Method and device for changing path of multi-hop terminal-network relay in wireless communication system

Abstract

A method performed by a first terminal in a wireless communication system comprises the steps of: establishing a sidelink PC5 unicast link with a second terminal; detecting reselection of a relay terminal; and transmitting, to a second terminal, a message related to the reselection, wherein the message includes a cause for the transmitting of the message.

Description

Method and device for changing the path of a multi-hop terminal network relay in a wireless communication system

[0001] The present disclosure relates to a wireless communication system, and more particularly, to a method and device for changing a path of a multi-hop terminal network relay in wireless communication.

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

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

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

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

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

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

[0008] The purpose of the present invention is to provide a method and device for changing the path of a multi-hop terminal network relay in wireless communication.

[0009] The technical problems to be achieved in the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned can be clearly understood by a person having ordinary skill in the technical field to which the present invention belongs from the description below.

[0010] The present invention, for solving the above-mentioned problem, is a method performed in a first terminal in a wireless communication system, comprising: a step of establishing a sidelink PC5 unicast link with a second terminal; a step of detecting reselection of a relay terminal; and a step of transmitting a message related to the reselection to the second terminal, wherein the message includes a cause for transmitting the message.

[0011] In one embodiment, the step of detecting reselection of the relay terminal is characterized in that the step of detecting the reselection is based on receiving a message related to the reselection from another relay terminal.

[0012] In one embodiment, the step of detecting reselection of the relay terminal is characterized in that the step of detecting the reselection is based on receiving a discovery message.

[0013] In one embodiment, the cause of transmitting the message is characterized by being one of relay terminal reselection, sidelink RLF (Radio Link Failure), and sidelink PC5 failure.

[0014] In addition, in another embodiment of the present invention, a method performed in a second terminal in a wireless communication system comprises the steps of establishing a sidelink PC5 unicast link with a first terminal; and, when the first terminal detects reselection of a relay terminal, receiving a message related to the reselection from the first terminal, wherein the message includes a cause for transmitting the message.

[0015] In addition, in another embodiment of the present invention, in a wireless communication system, a first terminal in the wireless communication system includes a transceiver capable of transmitting and receiving at least one signal; and a control unit coupled to the transceiver, wherein the control unit is configured to: establish a sidelink PC5 unicast link with a second terminal, detect reselection of a relay terminal, and transmit a message related to the reselection to the second terminal, wherein the message includes a cause for transmitting the message.

[0016] In addition, in another embodiment of the present invention, in a wireless communication system, a second terminal in the wireless communication system includes a transceiver capable of transmitting and receiving at least one signal; and a control unit coupled to the transceiver, wherein the control unit is configured to: establish a sidelink PC5 unicast link with a first terminal, and, when the first terminal detects reselection of a relay terminal, receive a message related to the reselection from the first terminal, wherein the message includes a cause for transmitting the message.

[0017] According to an embodiment of the present disclosure, a device and method for effectively providing a service in a wireless communication system can be provided.

[0018] The effects that can be obtained from the present disclosure are not limited to the effects mentioned above, and other effects that are not mentioned can be clearly understood by a person having ordinary skill in the art to which the present disclosure belongs from the description below.

[0019] FIG. 1 is a diagram illustrating the structure of a next-generation mobile communication system according to an embodiment of the present disclosure.

[0020] FIG. 2A is a diagram illustrating examples of scenarios for sidelink communication in a wireless communication system according to an embodiment of the present disclosure.

[0021] FIG. 2b is a diagram illustrating examples of scenarios for sidelink communication in a wireless communication system according to an embodiment of the present disclosure.

[0022] FIG. 2c is a diagram illustrating examples of scenarios for sidelink communication in a wireless communication system according to an embodiment of the present disclosure.

[0023] FIG. 2d is a diagram illustrating examples of scenarios for sidelink communication in a wireless communication system according to an embodiment of the present disclosure.

[0024] FIG. 3a is a diagram illustrating a path switch operation of a terminal network relay according to an embodiment of the present disclosure.

[0025] FIG. 3b is a diagram illustrating a path switch operation of a terminal network relay according to an embodiment of the present disclosure.

[0026] FIG. 3c is a diagram illustrating a path switch operation of a terminal network relay according to an embodiment of the present disclosure.

[0027] FIG. 3D is a diagram illustrating a path switch operation of a terminal network relay according to an embodiment of the present disclosure.

[0028] FIG. 4a is a flowchart illustrating a path switch operation of a terminal network relay according to an embodiment of the present disclosure.

[0029] FIG. 4b is a flowchart illustrating a path switch operation of a terminal network relay according to an embodiment of the present disclosure.

[0030] FIG. 4c is a flowchart illustrating a path switch operation of a terminal network relay according to an embodiment of the present disclosure.

[0031] FIG. 5A is a diagram illustrating a path switch operation of a multi-hop terminal network relay according to an embodiment of the present disclosure.

[0032] FIG. 5b is a diagram illustrating a path switch operation of a multi-hop terminal network relay according to an embodiment of the present disclosure.

[0033] FIG. 5c is a diagram illustrating a path switch operation of a multi-hop terminal network relay according to an embodiment of the present disclosure.

[0034] FIG. 5d is a diagram illustrating a path switch operation of a multi-hop terminal network relay according to an embodiment of the present disclosure.

[0035] FIG. 6 is a flowchart illustrating a path switch operation of a multi-hop terminal network relay according to an embodiment of the present disclosure.

[0036] FIG. 7A is a diagram illustrating an operation of a terminal reselecting a cell or relay terminal in a multi-hop terminal network relay according to an embodiment of the present disclosure.

[0037] FIG. 7b is a diagram illustrating an operation of a terminal reselecting a cell or relay terminal in a multi-hop terminal network relay according to an embodiment of the present disclosure.

[0038] FIG. 7c is a diagram illustrating an operation of a terminal reselecting a cell or relay terminal in a multi-hop terminal network relay according to an embodiment of the present disclosure.

[0039] FIG. 8 is a flowchart illustrating an operation of changing a path to a target relay terminal that is RRC IDLE or RRC INACTIVE in a path switch of a terminal network relay according to an embodiment of the present disclosure.

[0040] FIG. 9 is a flowchart illustrating an operation in which a target relay terminal reselects a cell or relay terminal during a path switch of a multi-hop terminal network relay according to an embodiment of the present disclosure.

[0041] FIG. 10 is a flowchart illustrating an operation in which a target relay terminal reselects a cell or relay terminal during a path switch of a multi-hop terminal network relay according to an embodiment of the present disclosure.

[0042] FIG. 11 is a flowchart illustrating an operation of a relay terminal transmitting a notification message in a path switch of a multi-hop terminal network relay according to an embodiment of the present disclosure.

[0043] FIG. 12 is a flowchart illustrating an operation for completing a path change in a path switch of a multi-hop terminal network relay according to an embodiment of the present disclosure.

[0044] FIG. 13 is a diagram illustrating terminal measurement and measurement report operations in a multi-hop terminal network relay according to an embodiment of the present disclosure.

[0045] FIG. 14 is a flowchart of an operation in which a source base station selects a target relay terminal that is a path switch target of a remote terminal in a multi-hop terminal network relay according to an embodiment of the present disclosure.

[0046] FIG. 15 is a flowchart of an operation in which a target base station selects a target relay terminal that is a target of a path switch of a remote terminal in a multi-hop terminal network relay according to an embodiment of the present disclosure.

[0047] FIG. 16 is a diagram illustrating the structure of a base station according to an embodiment of the present disclosure.

[0048] FIG. 17 is a diagram illustrating the structure of a terminal according to an embodiment of the present disclosure.

[0049] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the attached drawings.

[0050] In describing the embodiments, descriptions of technical details that are well known in the technical field to which the present disclosure pertains and are not directly related to the present disclosure will be omitted. This is to more clearly convey the gist of the present disclosure without obscuring it by omitting unnecessary explanations.

[0051] For the same reason, some components in the attached drawings are exaggerated, omitted, or schematically depicted. Furthermore, the dimensions of each component do not entirely reflect its actual size. Identical or corresponding components in each drawing are assigned the same reference numbers.

[0052] The advantages and features of the present disclosure, and methods for achieving them, will become clearer with reference to the embodiments described below in detail together with the accompanying drawings. However, the present disclosure is not limited to the embodiments disclosed below and may be implemented in various different forms. These embodiments are provided only to ensure that the disclosure of the present disclosure is complete and to fully inform those skilled in the art of the scope of the disclosure, and the present disclosure is defined only by the scope of the claims. Like reference numerals designate like elements throughout the specification. In addition, when describing the present disclosure, if a specific description of a related function or configuration is determined to unnecessarily obscure the gist of the present disclosure, a detailed description thereof will be omitted. In addition, the terms described below are terms defined in consideration of the functions of the present disclosure, and may vary depending on the intention or custom of the user or operator. Therefore, their definitions should be made based on the contents throughout the specification.

[0053] In explaining the embodiments of the present disclosure, the main target is New Radio (NR), which is a wireless access network, and the core network, packet core 5G System, or 5G Core Network, or NG Core (Next Generation Core) in the 5G mobile communication standard specified by 3GPP (3rd Generation Partnership Project), a mobile communication standard standardization organization. However, the main gist of the present disclosure can be applied to other communication systems with similar technical backgrounds with slight modifications within a range that does not significantly deviate from the scope of the present disclosure, and this will be possible at the discretion of a person skilled in the art of the present disclosure.

[0054] For convenience of explanation, some terms and names defined in the 3GPP standards (standards for 5G, NR, LTE, or similar systems) may be used below. However, the present disclosure is not limited by these terms and names, and can be equally applied to systems conforming to other standards.

[0055] Hereinafter, terms used in the description to identify connection nodes, terms referring to network objects (network entities), terms referring to messages, terms referring to interfaces between network entities, terms referring to various identification information, etc. are provided as examples for convenience of explanation. Therefore, the present disclosure is not limited to the terms used in the present disclosure, and other terms referring to objects with equivalent technical meanings may be used.

[0056] Hereinafter, the base station is an entity that performs resource allocation of a terminal, and may be at least one of a gNode B, an eNode B, a Node B, a BS (Base Station), a wireless access unit, a base station controller, or a node on a network. The terminal may include a UE (User Equipment), an MS (Mobile Station), a cellular phone, a smartphone, a computer, or a multimedia system capable of performing a communication function. In the present disclosure, downlink (DL) refers to a wireless transmission path of a signal transmitted from a base station to a terminal, and uplink (UL) refers to a wireless transmission path of a signal transmitted from a terminal to a base station.

[0057] At this time, it will be understood that each block of the processing flowchart drawings and combinations of the flowchart drawings can be performed by computer program instructions. These computer program instructions can be installed in a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing equipment, so that the instructions executed by the processor of the computer or other programmable data processing equipment create a means for performing the functions described in the flowchart block(s). These computer program instructions can also be stored in a computer-available or computer-readable memory that can direct a computer or other programmable data processing equipment to implement the functions in a specific manner, so that the instructions stored in the computer-available or computer-readable memory can also produce a manufactured item that includes an instruction means for performing the functions described in the flowchart block(s). Since the computer program instructions may be installed on a computer or other programmable data processing device, a series of operational steps may be performed on the computer or other programmable data processing device to create a computer-executable process, and the instructions that cause the computer or other programmable data processing device to perform the steps for performing the functions described in the flowchart block(s) may also provide steps for performing the functions described in the flowchart block(s).

[0058] Additionally, each block may represent a module, segment, or portion of code that contains one or more executable instructions for performing a specific logical function(s). It should also be noted that in some alternative implementation examples, the functions described in the blocks may occur out of order. For example, two blocks depicted in succession may actually be executed substantially concurrently, or the blocks may sometimes be executed in reverse order, depending on their respective functions.

[0059] Here, the term '~ part' used in the present embodiment means software or hardware components such as FPGA (field programmable gate array) or ASIC (application specific integrated circuit), and the '~ part' performs certain roles. However, the '~ part' is not limited to software or hardware. The '~ part' may be configured to be in an addressable storage medium and may be configured to play one or more processors. Therefore, as an example, the '~ part' includes components such as software components, object-oriented software components, class components, and task components, processes, functions, properties, procedures, subroutines, segments of program code, drivers, firmware, microcode, circuits, data, databases, data structures, tables, arrays, and variables. The functions provided within the components and '~ parts' may be combined into a smaller number of components and '~ parts' or further separated into additional components and '~ parts'. In addition, the components and '~parts' may be implemented to play one or more central processing units (CPUs) within the device or secure multimedia card. In addition, in the embodiment, the '~part' may include one or more processors.

[0060] 5G mobile communication technology defines a wide frequency band to enable fast transmission speeds and new services, and can be implemented not only in the sub-6GHz frequency band such as 3.5 gigahertz (3.5GHz), but also in the ultra-high frequency band called millimeter wave (mmWave) such as 28GHz and 39GHz ('Above 6GHz'). In addition, for 6G mobile communication technology, which is called the system after 5G communication (Beyond 5G), implementation in the terahertz band (for example, the 3 terahertz (3THz) band at 95GHz) is being considered to achieve a transmission speed that is 50 times faster than 5G mobile communication technology and an ultra-low latency time that is reduced to one-tenth.

