Apparatus and method for supporting session continuity in a wireless communication system

Abstract

A method performed by a user equipment (UE) in a wireless communication system is provided. The method includes: sending a registration request message for moving from a second public land mobile network (PLMN) to a first PLMN to an access and mobility function (AMF); receiving a registration acceptance message from the AMF, the registration acceptance message including first single network slice selection assistance information (S-NSSAI) corresponding to the first PLMN of the AMF; determining whether a second S-NSSAI associated with a protocol data unit (PDU) session established for the UE matches the first S-NSSAI, wherein the second S-NSSAI corresponds to the second PLMN; and locally updating the PDU session based on the result of the determination.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application is based on and claims the benefit of priority from Korean Patent Application No. 10-2019-0053245 filed on May 7, 2019, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. Technical Field

[0003] The present disclosure relates to an apparatus and method for supporting session continuity in a wireless communication system. Background Art

[0004] In order to meet the explosive growth in demand for wireless data services due to the commercialization of the fourth generation (4G) communication system, an improved fifth generation (5G) communication system or pre-5G communication system has been developed. For this reason, the 5G communication system or pre-5G communication system is called a super 4G network communication system or a post-long term evolution (LTE) system.

[0005] In order to achieve high data rates, it has been considered to implement 5G communication systems in ultra-high frequency millimeter wave (mmWave) bands (e.g., 60 GHz bands). In order to mitigate the path loss of radio waves in ultra-high frequency bands and increase the transmission distance of radio waves, beamforming, massive multiple input multiple output (MIMO), full dimensional MIMO (FD-MIMO), array antennas, analog beamforming, and massive antenna technology are being discussed for 5G communication systems.

[0006] In addition, in order to improve the system network, in the 5G communication system, technical development has been carried out on technologies such as evolved small cells, advanced small cells, cloud radio access network (RAN), ultra-dense networks, device to device communication (D2D), wireless backhaul, mobile networks, cooperative communication, coordinated multi-points (CoMP), and reception interference cancellation.

[0007] In addition, in 5G systems, hybrid frequency shift keying and quadrature amplitude modulation (FQAM) and sliding window superposition coding (SWSC) as advanced coding modulation (ACM) methods, as well as filter bank multi carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as advanced access technologies are also being developed.

[0008] At the same time, the Internet has evolved from a human-centered connection network where humans create and consume information to an Internet of Things (IoT) network that exchanges and processes various information between distributed components such as things. Internet of Everything (IoE) technology is also emerging, in which big data processing technology such as connection to cloud servers is combined with IoT technology. In order to implement IoT, technical components such as sensing technology, wired / wireless communication, and network infrastructure, service interface technology, and security technology are required. Recently, sensor networks, machine to machine (machine to machine, M2M) communication, machine type communication (machine type communication, MTC), etc. for connection between things are being studied. In the IoT environment, smart Internet technology (Internet technology, IT) services can also be provided, which create new value in human life by collecting and analyzing data generated from connected things. Through the integration and convergence of existing IT technologies with various industries, IoT can be applied to fields such as smart homes, smart buildings, smart cities, smart cars or connected cars, smart grids, health care, smart home appliances, advanced medical services, etc.

[0009] Therefore, various attempts have been made to apply 5G communication systems to IoT networks. For example, technologies such as sensor networks, M2M communications, MTC, etc. are being implemented by 5G communication technologies such as beamforming, MIMO, array antennas, etc. Using cloud RAN as the above-mentioned big data processing technology is an example of the convergence of 5G technology and IoT technology.

[0010] Since various services are provided based on the above description and in accordance with the development of mobile communication systems, a method is needed to effectively provide services for supporting interworking of, in particular, a 5G system (5G system, 5GS) and an evolved packet system (Evolved Packet System, EPS).

[0011] The above information is presented as background information only and to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with respect to the present disclosure. Summary of the invention

[0012] Aspects of the present disclosure are to solve at least the above problems and / or disadvantages, and to provide at least the advantages described below. Therefore, one aspect of the present disclosure is to provide an apparatus and method for supporting session continuity in a wireless communication system.

[0013] Additional aspects will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the embodiments presented in the disclosure.

[0014] According to one aspect of the present disclosure, a method performed by a user equipment (UE) in a wireless communication system is provided. The method includes: sending a registration request message for moving from a second public land mobile network (PLMN) to a first PLMN to an access and mobility function (AMF); receiving a registration acceptance message from the AMF, the registration acceptance message including a first single network slice selection assistance information (S-NSSAI) corresponding to the first PLMN of the AMF; determining whether a second S-NSSAI associated with a protocol data unit (PDU) session established for the UE matches the first S-NSSAI, wherein the second S-NSSAI corresponds to the second PLMN; and locally updating the PDU session based on the determined result.

[0015] According to another aspect of the present disclosure, the first S-NSSAI includes a first slice / service type (SST) of a first PLMN and a first mapped home PLMN (HPLMN) SST, the second S-NSSAI includes a second mapped HPLMN SST, and locally updating the PDU session based on the determined result includes: based on the determined result, locally updating the second S-NSSAI associated with the PDU session to the first S-NSSAI corresponding to the first PLMN of the AMF.

[0016] According to another aspect of the present disclosure, determining whether the second S-NSSAI matches the first S-NSSAI includes determining whether the first mapped HPLMN SST and the second mapped HPLMN SST are the same.

[0017] According to another aspect of the present disclosure, the first S-NSSAI also includes a first slice differentiator (SD) of the first PLMN and a first mapped HPLMN SD, the second S-NSSAI also includes a second mapped HPLMN SD, and determining whether the second S-NSSAI matches the first S-NSSAI also includes: determining whether the first mapped HPLMN SD and the second mapped HPLMN SD are the same.

[0018] According to another aspect of the present disclosure, by locally updating the second S-NSSAI to the first S-NSSAI based on the result of the determination, the PDU session is continuously used and is not released.

[0019] According to another aspect of the present disclosure, a method performed by an AMF in a wireless communication system is provided. The method includes receiving a registration request message for moving from a second PLMN to a first PLMN from a user equipment (UE); and sending a registration acceptance message to the UE, the registration acceptance message including a first S-NSSAI corresponding to the first PLMN of the AMF; wherein, based on determining whether the first S-NSSAI matches a second S-NSSAI associated with a PDU session established for the UE, the second S-NSSAI is locally updated to the first S-NSSAI, and wherein the second S-NSSAI corresponds to the second PLMN.

[0020] According to another aspect of the present disclosure, the first S-NSSAI includes a first SST and a first mapped HPLMNSST of a first PLMN, and the second S-NSSAI includes a second mapped HPLMN SST.

