Multicast-related communications

Abstract

One embodiment of the specification provides a method of an NG-RAN node performing communication related to multicast. The method can include the steps of receiving, from an AMF, a UE context release command message related to a first UE; determining, based on the reception of the UE context release command message, that the first UE moves from the 5GS to the EPS; and removing information related to the first UE from a context related to a multicast session.

Description

Technical Field

[0001] This disclosure relates to mobile communications. Background Technology

[0002] The 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) is a technology for achieving high-speed packet communication. Many proposals have been put forward for LTE goals, including those aimed at reducing costs for users and providers, improving service quality, and expanding and increasing coverage and system capacity. 3GPP LTE requires lower cost per bit, increased service availability, flexible use of frequency bands, a simple architecture, open interfaces, and sufficient power consumption in terminals as upper-layer requirements.

[0003] Requirements and specifications for developing new radio (NR) systems have already begun in the International Telecommunication Union (ITU) and 3GPP. 3GPP must identify and develop the technical components required for the successful standardization of the new RAT, thereby meeting both pressing market demands and the longer-term requirements set forth by the ITU Radiocommunication Sector (ITU-R) International Mobile Telecommunications (IMT)-2020 process. Furthermore, NR should be able to utilize any spectrum band ranging from at least 100 GHz, which can be used for wireless communication even in the more distant future.

[0004] NR aims to address all use cases, requirements, and deployment scenarios, including enhanced mobile broadband (eMBB), massive machine-type communications (mMTC), and ultra-reliable and low-latency communications (URLLC), with a single technology framework. NR should be inherently backward compatible.

[0005] Meanwhile, multicast communication (e.g., communication based on Multicast Broadcast Service (MBS)) has been introduced in 5G mobile communication. Terminals (e.g., User Equipment (UE)) and networks can perform multicast communication in 5GS (5G system) in a multicast manner.

[0006] By performing multicast communication in 5GS, terminals receiving multicast services (e.g., MBS services) can be moved to an evolved packet system (EPS). Then, in EPS, the terminal can receive the MBS services received in 5GS via broadcast communication supported by the Multimedia Broadcast & Multicast Service (MBMS) method.

[0007] On the other hand, according to existing technology, even after a UE moves from 5GS to EPS, 5GS does not remove the UE's existing multicast context (or MBS context). As a result, even if the terminal no longer performs multicast communication in 5GS, the 5G core network and base stations (e.g., Next Generation Radio Access Network (NG-RAN)) continue to struggle to provide services related to multicast communication to the terminal.

[0008] For example, even if the UE has left the 5GS, the base station may still perform unnecessary operations (such as continuously receiving multicast services for the UE from the User Plane Function (UPF)). Summary of the Invention

[0009] Technical issues

[0010] Therefore, the disclosure of this specification is intended to address the aforementioned problems.

[0011] Technical solution

[0012] To address the aforementioned issues, one disclosure of this specification provides a method for an NG-RAN node to perform multicast-related communications. This method may include the following steps: receiving a UE context release command message associated with a first UE from the AMF; determining, based on the received UE context release command message, that the first UE has moved from 5GS to EPS; and removing information associated with the first UE from the context associated with the multicast session.

[0013] To address the aforementioned issues, one disclosure of this specification provides an NG-RAN node for performing multicast-related communications. The NG-RAN node includes: at least one processor; and at least one memory storing instructions and electrically connected to the at least one processor during operation, wherein operations based on instructions executed by the at least one processor include: receiving a UE context release command message associated with a first UE from the AMF; determining, based on the received UE context release command message, that the first UE has moved from 5GS to EPS; and removing information associated with the first UE from the context associated with the multicast session.

[0014] To address the aforementioned issues, one disclosure of this specification provides a method for an AMF to perform multicast-related communications. The method includes the following steps: based on a first UE moving from 5GS to EPS, sending a UE context release command message related to the first UE to the NG-RAN node serving the first UE; and receiving a multicast distribution release request message from the NG-RAN node.

[0015] To address the aforementioned issues, one disclosure of this specification provides an AMF (Advanced Context Provider) for performing multicast-related communications. The AMF includes: at least one processor; and at least one memory storing instructions and electrically connected to the at least one processor during operation, wherein operations based on instructions executed by the at least one processor include: sending a UE context release command message related to the first UE to an NG-RAN node serving the first UE based on the first UE moving from 5GS to EPS; and receiving a multicast distribution release request message from the NG-RAN node.

[0016] Beneficial effects

[0017] The problems in the related technologies can be solved based on the disclosure in this specification.

[0018] The effects achievable through the specific examples in this specification are not limited to those listed above. For example, various technical effects may exist that can be understood or derived from this specification by one of ordinary skill in the art. Therefore, the specific effects of this specification are not limited to those explicitly described herein, and may include various effects that can be understood or derived from the technical features of this specification. Attached Figure Description

[0019] Figure 1 An example of a communication system applying embodiments of the present disclosure is shown.

[0020] Figure 2 An example of a wireless device applying embodiments of the present disclosure is shown.

[0021] Figure 3 An example of a wireless device applying embodiments of the present disclosure is shown.

[0022] Figure 4 This is a structural diagram of the next-generation mobile communication network.

[0023] Figure 5 This is an example diagram illustrating the predicted structure of next-generation mobile communications from the perspective of nodes.

[0024] Figure 6 An example of a system architecture for interoperability between 5G MBS and E-UTRAN / EPC is shown.

[0025] Figures 7a to 7c An example of the PDU session modification process for multicast departure is shown.

[0026] Figure 8a and Figure 8b An example of the process for generating a multicast session is shown.

[0027] Figure 9An example of a session exit process is shown.

[0028] Figure 10 An example of a signal flow diagram according to the third example disclosed in this specification is shown. Detailed Implementation

[0029] The following technologies, devices, and systems can be applied to a variety of wireless multiple access systems. Examples of multiple access systems include Code Division Multiple Access (CDMA) systems, Frequency Division Multiple Access (FDMA) systems, Time Division Multiple Access (TDMA) systems, Orthogonal Frequency Division Multiple Access (OFDMA) systems, Single-Carrier Frequency Division Multiple Access (SC-FDMA) systems, and Multi-Carrier Frequency Division Multiple Access (MC-FDMA) systems. CDMA can be implemented using radio technologies such as Universal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA can be implemented using radio technologies such as Global System for Mobile Communications (GSM), General Packet Radio Service (GPRS), or Enhanced Data Rate GSM Evolution (EDGE). OFDMA can be implemented using radio technologies such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, or Evolved UTRA (E-UTRA). UTRA is part of the Universal Mobile Telecommunications System (UMTS). The 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) is part of the Evolved UMTS (E-UMTS) using E-UTRA. 3GPP LTE employs OFDMA in DL and SC-FDMA in UL. The evolution of 3GPP LTE includes LTE-A (Advanced), LTE-A Pro, and / or 5G NR (New Radio).

[0030] For ease of description, the implementation of this disclosure is primarily described with respect to 3GPP-based wireless communication systems. However, the technical features of this disclosure are not limited thereto. For example, although the following detailed description is based on mobile communication systems corresponding to 3GPP-based wireless communication systems, the aspects of this disclosure that are not limited to 3GPP-based wireless communication systems are applicable to other mobile communication systems.

[0031] For any terms and techniques used in this disclosure that are not specifically described in this disclosure, please refer to wireless communication standards documents published prior to this disclosure.

[0032] In this disclosure, "A or B" can mean "A only", "B only", or "both A and B". In other words, "A or B" in this disclosure can be interpreted as "A and / or B". For example, "A, B or C" in this disclosure can mean "A only", "B only", "C only", or "any combination of A, B and C".

[0033] In this disclosure, a forward slash ( / ) or a comma (,) can mean "and / or". For example, "A / B" can mean "A and / or B". Therefore, "A / B" can mean "A only", "B only", or "both A and B". For example, "A, B, C" can mean "A, B, or C".

[0034] In this disclosure, "at least one of A and B" can mean "only A", "only B" or "both A and B". Furthermore, the expressions "at least one of A or B" or "at least one of A and / or B" in this disclosure can be interpreted as the same as "at least one of A and B".

[0035] Additionally, in this disclosure, "at least one of A, B, and C" may mean "only A," "only B," "only C," or "any combination of A, B, and C." Furthermore, "at least one of A, B, or C" or "at least one of A, B, and / or C" may mean "at least one of A, B, and C."

[0036] Furthermore, the brackets used in this disclosure may mean "for example". Specifically, when it is shown as "Control Information (PDCCH)", "PDCCH" can be cited as an example of "Control Information". In other words, "Control Information" in this disclosure is not limited to "PDCCH", and "PDCCH" can be cited as an example of "Control Information". In addition, even when shown as "Control Information (i.e., PDCCH)", "PDCCH" can be cited as an example of "Control Information".

[0037] The technical features described individually in one of the accompanying drawings of this disclosure can be implemented individually or simultaneously.

[0038] Although not limited thereto, the various descriptions, functions, processes, suggestions, methods and / or operation flowcharts disclosed herein can be applied to various fields requiring wireless communication and / or connectivity between devices (e.g., 5G).

[0039] In the following description, this disclosure will be described in more detail with reference to the accompanying drawings. Unless otherwise stated, the same reference numerals in the following drawings and / or description may refer to the same and / or corresponding hardware blocks, software blocks and / or functional blocks.

[0040] In the accompanying drawings, for example, a user equipment (UE) is shown. A UE can also be represented as a terminal or mobile device (ME). Additionally, a UE can be a laptop computer, mobile phone, PDA, smartphone, multimedia device, or other portable device, or it can be a fixed device such as a PC or vehicle-mounted device.

[0041] In the following text, UE is used as an example of a wireless communication device (or wireless apparatus or wireless device) capable of wireless communication. Operations performed by the UE can be performed by the wireless communication device. The wireless communication device may also be referred to as a wireless apparatus, wireless device, etc. In the following text, AMF may refer to an AMF node, SMF may refer to an SMF node, and UPF may refer to a UPF node.

[0042] The term “base station” as used below generally refers to a fixed station that communicates with wireless devices, and may be referred to by other terms such as evolved Node B (eNode B), evolved Node B (eNB), base transceiver system (BTS), access point, or next-generation Node B (gNB).

[0043] I. The techniques and processes disclosed in this specification

[0044] Figure 1 An example of a communication system applying embodiments of the present disclosure is shown.

[0045] Figure 1 The 5G use cases shown are merely illustrative, and the technical features of this disclosure can be applied to... Figure 1 Other 5G use cases not shown.

[0046] The three main requirement categories for 5G include (1) Enhanced Mobile Broadband (eMBB), (2) Massive Machine Type Communications (mMTC), and (3) Ultra Reliable and Low Latency Communications (URLLC).

[0047] Some use cases may require multiple categories for optimization, while others may focus solely on key performance indicators (KPIs). 5G uses a flexible and reliable approach to support these diverse use cases.

[0048] eMBB goes far beyond basic mobile internet access, encompassing a vast array of two-way work in the cloud and augmented reality, as well as media and entertainment applications. Data is one of the core drivers of 5G, and for the first time in the 5G era, dedicated voice services may not be available. In 5G, the expectation is to use the data connection provided by the communication system to simply process voice as an application. The primary reason for the increase in traffic is the increase in content size and the number of applications requiring high data transmission rates. As more devices connect to the internet, streaming services (audio and video), conversational video, and mobile internet access will be more widely used. Many of these applications require always-on connectivity to push real-time information and alerts to users. Cloud storage and applications are rapidly increasing in mobile communication platforms and can be applied to both work and entertainment. Cloud storage is a specific use case for accelerating the growth of uplink data transmission rates. 5G is also used for remote cloud work. When using haptic interfaces, 5G requires lower end-to-end latency to maintain a good user experience. Entertainment (e.g., cloud gaming and video streaming) is another core element increasing the demand for mobile broadband capabilities. Entertainment is essential for smartphones and tablets in any highly mobile environment, including trains, vehicles, and airplanes. Other use cases include augmented reality for entertainment and information retrieval. In this case, augmented reality requires very low latency and extremely low instantaneous data volumes.

[0049] Additionally, one of the most anticipated 5G use cases involves the ability to smoothly connect embedded sensors across all sectors (i.e., mMTC). The number of potential Internet of Things (IoT) devices is expected to reach 20.4 billion by 2020. Industrial IoT is one of the categories playing a leading role in enabling smart cities, asset tracking, smart utilities, agriculture, and security infrastructure through 5G.

[0050] URLLC encompasses new services that will transform industries through remote control of key infrastructure and ultra-reliable / available low-latency links (e.g., autonomous vehicles). For controlling smart grids, automating industry, enabling robotics, and controlling and regulating drones, levels of reliability and latency are critical.

[0051] 5G is the means to provide streaming services rated at hundreds of megabits per second to gigabits per second, and can complement fiber-to-the-home (FTTH) and cable-based broadband (or DOCSIS). Such high speeds are needed to deliver 4K or higher (6K, 8K, and higher) resolution TV, as well as virtual reality and augmented reality. Virtual reality (VR) and augmented reality (AR) applications include near-immersive sports events. Specific applications may require special network configurations. For example, for VR games, game companies need to integrate their core servers into the network operator's edge network servers to minimize latency.

