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

Abstract

Disclosed are a method for performing communication and a device therefor in a wireless communication system according to various embodiments. Disclosed are a device and method for: receiving a first discovery message; measuring signal strength related to multi-hop-based relay communication; and determining, on the basis of a first hop count value determined on the basis of the signal strength and a second hop count value included in the first discovery message, whether to transmit a second discovery message.

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 a relay UE to perform 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 for a first relay UE to perform communication according to one aspect may include: receiving a first discovery message; measuring a signal strength associated with relay communication based on multi-hop; and determining whether to transmit a second discovery message based on a first hop count value determined based on the signal strength and a second hop count value included in the first discovery message.

[0018] Alternatively, the second discovery message is characterized in that it is transmitted based on the first hop count value being greater than the second hop count value.

[0019] Alternatively, the second discovery message is not transmitted based on the first hop count value being less than or equal to the second hop count value.

[0020] Alternatively, the first relay UE receives configuration information for setting hop count regions based on two or more signal ranges, and the first hop count value is determined based on a hop count region corresponding to a signal range to which the signal strength belongs among the two or more signal ranges.

[0021] Alternatively, the two or more signal ranges are characterized in that they are determined based on e2e (end-to-end) QoS set for relay communication based on multi-hop.

[0022] Alternatively, the signal strength is characterized by being the strength of a signal between the base station and the first relay UE, or the reception strength of the first discovery message.

[0023] Alternatively, based on the first relay UE being in the in-coverage of the base station, the signal strength is the signal strength between the base station and the first relay UE, and based on the first relay UE being out of coverage, the signal strength is the reception strength of the first discovery message.

[0024] Alternatively, the second discovery message is characterized in that it is a discovery message that changes the second hop count value set in the first discovery message to the first hop count value.

[0025] Alternatively, the first relay UE is characterized as an intermediate relay UE that performs multi-hop U2N (UE-to-Network) relay communication between a relay UE and a remote UE that can be directly connected to a base station.

[0026] According to another aspect, a non-transitory computer-readable storage medium having recorded thereon instructions for performing a method for performing communication by the first relay UE described above may be provided.

[0027] According to another aspect, a first relay UE may be provided that performs the method for performing the communication described above.

[0028] According to another aspect, a processing device may be provided for controlling a first relay UE performing the above-described communication.

[0029] According to one embodiment, a relay UE in a wireless communication system can perform multi-hop based U2N relay communication more accurately and efficiently.

[0030] 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.

[0031] 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.

[0032] Figure 1 is a diagram for comparing and explaining V2X communication based on RAT before NR and V2X communication based on NR.

[0033] Figure 2 shows the structure of the LTE system.

[0034] Figure 3 shows the structure of the NR system.

[0035] Figure 4 shows the structure of a radio frame of NR.

[0036] Figure 5 shows the slot structure of an NR frame.

[0037] FIG. 6 illustrates a communication structure that can be provided in a 6G system according to one embodiment of the present disclosure.

[0038] FIG. 7 illustrates an electromagnetic spectrum according to one embodiment of the present disclosure.

[0039] Figure 8 shows a radio protocol architecture for SL communication.

[0040] Figure 9 shows a terminal performing V2X or SL communication.

[0041] Figure 10 shows resource units for V2X or SL communication.

[0042] FIG. 11 illustrates an example of a BWP according to one embodiment of the present disclosure.

[0043] 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.

[0044] Figure 13 is a diagram for explaining the control plane procedure of L2 U2N relay (UE-to-Network Relay).

[0045] Figures 14 to 16 are drawings for explaining a method of performing a path change in relay communication.

[0046] Figure 17 is a diagram for explaining multi-hop based U2N relay communication.

[0047] Figure 18 is a diagram illustrating a method for forwarding a discovery message based on signal strength.

[0048] FIG. 19 and FIG. 20 are diagrams for explaining a path switching method for maintaining service continuity in multi-hop U2N relay operation.

[0049] FIG. 21 is a diagram illustrating a method for a first relay UE to forward / transmit a discovery message for a multi-hop based U2N relay.

[0050] Figure 22 illustrates a communication system applied to the present invention.

[0051] Figure 23 illustrates a wireless device applicable to the present invention.

[0052] Figure 24 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.

[0053] Figure 25 illustrates a vehicle or autonomous vehicle to which the present invention is applied.

[0054] 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).

[0055] 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.

[0056] 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.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] For clarity, the description will focus on LTE-A or 5G NR, but the technical ideas of the embodiment(s) are not limited thereto.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] Figure 3 shows the structure of the NR system.

[0067] 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.

[0068] Figure 4 shows the structure of a radio frame of NR.

[0069] 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).

[0070] 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).

[0071] 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.

[0072] 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

[0073] 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.

[0074] SCS (15*2 u )N slot symb N frame,u slot N subframe,u slot 60KHz (u=2)12404

[0075] 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.

[0076] 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.

[0077] 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).

[0078] Frequency Range designationCorresponding frequency rangeSubcarrier Spacing (SCS)FR1450MHz - 6000MHz15, 30, 60kHzFR224250MHz - 52600MHz60, 120, 240kHz

[0079] 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).

[0080] Frequency Range designationCorresponding frequency rangeSubcarrier Spacing (SCS)FR1410MHz - 7125MHz15, 30, 60kHzFR224250MHz - 52600MHz60, 120, 240kHz

[0081] Figure 5 shows the slot structure of an NR frame.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] New network characteristics in 6G may include:

[0087] - Satellite integrated network

[0088] - 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).

[0089] - Seamless integration of wireless information and energy transfer

[0090] - 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.

[0091] Some general requirements for the new network characteristics of 6G, such as the above, may be as follows:

[0092] - small cell networks

[0093] - Ultra-dense heterogeneous network

[0094] - High-capacity backhaul

[0095] - 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.

[0096] - Softwarization and virtualization

[0097] Below, the core implementation technologies of the 6G system are described.

[0098] - 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.

[0099] - 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.

[0100] 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.

[0101] - Large-scale MIMO technology

[0102] - Hologram beamforming (HBF)

[0103] - Optical wireless technology

[0104] - Free-space optical transmission backhaul network (FSO backhaul network)

[0105] - Quantum communication

[0106] - Cell-free communication

[0107] - Integration of wireless information and power transmission

[0108] - Integration of wireless communication and sensing

[0109] - Integrated access and backhaul network

[0110] - Big data analysis

[0111] - Reconfigurable intelligent surface

[0112] - metaverse

[0113] - Blockchain

[0114] 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.

[0115] - 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.

[0116] 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.

[0117] Below, the SL synchronization signal (Sidelink Synchronization Signal, SLSS) and synchronization information are described.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] 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.

[0125] Figure 9 shows a terminal performing V2X or SL communication.

[0126] 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).

[0127] 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.

[0128] 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.

[0129] 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.

[0130] Figure 10 shows resource units for V2X or SL communication.

[0131] 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.

[0132] 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.

[0133] 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:

[0134] (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.

[0135] (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.

[0136] (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.

[0137] 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.

[0138] 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.

[0139] 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.

[0140] 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.

[0141] 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.

[0142] 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).

[0143] 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.

[0144] 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. The embodiment of FIG. 12 may be combined with various embodiments of the present disclosure.

[0145] 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.

[0146] 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.

[0147] In step S1210, 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.

[0148] 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.

[0149] 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.

[0150] 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.

[0151] 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.

[0152] Figure 13 is a diagram for explaining the control plane procedure of L2 U2N relay (UE-to-Network Relay).

[0153] 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.

[0154] 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.

[0155] A given scenario (TS 38.300) describes the control plane procedures of an L2 U2N relay as follows:

[0156] In step S1300, the remote UE and relay UE can perform a discovery procedure and establish a PC5-RRC connection in step S1301 based on the existing Rel-16 procedure.

[0157] 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.

[0158] 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.

[0159] 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.

[0160] 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.

[0161] 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.

[0162] 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.

