Method and apparatus for transmitting signal in wireless communication system

Abstract

The present invention relates to a wireless communication system and, more particularly, to a method and a wireless device therefor, the method comprising the steps of: transmitting an SL multicast transmission to a plurality of terminals; identifying reception response results of the plurality of terminals for the SL multicast transmission by monitoring a feedback signal in a PSFCH opportunity corresponding to the SL multicast transmission; and configuring a CWS for channel access of the SL transmission after the SL multicast transmission based on the reception response results of the plurality of terminals, in which the CWS is configured to have a larger value than a previous CWS if the reception response results of the plurality of terminals include even one NACK, and the CWS is reset to a CWS minimum value if the reception response results of the plurality of terminals are all considered as ACK.

Description

Technical Field

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

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

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

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

[0005] In order to reduce the path loss of radio waves and increase the transmission distance of radio waves in the mmWave band, in the 5G communication system, beamforming, massive multiple input / output (massive MIMO), full-dimensional MIMO (FD-MIMO), array antennas, analog beamforming, hybrid beamforming combining analog beamforming and digital beamforming, and massive antenna technology are discussed. In addition, for the network improvement of the system, in the 5G communication system, technology development related to evolved 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), mobile networks, cooperative communication, coordinated multipoint (CoMP), interference cancellation, etc. is being carried out. In addition, in the 5G system, hybrid FSK and QAM modulation (FQAM) and sliding window superposition coding (SWSC) as advanced coding modulation (ACM) schemes and filter bank multi-carrier (FBMC), non-orthogonal multiple access (NOMA) and sparse code multiple access (SCMA) as advanced connection technologies are being developed.

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

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

[0008] Sidelink (SL) refers to a communication scheme in which a direct link is established between user equipments (UEs), and the UEs directly exchange voice or data with each other without the intervention of a base station (BS). SL is considered a solution to reduce the burden on base stations due to the rapid increase in data traffic.

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

[0010] As more and more communication devices require greater communication capacity, there is a demand for mobile broadband communication improved from the legacy radio access technology (RAT). Therefore, a communication system considering services or UEs that are sensitive to reliability and latency is under discussion. The next generation radio access technology considering enhanced mobile broadband communication, massive MTC, ultra-reliable and low-latency communication (URLLC), etc. can be called a new radio access technology (RAT) or a new radio (NR). Even in NR, vehicle-to-everything (V2X) communication can be supported.

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

[0012] Technical issues

[0013] The present disclosure is intended to provide a method for efficiently transmitting a signal in a wireless communication system and a device using the method. Specifically, the present disclosure is intended to provide a channel access method for efficiently performing transmission in a wireless communication system and a device using the method.

[0014] Technical Solution

[0015] According to one aspect of the present disclosure, a user equipment (UE) for use in a wireless communication system is provided, the UE including a communication module, and a processor configured to control the communication module, wherein the processor is configured to perform sidelink (SL) multicast transmission to multiple UEs based on a channel access process using a first contention window size (CWS), identify reception response results of multiple UEs for the SL multicast transmission by monitoring a feedback signal in a physical sidelink feedback channel (PSFCH) opportunity corresponding to the SL multicast transmission, and configure a CWS for channel access of the SL transmission after the SL multicast transmission based on the reception response results of the multiple UEs, wherein, in a case where the reception response results of the multiple UEs include even one negative acknowledgment (NACK), the CWS is configured to have a value greater than the first CWS, and in a case where the reception response results of the multiple UEs are regarded as all ACKs, the CWS is reset to the CWS minimum value.

[0016] According to another aspect of the present disclosure, a method for use by a UE in a wireless communication system is provided, the method comprising: performing sidelink (SL) multicast transmission to multiple UEs based on a channel access process using a first contention window size (CWS); identifying reception response results of multiple UEs for the SL multicast transmission by monitoring a feedback signal in a physical sidelink feedback channel (PSFCH) opportunity corresponding to the SL multicast transmission; and configuring a CWS for channel access of SL transmission after the SL multicast transmission based on the reception response results of the multiple UEs, wherein, in a case where the reception response results of the multiple UEs include even one negative acknowledgment (NACK), the CWS is configured to have a value greater than the first CWS, and in a case where the reception response results of the multiple UEs are regarded as all ACKs, the CWS is reset to a CWS minimum value.

[0017] Preferably, the case where the reception response results of the plurality of UEs include at least one NACK may include a case where NACK is detected in a PSFCH opportunity.

[0018] Preferably, the case where the reception response results of multiple UEs are regarded as all ACKs may include a case where NACK is not detected in the PSFCH opportunity.

[0019] Preferably, a NACK-only feedback scheme may be configured for SL multicast transmission.

[0020] Preferably, SL multicast transmission can be performed through the physical sidelink shared channel (PSSCH).

[0021] Preferably, SL transmission can be performed through the physical sidelink shared channel (PSSCH).

[0022] Preferably, the UE may be configured to perform a backoff at the time of channel access for SL transmission based on a counter value randomly selected within the CWS.

[0023] Preferably, in case the CWS is configured to have a greater value than the first CWS, the CWS of all priority categories are configured to have the next greater value greater than the current CWS among the CWS values ​​allowed for each priority category.

[0024] Preferably, in case of resetting the CWS to the minimum CWS value, the CWS of all priority categories are configured to have the minimum value of the CWS corresponding to each priority category.

[0025] Preferably, the wireless communication system may include a 3rd Generation Partnership Project (3GPP) New Radio (NR) based wireless communication system, and the channel access procedure may include a Type 1 Channel Access Procedure (CAP).

[0026] According to another aspect of the present disclosure, a UE used in a wireless communication system is provided, the UE including a communication module and a processor, the processor being configured to control the communication module, wherein the processor is configured to perform a first side link (SL) transmission based on a channel access process using a first contention window size (CWS), and to perform a channel access process using a second CWS in order to attempt a second SL transmission after the first SL transmission, wherein, in a case where hybrid automatic repeat request acknowledgment (HARQ-ACK) feedback is enabled for the first SL transmission, the second CWS is reset to a minimum value based on a HARQ-ACK feedback result corresponding to the first SL transmission, or is configured to have a value greater than the first CWS, and in a case where the HARQ-ACK feedback is disabled for the first SL transmission, the second CWS is adjusted to have the same value as the CWS used for the most recent third SL transmission before the first SL transmission.

[0027] Preferably, whether HARQ-ACK feedback is enabled / disabled is indicated by sidelink control information (SCI) corresponding to the first SL transmission.

[0028] Advantageous Effects of the Invention

[0029] The present disclosure provides a method for efficiently transmitting a signal in a wireless communication system and a device using the method. In addition, the present disclosure provides a channel access method for efficiently performing transmission in a wireless communication system and a device using the method.

[0030] Effects obtainable from the present disclosure are not limited to the above-mentioned effects, and other effects not mentioned will be clearly understood from the following description by those skilled in the art to which the present disclosure belongs. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 An example of a radio frame structure used in a wireless communication system is illustrated;

[0032] Figure 2 An example of a downlink (DL) / uplink (UL) time slot structure in a wireless communication system is illustrated;

[0033] Figure 3 is a diagram for explaining physical channels used in a 3GPP system and a typical signal transmission method using the physical channels;

[0034] Figure 4 FIG. 1 illustrates an SS / PBCH block for initial cell access in a 3GPP NR system;

[0035] Figure 5 FIGURE 1 illustrates a process for transmitting control information and control channels in a 3GPP NR system;

[0036] Figure 6 FIG. 1 illustrates a control resource set (CORESET) in which a physical downlink control channel (PUCCH) may be transmitted in a 3GPP NR system;

[0037] Figure 7 A method for configuring a PDCCH search space in a 3GPP NR system is illustrated;

[0038] Figure 8 is a conceptual diagram illustrating carrier aggregation;

[0039] Fig. 9 is a diagram for explaining signal carrier communication and multi-carrier communication;

[0040] Fig.10 is a diagram showing an example in which a cross-carrier scheduling technique is applied;

[0041] Fig.11 Figure 1 shows the New Radio Unlicensed (NR-U) service environment;

[0042] Fig.12 Illustrate a communication method (e.g., wireless LAN) operating in an existing unlicensed frequency band;

[0043] Fig.13 Figure 4 shows a channel access process based on LBT category 4;

[0044] Fig.14 is a block diagram illustrating the configuration of a UE and a base station according to an embodiment of the present invention;

[0045] Fig.15 An example of a channel occupancy time (COT) configuration and corresponding operation is illustrated;

[0046] Fig.16 An example of a side link (SL) communication process is illustrated; and

[0047] Fig.17 and 18 An example of a channel access method according to the present disclosure is illustrated. DETAILED DESCRIPTION

[0048] The terms used in the specification adopt the currently widely used general terms as much as possible by considering the functions in the present invention, but these terms may be changed according to the intentions, habits and emergence of new technologies of the technicians in the field. In addition, in certain cases, there are terms arbitrarily selected by the applicant, and in this case, their meanings will be described in the corresponding description part of the present invention. Therefore, it is intended to disclose that the terms used in the specification should not be analyzed based only on the names of the terms, but should be analyzed based on the substantial meanings of the terms and contents in the entire specification.

[0049] Throughout the specification and the claims that follow, when it is described that an element is "connected" to another element, the element may be "directly connected" to the other element or "electrically connected" to the other element through a third element. In addition, unless explicitly described to the contrary, the word "comprising" will be understood to imply the inclusion of the elements without implying the exclusion of any other elements. Furthermore, in some exemplary embodiments, limitations such as "greater than or equal to" or "less than or equal to" based on a specific threshold value may be appropriately replaced with "greater than" or "less than", respectively.

[0050] The following technologies can be used in various wireless access systems: such as code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier-FDMA (SC-FDMA), etc. CDMA can be implemented by wireless technologies such as Universal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA can be implemented by wireless technologies such as Global System for Mobile Communications (GSM) / General Packet Radio Service (GPRS) / Enhanced Data Rates for GSM Evolution (EDGE). OFDMA can be implemented by wireless technologies such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, Evolved UTRA (E-UTRA), etc. UTRA is part of Universal Mobile Telecommunications System (UMTS). The 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) is a part of Evolved UMTS (E-UMTS) using Evolved UMTS Terrestrial Radio Access (E-UTRA), and LTE Advanced (A) is an evolved version of 3GPP LTE. 3GPP New Radio (NR) is a system designed separately from LTE / LTE-A, and is a system for supporting enhanced mobile broadband (eMBB), ultra-reliable low-latency communication (URLLC), and massive machine type communication (mMTC) services as requirements of IMT-2020. For the sake of clear description, 3GPP NR is mainly described, but the technical idea of ​​the present invention is not limited thereto.

[0051] Unless otherwise specified herein, the base station may include a next generation node B (gNB) defined in 3GPP NR. In addition, unless otherwise specified, the terminal may include a user equipment (UE). In the following, in order to help understand the description, each content is described separately by the embodiment, but each embodiment may be used in combination with each other. In this specification, the configuration of the UE may indicate the configuration by the base station. In more detail, the base station may configure the value of a parameter used in the operation of the UE or the wireless communication system by sending a channel or a signal to the UE.

[0052] Figure 1 An example of a radio frame structure used in a wireless communication system is illustrated.

