Method and apparatus for improving voice service quality in a wireless communication system

Abstract

The present disclosure relates to a communication method and system for converging a 5th generation (5G) communication system with an Internet of Things (IoT) technology to support a higher data rate than a 4th generation (4G) system. The present disclosure can be applied to smart services based on 5G communication technology and IoT-related technologies, such as smart homes, smart buildings, smart cities, vehicle interconnection, health care, digital education, smart retail, security and safety services.

Description

Technical Field

[0001] The present disclosure relates to a method for improving service quality in a mobile communication system. Background Art

[0002] In order to meet the demand for wireless data traffic that has increased since the deployment of 4G communication systems, a lot of efforts have been made to develop improved 5G or pre-5G communication systems. Therefore, 5G or pre-5G communication systems are also called "super 4G networks" or "post-LTE systems". 5G communication systems are considered to be implemented in higher (millimeter wave) frequency bands, for example, in the 60GHz band, thereby achieving 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 large antenna technology are discussed in 5G communication systems. In addition, in 5G communication systems, system network improvements are being developed based on, for example, advanced small cells, cloud radio access networks (RAN), ultra-dense networks, device-to-device (D2D) communications, wireless backhaul, active networks, collaborative communications, coordinated multi-point (CoMP), and receiving end interface elimination. In the 5G system, hybrid FSK and QAM modulation (FQAM) and sliding window superposition coding (SWSC) have been developed as advanced coding modulation (ACM), and filter bank multi-carrier (FBMC), non-orthogonal multiple access (NOMA) and sparse code multiple access (SCMA) have been developed as advanced access technologies.

[0003] The Internet, which is a human-centered connection network where people generate and consume information, has now evolved into the Internet of Things (IOT), in which distributed entities (e.g., things) exchange and process information without human intervention. The Internet of Everything (IoE), which is a combination of IoT technology and big data processing technology realized by connection with cloud servers, has emerged. Since technical elements such as "sensing technology", "wired / wireless communication and network facilities", "service interface technology" and "security technology" are required for the implementation of IoT, sensor networks, machine-to-machine (M2M) communication, machine type communication (MTC), etc. have been under research recently. Such an IoT environment can provide intelligent Internet technology services that create new value for human life by collecting and analyzing data generated among connected things. Through the integration and combination between existing information technology (IT) and various industry applications, IoT can be applied to a variety of fields, including smart homes, smart buildings, smart cities, smart cars or connected cars, smart grids, health care, smart appliances and advanced medical services.

[0004] In keeping with this, various attempts have been made to apply 5G communication systems to IoT networks. For example, technologies such as sensor networks, machine type communications (MTC), and machine-to-machine (M2M) communications can be implemented through beamforming, MIMO, and array antennas. The application of cloud radio access networks (RANs) as the big data processing technology described above can also be considered as an example of the convergence between 5G technology and IoT technology. Summary of the invention

[0005]

Technical issues

[0006] Meanwhile, due to the development of various IT technologies, network equipment has evolved into virtualized network functions (NFs) by applying virtualization technology, and virtualized NFs can be installed / operated in various clouds or data centers (DCs) because they are implemented in software form, thereby having no physical limitations. Specifically, NFs can be freely expanded / reduced (scaled) or installed / terminated according to service requirements, system capacity, and network load.

[0007] [Solution to the problem]

[0008] According to one aspect of the present disclosure, a method performed by a terminal in a wireless communication system is provided, the method comprising: determining whether a multiple access protocol data unit (MAPDU) session generated by a first access network and a second access network in a fifth generation system (5GS) is moved to an evolved packet system (EPS); sending a request message including a request type and session information; receiving a response message including information about the release of the MA PDU session generated by the second access network; and releasing a context related to a stored access traffic steering, switching, and segmentation (ATSSS), wherein the release of the MA PDU session generated by the second access network is triggered by a network entity.

[0009] In an exemplary embodiment, wherein the first access network is a 3rd Generation Partnership Project (3GPP) access network, and wherein the second access network is a non-3rd Generation Partnership Project (N3GPP) access network.

[0010] In an exemplary embodiment, the request type is an indicator related to handover.

[0011] In an exemplary embodiment, wherein sending the request message comprises sending multiple request messages according to multiple session identifiers, the session information is multiple pieces of session information, and wherein, when the session information is multiple pieces of session information, the multiple pieces of session information comprise multiple session identifiers. The multiple pieces of session information comprise session identifiers.

[0012] In an exemplary embodiment, there is no N26 interface for interworking between the 5GS and the EPS.

[0013] According to another aspect of the present disclosure, a method performed by a network entity in a wireless communication system is provided, the method comprising: when determining that a multiple access protocol data unit (MA PDU) session generated by a first access network and a second access network in a fifth generation system (5GS) is moved to an evolved packet system (EPS), receiving a request message including a request type and session information; triggering the release of the MA PDU session generated by the second access network based on the request type and session information of the received request message; and sending a response message, the response message including information about the release of the MA PDU session, wherein a context related to stored access traffic steering, switching, and segmentation (ATSSS) is released.

[0014] According to one aspect of the present disclosure, a terminal is provided, comprising: a transceiver capable of sending and receiving at least one signal; and a controller coupled to the transceiver, wherein the controller is configured to: determine whether a multiple access protocol data unit (MA PDU) session generated by a first access network and a second access network in a fifth generation system (5GS) is moved to an evolved packet system (EPS); send a request message including a request type and session information; receive a response message including information about the release of the MAPDU session generated by the second access network; and release a context related to a stored access traffic steering, switching and segmentation (ATSSS), wherein the release of the MA PDU session generated by the second access network is triggered by a network entity.

[0015] According to one aspect of the present disclosure, a network entity is provided, comprising: a transceiver capable of sending and receiving at least one signal; and a controller coupled to the transceiver, wherein the controller is configured to: when determining that a multiple access protocol data unit (MA PDU) session generated by a first access network and a second access network in a fifth generation system (5GS) is moved to an evolved packet system (EPS), receive a request message including a request type and session information; trigger the release of the MA PDU session generated using the second access network based on the request type and session information of the received request message; and send a response message, the response message including information about the release of the MA PDU session, wherein the context related to the stored access traffic steering, switching and segmentation (ATSSS) is released.

