Method and apparatus for supporting various services in wireless communication system

Abstract

The present disclosure relates to a fifth generation (5G) or quasi-5G communication system for supporting a higher data transmission rate than a fourth generation (4G) system such as long term evolution (LTE). The present disclosure provides a method for operating a terminal in a wireless communication system, the method comprising: performing communication with an access and mobility management function (AMF) in a first network; and sending a radio resource control (RRC) message including information about the AMF in a second network.

Description

Technical Field

[0001] The present disclosure relates generally to a wireless communication system, and more particularly, to a method and apparatus for supporting various services by supporting mobility of a terminal in a wireless communication system. Background Art

[0002] In order to meet the increased demand for wireless data services since the deployment of the fourth generation (4G) communication system, efforts have been made to develop an improved fifth generation (5G) or quasi-5G communication system. Therefore, the 5G or quasi-5G communication system is also called "super 4G network" or "post-long term evolution (LTE) system".

[0003] 5G communication systems are considered to be implemented in higher frequency (mmWave) bands (e.g., 60 GHz bands) in order to achieve higher data rates. In order to reduce the propagation loss of radio waves and increase the transmission distance, beamforming, massive multiple-input multiple-output (MIMO), full-dimensional MIMO (FD-MIMO), array antennas, analog beamforming, and massive antenna technologies are discussed in 5G communication systems.

[0004] Furthermore, in the 5G communication system, development of system network improvements is being conducted based on advanced small cells, cloud radio access networks (RAN), ultra-dense networks, device-to-device (D2D) communications, wireless backhaul, mobile networks, cooperative communications, coordinated multipoint (CoMP), receiving-end interference cancellation, etc. In the 5G system, hybrid frequency shift keying (FSK) with quadrature amplitude modulation (FQAM) and sliding window superposition coding (SWSC) as advanced coding modulation (ACM) have been developed, as well as filter bank multi-carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as advanced access technologies.

[0005] Due to the development of various information technologies (IT), network devices have evolved into virtualized network functions (NFs) by applying virtualization technology thereto, and virtualized NFs are implemented in the form of software that exceeds physical limitations and can therefore be installed / operated in different types of clouds or data centers (DCs). Specifically, NFs can be freely scaled up or down, installed (initialized), or terminated according to service requirements, system capacity, and network load.

[0006] In order to support various services in these various network structures, network slicing technology is introduced. Network slicing is a technology that uses a set of network functions (NFs) that support specific services to logically configure a network and separate the network from other slices. A terminal can access two or more slices while receiving various services.

[0007] The above information is presented as background information only to assist in understanding the present disclosure. No determination has been made, and no assertion has been made, as to whether any of the above may be applicable as prior art with respect to the present disclosure. Summary of the invention

[0008] Solution to the problem

[0009] Based on the above discussion, the present disclosure provides a method and apparatus for supporting various services by supporting mobility of a terminal in a wireless communication system.

[0010] In order to solve the above technical problems, various embodiments provide a method for operating a terminal in a wireless communication system. The method for operating a terminal includes: performing communication with an access and mobility management function (AMF) in a first network; and sending a radio resource control (RRC) message including information about the AMF in a second network.

[0011] Various embodiments provide an apparatus for a terminal in a wireless communication system. The apparatus for the terminal includes a transceiver and at least one processor, wherein the at least one processor is configured to: perform communication with an access and mobility management function (AMF) in a first network; and send a radio resource control (RRC) message including information about the AMF in a second network.

[0012] According to various embodiments, the present disclosure may provide a method and apparatus for supporting various services by supporting mobility of a terminal in a wireless communication system.

[0013] Effects obtainable according to the present disclosure may not be limited to the above-mentioned effects, and other effects not mentioned may be clearly understood by those skilled in the art to which the present disclosure pertains through the following description.

[0014] Before proceeding to the following detailed description, it may be helpful to set forth definitions of certain words and phrases used throughout this patent document: the terms "include" and "comprising" and their derivatives mean including without limitation; the term "or" is inclusive, meaning and / or; the phrases "associated with" and "associated with" and their derivatives may mean including, included, interconnected with, containing, contained within, connected to or connected with, coupled to or coupled with, communicable with, cooperating with, intertwined, juxtaposed, proximate to, bound to or bound with, having, having the property of, etc.; and the term "controller" means any device, system, or portion thereof that controls at least one operation, such device may be implemented in hardware, firmware, or software, or a particular combination of at least two thereof. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether local or remote.

[0015] In addition, the various functions described below can be implemented or supported by one or more computer programs, each of which is formed by a computer-readable program code and is included in a computer-readable medium. The terms "application" and "program" refer to one or more computer programs, software components, instruction sets, processes, functions, objects, classes, instances, related data or parts thereof suitable for being implemented with suitable computer-readable program codes. The phrase "computer-readable program code" includes any type of computer code, including source code, object code and executable code. The phrase "computer-readable medium" includes any type of medium that can be accessed by a computer, such as a read-only memory (ROM), a random access memory (RAM), a hard drive, a compact disk (CD), a digital video disc (DVD) or any other type of memory. "Non-transitory" computer-readable media excludes wired, wireless, optical or other communication links that transmit temporary electricity or other signals. Non-transitory computer-readable media include media that can permanently store data and media that can store and overwrite data later, such as rewritable optical disks or erasable memory devices.

[0016] Definitions for certain words and phrases are provided throughout this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description in conjunction with the accompanying drawings, wherein like reference numerals represent like parts:

[0018] Figure 1 A wireless communication system according to various embodiments is shown;

[0019] Figure 2 shows the configuration of a base station in a wireless communication system according to various embodiments;

[0020] Figure 3 shows a configuration of a terminal in a wireless communication system according to various embodiments;

[0021] Figure 4 shows the configuration of a communication unit in a wireless communication system according to various embodiments;

[0022] Figure 5 is a flow chart illustrating the operation of a terminal in a wireless communication system according to various embodiments;

[0023] Figure 6 An example of a 5G system structure based on SBA in a wireless communication system according to various embodiments is shown;

[0024] Figure 7 An example of a network structure in a wireless communication system according to various embodiments is shown;

[0025] Figure 8 The concept of network slicing (i.e., dedicated network) in a wireless communication system according to various embodiments is illustrated;

[0026] Fig. 9 An example of a process for supporting various services in a wireless communication system according to various embodiments is shown;

[0027] Fig.10 An example of a process for supporting various services in a wireless communication system according to various embodiments is shown;

[0028] Fig.11 An example of a process for supporting various services in a wireless communication system according to various embodiments is shown;

[0029] Fig.12 An example of a process for supporting various services in a wireless communication system according to various embodiments is shown; and

[0030] Fig.13 An example of a process of supporting various services in a wireless communication system according to various embodiments is shown. DETAILED DESCRIPTION

[0031] The following discussion Figures 1 to 13 The various embodiments used to describe the principles of the present disclosure in this patent document are illustrative only and should not be interpreted in any way to limit the scope of the present disclosure. Those skilled in the art will understand that the principles of the present disclosure can be implemented in any appropriately arranged system or device.

