Method and apparatus for supporting multicast services in a wireless communication system

Abstract

A method performed by a first entity in a wireless communication system is provided. The method includes: receiving a first request message for receiving a multicast service from a second entity, detecting information about a multicast session identifier (ID) from the first request message, requesting information about a fourth entity corresponding to the multicast session ID from a third entity when the first entity does not correspond to the information about the multicast session ID, receiving information about the fourth entity corresponding to the multicast session ID, identifying the fourth entity based on the information about the fourth entity, sending a multicast session join request message to the fourth entity, and receiving a message accepting the multicast session join from the fourth entity.

Description

Technical Field

[0001] The present disclosure relates to a method and apparatus for supporting multicast services in a wireless communication system. Background Art

[0002] The fifth generation (5G) mobile communication technology defines a wide frequency band, making high transmission rates and new services possible, and can be implemented not only in "below 6 GHz" frequency bands such as 3.5 GHz, but also in "above 6 GHz" frequency bands called millimeter (mm) waves including 28 GHz and 39 GHz. In addition, in order to achieve a transmission rate 50 times faster than that of 5G mobile communication technology and an ultra-low latency of one-tenth of that of 5G mobile communication technology, the implementation of the sixth generation (6G) mobile communication technology (referred to as a super 5G system) in the terahertz frequency band (e.g., 95 GHz to 3 THz frequency band) has been considered.

[0003] In the early stages of 5G mobile communication technology development, in order to support services and meet performance requirements associated with enhanced Mobile BroadBand (eMBB), Ultra Reliable Low Latency Communications (URLLC) and massive Machine-Type Communications (mMTC), standardization is already underway on the following items: beamforming and massive MIMO, used to mitigate radio wave path loss and increase radio wave transmission distance in millimeter waves; support for basic parameter sets (e.g., operating multiple subcarrier spacings) for efficient use of millimeter wave resources and dynamic operation of time slot formats; initial access technology to support multi-beam transmission and broadband; definition and operation of BandWidth Part (BWP); new channel coding methods, such as Low Density Parity Check (LDPC) codes for large amounts of data transmission and polar codes for highly reliable control information transmission; L2 preprocessing; and network slicing to provide dedicated networks dedicated to specific services.

[0004] Currently, in view of the services that 5G mobile communication technology will support, discussions are underway on improvements and performance enhancements of initial 5G mobile communication technology, and physical layer standardization is underway on technologies such as: Vehicle-to-everything (V2X), for assisting driving determination of autonomous vehicles based on information about the vehicle's location and status sent by the vehicle, and for enhancing user convenience; New Radio Unlicensed (NR-U), designed to make system operations comply with various regulatory requirements in unlicensed frequency bands; NR User Equipment (UE) energy saving; Non-Terrestrial Network (NTN), which is UE-satellite direct communication for providing coverage in areas where communication with terrestrial networks is unavailable; and positioning.

[0005] In addition, in terms of air interface architecture / protocol, standardization is already underway on technologies such as the following: Industrial Internet of Things (IIoT), which is used to support new services through interoperability and integration with other industries; Integrated Access and Backhaul (IAB), which is used to provide nodes for network service area expansion by supporting wireless backhaul links and access links in an integrated manner; Mobility enhancement, including conditional switching and dual active protocol stack (DAPS) switching; and two-step random access, which is used to simplify random access procedures (2-step random access channel (RACH) for NR). In terms of system architecture / services, standardization is also underway on the following: 5G baseline architecture (e.g., service-based architecture or service-based interface), which is used to combine network function virtualization (NFV) and software-defined networking (SDN) technologies; and Mobile Edge Computing (MEC), which is used to receive services based on UE location.

[0006] With the commercialization of 5G mobile communication systems, the already exponentially growing number of connected devices will be connected to the communication network, and accordingly, it is expected that enhanced functionality and performance of 5G mobile communication systems and integrated operations of connected devices will be necessary. To this end, new research related to the following items is planned: extended reality (eXtended Reality, XR) for effectively supporting augmented reality (Augmented Reality, AR), virtual reality (Virtual Reality, VR), mixed reality (Mixed Reality, MR), etc.; 5G performance improvement and complexity reduction by utilizing artificial intelligence (Artificial Intelligence, AI) and machine learning (Machine Learning, ML); AI service support; Metaverse service support; and drone communication.

[0007] In addition, such developments in 5G mobile communication systems will not only serve as a basis for developing new waveforms for providing terahertz band coverage for 6G mobile communication technology, multi-antenna transmission technology (such as full-dimensional MIMO (FD-MIMO), array antennas, and massive antennas), metamaterial-based lenses and antennas for improving terahertz band signal coverage, high-dimensional spatial multiplexing technology using orbital angular momentum (OAM), and reconfigurable intelligent surfaces (RIS); it will also serve as a basis for developing full-duplex technology for improving the frequency efficiency of 6G mobile communication technology and improving system networks, AI-based communication technology for implementing system optimization by utilizing satellites and AI from the design stage and internalizing end-to-end AI support functions, and next-generation distributed computing technology for implementing services with a level of complexity that exceeds the limits of UE operating capabilities by utilizing ultra-high performance communication and computing resources.

[0008] Accordingly, various attempts are being made to apply 5G communication systems to IoT. For example, 5G communication technologies such as sensor networks, machine-to-machine (M2M), and MTC are implemented through technologies including beamforming, MIMO, and array antennas. The application of cloud RAN, which is the above-mentioned big data processing technology, can be considered as an example of the fusion between 5G technology and IoT technology.

[0009] With the recent development of communication systems, various studies have been conducted to provide different network slices (or network slices) in 5G-based wireless communication systems.

[0010] The above information is presented as background information only to assist in understanding the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art. Summary of the invention

[0011] Technical issues

[0012] In order to send the same data to multiple user equipments (UEs) in a mobile network, data services need to be multicast / broadcasted. For example, a method for multicasting / broadcasting data is needed to provide TV / audio services, vehicle-to-everything (V2X) services, or large-scale consumer Internet of things (CIoT) services to multiple UEs in a specific area.

[0013] In addition, multicast / broadcast services are provided by multicast / broadcast service (MBS) technology in a 5G system (5GS) network. In this context, there is a need for a method for smoothly providing multicast / broadcast services even when a UE moves out of a service area of ​​a session management function (SMF) that manages an existing protocol data unit (PDU) session, or a method for continuously supporting multicast / broadcast services provided by a home network in a roaming network even when the UE roams.

[0014] Technical Solution

[0015] Aspects of the present disclosure address at least the above-mentioned problems and / or disadvantages and provide at least the advantages described below. Accordingly, one aspect of the present disclosure is to provide a method and apparatus for supporting multicast services in a wireless communication system.

[0016] Another aspect of the present disclosure is to provide a method and apparatus for smoothly providing multicast / broadcast in an environment where a user equipment (UE) roams in a wireless communication system.

[0017] Additional aspects will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the presented embodiments.

[0018] According to one aspect of the present disclosure, a method performed by a first entity in a wireless communication system is provided. The method includes: receiving a first request message for receiving a multicast service from a second entity; detecting information about a multicast session identifier (ID) from the first request message; when the first entity does not correspond to the information about the multicast session ID, requesting information about a fourth entity corresponding to the multicast session identifier (ID) from a third entity; receiving information about a fourth entity corresponding to the multicast session ID; identifying the fourth entity based on the information about the fourth entity; sending a multicast session join request message to the fourth entity; and receiving a message accepting the multicast session join from the fourth entity.

[0019] According to one aspect of the present disclosure, a first entity in a wireless communication system is provided. The first entity includes a transceiver and a processor coupled to the transceiver, the processor being configured to: receive a first request message for receiving a multicast service from a second entity; detect information about a multicast session identifier (ID) from the first request message; request information about a fourth entity corresponding to the multicast session ID from a third entity if the first entity does not correspond to the information about the multicast session ID; receive information about a fourth entity corresponding to the multicast session ID; identify the fourth entity based on the information about the fourth entity; send a multicast session join request message to the fourth entity; and receive a message accepting the multicast session join from the fourth entity.

[0020] Other aspects, advantages, and salient features of the disclosure will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses various embodiments of the disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The above and other aspects, features and advantages of certain embodiments of the present disclosure will become more apparent from the following description in conjunction with the accompanying drawings, in which:

[0022] Figure 1A is a simplified diagram illustrating a scenario in which a user equipment (UE) located outside a service area of ​​a service session management function (SMF) joins a multicast service according to an embodiment of the present disclosure;

[0023] Figure 1B is a simplified diagram illustrating a scenario in which a roaming UE joins a multicast service of a home network and a multicast service of a roaming network according to an embodiment of the present disclosure;

[0024] Figure 2A and Figure 2B is a diagram showing a signal flow of a procedure for processing a join request in an intermediate SMF (I-SMF) when a UE located outside a service area of ​​a serving SMF joins a multicast service according to various embodiments of the present disclosure;

[0025] Figure 3 is a diagram showing a signal flow of a procedure for processing a join request in a serving SMF when a UE located outside a service area of ​​the serving SMF joins a multicast service according to an embodiment of the present disclosure;

[0026] Figure 4A and Figure 4B is a diagram showing a signal flow of a procedure for processing a join request in a serving SMF to provide a multicast service through an intermediate multicast / broadcast SMF (I-MB-SMF) when a UE located outside a service area of ​​the serving SMF joins the multicast service according to various embodiments of the present disclosure;

[0027] Figure 5A and Figure 5B is a diagram illustrating a signal flow of a procedure for providing a service in a shared delivery method when a roaming UE joins a multicast service of a home operator according to various embodiments of the present disclosure;

[0028] Fig. 6A and Figure 6B is a diagram showing a signal flow of a procedure for providing a service in a separate delivery method when a roaming UE joins a multicast service of a home operator according to various embodiments of the present disclosure;

[0029] Fig. 7A and Figure 7B is a diagram showing a signal flow of a procedure for providing a service in a separate delivery method when a roaming UE joins a multicast service of a home operator according to various embodiments of the present disclosure;

[0030] Figure 8 is a block diagram showing an internal structure of a UE in a wireless communication system according to an embodiment of the present disclosure; and

[0031] Fig. 9 is a block diagram showing the internal structure of an access and mobility management function (AMF), an SMF, and a user plane function (UPF) according to an embodiment of the present disclosure.

