Method and apparatus for reporting channel state information for sidelink communication

Abstract

A method and apparatus for reporting channel state information of sidelink communication are disclosed. An operation method of a first terminal includes the following steps: sending information indicating a delay bound value of an SL CSI report to a second terminal; sending an SCI including CSI request information to the second terminal; and performing a monitoring operation to receive the SL CSI of the second terminal within a time period corresponding to the delay bound value starting from the sending time of the CSI request information.

Description

Technical Field

[0001] The present disclosure relates to a sidelink communication technology, and more particularly, to a technology for reporting channel state information of sidelink communication. Background Art

[0002] In order to handle the rapidly increasing wireless data after the commercialization of the fourth-generation (4G) communication systems (e.g., Long Term Evolution (LTE) communication systems, LTE-Advanced (LTE-A) communication systems), a fifth-generation (5G) communication system (e.g., New Radio (NR) communication system) that uses the frequency bands of 4G communication systems (e.g., frequency bands below 6 GHz) and higher frequency bands than those of 4G communication systems (e.g., frequency bands above 6 GHz) is considered. The 5G communication system can support Enhanced Mobile Broadband (eMBB) communication, Ultra-Reliable and Low-Latency communication (URLLC), massive Machine Type Communication (mMTC), etc.

[0003] The 4G communication system and the 5G communication system support Vehicle-to-Everything (V2X) communication (e.g., sidelink communication). The V2X communication supported in cellular communication systems such as 4G communication systems and 5G communication systems may be referred to as "Cellular-V2X (C-V2X) communication". The V2X communication (e.g., C-V2X communication) may include Vehicle-to-Vehicle (V2V) communication, Vehicle-to-Infrastructure (V2I) communication, Vehicle-to-Pedestrian (V2P) communication, Vehicle-to-Network (V2N) communication, etc.

[0004] In a cellular communication system, Vehicle-to-Everything (V2X) communication (e.g., Cellular-V2X (C-V2X) communication) can be performed based on sidelink communication technologies (e.g., Proximity-based Service (ProSe) communication technology, Device-to-Device (D2D) communication technology, etc.). For example, a sidelink channel can be established for vehicles participating in Vehicle-to-Vehicle (V2V) communication, and the sidelink channel can be utilized for communication between vehicles. Configured grant (CG) resources can be used to perform sidelink communication. The CG resources can be configured periodically, and the CG resources can be used to transmit periodic data (e.g., periodic sidelink data).

[0005] On the other hand, sidelink communication can be performed based on broadcast schemes, multicast schemes, and / or unicast schemes. In particular, sidelink communication based on the unicast scheme may require channel state information between terminals. SUMMARY OF THE INVENTION

[0006] TECHNICAL PROBLEM

[0007] An object of the present disclosure for solving the above problems is to provide a method and apparatus for reporting channel state information of sidelink communication.

[0008] TECHNICAL SOLUTION

[0009] According to a first exemplary embodiment of the present disclosure for achieving the above object, an operation method of a first terminal may include the following steps: sending information indicating a delay bound value of sidelink (SL) channel state information (CSI) report to a second terminal; sending sidelink control information (SCI) including CSI request information to the second terminal; and performing a monitoring operation to receive the SL CSI of the second terminal within a time period corresponding to the delay bound value starting from the time of sending the CSI request information.

[0010] Wherein, the operation method may further include retransmitting the CSI request information when the SL CSI of the second terminal is not received within the time period.

[0011] Wherein, when retransmitting the CSI request information, a reset delay bound value may be used instead of the delay bound value, and the reset delay bound value may be greater than or less than the delay bound value.

[0012] Wherein, the delay bound value may be set specific to the sidelink.

[0013] Wherein, the delay bound value may be set in units of time slots.

[0014] Among them, the delay bound value can be a time offset starting from the time when the CSI request information is sent.

[0015] Among them, the delay bound value can be set independently of the type of SL CSI, and the type of SL CSI can vary according to the information included in the SL CSI.

[0016] Among them, the SL CSI can include a Channel Quality Indicator (CQI) and a Rank Indicator (RI).

[0017] Among them, the SL CSI can be received on the Physical Side-link Shared Channel (PSSCH).

[0018] According to a second exemplary embodiment of the present disclosure for achieving the above object, a method for operating a second terminal may include the following steps: receiving, from a first terminal, a Radio Resource Control (RRC) message including information indicating a delay bound value of a Side-link (SL) Channel State Information (CSI) report; receiving, from the first terminal, Side-link Control Information (SCI) including CSI request information; generating SL CSI by performing a measurement operation based on a reference signal received from the first terminal; and transmitting the SL CSI to the first terminal within a time period corresponding to the delay bound value starting from the time when the CSI request information is received.

[0019] Among them, when the time period ends, the SL CSI may not be transmitted to the first terminal.

[0020] Among them, the delay bound value can be set specific to the side-link.

[0021] Among them, the delay bound value can be set in units of time slots and can start from the time when the CSI request information is received.

[0022] Among them, the delay bound value can be set independently of the type of SL CSI, and the type of SL CSI can vary according to the information included in the SL CSI.

[0023] Among them, the SL CSI can include a Channel Quality Indicator (CQI) and a Rank Indicator (RI).

[0024] According to a third exemplary embodiment of the present disclosure for achieving the above object, a first terminal may include: a processor; and a memory configured to store at least one instruction run by the processor. The at least one instruction is run to: send a radio resource control message, i.e., an RRC message, including information indicating a latency bound value of a sidelink (SL) channel state information (CSI) report, to a second terminal; send sidelink control information (SCI) including CSI request information to the second terminal; and perform a monitoring operation to receive the SL CSI of the second terminal within a time period corresponding to the latency bound value starting from the time of sending the CSI request information.

[0025] Wherein, the at least one instruction may be further run to retransmit the CSI request information when the SL CSI of the second terminal is not received within the time period, and when retransmitting the CSI request information, a reset latency bound value may be used instead of the latency bound value, and the reset latency bound value may be greater than or less than the latency bound value.

[0026] Wherein, the latency bound value may be set specifically for the sidelink and may be used for unicast sidelink communication.

[0027] Wherein, the latency bound value may be set in units of time slots and may start from the time of sending the CSI request information.

[0028] Wherein, the SL CSI may include a channel quality indicator (CQI) and a rank indicator (RI).

[0029] Advantageous Effects

[0030] According to an exemplary embodiment of the present disclosure, a transmitting terminal may send information required to measure sidelink (SL) channel state information (CSI) to a receiving terminal. The receiving terminal may measure the SL CSI based on the information received from the transmitting terminal and may send the SL CSI to the transmitting terminal. In particular, the SL CSI may be sent within a preconfigured time period. The transmitting terminal may perform sidelink communication with the receiving terminal based on the SL CSI. Therefore, the performance of sidelink communication can be improved. Brief Description of the Drawings

[0031] Figure 1 is a conceptual diagram showing a V2X communication scenario.

[0032] Figure 2 is a conceptual diagram showing an exemplary embodiment of a cellular communication system.

[0033] Figure 3 is a conceptual diagram showing an exemplary embodiment of a communication node constituting a cellular communication system.

[0034] Figure 4It is a block diagram showing an exemplary embodiment of the user plane protocol stack of a UE performing sidelink communication.

[0035] Figure 5 It is a block diagram showing a first exemplary embodiment of the control plane protocol stack of a UE performing sidelink communication.

[0036] Figure 6 It is a block diagram showing a second exemplary embodiment of the control plane protocol stack of a UE performing sidelink communication.

[0037] Figure 7 It is a sequence diagram showing a first exemplary embodiment of a method for reporting SL CSI.

[0038] Figure 8 It is a sequence diagram showing a second exemplary embodiment of a method for reporting SL CSI.

[0039] Figure 9 It is a sequence diagram showing a third exemplary embodiment of a method for reporting SL CSI.

[0040] Figure 10 It is a timing diagram showing a first exemplary embodiment of the transmission period of SL CSI.

[0041] Figure 11 It is a sequence diagram showing a fourth exemplary embodiment of a method for reporting SL CSI.