[0052] Along with numerous use cases for mobile communications in vehicles, automobiles are expected to become a significant new driving force in 5G. For example, passenger entertainment requires high concurrent capacity and highly mobile broadband. This is because future users will continue to expect high-quality connectivity regardless of their location and speed. Another use case in the automotive sector is AR dashboards. AR dashboards allow drivers to identify objects in the dark in addition to those seen through the windshield, and display distances and movement of objects by overlaying information to the driver. In the future, wireless modules will allow communication between vehicles, information exchange between vehicles and supporting infrastructure, and information exchange between vehicles and other connected devices (e.g., pedestrian-accompanying devices). Safety systems will guide alternative driving processes to enable drivers to drive more safely, thereby reducing the risk of accidents. The next stage will be remotely controlled or autonomous vehicles. This requires very high reliability and very fast communication between different autonomous vehicles and between vehicles and infrastructure. In the future, autonomous vehicles will perform all driving activities, and drivers will only focus on abnormal traffic that the vehicle cannot identify. The technical requirements for autonomous vehicles necessitate ultra-low latency and ultra-high reliability to increase traffic safety to levels unattainable by humans.

[0053] Smart cities and smart homes / buildings, termed smart societies, will be embedded in high-density wireless sensor networks. Distributed networks of smart sensors will identify conditions for cost-effective and energy-efficient maintenance in cities or homes. Similar configurations can be implemented for individual homes. Temperature sensors, window and heating controllers, burglar alarms, and home appliances will all be wirelessly connected. Many of these sensors typically have low data transmission rates, low power consumption, and low cost. However, certain types of devices may require real-time HD video for monitoring.

[0054] The consumption and distribution of energy, including heat or gas, are distributed at a higher level, necessitating automated control through distributed sensor networks. Smart grids collect information and use digital information and communication technologies to connect sensors to each other to act based on the collected information. Because this information can include the behavior of power companies and consumers, smart grids can improve fuel distribution, such as electricity, through methods that are efficient, reliable, economically feasible, production sustainable, and automated. Smart grids can also be viewed as another sensor network with low latency.

[0055] Mission-critical applications (e.g., e-health) are one of the use cases for 5G. The health sector encompasses numerous applications that can benefit from mobile communications. Communication systems can support telemedicine, enabling the delivery of clinical care in remote locations. Telemedicine can help reduce distance barriers and improve access to healthcare services that are not readily available in remote rural areas. Telemedicine is also used to administer critical treatments and save lives in emergencies. Mobile communication-based wireless sensor networks can provide remote monitoring and sensing of parameters such as heart rate and blood pressure.

[0056] Wireless and mobile communications are becoming increasingly important in industrial applications. The installation and maintenance costs of cabling are high. Therefore, the possibility of replacing cables with reconfigurable wireless links presents an attractive opportunity in many industrial sectors. However, to achieve this replacement, wireless connections need to be established with similar latency, reliability, and capacity as cables, and the management of wireless connections needs to be simplified. When connecting to 5G, low latency and a very low error probability become new requirements.

[0057] Logistics and freight tracking are important use cases for mobile communications, allowing inventory and packages to be tracked anywhere using location-based information systems. Logistics and freight use cases typically require low data rates, but demand location information with wide coverage and reliability.

[0058] Reference Figure 1 The communication system 1 includes wireless devices 100a to 100f, a base station (BS) 200, and a network 300. Although Figure 1 An example of a 5G network as a network for communication system 1 is shown, but the embodiments of this disclosure are not limited to 5G systems and can be applied to future communication systems other than 5G systems.

[0059] BS 200 and network 300 can be implemented as wireless devices, and a particular wireless device can operate as a BS / network node relative to other wireless devices.

[0060] Wireless devices 100a to 100f represent devices that perform communication using radio access technology (RAT) (e.g., 5G New RAT (NR) or LTE) and may be referred to as communication / radio / 5G devices. Wireless devices may include (but are not limited to) robots 100a, vehicles 100b-1 and 100b-2, extended reality (XR) devices 100c, handheld devices 100d, home appliances 100e, IoT devices 100f, and artificial intelligence (AI) devices / servers 400. For example, vehicles may include vehicles with wireless communication capabilities, autonomous vehicles, and vehicles capable of performing communication between vehicles. Vehicles may include unmanned aerial vehicles (UAVs) (e.g., drones). XR devices may include AR / VR / mixed reality (MR) devices and may take the form of head-up displays (HMDs), head-up displays (HUDs) installed in vehicles, televisions, smartphones, computers, wearable devices, home appliance devices, digital signage, vehicles, robots, etc. Handheld devices may include smartphones, smart tablets, wearable devices (e.g., smartwatches or smart glasses), and computers (e.g., laptops). Home appliances may include TVs, refrigerators, and washing machines. IoT devices may include sensors and smart meters.

[0061] In this disclosure, wireless devices 100a to 100f may be referred to as user equipment (UE). UE may include, for example, cellular phones, smartphones, laptop computers, digital broadcasting terminals, personal digital assistants (PDAs), portable multimedia players (PMPs), navigation systems, tablet PCs, tablet PCs, ultrabooks, vehicles, vehicles with autonomous driving capabilities, connected cars, UAVs, AI modules, robots, AR devices, VR devices, MR devices, holographic devices, public safety devices, MTC devices, IoT devices, medical devices, FinTech devices (or financial devices), security devices, weather / environment devices, devices related to 5G services, or devices related to the Fourth Industrial Revolution.

[0062] UAVs can be, for example, aircraft that are airborne by wireless control signals without anyone on board.

[0063] VR devices may include, for example, means for realizing objects or backgrounds in a virtual world. AR devices may include, for example, means for connecting objects or backgrounds in a virtual world to objects or backgrounds in the real world. MR devices may include, for example, means for merging objects or backgrounds in a virtual world into objects or backgrounds in the real world. Holographic devices may include, for example, means for recording and reproducing stereoscopic information using the interference phenomenon of light generated when two lasers, known as holography, meet.

[0064] Public safety devices may include, for example, image relay devices or image devices that can be worn on a user's body.

[0065] MTC devices and IoT devices can be, for example, devices that do not require direct human intervention or manipulation. For example, MTC devices and IoT devices can include smart meters, vending machines, thermometers, smart light bulbs, door locks, or various sensors.

[0066] For example, a medical device can be a device for the purpose of diagnosing, treating, alleviating, treating, or preventing disease. For example, a medical device can be a device for the purpose of diagnosing, treating, alleviating, or correcting injury or impairment. For example, a medical device can be a device for the purpose of examining, replacing, or modifying a structure or function. For example, a medical device can be a device for regulating pregnancy. For example, a medical device can include a device for treatment, a device for surgery, a device for (in vitro) diagnosis, a hearing aid, or a device for surgical procedures.

[0067] For example, a safety device can be an installation to prevent potential hazards and maintain safety. For example, a safety device can be a camera, closed-circuit television (CCTV), a recorder, or a black box.

[0068] For example, a FinTech device can be a device capable of providing financial services such as mobile payments. For instance, a FinTech device can include a payment device or a point-of-sale (POS) system.

[0069] Weather / environment devices may include, for example, devices for monitoring or predicting weather / environment.

[0070] Wireless devices 100a to 100f can connect to network 300 via BS 200. AI technology can be applied to wireless devices 100a to 100f, and wireless devices 100a to 100f can connect to AI server 400 via network 300. Network 300 can be configured using 3G, 4G (e.g., LTE), 5G (e.g., NR), and super 5G networks. Although wireless devices 100a to 100f can communicate with each other via BS 200 / network 300, wireless devices 100a to 100f can also perform direct communication (e.g., sidelink communication) without going through BS 200 / network 300. For example, vehicles 100b-1 and 100b-2 can perform direct communication (e.g., vehicle-to-vehicle (V2V) / vehicle-to-everything (V2X) communication). IoT devices (e.g., sensors) can perform direct communication with other IoT devices (e.g., sensors) or other wireless devices 100a to 100f.

[0071] Wireless communication / connections 150a, 150b, and 150c can be established between wireless devices 100a to 100f and / or between wireless devices 100a to 100f and BS 200 and / or between BS 200. In this document, wireless communication / connections can be established via various RATs (e.g., 5G NR) such as uplink / downlink communication 150a, sidelink communication (or device-to-device (D2D) communication) 150b, and inter-base station communication 150c (e.g., relay, integrated access and backhaul (IAB)). Wireless devices 100a to 100f and BS 200 / wireless devices 100a to 100f can send / receive radio signals to / from each other via wireless communication / connections 150a, 150b, and 150c. For example, wireless communication / connections 150a, 150b, and 150c can send / receive signals via various physical channels. Therefore, at least a portion of various configuration information configuration processes, various signal processing processes (e.g., channel coding / decoding, modulation / demodulation, and resource mapping / demapping), and resource allocation processes for transmitting / receiving radio signals can be performed based on various proposals of this disclosure.

[0072] AI refers to the field of studying artificial intelligence or the methods that can create it, and machine learning refers to the field that defines the various problems to be solved within the AI ​​and its methodologies. Machine learning is also defined as algorithms that improve the performance of a task through a stable experience of that task.

[0073] A robot is a machine that automatically processes or operates a given task through its own capabilities. Specifically, a robot with the ability to recognize its environment and make its own decisions to perform actions can be called an intelligent robot. Depending on its purpose or field of use, robots can be classified as industrial, medical, domestic, military, etc. Robots can utilize actuators or motors to perform various physical operations such as moving their joints. Mobile robots also include wheels, brakes, propellers, etc., on their actuators, allowing them to move on the ground or fly in the air.

[0074] Autonomous driving refers to the technology of driving itself, and autonomous vehicles refer to vehicles that drive with little or no user control. For example, autonomous driving can include lane keeping, automatic speed adjustment (e.g., adaptive cruise control), automatic driving along a set route, and automatic route planning when a destination is set. Vehicles include vehicles equipped with internal combustion engines, hybrid vehicles equipped with both internal combustion engines and electric motors, and electric vehicles equipped with electric motors, and can include trains, motorcycles, and automobiles. Autonomous vehicles can be considered as robots with autonomous driving capabilities.

[0075] Extended reality is collectively referred to as VR, AR, and MR. VR technology provides real-world objects and backgrounds solely through computer graphics (CG) images. AR technology provides virtual CG images on top of real-world object images. MR technology is a CG technique that combines virtual objects into the real world. MR technology is similar to AR technology in that they display real and virtual objects together. However, the difference lies in that in AR technology, virtual objects serve as a complementary form to real objects, while in MR technology, virtual and real objects serve as identical features.

[0076] NR supports multiple parameter sets (and / or multiple subcarrier spacings (SCS)) to support a variety of 5G services. For example, if the SCS is 15kHz, wide-area coverage can be supported in traditional cellular bands, and if the SCS is 30kHz / 60kHz, dense urban areas, lower latency, and wider carrier bandwidth can be supported. If the SCS is 60kHz or higher, bandwidths greater than 24.25GHz can be supported to overcome phase noise.

[0077] NR bands can be defined as two types of frequency ranges, namely FR1 and FR2. The numerical values ​​of the frequency ranges can be varied. For example, the frequency ranges of the two types (FR1 and FR2) can be shown in Table 1 below. For ease of explanation, in the frequency ranges used in NR systems, FR1 can mean "below 6 GHz" and FR2 can mean "above 6 GHz", and can be referred to as millimeter wave (mmW).

[0078] [Table 1]

[0079] Frequency range specification Corresponding frequency range Subcarrier spacing FR1 450MHz–6000MHz 15kHz, 30kHz, 60kHz FR2 24250MHz–52600MHz 60kHz, 120kHz, 240kHz

[0080] As described above, the frequency range of the NR system can be varied. For example, FR1 may include a frequency band from 410MHz to 7125MHz as shown in Table 2 below. That is, FR1 may include a frequency band of 6GHz (or 5850MHz, 5900MHz, 5925MHz, etc.) or higher. For example, the 6GHz (or 5850MHz, 5900MHz, 5925MHz, etc.) or higher frequency band included in FR1 may include unlicensed frequency bands. Unlicensed frequency bands can be used for various purposes (e.g., for vehicle communications (e.g., autonomous driving)).

[0081] [Table 2]

[0082] Frequency range specification Corresponding frequency range Subcarrier spacing FR1 410MHz–7125MHz 15kHz, 30kHz, 60kHz FR2 24250MHz–52600MHz 60kHz, 120kHz, 240kHz

[0083] Here, the radio communication technologies implemented in the wireless devices of this disclosure may include narrowband Internet of Things (NB-IoT) technologies for low-power communication, as well as LTE, NR, and 6G. For example, NB-IoT technology may be an example of low-power wide-area network (LPWAN) technology, implemented in specifications such as LTE Cat NB1 and / or LTE Cat NB2, and may not be limited to the names mentioned above. Additionally and / or alternatively, the radio communication technologies implemented in the wireless devices of this disclosure may communicate based on LTE-M technology. For example, LTE-M technology may be an example of LPWAN technology and may be referred to by various names such as enhanced machine-type communication (eMTC). For example, LTE-M technology may be implemented in at least one of various specifications such as 1) LTE Cat 0, 2) LTE Cat M1, 3) LTE Cat M2, 4) LTE non-bandwidth limited (non-BL), 5) LTE-MTC, 6) LTE machine-type communication, and / or 7) LTE M, and may not be limited to the names mentioned above. Additionally and / or alternatively, the radio communication technologies implemented in the wireless devices of this disclosure may include at least one of ZigBee, Bluetooth, and / or LPWAN, which take into account low-power communication, and may not be limited to the names mentioned above. For example, ZigBee technology may generate personal area networks (PANs) associated with low-power / low-power digital communication based on various specifications such as IEEE 802.15.4, and may be referred to by various names.