[0032] Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures. DETAILED DESCRIPTION

[0033] The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of the various embodiments of the present disclosure as defined by the claims and their equivalents. It includes various specific details to assist in such understanding, but these are to be regarded as exemplary only. Accordingly, it will be appreciated by those of ordinary skill in the art that various changes and modifications may be made to the various embodiments described herein without departing from the scope and spirit of the present disclosure. In addition, for the sake of clarity and conciseness, descriptions of well-known functions and configurations may be omitted.

[0034] The terms and words used in the following description and claims are not limited to the bibliographical meanings, but are merely used by the inventor to enable a clear and consistent understanding of the present disclosure. Accordingly, it will be apparent to those skilled in the art that the following description of various embodiments of the present disclosure is provided for illustrative purposes only and is not intended to limit the present disclosure as defined by the appended claims and their equivalents.

[0035] It should be understood that the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a component surface" includes reference to one or more of such surfaces.

[0036] For the same reason, some components shown in the drawings are exaggerated, omitted or schematically shown, and the drawing size of each component does not exactly reflect its actual size. In each of the drawings, the same reference numerals are assigned to the same or corresponding components.

[0037] The advantages and features of the present disclosure and the methods for achieving them will become apparent with reference to the embodiments described in detail below in conjunction with the accompanying drawings. However, the present disclosure can be implemented in various ways and is not limited to the embodiments set forth herein. On the contrary, these embodiments are provided to make the present disclosure complete and thorough, and its scope is fully conveyed to those skilled in the art, and the present disclosure is limited only by the appended claims. Throughout the specification, the same reference numerals represent the same components.

[0038] It will be understood that each frame of the flowchart diagram and the frame combination in the flowchart diagram can be implemented by computer program instructions. These computer program instructions can be loaded onto a processor of a general-purpose computer, a special-purpose computer or other programmable data processing device, so that the instructions executed by the processor of the computer or other programmable data processing device create a component for implementing the function specified in the (multiple) frame of the flowchart and / or the block diagram. These computer program instructions can also be stored in a computer-available or computer-readable memory, which can instruct the computer or other programmable data processing device to operate in a particular manner, so that the instructions stored in the computer-available or computer-readable memory produce an article of instruction components including the function specified in the (multiple) frame of the flowchart and / or the block diagram. Computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operations are performed on a computer or other programmable data processing device, thereby generating a computer-implemented process, so that the instructions executed on a computer or other programmable device provide operations for implementing the function / action specified in the (multiple) frame of the flowchart and / or the block diagram.

[0039] In addition, each block diagram may show a module, a fragment or a portion of a code including one or more executable instructions for performing (multiple) specific logical functions. In addition, it should be noted that in several modifications, the functions of these blocks may be performed in different orders. For example, two consecutive blocks may be performed substantially simultaneously, or may be performed in reverse order according to their functions.

[0040] The term "unit" used herein means but is not limited to software or hardware components that perform certain tasks, such as field programmable gate arrays (FPGA) or application specific integrated circuits (ASIC). The unit can be advantageously configured to reside on an addressable storage medium and be configured to execute on one or more processors. Therefore, for example, a unit can include components (such as software components, object-oriented software components, class components, and task components), processes, functions, attributes, programs, subroutines, program code segments, drivers, firmware, microcodes, circuits, data, databases, data structures, tables, arrays, and variables. The functions provided in components and "units" can be combined into fewer components and "units", or further separated into additional components and "units". In addition, components and "units" can be implemented as executing on one or more central processing units (CPUs) in a device or a secure multimedia card.

[0041] In addition, for the convenience of description, terms used in the following description to identify access nodes, terms representing messages, terms representing interfaces between network entities, terms representing various types of information, etc. are given. Accordingly, the present disclosure is not limited to the terms described below, and these terms may be replaced by other equivalent terms in a technical sense.

[0042] In an embodiment of the present disclosure, a base station (BS) as an entity that allocates resources to a user equipment (UE) may be at least one of a next generation node B (gNode B or gNB), an evolved node B (eNode B or eNB), a node B, a radio access unit, a base station controller (BSC), or a network node. In addition, the BS may be a network entity including at least one of an integrated access and backhaul (IAB) donor or an IAB node, the IAB donor being a gNB that provides network access to (multiple) UEs through a network of backhaul and access links, and the IAB node being a radio access network (RAN) node that supports (multiple) NR access links to (multiple) UEs and supports an NR backhaul link to the IAB donor or another IAB node in a new radio (NR) system. The UE may be wirelessly connected to the IAB donor through the IAB node, and may send and receive data to and from the IAB donor connected to at least one IAB node via the backhaul link.

[0043] In addition, UE may include a terminal, a mobile station (MS), a cellular phone, a smart phone, a computer, or various devices capable of performing communication functions. In the present disclosure, a downlink (DL) is a wireless transmission path for a signal sent from a BS to a UE, and an uplink (UL) is a wireless transmission path for a signal sent from a UE to a BS. Although a long term evolution (LTE) or advanced LTE (LTE-advanced, LTE-A) system may be described below as an example, the embodiments of the present disclosure are applicable to other communication systems with similar technical backgrounds or channel structures. For example, a communication system may include a fifth generation (5G) new radio (5G NR) developed after LTE-A, and 5G may be a concept covering traditional LTE, traditional LTE-A, and other similar services described below. In addition, as judged by those skilled in the art, the present disclosure may also be applicable to other communication systems through some modifications without greatly departing from the scope of the present disclosure.

[0044] For the convenience of description, terms indicating signals, terms indicating channels, terms indicating control information, terms indicating network entities, and terms indicating device components used in the following description are given. In addition, for the convenience of description, terms indicating nodes used in the following description, terms indicating messages, terms indicating interfaces between network entities, terms indicating various types of information, etc. are given. Accordingly, the present disclosure is not limited to the terms described below, and these terms may be replaced by other equivalent terms in a technical sense.

[0045] For ease of description, the present disclosure uses terms and names defined in the communication standards of the fourth generation (4G) and 5G systems (e.g., TS 23.401, TS 23.501, TS 23.502, and TS 23.503 of the 3rd Generation Partnership Project (3GPP). However, the present disclosure is not limited to the above terms and names. Accordingly, the terms or names defined in the present disclosure may be equally applied to systems conforming to other standards.

[0046] In the present disclosure, the terms 5G multicast / broadcast services (5MBS) system, 5G multicast system, and 5G MBS system are used interchangeably in the same meaning as the multicast and broadcast system of the 5G system.

[0047] Furthermore, although the present disclosure is described in the context of a multicast service, it will be apparent to those skilled in the art that the present disclosure may also be applied to a broadcast service.

[0048] Figure 1A is a simplified diagram illustrating a scenario in which a UE located outside a service area of ​​a service session management function (SMF) joins a multicast service according to an embodiment of the present disclosure.

[0049] The 5G standard (TS23.502) defines the service operations related to the protocol data unit (PDU) session and managing the sessions in Table 1 below among the network function (NF) services provided by the SMF.

[0050] Table 1 Table 5.2.8.1-1: NF services provided by SMF

[0051]

[0052]

[0053] Figure 1AThe 5G system structure supports a service-based interface, and the service-based interface related to SMF is defined as "Nsmf" as shown in Table 1 above. In Table 1, "Nsmf_PDUSession" means a service operating in a PDU session, and the service includes creation / deletion / modification of a PDU session. These operations can be performed by sending and receiving PDU session request / response messages between the access and mobility management function (AMF) and the SMF. As in the example of Table 1, in order to support PDU sessions, the SMF may receive a "Nsmf_PDUSession_CreateSMContext" request message from the AMF as a PDU session request message, and send a "Nsmf_PDUSession_CreateSMContext" response message to the AMF in response to the "Nsmf_PDUSession_CreateSMContext" request message in the association creation operation between the AMF and the SMF. For other service operations in Table 1, reference may be made to relevant standards, and a detailed description of these other service operations will be avoided in this article. Similarly, "Nsmf_MBSsession" refers to a service operating in an MBS session, and the service includes creation / deletion / modification operations of the MBS session, and these operations can be performed by sending and receiving MBS session request messages and MBS session response messages between AMF and multicast / broadcast-SMF (MB-SMF) or between SMF and MB-SMF.

[0054] Reference Figure 1A, a cellular system may include a user equipment (UE), a next generation radio access network (NG-RAN), an AMF, a multicast / broadcast user plane function (MB-UPF), an MB-SMF, a policy control function (PCF), an SMF, a user plane function (UPF), a network exposure function (NEF), a multicast / broadcast service function (MBSF), a multicast / broadcast service transport function (MBSTF), an application function (AF), an application server (AS), a user data repository (UDR), and an authentication server function (AUSF).

[0055] According to an embodiment of the present disclosure, AF / AS may be implemented as a vehicle-to-everything (V2X) application server, a cellular Internet of things (CIoT) application server, a mission-critical push to talk (MCPTT) application, a content provider, a TV or audio service provider, a streaming video service provider, etc. The terms AS and AF may be used for the same meaning.

