Method and apparatus for transmitting signals in a wireless communication system

Abstract

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

Description

[Technical Field]

[0001] The present invention relates to a new wireless communication system, and more particularly to a channel access method and an apparatus using the same in a wireless communication system. [Background technology]

[0002] Since the commercialization of 4G (4th generation) communication systems, efforts have been made to develop new 5G (5th generation) communication systems to meet the increasing demand for wireless data traffic. 5G communication systems are also called communication systems beyond 4G networks, post-LTE systems, or new radio (NR) systems. To achieve high data transmission rates, 5G communication systems include systems operating using ultra-high frequency (mmWave) bands above 6 GHz. Furthermore, to ensure coverage, communication systems operating using frequency bands below 6 GHz are also being considered for implementation in base stations and terminals.

[0003] The 3GPP (registered trademark, hereinafter the same) (3rd generation partnership project) NR system improves network spectral efficiency, allowing carriers to provide more data and voice services within a given bandwidth. Therefore, the 3GPP NR system is designed to meet the demand for high-speed data and media transmission in addition to high-capacity voice support. The advantages of the NR system include high throughput, low latency, support for frequency division duplex (FDD) and time division duplex (TDD) on the same platform, an improved end-user experience, and low operating costs due to a simple architecture.

[0004] For more efficient data processing, dynamic TDD in the NR system can use a scheme that varies the number of orthogonal frequency division multiplexing (OFDM) symbols available for uplink and downlink use according to the data traffic direction of users in the cell. For example, if the downlink traffic of a cell is greater than the uplink traffic, the base station can allocate a relatively large number of downlink OFDM symbols to a slot (or subframe). Information about the slot configuration needs to be transmitted to the terminal.

[0005] To mitigate the path loss of radio waves in the ultra-high frequency band and increase the transmission distance of radio waves, technologies being discussed for 5G communication systems include beamforming, massive array multiple input / output (massive MIMO), full dimensional multiple input / output (FD-MIMO), array antennas, analog beamforming, hybrid beamforming that combines analog beamforming and digital beamforming, and large scale antenna technologies. In addition, to improve the system's network, 5G communication systems are undergoing technological developments such as advanced small cells, advanced small cells, cloud radio access networks (cloud RAN), ultra-dense networks, device-to-device communication (D2D), vehicle-to-everything communication (V2X), wireless backhaul, non-terrestrial network communication (NTN), moving networks, cooperative communication, coordinated multi-points (CoMP), and interference cancellation.Other advanced coding modulation (ACM) techniques being developed for 5G systems include hybrid FSK and QAM modulation (FQAM) and sliding window superposition coding (SWSC), as well as advanced access technologies such as filter bank multi-carrier (FBMC), non-orthogonal multiple access (NOMA), and sparse code multiple access (SCMA).

[0006] Meanwhile, the Internet, a human-centered network where humans generate and consume information, is evolving into the IoT (Internet of Things) network, which exchanges and processes information among distributed components such as objects. IoE (Internet of Everything) technology, which combines big data processing technology through connections with cloud servers, is also emerging. To realize the IoT, technological elements such as sensing technology, wired and wireless communication and network infrastructure, service interface technology, and security technology are required. Recently, research has focused on sensor networks, machine-to-machine (M2M), and machine-type communication (MTC) technologies for connecting objects. In an IoT environment, intelligent IT (internet technology) services are provided that collect and analyze data generated by connected objects and create new value in human life. Through the integration and convergence of traditional IT technology and various industries, the IoT is being applied to areas such as smart homes, smart buildings, smart cities, smart or connected cars, smart grids, healthcare, smart home appliances, and advanced medical services.

[0007] Therefore, various attempts are being made to apply 5G communication systems to IoT networks. For example, technologies such as sensor networks, machine-to-machine, and MTC are being implemented using 5G communication technologies such as beamforming, MIMO, and array antennas. The application of cloud radio access networks (cloud RAN), the big data processing technology mentioned above, is also an example of the fusion of 5G and IoT technologies. Mobile communication systems are generally developed to provide voice services while ensuring user activity.

[0008] Sidelink (SL) is a communication method that establishes a direct link between terminals (User Equipment, UE) to directly transmit and receive voice or data between terminals without going through a base station (BS). SL is being considered as a solution to alleviate the burden on base stations due to the rapidly increasing data traffic.

[0009] V2X (vehicle-to-everything) refers to a communication technology that exchanges information with other vehicles, pedestrians, infrastructure, etc. using wired or wireless communications. V2X can be divided into four types: V2V (vehicle-to-vehicle), V2I (vehicle-to-infrastructure), V2N (vehicle-to-network), and V2P (vehicle-to-pedestrian). V2X communication may be provided via a PC5 interface and / or a Uu interface.

[0010] Meanwhile, as more communication devices require larger communication capacities, there is an increasing need for improved mobile broadband communication compared to existing radio access technologies (RATs). To this end, communication systems that take into account reliability- and latency-sensitive services or terminals are being discussed. Next-generation wireless access technologies that take into account improved mobile broadband communication, massive MTC, and ultra-reliable and low latency communication (URLLC) can be called new radio access technologies (RATs) or new radios (NRs). NRs may also support vehicle-to-everything (V2X) communication.

[0011] Meanwhile, for example, in SL communications associated with services having high or relatively high reliability requirements, SL HARQ feedback operations and / or mechanisms of the terminal may be useful. Summary of the Invention [Problem to be solved by the invention]

[0012] An object of the present invention is to provide a method for efficiently transmitting signals in a wireless communication system and an apparatus using the same. Specifically, an object of the present invention is to provide a channel access method for efficiently transmitting signals in a wireless communication system and an apparatus using the same. [Means for solving the problem]

[0013] As one aspect of the present invention, there is provided a terminal for use in a wireless communication system, the terminal including: a communication module; and a processor controlling the communication module, wherein the processor is configured to: transmit at least one PSSCH (physical sidelink shared channel) within a COT (channel occupancy time), where the at least one PSSCH includes at least one first PSSCH with HARQ-ACK (hybrid ARQ acknowledgment) feedback enabled; adjust a contention window size (CWS) based on the HARQ-ACK feedback for the at least one PSSCH in a reference interval; and perform a sidelink (SL) channel access procedure based on the adjusted CWS; wherein the reference interval is defined as starting from the beginning of the COT and ending at the end of a first slot in which the at least one first PSSCH is transmitted.

[0014] As another aspect of the present invention, there is provided a method for use by a terminal in a wireless communication system, the method comprising: transmitting at least one physical sidelink shared channel (PSSCH) within a channel occupancy time (COT), the at least one PSSCH including at least one first PSSCH with hybrid ARQ acknowledgment (HARQ-ACK) feedback enabled; adjusting a contention window size (CWS) based on the HARQ-ACK feedback for the at least one PSSCH in a reference interval; and performing a sidelink (SL) channel access procedure based on the adjusted CWS; the reference interval is defined as starting from the beginning of the COT and ending at the end of a first slot in which the at least one first PSSCH was transmitted.

[0015] Preferably, the HARQ-ACK feedback may include reception response information in an ACK / NACK (negative ACK) feedback format.

[0016] Preferably, when the at least one first PSSCH includes at least one second PSSCH indicating an ACK / NACK feedback scheme and at least one third PSSCH indicating a NACK-only feedback scheme, the reference interval may be defined as starting from the beginning of the COT and ending at the end of the first slot in which the at least one second PSSCH is transmitted.

[0017] Preferably, the plurality of PSSCHs may include at least one fourth PSSCH in which the HARQ-ACK feedback is not enabled.

[0018] Preferably, the COT may be the most recent COT initiated by the terminal.

[0019] Preferably, the CWS may be adjusted to a minimum value if the HARQ-ACK feedback for the at least one PSSCH transmission in the reference interval includes at least an ACK.

[0020] Preferably, if the HARQ-ACK feedback for the at least one PSSCH transmission in the reference period does not include an ACK, the CWS may be increased to the next larger value than the current CWS among the allowed CWS values.

[0021] Preferably, if the at least one first PSSCH is transmitted as a SL groupcast and the HARQ-ACK feedback for the at least one PSSCH transmission in the reference period includes at least one NACK (negative acknowledgment), the CWS is increased to a value greater than the current CWS among the allowed CWS values, and if all HARQ-ACK feedback for the at least one PSSCH transmission in the reference period are considered to be ACKs, the CWS may be adjusted to a minimum value.

[0022] Preferably, the terminal can perform the SL channel access procedure based on a randomly selected counter value within the adjusted CWS.

[0023] Preferably, the first slot in which the at least one first PSSCH is transmitted may be a slot in which the PSSCH transmission is performed on all resources allocated for PSSCH transmission. [Effects of the Invention]

[0024] The present invention provides a method for efficiently transmitting signals in a wireless communication system and an apparatus using the same. The present invention also provides a channel access method for efficiently transmitting signals in a wireless communication system and an apparatus using the same.

[0025] The effects obtained from the present invention are not limited to those mentioned above, and other effects not mentioned will be clearly understood by those having ordinary skill in the art to which the present invention pertains from the following description. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 is a diagram illustrating an example of a radio frame structure used in a wireless communication system. [Figure 2] 1 is a diagram illustrating an example of a downlink (DL) / uplink (UL) slot structure in a wireless communication system. [Figure 3]FIG. 1 is a diagram illustrating physical channels used in a 3GPP system (e.g., NR) and a general signal transmission method using the physical channels. [Figure 4] FIG. 1 illustrates an SS / PBCH block for initial cell access in a 3GPP NR system. [Figure 5] FIG. 1 illustrates a procedure for control information and control channel transmission in a 3GPP NR system. [Figure 6] A diagram showing a CORESET in which PDCCH is transmitted in a 3GPP NR system. [Figure 7] A diagram showing a method for setting a PDCCH search space in a 3GPP NR system. [Figure 8] FIG. 8 is a conceptual diagram illustrating carrier aggregation. [Figure 9] FIG. 1 is a diagram for explaining terminal carrier communication and multi-carrier communication. [Figure 10] A diagram showing an example in which a cross-carrier scheduling technique is applied. [Figure 11] FIG. 1 is a diagram illustrating an NR-U (NR-Unlicensed) service environment. [Figure 12] 1 is a diagram illustrating an existing communication system (e.g., wireless LAN) that operates in an unlicensed band. [Figure 13] A diagram showing the channel access process based on Category 4 LBT. [Figure 14] 2A and 2B are block diagrams showing the configurations of a terminal and a base station according to an embodiment of the present invention. [Figure 15] 10A and 10B are diagrams illustrating an example of COT (channel occupancy time) setting and operations based thereon. [Figure 16] FIG. 1 is a diagram illustrating a sidelink (SL) communication process. [Figure 17] FIG. 1 is a diagram illustrating a sidelink (SL) communication process. [Figure 18] FIG. 1 is a diagram illustrating a sidelink (SL) communication process. [Figure 19]FIG. 1 is a diagram illustrating a sidelink (SL) communication process. [Figure 20] FIG. 1 is a diagram illustrating a sidelink (SL) communication process. [Figure 21] FIG. 1 is a diagram illustrating a sidelink (SL) communication process. [Figure 22] FIG. 1 is a diagram illustrating a sidelink (SL) communication process. [Figure 23] FIG. 1 is a diagram illustrating a sidelink (SL) communication process. [Figure 24] FIG. 10 is a diagram illustrating an example of the structure within a slot of PSCCH / PSSCH / PSFCH (physical sidelink control channel / physical sidelink shared channel / physical sidelink feedback channel). [Figure 25] FIG. 1 is a diagram illustrating the structure of S-SSB (sidelink SSB). [Figure 26] FIG. 1 is a diagram illustrating a sidelink (SL) communication process. [Figure 27] 1 illustrates a channel connection method according to the present invention; [Figure 28] 1 illustrates a channel connection method according to the present invention; [Figure 29] FIG. 10 is a diagram illustrating an SL reference interval according to the present invention. [Figure 30] FIG. 10 is a diagram illustrating an SL reference interval according to the present invention. [Figure 31] 1 is a diagram illustrating an SL transmission method according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0027] The terms used in this specification are generally used as widely as possible, taking into consideration the functions of the present invention. However, these may vary depending on the intentions of those skilled in the art, practice, or the emergence of new technologies. In addition, in certain cases, the applicant may arbitrarily select terms. In such cases, the meaning of the terms will be described in the description of the relevant invention. Therefore, it is clear that the terms used in this specification should be interpreted based on the substantive meaning of the terms and the overall content of this specification, rather than simply the names of the terms.

[0028] Throughout this specification, when a component is said to be "connected" to another component, this includes not only "directly connected" but also "electrically connected" through other components in between. Furthermore, when a component is said to "comprise" a specific component, this does not mean excluding the other component, but also means including the other component, unless otherwise specified to the contrary. In addition, limitations such as "more than" or "less than" based on a specific threshold may be appropriately replaced with "more than" or "less than," respectively, depending on the embodiment.

[0029] The following technologies are used in various wireless access systems, such as CDMA (code division multiple access), FDMA (frequency division multiple access), TDMA (time division multiple access), OFDMA (orthogonal frequency division multiple access), and SC-FDMA (single carrier frequency division multiple access). CDMA is implemented in radio technologies such as UTRA (Universal Terrestrial Radio Access) and CDMA2000. TDMA is implemented in radio technologies such as GSM (Global System for Mobile communications), GPRS (General Packet Radio Service), and EDGE (Enhanced Data Rates for GSM Evolution). OFDMA is implemented in radio technologies such as IEEE802.11 (Wi-Fi), IEEE802.16 (WiMAX), IEEE802-20, and E-UTRA (Evolved UTRA). UTRA is part of UMTS (Universal Mobile Telecommunications System). 3GPP LTE (Long term evolution) is a part of E-UMTS (Evolved UMTS) that uses E-UTRA, and LTE-A (Advanced) is an evolved version of 3GPP LTE. 3GPP NR is a system designed separately from LTE / LTE-A and is a system for supporting eMBB (enhanced Mobile Broadband), URLLC (Ultra-Reliable and Low Latency Communication), and mMTC (massive Machine Type Communication) services, which are requirements of IMT-2020. For clarity of explanation, the following description will focus on 3GPP NR, but the technical concept of the present invention is not limited thereto.

[0030] Unless otherwise specified herein, the base station may include a next generation node B (gNB) defined in 3GPP NR. Also, unless otherwise specified, the terminal may include a user equipment (UE). Hereinafter, to facilitate understanding of the description, each content will be described as a separate embodiment, but each embodiment may be used in combination with each other. In this disclosure, "configuring" a terminal may mean configuration by a base station. Specifically, the base station may transmit a channel or a signal to the terminal to configure the operation of the terminal or parameter values ​​used in the wireless communication system.

[0031] FIG. 1 is a diagram illustrating an example of a radio frame structure used in a radio communication system.

[0032] Referring to FIG. 1, a radio frame used in a 3GPP NR system has a length of 10 ms (ΔfmaxNf / 100)*Tc). Each radio frame consists of 10 equally sized subframes (SF). Here, Δfmax=480*103 Hz, Nf=4096, Tc=1 / (Δfref*Nf,ref), Δfref=15*103 Hz, and Nf,ref=2048. The 10 subframes in a frame are numbered 0 to 9. Each subframe has a length of 1 ms and consists of one or more slots depending on the subcarrier spacing. More specifically, the subcarrier spacing that can be used in a 3GPP NR system is 15*2 μkHz. μ is the subcarrier spacing configuration factor and has values ​​from 0 to 4. That is, 15 kHz, 30 kHz, 60 kHz, 120 kHz, or 240 kHz is used as the subcarrier spacing. A 1-ms-long subframe consists of 2μ slots, each of which is 2-μms long. The 2μ slots in one subframe are numbered from 0 to 2μ-1. The slots in one radio frame are numbered from 0 to 10*2μ-1. Time resources are divided by at least one of the radio frame number (also called radio frame index), subframe number (also called subframe index), and slot number (or slot index).

[0033] 2 is a diagram illustrating an example of a downlink (DL) / uplink (UL) slot structure in a wireless communication system, and in particular, a resource grid structure of a 3GPP NR system.

[0034] There is one resource grid per antenna port. Referring to FIG. 2, a slot includes multiple OFDM symbols in the time domain and multiple resource blocks (RBs) in the frequency domain. An OFDM symbol also refers to one symbol interval. Unless otherwise specified, an OFDM symbol is simply referred to as a symbol. Hereinafter, the term "symbol" includes OFDM symbols, SC-FDMA symbols, DFTs-OFDM symbols, etc. Referring to FIG. 2, a signal transmitted from each slot is represented by a resource grid consisting of Nsize, μgrid, x*NRBSC subcarriers, and Nslotsymb OFDM symbols. Here, x=DL for the downlink resource grid and x=UL for the uplink resource grid. Nsize, μgrid, and x denote the number of resource blocks (RBs) according to the subcarrier spacing factor μ (x is DL or UL), and Nslotsymb denotes the number of OFDM symbols in a slot. NRBSC is the number of subcarriers constituting one RB, and NRBSC=12. Depending on the multiple access method, the OFDM symbol is called a cyclic prefix OFDM (CP-OFDM) symbol or a discrete Fourier transform spread OFDM (DFT-S-OFDM) symbol.

[0035] The number of OFDM symbols included in one slot may vary depending on the length of the cyclic prefix (CP). For example, a normal CP includes 14 OFDM symbols, while an extended CP includes 12 OFDM symbols. In a specific embodiment, the extended CP is used only with a subcarrier spacing of 60 kHz. For convenience of explanation, FIG. 2 illustrates a case where one slot consists of 14 OFDM symbols. However, the present invention is equally applicable to slots having other numbers of OFDM symbols. Referring to FIG. 2, each OFDM symbol includes Nsize, μgrid, and x*NRBSC subcarriers in the frequency domain. Subcarriers are classified into data subcarriers for transmitting data, reference signal subcarriers for transmitting reference signals, and guard bands. The carrier frequency is also called the center frequency (fc).

[0036] One RB is defined by NRBSC (e.g., 12) consecutive subcarriers in the frequency domain. Incidentally, a resource consisting of one OFDM symbol and one subcarrier is called a resource element (RE) or tone. Therefore, one RB consists of Nslotsymb*NRBSC resource elements. Each resource element in the resource grid is uniquely defined by an index pair (k, l) within one slot. k is an index ranging from 0 to Nsize, μgrid, x*NRBSC-1 in the frequency domain, and l is an index ranging from 0 to Nslotsymb-1 in the time domain.

[0037] In order for a terminal to receive a signal from a base station or transmit a base station signal, the time / frequency synchronization of the terminal must be aligned with the time / frequency synchronization of the base station, because if the base station and the terminal are not synchronized, the terminal cannot determine the time and frequency parameters required to demodulate DL signals and transmit UL signals at the correct time.

[0038] Each symbol in a radio frame operating in time division duplex (TDD) or unpaired spectrum consists of at least one downlink symbol (DL symbol), uplink symbol (UL symbol), or flexible symbol. A radio frame operating in frequency division duplex (FDD) or paired spectrum with a downlink carrier consists of downlink symbols or flexible symbols, and a radio frame operating with an uplink carrier consists of uplink symbols or flexible symbols. A downlink symbol allows downlink transmission but not uplink transmission, and an uplink symbol allows uplink transmission but not downlink transmission. Whether a flexible symbol is used for downlink or uplink depends on the signal.

[0039] Information about the type of each symbol, i.e., information indicating any one of downlink symbols, uplink symbols, and flexible symbols, is formed by a cell-specific (or common) RRC signal. The information about each symbol type is additionally formed by a UE-specific (or dedicated) RRC signal. The base station uses the cell-specific RRC signal to notify i) the period of the cell-specific slot configuration, ii) the number of slots having only downlink symbols from the beginning of the period of the cell-specific slot configuration, iii) the number of downlink symbols from the first symbol in the slot immediately following the slot having only downlink symbols, iv) the number of slots having only uplink symbols from the end of the period of the cell-specific slot configuration, and v) the number of uplink symbols from the last symbol in the slot immediately preceding the slot having only uplink symbols. Here, symbols that are not configured as either uplink or downlink symbols are flexible symbols.

[0040] If the information regarding the symbol type consists of the per-terminal RRC signal, the base station signals whether the flexible symbol is a downlink symbol or an uplink symbol by means of the cell-specific RRC signal. At this time, the per-terminal RRC signal cannot change the downlink symbol or the uplink symbol consisting of the cell-specific RRC signal into another symbol type. The per-terminal RRC signal signals, for each slot, the number of downlink symbols among the Nslotsymb symbols of the slot and the number of uplink symbols among the Nslotsymb symbols of the slot. At this time, the downlink symbols of the slot are continuously configured from the first symbol to the i-th symbol of the slot. Also, the uplink symbols of the slot are continuously configured from the j-th symbol to the last symbol of the slot (where i < j). In a slot, a symbol that is not configured as either an uplink symbol or a downlink symbol is a flexible symbol.

