Method and apparatus for radio link monitoring and radio link failure in sidelink communications

Abstract

Disclosed is a communication scheme and system for integrating IoT technology with a 5G communication system supporting a high data transmission rate exceeding that of a 4G system. The present disclosure can be applied to smart services (e.g., smart homes, smart buildings, smart cities, smart cars or connected cars, healthcare, digital education, retail business, security and safety-related services, etc.) based on 5G communication technology and IoT-related technology. Disclosed is a method and apparatus for performing radio link monitoring (RLM) and radio link failure (RLF) in a vehicle-to-everything (V2X) communication system.

Description

Technical Field

[0001] The present disclosure relates to a mobile communication system, and to a method and an apparatus thereof, in which a vehicle terminal supporting vehicle communication performs transmission or reception of signals with another vehicle terminal and a pedestrian portable terminal using a side link. Background Art

[0002] In order to meet the increased demand for wireless data traffic after the commercialization of the 4G communication system, efforts have been made to develop an improved 5G communication system or a pre-5G communication system. For this reason, the 5G communication system or the pre-5G communication system is referred to as a super 4G network communication system or a post-LTE system. In order to achieve high data transmission rates, the implementation of the 5G communication system in the millimeter wave band (e.g., the 60 GHz band) is being considered. In the 5G communication system, technologies such as beamforming, massive MIMO, full-dimensional MIMO (FD-MIMO), array antennas, analog beamforming, and large antennas are being discussed as a means of mitigating propagation path losses in the millimeter wave band and increasing the propagation transmission distance. In addition, the 5G communication system has developed technologies such as evolved small cells, advanced small cells, cloud radio access networks (RANs), ultra-dense networks, device-to-device communications (D2D), wireless backhaul, mobile networks, cooperative communications, coordinated multipoints (CoMP), and reception interference cancellation to improve the system network. In addition, 5G systems have developed advanced coding and modulation (ACM) schemes such as hybrid FSK and QAM modulation (FQAM) and sliding window superposition coding (SWSC), as well as advanced access technologies such as filter bank multi-carrier (FBMC), non-orthogonal multiple access (NOMA) and sparse code multiple access (SCMA).

[0003] Meanwhile, the Internet has evolved into an Internet of Things (IoT) network in which distributed components such as objects exchange and process information from a human-oriented connected network where humans generate and consume information. Internet of Everything (IoE) technology has emerged in which big data processing technology is combined with IoT technology through connection with cloud servers, etc. In order to realize IoT, technical factors such as sensing technology, wired / wireless communication, network infrastructure, service interface technology, and security technology are required, and research on technologies for connection between objects such as sensor networks, machine-to-machine (M2M) communication, and machine-type communication (MTC) has been conducted recently. In the IoT environment, by collecting and analyzing data generated in connected objects, smart Internet technology (IT) services can be provided to create new value for people's lives. IoT can be applied to fields such as smart homes, smart buildings, smart cities, smart cars, connected cars, smart grids, healthcare, smart appliances, or high-tech medical services through the integration of traditional information technology (IT) and various industries.

[0004] Therefore, various attempts have been made to apply 5G communication to IoT networks. For example, 5G communication technologies such as sensor networks, machine-to-machine (M2M) communication, and machine-type communication (MTC) have been implemented through technologies such as beamforming, MIMO, and array antennas. The application of cloud RAN as a big data processing technology can be an example of the fusion of 5G technology and IoT technology.

[0005] Vehicle-to-everything (V2X) technology using the 5G communication system is being studied, and it is expected that various services will be provided to users by using V2X.

[0006] The above information is provided as background information only to assist in understanding the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above may be applied as prior art with respect to the present disclosure. Summary of the invention

[0007] Technical issues

[0008] One aspect of the present disclosure is to provide a V2X system, and more particularly, to provide a method and apparatus for performing radio link monitoring (RLM) and radio link failure (RLF) in a process in which a vehicle terminal supporting V2X uses a side link to transmit or receive information with another vehicle terminal and a pedestrian portable terminal.

[0009] Solution

[0010] The present disclosure is to solve the above-mentioned problems and disadvantages and to provide at least the advantages described below.

[0011] According to one aspect of the present disclosure, a method performed by a terminal in a communication system is provided. The method includes transmitting data to another terminal on a side link, determining whether a radio link failure (RLF) associated with the side link is detected, and in the case of detecting the RLF, sending information indicating the occurrence of the RLF associated with the side link to a base station, wherein the terminal is connected to the base station.

[0012] According to another aspect of the present disclosure, a terminal in a communication system is provided. The terminal includes a transceiver and a controller, the controller being configured to transmit data to another terminal on a side link via the transceiver, determine whether a radio link failure (RLF) associated with the side link is detected, and in the case of detecting the RLF, send information indicating the occurrence of the RLF associated with the side link to a base station via the transceiver, wherein the terminal is connected to the base station. The present disclosure proposes a method in which the terminal performs radio link monitoring (RLM) and radio link failure (RLF) in side link communication.

[0013] Before proceeding to the following detailed description, it may be helpful to set forth definitions of certain words and phrases used throughout this patent document: the terms "include" and "including" and their derivatives mean inclusion rather than limitation; the term "or" is inclusive, meaning and / or; the phrases "associated" and "associated with" and their derivatives may mean to include, be contained within, be interconnected with, contain, be included within, be connected to or connected with, be coupled to or coupled with, be communicative with, cooperate with, interleave, juxtapose, be in proximity to, be bound to or bound with, have, have the property of, or similar terms; "controller" means any device, system, or part thereof that controls at least one operation, such device may be implemented in hardware, firmware, or software, or some combination of at least two thereof. It should be noted that the functionality associated with any particular controller may be centralized or distributed, whether locally or remotely.

[0014] In addition, the various functions described below can be implemented or supported by one or more computer programs, each of which is formed by a computer-readable program code and is specifically implemented in a computer-readable medium. The terms "application" and "program" refer to one or more computer programs, software components, instruction sets, programs, functions, objects, classes, instances, related data or parts thereof suitable for implementation in a suitable computer-readable program code. The phrase "computer-readable program code" includes any type of computer code, including source code, object code and executable code. The phrase "computer-readable medium" includes any type of medium that can be accessed by a computer, such as a read-only memory (ROM), a random access memory (RAM), a hard drive, a compact disk (CD), a digital video disk (DVD) or any other type of memory. "Non-transitory" computer-readable media do not include wired, wireless, optical or other communication links that transmit temporary electrical signals or other signals. Non-transitory computer-readable media include media in which data can be permanently stored and media in which data can be stored and then rewritten, such as rewritable optical disks or erasable storage devices.

[0015] Definitions for certain words and phrases are provided in this patent document, those of ordinary skill in the art should understand that in many, if not most instances, such definitions apply to prior, as well as future uses of such defined words and phrases.