[0163] In the above scenario, in addition to the connection setup procedure, for L2 UE-to-Network relay:

[0164] - RRC reconfiguration and RRC disconnection procedures can reuse legacy RRC procedures with message content / configuration design left in the WI phase.

[0165] - 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.

[0166] The setup procedure of U2N relay can be performed based on the following RRC messages (see 3GPP TS 38.331).

[0167] (1)RRCSetupRequest

[0168] The RRCSetupRequest message can be used to request the establishment of an RRC connection. The RRCSetupRequest message can be sent in the following manner.

[0169] -Signalling radio bearer: SRB0

[0170] - RLC-SAP: TM

[0171] - Logical channel: CCCH

[0172] - Direction: UE to Network

[0173] The RRCSetupRequest message can be configured as shown in Table 5 below.

[0174] -- ASN1START-- TAG-RRCSETUPREQUEST-STARTRRCSetupRequest ::= SEQUENCE {rrcSetupRequest RRCSetupRequest-IEs}RRCSetupRequest-IEs ::= SEQUENCE {ue-Identity InitialUE-Identity,establishmentCause EstablishmentCause,spare BIT STRING (SIZE (1))}InitialUE-Identity ::= CHOICE {ng-5G-S-TMSI-Part1 BIT STRING (SIZE (39)),randomValue BIT STRING (SIZE (39))}EstablishmentCause ::= ENUMERATED {emergency, highPriorityAccess, mt-Access, mo-Signalling,mo-Data, mo-VoiceCall, mo-VideoCall, mo-SMS, mps-PriorityAccess, mcs-PriorityAccess,spare6, spare5, spare4, spare3, spare2, spare1}-- TAG-RRCSETUPREQUEST-STOP-- ASN1STOP

[0175] (2)RRCSetup

[0176] The RRCSetup message can be used to establish SRB1. The RRCSetup message can be transmitted in the following manner.

[0177] -Signalling radio bearer: SRB0

[0178] - RLC-SAP: TM

[0179] - Logical channel: CCCH

[0180] - Direction: Network to UE

[0181] The RRCSetup message can be defined as shown in Table 6 below.

[0182] -- ASN1START-- TAG-RRCSETUP-STARTRRCSetup ::= SEQUENCE {rrc-TransactionIdentifier RRC-TransactionIdentifier,criticalExtensions CHOICE {rrcSetup RRCSetup-IEs,criticalExtensionsFuture SEQUENCE {}}}RRCSetup-IEs ::= SEQUENCE {radioBearerConfig RadioBearerConfig,masterCellGroup OCTET STRING (CONTAINING CellGroupConfig),lateNonCriticalExtension OCTET STRING OPTIONAL,nonCriticalExtension RRCSetup-v1700-IEs OPTIONAL}RRCSetup-v1700-IEs ::= SEQUENCE {sl-ConfigDedicatedNR-r17 SL-ConfigDedicatedNR-r16 OPTIONAL, -- Cond L2RemoteUEsl-L2RemoteUE-Config-r17 SL-L2RemoteUE-Config-r17OPTIONAL, -- Cond L2RemoteUEnonCriticalExtension SEQUENCE {} OPTIONAL}-- TAG-RRCSETUP-STOP-- ASN1STOP

[0183] (3)SL-L2RemoteUE-Config

[0184] IESL-L2RemoteUE-Config can be used to set configurations related to L2 U2N relay operation used in L2 U2N remote UE.

[0185] The SL-L2RemoteUE-Config message can be defined as shown in Table 7 below.

[0186] -- ASN1START-- TAG-SL-L2REMOTEUE-CONFIG-STARTSL-L2RemoteUE-Config-r17::= SEQUENCE {sl-SRAP-ConfigRemote-r17SL-SRAP-Config-r17OPTIONAL, --Need Msl-UEIdentityRemote-r17 RNTI-Value OPTIONAL, -- Cond FirstRRCReconfig...}-- TAG-SL-L2REMOTEUE-CONFIG-STOP-- ASN1STOP

[0187] (4)SL-SRAP-Config

[0188] IESL-SRAP-Config can be used to configure configurable SRAP parameters used by L2 U2N relay UEs and L2 U2N remote UEs (see 3GPP TS 38.351).

[0189] The SL-SRAP-Config message can be defined as shown in Table 8 below.

[0190] -- ASN1START-- TAG-SL-SRAP-CONFIG-STARTSL-SRAP-Config-r17 ::= SEQUENCE {sl-LocalIdentity-r17INTEGER(0..255)OPTIONAL, -- Need Msl-MappingToAddModList-r17 SEQUENCE (SIZE (1..maxLC-ID)) OF SL-MappingToAddMod-r17 OPTIONAL, -- Need Nsl-MappingToReleaseList-r17 SEQUENCE (SIZE (1..maxLC-ID)) OF SL-RemoteUE-RB-Identity-r17 OPTIONAL, -- Need N...}SL-MappingToAddMod-r17 ::= SEQUENCE {sl-RemoteUE-RB-Identity-r17 SL-RemoteUE-RB-Identity-r17, sl-EgressRLC-ChannelUu-r17 Uu-RelayRLC-ChannelID-r17OPTIONAL, -- Cond L2RelayUEsl-EgressRLC-ChannelPC5-r17 SL-RLC-ChannelID-r17OPTIONAL, -- Need N...}SL-RemoteUE-RB-Identity-r17 ::= CHOICE {srb-Identity-r17 INTEGER (0..3),drb-Identity-r17 DRB-Identity,...}-- TAG-SL-SRAP-CONFIG-STOP-- ASN1STOP

[0191] Below, we describe in detail how to switch paths / passes in relay communication.

[0192] Figures 14 to 16 are drawings for explaining a method of performing a path change in relay communication.

[0193] The service continuity procedure can be applied in mobility cases where a path is switched from an indirect path to a direct path or from a direct path to an indirect path when an L2 U2N remote UE and an L2 U2N relay UE belong to the same or different gNBs. This procedure can also be applied in mobility cases where a path is switched from an indirect path to an indirect path when two L2 U2N relay UEs belong to the same or different gNBs. In the case of a path switch between gNBs, the source gNB can trigger the path switch and determine the type of path switching (i.e., direct path or indirect path).

[0194] Referring to FIG. 14, the following procedure may be performed for an L2 U2N relay UE that switches / transitions from an indirect path to a direct path in the same gNB for service continuity of the L2 U2N relay.

[0195] 1. The Uu measurement configuration and measurement report signaling procedure can be performed to evaluate both relay link measurements and Uu link measurements. If the established measurement reporting criteria are met, the measurement results of the L2 U2N relay UE can be reported. The sidelink relay measurement report can include at least the source L2 ID of the L2 U2N relay UE, the serving cell ID (i.e., NCGI / NCI), and the sidelink measurement quantity result. The sidelink measurement quantity can be the SL-RSRP of the serving L2 U2N relay UE, and if SL-RSRP is not available, SD-RSRP can be used.

[0196] 2. The gNB may decide to switch the L2 U2N remote UE directly to the Uu path.

[0197] 3. The gNB may send an RRCReconfiguration message to the L2 U2N remote UE. The L2 U2N remote UE may stop user plane and control plane transmissions through the L2 U2N relay UE after receiving the RRCReconfiguration message containing the configuration for path switching.

[0198] 4. L2 U2N remote UE can synchronize with gNB and perform random access.

[0199] 5. The UE (e.g., the L2 U2N remote UE in the previous step) can send the RRCReconfigurationComplete message to the gNB via a direct path using the configuration provided in the RRCReconfiguration message. At this stage, the UE (e.g., the L2 U2N remote UE in the previous step) can use the RRC connection via a direct path to the gNB.

[0200] 6. The gNB can send an RRCReconfiguration message to the L2 U2N relay UE to reset / reconfigure the connection between the L2 U2N relay UE and the gNB. The RRCReconfiguration message to the L2 U2N relay UE can be sent at any time after step 3, depending on the gNB implementation (e.g., configuring Uu relay RLC channels and PC5 relay RLC channels for relay, configuring bearer mapping related to the L2 U2N remote UE).

