Terminal and method for use in wireless communication system

Abstract

Provided are a terminal in a wireless communication system and a method performed by the same, the method comprising: performing sidelink transmissions associated with a plurality of sidelink carriers; identifying whether all of the plurality of sidelink carriers are unavailable based on a hybrid automatic repeat request (HARQ) operation; identifying a detection of a sidelink radio link failure (RLF) if all of the plurality of sidelink carriers are unavailable; and transmitting information associated with the sidelink RLF to a base station.

Description

[0001] This case is a divisional application of the invention patent application with the application date of January 29, 2021, application number 202180024673.9, and invention name "Device and method for controlling sidelink auxiliary carrier in a wireless communication system". Technical Field

[0002] Various embodiments of the present disclosure relate to a wireless communication system, and more particularly, to a method and apparatus in which a terminal controls a sidelink carrier in the wireless communication system. Background Art

[0003] In order to meet the growing demand for wireless data services since the commercialization of the fourth generation (4G) communication system, efforts have been made to develop advanced fifth generation (5G) or pre-5G communication systems. For this reason, 5G or pre-5G communication systems are also called super 4G network communication systems or post-long term evolution (LTE) systems.

[0004] In order to achieve high data rates, 5G communication systems are being considered for implementation in ultra-high frequency (millimeter wave (mmWave)) bands (e.g., 60 GHz bands). In order to reduce the path loss of radio waves and increase the transmission range of radio waves in ultra-high frequency bands, beamforming, massive multiple-input multiple-output (MIMO), full-dimensional MIMO (FD-MIMO), array antennas, analog beamforming, and massive antenna technologies are being discussed.

[0005] In order to improve the system network, technologies for advanced small cells, cloud radio access networks (RAN), ultra-dense networks, device-to-device (D2D) communication, wireless backhaul, mobile networks, collaborative communications, coordinated multi-point (CoMP), receiving-end interference elimination, etc. are also developed in 5G communication systems.

[0006] In addition, in 5G systems, advanced coding and modulation (ACM) methods (e.g., hybrid frequency shift keying (FSK) and quadrature amplitude modulation (QAM) (FQAM), sliding window superposition coding (SWSC)) and advanced access technologies (e.g., filter bank multi-carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA)) have been developed.

[0007] The Internet has evolved from a human-centered connection network where humans generate and consume information to an Internet of Things (IoT) network that exchanges and processes information between distributed components (such as objects). Internet of Everything (IoE) technology, which combines big data processing technology connected to cloud servers and the like with IoT technology, has also emerged. In order to implement IoT, various technical elements such as sensing technology, wired / wireless communication and network infrastructure, service interface technology and security technology are required, so in recent years, technologies related to sensor networks for connecting objects, machine-to-machine (M2M) communication and machine type communication (MTC) have been studied. In the IoT environment, intelligent information technology (IT) services can be provided to collect and analyze data obtained from objects connected to each other to create new value in human life. Through the fusion and integration of existing IT and various industries, IoT can be applied to fields such as smart homes, smart buildings, smart cities, smart cars or connected cars, smart grids, healthcare, smart appliances and advanced medical services.

[0008] In this regard, various attempts have been made to apply 5G communication systems to IoT networks. For example, technologies related to sensor networks, M2M, MTC, etc. are implemented through 5G communication technologies such as beamforming, MIMO, and array antennas. The application of cloud RAN as a big data processing technology can also be considered an example of the fusion of 5G technology and IoT technology.

[0009] In addition, terminal direct communication (side link communication) using a 5G communication system has been studied, and terminal direct communication is applied to, for example, vehicle-to-everything (hereinafter referred to as "V2X") and is expected to provide various services to users.

[0010] As described above, since various services may be provided according to the development of a wireless communication system, a method for efficiently controlling a sidelink secondary carrier is particularly required. Summary of the invention

[0011] Technical issues

[0012] Various embodiments of the present disclosure provide an apparatus and method in which a terminal controls a sidelink carrier in a wireless communication system.

[0013] Technical Solution

[0014] The present disclosure may provide a first terminal for performing unicast communication between terminals in a wireless communication system. The first terminal may be configured to: send a packet to a second terminal via a first side link carrier; determine a failure of the first side link carrier based on at least one of the number of retransmissions of the sent packet, the number of receptions of a hybrid automatic repeat request (HARQ) negative acknowledgement (NACK) of the sent packet, and the number of consecutive out-of-sync (OOS) times of the first side link carrier; and determine whether to execute a radio link failure (RLF) handler or a carrier failure handler based on a result of the determination of the failure and the first side link carrier, wherein the carrier failure handler may be executed based on at least one of the connection state between the first terminal and the base station and the need for multi-carrier transmission.

[0015] The present disclosure provides a method performed by a terminal in a wireless communication system, the method comprising: performing sidelink transmission associated with multiple sidelink carriers; based on a hybrid automatic repeat request HARQ operation, identifying whether the multiple sidelink carriers are all unavailable; in a case where the multiple sidelink carriers are all unavailable, identifying the detection of a sidelink radio link failure RLF; and transmitting information associated with the sidelink RLF to a base station.

[0016] The present disclosure provides a terminal in a wireless communication system, the terminal comprising: a transceiver; and at least one processor, which is coupled to the transceiver and configured to: perform sidelink transmission associated with multiple sidelink carriers; based on a hybrid automatic repeat request HARQ operation, identify whether all of the multiple sidelink carriers are unavailable; in the case where all of the multiple sidelink carriers are unavailable, identify the detection of a sidelink radio link failure RLF; and transmit information associated with the sidelink RLF to a base station. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A wireless communication system according to an embodiment of the present disclosure is shown.

[0018] Figure 2 The configuration of a base station in a wireless communication system according to an embodiment of the present disclosure is shown.

[0019] Figure 3 The configuration of a terminal in a wireless communication system according to an embodiment of the present disclosure is shown.

[0020] Figure 4 A configuration of a communicator in a wireless communication system according to an embodiment of the present disclosure is shown.

[0021] Figure 5 The structure of wireless time-frequency resources in a wireless communication system according to an embodiment of the present disclosure is shown.

[0022] Fig. 6A is a diagram illustrating a scenario of side link communication according to an embodiment of the present disclosure.

[0023] Figure 6B is a diagram illustrating a scenario of side link communication according to an embodiment of the present disclosure.

[0024] Figure 6C is a diagram illustrating a scenario of side link communication according to an embodiment of the present disclosure.

[0025] Fig.6D is a diagram illustrating a scenario of side link communication according to an embodiment of the present disclosure.

[0026] Fig. 7A is a diagram for describing a transmission method for side link communication according to an embodiment of the present disclosure.

[0027] Figure 7B is a diagram for describing transmission of side link communication according to an embodiment of the present disclosure.

[0028] Fig. 8A and Figure 8B is a diagram for describing an operation of a terminal processing a side link carrier failure according to an embodiment of the present disclosure.

[0029] Fig. 9A , Fig. 9B and Fig. 9C is a diagram for describing an operation of a terminal processing a side link carrier failure according to an embodiment of the present disclosure.

[0030] Fig. 10A and Fig. 10B is a diagram for describing an operation of a terminal processing a side link carrier failure according to an embodiment of the present disclosure.

[0031] Fig.11A and Fig. 11B is a diagram for describing an operation of a terminal processing a side link carrier failure according to an embodiment of the present disclosure.

[0032] Fig. 12A and Fig. 12B is a diagram for describing an operation of a terminal processing a side link carrier failure according to an embodiment of the present disclosure.

[0033] Fig.13 is a diagram for describing an operation of a terminal processing carrier selection / reselection due to a sidelink carrier failure according to an embodiment of the present disclosure.

[0034] Fig.14A and Fig. 14B is a diagram for describing an operation of a terminal processing a side link carrier failure according to an embodiment of the present disclosure.

[0035] Fig.15A and Fig. 15B is a diagram showing the format of a medium access control (MAC) control element (CE) according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0036] Embodiments of the present disclosure may provide a first terminal for performing unicast communication between terminals in a wireless communication system. The first terminal may include a transceiver and at least one processor, the at least one processor being configured to: send a packet to a second terminal via a first side link carrier; determine a failure of the first side link carrier based on at least one of the number of retransmissions of the sent packet, the number of receptions of a hybrid automatic repeat request (HARQ) negative acknowledgement (NACK) of the sent packet, the number of receptions of a HARQ discontinuous transmission (DTX) of the sent packet, and the number of consecutive out-of-sync (OOS) of the first side link carrier; and determine whether to execute a radio link failure (RLF) handler or a carrier failure handler based on the result of the determination of the failure and the first side link carrier, wherein the carrier failure handler may be executed based on at least one of the connection state between the first terminal and the base station and the need for multi-carrier transmission.

[0037] In one embodiment, at least one processor of the first terminal may also be configured to: identify whether the first side link carrier is a primary carrier or a secondary carrier; when the first side link carrier is identified as a primary carrier, execute an RLF handling procedure based on a result of determining a fault; and when the first side link carrier is identified as a secondary carrier, execute a carrier fault handling procedure based on a result of determining a fault.

[0038] In one embodiment, at least one processor of the first terminal may also be configured to: determine, based on a result of determining the fault, whether there is a second side link carrier through which packets may be sent to the second terminal; when the second side link carrier does not exist, execute an RLF handling procedure; and when the second side link carrier exists, execute a carrier failure handling procedure for the first side link carrier.

[0039] In one embodiment, at least one processor of the first terminal may also be configured to: identify the connection status between the first terminal and the base station when executing a carrier fault handling procedure; send a first fault report message about the first side link carrier to the base station when the first terminal is connected to the base station, and receive configuration information about the new carrier from the base station; and execute a carrier selection or reselection procedure when the first terminal is not connected to the base station, wherein the first fault report message may include an identifier of the first side link carrier, radio bearer information about the first side link carrier, logical channel information about the first side link carrier, a channel congestion level measurement result of the transmission resource pool of the first side link carrier, and at least one of a packet reception ratio of the first side link carrier.

[0040] In one embodiment, at least one processor of the first terminal may also be configured to suspend use of the first side link carrier based on whether configuration information of a new carrier is received from the base station and at least one of a need for multi-carrier transmission, wherein the suspension of use of the first side link carrier may be performed before identifying the connection status between the first terminal and the base station, before sending a first fault report message to the base station, or before performing a carrier selection or reselection procedure.

[0041] In one embodiment, at least one processor of the first terminal may be further configured to: identify a need for multi-carrier transmission when the first terminal is not connected to a base station; and perform a carrier selection or reselection procedure based on the identified need for multi-carrier transmission.

[0042] In one embodiment, at least one processor of the first terminal can also be configured to: when executing a carrier failure handling procedure, determine whether there is an available carrier according to a carrier selection or reselection procedure; when there is an available carrier, send a packet to the second terminal through the available carrier; when there is no available carrier, identify the connection status between the first terminal and the base station; when the first terminal is connected to the base station, send a first fault report message of the first side link carrier to the base station; and when the first terminal is not connected to the base station, execute a carrier selection or reselection procedure.

[0043] In one embodiment, at least one processor of the first terminal may be further configured to: suspend use of the first side link carrier; and after suspending use of the first side link carrier, determine whether there is an available carrier according to a carrier selection or reselection procedure.

[0044] In one embodiment, a carrier selection or reselection procedure may be performed based on at least one of a carrier selection condition for a logical channel, a carrier selection condition for a sidelink flow, a carrier selection condition for a sidelink bearer, a channel congestion level, a reliability of a sidelink flow, a reliability of a sidelink bearer, and a sidelink signal quality.