[0084] Figure 2 An example of a wireless device applying embodiments of the present disclosure is shown.

[0085] Reference Figure 2 The first wireless device 100 and the second wireless device 200 can transmit radio signals to / receive radio signals from external devices via various RATs (e.g., LTE and NR).

[0086] exist Figure 2 In this context, {first wireless device 100 and second wireless device 200} can correspond to Figure 1 At least one of {wireless devices 100a to 100f and BS 200}, {wireless devices 100a to 100f and wireless devices 100a to 100f} and / or {BS 200 and BS200}.

[0087] The first wireless device 100 may include at least one transceiver (e.g., transceiver 106), at least one processing chip (e.g., processing chip 101), and / or one or more antennas 108.

[0088] The processing chip 101 may include at least one processor (e.g., processor 102) and at least one memory (e.g., memory 104). Figure 2 The memory 104 is shown as being included in the processing chip 101. Alternatively and / or alternatively, the memory 104 may be located outside the processing chip 101.

[0089] Processor 102 can control memory 104 and / or transceiver 106, and can be configured to implement the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts described in this disclosure. For example, processor 102 can process information in memory 104 to generate first information / signal, and then transmit a radio signal including the first information / signal via transceiver 106. Processor 102 can receive a radio signal including a second information / signal via transceiver 106, and then store the information obtained by processing the second information / signal in memory 104.

[0090] Memory 104 may be operatively connected to processor 102. Memory 104 may store various types of information and / or instructions. Memory 104 may store software code 105 that implements instructions, which, when executed by processor 102, perform the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts disclosed in this disclosure. For example, software code 105 may implement instructions that, when executed by processor 102, perform the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts disclosed in this disclosure. For example, software code 105 may control processor 102 to execute one or more protocols. For example, software code 105 may control processor 102 to execute one or more layers of a wireless interface protocol.

[0091] In this document, processor 102 and memory 104 may be part of a communication modem / circuit / chip designed to implement RAT (e.g., LTE or NR). Transceiver 106 may be connected to processor 102 and transmit and / or receive radio signals via one or more antennas 108. Each transceiver 106 may include a transmitter and / or a receiver. Transceiver 106 may be used interchangeably with radio frequency (RF) units. In this disclosure, first wireless device 100 may represent a communication modem / circuit / chip.

[0092] The second wireless device 200 may include at least one transceiver (e.g., transceiver 206), at least one processing chip (e.g., processing chip 201), and / or one or more antennas 208.

[0093] The processing chip 201 may include at least one processor (e.g., processor 202) and at least one memory (e.g., memory 204). Figure 2The memory 204 is shown as being included in the processing chip 201. Alternatively and / or alternatively, the memory 204 may be located outside the processing chip 201.

[0094] Processor 202 can control memory 204 and / or transceiver 206, and can be configured to implement the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts described in this disclosure. For example, processor 202 can process information in memory 204 to generate third information / signal, and then transmit a radio signal including the third information / signal via transceiver 206. Processor 202 can receive a radio signal including a fourth information / signal via transceiver 106, and then store the information obtained by processing the fourth information / signal in memory 204.

[0095] Memory 204 may be operatively connected to processor 202. Memory 204 may store various types of information and / or instructions. Memory 204 may store software code 205 that implements instructions, which, when executed by processor 202, perform the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts disclosed in this disclosure. For example, software code 205 may implement instructions that, when executed by processor 202, perform the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts disclosed in this disclosure. For example, software code 205 may control processor 202 to execute one or more protocols. For example, software code 205 may control processor 202 to execute one or more layers of a wireless interface protocol.

[0096] In this document, processor 202 and memory 204 may be part of a communication modem / circuit / chip designed to implement RAT (e.g., LTE or NR). Transceiver 206 may be connected to processor 202 and transmit and / or receive radio signals via one or more antennas 208. Each transceiver 206 may include a transmitter and / or a receiver. Transceiver 206 may be used interchangeably with an RF unit. In this disclosure, second wireless device 200 may represent a communication modem / circuit / chip.

[0097] The hardware elements of wireless devices 100 and 200 will be described in more detail below. One or more protocol layers can be implemented by (but are not limited to) one or more processors 102 and 202. For example, one or more processors 102 and 202 can implement one or more layers (e.g., functional layers such as the Physical (PHY) layer, Medium Access Control (MAC) layer, Radio Link Control (RLC) layer, Packet Data Convergence Protocol (PDCP) layer, Radio Resource Control (RRC) layer, and Service Data Adaptation Protocol (SDAP) layer). One or more processors 102 and 202 can generate one or more Protocol Data Units (PDUs) and / or one or more Service Data Units (SDUs) according to the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts disclosed in this disclosure. One or more processors 102 and 202 can generate messages, control information, data, or information according to the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts disclosed in this disclosure. One or more processors 102 and 202 may generate signals (e.g., baseband signals) including PDUs, SDUs, messages, control information, data, or information, in accordance with the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts disclosed in this disclosure, and provide the generated signals to one or more transceivers 106 and 206. One or more processors 102 and 202 may receive signals (e.g., baseband signals) from one or more transceivers 106 and 206, and acquire PDUs, SDUs, messages, control information, data, or information, in accordance with the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts disclosed in this disclosure.

[0098] One or more processors 102 and 202 may be referred to as controllers, microcontrollers, microprocessors, or microcomputers. One or more processors 102 and 202 may be implemented by hardware, firmware, software, or a combination thereof. As an example, one or more application-specific integrated circuits (ASICs), one or more digital signal processors (DSPs), one or more digital signal processing devices (DSPDs), one or more programmable logic devices (PLDs), or one or more field-programmable gate arrays (FPGAs) may be included in one or more processors 102 and 202. The descriptions, functions, processes, suggestions, methods, and / or operation flowcharts disclosed in this disclosure may be implemented using firmware or software, and the firmware or software may be configured to include modules, processes, or functions. Firmware or software configured to perform the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts disclosed in this disclosure may be included in one or more processors 102 and 202 or stored in one or more memories 104 and 204 for being driven by one or more processors 102 and 202. The descriptions, functions, processes, suggestions, methods and / or operation flowcharts disclosed in this disclosure can be implemented using software or firmware in the form of code, commands and / or command sets.

[0099] One or more memories 104 and 204 may be connected to one or more processors 102 and 202 and store various types of data, signals, messages, information, programs, code, instructions, and / or commands. One or more memories 104 and 204 may be configured with read-only memory (ROM), random access memory (RAM), electrically erasable programmable read-only memory (EPROM), flash memory, hard disk drive, registers, flash memory, computer-readable storage media, and / or combinations thereof. One or more memories 104 and 204 may be located internally and / or externally to one or more processors 102 and 202. One or more memories 104 and 204 may be connected to one or more processors 102 and 202 via various technologies such as wired or wireless connections.

[0100] One or more transceivers 106 and 206 can transmit user data, control information, and / or radio signals / channels mentioned in the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts disclosed in this disclosure to one or more other devices. One or more transceivers 106 and 206 can receive user data, control information, and / or radio signals / channels mentioned in the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts disclosed in this disclosure from one or more other devices. For example, one or more transceivers 106 and 206 can be connected to one or more processors 102 and 202 and transmit and receive radio signals. For example, one or more processors 102 and 202 can perform control to enable one or more transceivers 106 and 206 to transmit user data, control information, or radio signals to one or more other devices. One or more processors 102 and 202 can perform control to enable one or more transceivers 106 and 206 to receive user data, control information, or radio signals from one or more other devices.

[0101] One or more transceivers 106 and 206 may be connected to one or more antennas 108 and 208, and one or more transceivers 106 and 206 may be configured to transmit and receive user data, control information, and / or radio signals / channels mentioned in the descriptions, functions, processes, suggestions, methods, and / or operation flowcharts disclosed herein via one or more antennas 108 and 208. In this disclosure, one or more antennas 108 and 208 may be multiple physical antennas or multiple logical antennas (e.g., antenna ports).

[0102] One or more transceivers 106 and 206 can convert received user data, control information, radio signals / channels, etc., from RF band signals into baseband signals so that the received user data, control information, radio signals / channels, etc., can be processed by one or more processors 102 and 202. One or more transceivers 106 and 206 can also convert user data, control information, radio signals / channels, etc., processed by one or more processors 102 and 202 from baseband signals into RF band signals. For this purpose, one or more transceivers 106 and 206 may include (analog) oscillators and / or filters. For example, one or more transceivers 106 and 206, under the control of one or more processors 102 and 202, can up-convert OFDM baseband signals to OFDM signals using their (analog) oscillators and / or filters, and transmit the up-converted OFDM signals at the carrier frequency. One or more transceivers 106 and 206 can receive OFDM signals at a carrier frequency and, under the control of one or more processors 102 and 202, downconvert the OFDM signals to OFDM baseband signals via their (analog) oscillators and / or filters.

[0103] In the implementation of this disclosure, the UE can operate as a transmitting device in the uplink (UL) and as a receiving device in the downlink (DL). In the implementation of this disclosure, the BS can operate as a receiving device in the UL and as a transmitting device in the DL. Hereinafter, for ease of description, it is primarily assumed that the first radio device 100 acts as the UE and the second radio device 200 acts as the BS. For example, a processor 102 connected to, installed on, or started in the first radio device 100 can be configured to perform UE actions according to the implementation of this disclosure, or to control the transceiver 106 to perform UE actions according to the implementation of this disclosure. A processor 202 connected to, installed on, or started in the second radio device 200 can be configured to perform BS actions according to the implementation of this disclosure, or to control the transceiver 206 to perform BS actions according to the implementation of this disclosure.

[0104] In this disclosure, BS is also referred to as Node B (NB), eNodeB (eNB), or gNB.

[0105] Figure 3 An example of a wireless device applying embodiments of the present disclosure is shown.

[0106] Based on use cases / services (see reference) Figure 1 Wireless devices can be implemented in various forms.

[0107] Reference Figure 3Wireless devices 100 and 200 can correspond to Figure 2 The wireless devices 100 and 200 can be configured with various elements, components, units / parts, and / or modules. For example, each of the wireless devices 100 and 200 may include a communication unit 110, a control unit 120, a memory unit 130, and an additional component 140. The communication unit 110 may include a communication circuit 112 and a transceiver 114. For example, the communication circuit 112 may include... Figure 2 One or more processors 102 and 202 and / or Figure 2 One or more memories 104 and 204. For example, transceiver 114 may include... Figure 2 One or more transceivers 106 and 206 and / or Figure 2 One or more antennas 108 and 208. Control unit 120 is electrically connected to communication unit 110, memory unit 130, and add-on components 140, and controls the overall operation of each of wireless devices 100 and 200. For example, control unit 120 can control the electromechanical operation of each of wireless devices 100 and 200 based on programs / code / commands / information stored in memory unit 130. Control unit 120 can transmit information stored in memory unit 130 to an external source (e.g., other communication devices) via communication unit 110 through a wireless / wired interface, or store information received from an external source (e.g., other communication devices) via communication unit 110 through a wireless / wired interface in memory unit 130.

[0108] The add-on component 140 can be configured in various ways depending on the type of wireless devices 100 and 200. For example, the add-on component 140 may include at least one of a power supply unit / battery, an input / output (I / O) unit (e.g., an audio I / O port, a video I / O port), a drive unit, and a computing unit. Wireless devices 100 and 200 can be used in (but are not limited to) robotic applications. Figure 1 100a), vehicles ( Figure 1 100b-1 and 100b-2), XR device ( Figure 1 100c), handheld device ( Figure 1 100d), home appliances ( Figure 1 100e), IoT devices ( Figure 1 100f), digital broadcasting terminals, holographic devices, public safety devices, MTC devices, medical devices, FinTech devices (or financial devices), security devices, climate / environment devices, AI servers / devices ( Figure 1 400), BS ( Figure 1Wireless devices 100 and 200 can be implemented in the form of network nodes, etc., depending on the usage example / service and can be used in mobile or fixed locations.

[0109] exist Figure 3 In wireless devices 100 and 200, the various elements, components, units / parts, and / or modules as a whole can be connected to each other via a wired interface, or at least a portion thereof can be wirelessly connected via communication unit 110. For example, in each of wireless devices 100 and 200, control unit 120 and communication unit 110 can be wired connected, and control unit 120 and first units (e.g., 130 and 140) can be wirelessly connected via communication unit 110. Each element, component, unit / part, and / or module within wireless devices 100 and 200 may also include one or more elements. For example, control unit 120 may be configured by a collection of one or more processors. As an example, control unit 120 may be configured by a collection of communication control processors, application processors (APs), electronic control units (ECUs), graphics processing units, and memory control processors. As another example, memory unit 130 may be configured by RAM, DRAM, ROM, flash memory, volatile memory, non-volatile memory, and / or combinations thereof.

[0110] Figure 4 This is a structural diagram of the next-generation mobile communication network.

[0111] The 5GC (5G core) may include various components including Access and Mobility Management Functions (AMF) 410, Session Management Functions (SMF) 420, Policy Control Functions (PCF) 430, User Plane Functions (UPF) 44, Application Functions (AF) 450, Unified Data Management (UDM) data network 460, and Non-3GPP (3rd Generation Partnership Project) Interoperability Functions (N3IWF) 490, a portion of which are in Figure 4 As shown in the image.

[0112] UE 100 connects to the data network via UPF 440 through a next-generation radio access network (NG-RAN) including gNB 20.