[0056] According to an embodiment of the present disclosure, when AF / AS requests a multicast service, MBSF, which is a network function that manages multicast service sessions and controls traffic in the 5G system, and MBSTF, which is a multicast service media anchor that receives media from AS (or content provider) in 5GS and processes media traffic under the control of MBSF, receive the multicast service request from AF.

[0057] MBSF 120 may provide functions at the service level to support MBS in conjunction with AF and MB-SMF 130. In addition, MBSF 120 may select MB-SMF 130 that meets conditions and supports functions such as allocating a multicast session identifier (ID) or a multicast group ID to a multicast service.

[0058] MB-SMF 130 is an entity that manages a multicast session for a multicast service. MB-SMF 130 may control transmission of multicast data from MB-UPF 140 to a radio access network (RAN).

[0059] MB-UPF 140 may receive the multicast data directly from AF, or may receive the multicast data from MBSTF. In addition, MB-UPF 140 may forward the multicast data to a RAN node or UPF based on quality of service (QoS).

[0060] Reference Figure 1A , in the case where the service area of ​​SMF 110 is area A 100, when the UE moves to area B 101, the PDU session of the UE is served by the intermediate SMF (I-SMF) 111 in combination with SMF 110. When the UE wants to receive MBS in area B 101, the UE requests to join the desired MBS session, and requests to join through a PDU session modification request or a PDU session establishment request. The present disclosure proposes various embodiments of processing a join request when the UE makes a join request through a PDU session modification request. When there is no PDU session created, join is requested through a PDU session establishment request. According to an embodiment of the present disclosure, when a PDU session is not created for a data network name (DNN) or network slice (single network slice selection assistance information (S-NSSAI)) for a multicast service, the UE can make a join request by making a PDU session establishment request to the DNN or network slice (S-NSSAI).

[0061] Figure 1B is a simplified diagram illustrating a scenario in which a roaming UE joins a multicast service of a home network and a multicast service of a roaming network according to an embodiment of the present disclosure.

[0062] Specifically, in a case where a UE with a public land mobile network (PLMN) A as a home operator moves to a PLMN B and roams, when the UE wants to receive MBS, the UE requests to join a desired MBS session, and makes the join request through a PDU session modification request or a PDU session establishment request. The present disclosure proposes various embodiments of processing a join request when the UE makes a join request through a PDU session modification request for a PDU session routed to a PLMN from which the UE wants to obtain a multicast service.

[0063] When no PDU session has been created and is routed to the PLMN from which the UE wants to obtain the multicast service, the UE makes a join request through a PDU session establishment request routed to the PLMN. According to an embodiment of the present disclosure, when no PDU session has been created for a DNN or network slice (S-NSSAI) and a PLMN for a multicast service, the UE can make a join request by making a PDU session establishment request for the DNN or network slice (S-NSSAI) and the PLMN.

[0064] Figure 2A and Figure 2B is a diagram illustrating a signal flow of a procedure for processing a join request in an I-SMF when a UE located outside a service area of ​​a serving SMF joins a multicast service according to various embodiments of the present disclosure.

[0065] Among the NF services provided by the AMF that manages access, communication-related service operations are defined in the 5G standard (TS23.502) as described in Table 2 below.

[0066] Table 2 Table 5.2.2.1-1: AMF service list

[0067]

[0068]

[0069] In Table 2, "Namf_communication" means a service that enables communication between UE and NR, and the service includes operations such as creation / deletion / registration of UEContext. For other service operations in Table 2, reference can be made to the relevant standards, and a detailed description of these other service operations will be avoided in this article.

[0070] Reference Figure 2A and Figure 2B, at the request of the content provider 292 or the AF, in operation 200, a process of configuring a multicast service is started in the 5G network. According to an embodiment of the present disclosure, the multicast service ID or the multicast session ID for the multicast service requested in operation 200 is determined by the NEF / MBSF 291, the MB-SMF 290 for managing the multicast session is selected, and QoS information including information about the ID of the selected MB-SMF 290, information about the UE group that can receive the multicast service, etc. is stored in the unified data management (UDM) / UDR 280 or the NEF / MBSF 280 as an MBS session context together with the multicast session ID and the multicast service ID.

[0071] In operation 201, UE 230 registers with 5G and creates a PDU session, and the serving SMF 293 manages the PDU session. However, in operation 202, when UE 230 moves out of the service area of ​​the serving SMF 293, AMF 250 selects I-SMF 260 in consideration of the location of UE 230, and transmits a non-access stratum (NAS) message for controlling the PDU session to the serving SMF 293 through I-SMF 260, so that the serving SMF 293 can process the NAS message, or can control the tunnel information between RAN 240 and UPF.

[0072] In operation 203, the UE 230 receives information for receiving a multicast service through a multicast announcement message. According to an embodiment of the present disclosure, the multicast announcement message may include at least one of an MBS service ID, an MBS session ID, DNN information for a multicast service, an S-NSSAI for a multicast service, a source multicast Internet protocol (IP) address for multicast service traffic, information about an ID of a PLMN providing a multicast service, information about an area (i.e., a tracking area (TA)), information about a cell ID list, or geographic location information. The multicast announcement message may be sent to the UE 230 by an application or by a PCF in a UE route selection policy (URSP).

[0073] In operation 204, after receiving the multicast announcement message, the UE 230 determines to receive the multicast service and sends an MBS session join request message to the AMF 250. The MBS session join request message may include information such as the ID of the multicast service to be joined or the ID of the multicast session to be joined, and the PDU session establishment request message or the PDU session modification request message is sent to the I-SMF 260 in a NAS session management (SM) message through the AMF 250.

[0074] According to an embodiment of the present disclosure, since the UE 230 has already created a PDU session, the UE may use a PDU session modification request message.

[0075] When the UE 230 sends the MBS session join request message in the PDU session modification request message, in operation 205, the AMF 250 forwards the PDU session modification request message to the I-SMF 260. After receiving the PDU session modification request message, in operation 206, the I-SMF 260 recognizes that the MBS session join request message has been received, and processes the join request. That is, when the I-SMF 260 does not have an MBS session context for the multicast session ID, the I-SMF 260 detects the MB-SMF 290 that manages the multicast session ID. The I-SMF 260 requests both the multicast session ID and the MB-SMF information from the NRF, NEF, MBSF, PCF, or UDM, and receives the MB-SMF ID information or the MB-SMF address information. In operation 207, the I-SMF 260 selects the MB-SMF 290 based on the MB-SMF ID information or the MB-SMF address information in the received MB-SMF information.

[0076] In operation 208, the I-SMF 260 sends a multicast session join request message to the selected MB-SMF 290. The multicast session join request message may include at least one of a subscription permanent identifier (SUPI) of the UE 230, a generic public subscription identifier (GPSI) of the UE 230, or a multicast session ID. In operation 209, the MB-SMF 290 inquires the UDM, MBSF, or NEF whether to accept the join request of the UE 230, and determines whether to accept the join request based on the result of the inquiry. In operation 210, the MB-SMF 290 notifies the I-SMF 260 of the result of the join request through a join request response message, and when the join request is accepted, includes the MBS session context for the requested multicast session in the join request response message. The MBS session context may include MB-SMF ID information, QoS information, information of a UE group capable of receiving a multicast service, MBS session ID, MBS service ID, etc.

[0077] According to an embodiment of the present disclosure, before the join request is sent to the MB-SMF 290 in operation 208 , the I-SMF 260 may determine whether to accept the join request of the UE 230 by asking the UDM, MBSF, or NEF whether to accept the join request in operation 209 .

[0078] In operation 211, the I-SMF 260 sends the received PDU session modification request message to the service SMF 293 to process the PDU session modification request message, and also sends the MBS session context received in operation 210 to the service SMF 293 to associate the multicast session ID with the PDU session and store the association.

[0079] In operation 212, the service SMF 293 sends the result of processing the PDU session modification together with the information about the multicast session ID to the I-SMF 260 through the PDU session modification command message. That is, in operation 212, the service SMF 293 notifies the I-SMF 260 of the association between the multicast session ID and the PDU session. In operations 213, 214 and 215, an MBS Join ACK (confirmation) message is sent to the UE 230 together with the PDU session modification command message as a NAS SM message directed to the UE 230 for AN specific resource modification in operation 216. The service SMF 293 includes the MBS Join ACK message in the PDU session modification command message, or the I-SMF 260 includes the MBS Join ACK message in the PDU session modification command message received from the service SMF 293. Then, the PDU session modification command message is sent to the UE 230. In operation 213, the I-SMF 260 transmits the MBS session context and the PDU session information to the AMF 250, and in operation 214, the AMF 250 transmits the MBS session context and the PDU session information to the RAN 240. Accordingly, the RAN 240 obtains the association between the multicast session and the PDU session.

[0080] According to an embodiment of the present disclosure, when RAN 240 has created a shared tunnel for a multicast session, UE 230 receives traffic for the multicast session in operations 220 and 221. The shared tunnel is a tunnel for transmitting multicast data traffic for the multicast session from MB-UPF to RAN 240.

[0081] According to an embodiment of the present disclosure, in the case where a shared tunnel for a multicast session has not been created although the RAN 240 supports multicast, in operation 217, the RAN 240 sends an N2 session response message to the AMF 250 to request shared tunnel establishment. The N2 session response message includes the MB-SMF ID, the multicast session ID, and shared tunnel endpoint information for receiving multicast session traffic. The endpoint information may include the IP address of the RAN 240 and the shared tunnel ID.

