Method and apparatus for transmitting signal in wireless communication system

Abstract

The present invention relates to a wireless communication system and, in particular, to a method and a wireless device for: transmitting at least one PSSCH within a COT, the at least one PSSCH comprising at least one first PSSCH with enabled HARQ-ACK feedback; adjusting the CWS based on HARQ-ACK feedback for the at least one PSSCH in the reference duration; and performing an SL channel access procedure based on the adjusted CWS.

Description

Technical Field

[0001] The present invention relates to a wireless communication system. Specifically, the present invention relates to a channel access method in a wireless communication system and a device using the method. Background Art

[0002] After the commercialization of the fourth-generation (4G) communication system, in order to meet the increasing demand for wireless data services, efforts are being made to develop a new fifth-generation (5G) communication system. The 5G communication system is referred to as a super 4G network communication system, a post-LTE system, or a new radio (NR) system. To achieve a high data transmission rate, the 5G communication system includes a system operating using millimeter wave (mmWave) frequencies of 6 GHz or higher, and a communication system operating using frequencies of 6 GHz or lower in terms of ensuring coverage, such that implementation methods in base stations and terminals are under consideration.

[0003] The third-generation partnership project (3GPP) NR system improves the spectral efficiency of the network and enables communication providers to offer more data and voice services on a given bandwidth. Therefore, the 3GPP NR system is designed to meet the demand for high-speed data and media transmission in addition to supporting a large amount of voice. The advantages of the NR system are higher throughput and lower latency on the same platform, support for frequency-division duplexing (FDD) and time-division duplexing (TDD), and low operating costs due to an enhanced end-user environment and a simple architecture.

[0004] For more efficient data processing, the dynamic TDD of the NR system can use a method for changing the number of orthogonal frequency-division multiplexing (OFDM) symbols that can be used in the uplink and downlink according to the data traffic direction of cell users. For example, when the downlink traffic of a cell is greater than the uplink traffic, the base station can allocate multiple downlink OFDM symbols to a time slot (or subframe). Information on the time slot configuration should be sent to the terminal.

[0005] In order to mitigate the path loss of radio waves and increase the transmission distance of radio waves in the mmWave band, in the 5G communication system, beamforming, massive multiple-input / multiple-output (massive MIMO), full-dimensional MIMO (FD-MIMO), array antennas, analog beamforming, hybrid beamforming that combines analog beamforming and digital beamforming, and massive antenna technology have been discussed. In addition, for network improvement of the system, in the 5G communication system, technology development related to evolved small cells, advanced small cells, cloud radio access network (cloud RAN), ultra-dense network, device-to-device communication (D2D), vehicle-to-everything communication (V2X), wireless backhaul, non-terrestrial network communication (NTN), mobile network, cooperative communication, coordinated multi-point (CoMP), interference cancellation, etc. is underway. In addition, in the 5G system, hybrid FSK and QAM modulation (FQAM) and sliding window superposition coding (SWSC) as advanced coding modulation (ACM) schemes, and filter bank multicarrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA) as advanced connection technologies are being developed.

[0006] Meanwhile, in a human-centered connected network where humans generate and consume information, the Internet has evolved into an Internet of Things (IoT) network that exchanges information between distributed components such as objects. The Internet of Everything (IoE) technology that combines IoT technology with big data processing technology through connection to a cloud server is also emerging. To implement the IoT, technical elements such as sensing technology, wired / wireless communication and network infrastructure, service interface technology, and security technology are required, so in recent years, technologies such as sensor networks, machine-to-machine (M2M), and machine type communication (MTC) have been studied to connect between objects. In the IoT environment, intelligent Internet technology (IT) services can be provided that collect and analyze data generated from connected objects to create new value in human life. By the integration and hybridization of existing information technology (IT) and various industries, the IoT can be applied to fields such as smart home, smart building, smart city, smart car or connected car, smart grid, healthcare, smart appliances, and advanced medical services.

[0007] Therefore, various attempts have been made to apply the 5G communication system to the IoT network. For example, technologies such as sensor networks, machine-to-machine (M2M), and machine type communication (MTC) are implemented through technologies such as beamforming, MIMO, and array antennas. The application of cloud RAN as the above big data processing technology is an example of the integration of 5G technology and IoT technology. Generally, mobile communication systems are developed to provide voice services while ensuring the activities of users.

[0008] A side link (SL) refers to a communication scheme in which a direct link is established between user equipment (UEs), and the UEs directly exchange voice or data with each other without the intervention of a base station (BS). The SL is considered a solution to relieve the burden on the BS due to the rapidly increasing data traffic.

[0009] Vehicle-to-Everything (V2X) refers to a communication technology that exchanges information with other vehicles, pedestrians, and infrastructure objects through wired / wireless communication. V2X can be classified into four types, such as vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), vehicle-to-network (V2N), and vehicle-to-pedestrian (V2P). V2X communication can be provided through the PC5 interface and / or the Uu interface.

[0010] As more and more communication devices require greater communication capacity, there is a need for mobile broadband communication improved from legacy radio access technologies (RATs). Therefore, communication systems considering services or UEs sensitive to reliability and latency are under discussion. Next-generation radio access technologies considering enhanced mobile broadband communication, massive MTC, ultra-reliable and low-latency communication (URLLC), etc. can be referred to as new radio access technologies (RAT) or new radio (NR). Even in NR, vehicle-to-Everything (V2X) communication can be supported.

[0011] Meanwhile, in the case of SL communication involving services with high reliability requirements or relatively high reliability requirements, for example, the SL HARQ feedback operation and / or mechanism of the UE may be useful. Summary of the Invention

[0012] Technical Problem

[0013] The present disclosure aims to provide a method for efficiently transmitting signals in a wireless communication system and an apparatus using the method. Specifically, the present disclosure aims to provide a channel access method for efficiently performing transmission in a wireless communication system and an apparatus using the method.

[0014] Technical Solution

[0015] As an aspect of the present invention, there is provided a user equipment (UE) used in a wireless communication system, the UE including: a communication module; and a processor configured to control the communication module, wherein the processor is configured to transmit at least one physical sidelink shared channel (PSSCH) during a channel occupancy time (COT), the at least one PSSCH including at least one first PSSCH having enabled hybrid automatic repeat request acknowledgment (HARQ-ACK) feedback; during a reference duration, adjust a contention window size (CWS) based on the HARQ-ACK feedback for the at least one PSSCH; and perform a sidelink (SL) channel access procedure based on the adjusted CWS, and the reference duration is defined as starting from the beginning of the COT and until the end of a first time slot in which the at least one first PSSCH is transmitted.

[0016] As an aspect of the present invention, there is provided a method used by a UE in a wireless communication system, and the method includes: transmitting at least one physical sidelink shared channel (PSSCH) during a channel occupancy time (COT), the at least one PSSCH including at least one first PSSCH having enabled hybrid automatic repeat request acknowledgment (HARQ-ACK) feedback; during a reference duration, adjust a contention window size (CWS) based on the HARQ-ACK feedback for the at least one PSSCH; and perform a sidelink (SL) channel access procedure based on the adjusted CWS, and the reference duration is defined as starting from the beginning of the COT and until the end of a first time slot in which the at least one first PSSCH is transmitted.

[0017] Preferably, the HARQ-ACK feedback may include reception response information based on an ACK / negative ACK (NACK) feedback scheme.

[0018] Preferably, when the at least one first PSSCH includes at least one second PSSCH having an indicated ACK / NACK feedback scheme and at least one third PSSCH having an indicated only-NACK feedback scheme, the reference duration may be defined as starting from the beginning of the COT and until the end of a first time slot in which the at least one second PSSCH is transmitted.

[0019] Preferably, the at least one PSSCH may include at least one fourth PSSCH for which the HARQ-ACK feedback is not enabled.

[0020] Preferably, the COT may be the latest COT initiated by the UE.

[0021] Preferably, when the HARQ-ACK feedback for the at least one PSSCH transmission in the reference duration includes at least ACK, the CWS may be adjusted to the minimum value.

[0022] Preferably, when the HARQ-ACK feedback for the at least one PSSCH transmission in the reference duration does not include ACK, the CWS may be increased to the next value higher than the current CWS among the allowed CWS values.

[0023] Preferably, when the at least one first PSSCH is sent via SL multicast and the HARQ-ACK feedback for the at least one PSSCH transmission in the reference duration includes at least a negative acknowledgment (NACK), the CWS is increased to a value higher than the current CWS among the allowed CWS values, and when the HARQ-ACK feedback for the at least one PSSCH transmission in the reference duration is regarded as all ACKs, the CWS may be adjusted to the minimum value.

[0024] Preferably, the UE may perform the SL channel access procedure based on a counter value randomly selected within the adjusted CWS.

[0025] Preferably, the first time slot for transmitting the at least one first PSSCH may be the time slot for performing the PSSCH transmission via all resources allocated for the PSSCH transmission.

[0026] Advantages of the Invention

[0027] The present disclosure provides a method for effectively transmitting signals in a wireless communication system and an apparatus using the method. In addition, the present disclosure provides a channel access method for efficiently performing transmission in a wireless communication system and an apparatus using the method.

[0028] The effects obtainable from the present disclosure are not limited to those mentioned above, and other effects not mentioned will be clearly understood by those skilled in the art to which the present disclosure pertains from the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Illustrates an example of a radio frame structure used in a wireless communication system;

[0030] Figure 2 Illustrates an example of a downlink (DL) / uplink (UL) time slot structure in a wireless communication system;

[0031] Figure 3 Is a diagram for explaining a physical channel used in a 3GPP system and a typical signal transmission method using the physical channel;

[0032] Figure 4 Diagram of an SS / PBCH block for initial cell access in a 3GPP NR system;

[0033] Figure 5 Diagram of the process for transmitting control information and control channels in a 3GPP NR system;

[0034] Figure 6 Diagram of a control resource set (CORESET) in a 3GPP NR system where a physical downlink control channel (PUCCH) can be transmitted;

[0035] Figure 7 Diagram of a method for configuring a PDCCH search space in a 3GPP NR system;

[0036] Figure 8 Is a conceptual diagram illustrating carrier aggregation;

[0037] Figure 9 Is a diagram for explaining signal carrier communication and multi-carrier communication;

[0038] Figure 10 Is a diagram showing an example where cross-carrier scheduling technology is applied;

[0039] Figure 11 Diagram of a new radio unlicensed (NR-U) service environment;

[0040] Figure 12 Diagram of a communication method (e.g., wireless LAN) operating in an existing unlicensed band;

[0041] Figure 13 Diagram of a channel access process based on Category 4 LBT;

[0042] Figure 14 Is a block diagram illustrating the configuration of a UE and a base station according to an embodiment of the present invention;

[0043] Figure 15 Diagram of an example of channel occupancy time (COT) configuration and corresponding operations;

[0044] Figures 16 to 23 Diagram of an example of a sidelink (SL) communication process.

[0045] Figure 24 Diagram of the configuration of a physical sidelink control channel / physical sidelink shared channel / physical sidelink feedback channel (PSCCH / PSSCH / PSFCH) in a time slot.

[0046] Figure 25 Diagram of a sidelink SSB (S-SSB) structure.

[0047] Figure 26 Illustrate the sidelink (SL) communication process.

[0048] Figure 27 and 28 Illustrate an example of the channel access method according to the present invention.

[0049] Figure 29 and 30 Illustrate an example of the SL reference duration according to the present invention.

[0050] Figure 31 Illustrate the SL transmission method according to the present invention. Detailed implementation mode

[0051] The terms used in the specification adopt as much as possible the currently widely used general terms in consideration of the functions in the present invention, but these terms can be changed according to the intentions, habits of those skilled in the art and the emergence of new technologies. In addition, in specific cases, there are terms arbitrarily selected by the applicant, and in such cases, their meanings will be described in the corresponding description part of the present invention. Therefore, it is intended that the terms used in the specification should not be analyzed only based on the name of the term, but should be analyzed based on the substantial meanings of the terms and the content in the whole specification.

[0052] Throughout the specification and the following claims, when an element is described as "connected" to another element, the element can be "directly connected" to the other element or "electrically connected" to the other element through a third element. In addition, unless explicitly described to the contrary, the word "comprising" will be understood to imply including the said element, without implying the exclusion of any other element. Furthermore, in some exemplary embodiments, limitations such as "greater than or equal to" or "less than or equal to" based on a specific threshold can be appropriately replaced by "greater than" or "less than", respectively.

[0053] The following technologies can be used in various wireless access systems: such as Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier - FDMA (SC - FDMA), etc. CDMA can be implemented by wireless technologies such as Universal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA can be implemented by wireless technologies such as Global System for Mobile Communications (GSM) / General Packet Radio Service (GPRS) / Enhanced Data Rates for GSM Evolution (EDGE). OFDMA can be implemented by wireless technologies such as IEEE 802.11 (Wi - Fi), IEEE 802.16 (WiMAX), IEEE 802 - 20, Evolved UTRA (E - UTRA), etc. UTRA is part of the Universal Mobile Telecommunications System (UMTS). The 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) is part of the Evolved UMTS (E - UMTS) that uses Evolved UMTS Terrestrial Radio Access (E - UTRA), and LTE - Advanced (A) is an evolved version of 3GPP LTE. 3GPP New Radio (NR) is a system designed separately from LTE / LTE - A and is a system for supporting enhanced mobile broadband (eMBB), ultra - reliable low - latency communication (URLLC), and massive machine - type communication (mMTC) services as requirements of IMT - 2020. For clear description, 3GPP NR is mainly described, but the technical idea of the present invention is not limited thereto.

[0054] Unless otherwise specified herein, the base station may include a next - generation Node B (gNB) defined in 3GPP NR. In addition, unless otherwise specified, the terminal may include a User Equipment (UE). Hereinafter, for helping understanding the description, each content is described separately by embodiments, but each embodiment can be used in combination with each other. In this specification, the configuration of the UE may be indicated by the configuration of the base station. More specifically, the base station may configure the values of parameters used in the operation of the UE or the wireless communication system by sending channels or signals to the UE.

[0055] Figure 1 An example of the wireless frame structure used in the wireless communication system is illustrated.

[0056] Reference Figure 1 , the wireless frame (or radio frame) used in the 3GPP NR system may have a length of 10 ms (Δf max N f / 100)*T c ). In addition, the wireless frame includes 10 sub - frames (SFs) of equal size. Here, Δf max = 480*10 3 Hz, Nf = 4096, T c = 1 / (Δf ref * N f,ref ), Δf ref = 15 * 10 3 Hz, and N f,ref = 2048. Numbers from 0 to 9 can be assigned to 10 sub - frames within a radio frame respectively. The length of each sub - frame is 1 ms and it can include one or more time slots according to the sub - carrier spacing. More specifically, in the 3GPP NR system, the sub - carrier spacing that can be used is 15 * 2 μ kHz, and μ can have values of μ = 0 to 4 as sub - carrier spacing configurations. That is to say, 15 kHz, 30 kHz, 60 kHz, 120 kHz and 240 kHz can be used for sub - carrier spacing. A sub - frame with a length of 1 ms can include 2 μ time slots. In this case, the length of each time slot is 2 -μ ms. Numbers from 0 to 2 μ - 1 can be assigned to 2 μ time slots within a sub - frame respectively. In addition, numbers from 0 to 10 * 2 μ - 1 can be assigned to the time slots within a radio frame respectively. Time resources can be distinguished by at least one of the radio frame number (also known as radio frame index), sub - frame number (also known as sub - frame index) and time slot number (or time slot index).

[0057] Figure 2 The figure shows an example of the downlink (DL) / uplink (UL) time slot structure in a wireless communication system. In particular, Figure 2 it shows the structure of the resource grid of the 3GPP NR system.

[0058] There is a resource grid for each antenna port. Referring to Figure 2 , a time slot includes multiple orthogonal frequency - division multiplexing (OFDM) symbols in the time domain and multiple resource blocks (RBs) in the frequency domain. One OFDM symbol also refers to a symbol interval. Unless otherwise specified, the OFDM symbol can be abbreviated as a symbol. One RB includes 12 consecutive sub - carriers in the frequency domain. Referring to Figure 2 , the signal transmitted from each time slot can be represented by a resource grid including N size,μ grid,x * N RB sc sub - carriers and N slot symb OFDM symbols. Here, when the signal is a DL signal, x = DL, and when the signal is a UL signal, x = UL. N size,μ grid,xrepresents the number of resource blocks (RBs) according to the subcarrier spacing component μ (where x is DL or UL), and N slot symb represents the number of OFDM symbols in a time slot. N RB sc is the number of subcarriers that make up one RB and N RB sc = 12. The OFDM symbols can be referred to as cyclic prefix OFDM (CP - OFDM) symbols or discrete Fourier transform spread OFDM (DFT - s - OFDM) symbols according to the multiple access scheme.

[0059] The number of OFDM symbols included in a time slot can vary according to the length of the cyclic prefix (CP). For example, in the case of normal CP, a time slot includes 14 OFDM symbols, but in the case of extended CP, a time slot can include 12 OFDM symbols. In a specific embodiment, extended CP can only be used at a 60 kHz subcarrier spacing. In Figure 2 for the convenience of description, as an example, a time slot is configured with 14 OFDM symbols, but the embodiments of the present disclosure can be applied to time slots with different numbers of OFDM symbols in a similar manner. Referring to Figure 2 , each OFDM symbol includes N size,μ grid,x *N RB sc subcarriers in the frequency domain. The types of subcarriers can be divided into data subcarriers for data transmission, reference signal subcarriers for the transmission of reference signals, and guard bands. The carrier frequency is also referred to as the center frequency (fc).

[0060] One RB can be defined by N RB sc (e.g., 12) consecutive subcarriers in the frequency domain. For reference, a resource configured with one OFDM symbol and one subcarrier can be referred to as a resource element (RE) or a tone. Thus, one RB can be configured with N slot symb *N RB sc resource elements. Each resource element in the resource grid can be uniquely defined by a pair of indices (k, l) in a time slot. k can be the index assigned from 0 to N size,μ grid,x *N RB sc – 1 in the frequency domain, and l can be the index assigned from 0 to N slot symb – 1 in the time domain.

[0061] For the UE to receive signals from or transmit signals to the base station, the time / frequency of the UE may be synchronized with the time / frequency of the base station. This is because when the base station and the UE are synchronized, the UE can determine the time and frequency parameters necessary for demodulating DL signals at the correct time and transmitting UL signals.

[0062] Each symbol of a radio frame used in time division duplex (TDD) or unpaired spectrum may be configured with at least one of a DL symbol, a UL symbol, and a flexible symbol. A radio frame used as a DL carrier in frequency division duplex (FDD) or paired spectrum may be configured with a DL symbol or a flexible symbol, and a radio frame used as a UL carrier may be configured with a UL symbol or a flexible symbol. In a DL symbol, DL transmission is possible, but UL transmission is not available. In a UL symbol, UL transmission is possible, but DL transmission is not available. A flexible symbol may be determined to be used as DL or UL according to a signal.

[0063] Information about the type of each symbol, that is, information indicating any one of a DL symbol, a UL symbol, and a flexible symbol, may be configured with a cell-specific or common radio resource control (RRC) signal. In addition, information about the type of each symbol may be additionally configured with a UE-specific or dedicated RRC signal. The base station notifies, by using a cell-specific RRC signal, i) the period of a cell-specific time slot configuration, ii) the number of time slots having only DL symbols from the beginning of the period of the cell-specific time slot configuration, iii) the number of DL symbols from the first symbol of the time slot immediately following the time slot having only DL symbols, iv) the number of time slots having only UL symbols from the end of the period of the cell-specific time slot configuration, and v) the number of UL symbols from the last symbol of the time slot immediately preceding the time slot having only UL symbols. Here, a symbol not configured with any one of a UL symbol and a DL symbol is a flexible symbol.

[0064] When the information about the symbol type is configured with a UE-specific RRC signal, the base station can signal whether the flexible symbol is a DL symbol or a UL symbol with a cell-specific RRC signal. In this case, the UE-specific RRC signal cannot change a DL symbol or a UL symbol configured with a cell-specific RRC signal into another symbol type. The UE-specific RRC signal may signal the number of DL symbols among the N slot symb symbols of the corresponding time slot and the N slot symbThe number of UL symbols among the symbols. In this case, the DL symbols of the time slot can be continuously configured with the first symbol to the i-th symbol of the time slot. In addition, the UL symbols of the time slot can be continuously configured with the j-th symbol to the last symbol of the time slot (where i < j). In the time slot, the symbol not configured with any of the UL symbols and DL symbols is a flexible symbol.

[0065] The type of symbol configured with the above RRC signal can be referred to as semi-static DL / UL configuration. In the previously configured semi-static DL / UL configuration with the RRC signal, the flexible symbol can be indicated as a DL symbol, a UL symbol indication, or a flexible symbol through the dynamic time slot format information (SFI) sent on the physical DL control channel (PDCCH). In this case, the DL symbol or UL symbol configured with the RRC signal will not be changed to another symbol type. Table 1 illustrates the dynamic SFI that the base station can indicate to the UE.

[0066] [Table 1]

[0067]

[0068] In Table 1, D represents a DL symbol, U represents a UL symbol, and X represents a flexible symbol. As shown in Table 1, up to two DL / UL switches are allowed in one time slot.

[0069] Figure 3 is a diagram for explaining the physical channels used in the 3GPP system (e.g., NR) and the typical signal transmission methods using the physical channels.

[0070] If the power of the UE is turned on or the UE camps on a new cell, the UE performs initial cell search (S101). Specifically, the UE can synchronize with the BS during the initial cell search. To this end, the UE can receive the primary synchronization signal (PSS) and the secondary synchronization signal (SSS) from the base station to synchronize with the base station and obtain information such as the cell ID. Thereafter, the UE can receive the physical broadcast channel from the base station and obtain the broadcast information in the cell.