[0113] Data services can be provided to UE 100 even through untrusted non-3GPP access (e.g., wireless local area network (WLAN)). To connect non-3GPP access to the core network, an N3IWF 490 can be deployed.

[0114] The N3IWF 490 shown performs the function of managing interoperability between non-3GPP access and 5G systems. When UE 100 connects to a non-3GPP access (e.g., WiFi known as IEEE 801.11), UE 100 can connect to the 5G system through the N3IWF 490. The N3IWF 490 performs control signaling with the AMF 410 and connects to the UPF440 through the N3 interface for data transmission.

[0115] The AMF 410 shown can manage access and mobility in 5G systems. The AMF 410 can perform functions related to managing Non-Access Stratum (NAS) security. The AMF 410 can also perform functions related to handling mobility in idle states.

[0116] The UPF 440 shown is a gateway through which user data is sent / received. The UPF 440 can perform all or part of the user plane functions of a Serving Gateway (S-GW) and Packet Data Network Gateway (P-GW) for 4G mobile communications.

[0117] The UPF 440 serves as the boundary point between the Next Generation Radio Access Network (NG-RAN) and the core network, and maintains the data path between the gNB20 and SMF 420. Additionally, the UPF 440 acts as a mobility anchor point when the UE 100 moves within an area served by the gNB 20. The UPF 440 can perform PDU disposal functions. For mobility within the NG-RAN (defined after 3GPP Release 15), the UPF 440 can route packets. Furthermore, the UPF 440 can also serve as an anchor point for mobility with another 3GPP network (RANs defined before 3GPP Release 15, such as Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (UTRAN), Evolved (E)-UTRAN, or Global System for Mobile Communications (GERAN) / Enhanced Data Rate Global Evolution (EDGE) RAN). The UPF 440 can correspond to an endpoint of the data interface toward the data network.

[0118] The PCF 430 shown is a node that controls the operator's policies.

[0119] The AF 450 shown is a server used to provide various services to UE 100.

[0120] The UDM 460 shown is a server for managing subscriber information (e.g., a Home Subscriber Server (HSS) for 4G mobile communications). The UDM 460 stores and manages subscriber information in a Unified Data Repository (UDR).

[0121] The SMF 420 shown can perform the function of allocating Internet Protocol (IP) addresses to UEs. Additionally, the SMF can control Protocol Data Unit (PDU) sessions.

[0122] For reference, the reference numerals for AMF(410), SMF(420), PCF(430), UPF(440), AF(450), UDM(460), N3IWF(490), gNB(20) or UE(100) may be omitted in the following text.

[0123] Fifth-generation mobile communications support multiple parameter sets (e.g., multiple values ​​for subcarrier spacing (SCS)) to facilitate various services. For example, a SCS of 15 kHz supports wide-area coverage in traditional cellular bands. A SCS of 30 kHz / 60 kHz supports dense urban areas, lower latency, and wider carrier bandwidth. A SCS of 60 kHz or higher supports bandwidths greater than 24.25 GHz to overcome phase noise.

[0124] Figure 5 This is an example diagram illustrating the predicted structure of next-generation mobile communications from the perspective of nodes.

[0125] Reference Figure 5 The UE connects to the data network (DN) via the next-generation RAN (Radio Access Network).

[0126] Figure 5 The Control Plane Function (CPF) node shown can perform all or part of the Mobility Management Entity (MME) functions of fourth-generation mobile communications, as well as all or part of the control plane functions of the Serving Gateway (S-GW) and PDN (Packet Data Network)-Gateway (P-GW) of fourth-generation mobile communications. CPF nodes include Access and Mobility Management Function (AMF) nodes and Session Management Function (SMF) nodes.

[0127] The User Plane Function (UPF) node shown in the diagram is a gateway through which user data is sent and received. UPF nodes can perform all or part of the user plane functions of the S-GW and P-GW in fourth-generation mobile communications.

[0128] Figure 5 The Policy Control Function (PCF) node shown is configured to control the policies of the service provider.

[0129] The Application Function (AF) node shown is a server that provides various services to the UE.

[0130] As shown, a Unified Data Management (UDM) node is a server that manages subscriber information, such as the Home Subscriber Server (HSS) in 4G mobile communications. UDM nodes store and manage subscriber information in a Unified Data Repository (UDR).

[0131] The Authentication Server Function (AUSF) node, as shown, authenticates and manages the UE.

[0132] The Network Slice Selection Function (NSSF) node shown refers to the node that performs network slicing as described below.

[0133] The Network Open Function (NEF) shown is a node used to provide mechanisms to securely open the services and functions of the 5G core. For example, NEF open functions and events securely provide information from external applications to the 3GPP network, translate internal / external information, provide control plane parameters, and manage packet flow descriptions (PFDs).

[0134] Figure 5 The reference point shown is described below.

[0135] N1 represents the reference point between the UE and the AMF.

[0136] N2 represents the reference point between NG-RAN and AMF.

[0137] N3 represents the reference point between NG-RAN and UPF.

[0138] N4 represents the reference point between the SMF and UPF.

[0139] N5 represents the reference point between PCF and AF.

[0140] N6 represents the reference point between UPF and DN.

[0141] N7 represents the reference point between the SMF and PCF.

[0142] N8 represents the reference point between UDM and AMF.

[0143] N9 represents the reference point between UPFs.

[0144] N10 represents the reference point between UDM and SMF.

[0145] N11 represents the reference point between AMF and SMF.

[0146] N12 represents the reference point between AMF and AUSF.

[0147] N13 represents the reference point between UDM and AUSF.

[0148] N14 represents the reference point between AMFs.

[0149] N15 represents the reference point between the PCF and AMF in non-roaming scenarios, and the reference point between the AMF and PCF when accessing the network in roaming scenarios.

[0150] N16 represents the reference point between SMFs.

[0151] N22 represents the reference point between AMF and NSSF.

[0152] N30 represents the reference point between PCF and NEF.

[0153] N33 represents the reference point between AF and NEF.

[0154] exist Figure 5 In addition to the operator, third-party AFs can connect to 5GC through the network exposure function (NEF).

[0155] II. Technologies and processes related to the disclosure in this specification

[0156] The techniques and processes related to the disclosure herein are described below. Additionally, examples of the problems that the disclosure in this specification aims to solve may also be described below.

[0157] The following describes examples of the problems that this specification aims to solve.

[0158] Methods for supporting MBS (Multicast Service) in 5GS are discussed. For example, architectural enhancements for 5G MBS are discussed. For instance, methods for supporting MBS in 5GS to achieve the following objectives are discussed.

[0159] The goal of discussing how to support MBS in 5GS can be to identify and evaluate potential enhancements in the 5G system architecture to provide MBS services that can be used for various vertical businesses. Examples of objectives for schemes supporting MBS in 5GS are as follows:

[0160] - To support multicast / broadcast services, a framework can be defined that includes functional divisions between (R)AN and CN. For example, multicast / broadcast services can include self-organizing multicast / broadcast streams, transparent IPv4 / IPv6 multicast delivery, IPTV, over-the-air software delivery, group communication and broadcast / multicast Internet of Things (IoT) applications, V2X applications, public safety, etc.

[0161] - It can support different levels of service (e.g., transport-only mode and full service mode).

[0162] - Enable flexible (i.e., distributed and centralized) network deployment and operation (e.g., CP-UP separation).

[0163] - Handle whether QoS and PCC rules apply to multicast / broadcast services and how the relevant QoS and PCC rules apply to multicast / broadcast services.

[0164] - Support use cases and requirements for public safety (e.g., service continuity).

[0165] In NG-RAN, methods for supporting MBS in 5GS can be discussed based on NR, focusing on radio access technologies. Supporting UEs using or moving to access services that do not support multicast / broadcast can be considered.

[0166] Regarding MBS in 5GS, issues such as those illustrated in the following examples are discussed. For instance, when performing the conversion between NR / 5GC and E-UTRAN / EPC, methods for minimizing disruption to public safety services are discussed.

[0167] The specific explanation of this issue is as follows. As mentioned earlier, in the advanced MBS architecture, NRs based solely on NG-RAN (e.g., NG-RAN connected to 5GC) are considered RATs. That is to say, methods for supporting MBS via E-UTRA connected to 5GC have not yet been discussed.

[0168] This issue can be addressed, along with public safety services, for the deployment / deployment of Evolved Multimedia Broadcast and Multicast Services (eMBMS) based on Evolved Universal Terrestrial Radio Access Network (E-UTRAN) / Evolved Packet Core (EPC) and PLMNs with 5G MBS via NR / 5GC.

[0169] There may be situations where a UE receiving service delivered via multicast through NR / 5GC moves to E-UTRAN / EPC and uses eMBMS. Conversely, the opposite may also be true. How to handle the service via both EPC and 5GC, and how to handle mobility between RATs (multiple RATs), should be considered.

[0170] Therefore, solutions to this problem concerning public safety services can satisfy the following:

[0171] - For UEs residing on E-UTRAN (eMBMS) and UEs connected via NR to 5GC (via 5G MBS solution), the AF (e.g., Public Safety Group Communication System (GCS) Application Server (AS)) can provide the same multicast / broadcast services.

[0172] - Defines the procedure for a UE to perform inter-CN type mobility between EPC and 5GC during a multicast session.

[0173] The goal of solving this problem could be to minimize service interruptions and packet loss, and to achieve reconnection as quickly as possible during transitions between various systems.

[0174] Various solutions related to multicast transport are defined in existing technical documents (e.g., 3GPP TR 23.757v1.0.0). For example, integrated multicast and unicast transport in Solution #3: Part 6.3, multicast session management with dedicated MBS network functions in Solution #4: Part 6.4, and multicast service initiation in Solution #6: Part 6.6 are defined.

[0175] However, according to existing technology, multicast transmission of MBS is not supported in EPS. Therefore, when a UE receives MBS services in 5GS using multicast, when the UE moves from 5GS to EPS, it is necessary to support a method for the UE to continue receiving the corresponding MBS services in EPS using unicast.

[0176] Multicast transmission of MBS is not supported in EPS. Accordingly, when a UE receives MBS services in 5GS using a multicast method, it can continuously receive the corresponding MBS services in a non-multicast method (i.e., the broadcast method supported by EPS MBMS) when moving to EPS. MBS service continuity from 5GS to EPS can be achieved through the service layer.

[0177] Multicast transmission can be interpreted as sending services using the path / tunnel / resources established for the multicast group (assuming shared resources are used) instead of through service transmissions via a PDU session established by the UE. In the latter case, shared resources can be used in both the core network and radio segments, or only in the core network segment.

[0178] To support MBS service continuity from 5GS to EPS using the aforementioned service layer, solutions such as the following examples are discussed. The solutions described in the following examples will be referred to as "service layer continuity" between E-UTRAN / EPC MBMS and NR / 5GC MBS.

[0179] First, refer to Figure 6 The example will describe an example of a system architecture for interoperability (e.g., interoperability in the service layer) between 5G MBS and E-UTRAN / EPC.

[0180] Figure 6 An example of a system architecture for interoperability between 5G MBS and E-UTRAN / EPC is shown.

[0181] Figure 6 An example of a system architecture is shown that supports interoperability between E-UTRAN / EPC MBMS and 5GMBS in the service layer by co-locating BM-SC and MSF functions.

[0182] BM-SC+MSF can expose a common reference point to application functions. For application functions, TMGI is used as an identifier. TMGI can also be used as an identifier transmitted over E-UTRAN / EPC. For 5G MBS, the principle of TMGI and MBS context ID mapping can be used.

[0183] With interoperability support at the service layer, the TMGI / MBS context ID can always be set for the UE, regardless of whether the UE discovers and subscribes to the MBMS / MBS service via E-UTRAN or NR.

[0184] When the UE is camped on NR, the UE can use the MBS context ID to configure the MBS session context.

[0185] When the UE is camped on E-UTRAN, the UE can use the procedure for receiving MBMS for TMGI.

[0186] In the case of mobility, lossless mechanisms can be performed in the service layer between the UE and BM-SC+MSF.

[0187] Mobility-related processes may not be affected by the examples of the solutions described above.

[0188] When the UE moves to E-UTRAN / EPC, it can begin the process of receiving MBMS services for TMGI. In the case of mobility, lossless mechanisms can be performed at the service layer between the UE and BM-SC+MSF.

[0189] When the UE moves to NR / 5GC, it can initiate a procedure to receive 5G MBS transmissions for TMGI. In the case of mobility, a lossless mechanism can be performed at the service layer between the UE and BM-SC+MSF.

[0190] BM-SC+MSF can handle TMGI on two separate systems. BM-SC+MSF can handle potential retransmissions at the service layer.

[0191] The UE can switch between 5G MBS transmissions used for the same TMGI as MBMS reception in E-UTRAN.

[0192] By performing multicast communication in 5GS, terminals receiving multicast services (e.g., MBS services) can be moved to an evolved packet system (EPS). The terminals can then receive MBS services received in 5GS via broadcast communication supported by the Multimedia Broadcast & Multicast Service (MBMS) methods in EPS.

[0193] On the other hand, according to existing technology, even after a UE moves from 5GS to EPS, 5GS does not remove the UE's existing multicast context (or MBS context). As a result, even if the terminal no longer performs multicast communication in 5GS, there is a problem that the 5G core network and base stations (e.g., Next Generation Radio Access Network (NG-RAN)) continue to strive to provide the terminal with services related to multicast communication.

[0194] For example, even if the UE has left the 5GS, the base station may still perform unnecessary operations (such as continuously receiving the UE's multicast services from the User Plane Function (UPF)).

