Channel access method for performing transmission in unlicensed band, and device using the same

Abstract

To provide a base station of a wireless communication system.SOLUTION: The base station of 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 the terminal attempts a first fixed duration-based channel access for a first transmission being one of the uplink transmissions and fails in the first fixed duration-based channel access, attempt a second fixed duration-based channel access for a second transmission being a transmission following the first transmission.SELECTED DRAWING: Figure 20

Description

[Technical field]

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

[0002] Since the commercialization of 4G (4th generation) communication systems, efforts have been made to develop new 5G (5th generation) communication systems to meet the increasing demand for wireless data traffic. The 5G communication system is called a communication system beyond 4G network, a system beyond LTE system, or a new radio (NR) system. In order to achieve high data transmission rates, the 5G communication system includes a system operated using an ultra-high frequency (mmWave) band of 6 GHz or more, and from the viewpoint of ensuring coverage, a communication system operated using a frequency band of 6 GHz or less is also being considered for implementation in base stations and terminals.

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

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

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

[0006] Meanwhile, the Internet is a human-centered network where humans generate and consume information, and is evolving into the Internet of Things (IoT) network that exchanges and processes information between distributed components such as objects. The Internet of Everything (IoE) technology is also emerging, which combines big data processing technology through connection with cloud servers with IoT technology. To realize IoT, technological elements such as sensing technology, wired and wireless communication and network infrastructure, service interface technology, and security technology are required, and recently, technologies such as sensor networks for connecting objects, machine to machine (M2M), and machine type communication (MTC) are being researched. In the IoT environment, intelligent IT (internet technology) services are provided that collect and analyze data generated from connected objects and create new value in human life. IoT is 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 through the fusion and integration of conventional IT technology and various industries.

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

[0008] However, the mobile communication system has gradually expanded its service area from voice to data services, and has now developed to the extent that it can provide high-speed data services. However, due to the resource shortage phenomenon in the currently provided mobile communication system and the demand for higher speed services from users, a more advanced mobile communication system is required.

[0009] In recent years, as mobile traffic has increased rapidly with the proliferation of smart devices, existing licensed frequency spectrum or licensed frequency bands are finding it difficult to withstand the increasing data usage required to provide cellular communication services.

[0010] In this situation, the use of unlicensed frequency spectrum or unlicensed frequency bands (e.g., 2.4 GHz band, 5 GHz band, 6 GHz band, bands above 52.6 GHz, etc.) to provide cellular communication services is being discussed as a solution to the spectrum shortage problem.

[0011] Unlike licensed bands, where communication carriers secure exclusive frequency usage rights through procedures such as auctions, unlicensed bands may be used simultaneously by an unlimited number of communication devices, provided that they comply with a certain level of adjacent band protection regulations. As a result, when unlicensed bands are used for cellular communication services, it is difficult to guarantee the same level of communication quality as that provided by licensed bands, and interference problems may occur with wireless communication devices (e.g., wireless LAN devices) that have previously used unlicensed bands.

[0012] In order to use LTE and NR technologies in unlicensed bands, research should be conducted on coexistence methods with existing unlicensed band devices and methods for efficiently sharing radio channels with other wireless communication devices. In other words, a robust coexistence mechanism (RCM) needs to be developed so that devices using LTE and NR technologies in unlicensed bands do not affect existing unlicensed band devices. Summary of the Invention [Problem to be solved by the invention]

[0013] It is an object of one embodiment of the present invention to provide a channel access method for transmission in a wireless communication system operating in an unlicensed band and an apparatus using the same. [Means for solving the problem]

[0014] According to an embodiment of the present invention, a terminal for wirelessly communicating with a base station in an unlicensed band includes a communication module and a processor for controlling the communication module. The processor receives a grant for scheduling a plurality of uplink transmissions from the base station, and the terminal attempts a first fixed duration based channel access for a first transmission, which is one of the plurality of uplink transmissions, and, if the first fixed duration based channel access fails, attempts a second fixed duration based channel access for a second transmission, which is a transmission following the first transmission. The first fixed duration based channel access is a channel access in which, if a channel is sensed to be idle within a first fixed duration, the terminal performing the first fixed duration based channel access is allowed to immediately transmit after the first fixed duration. The second fixed duration based channel access is a channel access in which, if a channel is sensed to be idle during a second fixed duration, the terminal performing the second fixed duration based channel access is allowed to immediately transmit after the second fixed duration.

