Method for performing relay communication in wireless communication system, and device therefor

Abstract

Disclosed are a method for performing communication in a wireless communication system and a device therefor according to various embodiments. The device may: detect an RLF with respect to a first link formed for a U2N relay with a first cell; perform a reconfiguration procedure of the first link in which the RLF is detected, on the basis of the U2N relay in which a multi-hop is formed; and transmit, to a second cell, a first notification message including information on a plurality of UEs related to the multi-hop, on the basis of the configuration of the first link with the second cell through the reconfiguration procedure.

Description

Method for performing relay communication in a wireless communication system and device therefor

[0001] A method for performing multi-hop based relay communication in a wireless communication system and a device therefor are provided.

[0002] Wireless communication systems are multiple access systems that support communication with multiple users by sharing available system resources (e.g., bandwidth, transmission power, etc.). Examples of multiple access systems include code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access (SC-FDMA), and multi-carrier frequency division multiple access (MC-FDMA).

[0003] Sidelink (SL) refers to a communication method that establishes a direct link between user equipment (UE), allowing voice or data to be exchanged directly between terminals without going through a base station (BS). SL is being considered as a solution to address the burden on base stations due to rapidly increasing data traffic.

[0004] V2X (vehicle-to-everything) refers to a communication technology that exchanges information with other vehicles, pedestrians, and infrastructure-based objects through wired / wireless communication. V2X can be divided into four types: V2V (vehicle-to-vehicle), V2I (vehicle-to-infrastructure), V2N (vehicle-to-network), and V2P (vehicle-to-pedestrian). V2X communication can be provided through the PC5 interface and / or Uu interface.

[0005] Meanwhile, as more and more communication devices demand greater communication capacity, the need for improved mobile broadband communication compared to existing radio access technology (RAT) is emerging. Accordingly, communication systems that consider services or terminals sensitive to reliability and latency are being discussed. Next-generation wireless access technologies that consider improved mobile broadband communication, massive machine type communication (MTC), and ultra-reliable and low latency communication (URLLC) can be called new radio access technology (RAT) or new radio (NR). NR can also support vehicle-to-everything (V2X) communication.

[0006] Figure 1 is a diagram for comparing and explaining V2X communication based on RAT before NR and V2X communication based on NR.

[0007] In relation to V2X communication, in RATs prior to NR, methods for providing safety services based on V2X messages such as Basic Safety Message (BSM), Cooperative Awareness Message (CAM), and Decentralized Environmental Notification Message (DENM) were mainly discussed. V2X messages may include location information, dynamic information, attribute information, etc. For example, a terminal may transmit a CAM of a periodic message type and / or a DENM of an event triggered message type to another terminal.

[0008] For example, a CAM may include basic vehicle information such as dynamic vehicle status information, such as direction and speed, static vehicle data, such as dimensions, external lighting conditions, and route history. For example, a terminal may broadcast a CAM, and the latency of the CAM may be less than 100 ms. For example, in the event of an emergency, such as a vehicle breakdown or accident, a terminal may generate a DENM and transmit it to other terminals. For example, all vehicles within the transmission range of the terminal may receive the CAM and / or DENM. In this case, the DENM may have a higher priority than the CAM.

[0009] Since then, various V2X scenarios have been proposed in NR in relation to V2X communications. For example, various V2X scenarios may include vehicle platooning, advanced driving, extended sensors, and remote driving.

[0010] For example, based on vehicle platooning, vehicles can dynamically form groups and move together. For example, to perform platoon operations based on vehicle platooning, vehicles in the group can receive periodic data from the lead vehicle. For example, vehicles in the group can use this periodic data to narrow or widen the gap between vehicles.

[0011] For example, based on improved driving, vehicles can become semi-autonomous or fully automated. For example, each vehicle can adjust its trajectories or maneuvers based on data acquired from local sensors of nearby vehicles and / or nearby logical entities. Furthermore, for example, each vehicle can share driving intentions with nearby vehicles.

[0012] For example, based on extended sensors, raw data, processed data, or live video data acquired through local sensors can be exchanged between vehicles, logical entities, pedestrian terminals, and / or V2X application servers. Thus, for example, a vehicle can perceive its environment better than it can perceive using its own sensors.

[0013] For example, based on remote driving, a remote driver or V2X application can operate or control the remote vehicle for people who cannot drive or for remote vehicles located in hazardous environments. For example, in cases where the route is predictable, such as public transportation, cloud computing-based driving can be utilized to operate or control the remote vehicle. Additionally, access to a cloud-based back-end service platform, for example, can be considered for remote driving.

[0014] Meanwhile, a method to specify service requirements for various V2X scenarios, such as vehicle platooning, enhanced driving, expanded sensors, and remote driving, is being discussed in NR-based V2X communication.

[0015] The technical problem to be achieved by the present invention is to provide a method for performing multi-hop based U2N relay communication more accurately and efficiently.

[0016] The technical challenges are not limited to the technical challenges mentioned above, and other technical challenges not mentioned will be clearly understood by those skilled in the art to which the present invention pertains from the description below.

[0017] A method by a first relay UE (User Equipment) according to one aspect may include: detecting a radio link failure (RLF) for a first link formed with a first cell for a U2N (UE to Network) relay; performing a re-establishment procedure of the first link in which the RLF is detected based on the U2N relay in which multi-hops are formed; and transmitting a first notification message including information on a plurality of UEs related to the multi-hops to the second cell based on the first link being established with the second cell through the re-establishment procedure.

[0018] Alternatively, the first notification message is characterized in that it is a SUI (SidelinkUEInformation) message.

[0019] Alternatively, based on the transmission of the first notification message, the first relay UE is characterized in that it expects to receive an RRC (radio resource control) reset message for each of the plurality of UEs from the second cell.

[0020] Alternatively, the RRC reset message for each UE is characterized by including information for setting up SRB2 (Signaling Radio Bearer2) and DRB (Data Radio Bearer) for operation of the U2N relay.

[0021] Alternatively, the method further comprises the step of transmitting a second notification message for detection of the RLF to each of the plurality of UEs based on the failure of the re-establishment of the first link.

[0022] Alternatively, the second notification message is characterized in that Uu RLF is set as the notification cause value.

[0023] Alternatively, based on the failure of the re-establishment of the first link, the first relay UE is characterized in that it transmits the second notification message for the detection of the RLF only to a second relay UE directly connected to the first relay UE among the plurality of UEs.

[0024] Alternatively, based on the transmission of the second notification message, the SRB (Signaling Radio Bearer) and DRB (Data Radio Bearer) associated with the U2N relay are suspended.

[0025] According to another aspect, at least one non-transitory computer-readable storage medium having recorded thereon instructions for performing the method described above may be provided.

[0026] According to another aspect, a first relay UE performing the method described above may be provided.

[0027] According to another aspect, a processing device may be provided for controlling a first relay UE performing the method described above.

[0028] According to another aspect, the method may include: a step of detecting a radio link failure (RLF) for a first link formed for a multi-hop based U2N (UE to Network) relay, and performing a procedure for re-establishing the first link by a first relay UE; and a step of receiving, from the first relay UE, a first notification message including information on a plurality of UEs associated with the multi-hop based on completion of the re-establishment of the first link.

[0029] According to another aspect, a base station performing the above-described method may be provided.

[0030] According to one embodiment, multi-hop based U2N relay communication can be performed more accurately and efficiently in a wireless communication system.

[0031] The effects that can be obtained in various embodiments are not limited to the effects mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art to which the present invention pertains from the description below.

[0032] The drawings attached to this specification are intended to provide an understanding of the present invention, illustrate various embodiments of the present invention, and together with the description of the specification serve to explain the principles of the present invention.

[0033] Figure 1 is a diagram for comparing and explaining V2X communication based on RAT before NR and V2X communication based on NR.

[0034] Figure 2 shows the structure of the LTE system.

[0035] Figure 3 shows the structure of the NR system.

[0036] Figure 4 shows the structure of a radio frame of NR.

[0037] Figure 5 shows the slot structure of an NR frame.

[0038] FIG. 6 illustrates a communication structure that can be provided in a 6G system according to one embodiment of the present disclosure.

[0039] FIG. 7 illustrates an electromagnetic spectrum according to one embodiment of the present disclosure.

[0040] Figure 8 shows a radio protocol architecture for SL communication.

[0041] Figure 9 shows a terminal performing V2X or SL communication.

[0042] Figure 10 shows resource units for V2X or SL communication.

[0043] FIG. 11 illustrates an example of a BWP according to one embodiment of the present disclosure.

[0044] FIG. 12 illustrates a procedure for a terminal to perform V2X or SL communication according to a resource allocation mode, according to one embodiment of the present disclosure.

[0045] Figure 13 is a diagram for explaining the control plane procedure of L2 U2N relay (UE-to-Network Relay).

[0046] Figure 14 is a diagram for explaining multi-hop based U2N relay communication.

[0047] FIG. 15 is a diagram illustrating a method for a first relay UE performing a U2N relay operation to transmit a notification message.

[0048] FIG. 16 is a diagram illustrating a method for a base station to perform an RRC reconfiguration procedure for a first relay UE.

[0049] Figure 17 illustrates a communication system applied to the present invention.

[0050] Figure 18 illustrates a wireless device applicable to the present invention.

[0051] Figure 19 illustrates another example of a wireless device applicable to the present invention. The wireless device may be implemented in various forms depending on the use case / service.

[0052] Figure 20 illustrates a vehicle or autonomous vehicle to which the present invention is applied.

[0053] A wireless communication system is a multiple access system that supports communication with multiple users by sharing available system resources (e.g., bandwidth, transmission power, etc.). Examples of multiple access systems include code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access (SC-FDMA), and multi-carrier frequency division multiple access (MC-FDMA).

[0054] Sidelink refers to a communication method that establishes a direct link between user equipment (UE), allowing voice or data to be exchanged directly between terminals without going through a base station (BS). Sidelink is being considered as a solution to address the burden on base stations due to rapidly increasing data traffic.

[0055] V2X (vehicle-to-everything) refers to a communication technology that exchanges information with other vehicles, pedestrians, and infrastructure-based objects through wired / wireless communication. V2X can be divided into four types: V2V (vehicle-to-vehicle), V2I (vehicle-to-infrastructure), V2N (vehicle-to-network), and V2P (vehicle-to-pedestrian). V2X communication can be provided through the PC5 interface and / or Uu interface.

[0056] Meanwhile, as more and more communication devices demand greater communication capacity, the need for improved mobile broadband communication compared to existing radio access technology (RAT) is emerging. Accordingly, communication systems that consider services or terminals sensitive to reliability and latency are being discussed. Next-generation wireless access technologies that consider improved mobile broadband communication, massive MTC, and URLLC (Ultra-Reliable and Low Latency Communication) can be called new radio access technology (RAT) or new radio (NR). NR can also support V2X (vehicle-to-everything) communication.

