Communication method and apparatus in a wireless communication system supporting network slicing

Abstract

The present invention relates to a communication method and device in a wireless communication system supporting network slicing, [Solution] A method performed by a terminal in a wireless communication system supporting network slicing according to the present invention includes a step of the terminal sending a session establishment request message for a first network slice via a first access network, a step of receiving a session establishment rejection message via the first access network from a network entity managing sessions of the first network slice, and a step of deciding to handover to a second access network, which is the preferred access network of the terminal, if the session establishment rejection message includes information indicating exceeding the maximum number of sessions for the first network slice as a cause of rejection of the session establishment request.

Description

Technical Field

[0001] The present invention relates to a communication method and apparatus in a wireless communication system that supports network slicing.

Background Art

[0002] After the commercialization of 4G communication systems, efforts have been made to develop improved 5G communication systems or pre-5G communication systems to meet the increasing demand for wireless data traffic. For this reason, 5G communication systems or pre-5G communication systems are also referred to as communication systems Beyond 4G Network or Post LTE systems. To achieve higher data rates, it is considered that 5G communication systems will be implemented in the millimeter wave (mmWave) band (e.g., 60 GHz band, etc.). In order to mitigate the propagation loss of radio waves in the millimeter wave band and increase the transmission distance of radio waves, beamforming, massive multiple-input multiple-output (MIMO), full-dimensional MIMO (FD-MIMO), array antenna, analog beam forming, and large scale antenna technologies have been discussed in 5G communication systems.

[0003] In addition, for the improvement of the system network, in the 5G communication system, technologies such as evolved small cells, advanced small cells, cloud radio access network (cloud RAN), ultra-dense network, Device to Device communication (D2D), wireless backhaul, moving network, cooperative communication, Coordinated Multi-Points (CoMP), and interference cancellation at the receiving side have been developed. In addition, in the 5G system, Hybrid FSK and QAM Modulation (FQAM) as an Advanced Coding Modulation (ACM) technology, Sliding Window Superposition Coding (SWSC), and Filter Bank Multi Carrier (FBMC), non orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as advanced access technologies have been developed.

[0004] On the one hand, the Internet is evolving from a human-centered connection network where people generate and consume information to an IoT (Internet of Things) network that exchanges and processes information among distributed components such as things. IoE (Internet of Everything) technology, which combines IoT technology with big data processing technology through connection to cloud servers, etc., is also emerging. To realize IoT, technical elements such as sensing technology, wired and wireless communication and network infrastructure, service interface technology, and security technology are required. Therefore, recently, technologies such as sensor networks for connecting things, M2M (Machine to Machine) communication, and MTC (Machine Type Communication) have been studied.

[0005] In the IoT environment, by collecting and analyzing the data generated among connected things, intelligent IT (Internet Technology) services that create new value for human life can be provided. IoT can be applied to various fields such as smart homes, smart buildings, smart cities, smart cars or connected cars, smart grids, healthcare, smart appliances, and advanced medical services through the integration and combination between existing IT (information technology) technologies and various industries.

[0006] Accordingly, various attempts are being made to apply the 5G communication system to the IoT network. For example, 5G communication technologies such as sensor networks, M2M communication (Machine to Machine), and MTC (Machine Type Communication) are being implemented by techniques such as beamforming, MIMO, and array antennas. The application of cloud radio access network (cloud RAN) as the above-mentioned big data processing technology can also be said to be an example of the integration of 5G technology and IoT technology.

Summary of the Invention

Problems to be Solved by the Invention

[0007] An object of the present invention is to provide an efficient communication method and apparatus in a wireless communication system that supports network slicing.

[0008] Furthermore, an object of the present invention is to provide a session establishment method and apparatus that consider the number of sessions in a wireless communication system that supports network slicing.

[0009] Another object of the present invention is to provide an efficient session handover method and apparatus in a wireless communication system that supports network slicing.

Means for Solving the Problems

[0010] A method according to one aspect of the present invention made to achieve the above object is a method executed by a terminal in a wireless communication system that supports network slicing, the method including: a step of the terminal transmitting a session establishment request message for a first network slice via a first connected network; a step of the terminal receiving, from a network entity that manages the session of the first network slice, via the first connected network, a session establishment rejection message; and a step of the terminal determining a handover to a second connected network that is a priority connected network of the terminal when the session establishment rejection message includes information indicating an excess of the maximum number of sessions for the first network slice as a cause of rejection of the session establishment request.

[0011] A method according to another aspect of the present invention made to achieve the above object is a method executed by a network entity that manages sessions in a wireless communication system that supports network slicing. The method includes receiving, from a terminal via a first connection network, a session establishment request message for a first network slice; checking whether the current number of sessions using the first network slice exceeds an acceptable maximum number of sessions; and when the current number of sessions exceeds the acceptable maximum number of sessions, transmitting a session establishment rejection message including information indicating the exceeding of the maximum number of sessions as a cause of rejection of the session establishment request from the terminal.

[0012] A terminal according to one aspect of the present invention made to achieve the above object is a terminal in a wireless communication system that supports network slicing. The terminal includes a transceiver and a processor configured to transmit, via the transceiver, a session establishment request message for a first network slice via a first connection network, receive, via the transceiver, a session establishment rejection message from a network entity that manages the session of the first network slice via the first connection network, and determine a handover to a second connection network that is a priority connection network of the terminal when the session establishment rejection message includes information indicating an exceeding of a maximum number of sessions for the first network slice as a cause of rejection of the session establishment request.

[0013] A network entity according to one aspect of the present invention made to achieve the above object is a network entity that manages sessions in a wireless communication system supporting network slicing, and includes a network interface, and via the network interface, a session establishment request message for a first network slice is received from a terminal via a first connection network, and it is checked whether the current number of sessions using the first network slice exceeds an acceptable maximum number of sessions. When the current number of sessions exceeds the acceptable maximum number of sessions, a processor configured to transmit, via the network interface, a session establishment rejection message including information indicating the excess of the maximum number of sessions as a cause for rejecting the session establishment request of the terminal.

Advantages of the Invention

[0014] According to the present invention, an efficient communication method and apparatus in a wireless communication system supporting network slicing can be provided.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0016] Hereinafter, the operating principle of the present invention will be described in detail with reference to the drawings. The terms described hereinafter are terms defined in consideration of the functions in the present invention. Since these may vary depending on the intention or convention of the user, operator, etc., their definitions are determined according to the content throughout this specification.

[0017] The terms referring to network entities, terms referring to messages, etc. used in this specification are exemplified for convenience of explanation. Therefore, the description of the present invention is not limited to the terms described hereinafter, and other terms referring to objects having equivalent technical meanings can be used. Further, in this specification, terms and names defined in the 5G system specifications are used, but the present invention is not limited by those terms and names, and can be similarly applied to systems conforming to other specifications.

[0018] The apparatuses according to various embodiments of the present invention can be electronic apparatuses in various forms. The electronic apparatus includes, for example, a portable communication device (e.g., a smartphone), a portable multimedia device, a portable medical device, a camera, a wearable device, a home appliance, or a server. The electronic apparatus according to the embodiment of the present invention is not limited to the above-described apparatuses. It should be understood that various embodiments of the present invention and the terms used therein do not limit the technical features described in this specification to specific embodiments, but include various modifications, equivalents, or alternatives of the embodiments. Regarding the description of the drawings, similar or related components are denoted by the same reference numerals. The singular form of the noun corresponding to an item may include one or more of the above items unless otherwise clearly indicated in the relevant context.