[0195] Therefore, in this specification, when a UE moves to EPS after receiving multicast services in 5GS, operations such as sending a message to the 5G network indicating that the UE has left the multicast service are proposed to remove the MBS / multicast context existing for that UE in 5GS. An example of why 5GS should remove the UE's existing MBS / multicast context is as follows: This is because there is a problem: if 5GS does not remove the MBS / multicast context, even if the UE no longer receives multicast services, the 5G core network and NG-RAN must still strive to provide multicast services to the UE. Even if the UE is the only UE that NG-RAN should serve for multicast services, unnecessary operations may continue even after the UE leaves to EPS, potentially leading to the UE continuing to receive multicast services from UPF.

[0196] When a UE moves to E-UTRAN / EPC, it can begin the process of receiving MBMS services for TMGI. At this time, in order to remove the UE's 5G MBS context from the 5G CN (core network), for example, the UE may need to perform a process of leaving the multicast service.

[0197] When a UE moves to NR / 5GC, in order to receive 5G MBS transmissions for TMGI, the UE may need to trigger a process for establishing / modifying the multicast context and multicast stream via a PDU session modification procedure.

[0198] Mechanisms to reduce, eliminate, or recover packet loss can be implemented at the service layer between the UE and BM-SC+MBSF and / or at the application layer between the UE's application functions and the application client.

[0199] In the following text, combined with Figures 7a to 7c This section will describe an example of the process by which a UE leaves the multicast service through a PDU session modification procedure.

[0200] The following figures are used to explain specific examples of this specification. Since the names of specific devices or signals / messages / fields described in the figures are provided as examples, the technical features of this specification are not limited to the specific names used in the following figures.

[0201] Figures 7a to 7c An example of the PDU session modification process for multicast departure is shown.

[0202] 1) A UE can join one or more multicast services. At any time, a UE can decide to leave a multicast service.

[0203] Alternative Option 1: User plane signaling. Steps 2) and 3) below are examples of operations performed under Alternative Option 1:

[0204] 2) When a UE wants to leave one or more multicast services, the UE can send a user plane message (e.g., IGMP leave). The user plane message may include information related to the multicast service to be left (e.g., multicast address).

[0205] 3) Upon receiving a departure message, the UPF can perform an operation to notify the SMF. When the SMF receives the notification from the UPF, the SMF can initiate a PDU session modification procedure.

[0206] Alternative Solution 2: Control Plane Signaling. Steps 4) and 5) below are examples of operations performed under Alternative Solution 2:

[0207] 4) When a UE wants to leave one or more multicast services, the UE can send a PDU session modification request message to the AMF. The PDU session modification request message can include information related to the multicast service to be left (e.g., multicast address, etc.).

[0208] 5) AMF can call Nsmf_PDUSession_UpdateSMContext(SM context ID, N1 SM container (including PDU session modification request message containing related multicast service information) (e.g., departure indication, multicast service ID, etc.)).

[0209] When a UE receives multicast through a unicast PDU session, the following steps 6) to 14) can be applied:

[0210] When the SMF and MB-SMF are different, and when it is not necessary to distribute multicast data to other UEs within a PDU session (e.g., UEs served by the UPF) via unicast distribution, steps 6) to 8 below can be applied.

[0211] In this scenario, a shared tunnel between the UPF and MB-UPF may not be necessary.

[0212] 6) The SMF can send a request message [including multicast context / group ID] to the MB-SMF to terminate multicast distribution.

[0213] 7) Based on the information received in step 6), MB-SMF can update the multicast session context identified by the multicast context / group ID and configure MB-UPF so that MB-UPF no longer distributes multicast data to UPF.

[0214] 8) In response to step 6), the MB-SMF can acknowledge the multicast distribution termination request to the SMF. For example, the MB-SMF can send a multicast distribution release response message to the SMF.

[0215] 9) In order to terminate multicast data distribution via unicast PDU session and when performing steps 6) to 8), in order to also release the resources for receiving multicast data, SMF can reconfigure UPF.

[0216] The SMF can update the UE due to leaving the process. Additionally, when a dedicated QoS stream is used for unicast transmission of multicast data, the SMF can update the RAN to remove multicast QoS stream related information (e.g., mapped unicast QoS stream information) from the associated unicast PDU session.

[0217] 10) The SMF uses the Namf_Communication_N1N2Message (N2 SM message) transmission service. The SMF can request the AMF to notify the RAN node to release the QoS stream previously used to send multicast data. The N2 SM message can include unicast QoS stream information.

[0218] 11) A session modification request can be sent to the RAN. An N1 SM container (including PDU session modification command messages) can be provided to the UE.

[0219] 12) The RAN can perform necessary radio resource modifications.

[0220] 13) The RAN can send a session modification response message to the AMF.

[0221] 14) The AMF can pass the session modification response message received in step 13) to the SMF through the Nsmf_PDUSession_UpdateSMContext service.

[0222] When the UE receives multicast via multicast distribution, steps 15) to 25) can be applied.

[0223] 15) The SMF uses Namf_Communication_N1N2Message(N1 SM container(PDU session modification command(PDU session ID, multicast information([multicast context ID], multicast address))), N2 SM information) to deliver the service, requesting the AMF to notify the RAN node UE that it has left the indicated multicast group.

[0224] N2 SM information may include multicast stream information (multicast QoS stream ID and related QoS information) and the multicast service identifier that the UE intends to leave.

[0225] For reference, this information can also be deleted in step 15) when the mapped unicast QoS stream information, the association between unicast QoS streams and multicast QoS streams, and the unicast information of the N1SM container (i.e., the QoS rules for unicast streams) are added for multicast distribution.

[0226] 16) The AMF can send a session modification request message to the RAN. The session modification request message may include the multicast service ID and multicast stream information. The RAN can provide the UE with an N1 SM container (including PDU session modification commands).

[0227] The RAN can use the multicast service ID to remove the UE from the multicast session context. Additionally, it can remove associated multicast QoS streams and associated unicast QoS stream information from the UE context.

[0228] 17) The RAN can perform necessary radio resource modifications.

[0229] If the UE is the last UE to leave the indicated multicast service, the RAN releases the associated shared downlink tunnel between the RAN and MB-UPF, and steps 18) through 22) can be applied.

[0230] 18) The RAN node selects the AMF to reach the MB-SMF. The RAN node can send a multicast user plane distribution release request message (including MB-SMF ID, multicast context / group ID and downlink tunnel information) to the AMF.

[0231] 19) The AMF can send a multicast user plane distribution release request message (including MB-SMFID, multicast context / group ID and downlink tunnel information) to the MB-SMF.

[0232] 20) Regarding unicast transmission of multicast distribution sessions, MB-SMF can update the multicast session context identified by the multicast context ID and request MB-UPF to release the corresponding shared downlink tunnel resources.

[0233] 21) The SMF can send a multicast distribution session release response to the AMF.

[0234] 22) The AMF can deliver a multicast distribution session release response to the RAN node.

[0235] 23) In relation to multicast transmission in a multicast distribution session, after receiving a multicast distribution release response, the RAN may send a leave message (e.g., including MLD / IGMP leave information) to the MB-UPF to stop sending MBS data to that RAN node.

[0236] 24) The RAN can send a session modification response to the AMF.

[0237] 25) The AMF can pass the session modification response received in step 24) to the SMF through the Nsmf_PDUSession_UpdateSMContext service.

[0238] The operation of a UE sending a leave message from multicast service to the 5G network can only be used in dual-registration mode, in which the UE can move between systems and register with both EPS and 5GS. Furthermore, even in dual-registration mode, the UE can only send a leave message to the 5G network if it remains within 5GS coverage after moving from 5GS to EPS. In contrast, in single-registration mode, the UE cannot send a leave message to the 5G network after moving to EPS.

[0239] Methods for supporting MBS service continuity from 5GS to EPS through the service layer are discussed. However, in the prior art, when a UE receives multicast service in 5GS and then moves to EPS, there is no proposal to remove the MBS / multicast context existing in 5GS for the UE.

[0240] When supporting continuity of 5GS multicast transmission to EPS MBMS through the service layer, the existing MBS / multicast context of the UE needs to be removed in 5GS. Regardless of the EPS / 5GS interoperability method (e.g., single registration mode or dual registration mode), the removal of the MBS / multicast context must be performed in all methods.

[0241] III. Disclosure of this specification

[0242] The disclosures described later in this specification can be implemented in one or more combinations (e.g., combinations including at least one of the contents described below). Each of the figures represents an embodiment of this disclosure, but the embodiments in the figures can be implemented in combination with each other.

[0243] The methods described in this specification may consist of a combination of one or more operations / configurations / steps described below. The methods described below may be performed or used in combination or complementarily.

[0244] This specification discloses methods for supporting multicast communication when a UE moves to EPS while performing multicast communication in 5GS, through various examples. For example, when a UE moves from 5GS to EPS, the UE's 5GS multicast transmission can support service continuity based on the UE's EPS MBMS communication through the service layer. In the various examples disclosed in this specification, operations for removing the UE's existing MBS / multicast context (MBS context and / or multicast context) after the UE moves from 5GS to EPS are described. The operation of removing the UE's existing MBS / multicast context (MBS context and / or multicast context) after the UE moves from 5GS to EPS consists of a combination of one or more operations / configurations / steps from the various examples below.

[0245] In the disclosure of this specification, MBS may be interpreted as the same as MBMS (Multimedia Broadcasting / Multicast Service).

[0246] In this specification, MBS sessions can be interpreted as including MBS multicast sessions and MBS broadcast sessions. In this specification, MBS data and / or MBS services can be interpreted as including MBS multicast data and / or MBS multicast services as well as MBS broadcast data and / or MBS broadcast services.

[0247] In this specification, MBS session and MB session are used interchangeably. In other words, in this specification, MBS session and MB session can be used as terms with the same meaning.

[0248] In this specification, the terms "session" and "service" are used interchangeably. In other words, in this specification, "session" and "service" can be used as terms with the same meaning.

[0249] In the disclosure of this specification, multicast service, multicast session, and multicast group are used interchangeably. In other words, in the disclosure of this specification, multicast service, multicast session, and multicast group can be used as terms with the same meaning.

[0250] In the disclosure of this specification, NG-RAN may refer to gNB, and may include both gNB and next-generation eNB (ng-eNB).

[0251] To support MBS in Evolved General Packet Radio Service (GPRS) and Evolved Packet System (EPS), references can be made to TS 23.246V15.1.0, TS 23.468V15.1.0, TS 26.348V16.0.0, etc., and the following will primarily describe the contents disclosed in this specification.

[0252] For reference, in the following examples, the operation of removing the UE's existing MBS / multicast context in 5GS can be interpreted as the operation of removing / deleting the UE from the multicast session.

[0253] The operations presented in the examples in this specification can be applied to single-registration and dual-registration modes in the EPS / 5GS interoperability scheme, or only one of the two modes. For reference, in single-registration mode, there can be one active mobility state at a given time. For example, when the UE is in single-registration mode, it can be in 5GCNAS mode or EPC NAS mode. In dual-registration mode, the UE can maintain independent registration for 5GC and EPC. For example, in dual-registration mode, the UE can independently maintain a 5G-Globally Unique Temporary Identifier (GUTI) and an EPC-GUTI.

[0254] First, refer to Figure 8a and Figure 8b This section will describe an example of the process used to configure and create multicast sessions.

[0255] The following figures are used to explain specific examples of this specification. Since the names of specific devices or signals / messages / fields described in the figures are provided as examples, the technical features of this specification are not limited to the specific names used in the following figures.

[0256] Figure 8a and Figure 8b An example of the process for generating a multicast session is shown.

[0257] 1) The AF can request a TMGI from the 5GC, which is an identifier used to identify a new multicast session. The MB-SMF can then allocate the TMGI and provide it to the AF. The TMGI allocation process between the AF and the MB-SMF can be performed via NEF / MBSF. Here, MBSF stands for Multicast-Broadcast Service Function.

[0258] 2) The AF can perform service announcements to the UE. Through this, the AF can provide the UE with multicast session-related information, including TMGI (i.e., MBS session ID information).

[0259] 3) The AF can send an MBS session request message (i.e., MBS session ID information) including multicast session related information (such as TMGI) and QoS requirements to the NEF / MBSF in order to configure the multicast session as 5GS.

[0260] 4) NEF / MBSF can search for MB-SMFs that will serve multicast sessions. NEF / MBSF can perform this MB-SMF discovery through the Network Storage Function (NRF). NEF / MBSF can select an MB-SMF and send an MBS Session Creation Request message to the selected MB-SMF to configure the multicast session.

[0261] 5) The MB-SMF can send a message to the MB-UPF requesting the reservation of user plane resources for serving multicast sessions (e.g., a session request message).

[0262] 6) MB-UPF can send messages (e.g., session response messages) in response to MB-SMF requests.

[0263] 7) MB-SMF can send MBS session creation response messages to NEF / MBSF.

[0264] 8) NEF / MBSF can send MBS session response messages to AF.

[0265] (9a-9b) To enable a UE to join a multicast session, the UE can send a PDU session modification request message, which includes a join request, to the AMF. The PDU session modification request message can be sent from the AMF to the SMF. The join request may include the TMGI (i.e., MBS session ID information), which is identification information used to identify the multicast session.

[0266] 10) The SMF can check whether the UE can receive the service of the multicast session that the UE requests to join.

[0267] 11) If the SMF does not have the context / information of the multicast session it requested to join, the SMF can obtain the context / information about the multicast session from the MB-SMF. The SMF can use the NRF to search for the MB-SMF serving the multicast session.

