WO2025071168A1 - Method related to measurement report triggering in multi-hop relay and device therefor - Google Patents

Abstract

A method related to a second relay user equipment (UE), according to one embodiment, comprises: a step in which the second relay UE establishes a connection with a remote UE; a step in which the second relay UE receives a signal transmitted by a base station via a first relay UE; and a step in which the second relay UE transmits the signal to the remote UE, wherein the second relay UE is in a radio resource control (RRC) inactive state, and on the basis of a signal strength between the first relay UE and the second relay UE being less than or equal to a threshold, the second relay UE transmits information related to measurement reporting triggering to the remote UE.

Description

Method for triggering measurement reports in multi-hop relays and device therefor

An embodiment of the present invention relates to a method for triggering measurement reports in a multi-hop relay and a device therefor.

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 a CDMA (code division multiple access) system, an FDMA (frequency division multiple access) system, a TDMA (time division multiple access) system, an OFDMA (orthogonal frequency division multiple access) system, an SC-FDMA (single carrier frequency division multiple access) system, and an MC-FDMA (multi carrier frequency division multiple access) system.

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

V2X (vehicle-to-everything) refers to a communication technology that exchanges information with other vehicles, pedestrians, and objects with built-in infrastructure 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 the Uu interface.

Meanwhile, as more and more communication devices require greater communication capacity, there is a growing need for improved mobile broadband communication over existing Radio Access Technology (RAT). Accordingly, communication systems that consider services or terminals sensitive to reliability and latency are being discussed, and the next-generation radio access technology that considers improved mobile broadband communication, massive MTC (Machine Type Communication), URLLC (Ultra-Reliable and Low Latency Communication), etc. can be called new RAT (new radio access technology) or NR (new radio). V2X (vehicle-to-everything) communication can also be supported in NR.

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

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) have been 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.

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

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

For example, based on vehicle platooning, vehicles can dynamically form a group and move together. For example, in order to perform platoon operations based on vehicle platooning, vehicles belonging to the group can receive periodic data from the lead vehicle. For example, vehicles belonging to the group can use the periodic data to reduce or increase the gap between vehicles.

For example, based on improved driving, the vehicles can be 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. Additionally, for example, each vehicle can share driving intentions with nearby vehicles.

For example, based on the extended sensors, raw data or 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, the vehicle can perceive the environment better than it can perceive using its own sensors.

For example, based on remote driving, for a person who cannot drive or a remote vehicle located in a dangerous environment, a remote driver or V2X application can operate or control the remote vehicle. For example, in the case of predictable paths such as public transportation, cloud computing-based driving can be used to operate or control the remote vehicle. In addition, for example, access to a cloud-based back-end service platform can be considered for remote driving.

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 communications.

In one embodiment, measurement reporting triggering conditions are defined when a remote UE connected to a multi-hop U2N relay performs path switching.

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 belongs from the description below.

One embodiment is a method related to a second relay User Equipment (UE), wherein the second relay UE establishes a connection with a remote UE; the second relay UE receives a signal transmitted by a base station through a first relay UE; and the second relay UE transmits the signal to the remote UE, wherein the second relay UE is in an RRC (Radio Resource Control) inactive state, and based on a signal strength between the first relay UE and the second relay UE being less than or equal to a threshold, the second relay UE transmits information related to measurement reporting triggering to the remote UE.

One embodiment is a second relay UE (User Equipment), comprising at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the UE to perform at least the following: establish a connection with a remote UE; receive a signal transmitted by a base station through the first relay UE; and forward the signal to the remote UE, wherein the second relay UE is in an RRC inactive state, and based on a signal strength between the first relay UE and the second relay UE being less than or equal to a threshold, the second relay UE transmits information related to measurement reporting triggering to the remote UE.

One embodiment is a nonvolatile computer-readable medium having stored thereon program instructions for performing the following: establishing a connection with a remote UE; receiving a signal transmitted by a base station through a first relay UE; and transmitting the signal to the remote UE, wherein the second relay UE is in an RRC inactive state, and based on a signal strength between the first relay UE and the second relay UE being less than or equal to a threshold, the second relay UE transmits information related to measurement reporting triggering to the remote UE.

The above measurement reporting triggering may be related to path switching of the remote UE to the direct link.

The above signal strength can be either SD-RSRP (Sidelink Discovery-Reference Signal Received Power) or SL-RSRP (Sidelink-RSRP).

The transmission of information related to measurement reporting triggering of the second relay UE may be based on an indication of the first relay UE.

The transmission of information related to measurement reporting triggering of the second relay UE may be based on an indication of the base station.

The indication of the above base station may include at least one piece of information among measurement identities and measurement objects.

The at least one piece of information may be received via RRC (Radio Resource Control) signaling or MAC (Medium Access Control) CE (Control Element).

In one embodiment, even if an intermediate relay UE in a multi-hop is RRC inactive and thus cannot report measurements according to Measurement Events, measurement reporting can be enabled to perform path management (such as path switching).

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.

The drawings appended hereto are included to provide an understanding of the present invention and to illustrate various embodiments of the present invention and, together with the description of the specification, serve to explain the principles of the present invention.

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

Figure 2 shows the structure of the LTE system.

Figure 3 shows the structure of the NR system.

Figure 4 shows the structure of a radio frame of NR.

Figure 5 shows the slot structure of an NR frame.

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

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

Figure 8 shows a radio protocol architecture for SL communication.

Figure 9 shows a terminal performing V2X or SL communication.

Figure 10 shows resource units for V2X or SL communication.

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

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.