[0053] refer to Figure 1 , the radio frame (or radio frame) used in the 3GPP NR system may have a 10ms (Δf max N f / 100)*T c ) length. In addition, the wireless frame includes 10 subframes (SF) of equal size. Here, Δf max =480*10 3 Hz,Nf =4096,T c =1 / (Δf ref *N f,ref ), Δf ref =15*10 3 Hz, and N f,ref =2048. Numbers from 0 to 9 can be assigned to 10 subframes in one radio frame respectively. Each subframe has a length of 1 ms and can include one or more time slots according to the subcarrier spacing. More specifically, in the 3GPP NR system, the subcarrier spacing that can be used is 15*2 μ kHz, and μ can have a value of μ=0 to 4 as a subcarrier spacing configuration. That is, 15kHz, 30kHz, 60kHz, 120kHz, and 240kHz can be used for subcarrier spacing. One subframe with a length of 1ms may include 2 μ time slots. In this case, the length of each time slot is 2 -μ ms. It can be from 0 to 2 μ -1 are assigned to the 2 μ In addition, the time slots from 0 to 10*2 μ Numbers of -1 are respectively allocated to time slots in a radio frame. Time resources may be distinguished by at least one of a radio frame number (also referred to as a radio frame index), a subframe number (also referred to as a subframe index), and a time slot number (or a time slot index).

[0054] Figure 2 An example of a downlink (DL) / uplink (UL) time slot structure in a wireless communication system is illustrated. In particular, Figure 2 The structure of the resource grid of the 3GPP NR system is shown.

[0055] There is one resource grid per antenna port. Figure 2 , a time slot includes multiple orthogonal frequency division multiplexing (OFDM) symbols in the time domain and multiple resource blocks (RBs) in the frequency domain. An OFDM symbol also refers to a symbol interval. Unless otherwise specified, an OFDM symbol may be referred to as a symbol. An RB includes 12 consecutive subcarriers in the frequency domain. Reference Figure 2 , the signal transmitted from each time slot can be composed of N size,μ grid,x *N RB sc subcarriers and N slot symb Here, when the signal is a DL signal, x=DL, and when the signal is a UL signal, x=UL. N size,μ grid,xrepresents the number of resource blocks (RBs) according to the subcarrier spacing component μ (x is DL or UL), and N slot symb N represents the number of OFDM symbols in a time slot. RB sc is the number of subcarriers constituting one RB and N RB sc = 12. The OFDM symbol may be called a cyclic shift OFDM (CP-OFDM) symbol or a discrete Fourier transform spread OFDM (DFT-s-OFDM) symbol according to a multiple access scheme.

[0056] The number of OFDM symbols included in one slot may vary depending on the length of the cyclic prefix (CP). For example, in the case of a normal CP, one slot includes 14 OFDM symbols, but in the case of an extended CP, one slot may include 12 OFDM symbols. In a specific embodiment, the extended CP may be used only at a 60kHz subcarrier spacing. Figure 2 In the embodiment, for the convenience of description, one time slot is configured with 14 OFDM symbols as an example, but the embodiments of the present disclosure can be applied to time slots with different numbers of OFDM symbols in a similar manner. Figure 2 , each OFDM symbol includes N size,μ grid,x *N RB sc subcarriers. The types of subcarriers can be divided into data subcarriers for data transmission, reference signal subcarriers for transmission of reference signals, and guard bands. The carrier frequency is also called the center frequency (fc).

[0057] An RB can be composed of N RB sc For reference, a resource configured with one OFDM symbol and one subcarrier may be referred to as a resource element (RE) or tone. Thus, one RB can be configured with N slot symb *N RB sc resource elements. Each resource element in the resource grid can be uniquely defined by a pair of indices (k, l) in a time slot. k can be a random number from 0 to N in the frequency domain. size,μ grid,x *N RB sc –1 is the assigned index, and l can be from 0 to N in the time domain slot symb –1 The assigned index.

[0058] In order for a UE to receive or send signals from or to a base station, the UE's time / frequency may be synchronized with that of the base station. This is because when the base station and the UE are synchronized, the UE is able to determine the time and frequency parameters necessary to demodulate the DL signal and send the UL signal at the correct time.

[0059] Each symbol of a radio frame used in a time division duplex (TDD) or unpaired spectrum may be configured with at least one of a DL symbol, a UL symbol, and a flexible symbol. A radio frame used as a DL carrier in a frequency division duplex (FDD) or paired spectrum may be configured with a DL symbol or a flexible symbol, and a radio frame used as a UL carrier may be configured with a UL symbol or a flexible symbol. In a DL symbol, DL transmission is possible, but UL transmission is unavailable. In a UL symbol, UL transmission is possible, but DL transmission is unavailable. A flexible symbol may be determined to be used as DL or UL according to a signal.

[0060] Information about the type of each symbol, i.e., information indicating any one of a DL symbol, a UL symbol, and a flexible symbol, may be configured using a cell-specific or common radio resource control (RRC) signal. In addition, information about the type of each symbol may be additionally configured using a UE-specific or dedicated RRC signal. The base station notifies, by using a cell-specific RRC signal, i) the period of the cell-specific time slot configuration, ii) the number of time slots having only DL symbols from the beginning of the period of the cell-specific time slot configuration, iii) the number of DL symbols from the first symbol of the time slot immediately following the time slot having only DL symbols, iv) the number of time slots having only UL symbols from the end of the period of the cell-specific time slot configuration, and v) the number of UL symbols from the last symbol of the time slot immediately preceding the time slot having only UL symbols. Here, a symbol that is not configured with any one of the UL symbol and the DL symbol is a flexible symbol.

[0061] When the information about the symbol type is configured with a UE-specific RRC signal, the base station may signal whether the flexible symbol is a DL symbol or a UL symbol with a cell-specific RRC signal. In this case, the UE-specific RRC signal cannot change the DL symbol or UL symbol configured with the cell-specific RRC signal to another symbol type. The UE-specific RRC signal may signal the N of the corresponding time slot for each time slot. slot symb The number of DL symbols among the symbols and the corresponding time slot N slot symbThe number of UL symbols among the symbols. In this case, the DL symbols of the time slot can be continuously configured with the first symbol to the i-th symbol of the time slot. In addition, the UL symbols of the time slot can be continuously configured with the j-th symbol to the last symbol of the time slot (where i < j). In the time slot, the symbol that is not configured with any of the UL symbols and DL symbols is a flexible symbol.

[0062] The type of symbol configured with the above RRC signal can be referred to as semi-static DL / UL configuration. In the previously configured semi-static DL / UL configuration with the RRC signal, the flexible symbol can be indicated as a DL symbol, a UL symbol, or a flexible symbol through the dynamic time slot format information (SFI) sent on the physical downlink control channel (PDCCH). In this case, the DL symbol or UL symbol configured with the RRC signal will not be changed to another symbol type. Table 1 illustrates the dynamic SFI that the base station can indicate to the UE.

[0063] [Table 1]

[0064]

[0065] In Table 1, D represents a DL symbol, U represents a UL symbol, and X represents a flexible symbol. As shown in Table 1, up to two DL / UL switches are allowed in one time slot.

[0066] Figure 3 is a diagram for explaining the physical channels used in a 3GPP system (e.g., NR) and a typical signal transmission method using the physical channels.

[0067] If the power of the UE is turned on or the UE camps on a new cell, the UE performs initial cell search (S101). Specifically, the UE can synchronize with the BS during the initial cell search. To this end, the UE can receive the primary synchronization signal (PSS) and the secondary synchronization signal (SSS) from the base station to synchronize with the base station and obtain information such as the cell ID. Thereafter, the UE is able to receive the physical broadcast channel from the base station and obtain the broadcast information in the cell.

[0068] After the initial cell search is completed, the UE receives the physical downlink shared channel (PDSCH) according to the physical downlink control channel (PDCCH) and the information in the PDCCH, so that the UE can obtain more specific system information than the system information obtained through the initial cell search (S102). Here, the system information received by the UE is the cell common system information for the normal operation of the UE in the physical layer of the radio resource control (RRC), and is referred to as the remaining system information, or is referred to as the system information block (SIB)1.

[0069] When the UE initially accesses the base station or does not have radio resources for signal transmission (i.e., the UE is in RRC_IDLE mode), the UE can perform a random access procedure on the base station (operations S103 to S106). First, the UE can send a preamble through a physical random access channel (PRACH) (S103) and receive a response message for the preamble from the base station through a PDCCH and a corresponding PDSCH (S104). When the UE receives a valid random access response message, the UE sends data including an identifier of the UE, etc. to the base station through a physical uplink shared channel (PUSCH) indicated by a UL grant sent from the base station through the PDCCH (S105). Next, the UE waits for the reception of the PDCCH as an indication of the base station for conflict resolution. If the UE successfully receives the PDCCH through the UE's identifier (S106), the random access procedure is terminated. The UE can obtain UE-specific system information for normal operation of the UE in the physical layer in the RRC layer during the random access procedure. When the UE obtains the UE-specific system information, the UE enters the RRC connected mode (RRC_CONNECTED mode).

[0070] The RRC layer is used to generate or manage messages for controlling the connection between the UE and the radio access network (RAN). In more detail, in the RRC layer, the base station and the UE can perform broadcasting cell system information required for each UE in the cell, management of mobility and switching, measurement reporting of the UE, storage management including UE capability management and device management. Generally, because the update period of the signal transmitted in the RRC layer is longer than the transmission time interval (TTI) in the physical layer, the RRC signal is not changed and maintained for a relatively long interval.

[0071] After the above process, the UE receives PDCCH / PDSCH (S107) and sends a physical uplink shared channel (PUSCH) / physical uplink control channel (PUCCH) (S108) as a general UL / DL signal transmission process. In particular, the UE can receive downlink control information (DCI) through the PDCCH. The DCI may include control information such as resource allocation information for the UE. In addition, the format of the DCI may vary according to the intended use. The uplink control information (UCI) sent by the UE to the base station through the UL includes DL / UL ACK / NACK signals, channel quality indicators (CQI), precoding matrix indexes (PMI), rank indicators (RI), etc. Here, CQI, PMI and RI may be included in channel state information (CSI). In the 3GPP NR system, the UE can send control information such as the above-mentioned HARQ-ACK and CSI through PUSCH and / or PUCCH.

[0072] Figure 4 Illustration of SS / PBCH blocks used for initial cell access in a 3GPP NR system.

[0073] When the power is turned on or when you want to access a new cell, the UE can obtain time and frequency synchronization with the cell and perform an initial cell search process. The UE can detect the physical cell identifier NcellID of the cell during the cell search process. To this end, the UE can receive synchronization signals from the base station, such as the primary synchronization signal (PSS) and the secondary synchronization signal (SSS), and synchronize with the base station. In this case, the UE is able to obtain information such as a cell identifier (ID).

[0074] refer to Figure 4 (a) of the present invention will describe the synchronization signal (SS) in more detail. The synchronization signal can be classified into PSS and SSS. PSS can be used to obtain time domain synchronization and / or frequency domain synchronization, such as OFDM symbol synchronization and time slot synchronization. SSS can be used to obtain frame synchronization and cell group ID. Figure 4 (a) and Table 2, the SS / PBCH block can be configured with 20 consecutive RBs (=240 subcarriers) on the frequency axis, and can be configured with 4 consecutive OFDM symbols on the time axis. In this case, in the SS / PBCH block, the PSS is sent in the first OFDM symbol and the SSS is sent in the third OFDM symbol through the 56th to 182nd subcarriers. Here, the lowest subcarrier index of the SS / PBCH block is numbered from 0. In the first OFDM symbol in which the PSS is sent, the base station does not send signals through the remaining subcarriers, i.e., the 0th to 55th subcarriers and the 183rd to 239th subcarriers. In addition, in the third OFDM symbol in which the SSS is sent, the base station does not send signals through the 48th to 55th subcarriers and the 183rd to 191st subcarriers. The base station sends the physical broadcast channel (PBCH) through the remaining REs in the SS / PBCH block except for the above signals.