[0016] Technical Effects

[0017] According to the present disclosure, sidelink unicast and multicast communications may be supported more reliably. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings, wherein like reference numerals represent like parts:

[0019] Figure 1a A diagram showing an example of a system according to an embodiment;

[0020] Figure 1b A diagram showing another example of a system according to an embodiment;

[0021] Figure 2 A diagram showing an example of a V2X communication method implemented via a sidelink connection;

[0022] Figure 3 A diagram showing a method of performing RLM between a base station and a terminal in a conventional LTE and NR system;

[0023] Figure 4 A diagram showing an example of a method of performing RLM in an NR V2X system;

[0024] Figure 5 A diagram showing another example of a method of performing RLM in an NR V2X system;

[0025] Figure 6 A diagram showing an example of indicating whether to transmit an SL SS / PBCH block according to a scenario in a V2X communication method implemented using a side link;

[0026] Figure 7 A diagram showing an example of using SL SS / PBCH as an RLM measurement signal if SL SS / PBCH is transmitted from a terminal different from a terminal transmitting data in a V2X communication method implemented using a side link;

[0027] Figure 8 A block diagram showing an internal structure of a terminal according to an embodiment; and

[0028] Fig. 9 A block diagram showing the internal structure of a base station according to an embodiment. DETAILED DESCRIPTION

[0029] Discussed below Figures 1a to 9 , and the various embodiments used in this patent document to describe the principles of the present disclosure are merely exemplary and should not be interpreted in any way to limit the scope of the present disclosure. Those skilled in the art will understand that the principles of the present disclosure can be implemented in any suitably arranged system or device.

[0030] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0031] When describing the embodiments, descriptions of technologies known to those skilled in the art and not directly related to the present disclosure may be omitted. Such unnecessary descriptions are omitted to prevent the main idea of ​​the present disclosure from being obscured and to convey the main idea more clearly.

[0032] For the same reason, in the accompanying drawings, some elements may be exaggerated, omitted or schematically shown. In addition, the size of each element does not fully reflect the actual size. In the accompanying drawings, the same or corresponding elements are represented by the same reference numerals.

[0033] By referring to the embodiments of the present disclosure described in detail below in conjunction with the accompanying drawings, the advantages and features of the present disclosure and the methods for achieving these advantages and features will become apparent. However, the present disclosure is not limited to the embodiments described below, but can be implemented in various different ways. These embodiments are provided to enable the present disclosure to be supplemented and to fully illustrate the scope of the present disclosure to those skilled in the art. The present disclosure is limited only by the scope of the claims. Throughout the specification, the same or similar reference numerals represent the same or similar elements.

[0034] Here, it will be understood that each box of the flowchart diagram and the combination of boxes in the flowchart diagram 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 form a device for realizing the function specified in one or more flowchart boxes. 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 an article including an instruction device, and the instruction device realizes the function specified in one or more flowchart boxes. The computer program instructions can also be loaded on a computer or other programmable data processing device so that a series of operating steps are performed on the computer or other programmable device, thereby generating a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for realizing the function specified in one or more flowchart boxes.

[0035] And 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 functions involved, two frames shown in succession can actually be executed substantially simultaneously, or these frames can sometimes be executed in reverse order.

[0036] As used herein, "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, "unit" does not always have the meaning of being 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 parameters. The elements and functions provided by "unit" can be combined into a smaller number of element "units", or divided into a larger number of element "units". In addition, elements and "units" can be implemented as one or more CPUs in a reproduction device or a secure multimedia card. In addition, in one embodiment, "unit" can include one or more processors.

[0037] A detailed description of the embodiments is provided mainly with reference to the new RAN (NR) as a radio access network and the packet core as a core network (5G system, 5G core network or NG core: next generation core) in the 5G mobile communication standard specified by 3GPP, a standard organization for mobile communication standards. However, the subject matter of the present disclosure may be slightly modified without departing from the scope of the present disclosure and may be applied to other communication systems with similar technical backgrounds. Those skilled in the art may determine the modifications and applications thereof.

[0038] In the 5G system, in order to support the automation of the network, a network data collection and analysis function (NWDAF) may be defined, which is a network function that provides the function of analyzing and providing data collected in the 5G network. The NWDAF may provide the results obtained by collecting / storing / analyzing information from the 5G network to an unspecified network function (NF), and the analysis results may be used independently by each NF.

[0039] For ease of description, some terms and names defined in the 3rd Generation Partnership Project Long Term Evolution (3GPP LTE) standard (or the standard of 5G, NR, LTE or similar systems) may be used. However, the present disclosure is not limited to the terms and names and may be equally applied to a system based on another standard.

[0040] Hereinafter, the terms used to identify access nodes, terms related to network entities, terms related to messages, terms related to interfaces between network entities, terms used for various types of identification information, etc. are used only for convenience of description. Therefore, the terms are not limited to the terms used in the present disclosure, and other terms related to subjects with equivalent technical meanings may be used.

[0041] In order to meet the increased demand for wireless data traffic after the commercialization of the 4G communication system, efforts are being made to develop an improved 5G communication system (New Radio (NR)). In order to achieve high data transmission rates, the 5G communication system is designed to use resources in the ultra-high frequency (millimeter wave) band (e.g., the 28 GHz band). In the 5G communication system, technologies such as beamforming, massive MIMO, full-dimensional MIMO (FD-MIMO), array antennas, analog beamforming, and large antennas are being discussed to mitigate propagation path losses in the ultra-high frequency band and increase the propagation transmission distance. In addition, unlike LTE, the 5G communication system supports various subcarrier spacings such as 30 kHz, 60 kHz, 120 kHz, etc., including 15 kHz. The physical control channel is encoded using polar coordinate coding, and the physical data channel is encoded using low-density parity check (LDPC). In addition, cyclic prefix OFDM (CP-OFDM) as well as DFT-spread OFDM (DFT-S-OFDM) can be used as waveforms for uplink transmission. LTE supports hybrid ARQ (HARQ) retransmission performed in units of transport blocks. In contrast, the 5G system may additionally support HARQ retransmission in units of code block groups (CBGs), where code blocks (CBs) are bundled.

[0042] In the case of vehicle communication, V2X based on LTE has been standardized based on a device-to-device (D2D) communication structure in 3GPP Rel-14 and Rel-15. Currently, the effect of developing V2X based on 5G New Radio (NR) is taking shape. In NR V2X, it is expected to support unicast communication, groupcast (or multicast) communication, and broadcast communication between terminals. Unlike LTE V2X, which is used to send or receive basic safety information required for vehicles to travel on the road, NR V2X is used to provide advanced services such as advanced driving of vehicle platoons, extended sensors, or remote driving.

[0043] In the following, the side link refers to a signal transmission or reception path between terminals, which can be used interchangeably with the PC5 interface. In the following, the base station is a subject that performs resource allocation for the terminal, and can be a base station that supports V2X communication and normal cellular communication, or can be a base station that supports only V2X communication. That is, the base station refers to a 5G base station (gNB), a 4G base station (eNB), or a roadside unit (RSU). The terminal can be a mobile station, and can be a vehicle supporting vehicle-to-vehicle (V2V) communication, a mobile phone of a vehicle or pedestrian (i.e., a smartphone), a vehicle supporting vehicle-to-pedestrian (V2P) communication, a vehicle supporting vehicle-to-network (V2N) communication, a vehicle supporting vehicle-to-infrastructure (V2I) communication, a radio side unit (RSU) equipped with a terminal function, an RSU equipped with a base station function, an RSU equipped with some base station functions and some terminal functions, etc. The base station and the terminal can be connected through the Uu interface.

