COMMUNICATION RELATED TO NETWORK SLICE

One disclosure of the present specification provides a method by which an AMF performs communication related to a network slice. The method may comprise the steps of: receiving a PDU session establishment request message including information about a second PDU session; determining to forward a UE to a second RAN node supporting a second network slice; transmitting a message including information indicating that the UE needs to be forwarded to the second RAN node supporting the second network slice; receiving a handover required message; and transmitting a request message for deactivating the first PDU session related to a first network slice.

TECHNICAL FIELD

The present disclosure relates to mobile communication.

BACKGROUND

A method for supporting 5GC assisted cell selection to access a network slice (e.g., “Support of 5GC assisted cell selection to access network slice”) is required. A terminal receiving a service for a specific network slice (e.g. Single-Network Slice Selection Assistance Information (S-NSSAI)-1) through a specific frequency band, may try to get service for another network slice (e.g. S-NSSAI-2) through a different frequency band. In this case, it is necessary to discuss how to handle the PDU session being used in the existing S-NSSAI-1.

For example, there is a need to discuss how to steer a UE to a 5G-Access Network (AN) (e.g., a specific frequency band) that a 5G System (5GS) can support a network slice (e.g., a network slice the UE can use) will be discussed. When 5GS makes decision to steer a UE to an appropriate 5G-AN, information needed for 5GS needs to be discussed. In order to select an appropriate 5G-AN, it is necessary to discuss what information 5GS should provide to the UE and how to transmit this information to the UE. For example, after the NG-RAN rejects the UE's PDU session establishment request, in order for the terminal to receive service through a network slice related to the corresponding PDU session, the terminal must move to an NG-RAN (e.g., a second NG-RAN) supporting the corresponding network slice. And, after moving to the second NG-RAN, the terminal must start the PDU session establishment procedure again. Accordingly, there is a problem in that unnecessary signaling occurs and it may take a long time for the terminal to receive the service.

In addition, in the course of the UE moving to the second NG-RAN, the PDU session for which the UE was provided with a service in the first NG-RAN is released. When the terminal wants to receive a service using the first PDU session again, since the UE needs to perform a PDU session establishment procedure for creating a first PDPU session after moving to the first NG-RAN, unnecessary signaling may occur.

SUMMARY

Accordingly, a disclosure of the present specification has been made in an effort to solve the aforementioned problem.

In order to solve the above problems, one disclosure of the present specification provides a method for performing communication related to a network slice, the method performed by an AMF. The above method comprises: receiving a PDU session establishment request message including information on a second PDU session from a first RAN node; determining to move the UE to a second RAN node supporting the second network slice; transmitting a message including information indicating that the UE to be moved to the second RAN node supporting the second network slice to the first RAN node; receiving a handover required message including information about a first PDU session related to a first network slice supported by the first RAN node and cause information about for moving the UE to the second RAN node, from the first RAN node; and transmitting a request message for deactivating a first PDU session related to the first network slice is transmitted to a SMF.

In order to solve the above problems, one disclosure of the present specification provides an AMF performing communication related to a network slice. The AMF includes at least one processor; and at least one memory that stores instructions and is operatively electrically connectable with the at least one processor, wherein operations performed based on execution of the instructions by the at least one processor include: receiving a PDU session establishment request message including information on a second PDU session from a first RAN node; determining to move the UE to a second RAN node supporting the second network slice; transmitting a message including information indicating that the UE to be moved to the second RAN node supporting the second network slice to the first RAN node; receiving a handover required message including information about a first PDU session related to a first network slice supported by the first RAN node and cause information about for moving the UE to the second RAN node, from the first RAN node; and transmitting a request message for deactivating a first PDU session related to the first network slice is transmitted to a SMF.

In order to solve the above problems, one disclosure of the present specification provides a method for performing communication related to a network slice, the method performed by a first RAN. The above method comprises: receiving a PDU session establishment request message including information on a second PDU session from a UE; transmitting the PDU session establishment request message to an AMF; receiving a message including information indicating that the UE should be moved to a second RAN node supporting the second network slice, from the AMF; and transmitting a handover required message including information about a first PDU session related to a first network slice supported by the first RAN node and cause information for moving the UE to the second RAN node, to the AMF.

In order to solve the above problems, one disclosure of the present specification provides a first RAN node performing communication related to a network slice. The first RAN node includes at least one processor; and at least one memory that stores instructions and is operatively electrically connectable with the at least one processor, wherein operations performed based on execution of the instructions by the at least one processor include: receiving a PDU session establishment request message including information on a second PDU session from a UE; transmitting the PDU session establishment request message to an AMF; receiving a message including information indicating that the UE should be moved to a second RAN node supporting the second network slice, from the AMF; and transmitting a handover required message including information about a first PDU session related to a first network slice supported by the first RAN node and cause information for moving the UE to the second RAN node, to the AMF.

According to the disclosure of the present specification, it is possible to solve the problems of the related art.

Effects that can be obtained through specific examples of the present specification are not limited to the effects listed above. For example, various technical effects that a person having ordinary skill in the related art can understand or derive from the present specification may exist. Accordingly, the specific effects of the present specification are not limited to those explicitly described herein, and may include various effects that can be understood or derived from the technical characteristics of the present specification.

DETAILED DESCRIPTION

In the attached drawings, user equipments (UEs) are shown for example. The UE may also be denoted a terminal or mobile equipment (ME). In addition, the UE may be a laptop computer, a mobile phone, a PDA, a smartphone, a multimedia device, or other portable device, or may be a stationary device such as a PC or a car mounted device.

Hereinafter, the UE is used as an example of a wireless communication device (or a wireless apparatus, or a wireless device) capable of wireless communication. An operation performed by the UE may be performed by a wireless communication device. A wireless communication device may also be referred to as a wireless apparatus, a wireless device, or the like. Hereinafter, AMF may mean an AMF node, SMF may mean an SMF node, and UPF may mean a UPF node.

The term “base station” used hereinafter generally refers to a fixed station that communicates with a wireless device and may be denoted by other terms such as evolved-NodeB (eNodeB), evolved-NodeB (eNB), Base Transceiver System (BTS), access point, or Next generation NodeB (gNB).

I. Techniques and Procedures Applicable to the Disclosure of the Present Specification

FIG.1shows an example of a communication system to which implementations of the present disclosure is applied.

Partial use cases may require a plurality of categories for optimization and other use cases may focus only upon one key performance indicator (KPI). 5G supports such various use cases using a flexible and reliable method.

eMBB far surpasses basic mobile Internet access and covers abundant bidirectional work and media and entertainment applications in cloud and augmented reality. Data is one of 5G core motive forces and, in a 5G era, a dedicated voice service may not be provided for the first time. In 5G, it is expected that voice will be simply processed as an application program using data connection provided by a communication system. Main causes for increased traffic volume are due to an increase in the size of content and an increase in the number of applications requiring high data transmission rate. A streaming service (of audio and video), conversational video, and mobile Internet access will be more widely used as more devices are connected to the Internet. These many application programs require connectivity of an always turned-on state in order to push real-time information and alarm for users. Cloud storage and applications are rapidly increasing in a mobile communication platform and may be applied to both work and entertainment. The cloud storage is a special use case which accelerates growth of uplink data transmission rate. 5G is also used for remote work of cloud. When a tactile interface is used, 5G demands much lower end-to-end latency to maintain user good experience. Entertainment, for example, cloud gaming and video streaming, is another core element which increases demand for mobile broadband capability. Entertainment is essential for a smartphone and a tablet in any place including high mobility environments such as a train, a vehicle, and an airplane. Other use cases are augmented reality for entertainment and information search. In this case, the augmented reality requires very low latency and instantaneous data volume.

In addition, one of the most expected 5G use cases relates a function capable of smoothly connecting embedded sensors in all fields, i.e., mMTC. It is expected that the number of potential Internet-of-things (IoT) devices will reach 204 hundred million up to the year of 2020. An industrial IoT is one of categories of performing a main role enabling a smart city, asset tracking, smart utility, agriculture, and security infrastructure through 5G.

URLLC includes a new service that will change industry through remote control of main infrastructure and an ultra-reliable/available low-latency link such as a self-driving vehicle. A level of reliability and latency is essential to control a smart grid, automatize industry, achieve robotics, and control and adjust a drone.

5G is a means of providing streaming evaluated as a few hundred megabits per second to gigabits per second and may complement fiber-to-the-home (FTTH) and cable-based broadband (or DOCSIS). Such fast speed is needed to deliver TV in resolution of 4K or more (6K, 8K, and more), as well as virtual reality and augmented reality. Virtual reality (VR) and augmented reality (AR) applications include almost immersive sports games. A specific application program may require a special network configuration. For example, for VR games, gaming companies need to incorporate a core server into an edge network server of a network operator in order to minimize latency.

Automotive is expected to be a new important motivated force in 5G together with many use cases for mobile communication for vehicles. For example, entertainment for passengers requires high simultaneous capacity and mobile broadband with high mobility. This is because future users continue to expect connection of high quality regardless of their locations and speeds. Another use case of an automotive field is an AR dashboard. The AR dashboard causes a driver to identify an object in the dark in addition to an object seen from a front window and displays a distance from the object and a movement of the object by overlapping information talking to the driver. In the future, a wireless module enables communication between vehicles, information exchange between a vehicle and supporting infrastructure, and information exchange between a vehicle and other connected devices (e.g., devices accompanied by a pedestrian). A safety system guides alternative courses of a behavior so that a driver may drive more safely drive, thereby lowering the danger of an accident. The next stage will be a remotely controlled or self-driven vehicle. This requires very high reliability and very fast communication between different self-driven vehicles and between a vehicle and infrastructure. In the future, a self-driven vehicle will perform all driving activities and a driver will focus only upon abnormal traffic that the vehicle cannot identify. Technical requirements of a self-driven vehicle demand ultra-low latency and ultra-high reliability so that traffic safety is increased to a level that cannot be achieved by human being.

A smart city and a smart home/building mentioned as a smart society will be embedded in a high-density wireless sensor network. A distributed network of an intelligent sensor will identify conditions for costs and energy-efficient maintenance of a city or a home. Similar configurations may be performed for respective households. All of temperature sensors, window and heating controllers, burglar alarms, and home appliances are wirelessly connected. Many of these sensors are typically low in data transmission rate, power, and cost. However, real-time HD video may be demanded by a specific type of device to perform monitoring.

Consumption and distribution of energy including heat or gas is distributed at a higher level so that automated control of the distribution sensor network is demanded. The smart grid collects information and connects the sensors to each other using digital information and communication technology so as to act according to the collected information. Since this information may include behaviors of a supply company and a consumer, the smart grid may improve distribution of fuels such as electricity by a method having efficiency, reliability, economic feasibility, production sustainability, and automation. The smart grid may also be regarded as another sensor network having low latency.

Mission critical application (e.g., e-health) is one of 5G use scenarios. A health part contains many application programs capable of enjoying benefit of mobile communication. A communication system may support remote treatment that provides clinical treatment in a faraway place. Remote treatment may aid in reducing a barrier against distance and improve access to medical services that cannot be continuously available in a faraway rural area. Remote treatment is also used to perform important treatment and save lives in an emergency situation. The wireless sensor network based on mobile communication may provide remote monitoring and sensors for parameters such as heart rate and blood pressure.

Wireless and mobile communication gradually becomes important in the field of an industrial application. Wiring is high in installation and maintenance cost. Therefore, a possibility of replacing a cable with reconstructible wireless links is an attractive opportunity in many industrial fields. However, in order to achieve this replacement, it is necessary for wireless connection to be established with latency, reliability, and capacity similar to those of the cable and management of wireless connection needs to be simplified. Low latency and a very low error probability are new requirements when connection to 5G is needed.

Logistics and freight tracking are important use cases for mobile communication that enables inventory and package tracking anywhere using a location-based information system. The use cases of logistics and freight typically demand low data rate but require location information with a wide range and reliability.

Referring toFIG.1, the communication system1includes wireless devices100ato100f, base stations (BSs)200, and a network300. AlthoughFIG.1illustrates a 5G network as an example of the network of the communication system1, the implementations of the present disclosure are not limited to the 5G system, and can be applied to the future communication system beyond the 5G system.

The BSs200and the network300may be implemented as wireless devices and a specific wireless device may operate as a BS/network node with respect to other wireless devices.

The wireless devices100ato100frepresent devices performing communication using radio access technology (RAT) (e.g., 5G new RAT (NR)) or LTE) and may be referred to as communication/radio/5G devices. The wireless devices100ato100fmay include, without being limited to, a robot100a, vehicles100b-1and100b-2, an extended reality (XR) device100c, a hand-held device100d, a home appliance100e, an IoT device100f, and an artificial intelligence (AI) device/server400. For example, the vehicles may include a vehicle having a wireless communication function, an autonomous driving vehicle, and a vehicle capable of performing communication between vehicles. The vehicles may include an unmanned aerial vehicle (UAV) (e.g., a drone). The XR device may include an AR/VR/Mixed Reality (MR) device and may be implemented in the form of a head-mounted device (HMD), a head-up display (HUD) mounted in a vehicle, a television, a smartphone, a computer, a wearable device, a home appliance device, a digital signage, a vehicle, a robot, etc. The hand-held device may include a smartphone, a smartpad, a wearable device (e.g., a smartwatch or a smartglasses), and a computer (e.g., a notebook). The home appliance may include a TV, a refrigerator, and a washing machine. The IoT device may include a sensor and a smartmeter.

The UAV may be, for example, an aircraft aviated by a wireless control signal without a human being onboard.

The VR device may include, for example, a device for implementing an object or a background of the virtual world. The AR device may include, for example, a device implemented by connecting an object or a background of the virtual world to an object or a background of the real world. The MR device may include, for example, a device implemented by merging an object or a background of the virtual world into an object or a background of the real world. The hologram device may include, for example, a device for implementing a stereoscopic image of 360 degrees by recording and reproducing stereoscopic information, using an interference phenomenon of light generated when two laser lights called holography meet.

The public safety device may include, for example, an image relay device or an image device that is wearable on the body of a user.

The MTC device and the IoT device may be, for example, devices that do not require direct human intervention or manipulation. For example, the MTC device and the IoT device may include smartmeters, vending machines, thermometers, smartbulbs, door locks, or various sensors.

The medical device may be, for example, a device used for the purpose of diagnosing, treating, relieving, curing, or preventing disease. For example, the medical device may be a device used for the purpose of diagnosing, treating, relieving, or correcting injury or impairment. For example, the medical device may be a device used for the purpose of inspecting, replacing, or modifying a structure or a function. For example, the medical device may be a device used for the purpose of adjusting pregnancy. For example, the medical device may include a device for treatment, a device for operation, a device for (in vitro) diagnosis, a hearing aid, or a device for procedure.

The security device may be, for example, a device installed to prevent a danger that may arise and to maintain safety. For example, the security device may be a camera, a closed-circuit TV (CCTV), a recorder, or a black box.

The FinTech device may be, for example, a device capable of providing a financial service such as mobile payment. For example, the FinTech device may include a payment device or a point of sales (POS) system.

The weather/environment device may include, for example, a device for monitoring or predicting a weather/environment.

