Session management method and device for user plane path failure handling in wireless communication system

Abstract

The present disclosure provides a method performed by a first session management function (SMF) entity belonging to a home public land mobile network (HPLMN) in a wireless communication system, the method comprising the steps of: receiving, from a first user plane function (UPF) entity belonging to the HPLMN and disposed close to a visited region of a terminal, a first message for notifying a user plane path failure between a first UPF and a second UPF entity belonging to a visited public land mobile network (VPLMN) of the visited region; and transmitting, to a second SMF entity belonging to the VPLMN, a second message for requesting the release of a protocol data unit (PDU) session associated with the user plane path.

Description

Session management method and device for responding to user plane path failure in a wireless communication system

[0001] Embodiments of the present disclosure relate to a wireless communication system, and more specifically, the embodiments propose a session management method for responding to a failure occurring on a user plane path.

[0002] 5G mobile communication technology defines a wide frequency band to enable fast transmission speeds and new services, and can be implemented not only in the sub-6GHz frequency band such as 3.5 gigahertz (3.5GHz), but also in the ultra-high frequency band called millimeter wave (mmWave) such as 28GHz and 39GHz ('Above 6GHz'). In addition, for 6G mobile communication technology, which is called the system after 5G communication (Beyond 5G), implementation in the terahertz band (for example, the 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.

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

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

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

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

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

[0008] Embodiments of the present disclosure may have as a first purpose a session management method and device for responding to a failure that occurs on a user plane path.

[0009] The present disclosure relates to a method according to embodiments, wherein a method performed by a first session management function (SMF) entity belonging to a home public land mobile network (HPLMN) in a wireless communication system may include the steps of: receiving a first message from a first user plane function (UPF) entity belonging to the HPLMN and located close to a visited region of a terminal to notify of a failure of a user plane path between the first UPF and a second UPF entity belonging to a visited public land mobile network (VPLMN) of the visited region; and transmitting a second message to the second SMF entity belonging to the VPLMN to request release of a protocol data unit (PDU) session associated with the user plane path.

[0010] The method and device according to embodiments of the present disclosure can perform session management to respond to a failure that occurs on a user plane path set to transmit service traffic of a roaming terminal to a data center with a short transmission distance.

[0011] FIG. 1 is a diagram illustrating the structure of a wireless communication system according to embodiments of the present disclosure.

[0012] FIG. 2 is a drawing for explaining an example of user plane setup and occurrence of a failure according to embodiments of the present disclosure.

[0013] FIG. 3 is a diagram for explaining user plane setup for an HR PDU session according to embodiments of the present disclosure.

[0014] FIG. 4 is a diagram illustrating a method for detecting a user plane failure occurrence according to embodiments of the present disclosure.

[0015] FIG. 5 is a diagram illustrating the structure of a user terminal according to embodiments of the present disclosure.

[0016] FIG. 6 is a diagram illustrating the structure of a network entity according to embodiments of the present disclosure.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] The operating principles of embodiments of the present disclosure are described in detail with reference to the attached drawings. The terms described below are defined based on the functions of the present disclosure. These terms may vary depending on the intent or custom of the user or operator, and therefore, their definitions should be determined based on the overall content of this specification.

[0024] The terms used in this disclosure to refer to network entities, network functions, and objects of an Edge Computing system, as well as terms used to refer to messages and identification information, are provided for convenience of explanation. Therefore, the disclosure is not limited to the terms described below, and other terms that refer to objects with equivalent technical meanings may be used.

[0025] For convenience, the present disclosure uses terms and names defined in the 5G system specifications, but is not limited by the terms and names and can be equally applied to systems conforming to other specifications.

[0026] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the attached drawings. The attached drawings are provided to help understand embodiments of the present disclosure, and it should be noted that the contents of the present disclosure are 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 embodiments in 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 obscure the gist of the present disclosure. In addition, although the present disclosure describes various embodiments using terminology used in some communication standards (e.g., 3rd Generation Partnership Project (3GPP)), this is merely an example for the purpose of explanation. The various embodiments of the present disclosure can be easily modified and applied to other communication systems.

[0027] Hereinafter, an embodiment of the present invention will be described with reference to the attached drawings.

[0028] FIG. 1 is a diagram illustrating the structure of a 5G wireless communication system supporting a roaming terminal according to embodiments of the present disclosure.

