Method and apparatus for sidelink synchronization signal transmission and reception in communication system based on unlicensed band

Abstract

A method performed by a user equipment (UE) in a wireless communication system is provided. The method includes identifying whether a frequency band in which the UE operates corresponds to an unlicensed spectrum or a licensed spectrum; identifying a transmission period of a sidelink synchronization signal block (S-SSB) and a subcarrier spacing associated with the S-SSB; identifying the number of times of S-SSB emission in the period; and if the frequency band corresponds to the unlicensed spectrum, transmitting at least two S-SSBs, where the number of S-SSB transmissions is related to the subcarrier spacing, and wherein the S-SSBs are transmitted in accordance with whether the frequency band corresponds to the unlicensed spectrum or the licensed spectrum. And wherein the number of S-SSB transmissions in the case where the frequency band corresponds to the unlicensed spectrum is greater than the number of S-SSB transmissions in the case where the frequency band corresponds to the licensed spectrum.

Description

Technical Field

[0001] The present disclosure relates to the transmission and reception of sidelink information in a wireless communication system. More specifically, the present disclosure relates to the configuration of sidelink information in an unlicensed band and a method and apparatus for transmitting and receiving the sidelink information. Background Art

[0002] The fifth generation (5G) mobile communication technology defines a wide frequency band, making high transmission rates and new services possible, and can be implemented not only in "sub-6 gigahertz (GHz)" frequency bands such as 3.5 GHz, but also in "above 6 GHz" frequency bands (including 28 GHz and 39 GHz) called millimeter waves (mmWave). In addition, the implementation of the sixth generation (6G) mobile communication technology (called a super 5G system) in the terahertz (THz) frequency band (e.g., 95 GHz to 3 THz frequency band) has been considered to achieve a transmission rate fifty times faster than that of the 5G mobile communication technology and an ultra-low latency that is one-tenth of that of the 5G mobile communication technology.

[0003] At the beginning of the development of 5G mobile communication technology, in order to support services and meet the performance requirements related to enhanced mobile broadband (eMBB), ultra-reliable and low-latency communication (URLLC) and massive machine type communication (mMTC), standardization on beamforming and massive MIMO is underway to reduce radio wave path loss in millimeter waves and increase radio wave transmission distance, thereby supporting parameter sets for dynamic operation of millimeter wave resources and time slot formats for efficient utilization (for example, operating multiple subcarrier spacings), initial access technology for supporting multi-beam transmission and broadband, definition and operation of BWP (bandwidth part), new channel coding methods (such as LDPC (low-density parity check) codes for large-scale data transmission and polarization codes for high-reliability transmission of control information), L2 preprocessing, and network slicing for providing dedicated networks dedicated to specific services.

[0004] Currently, in view of the services supported by 5G mobile communication technology, discussions on the improvement and performance enhancement of initial 5G mobile communication technology are underway, and there is already physical layer standardization on the following technologies, for example, V2X (Vehicle-to-Everything) for assisting driving decisions by autonomous vehicles based on information about the location and status of the vehicle transmitted by the vehicle and for improving user convenience, NR-U (New Radio Unlicensed) for system operation designed to comply with various regulatory requirements in unlicensed bands, NR UE energy saving, and non-terrestrial network (NTN) for UE-satellite direct communication for providing coverage and positioning in areas where terrestrial network communications are not available.

[0005] In addition, the air interface architecture / protocols for the following technologies are being standardized, such as the Industrial Internet of Things (IIoT) for supporting new services through interworking and integration with other industries, IAB (Integrated Access and Backhaul) for providing nodes for network service area extension by supporting wireless backhaul links and access links in an integrated manner, mobility enhancement including conditional switching and DAPS (Dual Active Protocol Stack) switching, and two-step random access (2-step RACH for NR) for simplifying the random access process. The system architecture / services for the following technologies are also being standardized: 5G baseline architecture (e.g., service-based architecture or service-based interface) for combining network function virtualization (NFV) and software defined network (SDN) technologies, and mobile edge computing (MEC) for receiving services based on UE location.

[0006] With the commercialization of 5G mobile communication systems, the number of connected devices, which has been growing exponentially, will be connected to the communication network, and it is therefore expected that there will be a need to enhance the functions and performance of the 5G mobile communication systems and the integrated operations of the connected devices. To this end, new research is planned related to the following technologies: Extended Reality (XR) for effectively supporting AR (Augmented Reality), VR (Virtual Reality), MR (Mixed Reality), etc., as well as 5G performance improvement and complexity reduction by utilizing artificial intelligence (AI) and machine learning (ML), AI service support, virtual world service support, and drone communication.

[0007] In addition, such developments in 5G mobile communication systems will serve as a foundation for developing new waveforms for providing coverage in the terahertz band for 6G mobile communication technology, multi-antenna transmission technologies such as full-dimensional MIMO (FD-MIMO), array antennas, and large antennas, metamaterial-based lenses and antennas for improving the coverage of terahertz band signals, high-dimensional spatial multiplexing technology using OAM (orbital angular momentum), RIS (reconfigurable smart surface), full-duplex technology for increasing the frequency efficiency of 6G mobile communication technology and improving system networks, AI-based communication technology for achieving system optimization by utilizing satellites and AI (artificial intelligence) from the design stage and internalizing end-to-end AI support functions, and next-generation distributed computing technology for implementing services at a complexity level that exceeds the limits of UE operating capabilities by utilizing ultra-high-performance communication and computing resources.

[0008] The above information is presented only as background information to assist in understanding the present disclosure. No determination has been made, and no assertion has been made, as to whether any of the above may be used as prior art for the present disclosure. Summary of the invention

[0009] Technical issues

[0010] Aspects of the present disclosure are to at least solve the above-mentioned problems and / or disadvantages and to provide at least the following advantages. Therefore, one aspect of the present disclosure is to provide a method for configuring sidelink broadcast information in a sidelink communication system and a method and apparatus for transmitting and receiving the sidelink broadcast information.

[0011] Another aspect of the present disclosure is to provide a method for allocating resources for sidelink synchronization signal block (S-SSB) transmission.

[0012] Additional aspects will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the presented embodiments.

[0013] Technical Solutions

[0014] According to one aspect of the present disclosure, a method performed by a user equipment (UE) in a wireless communication system is provided. The method includes: identifying whether the frequency band in which the UE operates corresponds to an unlicensed spectrum or an authorized spectrum; identifying the transmission period of S-SSB and the subcarrier spacing associated with the S-SSB; identifying the number of S-SSB transmissions within the period; and transmitting at least two S-SSBs based on the number of S-SSB transmissions when the frequency band corresponds to the unlicensed spectrum, wherein the number of S-SSB transmissions is related to the subcarrier spacing and depends on whether the frequency band corresponds to the unlicensed spectrum or the authorized spectrum, and wherein the number of S-SSB transmissions when the frequency band corresponds to the unlicensed spectrum is greater than the number of S-SSB transmissions when the frequency band corresponds to the authorized spectrum.

[0015] According to another aspect of the present disclosure, a UE in a wireless communication system is provided. The UE includes a transceiver and a controller connected to the transceiver, wherein the controller is configured to: identify whether a frequency band in which the UE operates corresponds to an unlicensed spectrum or an authorized spectrum; identify a transmission period of an S-SSB and a subcarrier spacing associated with the S-SSB; identify the number of S-SSB transmissions within the period; and, if the frequency band corresponds to an unlicensed spectrum, transmit at least two S-SSBs based on the number of S-SSB transmissions, wherein the number of S-SSB transmissions is related to the subcarrier spacing and depends on whether the frequency band corresponds to an unlicensed spectrum or an authorized spectrum, and wherein the number of S-SSB transmissions when the frequency band corresponds to the unlicensed spectrum is greater than the number of S-SSB transmissions when the frequency band corresponds to the authorized spectrum.

[0016] According to another aspect of the present disclosure, a method performed by a UE in a wireless communication system is provided. The method includes: identifying whether the frequency band in which the UE operates corresponds to an unlicensed spectrum or an authorized spectrum; identifying the transmission period of the S-SSB and the subcarrier spacing associated with the S-SSB; and receiving at least two S-SSBs from another UE based on the number of S-SSB transmissions within the period when the frequency band corresponds to the unlicensed spectrum; wherein the number of S-SSB transmissions is related to the subcarrier spacing and depends on whether the frequency band corresponds to the unlicensed spectrum or the authorized spectrum; and wherein the number of S-SSB transmissions when the frequency band corresponds to the unlicensed spectrum is greater than the number of S-SSB transmissions when the frequency band corresponds to the authorized spectrum.

[0017] According to another aspect of the present disclosure, a UE in a wireless communication system is provided. The UE includes a transceiver and a controller connected to the transceiver, wherein the controller is configured to: identify whether a frequency band in which the UE operates corresponds to an unlicensed spectrum or an authorized spectrum; identify a transmission period of an S-SSB and a subcarrier spacing associated with the S-SSB; and receive at least two S-SSBs from another UE based on the number of S-SSB transmissions within the period when the frequency band corresponds to an unlicensed spectrum; wherein the number of S-SSB transmissions is related to the subcarrier spacing and depends on whether the frequency band corresponds to an unlicensed spectrum or an authorized spectrum; and wherein the number of S-SSB transmissions when the frequency band corresponds to the unlicensed spectrum is greater than the number of S-SSB transmissions when the frequency band corresponds to the authorized spectrum.

[0018] The technical problems to be achieved in the embodiments of the present disclosure are not limited to the above-mentioned technical problems, and other technical problems not mentioned herein will be clearly understood by those skilled in the art to which the present disclosure belongs from the following description.

[0019] Beneficial Effects

[0020] According to an embodiment of the present disclosure, the efficiency of a method for configuring sidelink broadcast information in a sidelink communication system and a process of transmitting and receiving the sidelink broadcast information may be improved.

[0021] In addition, according to an embodiment of the present disclosure, resources for S-SSB transmission can be effectively used in an unlicensed band.

[0022] Other aspects, advantages, and salient features of the disclosure will be apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses various embodiments of the disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The above and other aspects, features and advantages of certain embodiments of the present disclosure will become more apparent from the following description taken in conjunction with the accompanying drawings, in which:

[0024] Figure 1A An example of a coverage scenario in which all V2X UEs are located within the coverage of a base station in a wireless communication system according to an embodiment of the present disclosure is shown;

[0025] Figure 1B An example of a partial coverage scenario in which some V2X UEs are located outside the coverage of a base station in a wireless communication system according to an embodiment of the present disclosure is shown;

[0026] Figure 1C An example of an out-of-coverage scenario in which all V2X UEs are outside the coverage of a base station according to an embodiment of the present disclosure is shown;

[0027] Figure 1D An example of a scenario in which UEs located in different cells perform V2X communication with each other according to an embodiment of the present disclosure is shown;

[0028] Figure 2 A V2X communication method performed through a side link according to an embodiment of the present disclosure is shown;

[0029] Figure 3 A protocol of a sidelink UE according to an embodiment of the present disclosure is shown;

[0030] Figure 4 shows the types of synchronization signals that may be received by a sidelink UE according to an embodiment of the present disclosure;

[0031] Figure 5 The framework structure of the side link system according to an embodiment of the present disclosure is shown;

[0032] Figure 6 shows the structure of a sidelink synchronization channel according to an embodiment of the present disclosure;

[0033] Figure 7 shows the structure of a side link channel according to an embodiment of the present disclosure;

[0034] Figure 8 shows the types of synchronization signals that may be transmitted and received by a sidelink UE in an unlicensed band according to an embodiment of the present disclosure;

[0035] Fig. 9 An example of a synchronization signal transmission period according to an embodiment of the present disclosure is shown;

[0036] Fig.10 An example in which an S-SSB and a physical sidelink control channel (PSCCH) / physical sidelink shared channel (PSSCH) are transmitted / received in a frequency division multiplexing (FDM) form according to an embodiment of the present disclosure is shown;

[0037] Fig.11 shows the allocation of S-SSB transmission resources according to an embodiment of the present disclosure;

[0038] Fig.12 shows resources for S-SSB transmission according to an embodiment of the present disclosure;

[0039] Fig.13 shows resources for S-SSB transmission according to an embodiment of the present disclosure;

[0040] Fig.14 An example of an operation flow chart of a sidelink UE operating in an unlicensed band according to an embodiment of the present disclosure is shown;

[0041] Fig.15 is a block diagram showing the structure of a UE according to an embodiment of the present disclosure; and

[0042] Fig.16 is a block diagram showing the structure of a base station according to an embodiment of the present disclosure.