Wireless communication/connections150a,150band150cmay be established between the wireless devices100ato100fand/or between wireless device100ato100fand BS200and/or between BSs200. Herein, the wireless communication/connections may be established through various RATs (e.g., 5G NR) such as uplink/downlink communication150a, sidelink communication (or device-to-device (D2D) communication)150b, inter-base station communication150c(e.g., relay, integrated access and backhaul (IAB)), etc. The wireless devices100ato100fand the BSs200/the wireless devices100ato100fmay transmit/receive radio signals to/from each other through the wireless communication/connections150a,150band150c. For example, the wireless communication/connections150a,150band150cmay transmit/receive signals through various physical channels. To this end, at least a part of various configuration information configuring processes, various signal processing processes (e.g., channel encoding/decoding, modulation/demodulation, and resource mapping/de-mapping), and resource allocating processes, for transmitting/receiving radio signals, may be performed based on the various proposals of the present disclosure.

AI refers to the field of studying artificial intelligence or the methodology that can create it, and machine learning refers to the field of defining various problems addressed in the field of AI and the field of methodology to solve them. Machine learning is also defined as an algorithm that increases the performance of a task through steady experience on a task.

Robot means a machine that automatically processes or operates a given task by its own ability. In particular, robots with the ability to recognize the environment and make self-determination to perform actions can be called intelligent robots. Robots can be classified as industrial, medical, home, military, etc., depending on the purpose or area of use. The robot can perform a variety of physical operations, such as moving the robot joints with actuators or motors. The movable robot also includes wheels, brakes, propellers, etc., on the drive, allowing it to drive on the ground or fly in the air.

Autonomous driving means a technology that drives on its own, and autonomous vehicles mean vehicles that drive without user's control or with minimal user's control. For example, autonomous driving may include maintaining lanes in motion, automatically adjusting speed such as adaptive cruise control, automatic driving along a set route, and automatically setting a route when a destination is set. The vehicle covers vehicles equipped with internal combustion engines, hybrid vehicles equipped with internal combustion engines and electric motors, and electric vehicles equipped with electric motors, and may include trains, motorcycles, etc., as well as cars. Autonomous vehicles can be seen as robots with autonomous driving functions.

Extended reality is collectively referred to as VR, AR, and MR. VR technology provides objects and backgrounds of real world only through computer graphic (CG) images. AR technology provides a virtual CG image on top of a real object image. MR technology is a CG technology that combines and combines virtual objects into the real world. MR technology is similar to AR technology in that they show real and virtual objects together. However, there is a difference in that in AR technology, virtual objects are used as complementary forms to real objects, while in MR technology, virtual objects and real objects are used as equal personalities.

NR supports multiples numerologies (and/or multiple subcarrier spacings (SCS)) to support various 5G services. For example, if SCS is 15 kHz, wide area can be supported in traditional cellular bands, and if SCS is 30 kHz/60 kHz, dense-urban, lower latency, and wider carrier bandwidth can be supported. If SCS is 60 kHz or higher, bandwidths greater than 24.25 GHz can be supported to overcome phase noise.

FIG.2shows an example of wireless devices to which implementations of the present disclosure is applied.

Referring toFIG.2, a first wireless device100and a second wireless device200may transmit/receive radio signals to/from an external device through a variety of RATs (e.g., LTE and NR).

InFIG.2, {the first wireless device100and the second wireless device200} may correspond to at least one of {the wireless device100ato100fand the BS200}, {the wireless device100ato100fand the wireless device100ato100f} and/or {the BS200and the BS200} ofFIG.1.

The first wireless device100may include at least one transceiver, such as a transceiver106, at least one processing chip, such as a processing chip101, and/or one or more antennas108.

The processing chip101may include at least one processor, such a processor102, and at least one memory, such as a memory104. It is exemplarily shown inFIG.2that the memory104is included in the processing chip101. Additional and/or alternatively, the memory104may be placed outside of the processing chip101.

The processor102may control the memory104and/or the transceiver106and may be configured to implement the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts described in the present disclosure. For example, the processor102may process information within the memory104to generate first information/signals and then transmit radio signals including the first information/signals through the transceiver106. The processor102may receive radio signals including second information/signals through the transceiver106and then store information obtained by processing the second information/signals in the memory104.

The memory104may be operably connectable to the processor102. The memory104may store various types of information and/or instructions. The memory104may store a software code105which implements instructions that, when executed by the processor102, perform the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure. For example, the software code105may implement instructions that, when executed by the processor102, perform the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure. For example, the software code105may control the processor102to perform one or more protocols. For example, the software code105may control the processor102to perform one or more layers of the radio interface protocol.

Herein, the processor102and the memory104may be a part of a communication modem/circuit/chip designed to implement RAT (e.g., LTE or NR). The transceiver106may be connected to the processor102and transmit and/or receive radio signals through one or more antennas108. Each of the transceiver106may include a transmitter and/or a receiver. The transceiver106may be interchangeably used with radio frequency (RF) unit(s). In the present disclosure, the first wireless device100may represent a communication modem/circuit/chip.

The second wireless device200may include at least one transceiver, such as a transceiver206, at least one processing chip, such as a processing chip201, and/or one or more antennas208.

The processing chip201may include at least one processor, such a processor202, and at least one memory, such as a memory204. It is exemplarily shown inFIG.2that the memory204is included in the processing chip201. Additional and/or alternatively, the memory204may be placed outside of the processing chip201.

The processor202may control the memory204and/or the transceiver206and may be configured to implement the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts described in the present disclosure. For example, the processor202may process information within the memory204to generate third information/signals and then transmit radio signals including the third information/signals through the transceiver206. The processor202may receive radio signals including fourth information/signals through the transceiver106and then store information obtained by processing the fourth information/signals in the memory204.

The memory204may be operably connectable to the processor202. The memory204may store various types of information and/or instructions. The memory204may store a software code205which implements instructions that, when executed by the processor202, perform the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure. For example, the software code205may implement instructions that, when executed by the processor202, perform the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure. For example, the software code205may control the processor202to perform one or more protocols. For example, the software code205may control the processor202to perform one or more layers of the radio interface protocol.

Herein, the processor202and the memory204may be a part of a communication modem/circuit/chip designed to implement RAT (e.g., LTE or NR). The transceiver206may be connected to the processor202and transmit and/or receive radio signals through one or more antennas208. Each of the transceiver206may include a transmitter and/or a receiver. The transceiver206may be interchangeably used with RF unit. In the present disclosure, the second wireless device200may represent a communication modem/circuit/chip.

Hereinafter, hardware elements of the wireless devices100and200will be described more specifically. One or more protocol layers may be implemented by, without being limited to, one or more processors102and202. For example, the one or more processors102and202may implement one or more layers (e.g., functional layers such as physical (PHY) layer, media 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). The one or more processors102and202may generate one or more protocol data units (PDUs) and/or one or more service data unit (SDUs) according to the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure. The one or more processors102and202may generate messages, control information, data, or information according to the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure. The one or more processors102and202may generate signals (e.g., baseband signals) including PDUs, SDUs, messages, control information, data, or information according to the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure and provide the generated signals to the one or more transceivers106and206. The one or more processors102and202may receive the signals (e.g., baseband signals) from the one or more transceivers106and206and acquire the PDUs, SDUs, messages, control information, data, or information according to the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure.

The one or more processors102and202may be referred to as controllers, microcontrollers, microprocessors, or microcomputers. The one or more processors102and202may 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 the one or more processors102and202. The descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure may be implemented using firmware or software and the firmware or software may be configured to include the modules, procedures, or functions. Firmware or software configured to perform the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure may be included in the one or more processors102and202or stored in the one or more memories104and204so as to be driven by the one or more processors102and202. The descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure may be implemented using firmware or software in the form of code, commands, and/or a set of commands.

The one or more transceivers106and206may transmit user data, control information, and/or radio signals/channels, mentioned in the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure, to one or more other devices. The one or more transceivers106and206may receive user data, control information, and/or radio signals/channels, mentioned in the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure, from one or more other devices. For example, the one or more transceivers106and206may be connected to the one or more processors102and202and transmit and receive radio signals. For example, the one or more processors102and202may perform control so that the one or more transceivers106and206may transmit user data, control information, or radio signals to one or more other devices. The one or more processors102and202may perform control so that the one or more transceivers106and206may receive user data, control information, or radio signals from one or more other devices.

The one or more transceivers106and206may be connected to the one or more antennas108and208and the one or more transceivers106and206may be configured to transmit and receive user data, control information, and/or radio signals/channels, mentioned in the descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in the present disclosure, through the one or more antennas108and208. In the present disclosure, the one or more antennas108and208may be a plurality of physical antennas or a plurality of logical antennas (e.g., antenna ports).

The one or more transceivers106and206may convert received user data, control information, radio signals/channels, etc., from RF band signals into baseband signals in order to process received user data, control information, radio signals/channels, etc., using the one or more processors102and202. The one or more transceivers106and206may convert the user data, control information, radio signals/channels, etc., processed using the one or more processors102and202from the base band signals into the RF band signals. To this end, the one or more transceivers106and206may include (analog) oscillators and/or filters. For example, the one or more transceivers106and206can up-convert OFDM baseband signals to OFDM signals by their (analog) oscillators and/or filters under the control of the one or more processors102and202and transmit the up-converted OFDM signals at the carrier frequency. The one or more transceivers106and206may receive OFDM signals at a carrier frequency and down-convert the OFDM signals into OFDM baseband signals by their (analog) oscillators and/or filters under the control of the one or more processors102and202.

In the implementations of the present disclosure, a UE may operate as a transmitting device in uplink (UL) and as a receiving device in downlink (DL). In the implementations of the present disclosure, a BS may operate as a receiving device in UL and as a transmitting device in DL. Hereinafter, for convenience of description, it is mainly assumed that the first wireless device100acts as the UE, and the second wireless device200acts as the BS. For example, the processor(s)102connected to, mounted on or launched in the first wireless device100may be configured to perform the UE behavior according to an implementation of the present disclosure or control the transceiver(s)106to perform the UE behavior according to an implementation of the present disclosure. The processor(s)202connected to, mounted on or launched in the second wireless device200may be configured to perform the BS behavior according to an implementation of the present disclosure or control the transceiver(s)206to perform the BS behavior according to an implementation of the present disclosure.

FIG.3shows an example of a wireless device to which implementations of the present disclosure is applied.

FIG.4shows an example of a network node to which implementations of the present disclosure is applied.

FIG.4is a diagram illustrating the second wireless device200ofFIG.2or the wireless device200ofFIG.3described above in more detail, when the base station is divided into a central unit (CU) and a distributed unit (DU).

Referring toFIG.4, base station200may be connected to core network300. Base stations200may be connected to each other. For example, an interface between the base station200and the core network300may be referred to as NG. For example, an interface between base stations200may be referred to as Xn.

Base station200may be divided into CU210and DU220. That is, base station200may be hierarchically separated and operated. CU210may be connected to one or more DUs220. For example, an interface between the CU210and the DU220may be referred to as F1. The CU210may perform a function of upper layers of the base station200, and the DU220may perform a function of lower layers of the base station200. For example, the CU210may be a logical node hosting RRC, SDAP, and PDCP layers of the base station200(e.g., gNB). Alternatively, the CU (W32) may be a logical node hosting the RRC and PDCP layers of the base station200(e.g., ng-eNB). For example, DU220may be a logical node hosting the RLC, MAC and PHY layers of the base station.

The operation of DU220may be partially controlled by CU210. One DU220may support one or more cells. One cell may be supported by only one DU220. One DU220may be connected to one CU210, and one DU220may be connected to a plurality of CUs210according to appropriate implementation.

FIG.5shows an example of 5G system architecture to which implementations of the present disclosure is applied.

The 5G system (5GS) architecture consists of the following network functions (NF).Authentication Server Function (AUSF)Access and Mobility Management Function (AMF)Data Network (DN), e.g., operator services, Internet access or 3rd party servicesUnstructured Data Storage Function (UDSF)Network Exposure Function (NEF)Intermediate NEF (I-NEF)Network Repository Function (NRF)Network Slice Selection Function (NSSF)Policy Control Function (PCF)Session Management Function (SMF)Unified Data Management (UDM)Unified Data Repository (UDR)User Plane Function (UPF)UE radio Capability Management Function (UCMF)Application Function (AF)User Equipment (UE)(Radio) Access Network ((R)AN)5G-Equipment Identity Register (5G-EIR)Network Data Analytics Function (NWDAF)CHarging Function (CHF)

Furthermore, the following network functions may be considered.Non-3GPP InterWorking Function (N3IWF)Trusted Non-3GPP Gateway Function (TNGF)Wireline Access Gateway Function (W-AGF)

FIG.5depicts the 5G system architecture in the non-roaming case, using the reference point representation showing how various network functions interact with each other.

InFIG.5, for the sake of clarity of the point-to-point diagrams, the UDSF, NEF and NRF have not been depicted. However, all depicted Network Functions can interact with the UDSF, UDR, NEF and NRF as necessary.

For clarity, the UDR and its connections with other NFs, e.g., PCF, are not depicted inFIG.5. For clarity, the NWDAF and its connections with other NFs, e.g., PCF, are not depicted inFIG.5.

The 5G system architecture contains the following reference points:N1: Reference point between the UE and the AMF.N2: Reference point between the (R)AN and the AMF.N3: Reference point between the (R)AN and the UPF.N4: Reference point between the SMF and the UPF.N6: Reference point between the UPF and a Data Network.N9: Reference point between two UPFs.

The following reference points show the interactions that exist between the NF services in the NFs.N5: Reference point between the PCF and an AF.N7: Reference point between the SMF and the PCF.N8: Reference point between the UDM and the AMF.N10: Reference point between the UDM and the SMF.N11: Reference point between the AMF and the SMF.N12: Reference point between the AMF and the AUSF.N13: Reference point between the UDM and the AUSF.N14: Reference point between two AMFs.N15: represents a reference point between PCF and AMF, and a reference point between AMF and PCF of a visited network in a roaming scenario.N16: Reference point between two SMFs, (in roaming case between SMF in the visited network and the SMF in the home network).N22: Reference point between the AMF and the NSSF.N30: Reference point between PCF and NEF.N33: Reference point between AF and NEF.

In some cases, a couple of NFs may need to be associated with each other to serve a UE.

For reference, inFIG.5, an AF by a third party other than an operator may be connected to 5GC through NEF.

Hereinafter, network slicing to be introduced in next-generation mobile communication will be described.

Next-generation mobile communication introduces the concept of network slicing in order to provide various services through one network. Here, the network slicing is a combination of network nodes having functions necessary to provide a specific service. A network node constituting a slice instance may be a hardware independent node or a logically independent node.

Each slice instance may be composed of a combination of all nodes necessary to configure the entire network. In this case, one slice instance may independently provide a service to the UE.

Alternatively, the slice instance may be composed of a combination of some nodes among nodes constituting the network. In this case, the slice instance may not provide a service to the UE alone, but may provide a service to the UE in association with other existing network nodes. In addition, a plurality of slice instances may provide a service to the UE in association with each other.

A slice instance is different from a dedicated core network in that the entire network node including the Core Network (CN) node and the RAN can be separated. In addition, a slice instance is different from a dedicated core network in that network nodes can simply be logically separated.

For reference, for a network slice, quota may be used.

For example, a quota related to a network slice may include a quota for the maximum number of UEs. The quota for the maximum number of UEs may mean the maximum number of terminals that can use a network slice at the same time. As an example, each network slice information may include quota information for the maximum number of UEs (e.g., 10 pieces, 1000000 pieces, etc.).