[0045] In one embodiment, at least one processor of the first terminal may also be configured to: determine that the first side link carrier in which the fault is determined is used for unicast communication; and send a second fault report message of the first side link carrier to the second side link carrier based on the first side link carrier and the result of determining that the first side link carrier is used for unicast communication.

[0046] In one embodiment, the at least one processor of the first terminal may be further configured to: identify the existence of a new carrier for unicast communication based on a result of sending the second fault report message to the second terminal; and send information about the identified new carrier to the second terminal.

[0047] In one embodiment, the second fault report message may include at least one of an identifier notifying transmission suspension, an identifier of the first sidelink carrier, radio bearer information about the first sidelink carrier, and logical channel information about the first sidelink carrier.

[0048] In one embodiment, the second fault report message may be sent in a media access control (MAC) control element (CE) format and may indicate a mapping of a carrier corresponding to a signaling radio bearer (SRB) corresponding to PC5-radio resource control (RRC) or an SRB corresponding to PC5-S signaling.

[0049] Embodiments of the present disclosure may provide a base station for sending signals to / receiving signals from a terminal supporting sidelink communication in a wireless communication system. The base station may include a transceiver and at least one processor, the at least one processor being configured to: receive a first fault report message from the terminal, the first fault report message including information about a fault of a first sidelink carrier; configure carrier configuration information based on the received first fault report message, sidelink capability information about the terminal, and channel congestion level information; and send carrier configuration information to the terminal, wherein the carrier configuration information may include at least one of a carrier list, reference parameters related to activation of repeated transmission, transmission power, modulation and coding scheme (MCS) level, number of packet retransmissions, number of transmissions of hybrid automatic repeat request (HARQ) discontinuous transmission (DTX), and number of retransmissions of HARQ negative acknowledgement (NACK).

[0050] Embodiments of the present disclosure may provide an operating method for a first terminal for performing unicast communication between terminals in a wireless communication system. The operating method may include: sending a packet to a second terminal via a first side link carrier; determining a failure of the first side link carrier based on at least one of the number of retransmissions of the sent packet, the number of receptions of a hybrid automatic repeat request (HARQ) discontinuous transmission (DTX) of the sent packet, the number of receptions of a HARQ negative acknowledgement (NACK) of the sent packet, and the number of consecutive out-of-sync (OOS) times of the first side link carrier; and determining whether to execute a radio link failure (RLF) handler or a carrier failure handler based on the result of the determination of the failure and the first side link carrier, wherein the carrier failure handler may be executed based on at least one of the connection state between the first terminal and the base station and the need for multi-carrier transmission.

[0051] Public Mode

[0052] Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In the accompanying drawings, it will be understood that the same reference numerals represent the same components. In addition, when it is considered that functions and configurations well-known in the art may unnecessarily obscure the essence of the present disclosure, detailed description thereof is omitted.

[0053] In the following description of the embodiments in the specification, descriptions of technologies that are well known in the art and not directly related to the present disclosure are omitted. This is to clearly convey the gist of the present disclosure by omitting unnecessary explanations.

[0054] For the same reason, some components may be exaggerated, omitted or schematically shown in the drawings. In addition, the size of each component does not fully reflect the actual size. In each of the drawings, the same or corresponding components are presented with the same reference numerals.

[0055] By referring to the following detailed description of the embodiments and the accompanying drawings, the advantages and features of the present disclosure and the methods for realizing the same can be more easily understood. However, the embodiments of the present disclosure can be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. On the contrary, these embodiments of the present disclosure are provided to make the present disclosure thorough and complete, and to fully convey the scope of the embodiments of the present disclosure to those of ordinary skill in the art. Therefore, the scope of the present disclosure will be limited only by the appended claims. In the specification, the same components are represented by the same reference numerals.

[0056] In this regard, it will be understood that the combination of the blocks in the flowchart or process flow diagram can be performed by computer program instructions. Because these computer program instructions can be loaded into a processor of a general-purpose computer, a special-purpose computer, or another programmable data processing device, the instructions executed by the processor of the computer or another programmable data processing device generate components for implementing the functions specified in the (multiple) flowchart boxes. Because these computer program instructions can also be stored in a computer-available or computer-readable memory that instructs a computer or another programmable data processing device to operate in a particular manner, the instructions stored in the computer-available or computer-readable memory can produce products including instruction components for implementing the functions specified in the (multiple) flowchart boxes. Because computer program instructions can also be loaded onto a computer or another programmable data processing device, a series of operating steps can be performed on a computer or another programmable device to generate a computer-implemented process, and therefore the instructions executed on a computer or another programmable device can provide steps for implementing the functions specified in the (multiple) flowchart boxes.

[0057] In addition, each frame of the flow chart may represent a module, a fragment or a code portion, which includes one or more executable instructions for performing (multiple) specific logical functions. It should also be noted that in some alternative embodiments, the functions mentioned in the frame may not occur in order. For example, depending on the functions involved, two consecutive frames may be performed substantially simultaneously or in reverse order.

[0058] In addition, the term "unit" or "... device" used in the embodiment refers to a software or hardware component that plays a role, such as a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC). However, the term "unit" or "... device" is not limited to software or hardware. The term "unit" or "... device" can be configured in an addressable storage medium, or can be configured to reproduce one or more processors. Therefore, for example, the term "unit" or "... device" can refer to components such as software components, object-oriented software components, class components and task components, and can include processes, functions, attributes, procedures, subroutines, program code segments, drivers, firmware, microcodes, circuits, data, databases, data structures, tables, arrays and variables. The functions provided in components and "units" or "... devices" can be combined into fewer components and "units" or "... devices", or can be further divided into additional components and "units" or "... devices". In addition, components and "units" or "... devices" can be implemented to operate one or more central processing units (CPUs) in a device or a secure multimedia card.

[0059] When describing the embodiments of the present disclosure in detail, in the 5G mobile communication standard defined by the Third Generation Partnership Project (3GPP) which is a mobile communication standard organization group, the new radio access network (RAN) (NR) as a radio access network and the packet core (fifth generation (5G) system, 5G core network or next generation (NG) core) as a core network are the main targets, but the basic concepts of the present disclosure can be modified without departing from the scope of the present disclosure, and can be applied to other communication systems based on similar technical backgrounds, and can be applied based on the determination of ordinary technicians in this field.

[0060] In the 5G system, a network data collection and analysis function (NWDAF) may be defined to support network automation. NWDAF refers to a network function for providing functions for analyzing and providing data collected through the 5G network. NWDAF may collect / store / analyze information from the 5G network and may provide results to an unspecified network function (NF), and the results of the analysis may be used independently by each NF.

[0061] Hereinafter, for convenience of description, the present disclosure may use some of the terms and names defined in the 3GPP Long Term Evolution (LTE) standard (standards for 5G, New Radio (NR), LTE or similar systems). However, the present disclosure is not limited to these terms and names, and can be equally applied to communication systems that conform to other standards.

[0062] The present disclosure provides an apparatus and method in which a terminal (user equipment (UE)) handles a failure that may occur while using at least one side link (SL) carrier, and the UE performs transmission / reception based on SL unicast, SL multicast, and SL broadcast in a wireless communication system.

[0063] Hereinafter, the present disclosure relates to a method and apparatus for controlling a SL secondary carrier in a wireless communication system. In detail, the present disclosure is for a UE to process a failure occurring in a carrier when at least one carrier is used so as to support SL communication between UEs, and the present disclosure may include operations for a UE and a base station (BS) to determine a carrier failure for repeated transmission of SL multi-carriers and to process the carrier failure. According to an embodiment of the present disclosure, in order to perform direct communication between UEs through SL, the UE processes a failure occurring in a carrier and continuously sends / receives data through SL, so that the reliability of transmission / reception can be enhanced.

[0064] As used in the following description, for the convenience of description, a term indicating a signal, a term indicating a channel, a term indicating control information, a term indicating a network entity, and a term indicating a device component are exemplified. Accordingly, the present disclosure is not limited to the terms used herein, and other terms indicating objects with equivalent technical meanings may be used.

[0065] As used in the following description, for the convenience of description, terms identifying access nodes, terms indicating network entities, terms indicating messages, terms indicating interfaces between network entities, and terms indicating various pieces of identification information are exemplified. Accordingly, the present disclosure is not limited to the terms to be described below, and other terms indicating objects with equivalent technical meanings may be used.

[0066] Hereinafter, the term "BS" refers to an entity for allocating resources to a UE, and may be used interchangeably with at least one of a next generation Node B (gNode B), an evolved Node B (eNode B), a Node B, a BS, a radio access unit, a BS controller, and a node on a network. Examples of UEs may include UEs, mobile stations (MS), cellular phones, smart phones, computers, and multimedia systems capable of performing communication functions. However, these are merely examples, and BSs and UEs are not limited thereto. In the present disclosure, for convenience of description, eNode B (eNB) may be used interchangeably with gNode B (gNB). That is, a BS described as an eNB may represent a gNB. In the present disclosure, the term "UE" may refer to various wireless communication devices as well as mobile phones, narrowband Internet of Things (NB-IoT) devices, and sensors.

[0067] In the following description, the terms "physical channel" and "signal" may be used interchangeably with data or control signal. For example, the term "physical downlink shared channel (PDSCH)" refers to a physical channel through which data is transmitted, but PDSCH may also be used to refer to data. That is, in the present disclosure, the expression "transmission physical channel" may be equivalently interpreted as the expression "transmission of data or signal through a physical channel".

[0068] Hereinafter, in the present disclosure, high-layer signaling refers to a signal transmission method by which a BS sends a signal to a UE by using a downlink (DL) data channel of a physical layer, or a UE sends a signal to a BS by using an uplink (UL) data channel of a physical layer. High-layer signaling may be understood as radio resource control (RRC) signaling or a media access control (MAC) control element (CE).

[0069] In addition, in the present disclosure, expressions such as "greater than" or "less than" are used to determine whether a specific condition is satisfied or reached, but these expressions are only used to describe examples and do not exclude the meaning of "greater than or equal to" or "less than or equal to". A condition written with "greater than or equal to" can be replaced with "greater than", a condition written with "less than or equal to" can be replaced with "less than", and a condition written with "greater than or equal to ... and less than or equal to ..." can be replaced with "greater than ... and less than or equal to ...".

[0070] In addition, in the present disclosure, the embodiments will now be described by using terms and names defined in some communication standards (eg, 3GPP), but these embodiments are only examples of the description. The embodiments of the present disclosure can be easily modified and applied to other communication systems.

[0071] Figure 1 is a diagram of a wireless communication system according to an embodiment of the present disclosure.

[0072] refer to Figure 1 , shows a wireless communication system including BS 110, UE 120, and UE 130 as a part of nodes using a wireless channel. Figure 1 Only one BS is shown, but the wireless communication system may also include another BS that is the same as or similar to the BS 110 .

[0073] BS 110 refers to a network infrastructure that provides wireless access to UEs 120 and 130. BS 110 may have a coverage area defined as a specific geographic area based on a range for transmitting signals. BS 110 may also be referred to as an access point (AP), eNB, 5G node, gNB, wireless point, transmission / reception point (TRP), or other terms with equivalent technical meanings.

[0074] Each of UE 120 and UE 130 may refer to a device used by a user, and may communicate with BS110 through a wireless channel. A link from BS110 to UE 120 or UE 130 may be referred to as DL, and a link from UE 120 or UE 130 to BS110 may be referred to as UL. In addition, UE 120 and UE 130 may communicate with each other through a wireless channel. In this case, the link between UE 120 and UE 130 is referred to as SL, and SL may also be referred to as a PC5 interface. In some cases, at least one of UE 120 and UE 130 may operate without involving a user. That is, at least one of UE 120 and UE 130 is a device for performing machine type communication (MTC), and may not be carried by a user. In addition to a terminal, each of UE 120 and UE 130 may also be referred to as a "UE", "MS", "subscriber station", "remote terminal", "wireless terminal", "user equipment", or other terms with equivalent technical meanings.