[0075] [Table 2]

[0076]

[0077] The SS allows a total of 1008 unique physical layer cell IDs to be grouped into 336 physical layer cell identifier groups, each group including three unique identifiers, through a combination of three PSS and SSS, specifically so that each physical layer cell ID will be part of only one physical layer cell identifier group. cell ID =3N (1) ID +N (2) IDThe physical layer cell identifier group can be indicated by an index N ranging from 0 to 335. (1) ID and an index N ranging from 0 to 2 indicating a physical layer identifier in the physical layer cell identifier group (2) ID The UE can detect the PSS and identify one of the three unique physical layer identifiers. In addition, the UE can detect the SSS and identify one of the 336 physical layer cell IDs associated with the physical layer identifier. In this case, the sequence d of the PSS PSS (n) are as follows.

[0078] d PSS (n) = 1-2x(m)

[0079]

[0080] 0≤n<127

[0081] Here, x(i+7)=(x(i+4)+x(i))mod2 and is given as

[0082] [x(6) x(5) x(4) x(3) x(2) x(1) x(0)]=[1 1 1 0 1 1 0].

[0083] In addition, the sequence d of SSS SSS (n) are as follows.

[0084] d sss (n) = [1-2x 0 ((n+m 0 )mod127)][1-2x 1 ((n+m 1 )mod127)]

[0085]

[0086] 0≤n<127

[0087] here, and is given as

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

[0089] [x 1(6) x 1 (5) x 1 (4) x 1 (3) x 1 (2) x 1 (1) x 1 (0)] = [0 0 0 0 0 0 1].

[0090] A radio frame with a length of 10 ms can be divided into s Length of two half frames. Figure 4 (b) of the embodiment will describe the time slot in which the SS / PBCH block is sent in each half frame. The time slot in which the SS / PBCH block is sent may be any one of cases A, B, C, D and E. In case A, the subcarrier spacing is 15kHz and the starting time point of the SS / PBCH block is the ({2,8}+14*n)th symbol. In this case, at a carrier frequency of 3GHz or lower, n=0 or 1. In addition, at a carrier frequency higher than 3GHz and lower than 6GHz, it may be n=0, 1, 2, 3. In case B, the subcarrier spacing is 30kHz and the starting time point of the SS / PBCH block is {4,8,16,20}+28*n. In this case, at a carrier frequency of 3GHz or lower, n=0. In addition, at a carrier frequency higher than 3GHz and lower than 6GHz, it may be n=0, 1. In case C, the subcarrier spacing is 30kHz and the starting time point of the SS / PBCH block is the ({2,8}+14*n)th symbol. In this case, at a carrier frequency of 3 GHz or lower, n=0 or 1. In addition, at a carrier frequency higher than 3 GHz and lower than 6 GHz, it can be n=0, 1, 2, 3. In case D, the subcarrier spacing is 120 kHz and the starting time point of the SS / PBCH block is the ({4, 8, 16, 20} + 28*n)th symbol. In this case, at a carrier frequency of 6 GHz or higher, n=0, 1, 2, 3, 5, 6, 7, 8, 10, 11, 12, 13, 15, 16, 17, 18. In case E, the subcarrier spacing is 240 kHz and the starting time point of the SS / PBCH block is the ({8, 12, 16, 20, 32, 36, 40, 44} + 56*n)th symbol. In this case, at a carrier frequency of 6 GHz or higher, n=0, 1, 2, 3, 5, 6, 7, 8.

[0091] Figure 5 This figure shows the process of sending control information and control channels in the 3GPP NR system. Figure 5(a), the base station may add a cyclic redundancy check (CRC) masked (e.g., XORed) with a radio network temporary identifier (RNTI) to control information (e.g., downlink control information (DCI)) (S202). The base station may scramble the CRC with an RNTI value determined according to the purpose / target of each control information. The common RNTI used by one or more UEs can include at least one of a system information RNTI (SI-RNTI), a paging RNTI (P-RNTI), a random access RNTI (RA-RNTI), and a transmit power control RNTI (TPC-RNTI). In addition, the UE-specific RNTI may include at least one of a cell temporary RNTI (C-RNTI) and a CS-RNTI. Thereafter, the base station may perform rate matching (S206) according to the amount of resources used for PDCCH transmission after performing channel coding (e.g., polarity coding) (S204). Thereafter, the base station may multiplex DCI based on a PDCCH structure based on a control channel element (CCE) (S208). In addition, the base station may apply additional processes such as scrambling, modulation (e.g., QPSK), interleaving, etc. to the multiplexed DCI (S210), and then map the DCI to the resource to be transmitted. CCE is a basic resource unit for PDCCH, and one CCE may include multiple (e.g., six) resource element groups (REGs). One REG may be configured with multiple (e.g., 12) REs. The number of CCEs used for one PDCCH may be defined as an aggregation level. In a 3GPP NR system, an aggregation level of 1, 2, 4, 8, or 16 may be used. Figure 5 B is a diagram related to multiplexing of a CCE aggregation level and a PDCCH, and illustrates the type of CCE aggregation level for one PDCCH and CCEs transmitted in a control region accordingly.

[0092] Figure 6 Illustration of a control resource set (CORESET) in which a physical downlink control channel (PUCCH) can be transmitted in a 3GPP NR system.

[0093] CORESET is a time-frequency resource in which PDCCH (i.e., a control signal for UE) is transmitted. In addition, the search space to be described later can be mapped to one CORESET. Therefore, the UE can monitor the time-frequency domain designated as the CORESET instead of monitoring all frequency bands for PDCCH reception, and decode the PDCCH mapped to the CORESET. The base station can configure one or more CORESETs for each cell to the UE. The CORESET can be configured with a maximum of three consecutive symbols on the time axis. In addition, the CORESET can be configured in units of six consecutive PRBs on the frequency axis. Figure 5 In the embodiment of FIG. 1 , CORESET#1 is configured with continuous PRBs, while CORESET#2 and CORESET#3 are configured with discontinuous PRBs. A CORESET can be located in any symbol in a time slot. For example, in Figure 5 In an embodiment of the present invention, CORESET#1 starts at the first symbol of the time slot, CORESET#2 starts at the fifth symbol of the time slot, and CORESET#9 starts at the ninth symbol of the time slot.

[0094] Figure 7 A method for setting a PDCCH search space in a 3GPP NR system is illustrated.

[0095] In order to send the PDCCH to the UE, each CORESET may have at least one search space. In an embodiment of the present disclosure, the search space is a set of all time-frequency resources (hereinafter referred to as PDCCH candidates) that can be used to send the PDCCH of the UE. The search space may include a common search space that requires UEs of 3GPP NR to search together and a UE-specific search space or a UE-specific search space that requires a specific UE to search. In the common search space, the UE may monitor the PDCCH that is set so that all UEs in the cell belonging to the same base station search together. In addition, a UE-specific search space may be set for each UE so that the UE monitors the PDCCH allocated to each UE at a search space position that is different according to the UE. In the case of a UE-specific search space, since the limited control region to which the PDCCH can be allocated, the search space between the UEs may partially overlap and be allocated. Monitoring the PDCCH includes blind decoding of the PDCCH candidates in the search space. When the blind decoding is successful, it can be expressed as (successfully) detecting / receiving the PDCCH, and when the blind decoding fails, it can be expressed as not detecting / not receiving or not successfully detecting / receiving the PDCCH.

[0096] For convenience of explanation, a PDCCH that is scrambled with a group common (GC) RNTI previously known to one or more UEs in order to send DL control information to one or more UEs is referred to as a group common (GC) PDCCH or a common PDCCH. In addition, a PDCCH that is scrambled with an RNTI of a specific terminal that is already known to a specific UE in order to send UL scheduling information or DL ​​scheduling information to a specific UE is referred to as a PDCCH of a specific UE. A common PDCCH may be included in a common search space, and a UE-specific PDCCH may be included in a common search space or a UE-specific PDCCH.

[0097] The base station may signal each UE or UE group through the PDCCH about information related to resource allocation of the paging channel (PCH) and the downlink shared channel (DL-SCH) as transmission channels (i.e., DL grant) or information related to resource allocation of the uplink shared channel (UL-SCH) and the hybrid automatic repeat request (HARQ) (i.e., UL grant). The base station may send the PCH transport block and the DL-SCH transport block through the PDSCH. The base station may send data excluding specific control information or specific service data through the PDSCH. In addition, the UE may receive data excluding specific control information or specific service data through the PDSCH.

[0098] The base station can include information in the PDCCH about which UE (one or more UEs) the PDSCH data is sent to and how the PDSCH data will be received and decoded by the corresponding UE, and send the PDCCH. For example, assume that the DCI sent on a specific PDCCH is CRC-masked with RNTI "A", and the DCI indicates that the PDSCH is allocated to radio resources "B" (e.g., frequency position) and indicates transmission format information "C" (e.g., transport block size, modulation scheme, coding information, etc.). The UE monitors the PDCCH using the RNTI information that the UE has. In this case, if there is a UE that performs blind decoding on the PDCCH using the "A" RNTI, the UE receives the PDCCH and receives the PDSCH indicated by "B" and "C" through the information of the received PDCCH.

[0099] Table 3 shows an embodiment of a physical uplink control channel (PUCCH) used in a wireless communication system.

[0100] [Table 3]

[0101] PUCCH format OFDM symbol length Number of bits 0 1-2 ≤2 1 4-14 ≤2 2 1-2 ＞2 3 4-14 ＞2 4 4-14 ＞2

[0102] PUCCH can be used to transmit the following UL control information (UCI).

[0103] - Scheduling Request (SR): information for requesting UL UL-SCH resources.

[0104] -HARQ-ACK: A response to the PDCCH (indicating a DL SPS release) and / or a response to a DL transport block (TB) on the PDSCH. HARQ-ACK indicates whether the information successfully sent on the PDCCH or PDSCH is received. The HARQ-ACK response includes a positive ACK (abbreviated as ACK), a negative ACK (hereinafter referred to as NACK), a discontinuous transmission (DTX), or NACK / DTX. Here, the term HARQ-ACK is used in a mixed manner with HARQ-ACK / NACK and ACK / NACK. Generally, ACK can be represented by a bit value of 1, while NACK can be represented by a bit value of 0.

[0105] - Channel State Information (CSI): Feedback information about the DL channel. The UE generates it based on the CSI-Reference Signal (RS) sent by the base station. Multiple Input Multiple Output (MIMO) related feedback information includes Rank Indicator (RI) and Precoding Matrix Indicator (PMI). The CSI can be divided into CSI Part 1 and CSI Part 2 according to the information indicated by the CSI.

[0106] In the 3GPP NR system, five PUCCH formats can be used to support various service scenarios, various channel environments, and frame structures.

[0107] PUCCH format 0 is a format capable of delivering 1-bit or 2-bit HARQ-ACK information or SR. PUCCH format 0 can be transmitted through one or two OFDM symbols on the time axis and one PRB on the frequency axis. When PUCCH format 0 is transmitted in two OFDM symbols, the same sequence on the two symbols can be transmitted through different RBs. In this case, the sequence can be a sequence that is cyclically shifted (CS) from the base sequence used in PUCCH format 0. Through this, the UE can obtain frequency diversity gain. In more detail, the UE can receive the PUCCH format 0 according to the PUCCH format 0. bit BitUCI(M bit =1 or 2) to determine the cyclic shift (CS) value m cs In addition, the CS value m can be calculated by cs The cyclic shift sequence is mapped to one OFDM symbol and 12 REs of one RB to transmit a basic sequence of length 12. When the number of cyclic shifts available to the UE is 12 and M bit =1, 1-bit UCI 0 and 1 can be mapped to two cyclic shift sequences respectively, and the cyclic shift values ​​of the two cyclic shift sequences have a difference of 6. In addition, when M bit=2, 2-bit UCI 00, 01, 11 and 10 may be mapped to four cyclic shift sequences having a difference of 3 in cyclic shift value, respectively.