For example, a quota related to a network slice may include a quota for the maximum number of PDU sessions. The quota for the maximum number of PDU sessions may mean the maximum number of concurrent PDU sessions supported in the network slice. For example, the maximum number of concurrent (concurrent) PDU sessions supported in a network slice may mean the maximum number of PDU sessions established at the same time in one network slice related to a DNN (Data Network Name) defined by S-NSSAI.

In 5G mobile communication, network slice quota event notification may be supported in the network slice. For example, event notification about a quota related to a network slice may be supported. For example, an AF may request an event notification about a quota related to a network slice in 5GS. Then, AF may be notified of quota for attributes related to network slices in 5GS. For example, 5GS may inform the AF whether the quota for a particular attribute has reached a specified threshold. AF may then influence the 5GS routing decision.

FIG.6is an exemplary diagram illustrating an example of an architecture for implementing the concept of network slicing.

As can be seen with reference toFIG.6, the Core Network (CN) may be divided into several slice instances. Each slice instance may include one or more of a CP function node and a UP function node.

Each UE may use a network slice instance suitable for its own service through the RAN.

Unlike shown inFIG.6, each slice instance may share one or more of a CP function node and a UP function node with another slice instance. This will be described with reference toFIG.7as follows.

FIG.7is an exemplary diagram illustrating another example of an architecture for implementing the concept of network slicing.

Referring toFIG.7, a plurality of UP functional nodes is clustered, and similarly, a plurality of CP functional nodes is also clustered.

And, referring toFIG.7, slice instance #1 (or referred to as instance #1) in the core network includes the first cluster of UP functional nodes. And, the slice instance #1 shares a cluster of CP functional nodes with slice #2 (or referred to as instance #2). The slice instance #2 includes a second cluster of UP functional nodes.

The illustrated NSSF selects a slice (or instance) that can accommodate the service of the UE.

The illustrated UE may use service #1 through the slice instance #1 selected by the NSSF, and may use service #2 through the slice instance #2 selected by the NSSF.

For the PDU Session Establishment procedure, two different types of PDU Session Establishment procedures may exist as described below.A PDU Session Establishment procedure initiated by the UE.A PDU Session Establishment procedure initiated by the network. For this, the network may transmit a Device Trigger message to an application (or applications) of the UE.

FIGS.8aand8bare a signal flowchart illustrating an exemplary PDU session establishment procedure.

The procedure shown inFIGS.8aand8bassumes that the UE has already registered on the AMF according to the registration procedure. Therefore, it is assumed that the AMF has already acquired user subscription data from UDM.

1) The UE transmits a NAS message to the AMF. The message may include Single-Network Slice Selection Assistance Information (S-NSSAI), DNN, PDU session ID, a Request type, N1 SM information (including PDU Session Request), and so on.

Specifically, the UE includes the S-NSSAI from the allowed (allowed) NSSAI of the current access type. If information on the mapped NSSAI is provided to the UE, the UE may provide both the S-NSSAI based on the allowed NSSAI and the corresponding S-NSSAI based on the information of the mapped NSSAI. Here, the mapped NSSAI information is information that maps each S-NSSAI of the allowed NSSAI to the S-NASSI of the NSSAI configured for HPLMN.

More specifically, The UE may extract and store the information of the allowed S-NSSAI and the mapped S-NSSAI included in the registration accept message received from the network (i.e., AMF) in the registration procedure. Accordingly, the UE may transmit the PDU session establishment request message by including both the S-NSSAI based on the allowed NSSAI and the corresponding S-NSSAI based on the mapped NSSAI information.

In order to establish a new PDU session, the UE may generate a new PDU session ID.

By transmitting a NAS message having a PDU Session Establishment Request message included in N1 SM information, the PDU Session Establishment procedure that is initiated by the UE may be started. The PDU Session Establishment Request message may include a Request type, an SSC mode, and a protocol configuration option.

In case the PDU Session Establishment is for configuring a new PDU session, the Request type indicates “initial access”. However, in case an existing PDU session exists between the 3GPP access and the non-3GPP access, the Request type may indicate an “existing PDU session”.

The NAS message being transmitted by the UE is encapsulated within an N2 message by the AN. The N2 message is transmitted to the AMF and may include user location information and access technique type information.The N1 SM information may include an SM PDU DN request container including information on a PDU session authentication performed by an external DN.

2) In case the request type indicates an “initial request”, and in case the PDU session ID has not been used for the existing PDU session of the UE, the AMF may determine that the message corresponds to a request for a new PDU session.

If the NAS message does not include the S-NSSAI, the AMF may determine default S-NSSAI for the requested PDU session according to the UE subscription. The AMF may relate a PDU session ID with an ID of the SMF and may store the PDU session ID.

3) The AMF transmits an SM request message to the SMF. The SM request message may include a subscriber permanent ID, DNN, S-NSSAI, a PDU session ID, an AMD IF, N1 SM information, user location information, and an access technique type. The N1 SM information may include a PDU session ID and a PDU Session Establishment Request message.

The AMF ID is used for identifying an AMF providing services to the UE. The N1 SM information may include the PDU Session Establishment Request message, which is received from the UE.

4a) The SMF transmits a Subscriber Data Request message to the UDM. The Subscriber Data Request message may include a subscriber permanent ID and DNN.

In the above-described Process 3, in case the Request type indicates an “existing PDU session”, the SMF determines that the corresponding request is caused by a handover between the 3GPP access and the non-3GPP access. The SMF may identify the existing PDU session based on the PDU session ID.

In case the SMF has not yet searched the SN-related subscription data for the UE that is related to the DNN, the SMF may request the subscription data.

4b) The UDM may transmit a Subscription Data Response message to the SMF.

The subscription data may include an authenticated Request type, an authenticated SSC mode, and information on a default QoS profile.

The SMF may verify whether or not the UE request follows the user subscription and local policy. Alternatively, the SMF may reject the UE request via NAS SM signaling (including the related SM rejection cause), which is forwarded (or transferred) by the AMF, and then the SMF may notify to the AMF that this shall be considered as a release of the PDU session ID.

5) The SMF transmits a message to the DN through a UPF.

More specifically, in case the SMF is required to authorize/authenticate a PDU session establishment, the SMT selects a UPF and triggers the PDU.

If the PDU Session Establishment authentication/authority assignment fails, the SMF ends the PDU Session Establishment procedure and notifies the rejection to the UE.

6a) If dynamic PCC is distributed, the SMF selects a PCF.

6b) The SMF may start a PDU-CAN session establishment towards the PCF in order to obtain a default PCC rule for the PDU session. In case the Request type indicates an “existing PDU session”, the PCF may start a PDU-CAN session modification instead.

7) In case the Request type of Process 3 indicates an “initial request”, the SMF selects an SSC mode for the PDU session. If Process 5 is not performed, the SMF may also select a UPF. In case of Request type IPv4 or IPv6, the SMF may allocate an IP address/prefix for the PDU session.

8) In case dynamic PCC is deployed and the PDU-CAN session establishment is not yet completed, the SMF may begin (or start) PDU-CAN Session Start.

9) In case the Request type indicates an “initial request”, and in case Process 5 is not performed, the SMF may use the selected UPF and start an N4 Session Establishment procedure. And, otherwise, the SMF may use the selected and start an N4 Session Modification procedure.

9a) The SMF transmits an N4 Session Establishment/Modification request message to the UPF. And, the SMF may provide packet discovery, execution, and reporting rules of packets that are to be installed in the UPF for the PDU session. In case the SMF allocates CN tunnel information, the CN tunnel information may be provided to the UPF.

9b) By transmitting an N4 Session Establishment/Modification response message, the UPF may respond. In case the CN tunnel information is allocated by the UPF, the CN tunnel information may be provided to the SMF.

10) The SMF transmits an SM response message to the AMF. The message may include a cause, N2 SM information, and N1 SM information. The N2 SM information may include a PDU session ID, a QoS profile, and CN tunnel information. The N1 SM information PDU Session Establishment Accept message. The PDU Session Establishment Accept message may include an allowed QoS rule, an SSC mode, S-NSSAI, and allocated IPv4 address.

As information that shall be forwarded to the RAN by the AMF, the N2 SM information may include the following.CN Tunnel information: This corresponds to a core network address of an N3 tunnel corresponding to the PDU session.QoS Profile: This is used for providing mapping between a QoS parameter and a QoS flow identifier (QFI) to the RAN.PDU Session ID: This may be used for indicating a relation between AN resources for the UE and the PDU session to the UE via AN signaling for the UE.

Meanwhile, the N1 SM information includes a PDU Session Establishment Accept message that shall be provided to the UE by the AMF.

Multiple QoS rules may be included in the N1 SM information and the N2 SM information within the PDU Session Establishment Accept message.The SM response message also includes information enabling the PDU session ID and AMF to determine not only which target UE to use but also which access is to be used for the UE.

11) The AMF transmits an N2 PDU Session Request message to the RAN. The message may include N2 SM information and an NAS message. The NAS message may include a PDU session ID and a PDU Session Establishment Accept message.

The AMF may transmit an NAS message including a PDU session ID and a PDU Session Establishment Accept message. Additionally, the AMF may include the N2 SM information received from the SMF in the N2 PDU Session Request message and may then transmit the message including the N2 SM information to the RAN.

12) The RAN may perform a specific signaling exchange with a UE being related to the information received from the SMF.

The RAN also allocates RAN N3 tunnel information for the PDU session.

The RAN forwards the NAS message, which is provided in Process 10. The NAS message may include a PDU session ID and N1 SM information. The N1 SM information may include a PDU Session Establishment Accept message.

The RAN transmits the NAS message to the UE only in a case where a needed RAN resource is configured and allocation of RAN tunnel information is successful.

13) The RAN transmits an N2 PDU Session Response message to the AMF. The message may include a PDU session ID, a cause, and N2 SM information. The N2 SM information may include a PDU session ID, (AN) tunnel information, and a list of allowed/rejected QoS profiles.The RAN tunnel information may correspond to an access network address of an N3 tunnel corresponding to the PDU session.

14) The AMF may transmit an SM Request message to the SMF. The SM Request message may include N2 SM information. Herein, the AMF may forward the N2 SM information received from the RAN to the SMF.

15a) In an N4 session for the PDU session has not already been configured, the SMF may start an N4 Session Establishment procedure along with the UPF. Otherwise, the SMF may use the UPF to start an N4 Session Modification procedure. The SMF may provide AN tunnel information and CN tunnel information. The CN tunnel information shall be provided only in a case where the SMF selects the CN tunnel information in Process 8.

15b) The UPF may transmit an N4 Session Establishment/Modification Response message to the SMF.

16) The SMF may transmit an SM Response message to the AMF. When this process is ended (or completed), the AMF may forward the related event to the SMF. This occurs during a handover, in which the RAN tunnel information is modified or the AMF is re-deployed.

17) The SMF transmits information to the UE through the UPF. More specifically, in case of PDU Type IPv6, the SMF may generate an IPv6 Router Advertisement and may transmit the generated advertisement to the UE through the N4 and UPF.

18) In case the PDU Session Establishment Request is caused by a handover between the 3GPP access and the non-3GPP access, i.e., if the Request type is configured as an “existing PDU session”, the SMF releases the user plane through a source access (3GPP or non-3GPP access).

19) In case the ID of the SMF is not included in Process 4b by the UDM of the DNN subscription context, the SMF may call (or page or summon) a “UDM_Register UE serving NF service” including an SMF address and DNN. The UDM may store the ID, address, and DNN of the SMF.

During the procedure, if the PDU Session Establishment is not successful, the SMF notifies this to the AMF.

II. Techniques and Procedures Related to the Disclosure of the Present Specification

Techniques and procedures related to the disclosure herein are described below. In addition, examples of problems to be solved in the disclosure of the present specification may also be described below.

A method for supporting 5GC assisted cell selection to access a network slice (e.g., “Support of 5GC assisted cell selection to access network slice”) is required. For example, the present disclosure proposes examples of schemes for supporting 5GC support cell selection for accessing a network slice.

In particular, a terminal receiving a service for a specific network slice (e.g. Single-Network Slice Selection Assistance Information (S-NSSAI)-1) through a specific frequency band, may try to get service for S-NSSAI-2 through a different frequency band. In this case, it is necessary to discuss how to handle the PDU session being used in the existing S-NSSAI-1.

There may be a network slice that the UE wants to use. In this case, to use this network slice, the UE transmits Single-Network Slice Selection Assistance Information (S-NSSAI) related to this network slice to the network, the UE may attempt an operation of selecting a 5G Access Network (5G-AN) (e.g. a specific frequency band).

On the other hand, the UE must try to select 5G-AN until S-NSSAI is allowed, without the UE knowing whether 5G-AN supports S-NSSAI. It is necessary to discuss whether to support S-NSSAI-aware 5G-AN selection and how to support it.

In relation to this issue, when an operator manages different ranges of radio spectrums per network slice, a method of selecting a specific cell that can be used to access the network slice needs to be discussed. For example, the following examples need to be discussed:How does 5GS steer UEs to a 5G-AN (e.g. a specific frequency band) that can support the network slices that the UE can use.What information does 5GS need to take a decision to steer UE to a proper 5G-AN.What information should be provided to the UE to select a proper 5G-AN and how it is sent to the UE.

Hereinafter, with reference toFIG.9, an example of a conventional procedure for supporting radio spectrum attribute by CN assisted RAN control will be described.

The example ofFIG.9is an example of a conventional procedure for solving the problems described above.

If the network cannot accept the Requested NSSAI because it is not allowed within the current Tracking Area Identity (TAI), 5GC may provide the Requested NSSAI and the corresponding RAT/Frequency Selection Priority (RFSP) to the NG-RAN. The RAN may select a radio spectrum suitable for the UE. Regarding the example ofFIG.9, a series of events can be envisioned such as the following example:1. The Network Slice may be created for supporting specific radio spectrum to support vertical requirements, and other Network Slices, e.g. network slices related to eMBB, are created supporting the radio spectrum available for the operator.2. The UE may have a subscription for both the vertical Network Slice and an eMBB Network Slice.3. The subscription for the UE includes the vertical S-NSSAI and eMBB S-NSSAI and the eMBB S-NSSAI is marked as default;4. The UE has been registered in the network and been configured with a Configured NSSAI and provided an Allowed NSSAI including the eMBB but not the vertical Network Slice;5. The UE/user decides to use the vertical S-NSSAI and therefore issues a Requested NSSAI with only the vertical S-NSSAI.6. If at least one S-NSSAI in the Requested NSSAI is not allowed in the current TAI, the 5GC derive a Target NSSAI that is same as the Requested NSSAI (excluding any S-NSSAIs that are e.g. rejected for the PLMN).

The following drawings are made to explain a specific example of the present specification. Since the names of specific devices or names of specific signals/messages/fields described in the drawings are provided as examples, the technical features of the present specification are not limited to the specific names used in the drawings below.

FIG.9shows an example of a procedure for supporting radio spectrum attributes by CN-assisted RAN control.

The example ofFIG.9shows an example of a procedure performed when a UE registers in a TA defined as not supporting any of the S-NSSAIs of Requested NSSAI.

In the example ofFIG.9, the UE requests to be registered to vertical S-NSSAI while not using the radio spectrum defined for the vertical Network Slice.

1. The UE decides to use Vertical S-NSSAI and sends a Registration Request (Requested NSSAI=Vertical S-NSSAI). The RRC includes the GUAMI. NG-RAN selects AMF as per current procedures.