[0075] BS110, UE 120 and UE 130 can send and receive wireless signals in a millimeter wave (mmWave) band (e.g., 28 GHz, 30 GHz, 38 GHz or 60 GHz band). In this regard, in order to increase channel gain, BS110, UE 120 and UE 130 can perform beamforming. In this case, beamforming can include transmit beamforming and receive beamforming. That is, BS110, UE 120 and UE 130 can apply directivity to transmit signals or receive signals. To this end, BS110 and UE 120 and 130 can select service beams 112, 113, 121 and 131 through beam searching or beam management procedures. After selecting service beams 112, 113, 121 and 131, subsequent communications can be performed by using resources that are in a quasi-co-location (QCL) relationship with resources that transmit service beams 112, 113, 121 and 131.

[0076] The first antenna port and the second antenna port may be evaluated to be in a QCL relationship when a large-scale characteristic of a channel through which symbols on the first antenna port are transmitted can be inferred from a channel through which symbols on the second antenna port are transmitted. For example, the large-scale characteristic may include at least one of delay spread, Doppler spread, Doppler shift, average gain, average delay, and spatial receiver parameters.

[0077] Figure 1 The UE 120 and UE 130 shown may support vehicle communication. In the case of vehicle communication, in the LTE system, standardization of vehicle-to-everything (V2X) technology has been completed based on the device-to-device (D2D) communication structure in 3GPP Release 14 and Release 15, and recently, efforts have been made to develop V2X technology based on 5G NR. NR V2X will support unicast communication, groupcast (or multicast) communication, and broadcast communication between UEs. In addition, unlike LTE V2X which focuses on the transmission / reception of basic safety information for driving vehicles on the road, NR V2X focuses on providing further advanced services such as platooning, advanced driving, extended sensors, and remote driving.

[0078] V2X services can be divided into basic safety services and advanced services. Basic safety services may include detailed services such as collaborative awareness messages (CAM) or basic safety messages (BSM) services, left turn notification services, forward vehicle collision warning services, emergency vehicle approach notification services, forward obstacle warning services, and intersection signal information services, and V2X information may be sent / received by using broadcast, unicast, or multicast transmission methods. In advanced services, quality of service (QoS) requirements may be stronger than in basic safety services, and in order to send / receive V2X information within a specific vehicle group or to send / receive V2X information between two vehicles, a method of sending / receiving V2X information by using unicast and multicast transmission methods other than broadcast transmission methods is required. Advanced services may include detailed services such as platooning services, autonomous driving services, remote driving services, and extended sensor-based V2X services.

[0079] In the following, SL refers to the transmission / reception path of signals between UEs, and SL can be used interchangeably with the PC5 interface. BS is an entity that allocates resources to UE, and can support both V2X communication and general cellular communication, or can only support V2X communication. That is, BS can refer to NR BS (e.g., gNB), LTE BS (e.g., eNB) or road station unit (RSU). UE (or terminal) can include not only general UE or MS, but also vehicles supporting vehicle-to-vehicle (V2V) communication, vehicles supporting vehicle-to-pedestrian (V2P) communication or pedestrians' mobile phones (e.g., smart phones), vehicles supporting vehicle-to-network (V2N) communication, vehicles supporting vehicle-to-infrastructure (V2I) communication, RSUs with UE functions embedded therein, RSUs with BS functions embedded therein, or RSUs with part of BS functions and part of UE functions embedded therein. In addition, the V2X UE used in the following description may be referred to as UE. That is, in association with V2X communication, UE can be used as V2X UE.

[0080] The BS and the UE may be connected to each other through a Uu interface. UL refers to a radio link through which the UE sends data or a control signal to the BS, and DL refers to a radio link through which the BS sends data or a control signal to the UE.

[0081] Figure 2 is a block diagram of a configuration of a BS in a wireless communication system according to an embodiment of the present disclosure. Figure 2 The illustrated configuration may be understood as the configuration of the BS 110. The term "unit" or "device" used herein indicates a unit that processes at least one function or operation and may be implemented in hardware or software or in a combination of hardware and software.

[0082] refer to Figure 2 , BS 110 may include a wireless communicator 210, a backhaul communicator 220, a storage device 230, and a controller 240. However, the components of the BS are not limited to the foregoing examples. For example, the BS may include more or fewer components than those described above. In addition, the wireless communicator 210, the backhaul communicator 220, the storage device 230, and the controller 240 may be implemented in a single chip. In addition, the controller 240 may include at least one processor.

[0083] In one embodiment, wireless communicator 210 may perform the function of transmitting / receiving signals through a wireless channel. For example, wireless communicator 210 may perform conversion between a baseband signal and a bit string based on the physical layer specification of the system. For example, during data transmission, wireless communicator 210 may generate complex symbols by encoding and modulating the transmission bit string. In addition, during data reception, wireless communicator 210 may reconstruct the reception bit string by demodulating and decoding the baseband signal.

[0084] In addition, wireless communicator 210 may up-convert a baseband signal into a radio frequency (RF) band signal, and then may transmit the RF band signal via an antenna, and may down-convert an RF band signal received via an antenna into a baseband signal. To this end, wireless communicator 210 may include a transmit filter, a receive filter, an amplifier, a mixer, an oscillator, a digital-to-analog converter (DAC), an analog-to-digital converter (ADC), etc. In addition, wireless communicator 210 may include multiple transmit / receive paths. In addition, wireless communicator 210 may include at least one antenna array including multiple antenna elements.

[0085] In terms of hardware, wireless communicator 210 may be configured as a digital unit and an analog unit, and the analog unit may be configured as a plurality of sub-units depending on operating power, operating frequency, etc. The digital unit may be implemented as at least one processor (e.g., a digital signal processor (DSP)).

[0086] Wireless communicator 210 may transmit and receive signals as described above. Accordingly, all or some parts of wireless communicator 210 may be referred to as a "transmitter," "receiver," or "transceiver." In addition, in the following description, transmission and reception performed through a wireless channel may be used in the sense that the aforementioned processing is performed by wireless communicator 210.

[0087] The backhaul communicator 220 may provide an interface for communicating with other nodes in the network. That is, the backhaul communicator 220 may convert a bit string sent from the BS 110 to another node (e.g., another access node, another BS, a higher node, or a core network) into a physical signal, and may convert a physical signal received from another node into a bit string.

[0088] The storage device 230 may store data used for the operation of the BS 110, such as basic programs, applications, and configuration information. The storage device 230 may be configured as a volatile memory, a nonvolatile memory, or a combination of a volatile memory and a nonvolatile memory. In addition, the storage device 230 may provide the stored data at the request of the controller 240.

[0089] Controller 240 may control the overall operation of BS 110. For example, controller 240 may send and receive signals through wireless communicator 210 or backhaul communicator 220. In addition, controller 240 may write data to storage device 230 and read data from storage device 230. In addition, controller 240 may perform the functions of a protocol stack required by a communication standard. According to another embodiment, the protocol stack may be included in wireless communicator 210. To this end, controller 240 may include at least one processor. According to one embodiment, controller 240 may control BS 110 to perform operations according to an embodiment to be described below.

[0090] Figure 3 is a block diagram of a configuration of a UE in a wireless communication system according to an embodiment of the present disclosure.

[0091] Figure 3 The illustrated configuration may be understood as the configuration of UE 120. The term "unit" or "device" used herein indicates a unit that processes at least one function or operation and may be implemented in hardware or software or in a combination of hardware and software.

[0092] refer to Figure 3 , UE 120 may include a communicator 310, a storage device 320, and a controller 330. However, the components of UE 120 are not limited to the aforementioned examples. For example, UE 120 may include more or fewer components than the above components. In addition, the communicator 310, the storage device 320, and the controller 330 may be implemented in a single chip. In addition, the controller 330 may include at least one processor.

[0093] In one embodiment, the communicator 310 can perform a function for transmitting / receiving a signal through a wireless channel. For example, the communicator 310 can perform a conversion between a baseband signal and a bit string based on the physical layer specification of the system. For example, during data transmission, the communicator 310 can generate complex symbols by encoding and modulating the transmission bit string. In addition, during data reception, the communicator 310 can reconstruct the received bit string by demodulating and decoding the baseband signal. In addition, the communicator 310 can up-convert the baseband signal to an RF band signal, and then the RF band signal can be transmitted through an antenna, and the RF band signal received by the antenna can be down-converted to a baseband signal. For example, the communicator 310 may include a transmission filter, a reception filter, an amplifier, a mixer, an oscillator, a DAC, an ADC, etc.

[0094] In addition, the communicator 310 may include multiple transmit / receive paths. In addition, the communicator 310 may include at least one antenna array containing multiple antenna elements. In terms of hardware, the communicator 310 may be configured as a digital circuit and an analog circuit (e.g., a radio frequency integrated circuit (RFIC)). In this case, the digital circuit and the analog circuit may be implemented in one package. In addition, the communicator 310 may include multiple RF chains. In addition, the communicator 310 may perform beamforming.

[0095] The communicator 310 can transmit and receive signals as described above. Accordingly, all or some parts of the communicator 310 may be referred to as a "transmitter", "receiver" or "transceiver". In addition, in the following description, transmission and reception performed through a wireless channel may be used in the sense that the aforementioned processing is performed by the communicator 310.

[0096] The storage device 320 may store data used for the operation of the UE 120, such as basic programs, applications, or configuration information. The storage device 320 may be configured as a volatile memory, a non-volatile memory, or a combination of a volatile memory and a non-volatile memory. In addition, the storage device 320 may provide the stored data at the request of the controller 330.

[0097] The controller 330 controls the overall operation of the UE 120. For example, the controller 330 may send and receive signals through the communicator 310. In addition, the controller 330 may write data to the storage device 320 and read data from the storage device 320. In addition, the controller 330 may perform the functions of the protocol stack required by the communication standard. To this end, the controller 330 may include at least one processor or microprocessor, or may be a part of a processor. In addition, the communicator 310 and a part of the controller 330 may be referred to as a communication processor (CP). According to one embodiment, the controller 330 may control the UE 120 to perform the operation according to the embodiment to be described below.

[0098] Figure 4 A configuration of a communicator in a wireless communication system according to an embodiment of the present disclosure is shown.

[0099] Figure 4 Shows Figure 2 Wireless communicator 210 or Figure 3 An example of a detailed configuration of the communicator 310 is shown in FIG. Figure 4 Shown as Figure 2 Wireless communicator 210 or Figure 3 A component of a portion of the communicator 310 for performing beamforming.

[0100] refer to Figure 4 , the wireless communicator 210 or the communicator 310 may include an encoder and modulator 402 , a digital beamformer 404 , a plurality of transmission paths 406 - 1 to 406 -N, and an analog beamformer 408 .

[0101] The encoder and modulator 402 may perform channel coding. For channel coding, at least one of a low density parity check (LDPC) code, a convolutional code, or a polar code may be used. The encoder and modulator 402 may generate modulation symbols by performing constellation mapping.

[0102] The digital beamformer 404 may perform beamforming on a digital signal (e.g., a modulation symbol). To this end, the digital beamformer 404 may multiply the modulation symbol by a beamforming weight. In this case, the beamforming weight is used to change the amplitude and phase of the signal and may be referred to as a "precoding matrix," "precoder," etc. The digital beamformer 404 may output the modulation symbol digitally beamformed by the plurality of transmission paths 406-1 to 406-N. In this regard, according to a multiple-input multiple-output (MIMO) transmission technique, the modulation symbols may be multiplexed or the same modulation symbol may be provided to the plurality of transmission paths 406-1 to 406-N.

