Method and apparatus for transmitting or receiving a synchronization signal in a wireless communication system

Abstract

The present disclosure provides a communication method of a V2X terminal in a wireless communication network, the method comprising the steps of: receiving at least one side link synchronization signal from a plurality of side link synchronization sources based on priority information; and performing V2X communication based on the at least one received side link synchronization signal.

Description

Technical Field

[0001] The present disclosure relates to a method of transmitting and receiving a synchronization signal between terminals. Background Art

[0002] To meet the increased demand for wireless data services after the commercialization of the fourth generation (4G) communication system, efforts have been made to develop the fifth generation (5G) or pre-5G communication system. For this reason, 5G or pre-5G communication systems are called "super 4G network" communication systems or "post-long term evolution (post-LTE)" systems. The 5G communication system defined in the third generation partnership project (3GPP) is called the new radio (NR) system. To achieve high data rates, the implementation of 5G communication systems in ultra-high frequency or millimeter wave (mmWave) bands (e.g., 60GHz bands) is being considered. In order to reduce the path loss of radio waves and increase the transmission distance of radio waves in ultra-high frequency bands for 5G communication systems, various technologies such as beamforming, massive multiple input and multiple output (massive MIMO), full-dimensional MIMO (FD-MIMO), array antennas, analog beamforming, and massive antennas are being studied, and the above-mentioned various technologies are applied to NR systems. In order to improve the system network for 5G communication system, various technologies such as evolved small cells, advanced small cells, cloud radio access network (cloud RAN), ultra-dense network, device-to-device communication (D2D), wireless backhaul, mobile network, cooperative communication, coordinated multi-point (CoMP) and interference cancellation have been developed. In addition, for 5G communication system, advanced coding modulation (ACM) technologies such as hybrid frequency shift keying (FSK) and quadrature amplitude modulation (QAM) (FQAM) and sliding window overlap coding (SWSC) have been developed, and advanced access technologies such as filter bank multi-carrier (FBMC), non-orthogonal multiple access (NOMA) and sparse code multiple access (SCMA) have been developed.

[0003] The Internet has evolved from a human-based connection network in which people create and consume information to an Internet of Things (IoT) in which distributed elements such as objects exchange information with each other to process information. Internet of Everything (IoE) technology has emerged, in which IoT technology is combined with technology for processing big data through connection with a cloud server, for example. To realize IoT, various technical elements are required, such as sensing technology, wired / wireless communication and network infrastructure, service interface technology and security technology, so that in recent years, technologies related to sensor networks, machine-to-machine (M2M) communication and machine type communication (MTC) for connecting objects have been studied. In the IoT environment, intelligent Internet technology (IT) services can be provided to collect and analyze data obtained from connected objects to create new value for human life. As existing information technology (IT) and various industries aggregate and combine with each other, IoT can be applied to various fields, such as smart homes, smart buildings, smart cities, smart cars or interconnected cars, smart grids, health care, smart home appliances, and advanced medical services.

[0004] Various attempts are being made to apply 5G communication systems to IoT networks. For example, 5G communications such as sensor networks, M2M communications, MTC, etc. are being implemented by using technologies including beamforming, MIMO, array antennas, etc. Application of a cloud radio access network (cloud RAN) as the above-mentioned big data processing technology may be an example of the aggregation of 5G technology and IoT technology.

[0005] Since various services can be provided due to the above-mentioned technical features and development of the mobile communication system, a method for effectively controlling transmission and reception of a synchronization signal for efficient communication is required. Summary of the invention

[0006] Technical issues

[0007] The present disclosure provides an efficient communication method in a wireless communication network.

[0008] Technical Solution

[0009] The present disclosure relates to a method and apparatus for transmitting and receiving a side link synchronization signal to support high reliability and high data rate in an environment in which a fourth generation (4G) base station and a fifth generation (5G) base station coexist.

[0010] Technical Effects

[0011] According to the disclosed embodiments, an apparatus and method for efficiently providing a service in a mobile communication system are provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 An example of a system is illustrated for describing certain embodiments of the present disclosure.

[0013] Figure 2 An example of a vehicle-to-everything (V2X) communication method implemented through a side link (SL) according to an embodiment of the present disclosure is illustrated.

[0014] Figure 3 An example of the type of synchronization signal that a V2X UE may receive according to an embodiment of the present disclosure is illustrated.

[0015] Figure 4 An example of a case in which a V2X UE transmits and receives a side link synchronization signal (SLSS) according to an embodiment of the present disclosure is illustrated.

[0016] Figure 5 Another example of a case in which a V2X user equipment (UE) transmits and receives SLSS according to an embodiment of the present disclosure is illustrated.

[0017] Figure 6 The figure illustrates a specific structure of a UE according to an embodiment of the present disclosure.

[0018] Figure 7 The figure illustrates a specific structure of a base station (BS) according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0019] According to an embodiment of the present disclosure, a communication method performed by a vehicle-to-everything (V2X) user equipment (UE) in a wireless communication network may include: receiving at least one side link synchronization signal (SLSS) from multiple side link (SL) synchronization sources based on priority order information; and performing V2X communication based on the received at least one SLSS, wherein the multiple SL synchronization sources include a global navigation satellite system (GNSS), an evolved Node B (eNB), a next generation Node B (gNB) or another V2X UE, and the priority order of the eNB-based SLSS and the priority order of the gNB-based SLSS are equivalent.

[0020] Receiving at least one SLSS may include: receiving at least one of: a first type of SLSS received directly from a GNSS, a second type of SLSS received from a V2X UE directly synchronized with a GNSS, a third type of SLSS received from a V2X UE indirectly synchronized with a GNSS, a fourth type of SLSS received directly from an eNB or a gNB, a fifth type of SLSS received from a V2X UE directly synchronized with an eNB or a gNB, a sixth type of SLSS received from a V2X UE indirectly synchronized with an eNB or a gNB, and a seventh type of SLSS received from a preset V2X UE that is not directly or indirectly synchronized with a GNSS, an eNB, or a gNB.

[0021] The third type SLSS may be the SLSS received from a V2X UE directly synchronized with a GNSS, or a V2X UE synchronized with a GNSS indirectly synchronized with a GNSS, and the sixth type SLSS may be the SLSS received from a V2X UE directly synchronized with an eNB or a gNB, or a V2X UE synchronized with a base station indirectly synchronized with a base station.

[0022] The priority order information may include information on respective priority orders of the first to seventh type SLSSs.

[0023] The priority order information may include information in which the first type SLSS or the fourth type SLSS is configured to have the highest priority order.

[0024] The priority order information may be provided by one of the multiple base stations connected to the V2X UE, may be provided by a serving base station, or may be pre-configured.

[0025] Performing V2X communication based on at least one SLSS may further include selecting an SLSS when multiple SLSSs having the same priority order are received, and selecting an SLSS may include selecting an SLSS based on a comparison result between a preset threshold and reference signal received power (RSRP) values ​​of the multiple SLSSs having the same priority order.

[0026] Selecting an SLSS may include, when a plurality of SLSSs exceeds a preset threshold, selecting an SLSS having a maximum RSRP value, and when there are no plurality of SLSSs exceeding the preset threshold, selecting an SLSS based on timing information of the V2X UE.

[0027] The RSRP value may be measured through a demodulation reference signal (DMRS) transmitted through a physical sidelink broadcast channel (PSBCH) or a DMRS transmitted through a downlink broadcast channel.

[0028] The communication method may further include: obtaining SLSS transmission configuration information from the base station; and sending the SLSS configured by the base station to a preset V2X UE based on the SLSS transmission configuration information.

[0029] Sending the SLSS configured by the base station to a preset V2X UE may include: sending the SLSS configured by the base station to the preset V2X UE based on at least one of an RSRP threshold in the SLSS sending configuration information and an RSRP threshold of a system information block (SIB) received by the V2X UE, and when the V2X UE is connected to multiple base stations, the RSRP threshold may be configured to correspond to the multiple base stations respectively.

[0030] According to an embodiment of the present disclosure, a user equipment (UE) for vehicle-to-everything (V2X) may include: a transceiver; and at least one processor, coupled to the transceiver and configured to receive at least one side link synchronization signal (SLSS) from multiple side link (SL) synchronization sources based on priority order information, select an SLSS, and perform V2X communication based on the selected SLSS, wherein the multiple SL synchronization sources may include a global navigation satellite system (GNSS), an evolved Node B (eNB), a next generation Node B (gNB), or another V2X UE, and the priority order of the eNB-based SLSS and the priority order of the gNB-based SLSS may be equivalent.

