Method and apparatus for IMS multimedia session transition in wireless communication system

Abstract

The present disclosure relates to a 5G or 6G communication system for supporting a higher data transmission rate. Particularly, the present disclosure provides a method and an apparatus for media type transition in an IMS multimedia session in a mobile communication system (or a wireless communication system).

Description

Method and device for switching IMS multimedia sessions in wireless communication systems

[0001] The present invention relates to a method and apparatus for switching an IMS (IP multimedia subsystem) multimedia session in a wireless communication (or mobile communication) system.

[0002] 5G mobile communication technology defines a wide frequency band to enable fast transmission speeds and new services, and can be implemented not only in the sub-6GHz frequency band such as 3.5 gigahertz (3.5GHz), but also in the ultra-high frequency band called millimeter wave (mmWave) such as 28GHz and 39GHz ('Above 6GHz'). In addition, for 6G mobile communication technology, which is called the system after 5G communication (Beyond 5G), implementation in the terahertz band (for example, the 3 terahertz (3THz) band at 95GHz) is being considered to achieve a transmission speed that is 50 times faster than 5G mobile communication technology and an ultra-low latency time that is reduced to one-tenth.

[0003] In the early stages of 5G mobile communication technology, the goal is to support services and satisfy performance requirements for enhanced Mobile Broadband (eMBB), Ultra-Reliable Low-Latency Communications (URLLC), and massive Machine-Type Communications (mMTC). These include beamforming and massive MIMO to mitigate path loss of radio waves in ultra-high frequency bands and increase the transmission distance of radio waves, support for various numerologies (such as operation of multiple subcarrier intervals) and dynamic operation of slot formats for efficient use of ultra-high frequency resources, initial access technology to support multi-beam transmission and wideband, definition and operation of BWP (Bidth Part), new channel coding methods such as LDPC (Low Density Parity Check) codes for large-capacity data transmission and Polar Code for reliable transmission of control information, and L2 pre-processing (L2). Standardization has been made for network slicing, which provides dedicated networks specialized for specific services, and pre-processing.

[0004] Currently, discussions are underway to improve and enhance the initial 5G mobile communication technology in consideration of the services that 5G mobile communication technology was intended to support, and physical layer standardization is in progress for technologies such as V2X (Vehicle-to-Everything) to help autonomous vehicles make driving decisions and increase user convenience based on their own location and status information transmitted by vehicles, NR-U (New Radio Unlicensed) for the purpose of system operation that complies with various regulatory requirements in unlicensed bands, NR terminal low power consumption technology (UE Power Saving), Non-Terrestrial Network (NTN), which is direct terminal-satellite communication to secure coverage in areas where communication with terrestrial networks is impossible, and Positioning.

[0005] In addition, standardization of wireless interface architecture / protocols is in progress for technologies such as intelligent factories (Industrial Internet of Things, IIoT) to support new services through linkage and convergence with other industries, Integrated Access and Backhaul (IAB) that provides nodes for expanding network service areas by integrating wireless backhaul links and access links, Mobility Enhancement technology including Conditional Handover and Dual Active Protocol Stack (DAPS) handover, and 2-step random access (2-step RACH for NR) that simplifies random access procedures. Standardization is also in progress for system architecture / services such as 5G baseline architecture (e.g., Service-based Architecture, Service-based Interface) for grafting Network Functions Virtualization (NFV) and Software-Defined Networking (SDN) technologies, and Mobile Edge Computing (MEC) that provides services based on the location of the terminal.

[0006] Once these 5G mobile communication systems are commercialized, an explosive increase in connected devices will be connected to the communication network, necessitating enhanced functionality and performance of 5G mobile communication systems and integrated operation of these connected devices. To this end, new research will be conducted on improving 5G performance and reducing complexity, supporting AI services, supporting metaverse services, and drone communications by utilizing eXtended Reality (XR), Artificial Intelligence (AI), and Machine Learning (ML) to efficiently support Augmented Reality (AR), Virtual Reality (VR), and Mixed Reality (MR).

[0007] In addition, the development of these 5G mobile communication systems includes new waveforms to ensure coverage in the terahertz band of 6G mobile communication technology, multi-antenna transmission technologies such as Full Dimensional MIMO (FD-MIMO), Array Antenna, and Large Scale Antenna, metamaterial-based lenses and antennas to improve the coverage of terahertz band signals, high-dimensional spatial multiplexing technology using Orbital Angular Momentum (OAM), Reconfigurable Intelligent Surface (RIS) technology, as well as full duplex technology to improve the frequency efficiency and system network of 6G mobile communication technology, satellite, AI (Artificial Intelligence) from the design stage and AI-based communication technology that realizes system optimization by internalizing end-to-end AI support functions, and ultra-high-performance communication and computing resources to provide services with complexity that exceeds the limits of terminal computing capabilities. It can serve as a basis for the development of next-generation distributed computing technologies that can be realized by utilizing them.

[0008] IMS (IP (internet protocol) multimedia subsystem) multimedia call is to check during the call establishment procedure whether the status and conditions of the 5G network are in a state and condition that can provide IMS multimedia call. If the conditions cannot be met, the call is not established, or after the call is established, it is monitored and if the conditions cannot be met, the call is released.

[0009] For IMS-based 3D avatar calls currently being discussed in 3GPP, call quality can be sensitive to network conditions and conditions, such as the data size and data components of 3D avatar media. If 3D avatar calls are interrupted every time these conditions change, users will not be able to use the service reliably.

[0010] Therefore, depending on changes in network status and conditions, it may be necessary to convert a 3D avatar call to a 2D video call, convert a 3D avatar call to an audio call, or re-convert back to a 3D avatar call.

[0011] The present disclosure provides a method and device for switching or changing a media type during an IMS (Internet Protocol (IP) multimedia subsystem) session and a PDU (protocol data unit) session.

[0012] Additionally, the present disclosure provides a quality of service (QoS) measurement method and device necessary for an IMS function and / or a 5G core network function to determine when a media type switch is required and what type of media type to switch to.

[0013] FIG. 1 is a diagram illustrating a 5G system structure related to an embodiment of the present disclosure.

[0014] FIG. 2 is a diagram illustrating an IMS (IP (internet protocol) multimedia subsystem) network structure according to various embodiments of the present disclosure.

[0015] FIG. 3 is a diagram illustrating an example of a network structure including a data channel server in a communication system according to various embodiments of the present disclosure.

[0016] FIG. 4 is a diagram illustrating an example of switching media types of an IMS session in a communication system according to various embodiments of the present disclosure.

[0017] FIG. 5 is a diagram illustrating a mobile origination procedure that supports switching of media types of an IMS session in a communication system according to various embodiments of the present disclosure.

[0018] FIG. 6 is a diagram illustrating a policy control and charging (PCC) related procedure that supports switching of media types of an IMS session in a communication system according to various embodiments of the present disclosure.

[0019] FIG. 7 is a diagram illustrating a procedure related to a session management policy (SM Policy) that supports switching of media types of an IMS session in a communication system according to various embodiments of the present disclosure.

[0020] FIG. 8 is a diagram illustrating a procedure related to an operation of switching a media type of an IMS session in a communication system according to various embodiments of the present disclosure.

[0021] FIG. 9 is a diagram illustrating an example configuration of a network entity in a wireless communication system according to various embodiments of the present disclosure.

[0022] FIG. 10 is a diagram showing an example configuration of a base station in a wireless communication system according to various embodiments of the present disclosure.

[0023] FIG. 11 is a diagram showing an example configuration of a terminal in a wireless communication system according to various embodiments of the present disclosure.

[0024] The operating principle of the present invention will be described in detail with reference to the attached drawings below.

[0025] In describing the embodiments, descriptions of technical details that are well known in the technical field to which the present disclosure pertains and are not directly related to the present disclosure will be omitted. This is to ensure that the gist of the present disclosure is conveyed more clearly without obscuring it by omitting unnecessary explanations.

[0026] For the same reason, some components in the attached drawings are exaggerated, omitted, or schematically depicted. Furthermore, the dimensions of each component do not entirely reflect its actual size. Identical or corresponding components in each drawing are assigned the same reference numbers.

[0027] The advantages and features of the present disclosure, and methods for achieving them, will become clearer with reference to the embodiments described below in detail with the accompanying drawings. However, the present disclosure is not limited to the embodiments disclosed below and may be implemented in various different forms. These embodiments are provided solely to ensure that the present disclosure is complete and to fully inform those skilled in the art of the scope of the invention, and the present disclosure is defined solely by the scope of the claims. Like reference numerals designate like elements throughout the specification.

[0028] At this time, it will be understood that each block of the processing flowchart drawings and combinations of the flowchart drawings can be performed by computer program instructions. These computer program instructions can be installed in a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing equipment, so that the instructions executed by the processor of the computer or other programmable data processing equipment create a means for performing the functions described in the flowchart block(s). These computer program instructions can also be stored in a computer-available or computer-readable memory that can direct a computer or other programmable data processing equipment to implement the functions in a specific manner, so that the instructions stored in the computer-available or computer-readable memory can also produce a manufactured item that includes an instruction means for performing the functions described in the flowchart block(s). Since the computer program instructions may be installed on a computer or other programmable data processing device, a series of operational steps may be performed on the computer or other programmable data processing device to create a computer-executable process, and the instructions that cause the computer or other programmable data processing device to perform the steps for performing the functions described in the flowchart block(s) may also provide steps for performing the functions described in the flowchart block(s).