[0061] In the early stages of 5G mobile communication technology, the goal is to support services and meet performance requirements for enhanced Mobile Broadband (eMBB), Ultra-Reliable Low-Latency Communications (URLLC), and massive Machine-Type Communications (mMTC). These include beamforming and massive MIMO to mitigate path loss of radio waves in ultra-high frequency bands and increase the transmission distance of radio waves, support for various numerologies (such as operation of multiple subcarrier intervals) and dynamic operation of slot formats for efficient use of ultra-high frequency resources, initial access technology to support multi-beam transmission and wideband, definition and operation of BWP (Bidth Part), new channel coding methods such as LDPC (Low Density Parity Check) codes for large-capacity data transmission and Polar Code for reliable transmission of control information, and L2 pre-processing (L2). Standardization has been made for network slicing, which provides dedicated networks specialized for specific services, and pre-processing.

[0062] Currently, discussions are underway to improve and enhance the initial 5G mobile communication technology in consideration of the services that 5G mobile communication technology was intended to support, and physical layer standardization is in progress for technologies such as V2X (Vehicle-to-Everything) to help autonomous vehicles make driving decisions and increase user convenience based on their own location and status information transmitted by vehicles, NR-U (New Radio Unlicensed) for the purpose of system operation that complies with various regulatory requirements in unlicensed bands, NR terminal low power consumption technology (UE Power Saving), Non-Terrestrial Network (NTN), which is direct terminal-satellite communication to secure coverage in areas where communication with terrestrial networks is impossible, and Positioning.

[0063] In addition, standardization of radio interface architecture / protocols for technologies such as the Industrial Internet of Things (IIoT) to support new services through linkage and convergence with other industries, Integrated Access and Backhaul (IAB) to provide nodes for expanding network service areas by integrating wireless backhaul links and access links, Mobility Enhancement technology including Conditional Handover and Dual Active Protocol Stack (DAPS) handover, and 2-step random access (2-step RACH for NR) to simplify random access procedures is also in progress, and standardization of system architecture / services for 5G baseline architecture (e.g., Service-based Architecture, Service-based Interface) for grafting Network Functions Virtualization (NFV) and Software-Defined Networking (SDN) technologies, and Mobile Edge Computing (MEC) that provides services based on the location of the terminal is also in progress.

[0064] Once these 5G mobile communication systems are commercialized, an explosive increase in connected devices will be connected to the communication network, necessitating enhanced functionality and performance of 5G mobile communication systems and integrated operation of these connected devices. To this end, new research will be conducted on improving 5G performance and reducing complexity, supporting AI services, supporting metaverse services, and drone communications by utilizing eXtended Reality (XR), Artificial Intelligence (AI), and Machine Learning (ML) to efficiently support Augmented Reality (AR), Virtual Reality (VR), and Mixed Reality (MR).

[0065] In addition, the development of these 5G mobile communication systems includes new waveforms to ensure coverage in the terahertz band of 6G mobile communication technology, multi-antenna transmission technologies such as Full Dimensional MIMO (FD-MIMO), Array Antenna, and Large Scale Antenna, metamaterial-based lenses and antennas to improve the coverage of terahertz band signals, high-dimensional spatial multiplexing technology using Orbital Angular Momentum (OAM), Reconfigurable Intelligent Surface (RIS) technology, as well as full duplex technology to improve the frequency efficiency and system network of 6G mobile communication technology, satellite, AI (Artificial Intelligence) from the design stage and AI-based communication technology that realizes system optimization by internalizing end-to-end AI support functions, and ultra-high-performance communication and computing resources to provide services with complexity that exceeds the limits of terminal computing capabilities. It can serve as a basis for the development of next-generation distributed computing technologies that can be realized by utilizing them.

[0066] The present disclosure relates to a method and apparatus for performing a direct-to-indirect path switch (D2I path switch) from a direct path within a base station (gNB) or between base stations (inter-gNB) in a multi-hop UE-to-Network (U2N) relay of a wireless communication system, or an indirect-to-direct path switch (I2D path switch) from an indirect path to a direct path, or an indirect-to-indirect path switch (I2I path switch) from an indirect path to an indirect path. A remote terminal can transmit and receive uplink or downlink data to and from a base station via an indirect path through a relay terminal (Relay UE). The indirect path refers to a link between a remote terminal and a relay terminal, or a link between a relay terminal and a base station. The remote terminal can transmit and receive data to and from a relay terminal via a terminal-to-terminal link, and the relay terminal can transmit and receive data to and from a base station via a direct link. A relay terminal can transmit uplink data received from a remote terminal to a base station, and the relay terminal can transmit downlink data received from the base station to the remote terminal. Multi-hop relay may mean that there are at least two relay terminals. In multi-hop relay, if the relay terminal is in RRC IDLE or RRC INACTIVE, the relay terminal can perform cell reselection or relay reselection.If the relay terminal maintains the same cell or base station during cell or relay reselection, the relay terminal may not transmit a notification message, and the remote terminal may complete the path switch without performing an RRC re-establishment procedure. Remote terminals and relay terminals may add information for multi-hop relaying to the discovery message and report it to the base station.

[0067] FIG. 1 is a diagram illustrating the structure of a next-generation mobile communication system according to an embodiment of the present disclosure.

[0068] Referring to FIG. 1, a wireless access network of a next-generation mobile communication system (hereinafter referred to as NR or 5G) may be configured to include a next-generation base station (new radio node B, hereinafter referred to as NR gNB, gNB or base station) (120) and an NR CN (110, new radio core network). A user terminal (new radio user equipment, hereinafter referred to as NR UE or terminal) (150) may access an external network through the NR gNB (120) and the NR CN (110).

[0069] In Fig. 1, the NR gNB (120) may correspond to the eNB (140) of the LTE system. The NR gNB (120) is connected to the NR UE (150) via a wireless channel and may provide a service superior to that of the eNB (140). In the next-generation mobile communication system, since all user traffic is serviced through a shared channel, a device that collects status information such as the buffer status of UEs, available transmission power status, and channel status and performs scheduling is required, and the NR gNB (120) may be responsible for this. One NR gNB (120) can typically control multiple cells. In order to implement ultra-high-speed data transmission compared to LTE, a bandwidth greater than the maximum bandwidth of LTE can be used, and beamforming technology can be additionally grafted using the OFDM method as a wireless access technology. In addition, an Adaptive Modulation and Coding (AMC) method that determines a modulation scheme and a channel coding rate according to the channel status of the terminal can be applied. The NR CN (110) can perform functions such as mobility support and QoS settings. The NR CN (110) is a device that handles various control functions as well as mobility management functions for terminals and can be connected to multiple base stations. In addition, the next-generation mobile communication system can be linked with the LTE system, and the NR CN (110) can be connected to the MME (130) through a network interface. The MME (130) can be connected to the eNB (140).

[0070]

[0071] FIGS. 2A to 2D are diagrams illustrating examples of scenarios for sidelink communication in a wireless communication system according to an embodiment of the present disclosure.

[0072] Figure 2a illustrates an in-coverage (IC) scenario where sidelink terminals (220, 225) are located within the coverage (210) of a base station (200).

[0073] Referring to FIG. 2A, sidelink terminals (220, 225) can receive data and control information from a base station (200) via a downlink (DL), or transmit data and control information to the base station (200) via an uplink (UL). At this time, the data and control information may be data and control information for sidelink communication, or data and control information for general cellular communication rather than sidelink communication. In addition, the sidelink terminals (220, 225) can transmit and receive data and control information for sidelink communication via the sidelink. In addition, the first terminal (220) can receive data and control information from the base station (200) via a direct path via the DL or UL, or can receive data and control information from the base station (200) via an indirect path via a relay of the second terminal (225). The first terminal (220) may be referred to as a remote terminal (remote UE), and the second terminal (225) may be referred to as a relay terminal (relay UE). A scenario in which the first terminal (220) accesses the base station (200) through the second terminal (225) may be referred to as a UE-to-Network relay (U2N relay). In addition, the first terminal (220) may transmit and receive data and control information with the base station (200) by simultaneously using a direct path and an indirect path, and such a scenario may be referred to as a multi-path relay.

[0074] FIG. 2b illustrates a case of partial coverage (PC) in which a first terminal (220) among side link terminals is located within the coverage (210) of the base station (200) and a second terminal (225) is located outside the coverage (210) of the base station (200).

[0075] Referring to FIG. 2B, a first terminal (220) located within the coverage (210) of a base station (200) can receive data and control information from the base station (200) via downlink or transmit data and control information to the base station (200) via uplink. A second terminal (225) located outside the coverage of the base station (200) cannot directly receive data and control information from the base station (200) via downlink and cannot directly transmit data and control information to the base station (200) via uplink. The second terminal (225) can transmit and receive data and control information for sidelink communication with the first terminal (220) via sidelink.

[0076] FIG. 2c is an example of a case where sidelink terminals (e.g., first terminal (220), second terminal (225)) are located outside the coverage (210) of the base station (200) (out-of coverage, OOC).

[0077] Referring to FIG. 2c, the first terminal (220) and the second terminal (225) cannot receive data and control information from the base station via the downlink, and cannot transmit data and control information to the base station via the uplink. The first terminal (220) and the second terminal (225) can transmit and receive data and control information for sidelink communication via the sidelink.

[0078] FIG. 2D illustrates a case where a first terminal (220) and a second terminal (225) performing sidelink communication are connected to (e.g., in an RRC connection state) or camping on (e.g., in an RRC disconnection state, i.e., in an RRC idle or inactive state) different base stations (e.g., the first base station (200) and the second base station (205)) and perform inter-cell sidelink communication. At this time, referring to FIG. 2D, the first terminal (220) may be a sidelink transmitting terminal and the second terminal (225) may be a sidelink receiving terminal. Alternatively, the first terminal (220) may be a sidelink receiving terminal and the second terminal (225) may be a sidelink transmitting terminal. A first terminal (220) can receive a sidelink-only SIB (system information block) from a base station (200) to which it is connected (or at which it is camping), and a second terminal (225) can receive a sidelink-only SIB from another base station (205) to which it is connected (or at which it is camping). At this time, the information of the sidelink-only SIB received by the first terminal (220) may be different from the information of the sidelink-only SIB received by the second terminal (225). Therefore, in order to perform sidelink communication between terminals located in different cells, unification of information or additional assumptions and interpretation methods may be required. In addition, the first terminal (220) can receive data and control information from the first base station (200) through a direct path via DL or UL, or can receive data and control information from the second base station (205) through an indirect path via a relay of the second terminal (225). The first terminal (220) may be referred to as a remote terminal, and the second terminal (225) may be referred to as a relay terminal. A scenario in which the first terminal (220) connects to the second base station (205) via the second terminal (225) may be referred to as a terminal-network relay.In addition, the first terminal (220) can transmit and receive data and control information with the first base station (200) and the second base station (205) by simultaneously using a direct path and an indirect path, and this scenario can be called a multi-path relay.

[0079] In the examples of FIGS. 2A to 2D, for the sake of convenience of explanation, a sidelink system composed of two terminals (e.g., a first terminal (220) and a second terminal (225)) is described as an example; however, the present disclosure is not limited thereto and may also be applied to a sidelink system in which three or more terminals participate. In addition, the uplink and downlink between the base station (200) and the sidelink terminals may be referred to as a Uu interface, and the sidelink between the sidelink terminals may be referred to as a PC5 interface. In addition, a sidelink terminal located in an OOC where the base station (200) and the Uu interface are not connected may indirectly receive data and control information from the base station through a relay of another sidelink terminal located in an IC where the base station and the Uu interface are connected. In the following description, the uplink or downlink and the Uu interface may be used interchangeably, and the sidelink and the PC5 interface may be used interchangeably.

[0080] Meanwhile, in the present disclosure, a terminal may refer to a vehicle supporting vehicular-to-vehicular (V2V) communication, a vehicle supporting vehicular-to-pedestrian (V2P) communication, or a pedestrian's handset (e.g., a smartphone), a vehicle supporting vehicular-to-network (V2N) communication, or a vehicle supporting vehicular-to-infrastructure (V2I) communication. In addition, in the present disclosure, a terminal may refer to a road side unit (RSU) equipped with a terminal function, an RSU equipped with a base station function, or an RSU equipped with a part of a base station function and a part of a terminal function. In addition, it may refer to a terminal that supports proximity service (hereinafter referred to as ProSe) and terminal-to-terminal relay (e.g., end UE or relay UE of terminal-to-terminal relay) or terminal-to-network relay (e.g., remote UE or relay UE of terminal-to-network relay) using proximity service.

[0081] Additionally, in the present disclosure, a base station may be a base station that supports both sidelink and general cellular communication, or a base station that supports only sidelink. In this case, the base station may be a 5G base station (gNB), a 4G base station (eNB), or an RSU. Therefore, in the present disclosure, the base station may also be referred to as an RSU.

[0082]

[0083] FIGS. 3A to 3D are diagrams showing a path switch operation of a terminal network relay according to an embodiment of the present disclosure.