[0016] Before commencing the detailed description below, it may be helpful to set forth the definitions of certain words and phrases used throughout this patent document: the terms "include" and "comprise" and their derivatives mean including but not limited to; the term "or" is inclusive, meaning and / or; the phrases "associated with" and "associated with" and their derivatives may mean including, included within, interconnected with, containing, included within, connected to or connected with, coupled to or coupled with, communicable with, cooperating with, interleaved, juxtaposed, proximate to, bound to or bound with, having, or having the characteristics of, etc.; and the term "controller" means any device, system, or portion thereof that controls at least one operation, such device may be implemented by hardware, firmware, or software, or some combination of at least two thereof. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely.

[0017] 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 programming code and is embodied 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 implementation by appropriate 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 disk (DVD) or any other type of memory. "Non-transient" computer-readable media excludes wired, wireless, optical or other communication links that transmit transient electrical signals or other signals. Non-transient computer-readable media include media that permanently store data and media that can store data and can overwrite data later, such as rewritable optical disks or erasable memory devices.

[0018] Definitions are provided for certain words and phrases that appear 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.

[0019] [Beneficial effects of the present invention]

[0020] The present disclosure proposes a method and apparatus for improving voice service quality in a wireless communication system through various embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] For a more thorough understanding of the present disclosure and its advantages, reference will now be made to the following description taken in conjunction with the accompanying drawings, in which like reference numerals represent like parts:

[0022] Figure 1 is a view showing a structure of an SBA-based 5G system according to an embodiment;

[0023] Figure 2 is a diagram showing a network structure according to an embodiment;

[0024] Figure 3 is a diagram showing operations of a terminal and a network according to an embodiment;

[0025] Figure 4 is a diagram illustrating operations of a terminal and a network capable of more efficient operation when 5GC is combined with various types of NG-RAN (NR and E-UTRA) according to an embodiment;

[0026] Figure 5 is a view showing an operation for a terminal to select a network providing an optimal voice service according to an embodiment;

[0027] Fig. 6A is a diagram showing operations of a terminal, a base station, and a core (5GC and EPC) according to an embodiment;

[0028] Figure 6B is a diagram showing operations of a terminal, a base station, and a core (5GC and EPC) according to another embodiment;

[0029] Figure 7 is a diagram showing a configuration of a network entity according to the present disclosure;

[0030] Figure 8 is a view showing a flow of operations for continuously providing services by processing sessions when moving between a 5G network (5GS) and a 4G network (EPS) according to another embodiment;

[0031] Fig. 9 is a diagram showing the operation of an NF (AMF) of a network in another embodiment;

[0032] Fig.10 is a view showing the operation of a terminal supporting ASSS in another embodiment; and

[0033] Fig.11 is a view showing an operation of continuously providing services by processing sessions when moving between a 5G network (5GS) and a 4G network (EPS) according to another embodiment. DETAILED DESCRIPTION

[0034] Discussed below Figures 1 to 11 The various embodiments used to describe the principles of the present disclosure in this patent document are only illustrative and should not be construed in any way to limit the scope of the present disclosure. Those skilled in the art will appreciate that the principles of the present disclosure can be implemented in any appropriately arranged system or device.

[0035] Hereinafter, the operating principle of the present disclosure will be described in detail with reference to the accompanying drawings. In the following description, when it is determined that the detailed description of the known functions or configurations related to the present disclosure may unnecessarily obscure the subject matter of the present disclosure, the detailed description will be omitted. In addition, the terms described later are terms defined in consideration of the functions of the present disclosure and may vary according to the intention or practice of the user or operator. Therefore, the definition should be made based on the content throughout this specification.

[0036] For the convenience of description, the terms used to identify the connection nodes used in the following description, the terms referring to the network entities or network functions (NFs), the terms referring to the messages, the terms referring to the interfaces between the network entities, the 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.

[0037] For the convenience of the following description, the present disclosure uses the 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 these terms and names and can be applied to systems that comply with other standards.

[0038] Meanwhile, when describing the embodiments, attention will be paid to improving the quality of voice services when 5G and LTE (4G) systems coexist, but the subject matter of the present disclosure can be applied to any kind of wireless communication system and can be applied not only to voice services but also to other types of services (video calls, games, chats, etc.).

[0039] New system structures and protocols are needed to support various services of 5G, and in 3GPP, it has been decided to introduce a new technology called service-based architecture (SBA). The main characteristics of the service-based infrastructure are to divide the functionality of the NF defined in the 3GPP standard into service units, taking into account the above-mentioned virtualization technology, the introduction of cloud environment and the extension of web-based environment, and to use the HTTP / 2 protocol when implementing these services.

[0040] Figure 1 is a view showing the structure of an SBA-based 5G system according to an embodiment.

[0041] refer to Figure 1, Access and Mobility Management Function (AMF) is a network function (NF) that manages access and mobility for a terminal (UE). Session Management Function (SMF) is an NF that manages sessions for UEs. Session information includes QoS information, charging information, and packet processing information. User Plane Function (UPF) is an NF that processes user plane services and can be controlled by SMF. Although Figure 1 Not shown, the 5G system may include an Unstructured Data Storage Network Function (UDSF), where the UDSF is a NF that stores unstructured data and is able to store or retrieve any type of data at the request of another NF.

[0042] Figure 2 is a view showing a network structure according to an embodiment.

[0043] When describing the above figures and embodiments, when integrating the SGW and the packet data network gateway (PGW) for simplicity, it is assumed that the policy control and charging rule function (PCRF) and the policy control function (PCF) are integrated, but the main points and uses of the embodiments can be applied even when the foregoing contents are implemented independently. In addition, in the figures, an evolved universal terrestrial access network (E-UTRA) is shown, regardless of whether the terminal uses an evolved packet core (EPC) non-access layer (NAS) in the E-UTRA network (i.e., when the E-UTRA is connected to the mobility management entity (MME)) and uses a 5G core network (5GC) NAS in the E-UTRA network (i.e., when the E-UTRA is connected to the AMF), but in reality, corresponding implementation methods and usages in independent forms are possible.

[0044] Although not shown in the logical network structure, the cells of 5G-RAN and 4G (E-UTRA) can overlap with each other depending on the type of physical radio network construction. If the 5G cell coverage is not large enough in the early stages of 5G commercialization, it can be configured to support voice / video call services in a specific radio access technology (RAT). In addition, depending on the operator's configuration, if several types of core networks (5GC, EPC) coexist, voice / video call services can be configured to support only a specific core network. For example, depending on the commercialization timing, audio / video services can be configured to support only EPC but not 5GC.

[0045] If the voice / video call service is used while the terminal is registered in the network, the type of RAT or core network to which the terminal is currently connected should be changed, and the type should be converted to a RAT or core network that can support the voice / video call service. Such a conversion can be caused by explicitly sending a command or request message to the terminal in the network, or the terminal can operate in consideration of the current state.

