Method and device for multi-hop relay-based failure processing in wireless communication system

Abstract

A method and a device for multi-hop relay-based failure processing in a wireless communication system are disclosed. The method according to one embodiment of the present disclosure may comprise steps in which a first terminal: receives, from a second terminal, a first message related to a failure between the second terminal and a first network node; and transmits, to a third terminal, a second message generated by the first terminal on the basis of the first message. The second message can trigger connection re-establishment of the third terminal.

Description

Method and device for handling multi-hop relay-based failures in a wireless communication system

[0001] The present disclosure relates to a wireless communication system, and more particularly, to a multi-hop relay-based failure handling method and device in a wireless communication system.

[0002] The fifth generation (5G) wireless communication system, the successor to 4G LTE (long-term evolution), is a new, clean-slate mobile communication system characterized by high performance, low latency, and high availability. 5G NR (New Radio) can utilize all available spectrum resources, from low-frequency bands below 1 GHz, to intermediate-frequency bands between 1 GHz and 10 GHz, and to high-frequency (or millimeter wave) bands above 24 GHz. 6G wireless communication systems are being developed based on the underlying technologies of 5G wireless communication.

[0003] The 6G wireless communication system is being developed with the goals of (i) very high data rates per device, (ii) a very large number of connected devices, (iii) global connectivity, (iv) very low latency, (v) reduced energy consumption of battery-free Internet of Things (IoT) devices, (vi) ultra-reliable connectivity, and (vii) connected intelligence with machine learning capabilities. The vision of the 6G system can be divided into four aspects: intelligent connectivity, deep connectivity, holographic connectivity, and ubiquitous connectivity. Considering the requirements of the 6G system, such as a peak data rate of 1 Tbps per device, an end-to-end latency of 1 ms, a maximum spectrum efficiency of 100 bps / Hz, support for mobility of 1000 km / h, satellite integration, artificial intelligence (AI), autonomous vehicles, extended reality (XR), and haptic communication, various technologies are being researched.

[0004] The technical problem of the present disclosure is to provide a method and device for notifying a failure on a path in a multi-hop relay in a wireless communication system.

[0005] An additional technical problem of the present disclosure is to provide a method and device for re-establishing a connection based on a specific notification in a multi-hop relay of a wireless communication system.

[0006] The technical problems to be achieved in the present disclosure 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 disclosure belongs from the description below.

[0007] A method according to one embodiment of the present disclosure may include the steps of: receiving, by a first terminal, a first message from a second terminal, wherein the first message relates to a failure between the second terminal and a first network node; and transmitting, by the first terminal, a second message generated by the first terminal based on the first message to a third terminal. The second message may trigger connection re-establishment of the third terminal.

[0008] A method according to another embodiment of the present disclosure may include the steps of: receiving, by a third terminal, a second message generated by the first terminal based on the first message from the first terminal; and performing, by the third terminal, a connection re-establishment procedure triggered by the second message. The first message may be transmitted from the second terminal to the first terminal and may relate to a failure between the second terminal and the first network node.

[0009] According to the present disclosure, a method and device for notifying a failure on a path in a multi-hop relay in a wireless communication system can be provided.

[0010] According to the present disclosure, a method and device for re-establishing a connection based on a specific notification in a multi-hop relay of a wireless communication system can be provided.

[0011] 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 will be clearly understood by a person having ordinary skill in the art to which the present disclosure pertains from the description below.

[0012] The accompanying drawings, which are incorporated in and are part of the detailed description to aid in understanding the present disclosure, provide embodiments of the present disclosure and, together with the detailed description, describe the technical features of the present disclosure.

[0013] Figure 1 illustrates a flexible network topology to which some examples of the present disclosure may be applied.

[0014] FIG. 2 illustrates an example of a communication system to which some examples of the present disclosure may be applied.

[0015] FIG. 3 illustrates an example of a wireless device to which some examples of the present disclosure may be applied.

[0016] FIG. 4 exemplarily illustrates a communication procedure between a first node and a second node to which some examples of the present disclosure may be applied.

[0017] FIG. 5 illustrates an example of a user plane protocol stack for an L2 U2N relay to which the present disclosure may be applied.

[0018] FIG. 6 illustrates an example of a control plane protocol stack for an L2 U2N relay to which the present disclosure may be applied.

[0019] FIG. 7 illustrates an example of a protocol stack of a discovery message for a U2N relay to which the present disclosure may be applied.

[0020] FIG. 8 illustrates an example of an L2 U2N remote UE connection establishment procedure to which the present disclosure can be applied.

[0021] FIG. 9 illustrates an example of a procedure for U2N remote UE switching to a direct Uu cell to which the present disclosure may be applied.

[0022] FIG. 10 illustrates an example of a procedure for U2N remote UE switching to an indirect path to which the present disclosure may be applied.

[0023] FIG. 11 is a drawing for explaining an example of a method performed by a first terminal according to the present disclosure.

[0024] FIG. 12 is a drawing illustrating an example of a method performed by a third terminal according to the present disclosure.

[0025] Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The detailed description set forth below, together with the accompanying drawings, is intended to explain exemplary embodiments of the present disclosure and is not intended to represent the only embodiments in which the present disclosure may be practiced. The following detailed description includes specific details to provide a thorough understanding of the present disclosure. However, one of ordinary skill in the art will appreciate that the present disclosure may be practiced without these specific details.

[0026] In some cases, to avoid obscuring the concepts of the present disclosure, known structures and devices may be omitted or illustrated in block diagram form focusing on the core functions of each structure and device.

[0027] In the present disclosure, when a component is said to be "connected," "coupled," or "connected" to another component, this may include not only a direct connection but also an indirect connection in which another component exists between them. Furthermore, the terms "comprises" or "has" in the present disclosure specify the presence of the mentioned features, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups thereof.

[0028] In this disclosure, terms such as “first,” “second,” etc. are used only to distinguish one component from another and are not used to limit the components, and do not limit the order or importance between the components unless specifically stated otherwise. Accordingly, within the scope of this disclosure, a first component in one embodiment may be referred to as a second component in another embodiment, and similarly, a second component in one embodiment may be referred to as a first component in another embodiment.

[0029] The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to limit the scope of the claims. As used in the description of the embodiments and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly dictates otherwise.

[0030] In this disclosure, "A or B" can mean "only A," "only B," or "both A and B." In other words, "A or B" in this disclosure can be interpreted as "A and / or B." For example, "A, B or C" in this disclosure can mean "only A," "only B," "only C," or "any combination of A, B and C."

[0031] As used herein, a slash ( / ) or a comma may mean "and / or." For example, "A / B" may mean "A and / or B." Accordingly, "A / B" may mean "only A," "only B," or "both A and B." For example, "A, B, C" may mean "A, B, or C."

[0032] In the present disclosure, “at least one of A and B” may mean “only A,” “only B,” or “both A and B.” Additionally, in the present disclosure, the expressions “at least one of A or B” or “at least one of A and / or B” may be interpreted identically to “at least one of A and B.”

[0033] Additionally, in the present disclosure, “at least one of A, B and C” can mean “only A,” “only B,” “only C,” or “any combination of A, B and C.” Additionally, “at least one of A, B or C” or “at least one of A, B and / or C” can mean “at least one of A, B and C.”

[0034] Additionally, parentheses used in the present disclosure may mean "for example." Specifically, when indicated as "control information (PDCCH)", "PDCCH" may be described as an example of "control information." In other words, "control information" in the present disclosure is not limited to "PDCCH," and "PDCCH" may be described as an example of "control information." Furthermore, even when indicated as "control information (i.e., PDCCH)", "PDCCH" may be described as an example of "control information."

[0035] In the following description, 'when, if, in case of' can be replaced with 'based on'.

[0036] Technical features individually described in one drawing in this disclosure may be implemented individually or simultaneously.

[0037] In the present disclosure, a terminal or user equipment (UE) may be a portable device and may be a first node that receives a signal from a base station / second node / IAB (integrated access backhaul) node.

[0038] In the present disclosure, a base station (BS) may be a second node / IAB node / Transmission-Reception Point (TRP).

[0039] In the present disclosure, higher layer parameters may be parameters configured, pre-configured, or pre-defined for the terminal. For example, a base station or a network may transmit higher layer parameters to the terminal. For example, the higher layer parameters may be transmitted via radio resource control (RRC) signaling or medium access control (MAC) signaling.

[0040] In the present disclosure, "setting or defining" may be interpreted as being set to a device through predefined signaling (e.g., SIB (system information block), MAC, RRC) from a base station or network. In the present disclosure, "setting or defining" may be interpreted as being set to a device through separate signaling or being defined in advance without separate signaling.

[0041] In the present disclosure, transmitting or receiving a channel means transmitting or receiving information or a signal through the channel. For example, transmitting a control channel means transmitting control information or a signal through the control channel. Similarly, transmitting a data channel means transmitting data information or a signal through the data channel.

[0042] The technology described in the present disclosure can be used in various wireless communication systems such as CDMA (code division multiple access), FDMA (frequency division multiple access), TDMA (time division multiple access), OFDMA (orthogonal frequency division multiple access), and SC-FDMA (single carrier frequency division multiple access). CDMA can be implemented with wireless technologies such as UTRA (universal terrestrial radio access) or CDMA2000. TDMA can be implemented with wireless technologies such as GSM (global system for mobile communications) / GPRS (general packet radio service) / EDGE (enhanced data rates for GSM evolution). OFDMA can be implemented with wireless technologies such as IEEE (Institute of Electrical and Electronics Engineers) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, E-UTRA (evolved UTRA), LTE (long term evolution), and 5G NR.

[0043] The technology described in the present disclosure can be implemented with 6G wireless technology and applied to various 6G systems. For example, the 6G system can have key factors such as enhanced mobile broadband (eMBB), ultra-reliable low latency communications (URLLC), massive machine-type communication (mMTC), artificial intelligence (AI) integrated communication, tactile internet, high throughput, high network capacity, high energy efficiency, low backhaul and access network congestion, and enhanced data security.