[0201] 7. The AS layer of the L2 U2N relay UE or L2 U2N remote UE may instruct upper layers to release the PC5 unicast link after receiving the RRCReconfiguration message from the gNB. The timing of the link release depends on the UE implementation.

[0202] 8. The data path can be switched from an indirect path to a direct path between the UE (e.g., the former L2 U2N Remote UE) and the gNB. PDCP re-establishment or PDCP data recovery in the uplink can be performed by the UE (e.g., the former L2 U2N Remote UE) to ensure lossless forwarding during path switching, if configured by the gNB.

[0203] * Note 1: Step 8 can be performed at any time after Step 4. Step 8 can be performed independently of Steps 6 and 7.

[0204] Referring to FIG. 15, the gNB can select an L2 U2N relay UE in any RRC state, such as RRC_IDLE, RRC_INACTIVE, or RRC_CONNECTED, as a target L2 U2N relay UE for direct-to-indirect path switching. For service continuity of the L2 U2N remote UE, the following procedure can be used when the L2 U2N remote UE switches from the direct path to the indirect path on the same gNB through an L2 U2N relay UE in RRC_CONNECTED.

[0205] 1. An L2 U2N remote UE may report Uu measurements with one or more candidate L2 U2N relay UEs after measuring / discovering candidate L2 U2N relay UEs.

[0206] - An L2 U2N remote UE can filter out suitable L2 U2N relay UEs based on relay selection criteria before reporting. An L2 U2N remote UE should only report L2 U2N relay UE candidates that meet higher layer criteria.

[0207] - The report may include at least the L2 U2N relay UE ID, the serving cell ID of the L2 U2N relay UE, and information about the sidelink measurement quantity. SD-RSRP may be used as the sidelink measurement quantity.

[0208] 2. The gNB may decide to switch the L2 U2N remote UE to the target L2 U2N relay UE. Then, the gNB may send an RRCReconfiguration message to the target L2 U2N relay UE, which may include at least the local ID and L2 ID of the L2 U2N remote UE, the Uu Relay RLC channel and PC5 Relay RLC channel configuration for relay, and the bearer mapping settings.

[0209] 3. The gNB can send an RRCReconfiguration message to the L2 U2N Remote UE. The RRCReconfiguration message can include at least the L2 U2N Relay UE ID, the Remote UE's local ID, the PC5 Relay RLC channel configuration for relay traffic, and the associated end-to-end Uu radio bearer. After receiving the RRCReconfiguration message from the gNB, the L2 U2N Remote UE can stop user plane and control plane transmissions via the direct path.

[0210] 4. L2 U2N Remote UE can establish a PC5-RRC connection with the target L2 U2N Relay UE.

[0211] 5. The L2 U2N remote UE can complete the path switching procedure by sending an RRCReconfigurationComplete message to the gNB through the L2 U2N relay UE.

[0212] 6. The data path can be switched from a direct path to an indirect path between the L2 U2N remote UE and the gNB.

[0213] When the L2 U2N relay UE selected for switching from direct path to indirect path is in RRC_IDLE or RRC_INACTIVE, the L2 U2N remote UE may establish a PC5 link with the L2 U2N relay UE after receiving the path switching command, and trigger the L2 U2N relay UE to switch to RRC_CONNECTED state by sending an RRCReconfigurationComplete message through the L2 U2N relay UE. The procedure for the L2 U2N remote UE to switch to indirect path in Fig. 15 can also be applied when the L2 U2N relay UE selected for switching from direct path to indirect path is in RRC_IDLE or RRC_INACTIVE. However, there may be an exception that an RRCReconfiguration message is transmitted from the gNB to the L2 U2N relay UE after the L2 U2N relay UE switches to RRC_CONNECTED state in step '5'.

[0214] Referring to Figure 16, for service continuity of an L2 U2N remote UE, a direct path can be switched to an indirect path via an L2 U2N relay UE in RRC_CONNECTED state on another gNB. The specific procedure may be as follows.

[0215] 1. After measuring / discovering candidate L2 U2N relay UEs, an L2 U2N remote UE may report one or more candidate L2 U2N relay UEs and Uu measurements to the source gNB.

[0216] - An L2 U2N remote UE can filter out suitable L2 U2N relay UEs based on relay selection criteria before reporting Uu measurements. An L2 U2N remote UE needs to report only L2 U2N relay UE candidates that satisfy higher layer criteria.

[0217] - The report of Uu measurements may include at least the L2 U2N relay UE ID, the serving cell ID of the L2 U2N relay UE, and sidelink measurement quantity information. SD-RSRP may also be used as sidelink measurement quantity information.

[0218] 2. The source gNB may decide to trigger path switching for the L2 U2N remote UE through an indirect path to the target gNB based on the MeasurementReport and Radio Resource Management (RRM) information.

[0219] 3. The source gNB can prepare for path switching on the target side by sending a HANDOVER REQUEST message to the target gNB. The HANDOVER REQUEST message may include a remote UE L2 ID and a list of candidate target relay UE IDs belonging to a cell.

[0220] 4. Admission control can be performed at the target gNB.

[0221] 5. The target gNB may select one target relay UE from the list of candidate relay UEs provided by the source gNB and send an RRCReconfiguration message to the L2 U2N relay UE for relay configuration, which may include at least the local ID and L2 ID of the L2 U2N remote UE, Uu relay RLC channel and PC5 relay RLC channel configuration for relay, and bearer mapping configuration.

[0222] 6. The target gNB may send a HANDOVER REQUEST ACKNOWLEDGE message to the source gNB, which may include new RRC settings for the L2 U2N remote UE.

[0223] 7. The source gNB sends an RRCReconfiguration message to the L2 U2N remote UE, which may include at least the L2 U2N relay UE ID, the remote UE's local ID, the PC5 relay RLC channel configuration for relay traffic, and the associated Uu e2e radio bearer. The L2 U2N remote UE may stop user plane and control plane transmissions over the direct path after receiving the RRCReconfiguration message from the source gNB.

[0224] 8. The source gNB may transmit the SN STATUS TRANSFER message to the target gNB to convey the uplink PDCP SN receiver status and the downlink PDCP SN transmitter status of the DRB of the L2 U2N remote UE to which PDCP state preservation applies (i.e., in case of RLC AM).

[0225] 9. L2 U2N remote UE can establish a PC5 connection with L2 U2N relay UE.

[0226] 10. The L2 U2N remote UE can send an RRCReconfigurationComplete message to the target gNB through the L2 U2N relay UE.

[0227] 11. The data path can be switched from a direct path to an indirect path between the L2 U2N remote UE and the target gNB via the target L2 U2N relay UE.

[0228] 12. The target gNB can send a UE CONTEXT RELEASE message to notify the source gNB of the success of the path switching.

[0229] Below, we describe multi-hop based U2N relay communication in detail.

[0230] Figure 17 is a diagram for explaining multi-hop based U2N relay communication.

[0231] 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.

[0232] Hereinafter, for convenience of explanation, as illustrated in FIG. 17, a relay UE directly connected to a gNB is defined as relay UE1 (or last relay UE), a relay UE connected to relay UE1 is defined as relay UE2 (or intermediate relay UE), and another relay UE connected to relay UE2 is defined as relay UE3, etc. Alternatively, in this case, relay UE1 may be defined as Uu-SL relay UE, relay UE2, relay UE 3, etc. may be defined as SL-SL relay UEs.

[0233] Discovery message configuration and operation for multi-hop U2N relay operation

[0234] Figure 18 is a diagram illustrating a method for forwarding a discovery message based on signal strength.

[0235] Discovery procedures may be defined as 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 (Announce 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).