[0044] In the side links of V2X and D2D based on the conventional LTE system, only broadcast communication is supported, and the radio link monitoring (RLM) and radio link failure (RLF) functions are not supported. In particular, RLM is a function for measuring and monitoring the quality of the communication link. Based on the result of RLM, the terminal can report the link quality to a higher layer. Based on the link quality, the higher layer can determine whether to maintain the current communication link or declare RLF and connect the link again. In the case of NR V2X, unicast and multicast communications between terminals are considered. Therefore, in order to ensure the continuous connection of the communication link, RLM and RLF functions may be required.

[0045] In particular, if the RLM and RLF functions are not supported in advanced scenarios such as vehicle platooning, advanced driving, extended sensors, remote driving, etc. considered in NR V2X, the continuous connection of the service may not be guaranteed, which may seriously affect the performance of the provided service. For example, in the case of remote driving, if there is no attempt to restore the link via RLM and RLF even if the link quality is poor, the safety of the vehicle may not be guaranteed. In addition, in the case of a Uu interface between the base station and the terminal, the base station sends a measurement signal of RLM, and the terminal uses the signal to perform RLM and RLF operations. In the case of a side link (communication between terminals) of V2X, if the link quality is poor, the terminal that performs the transmission and the terminal that receives the data can reduce power consumption via RLM and RLF. In the case of supporting RLM and RLF in the terminal that transmits data, if the link quality associated with the transmission is poor, the leader terminal of the group in the service scenario (such as vehicle platooning) can transfer the leadership function to another terminal in order to support a more reliable vehicle platooning.

[0046] To support the above scenarios, unlike the conventional LTE V2X technology, NR V2X may need to perform RLM and RLF in the process of the vehicle terminal using the side link to send or receive information with another terminal and a pedestrian portable terminal. However, no discussion has been made in this regard. Therefore, the present disclosure provides a method for selecting and configuring a measurement signal for RLM. In addition, a method and apparatus for a terminal to perform RLM using a measurement signal and to operate according to the RLM result are provided.

[0047] Embodiments are provided to support the above-mentioned scenarios, and provide methods and apparatus for performing RLM and RLF between terminals in a sidelink environment supporting unicast and multicast communications.

[0048] <First Embodiment>

[0049] Figure 1a A diagram showing an example of a system according to an embodiment.

[0050] according to Figure 1a , the in-coverage scenario 100 is an example of a situation where all V2X terminals (UE-1 104 and UE-2 106) are located within the coverage area of ​​the base station 102.

[0051] In this case, all V2X terminals 104 and 106 may receive data and control information from the base station 102 via a downlink (DL), or may transmit data and control information to the base station via an uplink (UL). In this case, the data and control information may be data and control information for V2X communication. Alternatively, the data and control information may be data and control information for normal cellular communication. In addition, the V2X terminal may send or receive data and control information for V2X communication via a side link (SL).

[0052] The partial coverage scenario 110 is an example of a case where, among V2X terminals, UE-1 114 is located within the coverage area of ​​the base station 112, and UE-2 116 is located outside the coverage area of ​​the base station 112. The example according to the scenario 110 may be referred to as an example associated with partial coverage.

[0053] UE- 1 114 located within the coverage area of ​​base station 112 may receive data and control information from base station 112 via a downlink (DL) or may transmit data and control information to base station 112 via an uplink (UL).

[0054] UE-2 116 located outside the coverage area of ​​base station 112 may be unable to receive data and control information from base station 112 via a downlink and may be unable to transmit data and control information to base station 112 via an uplink.

[0055] UE-2 116 and UE-1 114 may perform transmission or reception of data and control information for V2X communication via the side link.

[0056] Out-of-coverage 120 is an example of a situation where all V2X terminals 122 and 124 are located outside the coverage area of ​​the base station (out-of-coverage).

[0057] Therefore, UE-1 122 and UE-2 124 may not be able to receive data and control information from the base station via the downlink, and may not be able to send data and control information to the base station via the uplink. UE-1 122 and UE-2 124 may perform transmission or reception of data and control information for V2X communication via the side link.

[0058] Figure 1b A diagram showing another example of a system according to an embodiment.

[0059] according to Figure 1b, the inter-cell V2X communication scenario 130 is an example of a case where V2X communication is performed between terminals located in different cells. Specifically, it is shown that in the scenario 130, the V2X transmitting terminal and the V2X receiving terminal access (RRC connection state) or camp (RRC connection release state, that is, RRC idle state) different base stations. In this case, UE-1 136 may be a V2X transmitting terminal, and UE-2 138 may be a V2X receiving terminal. Alternatively, UE-1 136 may be a V2X receiving terminal, and UE-2 138 may be a V2X transmitting terminal. UE-1 136 may receive a V2X dedicated system information block (SIB) from a base station 132 to which UE-1 136 accesses (or camps), and UE-2 138 may receive a V2X dedicated SIB from another base station 134 to which UE-2 138 accesses (or camps). In this case, the V2X dedicated SIB information received by UE-1 136 and the V2X dedicated SIB information received by UE-2 138 may be different from each other. Therefore, in order to perform V2X communication between terminals located in different cells, the information may be unified, or flexible parameter configuration may be supported via the relevant parameter configuration method and apparatus of the present disclosure.

[0060] Although Figure 1a and Figure 1b For ease of description, the V2X system is shown to include two terminals (UE-1 and UE-2), but the present disclosure is not limited thereto. In addition, the uplink and downlink between the base station and the V2X terminal may be referred to as a Uu interface, and the side link between the V2X terminals may be referred to as a PC5 interface. Therefore, these terms may be used interchangeably in the present disclosure.

[0061] Figure 2 A diagram showing an example of a V2X communication method implemented via a sidelink connection.

[0062] according to Figure 2 ,like Figure 2 As shown in 200 , a Tx terminal (UE- 1 202 or UE- 2 204 ) and an Rx terminal (UE- 2 204 or UE- 1 202 ) may perform one-to-one communication, which may be referred to as unicast communication.

[0063] like Figure 2 As shown in 210, the TX terminal and the RX terminal can perform one-to-many communication, which can be called groupcast or multicast.

[0064] exist Figure 2In 210, UE-1, UE-2, and UE-3 are included in a single group (Group A) 212, and perform multicast communication. UE-4, UE-5, UE-6, and UE-7 are included in another group (Group B) 214, and perform multicast communication. Each terminal performs multicast communication within the group to which the corresponding terminal belongs, and may not perform communication between different groups. Although Figure 2 210 in FIG. 2 shows two groups, but the present disclosure is not limited thereto.

[0065] although Figure 2 Although not shown in the figure, the V2X terminals can perform broadcast communication. Broadcast communication refers to the situation where all V2X terminals receive data and control information transmitted by the V2X transmitting terminal via the side link. For example, if Figure 2 In 210 , it is assumed that UE- 1 is a transmitting terminal for broadcasting, and then all terminals (UE- 2 , UE- 3 , UE- 4 , UE- 5 , UE- 6 , and UE- 7 ) can receive data and control information sent by UE- 1 .

