Communication method for terminal to communicate and device therefor in wireless communication system

Abstract

Disclosed are a method for a first terminal to perform relay communication and a device therefor in a wireless communication system according to various embodiments. Disclosed are a method and device, the method comprising the steps of: establishing an indirect path connected to a first base station via a second terminal; transmitting packet data units through the indirect path; and receiving an ACK related to the packet data units from the second terminal through the indirect path, wherein even when the ACK is received, the packet data units are discarded after the expiration of a timer on the basis of measurement reporting being triggered by the first base station.

Description

Method for a terminal to perform communication in a wireless communication system and device therefor

[0001] The present invention relates to a method for a terminal to perform relay communication through a relay terminal in a wireless communication system and a device therefor.

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

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

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

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

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

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

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

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

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

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

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

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

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

[0015] The technical problem to be solved by the present invention is to provide a method for performing relay communication more accurately and efficiently.

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

[0017] A method for a first terminal to perform relay communication in a wireless communication system according to one aspect includes the steps of forming an indirect path connected to a first base station through a second terminal; transmitting a packet data unit through the indirect path; and receiving an ACK (acknowledgement) related to the packet data unit from the second terminal through the indirect path, wherein based on a measurement report being triggered by the first base station, the packet data unit can be discarded after expiration of a first timer even if the ACK is received.

[0018] Alternatively, based on the measurement report not being triggered, the packet data unit is characterized in that the ACK is discarded based on reception.

[0019] Alternatively, the first timer is characterized in that it starts based on the trigger of the measurement report and the transmission of the packet data unit.

[0020] Alternatively, based on the measurement report not being triggered, the first timer is characterized in that it is not started even if the packet data unit is transmitted.

[0021] Alternatively, the first timer is characterized in that it is set for each transmission of the packet data unit.

[0022] Alternatively, the method further comprises the steps of: receiving a downlink packet data unit through the indirect path; and receiving an RRC (Radio Resource Control) reset message related to handover through the indirect path, wherein the indirect path is maintained for a preset time even if the RRC reset message is received.

[0023] Alternatively, the terminal is characterized in that transmission of data packets through the indirect path is restricted for the preset time.

[0024] Alternatively, the second timer associated with the handover is characterized in that it starts after the elapse of the preset time.

[0025] Alternatively, the packet data unit is characterized in that it is a PDCP (Packet Data Convergence Protocol) PDU (Protocol Data Unit).

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

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

[0028] According to one embodiment of the present invention, relay communication can be performed more accurately and efficiently in a wireless communication system.

[0029] 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.

[0030] The drawings attached to this specification are intended to provide an understanding of the present invention, illustrate various embodiments of the present invention, and together with the description of the specification serve to explain the principles of the present invention.

[0031] Figure 1 is a diagram for comparing and explaining V2X communication based on RAT before NR and V2X communication based on NR.

[0032] Figure 2 shows the structure of the LTE system.

[0033] Figure 3 shows the structure of the NR system.

[0034] Figure 4 shows the structure of a radio frame of NR.

[0035] Figure 5 shows the slot structure of an NR frame.

[0036] FIG. 6 illustrates a communication structure that can be provided in a 6G system according to one embodiment of the present disclosure.

[0037] FIG. 7 illustrates an electromagnetic spectrum according to one embodiment of the present disclosure.

[0038] Figure 8 shows a radio protocol architecture for SL communication.

[0039] Figure 9 shows a terminal performing V2X or SL communication.

[0040] Figure 10 shows resource units for V2X or SL communication.

[0041] FIG. 11 illustrates an example of a BWP according to one embodiment of the present disclosure.

[0042] 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.

[0043] Figure 13 illustrates a procedure for path switching from a direct path to an indirect path.

[0044] Figure 14 schematically illustrates how to switch from a direct route to an indirect route.

[0045] FIG. 15 and FIG. 16 are diagrams for explaining a procedure for U2U relay selection (UE-to-UE Relay Selection) without relay discovery.

[0046] Figure 17 schematically illustrates a flat protocol stack for L2 U2U relay.

[0047] Figure 18 is a diagram illustrating a method for resetting an RRC connection.

[0048] FIG. 19 is a diagram illustrating a method for performing indirect-to-indirect path switching between two gNBs.

[0049] Figure 20 is a diagram for explaining a method of indirect-to-indirect switching between Inter gNBs.

[0050] Figure 21 is a drawing for explaining a method in which a first terminal performs relay communication through a second terminal.

[0051] Figure 22 illustrates a communication system applied to the present invention.

[0052] Figure 23 illustrates a wireless device applicable to the present invention.

[0053] Figure 24 illustrates another example of a wireless device applicable to the present invention. The wireless device may be implemented in various forms depending on the use case / service.

[0054] Figure 25 illustrates a vehicle or autonomous vehicle to which the present invention is applied.

[0055] A wireless communication system is a multiple access system that supports communication with multiple users by sharing available system resources (e.g., bandwidth, transmission power, etc.). Examples of multiple access systems include code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access (SC-FDMA), and multi-carrier frequency division multiple access (MC-FDMA).

[0056] Sidelink refers to a communication method that establishes a direct link between user equipment (UE), allowing voice or data to be exchanged directly between terminals without going through a base station (BS). Sidelink is being considered as a solution to address the burden on base stations due to rapidly increasing data traffic.

[0057] V2X (vehicle-to-everything) refers to a communication technology that exchanges information with other vehicles, pedestrians, and infrastructure-based objects through wired / wireless communication. V2X can be divided into four types: V2V (vehicle-to-vehicle), V2I (vehicle-to-infrastructure), V2N (vehicle-to-network), and V2P (vehicle-to-pedestrian). V2X communication can be provided through the PC5 interface and / or Uu interface.

[0058] Meanwhile, as more and more communication devices demand greater communication capacity, the need for improved mobile broadband communication compared to existing radio access technology (RAT) is emerging. Accordingly, communication systems that consider services or terminals sensitive to reliability and latency are being discussed. Next-generation wireless access technologies that consider improved mobile broadband communication, massive MTC, and URLLC (Ultra-Reliable and Low Latency Communication) can be called new radio access technology (RAT) or new radio (NR). NR can also support V2X (vehicle-to-everything) communication.

[0059] The following technologies can be used in various wireless communication systems, such as CDMA (code division multiple access), FDMA (frequency division multiple access), TDMA (time division multiple access), OFDMA (orthogonal frequency division multiple access), and SC-FDMA (single carrier frequency division multiple access). CDMA can be implemented with wireless technologies such as UTRA (universal terrestrial radio access) or CDMA2000. TDMA can be implemented with wireless technologies such as GSM (global system for mobile communications) / GPRS (general packet radio service) / EDGE (enhanced data rates for GSM evolution). OFDMA can be implemented with wireless technologies such as IEEE (Institute of Electrical and Electronics Engineers) 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, and E-UTRA (evolved UTRA). IEEE 802.16m is an evolution of IEEE 802.16e, providing backward compatibility with systems based on IEEE 802.16e. UTRA is part of UMTS (universal mobile telecommunications system). 3GPP (3rd generation partnership project) LTE (long term evolution) is a part of E-UMTS (evolved UMTS) that uses E-UTRA (evolved-UMTS terrestrial radio access), employing OFDMA in the downlink and SC-FDMA in the uplink.LTE-A (advanced) is an evolution of 3GPP LTE.

[0060] 5G NR, the successor to LTE-A, is a new clean-slate mobile communications system featuring high performance, low latency, and high availability. 5G NR can utilize all available spectrum resources, from low-frequency bands below 1 GHz, mid-frequency bands between 1 GHz and 10 GHz, and high-frequency (millimeter wave) bands above 24 GHz.

[0061] For clarity, the description will focus on LTE-A or 5G NR, but the technical ideas of the embodiment(s) are not limited thereto.

[0062] Figure 2 illustrates the architecture of an applicable LTE system. This may be referred to as an Evolved-UMTS Terrestrial Radio Access Network (E-UTRAN) or a Long Term Evolution (LTE) / LTE-A system.

[0063] Referring to FIG. 2, the E-UTRAN includes a base station (20; BS) that provides a control plane and a user plane to a terminal (10). The terminal (10) may be fixed or mobile, and may be referred to by other terms such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), a mobile terminal (MT), a wireless device, etc. The base station (20) refers to a fixed station that communicates with the terminal (10), and may be referred to by other terms such as an evolved-NodeB (eNB), a base transceiver system (BTS), an access point, etc.

[0064] Base stations (20) can be connected to each other via the X2 interface. The base station (20) is connected to an EPC (Evolved Packet Core, 30) via the S1 interface, more specifically, to an MME (Mobility Management Entity) via the S1-MME, and to an S-GW (Serving Gateway) via the S1-U.

[0065] The EPC (30) consists of an MME, an S-GW, and a P-GW (Packet Data Network-Gateway). The MME holds information about terminal access and capabilities, and this information is primarily used for terminal mobility management. The S-GW is a gateway with the E-UTRAN as its endpoint, and the P-GW is a gateway with the PDN as its endpoint.

[0066] The layers of the radio interface protocol between the terminal and the network can be divided into L1 (Layer 1), L2 (Layer 2), and L3 (Layer 3) based on the three lower layers of the Open System Interconnection (OSI) standard model, which is widely known in communication systems. Among these, the physical layer belonging to Layer 1 provides an information transfer service using a physical channel, and the RRC (Radio Resource Control) layer located in Layer 3 controls radio resources between the terminal and the network. To this end, the RRC layer exchanges RRC messages between the terminal and the base station.

[0067] Figure 3 shows the structure of the NR system.

[0068] Referring to FIG. 3, the NG-RAN may include a gNB and / or an eNB that provides user plane and control plane protocol termination to the UE. FIG. 7 illustrates a case where only a gNB is included. The gNB and eNB are connected to each other via an Xn interface. The gNB and eNB are connected to the 5th generation core network (5G Core Network: 5GC) via the NG interface. More specifically, the gNB is connected to the access and mobility management function (AMF) via the NG-C interface, and the gNB is connected to the user plane function (UPF) via the NG-U interface.

[0069] Figure 4 shows the structure of a radio frame of NR.

[0070] Referring to FIG. 4, radio frames can be used for uplink and downlink transmission in NR. A radio frame has a length of 10 ms and can be defined as two 5 ms half-frames (Half-Frames, HF). A half-frame can include five 1 ms sub-frames (Subframes, SF). A sub-frame can be divided into one or more slots, and the number of slots within a sub-frame can be determined by the Subcarrier Spacing (SCS). Each slot can include 12 or 14 OFDM (A) symbols depending on the cyclic prefix (CP).

[0071] When normal CP is used, each slot can contain 14 symbols. When extended CP is used, each slot can contain 12 symbols. Here, the symbols can include OFDM symbols (or CP-OFDM symbols), SC-FDMA (Single Carrier - FDMA) symbols (or DFT-s-OFDM (Discrete Fourier Transform-spread-OFDM) symbols).

[0072] Table 1 below shows the number of symbols per slot ((N)) depending on the SCS setting (u) when normal CP is used. slot symb ), number of slots per frame ((N frame,u slot ) and the number of slots per subframe ((N subframe,u slot ) is an example.

[0073] SCS (15*2 u )N slot symb N frame,u slot N subframe,u slot 15KHz (u=0)1410130KHz (u=1)1420260KHz (u=2)14404120KHz (u=3)14808240KHz (u=4)1416016

[0074] 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.

[0075] SCS (15*2 u )N slot symb N frame,u slot N subframe,u slot 60KHz (u=2)12404

[0076] In an NR system, OFDM(A) numerology (e.g., SCS, CP length, etc.) may be set differently between multiple cells that are merged into a single terminal. Accordingly, the (absolute time) interval of a time resource (e.g., subframe, slot, or TTI) (conveniently referred to as TU (Time Unit)) consisting of the same number of symbols may be set differently between the merged cells.

[0077] In NR, multiple numerologies, or SCSs, can be supported to support various 5G services. For example, a 15 kHz SCS can support wide areas in traditional cellular bands, while a 30 kHz / 60 kHz SCS can support dense urban areas, lower latency, and wider carrier bandwidth. A 60 kHz or higher SCS can support bandwidths greater than 24.25 GHz to overcome phase noise.

[0078] The NR frequency band can be defined by two types of frequency ranges. The two types of frequency ranges can be FR1 and FR2. The numerical values ​​of the frequency ranges can be changed, and for example, the two types of frequency ranges can be as shown in Table 3 below. Among the frequency ranges used in the NR system, FR1 can mean the "sub 6 GHz range", and FR2 can mean the "above 6 GHz range" and can be called millimeter wave (mmW).

[0079] Frequency Range designationCorresponding frequency rangeSubcarrier Spacing (SCS)FR1450MHz - 6000MHz15, 30, 60kHzFR224250MHz - 52600MHz60, 120, 240kHz

[0080] As described above, the numerical value of the frequency range of the NR system can be changed. For example, FR1 may include a band from 410 MHz to 7125 MHz, as shown in Table 4 below. That is, FR1 may include a frequency band above 6 GHz (or 5850, 5900, 5925 MHz, etc.). For example, the frequency band above 6 GHz (or 5850, 5900, 5925 MHz, etc.) included within FR1 may include an unlicensed band. The unlicensed band may be used for various purposes, such as for vehicular communications (e.g., autonomous driving).

[0081] Frequency Range designationCorresponding frequency rangeSubcarrier Spacing (SCS)FR1410MHz - 7125MHz15, 30, 60kHzFR224250MHz - 52600MHz60, 120, 240kHz

[0082] Figure 5 shows the slot structure of an NR frame.

[0083] Referring to Figure 5, a slot includes multiple symbols in the time domain. For example, in the case of a normal CP, one slot may include 14 symbols, but in the case of an extended CP, one slot may include 12 symbols. Alternatively, in the case of a normal CP, one slot may include 7 symbols, but in the case of an extended CP, one slot may include 6 symbols.

[0084] A carrier includes multiple subcarriers in the frequency domain. An RB (Resource Block) can be defined as multiple (e.g., 12) consecutive subcarriers in the frequency domain. A BWP (Bandwidth Part) can be defined as multiple consecutive (P)RBs ((Physical) Resource Blocks) in the frequency domain, and can correspond to one numerology (e.g., SCS, CP length, etc.). A carrier can include up to N (e.g., 5) BWPs. Data communication can be performed through activated BWPs. Each element can be referred to as a Resource Element (RE) in the resource grid, and one complex symbol can be mapped to it.

