Channel access method for performing transmission in an unauthorized band and apparatus using the same

Abstract

A base station of a wireless communication system is disclosed. The base station of the wireless communication includes a communication module and a processor. The processor is configured to receive a grant for scheduling a plurality of uplink transmissions from the base station, and when a UE attempts a first fixed-duration-based channel access for a first transmission as one of the plurality of uplink transmissions and fails in the first fixed-duration-based channel access, attempt a second fixed-duration-based channel access for a second transmission as a transmission following the first transmission.

Description

Technical Field

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

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

[0003] The third-generation partnership project (3GPP) NR system improves the spectral efficiency of the network and enables communication providers to 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 number of voice calls. The advantages of the NR system are higher throughput and lower latency on the same platform, support for frequency-division duplexing (FDD) and time-division duplexing (TDD), and low operating costs due to an enhanced end-user environment and a simple architecture.

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

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

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

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

[0008] However, mobile communication systems are not only gradually expanding voice services but also data services, and have now developed to the extent of providing high-speed data services. However, in the current mobile communication systems that are providing services, due to resource shortage phenomena and users' high-speed service demands, a more advanced mobile communication system is needed.

[0009] In recent years, with the rapid increase in mobile services due to the popularization of smart devices, it has become increasingly difficult to cope with the increasing data usage for providing cellular communication services using only the existing licensed spectrum or licensed frequency bands.

[0010] In this context, methods for providing cellular communication services using unlicensed spectrum or unlicensed frequency bands (e.g., 2.4 GHz band, 5 GHz band, or higher frequency bands, etc.) are being discussed to solve the problem of lack of spectrum.

[0011] Different from the licensed frequency bands where telecommunication carriers ensure exclusive use rights through procedures such as auctions, in the unlicensed frequency band, multiple communication devices can be used simultaneously without restriction, provided that only a certain level of adjacent frequency band protection regulations are complied with. For this reason, when using the unlicensed frequency band for cellular communication services, it is difficult to guarantee the communication quality to the level provided in the licensed frequency band, and interference with existing wireless communication devices (e.g., wireless LAN devices) using the unlicensed frequency band is likely to occur.

[0012] In order to use LTE and NR technologies in the unlicensed frequency band, research on coexistence with existing devices used for the unlicensed frequency band and effective sharing of wireless channels with other wireless communication devices will be carried out in advance. That is, a robust coexistence mechanism (RCM) needs to be developed so that devices using LTE and NR technologies in the unlicensed frequency band do not affect existing devices used for the unlicensed frequency band. Summary of the Invention

[0013] Technical Problem

[0014] An object of an embodiment of the present invention is to provide a channel access method for performing transmission in a wireless communication system operating in an unlicensed frequency band and a device using the channel access method.

[0015] Technical Solution

[0016] According to an embodiment of the present invention, a user equipment (UE) for wireless communication with a base station in an unlicensed band includes a communication module and a processor controlling the communication module. The processor may be configured to receive a grant for scheduling a plurality of uplink transmissions from the base station, and when the UE attempts a first fixed-duration-based channel access for a first transmission as one of the plurality of uplink transmissions and fails in the first fixed-duration-based channel access, may be configured to attempt a second fixed-duration-based channel access for a second transmission as a transmission following the first transmission. The first fixed-duration-based channel access is a channel access in which when the channel is sensed idle within a first fixed duration, the UE allowed to perform the first fixed-duration-based channel access performs a transmission immediately after the first fixed duration. The second fixed-duration-based channel access is a channel access in which when the channel is sensed idle within a second fixed duration, the UE allowed to perform the second fixed-duration-based channel access performs a transmission immediately after the second fixed duration.

[0017] The first fixed duration may be shorter than the second fixed duration.

[0018] The first fixed duration may be 16 μs, and the second fixed duration may be 25 μs.

[0019] The grant may indicate the fixed-duration-based channel access as a channel access type and indicate a channel access priority for accessing the channel in which the plurality of uplink transmissions are performed.

[0020] The grant may indicate the first fixed-duration-based channel access as a channel access type.

[0021] The grant may include one or more grants for scheduling a plurality of uplink transmissions, and the plurality of uplink transmissions may be continuous without a time gap.

[0022] According to an embodiment of the present invention, a base station for wireless communication with a UE in an unlicensed band includes a communication module and a processor controlling the communication module. The processor may be configured to, when the duration of a transmission of the UE is less than a maximum channel occupancy time and the gap between the transmission of the UE and the transmission to the UE is not greater than a first fixed duration, perform the transmission to the UE immediately after the gap without sensing within the maximum channel occupancy time in the channel in which the transmission of the UE is performed. In this case, the first fixed duration is 16 μs.

[0023] The processor may be configured to, when the gap between the transmission of the UE and the transmission to the UE is not greater than a first fixed duration, and in the case of no sensing within a predetermined duration, perform the transmission to the UE immediately after the gap, and the predetermined duration may be a constraint applied to the base station transmission separately from the maximum channel occupancy time.

[0024] The processor may be configured to, when the gap between the transmission of the UE and the transmission to the UE is equal to the first fixed duration, attempt a first fixed-duration-based channel access in the channel in which the UE's transmission is performed. The first fixed-duration-based channel access may be a channel access in which the base station that is allowed to perform the first fixed-duration-based channel access performs a transmission immediately after the first fixed duration when the channel is sensed to be idle within the first fixed duration.

[0025] The processor may be configured to, when the gap between the transmission of the UE and the transmission to the UE is not greater than a second fixed duration, attempt a second fixed-duration-based channel access in the channel in which the UE's transmission is performed. The second fixed-duration-based channel access may be a channel access in which the base station that is allowed to perform the second fixed-duration-based channel access performs a transmission immediately after the second fixed duration when the channel is sensed to be idle during the second fixed duration. In this case, the second fixed duration is 25 μs.

[0026] The channel occupancy including the transmission of the UE and the transmission from the base station to the UE may be initiated by the base station.

[0027] The channel occupancy including the transmission of the UE and the transmission from the base station to the UE may be initiated by the UE.

[0028] According to an embodiment of the present invention, a method for operating a UE for wireless communication with a base station in an unlicensed frequency band may include: receiving a grant for scheduling a plurality of uplink transmissions from the base station; and when the UE attempts a first fixed-duration-based channel access for a first transmission as one of the plurality of uplink transmissions and fails in the first fixed-duration-based channel access, attempting a second fixed-duration-based channel access for a second transmission as a transmission following the first transmission. In this case, the first fixed-duration-based channel access may be a channel access in which the UE that is allowed to perform the first fixed-duration-based channel access performs a transmission immediately after the first fixed duration when the channel is sensed to be idle within the first fixed duration, and the second fixed-duration-based channel access may be a channel access in which the UE that is allowed to perform the second fixed-duration-based channel access performs a transmission immediately after the second fixed duration when the channel is sensed to be idle during the second fixed duration.

[0029] The first fixed duration may be shorter than the second fixed duration.

[0030] The first fixed duration may be 16 μs, and the second fixed duration may be 25 μs.

[0031] The grant may indicate a fixed-duration-based channel access as a channel access type and may indicate a channel access priority for accessing a channel in which multiple uplink transmissions are performed.

[0032] The grant may indicate a first fixed-duration-based channel access as a channel access type.

[0033] The grant may include one or more grants for scheduling multiple uplink transmissions, and the multiple uplink transmissions may continue without a time gap.

[0034] According to an embodiment of the present invention, a method for operating a base station for wireless communication with a UE in an unlicensed band includes, when a duration of a transmission of the UE is less than a maximum channel occupancy time and a gap between the transmission of the UE and a transmission to the UE is not greater than a first fixed duration, performing, without sensing, a transmission to the UE immediately after the gap within the maximum channel occupancy time in a channel in which the transmission of the UE is performed. In this case, the first fixed duration is 16 μs.

[0035] The method may further include, when the gap between the transmission of the UE and the transmission to the UE is not greater than the first fixed duration, performing, without sensing for a predetermined duration, a transmission to the UE immediately after the gap. In this case, the predetermined duration may be a constraint applied to the transmission of the base station separately from the maximum channel occupancy time.

[0036] The method may further include: when the gap between the transmission of the UE and the transmission to the UE is equal to the first fixed duration, attempting a first fixed-duration-based channel access in a channel in which the transmission of the UE is performed. In this case, the first fixed-duration-based channel access may be a channel access in which the base station that allows performing the first fixed-duration-based channel access when the channel is sensed idle within the first fixed duration performs a transmission immediately after the first fixed duration.

[0037] The method may further include attempting a second fixed-duration based channel access in a channel where the UE's transmission is performed when a gap between the UE's transmission and the transmission to the UE is not greater than a second fixed duration. In this case, the second fixed-duration based channel access may be a channel access where a base station that allows the second fixed-duration based channel access to be performed when the channel is sensed idle within the second fixed duration performs a transmission immediately after the second fixed duration. Additionally, the second fixed duration may be 25 μs.

[0038] Channel occupancy including the UE's transmission and the base station's transmission to the UE may be initiated by the base station.

[0039] Channel occupancy including the UE's transmission and the base station's transmission to the UE may be initiated by the UE.

[0040] Advantageous Effects

[0041] Embodiments of the present invention provide a channel access method for performing transmissions in a wireless communication system operating in an unlicensed band and an apparatus using the channel access method.

[0042] The effects to be achieved by the present invention are not limited to the above effects, and those of ordinary skill in the art will clearly understand other effects not mentioned from the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Illustrates an example of a radio frame structure used in a wireless communication system;

[0044] Figure 2 Illustrates an example of a downlink (DL) / uplink (UL) time slot structure in a wireless communication system;

[0045] Figure 3 Is a diagram for explaining a physical channel used in a 3GPP system and a typical signal transmission method using the physical channel;

[0046] Figure 4 Illustrates an SS / PBCH block for initial cell access in a 3GPP NR system;

[0047] Figure 5 Illustrates a process for transmitting control information and a control channel in a 3GPP NR system;

[0048] Figure 6 Illustrates a control resource set (CORESET) in a 3GPP NR system where a physical downlink control channel (PUCCH) can be transmitted;

[0049] Figure 7Diagram of a method for configuring a PDCCH search space in a 3GPP NR system;

[0050] Figure 8 It is a conceptual diagram illustrating carrier aggregation;

[0051] Figure 9 It is a diagram for explaining signal carrier communication and multi-carrier communication;

[0052] Figure 10 It is a diagram showing an example where cross-carrier scheduling technology is applied;

[0053] Figure 11 Diagram of a code block group (CBG) configuration and its time-frequency resource mapping according to an embodiment of the present invention;

[0054] Figure 12 Diagram of a process in which a base station performs TB-based transmission or CBG-based transmission according to an embodiment of the present invention, and a UE sends HARQ-ACK in response thereto;

[0055] Figure 13 Diagram of a new radio unlicensed (NR-U) service environment;

[0056] Figure 14 Diagram of an embodiment of an arrangement scenario of a UE and a base station in an NR-U service environment;

[0057] Figure 15 Diagram of a communication method (e.g., wireless LAN) operating in an existing unlicensed frequency band;

[0058] Figure 16 Diagram of a category 4 LBT-based channel access process according to an embodiment of the present invention;

[0059] Figure 17 Diagram of an embodiment of a method for adjusting a contention window size (CWS) based on HARQ-ACK feedback;

[0060] Figure 18 It is a block diagram illustrating the configuration of a UE and a base station according to an embodiment of the present invention;

[0061] Figure 19 Diagram of a situation where, according to an embodiment of the present invention, when the duration of a transmission within a channel occupancy initiated by an initiating node does not exceed the maximum channel occupancy time (MCOT) of the channel occupancy, a responding node performs a transmission within the channel occupancy time (COT) initiated by the initiating node;

[0062] Figure 20 Diagram of the operation of a UE when a downlink transmission does not occupy as much as the MCOT within a channel occupancy initiated by a base station and the base station schedules or configures the transmission of the UE according to an embodiment of the present invention. Detailed Embodiments

[0063] The terms used in the specification are adopted as the currently widely used general terms as much as possible in consideration of the functions in the present invention, but these terms may be changed according to the intentions, habits of those skilled in the art, and the emergence of new technologies. Additionally, in specific cases, there are terms arbitrarily selected by the applicant, and in such cases, their meanings will be described in the corresponding description part of the present invention. Therefore, it is intended that the terms used in the specification should not be analyzed only based on the name of the term, but should be analyzed based on the substantial meanings of the terms and the content throughout the specification.

[0064] Throughout the specification and the following claims, when an element is described as "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. Additionally, unless explicitly described to the contrary, the word "comprising" will be understood to imply including the said element without implying the exclusion of any other element. Furthermore, in some exemplary embodiments, limitations such as "greater than or equal to" or "less than or equal to" based on a specific threshold may be appropriately replaced with "greater than" or "less than", respectively.

[0065] The following technologies can be used in various wireless access systems: such as Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single-Carrier FDMA (SC-FDMA), etc. CDMA can be implemented by wireless technologies such as Universal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA can be implemented by wireless technologies such as Global System for Mobile Communications (GSM) / General Packet Radio Service (GPRS) / Enhanced Data Rates for GSM Evolution (EDGE). OFDMA can be implemented by wireless technologies such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, Evolved UTRA (E-UTRA), etc. UTRA is part of the Universal Mobile Telecommunications System (UMTS). The 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) is part of the Evolved UMTS (E-UMTS) 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 clear description, 3GPP NR is mainly described, but the technical idea of the present invention is not limited thereto.

[0066] Unless otherwise specified herein, a base station may include a next-generation node B (gNB) defined in 3GPP NR. In addition, unless otherwise specified, a terminal may include a user equipment (UE). Hereinafter, for the purpose of helping understanding the description, each content is described separately by an embodiment, but each embodiment may be used in combination with each other. In this specification, the configuration of the UE may indicate the configuration through the base station. More specifically, the base station may configure the value of a parameter used in the operation of the UE or the radio communication system by transmitting a channel or a signal to the UE.