[0042] Figure 12 It is a sequence diagram showing a fifth exemplary embodiment of a method for reporting SL CSI. Detailed Description

[0043] Although the present invention may have various modifications and alternative forms, specific embodiments are shown by way of example in the drawings and are described in detail. However, it should be understood that this description is not intended to limit the present invention to the specific embodiments, but on the contrary, the present invention will cover all modifications, equivalent forms, and alternative forms falling within the spirit and scope of the present invention.

[0044] Although terms such as "first", "second", etc. may be used herein with respect to various elements, these elements should not be construed as being limited by these terms. These terms are only used to distinguish one element from another. For example, without departing from the scope of the present invention, the first element may be referred to as the second element, and the second element may be referred to as the first element. The term "and / or" includes any combination and all combinations of one or more of the related listed items.

[0045] It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element, or intervening elements may be present. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, no intervening elements are present.

[0046] The terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the embodiments of the present invention. As used herein, the singular forms are also intended to include the plural forms unless the context clearly indicates otherwise. It will be further understood that when used herein, the terms "comprises," "comprising," "includes," and / or "including" specify the presence of the stated features, integers, steps, operations, elements, parts, and / or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, parts, and / or combinations thereof.

[0047] Unless otherwise defined, all terms, including technical and scientific terms, used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms defined in a general dictionary should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0048] Hereinafter, preferred exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In describing the present invention, for the sake of overall understanding, the same reference numerals refer to the same elements throughout the description of the drawings, and their repeated description will be omitted.

[0049] Figure 1 is a conceptual diagram showing a V2X communication scenario. As Figure 1 shown, V2X communication may include vehicle-to-vehicle (V2V) communication, vehicle-to-infrastructure (V2I) communication, vehicle-to-pedestrian (V2P) communication, vehicle-to-network (V2N) communication, etc. V2X communication may be supported by a cellular communication system (e.g., cellular communication system 140), and the V2X communication supported by the cellular communication system 140 may be referred to as "cellular-V2X (C-V2X) communication." Here, the cellular communication system 140 may include a 4G communication system (e.g., an LTE communication system or an LTE-A communication system), a 5G communication system (e.g., an NR communication system), etc.

[0050] V2V communication may include communication between a first vehicle 100 (e.g., a communication node located in vehicle 100) and a second vehicle 110 (e.g., a communication node located in vehicle 110). Various driving information such as speed, heading, time, location, etc. may be exchanged between vehicle 100 and vehicle 110 through V2V communication. For example, autonomous driving (e.g., platooning) may be supported based on the driving information exchanged through V2V communication. V2V communication supported in the cellular communication system 140 may be performed based on "sidelink" communication technologies (such as ProSe and D2D communication technologies, etc.). In particular, at least one sidelink channel established between vehicle 100 and vehicle 110 may be utilized to perform communication between vehicle 100 and vehicle 110.

[0051] V2I communication may include communication between vehicle #1 100 and infrastructure located by the roadside (e.g., a roadside unit (RSU) 120). The infrastructure 120 may also include traffic lights or street lights located by the roadside. For example, when performing V2I communication, communication may be performed between a communication node located in vehicle #1 100 and a communication node located in a traffic light. Traffic information, driving information, etc. may be exchanged between vehicle #1 100 and infrastructure 120 through V2I communication. V2I communication supported in the cellular communication system 140 may also be performed based on sidelink communication technologies (such as ProSe communication technology and D2D communication technology, etc.). In particular, a sidelink channel may be utilized to perform communication between vehicle #1 100 and infrastructure 120.

[0052] V2P communication may include communication between vehicle #1 100 (e.g., a communication node located in vehicle #1 100) and a person 130 (e.g., a communication node carried by person 130). Driving information of vehicle #1 100 such as speed, heading, time, location, etc. and movement information of person 130 may be exchanged between vehicle #1 100 and person 130 through V2P communication. A communication node located inside vehicle #1 100 or a communication node carried by person 130 may be configured to generate an alarm indicating danger by judging a dangerous situation based on the obtained driving information and movement information. V2P communication supported in the cellular communication system 140 may be performed based on sidelink communication technologies (such as ProSe communication technology and D2D communication technology, etc.). In particular, at least one sidelink channel may be utilized to perform communication between a communication node located in vehicle #1 100 or a communication node carried by person 130.

[0053] V2N communication may be communication between vehicle #1 100 (e.g., a communication node located in vehicle #1 100) and a server connected via a cellular communication system 140 (e.g., a cellular communication network). V2N communication may be performed based on 4G communication technology (e.g., LTE or LTE-A specified by the 3GPP standard) or 5G communication technology (e.g., NR specified by the 3GPP standard). Additionally, V2N communication may be performed based on Wireless Access in Vehicular Environments (WAVE) communication technology or Wireless Local Area Network (WLAN) communication technology defined in Institute of Electrical and Electronics Engineers (IEEE) 802.11, or based on Wireless Personal Area Network (WPAN) communication technology defined in IEEE 802.15.

[0054] On the other hand, the cellular communication system 140 supporting V2X communication may be configured as follows.

[0055] Figure 2 It is a conceptual diagram showing an exemplary embodiment of a cellular communication system.

[0056] As Figure 2 shown, the cellular communication system may include an access network, a core network, etc. The access network may include base stations 210, repeaters 220, user equipments (UEs) 231 to 236, etc. UEs 231 to 236 may include communication nodes located in Figure 1 vehicles 100 and 110, communication nodes located in Figure 1 infrastructure 120, Figure 1 communication nodes carried by persons 130, etc. When the cellular communication system supports 4G communication technology, the core network may include a Serving Gateway (S-GW) 250, a Packet Data Network (PDN) Gateway (P-GW) 260, a Mobility Management Entity (MME) 270, etc.

[0057] When the cellular communication system supports 5G communication technology, the core network may include a User Plane Function (UPF) 250, a Session Management Function (SMF) 260, an Access and Mobility Management Function (AMF) 270, etc. Alternatively, when the cellular communication system operates in a Non-Stand Alone (NSA) mode, the core network composed of an S-GW 250, a P-GW 260, and an MME 270 can support both 4G and 5G communication technologies, and the core network composed of a UPF 250, an SMF 260, and an AMF 270 can support both 5G and 4G communication technologies.

[0058] In addition, when the cellular communication system supports network slicing technology, the core network can be divided into multiple logical network slices. For example, a network slice supporting V2X communication (such as a V2V network slice, a V2I network slice, a V2P network slice, a V2N network slice, etc.) can be configured, and V2X communication can be supported through the V2X network slice configured in the core network.

[0059] Communication nodes (e.g., base stations, repeaters, UEs, S-GWs, P-GWs, MMEs, UPFs, SMFs, AMFs, etc.) that make up a cellular communication system can be configured to perform communication using at least one of the following communication technologies: Code Division Multiple Access (CDMA) technology, Time Division Multiple Access (TDMA) technology, Frequency Division Multiple Access (FDMA) technology, Orthogonal Frequency Division Multiplexing (OFDM) technology, Filtered OFDM technology, Orthogonal Frequency Division Multiple Access (OFDMA) technology, Single-Carrier FDMA (SC-FDMA) technology, Non-Orthogonal Multiple Access (NOMA) technology, Generalized Frequency Division Multiplexing (GFDM) technology, Filter Bank Multi-Carrier (FBMC) technology, Universal Filtered Multi-Carrier (UFMC) technology, and Space Division Multiple Access (SDMA) technology.

[0060] Communication nodes (e.g., base stations, repeaters, UEs, S-GWs, P-GWs, MMEs, UPFs, SMFs, AMFs, etc.) that make up a cellular communication system can be configured as follows.

[0061] Figure 3 It is a conceptual diagram showing an exemplary embodiment of a communication node that makes up a cellular communication system.

[0062] As Figure 3 shown, the communication node 300 may include at least one processor 310, a memory 320, and a transceiver 330 connected to a network for performing communication. Additionally, the communication node 300 may further include an input interface device 340, an output interface device 350, a storage device 360, etc. Each component included in the communication node 300 may be configured to communicate with each other when connected via a bus 370.

[0063] However, each component included in the communication node 300 may be connected to the processor 310 through a separate interface or a separate bus instead of the common bus 370. For example, the processor 310 may be connected to at least one of the memory 320, the transceiver 330, the input interface device 340, the output interface device 350, and the storage device 360 through a dedicated interface.