[0032] The terms used in the present disclosure are only used to describe specific embodiments, and are not intended to limit the present disclosure. Singular expressions may include plural expressions unless they are clearly different in context. Unless otherwise defined, all terms used herein (including technical terms and scientific terms) have the same meaning as the meaning generally understood by those skilled in the art to which the present disclosure belongs. Terms such as those defined in widely used dictionaries may be interpreted as having the meanings equal to the contextual meanings in the relevant technical field, and will not be interpreted as having ideal or too formal meanings, unless clearly defined in the present disclosure. In some cases, even the terms defined in the present disclosure should not be interpreted as excluding embodiments of the present disclosure.

[0033] Hereinafter, various embodiments of the present disclosure will be described based on a hardware method. However, various embodiments of the present disclosure include techniques using both hardware and software, and therefore various embodiments of the present disclosure may not exclude the software perspective.

[0034] Hereinafter, the present disclosure relates to a method and apparatus for supporting various services in a wireless communication system. Specifically, the present disclosure describes a technology for supporting various services by supporting mobility of a terminal in a wireless communication system.

[0035] Hereinafter, in the present disclosure, for the convenience of explanation, terms for identifying access nodes, terms referring to network entities or network functions (NFs), 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 described below, and other terms indicating objects having equivalent technical meanings may be used.

[0036] Hereinafter, for convenience of explanation, the present disclosure uses terms and names defined in the 3rd Generation Partnership Project Long Term Evolution (3GPP LTE) and 5G standards. However, the present disclosure is not limited to the terms and names and can be applied to systems conforming to other standards.

[0037] Figure 1 A wireless communication system according to various embodiments is shown. Figure 1 Base station 110, terminal 120, and terminal 130 are shown as parts of nodes using wireless channels in a wireless communication system. Figure 1 Only one base station is shown, but other base stations that are the same as or similar to base station 110 may also be included.

[0038] The base station 110 is a network infrastructure for providing wireless access to the terminals 120 and 130. The base station 110 includes a coverage area defined as a predetermined geographical area based on a distance in which signal transmission is possible. In addition to a base station, the base station 110 may also be referred to as an "access point (AP)", "eNodeB (eNB)", "5th generation node (5G node)", "radio point", "transmission / reception point (TRP)" or other terms having equivalent technical meanings thereof.

[0039] Each of the terminal 120 and the terminal 130 is a device used by a user and communicates with the base station 110 through a wireless channel. In some cases, at least one of the terminal 120 and the terminal 130 may be operated without user participation. That is, at least one of the terminal 120 and the terminal 130 is a device for performing machine type communication (MTC) and may not be carried by the user. In addition to the terminal, each of the terminal 120 and the terminal 130 may also be referred to as a "user equipment (UE)", "mobile station", "subscriber station" or "remote terminal", "wireless terminal", "user device" or other terms with equivalent technical meanings.

[0040] The base station 110, the terminal 120 and the terminal 130 can transmit or receive radio signals in the millimeter wave frequency band (e.g., 28 GHz, 30 GHz, 38 GHz and 60 GHz). Here, in order to improve the channel gain, the base station 110, the terminal 120 and the terminal 130 can perform beamforming. Here, beamforming may include transmit beamforming and receive beamforming. That is, the base station 110, the terminal 120 and the terminal 130 can give directionality to the transmitted signal or the received signal. To this end, the base station 110 and the terminals 120 and 130 can select the service beams 112, 113, 121 and 131 through a beam search or beam management process. After the service beams 112, 113, 121 and 131 are selected, subsequent communications are performed through resources that are in a quasi-co-located (QCL) relationship with the resources that have transmitted the service beams 112, 113, 121 and 131.

[0041] Figure 2 A configuration of a base station in a wireless communication system according to various embodiments is shown. Figure 2 The configuration shown in can be understood as the configuration of the base station 110. The term "unit" or a term ending with the suffix "device" used in the following description refers to a unit that processes at least one function or operation and can be implemented by hardware, software, or a combination of hardware and software.

[0042] refer to Figure 2 , the base station 110 includes a wireless communication unit 210 , a backhaul communication unit 220 , a storage device 230 , and a controller 240 .

[0043] The wireless communication unit 210 performs a function for sending or receiving a signal through a wireless channel. For example, the wireless communication unit 210 performs a conversion function between a baseband signal and a bit string according to the physical layer standard of the system. For example, when data is transmitted, the wireless communication unit 210 generates a complex symbol by encoding and modulating the transmitted bit string. In addition, when data is received, the wireless communication unit 210 reconstructs the received bit string by demodulating and decoding the baseband signal. In addition, the wireless communication unit 210 up-converts the baseband signal into a radio frequency (RF) band signal and transmits the RF signal through an antenna, and down-converts the RF band signal received through the antenna into a baseband signal.

[0044] To this end, the wireless communication unit 210 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a digital-to-analog converter (DAC), an analog-to-digital converter (ADC), etc. In addition, the wireless communication unit 210 may include multiple transmission / reception paths. In addition, the wireless communication unit 210 may include at least one antenna array configured by multiple antenna elements. In terms of hardware, the wireless communication unit 210 may include a digital unit and an analog unit, and the analog unit may include multiple subunits according to operating power, operating frequency, etc.

[0045] The wireless communication unit 210 transmits or receives a signal as described above. Therefore, all or part of the wireless communication unit 210 may be referred to as a "transmitter", "receiver", "transmitter / receiver" or "transceiver". In addition, in the following description, transmission or reception performed through a wireless channel may include performing the processing performed by the wireless communication unit 210 as described above.

[0046] The backhaul communication unit 220 provides an interface for performing communication with other nodes in the network. That is, the backhaul communication unit 220 converts a bit string sent from the base station 110 to another node (e.g., another access node, another base station, an upper node, and a core network) into a physical signal, and converts a physical signal received from another node into a bit string.

[0047] The storage device 230 stores data such as basic programs, application programs, and configuration information for the operation of the base station 110. The storage device 230 may include a volatile memory, a nonvolatile memory, or a combination of a volatile memory and a nonvolatile memory. The storage device 230 then provides the stored data according to a request of the controller 240.