[0085] Meanwhile, the wireless interface between terminals or between terminals and a network may be composed of an L1 layer, an L2 layer, and an L3 layer. In various embodiments of the present disclosure, the L1 layer may refer to a physical layer. Furthermore, for example, the L2 layer may refer to at least one of a MAC layer, an RLC layer, a PDCP layer, and an SDAP layer. Furthermore, for example, the L3 layer may refer to an RRC layer.

[0086] 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.

[0087] New network characteristics in 6G may include:

[0088] - Satellite integrated network

[0089] - Connected Intelligence: Unlike previous generations of wireless communication systems, 6G is revolutionary, upgrading the wireless evolution from "connected objects" to "connected intelligence." AI can be applied at every stage of the communication process (or at every signal processing step, as described below).

[0090] - Seamless integration of wireless information and energy transfer

[0091] - Ubiquitous super 3D connectivity: Access to networks and core network functions of drones and very low Earth orbit satellites will create super 3D connectivity in 6G ubiquitous.

[0092] Some general requirements for the new network characteristics of 6G, such as the above, may be as follows:

[0093] - small cell networks

[0094] - Ultra-dense heterogeneous network

[0095] - High-capacity backhaul

[0096] - Radar technology integrated with mobile technology: High-precision localization (or location-based services) through communications is a key feature of 6G wireless communication systems. Therefore, radar systems will be integrated with 6G networks.

[0097] - Softwarization and virtualization

[0098] Below, the core implementation technologies of the 6G system are described.

[0099] - Artificial Intelligence: Incorporating AI into communications can streamline and improve real-time data transmission. AI can use numerous analytics to determine how complex target tasks should be performed. This means AI can increase efficiency and reduce processing delays. Time-consuming tasks such as handovers, network selection, and resource scheduling can be performed instantly using AI. AI can also play a crucial role in machine-to-machine (M2M), machine-to-human, and human-to-machine communications. Furthermore, AI can facilitate rapid communication in brain-computer interfaces (BCIs). AI-based communication systems can be supported by metamaterials, intelligent structures, intelligent networks, intelligent devices, intelligent cognitive radios, self-sustaining wireless networks, and machine learning.

[0100] - THz communication (terahertz communication): Data rates can be increased by increasing the bandwidth. This can be achieved by using sub-THz communication with wide bandwidths and applying advanced massive MIMO technology. THz waves, also known as sub-millimeter waves, typically refer to the frequency range between 0.1 THz and 10 THz, with corresponding wavelengths ranging from 0.03 mm to 3 mm. The 100 GHz to 300 GHz band (sub-THz band) is considered a key part of the THz spectrum for cellular communications. Adding the sub-THz band to the mmWave band will increase the capacity of 6G cellular communications. Among the defined THz bands, 300 GHz to 3 THz lies in the far infrared (IR) frequency band. While part of the optical band, the 300 GHz to 3 THz band lies at the boundary of the optical band, immediately following the RF band. Therefore, this 300 GHz to 3 THz band exhibits similarities to RF.

[0101] Figure 7 illustrates the electromagnetic spectrum according to one embodiment of the present disclosure. The embodiment of Figure 7 can be combined with various embodiments of the present disclosure. Key characteristics of THz communications include (i) a widely available bandwidth to support very high data rates, and (ii) high path loss at high frequencies (highly directional antennas are essential). The narrow beamwidth generated by the highly directional antenna reduces interference. The small wavelength of THz signals allows for a much larger number of antenna elements to be integrated into devices and base stations operating in this band. This enables the use of advanced adaptive array techniques to overcome range limitations.

[0102] - Large-scale MIMO technology

[0103] - Hologram beamforming (HBF)

[0104] - Optical wireless technology

[0105] - Free-space optical transmission backhaul network (FSO backhaul network)

[0106] - Quantum communication

[0107] - Cell-free communication

[0108] - Integration of wireless information and power transmission

[0109] - Integration of wireless communication and sensing

[0110] - Integrated access and backhaul network

[0111] - Big data analysis

[0112] - Reconfigurable intelligent surface

[0113] - metaverse

[0114] - Block chain

[0115] Unmanned aerial vehicles (UAVs): UAVs, or drones, will be a key element in 6G wireless communications. In most cases, high-speed data wireless connectivity can be provided using UAV technology. Base stations (BSs) can be installed on UAVs to provide cellular connectivity. UAVs may offer specific capabilities not found in fixed BS infrastructure, such as easy deployment, robust line-of-sight links, and controlled mobility. During emergencies such as natural disasters, deploying terrestrial communications infrastructure is not economically feasible and sometimes cannot provide services in volatile environments. UAVs can easily handle these situations. UAVs will become a new paradigm in wireless communications. This technology facilitates three fundamental requirements for wireless networks: enhanced mobile broadband (eMBB), URLLC, and mMTC. UAVs can also support various purposes, such as enhancing network connectivity, fire detection, disaster emergency services, security and surveillance, pollution monitoring, parking monitoring, and accident monitoring. Therefore, UAV technology is recognized as one of the most important technologies for 6G communications.

[0116] - Autonomous driving (self-driving): V2X (vehicle to everything), a key element in building autonomous driving infrastructure, can be a technology that allows cars to communicate and share with various elements on the road for autonomous driving, such as vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) wireless communication. Fast transmission speeds and low-latency technologies are essential to maximize autonomous driving performance and ensure high safety. Furthermore, in the future, autonomous driving will go beyond simply providing warnings or guidance messages to drivers and may require active intervention in vehicle operation and direct control of the vehicle in dangerous situations. To this end, the amount of information that needs to be transmitted and received may become enormous, so 6G is expected to maximize autonomous driving with faster transmission speeds and lower latency than 5G.

[0117] Figure 8 illustrates a radio protocol architecture for SL communication. Specifically, Figure 8 (a) illustrates the user plane protocol stack of NR, and Figure 8 (b) illustrates the control plane protocol stack of NR.

[0118] Below, the SL synchronization signal (Sidelink Synchronization Signal, SLSS) and synchronization information are described.

[0119] SLSS is an SL-specific sequence and may include a Primary Sidelink Synchronization Signal (PSSS) and a Secondary Sidelink Synchronization Signal (SSSS). The PSSS may be referred to as a Sidelink Primary Synchronization Signal (S-PSS), and the SSSS may be referred to as a Sidelink Secondary Synchronization Signal (S-SSS). For example, length-127 M-sequences may be used for the S-PSS, and length-127 Gold sequences may be used for the S-SSS. For example, a terminal may detect an initial signal and acquire synchronization using the S-PSS. For example, a terminal may acquire detailed synchronization and detect a synchronization signal ID using the S-PSS and the S-SSS.

[0120] PSBCH (Physical Sidelink Broadcast Channel) may be a (broadcast) channel that transmits basic (system) information that a terminal must know first before transmitting or receiving an SL signal. For example, the basic information may be information related to SLSS, duplex mode (DM), TDD UL / DL (Time Division Duplex Uplink / Downlink) configuration, resource pool-related information, type of application related to SLSS, subframe offset, broadcast information, etc. For example, in NR V2X, for evaluating PSBCH performance, the payload size of PSBCH may be 56 bits, including a 24-bit CRC.

[0121] S-PSS, S-SSS and PSBCH may be included in a block format supporting periodic transmission (e.g., SL SS (Synchronization Signal) / PSBCH block, hereinafter referred to as S-SSB (Sidelink-Synchronization Signal Block)). The S-SSB may have the same numerology (i.e., SCS and CP length) as the PSCCH (Physical Sidelink Control Channel) / PSSCH (Physical Sidelink Shared Channel) in the carrier, and the transmission bandwidth may be within a (pre-)configured SL BWP (Sidelink BWP). For example, the bandwidth of the S-SSB may be 11 RBs (Resource Blocks). For example, the PSBCH may span 11 RBs. And, the frequency location of the S-SSB may be (pre-)configured. Therefore, the terminal does not need to perform hypothesis detection in the frequency to discover the S-SSB in the carrier.

[0122] 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.

[0123] 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.

[0124] 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.

[0125] Meanwhile, when the SCS is 60 kHz, two types of CP may be supported. In addition, the structure of the S-SSB transmitted by the transmitting terminal to the receiving terminal may be different depending on the CP type. For example, the CP type may be Normal CP (NCP) or Extended CP (ECP). Specifically, for example, when the CP type is NCP, the number of symbols to which the PSBCH is mapped within the S-SSB transmitted by the transmitting terminal may be 9 or 8. On the other hand, for example, when the CP type is ECP, the number of symbols to which the PSBCH is mapped within the S-SSB transmitted by the transmitting terminal may be 7 or 6. For example, the PSBCH may be mapped to the first symbol within the S-SSB transmitted by the transmitting terminal. For example, the receiving terminal receiving the S-SSB may perform an Automatic Gain Control (AGC) operation in the first symbol section of the S-SSB.

[0126] Figure 9 shows a terminal performing V2X or SL communication.

[0127] Referring to FIG. 9, the term "terminal" in V2X or SL communication may primarily refer to a user's terminal. However, if a network device such as a base station transmits and receives signals according to a communication method between terminals, the base station may also be considered a type of terminal. For example, terminal 1 may be a first device (100), and terminal 2 may be a second device (200).

[0128] For example, terminal 1 can select a resource unit corresponding to a specific resource within a resource pool, which represents a set of resources. Then, terminal 1 can transmit an SL signal using the resource unit. For example, terminal 2, which is a receiving terminal, can be configured with a resource pool in which terminal 1 can transmit a signal, and can detect a signal from terminal 1 within the resource pool.

[0129] 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.

[0130] 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.

[0131] Figure 10 shows resource units for V2X or SL communication.

[0132] Referring to Figure 10, the entire frequency resources of the resource pool can be divided into NF units, and the entire time resources of the resource pool can be divided into NT units. Therefore, a total of NF * NT resource units can be defined within the resource pool. Figure 13 illustrates an example where the resource pool repeats with a cycle of NT subframes.

[0133] As shown in Figure 10, a single resource unit (e.g., Unit #0) may appear periodically and repeatedly. Alternatively, to achieve diversity effects in the time or frequency dimensions, the index of the physical resource unit to which a single logical resource unit is mapped may change in a predetermined pattern over time. In this resource unit structure, a resource pool may refer to a set of resource units that a terminal wishing to transmit an SL signal can use for transmission.

[0134] Resource pools can be subdivided into several categories. For example, based on the content of the SL signal transmitted from each resource pool, resource pools can be categorized as follows:

[0135] (1) Scheduling Assignment (SA) may be a signal that includes information such as the location of resources used by a transmitting terminal for transmission of an SL data channel, MCS (Modulation and Coding Scheme) or MIMO (Multiple Input Multiple Output) transmission method required for demodulation of other data channels, and TA (Timing Advance). SA may also be transmitted multiplexed with SL data on the same resource unit, in which case the SA resource pool may mean a resource pool in which SA is multiplexed with SL data and transmitted. SA may also be called an SL control channel.

[0136] (2) The SL data channel (Physical Sidelink Shared Channel, PSSCH) may be a resource pool used by a transmitting terminal to transmit user data. If SA is multiplexed and transmitted together with SL data on the same resource unit, only the SL data channel excluding SA information may be transmitted from the resource pool for the SL data channel. In other words, the REs (Resource Elements) that were used to transmit SA information on individual resource units within the SA resource pool may still be used to transmit SL data in the resource pool of the SL data channel. For example, the transmitting terminal may transmit the PSSCH by mapping it to consecutive PRBs.

[0137] (3) A discovery channel may be a resource pool for transmitting terminals to transmit information such as their IDs. Through this, transmitting terminals can enable neighboring terminals to discover them.

[0138] Even if the content of the SL signal described above is the same, different resource pools may be used depending on the transmission and reception properties of the SL signal. For example, even if it is the same SL data channel or discovery message, it may be again divided into different resource pools depending on the transmission timing determination method of the SL signal (for example, whether it is transmitted at the time of reception of a synchronization reference signal or whether it is transmitted by applying a certain timing advance at the time of reception), the resource allocation method (for example, whether the base station designates transmission resources for individual signals to individual transmitting terminals or whether individual transmitting terminals independently select individual signal transmission resources within the resource pool), the signal format (for example, the number of symbols each SL signal occupies in one subframe or the number of subframes used for transmission of one SL signal), the signal strength from the base station, the transmission power strength of the SL terminal, etc.

[0139] 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.

[0140] Referring to Figure 11, a common resource block (CRB) may be a carrier resource block numbered from one end of a carrier band to the other. Furthermore, a PRB may be a numbered resource block within each BWP. Point A may indicate a common reference point for the resource block grid.

[0141] The BWP can be set by Point A, an offset from Point A (NstartBWP), and a bandwidth (NsizeBWP). For example, Point A can be an outer reference point of a PRB of a carrier where subcarrier 0 of all numerologies (e.g., all numerologies supported by the network on that carrier) are aligned. For example, the offset can be the PRB spacing between the lowest subcarrier in a given numerology and Point A. For example, the bandwidth can be the number of PRBs in a given numerology.

[0142] 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.

[0143] PSBCH (Physical Sidelink Broadcast Channel) may be a (broadcast) channel that transmits basic (system) information that a terminal must know first before transmitting or receiving an SL signal. For example, the basic information may be information related to SLSS, duplex mode (DM), TDD UL / DL (Time Division Duplex Uplink / Downlink) configuration, resource pool-related information, type of application related to SLSS, subframe offset, broadcast information, etc. For example, in order to evaluate PSBCH performance, in NR V2X, the payload size of PSBCH may be 56 bits, including a 24-bit CRC (Cyclic Redundancy Check).