[0108] PUCCH format 1 can deliver 1-bit or 2-bit HARQ-ACK information or SR. PUCCH format 1 can be transmitted through continuous OFDM symbols on the time axis and one PRB on the frequency axis. Here, the number of OFDM symbols occupied by PUCCH format 1 can be one of 4 to 14. More specifically, M bit =1 UCI is BPSK modulated. The UE can use quadrature phase shift keying (QPSK) to modulate M bit =2 for UCI. The signal is obtained by multiplying the modulated complex-valued symbol d(0) by a sequence of length 12. In this case, the sequence may be the base sequence for PUCCH format 0. The UE extends the even-numbered OFDM symbols to which PUCCH format 1 is allocated by a time axis orthogonal cover code (OCC) to send the obtained signal. PUCCH format 1 determines the maximum number of different UEs multiplexed in one RB according to the length of the OCC to be used. The demodulation reference signal (DMRS) may be extended with the OCC and mapped to the odd-numbered OFDM symbols of PUCCH format 1.

[0109] PUCCH format 2 can deliver more than 2 bits of UCI. PUCCH format 2 can be sent through one or two OFDM symbols on the time axis and one or more RBs on the frequency axis. When PUCCH format 2 is sent in two OFDM symbols, the sequences sent in different RBs through the two OFDM symbols can be the same as each other. Here, the sequence can be a plurality of modulated complex-valued symbols d(0), ..., d(M symbol -1). Here, M symbol It can be M bit / 2. Through this, the UE can obtain frequency diversity gain. More specifically, for M bit UCI(M bit >2) Perform bit-level scrambling, QPSK modulation, and map it to RBs of one or two OFDM symbols. Here, the number of RBs can be one of 1 to 16.

[0110] PUCCH format 3 or PUCCH format 4 can deliver more than 2 bits of UCI. PUCCH format 3 or PUCCH format 4 can be transmitted through continuous OFDM symbols on the time axis and one PRB on the frequency axis. The number of OFDM symbols occupied by PUCCH format 3 or PUCCH format 4 can be one of 4 to 14. Specifically, the UE uses π / 2-binary phase shift keying (BPSK) or QPSK to transmit the OFDM symbol. bit bits UCI (Mbit>2) are modulated to generate complex-valued symbols d(0) to d(M symb -1). Here, when π / 2-BPSK is used, M symb =M bit , and when using QPSK, M symb =M bit / 2. The UE may not apply block unit extension to PUCCH format 3. However, the UE may apply block unit extension to one RB (i.e., 12 subcarriers) using a PreDFT-OCC of length 12, so that PUCCH format 4 may have two or four multiplexing capabilities. The UE performs transmit precoding (or DFT precoding) on ​​the extended signal and maps it to each RE to transmit the extended signal.

[0111] In this case, the number of RBs occupied by PUCCH format 2, PUCCH format 3, or PUCCH format 4 may be determined according to the length of UCI transmitted by the UE and the maximum coding rate. When the UE uses PUCCH format 2, the UE may transmit HARQ-ACK information and CSI information together through the PUCCH. When the number of RBs that the UE may transmit is greater than the maximum number of RBs that may be used by PUCCH format 2, PUCCH format 3, or PUCCH format 4, the UE may not transmit some UCI information according to the priority of the UCI information, but may transmit only the remaining UCI information.

[0112] PUCCH format 1, PUCCH format 3, or PUCCH format 4 may be configured by RRC signaling to indicate frequency hopping in a time slot. When frequency hopping is configured, the index of the RB to be frequency hopped may be configured by RRC signaling. When PUCCH format 1, PUCCH format 3, or PUCCH format 4 is transmitted by N OFDM symbols of the time axis, the first hop may have floor(N / 2) OFDM symbols and the second hop may have ceiling(N / 2) OFDM symbols.

[0113] PUCCH format 1, PUCCH format 3 or PUCCH format 4 can be configured to be repeatedly transmitted in multiple time slots. In this case, the number K of time slots in which PUCCH is repeatedly transmitted can be configured by RRC signal. The repeatedly transmitted PUCCH must start at an OFDM symbol at a constant position in each time slot and have a constant length. When one OFDM symbol among the OFDM symbols of the time slot in which the UE should transmit the PUCCH is indicated as a DL symbol by RRC signal, the UE may not transmit the PUCCH in the corresponding time slot and delay the transmission of the PUCCH to the next time slot to transmit the PUCCH.

[0114] Meanwhile, in the 3GPP NR system, the UE can perform transmission / reception using a bandwidth equal to or less than the bandwidth of the carrier (or cell). To this end, the UE can receive a bandwidth portion (BWP) of a continuous bandwidth configured with some bandwidths in the carrier bandwidth. A UE operating according to TDD operation or in an unpaired spectrum can receive up to four DL / UL BWP pairs in one carrier (or cell). In addition, the UE can activate one DL / UL BWP pair. A UE operating according to FDD operation or in paired spectrum operation can receive up to four DL BWPs on a DL carrier (or cell) and up to four ULBWPs on a UL carrier (or cell). The UE can activate one DL BWP and one UL BWP for each carrier (or cell). The UE may not perform reception or transmission in time-frequency resources other than the activated BWP. The activated BWP may be referred to as an active BWP.

[0115] The base station may indicate the activated BWP among the BWPs configured by the UE through downlink control information (DCI). The BWP indicated by the DCI is activated, and the other configured BWPs are deactivated. In a carrier (or cell) operating with TDD, the base station may include a bandwidth part indicator (BPI) in the DCI for scheduling PDSCH or PUSCH, which indicates the BWP to be activated to change the DL / UL BWP pair of the UE. The UE may receive the DCI for scheduling PDSCH or PUSCH, and may identify the DL / UL BWP pair activated based on the BPI. For a DL carrier (or cell) operating with FDD, the base station may include a BPI indicating the BWP to be activated in the DCI for scheduling PDSCH to change the DL BWP of the UE. For a UL carrier (or cell) operating with FDD, the base station may include a BPI indicating the BWP to be activated in the DCI for scheduling PUSCH to change the UL BWP of the UE.

[0116] Figure 8 is a conceptual diagram illustrating carrier aggregation.

[0117] Carrier aggregation is a method in which a UE uses multiple frequency blocks or cells (in a logical sense) configured with UL resources (or component carriers) and / or DL ​​resources (or component carriers) as one large logical frequency band so that a wireless communication system uses a wider frequency band. One component carrier may also be referred to as a primary cell (PCell) or a secondary cell (SCell) or a primary SCell (PScell). However, hereinafter, for the convenience of description, the term "component carrier" is used.

[0118] refer to Figure 8 As an example of a 3GPP NR system, the entire system band may include up to 16 component carriers, and each component carrier may have a bandwidth of up to 400 MHz. A component carrier may include one or more physically contiguous subcarriers. Figure 8 In the figure, each component carrier is shown to have the same bandwidth, but this is only an example, and each component carrier may have a different bandwidth. In addition, although each component carrier is shown as being adjacent to each other on the frequency axis, the drawings are shown in a logical concept, and each component carrier may be physically adjacent to each other, or may be spaced apart.

[0119] A different center frequency may be used for each component carrier. Alternatively, a common center frequency may be used in physically adjacent component carriers. Figure 8 In the embodiment of the present invention, all component carriers are physically adjacent, then the center frequency A can be used in all component carriers. In addition, assuming that the respective component carriers are not physically adjacent to each other, the center frequency A and the center frequency B can be used in each component carrier.

[0120] When the total system frequency band is extended by carrier aggregation, the frequency band used for communication with each UE can be defined in units of component carriers. UE A can use 100 MHz as the total system frequency band and perform communication using all five component carriers. UE B 1 ~B 5 It is possible to perform communication using only a 20 MHz bandwidth and one component carrier. 1 and C 2 The 40 MHz bandwidth and two component carriers may be used to perform communication. The two component carriers may be logically / physically adjacent or non-adjacent. 1 represents the case of using two non-adjacent component carriers, and UE C 2 Indicates the case of using two adjacent component carriers.

[0121] Fig. 9 is a diagram for explaining signal carrier communication and multi-carrier communication. In particular, Fig. 9 (a) shows a single carrier subframe structure and Fig. 9 (b) shows a multi-carrier subframe structure.

[0122] refer to Fig. 9 (a), in the FDD mode, a general wireless communication system can perform data transmission or reception through a DL frequency band and a UL frequency band corresponding thereto. In another specific embodiment, in the TDD mode, the wireless communication system can divide a radio frame into a UL time unit and a DL time unit in the time domain, and perform data transmission or reception through the UL / DL time unit. Fig. 9 (b) of the present invention can aggregate three 20MHz component carriers (CCs) into each of UL and DL, so that a bandwidth of 60MHz can be supported. Each CC may be adjacent to or not adjacent to each other in the frequency domain. Fig. 9 (b) shows the case where the bandwidth of the UL CC and the bandwidth of the DL CC are the same and symmetrical, but the bandwidth of each CC can be determined independently. In addition, asymmetric carrier aggregation with different numbers of UL CCs and DL CCs is possible. The DL / UL CC allocated / configured to a specific UE through RRC may be referred to as a serving DL / UL CC for the specific UE.

[0123] The base station can perform communication with the UE by activating some or all of the UE's serving CCs or deactivating some CCs. The base station can change the CCs to be activated / deactivated and change the number of CCs to be activated / deactivated. If the base station allocates CCs available to the UE as cell-specific or UE-specific, at least one of the allocated CCs can be deactivated unless the CC allocation for the UE is completely reconfigured or the UE is switched. One CC that is not deactivated by the UE is called a primary CC (PCC) or a primary cell (PCell), and a CC that the base station can freely activate / deactivate is called a secondary CC (SCC) or a secondary cell (SCell).

[0124] At the same time, 3GPP NR uses the concept of cells to manage radio resources. A cell is defined as a combination of DL resources and UL resources, that is, a combination of DL CCs and UL CCs. A cell may be configured with DL resources alone, or may be configured with a combination of DL resources and UL resources. When carrier aggregation is supported, the link between the carrier frequency of the DL resources (or DL ​​CC) and the carrier frequency of the UL resources (or UL CC) may be indicated by system information. The carrier frequency refers to the center frequency of each cell or CC. The cell corresponding to the PCC is called the PCell, and the cell corresponding to the SCC is called the SCell. The carrier corresponding to the PCell in the DL is the DL PCC, and the carrier corresponding to the PCell in the UL is the UL PCC. Similarly, the carrier corresponding to the SCell in the DL is the DL SCC, and the carrier corresponding to the SCell in the UL is the UL SCC. Depending on the UE capabilities, the serving cell may be configured with one PCell and zero or more SCells. In the case of a UE that is in the RRC_CONNECTED state but is not configured for carrier aggregation or does not support carrier aggregation, only one serving cell is configured with only the PCell.

[0125] As described above, the term "cell" used in carrier aggregation is distinguished from the term "cell" referring to a certain geographical area where communication services are provided by one base station or one antenna group. That is, one component carrier may also be referred to as a scheduling cell, a scheduled cell, a primary cell (PCell), a secondary cell (SCell), or a primary SCell (PScell). However, in order to distinguish between a cell representing a certain geographical area and a cell of carrier aggregation, in the present disclosure, a cell of carrier aggregation is referred to as a CC, and a cell of a geographical area is referred to as a cell.

[0126] Fig.10 is a diagram showing an example in which cross-carrier scheduling technology is applied. When cross-carrier scheduling is set, the control channel sent through the first CC can use the carrier indicator field (CIF) to schedule the data channel sent through the first CC or the second CC. The CIF is included in the DCI. In other words, a scheduling cell is set, and the DL grant / UL grant sent in the PDCCH area of ​​the scheduling cell schedules the PDSCH / PUSCH of the scheduled cell. That is, there is a search area for multiple component carriers in the PDCCH area of ​​the scheduling cell. The PCell can basically be a scheduling cell, and a specific SCell can be designated as a scheduling cell by an upper layer.