[0015] The first fixed duration may be shorter than the second fixed duration.

[0016] The first fixed duration may be 16us and the second fixed duration may be 25us.

[0017] The grant may indicate a fixed duration based channel access as a channel access type and may indicate a channel access priority to be used for accessing the channel on which the multiple uplink transmissions are transmitted.

[0018] The grant may indicate the first fixed duration based channel access as a channel access type.

[0019] The grant may include one or more grants scheduling the uplink transmissions, the uplink transmissions being consecutive in time with no gaps.

[0020] A base station for wirelessly communicating with a terminal in an unlicensed band according to an embodiment of the present invention includes a communication module and a processor for controlling the communication module. When a duration of a transmission of the terminal is smaller than a maximum channel occupancy time and a gap between the transmission of the terminal and a transmission to the terminal is not larger than a first fixed duration, the processor transmits to the terminal within the maximum channel occupancy time without sensing immediately after the gap on a channel in which the transmission of the terminal is performed. In this case, the first fixed duration is 16 us.

[0021] If a gap between the transmission of the terminal and a transmission to the terminal is not greater than a first fixed duration, the processor transmits to the terminal immediately after the gap without sensing within a pre-specified duration, and the pre-specified duration may be a constraint applied to the transmission of the base station separately from the maximum channel occupancy time.

[0022] The processor may attempt a first fixed duration based channel access on a channel on which the transmission of the terminal is performed when a gap between the transmission of the terminal and the transmission to the terminal is equal to a first fixed duration. The first fixed duration based channel access may be a channel access in which a base station performing the first fixed duration based channel access is allowed to perform a transmission immediately after the first fixed duration when a channel is sensed to be idle within the first fixed duration.

[0023] If the gap between the transmission of the terminal and the transmission to the terminal is not greater than a second fixed duration, the processor attempts a second fixed duration based channel access on the channel on which the transmission of the terminal was made. The second fixed duration based channel access may be a channel access in which the base station performing the second fixed duration based channel access is allowed to transmit immediately after the second fixed duration if the channel is sensed to be idle during the second fixed duration. In this case, the second fixed duration may be 25us.

[0024] Channel occupation, including the transmission of the terminal and the transmission of the base station to the terminal, may be initiated by the base station.

[0025] Channel occupation, including the transmission of the terminal and the base station's transmission to the terminal, may be initiated by the terminal.

[0026] According to an embodiment of the present invention, a method for operating a terminal wirelessly communicating with a base station in an unlicensed band may include receiving, from the base station, a grant for scheduling a plurality of uplink transmissions; the terminal attempting a first fixed duration based channel access for a first transmission, which is one of the plurality of uplink transmissions; and, if the first fixed duration based channel access fails, attempting a second fixed duration based channel access for a second transmission, which is a transmission following the first transmission. Here, the first fixed duration based channel access may be a channel access in which the terminal performing the first fixed duration based channel access is allowed to transmit immediately after the first fixed duration when a 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 terminal performing the second fixed duration based channel access is allowed to transmit immediately after the second fixed duration when a channel is sensed to be idle during the second fixed duration.

[0027] The first fixed duration may be shorter than the second fixed duration.

[0028] The first fixed duration may be 16us and the second fixed duration may be 25us.

[0029] The grant may indicate a fixed duration based channel access as a channel access type and may indicate a channel access priority to be used for accessing the channel on which the multiple uplink transmissions are transmitted.

[0030] The grant may indicate the first fixed duration based channel access as a channel access type.