[0048] The controller 240 controls the overall operation of the base station 110. For example, the controller 240 sends or receives a signal through the wireless communication unit 210 or the backhaul communication unit 220. In addition, the controller 240 records data in the storage device 230 or reads data from the storage device 230. In addition, the controller 240 can perform the functions of the protocol stack required in the communication standard. To this end, the controller 240 may include at least one processor.

[0049] Figure 3 A configuration of a terminal in a wireless communication system according to various embodiments is shown. Figure 3 The configuration shown in can be understood as the configuration of the terminal 120. The term "unit" or a term ending with the suffix "device" used hereinafter refers to a unit that processes at least one function or operation and may be implemented by hardware, software, or a combination of hardware and software.

[0050] refer to Figure 3 The terminal 120 includes a communication unit 310 , a storage device 320 , and a controller 330 .

[0051] The communication unit 310 performs a function for sending or receiving a signal through a wireless channel. For example, the communication unit 310 performs a conversion function between a baseband signal and a bit string according to the physical layer standard of the system. For example, when data is transmitted, the communication unit 310 generates a complex symbol by encoding and modulating the transmitted bit string. In addition, when data is received, the communication unit 310 reconstructs the received bit string by demodulating and decoding the baseband signal. In addition, the communication unit 310 up-converts the baseband signal to an RF band signal and transmits the RF signal through an antenna, and down-converts the RF band signal received through the antenna to a baseband signal. For example, the communication unit 310 may include a transmit filter, a receive filter, an amplifier, a mixer, an oscillator, a DAC, and an ADC.

[0052] In addition, the communication unit 310 may include multiple transmit / receive paths. In addition, the communication unit 310 may include at least one antenna array including multiple antenna elements. In terms of hardware, the communication unit 310 may include digital circuits and analog circuits (e.g., radio frequency integrated circuits (RFIC)). Here, the digital circuits and analog circuits may be implemented in one package. In addition, the communication unit 310 may include multiple RF chains. In addition, the communication unit 310 may perform beamforming.

[0053] The communication unit 310 transmits or receives a signal as described above. Therefore, all or part of the communication unit 310 may be referred to as a "transmitter", "receiver", "transmitter / receiver" or "transceiver". In addition, in the following description, transmission and reception performed through a wireless channel may include performing the processing performed by the communication unit 310 as described above.

[0054] The storage device 320 stores data used for the operation of the terminal 120, such as basic programs, application programs, and configuration information. The storage device 320 may include a volatile memory, a nonvolatile memory, or a combination of a volatile memory and a nonvolatile memory. The storage device 320 then provides the stored data according to a request of the controller 330.

[0055] The controller 330 controls the overall operation of the terminal 120. For example, the controller 330 sends or receives a signal through the communication unit 310. In addition, the controller 330 records data in the storage device 320 or reads data from the storage device 320. In addition, the controller 330 can perform the functions of the protocol stack required by the communication standard. To this end, the controller 330 may include at least one processor or microprocessor, or may be part of a processor. In addition, the part of the communication unit 310 and the controller 330 may be referred to as a communication processor (CP).

[0056] Figure 4 A configuration of a communication unit in a wireless communication system according to various embodiments is shown. Figure 4 Shows Figure 2 The wireless communication unit 210 or Figure 3 An example of a detailed configuration of the communication unit 310 is shown. Specifically, Figure 4 Elements for performing beamforming are shown as Figure 2 A portion of the wireless communication unit 210 or Figure 3 Part of the communication unit 310.

[0057] refer to Figure 4 , the wireless communication unit 210 or the communication unit 310 includes a coding and modulation unit 402, a digital beamformer 404, a plurality of transmission paths 406-1 to 406-N, and an analog beamformer 408.

[0058] The coding and modulation unit 402 performs channel coding. In order to perform channel coding, at least one of a low density parity check (LDPC) code, a convolutional code, and a polarization code may be used. The coding and modulation unit 402 generates modulation symbols by performing constellation mapping.

[0059] The digital beamformer 404 performs beamforming of a digital signal (e.g., a modulation symbol). To this end, the digital beamformer 404 multiplies the modulation symbol by a beamforming weight. Here, the beamforming weight is used to change the amplitude and phase of the signal and may be referred to as a "precoding matrix", "precoder", etc. The digital beamformer 404 outputs the digitally beamformed modulation symbol via multiple transmission paths 406-1 to 406-N. Here, according to a multiple-input multiple-output (MIMO) transmission scheme, the modulation symbol may be multiplexed or the same modulation symbol may be provided via multiple transmission paths 406-1 to 406-N.

[0060] Multiple transmission paths 406-1 to 406-N convert the digital signal formed by digital beam into analog signal. To this end, each of multiple transmission paths 406-1 to 406-N may include an inverse fast Fourier transform (IFFT) operation unit, a cyclic prefix (CP) inserter, a DAC and an up-converter. The CP inserter is used for orthogonal frequency division multiplexing (OFDM) scheme, and can be excluded when other physical layer schemes (e.g., filter bank multi-carrier (FBMC)) are applied. That is, multiple transmission paths 406-1 to 406-N provide independent signal processing to multiple streams generated by digital beamforming. However, some of the elements of multiple transmission paths 406-1 to 406-N can be used together according to the implementation scheme.

[0061] The analog beamformer 408 performs beamforming of the analog signal. To this end, the digital beamformer 404 multiplies the analog signal by the beamforming weights. Here, the beamforming weights are used to change the amplitude and phase of the signal.

[0062] Figure 5 is a flow chart illustrating terminal operations in a wireless communication system according to various embodiments. Figure 5 A method of operating a terminal is shown.

[0063] refer to Figure 5 In operation 501, the terminal performs communication with an access and mobility management function (AMF) in a first network. According to an embodiment, the AMF is selected by considering a network slice used by the terminal in the first network.

[0064] In operation 502, the terminal sends a radio resource control (RRC) message including information about the AMF in the second network. According to an embodiment, the RRC message includes a tracking area update (TAU) request or an initial access request in the second network.

[0065] According to various embodiments, the present disclosure may further include: in the first network, receiving information about the network slice allowed for the UE from the AMF; and using the information about the network slice to generate an identifier of a dedicated core network (DCN).

[0066] According to an embodiment, the information about the AMF includes an identifier of the AMF or an identifier of a dedicated core network (DCN), and the identifier of the DCN includes information of a network slice used when the terminal moves from a first network to a second network. According to an embodiment, the information about the AMF includes an identifier of a mobility management entity (MME) or a temporary identifier of the UE.