[0029] Additionally, each block may represent a module, segment, or portion of code that contains one or more executable instructions for performing a specific logical function(s). It should also be noted that in some alternative implementation examples, the functions described in the blocks may occur out of order. For example, two blocks depicted in succession may actually be executed substantially concurrently, or the blocks may sometimes be executed in reverse order, depending on their respective functions.

[0030] Here, the term '~ unit' used in this embodiment means a software or hardware component such as an FPGA or ASIC, and the '~ unit' performs certain roles. However, the '~ unit' is not limited to software or hardware. The '~ unit' may be configured to be on an addressable storage medium and may be configured to regenerate one or more processors. Thus, as an example, the '~ unit' includes components such as software components, object-oriented software components, class components, and task components, processes, functions, attributes, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and variables. The functions provided within the components and '~ units' may be combined into a smaller number of components and '~ units' or further separated into additional components and '~ units'. In addition, the components and '~ units' may be implemented to regenerate one or more CPUs within a device or a secure multimedia card. Additionally, in the embodiment, '~bu' may include one or more processors.

[0031] The terms used in the following description to identify connection nodes, terms referring to network entities, terms referring to messages, terms referring to interfaces between network entities, and terms referring to various identification information are provided as examples for convenience of explanation. Therefore, the present disclosure is not limited to the terms described below, and other terms referring to objects with equivalent technical meanings may be used.

[0032] For convenience of explanation, this disclosure uses terms and names defined in the 3rd Generation Partnership Project Long Term Evolution (3GPP) LTE (3rd Generation Partnership Project Long Term Evolution) standards and the 3GPP 5G standards. However, this disclosure is not limited to these terms and names and can be equally applied to systems conforming to other standards.

[0033] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the attached drawings. At this time, it should be noted that the same components in the attached drawings are represented by the same reference numerals as much as possible. In addition, it should be noted that the attached drawings of the present disclosure are provided to aid in understanding the present disclosure, and the present disclosure is not limited to the forms or arrangements illustrated in the drawings of the present disclosure. In addition, detailed descriptions of well-known functions and configurations that may obscure the gist of the present disclosure will be omitted. It should be noted that in the following description, only the parts necessary for understanding the operation according to various embodiments of the present disclosure will be described, and the description of other parts will be omitted so as not to distract from the gist of the present disclosure. In addition, although the present disclosure describes various embodiments using terminology used in some communication standards (e.g., 3rd Generation Partnership Project (3GPP)), this is merely an example for explanation. The various embodiments of the present disclosure can be easily modified and applied to other communication systems.

[0034] In this disclosure, phrases such as “A / B”, “A and / or B”, “A or B”, “at least one of A and B”, “at least one of A or B”, “A, B, or C”, “at least one of A, B, and C”, and “at least one of A, B, or C” can each include any one of the items listed together in that phrase, or all possible combinations thereof. Terms such as “first”, “second”, or “first” or “second” may be used simply to distinguish the corresponding component from other corresponding components and do not limit the corresponding components in any other respect (e.g., importance or order).

[0035] Meanwhile, efforts are being made to develop improved 5G or pre-5G communication systems to meet the increasing demand for wireless data traffic following the commercialization of 4G communication systems. For this reason, 5G or pre-5G communication systems are also referred to as "Beyond 4G Network" or "Post-LTE" systems. The 5G communication system specified by 3GPP is called the New Radio (NR) system.

[0036] To achieve high data rates, 5G communication systems are being considered for implementation in ultra-high frequency (mmWave) bands (e.g., the 60 GHz band). To mitigate radio path loss and increase the transmission range of radio waves in ultra-high frequency bands, beamforming, massive MIMO (massive MIMO), full-dimensional MIMO (FD-MIMO), array antennas, analog beamforming, and large-scale antenna technologies have been discussed and applied to NR systems in 5G communication systems.

[0037] Additionally, to improve the network of the system, technologies such as evolved small cells, advanced small cells, cloud radio access networks (cloud RAN), ultra-dense networks, device-to-device communication (D2D), wireless backhaul, moving networks, cooperative communication, CoMP (Coordinated Multi-Points), and interference cancellation are being developed in 5G communication systems.

[0038] In addition, advanced coding modulation (ACM) methods such as FQAM (Hybrid FSK and QAM Modulation) and SWSC (Sliding Window Superposition Coding), as well as advanced access technologies such as FBMC (Filter Bank Multi Carrier), NOMA (non-orthogonal multiple access), and SCMA (sparse code multiple access) are being developed in 5G systems.

[0039] Meanwhile, the Internet is evolving from a human-centric network where humans create and consume information to an Internet of Things (IoT) network where information is exchanged and processed between distributed components, such as objects. The Internet of Everything (IoE) is also emerging, combining IoT technologies with big data processing technologies, such as those connected to cloud servers. To implement the IoT, technological elements such as sensing technologies, wireless and wired communication and network infrastructure, service interface technologies, and security technologies are required. Recently, research is being conducted on technologies such as sensor networks, Machine-to-Machine (M2M), and Machine-Type Communication (MTC) for connecting objects. In the IoT environment, intelligent IT (Internet Technology) services can be provided that collect and analyze data generated from connected objects to create new value for human life. IoT can be applied to areas such as smart homes, smart buildings, smart cities, smart or connected cars, smart grids, healthcare, smart appliances, and advanced medical services through the convergence and integration of existing IT (Information Technology) technologies with various industries.

[0040] Accordingly, various attempts are being made to apply 5G communication systems to IoT networks. For example, 5G communication such as sensor networks, machine-to-machine (M2M), and machine-type communication (MTC) are being implemented using techniques such as beamforming, MIMO, and array antennas. The application of cloud radio access networks (cloud RAN), a big data processing technology described above, can also be considered an example of the convergence of 5G and IoT technologies.

[0041] FIG. 1 is a diagram illustrating a 5G system structure related to an embodiment of the present disclosure.

[0042] Referring to FIG. 1, the 5G system architecture may include various components (i.e., network functions (NFs)) and may also be referred to as network nodes. FIG. 1 illustrates some of them, including an authentication server function (AUSF) device (110), an access and mobility management function (AMF) device (103), a session management function (SMF) device (104), a policy control function (PCF) device (107), an application function (AF) device (108), a unified data management (UDM) device (106), a data network (DN) (112), a user plane function (UPF) device (105), a (radio) access network (R)AN) (102), and a terminal, i.e., a user equipment (UE) (101). In addition, in FIG. 1, a Network Slice Selection Function (NSSF) device (109) and a Network Slice Specific Authentication and Authorization Function (NSSAAF) device (111) are exemplarily illustrated.

[0043] Each of the devices illustrated in FIG. 1 may be implemented as a single server or device, or as a network slice instance. When implemented as a network slice instance, two or more identical or different network slice instances may be implemented within a single server or device, or a single network slice instance may be implemented across two or more servers or devices.

[0044] Each NF can support the following functions:

[0045] AUSF (110) can process and store data for UE authentication.

[0046] AMF (103) can provide functions for access and mobility management per UE, and one UE can be connected to one AMF by default. Specifically, the AMF (103) provides signaling between core network (CN) nodes for mobility between 3GPP access networks, termination of a radio access network (RAN) CP interface (e.g., N2 interface), termination of NAS signaling (N1), NAS signaling security (NAS ciphering and integrity protection), AS security control, registration management (registration area management), connection management, idle mode UE reachability (including, for example, control and performance of paging retransmission), mobility management control (subscription and policy), intra-system mobility and inter-system mobility support, support for network slicing, SMF selection, lawful intercept (e.g., for AMF events and interfaces to the LI system), provision of forwarding of session management (SM) messages between UE and SMF, transparent proxy for SM message routing, access authentication, It may support functions such as access authorization including roaming permission check, provision of SMS message delivery between UE and Short Message Service Function (SMSF), security anchor function (SAF) and / or security context management (SCM).Some or all of these AMF (103) functions may be supported within a single AMF instance operating as one AMF.

[0047] DN (112) may mean, for example, an operator service, Internet access, or a third-party service. DN (112) may transmit a downlink protocol data unit (PDU) to UPF (105) or receive a PDU transmitted from UE (101) through UPF (105).

[0048] PCF (107) can receive information about packet flow from an application server and provide a function to determine policies such as mobility management and session management. Specifically, PCF (107) can support functions such as supporting a unified policy framework for controlling network operations, providing policy rules so that control plane functions (e.g., AMF, SMF, etc.) can enforce the policy rules, and implementing a front end for accessing related subscription information for policy determination within a user data repository (UDR).

[0049] The SMF (104) provides session management functions, and when a UE has multiple sessions, each session can be managed by a different SMF. Specifically, the SMF (104) can support functions such as session management (e.g., session establishment, modification, and termination, including tunnel maintenance between the UPF and the AN node), UE IP address allocation and management (optionally including authentication), selection and control of UP functions, traffic steering configuration for routing traffic from the UPF to the appropriate destination, termination of interfaces toward policy control functions, enforcement of the control portion of policies and QoS (quality of service), lawful intercept (for SM events and interfaces to the LI system), termination of the SM portion of NAS messages, downlink data notification, initiator of AN-specific SM information (delivered to the AN through N2 via the AMF), determination of the SSC mode of the session, and roaming functions. As described above, some or all of the functions of SMF (104) may be supported within a single SMF instance operating as a single SMF.

[0050] The UDM (106) can store user subscription data, policy data, etc. The UDM (106) can include two parts, namely, an application front end (FE) (not shown) and a user data repository (UDR) (not shown).