[0021] According to another aspect of the present disclosure, in a case where the first mapped HPLMN SST and the second mapped HPLMN SST are the same, the second S-NSSAI configured for the PDU session is locally updated to the first S-NSSAI.

[0022] According to another aspect of the present disclosure, the first S-NSSAI also includes a first SD and a first mapped HPLMN SD of the first PLMN, wherein the second S-NSSAI also includes a second mapped HPLMN SD, and wherein, when the first mapped HPLMN SD and the second mapped HPLMN SD are the same, the second S-NSSAI configured for the PDU session is locally updated to the first S-NSSAI.

[0023] According to another aspect of the present disclosure, by locally updating the second S-NSSAI to the first S-NSSAI based on the result of the determination, the PDU session is continuously used and is not released.

[0024] According to another aspect of the present disclosure, a user equipment (UE) in a wireless communication system is provided. The UE includes: a transceiver; and at least one processor, which is operably connected to the transceiver and is configured to: send a registration request message for moving from a second public land mobile network (PLMN) to a first PLMN to an AMF by controlling the transceiver; receive a registration acceptance message from the AMF by controlling the transceiver, the registration acceptance message including a first S-NSSAI corresponding to the first PLMN of the AMF; determine whether a second S-NSSAI associated with a PDU session established for the UE matches the first S-NSSAI, wherein the second S-NSSAI corresponds to the second PLMN; and locally update the PDU session based on the result of the determination.

[0025] According to another aspect of the present disclosure, an AMF in a wireless communication system is provided. The AMF includes: a transceiver; and at least one processor, which is operably connected to the transceiver and is configured to: receive a registration request message for moving from a second public land mobile network (PLMN) to a first PLMN from a UE by controlling the transceiver, and send a registration acceptance message to the UE by controlling the transceiver, wherein the registration acceptance message includes a first S-NSSAI corresponding to the first PLMN of the AMF; wherein, based on determining whether the first S-NSSAI matches the second S-NSSAI associated with the PDU session established for the UE, the second S-NSSAI is locally updated to the first S-NSSAI, and wherein the second S-NSSAI corresponds to the second PLMN.

[0026] Other aspects, advantages, and salient features of the present disclosure will become apparent to those skilled in the art from the following detailed description, which, in conjunction with the accompanying drawings, discloses various embodiments of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The above and other aspects, features and advantages of certain embodiments of the present disclosure will become more apparent from the following description in conjunction with the accompanying drawings, in which:

[0028] Figure 1 An interworking architecture between a 5G system (5GS) and an evolved packet system (EPS) in a non-roaming scenario according to an embodiment of the present disclosure is shown;

[0029] Figure 2 An interworking architecture between 5GS and EPS in a local breakout roaming scenario according to an embodiment of the present disclosure is shown;

[0030] Figure 3An interworking architecture between 5GS and EPS in a home-routed roaming scenario according to an embodiment of the present disclosure is shown;

[0031] Figure 4 An example of information received by a user equipment (UE) from a source public land mobile network (PLMN) and information received by the UE from a target PLMN according to an embodiment of the present disclosure is shown;

[0032] Figure 5A A handover process from a source PLMN to a target PLMN performed by a UE according to an embodiment of the present disclosure is shown;

[0033] Figure 5B A handover process from a source PLMN to a target PLMN performed by a UE according to an embodiment of the present disclosure is shown;

[0034] Figure 6 A process of registering with a target PLMN when a UE moves from a source PLMN to a target PLMN according to an embodiment of the present disclosure is shown;

[0035] Figure 7 A PDU session modification procedure is shown according to an embodiment of the present disclosure, which enables a UE to continuously use a Protocol Data Unit (PDU) session in a target PLMN after having moved from a source PLMN to the target PLMN;

[0036] Figure 8 A UE configuration update procedure for a UE to continuously use a PDU session in a target PLMN after having moved from a source PLMN to the target PLMN according to an embodiment of the present disclosure is shown;

[0037] Fig. 9 A method for providing session continuity for a UE according to an embodiment of the present disclosure is shown;

[0038] Fig.10 shows the configuration of a UE according to an embodiment of the present disclosure; and

[0039] Fig.11 The configuration of the network entity according to an embodiment of the present disclosure is shown.

[0040] Throughout the drawings, like reference numerals will be understood to refer to like parts, components and structures. DETAILED DESCRIPTION

[0041] The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of the various embodiments of the present disclosure as defined by the claims and their equivalents. It includes various specific details to assist in understanding, but these are merely exemplary. Therefore, it will be appreciated by those of ordinary skill in the art that various changes and modifications may be made to the various embodiments described herein without departing from the scope and spirit of the present disclosure. In addition, descriptions of well-known functions and configurations may be omitted for clarity and conciseness.

[0042] The terms used in the following description and claims are not limited to the bibliographical meanings, but are merely used to enable a clear and consistent understanding of the present disclosure. Therefore, it will be apparent to those skilled in the art that the following description of various embodiments of the present disclosure is provided for illustrative purposes only and is not intended to limit the present disclosure as defined by the appended claims and their equivalents.

[0043] It is to be understood that the singular forms "a", "an", and "the" include plural references unless the context clearly dictates otherwise. Thus, for example, reference to a "component surface" includes reference to one or more such surfaces. Unless otherwise defined, all terms used herein (including technical or scientific terms) have the same meanings as those commonly understood by a person of ordinary skill in the art to which the present disclosure belongs. Terms such as those defined in commonly used dictionaries are interpreted as having meanings that match the meanings in the context of the relevant technology, and are not interpreted as ideal or overly formal unless clearly defined otherwise. In some cases, even terms defined in the present disclosure cannot be interpreted as excluding embodiments of the present disclosure.

[0044] In various embodiments of the present disclosure described below, a hardware-based access method is described as an example. However, since various embodiments of the present disclosure include techniques using both hardware and software, various embodiments of the present disclosure do not exclude a software-based access method.

[0045] In the following description, when a detailed description of a related well-known function or structure is determined to make the present disclosure unclear, the detailed description will be omitted. Taking into account the functions in the present disclosure, the terms used in the present disclosure have been selected from common terms that are currently widely used. However, these terms may change according to the intentions of ordinary technicians in the field, case precedents, and with the emergence of new technologies. Therefore, the terms used in the present disclosure are defined based on their meaning relative to the content discussed in the entire specification, rather than being defined by their simple meanings.

[0046] In addition, for ease of explanation and clarity, each element shown in the drawings may be enlarged, omitted, or schematically shown. The size of each element shown does not reflect its actual size substantially. In each of the accompanying drawings, the same or corresponding elements are represented by the same reference numerals.

