Method and apparatus for supporting conditional path switch in wireless communication system

Abstract

The present disclosure relates to a 5G or 6G communication system for supporting higher data transmission rates. The present disclosure relates to a method and an apparatus for supporting a conditional path switch in a wireless communication system.

Description

Method and device for supporting conditional pass switches in wireless communication systems

[0001] The present disclosure relates to a wireless communication system, and more particularly, to a method and apparatus for supporting a conditional pass switch in a wireless communication system.

[0002] 5G mobile communication technology defines a wide frequency band to enable fast transmission speeds and new services, and can be implemented not only in the sub-6GHz frequency band such as 3.5 gigahertz (3.5GHz), but also in the ultra-high frequency band called millimeter wave (mmWave) such as 28GHz and 39GHz ('Above 6GHz'). In addition, for 6G mobile communication technology, which is called the system after 5G communication (Beyond 5G), implementation in the terahertz (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 present disclosure provides a method and device for supporting a conditional pass switch in a wireless communication system, thereby reducing the delay time of the pass switch and increasing the success rate.

[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] In order to solve the above-described problem, according to an embodiment of the present invention, a method performed by a first terminal of a wireless communication system may include the steps of: receiving, from the base station, a first message including first configuration information regarding a conditional path switching from a direct path with the base station to an indirect path via a second terminal; determining, based on the first configuration information regarding the conditional path switching, whether a path switching condition is satisfied; establishing a unicast connection for relay communication with the second terminal when the path switching condition is satisfied; and transmitting, to the base station via the second terminal, a second message regarding the completion of the path switching.

[0011] According to an embodiment, the first configuration information regarding the path switching may include at least one of identification information regarding the second terminal for relay operation, configuration information for the unicast connection, and information regarding the path switching condition.

[0012] According to an embodiment, the method may further include the steps of: receiving a terminal capability information request message requesting information on whether the first terminal supports conditional path switching from the base station; and transmitting a terminal capability information message including information on whether the first terminal supports conditional path switching to the base station.

[0013] According to an embodiment, the method may further include: receiving, from the base station, a third message including second configuration information regarding a conditional path switching from an indirect path through the second terminal to a direct path with the base station; determining, based on the second configuration information regarding the conditional path switching, whether a path switching condition is satisfied; performing a random access procedure with the base station when the path switching condition is satisfied; and releasing the unicast connection for relay communication with the second terminal.

[0014] In order to solve the above-described problem, according to an embodiment of the present invention, a method performed by a base station of a wireless communication system may include the steps of: determining to conditionally switch a direct path of a first terminal with the base station to an indirect path via a second terminal; transmitting a first message including relay terminal configuration information for the second terminal to operate as a relay terminal; transmitting a second message including first configuration information regarding the conditional path switching from the direct path with the base station to the indirect path via the second terminal to the first terminal; and receiving a third message regarding the completion of the path switching from the first terminal via the second terminal when a path switching condition based on the first configuration information regarding the conditional path switching is satisfied.

[0015] According to an embodiment, the first configuration information regarding the path switching may include at least one of identification information regarding the second terminal for relay operation, configuration information for the unicast connection, and information regarding the path switching condition.

[0016] According to an embodiment, the method may further include the steps of: transmitting, to the first terminal, a terminal capability information request message requesting information on whether the first terminal supports conditional path switching; and receiving, from the first terminal, a terminal capability information message including information on whether the first terminal supports conditional path switching.

[0017] According to an embodiment, the method may further include: transmitting, to the first terminal, a fourth message including second configuration information regarding a conditional path switching from an indirect path through the second terminal to a direct path with the base station; performing a random access procedure with the terminal when a path switching condition based on the first configuration information regarding the conditional path switching is satisfied; and transmitting, to the second terminal, a fifth message for releasing the relay terminal configuration information.

[0018] In order to solve the above-described problem, according to an embodiment of the present invention, a first terminal of a wireless communication system may include a transceiver; and a control unit connected to the transceiver, the control unit receiving a first message from the base station including first configuration information regarding a conditional path switching from a direct path with a base station to an indirect path via a second terminal, and determining whether a path switching condition is satisfied based on the first configuration information regarding the conditional path switching, and if the path switching condition is satisfied, establishing a unicast connection for relay communication with the second terminal, and transmitting a second message regarding the completion of the path switching to the base station via the second terminal.

[0019] In order to solve the above-described problem, according to an embodiment of the present invention, a base station of a wireless communication system may include a transceiver; and a control unit connected to the transceiver, the control unit determining to conditionally switch a direct path of a first terminal with the base station to an indirect path via a second terminal, transmitting a first message including relay terminal configuration information for operating the second terminal as a relay terminal to the second terminal, transmitting a second message including first configuration information regarding the conditional path switching of the direct path with the base station to the indirect path via the second terminal to the first terminal, and, when a path switching condition based on the first configuration information regarding the conditional path switching is satisfied, receiving a third message regarding the completion of the path switching from the first terminal via the second terminal.

[0020] According to one embodiment of the present disclosure, a device and method for effectively providing a service in a wireless communication system can be provided.

[0021] According to one embodiment of the present disclosure, a method and device for supporting a conditional pass switch in a wireless communication system can be provided to reduce the delay time of the pass switch and increase the success rate.

[0022] 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.

[0023] FIG. 1 is a diagram illustrating the structure of a next-generation mobile communication system according to an embodiment of the present disclosure.

[0024] FIG. 2 is a diagram illustrating a user plane wireless protocol structure of a next-generation mobile communication system according to an embodiment of the present disclosure.

[0025] FIG. 3 is a diagram illustrating a control plane wireless protocol structure of a next-generation mobile communication system according to an embodiment of the present disclosure.

[0026] FIG. 4 is a diagram illustrating the structure of a base station in a wireless communication system according to an embodiment of the present disclosure.

[0027] FIG. 5 is a diagram illustrating the structure of a terminal in a wireless communication system according to an embodiment of the present disclosure.

[0028] FIG. 6A is a diagram illustrating examples of scenarios for sidelink communication in a wireless communication system according to an embodiment of the present disclosure.

[0029] FIG. 6b is a diagram illustrating examples of scenarios for sidelink communication in a wireless communication system according to an embodiment of the present disclosure.

[0030] FIG. 6c is a diagram illustrating examples of scenarios for sidelink communication in a wireless communication system according to an embodiment of the present disclosure.

[0031] FIG. 6d is a diagram illustrating examples of scenarios for sidelink communication in a wireless communication system according to an embodiment of the present disclosure.

[0032] FIG. 6e is a diagram illustrating examples of scenarios for sidelink communication in a wireless communication system according to an embodiment of the present disclosure.

[0033] FIG. 7a is a diagram illustrating examples of a transmission method of sidelink communication in a wireless communication system according to an embodiment of the present disclosure.

[0034] FIG. 7b is a diagram illustrating examples of a transmission method of sidelink communication in a wireless communication system according to an embodiment of the present disclosure.

[0035] FIG. 8 is a diagram illustrating an example of a sidelink resource pool in a wireless communication system according to an embodiment of the present disclosure.

[0036] FIG. 9 is a diagram illustrating an example of a signal flow for allocating transmission resources of a side link in a wireless communication system according to an embodiment of the present disclosure.

[0037] FIG. 10 is a diagram illustrating another example of a signal flow for allocating transmission resources of a side link in a wireless communication system according to an embodiment of the present disclosure.

[0038] FIG. 11 is a diagram illustrating an example of a channel structure of a slot used for sidelink communication in a wireless communication system according to an embodiment of the present disclosure.

[0039] FIG. 12a is a diagram illustrating a user plane wireless protocol structure of a terminal-to-network relay according to an embodiment of the present disclosure.

[0040] FIG. 12b is a diagram illustrating a control plane wireless protocol structure of a terminal-to-network relay according to an embodiment of the present disclosure.

[0041] FIG. 13 is a diagram illustrating an example of a signal flow of an intra-gNB Direct-to-Indirect path switch operation in a terminal-to-network relay according to an embodiment of the present disclosure.

[0042] FIG. 14 is a diagram illustrating an example of a signal flow of an intra-gNB conditional Direct-to-Indirect path switch operation in a terminal-to-network relay according to an embodiment of the present disclosure.

[0043] FIG. 15 is a diagram illustrating an example of a signal flow of an inter-gNB Direct-to-Indirect path switch operation in a terminal-to-network relay according to an embodiment of the present disclosure.

[0044] FIGS. 16A and 16B are diagrams illustrating examples of signal flow of inter-gNB conditional Direct-to-Indirect path switch operation in a terminal-to-network relay according to an embodiment of the present disclosure.

[0045] FIG. 17 is a diagram illustrating an example of a signal flow of an intra-gNB Indirect-to-Direct path switch operation in a terminal-to-network relay according to an embodiment of the present disclosure.

[0046] FIG. 18 is a diagram illustrating an example of a signal flow of an intra-gNB conditional Indirect-to-Direct path switch operation in a terminal-to-network relay according to an embodiment of the present disclosure.

[0047] FIG. 19 is a diagram illustrating an example of a signal flow of an inter-gNB Indirect-to-Direct path switch operation in a terminal-to-network relay according to an embodiment of the present disclosure.

[0048] FIGS. 20A and 20B are diagrams illustrating examples of signal flow of inter-gNB conditional Indirect-to-Direct path switch operation in a terminal-to-network relay according to an embodiment of the present disclosure.

[0049] FIG. 21 is a diagram illustrating an example of a signal flow of an intra-gNB Indirect-to-Indirect path switch operation in a terminal-to-network relay according to an embodiment of the present disclosure.

[0050] FIGS. 22a and 22b are diagrams illustrating examples of signal flow of intra-gNB conditional Indirect-to-Indirect path switch operation in a terminal-to-network relay according to an embodiment of the present disclosure.

[0051] FIGS. 23A and 23B are diagrams illustrating examples of signal flow of inter-gNB Indirect-to-Indirect path switch operation in a terminal-to-network relay according to an embodiment of the present disclosure.

[0052] FIGS. 24A and 24B are diagrams illustrating examples of signal flows of inter-gNB conditional Indirect-to-Indirect path switch operations in a terminal-to-network relay according to an embodiment of the present disclosure.

[0053] FIGS. 25A and 25B are diagrams illustrating examples of signal flows of conditional path switch operations of multiple base stations and multiple relay terminals in a terminal-to-network relay according to an embodiment of the present disclosure.

[0054] FIG. 26a and FIG. 26b are diagrams illustrating examples of signal flow of a path switch according to the RRC connection status of a relay terminal in a terminal-to-network relay according to an embodiment of the present disclosure.

[0055] FIG. 27a and FIG. 27b are diagrams illustrating examples of signal flow of a path switch according to the RRC connection status of a relay terminal in a terminal-to-network relay according to an embodiment of the present disclosure.

[0056] FIG. 28a and FIG. 28b are diagrams illustrating examples of signal flows for an operation of pre-connecting a PC5 unicast link in a terminal-to-network relay according to an embodiment of the present disclosure.

[0057] FIG. 29a and FIG. 29b are diagrams illustrating examples of signal flows in an operation in which a remote terminal reports to a base station a relay terminal that is not suitable for a path switch during a conditional path switch operation in a terminal-to-network relay according to an embodiment of the present disclosure.

[0058] FIGS. 30A, 30B, and 30C are diagrams illustrating examples of signal flow when a remote terminal fails to perform a path switch during a conditional path switch operation in a terminal-to-network relay according to an embodiment of the present disclosure.

[0059] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the attached drawings.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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).

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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, IAB (Integrated Access and Backhaul) 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.

[0074] 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).

[0075] 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.

[0076] The present disclosure relates to a method and an apparatus for performing a path switch (path switching) from a direct path (direct path) to an indirect path (indirect path) (direct-to-indirect path switch, D2I path switch) within a base station (gNB) or between base stations (inter-gNB), or from an indirect path to a direct path (indirect-to-direct path switch, I2D path switch), or from an indirect path to an indirect path (indirect-to-indirect path switch, I2I path switch) when a remote terminal (remote UE) satisfies a specific condition in a UE-to-Network (U2N) relay of a wireless communication system. The remote terminal can transmit and receive uplink or downlink data to and from a base station through an indirect path via 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. A remote terminal can transmit and receive data with a relay terminal via a terminal-to-terminal link, and the relay terminal can transmit and receive data with a base station via a direct link. The relay terminal can transmit uplink data received from the remote terminal to the base station, and the relay terminal can transmit downlink data received from the base station to the remote terminal. In order to determine whether to change the direct path or indirect path of the remote terminal, the base station can instruct the remote terminal to measure relay terminals or cells around the remote terminal and receive a report. When a measurement report is transmitted using an indirect path, there may be a difference between the time at which the remote terminal transmits the measurement report to the relay terminal and the time at which the relay terminal transmits the measurement report to the base station.The base station can transmit an RRC message (e.g., RRCReconfiguration) to the remote terminal to indicate a pass switch. When the RRC message is transmitted using an indirect path, there may be a difference between the time when the base station transmits the RRC message to the relay terminal and the time when the relay terminal transmits the RRC message to the remote terminal. When the remote terminal performs a pass switch using an indirect path, it must transmit an RRC message (e.g., RRCReconfigurationComplete) to the base station to complete the pass switch after connecting a PC5 unicast link (PC5 unicast connection) with the target relay terminal, so a delay may occur during the time it takes to connect the PC5 unicast link. This delay due to the indirect path is a delay caused by the pass switch that is not considered in the existing handover. Compared to the existing handover, the channel conditions of the remote terminal or relay terminal may change by an amount equal to the delay time, which may increase the probability of pass switch failure. To solve this problem, the base station can transmit in advance to the remote terminal the settings for the conditional pass switch for the pass switch scenario (e.g., some or all of D2I, I2D, and I2I), and the remote terminal can perform the pass switch operation when a specific condition is satisfied, thereby reducing the delay caused by the indirect pass. According to an embodiment, the remote terminal can reduce the delay caused by the establishment of the PC5 unicast link by pre-connecting the PC5 unicast link with a candidate relay UE according to an instruction of the base station. According to an embodiment, the remote terminal can report to the base station when the information of the relay UE that is the target of the pass switch is changed.According to an embodiment, if a handover or pass switch fails, the remote terminal can apply the settings of a newly selected relay terminal during the RRC re-establishment process by referring to the settings previously transmitted by the base station and complete the pass switch.

[0077] FIG. 1 is a diagram illustrating the structure of a next-generation mobile communication system according to an embodiment of the present disclosure.

[0078] 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).

[0079] 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 buffer status, available transmission power status, and channel status of the UEs (150) and performs scheduling is required, and the NR gNB (120) may be responsible for this. One NR gNB (120) may typically control multiple cells. In the next-generation mobile communication system, in order to implement ultra-high-speed data transmission compared to LTE, a bandwidth greater than the maximum bandwidth of LTE may be used, and beamforming technology may be additionally grafted using the OFDM method as a wireless access technology. In addition, in the case of the next-generation mobile communication system, the Adaptive Modulation and Coding (AMC) method that determines the modulation scheme and channel coding rate according to the channel condition of the terminal (150) can be applied. The NR CN (110) can perform functions such as mobility support and QoS setting. The NR CN (110) is a device that is in charge of various control functions as well as the mobility management function for the terminal (150) and can be connected to a plurality of base stations (120, 140). In addition, the next-generation mobile communication system can also 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).

[0080] FIG. 2 is a diagram illustrating a user plane wireless protocol structure of a next-generation mobile communication system according to an embodiment of the present disclosure.

[0081] Referring to FIG. 2, the user plane wireless protocol of the next generation mobile communication system may be composed of SDAP (211), PDCP (212), RLC (213), MAC (214), and / or PHY (215) in the terminal (210). The base station (220) may be composed of SDAP (221), PDCP (222), RLC (223), MAC (224), and / or PHY (225). In the present disclosure, the term “may be composed of” may be replaced with the term “may include.” For example, the user plane wireless protocol of the next generation mobile communication system may be composed of SDAP (211), PDCP (212), RLC (213), MAC (214), and / or PHY (215) in the terminal (210).

[0082] The functions of SDAP (211, 221) may include at least some of the following functions, but are not limited thereto.

[0083] - Mapping between a QoS flow and a data radio bearer

[0084] - Marking QoS flow ID (QFI) in both DL and UL packets

[0085] The main functions of PDCP (212, 222) may include, but are not limited to, some of the following functions.

[0086] - Transfer of data (user plane or control plane)

[0087] - Maintenance of PDCP sequence numbers (PDCP SNs)

[0088] - Header compression and decompression using the ROHC protocol

[0089] - Header compression and decompression using EHC protocol

[0090] - Compression and decompression of uplink PDCP SDUs (DEFLATE based UDC only)

[0091] - Ciphering and deciphering

[0092] - Integrity protection and integrity verification

[0093] - Timer-based SDU discard

[0094] - Routing for split bearers (For split bearers, routing)

[0095] - 복제(Duplication)

[0096] - Reordering and in-order delivery

[0097] - Out-of-order delivery

[0098] - 중복 폐기(Duplicate discarding)

[0099] The main functions of RLC (213, 223) may include, but are not limited to, some of the following functions.

[0100] - Transfer of upper layer PDUs

[0101] - Sequence numbering independent of the one in PDCP (UM and AM)

[0102] - Error Correction through ARQ (AM only)

[0103] - Segmentation (AM and UM) and re-segmentation (AM only) of RLC SDUs

[0104] - Reassembly of SDU (AM and UM)

[0105] - Duplicate Detection (AM only)

[0106] - RLC SDU discard (AM and UM)

[0107] - RLC re-establishment

[0108] - Protocol error detection (AM only)

[0109] The main functions of MAC (214, 224) may include at least some of the following functions, but are not limited thereto.

[0110] - Mapping between logical channels and transport channels

[0111] - Multiplexing of MAC SDUs from one or more logical channels onto transport blocks (TB) to be delivered to the physical layer on transport channels

[0112] - Demultiplexing of MAC SDUs belonging to one or more logical channels (demultiplexing of MAC SDUs to one or different logical channels from transport blocks (TB) delivered from the physical layer on transport channels)

[0113] - Scheduling information reporting

[0114] - Error correction through HARQ

[0115] - Logical channel prioritization

[0116] - Priority handling between overlapping resources of one UE

[0117] The PHY layer (215, 225) can encode and modulate upper layer data to generate OFDM symbols, convert them into RF band signals, and transmit them via an antenna. In addition, the PHY layer (215, 225) can demodulate and decode received OFDM symbols and transmit them to the upper layer.

[0118] FIG. 3 is a diagram illustrating a control plane wireless protocol structure of a next-generation mobile communication system according to an embodiment of the present disclosure.

[0119] Referring to FIG. 3, the control plane wireless protocol of the next-generation mobile communication system may be composed of RRC (311), PDCP (312), RLC (313), MAC (314), and / or PHY (315) in a terminal (310). It may be composed of RRC (321), PDCP (322), RLC (323), MAC (324), and / or PHY (325) in a base station (320).

[0120] The functions of RRC (311, 321) may include at least some of the following functions.

[0121] - Broadcast of System Information related to AS and NAS

[0122] - Paging initiated by 5GC or NG-RAN

[0123] - Establishment, maintenance, and release of an RRC connection between the UE and NG-RAN, including: Addition, modification, and release of carrier aggregation; Addition, modification, and release of dual connectivity in NR or between E-UTRA and NR.

[0124] - Security functions including key management

[0125] - Establishment, configuration, maintenance and release of Signaling Radio Bearers (SRBs) and Data Radio Bearers (DRBs)

[0126] - Terminal mobility support (Mobility functions including: Handover and context transfer; UE cell selection and reselection and control of cell selection and reselection; Inter-RAT mobility.)

[0127] - QoS management functions

[0128] - UE measurement reporting and control of the reporting

[0129] - Detection of and recovery from radio link failure

[0130] - NAS message transfer (NAS message transfer to / from NAS from / to UE)

[0131] The main functions of PDCP (312, 322), RLC (313, 323), MAC (314, 324), and / or PHY (315 / 325) may follow the example of FIG. 2.

[0132] FIG. 4 is a diagram illustrating the structure of a base station in a wireless communication system according to an embodiment of the present disclosure.

[0133] Referring to FIG. 4, the base station may include a transceiver (405), a control unit (410), and / or a storage unit (415). The transceiver (405), the control unit (410), and the storage unit (415) 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 (405) and a control unit (410). In addition, the transceiver (405), the control unit (410), and the storage unit (415) may be implemented in the form of a single chip.

[0134] The transceiver (405) is a general term for the receiving unit and the transmitting unit (transmitter) 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 (405) may also be referred to as a communication unit, a transceiver, a wireless communication unit, etc. The transceiver (405) may transmit system information to the terminal, and may transmit a synchronization signal or a reference signal, for example. To this end, the transceiver (405) 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 a received signal. However, this is only one embodiment of the transceiver (405), and the components of the transceiver (405) are not limited to the RF transmitter and the RF receiver. The transceiver (405) may include wired and wireless transceivers, and may include various configurations for transmitting and receiving signals. In addition, the transceiver (405) may receive a signal through a communication channel (e.g., a wireless channel) and output it to the control unit (410), and transmit the signal output from the control unit (410) through the communication channel. In addition, the transceiver (405) may 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.

[0135] The storage unit (415) can store programs and data required for the operation of the base station. In addition, the storage unit (415) can store control information or data included in signals acquired from the base station. The storage unit (415) 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 (415) can store at least one of information transmitted and received through the transceiver unit (405) and information generated through the control unit (410).

[0136] In the present disclosure, the control unit (410) 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 (410) may control the overall operation of the base station according to the embodiment proposed in the present disclosure. For example, the control unit (410) may control the signal flow between each block to perform operations according to the flowchart described above, and may transmit and receive signals through the transceiver unit (405).

[0137] FIG. 5 is a diagram illustrating the structure of a terminal in a wireless communication system according to an embodiment of the present disclosure.

[0138] Referring to FIG. 5, the terminal may include a transceiver (505), a control unit (510), and / or a storage unit (515). The transceiver (505), the control unit (510), and the storage unit (515) 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 (505) and a control unit (510). In addition, the transceiver (505), the control unit (510), and the storage unit (515) may be implemented in the form of a single chip.

[0139] The transceiver (505) 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 (505) may also be referred to as a communication unit, a transceiver, a wireless communication unit, etc. The transceiver (505) may receive system information from the base station, and may receive a synchronization signal or a reference signal, for example. To this end, the transceiver (505) 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 (505), and the components of the transceiver (505) are not limited to the RF transmitter and the RF receiver. In addition, the transceiver (505) may include wired and wireless transceivers, and may include various configurations for transmitting and receiving signals. In addition, the transceiver (505) can receive a signal through a wireless channel and output it to the control unit (510), and transmit the signal output from the control unit (510) through the wireless channel. In addition, the transceiver (505) 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.

[0140] The storage unit (515) can store programs and data necessary for the operation of the terminal. In addition, the memory (515) can store control information or data included in signals obtained from the terminal. The storage unit (515) 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.

[0141] In the present disclosure, the control unit (510) 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 (510) may control the overall operation of the terminal according to the embodiment proposed in the present disclosure. For example, the control unit (510) may control the signal flow between each block to perform operations according to the flowchart described above, and may transmit and receive signals through the transceiver unit (405).

[0142] FIGS. 6A to 6E are diagrams illustrating examples of scenarios for sidelink communication in a wireless communication system according to an embodiment of the present disclosure.

[0143] FIG. 6a illustrates an in-coverage (IC) scenario where sidelink terminals (620, 625) are located within the coverage (610) of a base station (600).

[0144] Referring to FIG. 6A, sidelink terminals (620, 625) can receive data and control information from a base station (600) via a downlink (DL), or transmit data and control information to the base station (600) 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 (620, 625) can transmit and receive data and control information for sidelink communication via a sidelink (SL). In addition, the first terminal (620) can receive data and control information from the base station (600) via a direct path via a DL or UL, or can receive data and control information from the base station (600) via an indirect path via a relay of the second terminal (625). The first terminal (620) may be referred to as a remote terminal (remote UE), and the second terminal (625) may be referred to as a relay terminal (relay UE). A scenario in which the first terminal (620) accesses the base station (600) through the second terminal (625) may be referred to as a UE-to-Network relay (U2N relay). In addition, the first terminal (620) may transmit and receive data and control information with the base station (600) by simultaneously using a direct path and an indirect path, and such a scenario may be referred to as a multi-path relay.

[0145] FIG. 6b illustrates a case of partial coverage (PC) in which a first terminal (620) among side link terminals is located within the coverage (610) of the base station (600) and a second terminal (625) is located outside the coverage (610) of the base station (600).

[0146] Referring to FIG. 6B, a first terminal (620) located within the coverage (610) of a base station (600) can receive data and control information from the base station (600) via downlink or transmit data and control information to the base station (600) via uplink. A second terminal (625) located outside the coverage of the base station (600) cannot directly receive data and control information from the base station (600) via downlink, and cannot directly transmit data and control information to the base station (600) via uplink. The second terminal (625) can transmit data and control information for sidelink communication to the base station (600) via sidelink with the first terminal (620) and receive data and control information from the base station (600).

[0147] FIG. 6c is an example of a case where sidelink terminals (e.g., first terminal (620), second terminal (625)) are located out of coverage (OOC) of the base station (600) (610).

[0148] Referring to FIG. 6c, the first terminal (620) and the second terminal (625) 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 (620) and the second terminal (625) can transmit and receive data and control information for sidelink communication via the sidelink.

[0149] FIG. 6d illustrates a case where a first terminal (620) and a second terminal (625) performing sidelink communication are connected to (e.g., in an RRC connected state) or camping on (e.g., in an RRC disconnected state, i.e., in an RRC idle or inactive state) different base stations (e.g., the first base station (600) and the second base station (605)) and perform inter-cell sidelink communication. At this time, referring to FIG. 6d, the first terminal (620) may be a sidelink transmitting terminal and the second terminal (625) may be a sidelink receiving terminal. Alternatively, the first terminal (620) may be a sidelink receiving terminal and the second terminal (625) may be a sidelink transmitting terminal. A first terminal (620) can receive a sidelink-only SIB (system information block) from a base station (600) to which it is connected (or on which it is camping), and a second terminal (625) can receive a sidelink-only SIB from another base station (605) to which it is connected (or on which it is camping). At this time, the information of the sidelink-only SIB received by the first terminal (620) may be different from the information of the sidelink-only SIB received by the second terminal (625). 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 (620) can transmit and receive data and control information to and from the first base station (600) through a direct path via DL or UL, or can transmit and receive data and control information to and from the second base station (605) through an indirect path via a relay of the second terminal (625). The first terminal (620) may be called a remote terminal, and the second terminal (625) may be called a relay terminal.A scenario in which a first terminal (620) connects to a second base station (605) via a second terminal (625) may be referred to as a terminal-network relay. Furthermore, the first terminal (620) may transmit and receive data and control information with the first base station (600) and the second base station (605) simultaneously using direct and indirect paths, and such a scenario may be referred to as a multi-path relay.