[0046] Figure 3 2 is a diagram illustrating operations of a terminal and a network according to an embodiment.

[0047] In step 301, terminal 310 may select a system to connect to and request a connection, and then may send a request message to register with the system. The message may include the capabilities and usage configuration information of the terminal, and the usage configuration information may indicate whether the type of terminal requires a voice call (voice-centric).

[0048] In step 302, the base station 320 (NG-RAN, i.e., 5G-RAN or E-UTRAN interworking with 5GC) may include the NAS message received from the terminal 310 in the NGAP message and send it to the AMF 330. In this embodiment, the NAS message is a registration request, and the NGAP message may include the RAT type (NR or E-UTRA, etc.) currently accessed by the terminal.

[0049] In step 303, the AMF 330 may process the NAS request of the terminal and may receive subscription data from the user data management (UDM) unit 340 during the registration process. The subscription information may include whether voice services are allowed for the terminal (whether IP Multimedia Subsystem (IMS) services are allowed or IMS Data Network Name (DNN) is allowed).

[0050] In step 304, the AMF 330 may determine whether IMS voice service support is possible for the terminal 310. The AMF 330 may make a determination considering the information (capability, usage configuration, etc.) of the terminal received in step 301, the RAT type currently accessed by the terminal received from the NG-RAN 320 in step 302, and the subscription information received from the UDM unit 340 in step 303. Specifically, if the IMS voice service is supported only in a specific RAT even when the 5GC is the same according to the conditions of the operator network, a determination may be made by comparing with the RAT type received from the NG-RAN 320. In addition, the AMF 330 may additionally perform a terminal capability matching process and make a decision considering the result.

[0051] In addition, AMF 330 can determine the RAT frequency selection priority (RFSP) index to be applied to the terminal. Similarly, the usage configuration sent by the terminal and the IMS voice support indication on the PS session to be applied to the terminal can be considered. More specifically, if the usage configuration of the terminal is voice-centric, but IMS voice services cannot be provided in the current network, AMF330 can use the RFSP index to induce the terminal to stay in a RAT that can support voice services for as long as possible. On the other hand, if the usage configuration of the terminal is not voice-centric, the RFSP index can be used to induce the terminal to stay in a wireless network (NR, etc.) capable of high-speed data transmission.

[0052] In step 305, AMF 330 may send a registration accept message to terminal 310. If it is determined in step 304 that IMS voice service support is possible for the terminal, AMF 330 may send a registration accept message including an indication that IMS voice over PS session is supported. The message may be delivered to terminal 310 via NG-RAN 320 from step 306.

[0053] In step 307, the terminal 310 may perform an operation for selecting a voice domain according to whether the registration acceptance message received from the AMF 330 includes an indication of supporting IMS voice over PS session.

[0054] If there is no need to change the currently connected network (RAN and core) including the indication, the terminal 310 may perform operations for receiving voice services using the IMS network in step 308, which may include PDU session establishment and IMS registration through IMSDNN.

[0055] Figure 4 is a view showing operations of a terminal and a network that can perform more efficient operations when 5GC is combined with various types of NG-RAN (NR and E-UTRA) according to an embodiment.

[0056] In step 401, terminal 410 may select a system to access, request a connection, and then send a request message to register with the system. The message may include the capabilities and usage configuration information of the terminal, and the usage configuration information may indicate whether the type of terminal requires a voice call (voice-centric).

[0057] In step 402, the base station 420 (NG-RAN, i.e., 5G-RAN or E-UTRAN interworking with 5GC) may include the NAS message received from the terminal 410 in an NG application protocol (NGAP) message and pass it to the AMF 430. In this embodiment, the NAS message is a registration request, and the NGAP message may include the RAT type (NR or E-UTRA, etc.) currently accessed by the terminal.

[0058] In step 403, AMF 430 may process the NAS request of the terminal and may receive subscription data from UDM 440 during the registration process. The subscription information may include whether voice services are allowed for the terminal (whether IMS services are allowed, and whether IMS DNN is allowed).

[0059] In step 404, AMF 430 may determine whether IMS voice service support is possible for the terminal. AMF may make a decision considering the terminal information (capability, usage configuration, etc.) received in step 401 and the subscription information received from UDM 440 in step 403. Specifically, if IMS voice service is supported only in a specific RAT even when the 5GC is the same according to the condition of the operator network, AMF 430 may independently determine whether IMS voice service is available for each RAT. In addition, AMF 430 may additionally perform a terminal capability matching process and make a decision considering the result.

[0060] In addition, AMF 430 can determine the RFSP index to be applied to the terminal. Similarly, the usage configuration sent by the terminal and the IMS voice support indication on the PS session to be applied to the terminal can be considered. More specifically, if the usage configuration of the terminal is voice-centric, but IMS voice services cannot be provided in the current network, AMF 430 can use the RFSP index to induce the terminal to stay in the RAT that can support voice services as much as possible. On the contrary, if the usage configuration of the terminal is not voice-centric, the RFSP index can be used to induce the terminal to stay in a wireless network (NR, etc.) capable of high-speed data transmission.

[0061] In step 405, the AMF 430 may send a registration accept message to the terminal. After determining in step 404 that the terminal supports IMS voice services for each RAT type, the AMF 430 may configure the registration accept message with supported IMS voice over PS sessions for each RAT type and send it. For example, if the 5GC is configured to support voice services in the operator network, but the voice services are not supported by the NR linked to the 5GC, and only the E-UTRA linked to the 5GC supports voice services, the supported IMS voice over PS sessions may be configured to be supported for E-UTRA, and may be configured to be unsupported for NR, and the message may be delivered to the terminal through the NG-RAN from step 406.

[0062] In step 407, the terminal 410 may perform an operation for selecting a voice domain according to whether the registration acceptance message received from the AMF 430 includes an indication of supporting IMS voice over PS session and the RAT type of the current connection.

[0063] If the indication is included and the currently connected network (RAN and core) does not need to be changed, that is, when the indication of supporting IMS voice over PS session is received for the RAT type to which the terminal is currently connected, in step 408, the terminal can perform operations for receiving voice services through the IMS network, which may include PDU session establishment and IMS registration through the IMS DNN. In addition, the terminal stores the indication of supporting IMS voice over PS session configured for each RAT, and when the RAT accessed by the terminal changes in the future, the indication of supporting IMS voice over PS session should be used for the selection of the voice domain according to the indication for the RAT.