[0084] Referring to FIGS. 3A to 3D , a base station (300) provides services to a first terminal (320) and a second terminal (330) within a communication coverage (310). At this time, the base station (300) may be a base station (300) that supports a UE-to-Network (U2N) relay, the first terminal (320) may be a terminal capable of relay terminal operation in a U2N relay, the second terminal (330) may be a terminal capable of remote terminal operation in a U2N relay, and the third terminal (340) may be a terminal capable of relay terminal operation in a U2N relay. Alternatively, the first terminal (320), the second terminal (330), and the third terminal (340) may be a combination of terminals capable of both remote terminal operation and relay terminal operation in a U2N relay.

[0085] Referring to FIGS. 3A and 3B, in the situation of FIG. 3A, if the first terminal (320) satisfies the condition for operating as a U2N relay terminal, it can transmit a discovery message. A surrounding terminal (e.g., a second terminal (330)) can discover the first terminal (320) as a candidate U2N relay terminal. The second terminal (330) may move away from the signal range of the base station (300) due to movement or a change in channel conditions. The base station (300) can instruct the second terminal (330) to measure and report the signal strength of the surrounding U2N relay terminal. The base station (300) can instruct a path switch to continue providing service by connecting the second terminal (330), which is directly connected to the base station (300), to an indirect path through the first terminal (320) by referring to the measurement report of the second terminal (330). In situation 3b, the second terminal (330) can continue the service by switching to an indirect path through the first terminal (320) according to the instructions of the base station (300). This path switch may be called an intra-gNB direct-to-indirect path switch that switches from a direct path to an indirect path within the base station (300).

[0086] Referring to FIGS. 3A and 3B, in the situation of FIG. 3B, the base station (300) can instruct the second terminal (330) to measure and report the signal strength of the surrounding base station (300). The base station (300) can instruct a path switch to change the indirect path through the base station (300) and the first terminal (320) to a direct path of the base station (300) and continue the service by referring to the measurement report of the second terminal (330). In the situation of 3A, the second terminal (330) can continue the service by changing the indirect path through the first terminal (320) to a direct path of the base station (300) according to the instruction of the base station (300). This path switch can be called an intra-gNB indirect-to-direct path switch that changes from an indirect path to a direct path within the base station (300).

[0087] Referring to FIGS. 3C and 3D , if the third terminal (340) satisfies the conditions for operating as a U2N relay terminal, it can transmit a discovery message. A surrounding terminal (e.g., the second terminal (330)) can discover the third terminal (340) as a candidate U2N relay terminal. The second terminal (330) may move away from the signal range of the first terminal (320) currently servicing the U2N relay due to movement or a change in channel conditions. The base station (300) can instruct the second terminal (330) to measure and report the signal strength of the surrounding U2N relay terminal. The base station (300) can instruct a path switch to continue the service by connecting the second terminal (330), which is connected to the first terminal (320) through an indirect path, through an indirect path via the third terminal (340) by referring to the measurement report of the second terminal (330). The second terminal (330) can continue to provide service by switching to an indirect path via the third terminal (340) according to the instructions of the base station (300). This path switch may be called an intra-gNB indirect-to-indirect path switch that switches from an indirect path within the base station (300) to an indirect path.

[0088]

[0089] FIGS. 4A to 4C are flowcharts illustrating a path switch operation of a terminal network relay according to an embodiment of the present disclosure.

[0090] Referring to FIG. 4A, the base station (403) may be a base station (403) that supports U2N relay, the first terminal (401) may be a terminal capable of remote terminal operation in a U2N relay, and the second terminal (402) may be a terminal capable of relay terminal operation in a U2N relay. Alternatively, the first terminal (401) and the second terminal (402) may be a combination of terminals capable of both remote terminal operation and relay terminal operation in a U2N relay.

[0091] In step 404, the first terminal (401) can be directly connected to the base station (403) and transmit UL / DL data.

[0092] In step 405, the base station (403) may transmit a message to the first terminal (401) to confirm the functions supported by the first terminal (401). The message may be a UE capability enquiry message. The first terminal (401) may receive the UE capability enquiry message and respond with a UE capability information message for the items requested by the base station (403).

[0093] In step 406, the base station (403) can set measurement / reporting settings for U2N relay UEs and NR cells around the first terminal (401) to the first terminal (401). The base station (403) can set a measurement report to be sent when at least one of the conditions is satisfied, such as a PC5 RSRP (e.g., SL-RSRP or SD-RSRP) of a candidate relay UE of the first terminal (401) exceeds a specific threshold, is less than a specific threshold, or an RSRP with a serving cell or a neighboring cell of the first terminal (401) exceeds a specific threshold, or is less than a specific threshold.

[0094] In step 407, the first terminal (401) can discover surrounding U2N relays by transmitting and receiving discovery messages. The transmission and reception of discovery messages can be performed in parallel, regardless of the measurement / reporting settings of the base station (403).

[0095] At step 408, the first terminal (401) can report the measurement result to the base station (403). The measurement report can include serving cell information of the serving / candidate Relay UE, Layer-2 ID (L2ID) of the serving / candidate Relay UE, PC5 RSRP of the serving / candidate Relay UE, which can be obtained from the discovery message transmitted by the serving / candidate Relay UE, and can include at least one or more serving / candidate Relay UE information. In addition, the measurement report can include physical cell ID (PCI) of the NR cell, Uu RSRP of the NR cell, and can include at least one or more NR cell information.

[0096] In step 409, the base station (403) can determine an appropriate relay UE as a path switch target among candidate relay UEs as a target relay UE by referring to the measurement report transmitted by the first terminal (401).

[0097] At step 410, the base station (403) may transmit to the first terminal (401) a path switch configuration including settings for transmitting and receiving data on an indirect path for the path switch of the first terminal (401). This setting may include at least one of the L2ID of the target Relay UE, Sidelink Relay Adaptation Protocol (SRAP) settings, and PC5 relay RLC channel settings.

[0098] In step 411, the base station (403) may transmit settings for the Relay UE operation of the second terminal (402) to the second terminal (402). These settings may include at least one of the Remote UE's L2ID, SRAP settings, Uu relay RLC channel settings, and PC5 relay RLC channel settings.

[0099] At step 412, the first terminal (401) can establish a PC5 unicast link with the second terminal (402) if a PC5 unicast link connection with the second terminal (402) is required.

[0100] At step 413, the first terminal (401) can transmit a message notifying path switch completion to the base station (403) through an indirect pass through the second terminal (402).

[0101] At step 414, the first terminal (401) can transmit UL / DL data by being connected to the base station (403) and the second terminal (402) through an indirect path.

[0102] Referring to FIG. 4b, the base station (423) may be a base station (423) that supports U2N relay, the first terminal (421) may be a terminal capable of remote terminal operation in a U2N relay, and the second terminal (422) may be a terminal capable of relay terminal operation in a U2N relay. Alternatively, the first terminal (421) and the second terminal (422) may be a combination of terminals capable of both remote terminal operation and relay terminal operation in a U2N relay.

[0103] At step 424, the first terminal (421) can transmit UL / DL data by being connected to the base station (423) and the second terminal (422) through an indirect path.

[0104] At step 425, the base station (423) may transmit a message to the first terminal (421) to confirm the functions supported by the first terminal (421). The message may be a UE capability enquiry message. The first terminal (421) may receive the UE capability enquiry message and respond with a UE capability information message for the items requested by the base station (423).

[0105] In step 426, the base station (423) can set measurement / reporting settings for the serving / candidate U2N Relay UE and NR cell of the first terminal (421) to the first terminal (421). The base station (423) can set a measurement report to be sent when at least one of the conditions is satisfied, such as a PC5 RSRP (e.g., SL-RSRP or SD-RSRP) of the serving / candidate Relay UE of the first terminal (421) exceeds a specific threshold, is less than a specific threshold, or an RSRP with the serving cell or a neighboring cell of the first terminal (421) exceeds a specific threshold, or is less than a specific threshold.

[0106] At step 427, the first terminal (421) may report the measurement result to the base station (423). The measurement report may include serving cell information of the serving / candidate Relay UE, Layer-2 ID (L2ID) of the serving / candidate Relay UE, and PC5 RSRP of the serving / candidate Relay UE, which may be obtained from the discovery message transmitted by the serving / candidate Relay UE, and may include at least one piece of serving / candidate Relay UE information. In addition, the measurement report may include a physical cell ID (PCI) of the NR cell, a Uu RSRP of the NR cell, and may include at least one piece of NR cell information.

[0107] At step 428, the base station (423) can determine a path switch as a direct path of the base station (423) by referring to the measurement report transmitted by the first terminal (421).

[0108] At step 429, the base station (423) may transmit to the first terminal (421) a path switch configuration including settings for transmitting and receiving data directly on the path for the path switch of the first terminal (421). This setting may include a cell group configuration.

[0109] At step 430, the first terminal (421) can transmit a message notifying path switch completion to the base station (423) through a direct pass.

[0110] At step 431, the base station (423) can delete the first terminal (421) setting for the relay UE operation of the second terminal (422).

[0111] At step 432, the first terminal (421) or the second terminal (422) may release the PC5 unicast link with the second terminal (422) if it is necessary to release the PC5 unicast link with the second terminal (422) or the first terminal (421).

[0112] At step 433, the first terminal (421) is directly connected to the base station (423) and can transmit UL / DL data.

[0113] Referring to FIG. 4c, the base station (444) may be a base station (444) that supports a U2N relay, the first terminal (441) may be a terminal capable of remote terminal operation in a U2N relay, the second terminal (442) may be a terminal capable of relay terminal operation in a U2N relay, and the third terminal (443) may be a terminal capable of relay terminal operation in a U2N relay. Alternatively, the first terminal (441), the second terminal (442), and the third terminal (443) may be a combination of terminals capable of both remote terminal operation and relay terminal operation in a U2N relay.

[0114] At step 445, the first terminal (441) can transmit UL / DL data by being connected to the base station (444) and the second terminal (442) through an indirect path.

[0115] At step 446, the base station (444) may transmit a message to the first terminal (441) to confirm the functions supported by the first terminal (441). The message may be a UE capability enquiry message. The first terminal (441) may receive the UE capability enquiry message and respond with a UE capability information message for the items requested by the base station (444).

[0116] In step 447, the base station (444) can set measurement / reporting settings for the serving / candidate U2N Relay UE and NR cell of the first terminal (441) to the first terminal (441). The base station (444) can set a measurement report to be sent when at least one or more of the conditions are satisfied, such as a PC5 RSRP (e.g., SL-RSRP or SD-RSRP) of the serving / candidate Relay UE of the first terminal (441) exceeding a specific threshold, being less than a specific threshold, or an RSRP with the serving cell or a neighboring cell of the first terminal (441) exceeding a specific threshold, being less than a specific threshold, or being less than a specific threshold.

[0117] At step 448, the first terminal (441) can discover surrounding U2N relays by transmitting and receiving discovery messages. The transmission and reception of discovery messages can be performed in parallel, regardless of the measurement / reporting settings of the base station (444).

[0118] At step 449, the first terminal (441) may report the measurement result to the base station (444). The measurement report may include serving cell information of the serving / candidate Relay UE, Layer-2 ID (L2ID) of the serving / candidate Relay UE, and PC5 RSRP of the serving / candidate Relay UE, which may be obtained from the discovery message transmitted by the serving / candidate Relay UE, and may include at least one piece of serving / candidate Relay UE information. In addition, the measurement report may include a physical cell ID (PCI) of the NR cell, a Uu RSRP of the NR cell, and may include at least one piece of NR cell information.

[0119] At step 450, the base station (444) can determine a path switch through an indirect path via the third terminal (443) by referring to the measurement report transmitted by the first terminal (441).

[0120] In step 451, the base station (444) may transmit settings for the relay UE operation of the third terminal (443) to the third terminal (443). These settings may include at least one of the L2ID of the remote UE, SRAP settings, Uu relay RLC channel settings, and PC5 relay RLC channel settings.

[0121] At step 452, the base station (444) may transmit a path switch configuration to the first terminal (441) that includes settings for transmitting and receiving data on an indirect path for the path switch of the first terminal (441). This setting may include a cell group configuration.

[0122] At step 453, the first terminal (441) can establish a PC5 unicast link with the second terminal (442) if a PC5 unicast link connection with the third terminal (443) is required.

[0123] At step 454, the first terminal (441) can transmit a message notifying path switch completion to the base station (444) through an indirect pass through the third terminal (443).

[0124] At step 455, the base station (444) can delete the first terminal (441) setting for the relay UE operation of the second terminal (442).

[0125] At step 456, the first terminal (441) or the second terminal (442) may release the PC5 unicast link with the second terminal (442) if it is necessary to release the PC5 unicast link with the second terminal (442) or the first terminal (441).

[0126] At step 457, the first terminal (441) can transmit UL / DL data by connecting to the base station (444) and the third terminal (443) through an indirect path.

[0127]

[0128] FIGS. 5A to 5D are diagrams showing a path switch operation of a multi-hop terminal network relay according to an embodiment of the present disclosure.