[0031] At least one processor may be configured to receive at least one of: a first type SLSS received directly from a GNSS, a second type SLSS received from a V2X UE directly synchronized with the GNSS, a third type SLSS received from a V2X UE indirectly synchronized with the GNSS, a fourth type SLSS received directly from an eNB or a gNB, a fifth type SLSS received from a V2X UE directly synchronized with the eNB or the gNB, a sixth type SLSS received from a V2X UE indirectly synchronized with the eNB or the gNB, and

[0032] A seventh type of SLSS is received from a pre-defined V2X UE that is not synchronized directly or indirectly with a GNSS, eNB or gNB.

[0033] The third type SLSS may be the SLSS received from a V2X UE directly synchronized with a GNSS, or a V2X UE synchronized with a GNSS indirectly synchronized with a GNSS, and the sixth type SLSS may be the SLSS received from a V2X UE directly synchronized with an eNB or a gNB, or a V2X UE synchronized with a base station indirectly synchronized with a base station.

[0034] The priority order information may include information on respective priority orders of the first to seventh type SLSSs.

[0035] Disclosed Embodiments

[0036] Hereinafter, embodiments of the present disclosure will now be described more fully with reference to the accompanying drawings.

[0037] In the description of the following embodiments, descriptions of technologies that are well known in the prior art and not directly related to the present disclosure are omitted. This is to clearly convey the gist of the present disclosure by omitting unnecessary descriptions. The terms used in the specification are defined in consideration of the functions used in the present disclosure and may be changed according to the intention of the user or operator or the commonly used method. Therefore, the definition of the terms should be understood based on the entire description of this specification.

[0038] For the same reason, some elements in the figure are enlarged, omitted or schematically illustrated. In addition, the size of each element does not fully reflect the actual size. In the figures, the same or corresponding elements are represented by the same reference numerals.

[0039] The advantages and features of the present disclosure and methods of achieving the same will become apparent with reference to the embodiments of the present disclosure described in detail below with reference to the accompanying drawings. However, the present disclosure may be embodied in many different forms and should not be considered limited to the embodiments set forth herein; rather, these embodiments are provided so that the present disclosure will be thorough and complete and will fully convey to those skilled in the art the scope of the present disclosure, which is defined solely by the claims. Throughout the specification, like reference numerals represent like elements.

[0040] It will be understood that each block in the flowchart illustration, and the combination of blocks in the flowchart illustration can be implemented by computer program instructions. The computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, or other programmable data processing device, so that the instructions executed by the processor of the computer or other programmable data processing device produce a device for performing the functions specified in one or more flowchart blocks. The computer program instructions can also be stored in a computer-executable or computer-readable memory, which can guide the computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-executable or computer-readable memory produce a manufactured product, which includes an instruction device for performing the functions specified in one or more flowchart blocks. The computer program instructions can also be loaded onto a computer or other programmable data processing device, so that a series of operating steps are performed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide operations for implementing the functions specified in one or more flowchart blocks.

[0041] In addition, each block of the flowchart diagram can represent a module, segment or a part of code including one or more executable instructions for performing one or more specified logical functions. It should also be noted that in some alternative implementations, the functions marked in the block may not occur in order. For example, depending on the functions involved, the two blocks shown in succession can in fact be performed substantially simultaneously, or multiple blocks may sometimes be performed in reverse order.

[0042] As used in the present embodiment, the term "unit" refers to the software or hardware components that perform certain tasks, such as field programmable gate array (FPGA) or application specific integrated circuit (ASIC). However, the term "unit" is not meant to be limited to software or hardware. "Unit" can be configured in an addressable storage medium, or configured to operate one or more processors. Therefore, for example, "unit" can include component (such as software component, object-oriented software component, class component and task component) processing, function, attribute, process, subroutine, segment of program code, driver, firmware, microcode, circuit system, data, database, data structure, table, array and variable. The functionality provided in component and "unit" can be combined into fewer components and "unit", or can be further divided into additional components and "unit". Further, component and "unit" can be implemented as one or more central processing units (CPU) in operating device or secure multimedia card. In addition, in an embodiment, "unit" can include one or more processors.

[0043] When describing the embodiments of the present disclosure in particular, the new RAN (NR) as a radio access network and the packet core (5G system, 5G core network or NG core: Next Generation Core) as a core network in the 5G mobile communication standard defined by 3GPP which is a mobile communication standard organization group are the main targets, but the basic concepts of the present disclosure can be modified without departing from the scope of the present disclosure, and the basic concepts of the present disclosure can be applied to other communication systems based on a similar technical background, and the application can be made based on the determination of those skilled in the art.

[0044] In the 5G system, a network data collection and analysis function (NWDAF) may be defined to support network automation, and NWDAF refers to a network function for providing functions for analyzing and providing data collected via the 5G network. NWDAF may collect / store / analyze information from the 5G network, and may provide the results to an unspecified network function (NF), and the analysis results may be used independently by each NF.

[0045] For the convenience of description, the present disclosure uses some of the terms and names defined in the 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) standard (standards for 5G, NR, LTE or similar systems). However, the present disclosure is not limited to these terms and names, and can be equally applied to communication systems that conform to other standards.

[0046] Hereinafter, as used in the following description, terms identifying access nodes, terms indicating network entities, terms indicating messages, terms indicating interfaces between network entities, and terms indicating various pieces of identification information are exemplified for the convenience of description. Therefore, the present disclosure is not limited to the terms described below, and other terms indicating objects having equivalent technical meanings may be used.

[0047] In the present disclosure, a base station is an entity that allocates resources to a terminal, and may be at least one of a next generation node B (gNB), an evolved node B (eNB), a node B, a base station (BS), a radio access unit, a BS controller, and a node on a network. In the present disclosure, a terminal may include a user equipment (UE), a mobile station (MS), a cellular phone, a smart phone, a computer, or a multimedia system capable of performing a communication function. However, the present disclosure is not limited to the above examples.

[0048] Specifically, the present disclosure may be applied to 3GPP NR (fifth generation mobile communication standard). Based on 5G communication technology and Internet of Things (IoT) technology, the present disclosure may be applied to smart services (e.g., smart homes, smart buildings, smart cities, smart cars or connected cars, health care, digital education, retail, safety and security services). In the present disclosure, for the convenience of description, eNB may be used interchangeably with gNB. That is, a BS described by an eNB may represent a gNB. In addition, the term "terminal (UE)" may refer not only to mobile phones, NB-IoT devices, and sensors, but also to other wireless communication devices.

[0049] Although LTE, LTE-A, LTE Pro or 5G (or NR) systems are mentioned as examples in the following description, the embodiments of the present disclosure may also be applied to other communication systems with similar technical backgrounds or channel types. In addition, the embodiments of the present disclosure may also be applied to other communication systems by partial modification without significantly departing from the scope of the present disclosure based on the determination of those skilled in the art.

[0050] To meet the increased demand for wireless data services after the commercialization of 4G communication systems, efforts have been made to develop 5G communication systems. To achieve high data rates, 5G communication systems are designed to be implemented in ultra-high frequency bands (millimeter waves (mmWave)), for example, in a band of 28 GHz. In order to reduce the path loss of radio waves and increase the transmission distance of radio waves in ultra-high frequency bands for 5G communication systems, various technologies such as beamforming, massive multiple input and multiple output (massive MIMO), full-dimensional MIMO (FD-MIMO), array antennas, analog beamforming, and massive antennas are being studied. In addition, unlike LTE, 5G communication systems support various subcarrier spacings including 15 kHz, 30 kHz, 60 kHz, 120 kHz, etc., and the physical control channel uses polarization coding, and the physical data channel uses low-density parity check (LDPC). In addition, as a waveform for uplink transmission, not only cyclic prefix-orthogonal frequency division multiplexing (CP-OFDM) but also discrete Fourier transform-spread-orthogonal frequency division multiplexing (DFT-S-OFDM) is used. LTE can support hybrid automatic repeat request (HARQ) retransmission in units of transport blocks (TBs), but 5G can additionally support HARQ retransmission in units of code block groups (CBGs) in which multiple code blocks (CBs) are grouped.

[0051] In addition, to improve the system network for 5G communication systems, various technologies such as evolved small cells, advanced small cells, cloud radio access networks (cloud RAN), ultra-dense networks, device-to-device communication (D2D), wireless backhaul, vehicle communication networks (vehicle-to-everything (V2X)), cooperative communication, coordinated multi-point (CoMP), and interference cancellation have been developed.