[0144] S-PSS, S-SSS and PSBCH may be included in a block format supporting periodic transmission (e.g., SL SS (Synchronization Signal) / PSBCH block, hereinafter referred to as S-SSB (Sidelink-Synchronization Signal Block)). The S-SSB may have the same numerology (i.e., SCS and CP length) as the PSCCH (Physical Sidelink Control Channel) / PSSCH (Physical Sidelink Shared Channel) in the carrier, and the transmission bandwidth may be within a (pre-)configured SL BWP (Sidelink BWP). For example, the bandwidth of the S-SSB may be 11 RBs (Resource Blocks). For example, the PSBCH may span 11 RBs. And, the frequency location of the S-SSB may be (pre-)configured. Therefore, the terminal does not need to perform hypothesis detection in the frequency to discover the S-SSB in the carrier.

[0145] FIG. 12 illustrates a procedure for a terminal to perform V2X or SL communication according to a resource allocation mode, according to an embodiment of the present disclosure. The embodiment of FIG. 12 may be combined with various embodiments of the present disclosure.

[0146] Referring to (a) of FIG. 12, in resource allocation mode 1, the base station may schedule SL resources to be used by the terminal for SL transmission. For example, in step S1200, the base station may transmit information related to SL resources and / or information related to UL resources to the first terminal. For example, the UL resources may include PUCCH resources and / or PUSCH resources. For example, the UL resources may be resources for reporting SL HARQ feedback to the base station.

[0147] For example, a first terminal may receive information related to a dynamic grant (DG) resource and / or information related to a configured grant (CG) resource from a base station. For example, a CG resource may include a CG type 1 resource or a CG type 2 resource. In this specification, a DG resource may be a resource that a base station configures / allocates to the first terminal via downlink control information (DCI). In this specification, a CG resource may be a (periodic) resource that a base station configures / allocates to the first terminal via DCI and / or an RRC message. For example, in the case of a CG type 1 resource, the base station may transmit an RRC message including information related to the CG resource to the first terminal. For example, in the case of a CG type 2 resource, the base station may transmit an RRC message including information related to the CG resource to the first terminal, and the base station may transmit a DCI related to activation or release of the CG resource to the first terminal.

[0148] In step S1510, the first terminal may transmit a PSCCH (e.g., Sidelink Control Information (SCI) or 1st-stage SCI) to the second terminal based on the resource scheduling. In step S1220, the first terminal may transmit a PSSCH (e.g., 2nd-stage SCI, MAC PDU, data, etc.) related to the PSCCH to the second terminal. In step S1230, the first terminal may receive a PSFCH related to the PSCCH / PSSCH from the second terminal. For example, HARQ feedback information (e.g., NACK information or ACK information) may be received from the second terminal via the PSFCH. In step S1240, the first terminal may transmit / report HARQ feedback information to the base station via a PUCCH or a PUSCH. For example, the HARQ feedback information reported to the base station may be information generated by the first terminal based on the HARQ feedback information received from the second terminal. For example, the HARQ feedback information reported to the base station may be information generated by the first terminal based on a rule set in advance. For example, the DCI may be DCI for scheduling SL.

[0149] Referring to (b) of FIG. 12, in resource allocation mode 2, a terminal can determine an SL transmission resource within the SL resources set by the base station / network or within the preset SL resources. For example, the set SL resources or the preset SL resources may be a resource pool. For example, the terminal can autonomously select or schedule resources for SL transmission. For example, the terminal can perform SL communication by selecting a resource within the set resource pool. For example, the terminal can select a resource within a selection window by performing sensing and resource (re)selection procedures. For example, the sensing can be performed on a subchannel basis. For example, in step S1210, a first terminal that has selected a resource within the resource pool can transmit a PSCCH (e.g., Sidelink Control Information (SCI) or 1st-stage SCI) to a second terminal using the resource. In step S1220, the first terminal may transmit a PSSCH (e.g., 2nd-stage SCI, MAC PDU, data, etc.) related to the PSCCH to the second terminal. In step S1230, the first terminal may receive a PSFCH related to the PSCCH / PSSCH from the second terminal.

[0150] Referring to (a) or (b) of FIG. 12, for example, a first terminal may transmit an SCI to a second terminal on a PSCCH. Or, for example, the first terminal may transmit two consecutive SCIs (e.g., 2-stage SCIs) to the second terminal on the PSCCH and / or the PSSCH. In this case, the second terminal may decode the two consecutive SCIs (e.g., 2-stage SCIs) to receive the PSSCH from the first terminal. In this specification, an SCI transmitted on a PSCCH may be referred to as a 1st SCI, a 1st SCI, a 1st-stage SCI, or a 1st-stage SCI format, and an SCI transmitted on a PSSCH may be referred to as a 2nd SCI, a 2nd SCI, a 2nd-stage SCI, or a 2nd-stage SCI format.

[0151] Referring to (a) or (b) of FIG. 12, in step S1530, the first terminal may receive a PSFCH. For example, the first terminal and the second terminal may determine PSFCH resources, and the second terminal may use the PSFCH resources to transmit HARQ feedback to the first terminal.

[0152] Referring to (a) of FIG. 12, in step S1540, the first terminal may transmit SL HARQ feedback to the base station via PUCCH and / or PUSCH.

[0153] Figure 13 illustrates a procedure for path switching from a direct path to an indirect path.

[0154] The procedure illustrated in Figure 13 is based on the connection management and path switching procedures from direct to indirect paths described in the TR document (3GPP TR 38.836) related to Rel-17 NR SL. The remote UE needs to establish its own PDU session / DRB with the network before transmitting user plane data.

[0155] The PC5-RRC aspect PC5 unicast link establishment procedure of Rel-16 NR V2X can be reused to establish a secure unicast link for L2 U2N relay (layer 2 UE-to-Network relaying) between the remote UE and the relay UE before the remote UE establishes a Uu RRC connection with the network via the relay UE.

[0156] For both in-coverage and out-of-coverage scenarios, when a remote UE initiates the first RRC message for connection establishment with a gNB, the PC5 L2 configuration for transmission between the remote UE and the U2N relay UE can be based on the RLC / MAC configuration defined in the standard. The establishment of Uu SRB1 / SRB2 and DRB of the remote UE follows the legacy Uu configuration procedure for the L2 U2N relay. The high-level connection establishment procedure illustrated in Figure 13 applies to the L2 UE-to-Network Relay.

[0157] 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.

[0158] In step S1302, the remote UE can transmit the first RRC message (i.e., RRCSetupRequest) to establish a connection with the gNB via the relay UE using the default L2 configuration of PC5. The gNB responds to the remote UE with an RRCSetup message (S1303). The RRCSetup delivery to the remote UE uses the default configuration of PC5. If the relay UE is not initiated in RRC_CONNECTED, it must perform its own connection establishment upon receiving the message for the default L2 configuration of PC5.

[0159] In step S1304, the gNB and the relay UE perform a relay channel setup procedure via Uu. Depending on the configuration of the gNB, the relay / remote UE establishes an RLC channel for relaying SRB1 to the remote UE via PC5. This step prepares the relay channel for SRB1.

[0160] In step S1305, a remote UE SRB1 message (e.g., an RRCSetupComplete message) is transmitted to the gNB via the relay UE using the SRB1 relay channel over PC5. The remote UE is then RRC connected over Uu.

[0161] In steps S1306 and S1307, the remote UE and the gNB establish security according to legacy procedures, and the security message is transmitted through the Relay UE.

[0162] In steps S1308 and S1309, the gNB transmits RRCReconfiguration to the remote UE via the relay UE to set up the relay SRB2 / DRB. The remote UE responds by transmitting RRCReconfigurationComplete to the gNB via the relay UE.

[0163] In step S1310, the gNB establishes an additional RLC channel between the gNB and the relay UE for traffic relay. Depending on the configuration of the gNB, the relay / remote UE establishes an additional RLC channel between the remote UE and the relay UE for traffic relay.

[0164] For L2 UE-to-Network relay, in addition to the connection setup procedure:

[0165] - RRC reconfiguration and RRC disconnection procedures can reuse legacy RRC procedures with message content / configuration design left in the WI phase.

[0166] - The RRC connection re-establishment and RRC connection resumption procedures can be reused as a baseline by considering the connection establishment procedure of the L2 U2N relay above to handle relay-specific parts along with the message content / structure design. The message content / structure can be defined later.

[0167] Figure 14 schematically illustrates how to switch from a direct route to an indirect route.

[0168] 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.

[0169] Referring to FIG. 14, in step S1401, a remote UE may report one or more candidate relay UEs after measuring / discovering them. The remote UE may filter out appropriate relay UEs that meet higher layer criteria when reporting. The report of at least one candidate relay may include the relay UE's ID and SL RSRP information, wherein PC5 measurement-related details may be determined later.

[0170] 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).

[0171] In step S1404, the RRC reconfiguration message for the remote UE may include the ID of the target relay UE, the target Uu, and the PC5 configuration.

[0172] In step S1405, if a connection is not yet established, the remote UE establishes a PC5 connection with the target relay UE.

[0173] In step S1406, the remote UE feeds back RRCReconfigurationComplete to the gNB via the target path using the target configuration provided in RRCReconfiguration.

[0174] In step S1407, the data path is switched.

[0175] FIG. 15 and FIG. 16 are diagrams for explaining a procedure for U2U relay selection (UE-to-UE Relay Selection) without relay discovery.

[0176] Referring to a given scenario (TR 23.752 section 6.8), when a source UE wants to communicate with a target UE, the source UE may first try to find the target UE by transmitting a Direct Communication Request or Solicitation message containing target UE information. If the source UE cannot reach the target UE directly, the source UE may try to discover a UE-to-UE relay to reach the target UE, and may also trigger the relay to discover the target UE. The source UE may integrate the discovery of the target UE and / or the discovery / selection of a U2U relay based on the following two alternatives:

[0177] - Alternative 1: U2U relay discovery / selection can be integrated into the unicast link setup procedure (see clause 6.3.3 of TS 23.287).

[0178] - Alternative 2: U2U relay discovery / selection can be integrated into the Model B direct discovery procedure.

[0179] A new field may be added to the Direct Communication Request or Solicitation message to indicate whether a relay is available for communication. This new field may be defined as Relay_indication. When a (source) UE broadcasts a Direct Communication Request or Solicitation message, the request message may include Relay_indication indicating whether a U2U relay is available. Meanwhile, for Release 17, the value of Relay_indication may be assumed to be limited to a single hop.

[0180] When the U2U relay receives the request message with the Relay_indication set, the U2U relay can decide whether to forward the request message (i.e., modify the message and broadcast it nearby). For example, the U2U relay can decide whether to forward the request message by considering the Application ID, authorization policy (e.g., Relay for a specific ProSe service), current traffic load of the Relay, and radio conditions between the Source UE and the Relay UE if there is a Relay Service Code.

[0181] Alternatively, multiple U2U relays may be used to reach the target UE (case 1), or the target UE may directly receive the request message from the source UE (case 2). In this case, the target UE may choose whether to respond to either the first or the second case. For example, the target UE may choose whether to respond to either the first or the second case based on signal strength, local policy (e.g., traffic load of the UE-UE relay), relay service code (if any), and / or operator policy (e.g., always preferring direct communication or only using some specific UE-UE relays).

[0182] Alternatively, the source UE may receive responses to the request message from multiple U2U relays, or may receive responses to the request message directly from the target UE. In this case, the source UE may select a communication path (direct path or indirect path) based on signal strength or operator policy (e.g., always preferring direct communication or using only certain UE-UE relays).

[0183] Specifically, the above-described alternative 1 can be performed as described in Table 5 and FIG. 15.

[0184] 6.8.2 Procedures6.8.2.1 UE-to-UE relay discovery and selection is integrated into the unicast link establishment procedure (Alternative 1)Fig 14 illustrates the procedure of the proposed method.0. UEs are authorized to use the service provided by the UE-to-UE relays. UE-to-UE relays are authorized to provide service of relaying traffic among UEs. The authorization and the parameter provisioning can use solutions for KI#8, e.g. Sol#36. The authorization can be done when UEs / relays are registered to the network. Security related parameters may be provisioned so that a UE and a relay can verify the authorization with each other if needed.1. UE-1 wants to establish unicast communication with UE-2 and the communication can be either through direct link with UE-2 or via a UE-to-UE relay. Then UE-1 broadcasts Direct Communication Request with relay_indication enabled. The message will be received by relay-1, relay-2. The message may also be received by UE-2 if it is in the proximity of UE-1.UE-1 includes source UE info, target UE info, Application ID, as well as Relay Service Code if there is any. If UE-1 does not want relay to be involved in the communication, then it will made relay_indication disabled.NOTE 1: The data type of relay_indication can be determined in Stage 3. Details of Direct Communication Request / Accept messages will be determined in stage 3.2. Relay-1 and relay-2 decide to participate in the procedure. They broadcast a new Direct Communication Request message in their proximity without relay_indication enabled. If a relay receives this message, it will just drop it. When a relay broadcasts the Direct Communication Request message, it includes source UE info, target UE info and Relay UE info (e.g. Relay UE ID) in the message and use Relay's L2 address as the source Layer-2 ID. The Relay maintains association between the source UE information (e.g. source UE L2 ID) and the new Direct Communication Request.3.UE-2 receives the Direct Communication Requests from relay-1 and relay-2. UE-2 may also receive Direct Communication Request message directly from the UE-1 if the UE-2 is in the communication range of UE-1.4. UE-2 chooses relay-1 and replies with Direct Communication Accept message. If UE-2 directly receives the Direct Communication Request from UE-1, it may choose to setup a direct communication link by sending the Direct Communication Accept message directly to UE-1. After receiving Direct Communication Accept, a UE-to-UE relay retrieves the source UE information stored in step 2 and sends the Direct Communication Accept message to the source UE with its Relay UE info added in the message.After step 4, UE-1 and UE-2 have respectively setup the PC5 links with the chosen UE-to-UE relay.NOTE 2: The security establishment between the UE1 and Relay-1, and between Relay-1 and UE-2 are performed before the Relay-1 and UE-2 send Direct Communication Accept message.Details of the authentication / security establishment procedure are determined by SA WG3. The security establishment procedure can be skipped if there already exists a PC5 link between the source (or target) UE and the relay which can be used for relaying the traffic.5. UE-1 receives the Direct Communication Accept message from relay-1. UE-1 chooses path according to e.g. policies (e.g. always choose direct path if it is possible), signal strength, etc. If UE-1 receives Direct Communication Accept / Response message request accept directly from UE-2, it may choose to setup a direct PC5 L2 link with UE-2 as described in clause 6.3.3 of TS 23.287 [5], then step 6 is skipped.6a. For the L3 UE-to-UE Relay case, UE-1 and UE-2 finish setting up the communication link via the chosen UE-to-UE relay. The link setup information may vary depending on the type of relay, e.g. L2 or L3 relaying. Then UE-1 and UE-2 can communicate via the relay.Regarding IP address allocation for the source / remote UE, the addresses can be either assigned by the relay or by the UE itself (e.g. link-local IP address) as defined in clause 6.3.3 of TS 23.287 [5].6b. For the Layer 2 UE-to-UE Relay case, the source and target UE can setup an end-to-end PC5 link via the relay. UE-1 sends a unicast E2E Direct Communication Request message to UE-2 via the Relay-1, and UE-2 responds with a unicast E2E Direct Communication Accept message to UE-1 via the Relay-1. Relay-1 transfers the messages based on the identity information of UE-1 / UE-2 in the Adaptation Layer.NOTE 3: How Relay-1 can transfer the messages based on the identity information of UE-1 / UE-2 in the Adaptation Layer requires cooperation with RAN2 during the normative phase.NOTE 4: In order to make a relay or path selection, the source UE can setup a timer after sending out the Direct Communication Request for collecting the corresponding response messages before making a decision.Similarly, the target UE can also setup a timer after receiving the first copy of the Direct Communication Request / message for collecting multiple copies of the message from different paths before making a decision.NOTE 5: In the first time when a UE receives a message from a UE-to-UE relay, the UE needs to verify if the relay is authorized be a UE-to-UE relay. Similarly, the UE-to-UE relay may also need to verify if the UE is authorized to use the relay service. The verification details and the how to secure the communication between two UEs through a UE-to-UE relay is to be defined by SA WG3.