[0236] Hereinafter, a method for a relay UE to transmit or forward a discovery message based on discovery model A is described in detail. Meanwhile, it is assumed that a Uu-SL relay UE (e.g., relay UE1 in FIG. 17) has a hop count value of 0 or 1, and an SL-SL relay UE (e.g., relay UE2 in FIG. 17) has a hop count value of 1 or more or 2 or more.

[0237] (1) Transmission / forwarding of discovery messages based on hop count

[0238] The discovery message transmitted by the relay UE may include a hop count and / or a maximum hop count. The hop count may be transmitted in the following manner.

[0239] - Option 1

[0240] Relay UE1 (Uu-SL relay UE) can transmit a discovery message with a hop count set to 1 (or 0). Relay UE2 (SL-SL relay UE, or intermediate relay UE) that receives the discovery message can forward the discovery message or transmit its own discovery message including a hop count that increases the hop count included / set in the received discovery message by one (e.g., 2 (or 1)) if the signal strength of the received discovery message is greater than or equal to a predetermined threshold. Here, the discovery message can be transmitted or broadcast in a broadcast manner.

[0241] A discovery message transmitted by relay UE1 may include a maximum hop count. In this case, relay UE2 (SL-SL relay UE, or intermediate relay UE) receiving the discovery message may not generate / forward the discovery message if the value before / after adding its own hop count exceeds the maximum hop count. For example, the relay UE may check whether the hop count value set in the received discovery message or the value obtained by increasing the hop count value by 1 exceeds the maximum hop count. If the maximum hop count value is exceeded, relay UE2 may not trigger transmission of its own discovery message based on the received discovery message or may not forward the received discovery message. Conversely, if the value is less than or equal to the maximum hop count value, relay UE2 may trigger transmission of its own discovery message based on the received discovery message or may forward the received discovery message.

[0242] - Option 2

[0243] Relay UE1 (Uu-SL relay UE) may transmit a discovery message including a maximum hop count value (e.g., 3). In this case, relay UE2 (SL-SL relay UE) may set the maximum hop count of its own discovery message to a hop count value (e.g., 2) that is a decrease of the received maximum hop count by one, if the signal strength of the received discovery message is greater than or equal to a predetermined threshold, and broadcast / forward the discovery message. An SL-SL relay UE that receives a discovery message with a maximum hop count of 0 (or 1) may no longer generate or forward discovery messages based on the received discovery message.

[0244] (2) Hop count determination in relation to gNB

[0245] The hop count value that the relay UE can use may be set differently depending on the signal strength between the relay UE and the gNB, and / or whether it is in-coverage / Out of coverage (OoC). For example, a relay UE in which the signal strength between the gNBs falls within a specific range (range A area) may be a Uu-SL relay UE (hop count = 1 / 0, or hop count 1 / 0 area). A relay UE in which the signal strength between the gNBs falls within a specific range (range B area) may be a SL-SL relay UE (hop count = 2 / 1, or hop count 2 / 1 area). In this case, the ranges A and B that are set may have non-overlapping values ​​or partially overlapping values. Alternatively, a relay UE in-coverage may transmit a discovery message using 1 (or 0) as a hop count, and a relay UE in OoC may transmit a discovery message using a value other than 1 (or 0).

[0246] For example, the relay UE can determine the hop count value of the discovery message that it will forward or transmit based on signal strength range A and signal strength range B (wherein signal strength range A may be a range for higher signal strengths than signal strength range B) related to the signal strength between the gNB and the relay UE. For example, if the signal strength between the gNB and the relay UE falls within signal strength range A, the relay UE, as a Uu-SL relay UE, can determine the hop count of the discovery message to be 1 (or 0) (e.g., the minimum value). Alternatively, if the signal strength between the gNB and the relay UE falls within signal strength range B, the relay UE, as an SL-SL relay UE (or an intermediate relay UE), can determine the hop count of the discovery message to be 2 (or 1).

[0247] Alternatively, a relay UE belonging to in-coverage may determine / set the hop count of the discovery message as a Uu-SL relay UE to a value of 1 (or 0) (e.g., a minimum value), and a relay UE belonging to OoC may determine the hop count of the discovery message as a value of 2 (or 1, 3) as a SL-SL relay UE.

[0248] Meanwhile, the gNB can set different (Uu signal strength) thresholds or threshold ranges depending on the Quality of Service (QoS) parameters. This is because setting different thresholds for triggering discovery message transmission or determining the hop count of intermediate relay UEs based on the required QoS of the service that the gNB needs to transmit to the final remote UE can help meet the end-to-end QoS requirements.

[0249] (3) Forwarding of discovery messages from intermediate relay UEs

[0250] An SL-SL relay UE may be triggered to transmit a discovery message when the reception strength of the discovery message received from a Uu-SL relay UE is greater than or equal to a preset threshold. Whether a UE can be a Uu-SL relay UE or an SL-SL relay UE may be determined based on the (Uu) signal strength with respect to the gNB, as described in '(2)'.

[0251] Alternatively, a relay UE (i.e., a relay UE capable of direct connection with a gNB) can transmit a discovery message with a hop count set to 1( / 0). Among the SL-SL relay UEs that receive the discovery message, only the relay UEs belonging to an area where their hop counts correspond to 2 (e.g., when the signal strength between the gNB and the SL-SL relay UE falls within a signal strength range where the hop count corresponds to 2, or when they exist in an OoC) can trigger transmission of their own discovery message or perform forwarding of the received discovery message based on reception of the discovery message (and / or the discovery message received more than a preset threshold value) from the relay UE. The reason for this behavior is to prevent another relay UE belonging to the same hop count area from transmitting the discovery message transmitted by the relay UE with the hop count of 0 or 1 (or 1 or 2). For example, if another relay UE within the same hop count area forwards the discovery message, the intent / purpose of expanding the coverage of the multi-hop relay may be diminished. This also serves to prevent unnecessary discovery messages from being broadcast / forwarded.

[0252] For example, a hop count value (or hop count area) may be preset for each signal strength range with respect to the gNB, and the relay UE may determine its own hop count value based on the signal strength range to which the signal strength with respect to the gNB belongs, and transmit its own discovery message or forward the received discovery message based on the received discovery message if the determined hop count value is greater than the hop count value included / set in the received discovery message. For example, as illustrated in FIG. 18 (a), a hop count value of 1 may be mapped to a signal strength range A or a hop count 1 area corresponding to the signal strength range A, and a hop count value of 2 may be mapped to a signal strength range B or a hop count 2 area corresponding to the signal strength range B. At this time, the discovery message to be forwarded may be set / included with a hop count value corresponding to the signal strength range to which the signal strength with the gNB belongs (e.g., 2, which is 1 increased from the hop count set in the received discovery message) as described in '(2)'.

[0253] For example, referring to FIG. 18 (a), it may be desirable for a discovery message broadcast by a relay UE1 to trigger broadcast / forwarding of the discovery message at a relay UE2 that belongs to a different region from a hop count region (e.g., a hop count 1 region) of the relay UE1. Other relay UEs existing in the hop count 1 region to which the relay UE1 belongs may not forward the discovery message received from the relay UE1. For example, assuming that relay UE 1 (a) and relay UE 1 (b) belong to the same hop count region as relay UE1, relay UE 1 (a) and relay UE 1 (b) may not forward the discovery message received from the relay UE1. This can prevent unnecessary transmission triggering or forwarding of discovery messages by relay UEs that may have the same hop count.

[0254] (4) For relay UEs existing in OoC

[0255] An SL-SL relay UE that receives a discovery message transmitted by an SL-SL relay UE existing in OoC (Out-of-Coverage) cannot be defined in an area (range of signal strength, hop count area) such as (3) determined by the signal strength with respect to the gNB. Therefore, for an SL-SL relay UE existing in OoC, a range of signal strength and / or a hop count area for determining / setting a hop count can be defined using the SL-SL signal strength. For example, only an SL-SL relay UE existing in an area where the received SL signal strength (i.e., SD-RSRP, signal strength of the received discovery message) falls within a certain range can broadcast / forward the received discovery message. For example, a first hop count range may be set for a first signal strength range, and a second hop count range may be set for a second signal strength range (wherein a hop count value for the first hop count range may be smaller than a hop count value for the second hop count range). In this case, in relation to the first relay UE, an SL-SL relay UE belonging to the first hop count range may not forward a discovery message received from the first relay UE, and only an SL-SL relay UE belonging to the second hop count range may forward a discovery message received from the first relay UE.