[0019] As used herein, each of the phrases "A or B", "at least one of A and B", "at least one of A or B", "A, B, or C", "at least one of A, B, and C", and "at least one of A, B, or C" may include any one of the items listed together in the corresponding phrase of that phrase, or all possible combinations thereof. Terms such as "first", "second", or "first" or "second" are used merely to distinguish the component from other corresponding components and do not limit the component in other aspects (e.g., importance or order). When a certain (e.g., first) component is referred to as "coupled" or "connected" to another (e.g., second) component, with or without the terms "functionally" or "communicatively", it means that a certain component can be directly (e.g., wired), wirelessly, or via a third component, connected to another component.

[0020] Various embodiments of the present invention can be implemented as software including one or more instructions stored in a storage medium (e.g., built-in memory or external memory) that can be read by the above-described electronic device. For example, a processor of the electronic device calls and executes at least one of the one or more stored instructions from the storage medium. Thereby, the device is enabled to operate to execute at least one function according to the at least one called instruction. The one or more instructions may include code executable by a compiler-generated code or an interpreter. The storage medium readable by the electronic device is provided in the form of a non-transitory storage medium. Here, "non-transitory" merely means that the storage medium is a tangible device and does not include a signal (e.g., an electromagnetic wave), and this term does not distinguish between the case where data is stored semi-permanently in the storage medium and the case where it is stored temporarily.

[0021] According to one embodiment, the methods according to the various embodiments disclosed herein may be provided included in a computer program product. The computer program product can be traded as a commodity between a seller and a purchaser. The computer program product may be distributed in the form of a device-readable storage medium (e.g., CD-ROM, DVD-ROM), or via an application store (e.g., Play Store), or directly online (e.g., downloaded or uploaded) between two user devices (e.g., smartphones). In the case of online distribution, at least a part of the computer program product may be at least temporarily stored or temporarily generated in a device-readable storage medium such as the memory of a manufacturer's server, an application store's server, or a relay server.

[0022] According to various embodiments, each component may include one or more individuals. According to various embodiments, one or more of the components or operations may be omitted, or one or more other components or operations may be added. Alternatively or additionally, a plurality of components (e.g., modules or programs) may be integrated into one component. In this case, the integrated component can perform one or more functions of each of the plurality of components in the same or similar manner as those performed by the corresponding component among the plurality of components before integration. According to various embodiments, the operations performed by a module, program, or other component may be performed sequentially, in parallel, iteratively, or heuristically, or one or more of the operations may be performed in a different order, omitted, or one or more other operations may be added.

[0023] According to an embodiment of the present invention, an electronic device means various devices used by a user. For example, the electronic device means a terminal, a user equipment (UE), a mobile station, a subscriber station, a remote terminal, a wireless terminal, or a user device. For convenience, the electronic device is exemplified as a user equipment (UE), and embodiments of the present invention will be described below. Also, an AN (access network) provides a channel for wireless communication with the electronic device. The AN means a RAN (radio access network), a base station, an eNB, an eNodeB, a 5G node, a transmission / reception point (TRP), or a 5GNB (5th generation NodeB), etc.

[0024] The present invention relates to a method and apparatus for supporting various services in a wireless communication system. Specifically, the present invention describes a technique for supporting various services by managing a session using a network slice in a wireless communication system. In a wireless communication system that supports network slicing, traffic to different network slices is processed by different PDU (protocol data unit) sessions. A PDU session means an association between a data network that provides a PDU connection service and a terminal. Network slicing is understood as a technique for logically configuring a network with a set of network functions (NFs) that support various services with different characteristics, such as broadband communication services, massive IoT, mission critical services such as V2X (vehicle-to-everything), etc., and separating different network slices. Therefore, even if a communication failure occurs in a network slice, the communication of other network slices is not affected, and it is possible to provide a stable communication service. Hereinafter, the term "slice" used interchangeably in this specification means "network slice".

[0025] In such a network environment, when a single terminal is provided with various services, it is connected to two or more network slices. A network function is implemented as a software instance driven by hardware or a virtualized function instantiated on a network element or an appropriate platform.

[0026] Terms used to identify connection nodes (nodes) used in the description of the present invention, terms referring to network entities or network functions (NFs), terms referring to messages, terms referring to interfaces between network objects, terms referring to various identification information, etc. are exemplified for the convenience of explanation. Therefore, the present invention is not limited to the terms described below, and other terms referring to objects having equivalent technical meanings can be used.

[0027] Hereinafter, for the convenience of explanation, the present invention uses terms and names defined in 3GPP LTE (3rd generation partnership project long term evolution) and / or 5G specifications. However, the present invention is not limited to the above terms and names, and can be similarly applied to systems compliant with other specifications.

[0028] Furthermore, the network technology described in this specification can refer to standard specifications (for example, TS 23.501, 23.502) defined by ITU (International Telecommunication Union) or 3GPP (registered trademark), and each of the components included in the network environment of FIG. 1 described later means a physical entity or software that executes an individual function or hardware combined with software.

[0029] Furthermore, according to an embodiment of the present invention, a core network (CN) manages at least one of UE subscription information, mobility, access authorization, session establishment, traffic of data packets, or charging policies. The core network (CN) includes nodes (or entities) such as UPF (user plane function), AMF (access and mobility management function), SMF (session management function), UPF (user plane function), UDM (unified data management), PCF (policy control function), etc. For the description of the nodes (or entities) included in the core network (CN), reference can be made to the standard specifications defined by 3GPP (for example, TS 23.501, 23.502).

[0030] Hereinafter, for the sake of convenience of explanation, the object for exchanging information for connection control and state management will be referred to using the name of the NF (network function) (for example, AMF, SMF, NSSF (network slice selection function), etc.). However, the embodiments of the present invention can be similarly applied when the NF is actually implemented by instances (Instance, such as AMF Instance, SMF Instance, NSSF Instance, etc.).

[0031] FIG. 1 is a diagram showing the structure of a 5GS (fifth generation system) according to an embodiment of the present invention.

[0032] Referring to FIG. 1, the 5G core network includes an AMF 120, an SMF 135, a UPF 130, a PCF 140, a UDM 145, an NSSF 160, a NWDAF (network data analytics function) 165, an N3GPP (non-3GPP) access network 115, etc. In FIG. 1, reference numerals indicated by Nx, such as N2, N3, etc., represent known interfaces between NFs in the 5G core network. Since relevant descriptions can refer to the standard specification (TS 23.501), specific descriptions are omitted.

[0033] In FIG. 1, a terminal (user equipment: UE) 100 connects to the 5G core network via a 3GPP radio access network base station 110 and / or an N3GPP (Non-3GPP) access network 115. The terminal 100 connects to the AMF 120 via the N2 interface through the base station 110 and connects to the UPF 130 via the N3 interface. In addition to a base station, the base station 110 may be called by other terms having the same technical meaning as "access point (AP)", "eNodeB (eNB)", "5th generation node", "gNodeB (gNB)", or the like.