[0185] 상술한 대안 2은 표 6 및 도 16에 기술된 바와 같이 수행될 수 있다.

[0186] 6.8.2.2 UE-to-UE relay discovery and selection is integrated into Model B direct discovery procedure (Alternative 2)Depicted in Fig 15 is the procedure for UE-UE Relay discovery Model B, and the discovery / selection procedure is separated from hop by hop and end-to-end link establishment.1. UE-1 broadcasts discovery solicitation message carrying UE-1 info, target UE info (UE-2), Application ID, Relay Service Code if any, the UE-1 can also indicate relay_indication enabled.2. On reception of discovery solicitation, the candidate Relay UE-R broadcasts discovery solicitation carrying UE-1 info, UE-R info, Target UE info. The Relay UE-R uses Relay's L2 address as the source Layer-2 ID.3. The target UE-2 responds the discovery message. If the UE-2 receives discovery solicitation message in step 1, then UE-2 responds discovery response in step 3b with UE-1 info, UE-2 info.If not and UE-2 receives discovery solicitation in step 2, then UE-2 responds discovery response message in step 3a with UE-1 info, UE-R info, UE-2 info.4. On reception of discovery response in step 3a, UE-R sends discovery response with UE-1 info, UE-R info, UE-2 info. If more than one candidate Relay UEs responding discovery response message, UE-1 can select one Relay UE based on e.g. implementation or link qualification.5. The source and target UE may need to setup PC5 links with the relay before communicating with each other. Step 5a can be skipped if there already exists a PC5 link between the UE-1 and UE-R which can be used for relaying. Step 5b can be skipped if there already exists a PC5 link between the UE-2 and UE-R which can be used for relaying.6a. Same as step 6a described in clause 6.8.2.1.6b.For the Layer-2 UE-to-UE Relay, the E2E unicast Direct Communication Request message is sent from UE1 to the selected Relay via the per-hop link (established in steps 5a) and the Adaptation layer info identifying the peer UE (UE3) as the destination. The UE-to-UE Relay transfers the E2E messages based on the identity information of peer UE in the Adaptation Layer. The initiator (UE1) knows the Adaptation layer info identifying the peer UE (UE3) after a discovery procedure. UE3 responds with E2E unicast Direct Communication Accept message in the same way.NOTE 1: For the Layer 2 UE-to-UE Relay case, whether step5b is performed before step 6b or triggered during step 6b will be decided at normative phase.NOTE 2: How Relay-1 can transfer the messages based on the identity information of UE-1 / UE-2 in the Adaptation Layer requires cooperation with RAN2 during the normative phase.6.8.3 Impacts on services, entities and interfacesUE impacts to support new Relay related functions.

[0187] Figure 17(a) schematically illustrates a flat protocol stack for L2 U2U relay.

[0188] Figure 17(a) illustrates a user plane protocol stack for an L2 U2U relay, and Figure 17(b) illustrates a control plane protocol stack for an L2 U2U relay. Table 7 below provides a description of the architecture and protocol stack of the Layer-2 relay in relation to Figure 17.

[0189] 5.5 Layer-2 Relay5.5.1 Architecture and Protocol StackFor L2 UE-to-UE Relay architecture, the protocol stacks are similar to L2 UE-to-Network Relay other than the fact that the termination points are two Remote UEs. The protocol stacks for the user plane and control plane of L2 UE-to-UE Relay architecture are described in Figure 5.5.1-1 and Figure 5.5.1-2.An adaptation layer is supported over the second PC5 link (i.e. the PC5 link between Relay UE and Destination UE) for L2 UE-to-UE Relay. For L2 UE-to-UE Relay, the adaptation layer is put over RLC sublayer for both CP and UP over the second PC5 link. The sidelink SDAP / PDCP and RRC are terminated between two Remote UEs, while RLC, MAC and PHY are terminated in each PC5 link.For the first hop of L2 UE-to-UE Relay,- The N:1 mapping is supported by first hop PC5 adaptation layer between Remote UE SL Radio Bearers and first hop PC5 RLC channels for relaying.- The adaptation layer over first PC5 hop between Source Remote UE and Relay UE supports to identify traffic destined to different Destination Remote UEs.For the second hop of L2 UE-to-UE Relay,- The second hop PC5 adaptation layer can be used to support bearer mapping between the ingress RLC channels over first PC5 hop and egress RLC channels over second PC5 hop at Relay UE.- PC5 Adaptation layer supports the N:1 bearer mapping between multiple ingress PC5 RLC channels over first PC5 hop and one egress PC5 RLC channel over second PC5 hop and supports the Remote UE identification function.For L2 UE-to-UE Relay,- The identity information of Remote UE end-to-end Radio Bearer is included in the adaptation layer in first and second PC5 hop.- In addition, the identity information of Source Remote UE and / or the identity information of Destination Remote UE are candidate information to be included in the adaptation layer, which are to be decided in WI phase.

[0190] Meanwhile, according to a given scenario (RAN2#119-e, RAN2#120), multi-path relays were defined as in Tables 8 to 10.

[0191] RAN2#119-e> RAN2 anticipate benefits from multi-path in the following areas:-Relay and direct multi-path operation (including both scenarios 1 and 2) can provide efficient path switching between direct path and indirect path-The remote UE in multi-path operation can provide enhanced user data throughput and reliability compared to a single link-gNB can offload the direct connection of the remote UE in congestion to indirect connection via the relay UE (e.g. at different intra / inter-frequency cells)> RAN2 can confirm the justifiable benefits that multi-path with relay and UE aggregation can improve the throughput and reliability / robustness, e.g., for UE at the edge of a cell, and UE with limited UL transmission power.> The terms "relay UE" and "remote UE" are used for scenarios 1 and 2. FFS if we would use additional terms specific to scenario 2.>Confirm the remote UE in Scenario 1 and the remote UE in Scenario 2 as follows:- Scenario 1: the remote UE is connected to the same gNB using one direct path and one indirect path via 1) Layer-2 UE-to-Network relay,- Scenario 2: the remote UE is connected to the same gNB using one direct path and one indirect path via 2) via another UE (where the UE-UE inter-connection is assumed to be ideal).> RAN2 assumes that the relation between remote UE and relay UE in scenario 2 is pre-configured or static and how the relation is pre-configured or static is out of the 3GPP scope.> RAN2 deprioritizes discussion on authorization and association mechanism between remote UE and relay UE in scenario 2.> Support the following cell deployment scenarios for multi-path relaying in Rel-18:-Scenario C1: The relay UE and remote UE are served by a same cell.-Scenario C2: The relay UE and remote UE are served by different intra-frequency cells of a same gNB-Scenario C3: The relay UE and remote UE are served by different inter-frequency cells of a same gNB> Support the following sidelink scenarios for multi-path:- Scenario S1: SL TX / RX and Uu share the same carrier at the remote UE.- Scenario S2: SL TX / RX and Uu use different carriers at the remote UE.- Scenario S3: SL TX / RX and Uu share the same carrier at the relay UE.- Scenario S4: SL TX / RX and Uu use different carriers at the relay UE.>Support direct bearer (bearer mapped to direct path on Uu), indirect bearer (bearer mapped to indirect path via relay UE), and MP split bearer (bearer mapped to both paths, based on the existing split bearer framework).> For a MP split bearer in scenario 1, one PDCP entity at the remote UE is configured with one direct Uu RLC channel and one indirect PC5 RLC channel.-For upstream, a PDCP entity delivers to a Uu RLC entity and a PC5 RLC entity with SRAP entity in the remote UE side.- For downstream, a PDCP entity receives from a Uu RLC entity and a PC5 RLC entity with SRAP entity in the remote UE side.> FFS if we need to take decisions on the mapping of protocol entities in scenario 2.

[0192] RAN2#119bis-e>The following cases are to be supported for Scenario 1.- A. The remote UE operating only on the direct path adds the indirect path under the same gNB;- B. The remote UE operating only on the indirect path adds the direct path under the same gNB;- C. The remote UE operating in multi-path releases the indirect path;- D. The remote UE operating in multi-path releases the direct path;- G. The remote UE operating in multi-path changes to a new relay UE for the indirect path while keeping the direct path under the same gNB. FFS if this case would be supported via separate release-and-add (A+C in separate reconfigurations) or a single switch procedure (e.g. similar to i2i service continuity).> The following case is to be not supported for Scenario 1 as a group mobility scenario.- F.The remote UE configured with multi-path keeps the serving relay UE for the indirect path and the serving cell of the remote UE for the direct path while the serving relay UE changes the serving cell of the relay UE under the same gNB;> The following case can be supported via separate release-and-add for scenario 1 (B+D in separate reconfigurations):- E. The remote UE operating in multi-path changes the direct path to a different cell of the same gNB while using the serving relay UE for the indirect path under the same gNB.- FFS if a single procedure for this case would be supported.> The following cases are proposed to be supported for Scenario 2.- A. The remote UE configured only on the direct path adds the indirect path under the same gNB;- C. The remote UE configured with multi-path releases the indirect path;> The following case is proposed to be not supported for Scenario 2.- F.The remote UE configured with multi-path keeps the serving relay UE for the indirect path and the serving cell of the remote UE for the direct path while the serving relay UE changes the serving cell of the relay UE under the same gNB;> Whether to support the following case can be further discussed for Scenario 2.- B. The remote UE configured only on the indirect path adds the direct path under the same gNB;- D. The remote UE configured with multi-path releases the direct path;- E. The remote UE configured with multi-path changes the serving cell of the remote UE for the direct path while keeping the serving relay UE for the indirect path under the same gNB;- G. The remote UE configured with multi-path changes to a new relay UE for the indirect path while keeping the direct path under the same gNB.> For scenario 1, SRB1 and SRB2 can be configured on either the direct or the indirect path, or on both at least with duplication.FFS if they can be configured on different paths from one another.> For scenario 2, SRB1 and SRB2 can be configured at least on the direct path. FFS if there are restrictions on the configuration and if they can be configured on both paths.> FFS CPDU submission; if legacy CPDU submission behaviour is supported, the primary RLC entity of the MP split bearer for DRB can be configured on any of the paths for Scenario 1.> PDCP DRB duplication is supported for the MP split bearer in Scenario 1 based on the existing framework.> PDCP DRB duplication is supported for the MP split bearer in Scenario 2 based on the existing framework.> The relay UE is restricted to serve only one remote UE in Scenario 2.> For Scenario 2, different Uu logical channels are configured for identification of data directed to / originating from the relay UE and data relayed from / to the remote UE over the Uu link of the indirect path, as in Rel-17.> RAN2 assumes that in Scenario 2, without the adaptation layer over non-3GPP link, a PDCP PDU can be delivered to an intended PDCP entity or RLC entity for support of more than one RB over UE-to-UE link based on UE implementation.> RAN2 does not impose a requirement for interoperability between two UEs from different vendors for scenario 2 in this release.> RAN2 understand that UE identification in L2 PDU over non-3GPP link is not in 3GPP scope in Scenario 2.> Do not specify adaptation layer over UE-to-UE link for scenario 2 in RAN2.> UE identification is not needed over Uu link in Scenario 2, if relay UE serves only one remote UE and different Uu RLC channels can be assumed for the remote UE and the relay UE.> Working assumptions:- Bearer identification except LCID is not needed in L2 PDU over Uu link in Scenario 2. Only 1:1 bearer mapping is supported over Uu link for the indirect path. FFS how to configure the mapping.- Without the adaptation layer over Uu link in scenario 2, a PDCP PDU can be delivered to an intended PDCP entity or RLC entity for support of more than one RB over Uu link e.g. by configuring 1:1 bearer mapping and different Uu RLC channels for relay UE local traffic and relay traffic for PDU delivery.- Do not specify adaptation layer over Uu link for scenario 2 in RAN2.> Multi-path Relay is applicable to RRC_CONNECTED remote-UE, for scenario-1 and scenario-2.> Multi-path Relay is NOT applicable to RRC_IDLE remote-UE, for scenario-1 and scenario-2.> For multi-path Relay, support RRC_IDLE / RRC_INACTIVE target relay UE, for the path switching scenario where there is an addition of indirect path or a change of indirect path.> When UE operating in multi-path Relay, it performs RLM for Uu interface, for Scenario-1 and Scenario-2. For PC5 interface in Scenario-1, it performs sidelink RLF detection based on Rel-16 V2X specification.For UE-UE link in Scenario-2, whether / how to have failure detection is out of 3GPP scope.- FFS whether there is impact to layers under our control from a failure of the UE-UE link in scenario 2.> RAN2 aims at reusing R17 mechanism of paging delivery for R18 U2N Relay on the indirect path and legacy mechanism on the direct path, in the multi-path setting when paging is applicable for RRC_CONNECTED.> Multi-path Relay is NOT applicable to RRC Setup procedure, for scenario-1 and scenario-2.> Working assumption: For multi-path Relay Scenario-2, leave it to relay and remote UE implementation on how to trigger the RRC_IDLE / RRC_INACTIVE target relay UE to initiate RRC connection establishment procedure. RAN2 further discuss the solution for Scenario-1.> Multi-path Relay is NOT applicable to RRC_INACTIVE remote-UE, for scenario-1 and scenario-2.Support storing direct path configuration for potential resume as legacy operation (to single-path configuration), FFS if the UE can also store indirect path configuration and resume directly into multi-path.> Multi-path Relay is NOT applicable to RRC Resume procedure, for scenario-1 and scenario-2. RAN2 further study how for UE operating in multi-path Relay operate for RRC Re-establishment procedure.