[0268] 12) The MB-SMF sends N1 SM container N2 SM information to the AMF, which includes multicast QoS flow information for multicast sessions and PDU session modification command messages. For example, the SMF can send an Nsmf_PDUSession_UpdateSMContext response message to the AMF (including N2 SM information, which includes multicast QoS flow information for multicast sessions and PDU session modification command messages).

[0269] 13) The AMF can send information received from the MB-SMF to the NG-RAN (e.g., N2 SM information for multicast QoS flow information for multicast sessions and / or PDU session modification command messages).

[0270] (14a-14b) NG-RAN can send MBS session request messages to MB-SMF through AMF. For example, NG-RAN can send an N2 message containing an MBS session request message to AMF, and AMF can send an Nmbsmf_Reception request message containing an MBS session request message to MB-SMF.

[0271] 14c) MB-SMF can configure MB-UPF to send multicast session data using the 5GC shared MBS service delivery method.

[0272] 14d~14e) MB-SMF can send MBS session response messages (e.g. Nmbsmf_Reception response messages) to NG-RAN via AMF.

[0273] 15) The NG-RAN can receive AN-specific signaling (i.e., RRC message) and send the AN-specific signaling to the UE to generate radio resources for the multicast session. At this time, the NG-RAN can send the PDU session modification command message received in step 13 to the UE.

[0274] 16) NG-RAN can send a response message (e.g., an N2 message) to the AMF in response to messages received from the SMF via the AMF. For example, the response message may include a response message for a PDU session modification command.

[0275] 17) The AMF can deliver messages sent by the NG-RAN to the SMF. For example, the AMF can send an Nsmf_PDUSession_UpdateSMContext response message to the SMF that includes messages sent by the NG-RAN (e.g., a message that includes a response message to a PDU session modification command).

[0276] 18) The SMF can send response messages to the AMF (e.g., the Nsmf_PDUSession_UpdateSMContext response message).

[0277] In the following description, the disclosure of this specification will be described with reference to the first through fourth examples disclosed herein. The first through fourth examples described below can be combined to implement this specification.

[0278] 1. First example of disclosure in this specification

[0279] In the first example disclosed in this specification, an example of the operation of the AMF to remove the MBS / multicast context existing for a UE that has moved from the 5GS to the EPF will be described. The methods described in the example of the first example disclosed in this specification can be applied to procedures such as MBS session establishment using flexible radio resources. However, this is merely an example, and the methods described in the first example disclosed in this specification can be used in situations other than MBS session establishment using flexible radio resources.

[0280] First, refer to Figure 9 The examples will describe examples of session departure processes for various operations that can be applied to the first example disclosed herein.

[0281] The following figures are used to explain specific examples of this specification. Since the names of specific devices or signals / messages / fields described in the figures are provided as examples, the technical features of this specification are not limited to the specific names used in the following figures.

[0282] Figure 9 An example of a session exit process is shown.

[0283] For reference, according to Figure 9 The example session departure procedure can be based on the session departure procedure of TR 23.757v1.0.0. part 6.2.2.5.

[0284] The Session Leave procedure can be used to notify the 3GPP network that an MB session of interest to the UE has been terminated. During the Session Leave procedure, the distribution area of ​​the multicast session can be adjusted if necessary.

[0285] 0) At the application level, subliminal decisions regarding whether a UE should leave the group can be performed. For example, the UE's application layer can determine whether the UE should leave the MB session group.

[0286] 1) There may be a media stream before the UE leaves. In this case, the UE can receive the media via point-to-multipoint (PTM) or point-to-point (PTP).

[0287] 2) The UE can send an uplink (UL) NAS MB session leave request message (including a Temporary Mobile Group Identifier (TMGI)) to the AMF. The AMF can remove the TMGI from the UE context.

[0288] 3) The AMF can generate a DL NAS MB session departure response message and piggyback it on the N2 MB session departure message (including the Next Generation Application Protocol (NGAP) ID). NG-RAN can remove the TMGI from the NG-RAN UE context.

[0289] 4) NG-RAN can adjust PTM / PTP transmission if needed.

[0290] 5) If the UE is the last UE to use the MB session in this NG-RAN (i.e., the TMGI is no longer stored in the UE context of the NG-RAN node), then in order to stop the media streaming of this NG-RAN node, the NG-RAN can send a leave message (including the LL MC address (lower-layer multicast IP address)). The NG-RAN can then delete the MB session context.

[0291] 6) If the UE is the last UE that was part of the MB session in the AMF, then in order to unsubscribe from the MB session, the AMF can send an MB session release request message (including TMGI and AMF ID) to the MB-SMF. The MB-SMF can remove the AMF from the MB-SMF MB session context.

[0292] For a UE, if 5GC Individual MBS Service Delivery is applied, the AMF can instruct the SMF to stop 5GC Individual MBS Service Delivery for the MBS session within the PDU session. The SMF can instruct the PDU Session Anchor (PSA)-UPF to stop delivering MBS data streams to the PDU session. If the UE is the last UE to apply 5GC Individual MBS Service Delivery in the PSA-UPF, the SMF can instruct the PSA-UPF to leave the MB-UPF multicast tree.

[0293] 7) The MB-SMF can send an MB session release response message to the AMF. The AMF can delete the MB session context.

[0294] The AMF can identify that the UE has moved from 5GS to EPS. When the AMF identifies that the UE has moved from 5GS to EPS (for example, the AMF can identify this based on the operation of the AMF receiving a relocation completion notification message from the MME during a 5GS to EPS handover using the N26 interface, or receiving a context acknowledgment message from the MME during 5GS to EPS idle mode mobility using the N26 interface), the AMF can perform one or more of the following operations (Examples 1 to 3 described below). Additionally, even when the AMF identifies that the UE must move to EPS, the AMF can perform one or more of the following examples (Examples 1 to 3 described below):

[0295] Example 1) The AMF can provide the NG-RAN serving the UE with information that the UE no longer needs to receive multicast services. This information may include information identifying the multicast session in which the UE is receiving services (e.g., TMGI, MBS session ID, etc.). This information can be interpreted as instructing the NG-RAN to remove information about the UE from the context of the managed multicast session. In other words, when the NG-RAN receives this information from the AMF, it can remove the information about the UE from the context of the managed multicast session. Furthermore, this information can also be interpreted as instructing the UE to leave the multicast session.

[0296] This information can be sent by including it in a message sent by the AMF to the NG-RAN (e.g., the UE context release command message sent by the AMF to the NG-RAND during a 5GS to EPS handover using the N26 interface), or it can be included in a separate message and / or a new message (e.g., Figure 9 The example is described in step 3 of the N2 MB session departure message and is sent.

[0297] Example 2) AMF can execute Figure 9 The operations described in steps 6 and 7 of the example. This could mean that the UE (e.g., the UE to be leaving) is the last UE among those receiving multicast session services through the AMF. In this case, the operation performed by the AMF can be interpreted as notifying the MB-SMF that it no longer needs to serve the multicast session. For reference, "UE receiving multicast session services" can be interpreted as a UE managed and / or served by the AMF.

[0298] Example 3) The AMF may remove information about the UE from the context that is managed to serve the multicast session. For example, the AMF may remove information about the UE from the context that is managed to provide services related to the multicast session (e.g., multicast session-related context). The context may be the MB session context.

[0299] According to Example 1) above, the AMF may send information to the NG-RAN that the UE no longer needs to receive multicast services. As a reference, the information that the UE no longer needs to receive multicast services may include information identifying the multicast session for which the UE has received services (e.g., TMGI, MBS session ID, etc.). When the NG-RAN receives the information in Example 1) (e.g., the information that the UE no longer needs to receive multicast services) from the AMF, the NG-RAN may perform one or more of the following examples:

[0300] a) The NG-RAN may remove information about the UE from the context that is managed to serve the multicast session (e.g., context related to the multicast session). The context may be the MB session context. If the UE is the last UE among the UEs receiving the multicast session service (e.g., when the NG-RAN manages / serves the last UE among the UEs for the multicast session), the NG-RAN may additionally perform an operation to release the radio resources for the multicast session.

[0301] b) The NG-RAN may perform the operation of step 5) according to Figure 9 the example of. For example, if the UE is the last UE among the UEs receiving the multicast session service, the NG-RAN may perform an operation of no longer receiving traffic for the multicast session from the 5G core network (e.g., UPF or MB-UPF).

[0302] 2. Second example disclosed in this specification

[0303] In the second example disclosed in this specification, an example of the operation of the SMF removing the MBS / multicast context existing for the UE that has moved from 5GS to EPS will be described. The method described in the second example disclosed in this specification may be applied to processes such as integrated multicast and unicast transmission. However, this is only an example, and the method described in the second example disclosed in this specification may be used in cases other than processes such as integrated multicast and unicast transmission.

[0304] The SMF can identify that the UE has moved to EPS. For example, the SMF can identify that the UE has moved from 5GS to EPS based on the following operations: using step 2a of the 5GS to EPS handover procedure via the N26 interface (e.g., the SMF receives an Nsmf_PDUSession_ContextRequest message from the AMF), or step 10a (e.g., the SMF receives an Nsmf_PDUSession_UpdateSMContextRequest message from the AMF), or step 12e (e.g., the SMF receives an Nsmf_PDUSession_ReleaseSMContext message from the AMF), or step 14a (e.g., the SMF receives a Modify Bearer Request message from the SGW), or using TS 23.5024.11.1.3.2 of the N26 interface. Step 15 of the 5GS to EPS idle mode mobility procedure (e.g., AMF receiving a NUdm_UECM_DeregistrationNotification message from HSS+UDM), or step 15b (e.g., SMF receiving an Nsmf_PDUSession_ReleaseSMContext request message from AMF), or step 13 of the 5GS to EPS mobility procedure (e.g., UE requesting a PDN connection), or step 14 (e.g., a release procedure for a PDU session initiated by PGW-C+SMF for transmission), etc. If the SMF recognizes that the UE has moved to EPS, the SMF may perform one or more of the following examples (Example 1, Example 1a, Example 1b, Example 2, Example 3, etc.). Alternatively, when the SMF recognizes that the UE needs to move to EPS, it may perform one or more of the following operations. As described above, the SMF recognizing that the UE has moved to EPS or recognizing that the UE must move to EPS can be understood as the SMF recognizing that the UE needs to release a PDU session or the SMF receiving a PDU session release request from AMF.

[0305] Example 1) The SMF can provide the NG-RAN serving the UE with information that the UE no longer needs to receive multicast services. This information may include information identifying the multicast session the UE is serving (e.g., TMGI, MBS session ID, etc.). This information can be interpreted as instructing the NG-RAN to remove information about the UE from the context managed to serve the multicast session (e.g., the multicast session-related context). For example, when the NG-RAN receives information that the UE no longer needs to receive multicast services, the NG-RAN can remove information about the UE from the multicast session-related context. This information can be interpreted as indicating that the UE has left the multicast session.

[0306] Information sent by the SMF can be transmitted to the NG-RAN via the AMF. For example, information indicating that the UE no longer needs to receive multicast services can be included according to... Figures 7a to 7c The example is described in step 15 of the example, in the Namf_Communication_N1N2Message and is sent. For example, the SMF sends the Namf_Communication_N1N2Message (including information that the UE no longer needs to receive multicast services) to the AMF, and the AMF can send the information that the UE no longer needs to receive multicast services to the NG-RAN.

[0307] Examples 1a and 1b below are examples of MB-SMF performing the operations performed by SMF in Example 1) above.

[0308] Example 1a) In an example such as integrating multicast and unicast transmissions, the NG-RAN and MB-SMF can send and receive signaling via the AMF. In this case, the MB-SMF can provide the NG-RAN serving the UE with information that the UE no longer needs to receive multicast services. That is, the MB-SMF can perform the operations performed by the SMF in Example 1). To this end, if the SMF identifies that the UE has moved to the EPS (or if the SMF detects that the UE has stopped receiving multicast services), the SMF can notify the MB-SMF of this. When the SMF notifies the MB-SMF that the UE has moved to the EPS (or the UE has stopped receiving multicast services), the SMF can provide the MB-SMF with information about the NG-RAN node serving the UE. If the UE is receiving services for multiple multicast sessions, the SMF can provide the MB-SMF of each of the multiple multicast sessions serving the UE with information that the UE no longer needs to receive multicast services.

[0309] Example 1b) The MB-SMF can perform the operations performed by the SMF in Example 1). When the MB-SMF recognizes that the UE has moved to EPS (or detects that the UE has stopped receiving multicast services), the MB-SMF can provide the NG-RAN serving the UE with information that the UE no longer needs to receive multicast services. This information is provided to the NG-RAN via the AMF. That is, the information sent by the MB-SMF can be sent to the NG-RAN via the AMF. In order for the MB-SMF to recognize that the UE is moving to EPS, when a UE receiving multicast session services moves to EPS, the MB-SMF can subscribe to an event public service to notify the AMF of the UE's movement (if the service is subscribed, the AMF can notify the MB-SMF of the UE's movement). The events subscribed to by the MB-SMF in the AMF can be newly defined events (e.g., UE moves to EPS or interoperates with EPS), or events that the MB-SMF can infer from existing events (e.g., location reports, UE moving into or out of a subscribed "Region of Interest," the number of UEs served by the AMF and located in the "Region of Interest," time zone changes (UE time zone), access type changes (3GPP access or non-3GPP access), registration status changes (registered or deregistered), connection status changes (IDLE or CONNECTED), UE communication loss, UE reachability status, UE indication that SMS is turned off on NAS service, subscription-related ID changes (implicit subscription), UE type assignment code (TAC), frequent mobility re-registration, subscription-related ID addition (implicit subscription), user status information in 5GS, UE access behavior trends, events defined in the prior art (such as UE location trends), and the total number of mobility management transactions). Assume the MB-SMF performs operations to store / manage UEs receiving multicast sessions managed by the MB-SMF.