[0129] Referring to FIGS. 5A to 5D, the first base station (500) and the second base station (501) may be base stations supporting U2N relay or U2N multi-hop relay, the first terminal (510), the second terminal (520), and the fourth terminal (540) may be terminals capable of relay terminal operation in a U2N relay or U2N multi-hop relay, and the third terminal (530) may be a terminal capable of remote terminal operation in a U2N relay or U2N multi-hop relay. Alternatively, the first terminal (510), the second terminal (520), the third terminal (530), and the fourth terminal (540) may be a combination of terminals capable of both remote terminal operation and relay terminal operation in a U2N relay or U2N multi-hop relay.

[0130] Referring to FIG. 5A, the first terminal (510) is directly connected to the first base station (500) and can operate as a relay terminal. The second terminal (520) is indirectly connected to the first base station (500) with the first terminal (510) as a serving relay and can operate as a relay terminal. In this case, the second terminal (520) may be a remote terminal in a U2N relay or a relay terminal in a U2N multi-hop relay. The third terminal (530) is indirectly connected to the first base station (500) with the second terminal (520) as a serving relay. In the situation of FIG. 5B, the third terminal (530) may come close to the second base station (501) due to movement of the terminal or change in channel conditions, and the first base station (500) may determine a path switch to change the third terminal (530) to a direct path of the second base station (501). The third terminal (530) can connect to the direct path of the second base station (501) and continue the service according to the path switch setting of the first base station (500).

[0131] Referring to FIG. 5a, the first terminal (510) is directly connected to the first base station (500) and can operate as a relay terminal. The second terminal (520) is indirectly connected to the first base station (500) with the first terminal (510) as a serving relay and can operate as a relay terminal. In this case, the second terminal (520) may be a remote terminal in a U2N relay and a relay terminal in a U2N multi-hop relay. The third terminal (530) is indirectly connected to the first base station (500) with the second terminal (520) as a serving relay. In the situation of FIG. 5c, the third terminal (530) may come into proximity with the fourth terminal (540) due to movement of the terminal or change in channel conditions, and the fourth terminal (540) may be a U2N relay terminal connected to the second base station (501). The fourth terminal (540) may be directly connected to the second base station (501) or indirectly connected to the second base station (501) via one or more other relay terminals not shown in the drawing. The first base station (500) may determine a path switch that changes the third terminal (530) to an indirect path of the second base station (501). The third terminal (530) may connect to the indirect path of the second base station (501) and continue to provide service according to the path switch setting of the first base station (500).

[0132] Referring to FIG. 5A, the first terminal (510) is directly connected to the first base station (500) and can operate as a relay terminal. The second terminal (520) is indirectly connected to the first base station (500) with the first terminal (510) as a serving relay and can operate as a relay terminal. In this case, the second terminal (520) may be a remote terminal in a U2N relay or a relay terminal in a U2N multi-hop relay. The third terminal (530) is indirectly connected to the first base station (500) with the second terminal (520) as a serving relay. In the situation of FIG. 5D, the third terminal (530) may come close to the first terminal (510) due to movement of the terminal or changes in channel conditions. The first base station (500) may determine a path switch that changes the third terminal (530) to an indirect path of the first base station (500). The third terminal (530) can connect to the indirect path of the first base station (500) and continue the service according to the path switch setting of the first base station (500).

[0133] The first base station (500) and the second base station (501) may be the same base station or different base stations. For convenience of explanation, the first base station (500) and the second base station (501) are illustrated separately, and the movement of a terminal not shown in the drawing or one or more relay terminals not shown in the drawing may be included in the path switch operation of the multi-hop terminal network relay.

[0134]

[0135] FIG. 6 is a flowchart illustrating a path switch operation of a multi-hop terminal network relay according to an embodiment of the present disclosure.

[0136] Referring to FIG. 6, the base station (604) may be a base station (604) that supports U2N relay or U2N multi-hop relay, the second terminal (602) and the third terminal (603) may be terminals capable of relay terminal operation in a U2N relay or U2N multi-hop relay, and the first terminal (601) may be a terminal capable of remote terminal operation in a U2N relay or U2N multi-hop relay. Alternatively, the first terminal (601), the second terminal (602), and the third terminal (603) may be a combination of terminals capable of both remote terminal operation and relay terminal operation in a U2N relay or U2N multi-hop relay.

[0137] At step 605, the first terminal (601) can be connected to the base station (604) through a direct or indirect path to transmit UL / DL data.

[0138] At step 606, the second terminal (602) can be connected to the base station (604) through an indirect path via the third terminal (603) to transmit UL / DL data.

[0139] In step 607, the base station (604) may transmit a message to the first terminal (601) to check the functions supported by the first terminal (601). The message may be a UE capability enquiry message. The first terminal (601) may receive the UE capability enquiry message and respond with a UE capability information message for the items requested by the base station (604). For example, at least one of whether multi-hop U2N relay is supported, whether relay terminal operation in multi-hop U2N relay is supported, and whether remote terminal operation in multi-hop U2N relay is supported may be included.

[0140] In step 608, the base station (604) can set measurement / reporting settings for U2N relay UEs and NR cells around the first terminal (601) to the first terminal (601). The base station (604) can set a measurement report to be sent when at least one of the conditions is satisfied, such as a PC5 RSRP (e.g., SL-RSRP or SD-RSRP) of a candidate relay UE of the first terminal (601) exceeds a specific threshold, is less than a specific threshold, or an RSRP with a serving cell or a neighboring cell of the first terminal (601) exceeds a specific threshold, or is less than a specific threshold.

[0141] In step 609, the first terminal (601) can discover a U2N relay in the vicinity by transmitting and receiving a discovery message. The transmission and reception of the discovery message can operate in parallel regardless of the measurement / reporting settings of the base station (604). The second terminal (602) can transmit a discovery message related to a multi-hop network terminal relay if the base station (604) supports a multi-hop network terminal relay. Whether the base station (604) supports a multi-hop network terminal relay can be transmitted using an RRC message, etc. If the second terminal (602) is connected to the base station (604) through an indirect path, a relay terminal (e.g., a third terminal (603)) can transmit or indicate whether the serving cell or the serving base station (604) supports a multi-hop network terminal relay.

[0142] In step 610, the first terminal (601) may report the measurement result to the base station (604). The measurement report may include serving cell information of the serving / candidate Relay UE, Layer-2 ID (L2ID) of the serving / candidate Relay UE, and PC5 RSRP of the serving / candidate Relay UE, which may be obtained from a discovery message transmitted by the serving / candidate Relay UE, and may include at least one or more serving / candidate Relay UE information. In addition, the measurement report may include a physical cell ID (PCI) of the NR cell, a Uu RSRP of the NR cell, and may include at least one or more NR cell information.

[0143] In step 611, the base station (604) can determine a suitable relay UE as a path switch target among candidate relay UEs as a target relay UE (e.g., the second terminal (602)) by referring to the measurement report transmitted by the first terminal (601).

[0144] At step 612, the base station (604) may transmit to the third terminal (603) the settings for the relay UE operation of the third terminal (603). These settings may include at least one of the L2ID of the remote UE (e.g., the first terminal (601)), the L2ID of the next hop UE (e.g., the second terminal (602)), the SRAP settings, the Uu relay RLC channel settings, and the PC5 relay RLC channel settings.

[0145] At step 613, the base station (604) may transmit settings for the Relay UE operation of the second terminal (602) to the second terminal (602). These settings may include at least one of the L2ID of the Remote UE (e.g., the first terminal (601)), the L2ID of the next hop UE (e.g., the first terminal (601)), the SRAP settings, the PC5 relay RLC channel (UL), and the PC5 relay RLC channel (DL) settings.

[0146] At step 614, the base station (604) may transmit to the first terminal (601) a path switch configuration including settings for transmitting and receiving data on an indirect path for the path switch of the first terminal (601). This setting may include at least one of the L2ID of the target Relay UE, Sidelink Relay Adaptation Protocol (SRAP) settings, and PC5 relay RLC channel settings.

[0147] At step 615, the first terminal (601) can establish a PC5 unicast link with the second terminal (602) if a PC5 unicast link connection with the second terminal (602) is required.

[0148] At step 616, the first terminal (601) can transmit a message notifying path switch completion to the base station (604) through an indirect path through the second terminal (602) and the third terminal (603).

[0149] At step 617, the first terminal (601) can transmit UL / DL data by being connected to the base station (604) and an indirect path through the second terminal (602) and the third terminal (603).

[0150] In this drawing, for convenience of explanation, the first terminal (601), the second terminal (602), and the third terminal (603) are all depicted as being connected to the same base station (604). However, the first terminal (601) and the second terminal (602) may be connected to different base stations or cells. In addition, the first terminal (602), the second terminal (602), and the third terminal (603) may be connected to the base station (604) through an indirect path via one or more relay terminals.

[0151]

[0152] FIGS. 7A to 7C are diagrams showing an operation of a terminal reselecting a cell or relay terminal in a multi-hop terminal network relay according to an embodiment of the present disclosure.

[0153] Referring to FIGS. 7A to 7C, the first base station (700) and the second base station (701) may be base stations supporting U2N relay or U2N multi-hop relay, the first terminal (710) and the third terminal (730) may be terminals capable of relay terminal operation in a U2N relay or U2N multi-hop relay, and the second terminal (720) may be a terminal capable of remote terminal operation in a U2N relay or U2N multi-hop relay. Alternatively, the first terminal (710), the second terminal (720), and the third terminal (730) may be a combination of terminals capable of both remote terminal operation and relay terminal operation in a U2N relay or U2N multi-hop relay.

[0154] Referring to FIG. 7A, a second terminal (720) is connected to a first base station (700) through an indirect path via a first terminal (710) and can operate as a remote terminal. The first terminal (710) may be in an RRC IDLE or RRC INACTIVE state and may perform cell reselection or relay reselection. The second terminal (720) may be in an RRC IDLE or RRC INACTIVE state and may perform cell reselection or relay reselection. Cell reselection or relay reselection may be performed by comparing the signal strength (e.g., RSRP) or signal quality (e.g., RSRQ) of a serving cell or relay terminal in an RRC IDLE or RRC INACTIVE state with threshold values ​​for intra-frequency, inter-frequency, inter-RAT, etc. The terminal regards the reselected cell or relay terminal as a serving cell or serving relay, and can then access the reselected cell or relay terminal in operations such as RRC establishment for transition to the RRC CONNECTED state.

[0155] Referring to FIG. 7b, a second terminal (720) in RRC IDLE or RRC INACTIVE may move away from the first terminal (710) or closer to the second base station (701) compared to the situation in FIG. 7a due to movement of the terminal or change in channel conditions. The second terminal (720) may reselect a second base station (701) that satisfies the conditions and thresholds for cell or relay reselection.

[0156] Referring to FIG. 7c, the second terminal (720) in RRC IDLE or RRC INACTIVE may move away from the first terminal (710) or closer to the third terminal (730) compared to the situation in FIG. 7a due to movement of the terminal or change in channel conditions. The second terminal (720) may reselect the third terminal (730) that satisfies the conditions and thresholds for cell or relay reselection.

[0157]

[0158] FIG. 8 is a flowchart illustrating an operation of changing a path to a target relay terminal that is RRC IDLE or RRC INACTIVE in a path switch of a terminal network relay according to an embodiment of the present disclosure.

[0159] Referring to FIG. 8, the base station (803) may be a base station (803) that supports U2N relay, the second terminal (802) may be a terminal capable of relay terminal operation in a U2N relay, and the first terminal (801) may be a terminal capable of remote terminal operation in a U2N relay. Alternatively, the first terminal (801) and the second terminal (802) may be a combination of terminals capable of both remote terminal operation and relay terminal operation in a U2N relay.

[0160] At step 804, the second terminal (802) may be in an RRC IDLE or RRC INACTIVE state.

[0161] At step 805, the first terminal (801) is directly connected to the base station (803) and can exchange UL / DL data.

[0162] At step 806, the base station (803) may transmit a message to the first terminal (801) to check the functions supported by the first terminal (801). The message may be a UE capability enquiry message. The first terminal (801) may receive the UE capability enquiry message and respond with a UE capability information message for the items requested by the base station (803).

[0163] In step 807, the base station (803) can set measurement / reporting settings for U2N relay UEs and NR cells around the first terminal (801) to the first terminal (801). The base station (803) can set a measurement report to be sent when at least one of the conditions is satisfied, such as a PC5 RSRP (e.g., SL-RSRP or SD-RSRP) of a candidate relay UE of the first terminal (801) exceeds a specific threshold, is less than a specific threshold, or an RSRP with a serving cell or a neighboring cell of the first terminal (801) exceeds a specific threshold, or is less than a specific threshold.

[0164] In step 808, the first terminal (801) can discover surrounding U2N relays by transmitting and receiving discovery messages. The transmission and reception of discovery messages can be performed in parallel, regardless of the measurement / reporting settings of the base station (803).

[0165] At step 809, the first terminal (801) can report the measurement result to the base station (803). The measurement report can include serving cell information of the serving / candidate Relay UE, Layer-2 ID (L2ID) of the serving / candidate Relay UE, PC5 RSRP of the serving / candidate Relay UE, which can be obtained from the discovery message transmitted by the serving / candidate Relay UE, and can include at least one or more serving / candidate Relay UE information. In addition, the measurement report can include physical cell ID (PCI) of the NR cell, Uu RSRP of the NR cell, and can include at least one or more NR cell information.