[0193] RAN2#120> Support PCell on the direct path only when the UE is in multi-path operation, for both scenario 1 and scenario 2.> RAN2 confirms the following WA for Scenario 2.- Bearer identification except LCID is not needed in L2 PDU over Uu link in Scenario 2. Only 1:1 bearer mapping is supported over Uu link for the indirect path. FFS how to configure the mapping.- Without the adaptation layer over Uu link in scenario 2, a PDCP PDU can be delivered to an intended PDCP entity or RLC entity for support of more than one RB over Uu link e.g. by configuring 1:1 bearer mapping and different Uu RLC channels for relay UE local traffic and relay traffic for PDU delivery.- Do not specify adaptation layer over Uu link for scenario 2 in RAN2.> How to configure 1:1 bearer mapping and potential spec impact can be discussed in normative phase.> In principle, Mode 1 RA can be supported for the remote UE configured with multi-path in Scenario 1.> RAN2 confirms that split SRB can be configured with or without duplication as a baseline, for both scenarios (assuming it is supported in scenario 2 as proposed elsewhere). Further restrictions can be discussed in normative phase.> For scenario 2, non-split SRB1 / 2 is allowed to be configured on direct path.> Remote UE storing indirect path configuration (e.g., SRAP and PC5-RLC channel configurations) and resuming directly into multi-path configuration is not supported for scenario 1.> If CSS for SI is configured within the active BWP on PCell, the remote UE can perform direct system information acquisition on PCell as currently specified in 38.331; besides, dedicated signaling can be used to deliver SIB via SRB1 configured on direct and / or indirect path as currently specified in 38.331.> Upon detection of 3GPP-defined RLF failure in one path, remote UE (configured with MP) can report path failure via the alternative available path if SRB1 is configured on the alternative path or split SRB1 is configured.> PDCP Control PDU is not duplicated.> RAN2 do not define a control plane primary path concept in the study phase; FFS if something needs to be defined in normative work, but it should be driven by functionality and technical benefits.> Case B and case D are not supported for Scenario 2.> For Scenario 2, Case E is not supported.> For Scenario 2, whether to support Case G is discussed in normative phase, but RAN2 will not do additional work to enable it for Scenario 2 over Scenario 1.> Whether SRB1 / 2 can be configured in different path for Scenario 1 can be discussed in normative phase.> Whether non-split SRB1 / 2 is allowed to be configured on indirect path for scenario 2 and whether split SRB1 / 2 is supported for scenario 2 can be discussed in normative work.> Remote UE storing indirect path configuration or not and use it to resume to MP configuration in scenario 2 is not supported.> RAN2 will downselect the solution for triggering IDLE / INACTIVE relay UE to enter CONNECTED state from:- Option 1 (SL-RLC or UP-based approach (excluding SL-RLC1)),- Option 3 (PC5-RRC approach)- Option 4( RRCReconfigurationComplete-based approach), Discovery / PC5-S-based solution can be further discussed if initiated from SA2.> Multi-path relay study phase is complete and can proceed to normative work from RAN2 perspective, for both scenarios 1 and 2.

[0194] Meanwhile, with regard to improvements to NR sidelink relay, improvements as shown in Table 11 below were discussed in a given scenario (New Rel-18 WID on NR sidelink relay enhancements).

[0195] 3. Study the benefit and potential solutions for multi-path support to enhance reliability and throughput (e.g., by switching among or utilizing the multiple paths simultaneously) in the following scenarios [RAN2, RAN3]:A. A UE is connected to the same gNB using one direct path and one indirect path via 1) Layer-2 UE-to-Network relay, or 2) via another UE (where the UE-UE inter-connection is assumed to be ideal), where the solutions for 1) are to be reused for 2) without precluding the possibility of excluding a part of the solutions which is unnecessary for the operation for 2).Note 3A: Study on the benefit and potential solutions are to be completed in RAN#98 which will decide whether / how to start the normative work.Note 3B: UE-to-Network relay in scenario 1 reuses the Rel-17 solution as the baseline.Note 3C: Support of Layer-3 UE-to-Network relay in multi-path scenario is assumed to have no RAN impact and the work and solutions are subject to SA2 to progress.

[0196] Figure 18 is a diagram illustrating a method for resetting an RRC connection.

[0197] Referring to FIG. 18 (a), a UE may transmit an RRCReestablishmentRequest message requesting RRC reestablishment to a network, and the network may transmit an RRCReestablishment message to the UE to reset RRC based on the RRCReestablishmentRequest message. The UE may perform RRC reestablishment based on the RRCReestablishment, and upon completion of RRC reestablishment, may transmit an RRCReestablishmentComplete message to the network (see TS 38.331 5.3.7.1 to 5.3.7.6).

[0198] Also, referring to FIG. 18 (b), the UE may transmit an RRCReestablishmentRequest message requesting RRC reestablishment to the network, and the network may transmit an RRCSetup message to the UE for RRC reestablishment based on the RRCReestablishmentRequest message. The UE may perform RRC reestablishment based on the RRCSetup message, and when RRC reestablishment is completed, may transmit an RRCSetupComplete message to the network (see TS 38.331 5.3.7.1 to 5.3.7.6).

[0199] Regarding RRC reset, the timers are as shown in Table 12 below.

[0200] TimerStartStopAt expiryT301Upon transmission of RRCReestabilshmentRequestUpon reception of RRCReestablishment or RRCSetup message as well as when the selected cell becomes unsuitableGo to RRC_IDLET304Upon reception of RRCReconfiguration message including reconfigurationWithSync or upon conditional reconfiguration execution i.e. when applying a stored RRCReconfiguration message including reconfigurationWithSync.Upon successful completion of random access on the corresponding SpCell . For T304 of SCG, upon SCG release“For T304 of MCG, in case of the handover from NR or intra-NR handover, initiate the RRC re-establishment procedure; In case of handover to NR, perform the actions defined in the specifications applicable for the source RAT. If any DAPS bearer is configured and if there is no RLF in source PCell, initiate the failure information procedure.For T304 of SCG, inform network about the reconfiguration with sync failure by initiating the SCG failure information procedure as specified in 5.7.3."[3GPP TS 38.331]T316Upon transmission of theMCGFailureInformationmessageUpon receivingRRCRelease,RRCReconfigurationwithreconfigurationwithSyncfor the PCell,MobilityFromNRCommand,or upon initiating the re-establishment procedurePerform the actions as specified in 5.7.3b.5.

[0201] Meanwhile, in U2U or U2N communications, a method for lossless data transmission between gNBs in i2x cases needs to be considered. Regarding such lossless data transmission, the scenarios described in Tables 13 and 14 below can be considered. Here, the scenarios below can be defined based on the PDCP status reporting mechanism.

[0202] -- UL 동작의 경우 --- UL 시나리오 1: Relay UE delays its RLC Ack to Remote UE if successful transmission at Uu is not confirmed.- UL 시나리오 2: Remote UE's PDCP determines the PDCP SDUs for retransmission based on the PDCP SDUs indicated as missing according to the PDCP status report from target gNB.- UL 시나리오 3: Relay UE provides the full transmission status to Remote UE at PC5 RLC. Remote UE's RLC layer inform it to PDCP layer, which determines the PDCP SDUs for retransmission accordingly- UL 시나리오 4: For UL transmission, it is up to gNB implementation (of source or target gNB) to ensure lossless delivery during inter-gNB i2x path switching scenarios- UL 시나리오 5: gNB can reconfigure the relay UE until receiving all the UL data buffered in the relay UE.- UL 시나리오 6: Follow Rel-17 agreement on intra-gNB i2d path switch to address UL lossless data delivery in the inter-gNB i2x cases, i.e., No spec impact for ensuring UL PDCP lossless behaviour

[0203] -- DL 동작의 경우 --> DL 시나리오 1-Option 1: Relay UE delays its RLC Ack to source gNB if successful transmission at PC5 is not confirmed- Option 2: Relay UE provides the full transmission status to source gNB at PC5 RLC. The source gNB's RLC layer informs it to PDCP layer, which determines the PDCP SDUs for forwarding to target gNB accordingly> DL 시나리오 2: For DL, the data forwarding mechanism should be enhanced by RAN3 for the inter-gNB path switching scenario to forward all the PDCP SDUs in the buffer to the target gNB, and then, the target gNB re-transmits all the PDCP SDUs for which the successful delivery of the corresponding PDCP Data PDU has not been confirmed by PDCP status report in the target gNB after path switch.> DL 시나리오 3- Option 1: a simple indication that there is received data in the relay UE from the gNB, but not yet delivered to the remote UE successfully.Based on this indication, the source gNB can forward all the buffered PDCP PDUs (acknowledged or non-acknowledged from the lower layers) to the target gNBs.- Option 2: the indication includes further information, e.g., the number of TBs that is received from the gNB, but not delivered to the remote UE successfully yet, or the list of RLC SNs or the earliest RLC SN that the relay UE received from the gNB, but not delivered to the remote UE successfully yet. Based on the indication, the source gNB can identify which data has been acknowledged from the lower layers but still not delivered to the remote UE successfully so that those data should be forwarded to the target gNB.> DL 시나리오 4: To ensure lossless delivery during inter-gNB i2x path switching scenarios, the remote UE sends a PDCP status report to the source gNB triggered by measurement event (X1 or Z1, as applicable).> DL scenario 5: To ensure DL lossless delivery, upon receiving PDCP status report from Remote UE, the target gNB requests the source gNB to forward the DL packets that have not been acknowledged by Remote UE to it.> DL scenario 6: The remote UE can continue to receive the DL data buffered at the relay UE when the remote UE performs i2x path switching ie T304 or T420 is running.> DL scenario 7: For DL, the source gNB can forward all PDCP SDUs which are confirmed or not confirmed by lower layer to the target gNB. It is up to gNB implementation or RAN3 discussion to determine the SN from which the PDCP SDUs confirmed by lower layer should be forwarded.> DL scenario 8: Indicator from relay UE to gNB can be introduced to inform the DL data transmission condition.

[0204] In the following, a method for minimizing data loss when a remote UE connected to a source gNB via an indirect path through a relay UE performs a handover (HO) via a direct / indirect path in relation to the above-described scenario is described in detail.

[0205] Meanwhile, in the following, a source relay UE may mean a relay UE connected to a source gNB, and a target relay UE may mean a relay UE connected to a target gNB.

[0206] Indirect-to-indirect path switching to minimize data loss between heterogeneous gNBs

[0207] When indirect-to-indirect path switching / transitioning occurs between heterogeneous gNBs, DL data loss and / or UL data loss may occur. Below, methods for minimizing DL data loss and UL data loss are described in detail.

[0208] 1. Measures to minimize DL data loss

[0209] FIG. 19 is a diagram illustrating a method for performing indirect-to-indirect path switching between two gNBs.

[0210] As illustrated in Fig. 19, when performing indirect-to-indirect path switching / path switching between Inter gNBs, the following problems may occur in DL in terms of data loss.

[0211] For example, referring to FIG. 19, a source gNB may transmit PDCP PDUs 1, 2, 3, 4, 5 (number / ID) to a relay UE1, and receive an ACK for the RLC channel of the PDCP PDUs 1, 2, 3, 4, 5 (or the RLC channel corresponding to the PDCP PDUs 1, 2, 3, 4, 5) from the relay UE1 (or the source relay UE). When the source gNB receives an ACK for the RLC channel of the PDCP PDUs 1, 2, 3, 4, 5, it may discard all of the PDCP PDUs 1, 2, 3, 4, 5. Relay UE1 may transmit PDCP PDU 1 and 2 among the received PDCP PDUs 1, 2, 3, 4, and 5 to remote UE, and may store RLC PDUs corresponding to PDCP PDUs 3, 4, and 5 (meanwhile, relay UE does not have a PDCP layer) in its buffer. At this time, the remote UE may receive an RRCReconfiguration message related to HO (and / or path switching) from the source gNB. When the remote UE receives a message related to the HO command, it may transmit an RRCReconfigurationComplete message to relay UE2 (or target relay UE) or via a direct path. In this case, when the remote UE performs a status report, it may be expected that the remote UE will report to the target gNB that it has received only PDCP PDUs 1 and 2. However, the target gNB may request the source gNB to forward PDCP PDUs for PDCP PDUs 3, 4, and 5, as it has been reported from the source gNB that all of the PDCP PDUs 1, 2, 3, 4, and 5 have been transmitted. However, the source gNB may have discarded all of the PDCP PDUs 1, 2, 3, 4, and 5.Additionally, the target relay UE cannot transmit appropriate PDCP PDUs (e.g., PDCP PDUs 3, 4, 5) to the remote UE, resulting in data loss for PDCP PDUs 3, 4, and 5.

[0212] To minimize such DL data loss, the following methods need to be considered.

[0213] (1) A remote UE that receives an RRCReconfiguration message related to HO (Handover) from a source gNB may receive a HO command and maintain a connection with the source relay UE for a certain period of time. While the connection with the source relay UE is maintained, the remote UE may receive information / data in a buffer of the source relay UE from the source relay UE. The operation of receiving information / data in the buffer of the source relay UE from the source relay UE may be a separate operation from the operation of the remote UE transmitting an RRCReconfigurationComplete message to the target gNB / target relay UE. That is, in all cases where the remote UE succeeds / fails / in progresses in transmitting an RRCReconfigurationComplete message from the target gNB / target relay UE, the remote UE may maintain a connection with the source relay UE for a certain period of time. In other words, the remote UE can receive remaining data from the relay UE while maintaining the connection with the source relay UE for a certain period of time, regardless of whether an RRCReconfigurationComplete message is received in performing the HO procedure according to the HO command.