[0057] The following technologies 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, and E-UTRA (evolved UTRA). IEEE 802.16m is an evolution of IEEE 802.16e, providing backward compatibility with systems based on IEEE 802.16e. UTRA is part of UMTS (universal mobile telecommunications system). 3GPP (3rd generation partnership project) LTE (long term evolution) is a part of E-UMTS (evolved UMTS) that uses E-UTRA (evolved-UMTS terrestrial radio access), employing OFDMA in the downlink and SC-FDMA in the uplink.LTE-A (advanced) is an evolution of 3GPP LTE.

[0058] 5G NR, the successor to LTE-A, is a new clean-slate mobile communications system featuring high performance, low latency, and high availability. 5G NR can utilize all available spectrum resources, from low-frequency bands below 1 GHz, mid-frequency bands between 1 GHz and 10 GHz, and high-frequency (millimeter wave) bands above 24 GHz.

[0059] For clarity, the description will focus on LTE-A or 5G NR, but the technical ideas of the embodiment(s) are not limited thereto.

[0060] Figure 2 illustrates the architecture of an applicable LTE system. This may be referred to as an Evolved-UMTS Terrestrial Radio Access Network (E-UTRAN) or a Long Term Evolution (LTE) / LTE-A system.

[0061] Referring to FIG. 2, the E-UTRAN includes a base station (20; BS) that provides a control plane and a user plane to a terminal (10). The terminal (10) may be fixed or mobile, and may be referred to by other terms such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), a mobile terminal (MT), a wireless device, etc. The base station (20) refers to a fixed station that communicates with the terminal (10), and may be referred to by other terms such as an evolved-NodeB (eNB), a base transceiver system (BTS), an access point, etc.

[0062] Base stations (20) can be connected to each other via the X2 interface. The base station (20) is connected to an EPC (Evolved Packet Core, 30) via the S1 interface, more specifically, to an MME (Mobility Management Entity) via the S1-MME, and to an S-GW (Serving Gateway) via the S1-U.

[0063] The EPC (30) consists of an MME, an S-GW, and a P-GW (Packet Data Network-Gateway). The MME holds information about terminal access and capabilities, and this information is primarily used for terminal mobility management. The S-GW is a gateway with the E-UTRAN as its endpoint, and the P-GW is a gateway with the PDN as its endpoint.

[0064] The layers of the radio interface protocol between the terminal and the network can be divided into L1 (Layer 1), L2 (Layer 2), and L3 (Layer 3) based on the three lower layers of the Open System Interconnection (OSI) standard model, which is widely known in communication systems. Among these, the physical layer belonging to Layer 1 provides an information transfer service using a physical channel, and the RRC (Radio Resource Control) layer located in Layer 3 controls radio resources between the terminal and the network. To this end, the RRC layer exchanges RRC messages between the terminal and the base station.

[0065] Figure 3 shows the structure of the NR system.

[0066] Referring to FIG. 3, the NG-RAN may include a gNB and / or an eNB that provides user plane and control plane protocol termination to the UE. FIG. 7 illustrates a case where only a gNB is included. The gNB and eNB are connected to each other via an Xn interface. The gNB and eNB are connected to the 5th generation core network (5G Core Network: 5GC) via the NG interface. More specifically, the gNB is connected to the access and mobility management function (AMF) via the NG-C interface, and the gNB is connected to the user plane function (UPF) via the NG-U interface.

[0067] Figure 4 shows the structure of a radio frame of NR.

[0068] Referring to FIG. 4, radio frames can be used for uplink and downlink transmission in NR. A radio frame has a length of 10 ms and can be defined as two 5 ms half-frames (Half-Frames, HF). A half-frame can include five 1 ms sub-frames (Subframes, SF). A sub-frame can be divided into one or more slots, and the number of slots within a sub-frame can be determined by the Subcarrier Spacing (SCS). Each slot can include 12 or 14 OFDM (A) symbols depending on the cyclic prefix (CP).

[0069] When normal CP is used, each slot can contain 14 symbols. When extended CP is used, each slot can contain 12 symbols. Here, the symbols can include OFDM symbols (or CP-OFDM symbols), SC-FDMA (Single Carrier - FDMA) symbols (or DFT-s-OFDM (Discrete Fourier Transform-spread-OFDM) symbols).

[0070] Table 1 below shows the number of symbols per slot ((N)) depending on the SCS setting (u) when normal CP is used. slot symb ), number of slots per frame ((N frame,u slot ) and the number of slots per subframe ((N subframe,u slot ) is an example.

[0071] SCS (15*2 u )N slot symb N frame,u slot N subframe,u slot 15KHz (u=0)1410130KHz (u=1)1420260KHz (u=2)14404120KHz (u=3)14808240KHz (u=4)1416016

[0072] Table 2 illustrates the number of symbols per slot, the number of slots per frame, and the number of slots per subframe according to SCS when extended CP is used.

[0073] SCS (15*2 u )N slot symb N frame,u slot N subframe,u slot 60KHz (u=2)12404

[0074] In an NR system, OFDM(A) numerology (e.g., SCS, CP length, etc.) may be set differently between multiple cells that are merged into a single terminal. Accordingly, the (absolute time) interval of a time resource (e.g., subframe, slot, or TTI) (conveniently referred to as TU (Time Unit)) consisting of the same number of symbols may be set differently between the merged cells.

[0075] In NR, multiple numerologies, or SCSs, can be supported to support various 5G services. For example, a 15 kHz SCS can support wide areas in traditional cellular bands, while a 30 kHz / 60 kHz SCS can support dense urban areas, lower latency, and wider carrier bandwidth. A 60 kHz or higher SCS can support bandwidths greater than 24.25 GHz to overcome phase noise.

[0076] The NR frequency band can be defined by two types of frequency ranges. The two types of frequency ranges can be FR1 and FR2. The numerical values ​​of the frequency ranges can be changed, and for example, the two types of frequency ranges can be as shown in Table 3 below. Among the frequency ranges used in the NR system, FR1 can mean the "sub 6 GHz range", and FR2 can mean the "above 6 GHz range" and can be called millimeter wave (mmW).

[0077] Frequency Range designationCorresponding frequency rangeSubcarrier Spacing (SCS)FR1450MHz - 6000MHz15, 30, 60kHzFR224250MHz - 52600MHz60, 120, 240kHz

[0078] As described above, the numerical value of the frequency range of the NR system can be changed. For example, FR1 may include a band from 410 MHz to 7125 MHz, as shown in Table 4 below. That is, FR1 may include a frequency band above 6 GHz (or 5850, 5900, 5925 MHz, etc.). For example, the frequency band above 6 GHz (or 5850, 5900, 5925 MHz, etc.) included within FR1 may include an unlicensed band. The unlicensed band may be used for various purposes, such as for vehicular communications (e.g., autonomous driving).

[0079] Frequency Range designationCorresponding frequency rangeSubcarrier Spacing (SCS)FR1410MHz - 7125MHz15, 30, 60kHzFR224250MHz - 52600MHz60, 120, 240kHz

[0080] Figure 5 shows the slot structure of an NR frame.

[0081] Referring to Figure 5, a slot includes multiple symbols in the time domain. For example, in the case of a normal CP, one slot may include 14 symbols, but in the case of an extended CP, one slot may include 12 symbols. Alternatively, in the case of a normal CP, one slot may include 7 symbols, but in the case of an extended CP, one slot may include 6 symbols.

[0082] A carrier includes multiple subcarriers in the frequency domain. An RB (Resource Block) can be defined as multiple (e.g., 12) consecutive subcarriers in the frequency domain. A BWP (Bandwidth Part) can be defined as multiple consecutive (P)RBs ((Physical) Resource Blocks) in the frequency domain, and can correspond to one numerology (e.g., SCS, CP length, etc.). A carrier can include up to N (e.g., 5) BWPs. Data communication can be performed through activated BWPs. Each element can be referred to as a Resource Element (RE) in the resource grid, and one complex symbol can be mapped to it.

[0083] Meanwhile, the wireless interface between terminals or between terminals and a network may be composed of an L1 layer, an L2 layer, and an L3 layer. In various embodiments of the present disclosure, the L1 layer may refer to a physical layer. Furthermore, for example, the L2 layer may refer to at least one of a MAC layer, an RLC layer, a PDCP layer, and an SDAP layer. Furthermore, for example, the L3 layer may refer to an RRC layer.

[0084] FIG. 6 illustrates a communication structure that can be provided in a 6G system according to an embodiment of the present disclosure. The embodiment of FIG. 6 can be combined with various embodiments of the present disclosure.

[0085] New network characteristics in 6G may include:

[0086] - Satellite integrated network

[0087] - Connected Intelligence: Unlike previous generations of wireless communication systems, 6G is revolutionary, upgrading the wireless evolution from "connected objects" to "connected intelligence." AI can be applied at every stage of the communication process (or at every signal processing step, as described below).

[0088] - Seamless integration of wireless information and energy transfer

[0089] - Ubiquitous super 3D connectivity: Access to networks and core network functions of drones and very low Earth orbit satellites will create super 3D connectivity in 6G ubiquitous.

[0090] Some general requirements for the new network characteristics of 6G, such as the above, may be as follows:

[0091] - small cell networks

[0092] - Ultra-dense heterogeneous network

[0093] - High-capacity backhaul

[0094] - Radar technology integrated with mobile technology: High-precision localization (or location-based services) through communications is a key feature of 6G wireless communication systems. Therefore, radar systems will be integrated with 6G networks.

[0095] - Softwarization and virtualization

[0096] Below, the core implementation technologies of the 6G system are described.

[0097] - Artificial Intelligence: Incorporating AI into communications can streamline and improve real-time data transmission. AI can use numerous analytics to determine how complex target tasks should be performed. This means AI can increase efficiency and reduce processing delays. Time-consuming tasks such as handovers, network selection, and resource scheduling can be performed instantly using AI. AI can also play a crucial role in machine-to-machine (M2M), machine-to-human, and human-to-machine communications. Furthermore, AI can facilitate rapid communication in brain-computer interfaces (BCIs). AI-based communication systems can be supported by metamaterials, intelligent structures, intelligent networks, intelligent devices, intelligent cognitive radios, self-sustaining wireless networks, and machine learning.

[0098] - THz communication (terahertz communication): Data rates can be increased by increasing the bandwidth. This can be achieved by using sub-THz communication with wide bandwidths and applying advanced massive MIMO technology. THz waves, also known as sub-millimeter waves, typically refer to the frequency range between 0.1 THz and 10 THz, with corresponding wavelengths ranging from 0.03 mm to 3 mm. The 100 GHz to 300 GHz band (sub-THz band) is considered a key part of the THz spectrum for cellular communications. Adding the sub-THz band to the mmWave band will increase the capacity of 6G cellular communications. Among the defined THz bands, 300 GHz to 3 THz lies in the far infrared (IR) frequency band. While part of the optical band, the 300 GHz to 3 THz band lies at the boundary of the optical band, immediately following the RF band. Therefore, this 300 GHz to 3 THz band exhibits similarities to RF.