[0029] Referring to FIG. 1, a 5G system architecture supporting edge computing services may include various network functions (NFs), and FIG. 1 illustrates some of them, including an access and mobility management function (AMF), a session management function (SMF), a policy control function (PCF), a unified data management (UDM), a data network (DN) or a local part of DN capable of local access to the data network, a user plane function (UPF), a (radio) access network (R)AN, and a user equipment (UE).

[0030] Each NF can support the following functions:

[0031] AMF provides functions for access and mobility management at the UE level, and one UE can be connected to one AMF by default.

[0032] A DN can represent an operator service, an Internet connection, or a third-party service. The DN can transmit a downlink protocol data unit (PDU) to the UPF, or receive a PDU transmitted from a UE from the UPF. The "local part of DN" can represent a data network that is locally accessible as a part of the DN and has a short data transmission path. The "local part of DN" can be used to refer to a DN where an edge application server supporting an edge computing service is deployed. The Edge Data Network can refer to a data network where an edge computing server is deployed. The Edge Data Network can be referred to as a local part of a data network or a local data network (local part of DN or local DN).

[0033] PCF receives information about packet flows from application servers and provides the ability to determine policies for mobility management, session management, and other aspects. Specifically, PCF can support a unified policy framework for controlling network operations, provide policy rules so that control plane functions (e.g., AMF, SMF, etc.) can enforce them, and implement a front end for accessing relevant subscription information for policy decision-making within the unified data repository (UDR).

[0034] SMF provides session management functionality, and if a UE has multiple sessions, each session can be managed by a different SMF.

[0035] UDM can store user subscription data, policy data, etc.

[0036] The UPF can forward downlink PDUs received from the DN to the UE via the (R)AN, and forward uplink PDUs received from the UE via the (R)AN to the DN. ULCL (uplink classifier) ​​can refer to a UPF that has the function of classifying and transmitting uplinks. The L-UPF (local UPF) can perform the role of an end point (PDU Session Anchor) of a session transmitted to a local part of the DN. In a roaming scenario, the UPF of the VPLMN (visited public land mobile network) is deployed within the VPLMN and performs uplink / downlink data transmission under the control of the V-SMF, and the UPF of the HPLMN (home public land mobile network) can perform uplink / downlink data transmission under the control of the H-SMF.

[0037] The Edge Application Server Discovery Function (EASDF) processes domain name system (DNS) queries sent by terminals according to rules provided by the SMF. For example, the EASDF can forward DNS queries sent by terminals to a DNS server, receive DNS responses, send related reports to the SMF, and provide DNS responses to the terminals.

[0038] FIG. 2 is a drawing for explaining an example of user plane setup and occurrence of a failure according to embodiments of the present disclosure.

[0039] Referring to FIG. 2, one example of a scenario considered in the present disclosure is illustrated.

[0040] An HPLMN operator can deploy a Home UPF (H-UPF) in a cloud that can provide services by being located in a data center in the region of the country visited by the roaming terminal (the country of the VPLMN operator, hereinafter referred to as the roaming country). The HPLMN operator can deploy the H-UPF in the cloud where the data center is located in the region of the country visited by the roaming terminal and establish a connection with the V-UPF of the VPLMN where the roaming terminal is registered to establish a user plane for providing roaming services. There may be multiple VPLMN operators in the country visited by the roaming terminal. At a given point in time, a roaming terminal can generally register with one of the VPLMNs to receive roaming services. When providing a roaming service, a user plane connection can be established between the selected V-UPF and the H-UPF deployed by the HPLMN operator in the roaming country. The H-UPF deployed in the roaming country can be controlled by the H-SMF located in the HPLMN country (home country or HPLMN country). The H-SMF can perform user plane configuration for the H-UPF (H-UPF#1 in Fig. 2) deployed in the roaming country, and can also perform user plane configuration for a separate H-UPF (H-UPF#2 in Fig. 2) in the HPLMN country area. The HPLMN operator can use the H-SMF to provide a service to a roaming terminal through a short user plane path via the H-UPF#1 deployed in the roaming country. A failure may occur on the user plane path via H-UPF#1. The user plane path failure may indicate a failure on the path between the network (V-UPF) of a specific VPLMN operator (VPLMN A in Fig. 2) and H-UPF#1. The HPLMN operator can detect a user plane path failure between the H-UPF#1 and the V-UPF of the specific VPLMN operator, configure another user plane path, and maintain the roaming service.For example, an HPLMN operator can configure the user plane to bypass a failed path by establishing a user plane path using H-UPF#2 deployed in the HPLMN country instead of using H-UPF#1 deployed in the roaming country area. The following specific embodiments describe a method for detecting a user plane path failure and ensuring session service continuity by bypassing the failed path.