[0047] Reference will be made to the embodiments described in detail in conjunction with the accompanying drawings to illustrate the advantages and features of the present disclosure and the methods for achieving them. However, the present disclosure can be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. On the contrary, these embodiments are provided to make the present disclosure thorough and complete and to fully convey the scope of the present disclosure to those of ordinary skill in the art. Throughout the accompanying drawings, the same reference numerals represent the same elements.

[0048] Throughout the disclosure, the expression "at least one of a, b, or c" indicates: only a, only b, only c, both a and b, both a and c, both b and c, all of a, b, and c, or variations thereof.

[0049] Examples of the terminal may include a user equipment (UE), a mobile station (MS), a cellular phone, a smart phone, a computer, a multimedia system capable of performing a communication function, and the like.

[0050] In this disclosure, a controller may also be referred to as a processor or at least one processor.

[0051] Throughout the specification, a layer (or a layer arrangement) may also be referred to as an entity.

[0052] It will be understood that the blocks and combinations of flowcharts can be performed by computer program instructions. Because these computer program instructions can be loaded into a processor of a general-purpose computer, a special-purpose computer, or another programmable data processing device, the instructions executed by the processor of the computer or another programmable data processing device create units for performing the functions described in (one or more) flowchart blocks. Computer program instructions can be stored in a computer-usable or computer-readable memory, which can instruct a computer or another programmable data processing device to implement functions in a specific manner, so the instructions stored in the computer-usable or computer-readable memory can also produce a manufacturing item containing instruction units for performing the functions described in (one or more) flowchart blocks. Computer program instructions can also be loaded into a computer or another programmable data processing device, and therefore, when a series of operations are performed in a computer or other programmable data processing device, the instructions for operating the computer or other programmable data processing device by generating a computer-executed process can provide operations for performing the functions described in (one or more) flowchart blocks.

[0053] In addition, each block can represent a module, segment, or a part of code including one or more executable instructions for performing (one or more) specified logical functions. It should also be noted that in some embodiments, the functions mentioned in the block may occur out of order. For example, according to the corresponding function, the two blocks shown in succession can actually be performed substantially simultaneously, or these blocks can sometimes be performed in reverse order.

[0054] As used herein, the term "unit" refers to a software component or a hardware component, such as a field-programmable gate array (FPGA) or an application-specific integrated circuit (ASIC), and performs a specific function. However, the term "unit" is not limited to software or hardware. A "unit" can be formed in an addressable storage medium, or can be formed to operate one or more processors. Therefore, for example, the term "unit" can refer to components such as software components, object-oriented software components, class components, and task components, and can include processes, functions, attributes, procedures, subroutines, program code segments, drivers, firmware, microcodes, circuits, data, databases, data structures, tables, arrays, or variables. The functions provided by components and "units" can be associated with a smaller number of components and "units", or can be divided into additional components and "units". In addition, components and "units" can be embodied as reproducing one or more central processing units (CPUs) in a device or a secure multimedia card. As used herein, a "unit" can include at least one processor.

[0055] Hereinafter, the present disclosure relates to an apparatus and method for providing network slicing in a wireless communication system. In detail, the present disclosure describes a technology for providing session mobility in a mobile communication network system that provides a network slicing function in a wireless communication system.

[0056] Hereinafter, in the description, for the convenience of description, terms for identifying nodes, terms referring to signals, terms referring to channels, terms referring to control information, terms referring to network entities, terms referring to device components, terms referring to messages, terms referring to interfaces between network entities, terms referring to various identification information, etc. are exemplified. Therefore, the present disclosure is not limited to the terms mentioned below, and other terms having the same technical meanings may also be used therefor.

[0057] In addition, although the present disclosure describes various embodiments by using terms used in some communication protocols (e.g., the 3rd Generation Partnership Project (3GPP)), this is only for convenience of explanation. By being easily modified, various embodiments of the present disclosure can be applied to other communication systems.

[0058] As a future communication system after long term evolution (LTE), the 5G communication system supports services that meet various needs at the same time because the various needs of users and service providers are freely reflected. Services considered for the 5G communication system include enhanced mobile broadband (eMBB), massive machine-type communication (mMTC), and ultra-reliability and low-latency communication (URLLC).

[0059] According to an embodiment, eMBB may have the goal of providing an enhanced data rate faster than the data rate supported by the existing LTE, advanced LTE (LTE-A), or LTE-A pro (LTE-Pro). For example, in a 5G communication system, considering one base station, eMBB can provide a peak data rate of about 20Gbps for the downlink and a peak data rate of about 10Gbps for the uplink. In addition, the 5G communication system can provide a peak data rate and a simultaneously increased user-perceived UE data rate. In order to meet the requirements, various transmission / reception technologies may be required to be improved in the 5G communication system, including enhanced multiple-input multiple-output (MIMO) transmission technology. In addition, although the current LTE uses a maximum 20MHz transmission bandwidth in the 2Ghz band to transmit signals, in the 5G communication system, a frequency bandwidth of 20MHz or more is used in a frequency band of 3 to 6Ghz or 6Ghz or more, so that the data rate required in the 5G communication system can be met.

[0060] Meanwhile, in the 5G communication system, mMTC is considered to support application services such as the Internet of Things (IoT). In order to effectively provide IoT, mMTC may be required to support access to a large number of UEs within a cell, improve UE coverage, improve battery life, and reduce UE costs. IoT, which is attached to various sensors and various devices and provides communication functions, can support a large number of UEs in a cell, for example, 1,000,000 UEs / km 2. In addition, because the UE supporting mMTC is likely to be located in a shadow area that cannot be covered by a cell (such as a basement of a building), due to the characteristics of the service, a wider coverage may be required compared to other services provided in the 5G communication system. The UE supporting mMTC is configured with a low-cost UE, and since it is difficult to frequently replace the battery of the UE, a battery life time such as 10 to 15 years may be required.

[0061] Finally, URLLC, as a cellular-based wireless communication service for specific purposes (mission-critical), can be used for services such as remote control of robots or machinery, industrial automation, unmanned aerial vehicles, remote health care, emergency alerts, etc. Therefore, the communication provided by URLLC can have very low latency (ultra-low latency) and very high reliability (ultra-reliability). For example, a service supporting URLLC can meet an air interface latency of less than 0.5 milliseconds and have a 10 -5 Therefore, for services supporting URLLC, the 5G system may be required to provide a smaller transmission time interval (TTI) than other services, and at the same time allocate wide resources in the frequency band to ensure the reliability of the communication link.