[0064] The processor 310 may be configured to run at least one instruction stored in at least one of the memory 320 and the storage device 360. The processor 310 may refer to a central processing unit (CPU), a graphics processing unit (GPU), or a dedicated processor that executes the method according to an embodiment of the present disclosure. Each of the memory 320 and the storage device 360 may include at least one of a volatile storage medium and a non-volatile storage medium. For example, the memory 320 may include at least one of a read-only memory (ROM) and a random access memory (RAM).

[0065] Referring back to Figure 2 , in the communication system, the base station 210 may form a macro cell or a small cell, and may be connected to the core network through an ideal backhaul or a non-ideal backhaul. The base station 210 may be configured to send the signals received from the core network to the UEs 231 to 236 and the repeater 220, and may be configured to send the signals received from the UEs 231 to 236 and the repeater 220 to the core network. The UEs #1 231, #2 232, #4 234, #5 235, and #6 236 may belong to the cell coverage area of the base station 210. The UEs #1 231, #2 232, #4 234, #5 235, and #6 236 may connect to the base station 210 by performing a connection establishment process with the base station. The UEs #1 231, #2 232, #4 234, #5 235, and #6 236 may communicate with the base station 210 after connecting to the base station 210.

[0066] The repeater 220 can be connected to the base station 210 and can be configured to relay communications between the base station 210 and the UEs #3 233 and #4 234. In other words, the repeater 220 can be configured to send the signals received from the base station 210 to the UEs #3 233 and #4 234, and send the signals received from the UEs #3 233 and #4 234 to the base station 210. The UE #4 234 can belong to both the cell coverage of the base station 210 and the cell coverage of the repeater 220, while the UE #3 233 can belong to the cell coverage of the repeater 220. In other words, the UE #3 233 can be located outside the cell coverage of the base station 210. The UEs #3 233 and #4 234 can be connected to the repeater 220 by performing a connection establishment procedure with the repeater 220. The UEs #3 233 and #4 234 can be configured to communicate with the repeater 220 after being connected to the repeater 220.

[0067] The base station 210 and the repeater 220 can support multiple-input multiple-output (MIMO) technologies (e.g., single-user (SU)-MIMO, multi-user (MU)-MIMO, massive MIMO, etc.), coordinated multipoint (CoMP) communication technologies, carrier aggregation (CA) communication technologies, unlicensed band communication technologies (e.g., licensed assisted access (LAA), enhanced LAA (eLAA), etc.), sidelink communication technologies (e.g., ProSe communication technology, D2D communication technology), etc. The UEs #1 231, #2 232, #5 235, and #6 236 can be configured to perform operations corresponding to the base station 210 and operations supported by the base station 210. The UEs #3 233 and #4 234 can be configured to perform operations corresponding to the repeater 220 and operations supported by the repeater 220.

[0068] In particular, the base station 210 can be referred to as a Node B (NB), an evolved Node B (eNB), a Base Transceiver Station (BTS), a Radio Remote Head (RRH), a Transmission Reception Point (TRP), a Radio Unit (RU), a Road Side Unit (RSU), a radio transceiver, an access point, an access node, etc. The repeater 220 can be referred to as a small base station, a relay node, etc. Each of UE#1 231 to UE#6 236 can be referred to as a terminal, an access terminal, a mobile terminal, a station, a subscriber station, a mobile station, a portable subscriber station, a node, a device, an On-Broad Unit (OBU), etc.

[0069] On the other hand, the communication between UE#5 235 and UE#6 236 can be performed based on sidelink communication technologies (e.g., ProSe communication technology, D2D communication technology). The sidelink communication can be performed based on a one-to-one scheme or a one-to-many scheme. When performing V2V communication using sidelink communication technology, UE#5 235 can be a communication node in Figure 1 vehicle #1 100 located at Figure 1 and UE#6 236 can be a communication node in Figure 1 vehicle #2 110 located at Figure 1 When performing V2I communication using sidelink communication technology, UE#5 235 can be a communication node in Figure 1 vehicle #1 100 located at Figure 1 and UE#6 236 can be a communication node in

[0070] infrastructure 120 located at Figure 2 When performing V2P communication using sidelink communication technology, UE#5 235 can be a communication node in

[0071] [Table 1]

[0072] Side link communication scenario Location of UE#5 235 Location of UE#6 236 #A Outside the coverage area of base station 210 Outside the coverage area of base station 210 #B Within the coverage area of base station 210 Outside the coverage area of base station 210 #C Within the coverage area of base station 210 Within the coverage area of base station 210 #D Within the coverage area of base station 210 Within the coverage area of other base stations

[0073] On the other hand, the user plane protocol stack of the UEs (e.g., UE#5 235 and UE#6 236) performing sidelink communication can be configured as follows.

[0074] Figure 4 is a block diagram showing an exemplary embodiment of the user plane protocol stack of a UE performing sidelink communication.

[0075] As Figure 4 shown, UE#5 235 can be Figure 2 the UE#5 235 shown in Figure 2 and UE#6 236 can be the UE#6 236 shown in. The sidelink communication scenario between UE#5 235 and UE#6 236 can be one of sidelink communication scenarios #A to #D in Table 1. The user plane protocol stack of each of UE#5 235 and UE#6 236 can include a Physical (PHY) layer, a Medium Access Control (MAC) layer, a Radio Link Control (RLC) layer, and a Packet Data Convergence Protocol (PDCP) layer.

[0076] The sidelink communication between UE#5 235 and UE#6 236 can be performed using a PC5 interface (e.g., PC5-U interface). Layer 2 identifiers (IDs) (e.g., source layer 2 ID, destination layer 2 ID) can be used for sidelink communication, and the layer 2 ID can be an ID configured for V2X communication (e.g., V2X service). Additionally, in sidelink communication, hybrid automatic repeat request (HARQ) feedback operations can be supported, and RLC acknowledged mode (RLC AM) or RLC unacknowledged mode (RLC UM) can be supported.

[0077] On the other hand, the control plane protocol stack of the UEs (e.g., UE#5 235 and UE#6 236) performing sidelink communication can be configured as follows.

[0078] Figure 5 is a block diagram showing a first exemplary embodiment of the control plane protocol stack of a UE performing sidelink communication, Figure 6 is a block diagram showing a second exemplary embodiment of the control plane protocol stack of a UE performing sidelink communication.

[0079] As Figure 5 and Figure 6 shown, UE#5 235 can be Figure 2The UE#5 235 shown in Figure 2 the UE#6 236 shown in. The scenario of sidelink communication between the UE#5 235 and the UE#6 236 can be one of the sidelink communication scenarios #A to #D in Table 1. Figure 5 The control plane protocol stack shown in can be a control plane protocol stack for sending and receiving broadcast information (e.g., Physical Sidelink Broadcast Channel (PSBCH)).

[0080] Figure 5 The control plane protocol stack shown in can include a PHY layer, a MAC layer, an RLC layer, and a Radio Resource Control (RRC) layer. The sidelink communication between the UE#5 235 and the UE#6 236 can be performed using a PC5 interface (e.g., a PC5-C interface). Figure 6 The control plane protocol stack shown in can be a control plane protocol stack for one-to-one sidelink communication. Figure 6 The control plane protocol stack shown in can include a PHY layer, a MAC layer, an RLC layer, a PDCP layer, and a PC5 signaling protocol layer.

[0081] On the other hand, the channels used in the sidelink communication between the UE#5 235 and the UE#6 236 can include a Physical Sidelink Shared Channel (PSSCH), a Physical Sidelink Control Channel (PSCCH), a Physical Sidelink Discovery Channel (PSDCH), and a Physical Sidelink Broadcast Channel (PSBCH). The PSSCH can be used to send and receive sidelink data and can be configured in a UE (e.g., the UE#5 235 or the UE#6 236) by higher layer signaling. The PSCCH can be used to send and receive sidelink control information (SCI) and can also be configured in a UE (e.g., the UE#5 235 or the UE#6 236) by higher layer signaling.

[0082] The PSDCH can be used for the discovery process. For example, discovery signals can be sent via the PSDCH. The PSBCH can be used to send and receive broadcast information (e.g., system information). Additionally, demodulation reference signals (DM-RS), synchronization signals, etc. can be used in sidelink communication between UE#5 235 and UE#6 236. The synchronization signals can include a primary sidelink synchronization signal (PSSS) and a secondary sidelink synchronization signal (SSSS).