[0041] FIG. 3 is a diagram for explaining user plane setup for an HR PDU session according to embodiments of the present disclosure.

[0042] 301. When the SMF supports session branching in the H-UPF through operations such as home session breakout for the HR PDU session, the SMF can detect a failure on the user plane path between the H-UPF performing the session branching and the V-UPF. The SMF can receive a failure on the user plane path between the H-UPF and the V-UPF from the H-UPF (H-UPF#1 in Fig. 3). When a failure occurs in the user plane connection (or N9 tunnel) connected to the V-UPF, the H-UPF#1 can notify the H-SMF of the failure by sending an N4 Report message. The message that H-UPF#1 transmits to H-SMF may include at least one of UPF ID, list of events (status), Tunnel ID, serving network ID (or VPLMN ID), DNN, S-NSSAI, remote domain site failure flag (information indicating that a failure has occurred within the data center or region where H-UPF is deployed) and / or roaming UP path failure flag (information indicating that a failure has occurred along a roaming-only user plane path, for example, information indicating that a problem has occurred with a connection to a specific VPLMN or serving network). In addition, H-UPF#1 may distinguish whether the failure is a failure for H-UPF#1 or a failure for a path between the data center where H-UPF#1 is deployed (for example, a public cloud data center) and V-UPF, and report the result to H-SMF. Based on this determination, H-UPF#1 may select information to be included in an N4 report message that it transmits to H-SMF.

[0043] 302. H-SMF can send an acknowledgment to H-UPF#1 for the N4 report received from H-UPF#1.

[0044] 303. The H-SMF can detect that a user plane failure has occurred based on the information contained in the N4 report received from the H-UPF#1, and analyze or determine what type of failure has occurred or information about the path where the failure occurred (e.g., identifying or determining a specific serving network or VPLMN where the user plane path failure occurred). For example, the H-SMF can identify the VPLMN or serving network to which the path where the user plane failure occurred is connected using the VPLMN ID or serving network ID received from the H-UPF. Alternatively, the H-SMF can specify one of the user plane paths configured for roaming based on information such as TEID, UPF ID, DNN, S-NSSAI, etc. In addition, the H-SMF can determine that a failure has occurred in the connectivity of the region where the specific H-UPF is deployed when it receives a remote domain site failure flag. Additionally, when the H-SMF receives a roaming UP path failure flag, it can determine that a failure has occurred in the user plane for roaming services to the roaming partner network (or serving network, VPLMN) connected to the H-UPF.

[0045] H-SMF may make a decision to exclude H-UPF#1 from selection for future HR PDU session creation requests for the VPLMN.

[0046] 304. When the H-SMF determines that a specific type of failure has occurred on the user plane, the H-SMF may perform an UP path reconfiguration operation on the associated PDU sessions. For example, in the case of a failure on the path between a public cloud data center where H-UPF#1 is deployed and a V-UPF, the H-SMF may perform an N4 Session modification operation to perform an UP path reconfiguration on the currently created PDU sessions for the VPLMN on the UP path where the UP path failure event was detected. In addition, the H-SMF may perform a decision on whether to give priority to the release of the existing PDU sessions based on the SSC Mode (SSC mode 1, SSC mode 2, SSC mode 3) of the created PDU sessions. An embodiment may describe an operation on a PDU session to which SSC mode 2 is applied. If the H-SMF determines that there is a failure in the path between the public cloud data center where H-UPF#1 is deployed and the V-UPF, it may decide to select an H-UPF deployed in the HPLMN country (H-UPF#2 in Fig. 3) to establish a home routed PDU session, rather than selecting another H-UPF in the public cloud (e.g., an H-UPF deployed in duplicate or as a redundancy in a data center in the roaming country, or an H-UPF deployed in the public cloud of the visited country to branch the UP path to a specific serving PLMN).

[0047] H-SMF may perform N4 session modification procedure to send message to H-UPF#1 to stop downlink forwarding.

[0048] 305. The H-SMF can identify a path on which a user plane failure has occurred and specify the VPLMN, PDU session, and V-SMF corresponding to the identified path. The H-SMF can transmit a PDU session update request to the specified V-SMF. The PDU session update request message can include a PDU session release request indicator and PDU Session Release cause information (or PDU session release cause code). When the H-SMF performs a release for an HR PDU Session due to an UP path failure, it can include a cause value indicating a PDU Session Re-establishment request in the message transmitted to the V-SMF. The H-SMF can also provide the V-SMF with an SM Release PDU Session Command and protocol configuration options to be transmitted to the terminal.