[0071] After the initial cell search is completed, the UE receives the physical downlink shared channel (PDSCH) according to the physical downlink control channel (PDCCH) and the information in the PDCCH, so that the UE can obtain more specific system information than the system information obtained through the initial cell search (S102). Here, the system information received by the UE is the cell common system information for the normal operation of the UE in the physical layer of the radio resource control (RRC), and is referred to as the remaining system information, or is referred to as the system information block (SIB)1.

[0072] When the UE initially accesses the base station or does not have radio resources for signal transmission (i.e., the UE is in the RRC_IDLE mode), the UE can perform a random access procedure (operations S103 to S106) on the base station. First, the UE is able to send a preamble (S103) through the Physical Random Access Channel (PRACH) and receive a response message for the preamble from the base station through the PDCCH and the corresponding PDSCH (S104). When the UE receives a valid random access response message, the UE sends data including the UE's identifier, etc. to the base station through the Physical Uplink Shared Channel (PUSCH) indicated by the UL grant sent from the base station through the PDCCH (S105). Next, the UE waits for the reception of the PDCCH as an indication from the base station for conflict resolution. If the UE successfully receives the PDCCH through the UE's identifier (S106), the random access procedure is terminated. The UE can obtain UE-specific system information for the normal operation of the UE in the physical layer at the RRC layer during the random access procedure. When the UE obtains the UE-specific system information, the UE enters the RRC connected mode (RRC_CONNECTED mode).

[0073] The RRC layer is used to generate or manage messages for controlling the connection between the UE and the Radio Access Network (RAN). More specifically, in the RRC layer, the base station and the UE can perform functions such as broadcasting cell system information required for each UE in the cell, managing mobility and handover, measurement reporting of the UE, and storage management including UE capability management and device management. Generally, since the update period of the signals transmitted in the RRC layer is longer than the Transmission Time Interval (TTI) in the physical layer, the RRC signals are not changed and are maintained for a relatively long interval.

[0074] After the above process, the UE receives the PDCCH / PDSCH (S107) and sends the Physical Uplink Shared Channel (PUSCH) / Physical Uplink Control Channel (PUCCH) (S108) as a general UL / DL signal transmission process. In particular, the UE can receive Downlink Control Information (DCI) through the PDCCH. The DCI can include control information such as resource allocation information for the UE. Additionally, the format of the DCI can vary according to a predetermined use. The Uplink Control Information (UCI) sent by the UE to the base station through the UL includes DL / UL ACK / NACK signals, Channel Quality Indicator (CQI), Precoding Matrix Index (PMI), Rank Indicator (RI), etc. Here, the CQI, PMI, and RI can be included in the Channel State Information (CSI). In the 3GPP NR system, the UE can send control information such as the above-mentioned HARQ-ACK and CSI through the PUSCH and / or PUCCH.

[0075] Figure 4 The figure shows an SS / PBCH block for initial cell access in a 3GPP NR system.

[0076] When the power is turned on or when the UE wants to access a new cell, the UE can acquire time and frequency synchronization with the cell and perform an initial cell search procedure. The UE can detect the physical cell identifier NcellID of the cell during the cell search procedure. To this end, the UE can receive synchronization signals from the base station, for example, the primary synchronization signal (PSS) and the secondary synchronization signal (SSS), and synchronize with the base station. In this case, the UE can obtain information such as the cell identifier (ID).

[0077] Reference Figure 4 (a) of, the synchronization signal (SS) will be described in more detail. The synchronization signal can be classified into PSS and SSS. The PSS can be used to obtain time domain synchronization and / or frequency domain synchronization, such as OFDM symbol synchronization and slot synchronization. The SSS can be used to obtain frame synchronization and the cell group ID. Referring to Figure 4 (a) of and Table 2, the SS / PBCH block can be configured with 20 consecutive RBs (= 240 subcarriers) on the frequency axis and can be configured with 4 consecutive OFDM symbols on the time axis. In this case, in the SS / PBCH block, the PSS is transmitted in the first OFDM symbol and the SSS is transmitted in the third OFDM symbol through the 56th to 182nd subcarriers. Here, the lowest subcarrier index of the SS / PBCH block is numbered from 0. In the first OFDM symbol where the PSS is transmitted, the base station does not transmit signals through the remaining subcarriers, that is, the 0th to 55th subcarriers and the 183rd to 239th subcarriers. In addition, in the third OFDM symbol where the SSS is transmitted, the base station does not transmit signals through the 48th to 55th subcarriers and the 183rd to 191st subcarriers. The base station transmits the physical broadcast channel (PBCH) through the remaining REs in the SS / PBCH block other than the above signals.

[0078] [Table 2]

[0079]

[0080] The SS allows a total of 1008 unique physical layer cell IDs to be grouped into 336 physical layer cell identifier groups through the combination of three PSSs and SSSs, with each group including three unique identifiers. Specifically, such that each physical layer cell ID will be only part of one physical layer cell identifier group. Therefore, the physical layer cell ID N cell ID = 3N (1) ID + N (2) IDAn index N that can indicate a range of physical layer cell identifier groups from 0 to 335 (1) ID and an index N that can indicate a range of physical layer identifiers in the physical layer cell identifier group from 0 to 2 (2) ID are uniquely defined. The UE can detect the PSS and identify one of the three unique physical layer identifiers. In addition, the UE is able to detect the SSS and identify one of the 336 physical layer cell IDs associated with the physical layer identifier. In this case, the sequence d PSS (n) is as follows.

[0081]

[0082] Here, x(i + 7) = (x(i + 4) + x(i)) mod 2 and is given as

[0083] [x(6) x(5) x(4) x(3) x(2) x(1) x(0)] - [1 1 1 0 1 1 0].

[0084] In addition, the sequence d SSS (n) is as follows.

[0085]

[0086] Here, and is given as

[0087] [x0(6) x0(5) x0(4) x0(3) x0(2) x0(1) 0(0)] = [0 0 0 0 0 0 1]

[0088] [x1(6) x1(5) x1(4) x1(3) x1(2) x1(1) x1(0)] = [0 0 0 0 0 0 1].

[0089] A radio frame with a length of 10 ms can be divided into two half - frames with a length of 5 ms. Refer to Figure 4For (b) of , the time slots for transmitting SS / PBCH blocks in each half-frame will be described. The time slots for transmitting SS / PBCH blocks can be any one of cases A, B, C, D, and E. In case A, the subcarrier spacing is 15 kHz and the starting time point of the SS / PBCH block is the ({2,8}+14*n)-th symbol. In this case, at a carrier frequency of 3 GHz or lower, n = 0 or 1. Additionally, at a carrier frequency higher than 3 GHz and lower than 6 GHz, n can be 0, 1, 2, 3. In case B, the subcarrier spacing is 30 kHz and the starting time point of the SS / PBCH block is {4,8,16,20}+28*n. In this case, at a carrier frequency of 3 GHz or lower, n = 0. Additionally, at a carrier frequency higher than 3 GHz and lower than 6 GHz, n can be 0, 1. In case C, the subcarrier spacing is 30 kHz and the starting time point of the SS / PBCH block is the ({2,8}+14*n)-th symbol. In this case, at a carrier frequency of 3 GHz or lower, n = 0 or 1. Additionally, at a carrier frequency higher than 3 GHz and lower than 6 GHz, n can be 0, 1, 2, 3. In case D, the subcarrier spacing is 120 kHz and the starting time point of the SS / PBCH block is the ({4,8,16,20}+28*n)-th symbol. In this case, at a carrier frequency of 6 GHz or higher, n = 0, 1, 2, 3, 5, 6, 7, 8, 10, 11, 12, 13, 15, 16, 17, 18. In case E, the subcarrier spacing is 240 kHz and the starting time point of the SS / PBCH block is the ({8,12,16,20,32,36,40,44}+56*n)-th symbol. In this case, at a carrier frequency of 6 GHz or higher, n = 0, 1, 2, 3, 5, 6, 7, 8.

[0090] Figure 5 Illustrates the process of transmitting control information and control channels in the 3GPP NR system. Refer to Figure 5In (a) thereof, the base station may add a cyclic redundancy check (CRC) masked (e.g., by exclusive OR operation) with a radio network temporary identifier (RNTI) to control information (e.g., downlink control information (DCI)) (S202). The base station may scramble the CRC with an RNTI value determined according to the purpose / target of each control information. The common RNTIs used by one or more UEs may include at least one of a system information RNTI (SI-RNTI), a paging RNTI (P-RNTI), a random access RNTI (RA-RNTI), and a transmit power control RNTI (TPC-RNTI). In addition, the UE-specific RNTIs may include at least one of a cell temporary RNTI (C-RNTI) and a CS-RNTI. Thereafter, the base station may perform rate matching (S206) according to the amount of resources used for PDCCH transmission after performing channel coding (e.g., polar coding) (S204). Thereafter, the base station may multiplex the DCI based on a PDCCH structure based on control channel elements (CCEs) (S208). In addition, the base station may apply additional processes such as scrambling, modulation (e.g., QPSK), interleaving, etc. to the multiplexed DCI, and then map the DCI to the resources to be transmitted. A CCE is a basic resource unit for the PDCCH, and one CCE may include multiple (e.g., six) resource element groups (REGs). One REG may be configured with multiple (e.g., 12) resource elements (REs). The number of CCEs used for one PDCCH may be defined as the aggregation level. In the 3GPP NR system, aggregation levels of 1, 2, 4, 8, or 16 may be used. Figure 5 Figure B is related to the CCE aggregation level and the multiplexing of the PDCCH, and illustrates the type of CCE aggregation level for one PDCCH and the CCEs transmitted in the control region accordingly.

[0091] Figure 6 Illustrates a control resource set (CORESET) in the 3GPP NR system in which a physical downlink control channel (PDCCH) may be transmitted.

[0092] A CORESET is time-frequency resources in which PDCCH (i.e., control signals for UEs) are transmitted. In addition, search spaces to be described later can be mapped to a CORESET. Thus, a UE can monitor the time-frequency domain designated as a CORESET instead of monitoring all frequency bands for PDCCH reception, and decode the PDCCH mapped to the CORESET. A base station can configure one or more CORESETs for each cell for a UE. A CORESET can be configured with up to three consecutive symbols on the time axis. In addition, a CORESET can be configured in units of six consecutive PRBs on the frequency axis. In Figure 5 an embodiment, CORESET#1 is configured with consecutive PRBs, while CORESET#2 and CORESET#3 are configured with non-consecutive PRBs. A CORESET can be located in any symbol in a time slot. For example, in Figure 5 an embodiment, CORESET#1 starts from the first symbol of a time slot, CORESET#2 starts from the fifth symbol of the time slot, and CORESET#9 starts from the ninth symbol of the time slot.

[0093] Figure 7 The figure illustrates a method for setting a PDCCH search space in a 3GPP NR system.

[0094] To transmit PDCCH to a UE, each CORESET can have at least one search space. In an embodiment of the present disclosure, a search space is a set of all time-frequency resources (hereinafter, PDCCH candidates) that can be used to transmit PDCCH for a UE. A search space can include a common search space that requires UEs of 3GPP NR to search together and a UE-specific search space or UE-specific search spaces that require a specific UE to search. In the common search space, a UE can monitor PDCCH that is set such that all UEs in cells belonging to the same base station search together. In addition, a UE-specific search space can be set for each UE such that the UE monitors PDCCH allocated to each UE at search space positions that differ according to the UE. In the case of a UE-specific search space, since a limited control area for allocating PDCCH can be allocated, search spaces between UEs can partially overlap and be allocated. Monitoring PDCCH includes blindly decoding PDCCH candidates in a search space. When the blind decoding is successful, it can be expressed as (successfully) detecting / receiving PDCCH, while when the blind decoding fails, it can be expressed as not detecting / not receiving or not successfully detecting / receiving PDCCH.

[0095] For ease of explanation, a physical downlink control channel (PDCCH) that is scrambled with a group common (GC) RNTI known to one or more UEs in advance to send downlink control information to one or more UEs is referred to as a group common (GC) PDCCH or a common PDCCH. In addition, a PDCCH that is scrambled with an RNTI of a specific terminal known to a specific UE to send uplink scheduling information or downlink scheduling information to the specific UE is referred to as a UE-specific PDCCH. The common PDCCH can be included in a common search space, and the UE-specific PDCCH can be included in the common search space or the UE-specific search space.

[0096] The base station can signal to each UE or UE group via the PDCCH information regarding resource allocation related to the paging channel (PCH) and the downlink shared channel (DL-SCH) as transmission channels (i.e., DL grant) or information regarding resource allocation related to the uplink shared channel (UL-SCH) and hybrid automatic repeat request (HARQ) (i.e., UL grant). The base station can send the PCH transport block and the DL-SCH transport block via the PDSCH. The base station can send data excluding specific control information or specific service data via the PDSCH. In addition, the UE can receive data excluding specific control information or specific service data via the PDSCH.

[0097] The base station can include in the PDCCH information regarding to which UE(s) the PDSCH data is to be sent and how the PDSCH data is to be received and decoded by the corresponding UE, and send the PDCCH. For example, assume that the DCI sent on a specific PDCCH is CRC masked with an RNTI "A", and the DCI indicates that the PDSCH is allocated to radio resources "B" (e.g., frequency position) and indicates transmission format information "C" (e.g., transport block size, modulation scheme, coding information, etc.). The UE monitors the PDCCH using the RNTI information the UE has. In this case, if there is a UE that performs blind decoding of the PDCCH using the "A" RNTI, the UE receives the PDCCH and receives the PDSCH indicated by "B" and "C" based on the information of the received PDCCH.

[0098] Table 3 shows an embodiment of a physical uplink control channel (PUCCH) used in a wireless communication system.

[0099] [Table 3]

[0100] PUCCH format Length of OFDM symbol Number of bits 0 1-2 ≤2 1 4-14 ≤2 2 1-2 ＞2 3 4-14 ＞2 4 4-14 ＞2

[0101] The PUCCH can be used to send the following uplink control information (UCI).

[0102] - Scheduling Request (SR): Information used to request UL UL-SCH resources.

[0103] - HARQ-ACK: Response to PDCCH (indicating DL SPS release) and / or response to DL transport block (TB) on PDSCH. HARQ-ACK indicates whether the information successfully transmitted on PDCCH or PDSCH is received. HARQ-ACK responses include positive ACK (simply referred to as ACK), negative ACK (NACK hereinafter), discontinuous transmission (DTX), or NACK / DTX. Here, the term HARQ-ACK is used interchangeably with HARQ-ACK / NACK and ACK / NACK. Generally, ACK can be represented by bit value 1, while NACK can be represented by bit value 0.

[0104] - Channel State Information (CSI): Feedback information about DL channels. The UE generates it based on CSI-reference signals (RS) sent by the base station. Feedback information related to multiple-input multiple-output (MIMO) includes rank indicator (RI) and precoding matrix indicator (PMI). CSI can be divided into CSI part 1 and CSI part 2 according to the information indicated by CSI.

[0105] In the 3GPP NR system, five PUCCH formats can be used to support various service scenarios, various channel environments, and frame structures.

[0106] PUCCH format 0 is a format capable of delivering 1-bit or 2-bit HARQ-ACK information or SR. PUCCH format 0 can be transmitted through one or two OFDM symbols on the time axis and one PRB on the frequency axis. When PUCCH format 0 is transmitted in two OFDM symbols, the same sequence on the two symbols can be transmitted through different RBs. In this case, the sequence can be a sequence obtained by cyclic shift (CS) from the basic sequence used in PUCCH format 0. Through this, the UE can obtain frequency diversity gain. More specifically, the UE can determine the cyclic shift (CS) value m bit according to M bit -bit UCI (M cs = 1 or 2). Additionally, a basic sequence of length 12 can be transmitted by mapping the cyclic shift sequence based on a predetermined CS value m cs to 12 REs of one OFDM symbol and one RB. When the number of cyclic shifts available to the UE is 12 and M bit = 1, 1-bit UCI 0 and 1 can be mapped to two cyclic shift sequences respectively, and the cyclic shift values of the two cyclic shift sequences have a difference of 6. Additionally, when M bitWhen M = 2, the 2-bit UCI 00, 01, 11, and 10 can be respectively mapped to four cyclic shift sequences with a difference of 3 in the cyclic shift value.

[0107] PUCCH format 1 can carry 1-bit or 2-bit HARQ-ACK information or SR. PUCCH format 1 can be transmitted through consecutive OFDM symbols on the time axis and one PRB on the frequency axis. Here, the number of OFDM symbols occupied by PUCCH format 1 can be one of 4 to 14. More specifically, the UCI with M bit = 1 can be BPSK modulated. The UE can modulate the UCI with M bit = 2 using quadrature phase shift keying (QPSK). The signal is obtained by multiplying the modulated complex-valued symbol d(0) by a sequence of length 12. In this case, the sequence can be the basic sequence for PUCCH format 0. The UE extends the even-numbered OFDM symbols to which PUCCH format 1 is assigned by a time-axis orthogonal cover code (OCC) to transmit the obtained signal. PUCCH format 1 determines the maximum number of different UEs multiplexed in one RB according to the length of the OCC to be used. The demodulation reference signal (DMRS) can be extended by the OCC and mapped to the odd-numbered OFDM symbols of PUCCH format 1.

[0108] PUCCH format 2 can carry UCI of more than 2 bits. PUCCH format 2 can be transmitted through one or two OFDM symbols on the time axis and one or more RBs on the frequency axis. When PUCCH format 2 is transmitted in two OFDM symbols, the sequences transmitted in different RBs through the two OFDM symbols can be the same. Here, the sequence can be a plurality of modulated complex-valued symbols d(0),..., d(M symbol - 1). Here, M symbol can be M bit / 2. Through this, the UE can obtain a frequency diversity gain. More specifically, the M bit -bit UCI (M bit > 2) is bit-level scrambled, QPSK modulated, and mapped to the RBs of one or two OFDM symbols. Here, the number of RBs can be one of 1 to 16.

[0109] PUCCH format 3 or PUCCH format 4 can deliver UCI of more than 2 bits. PUCCH format 3 or PUCCH format 4 can be transmitted through consecutive OFDM symbols on the time axis and one PRB on the frequency axis. The number of OFDM symbols occupied by PUCCH format 3 or PUCCH format 4 can be one of 4 to 14. Specifically, the UE modulates M bit bits of UCI (M bit>2) using π / 2 - Binary Phase Shift Keying (BPSK) or QPSK to generate complex-valued symbols d(0) to d(M symb -1). Here, when using π / 2-BPSK, M symb =M bit , while when using QPSK, M symb =M bit / 2. The UE may not apply block unit extension to PUCCH format 3. However, the UE may use a PreDFT-OCC of length 12 to apply block unit extension to one RB (i.e., 12 subcarriers), so that PUCCH format 4 can have two or four multiplexing capabilities. The UE performs transmit precoding (or DFT precoding) on the extended signal and maps it to each RE to transmit the extended signal.

[0110] In this case, the number of RBs occupied by PUCCH format 2, PUCCH format 3, or PUCCH format 4 can be determined according to the length and maximum coding rate of the UCI sent by the UE. When the UE uses PUCCH format 2, the UE can send HARQ-ACK information and CSI information together through PUCCH. When the number of RBs that the UE can send is greater than the maximum number of RBs that PUCCH format 2, PUCCH format 3, or PUCCH format 4 can use, the UE can, according to the priority of the UCI information, not send some UCI information but only send the remaining UCI information.

[0111] PUCCH format 1, PUCCH format 3, or PUCCH format 4 can be configured by RRC signaling to indicate frequency hopping in a time slot. When frequency hopping is configured, the index of the RB to be frequency-hopped can be configured by RRC signaling. When PUCCH format 1, PUCCH format 3, or PUCCH format 4 is transmitted through N OFDM symbols on the time axis, the first hop can have floor(N / 2) OFDM symbols and the second hop can have ceiling(N / 2) OFDM symbols.

[0112] PUCCH format 1, PUCCH format 3, or PUCCH format 4 can be configured to be repetitively transmitted in multiple time slots. In this case, the number of time slots K for repetitively transmitting the PUCCH can be configured by an RRC signal. The repetitively transmitted PUCCH must start from an OFDM symbol at a constant position in each time slot and have a constant length. When one of the OFDM symbols among the OFDM symbols of the time slots in which the UE is supposed to transmit the PUCCH is indicated as a DL symbol by an RRC signal, the UE may not transmit the PUCCH in the corresponding time slot and delay the transmission of the PUCCH to the next time slot to transmit the PUCCH.

[0113] Meanwhile, in the 3GPP NR system, the UE can perform transmission / reception using a bandwidth equal to or less than the bandwidth of a carrier (or cell). To this end, the UE can receive a bandwidth part (BWP) configured with some bandwidth of the carrier bandwidth as a continuous bandwidth. The UE operating according to TDD operation or in an unpaired spectrum can receive up to four DL / UL BWP pairs in one carrier (or cell). In addition, the UE can activate one DL / UL BWP pair. The UE operating according to FDD operation or in a paired spectrum can receive up to four DL BWPs on a DL carrier (or cell) and receive up to four UL BWPs on a UL carrier (or cell). The UE can activate one DL BWP and one UL BWP for each carrier (or cell). The UE may not perform reception or transmission in time-frequency resources other than the activated BWP. The activated BWP can be referred to as an active BWP.