[0067] Figure 6 An example of an SBA-based 5G system structure in a wireless communication system according to various embodiments is shown.

[0068] In order to support various services of 5G, new system structures and protocols are required, and 3GPP has decided to introduce a new technology called service-based architecture (SBA). The main characteristics of the service-based architecture are to divide the functions of the NF defined in the 3GPP standard into service units by considering virtualization technology, the introduction of cloud environment, and the extension of web-based services, and to use the HTTP / 2 protocol when implementing services.

[0069] refer to Figure 6 , Access and Mobility Management Function (AMF) is a network function (NF) for managing mobility and wireless network access to UE. Session Management Function (SMF) is an NF for managing sessions for UE, and session information includes Quality of Service (QoS) information, charging information, and information about packet processing. User Plane Function (UPF) is an NF for processing user plane services and is controlled by SMF. Although not in Figure 1 As shown in , the 5G system may include an unstructured data storage network function (UDSF), and the UDSF is an NF for storing unstructured data, and can store or retrieve any type of data at the request of the NF. The functions and services provided by the AMF are similar to those of the mobility management entity (MME) in the 4G network, and the functions of the AMF and MME can be integrated with each other, or can be implemented or constructed in a way that their functions include each other.

[0070] At the same time, the network can be constructed / operated in the form of network slices to provide various services in the 5G / 4G communication system or to facilitate the isolation or management / operation of the network for each service. A network slice is a collection of NF / NEs used to configure the network to provide communication services. A 5G-based network slice may include AMF, SMF, UPF, next-generation radio access network (NG-RAN), and other network functions / network entities (NF / NE) interworking. A 4G-based network slice may include a mobility management entity (MME), a serving gateway (SGW), a packet data network gateway (PGW), and an evolved universal terrestrial radio access network (E-UTRAN) and other NF / NE interworking.

[0071] Depending on the service requirements and operator policies, the isolation level applied to each network slice may be different. Network slices of some service types are completely isolated, so the information exchange with other network slices is completely blocked, network slices of different service types may expose the least information segments, or other network slices of different types may expose all information segments. Since network slicing is understood as the concept of allocating a dedicated network to a specific service, network slicing and dedicated network have similar meanings in the present disclosure. In addition, in the case where the unit for implementing the concept of network slicing is configured as a network slice instance, the subject matter of the present disclosure is equally applied. That is, the present invention can be applied to the case where a network slice is replaced by a network slice instance.

[0072] Figure 7 An example of a network structure in a wireless communication system according to various embodiments is shown.

[0073] refer to Figure 7 , shows an example of a structure that provides service continuity by linking 5G and 4G networks. In order to control the same subscriber, the unified data management (UDM) and the home subscriber subsystem (HSS) need to be linked to each other, and the SMF / UPF needs to support the functions of the PGW to support session continuity (such as maintaining IP addresses). In addition, the AMF and MME can exchange information for supporting UE mobility between 5G and 4G through the N26 interface.

[0074] Figure 8 The concept of network slicing (i.e., dedicated network) in a wireless communication system according to various embodiments is shown.

[0075] refer to Figure 8, an example is shown in which each slice is completely isolated from each other, and this example corresponds to an aspect in which each slice has the highest security level. That is, when 5G / 4G interworking is supported in each slice, the 5G and 4G networks in the slice can exchange information with each other, but information exchange with other slices may not occur. In the above network structure, for each slice, RAN (NR-RAN or E-UTRAN) can be shared.

[0076] In the above network configuration, the UE can access the 5G network in slice #1 and receive services, and then can switch to 4G. Here, state information (UE context) and security information (security context) used to provide communication services to the UE can be exchanged only within the slice. However, if the base station accessed by the UE selects the evolved packet core (EPC) belonging to slice #2 instead of the EPC belonging to slice #1, the EPC may not provide continuity of communication services to the UE because the EPC may not receive UE information from the 5G core network (5GC) and the UE is in a state of not being registered in the corresponding operator network. In this case, since the service is temporarily unavailable to the user, the quality of service experienced by the user may deteriorate.

[0077] Fig. 9 An example of a process of supporting various services in a wireless communication system according to various embodiments is shown.

[0078] In operation 901, the UE performs a registration procedure to receive services through the 5G network. The detailed operations of the UE, RAN, and core network follow the standard, and in this case, the AMF is selected by considering the network slice to be used by the UE.

[0079] During the registration process, in operation 902, if there is service / slice information (UE usage type) allocated to the UE in the 4G network, the server (UDM / HSS) including subscription information about the user sends the subscription information (including service / slice information (UE usage type)) of the UE (user of the UE) that has requested registration to the AMF.

[0080] In operation 903, the AMF stores the received UE usage type of the UE. The stored UE usage type is one of the state information (UE context) and can be transmitted to another AMF.

[0081] In operation 904, the UE switches to the 4G network according to wireless conditions, service type, mobility, etc. In operation 905, the UE sends a request for receiving services in the 4G network to the evolved packet core (EPC, 4G core) through E-UTRAN. Here, according to the operating mode of the UE, the UE sends a tracking area update (TAU) request or an initial attachment request. The operating mode of the UE is determined based on whether the UE allows an attachment state in which a protocol data unit session (PDU session) does not exist. Messages related to the TAU request or initial access are included in a radio resource control (RRC) message sent by the UE to the E-UTRAN. The request message sent by the UE includes information that can find the AMF that has previously served the UE in the 5G network. This information can be sent via a mapped MME identifier or a temporary identifier assigned to the UE.

[0082] In operation 906, the E-UTRAN selects an MME for transmitting the request (TAU or initial access) from the UE. Here, the E-UTRAN selects the MME using the information received in operation 903. Here, since the mapped MME information transmitted by the UE may be information substantially indicating the AMF and may include information insufficient to find the MME associated with the AMF (ie, the MME and the AMF belong to the same slice), the E-UTRAN may select a third MME, that is, an MME that does not belong to the same slice.

[0083] In operation 907, the E-UTRAN transmits a non-access stratum (NAS) request sent by the UE to the selected MME. The message related to the NAS request includes an identifier (or address) of the AMF that has previously served the UE.

[0084] In operation 908, the MME uses the identifier of the AMF included in the request message of the UE to determine whether the AMF including the existing state information (UE context) of the UE can be interoperated with the MME itself or whether the MME and the AMF belong to the same slice. If interoperation is possible, the MME sends a message (context request) requesting state information (UE context) about the UE directly to the AMF. If interoperation is not possible, the MME sends a request to the UDM / HSS to receive additional information about the UE instead of requesting the state information (UE context) (indicated in operation 909).