[0099] Figure 7 illustrates the electromagnetic spectrum according to one embodiment of the present disclosure. The embodiment of Figure 7 can be combined with various embodiments of the present disclosure. Key characteristics of THz communications include (i) a widely available bandwidth to support very high data rates, and (ii) high path loss at high frequencies (highly directional antennas are essential). The narrow beamwidth generated by the highly directional antenna reduces interference. The small wavelength of THz signals allows for a much larger number of antenna elements to be integrated into devices and base stations operating in this band. This enables the use of advanced adaptive array techniques to overcome range limitations.

[0100] - Large-scale MIMO technology

[0101] - Hologram beamforming (HBF)

[0102] - Optical wireless technology

[0103] - Free-space optical transmission backhaul network (FSO backhaul network)

[0104] - Quantum communication

[0105] - Cell-free communication

[0106] - Integration of wireless information and power transmission

[0107] - Integration of wireless communication and sensing

[0108] - Integrated access and backhaul network

[0109] - Big data analysis

[0110] - Reconfigurable intelligent surface

[0111] - metaverse

[0112] - Block chain

[0113] Unmanned aerial vehicles (UAVs): UAVs, or drones, will be a key element in 6G wireless communications. In most cases, high-speed data wireless connectivity can be provided using UAV technology. Base stations (BSs) can be installed on UAVs to provide cellular connectivity. UAVs may offer specific capabilities not found in fixed BS infrastructure, such as easy deployment, robust line-of-sight links, and controlled mobility. During emergencies such as natural disasters, deploying terrestrial communications infrastructure is not economically feasible and sometimes cannot provide services in volatile environments. UAVs can easily handle these situations. UAVs will become a new paradigm in wireless communications. This technology facilitates three fundamental requirements for wireless networks: enhanced mobile broadband (eMBB), URLLC, and mMTC. UAVs can also support various purposes, such as enhancing network connectivity, fire detection, disaster emergency services, security and surveillance, pollution monitoring, parking monitoring, and accident monitoring. Therefore, UAV technology is recognized as one of the most important technologies for 6G communications.

[0114] - Autonomous driving (self-driving): V2X (vehicle to everything), a key element in building autonomous driving infrastructure, can be a technology that allows cars to communicate and share with various elements on the road for autonomous driving, such as vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) wireless communication. Fast transmission speeds and low-latency technologies are essential to maximize autonomous driving performance and ensure high safety. Furthermore, in the future, autonomous driving will go beyond simply providing warnings or guidance messages to drivers and may require active intervention in vehicle operation and direct control of the vehicle in dangerous situations. To this end, the amount of information that needs to be transmitted and received may become enormous, so 6G is expected to maximize autonomous driving with faster transmission speeds and lower latency than 5G.

[0115] Figure 8 illustrates a radio protocol architecture for SL communication. Specifically, Figure 8 (a) illustrates the user plane protocol stack of NR, and Figure 8 (b) illustrates the control plane protocol stack of NR.

[0116] Below, the SL synchronization signal (Sidelink Synchronization Signal, SLSS) and synchronization information are described.

[0117] SLSS is an SL-specific sequence and may include a Primary Sidelink Synchronization Signal (PSSS) and a Secondary Sidelink Synchronization Signal (SSSS). The PSSS may be referred to as a Sidelink Primary Synchronization Signal (S-PSS), and the SSSS may be referred to as a Sidelink Secondary Synchronization Signal (S-SSS). For example, length-127 M-sequences may be used for the S-PSS, and length-127 Gold sequences may be used for the S-SSS. For example, a terminal may detect an initial signal and acquire synchronization using the S-PSS. For example, a terminal may acquire detailed synchronization and detect a synchronization signal ID using the S-PSS and the S-SSS.

[0118] PSBCH (Physical Sidelink Broadcast Channel) may be a (broadcast) channel that transmits basic (system) information that a terminal must know first before transmitting or receiving an SL signal. For example, the basic information may be information related to SLSS, duplex mode (DM), TDD UL / DL (Time Division Duplex Uplink / Downlink) configuration, resource pool-related information, type of application related to SLSS, subframe offset, broadcast information, etc. For example, in NR V2X, for evaluating PSBCH performance, the payload size of PSBCH may be 56 bits, including a 24-bit CRC.

[0119] S-PSS, S-SSS and PSBCH may be included in a block format supporting periodic transmission (e.g., SL SS (Synchronization Signal) / PSBCH block, hereinafter referred to as S-SSB (Sidelink-Synchronization Signal Block)). The S-SSB may have the same numerology (i.e., SCS and CP length) as the PSCCH (Physical Sidelink Control Channel) / PSSCH (Physical Sidelink Shared Channel) in the carrier, and the transmission bandwidth may be within a (pre-)configured SL BWP (Sidelink BWP). For example, the bandwidth of the S-SSB may be 11 RBs (Resource Blocks). For example, the PSBCH may span 11 RBs. And, the frequency location of the S-SSB may be (pre-)configured. Therefore, the terminal does not need to perform hypothesis detection in the frequency to discover the S-SSB in the carrier.

[0120] Meanwhile, in the NR SL system, multiple numerologies having different SCS and / or CP lengths may be supported. In this case, as the SCS increases, the length of the time resource for a transmitting terminal to transmit an S-SSB may become shorter. Accordingly, the coverage of the S-SSB may decrease. Therefore, in order to ensure the coverage of the S-SSB, the transmitting terminal may transmit one or more S-SSBs to a receiving terminal within one S-SSB transmission period according to the SCS. For example, the number of S-SSBs that the transmitting terminal transmits to the receiving terminal within one S-SSB transmission period may be pre-configured or configured for the transmitting terminal. For example, the S-SSB transmission period may be 160 ms. For example, an S-SSB transmission period of 160 ms may be supported for all SCSs.

[0121] For example, when the SCS is 15 kHz at FR1, the transmitting terminal can transmit one or two S-SSBs to the receiving terminal within one S-SSB transmission period. For example, when the SCS is 30 kHz at FR1, the transmitting terminal can transmit one or two S-SSBs to the receiving terminal within one S-SSB transmission period. For example, when the SCS is 60 kHz at FR1, the transmitting terminal can transmit one, two, or four S-SSBs to the receiving terminal within one S-SSB transmission period.

[0122] For example, when the SCS is 60 kHz at FR2, the transmitting terminal can transmit 1, 2, 4, 8, 16, or 32 S-SSBs to the receiving terminal within one S-SSB transmission period. For example, when the SCS is 120 kHz at FR2, the transmitting terminal can transmit 1, 2, 4, 8, 16, 32, or 64 S-SSBs to the receiving terminal within one S-SSB transmission period.

[0123] Meanwhile, when the SCS is 60 kHz, two types of CP may be supported. In addition, the structure of the S-SSB transmitted by the transmitting terminal to the receiving terminal may be different depending on the CP type. For example, the CP type may be Normal CP (NCP) or Extended CP (ECP). Specifically, for example, when the CP type is NCP, the number of symbols to which the PSBCH is mapped within the S-SSB transmitted by the transmitting terminal may be 9 or 8. On the other hand, for example, when the CP type is ECP, the number of symbols to which the PSBCH is mapped within the S-SSB transmitted by the transmitting terminal may be 7 or 6. For example, the PSBCH may be mapped to the first symbol within the S-SSB transmitted by the transmitting terminal. For example, the receiving terminal receiving the S-SSB may perform an Automatic Gain Control (AGC) operation in the first symbol section of the S-SSB.

[0124] Figure 9 shows a terminal performing V2X or SL communication.

[0125] Referring to FIG. 9, the term "terminal" in V2X or SL communication may primarily refer to a user's terminal. However, if a network device such as a base station transmits and receives signals according to a communication method between terminals, the base station may also be considered a type of terminal. For example, terminal 1 may be a first device (100), and terminal 2 may be a second device (200).

[0126] For example, terminal 1 can select a resource unit corresponding to a specific resource within a resource pool, which represents a set of resources. Then, terminal 1 can transmit an SL signal using the resource unit. For example, terminal 2, which is a receiving terminal, can be configured with a resource pool in which terminal 1 can transmit a signal, and can detect a signal from terminal 1 within the resource pool.

[0127] Here, if terminal 1 is within the connection range of the base station, the base station can inform terminal 1 of the resource pool. On the other hand, if terminal 1 is outside the connection range of the base station, another terminal can inform terminal 1 of the resource pool, or terminal 1 can use a pre-configured resource pool.

[0128] In general, a resource pool can be composed of multiple resource units, and each terminal can select one or multiple resource units to use for its SL signal transmission.

[0129] Figure 10 shows resource units for V2X or SL communication.

[0130] Referring to Figure 10, the entire frequency resources of the resource pool can be divided into NF units, and the entire time resources of the resource pool can be divided into NT units. Therefore, a total of NF * NT resource units can be defined within the resource pool. Figure 10 illustrates an example where the resource pool repeats with a cycle of NT subframes.

[0131] As shown in Figure 10, a single resource unit (e.g., Unit #0) may appear periodically and repeatedly. Alternatively, to achieve diversity effects in the time or frequency dimensions, the index of the physical resource unit to which a single logical resource unit is mapped may change in a predetermined pattern over time. In this resource unit structure, a resource pool may refer to a set of resource units that a terminal wishing to transmit an SL signal can use for transmission.

[0132] Resource pools can be subdivided into several categories. For example, based on the content of the SL signal transmitted from each resource pool, resource pools can be categorized as follows:

[0133] (1) Scheduling Assignment (SA) may be a signal that includes information such as the location of resources used by a transmitting terminal for transmission of an SL data channel, MCS (Modulation and Coding Scheme) or MIMO (Multiple Input Multiple Output) transmission method required for demodulation of other data channels, and TA (Timing Advance). SA may also be transmitted multiplexed with SL data on the same resource unit, in which case the SA resource pool may mean a resource pool in which SA is multiplexed with SL data and transmitted. SA may also be called an SL control channel.

[0134] (2) The SL data channel (Physical Sidelink Shared Channel, PSSCH) may be a resource pool used by a transmitting terminal to transmit user data. If SA is multiplexed and transmitted together with SL data on the same resource unit, only the SL data channel excluding SA information may be transmitted from the resource pool for the SL data channel. In other words, the REs (Resource Elements) that were used to transmit SA information on individual resource units within the SA resource pool may still be used to transmit SL data in the resource pool of the SL data channel. For example, the transmitting terminal may transmit the PSSCH by mapping it to consecutive PRBs.

[0135] (3) A discovery channel may be a resource pool for transmitting terminals to transmit information such as their IDs. Through this, transmitting terminals can enable neighboring terminals to discover them.

[0136] Even if the content of the SL signal described above is the same, different resource pools may be used depending on the transmission and reception properties of the SL signal. For example, even if it is the same SL data channel or discovery message, it may be again divided into different resource pools depending on the transmission timing determination method of the SL signal (for example, whether it is transmitted at the time of reception of a synchronization reference signal or whether it is transmitted by applying a certain timing advance at the time of reception), the resource allocation method (for example, whether the base station designates transmission resources for individual signals to individual transmitting terminals or whether individual transmitting terminals independently select individual signal transmission resources within the resource pool), the signal format (for example, the number of symbols each SL signal occupies in one subframe or the number of subframes used for transmission of one SL signal), the signal strength from the base station, the transmission power strength of the SL terminal, etc.