Figure 13 is a drawing for explaining a method for performing a relay connection between a terminal and a base station.

Figure 14 schematically illustrates how to switch from a direct route to an indirect route.

FIGS. 15 to 17 are drawings related to various embodiments of the present invention.

Figure 18 illustrates a communication system applied to the present invention.

Figure 19 illustrates a wireless device that can be applied to the present invention.

Fig. 20 shows another example of a wireless device applied to the present invention. The wireless device can be implemented in various forms depending on the use-example/service.

Figure 21 illustrates a vehicle or autonomous vehicle to which the present invention is applied.

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 a CDMA (code division multiple access) system, an FDMA (frequency division multiple access) system, a TDMA (time division multiple access) system, an OFDMA (orthogonal frequency division multiple access) system, an SC-FDMA (single carrier frequency division multiple access) system, and an MC-FDMA (multi carrier frequency division multiple access) system.

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

V2X (vehicle-to-everything) refers to a communication technology that exchanges information with other vehicles, pedestrians, and objects with built-in infrastructure 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 the Uu interface.

Meanwhile, as more and more communication devices require greater communication capacity, there is a growing need for improved mobile broadband communication over existing Radio Access Technology (RAT). Accordingly, communication systems that consider services or terminals sensitive to reliability and latency are being discussed, and the next-generation radio access technology that considers improved mobile broadband communication, massive MTC, and URLLC (Ultra-Reliable and Low Latency Communication) can be called new RAT (new radio access technology) or NR (new radio). V2X (vehicle-to-everything) communication can also be supported in NR.

The following technology can be used in various wireless communication systems, such as CDMA (code division multiple access), FDMA (frequency division multiple access), TDMA (time division multiple access), OFDMA (orthogonal frequency division multiple access), and SC-FDMA (single carrier frequency division multiple access). CDMA can be implemented with wireless technologies such as UTRA (universal terrestrial radio access) or CDMA2000. TDMA can be implemented with wireless technologies such as GSM (global system for mobile communications)/GPRS (general packet radio service)/EDGE (enhanced data rates for GSM evolution). OFDMA can be implemented with wireless technologies such as IEEE (institute of electrical and electronics engineers) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, E-UTRA (evolved UTRA). 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.

5G NR is a new clean-slate type mobile communication system that is the successor technology to LTE-A and has the characteristics of high performance, low latency, and high availability. 5G NR can utilize all available spectrum resources, from low frequency bands below 1 GHz to intermediate frequency bands between 1 GHz and 10 GHz, and high frequency (millimeter wave) bands above 24 GHz.

For clarity of explanation, the description will focus on LTE-A or 5G NR, but the technical idea of the embodiment(s) is not limited thereto.

Figure 2 shows the structure of an applicable LTE system. This may be called an Evolved-UMTS Terrestrial Radio Access Network (E-UTRAN), or a Long Term Evolution (LTE)/LTE-A system.

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 called 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 called by other terms such as an evolved-NodeB (eNB), a base transceiver system (BTS), an access point, etc.

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

EPC (30) consists of MME, S-GW, and P-GW (Packet Data Network-Gateway). MME has terminal connection information or terminal capability information, and this information is mainly used for terminal mobility management. S-GW is a gateway with E-UTRAN as an end point, and P-GW is a gateway with PDN as an end point.

The layers of the Radio Interface Protocol between the terminal and the network can be divided into L1 (the first layer), L2 (the second layer), and L3 (the third layer) 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 the first layer provides an information transfer service using a physical channel, and the RRC (Radio Resource Control) layer located in the third layer 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.

Figure 3 shows the structure of the NR system.

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 the eNB are connected to each other via an Xn interface. The gNB and the eNB are connected to a 5th generation core network (5G Core Network: 5GC) via an NG interface. More specifically, they are connected to an access and mobility management function (AMF) via an NG-C interface, and to a user plane function (UPF) via an NG-U interface.

Figure 4 shows the structure of a radio frame of NR.

Referring to FIG. 4, a radio frame can be used in 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 subframes (Subframes, SF). A subframe can be divided into one or more slots, and the number of slots in a subframe can be determined according to the subcarrier spacing (SCS). Each slot can include 12 or 14 OFDM (A) symbols according to the cyclic prefix (CP).

When normal CP is used, each slot can include 14 symbols. When extended CP is used, each slot can include 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).

Table 1 below illustrates the number of symbols per slot ((N ^slot _symb ), the number of slots per frame ((N ^frame,u slot )) and the number of slots per subframe ((N ^subframe,u _slot )) depending on the SCS setting ( _u ) when normal CP is used.

SCS (15*2 ^u ) N ^slot _symb N ^frame,u _slot N ^subframe,u _slot 15KHz (u=0) 14 10 1 30KHz (u=1) 14 20 2 60KHz (u=2) 14 40 4 120KHz (u=3) 14 80 8 240KHz (u=4) 14 160 16

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.

SCS (15*2 ^u ) N ^slot _symb N ^frame,u _slot N ^subframe,u _slot 60KHz (u=2) 12 40 4

In an NR system, OFDM(A) numerology (e.g., SCS, CP length, etc.) may be set differently between multiple cells that are merged into one terminal. Accordingly, the (absolute time) section 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.

In NR, multiple numerologies or SCS can be supported to support various 5G services. For example, when the SCS is 15 kHz, wide area in traditional cellular bands can be supported, and when the SCS is 30 kHz/60 kHz, dense-urban, lower latency and wider carrier bandwidth can be supported. When the SCS is 60 kHz or higher, a bandwidth greater than 24.25 GHz can be supported to overcome phase noise.