[0150] FIG. 6E illustrates a case where a first terminal (620), a second terminal (625), and a third terminal (630) performing sidelink communication configure a terminal-to-terminal relay and perform sidelink communication. At this time, referring to FIG. 6E, the first terminal (620) may be a source End UE, which is an end terminal of the terminal-to-terminal relay, and the third terminal (630) may be a target End UE, which is an end terminal of the terminal-to-terminal relay. Alternatively, the first terminal (620) may be a target End UE, which is an end terminal of the terminal-to-terminal relay, and the third terminal (630) may be a source End UE, which is an end terminal of the terminal-to-terminal relay. The second terminal (625) may be a relay UE that relays data between end terminals in the terminal-to-terminal relay. The first terminal (620), the second terminal (625), and the third terminal (630) may be connected to the same or different base stations (e.g., RRC connected state), camped (e.g., RRC disconnected state, i.e., RRC idle or inactive state), performed inter-cell sidelink communication, or in OOC, as shown in the examples of FIGS. 6A to 6D.

[0151] In the examples of FIGS. 6A to 6E, for the sake of convenience of explanation, a sidelink system composed of two or three terminals (e.g., a first terminal (620), a second terminal (625), and a third terminal (630)) 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 (600, 605) 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 (600, 605) 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.

[0152] 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.

[0153] 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.

[0154] Figures 7a and 7b illustrate examples of transmission methods for sidelink communication in a wireless communication system according to an embodiment of the present disclosure. Figure 7a illustrates a unicast method, and Figure 7b illustrates a groupcast method.

[0155] Referring to FIG. 7a, a transmitting terminal (700) and a receiving terminal (705) can perform one-to-one communication (710). A transmission method such as FIG. 7a may be referred to as unicast communication.

[0156] Referring to FIG. 7b, transmitting terminals (730, 745) and receiving terminals (735, 740, 750, 755, 760) can perform one-to-many communication. A transmission method such as FIG. 7b may be referred to as groupcast or multicast.

[0157] In Fig. 7b, a first terminal (730), a second terminal (735), and a third terminal (740) form one group and perform groupcast communication, and a fourth terminal (745), a fifth terminal (750), a sixth terminal (755), and a seventh terminal (760) form another group and perform groupcast communication. The terminals perform groupcast communication within the group to which they belong, and can perform unicast, groupcast, or broadcast communication with at least one other terminal belonging to different groups. In Fig. 7b, two groups are exemplified, but the present disclosure is not limited thereto and can be applied even when a larger number of groups are formed.

[0158] Meanwhile, although not illustrated in FIG. 7A or FIG. 7B , sidelink terminals may also perform broadcast communication. Broadcast communication refers to a method in which all sidelink terminals receive data and control information transmitted by a sidelink transmitting terminal via the sidelink. For example, in FIG. 7B , if the first terminal (730) is a transmitting terminal, the remaining terminals (735, 740, 745, 750, 755, and 760) can receive data and control information transmitted by the first terminal (730).

[0159] The aforementioned sidelink unicast communication, groupcast communication, and broadcast communication can be supported in an in-coverage scenario, a partial-coverage scenario, or an out-of-coverage scenario.

[0160] FIG. 8 illustrates an example of a sidelink resource pool in a wireless communication system according to an embodiment of the present disclosure. A resource pool may be defined as a set of resources in the time and frequency domains used for sidelink transmission and reception.

[0161] Referring to FIG. 8, a resource allocation unit on the time axis within a resource pool may be one or more orthogonal frequency division multiplexing (OFDM) symbols. Additionally, a resource allocation unit on the frequency axis may be one or more physical resource blocks (PRBs).

[0162] When a resource pool is allocated in the time domain and frequency domain, the region comprised of resources indicated by hatching in FIG. 8 represents a region set as a resource pool in time and frequency. While the present disclosure describes a case where the resource pool is allocated non-contiguously in time, the present disclosure is not limited thereto and may also be applied to a case where the resource pool is allocated continuously in time. Furthermore, while the present disclosure describes a case where the resource pool is allocated continuously in frequency, the present disclosure is not limited thereto and may also be applied to a case where the resource pool is allocated non-contiguously in frequency.

[0163] Referring to FIG. 8, the time domain (800) of the configured resource pool exemplifies a case where resources are allocated non-contiguously in the time domain. In the time domain (800) of the resource pool, the unit of resource allocation on the time axis (resource granularity) may be a slot. Specifically, one slot composed of 14 OFDM symbols may be the basic unit of resource allocation on the time axis. Referring to the time domain (800) of the configured resource pool, shaded slots represent slots allocated to the resource pool in time, and the slots allocated to the resource pool in time may be indicated using system information. For example, the slots allocated to the resource pool in time may be indicated using the time-based resource pool configuration information in the SIB. Specifically, at least one slot set to the resource pool in time may be indicated through a bitmap. Referring to FIG. 8, physical slots (800) belonging to a non-contiguous resource pool on the time axis can be mapped to logical slots (825). In general, a set of slots belonging to a resource pool for a physical sidelink shared channel (PSSCH) can be expressed as (t0, t1, ..., ti, ,,, tTmax).

[0164] Referring to FIG. 8, the frequency domain (805) of the configured resource pool exemplifies a case where resources are allocated consecutively in the frequency domain. In the frequency domain (805) of the resource pool, the unit of resource allocation on the frequency axis may be a subchannel (810). Specifically, one subchannel (810) composed of one or more resource blocks (RBs) may be defined as a basic unit of resource allocation on the frequency. That is, the subchannel (810) may be defined as an integer multiple of an RB. Referring to FIG. 8, the subchannel size (sizeSubchannel) may be composed of five consecutive PRBs, but the present disclosure is not limited thereto, and the size of the subchannel may be set differently. In addition, one subchannel is generally composed of consecutive PRBs, but does not necessarily have to be composed of consecutive PRBs. The subchannel (810) may be a basic unit of resource allocation for the PSSCH. Additionally, a subchannel for the physical sidelink feedback channel (PSFCH) can be defined independently of the PSSCH.

[0165] Referring to FIG. 8, the starting position of a subchannel on a frequency in a resource pool can be indicated by startRB-Subchannel (815). When resource allocation on the frequency axis is performed in units of subchannels (810), the resource pool configuration on the frequency can be performed using configuration information for the RB index (startRB-Subchannel) (815) at which the subchannel starts, information for indicating how many RBs the subchannel consists of (sizeSubchannel) (810), and the total number of subchannels (numSubchannel). In addition, the resource pool configuration on the frequency can also be performed using configuration information for the RB index (EndRB-Subchannel) (820) at which the subchannel ends. According to various embodiments, the subchannels allocated to the resource pool on the frequency can be indicated using system information. For example, at least one of startRB-Subchannel, sizeSubchannel, EndRB-SubChannel, and numSubchannel can be indicated as frequency resource pool configuration information in the SIB. If the subchannel for the PSFCH is defined independently from the PSSCH, the subchannel configuration information of the PSFCH and the PSSCH can be indicated to the terminal respectively.

[0166] FIG. 9 illustrates an example of a signal flow for allocating sidelink transmission resources in a wireless communication system according to an embodiment of the present disclosure. FIG. 9 illustrates signal exchange between a transmitting terminal (901), a receiving terminal (902), and a base station (903).

[0167] As described below, the method by which a base station allocates transmission resources for sidelink communication may be referred to as Mode 1. Mode 1 is a method based on scheduled resource allocation by the base station. More specifically, in Mode 1 resource allocation, the base station can allocate resources used for sidelink transmission to RRC-connected terminals according to a dedicated scheduling method. Since the base station can manage the resources used for sidelink transmission, scheduled resource allocation can be advantageous for interference management and resource pool management (e.g., dynamic allocation and / or configured grant (CG)).

[0168] Referring to FIG. 9, in step 905, a transmitting terminal (901) may be in a camp-on state in a cell. In step 907, the transmitting terminal (901) that is camped on the cell (905) may receive a sidelink SIB from a base station (903). In step 909, the receiving terminal (902) may monitor sidelink communication based on a sidelink SIB or RRC message received from a base station (e.g., 903, but may be received from another base station), or an Rx resource pool included in pre-configuration. Here, the receiving terminal (902) refers to a terminal that receives data transmitted by the transmitting terminal (901). The sidelink SIB may be transmitted periodically or on demand. Additionally, the sidelink SIB may include at least one of sidelink resource pool information for sidelink communication, parameter setting information for sensing operation, information for setting sidelink synchronization, or carrier information for sidelink communication operating at different frequencies. Although steps 907 and 909 have been described sequentially above, this is for convenience of explanation, and steps 907 and 909 may be performed in parallel.

[0169] In step 913, when data traffic for sidelink communication is generated in the transmitting terminal (901), the transmitting terminal (901) may initiate an RRC connection procedure with the base station (903) to request transmission resources (915). Here, the RRC connection between the transmitting terminal (901) and the base station (903) may be referred to as Uu-RRC. The Uu-RRC connection may be performed before the data traffic of the transmitting terminal (901) is generated. In addition, in case of mode 1, the transmitting terminal (901) may perform transmission to the receiving terminal (902) via the sidelink when the Uu-RRC connection is established between the base station (903) and the receiving terminal (902). In addition, in case of mode 1, the transmitting terminal (901) may perform transmission to the receiving terminal (902) via the sidelink even when the Uu-RRC connection is not established between the base station (903) and the receiving terminal (902).

[0170] At step 915, the transmitting terminal (901) may request the base station (903) for transmission resources for transmitting sidelink data to the receiving terminal (902). At this time, the transmitting terminal (901) may request the base station (903) for transmission resources for the sidelink using at least one of a physical uplink control channel (PUCCH), an RRC message, or MAC CE. For example, when the MAC CE is used, the MAC CE may be a MAC CE for a buffer status report having a new format that includes at least one of an indicator for indicating that it is a buffer status report (BSR) for sidelink communication and information on the size of data stored in a buffer for device-to-device (D2D) communication (or V2X communication). Such a MAC CE may be referred to as a sidelink BSR MAC CE. In addition, when PUCCH is used, the transmitting terminal (901) can request sidelink resources through bits of a scheduling request (SR) transmitted through an uplink physical control channel. In addition, when an RRC message is used, the transmitting terminal (901) can transmit information about frequencies for transmission and reception of various types of sidelink communications, including sidelink discovery, sidelink data communication, and sidelink relay communication, and information about the receiving terminal (902) to the base station (903) through Uu-RRC, and at least one of the following information can be included through the same or different RRC messages.

[0171] * Frequency to be used for reception in sidelink communication

[0172] * Frequency to be used for transmission in sidelink communication

[0173] * Types of sidelink data transmitted in sidelink communication

[0174] * Period and size of sidelink data transmitted in sidelink communication

[0175] * Information on the target terminal receiving sidelink data transmitted in sidelink communication (target terminal ID, terminal capability, DRX information, etc.)

[0176] * QoS information of sidelink data transmitted in sidelink communication

[0177] * Cast type of sidelink data transmitted in sidelink communication

[0178] * RLC mode of sidelink data transmitted in sidelink communication

[0179] In step 915, PUCCH, MAC CE, and RRC messages can be used independently or mixed together depending on the purpose. Furthermore, although step 915 is described after step 913, this is for convenience of explanation. It can also be used to request resources for sidelink data to be transmitted in the unicast layer-2 link establishment procedure (911) for establishing a PC5 unicast link between a transmitting terminal (901) and a receiving terminal (902), and can be performed in parallel or simultaneously with other operations.

[0180] At step 917, the base station (903) can transmit an RRC message to the transmitting terminal (901) that includes information on transmission resources to be used by the transmitting terminal (901).

[0181] At step 919, the base station (903) can transmit DCI (downlink control information) to the transmitting terminal (901) via PDCCH.

[0182] Through steps 917 to 919, the base station (903) can instruct the transmitting terminal (901) to schedule sidelink communication with the receiving terminal (902). More specifically, the base station (903) can allocate sidelink transmission resources to the transmitting terminal (901) according to at least one of a dynamic grant (DG) method or a configured grant (CG) method.

[0183] In the case of the dynamic grant (DG) scheme, the base station (903) can allocate resources for at least one transport block (TB) transmission by transmitting a DCI (919) to the transmitting terminal (901). Sidelink scheduling information included in the DCI can include resource pool information, parameters related to initial transmission time and / or retransmission transmission time, and parameters related to a frequency allocation location information field. The DCI for the dynamic grant scheme can be CRC (cyclic redundancy check) scrambled based on a sidelink radio network temporary identifier (SL-RNTI) to indicate that the transmission resource allocation scheme is the dynamic grant scheme.

[0184] In the case of the configuration grant (CG) method, the base station (903) can periodically allocate resources for transmitting at least one TB to the transmitting terminal (901) through an RRC message (917) or can set the periodicity of the sidelink CG. Additionally, the base station (903) can activate and / or deactivate the previously configured CG or instruct retransmission by transmitting a DCI to the transmitting terminal (901). The sidelink scheduling information included in the DCI can include parameters related to the initial transmission time and / or the retransmission time, and parameters related to the frequency allocation location information field. In the case of the configuration grant method, the initial transmission time and / or the retransmission time and the frequency allocation location can be determined according to the transmitted DCI, and the resources can be repeated at the periodic interval of the CG. The DCI for the configuration grant scheme may be CRC scrambled based on the sidelink configured scheduling radio network temporary identifier (SL-CS-RNTI) to indicate that the transmission resource allocation scheme is the configuration grant scheme. Furthermore, the configuration grant scheme may be categorized into Type 1 CG and Type 2 CG.

[0185] When broadcast transmission is performed between transmitting and receiving terminals (901, 902), in steps 921 and 923, the transmitting terminal (901) can broadcast SCI and data to at least one receiving terminal (e.g., 902) via PSCCH and PSSCH without PC5 unicast link connection.

[0186] When unicast or groupcast transmission is performed between transmitting and receiving terminals (901, 902), in step 911, the transmitting terminal (901) can perform a unicast layer-2 link establishment procedure (911) for direct communication with other terminals (e.g., receiving terminal (902)). At this time, the upper layer (e.g., ProSe or V2X layer) of the transmitting and receiving terminals (901, 902) can provide a PC5 link ID and / or a source Layer-2 ID and a destination Layer-2 ID so that the AS layer of the transmitting and receiving terminals (901, 902) can identify the PC5 unicast link. The RRC connection between the terminals (901, 902) can be used in unicast communication, and is a logical RRC connection corresponding to a pair of source Layer-2 ID and destination Layer-2 ID. The RRC connection between these terminals (901, 902) may be referred to as PC5-RRC to distinguish it from Uu-RRC. In the case of groupcast transmission, a PC5-RRC connection may be individually established between a transmitting terminal and a receiving terminal within a group. Referring to FIG. 9, the Unicast layer-2 link establishment procedure (911) is depicted as an operation after reception (907) of a sidelink SIB, but the Unicast layer-2 link establishment procedure (911) may be performed before reception of the sidelink SIB, or may not be performed in the case of broadcast or groupcast transmission that does not require PC5-RRC. If a PC5-RRC connection is required, the Unicast layer-2 link establishment procedure (911) may be performed.

[0187] In step 921, the transmitting terminal (901) can transmit a first stage SCI (1st stage SCI) to the receiving terminal (902) via the PSCCH. In addition, in step 923, the transmitting terminal (901) can transmit a second stage SCI (2nd stage SCI) and sidelink data to the receiving terminal (902) via the PSSCH. In the case of mode 1, the transmitting terminal (901) can identify sidelink scheduling information included in the DCI received from the base station (903) and perform scheduling for the sidelink based on the sidelink scheduling information. The SCI can be divided into a first stage SCI transmitted via the PSCCH and a second stage SCI transmitted via the PSSCH, and the first stage SCI can include at least one of the following information.

[0188] * 우선순위(Priority)

[0189] * Frequency resource assignment

[0190] * Time resource assignment

[0191] * Resource reservation period

[0192] * DMRS (de-modulation reference signal) pattern

[0193] * 2nd-stage SCI 포맷(format)

[0194] * Beta_offset indicator

[0195] * Number of DMRS port

[0196] * Modulation and coding scheme

[0197] * Additional MCS table indicator

[0198] * PSFCH overhead indication

[0199] * Reserved

[0200] * Conflict information receiver flag

[0201] Priority can be transmitted or set in the upper layer, and can be specified as a maximum of 8 values ​​in 3 bits, such as 1 being 000, 2 being 001, etc. This value can have the highest value among the priorities of all logical channels or MAC CEs included in the TB scheduled by the corresponding SCI in the case of sidelink data. If a MAC CE or SCI for inter-UE coordination is transmitted, it can have a value set with an RRC parameter different from the priority of the corresponding MAC CE. If there is no setting of the RRC parameter, the Inter-UE Coordination Request MAC CE can have the highest value among the priorities of all logical channels or MAC CEs included in the TB to be transmitted to the UE receiving the corresponding MAC CE, and the Inter-UE Coordination Information MAC CE transmitted by the terminal receiving it to respond to the request can have the same value as the value corresponding to the Priority field in the Inter-UE Coordination Request MAC CE. Additionally, if the Inter-UE Coordination Information MAC CE is transmitted under a specific condition (e.g., when the RSRP of a resource reserved by a third terminal is higher than a specific value) rather than at the request of another terminal, the priority can be arbitrarily selected by the terminal from among values ​​1 to 8.

[0202] The reservation interval is indicated as a fixed value for the interval between TBs when resources for multiple TBs (i.e., multiple MAC PDUs (protocol data units)) are selected, and when resources for one TB are selected, the value of the interval between TBs may be indicated as '0'.

[0203] The 2nd-stage SCI may be included in the PSSCH resources indicated by the 1st-stage SCI transmitted in step 921 and may be transmitted together with data in step 923. The 2nd-stage SCI may include at least one of the following information:

[0204] * HARQ process number

[0205] * New data indicator

[0206] * Redundancy version

[0207] * Source ID

[0208] * Destination ID

[0209] * HARQ feedback enabled / disabled indicator

[0210] * Cast type indicator

[0211] * CSI request

[0212] * Zone ID

[0213] * Communication range requirement

[0214] * Providing / Requesting indicator

[0215] * Resource combinations

[0216] * First resource location

[0217] * Reference slot location

[0218] * Resource set type

[0219] * Lowest subchannel indices

[0220] * 우선순위(Priority)

[0221] * Number of subchannels

[0222] * Resource reservation period

[0223] * Resource selection window location

[0224] * Resource set type

[0225] * Padding bits

[0226] And, in step 925, the receiving terminal (902) can transmit to the transmitting terminal (901) whether the demodulation / decoding of the data received in steps 921 and 923 was successful or not through first HARQ feedback information. Here, the first HARQ feedback information includes ACK (success) or NACK (failure) information, and the receiving terminal (902) can transmit the first HARQ feedback information to the transmitting terminal (901) through a PSFCH channel. In step 927, the transmitting terminal (901) can transmit the transmission result to the base station (903) as second HARQ feedback information based on the first HARQ feedback information received from the receiving terminal (902). The second HARQ feedback can be transmitted to the base station (903) through a PUCCH. At this time, the second HARQ feedback information may or may not be the same as the first HARQ feedback information. In addition, the second HARQ feedback information can include a plurality of first HARQ feedback information. The plurality of first HARQ feedback information may include a plurality of HARQ feedback information received from a single receiving terminal, or may include one or a plurality of HARQ feedback information received from multiple terminals. Through the second HARQ feedback information, the base station (903) may be able to allocate resources for retransmission to the transmitting terminal (901), allocate resources for new transmission, or stop resource allocation when there are no more transmission resources to allocate to the transmitting terminal (901). The PUCCH transmission resource may be determined by DCI information that the base station (903) transmits to the transmitting terminal (901) on the PDCCH. The PSFCH (925) transmission resource may be determined by the SCI of the PSCCH or may be determined by a transmission resource region in which the PSSCH is transmitted and received.

[0227] FIG. 10 illustrates another example of a signal flow for allocating sidelink transmission resources in a wireless communication system according to an embodiment of the present disclosure. FIG. 10 illustrates signal exchange between a transmitting terminal (1001), a receiving terminal (1002), and a base station (1003).

[0228] As described below, the method in which a terminal directly allocates transmission resources of a sidelink through sensing in the sidelink may be referred to as Mode 2. Mode 2 may also be referred to as UE autonomous resource selection. Specifically, according to Mode 2, the base station (1003) may provide a sidelink transmission and reception resource pool for the sidelink to the terminal through a sidelink SIB or an RRC message (e.g., an RRCReconfiguration message or a PC5 RRC message), and the transmitting terminal (1001) may select the resource pool and resources according to established rules. Unlike Mode 1 described in FIG. 9 in which the base station is directly involved in resource allocation, Mode 2 described in FIG. 10 allows the transmitting terminal (1001) to autonomously select resources and transmit data based on a resource pool previously received through a sidelink SIB, an RRC message, or pre-configuration.

[0229] Referring to FIG. 10, in step 1005, a transmitting terminal (1001) may be in a camp-on state in a cell. In step 1007, the transmitting terminal (1001) that is camping on (1005) may receive a sidelink SIB from a base station (1003). In step 1009, the receiving terminal (1002) may monitor sidelink communication based on a sidelink SIB or RRC message received from a base station (e.g., 1003, but may be received from another base station), or an Rx resource pool included in pre-configuration. Here, the receiving terminal (1002) refers to a terminal that receives data transmitted by the transmitting terminal (1001). The sidelink SIB may be transmitted periodically or on demand. In addition, the sidelink SIB may include at least one of sidelink resource pool information for sidelink communication, parameter setting information for sensing operation, information for setting sidelink synchronization, or carrier information for sidelink communication operating at different frequencies. Although steps 1007 and 1009 have been described sequentially above, this is for convenience of explanation, and steps 1007 and 1009 may be performed in parallel. In the case of FIG. 9 described above, the base station (903) and the transmitting terminal (901) operate in a state in which RRC is connected, whereas in FIG. 10, the base station (1003) and the transmitting terminal (1001) may operate regardless of whether RRC is connected between the base station (1003) and the transmitting terminal (1001) in step 1013. That is, when the transmitting terminal (1001) is an IC, mode 2-based sidelink communication can be performed even when the RRC is connected, when the RRC is not connected and is in an idle or inactive state, or when it is OOC.Additionally, even when RRC is connected, the base station (1003) can be set to allow the transmitting terminal (1001) to autonomously select transmission resources without being directly involved in resource allocation.

[0230] In step 1013, when data traffic for sidelink communication is generated at the transmitting terminal (1001), the transmitting terminal (1001) may initiate an RRC connection procedure with the base station (1003) to request transmission resources (1015). Here, the RRC connection between the transmitting terminal (1001) and the base station (1003) may be referred to as Uu-RRC. The Uu-RRC connection may be performed before the transmitting terminal (1001) generates data traffic.

[0231] In step 1015, the transmitting terminal (1001) may request the base station (1003) for transmission resources for transmitting sidelink data to the receiving terminal (1002) using an RRC message. The transmitting terminal (1001) may transmit information about the frequency for transmitting and receiving various types of sidelink communication, including sidelink discovery, sidelink data communication, and sidelink relay communication, and the receiving terminal (1002) to the base station through Uu-RRC, and may include at least one of the information as in the example of FIG. 9 described above through the same or different RRC messages.

[0232] At step 1017, the base station (1003) can set a resource pool for the transmitting terminal (1001) based on the transmission resources requested from the transmitting terminal (1001).

[0233] At step 1019, the transmitting terminal (1001) can directly select time and frequency domain resources through sensing within the sidelink SIB (1007) of the base station (1003), or the RRC message (1017), or the transmission resource pool set by pre-configuration.

[0234] When broadcast transmission is performed between transmitting and receiving terminals (1001, 1002), in steps 1021 and 1023, the transmitting terminal (1001) can broadcast SCI and data to at least one receiving terminal (e.g., 1002) via PSCCH and PSSCH without PC5 unicast link connection.

[0235] When unicast or groupcast transmission is performed between transmitting and receiving terminals (1001, 1002), in step 1011, the transmitting terminal (1001) can perform a unicast layer-2 link establishment procedure (1011) for direct communication with other terminals (e.g., receiving terminal (1002)). At this time, the upper layer (e.g., ProSe or V2X layer) of the transmitting and receiving terminals (1001, 1002) can provide a PC5 link ID and / or a source Layer-2 ID and a destination Layer-2 ID so that the AS layer of the transmitting and receiving terminals (1001, 1002) can identify the PC5 unicast link. The RRC connection between the terminals (1001, 1002) can be used in unicast communication, and is a logical RRC connection corresponding to a pair of source Layer-2 ID and destination Layer-2 ID. The RRC connection between these terminals (1001, 1002) may be referred to as PC5-RRC to distinguish it from Uu-RRC. In the case of groupcast transmission, a PC5-RRC connection may be individually established between a transmitting terminal and a receiving terminal within a group. Referring to Fig. 10, the Unicast layer-2 link establishment procedure (1011) is depicted as an operation after reception (1007) of a sidelink SIB, but the Unicast layer-2 link establishment procedure (1011) may be performed before reception of the sidelink SIB, or may not be performed in the case of broadcast or groupcast transmission that does not require PC5-RRC. If a PC5-RRC connection is required, the Unicast layer-2 link establishment procedure (1011) may be performed.

[0236] In step 1021, the transmitting terminal (1001) can transmit a 1st stage SCI to the receiving terminal (1002) via the PSCCH. In addition, in step 1023, the transmitting terminal (1001) can transmit a 2nd stage SCI and sidelink data to the receiving terminal (1002) via the PSSCH. In case of mode 1, the transmitting terminal (901) can identify sidelink scheduling information included in the DCI received from the base station (903) and perform scheduling for the sidelink based on the sidelink scheduling information. In case of mode 2, the transmitting terminal (1001) can directly perform scheduling for the sidelink by performing sensing and transmission resource selection operations. The 1st stage SCI and the 2nd stage SCI used in steps 1021 and 1023 can be as in the example of FIG. 9.

[0237] And, in step 1025, the receiving terminal (1002) can transmit to the transmitting terminal (1001) whether the demodulation / decoding of the data received in steps 1021 and 1023 was successful through HARQ feedback information. Here, the HARQ feedback information includes ACK (success) or NACK (failure) information, and the receiving terminal (1002) can transmit the HARQ feedback information to the transmitting terminal (1001) through the PSFCH channel.

[0238] In addition, although not shown in FIG. 9 or FIG. 10, when any transmitting terminal (e.g., 1001) performs sidelink communication in OOC, mode 2 resource allocation can be used, and information for sidelink communication that can be used for this can use information stored in the terminal through pre-configuration or receive configuration information from the base station through a sidelink relay.

