Patent Publication Number: US-2021195543-A1

Title: Method and device for transmitting sidelink signal in wireless communication system

Description:
TECHNICAL FIELD 
     The present disclosure relates to a wireless communication system and, more particularly, to a method and device for selecting a synchronization reference and transmitting a sidelink signal. 
     BACKGROUND ART 
     Wireless communication systems have been widely deployed to provide various types of communication services such as voice or data. In general, a wireless communication system is a multiple access system that supports communication of multiple users by sharing available system resources (a bandwidth, transmission power, etc.). Examples of multiple access systems include a code division multiple access (CDMA) system, a frequency division multiple access (FDMA) system, a time division multiple access (TDMA) system, an orthogonal frequency division multiple access (OFDMA) system, a single carrier frequency division multiple access (SC-FDMA) system, and a multi carrier frequency division multiple access (MC-FDMA) system. 
     A wireless communication system uses various radio access technologies (RATs) such as long term evolution (LTE), LTE-advanced (LTE-A), and wireless fidelity (WiFi). 5th generation (5G) is such a wireless communication system. Three key requirement areas of 5G include (1) enhanced mobile broadband (eMBB), (2) massive machine type communication (mMTC), and (3) ultra-reliable and low latency communications (URLLC). Some use cases may require multiple dimensions for optimization, while others may focus only on one key performance indicator (KPI). 5G supports such diverse use cases in a flexible and reliable way. 
     eMBB goes far beyond basic mobile Internet access and covers rich interactive work, media and entertainment applications in the cloud or augmented reality (AR). Data is one of the key drivers for 5G and in the 5G era, we may for the first time see no dedicated voice service. In 5G, voice is expected to be handled as an application program, simply using data connectivity provided by a communication system. The main drivers for an increased traffic volume are the increase in the size of content and the number of applications requiring high data rates. Streaming services (audio and video), interactive video, and mobile Internet connectivity will continue to be used more broadly as more devices connect to the Internet. Many of these applications require always-on connectivity to push real time information and notifications to users. Cloud storage and applications are rapidly increasing for mobile communication platforms. This is applicable for both work and entertainment. Cloud storage is one particular use case driving the growth of uplink data rates. 5G will also be used for remote work in the cloud which, when done with tactile interfaces, requires much lower end-to-end latencies in order to maintain a good user experience. Entertainment, for example, cloud gaming and video streaming, is another key driver for the increasing need for mobile broadband capacity. Entertainment will be very essential on smart phones and tablets everywhere, including high mobility environments such as trains, cars and airplanes. Another use case is augmented reality (AR) for entertainment and information search, which requires very low latencies and significant instant data volumes. 
     One of the most expected 5G use cases is the functionality of actively connecting embedded sensors in every field, that is, mMTC. It is expected that there will be 20.4 billion potential Internet of things (IoT) devices by 2020. In industrial IoT, 5G is one of areas that play key roles in enabling smart city, asset tracking, smart utility, agriculture, and security infrastructure. 
     URLLC includes services which will transform industries with ultra-reliable/available, low latency links such as remote control of critical infrastructure and self-driving vehicles. The level of reliability and latency are vital to smart-grid control, industrial automation, robotics, drone control and coordination, and so on. 
     Now, multiple use cases will be described in detail. 
     5G may complement fiber-to-the home (FTTH) and cable-based broadband (or data-over-cable service interface specifications (DOCSIS)) as a means of providing streams at data rates of hundreds of megabits per second to giga bits per second. Such a high speed is required for TV broadcasts at or above a resolution of 4K (6K, 8K, and higher) as well as virtual reality (VR) and AR. VR and AR applications mostly include immersive sport games. A special network configuration may be required for a specific application program. For VR games, for example, game companies may have to integrate a core server with an edge network server of a network operator in order to minimize latency. 
     The automotive sector is expected to be a very important new driver for 5G, with many use cases for mobile communications for vehicles. For example, entertainment for passengers requires simultaneous high capacity and high mobility mobile broadband, because future users will expect to continue their good quality connection independent of their location and speed. Other use cases for the automotive sector are AR dashboards. These display overlay information on top of what a driver is seeing through the front window, identifying objects in the dark and telling the driver about the distances and movements of the objects. In the future, wireless modules will enable communication between vehicles themselves, information exchange between vehicles and supporting infrastructure and between vehicles and other connected devices (e.g., those carried by pedestrians). Safety systems may guide drivers on alternative courses of action to allow them to drive more safely and lower the risks of accidents. The next stage will be remote-controlled or self-driving vehicles. These require very reliable, very fast communication between different self-driving vehicles and between vehicles and infrastructure. In the future, self-driving vehicles will execute all driving activities, while drivers are focusing on traffic abnormality elusive to the vehicles themselves. The technical requirements for self-driving vehicles call for ultra-low latencies and ultra-high reliability, increasing traffic safety to levels humans cannot achieve. 
     Smart cities and smart homes, often referred to as smart society, will be embedded with dense wireless sensor networks. Distributed networks of intelligent sensors will identify conditions for cost- and energy-efficient maintenance of the city or home. A similar setup can be done for each home, where temperature sensors, window and heating controllers, burglar alarms, and home appliances are all connected wirelessly. Many of these sensors are typically characterized by low data rate, low power, and low cost, but for example, real time high definition (HD) video may be required in some types of devices for surveillance. 
     The consumption and distribution of energy, including heat or gas, is becoming highly decentralized, creating the need for automated control of a very distributed sensor network. A smart grid interconnects such sensors, using digital information and communications technology to gather and act on information. This information may include information about the behaviors of suppliers and consumers, allowing the smart grid to improve the efficiency, reliability, economics and sustainability of the production and distribution of fuels such as electricity in an automated fashion. A smart grid may be seen as another sensor network with low delays. 
     The health sector has many applications that may benefit from mobile communications. Communications systems enable telemedicine, which provides clinical health care at a distance. It helps eliminate distance barriers and may improve access to medical services that would often not be consistently available in distant rural communities. It is also used to save lives in critical care and emergency situations. Wireless sensor networks based on mobile communication may provide remote monitoring and sensors for parameters such as heart rate and blood pressure. 
     Wireless and mobile communications are becoming increasingly important for industrial applications. Wires are expensive to install and maintain, and the possibility of replacing cables with reconfigurable wireless links is a tempting opportunity for many industries. However, achieving this requires that the wireless connection works with a similar delay, reliability and capacity as cables and that its management is simplified. Low delays and very low error probabilities are new requirements that need to be addressed with 5G 
     Finally, logistics and freight tracking are important use cases for mobile communications that enable the tracking of inventory and packages wherever they are by using location-based information systems. The logistics and freight tracking use cases typically require lower data rates but need wide coverage and reliable location information. 
     DISCLOSURE 
     Technical Problem 
     The object of the present disclosure is to provide a method of selecting a synchronization reference from among synchronization sources including a new radio (NR) gNodeB (gNB) and transmitting and receiving a sidelink signal. 
     It will be appreciated by persons skilled in the art that the objects that could be achieved with the present disclosure are not limited to what has been particularly described hereinabove and the above and other objects that the present disclosure could achieve will be more clearly understood from the following detailed description. 
     Technical Solution 
     In one aspect of the present disclosure, a method of transmitting and receiving a sidelink signal by a user equipment (UE) in a wireless communication system is provided. The method may include: selecting a synchronization reference from among a plurality of synchronization sources based on priorities; and transmitting or receiving the sidelink signal based on the selected synchronization reference. The plurality of synchronization sources may include an eNodeB (eNB) and a gNodeB (gNB), and priorities between the eNB and the gNB may be configured by a base station or preconfigured by a network. 
     In another aspect of the present disclosure, a device for transmitting and receiving a sidelink signal in a wireless communication system is provided. The device may include a memory and a processor coupled to the memory. The processor may be configured to select a synchronization reference from among a plurality of synchronization sources based on priorities and transmit or receive the sidelink signal based on the selected synchronization reference. The plurality of synchronization sources may include an eNB and a gNB, and priorities between the eNB and the gNB may be configured by a base station or preconfigured by a network. 
     The eNB and the gNB may have the same priority. 
     The UE may receive the priorities through either higher layer signaling or physical layer signaling. 
     When the priorities are the same, the UE may select a synchronization reference with high reference signal received power (RSRP). 
     The RSRP may be measured based on at least one of a physical broadcast channel (PB CH) demodulation reference signal (DMRS), a synchronization signal, or channel state information (CSI). 
     The UE may transmit a timing difference between the eNB and the gNB to at least one of the eNB, the gNB, or another UE. 
     The UE may transmit a timing difference between the eNB and the gNB to either or both the eNB and the gNB over an uplink channel. 
     The UE may transmit a timing difference between the eNB and the gNB to another UE over a sidelink channel. 
     The timing difference may be determined based on synchronization signals received by the UE from the eNB and the gNB, respectively. 
     When the UE performs transmission based on a predetermined format or numerology, the UE may consider that the gNB has a higher priority than the eNB. 
     When the UE selects the synchronization reference with the high RSRP, an offset value, which is indicated by either higher layer signaling or physical layer signaling, may be applied to either RSRP related to the gNB or RSRP related to the eNB. 
     RSRP of the gNB may be measured for each synchronization signal block (SSB). 
     Advantageous Effects 
     According to the present disclosure, when a NR gNB and a long term evolution (LTE) eNB coexist, priorities for synchronization reference selection are defined, thereby cancelling unnecessary interference. 
     It will be appreciated by persons skilled in the art that the effects that could be achieved with the present disclosure are not limited to what has been particularly described hereinabove and other advantages of the present disclosure will be more clearly understood from the following detailed description. 
    
    
     
       DESCRIPTION OF DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the present disclosure and are incorporated in and constitute a part of this application, illustrate implementations of the present disclosure and together with the description serve to explain the principle of the disclosure. 
         FIG. 1  is a diagram showing a vehicle according to an implementation of the present disclosure. 
         FIG. 2  is a control block diagram of the vehicle according to an implementation of the present disclosure. 
         FIG. 3  is a control block diagram of an autonomous driving device according to an implementation of the present disclosure. 
         FIG. 4  is a block diagram of the autonomous driving device according to an implementation of the present disclosure. 
         FIG. 5  is a diagram showing the interior of the vehicle according to an implementation of the present disclosure. 
         FIG. 6  is a block diagram for explaining a vehicle cabin system according to an implementation of the present disclosure. 
         FIG. 7  illustrates the structure of an LTE system to which the present disclosure is applicable. 
         FIG. 8  illustrates a user-plane radio protocol architecture to which the present disclosure is applicable. 
         FIG. 9  illustrates a control-plane radio protocol architecture to which the present disclosure is applicable. 
         FIG. 10  illustrates the structure of a NR system to which the present disclosure is applicable. 
         FIG. 11  illustrates functional split between a next generation radio access network (NG-RAN) and a 5G core network (5GC) to which the present disclosure is applicable. 
         FIG. 12  illustrates the structure of a new radio (NR) radio frame to which the present disclosure is applicable. 
         FIG. 13  illustrates the slot structure of a NR frame to which the present disclosure is applicable. 
       As shown in  FIG. 14 , a method of reserving a transmission resource for a next packet when transmission resources are selected may be used. 
         FIG. 15  illustrates an example of physical sidelink control channel (PSCCH) transmission in sidelink transmission mode  3  or  4  to which the present disclosure is applicable. 
         FIG. 16  illustrates physical layer processing at a transmitting side to which the present disclosure is applicable. 
         FIG. 17  illustrates physical layer processing at a receiving side to which the present disclosure is applicable. 
         FIG. 18  illustrates a synchronization source or reference in vehicle-to-everything (V2X) communication to which the present disclosure is applicable. 
         FIGS. 19 to 21  illustrate flowcharts according to various implementations of the present disclosure. 
         FIGS. 22 to 28  are diagrams for explaining various devices to which the present disclosure is applicable. 
     