[0083] On the other hand, sidelink transmission modes (TM) can be classified into sidelink TM#1 to TM#4 as shown in Table 2 below.

[0084] [Table 2]

[0085]

[0086]

[0087] When sidelink TM#3 or TM#4 is supported, each of UE#5 235 and UE#6 236 can be configured to perform sidelink communication using a resource pool configured by the base station 210. The resource pool can be configured for each of sidelink control information and sidelink data.

[0088] The resource pool for sidelink control information can be configured based on RRC signaling procedures (e.g., dedicated RRC signaling procedures, broadcast RRC signaling procedures). The resource pool for receiving sidelink control information can be configured via a broadcast RRC signaling procedure. When sidelink TM#3 is supported, the resource pool for sending sidelink control information can be configured via a dedicated RRC signaling procedure. In particular, sidelink control information can be sent via resources scheduled by the base station 210 within the resource pool configured by the dedicated RRC signaling procedure. When sidelink TM#4 is supported, the resource pool for sending sidelink control information can be configured via a dedicated RRC signaling procedure or a broadcast RRC signaling procedure. In particular, sidelink control information can be sent via resources autonomously selected by the UE (e.g., UE#5 235 or UE#6 236) within the resource pool configured by the dedicated RRC signaling procedure or the broadcast RRC signaling procedure.

[0089] When side - link TM#3 is supported, a resource pool for transmitting and receiving side - link data may not be configured. In particular, side - link data can be transmitted and received through resources scheduled by the base station 210. When side - link TM#4 is supported, a resource pool for transmitting and receiving side - link data can be configured through a dedicated RRC signaling procedure or a broadcast RRC signaling procedure. In particular, side - link data can be transmitted and received through resources autonomously selected by a UE (e.g., UE#5 235 or UE#6 236) in a resource pool configured by a dedicated RRC signaling procedure or a broadcast RRC signaling procedure.

[0090] In the following, a method for re - transmitting side - link data will be described. In an exemplary embodiment, a HARQ response may be referred to as a "HARQ acknowledgement (HARQ - ACK)". A HARQ response can be an ACK or a negative ACK (NACK). Even when describing a method (e.g., transmission or reception of a signal) to be performed at a first communication node in a communication node, a corresponding second communication node can perform a method corresponding to the method performed at the first communication node (e.g., reception or transmission of a signal). In other words, when describing the operation of UE#1 (e.g., vehicle#1), a corresponding UE#2 (e.g., vehicle#2) can be configured to perform an operation corresponding to the operation of UE#1. Conversely, when describing the operation of UE#2, the corresponding UE#1 can be configured to perform an operation corresponding to the operation of UE#2. In the exemplary embodiments described below, the operation of a vehicle can be the operation of a communication node located in the vehicle.

[0091] In an exemplary embodiment, a signaling can be one or a combination of two or more of a high - layer signaling, a MAC signaling, and a physical (PHY) signaling. A message for high - layer signaling can be referred to as a "high - layer message" or a "high - layer signaling message". A message for MAC signaling can be referred to as a "MAC message" or a "MAC signaling message". A message for PHY signaling can be referred to as a "PHY message" or a "PHY signaling message". High - layer signaling can refer to operations of transmitting and receiving system information (e.g., Master Information Block (MIB), System Information Block (SIB)) and / or RRC messages. MAC signaling can refer to operations of transmitting and receiving MAC control elements (CE). PHY signaling can refer to operations of transmitting and receiving control information (e.g., Downlink Control Information (DCI), Uplink Control Information (UCI), SCI).

[0092] The sidelink signal can be a synchronization signal and a reference signal for sidelink communication. For example, the synchronization signal can be a Synchronization Signal / Physical Broadcast Channel (SS / PBCH) block, a Sidelink Synchronization Signal (SLSS), a Primary Sidelink Synchronization Signal (PSSS), a Secondary Sidelink Synchronization Signal (SSSS), etc. The reference signal can be a Channel State Information-Reference Signal (CSI-RS), a DM-RS, a Phase Tracking-Reference Signal (PT-RS), a Cell Specific Reference Signal (CRS), a Sounding Reference Signal (SRS), a Discovery Reference Signal (DRS), etc.

[0093] The sidelink channel can be a PSSCH, a PSCCH, a PSDCH, a PSBCH, a Physical Sidelink Feedback Channel (PSFCH), etc. Additionally, the sidelink channel can refer to a sidelink channel including a sidelink signal mapped to a specific resource in the corresponding sidelink channel. Sidelink communication can support broadcast services, multicast services, groupcast services, and unicast services.

[0094] Sidelink communication can be performed based on a single SCI scheme or a multi-SCI scheme. When using the single SCI scheme, data transmission (e.g., sidelink data transmission, Sidelink-Shared Channel (SL-SCH) transmission) can be performed based on a single SCI (e.g., the 1st-stage SCI). When using the multi-SCI scheme, two SCIs (e.g., the 1st-stage SCI and the 2nd-stage SCI) can be used to perform data transmission. The SCI can be sent through the PSCCH and / or the PSSCH. When using the single SCI scheme, the SCI (e.g., the 1st-stage SCI) can be sent through the PSCCH. When using the multi-SCI scheme, the 1st-stage SCI can be sent through the PSCCH, and the 2nd-stage SCI can be sent through the PSCCH or the PSSCH. The 1st-stage SCI can be referred to as the "First-stage SCI", and the 2nd-stage SCI can be referred to as the "Second-stage SCI".

[0095] The first-stage SCI may include one or more of the following information elements: priority information, frequency resource allocation information, time resource allocation information, resource reservation period information, DMRS mode information, second-stage SCI format information, beta_offset indicator, number of DMRS ports, and modulation and coding scheme (MCS) information. The second-stage SCI may include one or more of the following information elements: HARQ process identifier (ID), redundancy version (RV), source ID, destination ID, CSI request information, region ID, and communication range requirement.

[0096] On the other hand, sidelink communication may require channel state information (CSI) between terminals. In other words, sidelink communication may be performed based on CSI. CSI may include one or more of the following: Channel Quality Indicator (CQI), Rank Indicator (RI), and Precoding Matrix Indicator (PMI). Additionally, CSI may further include Reference Signal Received Power (RSRP), Reference Signal Received Quality (RSRQ), and / or Received Signal Strength Indicator (RSSI). In the following exemplary embodiments, methods for triggering an SL CSI report, methods for triggering SL CSI measurement, methods for configuring SL CSI measurement, methods for configuring an SL CSI report, etc. will be described. SL CSI may represent CSI for sidelink communication. In the following exemplary embodiments, CSI may represent SL CSI.

[0097] Figure 7 is a sequence diagram showing a first exemplary embodiment of a method for reporting SL CSI. Refer to Figure 7 , the communication system may include a first terminal and a second terminal. Sidelink communication may be performed between the first terminal and the second terminal. The first terminal may be Figure 2 UE#5235 shown in Figure 2 , and the second terminal may be Figure 3 UE#6236 shown in Figures 4 to 6The protocol stack shown. Each of the first terminal and the second terminal may support the sidelink TM defined in Table 2. The first terminal that transmits reference signals (e.g., CSI-RS, DMRS) may be referred to as the transmitting (Tx) terminal, and the second terminal that receives the reference signals may be referred to as the receiving (Rx) terminal.

[0098] The first terminal may be configured to generate information indicating the triggering of an SL CSI report. The triggering of the SL CSI report may be indicated implicitly or explicitly. In an exemplary embodiment, the "information indicating the triggering of an SL CSI report" may be referred to as "trigger indication information". The trigger indication information may indicate whether to trigger the SL CSI report. The trigger indication information may be included in at least one of the Phase 1 SCI and / or the Phase 2 SCI. For example, the CSI request information included in the Phase 2 SCI may be used as the trigger indication information. The first terminal may be configured to send the trigger indication information (e.g., an SCI including the trigger indication information) to the second terminal (S701). The second terminal may be configured to receive the SCI from the first terminal and identify the trigger indication information included in the SCI. The second terminal may be configured to determine that the SL CSI report is triggered based on the trigger indication information.