2. The AMF and NSSF performs Network Slice selection. As the Vertical S-NSSAI is not defined for the current TAI, the AMF/NSSF selects the eMBB S-NSSAI as Allowed NSSAI due to it is defined as the default Subscribed S-NSSAI;

3. The Allowed NSSAI has not been changed, but the fact that at least one of the S-NSSAIs in the Requested NSSAI is not allowed in the current TAI is taken as a trigger for AMF Policy Update towards the PCF, the AMF provides Allowed NSSAI, Subscribed RFSP and also a Target NSSAI with the content of the Requested NSSAI, where the AMF removes any S-NSSAI in Requested NSSAI that is not a Subscribed S-NSSAI.

4. The PCF may select RFSP for both the Allowed NSSAI and the Target NSSAI (without considering the current TAI) and send both to the AMF;

5. The AMF sends an N2 message to the NG-RAN with Allowed NSSAI and the corresponding RFSP Index, and in addition the AMF sends the Target NSSAI and the corresponding RFSP Index, and the NAS message that includes the eMBB S-NSSAI as Allowed NSSAI and the Vertical S-NSSAI as a rejected S-NSSAI for the RA.

6. The NG-RAN may forward the NAS message to the UE.

7. The NG-RAN determines the Radio Spectrum to be used in order to allow UE access to the Target NSSAI, and as the NG-RAN got the additional Target NSSAI and RFSP Index for the Target NSSAI the NG-RAN decides to move the UE accordingly;

8. The NG-RAN issues an RRC Release and includes cell reselection priorities or the NG-RAN performs a Reconfiguration and moves the UE according to the RFSP for the Target NSSAI;

For reference, steps 6 and 8 can possibly be done at the same time.

9. The UE realizes that the TAI is outside of the RA and issues a Registration Request and includes the Vertical S-NSSAI in the Requested NSSAI as the UE still wants to register to that Network Slice;

10. Network Slice selection is performed as per conventional procedures.

11. The AMF sends a Registration Accept as per current procedures and includes the Vertical S-NSSAI as Allowed NSSAI.

Note that, If the eMBB slice is not available on the radio spectrum dedicated to the vertical Network Slice, as these Network Slices are to be isolated, when an application in the UE requires connectivity for eMBB, the whole procedure is repeated with the UE adding the eMBB slice in a Requested NSSAI.

According to the example ofFIG.9, NG-RAN may support getting additional Target NSSAI and RFSP Index for the Target NSSAI, and support moving the UE accordingly. AMF may support a new or extended Policy Control Request Trigger condition when Allowed NSSAI is based on default Subscribed S-NSSAI(s) due to Requested NSSAI was not supported in the current TAI. The AMF may support providing Target NSSAI to the PCF in the Npcf_AMPolicyControl_Update Request message, and support receiving RFSP Index for the Target NSSAI in the Npcf_AMPolicyControl_Update Response message. The AMF may support providing Target NSSAI and RFSP Index for the Target NSSAI to NG-RAN in an N2 message. The PCF may support determining an RFSP for the Target NSSAI. The PCF may support extending the Access and mobility related policy control information with RFSP Index for the Target NSSAI.

Hereinafter, an example of a prior art in which Operating Band Information is provided together with Configured NSSAI will be described. What will be described below may be an example of a method for supporting 5GC assisted cell selection for accessing a network slice (e.g., “Support of 5GC assisted cell selection to access network slice”). In the provision of Operating Band Information, structural assumptions such as the following examples may be applied:The UE shall not simultaneously register to slices that are not all accessible on the same operating band(s). In other words, the UE shall not have S-NSSAIs in the Allowed NSSAI that are not all available in a common operating band

The UE may be provisioned with the operating band(s) that are allowed for each S-NSSAI in the PLMN. This information (e.g., Operating Band Information) is sent to the UE in the Configured NSSAI and Mapping of Configured NSSAI. It is then understood that the UE will only request slices that are all accessible in the same operating band(s) and the AMF will include in the Allowed NSSAI only S-NSSAI(s) that are all accessible in the same operating band(s). The RFSP Index will be determined based on the Allowed NSSAI.

According to the operation of the prior art, the serving AMF may determine a Registration Area such that all S-NSSAIs of the Allowed NSSAI for this Registration Area are available in all Tracking Areas of the Registration Area. However, the case where some cell(s) in the tracking area(s) do not support all of the slices in the Allowed NSSAI may be allowed. If some cell(s) in the tracking area(s) do not support all of the slices in the Allowed NSSAI, then the RFSP Index will be selected such that the UE will not select operating bands (i.e. cells) that do not allow the UE to simultaneously access all of the slices in the Allowed NSSAI.

When the UE is provisioned with a Configured NSSAI or Mapping of Configured NSSAI (i.e. pre-provisioned, provisioned during Registration, or provisioned during a UE Configuration Update), the UE is also provisioned with the operating band(s) of each S-NSSAI in the Configured S-NSSAI or Mapping of Configured NSSAI. In the case where the operator slice deployment is governed by frequency ranges (e.g. FR1 and FR2), the AMF may indicate that an S-NSSAI is supported on [FR1 only], [FR2 only] or [FR1+FR2] instead of explicitly listing out all the operating bands where each S-NSSAI is supported. The Default Configured NSSAI is not associated with any specific operating band information but may be associated with frequency range information.

The UE may take into account the operating band(s) of each S-NSSAI when the UE selects a cell to camp on and/or generates a Requested NSSAI, e.g. UE selects S-NSSAIs which are associated with the operating band that the UE is currently using and generates a Requested NSSAI based on the operating band.

If the UE is interested to access an S-NSSAI which is not supported on the currently camped operating band and not in the Allowed NSSAI, the UE may choose to re-select to the new operating band, initiate the radio connection, and send a Mobility Registration Update Request and include the S-NSSAI in the Requested NSSAI.

The Registration Accept message and UE Configuration Update Command from the AMF to the UE may be updated to include permissible operating band(s) of each S-NSSAI in the Configured S-NSSAI and to include permissible operating band(s) of each S-NSSAI in the Mapping of Configured S-NSSAI.

In the Registration and UE Configuration Update procedures, the AMF will only include S-NSSAIs in the UE's Allowed NSSAI that are all available via the UE's current operating band. The AMF may be locally provisioned with operating band information for each S-NSSAI.

The AMF may provide the UE with permissible operating band(s) for each S-NSSI in the Configured NSSAI and Mapping of Configured NSSAI. During the Registration and UE Configuration Update procedures, the UE may receive permissible operating band(s) for each S-NSSAI in the Configured NSSAI and Mapping of Configured NSSAI.

Hereinafter, examples of the prior art for Preferred frequency bands in Configured NSSAI will be described. What will be described below may be an example of a method for supporting 5GC assisted cell selection for accessing a network slice (e.g., “Support of 5GC assisted cell selection to access network slice”). In the description of Preferred frequency bands in Configured NSSAI, the following example assumptions can be applied:If the UE registers to a single network slice identified by S-NSSAI which is accessible on some preferred frequency band(s), then the UE considers the list of preferred band(s) of this S-NSSAI for Idle mode mobility.If the UE registers to multiple network slices which are accessible on different preferred frequency band(s), then the UE may consider the provided configuration from the RAN to follow carrier frequencies for Idle mode mobility.The AMF (or NSSF, or both) and the NG-RAN may be configured with the preferred frequency band(s) per S-NSSAI. With this, signaling enhancements to the N2 MM and N2 SM signaling are not needed.

The UE is provided with preferred frequency band(s) information per network slice (e.g. target carrier frequencies per S-NSSAI) in the Configured NSSAI. The preferred frequency band(s) are applicable to the S-NSSAIs of the Serving PLMN. The UE may use this information for cell selection in order to select the appropriate cell offering the S-NSSAI.

The parameter preferred frequency bands may include a list of target carrier frequencies containing one or more entries, and for each entry a carrier frequency priority index may be associated as well. For example, the priority index indicating the priority for scanning/selecting of a carrier frequency.

It is assumed that the serving AMF provides to the UE with Allowed NSSAI as per principles known in a prior art. However, the network (e.g. AMF or NSSF) in addition considers the RAN deployment and the frequency bands where the requested S-NSSAIs are available when creating the Allowed NSSAI.

After the Configured NSSAI has been updated and the UE is in Idle state, the UE determines which S-NSSAIs it wants to register with, i.e. the S-NSSAIs to be included in the Requested NSSAI. Then, the UE performs cell selection procedure considering the frequency priority (and the priority index) for the S-NSSAI(s) to be included in the Requested NSSAI.

The Configured NSSAI is provided to the UE during the Registration Accept message and UE Configuration Update Command transmitted from the AMF.

The generation of the Allowed NSSAI (and correspondingly the Rejected S-NSSAIs) in the AMF or NSSF should take into account the local configuration with the preferred frequency band(s) per S-NSSAI.

With respect to the cell selection procedure, the UE may first create a Requested NSSAI (e.g. based on the Configured NSSAI) to be included in the Registration Request message. The UE may then consider the list of target carrier frequencies for the S-NSSAI values included in the Requested NSSAI. If there are more than one S-NSSAIs in the Requested NSSAI, the UE may prioritize the S-NSSAIs, and consequently, prioritize the carrier frequencies to be used for cell selection. The prioritization of S-NSSAIs is up to UE internal configuration (e.g. from higher layers) or user priorities.

If a Service Request procedure or activation of User plane (UP) resourced for a PDU Session procedure result in use of multiple network slices operated in different frequency bands, the NG-RAN node may decide to activate Dual Connectivity in order to used different frequency bands simultaneously.

The AMF may take into account the preferred frequency bands per S-NSSAI when generating the Configured NSSAI, Allowed NSSAI and Rejected S-NSSAIs. The AMF may provide to the UE preferred frequency bands per S-NSSAI within the Configured NSSAI

If the UE is allowed to use multiple S-NSSAIs, when the UE is transferred to Idle mode the NG-RAN steers the UE to the preferred carrier frequencies(s) for camping. If multiple network slices operating in different frequency bands are to be used in Connected state, the NG-RAN can activate Dual Connectivity or Carrier Aggregation based on local configuration.

The UE may take into account the preferred frequency bands per S-NSSAI as provided in the Configured NSSAI for Idle mode mobility

Hereinafter, with reference toFIG.10, an example of a conventional procedure for steer a UE to a network slice of a different frequency band will be described.

The following drawings are made to explain a specific example of the present specification. Since the names of specific devices or names of specific signals/messages/fields described in the drawings are provided as examples, the technical features of the present specification are not limited to the specific names used in the drawings below.

FIG.10shows an example of a procedure for steering a UE to a network slice of a different frequency band.

In the example ofFIG.10, the following situation may be assumed. The Allowed NSSSAI allocated to the UE may include S-NSSAIs supported in other frequency bands. However, all S-NSSAIs may be supported in all Tracking Areas or Registration Areas.

1) The UE is in idle mode, registered via RAN-1 for S-NSSAI-1, which operates only in frequency band 1 (FB-1) and S-NSSAI-2, which operates only in frequency band 2 (FB-2).

2) An application in the UE needs to establish service on S-NSSAI-2 in FB-2.

3) The UE may establish RRC connection with RAN-1.

4) The UE triggers PDU Session Establishment Request on S-NSSAI-2 via RAN-1.

5) AMF is aware that RAN-1, via which the UE is connected, does not support S-NSSAI-2 and the AMF is aware that S-NSSAI-2 is supported by another RAN Node.

6) AMF requests RAN-1 to steer the UE to a RAN Node supporting S-NSSAI-2.

7) RAN-1 triggers inter-frequency cell change to RAN-2 which supports S-NSSAI-2 and is in UE's location.

8) AMF continues with the PDU Session establishment procedure on S-NSSAI-2 via RAN-2.

9) After PDU session on S-NSSAI-2 is released, the UE falls-back (e.g. re-selects back) to a cell in FB-1. This step is optional. If not implemented, the UE will stay on FB-2 until it is steered back to FB-1 due to a new service request on FB-2.

According to the example ofFIG.9, a UE cell fallback operation to a cell of an initial frequency band may be selectively performed. AMF may determine and request handover to a cell of a different frequency band.

A method for supporting 5GC assisted cell selection to access a network slice (e.g., “Support of 5GC assisted cell selection to access network slice”) is required. A terminal receiving a service for a specific network slice (e.g. Single-Network Slice Selection Assistance Information (S-NSSAI)-1) through a specific frequency band, may try to get service for another network slice (e.g. S-NSSAI-2) through a different frequency band. In this case, it is necessary to discuss how to handle the PDU session being used in the existing S-NSSAI-1. For example, there is a need to discuss how to steer a UE to a 5G-Access Network (AN) (e.g., a specific frequency band) that a 5G System (5GS) can support a network slice (e.g., a network slice the UE can use) will be discussed. When 5GS makes decision to steer a UE to an appropriate 5G-AN, information needed for 5GS needs to be discussed. In order to select an appropriate 5G-AN, it is necessary to discuss what information 5GS should provide to the UE and how to transmit this information to the UE.

Meanwhile, according to various examples described above, after the UE performs handover to RAN-2, the UE performs a PDU session establishment procedure for S-NSSAI-2 with RAN-2. Accordingly, there is a problem in that unnecessary signaling occurs and it may take a long time for the terminal to receive the service.

In other words, when the terminal tries to use a specific network slice, the UE may transmit a message requesting establishment of a PDU (Protocol Data Unit or Packet Data Unit) session related to this network slice to the Next Generation Radio Access Network (NG-RAN) and/or the core network. In this case, a network slice supported by the NG-RAN and a frequency band related to the network slice may be different from a specific network slice and frequency band related to the PDU session requested by the UE. According to the prior art, in this case, the NG-RAN must reject the UE's PDU session establishment request for the corresponding PDU session.

After the NG-RAN rejects the terminal's PDU session establishment request, in order for the terminal to receive service through the network slice related to the PDU session, the UE must move to the NG-RAN supporting the corresponding network slice. And, after moving to the corresponding NG-RAN, the terminal must start the PDU session establishment procedure again. Accordingly, there is a problem in that unnecessary signaling occurs and it may take a long time for the terminal to receive the service.

In addition, in the course of the UE moving to the second NG-RAN, the PDU session for which the UE was provided with a service in the first NG-RAN is released. When the terminal wants to receive a service using the first PDU session again, after the terminal moves back to the first NG-RAN, it is necessary to perform a PDU session establishment procedure for generating a first PDU session, unnecessary signaling may occur.

In addition, if the handover procedure and/or redirection procedure for moving the terminal to the second NG-RAN fails, the terminal may repeatedly request a PDU session establishment request for the second PDU session from the first NG-RAN. Unnecessary signaling in which the terminal repeatedly requests a PDU session establishment request may occur.

III. Disclosure of the Present Specification

Disclosures described later in this specification may be implemented in one or more combinations (e.g., a combination including at least one of the contents described below). Each of the drawings represents an embodiment of each disclosure, but the embodiments of the drawings may be implemented in combination with each other.

Description of the method proposed in the disclosure of this specification may be composed of a combination of one or more operations/configurations/steps described below. The following methods described below may be performed or used in combination or complementary.

In the disclosure of the present specification, examples of methods for efficiently deactivating a PDU session being serviced through an existing frequency band when the frequency band used by the terminal is changed according to the slice used will be described.

Some of the service operations (e.g., service operation between Core NFs) described in various examples of the disclosure of this specification may be newly defined service operations for the disclosure of this specification. In addition, some of the N2 messages between AMF and NG-RAN described below may be newly defined N2 messages for the disclosure of this specification. In addition, in some of the RRC messages between the NG-RAN and the UE described below, a new RRC message may be defined and used for the disclosure of this specification.