[0214] Alternatively, the source gNB may transmit a HO-related RRCReconfiguration message to the remote UE, while also transmitting a reconfiguration message for the relationship (e.g., bearer mapping) with the remote UE to the source relay UE. The relay UE may recognize that the SL connection with the remote UE is released or should be released based on reception of the reconfiguration message. Even in this case, if there are remaining RLC PDUs to be delivered to the remote UE in the RLC buffer of the source relay UE, the source relay UE may maintain the SL connection with the remote UE until all remaining RLC PDUs (Radio Link Control Protocol Data Units) are delivered to the remote UE, and may release the connection with the remote UE only after all remaining RLC PDUs are delivered.

[0215] (2) Alternatively, when the source gNB configures the relay UE / remote UE for measurement, it may configure the remote UE (or remote UE) to also report the PDCP SN (Sequence Number) in the measurement report. That is, the remote UE may also perform SN status reporting in the measurement report. In this case, a prohibit timer required for the SN status reporting may operate. When the prohibit timer operates, the remote UE may omit the SN status reporting in the measurement report. When the source gNB receives a measurement report further including the SN status reporting, it may perform an SN status reporting to the target gNB in ​​the HO decision that can minimize data loss of the remote UE based on the value of the SN status reporting of the remote UE.

[0216] (3) Alternatively, the remote UE may maintain a connection with the source relay UE for a predetermined period of time after receiving an HO-related RRCReconfiguration message from the source gNB. In this case, the predetermined period of time may be a value set by the gNB (via an RRC message) or may be defined as the duration of a new timer for maintaining the connection. The remote UE may start the timer when the HO-related RRCReconfiguration message is received, and may maintain an indirect path with the source gNB (via the source relay UE) during the operation time of the timer to receive DL data PDUs from the source relay UE. However, the remote UE may not be permitted to transmit UL data while the timer is running. When the timer expires, a HO-related timer (e.g., a T304 or T420 timer) may be started. The remote UE may transmit an RRCReconfigurationComplete message to the target gNB while the HO-related timer is running.

[0217] Alternatively, the source gNB may transmit an RRCReconfiguration message to the source relay UE to request the remote UE to release the configuration with the remote UE while transmitting an HO-related RRCReconfiguration message to the remote UE. In this case, the RRCReconfiguration message transmitted to the source relay UE may be configured to be applied after a certain period of time. This is to allow the source relay UE to transmit all remaining data PDUs remaining in its buffer to the remote UE during the certain period of time. During the certain period of time, the source relay UE may not be permitted to receive (UL) data from the remote UE. That is, the source gNB may set a specific timer while transmitting the RRCReconfiguration message to the source relay UE, and may configure the source relay UE to apply / set RRCReconfiguration when the specific timer expires.

[0218] (4) Alternatively, for a data packet operating in AM (Acknowledged Mode) RLC mode, the source relay UE may transmit a data PDU received from the source gNB to the remote UE and transmit an ACK to the source gNB only when an ACK for the data PDU is received from the remote UE. This operation may affect the operation of the t-reordering timer in that the time at which the source gNB receives the ACK is delayed, and thus may not be appropriate in terms of latency. Therefore, the above-described operation (the operation of the source relay UE transmitting an ACK to the source gNB after receiving an ACK from the remote UE) may be configured to be performed only when the measurement report is triggered. That is, in a general case (e.g., when the measurement report is not triggered), the source relay UE may transmit an RLC ACK to the gNB (without delay) when it receives a data PDU from the source gNB. In contrast, when the measurement report is triggered to the remote UE, the source relay UE may not transmit an ACK even if it has completed receiving the data PDU from the source gNB, but may transmit all of the data PDUs to the remote UE and, after receiving an ACK from the remote UE, transmit an ACK to the source gNB. Whether or not the measurement report is triggered to the remote UE may be notified by the remote UE to the source relay UE (e.g., PC5-RRC, indication), or the gNB may directly notify / configure the source relay UE.

[0219] Below, we describe in detail a method to minimize UL data loss when performing indirect-to-indirect switching between Inter gNBs.

[0220] 2. How to minimize UL data loss

[0221] Figure 20 is a diagram for explaining a method of indirect-to-indirect switching between Inter gNBs.

[0222] Referring to FIG. 20, when the remote UE performs UL transmission, the remote UE can transmit PDCP PDUs 1, 2, 3, 4, and 5 to the source gNB through the relay UE1 (hereinafter, source relay UE). The source relay UE has completed transmitting RLC PDUs corresponding to PDCP PDUs 1 and 2 among the received PDCP PDUs 1, 2, 3, 4, and 5 to the source gNB, and RLC PDUs corresponding to PDCP PDUs 3, 4, and 5 may not yet be transmitted to the source gNB and may be stored in a buffer of the source relay UE. In this case, the source gNB may transmit an RRCReconfiguration message related to HO to the remote UE. A remote UE that receives an RRCReconfiguration message related to HO can transmit a message (e.g., an RRCReconfigurationComplete message) regarding completion of HO to the target gNB via relay UE2 (hereinafter, referred to as target relay UE). When the remote UE performs a status report to the target gNB, the remote UE can be expected to report to the target gNB that it will transmit data for a status report for the next PDCP PDU (PDCP PDU 6 as illustrated in FIG. 20), as it determines that the data has been transmitted properly up to the time of receiving an ACK from the previous relay UE1.

[0223] Meanwhile, the remote UE may perform a status report for PDCP PDU 5 that has been transmitted so far, and whether to perform the status report (PDCP SN) based on the PDCP PDUs that have been transmitted so far or based on the PDCP PDUs to be newly sent may be determined according to the status report scheme. However, the target gNB may be reported with an SN that PDCP PDUs 1 and 2 have been received from the source gNB in ​​the HO decision, and may expect to receive data from the remote UE for PDCP PDU 3. However, the RLC PDUs related to PDCP PDUs 3, 4, and 5 previously transmitted by the remote UE are data that the source gNB does not know or cannot obtain, but are stored in the source relay UE, which is the previous relay UE. In such a situation, UL data loss may occur in the target gNB.

[0224] To minimize the loss of such UL data, the following methods may be considered.

[0225] (1) Since there is a possibility of receiving an HO command when the above measurement report is triggered, the remote UE may store / store the PDCP PDU for a certain period of time without discarding it even if it receives an ACK for all RLC PDUs related to the PDCP PDU from the source relay UE after transmitting the PDCP PDU. For this purpose, a new timer may be applied, and the new timer may operate after the PDCP PDU is transmitted and may expire after a certain period of time. In other words, the new timer may be started by the transmission of the PDCP PDU and may expire after operating for a certain period of time. When the new timer expires, the remote UE may remove / discard the stored PDCP PDU. Meanwhile, the new timer may operate for each transmission of the PDCP PDU. In other words, the new timer may be reset and start anew for each transmission of the PDCP PDU. Alternatively, the operation of storing PDCP PDUs without discarding them for a certain period of time after receiving an ACK based on the new timer may always be applied to the remote UE. For example, the remote UE may store PDCP PDUs / RLC PDUs for a relatively longer period of time compared to the general Uu direct operation while connected to the indirect path.

[0226] Alternatively, the new timer may be independently operated / set for each transmission of a PDCP PDU. For example, a first timer started by the transmission of the first PDCP PDU is set separately from the transmission of the second PDCP PDU, and the first timer is not stopped / reset even if the second PDCP PDU is transmitted. In this case, the first PDCP PDU may be discarded when the first timer expires, regardless of the operation of a separate first timer started by the transmission of the second PDCP PDU.

[0227] (2) In case of UL data transmission, the relay UE can transmit an ACK for reception of the RLC PDU related to the PDCP PDU to the remote UE only when it has completed transmitting all RLC PDUs related to the PDCP PDU received from the remote UE to the gNB (i.e., when it has received an RLC ACK from the gNB).

[0228] Alternatively, if a 1:N bearer mapping is established between the remote UE and the relay UE, RLC PDUs received from multiple remote UEs (or, even if received from the same remote UE, RLC PDUs having different RLC channel IDs) may be multiplexed into a single RLC PDU and transmitted to the gNB on the Uu link (or PC5 link). In this case, the relay UE may transmit an ACK for all RLC channels related to the received PDCP PDU when an ACK occurs on the Uu link (or PC5 link), and may transmit a NACK for all related RLC channels when a NACK occurs on the Uu link (or PC5 link). In this case, the time taken by the remote UE to receive an ACK / NACK from the relay UE may be much longer than the time taken by a normal UE to receive an ACK / NACK when the gNB transmits an RLC. Therefore, resetting a timer may be required. When operating based on the above, it may be determined / considered that the status number or SN between the source gNB and the remote UE matches.

[0229] (3) When the source gNB transmits an HO-related RRC reconfiguration message to the remote UE, the source relay UE connected to the source gNB may also configure the removal of a bearer related to the remote UE. When the source relay UE receives the bearer removal configuration from the gNB and RLC PDUs of the remote UE remain in its buffer (i.e., RLC PDUs not yet transmitted to the source gNB), the source relay UE may transmit all of the remaining RLC PDUs to the source gNB. This transmission operation of the remaining RLC PDUs may be performed regardless of an operation of releasing the SL connection with the remote UE according to a command of the source gNB. Alternatively, the source relay UE may release the connection with the remote UE or perform bearer re-mapping when all of the remaining RLC PDUs have been transmitted to the source gNB. The source gNB may additionally provide information about the reception of the residual RLC PDUs to the target gNB when all residual RLC PDUs are received from the source relay UE. To support such transmission operation of residual RLC PDUs, a specific timer (new timer) needs to be introduced. For example, when the (source) relay UE receives a new configuration from the serving (source) gNB to remove all configurations for a specific remote UE, the relay UE may be configured to apply / perform the new configuration after a certain period of time (the operation time of the specific timer).That is, when the new configuration is received and there are some RLC packets (i.e., residual RLC packets) among the RLC packets received from the remote UE at the relay UE that were not transmitted to the gNB, the relay UE may transmit the residual RLC packets to the gNB (or remote UE) during the operation of the specific timer (i.e., transmissions for the residual RLC packets may be performed until the timer expires, similar to the operation before receiving the new configuration). The specific timer may be set to the same value in the relay UE and the gNB. The gNB may also expect that the relay UE will maintain the existing configuration and transmit and receive the residual RLC packets (i.e., data for the remote UE ( / UL / DL)) until the timer expires.

[0230] (4) Alternatively, the source gNB may transmit an RRCReconfiguration message to the source relay UE to request the remote UE to release the configuration with the remote UE while transmitting an HO-related RRCReconfiguration message to the remote UE. In this case, the RRCReconfiguration message transmitted to the source relay UE may be configured to be applied after a certain period of time. This is to enable the source relay UE to transmit remaining data PDUs (or remaining RLC packets) remaining in its buffer for a certain period of time to the source gNB. The source relay UE may not be permitted to receive (new) data from the remote UE during the certain period of time. That is, the source gNB may set a specific timer related to the application of the RRCReconfiguration message while transmitting the RRCReconfiguration message to the source relay UE, and the RRCReconfiguration message may be applied when the specific timer expires. The source gNB may also perform an additional SN (sequence report) to the target gNB if it receives residual data PDUs (or residual data related to the remote UE) from the source relay UE after the HO command to the remote UE.

[0231] (5) Alternatively, for a data packet operating in AM RLC mode, the source relay UE may transmit a data PDU received from the remote UE to the source gNB, and may operate to transmit an ACK for the data PDU to the remote UE only when an ACK for the data PDU is received from the source gNB. This operation may affect the operation of the t-reordering timer in that the time at which the remote UE receives the ACK is delayed, and may be inappropriate in terms of delay. Therefore, this operation of transmitting an ACK for the data PDU to the remote UE may be configured to be performed only when a measurement report for the remote UE is triggered. In a general case (i.e., when a measurement report is not triggered), when the relay UE receives a data PDU from a remote UE, the relay UE may transmit an RLC ACK for the received data PDU to the remote UE (without delay). At this time, if a measurement report is triggered for the remote UE, the source relay UE does not transmit an ACK even if it receives a data PDU from the remote UE, but transmits all of the data PDUs to the source gNB and receives an ACK from the source gNB before transmitting an ACK for the data PDU to the remote UE. Whether a measurement report for the remote UE is triggered can be notified by the remote UE to the source relay UE (e.g., PC5-RRC, indication), or the source gNB can notify / configure the source relay UE.

[0232] (6) Alternatively, if the source gNB transmits an HO-related RRC message (e.g., RRCReconfiguration with sync) to the remote UE, it may separately instruct the (serving) relay UE associated with the remote UE to stop transmission and reception related to the relay. The instruction (or instruction information) may be delivered to the relay UE (or remote UE) as a MAC CE / DCI / RRC dedicated message. The relay UE that receives the instruction information may suspend some or all of Uu DL / UL and / or PC5-TX / TX.

[0233] In this way, the proposed method can perform handover (HO) between heterogeneous base stations while minimizing loss of UL / DL data when the remote UE changes path from an indirect path to an indirect path / direct path.

[0234] Figure 21 is a drawing for explaining a method in which a first terminal performs relay communication through a second terminal.

[0235] Referring to FIG. 21, an indirect path connected to a first base station through a second terminal can be formed (S211). For example, the first terminal can select the second terminal, which is a relay terminal, based on the signal strength of a discovery signal or the like, and can establish / establish a direct terminal communication link with the second terminal to form an indirect path connected to the first base station through the selected second terminal. Here, the first terminal can be a remote terminal as described above, and the second terminal can be a relay terminal (or, source relay terminal).

[0236] Next, the first terminal can transmit at least one packet data unit via the indirect path (S213). The packet data unit may be a PDCP (Packet Data Convergence Protocol) PDU (Protocol Data Unit) as described above. The at least one packet data unit can be transmitted to the first base station via the second terminal.