[0067] Figure 1 An example of a radio frame structure used in a radio communication system is illustrated.

[0068] Reference Figure 1 , a radio frame (or radio frame) used in the 3GPP NR system may have a length of 10 ms (Δf max N f / 100)*T c ). In addition, the radio frame includes 10 subframes (SFs) of equal size. Here, Δf max = 480*10 3 Hz, N f = 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 may be respectively assigned to the 10 subframes within one radio frame. The length of each subframe is 1 ms and may 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 values of μ = 0 to 4 as subcarrier spacing configurations. That is, 15 kHz, 30 kHz, 60 kHz, 120 kHz, and 240 kHz can be used for the subcarrier spacing. One subframe with a length of 1 ms may include 2 μ time slots. In this case, the length of each time slot is 2 -μ ms. Numbers from 0 to 2 μ - 1 may be respectively assigned to the 2 μ time slots within one subframe. In addition, numbers from 0 to 10*2 μ - 1 may be respectively assigned to the time slots within one radio frame. Time resources can 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 time slot index).

[0069] Figure 2 An example of a downlink (DL) / uplink (UL) time slot structure in a wireless communication system is shown. In particular, Figure 2 The structure of a resource grid of a 3GPP NR system is shown.

[0070] There is one resource grid per antenna port. Refer to Figure 2 , a time slot includes a plurality of orthogonal frequency division multiplexing (OFDM) symbols in the time domain and a plurality of resource blocks (RBs) in the frequency domain. One OFDM symbol also refers to a symbol interval. Unless otherwise specified, an OFDM symbol can be abbreviated as a symbol for simplicity. One RB includes 12 consecutive subcarriers in the frequency domain. Refer to Figure 2 , the signal transmitted from each time slot can be represented by a resource grid including N size,μ grid,x *N RB sc subcarriers and N slot symb OFDM symbols. Here, when the signal is a DL signal, x = DL, and when the signal is a UL signal, x = UL. N size,μ grid,x represents the number of resource blocks (RBs) according to the subcarrier spacing component μ (x is DL or UL), and N slot symb represents the number of OFDM symbols in a time slot. N RB sc is the number of subcarriers that make up one RB and N RB sc = 12. The OFDM symbol can be referred to as a cyclic prefix OFDM (CP-OFDM) symbol or a discrete Fourier transform spread OFDM (DFT-s-OFDM) symbol according to the multiple access scheme.

[0071] The number of OFDM symbols included in a time slot can vary according to the length of the cyclic prefix (CP). For example, in the case of a normal CP, a time slot includes 14 OFDM symbols, but in the case of an extended CP, a time slot can include 12 OFDM symbols. In a specific embodiment, the extended CP can only be used at a 60 kHz subcarrier spacing. In Figure 2 , for the convenience of description, as an example, a time slot is configured with 14 OFDM symbols, but the embodiments of the present disclosure can be applied to time slots with different numbers of OFDM symbols in a similar manner. Refer to Figure 2 , each OFDM symbol includes N size,μ grid,x *N RB scSub - carriers. The types of sub - carriers can be divided into data sub - carriers for data transmission, reference signal sub - carriers for the transmission of reference signals, and guard bands. The carrier frequency is also referred to as the center frequency (fc).

[0072] An RB can be defined by N RB sc (e.g., 12) consecutive sub - carriers in the frequency domain. For reference, a resource configured with one OFDM symbol and one sub - carrier can be called a resource element (RE) or a tone. Thus, an RB can be configured with N slot symb *N RB sc resource elements. Each resource element in the resource grid can be uniquely defined by a pair of indices (k, l) in a time slot. k can be the index assigned from 0 to N size,μ grid,x *N RB sc –1 in the frequency domain, and l can be the index assigned from 0 to N slot symb –1 in the time domain.

[0073] For the UE to receive signals from the base station or send signals to the base station, the time / frequency of the UE can be synchronized with the time / frequency of the base station. This is because when the base station and the UE are synchronized, the UE can determine the time and frequency parameters necessary to demodulate DL signals and send UL signals at the correct time.

[0074] Each symbol of a radio frame used in time - division duplex (TDD) or unpaired spectrum can be configured with at least one of DL symbols, UL symbols, and flexible symbols. A radio frame used as a DL carrier in frequency - division duplex (FDD) or paired spectrum can be configured with DL symbols or flexible symbols, while a radio frame used as a UL carrier can be configured with UL symbols or flexible symbols. In DL symbols, DL transmission is possible, but UL transmission is unavailable. In UL symbols, UL transmission is possible, but DL transmission is unavailable. A flexible symbol can be determined to be used as DL or UL according to the signal.

[0075] Information on the type of each symbol, i.e., information indicating any one of a DL symbol, a UL symbol, and a flexible symbol, can be configured with a cell-specific or common Radio Resource Control (RRC) signal. Additionally, information on the type of each symbol can be additionally configured with a UE-specific or dedicated RRC signal. The base station notifies, by using a cell-specific RRC signal, i) the period of the cell-specific slot configuration, ii) the number of slots having only DL symbols starting from the beginning of the period of the cell-specific slot configuration, iii) the number of DL symbols starting from the first symbol of the slot immediately following the slot having only DL symbols, iv) the number of slots having only UL symbols starting from the end of the period of the cell-specific slot configuration, and v) the number of UL symbols starting from the last symbol of the slot immediately preceding the slot having only UL symbols. Here, a symbol not configured with any one of a UL symbol and a DL symbol is a flexible symbol.

[0076] When the information on the symbol type is configured with a UE-specific RRC signal, the base station can signal whether the flexible symbol is a DL symbol or a UL symbol with a cell-specific RRC signal. In this case, the UE-specific RRC signal cannot change a DL symbol or a UL symbol configured with a cell-specific RRC signal to another symbol type. The UE-specific RRC signal can signal the number of DL symbols among the N slot symb symbols of the corresponding slot of each slot and the number of UL symbols among the N slot symb symbols of the corresponding slot. In this case, the DL symbols of the slot can be continuously configured from the first symbol to the i-th symbol of the slot. Additionally, the UL symbols of the slot can be continuously configured from the j-th symbol to the last symbol of the slot (where i < j). In a slot, a symbol not configured with any one of a UL symbol and a DL symbol is a flexible symbol.

[0077] The type of the symbol configured with the above RRC signal can be referred to as a semi-static DL / UL configuration. In the semi-static DL / UL configuration previously configured with an RRC signal, the flexible symbol can be indicated as a DL symbol, a UL symbol indication, or a flexible symbol by dynamic slot format information (SFI) sent on a Physical DL Control Channel (PDCCH). In this case, a DL symbol or a UL symbol configured with an RRC signal is not changed to another symbol type. Table 1 illustrates the dynamic SFI that the base station can indicate to the UE.

[0078] [Table 1]

[0079]

[0080] 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 in a time slot may be allowed.

[0081] Figure 3 It is a diagram for explaining physical channels used in a 3GPP system (e.g., NR) and a typical signal transmission method using the physical channels.

[0082] 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 may synchronize with the BS in the initial cell search. To this end, the UE may receive a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) from the base station to synchronize with the base station and obtain information such as a cell ID. Thereafter, the UE is able to receive a physical broadcast channel from the base station and obtain broadcast information in the cell.

[0083] After the initial cell search is completed, the UE receives a physical downlink shared channel (PDSCH) according to a physical downlink control channel (PDCCH) and 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 cell common system information for the normal operation of the physical layer in the UE's radio resource control (RRC), and is referred to as remaining system information, or is referred to as system information block (SIB) 1.

[0084] When the UE initially accesses the base station or does not have radio resources for signal transmission (i.e., the UE is in the RRC_IDLE mode), the UE may perform a random access procedure (operations S103 to S106) on the base station. First, the UE is able to transmit a preamble through a physical random access channel (PRACH) (S103) and receive a response message for the preamble from the base station through the PDCCH and the corresponding PDSCH (S104). When the UE receives a valid random access response message, the UE transmits data including the UE's identifier, 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 from the base station for conflict resolution. If the UE successfully receives the PDCCH through the UE's identifier (S106), the random access procedure is terminated. The UE may obtain UE-specific system information for the normal operation of the physical layer in the UE's 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).

[0085] The RRC layer is used to generate or manage messages for controlling the connection between a UE and a radio access network (RAN). More specifically, in the RRC layer, the base station and the UE can perform functions such as broadcasting cell system information required for each UE in the cell, managing mobility and handover, measurement reporting of the UE, and storage management including UE capability management and device management. Generally, since the update period of the signals transmitted in the RRC layer is longer than the transmission time interval (TTI) in the physical layer, the RRC signals are not changed and are maintained for a relatively long interval.

[0086] After the above process, the UE receives PDCCH / PDSCH (S107) and transmits 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 can include control information such as resource allocation information for the UE. Additionally, the format of the DCI can vary according to a predetermined use. The uplink control information (UCI) transmitted by the UE to the base station via the UL includes DL / UL ACK / NACK signals, a channel quality indicator (CQI), a precoding matrix index (PMI), a rank indicator (RI), etc. Here, the CQI, PMI, and RI can be included in the channel state information (CSI). In the 3GPP NR system, the UE can transmit control information such as the above-mentioned HARQ-ACK and CSI via the PUSCH and / or PUCCH.

[0087] Figure 4 The figure shows an SS / PBCH block for initial cell access in the 3GPP NR system.

[0088] When the power is turned on or when the UE wants to access a new cell, the UE can acquire time and frequency synchronization with the cell and perform an initial cell search 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, for example, a primary synchronization signal (PSS) and a secondary synchronization signal (SSS), from the base station and synchronize with the base station. In this case, the UE can obtain information such as the cell identifier (ID).

[0089] Reference Figure 4 of (a) will describe the synchronization signal (SS) in more detail. The synchronization signal can be classified into a PSS and an SSS. The PSS can be used to obtain time-domain synchronization and / or frequency-domain synchronization, such as OFDM symbol synchronization and slot synchronization. The SSS can be used to obtain frame synchronization and the cell group ID. Reference Figure 4As shown in (a) of [Table 2], the SS / PBCH block can be configured with 20 consecutive RBs ( = 240 sub - carriers) on the frequency axis and can be configured with 4 consecutive OFDM symbols on the time axis. In this case, in the SS / PBCH block, the PSS is transmitted in the first OFDM symbol and the SSS is transmitted in the third OFDM symbol through sub - carriers numbered 56 to 182. Here, the lowest sub - carrier index of the SS / PBCH block is numbered from 0. In the first OFDM symbol where the PSS is transmitted, the base station does not transmit signals through the remaining sub - carriers, i.e., sub - carriers numbered 0 to 55 and 183 to 239. In addition, in the third OFDM symbol where the SSS is transmitted, the base station does not transmit signals through sub - carriers numbered 48 to 55 and 183 to 191. The base station transmits the physical broadcast channel (PBCH) through the remaining REs in the SS / PBCH block other than the above signals.

[0090] [Table 2]

[0091]

[0092] The SS allows a total of 1008 unique physical - layer cell IDs to be grouped into 336 physical - layer cell identifier groups through the combination of three PSSs and SSSs, with each group including three unique identifiers. Specifically, such that each physical - layer cell ID will be only part of one physical - layer cell identifier group. Thus, the physical - layer cell ID N cell ID = 3N (1) ID + N (2) ID can be uniquely defined by an index N indicating the range of the physical - layer cell identifier group from 0 to 335 (1) ID and an index N indicating the range of the physical - layer identifier within the physical - layer cell identifier group from 0 to 2 (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 PSS (n) of the PSS is as follows.

[0093] d PSS (n)= 1 - 2x(m)

[0094]

[0095] 0 ≤ n < 127

[0096] Here, x(i + 7) = (x(i + 4) + x(i)) mod 2 and is given as

[0097] [x(6) x(5) x(4) x(3) x(2) x(1) x(0)] = [1 1 1 0 1 1 0].

[0098] In addition, the sequence d SSS (n) of the SSS is as follows.

[0099] d SSS (n) = [1 - 2x0((n + m0) mod 127)][1 - 2x1((n + m1) mod 127)]

[0100]

[0101]

[0102] 0 ≤ n < 127

[0103] Here, and is given as

[0104] [x0(6) x0(5) x0(4) x0(3) x0(2) x0(1) x0(0)] = [0 0 0 0 0 0 1]

[0105] [x1(6) x1(5) x1(4) x1(3) x1(2) x1(1) x1(0)] = [0 0 0 0 0 0 1].

[0106] A radio frame with a length of 10 ms can be divided into two half - frames with a length of 5 ms. Refer to Figure 4For (b), the time slots for transmitting SS / PBCH blocks in each half-frame will be described. The time slots for transmitting SS / PBCH blocks can be any of cases A, B, C, D, and E. In case A, the subcarrier spacing is 15 kHz and the starting time point of the SS / PBCH block is the ({2, 8}+14*n)-th symbol. In this case, at a carrier frequency of 3 GHz or lower, n = 0 or 1. Additionally, at a carrier frequency higher than 3 GHz and lower than 6 GHz, n can be 0, 1, 2, 3. In case B, the subcarrier spacing is 30 kHz and the starting time point of the SS / PBCH block is {4, 8, 16, 20}+28*n. In this case, at a carrier frequency of 3 GHz or lower, n = 0. Additionally, at a carrier frequency higher than 3 GHz and lower than 6 GHz, n can be 0, 1. In case C, the subcarrier spacing is 30 kHz and the starting time point of the SS / PBCH block is the ({2, 8}+14*n)-th symbol. In this case, at a carrier frequency of 3 GHz or lower, n = 0 or 1. Additionally, at a carrier frequency higher than 3 GHz and lower than 6 GHz, n can be 0, 1, 2, 3. In case D, the subcarrier spacing is 120 kHz and the starting time point of the SS / PBCH block is the ({4, 8, 16, 20}+28*n)-th symbol. In this case, at a carrier frequency of 6 GHz or higher, n = 0, 1, 2, 3, 5, 6, 7, 8, 10, 11, 12, 13, 15, 16, 17, 18. In case E, the subcarrier spacing is 240 kHz and the starting time point of the SS / PBCH block is the ({8, 12, 16, 20, 32, 36, 40, 44}+56*n)-th symbol. In this case, at a carrier frequency of 6 GHz or higher, n = 0, 1, 2, 3, 5, 6, 7, 8.