Hereinafter, slice and S-NSSAI may be used interchangeably as terms representing the same meaning.

In the procedures described in various examples of the disclosure herein below, certain actions/steps may be performed concurrently/parallel, or may be performed in an order different from the order described in the disclosure herein.

Basically, in the disclosure of this specification, assumptions such as the following examples may be applied. It is assumed that information on frequency bands available for each network slice is not configured in the terminal. In addition, NG-RAN-1 supports S-NSSAI-1 using Frequency Band 1 (FB-1) frequency band, and NG-RAN-2 supports S-NSSAI-2 using FB-2 frequency band. Assume.

On the other hand, it is assumed that the AMF has information on network slices supported by each NG-RAN and frequency band information on each network slice. The AMF may receive such information through NG signaling such as NG setup or RAN configuration update messages, alternatively, the AMF may receive such information through pre-configuration with Operations, Administration and Maintenance (OAM).

Hereinafter, the disclosure of the present specification will be described with reference to the first to fourth examples of the disclosure of the present specification. The first to fourth examples of the disclosure of the present specification described below may be implemented in combination.

1. First Example of the Disclosure of the Present Specification

Hereinafter, a first example of the disclosure of the present specification will be described with reference to the examples ofFIGS.11aand11bto the examples ofFIGS.13aand13b.

1-1. First Example of First Example of the Disclosure of the Present Specification

First, a first example of a first example of the disclosure of the present specification will be described with reference to examples ofFIGS.11aand11b.

The following drawings are made to explain a specific example of the present specification. Since the names of specific devices or names of specific signals/messages/fields described in the drawings are provided as examples, the technical features of the present specification are not limited to the specific names used in the drawings below.

FIGS.11aand11bshow signal flow diagrams according to a first example of a first example of the disclosure of the present specification.

The examples ofFIGS.11aand11bmay include an operation of requesting deactivation to the SMF for the PDU session that the AMF was serving through the existing frequency band during the process of changing the frequency band of the terminal using Next Generation (NG)-based handover.

Step 0: The terminal may be already registered in the network. In addition, it is assumed that the terminal receives allowed NSSAI=S-NSSAI-1 and S-NSSAI-2 from AMF. In addition, the terminal may be in a state of establishing an RRC connection with NG-RAN-1 and having one or more PDU sessions for S-NSSAI-1 through SMF-1.

Step 1: The terminal may transmit a PDU session establishment request message for S-NSSAI-2 to the network through RRC and N2 message in order to receive service using S-NSSAI-2. At this time, the terminal may transmit a PDU session establishment request message for S-NSSAI-2 by including information such as a Globally Unique AMF ID (GUAMI) received from AMF in a previously performed registration procedure.

Step 2: The AMF knows that NG-RAN-1 to which terminal UE is currently connected does not support S-NSSAI-2. For example, based on information about network slices supported by each NG-RAN and frequency band information about each network slice, the AMF knows that NG-RAN-1 to which the terminal is connected does not support S-NSSAI-2. Accordingly, the AMF may determine that the terminal should be moved to one of the other NG-RANs supporting S-NSSAI-2. Until the terminal moves to the NG-RAN supporting S-NSSAI-2, the AMF may stop processing the PDU session establishment request for S-NSSAI-2 transmitted by the UE.

Step 3: The AMF may notify NG-RAN-1 using N2 message that the terminal should be moved to one of the other NG-RANs supporting S-NSSAI-2.

Step 4: Since NG-RAN-1 does not support S-NSSAI-2, based on the N2 message received in Step 3, NG-RAN-1 may know that NG-RAN-1 needs to move the UE toward the NG-RAN (e.g., NG-RAN-2) supporting S-NSSAI-2 among neighboring NG-RANs. To this end (to move the terminal to an NG-RAN (e.g., NG-RAN-2) supporting S-NSSAI-2), NG-RAN-1 may request a measurement result report from the UE and receive the measurement result from the UE. Based on the measurement result received from the terminal, NG-RAN-1 determines whether handover for the terminal is possible and if handover is executed, NG-RAN-1 may determine its target cell.

NG-RAN-1 may initiate an NG-based handover procedure while transmitting a Handover Required message to AMF. The Handover Required message may include PDU session information for S-NSSAI-1 served by NG-RAN-1. In addition, the Handover Required message may include an indication or cause value indicating that the reason why the current handover procedure was started is that the UE needs to move to a frequency band served by S-NSSAI-2. To inform the AMF and target NG-RAN (here, NG-RAN-2), this indication or cause value may be included in the Handover Required message.

In addition, NG-RAN-1 may deliver the context of the PDU session for S-NSSAI-1 to the target NG-RAN (here, NG-RAN-2) in a source to target transparent container.

Step 5: The AMF confirms that the target NG-RAN (here, NG-RAN-2) does not support S-NSSAI-1, the AMF may decide to deactivate the PDU session for S-NSSAI-1. Accordingly, AMF transmits an Nsmf_PDUSession_UpdateSMContext Request message to each SMF managing PDU sessions for S-NSSAI-1, such that the AMF may request deactivation for each PDU session. The Nsmf_PDUSession_UpdateSMContext Request message may include PDU Session information for S-NSSAI-1 received from NG-RAN-1 in Step 4.

For reference, in Step 4, NG-RAN-1 may transmit an indication (or information) requesting deactivation of the PDU session for S-NSSAI-1 to the AMF.

Step 6: The SMF (e.g. SMF-1) uses the N4 Session Release procedure or the N4 Session Modification procedure, such that the SMF (e.g., SMF-1) may request the UPF to delete the AN Tunnel Info for N3 tunnel information for the PDU session for S-NSSAI-1 received in Step 5. By making such a request, the SMF can prevent additional data transmission to the NG-RAN.

Step 7: The SMF transmits Nsmf_PDUSession_UpdateSMContext Response message or other message to AMF, such that the SMF may inform that the PDU session deactivation requested by the AMF has been successfully processed. The message may include information (e.g., PDU session ID (s) for S-NSSAI-1 and reason for deactivation of the PDU session, etc.) for releasing radio resources in the NG-RAN for the deactivated PDU session.

Step 8: AMF may transmit a Handover Request message to NG-RAN-2 based on the information received in Steps 4 and 7. The Handover Request message may include information about the reason for starting the handover and information that the PDU session for the S-NSSAI-1 served by NG-RAN-1 has been deactivated.

For reference, the Handover Request message may not include PDU Session information that can be serviced in NG-RAN-2 at all. This is because the PDU session may be deactivated by performing steps 5 to 7. In order for NG-RAN-2 to not process a Handover Request message (e.g., a Handover Request message that does not include PDU Session information that can be served in NG-RAN-2) as an error, NG-RAN-1 may add a separate indication in addition to the cause to the Handover Required message and deliver it to NG-RAN-2 through AMF (e.g., see step 7 in the examples ofFIGS.13aand13bbelow). Alternatively, in order to prevent NG-RAN-2 from processing a Handover Request message (e.g., a Handover Request message that does not include PDU Session information that can be served in NG-RAN-2) as an error, without involvement of NG-RAN-1, the AMF may transmit a Handover Request message to NG-RAN-2 by directly adding an indication to the Handover Request message.

Step 9: NG-RAN-2 can accept handover because it knows that the terminal must move to the frequency band served by S-NSSAI-2 even if there is no PDU session that can service the current terminal. For example, even if there is no PDU Session in which NG-RAN-2 can service the current terminal, since NG-RAN-2 has identified the cause, NG-RAN-2 can accept handover because it knows that the terminal must move to the frequency band served by S-NSSAI-2. Therefore, NG-RAN-2 may transmit a Handover Request Acknowledge message to AMF.

Since the PDU session for S-NSSAI-1 has already been deactivated by SMF, and since NG-RAN-2 does not support S-NSSAI-1 by itself, NG-RAN-2 does not need to perform radio resource allocation for the PDU session for S-NSSAI-1. However, based on the information about the deactivated PDU session received in step 8 and the information included in the source to target transparent container, NG-RAN-2 may notify the UE that radio resources are released due to PDU session deactivation for S-NSSAI-1. In addition, NG-RAN-2 may include an RRC message including information for redirecting the UE to the frequency band used by S-NSSAI-2 in the Handover Request Acknowledge message and transmit it to AMF.

For reference, the Handover Request Acknowledge message and the Handover Command message may not include PDU session information that can be serviced to the UE through NG-RAN-2 at all. To ensure that the receiving node (e.g. AMF or NG-RAN-1) does not treat this case as an error, NG-RAN-2 or the AMF can deliver a separate indication in addition to the cause to the corresponding N2 message (e.g., see step 9 or step 10 in the examples ofFIGS.13aand13bbelow). That is, an indication to ignore the mandatory field related to the PDU session context may be added in each N2 message.

Step 10: The AMF may transmit a Handover Command message to NG-RAN-1 based on the information received in Step 9. At this time, the AMF may transmit the RRC message generated by NG-RAN-2 to NG-RAN-1 along with a Handover Command message. In addition, the AMF may transmit information about the deactivated PDU session for S-NSSAI-1 to NG-RAN-1 along with a Handover Command message by performing Step 5 to Step 7 operations.

Step 11: NG-RAN-1 delivers the RRC message received from NG-RAN-2 to the terminal. The corresponding RRC message may include information necessary for redirection to the frequency band used by S-NSSAI-2. At this time, the terminal may release all radio resources allocated for the PDU session for S-NSSAI-1 according to the contents of the RRC message generated by NG-RAN-2.

Step 12: The terminal can connect to NG-RAN-2 by transmitting an RRC message to NG-RAN-2 after the configuration for redirection is complete.

Step 13: NG-RAN-2 may notify that the terminal has successfully moved to NG-RAN-2 by sending a Handover Notify message to the AMF.

Step 14: The AMF may acknowledge that the handover procedure for the terminal has ended by receiving the Handover Notify message. After confirming that the handover procedure for the terminal has ended, the AMF may resume processing of the PDU session establishment request message for S-NSSAI-2, which was stopped in Step 2. For example, AMF may perform a PDU session establishment procedure for establishing a PDU session for S-NSSAI-2. For example, operations of steps 2 to 19 in the examples ofFIGS.8aand8bmay be performed.

1-2. Second Example of the First Example of the Disclosure of the Present Specification

Hereinafter, a second example of the first example of the disclosure of the present specification will be described with reference to the examples ofFIGS.12aand12b.

The following drawings are made to explain a specific example of the present specification. Since the names of specific devices or names of specific signals/messages/fields described in the drawings are provided as examples, the technical features of the present specification are not limited to the specific names used in the drawings below.

FIGS.12aand12bshow signal flow diagrams according to a second example of the first example of the disclosure of the present specification.

The examples ofFIGS.12aand12bmay include an operation of requesting deactivation of a PDU session in which the target NG-RAN is serving through an existing frequency band to the SMF, in the process of changing the frequency band of the terminal using NG-based handover.

In describing the examples ofFIGS.12aand12b, description of overlapping contents with the examples ofFIGS.11aand11bwill be omitted. In other words, the examples ofFIGS.12aand12bwill be described below focusing on differences between the examples ofFIGS.12aand12band the examples ofFIGS.11aand 1 lb.

Step 0: The terminal may be already registered in the network. In addition, it is assumed that the terminal receives allowed NSSAI=S-NSSAI-1 and S-NSSAI-2 from AMF. In addition, the terminal may be in a state of establishing an RRC connection with NG-RAN-1 and having one or more PDU sessions for S-NSSAI-1 through SMF-1.

Step 1: The terminal may transmit a PDU session establishment request message for S-NSSAI-2 to the network through RRC and N2 message in order to receive service using S-NSSAI-2. At this time, the terminal may transmit a PDU session establishment request message for S-NSSAI-2 by including information such as a Globally Unique AMF ID (GUAMI) received from AMF in a previously performed registration procedure.

Step 2: The AMF knows that NG-RAN-1 to which terminal UE is currently connected does not support S-NSSAI-2. For example, based on information about network slices supported by each NG-RAN and frequency band information about each network slice, the AMF knows that NG-RAN-1 to which the terminal is connected does not support S-NSSAI-2. Accordingly, the AMF may determine that the terminal should be moved to one of the other NG-RANs supporting S-NSSAI-2. Until the terminal moves to the NG-RAN supporting S-NSSAI-2, the AMF may stop processing the PDU session establishment request for S-NSSAI-2 transmitted by the UE.

Step 3: The AMF may notify NG-RAN-1 using N2 message that NG-RAN-1 should move the terminal to one of the other NG-RANs supporting S-NSSAI-2.

Step 4: Since NG-RAN-1 does not support S-NSSAI-2, based on the N2 message received in Step 3, NG-RAN-1 may know that NG-RAN-1 needs to move the UE toward the NG-RAN (e.g., NG-RAN-2) supporting S-NSSAI-2 among neighboring NG-RANs. To this end (to move the terminal to an NG-RAN (e.g., NG-RAN-2) supporting S-NSSAI-2), NG-RAN-1 may request a measurement result report from the UE and receive the measurement result from the UE. Based on the measurement result received from the terminal, NG-RAN-1 determines whether handover for the terminal is possible and if handover is executed, NG-RAN-1 may determine its target cell.

NG-RAN-1 may initiate an NG-based handover procedure while transmitting a Handover Required message to AMF. The Handover Required message may include PDU session information for S-NSSAI-1 served by NG-RAN-1. In addition, the Handover Required message may include an indication or cause value indicating that the reason why the current handover procedure was started is that the UE needs to move to a frequency band served by S-NSSAI-2. To inform the AMF and target NG-RAN (here, NG-RAN-2), this indication or cause value may be included in the Handover Required message.

Step 5: The AMF transmits an Nsmf_PDUSession_UpdateSMContext Request message to each SMF managing PDU sessions for S-NSSAI-1, such that the AMF may notify that the corresponding PDU session will be handed over to the target NG-RAN (here, NG-RAN-2). The corresponding message may include PDU Session information for S-NSSAI-1 received from NG-RAN-1 in Step 4.

Step 6: The SMF may first decide whether to accept handover for each PDU session for S-NSSAI-1. If the SMF accepts the handover, the SMF may be allocated with a new UL CN Tunnel Info for N3 tunnel for the corresponding PDU session from the UPF.

The SMF may transmit an Nsmf_PDUSession_UpdateSMContext Response message including information on the PDU session accepting for the handover to the target NG-RAN (here, NG-RAN-2) (e.g., PDU session ID, new UL CN Tunnel Info for N3 tunnel, etc.) and information on the PDU session that rejected handover to the target NG-RAN (e.g., PDU session ID, reason for rejection, etc.) to AMF.

Step 8: Based on the information received in Steps 4 and 7, AMF may transmit a Handover Request message to NG-RAN-2. The Handover Request message may include information about the reason why the handover started and information about the PDU session for the S-NSSAI-1 for which the SMF accepted the handover in Step 6.

Step 9: Since NG-RAN-2 cannot support S-NSSAI-1, it may reject the setup request for the PDU session for S-NSSAI-1. In this case, except for the PDU session for S-NSSAI-1, there may be no PDU session in which NG-RAN-2 can currently service the terminal. At this time, NG-RAN-2 may refer to the cause sent by NG-RAN-1 to prevent NG-RAN-2 from rejecting the corresponding handover procedure. For example, even if there is no PDU Session in which NG-RAN-2 can service the current terminal, since NG-RAN-2 has identified the cause, NG-RAN-2 can accept handover because it knows that the terminal must move to the frequency band served by S-NSSAI-2. Therefore, NG-RAN-2 may transmit a Handover Request Acknowledge message to AMF. In addition, NG-RAN-2 may inform AMF that the setup request for the PDU session for S-NSSAI-1 has been rejected (Example: List of rejected PDU sessions for S-NSSAI-1 and reasons) through the corresponding message.