[0103] A plurality of transmission paths 406-1 to 406-N can convert a digital signal formed by digital beamforming into an analog signal. To this end, each of the plurality of transmission paths 406-1 to 406-N can include an inverse fast Fourier transform (IFFT) operator, a cyclic prefix (CP) inserter, a DAC, and an up-converter. The CP inserter is provided for an orthogonal frequency division multiplexing (OFDM) method and can be excluded when different physical layer methods (e.g., filter bank multi-carrier (FBMC)) are applied. That is, a plurality of transmission paths 406-1 to 406-N can provide independent signal processing processes to a plurality of streams generated by digital beamforming. However, depending on the implementation method, some components of the plurality of transmission paths 406-1 to 406-N can be used in common.

[0104] The analog beamformer 408 can perform beamforming on the analog signal. To this end, the digital beamformer 404 can multiply the analog signal by a beamforming weight. In this regard, the beamforming weight can be used to change the amplitude and phase of the signal. In detail, based on the connection structure between the multiple transmission paths 406-1 to 406-N and the antenna, the analog beamformer 408 can be configured differently. For example, each of the multiple transmission paths 406-1 to 406-N can be connected to an antenna array. As another example, each of the multiple transmission paths 406-1 to 406-N can be connected to an antenna array. In addition, as another example, the multiple transmission paths 406-1 to 406-N can be adaptively connected to an antenna array or at least two antenna arrays.

[0105] Figure 5 The structure of wireless time-frequency resources in a wireless communication system according to an embodiment of the present disclosure is shown.

[0106] refer to Figure 5 In the radio resource domain, the horizontal axis represents the time domain, and the vertical axis represents the frequency domain. The minimum transmission unit in the time domain is an OFDM symbol or a discrete Fourier transform spread (DFT-S)-OFDM symbol, and one time slot 505 may include N symb OFDM symbols or DFT-S-OFDM symbols 530. Unlike a time slot, in the NR system, the length of a subframe may be defined as 1.0 ms, and the length of a radio frame 500 may be defined as 10 ms. The minimum transmission unit in the frequency domain is a subcarrier, and the bandwidth of the entire system transmission band may include a total of N BW subcarriers 525. Such as N symb and N BW Specific values ​​such as may vary from system to system.

[0107] The basic unit in the time-frequency domain resource domain is a resource element (RE) 510, and the RE 510 can be represented by an OFDM symbol index or by a DFT-S-OFDM symbol index and a subcarrier index. A resource block (RB) 515 can be defined as N in the frequency domain. RB 520 consecutive subcarriers. Generally, the minimum transmission unit of data is an RB unit, and in the NR system, generally N symb =14, N RB =12.

[0108] like Figure 5 The structure of the wireless time-frequency resource shown in FIG. 1 can be applied to the Uu interface. Figure 5 The structure of the wireless time-frequency resources shown can be similarly applied to SL.

[0109] Fig. 6A An example of a scenario of SL communication according to an embodiment of the present disclosure is shown.

[0110] Fig. 6A An in-coverage scenario is shown, in which SL UEs 620a and 620b are located within the coverage of a base station 610. SL UEs 620a and 620b may receive data and control information from BS 610 via DL, or may transmit data and control information to BS 610 via UL. In this case, the data and control information may be data and control information for SL communication, or may be data and control information for general cellular communication other than SL communication. Fig. 6A In the embodiment, SL UE 620a and 620b can send / receive data and information used for SL communication through SL.

[0111] Figure 6B An example of a scenario of SL communication according to an embodiment of the present disclosure is shown.

[0112] refer to Figure 6B , shows partial coverage, in which, among the SL UEs, a first UE 620a is located within the coverage of the BS 610, and a second UE 620b is located outside the coverage of the BS 610. The first UE 620a located within the coverage of the BS 610 may receive data and control information from the BS 610 via DL, or may transmit data and control information to the BS 610 via UL. The second UE 620b located outside the coverage of the BS 610 may not receive data and control information from the BS 610 via DL, and may not transmit data and control information to the BS 610 via UL. The second UE 620b may transmit / receive data and control information for SL communication to / from the first UE 620a via SL.

[0113] Figure 6C An example of a scenario of SL communication according to an embodiment of the present disclosure is shown.

[0114] refer to Figure 6C , shows a situation where SL UEs (e.g., first UE 620a and second UE 620b) are located outside the coverage of the BS. Accordingly, the first UE 620a and second UE 620b cannot receive data and control information from the BS via DL, and cannot send data and control information to the BS via UL. The first UE 620a and second UE 620b can send and receive data and control information for SL communication via SL.

[0115] Fig.6D An example of a scenario of SL communication according to an embodiment of the present disclosure is shown.

[0116] refer to Fig.6D , the first UE 620a and the second UE 620b performing SL communication may perform inter-cell SL communication in a connection state (e.g., RRC connection state) with different BSs (e.g., the first BS 610a and the second BS 610b) or in a camping state (e.g., RRC connection release state, i.e., RRC idle state). In this case, the first UE 620a may be a SL sending UE, and the second UE 620b may be a SL receiving UE. Alternatively, the first UE 620a may be a SL receiving UE, and the second UE 620b may be a SL sending UE. The first UE 620a may receive a SL dedicated system information block (SIB) from the BS 610a to which the first UE 620a is connected (or where the first UE 620a is camping), and the second UE 620b may receive a SL dedicated SIB from another BS 610b to which the second UE 620b is connected (or where the second UE 620b is camping). In this case, information about the SL-dedicated SIB received by the first UE 620a may be different from information about the SL-dedicated SIB received by the second UE 620b. Accordingly, it is necessary to unify information to perform SL communication between UEs located in different cells.

[0117] In the above FIG. 6A to FIG. 6DIn the example, for the convenience of description, a SL system composed of two UEs (e.g., a first UE 620a and a second UE 620b) has been described as an example, but the present disclosure is not limited thereto and can be applied to a SL system in which two or more UEs participate. In addition, the UL and DL between BS 610, 610a and 610b and SL UEs 620a and 620b can be referred to as Uu interfaces, and the SL between SL UEs can be referred to as PC5 interfaces. In the following description, UL or DL, Uu interface, SL and PC5 can be used interchangeably.

[0118] In addition, in the present disclosure, UE may refer to a vehicle supporting V2V communication, a vehicle supporting V2P communication or a pedestrian's mobile phone (e.g., a smart phone), a vehicle supporting V2N communication, or a vehicle supporting V2I communication. In addition, in the present disclosure, UE may refer to an RSU in which a UE function is embedded, an RSU in which a BS function is embedded, or an RSU in which a part of a BS function and a part of a UE function are embedded.

[0119] Fig. 7A and Figure 7B is a diagram for describing a transmission method for SL communication according to an embodiment of the present disclosure.

[0120] In detail, Fig. 7A A unicast method is shown, and Figure 7B A multicast method is shown.

[0121] refer to Fig. 7A , the sending UE 720a and the receiving UE 720b can perform one-to-one communication. Fig. 7A The transmission method shown may be referred to as unicast communication. Figure 7B , the sending UE 720a or 720d and the receiving UEs 720b, 720c, 720e, 720f and 720g can perform one-to-many communication. Figure 7B The transmission method shown may be referred to as multicast or multicast communication. Figure 7B In the example, the first UE 720a, the second UE 720b, and the third UE 720c may form one group and perform multicast communication, and the fourth UE 720d, the fifth UE 720e, the sixth UE 720f, and the seventh UE 720g may form another group and perform multicast communication. The UE may perform multicast communication within the group to which the UE belongs, and may perform unicast, multicast, or broadcast communication with one or more other UEs belonging to different groups. For convenience of description, Figure 7B Two groups are shown in FIG. 1 , but the present disclosure is not limited thereto and can be applied to a case where a large number of groups are formed.

[0122] In addition, although not Fig. 7A or Figure 7B , but the SL UE can perform broadcast communication. Broadcast communication refers to a method in which all SL UEs receive data and control information sent by the SL sending UE through the SL. For example, Figure 7B In the embodiment, when the first UE 720a is a transmitting UE, other UEs 720b, 720c, 720d, 720e, 720f and 720g may receive data and control information sent by the first UE 720a.

[0123] The aforementioned SL unicast communication, multicast communication, and broadcast communication are supported in an in-coverage scenario, a partial coverage scenario, or an out-of-coverage scenario.

[0124] In the case of NR SL, unlike LTE SL, a transmission type that supports a vehicle UE sending data to only one specific UE through unicast and a transmission type that supports a vehicle UE sending data to multiple specific UEs through multicast can be considered. For example, when considering a service scenario in which two or more vehicles are connected to one network and the vehicles are allowed to move together in a cluster, such as platooning, such unicast and multicast technologies may be useful. In detail, unicast communication can be used to control one specific UE by the leader UE of a group connected through platooning, and multicast communication can be used to simultaneously control a group consisting of multiple specific UEs.

[0125] The following method can be used for resource allocation in a V2X system.

[0126] (1) Mode 1 resource allocation

[0127] Scheduling resource allocation is a method in which a BS allocates resources for SL transmission to an RRC-connected UE in a dedicated scheduling method. The scheduling resource allocation method may be effective for interference management and resource pool management (dynamic allocation and / or semi-persistent transmission) because the BS can manage SL resources. When there is data to be sent to (multiple) other UEs, the UE in RRC connected mode can send information indicating the presence of data to be sent to (multiple) other UEs to the BS by using an RRC message or a MAC CE. For example, the RRC message sent by the UE to the BS may include a SidelinkUEInformation or a UEAssistanceInformation message, and the MAC CE may correspond to a buffer status report (BSR) MAC CE, which includes an indicator indicating a BSR for V2X communication and at least one of information about the size of data buffered for SL communication, a scheduling request (SR), and the like.

[0128] (2) Mode 2 Resource Allocation

[0129] Second, UE autonomous resource selection is a method in which the SL transmission / reception resource pool for V2X is provided to the UE as system information or an RRC message (e.g., an RRCReconfiguration message or a PC5-RRC message) and the UE selects the resource pool and resources according to defined rules. UE autonomous resource selection may correspond to one or more of the following resource allocation methods.

[0130] >UE autonomously selects SL resources for transmission.

[0131] >UE assists other UEs in SL resource selection.

[0132] >The UE is configured with NR configuration grant for SL transmission.

[0133] >UE schedules SL transmission of other UEs.

[0134] -UE resource selection methods may include zone mapping, sensing-based resource selection, and random selection.

[0135] -In addition, even if the UE exists within the coverage of the BS, in the scheduled resource allocation or UE autonomous resource selection mode, resource allocation or resource selection may not be performed. In this case, even if the UE exists within the coverage of the BS, the UE can perform V2X SL communication in a UE random selection method through an exceptionally configured SL transmission / reception resource pool (exceptional resource pool).

[0136] -In addition, when the UE for V2X communication exists outside the coverage of the BS, the UE can perform V2X SL communication through a preset SL transmission / reception resource pool.

[0137] The UE may send / receive data to / from another UE through at least one SL carrier. The data transmission / reception through the SL carrier may include at least one of a unicast method, a multicast method, and a broadcast method. The data transmission / reception through at least one SL carrier may include multi-carrier transmission for sending / receiving different packets of each carrier. The data transmission / reception through at least one SL carrier may include packet repetition transmission (packet repetition) for sending / receiving the same packet on at least one carrier. For example, repeated transmission may refer to an operation of transmitting the same Packet Data Convergence Protocol (PDCP) packet of a SL radio bearer through at least one SL carrier. During the operation of sending / receiving SL data to / from another UE through at least one carrier, the UE may determine whether a failure occurs in any carrier. Next, the operations of the UE and the BS determining whether a failure occurs in the SL carrier during data transmission / reception and handling the failure are described with reference to various embodiments.