[0066] Unlike LTE V2X, in NR V2X, it is possible to consider supporting the process of a vehicle terminal transmitting data only to a single predetermined node via unicast, and the process of a vehicle terminal transmitting data to multiple predetermined nodes via multicast. For example, when considering service scenarios such as vehicle platooning, unicast and multicast technologies can be effectively used. Vehicle platooning is a technology in which two or more vehicles are connected to a single network and move as a group. In particular, when a leading node in a group configured by a vehicle platoon wishes to control a predetermined node, unicast communication may be required, and when the leading node wishes to simultaneously control a group including multiple predetermined nodes, multicast communication may be required.

[0067] Figure 3 A diagram showing a method of performing RLM between a base station and a terminal in conventional LTE and NR systems.

[0068] For RLM, in operation 310 , the terminal 302 may receive a measurement signal from the base station 300 as follows.

[0069] - LTE terminals can use the cell-specific reference signal (CRS) as the measurement signal for RLM [see TS36.213 Section 4.2.1]

[0070] -NR terminals can use the synchronization signal / physical broadcast channel (SS / PBCH) blocks or the channel state information reference signal (CSI-RS), or both as measurement signals for RLM [see TS 36.213 Section 5].

[0071] Then, in operation 320, the terminal uses the measurement signal to measure the radio link quality. Then, in operation 330, the terminal uses the communication link quality measurement result to indicate the out-of-sync state or the in-sync state to the higher layer. In particular, if the communication link quality is worse than the threshold point Q out , the terminal indicates to the higher layer that the link quality is "out of sync". However, if the communication link quality is better than the threshold point Q in , then the terminal indicates that the link quality is "synchronized" with the higher layer. In the RAN4 standard, the threshold point Q out and Q in Defined as the Block Error Rate (BLER) [for LTE terminals, see TS 36.133 section 7.11, for NR terminals, see TS 38.133 section 8.1].

[0072] Based on the result of RLM in operation 330, the terminal may perform an operation related to RLF. If the lower layer continuously indicates "out of sync", the higher layer may operate a timer related to RLM. If the lower layer successfully indicates "in sync", the timer related to RLM may be suspended. If the timer that starts running expires, the terminal determines that it is RLF, suspends the timer related to RLM, and performs the following two operations.

[0073] - The terminal suspends uplink transmission to the base station.

[0074] ○ Uplink transmissions such as semi-persistent scheduling (SPS), channel state information including channel quality indicator (CQI), sounding reference signal (SRS), scheduling request (SR), etc. may be released.

[0075] -Perform the cell selection process to restore the link.

[0076] For more detailed related operations, see TS 36.331 for LTE terminals and TS 38.331 for NR terminals.

[0077] Figure 4 A diagram showing an example of a method for performing RLM in an NR V2X system. The NR V2X system may consider the following method for RLM.

[0078] -RLM is only performed in the receiving end

[0079] - Execute RLM in both the sender and receiver

[0080] The method of performing RLM only in the receiving end is as follows Figure 4 shown. Figure 4A transmitting end 410 and a receiving end 420 are shown. Generally, a transmitting end and a receiving end can be understood as a main body of a transmission signal and a main body of a reception signal. In a V2X system, a terminal can be a transmitting end or a receiving end. In addition, the receiving end 420 can be a single terminal or can be a plurality of terminals. In a case such as a vehicle formation, the receiving end 420 can be a plurality of terminals. For RLM, in operation 430, the transmitting end sends a measurement signal and the receiving end receives the measurement signal. Subsequently, in operation 440, the receiving end uses the measurement signal to measure the radio link quality. Subsequently, in operation 450, the receiving end uses the communication link quality measurement result to indicate an out-of-sync state or a in-sync state to a higher layer. Here, the terms "out-of-sync" or "in-sync" can be replaced with other terms.

[0081] Figure 5 A diagram showing another example of a method for performing RLM in an NR V2X system.

[0082] Different from Figure 4 , Figure 5 A method of performing RLM in a transmitting end and a receiving end is shown. Figure 5 A transmitting end 510 and a receiving end 520 are shown. Generally, a transmitting end and a receiving end can be understood as a subject of a transmission signal and a subject of a reception signal. In a V2X system, a terminal can be a transmitting end or a receiving end. In addition, the receiving end 520 can be a single terminal or can be a plurality of terminals. In a scenario such as a vehicle platoon, the receiving end 520 can be a plurality of terminals.

[0083] For RLM, in operation 530, the transmitting end transmits a measurement signal, and the receiving end receives the measurement signal. Figure 4 , the receiving end may also send a measurement signal to the transmitting end, and the transmitting end may receive the measurement signal. Therefore, the receiving end may measure the communication link quality in operation 540, and may use the measurement in operation 550 to indicate an out-of-sync state or an out-of-sync state to a higher layer. In addition, the transmitting end may measure the communication link quality in operation 560, and may use the measurement in operation 570 to indicate an out-of-sync state or an out-of-sync state to a higher layer. Here, the terms "out-of-sync" or "in-sync" may be replaced with other terms.

[0084] Already referenced Figure 4 and Figure 5 A method for performing RLM in an NR V2X system is described. In the NR V2X system, the following signals may be considered as measurement signals for RLM.

[0085] - SL SS / PBCH: refers to the sidelink synchronization signal block. SL SS / PBCH may include a sidelink synchronization signal and a physical sidelink broadcast channel. The sidelink synchronization signal includes a sidelink primary synchronization signal (SL PSS) and a sidelink secondary synchronization signal (SL SSS).

[0086] - SL CSI-RS: refers to the channel state information reference signal (CSR-RS) transmitted in the side link.

[0087] - SL DMRS: refers to the Demodulation Reference Signal (DMRS) transmitted in the side link.

[0088] - SL PTRS: refers to the Phase Tracking Reference Signal (PTRS) transmitted in the sidelink.

[0089] In the NR V2X system, the measurement signal for RLM is not limited to the above-mentioned candidate signals. One or more candidate signals may be considered as measurement signals, and the selection of the corresponding measurement signal and the configuration information associated with the measurement signal may be signaled through the radio resource control (RRC, hereinafter referred to as Uu-RRC) configured by the base station or the radio resource control (RRC, hereinafter referred to as PC-5 RRC) configured by the terminal.

[0090] In addition, if the measurement signal for RLM is configured to be measured restrictively in a predetermined time slot, the base station or the terminal can configure one or more groups of time slots for measuring the communication link quality of RLM, and the RLM measurement can be implemented in the configured time slot group. When configuring one or more groups of time slots for measuring the communication link quality of RLM, different groups can include different time slots, and these time slots do not overlap with each other. In this case, the time slot group for measuring the communication link quality of RLM can be configured by Uu-RRC or PC5-RRC. Configuring a group of time slots for measuring the communication link quality of RLM and enabling the terminal to measure RLM in the corresponding group of time slots can provide more accurate RLM measurement, which takes into account the interference environment that changes over time in an environment with interference.