[0041] The type of symbol configured by the RRC signal as described above can be called a semi-static DL / UL configuration. In the semi-static DL / UL configuration configured by the RRC signal previously, the flexible symbol may be indicated as a downlink symbol, an uplink symbol, or a flexible symbol by means of the dynamic SFI (slot format information) transmitted on the physical downlink control channel (PDCCH). At this time, the downlink symbol or the uplink symbol configured by the RRC signal is not changed into another symbol type. Table 1 exemplifies the dynamic SFI that the base station can indicate to the terminal.

[0042]

Table 1

[0043] In Table 1, D represents a downlink symbol, U represents an uplink symbol, and X represents a flexible symbol. As shown in Table 1, up to two DL / UL switchings may be allowed within one slot.

[0044] FIG. 3 is a diagram illustrating physical channels used in a 3GPP system (for example, NR) and a general signal transmission method using the physical channels.

[0045] When a terminal is powered on or newly enters a cell, the terminal performs an initial cell search (S101). Specifically, the terminal synchronizes with a base station during the initial cell search. To do this, the terminal receives a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) from the base station to synchronize with the base station and acquire information such as a cell index. Next, the terminal receives a physical broadcast channel from the base station to acquire broadcast information within the cell.

[0046] After completing the initial cell search, the terminal receives a physical downlink shared channel (PDSCH) via a physical downlink control channel (PDCCH) and information carried on the PDCCH to acquire more detailed system information than that acquired through the initial cell search (S102). Here, the system information transmitted to the terminal is cell-common system information for the terminal to operate correctly in a physical layer in Radio Resource Control (RRC), and is called remaining system information or system information block (SIB) 1.

[0047] When a terminal first connects to a base station or when there are no radio resources for signal transmission (when the terminal is in RRC_IDLE mode), the terminal can perform a random access procedure with the base station (steps S103 to S106). First, the terminal transmits a preamble on a physical random access channel (PRACH) (S103) and can receive a response message for the preamble from the base station on a PDCCH and a corresponding PDSCH (S104). If the terminal receives a valid random access response message, the terminal transmits data including its own identifier, etc. to the base station on a physical uplink shared channel (PUSCH) indicated by an uplink grant transmitted from the base station on the PDCCH (S105). Next, the terminal waits for reception of a PDCCH as instructed by the base station to resolve collisions. If the terminal successfully receives the PDCCH with its own identifier (S106), the random access procedure ends. During the random access procedure, the terminal can acquire terminal-specific system information required for the terminal to operate correctly in the physical layer of the RRC layer. If the terminal acquires the terminal-specific system information in the RRC layer, the terminal enters the RRC connected mode (RRC_CONNECTED mode).

[0048] The RRC layer is used to generate and manage messages for control between a terminal and a radio access network (RAN). Furthermore, the base station and terminal can broadcast cell system information required for all terminals in the cell, manage paging message transmission, manage mobility and handover, report terminal measurements and related control, and manage and store terminal capabilities at the RRC layer. Generally, the update of signals transmitted at the RRC layer (hereinafter referred to as RRC signals) is longer than the transmission / reception period (i.e., transmission time interval, TTI) at the physical layer, so that the RRC configuration can be maintained unchanged for a long period.

[0049] After the above procedures, the terminal receives a PDCCH / PDSCH (S107) and transmits a physical uplink shared channel (PUSCH) / physical uplink control channel (PUCCH) (S108) as a general uplink / downlink signal transmission procedure. In particular, the terminal receives downlink control information (DCI) via the PDCCH. The DCI includes control information such as resource allocation information for the terminal. The format of the DCI may vary depending on the purpose of use. The uplink control information (UCI) transmitted by the terminal to the base station via the uplink includes a downlink / uplink ACK / NACK signal, a channel quality indicator (CQI), a precoding matrix index (PMI), a rank indicator (RI), etc. Here, the CQI, PMI, and RI are included in channel state information (CSI). In the case of a 3GPP NR system, the terminal transmits control information such as the above-mentioned HARQ-ACK and CSI via the PUSCH and / or PUCCH.

[0050] FIG. 4 is a diagram illustrating an SS / PBCH block for initial cell access in a 3GPP NR system.

[0051] When a terminal is powered on or attempts to access a new cell, it acquires time and frequency synchronization with the cell and performs an initial cell search process. During the cell search process, the terminal detects the cell's physical cell identity (NcellID). To do this, the terminal receives synchronization signals, such as a primary synchronization signal (PSS) and a secondary synchronization signal (SSS), from the base station to synchronize with the base station. At this time, the terminal obtains information such as a cell identity (ID).

[0052] The synchronization signal (SS) will be described in more detail with reference to Figure 4(a). The synchronization signal is divided into a PSS and an SSS. The PSS is used to obtain time-domain synchronization and / or frequency-domain synchronization, such as OFDM symbol synchronization and slot synchronization. The SSS is used to obtain frame synchronization and a cell group ID. Referring to Figure 4(a) and Table 1, an SS / PBCH block consists of 20 consecutive RBs (=240 subcarriers) on the frequency axis and 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 via subcarriers 56 to 182. Here, the lowest subcarrier index in the SS / PBCH block starts from 0. In the first OFDM symbol in which the PSS is transmitted, the base station does not transmit signals via the remaining subcarriers, i.e., subcarriers 0 to 55 and 183 to 239. In addition, in the third OFDM symbol in which the SSS is transmitted, the base station does not transmit signals through subcarriers 48 to 55 and 183 to 191. The base station transmits a physical broadcast channel (PBCH) through the remaining REs in the SS / PBCH block excluding the signals.

[0053] [Table 2]

[0054] The SS groups a total of 1008 unique physical layer cell IDs (physical layer cell IDs) into 336 physical layer cell ID groups, each containing three unique identifiers, through the combination of three PSSs and SSSs. Specifically, each physical layer cell ID is part of only one physical layer cell ID group. Thus, the physical layer cell ID NcellID = 3N(1)ID + N(2)ID is uniquely defined by an index N(1)ID ranging from 0 to 335 indicating a physical layer cell ID group and an index N(2)ID ranging from 0 to 2 indicating a physical layer identifier within the physical layer cell ID group. The UE detects the PSS and identifies one of the three unique physical layer identifiers. The UE also detects the SSS and identifies one of the 336 physical layer cell IDs associated with the physical layer identifier. In this case, the PSS sequence dPSS(n) is as follows:

[0055]

number

[0056] where x(i+7)=(x(i+4)+x(i)) mod 2, Given that [x(6)x(5)x(4)x(3)x(2)x(1)x(0)]=[1110110].

[0057] Also, the SSS sequence dSSS(n) is as follows:

[0058]

number

[0059] where x0(i+7)=(x0(i+4)+x0(i))mod 2 x1(i+7)=(x1(i+1)+x1(i))mod 2, Given that [x0(6)x0(5)x0(4)x0(3)x0(2)x0(1) 0(0)]=[0000001], [x1(6)x1(5)x1(4)x1(3)x1(2)x1(1)x1(0)]=[0000001].

[0060] A 10-ms radio frame is divided into two 5-ms half-frames. Referring to FIG. 4(b), the slots in which SS / PBCH blocks are transmitted within each half-frame are described. The slots in which SS / PBCH blocks are transmitted are either Cases A, B, C, D, or E. In Case A, the subcarrier spacing is 15 kHz, and the start point of the SS / PBCH block is the {2, 8}+14*n symbol. Here, n = 0 or 1 for carrier frequencies below 3 GHz. Also, n = 0, 1, 2, or 3 for carrier frequencies above 3 GHz and below 6 GHz. In Case B, the subcarrier spacing is 30 kHz, and the start point of the SS / PBCH block is the {4, 8, 16, 20}+28*n symbol. Here, n = 0 for carrier frequencies below 3 GHz. Also, n = 0 or 1 for carrier frequencies above 3 GHz and below 6 GHz. In Case C, the subcarrier spacing is 30 kHz and the start of the SS / PBCH block is {2, 8}+14*n symbols, where n=0, 1 for carrier frequencies below 3 GHz. For carrier frequencies above 3 GHz and below 6 GHz, n=0, 1, 2, 3. In Case D, the subcarrier spacing is 120 kHz and the start of the SS / PBCH block is {4, 8, 16, 20}+28*n symbols, where n=0, 1, 2, 3, 5, 6, 7, 8, 10, 11, 12, 13, 15, 16, 17, 18 for carrier frequencies above 6 GHz. In Case E, the subcarrier spacing is 240 kHz and the start of the SS / PBCH block is {8, 12, 16, 20, 32, 36, 40, 44}+56*n symbols. In this case, n=0, 1, 2, 3, 5, 6, 7, 8 for carrier frequencies above 6 GHz.

[0061] 5 is a diagram showing a procedure for transmitting control information and a control channel in a 3GPP NR system. Referring to FIG. 5(a), a base station adds a cyclic redundancy check (CRC) masked (e.g., XORed) with a radio network temporary identifier (RNTI) to control information (e.g., DCI) S202. The base station scrambles the CRC with an RNTI value determined according to the purpose / target of each control information. The common RNTI used by one or more terminals includes 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). The UE-specific RNTI includes at least one of a cell temporary RNTI (C-RNTI), a CS-RNTI, or an MCS-C-RNTI. The base station then performs channel encoding (e.g., polar coding) S204 and rate-matching S206 according to the amount of resource(s) used for PDCCH transmission. The base station then multiplexes DCI(s) based on a CCE (control channel element)-based PDCCH structure S208. The base station then applies additional processes S210, such as scrambling, modulation (e.g., QPSK), and interleaving, to the multiplexed DCI(s) and maps them to resources to be transmitted. A CCE is the basic resource unit for the PDCCH, and one CCE consists of multiple (e.g., six) resource element groups (REGs). One REG consists of multiple (e.g., 12) REs. The number of CCEs used for one PDCCH is defined as the aggregation level. 3GPP NR systems use aggregation levels of 1, 2, 4, 8, or 16.FIG. 5(b) is a diagram relating to CCE aggregation levels and PDCCH multiplexing, showing the types of CCE aggregation levels used for one PDCCH and the CCE(s) transmitted in the control region accordingly.

[0062] FIG. 6 is a diagram showing a CORESET in which a PDCCH is transmitted in a 3GPP NR system.

[0063] A CORESET is a time-frequency resource over which a PDCCH, a control signal for a terminal, is transmitted. A search space, which will be described later, is mapped to one CORESET. Therefore, a terminal does not monitor all frequency bands to receive a PDCCH, but rather monitors a time-frequency region designated as a CORESET and decodes the PDCCH mapped to the CORESET. A base station configures one or more CORESETs for each cell of a terminal. A CORESET consists of up to three consecutive symbols on the time axis. A CORESET also consists of six consecutive PRBs on the frequency axis. In the embodiment of FIG. 5, CORESET#1 consists of consecutive PRBs, and CORESET#2 and CORESET#3 consist of non-consecutive PRBs. A CORESET can be located at any symbol within a slot. For example, in the embodiment of FIG. 5, CORESET#1 starts from the first symbol of the slot, CORESET#2 starts from the fifth symbol of the slot, and CORESET#9 starts from the ninth symbol of the slot.

[0064] FIG. 7 is a diagram illustrating a method for configuring a PDCCH search space in a 3GPP NR system.

[0065] At least one search space exists in each CORESET for transmitting a PDCCH to a terminal. In an embodiment of the present invention, the search space is a set of all time-frequency resources (hereinafter referred to as PDCCH candidates) on which the PDCCH of the terminal is transmitted. The search space includes a common search space that all 3GPP NR terminals should commonly search, and a terminal-specific or UE-specific search space that a specific terminal should search. In the common search space, all terminals in a cell belonging to the same base station monitor a PDCCH that is configured to be commonly searched. In addition, the terminal-specific search space is configured for each terminal so that the PDCCH allocated to each terminal is monitored at a different search space position depending on the terminal. In the case of a terminal-specific search space, the search spaces allocated to terminals may partially overlap due to the limited control region to which the PDCCH is allocated. Monitoring the PDCCH includes blind decoding of PDCCH candidates in the search space. If blind decoding is successful, the PDCCH is said to be (successfully) detected / received, and if blind decoding fails, the PDCCH is said to be undetected / unreceived or not successfully detected / received.

[0066] For convenience of explanation, a PDCCH scrambled with a group common (GC) RNTI already known by one or more terminals to transmit downlink control information to one or more terminals is referred to as a group common (GC) PDCCH or a common PDCCH. Also, a PDCCH scrambled with a terminal-specific RNTI already known by a specific terminal to transmit uplink scheduling information or downlink scheduling information to one specific terminal is referred to as a terminal-specific PDCCH. The common PDCCH is included in a common search space, and the terminal-specific PDCCH is included in the common search space or the terminal-specific PDCCH.

[0067] A base station notifies each terminal or a terminal group of information regarding resource allocation of transmission channels, i.e., DL Grant, for the paging channel (PCH) and downlink-shared channel (DL-SCH), or information regarding resource allocation of the UL-SCH and hybrid automatic repeat request (HARQ) (i.e., UL Grant), via a PDCCH. The base station transmits PCH transport blocks and DL-SCH transport blocks via a PDSCH. The base station transmits data excluding specific control information or specific service data via the PDSCH. Furthermore, terminals receive data excluding specific control information or specific service data via the PDSCH.

[0068] A base station transmits information on which terminal (one or more terminals) PDSCH data is transmitted to and how the terminal should receive and decode the PDSCH data, by including the information in a PDCCH. For example, assume that DCI transmitted through a specific PDCCH is CRC masked with RNTI "A," and the DCI indicates that the PDSCH is allocated to radio resource "B" (e.g., frequency location), and indicates transmission format information "C" (e.g., transmission block size, modulation scheme, coding information, etc.). A terminal monitors the PDCCH using its own RNTI information. In this case, if there is a terminal that blind decodes the PDCCH using RNTI "A," the terminal receives the PDCCH and receives the PDSCH indicated by "B" and "C" through the received PDCCH information.

[0069] Table 3 shows an example of a PUCCH used in a wireless communication system.

[0070] [Table 3]

[0071] The PUCCH is used to transmit the following uplink control information (UCI):

[0072] - SR (Scheduling Request): Information used to request uplink UL-SCH resources.

[0073] HARQ-ACK: A response to a PDCCH (indicating DL SPS release) and / or a response to an uplink transport block (TB) on a PDSCH. HARQ-ACK indicates whether information transmitted via a PDCCH or a PDSCH has been received. HARQ-ACK responses include a positive ACK (simply referred to as ACK), a negative ACK (hereinafter referred to as NACK), DTX (Discontinuous Transmission), or NACK / DTX. Here, the term HARQ-ACK is used interchangeably with HARQ-ACK / NACK and ACK / NACK. Generally, ACK is represented by a bit value of 1, and NACK is represented by a bit value of 0.

[0074] CSI: Feedback information for the downlink channel. It is generated by the terminal based on the CSI-RS (Reference Signal) transmitted by the base station. MIMO (multiple input multiple output)-related feedback information includes RI and PMI. CSI is divided into CSI part 1 and CSI part 2 according to the information indicated by the CSI.

[0075] In the 3GPP NR system, five PUCCH formats are used to support various service scenarios, various channel environments, and frame structures.

[0076] PUCCH format 0 is a format that transmits 1-bit or 2-bit HARQ-ACK information or SR. PUCCH format 0 is transmitted using one or two OFDM symbols on the time axis and one RB on the frequency axis. If PUCCH format 0 is transmitted using two OFDM symbols, the same sequence is transmitted in two symbols using different RBs. This allows the UE to obtain frequency diversity gain. More specifically, the UE determines a cyclic shift value mcs according to the Mbit-bit UCI (Mbit = 1 or 2), cyclically shifts a 12-length base sequence by the determined mcs value, maps the resulting sequence to one OFDM symbol and 12 REs of one PRB, and transmits it. If the number of cyclic shifts available to the UE is 12 and Mbit = 1, 1-bit UCIs 0 and 1 are represented by sequences corresponding to two cyclic shifts with a cyclic shift value difference of 6. Also, if Mbit=2, then 2-bit UCI 00, 01, 11, 10 is represented by a sequence corresponding to four cyclic shifts with a difference of three between the cyclic shift values.

[0077] PUCCH format 1 carries 1-bit or 2-bit HARQ-ACK information or SR. PUCCH format 1 is transmitted using 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 is one of 4 to 14. More specifically, UCI with Mbit=1 is modulated using BPSK. The UE modulates UCI with Mbit=2 using quadrature phase shift keying (QPSK). The modulated complex-valued symbol d(0) is multiplied by a sequence of length 12 to obtain a signal. The UE spreads the obtained signal using an orthogonal cover code (OCC) on the time axis to even-numbered OFDM symbols assigned to PUCCH format 1 and transmits it. In PUCCH format 1, the maximum number of different UEs multiplexed in the same RB can be determined depending on the length of the OCC used. In odd-numbered OFDM symbols of PUCCH format 1, a demodulation reference signal (DMRS) is spread by OCC and mapped.

[0078] PUCCH format 2 carries UCI of more than 2 bits. PUCCH format 2 is transmitted using one or two OFDM symbols on the time axis and one or more RBs on the frequency axis. If PUCCH format 2 is transmitted using two OFDM symbols, the same sequence is transmitted using different RBs across the two OFDM symbols. This allows the UE to obtain frequency diversity gain. More specifically, Mbit UCI (Mbit>2) is bit-level scrambled, QPSK modulated, and mapped to the RBs of one or two OFDM symbols. Here, the number of RBs is one of 1 to 16.

[0079] PUCCH format 3 or PUCCH format 4 transmits more than two bits of UCI. PUCCH format 3 or PUCCH format 4 is transmitted using 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 is one of 4 to 14. Specifically, the terminal modulates Mbit-bit UCI (Mbit>2) using π / 2-BPSK (Binary Phase Shift Keying) or QPSK to generate complex symbols d(0) to d(Msymb-1). Here, Msymb=Mbit when π / 2-BPSK is used, and Msymb=Mbit / 2 when QPSK is used. The terminal does not apply block-wise spreading to PUCCH format 3. However, the terminal may apply block-wise spreading to one RB (i.e., 12 subcarriers) using a PreDFT-OCC of length -12 so that PUCCH format 4 has a multiplexing capacity of 2 or 4. The terminal transmit precoding (or DFT-precoding) the spreaded signal, maps it to each RE, and transmits the spreaded signal.

[0080] In this case, the number of RBs occupied by PUCCH format 2, PUCCH format 3, or PUCCH format 4 is determined according to the length of UCI transmitted by the terminal and the maximum code rate. If the terminal uses PUCCH format 2, the terminal transmits both HARQ-ACK information and CSI information via the PUCCH. If the number of RBs that the terminal can transmit is greater than the maximum number of RBs that PUCCH format 2, PUCCH format 3, or PUCCH format 4 can use, the terminal does not transmit some UCI information and transmits only the remaining UCI information according to the priority of the UCI information.

[0081] PUCCH format 1, PUCCH format 3, or PUCCH format 4 is configured via RRC signaling to indicate frequency hopping within a slot. When frequency hopping is configured, the index of the RB to be frequency hopped is configured via RRC signaling. If PUCCH format 1, PUCCH format 3, or PUCCH format 4 is transmitted over N OFDM symbols on the time axis, the first hop has floor(N / 2) OFDM symbols, and the second hop has ceil(N / 2) OFDM symbols.

[0082] PUCCH format 1, PUCCH format 3, or PUCCH format 4 is configured to be repeatedly transmitted in multiple slots. In this case, the number K of slots in which the PUCCH is repeatedly transmitted is configured by an RRC signal. The repeatedly transmitted PUCCH should start from the same OFDM symbol position in each slot and have the same length. If the RRC signal indicates that any one of the OFDM symbols in a slot in which the UE should transmit the PUCCH is a DL symbol, the UE does not transmit the PUCCH from that slot but postpones its transmission to the next slot.

[0083] Meanwhile, in a 3GPP NR system, a terminal transmits and receives using a bandwidth that is smaller than or equal to the bandwidth of a carrier (or cell). To do so, the terminal is configured with a bandwidth part (BWP), which consists of a continuous portion of the carrier bandwidth. A terminal operating according to TDD or using an unpaired spectrum is configured with up to four DL / UL BWP pairs per carrier (or cell). The terminal also activates one DL / UL BWP pair. A terminal operating according to FDD or using a paired spectrum is configured with up to four DL BWPs per downlink carrier (or cell) and up to four UL BWPs per uplink carrier (or cell). The terminal activates one DL BWP and one UL BWP for each carrier (or cell). The terminal may not receive or transmit from time-frequency resources other than the activated BWP. An activated BWP is called an active BWP.