[0043] The same reference numerals are used throughout the drawings to denote the same elements. DETAILED DESCRIPTION

[0044] The following description is provided with reference to the accompanying drawings to assist in a comprehensive understanding of the various embodiments of the present disclosure as defined by the claims and their equivalents. The following description includes various specific details that are helpful for understanding, but these should be considered as exemplary only. Therefore, it will be appreciated by those of ordinary skill in the art that various changes and modifications may be made to the various embodiments described herein without departing from the scope and spirit of the present disclosure. In addition, for the sake of clarity and conciseness, descriptions of well-known functions and structures may be omitted.

[0045] The terms and words used in the following description and claims are not limited to the bibliographical meanings, but are merely used by the inventor to enable a clear and consistent understanding of the present disclosure. Therefore, it should be apparent to those skilled in the art that the following description of various embodiments of the present disclosure is provided for illustrative purposes only and is not intended to limit the present disclosure as defined by the appended claims and their equivalents.

[0046] It is to be understood that the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a component surface" includes reference to one or more of such surfaces.

[0047] When describing the embodiments, descriptions of technical contents known in the technical field to which the present disclosure belongs and not directly related to the present disclosure will be omitted. This is to convey the subject matter of the present disclosure more clearly without obscurity by omitting unnecessary descriptions.

[0048] For the same reason, some elements are exaggerated, omitted or schematically shown in the drawings. In addition, the size of each element depicted does not fully reflect the actual size. In the drawings, the same or corresponding elements are assigned the same reference numerals.

[0049] The advantages and features of the present disclosure and their implementation will become apparent through the embodiments described below with reference to the accompanying drawings. However, the present disclosure can be implemented in many different forms and should not be construed as being limited to the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure will be thorough and complete, and the scope of the present disclosure will be fully conveyed to those skilled in the art. The present disclosure is limited only by the scope of the appended claims. Throughout this specification, the same reference numerals refer to the same elements.

[0050] It should be understood that each frame of the flowchart description and the frame combination in the flowchart description can be implemented by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device produce a device for implementing the function specified in the flowchart frame. These computer program instructions can also be stored in a computer-available or computer-readable memory, which can instruct the computer or other programmable data processing device to operate in a particular manner, so that the instructions stored in the computer-available or computer-readable memory produce a product including an instruction device, which implements the function specified in the flowchart frame. The computer program instructions can also be loaded onto a computer or other programmable data processing device to cause a series of operation steps to be performed on a computer or other programmable device, thereby generating a computer-implemented process, so that the instructions executed on the computer or other programmable device provide operations for implementing the functions specified in the flowchart frame.

[0051] In addition, each frame of the flowchart diagram can represent a module, a code segment or a code portion, which includes one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions mentioned in the frame may not occur in order. For example, depending on the functionality involved, two frames shown in succession can actually be executed roughly at the same time, or these frames can sometimes be executed in reverse order.

[0052] As used herein, the term "unit" refers to a software element or hardware element that performs a predetermined function, such as a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC). However, the term "unit" does not always have the meaning that is limited to software or hardware. "Unit" can be constructed to be stored in an addressable storage medium or to execute one or more processors. Therefore, "unit" includes, for example, software elements, object-oriented software elements, class elements or task elements, processes, functions, attributes, programs, subroutines, program code segments, drivers, firmware, microcodes, circuits, data, databases, data structures, tables, arrays and variables. The function that elements and units provide can be combined into the function of fewer elements and units or separated into the function of more elements and units. In addition, elements and units can be implemented with one or more central processing units (CPUs) in an operating device or a secure multimedia card. In addition, in an embodiment, "unit" can include one or more processors.

[0053] The embodiments of the present disclosure will focus on describing the radio access network, i.e., the new radio (NR) and the packet core, i.e., the 5G system, the 5G core network, or the next generation (NG) core, in accordance with the 5G mobile communication standard specified by the 3rd Generation Partnership Project (3GPP), which is a mobile communication standardization organization. However, without departing from the scope of the present disclosure, the subject matter of the present disclosure may also be applicable to other communication systems with similar technical backgrounds after slight modifications, as will be apparent to those skilled in the art.

[0054] In the 5G system, a network data collection and analysis function (NWDAF) may be defined to support network automation, which is a network function that collects, analyzes, and provides data in a 5G network. NWDAF may collect information from the 5G network, store and analyze the collected information, and provide analysis results to unspecified network functions (NFs). The analysis results may be used independently in each NF.

[0055] For the convenience of description, some terms and names defined in 3GPP standards (such as 5G, NR, Long Term Evolution (LTE) or similar system standards) will be used. However, the present disclosure is not limited to these terms and names, and may also be applied to any other system conforming to any other standard.

[0056] In addition, for convenience, terms for identifying access nodes, terms referring to network entities, terms referring to messages, terms referring to interfaces between network entities, terms referring to various identification information, etc. are illustratively used. Therefore, the present disclosure is not limited to the terms used below, and other terms referring to subjects with equivalent technical meanings may be used.

[0057] To meet the demand for increased wireless data traffic since the deployment of the 4th generation (4G) communication system, efforts have been made to develop an improved 5G communication system (NR, New Radio). In order to achieve higher data rates, the 5G communication system is designed to enable resources in the extremely high frequency (mmWave) band (e.g., the 28 GHz band). In order to reduce the propagation loss of radio waves and increase the transmission distance, beamforming, massive multiple input multiple output (massive MIMO), full-dimensional MIMO (FD-MIMO), array antennas, analog beamforming, large antenna technology, etc. have been discussed and adopted in the 5G communication system. In addition, unlike LTE, the 5G communication system supports various subcarrier spacings, such as 15 kilohertz (kHz), 30kHz, 60kHz, and 120kHz, uses polarization coding for physical control channels, and uses low-density parity check (LDPC) for physical data channels. In addition, cyclic prefix orthogonal frequency division multiplexing (CP-OFDM) and discrete Fourier transform extended orthogonal frequency division multiplexing (DFT-S-OFDM) are used as waveforms for uplink transmission. LTE supports hybrid ARQ (HARQ) retransmission in units of transport blocks (TBs), while 5G can also support HARQ retransmission based on code block groups (CBGs) that bundle multiple code blocks (CBs).

[0058] Therefore, various attempts have been made to apply 5G communication systems to IoT networks. For example, technologies such as sensor networks, machine-to-machine (M2M) communications, and machine type communications (MTC) can be implemented through beamforming, MIMO, and array antennas. The application of cloud radio access networks (cloud RANs) as the above-mentioned big data processing technology can also be considered as an example of the fusion of 5G technology and IoT technology. Therefore, a variety of services can be provided to users in a communication system. In order to provide such services to users, methods and devices for providing corresponding services within the same time interval are required. One of such services provided in the 5G communication system is a service that meets low latency and high reliability requirements.

[0059] In the case of vehicle communication, LTE-based V2X has been standardized in 3GPP Release 14 and Release 15 based on a device-to-device (D2D) communication structure, and efforts are currently being made to develop 5G NR-based V2X. NR V2X supports unicast communication, groupcast (or multicast) communication, and broadcast communication between UEs. In addition, unlike LTE V2X, which aims to transmit or receive basic safety information required for vehicle road driving, NR V2X aims to provide more advanced services such as vehicle platooning, advanced driving, extended sensors, and remote driving.

[0060] Since the above-mentioned advanced services require higher data rates, NRV2X systems may require wider bandwidths than conventional 4G LTE V2X systems. To this end, it is necessary to support operations in high frequency bands and also solve coverage issues caused by frequency characteristics through analog beamforming. In such analog beamforming systems, methods and devices for acquiring beam information between transmitting UE and receiving UE are required.

[0061] Embodiments of the present disclosure are proposed to support the above-mentioned scenarios, and aim to provide a method of configuring sidelink broadcast information to perform sidelink synchronization between UEs, and a method and device for transmitting / receiving the sidelink broadcast information.

[0062] Figure 1A , Figure 1B , Figure 1C and Figure 1D is a diagram illustrating a system according to various embodiments of the present disclosure.

[0063] Figure 1A An example is shown of a situation in which all V2X UEs (e.g., UE-1 and UE-2) are within the coverage of a base station in a wireless communication system according to an embodiment of the present disclosure. Figure 1A The examples shown in can be referred to as examples of scenarios within coverage.

[0064] refer to Figure 1A , all V2X UEs located within the coverage area of ​​the base station can receive data and control information from the base station via a downlink (DL) or transmit data and control information to the base station via an uplink (UL). Such data and control information can be used for V2X communication or for normal cellular communication. In addition, the V2X UE can transmit / receive data and control information for V2X communication via a sidelink (SL).

[0065] Figure 1B An example is shown of a situation in which some V2X UEs (e.g., UE-1) are located within the coverage of a base station and other V2X UEs (e.g., UE-2) are located outside the coverage of the base station in a wireless communication system according to an embodiment of the present disclosure. Figure 1B The example shown may be referred to as an example of a partially covered scenario.

[0066] refer to Figure 1B, V2X UE-1 located within the coverage of the base station can receive data and control information from the base station via a downlink, or transmit data and control information to the base station via an uplink. V2X UE-2 located outside the coverage of the base station cannot receive data and control information from the base station via a downlink, and cannot transmit data and control information to the base station via an uplink. V2X UE-2 can transmit data and control information for V2X communication to UE-1 via a side link / receive data and control information for V2X communication from UE-1.

[0067] Figure 1C An example is shown of a situation in which all V2X UEs are outside the coverage of a base station in a wireless communication system according to an embodiment of the present disclosure. Figure 1C The example shown in can be referred to as an example of an out-of-coverage scenario.

[0068] refer to Figure 1C , UE-1 and UE-2 cannot receive data and control information from the base station through the downlink, and cannot transmit data and control information to the base station through the uplink. UE-1 and UE-2 can transmit / receive data and control information for V2X communication through the sidelink.

[0069] Figure 1D An example of a scenario in which UEs located in different cells perform V2X communication with each other in a wireless communication system according to an embodiment of the present disclosure is shown.

[0070] Figure 1D A case where a V2X transmitting UE and a V2X receiving UE are connected to different base stations (RRC connected state) or camped (RRC connection released state, i.e., RRC idle state) is shown. In this case, UE-1 may be a V2X transmitting UE, and UE-2 may be a V2X receiving UE. Alternatively, UE-1 may be a V2X receiving UE, and UE-2 may be a V2X transmitting UE. UE-1 may receive a V2X dedicated system information block (SIB) from a base station to which UE-1 is connected (or camped). UE-2 may receive a V2X dedicated SIB from another base station to which UE-2 is connected (camped). In this case, the information of the V2X dedicated SIB received by UE-1 and the information of the V2X dedicated SIB received by UE-2 may be the same as each other or may be different from each other. When the SIB information of the two is different from each other, each of UE-1 and UE-2 may receive different information for side link communication as SIB from the base station to which it is connected (or camped). In this case, unified information is required for side link communication between UEs located in different cells.

[0071] Although it is easy to describe, Figures 1A to 1DA V2X system consisting of two UEs (UE-1 and UE-2) is shown, but this is not a limitation of the present disclosure. In addition, the uplink and downlink between the base station and the V2X UE may be referred to as a Uu interface, and the side link between the V2X UEs may be referred to as a PC5 interface. Therefore, in the present disclosure, these terms may be used interchangeably.

[0072] Meanwhile, in the present disclosure, UE may refer to a device supporting device-to-device (D2D) communication, a vehicle supporting vehicle-to-vehicle (V2V) communication, a vehicle supporting vehicle-to-pedestrian (V2P) communication or a mobile phone (e.g., a smart phone) of a pedestrian, a vehicle supporting vehicle-to-network (V2N) communication, or a vehicle supporting vehicle-to-infrastructure (V2I) communication. In addition, UE may refer to a roadside unit (RSU) having a UE function, an RSU having a base station function, or an RSU having a portion of a base station function and a portion of a UE function.