[0064] Figure 5 is a view illustrating an operation for a terminal to select a network providing an optimal voice service according to an embodiment.

[0065] In step 501, the terminal may perform a registration procedure and may send a registration request message including a usage configuration configured in the terminal to the network. The usage configuration may include information indicating whether the terminal should receive a voice service.

[0066] In step 502, the terminal receives a registration response message from the network, which may include an indication of supporting IMS voice over PS session for each RAT type.

[0067] In step 503, the terminal may determine whether the usage configuration is voice-centric. If the usage configuration is voice-centric, the operation of step 504 may be performed, otherwise the entire process ends.

[0068] In step 504, the terminal may determine whether IMS voice is supported in the currently accessed RAT type based on the information received in step 502. If IMS voice is supported in the currently accessed RAT type, the terminal performs the operation of step 508, and may perform an operation for receiving IMS voice services, that is, establishing a PDU session through IMS DNN / APN and performing IMS registration. If not supported, the terminal may perform the operation of step 505. In step 505, the terminal may determine whether IMS voice is supported in another RAT type based on the information received in step 502. If IMS voice is supported in another RAT type, the terminal may perform the operation of step 507 to perform an operation of attempting to access a RAT that supports IMS voice. If IMS voice is not supported in another RAT type, the terminal may perform the operation of step 506 to perform another operation (combined attachment or TA / LA update in a 4G network or transition to a 2G / 3G network) to receive voice services.

[0069] In another embodiment of the present disclosure, a method for effectively providing a voice / video call service in a network structure in which E-UTRA is linked to 5GC in an operator network is proposed. At this time, both 5GC and EPC are constructed in the operator network. In this case, E-UTRAN becomes a network structure in the form of linking to both 5GC and EPC (refer to Figure 2 ). At this point, 5G-RAN using NR can exist in the operator network.

[0070] Fig. 6A is a view showing the operations of a terminal, a base station, and a core (5GC and EPC) according to an embodiment.

[0071] In step 601, the terminal 610 may perform a process of registering with the 5GC with the AMF 630. At this time, the terminal 610 may include an indication in the registration request message indicating that it supports the functions of the present embodiment, which can effectively handle the fallback of the voice (or video) call service. According to the network structure, the AMF 630 may deliver an indication of supporting IMS voice on a PS session and a fallback support indication to the registration acceptance message sent to the terminal. Although omitted in the drawings, the terminal 610 may perform a process for generating a PDU session for the IMS DNN and registering it with the IMS in order to use the voice (or video) call service. In addition, although omitted in the drawings, the AMF 630 may include an indication in the NG-AP message sent to the NG-RAN indicating that the terminal supports additional functions that can effectively handle fallback. Alternatively, the terminal 610 may include in the RRC message and send to the NG-RAN an indication indicating that it supports additional functions that can effectively handle fallback.

[0072] In step 602, when a voice (or video) call occurs (transmission / reception is possible), a procedure for IMS voice over PS session may be processed, and during the procedure, an addition to the IMS media QoS flow (which may be classified into a specific 5QI: 5QI=1, etc.) may be triggered, and the AMF 630 may notify the NG-RAN 620 in step 603.

[0073] In step 604, NG-RAN 620 (in this embodiment, E-UTRA linked to 5GC) may determine that fallback should be performed during the IMS media QoS flow processing process, and may start the fallback process for providing the voice (or video) service of the terminal. At this time, NG-RAN 620 may determine that the fallback process can be effectively performed based on information received from AMF 630 or UE 610. At this time, in this embodiment, unlike existing fallback technologies, effectively performing the fallback process may mean improving service quality by shortening the time from when voice services are used to when calls are possible, wherein the time from when voice services are used to when calls are possible is shortened by utilizing the same (E-UTAR) RAT accessed by the terminal before and after the fallback process. In step 604, NG-RAN / E-UTRAN may perform operations to optimize the fallback process. Since the RAT type of NG-RAN and E-UTRAN is the same as E-UTRA, NG-RAN and E-UTRAN can be implemented in the form of one device, and since the protocols and information used to communicate with the terminal and AMF are different, NG-RAN and E-UTRAN can be constructed in an independent form. In the former case, NG-RAN can directly generate and send information to be used by the terminal that falls back to E-UTRAN, and send it to the terminal when it is not necessary to change the cell to be accessed, which can shorten the independent radio state measurement process, induce the user to change only the core type to be accessed, or select the cell of E-UTRAN to be accessed and pass the information to the terminal in consideration of the current state and radio state of the terminal. In the latter case, NG-RAN can receive information from E-UTRAN and pass it to the terminal. In both cases, the information sent to the terminal may include information indicating that the reason for the terminal transition is fallback, information of the cell (which may be multiple cells) to be accessed by the terminal in E-UTRAN, and (if it is necessary to change the cell) parameters to be used by the terminal for initial access (part of the necessary information in SIB / MIB, such as MIB and SIB 1 / 2, etc.). In addition, NG-RAN can reserve uplink resources in advance (i.e., generate uplink grants) so that the terminal can immediately send messages on the uplink when initially connected to E-UTRAN, and send messages to the UE. If NG-RAN and E-UTRAN are independent, NG-RAN sends a resource allocation request to E-UTRAN to receive an uplink grant and send the grant to the terminal.

[0074] The information generated in step 605 may be sent to the terminal 610, and the method used at this time may be one of RRC Connection Release or NW-Triggered Handover. If the RRC Connection Release method is used, the terminal 610 may release the RRC connection with the NG-RAN in step 606, select a cell of the E-UTRAN using the information included in the Connection Release Command message (the E-UTRAN access information generated in step 604), and perform initial access. If the received information includes an uplink grant, the RRC Connection Generation message may be sent immediately without using an independent resource allocation request process. If the Handover method is used, the terminal 610 may perform a handover process from the NG-RAN to the E-UTRAN in step 606.

[0075] In step 607, the terminal 610 may perform an EPS and inter-system tracking area update procedure, and during this procedure, the context of the terminal may be transferred from the 5GC to the EPC, and the terminal may then register with the EPC to receive services. Afterwards, the terminal and the network may perform a procedure for receiving the remaining voice services (step 608).

[0076] Figure 6B is a view showing the operation of a terminal, a base station, a core (5GC and EPC) according to another embodiment.

[0077] In another embodiment, another method for improving quality by media stream processing when using fallback for voice (or video) call service is proposed. In this embodiment, the RAT type of NG-RAN linked to 5GC can be NR or E-UTRA. The main feature of this embodiment is to improve the service quality by preventing failures in the following: the process of adding an EPS bearer for IMS media transmission in EPS (E-UTRAN+EPC) after fallback occurs, or the condition of extended time for signaling.