[0044] Network structure

[0045] Figure 1 illustrates a flexible network topology to which some examples of the present disclosure may be applied.

[0046] To compensate for incomplete network coverage areas, a network topology that allows for more flexible and resilient split radio access networks (RANs) may be considered. For this purpose, various nodes, such as integrated access backhaul (IAB) nodes, relays, and radio frequency (RF) repeaters, as illustrated in Figure 1, may be applied, or a non-terrestrial network (NTN) may be integrated. For example, an IAB node may correspond to a node that provides wireless backhaul. For example, a relay may refer to any intermediate point, and in the case of a sidelink relay where a terminal functions as a relay, it may collectively refer to a terminal-to-network (U2N) relay and a terminal-to-terminal (U2U) relay. For example, an RF repeater may correspond to a node that simply performs the function of signal amplification and forwarding, or in the case of a network-controlled repeater, it may not only amplify and forward signals but also adjust its transmission and reception settings based on information provided by the network. For example, NTN nodes could be satellites or aircraft that provide NTN coverage that terrestrial networks struggle to provide. Beyond these examples, various intermediate points can be introduced to improve the network topology.

[0047] Referring to Figure 1, a split RAN can support the division of a base station into a centralized unit (CU) and one or more distributed units (DUs). The CU and DU can correspond to logical units. The CU can be further divided into a control plane (CP) portion and one or more user plane (UP) portions. Since a failure in the CU-CP affects not only the CU-UP but also the DUs, various intermediate points can be introduced to compensate for this.

[0048] An intermediate point may correspond to a terminal or a base station, depending on its relationship to other nodes. For example, an IAB node may include a mobile-termination (MT) portion and a unit (DU). The MT may connect the IAB node to a donor node. The unit (DU) of an IAB node may serve other terminals or connect to other IAB nodes to provide multi-hop wireless backhaul to the terminal. For example, an IAB node may correspond to a base station in its relationship to a user-side node, and to a terminal in its relationship to a network-side node.

[0049] In some examples of the present disclosure, the description of a terminal may equally apply not only to a user-side endpoint, but also to an intermediate point corresponding to a terminal in a relative relationship with a network-side endpoint. Similarly, in some examples of the present disclosure, the description of a base station may equally apply not only to a network-side endpoint, but also to an intermediate point corresponding to a base station in a relative relationship with a user-side endpoint. In most cases where there is no additional description of the operations of three or more entities, the communicating entities in the present disclosure are briefly described as terminals and / or base stations (or first nodes and / or second nodes), where the terms terminal and / or base stations (or first nodes and / or second nodes) are interpreted to include / replace any endpoint or any intermediate point in relation to other nodes.

[0050] As such, in some examples of the present disclosure, for the sake of simplicity of explanation, the subjects of the operation may be referred to as terminals and / or base stations (or first nodes and / or second nodes). In addition, the terms terminal and / or base station (or first node and / or second node) may also be interpreted / replaced as in the following examples: For example, the terminal (or first node) and the base station (or second node) may respectively correspond to the first endpoint and the second endpoint; may respectively correspond to the endpoint and the intermediate point; may respectively correspond to the intermediate point and the endpoint; or may respectively correspond to the first intermediate point and the second intermediate point.

[0051] In the present disclosure, there may be zero or more intermediate points between the base station and the terminal. If an intermediate point exists, it may correspond to an IAB node / relay / RF repeater / NTN node, or a node supporting other functions. The intermediate point may be a node with a fixed location or a node with an unfixed location.

[0052] Systems applicable to this disclosure

[0053] FIG. 2 illustrates an example of a communication system to which some examples of the present disclosure may be applied.

[0054] The communication system (100) applied to the present disclosure includes a wireless device (110), a network device (120), and a network (130). Here, the wireless device (110) refers to a device that performs communication using a wireless access technology (e.g., LTE, LTE-A, LTE-A pro, NR, 5G, 5G-A, 6G) and may be referred to as a communication / wireless / 5G / 6G device. Although not limited thereto, the wireless device (110) may include a robot (110a), a vehicle (110b-1, 110b-2), an XR (extended reality) device (110c), a hand-held device (110d), a home appliance (110e), an IoT (Internet of Things) device (110f), and an AI (artificial intelligence) device / server (110g). For example, the vehicle may include a vehicle equipped with a wireless communication function, an autonomous vehicle, a vehicle capable of performing vehicle-to-vehicle communication, etc. Here, the vehicle (110b-1, 110b-2) may include an unmanned aerial vehicle (UAV) (e.g., a drone). The XR device (110c) includes an augmented reality (AR) / virtual reality (VR) / mixed reality (MR) device, and may be implemented in the form of a head-mounted device (HMD), a head-up display (HUD) equipped in a vehicle, a television, a smartphone, a computer, a wearable device, a home appliance, digital signage, a vehicle, a robot, etc. The portable device (110d) may include a smartphone, a smart pad, a wearable device (e.g., a smart watch, smart glasses), a computer (e.g., a laptop, etc.), etc. The home appliance (110e) may include a TV, a refrigerator, a washing machine, etc. The IoT device (110f) may include a sensor, a smart meter, etc. The wireless device (110) may correspond to a terminal (or first node) or an intermediate point.The network device (120) may correspond to a base station (or second node) or another intermediate point. For example, the network device (120) may also be implemented as a wireless device (110), and a specific wireless device (120a) may act as a network device (120) to another wireless device (110).

[0055] Wireless devices (110a to 110f) can be connected to a network (130) via a network device (120). AI technology can be applied to the wireless devices (110a to 110f), and the wireless devices (110a to 110f) can be connected to an AI server (110g) via a network (130). The network (130) can be configured using a 3G network, a 4G (e.g., LTE) network, a 5G (e.g., NR), or a 6G network. The wireless devices (110a to 110f) can communicate with each other via the network device (120) / network (130), but can also communicate directly (e.g., sidelink communication) without going through the network device (120) / network (130). For example, vehicles (110b-1, 110b-2) can communicate directly (e.g., V2V (vehicle to vehicle) / V2X (vehicle to everything) communication). Additionally, an IoT device (110f) (e.g., a sensor) can communicate directly with another IoT device (e.g., a sensor) or another wireless device (110a to 110f).

[0056] Wireless communication / connection (150a, 150b, 150c) can be established between wireless devices (110a to 110f) / network devices (120), network devices (120) / network devices (120). Here, the wireless communication / connection can be established through various wireless access technologies such as uplink / downlink communication (150a), sidelink communication (150b) (or D2D communication), and communication between network devices (150c) (e.g., relay, IAB (integrated access backhaul)). Through the wireless communication / connection (150a, 150b, 150c), the wireless device and the network device / wireless device, and the network device and the network device can transmit / receive wireless signals to each other. For example, the wireless communication / connection (150a, 150b, 150c) can transmit / receive signals through various physical channels. To this end, based on various descriptions of the present disclosure, at least some of various configuration information setting processes for transmitting / receiving wireless signals, various signal processing processes (e.g., channel encoding / decoding, modulation / demodulation, resource mapping / demapping, etc.), resource allocation processes, etc., may be performed.

[0057] Device applicable to the present disclosure

[0058] FIG. 3 illustrates an example of a wireless device to which some examples of the present disclosure may be applied.

[0059] Referring to FIG. 3, the wireless device (200) can transmit and receive wireless signals via various wireless access technologies (e.g., LTE, LTE-A, LTE-A pro, NR, 5G, 5G-A, 6G). The wireless device (200) includes at least one processor (202) and at least one memory (204), and may additionally include at least one transceiver (206) and / or at least one antenna (208).

[0060] The processor (202) controls the memory (204) and / or the transceiver (206), and may be configured to implement the descriptions, functions, procedures, proposals, methods, and / or operational flowcharts disclosed in this document. For example, the processor (202) may process information in the memory (204) to generate first information / signal, and then transmit a wireless signal including the first information / signal via the transceiver (206). In addition, the processor (202) may receive a wireless signal including second information / signal via the transceiver (206), and then store information obtained from signal processing of the second information / signal in the memory (204). The memory (204) may be connected to the processor (202) and may store various information related to the operation of the processor (202). For example, the memory (204) may store software code including instructions for performing some or all of the processes controlled by the processor (202), or for performing the descriptions, functions, procedures, proposals, methods, and / or operational flowcharts disclosed herein. Here, the processor (202) and the memory (204) may be part of a communication modem / circuit / chip designed to implement wireless communication technology. The transceiver (206) may be connected to the processor (202) and may transmit and / or receive wireless signals via at least one antenna (208). The transceiver (206) may include a transmitter and / or a receiver. The transceiver (206) may be used interchangeably with an RF (radio frequency) unit. In the present disclosure, a wireless device may also mean a communication modem / circuit / chip.

[0061] Hereinafter, the hardware elements of the wireless device (200) will be described in more detail. Although not limited thereto, at least one protocol layer may be implemented by at least one processor (202). For example, at least one processor (202) may implement at least one layer (e.g., a functional layer such as physical (PHY), media access control (MAC), radio link control (RLC), packet data convergence protocol (PDCP), radio resource control (RRC), and service data adaptation protocol (SDAP)). At least one processor (202) may generate at least one Protocol Data Unit (PDU) and / or at least one Service Data Unit (SDU) according to the descriptions, functions, procedures, proposals, methods, and / or operation flowcharts disclosed in this document. At least one processor (202) may generate a message, control information, data, or information according to the descriptions, functions, procedures, proposals, methods, and / or operation flowcharts disclosed in this document. At least one processor (202) can generate a signal (e.g., a baseband signal) comprising a PDU, an SDU, a message, control information, data or information according to the functions, procedures, proposals and / or methods disclosed in this document, and provide the signal to at least one transceiver (206). At least one processor (202) can receive a signal (e.g., a baseband signal) from at least one transceiver (206) and obtain the PDU, SDU, message, control information, data or information according to the descriptions, functions, procedures, proposals, methods and / or operational flowcharts disclosed in this document.