[0082] In operation 218, upon receiving the N2 session response message, the AMF 250 sends the multicast session ID and information about the endpoint of the shared channel for receiving the multicast session traffic to the MB-SMF 290 corresponding to the MB-SMF ID in the Nsmf_MBSession_CreateSMContext request message or the Nsmf_MBSession_UpdateSMContext request message. In operation 219, the MB-SMF 290 sends the multicast session ID and information about the endpoint of the shared tunnel for receiving the multicast session traffic to the MB-UPF 270. In operation 220, the MB-UPF 270 sends the multicast data traffic received from the content provider 292 or the MBSTF to the RAN 240. The RAN 240 sends the multicast session traffic received through the shared tunnel in a point-to-multicast manner or a point-to-point manner. The information about the endpoint may include a tunnel ID and RAN address information as information for identifying a tunnel between the RAN and the MB-UPF 270 tunnel of the shared tunnel.

[0083] Figure 3 is a diagram showing a signal flow of a procedure for processing a join request in a serving SMF when a UE located outside a service area of ​​the serving SMF joins a multicast service according to an embodiment of the present disclosure.

[0084] Although Figure 2A and Figure 2B The method of directly processing the join request message by I-SMF is shown, but Figure 3 A method for processing a join request message by a service SMF is shown. According to an embodiment of the present disclosure, Figure 3 The embodiment replaces Figure 2A and Figure 2B Operations 206 to 212.

[0085] exist Figure 3 In an embodiment, when the AMF 250 receives a join request message in a PDU session modification request message from the UE 230, the AMF 250 identifies the I-SMF 260 for the corresponding PDU session, and includes the UE location information in the received PDU session modification request message when sending the PDU session modification request message received in the Nsmf_PDUSession_UpdateSM context message to the I-SMF 260. The UE location information may be a TA or a cell ID list.

[0086] Reference Figure 3, after receiving the PDU session modification request message, in operation 301, the I-SMF 260 sends a Nsmf_PDUSession_update request (join request (MBS session ID)) to the serving SMF 293. When the I-SMF 260 sends the Nsmf_PDUSession_update request (join request (MBS session ID)) to the serving SMF 293, the I-SMF 260 also sends the UE location information.

[0087] When SMF 293 does not have an MBS session context for an MBS session ID for a UE location, in operation 302, SMF 293 requests information about the ID of the MS-SMF controlling the MBS session ID for the UE location or the MBS session context by sending an Nnef_MBSsession_get request (MBS session ID, UE location) message to NEF / MBSF 291.

[0088] When there is no corresponding information in NEF / MBSF 291, SMF 293 obtains information about the ID of the MS-SMF controlling the MBS session ID for the UE location or the MBS session context from UDR 280 in operation 303. In operations 305 and 306, NEF / MBSF 291 sends the obtained MB-SMF ID information or MBS session context information to the serving SMF 293.

[0089] According to an embodiment of the present disclosure, the SMF may obtain information about the ID of the MS-SMF controlling the MBS session ID for the UE location or the MBS session context by using NRF, UDM, or PCF instead of NEF / MBSF 291.

[0090] In operation 307, the serving SMF 293 sends a multicast session join request message to the selected MB-SMF 290. According to an embodiment of the present disclosure, the multicast session join request message may include information about the SUPI or GPSI of the UE 230 and the multicast session ID. In operation 308, the MB-SMF 290 determines whether to accept the UE's join request by querying the UDM or NEF / MBSF 291. In operation 309, the MB-SMF 290 notifies the serving SMF 293 of the determination result on whether to accept the UE's join request through a join request response message. When the UE's join request is accepted, the join request response message includes an MBS session context for the requested multicast session. According to an embodiment of the present disclosure, the MBS session context may include MB-SMF ID information, QoS information, information about a UE group that can receive multicast services, an MBS session ID, an MBS service ID, and the like.

[0091] According to an embodiment of the present disclosure, in operation 307 , the serving I-SMF 260 may determine whether to accept the join request of the UE by querying the UDM or NEF / MBSF 291 before sending the join request to the MB-SMF 290 .

[0092] Figure 4A and Figure 4B It is a diagram showing a signal flow of a procedure for processing a join request by a serving SMF to provide a multicast service through an intermediate SMF (intermediate-MB-SMF, I-MB-SMF) when a UE located outside a service area of ​​the serving SMF joins a multicast service according to various embodiments of the present disclosure.

[0093] According to an embodiment of the present disclosure, when a UE wants to receive a multicast service outside the service area of ​​the MB-SMF, the I-SMF or AMF designates the I-MB-SMF as another MB-SMF that can provide the multicast service to the location of the UE and controls the shared tunnel from the MB-UPF to the RAN.

[0094] Reference Figure 4A and Figure 4B , as in Figure 2AAs in operations 200 to 203 of , multicast service configuration, network registration of UE and PDU session creation are performed, and UEs outside the service area of ​​the service SMF 293 receive the multicast service announcement message. That is, at the request of the content provider 292 or AF, the process of configuring the multicast service in the 5G network is performed. In this configuration process, the multicast service ID or multicast session ID for the requested multicast service is determined by the NEF / MBSF 291, the MB-SMF 290 for managing the multicast session is selected, and QoS information including information about the ID of the selected MB-SMF and information about the UE group that can receive the multicast service are stored in the UDR, UDM or NEF / MBSF as an MBS session context together with the multicast session ID and the multicast service ID. UE 230 registers with 5G and creates a PDU session. The PDU session is managed by the service SMF 293. However, when the UE 230 moves out of the service area of ​​the serving SMF 293, the AMF 250 selects the I-SMF 260 in consideration of the location of the UE 230, and sends a NAS message for controlling the PDU session to the serving SMF 293 through the I-SMF 260, so that the serving SMF 293 can process the NAS message, or the tunnel information between the RAN 240 and the UPF can be controlled. The UE 230 receives information for receiving the multicast service through the multicast announcement message. According to an embodiment of the present disclosure, the multicast announcement message may include at least one of the MBS service ID, the MBS session ID, the DNN information for the multicast service, the S-NSSAI for the multicast service, the source multicast IP address for the multicast service traffic, the information about the ID of the PLMN providing the multicast service, the information about the area (ie, TA), the information about the cell ID list, or the geographical location information. The multicast announcement message may be sent to the UE 230 by the application or by the PCF in the URSP.

[0095] Reference Figure 4A and Figure 4B , performed in operation 400 Figure 2A In operation 401, the UE 230 determines to join the MBS session and sends an MBS session join request message to the I-SMF 260. The MBS session join request message may include information such as the ID of the multicast service to be joined or the ID of the multicast session to be joined. The MBS session join request message is sent to the serving SMF 293 in a NAS SM message (e.g., a PDU session establishment request message or a PDU session modification request message) through the AMF 250.

[0096] According to an embodiment of the present disclosure, since the UE 230 has already created a PDU session, the UE 230 may use a PDU session modification request message.

[0097] When the UE 230 sends the MBS session join request message in the PDU session modification request message, the AMF 250 forwards the PDU session modification request message to the I-SMF 260. In operation 402, the I-SMF 260 sends the MBS session join request message in the Nsmf_PDUSession_update request (join request) message to the serving SMF 290. When the serving SMF 290 does not have the MBS session context for the multicast session ID, the serving SMF 290 detects the MB-SMF 290 that manages the multicast session ID. In operation 403, the serving SMF 290 processes the join request by sending the multicast session join request message to the MB-SMF 290. In operation 404, the MB-SMF 290 modifies or obtains information for receiving multicast session traffic from the MB-UPF 270. In operation 405, the MB-SMF 290 sends an MBS session context for the multicast session to the serving SMF 293 as a response message to the MBS session join request message, and the serving SMF 293 associates the multicast session ID with the PDU session and stores the association.

[0098] The MBS session context may include information about an MB-SMF ID, QoS information, information about a UE group capable of receiving a multicast service, an MBS session ID, an MBS service ID, and the like.

[0099] In operations 406 and 407, the serving SMF 293 may modify the PDU session with the UPF 470 in response to the received PDU session modification request, and then send an Nsmf_PDUSession_update response message to the I-SMF 260 in response to the PDU session modification request. The Nsmf_PDUSession_update response message is sent to the I-SMF 260 together with the information about the MB-SMF ID and the information about the MBS session context or as a separate message. In operation 408, the I-SMF 260 knows that the UE 230 is outside the service area corresponding to the MB-SMF ID, and therefore selects the MB-SMF within its service area as the I-MB-SMF 440.

[0100] According to an embodiment of the present disclosure, in the method of selecting an I-MB-SMF, upon receiving an MBS session join request message in operation 401, the AMF 360 may detect the MB-SMF available at the location of the UE through the NRF, and send information about the ID or address of the I-MB-SMF to the I-SMF 260, so that the I-SMF 260 may select the I-MB-SMF in operation 408.

[0101] According to an embodiment of the present disclosure, in the method of selecting an I-MB-SMF, operations 408 to 411 are not performed in advance, and when there is no corresponding shared tunnel in the RAN and therefore the RAN requests the AMF to establish a shared channel in operation 416, the AMF can discover the MB-SMF available at the location of the UE through the NRF, thereby recognizing that the MB-SMF corresponding to the MB-SMF ID included in the request received from the RAN is located in an unserviceable area, select the discovered MB-SMF as the I-MB-SMF as in operation 408, and send the MBS session context including the MB-SMF ID and the shared tunnel endpoint information of the RAN for the multicast session (e.g., information about the address and tunnel ID of the RAN) as in operation 417, so that the shared channel can be established. As in operation 418, the I-MB-SMF selects the MB-UPF from among the available MB-UPFs as the I-MB-UPF, and establishes a shared tunnel between the RAN and the I-MB-UPF by sending the shared tunnel endpoint information received from the RAN to the I-MB-UPF.

