided by 3GPP network functions, such as third parties, internal exposure / re-exposure, application functions, and edge computing. The NEF (113) receives information from other NF (s) (based on the exposed capability (s) of other NF (s)). The NEF (113) can store the received information as structured data using a standardized interface to a data storage network function. The stored information can be re-exposed to other NF (s) and AF (s) by the NEF (113) and used for other purposes, such as analysis.

[0061] NRF (115) supports service discovery. It receives NF discovery requests from NF instances and provides information about discovered NF instances to the NF instances. It also maintains available NF instances and the services they support.

[0062] Meanwhile, for convenience of explanation, FIG. 1 illustrates a reference model for a case where a UE (101) accesses one DN (110) using one PDU session, but the present disclosure is not limited thereto.

[0063] A UE (101) can access two (i.e., local and central) data networks simultaneously using multiple PDU sessions. In this case, two SMFs can be selected for different PDU sessions. However, each SMF can have the ability to control both the local UPF and the central UPF within the PDU session.

[0064] Additionally, the UE (101) may simultaneously access two (i.e., local and central) data networks provided within a single PDU session.

[0065] NSSF (114) can select a set of network slice instances serving UE (101). In addition, NSSF (114) can determine the allowed NSSAI (network slice selection assistance information) and, if necessary, perform mapping to subscribed single-network slice selection assistance information (S-NSSAI). In addition, NSSF (114) can determine the configured NSSAI and, if necessary, perform mapping to subscribed S-NSSAI. In addition, NSSF (114) can determine the set of AMFs used to serve UE or, depending on the configuration, can inquire NRF (115) to determine a list of candidate AMFs.

[0066] NRF (115) supports service discovery. It receives NF discovery requests from NF instances and provides information about discovered NF instances to the NF instances. It also maintains available NF instances and the services they support.

[0067] 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.

[0068] - N1: Reference point between UE and AMF

[0069] - N2: Reference point between (R)AN and AMF

[0070] - N3: Reference point between (R)AN and UPF

[0071] - N4: Reference point between SMF and UPF

[0072] - N5: Reference point between PCF and AF

[0073] - N6: Reference point between UPF and data network

[0074] - N7: Reference point between SMF and PCF

[0075] - N8: Reference point between UDM and AMF

[0076] - N9: Reference point between two core UPFs

[0077] - N10: Reference point between UDM and SMF

[0078] - N11: Reference point between AMF and SMF

[0079] - N12: Reference point between AMF and AUSF

[0080] - N13: Reference point between UDM and authentication server function (AUSF)

[0081] - N14: Reference point between two AMFs

[0082] - N15: Reference point between PCF and AMF for non-roaming scenarios, reference point between PCF and AMF in visited network for roaming scenarios.

[0083] - N26: Reference point between AMF and MME

[0084] In the following description, the term "terminal" may refer to UE (101), and the terms "UE" and "terminal" may be used interchangeably. In this case, unless specifically defined additionally, the term "terminal" should be understood as "UE (101).

[0085] Table 1 shows an example of a UE Route Selection Policy (URSP) rule.

[0086]

[0087] In 5GC (5G core), PCF can provide policy information to UE, and UE policy information can include URSP.

[0088] URSP is used by the UE to determine whether an application detected by the UE can be associated with an already established PDU Session, offloaded to a non-3GPP access outside the PDU Session, routed through a ProSe (proximity service) Layer-3 UE-to-Network Relay outside the PDU Session, or established and associated with a new PDU Session. A URSP can consist of one or more URSP rules, and a URSP rule can consist of a Traffic Descriptor (TD) and one or more Route Selection Components (RSC). Referring to [Table 1], a URSP rule can correspond to a TD and an RSC.

[0089] A Traffic Descriptor (TD) can contain matching criteria that can identify detected applications or application traffic. Specific examples include:

[0090] a) Application descriptor: Information that can designate a terminal application. For example, the application descriptor may include an APPID (application identifier), which is composed of an OSID (operating system identifier) ​​and an OSAPPID (operating system application identifier).

[0091] b) IP descriptor: Displays the IP address that indicates the destination address of the IP packet transmitted by the terminal. It can include an IP 3-tuple, i.e., the IP destination address, port number, and protocol.

[0092] c) Domain descriptor: The destination address of the server to which the terminal connects is expressed in FQDN (Fully Qualified Domain Name) format.

[0093] d) Non-IP descriptor: Information that can specify the recipient of non-IP data.

[0094] e) DNN (data network name): This is the data network name.

[0095] f) Connection Capability (CC): This corresponds to the type information that can specify the characteristics of the connected traffic, and can have values ​​such as IMS (IP Multimedia Subsystem), MMS (Multimedia Message Service), and Internet.

[0096] A Route Selection Component (RSC) may contain PDU Session attribute information to determine which PDU Session to associate an application or application traffic with when a traffic descriptor that can identify an application detected by the terminal is specified. Specific examples are as follows.

[0097] a) SSC (session and service continuity) mode selection (SSC Mode Selection): This is an element that specifies the continuity of sessions and services and can have values ​​such as SSC Mode 1, SSC Mode 2, and SSC Mode 3.

[0098] b) Network Slice Selection: Information that allows you to specify a network slice.

[0099] c) DNN Selection: This is the data network name.

[0100] d) PDU Session Type Selection: This is an element that can specify the type of PDU-Session, which can be IPv4, IPv6, or IPv4v6, or Ethernet, Non-IP.

[0101] e) Non-Seamless Offload indication: Indicates that the application's traffic can be offloaded via non-3GPP access that exists outside the PDU session.

[0102] f) ProSe Layer-3 UE-to-Network Relay Offload indication: Indicates that the application traffic can be offloaded through ProSe Layer-3 UE-to-Network Relay that exists outside the PDU session.

[0103] g) Access Type preference: This element indicates whether the PDU session is a PDU session connected via 3GPP access, a session connected via Non-3GPP access, or a session that supports Multi-Access connection using both 3GPP access and Non-3GPP access.

[0104] h) PDU Session Pair ID: This is an element that indicates an identifier that application traffic shares in a redundant PDU Session.

[0105] i) RSN (Redundancy Sequence Number): This is an element that indicates an identifier used in redundant transmission.

[0106] Multiple URSP rules (USRP rules) may be divided within a Policy Section (PS) of a UE Policy Container. In one embodiment of the present disclosure, multiple URSP rules may be divided and placed within multiple Policy Sections so as not to exceed the maximum allowable transmission size of the NAS layer. A single URSP rule may not be divided and placed across two PSs. A complete URSP rule may be included in a single Policy Section.

[0107] USRP rules can have priorities for each rule. In the example of Table 1, 'Route Selection Descriptor Precedence' can correspond to the priority of a URSP rule. According to one embodiment of the present disclosure, each URSP rule can include a URSP rule identifier that can identify the URSP rule. In the example of Table 1, 'Rule Precedence' can correspond to the URSP rule identifier. More specifically, the URSP rule identifier can refer to a traffic parameter that allows a terminal to distinguish a terminal application.

[0108] FIG. 2 is a diagram illustrating a network structure and interface of an EPS / 5GS interworking system according to one embodiment of the present disclosure.

[0109] 5GS may include a New Radio (NR) base station (NG-RAN (radio access node) or gNB (next generation node B)) (204) for wireless access of a terminal (UE) (201b), an access and mobility management function (AMF) (205), and, although not shown in FIG. 2, may also include a session management function (SMF), a user plane function (UPF), a policy control function (PCF), a network slice selection function (NSSF), a unified data management (UDM), a unified data repository (UDR), etc.

[0110] The EPS may include an E-UTRA base station (E-UTRAN (Evolved UMTS (Universal Mobile Telecommunications System) Terrestrial Radio Access Network) or eNB (evolved node B)) (202) for wireless access of a terminal (UE) (201a), a mobility management entity (MME) (203), a serving gateway (SGW) (206), a packet data network gateway (PGW) (the PGW may be composed of a PGW-U and a PGW-C), a policy and charging rule function (PCRF), a home subscriber server (HSS), etc.

[0111] According to one embodiment, the AMF (205) and the MME (203) may be Network Functions (NFs) that manage wireless network access and mobility for a terminal. The SMF, SGW, and PGW are NFs that manage sessions for the terminal, and the session information may include Quality of Service (QoS) information, charging information, and information about packet processing. In addition, the UPF and PGW are NFs that process user plane traffic (e.g., User Plane traffic) and are controlled by the SMF and SGW. The PCF and PCRF may be NFs that manage operator policies and / or PLMN policies for providing services in a wireless communication system. In addition, the PCF may be divided into a PCF that is responsible for Access and Mobility (AM) policies and UE policies, and a PCF that is responsible for Session Management (SM) policies. The PCF in charge of AM / UE policy and the PCF in charge of SM policy may be logically or physically separate NFs, or may be a single NF logically or physically. The UDM and HSS may be NFs that store and manage subscriber information (UE subscription) of terminals. The UDR may be an NF or database (DB) that stores and manages data. The UDR (212) may store subscription information of terminals and provide the subscription information of terminals to the UDM. In addition, the UDR (212) may store operator policy information and provide the operator policy information to the PCF. The NSSF may be an NF that performs the function of selecting network slice instances that serve terminals or determining NSSAI (Network Slice Selection Assistance Information).