[0073] In the present disclosure, V2X communication may refer to communication between UEs, communication between vehicles, or communication between vehicles and pedestrians, and may be used interchangeably with sidelink communication.

[0074] In addition, in the present disclosure, a base station is defined as a base station that supports both V2X communication and general cellular communication, or a base station that supports only V2X communication. A base station may refer to a 5G base station (gNB), a 4G base station (eNB), or an RSU. Unless otherwise specified in the present disclosure, base stations and RSUs may be used interchangeably.

[0075] Figure 2 A V2X communication method performed through a side link according to an embodiment of the present disclosure is shown.

[0076] refer to Figure 2 In part (a), a transmitting UE (eg, UE-1) and a receiving UE (eg, UE-2) may perform one-to-one communication, which may be referred to as unicast communication.

[0077] refer to Figure 2 In part (b), a transmitting UE (e.g., UE-1 or UE-4) and a receiving UE (e.g., UE-2 and UE-3, or UE-5, UE-6, and UE-7) can perform one-to-many communication, which may be referred to as groupcast or multicast communication.

[0078] refer to Figure 2 In part (b), UE-1, UE-2, and UE-3 may form a group (i.e., group A) and perform multicast communication, and UE-4, UE-5, UE-6, and UE-7 may form another group (i.e., group B) and perform multicast communication. Each UE performs multicast communication only within the group to which it belongs, and communication between different groups may be performed via unicast, multicast, or broadcast communication. Although Figure 2 Part (b) shows two groups for ease of description, but this is not a limitation of the present disclosure. The present disclosure can also be applied to any other situation in which more than two groups are formed.

[0079] although Figure 2 Although not shown in the figure, the V2X UE can also perform broadcast communication. Broadcast communication refers to the situation where all V2X UEs receive data and control information transmitted by the V2X transmitting UE via the side link. Figure 2 In part (b), assuming that UE-1 is a transmitting UE for broadcasting, all other UEs (e.g., UE-2, UE-3, UE-4, UE-5, UE-6, and UE-7) can receive data and control information transmitted by UE-1.

[0080] The sidelink unicast, multicast and broadcast communication methods according to embodiments of the present disclosure may be supported in in-coverage, partial coverage and out-of-coverage scenarios.

[0081] Resource allocation in the sidelink system may use the following method.

[0082] (1) Mode 1 resource allocation

[0083] Mode 1 resource allocation may refer to a method of resource allocation scheduled by a base station (i.e., scheduled resource allocation). Specifically, in mode 1 resource allocation, a base station may allocate resources for sidelink transmission to a UE connected to RRC in a dedicated scheduling method. The scheduling resource allocation method by the base station may be effective for interference management and resource pool management (dynamic allocation and / or semi-persistent transmission (SPS)) because the base station is able to manage sidelink resources. In the case where there is data to be transmitted to other UEs, the RRC-connected UE may use a radio resource control (RRC) message or a media access control (MAC) control element (CE) to transmit information, thereby notifying the base station that there is data to be transmitted to other UEs. For example, the RRC message may include a sidelink UE information message and / or a UE assistance information message. In addition, the MAC CE may be a buffer status report (BSR), a scheduling request (SR), etc., which includes at least one of an indicator indicating a BSR for V2X communication or information about the size of buffered data for sidelink communication. The mode 1 resource allocation method may be applied to a situation where a sidelink transmitting UE is within the coverage of a base station, because the sidelink transmitting UE receives resources scheduled by the base station.

[0084] (2) Mode 2 Resource Allocation

[0085] Mode 2 resource allocation may refer to a method in which a sidelink transmitting UE autonomously selects resources (i.e., UE autonomous resource selection). Specifically, in mode 2 resource allocation, the base station provides the UE with a sidelink transmit / receive resource pool for the sidelink via system information or an RRC message (e.g., an RRC reconfiguration message or a PC5-RRC message), and the transmitting UE that has received the transmit / receive resource pool selects the resource pool and resources according to a predetermined rule. Since the base station provides configuration information for the sidelink transmit / receive resource pool, the mode 2 resource allocation method may be applicable to situations in which the sidelink transmitting UE and the receiving UE are within the coverage of the base station. If the sidelink transmitting UE and the receiving UE exist outside the coverage of the base station, the sidelink transmitting UE and the receiving UE may perform mode 2 operation in a pre-configured transmit / receive resource pool. The UE autonomous resource selection method may include area mapping, sensing-based resource selection, or random selection.

[0086] (3) In addition, even if the UE is within the coverage of the base station, resource allocation or resource selection may not be performed through a scheduled resource allocation method (i.e., mode 1) or a UE autonomous resource selection method (i.e., mode 2). In this case, the UE may perform sidelink communication through a pre-configured sidelink transmit / receive resource pool.

[0087] The side link resource allocation method according to the above-mentioned embodiment of the present disclosure can be applied to various embodiments of the present disclosure.

[0088] Figure 3 A protocol of a sidelink UE according to an embodiment of the present disclosure is shown.

[0089] although Figure 3 , the application layer of UE-A and UE-B may perform service discovery. In this case, service discovery may include discovery of which sidelink communication method (e.g., unicast, multicast, or broadcast) will be performed by each UE. Figure 3 In the embodiment, it is assumed that UE-A and UE-B recognize that a unicast communication method will be performed through a service discovery process performed in an application layer. The sidelink UE may obtain information about a source identifier (ID) and a destination ID for sidelink communication during the service discovery process.

[0090] When the service discovery process is complete, you can Figure 3 The PC-5 signaling protocol layer shown executes the direct link connection establishment process between UEs. At this time, UE-A and UE-B can exchange security configuration information to achieve direct communication between UEs.

[0091] When the direct link connection establishment procedure between the UEs is completed, the PC-5 radio resource control (RRC) establishment procedure between the UEs can be Figure 3At this time, information about the capabilities of UE-A and UE-B can be exchanged, and access stratum (AS) layer parameter information for unicast communication can be exchanged.

[0092] When the PC-5 RRC establishment process is completed, UE-A and UE-B can perform unicast communication.

[0093] Although the above description is based on unicast communication as an example, it can also be extended to multicast communication. For example, among UE-A, UE-B and UE-C ( Figure 3 In the case where multicast communication is performed (not shown in the figure), UE-A and UE-B can perform service discovery for unicast communication, direct link establishment process between UEs and PC-5RRC establishment process as described above. In addition, UE-A and UE-C can also perform service discovery for unicast communication, direct link establishment process between UEs and PC-5RRC establishment process. Finally, UE-B and UE-C can also perform service discovery for unicast communication, direct link establishment process between UEs and PC-5RRC establishment process. That is to say, each pair of transmitting and receiving UEs participating in multicast communication can perform PC-5RRC establishment process for unicast communication, instead of performing a separate PC-5RRC establishment process for multicast communication. However, in the multicast method, it may not always be necessary to perform PC-5RRC establishment process for unicast communication. For example, there may be a situation where multicast communication is performed without PC-5RRC establishment, and in this case, the PC-5RRC establishment process for unicast transmission can be omitted.

[0094] The PC-5RRC establishment procedure for unicast or multicast communication can be applied to Figure 1A All coverage scenarios, Figure 1B Partial coverage scenarios, and Figure 1C If there is a UE that desires to perform unicast or multicast communication within the coverage of the base station, the UE may perform a PC-5 RRC establishment procedure before or after performing downlink or uplink synchronization with the base station.

[0095] Figure 4 The types of synchronization signals that may be received by a sidelink UE according to an embodiment of the present disclosure are shown.

[0096] refer to Figure 4 , the sidelink UE can receive sidelink synchronization signals from various sidelink synchronization sources as shown below.

[0097] -Sidelink UE can receive synchronization signals directly from the Global Navigation Satellite System (GNSS) or the Global Positioning System (GPS).

[0098] * In this case, the sidelink synchronization signal source can be GNSS.

[0099] -Sidelink UE can receive synchronization signals indirectly from GNSS or GPS.

[0100] *Indirectly receiving a synchronization signal from a GNSS may refer to a situation where a side link synchronization signal (SLSS) transmitted by a side link UE (e.g., UE-1) that is directly synchronized with the GNSS is received by another side link UE (e.g., UE-A). In this case, the side link UE (e.g., UE-A) that indirectly receives the synchronization signal may receive the synchronization signal from the GNSS through two hops. In another example, another side link UE (e.g., UE-2) (i.e., a UE that performs synchronization indirectly from the GNSS) that is synchronized with the SLSS transmitted by the side link UE (e.g., UE-1) that is directly synchronized with the GNSS may transmit the SLSS. The side link UE (e.g., UE-A) that receives the SLSS may receive the synchronization signal from the GNSS through three hops. Similarly, the side link UE (e.g., UE-A) that indirectly receives the synchronization signal may receive the synchronization signal from the GNSS through more than three hops.

[0101] *In this case, the sidelink synchronization signal source can be another sidelink UE (e.g. UE-1) synchronized with GNSS.

[0102] -Sidelink UE can receive synchronization signals directly from the LTE base station (eNB).

[0103] *Sidelink UE can directly receive the primary synchronization signal (PSS) / secondary synchronization signal (SSS) transmitted from the eNB.

[0104] *In this case, the sidelink synchronization signal source can be the eNB.

[0105] -Sidelink UE can receive synchronization signals indirectly from eNB.

[0106] *Indirectly receiving a synchronization signal from an eNB may refer to a situation where an SLSS transmitted by a sidelink UE (e.g., UE-1) that is directly synchronized with the eNB is received by another sidelink UE (e.g., UE-A). In this case, the sidelink UE (e.g., UE-A) that indirectly receives the synchronization signal may receive the synchronization signal from the eNB through two hops. In another example, another sidelink UE (e.g., UE-2) (i.e., a UE that performs synchronization indirectly from the eNB) that is synchronized with the SLSS transmitted by the sidelink UE (e.g., UE-1) that is directly synchronized with the eNB may transmit the SLSS. The sidelink UE (e.g., UE-A) that receives the SLSS may receive the synchronization signal from the eNB through three hops. Similarly, the sidelink UE (e.g., UE-A) that indirectly receives the synchronization signal may receive the synchronization signal from the eNB through more than three hops.

[0107] *In this case, the sidelink synchronization signal source can be another sidelink UE (e.g. UE-1) synchronized with the eNB.

[0108] -Sidelink UE can receive synchronization signals indirectly from the NR base station (gNB).

[0109] *Indirectly receiving a synchronization signal from a gNB may refer to a case where an SLSS transmitted by a sidelink UE (e.g., UE-1) that is directly synchronized with the gNB is received by another sidelink UE (e.g., UE-A). In this case, the sidelink UE (e.g., UE-A) that indirectly receives the synchronization signal may receive the synchronization signal from the gNB through two hops. In another example, another sidelink UE (e.g., UE-2) (i.e., a UE that performs synchronization indirectly from the gNB) that is synchronized with the SLSS transmitted by the sidelink UE (e.g., UE-1) that is directly synchronized with the gNB may transmit the SLSS. The sidelink UE (e.g., UE-A) that receives the SLSS may receive the synchronization signal from the gNB through three hops. Similarly, the sidelink UE (e.g., UE-A) that indirectly receives the synchronization signal may receive the synchronization signal from the gNB through more than three hops.

[0110] *In this case, the sidelink synchronization signal source can be another sidelink UE (e.g. UE-1) that is synchronized with the gNB.

[0111] - A sidelink UE (eg, UE-A) may directly receive a synchronization signal from another sidelink UE (eg, UE-B).

[0112] *When sidelink UE-B cannot detect SLSS transmitted from GNSS, gNB, eNB or another sidelink UE as a synchronization signal source, sidelink UE-B can transmit SLSS based on its own timing. Sidelink UE-A can directly receive SLSS transmitted by sidelink UE-B.

[0113] *In this case, the sidelink synchronization signal source can be the sidelink UE (e.g., UE-B).

[0114] A sidelink UE (eg, UE-A) may indirectly receive a synchronization signal from another sidelink UE (eg, UE-B).