[0102] In addition, the I-MB-SMF obtains the shared tunnel endpoint information (e.g., information about the ID or address of the I-MB-UPF and the tunnel ID) of the shared tunnel with the MB-UPF for the multicast session of the I-MB-UPF, and requests the shared tunnel establishment by sending the MBS session context including the MB-SMF ID and the shared tunnel endpoint information for the multicast session to the MB-SMF as in operation 419. As in operation 420, the MB-SMF forwards the information to the MB-UPF to create a shared tunnel between the MB-UPF and the I-MB-UPF, and thus finally creates a shared tunnel for the multicast session from the MB-UPF to the RAN. Therefore, the multicast traffic can be received as in operations 421 and 422.

[0103] When I-SMF 260 Figure 4AWhen the I-MB-SMF 440 is selected as in operation 408 of the RAN 240, the I-SMF 260 sends information about the MB-SMF ID and information about the MBS session context to the selected I-MB-SMF 440 in operation 409, and the I-MB-SMF 440 selects the I-MB-UPF 460 in operation 410 to establish a shared tunnel between the MB-UPF 270 and the RAN 240, and configures and sends tunnel information for sending a multicast session in operation 411.

[0104] In operations 412, 413, and 415, the I-SMF 260 sends the MBS Join ACK message together with the PDU Session Modification Command message as a NAS SM message directed to the UE 230. The serving SMF 293 includes the MBS Join ACK message in the PDU Session Modification Command message, or the I-SMF 260 includes the MBS Join ACK message in the PDU Session Modification Command message received from the serving SMF 293 for transmission to the UE 230.

[0105] In operation 412, the I-SMF 260 transmits the MBS session context including the MB-SMF ID and the I-MB-SMF ID and the information about the PDU session to the AMF 250. In operation 413, the AMF 250 transmits the information about the MBS session context including the MB-SMF ID and the I-MB-SMF ID and the information about the PDU session to the RAN 240. In operation 414, the RAN 240 obtains the association between the multicast session and the PDU session.

[0106] When the RAN 240 has created a shared tunnel for the multicast session, in operations 421 and 422 , the UE receives traffic for the multicast session.

[0107] On the contrary, when RAN 240 can support multicast and a shared tunnel for a multicast session has not been created, RAN 240 sends an N2 session response message to AMF 250 in operation 416 to request shared tunnel establishment. The N2 session response message includes I-MB-SMF ID or MB-SMF ID, multicast session ID, and shared tunnel endpoint information for receiving multicast session traffic. The endpoint information includes the IP address of the RAN node and the shared tunnel ID.

[0108] After receiving the N2 session response message, in operation 417, the AMF 250 sends the multicast session ID and the shared tunnel endpoint information for receiving the multicast session traffic to the I-MB-SMF 440 through the Nsmf_MBSession_CreateSMContext request message or the Nsmf_MBSession_UpdateSMContext request message. The I-MB-SMF 440 forwards the Nsmf_MBSession_CreateSMContext request message or the Nsmf_MBSession_UpdateSMContext request message to the MB-SMF 290. According to an embodiment of the present disclosure, in operation 417, the AMF 250 sends the MBS session context including the MB-SMF ID and the shared tunnel endpoint information (e.g., information about the address of the RAN and the tunnel ID) for the multicast session for the RAN to the I-MB-SMF 440 to establish a shared tunnel. In operation 418, the I-MB-SMF 440 forwards the shared tunnel endpoint information to the I-MB-UPF 460 to establish a shared tunnel between the RAN 240 and the I-MB-UPF 460. For a multicast session, the I-MB-SMF 440 obtains shared tunnel endpoint information for a shared tunnel with the MB-UPF, for example, information about the ID or address of the I-MB-UPF 460 and the tunnel ID. In operation 419, the I-MB-SMF 440 requests shared tunnel establishment by sending an MBS session context including the MB-SMF ID and the shared tunnel endpoint information for the multicast session to the MB-SMF 290. In operation 420, the MB-SMF 290 sends a shared tunnel establishment request message to the MB-UPF 270, and creates a shared tunnel between the MB-UPF 270 and the I-MB-UPF 460. In operation 421, the I-MB-UPF 460 finally transmits the multicast data traffic received from the content provider or MBSTF from the MB-UPF 270 to the RAN 240. In operation 422, the RAN 240 transmits the multicast session traffic received through the shared tunnel to the UE 230 in a point-to-multicast method or a point-to-point method.

[0109] Figure 5A and Figure 5B is a diagram illustrating a procedure for providing services in a shared delivery method when a roaming UE joins a multicast service of a home operator according to various embodiments of the present disclosure.

[0110] Reference Figure 5A and Figure 5B ,V and H in the entity name mean interviewed and owned, respectively.

[0111] Reference Figure 5A and Figure 5B In the case where a multicast service is configured in the home PLMN of the UE 230 and a multicast service announcement is made for the multicast service, in operation 500, the UE 230 registers in the visited PLMN and determines to use the multicast service.

[0112] UE 230 that has registered in the roaming network can use the multicast service provided by the roaming network and the multicast service provided by the home network. Therefore, after receiving the service announcement message, UE 230 should be able to identify the network that provides the multicast service. To this end, the service announcement message may refer to the PLMN ID included in the multicast session ID or the PLMN ID included in the multicast group ID, or may include a PLMN ID that identifies the network that provides the service.

[0113] In operation 501a, the roaming UE 230 creates and selects an appropriate PDU session according to the PLMN providing the expected multicast service. For example, in the case where there is no PDU session for the PLMN providing the service and the corresponding DNN or S-NSSAI, the UE 230 can request the PDU session establishment based on the DNN information and S-NSSAI included in the service announcement message, and in the case where there is a PDU session, in operation 501b, the UE 230 sends an MBS session join request to the AMF 250 through a PDU session modification request. Although the description is based on the assumption that the PDU session modification request is used in consideration of the assumption that the expected multicast service is provided by the home operator and the situation where a PDU session has been created for the DNN or S-NSSAI, the PDU session establishment request message can also be used in a similar manner.

[0114] The MBS session join request message may include information such as the ID of the multicast service to be joined or the ID of the multicast session to be joined. The MBS session join request message may be included in a NAS SM message (such as a PDU session establishment request message or a PDU session modification request message) and sent to the SMF through the AMF.

[0115] After receiving the MBS session join request message included in the PDU session modification request message from the UE 230, the AMF 250 sends the MBS session join request message to the V-SMF 530. In operation 502, the V-SMF 530 sends the MBS session join request message to the H-SMF 570 by using the Nsmf_PDUSession_update request (join request) message. In operations 503, 504, and 505, when the H-SMF 570 does not have an MBS session context for the multicast session ID, the H-SMF 570 detects and selects the H-MB-SMF 580 that manages the multicast session ID, and sends the multicast session join request message to the selected H-MB-SMF 580 to process the join request. For example, the H-MB-SMF 580 modifies or obtains information for receiving multicast session traffic from the H-MB-UPF 591 in operation 504, and in response sends an MBS session context for the multicast session to the H-SMF 570 in operation 505. The H-SMF 570 associates the multicast session ID with the PDU session based on the MBS session context and stores the association.

[0116] The MBS session context may include information about an H-MB-SMF ID, QoS information, information about a UE group capable of receiving a multicast service, an MBS session ID, an MBS service ID, and the like.

[0117] In operation 506, the H-SMF 570 may modify the PDU session with the H-UPF 590 according to the received PDU session modification request. In operation 507, the H-SMF 570 sends an Nsmf_PDUSession_update response message to the V-SMF 530 in response to the PDU session modification request. The Nsmf_PDUSession_update response message delivers information about the H-MB-SMF ID and information about the MBS session context to the V-SMF 530 together or as a separate message.

[0118] In operation 508 , the V-SMF 530 recognizes that the UE 230 is in its own network outside the service area corresponding to the H-MB-SMF ID, and selects an MB-SMF in its service area as the V-MB-SMF 540 .

[0119] According to an embodiment of the present disclosure, in another method of selecting V-MB-SMF, when AMF 250 receives an MBS session join request message in operation 501b, AMF 250 detects an MB-SMF available at the location of the UE through NRF, and selects the detected MB-SMF as V-MB-SMF. When AMF 250 sends an MBS join request message or a PDU session modification request or a PDU session establishment request message to V-SMF, AMF 250 may send information about the ID or address of V-MB-SMF together with information about H-SMF, so that V-SMF can select V-MB-SMF.

[0120] According to an embodiment of the present disclosure, in another method of selecting a V-MB-SMF, operations 508 to 511 are not performed in advance, and when there is no corresponding shared tunnel in the RAN and therefore the RAN requests the AMF to establish a shared channel in operation 516, the AMF can detect the MB-SMF available at the location of the UE through the NRF, thereby identifying that the H-MB-SMF corresponding to the H-MB-SMF ID included in the request received from the RAN is located in the home network, and select the detected MB-SMF as the V-MB-SMF. As in operation 517, for a multicast session, the AMF sends an MBS session context including the H-MB-SMF ID and the shared tunnel endpoint information of the RAN (e.g., information about the address and tunnel ID of the RAN), so that a shared channel can be established. As in operation 518, the V-MB-SMF selects an MB-UPF from among the available MB-UPFs as the V-MB-UPF, and establishes a shared tunnel between the RAN and the V-MB-UPF by sending the shared tunnel endpoint information received from the RAN to the V-MB-UPF. In addition, the V-MB-SMF obtains shared tunnel endpoint information (e.g., information about the ID or address of the V-MB-UPF and the tunnel ID) of the shared tunnel with the V-MB-UPF for the multicast session of the V-MB-UPF, and requests the shared tunnel establishment by sending the MBS session context including the H-MB-SMF ID and the shared tunnel endpoint information for the multicast session to the H-MB-SMF as in operation 519. As in operation 520, the H-MB-SMF sends information to the H-MB-UPF to establish a shared tunnel between the H-MB-UPF and the V-MB-UPF, and finally establishes a shared tunnel for the multicast session from the H-MB-UPF to the RAN. Therefore, multicast traffic can be received in operations 521 and 522.