[0049] 306. V-SMF can perform N4 session release operation for V-UPF using information received from H-SMF.

[0050] 307. V-SMF can transmit information to AMF for performing PDU session release and information received from H-SMF (PDU session release request indicator and PDU Session Release cause information or at least one of PDU session release cause code, SM Release PDU Session Command, and protocol configuration option).

[0051] 308. AMF may send to RAN an N2 Resource release request for a PDU session and information that must be transmitted to the terminal (PDU session release cause code, SM Release PDU Session Command and / or protocol configuration option).

[0052] 309. The RAN may transmit to the terminal an AN-specific resource modification request message for the corresponding PDU session and information received from the AMF (at least one of the PDU session release cause code, SM Release PDU Session Command, and protocol configuration option).

[0053] 310. RAN may send an acknowledgment to AMF for N2 resource release.

[0054] 311. AMF can receive a PDU session release accept message from the UE.

[0055] 312. AMF can send an acknowledgment to V-SMF informing it of the SM resource release result. AMF can also send secondary RAT usage data, user location information, etc. to V-SMF.

[0056] 313. The V-SMF may send a response message to the H-SMF for the PDU Session Update request. The response message may include the result of performing the PDU session release operation.

[0057] 314. H-SMF can perform N4 session release operation for H-UPF#1.

[0058] 315. The UE can send a request to create a new PDU session based on the PDU session command received in the previous step. The request to create a PDU session can be transmitted to the H-SMF through the AMF and V-SMF. The V-SMF can select the V-UPF based on the PDU session creation request received from the AMF and provide the H-SMF with information for setting up a user plane path for the V-UPF.

[0059] 316. H-SMF can select H-UPF#2 (an H-UPF located in a non-area where the user plane path is faulty and can connect to V-UPF) as the UPF to establish the UP path according to the PDU session creation request received from the UE. H-SMF can select a DNS server available in the area where H-UPF#2 is deployed, a DNS server available in the area deployed in the HPLMN country area, or H-EASDF available in the HPLMN country area.

[0060] 317. H-SMF can perform N4 session creation procedure to configure the selected H-UPF#2, and configure H-UPF#2 so that DNS query message can be transmitted to the DNS server or H-EASDF selected in the previous step. H-SMF can obtain and determine Maximum Transmission Unit (MTU) information according to the change in the roaming user plane path. H-SMF can obtain MTU information from OAM or UPF, or use information configured internally in H-SMF.

[0061] 318. H-SMF can send a response message to V-SMF for PDU session creation request. The response message can include H-UPF#2 and DNS server information (or H-EASDF information), and MTU information.

[0062] 319. V-SMF can configure V-UPF using information received from H-SMF. V-SMF can configure V-UPF to establish connection between V-UPF and H-UPF#2.

[0063] 320. The V-SMF can send a message to the AMF to convey information about the creation of a PDU session to the RAN and the UE. The message can include information received from the H-SMF (such as DNS server information, H-EASDF information, or MTU information). The AMF sends the PDU session creation-related message to the RAN and the UE. The UE can use the received DNS server or H-EASDF information to send a DNS query message. The UE can use the received MTU information to determine the single packet size to be transmitted.

[0064] FIG. 3 illustrates an example of a procedure in which a UPF is reselected and a user plane establishment of an HR PDU session is performed according to SSC mode 2 when a failure occurs on a Home PDU Session Anchor UPF path connected to a V-UPF in the absence of an H-UPF performing the role of an Uplink classifier or a branch point (If the H-SMF receives from the H-UPF the UP Path failure report for the path between the H-UPF (PSA) and V-UPF, the H-SMF triggers the change of the corresponding SSC mode 2 H-UPF to immediately establish a new HR PDU Session, i.e., to support the roaming UE via ordinary HR PDU Session). The present disclosure may include various embodiments in which an H-SMF triggers a user plane re-establishment according to SSC mode 2 when a failure occurs on a user plane path.