[0115] *Indirectly receiving a synchronization signal from another sidelink UE (e.g., UE-B) may refer to a situation where a SLSS transmitted by a sidelink UE-1 that is directly synchronized with the sidelink UE-B is received by the sidelink UE-A. In this case, the sidelink UE-A may receive a synchronization signal from the sidelink UE-B through two hops. In another example, the sidelink UE-2 synchronized with the SLSS transmitted by the sidelink UE-1 that is directly synchronized with the sidelink UE-B may transmit the SLSS. The sidelink UE-A receiving the SLSS may receive a synchronization signal from the sidelink UE-B through 3 hops. Similarly, the sidelink UE-A may receive a synchronization signal from the sidelink UE-B through more than 3 hops.

[0116] *In this case, the sidelink synchronization signal source may be another sidelink UE that is synchronized with the sidelink UE.

[0117] The sidelink UE may receive synchronization signals from the various synchronization signal sources described above, and may perform synchronization based on a synchronization signal transmitted from a synchronization signal source having a higher priority according to a pre-configured priority.

[0118] For example, the following priorities may be preconfigured in order from a synchronization signal having a high priority to a synchronization signal having a low priority.

[0119] - Situation A

[0120] 1) Synchronization signal transmitted directly from GNSS>2) Synchronization signal transmitted directly from GNSS by UE performing synchronization>3) Synchronization signal transmitted indirectly from GNSS by UE performing synchronization>4) Synchronization signal transmitted directly from eNB or gNB (eNB / gNB)>5) Synchronization signal transmitted directly from eNB / gNB by UE performing synchronization>6) Synchronization signal transmitted indirectly from eNB / gNB by UE performing synchronization>7) Synchronization signal transmitted directly or indirectly from GNSS or eNB / gNB by UE not performing synchronization.

[0121] Case A is an example of a case where a synchronization signal directly transmitted by GNSS has the highest priority. Alternatively, a case where a synchronization signal transmitted by an eNB or gNB (eNB / gNB) has the highest priority can be considered, and the following priorities can be pre-configured.

[0122] - Situation B

[0123] 1) Synchronization signal transmitted directly from eNB / gNB>2) Synchronization signal transmitted directly from eNB / gNB by UE performing synchronization>3) Synchronization signal transmitted indirectly from eNB / gNB by UE performing synchronization>4) Synchronization signal transmitted directly from GNSS>5) Synchronization signal transmitted directly from GNSS by UE performing synchronization>6) Synchronization signal transmitted indirectly from GNSS by UE performing synchronization>7) Synchronization signal transmitted directly or indirectly from GNSS or eNB / gNB by UE not performing synchronization.

[0124] Whether the sidelink UE should follow the priority of case A or the priority of case B can be configured by the base station or pre-configured / defined. For example, when the sidelink UE exists within the coverage of the base station (within the coverage), the base station can configure the sidelink UE through system information (SIB) or RRC signaling to follow the priority of case A or case B. If the sidelink UE exists outside the coverage of the base station (out of coverage), it can be pre-configured whether the sidelink UE should perform the sidelink synchronization process according to which priority in case A or case B.

[0125] At the same time, when the base station configures the above situation A to the sidelink UE through system information or RRC signaling, the base station can also configure whether the sidelink UE should consider priority 4 (a case of synchronization with a synchronization signal directly transmitted from an eNB or gNB (eNB / gNB)), priority 5 (a case of synchronization with a synchronization signal transmitted by a UE that is directly synchronized from an eNB / gNB), and priority 6 (a case of synchronization with a synchronization signal transmitted by a UE that is indirectly synchronized from an eNB / gNB) in situation A. That is, when the above situation A is configured and priority 4, priority 5, and priority 6 are further configured to be considered, all priorities of the above situation A (i.e., from priority 1 to priority 7) can be considered. On the other hand, when the above situation A is configured and priority 4, priority 5, and priority 6 are not configured to be considered, or when the above situation A is configured and priority 4, priority 5, and priority 6 are configured not to be considered, priority 4, priority 5, and priority 6 can be omitted in the above situation A (i.e., only priority 1, priority 2, priority 3, and priority 7 are considered).

[0126] The sidelink synchronization signal used in the present disclosure may refer to a sidelink synchronization signal block (S-SSB), which may include a sidelink primary synchronization signal (S-PSS), a sidelink secondary synchronization signal (S-SSS), and a physical sidelink broadcast channel (PSBCH). In this case, the S-PSS may be composed of a Zadoff-Chu sequence or an M sequence, and the S-SSS may be composed of an M sequence or a gold sequence. Similar to the PSS / SSS in a cellular system, the sidelink ID may be transmitted via a combination of the S-PSS and the S-SSS, or only via the S-SSS instead of such a combination. The PSBCH may transmit a master information block (MIB) for sidelink communications, similar to the physical broadcast channel (PBCH) of a cellular system.

[0127] In the present disclosure, the situation where the sidelink parameters are pre-configured in the sidelink UE can be mainly applied to the scenario where the sidelink UE is outside the coverage of the base station (out of coverage). The meaning of the parameters being pre-configured in the UE can be understood as using the values ​​stored in the UE when the UE is shipped from the factory. In another example, it may refer to the sidelink UE having accessed the base station and pre-acquired and stored the values ​​of the sidelink parameter information through RRC configuration. In yet another example, it may refer to the sidelink UE not having accessed the base station but having previously acquired and stored the values ​​of the sidelink system information from the base station.

[0128] Figure 5 The framework structure of the side link system according to an embodiment of the present disclosure is shown.

[0129] Figure 5 The system is shown using 1024 radio frames, but this is not a limitation. For example, a system may use less than or more than 1024 radio frames. How many radio frames the system uses may be configured or pre-configured by the base station. Specifically, when the sidelink UE is within the coverage of the base station, the sidelink UE may obtain information about the radio frames through the master information block (MIB) of the PBCH transmitted by the base station. When the sidelink UE is out of the coverage of the base station, information about the radio frames may be pre-configured in the sidelink UE.

[0130] refer to Figure 5 , the radio frame number and the system frame number may be treated equally. That is, the radio frame number "0" may correspond to the system frame number "0", and the radio frame number "1" may correspond to the system frame number "1". One radio frame may consist of 10 subframes, and one subframe may have a length of 1ms on the time axis. The number of time slots constituting one subframe may vary depending on the subcarrier spacing used in NR V2X, such as Figure 5For example, when a 15kHz subcarrier spacing is used in NR V2X communication, one subframe may be equal to one time slot. However, when a 30kHz subcarrier spacing and a 60kHz subcarrier spacing are used in NR V2X communication, one subframe may be equal to 2 time slots and 4 time slots, respectively. Figure 5 This is not shown in the figure, but this can even be applied to other cases where a subcarrier spacing of 120 kHz or more is used. That is, to summarize the number of time slots constituting one subframe, as the subcarrier spacing increases based on the subcarrier spacing of 15 kHz, the number of time slots constituting one subframe can increase by 2n, where n = 0, 1, 2, 3, ...

[0131] Figure 6 The structure of a sidelink synchronization channel according to an embodiment of the present disclosure is shown.

[0132] The sidelink synchronization channel can be represented by replacing it with a sidelink synchronization signal block (S-SSB).

[0133] refer to Figure 6 , one S-SSB may consist of 14 symbols in one slot. One S-SSB may consist of S-PSS, S-SSS, PSBCH, and a guard period (GAP). In this case, each of the S-PSS and S-SSS may consist of 2 OFDM symbols, the PSBCH may consist of 9 OFDM symbols, and the GAP (or GUARD) may consist of 1 OFDM symbol.

[0134] like Figure 6 As shown, S-PSS can be mapped to OFDM symbol indexes 1 and 2, S-SSS can be mapped to OFDM symbol indexes 3 and 4, and GAP can be mapped to the last OFDM symbol of S-SSB (i.e., OFDM symbol index 13). PSBCH can be mapped to the remaining OFDM symbols except S-PSS, S-SSS, and GAP. Figure 6 The S-PSS and S-SSS are shown to be located in consecutive symbols, but the S-PSS and S-SSS can be located separately with one symbol inserted in between. That is, the S-PSS can be mapped to OFDM symbol indexes 1 and 2, the S-SSS can be mapped to OFDM symbol indexes 4 and 5, and the PSBCH can be mapped to OFDM symbol indexes 0, 3, 6, 7, 8, 9, 10, 11, and 12. At the same time, although Figure 6 Not shown, a demodulation reference signal (DMRS) may be transmitted in each OFDM symbol to which the PSBCH is mapped.

[0135] The information transmitted through the PSBCH may include at least one of the following information.

[0136] 1. Frame number: This may be information indicating the frame number of the transmitted S-SSB (i.e., S-PSS, S-SSS, and PSBCH). When the sidelink UE transmitting the S-SSB is within the coverage of the base station, the frame number may be configured based on the system frame number of the base station where the sidelink UE is located. When the sidelink UE transmitting the S-SSB is outside the coverage of the base station, the frame number may be pre-configured based on the frame number of the UE transmitting the S-SSB. The frame number may consist of 10 bits.

[0137] 2. Downlink and uplink configuration information: such as Figure 1B As shown, a sidelink UE located within the coverage of a base station can perform sidelink communication with a sidelink UE located outside the coverage of the base station (partial coverage scenario). Figure 1B , the base station where UE-1 is located can operate as a time division duplex (TDD) system. In this case, the base station is composed of UE-2 and other UEs ( Figure 1B Specifically, when UE-1 receives control information and data information from a base station via a downlink, the sidelink control information and data information transmitted by UE-2 may interfere with the downlink signal received by UE-1. Figure 1B , when UE-1 is located at the edge of the coverage of the base station (i.e., far away from the base station) and UE-2 is positioned adjacent to UE-1, the interference problem may become serious. At the same time, when UE-1 transmits control information and data information to the base station via the uplink, the sidelink control information and data information transmitted by UE-2 may interfere with the UE-1 uplink signal received by the base station. However, since UE-2 is farther away from the base station than UE-1, the received signal from UE-2 may not cause much interference to the received signal from UE-1 at the receiver of the base station. In addition, since the base station can use more receiving antennas than the receiver of UE-1, more advanced receiving techniques such as interference cancellation can be used. Therefore, when comparing the case where UE-2's signal interferes with UE-1's receiver and the case where UE-2's signal interferes with the base station's receiver, the former case has a greater impact on system performance.

[0138] In order to solve the interference problem in the TDD system, the side link UE transmitting S-SSB within the coverage of the base station can transmit the TDD configuration information configured by the base station to the side link UE outside the coverage of the base station through the PSBCH (that is, the downlink and uplink configuration information that all UEs within the coverage of the base station must follow). After receiving the information through the PSBCH, the side link UE outside the coverage of the base station can configure the resource pool for transmitting / receiving side link control information and data information using only uplink subframes or uplink time slots (excluding downlink subframes, special subframes, downlink time slots and flexible time slots).

[0139] 3. Time slot index: reference Figure 5 , a system frame may consist of multiple subframes. In addition, a subframe may consist of multiple time slots, depending on the subcarrier spacing. Therefore, an indicator may be required to indicate in which time slot of the indicated frame number the S-SSB is transmitted. The time slot index may refer to information indicating the index of the time slot in which the S-SSB is transmitted in the frame index indicated by the frame number. For example, in a frame consisting of 10ms, subcarrier spacings of 15kHz, 30kHz, 60kHz, and 120kHz may consist of 10 time slots, 20 time slots, 40 time slots, and 80 time slots, respectively. Therefore, 7 bits may be required to transmit 80 time slot indices.