[0031] The grant may include one or more grants that schedule the uplink transmissions, the uplink transmissions being consecutive in time with no gaps.

[0032] According to an embodiment of the present invention, a method of operating a base station for wirelessly communicating with a terminal in an unlicensed band includes, when a duration of a transmission of the terminal is less than a maximum channel occupancy time and a gap between the transmission of the terminal and a transmission to the terminal is not greater than a first fixed duration, performing a transmission to the terminal within the maximum channel occupancy time without sensing immediately after the gap on a channel in which the transmission of the terminal is performed, wherein the first fixed duration is 16 us.

[0033] The method may further include, when a gap between the transmission of the terminal and a transmission to the terminal is not greater than a first fixed duration, performing a transmission to the terminal immediately after the gap without sensing within a pre-specified duration, where the pre-specified duration may be a constraint applied to the transmission of the base station separately from the maximum channel occupancy time.

[0034] The method may further include attempting a first fixed duration based channel access on a channel on which the transmission of the terminal is performed when a gap between the transmission of the terminal and a transmission to the terminal is equal to a first fixed duration, wherein the first fixed duration based channel access may be a channel access in which a base station performing the first fixed duration based channel access is allowed to perform a transmission immediately after the first fixed duration when a channel is sensed to be idle within the first fixed duration.

[0035] The method may further include attempting a second fixed duration based channel access on a channel on which the transmission of the terminal is performed when a gap between the transmission of the terminal and the transmission to the terminal is not greater than a second fixed duration. In this case, the second fixed duration based channel access may be a channel access in which a base station performing the second fixed duration based channel access is allowed to perform a transmission immediately after the second fixed duration when a channel is sensed to be idle during the second fixed duration. Also, the second fixed duration may be 25us.

[0036] Channel occupation, including the transmission of the terminal and the transmission of the base station to the terminal, may be initiated by the base station.

[0037] Channel occupation, including the transmission of the terminal and the base station's transmission to the terminal, may be initiated by the terminal. Effect of the Invention

[0038] One embodiment of the present invention provides a channel access method for transmitting in a wireless communication system operating in an unlicensed spectrum and an apparatus using the same.

[0039] The effects obtained from the present invention are not limited to those mentioned above, and other effects not mentioned will be clearly understood by those having ordinary skill in the art to which the present invention pertains from the following description. [Brief description of the drawings]

[0040] [Figure 1] FIG. 2 is a diagram illustrating an example of a radio frame structure used in a wireless communication system. [Diagram 2] FIG. 1 is a diagram illustrating an example of a downlink (DL) / uplink (UL) slot structure in a wireless communication system. [Diagram 3]FIG. 1 is a diagram illustrating physical channels used in a 3GPP system (e.g., NR) and a general signal transmission method using the physical channels. [Figure 4] A diagram showing SS / PBCH blocks for initial cell access in a 3GPP NR system. [Diagram 5] A diagram showing a procedure for control information and control channel transmission in a 3GPP NR system. [Figure 6] A diagram showing a CORESET in which a PDCCH is transmitted in a 3GPP NR system. [Figure 7] A diagram showing a method for setting a PDCCH search space in a 3GPP NR system. [Figure 8] FIG. 8 is a conceptual diagram illustrating carrier aggregation. [Figure 9] FIG. 2 is a diagram for explaining terminal carrier communication and multi-carrier communication. [Figure 10] A diagram showing an example in which a cross-carrier scheduling technique is applied. [Figure 11] FIG. 2 is a diagram illustrating a code block group (CBG) configuration and its time-frequency resource mapping according to an embodiment of the present invention. [Figure 12] A diagram showing 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 terminal transmits HARQ-ACK in response thereto. [Figure 13] FIG. 1 is a diagram showing an NR-U (NR-Unlicensed) service environment. [Figure 14] A diagram showing an embodiment of a deployment scenario of a terminal and a base station in an NR-U service environment. [Figure 15] FIG. 1 is a diagram showing an existing communication method (e.g., wireless LAN) that operates in an unlicensed band. [Figure 16] A diagram showing a channel access process based on Category 4 LBT in an embodiment of the present invention. [Figure 17]A diagram showing one embodiment of a method for adjusting a contention window size (CWS) based on HARQ-ACK feedback. [Figure 18] 2 is a block diagram showing the configuration of a terminal and a base station according to an embodiment of the present invention. [Figure 19] FIG. 11 is a diagram showing an embodiment of the present invention in which a responding node transmits within a COT initiated by an initiating node when the duration of the initiating node's transmission within the channel occupancy initiated by the initiating node does not exceed the MCOT of the channel occupancy. [Figure 20] A diagram showing the operation of a terminal in an embodiment of the present invention when downlink transmission cannot occupy MCOT within the channel occupancy initiated by the base station and the terminal's transmission is scheduled or configured by the base station. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0041] The terms used in this specification are selected as common terms currently widely used as much as possible in consideration of the functions in the present invention, but this may vary depending on the intentions, customs, or the emergence of new technologies of the engineers in this field. In addition, in certain cases, the applicant may arbitrarily select some terms, and in this case, the meaning will be described in the description of the relevant invention. Therefore, it is clear that the terms used in this specification should be analyzed based on the substantial meaning of the terms and the contents of this specification as a whole, rather than simply the names of the terms.