    
    
     BEST MODE 
     1. Driving 
     (1) Exterior of Vehicle 
       FIG. 1  is a diagram showing a vehicle according to an implementation of the present disclosure. 
     Referring to  FIG. 1 , a vehicle  10  according to an implementation of the present disclosure is defined as transportation traveling on roads or railroads. The vehicle  10  includes a car, a train, and a motorcycle. The vehicle  10  may include an internal-combustion engine vehicle having an engine as a power source, a hybrid vehicle having an engine and a motor as a power source, and an electric vehicle having an electric motor as a power source. The vehicle  10  may be a private own vehicle or a shared vehicle. The vehicle  10  may be an autonomous vehicle. 
     (2) Components of Vehicle 
       FIG. 2  is a control block diagram of the vehicle according to an implementation of the present disclosure. 
     Referring to  FIG. 2 , the vehicle  10  may include a user interface device  200 , an object detection device  210 , a communication device  220 , a driving operation device  230 , a main electronic control unit (ECU)  240 , a driving control device  250 , an autonomous driving device  260 , a sensing unit  270 , and a location data generating device  280 . Each of the object detection device  210 , communication device  220 , driving operation device  230 , main ECU  240 , driving control device  250 , autonomous driving device  260 , sensing unit  270 , and location data generating device  280  may be implemented as an electronic device that generates an electrical signal and exchanges the electrical signal from one another. 
     1) User Interface Device 
     The user interface device  200  is a device for communication between the vehicle  10  and a user. The user interface device  200  may receive a user input and provide information generated in the vehicle  10  to the user. The vehicle  10  may implement a user interface (UI) or user experience (UX) through the user interface device  200 . The user interface device  200  may include an input device, an output device, and a user monitoring device. 
     2) Object Detection Device 
     The object detection device  210  may generate information about an object outside the vehicle  10 . The object information may include at least one of information about the presence of the object, information about the location of the object, information about the distance between the vehicle  10  and the object, and information about the relative speed of the vehicle  10  with respect to the object. The object detection device  210  may detect the object outside the vehicle  10 . The object detection device  210  may include at least one sensor to detect the object outside the vehicle  10 . The object detection device  210  may include at least one of a camera, a radar, a lidar, an ultrasonic sensor, and an infrared sensor. The object detection device  210  may provide data about the object, which is created based on a sensing signal generated by the sensor, to at least one electronic device included in the vehicle  10 . 
     2.1) Camera 
     The camera may generate information about an object outside the vehicle  10  with an image. The camera may include at least one lens, at least one image sensor, and at least one processor electrically connected to the image sensor and configured to process a received signal and generate data about the object based on the processed signal. 
     The camera may be at least one of a mono camera, a stereo camera, and an around view monitoring (AVM) camera. The camera may acquire information about the location of the object, information about the distance to the object, or information about the relative speed thereof with respect to the object based on various image processing algorithms. For example, the camera may acquire the information about the distance to the object and the information about the relative speed with respect to the object from the image based on a change in the size of the object over time. For example, the camera may acquire the information about the distance to the object and the information about the relative speed with respect to the object through a pin-hole model, road profiling, etc. For example, the camera may acquire the information about the distance to the object and the information about the relative speed with respect to the object from a stereo image generated by a stereo camera based on disparity information. 
     The camera may be disposed at a part of the vehicle  10  where the field of view (FOV) is guaranteed to photograph the outside of the vehicle  10 . The camera may be disposed close to a front windshield inside the vehicle  10  to acquire front-view images of the vehicle  10 . The camera may be disposed in the vicinity of a front bumper or a radiator grill. The camera may be disposed close to a rear glass inside the vehicle  10  to acquire rear-view images of the vehicle  10 . The camera may be disposed in the vicinity of a rear bumper, a trunk, or a tail gate. The camera may be disposed close to at least one of side windows inside the vehicle  10  in order to acquire side-view images of the vehicle  10 . Alternatively, the camera may be disposed in the vicinity of a side mirror, a fender, or a door. 
     2.2) Radar 
     The radar may generate information about an object outside the vehicle  10  using electromagnetic waves. The radar may include an electromagnetic wave transmitter, an electromagnetic wave receiver, and at least one processor electrically connected to the electromagnetic wave transmitter and the electromagnetic wave receiver and configured to process a received signal and generate data about the object based on the processed signal. The radar may be a pulse radar or a continuous wave radar depending on electromagnetic wave emission. The continuous wave radar may be a frequency modulated continuous wave (FMCW) radar or a frequency shift keying (FSK) radar depending on signal waveforms. The radar may detect the object from the electromagnetic waves based on the time of flight (TOF) or phase shift principle and obtain the location of the detected object, the distance to the detected object, and the relative speed with respect to the detected object. The radar may be disposed at an appropriate position outside the vehicle  10  to detect objects placed in front, rear, or side of the vehicle  10 . 
     2.3) Lidar 
     The lidar may generate information about an object outside the vehicle  10  using a laser beam. The lidar may include a light transmitter, a light receiver, and at least one processor electrically connected to the light transmitter and the light receiver and configured to process a received signal and generate data about the object based on the processed signal. The lidar may operate based on the TOF or phase shift principle. The lidar may be a driven type or a non-driven type. The driven type of lidar may be rotated by a motor and detect an object around the vehicle  10 . The non-driven type of lidar may detect an object within a predetermined range from the vehicle  10  based on light steering. The vehicle  10  may include a plurality of non-driven type of lidars. The lidar may detect the object from the laser beam based on the TOF or phase shift principle and obtain the location of the detected object, the distance to the detected object, and the relative speed with respect to the detected object. The lidar may be disposed at an appropriate position outside the vehicle  10  to detect objects placed in front, rear, or side of the vehicle  10 . 
     3) Communication Device 
     The communication device  220  may exchange a signal with a device outside the vehicle  10 . The communication device  220  may exchange a signal with at least one of an infrastructure (e.g., server, broadcast station, etc.), another vehicle, and a terminal. The communication device  220  may include a transmission antenna, a reception antenna, and at least one of a radio frequency (RF) circuit and an RF element where various communication protocols may be implemented to perform communication. 
     For example, the communication device  220  may exchange a signal with an external device based on the cellular vehicle-to-everything (C-V2X) technology. The C-V2X technology may include LTE-based sidelink communication and/or NR-based sidelink communication. Details related to the C-V2X technology will be described later. 
     The communication device  220  may exchange the signal with the external device according to dedicated short-range communications (DSRC) technology or wireless access in vehicular environment (WAVE) standards based on IEEE 802.11p PHY/MAC layer technology and IEEE 1609 Network/Transport layer technology. The DSRC technology (or WAVE standards) is communication specifications for providing intelligent transport system (ITS) services through dedicated short-range communication between vehicle-mounted devices or between a road side unit and a vehicle-mounted device. The DSRC technology may be a communication scheme that allows the use of a frequency of 5.9 GHz and has a data transfer rate in the range of 3 Mbps to 27 Mbps. IEEE 802.11p may be combined with IEEE 1609 to support the DSRC technology (or WAVE standards). 
     According to the present disclosure, the communication device  220  may exchange the signal with the external device according to either the C-V2X technology or the DSRC technology. Alternatively, the communication device  220  may exchange the signal with the external device by combining the C-V2X technology and the DSRC technology. 
     4) Driving Operation Device 
     The driving operation device  230  is configured to receive a user input for driving. In a manual mode, the vehicle  10  may be driven based on a signal provided by the driving operation device  230 . The driving operation device  230  may include a steering input device (e.g., steering wheel), an acceleration input device (e.g., acceleration pedal), and a brake input device (e.g., brake pedal). 
     5) Main ECU 
     The main ECU  240  may control the overall operation of at least one electronic device included in the vehicle  10 . 
     6) Driving Control Device 
     The driving control device  250  is configured to electrically control various vehicle driving devices included in the vehicle  10 . The driving control device  250  may include a power train driving control device, a chassis driving control device, a door/window driving control device, a safety driving control device, a lamp driving control device, and an air-conditioner driving control device. The power train driving control device may include a power source driving control device and a transmission driving control device. The chassis driving control device may include a steering driving control device, a brake driving control device, and a suspension driving control device. The safety driving control device may include a seat belt driving control device for seat belt control. 
     The driving control device  250  includes at least one electronic control device (e.g., control ECU). 
     The driving control device  250  may control the vehicle driving device based on a signal received from the autonomous driving device  260 . For example, the driving control device  250  may control a power train, a steering, and a brake based on signals received from the autonomous driving device  260 . 
     7) Autonomous Driving Device 
     The autonomous driving device  260  may generate a route for autonomous driving based on obtained data. The autonomous driving device  260  may generate a driving plan for traveling along the generated route. The autonomous driving device  260  may generate a signal for controlling the movement of the vehicle  10  according to the driving plan. The autonomous driving device  260  may provide the generated signal to the driving control device  250 . 
     The autonomous driving device  260  may implement at least one advanced driver assistance system (ADAS) function. The ADAS may implement at least one of adaptive cruise control (ACC), autonomous emergency braking (AEB), forward collision warning (FCW), lane keeping assist (LKA), lane change assist (LCA), target following assist (TFA), blind spot detection (BSD), high beam assist (HBA), auto parking system (APS), PD collision warning system, traffic sign recognition (TSR), traffic sign assist (TSA), night vision (NV), driver status monitoring (DSM), and traffic fam assist (TJA). 
     The autonomous driving device  260  may perform switching from an autonomous driving mode to a manual driving mode or switching from the manual driving mode to the autonomous driving mode. For example, the autonomous driving device  260  may switch the mode of the vehicle  10  from the autonomous driving mode to the manual driving mode or from the manual driving mode to the autonomous driving mode based on a signal received from the user interface device  200 . 
     8) Sensing Unit 
     The sensing unit  270  may detect the state of the vehicle  10 . The sensing unit  270  may include at least one of an inertial measurement unit (IMU) sensor, a collision sensor, a wheel sensor, a speed sensor, an inclination sensor, a weight sensor, a heading sensor, a position module, a vehicle forward/backward movement sensor, a battery sensor, a fuel sensor, a tire sensor, a steering sensor, a temperature sensor, a humidity sensor, an ultrasonic sensor, an illumination sensor, and a pedal position sensor. Further, the IMU sensor may include at least one of an acceleration sensor, a gyro sensor, and a magnetic sensor. 
     The sensing unit  270  may generate data about the vehicle state based on a signal generated by at least one sensor. The vehicle state data may be information generated based on data detected by various sensors included in the vehicle  10 . The sensing unit  270  may generate vehicle attitude data, vehicle motion data, vehicle yaw data, vehicle roll data, vehicle pitch data, vehicle collision data, vehicle orientation data, vehicle angle data, vehicle speed data, vehicle acceleration data, vehicle tilt data, vehicle forward/backward movement data, vehicle weight data, battery data, fuel data, tire pressure data, vehicle internal temperature data, vehicle internal humidity data, steering wheel rotation angle data, vehicle external illumination data, data on pressure applied to the acceleration pedal, data on pressure applied to the brake pedal, etc. 
     9) Location Data Generating Device 
     The location data generating device  280  may generate data on the location of the vehicle  10 . The location data generating device  280  may include at least one of a global positioning system (GPS) and a differential global positioning system (DGPS). The location data generating device  280  may generate the location data on the vehicle  10  based on a signal generated by at least one of the GPS and the DGPS. In some implementations, the location data generating device  280  may correct the location data based on at least one of the IMU sensor of the sensing unit  270  and the camera of the object detection device  210 . The location data generating device  280  may also be called a global navigation satellite system (GNSS). 
     The vehicle  10  may include an internal communication system  50 . The plurality of electronic devices included in the vehicle  10  may exchange a signal through the internal communication system  50 . The signal may include data. The internal communication system  50  may use at least one communication protocol (e.g., CAN, LIN, FlexRay, MOST, or Ethernet). 
     (3) Components of Autonomous Driving Device 
       FIG. 3  is a control block diagram of the autonomous driving device  260  according to an implementation of the present disclosure. 
     Referring to  FIG. 3 , the autonomous driving device  260  may include a memory  140 , a processor  170 , an interface  180  and a power supply  190 . 
     The memory  140  is electrically connected to the processor  170 . The memory  140  may store basic data about a unit, control data for controlling the operation of the unit, and input/output data. The memory  140  may store data processed by the processor  170 . In hardware implementation, the memory  140  may be implemented as any one of a ROM, a RAM, an EPROM, a flash drive, and a hard drive. The memory  140  may store various data for the overall operation of the autonomous driving device  260 , such as a program for processing or controlling the processor  170 . The memory  140  may be integrated with the processor  170 . In some implementations, the memory  140  may be classified as a subcomponent of the processor  170 . 
     The interface  180  may exchange a signal with at least one electronic device included in the vehicle  10  by wire or wirelessly. The interface  180  may exchange a signal with at least one of the object detection device  210 , the communication device  220 , the driving operation device  230 , the main ECU  240 , the driving control device  250 , the sensing unit  270 , and the location data generating device  280  by wire or wirelessly. The interface  180  may be implemented with at least one of a communication module, a terminal, a pin, a cable, a port, a circuit, an element, and a device. 
     The power supply  190  may provide power to the autonomous driving device  260 . The power supply  190  may be provided with power from a power source (e.g., battery) included in the vehicle  10  and supply the power to each unit of the autonomous driving device  260 . The power supply  190  may operate according to a control signal from the main ECU  240 . The power supply  190  may include a switched-mode power supply (SMPS). 
     The processor  170  may be electrically connected to the memory  140 , the interface  180 , and the power supply  190  to exchange signals with the components. The processor  170  may be implemented with at least one of application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, micro-controllers, microprocessors, and electronic units for executing other functions. 
     The processor  170  may be driven by power supplied from the power supply  190 . The processor  170  may receive data, process the data, generate a signal, and provide the signal while the power is supplied thereto. 
     The processor  170  may receive information from other electronic devices included in the vehicle  10  through the interface  180 . The processor  170  may provide a control signal to other electronic devices in the vehicle  10  through the interface  180 . 
     The autonomous driving device  260  may include at least one printed circuit board (PCB). The memory  140 , the interface  180 , the power supply  190 , and the processor  170  may be electrically connected to the PCB. 
     (4) Operation of Autonomous Driving Device 
     1) Receiving Operation 