[0078] In step 611, the terminal 610 may perform a process of registering with the 5GC with the AMF. At this point, the terminal 610 may include a functional indication indicating that it supports the present embodiment in the registration request message, which may effectively handle the media bearer of the voice (or video) call service. According to the network structure, the AMF 630 may deliver an indication of supporting IMS voice on a PS session and a fallback support indication to the registration acceptance message sent to the terminal. Although omitted in the accompanying drawings, the terminal 610 may perform a process for creating a PDU session for the IMS DNN and registering it with the IMS in order to use the voice (or video) call service. In the process of generating a PDU session for the IMS DNN, the terminal and the SMF (+PGW-C) are able to inform each other that they support the function of effectively handling IMS voice media when a fallback occurs. This information may be directly included in the session management (SM) NAS message exchanged between the terminal 610 and the SMF (+PGW-C), or may be exchanged using a protocol configuration option (PCO).

[0079] When a voice (or video) call occurs (both sending and receiving are possible) in step 612, the process for IMS voice over PS session can be processed, and during the process, the addition of an IMS media QoS flow (which can be classified into a specific 5QI: 5QI=1, etc.) can be triggered, and the AMF 630 can provide its notification to the NG-RAN 620 in step 613.

[0080] In step 614, the NG-RAN (in this embodiment, E-UTRA linked to the 5GC) may determine that fallback should be performed during IMS media QoS flow processing and start the fallback process to provide voice (or video) services for the UE.

[0081] In step 615, the terminal 610 may perform the EPS fallback procedure using information of the message received from the NG-RAN.

[0082] In step 616, the terminal 610 may perform an inter-system tracking area update procedure. During this procedure, a default bearer for an IMS PDU session (PDN connection) may be generated.

[0083] In step 617, EPC (GW) 660 may know that the EPS fallback process is in progress, cancel the generation of the incomplete IMS media stream attempted in step 612, and perform operations to send and receive IMS media transmission using the default bearer of the IMS session. This operation may be applied only in the case of an exchange between the terminal and the network to support the function for effectively providing media processing when EPS fallback occurs in step 611, or may be implicitly applied to all terminals. In addition, such an operation may be applied only when the media stream generation fails (for example, resource allocation fails in the base station) or is unsuccessful for a predetermined time. The operation may include adding a packet filter for sending / receiving IMS media streams between the terminal and the network to the default bearer, or configuring the packet filter of the default bearer to match all, and GW660 may also explicitly notify PCF (PCRF) 670 that it uses the default bearer to provide media streams during the process (step 618).

[0084] Afterwards, in step 619, an IMS media stream is sent / received through the default bearer of the IMS PDN connection between the terminal and the network to enable a voice call. If an additional EPS bearer for sending the IMS media stream is generated later, the terminal and the network allow the IMS media stream to be sent through the newly generated dedicated bearer. Specifically, in the IMS media stream, the priority of the bearer mapping for processing is configured so that the newly generated dedicated bearer is higher than the default bearer. To this end, a process of modifying a packet filter for the default / dedicated bearer for the IMS PDN connection may be performed.

[0085] Figure 7 is a diagram showing the configuration of a network entity according to the present disclosure. Figure 7 , the network entity may include a transceiver 710, a controller 720, and a storage unit 730. The network entity of the present disclosure conceptually includes a network function, which may vary according to system implementations.

[0086] The network entity according to the embodiment may include a transceiver 710 and a controller 720 controlling the overall operation of the network entity. In addition, the transceiver 710 may include a transmitter 711 and a receiver 712.

[0087] The transceiver 710 may transmit or receive signals with other network entities. The transceiver 710 may receive system information, for example, from a base station, and may receive a synchronization signal or a reference signal.

[0088] The controller 720 can control the network entity to perform any of the above embodiments. On the other hand, the controller 720 and the transceiver 710 do not have to be implemented as independent modules, and can certainly be implemented as a single component in the form of a single chip. In addition, the controller 720 and the transceiver 710 can be electrically connected. In addition, for example, the controller 720 can be a circuit, a dedicated circuit, or at least one processor. In addition, the operation of the network entity can be implemented by providing a memory device, which stores the corresponding program code in any component in the network entity.

[0089] The network entity can be one of a base station (RAN), AMF, SMF, UPF, NF, NEF, NRF, CF, NSSF, UDM, AF, AUSF, SCP, UDSF, context storage device, OAM, EMS, configuration server and ID management server.

[0090] The storage unit 730 may store at least one of information transmitted and received by the transceiver 710 and information generated by the controller 720. For example, the storage unit 730 may store scheduling information related to RMSI transmission, PDCCH timeline position and period information related to RMSI, and the like.

[0091] Figure 8 The present invention is a view showing a flow of operations for continuously providing services by processing sessions when moving between a 5G network (5GS) and a 4G network (EPS) according to another embodiment. Specifically, another embodiment relates to a method for continuously providing services by processing sessions when a terminal moves between a 5G network (5GS) and a 4G network (EPS).

[0092] If the terminal 820 moves or transitions to the 4G network while receiving services by generating a multiple access (MA) PDU session via a 3GPP wireless network and a non-3GPP (N3GPP) wireless network in the 5G network, it may be necessary to process the session and reconfigure the transmission path. This is a necessary function when the 4G network cannot support MA PDU sessions through the N3GPP wireless network. Specifically, the present embodiment is intended to address the following situation: there is no N26 interface to support interaction between 5GS and EPS, in which case the AMF of 5GS and the MME of EPS cannot directly exchange terminal contexts. In the following detailed operations, PGW, PGW-C, and SMF may all refer to the same object. In this embodiment, the MA PDU session may be the same as an access traffic steering, switching, and segmentation (ATSSS) session. Alternatively, in the present disclosure, PDN connection and PDU session may have the same meaning.

[0093] Step 801. Terminal 820 is registered in 5GS and can receive services by generating a multiple access (MA) protocol data unit (PDU) session via both 3GPP and N3GPP wireless networks.

[0094] Step 802. For reasons such as mobility, radio conditions, service characteristics and network commands, the terminal 820 may decide to move to a 4G network (EPS).