[0052] The Internet has evolved from a human-based connection network in which people create and consume information to an Internet of Things (IoT) in which distributed elements such as objects exchange information with each other to process information. Internet of Everything (IoE) technology has emerged, in which IoT technology is combined with technology for processing big data through connection with a cloud server, for example. To realize IoT, various technical elements are required, such as sensing technology, wired / wireless communication and network infrastructure, service interface technology and security technology, so that in recent years, technologies related to sensor networks, machine-to-machine (M2M) communication and machine type communication (MTC) for connecting objects have been studied. In the IoT environment, intelligent Internet technology (IT) services can be provided to collect and analyze data obtained from connected objects to create new value for human life. As existing information technology (IT) and various industries aggregate and combine with each other, IoT can be applied to various fields, such as smart homes, smart buildings, smart cities, smart cars or interconnected cars, smart grids, health care, smart home appliances, and advanced medical services.

[0053] Various attempts are being made to apply 5G communication systems to IoT networks. For example, 5G communications such as sensor networks, M2M communications, MTC, etc. are being implemented by using technologies including beamforming, MIMO, array antennas, etc. The application of cloud radio access networks (cloud RAN) as the above-mentioned big data processing technology can be an example of the aggregation of 5G technology and IoT technology. Thus, multiple services can be provided to users in a communication system, and in order to provide multiple services to users, a method for providing each service within the same time period according to the characteristics of each service and an apparatus using the method are required. Various services provided by the 5G communication system are being studied, and one of the various services is a service that meets the needs of low latency and high reliability.

[0054] For vehicle communication, LTE-based V2X has been standardized in 3GPP Rel-14 and Rel-15 based on D2D communication architecture, and currently, 5G NR-based V2X is being developed. NR V2X supports unicast communication, groupcast (or multicast) communication, and broadcast communication between terminals. In addition, unlike LTE V2X, which is aimed at sending and receiving basic safety information for driving vehicles on the road, NR V2X aims to provide more advanced services such as platooning, advanced driving, extended sensors, remote driving, etc.

[0055] Compared with the traditional 4G system, the NR system operates in a relatively high frequency band, and therefore, due to the frequency characteristics, the NR system may have smaller coverage than the 4G system. To solve the coverage problem, dual connection (DC) management may be considered, in which the eNB (4G BS) providing wide coverage is used as an anchor node (or master node) for sending control information and data information, and the gNB (NR BS) with smaller coverage but can guarantee a high data rate is used as a secondary node for sending data information. Therefore, a specific V2X terminal can operate by synchronizing with the eNB, and another V2X terminal can operate by synchronizing with the gNB. To support this scenario, NR V2X requires a method and device for sending synchronization signals between terminals, which is different from the method and device of the traditional LTE D2D or LTE V2X technology.

[0056] Therefore, embodiments of the present specification are proposed to support the above-mentioned scenario, and an object is to provide a method and apparatus for transmitting and receiving a synchronization signal between terminals.

[0057] Figure 1 An example of a system is illustrated for describing certain embodiments of the present disclosure.

[0058] Figure 1(a) illustrates an example of a situation in which all V2X UEs (UE-1 and UE-2) are located within the coverage of a BS.

[0059] All V2X UEs may receive data and control information from the BS via a downlink (DL), or may transmit data and control information to the BS via an uplink (UL). According to certain embodiments, the data and control information transmitted and received by the V2X UE may be data and control information for V2X communication. Alternatively, the data and control information may be data and control information for general cellular communication. In addition, the V2X UE may transmit / receive data and control information for V2X communication via a sidelink (SL).

[0060] Figure 1 (b) of FIG. 5 illustrates an example of a case where UE-1 of the V2X UE is located within the coverage of the BS and UE-2 is located outside the coverage of the BS. Figure 1 The example of (b) may correspond to an example of partial coverage.

[0061] UE-1 located within the coverage of the BS can receive data and control information from the BS via DL, or can send data and control information to the BS via UL. UE-2 located outside the coverage of the BS cannot receive data and control information from the BS via DL, and cannot send data and control information to the BS via UL. UE-2 can send data and control information for V2X communication to UE-1 / receive data and control information for V2X communication from UE-1 via SL.

[0062] Figure 1 (c) illustrates an example of a situation where all V2X UEs are located outside the coverage of the BS. Therefore, UE-1 and UE-2 cannot receive data and control information from the BS through DL and cannot send data and control information to the BS through UL. UE-1 and UE-2 can send / receive data and control information for V2X communication through SL.

[0063] Figure 1 (d) of FIG. 4 illustrates an example of a scenario in which UEs located in different cells perform V2X communication therebetween. Figure 1In (d), the V2X transmitting UE and the V2X receiving UE access different BSs, are in a radio resource control (RRC) connection state (RRC connection) relative to different BSs, or camp on different BSs (RRC connection release state, i.e., RRC idle state). According to some embodiments, 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 BS to which UE-1 accesses (or to which UE-1 camps), and UE-2 may receive a V2X dedicated SIB from another BS to which UE-2 accesses (or to which UE-2 camps). According to certain embodiments, information of the V2X dedicated SIB received by UE-1 may be different from information of the V2X dedicated SIB received by UE-2. Therefore, it is necessary to unify (or synchronize) a plurality of pieces of information so as to perform V2X communication between UEs located in different cells.

[0064] For the convenience of description, Figure 1 The V2X system consisting of two UEs (UE-1 and UE-2) is illustrated, but is not limited thereto. In addition, the UL and DL between the BS and the V2X UE may each be referred to as a Uu interface, and the SL between the V2X UEs may be referred to as a PC5 interface. Therefore, they may be used interchangeably in the present disclosure.

[0065] In the present disclosure, a terminal may indicate a vehicle supporting vehicle-to-vehicle (V2V) communication, a vehicle supporting vehicle-to-pedestrian (V2P) communication or a pedestrian's handheld device (i.e., a smart phone), a vehicle supporting vehicle-to-network (V2N) communication, or a vehicle supporting vehicle-to-infrastructure (V2I) communication. In addition, in the present disclosure, a terminal may indicate a roadside unit (RSU) in which a terminal function is embedded, an RSU in which a BS function is embedded, or an RSU in which some BS functions and some terminal functions are embedded.

[0066] In addition, in the present disclosure, the predefined BS indicates a BS that supports both V2X communication and conventional cellular communication or a BS that supports only V2X communication. According to certain embodiments, the BS may indicate a 5G BS (gNB), a 4G BS (eNB), or an RSU. Therefore, unless there is a specific description in the present disclosure, the BS and the RSU may be used identically and thus may be used interchangeably.

[0067] Figure 2 An example of a V2X communication method implemented by SL according to an embodiment of the present disclosure is illustrated.

[0068] As in Figure 2In (a), the transmitting (TX) UE and the receiving (RX) UE may perform one-to-one communication, and this may be referred to as unicast communication. Figure 2 In (b), the TX UE and the RX UE may perform one-to-many communication, and this may be referred to as groupcast or multicast.

[0069] exist Figure 2 In (b), UE-1, UE-2 and UE-3 are shown to form a group A to perform groupcast communication, and UE-4, UE-5, UE-6 and UE-7 form another group B to perform groupcast communication. Each UE performs multicast communication only within the group to which each UE belongs, and does not perform communication between different groups. Figure 2 (b) illustrates two formed groups, but the present disclosure is not limited thereto.

[0070] Although Figure 2 Although not shown in FIG. 1 , the V2X UE may perform broadcast communication. Broadcast communication refers to a situation in which all V2X UEs receive data and control information transmitted from the V2X transmitting UE via the SL. For example, when assuming that Figure 2 In (b), when UE-1 is a transmitting UE for broadcasting, all UEs (UE-2, UE-3, UE-4, UE-5, UE-6 and UE-7) can receive data and control information sent from UE-1.

[0071] Figure 3 An example of the type of synchronization signal that a V2X UE may receive according to an embodiment of the present disclosure is illustrated.

[0072] Specifically, the V2X UE may receive the following side link synchronization signals from various side link synchronization signal sources.

[0073] -V2X UE can directly receive synchronization signals from the Global Navigation Satellite System (GNSS) or the Global Positioning System (GPS).

[0074] - In this case, the SL synchronization signal source can be GNSS.

[0075] -V2X UE can receive synchronization signals indirectly from GNSS or GPS.

[0076] - Indirectly receiving a synchronization signal from GNSS may indicate a case where V2X UE-A receives a side link synchronization signal (SLSS) transmitted from V2X UE-1 that is directly synchronized with GNSS. According to certain embodiments, V2X UE-A may receive a synchronization signal from GNSS via 2 hops. As another example, V2X UE-2 synchronized with SLSS transmitted from V2X UE-1 that is synchronized with GNSS may transmit SLSS. Upon receiving it, V2X UE-A may receive a synchronization signal from GNSS via 3 hops. Similarly, V2X UE-A may receive a synchronization signal from GNSS via 3 hops or more.

[0077] -In this case, the SL synchronization signal source can be another V2X UE synchronized with GNSS.