[0239] FIG. 11 illustrates an example of a channel structure of a slot used for sidelink communication in a wireless communication system according to an embodiment of the present disclosure. FIG. 11 illustrates physical channels mapped to slots for sidelink communication.

[0240] Referring to FIG. 11, an automatic control gain symbol (AGC) (1105) that can be used by a receiving terminal may be mapped to the first symbol of a slot (1100). Thereafter, a PSCCH (1110), a PSSCH (1115), a GUARD (1120), an AGC for a PSFCH (1125), a PSFCH (1130), and a GUARD (1135) may be sequentially mapped.

[0241] Before transmitting the PSCCH (1110) in the corresponding slot (1100), the transmitting terminal may transmit a signal for AGC purposes having the same information as the symbol in which the PSCCH (1110) is transmitted in one or more symbols. The AGC symbol (1105) may be used to enable the receiving terminal to properly perform AGC (automatic gain control) for adjusting the strength of the amplification when amplifying the power of the received signal. The signal for AGC may be referred to as a 'synchronization signal', a 'sidelink synchronization signal', a 'sidelink reference signal', a 'midamble', an 'initial signal', a 'wake-up signal' or other terms having an equivalent technical meaning therefor.

[0242] Using symbols transmitted at the beginning of a slot, a PSCCH (1110) containing control information is transmitted, followed by a PSSCH (1115) scheduled by the control information of the PSCCH (1110). At least a portion of the SCI, which is control information, may be mapped to the PSSCH (1115). Thereafter, a GUARD (1120) and an AGC (1125) for the PSFCH exist, and a PSFCH (1130), which is a physical channel transmitting feedback information, may be mapped.

[0243] In the case of Fig. 11, PSFCH (1130) is exemplified as being located in the second symbol from the back of the slot. By securing GUARD (1120), which is an empty period of a certain period of time, between PSSCH (1115) and PSFCH (1130), a terminal that has transmitted or received PSSCH (1115) can prepare (e.g., switch between transmission and reception) to transmit or receive PSFCH (1130). In addition, AGC (1125) for PSFCH (1130) may exist. GUARD (1135), which is an empty period of a certain period of time, may exist after PSFCH (1130).

[0244] A terminal may be preset with the location of a slot in which PSFCH (1130) can be transmitted. Pre-setting may refer to a procedure in which the slot is preset during the terminal's creation process, transmitted when the terminal connects to a sidelink-related system, transmitted from a base station when connected to a base station, or transmitted from another terminal.

[0245] In the embodiment of FIG. 11, it has been described that a preamble signal for performing AGC is transmitted separately in a physical channel structure within a sidelink slot. However, according to another embodiment, instead of transmitting a separate preamble signal, it is also possible for a receiver of a receiving terminal to perform an AGC operation using a physical channel for control information or data transmission while receiving a physical channel for control information or data transmission.

[0246] FIG. 12a is a diagram illustrating a user plane wireless protocol structure of a terminal-network relay according to an embodiment of the present disclosure.

[0247] Referring to FIG. 12A, a PC5 unicast link is established / formed between a first terminal (remote terminal) (1210) and a second terminal (1220) for transmitting and receiving data, and a Uu link is established / formed between a second terminal (relay terminal) (1220) and a base station (1230) for transmitting and receiving data. The second terminal (1220) can relay data transmitted by the first terminal (1210) to the base station (1230), and the second terminal (1220) can relay data transmitted by the base station (1230) to the first terminal (1210). Data transmission and reception between the first terminal (1210) and the base station (1230) via the second terminal (1220) may be referred to as a U2N relay, and may be referred to as an indirect path in the present disclosure to clarify that it is not a direct communication link with the base station (1230). The second terminal (1220), which constitutes the indirect path from the first terminal (1210) to the base station (1230) via the second terminal (1220), may be referred to as a serving relay.

[0248] The first terminal (1210) can transmit and receive data with the base station (1230) via a U2N relay, and may be referred to as a U2N remote terminal (remote UE), remote terminal, etc. The second terminal (1220) can transmit and receive data between the first terminal (1210) and the base station (1230) via a U2N relay, and may be referred to as a U2N relay terminal (relay UE), relay terminal, etc.

[0249] For transmitting and receiving user data through an indirect path, the user plane wireless protocols of the first terminal (1210), the second terminal (1210), and the base station (1230) may include Uu-SDAP (1211-1, 1231-1), Uu-PDCP (1212, 1232), PC5-SRAP (1213, 1221) and Uu-SRAP (1225, 1233), PC5-RLC (1214, 1222) and Uu-RLC (1226, 1234), PC5-MAC (1215, 1223) and Uu-MAC (1227, 1235), PC5-PHY (1216, 1224) and Uu-PHY (1228, 1236).

[0250] The functionality of Uu-SDAP (1211-1, 1231-1) may include at least some of the following functions, but is not limited to the functions described below.

[0251] - Mapping between a PC5 QoS flow and a SL-DRB for NR sidelink communication

[0252] - Marking PC5 QoS flow ID in unicast sidelink packets (marking PC5 QoS flow ID in unicast of NR sidelink communication packets)

[0253] The main functions of Uu-PDCP (1212, 1232) may include some of the following functions, but are not limited to the functions described below.

[0254] - Transfer of data (user plane or control plane)

[0255] - Maintenance of PDCP sequence numbers (PDCP SNs)

[0256] - Header compression and decompression using the ROHC protocol

[0257] - Header compression and decompression using EHC protocol

[0258] - Compression and decompression of uplink PDCP SDUs (DEFLATE based UDC only)

[0259] - Ciphering and deciphering

[0260] - Integrity protection and integrity verification

[0261] - Timer-based SDU discard

[0262] - Routing for split bearers (For split bearers, routing)

[0263] - Duplication

[0264] - Reordering and in-order delivery

[0265] - Out-of-order delivery

[0266] - Duplicate discarding

[0267] The main functions of PC5-SRAP (1213, 1221) and Uu-SRAP (1225, 1233) may include some of the following functions, but are not limited to the functions described below.

[0268] - Data transfer

[0269] - Determination of UE ID field and BEARER ID field for data packets

[0270] - Determination of egress link

[0271] - Determination of egress RLC channel

[0272] The main functions of PC5-RLC (1214, 1222) and Uu-RLC (1226, 1234) may include, but are not limited to, some of the following functions.

[0273] - Transfer of upper layer PDUs

[0274] - Sequence numbering independent of the one in PDCP (UM and AM)

[0275] - Error Correction through ARQ (AM only)

[0276] - Segmentation (AM and UM) and re-segmentation (AM only) of RLC SDUs

[0277] - Reassembly of SDU (AM and UM)

[0278] - Duplicate Detection (AM only)

[0279] - RLC SDU discard (AM and UM)

[0280] - RLC re-establishment

[0281] - Protocol error detection (AM only)

[0282] The main functions of PC5-MAC (1215, 1223) and Uu-MAC (1227, 1235) may include at least some of the following functions, but are not limited to the functions described below.

[0283] - Mapping between logical channels and transport channels

[0284] - Multiplexing of MAC SDUs from one or more logical channels onto transport blocks (TB) to be delivered to the physical layer on transport channels

[0285] - Demultiplexing of MAC SDUs belonging to one or more logical channels (demultiplexing of MAC SDUs to one or different logical channels from transport blocks (TB) delivered from the physical layer on transport channels)

[0286] - Scheduling information reporting

[0287] - Error correction through HARQ

[0288] - Logical channel prioritization

[0289] - Priority handling between overlapping resources of one UE

[0290] - Radio resource selection

[0291] PC5-PHY (1216, 1224) and Uu-PHY (1228, 1236) can encode and modulate upper layer data to generate OFDM symbols, convert them into RF band signals, and transmit them via an antenna. In addition, the PHY layer can demodulate and decode received OFDM symbols and transmit them to the upper layer.

[0292] FIG. 12b is a diagram illustrating a control plane wireless protocol structure of a terminal-network relay according to an embodiment of the present disclosure.

[0293] Referring to FIG. 12b, a PC5 unicast link is established / formed between a first terminal (remote terminal) (1210) and a second terminal (relay terminal) (1220) for transmitting and receiving sidelink data, and a Uu link is established / formed between the second terminal (1220) and a base station (1230) for transmitting and receiving data. The second terminal (1220) can relay data transmitted by the first terminal (1210) to the base station (1230), and the second terminal (1220) can relay data transmitted by the base station (1230) to the first terminal (1210). Data transmission and reception between the first terminal (1210) and the base station (1230) via the second terminal (1220) may be referred to as a U2N relay, and may be referred to as an indirect path in the present disclosure to clarify that it is not a direct communication link with the base station (1230). The second terminal (1220), which constitutes the indirect path from the first terminal (1210) to the base station (1230) via the second terminal (1220), may be referred to as a serving relay.

[0294] For transmission and reception of control data through direct path and indirect path, the control plane wireless protocols of the first terminal (1210), the second terminal (1210), and the base station (1230) may include Uu-RRC (1211-2, 1231-2), Uu-PDCP (1212, 1232), PC5-SRAP (1213, 1221) and Uu-SRAP (1225, 1233), PC5-RLC (1214, 1222) and Uu-RLC (1226, 1234), PC5-MAC (1215, 1223) and Uu-MAC (1227, 1235), PC5-PHY (1216, 1224) and Uu-PHY (1228, 1236).

[0295] The functionality of Uu-RRC (1211-2, 1231-2) may include at least some of the following functions, but is not limited to the functions described below.

[0296] - Broadcast of System Information related to AS and NAS

[0297] - Paging initiated by 5GC or NG-RAN

[0298] - Establishment, maintenance, and release of an RRC connection between the UE and NG-RAN, including: Addition, modification, and release of carrier aggregation; Addition, modification, and release of dual connectivity in NR or between E-UTRA and NR.

[0299] - Security functions including key management

[0300] - Establishment, configuration, maintenance and release of Signaling Radio Bearers (SRBs) and Data Radio Bearers (DRBs)

[0301] - Terminal mobility support (Mobility functions including: Handover and context transfer; UE cell selection and reselection and control of cell selection and reselection; Inter-RAT mobility.)

[0302] - QoS management functions

[0303] - UE measurement reporting and control of the reporting

[0304] - Detection of and recovery from radio link failure

[0305] - NAS message transfer (NAS message transfer to / from NAS from / to UE)

[0306] FIG. 13 is a diagram illustrating an example of a signal flow of an intra-gNB Direct-to-Indirect path switch operation in a terminal-to-network relay according to an embodiment of the present disclosure.

[0307] Referring to FIG. 13, the first terminal (remote terminal) (1301) may be a terminal capable of U2N remote operation, and may be directly connected to the first base station (1303) through a path to transmit and receive uplink and downlink data (step 1304). The second terminal (relay terminal) (1302) may be a terminal capable of U2N relay operation, and is connected to the first base station (1303).

[0308] In step 1305, the first base station (1303) may transmit an RRCReconfiguration message to the first terminal (1301) including a measurement configuration for measuring cells and U2N relay terminals around the first terminal (1301). The measurement configuration may include detailed information for measuring SS / PBCH block(s) or CSI-RS in intra-frequency or inter-frequency, detailed information for measuring sidelink communication or discovery messages transmitted in a sidelink frequency or transmission pool (Tx pool), etc. In addition, the measurement configuration may include detailed information about a condition or measurement event that triggers a measurement report.

[0309] At step 1306, if the first terminal (1301) can normally apply the settings of the RRCReconfiguration message received from the first base station (1303), it can transmit an RRC reconfiguration complete message (RRCReconfigurationComplete message) to the first base station (1303).

[0310] In step 1307, the first terminal (1301) may transmit a measurement report to the first base station (1303) if a condition or measurement event that triggers a measurement report included in the measurement configuration is satisfied. The measurement report may include at least one of the physical cell identity (PCI) of the serving cell and the surrounding cells, a measurement result according to the NR measurement quantity, the L2ID of the serving relay and the surrounding relay terminal, the serving cell ID of the measured relay terminal, and a measurement result according to the sidelink measurement quantity.

[0311] At step 1308, the first base station (1303) may determine a path switch (D2I (direct to indirect) path switch) to continue providing service by changing the direct path of the first terminal (1301) to an indirect path through the second terminal (1302) based on a measurement report received from the first terminal (1301) or other information not described in the present disclosure.

[0312] At step 1309, the first base station (1303) may transmit an RRCReconfiguration message including relay terminal configuration to the second terminal (1302). The RRCReconfiguration message may include information for use in the U2N relay operation of the second terminal (1302) or for operating as a U2N relay terminal. For example, the message may include at least one of an identifier of the first terminal (1301), a local ID, Uu Relay RLC channel and PC5 Relay RLC channel configurations for servicing the first terminal (1301) as a remote terminal, mapping of a bearer and a relay RLC channel, etc.

[0313] At step 1310, if the second terminal (1302) can normally apply the settings of the RRCReconfiguration message received from the first base station (1303), it can transmit an RRCReconfigurationComplete message to the first base station (1303).

[0314] In step 1311, the first base station (1303) may transmit an RRCReconfiguration message including a path switch configuration to the first terminal (1301). The RRCReconfiguration message may include information used for U2N relay operation of the first terminal (1301) or for operating as a U2N remote terminal. For example, the message may include at least one of an identifier of the second terminal (1302), a local ID, PC5 Relay RLC channel configuration, mapping of a bearer and a relay RLC channel, etc. for U2N relay operation with the second terminal (1302) as a relay terminal.

[0315] At step 1312, the first terminal (1301) may initiate a pass switch procedure based on information included in the RRCReconfiguration received from the first base station (1303). For example, the first terminal (1301) may establish a PC5 unicast link with the second terminal (1302).

[0316] At step 1313, the first terminal (1301) can complete the path switch by transmitting an RRCReconfigurationComplete message to the first base station (1303) through an indirect path via the second terminal (1302).

[0317] At step 1314, the first terminal (1301) is connected to the first base station (1303) through an indirect path via the second terminal (1302) and can transmit and receive uplink and downlink data.

[0318] FIG. 14 is a diagram illustrating an example of a signal flow of an intra-gNB conditional Direct-to-Indirect path switch operation in a terminal-to-network relay according to an embodiment of the present disclosure.

[0319] Referring to FIG. 14, the first terminal (remote terminal) (1401) may be a terminal capable of U2N remote operation, and may be directly connected to the first base station (1403) through a path to transmit and receive uplink and downlink data (step 1406). The second terminal (relay terminal) (1402) may be a terminal capable of U2N relay operation, and is connected to the first base station (1403).

[0320] In step 1404, the first terminal (1401) may notify the first base station (1403) that it is a terminal that supports a conditional path switch operation by transmitting a UECapabilityInformation message. Information included in the UECapabilityInformation may mean that the first terminal (1401) is a terminal that supports a conditional path switch operation, or may mean that the first terminal (1401) is a terminal that supports a conditional intra-gNB Direct-to-Indirect path switch operation. Different indicators may be provided for each remote terminal and relay terminal, or information indicating that it supports operations for multiple scenarios including a conditional path switch may be expressed by one or more indicators. When the first terminal (1401) receives a terminal capability information request message (UECapabilityEnquiry message, UE capability request message) from the first base station (1403), the first terminal (1401) may transmit the UECapabilityInformation message (UE capability information message) to the first base station (1403). In this case, the UECapabilityEnquiry message may include information requesting that the first terminal (1401) report its capability regarding whether it is a terminal that supports conditional path switch operation.

[0321] In step 1405, the second terminal (1402) may notify the first base station (1403) that it is a terminal that supports a conditional path switch operation by transmitting a UECapabilityInformation message. Information included in the UECapabilityInformation may mean that the second terminal (1402) is a terminal that supports a conditional path switch operation, or may mean that the second terminal (1402) is a terminal that supports a conditional intra-gNB Direct-to-Indirect path switch operation. Different indicators may be provided for each remote terminal and relay terminal, or information indicating that it supports operations for multiple scenarios including a conditional path switch may be expressed by one or more indicators. When the second terminal (1402) receives a terminal capability information request message (UECapabilityEnquiry message) from the first base station (1403), the second terminal (1402) may transmit the UECapabilityInformation message to the first base station (1403). In this case, the UECapabilityEnquiry message may include information requesting that the second terminal (1402) report its capability as to whether it is a terminal that supports conditional path switch operation.

[0322] Although the drawing illustrates that the first terminal (1401) transmits and receives uplink and downlink data to and from the base station (1403) in step 1406 after steps 1404 and 1405 of reporting terminal capability information, the present invention is not limited thereto. For example, while the first terminal (1401) is transmitting and receiving uplink and downlink data to and from the base station (1403), the first terminal (1401) may receive a terminal capability information report request from the base station (1403) and perform an operation of reporting terminal capability information accordingly. In addition, while the first terminal (1401) is transmitting and receiving uplink and downlink data to and from the base station (1403), the second terminal (1402) may receive a terminal capability information report request from the base station (1403) and perform an operation of reporting terminal capability information accordingly.

[0323] In step 1407, the first base station (1403) may transmit an RRCReconfiguration message to the first terminal (1401) that includes a measurement configuration for measuring cells and U2N relay terminals around the first terminal (1401). The measurement configuration may include detailed information for measuring SS / PBCH block(s) or CSI-RS in intra-frequency or inter-frequency, and detailed information for measuring sidelink communication or discovery messages transmitted in a sidelink frequency or transmission pool. In addition, the measurement configuration may include detailed information about a condition or measurement event that triggers a measurement report.

[0324] At step 1408, if the first terminal (1401) can normally apply the settings of the RRCReconfiguration message received from the first base station (1403), it can transmit an RRCReconfigurationComplete message to the first base station (1403).

[0325] In step 1409, the first terminal (1401) may transmit a measurement report to the first base station (1403) if a condition or measurement event that triggers a measurement report included in the measurement configuration is satisfied. The measurement report may include at least one of the following: a measurement result according to the PCI and NR measurement quantity of the serving cell and the surrounding cells, an L2ID of the serving relay and the surrounding relay terminal, a serving cell ID of the measured relay terminal, a measurement result according to the sidelink measurement quantity, etc.

[0326] At step 1410, the first base station (1403) may determine a path switch to continue providing service by changing the direct path of the first terminal (1401) to an indirect path via the second terminal (1402) based on a measurement report or other information not described in this disclosure. At this time, the first base station (1403) may determine a conditional path switch so that the path switch operation of the first terminal (1401) is not performed immediately, but is performed only when a specific condition is satisfied (conditional D2I path switch). The conditional path switch allows the remote terminal and relay terminal to prepare the path switch more quickly, thereby reducing delays that may occur in the indirect path and inter-gNB signaling.

[0327] In step 1411, the first base station (1403) may transmit an RRCReconfiguration message including relay terminal configuration to the second terminal (1402). The RRCReconfiguration message may include information used for U2N relay operation of the second terminal (1402) or for operating as a U2N relay terminal. For example, the message may include at least one of an identifier of the first terminal (1401), a local ID, Uu Relay RLC channel and PC5 Relay RLC channel configuration for servicing the first terminal (1401) as a remote terminal, mapping of a bearer and a relay RLC channel, etc.

[0328] At step 1412, if the second terminal (1402) can normally apply the settings of the RRCReconfiguration message received from the first base station (1403), it can transmit an RRCReconfigurationComplete message to the first base station (1403).

[0329] At step 1413, the first base station (1403) may transmit an RRCReconfiguration message including a conditional path switch configuration to the first terminal (1401). The RRCReconfiguration message may include information for use in the U2N relay operation of the first terminal (1401) or for operating as a U2N remote terminal. For example, the message may include at least one of an identifier of the second terminal (1402), a local ID, a PC5 Relay RLC channel configuration, a mapping of a bearer and a relay RLC channel, etc. for the U2N relay operation with the second terminal (1402) as a relay terminal. In addition, the message may include at least one condition for applying the path switch configuration, and each configuration may be distinguished by a conditional reconfiguration ID. The conditions for applying the Path switch configuration may be conditions in which RSRP, RSRQ, SINR, etc. measured by the first terminal (1401) using SSB, CSI-RS, etc. of the first base station (1403) (e.g., PCell) are lower or higher than a specific threshold, conditions in which SL-RSRP or SD-RSRP measured by the first terminal (1401) using PSCCH DMRS or PSSCH DMRS of the second terminal (1402) (e.g., a candidate relay terminal that can be distinguished by L2ID) are lower or higher than a specific threshold, conditions in which a specific point in time has passed since the first terminal (1401) received RRCReconfiguration from the first base station (1403), or conditions in which the range of relative / absolute time is present.The first base station (1403) can set different threshold values ​​for each measurement quantity to the first terminal (1401) (for example, the threshold values ​​of SL-RSRP and SD-RSRP may be different from each other), and if no threshold value is set, the first terminal (1401) may determine that the corresponding threshold condition is always satisfied, or may use another similar threshold value (for example, SD-RSRP when SL-RSRP is not set). The first base station (1403) may use a value and / or range based on absolute time (for example, UTC) or a value and / or range based on relative time (for example, the system frame number of the base station, SFN) to indicate a specific point in time to the first terminal (1401), and the minimum unit of time may be a slot, an SFN, a subframe number, ms, etc., and multiple units may be indicated (for example, indicated in units of 100 ms), and the units of time and range may be different. The conditions for applying these path switch settings may be in the form of an event that includes the conditions described above or other conditions.

[0330] At step 1414, if the first terminal (1401) can normally apply the settings of the RRCReconfiguration message received from the first base station (1403), it can transmit an RRCReconfigurationComplete message to the first base station (1403).

[0331] In step 1415, the first terminal (1401) can evaluate whether the conditions received from the first base station (1403) are satisfied (conditional reconfiguration evaluation). If two or more conditions are set for the first terminal (1401), the first terminal (1401) can perform an operation to apply the path switch configuration if at least one of the conditions is satisfied, or if all conditions are satisfied.

[0332] At step 1416, the first terminal (1401) can initiate a pass switch procedure (conditional reset execution) based on information included in RRCReconfiguration received from the first base station (1403).

[0333] At step 1417, the first terminal (1401) can connect (establish) a PC5 unicast link with the second terminal (1402).

[0334] At step 1418, the first terminal (1401) can complete the path switch by transmitting an RRCReconfigurationComplete message to the first base station (1403) through the second terminal (1402).

[0335] At step 1419, the first terminal (1401) is connected to the first base station (1403) through an indirect path via the second terminal (1402) and can transmit and receive uplink and downlink data.

[0336] FIG. 15 is a diagram illustrating an example of a signal flow of an inter-gNB Direct-to-Indirect path switch operation in a terminal-to-network relay according to an embodiment of the present disclosure.

[0337] Referring to FIG. 15, a first terminal (remote terminal) (1501) may be a terminal capable of U2N remote operation, and may be directly connected to a first base station (1502) through a path to transmit and receive uplink and downlink data (step 1505). A second terminal (relay terminal) (1503) may be a terminal capable of U2N relay operation, and is connected to a second base station (1504).

[0338] In step 1506, the first base station (1502) may transmit an RRCReconfiguration message to the first terminal (1501) including a measurement configuration configured to measure cells and U2N relay terminals around the first terminal (1501). The measurement configuration may include at least one of detailed information for measuring SS / PBCH block(s) or CSI-RS in intra-frequency or inter-frequency, detailed information for measuring sidelink communication or discovery messages transmitted in a sidelink frequency or transmission pool, etc. In addition, the measurement configuration may include at least one of detailed information about a condition or a measurement event that triggers a measurement report.

[0339] At step 1507, if the first terminal (1501) can normally apply the settings of the RRCReconfiguration message received from the first base station (1502), it can transmit an RRCReconfigurationComplete message to the first base station (1502).

[0340] In step 1508, the first terminal (1501) may transmit a measurement report to the first base station (1502) if a condition or measurement event that triggers a measurement report included in the measurement configuration is satisfied. The measurement report may include at least one of the following: a measurement result according to the PCI and NR measurement quantity of the serving cell and the surrounding cells, an L2ID of the serving relay and the surrounding relay terminal, a serving cell ID of the measured relay terminal, a measurement result according to the sidelink measurement quantity, etc.

[0341] At step 1509, the first base station (1502) may determine a path switch to continue providing service by changing the direct path of the first terminal (1501) to an indirect path through the second terminal (1503) whose serving cell is the cell of the second base station (1504) based on a measurement report received from the first terminal (1501) or other information not described in the present disclosure (D2I path switch).

[0342] At step 1510, the first base station (1502) may transmit a handover request (message) to the second base station (1504). The handover request message may include at least one piece of information, such as the L2ID of the first terminal (1501) and a list of relay candidate terminals (e.g., the second terminal (1503)), and the relay candidate terminals included in the list of candidate terminals may be limited to relay candidate terminals that are serviced in the cell that is the target of the handover request message.

[0343] At step 1511, the second base station (1504) may perform admission control. The second base station (1504) may determine whether to allow the first terminal (1501) to perform a pass switch using information included in the handover request message transmitted by the first base station (1502) or other information not described in the present disclosure. Furthermore, when multiple candidate terminals are included, one or more target relay terminals may be selected.

[0344] At step 1512, the second base station (1504) may transmit an RRCReconfiguration message including relay terminal configuration to the second terminal (1503) (e.g., a candidate relay terminal). The RRCReconfiguration message may include information for use in the U2N relay operation of the second terminal (1503) or for operating as a U2N relay terminal. For example, the message may include at least one of an identifier of the first terminal (1501), a local ID, Uu Relay RLC channel and PC5 Relay RLC channel configurations for servicing the first terminal (1501) as a remote terminal, mapping of a bearer and a relay RLC channel, etc.

[0345] At step 1513, if the second terminal (1503) can normally apply the settings of the RRCReconfiguration message received from the second base station (1504), it can transmit an RRCReconfigurationComplete message to the second base station (1504).

[0346] At step 1514, the second base station (1504) may transmit a handover request response message to the first base station (1502). The handover request response message may include information for use in the U2N relay operation of the first terminal (1501) or for operating as a U2N remote terminal. For example, the message may include at least one of an identifier of the second terminal (1503), a local ID, a C-RNTI, PC5 Relay RLC channel setup, mapping of a bearer and a relay RLC channel, etc. for the U2N relay operation with the second terminal (1503) as a relay terminal.

[0347] At step 1515, the first base station (1502) may transmit an RRCReconfiguration message including path switch settings to the first terminal (1501). The RRCReconfiguration message may include settings included in a handover request response message transmitted by the second base station (1504) to the first base station (1502).

[0348] At step 1516, the first base station (1502) may transmit an SN status transfer message to the second base station (1504). The SN status transfer message may include a sequence number indicating an uplink PDCP reception state and a downlink PDCP transmission state of the first terminal (1501), and may be transmitted per DRB according to the characteristics of the DRB of the first terminal (1501) (e.g., RLC AM).