[0114] The base station can indicate the activated BWP among the BWPs configured by the UE through downlink control information (DCI). The BWP indicated by the DCI is activated, and the other configured BWPs are deactivated. In a carrier (or cell) operating according to TDD operation, the base station can include a bandwidth part indicator (BPI) in the DCI for scheduling the PDSCH or PUSCH, and the bandwidth part indicator indicates the BWP to be activated to change the DL / UL BWP pair of the UE. The UE can receive the DCI for scheduling the PDSCH or PUSCH and can identify the DL / UL BWP pair activated based on the BPI. For a DL carrier (or cell) operating according to FDD operation, the base station can include a BPI indicating the BWP to be activated in the DCI for scheduling the PDSCH to change the DL BWP of the UE. For a UL carrier (or cell) operating according to FDD operation, the base station can include a BPI indicating the BWP to be activated in the DCI for scheduling the PUSCH to change the UL BWP of the UE.

[0115] Figure 8 is a conceptual diagram illustrating carrier aggregation.

[0116] Carrier aggregation is a method in which a UE uses multiple frequency blocks or (in a logical sense) cells configured with UL resources (or component carriers) and / or DL resources (or component carriers) as a large logical frequency band so that a wireless communication system can use a wider frequency band. A component carrier can also be referred to by terms such as primary cell (PCell) or secondary cell (SCell) or primary SCell (PScell). However, hereinafter, for the convenience of description, the term "component carrier" is used.

[0117] Reference Figure 8 , as an example of a 3GPP NR system, the entire system frequency band can include up to 16 component carriers, and each component carrier can have a bandwidth of up to 400 MHz. A component carrier can include one or more physically contiguous subcarriers. Although in Figure 8 it is shown that each component carrier has the same bandwidth, this is only an example, and each component carrier can have a different bandwidth. Additionally, although each component carrier is shown as being adjacent to each other on the frequency axis, the figures are shown in a logical concept, and each component carrier can be physically adjacent to each other or can be spaced apart.

[0118] Different center frequencies can be used for each component carrier. Additionally, a common center frequency can be used in physically adjacent component carriers. Assuming that in the embodiment of Figure 8 all component carriers are physically adjacent, then center frequency A can be used in all component carriers. Additionally, assuming that the respective component carriers are not physically adjacent to each other, then center frequency A and center frequency B can be used in each component carrier.

[0119] When expanding the total system frequency band through carrier aggregation, the frequency band used for communication with each UE can be defined in units of component carriers. UE A can use 100 MHz as the total system frequency band and use all five component carriers to perform communication. UE B1 - B5 can each use a 20 MHz bandwidth and use one component carrier to perform communication. UE C1 and C2 can each use a 40 MHz bandwidth and use two component carriers to perform communication. These two component carriers can be logically / physically adjacent or not adjacent. UE C1 represents the case of using two non - adjacent component carriers, while UE C2 represents the case of using two adjacent component carriers.

[0120] Figure 9 is a diagram for illustrating single - carrier communication and multi - carrier communication. In particular, Figure 9 (a) of Figure 9 shows a single - carrier subframe structure and (b) of

[0121] Reference Figure 9 As shown in (a) of Figure 9 , in the FDD mode, a general wireless communication system can perform data transmission or reception through a DL frequency band and a corresponding UL frequency band. In another specific embodiment, in the TDD mode, the wireless communication system can divide a radio frame into UL time units and DL time units in the time domain, and perform data transmission or reception through the UL / DL time units. Reference Figure 9 As shown in (b) of Figure 9 , it is possible to aggregate three 20 MHz component carriers (CCs) into each of the UL and DL, enabling support for a bandwidth of 60 MHz. Each CC can be adjacent or non - adjacent to each other in the frequency domain. Figure 9 Figure (b) of Figure 9 shows a case where the bandwidths of the UL CC and the DL CC are the same and symmetric, but it is possible to determine the bandwidth of each CC independently. In addition, asymmetric carrier aggregation with different numbers of UL CCs and DL CCs is possible. The DL / UL CCs allocated / configured to a specific UE through RRC can be referred to as the serving DL / UL CCs of the specific UE.

[0122] The base station can communicate with the UE by activating some or all of the serving CCs of the UE or deactivating some CCs. The base station can change the CCs to be activated / deactivated and the number of CCs to be activated / deactivated. If the base station allocates the CCs available to the UE as cell - specific or UE - specific, at least one of the allocated CCs can be deactivated unless the CC allocation for the UE is completely re - configured or the UE is switched. A CC not deactivated by the UE is referred to as the primary CC (PCC) or primary cell (PCell), and the CCs that the base station can freely activate / deactivate are referred to as secondary CCs (SCCs) or secondary cells (SCells).

[0123] Meanwhile, 3GPP NR uses the concept of cells to manage radio resources. A cell is defined as a combination of DL resources and UL resources, i.e., a combination of DL CC and UL CC. A cell can be configured with DL resources alone, or can be configured with a combination of DL resources and UL resources. When carrier aggregation is supported, the link between the carrier frequencies of the DL resources (or DL CC) and the UL resources (or UL CC) can be indicated by the system information. The carrier frequency refers to the center frequency of each cell or CC. The cell corresponding to the PCC is called the PCell, and the cell corresponding to the SCC is called the SCell. The carrier corresponding to the PCell in the DL is the DL PCC, and the carrier corresponding to the PCell in the UL is the UL PCC. Similarly, the carrier corresponding to the SCell in the DL is the DL SCC, and the carrier corresponding to the SCell in the UL is the UL SCC. Depending on the UE capabilities, the serving cell can be configured with one PCell and zero or more SCells. In the case of a UE in the RRC_CONNECTED state but not configured for carrier aggregation or not supporting carrier aggregation, there is only one serving cell configured with only the PCell.

[0124] As described above, the term "cell" used in carrier aggregation is distinguished from the term "cell" referring to a geographical area that provides communication services through a base station or an antenna group. That is, a component carrier can also be referred to as a scheduling cell, a scheduled cell, a primary cell (PCell), a secondary cell (SCell), or a primary SCell (PScell). However, to distinguish between the cell representing a geographical area and the cell in carrier aggregation, in this disclosure, the cell in carrier aggregation is referred to as a CC, and the cell of the geographical area is referred to as a cell.

[0125] Figure 10 FIG. is a diagram showing an example in which the cross-carrier scheduling technique is applied. When cross-carrier scheduling is set, the control channel transmitted through the first CC can use the Carrier Indicator Field (CIF) to schedule the data channel transmitted through the first CC or the second CC. The CIF is included in the DCI. In other words, a scheduling cell is set, and the DL grant / UL grant transmitted in the PDCCH area of the scheduling cell schedules the PDSCH / PUSCH of the scheduled cell. That is, there is a search area for multiple component carriers in the PDCCH area of the scheduling cell. The PCell can basically be the scheduling cell, and a specific SCell can be designated as the scheduling cell by the upper layer.

[0126] In Figure 10In the embodiment, it is assumed that three DL CCs are combined. Here, it is assumed that DL component carrier #0 is DLPCC (or PCell), and DL component carriers #1 and #2 are DL SCCs (or SCell). In addition, it is assumed that the DLPCC is set as the PDCCH monitoring CC. When cross-carrier scheduling is not configured by UE-specific (or UE group-specific or cell-specific) higher layer signaling, the CIF is disabled, and each DL CC can send only the PDCCH for scheduling its PDSCH without the CIF according to the NR PDCCH rules (non-cross-carrier scheduling, self-carrier scheduling). At the same time, if cross-carrier scheduling is configured by UE-specific (or UE group-specific or cell-specific) higher layer signaling, the CIF is enabled, and a specific CC (e.g., DL PCC) can use the CIF to send not only the PDCCH for scheduling the PDSCH of DL CC A but also the PDCCH for scheduling the PDSCH of another CC (cross-carrier scheduling). On the other hand, no PDCCH is sent in another DL CC. Therefore, the UE monitors the PDCCH without the CIF to receive the self-carrier scheduled PDSCH or monitors the PDCCH with the CIF to receive the cross-carrier scheduled PDSCH according to whether cross-carrier scheduling is configured for the UE.

[0127] On the other hand, Figure 9 and Figure 10 FIG. illustrates the subframe structure of the 3GPP LTE-A system, and the same or similar configurations can be applied to the 3GPP NR system. However, in the 3GPP NR system, Figure 9 and Figure 10 the subframe can be replaced by a time slot.

[0128] <Communication method in the unlicensed band>

[0129] Figure 11 FIG. illustrates the service environment of New Radio Unlicensed (NR-U).

[0130] Referring to Figure 11 , the service environments of NR technology 11 in the existing licensed band and unlicensed NR (NR-U) (i.e., NR technology 12 in the unlicensed band) can be provided to users. For example, in the NR-U environment, techniques such as carrier aggregation can be used to integrate NR technology 11 in the licensed band and NR technology 12 in the unlicensed band, which can contribute to the expansion of network capacity. In addition, in an asymmetric traffic structure with more downlink data than uplink data, NR-U can provide NR services optimized for various requirements or environments. For convenience, the NR technology in the licensed band is referred to as NR-L (licensed NR), and the NR technology in the unlicensed band is referred to as NR-U (unlicensed NR).

[0131] Figure 12 Illustrates a traditional communication scheme (e.g., wireless LAN) operating in an unlicensed band. Since most devices operating in the unlicensed band are based on "listen before talk" (LBT) operation, a clear channel assessment (CCA) technique that senses the channel for idleness before data transmission is performed.

[0132] Reference Figure 12 , a wireless LAN device (e.g., an AP or STA) checks whether the channel is busy by performing carrier sensing before transmitting data. When a radio signal of a predetermined intensity or higher intensity is sensed in the channel for data transmission, it is determined that the corresponding channel is busy, and the wireless LAN device delays access to the corresponding channel. Such a process is called clear channel assessment, and the signal level used to determine whether a signal is sensed is called the CCA threshold. Meanwhile, when no radio signal is sensed in the corresponding channel or when a radio signal with an intensity less than the CCA threshold is sensed, the channel is determined to be idle.

[0133] When the channel is determined to be idle, a terminal having data to transmit performs a backoff process after a deferral duration (e.g., arbitration inter-frame space (AIFS), PCF inter-frame space (PIFS), etc.). The deferral duration represents the shortest time the terminal needs to wait after the channel becomes idle. The backoff process allows the terminal to wait further for a predetermined time after the deferral duration. For example, the terminal prepares while reducing the slot time corresponding to the random number assigned to the terminal during the channel idle period in a contention window (CW), and a terminal that has completely exhausted the slot time can attempt to access the corresponding channel.

[0134] When the terminal successfully accesses the channel, the terminal can transmit data through the channel. After successfully transmitting the data, the CW size (CWS) is reset to the initial value (CWmin). On the contrary, when the data is not successfully transmitted, the CWS is increased to twice. As a result, a new random number is assigned to the terminal in a range twice as large as the previous random number range to perform the backoff process in the next CW. In a wireless LAN, only ACK is defined as the response information received for data transmission. Therefore, when ACK is received with respect to data transmission, the CWS is reset to the initial value, and when no feedback information is received with respect to data transmission, the CWS is increased to twice.

[0135] As described above, since the existing communication in the unlicensed band mainly operates based on LBT, the channel access in the NR-U system also performs LBT to coexist with existing devices. Specifically, according to the presence / absence / application method of LBT, the channel access method on the unlicensed band in NR can be classified into the following four categories.

[0136] ● Category 1: No LBT

[0137] The -Tx entity does not perform the LBT process for transmission.

[0138] ● Category 2: LBT without random backoff

[0139] - The Tx entity senses whether the channel is idle during a first interval without random backoff to perform transmission. That is, the Tx entity can perform transmission through the channel immediately after sensing that the channel is idle during the first interval. The first interval is an interval of a predetermined length immediately before the Tx entity performs transmission. According to an embodiment, the first interval can be an interval of 25 μs in length, but the present invention is not limited thereto.

[0140] ● Category 3: LBT with random backoff using a fixed-size CW

[0141] - The Tx entity obtains a random value within a fixed-size CW, sets it as the initial value N of a backoff counter (or backoff timer), and performs backoff by using the set backoff counter N. During the backoff process, whenever the channel is detected to be idle within a predetermined time slot period, the Tx entity decrements the backoff counter by 1. Here, the predetermined time slot period can be 9 μs, but the present invention is not limited thereto. The backoff counter N is decremented by 1 from the initial value, and when the value of the backoff counter N reaches 0, the Tx entity can perform transmission. At the same time, to perform backoff, the Tx entity first senses whether the channel is idle during a second interval (i.e., the deferral duration T d ). According to an embodiment of the present invention, the Tx entity can sense (determine) whether the channel is idle during the second interval based on whether the channel is idle during at least some periods (e.g., one time slot period) within the second interval. The second interval can be set based on the channel access priority level of the Tx entity and consists of a period of 16 μs and m consecutive time slot periods. Here, m is a value set according to the channel access priority level. When the channel is sensed to be idle during the second interval, the Tx entity performs channel sensing to decrement the backoff counter. On the other hand, when the channel is sensed to be busy during the backoff process, the backoff process stops. After stopping the backoff process, when the channel is sensed to be idle within an additional second interval, the Tx entity can resume backoff. In this way, in addition to the second interval, the Tx entity can also perform transmission when the channel is idle during the time slot period of the backoff counter N. In this case, the initial value of the backoff counter N is obtained within the fixed-size CW.

[0142] ● Category 4: LBT with random backoff by using a variable-size CW

[0143] - The Tx entity obtains a random value within a CW of variable size, sets this random value as the initial value of a backoff counter (or backoff timer) N, and performs backoff by using the set backoff counter N. More specifically, the Tx entity can adjust the size of the CW based on the HARQ-ACK information for a previous transmission, and obtain the initial value of the backoff counter N within the CW of the adjusted size. The specific process of performing backoff by the Tx entity is as described in Category 3. Except for the second interval, when the channel is idle during the time slot period of the backoff counter N, the Tx entity can perform transmission. In this case, the initial value of the backoff counter N is obtained within a CW of variable size.

[0144] In the above Categories 1 to 4, the Tx entity can be a base station or a UE. According to an embodiment of the present invention, the first type of channel access can refer to the channel access of Category 4, and the second type of channel access can refer to the channel access of Category 2.

[0145] Figure 13 The figure illustrates a channel access process based on Category 4 LBT according to an embodiment of the present invention.

[0146] To perform channel access, first, the Tx entity performs channel sensing (S302) within a deferral duration T d According to an embodiment of the present invention, the channel sensing in step S302 within the deferral duration T d can be performed by channel sensing within at least a part of the deferral duration T d For example, the channel sensing within the deferral duration T d can be performed by channel sensing during one time slot period within the deferral duration T d The Tx entity checks whether the channel is idle (S304) by performing channel sensing on the deferral duration T d If the channel is sensed to be idle within the deferral duration T d , the Tx entity proceeds to step S306. If the channel is not sensed to be idle (i.e., sensed to be busy) within the deferral duration T d , the Tx entity returns to step S302. The Tx entity repeats steps S302 to S304 until the channel is sensed to be idle within the deferral duration T d The deferral duration T d can be set based on the channel access priority level of the Tx entity, and this deferral duration T d consists of a period of 16 μs and m consecutive time slot periods. Here, m is a value set according to the channel access priority level.

[0147] Next, the Tx entity obtains a random value within a predetermined CW, sets this random value as the initial value N of the backoff counter (or backoff timer) (S306), and proceeds to step S308. The initial value of the backoff counter N is randomly selected from the values between 0 and CW. The Tx entity performs the backoff process by using the set backoff counter N. That is, the Tx entity performs the backoff process by repeating steps S308 to S316 until the value of the backoff counter N reaches 0. Meanwhile, Figure 13 The figure shows performing step S306 after sensing that the channel is idle for a deferral duration T d However, the present invention is not limited to this. That is, step S306 can be performed independently of steps S302 to S304 and can be performed before steps S302 to S304. When step S306 is performed before steps S302 to S304, if it is sensed through steps S302 to S304 that the channel is idle for a deferral duration T d then the Tx entity proceeds to step S308.

[0148] In step S308, the Tx entity checks whether the value of the backoff counter N is 0. If the value of the backoff counter N is 0, the Tx entity proceeds to step S320 to perform transmission. If the value of the backoff counter N is not 0, the Tx entity proceeds to step S310. In step S310, the Tx entity decrements the value of the backoff counter N by 1. According to an embodiment, the Tx entity can selectively decrement the value of the backoff counter during the channel sensing process of each time slot. In this case, step S310 can be skipped at least once through the selection of the Tx entity. Next, the Tx entity performs channel sensing for an additional time slot period (S312). The Tx entity checks whether the channel is idle through channel sensing within the additional time slot period (S314). If it is sensed that the channel is idle within the additional time slot period, the Tx entity returns to step S308. In this way, each time the channel is sensed to be idle within a predetermined time slot period, the Tx entity can decrement the backoff counter by 1. Here, the predetermined time slot period can be 9 μs, but the present invention is not limited to this.

[0149] In step S314, if the channel is not sensed to be idle (i.e., sensed as busy) in the additional time slot period, the Tx entity proceeds to step S316. In step S316, the Tx entity checks whether the channel is idle within an additional deferral duration T d According to an embodiment of the present invention, the channel sensing in step S316 can be performed in units of time slots. That is, the Tx entity checks whether the channel is sensed to be idle during all time slot periods of the additional deferral duration T d When the channel is sensed to be idle during all time slot periods of the additional deferral duration T dWhen a busy time slot is detected internally, the Tx entity immediately resumes step S316. When the channel is sensed to be idle during all time slot periods of the additional deferral duration T d the Tx entity returns to step S308.

[0150] On the other hand, if the value of the backoff counter N is 0 in the check of step S308, the Tx entity performs a transmission (S320). The Tx entity receives the HARQ-ACK feedback corresponding to the transmission (S322). The Tx entity can check whether the previous transmission was successful through the received HARQ-ACK feedback. Next, the Tx entity adjusts the CW size for the next transmission based on the received HARQ-ACK feedback (S324).

[0151] As described above, after sensing that the channel is idle within the deferral duration T d when the channel is idle within N additional time slot periods, the Tx entity can perform a transmission. As described above, the Tx entity can be a base station or a UE, and Figure 13 the channel access procedure of can be used for downlink transmission of the base station and / or uplink transmission of the UE.

[0152] Figure 14 is a block diagram showing the configurations of a UE and a base station according to an embodiment of the present invention. In an embodiment of the present invention, the UE can be implemented using various types of wireless communication devices or computing devices that ensure portability and mobility. The UE can be referred to as a user equipment (UE), a station (STA), a mobile subscriber (MS), etc. In addition, in an embodiment of the present invention, the base station controls and manages a cell corresponding to a service area (e.g., a macro cell, a femto cell, a pico cell, etc.), and performs functions such as signal transmission, channel assignment, channel monitoring, self-diagnosis, relaying, etc. The base station can be referred to as a next-generation node B (gNB) or an access point (AP).

[0153] As shown in the drawings, a UE 100 according to an embodiment of the present disclosure may include a processor 110, a communication module 120, a memory 130, a user interface 140, and a display unit 150.

[0154] First, the processor 110 can execute various instructions or programs and process data within the UE 100. In addition, the processor 110 can control the overall operation of each unit including the UE 100, and can control the transmission / reception of data between the units. Here, the processor 110 can be configured to perform the operations according to the embodiments described in the present invention. For example, the processor 110 can receive time slot configuration information, determine the time slot configuration based on the time slot configuration information, and perform communication according to the determined time slot configuration.

[0155] Next, the communication module 120 may be an integrated module that performs wireless communication using a wireless communication network and performs wireless LAN access using a wireless LAN. To this end, the communication module 120 can include multiple network interface cards (NICs) in an internal or external form, such as cellular communication interface cards 121 and 122 and an unlicensed band communication interface card 123. In the drawings, the communication module 120 is shown as an overall integrated module, but different from the drawings, each network interface card can be independently arranged according to the circuit configuration or usage.

[0156] The cellular communication interface card 121 can transmit or receive radio signals with at least one of the base station 200, an external device, and a server using a mobile communication network and provide cellular communication services in a first frequency band based on instructions from the processor 110. According to an embodiment, the cellular communication interface card 121 may include at least one NIC module using a frequency band less than 6 GHz. At least one NIC module of the cellular communication interface card 121 can independently perform cellular communication with at least one of the base station 200, an external device, and a server according to cellular communication standards or protocols in a frequency band below 6 GHz supported by the corresponding NIC module.

[0157] The cellular communication interface card 122 can transmit or receive radio signals with at least one of the base station 200, an external device, and a server using a mobile communication network and provide cellular communication services in a second frequency band based on instructions from the processor 110. According to an embodiment, the cellular communication interface card 122 may include at least one NIC module using a frequency band greater than 6 GHz. At least one NIC module of the cellular communication interface card 122 can independently perform cellular communication with at least one of the base station 200, an external device, and a server according to cellular communication standards or protocols in a frequency band above 6 GHz supported by the corresponding NIC module.

[0158] The unlicensed band communication interface card 123 transmits or receives radio signals with at least one of the base station 200, an external device, and a server using a third frequency band as an unlicensed band and provides unlicensed band communication services based on instructions from the processor 110. The unlicensed band communication interface card 123 may include at least one NIC module using an unlicensed band. For example, the unlicensed band may be a frequency band of 2.4 GHz, 5 GHz, 6 GHz, 7 GHz, or above 52.6 GHz. At least one NIC module of the unlicensed band communication interface card 123 can perform wireless communication with at least one of the base station 200, an external device, and a server independently or non-independently according to unlicensed band communication standards or protocols of the frequency band supported by the corresponding NIC module.