[0078] V2X UE can receive synchronization signals directly from LTE BS (eNB).

[0079] -V2X UE can directly receive the Primary Synchronization Signal (PSS) / Secondary Synchronization Signal (SSS) sent from the LTE BS.

[0080] -In this case, the SL synchronization signal source can be the eNB.

[0081] -V2X UE can receive synchronization signals indirectly from LTE BS (eNB).

[0082] - Receiving a synchronization signal indirectly from an eNB may indicate a case where the V2X UE-A receives an SLSS transmitted from a V2X UE-1 that is directly synchronized with the eNB. According to certain embodiments, the V2X UE-A may receive a synchronization signal from the eNB via 2 hops. As another example, the V2X UE-2 synchronized with the SLSS transmitted from the V2X UE that is directly synchronized with the eNB may transmit the SLSS. Upon receiving it, the V2X UE-A may receive a synchronization signal from the eNB via 3 hops. Similarly, the V2X UE-A may receive a synchronization signal from the eNB via 3 hops or more.

[0083] - In this case, the SL synchronization signal source can be another V2X UE synchronized with the eNB.

[0084] -V2X UE can receive synchronization signals indirectly from NR BS (gNB).

[0085] - Receiving a synchronization signal indirectly from a gNB may indicate a case where another V2X UE-A receives a SLSS transmitted from a V2X UE-1 directly synchronized with the gNB. According to certain embodiments, the V2X UE-A may receive a synchronization signal from the gNB via 2 hops. As another example, the V2X UE-2 synchronized with the SLSS transmitted from the V2X UE-1 directly synchronized with the gNB may transmit the SLSS. Upon receiving it, the V2X UE-A may receive a synchronization signal from the gNB via 3 hops. Similarly, the V2X UE-A may receive a synchronization signal from the gNB via 3 hops or more.

[0086] -In this case, the SL synchronization signal source can be another V2X UE synchronized with the gNB.

[0087] - V2X UE-A can directly receive synchronization signals from another V2X UE-B.

[0088] - In the case that V2X UE-B cannot detect SLSS transmitted from GNSS, gNB, eNB or another V2X UE as a synchronization signal source, V2X UE-B may transmit SLSS based on its own timing. V2X UE-A may directly receive SLSS transmitted from V2X UE-B.

[0089] -In this case, the SL synchronization signal source may correspond to the V2X UE.

[0090] - V2X UE-A may receive synchronization signals indirectly from another V2X UE-B.

[0091] - Indirectly receiving a synchronization signal from V2X UE-B may indicate a case where V2X UE-A receives a SLSS transmitted from V2X UE-1 that is directly synchronized with V2X UE-B. According to certain embodiments, V2X UE-A may receive a synchronization signal from V2X UE-B via 2 hops. As another example, V2X UE-2 synchronized with a SLSS transmitted from V2X UE-1 that is directly synchronized with V2X UE-B may transmit a SLSS. Upon receiving it, V2X UE-A may receive a synchronization signal from V2X UE-B via 3 hops. Similarly, V2X UE-A may receive a synchronization signal from V2X UE-B via 3 hops or more.

[0092] - In this case, the SL synchronization signal source can be another V2X UE synchronized with the V2X UE.

[0093] The SLSS described in the present disclosure may indicate a sidelink synchronization signal block (S-SSB). The S-SSB may be composed of a sidelink primary synchronization signal (S-PSS), a sidelink secondary synchronization signal (S-SSS), and a physical sidelink broadcast channel (PSBCH). According to certain embodiments, 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. However, the present disclosure is not limited thereto. Similar to the PSS / SSS in a cellular system, the sidelink ID may be sent through a combination of the S-PSS and S-SSS or only through the S-SSS without a combination thereof. As a physical broadcast channel (PBCH) in a cellular system, the PSBCH may send a master information block (MIB) for sidelink communication.

[0094] Figure 4 The diagram illustrates a situation where a V2X UE transmits and receives SLSS according to an embodiment of the present disclosure.

[0095] UE-1 may be present within the coverage of an eNB, and UE-2 may be present within the coverage of a gNB. UE-1 may be in an RRC connection configuration state (RRC connection state) or may be in an RRC connection configuration release state (RRC idle state) relative to the eNB. According to certain embodiments, it is assumed that UE-1 synchronizes DL with LTE PSS / SSS transmitted from the eNB. Similarly, UE-2 may be in an RRC connection configuration state (RRC connection state) or may be in an RRC connection configuration release state (RRC idle state) relative to the gNB. In addition, it is assumed that UE-2 synchronizes DL with NR PSS / SSS transmitted from the gNB. According to certain embodiments, UE-1 and UE-2 may have the capability to transmit NR SLSS, and UE-1 may have the capability to receive PSS / SSS from the eNB. When UE-1 is in an RRC connection state relative to the eNB, UE-1 may transmit SLSS in response to an RRC command from the eNB. For example, the eNB may configure whether UE-1 having the capability to transmit SLSS transmits SLSS by using UE-specific RRC parameters. Similarly, when UE-2 is in an RRC connected state with respect to the gNB, UE-2 may transmit SLSS in response to an RRC command from the gNB. For example, the gNB may configure whether UE-2, which has the capability to transmit SLSS, transmits SLSS by using UE-specific RRC parameters. UE-1 and UE-2 in the RRC connected state may be configured with parameters for transmitting SLSS from the eNB and gNB through UE-specific RRC, respectively. For example, the parameters may include at least one of a time, frequency, or code resource for transmission of the SLSS, an ID constituting the SLSS, and the like.

[0096] When UE-1 is in RRC idle state relative to the eNB, UE-1 can determine whether to send SLSS based on the reference signal received power (RSRP) threshold configured by the eNB through the SIB. For example, if the RSRP threshold configured by the eNB through the SIB is less than the RSRP value relative to the eNB, the RSRP value is measured by UE-1, and UE-1 has the ability to send SLSS, UE-1 can send SLSS. When UE-2 is in RRC idle state relative to the gNB, UE-2 can determine whether to send SLSS based on the RSRP threshold configured by the gNB through the SIB.

[0097] For example, when the RSRP threshold configured by the gNB through the SIB is less than the RSRP value measured by UE-2 relative to the gNB, and UE-2 has the ability to send SLSS, UE-2 can send SLSS. UE-1 and UE-2 in the RRC idle state can be configured with parameters for sending SLSS from the eNB and gNB through the SIB, respectively. For example, the parameters may include at least one of the time, frequency or code resources for sending SLSS, an ID constituting the SLSS, etc.

[0098] UE-1 and UE-2 may transmit SLSS by using parameters configured by the eNB and gNB, respectively. In this regard, UE-3 and UE-4 may exist outside the coverage of the eNB and gNB. For example, when it is assumed that the eNB operates in the f1 frequency band and the gNB operates in the f2 frequency band, UE-3 and UE-4 may perform SL communication in the f3 frequency band different from the coverage of f1 and f2. In this regard, as Figure 2 As shown, SL communication may correspond to one of unicast, multicast or broadcast communication schemes.

[0099] Depending on how UE-3 and UE-4 process the SLSS sent from UE-1 synchronized with the eNB and the SLSS sent from UE-2 synchronized with the gNB, the following methods can be considered.

[0100] -Alt1: UE-3 and UE-4 equally process the SLSS sent from UE-1 synchronized with the eNB and the SLSS sent from UE-2 synchronized with the gNB.

[0101] In this case, UE-3 and UE-4 do not need to distinguish the SLSS transmitted from UE-1 and UE-2. Therefore, UE-3 or UE-4 can perform the following operations based on the pre-configured SL RSRP threshold.

[0102] -UE-3 and UE-4 measure the RSRP of the SLSS transmitted from UE-1 and UE-2, and determine whether the measured RSRP meets the RSRP requirement. When both the SLSS transmitted from UE-1 and UE-2 meet the RSRP requirement, UE-3 and UE-4 compare them with the pre-configured SL RSRP threshold to determine whether the measured SL RSRP value is greater than the threshold. In this regard, RSRP measurement can be performed via a demodulation reference signal (DMRS) transmitted via PSBCH.

[0103] - In case the minimum RSRP requirement is met and there is one received SLSS with RSRP greater than the pre-configured SL RSRP threshold, the SLSS may be transmitted synchronously with the UE transmitting the one SLSS.

[0104] - In case the minimum RSRP requirement is met and there are two or more received SLSSs with RSRP greater than the pre-configured SL RSRP threshold, the SLSS may be transmitted synchronously with the UE transmitting the received SLSS with the largest RSRP.

[0105] - In case the minimum RSRP requirement is met and there is no received SLSS with RSRP greater than the pre-configured SL RSRP threshold, UE-3 or UE-4 may send SLSS based on its own timing.