[0107] Figure 5 Illustrates the process of transmitting control information and control channels in a 3GPP NR system. Refer to Figure 5In (a), the base station may add a Cyclic Redundancy Check (CRC) masked (e.g., by exclusive - or operation) with a Radio Network Temporary Identifier (RNTI) to control information (e.g., Downlink Control Information (DCI)) (S202). The base station may scramble the CRC with an RNTI value determined according to the purpose / target of each control information. The common RNTIs used by one or more UEs may include at least one of a System Information RNTI (SI - RNTI), a Paging RNTI (P - RNTI), a Random Access RNTI (RA - RNTI), and a Transmit Power Control RNTI (TPC - RNTI). In addition, UE - specific RNTIs may include at least one of a Cell Temporary RNTI (C - RNTI) and a CS - RNTI. Thereafter, the base station may perform rate matching (S206) according to the amount of resources used for PDCCH transmission after performing channel coding (e.g., polar coding) (S204). Thereafter, the base station may multiplex the DCI based on a Physical Downlink Control Channel (PDCCH) structure based on Control Channel Elements (CCEs) (S208). In addition, the base station may apply additional processes such as scrambling, modulation (e.g., QPSK), interleaving, etc. to the multiplexed DCI (S210), and then map the DCI to the resources to be transmitted. A CCE is the basic resource unit for the PDCCH, and one CCE may include multiple (e.g., six) Resource Element Groups (REGs). One REG may be configured with multiple (e.g., 12) Resource Elements (REs). The number of CCEs used for one PDCCH may be defined as the aggregation level. In the 3GPP NR system, aggregation levels of 1, 2, 4, 8, or 16 may be used. Figure 5 Figure (b) is related to the CCE aggregation level and the multiplexing of the PDCCH, and illustrates the type of CCE aggregation level for one PDCCH and the CCEs transmitted in the control region accordingly.

[0108] Figure 6 Illustrates a Control Resource Set (CORESET) in the 3GPP NR system in which a Physical Uplink Control Channel (PUCCH) can be transmitted.

[0109] A CORESET is time-frequency resources in which PDCCH (i.e., control signals for UEs) are transmitted. Additionally, a search space to be described later can be mapped to a CORESET. Thus, a UE can monitor the time-frequency domain designated as a CORESET instead of monitoring all frequency bands for PDCCH reception and decode the PDCCH mapped to the CORESET. A base station can configure one or more CORESETs for a UE for each cell. A CORESET can be configured with up to three consecutive symbols on the time axis. Additionally, a CORESET can be configured in units of six consecutive PRBs on the frequency axis. In Figure 5 the embodiment of, CORESET#1 is configured with consecutive PRBs, while CORESET#2 and CORESET#3 are configured with non-consecutive PRBs. A CORESET can be located in any symbol in a time slot. For example, in Figure 5 the embodiment of, CORESET#1 starts from the first symbol of a time slot, CORESET#2 starts from the fifth symbol of the time slot, and CORESET#9 starts from the ninth symbol of the time slot.

[0110] Figure 7 The figure illustrates a method for setting a PDCCH search space in a 3GPP NR system.

[0111] To transmit PDCCH to a UE, each CORESET can have at least one search space. In an embodiment of the present disclosure, a search space is a set of all time-frequency resources (hereinafter, PDCCH candidates) that can be used to transmit PDCCH for a UE. A search space can include a common search space that requires UEs of 3GPP NR to search jointly and a UE-specific search space or UE-specific search spaces that require a specific UE to search. In the common search space, a UE can monitor the PDCCH that is set such that all UEs in cells belonging to the same base station search jointly. Additionally, a UE-specific search space can be set for each UE such that the UE monitors the PDCCH assigned to each UE at a search space position that varies according to the UE. In the case of a UE-specific search space, since the limited control region where PDCCH can be allocated, the search spaces among UEs can partially overlap and be allocated. Monitoring PDCCH includes blindly decoding PDCCH candidates in the search space. When the blind decoding is successful, it can be expressed as (successfully) detecting / receiving the PDCCH, while when the blind decoding fails, it can be expressed as not detected / not received or not successfully detected / not received the PDCCH.

[0112] For ease of explanation, a physical downlink control channel (PDCCH) that is scrambled with a group common (GC) RNTI known to one or more UEs in advance to send downlink control information to one or more UEs is referred to as a group common (GC) PDCCH or a common PDCCH. In addition, a PDCCH that is scrambled with an RNTI of a specific terminal known to a specific UE to send uplink scheduling information or downlink scheduling information to the specific UE is referred to as a UE-specific PDCCH. The common PDCCH can be included in a common search space, and the UE-specific PDCCH can be included in the common search space or the UE-specific search space.

[0113] The base station can signal information related to resource allocation regarding the paging channel (PCH) and the downlink shared channel (DL-SCH) as transmission channels (i.e., DL grant) or information related to resource allocation regarding the uplink shared channel (UL-SCH) and hybrid automatic repeat request (HARQ) (i.e., UL grant) to each UE or UE group via the PDCCH. The base station can send the PCH transport block and the DL-SCH transport block via the PDSCH. The base station can send data excluding specific control information or specific service data via the PDSCH. In addition, the UE can receive data excluding specific control information or specific service data via the PDSCH.

[0114] The base station can include in the PDCCH information on which UE (one or more UEs) the PDSCH data is to be sent to and how the PDSCH data is to be received and decoded by the corresponding UE, and send the PDCCH. For example, assume that the DCI transmitted on a specific PDCCH is CRC masked with an RNTI "A", and the DCI indicates that the PDSCH is allocated to radio resource "B" (e.g., frequency position) and indicates transmission format information "C" (e.g., transport block size, modulation scheme, coding information, etc.). The UE monitors the PDCCH using the RNTI information the UE has. In this case, if there is a UE that performs blind decoding of the PDCCH using the "A" RNTI, the UE receives the PDCCH and receives the PDSCH indicated by "B" and "C" based on the information of the received PDCCH.

[0115] Table 3 shows an embodiment of a physical uplink control channel (PUCCH) used in a wireless communication system.

[0116] [Table 3]

[0117] PUCCH format Length of OFDM symbol Number of bits 0 1-2 ≤2 1 4-14 ≤2 2 1-2 ＞2 3 4-14 ＞2 4 4-14 ＞2

[0118] The PUCCH can be used to send the following uplink control information (UCI).

[0119] - Scheduling Request (SR): Information used to request UL UL-SCH resources.

[0120] - HARQ-ACK: Response to PDCCH (indicating DL SPS release) and / or response to DL transport block (TB) on PDSCH. HARQ-ACK indicates whether the information successfully transmitted on PDCCH or PDSCH is received. The HARQ-ACK response includes positive ACK (simply referred to as ACK), negative ACK (hereinafter NACK), discontinuous transmission (DTX), or NACK / DTX. Here, the term HARQ-ACK is used interchangeably with HARQ-ACK / NACK and ACK / NACK. Generally, ACK can be represented by bit value 1, while NACK can be represented by bit value 0.

[0121] - Channel State Information (CSI): Feedback information about DL channels. The UE generates it based on the CSI-Reference Signal (RS) sent by the base station. Feedback information related to multiple-input multiple-output (MIMO) includes Rank Indicator (RI) and Precoding Matrix Indicator (PMI). CSI can be divided into CSI part 1 and CSI part 2 according to the information indicated by CSI.

[0122] In the 3GPP NR system, five PUCCH formats can be used to support various service scenarios, various channel environments, and frame structures.

[0123] PUCCH format 0 is a format capable of delivering 1-bit or 2-bit HARQ-ACK information or SR. PUCCH format 0 can be sent through one or two OFDM symbols on the time axis and one PRB on the frequency axis. When PUCCH format 0 is sent in two OFDM symbols, the same sequence on the two symbols can be sent through different RBs. In this case, the sequence can be a sequence obtained by cyclic shift (CS) from the basic sequence used in PUCCH format 0. Through this, the UE can obtain frequency diversity gain. More specifically, the UE can determine the cyclic shift (CS) value m bit bit UCI (M bit = 1 or 2). Additionally, a basic sequence of length 12 can be sent by mapping the cyclic shift sequence based on the predetermined CS value m cs . to 12 REs of one OFDM symbol and one RB. When the number of cyclic shifts available to the UE is 12 and M cs = 1, 1-bit UCI 0 and 1 can be mapped to two cyclic shift sequences respectively, and the cyclic shift values of the two cyclic shift sequences have a difference of 6. Additionally, when M bit = 1 bitWhen M = 2, the 2-bit UCI 00, 01, 11, and 10 can be respectively mapped to four cyclic shift sequences with a difference of 3 in cyclic shift values.

[0124] PUCCH format 1 can carry 1-bit or 2-bit HARQ-ACK information or SR. PUCCH format 1 can be transmitted through consecutive OFDM symbols on the time axis and one PRB on the frequency axis. Here, the number of OFDM symbols occupied by PUCCH format 1 can be one of 4 to 14. More specifically, the UCI with M bit = 1 can be modulated by BPSK. The UE can modulate the UCI with M bit = 2 using quadrature phase shift keying (QPSK). The signal is obtained by multiplying the modulated complex-valued symbol d(0) by a sequence of length 12. In this case, the sequence can be the basic sequence for PUCCH format 0. The UE extends the even-numbered OFDM symbols assigned to PUCCH format 1 by a time-axis orthogonal cover code (OCC) to transmit the obtained signal. PUCCH format 1 determines the maximum number of different UEs multiplexed in one RB according to the length of the OCC to be used. The demodulation reference signal (DMRS) can be extended by the OCC and mapped to the odd-numbered OFDM symbols of PUCCH format 1.

[0125] PUCCH format 2 can carry UCI of more than 2 bits. PUCCH format 2 can be transmitted through one or two OFDM symbols on the time axis and one or more RBs on the frequency axis. When PUCCH format 2 is transmitted in two OFDM symbols, the sequences transmitted in different RBs through the two OFDM symbols can be the same. Here, the sequence can be a plurality of modulated complex-valued symbols d(0),..., d(M symbol - 1). Here, M symbol can be M bit / 2. Through this, the UE can obtain a frequency diversity gain. More specifically, the M bit -bit UCI (M bit > 2) is bit-level scrambled, QPSK modulated, and mapped to the RBs of one or two OFDM symbols. Here, the number of RBs can be one of 1 to 16.

[0126] PUCCH format 3 or PUCCH format 4 can deliver UCI of more than 2 bits. PUCCH format 3 or PUCCH format 4 can be transmitted through consecutive OFDM symbols on the time axis and one PRB on the frequency axis. The number of OFDM symbols occupied by PUCCH format 3 or PUCCH format 4 can be one of 4 to 14. Specifically, the UE modulates M bit bits of UCI (M bit>2) using π / 2 - Binary Phase Shift Keying (BPSK) or QPSK to generate complex-valued symbols d(0) to d(M symb -1). Here, when using π / 2-BPSK, M symb = M bit , while when using QPSK, M symb = M bit / 2. The UE may not apply block unit extension to PUCCH format 3. However, the UE may use a PreDFT-OCC of length 12 to apply block unit extension to one RB (i.e., 12 subcarriers), so that PUCCH format 4 can have two or four multiplexing capabilities. The UE performs transmit precoding (or DFT precoding) on the extended signal and maps it to each RE to transmit the extended signal.

[0127] In this case, the number of RBs occupied by PUCCH format 2, PUCCH format 3, or PUCCH format 4 can be determined according to the length and maximum coding rate of the UCI transmitted by the UE. When the UE uses PUCCH format 2, the UE can transmit HARQ-ACK information and CSI information together through the PUCCH. When the number of RBs that the UE can transmit is greater than the maximum number of RBs that PUCCH format 2, PUCCH format 3, or PUCCH format 4 can use, the UE can not transmit some UCI information according to the priority of the UCI information, but only transmit the remaining UCI information.

[0128] PUCCH format 1, PUCCH format 3, or PUCCH format 4 can be configured by RRC signaling to indicate frequency hopping in a time slot. When frequency hopping is configured, the index of the RB to be frequency-hopped can be configured by RRC signaling. When PUCCH format 1, PUCCH format 3, or PUCCH format 4 is transmitted through N OFDM symbols on the time axis, the first hop can have floor(N / 2) OFDM symbols and the second hop can have ceiling(N / 2) OFDM symbols.

[0129] PUCCH format 1, PUCCH format 3, or PUCCH format 4 can be configured to be repetitively transmitted in multiple time slots. In this case, the number of time slots K for repetitively transmitting the PUCCH can be configured by an RRC signal. The repetitively transmitted PUCCH must start from an OFDM symbol at a constant position in each time slot and have a constant length. When one of the OFDM symbols among the OFDM symbols of the time slots in which the UE is supposed to transmit the PUCCH is indicated as a DL symbol by an RRC signal, the UE may not transmit the PUCCH in the corresponding time slot and delay the transmission of the PUCCH to the next time slot to transmit the PUCCH.

[0130] Meanwhile, in the 3GPP NR system, the UE can perform transmission / reception using a bandwidth equal to or less than the bandwidth of a carrier (or cell). To this end, the UE can receive a bandwidth part (BWP) configured with some bandwidth of the carrier bandwidth as a continuous bandwidth. 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 a paired spectrum can receive up to four DL BWPs on a DL carrier (or cell) and receive up to four UL BWPs on a UL carrier (or cell). The UE can activate one DL BWP and one UL BWP for each carrier (or cell). The UE may not perform reception or transmission in time-frequency resources other than the activated BWP. The activated BWP can be referred to as an active BWP.