[0159] The memory 130 stores control programs used in the UE 100 and various data thereof. Such control programs may include prescribed programs required to perform wireless communication with at least one of the base station 200, external devices, and servers.

[0160] Next, the user interface 140 includes various input / output means provided in the UE 100. In other words, the user interface 140 can receive user input using various input means, and the processor 110 can control the UE 100 based on the received user input. In addition, the user interface 140 can perform output based on instructions from the processor 110 using various output means.

[0161] Next, the display unit 150 outputs various images on the display screen. The display unit 150 can output various display objects, such as the content executed by the processor 110 or the user interface, based on control instructions from the processor 110.

[0162] In addition, the base station 200 according to an embodiment of the present invention may include a processor 210, a communication module 220, and a memory 230.

[0163] First, the processor 210 can execute various instructions or programs and process internal data of the base station 200. In addition, the processor 210 can control the overall operation of each unit in the base station 200 and control the transmission and reception of data between each unit. Here, the processor 210 can be configured to perform operations according to the embodiments described in the present invention. For example, the processor 210 can signal the slot configuration and perform communication according to the signaled slot configuration.

[0164] Next, the communication module 220 can be an integrated module that performs wireless communication using a wireless communication network and performs wireless LAN access using a wireless LAN. To this end, the communication module 220 can include multiple network interface cards, such as cellular communication interface cards 221 and 222 and an unlicensed band communication interface card 223, in an internal or external form. In the drawings, the communication module 220 is shown as an overall integrated module, but different from the drawings, each network interface card can be independently arranged according to the circuit configuration or usage.

[0165] The cellular communication interface card 221 can transmit or receive radio signals with at least one of the UE 100, an external device, and a server by using a mobile communication network and provide cellular communication services in a first frequency band based on instructions from the processor 210. According to an embodiment, the cellular communication interface card 221 can include at least one NIC module using a frequency band less than 6 GHz. At least one NIC module of the cellular communication interface card 221 can independently perform cellular communication with at least one of the UE 100, an external device, and a server in a frequency band less than 6 GHz supported by the corresponding NIC module according to cellular communication standards or protocols.

[0166] The cellular communication interface card 222 can transmit or receive radio signals with at least one of the UE 100, an external device, and a server by using a mobile communication network and provide cellular communication services in a second frequency band based on instructions from the processor 210. According to an embodiment, the cellular communication interface card 222 can include at least one NIC module using a frequency band of 6 GHz or higher. At least one NIC module of the cellular communication interface card 222 can independently perform cellular communication with at least one of the UE 100, an external device, and a server in a frequency band of 6 GHz or higher supported by the corresponding NIC module according to cellular communication standards or protocols.

[0167] The unlicensed band communication interface card 223 transmits or receives radio signals with at least one of the UE 100, an external device, and a server by using a third frequency band as an unlicensed band and provides unlicensed band communication services based on instructions from the processor 210. The unlicensed band communication interface card 223 can include at least one NIC module using an unlicensed band. For example, the unlicensed band can be a frequency band of 2.4 GHz, 5 GHz, 6 GHz, 7 GHz, or above 52.6 GHz. At least one NIC module of the unlicensed band communication interface card 223 can independently or dependently perform wireless communication with at least one of the UE 100, an external device, and a server according to unlicensed band communication standards or protocols of the frequency band supported by the corresponding NIC module.

[0168] Figure 14 is a block diagram of the UE 100 and the base station 200 according to an embodiment of the present invention, and the blocks shown separately are logically divided elements of the device. Therefore, the foregoing elements of the device can be installed in a single chip or multiple chips according to the design of the device. In addition, a part of the configuration of the UE 100, such as the user interface 140, the display unit 150, etc., can be selectively provided in the UE 100. In addition, the user interface 140, the display unit 150, etc. can be additionally provided in the base station 200 when necessary.

[0169] Figure 15The figure illustrates the channel access procedure performed by a wireless communication device in an unlicensed band, as well as the LBT procedure used when the wireless communication device performs channel access in the unlicensed band. Specifically, the LBT procedure used when a wireless communication device according to an embodiment of the present invention performs channel access in the unlicensed band will be described. In particular, channel access can be configured in the wireless communication device in which the wireless communication device performs transmission according to the result of channel sensing within a time interval of a predetermined duration. In this case, a method for operating the wireless communication device when the wireless communication device fails to access the channel will be described. The specified duration mentioned above can be 16 μs.

[0170] For convenience of description, the wireless communication device that is the wireless endpoint initiating channel occupancy is referred to as the initiating node. Additionally, the wireless communication device that is the wireless endpoint communicating with the initiating node is referred to as the responding node. The initiating node can be a base station, and the responding node can be a UE. Additionally, the initiating node can be a UE, and the responding node can be a base station. When the initiating node wants to send data, the initiating node can perform channel access according to the channel access priority level determined according to the data type. In this case, the parameters for channel access can be determined according to the type of data. The parameters for channel access can include the minimum value of CW, the maximum value of CW, the maximum occupancy time (MCOT) which is the maximum duration that can occupy the channel in one channel occupancy, and the number of sensing time slots (m p ). Specifically, the initiating node can perform the above-mentioned Category 4 LBT according to the channel access priority level determined according to the data type.

[0171] Table 4 below shows an example of the parameter values for channel access according to the channel access priority level. Specifically, Table 4 shows the parameter values for channel access for each channel access priority level for downlink transmission in the LTE LAA system.

[0172] When the downlink channel transmitted by the wireless communication device includes data traffic, the deferral duration can be configured according to the channel access priority level of the traffic included in the downlink channel. In addition, the deferral duration can include an initial duration T f or one or more (m p ) slot durations T sl . In this case, the slot duration T sl can be 9 μs. The initial duration includes one idle slot duration T sl . Additionally, the number of slot durations (m p ) included in the deferral duration can be configured according to the above-mentioned channel access priority level. Specifically, the number of slot durations included in the deferral duration (mp ) It can be configured as shown in Table 4.

[0173] [Table 4]

[0174]

[0175] In addition, the wireless communication device can configure the range of CW values according to the channel access priority level. Specifically, the wireless communication device can set the value of CW to satisfy CW min,p <= CW <= CW max,p . In this case, the minimum value CW min,p and the maximum value CW max,p can be determined according to the channel access priority level. Specifically, the minimum value CW min,p and the maximum value CW max,p can be determined as shown in Table 4. The wireless communication device can set the minimum value CW min,p and the maximum value CW max,p during the counter value setting process. When the wireless communication device accesses a channel, the wireless communication device can adjust the value of CW, as described above with reference to Figure 13 . Additionally, in a wireless communication device in the unlicensed band, the MCOT T mcot，p can also be determined according to the channel access priority of the data included in the transmission as described above. Specifically, the MCOT can be determined as shown in Table 4. Therefore, it may not be allowed for the wireless communication device to perform continuous transmission for a time exceeding the MCOT in the unlicensed band. This is because the unlicensed band is a frequency band used by various wireless communication devices according to certain rules. In Table 4, when the value of the channel access priority level is p = 3 or p = 4, the unlicensed band is used for a long time as specified, and there are no wireless communication devices using other technologies. The wireless communication device can be configured with T mcot,p = 10 ms. Otherwise, the wireless communication device can be configured with T mcot,p = 8 ms.

[0176] Table 5 shows the parameter values for channel access for each channel access priority level for uplink transmission used in the LTE LAA system.

[0177] [Table 5]

[0178]

[0179] As described in Table 5, when one or more gaps are included in the transmission, the MCOT value of 6 ms can be increased to 8 ms. A gap represents the time from when transmission stops in a carrier until transmission resumes in the carrier. In this case, the minimum value of the gap duration is 100 μs. In addition, the maximum value of the transmission duration executed before including the gap is 6 ms. Further, the duration of the gap is not included in the channel occupancy time. When the value of the channel access priority level is 3 or 4 and it is guaranteed that no other radio access technology is used in the carrier where channel access is performed, the MCOT value can be 10 ms. In this case, another radio access technology can include Wi-Fi. Otherwise, the MCOT value can be determined as described in Note 1 of Table 5.

[0180] COT represents the time during which a wireless communication device occupies a channel. As described above, MCOT represents the maximum time for which an initiating node can continuously occupy a channel in any one of the carriers in the unlicensed band. However, as described above, gaps as intervals during which no transmission is performed can be included between multiple transmissions, and when gaps are included, the MCOT value can be applied differently.

[0181] <Side - link (SL) communication>

[0182] SL communication refers to a communication method that enables UEs to establish a direct link and directly exchange voice or data without going through a base station. In SL communication, Figure 14 the base station can be replaced by a UE. SL communication can be interchangeable with vehicle - to - everything (V2X) communication.

[0183] Figure 16 Examples of a UE and a base station for performing V2X or SL communication are shown.

[0184] Refer to Figure 16 , in V2X / SL communication, the term "UE" may mainly refer to a user's UE. However, when a network device such as a base station sends and receives signals according to the communication method between UEs, the base station can also be regarded as a type of UE.

[0185] UE 1 can select a resource unit corresponding to a specific resource from a resource pool that is a set of resources, and can operate by using this resource unit to send an SL signal. UE 2 as the receiving UE can receive the configuration of the resource pool for the signal sent by UE 1, and can detect the signal of UE 1 from the resource pool.

[0186] Here, when UE 1 is within the connection range of the base station, the base station can report the resource pool. However, when UE 1 is outside the connection range of the base station, another UE can report the resource pool, or the resource pool can be determined as a predetermined resource.

[0187] Figure 17 FIG. illustrates an example of a resource unit for V2X or SL communication.

[0188] Referring to Figure 17 , the resource pool may include multiple resource units, and each UE may select and use one or more resource units to send SL signals. All frequency resources of the resource pool may be divided into N F units, and all time resources of the resource pool may be divided into N T units. Therefore, a total of N F *N T resource units can be defined in the resource pool.

[0189] As Figure 17 shown, a resource unit (e.g., unit #0) can be repeated periodically. Alternatively, in order to obtain a diversity effect in the time or frequency dimension, the index of the physical resource unit mapped to by one logical resource unit can change over time in a predetermined pattern. In this structure of the resource unit, the resource pool can refer to the set of resource units that a UE wanting to send an SL signal can use for transmission.

[0190] The resource pool can be divided into multiple types. For example, according to the content of the SL signals sent in each resource pool, the resource pool can be classified as follows.

[0191] (1) Scheduling Assignment (SA) can be a signal including information such as the location of the resources used by the sending UE to send the SL data channel, the modulation and coding scheme (MCS) or the multiple-input multiple-output (MIMO) transmission method required to demodulate other data channels, and the timing advance (TA). SA can also be multiplexed and transmitted on the same resource unit as the SL data. In this case, the SA resource pool can refer to the resource pool in which SA is multiplexed and sent with the SL data. SA can also be referred to as the SL control channel.

[0192] (2) The SL data channel (Physical Sidelink Shared Channel: PSSCH) can be the resource pool used by the sending UE to send user data. If SA is multiplexed and sent on the same resource unit as the SL data, then only the SL data channel excluding the SA information can be sent in the resource pool of the SL data channel. That is, the resource elements (REs) used to send SA information on a single resource unit within the SA resource pool can still be used to send SL data in the resource pool for the SL data channel.

[0193] Hereinafter, resource allocation in SL will be described.

[0194] Figure 18 FIG. illustrates an example of the process by which a UE performs V2X or SL communication according to a transmission mode.

[0195] Reference Figure 18 , Figure 18 Figure (a) shows UE operations related to transmission mode 1 or transmission mode 3, and Figure 18 Figure (b) shows UE operations related to transmission mode 2 or transmission mode 4.

[0196] Reference Figure 18 As shown in Figure (a), in transmission mode 1 / 3, the base station performs resource scheduling on UE 1 through PDCCH (more specifically, downlink control information (DCI)), and UE 1 performs UE 2 SL / VTX communication according to the resource scheduling. UE 1 can send sidelink control information (SCI) to UE 2 through the physical sidelink control channel (PSCCH), and then send data based on the SCI through the physical sidelink shared channel (PSSCH). In LTE SL, transmission mode 1 can be applied to general SL communication, and transmission mode 3 can be applied to V2X SL communication.

[0197] Refer to Figure 18 Figure (b), in transmission mode 2 / 4, the UE can schedule resources autonomously. More specifically, in LTE SL, transmission mode 2 can be applied to general SL communication, where the UE can perform SL operations by autonomously selecting resources from the configured resource pool. Transmission mode 4 can be applied to V2X SL communication, where the UE can autonomously select resources within the selection window via the sensing / SA decoding process and then perform V2X SL operations. UE 1 can send SCI to UE 2 through the PSCCH, and then send data based on the SCI through the PSSCH. Hereinafter, the transmission mode can be abbreviated as mode. Processes related to sensing and resource (re)selection can be supported in resource allocation mode 2. The sensing process can be defined as decoding SCI from another UE and / or SL measurements. Decoding SCI during the sensing process can provide at least information about the SL resources indicated by the UE sending the SCI. When the SCI is decoded, the sensing process can use the L1 SL reference signal received power (RSRP) measurement based on the sidelink demodulation reference signal (DMRS). The resource (re)selection process can use the results of the sensing process to determine the resources for SL transmission.

[0198] Figure 19 An example of a method for a UE to select transmission resources for sending signals is shown.

[0199] Refer to Figure 19 , the UE can identify the transmission resources reserved by other UEs or the resources being used by other UEs by sensing within the sensing window, and can randomly select resources with less interference from the remaining resources excluding the reserved or used resources within the selection window.

[0200] For example, the UE may decode a PSCCH including information on the period of reserved resources within the sensing window, and may measure the PSSCH RSRP of resources periodically determined based on the PSCCH. The UE may exclude resources with PSSCH RSRP values exceeding a threshold from the selection window. Subsequently, the UE may randomly select SL resources among the remaining resources within the selection window.

[0201] Figure 20 FIG. illustrates examples of three broadcast types of NR side links.

[0202] Referring to Figure 20 , the NR side link supports three types of broadcasts: unicast, multicast, and broadcast. In unicast SL communication, the UE may perform one-to-one communication with another UE. In multicast SL communication, the UE may perform SL communication with one or more UEs in the group to which the UE belongs. Multicast SL communication may be replaced by using SL multicast communication, SL one-to-many communication, etc.

[0203] In the following, the hybrid automatic repeat request (HARQ) process in SL is described.

[0204] In SL unicast and multicast, HARQ feedback and HARQ combining in the physical layer may be supported. For example, when the receiving UE operates in resource allocation mode 1 or 2, the receiving UE may receive a PSSCH from the transmitting UE, and may send HARQ feedback on the PSSCH to the transmitting UE through the physical side link feedback channel (PSFCH) by using the side link feedback control information (SFCI) format.

[0205] For example, SL HARQ feedback may be enabled for multicast. That is, in non-CBG operation, two HARQ feedback options may be supported for multicast.

[0206] (1) Multicast option 1: After the receiving UE decodes the PSCCH targeted at the receiving UE, when the receiving UE fails to decode the transport block associated with the PSCCH, the receiving UE may send a HARQ-NACK to the transmitting UE through the PSFCH. However, when the receiving UE decodes the PSCCH targeted at the receiving UE and successfully decodes the transport block associated with the PSCCH, the receiving UE may not send a HARQ-ACK to the transmitting UE.

[0207] (2) Multicast Option 2: After the receiving UE decodes the PSCCH targeted for the receiving UE, when the receiving UE fails to decode the transport block associated with the PSCCH, the receiving UE may send a HARQ-NACK to the transmitting UE via the PSFCH. When the receiving UE decodes the PSCCH targeted for the receiving UE and successfully decodes the transport block associated with the PSCCH, the receiving UE may send a HARQ-ACK to the transmitting UE via the PSFCH.

[0208] For example, in SL communication related to services with high reliability requirements or services with relatively high reliability requirements, the SL HARQ feedback operation and / or mechanism of the UE may be useful. For example, in SL communication related to services with high reliability requirements, the operation of the receiving UE sending SL HARQ feedback to the transmitting UE of the service may help meet the high reliability requirements.

[0209] The HARQ feedback resource may include a HARQ feedback transmission resource and / or a HARQ feedback reception resource. For example, the HARQ feedback transmission resource may include a resource for sending HARQ feedback and / or a resource related to the transmission of HARQ feedback. For example, the HARQ feedback reception resource may include a resource for receiving HARQ feedback and / or a resource related to the reception of HARQ feedback.

[0210] The PSSCH resource may include a PSSCH transmission resource and / or a PSSCH reception resource. For example, the PSSCH transmission resource may include a resource for transmitting the PSSCH and / or a resource related to the transmission of the PSSCH. For example, the PSSCH reception resource may include a resource for receiving the PSSCH and / or a resource related to the reception of the PSSCH.

[0211] The PSCCH resource may include a PSCCH transmission resource and / or a PSSCH reception resource. For example, the PSCCH transmission resource may include a resource for transmitting the PSCCH and / or a resource related to the transmission of the PSCCH. For example, the PSCCH reception resource may include a resource for receiving the PSCCH and / or a resource related to the reception of the PSCCH.

[0212] The resource may include at least one of a time domain resource, a frequency domain resource, and / or a code domain resource.

[0213] When a resource conflict occurs in at least one of the PSSCH transmission, PSCCH transmission, and / or HARQ feedback transmission of a UE, the SL HARQ feedback process and / or operation of the UE may be difficult to operate correctly. For example, when a resource conflict occurs in at least one of the PSSCH transmission, PSCCH transmission, and / or HARQ feedback transmission of a UE, the overall SL HARQ feedback process and / or operation of the UE may be difficult to execute accurately.

[0214] When the receiving UE successfully receives the PSSCH, but there is an error in the HARQ feedback (e.g., HARQ ACK) due to a resource conflict, the transmitting UE may unnecessarily re - transmit the PSSCH to the receiving UE. For example, when the receiving UE fails to receive the PSSCH and does not deliver the HARQ feedback to the transmitting UE due to a resource conflict, the reliability or performance related to SL communication may be reduced. For example, when the receiving UE fails to receive the PSCCH and / or PSSCH sent from the transmitting UE, and due to a resource conflict, the HARQ NACK corresponding to the PSCCH or PSSCH is not correctly delivered to the transmitting UE, the reliability or performance related to SL communication may be reduced. Therefore, it is necessary to determine the HARQ feedback resources to avoid or minimize conflicts between multiple UEs.

[0215] The transmitting UE can send the PSCCH and / or PSSCH to the receiving UE. For example, the transmitting UE can send SL information to the receiving UE by using the PSCCH resource and / or PSSCH resource. For example, the SL information can include at least one of SL control information, SL data, SL packets, SL transport blocks (TBs), SL messages, and / or SL services.

[0216] The receiving UE can determine the HARQ feedback resources. Additionally, for example, the transmitting UE can determine the HARQ feedback resources.

[0217] The HARQ feedback resources can be configured to have an association or link with the PSSCH. For example, the HARQ feedback resources can include at least one of time - domain resources, frequency - domain resources, and / or code - domain resources. For example, the location of the HARQ feedback resources can be configured to have an association or link with the associated PSSCH resources. For example, based on a predefined function, the location of the HARQ feedback resources can be configured to have an association or link with the location of the associated PSSCH resources. For example, the HARQ feedback resources can be determined based on at least one of the information about the time - domain related to the PSSCH, the information about the frequency - domain related to the PSSCH, and the information about the code - domain related to the PSSCH.

[0218] Alternatively, for example, the HARQ feedback resource may be configured to be associated or linked with the PSCCH. For example, the location of the HARQ feedback resource may be configured to be associated or linked with the associated PSCCH resource. For example, based on a predefined function, the location of the HARQ feedback resource may be configured to be associated or linked with the location of the associated PSCCH resource. For example, the HARQ feedback resource may be determined based on at least one of information about the time domain related to the PSCCH, information about the frequency domain related to the PSCC, and / or information about the code domain related to the PSCCH.

[0219] The HARQ feedback resource can be configured in the form of a subset of the frequency resources used for PSSCH transmission and / or PSCCH transmission. For example, the frequency domain of the HARQ feedback resource can be configured in the form of a subset of the frequency domain of the associated PSSCH resource and / or PSCCH resource. For example, the frequency domain of the HARQ feedback resource may be included in the frequency domain of the PSSCH resource and / or PSCCH resource.

[0220] Figure 21 An example of a resource for transmitting HARQ feedback in the NR sidelink is illustrated.

[0221] Referring to Figure 21 , the transmitting UE can send the PSCCH and / or PSSCH to the receiving UE through four subchannels. In this case, the frequency domain of the HARQ feedback resource related to the PSCCH and / or PSSCH may be a subset of the frequency resources used by the transmitting UE to send the PSCCH or PSSCH.

[0222] A time gap can be configured between the HARQ feedback resource and the PSSCH resource. Alternatively, for example, a time gap can be configured between the HARQ feedback resource and the PSCCH resource. For example, considering the decoding ability and / or latency requirements of the UE (e.g., V2X messages and / or service-related latency requirements), a time interval can be configured between the time when the receiving UE receives the PSSCH and / or PSCCH and the time when the receiving UE sends the HARQ feedback. For example, considering the decoding ability and / or latency requirements of the UE, a time interval can be configured between the time when the transmitting UE receives the HARQ feedback and the time when the transmitting UE (re)transmits the PSSCH and / or PSCCH.

[0223] The time interval can be configured jointly within the resource pool. For example, the time gap can be configured jointly between different UEs within the resource pool. For example, the time gap can be configured jointly for the transmitting UE and the receiving UE. Thus, the UE can simply determine the HARQ feedback resource. For example, the time interval can be configured to be specific to the resource pool.