[0065] Although FIG. 3 describes a case where an H-UPF performing the role of an Uplink classifier or a branch point is not used, the present disclosure may include an embodiment in which a user plane configuration is performed in an H-SMF in response to a user plane failure when an H-UPF performing the role of an Uplink classifier or a branch point is used. For example, the H-SMF may perform the Removal of additional PDU Session Anchor and UL CL for HR-HSBO PDU Session for response to UP Path failure operation as follows in this situation. If the H-UPF#1 connected to the V-UPF of FIG. 3 performs the role of an Uplink classifier or a branch point to support session branching (HR-HSBO) in the HPLMN for an HR PDU session, the H-SMF may perform an operation of removing the Uplink Classifier and PDU Session Anchor H-UPF in response to a failure occurrence on the H-UPF#1 and V-UPF paths. (At the removal procedure, the H-SMF configures the UP path to support the roaming UE via HR PDU Session of which PSA is located in the home country and updates the DNS server information with replacing the H-EASDF or DNS server in the visited country with the DNS server in the home country)

[0066] In various embodiments of the present disclosure, the H-SMF may perform PDU Session release and PDU Session re-establishment trigger operations to respond to UP path failure between the H-UPF and V-UPF paths for an HR PDU session set to SSC mode 1 or SSC mode 2 (e.g., to receive a UP path failure report from the H-UPF and perform subsequent operations).

[0067] For example, H-SMF may receive an UP path failure occurrence report from H-UPF #1 in step 301 of FIG. 3 and perform a restoration operation for the UP path failure. At this time, the restoration operation for the UP path failure of the H-SMF may include an operation of deciding to immediately delete the PDU Session Context for H-UPF #1 that sent the UP path failure report, or an operation of maintaining the PDU session context for a certain period of time, waiting for recovery, and then deciding to delete it.

[0068] If the H-SMF decides to delete the PDU session context, the H-SMF may decide to perform a release for the corresponding HR PDU session and may transmit a PDU Session release request or command for the terminal to the V-SMF. The V-SMF may transmit the PDU Session release request or command received from the H-SMF to the AMF (see step 307 of FIG. 3), and the AMF may transmit the corresponding message to the terminal (see steps 308 and 309 of FIG. 3).

[0069] In order to respond to UP path failure, the PDU Session release request or command transmitted by the H-SMF to the terminal may include a cause value indicating a PDU Session re-establishment request. For example, the H-SMF may receive an UP path failure report from H-UPF#1, determine PDU session release according to the operator policy, and transmit a PDU Session release request or command to the terminal. If the PDU Session release command received by the terminal through step 309 of FIG. 3 includes a cause value indicating PDU Session re-establishment, the terminal may immediately perform a new PDU Session creation operation.

[0070] In various embodiments of the present disclosure, when an H-SMF receives an UP path failure report from an H-UPF that constitutes an HR PDU Session in which an H-SMF is created, the H-SMF may perform the following actions according to an operator policy. For example, when an H-SMF receives an UP path failure report for a path between an H-UPF and a V-UPF from an H-UPF deployed in a visited country or visited region in which an HR PDU Session is created, the H-SMF may decide to newly create an HR PDU Session through a new H-UPF deployed in the home country or home region, and the H-SMF may perform a PDU Session release, which includes an action of transmitting a PDU Session release request or command to the terminal that includes a cause value requesting PDU Session re-establishment.

[0071] In an embodiment of the present disclosure, when an H-SMF receives an UP path failure report for a path between an H-UPF and a V-UPF from an H-UPF deployed in a home country or home region where an HR PDU Session is created, the H-SMF may decide to create a new HR PDU Session through a new H-UPF deployed in the visited country or visited region, and the H-SMF may perform a PDU Session release operation including an operation of transmitting a PDU Session release request or command including a cause value requesting PDU Session re-establishment to the terminal.

[0072] The embodiment of the present disclosure can effectively maintain the quality of roaming service by quickly responding to the occurrence of UP path failure through duplication of the transmission path between one V-UPF and an H-UPF deployed in a home region and the transmission path between a V-UPF and an H-UPF deployed in a visited region.

[0073] FIG. 4 is a diagram illustrating a method for detecting a user plane failure occurrence according to embodiments of the present disclosure.

[0074] 401. The H-SMF may provide an N4 report instruction when performing an N4 association or N4 session management operation with H-UPF#1. The N4 report instruction may include a request for reporting and a detection method in the event of a user plane failure. The H-SMF may instruct the H-UPF to report information about the serving network ID or PLMN ID, DNN, and S-NSSAI in the event of a user plane failure.

[0075] 402. An H-UPF can send an echo request to a UPF with which it has a user plane path. For example, H-UPF #1 can send an echo request to a V-UPF to detect a failure on a user plane path for roaming services.

[0076] 403. A response to an echo request may not be received by H-UPF#1 due to a failure on the H-UPF#1 and V-UPF paths.