[0137] FIG. 11 illustrates an example of a BWP according to an embodiment of the present disclosure. The embodiment of FIG. 11 can be combined with various embodiments of the present disclosure. In the embodiment of FIG. 11, it is assumed that there are three BWPs.

[0138] Referring to Figure 11, a common resource block (CRB) may be a carrier resource block numbered from one end of a carrier band to the other. Furthermore, a PRB may be a numbered resource block within each BWP. Point A may indicate a common reference point for the resource block grid.

[0139] The BWP can be set by Point A, an offset from Point A (NstartBWP), and a bandwidth (NsizeBWP). For example, Point A can be an outer reference point of a PRB of a carrier where subcarrier 0 of all numerologies (e.g., all numerologies supported by the network on that carrier) are aligned. For example, the offset can be the PRB spacing between the lowest subcarrier in a given numerology and Point A. For example, the bandwidth can be the number of PRBs in a given numerology.

[0140] SLSS (Sidelink Synchronization Signal) is a SL (sidelink) specific sequence and may include PSSS (Primary Sidelink Synchronization Signal) and SSSS (Secondary Sidelink Synchronization Signal). The PSSS may be referred to as S-PSS (Sidelink Primary Synchronization Signal) and the SSSS may be referred to as S-SSS (Sidelink Secondary Synchronization Signal). For example, length-127 M-sequences may be used for S-PSS and length-127 Gold sequences may be used for S-SSS. For example, a terminal may detect an initial signal (signal detection) and obtain synchronization using S-PSS. For example, the terminal can obtain detailed synchronization using S-PSS and S-SSS and detect a synchronization signal ID.

[0141] PSBCH (Physical Sidelink Broadcast Channel) may be a (broadcast) channel that transmits basic (system) information that a terminal must know first before transmitting or receiving an SL signal. For example, the basic information may be information related to SLSS, duplex mode (DM), TDD UL / DL (Time Division Duplex Uplink / Downlink) configuration, resource pool-related information, type of application related to SLSS, subframe offset, broadcast information, etc. For example, in order to evaluate PSBCH performance, in NR V2X, the payload size of PSBCH may be 56 bits, including a 24-bit CRC (Cyclic Redundancy Check).

[0142] S-PSS, S-SSS and PSBCH may be included in a block format supporting periodic transmission (e.g., SL SS (Synchronization Signal) / PSBCH block, hereinafter referred to as S-SSB (Sidelink-Synchronization Signal Block)). The S-SSB may have the same numerology (i.e., SCS and CP length) as the PSCCH (Physical Sidelink Control Channel) / PSSCH (Physical Sidelink Shared Channel) in the carrier, and the transmission bandwidth may be within a (pre-)configured SL BWP (Sidelink BWP). For example, the bandwidth of the S-SSB may be 11 RBs (Resource Blocks). For example, the PSBCH may span 11 RBs. And, the frequency location of the S-SSB may be (pre-)configured. Therefore, the terminal does not need to perform hypothesis detection in the frequency to discover the S-SSB in the carrier.

[0143] FIG. 12 illustrates a procedure for a terminal to perform V2X or SL communication according to a resource allocation mode, according to an embodiment of the present disclosure. The embodiment of FIG. 12 may be combined with various embodiments of the present disclosure.

[0144] Referring to (a) of FIG. 12, in resource allocation mode 1, the base station may schedule SL resources to be used by the terminal for SL transmission. For example, in step S1200, the base station may transmit information related to SL resources and / or information related to UL resources to the first terminal. For example, the UL resources may include PUCCH resources and / or PUSCH resources. For example, the UL resources may be resources for reporting SL HARQ feedback to the base station.

[0145] For example, a first terminal may receive information related to a dynamic grant (DG) resource and / or information related to a configured grant (CG) resource from a base station. For example, a CG resource may include a CG type 1 resource or a CG type 2 resource. In this specification, a DG resource may be a resource that a base station configures / allocates to the first terminal via downlink control information (DCI). In this specification, a CG resource may be a (periodic) resource that a base station configures / allocates to the first terminal via DCI and / or an RRC message. For example, in the case of a CG type 1 resource, the base station may transmit an RRC message including information related to the CG resource to the first terminal. For example, in the case of a CG type 2 resource, the base station may transmit an RRC message including information related to the CG resource to the first terminal, and the base station may transmit a DCI related to activation or release of the CG resource to the first terminal.

[0146] In step S1510, the first terminal may transmit a PSCCH (e.g., Sidelink Control Information (SCI) or 1st-stage SCI) to the second terminal based on the resource scheduling. In step S1220, the first terminal may transmit a PSSCH (e.g., 2nd-stage SCI, MAC PDU, data, etc.) related to the PSCCH to the second terminal. In step S1230, the first terminal may receive a PSFCH related to the PSCCH / PSSCH from the second terminal. For example, HARQ feedback information (e.g., NACK information or ACK information) may be received from the second terminal via the PSFCH. In step S1240, the first terminal may transmit / report HARQ feedback information to the base station via a PUCCH or a PUSCH. For example, the HARQ feedback information reported to the base station may be information generated by the first terminal based on the HARQ feedback information received from the second terminal. For example, the HARQ feedback information reported to the base station may be information generated by the first terminal based on a rule set in advance. For example, the DCI may be DCI for scheduling SL.

[0147] Referring to (b) of FIG. 12, in resource allocation mode 2, a terminal can determine an SL transmission resource within the SL resources set by the base station / network or within the preset SL resources. For example, the set SL resources or the preset SL resources may be a resource pool. For example, the terminal can autonomously select or schedule resources for SL transmission. For example, the terminal can perform SL communication by selecting a resource within the set resource pool. For example, the terminal can select a resource within a selection window by performing sensing and resource (re)selection procedures. For example, the sensing can be performed on a subchannel basis. For example, in step S1210, a first terminal that has selected a resource within the resource pool can transmit a PSCCH (e.g., Sidelink Control Information (SCI) or 1st-stage SCI) to a second terminal using the resource. In step S1220, the first terminal may transmit a PSSCH (e.g., 2nd-stage SCI, MAC PDU, data, etc.) related to the PSCCH to the second terminal. In step S1230, the first terminal may receive a PSFCH related to the PSCCH / PSSCH from the second terminal.

[0148] Referring to (a) or (b) of FIG. 12, for example, a first terminal may transmit an SCI to a second terminal on a PSCCH. Or, for example, the first terminal may transmit two consecutive SCIs (e.g., 2-stage SCIs) to the second terminal on the PSCCH and / or the PSSCH. In this case, the second terminal may decode the two consecutive SCIs (e.g., 2-stage SCIs) to receive the PSSCH from the first terminal. In this specification, an SCI transmitted on a PSCCH may be referred to as a 1st SCI, a 1st SCI, a 1st-stage SCI, or a 1st-stage SCI format, and an SCI transmitted on a PSSCH may be referred to as a 2nd SCI, a 2nd SCI, a 2nd-stage SCI, or a 2nd-stage SCI format.

[0149] Referring to (a) or (b) of FIG. 12, in step S1530, the first terminal may receive a PSFCH. For example, the first terminal and the second terminal may determine PSFCH resources, and the second terminal may use the PSFCH resources to transmit HARQ feedback to the first terminal.

[0150] Referring to (a) of FIG. 12, in step S1540, the first terminal may transmit SL HARQ feedback to the base station via PUCCH and / or PUSCH.

[0151] Figure 13 is a diagram for explaining the control plane procedure of L2 U2N relay (UE-to-Network Relay).

[0152] The PC5-RRC aspect PC5 unicast link establishment procedure of Rel-16 NR V2X can be reused to establish a secure unicast link for L2 U2N relay (layer 2 UE-to-Network relaying) between the remote UE and the relay UE before the remote UE establishes a Uu RRC connection with the network via the relay UE.

[0153] For both in-coverage and out-of-coverage scenarios, when a remote UE initiates the first RRC message to establish a connection with a gNB, the PC5 L2 configuration for transmissions between the remote UE and the U2N relay UE can be based on the RLC / MAC configuration defined in the standard. The establishment of Uu SRB1 / SRB2 and DRB of the remote UE follows the legacy Uu configuration procedure for the L2 U2N relay.

[0154] A given scenario (TS 38.300) describes the control plane procedures of an L2 U2N relay as follows:

[0155] In step S1300, the remote UE and the relay UE can perform a discovery procedure and establish a PC5-RRC connection in step S1301 based on the existing Rel-16 procedure.

[0156] In step S1302, the remote UE can transmit the first RRC message (i.e., RRCSetupRequest) to establish a connection with the gNB via the relay UE using the default L2 configuration of PC5. The gNB responds to the remote UE with an RRCSetup message (S1303). The RRCSetup delivery to the remote UE uses the default configuration of PC5. If the relay UE is not initiated in RRC_CONNECTED, it must perform its own connection establishment upon receiving the message for the default L2 configuration of PC5.

[0157] In step S1304, the gNB and the relay UE perform a relay channel setup procedure via Uu. Depending on the configuration of the gNB, the relay / remote UE establishes an RLC channel for relaying SRB1 to the remote UE via PC5. This step prepares the relay channel for SRB1.

[0158] In step S1305, a remote UE SRB1 message (e.g., an RRCSetupComplete message) is transmitted to the gNB via the relay UE using the SRB1 relay channel over PC5. The remote UE is then RRC connected over Uu.

[0159] In steps S1306 and S1307, the remote UE and the gNB establish security according to legacy procedures, and the security message is transmitted through the Relay UE.

[0160] In steps S1308 and S1309, the gNB transmits RRCReconfiguration to the remote UE via the relay UE to set up the relay SRB2 / DRB. The remote UE responds by transmitting RRCReconfigurationComplete to the gNB via the relay UE.

[0161] In step S1310, the gNB establishes an additional RLC channel between the gNB and the relay UE for traffic relay. Depending on the configuration of the gNB, the relay / remote UE establishes an additional RLC channel between the remote UE and the relay UE for traffic relay.

[0162] In the above scenario, in addition to the connection setup procedure, for L2 UE-to-Network relay:

[0163] - RRC reconfiguration and RRC disconnection procedures can reuse legacy RRC procedures with message content / configuration design left in the WI phase.

[0164] - The RRC connection re-establishment and RRC connection resumption procedures can be reused as a baseline by considering the connection establishment procedure of the L2 U2N relay above to handle relay-specific parts along with the message content / structure design. The message content / structure can be defined later.

[0165] The above discovery procedure may define discovery model A and discovery model B. Discovery model A may be a method in which a relay UE periodically broadcasts a message announcing its presence (Announcement message). Discovery model B may be a method in which a device (remote UE) wishing to perform relay communication periodically broadcasts a message requesting relay communication (solicitation message) (see 3GPP TS 23.304).