[0224] The time interval can be configured or specified to be less than and / or equal to the minimum value among the latency budgets of co - existing services on the resource pool. For example, when service A and service B co - exist on the resource pool and the latency budget of service A is less than that of service B, the time gap can be configured or specified to be less than or equal to the waiting budget of service A.

[0225] The time interval can be specified such that the maximum number of re - transmissions related to the transport block (TB) specifically configured for the resource pool, the type of service, the priority of the service, the type of broadcast, and / or the QoS requirements of the service is fully supported / executed within the latency budget for the (relevant) service on the resource pool. For example, the maximum number of re - transmissions can be the maximum allowable number of re - transmissions including the initial transmission.

[0226] The time gap can be configured or specified to be greater than and / or equal to the maximum value among the decoding capabilities of the UE. For example, the decoding capability can be the processing time of the UE required from the time when the UE terminates / ends receiving the PSSCH to the time when the UE starts transmitting the PSSCH. Additionally / Alternatively, for example, the decoding capability can be the processing time of the UE required from the time when the UE terminates / ends receiving the PSCCH to the time when the UE starts transmitting the PSFCH. For example, the time gap can be configured or specified to be greater than and / or equal to the maximum value among the decoding capabilities of the UEs in the resource pool. For example, when UEs A, B, and C perform SL communication in the resource pool and the decoding capability of UE A is the lowest, the time gap can be configured or specified to be greater than or equal to the value of the processing time required from the time when the UE terminates / ends receiving the PSSCH and / or PSCCH of UE A to the time when UE A starts transmitting the PSFCH.

[0227] The time gap can be configured differently or independently according to the type of service, the priority of the service, the type of SL communication, the session related to the service, the PPP related to the service, the PPPR related to the service, the target block error rate (BLER) related to the service, the target signal - to - interference - plus - noise ratio (SINR) related to the service, the latency budget related to the service, and / or the UE capabilities. For example, the time gap can be configured differently or independently according to the type of service, the priority of the service, the type of SL communication, the session related to the service, the PPP related to the service, the PPPR related to the service, the target block error rate (BLER) related to the service, the target signal - to - interference - plus - noise ratio (SINR) related to the service, the latency budget related to the service, and / or the UE capabilities within the resource pool. For example, the type of SL communication can include at least one of unicast, multicast, and / or broadcast.

[0228] The receiving UE may send HARQ feedback to the transmitting UE. For example, the receiving UE may send HARQ feedback corresponding to the PSCCH and / or PSSCH to the transmitting UE. For example, the receiving UE may send HARQ feedback to the transmitting UE by using the HARQ feedback resource determined based on the PSCCH resource and / or PSSCH resource. For example, the transmitting UE may receive HARQ feedback from the receiving UE on the HARQ feedback resource determined based on the PSCCH resource and / or PSSCH resource.

[0229] When the receiving UE successfully receives the PSCCH and / or PSSCH, the HARQ feedback may be HARQ ACK. For example, when the receiving UE fails to receive the PSCCH and / or PSSCH, the HARQ feedback may be at least one of HARQ NACK and / or discontinuous transmission (DTX).

[0230] In the multicast where multiple UEs in a group perform SL communication with each other, the HARQ feedback resource can be configured in two forms.

[0231] (1) Option A: A common HARQ feedback resource can be configured for the receiving UEs. For example, when the transmitting UE sends the PSSCH and / or PSCCH to multiple receiving UEs, the HARQ feedback resource can be configured commonly for the multiple receiving UEs that have received the PSSCH and (or) PSCCH.

[0232] (2) Option B: Different or independent HARQ feedback resources can be configured for the receiving UEs. For example, different or independent HARQ feedback resources can be configured for each receiving UE or for each subgroup including one or more receiving UEs. For example, when the transmitting UE sends the PSSCH and / or PSCCH to multiple receiving UEs, different or independent HARQ feedback resources can be configured respectively for the multiple receiving UEs or for the multiple subgroups that have received the PSSCH and (or) PSCCH.

[0233] Option A may only be applicable to multicast option 1. For example, in multicast option 1, only when the PSCCH and / or PSSCH fails to be received, multiple receiving UEs can send HARQ NACK to the transmitting UE by using the HARQ feedback resource that is usually configured for multiple receiving users. For example, the HARQ NACK can be configured in the form of a single-frequency network (SFN). In this case, the transmitting UE may not receive the HARQ NACK sent by multiple receiving UEs individually. Therefore, the transmitting UE may not know which receiving UE has sent the HARQ NACK. However, the transmitting UE can know that at least one of the multiple receiving UEs has sent the HARQ NACK, and can retransmit the PSCCH and / or PSSCH to the multiple receiving UEs.

[0234] In Option A, the HARQ feedback resource structure related to unicast can be reused. Additionally / Alternatively, for example, in Option A, the overhead related to HARQ feedback resources can be reduced. However, in Option A, there may be a limitation that the transmitting UE cannot determine / identify DTX. For example, when the transmitting UE sends a PSSCH and / or a PSCCH to the receiving UE, the receiving UE may not receive the PSCCH that schedules the PSSCH. In this case, according to Option A, the receiving UE may not send a HARQ NACK to the transmitting UE. Therefore, the transmitting UE may misunderstand that the receiving UE has successfully received the PSSCH.

[0235] In Option B, in a group including multiple receiving UEs, different or independent HARQ feedback resources can be allocated to each receiving UE or each subgroup. Here, for example, according to Option B, as the number of receiving UEs or subgroups included in the group increases, a larger number of HARQ feedback resources may be required. For example, for a group including N receiving UEs, N - 1 HARQ feedback resources may be required. For example, Option B may be limited to the multicast Option 2.

[0236] Figure 22 The figure illustrates an example of the process for sending and receiving HARQ feedback on a PSCCH and / or a PSSCH.

[0237] Referring to Figure 22 , multiple receiving UEs can each send HARQ feedback to the transmitting UE. For example, multiple receiving UEs can each send HARQ feedback corresponding to a PSCCH and / or a PSSCH to the transmitting UE. Multiple receiving UEs can each send HARQ feedback to the transmitting UE by using HARQ feedback resources determined based on PSCCH resources and / or PSSCH resources.

[0238] When the receiving UE successfully receives a PSCCH and / or a PSSCH, the HARQ feedback can be a HARQ ACK. For example, when the receiving UE fails to receive a PSCCH and / or a PSSCH, the HARQ feedback can be at least one of a HARQ NACK and / or discontinuous transmission (DTX).

[0239] The UE can determine the HARQ feedback transmission power based on at least one of the following: the SL path loss value derived / obtained based on the reference signal on the SL channel, the SL RSRP value derived / obtained based on the reference signal on the SL channel, the SL RSRQ value derived / obtained based on the reference signal on the SL channel, the open-loop power control parameter, and / or the closed-loop power control parameter. For example, when the transmitting UE sends a reference signal to the receiving UE via the SL channel, the receiving UE can determine the HARQ feedback transmission power based on at least one of the following: the SL path loss value derived / obtained based on the reference signal on the SL channel, the SL RSRP value derived / obtained based on the reference signal on the SL channel, the SL RSRQ value derived / obtained based on the reference signal on the SL channel, the open-loop power control parameter, and / or the closed-loop power control parameter.

[0240] The reference signal on the SL channel can be predefined. The reference signal on the SL channel can be the DMRS sent on the PSSCH (i.e., PSSCH DMRS) or the DMDS sent on the PSCCH (i.e., PSCCH DMRS). The reference signal on the SL channel can be the CSI-RS transmitted on the PSSCH. The reference signal on the SL channel can be a reference signal for estimating the quality of the SL channel (e.g., CQI, PMI, or RI). For example, the reference signal on the SL channel can be a reference signal for measuring at least one of the SL path loss value, the SL RSRP value, and / or the SL RSRQ value.

[0241] The SL path loss can be the path loss in the link between the transmitting UE and the receiving UE. For example, the open-loop power control parameter and / or the closed-loop power control parameter can be preconfigured. For example, the open-loop power control parameter can include Po and / or the alpha value.

[0242] Po can be a power control parameter for averaging to meet the target error rate related to packet / message transmission (e.g., block error rate (BLER) or frame error rate (FER)). Additionally / alternatively, for example, Po can be a power control parameter related to the average received SINR between the transmitting UE and the receiving UE. For example, Po can be a UE-specific power control parameter, resource pool, type of service, service priority, QoS requirements related to the service, size of the (frequency) resource for SL transmission, MCS value for SL transmission, congestion level related to the resource pool (e.g., CBR), and / or type of broadcast. For example, when calculating / deriving the HARQ feedback transmission power based on the SL RSRP and / or SL RSRQ value / range, different Po values / ranges can be mapped / configured for each (preconfigured) SL RSRP or SL RSIQ value / range.

[0243] When deriving / calculating the HARQ feedback transmission power based on the SL path loss, the alpha value can be the weight applied to the (measured) path loss compensation. Additionally / Alternatively, when calculating / deriving the HARQ feedback transmission power based on the SL RSRP and / or SL RSRQ value / range, the alpha value can be the weight applied to the (measured) SL RSRP or SL RSRQ value / range. Additionally / Alternatively, when calculating / deriving the HARQ feedback transmission power based on the SL RSRP and / or SL RSRQ value / range, the alpha value can be the weight applied to the HARQ feedback transmission power consumption mapped / configured for each (measured) SL RSRP or SL RSIQ value / range. Here, the alpha value / range can be configured to be specific to the UE, resource pool, type of service, priority of service, QoS requirements related to the service, size of the (frequency) resource for SL transmission, MCS value for SL transmission, congestion level related to the resource pool (e.g., CBR), and / or type of broadcast. When calculating / deriving the HARQ feedback transmission power based on the SL RSRP and / or SL RSRQ value / range, different alpha values / ranges can be mapped / configured for each (pre-configured) SL RSRP or SL RSRQ value / range.

[0244] When calculating / deriving the HARQ feedback transmission power based on the SL RSRP and / or SL RSRQ value / range, different offset values / ranges can be mapped / configured for each (pre-configured) SL RSRP or SL RSIQ value / range. The UE that measures the SL RSRP and / or SL RSRQ can apply the offset related to the SL RSRP value and / or SL RSRQ value to the (pre-configured normalized or nominal) SL (HARQ feedback) (maximum) transmission power to determine the final HARQ feedback transmission power. Here, for example, the offset value / range can be configured to be specific to the UE, resource pool, type of service, priority of service, QoS requirements related to the service, size of the (frequency) resource for SL transmission, MCS value for SL transmission, congestion level related to the resource pool (e.g., CBR), and / or type of broadcast.

[0245] Different (normalized or nominal) (maximum) HARQ feedback transmission power value / ranges can be mapped / configured for each SL RSRP and / or SL RSRQ value / range. For example, the (normalized or nominal) (maximum) HARQ feedback transmission power value / range can be configured to be specific to the UE, resource pool, type of service, priority of service, QoS requirements related to the service, size of the (frequency) resource for SL transmission, MCS value for SL transmission, congestion level related to the resource pool (e.g., CBR), and / or type of broadcast.

[0246] The transmit power value related to the reference signal and / or the SL channel including the reference signal can be signaled to the UE via a predefined channel. The transmitting UE can send the transmit power value related to the reference signal and / or the SL channel including the reference signal to the receiving UE via the predefined channel. The predefined channel can be the PSCCH. The receiving UE can be a terminal that measures at least one of the SL path loss, SL RSRP, and / or SL RSRQ based on the reference signal.

[0247] The open-loop power control parameters (and / or the HARQ feedback transmission power values mapped / configured for each SL RSRP (and / or SL RSRQ) value / range (maximum or minimum)) can be configured differently or independently according to the type of service, the priority of the service, the type of SL communication (e.g., unicast, multicast, or broadcast), the congestion level (e.g., the channel busy rate (CBR)) (related to the resource pool), the session related to the service, the PPP related to the service, the PPPR related to the service, the target block error rate (BLER) related to the service, the target signal-to-interference-plus-noise ratio (SINR), the (minimum or maximum) target communication distance related to the service, and / or the delay budget related to the service. Additionally / Alternatively, for example, the closed-loop power control operations / parameters can be managed / configured differently or independently according to the type of service, the priority of the service, the type of SL communication (e.g., unicast, multicast, or broadcast), the congestion level (e.g., CBR) (related to the resource pool), the session related to the service, the PPP related to the service, the PPPR related to the service, the target block error rate (BLER) related to the service, the target signal-to-interference-plus-noise ratio (SINR) related to the service, the (minimum or maximum) target communication distance related to the service, and / or the delay budget related to the service.

[0248] The open-loop power control parameters related to the HARQ feedback can be configured differently or independently from the open-loop power control parameters related to the PSSCH and / or PSCCH. Additionally / Alternatively, the closed-loop power control operations / parameters related to the HARQ feedback can be managed / configured differently or independently from the closed-loop power control operations / parameters related to the PSSCH and / or PSCCH.

[0249] FDM of HARQ feedback resources may be only allowed or configured for receiving UEs whose distance from the transmitting UE that receives HARQ feedback is within a preset threshold. Additionally / Alternatively, FDM of HARQ feedback resources may be only allowed or configured for receiving UEs for which the SL path loss difference in the link between the transmitting UE and the receiving UE is within a preset threshold. Additionally / Alternatively, FDM of HARQ feedback resources may be only allowed or configured for receiving UEs for which the SL RSRP difference in the link between the transmitting UE and the receiving UE is within a preset threshold. Additionally / Alternatively, FDM of HARQ feedback resources may be only allowed or configured for receiving UEs for which the SL RSRQ difference in the link between the transmitting UE and the receiving UE is within a preset threshold.

[0250] When the distance difference between multiple receiving UEs and the transmitting UE is within a preset threshold, the multiple receiving UEs may send HARQ feedback through frequency division multiplexing resources on the frequency axis. Additionally / Alternatively, when the path loss difference between multiple receiving UEs and the transmitting UE is within a preset threshold, the multiple receiving UEs may send HARQ feedback through frequency division multiplexing resources on the frequency axis. Additionally / Alternatively, when the (measured) RSRP value difference between multiple receiving UEs and the transmitting UE is within a preset threshold, the multiple receiving UEs may send HARQ feedback through frequency division multiplexing resources on the frequency axis. Additionally / Alternatively, when the (measured) RSRQ value difference between multiple receiving UEs and the transmitting UE is within a preset threshold, the multiple receiving UEs may send HARQ feedback through frequency division multiplexing resources on the frequency axis.

[0251] It may not be desirable to frequency-division multiplex HARQ feedback resources between subgroups or UEs within a group. When power control related to HARQ feedback transmission is not applied, it may not be desirable to frequency-division multiplex HARQ feedback resources between different subgroups or different UEs within a group. When the difference in HARQ feedback reception power between different subgroups or different UEs within a group is greater than a preset threshold, it may not be desirable to frequency-division multiplex HARQ feedback resources between different subgroups or different UEs within a group. When the difference in SL path loss between different subgroups or different UEs within a group is greater than a preset threshold, it may not be desirable to frequency-division multiplex HARQ feedback resources between different subgroups or different UEs within a group. When the SL RSRP difference between different subgroups or different UEs within a group is greater than a preset threshold, it may not be desirable to frequency-division multiplex HARQ feedback resources between different subgroups or different UEs within a group. When the SL RSRQ difference between different subgroups or different UEs within a group is greater than a preset threshold, it may not be desirable to frequency-division multiplex HARQ feedback resources between different subgroups or different UEs within a group.

[0252] As shown in the above example, when it is not desired that the HARQ feedback resources are frequency division multiplexed, the HARQ feedback resources can be pseudo-randomly frequency division multiplexed based on at least one of the GUE_ID, the receiving UE-related identifier, the SL HARQ process ID, and / or the transmitting UE-related identifier. The HARQ feedback resources can be pseudo-randomly determined based on at least one of the GUE_ID, the receiving UE-related identifier, the SL HARQ process ID, and / or the transmitting UE-related identifier. For example, the HARQ feedback resources can be frequency division multiplexed or determined by a function with at least one of the GUE_ID, the receiving UE-related identifier, the SL HARQ process ID, and / or the transmitting UE-related identifier as input parameters. The HARQ feedback resources can be the HARQ feedback resources for each of the multiple UEs in the group. The HARQ feedback resources can be the HARQ feedback resources for each subgroup in the group. For example, the receiving UE-related identifier can be the destination ID. The transmitting UE-related identifier may be the source ID. The function can be predefined.

[0253] The transmitting UE can send the PSCCH and / or PSSCH to the receiving UE. The transmitting UE can send the SL information to the receiving UE by using the PSCCH resources and / or PSSCH resources. The SL information can include at least one of SL control information, SL data, SL packets, SL transport blocks (TBs), SL messages, and / or SL services.

[0254] The receiving UE can determine the HARQ feedback resources. Additionally, the transmitting UE can determine the HARQ feedback resources. For example, the receiving UE can be one of the multiple UEs performing multicast communication within the group.

[0255] The HARQ feedback resources can be determined based on at least one of the PSCCH resources, PSSCH resources, and / or GUE_ID. When multiple receiving UEs in the group feedback HARQ ACK or HARQ NACK to the transmitting UE by using different PSFCH resources, the multiple receiving UEs in the group can determine the HARQ feedback resources by using the GUE_ID. The resources can include at least one of time domain resources, frequency domain resources, and / or code domain resources. The GUE_ID can be information for identifying the UEs in the group.

[0256] The receiving UE can send HARQ feedback to the transmitting UE. The receiving UE can send HARQ feedback corresponding to the PSCCH and / or PSSCH to the transmitting UE. For example, the receiving UE can send HARQ feedback to the transmitting UE by using the HARQ feedback resources determined based on at least one of the PSCCH resources, PSSCH resources, and / or GUE_ID.

[0257] When the receiving UE successfully receives the PSCCH and / or PSSCH, the HARQ feedback can be HARQ ACK. When the receiving UE fails to receive the PSCCH and / or PSSCH, the HARQ feedback can be at least one of HARQ NACK and / or discontinuous transmission (DTX).

[0258] When the transmitting UE selects the PSSCH and / or PSCCH transmission resources through a sensing operation, there may be no conflict between the HARQ feedback transmission-related resources. When multiple transmitting UEs select different PSSCH and / or PSCCH transmission resources through a sensing operation, the HARQ feedback resources can be determined based on the PSSCH resources and / or PSCCH resources. Therefore, conflicts between HARQ feedback resources can be automatically avoided among UEs that select different PSSCH and / or PSCCH transmission resources based on a sensing operation.

[0259] When the transmitting UE sends the same PSSCH and / or PSCCH to multiple receiving UEs in a group, the multiple receiving UEs can determine the HARQ feedback resources by using different GUE_IDs. Therefore, even if multiple receiving UEs in a group receive the same PSSCH and / or PSCCH, conflicts between HARQ feedback resources can be prevented.

[0260] Figure 23 The figure illustrates an example of a process for transmitting and receiving HARQ feedback on the PSCCH and / or PSSCH in multicast SL communication.

[0261] Refer to Figure 23 , the ID used to identify UEs within a group can be assigned / specified to multiple UEs in the group. The ID can be referred to as an internal ID. The internal ID can be a destination or parameter, such as GUE_ID. For example, regarding a specific multicast service, the application layer can send information about the internal ID of the UE and information about the number of UEs in the group to the V2X layer. The UE can be the UE that transmits a specific multicast service. Regarding a specific multicast service, the application layer may not send information about the internal ID of another UE in the group to the V2X layer. The multicast service can include at least one of a multicast service, multicast data, multicast packets, and / or multicast messages.

[0262] When a transmitting UE wants to send first traffic related to multicast to multiple receiving UEs in a group, the application layer of the transmitting UE may send information about the internal ID of the transmitting UE and information about the number of UEs in the group to the V2X layer of the transmitting UE. The application layer of receiving UE 1 may send information about the internal ID of receiving UE 1 and information about the number of UEs in the group to the V2X layer of receiving UE 1. The application layer of receiving UE 2 may send information about the internal ID of receiving UE 2 and information about the number of UEs in the group to the V2X layer of receiving UE 2. The application layer of receiving UE 3 may send information about the internal ID of receiving UE 3 and information about the number of UEs in the group to the V2X layer of receiving UE 3. The application layer of receiving UE 4 may send information about the internal ID of receiving UE 4 and information about the number of UEs in the group to the V2X layer of receiving UE 4.

[0263] The V2X layer of the UE may send information about the internal ID of the UE and information about the number of UEs in the group to the AS layer of the UE. Additionally, for example, the V2X layer of the UE may also send an L2 ID (e.g., a source L2 ID or a destination L2 ID) and / or QoS information to the AS layer of the UE.

[0264] The transmitting UE may send a specific multicast traffic (S2110) to multiple receiving UEs. The specific multicast traffic may be sent via a PSSCH and / or a PSCCH.

[0265] Multiple receiving UEs may determine HARQ feedback resources (S2120). According to predefined rules, multiple receiving UEs (e.g., the AS layer of multiple receiving UEs) may determine resources for HARQ feedback on a specific multicast traffic based on information about their internal IDs and information about the number of UEs in the group.

[0266] The transmitting UE may determine resources for HARQ feedback (received by the transmitting UE). The transmitting UE may derive or determine resources for HARQ feedback from among multiple receiving UEs related to a specific multicast traffic based on information about its internal ID and information about the number of UEs in the group.