[0166] At step 810, the base station (803) may determine a suitable relay UE as a path switch target among candidate relay UEs as a target relay UE (e.g., the second terminal (802)) by referring to the measurement report transmitted by the first terminal (801). At this time, the second terminal (802) may be in an RRC IDLE or RRC INACTIVE state.

[0167] In step 811, the base station (803) may transmit to the first terminal (801) a path switch configuration including settings for transmitting and receiving data on an indirect path for the path switch of the first terminal (801). This setting may include at least one of the L2ID of the target Relay UE, Sidelink Relay Adaptation Protocol (SRAP) settings, and PC5 relay RLC channel settings.

[0168] At step 812, the first terminal (801) can establish a PC5 unicast link with the second terminal (802) if a PC5 unicast link connection with the second terminal (802) is required.

[0169] At step 813, the first terminal (801) can transmit a message notifying path switch completion to the base station (803) through an indirect pass through the second terminal (802).

[0170] At step 814, since the second terminal (802) is not in an RRC CONNECTED state with the base station (803), it can establish an RRC connection with the base station (803) to receive relay UE settings and transmission / reception resources for the first terminal (801) from the base station (803).

[0171] At step 815, the second terminal (802) may transmit a message (e.g., a sidelinkUEInformationNR message) requesting information and resources of the Remote UE to the base station (803). This message may include at least one of the Remote UE's L2ID and a local ID request used for SRAP.

[0172] At step 816, the base station (803) may transmit to the second terminal (802) the settings for the Relay UE operation of the second terminal (802). These settings may include at least one of the Remote UE's L2ID, SRAP settings, Uu relay RLC channel settings, and PC5 relay RLC channel settings.

[0173] At step 817, the second terminal (802) can transmit a message notifying the path switch completion transmitted by the first terminal (801) to the base station (803).

[0174] At step 818, the first terminal (801) can transmit UL / DL data by connecting to the base station (803) and the second terminal (802) through an indirect path.

[0175]

[0176] FIG. 9 is a flowchart illustrating an operation in which a target relay terminal reselects a cell or relay terminal during a path switch of a multi-hop terminal network relay according to an embodiment of the present disclosure.

[0177] Referring to FIG. 9, the first base station (904) and the second base station (905) may be base stations supporting U2N relay and U2N multi-hop relay, the second terminal (902) and the third terminal (903) may be terminals capable of relay terminal operation in a U2N relay or U2N multi-hop relay, and the first terminal (901) may be a terminal capable of remote terminal operation in a U2N relay or U2N multi-hop relay. Alternatively, the first terminal (901), the second terminal (902), and the third terminal (903) may be a combination of terminals capable of both remote terminal operation and relay terminal operation in a U2N relay or U2N multi-hop relay.

[0178] At step 906, the third terminal (903) is directly connected to the second base station (905) and can exchange UL / DL data.

[0179] At step 907, the first terminal (901) is directly connected to the first base station (904) and can exchange UL / DL data.

[0180] At step 908, the second terminal (902) may be in an RRC IDLE or RRC INACTIVE state.

[0181] In step 909, the base station may transmit a message to the first terminal (901) to check the functions supported by the first terminal (901). The message may be a UE capability enquiry message. The first terminal (901) may receive the UE capability enquiry message and respond with a UE capability information message for the items requested by the base station. For example, the message may include at least one of whether multi-hop U2N relay is supported, whether relay terminal operation in the multi-hop U2N relay is supported, and whether remote terminal operation in the multi-hop U2N relay is supported. In addition, the message may include whether path switching operation from the multi-hop U2N relay to a relay terminal in an RRC IDLE or RRC INACTIVE state is supported.

[0182] In step 910, the first base station (904) can set measurement / reporting settings for U2N relay UEs and NR cells around the first terminal (901) to the first terminal (901). The first base station (904) can set a measurement report to be sent when at least one of the conditions is satisfied, such as a PC5 RSRP (e.g., SL-RSRP or SD-RSRP) of a candidate relay UE of the first terminal (901) exceeds a specific threshold, is less than a specific threshold, or an RSRP with a serving cell or a neighboring cell of the first terminal (901) exceeds a specific threshold, or is less than a specific threshold.

[0183] In step 911, the first terminal (901) can discover surrounding U2N relays by transmitting and receiving discovery messages. The transmission and reception of discovery messages can be performed in parallel, regardless of the base station's measurement / reporting settings.

[0184] At step 912, the first terminal (901) can report the measurement result to the first base station (904). The measurement report can include serving cell information of the serving / candidate Relay UE, Layer-2 ID (L2ID) of the serving / candidate Relay UE, PC5 RSRP of the serving / candidate Relay UE, which can be obtained from the discovery message transmitted by the serving / candidate Relay UE, and can include at least one piece of serving / candidate Relay UE information. In addition, the measurement report can include a physical cell ID (PCI) of the NR cell, Uu RSRP of the NR cell, and can include at least one piece of NR cell information.

[0185] At step 913, the first base station (904) may determine an appropriate Relay UE among the candidate Relay UEs as a path switch target (e.g., the second terminal (902)) by referring to the measurement report transmitted by the first terminal (901). At this time, the second terminal (902) may be in an RRC IDLE or RRC INACTIVE state. If the first terminal (901) does not support the path switching operation in the above-described RRC IDLE or RRC INACTIVE state, the first base station (904) may not select the second terminal (902) as the target Relay UE.

[0186] At step 914, the second terminal (902) can select the third terminal (903) as the serving relay terminal through a relay reselection procedure.

[0187] At step 915, the second terminal (902) can select the second base station (905) as the serving base station through a cell reselection procedure.

[0188] At step 916, the first base station (904) may transmit to the first terminal (901) a path switch configuration including settings for transmitting and receiving data on an indirect path for the path switch of the first terminal (901). This configuration may include at least one of the L2ID of the target Relay UE, Sidelink Relay Adaptation Protocol (SRAP) settings, and PC5 relay RLC channel settings.

[0189] At step 917, the first terminal (901) can establish a PC5 unicast link with the second terminal (902) if a PC5 unicast link connection with the second terminal (902) is required.

[0190] At step 918, the first terminal (901) can transmit a message notifying path switch completion through an indirect pass through the second terminal (902).

[0191] At step 919, since the second terminal (902) is not in an RRC CONNECTED state with the second base station (905), it can establish an RRC connection with the second base station (905) to receive relay UE settings and transmission / reception resources for the first terminal (901) from the base station.

[0192] Referring to steps 914 and 915, when the second terminal (902) selects the third terminal (903) as the serving relay through relay reselection, the message transmitted by the second terminal (902) can be transmitted to the second base station (905) through an indirect path through the serving relay, and when the second terminal (902) selects the second base station (905) as the serving base station through cell reselection, the message transmitted by the second terminal (902) can be transmitted to the second base station (905) through a direct path.

[0193] At step 920, the second terminal (902) may transmit a message (e.g., a sidelinkUEInformationNR message) requesting information and resources of the Remote UE to the second base station (905). This message may include at least one of the Remote UE's L2ID and a local ID request used for SRAP.

[0194] At step 921, the second base station (905) may transmit to the second terminal (902) the settings for the Relay UE operation of the second terminal (902). These settings may include at least one of the Remote UE's L2ID, SRAP settings, Uu relay RLC channel settings, and PC5 relay RLC channel settings.

[0195] At step 922, the second terminal (902) can transmit a message notifying the path switch completion transmitted by the first terminal (901) to the second base station (905).

[0196] At step 923, even if the second base station (905) receives the path switch completion transmitted by the first terminal (901), it does not recognize that it is the first terminal (901). The context of the first terminal (901) is held by the first base station (904), and since it did not expect the first terminal (901) to perform a path switch completion, an error may occur.

[0197] In this drawing, for convenience of explanation, the second terminal (902) and the third terminal (903) are depicted as being connected to the second base station (905). However, the second terminal (902) and the third terminal (903) may be connected to different base stations or cells. In addition, the first base station (904) and the second base station (905) may be the same base station.

[0198]

[0199] FIG. 10 is a flowchart illustrating an operation in which a target relay terminal reselects a cell or relay terminal during a path switch of a multi-hop terminal network relay according to an embodiment of the present disclosure.

[0200] Referring to FIG. 10, the first base station (1004) and the second base station (1005) may be base stations supporting U2N relay and U2N multi-hop relay, the second terminal (1002) and the third terminal (1003) may be terminals capable of relay terminal operation in a U2N relay or U2N multi-hop relay, and the first terminal (1001) may be a terminal capable of remote terminal operation in a U2N relay or U2N multi-hop relay. Alternatively, the first terminal (1001), the second terminal (1002), and the third terminal (1003) may be a combination of terminals capable of both remote terminal operation and relay terminal operation in a U2N relay or U2N multi-hop relay.

[0201] At step 1006, the third terminal (1003) can be directly connected to the second base station (1005) to exchange UL / DL data.

[0202] At step 1007, the first terminal (1001) is directly connected to the first base station (1004) and can exchange UL / DL data.

[0203] At step 1008, the second terminal (1002) may be in an RRC IDLE or RRC INACTIVE state.

[0204] In step 1009, the first base station (1004) may transmit a message to the first terminal (1001) to check the functions supported by the first terminal (1001). The message may be a UE capability enquiry message. The first terminal (1001) may receive the UE capability enquiry message and respond with a UE capability information message for the items requested by the base station. For example, at least one of whether multi-hop U2N relay is supported, whether relay terminal operation in the multi-hop U2N relay is supported, and whether remote terminal operation in the multi-hop U2N relay is supported may be included. In addition, whether path switching operation from the multi-hop U2N relay to a relay terminal in an RRC IDLE or RRC INACTIVE state is supported may be included.

[0205] In step 1010, the first base station (1004) can set measurement / reporting settings for U2N relay UEs and NR cells around the first terminal (1001) to the first terminal (1001). The first base station (1004) can set a measurement report to be sent when at least one of the conditions is satisfied, such as a PC5 RSRP (e.g., SL-RSRP or SD-RSRP) of a candidate relay UE of the first terminal (1001) exceeds a specific threshold, is less than a specific threshold, or an RSRP with a serving cell or a neighboring cell of the first terminal (1001) exceeds a specific threshold, or is less than a specific threshold.

[0206] In step 1011, the first terminal (1001) can discover surrounding U2N relays by transmitting and receiving discovery messages. The transmission and reception of discovery messages can be performed in parallel, regardless of the base station's measurement / reporting settings.

[0207] In step 1012, the first terminal (1001) may report the measurement result to the first base station (1004). The measurement report may include serving cell information of the serving / candidate Relay UE, Layer-2 ID (L2ID) of the serving / candidate Relay UE, and PC5 RSRP of the serving / candidate Relay UE, which may be obtained from a discovery message transmitted by the serving / candidate Relay UE, and may include at least one piece of serving / candidate Relay UE information. In addition, the measurement report may include a physical cell ID (PCI) of the NR cell, a Uu RSRP of the NR cell, and may include at least one piece of NR cell information.

[0208] At step 1013, the first base station (1004) may determine an appropriate Relay UE as a path switch target among the candidate Relay UEs by referring to the measurement report transmitted by the first terminal (1001) as a target Relay UE (e.g., the second terminal (1002)). At this time, the second terminal (1002) may be in an RRC IDLE or RRC INACTIVE state. If the first terminal (1001) does not support the path switching operation in the above-described RRC IDLE or RRC INACTIVE state, the first base station (1004) may not select the second terminal (1002) as the target Relay UE.

[0209] At step 1014, the second terminal (1002) can select the third terminal (1003) as the serving relay terminal through a relay reselection procedure.

[0210] At step 1015, the second terminal (1002) can select the second base station (1005) as a serving base station through a cell reselection procedure.

[0211] At step 1016, the first base station (1004) may transmit to the first terminal (1001) a path switch configuration including settings for transmitting and receiving data on an indirect path for the path switch of the first terminal (1001). This setting may include at least one of the L2ID of the target relay UE, Sidelink Relay Adaptation Protocol (SRAP) settings, and PC5 relay RLC channel settings.

[0212] At step 1017, the second terminal (1002) may update the serving cell information included in the discovery message with the serving cell information of the newly reselected serving cell or serving relay. The serving cell information included in the discovery message may be as follows.

[0213]

[0214]

[0215]

[0216]

[0217]

[0218] When the second terminal (1002) operates as a remote terminal of another relay terminal, the PCell / camping cell information included in the SL-AccessInfo-L2U2N may be information on the PCell / camping cell of the serving relay terminal of the second terminal (1002).

[0219] At step 1017, the first terminal (1001) can detect a change in the contents of SL-AccessInfo-L2U2N through the discovery process and can detect cell or relay reselection of the relay UE.

[0220] In steps 1018 and 1019, if the first terminal (1001) detects cell or relay reselection of the target relay UE (e.g., the second terminal (1002)), the first terminal (1001) may stop the path switch and proceed with the RRC re-establishment procedure.