[0077] 404. H-UPF#1 can detect a UP path failure event if it does not receive a response to an echo request. H-UPF#1 can perform various actions to determine whether the user plane path failure is partial or whether all paths to the UPF have failed, as follows:

[0078] In option 1,

[0079] 405. H-UPF#1 can request another H-UPF (such as H-UPF#1` in the drawing, H-UPF#1``, a UPF that can be connected to a V-UPF, a UPF connected to a V-UPF, or a UPF deployed in the same data center) to perform a GTP-U echo. When H-UPF#1 requests to perform a GTP-U echo, it can also provide target UPF information (e.g., V-UPF identifier and address information, Tunnel ID).

[0080] 406. An H-UPF (H-UPF#1`, H-UPF#1``, etc.) that has received a GTP-U echo request from H-UPF#1 can perform a GTP-U echo request to V-UPF.

[0081] 407. Responses to echo requests sent by H-UPF#1` and H-UPF#1`` may not be received from V-UPF.

[0082] 408. H-UPF#1` and H-UPF#1`` can transmit the result of not receiving the corresponding echo response to H-UPF#1.

[0083] In the second option,

[0084] 405. H-UPF#1 can send an echo request to V-UPF to perform GTP-U echo for another H-UPF (H-UPF#1` in the drawing, H-UPF#1``, a UPF connectable to V-UPF, a UPF connected to V-UPF, or a UPF deployed in the same data center). The echo request message can include information about H-UPF#1`, H-UPF#1`` (address and identifier, tunnel ID, etc.).

[0085] 406~407. H-UPF#1`, H-UPF#1`` may not receive GTP-U echo requests for V-UPF.

[0086] 408. H-UPF#1` and H-UPF#1`` can send the result of not receiving the corresponding echo response to H-UPF#1.

[0087] In the third option,

[0088] 405. H-UPF#1 can send an N4 report message to H-SMF containing information about user plane path failure occurrence, TE ID (tunnel ID), serving network ID (or VPLMN ID), UPF ID, and UPF group ID.

[0089] 406. H-SMF may send a message to H-UPF#1`, H-UPF#1`` requesting that V-UPF perform user plane fault detection. The request message may include a GTP-U echo request indicator and V-UPF information (identifier and address information, tunnel ID, etc.).

[0090] 407. H-UPF#1` and H-UPF#1`` may transmit the echo request to V-UPF according to the GTP-U echo request. In addition, H-UPF#1` and H-UPF#1`` may not receive a response to the echo request from V-UPF.

[0091] 408. H-UPF#1` and H-UPF#1`` can report to H-SMF the results of non-receipt of response to Echo request. H-UPF#1` and H-UPF#1`` can report to H-SMF the failure on the user plane path with V-UPF.

[0092] For the embodiments of Option 1 and Option 2,

[0093] 409. H-UPF#1 can send an N4 report message to H-SMF containing information about user plane path failure occurrence, TE ID (tunnel ID), serving network ID (or VPLMN ID), UPF ID, and UPF group ID.

[0094] For embodiments of options 1 to 3,

[0095] 410. The H-SMF may perform operations to establish an UP path for a user plane path that has detected a failure through the preceding steps. The H-SMF may perform operations to reset the user plane path for the PDU sessions corresponding to the user plane path that has detected a failure. For example, the H-SMF may perform the procedure described in FIG. 3.

[0096] FIG. 5 is a diagram illustrating the structure of a user equipment (UE) according to embodiments of the present disclosure.

[0097] A terminal according to embodiments of the present disclosure may include a processor (520) that controls the overall operation of the terminal, a transceiver (500) including a transmitter and a receiver, and a memory (510). Of course, the present invention is not limited to the examples, and the terminal may include more or fewer components than those illustrated in FIG. 5. The terminal of FIG. 5 may correspond to the terminals described in FIGS. 1 to 4 .

[0098] According to embodiments of the present disclosure, the transceiver (500) can transmit and receive signals with network entities or other terminals. The signals transmitted and received with the network entities may include control information and data. In addition, the transceiver (500) can receive signals via a wireless channel, output them to the processor (520), and transmit the signals output from the processor (520) via the wireless channel.

[0099] According to embodiments of the present disclosure, the processor (520) can control the terminal to perform any one of the operations described above. Meanwhile, the processor (520), the memory (510), and the transceiver (500) do not necessarily have to be implemented as separate modules, and can of course be implemented as a single component in the form of a single chip. In addition, the processor (520) and the transceiver (500) can be electrically connected. In addition, the processor (520) can be an Application Processor (AP), a Communication Processor (CP), a circuit, an application-specific circuit, or at least one processor.