[0127] exist Fig.10In the embodiment of the present invention, it is assumed that three DL CCs are merged. Here, it is assumed that DL component carrier #0 is DL PCC (or PCell), and DL component carrier #1 and DL component carrier #2 are DL SCC (or SCell). In addition, it is assumed that DL PCC is set as a PDCCH monitoring CC. When cross-carrier scheduling is not configured by UE-specific (or UE group-specific or cell-specific) higher layer signaling, CIF is disabled, and each DL CC is able to send only the PDCCH for scheduling its PDSCH without CIF according to the NR PDCCH rule (non-cross-carrier scheduling, self-carrier scheduling). At the same time, if cross-carrier scheduling is configured by UE-specific (or UE group-specific or cell-specific) higher layer signaling, CIF is enabled, and a specific CC (e.g., DL PCC) can use CIF to send not only the PDCCH for scheduling the PDSCH of DL CC A but also the PDCCH for scheduling the PDSCH of another CC (cross-carrier scheduling). On the other hand, PDCCH is not sent in another DL CC. Therefore, the UE monitors a PDCCH not including a CIF to receive a PDSCH scheduled by a self-carrier, or monitors a PDCCH including a CIF to receive a PDSCH scheduled by a cross-carrier, according to whether cross-carrier scheduling is configured for the UE.

[0128] on the other hand, Fig. 9 and Fig.10 The subframe structure of the 3GPP LTE-A system is shown in the figure, and the same or similar configuration can be applied to the 3GPP NR system. However, in the 3GPP NR system, Fig. 9 and Fig.10 The subframes may be replaced by time slots.

[0129] <Communication Method in Unlicensed Band>

[0130] Fig.11 Figure 1 shows the service environment of New Radio Unlicensed (NR-U).

[0131] refer to Fig.11 , a service environment of NR technology 11 in the existing licensed band and unlicensed NR (NR-U) (i.e., NR technology 12 in the unlicensed band) can be provided to users. For example, in the NR-U environment, technologies such as carrier aggregation can be used to integrate NR technology 11 in the licensed band and NR technology 12 in the unlicensed band, which can contribute to the expansion of network capacity. In addition, in an asymmetric service structure with more downlink data than uplink data, NR-U can provide NR services optimized for various needs or environments. For convenience, the NR technology in the licensed band is referred to as NR-L (licensed NR), and the NR technology in the unlicensed band is referred to as NR-U (unlicensed NR).

[0132] Fig.12 A conventional communication scheme (eg, wireless LAN) operating in an unlicensed band is illustrated. Since most devices operating in an unlicensed band operate based on "Listen Before Talk" (LBT), a Clear Channel Assessment (CCA) technique of sensing a channel before data transmission is performed.

[0133] refer to Fig.12 , a wireless LAN device (e.g., an AP or a STA) checks whether a channel is busy by performing carrier sensing before sending data. When a radio signal of a predetermined strength or higher is sensed in a channel to send data, it is determined that the corresponding channel is busy, and the wireless LAN device delays access to the corresponding channel. Such a process is called a clear channel assessment, and the signal level used to decide whether a signal is sensed is called a CCA threshold. At the same time, when no radio signal is sensed in the corresponding channel or when a radio signal with a strength less than the CCA threshold is sensed, the channel is determined to be idle.

[0134] When it is determined that the channel is idle, the terminal with data to be sent performs a backoff process after a deferral duration (e.g., arbitration interframe space (AIFS), PCF IFS (PIFS), etc.). The deferral duration indicates the shortest time the terminal needs to wait after the channel is idle. The backoff process allows the terminal to further wait for a predetermined time after the deferral duration. For example, the terminal prepares while reducing the time slot time corresponding to the random number allocated to the terminal during the channel idle period in the contention window (CW), and the terminal that completely exhausts the time slot time can attempt to access the corresponding channel.

[0135] When the terminal successfully accesses the channel, the terminal can send data through the channel. After the data is successfully sent, the CW size (CWS) will be reset to the initial value (CWmin). On the contrary, when the data is not successfully sent, the CWS is increased by two times. As a result, a new random number is assigned to the terminal within a range that is twice larger than the previous random number range to perform a fallback process in the next CW. In a wireless LAN, only ACK is defined as receiving response information to data transmission. Therefore, when ACK is received with respect to data transmission, CWS is reset to the initial value, and when no feedback information is received with respect to data transmission, CWS is increased by two times.

[0136] As mentioned above, since existing communications in unlicensed bands are mainly operated based on LBT, channel access in the NR-U system also performs LBT to coexist with existing devices. Specifically, according to the presence / absence / application method of LBT, channel access methods on unlicensed bands in NR can be classified into the following four categories.

[0137] ●Category 1: No LBT

[0138] - The Tx entity does not perform the LBT procedure for transmission.

[0139] ●Category 2: LBT without random fallback

[0140] -The Tx entity senses whether the channel is idle during the first interval to perform transmission without random backoff. That is, the Tx entity may perform transmission through the channel immediately after sensing that the channel is idle during the first interval. The first interval is an interval of a predetermined length immediately before the Tx entity performs transmission. According to an embodiment, the first interval may be an interval of 25 μs in length, but the present invention is not limited thereto.

[0141] ● Category 3: LBT with random backoff using fixed-size CW

[0142] -The Tx entity obtains a random value within the fixed size CW, sets it as the initial value N of the backoff counter (or backoff timer), and performs backoff by using the set backoff counter N. In the backoff process, whenever the channel is detected to be in an idle state within a predetermined time slot period, the Tx entity reduces the backoff counter by 1. Here, the predetermined time slot period may be 9 μs, but the present invention is not limited thereto. The backoff counter N is reduced by 1 from the initial value, and when the value of the backoff counter N reaches 0, the Tx entity may perform transmission. At the same time, in order to perform backoff, the Tx entity first senses the first time interval (i.e., the delay duration T d ) during the second interval. According to an embodiment of the present invention, the Tx entity can sense (determine) whether the channel is idle during the second interval based on whether the channel is idle in at least some time periods (e.g., a time slot period) within the second interval. The second interval can be set based on the channel access priority level of the Tx entity and consists of a period of 16μs and m consecutive time slot periods. Here, m is a value set according to the channel access priority level. When the channel is sensed to be idle during the second interval, the Tx entity performs channel sensing to reduce the backoff counter. On the other hand, when the channel is sensed to be busy during the backoff process, the backoff process stops. After stopping the backoff process, when it is sensed that the channel is idle in the additional second interval, the Tx entity can resume the backoff. In this way, in addition to the second interval, the Tx entity can also perform transmission when the channel is idle during the time slot period of the backoff counter N. In this case, the initial value of the backoff counter N is obtained within a CW of a fixed size.

[0143] ● Category 4: LBT performs random backoff by using variable-sized CWs

[0144] -The Tx entity obtains a random value within a variable-sized CW, sets the random value as an initial value of a backoff counter (or backoff timer) N, and performs backoff by using the set backoff counter N. More specifically, the Tx entity may adjust the size of the CW based on the HARQ-ACK information for the previous transmission, and obtain the initial value of the backoff counter N within the CW of the adjusted size. The specific process of performing backoff by the Tx entity is as described in Category 3. In addition to the second interval, the Tx entity may perform transmission when the channel is idle during the time slot period of the backoff counter N. In this case, the initial value of the backoff counter N is obtained within the variable-sized CW.

[0145] In the above categories 1 to 4, the Tx entity may be a base station or a UE. According to an embodiment of the present invention, the first type of channel access may refer to category 4 channel access, and the second type of channel access may refer to category 2 channel access.

[0146] Fig.13 The diagram illustrates a channel access process based on Category 4 LBT according to an embodiment of the present invention.

[0147] To perform channel access, first, the Tx entity defers for a duration T d According to an embodiment of the present invention, the channel sensing can be performed within the delay time T d The channel sensing within at least a portion of the delay duration T in step S302 is performed d For example, by delaying the duration T d Channel sensing during a time slot period within a time slot is performed to delay the duration T d The Tx entity performs channel sensing within the delay duration T d Channel sensing is used to check whether the channel is idle (S304). If the delay duration T d If the channel is idle within the delay time T, the Tx entity proceeds to step S306. d If the channel is not sensed to be idle (i.e., busy) within the delay time T, the Tx entity returns to step S302. The Tx entity repeats steps S302 to S304 until the delay time T is reached. d The delay duration T can be set based on the channel access priority level of the Tx entity. d , and the delay duration is T d It consists of a 16 μs period and m consecutive time slot periods. Here, m is a value set according to the channel access priority level.

[0148] Next, the Tx entity obtains a random value within a predetermined CW, sets the random value as the initial value N of the backoff counter (or backoff timer) (S306), and proceeds to step S308. The initial value of the backoff counter N is randomly selected from a value between 0 and CW. The Tx entity performs the backoff process by using the set backoff counter N. That is, the Tx entity performs the backoff process by repeating steps S308 to S316 until the value of the backoff counter N reaches 0. At the same time, Fig.13 The figure shows that the channel is sensed after a delay of duration T d Step S306 is performed after the channel is idle for a period of time T, but the present invention is not limited thereto. That is, step S306 can be performed independently of steps S302 to S304, and can be performed before steps S302 to S304. When step S306 is performed before steps S302 to S304, if the channel is sensed by steps S302 to S304 to be idle for a period of time T, then the channel is idle for a period of time T. d If the Tx entity is idle, it proceeds to step S308.

[0149] In step S308, the Tx entity checks whether the value of the backoff counter N is 0. If the value of the backoff counter N is 0, the Tx entity proceeds to step S320 to perform transmission. If the value of the backoff counter N is not 0, the Tx entity proceeds to step S310. In step S310, the Tx entity reduces the value of the backoff counter N by 1. According to an embodiment, the Tx entity may selectively reduce the value of the backoff counter by 1 during the channel sensing process of each time slot. In this case, step S310 may be skipped at least once by the selection of the Tx entity. Next, the Tx entity performs channel sensing for the additional time slot period (S312). The Tx entity checks whether the channel is idle by channel sensing within the additional time slot period (S314). If it is sensed that the channel is idle within the additional time slot period, the Tx entity returns to step S308. In this way, whenever the channel is sensed to be idle within a predetermined time slot period, the Tx entity may reduce the backoff counter by 1. Here, the predetermined time slot period may be 9 μs, but the present invention is not limited thereto.

[0150] In step S314, if the channel is not sensed to be idle (ie, sensed to be busy) during the additional time slot period, the Tx entity proceeds to step S316. In step S316, the Tx entity checks whether the channel is idle during the additional deferral duration T d According to an embodiment of the present invention, the channel sensing in step S316 may be performed in units of time slots. That is, the Tx entity checks whether the additional delay duration T d Whether the channel is sensed to be idle during all time slot periods. dWhen a busy time slot is detected within the additional delay time T, the Tx entity immediately restarts step S316. d When the channel is sensed to be idle during all time slot periods, the Tx entity returns to step S308.

[0151] On the other hand, if the value of the backoff counter N is 0 in the check of step S308, the Tx entity performs the transmission (S320). The Tx entity receives the HARQ-ACK feedback corresponding to the transmission (S322). The Tx entity can check whether the previous transmission is successful through the received HARQ-ACK feedback. Next, the Tx entity adjusts the CW size for the next transmission based on the received HARQ-ACK feedback (S324).