[0099] The first terminal may be configured to transmit a reference signal (e.g., SL CSI-RS) (S702). The SL CSI-RS may be a CSI-RS for sidelink communication. Resources configured by a base station (e.g., the base station to which the first terminal is connected) may be utilized to transmit the reference signal. When the SL CSI report is triggered, the second terminal may be configured to perform a measurement operation based on the reference signal received from the first terminal (S703). The second terminal may be configured to generate an SL CSI based on the result of the measurement operation. The SL CSI may include one or more of CQI, RI, and PMI. The SL CSI may be instantaneous channel state information and / or cumulative channel state information (e.g., statistical channel state information, average channel state information). The SL CSI may be wideband channel state information.

[0100] The second terminal may be configured to send SL CSI to the first terminal (S704). For example, the second terminal may be configured to perform a sensing operation on sidelink resources, and when it is determined through the sensing operation that the sidelink resources are in an idle state, the second terminal may be configured to use the sidelink resources to send SL CSI. The SL CSI may be sent on a sidelink channel (e.g., PSSCH, PSCCH, PSFCH). For example, a MAC control element (CE) including the SL CSI may be sent on the sidelink channel. When a MAC CE including the SL CSI is sent on the PSSCH, the SL CSI may be multiplexed with the sidelink data in the PSSCH. The first terminal may be configured to receive the SL CSI from the second terminal and perform sidelink communication based on the SL CSI (e.g., sidelink communication based on a unicast scheme).

[0101] The time for sending the SL CSI (e.g., the latency bound value of the SL SCI report) may be set based on at least one of system information, RRC signaling, MAC signaling, and PHY signaling. The time for sending the SL CSI may be referred to as "sl-LatencyBound-CSI-Report". The time for sending the SL CSI may be set by the base station and / or the first terminal. For example, the first terminal (i.e., the sending terminal) may be configured to send an RRC message (e.g., an RRC reconfiguration sidelink message) including information indicating the time for sending the SL CSI (e.g., sl-LatencyBound-CSI-Report) to the second terminal. The information indicating the time for sending the SL CSI may be used for unicast-based sidelink communication between the first terminal and the second terminal. The time for sending the SL CSI may be set to a fixed value in the communication system.

[0102] The time for sending the SL CSI may be set specific to a resource pool, specific to an SL (e.g., specific to a link), or specific to a terminal dedicated (e.g., specific to a UE). The time for sending the SL CSI may be set in units of time slots and may indicate the latency bound starting from the time of receiving the trigger indication information (e.g., the time slot of receiving the stage 2 SCI). In other words, the time for sending the SL CSI may be indicated by a time slot offset starting from the time of receiving the stage 2 SCI including the trigger indication information (e.g., CSI request information). Alternatively, the time for sending the SL CSI may be indicated by a time slot offset starting from the time of receiving the stage 1 SCI associated with the stage 2 SCI including the trigger indication information (e.g., CSI request information). The time for sending the SL CSI may be set to one of 3 to 160.

[0103] In an exemplary embodiment, the time when the trigger indication information is received (or the time when the trigger indication information is sent) may be referred to as "N", and the time when the SL CSI is sent (or the time when the SL CSI is received) may be referred to as "K". In other words, K may be the delay bound value of the SL CSI report. N may indicate a specific symbol, a specific hour slot, a specific time slot, or a specific subframe within the time period for triggering the SL CSI report. K may be a time offset. Each of N and K may be set in units of symbols, hour slots, time slots, or subframes. Each of N and K may be an integer greater than or equal to 0. The time unit of N may be the same as the time unit of K. Alternatively, the time unit of N may be different from the time unit of K.

[0104] When the time unit of N is the same as the time unit of K, the time when the SL CSI is sent may be the (N + K)-th time slot after K time slots starting from the N-th time slot. In particular, the SL CSI may be sent in the (N + K)-th time slot. When the time unit is a subframe, the time when the SL CSI is sent may be the (N + K)-th subframe after K subframes starting from the N-th subframe. The time when the SL CSI is sent may be set based on a time unit other than the above time units. Even when the exemplary embodiment is described based on time slots, the exemplary embodiment may be applied to other time units (e.g., symbols, hour slots, subframes).

[0105] In a communication system, K (e.g., time offset, time slot offset) may be set to a fixed value, and the SL CSI report may be configured to be performed before the (N + K)-th time slot. The base station may be configured to set K and send system information (e.g., MIB, SIB) including K. Alternatively, the first terminal (e.g., the sending terminal) may be configured to set K and send a message (e.g., an RRC message) including K. In particular, K may be fixed to a value. When the SL CSI is not received in the (N + K)-th time slot, the first terminal (e.g., the sending terminal) may be configured to determine that the trigger indication information has not been applied to the second terminal (e.g., the receiving terminal). Alternatively, the first terminal may be configured to determine that the second terminal fails to reserve (e.g., ensure) resources for the SL CSI report. In particular, the first terminal may be configured to retransmit the trigger indication information to the second terminal to request the SL CSI report.

[0106] In addition, K (e.g., the time for sending SL CSI) can be set by RRC signaling and / or MAC signaling (e.g., MAC CE). Additionally, K can be set specific to a resource pool, specific to an SL (e.g., specific to a link), or specific to a terminal. When K is set specific to a resource pool, K can be included in the configuration information of the resource pool, and the configuration information of the resource pool can be sent by RRC signaling and / or MAC signaling. In particular, the same K can be used within the corresponding resource pool. When K is set specific to an SL, K can be included in the configuration information of the sidelink, and the configuration information of the sidelink can be sent by RRC signaling and / or MAC signaling. In particular, the same K can be used in the corresponding sidelink. When K is set specific to a terminal, K can be included in the dedicated configuration information, and the dedicated configuration information can be sent by RRC signaling and / or MAC signaling. In this case, K can be set independently for each terminal.

[0107] Moreover, K set by RRC signaling and / or MAC signaling can be semi-static information. Thus, K can be variable. For example, K can be changed by a combination of "RRC signaling and / or MAC signaling" and PHY signaling (e.g., SCI). Or, K can be changed only by using PHY signaling. In other words, K can be changed dynamically.

[0108] Table 3

[0109] Information bit K 00 4 01 6 10 8 11 12

[0110] The information bits of K defined in Table 3 can be set by higher layer signaling and / or system information. Two information bits can be used to indicate four K values. K can be sent together with trigger indication information.

[0111] Figure 8 is a sequence diagram showing a second exemplary embodiment of a method for reporting SL CSI.

[0112] Referring to Figure 8 , the communication system can include a first terminal and a second terminal. Sidelink communication can be performed between the first terminal and the second terminal. The first terminal can be Figure 2 UE#5 235 shown in Figure 2 , and the second terminal can be Figure 3 UE#6 236 shown in Figures 4 to 6The protocol stack shown in. Each of the first terminal and the second terminal may support the sidelink TM defined in Table 2. The first terminal that transmits reference signals (e.g., CSI-RS, DMRS) may be referred to as the transmitting (Tx) terminal, and the second terminal that receives the reference signals may be referred to as the receiving (Rx) terminal.

[0113] The first terminal may be configured to send feedback indication information and K (S801) to the second terminal. The feedback indication information and K may be included in the SCI (e.g., Phase 1 SCI and / or Phase 2 SCI). In another exemplary embodiment, K may be included in an RRC message sent from the first terminal, and the feedback indication information may be included in the SCI sent from the first terminal. Alternatively, the feedback indication information and K may be sent by the base station instead of the first terminal. For example, the base station may be configured to send an RRC message containing the feedback indication information and K. In particular, the feedback indication information may be "sl-CSI-Acquisition", and K may be "sl-LatencyBound-CSI-Report".

[0114] The second terminal may be configured to receive the feedback indication information and K from the first terminal or the base station. The second terminal may be configured to determine to trigger an SL CSI report based on the feedback indication information. K may start from the time when the feedback indication information is received. Accordingly, the second terminal may be configured to start a timer corresponding to K from the time when the feedback indication information is received.

[0115] The first terminal may be configured to transmit a reference signal (e.g., SL CSI-RS) (S802). The SL CSI-RS may be a CSI-RS for sidelink communication. Resources configured by the base station (e.g., the base station to which the first terminal is connected) may be used to transmit the reference signal. When an SL CSI report is triggered, the second terminal may be configured to perform a measurement operation based on the reference signal received from the first terminal (S803). The second terminal may be configured to generate an SL CSI based on the result of the measurement operation. The SL CSI may include one or more of CQI, RI, and PMI.