[0349] At step 1517, the first terminal (1501) may initiate a pass switch procedure based on information included in the RRCReconfiguration received from the first base station (1502). For example, the first terminal (1501) may connect (establish) a PC5 unicast link with the second terminal (1503).

[0350] At step 1518, the first terminal (1501) can complete the path switch by transmitting an RRCReconfigurationComplete message to the second base station (1504) through an indirect path via the second terminal (1503).

[0351] At step 1519, the second base station (1504) may transmit a UE context release message to the first base station (1502) to notify the success of the path switch of the first terminal (1501).

[0352] At step 1520, the first terminal (1501) is connected to the second base station (1504) through an indirect path via the second terminal (1503) and can transmit and receive uplink and downlink data.

[0353] FIGS. 16A and 16B are diagrams illustrating examples of signal flow of inter-gNB conditional Direct-to-Indirect path switch operation in a terminal-to-network relay according to an embodiment of the present disclosure.

[0354] Referring to FIGS. 16A and 16B, a first terminal (remote terminal) (1601) may be a terminal capable of U2N remote operation and may be directly connected to a first base station (1602) through a path to transmit and receive uplink and downlink data (step 1607). A second terminal (relay terminal) (1603) may be a terminal capable of U2N relay operation and is connected to a second base station (1604).

[0355] In step 1605, the first terminal (1601) may notify the first base station (1602) that it is a terminal that supports a conditional path switch operation by transmitting a UECapabilityInformation message. The information included in the UECapabilityInformation may mean that the first terminal (1601) is a terminal that supports a conditional path switch operation, or may mean that the first terminal (1601) is a terminal that supports a conditional inter-gNB Direct-to-Indirect path switch operation. Different indicators may be provided for each remote terminal and relay terminal, or information indicating that it supports operations for multiple scenarios including a conditional path switch may be expressed by one or more indicators. When the first terminal (1601) receives a terminal capability information request message (UECapabilityEnquiry message) from the first base station (1602), the first terminal (1601) may transmit the UECapabilityInformation message to the first base station (1602). In this case, the UECapabilityEnquiry message may include information requesting that the first terminal (1601) report its capability as to whether it is a terminal that supports conditional path switch operation.

[0356] In step 1606, the second terminal (1603) may notify the second base station (1604) that it is a terminal that supports a conditional path switch operation by transmitting a UECapabilityInformation message. The information included in the UECapabilityInformation may mean that the second terminal (1603) is a terminal that supports a conditional path switch operation, or that it is a terminal that supports a conditional inter-gNB Direct-to-Indirect path switch operation. Different indicators may be provided for each remote terminal and relay terminal, or information indicating that it supports operations for multiple scenarios including a conditional path switch may be expressed by one or more indicators. When the second terminal (1603) receives a terminal capability information request message (UECapabilityEnquiry message) from the second base station (1604), the second terminal (1603) may transmit the UECapabilityInformation message to the second base station (1604). In this case, the UECapabilityEnquiry message may include information requesting that the second terminal (1603) report its capability regarding whether it is a terminal that supports conditional path switch operation.

[0357] Although the drawing illustrates that the first terminal (1601) transmits and receives uplink and downlink data to and from the first base station (1602) in step 1607 after steps 1605 and 1606 of reporting terminal capability information, the present invention is not limited thereto. For example, while the first terminal (1601) is transmitting and receiving uplink and downlink data to and from the first base station (1602), the first terminal (1601) may receive a terminal capability information report request from the first base station (1602) and perform an operation of reporting terminal capability information accordingly. In addition, while the first terminal (1601) is transmitting and receiving uplink and downlink data to and from the first base station (1602), the second terminal (1603) may receive a terminal capability information report request from the second base station (1604) and perform an operation of reporting terminal capability information accordingly.

[0358] At step 1608, the first base station (1602) may transmit an RRCReconfiguration message to the first terminal (1601) including a measurement configuration configured to measure cells and U2N relay terminals around the first terminal (1601). The measurement configuration may include at least one of detailed information for measuring SS / PBCH block(s) or CSI-RS in intra-frequency or inter-frequency, detailed information for measuring sidelink communication or discovery message transmitted in a sidelink frequency or transmission pool, etc. In addition, the measurement configuration may include at least one of detailed information about a condition for triggering a measurement report or a measurement event.

[0359] At step 1609, if the first terminal (1601) can normally apply the settings of the RRCReconfiguration message received from the first base station (1602), it can transmit an RRCReconfigurationComplete message to the first base station (1602).

[0360] In step 1610, the first terminal (1601) may transmit a measurement report to the first base station (1602) if a condition or measurement event that triggers a measurement report included in the measurement configuration is satisfied. The measurement report may include at least one of the following: a measurement result according to the PCI and NR measurement quantity of the serving cell and the surrounding cells, an L2ID of the serving relay and the surrounding relay terminal, a serving cell ID of the measured relay terminal, a measurement result according to the sidelink measurement quantity, etc.

[0361] At step 1611, the first base station (1602) may determine a path switch to continue providing service by changing the direct path of the first terminal (1601) to an indirect path via the second terminal (1603) whose serving cell is the cell of the second base station (1604) based on a measurement report received from the first terminal (1601) or other information not described in the present disclosure. At this time, the first base station (1602) may determine a conditional path switch so that the path switch operation of the first terminal (1601) is not performed immediately, but is performed only when a specific condition is satisfied (conditional D2I path switch). The conditional path switch may enable the remote terminal and the relay terminal to prepare the path switch more quickly, thereby reducing delays that may occur in the indirect path and inter-gNB signaling.

[0362] At step 1612, the first base station (1602) may transmit a handover request to the second base station (1604). The handover request message may include at least one piece of information, such as the L2ID of the first terminal (1601) and a list of relay candidate terminals (e.g., the second terminal (1603)), and the relay candidate terminals included in the list of candidate terminals may be limited to relay candidate terminals served by the cell that is the target of the handover request message. In addition, the first base station (1602) may include an indicator indicating a conditional pass switch in the handover request message, and may include a value or indicator indicating the possibility that the first terminal (1601) may perform a pass switch to a terminal served by the corresponding cell.

[0363] At step 1613, the second base station (1604) may perform admission control. The second base station (1604) may determine whether to allow the first terminal (1601) to perform a pass switch using information included in the handover request message transmitted by the first base station (1602) or other information not described in the present disclosure. Furthermore, if multiple candidate terminals are included, one or more target relay terminals may be selected.

[0364] At step 1614, the second base station (1604) may transmit an RRCReconfiguration message including relay terminal configuration to the second terminal (1603) (e.g., a candidate relay terminal). The RRCReconfiguration message may include information for use in the U2N relay operation of the second terminal (1603) or for operating as a U2N relay terminal. For example, the message may include at least one of an identifier of the first terminal (1601), a local ID, Uu Relay RLC channel and PC5 Relay RLC channel configurations for servicing the first terminal (1601) as a remote terminal, mapping of a bearer and a relay RLC channel, etc.

[0365] At step 1615, if the second terminal (1603) can normally apply the settings of the RRCReconfiguration message received from the second base station (1604), it can transmit an RRCReconfigurationComplete message to the second base station (1604).

[0366] At step 1616, the second base station (1604) may transmit a handover request response message to the first base station (1602). The handover request response message may include information for use in the U2N relay operation of the first terminal (1601) or for operating as a U2N remote terminal. For example, the message may include at least one of an identifier of the second terminal (1603), a local ID, a C-RNTI, PC5 Relay RLC channel setup, mapping of a bearer and a relay RLC channel, etc. for the U2N relay operation with the second terminal (1603) as a relay terminal.

[0367] At step 1617, the first base station (1602) may transmit an RRCReconfiguration message including conditional path switch settings to the first terminal (1601). The RRCReconfiguration message may include settings included in a handover request response message transmitted by the second base station (1604) to the first base station (1602). In addition, the message may include at least one condition for applying the path switch settings, and each setting may be distinguished by a conditional reconfiguration ID. The conditions for applying the Path switch configuration may be conditions in which RSRP, RSRQ, SINR, etc. measured by the first terminal (1601) using SSB, CSI-RS, etc. of the first base station (1602) (e.g., PCell) are lower or higher than a specific threshold, conditions in which SL-RSRP or SD-RSRP measured by the first terminal (1601) using PSCCH DMRS or PSSCH DMRS of the second terminal (1603) (e.g., a candidate relay terminal that can be distinguished by L2ID) are lower or higher than a specific threshold, conditions in which a specific point in time has passed since the first terminal (1601) received RRCReconfiguration from the first base station (1602), or conditions in which the range of relative / absolute time is present. The first base station (1602) can set different threshold values ​​for each measurement quantity to the first terminal (1601) (for example, the threshold values ​​of SL-RSRP and SD-RSRP can be different from each other), and if no threshold value is set, the first terminal (1601) can determine that the threshold condition is always satisfied, or can use another similar threshold value (for example, SD-RSRP when SL-RSRP is not set).The first base station (1602) may use a value and / or range based on absolute time (e.g., UTC) or a value and / or range based on relative time (e.g., the base station's system frame number, SFN) to indicate a specific point in time to the first terminal (1601), and the minimum unit of time may be a slot, SFN, subframe number, ms, etc., and multiple units may be indicated as an indication unit (e.g., indicated in units of 100 ms), and the units of time and range may be different. The condition for applying such a path switch setting may be in the form of an event including the above-described conditions or other conditions.

[0368] At step 1618, if the first terminal (1601) can normally apply the settings of the RRCReconfiguration message received from the first base station (1602), the first terminal (1601) can transmit an RRCReconfigurationComplete message to the first base station (1602).

[0369] At step 1619, the first base station (1602) may transmit an Early SN status transfer message to the second base station (1604). The Early SN status transfer message may include a sequence number indicating an uplink PDCP reception status and a downlink PDCP transmission status of the first terminal (1601), and may be transmitted per DRB according to the characteristics of the DRB of the first terminal (1601) (e.g., RLC AM).

[0370] At step 1620, the first terminal (1601) can evaluate whether the conditions received from the first base station (1602) are satisfied (conditional reconfiguration evaluation). If two or more conditions are set for the first terminal (1601), the first terminal (1601) can perform an operation to apply the path switch configuration of a candidate relay terminal (e.g., the second terminal (1603)) that satisfies the conditions when at least one of the conditions is satisfied, or when all conditions are satisfied.

[0371] At step 1621, the first terminal (1601) can initiate a pass switch procedure (conditional reset execution) based on information included in RRCReconfiguration received from the first base station (1602).

[0372] At step 1622, the first terminal (1601) can connect (establish) a PC5 unicast link with the second terminal (1603).

[0373] At step 1623, the first terminal (1601) can complete the path switch by transmitting an RRCReconfigurationComplete message to the second base station (1604) through an indirect path via the second terminal (1603).

[0374] At step 1624, the second base station (1604) can transmit a handover success message to the first base station (1602) to notify the success of the path switch of the first terminal (1601).

[0375] At step 1625, the first base station (1602) may transmit an SN status transfer message to the second base station (1604). The SN status transfer message may include a sequence number indicating an uplink PDCP reception status and a downlink PDCP transmission status of the first terminal (1601), and may be transmitted per DRB according to the characteristics of the DRB of the first terminal (1601) (e.g., RLC AM).

[0376] At step 1626, the second base station (1604) may transmit a UE context release message to the first base station (1602) to notify the success of the path switch of the first terminal (1601).

[0377] At step 1627, the first terminal (1601) is connected to the second base station (1604) through an indirect path via the second terminal (1603) and can transmit and receive uplink and downlink data.

[0378] FIG. 17 is a diagram illustrating an example of a signal flow of an intra-gNB Indirect-to-Direct path switch operation in a terminal-to-network relay according to an embodiment of the present disclosure.

[0379] Referring to FIG. 17, the first terminal (remote terminal) (1701) may be a terminal capable of U2N remote operation, and may be connected to the first base station (1703) through an indirect path via the second terminal (relay terminal) (1702), which is a terminal capable of U2N relay operation, to transmit and receive uplink and downlink data (step 1704).

[0380] In operation 1705, the first base station (1703) may transmit an RRCReconfiguration message to the first terminal (1701) including a measurement configuration configured to measure cells and U2N relay terminals around the first terminal (1701). The measurement configuration may include at least one of detailed information for measuring SS / PBCH block(s) or CSI-RS in intra-frequency or inter-frequency, detailed information for measuring sidelink communication or discovery message transmitted in a sidelink frequency or transmission pool, etc. In addition, the measurement configuration may include at least one of detailed information about a condition for triggering a measurement report or a measurement event.

[0381] At step 1706, if the first terminal (1701) can normally apply the settings of the RRCReconfiguration message received from the first base station (1703), it can transmit an RRCReconfigurationComplete message to the first base station (1703).

[0382] At step 1707, the first terminal (1701) may transmit a measurement report to the first base station (1703) if a condition or measurement event that triggers a measurement report included in the measurement configuration is satisfied. The measurement report may include measurement results according to PCI and NR measurement quantities of the serving cell and neighboring cells, L2IDs of the serving relay and neighboring relay terminals, the serving cell ID of the measured relay terminal, and measurement results according to sidelink measurement quantities.

[0383] At step 1708, the first base station (1703) may determine a path switch (I2D (indirect to direct) path switch) to continue providing service by changing the indirect path of the first terminal (1701) through the second terminal (1702) to a direct path of the first base station (1703) based on a measurement report received from the first terminal (1701) or other information not described in the present disclosure.

[0384] At step 1709, the first base station (1703) may transmit an RRCReconfiguration message including path switch configuration to the first terminal (1701). The RRCReconfiguration message may include information for accessing the first base station (1703). For example, the message may include at least one of a target cell ID, a C-RNTI, a target gNB security algorithm, dedicated RACH resources, an association between RACH resources and SSB(s), an association between RACH resources and UE-specific CSI-RS configuration(s), common RACH resource(s), and system information of the target cell.

[0385] At step 1710, the first terminal (1701) may perform a random access procedure to the base station (1703). For example, the first terminal (1701) may perform random access to a corresponding cell according to the settings received from the first base station (1703) and may be allocated resources for transmitting RRCReconfigurationComplete from the first base station (1703).

[0386] At step 1711, the first terminal (1701) can complete the path switch by transmitting an RRCReconfiguration message to the first base station (1703).

[0387] At step 1712, the first base station (1703) may transmit an RRCReconfiguration message to the second terminal (1702) to release or delete the configuration for servicing the first terminal (1701) as a remote terminal. The RRCReconfiguration message may include relay terminal configuration information.

[0388] At step 1713, if the second terminal (1702) can normally apply the settings of the RRCReconfiguration message received from the first base station (1703), it can transmit an RRCReconfigurationComplete message to the first base station (1703).

[0389] At step 1714, the first terminal (1701) or the second terminal (1702) can perform a release procedure of the PC5 unicast link.

[0390] At step 1715, the first terminal (1701) is connected to the first base station (1703) through a direct pass and can transmit and receive uplink and downlink data.

[0391] FIG. 18 is a diagram illustrating an example of a signal flow of an intra-gNB conditional Indirect-to-Direct path switch operation in a terminal-to-network relay according to an embodiment of the present disclosure.

[0392] Referring to FIG. 18, the first terminal (remote terminal) (1801) may be a terminal capable of U2N remote operation, and may be connected to the first base station (1803) through an indirect path via the second terminal (relay terminal) (1802), which is a terminal capable of U2N relay operation, to transmit and receive uplink and downlink data (step 1806).

[0393] In step 1804, the first terminal (1801) may notify the first base station (1803) that it is a terminal that supports a conditional path switch operation by transmitting a UECapabilityInformation message. The information included in the UECapabilityInformation may mean that the first terminal (1801) is a terminal that supports a conditional path switch operation, or that it is a terminal that supports a conditional intra-gNB Indirect-to-Direct path switch operation. Different indicators may be provided for each remote terminal and relay terminal, or information indicating that it supports operations for multiple scenarios including a conditional path switch may be expressed by one or more indicators. When the first terminal (1801) receives a terminal capability information request message (UECapabilityEnquiry message) from the first base station (1803), the first terminal (1801) may transmit the UECapabilityInformation message to the first base station (1803). In this case, the UECapabilityEnquiry message may include information requesting that the first terminal (1801) report its capability as to whether it is a terminal that supports conditional path switch operation.

[0394] In step 1805, the second terminal (1802) may notify the first base station (1803) that it is a terminal that supports a conditional path switch operation by transmitting a UECapabilityInformation message. The information included in the UECapabilityInformation may mean that the second terminal (1802) is a terminal that supports a conditional path switch operation, or that it is a terminal that supports a conditional intra-gNB Indirect-to-Direct path switch operation. Different indicators may be used for each remote terminal and relay terminal, or information indicating that it supports operations for multiple scenarios including a conditional path switch may be expressed by one or more indicators. When the second terminal (1802) receives a terminal capability information request message (UECapabilityEnquiry message) from the first base station (1803), the second terminal (1802) may transmit the UECapabilityInformation message to the first base station (1803). In this case, the UECapabilityEnquiry message may include information requesting that the second terminal (1802) report its capability as to whether it is a terminal that supports conditional path switch operation.

[0395] Although the drawing illustrates that the first terminal (1801) transmits and receives uplink and downlink data to and from the first base station (1803) in step 1806 after steps 1804 and 1805 of reporting terminal capability information, the present invention is not limited thereto. For example, while the first terminal (1801) is transmitting and receiving uplink and downlink data to and from the first base station (1803), the first terminal (1801) may receive a terminal capability information report request from the first base station (1803) and perform an operation of reporting terminal capability information accordingly. In addition, while the first terminal (1801) is transmitting and receiving uplink and downlink data to and from the first base station (1803), the second terminal (1802) may receive a terminal capability information report request from the first base station (1803) and perform an operation of reporting terminal capability information accordingly.

[0396] At step 1807, the first base station (1803) may transmit an RRCReconfiguration message to the first terminal (1801) including a measurement configuration configured to measure cells and U2N relay terminals around the first terminal (1801). The measurement configuration may include at least one of detailed information for measuring SS / PBCH block(s) or CSI-RS in intra-frequency or inter-frequency, detailed information for measuring sidelink communication or discovery message transmitted in a sidelink frequency or transmission pool, etc. In addition, the measurement configuration may include at least one of detailed information about a condition for triggering a measurement report or a measurement event.

[0397] At step 1808, if the first terminal (1801) can normally apply the settings of the RRCReconfiguration message received from the first base station (1803), the first terminal (1801) can transmit an RRCReconfigurationComplete message to the first base station (1803).

[0398] In step 1809, the first terminal (1801) may transmit a measurement report to the first base station (1803) if a condition or measurement event that triggers a measurement report included in the measurement configuration is satisfied. The measurement report may include at least one of the following: a measurement result according to the PCI and NR measurement quantity of the serving cell and the surrounding cells, an L2ID of the serving relay and the surrounding relay terminal, a serving cell ID of the measured relay terminal, and a measurement result according to the sidelink measurement quantity.

[0399] At step 1810, the first base station (1803) may determine a path switch to continue providing service by changing the indirect path of the first terminal (1801) through the second terminal (1802) to a direct path of the first base station (1803) based on a measurement report received from the first terminal (1801) or other information not described in the present disclosure (conditional I2D path switch). At this time, the first base station (1803) may determine a conditional path switch so that the path switch operation of the first terminal (1801) is not performed immediately, but is performed only when a specific condition is satisfied. The conditional path switch can reduce delays that may occur in the indirect path and inter-gNB signaling by allowing the remote terminal and the relay terminal to prepare the path switch more quickly.

[0400] In step 1811, the first base station (1803) may transmit an RRCReconfiguration message including a path switch configuration to the first terminal (1801). The RRCReconfiguration message may include information for accessing the first base station (1803). For example, the message may include at least one of a target cell ID, a C-RNTI, a target gNB security algorithm, dedicated RACH resources, an association between RACH resources and SSB(s), an association between RACH resources and UE-specific CSI-RS configuration(s), common RACH resource(s), and system information of the target cell. In addition, at least one condition for applying the path switch configuration may be included, and each configuration may be distinguished by a conditional reconfiguration ID. The conditions for applying the Path switch configuration may be a condition in which RSRP, RSRQ, SINR, etc. measured by SSB, CSI-RS, etc. of the first terminal (1801) of the first base station (1803) (e.g., a Cell that can be distinguished by PCI) are lower or higher than a specific threshold, a condition in which SL-RSRP or SD-RSRP measured by PSCCH DMRS or PSSCH DMRS of the second terminal (1802) (e.g., a serving relay terminal that can be distinguished by L2ID) is lower or higher than a specific threshold, a condition in which a specific point in time has passed since the first terminal (1801) received RRCReconfiguration from the first base station (1803), or a condition in which a relative / absolute time range exists.The first base station (1803) can set different threshold values ​​for each measurement quantity to the first terminal (1801) (for example, the threshold values ​​of SL-RSRP and SD-RSRP can be different from each other), and if no threshold value is set, the first terminal (1801) can determine that the corresponding threshold condition is always satisfied, or can use another similar threshold value (for example, SD-RSRP when SL-RSRP is not set). The first base station (1803) can use a value and / or range based on absolute time (for example, UTC) or a value and / or range based on relative time (for example, the system frame number of the base station, SFN) to indicate a specific point in time to the first terminal (1801), and the minimum unit of time can be a slot, an SFN, a subframe number, ms, etc., and multiple units can be indicated (for example, indicated in units of 100 ms), and the units of time and range can be different. The conditions for applying these path switch settings may be in the form of an event that includes the conditions described above or other conditions.

[0401] At step 1812, if the first terminal (1801) can normally apply the settings of the RRCReconfiguration message received from the first base station (1803), it can transmit an RRCReconfigurationComplete message to the first base station (1803).

[0402] In step 1813, the first terminal (1801) can evaluate whether the conditions received from the first base station (1803) are satisfied (conditional reconfiguration evaluation). If two or more conditions are set for the first terminal (1801), the first terminal (1801) can perform an operation to apply the path switch configuration of a candidate cell (e.g., the first base station (1803)) that satisfies the conditions when at least one of the conditions is satisfied, or when all conditions are satisfied.

[0403] At step 1814, the first terminal (1801) can initiate a pass switch procedure (conditional reset execution) based on information included in RRCReconfiguration received from the first base station (1803).

[0404] At step 1815, the first terminal (1801) may perform a random access procedure to the first base station (1803). For example, the first terminal (1801) may perform random access to a corresponding cell according to the settings received from the first base station (1803) and may be allocated resources for transmitting RRCReconfigurationComplete from the first base station (1803).

[0405] At step 1816, the first terminal (1801) can complete the path switch by transmitting an RRCReconfiguration message to the first base station (1803).

[0406] At step 1817, the first base station (1803) may transmit an RRCReconfiguration message to the second terminal (1802) to release or delete the configuration for servicing the first terminal (1801) as a remote terminal. The RRCReconfiguration message may include relay terminal configuration information.

[0407] At step 1818, if the second terminal (1802) can normally apply the settings of the RRCReconfiguration message received from the first base station (1803), it can transmit an RRCReconfigurationComplete message to the first base station (1803).

[0408] At step 1819, the first terminal (1801) or the second terminal (1802) can perform a release procedure of the PC5 unicast link.

[0409] At step 1820, the first terminal (1801) is connected to the first base station (1803) through a direct pass and can transmit and receive uplink and downlink data.

[0410] FIG. 19 is a diagram illustrating an example of a signal flow of an inter-gNB Indirect-to-Direct path switch operation in a terminal-to-network relay according to an embodiment of the present disclosure.

[0411] Referring to FIG. 19, a first terminal (remote terminal) (1901) may be a terminal capable of U2N remote operation, and may be connected to a first base station (1903) through an indirect path via a second terminal (relay terminal) (1902), which is a terminal capable of U2N relay operation, to transmit and receive uplink and downlink data (step 1905).

[0412] In step 1906, the first base station (1903) may transmit an RRCReconfiguration message to the first terminal (1901) that includes a measurement configuration configured to measure cells and U2N relay terminals around the first terminal (1901). The measurement configuration may include at least one of detailed information for measuring SS / PBCH block(s) or CSI-RS in intra-frequency or inter-frequency, detailed information for measuring sidelink communication or discovery messages transmitted in a sidelink frequency or transmission pool. In addition, the measurement configuration may include at least one of detailed information about a condition or a measurement event that triggers a measurement report.

[0413] At step 1907, if the first terminal (1901) can normally apply the settings of the RRCReconfiguration message received from the first base station (1903), it can transmit an RRCReconfigurationComplete message to the first base station (1903).

[0414] In step 1908, the first terminal (1901) may transmit a measurement report to the first base station (1903) if a condition or measurement event that triggers a measurement report included in the measurement configuration is satisfied. The measurement report may include at least one of the following: a measurement result according to the PCI and NR measurement quantity of the serving cell and the surrounding cells, an L2ID of the serving relay and the surrounding relay terminal, a serving cell ID of the measured relay terminal, and a measurement result according to the sidelink measurement quantity.

[0415] At step 1909, the first base station (1903) may determine a path switch that continues to provide service by changing the indirect path of the first terminal (1901) through the second terminal (1902) to a direct path of the second base station (1904) based on a measurement report received from the first terminal (1901) or other information not described in the present disclosure (I2D path switch).

[0416] At step 1910, the first base station (1903) may transmit a handover request message to the second base station (1904). The handover request message may include at least one of a target cell ID, a KgNB, a C-RNTI used in the source gNB of the handover target UE, an RRM configuration, basic AS configuration, QoS flow and DRB mapping information, and information related to a beam reported by the UE.

[0417] At step 1911, the second base station (1904) may perform admission control. The second base station (1904) may determine whether to allow the first terminal (1901) to perform a pass switch using information included in the handover request message transmitted by the first base station (1903) or other information not described in the present disclosure.

[0418] At step 1912, the second base station (1904) may transmit a handover request response message to the first base station (1903). The handover request response message may include information for accessing the second base station (1904). For example, the message may include at least one of a target cell ID, a C-RNTI, a target gNB security algorithm, dedicated RACH resources, an association between RACH resources and SSB(s), an association between RACH resources and UE-specific CSI-RS configuration(s), common RACH resource(s), system information of the target cell, etc.

[0419] At step 1913, the first base station (1903) may transmit an RRCReconfiguration message including path switch settings to the first terminal (1901). The RRCReconfiguration message may include settings included in a handover request response message transmitted by the second base station (1904) to the first base station (1903).

[0420] At step 1914, the first base station (1903) may transmit an SN status transfer message to the second base station (1904). The SN status transfer message may include a sequence number indicating an uplink PDCP reception status and a downlink PDCP transmission status of the first terminal (1901), and may be transmitted per DRB according to the characteristics of the DRB of the first terminal (1901) (e.g., RLC AM).