[0084] The base station refers to the activated BWP among the BWPs configured for the UE as a DCI. The BWP indicated in the DCI is activated, and the other configured BWP(s) are deactivated. In a carrier (or cell) operating in TDD, the base station includes a bandwidth part indicator (BPI) indicating the activated BWP in the DCI scheduling the PDSCH or PUSCH to change the DL / UL BWP pair of the UE. The UE receives the DCI scheduling the PDSCH or PUSCH and identifies the activated DL / UL BWP pair based on the BPI. In a downlink carrier (or cell) operating in FDD, the base station includes a BPI indicating the activated BWP in the DCI scheduling the PDSCH to change the DL BWP of the UE. In an uplink carrier (or cell) operating in FDD, the base station includes a BPI indicating the activated BWP in the DCI scheduling the PDSCH to change the UE's UL BWP.

[0085] FIG. 8 is a conceptual diagram illustrating carrier aggregation.

[0086] Carrier aggregation refers to a method in which a wireless communication system uses a single large logical frequency band by using multiple frequency blocks or (logical) cells consisting of uplink resources (or component carriers) and / or downlink resources (or component carriers) in order to use a wider frequency band. For convenience of explanation, the term "component carrier" will be used hereinafter.

[0087] Referring to Figure 8, in an example of a 3GPP NR system, the entire system band includes up to 16 component carriers, each of which has a bandwidth of up to 400 MHz. A component carrier includes one or more physically contiguous subcarriers. While Figure 8 shows each component carrier having the same bandwidth, this is merely an example, and each component carrier may have a different bandwidth. Furthermore, although each component carrier is shown adjacent to each other on the frequency axis, this is shown only as a logical concept, and each component carrier may be physically adjacent to each other or separated from each other.

[0088] A different center frequency is used for each component carrier. Also, a common center frequency is used for physically adjacent component carriers. In the embodiment of Fig. 8, if it is assumed that all component carriers are physically adjacent, center frequency A is used for all component carriers. Also, if it is assumed that the component carriers are not physically adjacent, center frequency A and center frequency B are used for each component carrier.

[0089] When the entire system bandwidth is expanded by carrier aggregation, the frequency band used for communication with each terminal is defined in component carrier units. Terminal A uses the entire system bandwidth of 100 MHz and communicates using all five component carriers. Terminals B1 to B5 use only a 20 MHz bandwidth and communicate using one component carrier. Terminals C1 and C2 use only a 40 MHz bandwidth and communicate using two component carriers each. The two component carriers may or may not be logically / physically adjacent. The example in Figure 8 shows a case where terminal C1 uses two non-adjacent component carriers and terminal C2 uses two adjacent component carriers.

[0090] 9A and 9B are diagrams for explaining single-carrier communication and multi-carrier communication, in particular, FIG. 9A shows a subframe structure of a single carrier, and FIG. 9B shows a subframe structure of a multi-carrier.

[0091] Referring to FIG. 9(a), in an FDD mode, a typical wireless communication system transmits or receives data through one DL band and one corresponding UL band. In another specific embodiment, in a TDD mode, the wireless communication system divides a radio frame into uplink time units and downlink time units in the time domain, and transmits or receives data through the uplink / downlink time units. Referring to FIG. 9(b), three 20 MHz component carriers (CCs) are aggregated in each of the UL and DL to support a 60 MHz bandwidth. The CCs may be adjacent or non-adjacent to each other in the frequency domain. For convenience, FIG. 9(b) illustrates a case where the bandwidths of the UL CC and the DL CC are the same and symmetrical, but the bandwidths of each CC may be determined independently. Also, asymmetric carrier aggregation, in which the number of UL CCs and the number of DL CCs are different, is possible. The DL / UL CC allocated / configured to a specific terminal via RRC is referred to as the serving DL / UL CC of the specific terminal.

[0092] A base station communicates with a terminal by activating some or all of the serving CCs of the terminal or deactivating some of the CCs. The base station may change the activated / deactivated CCs or the number of activated / deactivated CCs. When a base station allocates CCs available to a terminal in a cell-specific or terminal-specific manner, at least one of the allocated CCs may not be deactivated unless the CC allocation for the terminal is completely reconfigured or the terminal performs a handover. A CC that is not deactivated by the terminal is called a primary CC (PCC) or PCell (primary cell), and a CC that the base station can activate / deactivate freely is called a secondary CC (SCC) or SCell (secondary cell).

[0093] Meanwhile, 3GPP NR uses the concept of a cell to manage radio resources. A cell is defined as a combination of downlink and uplink resources, i.e., a combination of DL CC and UL CC. A cell may consist of only DL resources or a combination of DL and UL resources. If carrier aggregation is supported, the linkage between the carrier frequency of DL resources (or DL ​​CC) and the carrier frequency of UL resources (or UL CC) is indicated by system information. Carrier frequency refers to the center frequency of each cell or CC. A cell corresponding to a PCC is called a PCell, and a cell corresponding to an SCC is called an SCell. The carrier corresponding to a PCell in the downlink is a DL PCC, and the carrier corresponding to a PCell in the uplink is a UL PCC. Similarly, the carrier corresponding to an SCell in the downlink is a DL SCC, and the carrier corresponding to an SCell in the uplink is a UL SCC. Depending on the terminal capacity, a serving cell(s) may consist of one PCell and zero or more SCells. For a UE in RRC_CONNECTED state but without carrier aggregation configured or without supporting carrier aggregation, there is only one serving cell consisting of only a PCell.

[0094] As described above, the term "cell" used in carrier aggregation is different from the term "cell" referring to a certain geographical area in which communication services are provided by one base station or one antenna group. However, in order to distinguish between a cell referring to a certain geographical area and a cell of carrier aggregation, in the present invention, a cell of carrier aggregation is referred to as a CC, and a cell of a geographical area is referred to as a cell.

[0095] 10 is a diagram illustrating an example in which a cross-carrier scheduling technique is applied. When cross-carrier scheduling is configured, a control channel transmitted over a first CC schedules a data channel transmitted over a first or second CC using a carrier indicator field (CIF). The CIF is included in the DCI. In other words, a scheduling cell is configured, and a DL grant / UL grant transmitted from the PDCCH region of the scheduling cell schedules the PDSCH / PUSCH of a scheduled cell. That is, the PDCCH region of the scheduling cell is the search space for multiple component carriers. The PCell is basically the scheduling cell, and a specific SCell is designated as the scheduling cell by a higher layer.

[0096] In the embodiment of Figure 10, it is assumed that three DL CCs are merged. Here, it is assumed that DL component carrier #0 is a DL PCC (or PCell), and DL component carrier #1 and DL component carrier #2 are DL SCCs (or SCells). It is also assumed that the DL PCCs are configured as PDCCH monitoring CCs. If cross-carrier scheduling is not configured by terminal-specific (or terminal-group-specific, or cell-specific) higher layer signaling, the CIF is disabled, and each DL CC transmits only a PDCCH that schedules its own PDSCH without a CIF according to the NR PDCCH rules (non-cross-carrier scheduling, self-carrier scheduling). On the other hand, 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) uses the CIF to transmit not only a PDCCH that schedules the PDSCH of DL CC A but also a PDCCH that schedules the PDSCH of another CC (cross-carrier scheduling). On the other hand, no PDCCH is transmitted on other DL CCs. Therefore, depending on whether cross-carrier scheduling is configured for the UE, the UE either monitors a PDCCH that does not include a CIF to receive a self-carrier scheduled PDSCH, or monitors a PDCCH that includes a CIF to receive a cross-carrier scheduled PDSCH.

[0097] 9 and 10 illustrate the subframe structure of the 3GPP LTE-A system, the same or similar structure can also be applied to the 3GPP NR system, however, in the 3GPP NR system, the subframes in FIG. 9 and 10 may be replaced with slots.

[0098] <Communication methods in unlicensed spectrum>

[0099] FIG. 11 illustrates an example of an NR-U (NR-Unlicensed) service environment.

[0100] Referring to Figure 11, a service environment in which NR technology 11 in a licensed spectrum and NR-U, which is NR technology 12 in an unlicensed spectrum, are integrated may be provided to users. For example, in an NR-U environment, NR technology 11 in a licensed spectrum and NR technology 12 in an unlicensed spectrum may be integrated using technologies such as carrier aggregation, which can contribute to network capacity expansion. Also, in an asymmetric traffic structure in which downlink data is relatively larger than uplink data, NR-U can provide NR services optimized according to various requirements or environments. For convenience, NR technology in a licensed spectrum is referred to as NR-L (NR-Licensed), and NR technology in an unlicensed spectrum is referred to as NR-U (NR-Unlicensed).

[0101] Figure 12 shows an existing communication system (e.g., wireless LAN) that operates in unlicensed bands. Devices that operate in unlicensed bands usually operate on a Listen-Before-Talk (LBT) basis, and perform Clear Channel Assessment (CCA) to sense the channel before transmitting data.

[0102] Referring to Figure 12, a WLAN device (e.g., AP, STA) performs carrier sensing before transmitting data to check whether a channel is busy. If a wireless signal of a certain strength or higher is detected from a channel to which data is to be transmitted, the channel is determined to be busy, and the WLAN device delays access to the channel. This process is called clear channel assessment, and the signal level that determines whether a signal is detected is called the CCA threshold. On the other hand, if no wireless signal is detected from the channel or a wireless signal of a strength lower than the CCA threshold is detected, the channel is determined to be idle.

[0103] If a channel is determined to be idle, a terminal with data to transmit performs a backoff procedure after a defer duration (e.g., Arbitration InterFrame Space (AIFS), PCF IFS (PIFS), etc.). The defer duration refers to the minimum time a terminal must wait after a channel becomes idle. The backoff procedure allows a terminal to wait any additional time after the defer deadline. For example, a terminal waits by decreasing a slot time equal to a random number assigned to the terminal within a contention window (CW) while the channel is idle, and a terminal that has exhausted all slot times can attempt to access the channel.

[0104] Once a terminal successfully accesses a channel, it can transmit data over the channel. If data transmission is successful, the contention window size (CWS) is reset to its initial value (CWmin). On the other hand, if data transmission fails, the CWS is doubled. As a result, the terminal is assigned a new random number within a range twice the previous random number range and performs a backoff procedure in the next CW. In WLANs, only ACK is defined as reception response information for data transmission. Therefore, if an ACK is received for data transmission, the CWS is reset to its initial value, and if no feedback information is received for data transmission, the CWS is doubled.

[0105] As mentioned above, since existing communications in unlicensed bands mostly operate on the LBT basis, channel access in the NR-U system also performs LBT for coexistence with existing devices. Specifically, channel access methods in unlicensed bands in NR can be divided into the following four categories depending on whether or not LBT is used / applied.

[0106] ●Category 1: No LBT

[0107] - The Tx entity does not perform the LBT procedure for transmission.

[0108] Category 2: LBT without random backoff

[0109] The Tx entity senses whether the channel is idle during a first interval without random backoff in order to transmit. That is, the Tx entity can transmit on the channel immediately after sensing the channel as idle during the first interval. The first interval is an interval of a pre-configured length immediately before the Tx entity transmits. According to one embodiment, the first interval may be 25 us long, but the present invention is not limited thereto.

[0110] Category 3: LBT with random backoff using a fixed-size CW

[0111] The Tx entity obtains a random number within a fixed-size CW, sets it as the initial value of a backoff counter (or backoff timer) N, and performs backoff using the set backoff counter N. That is, in the backoff procedure, the Tx entity decrements the backoff counter by one each time the channel is sensed as idle during a pre-set slot period. Here, the pre-set slot period may be 9 us, but the present invention is not limited thereto. The backoff counter N is decremented by one from its initial value, and when the value of the backoff counter N reaches 0, the Tx entity can transmit. Meanwhile, to perform backoff, the Tx entity first senses whether the channel is idle during a second interval (i.e., a defer period Td). According to an embodiment of the present invention, the Tx entity can sense (or determine) whether the channel is idle during the second interval depending on whether the channel is idle during at least a portion of the second interval (e.g., one slot period). The second interval may be set based on the channel access priority class of the Tx entity and consists of a period of 16 us and m consecutive slot periods, where m is the value set by the channel access priority class. If the Tx entity senses the channel as idle during the second interval, it performs channel sensing to decrease the backoff counter. On the other hand, if the channel is sensed as occupied during the backoff procedure, the backoff procedure is aborted. After aborting the backoff procedure, the Tx entity can resume backoff if the channel is sensed as idle during an additional second interval. In this way, the Tx entity can transmit if the channel is idle for the second interval plus the slot period of the backoff counter N. In this case, the initial value of the backoff counter N is obtained within a fixed-size CW.

[0112] Category 4: LBT with random backoff using variable-size CW

[0113] - The Tx entity obtains a random number within a variable-size CW, sets it as the initial value of a backoff counter (or backoff timer) N, and performs backoff using the set backoff counter N. More specifically, the Tx entity can adjust the size of the CW based on HARQ-ACK information for a previous transmission, and the initial value of the backoff counter N is obtained within a CW of the adjusted size. The specific process by which the Tx entity performs backoff is as described in Category 3. The Tx entity can transmit if the channel is idle during the second interval plus the slot period of the backoff counter N. In this case, the initial value of the backoff counter N is obtained within a variable-size CW.

[0114] In the above Categories 1 to 4, the Tx entity may be a base station or a terminal. According to the embodiments of the present invention, the first type channel access may refer to the channel access of Category 4, and the second type channel access may refer to the channel access of Category 2.

[0115] FIG. 13 illustrates a channel access process based on Category 4 LBT according to an embodiment of the present invention.

[0116] To perform channel access, the Tx entity first performs channel sensing for the defer period Td (S302). According to an embodiment of the present invention, the channel sensing for the defer period Td in step S302 may be performed by channel sensing for at least a portion of the defer period Td. For example, the channel sensing for the defer period Td may be performed by channel sensing for one slot period within the defer period Td. The Tx entity then determines whether the channel is idle through channel sensing for the defer period Td (S304). If the channel is sensed as idle for the defer period Td, the Tx entity proceeds to step S306. If the channel is not sensed as idle for the defer period Td (i.e., sensed as occupied), the Tx entity returns to step S302. The Tx entity repeats steps S302 to S304 until the channel is sensed as idle for the defer period Td. The defer period Td may be set based on the channel access priority class of the Tx entity and consists of a period of 16 us and m consecutive slot periods, where m is the value set by the channel access priority class.

[0117] Next, the Tx entity obtains a random number within a predetermined CW, sets the random number as the initial value of a backoff counter (or backoff timer) N (S306), and proceeds to step S308. The initial value of the backoff counter N is randomly selected from a range of values ​​from 0 to CW. The Tx entity performs a backoff procedure using the set backoff counter N. That is, the Tx entity performs the backoff procedure by repeating steps S308 to S316 until the value of the backoff counter N reaches 0. Meanwhile, in FIG. 13, step S306 is performed after the channel is sensed as being idle for the defer period Td, but the present invention is not limited thereto. That is, step S306 may be performed independently of steps S302 to S304, or may be performed before steps S302 to S304. If step S306 is performed before steps S302 to S304, the Tx entity proceeds to step S308 if steps S302 to S304 sense the channel as idle for the defer period Td.

[0118] In step S308, the Tx entity determines 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 and transmits. 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 one embodiment, the Tx entity may selectively decrement the value of the backoff counter by 1 during the channel sensing process for each slot. At this time, step S310 may be skipped at least once depending on the Tx entity's selection. Next, the Tx entity performs channel sensing for an additional slot period (S312). The Tx entity determines whether the channel is idle through channel sensing for the additional slot period (S314). If the channel is sensed as idle for the additional slot period, the Tx entity returns to step S308. In this manner, the Tx entity can decrement the backoff counter by 1 each time the channel is sensed as idle during a pre-set slot period, where the pre-set slot period may be 9 us, but the present invention is not limited thereto.

[0119] If the channel is not sensed as idle for the additional slot period in step S314 (i.e., sensed as occupied), the Tx entity proceeds to step S316. In step S316, the Tx entity determines whether the channel is idle for the additional defer period Td. According to an embodiment of the present invention, the channel sensing in step S316 may be performed on a slot-by-slot basis. That is, the Tx entity determines whether the channel is sensed as idle for the entire slot period of the additional defer period Td. If an occupied slot is detected within the additional defer period Td, the Tx entity immediately resumes step S316. If the channel is sensed as idle for the entire slot period of the additional defer period Td, the Tx entity returns to step S308.

[0120] On the other hand, if the value of the backoff counter N is confirmed as 0 in step S308, the Tx entity performs transmission (S320). The Tx entity receives HARQ-ACK feedback corresponding to the transmission (S322). The Tx entity can determine whether the previous transmission was successful based on 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).

[0121] In this way, after sensing the channel as idle for the defer period Td, the Tx entity can transmit if the channel is idle for N additional slot periods. As mentioned above, the Tx entity may be a base station or a terminal, and the channel access process of Figure 13 may be used for downlink transmissions of the base station and / or uplink transmissions of the terminal.

[0122] 14 is a block diagram illustrating the configuration of a terminal and a base station according to an embodiment of the present invention. In an embodiment of the present invention, the terminal may be implemented as any of various types of wireless communication devices or computing devices that ensure portability and mobility. The terminal may be referred to as a UE, a station (STA), a mobile subscriber (MS), etc. In addition, in an embodiment of the present invention, the base station controls and manages cells (e.g., macrocells, femtocells, picocells, etc.) corresponding to a service area, and performs functions such as signal transmission, channel assignment, channel monitoring, self-diagnosis, and relaying. The base station may be referred to as a next generation NodeB (gNB) or an access point (AP), etc.

[0123] As shown, a terminal 100 according to one embodiment of the present invention includes a processor 110 , a communication module 120 , a memory 130 , a user interface unit 140 , and a display unit 150 .

[0124] First, the processor 110 executes various commands or programs to process data within the terminal 100. The processor 110 also controls the overall operation of the terminal 100, including each unit, and controls the transmission and reception of data between the units. Here, the processor 110 is configured to perform operations according to the embodiments described in the present invention. For example, the processor 110 may receive slot configuration information, determine the slot configuration based on the information, and perform communication according to the determined slot configuration.

[0125] Next, the communication module 120 is an integrated module that performs wireless communication using a wireless communication network and wireless LAN access using a wireless LAN. To this end, the communication module 120 includes multiple network interface cards (NICs) such as cellular communication interface cards 121 and 122 and an unlicensed band communication interface card 123, either built-in or external. Although the communication module 120 is shown as an integrated module in the drawings, the network interface cards may be independently arranged depending on the circuit configuration or application, unlike the drawings.

[0126] The cellular communication interface card 121 transmits and receives wireless signals to and from at least one of the base station 200, an external device, and a server via a mobile communication network, and provides cellular communication services in a first frequency band based on instructions from the processor 110. According to one embodiment, the cellular communication interface card 121 includes at least one NIC module that utilizes a frequency band below 6 GHz. The at least one NIC module of the cellular communication interface card 121 independently performs cellular communication with at least one of the base station 200, the external device, and the server in accordance with a cellular communication standard or protocol for the frequency band below 6 GHz supported by the NIC module.

[0127] The cellular communication interface card 122 transmits and receives wireless signals to and from at least one of the base station 200, an external device, and a server using a mobile communication network, and provides cellular communication services in the second frequency band based on instructions from the processor 110. According to one embodiment, the cellular communication interface card 122 includes at least one NIC module that uses a frequency band above 6 GHz. The at least one NIC module of the cellular communication interface card 122 independently performs cellular communication with at least one of the base station 200, the external device, and the server in accordance with the cellular communication standard or protocol for the frequency band above 6 GHz that the NIC module supports.

[0128] The unlicensed band communication interface card 123 transmits and receives wireless signals to and from at least one of the base station 200, an external device, and a server via the third frequency band, which is an unlicensed band, and provides unlicensed band communication services based on instructions from the processor 110. The unlicensed band communication interface card 123 includes at least one NIC module that utilizes the unlicensed band. For example, the unlicensed band may be 2.4 GHz, 5 GHz, 6 GHz, 7 GHz, or 52.6 GHz or higher. The at least one NIC module of the unlicensed band communication interface card 123 independently or dependently performs cellular communication with at least one of the base station 200, the external device, and the server according to the unlicensed band communication standard or protocol of the frequency band supported by the NIC module.

[0129] The memory 130 stores control programs and various data used by the terminal 100. The control programs include predetermined programs required for the terminal 100 to perform wireless communication with at least one of the base station 200, an external device, and a server.

[0130] Next, the user interface 140 includes various types of input / output means provided in the terminal 100. That is, the user interface unit 140 receives user input using various input means, and the processor 110 controls the terminal 100 based on the received user input. Also, the user interface 140 performs output based on instructions from the processor 110 using various output means.

[0131] The display unit 150 then outputs various images to a display screen, and displays various display objects such as content or a user interface based on a control command from the processor 110.

[0132] The base station 200 according to the embodiment of the present invention also includes a processor 210 , a communication module 220 , and a memory 230 .

[0133] First, the processor 210 executes various instructions or programs to process data within the base station 200. The processor 210 also controls the overall operation of the base station 200, including each unit, and controls the transmission and reception of data between the units. Here, the processor 210 is configured to perform operations according to the embodiments described herein. For example, the processor 210 may signal slot configuration information and perform communication according to the signaled slot configuration.