[0116] When the timer corresponding to K has not expired, the second terminal may be configured to send SL CSI to the first terminal (S804). In other words, the SL CSI may be sent within K from the time when the trigger indication information is received. On the other hand, when the timer corresponding to K expires, the second terminal may not send the SL CSI. In other words, after K from the time when the trigger indication information is received, the SL CSI may not be sent. The SL CSI may be sent on a sidelink channel (e.g., PSSCH, PSCCH, PSFCH). The first terminal may be configured to receive the SL CSI from the second terminal and may perform sidelink communication based on the SL CSI (e.g., sidelink communication based on a unicast scheme).

[0117] Figure 9 is a sequence diagram showing a third exemplary embodiment of a method for reporting SL CSI.

[0118] Referring to Figure 9 , the communication system may include a first terminal and a second terminal. Sidelink communication may be performed between the first terminal and the second terminal. The first terminal may be Figure 2 UE#5 235 shown in Figure 2 , and the second terminal may be Figure 3 UE#6 236 shown in Figures 4 to 6 . Each of the first terminal and the second terminal may be configured the same as or similar to the communication node 300 shown in

[0119] . Each of the first terminal and the second terminal may support Figure 8 the protocol stack shown in Figure 8 . Each of the first terminal and the second terminal may support the sidelink TM defined in Table 2. The first terminal that transmits a reference signal (e.g., CSI-RS, DMRS) may be referred to as a transmitting (Tx) terminal, and the second terminal that receives the reference signal may be referred to as a receiving (Rx) terminal. Figure 8 Step S901 may be performed the same as or similar to step S801 shown in

[0120] Figure 10 . Step S902 may be performed the same as or similar to step S802 shown in

[0121] Referring to Figure 10, the time slot that receives the trigger indication information (e.g., the trigger indication information and K) can be time slot #N, and K can be set to 6. In this case, the transmission period of the SL CSI (e.g., the monitoring period of the SL CSI) can be from the end point of time slot #N to the end point of time slot #(N + 6). The second terminal can be configured to send the SL CSI to the first terminal during the transmission period of the SL CSI. The first terminal can be configured to perform a monitoring operation to receive the SL CSI during the monitoring period of the SL CSI. When the SL CSI is sent on the PSCCH, the first terminal can be configured to perform a monitoring operation on the PSCCH during the monitoring period of the SL CSI. When the SL CSI is sent on the PSSCH, the first terminal can be configured to perform a monitoring operation on the PSSCH during the monitoring period of the SL CSI.

[0122] Referring to Figure 9 and Figure 10 , the second terminal may not be able to send the SL CSI to the first terminal during the transmission period of the SL CSI. When the transmission period of the SL CSI ends (e.g., when the timer corresponding to K expires), the second terminal can be configured to stop the sensing operation of the sidelink resources for the SL CSI report. In other words, the second terminal can be configured to stop the transmission operation of the SL CSI. When the SL CSI is not received during the monitoring period of the SL CSI, the first terminal can be configured to stop the monitoring operation for obtaining the SL CSI. The monitoring operation can be stopped after time slot #(N + 6).

[0123] On the other hand, the PSCCH containing the SL CSI can be identified through various schemes. For example, a cyclic redundancy check (CRC) mask value or a scrambling sequence (e.g., a scrambling identifier (ID), a sequence ID) can be configured for the PSCCH containing the SL CSI. In particular, the second terminal can be configured to send the PSCCH containing the SL CSI by using the CRC mask value or the scrambling sequence. The CRC mask value of the PSCCH containing the SL CSI can be the same as the CRC mask value of the PSCCH containing the trigger indication information for triggering the corresponding SL CSI report. The scrambling sequence of the PSCCH containing the SL CSI can be the same as the scrambling sequence of the PSCCH including the trigger indication information for triggering the corresponding SL CSI report. The scrambling ID (e.g., the sequence ID) can be an ID set for the SL CSI report. The scrambling ID can be set specific to the resource pool, specific to the SL dedicated, or specific to the terminal.

[0124] In Figure 10In the exemplary embodiment shown, the second terminal may be configured to stop sensing operations on sidelink resources for SL CSI reporting starting from time slot #(N + 7). That is, operations for reporting SL CSI may be stopped. Even when sidelink resources are available (e.g., reservable) after time slot #(N + 6), operations for reporting SL CSI may be stopped.

[0125] When no SL CSI is received from the second terminal, the first terminal may be configured to retransmit the trigger indication information as needed. When K is indicated by PHY signaling (e.g., SCI), the first terminal may be configured to reset K and send an SCI containing the reset K. The reset K may be a value greater than or less than the previous K. The second terminal may be configured to identify the reset K by receiving the SCI and start a timer corresponding to the reset K.

[0126] When the first terminal that has not received SL CSI retransmits the trigger indication information, information indicating the retransmission of the trigger indication information (hereinafter referred to as "retransmission indicator") may also be sent. The retransmission indicator may indicate whether the trigger indication information is the initial trigger indication information or the retransmitted trigger indication information. In particular, the value of the SL CSI reported to the first terminal may vary based on whether the trigger indication information is retransmitted. When the retransmission indicator indicates the retransmitted trigger indication information, the second terminal may be configured to send the previous SL CSI (e.g., the SL CSI for which transmission has failed) to the first terminal. When the trigger indication information indicates the initial trigger indication information, the second terminal may be configured to send the current SL CSI to the first terminal.

[0127] On the other hand, the time for sending SL CSI (e.g., K) may be reset. The method for resetting the time for sending SL CSI may be as follows.

[0128] Figure 11 is a sequence diagram showing a fourth exemplary embodiment of a method for reporting SL CSI.

[0129] Referring to Figure 11 , the communication system may include a first terminal and a second terminal. Sidelink communication may be performed between the first terminal and the second terminal. The first terminal may be Figure 2 UE#5 235 shown in Figure 2 , and the second terminal may be Figure 3 UE#6 236 shown in Figures 4 to 6The protocol stack shown in the figure. Each of the first terminal and the second terminal may support the sidelink TM defined in Table 2. The first terminal that transmits reference signals (e.g., CSI-RS, DMRS) may be referred to as the transmitting (Tx) terminal, and the second terminal that receives the reference signals may be referred to as the receiving (Rx) terminal.

[0130] Step S1101 may be performed in the same or similar manner as Figure 9 the step S901 shown, step S1102 may be performed in the same or similar manner as Figure 9 the step S902 shown, and step S1103 may be performed in the same or similar manner as Figure 9 the step S903 shown. In step S1101, an SCI containing trigger indication information may be received in time slot #N. K may be set to 6. K may be set by RRC signaling (e.g., PC5 RRC signaling). The second terminal may not be able to send SL CSI to the first terminal before or in time slot #(N + 6), and the first terminal may not be able to receive SL CSI from the second terminal before or in time slot #(N + 6).

[0131] In particular, the first terminal may reset K. For example, the first terminal may set K to 12. The first terminal may be configured to send the trigger indication information and the reset K (e.g., 12) to the second terminal (S1104). The reset K may be sent via a MAC message and / or a PHY message. The information indicating the reset K sent in step S1104 may be configured based on Table 3. For example, the information indicating the reset K may be "11". Additionally, a retransmission indicator may also be sent to the second terminal in step S1104. The retransmission indicator may indicate that the trigger indication information is the trigger indication information for retransmission. The second terminal may be configured to receive the trigger indication information, the reset K, and the retransmission indicator from the first terminal. The second terminal may be configured to determine, based on the retransmission indicator, that the trigger indication information is the trigger indication information for retransmission, and perform a measurement operation on the reference signal according to the trigger indication information. Additionally, the second terminal may be configured to start a timer corresponding to the reset K from the time when the trigger indication information is received, and send SL CSI to the first terminal as a result of the measurement operation before the timer expires.