     Referring to  FIG. 4 , the processor  170  may perform a receiving operation. The processor  170  may receive data from at least one of the object detection device  210 , the communication device  220 , the sensing unit  270 , and the location data generating device  280  through the interface  180 . The processor  170  may receive object data from the object detection device  210 . The processor  170  may receive HD map data from the communication device  220 . The processor  170  may receive vehicle state data from the sensing unit  270 . The processor  170  may receive location data from the location data generating device  280 . 
     2) Processing/Determination Operation 
     The processor  170  may perform a processing/determination operation. The processor  170  may perform the processing/determination operation based on driving state information. The processor  170  may perform the processing/determination operation based on at least one of object data, HD map data, vehicle state data, and location data. 
     2.1) Driving Plan Data Generating Operation 
     The processor  170  may generate driving plan data. For example, the processor  170  may generate electronic horizon data. The electronic horizon data may be understood as driving plan data from the current location of the vehicle  10  to the horizon. The horizon may be understood as a point away from the current location of the vehicle  10  by a predetermined distance along a predetermined traveling route. Further, the horizon may refer to a point at which the vehicle  10  may arrive after a predetermined time from the current location of the vehicle  10  along the predetermined traveling route. 
     The electronic horizon data may include horizon map data and horizon path data. 
     2.1.1) Horizon Map Data 
     The horizon map data may include at least one of topology data, road data, HD map data and dynamic data. In some implementations, the horizon map data may include a plurality of layers. For example, the horizon map data may include a first layer matching with the topology data, a second layer matching with the road data, a third layer matching with the HD map data, and a fourth layer matching with the dynamic data. The horizon map data may further include static object data. 
     The topology data may be understood as a map created by connecting road centers with each other. The topology data is suitable for representing an approximate location of a vehicle and may have a data form used for navigation for drivers. The topology data may be interpreted as data about roads without vehicles. The topology data may be generated on the basis of data received from an external server through the communication device  220 . The topology data may be based on data stored in at least one memory included in the vehicle  10 . 
     The road data may include at least one of road slope data, road curvature data, and road speed limit data. The road data may further include no-passing zone data. The road data may be based on data received from an external server through the communication device  220 . The road data may be based on data generated by the object detection device  210 . 
     The HD map data may include detailed topology information including road lanes, connection information about each lane, and feature information for vehicle localization (e.g., traffic sign, lane marking/property, road furniture, etc.). The HD map data may be based on data received from an external server through the communication device  220 . 
     The dynamic data may include various types of dynamic information on roads. For example, the dynamic data may include construction information, variable speed road information, road condition information, traffic information, moving object information, etc. The dynamic data may be based on data received from an external server through the communication device  220 . The dynamic data may be based on data generated by the object detection device  210 . 
     The processor  170  may provide map data from the current location of the vehicle  10  to the horizon. 
     2.1.2) Horizon Path Data 
     The horizon path data may be understood as a potential trajectory of the vehicle  10  when the vehicle  10  travels from the current location of the vehicle  10  to the horizon. The horizon path data may include data indicating the relative probability of selecting a road at the decision point (e.g., fork, junction, crossroad, etc.). The relative probability may be calculated on the basis of the time taken to arrive at the final destination. For example, if the time taken to arrive at the final destination when a first road is selected at the decision point is shorter than that when a second road is selected, the probability of selecting the first road may be calculated to be higher than the probability of selecting the second road. 
     The horizon path data may include a main path and a sub-path. The main path may be understood as a trajectory obtained by connecting roads that are highly likely to be selected. The sub-path may be branched from at least one decision point on the main path. The sub-path may be understood as a trajectory obtained by connecting one or more roads that are less likely to be selected at the at least one decision point on the main path. 
     3) Control Signal Generating Operation 
     The processor  170  may perform a control signal generating operation. The processor  170  may generate a control signal on the basis of the electronic horizon data. For example, the processor  170  may generate at least one of a power train control signal, a brake device control signal, and a steering device control signal on the basis of the electronic horizon data. 
     The processor  170  may transmit the generated control signal to the driving control device  250  through the interface  180 . The driving control device  250  may forward the control signal to at least one of a power train  251 , a brake device  252  and a steering device  253 . 
     2. Cabin 
       FIG. 5  is a diagram showing the interior of the vehicle  10  according to an implementation of the present disclosure. 
       FIG. 6  is a block diagram for explaining a vehicle cabin system according to an implementation of the present disclosure. 
     Referring to  FIGS. 5 and 6 , a vehicle cabin system  300  (cabin system) may be defined as a convenience system for the user who uses the vehicle  10 . The cabin system  300  may be understood as a high-end system including a display system  350 , a cargo system  355 , a seat system  360 , and a payment system  365 . The cabin system  300  may include a main controller  370 , a memory  340 , an interface  380 , a power supply  390 , an input device  310 , an imaging device  320 , a communication device  330 , the display system  350 , the cargo system  355 , the seat system  360 , and the payment system  365 . In some implementations, the cabin system  300  may further include components in addition to the components described in this specification or may not include some of the components described in this specification. 
     1) Main Controller 
     The main controller  370  may be electrically connected to the input device  310 , the communication device  330 , the display system  350 , the cargo system  355 , the seat system  360 , and the payment system  365  and exchange signals with the components. The main controller  370  may control the input device  310 , the communication device  330 , the display system  350 , the cargo system  355 , the seat system  360 , and the payment system  365 . The main controller  370  may be implemented with at least one of application specific integrated circuits (ASIC s), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, micro-controllers, microprocessors, and electronic units for executing other functions. 
     The main controller  370  may include at least one sub-controller. In some implementations, the main controller  370  may include a plurality of sub-controllers. The plurality of sub-controllers may control the devices and systems included in the cabin system  300 , respectively. The devices and systems included in the cabin system  300  may be grouped by functions or grouped with respect to seats for users. 
     The main controller  370  may include at least one processor  371 . Although  FIG. 6  illustrates the main controller  370  including a single processor  371 , the main controller  371  may include a plurality of processors  371 . The processor  371  may be classified as one of the above-described sub-controllers. 
     The processor  371  may receive signals, information, or data from a user terminal through the communication device  330 . The user terminal may transmit signals, information, or data to the cabin system  300 . 
     The processor  371  may identify the user on the basis of image data received from at least one of an internal camera and an external camera included in the imaging device  320 . The processor  371  may identify the user by applying an image processing algorithm to the image data. For example, the processor  371  may identify the user by comparing information received from the user terminal with the image data. For example, the information may include information about at least one of the route, body, fellow passenger, baggage, location, preferred content, preferred food, disability, and use history of the user. 
     The main controller  370  may include an artificial intelligence agent  372 . The artificial intelligence agent  372  may perform machine learning on the basis of data acquired from the input device  310 . The artificial intelligence agent  372  may control at least one of the display system  350 , the cargo system  355 , the seat system  360 , and the payment system  365  on the basis of machine learning results. 
     2) Essential Components 
     The memory  340  is electrically connected to the main controller  370 . The memory  340  may store basic data about a unit, control data for controlling the operation of the unit, and input/output data. The memory  340  may store data processed by the main controller  370 . In hardware implementation, the memory  140  may be implemented as any one of a ROM, a RAM, an EPROM, a flash drive, and a hard drive. The memory  340  may store various types of data for the overall operation of the cabin system  300 , such as a program for processing or controlling the main controller  370 . The memory  340  may be integrated with the main controller  370 . 
     The interface  380  may exchange a signal with at least one electronic device included in the vehicle  10  by wire or wirelessly. The interface  380  may be implemented with at least one of a communication module, a terminal, a pin, a cable, a port, a circuit, an element and a device. 
     The power supply  390  may provide power to the cabin system  300 . The power supply  390  may be provided with power from a power source (e.g., battery) included in the vehicle  10  and supply the power to each unit of the cabin system  300 . The power supply  390  may operate according to a control signal from the main controller  370 . For example, the power supply  390  may be implemented as a SMPS. 
     The cabin system  300  may include at least one PCB. The main controller  370 , the memory  340 , the interface  380 , and the power supply  390  may be mounted on at least one PCB. 
     3) Input Device 
     The input device  310  may receive a user input. The input device  310  may convert the user input into an electrical signal. The electrical signal converted by the input device  310  may be converted into a control signal and provided to at least one of the display system  350 , the cargo system  355 , the seat system  360 , and the payment system  365 . The main controller  370  or at least one processor included in the cabin system  300  may generate a control signal based on an electrical signal received from the input device  310 . 
     The input device  310  may include at least one of a touch input unit, a gesture input unit, a mechanical input unit, and a voice input unit. The touch input unit may convert a touch input from the user into an electrical signal. The touch input unit may include at least one touch sensor to detect the user&#39;s touch input. In some implementations, the touch input unit may be implemented as a touch screen by integrating the touch input unit with at least one display included in the display system  350 . Such a touch screen may provide both an input interface and an output interface between the cabin system  300  and the user. The gesture input unit may convert a gesture input from the user into an electrical signal. The gesture input unit may include at least one of an infrared sensor and an image sensor to detect the user&#39;s gesture input. In some implementations, the gesture input unit may detect a three-dimensional gesture input from the user. To this end, the gesture input unit may include a plurality of light output units for outputting infrared light or a plurality of image sensors. The gesture input unit may detect the user&#39;s three-dimensional gesture input based on the TOF, structured light, or disparity principle. The mechanical input unit may convert a physical input (e.g., press or rotation) from the user through a mechanical device into an electrical signal. The mechanical input unit may include at least one of a button, a dome switch, a jog wheel, and a jog switch. Meanwhile, the gesture input unit and the mechanical input unit may be integrated. For example, the input device  310  may include a jog dial device that includes a gesture sensor and is formed such that jog dial device may be inserted/ejected into/from a part of a surrounding structure (e.g., at least one of a seat, an armrest, and a door). When the jog dial device is parallel to the surrounding structure, the jog dial device may serve as the gesture input unit. When the jog dial device protrudes from the surrounding structure, the jog dial device may serve as the mechanical input unit. The voice input unit may convert a user&#39;s voice input into an electrical signal. The voice input unit may include at least one microphone. The voice input unit may include a beamforming MIC. 
     4) Imaging Device 
     The imaging device  320  may include at least one camera. The imaging device  320  may include at least one of an internal camera and an external camera. The internal camera may capture an image of the inside of the cabin. The external camera may capture an image of the outside of the vehicle  10 . The internal camera may obtain the image of the inside of the cabin. The imaging device  320  may include at least one internal camera. It is desirable that the imaging device  320  includes as many cameras as the maximum number of passengers in the vehicle  10 . The imaging device  320  may provide an image obtained by the internal camera. The main controller  370  or at least one processor included in the cabin system  300  may detect the motion of the user from the image acquired by the internal camera, generate a signal on the basis of the detected motion, and provide the signal to at least one of the display system  350 , the cargo system  355 , the seat system  360 , and the payment system  365 . The external camera may obtain the image of the outside of the vehicle  10 . The imaging device  320  may include at least one external camera. It is desirable that the imaging device  320  include as many cameras as the maximum number of passenger doors. The imaging device  320  may provide an image obtained by the external camera. The main controller  370  or at least one processor included in the cabin system  300  may acquire user information from the image acquired by the external camera. The main controller  370  or at least one processor included in the cabin system  300  may authenticate the user or obtain information about the user body (e.g., height, weight, etc.), information about fellow passengers, and information about baggage from the user information. 
     5) Communication Device 
     The communication device  330  may exchange a signal with an external device wirelessly. The communication device  330  may exchange the signal with the external device through a network or directly. The external device may include at least one of a server, a mobile terminal, and another vehicle. The communication device  330  may exchange a signal with at least one user terminal. To perform communication, the communication device  330  may include an antenna and at least one of an RF circuit and element capable of at least one communication protocol. In some implementations, the communication device  330  may use a plurality of communication protocols. The communication device  330  may switch the communication protocol depending on the distance to a mobile terminal. 
     For example, the communication device  330  may exchange the signal with the external device based on the C-V2X technology. The C-V2X technology may include LTE-based sidelink communication and/or NR-based sidelink communication. Details related to the C-V2X technology will be described later. 
     The communication device  220  may exchange the signal with the external device according to DSRC technology or WAVE standards based on IEEE 802.11p PHY/MAC layer technology and IEEE 1609 Network/Transport layer technology. The DSRC technology (or WAVE standards) is communication specifications for providing ITS services through dedicated short-range communication between vehicle-mounted devices or between a road side unit and a vehicle-mounted device. The DSRC technology may be a communication scheme that allows the use of a frequency of 5.9 GHz and has a data transfer rate in the range of 3 Mbps to 27 Mbps. IEEE 802.11p may be combined with IEEE 1609 to support the DSRC technology (or WAVE standards). 
     According to the present disclosure, the communication device  330  may exchange the signal with the external device according to either the C-V2X technology or the DSRC technology. Alternatively, the communication device  330  may exchange the signal with the external device by combining the C-V2X technology and the DSRC technology. 
     6) Display System 
     The display system  350  may display a graphic object. The display system  350  may include at least one display device. For example, the display system  350  may include a first display device  410  for common use and a second display device  420  for individual use. 
     6.1) Common Display Device 