[0091] Subsequently, operations of the terminal after performing RLM in the NR V2X system are provided.

[0092] If Figure 4The method of performing RLM only in the receiving end is applied as shown, and the terminal corresponding to the receiving end can perform RLF-related operations based on the result of RLM. If the lower layer continuously indicates "out of sync", the higher layer of the terminal can operate the timer related to RLM. If the lower layer successfully indicates "synchronization", the timer related to RLM can be suspended. If the timer that starts the operation expires, the terminal corresponding to the receiving end can determine that RLF occurs, the timer related to RLM can be suspended, and one or more of the following processes can be performed to restore the link.

[0093] -The terminal corresponding to the receiving end suspends side link transmission.

[0094] ○ The sidelink transmissions to be released may include one or more of the following:

[0095] Semi-persistent scheduling (SPS), channel state information (CSI) feedback including channel quality indicator (CQI), HARQ feedback, sounding reference signal (SRS) and scheduling request (SR).

[0096] -In order to recover and reestablish the side link, the terminal corresponding to the receiving end may perform one or more of the following methods:

[0097] ○ The terminal corresponding to the receiving end notifies the base station that the corresponding side link is in the RLF state. This operation may correspond to the situation of the terminal within the coverage area.

[0098] ○ The terminal corresponding to the receiving end requests the base station to release the corresponding side link. This operation may correspond to the situation of the terminal within the coverage area.

[0099] ○ The terminal corresponding to the receiving end attempts to perform SL SS / PBCH block transmission. This operation can be performed by the terminal in the coverage area and the terminal out of the coverage area.

[0100] In addition, if Figure 4As shown, the method of performing RLM only in the receiving end is applied. Unlike the terminal corresponding to the receiving end, the terminal corresponding to the transmitting end may not perform processes 440 and 450 for RLM, but may indirectly identify the link quality and may determine the out-of-sync state or the in-sync state. The detailed method thereof is described with reference to the second embodiment. As described above, the side link of V2X is communication between terminals. Therefore, if the link quality is poor, the transmitting terminal and the receiving terminal receiving data can reduce power consumption via RLM and RLF (because data transmission can be blocked when communication conditions are poor). In the case where RLM and RLF are supported in the terminal transmitting data, if the link quality associated with the transmission is poor, the leading terminal of the group in the service scenario (e.g., a vehicle formation) may transfer the leading function to another terminal in order to support a more reliable vehicle formation. Therefore, if the terminal corresponding to the transmitting end determines that the side link is RLF according to the method of the second embodiment, the terminal corresponding to the transmitting end may perform one or more of the following processes in order to restore the link.

[0101] -The terminal corresponding to the transmitting end may suspend sidelink transmission.

[0102] o In this case, before suspending transmission, the terminal corresponding to the transmitting end may request the higher layer to send a keep-alive message. The keep-alive message may be sent to the terminal corresponding to the receiving end through the PC5 interface.

[0103] - A terminal corresponding to a transmitting end may perform sidelink transmission in a fallback mode. The fallback mode may be a mode in which data is transmitted using small-scale scheduling information (which may correspond to sidelink control information (SCI) in the present disclosure). That is, the transmitting end may transmit scheduling information using an SCI format having fewer bits than a conventionally used SCI format.

[0104] -In order to recover and reestablish the side link, the terminal corresponding to the transmitting end may perform one or more of the following methods:

[0105] ○ The terminal corresponding to the transmitting end notifies the base station that the corresponding side link is in the RLF state. This operation may correspond to the situation of the terminal within the coverage area.

[0106] ○ The terminal corresponding to the transmitting end requests the base station to release the corresponding side link. This operation may correspond to the situation of the terminal within the coverage area.

[0107] In the case of a vehicle platoon, the terminal corresponding to the transmitting terminal can request to change the leading terminal. This operation can be performed together with or separately from releasing the corresponding side link.

[0108] ○ The terminal corresponding to the transmitting end attempts to perform SL SS / PBCH block transmission. This operation can be performed by the terminal in the coverage area and the terminal out of the coverage area.

[0109] If the application Figure 5 The method for performing RLM in the transmitting end and the receiving end shown, first, the terminal corresponding to the receiving end can perform RLF related operations based on the result of RLM. If the lower layer continuously indicates "out of synchronization", the higher layer can operate the timer related to RLM. If the lower layer successfully indicates "synchronization", the timer related to RLM can be suspended. If the timer that starts the operation expires, the terminal corresponding to the receiving end can determine that RLF occurs, the timer related to RLM can be suspended, and one or more of the following processes can be performed to restore the link.

[0110] -The terminal corresponding to the receiving end suspends side link transmission.

[0111] ○ The sidelink transmissions to be released may include one or more of the following:

[0112] Semi-persistent scheduling (SPS), channel state information (CSI) feedback including channel quality indicator (CQI), HARQ feedback, sounding reference signal (SRS) and scheduling request (SR).

[0113] -In order to recover and reestablish the side link, the terminal corresponding to the receiving end may perform one or more of the following methods:

[0114] ○ The terminal corresponding to the receiving end notifies the base station that the corresponding side link is in the RLF state. This operation may correspond to the situation of the terminal within the coverage area.

[0115] ○ The terminal corresponding to the receiving end requests the base station to release the corresponding side link. This operation may correspond to the situation of the terminal within the coverage area.

[0116] ○ The terminal corresponding to the receiving end attempts to perform SL SS / PBCH block transmission. This operation can be performed by the terminal in the coverage area and the terminal out of the coverage area.

[0117] In addition, since the sender also Figure 5 RLM is performed, and the terminal corresponding to the transmitting end can perform RLF-related operations based on the result of RLM. If the lower layer continuously indicates "out of sync", the higher layer can operate the timer related to RLM. If the lower layer successfully indicates "in sync", the timer related to RLM can be suspended. If the timer that starts the operation expires, the terminal corresponding to the transmitting end can determine that it is RLF, can suspend the timer related to RLM, and can perform one or more of the following processes in order to restore the link.

[0118] -The terminal corresponding to the transmitting end may suspend sidelink transmission.

[0119] o In this case, before suspending transmission, the terminal corresponding to the transmitting end may request the higher layer to send a keep-alive message. The keep-alive message may be sent to the terminal corresponding to the receiving end through the PC5 interface.

[0120] - A terminal corresponding to a transmitting end may perform sidelink transmission in a fallback mode. The fallback mode may be a mode in which data is transmitted using small-scale scheduling information (which may correspond to sidelink control information (SCI) in the present disclosure). That is, the transmitting end may transmit scheduling information using an SCI format having fewer bits than a conventionally used SCI format.

[0121] -In order to recover and reestablish the side link, the terminal corresponding to the transmitting end may perform one or more of the following methods:

[0122] ○ The terminal corresponding to the transmitting end notifies the base station that the corresponding side link is in the RLF state. This operation may correspond to the situation of the terminal within the coverage area.

[0123] ○ The terminal corresponding to the transmitting end requests the base station to release the corresponding side link. This operation may correspond to the situation of the terminal within the coverage area.