[0121] When the V-SMF 530 selects the V-MB-SMF 540 as in operation 508, the V-SMF 530 transmits information about the H-MB-SMF ID and information about the MBS session context to the selected V-MB-SMF 540 through an MBS session update request message in operation 509. In operation 510, the V-MB-SMF 540 selects the V-MB-UPF 560 to establish a shared tunnel between the H-MB-UPF 591 and the RAN 240, and transmits tunnel information for transmitting a multicast session to the V-MB-UPF 560. In operation 511, the V-MB-SMF 540 transmits tunnel information for transmitting a multicast session to the V-SMF 530.

[0122] In operations 512, 513, and 515, the V-SMF 530 transmits the MBS Join ACK message together with the PDU Session Modification Command message as a NAS SM message directed to the UE 230 to the UE 230. The Serving SMF 293 includes the MBS Join ACK message in the PDU Session Modification Command message, or the V-SMF 530 includes the MBS Join ACK message in the PDU Session Modification Command message received from the H-SMF 570 for transmission to the UE 230. In operation 512, the V-SMF 530 transmits the MBS session context including the H-MB-SMF ID and the V-MB-SMF ID and the PDU session information to the AMF 250. In operation 513, the AMF 250 transmits the MBS session context including the H-MB-SMF ID or the V-MB-SMF ID and the PDU session information to the RAN 240. Accordingly, in operation 514, the RAN 240 obtains an association between the multicast session and the PDU session.

[0123] When the RAN 240 has established a shared tunnel for the multicast session, in operations 521 and 522 , the UE 230 receives traffic for the multicast session.

[0124] On the contrary, when RAN 240 can support multicast and a shared tunnel for a multicast session has not been established, RAN 240 sends an N2 session response message to AMF 250 in operation 516 to request shared tunnel establishment. The N2 session response message includes V-MB-SMF ID or H-MB-SMF ID, multicast session ID, and shared tunnel endpoint information for receiving multicast session traffic. The endpoint information includes the IP address of the RAN node and the shared tunnel ID.

[0125] After receiving the N2 session response message, in operation 517, the AMF 250 sends the multicast session ID and the shared tunnel endpoint information for receiving the multicast session traffic to the V-MB-SMF 540 through the Nsmf_MBSession_CreateSMContext request or the Nsmf_MBSession_UpdateSMContext request message. The V-MB-SMF 540 sends the Nsmf_MBSession_CreateSMContext request or the Nsmf_MBSession_UpdateSMContext request message to the H-MB-SMF 580. According to an embodiment of the present disclosure, in operation 517, the MBS session context including the H-MB-SMF ID and the shared tunnel endpoint information (e.g., information about the address and tunnel ID of the RAN 240) for the multicast session of the RAN 240 is sent to the V-MB-SMF 540 to establish a shared tunnel. In operation 518, the V-MB-SMF 540 sends the shared tunnel endpoint information to the V-MB-UPF 560 to establish a shared tunnel between the RAN 240 and the V-MB-UPF 560. The V-MB-SMF 540 obtains the shared tunnel endpoint information (e.g., information about the ID or address of the V-MB-UPF 560) and the tunnel ID of the shared tunnel with the H-MB-UPF 591 for the multicast session. In operation 519, the V-MB-SMF 540 requests the shared tunnel establishment by sending the MBS session context including the H-MB-SMF ID and the shared tunnel endpoint information for the multicast session to the H-MB-SMF 580. In operation 520, the H-MB-SMF 580 sends the MBS session context and the shared tunnel endpoint information to the H-MB-UPF 591, and establishes the shared tunnel between the H-MB-UPF 591 and the V-MB-UPF 560. In operation 521, the V-MB-UPF 560 finally transmits the multicast data traffic received from the content provider or MBSTF from the H-MB-UPF 591 to the RAN 240. In operation 522, the RAN 240 transmits the multicast session traffic received through the shared tunnel to the UE 230 in a point-to-multicast method or a point-to-point method.

[0126] exist Figure 5A and Figure 5BIn another embodiment, when the UE requests a PDU session establishment, the AMF 250 identifies the UE as having MBS capabilities in the process of negotiating UE capabilities during registration. When, upon receiving the PDU session establishment request, the AMF 250 identifies that the PDU session for DNN and S-NSSAI requested by the UE is a PDU session from the home route to which the UE subscribes, the AMF 250 selects an SMF having both MB-SMF functionality and SMF functionality in the visited PLMN as the V-SMF 530, and selects an SMF having an SMF functionality in the home PLMN as the H-SMF 570. In addition, the V-SMF 530 selects a UPF having both MB-UPF functionality and UPF functionality as the V-UPF 550. When selecting an SMF having both MB-SMF functionality and SMF functionality and selecting a UPF having both MB-UPF functionality and UPF functionality, the AMF 250 can detect a suitable SMF by requesting an SMF having both MBS capability and MB-SMF capability from the NRF, and the SMF can detect a suitable UPF by requesting an UPF having both MBS capability and MB-UPF capability from the NRF.

[0127] In this way, when V-SMF 530 and V-MB-SMF 540 are co-located and V-UPF 550 and V-MB-UPF 560 are co-located, operations 508, 509, and 511 are performed as internal operations of V-SMF 530 and thus no longer cause separate messages. In order to act as a control plane proxy for H-SMF 570 and H-MB-SMF 580, V-SMF 530 of the visited PLMN handles the service of PDU session through H-SMF and handles the service of MBS session through H-MB-SMF 580.

[0128] According to various embodiments of the present disclosure, when UE 230 receives a multicast service provided by a home network, the V-SMF 530 of the local network may receive a join request message from UE 230. When UE 230 makes an erroneous join request through a locally routed PDU session, V-SMF 530 may send a failure message for the join request to UE 230 in response to the join request message. According to an embodiment, the failure message may include a failure cause. The failure cause may include DNN information and cause information indicating, for example, "home PLMN does not support multicast services" or "multicast services are not supported". Upon receiving the failure message, UE 230 may recognize that UE 230 has selected a PDU session that does not match the information included in the service announcement message. When UE 230 selects another home-routed PDU session and makes a join request, or when a suitable home-routed PDU session is not created, UE 230 may make a join request while creating a home-routed PDU session.

[0129] Fig. 6A and Figure 6B is a diagram illustrating a signal flow of a procedure for providing a service in a separate delivery method when a roaming UE joins a multicast service of a home operator according to various embodiments of the present disclosure.

[0130] Reference Fig. 6A and Figure 6B In the case where a multicast service is configured in the home PLMN of the UE 230 and a multicast service announcement is made for the multicast service, in operation 600, the UE 230 registers in the visited PLMN and determines to use the multicast service, as described previously with reference to other figures. The UE 230 that has registered in the roaming network can use the multicast service provided by the roaming network and the multicast service provided by the home network. Therefore, after receiving the service announcement message, the UE 230 should be able to identify the network that provides the multicast service. To this end, the service announcement message may refer to the PLMN ID included in the multicast session ID or the PLMN ID included in the multicast group ID, or may include a PLMN ID that identifies the network that provides the service.

[0131] In operation 601a, the roaming UE 230 creates and selects a suitable PDU session according to the PLMN providing the expected multicast service. For example, in the case where there is no PDU session for the PLMN providing the service and the corresponding DNN or S-NSSAI, the UE 230 can request the establishment of the PDU session based on the DNN information and S-NSSAI included in the service announcement message, and in the case where there is a PDU session, in operation 601b, the UE 230 sends an MBS session join request through a PDU session modification request message.

[0132] Although the description is based on the assumption that the PDU session modification request is used taking into account the assumption that the expected multicast service is provided by the home operator and that a PDU session has already been created for the DNN or S-NSSAI, the PDU session establishment request message can also be used in a similar manner.

[0133] The MBS session join request message may include information such as the ID of the multicast service to be joined or the ID of the multicast session to be joined. The MBS session join request message may be included in a NAS SM message (such as a PDU session establishment request message or a PDU session modification request message) and sent to the service SMF 293 through the AMF 250.

[0134] After receiving the MBS session join request message included in the PDU session modification request message from the UE 230, the AMF 250 forwards the MBS session join request message to the V-SMF 530. In operation 602, the V-SMF 530 sends the MBS session join request message to the H-SMF 570 through the Nsmf_PDUSession_update request (join request) message. When the H-SMF 570 does not have an MBS session context for the multicast session ID, the H-SMF 570 detects and selects the H-MB-SMF 580 that manages the multicast session ID. In operation 603, the H-SMF 570 sends a multicast session join request message to the selected H-MB-SMF 580 to process the join request. For example, the H-MB-SMF 580 modifies or obtains information for receiving multicast session traffic from the H-MB-UPF 591 as in operation 604, and in response sends an MBS session context for the multicast session to the H-SMF 570 as in operation 605. The H-SMF 570 associates the multicast session ID with the PDU session based on the information for receiving the multicast session traffic and stores the association.

[0135] The MBS session context may include information about an H-MB-SMF ID, QoS information, information about a UE group capable of receiving a multicast service, an MBS session ID, an MBS service ID, and the like.

[0136] In operation 606, the H-SMF 570 may modify the PDU session with the H-UPF 590 according to the received PDU session modification request. In operation 607, the H-SMF 570 sends an Nsmf_PDUSession_update response message to the V-SMF 530 in response to the PDU session modification request. The Nsmf_PDUSession_update response message delivers information about the H-MB-SMF ID and information about the MBS session context to the V-SMF 530 together or as a separate message.