     The first display device  410  may include at least one display  411  to display visual content. The display  411  included in the first display device  410  may be implemented with at least one of a flat display, a curved display, a rollable display, and a flexible display. For example, the first display device  410  may include a first display  411  disposed behind a seat and configured to be inserted/ejected into/from the cabin, and a first mechanism for moving the first display  411 . The first display  411  may be disposed such that the first display  411  is capable of being inserted/ejected into/from a slot formed in a seat main frame. In some implementations, the first display device  410  may further include a mechanism for controlling a flexible part. The first display  411  may be formed to be flexible, and a flexible part of the first display  411  may be adjusted depending on the position of the user. For example, the first display device  410  may be disposed on the ceiling of the cabin and include a second display formed to be rollable and a second mechanism for rolling and releasing the second display. The second display may be formed such that images may be displayed on both sides thereof. For example, the first display device  410  may be disposed on the ceiling of the cabin and include a third display formed to be flexible and a third mechanism for bending and unbending the third display. In some implementations, the display system  350  may further include at least one processor that provides a control signal to at least one of the first display device  410  and the second display device  420 . The processor included in the display system  350  may generate a control signal based on a signal received from at last one of the main controller  370 , the input device  310 , the imaging device  320 , and the communication device  330 . 
     The display area of a display included in the first display device  410  may be divided into a first area  411   a  and a second area  411   b . The first area  411   a  may be defined as a content display area. For example, at least one of graphic objects corresponding to display entertainment content (e.g., movies, sports, shopping, food, etc.), video conferences, food menus, and augmented reality images may be displayed in the first area  411 . Further, a graphic object corresponding to driving state information about the vehicle  10  may be displayed in the first area  411   a . The driving state information may include at least one of information about an object outside the vehicle  10 , navigation information, and vehicle state information. The object information may include at least one of information about the presence of the object, information about the location of the object, information about the distance between the vehicle  10  and the object, and information about the relative speed of the vehicle  10  with respect to the object. The navigation information may include at least one of map information, information about a set destination, information about a route to the destination, information about various objects on the route, lane information, and information on the current location of the vehicle  10 . The vehicle state information may include vehicle attitude information, vehicle speed information, vehicle tilt information, vehicle weight information, vehicle orientation information, vehicle battery information, vehicle fuel information, vehicle tire pressure information, vehicle steering information, vehicle internal temperature information, vehicle internal humidity information, pedal position information, vehicle engine temperature information, etc. The second area  411   b  may be defined as a user interface area. For example, an artificial intelligence agent screen may be displayed in the second area  411   b . In some implementations, the second area  411   b  may be located in an area defined for a seat frame. In this case, the user may view content displayed in the second area  411   b  between seats. In some implementations, the first display device  410  may provide hologram content. For example, the first display device  410  may provide hologram content for each of a plurality of users so that only a user who requests the content may view the content. 
     6.2) Display Device for Individual Use 
     The second display device  420  may include at least one display  421 . The second display device  420  may provide the display  421  at a position at which only each passenger may view display content. For example, the display  421  may be disposed on the armrest of the seat. The second display device  420  may display a graphic object corresponding to personal information about the user. The second display device  420  may include as many displays  421  as the maximum number of passengers in the vehicle  10 . The second display device  420  may be layered or integrated with a touch sensor to implement a touch screen. The second display device  420  may display a graphic object for receiving a user input for seat adjustment or indoor temperature adjustment. 
     7) Cargo System 
     The cargo system  355  may provide items to the user according to the request from the user. The cargo system  355  may operate on the basis of an electrical signal generated by the input device  310  or the communication device  330 . The cargo system  355  may include a cargo box. The cargo box may include the items and be hidden under the seat. When an electrical signal based on a user input is received, the cargo box may be exposed to the cabin. The user may select a necessary item from the items loaded in the cargo box. The cargo system  355  may include a sliding mechanism and an item pop-up mechanism to expose the cargo box according to the user input. The cargo system  355  may include a plurality of cargo boxes to provide various types of items. A weight sensor for determining whether each item is provided may be installed in the cargo box. 
     8) Seat System 
     The seat system  360  may customize the seat for the user. The seat system  360  may operate on the basis of an electrical signal generated by the input device  310  or the communication device  330 . The seat system  360  may adjust at least one element of the seat by obtaining user body data. The seat system  360  may include a user detection sensor (e.g., pressure sensor) to determine whether the user sits on the seat. The seat system  360  may include a plurality of seats for a plurality of users. One of the plurality of seats may be disposed to face at least another seat. At least two users may sit while facing each other inside the cabin. 
     9) Payment System 
     The payment system  365  may provide a payment service to the user. The payment system  365  may operate on the basis of an electrical signal generated by the input device  310  or the communication device  330 . The payment system  365  may calculate the price of at least one service used by the user and request the user to pay the calculated price. 
     3. C-V2X 
     A wireless communication system is a multiple access system that supports communication of multiple users by sharing available system resources (a bandwidth, transmission power, etc.). Examples of multiple access systems include a CDMA system, an FDMA system, a TDMA system, an OFDMA system, an SC-FDMA system, and an MC-FDMA system. 
     Sidelink refers to a communication scheme in which a direct link is established between user equipments (UEs) and the UEs directly exchange voice or data without intervention of a base station (BS). The sidelink is considered as a solution of relieving the BS of the constraint of rapidly growing data traffic. 
     Vehicle-to-everything (V2X) is a communication technology in which a vehicle exchanges information with another vehicle, a pedestrian, and infrastructure by wired/wireless communication. V2X may be categorized into four types: vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), vehicle-to-network (V2N), and vehicle-to-pedestrian (V2P). V2X communication may be provided via a PC5 interface and/or a Uu interface. 
     As more and more communication devices demand larger communication capacities, there is a need for enhanced mobile broadband communication relative to existing RATs. Accordingly, a communication system is under discussion, for which services or UEs sensitive to reliability and latency are considered. The next-generation RAT in which eMBB, MTC, and URLLC are considered is referred to as new RAT or NR. In NR, V2X communication may also be supported. 
     Techniques described herein may be used in various wireless access systems such as code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier-frequency division multiple access (SC-FDMA), and so on. CDMA may be implemented as a radio technology such as universal terrestrial radio access (UTRA) or CDMA2000. TDMA may be implemented as a radio technology such as global system for mobile communications (GSM)/general packet radio service (GPRS)/Enhanced Data Rates for GSM Evolution (EDGE). OFDMA may be implemented as a radio technology such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, evolved-UTRA (E-UTRA), or the like. IEEE 802.16m is an evolution of IEEE 802.16e, offering backward compatibility with an IRRR 802.16e-based system. UTRA is a part of universal mobile telecommunications system (UMTS). 3 rd  generation partnership project (3GPP) long term evolution (LTE) is a part of evolved UMTS (E-UMTS) using evolved UTRA (E-UTRA). 3GPP LTE employs OFDMA for downlink (DL) and SC-FDMA for uplink (UL). LTE-advanced (LTE-A) is an evolution of 3GPP LTE. 
     A successor to LTE-A, 5th generation (5G) new radio access technology (NR) is a new clean-state mobile communication system characterized by high performance, low latency, and high availability. 5G NR may use all available spectral resources including a low frequency band below 1 GHz, an intermediate frequency band between 1 GHz and 10 GHz, and a high frequency (millimeter) band of 24 GHz or above. 
     While the following description is given mainly in the context of LTE-A or 5G NR for the clarity of description, the technical idea of the present disclosure is not limited thereto. 
       FIG. 7  illustrates the structure of an LTE system to which the present disclosure is applicable. This may also be called an evolved UMTS terrestrial radio access network (E-UTRAN) or LTE/LTE-A system. 
     Referring to  FIG. 7 , the E-UTRAN includes evolved Node Bs (eNBs)  20  which provide a control plane and a user plane to UEs  10 . A UE  10  may be fixed or mobile, and may also be referred to as a mobile station (MS), user terminal (UT), subscriber station (SS), mobile terminal (MT), or wireless device. An eNB  20  is a fixed station communication with the UE  10  and may also be referred to as a base station (BS), a base transceiver system (BTS), or an access point. 
     eNBs  20  may be connected to each other via an X2 interface. An eNB  20  is connected to an evolved packet core (EPC)  39  via an S1 interface. More specifically, the eNB  20  is connected to a mobility management entity (MME) via an S1-MME interface and to a serving gateway (S-GW) via an S1-U interface. 
     The EPC  30  includes an MME, an S-GW, and a packet data network-gateway (P-GW). The MME has access information or capability information about UEs, which are mainly used for mobility management of the UEs. The S-GW is a gateway having the E-UTRAN as an end point, and the P-GW is a gateway having a packet data network (PDN) as an end point. 
     Based on the lowest three layers of the open system interconnection (OSI) reference model known in communication systems, the radio protocol stack between a UE and a network may be divided into Layer 1 (L1), Layer 2 (L2) and Layer 3 (L3). These layers are defined in pairs between a UE and an Evolved UTRAN (E-UTRAN), for data transmission via the Uu interface. The physical (PHY) layer at L1 provides an information transfer service on physical channels. The radio resource control (RRC) layer at L3 functions to control radio resources between the UE and the network. For this purpose, the RRC layer exchanges RRC messages between the UE and an eNB. 
       FIG. 8  illustrates a user-plane radio protocol architecture to which the present disclosure is applicable. 
       FIG. 9  illustrates a control-plane radio protocol architecture to which the present disclosure is applicable. A user plane is a protocol stack for user data transmission, and a control plane is a protocol stack for control signal transmission. 
     Referring to  FIGS. 8 and 9 , the PHY layer provides an information transfer service to its higher layer on physical channels. The PHY layer is connected to the medium access control (MAC) layer through transport channels and data is transferred between the MAC layer and the PHY layer on the transport channels. The transport channels are divided according to features with which data is transmitted via a radio interface. 
     Data is transmitted on physical channels between different PHY layers, that is, the PHY layers of a transmitter and a receiver. The physical channels may be modulated in orthogonal frequency division multiplexing (OFDM) and use time and frequencies as radio resources. 
     The MAC layer provides services to a higher layer, radio link control (RLC) on logical channels. The MAC layer provides a function of mapping from a plurality of logical channels to a plurality of transport channels. Further, the MAC layer provides a logical channel multiplexing function by mapping a plurality of logical channels to a single transport channel. A MAC sublayer provides a data transmission service on the logical channels. 
     The RLC layer performs concatenation, segmentation, and reassembly for RLC serving data units (SDUs). In order to guarantee various quality of service (QoS) requirements of each radio bearer (RB), the RLC layer provides three operation modes, transparent mode (TM), unacknowledged mode (UM), and acknowledged Mode (AM). An AM RLC provides error correction through automatic repeat request (ARQ). 
     The RRC layer is defined only in the control plane and controls logical channels, transport channels, and physical channels in relation to configuration, reconfiguration, and release of RBs. An RB refers to a logical path provided by L1 (the PHY layer) and L2 (the MAC layer, the RLC layer, and the packet data convergence protocol (PDCP) layer), for data transmission between the UE and the network. 
     The user-plane functions of the PDCP layer include user data transmission, header compression, and ciphering. The control-plane functions of the PDCP layer include control-plane data transmission and ciphering/integrity protection. 
     RB establishment amounts to a process of defining radio protocol layers and channel features and configuring specific parameters and operation methods in order to provide a specific service. RBs may be classified into two types, signaling radio bearer (SRB) and data radio bearer (DRB). The SRB is used as a path in which an RRC message is transmitted on the control plane, whereas the DRB is used as a path in which user data is transmitted on the user plane. 
     Once an RRC connection is established between the RRC layer of the UE and the RRC layer of the E-UTRAN, the UE is placed in RRC_CONNECTED state, and otherwise, the UE is placed in RRC_IDLE state. In NR, RRC_INACTIVE state is additionally defined. A UE in the RRC_INACTIVE state may maintain a connection to a core network, while releasing a connection from an eNB. 
     DL transport channels carrying data from the network to the UE include a broadcast channel (BCH) on which system information is transmitted and a DL shared channel (DL SCH) on which user traffic or a control message is transmitted. Traffic or a control message of a DL multicast or broadcast service may be transmitted on the DL-SCH or a DL multicast channel (DL MCH). UL transport channels carrying data from the UE to the network include a random access channel (RACH) on which an initial control message is transmitted and an UL shared channel (UL SCH) on which user traffic or a control message is transmitted. 
     The logical channels which are above and mapped to the transport channels include a broadcast control channel (BCCH), a paging control channel (PCCH), a common control channel (CCCH), a multicast control channel (MCCH), and a multicast traffic channel (MTCH). 
     A physical channel includes a plurality of OFDM symbol in the time domain by a plurality of subcarriers in the frequency domain. One subframe includes a plurality of OFDM symbols in the time domain. An RB is a resource allocation unit defined by a plurality of OFDM symbols by a plurality of subcarriers. Further, each subframe may use specific subcarriers of specific OFDM symbols (e.g., the first OFDM symbol) in a corresponding subframe for a physical DL control channel (PDCCH), that is, an L1/L2 control channel. A transmission time interval (TTI) is a unit time for subframe transmission. 
       FIG. 10  illustrates the structure of a NR system to which the present disclosure is applicable. 
     Referring to  FIG. 10 , a next generation radio access network (NG-RAN) may include a next generation Node B (gNB) and/or an eNB, which provides user-plane and control-plane protocol termination to a UE. In  FIG. 10 , the NG-RAN is shown as including only gNBs, by way of example. A gNB and an eNB are connected to each other via an Xn interface. The gNB and the eNB are connected to a 5G core network (5GC) via an NG interface. More specifically, the gNB and the eNB are connected to an access and mobility management function (AMF) via an NG-C interface and to a user plane function (UPF) via an NG-U interface. 
       FIG. 11  illustrates functional split between the NG-RAN and the 5GC to which the present disclosure is applicable. 
     Referring to  FIG. 11 , a gNB may provide functions including inter-cell radio resource management (RRM), radio admission control, measurement configuration and provision, and dynamic resource allocation. The AMF may provide functions such as non-access stratum (NAS) security and idle-state mobility processing. The UPF may provide functions including mobility anchoring and protocol data unit (PDU) processing. A session management function (SMF) may provide functions including UE Internet protocol (IP) address allocation and PDU session control. 
       FIG. 12  illustrates the structure of a NR radio frame to which the present disclosure is applicable. 
     Referring to  FIG. 12 , a radio frame may be used for UL transmission and DL transmission in NR. A radio frame is 10 ms in length, and may be defined by two 5-ms half-frames. An HF may include five 1-ms subframes. A subframe may be divided into one or more slots, and the number of slots in an SF may be determined according to a subcarrier spacing (SCS). Each slot may include 12 or 14 OFDM(A) symbols according to a cyclic prefix (CP). 
     In a normal CP (NCP) case, each slot may include 14 symbols, whereas in an extended CP (ECP) case, each slot may include 12 symbols. Herein, a symbol may be an OFDM symbol (or CP-OFDM symbol) or an SC-FDMA symbol (or DFT-s-OFDM symbol). 
     Table 1 below lists the number of symbols per slot N slot   symb , the number of slots per frame N frame,u   slot , and the number of slots per subframe N subframe,u   slot  according to an SCS configuration μ in the NCP case. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 1 
               