[0166] Notification Message (see TS 38.331 5.8.9.10)

[0167] (1) Notification message transmission procedure

[0168] The procedure for a relay UE to send a Notification message to a remote UE can be used in the following situations: ① When a U2N relay UE sends a notification to a connected U2N remote UE; ② When an L2 U2U relay UE sends a notification about an end-to-end PC5 connection to its counterpart L2 U2U remote UE. This procedure can be initiated when the conditions defined in 5.8.9.10.2 are met on another hop link.

[0169] (2) Procedure initiation conditions

[0170] A relay UE may initiate the procedure when one of the following conditions is met: When the UE acts as a U2N relay UE, it may initiate the procedure when an RLF on the Uu link occurs (see 5.3.10), when an RRCReconfiguration with reconfigurationWithSync is received, when cell reselection occurs, or when an RRC connection failure of the L2 U2N relay UE occurs. This includes an RRC connection rejection (see 5.3.3.5 and 5.3.13.10), a T300 timer expiration (see 5.3.3.7), or an RRC resume failure (see 5.3.13.5). When the UE acts as a L2 U2U relay UE, it may initiate the procedure when it detects an RLF on the PC5 link with a mutual L2 U2U remote UE (see 5.8.9.3), or when a PC5-RRC connection release of the corresponding hop occurs (see 5.8.9.5).

[0171] (3) Actions related to transmission of NotificationMessageSidelink message

[0172] The actions related to NotificationMessageSidelink message transmission are as follows. If the UE acts as a U2N relay UE, if message transmission is initiated due to an RLF on the Uu link, the indicationType is set to relayUE-Uu-RLF. If it is initiated due to reconfigurationWithSync, it is set to relayUE-HO, if it is initiated due to cell reselection, it is set to relayUE-CellReselection, and if it is initiated due to a Uu RRC connection or resume failure, it is set to relayUE-Uu-RRC-Failure. Afterwards, the NotificationMessageSidelink message is submitted to the lower layer for transmission. If the UE acts as a L2 U2U relay UE, if message transmission is initiated due to a PC5 RLF occurrence or PC5-RRC connection release with an L2 U2U remote UE, the sl-IndicationType is set to relayUE-PC5-RLF, sl-DestinationIdentityRemoteUE is set to the corresponding remote UE, and the message is transmitted to the lower layer.

[0173] (4) Actions related to reception ofNotificationMessageSidelinkmessage

[0174] When a NotificationMessageSidelink message is received, the following actions are taken when the receiving UE acts as a U2N remote UE. If the message contains indicationType, the receiving UE is a L2 U2N remote UE in RRC_CONNECTED state, MP is configured and the direct path (MCG transmission) is not stopped, the indirect path transmission is stopped if indicationType is relayUE-HO. Otherwise, the indirect path failure information reporting procedure defined in 5.7.3c is performed. If the receiving UE does not have a running T301 timer, it initiates the RRC re-establishment procedure (5.3.7). If the receiving UE is a L3 U2N remote UE, or a L2 U2N remote UE but in RRC_IDLE or RRC_INACTIVE state, if the PC5-RRC connection is determined to be released, it notifies the upper layer of the PC5 unicast link release. Otherwise, the connection is maintained, and if indicationType is relayUE-HO or relayUE-CellReselection, cell reselection is considered to have occurred. As a note, for L3 U2N remote UEs or L2 U2N remote UEs in IDLE / INACTIVE state, whether to release or maintain the PC5 link depends on the terminal implementation, and may ignore the NotificationMessageSidelink message if T304 is running.

[0175] If the receiving UE is a L2 U2U remote UE and sl-IndicationType is set to relayUE-PC5-RLF, a PC5 RLF is notified to the upper layer for the L2 U2U remote UE, and the end-to-end PC5 connection for the mutual PC5 hop link for the remote UE is considered to have failed, and failure-related actions are taken according to the procedures defined in 5.8.9.3a. Note that whether to perform U2U relay reselection thereafter and whether to maintain or release the PC5 link with the U2U relay UE are determined by the upper layer.

[0176] Below, the definition of the notification message required for multi-hop based U2N operation and the method of transmitting the notification message are described in detail.

[0177] Notification message for multi-hop U2N relay operation

[0178] Figure 14 is a diagram for explaining multi-hop based U2N relay communication.

[0179] In the existing Rel-17 SL U2N relay operation, <gnb>-<Relay UE> -<Remote UE> Technology development has been conducted for such connection relationships. However, in the future, for multi-hop U2N relay operation, technology development may be required for a structure in which the gNB and remote UE are connected through relay UEs of multiple hops. When passing through relay UEs of multiple hops, greater coverage extension can be achieved than in the case of existing U2N.

[0180] Referring to FIG. 14, a remote UE can be connected to a gNB through relay UE3, relay UE2, and relay UE1 based on a multi-hop based U2N relay. For example, the remote UE can form an SL connection with relay UE3 based on L2 ID F and L2 ID E, relay UE3 can form an SL connection with relay UE2 based on L2 ID D and L2 ID C, relay UE2 can form an SL connection with relay UE1 based on L2 ID B and L2 ID A, and relay UE1 can form a Uu connection / Uu link with the base station. In this way, the remote UE can be connected to the gNB through a multi-hop based U2N operation.

[0181] In such a multi-hop based U2N operation, a Uu RLF may occur between the gNB and the relay UE1. In this case, the relay UE1 may transmit a notification message (e.g., transmit the notification message in the direction of the remote UE) to notify the occurrence of the RLF to the relay UE2, the relay UE3, and the remote UE (or the relay UE2 and the remote UE). For example, the relay UE1 may transmit a notification message to each of the relay UE2, the relay UE3, and the remote UE. For example, the relay UE1 may transmit a notification message to each of the relay UE2, the relay UE3, and the remote UE to notify the detection of an RLF for the Uu link. Alternatively, the relay UE1 may transmit the notification message only to the relay UE2, and the relay UE2 may transmit the notification message to the relay UE3 sequentially. When relay UE2 receives a notification message for Uu RLF from relay UE1, relay UE2 may release the SL between relay UE1 and relay UE2, generate a notification message with a cause value of the notification as Uu RLF, and transmit the notification message to relay UE3. Alternatively, relay UE2 may release the SL between relay UE1 and relay UE2 upon receipt of the notification message with a cause value of Uu RLF, but may also release the SL connection between relay UE2 and relay UE3 without transmitting a separate notification message to relay UE3. Relay UE3 may also release the SL connection with the remote UE by transmitting a notification message to the remote UE in a similar manner, or may release the SL connection with the remote UE without transmitting the notification message.

[0182] After an RLF occurs for a Uu link with a gNB, the relay UE1 may transmit a notification message including information about the occurrence of an RLF for the Uu link to other relay UEs and / or remote UEs connected to the SL, and the remote UE (and / or relay UE) receiving the notification message may suspend the SRB (Signaling Radio Bearer) and / or DRB (Data Radio Bearer) related to the Uu link.

[0183] Alternatively, the relay UE1 may first perform an RRC connection re-establishment / re-establishment procedure with another cell_B as follows, instead of immediately transmitting a notification message for the RLF of the Uu link. For example, if the U2N relay is based on multi-hop rather than single-hop, the relay UE1 may first perform an RRC connection re-establishment / re-establishment procedure with another cell_B as follows, instead of immediately transmitting a notification message for the RLF of the Uu link.

[0184] 1. If relay UE1 (or relay UE2,3) connected to gNB1 and / or cell_A successfully performs RRC connection re-establishment / re-establishment with gNB2 / cell_B, which is the same as or different from gNB1 / cell_A.

[0185] For example, when an RLF occurs for a Uu link with cell A, relay UE1 may perform a procedure to re-establish an RRC connection with another cell B belonging to the same gNB as the gNB to which cell A belongs. In this case, relay UE1 may perform an operation according to at least one of the following methods 1 and 2.

[0186] (1) Method 1

[0187] Relay UE1 may generate a PC5-RRC message to notify a remote UE (and / or relay UE2,3) of a 'new establishment' (or re-establishment). The remote UE, upon receiving the PC5-RRC message, may be triggered to transmit an RRC message (e.g., an RRCSetupRequest message) related to the remote UE to Cell B (a cell belonging to gNB 1 or gNB 2) to establish a new RRC connection establishment. Thereafter, the remote UE may expect to receive an RRC Setup message (via relay UE1) from Cell B (a cell belonging to gNB 1 or gNB 2). And / or, when the relay UE2 or relay UE3 also receives the PC5-RRC message, an action may be triggered to transmit an RRC message (e.g., an RRCSetupRequest message) related to the relay UE2 or relay UE3 to cell B (a cell belonging to gNB 1 or gNB 2) to establish a new RRC connection. Thereafter, the relay UE2 or relay UE3 may expect to receive an RRC Setup message (via relay UE1) from cell B (a cell belonging to gNB 1 or gNB 2).

[0188] (2) Method 2

[0189] After completing re-establishment (or re-establishment of RRC connection) with Cell B (or a cell belonging to gNB 1 or gNB 2), Relay UE1 may transmit a SidelinkUEInformation (SUI) message to Cell B to notify the presence of relay UE2 (or relay UE2 and relay UE3) and remote UEs connected to itself (SL). Cell B, receiving the SUI message, may be expected to transmit an RRCReconfiguration message (via relay UE1) to each of relay UE2 (or relay UE2 and relay UE3) and remote UEs connected to the relay UE1. For example, the relay UE1 may transmit the SUI message including information on a plurality of UEs performing U2N relay communication, and it may be expected that an RRCReconfiguration message for each of the plurality of UEs is received from Cell B, which received the SUI message. The above RRCReconfiguration message may include reconfiguration information that enables SRB2 / DRB configuration for RRC resume and / or relay operation. In addition, Cell B may provide information for configuring a Uu RLC channel between the gNB and the U2N relay UE and / or a PC5 relay RLC channel (between the relay UE and the remote / relay UE) for U2N relay operation. Alternatively, the above RRCReconfiguration message may further include information for configuring a Uu RLC channel between the gNB and the U2N relay UE and / or a PC5 relay RLC channel (between the relay UE and the remote / relay UE).

[0190] 2. If relay UE1 (or relay UE2,3) connected to gNB1 / cell_A fails to successfully re-establish / re-establish RRC connection with gNB2 / cell_B, which is the same as or different from gNB1 / cell_A.

[0191] Relay UE1 may generate a PC5-RRC message including information about a failure in re-establishment of an RRC connection, and transmit the PC5-RRC message to relay UE2, relay UE3, and / or remote UE. When the relay UE2, relay UE3, and / or remote UE receives the PC5-RRC message, procedures / actions related to RRC re-establishment, RRC resume, and / or relay reselection may be triggered. Alternatively, when the relay UE2, relay UE3, and / or remote UE receives the PC5-RRC message, procedures / actions related to RRC re-establishment, RRC resume, and / or relay reselection may be triggered while releasing a currently established configuration.

[0192] Meanwhile, the operations for relay UE1 and relay UE2 described above can be similarly applied to operations for relay UE2 and relay UE3. In this case, Uu-RLF may be replaced with SL-RLF.