[0051] The FE may include a UDM FE, which is responsible for location management, subscription management, and credential processing, and a PCF-FE, which is responsible for policy control. The UDR may store data required for the functions provided by the UDM-FE and policy profiles required by the PCF. Data stored in the UDR may include user subscription data and policy data, including subscription identifiers, security credentials, access and mobility-related subscription data, and session-related subscription data. The UDM-FE may access subscription information stored in the UDR and support functions such as authentication credential processing, user identification handling, access authentication, registration / mobility management, subscription management, and SMS management.

[0052] UPF (105) can transmit a downlink PDU received from DN (112) to UE (101) via (R)AN (102), and can transmit an uplink PDU received from UE (101) via (R)AN (102) to DN (112). Specifically, the UPF (105) may support an anchor point for intra / inter RAT mobility, an external PDU session point for interconnection to a Data Network, a user plane portion of packet routing and forwarding, packet inspection and policy rule enforcement, an uplink classifier to support lawful intercept, traffic usage reporting, routing of traffic flows to the Data Network, a branching point to support multi-homed PDU sessions, QoS handling for the user plane (e.g., packet filtering, gating, uplink / downlink rate enforcement), uplink traffic validation (service data flow (SDF) mapping between SDFs and QoS flows), transport level packet marking in uplink and downlink, downlink packet buffering and downlink data notification triggering functions, etc. Some or all of these functions of UPF (105) may be supported within a single UPF instance operating as a single UPF.

[0053] The AF (108) can interact with the 3GPP core network to provide services (e.g., support functions such as application impact on traffic routing, access to network capability exposure, and interaction with policy frameworks for policy control).

[0054] (R)AN(102) may be a general term for a new radio access network that supports both evolved E-UTRA, an evolved version of 4G radio access technology, and new radio (NR) (e.g., gNB).

[0055] The gNB provides functions for radio resource management (i.e., radio bearer control, radio admission control, connection mobility control, dynamic allocation of resources to the UE in uplink / downlink (i.e., scheduling), IP (internet protocol) header compression, encryption and integrity protection of user data streams, selection of an AMF (103) upon attachment of the UE (101) if routing to the AMF (103) is not determined from information provided to the UE (101), routing of user plane data to the UPF (105)(s), routing of control plane information to the AMF (103), connection setup and teardown, scheduling and transmission of paging messages (originating from the AMF), scheduling and transmission of system broadcast information (originating from the AMF or operating and maintenance (O&M)), measurement and measurement reporting configuration for mobility and scheduling, It can support functions such as transport level packet marking in uplink, session management, support for network slicing, QoS flow management and mapping to data radio bearers, support for UEs in inactive mode, NAS message distribution, NAS node selection, radio access network sharing, dual connectivity, and tight interworking between NR and E-UTRA.

[0056] UE (101) may refer to a user equipment. The user equipment may be referred to by terms such as terminal, mobile equipment (ME), or mobile station (MS). Furthermore, the user equipment may be a portable device such as a laptop, mobile phone, personal digital assistant (PDA), smartphone, or multimedia device, or may be a non-portable device such as a personal computer (PC) or vehicle-mounted device. Hereinafter, the user equipment (UE) or terminal will be referred to as such.

[0057] For clarity of explanation, the network exposure function (NEF) device and the NF repository function (NRF) device are not illustrated in FIG. 1, but all NFs illustrated in FIGS. 2 to 5 described below can interact with the NEF and NRF as needed.

[0058] Let's take a look at NRF. NRF (not shown in Figure 1) can support service discovery functionality. When receiving a second NF discovery request from a first NF instance, it can perform a second NF discovery operation and provide information about the discovered second NF instance to the first NF instance. It can also maintain a list of available NF instances and the services they support.

[0059] Meanwhile, for convenience of explanation, FIG. 1 illustrates a reference model for a case where a UE accesses one DN using one PDU session, but the present disclosure is not limited thereto.

[0060] A UE (101) can access two (i.e., local and central) data networks simultaneously using multiple PDU sessions. In this case, two SMFs can be selected for different PDU sessions. However, each SMF can have the ability to control both the local UPF and the central UPF within the PDU session.

[0061] Additionally, the UE (101) may simultaneously access two (i.e., local and central) data networks provided within a single PDU session.

[0062] The control plane components of 5GC can be considered as virtualized network functions (VNFs), and communication between these VNFs can be considered as RESTful-based API exchange, where one VNF provides services to other VNFs. This API-based communication interface between VNFs is called a Service Based Interface (SBI).

[0063] In the 3GPP system, a conceptual link connecting NFs within a 5G system is defined as a reference point. The following illustrates the reference points included in the 5G system architecture depicted in Figure 1. The 5G system architecture may define more reference points than those described below.

[0064] - N1: Reference point between UE and AMF

[0065] - N2: Reference point between (R)AN and AMF

[0066] - N3: Reference point between (R)AN and UPF

[0067] - N4: Reference point between SMF and UPF

[0068] - N5: Reference point between PCF and AF

[0069] - N6: Reference point between UPF and data network

[0070] - N7: Reference point between SMF and PCF

[0071] - N8: Reference point between UDM and AMF

[0072] - N9: Reference point between two core UPFs

[0073] - N10: Reference point between UDM and SMF

[0074] - N11: Reference point between AMF and SMF

[0075] - N12: Reference point between AMF and AUSF

[0076] - N13: Reference point between UDM and authentication server function (AUSF)

[0077] - N14: Reference point between two AMFs

[0078] - N15: Reference point between PCF and AMF for non-roaming scenarios, reference point between PCF and AMF in visited network for roaming scenarios.

[0079] In the following description, the term "terminal" may refer to UE (101), and the terms "UE" and "terminal" may be used interchangeably. In this case, unless specifically defined additionally, the term "terminal" should be understood as "UE (101).

[0080] A terminal establishes a session by connecting to a data network (e.g., a network providing Internet services) through a 5G system, and can distinguish each data network using an identifier called a Data Network Name (DNN). The DNN can be used to determine NFs, inter-NF interfaces, and operator policies related to the user plane when the terminal connects to a network system and a session. The DNN can be used, for example, to select SMFs and UPF(s) for a PDU session, and to select interface(s) (e.g., N6 interface) between a data network and UPF for a PDU session. In addition, the DNN can be used to determine a mobile communication operator's policy to be applied to a PDU session.

[0081] FIG. 2 is a diagram illustrating an IMS (IP (internet protocol) multimedia subsystem) network structure according to various embodiments of the present disclosure.

[0082] Referring to FIG. 2, a UE (User Equipment) (101) can communicate with other UEs (not shown) located in a remote IMS network (260) and IM CN subsystem components through an IM CN (IP Multimedia Core Network) subsystem. The IM CN subsystem can include a P-CSCF (210), an I / S-CSCF (220), an IMS AS (230), an (IMS) HSS (240), an IMS AGW (250), and / or an MRF (270), and the components can perform the following functions.

[0083] - P-CSCF (Proxy Call Session Control Function)(210): P-CSCF can perform the function of the first contact point for UE to access IMS.

[0084] - I / S-CSCF (Interrogating / Serving CSCF)(220): The I-CSCF can perform the function of a contact point for subscribers of a network operator or roaming users currently located in the service area of ​​the network operator. The S-CSCF can handle the actual user session state of the network.

[0085] - IMS AS (Application Server) (230): The IMS AS can provide and execute IM (Internet Multimedia) value-added services. Additionally, the IMS AS can influence SIP (Session Initiation Protocol) sessions by acting on behalf of services supported by the operator network.

[0086] - (IMS) HSS (Home Subscriber Server)(240): IMS HSS can act as a database that stores information about users.

[0087] - IMS-AGW (Access Gateway)(250): IMS-AGW is located in the media transmission path and can manage network addresses associated with inbound and outbound media streams.

[0088] - MRF (Media Resource Function)(270): MRF can perform various processing tasks related to media streams. MRF can be divided into MRFC (Multimedia Resource Function Controller), which is in charge of control, and MRFP (Multimedia Resource Function Processor), which is in charge of media processing.

[0089] Referring to FIG. 2, the interfaces between the above components can be expressed by the following reference points.

[0090] - Gm: Reference point Gm can support communication between the UE and the IM CN subsystem. For example, the UE can request network registration and session control through the Gm reference point. SIP, described below, can be used for the Gm reference point.

[0091] - Mw: Reference point Mw can support the exchange and transmission of signaling messages between CSCFs.

[0092] - ISC: Reference Point ISC can support the exchange of information required for services provided by the service platform (e.g., IMS AS) between the S-CSCF and the service platform.

[0093] - Sh: Reference point Sh can support the exchange of information required for the service provided by the service platform between the HSS and the service platform (e.g., IMS AS).

[0094] - Cx: Reference point Cx can support information transfer between HSS and CSCF.

[0095] - Mr' / Cr: Reference point Mr' can support interaction for session control between IMS AS and MRFC, and reference point Cr can support interaction for media control between IMS AS and MRFC.

[0096] - Iq: Reference point Iq can support the exchange of information required for allocation and release of transport addresses between P-CSCF and IMS AGW.

[0097] - Mb: Reference point Mb can support IMS media transfer between IMS components.

[0098] Referring to Fig. 2, a P-CSCF (210) supporting a Service Based Interface (SBI) can communicate with a Policy Control Function (PCF) (107). The interface between the P-CSCF (210) and the PCF (107) can be represented by reference point N5. The PCF (107) can support policy establishment and distribution for managing network operations, and the P-CSCF (210) supporting the SBI can be considered as an application function (AF: Application Function) that uses the service that the PCF (107) provides to other VNFs.