[0034] In FIG. 1, the N3GPP connected network 115 is an NF (Network Function) that operates as an N2 interface and an N3 interface termination for a terminal 100 connected via a connection network (Non-3GPP Access Network) not defined by 3GPP (for example, WiFi (registered trademark), etc.). For example, the N3GPP connected network 115 includes an N3IWF (Non-3GPP InterWorking Function), a TNGF (trusted non-3GPP gateway function), a W-AGF (wireline access gateway function), etc. The N3GPP connected network 115 processes N2 control plane signaling and N3 user plane packets. The terminal 100 connected to the N3GPP connected network 115 may be connected to the AMF 120 via the N2 interface and to the UPF 130 via the N3 interface through the N3GPP connected network 115.

[0035] In FIG. 1, the AMF (Access and Mobility Management Function) 120 is an NF (Network Function) that manages the wireless network connection (Access) and mobility of the terminal UE. The SMF (Session Management Function) 135 is an NF that manages the session of the terminal, and the session information may include information related to QoS (Quality of Service) information, charging information, packet processing, etc. The UPF (User Plane Function) 130 is an NF that processes user traffic (User Plane traffic) and is controlled by the SMF 135. The PCF (Policy Control Function) 140 is an NF that manages the operator policy for providing services in the wireless communication system. The UDM (User Data Management) 145 is an NF that stores and manages the subscription information of the terminal (UE subscription) (hereinafter referred to as terminal subscription information). The UDR (Unified Data Repository) 150 is an NF that stores and manages data, and the terminal subscription information stored in the UDR 150 can be used. The UDR 150 stores the terminal subscription information and provides the terminal subscription information to the UDM 145. Also, the UDR 150 stores the operator policy information and provides the operator policy information to the PCF 140. In FIG. 1, the NWDAF (Network Data Analytics Function) 165 is an NF that provides analysis information for the 5G system to operate. The NWDAF 165 collects data from other NFs ~ OAM (operations, administration and maintenance) that make up the 5G system, analyzes the collected data, and provides the analysis results to other NFs.

[0036] Among the NF services provided by the SMF 135 that manages a session, the service operations related to the PDU session are defined in the 5G specification (TS 23.502 V16.4.0) as shown in below.

[0037]

Table 1

[0038] The 5G system structure in Figure 1 supports service-based interfaces. The service-based interfaces related to the SMF 135 are defined as "Nsmf" as shown in the above . In , "Nsmf_PDUSession" means the service operating in the PDU session. The service includes operations such as creating / deleting / modifying the PDU session, and these operations are executed by sending and receiving PDU session request / response messages between the AMF 120 and the SMF 135.

[0039] Also, as in the example of , for the SMF 135 to support the PDU session, in the association create operation between the AMF 120 and the SMF 135, it receives the "Nsmf_PDUSession_CreateSMContext" request message, which is a PDU session request message, from the AMF 120, and as a response, it sends the "Nsmf_PDUSession_CreateSMContext" response message to the AMF 120. Also, as in the example of , for the SMF 135 to support the PDU session, in the association update operation between the AMF 120 and the SMF 135, it receives the "Nsmf_PDUSession_UptateSMContext" request message, which is a PDU session request message, from the AMF 120, and as a response, it sends the "Nsmf_PDUSession_UptateSMContext" response message to the AMF 120. Other service operations in refer to the relevant standards and specific descriptions are omitted.

[0040] Hereinafter, for the sake of convenience of explanation, the objects that exchange information for connection control and state management are collectively referred to as NFs and described. In this specification, the NF is described as an NF entity, and the NF according to the embodiment of the present invention is implemented by instances (AMF Instance, SMF Instance, NSSF Instance, etc., respectively).

[0041] In the present invention, an instance means that a specific NF exists in the form of software code, and in order to execute the function of the NF in a physical computing system (for example, a specific computing system existing on a core network), by allocating physical and / or logical resources from the computing system, the function of the NF is in a state where it can be executed. Therefore, an AMF Instance, an SMF Instance, an NSSF Instance, etc. each mean a state where physical and / or logical resources are allocated from a specific computing system existing on the core network for the operations of the AMF, SMF, NSSF, etc. and can be used. As a result, when there are physical AMF, SMF, NSSF devices, and an AMF Instance, an SMF Instance, an NSSF Instance that allocate and use physical and / or logical resources for the operations of the AMF, SMF, NSSF from a specific computing system existing on the network perform the same operations. Therefore, in the embodiments of the present invention, matters described as NF (AMF, SMF, UPF, NSSF, NRF (network repository function), SCP (service communication proxy), etc.) can be replaced by NF Instance, or conversely, matters described as NF Instance can be replaced by NF and applied. Similarly, in the embodiments of the present invention, matters described as Network slice may be replaced by Network slice instance, or conversely, matters described as Network slice instance may be replaced by Network slice and applied.

[0042] According to an embodiment of the present invention, in the 5G system defined by 3GPP, one network slice is referred to as S-NSSAI (Single-Network Slice Selection Assistance Information). Therefore, a network slice is identified by the S-NSSAI. The S-NSSAI is composed of an SST (Slice / Service Type) value and an SD (Slice Differentiator) value. The SST indicates the characteristics of the service supported by the slice (for example, eMBB (enhanced mobile broadband), MIoT (massive IoT), URLLC (ultra reliable low latency communications), V2X, etc.). The SD is a value used as an additional identifier for a specific service called SST.

[0043] NSSAI (network slice selection assistance information) can be composed of one or more S-NSSAI (single-network slice selection assistance information). Examples of NSSAI include Configured NSSAI stored in the terminal, Requested NSSAI requested by the terminal, Allowed NSSAI determined by an NF (for example, AMF, NSSF, etc.) in the 5G core network and permitted for the terminal to use, NSSAI subscribed by the terminal, etc., but this is only an example, and the examples of NSSAI are not limited to the above.

[0044] In the present invention, the terminal 100 is connected to at least one of a 3GPP access network and an N3GPP (non-3GPP) access network. Also, the terminal 100 is simultaneously connected to a 3GPP access network and an N3GPP (non-3GPP) access network and registered in the 5G system.

[0045] Here, the connection network is called by various names such as a base station, AN, AP (access point), etc. As an example, a 3GPP connection network is a network that uses a licensed band, and an N3GPP connection network is a network that uses an unlicensed band, but the network classification is not limited to this.

[0046] Specifically, the terminal 100 connects to the 3GPP base station 110 and performs a registration procedure with the AMF 120. During the registration procedure, the AMF 120 determines the allowed slice (Allowed NSSAI) available to the terminal 100 connected to the 3GPP base station 110 and assigns it to the terminal 100. This is referred to as the first allowed slice. The terminal 100 connects to the N3GPP connection network 115 and performs a registration procedure with the AMF 120. During the registration procedure, the AMF 120 determines the allowed slice (Allowed NSSAI) available to the terminal 100 connected to the N3GPP connection network 115 and assigns it to the terminal 100. This is referred to as the second allowed slice. The first allowed slice and the second allowed slice may include the same S-NSSAI or different S-NSSAIs. In the present invention, the first allowed slice and the second allowed slice can use the same S-NSSAI or different S-NSSAIs.

[0047] The mobile operator defines the size of the network resources available for each network slice. In the present invention, this is called the network slice policy (Network Slice policy or Slice policy or slice policy). The slice policy information includes at least one of the following information.