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 value of the frequency range 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 "sub 6GHz range", and FR2 can mean "above 6GHz range" and can be called millimeter wave (mmW).

Frequency Range designation Corresponding frequency range Subcarrier Spacing (SCS) FR1 450MHz - 6000MHz 15, 30, 60kHz FR2 24250MHz - 52600MHz 60, 120, 240kHz

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

Frequency Range designation Corresponding frequency range Subcarrier Spacing (SCS) FR1 410MHz - 7125MHz 15, 30, 60kHz FR2 24250MHz - 52600MHz 60, 120, 240kHz

Figure 5 shows the slot structure of an NR frame.

Referring to FIG. 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. Or, 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.

A carrier includes a plurality of subcarriers in the frequency domain. An RB (Resource Block) can be defined as a plurality (for example, 12) of consecutive subcarriers in the frequency domain. A BWP (Bandwidth Part) can be defined as a plurality of consecutive (P)RBs ((Physical) Resource Blocks) in the frequency domain and can correspond to one numerology (for example, SCS, CP length, etc.). A carrier can include at most N (for example, 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.

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 mean a physical layer. In addition, for example, the L2 layer may mean at least one of a MAC layer, an RLC layer, a PDCP layer, and an SDAP layer. In addition, for example, the L3 layer may mean an RRC layer.

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.

New network characteristics in 6G could include:

- Satellite integrated network

- Connected intelligence: Unlike previous generations of wireless communication systems, 6G is revolutionary and will update the wireless evolution from “connected things” to “connected intelligence.” AI can be applied at each stage of the communication process (or at each stage of signal processing, as described below).

- Seamless integration of wireless information and energy transfer

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

Some general requirements from the new network characteristics of 6G as mentioned above can be as follows:

- small cell networks

- Ultra-dense heterogeneous network

- High-capacity backhaul

- Radar technology integrated with mobile technology: High-precision localization (or location-based services) through communications is one of the functions of 6G wireless communication systems. Therefore, radar systems will be integrated with 6G networks.

- Softwarization and virtualization

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

- Artificial Intelligence: Introducing AI into communications can simplify and improve real-time data transmission. AI can use a lot of analytics to determine how complex target tasks are performed. In other words, AI can increase efficiency and reduce processing delays. Time-consuming tasks such as handover, network selection, and resource scheduling can be performed instantly using AI. AI can also play a significant role in M2M, machine-to-human, and human-to-machine communications. AI can also be a rapid communication in Brain Computer Interface (BCI). 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.

- THz communication (terahertz communication): The data rate can be increased by increasing the bandwidth. This can be done by using sub-THz communication with wide bandwidth and applying advanced massive MIMO technology. THz waves, also known as sub-millimeter waves, generally refer to the frequency band between 0.1 THz and 10 THz with corresponding wavelengths ranging from 0.03 mm to 3 mm. The 100 GHz–300 GHz band range (Sub THz band) is considered to be the main part of the THz band for cellular communications. Adding the Sub THz band to the mmWave band will increase the capacity of 6G cellular communications. Of the defined THz bands, 300 GHz–3 THz is in the far infrared (IR) frequency band. The 300 GHz–3 THz band is part of the optical band but is at the boundary of the optical band, just behind the RF band. Therefore, this 300 GHz–3 THz band shows similarities with RF.

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

- Large-scale MIMO technology

- Hologram beamforming (HBF)

- Optical wireless technology

- Free space optical transmission backhaul network (FSO backhaul network)

- Quantum communication

- Cell-free communication

- Integration of wireless information and power transmission

- Integration of wireless communication and sensing

- Integrated access and backhaul network

- Big data analysis

- Reconfigurable intelligent surface

- Metaverse

- Block-chain

- Unmanned aerial vehicles (UAV): UAVs or drones will be a crucial element in 6G wireless communications. In most cases, high-speed data wireless connectivity can be provided using UAV technology. The base station (BS) entity can be installed on the UAV to provide cellular connectivity. UAVs may have certain features not found in fixed BS infrastructure such as easy deployment, robust line-of-sight links, and freedom of movement with controlled mobility. During emergency situations such as natural disasters, deployment of terrestrial communication infrastructure is not economically feasible and sometimes cannot provide services in volatile environments. UAVs can easily handle such situations. UAVs will be a new paradigm in wireless communications. This technology facilitates three basic requirements of wireless networks namely eMBB, URLLC, and mMTC. UAVs can also support several 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.

- Autonomous driving (self-driving): V2X (vehicle to everything), a key element of 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) wireless communication and vehicle to infrastructure (V2I) wireless communication. In order to maximize the performance of autonomous driving and ensure high safety, fast transmission speed and low-latency technology are essential. In addition, in the future, autonomous driving may need to go beyond the level of delivering warnings or guidance messages to drivers and actively intervene in vehicle operation and directly control 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.

Fig. 8 shows a radio protocol architecture for SL communication. Specifically, Fig. 8 (a) shows a user plane protocol stack of NR, and Fig. 8 (b) shows a control plane protocol stack of NR.

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

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 (signal detection) and acquire synchronization using the S-PSS. For example, the terminal may acquire detailed synchronization and detect a synchronization signal ID using the S-PSS and the S-SSS.

PSBCH (Physical Sidelink Broadcast Channel) may be a (broadcast) channel through which basic (system) information that a terminal must know first before transmitting and receiving an SL signal is transmitted. 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.