[0221] At this time, if the cell or relay terminal (e.g., third terminal (1003)) reselected by the second terminal (1002) is the same serving cell (e.g., if gNB1 and gNB2 are the same cell or base station), the information of the PCell / camping cell included in the SL-AccessInfo-L2U2N may not detect the cell or relay reselection of the target relay UE. For example, the contents of the SL-AccessInfo-L2U2N may not change even if cell or relay reselection occurs.

[0222] The second terminal (1002) may include additional information in the discovery message, including cell / relay reselection information. For example, at least one identifier that can distinguish the serving relay UE (e.g., Layer-2 ID) and an identifier that can distinguish a direct path connection with the base station may be included.

[0223] The first terminal (1001) may include information indicating the ability to detect cell or relay reselection of the target Relay UE in the UE capability information based on this additional information.

[0224] The second terminal (1002) may include information indicating a capability including additional information related thereto in the UE capability information.

[0225]

[0226] FIG. 11 is a flowchart illustrating an operation of a relay terminal transmitting a notification message in a path switch of a multi-hop terminal network relay according to an embodiment of the present disclosure.

[0227] Referring to FIG. 11, the base station (1104) may be a base station (1104) that supports U2N relay and U2N multi-hop relay, the second terminal (1102) and the third terminal (1103) may be terminals capable of relay terminal operation in a U2N relay or U2N multi-hop relay, and the first terminal (1101) may be a terminal capable of remote terminal operation in a U2N relay or U2N multi-hop relay. Alternatively, the first terminal (1101), the second terminal (1102), and the third terminal (1103) may be a combination of terminals capable of both remote terminal operation and relay terminal operation in a U2N relay or U2N multi-hop relay.

[0228] At step 1105, the first terminal (1101) is connected to the base station (1104) through a direct path and can transmit and receive UL / DL data.

[0229] At step 1106, the third terminal (1103) may be in an RRC IDLE or RRC INACTIVE state, and the serving cell may be a base station (1104).

[0230] At step 1107, the second terminal (1102) may be in an RRC IDLE or RRC INACTIVE state, and the serving relay may be a third terminal (1103). The second terminal (1102) may be connected to the third terminal (1103) via a PC5 unicast link.

[0231] In step 1108, the base station (1104) may transmit a message to the first terminal (1101) to check the functions supported by the first terminal (1101). The message may be a UE capability enquiry message. The first terminal (1101) may receive the UE capability enquiry message and respond with a UE capability information message for the items requested by the base station (1104). For example, at least one of whether multi-hop U2N relay is supported, whether relay terminal operation in the multi-hop U2N relay is supported, and whether remote terminal operation in the multi-hop U2N relay is supported may be included. In addition, whether path switching operation from the multi-hop U2N relay to a relay terminal in an RRC IDLE or RRC INACTIVE state is supported may be included.

[0232] In step 1109, the base station (1104) can set measurement / reporting settings for U2N relay UEs and NR cells around the first terminal (1101) to the first terminal (1101). The base station (1104) can set a measurement report to be sent when at least one of the conditions is satisfied, such as a PC5 RSRP (e.g., SL-RSRP or SD-RSRP) of a candidate relay UE of the first terminal (1101) exceeds a specific threshold, is less than a specific threshold, or an RSRP with a serving cell or a neighboring cell of the first terminal (1101) exceeds a specific threshold, or is less than a specific threshold.

[0233] At step 1110, the first terminal (1101) can discover surrounding U2N relays by transmitting and receiving discovery messages. The transmission and reception of discovery messages can be performed in parallel, regardless of the measurement / reporting settings of the base station (1104).

[0234] In step 1111, the first terminal (1101) can report the measurement result to the base station (1104). The measurement report can include serving cell information of the serving / candidate Relay UE, Layer-2 ID (L2ID) of the serving / candidate Relay UE, PC5 RSRP of the serving / candidate Relay UE, which can be obtained from the discovery message transmitted by the serving / candidate Relay UE, and can include at least one or more serving / candidate Relay UE information. In addition, the measurement report can include physical cell ID (PCI) of the NR cell, Uu RSRP of the NR cell, and can include at least one or more NR cell information.

[0235] At step 1112, the base station (1104) may determine an appropriate Relay UE among the candidate Relay UEs as a target Relay UE (e.g., the second terminal (1102)) for path switching by referring to the measurement report transmitted by the first terminal (1101). At this time, the second terminal (1102) may be in an RRC IDLE or RRC INACTIVE state. If the first terminal (1101) does not support the operation of path switching to the above-described RRC IDLE or RRC INACTIVE state, the base station (1104) may not select the second terminal (1102) as the target Relay UE.

[0236] At step 1113, the base station (1104) may transmit to the first terminal (1101) a path switch configuration including settings for transmitting and receiving data on an indirect path for the path switch of the first terminal (1101). This setting may include at least one of the L2ID of the target Relay UE, Sidelink Relay Adaptation Protocol (SRAP) settings, and PC5 relay RLC channel settings.

[0237] At step 1114, the first terminal (1101) can establish a PC5 unicast link with the second terminal (1102) if a PC5 unicast link connection with the second terminal (1102) is required.

[0238] At step 1117, the relay terminal may transmit a notification message to the remote terminal if at least one of the following conditions is satisfied. For example, at least one of the following may be true: when Uu RLF occurs, when reconfigurationWithSync is received, when cell reselection (1115) is performed, and when RRC connection fails.

[0239] The U2N Relay UE may initiate the procedure when one of the following conditions is met:

[0240] 1> upon Uu RLF as specified in 5.3.10;

[0241] 1> upon reception of anRRCReconfigurationincluding thereconfigurationWithSync;

[0242] 1> upon cell reselection;

[0243] 1> upon L2 U2N Relay UE's RRC connection failure including RRC connection reject as specified in 5.3.3.5 and 5.3.13.10, and T300 expiry as specified in 5.3.3.7, and RRC resume failure as specified in 5.3.13.5;

[0244] When a third terminal (1103) performs cell reselection (step 1115), the third terminal (1103) can transmit a notification message to a second terminal (1102) corresponding to the remote terminal of the third terminal (1103) by setting the indicationType to relayUE-CellReselection. The method for setting and transmitting the contents of the notification message in various scenarios may be as follows.

[0245] The U2N Relay UE shall set the indication type as follows:

[0246] 1> if the UE initiates transmission of theNotificationMessageSidelinkmessage due to Uu RLF:

[0247] 2> set theindicationTypeasrelayUE-Uu-RLF;

[0248] 1> else if the UE initiates transmission of theNotificationMessageSidelinkmessage due to reconfiguration with sync:

[0249] 2> set theindicationTypeasrelayUE-HO;

[0250] 1> else if the UE initiates transmission of theNotificationMessageSidelinkmessage due to cell reselection:

[0251] 2> set theindicationTypeasrelayUE-CellReselection;

[0252] 1> if the UE initiates transmission of theNotificationMessageSidelinkmessage due to Uu RRC connection establishment / Resume failure:

[0253] 2> set theindicationTypeasrelayUE-Uu-RRC-Failure;

[0254] 1> submit theNotificationMessageSidelinkmessage to lower layers for transmission.

[0255] When the third terminal (1103) performs relay reselection (step 1116), a notification message transmission due to relay reselection may be added to the conditions described above. For example, a notification message may be transmitted due to the upon relay reselection condition.

[0256] When the third terminal (1103) transmits a notification message by reselecting the relay, it can indicate that the notification message is due to relay reselection under the conditions described above. For example, when transmission of the notification message begins due to relay reselection, the indicationType can be set to relayUE-RelayReselection.

[0257] If the serving cell or serving base station (1104) of the third terminal (1103) does not change as a result of relay selection or cell reselection, the notification message may not be transmitted or the notification message may not include indicationType.

[0258] At step 1117, when the second terminal (1102) receives a notification message transmitted by the third terminal (1103), the second terminal (1102) can release the PC5 unicast link with the third terminal (1103) and can detect that cell re-selection of the Relay UE has occurred based on the indicationType (step 1119).

[0259] Upon receiving theNotificationMessageSidelink, the U2N Remote UE shall:

[0260] 1> if theindicationTypeis included:

[0261] 2> if the UE is L2 U2N Remote UE in RRC_CONNECTED:

[0262] 3> if T301 is not running, initiate the RRC connection re-establishment procedure as specified in 5.3.7;

[0263] 2> else (the UE is L3 U2N Remote UE, or L2 U2N Remote UE in RRC_IDLE or RRC_INACTIVE):

[0264] 3> if the PC5-RRC connection with the U2N Relay UE is determined to be released:

[0265] 4> indicate upper layers to trigger PC5 unicast link release;

[0266] 3> else (ie, maintain the PC5 RRC connection):

[0267] 4> if the UE is L2 U2N Remote UE and theindicationTypeisrelayUE-HO or relayUE-CellReselection:

[0268] 5> consider cell re-selection occurs;

[0269] NOTE 1: For L3 U2N Remote UE, or L2 U2N Remote UE in RRC_IDLE or RRC_INACTIVE, it is up to Remote UE implementation whether to release or keep the PC5 unicast link.

[0270] NOTE 2: The L2 U2N Remote UE may ignore theNotificationMessageSidelinkif it does not release the PC5 unicast link in source side yet during an indirect-to-direct path switch, i.e. T304 is running.

[0271] In step 1118, the third terminal (1103) may include information about the serving cell or serving relay changed by cell reselection or relay reselection in the discovery message. The second terminal (1102) may detect cell reselection or relay reselection of the third terminal (1103) through the discovery message (step 1119). The contents of the discovery message of the third terminal (1103) and the detection of cell reselection or relay reselection of the second terminal (1102) may follow the example of FIG. 10. In addition, information that cell reselection or relay reselection was performed but the serving cell or serving base station (1104) did not change may be included. If the serving cell or serving base station (1104) does not change as a result of cell reselection or relay reselection, the second terminal (1102) may not transmit an additional notification message or may not perform RRC re-establishment. Additionally, information on the changed serving cell or serving base station (1104) after cell reselection or relay reselection may be included.

[0272] The second terminal (1102) may have a PC5 unicast link connection with the first terminal (1101). If the second terminal (1102) detects cell reselection or relay reselection, reception of Uu RLF, reconfigurationWithSync, or RRC connection failure of a serving relay terminal (e.g., the third terminal (1103)) through a notification message or discovery message, the second terminal (1102) may transmit a notification message to the first terminal (1101) to inform the first terminal (1101) of the corresponding information at step 1120. At this time, since the reception of the notification message by the second terminal (1102) does not correspond to the above-described notification message transmission condition, a transmission condition of the notification message may be added. For example, upon reception of a notification message, or through the contents of a notification message or relay discovery message transmitted by a serving relay terminal (e.g., a third terminal (1103)), at least one of cell reselection, relay reselection, Uu RLF, sidelink RLF, PC5 unicast link connection failure, RRC connection failure, and reconfigurationWithSync reception of the third terminal (1103) may be received. The notification message transmitted by the second terminal (1102) may include information about the third terminal (1103). For example, it may include information that the Uu RLF occurred in the serving relay of the second terminal (1102) other than the second terminal (1102) or in the upper relay of the second terminal (1102), and may include the L2ID of the serving relay or the upper relay, etc.

[0273] The first terminal (1101) can detect (step 1122) that a situation affecting the pass switch has occurred due to the conditions for transmitting a notification message, such as cell reselection or relay reselection of the second terminal (1102), the third terminal (1103), or the upper relay terminal, through the notification message transmitted by the second terminal (1102) or the contents of the discovery message transmitted by the second terminal (1102) (step 1121).

[0274] At step 1123, if the first terminal (1101) cannot complete the pass switch, it can start the RRC re-establishment procedure to continue the service through the cell or relay.

[0275]

[0276] FIG. 12 is a flowchart illustrating an operation for completing a path change in a path switch of a multi-hop terminal network relay according to an embodiment of the present disclosure.

[0277] Referring to FIG. 12, the base station (1204) may be a base station (1204) that supports U2N relay and U2N multi-hop relay, the second terminal (1202) and the third terminal (1203) may be terminals capable of relay terminal operation in a U2N relay or U2N multi-hop relay, and the first terminal (1201) may be a terminal capable of remote terminal operation in a U2N relay or U2N multi-hop relay. Alternatively, the first terminal (1201), the second terminal (1202), and the third terminal (1203) may be a combination of terminals capable of both remote terminal operation and relay terminal operation in a U2N relay or U2N multi-hop relay.

[0278] At step 1205, the first terminal (1201) is connected to the base station (1204) through a direct path and can transmit and receive UL / DL data.

[0279] At step 1206, the third terminal (1203) may be in an RRC IDLE or RRC INACTIVE state, and the serving cell may be a base station (1204).

[0280] At step 1207, the second terminal (1202) may be in an RRC IDLE or RRC INACTIVE state, and the serving relay may be a third terminal (1203). The second terminal (1202) may be connected to the third terminal (1203) via a PC5 unicast link.