[0048] - S-NSSAI - Maximum number of PDU Sessions - Method for aggregating the maximum number of sessions

[0049] The maximum number of sessions included in the slice policy information according to an embodiment of the present invention indicates the maximum number of sessions established using the S-NSSAI. The NF (for example, AMF, SMF, etc.) of the 5G core network counts the number of sessions that utilize a specific S-NSSAI established through the PDU Session Establishment procedure. According to an embodiment of the present invention, the maximum number of sessions indicates the maximum value of the number of sessions that utilize the corresponding S-NSSAI. For example, when the maximum number of sessions of the eMBB slice is 100,000 sessions, the 5G core network (or at least one network function within the 5G core network) may permit up to 100,000 sessions out of the session requests that include the S-NSSAI indicating the eMBB slice.

[0050] According to an embodiment of the present invention, the 5G core network (or at least one network function within the 5G core network) stores and manages the slice policy information in the NF. The slice policy information stored in the NF may be determined by the policy of the mobile network operator. The mobile network operator may store and update the slice policy information in the NF in an OAM (Operation, Administration and Maintenance) manner.

[0051] According to an embodiment of the present invention, the NF of the 5G core network (or at least one network function within the 5G core network) obtains the slice policy information from other NFs of the 5G core network.

[0052] Figure 2 is a diagram for explaining the PDU Session Establishment procedure according to an embodiment of the present invention. In Figure 2, since the basic operations of the UE 100, AN (200, 201), AMF 120, and SMF 135 are the same as the corresponding configurations in Figure 1, specific descriptions are omitted.

[0053] Referring to Figure 2, a terminal 100 according to an embodiment of the present invention connects to a First Access Network (AN) 200 and executes a PDU session establishment procedure. The First Access Network 200 is a 3GPP base station 110 or an N3GPP connected network 115.

[0054] In step 210, the terminal 100 connects to the First Access Network 200 and transmits a PDU Session Establishment Request message. The PDU Session Establishment Request message includes information about the slice that the terminal intends to use (i.e., requests session establishment). The information about the slice that the terminal intends to use may include an S-NSSAI.

[0055] The terminal 100 includes preferred Access Type information in the PDU Session Establishment Request message. The Preferred Access Type indicates the type of network connection (e.g., 3GPP connected network, Non-3GPP connected network, etc.) that the terminal 100 prefers for the S-NSSA to which the PDU session requested by the terminal is to be used.

[0056] According to an embodiment of the present invention, the Preferred Access Type is set in relation to the base station to which the terminal 100 is currently connected. In this case, the terminal 100 sets the type of network connection supported by the currently connected First Access Network 200 as the Preferred Access Type.

[0057] According to yet another embodiment, the Preferred Access Type is set regardless of the base station to which the terminal 100 is currently connected. In this case, the terminal 100 sets, as the Preferred Access Type, the type of connection network supported by the first base station 200 to which it is currently connected, or the type of connection network not supported by the first base station 200 to which it is currently connected. For example, although the first base station 200 to which the terminal 100 is currently connected is a 3GPP base station, the Preferred Access Type can be set to an N3GPP base station, or conversely, although the first base station 200 to which the terminal 100 is currently connected is an N3GPP base station, the Preferred Access Type can be set to a 3GPP base station.

[0058] In step 212, according to an embodiment of the present invention, the first base station 200 that has received the session establishment request message selects the AMF 120 that transmits the session establishment request message. The first base station 200 transmits the session establishment request message to the selected AMF 120. In step 214, the AMF 120 transmits a PDU session request message to the SMF 135. The PDU session request message includes at least one of the information included in the session establishment request message in step 210, for example, information regarding the slice that the terminal 100 intends to use (i.e., requests session establishment), and the Preferred Access Type.

[0059] As an example, the PDU session request message that the AMF 120 transmits to the SMF 135 can use the Nsmf_PDUSession_CreateSMContext Request message described in .

[0060] The SMF 135 processes the PDU session request. The SMF 135 determines whether the requested S-NSSAI is to be aggregated for the maximum session number. For example, the SMF 135 determines whether the requested S-NSSAI is to be aggregated for the maximum session number based on the local configuration information stored in the SMF 135. Alternatively, the SMF 135 may determine whether the requested S-NSSAI is to be aggregated for the maximum session number based on the subscription information of the terminal 100 received from the UDM 145. Alternatively, all the S-NSSAIs requested by the SMF 135 may be aggregated for the maximum session number. Also, the S-NSSAIs to be aggregated for the maximum session number may be determined for all or some of them, or determined / set in various ways by at least one combination of operator, region, time zone, traffic type, etc.

[0061] If the requested S-NSSAI is to be aggregated for the maximum session number, in step 216, before the SMF 135 confirms to permit session establishment for the terminal 100, the SMF 135 checks the slice availability with the NF 202 of the 5G core network (or at least one network function within the 5G core network). Here, the NF 202 can be various entities (or instances) such as the PCF 140, AMF 120, SMF 135, UPF 130, UDM 145, NWDAF 165, NSSF 160, UDR 150 or 3rd party, NEF (network exposure function) for AP (application function), Edge Computing, etc. (not shown in the figure).

[0062] For this purpose, SMF135 sends a Slice Availability request message to NF202. In another embodiment, when NF202 is the SMF, since the slice availability is directly determined by SMF135, the sending and receiving of the request / response messages in steps (216, 220) can be omitted. The Slice Availability request message in step 216 includes at least one of the target slice information (e.g., S-NSSAI, etc.), the connection network information of terminal 100 (e.g., 3GPP, non-3GPP, etc.), the Preferred Access Type, the terminal location information (e.g., TA (tracking area), etc.), and the terminal information (e.g., SUPI (subscription permanent identifier), 5G-GUTI (5G globally unique temporary identifier), etc.).

[0063] On the other hand, if the Nsmf_PDUSession_CreateSMContext Request message sent in step 214 includes the Preferred Access Type requested / set by terminal 100, SMF135 stores the Preferred Access Type.

[0064] According to yet another embodiment, SMF135 obtains the Preferred Access Type information regarding the S-NSSAI from UDM145 or PCF140. SMF135 stores the Preferred Access Type received from UDM145 or PCF140. According to yet another embodiment, SMF135 determines the Preferred Access Type of the S-NSSAI based on the operator policy (operator policy, local configuration, local policy, etc.). SMF135 stores the Preferred Access Type that complies with the operator policy.

[0065] When the Preferred Access Type information regarding the S-NSSAI is provided from the UDM145 or the PCF140, or when the Preferred Access Type of the S-NSSAI is determined based on the operator policy, the request message in step 210 may not include the Preferred Access Type information. In another embodiment, when the request message in step 210 includes the Preferred Access Type information and the Preferred Access Type information of the S-NSSAI is provided by the UDM145, the PCF140, or the operator policy as described above, among the multiple Preferred Access Types, the Preferred Access Type is determined according to a predetermined priority order.

[0066] In step 218, the NF202 checks the slice policy of the target slice (such as the S-NSSAI, etc.) received from the SMF135 and the current number of sessions of the target slice.

[0067] For example, the NF202 compares the maximum number of sessions included in the slice policy of the target slice with the current number of sessions of the target slice. If the current number of sessions of the target slice has not reached the maximum number of sessions (that is, if the current number of sessions is less than the maximum number of sessions), it is determined that the target slice is currently available. If the target slice is currently available, the NF202 increases the current number of sessions of the target slice by one based on the request message in step 216.