[0062] At least one processor (202) may be referred to as a controller, a microcontroller, a microprocessor, or a microcomputer. The at least one processor (202) may be implemented by hardware, firmware, software, or a combination thereof. For example, at least one application specific integrated circuit (ASIC), at least one digital signal processor (DSP), at least one digital signal processing device (DSPD), at least one programmable logic device (PLD), or at least one field programmable gate array (FPGA) may be included in the at least one processor (202). The descriptions, functions, procedures, proposals, methods, and / or operation flowcharts disclosed in this document may be implemented using firmware or software, and the firmware or software may be implemented to include modules, procedures, functions, etc. The descriptions, functions, procedures, proposals, methods, and / or operation flowcharts disclosed in this document may be included in the at least one processor (202), or may be stored in at least one memory (204) and driven by the at least one processor (202). The descriptions, functions, procedures, suggestions, methods and / or flowcharts disclosed in this document may be implemented using firmware or software in the form of code, instructions and / or sets of instructions.

[0063] At least one memory (204) can be connected to at least one processor (202) and can store various forms of data, signals, messages, information, programs, codes, instructions and / or commands. The at least one memory (204) can be configured as a read only memory (ROM), a random access memory (RAM), an erasable programmable read only memory (EPROM), a flash memory, a hard drive, a register, a cache memory, a computer readable storage medium and / or a combination thereof. The at least one memory (204) can be located internally and / or externally to the at least one processor (202). In addition, the at least one memory (204) can be connected to the at least one processor (202) via various technologies such as a wired or wireless connection.

[0064] At least one transceiver (206) can transmit user data, control information, wireless signals / channels, etc., mentioned in the methods and / or flowcharts of this document to at least one other device. At least one transceiver (206) can receive user data, control information, wireless signals / channels, etc. mentioned in the descriptions, functions, procedures, proposals, methods and / or flowcharts disclosed in this document from at least one other device. For example, at least one transceiver (206) can be connected to at least one processor (202) and can transmit and receive wireless signals. For example, at least one processor (202) can control at least one transceiver (206) to transmit user data, control information, or wireless signals to at least one other device. Furthermore, at least one processor (202) can control at least one transceiver (206) to receive user data, control information, or wireless signals from at least one other device. Additionally, at least one transceiver (206) may be connected to at least one antenna (208), and at least one transceiver (206) may be configured to transmit and receive user data, control information, wireless signals / channels, etc. mentioned in the descriptions, functions, procedures, proposals, methods and / or operational flowcharts disclosed in this document via at least one antenna (208). In this document, at least one antenna may be a plurality of physical antennas or a plurality of logical antennas (e.g., antenna ports). At least one transceiver (206) may convert the received wireless signals / channels, etc. from RF band signals to baseband signals in order to process the received user data, control information, wireless signals / channels, etc. using at least one processor (202).At least one transceiver (206) may convert user data, control information, wireless signals / channels, etc. processed by at least one processor (202) from a baseband signal to an RF band signal. For this purpose, at least one transceiver (206) may include an (analog) oscillator and / or filter.

[0065] The components of the wireless device described with reference to FIG. 3 may be referred to by different terms in terms of functionality. For example, the processor (202) may be referred to as a control unit, the transceiver (206) as a communication unit, and the memory (204) as a storage unit. In some cases, the communication unit may be used to mean at least a portion of the processor (202) and the transceiver (206).

[0066] The structure of the wireless device described with reference to FIG. 3 can be understood as the structure of at least a portion of various devices. For example, the structure of the wireless device illustrated in FIG. 3 can be at least a portion of various devices described with reference to FIG. 2 (e.g., a robot (110a), a vehicle (110b-1, 110b-2), an XR device (110c), a portable device (110d), a home appliance (110e), an IoT device (110f), an AI device / server (110g)). Furthermore, according to various embodiments, in addition to the components illustrated in FIG. 3, the device may further include other components.

[0067] For example, the device may be a portable device such as a smartphone, a smart pad, a wearable device (e.g., a smart watch, smart glasses), or a portable computer (e.g., a laptop, etc.). In this case, the device may further include at least one of a power supply unit that supplies power and includes a wired / wireless charging circuit, a battery, etc., an interface unit that includes at least one port for connection with another device (e.g., an audio input / output port, a video input / output port), and an input / output unit for inputting and outputting image information / signals, audio information / signals, data, and / or information input from a user.

[0068] For example, the device may be a mobile device such as a mobile robot, a vehicle, a train, an aerial vehicle (AV), a ship, etc. In this case, the device may further include at least one of a driving unit including at least one of an engine, a motor, a power train, wheels, brakes, and a steering unit of the device, a power supply unit including a wired / wireless charging circuit, a battery, etc. that supplies power, a sensor unit that senses status information, environmental information, and user information of the device or its surroundings, an autonomous driving unit that performs functions such as path maintenance, speed control, and destination setting, and a position measurement unit that obtains location information of the mobile device through a global positioning system (GPS) and various sensors.

[0069] For example, the device may be an XR device such as an HMD, a head-up display (HUD) installed in a vehicle, a television, a smartphone, a computer, a wearable device, a home appliance, a digital signage, a vehicle, a robot, etc. In this case, the device may further include at least one of a power supply unit that supplies power and includes a wired / wireless charging circuit, a battery, etc., an input / output unit that obtains control information, data, etc. from the outside and outputs the generated XR object, and a sensor unit that senses status information, environmental information, and user information of the device or the surroundings of the device.

[0070] For example, the device may be a robot that can be classified into industrial, medical, household, military, etc. types depending on the purpose or field of use. In this case, the device may further include at least one of a sensor unit that senses status information, environmental information, and user information of the device or its surroundings, and a driving unit that performs various physical actions, such as moving the robot joints.

[0071] For example, the device may be an AI device such as a TV, a projector, a smartphone, a PC, a laptop, a digital broadcasting terminal, a tablet PC, a wearable device, a set-top box (STB), a radio, a washing machine, a refrigerator, digital signage, a robot, a vehicle, etc. In this case, the device may further include at least one of an input unit that acquires various types of data from the outside, an output unit that generates output related to sight, hearing, or touch, a sensor unit that senses status information, environmental information, and user information of the device or its surroundings, and a training unit that trains a model composed of an artificial neural network using learning data.

[0072] The structure of the wireless device illustrated in FIG. 3 may be understood as a part of a terminal (or first node), or as a part of an intermediate point, or as a part of a base station (or second node). If the device illustrated in FIG. 3 is a base station (or second node), the device may further include a wired transceiver for front haul and / or back haul communications. If the front haul and / or back haul communications are based on wireless communications, at least one transceiver (206) illustrated in FIG. 3 may be used for front haul and / or backhaul communications, and a wired transceiver may not be included.

[0073] Communication procedures

[0074] FIG. 4 exemplarily illustrates a communication procedure between a first node and a second node to which some examples of the present disclosure may be applied.

[0075] FIG. 4 illustrates operations of a first node (110) (e.g., a terminal) and a second node (120) (e.g., a base station) transmitting and / or receiving data and operations performed prior thereto.

[0076] In step S101, the first node (110) and the second node (120) can perform synchronization. For example, the terminal (110) performs an initial cell search operation. Specifically, the terminal (110) can detect at least one synchronization signal transmitted from the base station (120) according to a predefined rule. Here, the synchronization signal can include a plurality of synchronization signals (e.g., a primary synchronization signal, a secondary synchronization signal) classified according to a structure or purpose. Through this, the terminal (110) can confirm the boundaries of the frame, subframe, slot, and / or symbol of the base station (120) and obtain information (e.g., a cell identifier) ​​about the base station (120).

[0077] In step S103, the first node (110) can obtain system information transmitted from the second node (120). For example, the system information is information related to the properties, characteristics, and / or capabilities of the base station (120) required to access the base station (120) and use the service, and can be classified according to the content (e.g., whether it is essential for access), transmission structure (e.g., the channel used, whether it is provided in an on-demand manner), etc., and can be classified into, for example, a master information block (MIB) and a system information block (SIB). If necessary, the terminal (110) can transmit a signal requesting system information before receiving the system information. Such requesting and providing of system information may be performed after a random access procedure described below.

[0078] In step S105, the first node (110) and the second node (120) can perform a random access procedure. For example, the terminal (110) can transmit and / or receive at least one message (e.g., a random access preamble, a random access response (RAR) message, etc.) for a random access procedure based on information related to a random access channel of the base station (120) obtained through system information (e.g., channel position, channel structure, structure of a supported preamble, etc.). For example, the terminal (110) may transmit a preamble (e.g., message 1 (MSG1)) over a random access channel, receive a random access response (RAR) message (e.g., message 2 (MSG2)), transmit a message (e.g., message 3 (MSG3)) including information related to the terminal (110) (e.g., identification information) using scheduling information included in the RAR message to the base station (120), and receive a message for contention resolution and / or connection establishment (e.g., message 4 (MSG4)). As another example, MSG1 and MSG3 may be transmitted and received as one message (e.g., message A (MSG A)), or MSG2 and MSG4 may be transmitted and received as one message (e.g., message B (MSG B)).

[0079] In step S107, the first node (110) and the second node (120) can perform signaling of control information. For example, the control information can be defined in various layers, such as a layer that controls a connection (e.g., a radio resource control (RRC) layer), a layer that handles mapping between logical channels and transmission channels (e.g., a media access control (MAC) layer), and a layer that handles physical channels (e.g., a physical (PHY) layer). For example, the terminal (110) and the base station (120) can perform at least one of signaling for establishing a connection, signaling for determining settings related to communication, and signaling for indicating allocated resources.