[0100] According to embodiments of the present disclosure, the memory (510) can store data such as basic programs, application programs, and setting information for the operation of the terminal. In particular, the memory (510) provides the stored data upon request of the processor (520). The memory (510) can be configured as a storage medium or a combination of storage media such as a ROM, a RAM, a hard disk, a CD-ROM, and a DVD. In addition, there can be a plurality of memories (510). In addition, the processor (520) can perform the above-described embodiments based on a program for performing the above-described embodiments of the present disclosure stored in the memory (510).

[0101] FIG. 6 is a diagram illustrating the structure of a network entity according to embodiments of the present disclosure.

[0102] A network entity according to embodiments of the present disclosure may include a processor (620) that controls the overall operation of the network entity, a transceiver (600) including a transmitter and a receiver, and a memory (610). Of course, the present invention is not limited to the example, and the network entity may include more or fewer components than those illustrated in FIG. 6. The base station of FIG. 6 may correspond to the network entities described in FIGS. 1 to 4 (e.g., H-SMF, H-UPF, V-SMF, V-UPF, RAN, etc.).

[0103] According to embodiments of the present disclosure, the transceiver (600) can transmit and receive signals with at least one of other network entities or terminals. The signals transmitted and received with at least one of the other network entities or terminals may include control information and data.

[0104] According to embodiments of the present disclosure, the processor (620) can control a network entity to perform any one of the operations described above. Meanwhile, the processor (620), memory (610), and transceiver (600) do not necessarily have to be implemented as separate modules, and may of course be implemented as a single component in the form of a single chip. Furthermore, the processor (620) and the transceiver (600) may be electrically connected. Furthermore, the processor (620) may be an Application Processor (AP), a Communication Processor (CP), a circuit, an application-specific circuit, or at least one processor.

[0105] According to embodiments of the present disclosure, the memory (610) can store data such as basic programs, application programs, and setting information for the operation of a network entity. In particular, the memory (610) provides the stored data upon request of the processor (620). The memory (610) can be configured as a storage medium or a combination of storage media such as a ROM, a RAM, a hard disk, a CD-ROM, and a DVD. In addition, there can be a plurality of memories (610). In addition, the processor (620) can perform the above-described embodiments based on a program for performing the above-described embodiments of the present disclosure stored in the memory (610).

[0106] It should be noted that the aforementioned configuration diagrams, examples of control / data signal transmission methods, examples of operational procedures, and configuration diagrams are not intended to limit the scope of the present disclosure. That is, not all components, entities, or operations described in the embodiments of the present disclosure should be construed as essential components for implementing the disclosure, and implementations may be made within a scope that does not detract from the essence of the disclosure even if only some components are included. Furthermore, each embodiment may be combined and operated as needed. For example, parts of the methods proposed in the present disclosure may be combined to operate network entities and terminals.

[0107] The operations of the base station or terminal described above can be realized by providing a memory device storing the corresponding program code in any component within the base station or terminal device. That is, the control unit of the base station or terminal device can execute the operations described above by reading and executing the program code stored in the memory device using a processor or CPU (Central Processing Unit).

[0108] The various components and modules of the entity, base station or terminal device described in this specification may be operated using hardware circuits, such as logic circuits based on complementary metal oxide semiconductors, firmware, software and / or hardware and firmware and / or software embedded in a machine-readable medium. For example, various electrical structures and methods may be implemented using electrical circuits such as transistors, logic gates and application-specific semiconductors.

[0109] When implemented in software, a computer-readable storage medium storing one or more programs (software modules) may be provided. The one or more programs stored in the computer-readable storage medium are configured for execution by one or more processors within an electronic device. The one or more programs include instructions that cause the electronic device to execute methods according to embodiments described in the claims or specification of the present disclosure.

[0110] 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.

[0111] Additionally, the program may be stored on an attachable storage device that is accessible via a communication network, such as the Internet, an intranet, a local area network (LAN), a wide local area network (WLAN), a storage area network (SAN), or a combination thereof. Such a storage device may be connected to a device implementing an embodiment of the present disclosure via an external port. Additionally, a separate storage device on the communication network may be connected to a device implementing an embodiment of the present disclosure.

[0112] In the specific embodiments of the present disclosure described above, components included in the disclosure are expressed singularly or plurally, depending on the specific embodiment presented. However, the singular or plural expressions are selected to suit the presented situation for convenience of explanation, and the present disclosure is not limited to singular or plural components. Components expressed in plural may be composed of singular elements, or components expressed in singular may be composed of plural elements.