[0140] 4. Coverage indicator: In the case where the synchronization signal of the base station (e.g., eNB / gNB) is configured to have a higher priority than GNSS, the S-SSB transmitted by the sidelink UE directly synchronized with the base station may have a priority over the S-SSB transmitted by any other sidelink UE, that is, a higher priority than the S-SSB transmitted by the sidelink UE directly or indirectly synchronized with the GNSS and the S-SSB transmitted by the sidelink UE directly or indirectly synchronized with the S-SSB transmitted by another sidelink UE. This may mean that the timing of the base station is transmitted by the sidelink UE located within the coverage of the base station to the sidelink UE located outside the coverage of the base station. In order to determine the priority, a 1-bit indicator indicating the coverage status may be included in the PSBCH. For example, when the 1-bit indicator is set to "1", it may mean that the sidelink UE transmitting the PSBCH is within the coverage of the base station. In addition, when the 1-bit indicator is set to "0", it may mean that the sidelink UE transmitting the PSBCH is outside the coverage of the base station. Alternatively, vice versa is also possible. Therefore, the sidelink UE receiving the PSBCH can determine whether any received S-SSB is transmitted from a sidelink UE within the coverage of the base station or from a sidelink UE outside the coverage of the base station. Based on this, it can be determined which S-SSB to match the sidelink synchronization (i.e., select the sidelink synchronization signal source).

[0141] At the same time, in addition to the above information, the PSBCH may also contain reserved bits that are not used in the current version. For example, it may include a reserved bit consisting of 2 bits or 1 bit, which can be used for UEs of subsequent versions (i.e., the sidelink UE of version 16 does not interpret the reserved bit, and if the reserved bit is used to introduce a new sidelink function in a version above version 17, the sidelink UE of versions above version 17 can interpret the corresponding bit).

[0142] In addition, the sidelink synchronization channel may be used in a licensed frequency band, an ITS frequency band which is a vehicle communication frequency band, or an unlicensed frequency band, and the sidelink synchronization channel information contained in the corresponding frequency bands may be the same or may be at least partially different.

[0143] refer to Figure 6 , in the sidelink synchronization channel, the frequency size of PSBCH is 132 subcarriers (11 PRBs), and the frequency size of S-PSS and S-SSS is 127 subcarriers. This may only apply to 5G NR V2X of Release 16, and may be configured to different values ​​or forms in subsequent releases.

[0144] Figure 7 The structure of a side link channel according to an embodiment of the present disclosure is shown.

[0145] refer to Figure 7 For sidelink data transmission and reception, the sidelink channel can basically consist of one adaptive gain controller (AGC) symbol for antenna gain control, three physical sidelink control channel (PSCCH) symbols, twelve physical sidelink shared channel (PSSCH) symbols and one GUARD symbol.

[0146] refer to Figure 7 , the number of symbols for each physical channel is only an example, and a different number of symbols can be set for each channel. PSSCH can contain not only data information, but also second control information (second SCI) indicated by the first control information (first SCI, sidelink control information) contained in PSCCH, or it can be composed of only PSSCH without second SCI information.

[0147] The first symbol is an AGC symbol and may consist of the same information as the second symbol. The reason why the AGC symbol is needed is as follows. One of the main characteristics of sidelink communication is that there may be multiple transmitters that wish to transmit, and they may be at different distances from the receiving end and have different transmit powers. Therefore, from the perspective of the receiving end, the received power strength may be different depending on which transmitter is conducting the sidelink communication. Therefore, since the receiving end needs time to correct for this difference, such as Figure 7 As shown, the first symbol is allocated as an AGC symbol.

[0148] PSCCH is a physical channel that transfers Sidelink Control Information (SCI) and can have at least one value of 10, 12, 15, 20, and 25 PRBs in one subchannel, which can be configured by higher layer signaling. Figure 7 The number of symbols of the PSCCH is shown as three symbols, but one symbol or two symbols are also possible and the value can be configured by higher layer signaling. The control information contained in the PSCCH is mapped from the lowest PRB index.

[0149] PSSCH is a physical channel that transmits sidelink data information (TB, transport block), and the second SCI information can be mapped from the first DMRS symbol transmitted on PSSCH. PSSCH can be transmitted in units of one subchannel. The size of a subchannel can have at least one value of 10, 12, 15, 20, 25, 50, 75, and 100 PRBs, and there can be 1 to a maximum of 27 subchannels within one SL BWP. In addition, when PSSCH and PSCCH have the same PRB, Figure 7 The 2nd, 3rd and 4th symbols in the signal can be changed to symbols composed entirely of PSCCH. Figure 7Although not shown separately, a reference signal demodulation reference signal (DMRS) for decoding PSSCH may be included in the 5th symbol. Figure 7 It is not shown separately, but the physical sidelink feedback channel (PSFCH) that conveys HARQ-ACK information for PSSCH instead of PSSCH can be present in the 12th and 13th symbols. If PSFCH is present, the 10th symbol can be a GUARD symbol. The purpose of introducing the GUARD symbol is that the UE receiving PSSCH requires a separate transition (switching) time to transmit PSFCH, and a symbol is added for this purpose. In addition, the reason why the 14th symbol is a GUARD symbol is similar to the above. Reference Figure 7 , as an example, this is because when a UE transmitting PSCCH / PSSCH in time slot n receives PSCCH / PSSCH from another UE in time slot + 1, or a UE receiving PSCCH / PSSCH in time slot n transmits PSCCH / PSSCH to another UE in time slot n+1, a switching time between transmission and reception is required. The transmission format transmitted by the UE in PSFCH is the same as PUCCH format 0 defined in the NR standard of 3GPP Release 15, and consists of one PRB based on the Zadoff-Chu sequence and repeated transmissions on two symbols. As mentioned above, the first of the two symbols of PFSCH can be used for AGC.

[0150] In the above description, the first control information may provide information related to resource allocation. For example, the first control information may include at least one of frequency resource information, time resource information, DMRS mode, second control information format, resource size to which the second control information is allocated, the number of DMRS ports, MCS, and whether to transmit PSFCH. In the above example, the DMRS mode is a field that notifies information about the DMRS allocated to the time and frequency resources for PSSCH reception, and the second control information format is a field that notifies the size and configuration information of the second control information transmitted on the PSSCH. In addition, the resource size to which the second control information is allocated is a field indicating the amount of resources to which the second control information is allocated to the PSSCH, and the number of DMRS ports is a field indicating information about the number of ports through which DMRS is transmitted. Modulation and Coding Scheme (MCS) is a field that indicates coding information in the PSSCH.

[0151] The second control information may provide UE-specific information or detailed information related to the corresponding service. For example, the second control information may be composed of at least one field of a HARQ process number, a new data indicator (NDI), a redundancy version (RV), a source ID, a destination ID, a HARQ feedback enable / disable indicator, a broadcast type indicator, and a CSI request. In the above example, NDI consists of 1 bit and is a field indicating whether the TB of the currently transmitted PSSCH is a retransmission or an initial transmission. In this field, if a switch occurs (from 1 to 0 or from 0 to 1), it is determined to be an initial (or new) transmission, and if no switch occurs, it is determined to be a retransmission. RV is a field indicating the starting point of the coded bit when the PSSCH is encoded based on low-density parity check (LDPC) coding. The source ID indicates the ID of the UE transmitting the PSSCH, and the destination ID indicates the ID of the UE receiving the PSSCH. The HARQ feedback enable / disable indicator is an indicator field indicating whether the HARQ feedback corresponding to the PSSCH transmission is transmitted, and the broadcast type indicator is a field indicating whether the PSSCH currently transmitted is unicast, groupcast or broadcast. The CSI request is a field including an instruction for the receiving UE to send the measured CSI information to the transmitting UE. The time resource for the sidelink communication can be set to one of 7 to 14 symbols within a time slot consisting of 14 symbols for each SL bandwidth part (BWP).

[0152] Figure 6 and Figure 7 The structures for transmitting / receiving synchronization channels and control / data channels for sidelink communications are described in . These structures can be applied to unlicensed bands, but there is the problem of complying with specific conditions due to different regulations and restrictions in each country or continent. One of them is the occupied channel bandwidth (OCB), and it is defined that the bandwidth containing 99% of the transmitted signal power should be contained in 80% to 100% of the nominal channel bandwidth where the signal is transmitted. For example, in an unlicensed band with a channel bandwidth of 20MHz, it can be seen that the UE meets the above regulations only when it unconditionally transmits at least 16MHz or more. For reference, the value of 80% is just an example and each country can have a different value.

[0153] However, in the case of UE, the use of wide bandwidth will have the effect of reducing the transmission distance by reducing the transmission power efficiency, thereby reducing the communication radius in the unlicensed band. Therefore, if each specific M PRB is allocated at least one PRB in terms of frequency, it is not necessary to allocate it continuously in the bandwidth of the signal allocated including 80% to 100% of the channel frequency bandwidth, then the above provisions can be met. Therefore, the method of allocating control or data information at regular intervals in frequency, rather than the method of continuously allocating such information, is called the interleaving method of resource allocation. For example, the interleaving block "m" can have a value of 0 to M-1. The value of "m" can be considered as the resource being actually allocated to the common resource block {m, M+m, 2M+m, 3M+m, ...}, and the value of "M" can have different values ​​according to the subcarrier spacing. The interleaving method does not have to be met in all countries and continents using unlicensed bands, and can be used only in countries and continents where certain relevant regulations must be met, and this configuration can be performed through higher layer signaling. However, in the case of sidelink communication, since it is necessary to support communication in an area outside the coverage area without separately configuring a base station, sidelink communication can be supported by considering GPS information, previously determined location information, or a staggered structure from the time the UE is manufactured in an area where relevant regulations are required.

[0154] use Figure 6 and Figure 7 Check whether the sidelink channel structure described in the OCB specification is met. Figure 6 In the case of a synchronization channel consisting of 11 PRBs in a system, it may be difficult to transmit the synchronization channel in a system having a channel frequency band bandwidth consisting of 100 PRBs. Figure 7 Taking the case of PSCCH / PSSCH consisting of 20 PRBs in a 20MHz band as an example, it may be difficult to transmit control / data channels in a system with a channel band bandwidth consisting of 100 PRBs. Since 100 PRBs is the number of possible PRBs in a 20MHz band with a subcarrier spacing of 15kHz, it is difficult to freely utilize the PRBs in such an environment. Figure 6 and Figure 7 Of course, since you can configure Figure 7 The PSCCH / PSSCH consists of 100 PRBs in the UE, so control / data channels can be transmitted while meeting the OCB requirement to a limited extent. However, since frequency division multiplexing (FDM) with other UEs is not allowed, only one UE can transmit / receive data at a specific time.

[0155] Figure 8 The types of synchronization signals that may be transmitted and received by a sidelink UE in an unlicensed band according to an embodiment of the present disclosure are shown.

[0156] Sidelink UEs operating in unlicensed bands can transmit / receive Figure 8 In addition to the synchronization signals shown above, it can also transmit / receive the above Figure 4 For the convenience of description, the UE receiving the synchronization signal in the unlicensed band is referred to as the sidelink UE-A.

[0157] Authorized band SSB may refer to a synchronization signal transmitted by a base station operating in an authorized band. Directly receiving an authorized band SSB may mean that the sidelink UE receives the SSB directly from a base station operating in an authorized band. Indirectly receiving an authorized band SSB may mean a situation where the sidelink UE-A receives a sidelink synchronization signal transmitted by a sidelink UE (e.g., UE-1) directly synchronized with the authorized band SSB. In this case, the sidelink UE-A may receive a synchronization signal from a base station operating in an authorized band through two hops. In another example, a second sidelink UE (e.g., UE-2) synchronized with an S-SSB transmitted by a first sidelink UE (e.g., UE-1) synchronized with a base station operating in an authorized band may transmit an S-SSB. After receiving the signal, the sidelink UE-A may receive a synchronization signal from a base station operating in an authorized band through three hops. Similarly, the sidelink UE-A may receive a synchronization signal from a base station operating in an authorized band through more than three hops. In this case, the sidelink synchronization signal source may be another sidelink UE (eg, UE-1) synchronized with the base station operating in the licensed band.

[0158] An unlicensed band SSB may refer to a synchronization signal transmitted by a base station operating in an unlicensed band. Directly receiving an unlicensed band SSB may mean that the sidelink UE receives the SSB directly from a base station operating in an unlicensed band. Indirectly receiving an unlicensed band SSB may mean a situation where the sidelink UE-A receives a sidelink synchronization signal transmitted by a first sidelink UE (e.g., UE-1) directly synchronized with the unlicensed band SSB. In this case, the sidelink UE-A may receive a synchronization signal from a base station operating in an unlicensed band through two hops. In another example, a second sidelink UE (e.g., UE-2) synchronized with an S-SSB transmitted by a first sidelink UE (e.g., UE-1) synchronized with a base station operating in an unlicensed band may transmit an S-SSB. Upon receiving the signal, the sidelink UE-A may receive a synchronization signal from a base station operating in an unlicensed band through three hops. Similarly, the sidelink UE-A may receive a synchronization signal from a base station operating in an unlicensed band through more than three hops. In this case, the sidelink synchronization signal source may be another sidelink UE (eg, UE-1) synchronized with the base station operating in the unlicensed band.