[0124] In the case of a vehicle platoon, the terminal corresponding to the transmitting terminal can request to change the leading terminal. This operation can be performed together with or separately from releasing the corresponding side link.

[0125] ○ The terminal corresponding to the transmitting end attempts to perform SL SS / PBCH block transmission. This operation can be performed by the terminal in the coverage area and the terminal out of the coverage area.

[0126] In addition, if a signaling requesting the release of a link is introduced in the NR V2X system when the terminal wishes to suspend the connection of the side link regardless of the results of RLM and RLF, the side link communication can be performed more reliably. For example, in a vehicle platoon scenario, when a terminal in a vehicle platoon wishes to leave the vehicle platoon, if the terminal sends a signaling requesting the release of a link to a terminal in the group, the terminal in the group can receive the corresponding signaling and unnecessary RLM may not be performed. In this case, prompt signaling may be required, and therefore, 1-bit information contained in the SCI may be used to request the release of the link. For example, if one bit is set to "1", the terminal receiving the SCI may understand that the terminal sending the SCI requests the release of the side link. The corresponding signaling is not limited to the vehicle platoon scheme, and may be considered only for unicast and multicast communications, rather than broadcast communications. In addition, both the terminal corresponding to the transmitting end and the terminal corresponding to the receiving end may send a signaling requesting the release of the link.

[0127] Figure 6A diagram showing an example of indicating whether to transmit an SL SS / PBCH block according to a scenario in a V2X communication method implemented using a side link.

[0128] It has been described that, for example, SL SS / PBCH, SL CSI-RS, SL DMRS and SL PTRS signals can be used as measurement signals for RLM in the NR V2X system. Figure 6 A diagram showing a case where SL SS / PBCH cannot be used as a measurement signal for RLM according to a V2X scenario.

[0129] Figure 6 600 in FIG. 1 shows a scenario in which both terminal 1 and terminal 2 are present in a cell coverage area and both terminals access a single base station. In this scenario, the two terminals perform synchronization using the Uu SS / PBCH signal transmitted by the base station. Therefore, if terminal 1 and terminal 2 perform communication using a side link, SL SS / PBCH is not transmitted.

[0130] Figure 6 610 in FIG. 610 shows a scenario where both terminal 1 and terminal 2 exist in the cell coverage area, but terminal 1 and terminal 2 access different base stations, and the base stations share resource pool information related to V2X. In this scenario, when terminal 1 and terminal 2 perform communication using the side link, SL SS / PBCH may or may not be transmitted according to conditions. Under the condition that terminal 1 and terminal 2 are synchronized with the corresponding base stations respectively, and the different base stations are synchronized, if terminal 1 and terminal 2 perform communication using the side link, SL SS / PBCH is not transmitted.

[0131] Otherwise, the corresponding base station transmits an indication to the corresponding terminal, indicating that synchronization needs to be established via V2X system information. If terminal 1 and terminal 2 perform communication using a side link, an SL SS / PBCH signal may be transmitted.

[0132] Then, Figure 6 620 in FIG. 1 shows a situation where terminal 1 is present in the cell coverage area and terminal 2 is outside the cell coverage area. In this scenario, when the reference signal received power (RSRP) of terminal 1 is lower than the threshold point set by the base station, terminal 1 can transmit the SL SS / PBCH signal. Then, terminal 2 can obtain synchronization using the SLSS / PBCH transmitted by terminal 1 in the cell coverage area.

[0133] Figure 6 630 in FIG. 6 shows a scenario where Terminal 1 and Terminal 2 are outside the cell coverage area. In this scenario, SL SS / PBCH transmitted by Terminal 1 or Terminal 2 can be used to achieve synchronization.

[0134] like Figure 6As shown in FIG. 1 , there may be a case where, depending on the V2X scenario, SL SS / PBCH cannot be used as a measurement signal for RLM. Figure 6 In 600 and 610, if the indication indicating the need for synchronization is not transmitted from the base station to the corresponding terminal, the SL SS / PBCH is not transmitted. In addition, there may be a terminal that cannot transmit the SL SS / PBCH due to the terminal's capability. Therefore, the configuration of the RLM measurement signal can be considered as follows.

[0135] -Alternative 1: In an environment where SL SS / PBCH can be transmitted, SL SS / PBCH is used as the RLM measurement signal. Otherwise, one or more of SL CSI-RS, SL DMRS, and SL PTRS may be used as the RLM measurement signal.

[0136] ○ If Figure 6 As shown, that is, in Figure 6 In 600 and 610, if the indication indicating that synchronization is required is not transmitted from the base station to the corresponding terminal, the SL SS / PBCH may not be used as the RLM measurement signal.

[0137] ○ In addition, for a terminal that cannot transmit SL SS / PBCH due to the capability of the terminal, SL SS / PBCH may not be used as an RLM measurement signal.

[0138] -Alternative 2: SL SS / PBCH and one or more of SL CSI-RS, SL DMRS and SL PTRS may be used as RLM measurement signals.

[0139] ○ Even in an environment where SL SS / PBCH can be transmitted, SL CSI-RS, SL DMRS, and SL PTRS can be configured as RLM measurement signals in addition to SL SS / PBCH.

[0140] -Alternative 3: SL SS / PBCH is not used as an RLM measurement signal. One or more of SL CSI-RS, SL DMRS, and SL PTRS may be used as an RLM measurement signal.

[0141] Figure 7 A diagram showing an example of using SL-SS / PBCH as an RLM measurement signal if SL-SS / PBCH is transmitted from a terminal different from a terminal transmitting data in a V2X communication method implemented using a side link.

[0142] according to Figure 7 , terminal 1 710 is a transmitting end that sends data, and terminal 2 720 is a receiving end that receives data sent by terminal 1 710. Figure 7As shown, terminal 1 710 and terminal 3 730 exist in the cell coverage area 700, but terminal 2 720 is outside the cell coverage area. In this case, terminal 2 720 can achieve synchronization based on SL SS / PBCH 732 transmitted by terminal 1 710 or terminal 3 730 existing in the cell coverage area 700.

[0143] If only a broadcast communication environment is considered, the RLM and RLF processes are not required. Accordingly, Terminal 2 720 performs synchronization based on the SL SS / PBCH 712 or 732 transmitted by Terminal 1 710 or Terminal 3 730, and receives data transmitted by Terminal 1 710. However, in unicast and multicast communications, it is important to ensure continuous connection of the service, so the RLM and RLF processes may be required. If Terminal 2 720 receives the SL SS / PBCH block 712 transmitted by Terminal 1 710 and achieves synchronization, the SL SS / PBCH block 712 may be effective as a measurement signal for RLM. However, if Figure 7 As shown, if terminal 2 720 receives SL SS / PBCH block 732 sent by terminal 3 730, achieves synchronization, and receives data sent by terminal 1 710, then SL SS / PBCH block 732 sent by terminal 3 730 is sent via the link between terminal 3 730 and terminal 2 720, and therefore, SL SS / PBCH block 732 may not be an RLM measurement signal that is effective for identifying the link quality between terminal 1 710 and terminal 2 720.