[0080] In step S109, the first node (110) and the second node (120) can transmit and / or receive data. For example, the terminal (110) and the base station (120) can process, transmit, and / or receive data based on signaling of control information. For example, when transmitting data, the terminal (110) or the base station (120) can perform at least one of channel encoding, rate matching, scrambling, constellation mapping, layer mapping, waveform modulation, antenna mapping, and resource mapping on information bits. For example, when receiving data, the terminal (110) or the base station (120) can perform at least one of signal extraction from resources, waveform demodulation for each antenna, signal arrangement considering layer mapping, constellation demapping, descrambling, and channel decoding.

[0081] sidelink relay

[0082] Sidelink relay can support 5G ProSe (proximity service) U2N (UE-to-network) relay function to provide network connectivity to U2N remote UE. Both L2 (layer 2) and L3 (layer 3) U2N relay architectures can be supported. The L3 U2N relay operates transparently to the serving RAN of the U2N relay UE and can be responsible for sidelink resource control. The U2N relay UE may be required to be in RRC_CONNECTED state to perform unicast data relay.

[0083] For L2 U2N relay, both the U2N relay UE and the U2N remote UE may be required to be in RRC_CONNECTED state for relayed unicast data transmission and reception. If all U2N remote UEs connected to the U2N relay UE are in RRC_INACTIVE or RRC_IDLE state, the U2N relay UE may be in RRC_IDLE, RRC_INACTIVE, or RRC_CONNECTED state.

[0084] A single unicast link can be established between one L2 U2N relay UE and one L2 U2N remote UE. The traffic of the U2N remote UE through a specific U2N relay UE and the U2N relay UE's own traffic can be separated into different Uu RLC channels on Uu.

[0085] FIG. 5 illustrates an example of a user plane protocol stack for an L2 U2N relay to which the present disclosure may be applied.

[0086] FIG. 6 illustrates an example of a control plane protocol stack for an L2 U2N relay to which the present disclosure may be applied.

[0087] Referring to FIGS. 5 and 6, the protocol structure of the side link relay is described below.

[0088] In the user plane and control plane protocol stacks of the L2 U2N relay architecture, the sidelink relay adaptation protocol (SRAP) sublayer can be located above the RLC sublayer. This can be applied to both the PC5 interface and the Uu interface. Uu SDAP, PDCP, and RRC can be terminated between the L2 U2N remote UE and the gNB. SRAP, RLC, MAC, and PHY can be terminated at each hop (e.g., the link between the L2 U2N remote UE and the L2 U2N relay UE, and the link between the L2 U2N relay UE and the gNB).

[0089] For uplink, the Uu SRAP sublayer may support UL bearer mapping between the PC5 relay RLC channel for relay and the Uu relay RLC channel via the Uu relay UE Uu interface. In addition, the Uu SRAP header may include identification information of the L2 U2N remote UE Uu radio bearer and the local remote UE ID to support L2 U2N remote UE identification for UL traffic. The PC5 SRAP sublayer may be responsible for UL bearer mapping between the remote UE Uu radio bearer and the PC5 relay RLC channel.

[0090] In the downlink, the Uu SRAP sublayer may support mapping and multiplexing of end-to-end radio bearers (e.g., signaling radio bearer (SRB), data radio bearer (DRB)) of remote UEs from the gNB to Uu relay RLC channels over the relay UE Uu interface. The gNB may include remote UE identification information in the Uu SRAP header to enable the relay UE to map received packets to the correct PC5 relay RLC channels. The local remote UE ID may be included in both the PC5 SRAP header and the Uu SRAP header, and the gNB may configure the local remote UE ID to the U2N relay UE and manage it to avoid collisions.

[0091] FIG. 7 illustrates an example of a protocol stack of a discovery message for a U2N relay to which the present disclosure may be applied.

[0092] Referring to Fig. 7, relay discovery of a side link relay is described below.

[0093] Various discovery models can be supported for U2N relay discovery. A U2N remote UE can transmit and monitor relay discovery messages in the RRC_IDLE, RRC_INACTIVE, or RRC_CONNECTED states. The network can broadcast thresholds used to determine whether a U2N remote UE should transmit a relay discovery request message.

[0094] Similarly, a U2N relay UE can transmit and monitor relay discovery messages in RRC_IDLE, RRC_INACTIVE, or RRC_CONNECTED states. The network can broadcast a maximum Uu RSRP (reference signal received power) threshold and / or a minimum Uu RSRP threshold, which are used by the U2N relay UE to determine whether to transmit relay discovery messages to U2N remote UEs. The network can provide relay discovery configuration via broadcast or dedicated signaling. The U2N remote UE and U2N relay UE can also operate as preset without separate signaling.

[0095] The resource pool used for NR sidelink communication can be used for relay discovery. Alternatively, the network may configure a dedicated resource pool for relay discovery. If a dedicated resource pool for relay discovery is configured, only that dedicated resource pool may be used for relay discovery. Sidelink power control for relay discovery messages may be the same as for NR sidelink communication. For relay discovery messages, encryption or integrity protection may not be applied at the PDCP layer. The UE can determine whether the gNB supports relay discovery, non-relay discovery, or both via system information block 12 (SIB12).

[0096] Relay selection / reselection in side link relays is described below.

[0097] A U2N remote UE can perform wireless measurements on the PC5 interface and use them for U2N relay selection and reselection. If there is no unicast PC5 connection between the U2N relay UE and the U2N remote UE, the U2N remote UE can use sidelink discovery-RSRP (SD-RSRP) measurements to assess whether the PC5 link quality to the U2N relay UE satisfies the relay selection criteria.

[0098] For relay reselection, the U2N remote UE can perform relay reselection trigger evaluation using sidelink-RSRP (SL-RSRP) measurements when there is data transmission from the U2N relay UE to the U2N remote UE. Either SL-RSRP or SD-RSRP may be used when there is no data transmission. If the PC5 link quality for the U2N relay UE measured by the U2N remote UE exceeds a configured threshold, the U2N relay UE can be considered compliant from a radio perspective.

[0099] A U2N remote UE may trigger U2N relay selection if the direct Uu signal strength is below a set threshold, or if instructed by a higher layer.

[0100] The U2N remote UE may trigger U2N relay reselection if the current PC5 signal strength of the U2N relay UE is below a (pre-)configured threshold, if the U2N relay UE has signaled cell (re-)selection, handover or Uu RLF (Radio Link Failure) via PC5-RRC signaling, if the U2N remote UE has received a PC5-S (signaling) link release message, if it has detected a PC5 RLF, or if instructed by higher layers.

[0101] FIG. 8 illustrates an example of an L2 U2N remote UE connection establishment procedure to which the present disclosure can be applied.

[0102] Referring to FIG. 8, the control plane procedure for L2 U2N relay in sidelink relay is described below.

[0103] A U2N remote UE may need to establish a PDU session / DRB with the network itself prior to transmitting user plane data. The NR vehicle-to-everything (V2X) PC5 unicast link establishment procedure may be reused to establish a secure unicast link between a U2N remote UE and a U2N relay UE before the U2N remote UE establishes a Uu RRC connection with the network via the U2N relay UE. The Uu SRB1 / SRB2 and DRB configuration of the U2N remote UE may follow the Uu setup procedure for the L2 U2N relay.

[0104] Connection establishment of a U2N remote UE may begin with relay discovery and PC5-RRC connection establishment. Subsequently, the U2N remote UE may send the first RRC message (e.g., RRCSetupRequest) to the gNB via the relay UE. If the U2N relay UE is not in RRC_CONNECTED state, it may need to initiate its own connection establishment upon receiving this message. The gNB responds with an RRCSetup message, which may be forwarded to the U2N remote UE, transmitted in Uu over the SRB0 relay channel, and in PC5 over the designated PC5 relay RLC channel. The gNB and the U2N relay UE may then perform a relay channel setup procedure over Uu, and the U2N relay / remote UE may establish a PC5 relay RLC channel for the SRB1 relay over PC5.

[0105] Subsequently, the U2N remote UE may complete the RRC connection over Uu by sending an RRCSetupComplete message to the gNB through the U2N relay UE. After that, the U2N remote UE and the gNB may perform the Uu security procedure, and the security message may be delivered through the U2N relay UE. Finally, the gNB may send an RRCReconfiguration message to the U2N remote UE for SRB2 / DRB configuration, and the U2N remote UE may respond with an RRCReconfigurationComplete message. In addition, the gNB may establish an additional Uu relay RLC channel between the gNB and the U2N relay UE for relay traffic, and a PC5 relay RLC channel between the U2N relay UE and the U2N remote UE.

[0106] Referring to FIGS. 9 and 10, service continuity for L2 U2N relay in sidelink relay is described.

[0107] FIG. 9 illustrates an example of a procedure for U2N remote UE switching to a direct Uu cell to which the present disclosure may be applied.

[0108] For service continuity of L2 U2N relay, when a U2N remote UE directly switches to a Uu path, measurement setup and measurement reporting procedures may be performed so that both relay link measurements and Uu link measurements can be evaluated. Measurement results from a U2N remote UE may be reported when the configured measurement reporting criteria are met, and the sidelink relay measurement report may include the source L2 ID of the U2N relay UE, the serving cell ID (e.g., NR cell global identity (NCGI)), and the sidelink measurement quantity.

[0109] The gNB may decide to switch the U2N remote UE to the direct Uu path and send an RRCReconfiguration message to the U2N remote UE. After receiving this message, the U2N remote UE may stop transmitting UP and CP through the U2N relay UE. The U2N remote UE may then synchronize with the gNB and perform random access.

[0110] The UE (which was a remote UE) sends RRCReconfigurationComplete to the gNB through a direct path, and from then on, the UE can use the RRC connection through the direct path with the gNB. The gNB can re-establish the connection between the U2N relay UE and the gNB by sending an RRCReconfiguration message to the U2N relay UE. The U2N relay UE or the U2N remote UE can initiate a PC5 unicast link release (PC5-S), and the data path can be switched from an indirect path to a direct path between the U2N remote UE and the gNB. During the path switching, DL / UL lossless transmission may be achieved according to the PDCP data recovery procedure.