[0099] An HSS (240) supporting SBI can communicate with an I / S-CSCF (220) supporting SBI via reference point N70, and can communicate with an IMS AS (230) supporting SBI via reference point N71. Similarly, the I / S-CSCF (220) supporting SBI and the IMS AS (230) supporting SBI can be regarded as AFs that use services provided by the HSS (240) supporting SBI, and the functions provided by the reference points N70 and N71 can be equivalent to the functions provided by reference points Cx and Sh, respectively.

[0100] The above SIP may be an application layer signaling protocol that specifies the procedures for intelligent terminals wishing to communicate on the Internet to identify each other, locate each other, and create, delete, or modify multimedia communication sessions between them. SIP is a request / response structure that controls the creation, modification, and termination of multimedia service sessions such as Internet-based conferences, telephones, voice mail, event notifications, and instant messaging. It can be used on both TCP and UDP, and by using SIP URLs, similar to email addresses, to distinguish each user, services can be provided regardless of IP address. SIP is text-based and was developed using many parts of HTTP and SMTP, making it easy to implement, and it can be combined with many other protocols used on the Internet to create various services, providing flexibility and extensibility. SIP is a simpler protocol corresponding to ITU-T's H.323. It was proposed as RFC 2543 by the IETF MMUSIC (Multiparty Multimedia Session Control) Working Group in 1999, and later revised by the separate ITEF SIP Working Group, and the RFC3261 standard was established in July 2002.

[0101] In order to provide a service (e.g., a real-time interaction service) in a communication system according to various embodiments of the present disclosure, there must be an agreement on the media session that constitutes the service between user UEs participating in the service. The communication system according to various embodiments of the present disclosure can perform an agreement on the media session through Session Description Protocol (SDP) negotiation to provide the service (e.g., a real-time interaction service).

[0102] The above SDP may be included in a SIP message. The SDP may be an ASCII-based protocol for describing a multimedia session and related scheduling information. The SDP may convey information about the media stream of the multimedia session so that the session can be joined. The multimedia session may be defined as a set of media streams for a duration, and the duration of the session may not necessarily be continuous. A multicast-based session on the Internet may basically have two purposes: a means of notifying the existence and duration of the session and a means of conveying session joining information. In a unicast environment, the latter may be the purpose. The SDP information may include the session name and purpose, session duration, session configuration media, media reception information, etc.

[0103] Below, various embodiments of the present disclosure are described assuming that the service provided in the communication system is a real-time interaction service, but are not limited thereto.

[0104] FIG. 3 is a diagram illustrating an example of a network structure including a data channel server in a communication system according to various embodiments of the present disclosure.

[0105] In a communication system according to various embodiments of the present disclosure, a web application for providing a service (e.g., a real-time interaction service) may be provided by a data channel application server (DCAS). The data channel application server may be located in an IMS operator network or a third-party network. In the present disclosure, the web application provided by the data channel application server may be referred to as a data channel application (DCA). A terminal participating in a service (e.g., a real-time interaction service) provided by the data channel application may exchange data required by the service directly or through an intermediate node with another terminal participating in the same service using a data channel (DC), and may communicate with the data channel application server using a bootstrap data channel (BDC).

[0106] Referring to (a) of FIG. 3, a communication system may include a UE (101) and an IM CN subsystem. The UE (101) may communicate with other UEs located in a remote IMS network (260) and components of the IM CN subsystem via the IM CN subsystem. The IM CN subsystem may include a P-CSCF (210), an I / S-CSCF (220), an IMS AS (230), an IMS HSS (240), an IMS AGW (250), a Data Channel Signaling Function (DCSF) (310), a Data Channel Media Function (DCMF) (320), an NEF (330), a Data Channel Application Server (340), and / or a Data Channel Application Repository (DCAR) (350).

[0107] The above data channel signaling function (310) can perform the following functions:

[0108] - Management and control of data channels, including bootstrap data channels.

[0109] - Data channel management and event generation / reception through communication with IMS AS

[0110] - Management and distribution control of data channel applications

[0111] - Communication with 5G network functions (NF) for providing data channel application services.

[0112] - Proxy role for resource distribution of data channel application server (340)

[0113] The above data application storage (350) can store and manage data channel applications and can be located inside or outside the data channel server (340).

[0114] Referring to (a) and (b) of FIG. 3, the data channel media function (320) and MRF (270) can perform the following functions:

[0115] - Management and control of media resources to be transmitted over data channels, including bootstrap data channels.

[0116] - Acts as a proxy for data exchange with the endpoint of the data channel connected to the terminal and other endpoints.

[0117] The above data channel media function (320) and MRF (270) can provide equivalent functions with different interfaces, and the operator can include only one of the data channel media function (320) and the MRF (270) in the data channel server (340), or both, in consideration of compatibility with other network equipment and user terminals.

[0118] FIG. 4 is a diagram illustrating an example of switching media types of an IMS session in a communication system according to various embodiments of the present disclosure.

[0119] Referring to FIG. 4, User#1 and User#2 can use multimedia services by establishing an IMS MMTel (Multi Media Telephony) session via IMS and 5GC. For example, the UE of User#1 and the UE of User#2 can perform avatar communication by establishing an IMS session for transmitting and / or receiving avatar media data. The IMS MMTel session can change the type of media data to be transmitted and / or received depending on changes in network conditions, user selection, and the status of the user device (e.g., UE). For example, if a change occurs in the network environment during the use of the IMS session for transmitting and / or receiving avatar media data established between the UE of User#1 and the UE of User#2, and a state occurs in which network resources suitable for transmitting and / or receiving video media data are allowed rather than for transmitting and / or receiving avatar media data, the IMS and 5GC can change to an IMS session for transmitting and / or receiving video media data. In other words, the media type of an IMS session can be changed / converted from avatar to video. While Figure 4 illustrates the transition between avatar and video media types, this is not a limitation. For example, at least one of avatar, video, audio, or text can be included in the media type of an IMS session.

[0120] FIG. 5 is a diagram illustrating a mobile origination procedure that supports switching of media types of an IMS session in a communication system according to various embodiments of the present disclosure.

[0121] Referring to FIG. 5, a terminal can establish an IMS session that supports switching of media types through the following procedure.

[0122] 1. The UE can determine whether it can perform media type switching during an IMS session (UE capability) based on user interaction, media processing capability of the UE, network request, and / or UE status.

[0123] 2. The UE may send a SIP INVITE request including an SDP Offer to the P-CSCF. The P-CSCF may be determined by a CSCF discovery mechanism. The SDP Offer may represent one or more media for a multimedia session. For example, it may include audio, video, and / or media that can be switched during the session. Examples of media that can be switched during the session may include audio, video, text, and avatar media. The SDP Offer may include at least one of audio, video, and / or media that can be switched during the session (e.g., avatar), and an indication of UE support for media type transition. If the UE determines in step 1 that it can perform media type switching during the IMS session based on user interaction, media processing capability of the UE, network request, and / or UE status, it may include the indication of UE support for media type transition in the SDP Offer.

[0124] 3. The P-CSCF can forward the SIP INVITE request of step 2 to the next hop CSCF. The P-CSCF may remember the next hop CSCF for the UE. For example, the P-CSCF may remember the next hop CSCF through the registration procedure. The next hop CSCF may be the S-CSCF or the S-CSCF responsible for the visiting UE.

[0125] 4. The S-CSCF (or I-CSCF) can perform service control. This service control may include authorizing the requested SDP based on the subscriber information of the user associated with the multimedia service. The multimedia service may include a service that supports switching media types during an IMS session.

[0126] 4a. The S-CSCF can determine whether it can perform media type switching during an IMS session (network capability) based on user or terminal requests, network conditions, and / or application requests. The S-CSCF can perform at least one of the following actions:

[0127] - If the S-CSCF receives an indication of UE support of media type transition in step 3, it can determine the network capability.

[0128] - Even if the S-CSCF does not receive an indication of UE support for media type transition in step 3, the S-CSCF can determine the network capability. For example, if the SDP Offer in step 3 includes media that can be switched during the session (e.g., an avatar), the S-CSCF can determine the network capability even if the UE does not receive the indication.

[0129] - If the S-CSCF does not receive an indication of UE support of media type transition in step 3, but receives information on whether the called terminal and / or the called network supports media type transition in step 6, the S-CSCF may perform the operation corresponding to step 4a after step 6.

[0130] 5. The S-CSCF may forward the SIP INVITE request of step 3 to the destination network. The S-CSCF may perform at least one of the following actions:

[0131] - If the S-CSCF determines in step 4a that the network cannot perform media type transition during the IMS session based on the request of the user or terminal, the network status, and / or the request of the application, it may forward the SIP INVITE request message excluding the UE Support of media type transition indicator from the SIP INVITE request content in step 3 to the called party.

[0132] - Even if the S-CSCF determines in step 4a that the network cannot perform media type transition during the IMS session based on the user or terminal request, network status, and / or application request, the S-CSCF may forward a SIP INVITE request message to the called party that includes at least one of audio, video, and / or media that can be switched during the session (e.g., avatar), and an indication of UE support for media type transition.

[0133] 6. The terminating network may provide a response to the Offer. The response may include media stream capabilities of the destination. For example, the response may include whether the destination has media stream capabilities for audio, video, and media that can be switched during the session (e.g., avatars). The response may include an indication of at least one of: whether the terminating UE can perform media type switching during the IMS session based on user interaction, media processing capabilities of the terminal, network requests, and / or terminal status (UE capability); and whether the terminating network can perform media type switching during the IMS session based on user or terminal requests, network status, and / or application requests (network capability).