[0159] Alternatively, the licensed band S-SSB may refer to a synchronization signal transmitted by a sidelink UE operating in a licensed band or a band for vehicle communications (Intelligent Transport Service (ITS) band). Sidelink UE-A may receive a synchronization signal directly from a sidelink UE-B operating in another licensed band. When sidelink UE-B fails to detect a synchronization signal transmitted from a GNSS, an unlicensed band base station, a licensed band base station, or another sidelink UE as a synchronization signal source, sidelink UE-B may transmit S-SSB based on its own timing. Sidelink UE-A may directly receive an S-SSB transmitted by a sidelink UE-B operating in a licensed band. In this case, the sidelink synchronization signal source may be a sidelink UE.

[0160] Sidelink UE-A can indirectly receive a synchronization signal from another sidelink UE-B. Indirectly receiving a synchronization signal from a sidelink UE-B operating in an authorized band may refer to a situation where the sidelink UE-A receives an S-SSB transmitted by a sidelink UE-1 directly synchronized with the sidelink UE-B. In this case, the sidelink UE-A can receive a synchronization signal from the sidelink UE-B operating in the authorized band through two hops. In another example, the sidelink UE-2 synchronized with the S-SSB transmitted by the sidelink UE-1 directly synchronized with the sidelink UE-B can transmit an S-SSB. After receiving the signal, the sidelink UE-A can receive a synchronization signal from the sidelink UE-B through 3 hops. Similarly, the sidelink UE-A can receive a synchronization signal from the sidelink UE-B operating in the authorized band through more than three hops. In this case, the sidelink synchronization signal source can be a sidelink UE operating in another authorized band synchronized with the sidelink UE.

[0161] An unlicensed band S-SSB may refer to a synchronization signal transmitted by a sidelink UE operating in an unlicensed band. Sidelink UE-A may receive a synchronization signal directly from a sidelink UE-B operating in another unlicensed band. When sidelink UE-B fails to detect a synchronization signal transmitted from a GNSS, an unlicensed band base station, a licensed band base station, or another sidelink UE as a synchronization signal source, sidelink UE-B may transmit an S-SSB based on its own timing. Sidelink UE-A may directly receive an S-SSB transmitted by a sidelink UE-B operating in an unlicensed band. In this case, the sidelink synchronization signal source may be a sidelink UE.

[0162] Sidelink UE-A can indirectly receive a synchronization signal from another sidelink UE-B. Indirectly receiving a synchronization signal from a sidelink UE-B operating in an unlicensed band may refer to a situation where the sidelink UE-A receives an S-SSB transmitted by a sidelink UE-1 directly synchronized with the sidelink UE-B. In this case, the sidelink UE-A can receive a synchronization signal from the sidelink UE-B operating in the unlicensed band through two hops. In another example, the sidelink UE-2 synchronized with the S-SSB transmitted by the sidelink UE-1 directly synchronized with the sidelink UE-B can transmit an S-SSB. After receiving the signal, the sidelink UE-A can receive a synchronization signal from the sidelink UE-B through 3 hops. Similarly, the sidelink UE-A can receive a synchronization signal from the sidelink UE-B operating in the licensed band through more than three hops. In this case, the sidelink synchronization signal source can be a sidelink UE operating in another licensed band synchronized with the sidelink UE.

[0163] When the sidelink UE-B fails to detect a synchronization signal transmitted from a GNSS, an unlicensed band base station, a licensed band base station, or another sidelink UE as a synchronization signal source, the sidelink UE-B may consider a separate timer for transmitting a synchronization signal based on its own timing. For example, when the sidelink UE-B fails to detect a synchronization signal transmitted from a GNSS, an unlicensed band base station, a licensed band base station, another sidelink UE operating in a licensed band, or another sidelink UE operating in an unlicensed band as a synchronization signal source within a certain period of time, the sidelink UE-B may transmit a synchronization signal based on its own timing.

[0164] The meaning of the timer may refer to a reference time point for transmitting a synchronization signal based on its own timing when a synchronization signal cannot be received from any other synchronization signal source during the corresponding timer time. If a synchronization signal is received from any other synchronization signal source within the timer time, the side link UE-B may transmit a synchronization signal by matching the corresponding synchronization signal source. The timer may be, for example, in units of time (such as 200ms) or in units of time slots (such as 200 time slots). In addition, different timer values ​​may be provided depending on the synchronization signal source. For example, the timer value of a synchronization signal transmitted by a licensed band base station or another side link UE operating in a licensed band may be 160ms, and the timer value of a synchronization signal transmitted by an unlicensed band base station or another side link UE operating in an unlicensed band may be 320ms.

[0165] A sidelink UE operating in an unlicensed band may receive synchronization signals from various synchronization signal sources as described above, and may synchronize based on synchronization signals transmitted from synchronization signal sources having higher priorities according to a preconfigured priority. For example, the following priorities may be preconfigured in order from synchronization signals having high priorities to synchronization signals having low priorities.

[0166] - Synchronization priority method 1: 1) Synchronization signal transmitted directly from GNSS > 2) Synchronization signal transmitted directly from GNSS by UE performing synchronization > 3) Synchronization signal transmitted indirectly from GNSS by UE performing synchronization > 4) Synchronization signal transmitted directly from a base station operating in an unlicensed band > 5) Synchronization signal transmitted directly from a base station operating in an unlicensed band by UE performing synchronization > 6) Synchronization signal transmitted indirectly from a base station operating in an unlicensed band by UE performing synchronization > 7) Synchronization signal transmitted directly or indirectly from GNSS or a base station operating in an unlicensed band by UE not performing synchronization

[0167] - Synchronization priority method 2: 1) Synchronization signal transmitted directly from GNSS > 2) Synchronization signal transmitted directly from GNSS by UE performing synchronization > 3) Synchronization signal transmitted indirectly from GNSS by UE performing synchronization > 4) Synchronization signal transmitted directly from a base station operating in a licensed band > 5) Synchronization signal transmitted directly from a base station operating in a licensed band by UE performing synchronization > 6) Synchronization signal transmitted indirectly from a base station operating in a licensed band by UE performing synchronization > 7) Synchronization signal transmitted directly from a base station operating in an unlicensed band > 8) Synchronization signal transmitted directly from a base station operating in an unlicensed band by UE performing synchronization > 9) Synchronization signal transmitted indirectly from a base station operating in an unlicensed band by UE performing synchronization > 10) Synchronization signal transmitted directly or indirectly from GNSS or a base station operating in a licensed band or an unlicensed band by a licensed band UE not performing synchronization > 11) Synchronization signal transmitted directly or indirectly from GNSS or a base station operating in a licensed band or an unlicensed band by an unlicensed band UE not performing synchronization

[0168] - Synchronization priority method 3: 1) Synchronization signal transmitted directly from GNSS > 2) Synchronization signal transmitted directly from GNSS by UE performing synchronization > 3) Synchronization signal transmitted indirectly from GNSS by UE performing synchronization > 4) Synchronization signal transmitted directly or indirectly from GNSS by unlicensed band UE not performing synchronization

[0169] Synchronization priority method 1 is a method applicable when the side link UE does not support authorized band operation. Synchronization priority method 2 is a method applicable when the side link UE supports both authorized band and unlicensed band operations. Specifically, it is a method that can be considered when the UE is able to apply the matching synchronization value in the authorized band to the timing in the unlicensed band. Synchronization priority method 3 is a method applicable when the UE does not support authorized band and unlicensed band Uu operations. This is just an example, and at least one of the above-mentioned synchronization priority methods can be applied regardless of the UE capabilities. In addition, the priority method can be determined based on the UE capabilities, or can be determined by the base station based on pre-configuration information or higher layer signaling configuration information. If the UE does not have GNSS capability, the priority of the synchronization signal related to GNSS can be omitted in the above-mentioned synchronization priority method. Synchronization priority methods 1, 2 and 3 are examples, and they can be applied in a changed order, or some operations can be omitted.

[0170] Fig. 9 A synchronization signal transmission period according to an embodiment of the present disclosure is shown.

[0171] refer to Fig. 9 , a sidelink UE operating in a licensed band may be able to transmit one to four S-SSBs with a period of 160ms depending on the subcarrier spacing. Fig. 9 , N1 represents the offset value from the starting time point of the period (e.g., 160ms) to the resource for transmitting the first S-SSB, and N2 represents the gap between the S-SSB transmission resources. For example, a sidelink UE operating in a licensed band transmits one S-SSB per 160ms period in a subcarrier spacing of 15kHz, one or two S-SSBs per 160ms period in a subcarrier spacing of 30kHz, and one, two or four S-SSBs per 160ms period in a subcarrier spacing of 60kHz. When multiple S-SSBs can be transmitted, the sidelink UE can transmit from the base station with a preconfigured value or a value configured by higher layer signaling. A sidelink UE operating in a licensed band can transmit S-SSBs through configured resources without allowing separate channel access.

[0172] However, a sidelink UE operating in an unlicensed band may transmit an S-SSB in a configured resource depending on whether the channel access is successful, and if the channel access fails, it must wait until the S-SSB resources arrive in the next cycle. Therefore, compared to the licensed band, the delay time for the sidelink UE operating in the unlicensed band to transmit the S-SSB may increase, which may affect the synchronization between the UEs operating in the unlicensed band. In addition, since there is a possibility of channel access failure in the unlicensed band compared to the licensed band, more S-SSB transmission candidate resources may need to be configured. To this end, a sidelink UE operating in an unlicensed band may be able to apply at least one of the following methods.

[0173] -Method 1-1: A sidelink UE operating in an unlicensed band may support transmitting more S-SSB candidates within the same subcarrier spacing compared to a sidelink UE operating in a licensed band. For example, a sidelink UE operating in an authorized band with a subcarrier spacing of 15kHz transmits one S-SSB every 160ms period, but a sidelink UE operating in an unlicensed band may transmit one or two S-SSBs. In another example, a sidelink UE operating in an authorized band with a subcarrier spacing of 30kHz transmits one or two S-SSBs every 160ms period, but a sidelink UE operating in an unlicensed band may transmit one, two, or four S-SSBs. The above examples are merely exemplary, and the maximum number of S-SSBs that can be transmitted in an unlicensed band with the same period and the same subcarrier spacing may be greater than the maximum number of S-SSBs that can be transmitted in a licensed band.

[0174] -Method 1-2: A sidelink UE operating in an unlicensed band may support S-SSB transmission with a shorter transmission period under the same subcarrier spacing as compared to a sidelink UE operating in a licensed band. For example, a sidelink UE operating in a licensed band with a subcarrier spacing of 15kHz transmits one S-SSB every 160ms, but a sidelink UE operating in an unlicensed band may transmit one S-SSB with a period less than 160ms, such as one every 80ms. Therefore, based on 160ms, a UE operating in an unlicensed band may transmit a total of two S-SSBs.

[0175] - Method 1-3: This method is a combination of Method 1-1 and Method 1-2. A sidelink UE operating in an unlicensed band may transmit more S-SSB candidates with a shorter transmission period than a sidelink UE operating in a licensed band.