[0085] Operation 909 corresponds to a case where it is difficult for the MME to receive status information (UE context) about the UE from the AMF, or to a case where the MMF cannot find the AMF associated with the MMF itself via the identifier sent by the UE. Here, before sending a status information (UE context) request, the MME requests additional information from the UDM / HSS for determining whether a request needs to be sent from the UE to another MME (i.e., belonging to a different slice / dedicated network). Here, the message used by the MME is an Authentication Information Request (AIR), and in this case, the MME configures and sends a flag that explicitly requests the slice / dedicated network information (UE usage type) of the subscriber (UE).

[0086] In operation 910, the UDM / HSS responds to the MME according to the request, and in response to the request, if the subscriber includes slice / dedicated network information (UE usage type), the MME sends an Authentication Information Answer (AIA) message including the slice / dedicated network information.

[0087] This process is performed to receive information for selecting an MME according to a slice / dedicated network structure, rather than actually performing authentication of the UE. Therefore, the MME may include an indication indicating the above request in an authentication information request (AIR) message, and therefore, the UDM / HSS may include only the requested information (except the authentication information) in an authentication information answer (AIA) message.

[0088] In operation 911, the MME uses the information received from the UDM / HSS to determine whether it is necessary to process the request from the UE in another MME (i.e., another slice / dedicated network). Here, the MME may use the address / identifier of the MME mapped to the specific UE usage type as configuration information. Here, information of the MME (MME group, MME identifier, etc.) used to process the request from the UE is specified.

[0089] In operation 912 , the MME transmits a request to the E-UTRAN indicating that the request from the UE is transmitted to another MME (or MME group) selected in operation 911 .

[0090] In operation 913, the E-UTRAN selects a new MME using the information transmitted by the MME, and subsequent operations perform the remaining part of the Tracking Area Update (TAU) or the initial attach procedure.

[0091] Fig.10 An example of a process of supporting various services in a wireless communication system according to various embodiments is shown.

[0092] In operation 1001, the UE performs a registration procedure to receive services through a 5G network. The detailed operations of the UE, RAN, and core network follow the standard, and in this case, the AMF is selected by considering the network slice to be used by the UE.

[0093] During the registration process, in operation 1002, if there is service / slice information (UE usage type) allocated to the UE in the 4G network, the server (UDM / HSS) including subscription information about the user sends the subscription information (including service / slice information (UE usage type)) of the UE (user of the UE) that has requested registration to the AMF.

[0094] In operation 1003, the AMF stores the received UE usage type of the UE. The stored UE usage type is one of the state information (UE context) and can be transmitted to another AMF.

[0095] In operation 1004, the UE switches to the 4G network according to wireless conditions, service type, mobility, etc. In operation 1005, the UE sends a request for receiving services in the 4G network to the evolved packet core (EPC, 4G core) through the E-UTRAN. Here, depending on the operating mode of the UE, the UE sends a tracking area update (TAU) request or an initial attachment request. The UE sends a radio resource control (RRC) message (which is sent by the UE to the E-UTRAN) including a TAU request or an initial access request. The request message sent by the UE includes information that can find the AMF that has previously served the UE in the 5G network. This information can be sent via a mapped MME identifier or a temporary identifier assigned to the UE.

[0096] In operation 1006, the E-UTRAN selects an MME for transmitting a request (Tracking Area Update (TAU) or initial access) from the UE. Here, the E-UTRAN selects the MME using the information received in operation 1003. Here, since the mapped MME information transmitted by the UE may be information substantially indicating the AMF and may include information insufficient to find an MME associated with the AMF (i.e., the MME and the AMF belong to the same slice), the UTRAN may select a third MME, i.e., an MME that does not belong to the same slice.

[0097] In operation 1007, the E-UTRAN transmits the NAS request sent by the UE to the selected MME. The message related to the NAS request includes an identifier (or address) of the AMF that has previously served the UE.

[0098] In operation 1008, the MME uses the identifier of the AMF included in the request message of the UE to determine whether the AMF including the existing state information (UE context) of the UE can interwork with the MME itself or whether the MME and the AMF belong to the same slice. If conventional processing is possible because interworking between the MME and the AMF is possible and the MME and the AMF belong to the same slice, the MME sends a message (context request) requesting state information (UE context) about the UE directly to the AMF. Otherwise, the MME needs to receive additional information from the AMF to determine whether the request from the UE needs to be sent to another MME (i.e., belonging to a different slice / dedicated network). Here, a method will be used in which the MME transmits a separate message or indication of the UE usage type for receiving the UE to the AMF, and in response to this, the AMF notifies the UE of the usage type. Another method is that if the MME sends a state information (UE context) request message including the identifier (or address) of the MME itself, similar to conventional processing, the AMF can determine that the MME that has sent the message can interwork with the AMF itself or the MME and the AMF do not belong to the same slice. If it is impossible to send the entire state information (UE context) according to the request from the MME, the AMF may send information for transmitting the request to another MME. Here, the AMF may notify the MME of the UE usage type, and may guide the MME that has made the request to select another MME (or MME group) corresponding to the UE usage type (indicated in operation 1009), otherwise, the AMF itself may select the information of the MME (or MME group) and notify the selected information.

[0099] In operation 1010 , the MME transmits a request to the E-UTRAN indicating that the request from the UE is transferred to another MME (or MME group) selected in operation 1009 .

[0100] In operation 1011, the E-UTRAN selects a new MME using the information transmitted by the MME, and performs the remaining part of the Tracking Area Update (TAU) or the initial attach procedure in a subsequent operation.

[0101] Fig.11 An example of a process of supporting various services in a wireless communication system according to various embodiments is shown.

[0102] In operation 1101, the UE performs a registration process in order to receive services through a 5G network. The detailed operations of the UE, RAN, and core network follow the standards, and in this case, the AMF is selected by considering the network slice to be used by the UE. During the above process, the UE may additionally include notifying the AMF whether the UE itself uses a dedicated core network identifier (DCN ID) in the 4G network to request a specific slice / dedicated network from the E-UTRAN, that is, notifying the UE whether it supports the enhancement of the dedicated core network (eDECOR) capability.

[0103] During the registration process, in operation 1102, if there is service / slice information (UE usage type) allocated to the UE in the 4G network, the server (UDM / HSS) including subscription information about the user sends the subscription information (including the service / slice information (UE usage type) allocated to the UE) of the UE (user of the UE) that has requested registration to the AMF.