[0095] Step 803. The terminal 820 may perform an operation for attaching to the 4G network. The terminal 820 sends an attach request message to the MME of the 4G network. At this time, the request message may include a request type of an attach or a PDN connection request included in the attach, and the request type may be a handover. In addition, information (APN) of a session may be included, in which the terminal continuously receives services by moving from 5GS to EPS during the attach process. Specifically, the terminal may additionally include a session identifier used in the 5GS in the PCO inserted in the attach request message.

[0096] Step 804. MME 840 may select PGW-C+SMF 860 using the subscription information received from the APN and the PGW information (more specifically, PGW-C+SMF) in the HSS / UDM received from the UE, and may send a create session request message for session creation. The message may include the ID of the terminal (subscriber), which indicates that the type of session creation is handover. In addition, RAT type information indicating that the wireless network currently being accessed by the terminal is 3GPP (or 4G LTE) may be included. In this process, the process of sending a message by the SGW between the MME and PGW-C+SMF is omitted.

[0097] Step 805. PGW-C+SMF 860 may process the received session creation request. If the session creation request message includes information indicating a handover and an MA PDU session has been generated for the target terminal, PGW-C+SMF 860 may trigger an operation to delete (release) the MA PDU session generated by the N3GPP wireless network. Specifically, PGW-C+SMF 860 may determine that the handover request during session creation is interworking in a 3GPP network (5GS and EPS) rather than handover between 3GPP and N3GPP wireless networks using the RAT type information included in the request message.

[0098] Step 806. PGW-C+SMF 860 may send a response to the session creation request.

[0099] Step 807. The rest of the attachment process can be performed. At this time, the terminal 820 can delete the stored ATSSS-related information from the internal information (terminal context for PDN connection) for the PDN connection moved from 5GS to EPS, that is, the policy or rules for ATSSS and the auxiliary information for measurement, etc. Similarly, for the PDN connection moved from 5GS to EPS, the stored ATSSS-related information, that is, the policy or rules for ATSSS, the auxiliary information for measurement, etc. can be deleted from the internal information (SM context or PGW context).

[0100] Step 808. If the additional PDU session is still there, the terminal can perform a process for switching the remaining sessions to the EPS, except for the PDU session that the terminal 820 switches to the EPS during the attachment process. More specifically, the terminal 820 can send a PDN connection creation request to the MME 840 to move from 5GS to EPS, including session information (APN) to receive services without interruption, and including the type of handover being requested. In addition, the terminal can additionally include a session identifier used in the 5GS in the PCO inserted in the request message.

[0101] Step 809. MME 840 may select PGW-C+SMF 860 using the subscription information received from the APN and the PGW information (more specifically, PGW-C+SMF) in the HSS / UDM received from the UE, and send a create session request message for session creation. The message may include the ID of the terminal (subscriber), an indicator indicating that the type of session creation is a handover. In addition, RAT type information indicating that the wireless network currently accessed by the terminal is 3GPP (or 4G LTE) may be included. In this process, the process of sending a message by the SGW between the MME and PGW-C+SMF is omitted.

[0102] Step 810. PGW-C+SMF 860 may process the received session creation request. If the session creation request message includes information indicating a handover and an MA PDU session has been generated for the target terminal, PGW-C+SMF 860 may trigger an operation to delete (release) the MA PDU session generated by the N3GPP wireless network. Specifically, PGW-C+SMF 860 may determine that the handover request during session creation is interworking in a 3GPP network (5GS and EPS) rather than handover between 3GPP and N3GPP wireless networks using the RAT type information included in the request message.

[0103] Step 811. PGW-C+SMF 860 may send a response to the session creation request.

[0104] Step 812. The rest of the PDN connection creation process can be performed. At this time, the terminal 820 can delete the stored ATSSS-related information from the internal information (terminal context for the PDN connection) for the PDN connection moved from 5GS to EPS, that is, the policy or rules for ATSSS and the auxiliary information for measurement. Similarly, for the PDN connection moved from 5GS to EPS, the SMF can also delete the stored ATSSS-related information from the internal information (SM context or PGW context), that is, the policy or rules for ATSSS and the auxiliary information for measurement.

[0105] Fig. 9 FIG. 1 is a view showing the operation of an NF (AMF) of a network in another embodiment.

[0106] Step 901. The AMF may receive a registration request message for a specific terminal (subscriber). In the present disclosure, it is assumed that the terminal supports the ATSSS function (ie, it includes a capability for ASSSS).

[0107] Step 902. The AMF may determine whether 4G network (EPS) interworking is supported for the corresponding terminal. This may be determined by considering the following: whether the terminal has E-UTRAN support capability, whether the EPS interworking scheme is supported by the UE, whether EPS interworking is supported in the NW, and whether EPS interworking is allowed according to the subscription type. If EPS interworking is supported, the process may transition to step 903; otherwise, the process may transition to step 905.

[0108] Step 903. If the corresponding terminal requires support for EPS interworking, the EPS interworking method that can be supported by the NW can be determined. Interworking methods with N26 interface (i.e., supporting N26 interface between MME and AMF) and interworking methods without N26 interface (i.e., not supporting N26 interface between MME and AMF) can be considered. If EPS interworking with N26 support is not possible, the process can be transferred to step 904.

[0109] Step 904. If the UE does not support EPS interworking with N26, even if ASSS is supported in the network and AMF, it can be determined that the terminal does not support ASSSS.

[0110] Step 905: AMF may decide whether to support ATSSS of NW.

[0111] Step 906. The AMF may send a registration response to the terminal in steps 904 and 905, including information about whether ASSS is supported. If ASSSS is not supported, an ASSSS support indicator may not be included, or an explicit indicator that ASSS is not supported may be included. On the other hand, in a situation where EPS interworking and ATSSS cannot be applied at the same time (i.e., ASSSS is supported, but only EPS interworking without N26 is supported), the NW (AMF) may decide whether to prioritize EPS interworking or ATSSS use. At this time, the AMF may consider the usage type of the terminal (i.e., whether it is voice-centric or data-centric), and in the case of a voice-centric type, priority may be given to EPS interworking, and in the case of a data-centric type, ASSSS may be considered first. Alternatively, the AMF may determine what to support based on the operator's configuration or the configuration of an independent operator. If priority is given to the use of EPS interworking, the AMF may indicate support for EPS interworking without N26 in the registration response sent to the terminal, and may indicate that ASSSS is not supported. Conversely, if ATSSS is used first, support for ASSSS may be indicated in the registration response, and support for EPS interworking may be indicated as not being supported.