[0281] In step 1208, the base station (1204) may transmit a message to the first terminal (1201) to check the functions supported by the first terminal (1201). The message may be a UE capability enquiry message. The first terminal (1201) may receive the UE capability enquiry message and respond with a UE capability information message for the items requested by the base station (1204). For example, the message may include at least one of whether multi-hop U2N relay is supported, whether relay terminal operation in the multi-hop U2N relay is supported, and whether remote terminal operation in the multi-hop U2N relay is supported. In addition, the message may include whether path switching operation from the multi-hop U2N relay to a relay terminal in an RRC IDLE or RRC INACTIVE state is supported. In addition, when cell reselection or relay reselection (e.g., procedure of FIG. 10) of a target Relay UE (e.g., second terminal (1202)) is detected during a path switch of a first terminal (1201), or a change of a target Relay UE or an upper Relay UE is detected based on a notification message (e.g., procedure of FIG. 11) of a target Relay UE (e.g., second terminal (1202)), the support for an operation that can complete a path switch procedure without performing RRC re-establishment according to an instruction of a base station (1204) may be included.

[0282] In step 1209, the base station (1204) can set measurement / reporting settings for U2N relay UEs and NR cells around the first terminal (1201) to the first terminal (1201). The base station (1204) can set a measurement report to be sent when at least one of the conditions is satisfied, such as a PC5 RSRP (e.g., SL-RSRP or SD-RSRP) of a candidate relay UE of the first terminal (1201) exceeds a specific threshold, is less than a specific threshold, or an RSRP with a serving cell or a neighboring cell of the first terminal (1201) exceeds a specific threshold, or is less than a specific threshold.

[0283] At step 1210, the first terminal (1201) can discover surrounding U2N relays by transmitting and receiving discovery messages. The transmission and reception of discovery messages can be performed in parallel, regardless of the measurement / reporting settings of the base station (1204).

[0284] In step 1211, the first terminal (1201) can report the measurement result to the base station (1204). The measurement report can include serving cell information of the serving / candidate Relay UE, Layer-2 ID (L2ID) of the serving / candidate Relay UE, PC5 RSRP of the serving / candidate Relay UE, which can be obtained from the discovery message transmitted by the serving / candidate Relay UE, and can include at least one piece of serving / candidate Relay UE information. In addition, the measurement report can include physical cell ID (PCI) of the NR cell, Uu RSRP of the NR cell, and can include at least one piece of NR cell information.

[0285] At step 1212, the base station (1204) may determine an appropriate Relay UE among the candidate Relay UEs for path switching as a target Relay UE (e.g., the second terminal (1202)) by referring to the measurement report transmitted by the first terminal (1201). At this time, the second terminal (1202) may be in an RRC IDLE or RRC INACTIVE state. If the first terminal (1201) does not support the operation of path switching to the above-described RRC IDLE or RRC INACTIVE state, the base station (1204) may not select the second terminal (1202) as the target Relay UE.

[0286] At step 1213, the base station (1204) may transmit a path switch configuration including a setting for transmitting and receiving data on an indirect path for the path switch of the first terminal (1201) to the first terminal (1201). This setting may include at least one of an L2ID of the target Relay UE, a Sidelink Relay Adaptation Protocol (SRAP) setting, and a PC5 relay RLC channel setting. The base station (1204) may instruct to complete the path switch procedure without performing an RRC re-establishment if it detects cell reselection or relay reselection (e.g., the procedure of FIG. 10) of the target Relay UE (e.g., the second terminal (1202)) while the path switch of the first terminal (1201) is in progress, or if it detects a change of the target Relay UE or an upper Relay UE based on a notification message (e.g., the procedure of FIG. 11) of the target Relay UE (e.g., the second terminal (1202)).

[0287] At step 1214, the first terminal (1201) can establish a PC5 unicast link with the second terminal (1202) if a PC5 unicast link connection with the second terminal (1202) is required.

[0288] At step 1215, the second terminal (1202) or the third terminal (1203) can perform cell reselection or relay reselection.

[0289] At step 1216, the first terminal (1201) can detect cell reselection, relay reselection, Uu RLF, SL RLF, reconfigurationWithSync reception, RRC connection failure, notification message reception, etc. of a target Relay UE (e.g., the second terminal (1202)) or an upper Relay UE (e.g., the third terminal (1203)) based on the procedure of FIG. 10 or FIG. 11.

[0290] At step 1217, if the base station (1204) instructs to complete the path switch procedure without performing RRC re-establishment, the first terminal (1201) may complete the path switch procedure by transmitting a path switch completion message to the target Relay UE (e.g., the second terminal (1202)) without performing RRC re-establishment. This instruction may be applied differently for each condition (e.g., cell reselection of the target Relay UE or upper Relay UE, relay reselection, Uu RLF, SL RLF, reconfigurationWithSync reception, RRC connection failure, notification message reception), and in case of cell reselection or relay reselection, the path switch procedure may be completed only when it is the same serving cell or the same base station (1204).

[0291] At step 1218, since the second terminal (1202) is not in an RRC CONNECTED state with the base station (1204), it can establish an RRC connection with the base station (1204) to receive relay UE settings and transmission / reception resources for the first terminal (1201) from the base station (1204).

[0292] At step 1219, the second terminal (1202) may transmit a message (e.g., a sidelinkUEInformationNR message) requesting information and resources of the Remote UE to the base station (1204). This message may include at least one of the Remote UE's L2ID and a local ID request used for SRAP.

[0293] At step 1220, the base station (1204) may transmit settings for the Relay UE operation of the second terminal (1202) to the second terminal (1202). These settings may include at least one of the Remote UE's L2ID, SRAP settings, Uu relay RLC channel settings, and PC5 relay RLC channel settings.

[0294] At step 1221, the second terminal (1202) can transmit a message notifying the path switch completion transmitted by the first terminal (1201) to the base station (1204).

[0295] At step 1222, the first terminal (1201) can transmit UL / DL data by connecting to the base station (1204) and the second terminal (1202) through an indirect path.

[0296]

[0297] FIG. 13 is a diagram illustrating terminal measurement and measurement report operations in a multi-hop terminal network relay according to an embodiment of the present disclosure.

[0298] In a multi-hop terminal network relay, a multi-hop relay terminal (1302, 1303) may include at least one of the following in the content of a discovery message to inform surrounding terminals (e.g., a remote terminal (1301)) of information that changes in various situations, including the example of FIG. 10.

[0299] - Hop count of relay terminal (can indicate the number of other relay terminals included in the situation where it is directly connected to the base station and in the indirect path)

[0300] - Direct path availability of relay terminals (can indicate a situation where the relay terminal is directly connected to the base station or is camping directly at the base station)

[0301] - Upper relay terminal information of the relay terminal (at least one of the L2ID of the upper relay terminal, RRC status information, and serving cell information of the upper relay terminal (e.g., SL-AccessInfo-L2U2N) may be included, and if there are multiple upper relay terminals, information on at least one relay terminal may be included.)

[0302] - Serving cell information (serving cell information obtained directly from the base station's SIB or information obtained from an upper relay terminal)

[0303] - RRC status of relay terminal (can indicate at least one of RRC CONNECTED, RRC IDLE, RRC INACTIVE, and RRC IDLE and RRC INACTIVE can be indicated with a single value)

[0304] At step 1305, if the relay terminal (1302, 1303) can include at least one of these pieces of information in the discovery message, the relay terminal can indicate whether to support the corresponding operation when transmitting UE capability information to the base station (1304). In addition, the relay terminal (1302, 1303) can indicate whether to support the multi-hop terminal network relay terminal operation, and this indicator can also indicate whether to support the operation of adding information to the discovery message.

[0305] In step 1306, if the remote terminal (1301) can receive a discovery message including information for a multi-hop relay operation, it can indicate whether to support the operation when transmitting UE capability information to the base station (1304). In addition, depending on the content of the discovery message, the relay terminal (1302, 1303) that transmitted the discovery message including specific content can be determined as a measurement target or a report target, or it can indicate whether to support an operation that can include only specific information in a measurement report message that is transmitted to the base station (1304) according to the instruction of the base station. The remote terminal (1301) can indicate whether to support a multi-hop terminal network remote terminal operation, and this indicator can also indicate whether to receive information related to a multi-hop terminal network relay that can be added to the discovery message.

[0306] At step 1307, the base station (1304) can set measurement / report settings for U2N relay terminals (1302, 1303) and NR cells around the remote terminal (1301) to the remote terminal (1301) based on the capability information of the remote terminal (1301).

[0307] The base station (1304) can be configured to send a measurement report when at least one of the conditions is satisfied, including that the PC5 RSRP (e.g., SL-RSRP or SD-RSRP) of a candidate relay UE (1302, 1303) measured by a remote terminal (1301) exceeds a specific threshold, is less than a specific threshold, or that the RSRP with the serving cell or neighboring cell of the first terminal exceeds a specific threshold, or is less than a specific threshold.

[0308] At step 1308, the base station (1304) may determine whether to include the candidate Relay UE in the measurement or measurement report based on the content of the discovery message transmitted by the candidate Relay UE measured by the remote terminal (1301), or may instruct the remote terminal (1301) to include additional specific information. For example, the base station (1304) may set at least one of the following conditions to the remote terminal (1301). Alternatively, the operation of the remote terminal (1301) may be implemented without the configuration of the base station (1304).

[0309] - When the candidate relay UE is directly connected to the base station

[0310] - If the indirect path of the candidate relay UE is less than a certain number of hops.

[0311] - When the serving cell or base station of the candidate relay UE is the same as the serving cell or base station of the remote terminal.

[0312] - When the serving cell or base station of the candidate relay UE is different from the serving cell or base station of the remote terminal.

[0313] - When the RRC connection status of the candidate relay UE is RRC CONNECTED

[0314] The base station (1304) may combine at least two of the above conditions in the measurement report conditions of the remote terminal (1301). For example, a candidate relay UE that satisfies both or at least one of the following conditions: the condition that the serving cell or base station of the candidate relay UE is different from the serving cell or base station of the remote terminal (1301) or the condition that the candidate relay UE is directly connected to the base station, may be a measurement target or included in a measurement report.

[0315] In step 1309, the remote terminal (1301) may include information corresponding to conditions designated for reporting or measurement by the base station (1304) in the measurement report. For example, if the indirect path of the candidate relay UE is less than a certain number of hops, the hop count of the relay UE included in the measurement report may be additionally included.

[0316] In step 1309, the remote terminal (1301) may also include information corresponding to unset conditions in the measurement report. For example, at least one piece of information included in a discovery message transmitted by a candidate relay terminal (1302, 1303) may be included in the measurement report.

[0317]

[0318] FIG. 14 is a flowchart of an operation in which a source base station selects a target relay terminal that is a path switch target of a remote terminal in a multi-hop terminal network relay according to an embodiment of the present disclosure.

[0319] When the path of the Remote UE is changed, the source gNB can select the target Relay UE if it is an intra-gNB, and if it is an inter-gNB, the source gNB can select the target gNB and transmit a list of candidate Relay UEs to the target gNB so that the target gNB can select the target Relay UE.

[0320] The source gNB can obtain the following information from the measurement report, for example, as shown in Fig. 13. (Step 1401)

[0321] - RRC state of candidate relay UE

[0322] - Uu direct path availability of candidate relay UE

[0323] - hop count of candidate relay UE

[0324] - RRC state and information of candidate Relay UEs and upper Relay UEs (e.g., L2ID, serving cell information, etc.)

[0325] The source base station can determine a path switch through the received information (step 1402), and if an intra-gNB path switch is possible (step 1403), it can use at least one of the following conditions to select a target Relay UE among candidate Relay UEs (step 1407).

[0326] - Only candidate relay UEs in RRC CONNECTED state are selected as target relay UEs (step 1404).

[0327] - If a candidate relay UE in RRC CONNECTED state and RRC IDLE or RRC INACTIVE can be selected, only the candidate relay UE in RRC CONNECTED state is selected as the target relay UE (step 1404).

[0328] - If only a candidate relay UE that is RRC IDLE or RRC INACTIVE can be selected as the target relay UE, the target relay UE is selected regardless of the RRC state (step 1404).

[0329] - Among the candidate relay UEs that are RRC CONNECTED, only the candidate relay UEs that can connect to the Uu direct path are selected as the target relay UE (step 1405).

[0330] - Among the candidate relay UEs that are RRC IDLE or RRC INACTIVE, only the candidate relay UEs that can connect to the Uu direct path are selected as the target relay UE (step 1405).

[0331] - When a candidate relay UE that is RRC IDLE or RRC INACTIVE can be selected among a terminal capable of Uu direct path connection and a terminal that is not capable of Uu direct path connection, only the candidate relay UE capable of Uu direct path connection is selected as the target relay UE (step 1405).

[0332] - If only a candidate Relay UE that is RRC IDLE or RRC INACTIVE can be selected as the target Relay UE, the target Relay UE is selected regardless of the Uu direct path connection (step 1405).

[0333] - If at least one of the upper relay UEs of the candidate relay UE that is RRC IDLE or RRC INACTIVE is RRC CONNECTED, the candidate relay UE is selected as the target relay UE by considering the case (for example, the number of terminals that are RRC CONNECTED in the indirect path is considered) (step 1406).

[0334] The source base station can select a target Relay UE and initiate an intra-gNB path switch procedure (step 1408).