[0042] Throughout the specification, when a certain component is "connected" to another component, this includes not only "direct connection" but also "electrical connection" through other components in between. Furthermore, when a certain component is "included" in a certain component, this does not mean excluding other components, but further includes other components, unless otherwise specified to the contrary. In addition, limitations such as "more than" or "less than" based on a specific threshold may be appropriately replaced with "more than" or "less than", respectively, depending on the embodiment.

[0043] The following technologies are 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 frequency division multiple access (SC-FDMA), etc. CDMA is implemented in radio technologies such as Universal Terrestrial Radio Access (UTRA) and CDMA2000. TDMA is implemented in radio technologies such as Global System for Mobile communications (GSM), General Packet Radio Service (GPRS), and Enhanced Data Rates for GSM Evolution (EDGE). OFDMA is implemented in radio technologies such as IEEE802.11 (Wi-Fi), IEEE802.16 (WiMAX), IEEE802-20, Evolved UTRA (E-UTRA), etc. UTRA is part of the Universal Mobile Telecommunication System (UMTS). 3GPP LTE (Long term evolution) is a part of E-UMTS (Evolved UMTS) that uses E-UTRA, and LTE-A (Advanced) is an evolved version of 3GPP LTE. 3GPP NR is a system designed separately from LTE / LTE-A, and is a system for supporting eMBB (enhanced Mobile BroadBand), URLLC (Ultra-Reliable and Low Latency Communication), and mMTC (massive Machine Type Communication) services, which are requirements of IMT-2020. For clarity of explanation, the following description will focus on 3GPP NR, but the technical idea of ​​the present invention is not limited thereto.

[0044] Unless otherwise specified in this specification, the base station may include a gNB (next generation node B) defined in 3GPP NR. Furthermore, unless otherwise specified, the terminal may include a UE (user equipment). Hereinafter, in order to facilitate understanding of the description, each content will be described as an individual embodiment, but each embodiment may be used in combination with each other. In this disclosure, the configuration of the terminal may mean the configuration by the base station. Specifically, the base station may transmit a channel or a signal to the terminal to configure the operation of the terminal or the value of a parameter used in the wireless communication system.

[0045] FIG. 1 is a diagram illustrating an example of a radio frame structure used in a wireless communication system.