[0112] At the same time, when determining whether IMS-based voice services are supported for the terminal, the NW (AMF) may consider both the capabilities of the terminal and the configuration of the NW. If the IMS voice service cannot be provided through the currently connected wireless network in the configuration of the NW, the EPS interaction with the N26 interface is not supported, and the EPS interaction without the N26 interface is supported. If the terminal provides the handover attachment to the 5GMM information as "not supported" in the registration request message, the response indicating the support for IMS voice on PS sessions through 3GPP access in the registration response message sent to the terminal may be "not supported". When the terminal receiving the registration response from the NW has a voice-centric usage type and receives IMS voice on PS sessions as "not supported", the terminal may try to first access another wireless network (4G or 3G) to receive voice services.

[0113] Fig.10 is a view showing the operation of a terminal supporting ATSSS in another embodiment.

[0114] Step 1001. The terminal may receive a registration response message from the AMF.

[0115] Step 1002. The terminal may determine whether the NW supports ASSSS through the response message received from the AMF. If the NW supports ASSSS, the process may proceed to step 1003; otherwise, the process may proceed to step 1005.

[0116] Step 1003. If the NW supports ATSSS, the terminal may determine whether EPS interworking is required and what the interworking support method is. To this end, it may be considered whether the terminal has E-UTRAN support capability, whether the NW supports EPS interworking, and whether the method supported by the NW is capable of interworking with an N26 interface (i.e., whether the N26 interface between the MME and the AMF is supported) and interworking without an N26 interface (i.e., the use of the N26 interface between the MME and the AMF is not supported). If EPS interworking needs to be applied to the terminal, but only EPS interworking without N26 is supported in the NW, the process may transition to step 1005; otherwise, it may transition to step 1004.

[0117] Step 1004. If the terminal does not need EPS interworking or does not support EPS access, or if the NW supports EPS interworking with N26, the terminal may determine that ATSSS may be used. Afterwards, the terminal may perform an ASSSS operation (request to add or modify an MA PDU session).

[0118] Step 1005. If only interworking without N26 is supported, the terminal may determine that ASSSS cannot be used even if the NW claims ASSSS support. Afterwards, the terminal may not perform ASSSS operations (requesting to add or modify an MA PDU session, etc.).

[0119] On the other hand, when the terminal cannot use both EPS interworking and ATSSS at the same time (that is, when ASSS is supported but accesses a network that only supports EPS interworking without N26), the terminal can decide whether to prioritize EPS interworking or ATSSS. This can be determined by considering the usage type of the terminal (that is, whether it is voice-centric or data-centric), or can be determined by local configuration of the terminal or independent user configuration (such as input through a user interface). The terminal can regard EPS interworking as a priority for the voice-centric type and ASSSS as a priority for the data-centric type.

[0120] At the same time, when determining whether to use voice services based on NW and IMS, the terminal can consider the capabilities of the terminal and the configuration of the NW together. If the terminal receives support for IMS voice on PS sessions accessed through 3GPP as "supported" through the 5GS network feature support in the registration response and receives support for interworking without N26 interface in the EPS interworking support method from the NW as "supported", but the terminal does not support the attach with switching (HO attach) function, the terminal can determine that it is impossible to use IMS-based voice services in the 5G network. In this case, if the service is voice-centric, the terminal can try to first access another wireless network (4G or 3G) for receiving voice services.

[0121] Fig.11 is a view showing an operation of continuously providing services by processing sessions when moving between a 5G network (5GS) and a 4G network (EPS) according to another embodiment.

[0122] Step 1101. Terminal 1120 may register in 5GS and may receive services by creating a MA PDU session over both 3GPP and N3GPP wireless networks.

[0123] Step 1102. For reasons such as mobility, radio conditions, service characteristics and network commands, the terminal 1120 may decide to transition to a 4G network (EPS).

[0124] Step 1103. The terminal 1120 may perform an operation for attaching to the 4G network. The terminal 1120 may send an attach request message to the MME of the 4G network. At this time, the request message may include a request type of an attach or a PDN connection request included in the attach, and the request type may be a handover. In addition, information (APN) of a session may be included, in which the terminal continuously receives services by moving from 5GS to EPS during the attach process. Specifically, the terminal may additionally include a session identifier used in the 5GS in the PCO inserted in the attach request message.

[0125] Step 1104. MME 1140 may select PGW-C+SMF 1160 using the subscription information received from the APN and the PGW information (more specifically, PGW-C+SMF) in the HSS / UDM received from the UE, and may send a create session request message for session creation. The message may include the ID of the terminal (subscriber), indicating that the type of session creation is handover. In addition, RAT type information may be included, indicating that the wireless network currently being accessed by the terminal is 3GPP (or 4G LTE). In this process, the process of sending a message by the SGW between the MME and PGW-C+SMF is omitted.

[0126] PGW-C+SMF 1160 may process the received session creation request.

[0127] Step 1105. PGW-C+SMF 1160 may send a response to the session creation request.

[0128] Step 1106. The remainder of the attach process may be performed.

[0129] Step 1107. If additional PDU sessions still exist in addition to the PDU sessions to which the terminal switches to the EPS during the attachment process, the terminal 1120 may perform a process for switching sessions to the EPS for the remaining sessions. More specifically, the terminal 1120 may send a PDN connection generation request to the MME 1140, including session information (APN) to receive services without interruption by moving from 5GS to EPS, and including the type of handover being requested to be generated. In addition, the terminal may additionally include a session identifier used in the 5GS in the PCO inserted in the request message.

[0130] Step 1108. MME 1140 may select PGW-C+SMF 1160 using the subscription information received from the APN and the PGW information (more specifically, PGW-C+SMF) in the HSS / UDM received from the UE, and may send a create session request message for session creation. The message may include the ID of the terminal (subscriber), which indicates that the type of session creation is handover. In addition, RAT type information may be included, which indicates that the wireless network currently being accessed by the terminal is 3GPP (or 4G LTE). In this process, the process of sending a message by the SGW between MME 1140 and PGW-C+SMF 1160 is omitted.

[0131] PGW-C+SMF 1160 may process the received session creation request.

[0132] Step 1109. PGW-C+SMF 1160 may send a response to the session creation request.

[0133] Step 1110. The rest of the PDN connection creation process may be performed.

[0134] Steps 1111 to 1112. For the session transitioned from 5GS to EPS in steps 1101 to 1106 or steps 1107 to 1110, PGW-C + SMF 1160 may start an operation for releasing related session information in 5GS. During this process, if the session transitioned to EPS is an MA PDU session and the session is established for both 3GPP access and non-3GPP access, PGW-C + SMF 1160 may perform a session release procedure for non-3GPP access.