[0144] Therefore, if Figure 7 As shown, if the SL SS / PBCH block is used as a measurement signal for RLM between the transmitting end and the receiving end in a side link environment supporting unicast and multicast communications, there may be a situation where the SL SS / PBCH block is invalid as a measurement signal for RLM. Therefore, as a method of using the SL SS / PBCH block as a measurement signal for RLM in the NR V2X system, the following method can be considered.

[0145] In unicast and multicast communications, the method of using SL SS / PBCH blocks as measurement signals for RLM is as follows.

[0146] -Alternative 1: Allow SL SS / PBCH blocks that are not valid for RLM (ie, SL SS / PBCH blocks transmitted via a link different from the side link whose communication link quality is to be measured) to be used as measurement for RLM.

[0147] -Alternative 2: Use a virtual cell ID to transmit a SL SS / PBCH block valid for RLM (ie, a SL SS / PBCH block transmitted using the sidelink whose communication link quality is to be measured).

[0148] -Alternative 3: Grouping physical cell IDs (or cell IDs) by distinguishing broadcast from unicast and multicast.

[0149] Among these methods, alternative 1 is a method of allowing the SL SS / PBCH block used to achieve synchronization to be used as a measurement signal for RLM, even if the synchronization is achieved by using the SL SS / PBCH block that is invalid for RLM. In the case of alternative 1, unicast and multicast communications can use the SL SS / PBCH block as a measurement signal for RLM without introducing an additional method, but the accuracy of RLM may be low, which is a disadvantage. Alternative 2 will be described in detail with reference to the third embodiment, and alternative 3 will be described in detail with reference to the fourth embodiment.

[0150] <Second Embodiment>

[0151] The second embodiment provides a method in which, if Figure 4 The application shown performs the method of RLM only in the receiving end, then the terminal corresponding to the transmitting end (although not performing the process for RLM like the terminal corresponding to the receiving end) indirectly identifies the link quality and determines the out-of-sync state or the in-sync state. Here, the terms "out-of-sync" or "in-sync" can be replaced by other terms. The terminal corresponding to the transmitting end may need to use an indirect method to identify the link quality because the terminal corresponding to the transmitting end does not receive the measurement signal of RLM. In this case, the following method can be considered.

[0152] -SL HARQ-ACK / NACK

[0153] -SL HARQ-NACK

[0154] - SL CSI Feedback

[0155] In the NR V2X system, it is planned to support the introduction of sidelink HARQ ACK / NACK and channel state information (CSI) feedback (hereinafter used interchangeably with feedback information) in a sidelink environment supporting unicast and multicast communications. In the case of HARQ, both HARQ-ACK and HARQ-NACK are supported in unicast communication (i.e., reception confirmation (ACK) and reception non-confirmation (NACK) are supported). However, in multicast communication, only HARQ-NACK is supported due to feedback overhead. In the case of CSI feedback, the terminal corresponding to the transmitting end can receive CSI feedback information periodically, aperiodically or semi-continuously based on the CSI-RS configuration and the channel state information report (CSI report) configuration. Therefore, the terminal corresponding to the transmitting end can use the above feedback information to determine the out-of-sync state or the in-sync state according to the following process.

[0156] - The terminal corresponding to the transmitting end defines a threshold point X for determining an out-of-sync state or a in-sync state.

[0157] - The threshold point X indicates the length of the duration during which no reception occurs after feedback information (eg, the above-mentioned SL HARQ-ACK / NACK, SL HARQ NACK, or CSI feedback) is last received.

[0158] - The value related to the threshold point X may be configured via Uu-RRC or PC5-RRC. Alternatively, the value may be defined in the standard.

[0159] - If no feedback information is received during the configured threshold point X, the physical layer of the terminal corresponding to the transmitting end may indicate to the higher layer that the link quality is "out of sync".

[0160] o If the link quality is identified as "out of sync", the threshold point X may be updated to twice the previous threshold point value.

[0161] - If the feedback information is received within the configured threshold point X, the physical layer of the terminal corresponding to the transmitting end can indicate that the link quality is "in sync".

[0162] o If the link quality is identified as "in sync", then the threshold point X may remain equal to the previous threshold point value.

[0163] The terminal corresponding to the transmitting end can identify the "out of sync" state or the "in sync" state according to the above method, and the terminal can perform RLF-related operations based on the result. If the lower layer continuously indicates "out of sync", the higher layer of the terminal corresponding to the transmitting end can operate the RLM-related timer. If the lower layer successfully indicates "in sync", the timer related to RLM can be suspended. If the timer that starts the operation expires, the terminal corresponding to the transmitting end can determine that it is RLF.

[0164] <Third Embodiment>

[0165] The third embodiment describes in detail the alternative 2 in the method of using the SL SS / PBCH block as the measurement signal of RLM in unicast and multicast communication. The following embodiment proposes a method of using a virtual cell ID to transmit a SL SS / PBCH block valid for RLM as a method of using the SL SS / PBCH block as a measurement signal for RLM. However, the suggestion of the present disclosure is not limited to the use for RLM measurement signals.

[0166] In the third embodiment, a process of transmitting a SL SS / PBCH block valid for RLM using a virtual cell ID may be performed as follows.

[0167] - In the case where a terminal within the cell coverage area transmits a SL SS / PBCH block, the terminal may transmit a SL SS / PBCH block generated using a physical cell ID.

[0168] - A terminal outside the cell coverage area searches for a synchronization signal, and if a synchronization signal is retrieved, the terminal performs synchronization using the synchronization signal.

[0169] -After synchronization, if the communication performed between the transmitting end and the receiving end is unicast and multicast communication, when transmitting the SL SS / PBCH block, the terminal within the cell coverage area can transmit the SL SS / PBCH block generated using the virtual cell ID.

[0170] ○ Virtual cell ID is used for unicast and multicast. For unicast and multicast, the virtual cell IDs may be set to be different from each other, or may be set to be the same.

[0171] ○ If the resource pools (time and frequency resource areas) for unicast and multicast are configured separately from the resource pool for broadcast, the virtual cell ID can be understood as the ID corresponding to the resource pools for unicast and multicast.

[0172] -Terminals outside the cell coverage area may adopt the SL SS / PBCH generated using the virtual cell ID as a measurement signal for RLM. In this case, terminals associated with unicast transmission or reception may adopt the SL SS / PBCH using the virtual cell ID for unicast as a measurement signal. Terminals associated with multicast transmission or reception may adopt the SL SS / PBCH using the virtual cell ID for multicast as a measurement signal. Alternatively, terminals associated with unicast and multicast transmission or reception may adopt the SL SS / PBCH using the virtual cell ID for unicast and multicast as a measurement signal.

[0173] ○ The terminal can reselect the SL SS / PBCH generated using the virtual cell ID as a new synchronization source, and can use this synchronization source to achieve synchronization.

[0174] According to the above method, in unicast and multicast communications, the SL SS / PBCH block can be used as a measurement signal effective for RLM.