[0131] The base station can indicate the activated BWP among the BWPs configured by the UE through downlink control information (DCI). The BWP indicated by the DCI is activated, and other configured BWPs are deactivated. In a carrier (or cell) operating according to TDD operation, the base station can include a bandwidth part indicator (BPI) in the DCI for scheduling the PDSCH or PUSCH, and the bandwidth part indicator indicates the BWP to be activated to change the DL / UL BWP pair of the UE. The UE can receive the DCI for scheduling the PDSCH or PUSCH and can identify the DL / UL BWP pair activated based on the BPI. For a DL carrier (or cell) operating according to FDD operation, the base station can include a BPI indicating the BWP to be activated in the DCI for scheduling the PDSCH to change the DL BWP of the UE. For a UL carrier (or cell) operating according to FDD operation, the base station can include a BPI indicating the BWP to be activated in the DCI for scheduling the PUSCH to change the UL BWP of the UE.

[0132] Figure 8 is a conceptual diagram illustrating the concept of carrier aggregation.

[0133] Carrier aggregation is a method in which a UE uses multiple frequency blocks or (in a logical sense) cells configured with UL resources (or component carriers) and / or DL resources (or component carriers) as a large logical frequency band so that a wireless communication system can use a wider frequency band. A component carrier can also be referred to by terms such as primary cell (PCell), secondary cell (SCell), or primary SCell (PScell). However, hereinafter, for the sake of description, the term "component carrier" is used.

[0134] Reference Figure 8 , as an example of a 3GPP NR system, the entire system frequency band can include up to 16 component carriers, and each component carrier can have a bandwidth of up to 400 MHz. A component carrier can include one or more physically contiguous subcarriers. Although each component carrier is shown in Figure 8 as having the same bandwidth, this is merely an example, and each component carrier can have a different bandwidth. Additionally, although each component carrier is shown as being adjacent to each other on the frequency axis, the drawings are shown in a logical concept, and each component carrier can be physically adjacent to each other or can be spaced apart.

[0135] Different center frequencies can be used for each component carrier. Additionally, a common center frequency can be used in physically adjacent component carriers. Assuming that all component carriers are physically adjacent in the embodiment of Figure 8 , the center frequency A can be used in all component carriers. Additionally, 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.

[0136] When expanding the total system frequency band through carrier aggregation, the frequency band used for communicating with each UE can be defined in units of component carriers. UE A can use 100 MHz as the total system frequency band and use all five component carriers to perform communication. UE B1 to B5 can only use a 20 MHz bandwidth and use one component carrier to perform communication. UE C1 and C2 can each use a 40 MHz bandwidth and use two component carriers to perform communication. These two component carriers can be logically / physically adjacent or not adjacent. UE C1 represents the case of using two non-adjacent component carriers, while UE C2 represents the case of using two adjacent component carriers.

[0137] Figure 9 are diagrams for illustrating signal carrier communication and multi-carrier communication. In particular, Figure 9 (a) of Figure 9 shows a single-carrier subframe structure and (b) of

[0138] Reference Figure 9 As shown in (a) of Figure 9 , in the FDD mode, a general wireless communication system can perform data transmission or reception through a DL frequency band and a corresponding UL frequency band. In another specific embodiment, in the TDD mode, the wireless communication system can divide a radio frame into UL time units and DL time units in the time domain, and perform data transmission or reception through the UL / DL time units. Reference Figure 9 As shown in (b) of Figure 9 , it is possible to aggregate three 20 MHz component carriers (CCs) into each of the UL and DL, enabling support for a bandwidth of 60 MHz. Each CC can be adjacent or non - adjacent to each other in the frequency domain. Figure 9 Figure (b) of Figure 9 shows a case where the bandwidths of the UL CC and the DL CC are the same and symmetric, but 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 CCs allocated / configured to a specific UE through RRC can be referred to as the serving DL / UL CCs of the specific UE.

[0139] The base station can communicate with the UE by activating some or all of the serving CCs of the UE or deactivating some CCs. The base station can change the CCs to be activated / deactivated and the number of CCs to be activated / deactivated. If the base station allocates the CCs available to the UE as cell - specific or UE - specific, at least one of the allocated CCs can be deactivated unless the CC allocation for the UE is completely re - configured or the UE is handed over. One CC not deactivated by the UE is called the primary CC (PCC) or primary cell (PCell), and the CCs that the base station can freely activate / deactivate are called secondary CCs (SCCs) or secondary cells (SCells).

[0140] Meanwhile, 3GPP NR uses the concept of a cell to manage radio resources. A cell is defined as a combination of DL resources and UL resources, i.e., a combination of a DL CC and a UL CC. A cell can be configured with DL resources alone or can be configured with a combination of DL resources and UL resources. When carrier aggregation is supported, the link between the carrier frequency of the DL resources (or DL CC) and the carrier frequency of the UL resources (or UL CC) can 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, a serving cell can be configured with one PCell and zero or more SCells. In the case of a UE in the RRC_CONNECTED state but not configured for carrier aggregation or not supporting carrier aggregation, there is only one serving cell configured with only the PCell.

[0141] As described above, the term "cell" used in carrier aggregation is distinguished from the term "cell" that refers to a geographical area that provides a communication service through a base station or a set of antennas. That is, a component carrier can also be referred to as a scheduling cell, a scheduled cell, a primary cell (PCell), a secondary cell (SCell), or a primary SCell (PScell). However, to distinguish between the cell representing a geographical area and the cell in carrier aggregation, in the present disclosure, the cell in carrier aggregation is referred to as a CC, and the cell in the geographical area is referred to as a cell.

[0142] Figure 10 is a diagram showing an example where the cross-carrier scheduling technique is applied. When cross-carrier scheduling is set, the control channel transmitted through the first CC can use the Carrier Indicator Field (CIF) to schedule the data channel transmitted through the first CC or the second CC. The CIF is included in the DCI. In other words, a scheduling cell is set, and the DL grant / UL grant transmitted in the PDCCH area of the scheduling cell schedules the PDSCH / PUSCH of the scheduled cell. That is, there is a search area for multiple component carriers in the PDCCH area of the scheduling cell. The PCell can basically be the scheduling cell, and a specific SCell can be designated as the scheduling cell by the upper layer.

[0143] In Figure 10In the embodiment, it is assumed that three DL CCs are combined. Here, it is assumed that DL component carrier #0 is the DLPCC (or PCell), and DL component carriers #1 and #2 are DL SCCs (or SCell). In addition, it is assumed that the DLPCC is set as the PDCCH monitoring CC. When cross-carrier scheduling is not configured by UE-specific (or UE-group-specific or cell-specific) higher layer signaling, the CIF is disabled, and each DL CC can send only the PDCCH for scheduling its PDSCH without the CIF according to the NR PDCCH rules (non-cross-carrier scheduling, self-carrier scheduling). At the same time, if cross-carrier scheduling is configured by UE-specific (or UE-group-specific or cell-specific) higher layer signaling, the CIF is enabled, and a specific CC (e.g., DL PCC) can use the CIF to send not only the PDCCH for scheduling the PDSCH of DL CC A but also the PDCCH for scheduling the PDSCH of another CC (cross-carrier scheduling). On the other hand, no PDCCH is sent in another DL CC. Therefore, the UE monitors the PDCCH without the CIF to receive the self-carrier scheduled PDSCH or monitors the PDCCH with the CIF to receive the cross-carrier scheduled PDSCH according to whether cross-carrier scheduling is configured for the UE.

[0144] On the other hand, Figure 9 and Figure 10 FIG. illustrates the subframe structure of the 3GPP LTE-A system, and the same or similar configuration can be applied to the 3GPP NR system. However, in the 3GPP NR system, Figure 9 and Figure 10 the subframe can be replaced by time slots.

[0145] Figure 11 FIG. illustrates the code block group (CBG) configuration and its time-frequency resource mapping according to an embodiment of the present invention. More specifically, Figure 11 (a) FIG. illustrates an embodiment of the CBG configuration included in one transport block (TB), and Figure 11 (b) FIG. illustrates the time-frequency resource mapping of the CBG configuration.

[0146] The channel code defines the maximum supported length. For example, the maximum supported length of the turbo code used in 3GPP LTE(-A) is 6144 bits. However, the length of the transport block (TB) transmitted on the PDSCH may be longer than 6144 bits. If the length of the TB is greater than the maximum supported length, the TB can be divided into code blocks (CBs) with a maximum length of 6144 bits. Each CB is the unit in which channel coding is performed. In addition, in order to perform retransmission effectively, several CBs can be grouped to configure a CBG. The UE and the base station need information on how to configure the CBG.

[0147] The CBGs and CBs within a TB can be configured according to various embodiments. According to an embodiment, the number of available CBGs can be determined as a fixed value, or can be configured using the RRC configuration information between the base station and the UE. In this case, the number of CBs is determined by the length of the TB, and the CBGs can be configured depending on the information of the determined number. According to another embodiment, the number of CBs to be included in one CBG can be determined as a fixed value, or can be configured using the RRC configuration information between the base station and the UE. In this case, if the number of CBs is determined by the length of the TB, the number of CBGs can be configured depending on the information about the number of CBs per CBG.

[0148] Reference Figure 11 Referring to the embodiment of (a), one TB can be divided into eight CBs. The eight CBs can be further grouped into four CBGs. The mapping relationship (or CBG configuration) between the CBs and CBGs can be statically configured between the base station and the UE, or can be established semi-statically using the RRC configuration information. According to another embodiment, the mapping relationship can be configured by dynamic signaling. When the UE receives the PDCCH sent by the base station, the UE can directly or indirectly identify the mapping relationship (or CBG configuration) between the CBs and CBGs through explicit information and / or implicit information. One CBG can contain only one CB, or can include all the CBs constituting one TB. As a reference, the techniques presented in the embodiments of the present invention can be applied regardless of the configuration of the CBs and CBGs.

[0149] Reference Figure 11 (b), map the CBGs constituting one TB to the time-frequency resources where the PDSCH is scheduled. According to an embodiment, each CBG can first be allocated on the frequency axis and then extended on the time axis. When the PDSCH composed of one TB including four CBGs is allocated to seven OFDM symbols, CBG0 can be transmitted on the first and second OFDM symbols, CBG1 can be transmitted on the second, third, and fourth OFDM symbols, CBG2 can be transmitted on the fourth, fifth, and sixth OFDM symbols, and CBG3 can be transmitted on the sixth and seventh OFDM symbols. The time-frequency mapping relationship allocated with the CBGs and the PDSCH can be determined between the base station and the UE. However, Figure 11 (b) The mapping relationship illustrated is for describing the embodiments of the present invention, and the techniques presented in the embodiments of the present invention can be applied regardless of the time-frequency mapping relationship of the CBGs.

[0150] Figure 12 Illustrate the process in which the base station performs TB-based transmission or CBG-based transmission, and the UE sends HARQ-ACK in response thereto. ReferenceFigure 12 The base station can configure a transmission scheme for the UE that is suitable for TB-based transmission and CBG-based transmission. The UE can send HARQ-ACK information bits via PUCCH or PUSCH according to the transmission scheme configured by the base station. The base station can configure the PDCCH to schedule the PDSCH to be sent to the UE. The PDCCH can schedule TB-based transmission and / or CBG-based transmission. For example, one TB or two TBs can be scheduled on the PDCCH. If one TB is scheduled, the UE must feedback 1-bit HARQ-ACK. If two TBs are scheduled, 2-bit HARQ-ACK must be fed back for each of the two TBs. To eliminate the ambiguity between the base station and the UE, there can be a predetermined order between each information bit of the 2-bit HARQ-ACK and the two TBs. As a reference, when the MIMO transmission rank or layer is low, one TB can be sent on one PDSCH, while when the MIMO transmission rank or layer is high, two TBs can be sent on one PDSCH.

[0151] The UE can send 1-bit TB-based HARQ-ACK for each TB to notify the base station whether the reception of each TB is successful. To generate the HARQ-ACK for one TB, the UE can check the reception error of the TB via the TB-CRC. When the TB-CRC for the TB is successfully checked, the UE generates an ACK of the HARQ-ACK for the TB. However, if a TB-CRC error occurs for the TB, the UE generates a NACK of the HARQ-ACK for the TB. The UE sends the TB-based HARQ-ACK generated as described above to the base station. The base station retransmits the TB that is responded with NACK in the TB-based HARQ-ACK received from the UE.

[0152] In addition, the UE may send 1-bit CBG-based HARQ-ACK for each CBG to notify the base station whether the reception of each CBG is successful. To generate the HARQ-ACK for a CBG, the UE may decode all CBs included in the CBG and check for reception errors of each CB through CB-CRC. When the UE successfully receives all CBs constituting a CBG (i.e., when all CB-CRCs are successfully checked), the UE generates an ACK for the HARQ-ACK of the CBG. However, when the UE does not successfully receive at least one of the CBs constituting a CBG (i.e., when at least one CB-CRC error occurs), the UE generates a NACK for the HARQ-ACK of the CBG. The UE sends the CBG-based HARQ-ACK generated as described above to the base station. The base station retransmits the CBGs that are responded with NACK among the CBG-based HARQ-ACKs received from the UE. According to an embodiment, the CB configuration of the retransmitted CBG may be the same as the CB configuration of the previously transmitted CBG. The length of the CBG-based HARQ-ACK information bits sent from the UE to the base station may be determined based on the number of CBGs transmitted through the PDSCH or the maximum number of CBGs configured with the RRC signal.