Since NG-RAN-2 rejected the setup request for the PDU session for S-NSSAI-1, it can notify the terminal that the radio resources for the corresponding PDU session have been released. In addition, NG-RAN-2 may transmit an RRC message including information for redirecting the terminal to the frequency band used by S-NSSAI-2 in the Handover Request Acknowledge message.

For reference, the Handover Request message may not include PDU Session information that can be serviced in NG-RAN-2 at all. In order for NG-RAN-2 to not process a Handover Request message (e.g., a Handover Request message that does not include PDU Session information that can be served in NG-RAN-2) as an error, NG-RAN-1 may add a separate indication in addition to the cause to the Handover Required message and deliver it to NG-RAN-2 through AMF (e.g., see step 7 in the examples ofFIGS.13aand13bbelow). Alternatively, in order to prevent NG-RAN-2 from processing a Handover Request message (e.g., a Handover Request message that does not include PDU Session information that can be served in NG-RAN-2) as an error, without involvement of NG-RAN-1, the AMF may transmit a Handover Request message to NG-RAN-2 by directly adding an indication to the Handover Request message.

For reference, even if NG-RAN-2 does not support S-NSSAI-1, after NG-RAN-2 accepts the handover request for the PDU session for S-NSSAI-1, by not allocating resources for actual data transmission, it is possible to prevent a handover procedure from being rejected. For example, as NG-RAN-2 refers to the cause or indication sent by NG-RAN-1, even if you do not support S-NSSAI-1, after accepting the handover request for the PDU session for S-NSSAI-1, it is also possible to avoid rejection of the corresponding handover procedure by not allocating resources for actual data transmission. In this case, NG-RAN-2 may include a separate indication for notifying NG-RAN-1, AMF, and SMF of this situation in the Handover Request Acknowledge message. Since the terminal may know that the radio resources for the PDU session for S-NSSAI-1 are not allocated by NG-RAN-2 through the RRC message, the terminal may not attempt uplink data transmission for the corresponding PDU session.

Step 10: The AMF may check the PDU session list for S-NSSAI-1 for which the setup request was rejected and the reason included in the Handover Request Acknowledge message of NG-RAN-2. After that, the AMF transmits Nsmf_PDUSession_UpdateSMContext Request message (including UP deactivate information) to each SMF (e.g., SMF-1), such that the AMF may request deactivation instead of release for the corresponding PDU session. The AMF may know this through the Handover cause transmitted by NG-RAN-1 in Step 4 and the Reject cause transmitted by NG-RAN-2 in Step 9, the AMF may also transmit a separate indication requesting deactivation of the corresponding PDU session together with the PDU session list for S-NSSAI-1 rejected by NG-RAN-2 in Step 9.

For reference, in Step 9, NG-RAN-2 may accept the PDU session list for S-NSSAI-1 and may not allocate resources for actual data transmission instead. In this case, NG-RAN-2 may inform the AMF of the situation through a separate indication. The AMF may request deactivation for the PDU session for S-NSSAI-1 from the SMF through the corresponding indication.

Step 11: The SMF (e.g., SMF-1) uses the N4 Session Release procedure or the N4 Session Modification procedure, such that the SMF (e.g., SMF-1) may request the UPF to delete the AN Tunnel Info for N3 tunnel information for the PDU session for S-NSSAI-1 received in Step 10. By making such a request, the SMF can prevent additional data transmission to the NG-RAN.

Step 12: The SMF may transmit Nsmf_PDUSession_UpdateSMContext Response message or other message to AMF, such that the SMF may inform that the PDU session deactivation requested by the AMF has been successfully processed. The message may include information about the deactivated PDU session (e.g., PDU session ID (s) for S-NSSAI-1 and the reason for deactivation of the PDU session, etc.).

Step 13: The AMF may transmit a Handover Command message to NG-RAN-1 based on the information received in Step 9. At this time, the AMF may also transmit the RRC message generated by NG-RAN-2 to NG-RAN-1. In addition, AMF can transmit information about the deactivated PDU session for S-NSSAI-1 to NG-RAN-1 along with a Handover Command message by performing operations of Step 10 to Step 12.

For reference, the Handover Request Acknowledge message and the Handover Command message may not include PDU session information that can be serviced to the UE through NG-RAN-2 at all. To ensure that the receiving node (e.g. AMF or NG-RAN-1) does not treat this case as an error, NG-RAN-2 or the AMF can deliver a separate indication in addition to the cause to the corresponding N2 message (e.g., see step 9 or step 10 in the examples ofFIGS.13aand13b). That is, an indication to ignore the mandatory field related to the PDU session context may be added in each N2 message.

Step 11: NG-RAN-1 delivers the RRC message received from NG-RAN-2 to the terminal. The corresponding RRC message may include information necessary for redirection to the frequency band used by S-NSSAI-2. At this time, the terminal may release all radio resources allocated for the PDU session for S-NSSAI-1.

Steps 15 to 17: may be performed in the same manner as Steps 12 to 14 of the example ofFIGS.11aand11b.

1-3. A Third Example of the First Example of the Disclosure of the Present Specification

Hereinafter, a third example of the first example of the disclosure of the present specification will be described with reference to the examples ofFIGS.13aand13b.

The following drawings are made to explain a specific example of the present specification. Since the names of specific devices or names of specific signals/messages/fields described in the drawings are provided as examples, the technical features of the present specification are not limited to the specific names used in the drawings below.

FIGS.13aand13bshow signal flow diagrams according to a third example of the first example of the disclosure of the present specification.

The examples ofFIGS.13aand13bmay include an operation of requesting in advance to the SMF deactivation for a PDU session in which the AMF is serving through an existing frequency band, before the AMF requests the NG-RAN-1 to change the frequency band of the UE,

In describing the examples ofFIGS.13aand13b, description of overlapping content with the examples ofFIGS.11aand11b(or the examples ofFIGS.12aand12b) will be omitted. In other words, the examples ofFIGS.13aand13bwill be described below, focusing on differences between the examples ofFIGS.13aand13band the examples ofFIGS.11aand11b(or the examples ofFIGS.12aand12b).

Step 0 to 2: Steps 0 to 2 in the example ofFIGS.13aand13bmay be performed in the same manner as steps 0 to 2 in the example ofFIGS.11aand11b.

Step 3: Since the AMF has information about network slices supported by each NG-RAN and frequency band information about each network slice, the AMF may determine whether there is an NG-RAN capable of simultaneously supporting S-NSSA-1 and S-NSSAI-2. If the AMF determines that there is no NG-RAN capable of simultaneously supporting S-NSSA-1 and S-NSSAI-2, the AMF may decide to first deactivate the PDU session for S-NSSAI-1. Accordingly, the AMF may request deactivation for each PDU session to each SMF by transmitting an Nsmf_PDUSession_UpdateSMContext Request message to each SMF managing PDU sessions for S-NSSAI-1. The Nsmf_PDUSession_UpdateSMContext Request message may include PDU Session information about S-NSSAI-1 currently being served in NG-RAN-1, which is currently stored in the AMF.

Steps 4 to 5: In the example ofFIGS.13aand13b, steps 4 to 5 may be performed in the same manner as steps 6 to 7 in the example ofFIGS.11aand11b.

Step 6: The AMF may notify NG-RAN-1 using N2 message that the UE should be moved to one of the other NG-RANs supporting S-NSSAI-2. In addition, the AMF may transmit the information for releasing radio resources for the deactivated PDU session received in Step 5 to the NG-RAN-1 by including it in the N2 message.

Step 7: Through the N2 message received in Step 6, NG-RAN-1 knows that the PDU session for S-NSSAI-1 has been deactivated. Since NG-RAN-1 knows that the PDU session for S-NSSAI-1 has been deactivated, NG-RAN-1 can release all radio resources for the corresponding PDU session. In addition, since NG-RAN-1 does not support S-NSSAI-2, based on the N2 message received in Step 3, NG-RAN-1 may know that NG-RAN-1 needs to move the UE toward the NG-RAN (e.g., NG-RAN-2) supporting S-NSSAI-2 among neighboring NG-RANs. To this end (to move the terminal to an NG-RAN (e.g., NG-RAN-2) supporting S-NSSAI-2), NG-RAN-1 may request a measurement result report from the UE and receive the measurement result from the UE. Based on the measurement result received from the terminal, NG-RAN-1 determines whether handover for the terminal is possible and if handover is executed, NG-RAN-1 may determine its target cell.

NG-RAN-1 may initiate an NG-based handover procedure while transmitting a Handover Required message to AMF. However, since the PDU session for S-NSSAI-1 has already been deactivated, there is no PDU session that can be moved to the target NG-RAN (here, NG-RAN-2) through the Handover Required message, such that it must be ensured that both NG-RAN-1 and NG-RAN2 does not treat this (e.g. Handover Required message) as an error. Based on the N2 message received from the AMF in Step 6 and the UE handover request to the NG-RAN supporting S-NSSAI-2, NG-RAN-1, this situation (e.g., a situation in which there is no PDU session that can be transferred to the target NG-RAN (here, NG-RAN-2) or a situation in which NG-RAN-1 must not process the handover request as an error) can be inferred. However, in order to prevent NG-RAN-2 from treating this situation as an error, NG-RAN-1 may add a separate indication (e.g., UE context transfer only indication) to the Handover Required message indicating that the current situation is a situation in which only the terminal context is delivered without the context for the PDU session. For example, NG-RAN-1 may add an indication to ignore the mandatory field PDU session resource list IE on the current Handover Required message.

In addition, the Handover Required message may include an indication or cause value indicating that the reason why the current handover procedure was started is that the UE needs to move to a frequency band served by S-NSSAI-2. To inform the AMF and target NG-RAN (here, NG-RAN-2), this indication or cause value may be included in the Handover Required message.

For reference, instead of adding a separate indication to the handover message that indicates that the NG-RAN-1 is in a situation where only the terminal context is delivered without the context for the PDU session, a new N2 message that can deliver only the terminal context to the target NG-RAN (e.g., NG-RAN-2) may be defined.

For reference, since NG-RAN-1 has released all radio resources for the PDU session for S-NSSAI-1, the RRC message (i.e., RRC HandoverPreparationInformation) delivered to the target NG-RAN through the Handover Required message may not include DRB-related information.

Step 8: AMF may transmit a Handover Request message to NG-RAN-2 based on the information received in Steps 5 and 7. The Handover Request message may include a separate indication notifying the reason why the handover started and the situation in which only the terminal context is delivered without the context for the PDU session.

Step 9: Even if NG-RAN-2 does not have a PDU Session that can service the current terminal, based on the cause and “UE context transfer only indication”, NG-RAN-2 can accept handover because it knows that the UE must move to the frequency band served by S-NSSAI-2. Therefore, NG-RAN-2 may transmit a Handover Request Acknowledge message to AMF.

The Handover Request Acknowledge message may also include an RRC message to be delivered to the UE through NG-RAN-1. The RRC message may include information necessary for the terminal to establish an RRC connection with NG-RAN-2. Due to the deactivation of the PDU session for S-NSSAI-1, the RRC message may not include DRB-related information. Therefore, the terminal receiving the corresponding RRC message can release radio resources for the corresponding PDU session. In addition, the RRC message may also include information for redirecting the terminal to the frequency band used by S-NSSAI-2.

Step 10: The AMF may transmit a Handover Command message to NG-RAN-1 based on the information received in Step 9. At this time, the AMF may transmit the RRC message generated by NG-RAN-2 together with the Handover Command message.

For reference, the Handover Request Acknowledge and Handover Command messages may not include PDU session information that can be serviced to the UE through NG-RAN-2 at all. In this case, in order to prevent the receiving node (e.g., AMF or NG-RAN-1) from treating it as an error, the AMF may add a separate indication to the corresponding N2 message and deliver it. That is, an indication to ignore the mandatory field related to the PDU session context may be added to each N2 message.

Step 11: NG-RAN-1 may forward the RRC message received from NG-RAN-2 to the UE. The corresponding RRC message may include information necessary for the terminal to perform redirection to the frequency band used by S-NSSAI-2. At this time, the terminal may release all radio resources allocated for the PDU session for S-NSSAI-1.

Steps 12 to 14: may be performed in the same manner as Steps 12 to 14 of the example ofFIGS.11aand11b.

2. A Second Example of the Disclosure of the Present Specification

Hereinafter, a second example of the disclosure of the present specification will be described with reference to the examples ofFIGS.14aand14bto the examples ofFIGS.15aand15b.

2-1. A First Example of the Second Example of the Disclosure of the Present Specification

First, a first example of the second example of the disclosure of the present specification will be described with reference to the examples ofFIGS.14aand14b.

The following drawings are made to explain a specific example of the present specification. Since the names of specific devices or names of specific signals/messages/fields described in the drawings are provided as examples, the technical features of the present specification are not limited to the specific names used in the drawings below.

FIGS.14aand14bshow signal flow diagrams according to the first example of the second example of the disclosure of the present specification.

The examples ofFIGS.14aand14bmay include an operation of requesting deactivation of a PDU session that the target NG-RAN or the AMF is serving through an existing frequency band to the SMF, when changing the frequency band of a terminal using Xn-based handover.

For reference, in describing the examples ofFIGS.14aand14b, descriptions of overlapping contents with the examples ofFIGS.11aand11b(or the examples ofFIGS.12aand12bor the example ofFIG.12) will be omitted. In other words, the examples ofFIGS.14aand14bwill be described below, focusing on differences between the example ofFIGS.14aand14band the example ofFIGS.11aand11b(or the example ofFIGS.12aand12bor the example ofFIG.12).

Steps 0 to 3: may be performed in the same manner as Steps 0 to 3 of the example ofFIGS.11aand11b.

Step 4: Since NG-RAN-1 does not support S-NSSAI-2, based on the N2 message received in Step 3, NG-RAN-1 may know that NG-RAN-1 needs to move the UE toward the NG-RAN (e.g., NG-RAN-2) supporting S-NSSAI-2 among neighboring NG-RANs. To this end (to move the terminal to an NG-RAN (e.g., NG-RAN-2) supporting S-NSSAI-2), NG-RAN-1 may request a measurement result report from the UE and receive the measurement result from the UE. Based on the measurement result received from the terminal, NG-RAN-1 determines whether handover for the terminal is possible and if handover is executed, NG-RAN-1 may determine its target cell.

NG-RAN-1 may initiate an Xn-based handover procedure while transmitting a Handover Request message to the target NG-RAN (here, NG-RAN-2). The Handover Request message may include PDU session information for S-NSSAI-1 that NG-RAN-1 is serving. In addition, the Handover Request message may include an indication or cause value notifying that the reason why the current handover procedure is started is that the UE needs to move to a frequency band served by S-NSSAI-2. This indication or cause value may be included in the Handover Request message to inform the target NG-RAN (here, NG-RAN-2).