[0152] As mentioned above, after sensing the channel for a delay duration T d After being idle for N additional time slots, the Tx entity may perform transmission when the channel is idle for N additional time slots. As described above, the Tx entity may be a base station or a UE, and Fig.13 The channel access procedure may be used for downlink transmission of a base station and / or uplink transmission of a UE.

[0153] Fig.14 is a block diagram showing the configuration of a UE and a base station according to an embodiment of the present invention. In an embodiment of the present invention, the UE can be implemented using various types of wireless communication devices or computing devices that ensure portability and mobility. The UE may be referred to as a user equipment (UE), a station (STA), a mobile subscriber (MS), and the like. In addition, in an embodiment of the present invention, the base station controls and manages cells (e.g., macro cells, femto cells, micro cells, etc.) corresponding to a service area, and performs functions such as signal transmission, channel designation, channel monitoring, self-diagnosis, relaying, and the like. The base station may be referred to as a next generation Node B (gNB) or an access point (AP).

[0154] As shown in the drawings, the UE 100 according to an embodiment of the present disclosure may include a processor 110 , a communication module 120 , a memory 130 , a user interface 140 , and a display unit 150 .

[0155] First, the processor 110 may execute various instructions or programs within the UE 100 and process data. In addition, the processor 100 may control the entire operation of each unit including the UE 100, and may control the transmission / reception of data between the units. Here, the processor 110 may be configured to perform operations according to the embodiments described in the present invention. For example, the processor 110 may receive time slot configuration information, determine the time slot configuration based on the time slot configuration information, and perform communication according to the determined time slot configuration.

[0156] Next, the communication module 120 may be an integrated module that performs wireless communication using a wireless communication network and performs wireless LAN access using a wireless LAN. To this end, the communication module 120 may include a plurality of network interface cards (NICs) such as cellular communication interface cards 121 and 122 and an unlicensed band communication interface card 123 in an internal or external form. In the drawings, the communication module 120 is shown as an integrally integrated module, but unlike the drawings, each network interface card can be independently arranged according to a circuit configuration or usage.

[0157] The cellular communication interface card 121 may send or receive a radio signal with at least one of the base station 200, the external device, and the server by using a mobile communication network and provide a cellular communication service in a first frequency band based on an instruction from the processor 110. According to an embodiment, the cellular communication interface card 121 may include at least one NIC module using a frequency band less than 6 GHz. At least one NIC module of the cellular communication interface card 121 may independently perform cellular communication with at least one of the base station 200, the external device, and the server according to a cellular communication standard or protocol in a frequency band below 6 GHz supported by the corresponding NIC module.

[0158] The cellular communication interface card 122 may send or receive a radio signal with at least one of the base station 200, the external device, and the server by using a mobile communication network and provide a cellular communication service in the second frequency band based on an instruction from the processor 110. According to an embodiment, the cellular communication interface card 122 may include at least one NIC module using a frequency band greater than 6 GHz. At least one NIC module of the cellular communication interface card 122 may independently perform cellular communication with at least one of the base station 200, the external device, and the server according to a cellular communication standard or protocol in a frequency band greater than 6 GHz supported by the corresponding NIC module.

[0159] The unlicensed band communication interface card 123 transmits or receives a radio signal with at least one of the base station 200, the external device, and the server by using the third frequency band as the unlicensed frequency band, and provides an unlicensed frequency band communication service based on an instruction from the processor 110. The unlicensed band communication interface card 123 may include at least one NIC module using the unlicensed frequency band. For example, the unlicensed frequency band may be a frequency band above 2.4 GHz, 5 GHz, 6 GHz, 7 GHz, or 52.6 GHz. At least one NIC module of the unlicensed band communication interface card 123 may independently or non-independently perform wireless communication with at least one of the base station 200, the external device, and the server according to the unlicensed frequency band communication standard or protocol of the frequency band supported by the corresponding NIC module.

[0160] The memory 130 stores a control program and various data thereof used in the UE 100. Such a control program may include a prescribed program required to perform wireless communication with at least one of the base station 200, an external device, and a server.

[0161] Next, the user interface 140 includes various input / output means provided in the UE 100. In other words, the user interface 140 may receive user input using various input means, and the processor 110 may control the UE 100 based on the received user input. In addition, the user interface 140 may perform output based on instructions from the processor 110 using various output means.

[0162] Next, the display unit 150 outputs various images on the display screen. The display unit 150 may output various display objects such as content or a user interface executed by the processor 110 based on a control instruction from the processor 110.

[0163] In addition, the base station 200 according to the embodiment of the present invention may include a processor 210 , a communication module 220 , and a memory 230 .

[0164] First, the processor 210 may execute various instructions or programs and process the internal data of the base station 200. In addition, the processor 210 may control the entire operation of each unit in the base station 200 and control the transmission and reception of data between the units. Here, the processor 210 may be configured to perform the operations according to the embodiments described in the present invention. For example, the processor 210 may signal a time slot configuration and perform communication according to the time slot configuration notified by the signal.

[0165] Next, the communication module 220 may be an integrated module that performs wireless communication using a wireless communication network and performs wireless LAN access using a wireless LAN. To this end, the communication module 220 may include a plurality of network interface cards such as cellular communication interface cards 221 and 222 and an unlicensed band communication interface card 223 in an internal or external form. In the drawings, the communication module 220 is shown as an integrally integrated module, but unlike the drawings, each network interface card can be independently arranged according to a circuit configuration or usage.

[0166] The cellular communication interface card 221 may send or receive a radio signal with at least one of the UE 100, the external device, and the server by using a mobile communication network and provide a cellular communication service in a first frequency band based on an instruction from the processor 210. According to an embodiment, the cellular communication interface card 221 may include at least one NIC module using a frequency band less than 6 GHz. At least one NIC module of the cellular communication interface card 221 may independently perform cellular communication with at least one of the base station 100, the external device, and the server according to a cellular communication standard or protocol in a frequency band less than 6 GHz supported by the corresponding NIC module.

[0167] The cellular communication interface card 222 may send or receive a radio signal with at least one of the UE 100, the external device, and the server by using a mobile communication network and provide a cellular communication service in the second frequency band based on an instruction from the processor 210. According to an embodiment, the cellular communication interface card 222 may include at least one NIC module using a frequency band of 6 GHz or higher. At least one NIC module of the cellular communication interface card 222 may independently perform cellular communication with at least one of the base station 100, the external device, and the server according to a cellular communication standard or protocol in a frequency band of 6 GHz or higher supported by the corresponding NIC module.

[0168] The unlicensed band communication interface card 223 transmits or receives a radio signal with at least one of the base station 100, the external device, and the server by using the third frequency band as the unlicensed frequency band, and provides an unlicensed frequency band communication service based on an instruction from the processor 210. The unlicensed band communication interface card 223 may include at least one NIC module using the unlicensed frequency band. For example, the unlicensed frequency band may be a frequency band above 2.4 GHz, 5 GHz, 6 GHz, 7 GHz, or 52.6 GHz. At least one NIC module of the unlicensed band communication interface card 223 may independently or dependently perform wireless communication with at least one of the base station 100, the external device, and the server according to the unlicensed frequency band communication standard or protocol of the frequency band supported by the corresponding NIC module.

[0169] Fig.14 1 is a block diagram illustrating a UE 100 and a base station 200 according to an embodiment of the present invention, and the blocks shown separately are logically divided elements of the device. Therefore, the aforementioned elements of the device can be installed in a single chip or multiple chips according to the design of the device. In addition, a part of the configuration of the UE 100, for example, a user interface 140, a display unit 150, etc., can be selectively provided in the UE 100. In addition, the user interface 140, the display unit 150, etc. can be additionally provided in the base station 200 when necessary.

[0170] Fig.15The diagram illustrates a channel access process performed by a wireless communication device in an unlicensed frequency band, and an LBT process used when the wireless communication device performs channel access in the unlicensed frequency band. Specifically, the LBT process used when a wireless communication device according to an embodiment of the present invention performs channel access in an unlicensed frequency band will be described. In particular, a channel access in which the wireless communication device performs transmission according to the result of channel sensing within a time interval of a predetermined duration can be configured in the wireless communication device. In this case, a method for operating a wireless communication device when the wireless communication device fails to access a channel will be described. The specified duration already mentioned above may be 16 μs.

[0171] For the convenience of description, a wireless communication device that serves as a wireless endpoint that initiates channel occupancy is referred to as an initiating node. In addition, a wireless communication device that serves as a wireless endpoint that communicates with an initiating node is referred to as a responding node. The initiating node may be a base station, and the responding node may be a UE. In addition, the initiating node may be a UE, and the responding node may be a base station. When the initiating node wants to send data, the initiating node may perform channel access according to a channel access priority level determined according to the data type. In this case, the parameters for channel access may be determined according to the type of data. The parameters for channel access may include a minimum value of CW, a maximum value of CW, a maximum occupancy time (MCOT) that is the maximum duration that a channel can be occupied in one channel occupancy, and the number of sensing time slots (m p ). Specifically, the initiating node may perform the above-mentioned category 4 LBT according to the channel access priority level determined according to the data type.

[0172] Table 4 below shows an example of parameter values ​​for channel access according to the channel access priority level. Specifically, Table 4 shows parameter values ​​for channel access for each channel access priority level for downlink transmission in the LTE LAA system.

[0173] When the downlink channel sent by the wireless communication device includes data services, the deferral duration can be configured according to the channel access priority level of the services included in the downlink channel. In addition, the deferral duration can include an initial duration T f or one or more (m p )Time slot duration T sl In this case, the time slot duration T sl It can be 9μs. The initial duration includes an idle time slot duration T sl In addition, the number of time slot durations (m) included in the deferral duration may be configured according to the above-mentioned channel access priority level. p Specifically, the number of time slot durations (m) included in the postponement durationp ) can be configured as shown in Table 4.

[0174] [Table 4]

[0175]

[0176] In addition, the wireless communication device can configure the range of CW values ​​according to the channel access priority level. Specifically, the wireless communication device can set the CW value to meet the CW min,p <=CW<=CW max,p In this case, the minimum value of CW is min,p and maximum CW max,p It can be determined according to the channel access priority level. Specifically, the minimum value CW min,p and maximum CW max,p It can be determined as shown in Table 4. The wireless communication device can set the minimum value CW of CW in the counter value setting process. min,p and maximum CW max,p When the wireless communication device accesses the channel, the wireless communication device can adjust the value of CW, as shown in the above reference Fig.13 In addition, in the wireless communication device of the unlicensed frequency band, the MCOT T can also be determined according to the channel access priority of the data included in the transmission as described above. mcot，p Specifically, MCOT can be determined as shown in Table 4. Therefore, the wireless communication device may not be allowed to perform continuous transmission for a time exceeding MCOT in the unlicensed band. This is because the unlicensed band is a frequency band used by various wireless communication devices according to certain rules. In Table 4, when the value of the channel access priority level is p=3 or p=4, the unlicensed band is used for a long time as specified, and there is no wireless communication device using other technologies, and the wireless communication device can be configured with T mcot,p =10ms. Otherwise, the wireless communication device can be configured with T mcot,p =8ms.

[0177] Table 5 shows parameter values ​​of channel access for each channel access priority level for uplink transmission used in the LTE LAA system.

[0178] [Table 5]

[0179]

[0180] As described in Table 5, when one or more gaps are included in the transmission, the MCOT value of 6ms can be increased to 8ms. The gap represents the time from when transmission is stopped in the carrier until transmission is resumed in the carrier. In this case, the minimum value of the gap duration is 100μs. In addition, the maximum value of the transmission duration performed before the gap is included is 6ms. In addition, the duration of the gap is not included in the channel occupancy time. When the value of the channel access priority level is 3 or 4 and it is guaranteed that no other radio access technology is used in the carrier where the channel access is performed, the value of MCOT can be 10ms. In this case, another wireless access technology may include Wi-Fi. Otherwise, the value of MCOT can be determined as described in Note 1 of Table 5.