[0112] The above instance may mean a state in which the NF exists in the form of software code, and physical and / or logical resources are allocated from a computing system (e.g., a specific computing system existing on a core network) to perform the function of the NF, thereby executing the function of the NF. For example, AMF Instance, SMF Instance, NSSF Instance, etc. may mean a state in which physical and / or logical resources can be allocated and used from a specific computing system existing on a core network for the operation of AMF, SMF, NSSF, etc. Accordingly, when a physical AMF, SMF, NSSF device exists and an AMF Instance, SMF Instance, NSSF Instance that is allocated and uses physical and / or logical resources from a specific computing system existing on a network for the operation of AMF, SMF, NSSF can perform the same operation.

[0113] The UDM of 5GS and the HSS of EPS can be configured as one combo node (referred to as UDM+HSS) (211). The UDM+HSS node (211) can store subscriber information of the terminal. The SMF of 5GS and the PGW-C of EPS can be configured as one combo node (referred to as SMF+PGW-C) (208). The PCF of 5GS and the Policy Control and Charging Rules Function (PCRF) of EPS can be configured as one combo node (referred to as PCF+PCRF). The UPF of 5GS and the PGW-U of EPS can be configured as one combo node (referred to as UPF+PGW-U) (207). The terminal can access the MME of the EPS through the E-UTRA base station to use the EPS network service. In addition, the terminal can access the AMF of 5GS through the NR base station to use the 5GS network service.

[0114] In Figure 2, the same reference numerals are used for terminals connected to EPS and terminals connected to 5GS. This is to indicate that the terminals can be connected to either EPS or 5GS.

[0115] In this way, one NF or network entity can support different network systems simultaneously, and such NF, network node, or network entity can be called a combo node, combo NF, combined node, integrated NF, interworking node, interworking NF, etc. as described above. In addition, the function of the NF exemplified by the combo node may be implemented through interworking between two or more network entities. In addition, for convenience of illustration and description, an NF that supports different network systems simultaneously may be indicated using the "+" symbol or the " / " symbol. For example, when SMF and PGW-C are configured as one combo node, it can be expressed as PGW-C / SMF, PGW-C+SMF, SMF / PGW-C, or SMF+PGW-C.

[0116] Terminals (201a, 201b) can establish a session by connecting to a data network (e.g., a network providing Internet services) through a 5GS or EPS system. At this time, the terminals can distinguish each data network using an identifier called a data network name (DNN) or an access point name (APN). To distinguish the data networks, the 5GS can use a DNN, and the EPS can use an APN. The DNN and the APN can be used to determine the NF, the interface between NFs, and the operator policy related to the user plane when the terminal connects to the network system and the session. The DNN and the APN can be understood as equivalent information and can transmit the same information. The DNN can be used, for example, to select an SMF and UPF(s) for a PDU session, and can be used to select an interface (e.g., an N6 interface)(s) between the data network and the UPF for the PDU session. Additionally, the above DNN can be used to determine a mobile carrier's policy to apply to a PDU session.

[0117] In the following embodiments, combo nodes such as UDM+HSS node, PCF+PCRF node, SMF+PGW-C node, UPF+PGW-C node, etc. are described by omitting the name of "node" for convenience of explanation. In addition, in the following embodiments, the definition of a message defined in one embodiment can be applied with the same meaning in other embodiments that utilize the same message.

[0118] The PCF can be divided into a session management-policy control function (SM-PCF) (210) responsible for session management policy (SM Policy) and a terminal-policy control function (UE-PCF) (209) responsible for mobility management policy (AM Policy) and / or terminal policy (UE Policy). The SM-PCF (210) can be connected to the SMF (208) via the N7 interface, but cannot be connected to the AMF (205). In other words, the SM-PCF (210) cannot support the N15 interface. The UE-PCF (209) can be connected to the AMF (205) via the N15 interface, but cannot be connected to the SMF (208). In other words, the UE-PCF (209) cannot support the N7 interface. The SM-PCF and the UE-PCF can be physically and / or logically located in one device or one PCF, but can be distinguished as different PCF instances.

[0119] The UE Policy provided by the PCF to the UE may include Access Network Discovery & Selection Policy (ANDSP), URSP, V2X Policy (V2XP), and / or ProSe Policy (ProSeP).

[0120] ANDSP: Contains policy information required when a terminal selects a non-3GPP access network.

[0121] URSP: Contains policy information required to route traffic going out of the terminal.

[0122] V2XP: Contains policy information that provides the configuration parameters required for a terminal to perform V2X communication.

[0123] ProSeP: Contains policy information that provides the configuration parameters required for the terminal to perform ProSe Direct Discovery, ProSe Direct Communication, ProSe UE-to-Network Relay, and Remote UE communication.

[0124] FIG. 3 illustrates an example of a method for determining establishment of a packet data network (PDN) connection by evaluating a URSP Rule in an EPS in consideration of the connection relationship between an APN, a DNN, and an S-NSSAI in a communication system supporting 5GS-EPS interworking according to one embodiment of the present disclosure.

[0125] The data network through which the terminal communicates via the core network can be identified using DNN in 5GS and APN in EPS.

[0126] Each APN or DNN may have a set of S-NSSAIs that it can support, and each NF or Network Entity in the core network may have a set of APNs or DNNs that it can support, and a set of S-NSSAIs that it can support.

[0127] For example, referring to FIG. 3, a core network can be sliced ​​into S-NSSAI#1, S-NSSAI#2, and S-NSSAI#3, and can be divided into SMF+PGW-C#1 supporting S-NSSAI#1 and S-NSSAI#3, and SMF+PGW-C#2 supporting S-NSSAI#2. All three slices can be supported by any APN / DNN. In addition, the MME and the AMF can be connected to two SMF+PGW-Cs (i.e., SMF+PGW-C#1 and SMF+PGW-C#2), respectively.

[0128] Based on the URSP Rule, a UE can utilize a PDU Session corresponding to a combination of S-NSSAI#1 and DNN for application traffic transmission in 5GS. If a UE wishes to continue using this PDU Session while migrating from 5GS to EPS, it must be connected to an entity that supports S-NSSAI#1 even when connected to the network via the MME.

[0129] The MME can select an SMF+PGW-C that supports the APN for which the UE has requested a PDN Connection based on the target APN. In a situation like Figure 3, the MME can select SMF+PGW-C#1 or SMF+PGW-C#2.

[0130] If SMF+PGW-C#1 is selected, and if the terminal and the network (e.g., SMF+PGW-C#1 itself) support 5GS-EPS interworking, SMF+PGW-C#1 can select one S-NSSAI among the S-NSSAIs supported by the target APN of the PDN Connection requested by the terminal, which is included in the Subscribed S-NSSAIs in the terminal's subscriber information and is not subject to Network Slice Specific Authorization Authentication, and designate it to the terminal. The terminal stores the designated S-NSSAI, and can request a PDN Session using this S-NSSAI value when the terminal moves to 5GS.

[0131] If SMF+PGW-C#1 has S-NSSAI#1 and S-NSSAI#3 as slices that satisfy the conditions that it can designate to the terminal's PDN Connection, SMF+PGW-C#1 can designate any one of S-NSSAI#1 and S-NSSAI#3. However, if it designates any one of them in this way, the following problems may occur.

[0132] For example, if the target slice is S-NSSAI#1 according to the URSP Rule for the application that the UE is trying to send and receive traffic through this PDN Connection, but SMF+PGW-C#1 can arbitrarily designate S-NSSAI#3, then when the UE moves to 5GS, the UE may have a problem in determining which value to request the PDU Session with: S-NSSAI#3, which was most recently provided by the network, or S-NSSAI#1, which was previously provided by the URSP Rule.

[0133] If the UE requests a PDU Session with S-NSSAI#3, the network may need to reconfigure the UE Contexts required to connect to the remaining NFs corresponding to S-NSSAI#3. For example, the N4 Session-related information of UPF+PGW-U#1 and SMF+PGW-C#1 may need to be moved to UPF+PGW-U#2. Even if the UE does not directly select S-NSSAI, a similar action may be required when the network hands over this PDN Connection to a PDU Session as the UE moves to 5GS. If the network is configured to unconditionally support only S-NSSAI#1 for the application, the network will reject the UE's PDU Session request without performing this reconfiguration, and the UE may consider re-requesting a PDU session using S-NSSAI#1 by evaluating the URSP Rule again.

[0134] In this situation, if SMF+PGW-C#1 had designated S-NSSAI#1, when the UE returns to 5GS, it would have been designated with the same slice as the URSP Rule, so there would be no judgment problem in the terminal, and the 5G core network would not have to perform additional operations due to the slice change, so the signaling load can be reduced.

[0135] As above, several methods can be provided to enable SMF+PGW-C to specify an appropriate S-NSSAI for the PDN Connection.