[0153] On the other hand, even when the UE successfully receives all CBGs included in the TB, a TB-CRC error for the TB may occur. In this case, the UE may perform a flip of the CBG-based HARQ-ACK in order to request a retransmission of the TB. That is, even when all CBGs included in the TB are successfully received, the UE may generate all CBG-based HARQ-ACK information bits as NACKs. When receiving the CBG-based HARQ-ACK feedback in which all HARQ-ACK information bits are NACKs, the base station retransmits all CBGs of the TB.

[0154] According to an embodiment of the present invention, CBG-based HARQ-ACK feedback can be used for the successful transmission of a TB. The base station can instruct the UE to send CBG-based HARQ-ACK. In this case, retransmission techniques based on CBG-based HARQ-ACK can be used. The CBG-based HARQ-ACK can be sent via PUCCH. Additionally, when UCI is configured to be sent via PUSCH, the CBG-based HARQ-ACK can be sent via PUSCH. In PUCCH, the configuration of HARQ-ACK resources can be configured via RRC signaling. Additionally, the actually transmitted HARQ-ACK resources can be indicated via the PDCCH that schedules the PDSCH sent based on CBG. The UE can send the HARQ-ACK for whether the sent CBG has been successfully received via one PUCCH resource indicated by the PDCCH among the PUCCH resources configured by RRC.

[0155] The base station can identify whether the UE has successfully received the CBG sent to the UE via the UE's CBG-based HARQ-ACK feedback. That is, via the HARQ-ACK for each CBG received from the UE, the base station can identify the CBGs that the UE has successfully received and the CBGs that the UE has failed to receive. The base station can perform CBG retransmission based on the received CBG-based HARQ-ACK. More specifically, the base station can only bundle and retransmit the CBGs in response to the failed HARQ-ACK in one TB. In this case, the CBGs in response to the successfully received HARQ-ACK are excluded from the retransmission. The base station can schedule the retransmitted CBGs as a PDSCH and send it to the UE.

[0156] <Communication method in an unlicensed band>

[0157] Figure 13 Illustrate the service environment of New Radio Unlicensed (NR-U).

[0158] Reference Figure 13 , the service environments of NR technology 11 in the existing licensed band and unlicensed NR (NR-U) (i.e., NR technology 12 in the unlicensed band) can be provided to users. For example, in the NR-U environment, techniques such as carrier aggregation can be used to integrate NR technology 11 in the licensed band and NR technology 12 in the unlicensed band, which can contribute to the expansion of network capacity. Additionally, in an asymmetric traffic structure with more downlink data than uplink data, NR-U can provide NR services optimized for various requirements or environments. For convenience, the NR technology in the licensed band is referred to as NR-L (licensed NR), and the NR technology in the unlicensed band is referred to as NR-U (unlicensed NR).

[0159] Figure 14 Illustrate the deployment scenarios of user equipment and base stations in an NR-U service environment. Due to the high-frequency characteristics, the radio communication range of the frequency band targeted by the NR-U service environment is short. Considering this, in an environment where existing NR-L services and NR-U services coexist, the deployment scenarios of user equipment and base stations can be a coverage model or a co-location model.

[0160] In the coverage model, the macro base station can perform wireless communication with X UEs and X' UEs in the macro area (32) by using an authorized carrier and is connected to multiple radio remote heads (RRHs) through the X2 interface. Each RRH can perform wireless communication with X UEs or X' UEs in a predetermined area (31) by using an unlicensed carrier. The frequency bands of the macro base station and the RRHs are different from each other to avoid interference, but it is necessary to quickly exchange data between the macro base station and the RRHs through the X2 interface to use the NR-U service as an auxiliary downlink channel for the NR-L service through carrier aggregation.

[0161] In the co-location model, the pico / femto base station can perform wireless communication with Y UEs by using both an authorized carrier and an unlicensed carrier. However, it may be restricted by the use of both NR-L services and NR-U services for downlink transmission by the pico / femto base station. The coverage range (33) of the NR-L service and the coverage range (34) of the NR-U service can be different according to the frequency band, transmission power, etc.

[0162] When performing NR communication in an unlicensed frequency band, traditional devices (e.g., wireless LAN (Wi-Fi) devices) that perform communication in the corresponding unlicensed frequency band may not demodulate NR-U messages or data. Therefore, traditional devices determine NR-U messages or data as a kind of energy to perform interference avoidance operations through energy detection techniques. That is, when the energy corresponding to the NR-U message or data is lower than -62 dBm or a certain energy detection (ED) threshold, the wireless LAN device can perform communication by ignoring the corresponding message or data. As a result, user equipment performing NR communication in the unlicensed frequency band may often be interfered with by wireless LAN devices.

[0163] Therefore, it is necessary to allocate or reserve a specific frequency band at a specific time to effectively implement NR-U technologies / services. However, since peripheral devices performing communication through the unlicensed frequency band attempt to access based on energy detection techniques, there is a problem of difficulty in performing efficient NR-U services. Therefore, to solve the NR-U technology, it is necessary to give priority to researching coexistence schemes with traditional unlicensed frequency band devices and schemes for effectively sharing radio channels. That is, it is necessary to develop a robust coexistence mechanism in which NR-U devices do not affect traditional unlicensed frequency band devices.

[0164] Figure 15 FIG. illustrates a conventional communication scheme (e.g., wireless LAN) operating in an unlicensed band. Since most devices operating in the unlicensed band are based on "listen before talk" (LBT) operation, a clear channel assessment (CCA) technique for sensing the channel's availability before data transmission is performed.

[0165] Reference Figure 15 , a wireless LAN device (e.g., AP or STA) checks whether the channel is busy by performing carrier sensing before sending data. When a radio signal of a predetermined intensity or higher is sensed in the channel for data transmission, the corresponding channel is determined to be busy, and the wireless LAN device delays access to the corresponding channel. Such a process is called clear channel assessment, and the signal level used to determine whether a signal is sensed is called the CCA threshold. Meanwhile, when no radio signal is sensed in the corresponding channel or when a radio signal with an intensity less than the CCA threshold is sensed, the channel is determined to be idle.

[0166] When the channel is determined to be idle, the terminal having data to send performs a backoff process after a deferral duration (e.g., arbitration interframe space (AIFS), PCF interframe space (PIFS), etc.). The deferral duration represents the shortest time the terminal needs to wait after the channel becomes idle. The backoff process allows the terminal to wait further for a predetermined time after the deferral duration. For example, the terminal prepares while reducing the slot time corresponding to the random number assigned to the terminal during the channel idle period in a contention window (CW), and the terminal that completely exhausts the slot time can attempt to access the corresponding channel.

[0167] When the terminal successfully accesses the channel, the terminal can send data through the channel. After successfully sending data, the CW size (CWS) is reset to the initial value (CWmin). Conversely, when the data is not successfully sent, the CWS is increased by a factor of two. As a result, a new random number is assigned to the terminal within a range twice as large as the previous random number range to perform the backoff process in the next CW. In wireless LAN, only ACK is defined as the response information received for data transmission. Therefore, when ACK is received for data transmission, the CWS is reset to the initial value, and when no feedback information is received for data transmission, the CWS is increased by a factor of two.

[0168] As described above, since existing communications in the unlicensed band mainly operate 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, the channel access methods on the unlicensed band in NR can be classified into the following four categories.

[0169] · Category 1: No LBT

[0170] - The Tx entity does not perform the LBT process for transmission.

[0171] · Category 2: LBT without random backoff

[0172] - The Tx entity senses whether the channel is idle during a first interval without random backoff to perform transmission. That is, the Tx entity can perform transmission through the channel immediately after sensing that the channel is idle during the first interval. The first interval is an interval of a predetermined length immediately before the Tx entity performs transmission. According to an embodiment, the first interval may be an interval of 25 μs in length, but the present invention is not limited thereto.

[0173] · Category 3: LBT with random backoff using a fixed - size CW

[0174] - The Tx entity obtains a random value within a fixed - size CW, sets it as the initial value N of a backoff counter (or backoff timer), and performs backoff by using the set backoff counter N. During the backoff process, whenever the channel is detected to be idle within a predetermined time - slot period, the Tx entity decrements the backoff counter by 1. Here, the predetermined time - slot period may be 9 μs, but the present invention is not limited thereto. The backoff counter N is decremented by 1 from the initial value, and when the value of the backoff counter N reaches 0, the Tx entity can perform transmission. At the same time, to perform backoff, the Tx entity first senses whether the channel is idle during a second interval (i.e., the deferral duration T d ). According to an embodiment of the present invention, the Tx entity can sense (determine) whether the channel is idle during the second interval based on whether the channel is idle during at least some periods (e.g., one time - slot period) within the second interval. The second interval can be set based on the channel access priority level of the Tx entity and consists of a period of 16 μs and m consecutive time - slot periods. Here, m is a value set according to the channel access priority level. When the channel is sensed to be idle during the second interval, the Tx entity performs channel sensing to decrement the backoff counter. On the other hand, when the channel is sensed to be busy during the backoff process, the backoff process stops. After stopping the backoff process, when the channel is sensed to be idle within an additional second interval, the Tx entity can resume backoff. In this way, in addition to the second interval, the Tx entity can also perform transmission when the channel is idle during the time - slot period of the backoff counter N. In this case, the initial value of the backoff counter N is obtained within the fixed - size CW.

[0175] · Category 4: LBT with random backoff by using a variable - size CW

[0176] - The Tx entity obtains a random value within a CW of variable size, sets this random value as the initial value of a backoff counter (or backoff timer) N, and performs backoff by using the set backoff counter N. More specifically, the Tx entity can adjust the size of the CW based on the HARQ-ACK information for a previous transmission, and obtain the initial value of the backoff counter N within the CW of the adjusted size. The specific process of performing backoff by the Tx entity is as described in Category 3. Except for the second interval, when the channel is idle during the time slot period of the backoff counter N, the Tx entity can perform transmission. In this case, the initial value of the backoff counter N is obtained within the CW of variable size.

[0177] In the above Categories 1 to 4, the Tx entity can be a base station or a UE. According to an embodiment of the present invention, the first type of channel access can refer to the channel access of Category 4, and the second type of channel access can refer to the channel access of Category 2.

[0178] Figure 16 The figure illustrates a channel access process based on Category 4 LBT according to an embodiment of the present invention.

[0179] To perform channel access, first, the Tx entity performs channel sensing (S302) within a deferral duration T d According to an embodiment of the present invention, the channel sensing in step S302 within the deferral duration T d can be performed by channel sensing within at least a part of the deferral duration T d For example, the channel sensing within the deferral duration T d can be performed by channel sensing during one time slot period within the deferral duration T d The Tx entity checks whether the channel is idle (S304) by performing channel sensing on the deferral duration T d If the channel is sensed to be idle within the deferral duration T d , the Tx entity proceeds to step S306. If the channel is not sensed to be idle (i.e., sensed to be busy) within the deferral duration T d , the Tx entity returns to step S302. The Tx entity repeats steps S302 to S304 until the channel is sensed to be idle within the deferral duration T d The deferral duration T d can be set based on the channel access priority level of the Tx entity, and this deferral duration T d consists of a period of 16 μs and m consecutive time slot periods. Here, m is a value set according to the channel access priority level.

[0180] Next, the Tx entity obtains a random value within a predetermined CW, sets this random value as the initial value N of the backoff counter (or backoff timer) (S306), and proceeds to step S308. The initial value of the backoff counter N is randomly selected from the values between 0 and CW. The Tx entity performs the backoff process by using the set backoff counter N. That is, the Tx entity performs the backoff process by repeating steps S308 to S316 until the value of the backoff counter N reaches 0. Meanwhile, Figure 16 The figure shows performing step S306 after sensing that the channel is idle for the deferral duration T d However, the present invention is not limited to this. That is, step S306 can be executed independently of steps S302 to S304 and can be executed before steps S302 to S304. When step S306 is executed before steps S302 to S304, if it is sensed through steps S302 to S304 that the channel is idle for the deferral duration T d then the Tx entity proceeds to step S308.

[0181] In step S308, the Tx entity checks whether the value of the backoff counter N is 0. If the value of the backoff counter N is 0, the Tx entity proceeds to step S320 to perform transmission. If the value of the backoff counter N is not 0, the Tx entity proceeds to step S310. In step S310, the Tx entity decrements the value of the backoff counter N by 1. According to an embodiment, the Tx entity can selectively decrement the value of the backoff counter during the channel sensing process of each time slot. In this case, step S310 can be skipped at least once through the selection of the Tx entity. Next, the Tx entity performs channel sensing on an additional time slot period (S312). The Tx entity checks whether the channel is idle through channel sensing within the additional time slot period (S314). If it is sensed that the channel is idle within the additional time slot period, the Tx entity returns to step S308. In this way, each time the channel is sensed to be idle within a predetermined time slot period, the Tx entity can decrement the backoff counter by 1. Here, the predetermined time slot period can be 9 μs, but the present invention is not limited to this.

[0182] In step S314, if the channel is not sensed to be idle (i.e., sensed as busy) in the additional time slot period, the Tx entity proceeds to step S316. In step S316, the Tx entity checks whether the channel is idle within an additional deferral duration T d According to an embodiment of the present invention, the channel sensing in step S316 can be performed in units of time slots. That is, the Tx entity checks whether the channel is sensed to be idle during all time slot periods of the additional deferral duration T d When the channel is sensed to be idle during all time slot periods of the additional deferral duration T dWhen a busy time slot is detected internally, the Tx entity immediately restarts step S316. When the channel is sensed idle during all time slot periods of the additional deferral duration T d the Tx entity returns to step S308.

[0183] On the other hand, if the value of the backoff counter N is 0 in the check of step S308, the Tx entity performs a transmission (S320). The Tx entity receives a HARQ-ACK feedback corresponding to the transmission (S322). The Tx entity can check whether the previous transmission was successful through the received HARQ-ACK feedback. Next, the Tx entity adjusts the CW size for the next transmission based on the received HARQ-ACK feedback (S324).