[0134] 7. S-CSCF can forward the Offer response to P-CSCF.

[0135] 8. The P-CSCF may perform QoS resource authorization. This QoS resource authorization may include instructing the PCRF or PCF to grant resources required for the current session. The P-CSCF may request the PCRF or PCF to report at least one of the following:

[0136] - When the QoS targets for the media streams that make up the current session (e.g., media streams for audio, video, and media that can be switched during the session (e.g., avatars)) cannot be met on the current network (or become able to be met again).

[0137] - Whether the media type of the current session needs to be switched

[0138] - Information about which media type the current session will be converted to (for example, if the current session's media type is 'avatar' and you want to convert it to 'video', you can report 'video')

[0139] 9. The P-CSCF can deliver to the UE an Offer Response based on the Offer Response of step 6 and the response of the PCF of step 8.

[0140] 10. The UE can decide on the set of media streams proposed for the current session and can confirm receipt of the Offer response. The UE can send a Response Confirmation to the P-CSCF. The Response Confirmation message can be an SDP that is identical to the SDP received in step 9 or a part thereof. If the SDP included in the Response Confirmation defines new media (i.e., proposes a media stream different from the media stream included in the SDP of the Offer response received in step 9), the procedure corresponding to step 8 can be performed, which can be performed after step 15.

[0141] 11. Resource reservations required for IP-CAN sessions can be performed.

[0142] 12. P-CSCF may forward the above response confirmation to S-CSCF.

[0143] 13. S-CSCF may forward the above response confirmation to the destination network.

[0144] 14. The receiving network may send an Acknowledgement for receipt of the above response confirmation.

[0145] 15. The S-CSCF may transmit an Acknowledgement of receipt of the above response confirmation to the P-CSCF.

[0146] 16. The P-CSCF may transmit an Acknowledgement to the UE regarding the receipt of the above response confirmation.

[0147] 17. When IP-CAN resource reservation is completed, the UE can send a Resource Reservation message or a Reservation Confirmation message containing a success result.

[0148] 18. The P-CSCF may forward the above resource reservation or reservation confirmation message to the S-CSCF.

[0149] 19. The S-CSCF may forward the above resource reservation or reservation confirmation message to the destination network.

[0150] 20. When IP-CAN resource reservation for a UE in the destination network is completed, the destination network UE can send a resource reservation or reservation confirmation message with a success result.

[0151] 21. The S-CSCF may forward a resource reservation or reservation confirmation message received from the destination network to the P-CSCF.

[0152] 22. The P-CSCF may forward the resource reservation or reservation confirmation message received from the destination network to the UE.

[0153] 23. The called UE can generate a ringing signal (a call connection tone is generated at the called terminal) and transmit it to the S-CSCF.

[0154] 24. The S-CSCF can transmit the above ringing signal to the P-CSCF.

[0155] 25. The P-CSCF can transmit the above ringing signal to the UE.

[0156] 26. The UE may notify the calling user that a call connection tone is ringing on the called user's terminal.

[0157] 27. When the called user receives the call, a SIP 200-OK message may be delivered.

[0158] 28. S-CSCF can forward the above SIP 200-OK message to P-CSCF.

[0159] 29. The P-CSCF may indicate to enable authorized media flows for the current session. Authorized media flows may include at least one of audio, video, or media that can be switched during the session (e.g., avatars).

[0160] 30. P-CSCF can forward the above SIP 200-OK message to the UE.

[0161] 31. The UE may initiate a media flow for the current session. The media flow for the current session may include at least one of audio, video, and media that can be switched during the session (e.g., an avatar).

[0162] 32. The UE can provide an Acknowledgement for the SIP 200-OK message to the P-CSCF.

[0163] 33. The P-CSCF may forward an Acknowledgement for the SIP 200-OK message responded by the UE to the S-CSCF.

[0164] 34. The S-CSCF may provide an Acknowledgement to the called UE for the SIP 200-OK message responded to by the UE.

[0165] Of course, the above-described procedures are not limited. At least one of the above-described procedures may be omitted. Alternatively, some of the above-described procedures may be combined, and new procedures may be added and organically combined with the above-described procedures.

[0166] FIG. 6 is a diagram illustrating a policy control and charging (PCC) related procedure that supports switching of media types of an IMS session in a communication system according to various embodiments of the present disclosure.

[0167] Descriptions of content overlapping with that in Figure 5 may be omitted. Figure 6 may be described primarily with reference to the procedures related to signaling interactions between the P-CSCF and PCRF / PCF described in Step 8 of Figure 5. However, the names of the messages used may vary.

[0168] Referring to FIG. 6, the terminal and the network can perform a PCC procedure that supports switching of media types through the following procedure.

[0169] 1. The UE can determine whether it can perform media type switching during an IMS session (UE capability) based on user interaction, media processing capability of the UE, network request, and / or UE status.

[0170] 2. The UE may send a SIP INVITE request including an SDP Offer to the P-CSCF. The P-CSCF may be determined by a CSCF discovery mechanism. The SDP Offer may represent one or more media for a multimedia session. For example, it may include audio, video, and / or media that can be switched during the session. Examples of media that can be switched during the session may include audio, video, text, and avatar media. The SDP Offer may include at least one of audio, video, and / or media that can be switched during the session (e.g., avatar), and an indication of UE support for media type transition. If the UE determines in step 1 that it can perform media type switching during the IMS session based on user interaction, media processing capability of the UE, network request, and / or UE status, it may include the indication of UE support for media type transition in the SDP Offer.

[0171] 3. The P-CSCF can identify connection information required for downlink. The connection information may include the IP address and port number(s) of the downlink IP flow(s).

[0172] 4. The P-CSCF can forward the SIP INVITE request of step 2 to the called party. This may include the actions of steps 3, 4, and 4a of FIG. 5.

[0173] 5. The P-CSCF may receive negotiated SDP parameters from the called party via SIP signaling interaction. The negotiated SDP parameters may include at least one of an indication of whether the IMS session can perform media type switching based on user interaction of the called UE, media processing capability of the terminal, network request, and / or terminal status (UE capability), or whether the IMS session can perform media type switching based on user or terminal request, network status, and / or application request of the called network (network capability). The operations of steps 6 and 7 of FIG. 5 may be included.

[0174] 6. The P-CSCF can identify connection information required for uplink. The connection information may include the IP address and port number(s) of uplink IP flow(s).

[0175] 7. The P-CSCF may request resources required for the current application session from the PCF. The Npcf_PolicyAuthorization_Create request message may be used to request resources required for the current application session. The P-CSCF may provide the PCF with session-related information required for session resource authorization. This information may include at least one of the following:

[0176] QoS Reference parameters or individual QoS parameters for the media streams that make up the current session (e.g., media streams for audio, video, and media that can be switched during the session (e.g., avatars)).

[0177] QoS parameter(s) that require measurement for the media streams that make up the current session (e.g., media streams for audio, video, and media that can be switched during the session (e.g., avatars)), and / or QoS Monitoring information that describes the QoS parameter(s).

[0178] Events that the P-CSCF would like to request a report from the PCF:

[0179] -- When the QoS targets for the media streams that make up the current session (e.g., audio, video, and media streams for switchable media (e.g., avatars) during the session) become unmet on the current network (or become met again).

[0180] -- Information about the above QoS Monitoring information and / or QoS Monitoring results

[0181] -- Whether to deactivate the service data flow corresponding to the media streams that make up the current session (e.g., media streams for audio, video, and media that can be switched during the session (e.g., avatars)).

[0182] -- The state of the signaling path corresponding to the media streams that make up the current session (e.g., audio, video, and media streams for media that can be switched during the session, such as avatars).

[0183] -- Whether the media type of the current session needs to be switched

[0184] -- Information about which media type the current session's media type should be converted to (for example, if the current session's media type is 'avatar' and you want to convert it to 'video', you can report 'video')

[0185] 8. PCF can store the application session-related information received in step 7, and can identify and bind the PDU session associated with the IMS session that will perform the media type conversion. PCF can create a resource for the application session received in step 7 and store the related information.

[0186] 9. PCF can respond by notifying P-CSCF that a resource has been created for the requested application. The Npcf_PolicyAuthorization_Create response message can be used.

[0187] 10. The P-CSCF can deliver to the UE an SDP answer based on the SDP Response of step 5 and the response of the PCF of step 9.

[0188] 11. The PCF can determine the PCC rule based on the information received in step 7 and the request of the AF (P-CSCF). The determined PCC rule can be delivered to the SMF through the SM Policy Association Establishment and / or SM Policy Association Modification procedures. The SMF that receives the PCC rule can create a rule for the UPF (e.g., a QoS Monitoring rule) and deliver and apply it to the UPF. As a more specific example, the PCF can provide the SMF with a QoS Monitoring policy that sets a QoS parameter appropriate for each media type (e.g., video, audio, text, avatar, etc.) that constitutes the current session as a threshold in order to determine whether the media type of the current session needs to be converted and / or information on which media type the media type of the current session will be converted to (e.g., if the media type of the current session is 'avatar' and you want to convert it to 'video', 'video'). The SMF can provide and apply the corresponding QoS Monitoring policy to the UPF. The UPF can measure the QoS status according to the QoS Monitoring policy and provide it to the SMF.