[0237] Next, the first terminal may receive an ACK (acknowledgement) or a message including an ACK for reception of the at least one packet data unit from the second terminal (S215). In this case, the first terminal may discard the at least one packet data unit transmitted through the indirect path stored in the buffer of the first terminal based on reception of the ACK. However, as described above, if the first timer set for the first terminal is running, the at least one packet data unit stored in the buffer may not be discarded even if the ACK is received.

[0238] Specifically, the first terminal may set the first timer to maintain the at least one packet data unit for a certain period of time in a specific case. The first timer may operate when the at least one packet data unit is transmitted after a measurement report (for handover or path change) is triggered from the first base station. In other words, the first timer does not operate only upon transmission of the at least one packet data unit. In this case, the first terminal may discard the at least one packet data unit if an ACK for the at least one packet data unit is received from the second terminal. Alternatively, when the at least one packet data unit is transmitted after a measurement report (for handover or path change) is triggered from the first base station, the first terminal may not discard the at least one packet data unit but may maintain storage in a buffer of the first terminal while the first timer is operating even if an ACK for the at least one packet data unit is received from the second terminal. That is, even if the first terminal performs a handover to the second base station, which is a target gNB, by receiving a message related to a handover according to a trigger of the measurement report, the first terminal can store the at least one packet data unit for a certain period of time by the first timer. In this case, even if the first terminal receives a request for transmission of some packet data units that were missed by the second base station to which the first terminal was handed over (i.e., some packet data units that the second terminal was unable to transmit to the first base station among the at least one packet data unit), the first terminal can transmit packet data units corresponding to the some packet data units to the second base station (via the target relay terminal). Meanwhile, the value of the first timer may be set based on the time required to complete the handover according to the handover request.

[0239] Alternatively, the first timer may be set for each transmission of the at least one packet data unit. For example, the 1-1 timer started by transmission of the first PDCP PDU may be set separately from transmission of the second PDCP PDU. That is, the 1-1 timer is not stopped / reset even if the second PDCP PDU is transmitted. In this case, the first PDCP PDU may be discarded when the 1-1 timer expires, regardless of the operation of a separate 1-2 timer started by transmission of the second PDCP PDU. In addition, the second PDCP PDU may be discarded when the 1-2 timer expires, regardless of the operation of the 1-1 timer.

[0240] Alternatively, the first terminal may receive a downlink packet data unit transmitted by the first base station via the indirect path. In addition, the first terminal may receive an RRC (Radio Resource Control) reconfiguration message related to a handover transmitted by the first base station via the indirect path. In this case, even if the RRC reconfiguration message is received, the first terminal may maintain a direct link between the terminals with the second terminal configured for the indirect path for a preset period of time. As described above, the first terminal may receive a data unit related to a remaining packet data unit stored in a buffer of the second terminal during the preset period of time. At this time, the first terminal may not transmit an uplink packet data unit via the indirect link during the preset period of time. In addition, the first terminal may not operate a timer (T304 or T420) related to the handover during the preset period of time, and may start the timer related to the handover after the preset period of time has elapsed.

[0241] In this way, the proposed invention can minimize data loss due to handover / route switching between base stations by not discarding the data for a certain period of time even when an ACK for the data unit transmitted by the remote UE is received from the relay UE. Alternatively, the proposed invention can minimize the increased burden on the buffer of the remote UE due to data retention by not discarding the data for a certain period of time only when a measurement report with a high possibility of handover / route switching between base stations is triggered.

[0242] Examples of communication systems to which the invention applies

[0243] Although not limited thereto, the various descriptions, functions, procedures, proposals, methods and / or operational flowcharts of the present invention disclosed in this document may be applied to various fields requiring wireless communication / connection (e.g., 5G) between devices.

[0244] Hereinafter, more specific examples will be provided with reference to the drawings. In the drawings / descriptions below, the same drawing reference numerals may represent identical or corresponding hardware blocks, software blocks, or functional blocks, unless otherwise described.

[0245] Figure 22 illustrates a communication system applied to the present invention.

[0246] Referring to FIG. 22, a communication system (1) applied to the present invention includes a wireless device, a base station, and a network. Here, the wireless device refers to a device that performs communication using a wireless access technology (e.g., 5G NR (New RAT), LTE (Long Term Evolution)) and may be referred to as a communication / wireless / 5G device. Although not limited thereto, the wireless device may include a robot (100a), a vehicle (100b-1, 100b-2), an XR (eXtended Reality) device (100c), a hand-held device (100d), a home appliance (100e), an IoT (Internet of Things) device (100f), and an AI device / server (400). For example, the vehicle may include a vehicle equipped with a wireless communication function, an autonomous vehicle, a vehicle capable of performing vehicle-to-vehicle communication, etc. Here, the vehicle may include an Unmanned Aerial Vehicle (UAV) (e.g., a drone). XR devices include AR (Augmented Reality) / VR (Virtual Reality) / MR (Mixed Reality) devices, and can be implemented in the form of HMD (Head-Mounted Device), HUD (Head-Up Display) installed in a vehicle, television, smartphone, computer, wearable device, home appliance, digital signage, vehicle, robot, etc. Mobile devices can include smartphone, smart pad, wearable device (e.g., smart watch, smart glass), computer (e.g., laptop, etc.), etc. Home appliances can include TV, refrigerator, washing machine, etc. IoT devices can include sensors, smart meters, etc. For example, base stations and networks can also be implemented as wireless devices, and a specific wireless device (200a) can act as a base station / network node to other wireless devices.

[0247] Wireless devices (100a to 100f) can be connected to a network (300) via a base station (200). Artificial Intelligence (AI) technology can be applied to the wireless devices (100a to 100f), and the wireless devices (100a to 100f) can be connected to an AI server (400) via the network (300). The network (300) can be configured using a 3G network, a 4G (e.g., LTE) network, a 5G (e.g., NR) network, etc. The wireless devices (100a to 100f) can communicate with each other via the base station (200) / network (300), but can also communicate directly (e.g., sidelink communication) without going through the base station / network. For example, vehicles (100b-1, 100b-2) can communicate directly (e.g., V2V (Vehicle to Vehicle) / V2X (Vehicle to Everything) communication). In addition, IoT devices (e.g., sensors) can communicate directly with other IoT devices (e.g., sensors) or other wireless devices (100a to 100f).

[0248] Wireless communication / connection (150a, 150b, 150c) can be established between wireless devices (100a~100f) / base stations (200), and base stations (200) / base stations (200). Here, wireless communication / connection can be achieved through various wireless access technologies (e.g., 5G NR) such as uplink / downlink communication (150a), sidelink communication (150b) (or, D2D communication), and communication between base stations (150c) (e.g., relay, IAB (Integrated Access Backhaul). Through wireless communication / connection (150a, 150b, 150c), wireless devices and base stations / wireless devices, and base stations and base stations can transmit / receive wireless signals to each other. For example, wireless communication / connection (150a, 150b, 150c) can transmit / receive signals through various physical channels. To this end, at least some of various configuration information setting processes for transmitting / receiving wireless signals, various signal processing processes (e.g., channel encoding / decoding, modulation / demodulation, resource mapping / demapping, etc.), and resource allocation processes can be performed based on various proposals of the present invention.

[0249] Examples of wireless devices to which the present invention is applied

[0250] Figure 23 illustrates a wireless device applicable to the present invention.

[0251] Referring to FIG. 23, the first wireless device (100) and the second wireless device (200) can transmit and receive wireless signals through various wireless access technologies (e.g., LTE, NR). Here, {the first wireless device (100), the second wireless device (200)} can correspond to {the wireless device (100x), the base station (200)} and / or {the wireless device (100x), the wireless device (100x)} of FIG. 22.

[0252] A first wireless device (100) includes one or more processors (102) and one or more memories (104), and may further include one or more transceivers (106) and / or one or more antennas (108). The processor (102) controls the memories (104) and / or the transceivers (106), and may be configured to implement the descriptions, functions, procedures, proposals, methods, and / or operational flowcharts disclosed in this document. For example, the processor (102) may process information in the memory (104) to generate first information / signal, and then transmit a wireless signal including the first information / signal via the transceiver (106). In addition, the processor (102) may receive a wireless signal including second information / signal via the transceiver (106), and then store information obtained from signal processing of the second information / signal in the memory (104). The memory (104) may be connected to the processor (102) and may store various information related to the operation of the processor (102). For example, the memory (104) may perform some or all of the processes controlled by the processor (102), or may store software code including commands for performing the descriptions, functions, procedures, proposals, methods, and / or operation flowcharts disclosed in this document. Here, the processor (102) and the memory (104) may be part of a communication modem / circuit / chipset designed to implement wireless communication technology (e.g., LTE, NR). The transceiver (106) may be connected to the processor (102) and may transmit and / or receive wireless signals via one or more antennas (108). The transceiver (106) may include a transmitter and / or a receiver. The transceiver (106) may be used interchangeably with an RF (Radio Frequency) unit. In the present invention, a wireless device may also mean a communication modem / circuit / chipset.

[0253] Specifically, the first wireless device or first 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 embodiments described in FIGS. 13 to 21.

[0254] The processor (102) controls the transceiver (106) to form an indirect path connected to the first base station through the second terminal, transmit a packet data unit through the indirect path, and receive an ACK (acknowledgement) related to the packet data unit from the second terminal through the indirect path. Here, based on the measurement report being triggered by the first base station, the packet data unit may be discarded after the expiration of the first timer even if the ACK is received.

[0255] Alternatively, a processing device may be configured, including a processor (102) and a memory (104) for controlling a first terminal performing relay communication. In this case, at least one processor; and at least one memory connected to the at least one processor and storing instructions, wherein the instructions, based on being executed by the at least one processor, cause the terminal to: form an indirect path connected to a first base station through a second terminal, transmit a packet data unit through the indirect path, and receive an ACK (acknowledgement) related to the packet data unit from the second terminal through the indirect path. Here, based on the measurement report being triggered by the first base station, the packet data unit may be discarded after the expiration of a first timer even if the ACK is received.

[0256] The second wireless device (200) includes one or more processors (202), one or more memories (204), and may further include one or more transceivers (206) and / or one or more antennas (208). The processor (202) controls the memories (204) and / or the transceivers (206), and may be configured to implement the descriptions, functions, procedures, proposals, methods, and / or operational flowcharts disclosed in this document. For example, the processor (202) may process information in the memory (204) to generate third information / signals, and then transmit a wireless signal including the third information / signals via the transceivers (206). Furthermore, the processor (202) may receive a wireless signal including fourth information / signals via the transceivers (206), and then store information obtained from signal processing of the fourth information / signals in the memory (204). The memory (204) may be connected to the processor (202) and may store various information related to the operation of the processor (202). For example, the memory (204) may perform some or all of the processes controlled by the processor (202), or may store software code including commands for performing the descriptions, functions, procedures, proposals, methods, and / or operation flowcharts disclosed in this document. Here, the processor (202) and the memory (204) may be part of a communication modem / circuit / chip designed to implement wireless communication technology (e.g., LTE, NR). The transceiver (206) may be connected to the processor (202) and may transmit and / or receive wireless signals via one or more antennas (208). The transceiver (206) may include a transmitter and / or a receiver. The transceiver (206) may be used interchangeably with an RF unit. In the present invention, a wireless device may also mean a communication modem / circuit / chip.

[0257] Specifically, the second wireless device or second terminal (200) may include a processor (202) and a memory (204) connected to a transceiver or RF transceiver (206). The memory (204) may include at least one program capable of performing operations related to the embodiments described in FIGS. 13 to 21.

[0258] Hereinafter, the hardware elements of the wireless device (100, 200) will be described in more detail. Although not limited thereto, one or more protocol layers may be implemented by one or more processors (102, 202). For example, one or more processors (102, 202) may implement one or more layers (e.g., functional layers such as PHY, MAC, RLC, PDCP, RRC, SDAP). One or more processors (102, 202) may generate one or more Protocol Data Units (PDUs) and / or one or more Service Data Units (SDUs) according to the descriptions, functions, procedures, proposals, methods, and / or operation flowcharts disclosed in this document. One or more processors (102, 202) may generate messages, control information, data, or information according to the descriptions, functions, procedures, proposals, methods, and / or operation flowcharts disclosed in this document. One or more processors (102, 202) can generate signals (e.g., baseband signals) including PDUs, SDUs, messages, control information, data or information according to the functions, procedures, proposals and / or methods disclosed herein, and provide the signals to one or more transceivers (106, 206). One or more processors (102, 202) can receive signals (e.g., baseband signals) from one or more transceivers (106, 206) and obtain PDUs, SDUs, messages, control information, data or information according to the descriptions, functions, procedures, proposals, methods and / or operational flowcharts disclosed herein.

[0259] One or more processors (102, 202) may be referred to as a controller, a microcontroller, a microprocessor, or a microcomputer. One or more processors (102, 202) may be implemented by hardware, firmware, software, or a combination thereof. For example, one or more Application Specific Integrated Circuits (ASICs), one or more Digital Signal Processors (DSPs), one or more Digital Signal Processing Devices (DSPDs), one or more Programmable Logic Devices (PLDs), or one or more Field Programmable Gate Arrays (FPGAs) may be included in one or more processors (102, 202). The descriptions, functions, procedures, proposals, methods, and / or operational flowcharts disclosed in this document may be implemented using firmware or software, and the firmware or software may be implemented to include modules, procedures, functions, etc. The descriptions, functions, procedures, suggestions, methods and / or operation flowcharts disclosed in this document may be implemented using firmware or software configured to perform one or more processors (102, 202) or stored in one or more memories (104, 204) and executed by one or more processors (102, 202). The descriptions, functions, procedures, suggestions, methods and / or operation flowcharts disclosed in this document may be implemented using firmware or software in the form of codes, instructions and / or sets of instructions.

[0260] One or more memories (104, 204) may be coupled to one or more processors (102, 202) and may store various forms of data, signals, messages, information, programs, codes, instructions, and / or commands. The one or more memories (104, 204) may be configured as ROM, RAM, EPROM, flash memory, hard drives, registers, cache memory, computer-readable storage media, and / or combinations thereof. The one or more memories (104, 204) may be located internally and / or externally to the one or more processors (102, 202). Additionally, the one or more memories (104, 204) may be coupled to the one or more processors (102, 202) via various technologies, such as wired or wireless connections.