[0136] For example, before a terminal requests a PDN Connection from EPS, it can determine whether to establish a PDN Connection by evaluating the URSP Rule, just like when requesting a PDU Session. More specifically, when determining the need to establish a new PDN Connection, the terminal does not only report / consider the target APN of the application that wants to send and receive traffic to determine whether a PDN Connection directed to the APN exists among the existing PDN Connections, but also reports / considers both the APN and the S-NSSAI indicated in the URSP Rule mapped to the relevant application to determine whether a PDN Connection directed to the APN and designated by the S-NSSAI exists among the existing PDN Connections. This may correspond to the terminal operating by considering the URSP Rule, which is a 5GS communication parameter, and further, the S-NSSAI, even though the terminal communicates via EPS. The terminal can request establishment of a new PDN Connection in order to transmit and receive application traffic corresponding to an APN and S-NSSAI that are not supported by the existing PDN Connection, and at this time, by providing the corresponding S-NSSAI to the SMF+PGW-C, if the SMF+PGW-C has multiple S-NSSAIs that it can designate and the S-NSSAI requested by the terminal is included in them, the SMF+PGW-C can designate the S-NSSAI requested by the terminal rather than arbitrarily determining it. This will be described in more detail based on the description of FIG. 4.

[0137] As another example, if SMF+PGW-C has multiple S-NSSAIs that it can designate, SMF+PGW-C can check whether there is a PDU Session that was using the S-NSSAI through UDM, and if there is a PDU Session that was using the S-NSSAI, it can check SMF data information about what the PDU Session ID was. If there is an S-NSSAI that uses the same PDU Session ID as the PDU Session ID provided by the terminal when requesting a PDN Connection, or if there is an S-NSSAI that uses the same PDU Session ID as the PDU Session ID to which the EPS Bearer that SMF+PGW-C is trying to connect is mapped, SMF+PGW-C can designate the S-NSSAI. This will be described in more detail based on the descriptions of FIGS. 5 and 8.

[0138] Figure 3 is a network structure that can also be considered in the procedures described in Figures 10 and 11. Therefore, the procedures of Figures 10 and 11 described below can be applied to the network structure of Figure 3 (i.e., when the SMF+PGW-C assigned to the same APN / DNN are different in EPS and 5GS, respectively).

[0139] FIG. 4 illustrates an example of a method for selecting an appropriate S-NSSAI when using a PDN connection through a 4G system (EPS) when a terminal is connected to a 5G core and then moves to a 4G core and / or when the terminal is connected to a 4G core, in a communication system supporting 5GS-EPS interworking according to one embodiment of the present disclosure.

[0140] Figure 4 is based on a structure with or without N26 connection between MME and AMF.

[0141] Referring to FIG. 4, at step 400, the UE may be registered with a 5G core network.

[0142] In step 401, the UE may decide to initiate at least one of a tracking area update (TAU) procedure, an E-UTRAN Initial Attach procedure, and a PDN Connectivity Request procedure when moving from 5GS to EPS and / or when connecting to EPS first.

[0143] If the UE initiates the TAU procedure, the UE may send a TAU Request message to the MME in step 402a. In step 402b, the MME may steer the UE to use the PDN Connection through the Initial Attach and / or PDN Connectivity Request procedures by sending a TAU Reject to the UE. Steps 402a and 402b may not be performed in some cases.

[0144] In step 403, the UE may send an Attach Request and / or PDN Connectivity Request message to the MME. This message may include at least one of an APN, a PDU Session ID, and an S-NSSAI corresponding to the target for which the UE wishes to establish a PDN Connection. The PDU Session ID and S-NSSAI may be provided by including them in a protocol configuration option (PCO). Before requesting a PDN Connection in EPS, the UE may determine whether to establish a PDN Connection by evaluating the URSP Rule, similar to when requesting a PDU Session in 5G. For example, the UE may look at both the APN and the S-NSSAI indicated in the URSP Rule mapped to the application for which it wishes to transmit and receive traffic, and determine whether a PDN Connection with the S-NSSAI designated while heading to the APN exists among the existing PDN Connections. If there is no PDN Connection corresponding to the combination of the APN and S-NSSAI, the UE may request a PDN Connection for the application.

[0145] When a UE is connected to an EPS, it looks at both the APN and the S-NSSAI to decide whether to use its existing PDN Connection or establish a new PDN Connection. This is a possible operation in a system where the APN / DNN and S-NSSAI are designated as URSP rule components that can be applied in EPS as well. How each component of the URSP rule in 5GS can be applied in EPS can be specified as in [Table 2] and [Table 3] below. [Table 2] and [Table 3] are examples and are not limiting.

[0146] Table 2 shows a mapping table for traffic descriptor parameters. Referring to [Table 2], it can be seen that in 5GS, a DNN can be designated to correspond to an APN in EPS. Table 3 shows a mapping table for route selection descriptor parameters. Referring to [Table 3], it can be seen that in 5GS, one or more DNN selections can be designated to correspond to one or more APN selections in EPS. In addition, it can be seen that in 5GS, one or more S-NSSAI selections (Network Slice Selections) can be designated not to be applied in EPS. Therefore, when the UE, as explained in step 403, is connected to the EPS, the operation of looking at both the APN and the S-NSSAI to decide whether to use the PDN Connection it already has or establish a new PDN Connection may mean that one or more S-NSSAI selections (Network Slice Selections) in 5GS are designated in [Table 3] to be applied as one or more S-NSSAI selections in the EPS.

[0147]

[0148]

[0149]

[0150]

[0151]

[0152]

[0153] In step 404, the MME may select an SGW and / or PGW (e.g., PGW-C) based on the APN included in the received request message.

[0154] In step 405, the MME may send a Create Session Request message to the SMF+PGW-C via the SGW. The Create Session Request message may include information received from the UE, such as an APN and / or a PCO, and the PCO may include a PDU Session ID and / or S-NSSAI.

[0155] At step 406, SMF+PGW-C can obtain information of Subscribed S-NSSAI(s) from subscriber information of UE through HSS+UDM.

[0156] In step 407, based on the information received in step 405 and / or the information received in step 406, the SMF+PGW-C can determine, among the S-NSSAIs supported by the APN requested by the UE, which belong to the Subscribed S-NSSAIs and are not subject to Network Slice Specific Authorization and Authentication (NSSAA). If the S-NSSAI requested by the UE is included among these S-NSSAIs, the SMF+PGW-C can preferentially select the S-NSSAI requested by the UE.

[0157] In step 408, SMF+PGW-C may send a Create Session Response message to the MME via SGW. The Create Session Response message may include a PCO, and SMF+PGW-C may include the S-NSSAI selected in step 407 in the PCO and forward it to the MME via SGW.

[0158] In step 409, the MME may forward the PCO received in step 408 to the eNodeB. At this time, the PCO may be forwarded via a downlink NAS transport / PDU connectivity accept message containing an initial context setup request or a bearer setup request / attach accept.

[0159] At step 410, the eNodeB may forward the PCO received at step 409 to the UE. At this time, the PCO may be forwarded to the UE via an RRC reconfiguration message or a separate RRC message.

[0160] The UE can check whether the S-NSSAI received through the PCO is the same as the S-NSSAI provided by the UE in step 403. If the UE provided the S-NSSAI to the network by including it in the PCO in step 403, and a different S-NSSAI is received, the UE may recognize that additional judgment may be required to select which slice to use between the S-NSSAI indicated by the URSP Rule and the S-NSSAI received in step 410 when requesting a PDU session through 5GS for this application. For example, if the S-NSSAI received through the PCO is the same as the S-NSSAI provided by the UE in step 403, the UE may perform the PDN Connectivity procedure or the Bearer Modification procedure based on the received S-NSSAI.

[0161] For example, if the S-NSSAI received through PCO is different from the S-NSSAI provided by the UE in step 403, the UE may select the S-NSSAI received through PCO rather than the S-NSSAI provided by the UE in step 403, and perform the PDN Connectivity procedure or the Bearer Modification procedure based on the selected S-NSSAI.

[0162] When the UE requests a PDU session for this application via 5GS after step 410, the UE may request a PDU session by selecting one S-NSSAI from among (1) S-NSSAI included in the URSP rule received when the UE was connected to 5GS, (2) S-NSSAI received separately other than the URSP rule when the UE was connected to 5GS, (3) S-NSSAI included in the URSP rule received when the UE was connected to EPS, and (4) S-NSSAI received separately via PCO other than the URSP rule when the UE was connected to EPS. (The UE may have some or all of the information (1) to (4). For example, if the UE has not yet connected to 5GS, the information (1) and (2) may not be available. As another example, if the UE does not support the function of receiving terminal policy from EPS, the information (3) may not be available.) In this case, a method for selecting one may include a method for the UE to select the S-NSSAI most recently received. The S-NSSAI provided by the UE in step 403 may be an example of (1) or (3). The S-NSSAI information received by the UE via PCO in step 410 may be an example of (4).

[0163] For example, if the S-NSSAI provided by the UE in step 403 is not the same as the S-NSSAI information received via PCO in step 410, the UE may recognize that the EPS network operates differently from the URSP rule that the UE currently has. In this state, if the UE moves to 5GS and requests a PDU session for this application through 5GS, the UE may not select the S-NSSAI information received in step 410 even if it is the most up-to-date information, but may evaluate the URSP rule received from 5GS or EPS to select the S-NSSAI. (In other words, even if the UE has information of (1), (3), and (4) and the information of (4) is the most up-to-date information, if the information of (4) does not match that of (1) or (3), the UE may select information of (1) or (3).)