[0062] The three services considered in the above-mentioned 5G communication system, namely eMBB, URLLC and mMTC, can be multiplexed and transmitted in one system. At this time, in order to meet the different requirements of various services, different transmission / reception technologies and transmission / reception parameters can be used between services. However, the above-mentioned mMTC, URLLC and eMBB are only examples of different service types, and the service types to which the present disclosure is applied are not limited to the above-mentioned examples.

[0063] In addition, in the following description, the embodiments of the present disclosure are described by taking LTE, LTE-A, LTE Pro, or 5G (or next generation mobile communication (NR)) systems as examples, but the embodiments of the present disclosure may also be applied to other communication systems with similar technical backgrounds or channel types. Furthermore, based on the determination of those skilled in the art, the embodiments of the present disclosure may be applied to other communication systems through some modifications thereof without departing from the scope of the present disclosure.

[0064] In the 3GPP standard, the 5G network system architecture and process are standardized. Mobile communication operators can provide various services in the 5G network. In order to provide each service, mobile communication operators need to meet the different service requirements of each service, such as latency, communication range, data rate, bandwidth, reliability, etc. To this end, mobile communication operators can configure network slices and allocate network resources suitable for specific services to each network slice or each group of network slices. Network resources can refer to the radio resource allocation of a base station or NF (network function) or logical resources provided by NF.

[0065] For example, a mobile communication operator may configure network slice A to provide mobile broadband services, configure network slice B to provide vehicle communication services, and configure network slice C to provide IoT services. That is, in a 5G network, corresponding services may be provided on network slices dedicated to the characteristics of each service. The single-network slice selection assistance information (S-NSSAI) defined in 3GPP may be used as a differentiator to distinguish (or identify) network slices. An S-NSSAI may be configured with an SST used in a home public land mobile network (PLMN) (HPLMN), an SD used in the HPLMN, an SST used in a visited PLMN (VPLMN), and an SD used in a VPLMN. Depending on the situation, each SST and SD constituting an S-NSSAI may or may not have a value.

[0066] Mobile communication operators can operate 5G networks and evolved packet systems (EPS) (or LTE) networks together. Mobile communication UEs can access the 5G network to use services and then move to the EPS network. Alternatively, mobile communication UEs can access the EPS network to use services and then move to the 5G network.

[0067] In the present disclosure, an intercommunication method between a 5G network system architecture and an EPS network system for providing a network slicing function is defined. Figure 1 , Figure 2 and Figure 3 The interworking architecture between the 5G system (5GS) and the EPS system is shown. The terms N1, N2, etc. shown around the line connecting each entity refer to the communication interface.

[0068] In addition, network operation and UE operation are defined so that UEs that use communication services by establishing a session connection in EPS can seamlessly use the services even when moving to 5GS.

[0069] Figure 1 An interworking architecture between 5GS and EPS in a non-roaming scenario according to an embodiment of the present disclosure is shown.

[0070] refer to Figure 1 , 5GS may include NR base stations such as the next generation radio access network (NG-RAN) 150, access and mobility management function (AMF) 145, session management function (SMF) 120, user plane function (UPF) 125, policy control function (PCF) 115, and unified data management (UDM) 110. EPS may include E-UTRA base stations (E-UTRAN) 140, mobility management entity (MME) 135, serving gateway (SGW) 130, packet gateway-user plane (PGW-U) 125, packet gateway-control plane (PGW-C) 120, policy and charging rules function (PCRF) 115, and home subscriber server (HSS) 110.

[0071] The UDM 110 of 5GS and the HSS 110 of EPS can be provided as a combined node. The SMF 120 of 5GS and the PGW-C 120 of EPS can also be provided as a combined node. The node of UDM+HSS 110 can store the subscriber information of the UE. The UPF 125 of 5GS and the PGW 125 of EPS can be provided as a combined node. The UE 155 can access the MME 135 of EPS via the E-UTRA base station 140 and use the EPS network services. In addition, the UE 155 can access the AMF 145 of 5GS via the NR base station 150 and use the 5GS network services.

[0072] Figure 2 An interworking architecture between 5GS and EPS in a local grooming roaming scenario according to an embodiment of the present disclosure is shown.

[0073] refer to Figure 2 , UE 260 can access MME 240 of EPS via E-UTRA base station 245 and use EPS network services. In addition, UE 260 can access AMF 250 of 5GS via NR base station 255 and use 5GS network services. In the interworking architecture between 5GS and EPS in local grooming roaming, the node of SMF+PGW-C 225 can be located in the VPLMN. Figure 2 It is divided into HPLMN and VPLMN. Figure 2 middle, Figure 1 The PCF+PCRF 115 in the HPLMN is divided into h-PCF+h-PCRF 215 in the HPLMN and v-PCF+v-PCRF 220 in the VPLMN. The remaining features 210, 225, 230 and 235 correspond to Figure 1 features, and therefore, further description is omitted.

[0074] Figure 3 An interworking architecture between 5GS and EPS in a home routing roaming scenario according to an embodiment of the present disclosure is shown.

[0075] refer to Figure 3 , UE 370 can access MME 335 of EPS via E-UTRA base station (E-UTRAN) 340 and use EPS network services. In addition, UE 370 can access AMF 360 of 5GS via NR base station 365 and use 5GS network services. In the interworking architecture between 5GS and EPS in home routing roaming, the node of SMF+PGW-C 320 can be located in the HPLMN. Figure 3 It is divided into HPLMN and VPLMN. Figure 3 middle, Figure 1 The PCF+PCRF 115 is divided into h-PCF+h-PCRF 315 in the HPLMN and v-PCF 345 in the VPLMN. The v-SMF 350 and UPF are in the VPLMN. The remaining features 310, 325 and 330 correspond to Figure 1 features, and therefore, further description is omitted.

[0076] The mobile communication system according to the embodiment of the present disclosure can support interworking between 5GS and EPS. For example, a UE that accesses the EPS system and generates a public data network or packet data network (PDN) connection (PDN connection) can move or switch to 5GS and continuously use the PDN connection generated in EPS in 5GS as a protocol data unit (PDU) session.

[0077] Specifically, the SMF+PGW-C 120, 225 or 320 that receives the PDN connectivity request message sent by the UE that has accessed the EPS can select the S-NSSAI for the PDN connection requested by the UE. The SMF+PGW-C 120, 225 or 320 can send the selected S-NSSAI information to the UE by including it as a protocol configuration option (PCO) in the PDN connectivity response message sent to the UE. The UE that has received the PDN connectivity response message establishes a PDN connection in the EPS and uses the service. After moving to the 5GS, by using the S-NSSAI in the form of PCO received from the SMF+PGW-C 120, 225 or 320 of the EPS, the UE can continuously use the PDN connection generated in the EPS as a PDU session in the 5GS. In the above embodiment, the EPS can be referred to as the source PLMN, and the 5GS can be referred to as the target PLMN.