[0267] When the application layer provides the V2X layer of the UE with information about the internal ID of the UE and information about the number of UEs in the group, the UE can determine or consider Multicast Option 1 or Multicast Option 2 as an (optional) HARQ feedback option for a specific multicast service. The V2X layer of the UE can determine or consider Multicast Option 1 or Multicast Option 2 as an (optional) HARQ feedback option for a specific multicast service. In addition, the UE can finally determine or consider Multicast Option 1 or Multicast Option 2 as an HARQ feedback option for a specific multicast service according to whether a predefined condition is met. When all HARQ feedback resources for multiple UEs participating in multicast are supported in the resource pool, the UE can finally determine or consider Multicast Option 2 as an HARQ feedback option for a specific multicast service. When all HARQ feedback resources for multiple UEs participating in multicast are not supported in the resource pool, the UE can finally determine or consider Multicast Option 1 as an HARQ feedback option for a specific multicast service. This determination can be performed in the AS layer of the UE.

[0268] When the application layer does not provide the V2X layer of the UE with information about the number of UEs in the group, the UE can determine or consider Multicast Option 1 as an HARQ feedback option for a specific multicast service. When the application layer does not provide the V2X layer of the UE with information about the internal ID of the UE and / or information about the number of UEs in the group, the UE can determine or consider Multicast Option 1 as an HARQ feedback option for a specific multicast service. For example, the V2X layer of the UE can determine or consider Multicast Option 1 as an HARQ feedback option for a specific multicast service.

[0269] When the application layer and / or the V2X layer provide the AS layer of the UE with information about the internal ID of the UE and information about the number of UEs in the group, the UE can determine or consider Multicast Option 1 or Multicast Option 2 as an (optional) HARQ feedback option for a specific multicast service. The AS layer of the UE can determine or consider Multicast Option 1 or Multicast Option 2 as an (optional) HARQ feedback option for a specific multicast service. In addition, the UE can finally determine or consider Multicast Option 1 or Multicast Option 2 as an HARQ feedback option for a specific multicast service according to whether a predefined condition is met. When all HARQ feedback resources for multiple UEs participating in multicast are supported in the resource pool, the UE can finally determine or consider Multicast Option 2 as an HARQ feedback option for a specific multicast service. When all HARQ feedback resources for multiple UEs participating in multicast are not supported in the resource pool, the UE can finally determine or consider Multicast Option 1 as an HARQ feedback option for a specific multicast service. This determination can be performed in the AS layer of the UE.

[0270] When the application layer and / or the V2X layer do not provide information about the number of UEs in the group to the AS layer of the UE, the UE may determine or consider Multicast Option 1 as the HARQ feedback option for a specific multicast service. When the application layer and / or the V2X layer do not provide information about the internal ID of the UE and / or information about the number of UEs in the group to the AS layer of the UE, the UE may determine or consider Multicast Option 1 as the HARQ feedback option for a specific multicast service. For example, the AS layer of the UE may determine or consider Multicast Option 1 as the HARQ feedback option for a specific multicast service.

[0271] In a resource pool-specific manner, it can be signaled to the UE whether at least one of Multicast Option 1 and / or Multicast Option 2 is supported. In a resource pool-specific manner, it can be signaled to the UE whether at least one of Multicast Option 1 and / or Multicast Option 2 is supported according to the type of service, the type of broadcast, or the QoS requirement. In a resource pool-specific manner, it can be signaled to the UE whether the PSFCH resources related to Multicast Option 1 are configured according to the type of service, the type of broadcast, or the QoS requirement. In a resource pool-specific manner, it can be signaled to the UE whether the PSFCH resources related to Multicast Option 2 are configured according to the type of service, the type of broadcast, or the QoS requirement.

[0272] The transmitting UE can receive HARQ feedback from multiple receiving UEs. The transmitting UE can receive HARQ feedback from multiple receiving UEs based on Multicast Option 1. For example, the transmitting UE can receive HARQ feedback based on Multicast Option 2 from multiple receiving UEs.

[0273] For a specific multicast service, HARQ feedback operations based on a specific multicast option may be required. In the case of high reliability requirements related to the service, when the transmitting UE sends a service to the receiving UE, the receiving UE needs to perform HARQ feedback operations based on Multicast Option 2. If the receiving UE performs HARQ feedback operations on the service based on Multicast Option 1, DTX may occur, and thus the receiving UE needs to perform HARQ feedback operations on the service with high reliability requirements based on Multicast Option 2. DTX may be the following problem: when the receiving UE fails to receive the PSCCH and does not send a NACK to the transmitting UE, the transmitting UE misinterprets that the receiving UE has successfully received the PSCCH and PSSCH. Due to DTX, it may be difficult to meet the reliability requirements of the service. Therefore, if a specific multicast option is not supported on the resource pool, or if a specific multicast option is not supported for the traffic and / or service, the transmitting UE can perform a blind retransmission operation. If the PSFCH resources related to a specific multicast option are not configured, the transmitting UE can perform a blind retransmission operation. The transmitting UE can perform a retransmission without receiving HARQ feedback from the receiving UE.

[0274] Figure 24 Configuration of PSCCH / PSSCH / PSCH in the illustrated time slot. Refer to Figure 24 , the time position of PSFCH in a time slot can be TDM with PSCCH / PSSCH.

[0275] Figure 25 Illustrated sidelink SSB (S-SSB) structure. Refer to Figure 28 , the UE can transmit S-SSB to synchronize with other UEs via the sidelink. For the order of symbols mapping the sidelink primary synchronization signal (S-PSS), sidelink secondary synchronization signal (S-SSS), and physical sidelink broadcast channel (PSBCH) in the S-SSB, refer to Figure 28 .

[0276] <Example: Channel Access for Sidelink (SL) Transmission>

[0277] First, the terms used in this document will be explained.

[0278] - Type 1 channel access procedure (CAP): A channel access procedure that includes random backoff (see Figure 13 ). Channel sensing can be performed based on a random value selected within the CW. When the channel is determined to be idle as a result of performing channel access, SL transmission can be performed.

[0279] - Type 2 CAP: A channel access procedure that does not include random backoff. Channel sensing can be performed during a fixed-length sensing period for channel transmission. According to the fixed-length sensing period, Type 2 CAP can be classified into Type 2A / 2B / 2C.

[0280] - Type 2A CAP: Before the SL transmission for transmission, SL transmission can be performed immediately after sensing whether the channel is idle within a sensing period of at least 25 μs. 25 μs includes a 16-μs period (T f ) and a sensing time slot (9 μs) immediately following it, and the 16-μs (T f ) period includes a sensing time slot (9 μs) from the beginning. When all the sensing time slots of 25 μs are sensed as idle, the channel is determined to be available within the 25-μs period.

[0281] - Type 2B CAP: Before the SL transmission for transmission, SL transmission can be performed immediately after sensing whether the channel is idle within a period of 16 μs (T f ). 16 μs (T f ) includes a sensing time slot within the last 9 μs of 16 μs. When the channel is sensed as idle for at least 4 μs within a total time of at least 5 μs including the sensing time slot where sensing occurs, the channel is determined to be idle.

[0282] - Type 2C CAP: It means that SL transmission is performed without performing channel sensing before SL transmission for transmission (i.e., without LBT). The maximum period for SL transmission can be limited to at most 584 μs.

[0283] - CO (or COT): CO means that a wireless communication device (e.g., UE) initiates a transmission in a channel and occupies the channel. COT means channel occupancy time.

[0284] - COT sharing: It means that the COT initiated by a wireless communication device (e.g., UE) is shared with the same / different wireless communication devices (e.g., see Figure 15 ).

[0285] - SL transmission: SL transmission includes the transmission of SL channels. SL channels include physical sidelink control channel (PSCCH), physical sidelink shared channel (PSSCH), physical sidelink feedback channel (PSFCH), etc.

[0286] - PSCCH / PSSCH: It represents PSSCH and / or PSSCH.

[0287] - Sidelink control information (SCI): SCI can be classified into first SCI (or SCI format 1) and second SCI (or SCI format 2). The first SCI is sent through PSCCH. The first SCI is used to schedule (i) PSSCH and (ii) the second SCI on PSSCH. For example, the first SCI includes time / frequency resource information for PSSCH reception, a priority indicator, second SCI format information, etc. The priority indicator indicates the priority of the traffic of PSSCH. The first SCI can be decoded by all UEs in a cell for channel sensing. However, the second SCI is decoded by each receiving UE and includes the remaining information required to decode PSSCH. PSSCH resources can be used to send the second SCI. For example, the second SCI includes HARQ process number, broadcast type indicator, source ID, destination ID, etc.

[0288] Figure 26 The figure shows the sidelink (SL) communication process. SL communication is a communication method that configures a direct link between UEs so that UEs can directly exchange voice or data, etc. without going through a base station. In the case of SL communication, Figure 14 the base station in

[0289] can be replaced by a UE. Figure 26, UE-A may send sidelink control information (SCI) to UE-B (S1602). The SCI may be classified into a first SCI and a second SCI. The first SCI may be sent via a physical sidelink control channel (PSCCH). The first SCI may include a part of the information required for physical sidelink shared channel (PSSCH) scheduling (e.g., resources / information for decoding the second SCI, DMRS pattern, antenna port, etc.), and may be decoded by all UEs in the cell for channel sensing. In contrast, the second SCI may be decoded by each receiving UE, and may include the remaining information required for PSSCH scheduling. The second SCI may be sent via PSSCH resources. Subsequently, UE-A may send PSSCH to UE-B (S1604). Via the PSSCH, data may be sent between UEs. In addition, unicast transmission and multicast transmission may be performed via the PSSCH. When HARQ feedback operation (HARQ-ACK enabled) for SL transmission (e.g., PSSCH) is supported / configured, UE-B may send HARQ-ACK feedback for the PSSCH to UE-A via a physical sidelink feedback channel (PSFCH) (1606). In contrast, when HARQ feedback operation (HARQ-ACK disabled) for SL transmission (e.g., PSSCH) is not supported / configured, UE-A may not expect explicit HARQ-ACK feedback for the PSSCH from UE-B.

[0290] 1) CWS adjustment for SL channel access

[0291] The present invention relates to a channel access method / process when performing SL transmission (e.g., PSSCH) in an unlicensed spectrum. Specifically, the present invention proposes a scheme for adjusting the CWS based on the (SL) transmission type (e.g., unicast / group transmission with HARQ-ACK, multicast transmission with only NACK, multicast transmission without HARQ-ACK, and broadcast transmission) in the case of adjusting the CWS for channel access in an unlicensed spectrum. Here, the channel access process using the CWS may include, for example, a type 1 channel access process (CAP) (or a channel access process based on random backoff with variable CW, category 4 (Cat-4) LBT). For example, when performing type 1 channel access for SL transmission, a wireless device (e.g., UE) may adjust the CWS based on the SL transmission type before performing type 1 channel access.

[0292] The transmission type (broadcast type) may be classified based on (i) the corresponding transmission type (e.g., unicast, multicast, broadcast) and (ii) the HARQ-ACK feedback scheme / mode (HARQ-ACK, only NACK, no HARQ-ACK) indicated / configured for the corresponding broadcast. This is not limited thereto, but the transmission types in this specification include the following.

[0293] Transmission with HARQ-ACK: A transmission that indicates the need for HARQ-ACK feedback (e.g., ACK, NACK). Thus, after performing a transmission to a receiving UE, the UE expects HARQ-ACK feedback (e.g., ACK or NACK) from the receiving UE for the corresponding transmission (i.e., explicit ACK / NACK). Here, the transmission includes unicast transmission or multicast transmission.

[0294] Transmission with only NACK: A transmission that allows only NACK as HARQ-ACK feedback. Thus, after performing a transmission to a receiving UE, the UE explicitly expects only NACK from the receiving UE as the HARQ-ACK feedback for the corresponding transmission. In this case, ACK (implicit ACK) can be implicitly fed back via the fact that no NACK for the corresponding transmission is detected / received. Here, the transmission includes multicast transmission.

[0295] – Transmission without HARQ-ACK: Indicates a transmission for which HARQ-ACK feedback is not allowed. That is, no HARQ-ACK scheme / mode is configured for the corresponding transmission. Thus, after performing a transmission to a receiving UE, the UE may not expect HARQ-ACK feedback from the receiving UE for the corresponding transmission. Here, the transmission includes multicast transmission or broadcast transmission.

[0296] For example, the transmission type can be indicated by a transmission type indicator in the second SCI. Table 6 lists the transmission types according to the transmission type indicator.

[0297] [Table 6]

[0298]

[0299] Unicast / group transmission with HARQ-ACK

[0300] A wireless device (e.g., UE) can send PSSCH via unicast or multicast transmission with HARQ-ACK. In this case, when performing a transmission in unlicensed spectrum, the UE can perform type 1 channel access. The UE can adjust the CWS when performing type 1 channel access to determine the time window for performing random backoff. A method for this is provided below.

[0301] In the case of transmitting PSSCH, the PSSCH transmission can be performed using the scheme of (a) sidelink resource allocation mode 1, in which the base station notifies the UE of the time and frequency resources for PSSCH transmission, or the scheme of (b) sidelink spatial resource allocation mode 2, in which a (single) resource pool is configured, and the UE senses the corresponding resource pool, selects resources, and allocates the actually transmittable resources. Here, the PSSCH can be transmitted using the PC-5 link. The PC-5 link can be a link for direct communication between devices.

[0302] Case 1) In the case of configuring a (single) resource pool, (a) the PSFCH resource period and (b) the minimum time interval allowing PSFCH reception after PSSCH can be configured. In this case, HARQ-ACK (e.g., for PSSCH) enabled / disabled for SL transmission can be configured. For example, the UE transmitting PSSCH can configure the HARQ-ACK enabled / disabled indicator in the second SCI to a predetermined value. For example, when the value of the HARQ-ACK enabled / disabled indicator indicates "1" (indicating enabled), the receiving UE receiving PSSCH can transmit the PSSCH in an available time slot after the minimum time interval from the PSSCH according to the PSSCH resource period. Thus, the UE transmitting PSSCH can receive (e.g., detect / monitor) the PSSCH and can receive HARQ-ACK information.

[0303] Specifically, when PSFCH resources are configured in the resource pool and the value of the HARQ-ACK enabled / disabled indicator is indicated as "1" (indicating enabled) via the second SCI, UE-A may expect the HARQ-ACK feedback for the PSSCH sent from UE-A to UE-B to be sent from UE-B to UE-A. In this case, when the HARQ-ACK sent from UE-B is available and there is at least one ACK in the corresponding HARQ-CK, UE-A can reset the current CWp to the minimum / initial value for each priority level (e.g., see Table 5) with respect to all priority levels. On the contrary, otherwise (e.g., when there is no ACK in the HARQ-ACK, all NACK), UE-A can increase the current CWp to the next higher value for each priority level (e.g., see Table 5) with respect to all priority levels. Subsequently, by using the configured / adjusted CWp value, UE-A can perform type 1 channel access when transmitting the PSSCH that UE-A is currently going to transmit. Here, the subscript p indicates the priority.

[0304] In addition, the UE transmitting the PSSCH may indicate a value of "0" (indicating disabled) via the HARQ-ACK enable / disable indicator in the second SCI. In this case, the UE may not expect an explicit HARQ-ACK from the receiving UE and may use the CWp value for the latest PSSCH transmission for type 1 channel access for the PSSCH that the transmitting UE is currently to transmit.

[0305] Case 2) In the case of configuring a (single) resource pool, since there is no configured PSFCH resource period and minimum time interval, there may be no PSFCH. In this case, the UE transmitting the PSSCH indicates a value of "0" (indicating disabled) via the HARQ-ACK enable / disable indicator in the second SCI, and the UE that receives this value may not send HARQ-ACK information after receiving the PSSCH because the configured PSSCH resource does not exist. In this case, the UE transmitting the PSSCH may not expect an explicit HARQ-ACK from the receiving UE and may thus not perform CWp adjustment based on the HARQ-ACK information. Therefore, it may be unclear for the UE transmitting the PSSCH which value to configure for the current CWp for subsequent PSSCH transmissions. To clarify this, when the channel access priority level of the PSSCH that the UE is currently to transmit has been used before, the UE may configure the current CWp as the CWp value corresponding to the same priority level that was recently (before transmitting the PSSCH) used (for PSSCH transmission) and may perform type 1 channel access.

[0306] Figure 27 The figure illustrates a channel access procedure according to an embodiment of the present invention. Figure 27 Corresponding to Case 1). Case 2) can be similarly executed.

[0307] Refer to Figure 27, UE-A can be configured with HARQ feedback enable / disable for SL transmission (e.g., PSSCH) (S1702). For example, UE-A can send an SCI for scheduling the PSSCH. Here, the SCI (e.g., the second SCI) can include a HARQ feedback enable / disable indicator. Subsequently, UE-A can perform channel access using the first CWS to send the PSSCH (S1704). Here, the PSSCH can be used for unicast transmission or multicast transmission. Additionally, the channel access can include type 1 channel access. When the value of the HARQ-ACK enable / disable indicator is set to "1" (enabled), UE-B can receive the PSSCH and can send the PSSCH in an available time slot after a minimum time interval from the PSSCH. In this case, when there is at least one ACK in the HARQ-ACK sent from UE-B, UE-A can reset the current CWp to the minimum / initial value for each priority level with respect to all priority levels (e.g., see Table 5). Otherwise (e.g., when there is no ACK in the HARQ-ACK, all NACKs), UE-A can increase the current CWp to the next higher value for each priority level with respect to all priority levels (e.g., see Table 5) (S1706a). Conversely, when the value of the HARQ-ACK enable / disable indicator is set to "0" (disabled), UE-A can use the CWp value used for the latest PSSCH transmission as the current CWp as it is, or when the channel access priority level of the PSSCH that UE-A is currently going to transmit has been used before, UE-A can use the CWp value used for the PSSCH transmission corresponding to the same priority level as the current CWp. Subsequently, by using the configured / adjusted CWp value, UE-A can perform channel access (e.g., type 1 channel access) when sending the PSSCH that UE-A is currently going to send (S1708).

[0308] Multicast transmission with only NACK

[0309] A wireless device (e.g., UE) can send the PSSCH via a multicast transmission with only NACK feedback. In this case, when performing transmission in the unlicensed spectrum, the UE can perform type 1 channel access. The UE can adjust the CWS when performing type 1 channel access to determine the time window for performing random backoff. A method for this is provided below. The following description can be extended to multicast transmission with HARQ-ACK, in which case the implicit ACK can be replaced with an explicit ACK.

[0310] When the UE sends the PSSCH via a multicast transmission configured with only NACK feedback, the UE can monitor (e.g., detect) the PSSCH occasion corresponding to the multicast transmission and can determine / identify the HARQ-ACK feedback for the multicast transmission. Here, the PSFCH occasion may include one or more PSFCH resources allocated to the group of UEs receiving the multicast transmission. When the result of monitoring the PSFCH occasion shows that no HARQ-ACK feedback (i.e., all implicit ACKs) is received from the group of UEs that are the target of the multicast transmission, the UE that sends the PSSCH can regard the reception response of the PSSCH as (all) ACKs and may not perform a retransmission of the multicast transmission. Therefore, when no HARQ-ACK feedback is received from the group of UEs at the PSFCH occasion desired by the UE, the UE that sends the PSSCH via the multicast transmission can reset the current CWp to the minimum / initial value for each priority level (e.g., see Table 5) with respect to all priority levels, as the CWp for type 1 channel access that needs to be performed for subsequent SL transmissions (e.g., PSSCH, without multicast transmission). That is, when the reception response results from multiple UEs corresponding to the multicast transmission are regarded as (all) ACKs (e.g., no NACK is detected at the PSFCH occasion), the current CWp can be reset to the minimum / initial value for each priority level with respect to all priority levels (e.g., see Table 5). When the group of UEs is to perform NACK feedback transmission at the PSFCH occasion, the UE that sends the PSSCH via the multicast transmission may not know whether the transmission did not occur due to a channel access failure or whether the group of UEs successfully received the previously sent PSSCH, and thus does not perform the NACK feedback transmission. Therefore, regardless of whether they are the same, the UE can reset the current CWp to the minimum / initial value for each priority level (e.g., see Table 5) with respect to all priority levels and can perform type 1 channel access when performing subsequent SL transmissions (e.g., PSSCH).

[0311] When the UE sends the PSSCH via a multicast transmission configured with only NACK feedback and receives HARQ-ACK feedback with all NACKs or HARQ ACK feedback with at least one NACK from the group of UEs that received the PSSCH, the user that sends the PSSCH can perform a retransmission of the multicast transmission. That is, when the result of monitoring the PSFCH occasion corresponding to the multicast shows that all NACKs or at least one NACK is detected at the corresponding PSCCH occasion, the UE that sends the PSSCH can perform a retransmission of the multicast transmission. In this case, it may be unclear which value needs to be configured as the CWp for type 1 channel access for the retransmission of the PSSCH for the UE that is to retransmit the PSSCH via the multicast transmission.