Step 5: Since NG-RAN-2 cannot support S-NSSAI-1, it may reject the setup request for the PDU session for S-NSSAI-1. In this case, except for the PDU session for S-NSSAI-1, there may be no PDU session in which NG-RAN-2 can currently service the terminal. At this time, NG-RAN-2 may refer to the cause sent by NG-RAN-1 to prevent NG-RAN-2 from rejecting the corresponding handover procedure. For example, even if there is no PDU Session in which NG-RAN-2 can service the current terminal, since NG-RAN-2 has identified the cause, NG-RAN-2 can accept handover because it knows that the terminal must move to the frequency band served by S-NSSAI-2. Therefore, NG-RAN-2 may transmit a Handover Request Acknowledge message to AMF. In addition, NG-RAN-2 may inform AMF that the setup request for the PDU session for S-NSSAI-1 has been rejected (Example: List of rejected PDU sessions for S-NSSAI-1 and reasons) through the corresponding message.

Since NG-RAN-2 rejected the setup request for the PDU session for S-NSSAI-1, it can notify the terminal that the radio resources for the corresponding PDU session have been released. In addition, NG-RAN-2 may transmit an RRC message including information for redirecting the terminal to the frequency band used by S-NSSAI-2 in the Handover Request Acknowledge message.

For reference, the Handover Request message transmitted in Step 4 may not include PDU Session information that can be serviced in NG-RAN-2 at all. In this case, NG-RAN-1 may include “Indication (or information) (e.g. it can be a separate indication or information other than cause) to prevent NG-RAN-2 from rejecting the Handover message (e.g. Handover message not to be treated as an error) “in the Handover Request message and Path Switch Request message and deliver it to NG-RAN-2.

For reference, even if NG-RAN-2 does not support S-NSSAI-1, after NG-RAN-2 accepts the handover request for the PDU session for S-NSSAI-1, by not allocating resources for actual data transmission, it is possible to prevent a handover procedure from being rejected. For example, as NG-RAN-2 refers to the cause or indication sent by NG-RAN-1, even if you do not support S-NSSAI-1, after accepting the handover request for the PDU session for S-NSSAI-1, it is also possible to avoid rejection of the corresponding handover procedure by not allocating resources for actual data transmission. In this case, NG-RAN-2 may include a separate indication for notifying NG-RAN-1, AMF, and SMF of this situation in the Handover Request Acknowledge message. Since the terminal may know that the radio resources for the PDU session for S-NSSAI-1 are not allocated by NG-RAN-2 through the RRC message, the terminal may not attempt uplink data transmission for the corresponding PDU session.

Steps 6 and 7: In the example ofFIGS.14aand14b, steps 6 to 7 may be performed in the same manner as steps 11 to 12 in the example ofFIGS.11aand11b.

Step 8: NG-RAN-2 may notify that the UE has successfully moved to NG-RAN-2 by transmitting a Path Switch Request message to the AMF. In addition, NG-RAN-2 may inform the AMF that the setup request for the PDU session for S-NSSAI-1 has been rejected (e.g. list of rejected PDU sessions for S-NSSAI-1 and reasons) through the corresponding message.

For reference, PDU session information that can be serviced in NG-RAN-2 may not be included in the Path Switch Request message at all. In order to prevent NG-RAN-2 from treating this case as an error, NG-RAN-2 may add a separate indication (e.g., see Step 7 in the example ofFIGS.15aand15b) in addition to the cause to the Path Switch Request message and transmit it to AMF. For example, an indication to ignore the mandatory field PDU Session Resource to be Switched in Downlink List IE may be added to the current Path Switch Request message.

Step 10: The AMF may check the PDU session list for S-NSSAI-1 for which the setup request was rejected and the reason included in the Path Switch Request message of NG-RAN-2. After that, the AMF transmits Nsmf_PDUSession_UpdateSMContext Request message (including UP deactivate information) to each SMF (e.g., SMF-1), such that the AMF may request deactivation instead of release for the corresponding PDU session. The AMF can know this through the cause sent by NG-RAN-2 in Step 8, the AMF may send a separate indication requesting deactivation of the corresponding PDU session together with the PDU session list for S-NSSAI-1 rejected by NG-RAN-2 in Step 8.

For reference, in Step 5, NG-RAN-2 may accept the PDU session list for S-NSSAI-1 and may not allocate resources for actual data transmission instead. In this case, NG-RAN-2 may inform the AMF of the situation through a separate indication. The AMF may request deactivation for the PDU session for S-NSSAI-1 from the SMF through the corresponding indication.

Step 10: The SMF (e.g., SMF-1) uses the N4 Session Release procedure or the N4 Session Modification procedure, such that the SMF (e.g., SMF-1) may request the UPF to delete the AN Tunnel Info for N3 tunnel information for the PDU session for S-NSSAI-1 received in Step 15. By making such a request, the SMF can prevent additional data transmission to the NG-RAN.

Step 11: The SMF may transmit Nsmf_PDUSession_UpdateSMContext Response message or other message to AMF, such that the SMF may inform that the PDU session deactivation requested by the AMF has been successfully processed. The message may include information about the deactivated PDU session (e.g., PDU session ID (s) for S-NSSAI-1 and the reason for deactivation of the PDU session, etc.).

Step 12: The AMF may respond to NG-RAN-2 through Path Switch Request Acknowledge message. As a result, the Path Switch Request Acknowledge message may not include PDU session information that can be serviced to the UE through NG-RAN-2 at all. In order to prevent NG-RAN-2 from treating this case as an error, a separate indication may be added to the Path Switch Request Acknowledge message and delivered. That is, an indication to ignore the mandatory field related to the PDU session context may be added in the corresponding message.

Step 13: After confirming that the handover procedure for the UE has ended, the AMF may resume processing of the PDU session establishment request for S-NSSAI-2. The AMF may perform a PDU session establishment procedure for S-NSSAI-2. For example, operations of steps 2 to 19 in the examples ofFIGS.8aand8bmay be performed.

2-2. A Second Example of a Second Example of the Disclosure of the Present Specification

Hereinafter, a second example of the second example of the disclosure of the present specification will be described with reference to the examples ofFIGS.15aand15b.

The following drawings are made to explain a specific example of the present specification. Since the names of specific devices or names of specific signals/messages/fields described in the drawings are provided as examples, the technical features of the present specification are not limited to the specific names used in the drawings below.

FIGS.15aand15bshow signal flow diagrams according to a second example of a second example of the disclosure of the present specification.

The examples ofFIGS.15aand15bmay include an operation in which the AMF requests the SMF for deactivation of a PDU session being serviced through an existing frequency band in advance, before the AMF requests the NG-RAN-1 to change the frequency band of the UE,

In describing the examples ofFIGS.15aand15b, a description of overlapping contents with the examples ofFIGS.11aand11bto14aand14bwill be omitted. In other words, the examples ofFIGS.15aand15bwill be described below focusing on differences between the examples ofFIGS.15aand15band the examples ofFIGS.11aand11bto14aand14b.

Steps 0 to 2: may be performed in the same manner as Steps 0 to 2 of the examples ofFIGS.11aand11b.

Steps 3 to 6: may be performed in the same manner as Steps 3 to 6 of the example ofFIGS.13aand13b.

Step 7: Through the N2 message received in Step 6, NG-RAN-1 knows that the PDU session for S-NSSAI-1 has been deactivated. Since NG-RAN-1 knows that the PDU session for S-NSSAI-1 has been deactivated, NG-RAN-1 can release all radio resources for the corresponding PDU session. In addition, since NG-RAN-1 does not support S-NSSAI-2, based on the N2 message received in Step 3, NG-RAN-1 may know that NG-RAN-1 needs to move the UE toward the NG-RAN (e.g., NG-RAN-2) supporting S-NSSAI-2 among neighboring NG-RANs. To this end (to move the terminal to an NG-RAN (e.g., NG-RAN-2) supporting S-NSSAI-2), NG-RAN-1 may request a measurement result report from the UE and receive the measurement result from the UE. Based on the measurement result received from the terminal, NG-RAN-1 determines whether handover for the terminal is possible and if handover is executed, NG-RAN-1 may determine its target cell.

NG-RAN-1 may initiate an NG-based handover procedure while transmitting a Handover Required message to AMF. However, since the PDU session for S-NSSAI-1 has already been deactivated, there is no PDU session that can be moved to the target NG-RAN (here, NG-RAN-2) through the Handover Required message, such that it must be ensured that both NG-RAN-1 and NG-RAN2 does not treat this (e.g. Handover Required message) as an error. Based on the N2 message received from the AMF in Step 6 and the UE handover request to the NG-RAN supporting S-NSSAI-2, NG-RAN-1, this situation (e.g., a situation in which there is no PDU session that can be transferred to the target NG-RAN (here, NG-RAN-2) or a situation in which NG-RAN-1 must not process the handover request as an error) can be inferred. However, in order to prevent NG-RAN-2 from treating this situation as an error, NG-RAN-1 may add a separate indication (e.g., UE context transfer only indication) to the Handover Required message indicating that the current situation is a situation in which only the terminal context is delivered without the context for the PDU session. For example, NG-RAN-1 may add an indication to ignore the mandatory field PDU session resource list IE on the current Handover Required message.

In addition, the Handover Request message may include an indication or cause value notifying that the reason why the current handover procedure is started is that the UE needs to move to a frequency band served by S-NSSAI-2. To inform the AMF and target NG-RAN (here, NG-RAN-2), this indication or cause value may be included in the Handover Request message.

For reference, instead of adding a separate indication to the handover message that indicates that the NG-RAN-1 is in a situation where only the terminal context is delivered without the context for the PDU session, a new N2 message that can deliver only the terminal context to the target NG-RAN (e.g., NG-RAN-2) may be defined.

For reference, since NG-RAN-1 has released all radio resources for the PDU session for S-NSSAI-1, the RRC message (i.e., RRC HandoverPreparationInformation) delivered to the target NG-RAN through the Handover Request message may not include DRB-related information.

Step 8: NG-RAN-2, based on Cause and “UE context transfer only indication”, since the terminal knows that it must move to the frequency band served by S-NSSAI-2, even if NG-RAN-2 does not have a PDU session that can serve the current UE, NG-RAN-2 can accept handover. Accordingly, NG-RAN-2 may transmit a Handover Request Acknowledge message to NG-RAN-1.

The Handover Request Acknowledge message may also include an RRC message to be delivered to the UE through NG-RAN-1. The RRC message may include information necessary for the terminal to establish an RRC connection with NG-RAN-2. Due to the deactivation of the PDU session for S-NSSAI-1, the RRC message may not include DRB-related information. Therefore, the terminal receiving the corresponding RRC message can release radio resources for the corresponding PDU session. In addition, the RRC message may also include information for redirecting the terminal to the frequency band used by S-NSSAI-2.

Steps 9 and 10: may be performed in the same manner as Steps 11 and 12 of the example ofFIGS.13aand13b.

Step 11: NG-RAN-2 may inform AMF that the UE has successfully moved to NG-RAN-2 through a Path Switch procedure. At this time, NG-RAN-2 may deliver the cause received from NG-RAN-1 in Step 7 to AMF. In addition, the Path Switch Request message (e.g., a message transmitted from NG-RAN-2 to AMF) and the Path Switch Request Acknowledge message (e.g., a message transmitted from AMF to NG-RAN-2) may not include PDU session information that can be serviced to the terminal through NG-RAN-2. In order to prevent NG-RAN-2 from treating this case as an error, a separate indication may be added to the N2 message (e.g., a Path Switch Request message or a Path Switch Request Acknowledge message) and delivered. That is, an indication to ignore the mandatory field related to the PDU session context may be added in the corresponding message.

Step 12: It may be performed in the same manner as Step 14 of the example ofFIGS.13aand13b.

3. Third example of the disclosure of the present specification.

Hereinafter, a third example of the disclosure of the present specification will be described with reference to the examples ofFIGS.16aand16b.

The following drawings are made to explain a specific example of the present specification. Since the names of specific devices or names of specific signals/messages/fields described in the drawings are provided as examples, the technical features of the present specification are not limited to the specific names used in the drawings below.

FIGS.16aand16bshow signal flow diagrams according to a third example of the disclosure of the present specification.

The examples ofFIGS.16aand16bmay include an operation in which the AMF prohibits notification of DL data from the SMF based on the priority between the slice currently used by the terminal and the slice to which the terminal newly receives service, when changing the frequency band of the terminal using RRC release.

In describing the examples ofFIGS.16aand16b, descriptions of overlapping contents with the examples ofFIGS.11aand11bto15aand15bwill be omitted. In other words, the examples ofFIGS.16aand16bwill be described below focusing on differences between the examples ofFIGS.16aand16band the examples ofFIGS.11aand11bto15aand15b.

Steps 0 to 3: may be performed in the same manner as Steps 0 to 3 of the example ofFIGS.11aand11b.

Step 4: Since NG-RAN-1 does not support S-NSSAI-2, based on the N2 message received in Step 3, NG-RAN-1 may know that NG-RAN-1 needs to move the UE toward the NG-RAN (e.g., NG-RAN-2) supporting S-NSSAI-2 among neighboring NG-RANs. Due to unavailability of handover or other reasons, NG-RAN-1 may decide to perform RRC release with redirection for the UE. In this case, RRC release with redirection may mean redirection from the frequency band used by S-NSSAI-1 to the frequency band used by S-NSSAI-2. For reference, “other reason” may include, for example, a case where an operator configures NG-RAN-1 to perform RRC release with redirection instead of handover.

NG-RAN-1 can start the AN release procedure by sending a UE Context Release Request message to AMF for redirection to the frequency band used by S-NSSAI-2. The UE Context Release Request message may include a cause value notifying that context release has started to change the frequency band of the UE. In addition, the UE Context Release Request message may include a list of PDU session IDs for S-NSSAI-1 in an active state.

Step 5: The AMF may transmit a UE Context Release Command message including the cause value received in Step 4 to NG-RAN-1.

Step 6: NG-RAN-1 may transmit an RRC Release message including information necessary for redirection to the frequency band used by S-NSSAI-2 to the UE. Therefore, the terminal may release all radio resources allocated for the PDU session for S-NSSAI-1.

Step 7: When the release of radio resources is completed, NG-RAN-1 may respond to the AMF by transmitting a UE Context Release Complete message.

Step 8: The AMF may notify that the AN release procedure has started by sending an Nsmf_PDUSession_UpdateSMContext Request message to SMF-1. To notify that the AN release procedure has started, the AMF may include the cause value received in Step 4 in the Nsmf_PDUSession_UpdateSMContext Request message. At this time, the AMF may request deactivation instead of release for the corresponding PDU session while transmitting the Nsmf_PDUSession_UpdateSMContext Request message with the list of PDU session IDs for S-NSSAI-1 in active state received in Step 4 as well. Through this, the AMF can prevent additional data transmission to the NG-RAN.

The AMF may determine whether the priority of NSSAI-2 is higher than the priority of S-NSSAI-1. If AMF determines that the priority of S-NSSAI-2 is higher than that of S-NSSAI-1 (that is, if the service provided through S-NSSAI-2 is determined to be more important), the AMF may transmit an indication (or information) that not notifying AMF of DL data (e.g. DL data) even if DL data arrives after the deactivation process for the PDU session for S-NSSAI-1 is finished with Nsmf_PDUSession_UpdateSMContext Request message.

Step 9: The SMF may notify the AMF that the PDU session deactivation requested by the NG-RAN has been successfully processed by using the Nsmf_PDUSession_UpdateSMContext Response message or other messages.

Step 10: Based on the redirection information received in Step 6, the UE accesses NG-RAN-2 through a new frequency band and establishes an RRC connection.

Step 11: NG-RAN-2 sends an N2 message to AMF to inform that the corresponding terminal has accessed through NG-RAN-2.