[0193] Alternatively, the proposed method described above can also be naturally applied to operations for devices / sensors performing the Internet of Things (IoT) or Machine to Machine (M2M) to connect to a network or another device through other sensors / devices. In this case, the remote UE may be a device / sensor that attempts to connect to a network (or another sensor / device) through another sensor / device, and the relay UE may be a sensor / device that relays a connection to another sensor / device or a network.

[0194] FIG. 15 is a diagram illustrating a method for a first relay UE performing a U2N relay operation to transmit a notification message.

[0195] As described above, the first relay UE can perform a relay operation to relay data transmission and reception between a base station or cell and a remote UE. For example, the first relay UE can be directly connected (or Uu link) with a base station or cell (hereinafter, referred to as a first cell) and SL-connected with another relay UE (e.g., a second relay UE) toward the remote UE. For example, the first relay UE can form a direct connection with the base station / cell for U2N relay and SL-connected or directly connected with the second relay UE. The second relay UE can be SL-connected or directly connected with a third relay UE, and the third relay UE can be SL-connected or directly connected to a remote UE. In the following, for convenience of explanation, it is assumed that U2N relay is performed through multi-hops connected in the order of the first cell - the first relay UE - the second relay UE - the third relay UE - the remote UE.

[0196] The first relay UE that has formed such a connection can detect whether a radio link failure (RLF) occurs for the Uu connection (hereinafter, the first link), which is a connection with the first cell for U2N relay. The following describes in detail a method for the first relay UE to transmit a notification message when an RLF is detected in the first link with the first cell.

[0197] Referring to FIG. 15, a first relay UE may detect an RLF for a first link directly connected to a first cell (S151). For example, the first relay UE may continuously monitor a connection status for the first link, and may monitor whether an RLF for the first link has occurred based on connection status information for the first link. For example, the first relay UE may activate a T310 timer if the number of Out-of-Sync Indications for the first link (e.g., based on decoding failures of DL signals, CRC errors, signal quality, etc.) is greater than or equal to a specific number (e.g., N310 times). The first relay UE may determine that an RLF for the first link has occurred if the T310 timer expires without interruption due to satisfaction of a specific condition (e.g., reception / detection of In-Sync Indications greater than or equal to N311 times) (see TS 38.331).

[0198] Next, the first relay UE may perform a procedure for re-establishing the first link in which the RLF occurs when the U2N relay is based on multiple hops (e.g., when the first cell and the remote UE are connected through multiple relay UEs) (S153). For example, when the U2N relay is based on multiple hops, the first relay UE may preferentially perform a procedure for re-establishing the first link in which the RLF is detected without transmitting a notification message for the detection of the RLF to other relay UEs / remote UEs forming the multi-hops. For example, the first relay UE may transmit an RRC Re-establishment message to a second cell, which is another discovered cell (e.g., another cell belonging to the same gNB as the first cell), to perform a re-establishment procedure for the first link for the U2N relay. Meanwhile, in the case of a single-hop U2N relay rather than a multi-hop relay, the first relay UE can directly transmit a notification message regarding RLF detection of the first link to the remote UE without performing a procedure for resetting the first link.

[0199] Next, the first relay UE may transmit a first notification message to the second cell, which includes information about a plurality of UEs associated with the multi-hop, based on the re-establishment of the first link to the second cell (S155). Here, the first notification message may be a SidelinkUEInformation (SUI) message as described above.

[0200] For example, a first relay UE may perform a reconfiguration procedure of the first link based on detection of an RLF for the first link for U2N relay, and change the cell for the first link where the RLF is detected from the first cell to the second cell through the reconfiguration procedure. In this case, the first relay UE may provide information about a plurality of UEs performing the U2N relay to the second cell. Here, the information about the plurality of UEs may include information necessary for the second cell to set an RLC channel, SRB / DRB, etc. for each of the plurality of UEs (e.g., an L2 ID, a C-RNTI, and / or a local ID of each of the plurality of UEs). In this case, the first relay UE may continue / maintain the U2N relay communication through the second cell without transmitting a notification message about the RLF detection to the plurality of UEs.

[0201] In this case, when the first relay UE transmits the first notification message to the second cell, the first relay UE may expect that the second cell transmits an RRC reconfiguration message for RRC reconfiguration for each of the plurality of UEs. When an RRC reconfiguration message corresponding to each UE is received from the second cell, the first relay UE may forward the RRC reconfiguration message so that the received RRC reconfiguration message is delivered to the corresponding UE. For example, when the first relay UE receives an RRC reconfiguration message for a remote UE from the second cell, the first relay UE may forward the RRC reconfiguration message for the remote UE to the second relay UE, and the second relay UE may deliver the RRC reconfiguration message for the remote UE to the remote UE (or the third relay UE). Here, the RRC reconfiguration message for each of the plurality of UEs may include information for setting up a Signaling Radio Bearer2 (SRB2) and a Data Radio Bearer (DRB) for the operation of the U2N relay.

[0202] Alternatively, the re-establishment of the first link to the second cell may fail. In this case, the first relay UE may transmit a second notification message regarding the detection of the RLF to each of the plurality of UEs, similarly to the existing method. For example, the first relay UE may transmit a second notification message to the second relay UE, a second notification message to the third relay UE, and a second notification message to the remote UE. At this time, the notification cause value of the second notification message may be set to a value corresponding to Uu RLF. Alternatively, the first relay UE may transmit the second notification message regarding the detection of the RLF only to the second relay UE directly connected to the first relay UE among the plurality of UEs. In this case, the second relay UE that receives the second notification message may transmit the second notification message to the third relay UE, and the third relay UE may also transmit the second notification message to the remote UE. Here, the second relay UE that receives the second notification message may release the SL connection or the direct connection with the first relay UE. Alternatively, the second relay UE that receives the second notification message may release the SL connection or direct connection with the first relay UE, but may not forward the notification message to the third relay UE. Meanwhile, if the first relay UE transmits the second notification message, the remote UE that receives it may suspend the SRB (Signaling Radio Bearer) and DRB (Data Radio Bearer) related to the U2N relay.

[0203] FIG. 16 is a diagram illustrating a method for a base station to perform an RRC reconfiguration procedure for a first relay UE.

[0204] Referring to FIG. 16, a base station (or a second cell) may perform a re-establishment procedure for a first link for a U2N relay with a first relay UE (S161). Here, the first relay UE may be a relay UE that attempts to re-establish the first link through another cell in response to detection of an RLF for the first link with the first cell as described above. For example, the base station may receive an RRC Re-establishment message from the first relay UE and perform a procedure for re-establishing the first link for the U2N relay. Here, the base station may be a second cell, which is another cell connected to the same gNB as the first cell.

[0205] Next, the base station may receive a first notification message including information about a plurality of UEs related to the multi-hop from the first relay UE when the first link is formed / established with the first relay UE through the reconfiguration procedure (S163). Here, the first notification message may be a SidelinkUEInformation (SUI) message as described above. Here, the information about the plurality of UEs may include information necessary for establishing an RLC channel, SRB / DRB, etc. (e.g., L2 ID, C-RNTI, and / or local ID of each of the plurality of UEs).

[0206] Next, the base station can transmit an RRC reconfiguration message for each of the plurality of UEs to the first relay UE based on the first notification message (S165). Specifically, the base station can generate an RRC reconfiguration message for reconfiguring an RRC connection for each of the plurality of UEs based on information about the plurality of UEs, and provide the generated RRC reconfiguration message to each of the plurality of UEs through the first relay UE. For example, the base station can transmit the RRC reconfiguration message including information for setting up an SRB2 (Signaling Radio Bearer2) and a DRB (Data Radio Bearer) related to the operation of the U2N relay for each UE based on information about the plurality of UEs.

[0207] In this way, the proposed invention can prevent unnecessary release of multiple links related to multi-hops as much as possible by having a relay UE that detects an RLF for a Uu link for multi-hop based U2N relay directly perform a direct Uu link re-establishment procedure with another cell. Alternatively, the proposed invention can ensure that RRC re-establishment related to multi-hop U2N relay is performed quickly by having a relay UE that has successfully performed a Uu link re-establishment procedure directly provide information about the UEs that formed the multi-hop to the new cell that formed the Uu link.

[0208] Examples of communication systems to which the invention applies

[0209] Although not limited thereto, the various descriptions, functions, procedures, proposals, methods and / or operational flowcharts of the present invention disclosed in this document may be applied to various fields requiring wireless communication / connection (e.g., 5G) between devices.

[0210] Hereinafter, more specific examples will be provided with reference to the drawings. In the drawings / descriptions below, the same drawing reference numerals may represent identical or corresponding hardware blocks, software blocks, or functional blocks, unless otherwise described.

[0211] Figure 17 illustrates a communication system applied to the present invention.

[0212] Referring to FIG. 17, a communication system (1) applied to the present invention includes a wireless device, a base station, and a network. Here, the wireless device refers to a device that performs communication using a wireless access technology (e.g., 5G NR (New RAT), LTE (Long Term Evolution)) and may be referred to as a communication / wireless / 5G device. Although not limited thereto, the wireless device may include a robot (100a), a vehicle (100b-1, 100b-2), an XR (eXtended Reality) device (100c), a hand-held device (100d), a home appliance (100e), an IoT (Internet of Things) device (100f), and an AI device / server (400). 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 may include an Unmanned Aerial Vehicle (UAV) (e.g., a drone). XR devices include AR (Augmented Reality) / VR (Virtual Reality) / MR (Mixed Reality) devices, and can be implemented in the form of HMD (Head-Mounted Device), HUD (Head-Up Display) installed in a vehicle, television, smartphone, computer, wearable device, home appliance, digital signage, vehicle, robot, etc. Mobile devices can include smartphone, smart pad, wearable device (e.g., smart watch, smart glass), computer (e.g., laptop, etc.), etc. Home appliances can include TV, refrigerator, washing machine, etc. IoT devices can include sensors, smart meters, etc. For example, base stations and networks can also be implemented as wireless devices, and a specific wireless device (200a) can act as a base station / network node to other wireless devices.

[0213] Wireless devices (100a to 100f) can be connected to a network (300) via a base station (200). Artificial Intelligence (AI) technology can be applied to the wireless devices (100a to 100f), and the wireless devices (100a to 100f) can be connected to an AI server (400) via the network (300). The network (300) can be configured using a 3G network, a 4G (e.g., LTE) network, a 5G (e.g., NR) network, etc. The wireless devices (100a to 100f) can communicate with each other via the base station (200) / network (300), but can also communicate directly (e.g., sidelink communication) without going through the base station / network. For example, vehicles (100b-1, 100b-2) can communicate directly (e.g., V2V (Vehicle to Vehicle) / V2X (Vehicle to Everything) communication). In addition, IoT devices (e.g., sensors) can communicate directly with other IoT devices (e.g., sensors) or other wireless devices (100a to 100f).