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 a carrier, and a transmission bandwidth may be within a (pre-)configured SL BWP (Sidelink BWP). For example, the bandwidth of the S-SSB may be 11 RB (Resource Block). 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 frequency to discover the S-SSB in the carrier.

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.

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.

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.

Meanwhile, when SCS is 60 kHz, two types of CP can 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 in 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 in the S-SSB transmitted by the transmitting terminal may be 7 or 6. For example, the PSBCH may be mapped to the first symbol in the S-SSB transmitted by the transmitting terminal. For example, the receiving terminal receiving the S-SSB may perform an AGC (Automatic Gain Control) operation in the first symbol section of the S-SSB.

Figure 9 shows a terminal performing V2X or SL communication.

Referring to Fig. 9, the term terminal in V2X or SL communication may mainly mean a user's terminal. However, if a network device such as a base station transmits and receives a signal 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).

For example, terminal 1 can select a resource unit corresponding to a specific resource within a resource pool, which means a set of a series 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 of terminal 1 within the resource pool.

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.

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.

Figure 10 shows resource units for V2X or SL communication.

Referring to Fig. 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. Accordingly, a total of NF * NT resource units can be defined within the resource pool. Fig. 13 shows an example in which the resource pool repeats with a period of NT subframes.

As shown in Fig. 10, one resource unit (e.g., Unit #0) may appear repeatedly periodically. Or, in order to obtain a diversity effect in the time or frequency dimension, the index of the physical resource unit to which one logical resource unit is mapped may change in a pre-determined pattern over time. In the structure of such resource units, a resource pool may mean a set of resource units that a terminal that wishes to transmit an SL signal can use for transmission.

Resource pools can be subdivided into several types. For example, depending on the content of the SL signal transmitted from each resource pool, resource pools can be divided as follows.

(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, and in this 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.

(2) 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 SL data channels excluding SA information may be transmitted in the resource pool for the SL data channel. In other words, REs (Resource Elements) 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, a transmitting terminal may transmit PSSCH by mapping it to consecutive PRBs.

(3) The discovery channel may be a resource pool for transmitting terminals to transmit information such as their IDs. Through this, the transmitting terminals can enable adjacent terminals to discover themselves.

Even when the content of the SL signal described above is the same, different resource pools may be used depending on the transmission/reception properties of the SL signal. For example, even when 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 of individual signals to individual transmitting terminals or whether individual transmitting terminals select individual signal transmission resources on their own within the resource pool), the signal format (for example, the number of symbols that 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.

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.

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

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

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.

PSBCH (Physical Sidelink Broadcast Channel) may be a (broadcast) channel through which basic (system) information that a terminal must know first before transmitting and receiving an SL signal is transmitted. 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).

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 a carrier, and a transmission bandwidth may be within a (pre-)configured SL BWP (Sidelink BWP). For example, the bandwidth of the S-SSB may be 11 RB (Resource Block). 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 frequency to discover the S-SSB in the carrier.

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

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

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

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

Referring to (b) of FIG. 12, in resource allocation mode 2, a terminal can determine an SL transmission resource within an SL resource set by a base station/network or a preset SL resource. For example, the set SL resource or the preset SL resource 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 by itself within the set resource pool. For example, the terminal can select a resource by itself 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 by itself within a resource pool can transmit a PSCCH (e.g., SCI (Sidelink Control Information) or 1st-stage SCI) to a second terminal using the resource. In step S1220, the first terminal can 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 can receive a PSFCH related to the PSCCH/PSSCH from the second terminal.

Referring to (a) or (b) of FIG. 12, for example, the first terminal may transmit an SCI to the second terminal on the 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, the SCI transmitted on the PSCCH may be referred to as a 1st SCI, a 1st SCI, a 1st-stage SCI, or a 1st-stage SCI format, and the SCI transmitted on the PSSCH may be referred to as a 2nd SCI, a 2nd SCI, a 2nd-stage SCI, or a 2nd-stage SCI format.

Referring to (a) or (b) of FIG. 12, in step S1530, the first terminal can receive the PSFCH. For example, the first terminal and the second terminal can determine the PSFCH resource, and the second terminal can transmit the HARQ feedback to the first terminal using the PSFCH resource.

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

Figure 13 is a drawing for explaining a method for performing a relay connection between a terminal and a base station.

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

In step S1302, the remote UE can transmit the first RRC message (i.e., RRCSetupRequest) to establish 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 started in RRC_CONNECTED, it needs to perform its own connection establishment upon receiving the message for the default L2 configuration of PC5.

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 sets up an RLC channel to relay SRB1 to the remote UE via PC5. This step prepares a relay channel for SRB1.

In step S1305, a remote UE SRB1 message (e.g., an RRCSetupComplete message) is transmitted to the gNB through the relay UE using the SRB1 relay channel over PC5. And the remote UE is RRC connected over Uu.

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

In steps S1308 and S1309, the gNB sends RRCReconfiguration to the remote UE through the relay UE to set up relay SRB2/DRB. The remote UE sends RRCReconfigurationComplete to the gNB through the relay UE in response.

In step S1310, the gNB sets up 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 sets up an additional RLC channel between the remote UE and the relay UE for traffic relay.

For L2 UE-to-Network relay, in addition to the connection setup procedure:

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

- RRC connection re-establishment and RRC connection resumption procedures can reuse existing RRC procedures as a baseline by considering the connection establishment procedure of the above L2 U2N relay to handle relay-specific parts along with message content/composition design. Message content/composition can be defined later.

Figure 14 schematically illustrates how to switch from a direct route to an indirect route.