[0078] In addition, the 5G mobile communication system can support inter-PLMN mobility. For example, a UE that has registered with PLMN A and generated a PDU session can switch to PLMN B and continue to use the PDU session.

[0079] Specifically, a UE that has accessed the 5GS system of PLMN A can determine the S-NSSAI to be used in the PDU session based on the UE route selection policy (URSP) information stored in the UE to establish the PDU session. The UE can send a PDU session establishment request message including the selected S-NSSAI to SMF 120. The SMF 120 that has received the PDU session establishment request message can store the S-NSSAI included in the request message and send a PDU session establishment response to the UE. The UE that has received the PDU session establishment response message can establish a PDU session in the 5GS of PLMN A and use the service. After moving to the 5GS of PLMN B, the UE can continuously use the PDU session generated in the 5GS of PLMN A in the 5GS of PLMN B. By continuously using the PDU session, when the UE moves from the source PLMN to the target PLMN, the process of releasing the established PDU session can be omitted. In addition, by continuously using the PDU session, when the UE moves from the source PLMN to the target PLMN, the process of establishing a new PDU session different from the established PDU session may not be performed. That is, by updating the context of the established PDU session (e.g., S-NSSAI update) according to an embodiment of the present disclosure, when the UE moves from the source PLMN to the target PLMN, the PDU session release and / or establishment process may be omitted. In the above embodiment, the 5GS of PLMN A may be referred to as the source PLMN, and the 5GS of PLMN B may be referred to as the target PLMN.

[0080] Figure 4 An example of information received by the UE from a source PLMN and information received by the UE from a target PLMN according to an embodiment of the present disclosure is shown.

[0081] refer to Figure 4 , the UE may store the S-NSSAI information of the PDN connection or PDU session generated from the source PLMN. The UE may store the S-NSSAI as context information of the PDN connection or PDU session. The S-NSSAI may include at least one of the values ​​of the SST 400 used in the HPLMN, the SD 401 used in the HPLMN, the SST 405 used in the VPLMN, or the SD 406 used in the VPLMN. When the UE generates a PDN connection in the EPC, the S-NSSAI may be S-NSSAI information in the form of a PCO received from the SMF+PGW-C 120, 225, or 320. Alternatively, when the UE generates a PDU session in the 5GS, the S-NSSAI may be S-NSSAI information selected by the UE based on the URSP stored in the UE.

[0082] After moving to the target PLMN, by using Figures 5A to 8 According to the process shown in , the UE can receive S-NSSAI from the target PLMN to continuously move from the PDN connection to the PDU session. The S-NSSAI received by the UE from the target PLMN may include at least one of the values ​​of SST 410 used in the HPLMN, SD 411 used in the HPLMN, SST 415 used in the VPLMN, or SD 416 used in the VPLMN.

[0083] The UE may store the S-NSSAI information received from the target PLMN and update the context of the PDU session stored in the UE. For example, the UE may change the SST 400 used in the HPLMN to the SST 410 used in the HPLMN received from the target PLMN. In addition, the UE may change the SD 401 used in the HPLMN to the SD 411 used in the HPLMN received from the target PLMN. Further, the UE may change the SST 405 used in the VPLMN to the SST 415 used in the VPLMN received from the target PLMN. Further, the UE may change the SD 406 used in the VPLMN to the SD 416 used in the VPLMN received from the target PLMN. When the UE does not receive at least one piece of information about SST 410 used in the HPLMN, SD 411 used in the HPLMN, SST 415 used in the VPLMN, or SD 416 used in the VPLMN from the target PLMN, the UE may use at least one piece of information about SST 400 used in the HPLMN, SD 401 used in the HPLMN, SST 405 used in the VPLMN, or SD 406 used in the VPLMN (which are stored as the context of the PDU session in the source PLMN) without change, or may configure the field of the information not received from the target PLMN to be empty.

[0084] Figure 5A and Figure 5B A handover process from a source PLMN to a target PLMN performed by a UE according to various embodiments of the present disclosure is illustrated.

[0085] refer to Figure 5AIn operation 7, the Nsmf_PDUSession_UpdateSMContext response (Nsmf_PDUSession_UpdateSMContext Response) message sent by the SMF 510 to the target-AMF (T-AMF) 505 may include the S-NSSAI information for the PDU session. The S-NSSAI information may include at least one piece of information about the SST 410 used in the HPLMN, the SD 411 used in the HPLMN, the SST 415 used in the VPLMN, or the SD 416 used in the VPLMN. The T-AMF 505 that receives the S-NSSAI information for the PDU session from the SMF 510 may store the received S-NSSAI information and / or the PDU session information related to the S-NSSAI information.

[0086] The Namf_Communication_CreateUEContext response (Namf_Communication_CreateUEContextResponse) message sent by the T-AMF 505 to the source-AMF (source-AMF, S-AMF) 503 in operation 12 may include the S-NSSAI and / or PDU session information received by the T-AMF 505 from the SMF 510 in operation 7. The S-AMF 503 that receives the S-NSSAI information for the PDU session from the T-AMF 505 may store the received S-NSSAI information and / or the PDU session information related to the S-NSSAI information.

[0087] refer to Figure 5B In operation 1 and operation 2, the handover command (Handover Command) message sent by the S-AMF 503 to the UE 501 via the source-NG-RAN (S-NG-RAN) 502 may include the S-AMF 503 Figure 5A The process shown in FIG. 5A receives the S-NSSAI and / or PDU session information from the T-AMF 505. The UE 501 that receives the S-NSSAI information for the PDU session from the S-AMF 503 may store the received S-NSSAI information and / or the PDU session information related to the S-NSSAI information and update the related PDU session context. Figure 5A Operations 1, 2, 3, 4, 5, 6a, 6b, 6c, 6d, 8, 9, 10, 11a, 11b, 11c, 11d, 11e and 11f are described, and further description is omitted. Figure 5BOperations 2a, 2b, 2c, 3a, 3b, 4, 5, 6a, 6b, 6c, 7, 8a, 8b, 9a, 9b, 10a, 10b, 11, 12, 13a, 13b, 14a, 14b, 15a and 15b are described below and any further description is omitted.