[0176] -Method 1-4: If a sidelink UE operating in an unauthorized band has m transmit candidates within one S-SSB transmission period, the actual S-SSB transmission can be restricted to at most n (n < m) per transmission period. For example, in the case where at most two S-SSB resources are configured per 160 ms period based on a 15 kHz subcarrier spacing and at most only one S-SSB can be transmitted (m = 2, n = 1), if the sidelink UE successfully performs channel access and transmits an S-SSB in the first S-SSB resource, it can skip the channel access and S-SSB transmission in the second S-SSB resource. On the other hand, when the S-SSB cannot be transmitted due to a channel access failure in the first S-SSB resource, the sidelink UE can attempt to perform channel access in the second S-SSB resource and transmit the S-SSB according to whether the channel access is successful. In another example, in the case where at most four S-SSB resources are configured per 160 ms period based on a 30 kHz subcarrier spacing and at most only two S-SSBs can be transmitted (m = 4, n = 2), if the sidelink UE successfully performs channel access and transmits S-SSBs in the first and second S-SSB resources, it can skip the channel access and S-SSB transmission in the third and fourth S-SSB resources. On the other hand, when the S-SSB cannot be transmitted due to a channel access failure in the first S-SSB resource, the sidelink UE can attempt to perform channel access in at least the second and third S-SSB resources and transmit the S-SSB according to whether the channel access is successful. In summary, if the UE successfully performs channel access and transmits an S-SSB for at least two S-SSB resources, it can skip the channel access and S-SSB transmission for the remaining S-SSB resources within the period. In this way, more S-SSB transmission candidate resources can be allocated to UEs operating in the unauthorized band, and the number of UEs actually using S-SSB resources to transmit S-SSBs can be increased. This method can be applied as at least one of the above methods 1-1, 1-2, and 1-3.

[0177] At the same time, the S-SSB resources configured for transmission by the sidelink UE operating in the authorized frequency band are not considered to be resource regions for sidelink control / data information transmission / reception. In other words, if there are resources for the sidelink UE to transmit S-SSB in time slot n, time slot n is excluded from resource selection for sidelink control / data information transmission / reception. If UE-2 transmits sidelink control information or data information with different frequency resources in the time resource region in which UE-1 transmits S-SSB, UE-1 and UE-2 cannot be synchronized with each other because UE-2 cannot receive the S-SSB transmitted by UE-1. The reason for doing this is to enable all UEs to listen to synchronization signals in environments such as vehicle communications. Basically, since the sidelink UE operates in a half-duplex type, it can only receive or transmit at a specific point in time.

[0178] Even in the case of a side link UE operating in an unlicensed band, as in the licensed band, the resources configured for S-SSB (i.e., time resources) can be excluded from the resource selection for the transmission and reception of side link control / data information. However, as described above, the side link UE operating in the unlicensed band may fail in channel access, so more S-SSB candidate resources need to be configured compared to the licensed band. The fact that many S-SSB candidate resources are configured may mean that the available resources that can actually transmit and receive side link control / data information are reduced. For example, when S-SSB is transmitted with a period of 160ms using a 1ms time resource, the remaining 159ms of resources can be used for side link control and data information. However, if S-SSB can be transmitted with a period of 160ms using a 10ms time resource, only 150ms of remaining resources can be used for side link control and data information. Therefore, in the unlicensed band, compared with the licensed band, not only more S-SSB candidate resources need to be provided, but also the reduction of available resources for side link control and data information needs to be minimized. To solve this problem, a UE operating in an unlicensed band may be able to consider at least one or a combination of the following methods.

[0179] -Method 2-1: PSCCH / PSSCH and S-SSB may be frequency division multiplexed (FDMed). In an unlicensed band, PSCCH / PSSCH for unlicensed band sidelink communication may be transmitted and received in a frequency region other than a frequency region in which S-SSB is configured within a time resource (e.g., a time slot) in which S-SSB is transmitted.

[0180] Fig.10 A case where S-SSB and PSCCH / PSSCH are transmitted / received in FDM form according to an embodiment of the present disclosure is shown.

[0181] refer to Fig.10, the side link UE transmitting S-SSB 1002, the UE transmitting PSCCH / PSSCH 1000, and the UE transmitting PSCCH / PSSCH 1004 may be completely identical to each other, partially identical to each other, or completely different from each other. Fig.10 It is only an example, and other cases where the number of PSCCH / PSSCH is one or more than two are also possible.

[0182] The frequency resources for S-SSB transmission may exist so as to be separated from the frequency resources for PSCCH / PSSCH transmission by a guard band. The reason for the existence of the guard band is to ensure the reception performance of the UE receiving S-SSB. Specifically, since the frequency filtering of the UE transmitting PSCCH / PSSCH in the frequency band adjacent to the S-SSB may be incomplete, part of the power of the transmitted PSCCH / PSSCH may be transferred to the S-SSB band. Therefore, the receiving end for receiving S-SSB may receive a part of the PSCCH / PSSCH transmission signal transmitted in the adjacent frequency band together with the transmission signal of S-SSB. In another example, since the UE receiving S-SSB is likely to be in a situation where time and frequency synchronization are not accurately matched, it may attempt to receive S-SSB in a wider frequency band than the frequency resources allocated to S-SSB. Therefore, when PSCCH / PSSCH exists in a frequency band adjacent to S-SSB, the side link receiving UE can receive both S-SSB and PSCCH / PSSCH, and therefore the S-SSB reception performance may be reduced. Therefore, the size of the guard band may be configured by the base station via higher layer signaling, or may be fixed to a preconfigured value without higher layer signaling configuration.

[0183] In addition, despite the Fig.10 It is assumed that only PSCCH and PSSCH are transmitted, but PSFCH may also be transmitted.

[0184] refer to Fig.10 As shown in 1000, 1002, and 1004, S-SSB and PSCCH / PSSCH can be transmitted and received in the same time slot, and as shown in 1010, multiple PSCCH / PSSCH can be transmitted and received in one S-SSB time slot. Conversely, multiple S-SSBs can be transmitted and received in one PSCCH / PSSCH time slot. In addition, the subcarrier spacing applied to PSCCH / PSSCH transmission and the subcarrier spacing applied to S-SSB transmission can be the same or different from each other.

[0185] Although Method 2-1 has described that the S-SSB is transmitted in the form of FDM with PSCCH / PSSCH, it will be common to transmit the S-SSB in the form of FDM and time division multiplexing (TDM) with PSCCH / PSSCH.

[0186] Fig.11 The allocation of S-SSB transmission resources according to an embodiment of the present disclosure is shown.

[0187] The UE basically has the same sidelink communication resource pool, and usually transmits PSCCH / PSSCH by selecting one of the resources divided into time slot units in the time domain and sub-channel units in the frequency domain. In this case, the sidelink UE can understand from the perspective of the resource pool that the resource area for transmitting and receiving S-SSB is occupied by a specific time slot and a specific sub-channel. Therefore, the UE can perform sidelink communication by selecting resources from the remaining resource pool except for the resource area for transmitting / receiving S-SSB.

[0188] Fig.11 The case where the resource region for transmitting S-SSB is slot n+3 and subchannels k+2 and k+3 is shown. This resource region cannot be used for PSCCH / PSSCH transmission and can be used by sidelink UEs that intend to transmit S-SSB. Fig.11 is only an example of a resource area to which the S-SSB is allocated. From the perspective of time resources, the S-SSB may exist continuously or discontinuously in multiple time slots, and from the perspective of frequency resources, the S-SSB may exist only in one subchannel, or may exist continuously or discontinuously in two or more subchannels. Specifically, the number of subchannels occupied by the S-SSB may vary depending on the number of physical resource blocks (PRBs) contained in the subchannel. In addition, regardless of whether the resources are occupied by the S-SSB, for reserved resources that are not allocated for sidelink communications, specific time slot indices and specific numbers of subchannels can be used, and S-SSB transmissions can also be performed within these reserved resources.

[0189] refer to Fig.11 , the guard band may exist alone in the S-SSB resource 1100 and may be configured from the base station through higher layer signaling, or may be pre-configured without separate signaling.

[0190] In addition, since, as described above, a UE transmitting PSCCH / PSSCH in a time slot for transmitting S-SSB cannot receive S-SSB transmitted by another UE, a UE having a higher priority for obtaining synchronization through S-SSB reception can lower the priority of selecting the corresponding time slot. In other words, when a UE performing sidelink communication receives a PSCCH / PSSCH in a time slot for S-SSB transmission ( Fig.11 The time slot n+3 in the transmission) and the time slot not used for S-SSB transmission ( Fig.11When selecting PSCCH / PSSCH transmission resources in the time slots other than time slot n+3 in the time slots other than time slot n+3, resources for sidelink communication can be selected by considering the two time slots differently. For example, the resources for sidelink communication can be selected by first searching the time slots where S-SSB is not transmitted ( Fig.11 Then if there is no available resource, further search for the time slot where S-SSB can be transmitted ( Fig.11 This can be applied to the case where the sidelink UE operates in a mode of autonomous resource selection. In addition, the time slot for transmitting S-SSB may not allow PSFCH transmission. Fig.11 , as an example, when S-SSB can be transmitted in time slot n+3, PSFCH transmission can be allowed only in time slots other than time slot n+3. The resource region for transmitting S-SSB or the resources reserved therefor can be configured from the base station via higher layer signaling or using preconfigured information.

[0191] -Method 2-2: PSCCH / PSSCH and S-SSB may be FDM and TDM. Specifically, this may mean that S-SSB is transmitted in a specific symbol within a time slot in which PSCCH / PSSCH is transmitted and received.

[0192] Fig.12 Resources used for S-SSB transmission according to an embodiment of the present disclosure are shown.

[0193] refer to Fig.12 As an example, the case where the resources capable of transmitting S-SSB are time slot n+3 and subchannels k+2 and k+3 is shown. In time slot n+3, S-SSB can be transmitted in multiple symbols less than 14 symbols. In addition, instead of the above reference Figure 6 The S-SSB structure described above may transmit an S-SSB 1002 including only the S-PSS and the S-SSS. Alternatively, even though the S-SSB is composed of the S-PSS, the S-SSS, and the PSBCH, the S-SSB may be configured in a form in which the PSBCH occupies a smaller number of symbols by having a smaller payload than a side link operating in a licensed band. Figure 6 The S-SSB consisting of 14 symbols is considered in Fig.12 The S-SSB considered in may consist of fewer symbols. If only S-PSS and S-SSS are included, an S-SSB consisting of 4 symbols may be transmitted. Fig.12 , S-SSB transmission resources 1200 are not used for transmission / reception of PSCCH / PSSCH, and the sidelink UE can perform sidelink communication by selecting the remaining resource region except the corresponding resources.

[0194] There may be a guard band in the S-SSB transmission resource 1200, and as described above in method 2-1, the number of subchannels occupied by the S-SSB may vary depending on the number of PRBs contained in the subchannel. In addition, reserved resources may be considered to replace the S-SSB resource area, and the sidelink UE that wishes to transmit PSCCH / PSSCH may select resources for PSCCH / PSSCH transmission from the remaining resources except the reserved resources. In addition, the main difference from method 2-1 is that PSCCH / PSSCH transmission may be performed within the corresponding resource area even in the time slot in which the S-SSB is transmitted. Fig.12 Differently, the resource location of the S-SSB may be in the first part or the last part of the time slot. The resource region for transmitting the S-SSB or the resources reserved therefor may be configured from the base station via higher layer signaling or using preconfigured information.

[0195] -Method 2-3: Method 2-3 is similar to Method 2-2, but it is a method in which side link data information or control information for which FDM is performed on a frequency basis exists in a time resource region for transmitting S-SSB without a separate guard band.

[0196] Fig.13 Resources used for S-SSB transmission according to an embodiment of the present disclosure are shown.

[0197] refer to Fig.13 , the S-SSB allocated in four symbols can be transmitted, and in this case, the resources allocated for the S-SSB can be considered for rate matching for the PSSCH. Figure 6 Compared to the S-SSB described in , the S-SSB may have a form including only the P-SSS and the S-SSS, or may have a form in which a PSBCH having a smaller payload size is added. Fig.13 In the case where the UE transmitting the PSCCH / PSSCH and the UE transmitting the PSBCH are the same or different from each other, Fig.13 In the case of a PSCCH / PSSCH, the PSSCH of FDM can be allocated in the symbol transmitting the S-SSB. If the UE transmitting the PSCCH / PSSCH is different from the UE transmitting the PSBCH, Fig.13 In the case of S-SSB, the FDM PSSCH may not be allocated in the symbol for transmitting S-SSB. Fig.13 Allocation to one subchannel is considered, but any other allocation to multiple subchannels may be possible. In addition, in a time slot where PSFCH is allocated, S-SSB resources may not be allocated. In other words, PSFCH may not be transmitted in a time slot where S-SSB can be transmitted and received.