A direct remote UE can be switched to an indirect relay UE for service continuity of L2 U2N relay based on the procedure illustrated in Fig. 14.

Referring to FIG. 14, in step S1401, the remote UE may report one or more candidate relay UEs after measuring/discovering the candidate relay UEs. The remote UE may filter appropriate relay UEs that meet upper layer criteria when reporting. The report of at least one candidate relay may include ID and SL RSRP information of the relay UE, where PC5 measurement related details may be determined later.

In step S1402, the gNB decides to switch to the target relay UE and the target (re)configuration is optionally transmitted to the relay UE (S1403).

In step S1404, the RRC reconfiguration message to the remote UE may include the ID of the target relay UE, the target Uu, and the PC5 configuration.

In step S1405, if the connection is not yet established, the remote UE establishes a PC5 connection with the target relay UE.

In step S1406, the remote UE feeds back RRCReconfigurationComplete to the gNB through the target path using the target configuration provided in RRCReconfiguration.

In step S1407, the data path is switched.

Meanwhile, with respect to the U2N (UE to Network) relay described above, a multi-hop U2N relay is being discussed in which data is transmitted/received from a gNB to a remote UE via multiple hops. Fig. 15 shows a rough configuration of a multi-hop U2N relay operation. In Figs. 15(a) and (b), Relay UE 1, which is 1 hop from the gNB, may be called the last relay UE, and Relay UE 2, which is 1 hop from the remote UE, may be called the intermediate relay UE. In Fig. 15(c), the last relay UE may be called Relay UE 1, Relay UE 2 may be called intermediate relay UE 2, and Relay UE 3 may be called intermediate relay UE 1.

Meanwhile, in the conventional technology, when the base station sets Measurement Events and the RSRP for the serving cell corresponds to the Measurement Events, the measurement report of the UE is triggered. The Measurement Events may include Serving becomes better than threshold, Serving becomes worse than threshold, Neighbour becomes offset better than SpCell, Neighbour becomes better than threshold, SpCell becomes worse than threshold1 and neighbour becomes better than threshold2, Neighbour becomes offset better than SCell. For a detailed description thereof, refer to 3GPP TS 38.331, 5.5.4 Measurement report triggering, which corresponds to the conventional technology of the present invention.

However, the measurement reporting triggering conditions when a remote UE connected to a multi-hop U2N relay performs path switching may be different from the measurement reporting triggering conditions of a conventional single-hop U2N relay UE.

Therefore, in the following embodiment of the present invention, a measurement reporting triggering condition for path switching of a remote UE connected to a multi-hop U2N relay is proposed. The following description may be based on the connection relationship illustrated in Fig. 15(a). However, the following description is not limited to the connection relationship illustrated in Fig. 15(a), and is also applicable when the number of intermediate relay UEs increases.

Referring to FIG. 15, relay UE1 is a first relay UE and corresponds to an intermediate relay UE. In addition, relay UE2 is a second relay UE and corresponds to an intermediate relay UE. The intermediate relay UE may be a relay UE that is one hop from a remote UE and corresponds to intermediate relay UE 1, and the relay UE that is one hop from a remote UE and corresponds to intermediate relay UE 2. That is, the relay number of the intermediate relay UE may increase in proportion to the number of hops with the remote UE.

According to one embodiment, a second relay UE (User Equipment) can establish a connection with a remote UE (S1601 of FIG. 16). The second relay UE can receive a signal transmitted by a base station through the first relay UE (S1602). The second relay UE can transmit the signal to the remote UE (S1603).

Here, the second relay UE is in an RRC inactive state, and based on the signal strength between the first relay UE and the second relay UE being less than or equal to a threshold, the second relay UE can transmit information related to measurement reporting triggering to the remote UE. The measurement reporting triggering may be related to path switching of the remote UE to the direct link. Accordingly, the remote UE that has received the information related to the measurement reporting triggering can perform measurement on surrounding UEs (candidate relay UE(s)). In addition, the remote UE can transmit the measurement result to the second relay UE in order to report the measurement result to the base station. Through this procedure, the remote UE can perform path switching to the direct link (path switching from multi-hop indirect to direct). In addition, the remote UE can perform path switching to the indirect link through a specific relay UE corresponding to the measurement result.

In the above description, if an indication to trigger measurement reporting is received from (another) relay UE connected to the remote UE, for example, if the SL signal strength (e.g., SD-RSRP, SL-RSRP) measured by the relay UE2 between the relay UE2 and the remote UE is less than a defined threshold, or (and/or) the SL signal strength measured by the relay UE2 between the relay UE1 and the relay UE2 is less than a defined threshold, the relay UE2 may transmit an indication to the remote UE.

The measurement reporting triggering of the remote UE according to the embodiment of the present invention as described above is different from the conventional general measurement reporting triggering or the measurement reporting triggering in the U2N relay in that i) the intermediate relay UE, not the remote UE, is the actual triggering subject, and ii) it is based on the signal strength of the link between the intermediate relay UE and the intermediate relay UE or the link between the intermediate relay UE and the base station, not the signal strength of the link of the remote UE.

According to the above description, in a case where the intermediate relay UE in multi-hop is RRC inactive and cannot perform measurement reports according to Measurement Events and the remote UE neither knows nor reports the degradation of the intermediate link quality, relay communication can be performed more efficiently by triggering a measurement report from the intermediate relay UE to the remote UE when the quality of the intermediate link deteriorates. That is, even in a case where the intermediate relay UE is RRC inactive in multi-hop and cannot perform measurement reports according to Measurement Events, measurement reporting can be enabled to perform path management (such as path switching).