[0134] Next, the communication module 220 is an integrated module that performs wireless communication using a wireless communication network and wireless LAN access using a wireless LAN. To this end, the communication module 220 includes multiple network interface cards, such as cellular communication interface cards 221 and 222 and an unlicensed band communication interface card 223, either built-in or externally mounted. Although the communication module 220 is shown as an integrated module in the drawings, the network interface cards may be independently arranged depending on the circuit configuration or application, unlike the drawings.

[0135] The cellular communication interface card 221 transmits and receives wireless signals to and from at least one of the terminal 100, the external device, and the server using a mobile communication network, and provides cellular communication services in the first frequency band based on instructions from the processor 210. According to one embodiment, the cellular communication interface card 221 includes at least one NIC module that uses a frequency band below 6 GHz. The at least one NIC module of the cellular communication interface card 221 independently performs cellular communication with at least one of the terminal 100, the external device, and the server according to a cellular communication standard or protocol for the frequency band below 6 GHz supported by the NIC module.

[0136] The cellular communication interface card 222 transmits and receives wireless signals to and from at least one of the terminal 100, an external device, and a server using a mobile communication network, and provides cellular communication services in the second frequency band based on instructions from the processor 210. According to one embodiment, the cellular communication interface card 222 includes at least one NIC module that uses a frequency band above 6 GHz. The at least one NIC module of the cellular communication interface card 222 independently performs cellular communication with at least one of the terminal 100, the external device, and the server according to a cellular communication standard or protocol for the 6 GHz or higher frequency band supported by the NIC module.

[0137] The unlicensed band communication interface card 223 transmits and receives wireless signals to and from at least one of the terminal 100, an external device, and a server using the third frequency band, which is an unlicensed band, and provides unlicensed band communication services based on instructions from the processor 210. The unlicensed band communication interface card 223 includes at least one NIC module that uses the unlicensed band. For example, the unlicensed band may be 2.4 GHz, 5 GHz, 6 GHz, 7 GHz, or 52.6 GHz or higher. The at least one NIC module of the unlicensed band communication interface card 223 independently or dependently performs cellular communication with at least one of the terminal 100, an external device, and a server according to the unlicensed band communication standard or protocol of the frequency band supported by the NIC module.

[0138] The terminal 100 and base station 200 shown in Figure 14 are block diagrams according to one embodiment of the present invention, and the separate blocks indicate logically distinct device elements. Therefore, the above-described device elements may be mounted on one chip or multiple chips depending on the device design. In addition, some components of the terminal 100, such as the user interface 150 and the display unit 150, may be selectively provided in the terminal 100. In addition, the user interface 140 and the display unit 150 may be additionally provided in the base station 200 as needed.

[0139] A channel access procedure performed by a wireless communication device in an unlicensed band will be described using Figure 15. An LBT procedure used when a wireless communication device performs channel access in an unlicensed band will be described. In particular, a channel access in which the wireless communication device performs transmission based on the result of channel sensing within a time interval of a pre-specified duration may be set for the wireless communication device. At this time, if the wireless communication device fails to access the channel, an operation method of the wireless communication device will be described. The pre-specified duration mentioned above may be 16 us.

[0140] For ease of explanation, a wireless communication device that is a wireless endpoint initiating channel occupancy is referred to as an initiating node. Furthermore, a wireless communication device that is a wireless endpoint communicating with the initiating node is referred to as a responding node. The initiating node may be a base station, and the responding node may be a mobile station. Alternatively, the initiating node may be a mobile station, and the responding node may be a base station. When the initiating node attempts to transmit data, the initiating node may perform channel access based on a channel access priority class determined according to the type of data. At this time, parameters used for channel access may be determined according to the type of data. The parameters used for channel access may include at least one of a minimum CW value, a maximum CW value, a maximum channel occupancy time (MCOT), which is the maximum duration for occupying a channel in one channel occupancy, and the number of sensing slots (mp). Specifically, the initiating node may perform the above-described Category 4 LBT based on a channel access priority class determined according to the type of data.

[0141] Table 4 below shows an example of parameter values ​​used for channel access based on channel access priority classes. Specifically, Table 4 shows parameter values ​​used for channel access for each channel access priority class for downlink transmission in the LTE LAA system.

[0142] When a downlink channel transmitted by a wireless communication device includes data traffic, a defer duration may be set based on the channel access priority class of the traffic included in the downlink channel. The defer duration may include one or more (mp) slot durations (Tsl) of an initial duration (Tf). The duration of the slot duration (Tsl) may be 9 us. The initial duration includes one idle slot duration (Tsl). The number of slot durations (mp) included in the defer duration may be set based on the channel access priority class, as described above. Specifically, the number of slot durations (mp) included in the defer duration may be set as shown in Table 4.

[0143] [Table 4]

[0144] Furthermore, the wireless communication device may set a CW value range according to the channel access priority class. Specifically, the wireless communication device may set the CW value so that CWmin,p<=CW<=CWmax,p. In this case, the minimum value (CWmin,p) and maximum value (CWmax,p) of the CW may be determined according to the channel access priority class. Specifically, the minimum value (CWmin,p) and maximum value (CWmax,p) of the CW may be determined as shown in Table 4. The wireless communication device may set the minimum value (CWmin,p) and maximum value (CWmax,p) of the CW in the counter value setting procedure. When the wireless communication device accesses a channel, the wireless communication device may adjust the CW value as described above with reference to FIG. 13. Furthermore, in an unlicensed band, the MCOT (Tmcot,p) may be determined according to the channel access priority of the data included in the transmission, as described above. Specifically, the MCOT may be determined as shown in Table 4. As a result, the wireless communication device may not be permitted to transmit continuously in an unlicensed band for a time exceeding the MCOT. This is because the unlicensed band is a frequency band that various wireless communication devices use according to certain rules. In Table 4, if the value of the channel access priority class is p=3 or p=4, and there are no wireless communication devices using other technologies that use the unlicensed band for a long term in accordance with the regulations, the wireless communication device can set Tmcot,p=10ms. Otherwise, the wireless communication device can set Tmcot,p=8ms.

[0145] Table 5 shows parameter values ​​used for channel access by channel access priority class for uplink transmission used in the LTE LAA system.

[0146] [Table 5]

[0147] As described in Table 5, the value of MCOT of 6 ms may increase to 8 ms when one or more gaps are included in the transmission. A gap means the time from when transmission is interrupted on a certain carrier until transmission resumes on that carrier. At this time, the minimum value of the duration of the gap is 100 us. Also, the maximum value of the duration of the transmission performed before the gap is included is 6 ms. Also, the duration of the gap is not included in the channel occupancy time. When the value of the channel access priority class is 3 or 4 and it is guaranteed that no other radio connection technology is used in the carrier where channel access is performed, the value of MCOT may be 10 ms. At this time, other radio connection technologies may include Wi-Fi. In other cases, the value of MCOT may be determined as described in Note 1 of Table 5.

[0148] COT represents the time during which a wireless communication device occupies a channel. As described above, MCOT represents the maximum time that the start node can continuously occupy a channel in any one carrier in the unlicensed band. However, as described above, gaps, which are intervals during which no transmission is performed, may be included between multiple transmissions, and when gaps are included, the value of MCOT may be applied differently.

[0149] <SL (sidelink) communication>

[0150] SL communication refers to a communication method in which a direct link is established between terminals and voice or data, etc. is directly exchanged between terminals without going through a base station. In SL communication, in FIG. 14, the base station may be replaced by a terminal. SL communication may be used in the same sense as V2X (Vehicle-to-everything) communication.

[0151] FIG. 16 shows an example of a terminal and a base station for performing V2X or SL communication.

[0152] 16, the term "terminal" in V2X / SL communication may primarily refer to a user's terminal. However, when network equipment such as a base station transmits and receives signals through a terminal-to-terminal communication method, the base station may also be considered a type of terminal.

[0153] Terminal 1 can operate to select a resource unit corresponding to a specific resource from a resource pool, which means a collection of resources, and transmit an SL signal using the resource unit. Terminal 2, which is a receiving terminal, is configured with a resource pool to which terminal 1 can transmit a signal, and can detect the signal of terminal 1 from the resource pool.

[0154] Here, when the terminal 1 is within the coverage area of ​​the base station, the base station may inform the terminal of the resource pool, whereas when the terminal 1 is outside the coverage area of ​​the base station, another terminal may inform the terminal of the resource pool, or the resource pool may be determined as a predetermined resource.

[0155] FIG. 17 is a diagram illustrating an example of a resource unit for V2X or SL communication.

[0156] Referring to Figure 17, a resource pool may be configured with a plurality of resource units, and each terminal may select one or more resource units to use for its SL signal transmission. F The total time resources in the resource pool can be divided into N T Therefore, the total number of N F *N T Resource units may be defined within a resource pool.

[0157] As shown in Figure 17, one resource unit (e.g., Unit #0) may appear repeatedly periodically. Alternatively, to obtain a diversity effect in the time or frequency dimension, the index of the physical resource unit to which one logical resource unit is mapped may change over time in a predetermined pattern. In such a resource unit structure, a resource pool may refer to a set of resource units available for transmission by a terminal that wishes to transmit an SL signal.

[0158] The resource pools may be subdivided into various types. For example, the resource pools may be classified as follows according to the content of the SL signals transmitted in each resource pool:

[0159] (1) A Scheduling Assignment (SA) may be a signal including information such as the location of resources used by a transmitting terminal for transmitting an SL data channel, a Modulation and Coding Scheme (MCS) or a Multiple Input Multiple Output (MIMO) transmission method, and a Timing Advance (TA) required for demodulating other data channels. The SA may be multiplexed and transmitted together with SL data on the same resource unit, and in this case, the SA resource pool may refer to a resource pool in which the SA is multiplexed and transmitted together with the SL data. The SA may also be referred to as an SL control channel.

[0160] (2) The SL data channel (Physical Sidelink Shared Channel, PSSCH) may be a resource pool used by a transmitting terminal to transmit user data. If SA is multiplexed and transmitted together with SL data on the same resource unit, only the SL data channel excluding SA information may be transmitted in the resource pool for the SL data channel. In other words, REs (Resource Elements) used to transmit SA information on individual resource units in the SA resource pool may still be used to transmit SL data in the resource pool for the SL data channel.

[0161] Below, resource allocation is explained in SL.

[0162] FIG. 18 shows an example of a procedure for a terminal to perform V2X or SL communication in transmission mode.

[0163] Referring to FIG. 18, (a) of FIG. 18 shows the terminal operation associated with transmission mode 1 or transmission mode 3, and (b) of FIG. 18 shows the terminal operation associated with transmission mode 2 or transmission mode 4.

[0164] Referring to (a) of FIG. 18, in transmission modes 1 / 3, a base station performs resource scheduling for terminal 1 using a PDCCH (more specifically, Downlink Control Information (DCI)), and terminal 1 performs SL / V2X communication with terminal 2 through the resource scheduling. Terminal 1 transmits sidelink control information (SCI) to terminal 2 through a physical sidelink control channel (PSCCH), and then can transmit data based on the SCI through a physical sidelink shared channel (PSSCH). In the case of LTE SL, transmission mode 1 may be applied to general SL communication, and transmission mode 3 may be applied to V2X SL communication.

[0165] Referring to (b) of FIG. 18, in transmission mode 2 / 4, a terminal can independently schedule resources. More specifically, in the case of LTE SL, transmission mode 2 is applied to general SL communication, and a terminal can independently select resources from a configured resource pool to perform SL operation. Transmission mode 4 is applied to V2X SL communication, and a terminal can independently select resources within a selection window through a sensing / SA decoding process, etc., and then perform V2X SL operation. Terminal 1 can transmit an SCI to terminal 2 via a PSCCH and then transmit data based on the SCI via a PSSCH. Hereinafter, the transmission mode may be abbreviated as "mode." Procedures related to sensing and resource (re)selection may be supported in resource allocation mode 2. The sensing procedure may be defined as decoding an SCI from other terminals and / or SL measurements. Decoding the SCI in the sensing procedure may provide at least information regarding the SL resource indicated by the terminal transmitting the SCI. When the SCI is decoded, the sensing procedure can use L1 SL Reference Signal Received Power (RSRP) measurements based on SL Demodulation Reference Signal (DMRS), and the resource (re)selection procedure can use the results of the sensing procedure to determine the resources for SL transmission.

[0166] FIG. 19 shows an example of a method for a terminal to select a transmission resource for transmitting a signal.

[0167] Referring to FIG. 19, a terminal can grasp transmission resources reserved by other terminals or resources used by other terminals by sensing within the sensing window, and after eliminating these within the selection window, can randomly select a resource from the remaining resources with the least interference.

[0168] For example, the terminal may decode a PSCCH containing information about the periodicity of reserved resources within a sensing window and measure the PSSCH RSRP at resources periodically determined based on the PSCCH. The terminal may exclude resources whose PSSCH RSRP values ​​exceed a threshold from the selection window. The terminal may then randomly select an SL resource from the remaining resources in the selection window.

[0169] FIG. 20 shows an example of three cast types for the NR side link.

[0170] Referring to FIG. 20, the NR sidelink supports three cast types: unicast, groupcast, and broadcast. In unicast-type SL communication, a terminal can perform one-to-one communication with other terminals. In groupcast-type SL communication, a terminal can perform SL communication with one or more terminals in a group to which the terminal belongs. Groupcast-type SL communication may be replaced by SL multicast communication, SL one-to-many communication, etc.

[0171] The following describes the HARQ (Hybrid Automatic Repeat Request) procedure in SL.

[0172] In SL unicast and groupcast, HARQ feedback and HARQ combining in the physical layer may be supported. For example, when a receiving terminal operates in resource allocation mode 1 or 2, the receiving terminal can receive a PSSCH from a transmitting terminal, and the receiving terminal can transmit HARQ feedback for the PSSCH to the transmitting terminal using a sidelink feedback control information (SFCI) format in a physical sidelink feedback channel (PSFCH).

[0173] For example, SL HARQ feedback may be enabled for groupcast, i.e., in non-CBG operation, two HARQ feedback options may be supported for groupcast.

[0174] (1) Groupcast Option 1: After a receiving terminal decodes a PSCCH targeted at the receiving terminal, if the receiving terminal fails to decode a transmission block associated with the PSCCH, the receiving terminal can transmit a HARQ-NACK to the transmitting terminal on a PSFCH. On the other hand, if the receiving terminal decodes a PSCCH targeted at the receiving terminal and successfully decodes a transmission block associated with the PSCCH, the receiving terminal does not need to transmit a HARQ-ACK to the transmitting terminal.

[0175] (2) Groupcast Option 2: After a receiving terminal decodes a PSCCH targeted at the receiving terminal, if the receiving terminal fails to decode a transmission block associated with the PSCCH, the receiving terminal can transmit a HARQ-NACK to the transmitting terminal on a PSFCH. If the receiving terminal decodes a PSCCH targeted at the receiving terminal and successfully decodes a transmission block associated with the PSCCH, the receiving terminal can transmit a HARQ-ACK to the transmitting terminal on a PSFCH.

[0176] Meanwhile, for example, in SL communication related to a service having a high reliability requirement or a service having a relatively high reliability requirement, an SL HARQ feedback operation and / or mechanism of the UE may be useful. For example, in SL communication related to a service having a high reliability requirement, an operation in which a UE receiving the service transmits SL HARQ feedback to a UE transmitting the service may be useful to meet the high reliability requirement.

[0177] The HARQ feedback resources may include HARQ feedback transmission resources and / or HARQ feedback reception resources. For example, the HARQ feedback transmission resources may include resources for transmitting HARQ feedback and / or resources associated with transmitting HARQ feedback. For example, the HARQ feedback reception resources may include resources for receiving HARQ feedback and / or resources associated with receiving HARQ feedback.

[0178] The PSSCH resources may include PSSCH transmission resources and / or PSSCH reception resources. For example, the PSSCH transmission resources may include resources for transmitting the PSSCH and / or resources associated with transmitting the PSSCH. For example, the PSSCH reception resources may include resources for receiving the PSSCH and / or resources associated with receiving the PSSCH.

[0179] The PSCCH resources may include PSCCH transmission resources and / or PSCCH reception resources. For example, the PSCCH transmission resources may include resources for transmitting the PSCCH and / or resources associated with transmitting the PSCCH. For example, the PSCCH reception resources may include resources for receiving the PSCCH and / or resources associated with receiving the PSCCH.

[0180] The resources may include at least one of a time domain resource, a frequency domain resource, and / or a code domain resource.

[0181] If a resource collision occurs in at least one of the PSSCH transmission, PSCCH transmission, and / or HARQ feedback transmission of the terminal, the SL HARQ feedback procedure and / or operation of the terminal may not operate correctly. For example, if a resource collision occurs in at least one of the PSSCH transmission, PSCCH transmission, and / or HARQ feedback transmission of the terminal, the SL HARQ feedback procedure and / or operation of the terminal may not be performed correctly.

[0182] If a receiving terminal successfully receives a PSSCH but an error occurs in the HARQ feedback (e.g., HARQ ACK) due to resource collision, the transmitting terminal may have to retransmit the PSSCH to the receiving terminal extra. For example, if a receiving terminal fails to receive a PSSCH and the HARQ feedback is not delivered to the transmitting terminal due to resource collision, reliability or performance related to SL communication may be degraded. For example, if a receiving terminal fails to receive a PSCCH and / or PSSCH transmitted from a transmitting terminal and the HARQ NACK corresponding to the PSCCH and / or PSSCH is not delivered correctly to the transmitting terminal due to resource collision, reliability or performance related to SL communication may be degraded. Therefore, the HARQ feedback resource needs to be determined so as to avoid or minimize collisions between multiple terminals.

[0183] The transmitting terminal may transmit the PSCCH and / or the PSSCH to the receiving terminal. For example, the transmitting terminal may transmit SL information to the receiving terminal using the PSCCH resource and / or the PSSCH resource. For example, the SL information may include at least one of SL control information, SL data, SL packets, SL TBs (Transport Blocks), SL messages, and / or SL services.

[0184] The receiving terminal can determine the HARQ feedback resource. In addition, for example, the transmitting terminal can determine the HARQ feedback resource.

[0185] The HARQ feedback resource may be configured to be associated or linked with the PSSCH. For example, the HARQ feedback resource may include at least one of a time domain resource, a frequency domain resource, and / or a code domain resource. For example, the location of the HARQ feedback resource may be configured to be associated or linked with the associated PSSCH resource. For example, the location of the HARQ feedback resource may be configured to be associated or linked with the location of the associated PSSCH resource based on a predefined function. For example, the HARQ feedback resource may be determined based on at least one of information related to the time domain associated with the PSSCH, information related to the frequency domain associated with the PSSCH, and / or information related to the code domain associated with the PSSCH.

[0186] And / or, for example, the HARQ feedback resource may be configured to have an association or linkage with the PSCCH. For example, the location of the HARQ feedback resource may be configured to have an association or linkage with the linked PSCCH resource. For example, the location of the HARQ feedback resource may be configured to have an association or linkage with the location of the linked PSCCH resource based on a predefined function. For example, the HARQ feedback resource may be determined based on at least one of information on a time domain associated with the PSCCH, information on a frequency domain associated with the PSCCH, and / or information on a code domain associated with the PSCCH.

[0187] The HARQ feedback resource may be configured in the form of a subset of frequency resources used for PSSCH transmission and / or PSCCH transmission. For example, the frequency domain of the HARQ feedback resource may 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.

[0188] FIG. 21 shows an example of resources for transmitting HARQ feedback on the NR sidelink.

[0189] 21, a transmitting terminal may transmit a PSCCH and / or a PSSCH to a receiving terminal on four subchannels. In this case, the frequency domain of the HARQ feedback resource associated with the PSCCH and / or PSSCH may be a subset of the frequency resources used by the transmitting terminal to transmit the PSCCH and / or PSSCH.

[0190] A time gap between the HARQ feedback resource and the PSSCH resource may be configured. And / or, for example, a time gap between the HARQ feedback resource and the PSCCH resource may be configured. For example, taking into consideration the decoding capability and / or delay requirements (e.g., V2X message and / or service-related delay requirements) of the terminal, a time gap may be configured between the time when the receiving terminal receives the PSSCH and / or PSCCH and the time when the receiving terminal transmits the HARQ feedback. For example, taking into consideration the decoding capability and / or delay requirements of the terminal, a time gap may be configured between the time when the transmitting terminal receives the HARQ feedback and the time when the transmitting terminal (re-)transmits the PSSCH and / or PSCCH.

[0191] The time gap may be commonly configured within a resource pool. For example, the time gap may be commonly configured among different terminals within a resource pool. For example, the time gap may be commonly configured for the transmitting terminal and the receiving terminal. Therefore, terminals can easily determine HARQ feedback resources. For example, the time gap may be resource-pool-specifically configured.

[0192] The time gap may be set or specified to be smaller than and / or equal to the smallest latency budget of services coexisting on the resource pool. For example, if service A and service B coexist on the resource pool and the latency budget of service A is smaller than the latency budget of service B, the time gap may be set or specified to be smaller than or equal to the latency budget of service A.