               
                   
               
               
                 SCS (15*2u) 
                 N slot   symb   
                 N frame, u   slot   
                 N subframe, u   slot   
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                  15 KHz (u = 0) 
                 14 
                 10 
                 1 
               
               
                  30 KHz (u = 1) 
                 14 
                 20 
                 2 
               
               
                  60 KHz (u = 2) 
                 14 
                 40 
                 4 
               
               
                 120 KHz (u = 3) 
                 14 
                 80 
                 8 
               
               
                 240 KHz (u = 4) 
                 14 
                 160 
                 16 
               
               
                   
               
            
           
         
       
     
     Table 2 below lists the number of symbols per slot, the number of slots per frame, and the number of slots per subframe according to an SCS in the ECP case. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 2 
               
               
                   
               
               
                 SCS (15*2{circumflex over ( )}u) 
                 N slot   symb   
                 N frame, u   slot   
                 N subframe, u   slot   
               
               
                   
               
             
            
               
                 60 KHz (u = 2) 
                 12 
                 40 
                 4 
               
               
                   
               
            
           
         
       
     
     In the NR system, different OFDM(A) numerologies (e.g., SCSs, CP lengths, etc.) may be configured for a plurality of cells aggregated for one UE. Thus, the (absolute) duration of a time resource (e.g., SF, slot, or TTI) including the same number of symbols may differ between the aggregated cells (such a time resource is commonly referred to as a time unit (TU) for convenience of description). 
       FIG. 13  illustrates the slot structure of a NR frame to which the present disclosure is applicable. 
     Referring to  FIG. 13 , one slot includes a plurality of symbols in the time domain. For example, one slot may include 14 symbols in a normal CP and 12 symbols in an extended CP. Alternatively, one slot may include 7 symbols in the normal CP and 6 symbols in the extended CP. 
     A carrier may include a plurality of subcarriers in the frequency domain. A resource block (RB) is defined as a plurality of consecutive subcarriers (e.g., 12 subcarriers) in the frequency domain. A bandwidth part (BWP) may be defined as a plurality of consecutive (P)RBs in the frequency domain, and the BWP may correspond to one numerology (e.g., SCS, CP length, etc.). The carrier may include up to N (e.g., 5) BWPs. Data communication may be conducted in an activated BWP. In a resource grid, each element is referred to as a resource element (RE), and one complex symbol may be mapped thereto. 
     As shown in  FIG. 14 , when transmission resources are selected, the transmission resource for a next packet may also be reserved. 
       FIG. 14  illustrates an example of transmission resource selection to which the present disclosure is applicable. 
     In V2X communication, transmission may be performed twice for each MAC PDU. For example, referring to  FIG. 14 , when resources for initial transmission are selected, resources for retransmission may also be reserved apart from the resources for initial transmission by a predetermined time gap. A UE may identify transmission resources reserved or used by other UEs through sensing in a sensing window, exclude the transmission resources from a selection window, and randomly select resources with less interference from among the remaining resources. 
     For example, the UE may decode a physical sidelink control channel (PSCCH) including information about the cycle of reserved resources within the sensing window and measure physical sidelink shared channel (PSSCH) reference signal received power (RSRP) on periodic resources determined based on the PSCCH. The UE may exclude resources with PSCCH RSRP more than a threshold from the selection window. Thereafter, the UE may randomly select sidelink resources from the remaining resources in the selection window. 
     Alternatively, the UE may measure received signal strength indication (RSSI) for the periodic resources in the sensing window and identify resources with less interference (for example, the bottom 20 percent). After selecting resources included in the selection window from among the periodic resources, the UE may randomly select sidelink resources from among the resources included in the selection window. For example, when the UE fails to decode the PSCCH, the UE may apply the above-described method. 
       FIG. 15  illustrates an example of PSCCH transmission in sidelink transmission mode  3  or  4  to which the present disclosure is applicable. 
     In V2X communication, that is, in sidelink transmission mode  3  or  4 , a PSCCH and a PSSCH are frequency division multiplexed (FDM) and transmitted, unlike sidelink communication. Since latency reduction is important in V2X in consideration of the nature of vehicle communication, the PSCCH and PSSCH are FDM and transmitted on the same time resources but different frequency resources. Referring to  FIG. 15 , the PSCCH and PSSCH may not be contiguous to each other as illustrated in  FIG. 15 ( a )  or may be contiguous to each other as illustrated in  FIG. 15 ( b ) . A subchannel is used as a basic transmission unit. The subchannel may be a resource unit including one or more RBs in the frequency domain within a predetermined time resource (e.g., time resource unit). The number of RBs included in the subchannel (i.e., the size of the subchannel and the starting position of the subchannel in the frequency domain) may be indicated by higher layer signaling. The example of  FIG. 15  may be applied to NR sidelink resource allocation mode  1  or  2 . 
     Hereinafter, a cooperative awareness message (CAM) and a decentralized environmental notification message (DENM) will be described. 
     In V2V communication, a periodic message type of CAM and an event-triggered type of DENM may be transmitted. The CAM may include dynamic state information about a vehicle such as direction and speed, vehicle static data such as dimensions, and basic vehicle information such as ambient illumination states, path details, etc. The CAM may be 50 to 300 bytes long. In addition, the CAM is broadcast, and the latency thereof should be less than 100 ms. The DENM may be generated upon the occurrence of an unexpected incident such as a breakdown, an accident, etc. The DENM may be shorter than 3000 bytes, and it may be received by all vehicles within the transmission range thereof. The DENM may be prioritized over the CAM. 
     Hereinafter, carrier reselection will be described. 
     The carrier reselection for V2X/sidelink communication may be performed by MAC layers based on the channel busy ratio (CBR) of configured carriers and the ProSe per-packet priority (PPPP) of a V2X message to be transmitted. 
     The CBR may refer to a portion of sub-channels in a resource pool where S-RSSI measured by the UE is greater than a preconfigured threshold. There may be a PPPP related to each logical channel, and latency required by both the UE and BS needs to be reflected when the PPPP is configured. In the carrier reselection, the UE may select at least one carrier among candidate carriers in ascending order from the lowest CBR. 
     Hereinafter, physical layer processing will be described. 
     A transmitting side may perform the physical layer processing on a data unit to which the present disclosure is applicable before transmitting the data unit over an air interface, and a receiving side may perform the physical layer processing on a radio signal carrying the data unit to which the present disclosure is applicable. 
       FIG. 16  illustrates physical layer processing at a transmitting side to which the present disclosure is applicable. 
     Table 3 shows a mapping relationship between UL transport channels and physical channels, and Table 4 shows a mapping relationship between UL control channel information and physical channels. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                 Transport  
                 Physical  
               
               
                   
                 channel 
                 channel 
               
               
                   
                   
               
             
            
               
                   
                 UL-SCH 
                 PUSCH 
               
               
                   
                 RACH 
                 PRACH 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
                 TABLE 4 
               
               
                   
                   
               
               
                   
                 Control  
                 Physical  
               
               
                   
                 information 
                 channel 
               
               
                   
                   
               
             
            
               
                   
                 UCI 
                 PUCCH,  
               
               
                   
                   
                 PUSCH 
               
               
                   
                   
               
            
           
         
       
     
     Table 5 shows a mapping relationship between DL transport channels and physical channels, and Table 6 shows a mapping relationship between DL control channel information and physical channels. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 5 
               
               
                   
                   
               
               
                   
                 Transport  
                 Transport  
               
               
                   
                 channel 
                 channel 
               
               
                   
                   
               
             
            
               
                   
                 DL-SCH 
                 PDSCH 
               
               
                   
                 BCH 
                 PBCH 
               
               
                   
                 PCH 
                 PDSCH 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
                 TABLE 6 
               
               
                   
                   
               
               
                   
                 Control  
                 Physical  
               
               
                   
                 information 
                 channel 
               
               
                   
                   
               
             
            
               
                   
                 DCI 
                 PDCCH 
               
               
                   
                   
               
            
           
         
       
     
     Table 7 shows a mapping relationship between sidelink transport channels and physical channels, and Table 8 shows a mapping relationship between sidelink control channel information and physical channels. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 7 
               
               
                   
                   
               
               
                   
                 Transport  
                 Transport  
               
               
                   
                 channel 
                 channel 
               
               
                   
                   
               
             
            
               
                   
                 SL-SCH 
                 PSSCH 
               
               
                   
                 SL-BCH 
                 PSBCH 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
                 TABLE 8 
               
               
                   
                   
               
               
                   
                 Control  
                 Transport  
               
               
                   
                 information 
                 channel 
               
               
                   
                   
               
             
            
               
                   
                 SCI 
                 PSCCH 
               
               
                   
                   
               
            
           
         
       
     
     Referring to  FIG. 16 , a transmitting side may encode a TB in step S 100 . The PHY layer may encode data and a control stream from the MAC layer to provide transport and control services via a radio transmission link in the PHY layer. For example, a TB from the MAC layer may be encoded to a codeword at the transmitting side. A channel coding scheme may be a combination of error detection, error correction, rate matching, interleaving, and control information or a transport channel demapped from a physical channel. Alternatively, a channel coding scheme may be a combination of error detection, error correcting, rate matching, interleaving, and control information or a transport channel mapped to a physical channel. 
     In the LTE system, the following channel coding schemes may be used for different types of transport channels and different types of control information. For example, channel coding schemes for respective transport channel types may be listed as in Table 9. For example, channel coding schemes for respective control information types may be listed as in Table 10. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE 9 
               
               
                   
                   
               
               
                   
                 Transport  
                 Channel  
               
               
                   
                 channel 
                 coding scheme 
               
               
                   
                   
               
             
            
               
                   
                 UL-SCH 
                 LDPC  
               
               
                   
                 DL-SCH 
                 (Low Density 
               
               
                   
                 SL-SCH 
                 Parity Check) 
               
               
                   
                 PCH 
                   
               
               
                   
                 BCH 
                 Polar code 
               
               
                   
                 SL-BCH 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                   
                 TABLE 10 
               
               
                   
                   
               
               
                   
                 Control  
                 Channel  
               
               
                   
                 information 
                 coding scheme 
               
               
                   
                   
               
             
            
               
                   
                 DCI 
                 Polar code 
               
               
                   
                 SCI 
                   
               
               
                   
                 UCI 
                 Block code,  
               
               
                   
                   
                 Polar code 
               
               
                   
                   
               
            
           
         
       