In the above description, the information transmission related to the measurement reporting triggering of the second relay UE may be based on the indication of the first relay UE. That is, the relay UE1 may transmit an indication to trigger measurement reporting to the remote UE via the relay UE2. In this case, this indication may be transmitted when the Uu/SL signal strength measured by the relay UE2 is below each threshold.

Alternatively, the information transmission related to the measurement reporting triggering of the second relay UE may be based on the indication of the base station. The indication of the base station may include at least one piece of information of measurement identities and measurement objects, and the at least one piece of information may be received via RRC (Radio Resource Control) signaling or MAC (Medium Access Control) CE (Control Element). That is, the gNB may indicate to the remote UE to trigger measurement reporting. In this case, the gNB may indicate to the remote UE which measurement values to report (e.g., measurement identities, measurement objects, etc.), and the indication may be transmitted via RRC/MAC_CR, etc. This means that when the gNB receives measurement reporting from the intermediate relay UE and determines that path switching of the remote UE is necessary based on the measurement reporting, it may transmit this indication to the remote UE. (i.e., an indication to the gNB to report measurement values (candidate relay UE, candidate Uu link, etc.) without a measurement reporting triggering condition in the remote UE)

Meanwhile, measurement reporting can be triggered when the signal strength of the current hop of the remote UE (e.g., the SL signal strength between relay UE2 and remote UE in the figure below) is lower than a defined (RRC dedicated, SIB, pre-configuration) threshold, or when the signal strength of the current hop of the remote UE (e.g., the SL signal strength between relay UE2 and remote UE) is lower than a defined (RRC dedicated, SIB, pre-configuration) threshold and the neighbor Uu link signal strength/gain is greater than the threshold.

The above signal strength can be one of SD-RSRP (Sidelink Discovery-Reference Signal Received Power) or SL-RSRP (Sidelink-RSRP). In the above description, path switching of the remote UE includes path switching to a link via a base station, another candidate relay UE, and, as illustrated in FIG. 17, path switching to a different base station (gNB B) from the base station (gNB) of the previous path is also possible.

In connection with the above description, a second relay UE (User Equipment) includes at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the UE to perform at least the following: establishing a connection with a remote UE; receiving a signal transmitted by a base station through the first relay UE; and forwarding the signal to the remote UE, wherein the second relay UE is in an RRC inactive state, and based on a signal strength between the first relay UE and the second relay UE being less than or equal to a threshold, the second relay UE can transmit information related to measurement reporting triggering to the remote UE.

Also, in connection with the above description, a nonvolatile computer-readable medium having stored thereon program instructions for performing the following: establishing a connection with a remote UE; receiving a signal transmitted by a base station through a first relay UE; and transmitting the signal to the remote UE, wherein the second relay UE is in an RRC inactive state, and based on a signal strength between the first relay UE and the second relay UE being less than or equal to a threshold, the second relay UE can transmit information related to measurement reporting triggering to the remote UE.

Below, an embodiment of path switching from multi-hop indirect to single/multi-hop indirect, such as in FIG. 15, is disclosed.

It is assumed that the discovery message is transmitted with the total number of reachable hops (hop count) from the corresponding relay UE to the relay UE that is directly accessible to the gNB.

An intermediate relay UE that receives a discovery message (/integrated DCR, solicitation/response discovery message) can forward the received message by adding +1 to the hop count, which is one of the elements in the discovery message. At this time, the hop count may be a value representing the hop count required for the current relay UE to reach the gNB (/hop count required to reach a relay UE accessible to the gNB).

In this operation, a maximum hop count may be set. That is, if the hop count in the discovery message received by the relay UE exceeds the set max value (same as the /max value), the relay UE may drop the received discovery message without forwarding it. This is to prevent the discovery message from being transmitted with too many hop counts. Since the value of the maximum hop count may be set differently depending on the QoS (/PQI/PDB) of the data to be transmitted, it may be a value set by the remote UE/relay UE (/gNB) that initiated the discovery message. If set by the remote/relay UE, it can determine which value of the maximum hop count to use when initiating its discovery message based on the maximum hop count set for each QoS (which may vary depending on /QoS), and transmit the discovery message including the maximum hop count.

A relay UE that receives discovery messages from multiple other intermediate (/initiate) relay UEs may forward only the discovery message with the lowest hop count when forwarding discovery messages. Or, it may forward the discovery message with the lowest hop count among the discovery messages belonging to the same cell (in this case, all discovery messages forwarded by the relay UE may belong to different cells).

It is also assumed that the remote UE knows which hop it is currently connected to from the gNB (and which hop it is connected to from a relay UE that is directly accessible to the gNB).

- If the remote UE's current hop count is greater than or equal to a defined threshold,

- (and/or) if the hop count included in the discovery message transmitted by the candidate relay UE is less than or equal to a defined threshold (including a single hop);

- (and/or) if the current hop count of the remote UE differs from the hop count transmitted by the candidate relay UE by a preset threshold,

Measurement reporting of a remote UE can be triggered by any one or a combination of the above conditions. The reason why hop count is considered as a triggering criterion for measurement reporting is because hop count is related to the latency of data transmission/reception.

(When the hop count is a criterion for relay (re)selection,) the order of the list in which the remote UE reports the candidate relay UE when reporting the measurement report can be determined by considering the hop count.