[0138] Fig. 8A and Figure 8B is a diagram for describing an operation of a UE processing a SL carrier failure according to an embodiment of the present disclosure.

[0139] According to an embodiment of the present disclosure, a method for a UE to manage a SL carrier in a wireless communication system may include: determining, by the UE, a failure of a secondary carrier, and sending the failure of the secondary carrier to a BS; determining, by the UE, a failure of the secondary carrier, and performing an operation of selecting / reselecting the secondary carrier; determining, by the UE, a failure of the secondary carrier, and sending the failure of the secondary carrier to a counterpart UE.

[0140] Fig. 8A The embodiments of the present invention may be applied to a case where a carrier used for multi-carrier transmission or repeated transmission is divided into a primary carrier or a non-primary carrier. Figure 8B The embodiments may be applied to the case where there is no separate division between carriers for multi-carrier transmission or repeated transmission.

[0141] refer to Fig. 8A , in operation 801, the UE may perform an operation of sending a packet through at least one SL carrier. In operation 803, the UE may determine a failure of the SL carrier. The method by which the UE determines a failure of the SL carrier in operation 803 is described below. When the UE determines a failure of the SL carrier in operation 803, the UE may determine whether the carrier on which the failure has occurred is a primary carrier in operation 805. When the UE determines in operation 805 that the carrier on which the failure has occurred is a primary carrier, the UE may determine in operation 807 that the failure is a SL radio link failure (RLF). When the UE determines in operation 805 that the carrier on which the failure has occurred is a non-primary carrier, the UE may perform a carrier failure handling procedure in operation 809. In one embodiment, the UE may determine to continue using the non-primary carrier on which the failure has occurred by performing a carrier failure handling procedure on the non-primary carrier on which the failure has occurred until a new carrier is configured. In another embodiment, the UE may determine to suspend the use of the non-primary carrier on which the failure has occurred, while performing a carrier failure handling procedure on the non-primary carrier on which the failure has occurred. Reference will be made to 9A to 12B The detailed operation of suspending and resuming the use of the non-primary carrier in which a failure has occurred is described in an embodiment of the present invention. When the UE determines in operation 803 that no failure has occurred in the SL carrier, the UE may proceed to operation 811. In one embodiment, when the UE determines in operation 807 that the failure is an SLRLF, the access layer (AS) of the UE may send an RLF indication (e.g., a PC5 RRC failure indication) to an upper layer (e.g., a V2X layer). When it is determined that the failure is an RLF, the AS layer of the UE may send an RLF indication to the network (NW). This corresponds to a case where the UE is connected to the NW.

[0142] The RLF indication sent by the UE to the NW may include the following embodiments.

[0143]

[0144] refer to Figure 8B , in operation 851, the UE may perform an operation of sending a packet through at least one SL carrier. In operation 853, the UE may determine a failure of the SL carrier. The following describes a method by which the UE determines a failure of the SL carrier in operation 853. When the UE determines in operation 853 that a failure has occurred in the SL carrier, the UE may determine in operation 855 whether there is an available carrier among the SL carriers used for packet transmission. When the UE determines in operation 855 that there is no available carrier, the UE may determine in operation 857 that the failure is a SL RLF. When the UE determines in operation 855 that there is an available carrier, the UE may perform a carrier failure handling procedure in operation 859. When it is not determined in operation 853 that a failure has occurred in the SL carrier, the UE may proceed to operation 861. In one embodiment, the UE may determine to continue using the carrier in which the failure has occurred by performing a carrier failure handling procedure on the carrier in which the failure has occurred until a new carrier is configured. In another embodiment, the UE may determine to suspend the use of the carrier in which the failure has occurred while performing a carrier failure handling procedure on the carrier in which the failure has occurred. Detailed operations of suspending and resuming use of a carrier in which a failure has occurred will be described with reference to the embodiments of FIGS. 9 to 12 .

[0145] exist Fig. 8A Operation 803 and Figure 8B The criteria for determining whether a failure has occurred in the SL carrier in operation 853 may include at least one or a combination of the following cases.

[0146] (1) When determining that a radio link control (RLC) packet retransmission of a packet transmitted through the SL carrier has reached a maximum value, the UE may determine that the SL carrier is in a failure state.

[0147] (2) When it is determined that the Hybrid Automatic Repeat Request (HARQ) Negative Acknowledgement (NACK) (i.e., HARQ Discontinuous Transmission (HARQ DTX)) of the packet transmitted through the SL carrier has reached a maximum value, the UE may determine that the SL carrier is in a fault state. In one embodiment, the UE may determine whether the HARQ NACK (i.e., HARQ DTX) has reached a maximum value for a certain time. In another embodiment, the UE may determine whether the HARQ NACK (i.e., HARQ DTX) has reached a maximum value regardless of the time.

[0148] (3) When it is determined that the continuous out-of-sync (synch) (hereinafter referred to as OOS) of the SL carrier has reached a maximum value, the UE may determine that the SL carrier is in a fault state. In one embodiment, the UE may determine whether the continuous OOS has reached a maximum value for a certain time. In another embodiment, the UE may determine whether the continuous OOS has reached a maximum value regardless of the time.

[0149] (4) When it is determined that the SL measurement value of the SL carrier is lower than the set threshold, the UE can determine that the SL carrier is in a fault state. For example, for the measurement of the SL carrier, the DMRS reference signal can be measured, and the measurement value and threshold of the SL carrier can be defined as, for example, the SL-RSRP value. When it is determined that the measurement value SL-RSRP of the DMRS reference signal of the SL carrier is lower than the set threshold SL-RSRP, the UE can determine that the SL carrier is in a fault state.

[0150] (5) When it is determined that the measured value of the channel busy ratio of the SL carrier is higher than the set threshold, that is, when it is determined that the SL carrier is busy, the UE can determine that the SL carrier is in a fault state. For example, the channel busy ratio of the SL carrier can be determined as the ratio of the transmission resources determined to be in use by the SL carrier to all transmission resources of the SL carrier. When the SL carrier is configured with at least one transmission resource pool, the UE can measure the channel busy ratio of the transmission resource pool currently set and used, and determine whether there is a fault in the SL carrier.

[0151] Table 1 shows the Fig. 8A An example of operations of an embodiment of the present invention used by a UE to determine carrier failure based on RLC packet retransmissions.

[0152] [Table 1]

[0153]

[0154] Table 2 shows the Figure 8B An example of operations of an embodiment of the present invention used by a UE to determine carrier failure based on RLC packet retransmissions.

[0155] [Table 2]

[0156]

[0157] When UE Fig. 8A Operation 807 and Figure 8BWhen it is determined in operation 857 that SL RLF has occurred, in one embodiment, the AS layer of the UE may send a SL RLF occurrence notification (e.g., PC5 RRC failure indication) to an upper layer (e.g., V2X layer) of the UE. In one embodiment, when the UE is connected to the BS (i.e., when the UE is in the RRC_CONNECTED state), the UE may send a SL RLF occurrence notification to the BS. When the UE sends the SL RLF occurrence notification to the BS, the UE may additionally report information about at least one carrier in use and in which a failure is determined, a channel congestion level measurement result of a transmission resource pool of at least one carrier in use and in which a failure is determined, and at least one of a packet reception ratio of at least one carrier in use and in which a failure is determined, or a combination thereof.

[0158] In other words, consider Fig. 8A and Figure 8B In both embodiments, a UE may send a packet to another UE via a SL carrier, determine a failure of the SL carrier based on the sent packet, and determine whether to perform an RLF handling procedure or a carrier failure handling procedure based on a result of the determination and the SL carrier.

[0159] In addition, the UE may determine whether the SL carrier is a primary carrier, and may determine whether to perform an RLF handling procedure or a carrier failure handling procedure based on a result of the determination.

[0160] In addition, the UE may determine whether there is an available carrier other than the SL carrier, and may determine whether to perform the RLF handling procedure or the carrier failure handling procedure based on a result of the determination.

[0161] Fig. 9A , Fig. 9B and Fig. 9C is a diagram for describing an operation of a UE processing a SL carrier failure according to an embodiment of the present disclosure.

[0162] According to an embodiment of the present disclosure, Fig. 9A , Fig. 9B and Fig. 9C The carrier fault handler can correspond to Fig. 8A and Figure 8B Carrier fault handling procedures 809 and 859.

[0163] refer to Fig. 9A , shows an operation method in which a UE performs a carrier failure handling procedure without suspending the use of a carrier determined to have failed. When the UE receives configuration information about a new carrier or repeated transmission is disabled, by performing Fig. 9AAlternatively, when the UE receives configuration information about a new carrier and repeated transmission is disabled, by performing Fig. 9A According to the procedure, the UE may suspend the use of the carrier determined to have failed (failed carrier). For example, when repeated transmission is disabled, the UE may determine that multi-carrier transmission is not required.

[0164] In one embodiment, the UE may initiate a carrier failure handling procedure in operation 901. In operation 903, the UE may determine whether the UE is connected to the BS (RRC_CONNECTED). When the UE determines in operation 903 that the UE is connected to the BS, the UE may perform a carrier failure reporting procedure in operation 905. The BS may receive a carrier failure report message from the UE, determine the UE's need for a new carrier, and, when necessary, configure new carrier information for the UE. When the UE determines in operation 903 that the UE is not connected to the BS (one of RRC_IDLE, RRC_INACTIVE, or OUT-OF-COVERAGE), the UE may determine in operation 907 whether a multi-carrier use condition is valid or whether a repeated transmission execution condition is valid. For example, when the repeated transmission execution condition is valid, it may be necessary to use multiple carriers. When it is determined in operation 907 that the multi-carrier use condition is valid or the repeated transmission execution condition is valid, the UE may perform a carrier selection / reselection procedure in operation 909. That is, when it is necessary to perform repeated transmission, the UE may determine that a procedure for selecting a carrier through which packets are to be repeatedly transmitted is necessary. When it is determined that the multi-carrier use condition is valid or the repeated transmission execution condition is valid, the UE in the RRC_IDLE / RRC_INACTIVE state or the UE in the OUT-OF-COVERAGE state can perform an operation of selecting / reselecting a carrier based on the configuration of the system information message or the pre-configured configuration. When it is determined that it is no longer necessary to perform multi-carrier transmission or to perform repeated transmission, the UE can determine that the procedure for selecting a carrier through which packets will be repeatedly transmitted is unnecessary. For example, when it is no longer necessary to perform repeated transmission, it may not be necessary to use multiple carriers. When it is determined in operation 907 that the multi-carrier use condition is invalid or the repeated transmission execution condition is invalid, the UE can proceed to operation 911 to end the carrier failure handling procedure.

[0165] Fig. 9B The UE suspends the use of a carrier determined to have failed and performs a carrier failure handling procedure. Fig. 9B, the UE may initiate a carrier failure handling procedure in operation 951. In operation 953, the UE may suspend the use of the carrier (faulty carrier) determined to have failed. In operation 955, the UE may determine whether the UE is connected to the BS (RRC_CONNECTED). When it is determined in operation 955 that the UE is connected to the BS, in operation 957, the UE may perform a carrier failure reporting procedure. That is, the UE may perform a reporting procedure for the carrier determined to have failed. The BS may receive a carrier failure report message from the UE, determine the need for a new carrier for the UE, and configure new carrier information for the UE when necessary. When the UE determines in operation 955 that the UE is not connected to the BS (one of RRC_IDLE, RRC_INACTIVE, or OUT-OF-COVERAGE), the UE may determine in operation 959 whether a multi-carrier usage condition is valid or whether a repeated transmission execution condition is valid. When it is determined that the multi-carrier usage condition is valid or the repeated transmission execution condition is valid, the UE in the RRC_IDLE / RRC_INACTIVE state or the UE in the OUT-OF-COVERAGE state can perform the operation of selecting / reselecting the carrier based on the configuration of the system information message or the pre-configured configuration. When it is determined in operation 959 that the multi-carrier usage condition is valid or the repeated transmission execution condition is valid, the UE can perform the carrier selection / reselection procedure in operation 961. That is, when it is necessary to perform repeated transmission, the UE can determine that a procedure for selecting a carrier through which packets will be repeatedly transmitted is necessary. When it is determined that it is no longer necessary to perform repeated transmission, the UE can determine that a procedure for selecting a carrier through which packets will be repeatedly transmitted is unnecessary. When it is determined in operation 959 that the multi-carrier usage condition is invalid or the repeated transmission execution condition is invalid, the UE can proceed to operation 963 to end the carrier failure handling procedure.