[0189] 12. The PCF can detect that the media type of the PDU session needs to be switched. As a more specific example based on the example described in step 11 above, if there is a media type that exceeds the QoS parameter threshold included in the QoS Monitoring policy, the SMF can report the media type exceeding the QoS parameter threshold to the PCF in step 12. The PCF can consider the media type exceeding the threshold reported by the SMF and the media type of the current session, and if the media type suitable for the current session is different from the media type of the current session, it can determine that the media type of the PDU session needs to be switched in step 12. For example, after step 11, when the IMS session and PDU session establishment procedures are completed and an avatar media-based call session is established between the calling UE and the called UE, if the SMF performs QoS Monitoring via the UPF and the measured PDB (Packet Delay Budget, delay budget between the UE and the UPF) value exceeds the PDB threshold for the avatar media type, the SMF can report information related to the measured PDB value to the PCF. If the PCF determines, based on the information received from the SMF, that the network condition cannot satisfy the PDB value for the avatar media type but can satisfy the PDB value for the video media type, the PCF can determine that the call session established between the calling UE and the called UE needs to be switched from avatar media-based to video media-based.

[0190] 13. If the PCF detects that an event corresponding to the content requested by the P-CSCF (AF) in step 7 has occurred, the PCF may report the information requested by the P-CSCF (AF). In addition, if the PCF detects that a media type conversion of the PDU session is required in step 12 and is requested to report a media type conversion requirement in step 7, the PCF may report to the P-CSCF (AF) that a media type conversion is required. The Npcf_PolicyAuthorization_Notify request message may be used to report that a media type conversion is required.

[0191] 14. The P-CSCF (AF) may respond to the PCF regarding the report regarding the requested information. The Npcf_PolicyAuthorization_Notify response message may be used. The P-CSCF (AF) may perform the procedures required for session modification based on the report received from the PCF. For example, if the P-CSCF (AF) receives a report that the media type of the session needs to be switched / changed or determines that the media type of the session needs to be switched / changed, it may trigger (initiate) the IMS procedure required for switching / changing the media type of the session. The IMS procedure required for switching / changing the media type of the session is described in steps 10 to 17 of Fig. 8.

[0192] Of course, the above-described procedures are not limited. At least one of the above-described procedures may be omitted. Alternatively, some of the above-described procedures may be combined, and new procedures may be added and organically combined with the above-described procedures.

[0193] FIG. 7 is a diagram illustrating a procedure related to a session management policy (SM Policy) that supports switching of media types of an IMS session in a communication system according to various embodiments of the present disclosure.

[0194] Descriptions of content overlapping with those in Figures 5 and 6 may be omitted. Figure 7 may be described primarily with respect to the procedures related to the signaling interactions between the PCF and SMF described in steps 7 to 12 of Figure 6. However, the names of the messages used may vary.

[0195] Referring to FIG. 7, the terminal and the network can perform the SM Policy procedure that supports switching of media types through the following procedure.

[0196] 1. The P-CSCF can request resources required for the current application session from the PCF. The Npcf_PolicyAuthorization_Create request message can be used. The P-CSCF can provide the PCF with session-related information required for session resource authorization. This information can be information related to events and events that the P-CSCF, as an AF, wishes to receive reports from the PCF. This information can be provided to the PCF as a Policy Control Request Trigger (PCRT). This information can include at least one of the following:

[0197] - QoS Reference parameters or individual QoS parameters for the media streams that make up the current session (e.g., media streams for audio, video, and media that can be switched during the session (e.g., avatars)).

[0198] - QoS parameter(s) that require measurement for the media streams that make up the current session (e.g., media streams for audio, video, and media that can be switched during the session (e.g., avatars)), and / or QoS Monitoring information that describes the QoS parameter(s).

[0199] - Events that the P-CSCF would like to request a report from the PCF:

[0200] -- When the QoS targets for the media streams that make up the current session (e.g., audio, video, and media streams for switchable media (e.g., avatars) during the session) become unmet on the current network (or become met again).

[0201] -- Information about the above QoS Monitoring information and / or QoS Monitoring results

[0202] -- Whether to deactivate the service data flow corresponding to the media streams that make up the current session (e.g., media streams for audio, video, and media that can be switched during the session (e.g., avatars)).

[0203] -- The state of the signaling path corresponding to the media streams that make up the current session (e.g., audio, video, and media streams for media that can be switched during the session, such as avatars).

[0204] -- Whether the media type of the current session needs to be switched

[0205] -- Information about which media type the current session's media type should be converted to (for example, if the current session's media type is 'avatar' and you want to convert it to 'video', you can report 'video')

[0206] 2. Based on the application session-related information received in step 1, the PCF can identify a PDU session associated with an IMS session that requires a media type conversion, and detect that modification of the associated PDU session is required. For example, based on the information received in step 1, the PCF may determine that QoS Monitoring is required, or that conversion / change of the session's media type may be required during the session. In addition, if the PCF determines that QoS Monitoring is required or that it needs to receive reports from the SMF on QoS measurements, network status, etc. to determine whether conversion / change of the session's media type is required during the session, the PCF may determine that modification of the PDU session is required to provide the SMF with information related to the determination.

[0207] 3. The PCF can determine the PCC rule based on the information received in Step 1 and the request from the AF (P-CSCF). The determined PCC rule can be delivered to the SMF through the SM Policy Association Establishment and / or SM Policy Association Modification procedures.

[0208] 4. The PCF may provide the PCC rule determined in step 3 to the SMF. The policy information provided to the SMF may include policy information for the PDU session and a Policy Control Request Trigger applicable to the SM Policy Association (an association established for SM Policy management between the PCF and the SMF). The Policy Control Request Trigger (PCRT) may include an event that the PCF wishes to be reported to from the SMF and information related to the event based on a request from the P-CSCF (AF) in step 1 and / or a decision by the PCF in step 3. The Npcf_SMPolicyControl_UpdateNotify request message may be used. The event and information related to the event that may be provided to the PCRT may include at least one of the following:

[0209] - QoS Reference parameters or individual QoS parameters for the media streams that make up the current session (e.g., media streams for audio, video, and media that can be switched during the session (e.g., avatars)).

[0210] - QoS parameter(s) that require measurement for the media streams that make up the current session (e.g., media streams for audio, video, and media that can be switched during the session (e.g., avatars)), and / or QoS Monitoring information that describes the QoS parameter(s).

[0211] - Events that the P-CSCF would like to request a report from the PCF:

[0212] -- When the QoS targets for the media streams that make up the current session (e.g., audio, video, and media streams for switchable media (e.g., avatars) during the session) become unmet on the current network (or become met again).

[0213] -- Information about the above QoS Monitoring information and / or QoS Monitoring results

[0214] -- Whether to deactivate the service data flow corresponding to the media streams that make up the current session (e.g., media streams for audio, video, and media that can be switched during the session (e.g., avatars)).

[0215] -- The state of the signaling path corresponding to the media streams that make up the current session (e.g., audio, video, and media streams for media that can be switched during the session, such as avatars).

[0216] -- Whether the media type of the current session needs to be switched

[0217] -- Information about which media type the current session's media type should be converted to (for example, if the current session's media type is 'avatar' and you want to convert it to 'video', you can report 'video')

[0218] 5. The SMF may respond to the PCF that it has received the Policy information and / or PCRT of step 4 above. The Npcf_SMPolicyControl_UpdateNotify response message may be used to respond that it has received the Policy information and / or PCRT of step 4.

[0219] 6. SMF can detect that the condition of PCRT received in step 4 above has been satisfied.

[0220] 7. The SMF may provide the PCF with information that must be reported based on the conditions of the PCRT detected in step 6 and received in step 4. The Npcf_SMPolicyControl_Update request message may be used to provide the PCF with the information that must be reported.

[0221] 8. The PCF can provide the AF (P-CSCF) with information that must be reported to the AF (P-CSCF) based on the conditions of the PCRT detected in the above step 7 and the conditions of the corresponding PCRT received in the above step 1.

[0222] 9. Based on the information received in step 8, the P-CSCF may determine whether a codec used for the media type of the current session and / or a media flow corresponding to the media type of the current session needs to be changed and how to do so. For example, the media type of the current session may be avatar, but based on the information received in step 8, it may be determined that it needs to be changed to a video type, and how to change it to a video type (e.g., what codec to use for the video type, whether a media flow corresponding to the video type should be established, whether the media flow can be changed using existing resources, whether resources corresponding to the media flow corresponding to the avatar type should be released, etc.). The above determination may require interaction with the S-CSCF, and / or the calling UE, the called network, and / or the called UE. The operations of steps 10 to 17 of FIG. 8 described below may correspond to the above-described description.

[0223] 10. The P-CSCF may provide the PCF with the information required to update the PDU session based on the information received in step 8 and the judgment and result of step 9. For example, when changing from an avatar type to a video type, the P-CSCF may provide the QoS Reference parameter or individual QoS parameter for the video type. In addition, if there is a change in the information and request provided in step 1, the P-CSCF may provide updated information. The Npcf_PolicyAuthorization_Update request message may be used to provide the information required to update the PDU session.

[0224] 11. PCF can store the application session-related information received in step 10, identify the PDU session associated with the IMS session requiring media type conversion, and bind them together. PCF can create resources for the application session associated with the information received in step 10, and store the related information.

[0225] 12. The PCF may respond by notifying the P-CSCF that a resource has been created for the application requested. The Npcf_PolicyAuthorization_Update response message may be used to notify the P-CSCF that a resource has been created for the application requested.

[0226] 13. The PCF can determine the PCC rule based on the information received in step 10 and the request from the AF (P-CSCF). The determined PCC rule can be delivered to the SMF through the SM Policy Association Establishment and / or SM Policy Association Modification procedures.