[0310] Example 2) The SMF can remove information about the UE from the context managed to serve the multicast session (e.g., multicast session-related context). This can be interpreted as removing the UE context stored by the SMF for the multicast session. As proposed in this specification, the SMF may need to store / manage the context for each multicast session.

[0311] Example 3) The SMF considers that the UE has left the multicast session. In addition, the SMF can notify other SMFs serving the multicast session that the UE has left (i.e., when another SMF or MB-SMF is serving the multicast session).

[0312] In Examples 1) through 3) above, if the SMF (i.e., the SMF of the PDU session serving the UE) and the SMF of the multicast session serving the UE (e.g., assuming the SMF is MB-SMF) are different, the SMF can perform the operations of Examples 1) and / or 2) after interacting with the MB-SMF.

[0313] In Examples 1) to 3) above, the SMF can be the SMF of the service PDU session through which the UE sends a join request to receive multicast services.

[0314] Based on Example 1) above, the SMF can send information to the NG-RAN that the UE no longer needs to receive multicast services. When the NG-RAN receives the information described in 1) above from the SMF (e.g., information that the UE no longer needs to receive multicast services), the NG-RAN can perform one or more of the following operations.

[0315] a) NG-RAN can remove information about the UE from the context in which the multicast session is managed (e.g., the context associated with the multicast session). If the UE is the last UE to receive multicast session services (e.g., the last UE managed / served by NG-RAN for the multicast session), NG-RAN can additionally perform the operation of releasing radio resources used for the multicast session.

[0316] b) NG-RAN implementation based on Figure 9 The example is step 18 of the operation. NG-RAN execution. Figure 9 The steps after step 18 in the example can be referenced. Figure 9 The example includes steps 19 and subsequent operations. For instance, if the UE is the last UE among those receiving multicast session services, the NG-RAN can perform the operation of no longer receiving multicast session services from the 5G core network (e.g., UPF or MB-UPF).

[0317] 3. The third example disclosed in this specification

[0318] In the third example disclosed in this specification, an example of NG-RAN removing the MBS / multicast context that exists for a UE that has moved from 5GS to EPF will be described.

[0319] NG-RAN can identify whether a UE has moved to EPS or should move to EPS. For example, NG-RAN can identify whether a UE has moved to EPS or needs to move to EPS based on actions such as: step 1 of the 5GS to EPS handover procedure using the N26 interface (e.g., NG-RAN sending a handover request message to the AMF), or step 11a (e.g., the AMF sending a handover command message to NG-RAN), or step 21c (e.g., the AMF sending a UE context release command message to NG-RAN), or when NG-RAN redirects the UE to EPS (this can be interpreted as a redirected RRC connection release or a redirected RRC release or NG-RAN sending an RRC Release message to the UE (including redirected E-UTRA carrier information)). If NG-RAN identifies that a UE has moved to EPS or needs to move to EPS, NG-RAN can perform one or more of the following examples.

[0320] Example 1) NG-RAN can remove information about the UE from the context managed to serve a multicast session (e.g., a multicast session-related context). The context can be an MB session context. If the UE is the last UE among those receiving multicast session services, NG-RAN can additionally perform the operation of releasing radio resources used for the multicast session.

[0321] Example 2) If the NG-RAN is the last UE among the UEs receiving multicast session services, the NG-RAN can perform the operation of no longer receiving multicast sessions from the 5G core network (e.g., UPF or MB-UPF). For reference, the operation of the service regarding the NG-RAN no longer receiving multicast sessions from the 5G core network (e.g., UPF or MB-UPF) (e.g., the first example b) of this specification and the second example b) of this specification can be referred to.

[0322] Example 3) The NG-RAN can provide the 5G core network with information that the UE no longer needs to receive multicast services. This information may include information identifying the multicast session in which the UE is receiving services (e.g., TMGI, MBS session ID, etc.). This information can be interpreted as instructing the 5G core network to remove information about the UE from the context managed to serve the multicast session (e.g., the multicast session-related context). For example, when the 5G core network receives information from the NG-RAN that the UE no longer needs to receive multicast services, it can remove information about the UE from the multicast session-related context. This information can be interpreted as indicating that the UE has left the multicast session. Here, the 5G core network can represent one or more network functions (e.g., AMF, SMF, MB-SMF, etc.). If the above information needs to be delivered to multiple 5G core network functions, if the NG-RAN provides this information to one NF, the receiving NF can forward the information to other NFs.

[0323] Based on the description of the third embodiment disclosed in this specification, it can be applied as follows.

[0324] The following description applies to the service layer continuity between E-UTRAN / EPC MBMS and NR / 5GC MBS.

[0325] It can be assumed that the 5G CN (core network) knows that the UE has moved to the EPC, and therefore the 5G CN knows when to trigger the UE MBS context removal. For reference, according to existing technology, how the 5G CN understands that the UE has moved to the EPC and how the 5G CN triggers the UE MBS context removal are not discussed at all.

[0326] In this regard, this document describes examples of how the 5G CN understands that the UE has moved to the EPC and / or how the 5G CN triggers the removal of the UE's MBS context.

[0327] Mobility-related processes may not be affected by the contents described in this specification.

[0328] When the UE moves to E-UTRAN / EPC, the UE can begin the procedure defined in the prior art for receiving MBMS services for TMGI.

[0329] In the case of N26-based interoperability from 5GS to EPS, the source NG-RAN can receive a UE context release command message from the AMF. When the source NG-RAN releases resources for the PDU session associated with the UE due to the UE context message, the source NG-RAN can remove the UE from the multicast session context (if the multicast session context exists). If the UE is the last UE in the multicast session context, the source NG-RAN can perform a multicast user plane distribution release operation for the multicast service (which may correspond to...). Figures 7a to 7c Steps 17 to 25 in the process.

[0330] For interoperability without an N26 interface (interoperability from 5GS to EPS), the UE can perform a procedure for leaving the multicast service (e.g., in...). Figures 7a to 7c (The process described in the example). Then, the source NG-RAN can remove the UE from the multicast session context (if the multicast session context exists). The UE can trigger such a process depending on its implementation.

[0331] When the UE moves to NR / 5GC, in order to receive 5G MBS transmissions for TMGI, the UE can trigger multicast context and multicast stream establishment / modification through the PDU session modification process.

[0332] Mechanisms to reduce, eliminate, or recover packet loss can be implemented at the service layer between the UE and BM-SC+MBSF and / or at the application layer between the UE's application functions and the application client.

[0333] Mechanisms for reducing, eliminating, or recovering packet loss can be implemented at the service layer between the UE and the Broadcast and Multicast Service Center (BM-SC) + MBSF and / or at the application layer between the UE's application functions and application clients.

[0334] 4. The fourth example disclosed in this specification

[0335] In the fourth example disclosed in this specification, an example of an operation by which the AF (or application server or content provider) removes an existing MBS / multicast context for a UE that has moved to EPS will be described.

[0336] The AF can identify that the UE has moved to the EPS. For example, the AMF can explicitly or implicitly provide information that the UE has moved to the EPS, or the AMF can explicitly or implicitly receive information from the UE that the UE has moved from the 5G core network and / or EPC to the EPS. When the AMF identifies that the UE has moved to the EPS, the AMF can perform operations such as those shown in the following examples.

[0337] Example 1) The AF can provide the 5G core network with information that the UE no longer needs to receive multicast services. This information may include information identifying the multicast session the UE was serving (e.g., TMGI, MBS session ID, etc.). This information can be interpreted as instructing the 5G core network and / or NG-RAN (the NG-RAN serving the UE) to remove information about the UE from the context managed to serve the multicast session. For example, when the 5G core network and / or NG-RAN receive information that the UE no longer needs to receive multicast services, they can remove information about the UE from the multicast session-related context. This information can be interpreted as indicating that the UE has left the multicast session. The AF can also provide the 5G core network and / or NG-RAN with the UE's last location information in the 5GS (UE's last camped location) (e.g., cell ID, TAI, etc.). The AF can receive the UE's last location information in the 5GS (UE's last camped location) from the UE, from the 5G core network, and / or from the EPC. AF uses the location information of the UE's last location in 5GS (UE's last camp) (e.g., cell ID, TAI, etc.), and the 5G core network can determine the NG-RAN and / or AMF serving the UE.

[0338] When the AF provides the SMF with information that the UE no longer needs to receive multicast services, the AF can provide this information to the SMF of the PDU session that the UE is using for multicast service join / leave requests. To this end, the AF can use the UE's IP address information (which can be provided from the UE, the 5G core network, and / or the EPC) for the PDU session to allow the 5G core network to determine the SMF of the serving PDU session.

[0339] In the above context, the 5G core network can refer to one or more of MB-SMF, SMF, and AMF. NG-RAN can receive information provided by AF through 5G core network functions. When the UE no longer needs to receive multicast information, it needs to deliver services to multiple 5G core network functions. If AF provides information to one NF, the NF receiving the information can forward it to other NFs.

[0340] When NG-RAN receives the information described in Example 1 (e.g., the UE no longer needs to receive information about multicast services), NG-RAN may perform one or more of the following operations:

[0341] a) NG-RAN can remove information about the UE from the context in which the multicast session is managed to serve the multicast session (e.g., the context associated with the multicast session). If the UE is the last UE among those receiving multicast session services, NG-RAN can additionally perform the operation of releasing radio resources used for the multicast session.

[0342] b) If the NG-RAN is the last UE among the UEs receiving multicast session services, the NG-RAN may perform the operation of no longer receiving multicast sessions from the 5G core network (e.g., UPF or MB-UPF). For reference, the operation of the NG-RAN no longer receiving multicast sessions from the 5G core network (e.g., UPF or MB-UPF) (e.g., the first example b) of this specification and the second example b) of this specification can be referred to.

[0343] In the following text, reference will be made to Figure 10 The examples describe various examples of operation based on the third examples disclosed in this specification. For reference, according to... Figure 10 The descriptions are merely examples, and the scope of this specification is not limited to... Figure 10 For example, in the operations described in the various examples disclosed in this specification, Figure 10 Operations not shown in the examples may also be included within the scope of disclosure in this specification.

[0344] exist Figure 10 The examples disclosed here focus on various operations related to removing existing MBS / multicast contexts for UEs that have moved from 5GS to EPF within the NG-RAN, but these are merely examples. The various operations described in the first through fourth examples disclosed in this specification can also be used in conjunction with... Figure 10 The example is executed in the same way.

[0345] The following figures are used to explain specific examples of this specification. Since the names of specific devices or signals / messages / fields described in the figures are provided as examples, the technical features of this specification are not limited to the specific names used in the following figures.

[0346] Figure 10 An example of a signal flow diagram according to the third example disclosed in this specification is shown.

[0347] For reference, Figure 10 In the example shown, data and business can be used interchangeably as terms with the same meaning.

[0348] 1) Assume the UE joins the multicast session to be received. The UE can receive data for the multicast session joined by the UE. In this embodiment, assume the NG-RAN receives multicast session data from the MB-UPF using the 5GC shared MBS service delivery method, and the NG-RAN performs the operation of sending multicast session data to the UE. The 5GC shared MBS service delivery method can refer to a multicast transmission method. For multicast session data transmission, the multicast session must be configured (e.g., set up), and the multicast session must be created. For reference, procedures related to the configuration and / or creation of multicast sessions can be performed, as described above. Figure 8a and Figure 8b In the examples described in the examples, it is possible to execute Figure 10 Before step 1, perform the processes related to the configuration and / or generation of the multicast session.

[0349] 2) The UE can move from 5GS to EPS. As the UE moves from 5GS to EPS (e.g., as the UE moves, it can move out of the coverage of 5GS and receive service from EPS), a handover process from 5GS to EPS can be performed (e.g., a handover process using the N26 interface). For reference, the specific operations performed in step 2 can be considered as including the operations performed using the N26 interface during the prior art 5GS to EPS handover process up to step 21c (V-SMF and V-UPF deletion of indirect data forwarding tunnels).

[0350] For multicast sessions, the same service can be provided in the MBMS scheme within EPS (or the target E-UTRAN). That is, with multicast and MBMS sessions (or broadcast sessions) identified by the same TMGI serving in 5GS and EPS respectively, services can be provided to the UE via MBMS in EPS. This could mean interoperability or continuity is supported through the service layer of MBS for 5GS and MBMS for EPS.

[0351] In other words, PDU sessions and QoS flows moved from 5GS to EPS based on the handover process are not used to serve multicast sessions. That is, PDU sessions and QoS flows moved from 5GS to EPS based on the handover process are not used to transmit data / services for multicast sessions. For example, a UE can receive services associated with an MBMS session (or broadcast session) identified by the same TMGI as the multicast session service provided in 5GS via the MBMS transmission method (i.e., broadcast transmission method) in EPS. Therefore, even if a UE moves from 5GS to EPS, a handover process can be performed for a PDU session used to provide services other than multicast sessions (i.e., data / traffic used to transmit other services). One of the PDU sessions moved from 5GS to EPS can be the PDU session used when a UE requests to join or leave a multicast session. In this case, the reason for moving the PDU session to EPS is to provide services in EPS other than multicast session services.