[0181] COT represents the time that a wireless communication device occupies a channel. As described above, MCOT represents the maximum time that an initiating node can continuously occupy a channel in any one carrier of an unlicensed band. However, as described above, a gap as an interval during which no transmission is performed may be included between multiple transmissions, and when a gap is included, the value of MCOT may be applied differently.

[0182] <Embodiment: Channel Access for Sidelink (SL) Transmission>

[0183] Fig.16 An example of a SL communication process is shown. SL communication refers to a communication scheme in which a direct link is established between UEs and the UEs directly exchange voice or data with each other without the intervention of a base station. In the case of SL communication, Fig.14 The base station in can be replaced by UE.

[0184] refer to Fig.16, UE-A can send sidelink control information (SCI) to UE-B (S1602). SCI can be divided into a first SCI and a second SCI. The first SCI is sent via a physical sidelink control channel (PSCCH). The first SCI includes some information required for physical sidelink shared channel (PSSCH) scheduling (for example, resources / information for decoding the second SCI, DMRS pattern, antenna port, etc.), and can be decoded by all UEs in the cell for channel sensing. On the other hand, the second SCI is decoded by each receiving UE and includes the remaining information required for PSSCH scheduling. The second SCI can be sent using PSSCH resources. Thereafter, UE-A can send PSSCH to UE-B (S1604). Data can be sent between UEs via PSSCH. In addition, unicast transmission and multicast transmission can be performed via PSSCH. When HARQ feedback operation is supported / configured for SL transmission (e.g., PSSCH) (HARQ-ACK is enabled), UE-B can send HARQ-ACK feedback for PSSCH to UE-A via a physical side link feedback channel (PSFCH) (S1606). On the other hand, when HARQ feedback operation for SL transmission (e.g., PSSCH) is not supported / configured (HARQ-ACK is disabled), UE-A does not expect explicit HARQ-ACK feedback for PSSCH from UE-B.

[0185] The present disclosure relates to a channel access scheme / process for performing SL transmission (e.g., PSSCH) on an unlicensed spectrum. Specifically, the present disclosure proposes a scheme for adjusting CWS for channel access on an unlicensed spectrum, wherein the CWS is adjusted according to the type of (SL) transmission (e.g., unicast / group transmission with HARQ-ACK, multicast transmission with only NACK, multicast transmission without HARQ-ACK, and broadcast transmission). Here, the channel access process using CWS includes, for example, a type 1 channel access procedure (CAP) (or, category 4 (Cat-4) LBT, a random backoff-based channel access process with variable CW). For example, when performing type 1 channel access for SL transmission, a wireless device (e.g., UE) can adjust the CWS based on the type of SL transmission before performing type 1 channel access.

[0186] The transmission type can be distinguished based on (i) the type of the corresponding transmission (e.g., unicast, groupcast, and broadcast) and (ii) the HARQ-ACK feedback scheme / mode established for the corresponding transmission (HARQ-ACK, NACK only, and no HARQ-ACK). In this specification, the transmission type includes but is not limited to the following.

[0187] - Transmission with HARQ-ACK: refers to a transmission that requires HARQ-ACK feedback (e.g., ACK, NACK). Therefore, the UE sends a transmission to a receiving UE and expects HARQ-ACK feedback (e.g., ACK or NACK) from the receiving UE regarding the corresponding transmission (i.e., explicit ACK / NACK). Here, the transmission includes a unicast transmission or a multicast transmission.

[0188] - Transmission with only NACK: refers to a transmission in which only NACK is allowed as HARQ-ACK feedback. Therefore, the UE sends a transmission to a receiving UE and explicitly expects only NACK from the receiving UE as HARQ-ACK feedback for the corresponding transmission. In this case, an ACK is indirectly fed back based on the fact that a NACK for the corresponding transmission has not been detected / received (i.e., an implicit ACK). Here, the transmission includes a multicast transmission.

[0189] - Transmission without HARQ-ACK: refers to a transmission for which HARQ-ACK feedback is not allowed. In other words, this refers to a situation in which a HARQ-ACK scheme / mode is not configured for the corresponding transmission. Therefore, the UE sends a transmission to a receiving UE and then does not expect HARQ-ACK feedback from the receiving UE regarding the transmission. Here, the transmission includes a multicast transmission or a broadcast transmission.

[0190] Unicast / multicast transmission with HARQ-ACK

[0191] As with unicast or multicast transmissions with HARQ-ACK, a wireless device (e.g., UE) may transmit a PSSCH. When performing transmissions in unlicensed spectrum, the UE may perform a Type 1 channel access. The UE may adjust the CWS to determine a time window (i.e., CW) in which to perform a random backoff when performing a Type 1 channel access. Suggestions for performing this method are given below.

[0192] First, in the case of PSSCH transmission, PSSCH transmission can be performed using: (a) a side link resource allocation mode 1 scheme, in which the base station notifies the UE of the time and frequency resources for PSSCH transmission, or (b) a side link resource allocation mode 2 scheme, in which (one) resource pool is configured, and the UE senses the corresponding resource pool, selects resources, and then allocates actually transmittable resources. Here, PSSCH can be transmitted using a PC-5 link. A PC-5 link refers to a link used for direct communication between devices.

[0193] Case 1) When (one) resource pool is established, (a) the PSFCH resource period and (b) the minimum time gap in which the PSFCH can be received after the PSSCH can be configured. In this case, whether to enable / disable HARQ-ACK feedback for SL transmission (e.g., PSSCH) can be configured. For example, a UE for sending PSSCH can configure the HARQ-ACK enable / disable indicator included in the second SCI to have a specific value. For example, when the HARQ-ACK enable / disable indicator is configured to have a value of "1" (meaning enabled), the receiving UE can receive the PSSCH and then send the PSFCH in an available time slot after the minimum time gap from the PSSCH according to the PSFCH resource period. Therefore, the UE that has sent the PSSCH can receive (e.g., detect / monitor) the PSFCH and receive the HARQ-ACK information.

[0194] Specifically, when PSFCH resources are configured in the resource pool and the HARQ-ACK enable / disable indicator is indicated as a value of "1" (meaning enabled) via the second SCI, UE-A can expect HARQ-ACK feedback regarding the PSSCH sent by UE-A to UE-B to be sent from UE-B to UE-A. When the HARQ-ACK sent from UE-B is available and there is at least one ACK in the corresponding HARQ-ACK, UE-A can reset the current CWp to the minimum / initial value for each priority category relative to all priority categories (e.g., see Table 5). Otherwise (e.g., there is no ACK in the HARQ-ACK; all NACKs), UE-A can increase the current CWp to the next possible higher value for each priority category relative to all priority categories (e.g., see Table 5). Thereafter, by using the configured / adjusted CWp value, UE-A can perform type 1 channel access during the transmission of the PSSCH currently to be sent. Here, the subscript p indicates the priority category.

[0195] In addition, the UE transmitting the PSSCH may indicate a value of "0" (meaning disabled) via the HARQ-ACK enable / disable indicator included in the second SCI. In this case, the UE does not expect an explicit HARQ-ACK from the receiving UE, and may use the CWp value that has been used for the most recent previous PSSCH transmission as is for the type 1 channel access performed during the transmission of the PSSCH currently to be transmitted.

[0196] Case 2) When (one) resource pool is configured, there may be a situation where there are no PSFCH resources because the PSFCH resource period and minimum time gap are not configured. In this case, the UE that is allowed to send PSSCH indicates a value of "0" (meaning disabled) via the HARQ-ACK enable / disable indicator included in the second SCI, and the UE that has received the indication may not send HARQ-ACK information because there is no PSFCH resource set after receiving the PSSCH. Here, the UE that has sent the PSSCH may not expect an explicit HARQ-ACK from the receiving UE, so that the UE may not perform CWp adjustment based on the HARQ-ACK information. Therefore, the UE that has sent the PSSCH may be unclear about the value to be configured as the current CWp when sending the next PSSCH. In order to resolve this ambiguity, when the channel access priority category of the PSSCH currently to be sent has been used before, the UE can perform type 1 channel access by configuring the current CWp (before PSSCH transmission) to have a CWp value corresponding to the same priority category that has been used most recently before (for PSSCH transmission).

[0197] Fig.17 A channel access process according to an example of the present disclosure is illustrated. Fig.17 Corresponding to case 1), case 2) can be performed similarly thereto.

[0198] refer to Fig.17, UE-A can configure whether to enable / disable HARQ feedback for SL transmission (e.g., PSSCH) (S1702). For example, UE-A can send an SCI for scheduling PSSCH. Here, the SCI (e.g., a second SCI) may include a HARQ feedback enable / disable indicator. Thereafter, UE-A may perform channel access using a first CWS to send PSSCH (S1704). Here, PSSCH may be used for unicast transmission or multicast transmission. In addition, channel access includes type 1 channel access. When the HARQ-ACK enable / disable indicator is configured to have a value of "1" (enabled), UE-B may receive PSSCH and then send PSFCH in an available time slot after a minimum time interval with PSSCH. In this case, when there is at least one ACK in the HARQ-ACK sent from UE-B, UE-A may reset the current CWp to a minimum / initial value for each priority category relative to all priority categories (e.g., see Table 5). Otherwise (e.g., no ACK in HARQ-ACK; all NACKs), UE-A may increase the current CWp to the next possible higher value for each priority category relative to all priority categories (e.g., see Table 5) (S1706a). On the other hand, when the HARQ-ACK enable / disable indicator is configured to have a value of "0" (disabled), UE-A may use the CWp value that has been used for the most recent previous PSSCH transmission as the current CWp as is, or, when the channel access priority category of the PSSCH currently to be sent has been previously used, the UE may use the CWp value that has been used for the PSSCH transmission corresponding to the same priority category as the current CWp as is. Thereafter, by using the configured / adjusted CWp value, UE-A may perform channel access (e.g., type 1 channel access) during the PSSCH transmission currently to be sent (S1708).

[0199] Multicast transmission with NACK-only

[0200] As a multicast transmission with only NACK feedback, a wireless device (e.g., UE) can send PSSCH. In this case, the UE can perform type 1 channel access when performing transmission in unlicensed spectrum. The UE can adjust the CWS to determine the time window for performing random backoff when performing type 1 channel access. Suggestions for performing this method are given below. The following description can also be extended to multicast transmission with HARQ-ACK and in this case, the implicit ACK is replaced by an explicit ACK.

[0201] When a UE sends a PSSCH via a multicast transmission configured with only NACK feedback, the UE may determine / verify HARQ-ACK feedback for the multicast transmission by monitoring (e.g., detecting) a PSFCH opportunity corresponding to the multicast transmission. Here, the PSFCH opportunity includes one or more PSFCH resources allocated to a group of UEs that have received the multicast transmission. When HARQ-ACK feedback (i.e., all implicit ACKs) is not received from the UE group that is a recipient of the multicast transmission as a result of monitoring the PSFCH opportunity, the UE that has sent the PSSCH regards the response to the PSSCH reception as (all) ACKs and does not perform retransmission of the multicast transmission. Therefore, when the UE does not receive any HARQ-ACK feedback from the UE group in the PSFCH opportunity expected by the UE, the UE that has sent the PSSCH via the multicast transmission may reset the current CWp to a minimum / initial value for each priority category (e.g., see Table 5) relative to all priority categories as the CWp for type 1 channel access that should be performed during the next SL transmission to be sent (e.g., PSSCH; not necessarily a multicast transmission). In other words, when the received response results corresponding to the multicast transmission from multiple UEs are regarded as (all) ACKs (i.e., no NACK is detected at all in the PSFCH opportunity), the UE can reset the current CWp to a minimum / initial value for each priority category relative to all priority categories (e.g., see Table 5). When a group of UEs want to send NACK feedback at the PSFCH opportunity, the UE that has sent the PSSCH through the multicast transmission may not know whether the transmission was unsuccessful due to a channel access failure, or whether the UE group that has successfully received the previously sent PSSCH did not send NACK feedback, and therefore, regardless of these, the UE can reset the current CWp to a minimum / initial value for each priority category relative to all priority categories (e.g., see Table 5) to perform type 1 channel access during the next SL transmission (e.g., PSSCH) to be sent.