For example, when a remote UE reports a candidate relay UE, the ID of the relay UE with a small hop count is listed up first and reported. When the hop counts are the same, the candidate relay UEs with the same hop count can be listed up in descending order of SL signal strength (e.g., SD_RSRP) and reported. At this time, the reported values can be the L2 ID of the candidate relay UE and the cell ID (/gNB ID) to which the candidate relay UE can be connected, similar to the Rel-17 U2N relay operation. In addition, the hop count and SL signal strength of the candidate relay UE can be included and transmitted to the gNB.

In the above technology, the relay UE can be extended to include gNB, IAB-node, etc. In the above description, ‘(/)’ means ‘(and/or)’.

Examples of communication systems to which the invention applies

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/connectivity (e.g., 5G) between devices.

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

Figure 18 illustrates a communication system applied to the present invention.

Referring to FIG. 18, a communication system (1) applied to the present invention includes a wireless device, a base station, and a network. Here, the wireless device means 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 Thing) 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 a UAV (Unmanned Aerial Vehicle) (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. Portable devices can include smartphone, smart pad, wearable device (e.g., smart watch, smart glass), computer (e.g., laptop, 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.

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). Also, IoT devices (e.g., sensors) can communicate directly with other IoT devices (e.g., sensors) or other wireless devices (100a to 100f).

Wireless communication/connection (150a, 150b, 150c) can be established between wireless devices (100a to 100f)/base stations (200), and base stations (200)/base stations (200). Here, the 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 the wireless communication/connection (150a, 150b, 150c), a wireless device and a base station/wireless device, and a base station and a base station can transmit/receive wireless signals to/from each other. For example, the 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.

Examples of wireless devices to which the present invention is applied

Figure 19 illustrates a wireless device that can be applied to the present invention.

Referring to FIG. 19, 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. 18.

A first wireless device (100) includes one or more processors (102) and one or more memories (104), and may additionally include one or more transceivers (106) and/or one or more antennas (108). The processor (102) controls the memory (104) and/or the transceiver (106), and may be configured to implement the descriptions, functions, procedures, suggestions, 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). Additionally, 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 codes including instructions for performing the descriptions, functions, procedures, proposals, methods, and/or operational 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.

Specifically, the first wireless device or terminal (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 above embodiments.

The processor (102) can perform the following operations.

Establishing a connection with a remote UE; receiving a signal transmitted by a base station through a first relay UE; and forwarding the signal to the remote UE, wherein the second relay UE is in an RRC inactive state, and based on a signal strength between the first relay UE and the second relay UE being less than or equal to a threshold, the second relay UE can transmit information related to measurement reporting triggering to the remote UE.

The second wireless device (200) includes one or more processors (202), one or more memories (204), and may additionally include one or more transceivers (206) and/or one or more antennas (208). The processor (202) may be configured to control the memories (204) and/or the transceivers (206), and implement the descriptions, functions, procedures, suggestions, 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). Additionally, 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 codes including commands for performing the descriptions, functions, procedures, proposals, methods, and/or operational 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.

Hereinafter, 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 operational 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 operational 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, suggestions and/or methodologies 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, suggestions, methods and/or operational flowcharts disclosed herein.

The one or more processors (102, 202) may be referred to as a controller, a microcontroller, a microprocessor, or a microcomputer. The 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 the one or more processors (102, 202). The descriptions, functions, procedures, suggestions, 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 operational flowcharts disclosed in this document may be implemented using firmware or software configured to perform one or more of the following: included in one or more processors (102, 202), or stored in one or more memories (104, 204) and driven by one or more of the processors (102, 202). The descriptions, functions, procedures, suggestions, methods and/or operational flowcharts disclosed in this document may be implemented using firmware or software in the form of codes, instructions and/or sets of instructions.

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 comprised of 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.

One or more transceivers (106, 206) can transmit user data, control information, wireless signals/channels, etc., as described 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 described in the descriptions, functions, procedures, suggestions, methods and/or flowcharts of this document, from one or more other devices. For example, one or more transceivers (106, 206) can be coupled 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, and the like, as described 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) may 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 processed user data, control information, wireless signals/channels, etc. from baseband signals to RF band signals using one or more processors (102, 202). For this purpose, one or more transceivers (106, 206) may include an (analog) oscillator and/or filter.

Examples of wireless devices to which the present invention is applied

Fig. 20 shows another example of a wireless device applied to the present invention. The wireless device can be implemented in various forms depending on the use-example/service (see Fig. 18).

Referring to FIG. 20, the wireless device (100, 200) corresponds to the wireless device (100, 200) of FIG. 19 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 an additional element (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. 20. For example, the transceiver(s) (114) may include one or more transceivers (106, 206) and/or one or more antennas (108, 208) of FIG. 19. The control unit (120) is electrically connected to the communication unit (110), the memory unit (130), and the additional elements (140) and controls overall operations of the wireless device. For example, the control unit (120) may control electrical/mechanical operations of the wireless device based on programs/codes/commands/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).

The additional element (140) may be configured in various ways depending on the type of the wireless device. For example, the additional element (140) may include at least one of a power unit/battery, an input/output unit (I/O unit), a driving unit, and a computing unit. Although not limited thereto, the wireless device may be implemented in the form of a robot (FIG. 18, 100a), a vehicle (FIG. 18, 100b-1, 100b-2), an XR device (FIG. 18, 100c), a portable device (FIG. 18, 100d), a home appliance (FIG. 18, 100e), an IoT device (FIG. 18, 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. 18, 400), a base station (FIG. 18, 200), a network node, etc. Wireless devices may be mobile or stationary, depending on the use/service.