[0068] According to another example, for example, the NF202 compares the maximum number of sessions of the slice policy of the target slice with the current number of sessions of the target slice. If the current number of sessions of the target slice has reached the maximum number of sessions (that is, if the current number of sessions is equal to the maximum number of sessions), the NF202 determines that the target slice is not currently available.

[0069] In step 220, NF202 sends a Slice Availability response message to SMF135. The Slice Availability response message includes at least one of the target slice information (e.g., S-NSSAI, etc.) and the availability of the target slice (e.g., an indicator indicating available or unavailable, a cause value for available or unavailable, etc.).

[0070] Based on whether the slice received from NF202 is available or not, SMF135 determines whether to permit session establishment. For example, when NF202 replies that the slice (S-NSSAI) is available, SMF135 decides to accept the PDU session establishment request using the slice (S-NSSAI). In another embodiment, for example, when NF202 sends a message indicating that the slice (S-NSSAI) is unavailable, SMF135 decides to reject the PDU session establishment request using the slice (S-NSSAI).

[0071] In step 222, SMF135 sends a response message to the session establishment request message received in step 214 to AMF120. As an example, the response message uses the Nsmf_PDUSession_CreateSMContext Response message described in .

[0072] If SMF135 decides to accept the PDU session establishment request using the slice (S-NSASI), the response message in step 222 sent by SMF135 to AMF120 includes a PDU session establishment acceptance message (or information indicating acceptance). If SMF135 decides to reject the PDU session establishment request using the slice (S-NSASI), the response message in step 222 sent by SMF135 to AMF120 includes a PDU session establishment rejection message (or information indicating rejection).

[0073] After that, in steps 224 to 226, the AMF 120 transmits the PDU session establishment acceptance / rejection message received from the SMF 135 to the terminal 100 via the first base station 200.

[0074] FIG. 3 is a diagram for explaining a PDU session establishment procedure according to an embodiment of the present invention. In FIG. 3, the basic operations of the UE 100, AN (200, 201), AMF 120, and SMF 135 are the same as those of the corresponding configurations in FIG. 1, and thus specific descriptions are omitted. And the procedure in FIG. 3 assumes a procedure performed in a state where the session of the S-NSSAI requested by the terminal 100 is established according to the procedure in FIG. 2.

[0075] Referring to FIG. 3, a terminal 100 according to an embodiment of the present invention connects to a second base station (Second Access Network) 201 and executes a PDU session establishment procedure. The second base station 201 is a 3GPP base station 110 or an N3GPP connection network 115.

[0076] In step 310, the terminal 100 connects to the second base station 201 and transmits a PDU session establishment request message. The PDU session establishment request message includes information about the slice that the terminal 100 intends to use (i.e., requests session establishment). The information about the slice that the terminal 100 intends to use includes the S-NSSAI. Further, the S-NSSAI may be the same as or different from the S-NSSAI being used in the PDU session established by the terminal 100 via the first base station 200 according to the procedure shown in FIG. 2.

[0077] Also, the terminal 100 includes the above-mentioned preferred access type information in the session establishment request message in step 310. The Preferred Access Type indicates the type of connection network (e.g., 3GPP connection network, Non-3GPP connection network, etc.) that the terminal 100 prefers for the S-NSSAI used for the PDU session requested by the terminal, with respect to the S-NSSAI. According to an embodiment of the present invention, the Preferred Access Type is set in relation to the base station to which the terminal 100 is currently connected. In this case, the terminal 100 sets the type of connection network supported by the second base station 201 to which it is currently connected as the Preferred Access Type. According to yet another embodiment, the Preferred Access Type is set regardless of the base station to which the terminal 100 is currently connected. In this case, the terminal 100 sets the type of connection network supported by the second base station 201 to which it is currently connected or the type of connection network not supported by the second base station 201 to which it is currently connected as the Preferred Access Type. For example, although the second base station 200 to which the terminal 100 is currently connected is an N3GPP base station, the Preferred Access Type may be set to a 3GPP base station, or conversely, although the second base station 200 is a 3GPP base station, the Preferred Access Type may be set to an N3GPP base station.

[0078] According to an embodiment of the present invention, when the session establishment request message transmitted in step 210 of FIG. 2 includes the Preferred Access Type of S-NSSAI, the session establishment request message transmitted in step 310 of FIG. 3 may not include the Preferred Access Type. In another embodiment, the terminal 100 that attempts to change the Preferred Access Type of the S-NSSAI requested in step 210 of FIG. 2 includes the changed / updated Preferred Access Type in the session establishment request message transmitted in step 310 of FIG. 3. For example, the terminal 100 indicates the Preferred Access Type of the S-NSSAI to the 3GPP access network in step 210, but changes it to the Non-3GPP access network in step 310.

[0079] Also, in an embodiment of the present invention, the terminal 100 sets the request type of the PDU session establishment request message to "initial request".

[0080] In step 312, according to an embodiment of the present invention, the second base station 201 that receives the session establishment request message selects the AMF 120 that transmits the session establishment request message. The second base station 201 transmits the session establishment request message to the selected AMF 120.

[0081] In step 314, the AMF 120 transmits a PDU session request message to the SMF 135. The PDU session request message includes at least one of the information included in the session establishment request message in step 310, for example, information about the slice that the terminal 100 attempts to use (i.e., requests session establishment), and the Preferred Access Type.

[0082] When the request type of the PDU session request message is "initial request", the PDU session request message that the AMF 120 sends to the SMF 135 uses, for example, the Nsmf_PDUSession_CreateSMContext Request message described in .

[0083] The SMF 135 processes the PDU session request. The SMF 135 determines whether the requested S-NSSAI is subject to the aggregation of the maximum number of sessions. For example, the SMF 135 determines whether the requested S-NSSAI is subject to the aggregation of the maximum number of sessions based on the local policy information (local configuration) stored in the SMF 135. Alternatively, the SMF 135 may determine whether the requested S-NSSAI is subject to the aggregation of the maximum number of sessions based on the subscription information received from the UDM 145. Alternatively, all the S-NSSAIs requested by the SMF 135 may be subject to the aggregation of the maximum number of sessions. Also, the S-NSSAI subject to the aggregation of the maximum number of sessions may be determined for all or part of them, or may be determined / set in various ways by at least one combination of operator, region, time zone, and traffic type.

[0084] When the required S-NSSAI is subject to the aggregation of the maximum number of sessions, in step 316, before confirming to permit the terminal 100 to establish a session, the SMF 135 checks the slice availability with the NF 202 of the 5G core network (or at least one network function within the 5G core network). For this purpose, the SMF 135 sends a Slice Availability request message to the NF 202. Here, the NF 202 can be various entities (or instances) as described in the embodiment of FIG. 2. The Slice Availability request message includes at least one of the target slice information (e.g., S-NSSAI, etc.), the terminal's connected network information (e.g., 3GPP, non-3GPP, etc.), the Preferred Access Type, the terminal location information (e.g., TA, etc.), and the terminal information (e.g., SUPI, 5G-GUTI, etc.).

[0085] On the other hand, when the Nsmf_PDUSession_CreateSMContext Request message sent in step 314 includes the Preferred Access Type requested / set by the terminal 100, the SMF 135 stores the Preferred Access Type. For example, when there is no Preferred Access Type for the S-NSSAI, the SMF 135 stores the Preferred Access Type. Alternatively, when there is a Preferred Access Type for the corresponding S-NSSAI, the SMF 135 updates the stored Preferred Access Type with the newly received Preferred Access Type information.