[0214] Wireless communication / connection (150a, 150b, 150c) can be established between wireless devices (100a~100f) / base stations (200), and base stations (200) / base stations (200). Here, wireless communication / connection can be achieved through various wireless access technologies (e.g., 5G NR) such as uplink / downlink communication (150a), sidelink communication (150b) (or D2D communication), and communication between base stations (150c) (e.g., relay, IAB (Integrated Access Backhaul). Through wireless communication / connection (150a, 150b, 150c), wireless devices and base stations / wireless devices, and base stations and base stations can transmit / receive wireless signals to each other. For example, wireless communication / connection (150a, 150b, 150c) can transmit / receive signals through various physical channels. To this end, 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.), and resource allocation processes can be performed based on various proposals of the present invention.

[0215] Examples of wireless devices to which the present invention is applied

[0216] Figure 18 illustrates a wireless device applicable to the present invention.

[0217] Referring to FIG. 18, the first wireless device (100) and the second wireless device (200) can transmit and receive wireless signals through various wireless access technologies (e.g., LTE, NR). Here, {the first wireless device (100), the second wireless device (200)} can correspond to {the wireless device (100x), the base station (200)} and / or {the wireless device (100x), the wireless device (100x)} of FIG. 17.

[0218] A first wireless device (100) includes one or more processors (102) and one or more memories (104), and may further include one or more transceivers (106) and / or one or more antennas (108). The processor (102) controls the memories (104) and / or the transceivers (106), and may be configured to implement the descriptions, functions, procedures, proposals, methods, and / or operational flowcharts disclosed in this document. For example, the processor (102) may process information in the memory (104) to generate first information / signal, and then transmit a wireless signal including the first information / signal via the transceiver (106). In addition, the processor (102) may receive a wireless signal including second information / signal via the transceiver (106), and then store information obtained from signal processing of the second information / signal in the memory (104). The memory (104) may be connected to the processor (102) and may store various information related to the operation of the processor (102). For example, the memory (104) may perform some or all of the processes controlled by the processor (102), or may store software code including commands for performing the descriptions, functions, procedures, proposals, methods, and / or operation flowcharts disclosed in this document. Here, the processor (102) and the memory (104) may be part of a communication modem / circuit / chipset designed to implement wireless communication technology (e.g., LTE, NR). The transceiver (106) may be connected to the processor (102) and may transmit and / or receive wireless signals via one or more antennas (108). The transceiver (106) may include a transmitter and / or a receiver. The transceiver (106) may be used interchangeably with an RF (Radio Frequency) unit. In the present invention, a wireless device may also mean a communication modem / circuit / chipset.

[0219] Specifically, the first wireless device or first relay UE (100) may include a processor (102) and a memory (104) connected to a transceiver (106). The memory (104) may include at least one program capable of performing operations related to the embodiments described in FIGS. 14 to 16.

[0220] A processor (102) controls a transceiver (106) to detect a radio link failure (RLF) for a first link formed with a first cell for a U2N (UE to Network) relay, perform a re-establishment procedure for the first link in which the RLF is detected based on the U2N relay in which multi-hops are formed, and transmit a first notification message including information on a plurality of UEs related to the multi-hop to the second cell based on the establishment of the first link with the second cell through the re-establishment procedure.

[0221] Alternatively, a processing device including a processor (102) and a memory (104) may be configured. In this case, at least one processor; and at least one memory connected to the at least one processor and storing instructions, wherein the instructions can perform operations based on being executed by the at least one processor. The operations may include detecting a radio link failure (RLF) for a first link formed with a first cell for a U2N (UE to Network) relay, performing a re-establishment procedure of the first link for which the RLF is detected based on the U2N relay for which multi-hops are formed, and transmitting a first notification message including information on a plurality of UEs associated with the multi-hops to the second cell based on the first link being established with the second cell through the re-establishment procedure. In addition, a non-transitory storage medium recording instructions for the operations may be configured.

[0222] The second wireless device (200) includes one or more processors (202), one or more memories (204), and may further include one or more transceivers (206) and / or one or more antennas (208). The processor (202) controls the memories (204) and / or the transceivers (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 third information / signals, and then transmit a wireless signal including the third information / signals via the transceivers (206). Furthermore, the processor (202) may receive a wireless signal including fourth information / signals via the transceivers (206), and then store information obtained from signal processing of the fourth information / signals 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 perform some or all of the processes controlled by the processor (202), or may store software code including commands for performing the descriptions, functions, procedures, proposals, methods, and / or operation flowcharts disclosed in this document. Here, the processor (202) and the memory (204) may be part of a communication modem / circuit / chip designed to implement wireless communication technology (e.g., LTE, NR). The transceiver (206) may be connected to the processor (202) and may transmit and / or receive wireless signals via one or more antennas (208). The transceiver (206) may include a transmitter and / or a receiver. The transceiver (206) may be used interchangeably with an RF unit. In the present invention, a wireless device may also mean a communication modem / circuit / chip.

[0223] Specifically, the second wireless device or base station (200) may include a processor (202) and a memory (204) connected to a transceiver (206). The memory (204) may include at least one program capable of performing operations related to the embodiments described in FIGS. 14 to 16.

[0224] A processor (202) controls a transceiver (206) to detect a radio link failure (RLF) for a first link formed for a multi-hop based U2N (UE to Network) relay and perform a procedure for re-establishing the first link with a first relay UE, and based on completion of the re-establishment of the first link, receive a first notification message including information on a plurality of UEs related to the multi-hop from the first relay UE.

[0225] Hereinafter, the hardware elements of the wireless device (100, 200) will be described in more detail. Although not limited thereto, one or more protocol layers may be implemented by one or more processors (102, 202). For example, one or more processors (102, 202) may implement one or more layers (e.g., functional layers such as PHY, MAC, RLC, PDCP, RRC, SDAP). One or more processors (102, 202) may generate one or more Protocol Data Units (PDUs) and / or one or more Service Data Units (SDUs) according to the descriptions, functions, procedures, proposals, methods, and / or operation flowcharts disclosed in this document. One or more processors (102, 202) may generate messages, control information, data, or information according to the descriptions, functions, procedures, proposals, methods, and / or operation flowcharts disclosed in this document. One or more processors (102, 202) can generate signals (e.g., baseband signals) including PDUs, SDUs, messages, control information, data or information according to the functions, procedures, proposals and / or methods disclosed herein, and provide the signals to one or more transceivers (106, 206). One or more processors (102, 202) can receive signals (e.g., baseband signals) from one or more transceivers (106, 206) and obtain PDUs, SDUs, messages, control information, data or information according to the descriptions, functions, procedures, proposals, methods and / or operational flowcharts disclosed herein.

[0226] One or more processors (102, 202) may be referred to as a controller, a microcontroller, a microprocessor, or a microcomputer. One or more processors (102, 202) may be implemented by hardware, firmware, software, or a combination thereof. For example, one or more Application Specific Integrated Circuits (ASICs), one or more Digital Signal Processors (DSPs), one or more Digital Signal Processing Devices (DSPDs), one or more Programmable Logic Devices (PLDs), or one or more Field Programmable Gate Arrays (FPGAs) may be included in one or more processors (102, 202). The descriptions, functions, procedures, proposals, methods, and / or operational 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, suggestions, methods and / or operation flowcharts disclosed in this document may be implemented using firmware or software configured to perform one or more processors (102, 202) or stored in one or more memories (104, 204) and executed by one or more processors (102, 202). The descriptions, functions, procedures, suggestions, methods and / or operation flowcharts disclosed in this document may be implemented using firmware or software in the form of codes, instructions and / or sets of instructions.

[0227] One or more memories (104, 204) may be coupled to one or more processors (102, 202) and may store various forms of data, signals, messages, information, programs, codes, instructions, and / or commands. The one or more memories (104, 204) may be configured as ROM, RAM, EPROM, flash memory, hard drives, registers, cache memory, computer-readable storage media, and / or combinations thereof. The one or more memories (104, 204) may be located internally and / or externally to the one or more processors (102, 202). Additionally, the one or more memories (104, 204) may be coupled to the one or more processors (102, 202) via various technologies, such as wired or wireless connections.

[0228] One or more transceivers (106, 206) can transmit user data, control information, wireless signals / channels, etc., as mentioned in the methods and / or flowcharts of this document, to one or more other devices. One or more transceivers (106, 206) can receive user data, control information, wireless signals / channels, etc., as mentioned in the descriptions, functions, procedures, proposals, methods and / or flowcharts of this document, from one or more other devices. For example, one or more transceivers (106, 206) can be connected to one or more processors (102, 202) and can transmit and receive wireless signals. For example, one or more processors (102, 202) can control one or more transceivers (106, 206) to transmit user data, control information, or wireless signals to one or more other devices. Additionally, one or more processors (102, 202) may control one or more transceivers (106, 206) to receive user data, control information, or wireless signals from one or more other devices. Additionally, one or more transceivers (106, 206) may be coupled to one or more antennas (108, 208), and one or more transceivers (106, 206) may be configured to transmit and receive user data, control information, wireless signals / channels, or the like, as referred to in the descriptions, functions, procedures, proposals, methods, and / or operational flowcharts disclosed herein, via one or more antennas (108, 208). In this document, one or more antennas may be multiple physical antennas or multiple logical antennas (e.g., antenna ports). One or more transceivers (106, 206) can convert received user data, control information, 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 one or more processors (102, 202).One or more transceivers (106, 206) may convert user data, control information, wireless signals / channels, etc. processed by one or more processors (102, 202) from baseband signals to RF band signals. For this purpose, one or more transceivers (106, 206) may include an (analog) oscillator and / or filter.

[0229] Examples of wireless devices to which the present invention is applied

[0230] Figure 19 illustrates another example of a wireless device applicable to the present invention. The wireless device may be implemented in various forms depending on the use case / service (see Figure 17).

[0231] Referring to FIG. 19, the wireless device (100, 200) corresponds to the wireless device (100, 200) of FIG. 18 and may be composed of various elements, components, units / units, and / or modules. For example, the wireless device (100, 200) may include a communication unit (110), a control unit (120), a memory unit (130), and additional elements (140). The communication unit may include a communication circuit (112) and a transceiver(s) (114). For example, the communication circuit (112) may include one or more processors (102, 202) and / or one or more memories (104, 204) of FIG. 19. For example, the transceiver(s) (114) may include one or more transceivers (106, 206) and / or one or more antennas (108, 208) of FIG. 18. The control unit (120) is electrically connected to the communication unit (110), the memory unit (130), and the additional elements (140) and controls the overall operation of the wireless device. For example, the control unit (120) may control the electrical / mechanical operation of the wireless device based on the program / code / command / information stored in the memory unit (130). In addition, the control unit (120) may transmit information stored in the memory unit (130) to an external device (e.g., another communication device) via a wireless / wired interface through the communication unit (110), or store information received from an external device (e.g., another communication device) via a wireless / wired interface in the memory unit (130).