     
     For transmission of a TB (e.g., a MAC PDU), the transmitting side may attach a CRC sequence to the TB. Thus, the transmitting side may provide error detection for the receiving side. In sidelink communication, the transmitting side may be a transmitting UE, and the receiving side may be a receiving UE. In the NR system, a communication device may use an LDPC code to encode/decode a UL-SCH and a DL-SCH. The NR system may support two LDPC base graphs (i.e., two LDPC base metrics). The two LDPC base graphs may be LDPC base graph 1 optimized for a small TB and LDPC base graph 2 optimized for a large TB. The transmitting side may select LDPC base graph 1 or LDPC base graph 2 based on the size and coding rate R of a TB. The coding rate may be indicated by an MCS index, I_MCS. The MCS index may be dynamically provided to the UE by a PDCCH that schedules a PUSCH or PDSCH. Alternatively, the MCS index may be dynamically provided to the UE by a PDCCH that (re)initializes or activates UL configured grant type 2 or DL semi-persistent scheduling (SPS). The MCS index may be provided to the UE by RRC signaling related to UL configured grant type 1. When the TB attached with the CRC is larger than a maximum code block (CB) size for the selected LDPC base graph, the transmitting side may divide the TB attached with the CRC into a plurality of CBs. The transmitting side may further attach an additional CRC sequence to each CB. The maximum code block sizes for LDPC base graph 1 and LDPC base graph 2 may be 8448 bits and 3480 bits, respectively. When the TB attached with the CRC is not larger than the maximum CB size for the selected LDPC base graph, the transmitting side may encode the TB attached with the CRC to the selected LDPC base graph. The transmitting side may encode each CB of the TB to the selected LDPC basic graph. The LDPC CBs may be rate-matched individually. The CBs may be concatenated to generate a codeword for transmission on a PDSCH or a PUSCH. Up to two codewords (i.e., up to two TBs) may be transmitted simultaneously on the PDSCH. The PUSCH may be used for transmission of UL-SCH data and layer-1 and/or layer-2 control information. While not shown in  FIG. 16 , layer-1 and/or layer-2 control information may be multiplexed with a codeword for UL-SCH data. 
     In steps S 101  and S 102 , the transmitting side may scramble and modulate the codeword. The bits of the codeword may be scrambled and modulated to produce a block of complex-valued modulation symbols. 
     In step S 103 , the transmitting side may perform layer mapping. The complex-valued modulation symbols of the codeword may be mapped to one or more MIMO layers. The codeword may be mapped to up to four layers. The PDSCH may carry two codewords, thus supporting up to 8-layer transmission. The PUSCH may support a single codeword, thus supporting up to 4-layer transmission. 
     In step S 104 , the transmitting side may perform precoding transform. A DL transmission waveform may be general OFDM using a CP. For DL, transform precoding (i.e., discrete Fourier transform (DFT)) may not be applied. 
     A UL transmission waveform may be conventional OFDM using a CP having a transform precoding function that performs DFT spreading which may be disabled or enabled. In the NR system, transform precoding, if enabled, may be selectively applied to UL. Transform precoding may be to spread UL data in a special way to reduce the PAPR of the waveform. Transform precoding may be a kind of DFT. That is, the NR system may support two options for the UL waveform. One of the two options may be CP-OFDM (same as DL waveform) and the other may be DFT-s-OFDM. Whether the UE should use CP-OFDM or DFT-s-OFDM may be determined by the BS through an RRC parameter. 
     In step S 105 , the transmitting side may perform subcarrier mapping. A layer may be mapped to an antenna port. In DL, transparent (non-codebook-based) mapping may be supported for layer-to-antenna port mapping, and how beamforming or MIMO precoding is performed may be transparent to the UE. In UL, both non-codebook-based mapping and codebook-based mapping may be supported for layer-to-antenna port mapping. 
     For each antenna port (i.e. layer) used for transmission of a physical channel (e.g. PDSCH, PUSCH, or PSSCH), the transmitting side may map complex-valued modulation symbols to subcarriers in an RB allocated to the physical channel. 
     In step S 106 , the transmitting side may perform OFDM modulation. A communication device of the transmitting side may add a CP and perform inverse fast Fourier transform (IFFT), thereby generating a time-continuous OFDM baseband signal on an antenna port p and a subcarrier spacing (SPS) configuration u for an OFDM symbol  1  within a TTI for the physical channel. For example, for each OFDM symbol, the communication device of the transmitting side may perform IFFT on a complex-valued modulation symbol mapped to an RB of the corresponding OFDM symbol. The communication device of the transmitting side may add a CP to the IFFI signal to generate an OFDM baseband signal. 
     In step S 107 , the transmitting side may perform up-conversion. The communication device of the transmitting side may upconvert the OFDM baseband signal, the SCS configuration u, and the OFDM symbol  1  for the antenna port p to a carrier frequency f0 of a cell to which the physical channel is allocated. 
     Processors  102  and  202  of  FIG. 23  may be configured to perform encoding, scrambling, modulation, layer mapping, precoding transformation (for UL), subcarrier mapping, and OFDM modulation. 
       FIG. 17  illustrates PHY-layer processing at a receiving side to which the present disclosure is applicable. 
     The PHY-layer processing of the receiving side may be basically the reverse processing of the PHY-layer processing of a transmitting side. 
     In step S 110 , the receiving side may perform frequency downconversion. A communication device of the receiving side may receive a radio frequency (RF) signal in a carrier frequency through an antenna. A transceiver  106  or  206  that receives the RF signal in the carrier frequency may downconvert the carrier frequency of the RF signal to a baseband to obtain an OFDM baseband signal. 
     In step S 111 , the receiving side may perform OFDM demodulation. The communication device of the receiving side may acquire complex-valued modulation symbols by CP detachment and fast Fourier transform (IFFT). For example, for each OFDM symbol, the communication device of the receiving side may remove a CP from the OFDM baseband signal. The communication device of the receiving side may then perform FFT on the CP-free OFDM baseband signal to obtain complex-valued modulation symbols for an antenna port p, an SCS u, and an OFDM symbol  1 . 
     In step S 112 , the receiving side may perform subcarrier demapping. Subcarrier demapping may be performed on the complex-valued modulation symbols to obtain complex-valued modulation symbols of the physical channel. For example, the processor of a UE may obtain complex-valued modulation symbols mapped to subcarriers of a PDSCH among complex-valued modulation symbols received in a BWP. 
     In step S 113 , the receiving side may perform transform de-precoding. When transform precoding is enabled for a UL physical channel, transform de-precoding (e.g., inverse discrete Fourier transform (IDFT)) may be performed on complex-valued modulation symbols of the UL physical channel. Transform de-precoding may not be performed for a DL physical channel and a UL physical channel for which transform precoding is disabled. 
     In step S 114 , the receiving side may perform layer demapping. The complex-valued modulation symbols may be demapped into one or two codewords. 
     In steps S 115  and S 116 , the receiving side may perform demodulation and descrambling. The complex-valued modulation symbols of the codewords may be demodulated and descrambled into bits of the codewords. 
     In step S 117 , the receiving side may perform decoding. The codewords may be decoded into TBs. For a UL-SCH and a DL-SCH, LDPC base graph 1 or LDPC base graph 2 may be selected based on the size and coding rate R of a TB. A codeword may include one or more CBs. Each coded block may be decoded into a CB to which a CRC has been attached or a TB to which a CRC has been attached, by the selected LDPC base graph. When CB segmentation has been performed for the TB attached with the CRC at the transmitting side, a CRC sequence may be removed from each of the CBs each attached with a CRC, thus obtaining CBs. The CBs may be concatenated to a TB attached with a CRC. A TB CRC sequence may be removed from the TB attached with the CRC, thereby obtaining the TB. The TB may be delivered to the MAC layer. 
     Each of processors  102  and  202  of  FIG. 22  may be configured to perform OFDM demodulation, subcarrier demapping, layer demapping, demodulation, descrambling, and decoding. 
     In the above-described PHY-layer processing on the transmitting/receiving side, time and frequency resources (e.g., OFDM symbol, subcarrier, and carrier frequency) related to subcarrier mapping, OFDM modulation, and frequency upconversion/downconversion may be determined based on a resource allocation (e.g., an UL grant or a DL assignment). 
     Synchronization acquisition of a sidelink UE will be described below. 
     In TDMA and FDMA systems, accurate time and frequency synchronization is essential. Inaccurate time and frequency synchronization may lead to degradation of system performance due to inter-symbol interference (ISI) and inter-carrier interference (ICI). The same is true for V2X. For time/frequency synchronization in V2X, a sidelink synchronization signal (SLSS) may be used in the PHY layer, and master information block-sidelink-V2X (MIB-SL-V2X) may be used in the RLC layer. 
       FIG. 18  illustrates a V2X synchronization source or reference to which the present disclosure is applicable. 
     Referring to  FIG. 18 , in V2X, a UE may be synchronized with a GNSS directly or indirectly through a UE (within or out of network coverage) directly synchronized with the GNSS. When the GNSS is configured as a synchronization source, the UE may calculate a direct subframe number (DFN) and a subframe number by using a coordinated universal time (UTC) and a (pre)determined DFN offset. 
     Alternatively, the UE may be synchronized with a BS directly or with another UE which has been time/frequency synchronized with the BS. For example, the BS may be an eNB or a gNB. For example, when the UE is in network coverage, the UE may receive synchronization information provided by the BS and may be directly synchronized with the BS. Thereafter, the UE may provide synchronization information to another neighboring UE. When a BS timing is set as a synchronization reference, the UE may follow a cell associated with a corresponding frequency (when within the cell coverage in the frequency), a primary cell, or a serving cell (when out of cell coverage in the frequency), for synchronization and DL measurement. 
     The BS (e.g., serving cell) may provide a synchronization configuration for a carrier used for V2X or sidelink communication. In this case, the UE may follow the synchronization configuration received from the BS. When the UE fails in detecting any cell in the carrier used for the V2X or sidelink communication and receiving the synchronization configuration from the serving cell, the UE may follow a predetermined synchronization configuration. 
     Alternatively, the UE may be synchronized with another UE which has not obtained synchronization information directly or indirectly from the BS or GNSS. A synchronization source and a preference may be preset for the UE. Alternatively, the synchronization source and the preference may be configured for the UE by a control message provided by the BS. 
     A sidelink synchronization source may be related to a synchronization priority. For example, the relationship between synchronization sources and synchronization priorities may be defined as shown in Table 11. Table 11 is merely an example, and the relationship between synchronization sources and synchronization priorities may be defined in various manners. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 11 
               
               
                   
                   
               
               
                   
                   
                   
                 BS-based synchronization 
               
               
                   
                   
                 GNSS-based  
                 (eNB/gNB-based  
               
               
                   
                 Priority 
                 synchronization 
                 synchronization) 
               
               
                   
                   
               
             
            
               
                   
                 P0 
                 GNSS 
                 BS 
               
               
                   
                 P1 
                 All UEs directly  
                 All UEs directly  
               
               
                   
                   
                 synchronized  
                 synchronized with BS 
               
               
                   
                   
                 with GNSS 
                   
               
               
                   
                 P2 
                 All UEs indirectly 
                 All UEs indirectly  
               
               
                   
                   
                 synchronized  
                 synchronized with BS 
               
               
                   
                   
                 with GNSS 
                   
               
               
                   
                 P3 
                 All other UEs 
                 GNSS 
               
               
                   
                 P4 
                 N/A 
                 All UEs directly  
               
               
                   
                   
                   
                 synchronized with GNSS 
               
               
                   
                 P5 
                 N/A 
                 All UEs indirectly  
               
               
                   
                   
                   
                 synchronized with GNSS 
               
               
                   
                 P6 
                 N/A 
                 All other UEs 
               
               
                   
                   
               
            
           
         
       