[0198] At the same time, as mentioned above Figure 6 As described in the description of , the type of information transmitted through the PSBCH may include a frame number, downlink and uplink configuration information, a time slot index, and a coverage indicator. However, this may be information limited to sidelink UEs communicating in a licensed band, and sidelink UEs communicating in an unlicensed band may also consider at least one of the following information.

[0199] 5. Channel access type indicator: This is information indicating whether channel access is performed in a frame-based equipment (FBE) scheme or a load-based equipment (LBE) scheme. FBE is the same as semi-static channel access, and LBE is the same as dynamic channel access. In the semi-static channel access scheme, the UE attempts channel access through a sensing window set in a regular period. If the channel access is successful, the UE can freely transmit and receive sidelink data within a certain interval, and if the channel access fails, the UE waits until the sensing window present in the next period. In the dynamic channel access scheme, if there is data to be sent via the side link, the UE considers the backoff counter. If the value of the backoff counter is 0, the UE attempts channel access, and once channel access is performed, the UE transmits data. If the channel access fails, the UE does not reduce the value of the backoff counter or sets it to a specific value. In order for the backoff counter value to decrease, the channel must be in an idle state in each specific sensing slot (e.g., 9us). Since the sidelink UE operating in the unlicensed band needs to know how to perform channel access in its area before performing sidelink communication, the channel access type indicator information may be required.

[0200] In the case of a UE communicating in an unlicensed band, since all frames or time slots may be used for communication in uplink, downlink or sidelink, the "downlink and uplink configuration information" provided by the sidelink UE operating in the licensed band via the PSBCH may not be necessary. In addition, it may be advantageous for a UE communicating in an unlicensed band to transmit and receive data by attempting to occupy a channel by itself without any assistance from a base station, and if only GNSS is prioritized to match the synchronization signal, coverage indicator information may not be required.

[0201] Fig.14 An example of an operation flow chart of a sidelink UE operating in an unlicensed band according to an embodiment of the present disclosure is shown.

[0202] Fig.14 Some operations in can be omitted, and two or more operations can be combined and performed as one step. In addition, Fig.14 The order of operations can be changed.

[0203] If the sidelink UE operating in the unlicensed band is not synchronized with any synchronization source before transmitting the synchronization signal, it may receive the synchronization signal in a resource where the synchronization signal configured or preconfigured by higher layer signaling from the base station is transmitted and received at operation 1401 .

[0204] If multiple synchronization signals are detected, the side link UE may select a specific synchronization signal source according to the above-mentioned synchronization priority sorting method (e.g., synchronization priority sorting method 1, synchronization priority sorting method 2, synchronization priority sorting method 3), and receive a synchronization signal from the selected synchronization signal source at operation 1402.

[0205] If the sidelink UE is synchronized with a specific synchronization source, operations 1401 and 1402 may be omitted.

[0206] In addition, the sidelink UE may perform S-SSB transmission at operation 1403 considering at least one embodiment or any combination of embodiments of the present disclosure.

[0207] For example, the sidelink UE may identify whether the frequency band in which the UE operates corresponds to an unlicensed frequency band / spectrum or an authorized frequency band / spectrum. The sidelink UE may identify the period of S-SSB transmission and the subcarrier spacing associated with the S-SSB. The sidelink UE may identify the number of S-SSB transmissions within the period. The number of S-SSB transmissions may be related to the subcarrier spacing and depends on whether the frequency band corresponds to an unlicensed spectrum or an authorized spectrum. For the same subcarrier spacing, the number of S-SSB transmissions in the case of an unlicensed frequency band / spectrum is greater than the number of S-SSB transmissions in the case of an authorized frequency band / spectrum. The sidelink UE may transmit an S-SSB within the period based on the number of S-SSB transmissions. When the frequency band in which the UE operates corresponds to an unlicensed frequency band / spectrum, the sidelink UE may transmit at least two S-SSBs within the period. As an example, in the case where the frequency band in which the UE operates corresponds to an unlicensed frequency band / spectrum, the period is 160ms, and the subcarrier spacing is 15kHz, the number of S-SSB transmissions may be 2.

[0208] The S-SSB transmitted by a sidelink UE may be received by another sidelink UE.

[0209] Fig.15 is a block diagram showing the structure of a UE according to an embodiment of the present disclosure.

[0210] refer to Fig.15 , the UE may include a transceiver (1501), a UE controller (1502) and a storage device (1503). In the present disclosure, the UE controller may be defined as a circuit, an application specific integrated circuit or at least one processor.

[0211] The transceiver (1501) can transmit / receive signals to / from other network entities. For example, the transceiver can receive system information from a base station and can receive synchronization signals or reference signals. In addition, the transceiver can transmit / receive signals to / from other UEs.

[0212] According to the embodiments presented in the present disclosure, the UE controller (1502) can control the overall operation of the UE. For example, the UE controller can control the signal flow between blocks to perform operations according to the above figures and flowcharts. Specifically, the UE controller can operate in response to control signals from the base station and exchange messages or signals with other UEs and / or base stations.

[0213] The storage device (1503) may store at least one of information transmitted / received by the transceiver and information generated by the UE controller.

[0214] Fig.16 is a block diagram showing the structure of a base station according to an embodiment of the present disclosure.

[0215] refer to Fig.16 , the base station may include a transceiver (1601), a base station controller (1602) and a storage device (1603). In the present disclosure, the base station controller may be defined as a circuit, an application specific integrated circuit or at least one processor.

[0216] The transceiver (1601) can transmit / receive signals to / from other network entities. For example, the transceiver can transmit system information to the UE, and can transmit a synchronization signal or a reference signal.

[0217] The base station controller (1602) may control the overall operation of the base station according to the embodiments proposed in the present disclosure. For example, the base station controller may control the operations proposed in the present disclosure to manage and reduce interference with neighboring base stations. Specifically, the base station controller may transmit a control signal to the UE to control the operation of the UE or exchange messages or signals with the UE.

[0218] The storage device (1603) may store at least one of information transmitted / received by the transceiver and information generated by the base station controller.

[0219] While the disclosure has been shown and described with reference to various embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the disclosure as defined by the appended claims and their equivalents.

Claims

1. A method performed by a user equipment UE in a wireless communication system, the method include: identifying whether a frequency band in which the UE operates corresponds to an unlicensed spectrum or a licensed spectrum; Identifying a transmission period of a sidelink synchronization signal block S-SSB and a subcarrier spacing associated with said S-SSB; identifying the number of S-SSB transmissions within the period; as well as transmitting at least two S-SSBs based on a number of S-SSB transmissions in a case where the frequency band corresponds to the unlicensed spectrum, wherein the number of S-SSB transmissions is related to the subcarrier spacing and depends on whether the frequency band corresponds to the unlicensed spectrum or the licensed spectrum, and The number of S-SSB transmissions when the frequency band corresponds to the unlicensed spectrum is greater than the number of S-SSB transmissions when the frequency band corresponds to the licensed spectrum.

2. The method of claim 1, wherein when the frequency band corresponds to the unlicensed spectrum, the period is 160 ms, and the subcarrier spacing is 15 kHz, the number of S-SSB transmissions is 2.

3. The method of claim 1, wherein transmitting the at least two S-SSBs include: identifying whether an S-SSB on a first resource among resources corresponding to the number of S-SSB transmissions is successfully transmitted; In a case where the S-SSB on the first resource is not successfully transmitted, performing a channel access procedure on a second resource among the resources corresponding to the number of times the S-SSB is transmitted; as well as In case the channel access procedure is successful, S-SSB is transmitted on the second resource.

4. The method of claim 1, wherein the S-SSB comprises a sidelink primary synchronization signal S-PSS, a sidelink secondary synchronization signal S-SSS, and a physical sidelink broadcast channel PSBCH. 5 . The method of claim 4 , wherein, in a case where the frequency band corresponds to the unlicensed spectrum, the PSBCH includes information indicating a channel access type.

6. The method of claim 1, further comprising: include: In symbols other than symbols in which at least one S-SSB is transmitted in a slot, a physical side link control channel PSCCH or a physical side link shared channel PSSCH is transmitted.

7. The method of claim 1, wherein the at least two S-SSBs are received from a base station or another UE operating in the unlicensed spectrum.

8. A user equipment UE in a wireless communication system, the UE include: Transceiver; as well as A controller is connected to the transceiver and is configured to: identifying whether a frequency band in which the UE operates corresponds to an unlicensed spectrum or a licensed spectrum; identifying a transmission period of a sidelink synchronization signal block S-SSB and a subcarrier spacing associated with said S-SSB, identifying the number of S-SSB transmissions within the period, and transmitting at least two S-SSBs based on a number of S-SSB transmissions in a case where the frequency band corresponds to the unlicensed spectrum, wherein the number of S-SSB transmissions is related to the subcarrier spacing and depends on whether the frequency band corresponds to the unlicensed spectrum or the licensed spectrum, and The number of S-SSB transmissions when the frequency band corresponds to the unlicensed spectrum is greater than the number of S-SSB transmissions when the frequency band corresponds to the licensed spectrum.

9. The UE of claim 8, wherein when the frequency band corresponds to the unlicensed spectrum, the period is 160 ms, and the subcarrier spacing is 15 kHz, the number of S-SSB transmissions is 2.

10. The UE according to claim 8, wherein the controller is further configured to: identifying whether an S-SSB on a first resource among resources corresponding to the number of S-SSB transmissions is successfully transmitted, In a case where the S-SSB on the first resource is not successfully transmitted, performing a channel access procedure on a second resource among the resources corresponding to the number of times the S-SSB is transmitted, and In case the channel access procedure is successful, S-SSB is transmitted on the second resource.

11. The UE according to claim 8, The S-SSB includes a sidelink primary synchronization signal S-PSS, a sidelink secondary synchronization signal S-SSS and a physical sidelink broadcast channel PSBCH, and Wherein, in a case where the frequency band corresponds to the unlicensed spectrum, the PSBCH includes information indicating a channel access type.

12. The UE according to claim 8, wherein the controller is further configured to: transmitting a physical side link control channel PSCCH or a physical side link shared channel PSSCH in symbols other than symbols in which at least one S-SSB is transmitted in a time slot, The at least two S-SSBs are received from a base station or another UE operating in the unlicensed spectrum.

13. A method performed by a user equipment UE in a wireless communication system, the method include: identifying whether a frequency band in which the UE operates corresponds to an unlicensed spectrum or a licensed spectrum; Identifying a transmission period of a sidelink synchronization signal block S-SSB and a subcarrier spacing associated with said S-SSB; as well as receiving at least two S-SSBs from another UE based on the number of S-SSB transmissions within the period, in a case where the frequency band corresponds to the unlicensed spectrum, wherein the number of S-SSB transmissions is related to the subcarrier spacing and depends on whether the frequency band corresponds to the unlicensed spectrum or the licensed spectrum, and The number of S-SSB transmissions when the frequency band corresponds to the unlicensed spectrum is greater than the number of S-SSB transmissions when the frequency band corresponds to the licensed spectrum.

14. The method of claim 13, wherein when the frequency band corresponds to the unlicensed spectrum, the period is 160 ms, and the subcarrier spacing is 15 kHz, the number of S-SSB transmissions is 2.

15. A user equipment UE in a wireless communication system, the UE include: Transceiver; as well as A controller is connected to the transceiver and is configured to: identifying whether a frequency band in which the UE operates corresponds to an unlicensed spectrum or a licensed spectrum; identifying a transmission period of a sidelink synchronization signal block S-SSB and a subcarrier spacing associated with said S-SSB, and receiving at least two S-SSBs from another UE based on the number of S-SSB transmissions within the period, in a case where the frequency band corresponds to the unlicensed spectrum, wherein the number of S-SSB transmissions is related to the subcarrier spacing and depends on whether the frequency band corresponds to the unlicensed spectrum or the licensed spectrum, and The number of S-SSB transmissions when the frequency band corresponds to the unlicensed spectrum is greater than the number of S-SSB transmissions when the frequency band corresponds to the licensed spectrum.

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