[0352] 3) NG-RAN can identify that the UE has moved from 5GS to EPS, or NG-RAN can identify that the UE should move to EPS. As NG-RAN receives the UE context release command message from AMF during the handover process from 5GS to EPS via the N26 interface, NG-RAN can identify that the UE has moved from 5GS to EPS, or NG-RAN can identify that the UE should move to EPS.

[0353] Despite Figure 10 The example is not shown, but the NG-RAN that receives the UE context release command message can send a UE context release complete message to the AMF.

[0354] If NG-RAN knows that the UE has moved from 5GS to EPS, or if NG-RAN knows that the UE should move to EPS, then NG-RAN can perform one or more of the operations described in steps 4 to 6 below.

[0355] NG-RAN can identify a UE's movement from 5GS to EPS by receiving a UE context release command message from the AMF. However, this is merely an example, and NG-RAN can identify a UE's movement from 5GS to EPS based on other information, rather than simply receiving a UE context release command message from the AMF. For example, based on the operation related to step 1 in the handover process from 5GS to EPS using the N26 interface (e.g., the step where NG-RAN sends a handover request message to the AMF), or the operation related to step 11a in the handover process from 5GS to EPS using the N26 interface (the step where NG-RAN receives a handover command message from the AMF), NG-RAN can know that the UE has moved to EPS or left 5GS. Alternatively, NG-RAN can know that the UE has moved to EPS or left 5GS by redirecting the UE to EPS (e.g., redirection can be interpreted as NG-RAN performing an RRC connection release with redirection or an RRC release with redirection, or redirection can be interpreted as performing an operation to send an RRC Release message to the UE including E-UTRA bearer information redirected by NG-RAN).

[0356] 4) NG-RAN can remove information about the UE from the context managed to serve multicast sessions (which may be MB session context) (e.g., multicast session related context).

[0357] 5) Step 5 can be performed after the UE moves to EPS. If the UE moves to EPS in step 2, the UE can receive data received based on the multicast session in 5GS based on the MBMS method in EPS.

[0358] 6) NG-RAN can check if the UE is the last UE among those receiving multicast session services. If the UE is the last UE, NG-RAN can perform an operation to stop receiving data from the 5G core network (e.g., UPF or MB-UPF). The operation to stop receiving data from the 5G core network (e.g., UPF or MB-UPF) may include, for example, one or more of the following steps 7 to 11.

[0359] 7-8) NG-RAN can send a message to MB-SMF requesting the release of multicast distribution for a multicast session (e.g., sending a multicast distribution release request message) via AMF. The release request can be interpreted as a multicast user plane distribution release request.

[0360] 9-10) NG-RAN can receive response messages (e.g., multicast distribution release response messages) to multicast distribution release requests from MB-SMF via AMF.

[0361] 11) The NG-RAN may request the MB-UPF to stop transmitting multicast data. For example, the NG-RAN may send a message to the MB-UPF to leave a multicast transmission (e.g., a multicast leave message (including Internet Group Management Protocol (IGMP) / Multicast Listen Discovery (MLD))). For reference, the NG-RAN may additionally perform the operation of releasing radio resources used for multicast sessions.

[0362] If the NG-RAN identifies that the UE has moved from 5GS to EPS, the NG-RAN can additionally provide the 5G core network with information indicating that the UE no longer needs to receive multicast services. This information may include information identifying the multicast session served by the UE (e.g., TMGI, MBS session ID, etc.). This information (e.g., information indicating that the UE no longer needs to receive multicast services) can be interpreted as instructing the 5G core network to remove information about the UE from the context of the managed multicast session. In other words, when the 5G core network receives information that the UE no longer needs to receive multicast services, it can remove information about the UE from the context of the managed multicast session. This information can be interpreted as indicating that the UE has left the multicast session. The 5G core network can represent one or more network functions (e.g., AMF, SMF, MB-SMF, etc.). When this information (e.g., the UE no longer needs to receive multicast service information) needs to be delivered to multiple 5G core network functions, if NG-RAN provides the information in one NF (e.g., the UE no longer needs to receive multicast service information), then the NF receiving the information can send the information to other NFs (e.g., the UE no longer needs to receive multicast service information).

[0363] The descriptions of various examples in this specification can be applied when using the 5GC shared MBS service delivery method as a multicast session transmission method from the network to the UE. Furthermore, the descriptions of various examples in this specification can also be applied even when using the 5GC individual MBS service delivery method. Here, the 5GC shared MBS service delivery method and the 5GC individual MBS service delivery method can refer to prior art MBS service delivery related processes.

[0364] In the various examples disclosed in this specification, if a UE enters / moves to EPS after receiving multicast service in 5GS, the UE can be considered to have already performed a leave request in the corresponding multicast service, even if the UE does not explicitly execute a leave request to 5GC. That is, the UE can be considered to have performed a leave locally within the multicast service. Then, if the UE enters / moves from EPS to 5GS, the UE can execute an join request to 5GC to receive multicast service.

[0365] As described in the various examples disclosed in this specification, the AMF can identify that the UE has moved to the EPS. To enable the AMF to provide multicast session services to the NG-RAN serving the UE, it can instruct the removal of information about the UE from the management context. If the UE is the last UE among those receiving multicast session services, the AMF can notify the MB-SMF that it no longer needs to serve the multicast session. The AMF can remove information about the UE from the context managed to serve the multicast session.

[0366] Based on the disclosure of various examples in this specification, NG-RAN can identify whether a UE has moved from 5GS to EPS or should move from 5GS to EPS. NG-RAN can remove information about a UE that has moved to EPS from the context associated with the multicast session. If the UE that has moved to EPS is the last UE to use the multicast session, NG-RAN can delete the multicast session itself.

[0367] Based on the disclosures of various examples in this specification, if the continuity of movement from 5GS multicast communication to EPS MBMS is supported through the service layer, unnecessary resource waste and management operations caused by the 5G core network and / or NG-RAN continuing to provide multicast services to the UE can be prevented by removing the MBS / multicast context existing for the UE in 5GS. Furthermore, as described in the various examples disclosed in this specification, if a terminal moves from 5GS to EPS, networks such as base stations (e.g., NG-RAN) can efficiently perform communication by effectively removing terminal information from the context associated with multicast communication. Additionally, when the UE that has moved to EPS is the last UE to use the multicast session, communication can be performed efficiently by deleting the entire context associated with multicast communication.

[0368] For reference, the operation of the terminal (e.g., UE) described in this specification can be achieved through the above... Figures 1 to 3 This is implemented using a device. For example, the terminal (e.g., UE) can be... Figure 1 The first device 100 or the second device 200. For example, the operation of the terminal (e.g., UE) described herein can be processed by one or more processors 102 or 202. The operation of the terminal described herein can be stored in one or more memories 104 or 204 in the form of instructions / programs (e.g., instructions, executable code) executable by one or more processors 102 or 202. One or more processors 102 or 202 control one or more memories 104 or 204 and one or more transceivers 105 or 206, and can perform the operation of the terminal (e.g., UE) described herein by executing the instructions / programs stored in one or more memories 104 or 204.

[0369] Additionally, instructions for performing operations of the terminal (e.g., UE) described in this specification may be stored in a non-volatile computer-readable storage medium on which the instructions are recorded. The storage medium may include one or more memories 104 or 204. Furthermore, the instructions recorded in the storage medium may be executed by one or more processors 102 or 202 to perform the operations of the terminal (e.g., UE) described in this specification.

[0370] For reference, the operation of network nodes (e.g., AMF, SMF, UPF, MB-SMF, MB-UPF, NRF, NEF, MBSF, NEF / MBSF, AF, MME, SMF+PGW-C, IPF+PGW-U, NEF / MBSF, UDR, PCF, content providers, BM-SC+MSF, MBMS-GW, etc.) or base stations (e.g., NG-RAN, gNB, eNB, RAN, E-UTRAN, etc.) described herein can be performed as described below. Figures 1 to 3 This is achieved through devices. For example, a network node or base station could be... Figure 1 First device 100a or Figure 1 The second device 100b. For example, the operation of the network node or base station described herein can be processed by one or more processors 102 or 202. The operation of the terminal described herein can be stored in one or more memories 104 or 204 in the form of instructions / programs (e.g., instructions, executable code) executable by one or more processors 102 or 202. One or more processors 102 or 202 can perform the operation of the network node or base station described herein by controlling one or more memories 104 or 204 and one or more transceivers 106 or 206 and executing the instructions / programs stored in one or more memories 104 or 204.

[0371] Additionally, instructions for performing the operations of the network node or base station described in this specification may be stored in a non-volatile (or non-transitory) computer-readable storage medium. The storage medium may include one or more memories 104 or 204. Furthermore, the instructions recorded in the storage medium are executed by one or more processors 102 or 202 to perform the operations of the network node or base station.

[0372] Preferred embodiments have been described above by way of example, but the disclosure of this specification is not limited to this particular embodiment, and therefore improvements, modifications and variations are possible.

[0373] In the exemplary systems described above, these methods are based on flowcharts that are described as a series of steps or blocks, but are not limited to the order in which the steps are described. Some steps may occur in a different order or simultaneously with other steps as described above. Furthermore, those skilled in the art will understand that the steps shown in the flowcharts are not exclusive and may include other steps, or one or more steps in the flowchart may be deleted without affecting the scope of the claims.

[0374] The claims described herein can be combined in various ways. For example, the technical features of the method claims in this specification can be combined and implemented as an apparatus, and the technical features of the apparatus claims in this specification can be combined and implemented as a method. Furthermore, the technical features of the method claims and the apparatus claims in this specification can be combined to implement an apparatus, and the technical features of the method claims and the apparatus claims in this specification can be combined and implemented as a method.

Claims

1. A method performed by a next-generation radio access network (NG-RAN), the method comprising the following steps: Receives a UE context release command message related to the first user equipment (UE) from the Access and Mobility Management Function (AMF); as well as The handover process from 5GS to Evolved Packet System (EPS) was used for the first UE, removing the first UE from the context associated with the multicast session in the 5GS. Wherein, based on the first UE being switched to the EPS, the EPS provides the same multicast service as the multicast session based on Multimedia Broadcast and Multicast Service (MBMS).

2. The method according to claim 1, further comprising the following steps: Determine whether the first UE is the last of one or more UEs associated with the multicast session.

3. The method according to claim 2, further comprising the following steps: Based on the fact that the first UE is the last of one or more UEs using the multicast session, all contexts related to the multicast session are deleted.

4. The method according to claim 2, further comprising the following steps: Based on the premise that the first UE is the last of one or more UEs using the multicast session, a multicast distribution release request message is sent to the AMF.

5. The method according to claim 4, further comprising the following step: Receive a multicast distribution release response message from the AMF in response to the multicast distribution release request message.

6. The method according to claim 2, further comprising the following step: A multicast leave message is sent to the Multicast Broadcast User Plane Function (MB-UPF) that manages the multicast session to request the cessation of data transmission associated with the multicast session.

7. The method according to claim 1, further comprising the following steps: It is determined that the first UE is to be switched from the 5GS to the EPS.

8. The method according to claim 1, in, The step of removing the first UE from the context associated with the multicast session is also based on the first UE having one or more unicast protocol data unit (PDU) sessions that have moved from the 5GS to the EPS.

9. A next-generation radio access network (NG-RAN), the NG-RAN comprising: At least one processor; as well as At least one memory, the at least one memory storing instructions and being operatively electrically connectable to the at least one processor; The operations performed based on the execution of the instruction by the at least one processor include: Receives a UE context release command message related to the first user equipment (UE) from the Access and Mobility Management Function (AMF); and The handover process from 5GS to Evolved Packet System (EPS) was used for the first UE, removing the first UE from the context associated with the multicast session in the 5GS. Wherein, based on the first UE being switched to the EPS, the EPS provides the same multicast service as the multicast session based on Multimedia Broadcast and Multicast Service (MBMS).

10. The NG-RAN according to claim 9, wherein, The operation also includes: Determine whether the first UE is the last of one or more UEs associated with the multicast session.

11. The NG-RAN according to claim 10, wherein, The operation also includes: Based on the fact that the first UE is the last of one or more UEs using the multicast session, all contexts related to the multicast session are deleted.

12. The NG-RAN according to claim 10, wherein, The operation also includes: Based on the premise that the first UE is the last of one or more UEs using the multicast session, a multicast distribution release request message is sent to the AMF.

13. The NG-RAN according to claim 10, wherein, The operation also includes: It is determined that the first UE is to be switched from the 5GS to the EPS.

14. A method performed by an Access and Mobility Management Function (AMF), the method comprising the following steps: Send a UE context release command message related to the first user equipment (UE) to the next-generation radio access network (NG-RAN); as well as The handover process from 5GS to Evolved Packet System (EPS) is used for the first User Equipment (UE), and the NG-RAN removes the first UE from the context associated with the multicast session. Wherein, based on the first UE moving to the EPS, the EPS provides the same multicast service as the multicast session in the 5GS based on Multimedia Broadcast and Multicast Service (MBMS).

15. The method of claim 14, further comprising the step of: Receive a multicast distribution release request message from the NG-RAN.

16. The method of claim 15, further comprising the step of: Based on receiving the multicast distribution release request message, the multicast distribution release request message is sent to the multicast broadcast session management function MB-SMF associated with the multicast session.

17. The method of claim 16, further comprising the step of: Receive a multicast distribution release response message from the MB-SMF; and Send the multicast distribution release response message to the NG-RAN.

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