[0164] For example, if the S-NSSAI provided by the UE in step 403 is the same as the S-NSSAI information received via PCO in step 410, the UE can recognize that the EPS network is operating in accordance with the URSP rule that the UE currently has. In this state, when the UE moves to 5GS and requests a PDU session for this application via 5GS, the UE can select the S-NSSAI by considering the latest information of the S-NSSAI provided by the UE in step 403 and the S-NSSAI information received via PCO in step 410 to be the same.

[0165] The above is explained in more detail in the description of Fig. 9.

[0166] In the above, the situation where the UE selects an S-NSSAI based on the information about the S-NSSAI for an application it has (e.g., (1) to (4)) is explained based on the case where the UE moves to 5GS and requests a PDU session. In addition, if the network provides a new URSP rule while the UE is in EPS or 5GS and the UE needs to evaluate the URSP rule again, or if the UE needs to evaluate the URSP rule for reasons such as terminal configuration, user request, network request, etc., the UE may also need to select an S-NSSAI based on the information about the S-NSSAI for an application it has.

[0167] The above can also be applied to procedures described in other drawings.

[0168] At step 411, the Attach or PDN Connectivity procedure may be completed and any necessary Bearer Modification procedure may be performed.

[0169] FIG. 5 illustrates an example of a method for selecting an appropriate S-NSSAI when using a PDN connection through a 4G system (EPS) when a terminal is connected to a 5G core and then moves to a 4G core and / or when the terminal is connected to a 4G core, in a communication system supporting 5GS-EPS interworking according to one embodiment of the present disclosure.

[0170] Figure 5 corresponds to the case where the UE does not provide S-NSSAI to the network in step 403 of Figure 4.

[0171] Referring to FIG. 5, at step 500, the UE may be registered with a 5G core network.

[0172] In step 501, the UE may decide to initiate at least one of the TAU procedure, the E-UTRAN Initial Attach procedure, and the PDN Connectivity Request procedure when moving from 5GS to EPS and / or when connecting to EPS first.

[0173] If the UE initiates the TAU procedure, the UE may send a TAU Request message to the MME in step 502a. In step 502b, the MME may steer the UE to use the PDN Connection through the Initial Attach and / or PDN Connectivity Request procedures by sending a TAU Reject to the UE. Steps 502a and 502b may not be performed in some cases.

[0174] In step 503, the UE may send an Attach Request and / or PDN Connectivity Request message to the MME. This message may include at least one of an APN and a PDU Session ID corresponding to the target for which the UE wishes to establish a PDN Connection. The PDU Session ID may be included in the PCO and provided. Before requesting a PDN Connection in the EPS, the UE may determine whether to establish a PDN Connection by evaluating the URSP Rule, similar to when requesting a PDU Session in 5G. For example, based on both the APN and the S-NSSAI indicated in the URSP Rule mapped to the application to be transmitted and received, it may be determined whether a PDN Connection with the S-NSSAI designated and directed to the APN exists among the existing PDN Connections. If there is no PDN Connection corresponding to the combination of the APN and the S-NSSAI, the UE may request a PDN Connection for the application.

[0175] In step 504, the MME may select an SGW and / or PGW (e.g., PGW-C) based on the APN included in the received request message.

[0176] In step 505, the MME may send a Create Session Request message to the SMF+PGW-C via the SGW. The Create Session Request message may include information received from the UE, such as an APN and / or a PCO, and the PCO may include a PDU Session ID.

[0177] At step 506, SMF+PGW-C can obtain information of Subscribed S-NSSAI(s) from subscriber information of UE through HSS+UDM.

[0178] In step 507, the SMF+PGW-C can obtain UE Context information registered as SMF data in the subscriber information of the UE through the HSS+UDM. For example, in requesting this information, the SMF+PGW-C can provide at least one of a subscriber identifier (e.g., SUPI) and a slice ID (e.g., S-NSSAI) to the HSS+UDM. At this time, the slice ID can be the S-NSSAI of a slice supported by the SMF+PGW-C, a slice supported by an APN requested by the UE, and / or a slice included in the Subscribed S-NSSAI received in step 506. The HSS+UDM can provide the SMF+PGW-C with a PDU Session ID corresponding to the SUPI and the S-NSSAI. As another example, the SMF+PGW-C can provide at least one of the SUPI and the PDU Session to the HSS+UDM, and the HSS+UDM can provide the S-NSSAI corresponding thereto. The operation for this step is described in more detail in FIGS. 6a and 6b. If SMF+PGW-C has received UE Context and / or SM Context from AMF before step 507, or if SMF+PGW-C has not deleted and maintained UE Context and / or SM Context, and if SMF+PGW-C can determine S-NSSAI corresponding to SUPI and PDU Session ID based on at least one of these pieces of information (i.e., if it can determine what S-NSSAI is selected for the corresponding PDU Session), step 507 may be omitted. In this case, SMF+PGW-C can use S-NSSAI information determined based on at least one of UE Context and / or SM Context in step 508.

[0179] In step 508, SMF+PGW-C can determine, based on the information received in step 505, the information received in step 506, and the information received in step 507 (or the context information that SMF+PGW-C could use without going through HSS+UDM in step 507), among the S-NSSAIs supported by the APN requested by the UE, the S-NSSAI(s) that belong to the Subscribed S-NSSAIs and are not subject to Network Slice Specific Authorization and Authentication, and if among these S-NSSAI(s), there is an S-NSSAI corresponding to the PDU Session ID requested by the UE, this S-NSSAI can be preferentially selected.

[0180] In step 509, SMF+PGW-C may send a Create Session Response message to the MME via SGW. The Create Session Response message may include a PCO, and SMF+PGW-C may include the S-NSSAI selected in step 508 in the PCO and forward it to the MME via SGW.

[0181] In step 510, the MME may forward the PCO received in step 509 to the eNodeB. At this time, the PCO may be forwarded via a downlink NAS transport / PDU connectivity accept message containing a TAU accept / initial context setup request or a bearer setup request / attach accept.

[0182] In step 511, the eNodeB may forward the PCO received in step 510 to the UE. At this time, the PCO may be forwarded to the UE via an RRC reconfiguration message, a separate RRC message, or a TAU accept message. The PCO may include the S-NSSAI selected for PDN connection.

[0183] In step 512, the terminal may perform an Attach or PDN Connectivity procedure or a Bearer Modification procedure based on the received S-NSSAI. The Attach or PDN Connectivity procedure may be completed, and the required Bearer Modification procedure may be performed.

[0184] FIG. 6a and FIG. 6b illustrate an example of a procedure in which an SMF+PGW-C obtains UE Context information registered as SMF data in subscriber information of a UE through an HSS+UDM according to an embodiment of the present disclosure.

[0185] FIG. 6a and FIG. 6b are specific signaling of steps 506 to 507 of FIG. 5, which can be performed in combination with the operation of FIG. 5.

[0186] Referring to FIG. 6a, at step 600, SMF+PGW-C may receive a Create Session Request message. Step 600 may correspond to step 505 of FIG. 5.

[0187] In step 601, SMF+PGW-C may send a Nudm_SDM_Get Request message containing SUPI to HSS+UDM, and in response, may receive a Nudm_SDM_Get Response message containing information of Subscribed S-NSSAI(s) in step 602.

[0188] In step 603, SMF+PGW-C can determine, among the S-NSSAIs supported by the APN requested by the UE, which S-NSSAI(s) belong to the Subscribed S-NSSAIs and are not subject to Network Slice Specific Authorization and Authentication, and if there is one or more such S-NSSAIs, step 604a can be performed.

[0189] In step 604a, the SMF+PGW-C may request UE Context information as SMF data registered in the HSS+UDM for one or more S-NSSAIs derived in step 603. For example, the SMF+PGW-C may provide SUPI and / or S-NSSAI to the HSS+UDM using the Nudm_SDM_Get Request message. This message may be sent for the target S-NSSAI that the SMF+PGW-C wishes to confirm from the HSS+UDM.

[0190] In step 605a, the HSS+UDM may provide the SMF+PGW-C with UE Context information as SMF data that can obtain SUPI and S-NSSAI as Data Key and Sub Data Key among the information stored as subscriber data. For example, the HSS+UDM may provide the SMF+PGW-C with the PDU Session ID corresponding to SUPI and S-NSSAI using the Nudm_SDM_Get Response message. This may mean that before step 604a, a PDU Session corresponding to the PDU Session ID was established for the UE, and this PDU Session corresponds to the combination of the APN / DNN and S-NSSAI.

[0191] In step 606a, SMF+PGW-C may preferentially select the S-NSSAI corresponding to the PDU Session ID requested by the UE among the PDU Session ID(s) received in step 605a, if the PDU Session ID is included.

[0192] Meanwhile, referring to FIG. 6b, at step 600, SMF+PGW-C may receive a Create Session Request message. Step 600 may correspond to step 505 of FIG. 5.

[0193] In step 601, SMF+PGW-C may send a Nudm_SDM_Get Request message containing SUPI to HSS+UDM, and in response, may receive a Nudm_SDM_Get Response message containing information of Subscribed S-NSSAI(s) in step 602.