[0421] At step 1915, the first terminal (1901) may perform a random access procedure to the second base station (1904). For example, the first terminal (1901) may perform random access to a target cell (e.g., a cell that can be distinguished by PCI) according to the settings received from the first base station (1903) and may be allocated resources for transmitting RRCReconfigurationComplete from the second base station (1904).

[0422] At step 1916, the first terminal (1901) can complete the path switch by transmitting an RRCReconfiguration message to the second base station (1904).

[0423] At step 1917, the second base station (1904) may transmit a UE context release message to the first base station (1903) to notify the success of the path switch of the first terminal (1901).

[0424] At step 1918, the first base station (1903) may transmit an RRCReconfiguration message to the second terminal (1902) to release or delete the configuration for servicing the first terminal (1901) as a remote terminal to the second terminal (1902). The RRCReconfiguration message may include relay terminal configuration information.

[0425] At step 1919, if the second terminal (1902) can normally apply the settings of the RRCReconfiguration message received from the first base station (1903), it can transmit an RRCReconfigurationComplete message to the first base station (1903).

[0426] At step 1920, the first terminal (1901) or the second terminal (1902) can perform a release procedure of the PC5 unicast link.

[0427] At step 1921, the first terminal (1901) is connected to the second base station (1904) through a direct pass and can transmit and receive uplink and downlink data.

[0428] FIGS. 20A and 20B are diagrams illustrating examples of signal flow of inter-gNB conditional Indirect-to-Direct path switch operation in a terminal-to-network relay according to an embodiment of the present disclosure.

[0429] Referring to FIGS. 20A and 20B, a first terminal (remote terminal) (2001) may be a terminal capable of U2N remote operation, and may be connected to a first base station (2003) through an indirect path via a second terminal (relay terminal) (2002), which is a terminal capable of U2N relay operation, to transmit and receive uplink and downlink data (step 2007).

[0430] In step 2005, the first terminal (2001) may notify the first base station (2003) that it is a terminal that supports a conditional path switch operation by transmitting a UECapabilityInformation message. Information included in the UECapabilityInformation may mean that the first terminal (2001) is a terminal that supports a conditional path switch operation, or may mean that the first terminal (2001) is a terminal that supports a conditional inter-gNB Indirect-to-Direct path switch operation. Different indicators may be provided for each remote terminal and relay terminal, or information indicating that it supports operations for multiple scenarios including a conditional path switch may be expressed by one or more indicators. When the first terminal (2001) receives a terminal capability information request message (UECapabilityEnquiry message) from the first base station (2003), the first terminal (2001) may transmit the UECapabilityInformation message to the first base station (2003). In this case, the UECapabilityEnquiry message may include information requesting that the first terminal (2001) report its capability regarding whether it is a terminal that supports conditional path switch operation.

[0431] In step 2006, the second terminal (2002) may notify the second base station (2004) that it is a terminal that supports a conditional path switch operation by transmitting a UECapabilityInformation message. The information included in the UECapabilityInformation may mean that the first terminal (2001) is a terminal that supports a conditional path switch operation, or that it is a terminal that supports a conditional inter-gNB Indirect-to-Direct path switch operation. Different indicators may be provided for each remote terminal and relay terminal, or information indicating that it supports operations for multiple scenarios including a conditional path switch may be expressed by one or more indicators. When the second terminal (2002) receives a terminal capability information request message (UECapabilityEnquiry message) from the second base station (2004), it may transmit the UECapabilityInformation message to the second base station (2004). In this case, the UECapabilityEnquiry message may include information requesting that the second terminal (2002) report its capability as to whether it is a terminal that supports conditional path switch operation.

[0432] Although the drawing illustrates that the first terminal (2001) transmits and receives uplink and downlink data to and from the first base station (2003) in step 2007 after steps 2005 and 2006 of reporting terminal capability information, it is not limited thereto. For example, while the first terminal (2001) is transmitting and receiving uplink and downlink data to and from the first base station (2003), it may perform an operation of receiving a terminal capability information report request from the first base station (2003) and reporting the terminal capability information accordingly. In addition, while the first terminal (2001) is transmitting and receiving uplink and downlink data to and from the first base station (2003), the second terminal (2002) may receive a terminal capability information report request from the first base station (2003) and report the terminal capability information accordingly.

[0433] In step 2008, the first base station (2003) may transmit an RRCReconfiguration message to the first terminal (2001) including a measurement configuration configured to measure cells and U2N relay terminals around the first terminal (2001). The measurement configuration may include at least one of detailed information for measuring SS / PBCH block(s) or CSI-RS in intra-frequency or inter-frequency, detailed information for measuring sidelink communication or discovery message transmitted in a sidelink frequency or transmission pool, etc. In addition, the measurement configuration may include at least one of detailed information about a condition for triggering a measurement report or a measurement event.

[0434] At step 2009, if the first terminal (2001) can normally apply the settings of the RRCReconfiguration message received from the first base station (2003), it can transmit an RRCReconfigurationComplete message to the first base station (2003).

[0435] In step 2010, the first terminal (2001) may transmit a measurement report to the first base station (2003) if a condition or measurement event that triggers a measurement report included in the measurement configuration is satisfied. The measurement report may include at least one of the following: a measurement result according to the PCI and NR measurement quantity of the serving cell and the surrounding cells, an L2ID of the serving relay and the surrounding relay terminal, a serving cell ID of the measured relay terminal, and a measurement result according to the sidelink measurement quantity.

[0436] At step 2011, the first base station (2003) may determine a path switch to continue providing service by changing the indirect path of the first terminal (2001) through the second terminal (2002) to a direct path of the second base station (2004) based on a measurement report received from the first terminal (2001) or other information not described in the present disclosure. At this time, the first base station (2003) may determine a conditional path switch so that the path switch operation of the first terminal (2001) is not performed immediately, but is performed only when a specific condition is satisfied (conditional I2D path switch). The conditional path switch may enable the remote terminal and the relay terminal to prepare the path switch more quickly, thereby reducing delays that may occur in the indirect path and inter-gNB signaling.

[0437] At step 2012, the first base station (2003) may transmit a handover request to the second base station (2004). The handover request message may include at least one of a target cell ID, a KgNB, a C-RNTI used in the source gNB of the handover target terminal, an RRM configuration, basic AS configuration, QoS flow and DRB mapping information, and information related to a beam reported by the UE. The first base station (2003) may include an indicator indicating a conditional pass switch in the handover request message, and may include a value or indicator indicating the possibility that the first terminal (2001) may pass switch to the corresponding cell.

[0438] In step 2013, the second base station (2004) may perform admission control. The second base station (2004) may determine whether to allow the first terminal (2001) to perform a pass switch using information included in the handover request message transmitted by the first base station (2003) or other information not described in the present disclosure.

[0439] At step 2014, the second base station (2004) may transmit a handover request response message to the first base station (2003). The handover request response message may include information for accessing the second base station (2004). For example, the message may include at least one of a target cell ID, a C-RNTI, a target gNB security algorithm, dedicated RACH resources, an association between RACH resources and SSB(s), an association between RACH resources and UE-specific CSI-RS configuration(s), common RACH resource(s), system information of the target cell, etc.

[0440] In step 2015, the first base station (2003) may transmit an RRCReconfiguration message including path switch settings to the first terminal (2001). The RRCReconfiguration message may include settings included in a handover request response message transmitted by the second base station (2004) to the first base station (2003). In addition, the message may include at least one condition for applying the path switch settings, and each setting may be distinguished by a conditional reconfiguration ID. The conditions for applying the Path switch configuration may be conditions in which RSRP, RSRQ, SINR, etc. measured by the first terminal (2001) using SSB, CSI-RS, etc. of the second base station (2004) (e.g., a candidate cell that can be distinguished by PCI) are lower or higher than a specific threshold, conditions in which SL-RSRP or SD-RSRP measured by the first terminal (2001) using PSCCH DMRS or PSSCH DMRS of the second terminal (2002) (a serving relay terminal) are lower or higher than a specific threshold, conditions in which a specific point in time has passed since the first terminal (2001) received RRCReconfiguration from the first base station (2003), or conditions in which a relative / absolute time range exists. The first base station (2003) can set different threshold values ​​for each measurement quantity to the first terminal (2001) (for example, the threshold values ​​of SL-RSRP and SD-RSRP can be different from each other), and if no threshold value is set, the first terminal (2001) can determine that the threshold condition is always satisfied, or can use another similar threshold value (for example, SD-RSRP when SL-RSRP is not set).The first base station (2003) may use a value and / or range based on absolute time (e.g., UTC) or a value and / or range based on relative time (e.g., the base station's system frame number, SFN) to indicate a specific point in time to the first terminal (2001), and the minimum unit of time may be a slot, SFN, subframe number, ms, etc., and multiple units may be indicated as an indication unit (e.g., indicated in units of 100 ms), and the units of time and range may be different. The condition for applying such a path switch setting may be in the form of an event including the above-described conditions or other conditions.

[0441] In step 2016, if the first terminal (2001) can normally apply the settings of the RRCReconfiguration message received from the first base station (2003), it can transmit an RRCReconfigurationComplete message to the first base station (2003).

[0442] At step 2017, the first base station (2003) may transmit an Early SN status transfer message to the second base station (2004). The Early SN status transfer message may include a sequence number indicating an uplink PDCP reception status and a downlink PDCP transmission status of the first terminal (2001), and may be transmitted per DRB according to the characteristics of the DRB of the first terminal (2001) (e.g., RLC AM).

[0443] In step 2018, the first terminal (2001) can evaluate whether the conditions received from the first base station (2003) are satisfied (conditional reconfiguration evaluation). If two or more conditions are set for the first terminal (2001), the first terminal (2001) can perform an operation to apply the path switch configuration of a candidate cell (e.g., the second base station (2004)) that satisfies the conditions when at least one of the conditions is satisfied, or when all conditions are satisfied.

[0444] At step 2019, the first terminal (2001) can initiate a pass switch procedure (conditional reset execution) based on information included in RRCReconfiguration received from the first base station (2003).

[0445] In step 2020, the first terminal (2001) may perform a random access procedure to the second base station (2004). For example, the first terminal (2001) may perform random access to a corresponding cell according to the settings received from the first base station (2003) and may be allocated resources for transmitting RRCReconfigurationComplete from the second base station (2004).

[0446] At step 2021, the first terminal (2001) can complete the path switch by transmitting an RRCReconfiguration message to the second base station (2004).

[0447] At step 2022, the second base station (2004) can transmit a handover success message to the first base station (2003) to notify the success of the path switch of the first terminal (2001).

[0448] At step 2023, the first base station (2003) may transmit an SN status transfer message to the second base station (2004). The SN status transfer message may include a sequence number indicating an uplink PDCP reception status and a downlink PDCP transmission status of the first terminal (2001), and may be transmitted per DRB according to the characteristics of the DRB of the first terminal (2001) (e.g., RLC AM).

[0449] At step 2024, the second base station (2004) can transmit a UE context release message to the first base station (2003) to notify the success of the path switch of the first terminal (2001).

[0450] At step 2025, the first base station (2003) may transmit an RRCReconfiguration message to the second terminal (2002) to release or delete the configuration for servicing the first terminal (2001) as a remote terminal. The RRCReconfiguration message may include relay terminal configuration information.

[0451] At step 2026, if the second terminal (2002) can normally apply the settings of the RRCReconfiguration message received from the first base station (2003), it can transmit an RRCReconfigurationComplete message to the first base station (2003).

[0452] At step 2027, the first terminal (2001) or the second terminal (2002) can proceed with the release procedure of the PC5 unicast link.

[0453] At step 2028, the first terminal (2001) is directly connected to the second base station (2004) through a path and can transmit and receive uplink and downlink data.

[0454] FIG. 21 is a diagram illustrating an example of a signal flow of an intra-gNB Indirect-to-Indirect path switch operation in a terminal-to-network relay according to an embodiment of the present disclosure.

[0455] Referring to FIG. 21, a first terminal (remote terminal) (2101) may be a terminal capable of U2N remote operation, and may be connected to a first base station (2104) through an indirect path via a second terminal (serving relay terminal) (2102), which is a terminal capable of U2N relay operation, to transmit and receive uplink and downlink data (step 2105). A third terminal (relay terminal) (2103) may be a terminal capable of U2N relay operation, and is connected to the first base station (2104).

[0456] In step 2106, the first base station (2104) may transmit an RRCReconfiguration message to the first terminal (2101) including a measurement configuration configured to measure cells and U2N relay terminals around the first terminal (2101). The measurement configuration may include at least one of detailed information for measuring SS / PBCH block(s) or CSI-RS in intra-frequency or inter-frequency, detailed information for measuring sidelink communication or discovery message transmitted in a sidelink frequency or transmission pool, etc. In addition, the measurement configuration may include at least one of detailed information about a condition or a measurement event that triggers a measurement report.

[0457] At step 2107, if the first terminal (2101) can normally apply the settings of the RRCReconfiguration message received from the first base station (2104), the first terminal (2101) can transmit an RRCReconfigurationComplete message to the first base station (2104).

[0458] In step 2108, the first terminal (2101) may transmit a measurement report to the first base station (2104) if a condition or measurement event that triggers a measurement report included in the measurement configuration is satisfied. The measurement report may include at least one of the following: a measurement result according to the PCI and NR measurement quantity of the serving cell and the surrounding cells, an L2ID of the serving relay and the surrounding relay terminal, a serving cell ID of the measured relay terminal, a measurement result according to the sidelink measurement quantity, etc.

[0459] At step 2109, the first base station (2104) may determine a path switch that continues to provide service by changing the indirect path of the first terminal (2101) through the second terminal (2102) to the indirect path through the third terminal (2103) based on the measurement report received from the first terminal (2101) or other information not described in the present disclosure (I2I (indirect to indirect) path switch).

[0460] At step 2110, the first base station (2104) may transmit an RRCReconfiguration message including relay terminal configuration to the third terminal (2103). The RRCReconfiguration message may include information used for U2N relay operation of the third terminal (2103) or for operating as a U2N relay terminal. For example, the message may include at least one of an identifier of the first terminal (2101), a local ID, Uu Relay RLC channel and PC5 Relay RLC channel configuration for servicing the first terminal (2101) as a remote terminal, mapping of a bearer and a relay RLC channel, etc.

[0461] In step 2111, if the third terminal (2103) can normally apply the settings of the RRCReconfiguration message received from the first base station (2104), it can transmit an RRCReconfigurationComplete message to the first base station (2104).

[0462] At step 2112, the first base station (2104) may transmit an RRCReconfiguration message including a path switch configuration to the first terminal (2101). The RRCReconfiguration message may include information for use in the U2N relay operation of the first terminal (2101) or for operating as a U2N remote terminal. For example, the message may include at least one of an identifier of the third terminal (2103), a local ID, PC5 Relay RLC channel configuration, mapping of a bearer and a relay RLC channel, etc. for the U2N relay operation with the third terminal (2103) as a relay terminal.

[0463] At step 2113, the first terminal (2101) may initiate a pass switch procedure based on information included in the RRCReconfiguration received from the first base station (2104). The first terminal (2101) may connect (establish) a PC5 unicast link with the third terminal (2103).

[0464] At step 2114, the first terminal (2101) can complete the path switch by transmitting an RRCReconfigurationComplete message to the first base station (2104) through an indirect path via the third terminal (2103).

[0465] At step 2115, the first base station (2104) may transmit an RRCReconfiguration message to the second terminal (2102) to release or delete the configuration for servicing the first terminal (2101) as a remote terminal. The RRCReconfiguration message may include relay terminal configuration information.

[0466] At step 2116, if the second terminal (2102) can normally apply the settings of the RRCReconfiguration message received from the first base station (2104), it can transmit an RRCReconfigurationComplete message to the first base station (2104).

[0467] At step 2117, the first terminal (2101) or the second terminal (2102) can proceed with the release procedure of the PC5 unicast link.

[0468] At step 2118, the first terminal (2101) is connected to the first base station (2104) through an indirect path via the third terminal (2103) and can transmit and receive uplink and downlink data.

[0469] FIGS. 22a and 22b are diagrams illustrating examples of signal flow of intra-gNB conditional Indirect-to-Indirect path switch operation in a terminal-to-network relay according to an embodiment of the present disclosure.

[0470] Referring to FIGS. 22A and 22B, a first terminal (remote terminal) (2201) may be a terminal capable of U2N remote operation, and may be connected to a first base station (2204) through an indirect path via a second terminal (serving relay terminal) (2202), which is a terminal capable of U2N relay operation, to transmit and receive uplink and downlink data (step 2207). A third terminal (relay terminal) (2203) may be a terminal capable of U2N relay operation, and is connected to the first base station (2204).

[0471] In step 2205, the first terminal (2201) may notify the first base station (2204) that it is a terminal that supports a conditional path switch operation by transmitting a UECapabilityInformation message. Information included in the UECapabilityInformation may mean that the first terminal (2201) is a terminal that supports a conditional path switch operation, or may mean that the first terminal (2201) is a terminal that supports a conditional intra-gNB Indirect-to-Indirect path switch operation. Different indicators may be provided for each remote terminal and relay terminal, or information indicating that it supports operations for multiple scenarios including a conditional path switch may be expressed by one or more indicators. When the first terminal (2201) receives a terminal capability information request message (UECapabilityEnquiry message) from the first base station (2204), the first terminal (2201) may transmit the UECapabilityInformation message to the first base station (2204). In this case, the UECapabilityEnquiry message may include information requesting that the first terminal (2201) report its capability regarding whether it is a terminal that supports conditional path switch operation.

[0472] In step 2206, the third terminal (2203) may transmit a UECapabilityInformation message to the first base station (2204) to inform that the third terminal (2203) is a terminal that supports a conditional path switch operation. The information included in the UECapabilityInformation may mean that the first terminal (2201) is a terminal that supports a conditional path switch operation, or that the first terminal (2201) is a terminal that supports a conditional intra-gNB Indirect-to-Indirect path switch operation. Different indicators may be used for each remote terminal and relay terminal, or information indicating that operations for multiple scenarios including a conditional path switch are supported may be expressed by one or more indicators. When the third terminal (2203) receives a terminal capability information request message (UECapabilityEnquiry message) from the first base station (2204), the third terminal (2203) may transmit the UECapabilityInformation message to the first base station (2204). In this case, the UECapabilityEnquiry message may include information requesting that the third terminal (2203) report its capability regarding whether it is a terminal that supports conditional path switch operation.

[0473] Although the drawing illustrates that the first terminal (2201) transmits and receives uplink and downlink data to and from the first base station (2204) in step 2207 after steps 2205 and 2206 of reporting terminal capability information, the present invention is not limited thereto. For example, while the first terminal (2201) is transmitting and receiving uplink and downlink data to and from the first base station (2204), the first terminal (2201) may receive a terminal capability information report request from the first base station (2204) and perform an operation of reporting terminal capability information accordingly. In addition, while the first terminal (2201) is transmitting and receiving uplink and downlink data to and from the first base station (2204), the third terminal (2203) may receive a terminal capability information report request from the first base station (2204) and perform an operation of reporting terminal capability information accordingly.

[0474] At step 2208, the first base station (2204) may transmit an RRCReconfiguration message to the first terminal (2201) including a measurement configuration configured to measure cells and U2N relay terminals around the first terminal (2201). The measurement configuration may include at least one of detailed information for measuring SS / PBCH block(s) or CSI-RS in intra-frequency or inter-frequency, detailed information for measuring sidelink communication or discovery message transmitted in a sidelink frequency or transmission pool, etc. In addition, the measurement configuration may include at least one of detailed information about a condition or a measurement event that triggers a measurement report.

[0475] At step 2209, if the first terminal (2201) can normally apply the settings of the RRCReconfiguration message received from the first base station (2204), it can transmit an RRCReconfigurationComplete message to the first base station (2204).

[0476] In step 2210, if the first terminal (2201) satisfies a condition or measurement event that triggers a measurement report included in the measurement configuration, the first terminal (2201) may transmit a measurement report to the first base station (2204). The measurement report may include at least one of the following: measurement results according to PCI and NR measurement quantities of the serving cell and neighboring cells, L2ID of the serving relay and neighboring relay terminals, serving cell ID of the measured relay terminal, measurement results according to sidelink measurement quantities, etc.

[0477] At step 2211, the first base station (2204) may determine a path switch to continue providing service by changing the indirect path of the first terminal (2201) through the second terminal (2202) to an indirect path through the third terminal based on a measurement report received from the first terminal (2201) or other information not described in the present disclosure. At this time, the first base station (2204) may determine a conditional path switch so that the path switch operation of the first terminal (2201) is not performed immediately, but is performed only when a specific condition is satisfied (conditional I2I path switch). The conditional path switch can reduce delays that may occur in the indirect path and inter-gNB signaling by allowing the remote terminal and the relay terminal to prepare the path switch more quickly.

[0478] At step 2212, the first base station (2204) may transmit an RRCReconfiguration message including relay terminal configuration to the third terminal (2203). The RRCReconfiguration message may include information for use in the U2N relay operation of the third terminal (2203) or for operating as a U2N relay terminal. For example, the message may include at least one of an identifier of the first terminal (2201), a local ID, Uu Relay RLC channel and PC5 Relay RLC channel configuration for servicing the first terminal (2201) as a remote terminal, mapping of a bearer and a relay RLC channel, etc.

[0479] At step 2213, if the third terminal (2203) can normally apply the settings of the RRCReconfiguration message received from the first base station (2204), it can transmit an RRCReconfigurationComplete message to the first base station (2204).

[0480] At step 2214, the first base station (2204) may transmit an RRCReconfiguration message including a conditional path switch configuration to the first terminal (2201). The RRCReconfiguration message may include information for use in the U2N relay operation of the first terminal (2201) or for operating as a U2N remote terminal. For example, the message may include at least one of an identifier of the third terminal (2203), a local ID, a PC5 Relay RLC channel configuration, a mapping of a bearer and a relay RLC channel, etc. for the U2N relay operation with the third terminal (2203) as a relay terminal. In addition, at least one condition for applying the path switch configuration may be included, and each configuration may be distinguished by a conditional reconfiguration ID. The conditions for applying the Path switch configuration may be a condition in which the SL-RSRP or SD-RSRP measured by the PSCCH DMRS or PSSCH DMRS of the second terminal (2202) (serving relay terminal) is lower or higher than a specific threshold value, or a condition in which the SL-RSRP or SD-RSRP measured by the PSCCH DMRS or PSSCH DMRS of the third terminal (2203) (e.g., a candidate relay terminal that can be distinguished by L2ID) is lower or higher than a specific threshold value, a condition in which a specific point in time has passed since the first terminal (2201) received RRCReconfiguration from the first base station (2204), or a condition in which the relative / absolute time range is present.The first base station (2204) can set different threshold values ​​for each measurement quantity to the first terminal (2201) (for example, the threshold values ​​of SL-RSRP and SD-RSRP may be different from each other), and if no threshold value is set, the first terminal (2201) can determine that the threshold condition is always satisfied, or can use another similar threshold value (for example, SD-RSRP when SL-RSRP is not set). The first base station (2204) can use a value and / or range based on absolute time (for example, UTC) or a value and / or range based on relative time (for example, the system frame number of the base station, SFN) to indicate a specific point in time to the first terminal (2201), and the minimum unit of time can be a slot, an SFN, a subframe number, ms, etc., and multiple units can be indicated (for example, indicated in units of 100 ms), and the units of time and range can be different. The conditions for applying these path switch settings may be in the form of an event that includes the conditions described above or other conditions.

[0481] At step 2215, if the first terminal (2201) can normally apply the settings of the RRCReconfiguration message received from the first base station (2204), it can transmit an RRCReconfigurationComplete message to the first base station (2204).

[0482] In step 2216, the first terminal (2201) can evaluate whether the conditions received from the first base station (2204) are satisfied (conditional reconfiguration evaluation). If two or more conditions are set for the first terminal (2201), the first terminal (2201) can perform an operation to apply the path switch configuration of a candidate relay terminal (e.g., the third terminal (2203)) that satisfies the conditions when at least one of the conditions is satisfied, or when all conditions are satisfied.

[0483] At step 2217, the first terminal (2201) can initiate a pass switch procedure (conditional reset execution) based on information included in RRCReconfiguration received from the first base station (2204).

[0484] At step 2218, the first terminal (2201) can connect (establish) a PC5 unicast link with the third terminal (2203).

[0485] At step 2219, the first terminal (2201) can complete the path switch by transmitting an RRCReconfigurationComplete message to the first base station (2204) through the third terminal (2203).

[0486] At step 2220, the first base station (2204) may transmit an RRCReconfiguration message to the second terminal (2202) to release or delete the configuration for servicing the first terminal (2201) as a remote terminal. The RRCReconfiguration message may include relay terminal configuration information.

[0487] In step 2221, if the second terminal (2202) can normally apply the settings of the RRCReconfiguration message received from the first base station (2204), it can transmit an RRCReconfigurationComplete message to the first base station (2204).

[0488] At step 2222, the first terminal (2201) or the second terminal (2202) can perform a release procedure of the PC5 unicast link.

[0489] At step 2223, the first terminal (2201) is connected to the first base station (2204) through an indirect path via the third terminal (2203) and can transmit and receive uplink and downlink data.

[0490] FIGS. 23A and 23B are diagrams illustrating examples of signal flow of inter-gNB Indirect-to-Indirect path switch operation in a terminal-to-network relay according to an embodiment of the present disclosure.

[0491] Referring to FIGS. 23A and 23B, a first terminal (remote terminal) (2301) may be a terminal capable of U2N remote operation, and may be connected to a first base station (2303) through an indirect path via a second terminal (serving relay terminal) (2302), which is a terminal capable of U2N relay operation, to transmit and receive uplink and downlink data (step 2306). A third terminal (relay terminal) (2304) may be a terminal capable of U2N relay operation, and is connected to a second base station (2305).

[0492] In step 2307, the first base station (2303) may transmit an RRCReconfiguration message to the first terminal (2301) including a measurement configuration configured to measure cells and U2N relay terminals around the first terminal (2301). The measurement configuration may include at least one of detailed information for measuring SS / PBCH block(s) or CSI-RS in intra-frequency or inter-frequency, detailed information for measuring sidelink communication or discovery message transmitted in a sidelink frequency or transmission pool, etc. In addition, the measurement configuration may include at least one of detailed information about a condition for triggering a measurement report or a measurement event.

[0493] At step 2308, if the first terminal (2301) can normally apply the settings of the RRCReconfiguration message received from the first base station (2303), it can transmit an RRCReconfigurationComplete message to the first base station (2303).

[0494] In step 2309, the first terminal (2301) may transmit a measurement report to the first base station (2303) if a condition or measurement event that triggers a measurement report included in the measurement configuration is satisfied. The measurement report may include at least one of the following: a measurement result according to the PCI and NR measurement quantity of the serving cell and the surrounding cells, an L2ID of the serving relay and the surrounding relay terminal, a serving cell ID of the measured relay terminal, a measurement result according to the sidelink measurement quantity, etc.