[0111] FIG. 10 illustrates an example of a procedure for U2N remote UE switching to an indirect path to which the present disclosure may be applied.

[0112] The gNB may select a U2N relay UE in RRC_IDLE, RRC_INACTIVE, or RRC_CONNECTED state as the target U2N relay UE for switching from the direct path to the indirect path. For service continuity of the L2 U2N remote UE, when the U2N remote UE switches to the indirect path via a U2N relay UE in RRC_CONNECTED state, the U2N remote UE may report one or more candidate U2N relay UEs and Uu measurements.

[0113] The gNB may decide to switch the U2N remote UE to the target U2N relay UE and may send an RRCReconfiguration message to the target U2N relay UE. This message may include the remote UE's local ID and L2 ID, Uu and PC5 relay RLC channel configuration for relay, and bearer mapping configuration. The gNB may then send an RRCReconfiguration message to the U2N remote UE, which may include the U2N relay UE ID, PC5 relay RLC channel configuration for relay traffic, and the associated end-to-end radio bearer(s).

[0114] After receiving this message, the U2N remote UE can stop transmitting UP and CP over Uu and establish a PC5 connection with the target U2N relay UE. The U2N remote UE can complete the path switching procedure by sending an RRCReconfigurationComplete message to the gNB through the relay UE. The data path can then be switched from a direct path to an indirect path between the U2N remote UE and the gNB. A similar procedure can be applied when the selected U2N relay UE is in RRC_IDLE or RRC_INACTIVE state, in which case the PC5 link establishment can be performed before receiving the RRCReconfiguration message.

[0115] Failure handling in multi-hop relays

[0116] When a relay UE and a remote UE are equipped with U2N relay capabilities, the relay UE within network coverage can provide an indirect path connection to the network to the U2N remote UE(s). In this case, a remote UE outside network coverage does not have a direct path to the network and can indirectly connect to the network through an indirect path via the U2N relay within network coverage.

[0117] When a remote UE moves away from a relay UE or the relay UE moves out of network coverage, the remote UE can support multi-hop (MH) operation consisting of a single indirect path through multiple U2N relay UEs. That is, in contrast to the case where there is only one relay UE between the remote UE and the network, the case where there are multiple relay UEs between the remote UE and the network can be supported.

[0118] For example, assuming a 2-hop U2N relay, the indirect path may consist of a remote UE - a first relay UE - a last relay UE - a gNB. The indirect path may support communication in the direction from the remote UE to the gNB, and / or communication in the direction from the gNB to the remote UE.

[0119] For example, assuming a 3-hop U2N relay, the indirect path may consist of a remote UE - a first relay UE - a second relay UE - a last relay UE - a gNB. The indirect path may support communication in the direction from the remote UE to the gNB, and / or communication in the direction from the gNB to the remote UE. The first relay UE is directly connected to the remote UE, and the last relay UE is directly connected to the gNB.

[0120] In MH relay, the last relay UE may also be referred to as the root relay UE. The remaining relay UEs (in the example above, the first and second relay UEs) excluding the last relay may also be referred to as intermediate relay UEs.

[0121] The relationship between directly connected UEs of an indirect path including MH relay(s) can be defined as follows. Among the directly connected UEs, a remote UE or a UE that is relatively closer to a remote UE can be referred to as a child UE of the last / root relay UE or a UE that is relatively closer to a network node. Among the directly connected UEs, a UE that is relatively closer to the last / root relay UE or a network node can be referred to as a parent UE of the remote UE or a UE that is relatively closer to the remote UE. For example, in the configuration of remote UE - first relay UE - second relay UE - last relay UE - gNB of the above-described 3-hop U2N relay, the remote UE is a child UE of the first relay UE, and the second relay UE corresponds to a parent UE of the first relay UE. Similarly, the first relay UE is a child UE of the second relay UE, and the last relay UE corresponds to a parent UE of the second relay UE.

[0122] In a conventional relay architecture, only one U2N relay UE on the indirect path can report a connection failure detected by the relay UE to the remote UE. If this signaling constraint were applied to the MH relay architecture, the last relay UE would not be able to directly notify the remote UE even if it detects a connection failure. Consequently, the remote UE would be unable to properly handle failures occurring on the indirect path.

[0123] This disclosure describes various examples of notification based on connection failure, etc. in an MH relay structure, and / or connection re-establishment accordingly.

[0124] FIG. 11 is a drawing for explaining an example of a method performed by a first terminal according to the present disclosure.

[0125] In step S1110, the first terminal may receive a first message related to a failure between the second terminal and the first network node from the second terminal.

[0126] In some examples, the failure between the second terminal and the first network node may include a radio link failure at a terminal-to-network interface (e.g., a Uu interface) between the second terminal and a first cell of the first network node.

[0127] In some examples, the first message may include a higher layer (e.g., RRC) message over a terminal-to-terminal interface (e.g., a PC5 / SL interface).

[0128] In step S1120, the first terminal can transmit a second message generated based on the first message to the third terminal.

[0129] In some examples, the second message may trigger connection re-establishment of the third terminal. For example, the connection re-establishment may include RRC connection re-establishment.

[0130] In some examples, the second terminal may be a parent terminal of the first terminal, and the third terminal may be a child terminal of the first terminal.

[0131] In some examples, the second message may include a higher layer (e.g., RRC) message over a terminal-to-terminal interface (e.g., a PC5 / SL interface).

[0132] In some examples, the second message may be reconstructed based on information contained in the first message.

[0133] In some examples, additional information may be provided to a third terminal by the first terminal. For example, the additional information may be provided to the third terminal by the first terminal via a second message.

[0134] For example, the additional information may be based on the first message. For example, the additional information may be based on information related to a failure between the second terminal and the first network node included in the first message. For example, the additional information may correspond to information indicating a specific value / state / type / action (e.g., reselection of a relay terminal) based on information related to a failure between the second terminal and the first network node included in the first message.

[0135] For example, the additional information may include: instruction information based on information related to a failure between the second terminal and the first network node included in the first message; information about re-establishing a connection between the first terminal and a first cell of the first network node (e.g., the cell where the failure occurred / detected); information about re-establishing a connection between the first terminal and a second cell of the first network node; information about re-establishing a connection between the first terminal and a third cell of the second network node; and / or information about a fourth terminal. For example, the third terminal may attempt to re-establish a connection with the first cell, re-establish a connection with the second cell, re-establish a connection with the third cell, and / or re-establish a connection through the fourth terminal based on the additional information.

[0136] In some examples, the first terminal, the second terminal, the third terminal, and the fourth terminal may correspond to U2N relay terminals. Alternatively, the first terminal, the second terminal, and the fourth terminal may correspond to U2N relay terminals, and the third terminal may correspond to a remote terminal.

[0137] Additionally or alternatively to the example described with reference to FIG. 11, a third message may be transmitted by the first terminal to the third terminal based on a wireless link failure in the terminal-to-terminal interface (e.g., PC5 / SL interface) between the first terminal and the second terminal, triggering connection re-establishment of the third terminal. Accordingly, the third terminal may attempt connection re-establishment.

[0138] The method described in the example of FIG. 11 may be performed by the wireless device (200) of FIG. 3 corresponding to the first node (110) of FIG. 2 described above. For example, one or more processors (202) of the wireless device (200) of FIG. 3 may be configured to receive a first message related to a failure between a second terminal and a first network node from the second terminal via one or more transceivers (206); and to transmit a second message generated by the wireless device (200) based on the first message to a third terminal via the one or more transceivers. Furthermore, one or more memories (204) of the wireless device (200) may store instructions for performing the method described in the example of FIG. 11 or the examples described below when executed by one or more processors (202).

[0139] FIG. 12 is a drawing illustrating an example of a method performed by a third terminal according to the present disclosure.

[0140] In step S1210, the third terminal can receive, from the first terminal, a second message generated by the first terminal based on the first message.

[0141] In some examples, the first message may be a message transmitted from the second terminal to the first terminal. Additionally, the first message may be a message related to a failure between the second terminal and the first network node.

[0142] In step S1220, the third terminal can perform a connection re-establishment procedure triggered by the second message.

[0143] In the example of Fig. 12, the specific features of the first message, the second message, the first terminal, the second terminal, the third terminal, and connection re-establishment are the same as the description referring to the example of Fig. 11, so redundant descriptions are omitted.

[0144] The method described in the example of FIG. 12 may be performed by the wireless device (200) of FIG. 3 corresponding to the second node (120) of FIG. 2 described above. For example, one or more processors (202) of the wireless device (200) of FIG. 3 may be configured to receive a second message generated by the first terminal based on the first message from the first terminal through one or more transceivers (206), and to perform a connection re-establishment procedure triggered by the second message. Furthermore, one or more memories (204) of the wireless device (200) may store commands for performing the method described in the example of FIG. 12 or the examples described below when executed by one or more processors (202).

[0145] Below, specific examples of the present disclosure for notification based on connection failure, etc., and / or connection re-establishment accordingly in a multi-hop (MH) relay architecture are described.

[0146] Example 1

[0147] This embodiment describes basic features applicable to other embodiments of the present disclosure.

[0148] In the examples of the present disclosure, a 2-hop U2N relay is assumed for a remote UE. In this case, relay UE1 may be the first relay UE directly connected to the remote UE based on a PC5 unicast link, and relay UE2 may be the last relay UE directly connected to the gNB based on a Uu connection.

[0149] The examples of the present disclosure can also be applied to a multi-hop structure of more than 2 hops. In the case of more than 2 hops, additional intermediate relay UE(s) may exist between the first relay UE and the last relay UE (e.g., the root relay UE). For example, a 3-hop U2N relay for a remote UE may be composed of the remote UE - the first relay UE - the second relay UE - the last relay UE - the gNB. In this case, the second relay UE corresponds to an additional intermediate relay UE compared to the 2-hop U2N relay.