Step 12: The AMF may notify the SMF that a mobility event for the UE has occurred by sending a Namf_EventExposure_Notify message to the SMF-2. For example, the AMF may transmit a Namf_EventExposure_Notify message including information that the location of the UE has changed (e.g., UE location change) to the SMF.

Step 13: After confirming that the redirection procedure for the terminal has ended, the AMF may resume processing of the PDU session establishment request for S-NSSAI-2, which was stopped in Step 2.

4. The Fourth Example of the Disclosure of the Present Specification

Hereinafter, a fourth example of the disclosure of this specification will be described with reference to the examples ofFIGS.17aand17b.

The following drawings are made to explain a specific example of the present specification. Since the names of specific devices or names of specific signals/messages/fields described in the drawings are provided as examples, the technical features of the present specification are not limited to the specific names used in the drawings below.

FIGS.17aand17bshow signal flow charts according to a fourth example of the disclosure of the present specification.

The examples ofFIGS.17aand17bmay include an operation for preventing the terminal from repeatedly transmitting a PDU session establishment request for a PDU session related to a slice to be newly serviced, when it was tried to change the frequency band of a terminal using handover, but handover fails.

For reference, in the examples ofFIGS.17aand17b, operations related to Xn-based handover (e.g., steps 4a to 4c) and NG-based handover (e.g., steps 5a to 5c) may be selectively performed. For example, after an Xn-based Handover-related operation (e.g., steps 4a to 4c) or an NG-based handover-related operation (e.g., steps 5a to 5c) is performed, operations related to RRCRelesase with Back-off timer (e.g., steps 6a and 6b) and RRC Release with Redirection (e.g., steps 6c and 6d) may be performed.

In describing the examples ofFIGS.17aand17b, descriptions of overlapping contents with the examples ofFIGS.11aand11bto16aand16bwill be omitted. In other words, the examples ofFIGS.17aand17bwill be described below focusing on differences between the examples ofFIGS.17aand17band the examples ofFIGS.11aand11bto16aand16b.

Steps 0 to 1: may be performed in the same manner as Steps 0 to 1 of the examples ofFIGS.11aand11b.

Step 2: The AMF knows that NG-RAN-1 to which terminal UE is currently connected does not support S-NSSAI-2. For example, based on information about network slices supported by each NG-RAN and frequency band information about each network slice, the AMF knows that NG-RAN-1 to which the terminal is connected does not support S-NSSAI-2. Accordingly, the AMF may determine that the terminal should be moved to one of the other NG-RANs supporting S-NSSAI-2. Until the terminal moves to the NG-RAN supporting S-NSSAI-2, the AMF may stop processing the PDU session establishment request for S-NSSAI-2 transmitted by the UE.

For reference, as in Step 3 of the example ofFIGS.13aand13bor Step 3 of the example ofFIGS.15aand15b, before Step 3 is performed, the AMF may perform an operation for deactivation of the PDU session for S-NSSAI-1. In this case (when an operation for deactivation for the PDU session for S-NSSAI-1 is performed), the examples ofFIGS.15aand15bmay be referred to when Xn-based handover related operations are performed, the examples ofFIGS.13aand13bmay be referred to when performing an operation related to NG-based handover.

Step 3: The AMF may notify NG-RAN-1 using N2 message that the UE should be moved to one of the other NG-RANs supporting S-NSSAI-2. Depending on whether NG-RAN-1 selects Xn-based handover or NG-RAN-1 selects NG-based handover, steps 4a to 4c or steps 5a to 5c may be performed.

NG-RAN-1 may determine whether to perform Xn-based Handover or NG-based Handover. When NG-RAN-1 determines to perform Xn-based handover, the following steps 4a to 4c may be performed. When NG-RAN-1 determines to perform NG-based handover, the following steps 5a to 5c may be performed.

Step 4a to 4c: When NG-RAN-1 selects Xn-based Handover, Steps 4a to 4c may be performed. Since NG-RAN-1 does not support S-NSSAI-2, based on the N2 message received in Step 3, NG-RAN-1 may know that NG-RAN-1 needs to move the UE toward the NG-RAN (e.g., NG-RAN-2) supporting S-NSSAI-2 among neighboring NG-RANs. To this end (to move the terminal to an NG-RAN (e.g., NG-RAN-2) supporting S-NSSAI-2), NG-RAN-1 may request a measurement result report from the UE and receive the measurement result from the UE. Based on the measurement result received from the terminal, NG-RAN-1 determines whether handover for the terminal is possible and if handover is executed, NG-RAN-1 may determine its target cell.

NG-RAN-1 may initiate an Xn-based handover procedure while transmitting a Handover Request message to the target NG-RAN (here, NG-RAN-2). The Handover Request message may include PDU session information for S-NSSAI-1 that NG-RAN-1 is serving. In addition, the Handover Request message may include an indication or cause value notifying that the reason why the current handover procedure is started is that the UE needs to move to a frequency band served by S-NSSAI-2. This indication or cause value may be included in the Handover Request message to inform the target NG-RAN (here, NG-RAN-2).

In step 4b, NG-RAN-2 may reject handover due to reasons such as lack of radio resources and non-support of handover consisting only of the terminal context. In this case, NG-RAN-2 may transmit a Handover Preparation Failure message including information on the reason why handover failed (e.g., failure cause) to NG-RAN-1.

In Step 4c, NG-RAN-1 can inform AMF of the failure cause received in Step 4b, thereby notifying the failure of the handover for the corresponding UE and the reason for the failure. After Step 4c is performed, the procedures of Steps 6a to 6d may be performed.

For reference, before Step 3 is performed, as in Step 3 of the example ofFIGS.13aand13bor Step 3 of the example ofFIGS.15aand15b, when the AMF performs an operation for deactivation of the PDU session for S-NSSAI-1, the examples ofFIGS.15aand15bmay be referred to instead of Step 4 ofFIGS.17aand17b. For example, instead of Step 4a ofFIGS.17aand17b, operations of Steps 3 to 7 of the example ofFIGS.15aand15bmay be performed, after that, Steps 4b and4cofFIGS.17aand17bmay be performed.

Step 5a to 5c: When NG-RAN-1 selects NG-based Handover, Steps 4a to 4c may be performed. Since NG-RAN-1 does not support S-NSSAI-2, based on the N2 message received in Step 3, NG-RAN-1 may know that NG-RAN-1 needs to move the UE toward the NG-RAN (e.g., NG-RAN-2) supporting S-NSSAI-2 among neighboring NG-RANs. To this end (to move the terminal to an NG-RAN (e.g., NG-RAN-2) supporting S-NSSAI-2), NG-RAN-1 may request a measurement result report from the UE and receive the measurement result from the UE. Based on the measurement result received from the terminal, NG-RAN-1 determines whether handover for the terminal is possible and if handover is executed, NG-RAN-1 may determine its target cell.

In step 5a, NG-RAN-1 may start the NG-based handover procedure by sending a Handover Required message to the AMF. Step 5a may be performed in the same manner as Steps 4 to 8 of the examples ofFIGS.11aand11b. Alternatively, Step 5a may be performed in the same manner as Steps 4 to 8 of the examples ofFIGS.12aand12b.

In step 5b, NG-RAN-2 may reject handover due to reasons such as lack of radio resources and non-support of handover consisting only of the terminal context. In this case, NG-RAN-2 may transmit a Handover Preparation Failure message including information on the reason why handover failed (e.g., failure cause) to NG-RAN-1.

In Step 5c, the AMF may notify NG-RAN-1 of the failure cause received in Step 5b and the failure of the handover for the corresponding terminal and its reason. After Step 5c is performed, the procedures of Steps 6a to 6d may be performed.

For reference, before Step 3 is performed, as in Step 3 of the example ofFIGS.13aand13b, when AMF performs an operation for deactivation for the PDU session for S-NSSAI-1, examples ofFIGS.13aand13bmay be referred to instead of Step 5 ofFIGS.17aand17b. For example, instead of Step 5a ofFIGS.17aand17b, operations of Steps 3 to 8 of the example ofFIGS.13aand13bmay be performed, after that, Steps 5b and 5c ofFIGS.17aand17bmay be performed.

Step 6a-6d: Based on Step 4c or Step 5b, the AMF may know that the handover procedure for the UE in the NG-RAN has failed.

By performing Steps 6a and 6b, the AMF notifies the terminal that PDU session establishment for S-NSSAI-2 has failed, the AMF may provide a failure reason (e.g., New cause) and a back-off timer to the UE. Through this operation, the AMF can prevent the UE from attempting a PDU session establishment request for the PDU session for S-NSSAI-2 for a certain period of time.

Alternatively, by performing the operations of step 6c and step 6d, the AMF may make NG-RAN-1 start an RRC release procedure for redirecting the terminal to the frequency band used by S-NSSAI-2.

For reference, before Step 3 is performed, as in the example ofFIGS.13aand13bor the example ofFIGS.15aand15b, when the AMF performs an operation for deactivation for the PDU session for S-NSSAI-1, a procedure for re-activating the already deactivated PDU session for S-NSSAI-1 may be performed. For example, after NG-RAN-1 re-allocates radio resources for the PDU session for S-NSSAI-1, it can notify the UE through an RRC reconfiguration message.

For reference, in step 1 or step 2 of the example ofFIGS.11aand11bto the example ofFIGS.17aand17b, in order for the UE to receive a service using S-NSSAI-2, it has been described that an operation of transmitting a PDU session establishment request message for S-NSSAI-2 is performed first, and subsequent operations are performed. However, this is only an example, and the scope of the disclosure of this specification may include a case where the UE has already established a PDU session for S-NSSAI-2 before performing step 1 or step 2 of the examples ofFIGS.11aand11bto the examples ofFIGS.17aand17b. In this case, in step 1 or step 2 of the example ofFIGS.11aand11bto the example ofFIGS.17aand17b, the UE may perform an operation of transmitting a NAS message requesting to receive service, by using S-NSSAI-2 (i.e., through a PDU session for S-NSSAI-2). After the UE transmits the NAS message, subsequent operations (e.g., moving the UE to a frequency band capable of serving S-NSSAI-2) after step 1 or step 2 of the example ofFIGS.11aand11bto the example ofFIGS.17aand17bmay be performed. Here, the NAS message may be a Service Request, Registration Request, or a newly defined NAS message. This NAS message may include the ID of the PDU session for the S-NSSAI-2, which may be in the form of List Of PDU Sessions To Be Activated or in the form of other parameters.

According to the description in the disclosure of the present specification with reference to various examples, an operation for supporting frequency band movement according to a specific slice request of a terminal may be performed in a mobile communication system. The core network (e.g., AMF, SMF, UPF) can confirm that it is necessary to move the UE to an NG-RAN supporting the network slice requested by the UE. The core network (e.g., AMF, SMF, UPF) may notify the radio network (e.g., NG-RAN) that it is necessary to move the terminal to the NG-RAN supporting the network slice requested by the terminal. the radio network (e.g., NG-RAN) may cause the UE to move to another frequency band through a handover or RRC release message. The core network (e.g., AMF, SMF, UPF) may perform deactivation for a specific PDU session based on the result of the request.

According to the disclosure of this specification with reference to various examples, during the PDU Session Establishment process, by handover/redirection of the UE to the NG-RAN capable of supporting the slice and frequency band related to the PDU Session requested by the UE, a service through the corresponding slice can be efficiently provided to the terminal. In addition, by performing deactivation on the first PDU session related to the network slice supported by the first NG-RAN, when the UE wants to use the first PDU session again, efficient communication can be provided. For example, the terminal does not need to perform the PDU session establishment procedure again for the first PDU session. In addition, if the handover procedure and/or redirection procedure for moving the terminal to the second NG-RAN fails, efficient signaling is possible by preventing the UE from repeatedly requesting a PDU session establishment request for the second PDU session to the first NG-RAN.

According to the description in the disclosure of this specification with reference to various examples, before a terminal moves to another frequency band, it is possible to efficiently deactivate a PDU session being serviced through an existing frequency band. By efficiently deactivating a PDU session in service through an existing frequency band, it is possible to prevent a situation in which DL data is unnecessarily transmitted to the RAN. In addition, the terminal may deactivate the PDU session (e.g., the PDU session related to the first network slice) received through the first NG-RAN without releasing it. Accordingly, after the terminal is provided with the service through the second NG-RAN, when the UE returns to the first NG-RAN and wants to receive service again through the PDU session (e.g., PDU session related to the first network slice) that was used previously, by activating an inactive PDU session without the need to establish a new PDU session, the terminal can efficiently receive service. In addition, if the handover procedure for moving the terminal to another frequency band fails, by preventing the UE from repeatedly transmitting the PDU session establishment request message to the network, unnecessary signaling can be reduced.

For reference, the operation of the terminal (e.g., UE) described in this specification may be implemented by the apparatus ofFIGS.1to3described above. For example, the terminal (e.g., UE) may be the first device100or the second device200ofFIG.2. For example, an operation of a terminal (e.g., UE) described herein may be processed by one or more processors102or202. The operation of the terminal described herein may be stored in one or more memories104or204in the form of an instruction/program (e.g. instruction, executable code) executable by one or more processors102or202. One or more processors102or202control one or more memories104or204and one or more transceivers105or206, and may perform the operation of the terminal (e.g., UE) described herein by executing instructions/programs stored in one or more memories104or204.

In addition, instructions for performing an operation of a terminal (e.g., UE) described in the disclosure of the present specification may be stored in a non-volatile computer-readable storage medium in which it is recorded. The storage medium may be included in one or more memories104or204. And, the instructions recorded in the storage medium may be executed by one or more processors102or202to perform the operation of the terminal (e.g., UE) described in the disclosure of the present specification.

For reference, the operation of a network node (e.g., AMF, SMF, UPF, PCF, UDM, DN etc.) or base station (e.g., NG-RAN, gNB, eNB, RAN, E-UTRAN etc.) described herein may be implemented by the apparatus ofFIGS.1to3to be described below. For example, a network node or a base station may be the first device100ofFIG.2or the second device200ofFIG.2. For example, the operation of a network node or base station described herein may be processed by one or more processors102or202. The operation of the terminal described herein may be stored in one or more memories104or204in the form of an instruction/program (e.g. instruction, executable code) executable by one or more processors102or202. One or more processors102or202may perform the operation of a network node or a base station described herein, by controlling one or more memories104or204and one or more transceivers106or206and executing instructions/programs stored in one or more memories104or204.

In addition, instructions for performing the operation of the network node or base station described in the disclosure of this specification may be stored in a non-volatile (or non-transitory) computer-readable storage medium. The storage medium may be included in one or more memories104or204. And, the instructions recorded in the storage medium are executed by one or more processors102or202, so that the operations of a network node or base station are performed.

In the above, preferred embodiments have been exemplarily described, but the disclosure of the present specification is not limited to such specific embodiments, and thus, modifications, changes, or can be improved.

In the exemplary system described above, the methods are described on the basis of a flowchart as a series of steps or blocks, but are not limited to the order of the steps described, some steps may occur in a different order or concurrent with other steps as described above. In addition, those skilled in the art will understand that the steps shown in the flowchart are not exclusive and that other steps may be included or that one or more steps of the flowchart may be deleted without affecting the scope of rights.

The claims described herein may be combined in various ways. For example, the technical features of the method claims of the present specification may be combined and implemented as an apparatus, and the technical features of the apparatus claims of the present specification may be combined and implemented as a method. In addition, the technical features of the method claim of the present specification and the technical features of the apparatus claim may be combined to be implemented as an apparatus, and the technical features of the method claim of the present specification and the technical features of the apparatus claim may be combined and implemented as a method.