[0086] According to yet another embodiment, the SMF 135 obtains the preferred Access Type information regarding the S-NSSAI from the UDM 145 or the PCF 140. The SMF 135 stores the Preferred Access Type received from the UDM 145 or the PCF 140. According to yet another embodiment, the SMF 135 determines the Preferred Access Type of the S-NSSAI based on the operator policy (such as operator policy, local configuration, local policy, etc.). The SMF 135 stores the Preferred Access Type according to the operator policy.

[0087] When the Preferred Access Type information of the S-NSSAI is provided from the UDM 145 or the PCF 140, or the Preferred Access Type of the S-NSSAI is determined based on the operator policy, the request message in step 310 may not include the Preferred Access Type information. In another embodiment, when the request message in step 310 includes the Preferred Access Type information and the Preferred Access Type information of the S-NSSAI is provided by the UDM 145, the PCF 140, or the operator policy as described above, the Preferred Access Type is determined according to a predetermined priority among the multiple Preferred Access Types.

[0088] In step 318, the NF 202 checks the slice policy of the target slice (such as S-NSSAI, etc.) received from the SMF 135 and the current number of sessions of the target slice.

[0089] For example, NF202 compares the maximum number of sessions included in the slice policy of the target slice with the current number of sessions of the target slice. If the current number of sessions of the target slice has not reached the maximum number of sessions, NF202 determines that the target slice is currently available. If the target slice is currently available, NF202 increases the current number of sessions of the target slice by one based on the request message in step 316.

[0090] According to another example, for example, NF202 compares the maximum number of sessions of the slice policy of the target slice with the current number of sessions of the target slice. If the current number of sessions of the target slice has reached the maximum number of sessions, NF202 determines that the target slice is not currently available.

[0091] In step 320, NF202 sends a Slice Availability response message to SMF135. The Slice Availability response message includes at least one of the target slice information (for example, S-NSSAI, etc.) and the availability of the target slice (for example, an indicator indicating available or unavailable, a cause value for available or unavailable, etc.).

[0092] SMF135 determines whether session establishment is permitted according to the availability of the slice received from NF202. For example, when NF202 returns that the slice (S-NSSAI) is available, SMF135 decides to accept the PDU session establishment request using the slice (S-NSSAI). In another embodiment, for example, when NF202 sends a message indicating that the slice (S-NSSAI) is unavailable, SMF135 decides to reject the PDU session establishment request using the slice (S-NSSAI).

[0093] In step 322, the SMF 135 sends a response message to the session establishment request message received in step 314 to the AMF 120. As an example, the response message uses the Nsmf_PDUSession_CreateSMContext Response message described in .

[0094] If the SMF 135 decides to reject a PDU session establishment request that uses a slice (S-NSASI), the response message in step 322 sent by the SMF 135 to the AMF 120 includes a PDU session establishment rejection message (or information indicating rejection). If the SMF 135 decides to accept a PDU session establishment request that uses a slice (S-NSASI), the response message in step 322 sent by the SMF 135 to the AMF 120 includes a PDU session establishment acceptance message (or information indicating acceptance).

[0095] In steps 324 to 326, the AMF 120 sends the PDU session establishment acceptance / rejection message received from the SMF 135 to the terminal 100 via the second base station 201.

[0096] On the other hand, in the embodiments of FIGS. 2 and 3, the above-described PDU session establishment rejection message includes a value (cause value) indicating the cause of rejection.

[0097] According to the embodiments of the present invention, the value indicating the cause of rejection is a value indicating that the reason is reaching the maximum number of sessions (for example, Quota is overflown, excess of the quota, etc.). The SMF 135 sets the value indicating the cause of rejection based on the information received from the NF 202 in steps (220, 320).

[0098] According to another example, the value indicating the cause of rejection may be the reaching of the maximum number of sessions and may be a value indicating that session handover is possible. In steps (220, 320), SMF135 sets a value indicating the cause of rejection based on at least one of the information received from NF202, the session-related context (SM context) of terminal 100, and the preferred Access Type of the S-NSSAI.

[0099] For example, via the first base station 200, a PDU session for the S-NSSAI is established, and the terminal 100 in use requests the establishment of a PDU session using the same S-NSSAI via the second base station 201. Currently, when the corresponding S-NSSAI is not available (quota is overflown), SMF135 sets a value indicating the cause of rejection, which is a value indicating that the maximum number of sessions has been reached but session handover is possible. In this way, when SMF135 sets the value indicating the cause of rejection, it considers the preferred Access Type. For example, based on the preferred Access Type, the preferred type of connection network between the first base station 200 and the second base station 201 is determined. If the connection network supported by the second base station 201 for which the PDU session is requested is more preferred than the connection network supported by the first base station 200 using the PDU session, SMF135 sets a value indicating that session handover is possible as the value indicating the rejection of the session establishment request.

[0100] In addition, the PDU session establishment rejection message includes a back-off time associated with the rejected S-NSSAI. The back-off time means that the terminal 100 does not perform a specific operation (e.g., SM NAS signaling) during the period when the back-off time is set. For example, during the time set as the back-off time, the terminal 100 may not be able to send a new PDU session request for the S-NSSAI during the time set as the back-off time associated with the S-NSSAI included in the PDU session establishment rejection message. The inability to send a new PDU session request for the S-NSSAI means that a PDU session establishment request message including the S-NSSAI as a network slice and setting the request type to "initial request" cannot be sent. Furthermore, the back-off time may not affect a specific operation performed by the terminal 100. For example, during the period set as the back-off time, the terminal 100 performs a PDU session handover or a PDU session modification procedure. The PDU session handover procedure means that a PDU session establishment request message including the S-NSSAI as a network slice and setting the request type to "Existing PDU Session" can be sent. The PDU session modification procedure means sending a PDU Session Modification Request message including the S-NSSAI to the network slice.

[0101] Upon receiving the PDU session establishment rejection message, the terminal 100 can know that the PDU session request has been rejected due to reaching the maximum number of sessions based on the cause value included in the PDU session establishment rejection message.

[0102] The terminal 100 determines the next operation based on at least one of the information received in steps (226, 326) and the session-related information stored by the terminal 100.

[0103] The terminal 100 according to an embodiment of the present invention requests a PDU session again after the time set for the back-off time included in the PDU session establishment rejection message has elapsed. After the back-off time has elapsed (after the back-off timer expires), the request type of the PDU session request message for the re-request may be set to "initial request". The back-off time applies regardless of the connected network for the same PLMN (public land mobile network).

[0104] Furthermore, the terminal 100 according to another embodiment determines to move (handover) a PDU session established via the first base station 200 to the second base station 201. The terminal 100 requests a session handover before the back-off time has elapsed (before the back-off timer expires), and the request type of the PDU session request message for requesting the session handover is set to "existing PDU session". At this time, the PDU session established via the first base station 200 and the PDU session moved to the second base station 201 may be sessions using the same S-NSSAI. The session handover procedure according to an embodiment of the present invention is described in detail in FIG. 4.