     
     Whether to use GNSS-based synchronization or BS-based synchronization may be (pre)determined. In a single-carrier operation, the UE may derive its transmission timing from an available synchronization reference with the highest priority. 
     In the conventional sidelink communication, the GNSS, eNB, and UE may be set/selected as the synchronization reference as described above. In NR, the gNB has been introduced so that the NR gNB may become the synchronization reference as well. However, in this case, the synchronization source priority of the gNB needs to be determined. In addition, a NR UE may neither have an LTE synchronization signal detector nor access an LTE carrier (non-standalone NR UE). In this situation, the timing of the NR UE may be different from that of an LTE UE, which is not desirable from the perspective of effective resource allocation. For example, if the LTE UE and NR UE operate at different timings, one TTI may partially overlap, resulting in unstable interference therebetween, or some (overlapping) TTIs may not be used for transmission and reception. To this end, various implementations for configuring the synchronization reference when the NR gNB and LTE eNB coexist will be described based on the above discussion. Herein, the synchronization source/reference may be defined as a synchronization signal used by the UE to transmit and receive a sidelink signal or derive a timing for determining a subframe boundary. Alternatively, the synchronization source/reference may be defined as a subject that transmits the synchronization signal. If the UE receives a GNSS signal and determines the subframe boundary based on a UTC timing derived from the GNSS, the GNSS signal or GNSS may be the synchronization source/reference. 
     Implementations 
     According to an implementation of the present disclosure, the (sidelink) UE may select the synchronization reference from among a plurality of synchronization sources based on priorities thereof and then transmit or receive a sidelink signal based on the selected synchronization reference. The priorities of the eNB and gNB may be configured by the BS or preconfigured by the network. Specifically, in the case of an in-coverage UE, the priorities may be configured by the BS. In the case of an out-of-coverage UE, the priorities may be preconfigured by the network. The plurality of synchronization sources may include both the eNB and gNB, and the eNB and gNB may have the same priority. In other words, the LTE eNB may have the same priority as that of the gNB. Regarding the priority of Table 11, the BS may refer to both the eNB and gNB, or the BS may be replaced with the eNB/gNB. When the priorities of the eNB and gNB are set equal to each other, interference caused by signal transmission at the UE may be significantly reduced. When synchronization signals from the eNB and gNB are capable of being detected, if a specific type of BS has a high synchronization source priority, strong asynchronous interference to communication with the other type of BS may be mitigated. Specifically, when the UE is located close to the eNB (that is, when the UE is farther away from the gNB than the eNB), the UE may be capable of detecting a synchronization signal from the gNB. In this case, if the synchronization source priority of the gNB is higher than that of the eNB, the UE may calculate time/frequency synchronization from the synchronization signal from the gNB and then transmit a sidelink signal based on the calculated time/frequency synchronization. If the eNB and gNB are not synchronized, the sidelink signal transmission at the corresponding UE may cause strong asynchronous interference to communication with the eNB (since the corresponding UE is closer to the eNB, the interference level increases). If the eNB and gNB have the same priority, the impact of the inference may be reduced. 
     In another example, the gNB may have a higher priority than the UE, or the gNB may be excluded from synchronization source priorities. 
     The UE may receive the priorities through either higher layer signaling or physical layer signaling. For example, as shown in  FIG. 19 , the UE may receive priority-related information (sidelink synchronization priority information, priority information, information provided by the network, etc.) from the gNB through a physical layer or higher layer signal. For example, some or all of the following: the synchronization source priority of the gNB, information about whether the gNB is used as the synchronization reference, the synchronization source priority of the gNB when the gNB is used as the synchronization reference, the priority of an SLSS transmitted from a UE directly synchronized with the gNB (gNB direct SLSS), the priority of an SLSS transmitted from a UE indirectly synchronized with the gNB (gNB in-direct SLSS), a priority relationship with the LTE eNB, and a priority relationship with an eNB direct SLSS or eNB indirect SLSS may be signaled to the UE (or preconfigured for the UE) through a physical layer or higher layer signal from the gNB or eNB. 
     When the eNB and gNB have the same priority, the UE may select the synchronization reference based on signal strength (e.g., RSRP, RSRQ, etc.). That is, when the eNB and gNB has the same priority, the UE may select a synchronization reference with high RSRP. The RSRP/RSRQ may be measured based on at least one of a PBCH DMRS, a synchronization signal, or channel state information (CSI). For example, the RSRP/RSRQ may be SS-RSRP/RSRQ, CSI-RSRP/RSRQ, etc. The RSRP/RSRQ may be measured for each synchronization signal block (SSB) of the gNB. In the case of the gNB, the RSRP may vary for each beam due to multi-beam transmission. In this case, the RSRP measured for each beam (or each SSB) may be compared with the RSRP of the LTE eNB. Alternatively, the average/maximum/minimum/filtered value of RSRP of multiple beams may be compared with the RSRP of the LTE eNB. 
     When the UE selects a synchronization reference with high RSRP/RSRQ, an offset value, which is indicated by either physical layer signaling or higher layer signaling, may be applied to either the RSRP/RSRQ related to the gNB or the RSRP/RSRQ related to the eNB. To give bias to a specific type of BS, an RSRP offset may be defined. The RSRP offset may be signaled by the eNB or gNB to the UE through a physical layer or higher layer signal. 
     The network may properly determine the synchronization source priority of the gNB depending on the state or capability of the UE. The determination depending on the UE state may be interpreted as follows. When there are many NR non-standalone UEs, the LTE eNB has a higher priority. Otherwise, the NR gNB has a higher priority. 
     Together with or separately from the above-described synchronization reference selection, the UE may transmit a timing difference between the eNB and gNB to at least one of the eNB, the gNB, and another UE. In other words, the UE may transmit the timing difference between the eNB and gNB to either or both the eNB and gNB over a UL channel or transmit the timing difference between the eNB and gNB to the other UE over a sidelink channel. The timing difference may be determined from synchronization signals received by the UE from the eNB and gNB, respectively. If the UE is capable of detecting both the synchronization signals from the LTE eNB and NR gNB or both an LTE SLSS and a NR SLSS, the UE may signal a timing difference between two different synchronization references, which is derived from the different BSs, to a neighboring UE through a physical layer or higher layer signal. Alternatively, the UE may signal the timing difference to the network through a physical layer or higher layer signal. For example, as shown in  FIG. 20 , the UE may feed back information about the timing difference between the eNB and gNB or information about the timing difference between the LTE SLSS and NR SLSS at the request of the gNB or eNB. In another example, as shown in  FIG. 21 , the UE may signal the information about the timing difference between the eNB and gNB or the information about the timing difference between the LTE SLSS and NR SLSS to another UE. 
     According to the above-described configuration, the UE may detect a timing difference between different BSs and provide the timing difference to a neighboring UE or a neighboring BS. That is, the UE may assist a UE unaware of the timing difference in establishing synchronization or allow the BS to adjust its timing, thereby establishing synchronization between the NR gNB and LTE eNB. 
     When the UE performs transmission based on a predetermined format or numerology, the UE may assume that the gNB has a higher priority than the eNB. For example, when the UE performs transmission based on a 5G-related format or numerology, the UE may select the gNB as the synchronization reference. When the UE transmits its message based on a NR format (numerology) (for example, when service requirements are capable of being satisfied by only the NR format (numerology)), the UE may prioritize a NR gNB SYNCH (or NR SLSS). The reason for this is to protect NR communication when LTE and NR are deployed asynchronously. 
     As another example related to the priority, when the UE uses the LTE eNB as the synchronization reference, an SLSS transmitted from the UE may have a higher priority than the gNB. The reason for this is to align NR UEs with an LTE timing if possible and to allow a UE with no eNB synchronization signal detector to follow the LTE timing effectively. In this case, it is assumed that the NR UE has an LTE SLSS detector. When the LTE eNB is prioritized as described above, time division multiplexing (TDM) may be effectively applied between a UE operating based on LTE sidelink and a UE operating based on NR sidelink. 
     A gNB at a predetermined carrier frequency or higher may be configured not to be used as the synchronization reference. The gNB at the predetermined carrier frequency or higher may be interpreted as a BS operating at a frequency band higher than a specific frequency band among BSs (including at least one of one or more eNBs and one or more gNBs). In general, since the NR frequency band is higher than the LTE frequency band, the gNB may correspond to the above-described BS. The coverage of the gNB may decrease at the predetermined carrier frequency or higher so that there may be a small number of UEs in the coverage of the gNB. In this case, it is not suitable that the gNB is used as the synchronization source. Among gNBs, gNBs operating below a predetermined frequency may operate as the synchronization reference, and the network may signal to the UE the gNBs operating as the synchronization reference through a physical layer or higher layer signal. The network may determine synchronization source priorities for multiple frequencies. For example, the priorities may be determined as follows: carrier A, carrier B, and carrier C. The reason for this is to allow the UE to prioritize and select a specific frequency when observing the gNB or eNB on multiple CCs. As described above, since an eNB/gNB at a specific frequency has a wider coverage, the eNB/gNB at the corresponding frequency may become a more suitable synchronization reference. 
     As a further example related to the priority, the synchronization source priority may vary depending on the capability of the UE. For example, whether the LTE eNB or LTE SLSS is considered may be determined depending on whether an LTE Uu Tx/Rx chain and/or an LTE sidelink synchronization Tx/Rx chain is implemented. When the UE is implemented to have the LTE Uu Tx/Rx chain and LTE sidelink synchronization Tx/Rx chain, the network may signal to the UE the synchronization source priority of the LTE eNB or LTE SLSS through a physical layer or higher layer signal. When the UE is implemented to have only the LTE sidelink synchronization Tx/Rx chain without the LTE Uu Tx/Rx chain, the network may signal the synchronization source priority of the LTE SLSS through a physical layer or higher layer signal. 
     The synchronization source priority may be configured differently depending on the multi-carrier capability of the UE or the band or band combination supported by the UE. For example, when a specific UE is capable of accessing only a NR band, the NR gNB may be configured for the corresponding UE. Further, a gNB-related SLSS (gNB direct or indirect SLSS), an independent SLSS (out coverage), and/or a GNSS-based synchronization source priority may also be configured. As another example, when a UE is capable of accessing an LTE band, the synchronization source priority of the LTE eNB may be preconfigured or signaled to the UE through a higher layer signal. 
     The LTE eNB may have a higher (or lower) priority than the gNB. In this case, the gNB may have a higher priority than the UE or excluded from synchronization source priorities. In this case, the gNB may have a higher priority than the UE or excluded from synchronization source priorities. 
     The NR SLSS and/or a physical sidelink broadcast channel (PSBCH) may be equal or similar to the LTE SLSS and/or an LTE PSBCH. For example, the NR SLSS may have a structure in which a primary sidelink synchronization signal (PSSS) and a secondary sidelink synchronization signal (SSSS) are repeated twice in one subframe (or slot). The sequence generation for the PSSS/SSSS may be the same as that for a PSSS/SSSS of the LTE SLSS, or the PSSS/SSSS of the NR SLSS may have some similar characteristics to the PSSS/SSSS of the LTE SLSS. When (a part or the entirety of) the LTE SLSS detector is capable of being reused as a NR SLSS detector, implementation complexity may be reduced. For example, the NR SLSS and LTE SLSS may have the same the PSSS/SSSS, but those may be arranged in different symbols. 
     Since the LTE PSSS/SSSS is generated based on an SC-FDMA waveform, the following subcarrier mapping method may be used to generate the NR PSSS/SSSS. In this subcarrier mapping method, a half subcarrier is shifted with respect to a DC subcarrier in the direction of the DC subcarrier without puncturing the DC subcarrier. The subcarrier mapping method may be applied to PSBCH/PSSCH/PSCCH transmission. The subcarrier mapping method may be determined by network signaling. For example, the network may instruct to use a legacy subcarrier mapping method for LTE sidelink through a physical layer or higher layer signal. When the network does not transmit the above signaling or when the network instructs not to use the subcarrier mapping method for LTE sidelink, the subcarrier mapping method used in NR may be adopted. 
     The present disclosure is not limited to D2D communication. That is, the disclosure may be applied to UL or DL communication, and in this case, the proposed methods may be used by a BS, a relay node, etc. 
     Since each of the examples of the proposed methods may be included as one method for implementing the present disclosure, it is apparent that each example may be regarded as a proposed method. Although the proposed methods may be implemented independently, some of the proposed methods may be combined (or merged) for implementation. In addition, it may be regulated that information on whether the proposed methods are applied (or information on rules related to the proposed methods) should be transmitted from a BS to a UE or from a transmitting UE to a receiving UE through a predefined signal (e.g., a physical layer signal, a higher layer signal, etc.). 
     Device Configurations According to Implementations of the Present Disclosure 
     Hereinbelow, a device to which the present disclosure is applicable will be described. 
       FIG. 22  illustrates a wireless communication device according to an implementation of the present disclosure. 
     Referring to  FIG. 22 , a wireless communication system may include a first device  9010  and a second device  9020 . 
     The first device  9010  may be a BS, a network node, a transmitting UE, a receiving UE, a radio device, a wireless communication device, a vehicle, an autonomous driving vehicle, a connected car, a drone (unmanned aerial vehicle (UAV)), an artificial intelligence (AI) module, a robot, an augmented reality (AR) device, a virtual reality (VR) device, a mixed reality (MR) device, a hologram device, a public safety device, an MTC device, an IoT device, a medical device, a FinTech device (or financial device), a security device, a climate/environment device, a device related to 5G services, or a device related to the fourth industrial revolution field. 
     The second device  9020  may be a BS, a network node, a transmitting UE, a receiving UE, a radio device, a wireless communication device, a vehicle, an autonomous driving vehicle, a connected car, a drone (UAV), an AI module, a robot, an AR device, a VR device, an MR device, a hologram device, a public safety device, an MTC device, an IoT device, a medical device, a FinTech device (or financial device), a security device, a climate/environment device, a device related to 5G services, or a device related to the fourth industrial revolution field. 
     For example, the UE may include a portable phone, a smart phone, a laptop computer, a terminal for digital broadcasting, a personal digital assistants (PDA), a portable multimedia player (PMP), a navigator, a slate personal computer (PC), a tablet PC, an ultrabook, a wearable device (e.g., watch type terminal (smartwatch), glass type terminal (smart glass), head mounted display (HMD)), etc. For example, the HMD may be a display device worn on the head. The HMD may be used to implement VR, AR, or MR. 