[0132] In addition, for each retransmission of the trigger indication information, K can be increased or decreased at a pre-configured rate. For example, if the initial K is 6, then for each retransmission of the trigger indication information, K can be increased by 2. Alternatively, for each retransmission of the trigger indication information, K can be doubled. Additionally, a maximum value of K can be set, and K can be set not to exceed the maximum value. Each of the increment amount, decrement amount, increment rate, decrement rate, and maximum value of K can be set by at least one of system information, RRC messages (e.g., PC5 RRC messages), MAC messages, and PHY messages. Each of the increment amount, decrement amount, increment rate, decrement rate, and maximum value of K can be set specific to a resource pool, specific to a sidelink, or specific to a terminal. The maximum number of retransmissions of the trigger indication information can be set, and the maximum number of retransmissions can be set by at least one of system information, RRC messages (e.g., PC5 RRC messages), MAC messages, and PHY messages.

[0133] Based on the type of SL CSI, the method for setting K and / or the method for resetting K (e.g., the method for changing K) can vary. Referring to Tables 4 and 5 below, the increment amount or decrement amount of K can vary according to the type of SL CSI (e.g., instantaneous channel state information, average channel state information, filtered channel state information).

[0134] Table 4

[0135]

[0136] Table 5

[0137]

[0138] The average / filtered channel state information can be the channel state information for a longer time period than the instantaneous channel state information. In Table 4, the K for the average / filtered channel state information can be set to be equal to or greater than the K for the instantaneous channel state information. For each retransmission of the trigger indication information, the K for the average / filtered channel state information can be doubled. For each retransmission of the trigger indication information, the K for the instantaneous channel state information can be halved.

[0139] In Table 5, for each retransmission of the trigger indication information, the K for the average / filtered channel state information can be increased by 2, and the K for the instantaneous channel state information can remain unchanged even when the trigger indication information is retransmitted. The type of SL CSI can be set by at least one of system information, RRC messages, MAC messages, and PHY messages. For example, the type of SL SCI can be set by the base station or the first terminal. Each of the first terminal and the second terminal can reset K based on the reset method according to the SL CSI type.

[0140] Table 4 or Table 5 can be configured by higher layer signaling, and each of the first terminal and the second terminal can be configured to determine K based on Table 4 or Table 5 according to the type of SL CSI and the number of retransmissions of the triggering indication information. In another exemplary embodiment, the increase / decrease amount or increase / decrease rate according to the type of SL CSI can be set by higher layer signaling, and each of the first terminal and the second terminal can be configured to determine K based on the type of SL CSI and the number of retransmissions of the triggering indication information.

[0141] The type of SL CSI may not be limited to instantaneous channel state information, average channel state information, and filtered channel state information. For example, the type of SL CSI may vary according to CQI, RI, and / or PMI. The first type of SL CSI may include CQI and RI, and the second type of SL CSI may include PMI.

[0142] In addition, K may be sent together with the triggering indication information. In other words, K may be sent each time in the step of sending the triggering indication information. In particular, the second terminal can be configured to update the timer according to the received K. When K is reset according to a pre-configured increase / decrease amount or increase / decrease rate, a situation may occur where the second terminal sends SL CSI to the first terminal but the first terminal does not receive the SL CSI. This problem may occur when the K recognized by the first terminal is different from the K recognized by the second terminal. To avoid this problem, when K is reset according to a pre-configured increase / decrease amount or increase / decrease rate for each transmission of the triggering indication information, information indicating whether the corresponding triggering indication information is a triggering indication information for retransmission (e.g., a retransmission indicator) can be explicitly or implicitly indicated by the SCI.

[0143] If the second terminal sends SL CSI to the first terminal but the first terminal does not receive the SL CSI, the first terminal can be configured to send the triggering indication information to the second terminal for retransmission of the SL CSI. The second terminal that sends the SL CSI can be configured to recognize the triggering indication information received from the first terminal as new triggering indication information (e.g., initial triggering indication information). In particular, the K applied to the first terminal may be different from the K applied to the second terminal. When the first terminal notifies the second terminal of K together with the triggering indication information, the second terminal can be configured to identify whether the current triggering indication information is initial triggering indication information or retransmitted triggering indication information based on K. In addition, the second terminal can be configured to determine the number of times the current triggering indication information has been retransmitted based on K. The above solution can be understood as a solution in which the retransmission indicator is sent together with the triggering indication information.

[0144] A toggle bit can be utilized to replace K to indicate whether the triggering indication information is the initial triggering indication information or the retransmitted triggering indication information. To indicate whether the triggering indication information is the initial triggering indication information or the retransmitted triggering indication information, a specific field (e.g., the field included in the SCI) can be reused, or a new field can be used.

[0145] When there are multiple SL CSIs in the second terminal, the information indicating whether the triggering indication information included in the SCI is retransmitted can be used to indicate one or more of the multiple SL CSIs. The multiple SL CSIs can be divided based on the time of measuring each SL CSI.

[0146] Table 6

[0147] Trigger indication information Description 00 No SL CS report is triggered 01 SL CSI report is triggered 10 First retransmission of trigger indication information 11 Second retransmission of trigger indication information

[0148] Referring to Table 6, the triggering indication information included in the SCI (e.g., the Phase 1 SCI or the Phase 2 SCI) can be configured as 2 bits. The triggering indication information set to "01" can indicate the initial triggering indication information. The second terminal can be configured to identify the retransmission times of the triggering indication information based on the triggering indication information included in the SCI. Alternatively, the field included in the SCI can be reused to indicate the content defined in Table 6. The field included in the SCI can implicitly indicate the content defined in Table 6.

[0149] When K significantly increases, the probability of SL CSI reporting failure due to sensing failure of the sidelink resources in the second terminal (e.g., the receiving terminal) will decrease. When K has a small value, the monitoring period of the SL CSI in the first terminal (e.g., the transmitting terminal) (e.g., the monitoring period of the PSCCH or PSSCH including the SL CSI) can be reduced, and the reporting process of the SL CSI can be completed quickly.

[0150] The first terminal can be configured to identify the state of the sidelink resources capable of transmitting the SL CSI based on the Channel Busy Ratio (CBR) of the sidelink, and can be configured to increase or decrease K based on the identified result. In response to determining that the number of terminals using and / or desiring to use the resources belonging to the resource pool is small based on the CBR, the first terminal can be configured to determine that increasing K is meaningless. In particular, the first terminal can be configured to maintain or decrease K and send the same K (or the decreased K) together with the triggering indication information.

[0151] In response to a large number of terminals that use and / or wish to use resources belonging to a resource pool based on CBR determination, the first terminal may increase K. In other words, the first terminal may be configured to send the increased K together with the trigger indication information. In particular, the probability of SL CSI reporting failure due to sensing failure of sidelink resources can be reduced. In the above operations, in addition to CBR, a combination of parameters related to the channel state (e.g., channel condition) can also be used.

[0152] In the step of retransmitting the trigger indication information based on a specific threshold of the used parameters, an increased K or a decreased K can be transmitted. To reset K, conditions related to the threshold of the parameters used by the first terminal can be configured. For example, the increase amount or decrease amount of K can be set for each of the cases where the parameter is greater than or equal to the threshold and the case where the parameter is less than the threshold. Alternatively, the increase rate or decrease rate of K can be set for each of the cases where the parameter is greater than or equal to the threshold and the case where the parameter is less than the threshold.

[0153] When using one or more parameters, the increase / decrease amount and / or increase / decrease rate of K can be determined based on the threshold of each of the one or more parameters. In particular, the threshold can be set by one or more of system information, RRC signaling, MAC signaling, and PHY signaling. The threshold can be set specific to the resource pool, specific to the sidelink, or specific to the terminal.

[0154] On the other hand, in Figure 8 、 Figure 9 and Figure 11 In the exemplary embodiment shown, the time offset (e.g., slot offset) can start from the time when the trigger indication information is received (or, the time when the trigger indication information is sent). Alternatively, the time offset can start from the sidelink resources configured for data transmission.

[0155] Figure 12 is a sequence diagram showing a fifth exemplary embodiment of a method for reporting SL CSI.

[0156] Referring to Figure 12 , the communication system may include a first terminal and a second terminal. Sidelink communication can be performed between the first terminal and the second terminal. The first terminal may be Figure 2 UE#5 235 shown in Figure 2 , and the second terminal may be Figure 3 UE#6 236 shown in Figures 4 to 6The protocol stack shown in [Figure 0]. Each of the first terminal and the second terminal may support the sidelink TM defined in Table 2. The first terminal that transmits reference signals (e.g., CSI-RS, DMRS) may be referred to as the transmitting (Tx) terminal, and the second terminal that receives the reference signals may be referred to as the receiving (Rx) terminal.