[0105] As described in the embodiment of FIG. 2 and / or the embodiment of FIG. 3, the PDU session establishment rejection message includes a cause value indicating the cause of rejection. When the cause value indicating the rejection of the session establishment request includes a value indicating that a session handover is possible, the handover procedure of FIG. 4 described later is triggered. Therefore, the embodiment of FIG. 2 and / or the embodiment of FIG. 3 and the embodiment of FIG. 4 are implemented in combination.

[0106] FIG. 4 is a diagram for explaining a PDU Session Handover procedure according to an embodiment of the present invention. The embodiment of FIG. 4 assumes a situation where the terminal 100 is using a PDU session via the first base station 200.

[0107] Referring to FIG. 4, the terminal 100 according to an embodiment of the present invention determines to hand over the PDU session being used via the first base station 200 to the second base station 201.

[0108] In step 410, the terminal 100 connects to the second base station 201 for session handover and transmits a PDU Session Establishment Request message. The terminal 100 sets the request type of the PDU session establishment request message to, for example, "existing PDU session".

[0109] The session establishment request message includes the PDU Session ID of the PDU session that the terminal 100 is currently using and is the target of session handover.

[0110] The session establishment request message includes information about the slice that the terminal 100 intends to use. The information about the slice that the terminal 100 intends to use includes the S-NSSAI. The S-NSSAI is the same as the S-NSSAI being used in the PDU session being used via the first base station 200 to which the terminal 100 intends to hand over.

[0111] In step 412, according to an embodiment of the present invention, the second base station 201 that has received the session establishment request message selects the AMF to which the session establishment request message is to be transmitted. The second base station 201 transmits the session establishment request message to the selected AMF 120.

[0112] In step 414, the AMF 120 sends a PDU session request message to the SMF 135. When the request type of the PDU session request message is "existing PDU session", the PDU session request message sent by the AMF 120 to the SMF 135 is, for example, the Nsmf_PDUSession_UptateSMContext Request message described in . That is, instead of a new SM (session management) Context generation request, it may be a request to update the session management context (SM (Session Management) Context) related to the PDU session in use via the first base station 200. The session management context may include information related to the PDU session, such as the PDU Session ID, the connection network type in which the PDU session is in use, and the like.

[0113] The SMF 135 processes the PDU session request. The SMF 135 determines whether the requested S-NSSAI is subject to the aggregation of the maximum number of sessions. For example, the SMF 135 determines whether the requested S-NSSAI is subject to the aggregation of the maximum number of sessions based on the local policy information (local configuration) stored in the SMF 135. Alternatively, the SMF 135 may determine whether the requested S-NSSAI is subject to the aggregation of the maximum number of sessions based on the subscription information received from the UDM 145. Alternatively, all the S-NSSAIs requested by the SMF 135 may be subject to the aggregation of the maximum number of sessions.

[0114] If the requested S-NSSAI is subject to the aggregation of the maximum number of sessions and the request type is "existing PDU session", the SMF 135 can see that the PDU session request is for establishing a PDU session at the first base station 200 and handing over the currently used PDU session to the second base station 201. The SMF 135 checks the session context corresponding to the PDU Session ID included in the PDU session request message (i.e., the PDU Session ID of the PDU session that the terminal 100 is currently using and is the target of session handover). If there is a PDU session corresponding to the PDU Session ID, the SMF 135 decides to hand over the PDU session established and in use at the first base station 200 to the second base station 201. Thereby, the SMF 135 decides that it is not necessary to check the slice availability related to the maximum number of sessions. That is, by handing over the PDU session in use via the first base station 200 to the second base station 201, it is determined that it is not necessary to be counted in the aggregation of the currently used session number. Therefore, the SMF 135 may not execute the slice availability check steps of steps 416 to 420. Alternatively, the SMF 135 executes steps 416 to 420 to notify the NF 202 that the type of the connection network of the PDU session used by the terminal 100 for the S-NSSAI is changed (for example, changed from the connection network supported by the first base station 200 to the connection network supported by the second base station 201).

[0115] In step 422, the SMF 135 sends a response message to the session establishment request message received in step 414 to the AMF 120. Such a response message is, for example, the Nsmf_PDUSession_UptateSMContext Response message described in .

[0116] When SMF135 decides to approve the PDU session handover using slice (S-NSASI), the response message in step 422 that SMF135 sends to AMF120 includes a PDU session establishment approval message indicating session handover permission. When SMF135 decides to reject the PDU session handover using slice (S-NSASI), although not shown in the figure, the response message in step 422 that SMF135 sends to AMF120 includes a PDU session establishment rejection message indicating session handover rejection.

[0117] In steps 424 - 426, AMF120 sends the PDU session establishment approval message received from SMF135 to terminal 100 via the second base station 201. The operation when a PDU session establishment rejection message is sent is also executed in the same way.

[0118] After that, terminal 100 that has received the PDU session establishment approval message can know that the PDU session in use has been successfully handed over to the second base station 201 via the first base station 200.

[0119] SMF135 that has processed the session handover decides in step 428a to release the PDU session established via the first base station 200 and executes the PDU session release procedure.

[0120] Alternatively, terminal 100 that has confirmed the success of the session handover decides in step 428b to release the PDU session established via the first base station 200 and executes the PDU session release procedure.

[0121] Alternatively, in steps (428c, 428d), SMF135 that has processed the session handover and terminal 100 that has confirmed the success of the session handover each delete the PDU session information related to the first base station 200.

[0122] In the embodiment of FIG. 4, the PDU session release is executed via step 428a, step 428b, or step (428c, d).

[0123] Also, according to an embodiment of the present invention, the PDU session handover procedure shown in FIG. 4 may occur when the terminal 100 cannot use a slice (S-NSSAI) via the first base station 200 (for example, when the S-NSSAI is not included in the Allowed NSSAI for the first base station 200, when the S-NSSAI is included in the rejected S-NSSAI for the first base station 200, when the registration of the terminal via the first base station 200 is deregistered, etc.). In this case, the AMF 120 performs the following operations to maintain the PDU session-related SM context stored in the SMF 135 in preparation for the procedure of FIG. 4 to occur.

[0124] The AMF 120 that determines that the Allowed NSSAI for the first base station 200 does not include the S-NSSAI does not immediately execute the operation of excluding the S-NSSAI from the Allowed NSSAI for the first base station 200, but executes it after a certain time (for example, after the expiration of the timer) has elapsed.

[0125] Alternatively, the AMF 120 that determines to include the S-NSSAI in the rejected S-NSSAI for the first base station 200 does not immediately execute the operation of including the S-NSSAI in the rejected S-NSSAI for the first base station 200, but executes it after a certain time (for example, after the expiration of the timer) has elapsed.

[0126] Alternatively, the AMF 120 that determines to deregister the terminal via the first base station 200 does not immediately execute the deregistration of the terminal via the first base station 200, but performs it after a certain time (for example, after the expiration of the timer) has elapsed.

[0127] Alternatively, when the terminal 100 cannot use a slice (S-NSSAI) via the first base station 200, the AMF 120 does not immediately instruct the SMF 135 to delete the SM context related to the PDU session, but instructs it after a certain period of time (for example, after the expiration of a timer) has elapsed. To instruct the SMF 135 to delete the SM context related to the PDU session, the AMF 120 sends the Nsmf_PDUSession_UpdateSMContext, or the Nsmf_PDUSession_ReleaseSMContextRequest message exemplified in . The SMF 120 that has received the Nsmf_PDUSession_UpdateSMContext, or the Nsmf_PDUSession_ReleaseSMContextRequest message, deletes the related SM context.