[0495] At step 2310, the first base station (2303) may determine a path switch to continue providing the service by changing the indirect path of the first terminal (2301) through the second terminal (2302) to an indirect path through the third terminal (2304) whose cell is the serving cell of the second base station (2305) based on a measurement report received from the first terminal (2301) or other information not described in the present disclosure (I2I path switch decision to another gNB via relay).

[0496] In step 2311, the first base station (2303) may transmit a handover request to the second base station (2305). The handover request message may include at least one of the L2ID of the first terminal (2301) and a list of relay candidate terminals (e.g., the second terminal (2302)), and the relay candidate terminals included in the list of candidate terminals may be limited to relay candidate terminals that are serviced in the cell that is the target of the handover request message.

[0497] At step 2312, the second base station (2305) may perform admission control. The second base station (2305) may determine whether to allow the first terminal (2301) to perform a pass switch using information included in the handover request message transmitted by the first base station (2303) or other information not described in the present disclosure. Furthermore, when multiple candidate terminals are included, one or more target relay terminals may be selected.

[0498] At step 2313, the second base station (2305) may transmit an RRCReconfiguration message including relay terminal configuration to the third terminal (2304) (e.g., the selected target relay terminal). The RRCReconfiguration message may include information for use in the U2N relay operation of the third terminal (2304) or for operating as a U2N relay terminal. For example, the message may include at least one of an identifier of the first terminal (2301), a local ID, Uu Relay RLC channel and PC5 Relay RLC channel configurations for servicing the first terminal (2301) as a remote terminal, mapping of a bearer and a relay RLC channel, etc.

[0499] At step 2314, if the third terminal (2304) can normally apply the settings of the RRCReconfiguration message received from the second base station (2305), it can transmit an RRCReconfigurationComplete message to the second base station (2305).

[0500] At step 2315, the second base station (2305) may transmit a handover request response message to the first base station (2303). The handover request response message may include information for use in the U2N relay operation of the first terminal (2301) or for operating as a U2N remote terminal. For example, the message may include at least one of an identifier of the third terminal (2304), a local ID, a C-RNTI, PC5 Relay RLC channel setup, mapping of a bearer and a relay RLC channel, etc. for the U2N relay operation with the third terminal (2304) as a relay terminal.

[0501] At step 2316, the first base station (2303) may transmit an RRCReconfiguration message including path switch settings to the first terminal (2301). The RRCReconfiguration message may include settings included in a handover request response message transmitted by the second base station (2305) to the first base station (2303).

[0502] At step 2317, the first base station (2303) may transmit an SN status transfer message to the second base station (2305). The SN status transfer message may include a sequence number indicating an uplink PDCP reception status and a downlink PDCP transmission status of the first terminal (2301), and may be transmitted per DRB according to the characteristics of the DRB of the first terminal (2301) (e.g., RLC AM).

[0503] At step 2318, the first terminal (2301) may initiate a pass switch procedure based on information included in the RRCReconfiguration received from the first base station (2303). The first terminal (2301) may connect (establish) a PC5 unicast link with the second terminal (2302).

[0504] At step 2319, the first terminal (2301) can complete the path switch by transmitting an RRCReconfigurationComplete message to the second base station (2305) through an indirect path via the third terminal (2304).

[0505] At step 2320, the second base station (2305) can transmit a UE context release message to the first base station (2303) to notify the success of the path switch of the first terminal (2301).

[0506] At step 2321, the first base station (2303) may transmit an RRCReconfiguration message to the second terminal (2302) to release or delete the configuration for servicing the first terminal (2301) as a remote terminal. The RRCReconfiguration message may include relay terminal configuration information.

[0507] At step 2322, if the second terminal (2302) can normally apply the settings of the RRCReconfiguration message received from the first base station (2303), it can transmit an RRCReconfigurationComplete message to the first base station (2303).

[0508] At step 2323, the first terminal (2301) or the second terminal (2302) can proceed with the release procedure of the PC5 unicast link.

[0509] At step 2324, the first terminal (2301) is connected to the second base station (2305) through an indirect path via the third terminal and can transmit and receive uplink and downlink data.

[0510] FIGS. 24A and 24B are diagrams illustrating examples of signal flows of inter-gNB conditional Indirect-to-Indirect path switch operations in a terminal-to-network relay according to an embodiment of the present disclosure.

[0511] Referring to FIGS. 24A and 24B, a first terminal (remote terminal) (2401) may be a terminal capable of U2N remote operation, and may be connected to a first base station (2403) through an indirect path via a second terminal (serving relay terminal) (2402), which is a terminal capable of U2N relay operation, to transmit and receive uplink and downlink data (step 2408). A third terminal (relay terminal) (2404) may be a terminal capable of U2N relay operation, and is connected to a second base station (2405).

[0512] In step 2406, the first terminal (2401) may notify the first base station (2403) that it is a terminal that supports a conditional path switch operation by transmitting a UECapabilityInformation message. The information included in the UECapabilityInformation may mean that the first terminal (2401) is a terminal that supports a conditional path switch operation, or that it is a terminal that supports a conditional inter-gNB Indirect-to-Indirect path switch operation. Different indicators may be provided for each remote terminal and relay terminal, or information indicating that it supports operations for multiple scenarios including a conditional path switch may be expressed by one or more indicators. When the first terminal (2401) receives a terminal capability information request message (UECapabilityEnquiry message) from the first base station (2403), the first terminal (2401) may transmit the UECapabilityInformation message to the first base station (2403). In this case, the UECapabilityEnquiry message may include information requesting that the first terminal (2401) report its capability regarding whether it is a terminal that supports conditional path switch operation.

[0513] In step 2407, the third terminal (2404) may notify the second base station (2405) that it is a terminal that supports a conditional path switch operation by transmitting a UECapabilityInformation message. The information included in the UECapabilityInformation may mean that the first terminal (2401) is a terminal that supports a conditional path switch operation, or that it is a terminal that supports a conditional inter-gNB Indirect-to-Indirect path switch operation. Different indicators may be provided for each remote terminal and relay terminal, or information indicating that it supports operations for multiple scenarios including a conditional path switch may be expressed by one or more indicators. When the third terminal (2404) receives a terminal capability information request message (UECapabilityEnquiry message) from the second base station (2405), it may transmit the UECapabilityInformation message to the second base station (2405). In this case, the UECapabilityEnquiry message may include information requesting that the third terminal (2404) report its capability as to whether it is a terminal that supports conditional path switch operation.

[0514] Although the drawing illustrates that the first terminal (2401) transmits and receives uplink and downlink data to and from the first base station (2403) in step 2408 after steps 2406 and 2407 of reporting terminal capability information, the present invention is not limited thereto. For example, while the first terminal (2401) is transmitting and receiving uplink and downlink data to and from the first base station (2403), the first terminal (2401) may receive a terminal capability information report request from the first base station (2403) and perform an operation of reporting terminal capability information accordingly. In addition, while the first terminal (2401) is transmitting and receiving uplink and downlink data to and from the first base station (2403), the third terminal (2404) may receive a terminal capability information report request from the second base station (2405) and perform an operation of reporting terminal capability information accordingly.

[0515] In step 2409, the first base station (2403) may transmit an RRCReconfiguration message to the first terminal (2401) including a measurement configuration configured to measure cells and U2N relay terminals around the first terminal (2401). The measurement configuration may include at least one of detailed information for measuring SS / PBCH block(s) or CSI-RS in intra-frequency or inter-frequency, detailed information for measuring sidelink communication or discovery messages transmitted in a sidelink frequency or transmission pool, etc. In addition, the measurement configuration may include at least one of detailed information about a condition for triggering a measurement report or a measurement event.

[0516] At step 2410, if the first terminal (2401) can normally apply the settings of the RRCReconfiguration message received from the first base station (2403), the first terminal (2401) can transmit an RRCReconfigurationComplete message to the first base station (2403).

[0517] In step 2411, if a condition or measurement event that triggers a measurement report included in the measurement configuration is satisfied, the first terminal (2401) may transmit a measurement report to the first base station (2403). The measurement report may include at least one of the following: a measurement result according to the PCI and NR measurement quantity of the serving cell and the surrounding cells, an L2ID of the serving relay and the surrounding relay terminal, a serving cell ID of the measured relay terminal, and a measurement result according to the sidelink measurement quantity.

[0518] At step 2412, the first base station (2403) may determine a path switch to continue providing service by changing the indirect path of the first terminal (2401) through the second terminal (2402) to an indirect path through the third terminal (2404) whose cell of the second base station (2405) is the serving cell, based on the measurement report received from the first terminal (2401) or other information not described in the present disclosure. At this time, the first base station (2403) may determine a conditional path switch so that the path switch operation of the first terminal (2401) is not performed immediately, but is performed only when a specific condition is satisfied (conditional I2I path switch decision to another gNB via relay). The conditional path switch may enable the remote terminal and the relay terminal to prepare the path switch more quickly, thereby reducing delays that may occur in the indirect path and inter-gNB signaling.

[0519] At step 2413, the first base station (2403) may transmit a handover request to the second base station (2405). The handover request message may include at least one of the L2ID of the first terminal (2401) and a list of relay candidate terminals (e.g., the second terminal (2402)), and the relay candidate terminals included in the list of candidate terminals may be limited to relay candidate terminals served by the cell that is the target of the handover request message. The first base station (2403) may include an indicator indicating a conditional pass switch in the handover request message, and may include a value or indicator indicating the possibility that the first terminal (2401) may perform a pass switch to a terminal served by the corresponding cell.

[0520] At step 2414, the second base station (2405) may perform admission control. The second base station (2405) may determine whether to allow the first terminal (2401) to perform a pass switch using information included in the handover request message transmitted by the first base station (2403) or other information not described in the present disclosure. Furthermore, if multiple candidate terminals are included, one or more target relay terminals may be selected.

[0521] At step 2415, the second base station (2405) may transmit an RRCReconfiguration message including relay terminal configuration to the third terminal (2404) (e.g., the selected target relay terminal). The RRCReconfiguration message may include information for use in the U2N relay operation of the third terminal (2404) or for operating as a U2N relay terminal. For example, the message may include at least one of an identifier of the first terminal (2401), a local ID, Uu Relay RLC channel and PC5 Relay RLC channel configuration for servicing the first terminal (2401) as a remote terminal, mapping of a bearer and a relay RLC channel, etc.

[0522] At step 2416, if the third terminal (2404) can normally apply the settings of the RRCReconfiguration message received from the second base station (2405), it can transmit an RRCReconfigurationComplete message to the second base station (2405).

[0523] At step 2417, the second base station (2405) may transmit a handover request response message to the first base station (2403). The handover request response message may include information for use in the U2N relay operation of the first terminal (2401) or for operating as a U2N remote terminal. For example, the message may include at least one of an identifier of the third terminal (2404), a local ID, a C-RNTI, PC5 Relay RLC channel setup, mapping of a bearer and a relay RLC channel, etc. for the U2N relay operation with the third terminal (2404) as a relay terminal.

[0524] At step 2418, the first base station (2403) may transmit an RRCReconfiguration message including conditional path switch settings to the first terminal (2401). The RRCReconfiguration message may include settings included in a handover request response message transmitted by the second base station (2405) to the first base station (2403). In addition, the message may include at least one condition for applying the path switch settings, and each setting may be distinguished by a conditional reconfiguration ID. The conditions for applying the Path switch configuration may be a condition in which the SL-RSRP or SD-RSRP measured by the PSCCH DMRS or PSSCH DMRS of the second terminal (2402) (serving relay terminal) is lower or higher than a specific threshold value, or a condition in which the SL-RSRP or SD-RSRP measured by the PSCCH DMRS or PSSCH DMRS of the third terminal (2404) (e.g., a candidate relay terminal that can be distinguished by L2ID) is lower or higher than a specific threshold value, a condition in which a specific point in time has passed since the first terminal (2401) received RRCReconfiguration from the first base station (2403), or a condition in which the relative / absolute time range is present. The first base station (2403) can set different threshold values ​​for each measurement quantity to the first terminal (2401) (for example, the threshold values ​​of SL-RSRP and SD-RSRP can be different from each other), and if no threshold value is set, the first terminal (2401) can determine that the threshold condition is always satisfied, or can use another similar threshold value (for example, SD-RSRP when SL-RSRP is not set).The first base station (2403) may use a value and / or range based on absolute time (e.g., UTC) or a value and / or range based on relative time (e.g., the base station's system frame number, SFN) to indicate a specific point in time to the first terminal (2401), and the minimum unit of time may be a slot, SFN, subframe number, ms, etc., and multiple units may be indicated as an indication unit (e.g., indicated in units of 100 ms), and the units of time and range may be different. The condition for applying such a path switch setting may be in the form of an event including the above-described conditions or other conditions.

[0525] At step 2419, if the first terminal (2401) can normally apply the settings of the RRCReconfiguration message received from the first base station (2403), it can transmit an RRCReconfigurationComplete message to the first base station (2403).

[0526] At step 2420, the first base station (2403) may transmit an Early SN status transfer message to the second base station (2405). The Early SN status transfer message may include a sequence number indicating an uplink PDCP reception status and a downlink PDCP transmission status of the first terminal (2401), and may be transmitted for each DRB according to the characteristics of the DRB of the first terminal (2401) (e.g., RLC AM).

[0527] In step 2421, the first terminal (2401) can evaluate whether the conditions received from the first base station (2403) are satisfied (conditional reconfiguration evaluation). If two or more conditions are set for the first terminal (2401), the first terminal (2401) can perform an operation to apply the path switch configuration of a candidate relay terminal (e.g., the third terminal (2404)) that satisfies the conditions when at least one of the conditions is satisfied, or when all conditions are satisfied.

[0528] At step 2422, the first terminal (2401) can initiate a pass switch procedure (conditional reset execution) based on information included in RRCReconfiguration received from the first base station (2403).

[0529] At step 2423, the first terminal (2401) can connect (establish) a PC5 unicast link with the third terminal (2404).

[0530] At step 2424, the first terminal (2401) can complete the path switch by transmitting an RRCReconfigurationComplete message to the second base station (2405) through an indirect path via the third terminal (2404).

[0531] At step 2425, the second base station (2405) can transmit a handover success message to the first base station (2403) to notify the success of the path switch of the first terminal (2401).

[0532] At step 2426, the first base station (2403) may transmit an SN status transfer message to the second base station (2405). The SN status transfer message may include a sequence number indicating an uplink PDCP reception status and a downlink PDCP transmission status of the first terminal (2401), and may be transmitted per DRB according to the characteristics of the DRB of the first terminal (2401) (e.g., RLC AM).

[0533] At step 2427, the second base station (2405) can transmit a UE context release message to the first base station (2403) to notify the success of the path switch of the first terminal (2401).

[0534] At step 2428, the first base station (2403) may transmit an RRCReconfiguration message to the second terminal (2402) to release or delete the configuration for servicing the first terminal (2401) as a remote terminal. The RRCReconfiguration message may include relay terminal configuration information.

[0535] At step 2429, if the second terminal (2402) can normally apply the settings of the RRCReconfiguration message received from the first base station (2403), it can transmit an RRCReconfigurationComplete message to the first base station (2403).

[0536] At step 2430, the first terminal (2401) or the second terminal (2402) can perform a release procedure of the PC5 unicast link.

[0537] At step 2431, the first terminal (2401) is connected to the second base station (2405) through an indirect path via the third terminal and can transmit and receive uplink and downlink data.

[0538] FIGS. 25A and 25B are diagrams illustrating examples of signal flows of conditional path switch operations of multiple base stations and multiple relay terminals in a terminal-to-network relay according to an embodiment of the present disclosure.

[0539] Referring to FIGS. 25a and 25b, a first terminal (remote terminal) (2501) may be a terminal capable of U2N remote operation and is connected to a first base station (2502), a second terminal (first relay terminal) (2503) may be a terminal capable of U2N relay operation and is connected to a second base station (2504), and a third terminal (second relay terminal) (2505) may be a terminal capable of U2N relay operation and is connected to a third base station (2506).

[0540] Although not shown, a request and reporting procedure for terminal capability information indicating whether a terminal supports conditional path switch operation can be performed between a first terminal (2501) and a first base station (2502), between a second terminal (2503) and a second base station (2504), and between a third terminal (2505) and a third base station (2506).

[0541] In step 2507, the first base station (2502) may transmit an RRCReconfiguration message to the first terminal (2501) including a measurement configuration configured to measure cells and U2N relay terminals around the first terminal (2501). The measurement configuration may include at least one of detailed information for measuring SS / PBCH block(s) or CSI-RS in intra-frequency or inter-frequency, detailed information for measuring sidelink communication or discovery message transmitted in a sidelink frequency or transmission pool, etc. In addition, the measurement configuration may include at least one of detailed information about a condition for triggering a measurement report or a measurement event.

[0542] At step 2508, if the first terminal (2501) can normally apply the settings of the RRCReconfiguration message received from the first base station (2502), it can transmit an RRCReconfigurationComplete message to the first base station (2502).

[0543] In step 2509, the first terminal (2501) may transmit a measurement report to the first base station (2502) if a condition or measurement event that triggers a measurement report included in the measurement configuration is satisfied. The measurement report may include at least one of the following: a measurement result according to the PCI and NR measurement quantity of the serving cell and the surrounding cells, an L2ID of the serving relay and the surrounding relay terminal, a serving cell ID of the measured relay terminal, and a measurement result according to the sidelink measurement quantity.

[0544] At step 2510, if the first base station (2502) determines that it is possible for the first terminal (2501) to change to an indirect path via the second terminal (2503) whose cell of the second base station (2504) is a serving cell or an indirect path via the third terminal (2505) whose cell of the third base station (2506) is a serving cell based on a measurement report received from the first terminal (2501) or other information not described in the present disclosure, the first base station (2502) may determine a conditional path switch that is performed in parallel to multiple base stations and multiple candidate relay terminals (conditional D2I path switch decision to another gNB via relay).

[0545] In step 2511, the first base station (2502) may transmit a handover request in parallel to the second base station (2504) and the third base station (2506). The handover request message may include at least one of the L2ID of the first terminal (2501) and a list of relay candidate terminals (e.g., the second terminal (2503) or the third terminal (2505)), and the relay candidate terminals included in the list of candidate terminals may be limited to relay candidate terminals that are serviced in the cell that is the target of the handover request message.

[0546] At step 2512, the second base station (2504) and the third base station (2506) may perform admission control. The second base station (2504) and the third base station (2506) may determine whether to allow the first terminal (2501) to perform a pass switch using information included in the handover request message transmitted by the first base station (2502) or other information not described in the present disclosure. In addition, when multiple candidate terminals are included, one or more target relay terminals may be selected.

[0547] At step 2513, the second base station (2504) can transmit an RRCReconfiguration message including relay terminal settings to the second terminal (2503) (e.g., the target relay terminal selected by the second base station (2504), and the third base station (2506) can transmit an RRCReconfiguration message including relay terminal settings to the third terminal (2505) (e.g., the target relay terminal selected by the third base station (2506). The RRCReconfiguration message can include information used for U2N relay operation of the second terminal (2503) or the third terminal (2505) or for operating as a U2N relay terminal. For example, the message can include at least one of an identifier of the first terminal (2501) for servicing the first terminal (2501) as a remote terminal, a local ID, Uu Relay RLC channel and PC5 Relay RLC channel settings, mapping of bearer and relay RLC channels, etc.

[0548] In step 2514, if the second terminal (2503) can normally apply the settings of the RRCReconfiguration message received from the second base station (2504), it can transmit an RRCReconfigurationComplete message to the second base station (2504), and if the third terminal (2505) can normally apply the settings of the RRCReconfiguration message received from the third base station (2506), it can transmit an RRCReconfigurationComplete message to the third base station (2506).

[0549] At step 2515, the second base station (2504) may transmit a handover request response message to the first base station (2502). The handover request response message may include information for use in the U2N relay operation of the first terminal (2501) or for operating as a U2N remote terminal. For example, the message may include at least one of an identifier of the second terminal (2503), a local ID, a C-RNTI, PC5 Relay RLC channel setup, mapping of a bearer and a relay RLC channel, etc. for the U2N relay operation with the second terminal (2503) as a relay terminal.

[0550] At step 2516, the third base station (2506) may transmit a handover request response message to the first base station (2502). The handover request response message may include information for use in the U2N relay operation of the first terminal (2501) or for operating as a U2N remote terminal. For example, the message may include at least one of an identifier of the third terminal (2505), a local ID, a C-RNTI, PC5 Relay RLC channel setup, mapping of a bearer and a relay RLC channel, etc. for the U2N relay operation with the third terminal (2505) as a relay terminal.

[0551] At step 2517, the first base station (2502) may transmit an RRCReconfiguration message including a conditional path switch configuration to the first terminal (2501). The RRCReconfiguration message may include the configuration included in the handover request response message transmitted by the second base station (2504) to the first base station (2502) and the configuration included in the handover request response message transmitted by the third base station (2506) to the first base station (2502). In addition, at least one condition for applying the path switch configuration may be included, and each configuration may be distinguished by a conditional reconfiguration ID. The conditions for applying the Path switch configuration may be a condition in which the RSRP, RSRQ, SINR, etc. measured by the SSB, CSI-RS, etc. of the first terminal (2501) of the first base station (2502) (e.g., PCell) are lower or higher than a specific threshold, a condition in which the SL-RSRP or SD-RSRP measured by the PSCCH DMRS or PSSCH DMRS of the second terminal (2503) (e.g., candidate relay terminal) are lower or higher than a specific threshold, a condition in which the SL-RSRP or SD-RSRP measured by the PSCCH DMRS or PSSCH DMRS of the third terminal (2505) (e.g., candidate relay terminal) are lower or higher than a specific threshold, a condition in which a specific point in time has passed since the first terminal (2501) received RRCReconfiguration from the first base station (2502), or a condition in which the range of relative / absolute time is present.The first base station (2502) can set different threshold values ​​for each measurement quantity to the first terminal (2501) (for example, the threshold values ​​of SL-RSRP and SD-RSRP may be different from each other), and if no threshold value is set, the first terminal (2501) can determine that the corresponding threshold condition is always satisfied, or can use another similar threshold value (for example, SD-RSRP when SL-RSRP is not set). The first base station (2502) can use a value and / or range based on absolute time (for example, UTC) or a value and / or range based on relative time (for example, the system frame number of the base station, SFN) to indicate a specific point in time to the first terminal (2501), and the minimum unit of time can be a slot, an SFN, a subframe number, ms, etc., and multiple units can be indicated (for example, indicated in units of 100 ms), and the units of time and range can be different. The conditions for applying these path switch settings may be in the form of an event that includes the conditions described above or other conditions.

[0552] At step 2518, if the first terminal (2501) can normally apply the settings of the RRCReconfiguration message received from the first base station (2502), it can transmit an RRCReconfigurationComplete message to the first base station (2502).

[0553] At step 2519, the first base station (2502) may transmit an Early SN status transfer message to the second base station (2504). The Early SN status transfer message may include a sequence number indicating an uplink PDCP reception status and a downlink PDCP transmission status of the first terminal (2501), and may be transmitted per DRB according to the characteristics of the DRB of the first terminal (2501) (e.g., RLC AM).

[0554] At step 2520, the first base station (2502) may transmit an Early SN status transfer message to the third base station (2506). The Early SN status transfer message may include a sequence number indicating an uplink PDCP reception status and a downlink PDCP transmission status of the first terminal (2501), and may be transmitted for each DRB according to the characteristics of the DRB of the first terminal (2501) (e.g., RLC AM).

[0555] In step 2521, the first terminal (2501) can evaluate whether the conditions received from the first base station (2502) are satisfied (conditional reconfiguration evaluation). If two or more conditions are set for the first terminal (2501), the first terminal (2501) can perform an operation to apply the path switch configuration of a candidate relay terminal (e.g., the second terminal (2503)) that satisfies the conditions when at least one of the conditions is satisfied, or when all conditions are satisfied.

[0556] At step 2522, the first terminal (2501) can initiate a pass switch procedure (conditional reset execution) based on information included in RRCReconfiguration received from the first base station (2502).

[0557] At step 2523, the first terminal (2501) can connect (establish) a PC5 unicast link with the second terminal (2503).

[0558] At step 2524, the first terminal (2501) can complete the path switch by transmitting an RRCReconfigurationComplete message to the second base station (2504) through an indirect path via the second terminal (2503).

[0559] At step 2525, the second base station (2504) can transmit a handover success message to the first base station (2502) to notify the success of the path switch of the first terminal (2501).

[0560] At step 2526, the first base station (2502) may transmit an SN status transfer message to the second base station (2504). The SN status transfer message may include a sequence number indicating an uplink PDCP reception status and a downlink PDCP transmission status of the first terminal (2501), and may be transmitted per DRB according to the characteristics of the DRB of the first terminal (2501) (e.g., RLC AM).

[0561] At step 2527, the second base station (2504) may transmit a UE context release message to the first base station (2502) to notify the success of the path switch of the first terminal (2501). Although not shown in the drawing, if a conditional path switch is being performed on two or more different candidate relay terminals in the second base station (2504) or the same cell of the second base station (2504), since the first terminal (2501) has connected to one of the relay terminals, it is determined that the path switch is no longer performed on the remaining terminals, and an RRCReconfiguration message may be transmitted to the unconnected candidate terminals to release or delete the configuration for servicing the first terminal (2501) as a remote terminal. The RRCReconfiguration message may include relay terminal configuration information.

[0562] At step 2528, the first base station (2502) may transmit a handover cancellation message to the third base station (2506) to inform the first terminal (2501) that it will no longer perform a path switch to the third base station (2506) or a cell of the third base station (2506) or a candidate relay terminal that serves the cell of the third base station (2506).

[0563] At step 2529, the third base station (2506) can transmit an RRCReconfiguration message to the third terminal (2505) to release or delete the configuration for servicing the first terminal (2501) as a remote terminal configured for the third terminal (2505). The RRCReconfiguration message can include relay terminal configuration information. Although not shown in the drawing, if a conditional path switch is in progress for two or more different candidate relay terminals in the same cell of the third base station (2506) or the third base station (2506), the RRCReconfiguration message can be transmitted to the unconnected candidate terminals when it is determined that the path switch is no longer in progress, to release or delete the configuration for servicing the first terminal (2501) as a remote terminal.

[0564] At step 2530, if the second terminal (2503) can normally apply the settings of the RRCReconfiguration message received from the third base station (2506), it can transmit an RRCReconfigurationComplete message to the third base station (2506).

[0565] At step 2531, the first terminal (2501) is connected to the second base station (2504) through an indirect path via the second terminal and can transmit and receive uplink and downlink data.

[0566] Although Figure 25 illustrates a Direct-to-Indirect path switch as an example, it can also be applied to various path switch scenarios not included in the example in the drawing.