[0227] 14. The PCF may provide the SMF with the PCC rule and PCRT determined in step 13. In addition, if there is a change in the information and request provided in step 4, the PCF may provide updated information. The Npcf_PolicyAuthorization_Update response message may be used to provide updated information. The SMF may apply any necessary modifications to the PDU session to the UPF, AMF, RAN, and / or UE based on the information received in step 14. If the actions in steps 9 to 14 were actions to change the media type of the session, the UE may continue the IMS session and PDU session with the called UE based on the changed media type.

[0228] Of course, the above-described procedures are not limited. At least one of the above-described procedures may be omitted. Alternatively, some of the above-described procedures may be combined, and new procedures may be added and organically combined with the above-described procedures.

[0229] FIG. 8 is a diagram illustrating a procedure related to an operation of switching a media type of an IMS session in a communication system according to various embodiments of the present disclosure.

[0230] Descriptions of content overlapping with those in FIGS. 5 to 7 may be omitted. FIG. 8 may focus on the process in which the PCF converts the IMS session and PDU session established with the avatar media type in the procedures of FIGS. 5 to 7 to the video or audio media type based on the QoS monitoring results measured by the SMF. However, the names of the messages used may vary.

[0231] Referring to FIG. 8, the terminal and the network can perform a procedure to support switching of media types through the following procedure.

[0232] 1. The calling UE and the called UE can establish an avatar media type call by establishing an IMS session and a PDU session between the calling network and the called network. An example of a method for indicating the avatar media type may be the setting m="avatar" in the SDP offer message. The method for indicating the avatar media type is not limited to the above description.

[0233] 2. The P-CSCF may request the PCF to report whether the avatar call of step 1 requires a media switch / change in the middle of the call. For example, the call of the avatar media type of step 1 may include a media type switch / change function in the middle of the call. As another example, the call may be determined to support the media type switch / change function in the middle of the call based on the indicators regarding the media type switch support of the terminal or network described in FIGS. 5 to 8. In this case, the P-CSCF may request the PCF for an event that requires a media switch / change in the middle of the call and information related thereto. The P-CSCF may provide the PCF with a PCRT that can notify that 'a media type switch is required'. The Npcf_PolicyAuthorization Subscribe message may be used to provide the PCF with a PCRT that can notify that 'a media type switch is required'.

[0234] 3. PCF can determine the policy information and / or QoS monitoring information necessary to determine whether media type switching is necessary. For example, a QoS monitoring rule can be created that uses QoS parameter values ​​appropriate for avatar, video, and / or audio calls as thresholds.

[0235] 4. The PCF may provide the SMF with a PCRT that enables the SMF to report the information determined in step 3 and / or related information. For example, the PCF may provide the SMF with a PCRT that may indicate that a 'media type switch is required' and / or QoS monitoring information necessary to determine whether a media type switch is required. The Npcf_SMPolicyControl_UpdateNotify Request message may be used to provide the SMF with the QoS monitoring information.

[0236] 5. SMF can apply the policy information and / or QoS monitoring information received in step 4 above.

[0237] 6. The SMF can detect the status of the PDU session. For example, based on the QoS monitoring information received in step 4, if the QoS status of the current session exceeds the threshold of QoS parameters suitable for avatar calls but does not exceed the threshold of QoS parameters suitable for video and / or audio calls, it can detect the need to switch the media type from avatar to video and / or audio.

[0238] 7. Based on the status of the PDU session detected in step 6, the SMF can determine that the conditions of the PCRT received in step 4 are satisfied, and can provide a report to the PCF including information related to whether the conditions of the PCRT received in step 4 are satisfied. For example, the SMF can provide the PCF with the QoS monitoring result that the 'media type conversion is required' condition is satisfied, and that this information can assist in making a media type conversion decision.

[0239] 8. Based on the information received in step 7, the PCF can determine whether to switch the media type and / or how to switch the media type. For example, the PCF can determine that the 'media type switching required' condition received in step 7 is satisfied and that switching to a video and / or audio call is possible based on the QoS monitoring results provided together.

[0240] 9. Based on the judgment in step 8, the PCF can determine to the P-CSCF that the conditions of the PCRT received in step 2 are satisfied, and can provide the P-CSCF with a report including information related to whether the conditions of the PCRT received in step 2 are satisfied. For example, the PCF can inform the P-CSCF that the condition 'media type conversion is required' is satisfied, and that conversion to a video and / or audio call is possible as information that can assist in the media type conversion decision.

[0241] 10. Based on the information received in step 9, the P-CSCF can determine whether a change in the media flow corresponding to the media type of the current session is required and how to change it. The P-CSCF can provide the S-CSCF with media type conversion information as the information required to change the media flow corresponding to the media type of the current session. The SIP INFORMATION or SIP re-INVITE message can be used. For example, the P-CSCF can determine whether codec renegotiation between the calling network / UE and the called network / UE is required based on the generation of SDP with m="video" or m="audio" in the media type conversion information, through the S-CSCF.

[0242] 11. Based on the media type conversion information and / or subscriber information (which can be confirmed from HSS / UDM) received in step 10, the S-CSCF can determine the codec of the media type to be changed and the necessary changes to the media flow of the media type (e.g., whether a new media flow should be established, whether existing resources can be utilized, whether the media flow and resources of the previous media type should be released, etc.).

[0243] 12. Based on the determination result of step 11, the S-CSCF may provide the calling UE with an indication requesting codec renegotiation to the UE and / or information required for media type switching via the P-CSCF. The information required for media type switching may include information regarding the media type to be switched to (e.g., video and / or audio). The SIP INFORMATION or SIP re-INVITE message may be used to provide the indication requesting codec renegotiation to the UE and / or information required for media type switching.

[0244] 13. The P-CSCF may forward the information of step 12 to the UE. The SIP INFORMATION or SIP re-INVITE message may be used.

[0245] 14. The UE may stop existing media transmission based on the information received in step 13. For example, avatar media transmission may be stopped.

[0246] 15. The UE may perform codec renegotiation with the destination network / UE based on the media type switching information received in step 13. At this time, the UE may provide the codec information provided in the media type switching information to the destination network / UE.

[0247] 16. The UE may start transmitting new media type data using the codec determined based on the result of step 15. For example, the UE may start transmitting video and / or audio data.

[0248] 17. The calling network / UE and the called network / UE may continue the video and / or audio call as indicated in the media type switching information.

[0249] Of course, the above-described procedures are not limited. At least one of the above-described procedures may be omitted. Alternatively, some of the above-described procedures may be combined, and new procedures may be added and organically combined with the above-described procedures.

[0250] FIG. 9 is a diagram illustrating an example configuration of a network entity in a wireless communication system according to various embodiments of the present disclosure.

[0251] The network entity of FIG. 9 may be one of the network entities described in the embodiments of FIGS. 1 to 8.

[0252] A network entity according to one embodiment of the present disclosure may include a processor (910) that controls the overall operation of the network entity, a transceiver (920) including a transmitter and a receiver, and a memory (930). Of course, the present invention is not limited to the above example, and the network entity may include more or fewer components than those illustrated in FIG. 9.

[0253] According to one embodiment of the present disclosure, the transceiver (920) can transmit and receive signals with at least one of other network entities or terminals. The transmitted and received signals may include at least one of control information and data. If the network entity of FIG. 9 is a core network entity (NF), the signals transmitted and received between the network entity and the terminal may be transmitted and received via the RAN.

[0254] According to one embodiment of the present disclosure, the processor (910) may control the overall operation of the corresponding network entity to perform an operation according to one or a combination of two or more of the embodiments of FIGS. 1 to 7 described above. Meanwhile, the processor (910), the transceiver (920), and the memory (930) do not necessarily have to be implemented as separate modules, and may of course be implemented as a single component in the form of a single chip. In addition, the processor (910) may be an Application Processor (AP), a Communication Processor (CP), a circuit, an application-specific circuit, or at least one processor. The transceiver (920) may include at least one communication interface for transmitting and receiving signals with another network entity via wired / wireless.

[0255] According to one embodiment of the present disclosure, the memory (930) can store data such as basic programs, application programs, and setting information for the operation of the corresponding network entity. In addition, the memory (930) provides the stored data upon request of the processor (910). The memory (930) can be configured as a storage medium or a combination of storage media such as a ROM, a RAM, a hard disk, a CD-ROM, and a DVD. In addition, there can be a plurality of memories (930). In addition, the processor (910) can perform at least one of the above-described embodiments based on a program for performing an operation according to at least one of the above-described embodiments of the present disclosure stored in the memory (930).

[0256] FIG. 10 is a diagram illustrating an example configuration of a base station in a wireless communication system according to various embodiments of the present disclosure. The base station of FIG. 10 may refer to the RAN node described in the embodiments of FIGS. 1 to 8.

[0257] A base station according to one embodiment of the present disclosure may include a processor (1010) that controls the overall operation of the base station, a transceiver (1020) including a transmitter and a receiver, and a memory (1030). Of course, the present invention is not limited to the above example, and the base station may include more or fewer components than those illustrated in FIG. 10.

[0258] According to one embodiment of the present disclosure, a transceiver (1020) can transmit and receive signals with at least one of a terminal, another base station, or a network entity. The transmitted and received signals can include at least one of control information and data.