[0202] Meanwhile, when PSSCH is transmitted via multicast transmission configured with NACK-only feedback and then HARQ-ACK feedback with all NACKs or HARQ-ACK feedback with at least one NACK is received from a group of UEs that have received PSSCH, the UE that has transmitted PSSCH may perform retransmission of the multicast transmission. In other words, as a result of monitoring the PSFCH timing corresponding to the multicast, when all NACKs or at least one NACK is detected in the corresponding PSFCH timing, the UE that has transmitted PSSCH may perform retransmission of the multicast transmission. In this case, a UE that wants to retransmit PSSCH via multicast transmission may be confused about the value of CWp to be configured for type 1 channel access that should be performed when retransmitting PSSCH.

[0203] 1. As an example, by considering that a UE is to send a PSSCH as a retransmission of a multicast transmission, when a group of UEs sends HARQ-ACK feedback with all NACKs and a UE that has sent a PSSCH receives HARQ-ACK feedback with all NACKs, or when HARQ-ACK feedback with at least one NACK is received from a group of UEs, the UE may use a method for performing CW adjustment after receiving a NACK. For example, a UE that has sent a PSSCH via a multicast transmission may increase the current CWp to the next possible higher value for each priority category relative to all priority categories, and perform a type 1 channel access during the next PSSCH transmission to be sent. In other words, when the reception response results corresponding to the multicast transmission from multiple UEs are regarded as non-(all) ACKs (e.g., at least one NACK is detected in a PSFCH opportunity), the UE may increase the current CWp to the next possible higher value for each priority category relative to all priority categories (e.g., see Table 5).

[0204] 2. As another example, when HARQ-ACK feedback with at least one NACK is received from a group of UEs, the UE that has sent PSSCH can determine that at least one UE in the group has successfully received PSSCH, except for the case where a group of UEs sends HARQ-ACK feedback with all NACKs. In this case, the UE that has sent PSSCH can determine that the channel is not congested from a channel access perspective and can perform CW adjustment after receiving ACK feedback. For example, the UE that has sent PSSCH can reset the current CWp to the minimum / initial value for each priority category relative to all priority categories to perform type 1 channel access during the next PSSCH transmission to be sent (e.g., see Table 5).

[0205] Fig.18 FIG. 1 illustrates a channel access process according to an example of the present disclosure. Fig.18, UE-A may perform channel access by using the first CWS to perform multicast transmission (S1802). Here, the multicast transmission may be performed via the PSSCH. In addition, the channel access may include type 1 channel access. Thereafter, UE-A may monitor the PSFCH (timing / resource) corresponding to the multicast transmission (S1804). When, as a result of the monitoring, the HARQ feedback result is regarded as all ACKs (e.g., no NACK is detected at all in the PSFCH timing / resource), UE-A may reset the current CWp to a minimum / initial value for each priority category relative to all priority categories (e.g., see Table 5) (S1806a). On the other hand, when the HARQ feedback result is not regarded as all ACKs (e.g., at least one NACK is detected in the PSFCH timing / resource), UE-A may increase the current CWp to the next possible higher value for each priority category relative to all priority categories (e.g., see Table 5) (S1806b). Thereafter, by using the configured / adjusted CWp value, UE-A may perform channel access (e.g., type 1 channel access) for the transmission of the SL transmission (e.g., PSSCH) currently to be sent (after the multicast transmission) (S1808). Here, the HARQ feedback scheme configured for the multicast transmission includes a NACK-only feedback scheme.

[0206] When PSSCH is transmitted via multicast transmission configured with only NACK feedback, a sidelink resource allocation mode 1 scheme in which the base station notifies the UE of the time / frequency resources for PSSCH transmission may be performed, or a sidelink resource allocation mode 2 scheme in which one resource pool is configured and resources are selected by sensing the resource pool, and then the actually transmittable resources are allocated may be performed. At the same time, when (one) resource pool is configured, there may be a situation where there are no PSFCH resources due to the unconfigured PSFCH resource period and minimum time gap. In this case, the UE allowed to transmit PSSCH indicates a value of "0" (meaning disabled) by the HARQ-ACK enable / disable indicator included in the second SCI, and the UE that has received the PSSCH cannot send HARQ-ACK information, which is based on feedback information of only NACK, because there is no configured PSFCH resource after receiving the PSSCH. Here, the UE that has transmitted the PSSCH cannot expect an explicit HARQ-ACK from the receiving UE, and therefore the UE may not be able to perform CWp adjustment based on the HARQ-ACK information. Therefore, a UE that has transmitted a PSSCH may be ambiguous about the value to be configured as the current CWp value when transmitting the next PSSCH. To resolve this ambiguity, when the channel access priority category of the PSSCH currently to be transmitted has been used before, the UE may perform Type 1 channel access by configuring the current CWp (before PSSCH transmission) to have a CWp value corresponding to the same priority category that was most recently used before (PSSCH transmission).

[0207] Alternatively, the UE for transmitting the PSSCH may indicate a value of "0" (meaning disabled) via a HARQ-ACK enable / disable indicator included in the second SCI. In this case, the UE does not expect an explicit HARQ-ACK from the receiving UE, and may use the CWp value that has been used for the most recent previous PSSCH transmission as is for type 1 channel access performed during the PSSCH transmission currently to be transmitted.

[0208] Although the method and system of the present invention have been described in conjunction with specific embodiments, some or all of its components or operations may be implemented using a computing system having a general hardware architecture.

[0209] The above description of the present invention is only exemplary, and those skilled in the art to which the present invention belongs will understand that various modifications and changes can be made without changing the technical spirit or basic features of the present invention. Therefore, it should be interpreted that the above embodiments are illustrative rather than restrictive in all aspects. For example, each component described as a single type can be implemented in a distributed manner, and similarly, the components described as distributed can also be implemented in a combined form.

[0210] The scope of the present invention is indicated by the appended claims rather than the detailed description, and it should be understood that all changes or modifications derived from the meaning and scope of the claims and their equivalents are included in the scope of the present invention.

Claims

1. A user equipment (UE) for use in a wireless communication system, the UE include: Communication module; as well as a processor configured to control the communication module, Wherein, the processor is configured as follows: performing a sidelink (SL) multicast transmission to a plurality of UEs based on a channel access procedure using a first contention window size (CWS); Identifying reception response results of the plurality of UEs for the SL multicast transmission by monitoring a feedback signal in a physical sidelink feedback channel (PSFCH) opportunity corresponding to the SL multicast transmission; and Based on the reception response results of the multiple UEs, configuring a CWS for channel access of the SL transmission after the SL multicast transmission, wherein, in a case where the reception response results of the plurality of UEs include even one negative acknowledgement (NACK), the CWS is configured to have a value greater than the first CWS, and Wherein, when the reception response results of the multiple UEs are regarded as all ACKs, the CWS is reset to the minimum CWS value.

2. The UE according to claim 1, in, The case where the reception response results of the plurality of UEs include at least one NACK includes a case where a NACK is detected in the PSFCH opportunity.

3. The UE according to claim 1, in, The case where the reception response results of the plurality of UEs are regarded as all ACKs includes a case where no NACK is detected in the PSFCH opportunity.

4. The UE according to claim 1, in, A NACK-only feedback scheme is configured for the SL multicast transmission.

5. The UE according to claim 1, in, At least one of the SL multicast transmission and the SL transmission is performed through a physical sidelink shared channel (PSSCH).

6. The UE according to claim 1, in, The UE is configured to perform a backoff at a time of channel access for the SL transmission based on a counter value randomly selected within the CWS.

7. The UE according to claim 1, in, In case the CWS is configured to have a greater value than the first CWS, the CWSs of all priority categories are configured to have the next greater value greater than the current CWS among the CWS values ​​allowed for each priority category.

8. The UE according to claim 1, in, In the case where the CWS is reset to the CWS minimum value, the CWSs of all priority categories are configured to have the minimum value of the CWS corresponding to each priority category.

9. The UE according to claim 1, in, The wireless communication system includes a 3rd Generation Partnership Project (3GPP) New Radio (NR) based wireless communication system, and the channel access procedure includes a Type 1 Channel Access Procedure (CAP).

10. A method for use by a user equipment (UE) in a wireless communication system, the method include: performing a sidelink (SL) multicast transmission to a plurality of UEs based on a channel access procedure using a first contention window size (CWS); Identifying reception response results of the plurality of UEs for the SL multicast transmission by monitoring a feedback signal in a physical sidelink feedback channel (PSFCH) opportunity corresponding to the SL multicast transmission; as well as Based on the reception response results of the multiple UEs, configuring a CWS for channel access of the SL transmission after the SL multicast transmission, wherein, in a case where the reception response results of the plurality of UEs include even one negative acknowledgement (NACK), the CWS is configured to have a value greater than the first CWS, and Wherein, when the reception response results of the multiple UEs are regarded as all ACKs, the CWS is reset to the minimum CWS value.

11. The method according to claim 10, in, The case where the reception response results of the plurality of UEs include at least one NACK includes a case where a NACK is detected in the PSFCH opportunity.

12. The method according to claim 10, in, The case where the reception response results of the plurality of UEs are regarded as all ACKs includes a case where no NACK is detected in the PSFCH opportunity.

13. The UE according to claim 10, in, A NACK-only feedback scheme is configured for the SL multicast transmission.

14. The method according to claim 10, in, At least one of the SL multicast transmission and the SL transmission is performed through a physical sidelink shared channel (PSSCH).

15. The method of claim 10, further comprising performing, by the UE, a backoff at a time of channel access for the SL transmission based on a counter value randomly selected within the CWS.

16. The method according to claim 10, in, In case the CWS is configured to have a greater value than the first CWS, the CWSs of all priority categories are configured to have the next greater value greater than the current CWS among the CWS values ​​allowed for each priority category.

17. The method according to claim 10, in, In the case where the CWS is reset to the CWS minimum value, the CWSs of all priority categories are configured to have the minimum value of the CWS corresponding to each priority category.

18. The method according to claim 10, in, The wireless communication system includes a 3rd Generation Partnership Project (3GPP) New Radio (NR) based wireless communication system, and the channel access procedure includes a Type 1 Channel Access Procedure (CAP).

19. A user equipment (UE) used in a wireless communication system, the UE include: Communication module; as well as a processor configured to control the communication module, Wherein, the processor is configured to: performing a first side link (SL) transmission based on a channel access procedure using a first contention window size (CWS); and performing a channel access procedure using the second CWS in order to attempt a second SL transmission subsequent to the first SL transmission, Wherein, when hybrid automatic repeat request acknowledgement (HARQ-ACK) feedback is enabled for the first SL transmission, based on the HARQ-ACK feedback result corresponding to the first SL transmission, the second CWS is reset to a minimum value, or is configured to have a value greater than the first CWS, and Wherein, in a case where the HARQ-ACK feedback is disabled for the first SL transmission, the second CWS is adjusted to have the same value as the CWS used for the most recent third SL transmission before the first SL transmission.

20. The UE according to claim 19, in, Whether the HARQ-ACK feedback is enabled / disabled is indicated by sidelink control information (SCI) corresponding to the first SL transmission.

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