[0194] In step 603, SMF+PGW-C can determine, among the S-NSSAIs supported by the APN requested by the UE, which S-NSSAI(s) belong to the Subscribed S-NSSAIs and are not subject to Network Slice Specific Authorization and Authentication, and if there is one or more such S-NSSAIs, step 604b can be performed.

[0195] In step 604b, SMF+PGW-C may request UE Context information as SMF data registered in HSS+UDM using PDU Session ID. For example, SMF+PGW-C may provide SUPI and / or PDU Session ID to HSS+UDM using Nudm_SDM_Get Request message.

[0196] In step 605b, the HSS+UDM may provide the SMF+PGW-C with UE Context information as SMF data, which can be obtained by using the Data Key and Sub Data Key for SUPI and PDU Session ID among the information stored as subscriber data. For example, the HSS+UDM may provide the S-NSSAI corresponding to the SUPI and PDU Session ID to the SMF+PGW-C using the Nudm_SDM_Get Response message. This may mean that before step 604b, a PDU Session corresponding to the PDU Session ID was established for the UE, and this PDU Session corresponds to the combination of the APN / DNN and the S-NSSAI.

[0197] In step 606b, SMF+PGW-C may preferentially select the S-NSSAI requested by the UE among the S-NSSAI(s) received in step 605b, if the S-NSSAI requested by the UE is included. If the UE does not request the S-NSSAI but requests the PDU Session ID, the S-NSSAI corresponding to the PDU Session ID may be preferentially selected.

[0198] FIG. 7 illustrates a method for causing an MME to reselect SMF+PGW-C when an S-NSSAI requested by a UE and / or an S-NSSAI corresponding to a PDU Session ID requested by the UE is an S-NSSAI that cannot be supported by SMF+PGW-C according to one embodiment of the present disclosure.

[0199] FIG. 7 can be performed in combination with the procedure of FIG. 4 or FIG. 5 described above.

[0200] Referring to FIG. 7, in step 701, the MME may send a Create Session Request message to SMF+PGW-C#1 via SGW#1. Step 701 may correspond to step 405 of FIG. 4 or step 505 of FIG. 5.

[0201] In step 702, SMF+PGW-C#1 can check whether the S-NSSAI requested by the UE and / or the S-NSSAI corresponding to the PDU Session ID requested by the UE are S-NSSAIs that can be supported by SMF+PGW-C#1.

[0202] In step 703, if the S-NSSAI requested by the UE and / or the S-NSSAI corresponding to the PDU Session ID requested by the UE is an S-NSSAI that the SMF+PGW-C#1 cannot support, the SMF+PGW-C#1 may provide the MME with at least one of a failure result (failure) or a failure reason (cause) as a response to the session creation request through the SGW#1.

[0203] For example, the reason for failure may be provided as a cause code, or in the form of an indication or information expressing the reason. The reason may include at least one of the following: the fact that SMF+PGW-C#1 cannot support the S-NSSAI requested in step 701, or the fact that the PGW-C needs to be reselected. Additionally, if the SMF+PGW-C#1 knows it, it may provide the MME with the address or ID of the target SMF+PGW-C to be reselected. The SMF+PGW-C#1 may know the target SMF+PGW-C to be reselected based on information obtained through NRF or UDM, or network configuration information.

[0204] In step 704, the MME may reselect an SGW and / or PGW-C based on the information received in step 703.

[0205] In step 705a or 705b, the MME may resend a session creation request message to SMF+PGW-C#2 via SGW#1 or SGW#2.

[0206] At step 706, SMF+PGW-C#2 can select one S-NSSAI for PDN Connection.

[0207] In step 707a or 707b, SMF+PGW-C#2 may send a session creation response message to the MME via SGW#1 or SGW#2. The session creation response message may include a PCO containing the S-NSSAI selected for PDN connection. That is, SMF+PGW-C#2 may provide the MME with the selected S-NSSAI using the PCO. This PCO may be delivered from the MME to the UE via E-UTRAN.

[0208] FIGS. 8A and 8B illustrate examples of a method for selecting an appropriate S-NSSAI when using a PDN connection through a 4G system (EPS) when a terminal is connected to a 5G core and then moves to a 4G core and / or when the terminal is connected to a 4G core in a communication system supporting 5GS-EPS interworking according to one embodiment of the present disclosure.

[0209] Figure 8 is based on a structure with or without N26 connection between MME and AMF.

[0210] Referring to FIG. 8, at step 800, the UE may have set up a PDU Session and QoS flow in 5GS.

[0211] At step 801a, the UE may decide to initiate a TAU procedure when moving from 5GS to EPS.

[0212] If the UE initiates the TAU procedure, the UE may send a TAU Request message to the MME in step 802a.

[0213] In step 803a, the MME may request a context from the AMF according to the TAU request.

[0214] Instead of steps 801a to 803a, the handover procedure for moving the UE from 5GS to EPS may be initiated by the NG-RAN at step 804a. In this case, the NG-RAN may send a handover request to the AMF.

[0215] In step 805, the AMF may request context information that can be mapped to a PDN Connection for the PDU Session to be moved to the EPS from the SMF+PGW-C. For example, the Nsmf_PDUSession_Context Request message may be used to request SM context information of the PDN Connection Context type. If requesting other types of information, the request may be indicated as requesting all types of information.

[0216] In step 806, SMF+PGW-C may provide AMF with context information that can be mapped to PDN Connection for the PDU Session to be moved to EPS. For example, SMF+PGW-C may provide PDN Connection Context using Nsmf_PDUSessionContext Response message, which may include EPS Bearer context information mapped to QoS flow and EPS Bearer ID assigned to it.

[0217] The AMF may convey information corresponding to the PDN Connection Context to the MME using (i) a Context Response in step 803b if there was a request from the TAU in step 802a, or (ii) a Relocation Request in step 804b if there was a Handover request in step 804a.

[0218] At step 807, the TAU or Handover procedure may continue.

[0219] In step 808, the MME may request the SGW to establish a session or modify a bearer. This request may include bearer context information corresponding to the target to be transferred from 5GS to EPS, and may include the assigned EBI (EPS bearer ID)(s).

[0220] In step 809, the SGW may request a bearer modification to the SMF+PGW-C. This request may include the content requested by the MME received in step 808 (e.g., bearer context information including the allocated EBI).

[0221] In step 810, SMF+PGW-C may determine the PDU Session ID of the PDU Session mapped to the EBI based on the information received in step 809. The PDU Session ID may or may not be included in the message of steps 808 to 809.

[0222] Steps 811 to 813 may correspond to steps 506 to 508 of FIG. 5. Accordingly, the description of FIG. 5 may be referred to.

[0223] At step 814, SMF+PGW-C may send a bearer modification response message to SGW, and at step 815, SGW may send a session establishment or bearer modification response message to MME based on the received bearer modification response message.

[0224] If there is a TAU request, the MME may send a TAU Accept to the UE via the eNodeB at step 816.

[0225] At step 817, the TAU or Handover procedure may be completed.

[0226] In step 818, SMF+PGW-C may initiate a PDN GW initiated bearer modification procedure to provide the S-NSSAI to the UE if an S-NSSAI for the PDN Connection was selected in step 13. This procedure may not perform a bearer QoS update. SMF+PGW-C may send a message to the MME via the SGW to provide the selected S-NSSAI to the UE using a PCO. For example, SMF+PGW-C may use an Update Bearer Request message to deliver a PCO containing the S-NSSAI selected for the PDN Connection to the MME via the SGW.

[0227] At step 819, the MME may send a message to the UE via the eNodeB to forward the PCO to the UE. For example, the MME may use the NAS Transport message to forward the PCO containing the S-NSSAI selected for the PDN Connection to the UE via the eNodeB.

[0228] FIG. 9 is a diagram for explaining a method for determining establishment of a PDN connection by evaluating a URSP Rule in EPS in consideration of the connection relationship between an APN, a DNN, an S-NSSAI, and an Application in a communication system supporting 5GS-EPS interworking according to one embodiment of the present disclosure.

[0229] In the description of Fig. 9, parts that overlap with the description of Figs. 3 to 8 may be omitted.

[0230] An APN or DNN may have a set of S-NSSAIs that it can support. Additionally, an application may be configured to connect to an APN (or DNN), or a combination of a DNN (or APN) and an S-NSSAI.

[0231] The combination of APN / DNN and S-NSSAI and the relationship with the application are described in the URSP Rule, and the terminal can establish a PDU Session / PDN Connection and perform routing of application traffic according to the URSP Rule.

[0232] Referring to (A) of FIG. 9, application #1 (APP#1) may be designated to be connected to a combination of APN / DNN and S-NSSAI#1, and application #2 (APP#2) may be connected to a combination of APN / DNN and S-NSSAI#2, and the APN / DNN to which application #1 and application #2 are connected may have the same value. However, this is only an example, and the APN / DNN to which application #1 and application #2 are connected may have different values.

[0233] Fig. 9(B) illustrates an example of a communication system that supports 5GS-EPS interworking that can be connected to an APN or a DNN. Referring to Fig. 9(B), a single SMF+PGW-C supporting the connection of an APN / DNN may be designated. That is, for the same APN / DNN, the SMF+PGW-C may be the same in EPS and 5GS. Accordingly, this SMF+PGW-C may provide connection to the same APN / DNN through one or more S-NSSAIs.