[0166] Fig. 9C The UE suspends the use of a carrier determined to be faulty (faulty carrier) while performing a reporting procedure on the carrier determined to be faulty. Fig. 9C , the UE may initiate a carrier failure handling procedure in operation 981. In operation 983, the UE may determine whether the UE is connected to the BS (RRC_CONNECTED). In one embodiment, when it is determined in operation 983 that the UE is connected to the BS, in operation 985, the UE may suspend the use of the carrier determined to have failed. The UE may perform a carrier failure reporting procedure in operation 987. In another embodiment, after performing the carrier failure reporting procedure in operation 987, the UE may suspend the use of the carrier determined to have failed. The BS may receive a carrier failure report message from the UE, determine the UE's need for a new carrier, and, when necessary, configure new carrier information for the UE.

[0167] When it is determined in operation 983 that the UE is not connected to the BS (one of RRC_IDLE, RRC_INACTIVE, or OUT-OF-COVERAGE), the UE may determine in operation 989 whether the multi-carrier transmission condition is valid or whether the repeated transmission execution condition is valid. When it is determined that the multi-carrier transmission condition is valid or the repeated transmission execution condition is valid, the UE in the RRC_IDLE / RRC_INACTIVE state or the UE in the OUT-OF-COVERAGE state may perform an operation of selecting / reselecting a carrier based on the configuration of the system information message or the pre-configured configuration. When it is determined in operation 989 that the multi-carrier transmission condition is valid or the repeated transmission execution condition is valid, the UE may perform a carrier selection / reselection procedure in operation 991. That is, when it is necessary to perform repeated transmission, the UE may determine that a procedure for selecting a carrier through which packets are to be repeatedly transmitted is necessary. When it is determined that it is no longer necessary to perform repeated transmission, the UE may determine that a procedure for selecting a carrier through which packets are to be repeatedly transmitted is unnecessary. When it is determined in operation 989 that the multi-carrier transmission condition is invalid or the repeated transmission execution condition is invalid, the UE may proceed to operation 993 to end the carrier failure handling procedure.

[0168] The operation of the reporting procedure for the carrier determined to have failed (failed carrier) performed by the UE in operations 905, 957 and / or 987 may include an embodiment of the SLFailureInformation message in [Table 3]. The SLFailureInformation message may be replaced with a SidelinkUEInformationNR message.

[0169] [Table 3]

[0170]

[0171] An embodiment of the SLFailureInformation message transmitted by the UE to the BS in operations 905, 957 and / or 987 may be shown in [Table 4].

[0172] [Table 4]

[0173]

[0174] The SLFailureInformation message in operations 905, 957 and / or 987 may include at least one or a combination of the information fragments in [Table 5].

[0175] [Table 5]

[0176]

[0177] In operations 905, 957, and / or 987, the UE may report at least one of a channel congestion level measurement result of a transmission resource pool of at least one carrier in use and in which a fault is determined, a packet reception ratio of at least one carrier in use and in which a fault is determined, and a channel measurement result value of at least one carrier in use and in which a fault is determined, or a combination thereof. The UE may report at least one of a channel congestion level measurement result of a transmission resource pool of at least one carrier in use, a packet reception ratio of at least one carrier in use, and a channel measurement result value of at least one carrier in use and in which a fault is determined, or a combination thereof.

[0178] In operations 905, 957, and / or 987, the UE may report information about at least one new carrier determined to be available to the BS. Figures 9A to 9C , the UE may determine whether to perform a reporting procedure for a carrier determined to have failed (faulty carrier) based on the connection status with the BS, and may determine whether to perform a carrier selection / reselection procedure based on whether multi-carrier transmission is valid or whether repeated transmission is valid. In addition, the UE may suspend the use of the carrier determined to have failed (faulty carrier), delete the configuration of the carrier, and perform an operation to determine the connection status with the BS. Alternatively, the UE may not suspend the use of the carrier determined to have failed (faulty carrier), or after performing an operation to determine the connection status with the BS, the UE may suspend the use of the carrier determined to have failed (faulty carrier) and delete the configuration of the carrier.

[0179] Fig. 10A and Fig. 10B is a diagram for describing an operation of a UE processing a SL carrier failure according to an embodiment of the present disclosure.

[0180] According to an embodiment of the present disclosure, Fig. 10A and Fig. 10B The carrier fault handler can correspond to Fig. 8A and Figure 8B Carrier fault handling procedures 809 and 859.

[0181] Fig. 10A The operation of the UE suspending the use of a carrier determined to have failed and performing a carrier failure handling procedure is shown. Fig. 10AIn operation 1001, the UE may initiate a carrier failure handling procedure. In operation 1003, the UE may suspend the use of the carrier determined to have failed (faulty carrier) and delete the configuration of the carrier. In operation 1005, the UE may determine whether the UE is connected to the BS (RRC_CONNECTED). When the UE determines in operation 1005 that the UE is connected to the BS, the UE may perform a carrier failure reporting procedure in operation 1007. The BS may receive a carrier failure report message from the UE, determine the UE's need for a new carrier, and, when necessary, configure new carrier information for the UE. The carrier failure reporting procedure in operation 1007 may be the same as that described above with reference to FIG. Fig. 9A The same as operation 905 described above. When it is determined in operation 1005 that the UE is not connected to the BS (one of RRC_IDLE, RRC_INACTIVE, or OUT-OF-COVERAGE), the UE may perform a carrier selection / reselection procedure in operation 1009. When it is determined that the multi-carrier use condition is valid or the repeated transmission execution condition is valid, the UE in the RRC_IDLE / RRC_INACTIVE state or the UE in the OUT-OF-COVERAGE state may perform an operation of selecting / reselecting a carrier based on a configuration of a system information message or a pre-configured configuration.

[0182] Fig. 10B The operation of the UE performing the carrier failure handling procedure without suspending the use of the carrier determined to have failed is shown. Fig. 10B When the UE obtains configuration information about the new carrier by performing a carrier selection / reselection procedure, the UE may suspend the use of the carrier determined to have failed (faulty carrier). In one embodiment, when the UE itself performs a carrier selection / reselection procedure, the configuration information about the new carrier may be obtained. In another embodiment, the configuration information about the new carrier may be obtained from the BS. That is, the BS may receive a carrier failure report message from the UE, determine the UE's need for a new carrier, and, when necessary, configure new carrier information for the UE. When the UE performs a carrier selection / reselection procedure by performing a carrier selection / reselection procedure, the BS may suspend the use of the carrier determined to have failed (faulty carrier). In one embodiment, when the UE performs a carrier selection / reselection procedure by itself, the configuration information about the new carrier may be obtained. In another embodiment, the configuration information about the new carrier may be obtained from the BS. That is, the BS may receive a carrier failure report message from the UE, determine the UE's need for a new carrier, and, when necessary, configure new carrier information for the UE. Fig. 10B When it is determined that repeated transmission is disabled according to the procedure, the UE may suspend the use of the carrier determined to have failed (faulty carrier) and delete the configuration of the carrier.

[0183] refer to Fig. 10B , the UE may initiate a carrier failure handling procedure in operation 1051. In operation 1053, the UE may determine whether the UE is connected to the BS (RRC_CONNECTED). When the UE determines in operation 1053 that the UE is connected to the BS, the UE may perform a carrier failure reporting procedure in operation 1055. The carrier failure reporting procedure in operation 1055 may be the same as that described above with reference to Fig. 9AThe BS may receive a carrier failure report message from the UE, determine the UE's need for a new carrier, and, when necessary, configure new carrier information for the UE. When it is determined in operation 1053 that the UE is not connected to the BS (one of RRC_IDLE, RRC_INACTIVE, or OUT-OF-COVERAGE), the UE may perform a carrier selection / reselection procedure in operation 1057. When it is determined that a multi-carrier usage condition is valid or a repeated transmission execution condition is valid, a UE in the RRC_IDLE / RRC_INACTIVE state or a UE in the OUT-OF-COVERAGE state may perform an operation of selecting / reselecting a carrier based on a configuration of a system information message or a pre-configured configuration. In other words, based on Fig. 10A or Fig. 10B , based on the connection status with the BS, the UE may determine whether to perform a reporting procedure for the carrier where a failure has occurred (alternatively, a new carrier may be configured by the BS), or may determine whether to perform a carrier selection / reselection procedure. In addition, the UE may suspend the use of the carrier where a failure has occurred (failure carrier), delete the configuration of the carrier, and perform a procedure for determining the connection status with the BS. Alternatively, the UE may not suspend the use of the failure carrier, or after performing the procedure for determining the connection status with the BS, may suspend the use of the failure carrier and delete the configuration of the carrier.

[0184] Fig.11A and Fig. 11B is a diagram for describing an operation of a UE processing a SL carrier failure according to an embodiment of the present disclosure.

[0185] According to an embodiment of the present disclosure, Fig.11A and Fig. 11B The carrier fault handler can correspond to Fig. 8A and Figure 8B Carrier fault handling procedures 809 and 859.

[0186] Fig.11A The UE suspends the use of a carrier determined to be faulty (faulty carrier) and deletes the configuration of the carrier, while performing a reporting procedure for the carrier determined to be faulty. Fig.11A , the UE may initiate a carrier failure handling procedure in operation 1101. In operation 1103, the UE may determine whether the UE is connected to the BS (RRC_CONNECTED). In one embodiment, when it is determined in operation 1103 that the UE is connected to the BS, in operation 1105, the UE may suspend the use of the carrier determined to have failed and delete the configuration of the carrier. The UE may perform a carrier failure reporting procedure in operation 1107. The carrier failure reporting procedure in operation 1107 may be the same as described above with reference to Fig. 9AThe same as operation 905 described above. In another embodiment, after performing the carrier failure reporting procedure in operation 1107, the UE may suspend the use of the carrier determined to have failed and delete the configuration of the carrier. The BS may receive a carrier failure report message from the UE, determine the UE's need for a new carrier, and configure new carrier information for the UE when necessary. When it is determined in operation 1103 that the UE is not connected to the BS (one of RRC_IDLE, RRC_INACTIVE, or OUT-OF-COVERAGE), the UE may perform a carrier selection / reselection procedure in operation 1109. When it is determined that a multi-carrier usage condition is valid or a repeated transmission execution condition is valid, a UE in an RRC_IDLE / RRC_INACTIVE state or a UE in an OUT-OF-COVERAGE state may perform an operation of selecting / reselecting a carrier based on the configuration of a system information message or a pre-configured configuration.