[0312] 1. For example, by considering that the UE transmits the PSSCH as a retransmission of a multicast transmission, when all NACKs are sent as HARQ-ACK feedback by the group of UEs and the UE transmitting the PSSCH receives the same NACK, or when HARQ-ACK feedback with at least one NACK is received from the group of UEs, the CW adjustment scheme can be used when receiving the NACK. For example, for all priority levels, the UE transmitting the PSSCH via multicast transmission can increase the current CWp to the next higher value for each priority level, and can perform type 1 channel access for subsequent PSSCH transmissions. That is, when the reception response results from multiple UEs corresponding to the multicast transmission are considered not to be (all) ACKs (e.g., at least one NACK is detected in the PSFCH occasion), the UE can increase the current CWp to the next higher value for each priority level (e.g., see Table 5). Alternatively, transmissions of one or more PSSCHs can be performed, and multiple feedbacks of PSSCHs with different multicasts from the same UE group, or multiple feedbacks from multiple UE groups with different group broadcasts, can be expected. In this case, the UE transmitting the multicast counts the number of NACKs from the receiving UEs, and when the number of NACKs is greater than or equal to Z% (here, Z is a natural number greater than 0 and less than or equal to 100), the UE can increase the current CWp to the next higher value for each priority level in the same way as when performing CW adjustment upon receiving the NACK. Otherwise, the UE can reset the current CWp to the minimum value for each priority level for all priority levels. For example, the value of Z% can be set to 80% in the same way as LTE-LAA. Alternatively, in the case where at least one ACK is received and is available in NR-U, in order to achieve the same operation as when the configuration is executed to reset the current CWp to the minimum value for each priority level, the value of Z% can be set to 100%, such that only when all NACKs are received, i.e., there is no implicit ACK, the UE can increase the current CWp to the next higher value for each priority level. Otherwise, that is, when there is at least one implicit ACK, the UE can be configured to reset the current CWp to the minimum value for each priority level for all priority levels.

[0313] 2. As another example, when receiving HARQ-ACK feedback with at least one NACK from a group of UEs, except for the case where the group of UEs sends HARQ ACK feedback with all NACKs, the UE that transmits the PSSCH can determine that at least one UE in the group of UEs can successfully receive the PSSCH. In this case, from the perspective of channel access, the UE can determine that this is not channel congestion and can use the CW adjustment scheme when receiving ACK feedback. For example, the UE that transmits the PSSCH can reset the current CWp to the minimum / initial value for each priority level with respect to all priority levels, and can perform type 1 channel access for subsequent PSSCH transmissions (e.g., see Table 5). Otherwise, the UE can increase the current CWp to the next higher value for each priority level with respect to all priority levels.

[0314] Figure 28 FIG. illustrates a channel access process according to an embodiment of the present invention. Referring to Figure 28 , UE-A can perform channel access using the first CWS to transmit a multicast transmission (S1802). Here, the multicast transmission can be performed via the PSSCH. In addition, the channel access can include type 1 channel access. Subsequently, UE-A can monitor the PSFCH (timing / resource) corresponding to the multicast transmission (S1804). When the monitoring result shows that the HARQ feedback result is regarded as all ACKs (e.g., no NACK is detected in the PSFCH timing / resource), UE-A can reset the current CWp to the minimum / initial value for each priority level with respect to all priority levels (e.g., see Table 5) (S1806a). On the contrary, when the HARQ feedback result is not regarded as all ACKs (e.g., at least one NACK is detected in the PSFCH timing / resource), UE-A can increase the current CWp to the next higher value for each priority level with respect to all priority levels (e.g., see Table 5) (1806b). Subsequently, by using the configured / adjusted CWp value, UE-A can perform channel access (e.g., type 1 channel access) when transmitting the SL transmission (e.g., PSSCH) that UE-A currently wants to transmit (after the multicast transmission) (S1808). Here, the HARQ feedback scheme indicated / configured in the multicast transmission can include only the NACK feedback scheme.

[0315] When transmitting the PSSCH via multicast transmission configured with only NACK feedback, the base station may execute the scheme of sidelink resource allocation mode 1 for notifying the UE of the time / frequency resources for PSSCH transmission, or may execute the operation of sidelink resource allocation mode 2 of configuring a single resource pool, sensing the corresponding resource pool, selecting resources, and allocating the actually transmittable resources. In the case of configuring (a single) resource pool, since the PSFCH resource period and the minimum time interval are not configured, there may be no PSFCH. In this case, the UE transmitting the PSSCH indicates a value of "0" (indicating disabled) via the HARQ-ACK enable / disable indicator in the second SCI, and the UE receiving this value may not send HARQ-ACK information, that is, only NACK feedback information, after receiving the PSSCH because the configured PSSCH resources do not exist. In this case, the UE transmitting the PSSCH may not expect an explicit HARQ-ACK from the receiving UE and may therefore not perform CWp adjustment based on the HARQ-ACK information. Therefore, for the UE transmitting the PSSCH, it may be unclear which value to configure as the current CWp for subsequent PSSCH transmissions. To clarify this, when the channel access priority level of the PSSCH currently to be transmitted by the UE has been used before, the UE may configure the current CWp as the CWp value corresponding to the same priority level (for PSSCH transmission) used most recently (before transmitting the PSSCH), and may perform type 1 channel access.

[0316] Alternatively, the UE transmitting the PSSCH may indicate a value of "0" (indicating disabled) via the HARQ-ACK enable / disable indicator in the second SCI. In this case, the UE may not expect an explicit HARQ-ACK from the receiving UE, and for type 1 channel access performed for the PSSCH currently to be transmitted by the transmitting UE, the CWp value most recently used for PSSCH is used.

[0317] 2. Definition of sidelink (SL) reference duration

[0318] As described above (for example, refer to Figure 27 and 28) When the transmitting UE performs CWS adjustment before performing type 1 channel access, it can receive HARQ-ACK feedback from the receiving UE as feedback for a previous SL transmission. In this case, it may be necessary to define the duration on the time axis of the CWS adjustment that the transmitting UE can use for type 1 channel access. This can be defined as the SL reference duration. According to an embodiment of the present invention, in the case of receiving HARQ-ACK feedback, the transmitting UE can perform CW adjustment for type 1 channel access based on the HARQ-ACK feedback for SL transmission (e.g., PSSCH / PSCH transmission) during the SL reference duration.

[0319] The SL reference duration can be configured according to the following method.

[0320] The SL reference duration can correspond to the latest COT obtained when the transmitting UE performs type 1 channel access to initiate a COT. In addition, (in the latest COT) when the PSSCH is transmitted via all resources allocated for PSSCH transmission (including at least unicast data transmission), the SL reference duration can be configured to start from the beginning of the latest COT and end at (or until) the end of the first time slot corresponding to one time slot (among the corresponding time slots). Here, the first time slot is the first time slot among the time slots in which the PSSCH including unicast data transmission is transmitted. In addition, (in the latest COT,) when the PSSCH is transmitted via all resources allocated for the transmission of the PSSCH configured with enabled HARQ-ACK feedback, the SL reference duration can be configured to start from the beginning of the latest COT and end at the end of the first time slot corresponding to one time slot (from among the corresponding time slots). The SL reference duration starts from the beginning of the latest COT because channel access occurs before each transmission start point, and thus the transmission performed from the start of the COT can effectively reflect the congestion of the channel. Here, the first time slot is the first time slot among the time slots in which the PSSCH configured with enabled HARQ-ACK feedback is transmitted. Figure 29 The figure shows the case where the SL reference duration is configured to start from the beginning of the latest COT initiated by the UE and end at (or until) the end of the first time slot among the time slots in which the PSSCH configured with enabled HARQ-ACK feedback is to be transmitted. The SL transmission can include a PSSCH not configured with enabled HARQ-ACK feedback, and these PSSCHs are not considered at the end of the configured SL reference duration. In addition, the latest COT initiated by the UE can include multiple SL transmission bursts. In this case, the SL reference duration can also be configured to start from the beginning of the COT and end at the end of the first time slot among the time slots in which the PSSCH configured with enabled HARQ-ACK feedback will be transmitted.

[0321] For example, the resources starting from the beginning of the latest COT and allocated for a time slot for PSSCH transmission can be configured with one or more RB sets (20 MHz LBT execution units). In this case, when the channel access is successful and the PSSCH is transmitted as it is in the allocated resources, the SL reference duration can be configured to start from the beginning of the latest COT and end at the end of the (first) time slot corresponding to one time slot. Here, the PSSCH can be limited to the PSSCH including unicast data transmission. In addition, the PSSCH may be limited to the PSSCH configured with enabled HARQ-ACK feedback. The UE can apply the CWS adjustment scheme described in the present invention based on the ACK / NACK feedback of the HARQ-ACK corresponding to the PSSCH transmitted in the SL reference duration.

[0322] As another example, the SL reference duration can be configured according to the following method. In this method, as the resources for PSSCH transmission, multiple consecutive time slot transmissions (MCSt) can be considered. As described above, the SL reference duration can correspond to the latest COT obtained when the transmitting UE performs type 1 channel access to initiate the COT, and when the PSSCH is transmitted via all the resources allocated for the transmission of the PSSCH including at least unicast data transmission, or when the PSSCH is transmitted by occupying the entire single time slot via all the resources allocated for the transmission of the PSSCH configured with enabled HARQ-ACK feedback, the SL reference duration can be configured to start from the beginning of the latest COT and end at the end of the first time slot corresponding to one time slot. Via all the resources allocated for the transmission of the PSSCH configured with enabled HARQ-ACK feedback, the PSSCH can be transmitted by occupying a partial time slot of one time slot, and the MCSt can be used in subsequent time slots to continuously transmit the PSSCH. In this case, the SL reference duration can be configured to start from the beginning of the latest COT, include the partial time slot, and end at the end of the time slot in which the PSSCH is continuously transmitted using the MCSt in subsequent time slots. The UE can apply the CWS adjustment scheme described in the present invention based on the ACK / NACK feedback of the HARQ-ACK corresponding to the PSSCH transmitted in the SL reference duration.

[0323] For example, the resources starting from the latest COT and allocated to a time slot for PSSCH transmission can configure one or more RB sets (20MHz LBT execution units), and the PSSCH occupies a partial time slot of a time slot, and the MCSt can be used in subsequent time slots to continuously transmit the PSSCH. When the channel access is successful in the partial time slot and the PSSCH transmission is performed using the MCSt, the SL reference duration can be configured to start at the beginning of the latest COT, including the partial time slot, and end at the end of the time slot in which the PSSCH is continuously transmitted using the MCSt in subsequent time slots. The UE can apply the CWS adjustment scheme described in the present invention based on the ACK / NACK feedback of the HARQ-ACK corresponding to the PSSCH transmitted in the SL reference duration.

[0324] As another example, the SL reference duration can be configured according to the following method. The SL reference duration can correspond to the latest COT obtained when the transmitting UE performs type 1 channel access to initiate the COT. More specifically, the SL reference duration can be configured to (start from the beginning of the latest COT and) end at the end of the first burst in the latest COT, in which all the resources allocated for transmitting the PSSCH, including at least unicast data transmission, are transmitted. Alternatively, the SL reference duration can be configured to (start from the beginning of the latest COT and) end at the end of the first burst in the latest COT, in which all the resources allocated for transmitting the PSSCH, including the transmission of the PSSCH configured with enabled HARQ-ACK feedback, are transmitted. That is, when a part of the PSSCH transmission configured by the transmitting UE in the latest COT is transmitted, for example, when two RB sets are allocated to the first time slot in the COT corresponding to the latest COT, the channel access in one channel fails and the PSSCH is transmitted in one RB set, the SL reference duration may not be configured to end at the end of the first time slot. In this case, the SL reference duration can be configured to (start from the beginning of the latest COT and) end at the first transmission burst transmitted by the transmitting UE, that is, the burst of continuous PSSCH transmission including the transmission of the first time slot. In addition, in the case where there is no PSSCH transmission including unicast data transmission or transmission of the PSSCH configured with enabled HARQ-ACK feedback in the first time slot, the transmitting UE can configure the SL reference duration to (start from the beginning of the latest COT and) end at the first transmission burst transmitted by the transmitting UE, that is, the burst of continuous PSSCH transmission including the transmission of the first time slot when there is a PSSCH transmission including at least unicast data transmission or transmission of the PSSCH configured with enabled HARQ-ACK-feedback in the first transmission burst including the first time slot.

[0325] In an example of the present invention, when configuring the SL reference duration considering the transmission of the PSSCH with HARQ-ACK feedback enabled, only NACK or explicit HARQ-ACK (i.e., ACK or NACK) can be used as the feedback scheme for HARQ-ACK. Here, when the SL reference duration starts from the beginning of the latest COT initiated by the UE, the configuration of the SL reference duration may be at the end of the configuration of the SL reference duration. Preferably, in the case of configuring the SL reference duration in the present invention, when HARQ-ACK feedback is enabled for the PSSCH transmission sent via unicast or multicast, only the case of using explicit HARQ-ACK feedback (indicated as the HARQ-ACK feedback scheme for unicast or multicast transmission) may be considered. That is, in the case of configuring the SL reference duration, the HARQ-ACK feedback scheme may be limited to explicit HARQ-ACK feedback for unicast or multicast transmission. Specifically, the SL reference duration can be configured by considering: (1) enabling HARQ-ACK feedback, and (2) sending the PSSCH for which the HARQ-ACK feedback scheme is indicated as explicit HARQ-ACK. Here, (1) can be indicated by the HARQ-ACK enable / disable indicator of the second SCI, and (2) can be indicated by the transmission type indicator of the first SCI (see Table 6). Figure 30 The figure shows the case where the HARQ-ACK feedback scheme for unicast or multicast transmission is limited to explicit HARQ-ACK when configuring the SL reference duration. Alternatively, when HARQ-ACK feedback for unicast or multicast transmission is enabled, only the NACK scheme and the explicit HARQ-ACK feedback scheme can be regarded as the HARQ ACK feedback schemes for unicast or unicast transmission.

[0326] Figure 31 The figure shows the SL transmission method according to an embodiment of the present invention. Refer to Figure 31 , the UE transmits at least one PSSCH in the COT, and the plurality of PSSCHs may include at least one first PSSCH with HARQ-ACK feedback enabled (S3102). Subsequently, the UE may adjust the CWS based on the HARQ-ACK feedback for at least one PSSCH during the reference duration, and may perform the SL channel access procedure based on the adjusted CWS (S3104 to 3106). Here, the reference duration may be defined as starting from the beginning of the COT and ending at the end of the first time slot in which at least one first PSSCH is transmitted (or, and until).

[0327] Here, the HARQ-ACK feedback may include reception response information based on an ACK / negative ACK (NACK) feedback scheme. In addition, when at least one first PSSCH includes at least one second PSSCH having an indicated ACK / NACK feedback scheme and at least one third PSSCH having an indicated NACK-only feedback scheme, the reference duration may be defined as starting from the beginning of the COT and ending at the end of the first time slot in which at least one second PSCH is transmitted. In addition, a plurality of PSSCHs may include at least one fourth PSSCH for which HARQ-ACK feedback is not enabled. In addition, the COT may be the latest COT initiated by the UE.

[0328] Here, when the HARQ-ACK feedback for at least one PSSCH transmission in the reference duration includes at least an ACK, the CWS may be adjusted to the minimum value. In addition, when the HARQ-ACK feedback for at least one PSSCH transmission in the reference duration does not include an ACK, the CWS may be increased to the next value among the allowed CWS values that is higher than the current CWS.

[0329] Here, in the case of transmitting at least one first PSSCH via SL multicast, when the HARQ-ACK feedback for at least one PSSCH transmission in the reference duration includes at least one negative acknowledgment (NACK), the CWS may be increased to a value among the allowed CWS values that is higher than the current CWS, and when the HARQ ACK feedback for at least one PSSCH transmission in the reference duration is regarded as all ACKs, the CWS may be adjusted to the minimum value.

[0330] Here, based on a counter value randomly selected within the adjusted CWS, the UE may perform an SL channel access procedure. In addition, the first time slot for transmitting at least one first PSSCH may be the time slot in which PSSCH transmission is performed via all resources allocated for PSSCH transmission.

[0331] CWS adjustment when using one or more SL HARQ-ACK feedback schemes

[0332] As described above, the UE may adjust the CWS based on the SL reference duration, where the UE performs transmission before performing type 1 channel access. Specifically, the UE may adjust the CWS based on the HARQ-ACK feedback for SL transmission within the SL reference duration. In this case, the SL reference duration may include one or more (e.g., multiple) transmission types (e.g., unicast transmission with HARQ-ACK (ACK or NACK), multicast transmission with HARQ-QCK, multicast transmission with only NACK, multicast transmission without HARQ-ACK, and broadcast transmission). In this case, for the UE that performs channel access by performing CWS adjustment, it may be unclear whether the feedback corresponding to any one PSSCH transmission or the feedback corresponding to one or more PSSCH transmissions needs to be configured as the reference transmission corresponding to the HARQ-ACK feedback to determine the CWS. Therefore, a method for configuring the reference transmission and a solution for the UE to adjust the CWS according to this method are provided.

[0333] A. For example, in the case where the UE operates using different SL-HARQ feedback schemes, the SL reference duration may include one or more PSSCH transmissions configured with multiple types enabling SL HARQ-ACK feedback (e.g., unicast transmission (ACK / NACK), multicast transmission with option 1 (only NACK) or option 2 (ACK / NACK)). In this case, regardless of whether it is unicast transmission or multicast transmission, or whether it is configured to send ACK / NACK or send only NACK as the HARQ-ACK feedback, the reference PSSCH transmission may be configured based on the PSSCH transmission configured with enabling SL HARQ-ACK feedback. Specifically, the reference PSSCH transmission may be configured according to the following three methods, and the UE may adjust the CWS based on the HARQ-ACK feedback for the reference PSSCH transmission.

[0334] A-1. By using the PSSCH transmission in the foremost time slot in the time axis among the PSSCH transmissions configured with enabling SL HARQ-ACK feedback in the SL reference duration (hereinafter referred to as the reference PSSCH transmission) as the reference, the CWS may be configured based on the HARQ-ACK feedback corresponding to the reference. In the case of transmission in the unlicensed band, before performing the transmission, channel access may be performed before the start point of the transmission, and thus the start point of the transmission may most effectively reflect the congestion level indicating whether the unlicensed band channel is idle or busy.

[0335] When at least an ACK is received as the HARQ-ACK feedback corresponding to the reference PSSCH transmission, a reset to CW_p = CW_min,p can be performed. Here, in the case of resetting to CW_p = CW_min,p, one of the following two methods can be used.

[0336] 1) For each priority level p ∈ {1, 2, 3, 4}, CW_p = CW_min,p

[0337] 2) For each priority level p ∈ {1, 2, 3, 4}, CW_p = CW_min,p

[0338] Otherwise (i.e., when no ACK is received, all NACKs), an increase in CW_p can be performed. Here, in the case of increasing CW_p, one of the following two methods can be used.

[0339] 1) Increase CW_p for each priority level p ∈ {1, 2, 3, 4} to the next higher allowed value

[0340] 2) Increase CW_p for each priority level p ∈ {1, 2, 3, 4} to the next higher allowed value

[0341] When a single SL HARQ-ACK feedback scheme is used for the reference PSSCH transmission, as described above, the CWS adjustment scheme used in the single SL HARQ ACK feedback scheme can be used in the same way.

[0342] A-2. By using at least one PSSCH transmission (hereinafter referred to as the reference PSSCH transmission) configured to perform a PSSCH transmission from among the PSSCH transmissions with SL HARQ-ACK feedback enabled in the SL reference duration as a reference, the CWS can be configured based on the HARQ-ACK feedback corresponding to the reference. In the case of transmission in the unlicensed band, before performing the transmission, channel access can be performed before the start point of the transmission, and thus the start point of the transmission can most effectively reflect the degree of congestion indicating whether the unlicensed band channel is idle or busy. Although channel access is performed before the start point of the transmission, the channel access is successful in the time slot, and partial time slot transmission may occur. In this case, when determining the degree of channel congestion based only on the partial time slot transmission, there may be a probability of NACK occurring due to the partial PSSCH transmission in the partial time slot rather than the degree of channel congestion. Therefore, when performing CWS adjustment based on channel congestion, using only a single time slot as a partial time slot may not be sufficient, and thus the configuration based on the corresponding scheme may be appropriate.

[0343] When at least ACK is received as the HARQ-ACK feedback corresponding to the reference PSSCH transmission, reset to CW_p = CW_min,p can be performed. Here, in the case of resetting to CW_p = CW_min,p, one of the following two methods can be used.

[0344] 1) For each priority level p ∈ {1, 2, 3, 4}, CW_p = CW_min,p

[0345] 2) For each priority level p ∈ {1, 2, 3, 4}, CW_p = CW_min,p

[0346] Otherwise (i.e., when no ACK is received and all are NACK), increasing CW_p can be performed. Here, in the case of increasing CW_p, one of the following two methods can be used.

[0347] 1) Increase CW_p for each priority level p ∈ {1, 2, 3, 4} to the next higher allowed value

[0348] 2) Increase CW_p for each priority level p ∈ {1, 2, 3, 4} to the next higher allowed value

[0349] A-3. By using all PSSCH transmissions (hereinafter referred to as reference PSSCH transmissions) configured to perform HARQ feedback transmissions among the PSSCH transmissions with SL HARQ-ACK feedback enabled in the SL reference duration as a reference, the CWS can be configured based on the HARQ-ACK feedback corresponding to the reference. In the case of transmission in the unlicensed band, when there is at least HARQ-ACK feedback for a previously performed transmission, the transmitting UE can determine that the channel is idle and the channel access is successful in association with the congestion degree of the unlicensed band channel. Therefore, a scheme of using all PSSCH transmissions as a reference and performing CWS adjustment based on the HARQ-ACK feedback corresponding to the reference may be appropriate.

[0350] When at least ACK is received as the HARQ-ACK feedback corresponding to the reference PSSCH transmission, reset to CW_p = CW_min,p can be performed. Here, in the case of resetting to CW_p = CW_min,p, one of the following two methods can be used.

[0351] 1) For each priority level p ∈ {1, 2, 3, 4}, CW_p = CW_min,p

[0352] 2) For each priority level p ∈ {1, 2, 3, 4}, CW_p = CW_min,p

[0353] Otherwise (i.e., when no ACK is received, all NACKs), CW_p can be increased. Here, in the case of increasing CW_p, one of the following two methods can be used.