[0150] In the present disclosure, a remote UE can discover a relay UE and connect to a network (NW) through the relay UE as follows:

[0151] - Step 1: U2U / U2N discovery (and U2U relay establishment) can be performed for remote UEs within NW coverage - Relay UE1 - Relay UE2.

[0152] -- Alternative 1a: During the U2N relay establishment procedure, relay UE1 and / or relay UE2 may enter the RRC_CONNECTED state.

[0153] -- Alternative 1b: Discovery message or PC5-RRC can trigger RRC configuration of relay UE1 and relay UE2 before U2N relay establishment.

[0154] -- PC5-RRC between remote UE and relay UE2 may require U2U relay connection for paging, system information, or failure notification.

[0155] --- If a U2U relay is not established between the remote UE and the relay UE2, the relay UE1 can forward the PC5-RRC message from the remote UE to the relay UE2, or from the relay UE2 to the remote UE, based on the path information between the remote UE and the relay UE2.

[0156] - Step 2: U2N relay establishment of relay UE1 can be performed via relay UE2, with or without RRC establishment of relay UE1 / UE2.

[0157] -- Alternative 2a: Can be triggered by relay UE1 as a remote UE.

[0158] -- Alternative 2b: Can be triggered by a remote UE that knows of a relay UE2 within NW coverage (e.g. by sending a remote RRC request message over SRB or by a PC5-RRC message).

[0159] -- Failure to establish a U2N relay (e.g. RRC connection failure of relay UE1 or UE2 or U2N relay not established by gNB) may trigger relay reselection by relay UE1.

[0160] --- Relay UE1 can trigger relay reselection of remote UE by sending PC5-RRC message.

[0161] -- Relay reselection of relay UE1 can trigger retransmission of remote RRC request message by relay UE1 or remote UE by sending PC5-RRC message.

[0162] - Step 3: By sending an RRC request message through SRB, a U2N relay of a remote UE can be established through relay UE1 / UE2, and an RRC setup can be received from the gNB.

[0163] Specifically, the remote UE can establish an RRC connection to the remote UE - relay UE1 - relay UE2 - gNB as follows:

[0164] - For L2 U2N relay operation, the following RRC state combinations can be supported:

[0165] -- Both the U2N relay UE and the U2N remote UE may be required to be in RRC CONNECTED state for transmission / reception of relayed unicast data; and

[0166] --- All intermediate relay UEs may be required to be in RRC_CONNECTED state for MH.

[0167] -- As long as all U2N remote UE(s) connected to the U2N relay UE are in RRC_IDLE, RRC_INACTIVE or RRC_CONNECTED state, the U2N relay UE may be in RRC_IDLE, RRC_INACTIVE or RRC_CONNECTED state.

[0168] - U2N remote UE and U2N relay UE1 can perform a discovery procedure and establish a PC5-RRC connection.

[0169] -- If it is not in network coverage or does not exceed a threshold, the remote UE may send a PC5-RRC message to relay UE1 to trigger U2N relay RRC connection establishment via another relay UE (e.g. relay UE2) (or if it is in network coverage and exceeds a threshold, it may trigger Uu RRC connection establishment).

[0170] -- To indicate that the U2N relay RRC connection setup is successful, the relay UE2 may send a PC5-RRC message to the remote UE.

[0171] - U2N remote UE and U2N Relay UE2 can perform discovery procedure and establish PC5-RRC connection using L2 U2U relay.

[0172] -- If within network coverage, the remote UE may send a PC5-RRC message to the relay UE2 to trigger Uu RRC connection establishment (or if not within network coverage, it may trigger U2N RRC connection establishment via another relay UE (e.g., relay UE2).

[0173] -- To indicate that the Uu RRC connection establishment is successful, the relay UE2 may send a PC5-RRC message to the remote UE.

[0174] - Using the specified PC5 relay RLC channel setup, the U2N remote UE can send a first remote RRC message (e.g., RRCSetupRequest) for connection establishment with the gNB via the relay UE1.

[0175] -- If the U2N relay UE1 is not in RRC_CONNECTED state but is within network coverage (e.g. camping on a suitable cell), it may be required to perform connection establishment itself when receiving a message on a specific PC5 relay RLC channel.

[0176] -- If the U2N relay UE1 is not out of network coverage (e.g., not camping on a suitable cell), the U2N relay UE1 can send a first relay RRC message (e.g., RRCSetupRequest) to establish a connection with the gNB via the relay UE2, using a specified PC5 relay RLC channel configuration.

[0177] --- During the RRC connection establishment procedure of the relay UE, the gNB may set up SRB0 to relay the Uu relay RLC channel to the U2N relay UE. The gNB may respond with an RRCSetup message to the U2N remote UE. The RRCSetup message may be sent to the U2N remote UE using the SRB0 relay channel over Uu and a specific PC5 relay RLC channel over PC5.

[0178] --- Alternative 1: Relay UE2 can send the first relay RRC message and the first remote RRC message to gNB as a single RRC message or as a combined RRC message.

[0179] ---- The first relay RRC message may include a first remote RRC message in an RRC container.

[0180] --- Alternative 2: After the relay UE2 transmits the first relay RRC message to the gNB, it can transmit the first remote RRC message to the gNB without receiving an RRCSetup message for the first relay RRC message.

[0181] --- Alternative 3: After the relay UE2 transmits the first relay RRC message to the gNB, it may transmit the first remote RRC message to the gNB after receiving the RRCSetup message for the first relay RRC message.

[0182] --- Alternative 4: Relay UE2 may transmit the first relay RRC message to gNB, and then transmit the RRCSetupComplete message for the first relay RRC message, and then transmit the first remote RRC message to gNB.

[0183] --- Alternative 5: After the relay UE2 transmits the first relay RRC message to the gNB, it may transmit a sidelink UE information message and a first remote RRC message indicating a PC5-RRC connection with the remote UE to the gNB.

[0184] - The gNB and U2N relay UE2 can perform a relay channel establishment procedure via Uu. Depending on the configuration from the gNB, the U2N relay UE1 / UE2 can establish a PC5 relay RLC channel to relay SRB1 toward the U2N relay UE1 / UE2 via PC5.

[0185] -- Here, relay UE2 can be configured as a remote UE through relay UE1.

[0186] - The RRCSetupComplete message can be sent to the gNB by the U2N relay UE1 via the U2N relay UE2 using the SRB1 relay channel established on the U2N relay UE2 over Uu and the SRB1 relay channel over PC5. The U2N relay UE1 can then be RRC connected over Uu.

[0187] - U2N relay UE1 and gNB establish security according to the Uu procedure, and security messages can be transmitted through U2N relay UE2.

[0188] - The gNB and U2N relay UE1 can perform a relay channel setup procedure via relay UE2. Depending on the configuration from the gNB, the U2N relay / remote UE can establish a PC5 relay RLC channel for relaying SRB1 towards the U2N remote / relay UE via PC5.

[0189] - The RRCSetupComplete message can be sent to the gNB by the U2N remote UE via the U2N relay UEs using the SRB1 relay channel on PC5 and the SRB1 relay channel configured to the U2N relay UE on Uu. The U2N remote UE can then be RRC connected via Uu.

[0190] - U2N remote UE and gNB establish security according to the Uu procedure, and security messages can be transmitted through U2N relay UEs.

[0191] - The gNB can set up the SRB2 / DRB for relay purposes by sending an RRCReconfiguration message to the U2N relay UE1 via the U2N relay UE2. The U2N relay UE1 can send an RRCReconfigurationComplete message to the gNB via the U2N relay UE2 in response.

[0192] - The gNB can send an RRCReconfiguration message to the U2N remote UE via the U2N relay UEs to set up the SRB2 / DRB for relay purposes. The U2N remote UE can send an RRCReconfigurationComplete message to the gNB via the U2N relay UE in response. In addition, the gNB can establish an additional Uu relay RLC channel between the gNB and the U2N relay UE, and a PC5 relay RLC channel for relay traffic between the U2N relay UE and the U2N remote UE.

[0193] - After entering RRC_CONNECTED via multi-hop U2N relay UEs, the U2N remote UE in RRC_CONNECTED can request SIB(s) via the U2N relay UE using the on-demand SIB framework.

[0194] For multi-hop U2N relay, the local remote UE ID can be configured by the gNB.

[0195] - The local remote UE ID can be included in both the PC5 SRAP header and the Uu SRAP header. For L2 U2N relay UEs, the local remote UE ID to be used in the SRAP header can be configured by the gNB. The L2 U2N remote UE can obtain the local remote ID from the gNB via Uu RRC messages including RRCSetup, RRCReconfiguration, RRCResume, and RRCReestablishment.

[0196] Example 2

[0197] This embodiment assumes a multi-hop relay structure of remote UE - relay UE1 - relay UE2 - gNB1. In this multi-hop relay structure, the failure handling of UEs in the case where a failure is detected in the Uu interface (e.g., the terminal-to-network interface between relay UE2 and cell 1 of gNB1) and / or the PC5 / sidelink (SL) interface (e.g., the terminal-to-terminal interface between relay UE1 and relay UE2) is described below.

[0198] - It can be assumed that a Uu RLF or Uu reconfiguration failure with gNB1 is declared, or a PC5 / SL RLF or PC5 / SL reconfiguration failure between U2N relay UE1 and UE2 is detected. In this case, the U2N relay UE2 can notify the failure declaration / detection by sending a PC5-RRC message to its connected U2N remote UE(s) and relay UE1. Even in the case of a PC5 / SL RLF or reconfiguration failure between relay UE1 and relay UE2, it can be assumed that message transmission and reception between relay UE1 and relay UE2 is not completely impossible, and therefore, the failure on the PC5 / SL interface may be notified from relay UE2 to relay UE1, or relay UE1 may detect the failure on the PC5 / SL interface with relay UE2 by itself.