[0175] <Fourth Embodiment>

[0176] The fourth embodiment describes in detail Alternative Scheme 3 in a method of using SL SS / PBCH blocks as measurement signals for RLM in unicast and multicast communications. Although this embodiment proposes a method of grouping physical cell IDs by distinguishing broadcast from unicast and multicast as a method of using SL SS / PBCH blocks as measurement signals for RLM, the proposal of the present disclosure is not limited to measurement signals for RLM. In other words, the content of the present disclosure may be a method of designing a synchronization signal for a side link. In an NR V2X system, in addition to broadcast communication, unicast and multicast communication may also be supported. In addition, as Figure 7 As described above, there may be situations where SL SS / PBCH is invalid as a measurement signal for RLM in unicast and multicast communications. Therefore, the synchronization signal needs to be designed to be suitable for the communication environment.

[0177] In the case of the NR system, there are 1008 physical cell IDs, and the physical cell IDs are divided into four groups. In this case, each group can include 252 unique physical cell IDs. In this case, the physical cell ID It can be expressed by the formula given below.

[0178] [Equation 1]

[0179]

[0180] In equation 1, represents the physical cell ID group, and Indicates the physical cell ID in the physical cell ID group.

[0181] In this case, the physical side link ID Can have ,According to the purpose of use, IDs can be divided into four groups as shown below.

[0182] Group 1: {0, 1, ..., 251}

[0183] Group 2: {252, 253, ..., 503}

[0184] Group 3: {504, 505, ..., 755}

[0185] Group 4: {755, 756, ..., 1007}

[0186] The physical side link ID is divided into four groups to distinguish between broadcast, unicast and multicast, and to identify whether the terminal transmitting the SL SS / PBCH block is within or outside the cell coverage area. Therefore, the physical cell ID group can be classified according to the following purposes.

[0187] - Broadcast within the coverage area

[0188] -Unicast and multicast within coverage area

[0189] - In case of out of coverage, broadcast

[0190] -Unicast and multicast in case of out-of-coverage

[0191] For example, grouping as shown below is possible. However, the order of grouping may be changed.

[0192] - Group 1: Broadcast within coverage,

[0193] - Group 2: Unicast and multicast in coverage situations

[0194] - Group 3: Broadcasting in case of out-of-coverage

[0195] - Group 4: Unicast and multicast in out-of-coverage situations

[0196] According to the above method, in unicast and multicast communications, the SL SS / PBCH block can be used as a measurement signal effective for RLM.

[0197] In connection with identifying in-coverage and out-of-coverage, if no cell having a frequency configured to perform sidelink operation and satisfying the S criterion (which is a criterion for cell selection or cell reselection) is detected, the terminal may determine that the terminal itself is out-of-coverage. TS 36.304 Section 11.4 describes this in detail.

[0198] Furthermore, whether the terminal performs broadcast, unicast, or multicast transmission or reception may be configured via a higher layer signal.

[0199] exist Figure 8 and Fig. 9 An apparatus for implementing an embodiment is shown in FIG.

[0200] Figure 8 FIG. 2 is a block diagram showing the internal structure of a terminal according to an embodiment. Figure 8As shown, the terminal may include a terminal receiver 800, a terminal transmitter 804 and a terminal processor 802. In this embodiment, the terminal receiver 800 and the terminal transmitter 804 are generally referred to as a transceiver. The transceiver can perform transmission or reception of a signal with a base station or another terminal. The signal may include a synchronization signal, a reference signal, control information and data. To this end, the transceiver includes an RF transmitter that up-converts and amplifies the frequency of the transmitted signal, an RF receiver that low-noise amplifies the received signal and down-converts the frequency, etc. In addition, the transceiver outputs a signal received via a wireless channel to the terminal processor 802, and transmits a signal output from the terminal processor 802 via a wireless channel. The terminal processor 802 can control a series of processes so that the terminal operates according to the above-mentioned embodiment.

[0201] Fig. 9 FIG. 4 is a block diagram showing the internal structure of a base station according to an embodiment. Fig. 9 As shown, the base station may include a base station receiver 901, a base station transmitter 905, and a base station processor 903. In an embodiment, the base station receiver 901 and the base station transmitter 905 are generally referred to as a transceiver. The transceiver can perform transmission or reception of a signal with a terminal. The signal may include a synchronization signal, control information, and data. To this end, the transceiver includes an RF transmitter that up-converts and amplifies the frequency of the transmitted signal, an RF receiver that low-noise amplifies the received signal and down-converts the frequency, and the like. In addition, the transceiver outputs a signal received via a wireless channel to the base station processor 903, and transmits a signal output from the base station processor 903 via a wireless channel. The base station processor 903 can control a series of processes so that the base station operates according to the above-mentioned embodiment.

[0202] In the above detailed embodiments of the present disclosure, the components included in the present disclosure are represented in the singular or plural, depending on the detailed embodiments presented. However, the singular form or plural form is selected to facilitate the description suitable for the presented situation, and the various embodiments of the present disclosure are not limited to its single element or multiple elements. In addition, multiple elements expressed in the specification can be configured as a single element, or a single element in the specification can be configured as multiple elements.

[0203] Although the embodiments have been described in the detailed description of the present disclosure, the present disclosure may be modified in various forms without departing from the scope of the present disclosure. Therefore, the scope of the present disclosure should not be defined as limited to the embodiments, but should be defined by the appended claims and their equivalents.

[0204] Although the present disclosure has been described with various embodiments, various changes and modifications may occur to those skilled in the art. The present disclosure is intended to encompass such changes and modifications as fall within the scope of the appended claims.

Claims

1. A method performed by a terminal in a communication system, the method comprising: sending data to another terminal on a side link; determining, based on sidelink hybrid automatic repeat request HARQ information for sidelink data, whether a radio link failure RLF associated with the sidelink is detected; as well as In case the RLF associated with the side link is detected, sending information indicating the occurrence of the RLF associated with the side link to a base station, The terminal is connected to the base station. wherein, in response to not receiving the sidelink HARQ information during a threshold period, determining that the RLF is detected, and The threshold starts from the timing of the last reception of the sidelink HARQ information.

2. The method according to claim 1, wherein: The threshold is preconfigured or configured by higher layer signaling received from the base station.

3. The method according to claim 1, wherein: The sidelink HARQ information includes HARQ-ACK or HARQ-NACK.

4. A terminal in a communication system, the terminal comprising: Transceiver; A controller configured to: sending data to another terminal on a side link via the transceiver, determining whether a radio link failure (RLF) associated with the sidelink is detected based on the sidelink hybrid automatic repeat request (HARQ) information for the sidelink data, and In case the RLF associated with the side link is detected, sending information indicating the occurrence of the RLF associated with the side link to a base station by the transceiver, The terminal is connected to the base station. wherein, in response to not receiving the sidelink HARQ information during a threshold period, determining that the RLF is detected, and The threshold starts from the timing of the last reception of the sidelink HARQ information.

5. The terminal according to claim 4, wherein: The threshold is preconfigured or configured by higher layer signaling received from the base station.

6. The terminal according to claim 4, wherein: The sidelink HARQ information includes HARQ-ACK or HARQ-NACK.

Images