[0113] While the detailed description of the present disclosure has described specific embodiments, it should be understood that various modifications are possible without departing from the scope of the present disclosure. Therefore, the scope of the present disclosure should not be limited to the described embodiments, but should be determined not only by the scope of the claims described below but also by equivalents thereof. In other words, it will be apparent to those skilled in the art that other modifications based on the technical idea of ​​the present disclosure are possible. In addition, each embodiment can be combined and operated as needed. For example, parts of the methods proposed in the present disclosure can be combined to operate a base station and a terminal. In addition, although the embodiments have been presented based on a 5G, NR system, other modifications based on the technical idea of ​​the embodiments can be implemented in other systems such as LTE, LTE-A, and LTE-A-Pro systems.

[0114] While the detailed description of this disclosure has described specific embodiments, it should be understood that various modifications are possible without departing from the scope of this disclosure. Therefore, the scope of this disclosure should not be limited to the described embodiments, but should be defined not only by the scope of the claims described below, but also by equivalents thereof.

Claims

1. A method performed by a first SMF (session management function) entity belonging to a home public land mobile network (HPLMN) in a wireless communication system, A step of receiving a first message from a first user plane function (UPF) entity belonging to the HPLMN and positioned close to a visited region of a terminal, for notifying a failure of a user plane path between the first UPF and a second UPF entity belonging to a visited public land mobile network (VPLMN) of the visited region; A method comprising the step of transmitting a second message to a second SMF entity belonging to the VPLMN, requesting release of a protocol data unit (PDU) session associated with the user plane path.

2. A method in the first paragraph, wherein the second message includes a cause value indicating a PDU Session Re-establishment request.

3. In paragraph 1, A step of receiving a third message requesting creation of a new PDU session; and A method further comprising the step of selecting a third UPF entity belonging to the HPLMN for establishing a new user plane path based on the third message.

4. In paragraph 3, A method further comprising the step of selecting a domain name system (DNS) server associated with the third UPF entity.

5. A method in the first paragraph, wherein the first message relates to an N4 report message, and the second message includes a PDU session release request message.

6. A method performed by a first UPF (user plane function) entity belonging to a home public land mobile network (HPLMN) in a wireless communication system and located close to a visited region of a terminal, A step of identifying a failure of a user plane path between the first UPF entity and a second UPF entity belonging to a visited public land mobile network (VPLMN) of the visited region of the terminal; and A method comprising the step of transmitting a first message to a first SMF (session management function) entity belonging to the HPLMN to notify a failure of the user plane path.

7. In paragraph 6, A method wherein the first message includes at least one of information for identifying the VPLMN and information for identifying the second UPF entity.

8. In paragraph 6, The above first message relates to the N4 report message, method.

9. In the first SMF (session management function) entity belonging to the HPLMN (home public land mobile network) of the wireless communication system, Transmitter and receiver; and Including a control unit connected to the above transmitter and receiver, The above control unit: Receive a first message from a first user plane function (UPF) entity belonging to the HPLMN and located close to a visited region of a terminal to notify a failure of a user plane path between the first UPF and a second UPF entity belonging to a visited public land mobile network (VPLMN) of the visited region, A first SMF entity configured to transmit a second message to a second SMF entity belonging to said VPLMN, requesting release of a protocol data unit (PDU) session associated with said user plane path.

10. The first SMF entity in paragraph 9, wherein the second message includes a cause value indicating a PDU Session Re-establishment request.

11. In paragraph 9, the control unit: Receive a third message to request creation of a new PDU session, A first SMF entity configured to select a third UPF entity belonging to the HPLMN for establishing a new user plane path based on the third message.

12. In paragraph 9, the control unit: A first SMF entity configured to select a domain name system (DNS) server associated with the third UPF entity.

13. A first SMF entity in paragraph 9, wherein the first message relates to an N4 report message and the second message includes a PDU session release request message.

14. In a first UPF (user plane function) entity belonging to a home public land mobile network (HPLMN) of a wireless communication system and located close to a visited region of a terminal, Transmitter and receiver; and Including a control unit connected to the above transmitter and receiver, The above control unit: Identifying a failure of a user plane path between the first UPF entity and a second UPF entity belonging to a visited public land mobile network (VPLMN) in the visited region of the terminal, and A first UPF entity configured to transmit a first message to a first SMF (session management function) entity belonging to the HPLMN to notify a failure of the user plane path.

15. In paragraph 14, The first message includes at least one of information for identifying the VPLMN and information for identifying the second UPF entity, The first message above is related to the N4 report message, the first UPF entity.

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