[0567] FIG. 26a and FIG. 26b are diagrams illustrating examples of signal flow of a path switch according to the RRC connection status of a relay terminal in a terminal-to-network relay according to an embodiment of the present disclosure.

[0568] Referring to FIGS. 26a and 26b, a first terminal (remote terminal) (2601) may be a terminal capable of U2N remote operation and is directly connected to a first base station (2602) via a path. A second terminal (relay terminal) (2603) may be a terminal capable of U2N relay operation and is in an RRC connected state with a second base station (2604).

[0569] In step 2605, the first terminal (2601) may notify the first base station (2602) that it is a terminal that supports a conditional path switch operation by transmitting a UECapabilityInformation message. The information included in the UECapabilityInformation may mean that the first terminal (2601) is a terminal that supports a conditional path switch operation, or that it is a terminal that supports a conditional intra-gNB Direct-to-Indirect path switch operation, or that it is a terminal that supports a conditional intra-gNB Direct-to-Indirect path switch operation to a candidate relay terminal in an RRC CONNECTED state. Different indicators may be provided for each remote terminal and relay terminal, or information indicating that it supports operations for multiple scenarios including a conditional path switch may be expressed by one or more indicators. When the first terminal (2601) receives a terminal capability information request message (UECapabilityEnquiry message) from the first base station (2602), the first terminal (2601) may transmit the UECapabilityInformation message to the first base station (2602). In this case, the UECapabilityEnquiry message may include information requesting that the first terminal (2601) report its capability as to whether it is a terminal that supports conditional path switch operation.

[0570] In step 2606, the second terminal (2603) may notify the second base station (2604) that it is a terminal that supports a conditional path switch operation by transmitting a UECapabilityInformation message. The information included in the UECapabilityInformation may mean that the second terminal (2603) is a terminal that supports a conditional path switch operation, a terminal that supports a conditional Direct-to-Indirect path switch operation, or a relay terminal that supports a conditional intra-gNB Direct-to-Indirect path switch operation in an RRC CONNECTED state. Different indicators may be provided for each remote terminal and relay terminal, or information indicating that it supports operations for multiple scenarios including a conditional path switch may be expressed by one or more indicators. When the second terminal (2603) receives a terminal capability information request message (UECapabilityEnquiry message) from the second base station (2604), the second terminal (2603) may transmit the UECapabilityInformation message to the second base station (2604). In this case, the UECapabilityEnquiry message may include information requesting that the second terminal (2603) report its capability as to whether it is a terminal that supports conditional path switch operation.

[0571] In step 2607, the first base station (2602) may transmit an RRCReconfiguration message to the first terminal (2601) including a measurement configuration configured to measure cells and U2N relay terminals around the first terminal (2601). The measurement configuration may include at least one of detailed information for measuring SS / PBCH block(s) or CSI-RS in intra-frequency or inter-frequency, detailed information for measuring sidelink communication or discovery message transmitted in a sidelink frequency or transmission pool, etc. In addition, the measurement configuration may include at least one of detailed information about a condition or a measurement event that triggers a measurement report.

[0572] At step 2608, if the first terminal (2601) can normally apply the settings of the RRCReconfiguration message received from the first base station (2602), it can transmit an RRCReconfigurationComplete message to the first base station (2602).

[0573] In step 2609, the first terminal (2601) may transmit a measurement report to the first base station (2602) if a condition or measurement event that triggers a measurement report included in the measurement configuration is satisfied. The measurement report may include at least one of the following: a measurement result according to the PCI and NR measurement quantity of the serving cell and the surrounding cells, an L2ID of the serving relay and the surrounding relay terminal, a serving cell ID of the measured relay terminal, a measurement result according to the sidelink measurement quantity, etc.

[0574] At step 2610, the first base station (2602) may determine a path switch to continue providing service by changing the direct path of the first terminal (2601) to an indirect path via the second terminal (2603) whose serving cell is the cell of the second base station (2604) based on the measurement report received from the first terminal (2601) or other information not described in the present disclosure. At this time, the first base station (2602) may determine a conditional path switch so that the path switch operation of the first terminal (2601) is not performed immediately, but is performed only when a specific condition is satisfied (conditional D2I path switch decision to another gNB via relay). The conditional path switch may allow the remote terminal and the relay terminal to prepare the path switch more quickly, thereby reducing delays that may occur in the indirect path and inter-gNB signaling.

[0575] At step 2611, the first base station (2602) may transmit a handover request to the second base station (2604). The handover request message may include at least one of the L2ID of the first terminal (2601) and a list of relay candidate terminals (e.g., the second terminal (2603)), and the relay candidate terminals included in the list of candidate terminals may be limited to relay candidate terminals served by the cell that is the target of the handover request message. In addition, the first base station (2602) may include an indicator indicating a conditional pass switch in the handover request message, and may include a value or indicator indicating the possibility that the first terminal (2601) may perform a pass switch to a terminal served by the corresponding cell.

[0576] At step 2612, the second base station (2604) may perform admission control. The second base station (2604) may determine whether to allow the first terminal (2601) to perform a pass switch using information included in the handover request message transmitted by the first base station (2602) or other information not described in the present disclosure. Furthermore, if multiple candidate terminals are included, one or more target relay terminals may be selected.

[0577] At step 2613, the second base station (2604) may transmit an RRCReconfiguration message including relay terminal configuration to the second terminal (2603) (e.g., the selected target relay terminal). The RRCReconfiguration message may include information for use in the U2N relay operation of the second terminal (2603) or for operating as a U2N relay terminal. For example, the message may include at least one of an identifier of the first terminal (2601), a local ID, Uu Relay RLC channel and PC5 Relay RLC channel configuration, mapping of bearer and relay RLC channels, etc. for servicing the first terminal (2601) as a remote terminal. At this time, the second base station (2604) may not perform an operation of transmitting the RRCReconfiguration message to the second terminal (2603) using a value or indicator indicating the possibility of a pass switch or other information not described in the present disclosure. If the first terminal (2601) performs a path switch while the target relay terminal is in an RRC connection state, a faster path switch operation can be ensured by pre-configuring RRCReconfiguration. However, if the target relay terminal subsequently transitions to an RRC IDLE or INACTIVE state, the operation of transmitting an RRCReconfiguration message to the second terminal (2603) may not be performed as this may result in signaling overhead.

[0578] At step 2614, if the second terminal (2603) can normally apply the settings of the RRCReconfiguration message received from the second base station (2604), it can transmit an RRCReconfigurationComplete message to the second base station (2604).

[0579] At step 2615, the second base station (2604) may transmit a handover request response message to the first base station (2602). The handover request response message may include information for use in the U2N relay operation of the first terminal (2601) or for operating as a U2N remote terminal. For example, the message may include at least one of an identifier of the second terminal (2603), a local ID, a C-RNTI, PC5 Relay RLC channel setup, mapping of a bearer and a relay RLC channel, etc. for the U2N relay operation with the second terminal (2603) as a relay terminal.

[0580] At step 2616, the first base station (2602) may transmit an RRCReconfiguration message including conditional path switch settings to the first terminal (2601). The RRCReconfiguration message may include settings included in a handover request response message transmitted by the second base station (2604) to the first base station (2602). In addition, the message may include at least one condition for applying the path switch settings, and each setting may be distinguished by a conditional reconfiguration ID. The conditions for applying the Path switch configuration may be conditions in which RSRP, RSRQ, SINR, etc. measured by the first terminal (2601) using SSB, CSI-RS, etc. of the first base station (2602) (e.g., PCell) are lower or higher than a specific threshold, conditions in which SL-RSRP or SD-RSRP measured by the first terminal (2601) using PSCCH DMRS or PSSCH DMRS of the second terminal (2603) (e.g., a candidate relay terminal that can be distinguished by L2ID) are lower or higher than a specific threshold, conditions in which a specific point in time has passed since the first terminal (2601) received RRCReconfiguration from the first base station (2602), or conditions in which the range of relative / absolute time is present. The first base station (2602) can set different threshold values ​​for each measurement quantity to the first terminal (2601) (for example, the threshold values ​​of SL-RSRP and SD-RSRP can be different from each other), and if no threshold value is set, the first terminal (2601) can determine that the threshold condition is always satisfied, or can use another similar threshold value (for example, SD-RSRP when SL-RSRP is not set).The first base station (2602) may use a value and / or range based on absolute time (e.g., UTC) or a value and / or range based on relative time (e.g., the base station's system frame number, SFN) to indicate a specific point in time to the first terminal (2601), and the minimum unit of time may be a slot, an SFN, a subframe number, ms, etc., and multiple units may be indicated as an indication unit (e.g., indicated in units of 100 ms), and the units of time and range may be different. The condition for applying such a path switch setting may be in the form of an event including the above-described conditions or other conditions.

[0581] At step 2617, if the first terminal (2601) can normally apply the settings of the RRCReconfiguration message received from the first base station (2602), the first terminal (2601) can transmit an RRCReconfigurationComplete message to the first base station (2602).

[0582] At step 2618, the first base station (2602) may transmit an Early SN status transfer message to the second base station (2604). The Early SN status transfer message may include a sequence number indicating an uplink PDCP reception status and a downlink PDCP transmission status of the first terminal (2601), and may be transmitted per DRB according to the characteristics of the DRB of the first terminal (2601) (e.g., RLC AM).

[0583] At step 2619, the second base station (2604) may transmit an RRCRelease message to change the RRC connection state of the second terminal (2603) to RRC IDLE or INACTIVE when it is determined that there is no need to maintain the RRC connection state of the second terminal (2603) or when the second terminal (2603) requests it.

[0584] At step 2620, the second terminal (2603) receives the RRCRelease message and may enter the RRC IDLE or RRC INACTIVE state.

[0585] At step 2621, the second terminal (2603) may establish an RRC connection with the second base station (2604) and enter the RRC CONNECTED state due to circumstances such as the need to connect to a network or data to be received from the network.

[0586] At step 2622, the second base station (2604) can transmit an RRCReconfiguration message including relay terminal configuration to the second terminal (2603) (e.g., the selected target relay terminal). The RRCReconfiguration message can include information for use in the U2N relay operation of the second terminal (2603) or for operating as a U2N relay terminal. For example, the message can include at least one of an identifier of the first terminal (2601), a local ID, Uu Relay RLC channel and PC5 Relay RLC channel configuration, mapping of bearer and relay RLC channels, etc. for servicing the first terminal (2601) as a remote terminal. The second base station (2604) can transmit RRCReconfiguration whenever the target relay terminal enters an RRC connection state to perform a faster path switch operation. However, if the target relay terminal subsequently transitions to the RRC IDLE or INACTIVE state, the operation of transmitting the RRCReconfiguration message to the second terminal (2603) may not be performed because it may result in signaling overhead.

[0587] At step 2623, if the second terminal (2603) can normally apply the settings of the RRCReconfiguration message received from the second base station (2604), it can transmit an RRCReconfigurationComplete message to the second base station (2604).

[0588] At step 2624, the first terminal (2601) can evaluate whether the conditions received from the first base station (2602) are satisfied (conditional reconfiguration evaluation). If two or more conditions are set for the first terminal (2601), the first terminal (2601) can perform an operation to apply the path switch configuration of a candidate relay terminal (e.g., the second terminal (2603)) that satisfies the conditions if at least one of the conditions is satisfied, or if all conditions are satisfied.

[0589] At step 2625, the first terminal (2601) can initiate a pass switch procedure (conditional reset execution) based on information included in RRCReconfiguration received from the first base station (2602).

[0590] At step 2626, the first terminal (2601) can connect (establish) a PC5 unicast link with the second terminal (2603).

[0591] At step 2627, the first terminal (2601) can complete the path switch by transmitting an RRCReconfigurationComplete message to the second base station (2604) through an indirect path via the second terminal (2603).

[0592] In some embodiments, the second base station (2604) may not transmit the RRCReconfiguration message including the relay terminal configuration to the second terminal (2603) (e.g., the selected target relay terminal). In this case, the second terminal (2603) may transmit a message (e.g., SidelinkUEInformationNR) to the second base station (2604) to receive the relay terminal configuration from the second base station (2604) at step 2628. The SidelinkUEInformationNR message may include an indicator requesting the second base station (2604) to configure the relay terminal with the first terminal (2601) as a remote terminal, and may include the L2ID of the first terminal (2601). When the second terminal (2603) receives an RRCReconfigurationComplete message from the first terminal (2601), even if there is no setting (e.g., local ID, L2ID information of the first terminal (2601), Uu relay RLC channel, etc.) for transmission to the second base station (2604), the second terminal (2603) may request resources for transmitting the RRCReconfigurationComplete message received from the first terminal (2601) to the second base station (2604) without discarding the message transmitted by the first terminal (2601).

[0593] At step 2629, the second base station (2604) may transmit an RRCReconfiguration message including relay terminal settings to the second terminal (2603) (e.g., the terminal to which the first terminal (2601) connects). The RRCReconfiguration message may include information used for U2N relay operation of the second terminal (2603) or for operating as a U2N relay terminal. For example, the message may include at least one of an identifier of the first terminal (2601), a local ID, Uu Relay RLC channel and PC5 Relay RLC channel settings, mapping of bearer and relay RLC channels, etc. for servicing the first terminal (2601) as a remote terminal. A method in which the target relay terminal receives an RRCReconfigurationComplete message from the remote terminal and receives settings from the base station may reduce signaling overhead.

[0594] At step 2630, if the second terminal (2603) can normally apply the settings of the RRCReconfiguration message received from the second base station (2604), it can transmit an RRCReconfigurationComplete message to the second base station (2604).

[0595] At step 2631, the second terminal (2603) can transmit the RRCReconfigurationComplete message received from the first terminal (2601) to the second base station (2604) through the Uu Relay RLC channel.

[0596] At step 2632, the second base station (2604) can transmit a handover success message to the first base station (2602) to notify the success of the path switch of the first terminal (2601).

[0597] At step 2633, the first base station (2602) may transmit an SN status transfer message to the second base station (2604). The SN status transfer message may include a sequence number indicating an uplink PDCP reception status and a downlink PDCP transmission status of the first terminal (2601), and may be transmitted per DRB according to the characteristics of the DRB of the first terminal (2601) (e.g., RLC AM).

[0598] At step 2634, the second base station (2604) may transmit a UE context release message to the first base station (2602) to notify the success of the path switch of the first terminal (2601).

[0599] At step 2635, the first terminal (2601) is connected to the second base station (2604) through an indirect path via the second terminal (2603) and can transmit and receive uplink and downlink data.

[0600] Although Figure 26 illustrates a Direct-to-Indirect path switch as an example, it can also be applied to various path switch scenarios not included in the example in the drawing.

[0601] FIG. 27a and FIG. 27b are diagrams illustrating examples of signal flow of a path switch according to the RRC connection status of a relay terminal in a terminal-to-network relay according to an embodiment of the present disclosure.

[0602] Referring to FIGS. 27a and 27b, a first terminal (remote terminal) (2701) may be a terminal capable of U2N remote operation and is directly connected to a first base station (2702) via a path. A second terminal (relay terminal) (2703) may be a terminal capable of U2N relay operation and is in an RRC connected state with a second base station (2704).

[0603] In step 2705, the first terminal (2701) may notify the first base station (2702) that it is a terminal that supports a conditional path switch operation by transmitting a UECapabilityInformation message. Information included in the UECapabilityInformation may mean that the first terminal (2701) is a terminal that supports a conditional path switch operation or that it is a terminal that supports a conditional Direct-to-Indirect path switch operation. Different indicators may be used for each remote terminal and relay terminal, or information that it supports operations for multiple scenarios including a conditional path switch may be expressed by one or more indicators. When the first terminal (2701) receives a terminal capability information request message (UECapabilityEnquiry message) from the first base station (2702), the first terminal (2701) may transmit the UECapabilityInformation message to the first base station (2702). In this case, the UECapabilityEnquiry message may include information requesting that the first terminal (2701) report a capability regarding whether the first terminal supports a conditional path switch operation.

[0604] In step 2706, the second terminal (2703) may notify the second base station (2704) that it is a terminal that supports a conditional path switch operation by transmitting a UECapabilityInformation message. The information included in the UECapabilityInformation may mean that the second terminal (2703) is a terminal that supports a conditional path switch operation, or that it is a terminal that supports a conditional Direct-to-Indirect path switch operation. In addition, it may mean that the terminal supports an operation of receiving SRB1 (e.g., RRCREconfiguration) from a remote terminal in an RRC IDLE or INACTIVE state and instructing the base station to connect the remote terminal. Different indicators may be provided for each remote terminal and relay terminal, or information indicating that it supports operations for multiple scenarios including a conditional path switch may be expressed as one or more indicators. When a second terminal (2703) receives a terminal capability information request message (UECapabilityEnquiry message) from a second base station (2704), the second terminal (2703) may transmit the UECapabilityInformation message to the second base station (2704). In this case, the UECapabilityEnquiry message may include information requesting that the second terminal (2703) report its capability regarding whether it is a terminal that supports conditional path switch operation.

[0605] In step 2707, the first base station (2702) may transmit an RRCReconfiguration message to the first terminal (2701) including a measurement configuration configured to measure cells and U2N relay terminals around the first terminal (2701). The measurement configuration may include at least one of detailed information for measuring SS / PBCH block(s) or CSI-RS in intra-frequency or inter-frequency, detailed information for measuring sidelink communication or discovery message transmitted in a sidelink frequency or transmission pool, etc. In addition, the measurement configuration may include at least one of detailed information about a condition for triggering a measurement report or a measurement event.

[0606] At step 2708, if the first terminal (2701) can normally apply the settings of the RRCReconfiguration message received from the first base station (2702), the first terminal (2701) can transmit an RRCReconfigurationComplete message to the first base station (2702).

[0607] In step 2709, the first terminal (2701) may transmit a measurement report to the first base station (2702) if a condition or measurement event that triggers a measurement report included in the measurement configuration is satisfied. The measurement report may include at least one of the following: a measurement result according to the PCI and NR measurement quantity of the serving cell and the surrounding cells, an L2ID of the serving relay and the surrounding relay terminal, a serving cell ID of the measured relay terminal, a measurement result according to the sidelink measurement quantity, etc.

[0608] At step 2710, the first base station (2702) may determine a path switch to continue providing service by changing the direct path of the first terminal (2701) to an indirect path via the second terminal (2703) whose serving cell is the cell of the second base station (2704) based on the measurement report received from the first terminal (2701) or other information not described in the present disclosure. At this time, the first base station (2702) may determine a conditional path switch so that the path switch operation of the first terminal (2701) is not performed immediately, but is performed only when a specific condition is satisfied (conditional D2I path switch decision to another gNB via relay). The conditional path switch may reduce delays that may occur in the indirect path and inter-gNB signaling by allowing the remote terminal and the relay terminal to prepare the path switch more quickly.

[0609] At step 2711, the first base station (2702) may transmit a handover request to the second base station (2704). The handover request message may include at least one of the L2ID of the first terminal (2701) and a list of relay candidate terminals (e.g., the second terminal (2703)), and the relay candidate terminals included in the list of candidate terminals may be limited to relay candidate terminals served by the cell that is the target of the handover request message. In addition, the first base station (2702) may include an indicator indicating a conditional pass switch in the handover request message, and may include a value or indicator indicating the possibility that the first terminal (2701) may perform a pass switch to a terminal served by the corresponding cell.

[0610] At step 2712, the second base station (2704) may perform admission control. The second base station (2704) may determine whether to allow the first terminal (2701) to perform a pass switch using information included in the handover request message transmitted by the first base station (2702) or other information not described in the present disclosure. Furthermore, if multiple candidate terminals are included, one or more target relay terminals may be selected.

[0611] At step 2713, the second base station (2704) may transmit an RRCReconfiguration message including relay terminal configuration to the second terminal (2703) (e.g., the selected target relay terminal). The RRCReconfiguration message may include information for use in the U2N relay operation of the second terminal (2703) or for operating as a U2N relay terminal. For example, the message may include at least one of an identifier of the first terminal (2701), a local ID, Uu Relay RLC channel and PC5 Relay RLC channel configuration, mapping of bearer and relay RLC channels, etc. for servicing the first terminal (2701) as a remote terminal. At this time, the second base station (2704) may not perform an operation of transmitting the RRCReconfiguration message to the second terminal (2703) using a value or indicator indicating pass switchability or other information not described in the present disclosure. If the first terminal (2701) performs a path switch while the target relay terminal is in an RRC connection state, a faster path switch operation can be ensured by pre-configuring RRCReconfiguration. However, if the target relay terminal subsequently transitions to an RRC IDLE or INACTIVE state, the operation of transmitting an RRCReconfiguration message to the second terminal (2703) may not be performed as this may result in signaling overhead.

[0612] At step 2714, if the second terminal (2703) can normally apply the settings of the RRCReconfiguration message received from the second base station (2704), it can transmit an RRCReconfigurationComplete message to the second base station (2704).

[0613] At step 2715, the second base station (2704) may transmit a handover request response message to the first base station (2702). The handover request response message may include information for use in the U2N relay operation of the first terminal (2701) or for operating as a U2N remote terminal. For example, the message may include at least one of an identifier of the second terminal (2703), a local ID, a C-RNTI, PC5 Relay RLC channel setup, mapping of a bearer and a relay RLC channel, etc. for the U2N relay operation with the second terminal (2703) as a relay terminal.

[0614] At step 2716, the first base station (2702) may transmit an RRCReconfiguration message including conditional path switch settings to the first terminal (2701). The RRCReconfiguration message may include settings included in a handover request response message transmitted by the second base station (2704) to the first base station (2702). In addition, the message may include at least one condition for applying the path switch settings, and each setting may be distinguished by a conditional reconfiguration ID. The conditions for applying the Path switch configuration may be conditions in which RSRP, RSRQ, SINR, etc. measured by the first terminal (2701) using SSB, CSI-RS, etc. of the first base station (2702) (e.g., PCell) are lower or higher than a specific threshold, conditions in which SL-RSRP or SD-RSRP measured by the first terminal (2701) using PSCCH DMRS or PSSCH DMRS of the second terminal (2703) (e.g., a candidate relay terminal that can be distinguished by L2ID) are lower or higher than a specific threshold, conditions in which a specific point in time has passed since the first terminal (2701) received RRCReconfiguration from the first base station (2702), or conditions in which the range of relative / absolute time is present. The first base station (2702) can set different threshold values ​​for each measurement quantity to the first terminal (2701) (for example, the threshold values ​​of SL-RSRP and SD-RSRP can be different from each other), and if no threshold value is set, the first terminal (2601) can determine that the threshold condition is always satisfied, or can use another similar threshold value (for example, SD-RSRP when SL-RSRP is not set).The first base station (2702) may use a value and / or range based on absolute time (e.g., UTC) or a value and / or range based on relative time (e.g., the base station's system frame number, SFN) to indicate a specific point in time to the first terminal (2701), and the minimum unit of time may be a slot, SFN, subframe number, ms, etc., and multiple units may be indicated as an indication unit (e.g., indicating in units of 100 ms), and the units of time and range may be different. The condition for applying such a path switch setting may be in the form of an event including the above-described conditions or other conditions.

[0615] At step 2717, if the first terminal (2701) can normally apply the settings of the RRCReconfiguration message received from the first base station (2702), the first terminal (2701) can transmit an RRCReconfigurationComplete message to the first base station (2702).

[0616] At step 2718, the first base station (2702) may transmit an Early SN status transfer message to the second base station (2704). The Early SN status transfer message may include a sequence number indicating an uplink PDCP reception status and a downlink PDCP transmission status of the first terminal (2701), and may be transmitted per DRB according to the characteristics of the DRB of the first terminal (2701) (e.g., RLC AM).

[0617] At step 2719, the second base station (2704) may transmit an RRCRelease message to change the RRC connection state of the second terminal (2703) to RRC IDLE or INACTIVE when it is determined that there is no need to maintain the RRC connection state of the second terminal (2703) or when the second terminal (2703) requests it.

[0618] At step 2720, the second terminal (2703) receives an RRCRelease message and may enter an RRC IDLE or RRC INACTIVE state.

[0619] In step 2721, the first terminal (2701) can evaluate whether the conditions received from the first base station (2702) are satisfied (conditional reconfiguration evaluation). If two or more conditions are set for the first terminal (2701), the first terminal (2701) can perform an operation to apply the path switch configuration of a candidate relay terminal (e.g., the second terminal (2703)) that satisfies the conditions when at least one of the conditions is satisfied, or when all conditions are satisfied.

[0620] At step 2722, the first terminal (2701) can initiate a pass switch procedure (conditional reset execution) based on information included in RRCReconfiguration received from the first base station (2702).

[0621] At step 2723, the first terminal (2701) can connect (establish) a PC5 unicast link with the second terminal (2703).

[0622] At step 2724, the first terminal (2701) can complete the path switch by transmitting an RRCReconfigurationComplete message to the second base station (2704) through an indirect path via the second terminal (2703).

[0623] In some embodiments, the second base station (2704) may not transmit an RRCReconfiguration message including relay terminal configuration to the second terminal (2703) (e.g., the selected target relay terminal). In this case, the second terminal (2703) may establish (establish) an RRC connection in order to transmit a message (e.g., SidelinkUEInformationNR) to the second base station (2704) to receive relay terminal configuration from the second base station (2704) at step 2725. At this time, an indicator informing the base station that the purpose of the RRC connection is to connect a remote terminal or an L2ID of a remote terminal (e.g., the first terminal (2701)) may be included during the RRC connection process.

[0624] At step 2726, the second terminal (2703) may transmit a message (e.g., SidelinkUEInformationNR) to the second base station (2704) for receiving relay terminal configuration from the second base station (2704). The SidelinkUEInformationNR message may include an indicator requesting the second base station (2704) to configure relay terminals with the first terminal (2701) as a remote terminal, and may include the L2ID of the first terminal (2701). At this time, even if the second terminal (2703) does not have a setting (e.g., local ID, L2ID information of the first terminal (2701), Uu relay RLC channel, etc.) for transmitting the RRCReconfigurationComplete message received from the first terminal (2701) to the second base station (2704), the second terminal (2703) may not discard the message transmitted by the first terminal (2701) and may request a resource for transmitting the RRCReconfigurationComplete message received from the first terminal (2701) to the second base station (2704).

[0625] At step 2727, the second base station (2704) may transmit an RRCReconfiguration message including relay terminal settings to the second terminal (2703) (e.g., the terminal to which the first terminal (2701) connects). The RRCReconfiguration message may include information used for U2N relay operation of the second terminal (2703) or for operating as a U2N relay terminal. For example, the message may include at least one of an identifier of the first terminal (2701) for servicing the first terminal (2701) as a remote terminal, a local ID, Uu Relay RLC channel and PC5 Relay RLC channel settings, mapping of bearer and relay RLC channels, etc. The method in which the target relay terminal receives the RRCReconfigurationComplete message from the remote terminal and receives the settings from the base station may reduce signaling overhead. Additionally, if the second base station (2704) can confirm the connection of the remote terminal during the RRC connection process, it can transmit a message for configuring the relay terminal without receiving a relay terminal configuration request message (e.g., SidelinkUEInformationNR).