[0256] For example, referring to FIG. 18 (b), the area of ​​an SL-SL relay UE that can generate its own discovery message based on a discovery message received from relay UE2 or forward the received discovery message can be defined / configured based on the signal strength of the SL received (from the relay UE1). The discovery message transmitted by relay UE1 can also be configured to be transmitted only to relay UE2 in the hop count 2 area. For example, an SL-SL relay UE (e.g., relay UE 1(a), relay UE 1(b)) whose SL signal strength with relay UE1 falls within a first hop count range does not forward the discovery message received from relay UE1, and an SL-SL relay UE (e.g., relay UE2) whose SL signal strength with relay UE1 falls within a second hop count range can forward the discovery message received from relay UE1.

[0257] However, the above-described forwarding / forwarding operation (operation according to '(3)' and / or '(4)') may be suitable when there are many suitable relay UEs around relay UE1 to forward / broadcast discovery messages for the remote UE. Conversely, the above-described forwarding / forwarding operation may not be suitable when there are not enough relay UEs to forward the discovery messages of relay UE1. Therefore, the following methods may be considered as methods to supplement the situation in which the above-described forwarding / forwarding operation is not suitable. The following methods may be methods to prevent too many discovery messages from being forwarded / broadcasted through multiple hops.

[0258] - Relay UE1 can transmit message A to find out how many potential candidate (SL-SL) relay UEs exist in the surrounding before transmitting the discovery message. In this case, the surrounding candidate relay UE that received the message A can transmit a response message B to the message A to relay UE1 if it can become a candidate relay UE (i.e., if the reception strength of the received message A is higher than a set specific reception strength). The relay UE1 selects some of the candidate relay UEs that responded and transmits a discovery message including the (L2 / User Info) ID of the relay UE(s) for the selected some. Among the candidate relay UEs that received the discovery message, only the relay UE whose ID is included in the discovery message can broadcast / forward the discovery message. Alternatively, the candidate relay UE may transmit a response message B including information about the signal strength for the message A it received, and the relay UE1 receiving the response message B may transmit a discovery message including a setting for a signal strength range corresponding to a hop count 2 region based on the information about the signal strength. Here, the setting for the signal strength range corresponding to the hop count 2 region may be information for specifying a candidate relay UE to which its discovery message will be broadcast / forwarded. If the candidate relay UE2 receiving such a discovery message belongs to the hop count 2 region according to the signal strength range (and / or if the reception strength of the discovery message is equal to or greater than a preset specific threshold value), the received discovery message may be forwarded / broadcasted.

[0259] - Alternatively, a timer may be set for the relay UE2 to receive the discovery message and broadcast / forward the discovery message again. If the signal strength of the discovery message falls within a specific signal strength range or a specific hop count region, a timer associated with the specific signal strength range or the specific hop count region may be set. When the relay UE2 receives the discovery message, the relay UE2 may start / run a timer corresponding to its own hop count region, and may overhear a discovery message transmitted by another candidate relay UE2' (e.g., a relay UE having the same hop count value as the relay UE that it wishes to transmit) until the timer expires. At this time, the relay UE2 may also broadcast / trigger its own discovery message after the expiration of the timer if the number of other candidate relay UE2's transmitting the discovery message before the expiration of the timer is less than or equal to the specific number set. If the number of other candidate relay UE2's transmitting discovery messages while overhearing exceeds a certain number set, relay UE2 releases the running timer and also drops forwarding of the received discovery messages, so that it no longer broadcasts / triggers discovery messages. This is because it has determined that there are sufficient candidate relay UEs other than itself to forward discovery messages.

[0260] - To prevent duplicate discovery messages from being propagated through multiple candidate relay UEs, the discovery message (header such as / MAC / RLC / SRAP / RRC) may include a sequence number (SN). For example, the discovery message broadcast by relay UE1 may increase the SN value each time the same message is generated. In this case, the intermediate SL-SL relay UE that receives it may broadcast / forward only one discovery message and drop other discovery messages when it receives multiple discovery messages with the same SN value through different paths.

[0261] (5) Information related to forwarding of discovery messages

[0262] When an SL-SL relay UE receives a discovery message, the SL-SL relay UE may decide whether to broadcast / forward the discovery message based on at least one of the following pieces of information. The information may be included in the discovery message or in a header such as MAC / RLC / SRAP / RRC.

[0263] - An indication indicating that this is a discovery message for multi-hop operation.

[0264] - Release information (Rel-18 / Rel19). For example, in Rel-19, the relay UE can broadcast / forward discovery messages if the maximum hop count is not exceeded or the hop count is not 0.

[0265] - When the number of multi-hops is limited in a 3-hop U2N operation including Uu hops, relay UE1 can broadcast a discovery message with {multi-hop enable = '1'} set. Relay UE2, which receives and broadcasts / forwards this, can transmit it by toggling {multi-hop enable = '0'}. That is, other relay UE2s may not broadcast / transmit the discovery message with "multi-hop enable = '0'" set for forwarding. In this case, it is possible to prevent a discovery message that has been forwarded once from being re-forwarded through multiple hops.

[0266] Alternatively, the SL-SL relay UE2 may independently transmit (initiate) the discovery message regardless of whether it received a discovery message from the Uu-SL relay UE1. In this case, the SL-SL relay UE (or the SL-SL relay UE2) may transmit the discovery message including information indicating that it is a relay UE that cannot directly connect to the gNB. Alternatively, when the hop count value based on the signal strength with respect to the gNB is 2 as described in '(2)' and / or '(3)' (e.g., it is in a location that cannot directly connect to the gNB), the relay UE may transmit the discovery message including information indicating that it is a relay UE that cannot directly connect to the gNB.

[0267] Alternatively, the Uu-SL relay UE, which has received a discovery message from the SL-SL relay UE2, may broadcast (initiate / trigger) the transmission of the discovery message (this may be an action only if the signal strength of the discovery message received from the SL-SL relay UE is greater than a certain threshold value). At this time, the Uu-SL relay UE may include information indicating that it is a relay UE capable of establishing a direct connection with the gNB in ​​the discovery message.

[0268] Alternatively, the SL-SL relay UE2, which initiated the transmission of the discovery message, may further include information in the discovery message indicating that it has not discovered the Uu-SL relay UE1 if it has not yet discovered the Uu-SL relay UE1 with which it can SL connect in the discovery message transmission. For example, the SL-SL relay UE may indicate in the discovery message whether it has discovered the Uu-SL relay UE. A remote UE receiving this may further consider the additionally indicated information to decide whether to select the SL-SL relay UE2.

[0269] Meanwhile, in the existing Rel-17 U2N operation, when an RLF (Radio Link Failure) occurs between a relay UE and a remote UE, the relay UE reports information about the detected RLF to the gNB, and the remote UE can perform re-establishment by selecting an indirect path and / or a direct path.

[0270] Below, the operation of the relay UE and / or remote UE when an RLF occurs in multi-hop U2N relay operation is described in detail.

[0271] RLF Processing Method for Multi-Hop U2N Relay Operation

[0272] Referring to FIG. 17, relay UE1 may be a Uu-SL relay UE directly connected to a gNB, and relay UE2 may be an SL-SL relay UE connected to relay UE1 via SL.

[0273] In multi-hop U2N relay operation, if a remote UE detects an RLF between its connected SL-SL relay UE and the remote UE, the remote UE can trigger relay reselection and perform reestablishment via direct and / or indirect paths (same as existing rel-17 SL relay operation).