[0106] - In the case that the SL RSRP measurement results of UE-1 and UE-2 received by UE-3 and UE-4 meet the minimum SL RSRP requirement and are all greater than the pre-configured SL RSRP threshold, UE-3 can synchronize with UE-1 through the operations described above (such as Figure 4 As shown, it is assumed that UE-3 is closer to UE-1 than UE-2). In addition, UE-4 can synchronize with UE-2 through the operations described above (such as Figure 4 As shown, it is assumed that UE-4 is closer to UE-2 than UE-1).

[0107] - Under this assumption, when UE-3 and UE-4 perform unicast, multicast or broadcast communication, the synchronization between UE-3 and UE-4 may be different (may not match) because UE-3 and UE-4 are synchronized with different SL synchronization signal sources. To solve this problem, UE-3 can send SL control information and data information to UE-4 in synchronization with the timing of UE-1, and when UE-3 receives SL control information and data information from UE-4, UE-3 can be synchronized with the timing of UE-4. However, this situation may increase the complexity of the UE because the UE must perform tracking on different timings. In addition, in unicast and multicast communications, the sending UE and the receiving UE perform feedback therebetween, and therefore, when the sending timing and the receiving timing are different, switching timing may be required to adjust the difference, and this may be the cause of performance deterioration of SL communications that are sensitive (strict) to waiting time requirements.

[0108] -In the above example, it is assumed that the SL RSRP threshold is preconfigured, however, the SL RSRP threshold may be sent from UE-1 and UE-2 through the PSBCH. In addition, according to certain embodiments, the SL RSRP threshold may be configured for each of unicast, groupcast, and broadcast. That is, different SL RSRP thresholds may be sent through the PSBCH for each of the V2X communication schemes.

[0109] -In addition, in the above example, it is assumed that SL RSRP measurement is performed by DMRS transmitted via PSBCH, but the present disclosure is not limited thereto. For example, SL RSRP measurement may be performed by DMRS transmitted via SL control channel, DMRS transmitted via SL feedback channel, or DMRS transmitted via SL data channel. As another example, SL RSRP measurement may be performed by a signal for SL measurement (e.g., a channel state information reference signal (CSI-RS)) transmitted via SL data channel.

[0110] -Alt1: UE-3 and UE-4 process the SLSS sent from UE-1 synchronized with the eNB and the SLSS sent from UE-2 synchronized with the gNB differently.

[0111] -To solve the problem of Alt1, the SLSS sent from UE-1 synchronized with the eNB and the SLSS sent from UE-2 synchronized with the gNB are sent differently so that when UE-3 or UE-4 receives them, UE-3 or UE-4 can identify the corresponding SLSS.

[0112] - According to certain embodiments, the SLSS transmitted from the UE-1 synchronized with the eNB and the SLSS transmitted from the UE-2 synchronized with the gNB may use different sidelink synchronization signal IDs (SLSSIDs). In more detail, the X cell IDs may be divided into 3 or 4 groups and managed. For example, the following provides a case in which the X cell IDs are divided into 3 groups and managed. X1 of the X cell IDs may be used as SLSS transmission IDs for SLSS transmission by a UE present in the coverage of the eNB, X2 of the X cell IDs may be used as SLSS transmission IDs for SLSS transmission by a UE present in the coverage of the gNB, and X3 of the X cell IDs may be used as SLSS transmission IDs for SLSS transmission by a UE not present in the coverage of the eNB and the gNB. In this regard, a UE present in the coverage of the eNB but not synchronized with the PSS / SSS from the eNB but directly synchronized with the GNSS may use at least one of the X1 SLSSIDs. In this regard, a UE not directly synchronized with the GNSS cannot use an ID used by a UE directly synchronized with the GNSS as an ID for SLSS transmission. Similarly, a UE that is present within the coverage of a gNB but is not synchronized with the PSS / SSS from the gNB but is directly synchronized with the GNSS may use at least one of the X2 SLSSIDs. In this regard, a UE that is not directly synchronized with the GNSS may not use an ID used by a UE that is directly synchronized with the GNSS as an ID for SLSS transmission. In this regard, X1+X2+X3≤X may be achieved.

[0113] -As another example, the following provides a case where X cell IDs are divided into 4 groups and managed. X1, X2, and X3 among the X cell IDs are equivalent to the case where 3 groups are managed (i.e., X1 is related to eNB coverage, X2 is related to gNB coverage, and X3 is related to outside coverage). The difference is that the ID used by the UE directly synchronized with the GNSS within the coverage of the eNB and gNB is not used in X1 and X2 but in X4 which is another group. The number of IDs of the SLSS configuring X4 may be at least one. In this regard, X1+X2+X3+X4≤X can be achieved.

[0114] -In the above example, the definition uses different IDs, but the present disclosure is not limited to this. For example, by using the same ID and different sequences, the SLSS sent from UE-1 synchronized with the eNB can be distinguished from the SLSS sent from UE-2 synchronized with the gNB.

[0115] -As another method of solving the problem of Alt1, the SLSS sent from UE-1 synchronized with the eNB and the SLSS sent from UE-2 synchronized with the gNB are sent equally, but by using an identifier sent via PSBCH, it can be identified whether it is the SLSS sent from the UE synchronized with the eNB or the SLSS sent from the UE synchronized with the gNB.

[0116] -For example, UE-1 may add a 1-bit indicator indicating OFF to a PSBCH to be transmitted by UE-1, and may transmit the PSBCH. UE-2 may add a 1-bit indicator indicating ON to a PSBCH to be transmitted by UE-2, and may transmit the PSBCH. Upon receiving it, UE-3 and UE-4 may decode the PSBCH, thereby determining whether the SLSS is transmitted from UE-1 (i.e., whether it is transmitted from a UE synchronized with an eNB) or from UE-2 (i.e., whether it is transmitted from a UE synchronized with a gNB).

[0117] - Different from the above example, UE-1 may add a 1-bit indicator indicating on to the PSBCH and may transmit the PSBCH, and UE-2 may add a 1-bit indicator indicating off to the PSBCH to be transmitted by UE-2 and may transmit the PSBCH.

[0118] -In this example, the description assumes that the indicator sent through the PSBCH is 1 bit, but the present disclosure is not limited to this. For example, the indicator can be 2 bits. In this case, it can be additionally identified that it is an SLSS sent from a UE synchronized with the GNSS. As another example, in this example, UE-1 and UE-2 are specified as UEs (1 hop) directly synchronized with the eNB and gNB, respectively, but when 3 bits or more are used, it can be determined whether they are SLSS sent from UEs directly synchronized with the gNB and eNB via 1 hop or whether they are SLSS sent from UEs synchronized with the gNB and eNB indirectly (e.g., via 2 hops). Similarly, it can be determined whether it is an SLSS sent from a UE directly synchronized with the GNSS via 1 hop, or whether it is an SLSS sent from a UE synchronized with the GNSS indirectly (e.g., via 2 hops).

[0119] Figure 5 Another example of a case in which a V2X UE transmits and receives SLSS is illustrated.

[0120] Specifically, the example relates to a case in which a V2X UE transmits and receives SLSS in an E-UTRA and NR dual connectivity (EN-DC) environment in which an eNB and a gNB coexist. The 5G system operates at a relatively high frequency band compared to the conventional 4G system, so that the 5G system may have smaller coverage than the 4G system due to frequency characteristics. To solve the coverage problem, DC may be considered, in which an eNB providing wide coverage is used as an anchor node (or master node) for sending control information and data information, and a gNB having a smaller coverage but which can guarantee a high data rate is used as a secondary node for sending data information. In a DC environment, some V2X UEs may exist within the coverage of the eNB, but some may exist outside the coverage of the gNB (e.g., UE-1). In addition, some V2X UEs may exist within the coverage of both the eNB and the gNB (e.g., UE-2). In this regard, UE-1 may receive information for SLSS transmission from the eNB, and UE-2 may receive information for SLSS transmission from the gNB. When receiving SLSS, UE-3 may receive information for SLSS transmission by using a reference Figure 4 The described method is synchronized with UE-1 or UE-2. In this regard, it is assumed that UE-1 and UE-2 are UEs with the capability to support EN-DC.