[0184] As described above, after sensing that the channel is idle within the deferral duration T d when the channel is idle during N additional time slot periods, the Tx entity can perform a transmission. As described above, the Tx entity can be a base station or a UE, and Figure 16 the channel access procedure of can be used for downlink transmission of a base station and / or uplink transmission of a UE.

[0185] Hereinafter, a method for adaptively adjusting the CWS when accessing a channel in an unlicensed band is proposed. The CWS can be adjusted based on UE (User Equipment) feedback, and the UE feedback for CWS adjustment can include HARQ-ACK feedback and CQI / PMI / RI. In the present invention, a method for adaptively adjusting the CWS based on HARQ-ACK feedback is proposed. The HARQ-ACK feedback includes at least one of ACK, NACK, DTX, and NACK / DTX.

[0186] As described above, even in a wireless LAN system, the CWS is adjusted based on ACK. When an ACK feedback is received, the CWS is reset to the minimum value (CWmin), and when no ACK feedback is received, the CWS is increased. However, in a cellular system, a CWS adjustment method considering multiple access is required.

[0187] First, for the purpose of describing the present invention, the following terms are defined.

[0188] - Set of HARQ-ACK feedback values (i.e., HARQ-ACK feedback set): Refers to the HARQ-ACK feedback values used for CWS update / adjustment. The HARQ-ACK feedback set is decoded when determining the CWS and corresponds to the available HARQ-ACK feedback values. The HARQ-ACK feedback set includes HARQ-ACK feedback values for one or more DL (channel) transmissions (e.g., PDSCH) on an unlicensed band carrier (e.g., Scell, NR-U cell). The HARQ-ACK feedback set may include HARQ-ACK feedback values for DL (channel) transmissions (e.g., PDSCH), for example, multiple HARQ-ACK feedback values fed back from multiple UEs. The HARQ-ACK feedback value may indicate the reception response information for a code block group (CBG) or a transport block (TB) and may indicate any one of ACK, NACK, DTX, or NACK / DTX. Depending on the context, the HARQ-ACK feedback value may be mixed with terms such as HARQ-ACK value, HARQ-ACK information bit, and HARQ-ACK response.

[0189] - Reference window: Refers to the time interval in which DL transmissions (e.g., PDSCH) corresponding to the HARQ-ACK feedback set are performed in an unlicensed carrier (e.g., Scell, NR-U cell). According to an embodiment, the reference window may be defined in units of time slots or sub-frames. The reference window may indicate one or more specific time slots (or sub-frames). According to an embodiment of the present invention, a specific time slot (or reference time slot) may include the start time slot of the most recent DL transmission burst, where it is expected that at least some HARQ-ACK feedback is available.

[0190] Figure 17 Illustrates an embodiment of a method for adjusting the contention window size (CWS) based on HARQ-ACK feedback. In Figure 17 's embodiment, the Tx entity may be a base station and the Rx entity may be a UE, but the present invention is not limited thereto. Additionally, although Figure 17 's embodiment assumes a channel access procedure for DL transmissions of the base station, at least some configurations may be applied to the channel access procedure of the UE's UL transmissions.

[0191] Refer to Figure 17 , the Tx entity sends the nth DL transmission burst (S402) on an unlicensed band carrier (e.g., Scell, NR-U cell), and then, if an additional DL transmission is needed, the Tx entity may send the (n + 1)th DL transmission burst based on LBT channel access (S412). Here, the transmission burst indicates the transmission through one or more adjacent time slots (or sub-frames). Figure 17The figure illustrates a channel access procedure and a CWS adjustment method based on the above-described first type of channel access (i.e., Category 4 channel access).

[0192] First, the Tx entity receives HARQ-ACK feedback corresponding to PDSCH transmission on an unlicensed band carrier (e.g., Scell, NR-U cell) (S404). The HARQ-ACK feedback for CWS adjustment includes the HARQ-ACK feedback corresponding to the most recent DL transmission burst (i.e., the nth DL transmission burst) on the unlicensed band carrier. More specifically, the HARQ-ACK feedback for CWS adjustment includes the HARQ-ACK feedback corresponding to PDSCH transmission on a reference window within the most recent DL transmission burst. The reference window may indicate one or more specific time slots (or sub-frames). According to an embodiment of the present invention, the specific time slot (or reference time slot) includes the start time slot of the most recent DL transmission burst, where it is expected that at least some HARQ-ACK feedback is available.

[0193] When the HARQ-ACK feedback is received, a HARQ-ACK value is obtained for each transport block (TB). The HARQ-ACK feedback includes at least one of a HARQ-ACK bit sequence based on the TB and a HARQ-ACK based on a codeblock group (CBG). When the HARQ-ACK feedback is a HARQ-ACK bit sequence based on the TB, one HARQ-ACK information bit is obtained per TB. On the other hand, when the HARQ-ACK feedback is a HARQ-ACK bit sequence based on the CBG, N HARQ-ACK information bits are obtained per TB. Here, N is the maximum number of CBGs per TB configured in the Rx entity for PDSCH transmission. According to an embodiment of the present invention, the HARQ-ACK value for each TB of the HARQ-ACK feedback used for CWS determination can be used to determine the HARQ-ACK value for each TB. More specifically, when the HARQ-ACK feedback is a HARQ-ACK bit sequence based on the TB, one HARQ-ACK information bit of the TB is determined as the HARQ-ACK value. However, when the HARQ-ACK feedback is a HARQ-ACK bit sequence based on the CBG, one HARQ-ACK value can be determined based on the N HARQ-ACK information bits corresponding to the CBGs included in the TB.

[0194] Next, the Tx entity adjusts the CWS based on the HARQ-ACK value determined in step S404 (S406). That is, the Tx entity determines the CWS based on the HARQ-ACK value determined using the HARQ-ACK information bit for each TB of the HARQ-ACK feedback. More specifically, the CWS can be adjusted based on the ratio of NACKs among the HARQ-ACK values. First, variables can be defined as follows.

[0195] - p: Priority level value

[0196] - CW_min_p: Predetermined minimum CWS for priority level p

[0197] - CW_max_p: Predetermined maximum CWS for priority level p

[0198] - CW_p: CWS used to transmit priority level p. CW_p is set to any one of multiple CWS values between CW_min_p and CW_max_p included in the set of allowed CWSs for priority level p.

[0199] According to an embodiment of the present invention, the CWS can be determined according to the following steps.

[0200] Step A-1): For each priority level p, set CW_p to CW_min_p. In this case, the priority levels p include {1, 2, 3, 4}.

[0201] Step A-2): When the ratio of NACKs among the HARQ-ACK values of the PDSCH transmissions in the reference window k is Z% or higher, for each priority level p, increase CW_p to the next highest allowed value (also, remain in step A-2). Otherwise, step A advances to step A-1. Here, Z is a predetermined integer in the range of 0 ≤ Z ≤ 100, and according to the embodiment, it can be set to one of {30, 50, 70, 80, 100}.

[0202] Here, the reference window k includes the starting time slot (or subframe) most recently transmitted by the Tx entity. Additionally, the reference window k is a time slot (or subframe) in which at least some HARQ-ACK feedback is expected to be possible. If CW_p = CW_max_p, the next highest allowed value for CW_p adjustment is CW_max_p.

[0203] Next, the Tx entity selects a random value within the CWS determined in step S406 and sets this random value as the initial value of the backoff counter N (S408). The Tx entity performs backoff by using the set backoff counter N (S410). That is, for each time slot period in which the channel is sensed to be idle, the Tx entity can decrement the backoff counter by 1. When the value of the backoff counter reaches 0, the Tx entity can transmit the (n + 1)th DL transmission burst in the channel (S412).

[0204] Meanwhile, during the above CWS adjustment process, it is necessary to determine whether not only ACK and NACK but also DTX or NACK / DTX are considered in HARQ-ACK feedback. According to an embodiment of the present invention, depending on whether the transmission in the unlicensed band is based on self-carrier scheduling or cross-carrier scheduling, it can be determined whether DTX or NACK / DTX is considered together during the CWS adjustment process.

[0205] In self-carrier scheduling, the DL transmission (e.g., PDSCH) on the unlicensed band carrier is scheduled by a control channel (e.g., (E)PDCCH) transmitted on the same unlicensed band carrier. Here, since DTX indicates the failure of the DL transmission performed by a hidden node or the like in the unlicensed band carrier, it can be used together with NACK for CWS adjustment. In addition, DTX is one of the methods in which the UE notifies the base station that although the base station has transmitted a control channel (e.g., (E)PDCCH) including scheduling information to the UE, the UE fails to decode the control channel. DTX can be determined only by the HARQ-ACK feedback value, or can be determined by considering the HARQ-ACK feedback value and the actual scheduling situation. According to an embodiment of the present invention, in the case of self-carrier scheduling, DTX and NACK / DTX can be counted as NACKs for CWS adjustment. That is, when the ratio of the sum of NACK, DTX, and NACK / DTX among the HARQ-ACK values for the PDSCH transmission in the reference window k is equal to or greater than Z%, the CWS is increased to the next highest allowed value. Otherwise, the CWS is reset to the minimum value.

[0206] In cross-carrier scheduling, the DL transmission (e.g., PDSCH) on the unlicensed band carrier can be scheduled by a control channel (e.g., (E)PDCCH) transmitted on the licensed band carrier. In this case, since the DTX feedback is used to determine the decoding situation of the UE for the control channel transmitted on the licensed band carrier, it is not helpful for adaptively adjusting the CWS for channel access in the unlicensed band. Therefore, according to an embodiment of the present invention, in the case of cross-carrier scheduling from the licensed band, DTX can be ignored for CWS determination. That is, for CWS adjustment, when calculating the ratio of NACK, only ACK and NACK can be considered, or only ACK, NACK, and NACK / DTX can be considered. Therefore, DTX can be excluded when calculating the ratio of NACK.

[0207] Figure 18It is a block diagram showing the configurations of a UE and a base station according to an embodiment of the present invention. In an embodiment of the present invention, the UE can be implemented using various types of wireless communication devices or computing devices that ensure portability and mobility. The UE can be referred to as a user equipment (UE), a station (STA), a mobile subscriber (MS), etc. In addition, in an embodiment of the present invention, the base station controls and manages a cell corresponding to a service area (e.g., a macro cell, a femto cell, a pico cell, etc.), and performs functions such as signal transmission, channel assignment, channel monitoring, self-diagnosis, relaying, etc. The base station can be referred to as a next-generation node B (gNB) or an access point (AP).

[0208] As shown in the accompanying drawings, a UE 100 according to an embodiment of the present disclosure may include a processor 110, a communication module 120, a memory 130, a user interface 140, and a display unit 150.

[0209] First, the processor 110 may execute various instructions or programs and process data within the UE 100. In addition, the processor 100 may control the overall 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 a time slot configuration based on the time slot configuration information, and perform communication according to the determined time slot configuration.

[0210] 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 multiple network interface cards (NICs) in an internal or external form, such as cellular communication interface cards 121 and 122 and an unlicensed band communication interface card 123. In the accompanying drawings, the communication module 120 is shown as an overall integrated module, but different from the accompanying drawings, each network interface card can be independently arranged according to the circuit configuration or usage.

[0211] The cellular communication interface card 121 may transmit or receive radio signals to / from at least one of the base station 200, an external device, and a server using a mobile communication network and provide cellular communication services in a first band based on instructions from the processor 110. According to an embodiment, the cellular communication interface card 121 may include at least one NIC module using a 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, an external device, and a server in a sub-6 GHz band supported by the corresponding NIC module according to a cellular communication standard or protocol.

[0212] The cellular communication interface card 122 can transmit or receive radio signals with at least one of the base station 200, external devices, and servers through the use of a mobile communication network and provide cellular communication services in a second frequency band based on instructions from the processor 110. According to an embodiment, the cellular communication interface card 122 may include at least one NIC module using a frequency band greater than 6 GHz. At least one NIC module of the cellular communication interface card 122 can independently perform cellular communication with at least one of the base station 200, external devices, and servers in a frequency band above 6 GHz supported by the corresponding NIC module according to cellular communication standards or protocols.

[0213] The unauthorized band communication interface card 123 transmits or receives radio signals with at least one of the base station 200, external devices, and servers through the use of a third frequency band as an unauthorized band and provides unauthorized band communication services based on instructions from the processor 110. The unauthorized band communication interface card 123 may include at least one NIC module using an unauthorized band. For example, the unauthorized band may be a frequency band of 2.4 GHz, 5 GHz, 6 GHz, 7 GHz, or above 52.6 GHz. At least one NIC module of the unauthorized band communication interface card 123 can perform wireless communication with at least one of the base station 200, external devices, and servers independently or non-independently according to unauthorized band communication standards or protocols of the frequency band supported by the corresponding NIC module.

[0214] The memory 130 stores control programs used in the UE 100 and various data thereof. Such control programs may include prescribed programs required to perform wireless communication with at least one of the base station 200, external devices, and servers.

[0215] Next, the user interface 140 includes various input / output means provided in the UE 100. In other words, the user interface 140 can use various input means to receive user input, and the processor 110 can control the UE 100 based on the received user input. In addition, the user interface 140 can use various output means to perform output based on instructions from the processor 110.

[0216] Next, the display unit 150 outputs various images on a display screen. The display unit 150 can output various display objects, such as content executed by the processor 110 or a user interface, based on control instructions from the processor 110.

[0217] In addition, the base station 200 according to an embodiment of the present invention may include a processor 210, a communication module 220, and a memory 230.

[0218] First, the processor 210 may execute various instructions or programs and process internal data of the base station 200. In addition, the processor 210 may control the overall 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 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 signaled time slot configuration.

[0219] 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, in an internal or external form, a plurality of network interface cards, such as cellular communication interface cards 221 and 222 and an unlicensed band communication interface card 223. In the drawings, the communication module 220 is shown as an overall integrated module, but different from the drawings, each network interface card can be independently arranged according to the circuit configuration or usage.