[0274] When an SL-SL relay UE detects an RLF for an SL connection or link with a remote UE, the SL-SL relay UE may report information about the detection of the RLF to the gNB via a previous relay UE. Here, the previous relay UE may be a relay UE toward the gNB (e.g., a Uu-SL relay UE, or another SL-SL relay UE connected toward the gNB in ​​case of multi-hop based U2N operation / communication) as illustrated in FIG. 17. When reporting information about the RLF, the SL-SL relay UE may also report the (L2 / local) ID of the remote UE via the method described below.

[0275] - The SL-SL relay UE may transmit a SUI (SidelinkUEInformationNR) message indicating the SL RLF it has detected to the gNB. At this time, the SL-SL relay UE may transmit the (L2 / local) ID of the relay UE and / or remote UE connected to the SL connection / link in which the SL RLF was detected together with the SUI message in order to inform which relay UE and / or remote UE it has detected the SL RLF for. At this time, the SUI message may include a SARP header including the (L2 / local) ID of the SL-SL relay UE. According to this method, the intermediate relay UE transmitting the SUI message cannot be aware that an SL RLF has occurred, and only the gNB can be aware that an SL RLF has occurred. However, since the gNB performs all the necessary configuration in multi-hop based U2N relay operation, it may be sufficient for the gNB alone to know which SL connection (or hop) to which relay UE and / or remote UE has the RLF.

[0276] - The SL-SL relay UE notifies its previous relay UE that it has detected an RLF. The previous relay UE, upon receiving this, may notify its previous relay UE. In this case, additional information may be included regarding which relay UE and remote UE the SL RLF occurred between. In this way, the SL RLF can be reported to the gNB. In this case, while the information regarding the detection of the RLF is being transmitted to the gNB, all intermediate relay UEs that report the occurrence of an SL RLF between which relay UE and / or remote UE can also be aware. The intermediate relay UE(s) that are aware of this may themselves release the settings related to the remote UE (e.g., SL bearer mapping relationship for end-to-end bearer, etc.).

[0277] Alternatively, if an intermediate relay UE detects an SL RLF for an SL connection with a previous relay UE (e.g., if relay UE2 detects an RLF between relay UE2 and relay UE1 in FIG. 17), the intermediate relay UE may inform information about the detection of the RLF in the following manner.

[0278] - The intermediate relay UE can notify the next relay UE (relay UE connected in the direction of the remote UE) / remote UE associated with the next SL connection or link (e.g., an SL connection / link that has a bearer / RLC_channel mapping relationship with the previous SL connection) of the detection of the RLF. The next relay UE, upon receiving this, can perform operations similar to those of the intermediate relay UE. For example, the next relay UE can notify the next relay UE and / or remote UE connected to the next SL connection of the SL connection from which it received its RLF notification. The remote UE, which has received this information about the detection of the RLF, can perform direct / indirect RRC reestablishment. In addition, the relay UE that detected the RLF can also perform RRC reestablishment directly / indirectly if there is no other remote UE / relay UE connected to the relay UE.

[0279] - Alternatively, if the relay UE detects an SL RLF for an SL connection with a previous relay UE, the relay UE may generate / forward a notification message regarding the detection of the SL RLF. In this case, the notification message may include an SRAP header. In this case, the SRAP header must include the (local / L2) ID of the remote UE corresponding to the target. For this, the intermediate relay UE that detected the RLF must know the L2 ID of the target remote UE.

[0280] - Alternatively, if the relay UE detects an SL RLF for the SL connection with the previous relay UE, the relay UE may also release the SL connection with the next relay UE / remote UE. At this time, the relay UE may also signal the RLF of the previous link through the cause value of the SL connection.

[0281] Alternatively, the above-described methods may be equally applicable when the Uu-SL relay UE detects Uu RLF.

[0282] - For example, when a Uu-SL relay UE detects a Uu RLF, the Uu-SL relay UE can generate a notification message regarding the detection of the Uu RLF and forward the notification message to the SL-SL relay UE connected to it. The SL-SL relay UE that receives the notification message can forward the notification message to the next hop toward the remote UE. Alternatively, the SL-SL relay UE can receive the notification message and generate its own notification message. In this case, the cause value of the notification message of the SL-SL relay UE can be set to be the same as the cause value of the received notification message. For example, even if the SL-SL relay UE generates the notification message, the cause value of the generated notification message may be Uu-RLF (and / or Uu link failure, HO, etc.).

[0283] - The RLF described above can also be replaced with beam failure (and / or HO failure). For example, when beam failure (and / or HO failure) occurs, relay UE1 (and / or relay UE2) can notify information about beam failure (and / or HO failure) to remote UE, in which case, SRB (Signaling Radio Bearer) / DRB (Data Radio Bearer) configured for remote UE can be suspended. Meanwhile, when beam recovery or handover recovery (beam recovery( / HO recovery)) is successful, relay UE1 (and / or relay UE2) can notify information about this to remote UE, and suspension of SRB (Signaling Radio Bearer) / DRB (Data Radio Bearer) configured for remote UE can be released.

[0284] - Alternatively, if the remote UE receives a notification message notifying that an RLF has occurred on the Uu link / Uu connection via the relay UE2, the remote UE may trigger an RRCReestablishment or a relay re-selection. If such an RRCReestablishment operation of the remote UE can be a subsequent procedure of suspending an SRB / DRB, a timer related to the suspending of the SRB / DRB may be set. For example, when the remote UE receives the notification message (regarding the occurrence of an RLF), the timer may be started, and the SRB / DRB for the remote UE may be suspended. Thereafter, if the remote UE receives a notification message indicating that the Uu connection has been recovered, the timer may be stopped. Alternatively, if no notification message regarding the recovery of the connection in which an RLF has occurred is received by the timer expires, the remote UE may trigger an RRCReestablishment or a relay re-selection procedure.

[0285] - Alternatively, in multi-hop U2N operation, if relay UE2 receives a notification message for Uu-RLF from relay UE1 (Rel-17 U2N operation), relay UE2 may perform RRC reestablishment (directly / indirectly) without forwarding to relay UE3 and / or remote UE. In this case, if relay UE2 succeeds in RRC reestablishment, relay UE2 may notify relay UE3 and / or remote UE connected to it of information about the success of RRC reestablishment. This notification operation of information about the success of RRC reestablishment may be performed only when relay UE2 performs reestablishment to a different gNB / cell than the gNB / cell connected to the existing relay UE1. Relay UE3 and / or remote UE that receive this may trigger operations such as RRC reestablishment / RRC resume. Alternatively, if the relay UE2 performs RRC reestablishment upon receiving a Uu-RLF notification message from the relay UE1 but fails, the relay UE2 may forward the notification message (the message it has stored) for notifying the Uu-RLF to the relay UE3 and / or the remote UE, or may generate and deliver a new notification message for notifying the Uu-RLF. This operation may be advantageous in terms of service continuity and reducing the delay required for connection establishment when the remote UE performs RRC resume / reestablishment while maintaining the relationship with the currently connected multi-hop relay UEs rather than having the remote UE find a new relay UE and establish a new multi-hop connection when connected through multiple hops.

[0286] - Alternatively, the case of the above Uu RLF can be equally applied to the case of the SL RLF of the relay UE2 (e.g., the SL RLF for the SL connection between the relay UE2 and the relay UE1) (provided that a recovery operation is defined for the SL).

[0287] In this way, the proposed method described above can notify information about RLF detection to a remote UE or gNB when an RLF is detected at an intermediate relay UE in a multi-hop U2N relay operation, thereby enabling the remote UE to appropriately and quickly perform an operation in response to the detection of the RLF, or effectively receive new settings from the gNB.

[0288] Multi-hop U2N relay operation is likely to be addressed in rel-19 SL relay. Multi-hop U2N relay operation can be structured to transmit and receive data from the gNB to the remote UE via multiple hops, similar to the existing U2N operation. Path switching considering service continuity can also be performed in multi-hop U2N relay operation. Below, a method for efficiently performing path switching in such multi-hop U2N relay operation is described in detail.