[0121] In order to enhance the coverage performance of SLSS transmitted from UEs present in the cell coverage, SLSS transmitting UEs present in the same cell may need to transmit the same signal. That is, the same SLSS ID and the same PSBCH may be transmitted. In more detail, when it is assumed that two UEs exist in the same cell and transmit SLSS, the two UEs may transmit the same SLSS ID and PSBCH with the same content. When receiving, the UE receives a signal obtained by combining two identical signals, and therefore, the receiving power can be amplified. However, as in Figure 5 In the case where UE-1 and UE-2 exist within the coverage of the same eNB, UE-1 can send SLSS based on the parameters configured (or indicated) by the eNB, and UE-2 can send SLSS based on the parameters configured (or indicated) by the gNB. Therefore, when UE-1 and UE-2 send the same SLSS, the coverage of the SLSS can be reduced. In addition, when UE-1 and UE-2 send SLSS configured with different parameters, although in Figure 5 Not shown, interference may occur in a DL received signal of another cellular UE, or interference may occur in a UL signal of another cellular UE received by the eNB or gNB.

[0122] To solve this problem, UE-1 is required to detect the existence of gNB in ​​advance, or UE-2 is required to detect the existence of eNB in ​​advance. To enable this pre-detection, UE-1 and UE-2 are required to be in RRC connected state with respect to eNB as the master node. This is because the eNB as the master node sends the information of the existence or non-existence of the secondary node to the UE through RRC configuration. The UE should be designed to perform V2X operations with respect to the eNB or gNB not only in the RRC connected state but also in the RRC idle state.

[0123] As mentioned above, considering the coverage of SLSS, it is required Figure 5 UE-1 and UE-2 are shown to send the same SLSS, but the parameters used by the eNB and gNB, such as reference timing, subcarrier spacing, waveform (i.e., DFT-S-OFDM or CP-OFDM), CP length, etc., may be different in the eNB and gNB. Therefore, it may not be possible for UE-1 and UE-2 to send the same SLSS. In this case, UE-1 and UE-2 may operate as follows.

[0124] - Alt1: The master node may indicate, through system information, the configuration of whether the UE is synchronized with the timing of the master node or the timing of the secondary node, and the UE is within the coverage of the master node.

[0125] -like Figure 5 As shown, in an EN-DC environment, UE-1 and UE-2 can receive a V2X dedicated SIB sent by an eNB, and can obtain priority order information for the selection of an SL synchronization signal source included in the SIB. For example, in response to receiving a configuration that the eNB timing has a priority order higher than the gNB timing, UE-1 and UE-2 can send SLSS based on the eNB timing. Conversely, in response to receiving a configuration that the eNB timing has a priority order lower than the gNB timing, UE-1 and UE-2 can send SLSS based on the gNB timing. This configuration can be sent as a V2X dedicated SIB by using the following various methods.

[0126] -V2X dedicated SIB may include SL synchronization signal source information. When the SL synchronization signal source is configured as eNB, the UE sending SLSS may send SLSS based on the eNB timing. When the SL synchronization signal source is configured as gNB, the UE sending SLSS may send SLSS based on the gNB timing.

[0127] - As another example, 1-bit information may be used. That is, "1" may indicate timing synchronization with the primary node, and "0" may indicate timing synchronization with the secondary node.

[0128] - As another example, the aforementioned SL synchronization signal source information may include an identifier of a cell. That is, when the SL synchronization signal source is configured as cell ID A, the UE may send SLSS based on the timing of the cell with cell ID A.

[0129] -Through the aforementioned SL synchronization signal source information, information indicating the priority order of GNSS and base stations may be additionally transmitted. That is, the priority order information about one of eNB>gNB>GNSS / gNB>eNB>GNSS / eNB>GNSS>gNB / gNB>GNSS>eNB / GNSS>gNB>eNB / GNSS>eNB>gNB may be transmitted to the UE by using 3-bit information of the V2X dedicated SIB.

[0130] -The above example corresponds to the operation of a UE in an RRC idle state relative to the master node, and a UE in an RRC connected state relative to the master node can receive SL synchronization signal source information from the master node through UE-specific RRC configuration.

[0131] - A UE that is within the coverage of the master node but is not configured with the SL synchronization signal source information or a UE that is outside the coverage can be managed by considering that the eNB and gNB have the same priority order (i.e., Figure 4 Alt1 in the example or based on a pre-configured priority rule, determine whether to synchronize with the eNB timing or whether to synchronize with the gNB timing.

[0132] -EN-DC management scenarios can be classified into synchronous EN-DC in which the eNB and gNB operate by being synchronized with each other with respect to timing, and asynchronous EN-DC in which the eNB and gNB operate by being asynchronous with respect to timing. In synchronous EN-DC, the eNB and gNB can each be synchronized with GNSS or can be synchronized with each other with respect to timing via signaling between the eNB and gNB without GNSS, and can operate. In the management of synchronous EN-DC, since the timing synchronization of the eNB and gNB is the same, the UE-1 or UE-2 to send SLSS can be synchronized with one of the eNB timing or the gNB timing. Therefore, it can be additionally indicated to the UE through the V2X dedicated SIB or UE-specific RRC signaling that it is a synchronous EN-DC or an asynchronous EN-DC, and the UE sends the SLSS. As a signaling scheme to support this operation, one of the following methods can be used.

[0133] -One bit may be used to indicate whether it is synchronous EN-DC or asynchronous EN-DC. For example, when it is synchronous EN-DC, a specific bit field of the V2X-dedicated SIB or the UE-specific RRC may be set to "1". In addition, when it is asynchronous EN-DC, the specific field may be set to "0". When set to "1", the UE sending the SLSS may send the SLSS according to the eNB or gNB timing. According to certain embodiments, the UE may randomly select one of the eNB or gNB timings or may synchronize with the timing of the BS that provides the maximum RSRP. When set to "0", the UE may select the eNB or gNB as the SL signal source based on predefined rules. For example, it may be predefined that the priority order of the eNB is always higher than the priority order of the gNB. In this case, the UE may send the SLSS based on the eNB timing.

[0134] -As another example, when information about the priority order of eNB and gNB is included in the V2X dedicated SIB or UE-specific RRC parameters, the UE may assume asynchronous EN-DC and may select the SL synchronization signal source according to the priority order. When information about the priority order of eNB and gNB is not included in the V2X dedicated SIB or UE-specific RRC parameters, the UE may assume synchronous EN-DC and may randomly select one of the eNB or gNB timing or may synchronize with the timing of the BS that provides the maximum RSRP.

[0135] -In the above examples, the EN-DC environment in which the master node is an eNB and the secondary node is a gNB is mainly illustrated, but the present disclosure is not limited thereto. For example, even in the NE-DC environment in which the master node is a gNB and the secondary node is an eNB, the UE can select the SL synchronization signal source according to the configuration of the master node by using the various methods described above. As another example, even in the NN-DC environment in which the master node is a gNB and the secondary node is a gNB, the UE can select the SL synchronization signal source according to the configuration of the master node by using the various methods described above.

[0136] - Alt2: The UE may follow a predefined rule of being synchronized with the timing of the primary node or the timing of the secondary node.

[0137] -Alt2 may be used in an environment where a BS such as an eNB or gNB does not exist. The predefined rules may vary and at least one of the priorities may be used.

[0138] -GNSS>eNB>gNB>NR-UE (The priority order becomes higher to the left and lower to the right.)

[0139] -GNSS>gNB>eNB>NR-UE

[0140] -eNB>gNB>GNSS>NR-UE

[0141] -eNB>GNSS>gNB>NR-UE

[0142] - It is possible to pre-configure which of the above rules to use (pre-configuration).

[0143] -Alt3: A combination of Alt1 and Alt2 can exist.

[0144] - For example, some priorities may satisfy predefined rules and other priorities may be configured. That is, whether to place the priority order on GNSS or on BS timing may be preconfigured or may be configured by the eNB / gNB. In addition, the priority order between eNB and gNB may always satisfy the defined rules (e.g., eNB always has a higher or equal priority order than gNB).

[0145] You may request information about when the Figure 4 and 5 The process of UE-1 and UE-2 sending SLSS within the cell coverage of . Figure 4 In the embodiment, when UE-1 is in an RRC connected state with respect to the eNB, UE-1 may be configured with a command for the transmission of SLSS from the eNB through a UE-specific RRC. Similarly, when UE-2 is in an RRC connected state with respect to the gNB, UE-2 may be configured with a command for the transmission of SLSS from the gNB through a UE-specific RRC. In this regard, it may be assumed that UE-1 and UE-2 have the capability to transmit SLSS. However, as Figure 5 UE-2 that is present within the coverage of both the eNB and the gNB may be configured with the transmission of SLSS from both the eNB and the gNB. In this case, UE-2 may assume that the command sent from the master node has a higher priority order than the command sent from the secondary node. For example, in the case where the eNB commands the transmission of SLSS and the gNB does not command the transmission of SLSS, the UE may follow the command from the eNB (in the case where the master node is the eNB in ​​an EN-DC environment) or may follow the command from the gNB (in the case where the master node is the gNB in ​​an NE-DC environment or in the case where the master node is the gNB in ​​an NN-DC environment).