[0135] Step 1113. For the PDN connection moved from 5GS to EPS (a session moved to EPS through the above attachment process or an additional PDN connection establishment process), the terminal 1120 may delete the stored information related to ATSSS from the internal information (terminal context for PDN connection), i.e., policies or rules for ATSSS, auxiliary information for measurement, etc. Similarly, the SMF may also delete the stored information related to ATSSS from the internal information (terminal context for PDN connection) for the PDN connection moved from 5GS to EPS, i.e., policies or rules for ATSSS and auxiliary information for measurement.

[0136] In the above embodiments, the order of the operations may be changed or the operations may be performed in parallel. For example, if the terminal generates two PDU sessions in the 5G network and then switches to the EPS, during the attachment process, the terminal may switch to the first session and perform steps 1111 to 1113, and may switch to the second PDU session and perform steps 1111 to 1113.

[0137] It should be pointed out that Figures 1 to 11 The configuration diagrams, example diagrams of control / data signal transmission methods, example diagrams of operation processes, and other configuration diagrams shown in are not intended to limit the scope of the present disclosure. That is, Figures 1 to 11 All components, entities or operational steps described in the disclosure should not be construed as essential components of the embodiments of the present disclosure, and implementations including only some components may be implemented without departing from the scope of the present disclosure.

[0138] The above operations of the base station or terminal can be implemented by providing a storage device that stores the corresponding program code in any component in the base station or terminal device. That is, the controller of the base station or terminal device can perform the above operations by reading and executing the program code stored in the storage device by a processor or a central processing unit (CPU).

[0139] The entities, components, modules, etc. of the base station or terminal device described herein may be operated using hardware circuits such as complementary metal-oxide-semiconductor based logic circuits, hardware circuits such as firmware and software, and / or a combination of firmware and / or software embedded in a machine-readable medium. For example, various electrical structures and methods may be implemented using transistors, logic gates, and circuits such as custom semiconductors.

[0140] In the specific implementation of the present disclosure, specific embodiments have been described, but various modifications are possible without departing from the scope of the present disclosure. Therefore, the scope of the present disclosure should not be interpreted as being limited to the embodiments, but should be determined not only by the scope of the following claims, but also by the scope of the equivalents of the claims.

[0141] Although the present disclosure has been described with various embodiments, various changes and modifications may be suggested to one skilled in the art. It is intended that the present disclosure encompass such changes and modifications as fall within the scope of the appended claims.

Claims

1. A method performed by a terminal in a wireless communication system, the method comprising: Establishing a multiple access protocol data unit MA PDU session in a 3rd Generation Partnership Project 3GPP access and a non-3rd Generation Partnership Project N3GPP access in a fifth generation system 5GS; after establishing the MA PDU session, determining whether the MA PDU session is moved to the EPS without an N26 interface between the 5GS and an evolved packet system EPS; and releasing a context related to access traffic steering, switching and splitting ATSSS, wherein the context related to ASSSS is associated with ATSSS rules and measurement assistance information for the MA PDU session, The release of the MA PDU session is triggered by the network entity in the 5GS through the N3GPP access.

2. The method according to claim 1, further comprising: sending a request message to the network entity, The request message includes a request type and session information.

3. The method according to claim 2, wherein: The request type is an indicator related to handover.

4. The method according to claim 2, wherein: Sending the request message includes: sending multiple request messages according to multiple session identifiers, and The multiple pieces of session information including session information for the MA PDU session include the multiple session identifiers.

5. A method performed by a network entity in a wireless communication system, the method comprising: Triggering the release of a multiple access protocol data unit (MA) PDU session via non-3GPP access; as well as releasing a context related to access traffic steering, switching and splitting ATSSS, wherein the context related to ASSSS is associated with ATSSS rules and measurement assistance information for the MA PDU session, wherein the MA PDU session is established in both the 3rd Generation Partnership Project 3GPP access and the N3GPP access in the 5GS, and Wherein, the MA PDU session is moved to the EPS without an N26 interface between the 5GS and the Evolved Packet System EPS.

6. The method according to claim 5, further comprising: Receive a request message from a terminal, and The request message includes a request type and session information.

7. The method according to claim 6, wherein: The request type is an indicator related to handover.

8. The method according to claim 6, receiving the request message comprises: receiving a plurality of request messages according to the plurality of session identifiers, and The multiple pieces of session information including session information for the MA PDU session include the multiple session identifiers.

9. A terminal, comprising: a transceiver capable of transmitting and receiving at least one signal; as well as a controller coupled to the transceiver, Wherein, the controller is configured as: Establishing a multiple access protocol data unit MA PDU session in a 3rd Generation Partnership Project 3GPP access and a non-3rd Generation Partnership Project N3GPP access in a fifth generation system 5GS; after establishing the MA PDU session, determining whether the MA PDU session is moved to the EPS without an N26 interface between the 5GS and an evolved packet system EPS; and releasing a context related to access traffic steering, switching and splitting ATSSS, wherein the context related to ASSSS is associated with ATSSS rules and measurement assistance information for the MA PDU session, The release of the MA PDU session is triggered by the network entity in the 5GS through the N3GPP access.

10. The terminal according to claim 9, in, The controller is further configured to send a request message to the network entity, and The request message includes a request type and session information. The terminal according to claim 10 , wherein: The request type is an indicator related to handover.

12. The terminal according to claim 10, wherein: The controller is configured to send a plurality of request messages according to a plurality of session identifiers, and The multiple pieces of session information including session information for the MA PDU session include the multiple session identifiers.

13. A network entity, comprising: a transceiver capable of transmitting and receiving at least one signal; as well as a controller coupled to the transceiver, Wherein, the controller is configured as: Triggering the release of a Multiple Access Protocol Data Unit (MA) PDU session via non-3GPP access; and releasing a context related to access traffic steering, switching and splitting ATSSS, wherein the context related to ASSSS is associated with ATSSS rules and measurement assistance information for the MA PDU session, wherein the MA PDU session is established in both the 3rd Generation Partnership Project 3GPP access and the N3GPP access in the 5GS, and Wherein, the MA PDU session is moved to the EPS without an N26 interface between the 5GS and the Evolved Packet System EPS.

14. The network entity according to claim 13, in, The controller is further configured to receive a request message from a terminal, and The request message includes a request type and session information.

15. The network entity according to claim 14, wherein: The controller is further configured to receive a plurality of request messages according to a plurality of session identifiers, wherein the plurality of pieces of session information including session information for the MA PDU session include the plurality of session identifiers, and The request type is an indicator related to switching.

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