[0104] In operation 1103, the AMF determines the slice / dedicated core network information (DCN ID) to be used for the UE when moving to the 4G network. Here, in determining the DCN ID, the slice information allowed in the 5G network (allowed network slice selection assistance information, allowed NSSAI), the UE usage type received via the subscription information in operation 1102, and the information configured for the AMF are considered. In addition, based on the subscription information of the UE, the AMF considers whether there is a subscribed DNN that allows 4G interworking among the subscribed DNNs of the UE, and considers the capabilities of the UE that has sent the request.

[0105] In operation 1104, if there are slices allowed for the UE, the AMF sends a registration accept message to the UE, and the message includes the allowed slice information (allowed NSSAI) and the DCN ID determined in operation 1103. Here, the DCN ID may be configured in the form of a mapping of each single network slice selection assistance information (S-NSSAI) included in the allowed slice information (allowed NSSAI), or may be transmitted as a representative value of the UE (rather than the value of each S-NSSAI).

[0106] In operation 1105, the UE switches to the 4G network according to wireless conditions, service type, mobility, etc. In operation 1106, the UE sends a request for receiving services in the 4G network to the evolved packet core (EPC, 4G core) through E-UTRAN. Here, depending on the operating mode of the UE, the UE sends a tracking area update (TAU) request or an initial attachment request. Messages related to the TAU request or the initial access request are included in a radio resource control (RRC) message sent by the UE to the E-UTRAN. The request message sent by the UE includes information that enables finding the AMF that has previously served the UE in the 5G network. This information can be sent via a mapped MME identifier or a temporary identifier assigned to the UE. In addition, the UE can send an RRC message including the DCN ID received in operation 1104.

[0107] In operation 1107, the E-UTRAN selects an MME for transmitting a request (Tracking Area Update (TAU) or initial access) from the UE. Here, the E-UTRAN selects the MME using the DCN ID explicitly sent by the UE in operation 1105. If the MME selected using the DCN ID is different from the MME selected using the mapped MME identifier (or MME group identifier), the E-UTRAN may preferentially use the MME selected using the DCN ID.

[0108] In operation 1108, the E-UTRAN transmits the NAS request sent by the UE to the selected MME. The message related to the NAS request includes an identifier (or address) of the AMF that has previously served the UE.

[0109] In operation 1109, the MME sends a request for state information (UE context) to the AMF using the identifier of the AMF included in the request message of the UE, and in response to the request, the MME receives the state information (UE context) in operation 1110. In operation 1107, since an MME belonging to the same slice / dedicated network as that of the AMF can be selected, the request for state information (UE context) can be successfully processed.

[0110] According to operation 1111, the remaining part of the Tracking Area Update (TAU) or the initial attach procedure is performed. During this process, the MME may compare the information received from the AMF, the information received from the UDM / HSS, and the DCN ID requested by the UE, and may perform verification of the request from the UE.

[0111] Fig.12 An example of a process of supporting various services in a wireless communication system according to various embodiments is shown.

[0112] In operation 1201, the UE performs a registration procedure to receive services through the 5G network. The detailed operations of the UE, RAN, and core network follow the standard, and in this case, the AMF is selected by considering the network slice to be used by the UE.

[0113] During the registration process, in operation 1002, if there is service / slice information (UE usage type) allocated to the UE in the 4G network, the server (UDM / HSS) including subscription information about the user sends the subscription information (including service / slice information (UE usage type)) of the UE (user of the UE) that has requested registration to the AMF.

[0114] In operation 1203, the AMF determines the slice / dedicated core network information (DCN ID) to be used for the UE when moving to the 4G network. Here, in determining the DCN ID, the slice information allowed in the 5G network (allowed NSSAI), the UE usage type received via the subscription information in operation 1202, and the information configured for the AMF are considered. In addition, the AMF considers whether there is a subscribed DNN that allows 4G interworking among the UE's subscribed DNNs based on the UE's subscription information, and considers the capabilities of the UE that has sent the request.

[0115] In operation 1204, if there are slices allowed for the UE, the AMF sends a registration accept message to the UE, and the message includes allowed slice information (allowed NSSAI).

[0116] In operation 1205, the UE may generate a protocol data unit (PDU) session based on the allowed slice information and the UE's own service conditions.

[0117] In operation 1206, the UE switches to the 4G network according to wireless conditions, service type, mobility, etc. In operation 1207, the UE sends a request for receiving services in the 4G network to the evolved packet core (EPC, 4G core) through the E-UTRAN. Here, depending on the operating mode of the UE, the UE sends a tracking area update (TAU) request or an initial attachment request. Messages related to the TAU request or the initial access request are included in a radio resource control (RRC) message sent by the UE to the E-UTRAN. The request message sent by the UE includes information that enables finding the AMF that has previously served the UE in the 5G network. This information can be sent via a mapped MME identifier or a temporary identifier assigned to the UE.

[0118] During the above process, the UE may generate a DCN ID according to whether the slice is used in the UE's own 5G network, and include the generated DCN ID in an RRC message and send the RRC message. In the current embodiment, since the UE does not explicitly receive a DCN ID from the network, the UE uses the slice information to generate a mapped DCN ID.

[0119] The UE may generate a mapped DCN ID by copying only the slice / service type (SST) portion of the slice information (S-NSSAI) used by the UE itself, or may generate a DCN ID by copying 16 bits in the S-NSSAI. If the UE uses multiple slices, the UE's selection of the S-NSSAI to be used when generating the mapped DCN ID may differ depending on the UE implementation.

[0120] In operation 1208, the E-UTRAN selects an MME for transmitting a request (Tracking Area Update (TAU) or initial access) from the UE. Here, the E-UTRAN selects the MME using the DCN ID explicitly sent by the UE in operation 1207. If the MME selected using the DCN ID is different from the MME selected using the mapped MME identifier (or MME group identifier), the E-UTRAN may preferably use the MME selected using the DCN ID. If the MME associated with the E-UTRAN cannot be selected via the DCN ID sent by the UE, the MME selected using the MME identifier (or MME group identifier) ​​mapped to the MME may preferably be used.

[0121] In operation 1209, the E-UTRAN transmits the NAS request sent by the UE to the selected MME. The message related to the NAS request includes an identifier (or address) of the AMF that has previously served the UE.

[0122] In operation 1210, the MME sends a request for status information (UE context) to the AMF using an identifier of the AMF included in the request message of the UE, and in operation 1211, in response to the request, the MME receives the status information (UE context).

[0123] In operation 1212, the MME may compare the information received from the AMF, the information received from the UDM / HSS, and the DCN ID requested by the UE, and may perform verification of the request from the UE.

[0124] According to operation 1213, the remaining procedures of the Tracking Area Update (TAU) or the initial attach are performed.