[0187] Fig. 11B The operation of the UE suspending the use of a carrier determined to have failed while performing a carrier selection / reselection procedure is shown. Fig. 11B , the UE may initiate a carrier failure handling procedure in operation 1151. In operation 1153, the UE may determine whether the UE is connected to the BS (RRC_CONNECTED). When the UE determines in operation 1153 that the UE is connected to the BS, the UE may perform a carrier failure reporting procedure in operation 1155. The carrier failure reporting procedure in operation 1155 may be the same as that in the above reference. Fig. 9A The operation 905 described above is the same. The BS may receive a carrier failure report message from the UE, determine the UE's need for a new carrier, and, when necessary, configure new carrier information for the UE. In one embodiment, when it is determined in operation 1153 that the UE is not connected to the BS (one of RRC_IDLE, RRC_INACTIVE, or OUT-OF-COVERAGE), the UE may suspend the use of the carrier determined to have failed, and delete the configuration of the carrier. In addition, the UE may perform a carrier selection / reselection procedure in operation 1159. When it is determined that a multi-carrier usage condition is valid or a repeated transmission execution condition is valid, a UE in an RRC_IDLE / RRC_INACTIVE state or a UE in an OUT-OF-COVERAGE state may perform an operation of selecting / reselecting a carrier based on the configuration of a system information message or a pre-configured configuration. In another embodiment, after performing the carrier selection / reselection procedure in operation 1159, the UE may suspend the use of the carrier determined to have failed, and delete the configuration of the carrier. In other words, based on Fig.11A or Fig. 11BBased on the connection status with the BS, the UE can determine whether to perform a reporting procedure for the carrier determined to have failed (faulty carrier), or can determine whether to perform a carrier selection / reselection procedure. In addition, the UE can determine the connection status with the BS, and when the UE is connected to the BS, the use of the carrier determined to have failed (faulty carrier) can be suspended and the configuration of the carrier can be deleted, or when the UE is not connected to the BS, the use of the carrier determined to have failed (faulty carrier) can be suspended and the configuration of the carrier can be deleted.

[0188] Fig. 12A and Fig. 12B is a diagram for describing an operation of a UE processing a SL carrier failure according to an embodiment of the present disclosure.

[0189] According to an embodiment of the present disclosure, Fig. 12A and Fig. 12B The carrier fault handler can correspond to Fig. 8A and Figure 8B Carrier fault handling procedures 809 and 859.

[0190] refer to Fig. 12A , illustrates operations for a UE to determine a failure of a carrier, perform carrier selection / reselection, and then report the failure to a BS when it is determined that there is no available carrier. Fig. 12A It is shown that the UE may determine to continue to use the carrier determined to have failed while performing a carrier failure handling procedure, or may suspend the use of the carrier determined to have failed while performing a reporting procedure for the carrier determined to have failed (failed carrier). In one embodiment, the UE may initiate a carrier failure handling procedure in operation 1201. The UE may perform a carrier selection / reselection procedure in operation 1203. While performing the carrier selection / reselection procedure, in operation 1205, the UE may determine whether there is an available carrier. When it is determined that there is an available carrier according to the determination in operation 1205, the UE may proceed to operation 1211. In operation 1211, the UE may suspend the use of the carrier determined to have failed. When it is determined in operation 1205 that there is no available carrier, in operation 1207, the UE may determine whether the UE is connected to the BS (RRC_CONNECTED). When it is determined in operation 1207 that the UE is connected to the BS, the UE may perform a carrier failure reporting procedure in operation 1209. The carrier failure reporting procedure in operation 1209 may be the same as that described in the above reference. Fig. 9AThe same as operation 905 described above. The UE may suspend the use of the carrier determined to have failed. The BS may receive a carrier failure report message from the UE, determine the need of the UE for a new carrier, and configure new carrier information for the UE when necessary. When it is determined in operation 1207 that the UE is not connected to the BS (one of RRC_IDLE, RRC_INACTIVE, or OUT-OF-COVERAGE), the UE may perform operation 1203. That is, when it is determined that the multi-carrier use condition is valid or the repeated transmission execution condition is valid, the UE in the RRC_IDLE / RRC_INACTIVE state or the UE in the OUT-OF-COVERAGE state may perform an operation of selecting / reselecting a carrier based on the configuration of the system information message or the pre-configured configuration. In the case of operation 1211 in which it is determined in operation 1205 that there is an available carrier, or when it is determined in operation 1205 that there is no available carrier and after it is determined in operation 1207 that the UE is connected to the BS, when a failure report message is sent to the BS in operation 1209, the UE may suspend the use of the carrier determined to have failed (failure carrier).

[0191] refer to Fig. 12B , illustrates operations for a UE to determine a failure of a carrier, perform a carrier selection / reselection procedure, and then report the failure to a BS when it is determined that there is no available carrier. Fig. 12B The operation of the UE suspending the use of a carrier determined to have failed and performing a carrier failure handling procedure is shown. In one embodiment, the UE may initiate a carrier failure handling procedure in operation 1251. In operation 1253, the UE may suspend the use of a carrier determined to have failed. The UE may perform a carrier selection / reselection procedure in operation 1255. While performing the carrier selection / reselection procedure, in operation 1257, the UE may determine whether there is an available carrier. When it is determined that there is an available carrier according to the determination in operation 1257, the UE may proceed to operation 1263. When it is determined in operation 1257 that there is no available carrier, in operation 1259, the UE may determine whether the UE is connected to the BS (RRC_CONNECTED). When it is determined in operation 1259 that the UE is connected to the BS, the UE may perform a carrier failure reporting procedure in operation 1261. The carrier failure reporting procedure in operation 1261 may be the same as that described above with reference to FIG. Fig. 9A The BS may receive a carrier failure report message from the UE, determine the need of the UE for a new carrier, and, when necessary, configure new carrier information for the UE. When it is determined in operation 1259 that the UE is not connected to the BS (i.e., when it is determined that the state is one of RRC_IDLE, RRC_INACTIVE, or OUT-OF-COVERAGE), the UE may perform operation 1255. In other words, based on Fig. 12A or Fig. 12B , the UE can determine whether there is an available carrier, and when there is no available carrier, determine whether to perform a reporting procedure for the carrier determined to have failed (faulty carrier) based on the connection status with the BS, and determine whether to perform a carrier selection / reselection procedure based on the effectiveness of repeated transmission. In addition, after sending a fault report message to the BS, the UE can suspend the use of the carrier determined to have failed (faulty carrier) and perform a carrier selection / reselection procedure, may not suspend the use of the carrier determined to have failed (faulty carrier), or may suspend the use of the carrier determined to have failed (faulty carrier).

[0192] Fig.13 is a diagram for describing an operation of a UE processing carrier selection / reselection due to SL carrier failure according to an embodiment of the present disclosure.

[0193] According to an embodiment of the present disclosure, Fig.13 The carrier selection / reselection procedure may correspond to Fig. 9A , Fig. 9B and Fig. 9C The carrier selection / reselection procedures 909, 961 and 991, Fig. 10A and Fig. 10B The carrier selection / reselection procedures 1009 and 1057, Fig.11A and Fig. 11B The carrier selection / reselection procedures 1109 and 1159, and Fig. 12A and Fig. 12B Carrier selection / reselection procedures 1203 and 1255.

[0194] refer to Fig.13, the UE may determine in operation 1301 to initiate a carrier selection / reselection procedure. In operation 1303, the UE may determine whether a configuration for a carrier selection condition is obtained. The carrier selection condition may include at least one or a combination of a condition for selecting a carrier for a logical channel, a condition for selecting a carrier for an SL stream, and a condition for selecting a carrier for an SL bearer. The condition may be configured based on at least one or a combination of a channel congestion level, a reliability required for an SL stream, a reliability required for an SL bearer, a delay budget required for an SL stream, and a delay budget required for an SL bearer. The configuration of the carrier selection condition may be obtained through network configuration information, or may be obtained through preconfigured information. According to the configuration of the carrier selection condition, the UE may select a carrier through which multi-carrier transmission or repeated transmission is performed. In addition, when the UE selects a new carrier for unicast communication based on multi-carrier transmission or repeated transmission with the peer UE, taking into account the capability information about the SL band support of the UE itself and the peer UE (a list of supportable bands for a SL band combination only or for a SL / Uu band combination), the UE may select a SL carrier supported by two UEs for multi-carrier transmission or repeated transmission. In operation 1305, the UE may determine whether any carrier satisfies the carrier selection condition. When it is determined in operation 1307 that any carrier satisfies the carrier selection condition, the UE may select the carrier in operation 1309. When one or more carriers satisfying the carrier selection condition are selected according to the determination in operation 1309, the UE may determine a carrier by at least one or a combination of the following methods: (1) a method of randomly selecting a carrier from among a plurality of carriers; (2) a method of selecting a carrier with the lowest channel congestion level from among a plurality of carriers; (3) a method of selecting a carrier with the best SL signal quality (e.g., SL reference signal received power (SL-RSRP)) from among a plurality of carriers; and (4) a method of selecting the first carrier satisfying the carrier selection condition. When it is determined in operation 1307 that no carrier satisfies the carrier selection condition, the UE may not select a carrier in operation 1311.

[0195] In one embodiment, when executing Fig.13 While performing the carrier selection / reselection procedure, the UE may continue to use the carrier determined to have failed. The use of the carrier determined to have failed may continue until a new carrier is selected. In another embodiment, the UE may suspend the use of the carrier determined to have failed and perform Fig.13 Carrier selection / reselection procedures.

[0196] exist FIG. 8A to FIG. 13 The operations of the network receiving the SLFailureInformation message sent by the UE in the procedure may include the following operations.

[0197] When the network receives the SLFailureInformation message, considering the information reported together with the SLFailureInformation message, the SL capability information about the UE, the capability information about the SL band support of the UE (only for SL band combination or for the list of supportable bands for SL / Uu band combination), available carrier information, carrier channel congestion level and carrier signal quality, the network can configure the carrier configuration information for the UE by selecting another carrier to be used for repeated transmission and multi-carrier transmission. The network can instruct the UE and other UEs to measure and report channel congestion levels for carriers and resource pools. The network can adjust the transmission parameters for carriers and resource pools (for example, carrier set information, reference parameters for activating repeated transmission, transmission power, modulation and coding scheme (MCS) level, or number of HARQ retransmissions), and send configuration information about the new transmission parameters to the UE and other UEs.

[0198] Fig.14A and Fig. 14B is a diagram for describing an operation of a UE processing a SL carrier failure according to an embodiment of the present disclosure.

[0199] According to an embodiment of the present disclosure, Fig.14A and Fig. 14B The carrier fault handler can correspond to Fig. 8A and Figure 8B Carrier fault handling procedures 809 and 859.

[0200] refer to Fig.14A and Fig. 14B , shows an operation of a UE that has determined a SL carrier failure to notify a counterpart UE in unicast communication of the carrier failure while performing unicast-based data transmission (e.g., repeated transmission and / or multi-carrier transmission) by using one or more SL carriers. In one embodiment, Fig.14A and Fig. 14B The procedure may be performed when two UEs determine to suspend the use of a carrier determined to have failed (failure carrier), the carrier being used for unicast communication. In another embodiment, Fig.14A and Fig. 14B The procedure may be performed when two UEs determine to handle a SL failure without suspending use of a carrier determined to have failed (failure carrier), the carrier being used for unicast communication.

[0201] refer to Fig.14A, the UE may determine in operation 1401 to initiate a carrier failure handling procedure. In operation 1403, the UE may determine whether the carrier determined to have failed is being used for unicast communication. When it is determined in operation 1403 that the carrier determined to have failed (failure carrier) is not used for unicast communication, the UE may proceed to operation 1409. When it is determined in operation 1403 that the carrier determined to have failed (failure carrier) is used for unicast communication, the UE may determine in operation 1405 whether it is necessary to perform a carrier failure reporting procedure for the opposite UE. In one embodiment, according to Fig. 8A In an embodiment of the present invention, the condition for determining in operation 1405 that it is necessary to perform a carrier failure reporting procedure for the opposite UE may include whether the carrier corresponds to a non-primary carrier. Figure 8B In an embodiment of the present invention, the condition for determining in operation 1405 that it is necessary to perform a carrier failure reporting procedure for the opposite UE may include whether there is at least one carrier that can be used for unicast communication between the two UEs. When it is determined in operation 1405 to report the carrier failure to the opposite UE, in operation 1407, the UE may perform a reporting procedure for the carrier determined to have failed. When it is determined in operation 1405 that it is not necessary to report the carrier failure to the opposite UE, the UE may proceed to operation 1409.