[0220] The cellular communication interface card 221 may transmit or receive radio signals to / from at least one of the UE 100, an external device, and a server using a mobile communication network and provide cellular communication services 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, an external device, and a server according to a cellular communication standard or protocol in a frequency band less than 6 GHz supported by the corresponding NIC module.

[0221] The cellular communication interface card 222 may transmit or receive radio signals to / from at least one of the UE 100, an external device, and a server using a mobile communication network and provide cellular communication services in a 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, an external device, and a server according to a cellular communication standard or protocol in a frequency band of 6 GHz or higher supported by the corresponding NIC module.

[0222] The unauthorized band communication interface card 223 transmits or receives radio signals with at least one of the base station 100, external devices, and a server by using a third band as an unauthorized band, and provides unauthorized band communication services based on instructions from the processor 210. The unauthorized band communication interface card 223 may include at least one NIC module that uses an unauthorized band. For example, the unauthorized band may be a band of 2.4 GHz, 5 GHz, 6 GHz, 7 GHz, or a band of 52.6 GHz or higher. At least one NIC module of the unauthorized band communication interface card 223 may perform wireless communication with at least one of the base station 100, external devices, and a server independently or dependently according to an unauthorized band communication standard or protocol of a band supported by the corresponding NIC module.

[0223] Figure 18 FIG. is a block diagram of 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 foregoing elements of the device may 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, the user interface 140, the display unit 150, etc., may be selectively provided in the UE 100. In addition, the user interface 140, the display unit 150, etc., may be additionally provided in the base station 200 when necessary.

[0224] Reference will be made to Figure 19 Describe the channel access process performed by a wireless communication device in an unauthorized band according to an embodiment of the present invention. Specifically, the LBT process used when a wireless communication device according to an embodiment of the present invention performs channel access in an unauthorized band will be described. In particular, a channel access in which a wireless communication device performs transmission according to the result of channel sensing within a time interval of a predetermined duration may be configured in the wireless communication device. In this case, a method for operating the wireless communication device when the wireless communication device fails to access a channel will be described. The specified duration mentioned above may be 16 μs.

[0225] For ease of description, a wireless communication device that is a wireless endpoint initiating channel occupancy is referred to as an initiating node. Additionally, a wireless communication device that is a wireless endpoint communicating with the initiating node is referred to as a responding node. The initiating node can be a base station, and the responding node can be a UE. Additionally, the initiating node can be a UE, and the responding node can be a base station. When the initiating node wants to send data, the initiating node can perform channel access according to the channel access priority level determined based on the data type. In this case, parameters for channel access can be determined according to the type of data. The parameters for channel access can include the minimum value of CW, the maximum value of CW, the maximum occupancy time (MCOT) which is the maximum duration that can occupy the channel in one channel occupancy, and the number of sensing time slots (m p ) of any one of them. Specifically, the initiating node can perform the above-mentioned Category 4 LBT according to the channel access priority level determined based on the data type.

[0226] Table 4 below shows an example of the parameter values for channel access according to the channel access priority level. Specifically, Table 4 shows the parameter values for channel access for each channel access priority level for downlink transmission in the LTE LAA system.

[0227] When the downlink channel sent by the wireless communication device includes data traffic, the deferral duration can be configured according to the channel access priority level of the traffic included in the downlink channel. Additionally, the deferral duration can include an initial duration T f or one or more (m p ) time slot durations T sl . In this case, the time slot duration T sl can be 9 μs. The initial duration includes one idle time slot duration T sl . Additionally, the number of time slot durations (m p ) included in the deferral duration can be configured according to the above-mentioned channel access priority level. Specifically, the number of time slot durations (m p ) included in the deferral duration can be configured as shown in Table 4.

[0228] [Table 4]

[0229]

[0230] Additionally, the wireless communication device can configure the range of CW values according to the channel access priority level. Specifically, the wireless communication device can set the value of CW to satisfy CW min,p <= CW <= CW max,p . In this case, the minimum value of CW, CW min,p and the maximum value CWmax,p can be determined according to the channel access priority level. Specifically, the minimum value CW of CW min,p and the maximum value CW of CW max,p can be determined as shown in Table 4. The wireless communication device can set the minimum value CW of CW and the maximum value CW of CW during the counter value setting process min,p and the maximum value CW of CW max,p . When the wireless communication device accesses a channel, the wireless communication device can adjust the value of CW as described above with reference to Figures 15 to 17 . In addition, in a wireless communication device in an unlicensed band, the MCOT can also be determined according to the channel access priority of the data included in the transmission as described above mcot，p . Specifically, the MCOT can be determined as shown in Table 4. Therefore, it may not be allowed for the wireless communication device to perform continuous transmission for a time exceeding the MCOT in the unlicensed band. This is because the unlicensed band is a frequency band used by various wireless communication devices according to certain rules. In Table 4, when the value of the channel access priority level is p = 3 or p = 4, and the unlicensed band is used for a long time as specified and there is no wireless communication device using other technologies, the wireless communication device can be configured with T mcot,p = 10 ms. Otherwise, the wireless communication device can be configured with T mcot,p = 8 ms.

[0231] Table 5 shows the parameter values for channel access of each channel access priority level for uplink transmission used in the LTE LAA system.

[0232] [Table 5]

[0233]

[0234] As described in Table 5, when one or more gaps are included in the transmission, the MCOT value of 6 ms can be increased to 8 ms. A gap represents the time from stopping transmission in a carrier until resuming transmission in the carrier. In this case, the minimum value of the gap duration is 100 μs. In addition, the maximum value of the transmission duration executed before including the gap is 6 ms. 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 ensured that no other radio access technology is used in the carrier where channel access is performed, the value of MCOT can be 10 ms. In this case, another radio access technology can include Wi-Fi. Otherwise, the value of MCOT can be determined as described in Note 1 of Table 5.

[0235] COT represents the time during which a wireless communication device occupies a channel. As described above, MCOT represents the maximum time during which an initiating node can continuously occupy a channel in any one of the carriers in the unlicensed band. However, as described above, gaps as intervals during which no transmission is performed can be included between multiple transmissions, and when gaps are included, the value of MCOT can be applied differently.

[0236] Figure 19 The figure shows that when the duration of the transmission of the initiating node within the channel occupancy initiated by the initiating node does not exceed the MCOT of the channel occupancy, the responding node performs a transmission within the channel occupancy initiated by the initiating node. That is, Figure 19 The figure shows that after the initiating node completes a transmission in any one channel, the responding node performs a transmission in that channel. As described above, it can be described as a shared channel occupancy in which the initiating node and the responding node perform transmissions in one channel.

[0237] If the duration of the transmission of the initiating node is less than the duration of the MCOT, the responding node can perform a transmission within the channel occupancy initiated by the initiating node. Figure 19 The situation is shown where the gap between the transmission of the initiating node and the transmission of the responding node is 16 μs. In this case, the method for the responding node to perform channel access may be problematic.

[0238] In an embodiment of the present invention, when the duration of the gap is not greater than a first duration, the responding node can perform a transmission immediately after the gap without sensing. Specifically, the responding node can perform the above-described type 1 channel access. The first duration can be 16 μs, and this can be applied to the embodiments described later. In an embodiment, additional constraints other than the MCOT can be applied to the duration of the transmission of the responding node. In a specific embodiment, the responding node can perform a transmission within a predetermined duration. In this case, the predetermined duration can be a constraint applied to the transmission of the responding node separately from the MCOT. Specifically, the predetermined duration can be 584 μs.

[0239] In an embodiment of the present invention, when the duration of the gap is the same as the first duration, the responding node may perform a first fixed-duration-based channel access for the transmission following the gap. The first fixed-duration-based channel access is a channel access in which a wireless communication device that is allowed to perform the first fixed-duration-based channel access performs a transmission immediately after a first fixed duration when the channel is sensed idle within the first fixed duration. Specifically, in the first fixed-duration-based channel access, the wireless communication device performs channel sensing within the first fixed duration and performs a transmission on the channel when the channel is sensed idle within the fixed duration. The first fixed-duration-based channel access may be the above-mentioned Category 2 LBT. In this embodiment, the initiating node may implicitly or explicitly indicate the first fixed-duration-based channel access to the responding node. For example, a base station serving as the initiating node may indicate the first fixed-duration-based channel access to the responding node by using a grant.

[0240] In an embodiment of the present invention, when the gap between consecutive scheduled or granted transmissions within a channel occupancy initiated by an initiating node is no greater than a second fixed duration, the node performing a second transmission may perform a second fixed-duration-based channel access. The second fixed-duration-based channel access is a channel access in which a wireless communication device that is allowed to perform the second fixed-duration-based channel access performs a transmission immediately after a second fixed duration when the channel is idle for a second fixed duration. Specifically, in the second fixed-duration-based channel access, the wireless communication device performs channel sensing within the second fixed duration and performs a transmission on the channel when the channel is sensed idle within the fixed duration. The second fixed duration may be greater than the above-mentioned first fixed duration. Specifically, the second duration may be 25 μs, and this may be applied to the embodiments described later. In addition, even if an uplink transmission is not followed by a downlink transmission within the same channel occupancy, the UE may perform a second fixed-duration-based channel access for the uplink transmission after the uplink transmission. In addition, even when a downlink transmission is not followed by an uplink transmission within the same channel occupancy, the UE may perform a second fixed-duration-based channel access for the uplink transmission. Additionally, when the interval between an uplink transmission and a subsequent downlink transmission within the same channel occupancy is greater than 16 μs and no greater than 25 μs, the base station may perform a second fixed-duration-based channel access for the downlink transmission.

[0241] Embodiments applied when the gap is no greater than the first fixed duration will be described. In this case, the first fixed duration may be 16 μs as described above.

[0242] When the gap is not greater than the first fixed duration, a response node that performs a transmission following the gap can perform the transmission immediately without sensing, or can perform the transmission by performing a first fixed-duration-based channel access. In this case, depending on whether the transmission following the gap includes traffic or data traffic that may be classified as determining the channel access priority level, the response node can perform the transmission immediately without sensing, or can perform the transmission by performing a first fixed-duration-based channel access. Specifically, when the response node sends a HARQ-ACK feedback for data traffic sent from the initiating node, the response node can perform the transmission immediately without sensing.

[0243] In another specific embodiment, when the response node sends uplink control information (UCI) for data traffic sent from the initiating node, the response node can perform the transmission immediately without sensing.

[0244] In another specific embodiment, when the response node sends SRS, the response node can perform the transmission immediately without sensing.

[0245] In another specific embodiment, when the response node sends a physical random access channel (PRACH), the response node can perform the transmission immediately without sensing.

[0246] In the above embodiments, when the response node performs a transmission including data traffic immediately after the gap, the response node can perform a first fixed-duration-based channel access. Specifically, when the data traffic is scheduled or configured by the initiating node, the response node can perform a first fixed-duration-based channel access. When the data traffic can be classified as traffic or determining the channel access priority level of the data traffic, the response node can perform a first fixed-duration-based channel access.

[0247] In the above embodiments, the response node performing the transmission immediately without sensing can indicate that the initiating node performs the above-mentioned category 4 channel access. As described above, the first fixed-duration-based channel access can be category 2 LBT.

[0248] In a COT initiated by the initiating node, the initiating node can perform a transmission following the transmission of the response node. In this case, in the COT initiated by the initiating node, the gap between the transmission of the initiating node and the subsequent transmission of the response node can be not greater than the first fixed duration. Depending on whether the transmission after the gap includes traffic that can be classified as determining the access priority level or data traffic, the initiating node can perform the transmission immediately without sensing, or can perform the transmission by performing a first fixed-duration-based channel access.

[0249] Specifically, when the initiating node only sends control information for scheduling data transmitted by the responding node, the initiating node can perform transmission immediately without sensing. In this case, the control information can be at least one of only PDCCH, group common signaling, paging, only reference signal, tracking reference signal (TRS), RACH message 4, or handover command.

[0250] In yet another specific embodiment, when the initiating node only sends broadcast information, the initiating node can perform transmission immediately without sensing. In this case, the broadcast information can be at least one of discovery reference signal (DRS), SS / PBCH block, type 0-PDCCH, or remaining system information (RMSI).

[0251] In the above embodiments, when the initiating node performs a transmission including data traffic immediately after a gap, the initiating node can perform a first fixed-duration based channel access. Specifically, when the data traffic is scheduled for or configured for the responding node, the initiating node can perform a first fixed-duration based channel access. When the data traffic is classified as a service or data traffic that determines the channel access priority level, the initiating node can perform a first fixed-duration based channel access.

[0252] In the above embodiments, the initiating node performing transmission immediately without sensing can indicate that the initiating node performs the aforementioned category 4 channel access. As described above, the first fixed-duration based channel access can be category 2 LBT.

[0253] In the above embodiments, the initiating node can be a base station, and the responding node can be a UE. That is, in the above embodiments, channel occupancy can be initiated by the base station. Additionally, the initiating node can be a UE, and the responding node can be a base station. That is, in the above embodiments, channel occupancy can be initiated by the UE.

[0254] In the above embodiments, the node performing transmission after a gap can perform the transmission within the MCOT.

[0255] Figure 20 The figure illustrates the operation of the UE when the current downlink transmission according to an embodiment of the present invention does not occupy as much as the MCOT within the COT initiated by the base station and the transmission of the UE is scheduled or configured by the base station.

[0256] As Figure 20 shown, the gap between the downlink transmission of the base station and the uplink transmission of the UE is 16 μs. In Figure 20In case of (a), the downlink transmission includes a plurality of UL grants for scheduling PUSCH transmissions on a slot-by-slot basis. The UE sends PUSCH in a plurality of slots based on the plurality of UL grants. In Figure 20 In case of (b), the downlink transmission includes one UL grant for scheduling PUSCH transmissions in a plurality of slots. The UE sends PUSCH in a plurality of slots based on the UL grant. In Figure 20 In, the scheduling of the uplink transmission is performed within the channel occupancy obtained by the base station as the initiating node, but the configuration or scheduling of the uplink transmission can be performed before the channel occupancy. Even in such a case, the embodiments described later can be applied.