[0193] The time gap may be specified such that a maximum number of Transport Block (TB)-related retransmissions configured for a resource pool, a service type, a service priority, a broadcast type, and / or a service's QoS requirements can be supported / performed within the delay budget for the (associated) services on the resource pool. For example, the maximum number of retransmissions may be the maximum number of allowed retransmissions, including the initial transmission.

[0194] The time gap may be set or specified to be greater than and / or equal to the largest value among the decoding capabilities of the terminals. Here, for example, the decoding capability may be the terminal processing time required from the end / end of PSSCH reception of the terminal to the start of PSFCH transmission of the terminal. And / or, for example, the decoding capability may be the terminal processing time required from the end / end of PSCCH reception of the terminal to the start of PSFCH transmission of the terminal. For example, the time gap may be set or specified to be greater than and / or equal to the largest value among the decoding capabilities of the terminals in a resource pool. For example, if terminal A, terminal B, and terminal C perform SL communication in a resource pool and terminal A has the worst decoding capability, the time gap may be set or specified to be greater than or equal to the processing time required from the end / end of PSSCH and / or PSCCH reception of terminal A to the start of PSFCH transmission of terminal A.

[0195] The time gap may be set differently or independently for each of a service type, a service priority, a SL communication type, a service-related session, a service-related PPPP, a service-related PPPR, a service-related target Block Error Rate (BLER), a service-related target Signal to Interference plus Noise Ratio (SINR), a service-related delay budget, and / or a terminal capability. For example, the time gap may be set differently or independently for each of a service type, a service priority, a SL communication type, a service-related session, a service-related PPPP, a service-related PPPR, a service-related target BLER, a service-related target SINR, a service-related delay budget, and / or a terminal capability within a resource pool. For example, the SL communication type may include at least one of unicast, groupcast, and / or broadcast.

[0196] The receiving terminal may transmit HARQ feedback to the transmitting terminal. For example, the receiving terminal may transmit HARQ feedback corresponding to the PSCCH and / or PSSCH to the transmitting terminal. For example, the receiving terminal may transmit the HARQ feedback to the transmitting terminal using HARQ feedback resources determined based on the PSCCH resources and / or PSSCH resources. For example, the transmitting terminal may receive HARQ feedback from the receiving terminal on HARQ feedback resources determined based on the PSCCH resources and / or PSSCH resources.

[0197] If the receiving terminal successfully receives the PSCCH and / or the PSSCH, the HARQ feedback may be a HARQ ACK. For example, if the receiving terminal fails to receive the PSCCH and / or the PSSCH, the HARQ feedback may be at least one of a HARQ NACK and / or a discontinuous detection (DTX).

[0198] In the case of groupcast, in which multiple terminals in a group perform SL communication with each other, the HARQ feedback resource may be embodied in two forms.

[0199] (1) Option A: A common HARQ feedback resource may be configured among receiving terminals. For example, when a transmitting terminal transmits a PSSCH and / or a PSCCH to multiple receiving terminals, a common HARQ feedback resource may be configured for the multiple receiving terminals that receive the PSSCH and / or the PSCCH.

[0200] (2) Option B: Different or independent HARQ feedback resources may be configured between receiving terminals. For example, different or independent HARQ feedback resources may be configured for each receiving terminal or for each subgroup including one or more receiving terminals. For example, when a transmitting terminal transmits PSSCH and / or PSCCH to multiple receiving terminals, different or independent HARQ feedback resources may be configured for each of multiple receiving terminals or multiple subgroups that receive the PSSCH and / or PSCCH.

[0201] Option A may be applied only to the groupcast option 1. For example, in groupcast option 1, multiple receiving terminals can transmit a HARQ NACK to a transmitting terminal using a HARQ feedback resource commonly configured for the multiple receiving terminals only when they fail to receive a PSCCH and / or a PSSCH. For example, the HARQ NACK may be implemented in the form of a single frequency network (SFN). In this case, the transmitting terminal may not be able to separately receive HARQ NACKs transmitted by multiple receiving terminals. Therefore, the transmitting terminal may not know which receiving terminals have transmitted a HARQ NACK. However, the transmitting terminal can know that at least one receiving terminal among the multiple receiving terminals has transmitted a HARQ NACK, and the transmitting terminal can retransmit the PSCCH and / or PSSCH to the multiple receiving terminals.

[0202] In Option A, the unicast-related HARQ feedback resource structure may be reused. And / or, for example, in Option A, overhead associated with the HARQ feedback resource may be reduced. On the other hand, in Option A, there is a limitation that the transmitting terminal cannot distinguish / recognize DTX. For example, when the transmitting terminal transmits the PSSCH and / or the PSCCH to the receiving terminal, the receiving terminal may fail to receive the PSCCH that schedules the PSSCH. In this case, according to Option A, the receiving terminal may not transmit a HARQ NACK to the transmitting terminal. This may cause a problem in which the transmitting terminal mistakenly believes that the receiving terminal has successfully received the PSSCH.

[0203] In Option B, different or independent HARQ feedback resources may be allocated to each receiving terminal or subgroup within a group including multiple receiving terminals. Here, for example, according to Option B, the greater the number of receiving terminals or subgroups included in the group, the greater the amount of HARQ feedback resources may be required. For example, for a group including N receiving terminals, N-1 HARQ feedback resources may be required. For example, Option B may be applied only to Groupcast Option 2.

[0204] FIG. 22 shows an example of a procedure for transmitting and receiving HARQ feedback for PSCCH and / or PSSCH.

[0205] 22, multiple receiving terminals may transmit HARQ feedback to a transmitting terminal, respectively. For example, multiple receiving terminals may transmit HARQ feedback corresponding to the PSCCH and / or PSSCH to a transmitting terminal, respectively. Multiple receiving terminals may transmit the HARQ feedback to a transmitting terminal, respectively, using HARQ feedback resources determined based on the PSCCH resources and / or PSSCH resources.

[0206] If the receiving terminal successfully receives the PSCCH and / or the PSSCH, the HARQ feedback may be a HARQ ACK. For example, if the receiving terminal fails to receive the PSCCH and / or the PSSCH, the HARQ feedback may be at least one of a HARQ NACK and / or a discontinuous detection (DTX).

[0207] The terminal can determine the HARQ feedback transmit power based on at least one of an SL path loss value derived / obtained based on a reference signal on the SL channel, an SL RSRP value derived / obtained based on a reference signal on the SL channel, an SL RSRQ value derived / obtained based on a reference signal on the SL channel, an open-loop power control parameter, and / or a closed-loop power control parameter. For example, when the transmitting terminal transmits a reference signal to the receiving terminal over the SL channel, the receiving terminal can determine the HARQ feedback transmit power based on at least one of an SL path loss value derived / obtained based on a reference signal on the SL channel, an SL RSRP value derived / obtained based on a reference signal on the SL channel, an SL RSRQ value derived / obtained based on a reference signal on the SL channel, an open-loop power control parameter, and / or a closed-loop power control parameter.

[0208] The reference signal on the SL channel may be predefined. The predefined reference signal on the SL channel may be a DMRS transmitted on a PSSCH (i.e., a PSSCH DMRS) or a DMRS transmitted on a PSCCH (i.e., a PSCCH DMRS). The reference signal on the SL channel may be a CSI-RS transmitted on a PSSCH. The predefined reference signal on the SL channel may be a reference signal used for estimating the quality of the SL channel (e.g., a CQI, a PMI, and an RI). For example, the reference signal on the SL channel may be a reference signal used for measuring at least one of an SL path loss value, an SL RSRP value, and / or an SL RSRQ value.

[0209] The predefined SL path loss may be a path loss for a link between the transmitting terminal and the receiving terminal. For example, open-loop power control parameters and / or closed-loop power control parameters may be pre-configured. For example, the open-loop power control parameters may include Po and / or alpha values.

[0210] Po may be a power control parameter for satisfying a packet / message transmission-related target error rate (e.g., Block Error Rate (BLER), Frame Error Rate (FER)) on average. And / or, for example, Po may be a power control parameter related to the average received SINR of a transmitting terminal and a receiving terminal. For example, Po may be a power control parameter specific to a terminal, a resource pool, a service type, a service priority, a QoS requirement related to a service, a (frequency) resource size used for SL transmission, an MCS value used for SL transmission, a resource pool-related congestion level (e.g., CBR), and / or a cast type. For example, when the HARQ feedback transmission power is calculated / derived based on the SL RSRP and / or SL RSRQ value / range, different Po values / ranges may be mapped / set for each (pre-configured) SL RSRP and / or SL RSRQ value / range.

[0211] When the HARQ feedback transmit power is derived / calculated based on the SL path loss, the alpha value may be a weight applied to the (measured) path loss compensation. And / or when the HARQ feedback transmit power is calculated / derived based on the SL RSRP and / or SL RSRQ value / range, the alpha value may be a weight applied to the (measured) SL RSRP and / or SL RSRQ value / range. And / or when the HARQ feedback transmit power is calculated / derived based on the SL RSRP and / or SL RSRQ value / range, the alpha value may be a weight applied to the HARQ feedback transmit power mapped / configured for each (measured) SL RSRP and / or SL RSRQ value / range. Here, the alpha value / range may be set specifically for the UE, resource pool, service type, service priority, QoS requirements associated with the service, (frequency) resource size used for SL transmission, MCS value used for SL transmission, resource pool-related congestion level (e.g., CBR), and / or type of channel. When the HARQ feedback transmission power is calculated / derived based on the SL RSRP and / or SL RSRQ value / range, different alpha values / ranges may be mapped / set for each (pre-configured) SL RSRP and / or SL RSRQ value / range.

[0212] When the HARQ feedback transmit power is calculated / derived based on the SL RSRP and / or SL RSRQ value / range, different offset values / ranges may be mapped / configured for each (pre-configured) SL RSRP and / or SL RSRQ value / range. A UE that has measured the SL RSRP and / or SL RSRQ may determine the final HARQ feedback transmit power by applying an offset associated with the SL RSRP value and / or SL RSRQ value to the (pre-configured normalized or nominal) SL (HARQ feedback) (maximum) transmit power. Here, for example, the offset value / range may be configured specifically for the UE, resource pool, service type, service priority, QoS requirements associated with the service, the (frequency) resource size used for SL transmission, the MCS value used for SL transmission, the resource pool-related congestion level (e.g., CBR), and / or the type of broadcast.

[0213] Different (normalized or nominal) (maximum) HARQ feedback transmit power values / ranges may be mapped / configured for each SL RSRP and / or SL RSRQ value / range. For example, the (normalized or nominal) (maximum) HARQ feedback transmit power value / range may be configured specifically for a terminal, a resource pool, a type of service, a priority of the service, a QoS requirement associated with the service, a (frequency) resource size used for SL transmission, an MCS value used for SL transmission, a resource pool-related congestion level (e.g., CBR), and / or a type of broadcast.

[0214] The reference signal and / or a transmission power value associated with the SL channel including the reference signal may be signaled to a terminal on a predefined channel. A transmitting terminal may transmit the reference signal and / or a transmission power value associated with the SL channel including the reference signal to a receiving terminal on a predefined channel. The predefined channel may be a PSCCH. The receiving terminal may be a terminal that measures at least one of SL path loss, SL RSRP, and / or SL RSRQ based on the reference signal.

[0215] The open-loop power control parameters (and / or the (maximum or minimum) HARQ feedback transmit power values ​​mapped / set for each SL RSRP (and / or SL RSRQ) value / range) may be set differently or independently for each service type, service priority, SL communication type (e.g., unicast, groupcast, broadcast), (resource pool-related) congestion level (e.g., CBR (Channel Busy Ratio)), session associated with the service, PPPP associated with the service, PPPR associated with the service, target Block Error Rate (BLER) associated with the service, target Signal to Interference plus Noise Ratio (SINR) associated with the service, (minimum or maximum) target communication distance associated with the service, and / or delay budget associated with the service. And / or, for example, the closed-loop power control operation / parameters may be operated / configured differently or independently for each type of service, priority of the service, type of SL communication (e.g., unicast, groupcast, broadcast), (resource pool-related) congestion level (e.g., CBR), session associated with the service, PPPP associated with the service, PPPR associated with the service, target Block Error Rate (BLER) associated with the service, target Signal to Interference plus Noise Ratio (SINR) associated with the service, target communication distance (minimum or maximum) associated with the service, and / or delay budget associated with the service.

[0216] Open-loop power control parameters associated with the HARQ feedback may be configured differently or independently from the open-loop power control parameters associated with the PSSCH and / or PSCCH, and / or closed-loop power control operations / parameters associated with the HARQ feedback may be operated / configured differently or independently from the closed-loop power control operations / parameters associated with the PSSCH and / or PSCCH.

[0217] FDM of HARQ feedback resources may be allowed or configured only for receiving terminals whose distance difference from the transmitting terminal receiving the HARQ feedback is within a predetermined threshold; and / or FDM of HARQ feedback resources may be allowed or configured only for receiving terminals whose SL path loss difference for the link between the transmitting terminal and the receiving terminal is within a predetermined threshold; and / or FDM of HARQ feedback resources may be allowed or configured only for receiving terminals whose SL RSRP difference for the link between the transmitting terminal and the receiving terminal is within a predetermined threshold; and / or FDM of HARQ feedback resources may be allowed or configured only for receiving terminals whose SL RSRQ difference for the link between the transmitting terminal and the receiving terminal is within a predetermined threshold.

[0218] If a distance difference between a plurality of receiving terminals and a transmitting terminal is within a predetermined threshold, the plurality of receiving terminals can transmit HARQ feedback on FDM resources on the frequency axis. And / or if a path loss difference between a plurality of receiving terminals and a transmitting terminal is within a predetermined threshold, the plurality of receiving terminals can transmit HARQ feedback on FDM resources on the frequency axis. And / or if a (measured) RSRP value difference between a plurality of receiving terminals and a transmitting terminal is within a predetermined threshold, the plurality of receiving terminals can transmit HARQ feedback on FDM resources on the frequency axis. And / or if a (measured) RSRQ value difference between a plurality of receiving terminals and a transmitting terminal is within a predetermined threshold, the plurality of receiving terminals can transmit HARQ feedback on FDM resources on the frequency axis.

[0219] It may not be preferable to FDM HARQ feedback resources between terminals or subgroups within a group. When HARQ feedback transmission-related power control is not applied, it may not be preferable to FDM HARQ feedback resources between different terminals or different subgroups within a group. When the HARQ feedback reception power difference between different terminals or different subgroups within a group is greater than a preset threshold, it may not be preferable to FDM HARQ feedback resources between different terminals or different subgroups within a group. When the SL path loss difference between different terminals or different subgroups within a group is greater than a preset threshold, it may not be preferable to FDM HARQ feedback resources between different terminals or different subgroups within a group. When the SL RSRP difference between different terminals or different subgroups within a group is greater than a preset threshold, it may not be preferable to FDM HARQ feedback resources between different terminals or different subgroups within a group. If the SL RSRQ difference between different terminals or different subgroups in a group is greater than a preset threshold, it may not be preferable to FDM the HARQ feedback resources between different terminals or different subgroups in the group.

[0220] As in the above example, when it is not preferable to FDM the HARQ feedback resource, the HARQ feedback resource may be pseudo-randomly TDMed based on at least one of the GUE_ID, the receiving terminal-associated identifier, the SL HARQ process ID, and / or the transmitting terminal-associated identifier. The HARQ feedback resource may be pseudo-randomly determined based on at least one of the GUE_ID, the receiving terminal-associated identifier, the SL HARQ process ID, and / or the transmitting terminal-associated identifier. For example, the HARQ feedback resource may be TDMed or determined by a function having at least one of the GUE_ID, the receiving terminal-associated identifier, the SL HARQ process ID, and / or the transmitting terminal-associated identifier as an input parameter. The HARQ feedback resource may be a HARQ feedback resource for each of a plurality of terminals in a group. The HARQ feedback resource may be a HARQ feedback resource for each of subgroups in a group. For example, the receiving terminal-associated identifier may be a destination ID. The sending terminal related identifier may be a source ID. The function may be predefined.

[0221] The transmitting terminal can transmit a PSCCH and / or a PSSCH to the receiving terminal. The transmitting terminal can transmit SL information to the receiving terminal using a PSCCH resource and / or a PSSCH resource. 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.

[0222] The receiving terminal can determine the HARQ feedback resource. Furthermore, the transmitting terminal can determine the HARQ feedback resource. For example, the receiving terminal may be any one of a plurality of terminals performing groupcast communication within a group.

[0223] The HARQ feedback resource may be determined based on at least one of the PSCCH resource, the PSSCH resource, and / or a GUE_ID. When multiple receiving terminals in a group feed back HARQ ACK or HARQ NACK to a transmitting terminal using different PSFCH resources, the multiple receiving terminals in the group can determine the HARQ feedback resource using a GUE_ID. The resource may include at least one of a time domain resource, a frequency domain resource, and / or a code domain resource. The GUE_ID may be information for identifying terminals in the group.

[0224] The receiving terminal may transmit HARQ feedback to the transmitting terminal. The receiving terminal may transmit HARQ feedback corresponding to the PSCCH and / or PSSCH to the transmitting terminal. For example, the receiving terminal may transmit the HARQ feedback to the transmitting terminal using a HARQ feedback resource determined based on at least one of the PSCCH resource, the PSSCH resource, and / or GUE_ID.

[0225] If the receiving terminal successfully receives the PSCCH and / or the PSSCH, the HARQ feedback may be a HARQ ACK. If the receiving terminal fails to receive the PSCCH and / or the PSSCH, the HARQ feedback may be at least one of a HARQ NACK and / or a discontinuous detection (DTX).

[0226] When a transmitting terminal selects PSSCH and / or PSCCH transmission resources through a sensing operation, a problem of collision of HARQ feedback transmission related resources does not occur. When multiple transmitting terminals select different PSSCH and / or PSCCH transmission resources through a sensing operation, the HARQ feedback resource may be determined based on the PSSCH resource and / or PSCCH resource. Therefore, collision of HARQ feedback resources can be automatically avoided between terminals that select different PSSCH and / or PSCCH transmission resources through a sensing operation.

[0227] When a transmitting terminal transmits the same PSSCH and / or PSCCH to multiple receiving terminals in a group, the multiple receiving terminals can determine HARQ feedback resources using different GUE_IDs, thereby preventing collision of HARQ feedback resources even when multiple receiving terminals in a group receive the same PSSCH and / or PSCCH.

[0228] FIG. 23 shows an example of a procedure for transmitting and receiving HARQ feedback for PSCCH and / or PSSCH in groupcast SL communication.

[0229] Referring to FIG. 23, IDs for identifying terminals within a group may be assigned / assigned to multiple terminals within the group. The IDs may be referred to as inner IDs. The inner IDs may be an application or parameter such as GUE_ID. For example, for specific groupcast traffic, an application layer may transmit information regarding the inner IDs of terminals and information regarding the number of terminals in the group to the V2X layer. The terminal may be the terminal transmitting the specific groupcast traffic. For specific groupcast traffic, the application layer may not transmit information regarding the inner IDs of other terminals in the group to the V2X layer. The groupcast traffic may include at least one of a groupcast service, groupcast data, groupcast packets, and / or groupcast messages.

[0230] When a transmitting terminal intends to transmit first traffic related to groupcast to multiple receiving terminals in a group, the application layer of the transmitting terminal can transmit information regarding the internal ID of the transmitting terminal and information regarding the number of terminals in the group to the V2X layer of the transmitting terminal. The application layer of receiving terminal 1 can transmit information regarding the internal ID of receiving terminal 1 and information regarding the number of terminals in the group to the V2X layer of the receiving terminal 1. The application layer of receiving terminal 2 can transmit information regarding the internal ID of receiving terminal 2 and information regarding the number of terminals in the group to the V2X layer of the receiving terminal 2. The application layer of receiving terminal 3 can transmit information regarding the internal ID of receiving terminal 3 and information regarding the number of terminals in the group to the V2X layer of the receiving terminal 3. The application layer of receiving terminal 4 can transmit information regarding the internal ID of receiving terminal 4 and information regarding the number of terminals in the group to the V2X layer of the receiving terminal 4.

[0231] The V2X layer of the terminal may transmit information about the internal ID of the terminal and information about the number of terminals in the group to the AS layer of the terminal. For example, the V2X layer of the terminal may also transmit L2 ID (e.g., source L2 ID, destination L2 ID) and / or QoS information to the AS layer of the terminal.

[0232] The transmitting terminal may transmit specific groupcast traffic to a plurality of receiving terminals (S2110). The specific groupcast traffic may be transmitted on the PSSCH and / or the PSCCH.

[0233] The receiving terminals may determine HARQ feedback resources (S2120). The receiving terminals (e.g., AS layers of the receiving terminals) may determine HARQ feedback resources for specific groupcast traffic based on information about their own internal IDs and information about the number of terminals in the group according to a predefined rule.