[0125] At the same time, various embodiments propose technologies that enable the user plane function (UPF) and session management function (SMF) supporting 5G-4G intercommunication in a network in which a 5G core network (5GC) is introduced to be used in a 4G-dedicated UE. According to an embodiment, the SMF supports the functions of the packet data network gateway control plane (PGW-C), and the UPF supports the functions of the packet data network gateway user plane (PGW-U). In this case, the target UE is a UE supporting 4G (LTE / Evolved Packet System (EPS)) (i.e., a UE supporting only EPC NAS), and the subscription information needs to be configured to allow access to the 5G system (5GS). Allowing access to 5GS can be specifically expressed as not including 5GC in the core network type restriction in the subscription information.

[0126] The UE performs an access request (Tracking Area Update (TAU) or initial attachment) through the E-UTRAN, and the MME that has received the access request receives subscription information including allowing 5GS access for the UE from the UDM / HSS. Here, in the process of generating / adding a PDN connection, in a network configuration in which 4G services through SMF / UPF are allowed, the MME can select SMF / UPF in the PGW selection process for the 4G UE.

[0127] Here, since the session management function + packet data network gateway-control (SMF+PGW-C) is a device for 5G, but the UE only supports 4G, there is no need to add new parameters newly added for 5G to the parameters sent to the UE. In addition, unlike the 5G UE, the 4G UE itself cannot generate a PDU session ID, but the operation for the SMF / UPF requires the generation of a PDU session ID. Therefore, the SMF / UPF (rather than the UE) generates a PDU session ID only when connecting to a 4G UE, and uses the PDU session ID to communicate with the unified data management (UDM) / policy control function (PCF).

[0128] Meanwhile, during the above process, a method for SMF+PGW-C to identify whether the UE is a 5G-supported UE is required. According to an embodiment, the UE sends whether the UE itself supports 5G (i.e., whether the UE supports 5G NAS) by means of a protocol control option (PCO) or an extended PCO (ePCO) included in a request message, which is sent to the SMF-PGW-C to establish a PDN connection. Whether 5G is supported in the direction in which the UE performs transmission to the network in the PCO / ePCO may be added as an information element (IE) of an additional parameter list in the PCO. In order to implement the above configuration, the container includes as its content a container identifier indicating whether the container includes a specific IE for indicating whether the UE supports 5G, its length, and information indicating whether the UE supports 5G.

[0129] During the process of generating a PDN connection, the SMF / PGW-C receives information about whether the UE supports 5G through the PCO / ePCO. In the case where the information about whether the UE supports 5G is explicitly included, the SMF / PGW-C determines that the UE supports 5G, and if the information about whether the UE supports 5G is not explicitly included, the SMF / PGW-C determines that the UE does not support 5G.

[0130] According to another embodiment, in the case where the UE includes a parameter newly added in 5G in the PCO or ePCO of the request message, rather than in the case where the UE explicitly notifies the SMF / PGW-C whether the UE supports 5G, the SMF / PGW-C determines that the UE supports 5G. When the PDU session ID among the parameters newly added in 5G is included in the PCO or ePCO of the message requested to establish a PDN connection, the SMF / PGW-C determines that the UE supports 5G, and if the PDU session ID is not included in the PCO or ePCO, the SMF / PGW-C determines that the UE does not support 5G and generates the PUD session ID by itself.

[0131] Alternatively, the UE may notify the SMF / PGW-C of whether the UE supports 5G and a 5G Session Management (5GSM) cause value among the parameters newly added for 5G in the PCO or ePCO of the message requested to establish the PDN connection. That is, if the 5GSM cause value is included in the request from the UE, the SMF / PGW-C determines that the UE supports 5G, and if the 5GSM cause value is not included in the request from the UE, the SMF / PGW-C determines that the UE does not support 5G.

[0132] In the above embodiment, when it is determined that the UE supports only 4G, the SMF / PGW-C does not need to add the parameters newly added for 5G to the parameters sent to the UE, and in the direction in which the parameters are sent from the network to the UE, the 5G parameters do not need to be included in the PCO / ePCO. In addition, unlike the 5G UE, the 4G UE cannot generate a PDU session ID by itself, but the operation for the SMF / UPF requires the generation of a PDU session ID. Therefore, the SMF / UPF (rather than the UE) generates a PDU session ID only when the 4G UE performs access, and uses the PDU session ID to interwork with the UDM / PCF.

[0133] Fig.13 An example of a process of supporting various services in a wireless communication system according to various embodiments is shown.

[0134] Fig.13 The embodiments may be performed by a 5G network. Fig.13The embodiments of can be performed by any network function (NF) configuring the 5G network. However, Fig.13 The embodiments mainly describe the operation of AMF.

[0135] In operation 1301, the AMF may receive a deregistration request message from the UE. The deregistration request message includes a temporary identifier of the UE (e.g., a 5G Global Unique Temporary Identifier (GUTI)), a type of deregistration request (shutdown, etc.) from the UE, or an access type to be deregistered (e.g., 3GPP, non-3GPP, or both).

[0136] In operation 1302, the AMF may determine whether there is a PDU session established for the UE that is currently performing the request. If the UE specifies an access type, it may be determined whether the PDU session is established based on whether there is a PDU session in an established state for the corresponding access type. The AMF may consider whether the PDU session established for the UE that has performed the request is activated. The activation of the PDU session may be represented by configuring resources (i.e., a tunnel) for the corresponding UE so that user plane data can be sent or received between the access node (AN) and the UPF. If there is an established or activated PDU session, the AMF may determine whether the public land mobile network (PLMN) has activated the second (2 nd )RAT usage report. More specifically, the PLMN performs configuration so that 2 nd The AMF may determine that the condition is met in case the RAT usage report is applied to an established or activated PDU session.

[0137] In the following operations 1303 to 1305 or operations 1306 to 1309, only one process selected between operations 1303 to 1305 and operations 1306 to 1309 is performed according to the determination made in the above operation 1302. If two or more PDU sessions are established for the UE, the AMF may select a PDU session based on two or more PDU sessions. nd The RAT usage report selectively applies operations 1303 to 1304 or operations 1306 to 1308 whether it is applied to each PDU session.

[0138] In operation 1303, if application 2 is not required nd If the RAT usage report is not available, the AMF can send a PDU session release request message to the SMF. If multiple PDU sessions have been established for the UE, this process can be performed for each PDU session.

[0139] In operation 1304, the AMF may receive a PDU session release response from the SMF. In addition, the remaining operations of the PDU session release (e.g., PCF and policy termination) may be performed.

[0140] In operation 1305, if a response to the deregistration request received from the UE needs to be sent, in response thereto, the AMF may send a deregistration acceptance message to the UE. In addition, the AMF may perform an operation of releasing the N2 signaling connection with the base station.