[0257] The initiating node can be a base station, and the responding node can be a UE. When the gap between the transmission of the initiating node and the transmission of the responding node is a first fixed duration, the base station can implicitly or explicitly indicate the first fixed-duration-based channel access. For example, the base station as the initiating node can indicate the first fixed-duration-based channel access to the responding node by using a UL grant. In this case, the UE senses the channel within the first fixed duration. When the channel is sensed idle during the first duration, the UE performs transmission immediately after the first fixed duration. When the channel is sensed busy during the first duration, the method for operating the UE is problematic. Specifically, as described above, the uplink transmission of the UE can be scheduled or configured over a plurality of slots. In this case, even if the UE fails to access the channel in the first slot among the plurality of slots, channel access for uplink transmission may be required in slots other than the first slot among the plurality of slots. In this case, a method for operating the UE will be described. For convenience of description, a plurality of slots for scheduling or configuring the uplink transmission of the UE are represented by {slot(n), slot(n + 1), slot(n + 2), …, slot(n + k - 1)}, and k represents the number of the plurality of slots.

[0258] For the UE, a plurality of uplink transmissions can be scheduled or configured. The plurality of uplink transmissions can be continuous without a gap. Specifically, the UE can receive a grant for scheduling a plurality of uplink transmissions from the base station. The grant refers to downlink control information (DCI) and can include a DL grant or a UL grant for scheduling the uplink transmission. In a specific embodiment, the DL grant or the UL grant can indicate the fixed-duration-based channel access as the channel access type and can indicate the channel access priority for accessing the channel in which the plurality of uplink transmissions are performed. In this case, the DL grant or the UL grant can indicate the first fixed-duration-based channel access as the channel access type.

[0259] The UE may perform first fixed-duration channel access for a first transmission attempt as one of multiple uplink transmissions, and when the first fixed-duration channel access fails, the UE may perform first fixed-duration channel access for a second transmission attempt as a transmission following the first transmission. When the UE succeeds in the first fixed-duration channel access, the UE may perform the second transmission. In a particular embodiment, the UE may perform first fixed-duration channel access for uplink transmission for each of the remaining time slots slot(n+1), slot(n+2),..., slot(n+k-1) after the first time slot slot(n) among multiple time slots..

[0260] In another specific embodiment, the UE may perform first fixed-duration channel access for uplink transmission a predetermined number of times in the remaining time slots slot(n+1), slot(n+2),..., slot(n+k-1) after the first time slot slot(n) among multiple time slots. In this case, the predetermined number of times may be limited to k-1.

[0261] In yet another specific embodiment, the UE may attempt a first fixed-duration-based channel access for a first transmission as one of multiple uplink transmissions, and when the first fixed-duration-based channel access fails, depending on whether the channel is continuously sensed as idle, the UE may attempt the first fixed-duration-based channel access or a random backoff-based access for a second transmission that follows the first transmission. When the UE fails in the first fixed-duration-based channel access in the first time slot slot(n) and continuously senses the channel as idle after the UE's channel access fails, the UE may attempt the first fixed-duration-based channel access for the second transmission. In this case, when the UE succeeds in the first fixed-duration-based channel access, the UE may perform the second transmission. Additionally, when the UE fails in the first fixed-duration-based channel access in the first time slot slot(n) and does not continuously sense the channel as idle after the UE's channel access fails, the UE may perform a random backoff-based channel access for uplink transmission in the remaining time slots slot(n+1), slot(n+2),..., slot(n+k-1) after the first time slot slot(n) of the multiple time slots. When the UE successfully performs the random backoff-based channel access, the UE may perform the second transmission. In this case, when the random backoff-based channel access is indicated to the UE as a channel access method in the first time slot slot(n) or in the remaining time slots slot(n+1), slot(n+2),.., slot(n+k-1) after the first time slot of the multiple time slots by DCI, the UE may perform the random backoff-based channel access by using the channel access priority level indicated by the DCI. When another channel access method other than the random backoff-based channel access is indicated to the UE as a channel access method in all of the multiple time slots slot(n), slot(n+1), slot(n+2),..., slot(n+k-1) by DCI, the UE may perform the random backoff-based channel access for uplink transmission by using the channel access priority level indicated by the scheduled DCI. To this end, when the base station indicates the fixed-duration-based channel access in the DCI, the base station may indicate the channel access priority level for obtaining access to the channel in the DCI. Specifically, when the base station indicates the first fixed-duration-based channel access in the DCI, the base station may indicate the channel access priority level for obtaining access to the channel in the DCI.

[0262] In yet another specific embodiment, the UE may attempt a first fixed-duration-based channel access for a first transmission that is one of multiple uplink transmissions, and when the first fixed-duration-based channel access fails, the UE may attempt a second fixed-duration-based channel access for a second transmission that is a transmission following the first transmission. When the UE succeeds in the second fixed-duration-based channel access, the UE may perform the second transmission. Specifically, after the first fixed-duration-based channel access fails for the UE in the first time slot slot(n), the UE may be in each sensing time slot T slSense whether the UE is idle. When the UE fails in the first fixed-duration channel access in the first time slot slot(n) and continuously senses the channel idle after the channel access failure by the UE, the UE may perform a second fixed-duration channel access for uplink transmission in the remaining time slots slot(n+1), slot(n+2),..., slot(n+k-1) after the first time slot slot(n) among a plurality of time slots. This is performed by taking into account that the first fixed-duration channel access can be performed when the gap is the first fixed-duration period, and the channel access fails in the first time slot slot(n), and thus the gap between transmissions is increased. When the UE fails in the first fixed-duration channel access in the first time slot slot(n) and does not continuously sense the channel idle after the channel access failure by the UE, the UE may perform a random-backoff-based channel access for uplink transmission in the remaining time slots slot(n+1), slot(n+2),..., slot(n+k-1) after the first time slot slot(n) among a plurality of time slots. When the random-backoff-based channel access by the UE is successful, the UE may perform a second transmission. In this case, when the random-backoff-based channel access as a channel access method is indicated to the UE by DCI in the first time slot slot(n) or the remaining time slots slot(n+1), slot(n+2),..., slot(n+k-1) after the first time slot slot(n) among a plurality of time slots, the UE may perform the random-backoff-based channel access by using the channel access priority level indicated by the DCI. When another channel access method other than the random-backoff-based channel access is indicated to the UE by DCI as a channel access method in all of the plurality of time slots slot(n), slot(n+1), slot(n+2),..., slot(n+k-1), the UE may perform the random-backoff-based channel access for uplink transmission by using the channel access priority level indicated by the scheduled DCI. To this end, when the base station indicates the fixed-duration channel access in the DCI, the base station may indicate the channel access priority level for obtaining access to the channel in the DCI. Specifically, when the base station indicates the first fixed-duration channel access in the DCI, the base station may indicate the channel access priority level for obtaining access to the channel in the DCI.

[0263] In yet another specific embodiment, a gap of a first fixed duration may be configured between a transmission from a base station and an uplink transmission that a UE intends to send, and thus the UE may switch the channel access type to a first fixed-duration-based channel access for a first transmission that is one of multiple uplink transmissions. In this case, when the first fixed-duration-based channel access fails, the UE may attempt channel access according to the channel access type indicated by DCI for a second transmission that is a transmission following the first transmission. When the UE successfully accesses the channel, the UE may perform the second transmission. Specifically, when the first fixed-duration-based channel access of the UE fails in a first time slot slot(n), the UE may perform channel access for an uplink transmission according to the channel access type indicated by DCI in the remaining time slots slot(n + 1), slot(n + 2), …, slot(n + k - 1) after the first time slot slot(n) among multiple time slots. In addition, when multiple grants schedule uplink transmissions over multiple time slots, the channel access type for an uplink transmission may be indicated for each time slot. The UE may perform channel access for an uplink transmission according to the channel access type indicated for each of the remaining time slots slot(n + 1), slot(n + 2),..., slot(n + k - 1) after the first time slot slot(n) among multiple time slots. In an embodiment, when the channel access type indicated by DCI is the first fixed-duration-based channel access, the operation of the UE may be the same as that of the first and second embodiments described. However, when the channel access type indicated by DCI is not the first fixed-duration-based channel access, the operation of the UE is different from that of the first and second embodiments described.

[0264] In yet another specific embodiment, when the first fixed-duration-based channel access of the UE fails in a first time slot slot(n), the UE may perform random-backoff-based channel access for an uplink transmission in the remaining time slots slot(n + 1), slot(n + 2), …, slot(n + k - 1) after the first time slot slot(n) among multiple time slots. This takes into account the possibility that the channel is not idle and is busy due to other nodes using the unlicensed band. Specifically, in an embodiment, when the channel is sensed as busy rather than idle through the first fixed-duration-based channel access, even if the first fixed-duration-based channel access or the second fixed-duration-based channel access is continuously performed, the channel is busy due to other nodes, and thus the channel is likely not to be idle and is busy. Therefore, this is a method in which the UE performs an uplink transmission after performing random-backoff-based channel access for transmissions in slot(n + 1) and subsequent time slots.

[0265] In the above embodiments, the channel access based on random backoff may be Category 4 LBT.

[0266] Regarding the case of scheduling uplink transmissions, previous embodiments of the present invention have been described, with an emphasis on the case of scheduling uplink transmissions through scheduling grants. Even when resources in terms of time and frequency are configured by RRC configuration and the UE performs uplink transmissions within the configured resources, the above embodiments can also be applied.

[0267] Although the methods and systems of the present invention have been described in conjunction with specific embodiments, some or all of its components or operations can be implemented using a computing system with a general hardware architecture.

[0268] The above description of the present invention is merely exemplary, and those skilled in the art to which the present invention pertains will understand that various modifications and changes can be made without departing from the technical spirit or basic characteristics of the present invention. Therefore, it should be construed that the above embodiments are illustrative in all aspects rather than restrictive. For example, each component described as a single type can be implemented in a distributed manner, and similarly, components described as distributed can also be implemented in a combined form.

[0269] The scope of the present invention is indicated by the appended claims rather than the detailed description, and it should be understood that all changes or modifications derived from the meaning and scope of the claims and their equivalents are included within the scope of the present invention.

Claims

1. A user equipment (UE) configured to operate in a 3rd Generation Partnership Project New Radio (3GPP NR) based wireless communication system that supports operation in an unlicensed frequency band, the UE comprising: A communication module; And A processor that controls the communication module, Wherein, the processor is configured to: Receive at least one UL grant for scheduling a plurality of consecutive uplink (UL) transmissions on the unlicensed frequency band, wherein the at least one UL grant indicates the channel access type as at least one of the following: - A first channel access type based on fallback, and - A second channel access type based only on a fixed sensing duration, the fixed sensing duration having a plurality of time lengths including 16 μs and 25 μs; Based on the indicated channel access type, attempt a first channel access to transmit a UL transmission that is not the last UL transmission among the plurality of consecutive UL transmissions on the unlicensed frequency band; And Based on (1) the first channel access corresponding to the second channel access type with a fixed sensing duration of 16 μs, and (2) the first channel access failing, attempt a second channel access according to the second channel access type with a fixed sensing duration of 25 μs to transmit the next UL transmission among the plurality of consecutive UL transmissions.

2. The UE according to claim 1, wherein, Receive the at least one UL grant via at least one physical downlink control channel (PDCCH), and the plurality of consecutive UL transmissions include a plurality of consecutive physical uplink shared channel (PUSCH) transmissions.

3. The UE according to claim 1, wherein, The plurality of consecutive UL transmissions are within a channel occupancy time (COT) initiated based on a downlink (DL) transmission.

4. The UE according to claim 1, wherein, The UL grant further indicates a channel access priority associated with the indicated channel access type.

5. The UE according to claim 1, wherein, The at least one UL grant includes a single UL grant, and the single UL grant is used to schedule all of the plurality of consecutive UL transmissions, or wherein the at least one UL grant includes a plurality of UL grants, and each UL grant is used to schedule a respective one of the plurality of consecutive UL transmissions.

6. A method performed by a user equipment (UE) in a 3rd Generation Partnership Project New Radio (3GPP NR) based wireless communication system that supports operation in an unlicensed frequency band, the method comprising: Receive at least one UL grant for scheduling a plurality of consecutive uplink (UL) transmissions on the unlicensed frequency band, wherein the at least one UL grant indicates the channel access type as at least one of the following: - A first channel access type based on fallback, and - A second channel access type based only on a fixed sensing duration, the fixed sensing duration having a plurality of time lengths including 16 μs and 25 μs; Based on the indicated channel access type, attempt a first channel access to transmit a UL transmission that is not the last UL transmission among the plurality of consecutive UL transmissions on the unlicensed frequency band; And Based on (1) the first channel access corresponding to the second channel access type with a fixed sensing duration of 16 μs, and (2) the failure of the first channel access, attempt a second channel access according to the second channel access type with a fixed sensing duration of 25 μs to transmit the next UL transmission among the plurality of consecutive UL transmissions.

7. The method according to claim 6, wherein, Receive the at least one UL grant via at least one physical downlink control channel (PDCCH), and the plurality of consecutive UL transmissions include a plurality of consecutive physical uplink shared channel (PUSCH) transmissions.

8. The method according to claim 6, wherein, The plurality of consecutive UL transmissions are within a channel occupancy time (COT) initiated based on a downlink (DL) transmission.

9. The method according to claim 6, wherein The UL grant further indicates a channel access priority associated with the indicated channel access type.

10. The method according to claim 6, wherein The at least one UL grant includes a single UL grant, and the single UL grant is used to schedule all of the plurality of consecutive UL transmissions, or wherein the at least one UL grant includes a plurality of UL grants, and each UL grant is used to schedule a corresponding one of the plurality of consecutive UL transmissions.

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