[0234] The transmitting terminal can determine the HARQ feedback resource (that it should receive). The transmitting terminal can derive or determine the HARQ feedback resource of the plurality of receiving terminals associated with specific groupcast traffic based on information about its internal ID and information about the number of terminals in the group.

[0235] When the application layer provides information about the internal ID of the terminal and information about the number of terminals in the group to the V2X layer of the terminal, the terminal can determine or consider either the groupcast option 1 or the groupcast option 2 as a (selectable) HARQ feedback option for the specific groupcast traffic. The V2X layer of the terminal can determine or consider either the groupcast option 1 or the groupcast option 2 as a (selectable) HARQ feedback option for the specific groupcast traffic. Furthermore, depending on whether a preset condition is met, the terminal can finally determine or consider either the groupcast option 1 or the groupcast option 2 as the HARQ feedback option for the specific groupcast traffic. When respective HARQ feedback resources for multiple terminals participating in groupcast are all supported in a resource pool, the terminal can finally determine or consider the groupcast option 2 as the HARQ feedback option for the specific groupcast traffic. If the resource pool does not support all HARQ feedback resources for multiple terminals participating in groupcast, the terminal may ultimately determine or consider groupcast option 1 as the HARQ feedback option for the specific groupcast traffic. This determination may be made in the AS layer of the terminal.

[0236] If an application layer does not provide information regarding the number of terminals in a group to a V2X layer of a terminal, the terminal can determine or consider groupcast option 1 as the HARQ feedback option for the specific groupcast traffic. If an application layer does not provide information regarding an internal ID of the terminal and / or information regarding the number of terminals in a group to a V2X layer of a terminal, the terminal can determine or consider groupcast option 1 as the HARQ feedback option for the specific groupcast traffic. For example, the V2X layer of the terminal can determine or consider groupcast option 1 as the HARQ feedback option for the specific groupcast traffic.

[0237] When the application layer and / or V2X layer provides information about the internal ID of the terminal and information about the number of terminals in the group to the AS layer of the terminal, the terminal can determine or consider either the groupcast option 1 or the groupcast option 2 as a (selectable) HARQ feedback option for the specific groupcast traffic. The AS layer of the terminal can determine or consider either the groupcast option 1 or the groupcast option 2 as a (selectable) HARQ feedback option for the specific groupcast traffic. Furthermore, depending on whether a preset condition is met, the terminal can finally determine or consider either the groupcast option 1 or the groupcast option 2 as the HARQ feedback option for the specific groupcast traffic. When respective HARQ feedback resources for multiple terminals participating in groupcast are all supported in a resource pool, the terminal can finally determine or consider the groupcast option 2 as the HARQ feedback option for the specific groupcast traffic. If the resource pool does not support all HARQ feedback resources for multiple terminals participating in groupcast, the terminal may ultimately determine or consider groupcast option 1 as the HARQ feedback option for the specific groupcast traffic. This determination may be made in the AS layer of the terminal.

[0238] If the application layer and / or V2X layer does not provide information regarding the number of terminals in a group to the AS layer of the terminal, the terminal can determine or consider groupcast option 1 as the HARQ feedback option for the specific groupcast traffic. If the application layer and / or V2X layer does not provide information regarding the internal ID of the terminal and / or information regarding the number of terminals in a group to the AS layer of the terminal, the terminal can determine or consider groupcast option 1 as the HARQ feedback option for the specific groupcast traffic. For example, the AS layer of the terminal can determine or consider groupcast option 1 as the HARQ feedback option for the specific groupcast traffic.

[0239] In a resource pool specific manner, whether or not at least one of Groupcast Option 1 and / or Groupcast Option 2 is supported may be signaled to the terminal. In a resource pool specific manner, whether or not at least one of Groupcast Option 1 and / or Groupcast Option 2 is supported may be signaled to the terminal on a service type, a cast type, or a QoS requirement basis. In a resource pool specific manner, whether or not PSFCH resources associated with Groupcast Option 1 are configured may be signaled to the terminal on a service type, a cast type, or a QoS requirement basis. In a resource pool specific manner, whether or not PSFCH resources associated with Groupcast Option 2 are configured may be signaled to the terminal on a service type, a cast type, or a QoS requirement basis.

[0240] The transmitting terminal can receive HARQ feedback from multiple receiving terminals. The transmitting terminal can receive groupcast option 1-based HARQ feedback from multiple receiving terminals. For example, the transmitting terminal can receive groupcast option 2-based HARQ feedback from multiple receiving terminals.

[0241] A specific groupcast option-based HARQ feedback operation may be required for specific groupcast traffic. If a reliability requirement associated with a service is high, when a transmitting terminal transmits the service to a receiving terminal, the receiving terminal must perform a groupcast option 2-based HARQ feedback operation. If the receiving terminal performs a groupcast option 1-based HARQ feedback operation for the service, a DTX problem may occur. Therefore, the receiving terminal must perform a groupcast option 2-based HARQ feedback operation for a service with a high reliability requirement. The DTX problem may occur when the receiving terminal fails to receive the PSCCH and does not send a NACK to the transmitting terminal, causing the transmitting terminal to mistakenly believe that the receiving terminal has successfully received the PSCCH and PSSCH. The DTX problem may cause the reliability requirement of the service to not be met. Therefore, if a specific groupcast option is not supported in the resource pool, the transmitting terminal may perform a blind retransmission operation if the specific groupcast option is not supported for the traffic and / or service. If a PSFCH resource associated with a specific groupcast option is not configured, the transmitting terminal may perform a blind retransmission operation. The transmitting terminal can perform retransmission without receiving HARQ feedback from the receiving terminal.

[0242] 24 illustrates an example of the configuration of PSCCH / PSSCH / PSFCH within a slot. Referring to FIG. 24, the time position of the PSFCH within one slot may be TDM'd with the PSCCH / PSSCH.

[0243] Figure 25 illustrates the structure of a Sidelink SSB (S-SSB). Referring to Figure 28, a UE can transmit an S-SSB to synchronize with another UE on the sidelink. Figure 28 shows the order of symbols to which an S-PSS (Sidelink Primary Synchronization Signal), an S-SSS (Sidelink Secondary Synchronization Signal), and a PSBCH (Physical Sidelink Broadcast Channel) are mapped within the S-SSB.

[0244] <Example: Channel access for SL (sidelink) transmission>

[0245] First, the terms used in the present invention will be explained.

[0246] - Type 1 Channel Access Procedure (CAP): A channel access procedure that includes a random backoff (see FIG. 13). Channel sensing may be performed based on a random value selected within the CW. If the channel is determined to be idle as a result of channel access, SL transmission may be performed.

[0247] - Type 2 CAP: A channel access procedure that does not include random backoff. Channel sensing may be performed in a fixed-length sensing interval for channel transmission. It may be classified into Type 2A / 2B / 2C depending on the fixed-length sensing interval.

[0248] - Type 2A CAP: Before sending a SL, the channel is sensed for at least 25 μs as a sensing period, and then the SL can be sent immediately. 25 μs is 16 μs (T f ) section and one immediately following sensing slot (9 μs), fThe 25 μs interval includes one sensing slot (9 μs) from the beginning. If all sensing slots of the 25 μs interval are sensed as idle, the channel is determined to be valid for the 25 μs interval.

[0249] - Type 2B CAP: 16 μs (T f ) and then immediately perform SL transmission after sensing whether the channel is idle. f ) contains one sensing slot within the last 9 μs of the 16 μs. A channel is determined to be idle if it is sensed as idle for a total period of at least 5 μs with at least 4 μs in which sensing occurs within the sensing slot.

[0250] - Type 2C CAP: This means that SL transmission is performed without channel sensing before transmission (i.e., No LBT). The maximum duration for SL transmission may be limited to a maximum of 584 μs.

[0251] CO (or COT): CO means that a wireless communication device (e.g., UE) has started transmitting on the channel and is occupying the channel. COT stands for channel occupation time.

[0252] - COT sharing: means that the COT initiated by a wireless communication device (e.g., UE) is shared with the same / other wireless communication devices (e.g., see FIG. 15).

[0253] SL transmission: SL transmission includes transmission of SL channels, such as a physical sidelink control channel (PSCCH), a physical sidelink shared channel (PSSCH), and a physical sidelink feedback channel (PSFCH).

[0254] PSCCH / PSSCH: means PSSCH and / or PSSCH.

[0255] - SCI (sidelink control information): SCI is 1 st SCI (or SCI format 1) and 2 nd It may be distinguished from SCI (or SCI Format 2). st SCI is transmitted on the PSCCH. st SCI is (i) PSSCH, and (ii) 2 on PSSCH. nd Used to schedule SCIs. For example, 1 st The SCI contains time / frequency resource information for PSSCH reception, a priority indicator, and nd It includes SCI format information, etc. The priority indicator indicates the traffic priority of the PSSCH. st The SCI may be decoded by all terminals in the cell for channel sensing. nd The SCI is decoded by each receiving terminal and contains the remaining information needed for PSSCH decoding. nd The SCI may be transmitted on a PSSCH resource. For example, nd The SCI includes a HARQ process number, a cast type indicator, a source ID, a destination ID, and the like.

[0256] Figure 26 illustrates an example of a SL communication process. SL communication refers to a communication method in which a direct link is established between terminals and voice or data is directly transmitted and received between terminals without going through a base station. In SL communication, the base station in Figure 14 may be replaced by a terminal.

[0257] Referring to FIG. 26, UE-A can transmit sidelink control information (SCI) to UE-B (S1602). st SCI and 2 nd It may be distinguished from SCI. st SCI is transmitted on the physical sidelink control channel (PSCCH).st The SCI contains some information required for PSSCH (physical sidelink shared channel) scheduling (e.g., 2 nd The SCI includes resources / information for decoding the SCI, DMRS patterns, antenna ports, etc., and may be decoded by all terminals in the cell for channel sensing. nd The SCI is decoded by each receiving terminal and contains the remaining information required for PSSCH scheduling. nd The SCI may be transmitted on the PSSCH resource. Then, UE-A can transmit the PSSCH to UE-B (S1604). End-to-end data may be transmitted on the PSSCH. Unicast transmission and groupcast transmission may also be performed on the PSSCH. If HARQ feedback operation is supported / configured for SL transmission (e.g., PSSCH) (HARQ-ACK enabled), UE-B can transmit HARQ-ACK feedback for the PSSCH to UE-A on the physical sidelink feedback channel (PSFCH) (S1606). On the other hand, if HARQ feedback operation is not supported / configured for SL transmission (e.g., PSSCH) (HARQ-ACK disabled), UE-A does not expect explicit HARQ-ACK feedback for the PSSCH from UE-B.

[0258] 1) CWS adjustment for SL channel connection

[0259] The present invention relates to a channel access method / procedure for SL transmission (e.g., PSSCH) over an unlicensed spectrum. Specifically, the present invention proposes a method for adjusting a CWS according to a SL transmission type (e.g., unicast / group transmission with HARQ-ACK, groupcast transmission with NACK only, groupcast transmission without HARQ-ACK, and broadcast transmission) when adjusting a CWS for channel access over an unlicensed spectrum. Here, the channel access procedure using a CWS includes, for example, a Type 1 channel access procedure (CAP) (or a Cat-4 (category 4) LBT, a random backoff-based channel access procedure with a variable CW). For example, when a Type 1 channel access is performed for SL transmission, a wireless device (e.g., a terminal) can adjust a CWS based on the type of SL transmission before performing the Type 1 channel access.

[0260] The transmission type may be classified based on (i) the type of transmission (e.g., unicast, groupcast, broadcast), and (ii) the HARQ-ACK feedback scheme / mode (HARQ-ACK, NACK only, no HARQ-ACK) indicated / configured for the transmission. As used herein, the transmission type includes, but is not limited to, the following:

[0261] - transmission with HARQ-ACK: refers to a transmission that requires HARQ-ACK feedback (e.g., ACK, NACK). Therefore, after a terminal transmits a transmission to a receiving terminal, the terminal expects HARQ-ACK feedback (e.g., ACK or NACK) for the transmission from the receiving terminal (i.e., explicit ACK / NACK). Here, the transmission includes unicast transmission or groupcast transmission.

[0262] - transmission w / NACK only: This refers to a transmission in which only NACK is allowed as HARQ-ACK feedback. Therefore, after a terminal transmits a transmission to a receiving terminal, it can explicitly expect only NACK as HARQ-ACK feedback for that transmission from the receiving terminal. In this case, ACK is indirectly fed back because no NACK is detected / received for that transmission (i.e., implicit ACK). Here, transmission includes groupcast transmission.

[0263] - transmission w / o HARQ-ACK: This refers to a transmission in which HARQ-ACK feedback is not permitted. That is, this refers to a case in which the HARQ-ACK scheme / mode is not configured for the transmission. Therefore, after transmitting a transmission to a receiving terminal, the terminal does not expect HARQ-ACK feedback for the transmission from the receiving terminal. Here, the transmission includes a groupcast transmission or a broadcast transmission.

[0264] For example, the transmission type is 2 nd The transmission type may be indicated by a transmission type indicator in the SCI. Table 6 shows the transmission type by transmission type indicator.

[0265] [Table 6]

[0266] Unicast / group transmission with HARQ-ACK

[0267] A wireless device (e.g., a terminal) can transmit PSSCH via unicast or groupcast transmission with HARQ-ACK. When transmitting in an unlicensed spectrum, the terminal can perform Type 1 channel access. When performing Type 1 channel access, the terminal can adjust CWS to determine the time window for random backoff. A method for this purpose is proposed below.

[0268] First, when transmitting a PSSCH, the PSSCH transmission may be performed in either (a) a sidelink resource allocation mode 1 manner in which a base station notifies a terminal of time and frequency resources for PSSCH transmission, or (b) a sidelink resource allocation mode 2 manner in which (one) resource pool is configured, the terminal senses the resource pool, selects resources, and then allocates resources that can actually be transmitted. Here, the PSSCH may be transmitted over a PC-5 link. The PC-5 link refers to a link for direct communication between devices.

[0269] Case 1) When (one) resource pool is configured, (a) the PSFCH resource period and (b) the minimum time gap in which PSFCH reception is possible after PSSCH may be configured. In this case, HARQ-ACK enabling / disabling may be configured for SL transmission (e.g., PSSCH). For example, a terminal transmitting a PSSCH may receive 2 nd The HARQ-ACK enabled / disabled indicator in the SCI can be set to a specific value. For example, if the value of the HARQ-ACK enabled / disabled indicator is set to '1' (meaning enabled), the receiving terminal can transmit the PSFCH in an available slot after the minimum time gap from the PSSCH according to the PSFCH resource period after receiving the PSSCH. This allows the terminal that transmitted the PSSCH to receive (e.g., detect / monitor) the PSFCH and receive HARQ-ACK information.

[0270] Specifically, PSFCH resources are set in the resource pool, and ndWhen the value of the HARQ-ACK enabled / disabled indicator in the SCI is '1' (meaning enabled), UE-A can expect UE-B to transmit HARQ-ACK feedback for the PSSCH transmitted from UE-A to UE-B to UE-A. In this case, if the HARQ-ACK transmitted from UE-B is available and there is at least one ACK in the HARQ-ACK, UE-A can reset the current CWp for all priority classes to the minimum / initial value for each priority class (see, for example, Table 5). On the other hand, if this is not the case (e.g., there is no ACK in the HARQ-ACK; All NACKs), UE-A can increase the current CWp for all priority classes to the next highest possible value for each priority class (see, for example, Table 5). Then, using the set / adjusted CWp value, UE-A can perform Type 1 channel connection when transmitting the PSSCH to be currently transmitted. Here, the subscript p represents the priority class.

[0271] In addition, the terminal that transmits the PSSCH is nd The HARQ-ACK enabled / disabled indicator in the SCI can be used to specify a value of "0" (meaning disabled). In this case, the terminal does not expect an explicit HARQ-ACK from the receiving terminal, and the CWp value used for the previous PSSCH transmission can be used for the Type 1 channel connection when transmitting the current PSSCH.

[0272] Case 2) When one resource pool is configured, the PSFCH resource period and minimum time gap are not set, and there may be no PSFCH resource. In this case, the terminal transmitting the PSSCH may ndA terminal that receives a HARQ-ACK enabled / disabled indicator in the SCI with a value of '0' (meaning disabled) cannot transmit HARQ-ACK information because there are no PSFCH resources configured after receiving the PSSCH. In this case, the terminal that transmitted the PSSCH cannot expect an explicit HARQ-ACK from the receiving terminal and therefore cannot adjust the CWp based on the HARQ-ACK information. Therefore, the terminal that transmitted the PSSCH may be unclear as to what value it should set the current CWp to when transmitting the next PSSCH. To resolve this, if the channel access priority class of the PSSCH to be currently transmitted has been used previously, the terminal may perform Type 1 channel access by setting the current CWp (before transmitting the PSSCH) to a CWp value corresponding to the same priority class used most recently (for transmitting the PSSCH).

[0273] 27 illustrates a channel connection process according to an embodiment of the present invention. FIG. 27 corresponds to Case 1). Case 2 may be performed similarly.

[0274] Referring to FIG. 27, UE-A may configure HARQ-feedback enabling / disabling for SL transmission (e.g., PSSCH) (S1702). For example, UE-A may transmit an SCI for scheduling PSSCH. Here, the SCI (e.g., 2 ndThe HARQ-ACK enabled / disabled indicator may include a HARQ-feedback enabled / disabled indicator. UE-A may then perform channel access using the first CWS to transmit the PSSCH (S1704). Here, the PSSCH may be used for unicast transmission or groupcast transmission. The channel access may also include Type 1 channel access. If the value of the HARQ-ACK enabled / disabled indicator is set to '1' (enabled), UE-B can transmit the PSFCH in an available slot after the minimum time gap from the PSSCH after receiving the PSSCH. In this case, if there is at least one ACK for the HARQ-ACK transmitted from UE-B, UE-A can reset the current CWp for all priority classes to the minimum / initial value for each priority class (see, for example, Table 5). On the other hand, if not (e.g., if there is no ACK in the HARQ-ACK; All NACK), UE-A may increase the current CWp to the next highest possible value for each priority class for all priority classes (e.g., see Table 5) (S1706a). On the other hand, if the value of the HARQ-ACK enabled / disabled indicator is set to '0' (disabled), UE-A may use the CWp value used in the most recent PSSCH transmission as the current CWp, or if the channel access priority class of the PSSCH to be currently transmitted was previously used, the UE may use the CWp value used in the PSSCH transmission corresponding to the same priority class as the current CWp. Then, UE-A may perform channel access (e.g., Type 1 channel access) when transmitting the PSSCH to be currently transmitted using the set / adjusted CWp value (S1708).

[0275] Groupcast transmission w / NACK only

[0276] As a groupcast transmission with NACK-only feedback, a wireless device (e.g., a terminal) can transmit a PSSCH. In this case, when transmitting in an unlicensed spectrum, the terminal can perform Type 1 channel access. When performing Type 1 channel access, the terminal can adjust the CWS to determine a time window for performing random backoff. A method for this is proposed below. The following description can also be extended to groupcast transmission with HARQ-ACK, in which case implicit ACK can be replaced with explicit ACK.

[0277] When a terminal transmits a PSSCH as a groupcast transmission configured with NACK-only feedback, the terminal may monitor (e.g., detect) a PSFCH opportunity corresponding to the groupcast transmission to determine / confirm HARQ-ACK feedback for the groupcast transmission. Here, the PSFCH opportunity includes one or more PSFCH resources allocated to a group of terminals that receive the groupcast transmission. If, as a result of monitoring the PSFCH opportunity, no HARQ-ACK feedback is received from a group of terminals that are intended to receive the groupcast transmission (i.e., all implicit ACK), the terminal that transmitted the PSSCH considers the reception response for the PSSCH to be (All) ACK and does not perform a retransmission for the groupcast transmission. Therefore, if a terminal that has transmitted a PSSCH as a groupcast transmission does not receive any HARQ-ACK feedback from a group of terminals in the PSFCH opportunity that the terminal expects, the terminal can reset the current CWp for all priority classes to the minimum / initial value for each priority class as the CWp for Type 1 channel connection that must be performed when transmitting the next SL transmission (e.g., PSSCH; not necessarily groupcast transmission) to the minimum / initial value for each priority class (see, for example, Table 5). That is, if the reception response results from multiple terminals corresponding to the groupcast transmission are considered to be (All) ACK (e.g., no NACK is detected in the PSFCH opportunity), the terminal can reset the current CWp for all priority classes to the minimum / initial value for each priority class (see, for example, Table 5). When a group of terminals attempts to transmit NACK feedback on a PSFCH opportunity, the terminals that transmitted the PSSCH as groupcast transmission cannot know whether the channel connection failed and the transmission was not possible, or whether the terminals in the group received the previously transmitted PSSCH well and did not transmit NACK feedback. Therefore, regardless of this, the current CWp for all priority classes is reset to the minimum / initial value for each priority class (see, for example, Table 5), and Type 1 channel connection can be performed when transmitting the next SL transmission (e.g., PSSCH) to be transmitted.