[0088] Figure 6 A process of registering with a target PLMN when a UE moves from a source PLMN to a target PLMN according to an embodiment of the present disclosure is shown.

[0089] refer to Figure 6 , the UE 601 may send a registration request message to the new AMF 603 in operations 1-3. The UE 601 may send a registration request message for moving from a source PLMN to a target PLMN to the new AMF 603. The UE 601 may send the registration request message to the new AMF 603 via the (R)AN. The Nsmf_PDUSession_UpdateSMContext to Nsmf_PDUSession_ReleaseSMContext message sent by the SMF 606 to the new AMF 603 relative to the old AMF 604 in operation 17 may include S-NSSAI information for the PDU session. The S-NSSAI information may include at least one piece of information about the SST 410 used in the HPLMN, the SD 411 used in the HPLMN, the SST 415 used in the VPLMN, or the SD 416 used in the VPLMN. The new AMF 603 that receives the S-NSSAI information for the PDU session from the SMF 606 may store the received S-NSSAI information and / or the PDU session information related to the S-NSSAI information. The PCF 605, the authentication server function (AUSF) 607, and the UDM 608 are shown, but are not further described.

[0090] In operation 21, the RegistrationAccept message sent by the new AMF 603 to the UE 601 via the (R)AN 602 may include the S-NSSAI and / or PDU session information received by the new AMF 603 from the SMF 606. The UE 601 that receives the S-NSSAI information for the PDU session from the new AMF 603 may store the received S-NSSAI information and / or the PDU session information related to the S-NSSAI information, and locally update the related PDU session context. For example, the UE 601 may determine whether the S-NSSAI associated with the PDU session established for the UE 601 but not yet updated matches the received S-NSSAI for the PDU session received from the AMF 603, and may update the established PDU session based on the result of the determination. As shown in the figure, the description is given. Figure 6 Operations 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14a, 14b, 14c, 14d, 14e, 15, 16, 18, 19, 19a, 19b, 19c, 21, 21b, 22, 23 and 24 of the present invention are described below, and further description is omitted.

[0091] Figure 7 A PDU session modification procedure according to an embodiment of the present disclosure is shown, which enables a UE to continuously use a PDU session in a target PLMN after having moved from a source PLMN to the target PLMN.

[0092] refer to Figure 7 , the Nsmf_PDUSession_UpdateSMContext message in operation 3a, the Namf_Communication_N1N2MessageTransfer message in operation 3b, and the Nsmf_PDUSessionSMContextStatusNotify message in operation 3c (sent by SMF 704 to AMF 703) may include S-NSSAI information for the PDU session. The S-NSSAI information may include at least one piece of information about the SST 410 used in the HPLMN, the SD 411 used in the HPLMN, the SST 415 used in the VPLMN, or the SD 416 used in the VPLMN. The AMF 703, which receives the S-NSSAI information for the PDU session from the SMF 704, may store the received S-NSSAI information and / or the PDU session information related to the S-NSSAI information. The PCF 707, the UDM 706, and the UPF 705 are shown, but are not further described.

[0093] The N2SessionRequest message in operation 4 and the AN-specific resource modification message in operation 5 sent by the AMF 703 to the UE 701 via the RAN 702 may include the S-NSSAI and / or PDU session information received by the AMF 703 from the SMF 704. The UE 701 that receives the S-NSSAI information for the PDU session from the AMF 703 may store the received S-NSSAI information and / or the PDU session information related to the S-NSSAI information, and update the related PDU session context. As shown in FIG. Figure 7 Operations 1, 1a, 1b, 1c, 1d, 1e, 1f, 2, 2a, 2b, 6, 7a, 7b, 8a, 8b, 9, 10, 11a, 11b, 12a, 12b and 13 are described below and any further description is omitted.

[0094] Figure 8 A UE configuration update procedure for a UE to continuously use a PDU session in a target PLMN after having moved from a source PLMN to the target PLMN according to an embodiment of the present disclosure is shown.

[0095] refer to Figure 8 , in operation 0, SMF 804 may trigger a UE configuration update procedure to AMF 803. SMF 804 may send S-NSSAI information and / or PDU session information for a PDU session to AMF 803. S-NSSAI may include at least one piece of information about SST 410 used in HPLMN, SD 411 used in HPLMN, SST 415 used in VPLMN, or SD416 used in VPLMN. AMF 803, which receives the S-NSSAI information for the PDU session from SMF 804, may store the received S-NSSAI information and / or PDU session information related to the S-NSSAI information. UDM 805 is shown, but is not further described.

[0096] In operation 1, the UE Configuration Update Command message sent by the AMF 803 to the UE 801 via the (R) AN 802 may include the S-NSSAI and / or PDU session information received by the AMF 803 from the SMF 804. The UE 801 that receives the S-NSSAI information for the PDU session from the AMF 803 may store the received S-NSSAI information and / or the PDU session information related to the S-NSSAI information, and update the related PDU session context. As shown in FIG. Figure 8 Operations 2a, 2b, 2c, 2d, 3a, 3b, 3c and 4 are described below and any further description is omitted.

[0097] According to the embodiment of the present disclosure, the UE can Figure 6 The process shown in Figure 6 A Registration Accept message is received in operation 21. The Registration Accept message may include mapping information of allowed NSSAI and / or allowed NSSAI that the UE can use in the corresponding PLMN. The allowed NSSAI may include one or more S-NSSAI that the UE can use in the PLMN and provided by the serving PLMN. The mapping of allowed S-NSSAI may include one or more S-NSSAI that the UE can use in the PLMN and provided by the serving PLMN, and S-NSSAI information of the HPLMN mapped to each S-NSSAI. An example of mapping allowed NSSAI and allowed NSSAI is given below.

[0098] {(HPLMN SST-A; HPLMN SD-A), (VPLMN SST-E, VPLMN SD-E)},

[0099] {(HPLMN SST-C; HPLMN SD-C), (VPLMN SST-D, VPLMN SD-D)},

[0100] {(HPLMN SST-F; HPLMN SD-F), (VPLMN SST-G, VPLMN SD-G)}

[0101] In the detailed description of the above example, the UE can access the serving PLMN and use three slices provided by the serving PLMN, namely, (VPLMN SST-E, VPLMN SD-E), (VPLMN SST-D, VPLMN SD-D), and (VPLMN SST-G, VPLMN SD-G). The slices of each VPLMN can be mapped to (HPLMN SST-A, HPLMN SD-A), (HPLMN SST-C, HPLMN SD-C), and (HPLMN SST-F, HPLMN SD-F).