[0259] According to one embodiment of the present disclosure, the processor (1010) may control the overall operation of the base station to perform operations according to one or a combination of two or more of the embodiments of FIGS. 1 to 7 described above. Meanwhile, the processor (1010), the transceiver (1020), and the memory (1030) do not necessarily have to be implemented as separate modules, and may of course be implemented as a single component in the form of a single chip. In addition, the processor (1010) may be an Application Processor (AP), a Communication Processor (CP), a circuit, an application-specific circuit, or at least one processor. The transceiver (1020) may include at least one communication interface for transmitting and receiving signals wired / wirelessly to and from a terminal, another base station, or a network entity.

[0260] According to one embodiment of the present disclosure, the memory (1030) can store data such as basic programs, application programs, and setting information for the operation of the corresponding base station. In addition, the memory (1030) provides the stored data upon request of the processor (1010). The memory (1030) can be configured as a storage medium or a combination of storage media such as a ROM, a RAM, a hard disk, a CD-ROM, and a DVD. In addition, there can be a plurality of memories (1030). In addition, the processor (1010) can perform at least one of the above-described embodiments based on a program for performing an operation according to at least one of the above-described embodiments of the present disclosure stored in the memory (1030).

[0261] FIG. 11 is a diagram showing an example configuration of a terminal in a wireless communication system according to various embodiments of the present disclosure.

[0262] A terminal according to one embodiment of the present disclosure may include a processor (1110) that controls the overall operation of the terminal, a transceiver (1120) including a transmitter and a receiver, and a memory (1130). Of course, the present invention is not limited to the above example, and the terminal may include more or fewer components than those illustrated in FIG. 11.

[0263] According to one embodiment of the present disclosure, a transceiver (1120) can transmit and receive signals with at least one other terminal, base station, or network entity. The transmitted and received signals can include at least one of control information and data.

[0264] According to one embodiment of the present disclosure, the processor (1110) may control the overall operation of the terminal to perform an operation according to one or a combination of two or more of the embodiments of FIGS. 1 to 7 described above. Meanwhile, the processor (1110), the transceiver (1120), and the memory (1130) do not necessarily have to be implemented as separate modules, and may of course be implemented as a single component in the form of a single chip. In addition, the processor (1110) may be an Application Processor (AP), a Communication Processor (CP), a circuit, an application-specific circuit, or at least one processor. The transceiver (1120) may include at least one communication interface for transmitting and receiving signals with another terminal, a base station, or a network entity via wired / wireless.

[0265] According to one embodiment of the present disclosure, the memory (1130) can store data such as basic programs, application programs, and setting information for the operation of the terminal. In addition, the memory (1130) provides the stored data upon request of the processor (1110). The memory (1130) can be configured as a storage medium or a combination of storage media such as a ROM, a RAM, a hard disk, a CD-ROM, and a DVD. In addition, there can be a plurality of memories (1130). In addition, the processor (1110) can perform at least one of the above-described embodiments based on a program for performing an operation according to at least one of the above-described embodiments of the present disclosure stored in the memory (1130).

[0266] In the specific embodiments of the present disclosure described above, components included in the present disclosure are expressed singularly or plurally, depending on the specific embodiment presented. However, the singular or plural expressions are selected to suit the presented situation for convenience of explanation, and the present disclosure is not limited to singular or plural components. Components expressed in plural may be composed of singular elements, or components expressed in singular may be composed of plural elements.

[0267] Meanwhile, the embodiments of the present disclosure disclosed in this specification and drawings are merely specific examples to easily explain the technical contents of the present disclosure and to help the understanding of the present disclosure, and are not intended to limit the scope of the present disclosure. That is, it may be obvious to a person having ordinary skill in the art to which the present disclosure pertains that other modified examples based on the technical idea of ​​the present disclosure are possible. In addition, each of the above embodiments may be combined and operated with each other as needed. For example, parts of one embodiment of the present disclosure and another embodiment may be combined with each other to operate a base station and a terminal. In addition, other modified examples based on the technical idea of ​​the above embodiments may be implemented in various systems such as an FDD LTE system, a TDD LTE system, a 5G or NR system.

[0268] The methods according to the embodiments described in the claims or specification of the present disclosure may be implemented in the form of hardware, software, or a combination of hardware and software.

[0269] When implemented in software, a computer-readable storage medium storing one or more programs (software modules) may be provided. The one or more programs stored in the computer-readable storage medium are configured for execution by one or more processors within an electronic device. The one or more programs include instructions that cause the electronic device to execute methods according to the embodiments described in the claims or specification of the present disclosure.

[0270] These programs (software modules, software) may be stored in a non-volatile memory including random access memory, flash memory, read only memory (ROM), electrically erasable programmable read only memory (EEPROM), magnetic disc storage devices, compact disc ROMs (CD-ROMs), digital versatile discs (DVDs) or other forms of optical storage devices, magnetic cassettes, or may be stored in a memory configured as a combination of some or all of these. In addition, each configuration memory may include multiple copies.

[0271] Additionally, the program may be stored in an attachable storage device that is accessible via a communication network such as the Internet, an intranet, a local area network (LAN), a wide local area network (WLAN), a storage area network (SAN), or a combination thereof. Such a storage device may be connected to a device performing an embodiment of the present disclosure via an external port. Additionally, a separate storage device on the communication network may be connected to a device performing an embodiment of the present disclosure.

[0272] Meanwhile, a part or all of one or more embodiments proposed in the present disclosure may be applied in combination with a part or all of one or more other embodiments, and such combination forms are also included within the scope of the present disclosure.

[0273] Meanwhile, the embodiments disclosed in the specification and drawings described above are merely specific examples to easily explain and aid understanding of the contents of the present disclosure, and are not intended to limit the scope of the present disclosure. Therefore, the scope of the present disclosure should be interpreted to include all changes or modifications derived based on the technical concept of the present disclosure, in addition to the embodiments disclosed herein. Furthermore, each of the above embodiments may be combined and operated as needed, as long as there is no technical contradiction.

Claims

1. A method performed by a first network entity of a wireless communication system, A step of receiving first information related to a conversion of a media type from a second network entity; and A step of identifying whether codec renegotiation is required based on the first information above, A method wherein the above codec renegotiation relates to a change of the codec of the above media type between the calling network or calling terminal and the called network or called terminal.

2. In paragraph 1, The reception of the first information is based on the second information transmitted from the second network entity to the PCF (policy control function) entity, A method wherein the second information includes a condition for identifying whether a conversion of the media type is required.

3. In paragraph 1, A method, wherein the first information includes information required to change a media flow corresponding to a media type of the current session.

4. In paragraph 1, The first network entity and the second network entity are included in an IM (IP (internet protocol) multimedia) CN (core network) subsystem, The above first network entity is a serving-call session control function (S-CSCF), A method, wherein the second network entity is a P-CSCF (proxy CSCF) entity.

5. A method performed by a second network entity of a wireless communication system, A step for transmitting first information related to conversion of media type to a PCF (policy control function) entity; A step of receiving information on whether a condition included in the first information is satisfied and second information from the PCF entity; and A step of transmitting said second information to a first network entity, Whether codec renegotiation is required is based on the second information above. A method wherein the above codec renegotiation relates to a change of the codec of the above media type between the calling network or calling terminal and the called network or called terminal.

6. In paragraph 5, The transmission of the above second information is based on the above conditions, A method wherein the above condition is for identifying whether conversion of the above media type is required.

7. In paragraph 5, A method, wherein the second information includes information required to change a media flow corresponding to a media type of the current session.

8. In paragraph 5, The first network entity and the second network entity are included in an IM (IP (internet protocol) multimedia) CN (core network) subsystem, The above first network entity is a serving-call session control function (S-CSCF), A method, wherein the second network entity is a P-CSCF (proxy CSCF) entity.

9. In the first network entity of the wireless communication system, Transmitter and receiver; and At least one control unit connected to the above transceiver unit, At least one of the above control units: Receive first information related to a conversion of a media type from a second network entity, It is set to identify whether codec renegotiation is required based on the above first information, The above codec renegotiation is a first network entity relating to a change of the codec of the above media type between the calling network or calling terminal and the called network or called terminal.

10. In paragraph 9, The reception of the first information is based on second information transmitted from the second network entity to the PCF (policy control function) entity, A first network entity, wherein the second information includes a condition for identifying whether a conversion of the media type is required.

11. In paragraph 9, A first network entity, wherein the first information includes information required for changing a media flow corresponding to the media type of the current session.

12. In paragraph 9, The first network entity and the second network entity are included in an IM (IP (internet protocol) multimedia) CN (core network) subsystem, The above first network entity is a serving-call session control function (S-CSCF), The first network entity, wherein the second network entity is a P-CSCF (proxy CSCF) entity.

13. In a second network entity of a wireless communication system, Transmitter and receiver; and At least one control unit connected to the above transceiver unit, At least one of the above control units: As a PCF (policy control function) entity, it transmits the first information related to the conversion of media type, Receive information on whether the condition included in the first information is satisfied and second information from the above PCF entity, As a first network entity, it is set to transmit said second information, Whether codec renegotiation is required is based on the second information above. The above codec renegotiation is a second network entity regarding a change of the codec of the above media type between the calling network or calling terminal and the called network or called terminal.

14. In paragraph 13, The transmission of the above second information is based on the above conditions, The above condition is to identify whether conversion of the above media type is required, A second network entity, wherein the second information includes information required to change a media flow corresponding to the media type of the current session.

15. In paragraph 13, The first network entity and the second network entity are included in an IM (IP (internet protocol) multimedia) CN (core network) subsystem, The above first network entity is a serving-call session control function (S-CSCF), A second network entity, wherein the second network entity is a P-CSCF (proxy CSCF) entity.

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