[0289] A path switching method for maintaining service continuity in multi-hop U2N relay operation.

[0290] FIG. 19 and FIG. 20 are diagrams for explaining a path switching method for maintaining service continuity in multi-hop U2N relay operation.

[0291] As described with reference to FIG. 17, a relay UE directly connected to a gNB is defined as relay UE1 (or last relay UE), a relay UE connected to relay UE1 is defined as relay UE2 (or intermediate relay UE), and another relay UE connected to relay UE2 is defined as relay UE3, etc. Alternatively, in this case, relay UE1 may be defined as Uu-SL relay UE, relay UE2, relay UE 3, etc. may be defined as SL-SL relay UEs. In the following, considering that a candidate relay UE selected by a remote UE connected via a multi-hop based U2N relay for path switching may be an IDLE / INACTIVE state UE, a method is proposed for a remote UE to report information related thereto to the gNB.

[0292] Referring to FIG. 19, the remote UE can perform a path switch from a path indicated by a dotted line to a path indicated by a solid line, or from a path indicated by a solid line to a path indicated by a dotted line.

[0293] An intermediate relay UE (SL-SL relay UE or relay UE2) may attempt to connect to the gNB through another relay UE when in RRC IDLE / INACTIVE state. The intermediate relay UE may choose which relay UE to establish a connection with the gNB through, or the remote UE or the serving gNB of the remote UE may configure / instruct it.

[0294] An intermediate relay UE (e.g., relay UE2) can know information about other relay UEs (e.g., relay UE1-1, relay UE1-2, etc.). At this time, information about other relay UEs may mean information about the (connected, camping on) cell ID, gNB ID, PLMN (Public Land Mobile Network) ID, etc. of the corresponding relay UE. The intermediate relay UE (or relay UE2) can transmit a discovery message including a list of possible cell IDs, a list of gNB IDs, and a list of PLMN IDs that it can access through another relay UE (e.g., relay UE1) by using information about several other relay UEs (e.g., relay UE1-1, 1-2, etc. that are directly connected or can be connected to a gNB). This operation may be possible only when the relay UE (e.g., relay UE2) is in an IDLE / INACTIVE state. If the intermediate relay UE is in CONNECTED state, the intermediate relay UE may send a discovery message containing the gNB / cell / PLMN ID to which it already belongs.

[0295] A remote UE that receives a discovery message from such an intermediate relay UE may report to the gNB information about the gNB / cell / PLMN ID list and information about the ID of a candidate relay UE (e.g., relay UE2). This information may be information for reporting the possibility of which cell ID, gNB ID, and PLMN ID may be used to connect to the gNB when the candidate relay UE is selected. In this case, the gNB may transmit (to the remote UE) an RRC message ( / RRCReconfiguration message) including information about which cell ID, gNB ID, and / or PLMN ID the relay UE will use to connect to the gNB (via an indirect path) when the candidate relay UE is selected for path switching.

[0296] When a remote UE receives an RRC message including a path switching command, the remote UE may select an intermediate relay UE (e.g., relay UE2) included in the RRC message, establish an SL connection with the selected intermediate relay UE, and may transmit / instruct the selected intermediate relay UE (e.g., relay UE2) information about which gNB ID / cell_ID / PLMN_ID indicated by the gNB to connect to. The intermediate relay UE (e.g., relay UE2) that has received such an instruction / command (in IDLE / INACTIVE state) may select a relay UE (e.g., another intermediate relay UE or Uu-SL relay UE) suitable for the instruction / command. Here, when the selected relay UE is an SL-SL UE, the intermediate relay UE may perform operations similar to those of the remote UE.

[0297] Alternatively, the RRC message containing the path switching command transmitted by the gNB to the remote UE may include the ID of an intermediate relay UE (L2 / local / user Info) that the remote UE should select for the SL connection and the ID of a relay UE (L2 / local / user Info) that can be directly connected to the gNB to which the intermediate relay UE should ultimately be connected (even if it passes through another SL-SL relay UE in the middle due to multi-hop). The remote UE receiving this may establish an SL connection with the intermediate relay UE included in the RRC message, and may transmit (to the intermediate relay UE) the L2 ID of a possible relay UE that can be directly connected to the gNB, which was received from the gNB through an SL-RRC message (a message used for establishing the SL connection or a separate message). The intermediate relay UE receiving this may find a Uu-SL relay UE that can be directly connected to the indicated gNB and establish an SL connection. If the relay UE that has established the SL connection is still an SL-SL relay UE, the SL-SL relay UE can perform operations similar to the above-described remote UE.

[0298] Referring to FIG. 20, relay UE2-1 may be connected to the gNB through each of another relay UE1-1, relay UE1-2, or relay UE1-3, as shown by the dotted line connecting relay UE1-1, relay UE1-2, or relay UE1-3 to the gNB. In this case, the cell IDs to which each of relay UE1-1, relay UE1-2, or relay UE1-3 belongs may be different. Therefore, the discovery message broadcast / unicast by relay UE2-1 (in IDLE / INACTIVE state) may include the L2 ID (or local / user Info ID) of candidate relay UEs (relay UE1-1, relay UE1-2, and / or relay UE1-3) that can be directly connected / accessed to the gNB, and the (connected / camping on) cell ID, gNB ID, and PLMN ID information of candidate relay UEs (relay UE1-1, relay UE1-2, and / or relay UE1-3) associated with each L2 ID. Another intermediate relay UE (or remote UE) that receives this may include the information contained in the discovery message of the relay UE2-1 when broadcasting its own discovery message. Unlike as illustrated in FIG. 20, even if there are more hops, the discovery message transmitted by the intermediate SL-SL relay UE may only include information about candidate relay UEs that can be directly connected to the gNB. This is because, from the remote UE's perspective, it is important to know which cell ID and gNB ID it is connected to, and it may not need to know the IDs of the intermediate relay UEs that constitute the multi-hops.

[0299] A remote UE that receives such a discovery message may report the measurement result through a measurement report, including information about the ID of the candidate relay UE2 it received and information about which gNB, cell ID and / or PLMN ID can be connected, along with the (L2 / local / User Info) IDs of each of the relay UE1-1, relay UE1-2 and / or relay UE1-3. The gNB that receives this report may transmit an RRC message to the remote UE if it determines that path switching is necessary. The RRC message may include information about which path to select toward a relay UE that can be directly connected to the gNB. For example, the information about which path to select may include information such as the (L2 / local / User Info) ID of the relay UE that can be directly connected to the gNB or the cell / gNB / PLMN ID that can be connected through the relay UE.

[0300] FIG. 21 is a diagram illustrating a method for a first relay UE to forward / transmit a discovery message for a multi-hop based U2N relay.

[0301] The first relay UE can support U2N relay communication / operation between the base station and the remote UE. As described above, the first relay UE can be an intermediate relay UE or SL-SL relay UE located between the last relay UE (or Uu-SL relay UE) directly connected to the base station for U2N relay communication / operation and the remote UE (or another relay UE connected to the remote UE via SL).

[0302] Referring to FIG. 21, a first relay UE may receive a first discovery message (S211). Here, the first discovery message may be a discovery message transmitted by the relay UE based on the discovery model A described above. Alternatively, the first discovery message may be a discovery message for multi-hop based U2N relay communication.

[0303] Next, the first relay UE can measure the signal strength / signal quality associated with the multi-hop based relay communication (S213). For example, the first relay UE can measure the reception strength of a signal received from a base station or the reception strength of the first discovery message. For example, if the first relay UE is located within the in-coverage of the base station, the first relay UE can measure the signal strength between the base station and itself. If the first relay UE is not located within the in-coverage of the base station (out-coverage), the first relay UE can measure the signal strength (e.g., the reception strength of the first discovery message) between itself and the relay UE that transmitted the first discovery message. Such measurement of the signal strength / signal quality associated with the relay communication may be an operation for determining a hop count or a hop count value corresponding to the first relay UE as described above.