[0157] The first terminal may be configured to send an SCI (e.g., a phase 2 SCI) including trigger indication information (e.g., CSI request information) to the second terminal (S1201). In step S1201, K (e.g., information about the time for sending SL CSI) may be sent together with the trigger indication information. Additionally, K may be sent via an RRC message (e.g., a PC5 RRC message), and the trigger indication information may be sent via an SCI. Alternatively, K may be set by the base station. The second terminal may be configured to receive the trigger indication information and / or K from the first terminal. Alternatively, the second terminal may be configured to receive K from the base station.

[0158] The first terminal may be configured to send reference signals (S1202). The reference signals may be sent via sidelink resources configured by the base station. When triggering an SL CSI report, the second terminal may be configured to perform a measurement operation based on the reference signals received from the first terminal (S1203). The second terminal may be configured to generate SL CSI as a result of the measurement operation. When receiving the trigger indication information in time slot #N, the second terminal may be configured to send the SL CSI to the first terminal in time slot #(N + L - K) (S1204). The SL CSI may be sent on the PSCCH, PSSCH, and / or PSFCH. In particular, L may represent the time period from the time of receiving the trigger indication information to the sidelink resources scheduled by the SCI associated with the trigger indication information (or an SCI not associated with the corresponding trigger indication information). L may be set in units of symbols, mini-slots, time slots, or sub-frames. Additionally, L may be an integer greater than or equal to 0.

[0159] The first terminal may be configured to perform a monitoring operation to receive the SL CSI in the time period from time slot #N to time slot #(N + L - K). When receiving the SL CSI in time slot #(N + L - K), the first terminal may be configured to determine the received SL CSI as a valid SL CSI. On the other hand, when receiving the SL CSI after time slot #(N + L - K), the first terminal may be configured to determine the received SL CSI as an invalid SL CSI. In this case, the first terminal may discard the SL CSI.

[0160] The first terminal may be configured to send SL data to the second terminal in the side link resource scheduled by the SCI (S1205). The second terminal may be configured to receive SL data from the first terminal by performing a monitoring operation on the side link resource scheduled by the SCI. The above operation may also be applied when there is SL data of a terminal different from the second terminal receiving the trigger indication information in the first terminal.

[0161] In another exemplary embodiment, K may start from the side link resource scheduled by SCI. In particular, the second terminal may be configured to send SL CSI to the first terminal in time slot #(N+L+K). The first terminal may be configured to perform a monitoring operation in a time interval from time slot #N to time slot #(N+L+K) to obtain SL CSI.

[0162] The time for sending SL CSI (for example, the delay limit value of SL CSI report) can be set based on the processing time for SL CSI and / or the processing time for SL data transmission in the first terminal. The time for sending SL CSI can be a fixed value in the communication system. The time for sending SL CSI can be set by one or more of system information, RRC signaling, MAC signaling and PHY signaling. The time for sending SL CSI can be set specific to the resource pool, specific to the side link or specific to the terminal. Figure 8 , Figure 9 and / or Figure 11 The exemplary embodiments shown in FIG. 1 can be applied to Figure 12 An exemplary embodiment is shown in .

[0163] The exemplary embodiments of the present disclosure may be implemented as program instructions that can be run by various computers and recorded on a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, or a combination thereof. The program instructions recorded on the computer-readable medium may be specifically designed and configured for the present disclosure, or may be known and available to those skilled in the art of computer software.

[0164] Examples of computer-readable media may include hardware devices such as ROM, RAM, and flash memory, which are specifically configured to store and run program instructions. Examples of program instructions include machine code generated by a compiler, for example, and high-level language codes that can be run by a computer using an interpreter. The above exemplary hardware devices may be configured to operate as at least one software module to perform embodiments of the present disclosure, and vice versa.

[0165] Although the embodiments of the present disclosure and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the present disclosure as described in the claims.

Claims

1. A method for operating a first terminal in a communication system, the method comprising the following steps: Sending information indicating a latency bound value of sidelink (SL) channel state information (CSI) report to a second terminal; Sending sidelink control information (SCI) to the second terminal, the SCI including information for triggering a CSI report, wherein the information for triggering the CSI report causes a timer associated with the latency bound value to be started; And Performing a monitoring operation to receive the SL CSI of the second terminal within a time period corresponding to the latency bound value starting from the time of sending the information for triggering the CSI report; wherein the timer starts in response to the triggering of the CSI report, and wherein if the timer expires, the CSI report is cancelled; otherwise, the SL CSI is sent to the first terminal.

2. The method according to claim 1, further comprising retransmitting the information for triggering the CSI report when the SL CSI of the second terminal is not received within the time period.

3. The method according to claim 2, wherein In response to the retransmission of the information for triggering the CSI report, a reset latency bound value is used to replace the latency bound value, and the reset latency bound value is greater than or less than the latency bound value.

4. The method according to claim 1, wherein The latency bound value is set specifically for the sidelink.

5. The method according to claim 1, wherein The latency bound value is set in units of time slots.

6. The method according to claim 1, wherein, The latency bound value is a time offset starting from the time of sending the information for triggering the CSI report.

7. The method according to claim 1, wherein The latency bound value is set independently of the type of the SL CSI, and the type of the SL CSI varies according to the information contained in the SL CSI.

8. The method according to claim 1, wherein The SL CSI includes a channel quality indicator (CQI) and a rank indicator (RI).

9. The method according to claim 1, wherein, The SL CSI is received on a physical sidelink shared channel (PSSCH).

10. A method for operating a second terminal in a communication system, the method comprising the following steps: Receiving a radio resource control (RRC) message from a first terminal, the RRC message containing information indicating a latency bound value of sidelink (SL) channel state information (CSI) report; Receiving sidelink control information (SCI) from the first terminal, the SCI including information for triggering a CSI report; In response to the triggering of the CSI report, starting a timer associated with the latency bound value; If the timer expires, cancelling the CSI report; Otherwise, sending the SL CSI to the first terminal within a time period corresponding to the latency bound value starting from the time of receiving the information for triggering the CSI report.

11. The method according to claim 10, wherein When the time period ends, the SL CSI is not sent to the first terminal.

12. The method according to claim 10, wherein, The latency bound value is set specifically for the sidelink.

13. The method according to claim 10, wherein, The latency bound value is set in units of time slots and starts from the time of receiving the information for triggering the CSI report.

14. The method according to claim 10, wherein, The latency bound value is set independently of the type of the SL CSI, and the type of the SL CSI varies according to the information contained in the SL CSI.

15. The method according to claim 10, wherein The SL CSI includes a channel quality indicator, i.e., CQI, and a rank indicator, i.e., RI.

16. A first terminal, which is the first terminal in a communication system, includes: A processor; And A memory storing at least one instruction to be run by the processor, Wherein, the at least one instruction is run to: Send information indicating a latency bound value of a sidelink channel state information report, i.e., an SL CSI report, to a second terminal; Send sidelink control information, i.e., SCI, to the second terminal, the SCI including information for triggering a CSI report, wherein the information for triggering a CSI report causes a timer associated with the latency bound value to be started; and Perform a monitoring operation to receive the SL CSI of the second terminal within a time period corresponding to the latency bound value starting from the time of sending the information for triggering a CSI report, Wherein, the timer starts in response to the CSI report being triggered, and Wherein, if the timer expires, the CSI report is cancelled; otherwise, the SL CSI is sent to the first terminal.

17. The first terminal according to claim 16, wherein, The at least one instruction is further run to: when the SL CSI of the second terminal is not received within the time period, retransmit the information for triggering a CSI report, and in response to the information for triggering a CSI report being retransmitted, use a reset latency bound value to replace the latency bound value, and the reset latency bound value is greater than or less than the latency bound value.

18. The first terminal according to claim 16, wherein, The latency bound value is set specifically for a sidelink and is used for unicast sidelink communication.

19. The first terminal according to claim 16, wherein, The latency bound value is set in units of time slots and starts from the time of sending the information for triggering a CSI report.

20. The first terminal according to claim 16, wherein, The SL CSI includes a channel quality indicator, i.e., CQI, and a rank indicator, i.e., RI.

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