[0261] One or more transceivers (106, 206) can transmit user data, control information, wireless signals / channels, etc., as mentioned in the methods and / or flowcharts of this document, to one or more other devices. One or more transceivers (106, 206) can receive user data, control information, wireless signals / channels, etc., as mentioned in the descriptions, functions, procedures, proposals, methods and / or flowcharts of this document, from one or more other devices. For example, one or more transceivers (106, 206) can be connected to one or more processors (102, 202) and can transmit and receive wireless signals. For example, one or more processors (102, 202) can control one or more transceivers (106, 206) to transmit user data, control information, or wireless signals to one or more other devices. Additionally, one or more processors (102, 202) may control one or more transceivers (106, 206) to receive user data, control information, or wireless signals from one or more other devices. Additionally, one or more transceivers (106, 206) may be coupled to one or more antennas (108, 208), and one or more transceivers (106, 206) may be configured to transmit and receive user data, control information, wireless signals / channels, or the like, as referred to in the descriptions, functions, procedures, proposals, methods, and / or operational flowcharts disclosed herein, via one or more antennas (108, 208). In this document, one or more antennas may be multiple physical antennas or multiple logical antennas (e.g., antenna ports). One or more transceivers (106, 206) can convert received user data, control information, wireless signals / channels, etc. from RF band signals to baseband signals in order to process the received user data, control information, wireless signals / channels, etc. using one or more processors (102, 202).One or more transceivers (106, 206) may convert user data, control information, wireless signals / channels, etc. processed by one or more processors (102, 202) from baseband signals to RF band signals. For this purpose, one or more transceivers (106, 206) may include an (analog) oscillator and / or filter.

[0262] Examples of wireless devices to which the present invention is applied

[0263] Figure 24 illustrates another example of a wireless device applicable to the present invention. The wireless device may be implemented in various forms depending on the use case / service (see Figure 22).

[0264] Referring to FIG. 24, the wireless device (100, 200) corresponds to the wireless device (100, 200) of FIG. 23 and may be composed of various elements, components, units / units, and / or modules. For example, the wireless device (100, 200) may include a communication unit (110), a control unit (120), a memory unit (130), and additional elements (140). The communication unit may include a communication circuit (112) and a transceiver(s) (114). For example, the communication circuit (112) may include one or more processors (102, 202) and / or one or more memories (104, 204) of FIG. 24. For example, the transceiver(s) (114) may include one or more transceivers (106, 206) and / or one or more antennas (108, 208) of FIG. 23. The control unit (120) is electrically connected to the communication unit (110), the memory unit (130), and the additional elements (140) and controls the overall operation of the wireless device. For example, the control unit (120) may control the electrical / mechanical operation of the wireless device based on the program / code / command / information stored in the memory unit (130). In addition, the control unit (120) may transmit information stored in the memory unit (130) to an external device (e.g., another communication device) via a wireless / wired interface through the communication unit (110), or store information received from an external device (e.g., another communication device) via a wireless / wired interface in the memory unit (130).

[0265] The additional element (140) may be configured in various ways depending on the type of the wireless device. For example, the additional element (140) may include at least one of a power unit / battery, an input / output (I / O) unit, a driving unit, and a computing unit. Although not limited thereto, the wireless device may be implemented in the form of a robot (Fig. 22, 100a), a vehicle (Fig. 22, 100b-1, 100b-2), an XR device (Fig. 22, 100c), a portable device (Fig. 22, 100d), a home appliance (Fig. 22, 100e), an IoT device (Fig. 22, 100f), a digital broadcasting terminal, a hologram device, a public safety device, an MTC device, a medical device, a fintech device (or a financial device), a security device, a climate / environmental device, an AI server / device (Fig. 22, 400), a base station (Fig. 22, 200), a network node, etc. Wireless devices may be mobile or stationary depending on the use / service.

[0266] In FIG. 24, various elements, components, units / parts, and / or modules within the wireless device (100, 200) may be entirely interconnected via a wired interface, or at least some may be wirelessly connected via a communication unit (110). For example, within the wireless device (100, 200), the control unit (120) and the communication unit (110) may be wired, and the control unit (120) and a first unit (e.g., 130, 140) may be wirelessly connected via the communication unit (110). In addition, each element, component, unit / part, and / or module within the wireless device (100, 200) may further include one or more elements. For example, the control unit (120) may be composed of a set of one or more processors. For example, the control unit (120) may be composed of a set of a communication control processor, an application processor, an electronic control unit (ECU), a graphics processing processor, a memory control processor, etc. As another example, the memory unit (130) may be composed of RAM (Random Access Memory), DRAM (Dynamic RAM), ROM (Read Only Memory), flash memory, volatile memory, non-volatile memory, and / or a combination thereof.

[0267] Examples of vehicles or autonomous vehicles to which the present invention is applied

[0268] Figure 25 illustrates a vehicle or autonomous vehicle applicable to the present invention. The vehicle or autonomous vehicle may be implemented as a mobile robot, car, train, manned / unmanned aerial vehicle (AV), ship, etc.

[0269] Referring to FIG. 25, a vehicle or autonomous vehicle (100) may include an antenna unit (108), a communication unit (110), a control unit (120), a driving unit (140a), a power supply unit (140b), a sensor unit (140c), and an autonomous driving unit (140d). The antenna unit (108) may be configured as a part of the communication unit (110). Blocks 110 / 130 / 140a to 140d correspond to blocks 110 / 130 / 140 of FIG. 24, respectively.

[0270] The communication unit (110) can transmit and receive signals (e.g., data, control signals, etc.) with external devices such as other vehicles, base stations (e.g., base stations, road side units, etc.), and servers. The control unit (120) can control elements of the vehicle or autonomous vehicle (100) to perform various operations. The control unit (120) can include an ECU (Electronic Control Unit). The drive unit (140a) can drive the vehicle or autonomous vehicle (100) on the ground. The drive unit (140a) can include an engine, a motor, a power train, wheels, brakes, a steering device, etc. The power supply unit (140b) supplies power to the vehicle or autonomous vehicle (100) and can include a wired / wireless charging circuit, a battery, etc. The sensor unit (140c) can obtain vehicle status, surrounding environment information, user information, etc. The sensor unit (140c) may include an IMU (inertial measurement unit) sensor, a collision sensor, a wheel sensor, a speed sensor, an incline sensor, a weight detection sensor, a heading sensor, a position module, a vehicle forward / backward sensor, a battery sensor, a fuel sensor, a tire sensor, a steering sensor, a temperature sensor, a humidity sensor, an ultrasonic sensor, an illuminance sensor, a pedal position sensor, etc. The autonomous driving unit (140d) may implement a technology for maintaining a driving lane, a technology for automatically controlling speed such as adaptive cruise control, a technology for automatically driving along a set path, a technology for automatically setting a path and driving when a destination is set, etc.

[0271] For example, the communication unit (110) can receive map data, traffic information data, etc. from an external server. The autonomous driving unit (140d) can generate an autonomous driving route and driving plan based on the acquired data. The control unit (120) can control the drive unit (140a) so that the vehicle or autonomous vehicle (100) moves along the autonomous driving route according to the driving plan (e.g., speed / direction control). During autonomous driving, the communication unit (110) can irregularly / periodically acquire the latest traffic information data from an external server and can acquire surrounding traffic information data from surrounding vehicles. In addition, during autonomous driving, the sensor unit (140c) can acquire vehicle status and surrounding environment information. The autonomous driving unit (140d) can update the autonomous driving route and driving plan based on newly acquired data / information. The communication unit (110) can transmit information regarding the vehicle location, autonomous driving route, driving plan, etc. to the external server. External servers can predict traffic information data in advance using AI technology or other technologies based on information collected from vehicles or autonomous vehicles, and provide the predicted traffic information data to the vehicles or autonomous vehicles.

[0272] Here, the wireless communication technology implemented in the wireless device (XXX, YYY) of the present specification may include not only LTE, NR, and 6G, but also Narrowband Internet of Things for low-power communication. At this time, for example, NB-IoT technology may be an example of LPWAN (Low Power Wide Area Network) technology, and may be implemented with standards such as LTE Cat NB1 and / or LTE Cat NB2, and is not limited to the above-described names. Additionally or alternatively, the wireless communication technology implemented in the wireless device (XXX, YYY) of the present specification may perform communication based on LTE-M technology. At this time, for example, LTE-M technology may be an example of LPWAN technology, and may be called by various names such as eMTC (enhanced Machine Type Communication). For example, LTE-M technology can be implemented by at least one of various standards such as 1) LTE CAT 0, 2) LTE Cat M1, 3) LTE Cat M2, 4) LTE non-BL (non-Bandwidth Limited), 5) LTE-MTC, 6) LTE Machine Type Communication, and / or 7) LTE M, and is not limited to the above-described names. Additionally or alternatively, the wireless communication technology implemented in the wireless device (XXX, YYY) of the present specification can include at least one of ZigBee, Bluetooth, and Low Power Wide Area Network (LPWAN) considering low-power communication, and is not limited to the above-described names. For example, ZigBee technology can create PAN (personal area networks) related to small / low-power digital communication based on various standards such as IEEE 802.15.4, and can be called by various names.

[0273] The embodiments described above are combinations of components and features of the present invention in a predetermined form. Each component or feature should be considered optional unless explicitly stated otherwise. Each component or feature may be implemented without being combined with other components or features. Furthermore, it is also possible to form an embodiment of the present invention by combining some components and / or features. The order of operations described in the embodiments of the present invention may be changed. Some components or features of one embodiment may be included in another embodiment or may be replaced with corresponding components or features of another embodiment. It is self-evident that claims that do not have an explicit citation relationship in the patent claims may be combined to form an embodiment or may be incorporated as a new claim through a post-application amendment.

[0274] In this document, embodiments of the present invention have been described primarily focusing on the signal transmission and reception relationship between a terminal and a base station. This transmission and reception relationship is equally / similarly extended to signal transmission and reception between a terminal and a relay or a base station and a relay. Certain operations described as being performed by a base station in this document may, in some cases, be performed by its upper node. That is, it is obvious that various operations performed for communication with a terminal in a network composed of multiple network nodes including a base station may be performed by the base station or other network nodes other than the base station. The base station may be replaced by terms such as fixed station, Node B, eNode B (eNB), and access point. In addition, the terminal may be replaced by terms such as UE (User Equipment), MS (Mobile Station), MSS (Mobile Subscriber Station).

[0275] Embodiments of the present invention may be implemented by various means, for example, hardware, firmware, software, or a combination thereof. In the case of hardware implementation, an embodiment of the present invention may be implemented by one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, etc.

[0276] When implemented via firmware or software, an embodiment of the present invention may be implemented in the form of modules, procedures, functions, etc. that perform the functions or operations described above. The software code may be stored in a memory unit and executed by a processor. The memory unit may be located within or outside the processor and may exchange data with the processor via various known means.

[0277] It will be apparent to those skilled in the art that the present invention can be embodied in other specific forms without departing from the scope of the invention. Therefore, the above detailed description should not be construed as limiting in any respect, but rather as illustrative. The scope of the present invention should be determined by a reasonable interpretation of the appended claims, and all modifications within the scope of equivalents of the present invention are intended to be included within the scope of the present invention.

[0278] The embodiments of the present invention as described above can be applied to various mobile communication systems.

Claims

1. In a method for a first terminal to perform relay communication in a wireless communication system, A step of forming an indirect path connected to the first base station through the second terminal; A step of transmitting a packet data unit through the above indirect path; and A step of receiving an ACK (acknowledgement) related to the packet data unit from the second terminal through the indirect path, A method wherein, based on a measurement report being triggered by the first base station, the packet data unit is discarded after the expiration of the first timer even if the ACK is received.

2. In paragraph 1, A method characterized in that the packet data unit is discarded based on the reception of the ACK, based on the measurement report not being triggered.

3. In paragraph 1, A method, characterized in that the first timer is started based on a trigger of the measurement report and transmission of the packet data unit.

4. In paragraph 1, A method characterized in that the first timer is not started even if the packet data unit is transmitted based on the measurement report not being triggered.

5. In paragraph 1, A method, characterized in that the first timer is set for each transmission of the packet data unit.

6. In paragraph 1, A step of receiving a downlink packet data unit through the above indirect path; and Further comprising the step of receiving an RRC (Radio Resource Control) reset message related to handover through the above indirect path, A method characterized in that the indirect path is maintained for a preset time even if the RRC reset message is received.

7. In paragraph 6, A method characterized in that the terminal is restricted from transmitting data packets through the indirect path for the preset time.

8. In paragraph 6, A method, characterized in that the second timer associated with the handover is started after the elapse of the preset time.

9. In paragraph 1, A method, characterized in that the above packet data unit is a PDCP (Packet Data Convergence Protocol) PDU (Protocol Data Unit).

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

11. In a first terminal performing relay communication in a wireless communication system, RF (Radio Frequency) transmitter and receiver; and A processor connected to the RF transceiver, The processor controls the RF transceiver to form an indirect path connected to the first base station through the second terminal, transmits a packet data unit through the indirect path, and receives an ACK (acknowledgement) related to the packet data unit from the second terminal through the indirect path. A first terminal, wherein the packet data unit is discarded after the expiration of the first timer even if the ACK is received, based on the measurement report being triggered by the first base station.

12. In paragraph 11, A first terminal, characterized in that the packet data unit is discarded based on the reception of the ACK, based on the measurement report not being triggered.

13. In paragraph 11, A first terminal, characterized in that the first timer is started based on a trigger of the measurement report and transmission of the packet data unit.

14. In paragraph 11, A first terminal, characterized in that the first timer is not started even if the packet data unit is transmitted based on the above measurement report not being triggered.

15. In a processing device that controls a first terminal performing relay communication in a wireless communication system, at least one processor; and At least one memory connected to said at least one processor and storing instructions, said instructions being executed by said at least one processor, wherein said first terminal causes: Forming an indirect path connected to a first base station through a second terminal, transmitting a packet data unit through the indirect path, and receiving an ACK (acknowledgement) related to the packet data unit from the second terminal through the indirect path, A processing device, wherein the packet data unit is discarded after the expiration of the first timer, even if the ACK is received, based on the measurement report being triggered by the first base station.

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