[0046] Referring to FIG. 1, a radio frame used in a 3GPP NR system has a length of 10 ms (ΔfmaxNf / 100)*Tc). The radio frame also consists of 10 equally sized subframes (SF), where Δfmax=480*103 Hz, Nf=4096, Tc=1 / (Δfref*Nf,ref), Δfref=15*103 Hz, and Nf,ref=2048. The 10 subframes in one frame are numbered from 0 to 9. Each subframe has a length of 1 ms and consists of one or more slots depending on the subcarrier spacing. More specifically, the subcarrier spacing that can be used in a 3GPP NR system is 15*2μkHz. μ is a subcarrier spacing configuration factor, and has a value of μ=0 to 4. That is, 15 kHz, 30 kHz, 60 kHz, 120 kHz, or 240 kHz is used as the subcarrier spacing. A 1 ms long subframe consists of 2μ slots. In this case, the length of each slot is 2-μms. The 2μ slots in one subframe are numbered from 0 to 2μ-1. Also, the slots in one radio frame are numbered from 0 to 10*2μ-1. Time resources are divided by at least one of the radio frame number (also called radio frame index), subframe number (also called subframe index), and slot number (or slot index).

[0047] FIG2 illustrates an example of a downlink (DL) / uplink (UL) slot structure in a wireless communication system, and in particular, illustrates a resource grid structure in a 3GPP NR system.

[0048] There is one resource grid per antenna port. Referring to FIG. 2, a slot includes a plurality of OFDM symbols in the time domain and a plurality of resource blocks (RBs) in the frequency domain. An OFDM symbol also means one symbol period. Unless otherwise specified, an OFDM symbol is simply referred to as a symbol. In the following description, a symbol includes an OFDM symbol, an SC-FDMA symbol, a DFTs-OFDM symbol, and the like. Referring to FIG. 2, a signal transmitted from each slot is represented by a resource grid consisting of Nsize, μgrid, x*NRBSC subcarriers, and Nslotsymb OFDM symbols. Here, x=DL for a downlink resource grid, and x=UL for an uplink resource grid. Nsize, μgrid, and x indicate the number of resource blocks (RBs) according to a subcarrier spacing factor μ (x is DL or UL), and Nslotsymb indicates the number of OFDM symbols in a slot. NRBSC is the number of subcarriers constituting one RB, and NRBSC=12. Depending on the multiple access scheme, the OFDM symbol is called a cyclic prefix OFDM symbol (CP-OFDM) symbol or a discrete Fourier transform spread OFDM symbol (DFT-S-OFDM).

[0049] The number of OFDM symbols included in one slot may vary depending on the length of a cyclic prefix (CP). For example, a normal CP includes 14 OFDM symbols in one slot, while an extended CP includes 12 OFDM symbols in one slot. In a specific embodiment, the extended CP is used only at a subcarrier interval of 60 kHz. For convenience of explanation, FIG. 2 illustrates a case where one slot includes 14 OFDM symbols, but the embodiment of the present invention is also applied to slots having other numbers of OFDM symbols in the same manner. Referring to FIG. 2, each OFDM symbol includes Nsize, μgrid, and x*NRBSC subcarriers in the frequency domain. The types of subcarriers are divided into data subcarriers for transmitting data, reference signal subcarriers for transmitting a reference signal, and guard bands. The carrier frequency is also called a center frequency (fc).

[0050] One RB is defined by NRBSC (e.g., 12) consecutive subcarriers in the frequency domain. Incidentally, a resource consisting of one OFDM symbol and one subcarrier is called a resource element (RE) or tone. Thus, one RB consists of Nslotsymb*NRBSC resource elements. Each resource element in the resource grid is uniquely defined by an index pair (k, l) in one slot. k is an index ranging from 0 to Nsize,μgrid,x*NRBSC-1 in the frequency domain, and l is an index ranging from 0 to Nslotsymb-1 in the time domain.

[0051] In order for a terminal to receive a signal from a base station or transmit a base station signal, the time / frequency synchronization of the terminal should be aligned with the time / frequency synchronization of the base station, because if the base station and the terminal are not synchronized, the terminal cannot determine the time and frequency parameters required to demodulate DL signals and transmit UL signals at the correct time.