[0278] Meanwhile, when a PSSCH is transmitted as a groupcast transmission configured with NACK-only feedback, and HARQ-ACK feedback having all NACKs or at least one NACK is received from a group of terminals that have received the PSSCH, the terminal that transmitted the PSSCH can perform a retransmission for the groupcast transmission. That is, when all NACKs or at least one NACK are detected in the PSFCH opportunity as a result of monitoring the PSFCH opportunity corresponding to the groupcast transmission, the terminal that transmitted the PSSCH can perform a retransmission for the groupcast transmission. In this case, a terminal that intends to retransmit the PSSCH as a groupcast transmission may be unclear as to what value to set as CWp for Type 1 channel access that must be performed when retransmitting the PSSCH.

[0279] 1. As an example, considering that a UE transmits a PSSCH as a retransmission of a groupcast transmission, if all UEs in a group transmit HARQ-ACK feedback with NACK and the UE that transmitted the PSSCH receives this, or if HARQ-ACK feedback with at least one NACK is received from a UE in a group, a method of performing CW adjustment when receiving a NACK can be used. For example, a UE that transmitted a PSSCH as a groupcast transmission can increase the current CWp for all priority classes to the next highest possible value for each priority class and perform Type 1 channel connection when transmitting the next PSSCH to be transmitted. That is, if the reception response results from multiple UEs corresponding to the groupcast transmission are considered to be Not (All) ACK (e.g., at least one NACK is detected in a PSFCH opportunity), the current CWp for all priority classes can be increased to the next highest possible value for each priority class (see, for example, Table 5). Alternatively, one or more PSSCH transmissions may be performed, and multiple feedbacks for PSSCHs having different groupcasts for the same UE group may be expected, or multiple feedbacks from multiple UE groups having different groupcasts may be expected. In this case, the UE that transmitted the groupcast counts the number of NACKs from the receiving UEs, and if the number of NACKs is equal to or greater than Z% (where Z is a natural number greater than 0 and equal to or less than 100), the UE may increase the current CWp for each priority class to the next highest possible value, such as performing CW adjustment when receiving a NACK. Otherwise, the UE may reset the current CWp for all priority classes to the minimum value for each priority class. As an example, the value of Z% may be set to 80% as in LTE-LAA.Alternatively, to operate as if the current CWp is set to the minimum value for each priority class when at least one ACK is received and available in the NR-U, the value of Z% can be set to 100% and only if all NACKs are received, i.e., if none are considered to be implicit ACKs, the current CWp for each priority class can be increased to the next highest possible value for all priority classes. Otherwise, i.e., if at least one is considered to be an implicit ACK, the UE can be configured to reset the current CWp for all priority classes to the minimum value for each priority class.

[0280] 2. As another example, if all terminals in a group transmit HARQ-ACK feedback with NACK, but HARQ-ACK feedback with at least one NACK is received from the terminals in a group, the terminal that transmitted the PSSCH can determine that at least one terminal in the group has received the PSSCH properly. In this case, it can be determined that there is no channel congestion from the perspective of channel access, and a method of performing CW adjustment when receiving ACK feedback can be used. For example, the terminal that transmitted the PSSCH can reset the current CWp for all priority classes to the minimum / initial value for each priority class and perform Type 1 channel access when transmitting the next PSSCH to be transmitted (see, for example, Table 5). Otherwise, the current CWp for each priority class can be increased to the next highest possible value.

[0281] FIG. 28 illustrates a channel access procedure according to an embodiment of the present invention. Referring to FIG. 28, UE-A may perform channel access using a first CWS to transmit a groupcast transmission (S1802). Here, the groupcast transmission may be performed using a PSSCH. The channel access may also include Type 1 channel access. Then, UE-A may monitor a PSFCH (opportunity / resource) corresponding to the groupcast transmission (S1804). As a result of the monitoring, if the HARQ feedback result is deemed to be All ACK (e.g., no NACK is detected in the PSFCH opportunity / resource), UE-A may reset the current CWp for all priority classes to the minimum / initial value for each priority class (e.g., see Table 5) (S1806a). On the other hand, if the HARQ feedback result is not considered to be All ACK (e.g., at least one NACK is detected in the PSFCH opportunity / resource), UE-A may increase the current CWp to the next highest possible value for each priority class for all priority classes (e.g., see Table 5) (S1806b). Then, using the set / adjusted CWp value, UE-A may perform channel access (e.g., Type 1 channel access) when transmitting the SL transmission (e.g., PSSCH) that it is currently attempting to transmit (after groupcast transmission) (S1808). Here, the HARQ-feedback scheme indicated / set for groupcast transmission includes a NACK-only feedback scheme.

[0282] When transmitting PSSCH as groupcast transmission configured with NACK-only feedback, the base station can perform a sidelink resource allocation mode 1 method in which the base station notifies the terminal of time / frequency resources for PSSCH transmission, or it can perform a sidelink resource allocation mode 2 operation in which a single resource pool is configured, the base station senses the resource pool to select resources, and then allocates actually transmittable resources. Meanwhile, when (a single) resource pool is configured, there may be cases where the PSFCH resource period and minimum time gap are not configured and there are no PSFCH resources. In this case, the terminal transmitting PSSCH may perform a sidelink resource allocation mode 2 method in which the base station notifies the terminal of time / frequency resources for PSSCH transmission, or it can perform a sidelink resource allocation mode 2 operation in which a single resource pool is configured, the base station senses the resource pool to select resources, and then allocates actually transmittable resources. nd The HARQ-ACK enabled / disabled indicator in the SCI is used to indicate a value of '0' (meaning disabled). A terminal that receives this cannot transmit HARQ-ACK information, which is NACK-only feedback information, because there are no configured PSFCH resources after receiving the PSSCH. In this case, the terminal that transmitted the PSSCH cannot expect an explicit HARQ-ACK from the receiving terminal and therefore cannot adjust the CWp based on the HARQ-ACK information. Therefore, the terminal that transmitted the PSSCH may be unclear as to what value it should set the current CWp value to when transmitting the next PSSCH. To resolve this, if the channel access priority class of the PSSCH to be currently transmitted has been used previously, the terminal may perform Type 1 channel access by setting the current CWp to a CWp value corresponding to the same priority class used most recently (for PSSCH transmission) (before PSSCH transmission).

[0283] Alternatively, the terminal transmitting the PSSCH is nd The HARQ-ACK enabled / disabled indicator in the SCI can be used to specify a value of "0" (meaning disabled). In this case, the terminal does not expect an explicit HARQ-ACK from the receiving terminal, and can use the CWp value used for the most recent PSSCH transmission as is for the Type 1 channel connection performed when transmitting the current PSSCH.

[0284] 2. Definition of Sidelink reference duration

[0285] As described above (see, for example, FIGS. 27 and 28), when a transmitting terminal performs CWS adjustment before establishing a Type 1 channel access, HARQ-ACK feedback may be received from a receiving terminal as feedback for a previous SL transmission. In this case, a time interval that the transmitting terminal can use for CWS adjustment for the Type 1 channel access needs to be defined. This can be defined as an SL reference interval. According to an example of the present invention, when HARQ-ACK feedback is received, the transmitting terminal can perform CWS adjustment for the Type 1 channel access based on the HARQ-ACK feedback for the SL transmission (e.g., PSSCH / PSCCH transmission) within the SL reference interval.

[0286] The SL reference interval may be set in the following manner.

[0287] First, the SL reference interval may correspond to the most recent COT acquired when the transmitting terminal performs Type 1 channel access to start the COT. Furthermore, when the PSSCH is transmitted in all resources allocated for transmitting a PSSCH including at least unicast data transmission (in the most recent COT), the SL reference interval may be set to extend from the beginning of the most recent COT to the end of the first slot (among the slots) based on one slot. Here, the first slot refers to the first slot among the slots in which the PSSCH including unicast data transmission is transmitted. Furthermore, when the PSSCH is transmitted in all resources allocated for transmitting a PSSCH configured to enable HARQ-ACK feedback (in the most recent COT), the SL reference interval may be set to extend from the beginning of the most recent COT to the end of the first slot (among the slots) based on one slot. Starting the SL reference interval from the beginning of the most recent COT is effective in reflecting the degree of channel congestion, since channel access occurs before the start of each transmission. Here, the first slot refers to the first slot among the slots in which a PSSCH configured to enable HARQ-ACK feedback is transmitted. Figure 29 illustrates an example in which the SL reference interval is set to extend from the beginning of the most recent COT started by the UE to the end of the first slot among the slots in which a PSSCH configured to enable HARQ-ACK feedback is transmitted. SL transmission may include a PSSCH not configured to enable HARQ-ACK feedback, which is not taken into consideration when setting the end of the SL reference interval. Furthermore, the most recent COT started by the UE may include multiple SL transmission bursts. In this case, the SL reference interval may also be set to extend from the beginning of the COT to the end of the first slot among the slots in which a PSSCH configured to enable HARQ-ACK feedback is transmitted.

[0288] For example, resources allocated for PSSCH transmission in one slot starting from the beginning of the most recent COT may consist of one or more RB sets (LBT execution units in units of 20 MHz). In this case, if channel access is successful and PSSCH transmission is performed using the allocated resources, the SL reference period may be set to extend from the beginning of the most recent COT to the end of the (first) slot corresponding to one slot. Here, the PSSCH is limited to a PSSCH including unicast data transmission. Furthermore, the PSSCH is limited to a PSSCH configured to enable HARQ-ACK feedback. The terminal can apply the CWS adjustment method described in the present invention based on the ACK / NACK feedback of the HARQ-ACK corresponding to the PSSCH transmitted in the SL reference period.

[0289] As another example, the SL reference interval may be set by the following method. In this method, multiple consecutive slot transmissions (MCSt) may be considered as resources for PSSCH transmission. As described above, the SL reference interval may correspond to the most recent COT acquired when the transmitting terminal performs Type 1 channel access to start the COT. When the PSSCH is transmitted in all resources allocated for transmission of a PSSCH including at least unicast data transmission, or when the PSSCH is transmitted occupying an entire slot in all resources allocated for transmission of a PSSCH configured to enable HARQ-ACK feedback, the SL reference interval may be set to start from the beginning of the most recent COT and extend to the end of the first slot, starting from one slot. On the other hand, in all resources allocated for transmission of a PSSCH configured to enable HARQ-ACK feedback, the PSSCH may occupy a partial slot of one slot, and the PSSCH may be transmitted continuously in the following slots using MCSt. In this case, the SL reference interval may be set to start from the beginning of the most recent COT, include a partial slot, and extend to the end of the slot in which the PSSCH is continuously transmitted in the MCSt in the subsequent slots. The UE may apply the CWS adjustment method described in the present invention based on the ACK / NACK feedback of the HARQ-ACK corresponding to the PSSCH transmitted in the SL reference interval.

[0290] For example, resources allocated for transmitting the PSSCH in one slot starting from the beginning of the most recent COT may consist of one or more RB sets (LBT execution units in units of 20 MHz), the PSSCH may occupy a partial slot of one slot, and the PSSCH may be continuously transmitted in the subsequent slots using MCSt. When channel access is successful in the partial slot and the PSSCH is subsequently transmitted in the subsequent slots using MCSt, the SL reference period may be set to start from the beginning of the most recent COT, include the partial slot, and continue until the end of the subsequent slots in which the PSSCH is continuously transmitted in the MCSt. The terminal may apply the CWS adjustment method described in the present invention based on the ACK / NACK feedback of the HARQ-ACK corresponding to the PSSCH transmitted in the SL reference period.

[0291] As yet another example, the SL reference interval may be set in the following manner. The SL reference interval may correspond to the most recent COT obtained when the transmitting terminal performs Type 1 channel access to start the COT. More specifically, the SL reference interval may be set (starting from the beginning of the most recent COT) to the end of the first burst in the most recent COT in which all resources allocated for PSSCH transmission, including at least unicast data transmission, are transmitted. Alternatively, the SL reference interval may be set (starting from the beginning of the most recent COT) to the end of the first burst in the most recent COT in which all resources allocated for PSSCH transmission, including PSSCH transmission with HARQ-ACK feedback enabled, are transmitted. That is, if only a portion of the PSSCH transmissions set by the transmitting terminal in the most recent COT, for example, if two RB sets are allocated to the first slot in the CO corresponding to the most recent COT but channel connection fails on one channel and the PSSCH is transmitted using one RB set, the SL reference interval cannot be set to the end of the first slot. In this case, the SL reference interval may be set to the first transmission burst transmitted by the transmitting terminal (starting from the beginning of the most recent COT), i.e., up to the burst for consecutive PSSCH transmissions including the transmission of the first slot. Similarly, even if there is no PSSCH transmission including unicast data transmission or PSSCH transmission with HARQ-ACK feedback enabled in the first slot, if there is a PSSCH transmission including at least unicast data transmission or a PSSCH transmission with HARQ-ACK feedback enabled in the first transmission burst including the first slot, the transmitting terminal can set the SL reference period from the beginning of the most recent COT to the first transmission burst transmitted by the transmitting terminal, i.e., the burst for consecutive PSSCH transmissions including the transmission of the first slot.

[0292] In an example of the present invention, when configuring the SL reference interval, if PSSCH transmission configured to enable HARQ-ACK feedback is taken into consideration, NACK-only or explicit HARQ-ACK feedback (i.e., ACK or NACK) feedback may be used as the HARQ-ACK feedback scheme. Here, if the SL reference interval starts from the beginning of the most recent COT started by the UE, configuring the SL reference interval may mean setting the end of the SL reference interval. Preferably, when configuring the SL reference interval in the present invention, if HARQ-ACK feedback is enabled for PSSCH transmission transmitted via unicast or groupcast, only the case where the indicated explicit HARQ-ACK feedback is used as the HARQ-ACK feedback scheme for unicast or groupcast transmission may be considered. That is, when configuring the SL reference interval, the HARQ-ACK feedback scheme may be limited to explicit HARQ-ACK feedback for unicast or groupcast transmission. Specifically, the SL reference period may be configured in consideration of (1) HARQ-ACK feedback being enabled and (2) the transmission of a PSSCH in which the HARQ-ACK feedback method is indicated as explicit HARQ-ACK feedback. nd The HARQ-ACK enabled / disabled indicator in the SCI indicates this. nd It may be indicated by the transmission type indicator of the SCI (see Table 6). Figure 30 illustrates a case where the HARQ-ACK feedback scheme for unicast or groupcast transmission is limited to explicit HARQ-ACK feedback when configuring the SL reference interval. Alternatively, when HARQ-ACK feedback is enabled for unicast or groupcast transmission, both NACK-only and explicit HARQ-ACK feedback schemes may be considered as the HARQ-ACK feedback scheme indicated for unicast or groupcast transmission.

[0293] 31 illustrates an SL transmission method according to one embodiment of the present invention. Referring to FIG. 31, a terminal transmits at least one PSSCH within a COT, and the multiple PSSCHs may include at least one first PSSCH for which HARQ-ACK feedback is enabled (S3102). Then, the terminal adjusts a CWS based on the HARQ-ACK feedback for the at least one PSSCH in a reference interval, and may perform an SL channel access procedure based on the adjusted CWS (S3104 to 3106). Here, the reference interval may be defined as from the beginning of the COT to the end of a first slot in which the at least one first PSSCH is transmitted.

[0294] Here, the HARQ-ACK feedback may include reception response information according to an ACK / NACK (negative ACK) feedback scheme. Furthermore, when the at least one first PSSCH includes at least one second PSSCH for which an ACK / NACK feedback scheme is indicated and at least one third PSSCH for which a NACK-only feedback scheme is indicated, the reference period may be defined as a period from the beginning of the COT to the end of the first slot in which the at least one second PSSCH is transmitted. Furthermore, the plurality of PSSCHs may include at least one fourth PSSCH for which the HARQ-ACK feedback is not enabled. Furthermore, the COT may be the most recent COT initiated by the terminal.

[0295] Here, if the HARQ-ACK feedback for the at least one PSSCH transmission in the reference interval includes at least an ACK, the CWS may be adjusted to a minimum value, or if the HARQ-ACK feedback for the at least one PSSCH transmission in the reference interval does not include an ACK, the CWS may be increased to the next largest value among the allowed CWS values.

[0296] Here, if the at least one first PSSCH is transmitted as a SL groupcast and the HARQ-ACK feedback for the at least one PSSCH transmission in the reference period includes at least one NACK (negative acknowledgment), the CWS may be increased to a value greater than the current CWS among the allowable CWS values, and if all HARQ-ACK feedback for the at least one PSSCH transmission in the reference period are considered to be ACKs, the CWS may be adjusted to a minimum value.

[0297] Here, the terminal may perform the SL channel access procedure based on a counter value randomly selected within the adjusted CWS. Also, the first slot in which the at least one first PSSCH is transmitted may be a slot in which the PSSCH transmission is performed on all resources allocated for PSSCH transmission.

[0298] CWS adjustment when more than one SL HARQ-ACK feedback scheme is used

[0299] As described above, before performing Type 1 channel access, the terminal can adjust the CWS based on the SL reference period in which the terminal performed transmission. Specifically, the terminal can adjust the CWS based on HARQ-ACK feedback for SL transmission in the SL reference period. In this case, the SL reference period may include one or more (e.g., multiple) transmission types (e.g., unicast transmission with HARQ-ACK (ACK or NACK), groupcast transmission with HARQ-ACK, groupcast transmission with NACK only, groupcast transmission with no HARQ-ACK, and broadcast transmission). In this case, it may be unclear for the terminal performing channel access by adjusting the CWS whether to set the reference transmission corresponding to the HARQ-ACK feedback for determining the CWS as feedback corresponding to one PSSCH transmission or one or more PSSCH transmissions. Therefore, a method for setting the reference transmission and a method for the terminal to adjust the CWS accordingly are proposed.

[0300] A. As an example, when a UE operates using different SL-HARQ feedback schemes, one or more PSSCH transmissions configured as SL HARQ-ACK feedback enabled of multiple types (e.g., unicast transmission (ACK / NACK), groupcast transmission with option 1 (NACK only), or option 2 (ACK / NACK)) may be included in the SL reference period. In this case, regardless of whether the transmission is unicast or groupcast, whether the HARQ-ACK feedback is configured to transmit ACK / NACK, or whether the HARQ-ACK feedback is configured to transmit NACK-only, a reference PSSCH transmission can be configured based on the PSSCH transmission configured as SL HARQ-ACK feedback enabled. Specifically, a reference PSSCH transmission can be configured using the following three methods, and the UE can adjust the CWS based on the HARQ-ACK feedback for the reference PSSCH transmission.

[0301] A-1. Among the PSSCH transmissions set as SL HARQ-ACK feedback enabled in the SL reference period, the PSSCH transmission in the slot leading the time axis (hereinafter referred to as the reference PSSCH transmission) is used as a reference, and the CWS can be configured based on the corresponding HARQ-ACK feedback. When transmitting in an unlicensed band, a channel connection is performed before the start of transmission, so that the congestion level of the unlicensed band channel at the start of transmission can be best reflected, whether it is idle or busy.

[0302] If at least an ACK is received as HARQ-ACK feedback corresponding to the reference PSSCH transmission, CW_p may be reset to CW_min,p. Here, when resetting to CW_p=CW_min,p, one of the following two methods may be used.

[0303] 1)CW_p=CW_min,p for each priority class p∈{1,2,3,4}

[0304] 2)CW_p=CW_min,p for every priority class p∈{1,2,3,4}

[0305] Otherwise (i.e., when no ACK is received; All NACKs), CW_p may be increased. Here, when increasing CW_p, one of the following two methods may be used.

[0306] 1)increase CW_p for every priority class p∈{1,2,3,4} to the next higher allowed value

[0307] 2)increase CW_p for each priority class p∈{1,2,3,4} to the next higher allowed value

[0308] When the single SL HARQ-ACK feedback scheme is used for the reference PSSCH transmission, the CWS adjustment scheme used in the single SL HARQ-ACK feedback scheme can be used in the same way as the scheme proposed above.

[0309] A-2. Among PSSCH transmissions configured as SL HARQ-ACK feedback enabled in the SL reference period, at least one PSSCH transmission configured to transmit HARQ feedback (hereinafter referred to as the reference PSSCH transmission) can be used as a reference, and a CWS can be configured based on the corresponding HARQ-ACK feedback. When transmitting in an unlicensed band, channel access is performed before the start of transmission prior to transmission, so that the congestion level of the unlicensed band channel, whether it is idle or in use at the start of transmission, can be best reflected. Meanwhile, even if channel access is performed before the start of transmission, channel access may be successful within a slot, resulting in partial slot transmission. In this case, determining channel congestion based solely on partial slot transmission may result in NACK due to partial PSSCH transmission in the partial slot, rather than channel congestion. Therefore, when adjusting a CWS to reflect channel congestion, a single partial slot may be insufficient, and therefore this configuration may be appropriate.

[0310] If at least an ACK is received as HARQ-ACK feedback corresponding to the reference PSSCH transmission, CW_p may be reset to CW_min,p. Here, when resetting to CW_p=CW_min,p, one of the following two methods may be used.