[0234] In order for the MME to provide a PDN Connection to the UE, when selecting an SMF+PGW-C, the MME can check the APN value for the PDN Connection and select the SMF+PGW-C specified in this APN.

[0235] SMF+PGW-C can transmit data traffic to APN / DNN through one or more UPF+PGW-U.

[0236] Figure 9 (B) is a network structure that can also be considered in the procedures described in Figures 4 to 8. Therefore, the procedures of Figures 4 to 8 can also be applied to a network structure such as Figure 9 (B).

[0237] Referring to (C) of FIG. 9, in step 1, the UE may be using a PDN Connection for App#1 in EPS. If the UE and the network support 5GS-EPS interworking, a PDU Session ID may be assigned to this PDN Connection. Additionally, an S-NSSAI may be determined for this PDN Connection. For example, the UE may be using a PDN Connection for App#1 in EPS, and this PDN Connection may be assigned PDU Session ID#1. This PDN Connection may be a PDU Session established in 5GS that has been moved to EPS, or may be a PDN Connection established in EPS. SMF+PGW-C may have designated S-NSSAI#1 for this PDN Connection.

[0238] While the UE is using the PDN Connection for App#1 in the EPS, traffic for App#2 may occur. In step 2, the UE can check whether there is a PDN Connection that provides a connection to the same APN as the APN value specified for App#2. The UE can confirm that the PDN Connection established in step 1 provides a connection to the same APN value as the APN value specified for App#2, and can decide to transmit the traffic for App#2 through this PDN Connection as well. In this way, the method by which the UE determines whether to establish a new PDN Connection or use the existing PDN Connection based on the APN / DNN specified for the newly generated application among the PDN Connections it already has can be distinguished from the determination made by looking at both the APN / DNN and the S-NSSAI in step 403 of FIG. 4. In other words, this can mean that one or more S-NSSAI selections (Network Slice Selections) in 5GS in [Table 3] are designated as not applicable to the EPS.

[0239] While the UE is transmitting traffic of App#1 and App#2 through the PDN Connection assigned PDU Session ID#1, it can move from EPS to 5GS. At this time, the UE can evaluate the URSP Rule and find that App#2 is assigned to the combination of APN / DNN and S-NSSAI#2, not the combination of APN / DNN and S-NSSAI#1 used in steps 1 and 2. In step 3, the UE can confirm that there is no existing PDN Session assigned to the combination of APN / DNN and S-NSSAI#2, and can perform the PDU Session Establishment procedure by assigning PDU Session ID#2 as a new PDU Session ID.

[0240] Additionally, in step 4, the UE can determine whether the PDN Connection specified by the combination of APN / DNN and S-NSSAI#1 should be continuously moved to 5GS based on the result of evaluating the URSP Rule. For example, if traffic from App#1 has not occurred for a certain period of time and traffic for other Applications specified by the combination of APN / DNN and S-NSSAI#1 has not occurred, the UE can determine that there is no need to move this PDN Connection to 5GS. If the UE determines that there is no need to move the existing PDN Connection to 5GS, the UE can request the network for PDU Session Modification or PDU Session Release using the PDU Session ID (e.g., PDU Session ID#1) assigned to the existing PDN Connection. The network can determine whether to modify or release part / all of the existing PDN Connection requested by the UE.

[0241] The rescue procedures of steps 3 and 4 are described in Figures 10 and 11.

[0242] FIG. 10 illustrates an example of a method for selecting an appropriate S-NSSAI when using a PDU Session via 5GS when a terminal is connected to a 4G core and then moves to a 5G core and / or when the terminal is connected to a 5G core in a communication system supporting 5GS-EPS interworking according to one embodiment of the present disclosure.

[0243] Figure 10 is based on a structure with or without N26 connection between MME and AMF.

[0244] Referring to FIG. 10, at step 1000, the UE may have registered (Attach) to the EPS or set up a PDN Connection.

[0245] At step 1001, the UE may move from EPS to 5GS through Handover and / or Registration procedures.

[0246] In step 1002, the UE may evaluate / re-evaluate the URSP rule to connect to the 5GS. Based on the evaluation / re-evaluation result, if there is a PDN Connection designated with an S-NSSAI that is not identical to the S-NSSAI that matches the URSP rule among the PDN Connections that were previously used in the EPS, the UE may decide to establish a PDU Session using a new PDU Session ID. This may correspond to step 3 of (C) of FIG. 9. Based on the evaluation / re-evaluation result of the URSP rule, if the UE determines that there is no longer any traffic that matches the URSP rule among the PDN Connections that were previously used in the EPS or that there is no need to move the PDN Connection to the 5GS, the UE may decide to perform PDU Session Modification and / or PDU Session Release using the PDU Session ID assigned to the PDN Connection. This may correspond to step 4 of (C) of FIG. 9.

[0247] In step 1003, if the UE determines in step 1002 that there is a PDN Connection designated with an S-NSSAI that is not identical to the S-NSSAI matching the URSP rule among the PDN Connections previously used in the EPS, and thus decides to establish a PDU Session using a new PDU Session ID, the UE may send a PDU Session Establishment request message to the AMF via the NG-RAN. The request message may provide at least one of the newly assigned PDU Session ID, the DNN and S-NSSAI matching the URSP Rule, and / or auxiliary information for correction. The auxiliary information for correction may include at least one of the PDU Session ID assigned to the PDN Connection designated with an S-NSSAI that is not identical to the S-NSSAI matching the URSP rule, or the designated S-NSSAI.

[0248] In step 1004, the AMF may request a PDU Session Establishment to the SMF+PGW-C based on the information received in step 1003. For example, the PDU Session Establishment request may be transmitted to the SMF+PGW-C via the Nsmf_PDUSession_CreateSMContext message. The PDU Session Establishment request message may include information received from the AMF (e.g., a newly allocated PDU Session ID, a DNN and S-NSSAI matching the URSP Rule, and / or auxiliary information for correction).

[0249] At step 1005, the PDU Session Establishment procedure may be completed.

[0250] In step 1006, if the SMF+PGW-C receives the auxiliary information for correction in step 1004, it can determine whether a modification and / or release procedure for the existing PDN Connection is required based on this information. For example, if the auxiliary information for correction includes a PDU Session ID, it can determine whether to release the EPS bearer for the PDN Connection corresponding to the PDU Session ID. As another example, if the auxiliary information for correction includes an S-NSSAI, it can determine whether to release the EPS bearer for the PDN Connection for which the S-NSSAI is specified. If the SMF+PGW-C determines that a modification and / or release procedure is required, step 1010 can be performed.

[0251] In step 1007, if the UE determines that there is no longer any traffic matching the URSP rule among the PDN Connections that were previously used in the EPS in step 1002 or that there is no need to move the PDN Connection to 5GS, and thus decides to perform PDU Session Modification and / or PDU Session Release using the PDU Session ID assigned to the PDN Connection, the UE may send a PDU Session Modification or PDU Session Release request message to the AMF via the NG-RAN. The PDU Session Modification or PDU Session Release request message may include at least one of the PDU Session ID assigned to the existing PDN Connection to be modified / released and / or auxiliary information for correction. Auxiliary information for correction may include at least one of an S-NSSAI assigned to a PDN Connection that is not identical to an S-NSSAI matching the URSP rule, or an S-NSSAI that is identical to an S-NSSAI matching the URSP rule.

[0252] In step 1008, AMF may request PDU Session Modification or Release to SMF+PGW-C based on the information received in step 1007. For example, this request message may be transmitted to SMF+PGW-C via Nsmf_PDUSession_UpdateSMContext message. The request message may include information received from AMF (e.g., PDU Session ID assigned to an existing PDN Connection to be modified / released, and / or auxiliary information for correction).

[0253] At step 1009, the PDU Session Modification or Release procedure may be completed.

[0254] In step 1010, the SMF+PGW-C may determine whether to release the existing PDN Connection based on a request from the UE and / or AMF or a specific criterion. For example, if the UE and / or AMF requests it, or if no traffic has been transmitted through the PDN Connection for a certain period of time, the SMF+PGW-C may determine that the PDN Connection can be released. Alternatively, if the PDN Connection is determined to be always connected, the SMF+PGW-C may decide not to release the PDN Connection even if the UE and / or AMF requests it or if no traffic has been transmitted through the PDN Connection for a certain period of time. If the SMF+PGW-C determines to release the PDN Connection, a Bearer modification or Bearer release procedure may be performed.

[0255] FIG. 11 illustrates an example of a method for selecting an appropriate S-NSSAI when using a PDU Session via 5GS when a terminal is connected to a 4G core and then moves to a 5G core and / or when the terminal is connected to a 5G core in a communication system supporting 5GS-EPS interworking according to one embodiment of the present disclosure.

[0256] Figure 11 is based on a structure with or without N26 connection between MME and AMF.

[0257] Referring to FIG. 11, at step 1100, the UE may have registered (Attach) to EPS or set up a PDN Connection.

[0258] In step 1101, the UE may evaluate / re-evaluate the URSP rule. Based on the evaluation / re-evaluation result, if there is a PDN Connection with an S-NSSAI that is not identical to the S-NSSAI that matches the URSP rule among the PDN Connections that were previously used in the EPS, the UE may determine that the S-NSSAI must be corrected when moving to 5GS.