[0202] refer to Fig. 14B , shows an operation for a UE that has determined a carrier failure to perform a reporting procedure for a carrier that has been determined to have failed (faulty carrier) and to notify a counterpart UE in unicast communication of information about the new carrier when there is a carrier newly selected for unicast communication. In one embodiment, the UE may determine in operation 1451 to initiate a carrier failure handling procedure. In operation 1453, the UE may determine whether the carrier that has been determined to have failed is used for unicast communication. When it is determined in operation 1453 that the carrier that has been determined to have failed (faulty carrier) is not used for unicast communication, the UE may proceed to operation 1463. When it is determined in operation 1453 that the carrier that has been determined to have failed (faulty carrier) is used for unicast communication, in operation 1455, the UE may determine whether it is necessary to perform a carrier failure reporting procedure for the counterpart UE. In one embodiment, according to Fig. 8A In an embodiment of the present invention, the condition for determining in operation 1455 that it is necessary to perform a carrier failure reporting procedure for the opposite UE may include whether the carrier corresponds to a non-primary carrier. Figure 8BIn an embodiment, the condition for determining in operation 1455 that it is necessary to perform a carrier failure reporting procedure for the peer UE may include whether there is at least one carrier that can be used for unicast communication between the two UEs. When the UE determines in operation 1455 to report the carrier failure to the peer UE, in operation 1457, the UE may perform a reporting procedure on the carrier determined to have failed. When the UE determines in operation 1455 that it is not necessary to report the carrier failure to the peer UE, the UE may proceed to operation 1463. In operation 1459, the UE may determine whether the new carrier is configured for unicast communication based on multi-carrier transmission or repeated transmission with the peer UE. When the UE selects a new carrier for unicast communication based on multi-carrier transmission or repeated transmission with the peer UE, taking into account the capability information about the SL band support of the UE itself and the peer UE (only for the SL band combination or for the list of supportable bands for the SL / Uu band combination), the UE may select a SL carrier supported by the two UEs for the purpose of multi-carrier transmission or repeated transmission. When it is determined in operation 1459 that the new carrier is configured, the UE may transmit a message notifying information about the new carrier to the counterpart UE in operation 1461. When it is determined in operation 1459 that the new carrier is not configured, the UE may proceed to operation 1463.

[0203] An embodiment of the SLFailureInformationSidelink message configured by the UE in operations 1407 and 1457 and sent to the counterpart UE in unicast communication can be shown in [Table 6].

[0204] [Table 6]

[0205]

[0206] The SLFailureInformationSidelink message in operations 1407 and 1457 may include at least one or a combination of a plurality of pieces of information in [Table 7].

[0207] [Table 7]

[0208]

[0209] According to an embodiment of the present disclosure, the SLFailureInformationSidelink message in operations 1407 and 1457 may be used as a message notifying that the transmission of the carrier determined to have failed is suspended. Fig.14A or Fig. 14B, the UE can determine whether to perform a reporting procedure on a carrier determined to have failed (faulty carrier) based on whether the SL unicast connection is established and whether a fault reporting procedure is necessary. In addition, the UE can select a new carrier after reporting the carrier determined to have failed (faulty carrier), and can send a new carrier report message. When the UE selects a new carrier for unicast communication based on multi-carrier transmission or repeated transmission with the peer UE, considering the capability information about the SL band support of the UE itself and the peer UE (only for SL band combination or for the list of supportable bands for SL / Uu band combination), the UE can select a SL carrier supported by two UEs for the purpose of multi-carrier transmission or repeated transmission.

[0210] FIG. 8A to FIG. 14B Some or all of the embodiments shown may be combined, and the UE may operate based on the combined embodiments.

[0211] Fig.15A and Fig. 15B is a diagram showing the format of a MAC CE according to an embodiment of the present disclosure.

[0212] refer to Fig.15A According to the embodiments of the present disclosure, the above reference Fig.14A and Fig. 14B The carrier failure report message in the described operations 1407 and 1457 may be sent in the PC5 MAC CE format. For example, when it is assumed that repeated transmission may be performed on 8 carriers, the SL DRBi (Si) may indicate the carrier mapping corresponding to the SL radio bearer. The Si value may be configured as 0 or 1, 0 may indicate a carrier failure, and 1 may indicate a carrier activity.

[0213] According to one embodiment, signaling for notifying the peer UE of the suspension of transmission of a carrier may be sent in the PC5 MAC CE. For example, when it is assumed that repeated transmission can be performed on 8 carriers, Si may indicate the carrier mapping corresponding to the SL radio bearer. The Si value may be configured as 0 or 1, 0 may indicate carrier suspension, and 1 may indicate carrier activity.

[0214] refer to Fig. 15BAccording to an embodiment of the present disclosure, in addition to the SL data radio bearer (DRB), the carrier failure report message may also indicate mapping of carriers corresponding to signaling radio bearers (SRBs) corresponding to PC5-RRC, SRBs corresponding to PC5-S signaling, and the like. The carrier failure report message may indicate a carrier failure when the PC5-RRC field value is configured as 0, and may indicate a carrier activity when the PC5-RRC field value is configured as 1. The carrier failure report message may indicate a carrier failure when the PC5-S field value is configured as 0, and may indicate a carrier activity when the PC5-S field value is configured as 1.

[0215] According to an embodiment of the present disclosure, in addition to the SL DRB, the message notifying the suspension of transmission of the carrier may indicate the mapping of the carrier corresponding to the SRB corresponding to the PC5-RRC, the SRB corresponding to the PC5-S signaling, etc. The message notifying the suspension of transmission of the carrier may indicate the suspension of the carrier when the PC5-RRC field value is configured as 0, and may indicate the carrier activity when the PC5-RRC field value is configured as 1. The message notifying the suspension of transmission of the carrier may indicate the suspension of the carrier when the PC5-S field value is configured as 0, and may indicate the carrier activity when the PC5-S field value is configured as 1.

[0216] The SLFailureInformationSidelink message, the PC5 MAC CE for reporting a carrier failure, and the PC5 MAC CE for notifying the suspension of transmission of a carrier may be sent via any available carrier used between two UEs, or may be sent via the primary carrier. Different PC5 logical channel IDs (PC5 LCIDs) may be configured for the PC5 MAC CE for reporting a carrier failure and the PC5 MAC CE for notifying the suspension of transmission of a carrier.

[0217] The methods according to the claims of the present disclosure or the embodiments described herein may be implemented in hardware or software or in a combination of hardware and software.

[0218] When these methods are implemented with software, a computer-readable recording medium having one or more programs (software modules) stored therein may be provided. One or more programs stored in the computer-readable storage medium are configured to be executable by one or more processors in an electronic device. One or more programs include instructions that cause an electronic device to perform a method according to the claims of the present disclosure or the embodiments described herein.

[0219] The program (e.g., software module or software) may be stored in a random access memory (RAM), a non-volatile memory including flash memory, a read-only memory (ROM), an electrically erasable programmable read-only memory (EEPROM), a magnetic disk storage device, a compact disk (CD-ROM), a digital versatile disk (DVD), another type of optical storage device, or a magnetic tape cassette. Alternatively, the program may be stored in a memory including any combination of some or all of the above storage media. In addition, each memory may include multiple memories.

[0220] In addition, the program can be stored in an attachable storage device accessible via a communication network, such as the Internet, an intranet, a local area network (LAN), a wireless LAN (WLAN), or a storage area network (SAN) or a combination thereof. Such a storage device can access the apparatus for executing the embodiments of the present disclosure through an external port. In addition, a separate storage device on a communication network can access the apparatus for executing the embodiments of the present disclosure.

[0221] In the foregoing embodiments of the present disclosure, the components included in the present disclosure are expressed in the singular or plural form according to the embodiments of the present disclosure. However, for the convenience of description, the singular or plural form is appropriately selected, and the present disclosure is not limited thereto. In this way, the components expressed in the plural form may also be configured as a single component, and the components expressed in the singular form may also be configured as multiple components.

[0222] Although specific embodiments have been described in the detailed description of the present disclosure, various modifications may be made without departing from the scope of the present disclosure. Therefore, the scope of the present disclosure should not be limited to the foregoing embodiments of the present disclosure, but should be determined by the appended claims and their equivalents.

Claims

1. A method performed by a terminal in a wireless communication system, the method comprising: performing sidelink transmissions associated with a plurality of sidelink carriers; Based on a hybrid automatic repeat request (HARQ) operation, identifying whether all of the multiple sidelink carriers are unavailable; In a case where all of the plurality of side link carriers are unavailable, identifying detection of a side link radio link failure RLF; as well as Information associated with the sidelink RLF is transmitted to a base station.

2. The method according to claim 1, further comprising: In a case where at least one of the plurality of sidelink carriers is available and a sidelink carrier failure occurs in the sidelink carrier, information associated with the sidelink carrier failure is transmitted to a base station.

3. The method according to claim 2, wherein: The information associated with the sidelink carrier failure includes a parameter indicating a destination identification of the sidelink carrier failure and a parameter indicating a sidelink carrier associated with the sidelink carrier failure.

4. The method according to claim 1, further comprising: In case at least one of the plurality of sidelink carriers is available and a sidelink carrier failure occurs in the sidelink carrier, a carrier selection or reselection procedure is performed.

5. The method according to claim 4, wherein: The carrier selection or reselection procedure is performed based on the carrier selection or reselection configuration information.

6. The method according to claim 5, wherein: The carrier selection or reselection configuration information is received from a base station.

7. The method according to claim 5, wherein: The carrier selection or reselection configuration information includes information related to the logical channel and information related to the channel busy rate CBR.

8. The method according to claim 7, wherein: Executing the carrier selection or reselection procedure includes: A carrier with the lowest CBR is selected from one or more candidate carriers for carrier selection or reselection.

9. The method according to claim 4, wherein: The carrier selection or reselection procedure is associated with multi-carrier transmission related capability information for unicast.

10. The method according to claim 1, wherein: The terminal is in a radio resource control RRC connected state.

11. A terminal in a wireless communication system, the terminal comprising: Transceiver; as well as at least one processor coupled to the transceiver and configured to: performing sidelink transmissions associated with a plurality of sidelink carriers; Based on a hybrid automatic repeat request (HARQ) operation, identifying whether all of the multiple side link carriers are unavailable; In a case where all of the plurality of side link carriers are unavailable, identifying detection of a side link radio link failure RLF; as well as Information associated with the sidelink RLF is transmitted to a base station.

12. The terminal according to claim 11, wherein: The at least one processor is further configured to: In a case where at least one of the plurality of sidelink carriers is available and a sidelink carrier failure occurs in the sidelink carrier, information associated with the sidelink carrier failure is transmitted to a base station.

13. The terminal according to claim 12, wherein: The information associated with the sidelink carrier failure includes a parameter indicating a destination identification of the sidelink carrier failure and a parameter indicating a sidelink carrier associated with the sidelink carrier failure.

14. The terminal according to claim 11, wherein: The at least one processor is further configured to: In case at least one of the plurality of sidelink carriers is available and a sidelink carrier failure occurs in the sidelink carrier, a carrier selection or reselection procedure is performed.

15. The terminal according to claim 14, wherein: The carrier selection or reselection procedure is performed based on the configuration information of the carrier selection or reselection.

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