[0128] Alternatively, when the terminal 100 cannot use a slice (S-NSSAI) via the first base station 200, the AMF 120 instructs the SMF 135 to delete the SM context related to the PDU session after a specific period of time has elapsed. For example, the Nsmf_PDUSession_UpdateSMContext, or the Nsmf_PDUSession_ReleaseSMContextRequest message exemplified in that the AMF 120 sends to instruct the SMF 135 to delete the SM context related to the PDU session contains time information (timer). The SMF 120 that has received the Nsmf_PDUSession_UpdateSMContext, or the Nsmf_PDUSession_ReleaseSMContextRequest message, deletes the related SM context after the time included in the received message has elapsed (after timer expires).

[0129] FIG. 5 is a diagram showing a configuration example of the UE 100 according to an embodiment of the present invention.

[0130] Referring to FIG. 5, the UE 100 is implemented to include a processor 502 that performs wireless communication and a transceiver 504 in accordance with the communication method defined in the communication system having the configuration of FIG. 1. The processor 501 controls the operation of the transceiver 903 and controls the entire apparatus to execute a session establishment procedure and a session handover procedure in accordance with the method described in at least one of the embodiments of FIGS. 1 to 4.

[0131] FIG. 6 is a diagram showing the configuration of a network entity (or NF) according to an embodiment of the present invention. The network entity (or NF) is one of the components excluding the UE 100 in the configuration of FIG. 1.

[0132] The network entity (or NF) in FIG. 6 is implemented to include a processor 602 that performs wired / wireless communication and a communication interface 604 in accordance with the communication method defined in the communication system having the configuration of FIG. 1. The processor 602 controls the operation of the communication interface 604 and controls the entire apparatus to execute a session establishment procedure and a session handover procedure in accordance with the method described in at least one of the embodiments of FIGS. 1 to 4.

[0133] In the detailed description of the present invention, specific embodiments have been described, but it goes without saying that various modifications are possible without departing from the technical scope of the present invention. Therefore, the technical scope of the present invention should not be defined as being limited to the described embodiments, but should be defined by those equivalent to the technical scope of the present invention.

Description of Reference Numerals

[0134] 100 UE (Terminal) 110 RAN (Base Station) 115 N3GPP Connected Network 120 AMF 130 UPF 135 SMF 140 PCF 145 UDM 150 UDR 160 NSSF 165 NWDAF 200 First AN (First base station) 201 Second AN (Second base station) 202 NF 502, 602 Processor 504 Transceiver 604 Communication interface

Claims

1. A method performed by a network entity in a wireless communication system including a 3GPP (3rd generation partnership project) connected network and a non-3GPP (non-3GPP) connected network, comprising: receiving, from an SMF (Session Management Function), a request message including information on an access type for a network slice related to a PDU (protocol data unit) session, information indicating an identifier of the PDU session, an identifier of the network slice, and an identifier of a user equipment (UE) related to the PDU session, wherein the information on the access type includes at least one of the 3GPP connected network and the non-3GPP connected network; determining, based on the request message, whether to increase a current number of PDU sessions for the network slice. [[ / ]]

2. The method according to claim 1, wherein the network entity is set to a maximum number of PDU sessions for an S-NSSAI (single-network slice selection assistance information) for identifying the network slice.

3. The method according to claim 1, wherein the network entity receives the request message in a step of confirming availability related to the network slice.

4. The method according to claim 1, wherein the network entity receives the information on the access type from the SMF in a PDU session establishment procedure.

5. The method according to claim 1, wherein the non-3GPP connected network includes a wireless LAN.

6. A network entity in a wireless communication system including a 3GPP (3rd generation partnership project) connected network and a non-3GPP (non-3GPP) connected network, comprising: a transceiver Receive, from the SMF (session management function) via the transceiver, a request message including information on the access type for a network slice related to a PDU (protocol data unit) session, information indicating an identifier of the PDU session, an identifier of the network slice, and an identifier of a user equipment (UE) related to the PDU session, wherein the information on the access type includes at least one of the 3GPP connection network and the non-3GPP connection network. A processor configured to determine whether to increase a current number of PDU sessions for the network slice based on the request message. A network entity, characterized by including the above.

7. The network entity according to claim 6, characterized in that the network entity is set to a maximum number of PDU sessions for the S-NSSAI (single-network slice selection assistance information) for identifying the network slice.

8. The network entity according to claim 6, characterized in that the processor is configured to receive the request message in a step of checking the availability related to the network slice via the transceiver.

9. The network entity according to claim 6, characterized in that the processor is configured to receive the information on the access type from the SMF in a PDU session establishment procedure via the transceiver.

10. The network entity according to claim 6, characterized in that the non-3GPP connection network includes a wireless LAN.

11. The first connection network is one of a 3GPP (3rd generation partnership project) connection network and a non-3GPP (non-3GPP) connection network, and the second connection network is the other one of the 3GPP connection network and the non-3GPP connection network. In a wireless communication system including the first connection network and the second connection network, a method executed by an SMF (session management function), receiving, from an AMF (access and mobility management function), a first request message related to a PDU (protocol data unit) session establishment procedure of a terminal to the second connection network; when the first request message is for requesting a PDU session handover from the first connection network to the second connection network, transmitting a response message to the AMF in response to receiving the first request message without interaction for checking network slice availability related to the number of PDU sessions per network slice. The method is characterized by including the above steps.

12. The method according to claim 11, wherein the first request message includes a request type indicating an existing PDU session for the PDU session handover.

13. The method according to claim 11, further comprising, when the first request message is for requesting establishment of a new PDU session of the terminal, transmitting a second request message for checking network slice availability to a network entity responsible for checking network slice availability.

14. The method according to claim 11, wherein the first request message includes information regarding a connection type (Access Type) of a PDU session currently used by the terminal in the first connection network.

15. The method according to claim 11, wherein the non-3GPP connection network includes a wireless LAN.

16. The first connection network is one of a 3GPP (3rd generation partnership project) connection network and a non-3GPP (non-3GPP) connection network, the second connection network is the other one of the 3GPP connection network and the non-3GPP connection network, and an SMF (session management function) in a wireless communication system including the first connection network and the second connection network, a communication interface, and receiving, from an AMF (access and mobility management function) via the communication interface, a first request message related to a PDU (protocol data unit) session establishment procedure of a terminal to the second connection network, a processor configured to transmit a response message to the AMF via the communication interface in response to the reception of the first request message without interaction for confirmation of network slice availability related to the number of PDUs per network slice when the first request message is for requesting a PDU session handover from the first connection network to the second connection network. An SMF characterized by including.

17. The SMF according to claim 16, wherein the first request message includes a request type indicating an existing PDU session for the PDU session handover.

18. The processor is further configured to transmit, via the communication interface, a second request message for confirmation of network slice availability to a network entity responsible for confirmation of network slice availability when the first request message is for requesting establishment of a new PDU session of the terminal. The SMF according to claim 16, characterized in that

19. The SMF according to claim 16, wherein the first request message includes information on a connection type (Access Type) of a PDU session currently used by the terminal in the first connection network.

20. The SMF according to claim 16, wherein the non-3GPP connection network includes a wireless LAN.

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