[0146] As another example, Figure 4UE-1 and UE-2 in the RRC idle state may be in an RRC idle state relative to each of the eNB and the gNB. In this case, UE-1 and UE-2 may receive a UE-specific RRC command from the eNB / gNB regarding the transmission of the SLSS. Therefore, a procedure regarding when to transmit the SLSS by the UE in the RRC idle state may be requested. For example, UE-1 in an RRC idle state relative to the eNB may receive a V2X-dedicated SIB transmitted by the eNB, and may obtain an RSRP threshold included in the SIB. Then, UE-1 may compare the RSRP threshold with an RSRP measurement value measured by UE-1 relative to the eNB. When the measured RSRP is less than the RSRP threshold configured by the eNB, UE-1 may transmit the SLSS. Similarly, UE-2 in an RRC idle state relative to the gNB may receive a V2X-dedicated SIB transmitted by the gNB, and may obtain an RSRP threshold included in the SIB. Then, UE-2 may compare the RSRP threshold with an RSRP measurement value measured by UE-2 relative to the gNB. UE-2 may send SLSS when the measured RSRP is less than the RSRP threshold configured by the gNB.

[0147] The above operations can also be applied to Figure 5 However, because Figure 5 UE-2 in the example exists within the coverage of both the gNB and the eNB, and when SLSS is transmitted based on the RSRP threshold configured by the gNB, interference may occur to another UE that exists outside the coverage of the gNB and exists within the coverage of the eNB. In addition, the reason for transmitting SLSS based on the RSRP threshold is that only when a UE located at the cell boundary transmits SLSS, UE-3 that exists outside the cell coverage can receive it. Therefore, UE-2 may be located at a place that is a cell boundary of the gNB but not a cell boundary of the eNB (for example, when UE-2 is located at Figure 5 In this case, even if UE-2 meets the RSRP threshold configured by the gNB and thus sends SLSS, the SLSS may not reach UE-3.

[0148] To solve this problem, you can consider the following actions.

[0149] The master node can configure the thresholds for the master node and the thresholds for the secondary node through the V2X-specific SIB. For example, RSRP threshold 1 and RSRP threshold 2. A UE with the ability to send SLSS can compare RSRP-1 and RSRP-2 with the configured RSRP threshold 1 and RSRP threshold 2 respectively, where RSRP-1 is measured by the UE with respect to the master node and RSRP-2 is measured by the UE with respect to the secondary node. The UE can send SLSS only when both RSRP-1 < RSRP threshold 1 and RSRP-2 < RSRP threshold 2 are satisfied. At this time, the UE is in the RRC idle state and thus cannot detect the presence of the secondary node. For this, the ID of the secondary node for which the UE must measure RSRP can be included in the V2X-specific SIB.

[0150] When only one RSRP threshold is configured in the V2X-specific SIB, the UE can measure the RSRP with respect to the BS where the UE camps (eNB for UE-1 and gNB for UE-2). When the measured RSRP value is less than the configured RSRP threshold, the UE can send SLSS.

[0151] Although not shown in Figure 5 Since UE-2 is within the coverage of the gNB and the coverage of the eNB, UE-2 can receive the NR SSB from the gNB and can receive the PSS / SSS from the eNB. In this case, UE-2 can perform operations similar to UE-3. For example, the following operations can be considered.

[0152] - Alt1: The master node can configure the UEs in the coverage of the master node through system information or UE-specific RRC signaling as to whether it is synchronized with the timing of the master node or whether it is synchronized with the timing of the secondary node.

[0153] - As Figure 5 shown, UE-2 in the EN-DC environment can receive the V2X-specific SIB sent from the eNB and can obtain the priority order information regarding the selection of the SL synchronization signal source included in the SIB.

[0154] - As shown in 5, UE-2 in the EN-DC environment can obtain the priority order information regarding the selection of the SL synchronization signal source through UE-specific RRC signaling sent from the eNB.

[0155] - Alt2: Even if the serving BS is not the master node, the serving cell can configure the UEs in the coverage of the serving cell through system information or UE-specific RRC signaling as to whether it is synchronized with the timing of the master node or whether it is synchronized with its own (the serving cell) timing for transmission and reception.

[0156] - As Figure 5UE-2 in the EN-DC environment shown can receive the V2X dedicated SIB sent from the gNB, and can obtain priority order information about the selection of SL synchronization signal sources included in the SIB.

[0157] - As shown in Figure 5, UE-2 in an EN-DC environment can obtain priority order information about the selection of SL synchronization signal sources through UE-specific RRC signaling sent from the gNB.

[0158] - Alt3: The UE may satisfy a predefined rule on whether to synchronize with the timing of the primary node or whether to synchronize with the timing of the secondary node.

[0159] Therefore, the present disclosure relates to a method for sending and receiving a synchronization signal between UEs in a wireless communication system, and more specifically, provides embodiments of a method and device for sending and receiving SLSS in an environment where 4G BS and 5G BS coexist.

[0160] Figure 6 The figure illustrates a specific structure of a UE according to an embodiment of the present disclosure.

[0161] like Figure 6 As shown, the UE of the present disclosure may include a processor 601, a transceiver 602, and a memory 603. However, the elements of the UE are not limited to the examples described above. For example, the UE may include more elements than the elements described above or may include fewer elements than the elements described above. In addition, the processor 601, the transceiver 602, and the memory 603 may be implemented as one chip.

[0162] According to certain embodiments, the processor 601 may control a series of processes to allow the UE to operate according to the above-mentioned embodiments of the present disclosure. For example, the processor 601 may control the elements of the UE to perform the method of sending and receiving the synchronization signal of the SLUE according to the embodiments of the present disclosure. The processor 601 may refer to a plurality of processors, and may perform the synchronization signal sending and receiving operations of the SL UE described above by executing the program stored in the memory 603.

[0163] In addition, according to some embodiments, the processor 601 may control the transceiver 602 to send a synchronization signal to or receive a synchronization signal from a GPS, a GNSS, a SL UE such as a V2X UE, or a BS. In addition, when multiple synchronization signals are received, the processor 601 may identify the multiple synchronization signals received, and may perform synchronization based on a synchronization signal selected according to a preset standard or priority order.

[0164] In addition, according to some embodiments, the processor 601 may determine which synchronization signal corresponding to which node is to be sent. According to some embodiments, the synchronization signal configuration information may include information indicating which node's timing is to be synchronized, priority order information, and identification information about whether it is a synchronous EN-DC or an asynchronous EN-DC, but the present disclosure is not limited thereto, and therefore, the synchronization signal configuration information may include all information associated with the synchronization signal.

[0165] The transceiver 602 may send a signal to a BS or receive a signal from a BS. The signal sent to the BS or received from the BS may include control information and data. The transceiver 602 may include a radio frequency (RF) transmitter configured to up-convert and amplify the frequency of the transmitted signal, and an RF receiver configured to low-noise amplify the received signal and down-convert its frequency. However, the configuration of the transceiver 602 is only an example, and the elements of the transceiver 602 are not limited to the RF transmitter and the RF receiver. In addition, the transceiver 602 may receive a signal by using a radio channel and output the signal to the processor 601, and may send a signal output from the processor 601 by using a radio channel.

[0166] According to certain embodiments, the memory 603 may store programs and data required for UE operation. In addition, the memory 603 may store control information or data included in a signal sent or received by the UE. The memory 603 may include any or a combination of storage media such as a read-only memory (ROM), a random access memory (RAM), a hard disk, a compact (CD)-ROM, and a digital versatile disk (DVD). In addition, the memory 603 may refer to a plurality of memories. According to certain embodiments, the memory 603 may store a program for performing operations of sending and receiving synchronization signals in SL communication according to the embodiments of the present disclosure described above.

[0167] Figure 7 FIG. 1 illustrates a specific structure of a BS according to an embodiment of the present disclosure.

[0168] like Figure 7 As shown, the BS of the present disclosure may include a processor 701, a transceiver 702, and a memory 703. However, the elements of the BS are not limited to the examples described above. For example, the BS may include more elements than the elements described above or may include fewer elements than the elements described above. In addition, the processor 701, the transceiver 702, and the memory 703 may be implemented as one chip.

[0169] The processor 701 may control a series of processes to allow the BS to operate according to the above-mentioned embodiments of the present disclosure. For example, the processor 701 may control elements of the BS to perform a method of transmitting and receiving a synchronization signal in a wireless communication system according to an embodiment of the present disclosure.