[0626] At step 2728, if the second terminal (2703) can normally apply the settings of the RRCReconfiguration message received from the second base station (2704), it can transmit an RRCReconfigurationComplete message to the second base station (2704).

[0627] At step 2729, the second terminal (2703) can transmit the RRCReconfigurationComplete message received from the first terminal (2701) to the second base station (2704) through the Uu Relay RLC channel.

[0628] At step 2730, the second base station (2704) can transmit a handover success message to the first base station (2702) to notify the success of the path switch of the first terminal (2701).

[0629] At step 2731, the first base station (2702) may transmit an SN status transfer message to the second base station (2704). The SN status transfer message may include a sequence number indicating an uplink PDCP reception status and a downlink PDCP transmission status of the first terminal (2701), and may be transmitted per DRB according to the characteristics of the DRB of the first terminal (2701) (e.g., RLC AM).

[0630] At step 2732, the second base station (2704) may transmit a UE context release message to the first base station (2702) to notify the success of the path switch of the first terminal (2701).

[0631] At step 2733, the first terminal (2701) is connected to the second base station (2704) through an indirect path via the second terminal (2703) and can transmit and receive uplink and downlink data.

[0632] Although Figure 27 illustrates a Direct-to-Indirect path switch as an example, it can also be applied to various path switch scenarios not included in the example in the drawing.

[0633] FIG. 28a and FIG. 28b are diagrams illustrating examples of signal flows for an operation of pre-connecting a PC5 unicast link in a terminal-to-network relay according to an embodiment of the present disclosure.

[0634] Referring to FIGS. 28a and 28b, a first terminal (remote terminal) (2801) may be a terminal capable of U2N remote operation and is connected to a first base station (2804), a second terminal (first relay terminal) (2802) may be a terminal capable of U2N relay operation and is connected to the first base station (2804), and a third terminal (second relay terminal) (2803) may be a terminal capable of U2N relay operation and is connected to the first base station (2804).

[0635] In step 2805, the first terminal (2801) may notify the first base station (2804) that it is a terminal that supports a conditional path switch operation by transmitting a UECapabilityInformation message. The information included in the UECapabilityInformation may mean that the first terminal (2801) is a terminal that supports a conditional path switch operation, or that it is a terminal that supports a conditional Direct-to-Indirect path switch operation. In addition, it may mean a terminal that can connect a relay terminal and a PC5 unicast link before remote, relay terminal configuration, or path switch configuration application. Different indicators may be provided for each remote terminal and relay terminal, or information that it supports operations for multiple scenarios including a conditional path switch may be expressed by one or more indicators. When the first terminal (2801) receives a terminal capability information request message (UECapabilityEnquiry message) from the first base station (2804), the first terminal (2801) may transmit the UECapabilityInformation message to the first base station (2804). In this case, the UECapabilityEnquiry message may include information requesting that the first terminal (2801) report its capability as to whether it is a terminal that supports conditional path switch operation.

[0636] In step 2806, the second terminal (2802) may notify the first base station (2804) that it is a terminal that supports a conditional path switch operation by transmitting a UECapabilityInformation message. The information included in the UECapabilityInformation may mean that the second terminal (2802) is a terminal that supports a conditional path switch operation, or that it is a terminal that supports a conditional Direct-to-Indirect path switch operation. In addition, it may mean a terminal that can connect a remote terminal and a PC5 unicast link before remote, relay terminal configuration, or path switch configuration application. Different indicators may be provided for each remote terminal and relay terminal, or information indicating that it supports operations for multiple scenarios including a conditional path switch may be expressed by one or more indicators. When the second terminal (2802) receives a terminal capability information request message (UECapabilityEnquiry message) from the first base station (2804), it may transmit the UECapabilityInformation message to the first base station (2804). In this case, the UECapabilityEnquiry message may include information requesting that the second terminal (2802) report its capability as to whether it is a terminal that supports conditional path switch operation.

[0637] In step 2807, the third terminal (2803) may notify the first base station (2804) that it is a terminal that supports a conditional path switch operation by transmitting a UECapabilityInformation message. The information included in the UECapabilityInformation may mean that the third terminal (2803) is a terminal that supports a conditional path switch operation, or that it is a terminal that supports a conditional Direct-to-Indirect path switch operation. In addition, it may mean a terminal that can connect a remote terminal and a PC5 unicast link before remote, relay terminal configuration, or path switch configuration application. Different indicators may be provided for each remote terminal and relay terminal, or information that supports operations for multiple scenarios including a conditional path switch may be expressed by one or more indicators. When the third terminal (2803) receives a terminal capability information request message (UECapabilityEnquiry message) from the first base station (2804), the third terminal (2803) may transmit the UECapabilityInformation message to the third base station (2803). In this case, the UECapabilityEnquiry message may include information requesting that the second terminal (2802) report its capability as to whether it is a terminal that supports conditional path switch operation.

[0638] In step 2808, the first base station (2804) may transmit an RRCReconfiguration message to the first terminal (2801) including a measurement configuration configured to measure cells and U2N relay terminals around the first terminal (2801). The measurement configuration may include at least one of detailed information for measuring SS / PBCH block(s) or CSI-RS in intra-frequency or inter-frequency, detailed information for measuring sidelink communication or discovery messages transmitted in a sidelink frequency or transmission pool, etc. In addition, the measurement configuration may include at least one of detailed information about a condition for triggering a measurement report or a measurement event.

[0639] At step 2809, if the first terminal (2801) can normally apply the settings of the RRCReconfiguration message received from the first base station (2804), it can transmit an RRCReconfigurationComplete message to the first base station (2804).

[0640] In step 2810, the first terminal (2801) may transmit a measurement report to the first base station (2804) if a condition or measurement event that triggers a measurement report included in the measurement configuration is satisfied. The measurement report may include at least one of the following: a measurement result according to the PCI and NR measurement quantity of the serving cell and the surrounding cells, an L2ID of the serving relay and the surrounding relay terminal, a serving cell ID of the measured relay terminal, and a measurement result according to the sidelink measurement quantity.

[0641] At step 2811, if the first base station (2804) determines that the first terminal (2801) can switch to an indirect path via the second terminal (2802) or an indirect path via the third terminal (2803) based on a measurement report received from the first terminal (2801) or other information not described in the present disclosure, the first base station (2804) can determine a conditional path switch that is performed in parallel to multiple candidate relay terminals (conditional I2I path switch decision). The conditional path switch can reduce delays that may occur in the indirect path and inter-gNB signaling by allowing the remote terminal and the relay terminal to prepare the path switch more quickly.

[0642] At step 2812, the first base station (2804) may transmit an RRCReconfiguration message including relay terminal configuration to the second terminal (2802) and the third terminal (2803). The RRCReconfiguration message may include information for use in U2N relay operation of the second terminal (2802) or the third terminal (2803) or for operating as a U2N relay terminal. For example, the message may include at least one of an identifier of the first terminal (2801), a local ID, Uu Relay RLC channel and PC5 Relay RLC channel configuration, mapping of a bearer and a relay RLC channel, etc. for servicing the first terminal (2801) as a remote terminal.

[0643] In step 2813, if the second terminal (2802) can normally apply the settings of the RRCReconfiguration message received from the first base station (2804), it can transmit an RRCReconfigurationComplete message to the first base station (2804), and if the third terminal (2803) can normally apply the settings of the RRCReconfiguration message received from the first base station (2804), it can transmit an RRCReconfigurationComplete message to the first base station (2804).

[0644] At step 2814, the first base station (2804) may transmit an RRCReconfiguration message including a conditional path switch configuration to the first terminal (2801). The RRCReconfiguration message may include information used for the U2N relay operation of the first terminal (2801) or for operating as a U2N remote terminal. For example, the message may include at least one of an identifier of the second terminal (2802), a local ID, a PC5 Relay RLC channel configuration, a mapping of a bearer and a relay RLC channel, etc. for the U2N relay operation with the second terminal (2802) as a relay terminal, and at least one of an identifier of the third terminal (2803), a local ID, a PC5 Relay RLC channel configuration, a mapping of a bearer and a relay RLC channel, etc. for the U2N relay operation with the third terminal (2803) as a relay terminal. Additionally, the message may include at least one condition for applying a path switch setting, and each setting may be distinguished by a conditional reconfiguration ID.The conditions for applying the Path switch configuration may be a condition in which the RSRP, RSRQ, SINR, etc. measured by the SSB, CSI-RS, etc. of the first terminal (2801) of the first base station (2804) (e.g., PCell) are lower or higher than a specific threshold, a condition in which the SL-RSRP or SD-RSRP measured by the PSCCH DMRS or PSSCH DMRS of the second terminal (2802) (e.g., candidate relay terminal) are lower or higher than a specific threshold, a condition in which the SL-RSRP or SD-RSRP measured by the PSCCH DMRS or PSSCH DMRS of the third terminal (2803) (e.g., candidate relay terminal) are lower or higher than a specific threshold, a condition in which a specific point in time has passed since the first terminal (2801) received RRCReconfiguration from the first base station (2804), or a condition in which the range of relative / absolute time is present. The first base station (2804) can set different threshold values ​​for each measurement quantity to the first terminal (2801) (for example, the threshold values ​​of SL-RSRP and SD-RSRP may be different from each other), and if no threshold value is set, the first terminal (2801) can determine that the corresponding threshold condition is always satisfied, or can use another similar threshold value (for example, SD-RSRP when SL-RSRP is not set). The first base station (2804) can use a value and / or range based on absolute time (for example, UTC) or a value and / or range based on relative time (for example, the system frame number of the base station, SFN) to indicate a specific point in time to the first terminal (2801), and the minimum unit of time can be a slot, an SFN, a subframe number, ms, etc., and multiple units can be indicated (for example, indicated in units of 100 ms), and the units of time and range can be different.The conditions for applying these path switch settings may be in the form of events that include the conditions described above or other conditions. In addition, they may include an indicator or threshold value (e.g., SL-RSRP or SD-RSRP) that indicates that a common or terminal-specific PC5 unicast link connection to a candidate relay terminal (e.g., the second terminal (2802) or the third terminal (2803)) is to be established before the conditions are satisfied.

[0645] At step 2815, if the first terminal (2801) can normally apply the settings of the RRCReconfiguration message received from the first base station (2804), it can transmit an RRCReconfigurationComplete message to the first base station (2804).

[0646] At step 2816, the first terminal (2801) can connect (establish) a PC5 unicast link with the second terminal (2802) based on the conditional path switch configuration received from the first base station (2804). The first terminal (2801) can compare the SL-RSRP or SD-RSRP with the indicator or the candidate relay terminal and the threshold value to determine whether to connect. Alternatively, if there is no PC5 unicast link connection indicator or threshold value, the first terminal (2801) may or may not always connect the PC5 unicast link with the second terminal (2802). The operation of connecting the PC5 unicast link in advance (early PC5 unicast link establishment) can reduce the delay time compared to the operation of connecting the PC5 unicast link after the condition is satisfied.

[0647] At step 2817, the first terminal (2801) can establish a PC5 unicast link with the third terminal (2803) based on the conditional path switch configuration received from the first base station (2804). The first terminal (2801) can compare the SL-RSRP or SD-RSRP with the indicator or the candidate relay terminal and the threshold value to determine whether to establish a connection. Alternatively, if there is no PC5 unicast link establishment indicator or threshold value, the first terminal (2801) may always establish a PC5 unicast link with the third terminal (2803) or may not always establish a PC5 unicast link. The operation of establishing a PC5 unicast link in advance (early PC5 unicast link establishment) can reduce the delay time compared to the operation of establishing a PC5 unicast link after a condition is satisfied.

[0648] In step 2818, the first terminal (2801) can evaluate whether the conditions received from the first base station (2804) are satisfied (conditional reconfiguration evaluation). If two or more conditions are set for the first terminal (2801), the first terminal (2801) can perform an operation to apply the path switch configuration of a candidate relay terminal (e.g., the third terminal (2803)) that satisfies the conditions when at least one of the conditions is satisfied, or when all conditions are satisfied.

[0649] At step 2819, the first terminal (2801) may initiate a path switch procedure (conditional reconfiguration execution) based on the information included in the RRCReconfiguration received from the first base station (2804). In the drawing, it is assumed that the third terminal (2803) satisfies the condition. At this time, although not shown in the drawing, if a terminal that satisfies the path switch condition (e.g., the third terminal (2803)) is not connected to a PC5 unicast link, the first terminal (2801) may connect (establish) a PC5 unicast link with the third terminal (2803). In addition, if a PC5 unicast link is already connected to the third terminal (2803) at step 2817, the first terminal (2801) may not trigger a PC5 unicast link connection to a higher layer (e.g., a ProSe layer). The L2ID of the candidate relay terminals (e.g., the second terminal (2802) and the third terminal (2803)) received by the first terminal (2801) from the first base station (2804) may be an L2ID for discovery purposes rather than an L2ID for communication purposes. In steps 2816 and 2817, when the first terminal (2801) connects the PC5 unicast link before the pass switch procedure, a procedure for mapping or storing the discovery L2ID and the communication L2ID of the candidate relay terminal may be required in order to connect to the same candidate relay terminal.

[0650] At step 2820, the first terminal (2801) can complete the path switch by transmitting an RRCReconfigurationComplete message to the first base station (2804) through an indirect path via the third terminal (2803).

[0651] At step 2821, the first base station (2804) may transmit an RRCReconfiguration message to the second terminal (2802) to release or delete the configuration for servicing the first terminal (2801) as a remote terminal. The RRCReconfiguration message may include relay terminal configuration information.

[0652] At step 2822, if the second terminal (2802) can normally apply the settings of the RRCReconfiguration message received from the first base station (2804), it can transmit an RRCReconfigurationComplete message to the first base station (2804).

[0653] At step 2823, the first terminal (2801) or the second terminal (2802) can perform a release procedure of the PC5 unicast link if the PC5 unicast link for the U2N relay is connected.

[0654] At step 2824, the first terminal (2801) is connected to the first base station (2804) through an indirect path via the third terminal (2803) and can transmit and receive uplink and downlink data.

[0655] Although Figure 28 illustrates a Direct-to-Indirect path switch as an example, it can also be applied to various path switch scenarios not included in the example in the drawing.

[0656] FIG. 29a and FIG. 29b are diagrams illustrating examples of signal flows in an operation in which a remote terminal reports to a base station a relay terminal that is not suitable for a path switch during a conditional path switch operation in a terminal-to-network relay according to an embodiment of the present disclosure.

[0657] Referring to FIGS. 29a and 29b, a first terminal (remote terminal) (2901) may be a terminal capable of U2N remote operation and is connected to a first base station (2902), and a second terminal (relay terminal) (2903) may be a terminal capable of U2N relay operation and is connected to a second base station (2904).

[0658] In step 2905, the first terminal (2901) may notify the first base station (2902) that it is a terminal that supports a conditional path switch operation by transmitting a UECapabilityInformation message. The information included in the UECapabilityInformation may mean that the first terminal (2901) is a terminal that supports a conditional path switch operation, or that it is a terminal that supports a conditional Direct-to-Indirect path switch operation. In addition, it may mean a terminal that can connect a relay terminal and a PC5 unicast link before remote, relay terminal configuration, or path switch configuration application. In addition, it may mean a terminal that can report a failure of a candidate relay terminal to the base station. The remote terminal and the relay terminal may have different indicators, or information that supports operations for multiple scenarios including a conditional path switch may be expressed as one or more indicators. When a first terminal (2901) receives a terminal capability information request message (UECapabilityEnquiry message) from a first base station (2902), the first terminal (2901) may transmit the UECapabilityInformation message to the first base station (2902). In this case, the UECapabilityEnquiry message may include information requesting that the first terminal (2901) report its capability regarding whether it is a terminal that supports conditional path switch operation.

[0659] In step 2906, the second terminal (2903) may notify the second base station (2904) that it is a terminal that supports a conditional path switch operation by transmitting a UECapabilityInformation message. The information included in the UECapabilityInformation may mean that the second terminal (2903) is a terminal that supports a conditional path switch operation, or that it is a terminal that supports a conditional Direct-to-Indirect path switch operation. In addition, it may mean a terminal that can connect a remote terminal and a PC5 unicast link before remote, relay terminal configuration, or path switch configuration application. Different indicators may be provided for each remote terminal and relay terminal, or information that supports operations for multiple scenarios including a conditional path switch may be expressed by one or more indicators. When the second terminal (2903) receives a terminal capability information request message (UECapabilityEnquiry message) from the second base station (2904), it may transmit the UECapabilityInformation message to the second base station (2904). In this case, the UECapabilityEnquiry message may include information requesting that the second terminal (2903) report its capability regarding whether it is a terminal that supports conditional path switch operation.

[0660] In step 2907, the first base station (2902) may transmit an RRCReconfiguration message to the first terminal (2901) including a measurement configuration configured to measure cells and U2N relay terminals around the first terminal (2901). The measurement configuration may include at least one of detailed information for measuring SS / PBCH block(s) or CSI-RS in intra-frequency or inter-frequency, detailed information for measuring sidelink communication or discovery messages transmitted in a sidelink frequency or transmission pool, etc. In addition, the measurement configuration may include at least one of detailed information about a condition for triggering a measurement report or a measurement event.

[0661] At step 2908, if the first terminal (2901) can normally apply the settings of the RRCReconfiguration message received from the first base station (2902), it can transmit an RRCReconfigurationComplete message to the first base station (2902).

[0662] In step 2909, the first terminal (2901) may transmit a measurement report to the first base station (2902) if a condition or measurement event that triggers a measurement report included in the measurement configuration is satisfied. The measurement report may include at least one of the following: a measurement result according to the PCI and NR measurement quantity of the serving cell and the surrounding cells, an L2ID of the serving relay and the surrounding relay terminal, a serving cell ID of the measured relay terminal, a measurement result according to the sidelink measurement quantity, etc.

[0663] At step 2910, the first base station (2902) may determine a path switch to continue providing service by changing the direct path of the first terminal (2901) to an indirect path via the second terminal (2903) whose serving cell is the cell of the second base station (2904) based on a measurement report received from the first terminal (2901) or other information not described in the present disclosure. At this time, the first base station (2902) may determine a conditional path switch so that the path switch operation of the first terminal (2901) is not performed immediately, but is performed only when a specific condition is satisfied (conditional D2I path switch decision to another gNB via relay). The conditional path switch may allow the remote terminal and the relay terminal to prepare the path switch more quickly, thereby reducing delays that may occur in the indirect path and inter-gNB signaling.

[0664] In step 2911, the first base station (2902) may transmit a handover request to the second base station (2904). The handover request message may include at least one of the L2ID of the first terminal (2901) and a list of relay candidate terminals (e.g., the second terminal (2903)), and the relay candidate terminals included in the list of candidate terminals may be limited to relay candidate terminals served by the cell that is the target of the handover request message. In addition, the first base station (2902) may include an indicator indicating a conditional pass switch in the handover request message, and may include a value or indicator indicating the possibility that the first terminal (2901) may perform a pass switch to a terminal served by the corresponding cell.

[0665] At step 2912, the second base station (2904) may perform admission control. The second base station (2904) may determine whether to allow the first terminal (2901) to perform a pass switch using information included in the handover request message transmitted by the first base station (2902) or other information not described in the present disclosure. Furthermore, if multiple candidate terminals are included, one or more target relay terminals may be selected.

[0666] At step 2913, the second base station (2904) may transmit an RRCReconfiguration message including relay terminal configuration to the second terminal (2903) (e.g., the selected target relay terminal). The RRCReconfiguration message may include information used for U2N relay operation of the second terminal (2903) or for operating as a U2N relay terminal. For example, the message may include at least one of an identifier of the first terminal (2901), a local ID, Uu Relay RLC channel and PC5 Relay RLC channel configurations for servicing the first terminal (2901) as a remote terminal, mapping of bearer and relay RLC channels, etc.

[0667] At step 2914, if the second terminal (2903) can normally apply the settings of the RRCReconfiguration message received from the second base station (2904), it can transmit an RRCReconfigurationComplete message to the second base station (2904).

[0668] At step 2915, the second base station (2904) may transmit a handover request response message to the first base station (2902). The handover request response message may include information for use in the U2N relay operation of the first terminal (2901) or for operating as a U2N remote terminal. For example, the message may include at least one of an identifier of the second terminal (2903), a local ID, a C-RNTI, PC5 Relay RLC channel setup, mapping of a bearer and a relay RLC channel, etc. for the U2N relay operation with the second terminal (2903) as a relay terminal.

[0669] At step 2916, the first base station (2902) may transmit an RRCReconfiguration message including conditional path switch settings to the first terminal (2901). The RRCReconfiguration message may include settings included in a handover request response message transmitted by the second base station (2904) to the first base station (2902). In addition, the message may include at least one condition for applying the path switch settings, and each setting may be distinguished by a conditional reconfiguration ID. The conditions for applying the Path switch configuration may be conditions in which RSRP, RSRQ, SINR, etc. measured by the first terminal (2901) using SSB, CSI-RS, etc. of the first base station (2902) (e.g., PCell) are lower or higher than a specific threshold, conditions in which SL-RSRP or SD-RSRP measured by the first terminal (2901) using PSCCH DMRS or PSSCH DMRS of the second terminal (2903) (e.g., a candidate relay terminal that can be distinguished by L2ID) are lower or higher than a specific threshold, conditions in which a specific point in time has passed sinc...

Claims

1. A method performed by a first terminal of a wireless communication system, A step of receiving a first message from a base station, the first message including first configuration information regarding a conditional path switching from a direct path with the base station to an indirect path via a second terminal; A step of determining whether a path switching condition is satisfied based on the first setting information regarding the conditional path switching; If the above path switching condition is satisfied, a step of establishing a unicast connection for relay communication with the second terminal; and A method comprising the step of transmitting a second message regarding completion of a path change to the base station through the second terminal.

2. In paragraph 1, A method characterized in that the first configuration information regarding the path switching includes at least one of identification information regarding the second terminal for relay operation, configuration information for the unicast connection, and information regarding the path switching condition.

3. In paragraph 1, A step of receiving a terminal capability information request message requesting information on whether the first terminal supports conditional path switching from the base station; and A method characterized by further comprising the step of transmitting a terminal capability information message including information on whether the first terminal supports conditional path switching to the base station.

4. In paragraph 1, A step of receiving a third message from the base station, which includes second setting information regarding conditional path switching from an indirect path through the second terminal to a direct path with the base station; A step of determining whether a path switching condition is satisfied based on the second setting information regarding the conditional path switching; If the above path switching condition is satisfied, a step of performing a random access procedure with the base station; and A method characterized by further comprising the step of releasing the unicast connection for relay communication with the second terminal.

5. A method performed by a base station of a wireless communication system, A step of determining to conditionally change the direct path of the first terminal to the base station to an indirect path via the second terminal; A step of transmitting a first message including relay terminal setting information for operation as a relay terminal of the second terminal to the second terminal; A step of transmitting a second message to the first terminal, which includes first setting information regarding the conditional path switching from the direct path with the base station to the indirect path via the second terminal; and A method comprising the step of receiving a third message regarding completion of a path change from the first terminal through the second terminal when a path change condition based on the first setting information regarding the conditional path change is satisfied.

6. In paragraph 5, A method characterized in that the first configuration information regarding the path switching includes at least one of identification information regarding the second terminal for relay operation, configuration information for the unicast connection, and information regarding the path switching condition.

7. In paragraph 5, A step of transmitting a terminal capability information request message to the first terminal, requesting information on whether the first terminal supports conditional path switching; and A method further comprising the step of receiving a terminal capability information message from the first terminal, the terminal capability information message including information on whether the first terminal supports conditional path switching.

8. In paragraph 5, A step of transmitting a fourth message including second configuration information regarding conditional path switching from an indirect path through the second terminal to a direct path with the base station to the first terminal; A step of performing a random access procedure with the terminal when the path switching condition based on the first setting information regarding the conditional path switching is satisfied; and A method characterized by further comprising the step of transmitting a fifth message to the second terminal for releasing the relay terminal setting information.

9. In the first terminal of the wireless communication system, Transmitter and receiver; and Connected to the above transmitter and receiver, Receive a first message from the base station, which includes first configuration information regarding a conditional path change from a direct path to an indirect path via a second terminal; Based on the first setting information regarding the above conditional path switching, determine whether the path switching condition is satisfied, If the above path switching condition is satisfied, a unicast connection for relay communication is established with the second terminal, A first terminal including a control unit that transmits a second message regarding completion of a path change to the base station through the second terminal.

10. In paragraph 8, A first terminal, characterized in that the first setting information regarding the path switching includes at least one of identification information regarding the second terminal for relay operation, setting information for the unicast connection, and information regarding the path switching condition.

11. In paragraph 9, the control unit, Receive a terminal capability information request message requesting information on whether the first terminal supports conditional path switching from the base station; A first terminal characterized in that it transmits to the base station a terminal capability information message including information on whether the first terminal supports conditional path switching.

12. In paragraph 9, the control unit, Receive a third message from the base station that includes second configuration information regarding conditional path switching from an indirect path through the second terminal to a direct path with the base station, Based on the second setting information regarding the above conditional path switching, determine whether the path switching condition is satisfied, If the above path switching condition is satisfied, a random access procedure is performed with the base station, A first terminal characterized by releasing the unicast connection for relay communication with the second terminal.

13. In a base station of a wireless communication system, Transmitter and receiver; and Connected to the above transmitter and receiver, It is decided to conditionally change the direct path of the first terminal to the base station to an indirect path via the second terminal, Transmitting a first message including relay terminal setting information for operation as a relay terminal of the second terminal to the second terminal, Transmitting a second message to the first terminal, which includes first setting information regarding the conditional path switching from the direct path with the base station to the indirect path via the second terminal, A base station including a control unit that receives a third message regarding completion of a path change from the first terminal through the second terminal when a path change condition based on the first setting information regarding the conditional path change is satisfied.

14. In the 13th paragraph, the control unit, Transmitting a terminal capability information request message to the first terminal requesting information on whether the first terminal supports conditional path switching, A base station characterized by receiving a terminal capability information message from the first terminal that includes information on whether the first terminal supports conditional path switching.

15. In the 13th paragraph, the control unit, Transmitting a fourth message including second configuration information regarding conditional path switching from an indirect path through the second terminal to a direct path with the base station to the first terminal, If the path switching condition based on the first setting information regarding the above conditional path switching is satisfied, a random access procedure is performed with the terminal, A base station characterized by transmitting a fifth message for releasing the relay terminal setting information to the second terminal.

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