[0102] A UE that has received the mapping of allowed NSSAI and allowed NSSAI may Figure 4 The information in the source PLMN is compared with the above-mentioned mapping information of allowed NSSAI and allowed NSSAI, and the available slice information for the PDU session in the target PLMN is generated. For example, refer to Figure 4 , the UE may store the SST 400 used in the HPLMN and / or the SD 401 used in the HPLMN and store the SST 400 used in the HPLMN with the SD 401 used in the HPLMN. Figure 6 The SST value used in the HPLMN and / or the SD value used in the HPLMN received in operation 21 are compared. For example, {(HPLMN SST-A, HPLMN SD-A), (VPLMN SST-E, VPLMN SD-E)} as the values ​​of the allowed NSSAI may be determined, which include the HPLMN SST-A and the HPLMN SD-A which are the values ​​of the SST 400 used in the HPLMN and the values ​​of the SD 401 used in the HPLMN, respectively, stored in the UE. The UE may determine the values ​​of the VPLMN S-NSSAI (i.e., VPLMN SST-E and VPLMN SD-E) of the HPLMN S-NSSAI mapped to the above-mentioned allowed NSSAI as the values ​​of the SST 415 used in the target PLMN and the SD 416 used in the target PLMN, and update the relevant PDU session context. The updating of the relevant PDU session context may mean determining the values ​​of the VPLMN S-NSSAI mapped to the HPLMN S-NSSAI of the above-mentioned allowed NSSAI, i.e., VPLMN SST-E and VPLMN SD-E, as the values ​​of SST 415 used in the target PLMN and SD 416 used in the target PLMN.

[0103] Fig. 9 A method for UE to provide session continuity according to an embodiment of the present disclosure is shown.

[0104] refer to Fig. 9, in operation 910, the UE may send a registration request message for moving from a second public land mobile network (PLMN) to a first PLMN to an access and mobility function (AMF).

[0105] In operation 920, the UE may receive a registration accept message including first single network slice selection assistance information (S-NSSAI) corresponding to a first PLMN of the AMF from the AMF.

[0106] In operation 930, the UE may compare a second S-NSSAI associated with a protocol data unit (PDU) session established for the UE with the first S-NSSAI, wherein the second S-NSSAI corresponds to the second PLMN.

[0107] In operation 940 , the UE may locally update the PDU session based on the comparison result.

[0108] Fig.10 The configuration of a UE according to an embodiment of the present disclosure is shown.

[0109] refer to Fig.10 , the UE of the present disclosure may include a transceiver 1010, a memory 1020, and a processor 1030. The processor 1030, the transceiver 1010, and the memory 1020 of the UE may operate according to the above-mentioned communication method of the UE. However, the constituent elements of the UE are not limited to the above description. For example, the UE may include more or fewer constituent elements than the above-mentioned constituent elements. In addition, the processor 1030, the transceiver 1010, and the memory 1020 may be implemented in the form of a chip. In addition, the processor 1030 may include at least one processor.

[0110] The transceiver 1010 (collectively referring to the receiver of the UE and the transmitter of the UE) can transmit and receive signals with the base station. The signals transmitted and received with the base station may include control information and data. To this end, the transceiver 1010 may include an RF transmitter for up-converting and amplifying the frequency of the transmitted signal and an RF receiver for low-noise amplifying the received signal and down-converting its frequency. However, this is only one embodiment of the transceiver 1010, and the components of the transceiver 1010 are not limited to the RF transmitter and the RF receiver.

[0111] In addition, the transceiver 1010 may receive a signal through a wireless channel and output the signal to the processor 1030 , and transmit a signal output from the processor 1030 through a wireless channel.

[0112] The memory 1020 may store programs and data required for the UE to operate. In addition, the memory 1020 may store control information or data included in a signal obtained by the UE. The memory 1020 may include a storage medium such as a ROM, a RAM, a hard disk, a CD-ROM, and a DVD, or a combination thereof.

[0113] The processor 1030 may control a series of processes so that the UE operates according to the above-mentioned embodiments of the present disclosure. For example, the processor 1030 may receive a control signal and a data signal through the transceiver 1010 and process the received control signal and data signal. In addition, the processor 1030 may send the processed control signal and data signal to the transceiver 1010.

[0114] Fig.11 The configuration of the network entity according to an embodiment of the present disclosure is shown.

[0115] like Fig.11 As shown in , the network entity of the present disclosure may include a transceiver 1110, a memory 1120, and a processor 1130. The processor 1130, the transceiver 1110, and the memory 1120 of the network entity may operate according to the above-mentioned communication method of the network entity. However, the constituent elements of the network entity are not limited to the above description. For example, the network entity may include more or fewer constituent elements than the above-mentioned constituent elements. In addition, the processor 1130, the transceiver 1110, and the memory 1120 may be implemented in the form of one chip. In addition, the processor 1130 may include at least one processor. The various network entities described in the present disclosure (e.g., AMF, SMF, base station, etc.) may correspond to Fig.11 network entity.

[0116] The transceiver 1110 (collectively referring to the receiver of the network entity and the transmitter of the network entity) can transmit and receive signals with the base station. The signals transmitted and received with the base station may include control information and data. To this end, the transceiver 1110 may include an RF transmitter for up-converting and amplifying the frequency of the transmitted signal and an RF receiver for low-noise amplifying the received signal and down-converting its frequency. However, this is only one embodiment of the transceiver 1110, and the components of the transceiver 1110 are not limited to the RF transmitter and the RF receiver.

[0117] In addition, the transceiver 1110 may receive a signal through a wireless channel and output the signal to the processor 1130 , and transmit a signal output from the processor 1130 through a wireless channel.

[0118] The memory 1120 may store programs and data required for the operation of the network entity. In addition, the memory 1120 may store control information or data included in a signal obtained by the network entity. The memory 1120 may include a storage medium such as a ROM, a RAM, a hard disk, a CD-ROM, and a DVD, or a combination thereof.

[0119] The processor 1130 may control a series of processes so that the network entity operates according to the above-mentioned embodiments of the present disclosure. For example, the processor 1130 may receive a control signal and a data signal through the transceiver 1110 and process the received control signal and data signal. In addition, the processor 1130 may send the processed control signal and data signal to the transceiver 1110.

[0120] The methods according to the embodiments described in the claims or the specification of the present disclosure may be implemented by hardware, software, or a combination of hardware and software.

[0121] When implemented by software, a computer-readable storage medium or computer program product for storing one or more programs (software modules) may be provided. One or more programs may be stored in a non-transitory computer-readable storage medium or computer program product and configured to be executed by one or more processors in an electronic device. One or more programs may include instructions for causing an electronic device to perform a method according to an embodiment described in the claims or specification of the present disclosure.