[0170] The transceiver 702 may send a signal to or receive a signal from the UE. The signal sent to or received from the UE may include control information and data. The transceiver 702 may include an RF transmitter configured to up-convert and amplify the frequency of the transmitted signal, and an RF receiver configured to low-noise amplify the received signal and down-convert its frequency. However, the configuration of the transceiver 702 is only an example, and the elements of the transceiver 702 are not limited to the RF transmitter and the RF receiver. In addition, the transceiver 702 may receive a signal and output a signal to the processor 701 by using a radio channel, and may send a signal output from the processor 701 by using a radio channel. The processor 701 may refer to a plurality of processors, and may execute the method of sending and receiving a synchronization signal in a wireless communication system according to an embodiment of the present disclosure by executing a program stored in the memory 703.

[0171] According to certain embodiments, the memory 703 may store programs and data required for BS operation. In addition, the memory 703 may store control information or data included in a signal sent or received by the BS. The memory 703 may include any or a combination of storage media such as ROM, RAM, hard disk, CD-ROM and DVD. In addition, the memory 703 may refer to multiple memories. According to certain embodiments, the memory 703 may store a program for executing a method for controlling transmission power in a wireless communication system according to an embodiment of the present disclosure. The method according to an embodiment of the present disclosure as described herein or in the following claims may be implemented as hardware, software, or a combination of hardware and software.

[0172] When implemented as software, a computer-readable storage medium storing one or more programs (e.g., software modules) may be provided. The one or more programs stored in the computer-readable storage medium are configured to be executed by one or more processors in an electronic device. The one or more programs include instructions that direct the electronic device to perform a method according to an embodiment of the present disclosure as described herein or in the following claims.

[0173] The program (e.g., software module or software) may be stored in a non-volatile memory, including RAM or flash memory, ROM, electrically erasable programmable read-only memory (EEPROM), magnetic disk storage, CD-ROM, DVD, another optical storage device, or a magnetic tape cassette. Alternatively, the program may be stored in a memory comprising a combination of some or all of the above storage media. A plurality of such memories may be included.

[0174] In addition, the program can be stored in an attachable storage device accessible through any or a combination of communication networks, such as the Internet, an intranet, a local area network (LAN), a wide LAN (WLAN), and a storage area network (SAN). The storage device can be connected to the device according to the embodiments of the present disclosure through an external port. Another storage device on the communication network can also be connected to the device performing the embodiments of the present disclosure.

[0175] In the foregoing embodiments of the present disclosure, the elements included in the present disclosure are expressed in singular or plural form according to the embodiments of the present disclosure. However, the singular or plural form is appropriately selected for the convenience of description, and the present disclosure is not limited thereto. Thus, the elements expressed in plural form may also be configured as a single element, and the elements expressed in singular form may also be configured as multiple elements.

[0176] Meanwhile, the embodiments of the present disclosure described with reference to this specification and the accompanying drawings only illustrate specific examples to easily facilitate the description and understanding of the present disclosure, and are not intended to limit the scope of the present disclosure. In other words, it is obvious to those skilled in the art that other modifications based on the technical concepts of the present disclosure are feasible. In addition, when necessary, the embodiments can be combined to achieve. For example, the BS and the UE can operate in a manner that a part of an embodiment of the present disclosure is combined with a part of another embodiment of the present disclosure. The embodiments of the present disclosure can also be applied to other communication systems, and various modifications based on the technical concepts of the embodiments of the present disclosure can be made.

Claims

1. A communication method performed by a vehicle-to-everything (V2X) user equipment (UE) in a wireless communication network, the communication method comprising: receiving at least one side link synchronization signal SLSS from a plurality of side link SL synchronization sources based on the priority order information; When a plurality of SLSSs having the same priority order are received and the reference signal received powers RSRP of the plurality of SLSSs exceed a preset threshold, selecting the SLSS having the largest RSRP value; as well as When a plurality of SLSSs having the same priority order are received and there is no SLSS exceeding a preset threshold among the plurality of SLSSs, selecting the SLSS based on the timing information of the V2X UE, Among them, multiple SL synchronization sources include a global navigation satellite system GNSS, an evolved Node B eNB, a next-generation Node B gNB or another V2X UE, and the priority order of the eNB-based SLSS and the priority order of the gNB-based SLSS are equivalent.

2. The communication method according to claim 1, wherein: Receiving at least one SLSS includes receiving at least one of: a first type of SLSS received directly from a GNSS, a second type of SLSS received from a V2X UE directly synchronized with a GNSS, a third type of SLSS received from a V2X UE indirectly synchronized with a GNSS, a fourth type of SLSS received directly from an eNB or a gNB, a fifth type of SLSS received from a V2X UE directly synchronized with an eNB or a gNB, a sixth type of SLSS received from a V2X UE indirectly synchronized with an eNB or a gNB, and A seventh type of SLSS is received from a pre-defined V2X UE that is not synchronized directly or indirectly with a GNSS, eNB or gNB.

3. The communication method according to claim 2, wherein: The third type SLSS is an SLSS received from a V2X UE synchronized with a V2X UE that is indirectly synchronized with a GNSS, and Among them, the sixth type SLSS is the SLSS received from the V2X UE synchronized with the V2X UE indirectly synchronized with the base station.

4. The communication method according to claim 2, wherein: The priority order information includes information on respective priority orders of the first type SLSS to the seventh type SLSS.

5. The communication method according to claim 4, wherein: The priority order information includes information in which the first type SLSS or the fourth type SLSS is configured to have the highest priority order.

6. The communication method according to claim 1, wherein: The priority order information is provided by one of the multiple base stations connected to the V2X UE, provided by the serving base station, or pre-configured.

7. The communication method according to claim 1, wherein: The RSRP value is measured by a demodulation reference signal DMRS transmitted through a physical sidelink broadcast channel PSBCH or a DMRS transmitted through a downlink broadcast channel.

8. The communication method according to claim 1, further comprising: Obtain SLSS transmission configuration information from the base station; and The SLSS configured by the base station is sent to the preset V2X UE based on the SLSS sending configuration information.

9. The communication method according to claim 8, wherein: The sending of the SLSS configured by the base station to the preset V2X UE includes: sending the SLSS configured by the base station to the preset V2X UE based on at least one of an RSRP threshold in the SLSS sending configuration information and an RSRP threshold of a system information block SIB received by the V2X UE, In which, when the V2X UE is connected to multiple base stations, the RSRP threshold is configured to correspond to the multiple base stations respectively.

10. A user equipment UE for vehicle-to-everything V2X, the UE comprising: Transceiver; and at least one processor coupled to the transceiver and configured to: receiving at least one side link synchronization signal SLSS from a plurality of side link SL synchronization sources based on the priority order information, selecting one SLSS, When a plurality of SLSSs having the same priority order are received and the reference signal received powers RSRP of the plurality of SLSSs exceed a preset threshold, selecting the SLSS having the largest RSRP value; as well as When a plurality of SLSSs having the same priority order are received and there is no SLSS exceeding a preset threshold among the plurality of SLSSs, selecting the SLSS based on the timing information of the V2X UE, Among them, multiple SL synchronization sources include a global navigation satellite system GNSS, an evolved Node B eNB, a next-generation Node B gNB, or another V2X UE, and the priority order of the eNB-based SLSS and the priority order of the gNB-based SLSS are equivalent.

11. The UE according to claim 10, wherein: The at least one processor is configured to receive at least one of: a first type of SLSS received directly from a GNSS, a second type of SLSS received from a V2X UE directly synchronized with a GNSS, a third type of SLSS received from a V2X UE indirectly synchronized with a GNSS, a fourth type of SLSS received directly from an eNB or a gNB, a fifth type of SLSS received from a V2X UE directly synchronized with an eNB or a gNB, a sixth type of SLSS received from a V2X UE indirectly synchronized with an eNB or a gNB, and A seventh type of SLSS is received from a pre-defined V2X UE that is not synchronized directly or indirectly with a GNSS, eNB or gNB.

12. The UE according to claim 11, wherein: The third type SLSS is an SLSS received from a V2X UE synchronized with a V2X UE that is indirectly synchronized with a GNSS, and Among them, the sixth type SLSS is the SLSS received from the V2X UE synchronized with the V2X UE indirectly synchronized with the base station.

13. The UE according to claim 11, wherein: The priority order information includes information on respective priority orders of the first type SLSS to the seventh type SLSS.

14. The UE according to claim 10, wherein: The RSRP value is measured by a demodulation reference signal DMRS transmitted through a physical sidelink broadcast channel PSBCH or a DMRS transmitted through a downlink broadcast channel.

15. The UE according to claim 10, wherein: The at least one processor is further configured to: Obtain SLSS transmission configuration information from the base station; and The SLSS configured by the base station is sent to the preset V2X UE based on the SLSS sending configuration information.

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