[0141] In operation 1306, if 2 nd If the RAT usage report is applied to the UE, the AMF may not immediately perform the process of releasing the PDU session with the SMF. The AMF may send a deregistration acceptance message to the UE as needed.

[0142] In operation 1307, if 2 nd If the RAT usage report is applied to the UE, the AMF may not immediately perform the process of releasing the PDU session with the SMF, and may wait until the signaling connection with the access node (AN) is released. The above operation may be performed so as to receive 2 from the AN during the operation of releasing the signaling connection with the AN. nd RAT uses data information and nd The RAT usage data information is sent to the SMF together with the PDU session release request. Releasing the signaling connection with the AN corresponds to the case where the AMF sends an N2 UE context release request to the AN and receives a response thereto, or receives a message from the AN notifying that the UE context release has occurred.

[0143] In operation 1308, after the signaling connection with the AN is released, the AMF sends a PDU session release request message to the SMF. If multiple PDU sessions have been established for the UE, this process can be performed for each PDU session. nd RAT uses data reporting and receives 2 from AN nd RAT uses data information, then AMF can nd The RAT usage data information is included in the PDU session release request message (Nsmf_PDUSession_ReleaseSMContextRequest).

[0144] In operation 1309, AMF may receive a message indicating a PDU session release response from SMF. In addition, AMF may perform the remaining operations (e.g., PCF and policy termination) of PDU session release.

[0145] at the same time, Fig.13The embodiments may also be applied to the case where the 5G network deregisters the UE (i.e., NW-initiated deregistration) instead of the case where the AMF receives a deregistration request from the UE. The case where the 5G network deregisters the UE (NW-initiated deregistration) may include at least one of the following cases: the case where the AMF receives a request to deregister the UE from the UDM if the UE's subscription information is deleted; the case where communication with the UE is not performed until a timer inside the AMF expires; or the case where the UE requires the operator's intervention to be deregistered. When the 5G network deregisters the UE (NW-initiated deregistration), in Fig.13 In an embodiment of the present invention, operation 1301 may not be performed, and after the AMF determines to deregister the UE, subsequent operations from operation 1302 may be applied.

[0146] The methods disclosed in the claims of the present disclosure and / or the methods according to the various embodiments described in the specification may be implemented in the form of hardware, software, or a combination of hardware and software.

[0147] When the method is implemented by software, a computer-readable storage medium for storing one or more programs (software modules) may be provided. One or more programs stored in the computer-readable storage medium may be configured to be executed by one or more processors in an electronic device. At least one program may include instructions that cause an electronic device to perform the method according to the various embodiments of the present disclosure as defined in the appended claims and / or disclosed herein.

[0148] The program (software module or software) can be stored in a non-volatile memory, including random access memory and flash memory, read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), magnetic disk storage device, compact disk-ROM (CD-ROM), digital versatile disk (DVD), or other types of optical storage devices, or magnetic tape cassettes. Alternatively, any combination of some or all of them can form the memory in which the program is stored. In addition, a plurality of such memories can be included in the electronic device.

[0149] In addition, the program can be stored in an attachable storage device that can access the electronic device through a communication network (such as the Internet, an intranet, a local area network (LAN), a wide area network (WLAN), and a storage area network (SAN) or a combination thereof). Such a storage device can access the electronic device via an external port. In addition, a separate storage device on a communication network can access the portable electronic device.

[0150] In the above detailed embodiments of the present disclosure, the elements included in the present disclosure are expressed in the singular or plural, depending on the detailed embodiments presented. However, for ease of description, the singular form or the plural form is appropriately selected according to the presented situation, and the present disclosure is not limited to the elements expressed in the singular or plural. Therefore, the elements expressed in the plural may also include a single element, or the elements expressed in the singular may also include multiple elements.

[0151] Although the present disclosure has been described using various embodiments, various changes and modifications may be suggested to one skilled in the art. The present disclosure is intended to encompass such changes and modifications as fall within the scope of the appended claims.

Claims

1. A method for operating a network node in a wireless communication system, the method comprising: receiving a deregistration request message from a user equipment UE supporting a first radio access technology RAT and a second RAT; determining whether a usage report of the second RAT is required for a protocol data unit (PDU) session established for the UE; In case usage reporting of the second RAT is required for the PDU session, sending a deregistration accept message to the UE and sending an N2 UE context release request message for N2 signaling connection release to a radio access node RAN associated with the UE; Waiting for completion of N2 signaling connection release to receive a usage report of the second RAT from the RAN; as well as Send a PDU session release request message to the session management function SMF to release the PDU session.

2. The method according to claim 1, further comprising: During completion of the N2 signaling connection release, a usage report of the second RAT is received from the RAN.

3. The method according to claim 1, wherein: The deregistration request message includes at least one of a 5th generation globally unique temporary identifier 5G-GUTI, a deregistration type, or an access type.

4. The method according to claim 1, further comprising: In case that a usage report of the second RAT is not required for the PDU session, sending a PDU session release request message to the session management function SMF to release the PDU session; as well as Receive PDU Session Release Response message from SMF.

5. The method according to claim 1, further comprising: Identifies the protocol data unit (PDU) session established for the UE.

6. A network node in a wireless communication system, the network node comprising: Transceiver; as well as At least one processor is coupled to the transceiver and is configured to: receiving a deregistration request message from a user equipment UE supporting a first radio access technology RAT and a second RAT, determining whether usage reporting of the second RAT is required for a protocol data unit (PDU) session established for the UE, In case usage reporting of the second RAT is required for the PDU session, a deregistration accept message is sent to the UE, and an N2 UE context release request message for N2 signaling connection release is sent to a radio access node RAN associated with the UE, Waiting for completion of N2 signaling connection release to receive a usage report of the second RAT from the RAN, and Send a PDU session release request message to the session management function SMF to release the PDU session.

7. The network node according to claim 6, wherein: The at least one processor is further configured to: During completion of the N2 signaling connection release, a usage report of the second RAT is received from the RAN.

8. The network node according to claim 6, wherein: The deregistration request message includes at least one of a 5th generation globally unique temporary identifier 5G-GUTI, a deregistration type, or an access type.

9. The network node according to claim 6, wherein: The at least one processor is further configured to: In the case where a usage report of the second RAT is not required for the PDU session, a PDU session release request message is sent to the session management function SMF to release the PDU session, and a PDU session release response message is received from the SMF.

10. The network node according to claim 6, wherein: The at least one processor is further configured to: Identifies the protocol data unit (PDU) session established for the UE.

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