[0199] -- Upon receiving a PC5-RRC message indicating a Uu / PC5 / SL link failure or re-establishment failure, the U2N relay UE1 may trigger RRC connection re-establishment and / or report the Uu / PC5 / SL link failure or re-establishment failure to gNB1. The relay UE1 may inform the remote UE about the Uu / PC5 / SL link failure or re-establishment failure as follows:

[0200] --- Alternative 1: Relay UE1 may generate a PC5-RRC message to inform the U2N remote UE(s) to which it is connected of the Uu RLF / reset failure. Upon receiving the PC5-RRC message from Relay UE1, the U2N remote UE may suspend SRB(s) / DRB(s) and / or trigger RRC connection re-establishment.

[0201] --- Alternative 2: The relay UE1 may forward the PC5-RRC message (received from the relay UE2) to the remote UE to inform the remote UE(s) to which it is connected of the Uu RLF / reset failure. Upon receiving the PC5-RRC message from the relay UE2 forwarded by the relay UE1, the U2N remote UE may suspend SRB(s) / DRB(s) and / or trigger RRC connection re-establishment. Here, unlike forwarding (or encapsulating and forwarding) the PC5-RRC message from the relay UE2 in Alternative 2, the PC5-RRC message generated by the relay UE1 and transmitted to the remote UE in Alternative 1 may correspond to a message in which the relay UE1 obtains information included in the PC5-RRC message from the relay UE2 and reconstructs a message to be transmitted to the remote UE based on the obtained information.

[0202] -- If U2N relay UE1 successfully completes RRC connection re-establishment with gNB2 / cell2 that is the same / different from gNB1 / cell1 (e.g. cell1 of gNB1 where Uu interface failure with relay UE2 occurred, or cell2 other than cell1 of gNB1, or any cell of gNB2 other than gNB1), it can act as follows:

[0203] --- Alternative 1: The U2N relay UE1 may send a PC5-RRC message indicating a "new establishment" to the U2N remote UE(s) to which it is connected. Upon receiving the PC5-RRC message, the U2N remote UE may send a first remote RRC message (e.g., RRCSetupRequest) to gNB2 / Cell2 via the U2N relay UE1 for new RRC connection establishment. The U2N remote UE may then receive an RRC setup message from gNB2 / Cell2 via the U2N relay UE1.

[0204] --- Alternative 2: The U2N relay UE1 may send a PC5-RRC message indicating "re-establishment" to the U2N remote UE(s) to which it is connected. Upon receiving the PC5-RRC message, the U2N remote UE may send an RRC connection re-establishment request message to gNB2 / Cell2 via the U2N relay UE1. The U2N remote UE may then receive an RRC re-establishment message from gNB2 / Cell2 via the U2N relay UE1.

[0205] --- Alternative 3: The U2N relay UE1 may send sidelink UE information to inform the gNB about the PC5-RRC connection with the U2N remote UE(s). Upon receiving the sidelink UE information, the gNB may send an RRCReconfiguration message to the U2N remote UE through the U2N relay UE1 to resume and / or reconfigure the SRB2 / DRB(s) for relay purposes. The U2N remote UE may respond by sending an RRCReconfigurationComplete message to the gNB through the U2N relay UE. In addition, the gNB may configure additional Uu relay RLC channel(s) between the gNB and the U2N relay UE, and PC5 relay RLC channel(s) between the U2N relay UE and the U2N remote UE for relay traffic.

[0206] -- If U2N relay UE1 has not successfully completed (or completed but not successfully completed) RRC connection re-establishment with gNB2 / cell2 which is the same / different from gNB1 / cell1, U2N relay UE1 can act as follows:

[0207] --- Alternative 1: Relay UE1 can generate a PC5-RRC message indicating PC5 / Uu-RLF and send it to its connected U2N remote UE(s). The U2N remote UE receiving the PC5-RRC message from relay UE1 can trigger RRC connection re-establishment.

[0208] --- Alternative 2: Relay UE1 may forward the PC5-RRC message received from relay UE2 to its connected U2N remote UE(s) to inform them of PC5 / Uu-RLF. Upon receiving the PC5-RRC message from relay UE2 (forwarded by relay UE1), the U2N remote UE may trigger RRC connection re-establishment.

[0209] - The U2N remote UE may trigger connection re-establishment when it detects a Uu / PC5 RLF generated by the U2N remote UE or U2N relay UE1 or U2N relay UE2, for example, based on a PC5-RRC message.

[0210] Example 3

[0211] This embodiment relates to U2U relay establishment and system information (SI) / paging reception of a remote UE.

[0212] In the examples of the present disclosure, before or after a multi-hop U2N connection is established for a remote UE, the remote UE and the relay UEs can perform U2U relay establishment for remote UE - relay UE1 - relay UE2 - gNB as follows:

[0213] - L2 U2N remote UE can perform U2U relay establishment with L2 U2N relay UE2 through U2N relay UE1 for end-to-end SL-SRB 0 / 1 / 2 / 3 (not SL-DRB) establishment.

[0214] - A U2N remote UE may be allowed to receive all necessary SIBs over the Uu interface, regardless of whether it has a PC5 connection with the relay UE2. A U2N remote UE may also receive system information from the relay UE after establishing a U2U relay PC5 connection with the U2N relay UE2.

[0215] - A U2N remote UE in RRC_IDLE or RRC_INACTIVE state can use a PC5-RRC message via relay UE1 to inform U2N relay UE2 of the requested SIB type(s).

[0216] -- After that, the U2N relay UE2 can trigger an on-demand SI(s) / SIB(s) acquisition procedure according to its RRC state (if necessary) and transmit the acquired SI / SIB to the U2N remote UE through PC5-RRC of the U2U SL-SRB.

[0217] - A U2N remote UE in RRC_IDLE or RRC_INACTIVE state can inform the U2N relay UE1 of the requested SIB type(s) via a PC5-RRC message. Afterwards, the U2N relay UE1 in RRC_IDLE or RRC_INACTIVE state can inform the U2N relay UE2 of the requested SIB type(s) via a PC5-RRC message.

[0218] -- After that, the U2N relay UE2 can trigger an on-demand SI(s) / SIB(s) acquisition procedure according to its RRC state (if necessary) and transmit the acquired SI / SIB to the U2N remote UE through PC5-RRC of the U2U SL-SRB.

[0219] --- Alternatively, the U2N relay UE2 may transmit the acquired SI(s) / SIB(s) to the U2N relay UE1 via PC5-RRC, and the U2N relay UE1 may transmit the acquired SI(s) / SIB(s) to the U2N remote UE via PC5-RRC.

[0220] For U2U connections to remote UEs that have established or are attempting to establish a multi-hop U2N relay, existing local IDs may be used between the remote UE and the relay UE2.

[0221] - The SRAP sublayer of the L2 U2U remote UE supports identification of itself and its peer L2 U2U remote UE. Local IDs can be assigned by the L2 U2U relay UE to identify both L2 U2U remote UEs. For the two local IDs, one can identify the L2 U2U remote UE and the other can identify the peer L2 U2U remote UE. The local ID of the peer L2 U2U remote UE and the local ID of the L2 U2U remote UE can be conveyed to the L2 U2U remote UE by the L2 U2U relay UE along with the corresponding L2 ID of the peer L2 U2U remote UE. The SRAP header can include identification information of the end-to-end PC5 radio bearer and the two local IDs. The peer L2 U2U remote UE can match the received packet with a specific sidelink PDCP entity that has the correct end-to-end PC5 radio bearer of the L2 U2U remote UE.

[0222] A remote UE that has established or is attempting to establish a multi-hop U2N relay can request SI / paging monitoring and receive SI / paging through multiple relay UEs as follows:

[0223] - Option 1: U2U-based SI / paging forwarding

[0224] -- Before SI / Paging forwarding, the L2 U2N remote UE may perform U2U relay establishment with the L2 U2N relay UE2 via the U2N relay UE1 to establish end-to-end SL-SRB 0 / 1 / 2 / 3 (not SL-DRB). For example, for SI / Paging forwarding, the remote UE may establish a U2U connection with the last relay UE, e.g., U2N relay UE2, via intermediate UE(s), e.g., U2N relay UE1.

[0225] -- A remote UE can indirectly request SI / paging monitoring to a U2N relay UE2 through a U2N relay UE1 based on a U2U connection.

[0226] -- When receiving a request indirectly from a remote UE, the U2N relay UE2 can monitor the SI / paging status of the remote UE and then forward the SI / paging message of the remote UE to the remote UE through the U2N relay UE1 based on the U2U connection.

[0227] - Option 2: Non-U2U based SI / Paging forwarding

[0228] -- The remote UE may not have a U2U connection with the last relay UE, e.g., U2N relay UE2, via intermediate UE(s), e.g., U2N relay UE1.

[0229] -- The remote UE can request SI / paging monitoring on the SI / paging opportunity of the remote UE to the U2N relay UE1 via the first PC5-RRC message generated by the remote UE, and then the U2N relay UE1 can request SI / paging monitoring on the SI / paging opportunity of the remote UE to the U2N relay UE2 via the second PC5-RRC message generated by the U2N relay UE1.

[0230] -- Upon receiving a request from U2N relay UE1, U2N relay UE2 may monitor SI / paging opportunities of remote UE, and then transmit the SI / paging message of the remote UE to U2N relay UE1 through the third PC5-RRC message generated by U2N relay UE2. Upon receiving the SI / paging message of the remote UE, U2N relay UE1 may forward the SI / paging message of the remote UE to the remote UE through the fourth PC5-RRC message generated by U2N relay UE1.

[0231] - Option 3: Dedicated SI / Paging via U2N Relay UE

[0232] -- The remote UE may be required to be in the RRC_CONNECTED state, either directly or indirectly, by establishing a multi-hop U2N relay or by being located within NW coverage.

[0233] -- The gNB can send a dedicated SI / paging message to the remote UE over a multi-hop U2N connection. Upon receiving the SI / paging message, the relay UE can forward the dedicated SI / paging to the remote UE over the U2N connection.