[0311] 1)CW_p=CW_min,p for each priority class p∈{1,2,3,4}

[0312] 2)CW_p=CW_min,p for every priority class p∈{1,2,3,4}

[0313] 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 may be used.

[0314] 1)increase CW_p for every priority class p∈{1,2,3,4} to the next higher allowed value

[0315] 2)increase CW_p for each priority class p∈{1,2,3,4} to the next higher allowed value

[0316] A-3. Among PSSCH transmissions configured as SL HARQ-ACK feedback enabled in the SL reference period, all PSSCH transmissions configured to transmit HARQ feedback (hereinafter referred to as reference PSSCH transmissions) can be used as a reference and CWS can be configured based on the corresponding HARQ-ACK feedback. When transmitting in an unlicensed band, if there is at least one HARQ-ACK feedback for a previously transmitted transmission, the transmitting terminal can determine that the channel is idle in terms of the congestion level for the unlicensed band channel and that channel connection has been successful. Therefore, a method of adjusting CWS based on the corresponding HARQ-ACK feedback for all PSSCH transmissions can be appropriate.

[0317] If at least an ACK is received as HARQ-ACK feedback corresponding to the reference PSSCH transmission, CW_p may be reset to CW_min,p. Here, when resetting to CW_p=CW_min,p, one of the following two methods may be used.

[0318] 1)CW_p=CW_min,p for each priority class p∈{1,2,3,4}

[0319] 2)CW_p=CW_min,p for every priority class p∈{1,2,3,4}

[0320] 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 may be used.

[0321] 1)increase CW_p for every priority class p∈{1,2,3,4} to the next higher allowed value

[0322] 2)increase CW_p for each priority class p∈{1,2,3,4} to the next higher allowed value

[0323] B. As an example, when a UE operates using different SL-HARQ feedback schemes, one or more PSSCH transmissions configured as SL HARQ-ACK feedback enabled of multiple types (e.g., unicast (ACK / NACK), groupcast with option 1 (NACK only), or option 2 (ACK / NACK)) may be included in the SL reference period. In this case, groupcast transmissions with NACK only may be excluded first, and a reference PSSCH transmission may be configured based on a PSSCH transmission configured as SL HARQ-ACK feedback enabled, regardless of whether it is a unicast transmission or a groupcast transmission. For example, the UE may configure a reference PSSCH transmission using the following three methods and adjust the CWS based on the HARQ-ACK ACK / NACK feedback for the reference PSSCH transmission:

[0324] B-1. Among PSSCH transmissions configured as SL HARQ-ACK feedback enabled in the SL reference period, the PSSCH transmission in the slot leading the time axis (hereinafter referred to as the reference PSSCH transmission) is used as a reference, and CWS can be configured based on the corresponding HARQ-ACK ACK / NACK feedback. When transmitting in an unlicensed band, channel connection is performed before the start of transmission, so that the congestion level of the unlicensed band channel at the start of transmission, whether it is idle or in use, can be best reflected.

[0325] If at least ACK is received as HARQ-ACK ACK / NACK feedback corresponding to the reference PSSCH transmission, CW_p may be reset to CW_min,p. Here, when resetting to CW_p=CW_min,p, one of the following two methods may be used.

[0326] 1)CW_p=CW_min,p for each priority class p∈{1,2,3,4}

[0327] 2)CW_p=CW_min,p for every priority class p∈{1,2,3,4}

[0328] 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 may be used.

[0329] 1)increase CW_p for every priority class p∈{1,2,3,4} to the next higher allowed value

[0330] 2)increase CW_p for each priority class p∈{1,2,3,4} to the next higher allowed value

[0331] When the single SL HARQ-ACK feedback scheme is used for the reference PSSCH transmission, the CWS adjustment scheme used in the single SL HARQ-ACK feedback scheme can be used in the same way as the scheme proposed above.

[0332] B-2. Among PSSCH transmissions configured as SL HARQ-ACK feedback enabled in the SL reference period, at least one PSSCH transmission configured to transmit HARQ-ACK ACK / NACK feedback (hereinafter referred to as the reference PSSCH transmission) can be used as a reference to configure a CWS based on the corresponding HARQ-ACK ACK / NACK feedback. Since channel access is performed before the start of transmission prior to transmission in the unlicensed band, it can best reflect the congestion level of the unlicensed band channel, whether it is idle or in use at the start of transmission. Furthermore, even if channel access is performed before the start of transmission, partial slot transmission may occur due to successful channel access within the slot. Determining channel congestion based solely on partial slot transmission may result in NACKs occurring due to partial PSSCH transmission in the partial slot, rather than channel congestion. Therefore, when adjusting a CWS to reflect channel congestion, a single partial slot may be insufficient, and thus configuring this method may be appropriate.

[0333] When at least ACK is received as HARQ-ACK feedback corresponding to the reference PSSCH transmission, CW_p can be reset to CW_min,p. Here, when resetting to CW_p=CW_min,p, one of the following two methods may be used.

[0334] 1)CW_p=CW_min,p for each priority class p∈{1,2,3,4}

[0335] 2)CW_p=CW_min,p for every priority class p∈{1,2,3,4}

[0336] 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 may be used.

[0337] 1)increase CW_p for every priority class p∈{1,2,3,4} to the next higher allowed value

[0338] 2)increase CW_p for each priority class p∈{1,2,3,4} to the next higher allowed value

[0339] B-3. ​​Among PSSCH transmissions configured as SL HARQ-ACK feedback enabled in the SL reference period, all PSSCH transmissions configured to transmit HARQ-ACK ACK / NACK feedback (hereinafter referred to as reference PSSCH transmissions) may be used as a reference and the CWS may be configured based on the corresponding HARQ-ACK ACK / NACK feedback. When transmitting in an unlicensed band, if there is at least one HARQ-ACK feedback for a previously transmitted transmission, the transmitting terminal may determine that the channel is idle in terms of the congestion level for the unlicensed band channel and that channel connection has been successful. Therefore, it may be reasonable to adjust the CWS based on the corresponding HARQ-ACK feedback for all PSSCH transmissions configured to transmit HARQ-ACK ACK / NACK feedback.

[0340] When at least ACK is received as HARQ-ACK feedback corresponding to the reference PSSCH transmission, CW_p can be reset to CW_min,p. Here, when resetting to CW_p=CW_min,p, one of the following two methods may be used.

[0341] 1)CW_p=CW_min,p for each priority class p∈{1,2,3,4}

[0342] 2)CW_p=CW_min,p for every priority class p∈{1,2,3,4}

[0343] Otherwise (i.e., when no ACK is received; All NACK), CW_p can be increased. Here, when increasing CW_p, one of the following two methods may be used.

[0344] 1)increase CW_p for every priority class p∈{1,2,3,4} to the next higher allowed value

[0345] 2)increase CW_p for each priority class p∈{1,2,3,4} to the next higher allowed value

[0346] C. As yet another example, when a UE operates using different SL-HARQ feedback schemes, one or more PSSCH transmissions configured as SL HARQ-ACK feedback enabled of multiple types (e.g., unicast (ACK / NACK), groupcast with option 1 (NACK only), or option 2 (ACK / NACK)) may be included in the SL reference period. In this case, the groupcast transmission may be excluded first, and a reference PSSCH transmission may be configured based on a PSSCH configured as SL HARQ-ACK feedback enabled in a unicast transmission and configured to transmit an ACK / NACK as a HARQ-ACK. For example, the UE may configure a reference PSSCH transmission using the following three methods and adjust the CWS based on the HARQ-ACK ACK / NACK feedback for the reference PSSCH transmission:

[0347] C-1. Among the PSSCH transmissions set as SL HARQ-ACK feedback enabled in the SL reference period, the PSSCH transmission in the slot leading the time axis (hereinafter referred to as the reference PSSCH transmission) is used as a reference, and the CWS can be configured based on the corresponding HARQ-ACK ACK / NACK feedback. When transmitting in an unlicensed band, channel connection is performed before the start of transmission, so that the start of transmission can best reflect the congestion level of the unlicensed band channel, whether it is idle or in use.

[0348] If at least ACK is received as HARQ-ACK ACK / NACK feedback corresponding to the reference PSSCH transmission, CW_p may be reset to CW_min,p. Here, when resetting to CW_p=CW_min,p, one of the following two methods may be used.

[0349] 1)CW_p=CW_min,p for each priority class p∈{1,2,3,4}

[0350] 2)CW_p=CW_min,p for every priority class p∈{1,2,3,4}

[0351] 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 may be used.

[0352] 1)increase CW_p for every priority class p∈{1,2,3,4} to the next higher allowed value

[0353] 2)increase CW_p for each priority class p∈{1,2,3,4} to the next higher allowed value

[0354] When the single SL HARQ-ACK feedback scheme is used for the reference PSSCH transmission, the CWS adjustment scheme used in the single SL HARQ-ACK feedback scheme can be used in the same way as the scheme proposed above.

[0355] C-2. Among PSSCH transmissions configured as SL HARQ-ACK feedback enabled in the SL reference period, at least one PSSCH transmission configured to transmit HARQ-ACK ACK / NACK feedback (hereinafter referred to as the reference PSSCH transmission) can be used as a reference to configure the CWS based on the corresponding HARQ-ACK ACK / NACK feedback. Since channel access is performed before the start of transmission prior to transmission in the unlicensed band, it can best reflect the congestion level of the unlicensed band channel, whether it is idle or in use at the start of transmission. Furthermore, even if channel access is performed before the start of transmission, partial slot transmission may occur due to successful channel access within the slot. Determining channel congestion based solely on partial slot transmission may result in NACKs due to partial PSSCH transmission in the partial slot, rather than channel congestion. Therefore, when adjusting the CWS to reflect channel congestion, a single partial slot may be insufficient, and therefore, configuring this method may be appropriate.

[0356] When at least ACK is received as HARQ-ACK feedback corresponding to the reference PSSCH transmission, CW_p can be reset to CW_min,p. Here, when resetting to CW_p=CW_min,p, one of the following two methods may be used.

[0357] 1)CW_p=CW_min,p for each priority class p∈{1,2,3,4}

[0358] 2)CW_p=CW_min,p for every priority class p∈{1,2,3,4}

[0359] If not, CW_p can be increased. Here, when increasing CW_p, one of the following two methods may be used.

[0360] 1)increase CW_p for every priority class p∈{1,2,3,4} to the next higher allowed value

[0361] 2)increase CW_p for each priority class p∈{1,2,3,4} to the next higher allowed value

[0362] C-3. Among PSSCH transmissions configured as SL HARQ-ACK feedback enabled in the SL reference period, all PSSCH transmissions configured to transmit HARQ-ACK ACK / NACK feedback (hereinafter referred to as reference PSSCH transmissions) can be used as a reference and the CWS can be configured based on the corresponding HARQ-ACK ACK / NACK feedback. When transmitting in an unlicensed band, if there is at least one HARQ-ACK feedback for a previously transmitted transmission, the transmitting terminal can determine that the channel is idle in terms of the congestion level for the unlicensed band channel and that channel connection has been successful. Therefore, it may be reasonable to adjust the CWS based on the corresponding HARQ-ACK feedback for all PSSCH transmissions configured to transmit HARQ-ACK ACK / NACK feedback.

[0363] When at least ACK is received as HARQ-ACK feedback corresponding to the reference PSSCH transmission, CW_p can be reset to CW_min,p. Here, when resetting to CW_p=CW_min,p, one of the following two methods may be used.

[0364] 1)CW_p=CW_min,p for each priority class p∈{1,2,3,4}

[0365] 2)CW_p=CW_min,p for every priority class p∈{1,2,3,4}

[0366] 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 may be used.

[0367] 1)increase CW_p for every priority class p∈{1,2,3,4} to the next higher allowed value

[0368] 2)increase CW_p for each priority class p∈{1,2,3,4} to the next higher allowed value

[0369] CWS adjustment by S-SSB and PSFCH transmission when connecting to SL channel

[0370] The present invention relates to a channel access method for SL transmission using unlicensed spectrum. Specifically, when Type 1 channel access is performed for S-SSB and PSFCH transmission, CWS is adjusted before Type 1 channel access is performed. The present invention proposes a method for adjusting this CWS.

[0371] In PSSCH transmission, a transmitting terminal transmits a PSSCH to a receiving terminal and receives HARQ-ACK feedback for the PSSCH from the receiving terminal. In this case, the transmitting terminal determines channel collision and channel status from the perspective of channel access from the HARQ-ACK feedback, and can adjust the CWS before performing Type 1 channel access when performing the next transmission. For example, as described in this specification, the transmitting terminal can reset the CWS to the minimum value or increase it within the next allowed value range based on the HARQ-ACK feedback in response to an ACK or NACK. More specifically, when HARQ-ACK feedback is enabled, a terminal transmitting a PSSCH can reset the CWS to the minimum value or increase it within the next allowed value range in response to an ACK or NACK using the HARQ-ACK feedback from the receiving terminal, i.e., using HARQ-ACK feedback information transmitted in the PSFCH. However, a terminal that receives a PSSCH and transmits a PSFCH via Type 1 channel access does not receive separate feedback for the PSFCH transmission from the PSFCH receiving terminal. Therefore, when a terminal that has transmitted a PSFCH via Type 1 channel connection transmits an SL channel / signal as its next transmission, it is necessary to define a CWS adjustment method that can be used for the next transmission. Furthermore, in an NR SL communication system, a transmitting terminal can transmit an S-SSB or a sidelink SS / PSBCH block to a receiving terminal as shown in FIG. 25. The receiving terminal can establish an initial connection using the S-SSB or sidelink SS / PSBCH block received from the transmitting terminal. After the transmitting terminal transmits an S-SSB to the receiving terminal, the transmitting terminal does not receive any separate feedback regarding the S-SSB transmission from the terminal that received the S-SSB. Therefore, when a terminal that has transmitted an S-SSB via Type 1 channel connection transmits an SL channel / signal as its next transmission, it is necessary to define a CWS adjustment method that can be used for the next transmission.Therefore, the present invention proposes a CWS adjustment method that can be used for the next transmission by a terminal that has performed Type 1 channel access and transmitted a PSFCH or S-SSB.

[0372] As an example of the present invention, since a terminal that has transmitted an S-SSB cannot expect an explicit HARQ-ACK corresponding to the S-SSB transmission, it may be unclear what value the CWp value should be set to when transmitting an SL channel / signal as the next transmission. For example, a terminal that has transmitted an S-SSB cannot expect an explicit HARQ-ACK and cannot adjust the CWp based on the HARQ-ACK information. Therefore, if the channel access priority class of the SL channel / signal that the terminal that has transmitted the S-SSB is currently attempting to transmit has been used previously, the terminal can perform Type 1 channel access by setting the CWp value to the most recently used value.

[0373] As another example of the present invention, even in the case of a terminal that has transmitted a PSFCH, an explicit HARQ-ACK corresponding to the PSFCH transmission cannot be expected, so it may be unclear what value the CWp value should be set to when transmitting an SL channel / signal as the next transmission. For example, a terminal that has transmitted a PSFCH cannot expect an explicit HARQ-ACK and cannot adjust the CWp based on the HARQ-ACK information. Therefore, if the channel access priority class of the SL channel / signal that the terminal is currently attempting to transmit has been used previously, the terminal that has transmitted a PSFCH can perform Type 1 channel access by setting the CWp value to the most recently used value.

[0374] As yet another example of the present invention, a terminal that receives a PSSCH can perform Type 1 channel access to the terminal that transmitted the PSSCH, transmit a PSFCH, and then transmit an SL channel / signal as the next transmission. In this case, a retransmission of the PSSCH transmission corresponding to the PSFCH transmission occurs, and the terminal that transmitted the PSFCH may receive the PSSCH retransmission. In this case, the terminal considers that the PSSCH retransmission has occurred as an implicit response to the previously transmitted PSFCH, and can increase the CWS within the next allowed value range. Meanwhile, if the terminal that previously transmitted the PSFCH receives a PSSCH or PSCCH as a new transmission rather than a retransmission, the terminal that intends to transmit the PSFCH (as the next transmission) can reset the CWS to the minimum value.

[0375] Although the methods and systems of the present invention have been described in connection with particular embodiments, some or all of their components or operations may be implemented using a computing system having a general-purpose hardware architecture.

[0376] The above description of the present invention is for illustrative purposes only, and those skilled in the art will understand that the present invention can be easily modified into other specific forms without changing the technical spirit or essential features of the present invention. Therefore, the above-described embodiments should be understood to be illustrative in all respects and not restrictive. For example, each component described as a single component may be implemented in a distributed form, and similarly, each component described as a distributed component may be implemented in a combined form.

[0377] The scope of the present invention is indicated by the claims set forth below rather than by the above detailed description, and any modifications or variations derived from the meaning and scope of the claims and their equivalents should be construed as being within the scope of the present invention. [Explanation of symbols]

[0378] 1 device 2. Terminal 11 NR technology 12 NR technology 100 devices 110 processors 120 Communication Module 121 Cellular communication interface card 122 Cellular communication interface card 123 Unlicensed Spectrum Communication Interface Card 130 memory 140 User Interface 150 display units 200 base stations 210 processor 220 Communication Module 221 Cellular communication interface card 222 Cellular communication interface card 223 Unlicensed Spectrum Communication Interface Card 230 memory

Claims

1. 1. A terminal (UE) configured to operate in a wireless communication system, comprising: a communication module; a processor configured to control the communication module; The processor: Transmitting a first sidelink (SL) communication in a channel occupancy (CO), the first sidelink (SL) communication including a physical sidelink shared channel (PSSCH) with hybrid ARQ acknowledgment (HARQ-ACK) feedback, the HARQ-ACK feedback including explicit HARQ-ACK feedback and NACK-only feedback; adjusting a contention window (CW) based on the HARQ-ACK feedback corresponding to a PSSCH in a reference period for the CO to transmit the second SL communication for which the explicit HARQ-ACK feedback is enabled; configured to transmit the second SL communication using a channel access procedure based on the adjusted CW; The reference interval is defined as the interval starting from the beginning of the CO to the end of the first slot, and at least one PSSCH with the explicit HARQ-ACK feedback is transmitted in the first SL communication.

2. The UE of claim 1 , wherein the explicit HARQ-ACK feedback includes an ACK / NACK (negative ACK).

3. The UE of claim 1 , wherein the CO is the most recent CO initiated by the UE.

4. The UE of claim 1 , wherein the CW is adjusted to a minimum value if the HARQ-ACK feedback corresponding to the PSSCH in the reference interval includes at least an ACK.

5. The UE of claim 1 , wherein if the HARQ-ACK feedback corresponding to the PSSCH in the reference interval does not include an ACK, the CW is increased to the next highest allowed value.

6. When all HARQ-ACK feedbacks corresponding to the groupcast PSSCH in the reference interval are regarded as ACKs, the CW is adjusted to a minimum value; The UE of claim 1, wherein the CW is increased to a larger allowed value if the HARQ-ACK feedback corresponding to the groupcast PSSCH in the reference period includes at least one negative acknowledgment (NACK).

7. The UE described in claim 1, wherein the first SL communication includes at least one PSSCH in which the HARQ-ACK feedback is not enabled.

8. 1. A method performed by a terminal (UE) configured to operate in a wireless communication system, comprising: transmitting a first sidelink (SL) communication in a channel occupancy (CO), the first SL communication comprising a physical sidelink shared channel (PSSCH) with hybrid ARQ acknowledgment (HARQ-ACK) feedback, the HARQ-ACK feedback comprising explicit HARQ-ACK feedback and NACK-only feedback; adjusting a contention window (CW) based on the HARQ-ACK feedback corresponding to a PSSCH in a reference interval for the CO to transmit the second SL communication for which explicit HARQ-ACK feedback is enabled; transmitting the second SL communication using a channel access procedure based on the adjusted CW; The method, wherein the reference interval is defined as the interval starting from the beginning of the CO to the end of the first slot, and at least one PSSCH with the explicit HARQ-ACK feedback is transmitted in the first SL communication.

9. The method of claim 8, wherein the explicit HARQ-ACK feedback includes an ACK / NACK (negative ACK).

10. The method of claim 8 , wherein the CO is the most recent CO initiated by the UE.

11. The method of claim 8, wherein the CW is adjusted to a minimum value if the HARQ-ACK feedback corresponding to the PSSCH in the reference interval includes at least an ACK.

12. The method of claim 8, wherein if the HARQ-ACK feedback corresponding to the PSSCH in the reference interval does not contain an ACK, the CW is increased to the next highest allowed value.

13. The method of claim 12, wherein the CW is adjusted to a minimum value when all HARQ-ACK feedbacks corresponding to the groupcast PSSCH in the reference interval are regarded as ACKs; The method of claim 8, wherein the CW is increased to a larger allowed value if the HARQ-ACK feedback corresponding to the groupcast PSSCH in the reference interval includes at least one negative acknowledgment (NACK).

14. The method described in claim 8, wherein the first SL communication includes at least one PSSCH in which the HARQ-ACK feedback is not enabled.

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