[0354] 1) Increase CW_p for each priority level p ∈ {1, 2, 3, 4} to the next higher allowed value

[0355] 2) Increase CW_p for each priority level p ∈ {1, 2, 3, 4} to the next higher allowed value

[0356] B. For example, the UE operates using different SL-HARQ feedback schemes and is configured with one or more PSSCH transmissions of multiple types (e.g., unicast (ACK / NACK), multicast with option 1 (only NACK), or option 2 (ACK / NACK)) enabling SL HARQ-ACK feedback that can be included in the SL reference duration. In this case, multicast transmissions with only NACK can be excluded first, and the reference PSSCH transmission can be configured based on the transmission of the PSSCH configured with enabling SL HARQ-ACK feedback, regardless of whether it is a unicast or multicast transmission. For example, the UE can configure the reference PSSCH transmission according to the following three methods and can adjust CWS based on the HARQ-ACK ACK / NACK feedback for the reference PSSCH transmission.

[0357] B-1. By using the PSSCH transmission (hereinafter referred to as the reference PSSCH transmission) that is the foremost in the time axis among the PSSCH transmissions configured with enabling SL HARQ-ACK feedback in the SL reference duration as a reference, CWS can be configured based on the HARQ-ACK ACK / NACK feedback corresponding to the reference. In the case of transmission in the unlicensed band, before performing the transmission, channel access can be performed before the start point of the transmission, and thus the start point of the transmission can most effectively reflect the congestion level indicating whether the unlicensed band channel is idle or busy.

[0358] When at least ACK is received as the HARQ-ACK ACK / NACK feedback corresponding to the reference PSSCH transmission, reset to CW_p = CW_min,p can be performed. Here, in the case of resetting to CW_p = CW_min,p, one of the following two methods can be used.

[0359] 1) For each priority level p ∈ {1, 2, 3, 4}, CW_p = CW_min,p

[0360] 2) For each priority level p ∈ {1, 2, 3, 4}, CW_p = CW_min,p

[0361] Otherwise (i.e., when no ACK is received, all NACKs), CW_p can be increased. Here, when increasing CW_p, one of the following two methods can be used.

[0362] 1) Increase CW_p for each priority level p ∈ {1, 2, 3, 4} to the next higher allowed value

[0363] 2) Increase CW_p for each priority level p ∈ {1, 2, 3, 4} to the next higher allowed value

[0364] When a single SL HARQ-ACK feedback scheme is used for reference PSSCH transmission, as described above, the CWS adjustment scheme used in the single SL HARQ ACK feedback scheme can be used in the same way.

[0365] B-2. By using a PSSCH transmission (hereinafter referred to as a reference PSSCH transmission) configured to perform at least one PSSCH transmission from among PSSCH transmissions configured with SL HARQ-ACK feedback enabled during the SL reference duration as a reference, the CWS can be configured based on the HARQ-ACK / NACK feedback corresponding to the reference. Before performing a transmission in the unlicensed band, channel access can be performed before the start point of the transmission, and thus the start point of the transmission can most effectively reflect the congestion level indicating whether the unlicensed band channel is idle or busy. Although channel access is performed before the start point of the transmission, the channel access is successful in a time slot, and partial time slot transmissions may occur. In the case of determining the channel congestion level based only on partial time slot transmissions, there may be a probability of NACK occurring due to partial PSSCH transmissions in a partial time slot rather than the congestion level of the channel. Therefore, when performing CWS adjustment based on channel congestion, using only a single time slot as a partial time slot may not be sufficient, and thus a configuration based on the corresponding scheme may be appropriate. When at least an ACK is received as the HARQ-ACK feedback corresponding to the reference PSSCH transmission, a reset to CW_p = CW_min,p can be performed.

[0366] Here, when resetting to CW_p = CW_min,p, one of the following two methods can be used.

[0367] 1) For each priority level p ∈ {1, 2, 3, 4}, CW_p = CW_min,p

[0368] 2) For each priority level p ∈ {1, 2, 3, 4}, CW_p = CW_min,p

[0369] Otherwise (i.e., when no ACK is received, all NACKs), CW_p can be increased. Here, when increasing CW_p, one of the following two methods can be used.

[0370] 1) Increase CW_p for each priority level p ∈ {1, 2, 3, 4} to the next higher allowed value

[0371] 2) Increase CW_p for each priority level p ∈ {1, 2, 3, 4} to the next higher allowed value

[0372] B-3. By using all PSSCH transmissions (hereinafter referred to as reference PSSCH transmissions) configured to perform HARQ-ACK ACK / NACK feedback transmissions among the PSSCH transmissions configured to perform SL HARQ-ACK feedback enabled during the SL reference duration as a reference, CWS can be configured based on the HARQ-ACK ACK / NACK feedback corresponding to the reference. In the case of transmissions in the unlicensed band, when there is at least HARQ-ACK feedback for a previously performed transmission, the transmitting UE can determine that the channel is idle and the channel access is successful in association with the congestion level of the unlicensed band channel. Therefore, a scheme of using all PSSCH transmissions configured to perform HARQ-ACK ACK / NACK feedback transmissions as a reference and performing CWS adjustment based on the HARQ-ACK feedback corresponding to the reference may be appropriate.

[0373] When at least an ACK is received as the HARQ-ACK feedback corresponding to the reference PSSCH transmission, a reset to CW_p = CW_min,p can be performed. Here, when resetting to CW_p = CW_min,p, one of the following two methods can be used.

[0374] 1) For each priority level p ∈ {1, 2, 3, 4}, CW_p = CW_min,p

[0375] 2) For each priority level p ∈ {1, 2, 3, 4}, CW_p = CW_min,p

[0376] Otherwise (i.e., when no ACK is received, all NACKs), CW_p can be increased. Here, when increasing CW_p, one of the following two methods can be used.

[0377] 1) Increase CW_p for each priority level p ∈ {1, 2, 3, 4} to the next higher allowed value

[0378] 2) Increase CW_p for each priority level p ∈ {1, 2, 3, 4} to the next higher allowed value

[0379] C. As another example, the UE operates using different SL-HARQ feedback schemes and is configured with one or more PSSCH transmissions enabling SL HARQ-ACK feedback of multiple types (e.g., unicast (ACK / NACK), multicast with option 1 (only NACK), or option 2 (ACK / NACK)) that can be included in the SL reference duration. In this case, multicast transmissions are excluded first, and the reference PSSCH transmission can be configured based on the PSSCH with SL HARQ-ACK feedback enabled in the unicast transmission and is configured to send ACK / NACK as HARQ-ACK. For example, the UE can configure the reference PSSCH transmission according to the following three methods and can adjust the CWS based on the HARQ-ACK ACK / NACK feedback for the reference PSSCH transmission.

[0380] C-1. By using the PSSCH transmission in the foremost time slot in the time axis among the PSSCH transmissions configured with SL HARQ-ACK feedback enabled in the SL reference duration (hereinafter referred to as the reference PSSCH transmission) as a reference, the CWS can be configured based on the HARQ-ACK / NACK feedback corresponding to the reference. In the case of transmissions in the unlicensed band, before performing the transmission, channel access can be performed before the start point of the transmission, and thus the start point of the transmission can most effectively reflect the congestion level indicating whether the unlicensed band channel is idle or busy.

[0381] When at least ACK is received as the HARQ-ACK ACK / NACK feedback corresponding to the reference PSSCH transmission, a reset to CW_p = CW_min,p can be performed. Here, in the case of resetting to CW_p = CW_min,p, one of the following two methods can be used.

[0382] 1) For each priority level p ∈ {1, 2, 3, 4}, CW_p = CW_min,p

[0383] 2) For each priority level p ∈ {1, 2, 3, 4}, CW_p = CW_min,p

[0384] Otherwise (i.e., when no ACK is received, all NACK), an increase in CW_p can be performed. Here, in the case of increasing CW_p, one of the following two methods can be used.

[0385] 1) Increase CW_p for each priority level p ∈ {1, 2, 3, 4} to the next higher allowed value

[0386] 2) Increase the CW_p for each priority level p ∈ {1, 2, 3, 4} to the next higher allowed value

[0387] When a single SL HARQ-ACK feedback scheme is used for reference PSSCH transmission, as described above, the CWS adjustment scheme used in the single SL HARQ ACK feedback scheme can be used in the same way.

[0388] C-2. By using a PSSCH transmission configured to perform at least one PSSCH transmission (hereinafter referred to as a reference PSSCH transmission) among the PSSCH transmissions with SL HARQ-ACK feedback enabled in the SL reference duration as a reference, the CWS can be configured based on the HARQ-ACK / NACK feedback corresponding to the reference. Before performing transmission in the unlicensed band, channel access can be performed before the start point of the transmission, and thus the start point of the transmission can most effectively reflect the congestion level indicating whether the unlicensed band channel is idle or busy. Although channel access is performed before the start point of the transmission, channel access is successful in the time slot, and partial time slot transmission may occur. In the case where the congestion level of the channel is determined only based on partial time slot transmission, there may be a probability of NACK occurring due to partial PSSCH transmission in the partial time slot rather than the congestion level of the channel. Therefore, when performing CWS adjustment based on channel congestion, using only a single time slot as a partial time slot may not be sufficient, and thus the configuration based on the corresponding scheme may be appropriate.

[0389] When at least ACK is received as the HARQ-ACK feedback corresponding to the reference PSSCH transmission, resetting to CW_p = CW_min,p can be performed. Here, in the case of resetting to CW_p = CW_min,p, one of the following two methods can be used.

[0390] 1) For each priority level p ∈ {1, 2, 3, 4}, CW_p = CW_min,p

[0391] 2) For each priority level p ∈ {1, 2, 3, 4}, CW_p = CW_min,p

[0392] Otherwise, increasing CW_p can be performed. Here, in the case of increasing CW_p, one of the following two methods can be used.

[0393] 1) Increase the CW_p for each priority level p ∈ {1, 2, 3, 4} to the next higher allowed value

[0394] 2) Increase the CW_p for each priority level p ∈ {1, 2, 3, 4} to the next higher allowed value

[0395] C-3. By using all PSSCH transmissions (hereinafter referred to as reference PSSCH transmissions) configured to perform HARQ-ACK ACK / NACK feedback transmissions among the PSSCH transmissions configured to perform SL HARQ-ACK feedback enabled during the SL reference duration as a reference, the CWS can be configured based on the HARQ-ACK ACK / NACK feedback corresponding to the reference. In the case of transmissions in the unlicensed band, when there is at least HARQ-ACK feedback for a previously performed transmission, the transmitting UE can determine that the channel is idle and the channel access is successful in association with the congestion level of the unlicensed band channel. Therefore, a scheme of using all PSSCH transmissions configured to perform HARQ-ACK ACK / NACK feedback transmissions as a reference and performing CWS adjustment based on the HARQ-ACK feedback corresponding to the reference may be appropriate.

[0396] When at least ACK is received as the HARQ-ACK feedback corresponding to the reference PSSCH transmission, resetting to CW_p = CW_min,p can be performed. Here, in the case of resetting to CW_p = CW_min,p, one of the following two methods can be used.

[0397] 1) For each priority level p ∈ {1, 2, 3, 4}, CW_p = CW_min,p

[0398] 2) For each priority level p ∈ {1, 2, 3, 4}, CW_p = CW_min,p

[0399] Otherwise (i.e., when no ACK is received and all are NACK), increasing CW_p can be performed. Here, in the case of increasing CW_p, one of the following two methods can be used.

[0400] 1) Increase CW_p for each priority level p ∈ {1, 2, 3, 4} to the next higher allowed value

[0401] 2) Increase CW_p for each priority level p ∈ {1, 2, 3, 4} to the next higher allowed value

[0402] CWS adjustment associated with S-SSB and PSFCH transmission in the case of SL channel access

[0403] The present invention relates to a channel access method when performing SL transmission using unlicensed spectrum. Specifically, in the case of performing type 1 channel access to perform S-SSB and PSFCH transmissions, the CWS is adjusted before performing category 1 channel access, and the present invention proposes a CWS adjustment scheme.

[0404] In the case of PSSCH transmission, the transmitting UE receives PSSCH transmission from the receiving UE and receives HARQ-ACK feedback for the PSSCH from the receiving UE. In this case, in the process where the transmitting UE identifies channel conflicts and channel states via HARQ-ACK feedback from the perspective of channel access and performs subsequent transmissions, the transmitting UE may adjust the CWS before performing type 1 channel access. For example, as described in this specification, the transmitting UE may reset the CWS to the minimum value according to ACK or NACK based on HARQ-ACK feedback, or may increase the CWS within the range of the next allowed value. More specifically, when HARQ-ACK feedback is enabled, the UE performing PSSCH transmission may reset the CWS to the minimum value, or may increase the CWS within the range of the next allowed value based on ACK or NACK of the feedback via HARQ-ACK from the receiving UE, that is, HARQ-ACK feedback information transmitted via PSSCH. However, the UE receiving PSSCH and performing PSFCH transmission via type 1 channel access may not separately receive feedback for PSFCH transmission from the UE receiving PSFCH. Therefore, when the UE transmitting PSFCH via type 1 channel access transmits SL channels / signals in subsequent transmissions, a scheme for adjusting the CWS for subsequent transmissions may need to be defined. In addition, in the NRSL communication system, as Figure 25 shown, the transmitting UE may transmit an S-SSB or a sidelink SS / PSBCH block to the receiving UE. The receiving UE may perform initial access by using the S-SSB or the sidelink SS / PSBCH block received from the transmitting UE. After transmitting the S-SSB to the receiving UE, the transmitting UE may not separately receive feedback for S-SSB transmission from the UE receiving the S-SSB. Therefore, when the UE transmitting the S-SSB via type 1 channel access transmits SL channels / signals in subsequent transmissions, a scheme for adjusting the CWS for subsequent transmissions may need to be defined. Therefore, the present invention proposes a scheme for adjusting the CWS: the UE performing type 1 channel access and transmitting PSFCH or S-SSB can be used for subsequent transmissions.

[0405] As an example of the present invention, the UE transmitting the S-SSB may not expect an explicit HARQ-ACK corresponding to the S-SSB transmission, and thus when the UE transmits SL channels / signals in subsequent transmissions, it may not be clear which value needs to be configured for the CWp value. For example, the UE transmitting the S-SSB may not expect an explicit HARQ-ACK and may not perform CWp adjustment based on HARQ-ACK information. Therefore, in the case of the UE transmitting the S-SSB, when previously using the channel access priority level of the SL channel / signal that the UE is currently to transmit, the UE may configure the CWp value to the most recently used value and perform type 1 channel access.

[0406] As an example of the present invention, also in the case of a UE transmitting a PSFCH, the UE may not expect an explicit HARQ-ACK corresponding to the PSFCH transmission, and thus when the UE transmits an SL channel / signal in a subsequent transmission, it may not be clear which value needs to be configured for the CWp value. For example, a UE transmitting a PSFCH may not expect an explicit HARQ-ACK and may not perform CWp adjustment based on the HARQ-ACK information. Therefore, in the case of a UE transmitting a PSFCH, when the channel access priority level of the SL channel / signal that the UE is currently to transmit was previously used, the UE may configure the CWp value to the most recently used value and perform type 1 channel access.

[0407] As another example of the present invention, a UE receiving a PSSCH performs type 1 channel access, transmits the PSSCH to the UE transmitting the PSSCH, and may transmit an SL channel / signal in a subsequent transmission. In this case, a retransmission of the PSSCH transmission corresponding to the PSFCH transmission may occur, and thus the UE performing the PSFCH transmission may receive the PSSCH retransmission. In this case, the UE may regard the PSSCH retransmission as an implicit response to the previously transmitted PSSCH and may increase the CWS within the range of the next allowed value. When the UE transmitting the PSFCH receives a PSSCH or a PSCCH (as opposed to a retransmission) in a new transmission, the UE to transmit the PSCCH (in a subsequent transmission) may reset the corresponding CWS to the minimum value.

[0408] Although the methods and systems of the present invention have been described in connection with specific embodiments, some or all of their components or operations can be implemented using a computing system having a general hardware architecture.

[0409] The above description of the present invention is merely exemplary, and those skilled in the art to which the present invention pertains will understand that various modifications and changes can be made without departing from the technical spirit or basic characteristics of the present invention. Therefore, the above embodiments should be construed as illustrative in all respects and not restrictive. For example, each component described as a single type can be implemented in a distributed manner, and similarly, components described as distributed can also be implemented in a combined form.

[0410] The scope of the present invention is indicated by the appended claims rather than the detailed description, and it should be understood that all changes or modifications derived from the meaning and scope of the claims and their equivalents are included within the scope of the present invention.

Claims

1. A user equipment (UE) used in a wireless communication system, the UE comprising: A communication module; And A processor configured to control the communication module, Wherein, the processor is configured to: Transmit at least one physical sidelink shared channel (PSSCH) during a channel occupancy time (COT), the at least one PSSCH including at least one first PSSCH with enabled hybrid automatic repeat request acknowledgement (HARQ-ACK) feedback; During a reference duration, adjust a contention window size (CWS) based on the HARQ-ACK feedback for the at least one PSSCH; and Perform a sidelink (SL) channel access procedure based on the adjusted CWS, and Wherein, the reference duration is defined as starting from the beginning of the COT and until the end of the first time slot in which the at least one first PSSCH is transmitted.

2. The UE according to claim 1, wherein The HARQ-ACK feedback includes reception response information based on an ACK / negative ACK (NACK) feedback scheme.

3. The UE according to claim 1, wherein, In a case where the at least one first PSSCH includes at least one second PSSCH with an indicated ACK / NACK feedback scheme and at least one third PSSCH with an indicated only-NACK feedback scheme, the reference duration is defined as starting from the beginning of the COT and until the end of the first time slot in which the at least one second PSSCH is transmitted.

4. The UE according to claim 1, wherein, The at least one PSSCH includes at least one fourth PSSCH for which the HARQ-ACK feedback is not enabled.

5. The UE according to claim 1, wherein, The COT is the latest COT initiated by the UE.

6. The UE according to claim 1, wherein, In a case where the HARQ-ACK feedback for the at least one PSSCH transmission during the reference duration includes at least ACK, the CWS is adjusted to a minimum value.

7. The UE according to claim 1, wherein, In a case where the HARQ-ACK feedback for the at least one PSSCH transmission during the reference duration does not include ACK, the CWS is increased to the next value higher than the current CWS among the allowed CWS values.

8. The UE according to claim 1, wherein, In a case where the at least one first PSSCH is transmitted via SL multicast and the HARQ-ACK feedback for the at least one PSSCH transmission during the reference duration includes at least a negative acknowledgement (NACK), the CWS is increased to a value higher than the current CWS among the allowed CWS values, and Wherein, in a case where the HARQ-ACK feedback for the at least one PSSCH transmission during the reference duration is regarded as all ACK, the CWS is adjusted to a minimum value.

9. The UE according to claim 1, wherein, The UE performs the SL channel access procedure based on a counter value randomly selected within the adjusted CWS.

10. The UE according to claim 1, wherein, The first time slot in which the at least one first PSSCH is transmitted is a time slot in which the PSSCH transmission is performed via all resources allocated for PSSCH transmission.

11. A method used by a user equipment (UE) in a wireless communication system, the method comprising: Transmit at least one Physical Sidelink Shared Channel (PSSCH) during a Channel Occupation Time (COT), where the at least one PSSCH includes at least one first PSSCH with enabled Hybrid Automatic Repeat Request Acknowledgement (HARQ-ACK) feedback; During a reference duration, adjust a contention window size (CWS) based on the HARQ-ACK feedback for the at least one PSSCH; and Perform a sidelink (SL) channel access procedure based on the adjusted CWS, and wherein the reference duration is defined as starting from the beginning of the COT and until the end of the first time slot in which the at least one first PSSCH is transmitted.

12. The method according to claim 11, wherein, The HARQ-ACK feedback includes reception response information based on an ACK / Negative ACK (NACK) feedback scheme.

13. The method according to claim 11, wherein, In a case where the at least one first PSSCH includes at least one second PSSCH with an indicated ACK / NACK feedback scheme and at least one third PSSCH with an indicated NACK-only feedback scheme, the reference duration is defined as starting from the beginning of the COT and until the end of the first time slot in which the at least one second PSSCH is transmitted.

14. The method according to claim 11, wherein, The at least one PSSCH includes at least one fourth PSSCH for which the HARQ-ACK feedback is not enabled.

15. The method according to claim 11, wherein, The COT is the latest COT initiated by the UE.

16. The method according to claim 11, wherein, In a case where the HARQ-ACK feedback for the at least one PSSCH transmission during the reference duration includes at least an ACK, the CWS is adjusted to a minimum value.

17. The method according to claim 11, wherein In a case where the HARQ-ACK feedback for the at least one PSSCH transmission during the reference duration does not include an ACK, the CWS is increased to the next value higher than the current CWS among the allowed CWS values.

18. The method according to claim 11, wherein In a case where the at least one first PSSCH is transmitted via SL multicast and the HARQ-ACK feedback for the at least one PSSCH transmission during the reference duration includes at least a Negative Acknowledgement (NACK), the CWS is increased to a value higher than the current CWS among the allowed CWS values, and wherein, in a case where the HARQ-ACK feedback for the at least one PSSCH transmission during the reference duration is regarded as all ACKs, the CWS is adjusted to a minimum value.

19. The method according to claim 11, wherein, The UE performs the SL channel access procedure based on a counter value randomly selected within the adjusted CWS.

20. The method according to claim 11, wherein, The first time slot in which the at least one first PSSCH is transmitted is the time slot in which the PSSCH transmission is performed via all resources allocated for PSSCH transmission.

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