[0259] At step 1102, the UE can move from EPS to 5GS through the Registration procedure.

[0260] Specifically, the UE can send a Registration Request message to the AMF via the NG-RAN. This request message can include at least one of the following information: “Mobility Registration Update”, “5G-GUTI mapped from EPS GUTI”, and “moving from EPC”. Based on this information, the AMF can determine that the UE is moving from EPS to 5GS. The UE can evaluate / re-evaluate the URSP rule to connect to 5GS. Based on the result, if there is a PDN Connection designated with an S-NSSAI that is not identical to the S-NSSAI matching the URSP rule among the PDN Connections that were previously used in the EPS, the Registration Request message can include auxiliary information for correction. The auxiliary information for correction can include at least one of the S-NSSAI assigned to the PDN Connection designated with an S-NSSAI that is not identical to the S-NSSAI matching the URSP rule, or the S-NSSAI that is identical to the S-NSSAI matching the URSP rule. For example, both the S-NSSAI to be corrected and the correct S-NSSAI may be included in the supplementary information for correction. Alternatively, the S-NSSAI to be corrected information may be in a form other than the supplementary information for correction, and the supplementary information for correction may only include the correct S-NSSAI.

[0261] At step 1103, the registration procedure can be completed.

[0262] In step 1104, the AMF may determine whether to correct the specified S-NSSAI for the PDN Connection / PDU session that was previously used in the EPS based on the information received in step 1102. For example, if the AMF can know the information of an incorrect S-NSSAI that does not match the URSP rule (S-NSSAI to be corrected) and an S-NSSAI that matches the URSP rule (correct S-NSSAI), the AMF may trigger a procedure to correct the incorrect S-NSSAI that does not match the URSP rule (S-NSSAI to be corrected).

[0263] In step 1105, the AMF may request the SMF+PGW-C to perform PDU Session Modification or PDU Session Release to correct the S-NSSAI. For example, this request may be transmitted to the SMF+PGW-C via the Nsmf_PDUSession_UpdateSMContext message. This request may include assistance information for correction. The assistance information for correction may include at least one of the S-NSSAI to be corrected or the correct S-NSSAI, and the format in which this information is provided is not limited to the field called 'Assistance information for correction'.

[0264] At step 1106, the PDU Session Modification or Release procedure may be completed.

[0265] In step 1107, SMF+PGW-C may determine whether to release the existing PDN Connection based on a request from AMF or specific criteria. For example, if AMF requests it or if no traffic has been transmitted through the PDN Connection for a certain period of time, SMF+PGW-C may determine that the PDN Connection can be released. Alternatively, if it is determined that the PDN Connection should always be connected, SMF+PGW-C may decide not to release the PDN Connection even if AMF requests it or if no traffic has been transmitted through the PDN Connection for a certain period of time. If SMF+PGW-C decides to release the PDN Connection, a bearer modification or bearer release procedure may be performed.

[0266] FIGS. 12A and 12B illustrate examples of a method for selecting an appropriate S-NSSAI when using a PDN connection through a 4G system (EPS) when a terminal is connected to a 5G core and then moves to a 4G core and / or when the terminal is connected to a 4G core, in a communication system supporting 5GS-EPS interworking according to one embodiment of the present disclosure.

[0267] FIG. 12 is a drawing for explaining an example of a method for handling a case where SMF+PGW-C does not support S-NSSAI when UE provides S-NSSAI while making a PDN Connection request to SMF+PGW-C in the method described in FIG. 4.

[0268] Steps 0 to 7 and steps 8 to 11 of FIG. 12 can operate identically / similarly to steps 0 to 7 and steps 8 to 11 of FIG. 4, and description of overlapping contents is omitted.

[0269] Figure 12 further illustrates steps 7a, 7b, and 7c.

[0270] Step 7a: If it is determined in step 7 that the SMF+PGW-C (or the PGW part of this SMF+PGW-C) does not support the S-NSSAI (requested by the UE) received in step 5, then another SMF+PGW-C (or another PGW) that supports this S-NSSAI can be selected.

[0271] Step 7b: The SMF+PGW-C (or the PGW part of this SMF+PGW-C) may forward the Create Session Request message received from the SGW in Step 5 to another SMF+PGW-C (or another PGW) selected in Step 7a. The forwarded Create Session Request message may include the S-NSSAI requested by the UE. At least one of the following may be included or applied when forwarding the message:

[0272] - The destination IP address of this message can be the IP address of the selected SMF+PGW-C (or the selected PGW);

[0273] - This message may be provided with the CSRMFI (Create Session Request Message Forwarding Indication) value set to a value other than '1' or '0'. This value may mean that the Create Session Request Message was forwarded from the PGW. In other words, it may mean that the SGW forwarded the message sent by the SGW to another PGW, rather than sending it to the PGW. Depending on the network configuration, if it is set to a value other than '0' and '1', it may additionally mean that the message was forwarded from the PGW and that it was forwarded because it did not match the S-NSSAI requested by the UE; or

[0274] - The source IP address and UDP port of this message can be the IP address and UDP port of the SMF+PGW-C that delivers the Create Session Request message.

[0275] The SMF+PGW-C (or PGW) that sends the Create Session Request message can be called the Forwarding SMF+PGW-C (or Forwarding PGW), or the Source SMF+PGW-C (or Source PGW). The SMF+PGW-C (or PGW) that receives the Create Session Request message can be called the Selected SMF+PGW-C (or Selected PGW), or the Target SMF+PGW-C (or Target PGW).

[0276] Step 7c: The selected SMF+PGW-C (or PGW) may perform the actions performed by the Forwarding SMF+PGW-C in Step 7 from its own perspective based on the contents of the Create Session Request message received in Step 7b. These actions may include selecting the S-NSSAI requested by the UE as the S-NSSAI for this PDN Connection and deciding to accept the request to establish this PDN Connection. In case of accepting the PDN Connection, the selected SMF+PGW-C may respond to the Forwarding SMF+PGW-C with the S-NSSAI selected for the PDN Connection using a Create Session Response message. For example, the S-NSSAI selected for the PDN Connection may be the S-NSSAI requested by the UE received in Step 7c. In response to receiving CSRMFI set to any value other than '1' or '0' in step 7b, the selected SMF+PGW-C may send the PGW FQDN value as its PGW node name information along with the Create Session Response. The forwarding SMF+PGW-C may forward the received Create Session Response message to the SGW in step 8.

[0277] FIGS. 13a and 13b illustrate examples of a method for selecting an appropriate S-NSSAI when using a PDN connection through a 4G system (EPS) when a terminal is connected to a 5G core and then moves to a 4G core and / or when the terminal is connected to a 4G core, in a communication system supporting 5GS-EPS interworking according to one embodiment of the present disclosure.

[0278] FIG. 13 is a drawing for explaining an example of a method for handling a case in which SMF+PGW-C does not support S-NSSAI when UE provides S-NSSAI while making a PDN Connection request to SMF+PGW-C in the method described in FIG. 4.

[0279] Steps 0 to 7 and steps 8 to 11 of FIG. 13 can operate identically / similarly to steps 0 to 7 and steps 8 to 11 of FIG. 4, and description of overlapping contents is omitted.

[0280] Figure 13 may contain content that overlaps with that of Figure 12.

[0281] Figure 13 further illustrates steps 7a, 7b, 7c, and 7d.

[0282] Step 7a: If it is determined in step 7 that the SMF+PGW-C (or the PGW part of this SMF+PGW-C) does not support the S-NSSAI (requested by the UE) received in step 5, then another SMF+PGW-C (or another PGW) that supports this S-NSSAI can be selected.

[0283] Step 7b: SMF+PGW-C (or PGW part of this SMF+PGW-C) may reject the Create Session Request in Step 5 if the MME has indicated (via SGW) that it supports PGW redirection in Step 5 or the SMF+PGW-C itself does not support forwarding the request message to the SMF+PGW-C (or PGW) selected in Step 7a. The SMF+PGW-C may provide the rejection of the Create Session Request via a Create Session Response message. The Create Session Response message may include the reason for rejection and / or the FQDN or IP address of the selected SMF+PGW-C. The reason for rejection may include 'PGW mismatch with network slice requested by the UE'. Depending on the network settings, the reason for rejection can be recycled as 'PGW mismatch with network slice subscribed by the UE'.

[0284] The SMF+PGW-C (or PGW) that transmits the message in step 7b may be called the Forwarding SMF+PGW-C (or Forwarding PGW), or the Source SMF+PGW-C (or Source PGW). The SMF+PGW-C (or PGW) that receives the message in step 7c may be called the Selected SMF+PGW-C (or Selected PGW), or the Target SMF+PGW-C (or Target PGW).

[0285] Step 7c: If the MME (via the SGW) receives a Create Session Response in Step 7b with the rejection reason that the network slice to which the UE has joined or the network slice requested by the UE does not match the PGW, the MME may perform the action of sending a Create Session Request message (via the SGW) to the Target SMF+PGW-C (or the Target PGW). This Create Session Request message may include the S-NSSAI requested by the UE. This action may correspond to attempting to perform the action performed by the MME in Step 5 to the Target SMF+PGW-C. Therefore, the description of Step 5 may be referred to.