[0137] In operations 608, 609, and 611, the V-SMF 530 sends the MBS Join ACK message together with the PDU Session Modification Command message as a NAS SM message directed to the UE 230. The SMF includes the MBS Join ACK message in the PDU Session Modification Command message, or the V-SMF 530 includes the MBS Join ACK message in the PDU Session Modification Command message received from the H-SMF 570 for transmission to the UE 230.

[0138] In operation 608, the V-SMF 530 sends the MBS session context and PDU session information including the H-MB-SMF ID to the AMF 250. In operation 609, the V-SMF 530 sends the MBS session context and PDU session information including the H-MB-SMF ID to the RAN 240. Accordingly, the RAN 240 obtains the association between the multicast session and the PDU session.

[0139] When the RAN 240 does not support shared tunnels or must send data in a separate delivery method as in operation 610, the RAN 240 sends an N2 session response message to the AMF 250 in operation 612 to request tunnel establishment. The N2 session response message may include tunnel endpoint information for receiving multicast session traffic for the PDU session. The endpoint information includes the IP address of the RAN 240 and the tunnel ID.

[0140] In operation 613, upon receiving the N2 session response message, the AMF 250 transmits the tunnel information of the RAN 240 for separate delivery to the V-SMF 530. In operation 614, the V-SMF 530 may transmit the tunnel information of the RAN 240 together with the multicast session ID to the V-UPF 550, and obtain endpoint information about a separate tunnel for receiving multicast session traffic from the V-UPF 550. The endpoint information includes an ID address of the V-UPF 550 and a tunnel ID.

[0141] In addition, since the V-SMF 530 knows in advance the H-MB-SMF and the MBS session context that provide the multicast session ID, the V-SMF 530 sends the multicast session ID, the endpoint information about the separate tunnel of the V-UPF 550 for receiving the multicast session traffic, and the indication of requesting separate delivery to the H-MB-SMF 580. In addition, in operation 620, the H-MB-SMF 580 sends the received information about the separate tunnel together with the multicast session ID to the H-MB-UPF 591, so that the H-MB-UPF 591 can send the multicast service traffic to the V-UPF 550 through separate delivery.

[0142] In operation 617, the V-UPF 550 finally transmits the multicast data traffic received from the content provider or MBSTF from the H-MB-UPF 591 to the RAN 240. In operation 618, the RAN 240 transmits the multicast session traffic received through the separate tunnel to the UE 230 in a point-to-multicast method or a point-to-point method.

[0143] According to an embodiment of the present disclosure, instead of the separate delivery establishment process of operation 615, the H-MB-SMF 580 can send the tunnel endpoint information of the V-UPF 550 together with the multicast session ID to the MBSF, and the MBSF can send the information to the MBSTF so that the MBSTF can directly send the multicast data traffic to the V-UPF 550.

[0144] According to an embodiment of the present disclosure, the separate delivery establishment process of operation 615 may be requested by V-SMF 530 forwarding the request to H-SMF 570 and H-SMF 570 forwarding the request to H-MB-SMF 580, instead of V-SMF 530 making a direct request to H-MB-SMF 580.

[0145] According to various embodiments of the present disclosure, when UE 230 receives a multicast service provided by a home network, the V-SMF 530 of the local network may receive a join request message from UE 230. When UE 230 makes an erroneous join request through a locally routed PDU session, V-SMF 530 may send a failure message for the join request to UE 230 in response to the join request message. According to an embodiment, the failure message may include a failure cause. The failure cause may include DNN information and cause information indicating, for example, "home PLMN does not support multicast services" or "multicast services are not supported". Upon receiving the failure message, UE 230 may recognize that UE 230 has selected a PDU session that does not match the information included in the service announcement message. When UE 230 selects another home-routed PDU session and makes a join request, or when a suitable home-routed PDU session is not created, UE 230 may make a join request, thereby creating a home-routed PDU session.

[0146] Fig. 7A and Figure 7B is a diagram illustrating a signal flow of a procedure for providing a service in a separate delivery method when a roaming UE joins a multicast service of a home operator according to various embodiments of the present disclosure.

[0147] Reference Fig. 7A and Figure 7B In operation 700, in the case where a multicast service is configured in the home PLMN of the UE 230 and a multicast service announcement is made for the multicast service, in operation 600, the UE 230 registers in the visited PLMN and determines to use the multicast service, as described previously with reference to other figures. The UE 230 that has registered in the roaming network can use the multicast service provided by the roaming network and the multicast service provided by the home network. Therefore, after receiving the service announcement message, the UE 230 should be able to identify the network that provides the multicast service. To this end, the service announcement message may refer to the PLMN ID included in the multicast session ID or the PLMN ID included in the multicast group ID, or may include a PLMN ID that identifies the network that provides the service.

[0148] In operation 701a, the roaming UE 230 creates and selects a suitable PDU session according to the PLMN providing the expected multicast service. For example, in the case where there is no PDU session for the PLMN providing the service and the corresponding DNN or S-NSSAI, the UE 230 can request the establishment of the PDU session based on the DNN information and S-NSSAI included in the service announcement message, and in the case where there is a PDU session, in operation 701b, the UE 230 sends an MBS session join request through a PDU session modification request message.

[0149] Although the description is based on the assumption that the PDU session modification request is used taking into account the assumption that the expected multicast service is provided by the home operator and that a PDU session has already been created for the DNN or S-NSSAI, the PDU session establishment request message can also be used in a similar manner.

[0150] The MBS session join request message may include information such as the ID of the multicast service to be joined or the ID of the multicast session to be joined. The MBS session join request message may be included in a NAS SM message (such as a PDU session establishment request message or a PDU session modification request message) and sent to the V-SMF 530 through the AMF 250.

[0151] After receiving the MBS session join request message included in the PDU session modification request message from the UE 230, the AMF 250 forwards the MBS session join request message to the V-SMF 530. In operation 702, the V-SMF 530 sends the MBS session join request message to the H-SMF 570 through the Nsmf_PDUSession_update request (join request) message. When the H-SMF 570 does not have an MBS session context for the multicast session ID, the H-SMF 570 detects and selects the H-MB-SMF 580 that manages the multicast session ID. As in operation 703, the H-SMF 570 sends a multicast session join request message to the selected H-MB-SMF 580 to process the join request. For example, the H-MB-SMF 580 modifies or obtains information for receiving multicast session traffic from the H-MB-UPF 591 as in operation 704, and in response sends an MBS session context for the multicast session to the H-SMF 570 as in operation 705. The H-SMF 570 associates the multicast session ID with the PDU session and stores the association.

[0152] The MBS session context may include information about an H-MB-SMF ID, QoS information, information about a UE group capable of receiving a multicast service, an MBS session ID, an MBS service ID, and the like.

[0153] In operation 706, the H-SMF 570 may modify the PDU session with the H-UPF 590 according to the received PDU session modification request. In operation 707, the H-SMF 570 sends an Nsmf_PDUSession_update response message to the V-SMF 530 in response to the PDU session modification request. The H-SMF 570 sends information about the H-MB-SMF ID and information about the MBS session context together or as a separate message to the V-SMF 530 through the Nsmf_PDUSession_update response message. In operations 708, 709, and 711, the V-SMF 530 sends an MBS join ACK message together with the PDU session modification command message as a NAS SM message directed to the UE 230 to the UE 230. The SMF includes the MBS Add ACK message in the PDU Session Modification Command message, or the V-SMF 530 includes the MBS Add ACK message in the PDU Session Modification Command message received from the H-SMF 570 for transmission to the UE 230.

[0154] Specifically, in operation 708, the V-SMF 530 sends the MBS session context and PDU session information including the H-MB-SMF ID to the AMF 250. In operation 709, the V-SMF 530 sends the MBS session context and PDU session information including the H-MB-SMF ID to the RAN 240. Accordingly, the RAN 240 obtains the association between the multicast session and the PDU session.

[0155] When the RAN 240 does not support shared tunnels or must send data in a separate delivery method as in operation 710, the RAN 240 sends an N2 session response message to the AMF 250 in operation 712 to request tunnel establishment. The N2 session response message may include tunnel endpoint information for receiving multicast session traffic for the PDU session. The endpoint information includes the IP address of the RAN 240 and the tunnel ID.

[0156] In operation 713, upon receiving the N2 session response message, the AMF 250 transmits the tunnel information of the RAN 240 for separate delivery to the V-SMF 530. In operation 714, the V-SMF 530 may transmit the tunnel information of the RAN 240 together with the multicast session ID to the V-UPF 550, and obtain endpoint information about a separate tunnel for receiving multicast session traffic from the V-UPF 550. The endpoint information includes an ID address of the V-UPF 550 and a tunnel ID.

[0157] In operation 715, the V-SMF 530 sends the multicast session ID, the endpoint information of the separate tunnel of the V-UPF 550 for receiving the multicast session traffic, and the indication of requesting separate delivery to the H-SMF 570 through the Nsmf_MBSession_CreateSMContext request or Nsmf_MBSession_UpdateSMContext request message. In operation 716, the H-SMF 570 sends the received information about the separate tunnel together with the multicast session ID to the H-UPF 590 to set the tunnel information for sending the multicast service traffic to the V-UPF 550 through the separate delivery of the H-UPF 590. In addition, the H-SMF 570 may obtain the endpoint information of the separate tunnel of the H-UPF 590 to receive the multicast session traffic from the H-MB-UPF 591. In operation 717, the H-SMF 570 may send a message requesting the establishment of separate delivery to the H-MB-SMF 580. The request message may include an indication requesting establishment of individual delivery, a multicast session ID, and tunnel information for individual delivery of the H-UPF 590. The tunnel information for individual delivery of the H-UPF 590 includes information on an address of the H-UPF 590 and a tunnel ID.

[0158] In operation 718, upon receiving the request message, H-MB-SMF 580 sends the multicast session ID and endpoint information about the separate tunnel of H-UPF 590 to H-MB-UPF 591 in order to establish a tunnel for separate delivery. In operation 719, H-MB-SMF 580 may notify H-SMF 570 of the result of the separate tunnel establishment.