[0122] Such a program (software module, software) may be stored in a non-volatile memory, including random access memory or flash memory, read-only memory (ROM), electrically erasable programmable read only memory (EEPROM), magnetic disk storage, compact disk ROM (CD-ROM), digital versatile disk (DVD), or other types of optical storage devices, or cassette tapes. Alternatively, the program may be stored in a memory including a combination of some or all of them. In addition, multiple component memories may be included.

[0123] In addition, the program can be stored in an attachable storage device that can be accessed via a communication network such as the Internet, an intranet, a local area network (LAN), a wide area LAN (WLAN), and a storage area network (SAN), or a combination thereof. The storage device can access the device that executes the embodiments of the present disclosure through an external port. In addition, a separate storage device on a communication network can access the device that executes the embodiments of the present disclosure.

[0124] In the above detailed embodiments of the present disclosure, the constituent elements included in the present disclosure are expressed in singular form or plural form according to the detailed embodiments. However, for the convenience of explanation, the singular or plural expression suitable for a given situation is selected, and the present disclosure is not limited to the constituent elements in singular or plural form. Even the constituent elements of the plural expression can also be composed of a single constituent element, and vice versa.

[0125] According to the devices and methods of various embodiments of the present disclosure, by providing support for session continuity in a mobile communication network system with a network slicing function, the mobile communication system can effectively provide services.

[0126] Effects obtainable from the present disclosure are not limited to the above-mentioned effects, and other effects not mentioned can be clearly understood from the above description by those skilled in the art to which the present disclosure pertains.

[0127] While the present disclosure has been shown and described with reference to various embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents.

[0128] In addition, each embodiment can be operated in combination with each other when necessary. For example, parts of one embodiment of the present disclosure and another embodiment can be combined with each other. Furthermore, the embodiment can be implemented in other systems, for example, LTE systems, 5G or NR systems, and other modified examples based on the technical concepts of the above-mentioned embodiments.

Claims

1. A method performed by a user equipment UE in a wireless communication system, the method comprising: identifying information related to single network slice selection assistance information, S-NSSAI, of a first public land mobile network, PLMN, wherein the information related to the S-NSSAI of the first PLMN is associated with a protocol data unit, PDU session, and wherein the information related to the S-NSSAI of the first PLMN comprises a first S-NSSAI and a second S-NSSAI; Sending a registration request message of the second PLMN to the access and mobility management function AMF entity; receiving a registration accept message from the AMF entity, the registration accept message including allowed network slice selection assistance information NSSAI, wherein the allowed NSSAI includes a third S-NSSAI and a fourth S-NSSAI mapped to the third S-NSSAI; identifying whether a second S-NSSAI associated with the PDU session matches a fourth S-NSSAI; and In a case where the second S-NSSAI matches the fourth S-NSSAI, the first S-NSSAI associated with the PDU session is updated to the third S-NSSAI.

2. The method according to claim 1, in, The first S-NSSAI includes the first slice / service type SST, Wherein, the second S-NSSAI includes a second SST, wherein the third S-NSSAI includes a third SST, and Among them, the fourth S-NSSAI mapped to the third S-NSSAI includes a fourth SST.

3. The method according to claim 2, wherein: Identifying whether a second S-NSSAI associated with the PDU session matches a fourth S-NSSAI includes: Identify whether a second SST included in a second S-NSSAI associated with the PDU session matches a fourth SST included in a fourth S-NSSAI mapped to the third S-NSSAI.

4. The method according to claim 1, in, The first S-NSSAI further comprises a first slice differentiator SD, Wherein, the second S-NSSAI also includes a second SD, wherein the third S-NSSAI also includes a third SD, and The fourth S-NSSAI mapped to the third S-NSSAI also includes a fourth SD.

5. The method according to claim 4, in, Identifying whether a second S-NSSAI associated with the PDU session matches a fourth S-NSSAI includes: Identify whether a second SD included in a second S-NSSAI associated with the PDU session matches a fourth SD included in a fourth S-NSSAI mapped to the third S-NSSAI.

6. The method according to claim 1, wherein: using the PDU session established in the first PLMN in the second PLMN by updating the first S-NSSAI to a third S-NSSAI, and After the UE moves from the first PLMN to the second PLMN, the PDU session is continuously used and is not released.

7. A user equipment UE in a wireless communication system, the UE comprising: Transceiver; and at least one processor operably connected to the transceiver and configured to: identifying information related to single network slice selection assistance information, S-NSSAI, of a first public land mobile network, PLMN, wherein the information related to the S-NSSAI of the first PLMN is associated with a protocol data unit, PDU session, and wherein the information related to the S-NSSAI of the first PLMN comprises a first S-NSSAI and a second S-NSSAI, Sending a registration request message of the second PLMN to an access and mobility management function AMF entity by controlling the transceiver, receiving a registration accept message from the AMF entity by controlling the transceiver, wherein the registration accept message includes allowed network slice selection assistance information NSSAI, wherein the allowed NSSAI includes a third S-NSSAI and a fourth S-NSSAI mapped to the third S-NSSAI, identifying whether a second S-NSSAI associated with the PDU session matches a fourth S-NSSAI, and In a case where the second S-NSSAI matches the fourth S-NSSAI, the first S-NSSAI associated with the PDU session is updated to the third S-NSSAI.

8. The UE according to claim 7, in, The first S-NSSAI includes a first slice / service type SST, Wherein, the second S-NSSAI includes a second SST, wherein the third S-NSSAI includes a third SST, and Among them, the fourth S-NSSAI mapped to the third S-NSSAI includes a fourth SST.

9. The UE according to claim 8, wherein: The at least one processor is further configured to identify whether a second SST included in a second S-NSSAI associated with the PDU session matches a fourth SST included in a fourth S-NSSAI mapped to a third S-NSSAI.

10. The UE according to claim 7, in, The first S-NSSAI further comprises a first slice differentiator SD, Wherein, the second S-NSSAI also includes a second SD, wherein the third S-NSSAI also includes a third SD, and The fourth S-NSSAI mapped to the third S-NSSAI also includes a fourth SD.

11. The UE according to claim 10, in, The at least one processor is further configured to identify whether a second SD included in a second S-NSSAI associated with the PDU session matches a fourth SD included in a fourth S-NSSAI mapped to a third S-NSSAI.

12. The UE according to claim 7, wherein: using the PDU session established in the first PLMN in the second PLMN by updating the first S-NSSAI to a third S-NSSAI, and After the UE moves from the first PLMN to the second PLMN, the PDU session is continuously used and is not released.

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