[0286] Step 7d: Target SMF+PGW-C (or Target PGW) may perform the actions performed by Forwarding SMF+PGW-C in Step 7 from its own perspective based on the contents of the Create Session Request message received in Step 7c. This action may include selecting the S-NSSAI requested by the UE as the S-NSSAI for this PDN Connection and accepting the request to establish this PDN Connection. Target SMF+PGW-C may respond to MME (via SGW) with a Create Session Response message. This action may correspond to Step 8 of FIG. 4. Target SMF+PGW-C may provide the selected S-NSSAI for this PDN Connection via PCO. The selected S-NSSAI may be the S-NSSAI requested by the UE received in Step 7c.

[0287] FIG. 14 is a block diagram of a network entity and / or terminal according to an embodiment of the present disclosure.

[0288] Network entities and terminals can perform the embodiments and / or methods proposed in the present disclosure.

[0289] For example, a network entity may include at least one NF (e.g., base station, RAN, MME, AMF, SGW, SMF, SMF+PGW-C, UPF, UPF+PGW-U, HSS+UDM, etc.) depending on the system implementation.

[0290] For example, referring to FIG. 14, each of the network entities and / or terminals may include a transceiver (1420), a control unit (processor) (1410), and / or a storage unit (memory) (not shown). However, the components of the network entity and / or terminal according to one embodiment are not limited to the above-described examples. According to other embodiments, the network entity and / or terminal may include more or fewer components than the components described above. In addition, in certain cases, the transceiver, the control unit, and the storage unit may be implemented in the form of a single chip.

[0291] For example, the transceiver (1420) may be configured with a transmitter (1425) and a receiver (1423) according to another embodiment. The transceiver may transmit and receive signals with 3GPP network functions and / or terminals. The transceiver may transmit and receive signals with terminals or other network entities. The signals may include control information and data. In addition, the transceiver may receive signals through a wireless channel and output them to the control unit, and transmit the signals output from the control unit through the wireless channel.

[0292] For example, the control unit may control a series of processes that a network entity and / or a terminal may perform according to the embodiments of the present disclosure described above. The control unit may include at least one processor. For example, the control unit may include a communication processor (CP) that performs control for communication and an application processor (AP) that controls upper layers such as application programs. In one embodiment, the control unit (1410) may be a circuit, an application-specific circuit, or at least one processor.

[0293] The storage unit can store information or data included in a signal obtained from a network entity and / or a terminal, and can have an area for storing data required for control of the control unit and data generated during control by the control unit.

[0294] Additionally, the operations of a network entity or terminal can be realized by providing a memory device storing the corresponding program code to a component within the network entity or terminal (e.g., the control unit (1410) and / or other components not shown).

[0295] The methods according to the embodiments described in the claims or specification of the present disclosure may be implemented in the form of hardware, software, or a combination of hardware and software.

[0296] When implemented in software, a computer-readable storage medium storing one or more programs (software modules) may be provided. The one or more programs stored in the computer-readable storage medium are configured for execution by one or more processors within an electronic device. The one or more programs include instructions that cause the electronic device to execute methods according to the embodiments described in the claims or specification of the present disclosure.

[0297] 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.

[0298] Additionally, the program may be stored on an attachable storage device that is accessible via a communication network, such as the Internet, an intranet, a local area network (LAN), a wide local area network (WLAN), a storage area network (SAN), or a combination thereof. Such a storage device may be connected to a device 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.

[0299] In the specific embodiments of the present disclosure described above, components included in the invention are expressed in the singular or plural form, depending on the specific embodiment presented. However, the singular or plural expressions are selected to suit the presented situation for convenience of explanation, and the present disclosure is not limited to singular or plural components. Components expressed in the plural form may be composed of singular elements, or components expressed in the singular form may be composed of plural elements.

[0300] Meanwhile, the embodiments of the present disclosure disclosed in this specification and drawings are merely specific examples presented to easily explain the technical content of the present disclosure and facilitate understanding of the present disclosure, and are not intended to limit the scope of the present disclosure. In other words, it will be apparent to those skilled in the art to which the present disclosure pertains that other modifications based on the technical concept of the present disclosure are possible. Furthermore, the above-described embodiments may be combined and operated as needed.

[0301] Meanwhile, the order of description in the drawings explaining the method of the present disclosure does not necessarily correspond to the order of execution, and the order of precedence may be changed or executed in parallel.

[0302] Alternatively, the drawings illustrating the method of the present disclosure may omit some components and include only some components without detracting from the essence of the present disclosure.

[0303] In addition, the method of the present disclosure may be implemented by combining some or all of the contents included in each embodiment within a scope that does not harm the essence of the invention.

[0304] Various embodiments of the present disclosure have been described above. The foregoing description of the present disclosure is for illustrative purposes only, and the embodiments of the present disclosure are not limited to the disclosed embodiments. Those skilled in the art will appreciate that the present disclosure can be readily modified into other specific forms without altering the technical spirit or essential characteristics of the present disclosure. The scope of the present disclosure is indicated by the claims described below rather than the detailed description above, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present disclosure.

Claims

1. A method performed by a first core node of a wireless communication system, A step of receiving a packet data network (PDN) connection creation request including a packet data unit (PDU) session ID and single-network slice selection assistance information (S-NSSAI) provided from a terminal; A step of obtaining a subscribed S-NSSAI for the terminal from unified data management (UDM); A step of determining an S-NSSAI associated with a PDN connection based on the S-NSSAI provided from the terminal, the subscribed S-NSSAI, and at least one S-NSSAI supported by the first core node; and A step of transmitting a response message including the determined S-NSSAI to the terminal; How to include.

2. In paragraph 1, A step of determining whether the S-NSSAI provided from the terminal is supported by the first core node; and A step of determining another core node that supports the S-NSSAI provided from the terminal when the S-NSSAI provided from the terminal is not supported by the first core node; How to include more.

3. In paragraph 2, A method further comprising the step of transmitting information and a rejection cause for the other core node determined above to the second core node.

4. In paragraph 1, The PDU session ID and S-NSSAI provided from the terminal are provided to the first core node through a protocol configuration option (PCO). A method in which the above-determined S-NSSAI is transmitted to the terminal via PCO.

5. In a method performed by a terminal of a wireless communication system, A step of transmitting a packet data network (PDN) connection creation request including a packet data unit (PDU) session ID and single-network slice selection assistance information (S-NSSAI) to a first core node; and A step of receiving a response message including an S-NSSAI determined in association with a PDN connection from the first core node, A method in which the determined S-NSSAI is determined based on an S-NSSAI provided from the terminal, a subscribed S-NSSAI for the terminal obtained from unified data management (UDM), and at least one S-NSSAI supported by the first core node.

6. In paragraph 5, A step of evaluating the URSP (UE route selection policy) rule set in the terminal; and A step of determining the S-NSSAI to be included in the PDN connection creation request based on the above evaluation. How to include more.

7. In paragraph 5, The above PDU session ID and S-NSSAI are transmitted to the first core node through a protocol configuration option (PCO), A method in which the above-determined S-NSSAI is received from the first core node via a PCO.

8. In the first core node of the 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, such that said first core node A step of receiving a packet data network (PDN) connection creation request including a packet data unit (PDU) session ID and single-network slice selection assistance information (S-NSSAI) provided from a terminal, A step of obtaining a subscribed S-NSSAI for the terminal from unified data management (UDM), A step of determining an S-NSSAI associated with a PDN connection based on the S-NSSAI provided from the terminal, the subscribed S-NSSAI, and at least one S-NSSAI supported by the first core node, and A step of transmitting a response message including the determined S-NSSAI to the terminal. Memory that stores instructions to perform; A first core node including .

9. In paragraph 8, The above command causes the first core node to A step of determining whether the S-NSSAI provided from the terminal is supported by the first core node; and A step of determining another core node that supports the S-NSSAI provided from the terminal when the S-NSSAI provided from the terminal is not supported by the first core node; The first core node to perform more.

10. In paragraph 9, The above command causes the first core node to A first core node further performing the step of transmitting information and a rejection cause to the other core node determined above to the second core node.

11. In paragraph 8, The PDU session ID and S-NSSAI provided from the terminal are provided to the first core node through a protocol configuration option (PCO). The above-determined S-NSSAI is transmitted to the terminal through the PCO, the first core node.

12. In the terminal 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, so that said terminal A step of transmitting a packet data network (PDN) connection creation request including a packet data unit (PDU) session ID and single-network slice selection assistance information (S-NSSAI) to a first core node, and A step of receiving a response message including an S-NSSAI determined in association with a PDN connection from the first core node. including a memory that stores instructions to perform the The terminal in which the above-determined S-NSSAI is determined based on the S-NSSAI provided from the terminal, the subscribed S-NSSAI for the terminal obtained from unified data management (UDM), and at least one S-NSSAI supported by the first core node.

13. In paragraph 12, The above command is, the terminal A step of evaluating the URSP (UE route selection policy) rule set in the terminal; and A step of determining the S-NSSAI to be included in the PDN connection creation request based on the above evaluation. A terminal that allows you to perform more.

14. In paragraph 12, The above PDU session ID and S-NSSAI are transmitted to the first core node through a protocol configuration option (PCO), The above-determined S-NSSAI is received by the terminal from the first core node via PCO.

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