In FIG. 20, 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 the first unit (e.g., 130, 140) may be wirelessly connected via the communication unit (110). In addition, each element, component, unit/part, and/or module within the wireless device (100, 200) may further include one or more elements. For example, the control unit (120) may be composed of one or more processor sets. For example, the control unit (120) may be composed of a set of a communication control processor, an application processor, an electronic control unit (ECU), a graphic 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.

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

Fig. 21 illustrates a vehicle or autonomous vehicle applied to the present invention. The vehicle or autonomous vehicle may be implemented as a mobile robot, a car, a train, a manned/unmanned aerial vehicle (AV), a ship, etc.

Referring to FIG. 21, 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. 20, respectively.

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.), servers, etc. 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, a light 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.

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 a driving plan based on the acquired data. The control unit (120) can control the driving 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, the sensor unit (140c) can acquire vehicle status and surrounding environment information during autonomous driving. The autonomous driving unit (140d) can update the autonomous driving route and driving plan based on the newly acquired data/information. The communication unit (110) can transmit information on the vehicle location, autonomous driving route, driving plan, etc. to an external server. An external server can predict traffic information data in advance using AI technology, etc. based on information collected from vehicles or autonomous vehicles, and provide the predicted traffic information data to the vehicles or autonomous vehicles.

Here, the wireless communication technology implemented in the wireless device (XXX, YYY) of the present specification may include LTE, NR, and 6G, as well as 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, the 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, the 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.

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 in a form that is not combined with other components or features. In addition, 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 obvious that claims that do not have an explicit citation relationship in the scope of the patent may be combined to form an embodiment or included as a new claim by post-application amendment.

In this document, the embodiments of the present invention have been mainly described with a focus on the signal transmission/reception relationship between a terminal and a base station. This transmission/reception relationship is equally/similarly extended to signal transmission/reception between a terminal and a relay or a base station and a relay. A specific operation 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 a plurality of 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 with terms such as a fixed station, a Node B, an eNode B (eNB), an access point, etc. In addition, the terminal may be replaced with terms such as a UE (User Equipment), an MS (Mobile Station), an MSS (Mobile Subscriber Station), etc.

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

In the case of implementation by firmware or software, one embodiment of the present invention may be implemented in the form of a module, procedure, function, etc. that performs the functions or operations described above. The software code may be stored in a memory unit and may be driven by a processor. The memory unit may be located inside or outside the processor and may exchange data with the processor by various means already known.

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 present invention. Therefore, the above detailed description should not be construed as limiting in all aspects, but should be considered as illustrative. The scope of the present invention should be determined by a reasonable interpretation of the appended claims, and all changes within the equivalent scope of the present invention are included in the scope of the present invention.

The embodiments of the present invention as described above can be applied to various mobile communication systems.

Claims (15)

In a method related to a second relay UE (User Equipment), The second relay UE establishes a connection with the remote UE; The second relay UE receives a signal transmitted by the base station through the first relay UE; and The second relay UE transmits the signal to the remote UE; Including, The above second relay UE is in RRC (Radio Resource Control) inactive state, A method wherein, based on a signal strength between the first relay UE and the second relay UE being below a threshold, the second relay UE transmits information related to measurement reporting triggering to the remote UE. In the first paragraph, A method wherein the above measurement reporting triggering is related to path switching to the direct link of the remote UE. In the first paragraph, The method wherein the signal strength is one of SD-RSRP (Sidelink Discovery-Reference Signal Received Power) or SL-RSRP (Sidelink-RSRP). In the first paragraph, A method wherein the transmission of information related to measurement reporting triggering of the second relay UE is based on an indication of the first relay UE. In the first paragraph, A method wherein information transmission related to measurement reporting triggering of the second relay UE is based on an indication of the base station. In paragraph 5, A method wherein the indication of the base station includes at least one piece of information among measurement identities and measurement objects. In the first paragraph, A method, wherein at least one of the above information is received via RRC (Radio Resource Control) signaling or MAC (Medium Access Control) CE (Control Element). In the second relay UE (User Equipment), at least one processor; and At least one memory having stored therein instructions that, when executed by said at least one processor, cause said UE to perform at least the following: Establish a connection with a remote UE; Receive the signal transmitted by the base station through the first relay UE; Transmit the above signal to the remote UE; Including, The above second relay UE is in RRC inactive state, A second relay UE that transmits information related to measurement reporting triggering to the remote UE based on the signal strength between the first relay UE and the second relay UE being below a threshold. In Article 8, The above measurement reporting triggering is related to path switching of the remote UE to the direct link, the second relay UE. In Article 8, The above signal strength is either SD-RSRP (Sidelink Discovery-Reference Signal Received Power) or SL-RSRP (Sidelink-RSRP), the second relay UE. In Article 8, The second relay UE transmits information related to the measurement reporting triggering of the second relay UE based on the indication of the first relay UE. In Article 8, The second relay UE transmits information related to the measurement reporting triggering based on the indication of the base station. In Article 12, The indication of the above base station is a second relay UE including at least one piece of information among measurement identities and measurement objects. In Article 8, A second relay UE, wherein at least one of the above information is received via RRC (Radio Resource Control) signaling or MAC (Medium Access Control) CE (Control Element). A nonvolatile computer-readable medium having stored thereon program instructions for performing the following: Establish a connection with a remote UE; Receive the signal transmitted by the base station through the first relay UE; Transmit the above signal to the remote UE; Including, The above second relay UE is in RRC inactive state, A medium in which the second relay UE transmits information related to measurement reporting triggering to the remote UE based on the signal strength between the first relay UE and the second relay UE being below a threshold.

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