[0232] The additional element (140) may be configured in various ways depending on the type of the wireless device. For example, the additional element (140) may include at least one of a power unit / battery, an input / output unit (I / O unit), a driving unit, and a computing unit. Although not limited thereto, the wireless device may be implemented in the form of a robot (Fig. 17, 100a), a vehicle (Fig. 17, 100b-1, 100b-2), an XR device (Fig. 17, 100c), a portable device (Fig. 17, 100d), a home appliance (Fig. 17, 100e), an IoT device (Fig. 17, 100f), a digital broadcasting terminal, a hologram device, a public safety device, an MTC device, a medical device, a fintech device (or a financial device), a security device, a climate / environmental device, an AI server / device (Fig. 17, 400), a base station (Fig. 17, 200), a network node, etc. Wireless devices may be mobile or stationary depending on the use / service.

[0233] In FIG. 19, various elements, components, units / parts, and / or modules within the wireless device (100, 200) may be entirely interconnected via a wired interface, or at least some may be wirelessly connected via a communication unit (110). For example, within the wireless device (100, 200), the control unit (120) and the communication unit (110) may be wired, and the control unit (120) and a first unit (e.g., 130, 140) may be wirelessly connected via the communication unit (110). In addition, each element, component, unit / part, and / or module within the wireless device (100, 200) may further include one or more elements. For example, the control unit (120) may be composed of one or more processor sets. For example, the control unit (120) may be composed of a set of a communication control processor, an application processor, an electronic control unit (ECU), a graphics processing processor, a memory control processor, etc. As another example, the memory unit (130) may be composed of RAM (Random Access Memory), DRAM (Dynamic RAM), ROM (Read Only Memory), flash memory, volatile memory, non-volatile memory, and / or a combination thereof.

[0234] Examples of vehicles or autonomous vehicles to which the present invention is applied

[0235] Figure 20 illustrates a vehicle or autonomous vehicle applicable to the present invention. The vehicle or autonomous vehicle may be implemented as a mobile robot, car, train, manned / unmanned aerial vehicle (AV), ship, etc.

[0236] Referring to FIG. 20, a vehicle or autonomous vehicle (100) may include an antenna unit (108), a communication unit (110), a control unit (120), a driving unit (140a), a power supply unit (140b), a sensor unit (140c), and an autonomous driving unit (140d). The antenna unit (108) may be configured as a part of the communication unit (110). Blocks 110 / 130 / 140a to 140d correspond to blocks 110 / 130 / 140 of FIG. 19, respectively.

[0237] The communication unit (110) can transmit and receive signals (e.g., data, control signals, etc.) with external devices such as other vehicles, base stations (e.g., base stations, road side units, etc.), and servers. The control unit (120) can control elements of the vehicle or autonomous vehicle (100) to perform various operations. The control unit (120) can include an ECU (Electronic Control Unit). The drive unit (140a) can drive the vehicle or autonomous vehicle (100) on the ground. The drive unit (140a) can include an engine, a motor, a power train, wheels, brakes, a steering device, etc. The power supply unit (140b) supplies power to the vehicle or autonomous vehicle (100) and can include a wired / wireless charging circuit, a battery, etc. The sensor unit (140c) can obtain vehicle status, surrounding environment information, user information, etc. The sensor unit (140c) may include an IMU (inertial measurement unit) sensor, a collision sensor, a wheel sensor, a speed sensor, an incline sensor, a weight detection sensor, a heading sensor, a position module, a vehicle forward / backward sensor, a battery sensor, a fuel sensor, a tire sensor, a steering sensor, a temperature sensor, a humidity sensor, an ultrasonic sensor, an illuminance sensor, a pedal position sensor, etc. The autonomous driving unit (140d) may implement a technology for maintaining a driving lane, a technology for automatically controlling speed such as adaptive cruise control, a technology for automatically driving along a set path, a technology for automatically setting a path and driving when a destination is set, etc.

[0238] For example, the communication unit (110) can receive map data, traffic information data, etc. from an external server. The autonomous driving unit (140d) can generate an autonomous driving route and driving plan based on the acquired data. The control unit (120) can control the drive unit (140a) so that the vehicle or autonomous vehicle (100) moves along the autonomous driving route according to the driving plan (e.g., speed / direction control). During autonomous driving, the communication unit (110) can irregularly / periodically acquire the latest traffic information data from an external server and can acquire surrounding traffic information data from surrounding vehicles. In addition, during autonomous driving, the sensor unit (140c) can acquire vehicle status and surrounding environment information. The autonomous driving unit (140d) can update the autonomous driving route and driving plan based on newly acquired data / information. The communication unit (110) can transmit information regarding the vehicle location, autonomous driving route, driving plan, etc. to the external server. External servers can predict traffic information data in advance using AI technology or other technologies based on information collected from vehicles or autonomous vehicles, and provide the predicted traffic information data to the vehicles or autonomous vehicles.

[0239] Here, the wireless communication technology implemented in the wireless device (XXX, YYY) of the present specification may include not only LTE, NR, and 6G, but also Narrowband Internet of Things for low-power communication. At this time, 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 wireless device (XXX, YYY) of the present specification may perform communication based on LTE-M technology. At this time, 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 wireless device (XXX, YYY) of the present specification 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 PAN (personal area networks) related to small / low-power digital communication based on various standards such as IEEE 802.15.4, and can be called by various names.

[0240] The embodiments described above are combinations of components and features of the present invention 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 an embodiment of the present invention by combining some components and / or features. The order of operations described in the embodiments of the present invention 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 an embodiment or may be incorporated as a new claim through a post-application amendment.

[0241] In this document, embodiments of the present invention have been described primarily focusing on the signal transmission and reception relationship between a terminal and a base station. This transmission and reception relationship is equally / similarly extended to signal transmission and reception between a terminal and a relay or a base station and a relay. Certain operations described as being performed by a base station in this document may, in some cases, be performed by its upper node. That is, it is obvious that various operations performed for communication with a terminal in a network composed of multiple network nodes including a base station may be performed by the base station or other network nodes other than the base station. The base station may be replaced by terms such as fixed station, Node B, eNode B (eNB), and access point. In addition, the terminal may be replaced by terms such as UE (User Equipment), MS (Mobile Station), MSS (Mobile Subscriber Station).

[0242] Embodiments of the present invention may be implemented by various means, for example, hardware, firmware, software, or a combination thereof. In the case of hardware implementation, an embodiment of the present invention may be implemented by one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, etc.

[0243] When implemented via firmware or software, an embodiment of the present invention may be implemented in the form of modules, procedures, functions, etc. that perform the functions or operations described above. The software code may be stored in a memory unit and executed by a processor. The memory unit may be located within or outside the processor and may exchange data with the processor via various known means.

[0244] It will be apparent to those skilled in the art that the present invention can be embodied in other specific forms without departing from the scope of the invention. Therefore, the above detailed description should not be construed as limiting in any respect, but rather as illustrative. The scope of the present invention should be determined by a reasonable interpretation of the appended claims, and all modifications within the scope of equivalents of the present invention are intended to be included within the scope of the present invention.

[0245] The embodiments of the present invention as described above can be applied to various mobile communication systems.< / gnb>

Claims

1. In a method using a first relay UE (User Equipment), A step of detecting a radio link failure (RLF) for a first link formed with a first cell for U2N (UE to Network) relay; A step of performing a reset procedure of the first link in which the RLF is detected based on the U2N relay in which multi-hop is formed; and A method comprising: a step of transmitting a first notification message including information about a plurality of UEs associated with the multi-hop to the second cell based on the establishment of the first link with the second cell through the resetting procedure; 2. In paragraph 1, A method, characterized in that the first notification message is a SUI (SidelinkUEInformation) message.

3. In paragraph 1, A method characterized in that, based on the transmission of the first notification message, the first relay UE expects to receive an RRC (radio resource control) reset message for each of the plurality of UEs from the second cell.

4. In paragraph 3, A method, characterized in that the RRC reset message for each UE includes information for setting up SRB2 (Signaling Radio Bearer2) and DRB (Data Radio Bearer) for operation of the U2N relay.

5. In paragraph 1, A method characterized in that it further comprises the step of transmitting a second notification message for detection of the RLF to each of the plurality of UEs based on the failure of the re-establishment of the first link.

6. In paragraph 5, A method characterized in that the notification cause value of the second notification message is set to a value corresponding to Uu RLF.

7. In paragraph 1. A method characterized in that, based on the failure of the re-establishment of the first link, the first relay UE transmits a second notification message regarding the detection of the RLF only to a second relay UE directly connected to the first relay UE among the plurality of UEs.

8. In paragraph 1, A method characterized in that, based on the transmission of the second notification message, the SRB (Signaling Radio Bearer) and DRB (Data Radio Bearer) associated with the U2N relay are suspended.

9. In at least one non-transitory computer-readable medium, Contains instructions that perform operations when executed by at least one processor, The above actions are, Detect RLF (radio link failure) for the first link formed with the first cell for U2N (UE to Network) relay; Performing a reset procedure of the first link in which the RLF is detected based on the U2N relay in which multi-hop is formed; At least one non-transitory computer-readable medium comprising transmitting a first notification message to the second cell, the first notification message including information about a plurality of UEs associated with the multi-hop based on the establishment of the first link with the second cell through the resetting procedure.

10. In the first relay UE (User Equipment), RF (Radio Frequency) transmitter and receiver; and A processor connected to the RF transceiver, A first relay UE, wherein the processor detects a radio link failure (RLF) for a first link formed with a first cell for a U2N (UE to Network) relay, performs a reconfiguration procedure for the first link in which the RLF is detected based on the U2N relay in which multi-hops are formed, and transmits a first notification message including information on a plurality of UEs related to the multi-hops to the second cell based on the first link being established with the second cell through the reconfiguration procedure.

11. In paragraph 10, A first relay UE, characterized in that the first notification message is a SUI (SidelinkUEInformation) message.

12. In paragraph 11, A first relay UE, characterized in that, based on the transmission of the first notification message, the first relay UE expects to receive an RRC re-establishment message for each of the plurality of UEs from the second cell.

13. In a processing device controlling the first relay UE (User Equipment), at least one processor; and At least one memory connected to said at least one processor and storing instructions that perform operations when executed by said at least one processor; The above actions are, Detect RLF (radio link failure) for the first link formed with the first cell for U2N (UE to Network) relay; Performing a reset procedure of the first link in which the RLF is detected based on the U2N relay in which multi-hop is formed; and A processing device comprising transmitting a first notification message including information about a plurality of UEs associated with the multi-hop to the second cell based on the establishment of the first link with the second cell through the resetting procedure.

14. In the method by the base station, A step for performing a procedure for resetting the first link by a first relay UE that detects a radio link failure (RLF) for the first link formed for a multi-hop based U2N (UE to Network) relay; and A method comprising: receiving a first notification message including information about a plurality of UEs associated with the multi-hop from the first relay UE based on completion of the re-establishment of the first link; 15. At the base station, RF (Radio Frequency) transmitter and receiver; and A processor connected to the RF transceiver, A base station, wherein the processor controls the RF transceiver to detect a radio link failure (RLF) for a first link formed for a multi-hop based U2N (UE to Network) relay and performs a procedure for re-establishing the first link with a first relay UE, and receives a first notification message including information on a plurality of UEs related to the multi-hop from the first relay UE based on completion of the re-establishment of the first link.

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