[0234] - For example, a relay UE and a remote UE can perform the following actions for SI / paging delivery:

[0235] -- An intermediate relay UE and / or a root relay UE may receive multiple SI / paging requests (e.g., including multiple SI / paging opportunity lists) from multiple remote UEs and / or multiple intermediate relay UEs.

[0236] -- When both the U2N relay UE and the U2N remote UE are in RRC IDLE or RRC INACTIVE, the U2N relay UE2 may monitor the SI / paging opportunities of the connected U2N remote UE. If the U2N relay UE is required to monitor the paging of the U2N remote UE, the U2N relay UE2 may be required to monitor all POs (paging opportunities) of the U2N remote UE.

[0237] -- A U2N remote UE in RRC_IDLE can request PO monitoring by providing 5G-S-TMSI (5G-serving-temporary mobile subscriber identity) and a UE-specific DRX (discontinuous reception) cycle configured by a higher layer to the U2N relay UE2. A U2N remote UE in RRC_INACTIVE can provide the minimum of two UE-specific DRX cycles (5G-S-TMSI and I-RNTI (inactive-radio network temporary identifier)) configured by a higher layer and configured by RAN for PO monitoring to the U2N relay UE2.

[0238] --- L2 U2N relay UE2 can inform the gNB of remote UE information (e.g., 5G-S-TMSI / I-RNTI) via SidelinkUEInformationNR message for paging forwarding. The U2N relay UE can receive the paging message, check the 5G-S-TSMI / I-RNTI, and send the related SI / paging record to the remote UE.

[0239] -- When U2N Relay UE2 is RRC CONNECTED and U2N Remote UE(s) are RRC_IDLE or RRC_INACTIVE, two options can be applied for SI / Paging delivery:

[0240] --- A U2N relay UE2 may monitor the SI window and / or PO of connected U2N remote UE(s) when the active DL BWP of the U2N relay UE is set to CORESET and SI / Paging search space.

[0241] --- Forwarding of SI / paging of U2N remote UE can be performed via dedicated RRC message sent from gNB to U2N relay UE2. RRC_CONNECTED The dedicated RRC message for sending remote UE paging to relay UE2 can include one or more remote UE IDs (5G-S-TMSI or I-RNTI).

[0242] According to the various examples of the present disclosure described above, multi-hop operation for relay UEs and remote UEs can be established by the network, and failures occurring on a U2N relay indirect path can be accurately and efficiently handled. For example, when terminals support U2N relay functionality via sidelink, failures on a multi-hop relay indirect path can be notified to one or more other entities, thereby triggering connection re-establishment.

[0243] According to the examples of the present disclosure, multi-hop operation can be accurately and efficiently provided on an indirect path through multiple U2N relays, compared to the prior art where multi-hop operation could not be provided.

[0244] The embodiments described above are combinations of components and features of the present disclosure in a predetermined form. Each component or feature should be considered optional unless explicitly stated otherwise. Each component or feature may be implemented without being combined with other components or features. Furthermore, it is also possible to form embodiments of the present disclosure by combining some components and / or features. The order of operations described in the embodiments of the present disclosure may be changed. Some components or features of one embodiment may be included in another embodiment or may be replaced with corresponding components or features of another embodiment. It is self-evident that claims that do not have an explicit citation relationship in the patent claims may be combined to form embodiments or incorporated as new claims through post-application amendments.

[0245] It will be apparent to those skilled in the art that the present disclosure may be embodied in other specific forms without departing from the essential characteristics thereof. Therefore, the above detailed description should not be construed as limiting in any respect, but rather as illustrative. The scope of the present disclosure should be determined by a reasonable interpretation of the appended claims, and all modifications within the scope of equivalents of the present disclosure are intended to be included within the scope of the present disclosure.

[0246] The scope of the present disclosure includes software or machine-executable instructions (e.g., an operating system, an application, firmware, a program, etc.) that cause operations according to the methods of various embodiments to be executed on a device or a computer, and a non-transitory computer-readable medium having such software or instructions stored thereon and executable on the device or computer. Instructions that can be used to program a processing system to perform the features described in the present disclosure can be stored on / in a storage medium or a computer-readable storage medium, and a computer program product including such a storage medium can be used to implement the features described in the present disclosure. The storage medium can include, but is not limited to, high-speed random access memory, such as DRAM, SRAM, DDR RAM, or other random access solid state memory devices, and can include non-volatile memory, such as one or more magnetic disk storage devices, optical disk storage devices, flash memory devices, or other non-volatile solid state storage devices. The memory optionally includes one or more storage devices remotely located from the processor(s). The memory or, alternatively, the non-volatile memory device(s) within the memory comprise a non-transitory computer-readable storage medium. The features described in this disclosure may be incorporated into software and / or firmware stored on any of the machine-readable media, which may control the hardware of the processing system and allow the processing system to interact with other mechanisms that utilize results according to embodiments of the present disclosure. Such software or firmware may include, but is not limited to, application code, device drivers, operating systems, and execution environments / containers.

[0247] Here, the wireless communication technology implemented in the device of the present disclosure may include not only LTE, NR, and 6G, but also Narrowband Internet of Things for low-power communication. For example, NB-IoT technology may be an example of LPWAN (Low Power Wide Area Network) technology and may be implemented with standards such as LTE Cat NB1 and / or LTE Cat NB2, and is not limited to the above-described names. Additionally or alternatively, the wireless communication technology implemented in the device of the present disclosure may perform communication based on LTE-M technology. For example, LTE-M technology may be an example of LPWAN technology and may be called by various names such as eMTC (enhanced Machine Type Communication). For example, LTE-M technology can be implemented by at least one of various standards such as 1) LTE CAT 0, 2) LTE Cat M1, 3) LTE Cat M2, 4) LTE non-BL (non-Bandwidth Limited), 5) LTE-MTC, 6) LTE Machine Type Communication, and / or 7) LTE M, and is not limited to the above-described names. Additionally or alternatively, the wireless communication technology implemented in the device (100, 200) of the present disclosure can include at least one of ZigBee, Bluetooth, and Low Power Wide Area Network (LPWAN) considering low-power communication, and is not limited to the above-described names. For example, ZigBee technology can create personal area networks (PAN) related to small / low-power digital communication based on various standards such as IEEE 802.15.4, and can be called by various names.

[0248] The method proposed in this disclosure is explained with a focus on examples applied to 3GPP LTE / LTE-A, 5G, and 6G systems, but can be applied to various wireless communication systems in addition to 3GPP LTE / LTE-A, 5G, and 6G systems.

Claims

1. A step of receiving a first message related to a failure between the second terminal and the first network node from the second terminal by the first terminal; and A step of transmitting a second message generated by the first terminal based on the first message to a third terminal by the first terminal, A method wherein the second message triggers re-establishment of a connection of the third terminal.

2. In paragraph 1, A method wherein the failure comprises a wireless link failure at a terminal-to-network interface between the second terminal and the first cell of the first network node.

3. In paragraph 2, A method wherein the terminal-to-network interface comprises a Uu interface.

4. In paragraph 1, A method wherein at least one of the first message or the second message comprises an upper layer message on a terminal-to-terminal interface.

5. In paragraph 4, A method wherein the terminal-to-terminal interface comprises a PC5 interface.

6. In paragraph 4, A method wherein the upper layer includes a radio resource control (RRC) layer.

7. In paragraph 1, A method wherein the second message is reconstructed based on information included in the first message.

8. In paragraph 1, Additional information is provided to the third terminal by the first terminal through the second message, Additional information above: Instruction information based on information related to a failure between the second terminal and the first network node included in the first message; or Information about re-establishment of connection between the first terminal and the first cell of the first network node, the first cell being related to the failure; or Information about re-establishing a connection between the first terminal and the second cell of the first network node; or Information on re-establishment of connection between the first terminal and the third cell of the second network node; or Information about Terminal 4 A method comprising:

9. In paragraph 8, A method in which the third terminal attempts to re-establish a connection with the first cell, with the second cell, with the third cell, or through the fourth terminal based on the additional information.

10. In paragraph 8, The first terminal, the second terminal, the third terminal, and the fourth terminal correspond to terminal-to-network (U2N) relay terminals; or, A method wherein the first terminal, the second terminal, and the fourth terminal correspond to the U2N relay terminal, and the third terminal corresponds to a remote terminal.

11. In paragraph 1, Based on a wireless link failure at the terminal-to-terminal interface between the first terminal and the second terminal: A method in which a third message triggering connection re-establishment of the third terminal is transmitted to the third terminal by the first terminal.

12. In paragraph 1, A method wherein the above connection re-establishment includes RRC connection re-establishment.

13. In paragraph 1, The above second terminal is a parent terminal of the above first terminal, A method wherein the third terminal is a child terminal of the first terminal.

14. One or more transceivers; and comprising one or more processors connected to said one or more transceivers, One or more of the above processors: Receiving a first message related to a failure between a second terminal and a first network node from the second terminal via the one or more transceivers; A second message generated by the first terminal based on the first message is set to be transmitted to the third terminal through the one or more transceivers, The second message triggers re-establishment of the connection of the third terminal, the first terminal.

15. A step of receiving a second message generated by the first terminal based on the first message from the first terminal by the third terminal; and A step of performing a connection re-establishment procedure triggered by the second message by the third terminal, A method wherein the first message is transmitted from the second terminal to the first terminal and relates to a failure between the second terminal and the first network node.

16. One or more transmitters and receivers; and comprising one or more processors connected to said one or more transceivers, One or more of the above processors: Receive a second message generated by the first terminal based on the first message from the first terminal through the one or more transceivers; and It is set to perform a connection re-establishment procedure triggered by the above second message, The first message is transmitted from the second terminal to the first terminal, and is related to a failure between the second terminal and the first network node.

17. One or more processors; and A processing device comprising one or more computer memories operatively connected to said one or more processors and storing instructions for performing a method according to any one of claims 1 to 13 based on execution by said one or more processors.

18. One or more non-transitory computer-readable media storing one or more instructions that are executed by one or more processors to control the performance of a method according to any one of claims 1 to 13.

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