[0159] Therefore, in operation 720, the multicast data traffic received from the content provider or MBSTF is finally transmitted from the H-MB-UPF 591 to the RAN 240 through the H-UPF 590 and the V-UPF 550. In operation 721, the RAN 240 transmits the multicast session traffic received through the separate tunnel to the UE 230 in a point-to-multicast method or a point-to-point method.

[0160] According to an embodiment of the present disclosure, instead of the separate delivery establishment process of operations 715 and 716, the H-SMF 570 can send the tunnel endpoint information of the H-UPF 590 together with the multicast session ID to the MBSF, and the MBSF can send the information to the MBSTF so that the MBSTF can directly send the multicast data traffic to the H-UPF 590.

[0161] According to an embodiment of the present disclosure, instead of requesting a separate delivery establishment process of operations 717 and 718, the H-SMF 570 may send the tunnel endpoint information of the H-UPF 590 together with the multicast session ID to the MBSF through the H-MB-SMF 580, and the MBSF may send the information to the MBSTF so that the MBSTF may directly send the multicast data traffic to the H-UPF 590.

[0162] According to various embodiments of the present disclosure, when the UE 230 receives a multicast service provided by the home network, the V-SMF 530 of the local network may receive a join request message from the UE 230. When the UE 230 makes an erroneous join request through a locally routed PDU session, the V-SMF 530 may send a failure message for the join request to the UE 230 in response to the join request message. According to one embodiment, the failure message may include a failure cause. The failure cause may include DNN information and cause information indicating, for example, "the home PLMN does not support multicast services" or "multicast services are not supported". Upon receiving the failure message, the UE 230 may recognize that the UE 230 has selected a PDU session that does not match the information included in the service announcement message. When the UE 230 selects another home-routed PDU session and makes a join request, or when a suitable home-routed PDU session is not created, the UE 230 may make a join request, thereby creating a home-routed PDU session.

[0163] Figure 8 is a block diagram illustrating a UE in a wireless communication system according to an embodiment of the present disclosure.

[0164] Figure 8 The embodiment of the UE shown is only an example, so Figure 8 The scope of the present disclosure is not limited to any particular implementation of the UE.

[0165] Reference Figure 8 , the UE includes an antenna 805, a radio frequency (RF) transceiver 810, a transmission (TX) processing circuit 815, a microphone 820, and a reception (RX) processing circuit 825. The UE also includes a speaker 830, a processor 840, an input / output (I / O) interface (IF) 845, a touch screen 850, a display 855, and a memory 860. The memory 860 includes an operating system (OS) 861 and one or more applications 862.

[0166] The RF transceiver 810 receives RF signals from a BS in the network via an antenna 805. The RF transceiver 810 down-converts the received RF signals to an intermediate frequency (IF) signal or a baseband signal. The RX processing circuit 825 filters, decodes and / or digitizes the baseband or IF signal received from the RF transceiver 810 to generate a processed baseband signal. The RX processing circuit 825 sends the processed baseband signal to a speaker 830 (e.g., for voice data) or a processor 840 (e.g., for web browsing data) for additional processing.

[0167] The TX processing circuit 815 receives analog or digital voice data from the microphone 820, or receives other output baseband data (such as network data, email, or interactive video game data) from the processor 840. The TX processing circuit 815 encodes, multiplexes, and / or digitizes the output baseband data to generate a baseband or IF signal. The RF transceiver 810 up-converts the processed baseband or IF signal received from the TX processing circuit 815 into an RF signal to be transmitted through the antenna 805.

[0168] The processor 840 may include at least one processor or other processing device, and may execute an OS 861 stored in the memory 860 to provide overall control for the UE. For example, the processor 840 may control the RF transceiver 810, the RX processing circuit 825, and the TX processing circuit 815 to receive DL channel signals and to send UL channel signals according to known principles. In some embodiments, the processor 840 includes at least one microprocessor or microcontroller.

[0169] In various embodiments of the present disclosure, the processor 840 provides overall control for operations related to a method for providing a multicast service in a 5G network system that provides a multicast / broadcast service. That is, the processor 840 controls the overall operations related to the method for providing a multicast service in a 5G network system that provides a multicast / broadcast service, as previously described with reference to Figure 1A , Figure 1B , Figure 2A , Figure 2B , Figure 3 , Figure 4A , Figure 4B , Figure 5A , Figure 5B , Fig. 6A , Figure 6B , Fig. 7A and Figure 7B described.

[0170] The processor 840 can move data into or out of the memory 860 when the ongoing process requires it. In some embodiments, the processor 840 is configured to execute the application 862 based on the OS program 861 or in response to a signal received from the BS or operator. In addition, the processor 840 is coupled to the I / O interface 845, and the I / O interface 845 provides the UE with a connection to other devices such as laptops and handheld computers. The I / O interface 845 is a communication path between these accessories and the processor 840.

[0171] The processor 840 is also coupled to a touch screen 850 and a display 855. An operator of the UE can input data into the UE by using the touch screen 850. The display 855 can be a liquid crystal display (LCD), a light emitting diode (LED) display, or other display capable of presenting text and / or at least limited graphics (e.g., from a website).

[0172] The memory 860 is coupled to the processor 840. A portion of the memory 860 may include random access memory (RAM), and the remainder of the memory 860 may include flash memory or other read-only memory (ROM).

[0173] although Figure 8 An example of a UE is shown, but the Figure 8 Make various modifications. For example, Figure 8 The various components shown may be combined, further divided, or omitted, and other components may be added as needed. In addition, in certain examples, the processor 840 may be divided into one or more central processing units (CPUs) and multiple processors, such as one or more graphics processing units (GPUs). In addition, even if the UE is configured as Figure 8 A UE may be configured to operate as a mobile phone or smartphone, a UE may also be configured to operate as any other type of mobile or fixed device.

[0174] Fig. 9 is a block diagram showing the internal structure of AMF, SMF and UPF according to an embodiment of the present disclosure.

[0175] Reference Fig. 9, AMF, SMF and UPF 900 include a receiver 910, a transmitter 920 and a controller 930. In addition, AMF, SMF and UPF 900 can be implemented to include a communication interface and a processor for communicating with (multiple) other network entities in the core network of the 5G system. In addition, AMF, SMF and UPF 900 can be implemented by including the functions of AMF, SMF and UPF 900 in a server.

[0176] The controller 930 provides overall control to the AMF, SMF and UPF 900, and in particular provides overall control to operations related to multicast. Figure 1A , Figure 1B , Figure 2A , Figure 2B , Figure 3 , Figure 4A , Figure 4B , Figure 5A , Figure 5B , Fig. 6A , Figure 6B , Fig. 7A and Figure 7B AMF, SMF and UPF are controlled in the same manner as described, so a detailed description of the control operation will be omitted in this article.

[0177] The receiver 910 receives various messages, information, etc. under the control of the controller 930 .

[0178] The transmitter 920 transmits various messages, information, etc. under the control of the controller 930.

[0179] Although the receiver 910, the transmitter 920 and the controller 930 are Fig. 9 910, the transmitter 920, and the controller 930 are shown as being configured as separate units, but at least two of the receiver 910, the transmitter 920, and the controller 930 may be integrated into one unit. In addition, the receiver 910, the transmitter 920, and the controller 930 may be implemented as at least one processor.

[0180] While the present disclosure has been shown and described with reference to various embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made without departing from the spirit and scope of the present disclosure as defined by the appended claims and their equivalents.

Claims

1. A method performed by a user equipment UE in a wireless communication system, the method comprising: receiving a service announcement including a public land mobile network PLMN identifier ID; In case there is an existing protocol data unit (PDU) session associated with a multicast / broadcast service (MBS) session, sending a PDU session modification request message including a join request for the MBS session to a network entity; and In the absence of a PDU session established with the data network name DNN and single network slice selection assistance information S-NSSAI for the MBS session, a PDU session establishment request message for the PDU session is sent to the network entity, and the PDU session establishment request message includes the join request.

2. The method according to claim 1, wherein: The service announcement also includes an MBS session ID, the DNN and the S-NSSAI.

3. The method according to claim 1, wherein: The PDU session modification request message or the PDU session establishment request message further includes an MBS session ID.

4. The method according to claim 1, further comprising: A PDU session modification command message is received in response to the PDU session modification request message.

5. The method according to claim 1, in, The network entity is the access management function AMF.

6. The method according to claim 1, wherein: MBS session data is received using point-to-point PTP or point-to-multicast PTM transmission.

7. A user equipment UE in a wireless communication system, the UE comprising: Transceiver; as well as A processor coupled to the transceiver and configured to: receiving a service announcement including a public land mobile network PLMN identifier ID; In case there is an existing protocol data unit (PDU) session associated with a multicast / broadcast service (MBS) session, sending a PDU session modification request message including a join request for the MBS session to a network entity; and In the absence of a PDU session established with the data network name DNN and single network slice selection assistance information S-NSSAI for the MBS session, a PDU session establishment request message for the PDU session is sent to the network entity, wherein the PDU session establishment request message includes the join request.

8. The UE according to claim 7, wherein: The service announcement also includes an MBS session ID, the DNN and the S-NSSAI.

9. The UE according to claim 7, wherein: The PDU session modification request message or the PDU session establishment request message further includes an MBS session ID.

10. The UE according to claim 7, wherein: The processor is further configured to: A PDU session modification command message is received in response to the PDU session modification request message.

11. The UE according to claim 7, in, The network entity is the access management function AMF.

12. The UE according to claim 7, wherein: The MBS session data is received using point-to-point PTP or point-to-multicast PTM transmission.

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