[0335] The source base station may use at least one of the following conditions to select a target gNB for an inter-gNB path switch (step 1412) when an intra-gNB path switch is not possible (step 1403).

[0336] - Select the serving base station of the candidate relay UE in RRC CONNECTED state as the target gNB (step 1409)

[0337] - If a candidate relay UE in RRC CONNECTED state and RRC IDLE or RRC INACTIVE can be selected, the serving base station of the candidate relay UE in RRC CONNECTED state is selected as the target gNB (step 1409).

[0338] - If only the candidate relay UE in RRC IDLE or RRC INACTIVE state can be identified, the serving base station of the candidate relay UE is selected as the target gNB regardless of the RRC state (step 1409).

[0339] - Among the RRC CONNECTED candidate relay UEs, the serving base station of the candidate relay UE capable of Uu direct path connection is selected as the target gNB (step 1410).

[0340] - Select the serving base station of the candidate relay UE that can connect to the Uu direct path among the candidate relay UEs that are RRC IDLE or RRC INACTIVE as the target gNB (step 1410).

[0341] - When a terminal capable of Uu direct path connection and a terminal capable of Uu direct path connection can be selected among candidate relay UEs that are RRC IDLE or RRC INACTIVE, the serving base station of the candidate relay UE capable of Uu direct path connection is selected as the target gNB (step 1410).

[0342] - If only the candidate relay UE in RRC IDLE or RRC INACTIVE state can be identified, the serving base station of the candidate relay UE is selected as the target gNB regardless of the Uu direct path connection (step 1410).

[0343] - If at least one of the upper relay UEs of the candidate relay UE that is RRC IDLE or RRC INACTIVE is RRC CONNECTED, the serving base station of the candidate relay UE is selected as the target gNB by considering the case (for example, considering the number of terminals that are RRC CONNECTED in the indirect path) (step 1411).

[0344] The source gNB may transmit candidate relay UEs that satisfy at least one of the above conditions to the target gNB. Information about one or more candidate relay UEs may be included, and the information may be at least one of the pieces of information included in the measurement report reported by the remote terminal for each candidate relay UE. (Step 1413)

[0345] The path switch decision of the source gNB (step 1402) can be completed after the target Relay UE or target gNB is determined. For example, if there is no suitable target Relay UE among the candidate Relay UEs or no suitable target gNB among the serving gNBs of the candidate Relay UEs, the path switch may not be performed.

[0346]

[0347] FIG. 15 is a flowchart of an operation in which a target base station selects a target relay terminal that is a target of a path switch of a remote terminal in a multi-hop terminal network relay according to an embodiment of the present disclosure.

[0348] During an inter-gNB path switch, the target gNB can receive at least one candidate relay UE from the source gNB in ​​a handover request message (step 1501). The target gNB can perform admission control (step 1502) based on the lack of resources for service after the path switch of the remote UE, the expected number of terminals, resource usage rate, etc., and, based on the result, can send a message to the source gNB rejecting the path switch of the remote UE (step 1508).

[0349] If the admission control of the remote UE is passed, the target gNB may use at least one of the following conditions to select the target relay UE among the candidate relay UEs (step 1507).

[0350] - Only candidate relay UEs in RRC CONNECTED state are selected as target relay UEs (step 1503).

[0351] - When a candidate relay UE in RRC CONNECTED state and RRC IDLE or RRC INACTIVE can be selected, only the candidate relay UE in RRC CONNECTED state is selected as the target relay UE (step 1503).

[0352] - If only a candidate relay UE that is RRC IDLE or RRC INACTIVE can be selected as the target relay UE, the target relay UE is selected regardless of the RRC state (step 1503).

[0353] - Among the candidate relay UEs that are RRC CONNECTED, only the candidate relay UEs that can connect to the Uu direct path are selected as the target relay UE (step 1504).

[0354] - Among the candidate relay UEs that are RRC IDLE or RRC INACTIVE, only the candidate relay UEs that can connect to the Uu direct path are selected as the target relay UE (step 1504).

[0355] - When a candidate relay UE that is RRC IDLE or RRC INACTIVE can be selected among a terminal capable of Uu direct path connection and a terminal that is not capable of Uu direct path connection, only the candidate relay UE capable of Uu direct path connection is selected as the target relay UE (step 1504).

[0356] - If only a candidate Relay UE that is RRC IDLE or RRC INACTIVE can be selected as the target Relay UE, the target Relay UE is selected regardless of the Uu direct path connection (step 1504).

[0357] - If at least one of the upper relay UEs of a candidate relay UE that is RRC IDLE or RRC INACTIVE is RRC CONNECTED, the candidate relay UE is selected as the target relay UE by considering the case (for example, the number of terminals that are RRC CONNECTED in the indirect path is considered) (step 1505).

[0358] A target Relay UE can be selected among candidate Relay UEs (step 1506).

[0359] If the target gNB cannot select the target Relay UE among the candidate Relay UEs (step 1507), the target gNB can send a message rejecting the path switch of the remote UE to the source gNB (step 1508).

[0360] If the target gNB selects the target Relay UE, the target gNB can transmit a handover request acknowledgement message (step 1509) to the source gNB, including AS settings to be used by the target gNB to perform path switching of the remote UE.

[0361]

[0362] FIG. 16 is a diagram illustrating the structure of a base station according to an embodiment of the present disclosure.

[0363] Referring to FIG. 16, the base station may include a transceiver (1605), a control unit (1610), and a storage unit (1615). The transceiver (1605), the control unit (1610), and the storage unit (1615) may operate according to the communication method of the base station described above. The network device may also correspond to the structure of the base station. However, the components of the base station are not limited to the examples described above. For example, the base station may include more or fewer components than the components described above. For example, the base station may include a transceiver (1605) and a control unit (1610). In addition, the transceiver (1605), the control unit (1610), and the storage unit (1615) may be implemented in the form of a single chip.

[0364] The transceiver (1605) is a general term for the receiving unit and the transmitting unit of the base station, and can transmit and receive signals with terminals, other base stations, or other network devices. At this time, the transmitted and received signals may include control information and data. The transceiver (1605) may transmit system information to the terminal, for example, and may transmit a synchronization signal or a reference signal. To this end, the transceiver (1605) may be configured with an RF transmitter that up-converts and amplifies the frequency of a transmitted signal, and an RF receiver that low-noise amplifies and down-converts the frequency of a received signal. However, this is only one embodiment of the transceiver (1605), and the components of the transceiver (1605) are not limited to the RF transmitter and RF receiver. The transceiver (1605) may include wired and wireless transceivers, and may include various configurations for transmitting and receiving signals. In addition, the transceiver (1605) can receive a signal through a communication channel (e.g., a wireless channel) and output it to the control unit (1610), and transmit the signal output from the control unit (1610) through the communication channel. In addition, the transceiver (1605) can receive a communication signal and output it to the processor, and transmit the signal output from the processor to a terminal, another base station, or another entity through a wired or wireless network.

[0365] The storage unit (1615) can store programs and data required for the operation of the base station. In addition, the storage unit (1615) can store control information or data included in signals acquired from the base station. The storage unit (1615) can be configured as a storage medium or a combination of storage media, such as a ROM, a RAM, a hard disk, a CD-ROM, and a DVD. In addition, the storage unit (1615) can store at least one of information transmitted and received through the transceiver unit (1605) and information generated through the control unit (1610).

[0366] In the present disclosure, the control unit (1610) may be defined as a circuit or application-specific integrated circuit, or at least one processor. The processor may include a communication processor (CP) that performs control for communication and an application processor (AP) that controls upper layers such as application programs. The control unit (1610) may control the overall operation of the base station according to the embodiment proposed in the present disclosure. For example, the control unit (1610) may control the signal flow between each block to perform operations according to the flowchart described above.

[0367]

[0368] FIG. 17 is a diagram illustrating the structure of a terminal according to an embodiment of the present disclosure.

[0369] Referring to FIG. 17, the terminal may include a transceiver (1705), a control unit (1710), and a storage unit (1715). The transceiver (1705), the control unit (1710), and the storage unit (1715) may operate according to the communication method of the terminal described above. However, the components of the terminal are not limited to the examples described above. For example, the terminal may include more or fewer components than the components described above. For example, the terminal may include a transceiver (1705) and a control unit (1710). In addition, the transceiver (1705), the control unit (1710), and the storage unit (1715) may be implemented in the form of a single chip.

[0370] The transceiver (1705) is a general term for the receiving unit and the transmitting unit of the terminal, and can transmit and receive signals with a base station, another terminal, or a network entity. The signals transmitted and received with the base station may include control information and data. The transceiver (1705) may, for example, receive system information from the base station and receive a synchronization signal or a reference signal. To this end, the transceiver (1705) may be configured with an RF transmitter that up-converts and amplifies the frequency of a transmitted signal, and an RF receiver that low-noise amplifies and frequency-downconverts the received signal. However, this is only one embodiment of the transceiver (1705), and the components of the transceiver (1705) are not limited to the RF transmitter and RF receiver. In addition, the transceiver (1705) may include wired and wireless transceivers, and may include various configurations for transmitting and receiving signals. In addition, the transceiver (1705) can receive a signal through a wireless channel and output it to the control unit (1710), and transmit the signal output from the control unit (1710) through the wireless channel. In addition, the transceiver (1705) can receive a communication signal and output it to the processor, and transmit the signal output from the processor to a network entity through a wired or wireless network.

[0371] The storage unit (1715) can store programs and data necessary for the operation of the terminal. In addition, the memory (1715) can store control information or data included in signals acquired from the terminal. The storage unit (1715) can be configured as a storage medium or a combination of storage media, such as a ROM, a RAM, a hard disk, a CD-ROM, and a DVD.

[0372] In the present disclosure, the control unit (1710) may be defined as a circuit or application-specific integrated circuit, or at least one processor. The processor may include a communication processor (CP) that performs control for communication and an application processor (AP) that controls upper layers such as application programs. The control unit (1710) may control the overall operation of the terminal according to the embodiment proposed in the present disclosure. For example, the control unit (1710) may control the signal flow between each block to perform operations according to the flowchart described above.

Claims

1. In a method performed in a first terminal in a wireless communication system, Step of establishing a second terminal and sidelink PC5 unicast link; A step of detecting reselection of a relay terminal; and Including a step of transmitting a message related to the reselection to the second terminal, A method, characterized in that the message includes a cause for transmitting the message.

2. In the first paragraph, the step of detecting reselection of the relay terminal comprises: A method characterized in that the step of detecting the reselection is based on receiving a message related to the reselection from another relay terminal.

3. In the first paragraph, the step of detecting reselection of the relay terminal comprises: A method characterized in that the step of detecting the reselection is based on receiving a discovery message.

4. In paragraph 1, A method characterized in that the cause of transmitting the above message is one of relay terminal reselection, sidelink RLF (Radio Link Failure), and sidelink PC5 failure.

5. In a method performed in a second terminal in a wireless communication system, A step of establishing a first terminal and a sidelink PC5 unicast link; and When the first terminal detects reselection of a relay terminal, a step of receiving a message related to the reselection from the first terminal is included. A method, characterized in that the message includes a cause for transmitting the message.

6. In the fifth paragraph, the step of detecting reselection of the relay terminal comprises: A method characterized in that the first terminal detects the reselection based on receiving a message related to the reselection from another relay terminal.

7. In the fifth paragraph, the step of detecting reselection of the relay terminal comprises: A method characterized in that the first terminal detects the reselection based on receiving a discovery message.

8. In paragraph 5, A method characterized in that the cause of transmitting the above message is one of relay terminal reselection, sidelink RLF (Radio Link Failure), and sidelink PC5 failure.

9. In a wireless communication system, in the first terminal, A transceiver capable of transmitting and receiving at least one signal; and Including a control unit coupled with the above transmitter and receiver, The above control unit: Establish a second terminal and sidelink PC5 unicast link, Detecting reselection of relay terminals, and configured to transmit a message related to the reselection to the second terminal; A first terminal, characterized in that the message includes a cause for transmitting the message.

10. In paragraph 9, the control unit: A first terminal, characterized in that the step of detecting the reselection is based on receiving a message related to the reselection from another relay terminal.

11. In paragraph 9, the control unit: A first terminal, characterized in that the step of detecting the reselection is based on receiving a discovery message.

12. In paragraph 9, A first terminal, characterized in that the cause of transmitting the above message is one of relay terminal reselection, sidelink RLF (Radio Link Failure), and sidelink PC5 failure.

13. In a second terminal in a wireless communication system, A transceiver capable of transmitting and receiving at least one signal; and Including a control unit coupled with the above transmitter and receiver, The above control unit: Establish a first terminal and sidelink PC5 unicast link, and When the first terminal detects reselection of the relay terminal, it is configured to receive a message related to the reselection from the first terminal, A method, characterized in that the message includes a cause for transmitting the message.

14. In paragraph 13, A second terminal, characterized in that the first terminal detects the reselection based on receiving a message related to the reselection from another relay terminal.

15. In paragraph 13, A second terminal, characterized in that the cause of transmitting the above message is one of relay terminal reselection, sidelink RLF (Radio Link Failure), and sidelink PC5 failure.

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