     For example, the drone may be a flying object controlled by radio control signals without a human pilot. For example, the VR device may include a device for implementing an object or background in a virtual world. For example, the AR device may include a device for connecting an object or background in a virtual world to an object or background in the real world. For example, the MR device may include a device for merging an object or background in a virtual world with an object or background in the real world. For example, the hologram device may include a device for implementing a 360-degree stereographic image by recording and playing back stereographic information based on a light interference phenomenon generated when two lasers called holography are met. For example, the public safety device may include a video relay device or imaging device capable of being worn on a user&#39;s body. For example, the MTC and IOT devices may be a device that does not require direct human intervention or manipulation. For example, the MTC and IoT devices may include a smart meter, a vending machine, a thermometer, a smart bulb, a door lock, or various sensors. For example, the medical device may be a device used for diagnosing, treating, mitigating, handling, or preventing a disease. For example, the medical device may be a device used for diagnosing, treating, mitigating, or correcting an injury or obstacle. For example, the medical device may be a device used for testing, substituting, or modifying a structure or function. For example, the medical device may be a device used for controlling pregnancy. For example, the medical device may include a device for medical treatment, a device for operation, a device for (external) diagnosis, a hearing aid, or a device for surgery. For example, the security device may be a device installed to prevent a potential danger and maintain safety. For example, the security device may be a camera, a CCTV, a recorder, or a black box. For example, the FinTech device may be a device capable of providing financial services such as mobile payment. For example, the FinTech device may include a payment device or point of sales (POS). For example, the climate/environment device may include a device for monitoring or predicting the climate/environment. 
     The first device  9010  may include at least one processor such as a processor  9011 , at least one memory such as a memory  9012 , and at least one transceiver such as a transceiver  9013 . The processor  9010  may perform the above-described functions, procedures, and/or methods. The processor  9010  may implement one or more protocols. For example, the processor  9010  may implement one or more radio interface protocol layers. The memory  9012  is connected to the processor  9010  and may store various forms of information and/or instructions. The transceiver  9013  is connected to the processor  9010  and may be controlled to transmit and receive radio signals. 
     The second device  9020  may include at least one processor such as a processor  9021 , at least one memory such as a memory  9022 , and at least one transceiver such as a transceiver  9023 . The processor  9021  may perform the above-described functions, procedures, and/or methods. The processor  9021  may implement one or more protocols. For example, the processor  9021  may implement one or more radio interface protocol layers. The memory  9022  is connected to the processor  9021  and may store various forms of information and/or instructions. The transceiver  9023  is connected to the processor  9021  and may be controlled to transmit and receive radio signals. 
     The memory  9012  and/or memory  9022  may be connected inside or outside the processor  9011  and/or the processor  9021 , respectively. Further, the memory  9012  and/or memory  9022  may be connected to other processors through various technologies such as a wired or wireless connection. 
     The first device  9010  and/or the second device  9020  may have one or more antennas. For example, an antenna  9014  and/or an antenna  9024  may be configured to transmit and receive radio signals. 
       FIG. 23  illustrates a wireless communication device according to an implementation of the present disclosure. 
       FIG. 23  shows a more detailed view of the first or second device  9010  or  9020  of  FIG. 22 . However, the wireless communication device of  FIG. 23  is not limited to the first or second device  9010  or  9020 . The wireless communication device may be any suitable mobile computing device for implementing at least one configuration of the present disclosure such as a vehicle communication system or device, a wearable device, a portable computer, a smart phone, etc. 
     Referring to  FIG. 23 , the wireless communication device (UE) may include at least one processor (e.g., DSP, microprocessor, etc.) such as a processor  9110 , a transceiver  9135 , a power management module  9105 , an antenna  9140 , a battery  9155 , a display  9115 , a keypad  9120 , a GPS chip  9160 , a sensor  9165 , a memory  9130 , a subscriber identification module (SIM) card  9125  (which is optional), a speaker  9145 , and a microphone  9150 . The UE may include at least one antennas. 
     The processor  9110  may be configured to implement the above-described functions, procedures, and/or methods. In some implementations, the processor  9110  may implement one or more protocols such as radio interface protocol layers. 
     The memory  9130  is connected to the processor  9110  and may store information related to the operations of the processor  9110 . The memory  9130  may be located inside or outside the processor  9110  and connected to other processors through various techniques such as wired or wireless connections. 
     A user may enter various types of information (e.g., instructional information such as a telephone number) by various techniques such as pushing buttons of the keypad  9120  or voice activation using the microphone  9150 . The processor  9110  may receive and process the information from the user and perform appropriate functions such as dialing the telephone number. For example, the processor  9110  data may retrieve data (e.g., operational data) from the SIM card  9125  or the memory  9130  to perform the functions. As another example, the processor  9110  may receive and process GPS information from the GPS chip  9160  to perform functions related to the location of the UE, such as vehicle navigation, map services, etc. As a further example, the processor  9110  may display various types of information and data on the display  9115  for user reference and convenience. 
     The transceiver  9135  is connected to the processor  9110  and may transmit and receives a radio signal such as an RF signal. The processor  9110  may control the transceiver  9135  to initiate communication and transmit radio signals including various types of information or data such as voice communication data. The transceiver  9135  includes a receiver and a transmitter to receive and transmit radio signals. The antenna  9140  facilitates the radio signal transmission and reception. In some implementations, upon receiving radio signals, the transceiver  9135  may forward and convert the signals to baseband frequency for processing by the processor  9110 . Various techniques may be applied to the processed signals. For example, the processed signals may be transformed into audible or readable information to be output via the speaker  9145 . 
     In some implementations, the sensor  9165  may be coupled to the processor  9110 . The sensor  9165  may include one or more sensing devices configured to detect various types of information including, but not limited to, speed, acceleration, light, vibration, proximity, location, image, and so on. The processor  9110  may receive and process sensor information obtained from the sensor  9165  and perform various types of functions such as collision avoidance, autonomous driving, etc. 
     In the example of  FIG. 23 , various components (e.g., camera, universal serial bus (USB) port, etc.) may be further included in the UE. For example, a camera may be coupled to the processor  9110  and used for various services such as autonomous driving, vehicle safety services, etc. 
     The UE of  FIG. 23  is merely exemplary, and implementations are not limited thereto. That is, in some scenarios, some components (e.g., keypad  9120 , GPS chip  9160 , sensor  9165 , speaker  9145 , and/or microphone  9150 ) may not be implemented in the UE. 
       FIG. 24  illustrates a transceiver of a wireless communication device according to an implementation of the present disclosure. Specifically,  FIG. 24  shows a transceiver that may be implemented in a frequency division duplex (FDD) system. 
     In the transmission path, at least one processor such as the processor described in  FIGS. 22 and 23  may process data to be transmitted and then transmit a signal such as an analog output signal to a transmitter  9210 . 
     In the transmitter  9210 , the analog output signal may be filtered by a low-pass filter (LPF)  9211 , for example, to remove noises caused by prior digital-to-analog conversion (ADC), upconverted from baseband to RF by an upconverter (e.g., mixer)  9212 , and amplified by an amplifier  9213  such as a variable gain amplifier (VGA). The amplified signal may be filtered again by a filter  9214 , further amplified by a power amplifier (PA)  9215 , routed through duplexer  9250  and antenna switch  9260 , and transmitted via an antenna  9270 . 
     In the reception path, the antenna  9270  may receive a signal in a wireless environment. The received signal may be routed through the antenna switch  9260  and duplexer  9250  and sent to a receiver  9220 . 
     In the receiver  9220 , the received signal may be amplified by an amplifier such as a low noise amplifier (LNA)  9223 , filtered by a band-pass filter  9224 , and downconverted from RF to baseband by a downconverter (e.g., mixer)  9225 . 
     The downconverted signal may be filtered by an LPF  9226  and amplified by an amplifier such as a VGA  9227  to obtain an analog input signal, which is provided to the at least one processor such as the processor. 
     Further, a local oscillator (LO)  9240  may generate and provide transmission and reception LO signals to the upconverter  9212  and downconverter  9225 , respectively. 
     In some implementations, a phase locked loop (PLL)  9230  may receive control information from the processor and provide control signals to the LO  9240  to generate the transmission and reception LO signals at appropriate frequencies. 
     Implementations are not limited to the particular arrangement shown in  FIG. 24 , and various components and circuits may be arranged differently from the example shown in  FIG. 24 . 
       FIG. 25  illustrates a transceiver of a wireless communication device according to an implementation of the present disclosure. Specifically,  FIG. 25  shows a transceiver that may be implemented in a time division duplex (TDD) system. 
     In some implementations, a transmitter  9310  and a receiver  9320  of the transceiver in the TDD system may have one or more similar features to those of the transmitter and the receiver of the transceiver in the FDD system. Hereinafter, the structure of the transceiver in the TDD system will be described. 
     In the transmission path, a signal amplified by a PA  9315  of the transmitter may be routed through a band selection switch  9350 , a BPF  9360 , and an antenna switch(s)  9370  and then transmitted via an antenna  9380 . 
     In the reception path, the antenna  9380  may receive a signal in a wireless environment. The received signals may be routed through the antenna switch(s)  9370 , the BPF  9360 , and the band selection switch  9350  and then provided to the receiver  9320 . 
       FIG. 26  illustrates sidelink operations of a wireless device according to an implementation of the present disclosure. The sidelink operations of the wireless device shown in  FIG. 26  are merely exemplary, and the wireless device may perform sidelink operations based on various techniques. The sidelink may correspond to a UE-to-UE interface for sidelink communication and/or sidelink discovery. The sidelink may correspond to a PC5 interface as well. In a broad sense, the sidelink operation may mean information transmission and reception between UEs. Various types of information may be transferred through the sidelink. 
     Referring to  FIG. 26 , the wireless device may obtain sidelink-related information in step S 9410 . The sidelink-related information may include at least one resource configuration. The wireless device may obtain the sidelink-related information from another wireless device or a network node. 
     After obtaining the sidelink-related information, the wireless device may decode the sidelink-related information in step S 9420 . 
     After decoding the sidelink-related information, the wireless device may perform one or more sidelink operations based on the sidelink-related information in step S 9430 . The sidelink operation(s) performed by the wireless device may include at least one of the operations described herein. 
       FIG. 27  illustrates sidelink operations of a network node according to an implementation of the present disclosure. The sidelink operations of the network node shown in  FIG. 27  are merely exemplary, and the network node may perform sidelink operations based on various techniques. 
     Referring to  FIG. 27 , the network node may receive sidelink-related information from a wireless device in step S 9510 . For example, the sidelink-related information may correspond to Sidelink UE Information, which is used to provide sidelink information to a network node. 
     After receiving the sidelink-related information, the network node may determine whether to transmit one or more sidelink-related instructions based on the received information in step S 9520 . 
     When determining to transmit the sidelink-related instruction(s), the network node may transmit the sidelink-related instruction(s) to the wireless device in S 9530 . In some implementations, upon receiving the instruction(s) transmitted from the network node, the wireless device may perform one or more sidelink operations based on the received instruction(s). 
       FIG. 28  illustrates the implementation of a wireless device and a network node according to an implementation of the present disclosure. The network node may be replaced with a wireless device or a UE. 
     Referring to  FIG. 28 , a wireless device  9610  may include a communication interface  9611  to communicate with one or more other wireless devices, network nodes, and/or other entities in the network. The communication interface  9611  may include one or more transmitters, one or more receivers, and/or one or more communications interfaces. The wireless device  9610  may include a processing circuitry  9612 . The processing circuitry  9612  may include at least one processor such as a processor  9613  and at least one memory such as a memory  9614 . 
     The processing circuitry  9612  may be configured to control at least one of the methods and/or processes described herein and/or enable the wireless device  9610  to perform the methods and/or processes. The processor  9613  may correspond to one or more processors for performing the wireless device functions described herein. The wireless device  9610  may include the memory  9614  configured to store the data, programmable software code, and/or information described herein. 
     In some implementations, the memory  9614  may store software code  9615  including instructions that allow the processor  9613  to perform some or all of the above-described processes when driven by the at least one processor such as the processor  9613 . 
     For example, the at least one processor such as the processor  9613  configured to control at least one transceiver such as a transceiver  2223  may process at least one processor for information transmission and reception. 
     A network node  9620  may include a communication interface  9621  to communicate with one or more other network nodes, wireless devices, and/or other entities in the network. The communication interface  9621  may include one or more transmitters, one or more receivers, and/or one or more communications interfaces. The network node  9620  may include a processing circuitry  9622 . The processing circuitry  9622  may include a processor  9623  and a memory  9624 . 
     In some implementations, the memory  9624  may store software code  9625  including instructions that allow the processor  9623  to perform some or all of the above-described processes when driven by at least one processor such as the processor  9623 . 
     For example, the at least one processor such as the processor  9623  configured to control at least one transceiver such as a transceiver  2213  may process at least one processor for information transmission and reception. 
     The above-described implementations may be embodied by combining the structural elements and features of the present disclosure in various ways. Each structural element and feature may be selectively considered unless specified otherwise. Some structural elements and features may be implemented without any combination with other structural elements and features. However, some structural elements and features may be combined to implement the present disclosure. The operation order described herein may be changed. Some structural elements or feature in an implementation may be included in another implementation or replaced with structural elements or features suitable for the other implementation. 
     The above-described implementations of the present disclosure may be embodied through various means, for example, hardware, firmware, software, or any combination thereof. In a hardware configuration, the methods according the present disclosure may be achieved by at least one of one or more ASICs, one or more DSPs, one or more DSPDs, one or more PLDs, one or more FPGAs, one or more processors, one or more controllers, one or more microcontrollers, one or more microprocessors, etc. 
     In a firmware or software configuration, the methods according to the present disclosure may be implemented in the form of a module, a procedure, a function, etc. Software code may be stored in a memory and executed by a processor. The memory may be located inside or outside the processor and exchange data with the processor via various known means. 
     Those skilled in the art will appreciate that the present disclosure may be carried out in other specific ways than those set forth herein without departing from the spirit and essential characteristics of the present disclosure. Although the present disclosure has been described based on the 3GPP LTE/LTE-A system or 5G system (NR system), the present disclosure is also applicable to various wireless communication systems. 
     INDUSTRIAL APPLICABILITY 
     The above-described implementations of the present disclosure are applicable to various mobile communication systems.