[0304] Next, the first relay UE can determine a first hop count value based on the signal strength, and determine whether to transmit a second discovery message based on the first hop count value and the second hop count value included in the first discovery message (S215).

[0305] Specifically, as described above, the first relay UE may be provided with configuration information for a hop count area for each signal strength range in advance. For example, the configuration information may include information for configuring a first hop count area for a first signal strength range between a first signal strength and a second signal strength (e.g., an area having a hop count value of 0 or 1), a second hop count area for a second signal strength range between a third signal strength and a fourth signal strength (e.g., an area having a hop count value of 1 or 2), etc. Alternatively, the base station may determine / configure the hop count area for each signal strength range based on an e2e QoS (Quality of Service) configured in a multi-hop based U2N relay communication.

[0306] In this case, the first relay UE may determine a signal strength range to which the measured signal strength belongs and a hop count area corresponding to the signal strength range, and may determine a hop count value for the determined hop count area as the first hop count value. The first relay UE may compare the determined first hop count value with a second hop count value included in the first discovery message to determine whether to transmit a second discovery message based on the first discovery message. Here, the second discovery message may be a discovery message in which the second hop count value in the first discovery message is changed to the first hop count value, or a discovery message that forwards the first discovery message. For example, the first relay UE may transmit the second discovery message when the first hop count value is greater than the second hop count value. Conversely, if the first hop count value is less than or equal to the second hop count value, the first relay UE may drop / skip transmission of the second discovery message (or forwarding operation for the first discovery message).

[0307] For example, if a signal strength measured by a first relay UE in relation to a base station falls within a second signal strength range, and the second signal strength range is a second hop count region in which a hop count value of 2 is set, the first relay UE may determine the first hop count value associated with its own discovery message to be 2. At this time, if a first discovery message having a second hop count value greater than or equal to 2 is received, the first relay UE may not transmit the second discovery message based on reception of the first discovery message (or may not perform a forwarding operation for the first discovery message). Conversely, if a first discovery message having a second hop count value less than 2 is received, the first relay UE may transmit the second discovery message based on reception of the first discovery message (or may perform a forwarding operation for the first discovery message). In this way, the first relay UE can use the hop count value determined based on the measured signal strength in relation to the U2N relay communication to determine whether to perform a forwarding operation based on the reception of the discovery message or to transmit its own discovery message. In other words, the range of discovery messages that the first relay UE can forward may be limited based on the measured signal strength in relation to the U2N relay communication.

[0308] In this way, the proposed invention can prevent the forwarding of discovery messages that would diminish the purpose / intent of expanding the coverage of a multi-hop relay in a multi-hop U2N relay operation. Alternatively, the proposed invention can prevent the propagation of duplicate discovery messages by relay UEs in the same hop count area based on signal strength.

[0309] Examples of communication systems to which the invention applies

[0310] 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.

[0311] 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.

[0312] Figure 22 illustrates a communication system applied to the present invention.

[0313] Referring to FIG. 22, 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.

[0314] 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).

[0315] 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.

[0316] Examples of wireless devices to which the present invention is applied

[0317] Figure 23 illustrates a wireless device applicable to the present invention.

[0318] Referring to FIG. 23, 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. 22.

[0319] 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.

[0320] 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 20.

[0321] The processor (102) can control the transceiver (106) to receive a first discovery message, measure a signal strength related to relay communication based on multi-hop, and determine whether to transmit a second discovery message based on a first hop count value determined based on the signal strength and a second hop count value included in the first discovery message.

[0322] Alternatively, a processing device may be configured including a processor (102) and a memory (104). 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, based on being executed by the at least one processor, cause the first relay UE to: receive a first discovery message, measure a signal strength associated with a multi-hop based relay communication, and determine whether to transmit a second discovery message based on a first hop count value determined based on the signal strength and a second hop count value included in the first discovery message.

[0323] 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). In addition, 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.

[0324] 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.

[0325] 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.

[0326] 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.

[0327] 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.

[0328] Examples of wireless devices to which the present invention is applied

[0329] Figure 24 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 22).

[0330] Referring to FIG. 24, the wireless device (100, 200) corresponds to the wireless device (100, 200) of FIG. 23 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. 24. For example, the transceiver(s) (114) may include one or more transceivers (106, 206) and / or one or more antennas (108, 208) of FIG. 23. 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).

[0331] 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 (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. 22, 100a), a vehicle (Fig. 22, 100b-1, 100b-2), an XR device (Fig. 22, 100c), a portable device (Fig. 22, 100d), a home appliance (Fig. 22, 100e), an IoT device (Fig. 22, 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. 22, 400), a base station (Fig. 22, 200), a network node, etc. Wireless devices may be mobile or stationary depending on the use / service.

[0332] In FIG. 24, 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 a set of one or more processors. 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.

[0333] Examples of vehicles or autonomous vehicles to which the present invention is applied

[0334] Figure 25 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.

[0335] Referring to FIG. 25, 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. 24, respectively.

[0336] 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.

[0337] 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.

[0338] 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.

[0339] 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.

[0340] 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).

[0341] 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.

[0342] 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.

[0343] 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.

[0344] 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), Step of receiving the first discovery message; A step of measuring signal strength related to relay communication based on multi-hop; and A method comprising: a step of determining whether to transmit a second discovery message based on a first hop count value determined based on the signal strength and a second hop count value included in the first discovery message; 2. In paragraph 1, A method characterized in that the second discovery message is transmitted based on the first hop count value being greater than the second hop count value.

3. In paragraph 1, A method characterized in that the second discovery message is not transmitted based on the first hop count value being less than or equal to the second hop count value.

4. In paragraph 1, The first relay UE receives configuration information for setting hop count areas based on two or more signal ranges, A method characterized in that the first hop count value is determined based on a hop count region corresponding to a signal range to which the signal strength belongs among the two or more signal ranges.

5. In paragraph 4, A method characterized in that the two or more signal ranges are determined based on an e2e (end-to-end) QoS (Quality of Service) set for relay communication based on multi-hop.

6. In paragraph 1, A method, characterized in that the signal strength is the strength of a signal between a base station and the first relay UE or the reception strength of the first discovery message.

7. In paragraph 1, Based on the first relay UE belonging to the in-coverage of the base station, the signal strength is the signal strength between the base station and the first relay UE, A method, characterized in that the signal strength is the reception strength of the first discovery message, based on the first relay UE being out of coverage.

8. In paragraph 1, A method, characterized in that the second discovery message is a discovery message that changes the second hop count value set in the first discovery message to the first hop count value.

9. In paragraph 1, A method, characterized in that the first relay UE is an intermediate relay UE that performs multi-hop U2N (UE-to-Network) relay communication between a relay UE and a remote UE that can be directly connected to a base station.

10. A computer-readable recording medium recording a program for performing the method described in paragraph 1.

11. 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 controls the RF transceiver to receive a first discovery message, measures a signal strength associated with multi-hop based relay communication, and determines whether to transmit a second discovery message based on a first hop count value determined based on the signal strength and a second hop count value included in the first discovery message.

12. In paragraph 11, A first relay UE, characterized in that the second discovery message is transmitted based on the first hop count value being greater than the second hop count value.

13. In paragraph 11, A first relay UE, characterized in that the second discovery message is not transmitted based on the first hop count value being less than or equal to the second hop count value.

14. In paragraph 11, The first relay UE receives configuration information for setting hop count areas based on two or more signal ranges, A first relay UE, characterized in that the first hop count value is determined based on a hop count area corresponding to a signal range to which the signal strength belongs among the two or more signal ranges.

15. 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, said instructions being executed by said at least one processor, wherein said first relay UE causes: A processing device that receives a first discovery message, measures a signal strength associated with a multi-hop based relay communication, and determines whether to transmit a second discovery message based on a first hop count value determined based on the signal strength and a second hop count value included in the first discovery message.

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