[0052] Each symbol of a radio frame operating in time division duplex (TDD) or unpaired spectrum consists of at least one of downlink symbol (DL symbol), uplink symbol (UL symbol) or flexible symbol. A radio frame operating in frequency division duplex (FDD) or paired spectrum with a downlink carrier consists of downlink symbols or flexible symbols, and a radio frame operating with an uplink carrier consists of uplink symbols or flexible symbols. A downlink symbol allows downlink transmission but not uplink transmission, and an uplink symbol allows uplink transmission but not downlink transmission. Whether a flexible symbol is used in the downlink or uplink is determined depending on the signal.

[0053] Information on the type of each symbol, i.e., information indicating any one of the downlink symbol, the uplink symbol, and the flexible symbol, is composed of a cell-specific (cell-specific or common) RRC signal. In addition, the information on the type of each symbol is additionally composed of a specific terminal (UE-specific or dedicated) RRC signal. The base station uses the cell-specific RRC signal to inform i) the period of the cell-specific slot configuration, ii) the number of slots having only downlink symbols from the beginning of the period of the cell-specific slot configuration, iii) the number of downlink symbols from the first symbol in the slot immediately after the slot having only downlink symbols, iv) the number of slots having only uplink symbols from the end of the period of the cell-specific slot configuration, and v) the number of uplink symbols from the last symbol in the slot immediately before the slot having only uplink symbols. Here, a symbol that is not configured as either an uplink symbol or a downlink symbol is a flexible symbol.

[0054] If the information regarding the symbol type consists of the UE-specific RRC signal, the base station signals, by means of the cell-specific RRC signal, whether the flexible symbol is a downlink symbol or an uplink symbol. At this time, the UE-specific RRC signal cannot change a downlink symbol or an uplink symbol consisting of the cell-specific RRC signal to another symbol type. The UE-specific RRC signal signals, for each slot, the number of downlink symbols among the Nslotsymb symbols of the slot and the number of uplink symbols among the Nslotsymb symbols of the slot. At this time, the downlink symbols of the slot are continuously configured from the first symbol to the i-th symbol of the slot. Also, the uplink symbols of the slot are continuously configured from the j-th symbol to the last symbol of the slot (where i < j). In a slot, a symbol that is not configured as either an uplink symbol or a downlink symbol is a flexible symbol.

[0055] The type of symbol configured by the RRC signal as described above can be called a semi-static DL / UL configuration. In the semi-static DL / UL configuration configured by the RRC signal previously, the flexible symbol may be indicated as a downlink symbol, an uplink symbol, or a flexible symbol by the dynamic SFI (slot format information) transmitted on the physical downlink control channel (PDCCH). At this time, a downlink symbol or an uplink symbol configured by the RRC signal is not changed to another symbol type. Table 1 exemplifies the dynamic SFI that the base station can indicate to the UE.

[0056]

Table 1

[0057] In Table 1, D represents a downlink symbol, U represents an uplink symbol, and X represents a flexible symbol. As shown in Table 1, up to two DL / UL switchings may be allowed in one slot.

[0058] FIG. 3 is a diagram illustrating physical channels used in a 3GPP system (eg, NR) and a general signal transmission method using the physical channels.

[0059] When a terminal is powered on or enters a new cell, the terminal performs an initial cell search operation S101. More specifically, the terminal synchronizes with a base station in the initial cell search. To this end, the terminal receives a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) from the base station to synchronize with the base station and obtain information such as a cell index. Next, the terminal receives a physical broadcast channel from the base station to obtain broadcast information within the cell.

[0060] After completing the initial cell search, the terminal receives a physical downlink shared channel (PDSCH) through a physical downlink control channel (PDCCH) and information carried on the PDCCH to obtain more detailed system information than the system information obtained through the initial cell search (S102). Here, the system information transmitted to the terminal is cell-common system information for the terminal to operate correctly in a physical layer in Radio Resource Control (RRC), and is called remaining system information or system information block (SIB) 1.

[0061] When a terminal first connects to a base station or when there are no radio resources for signal transmission (when the terminal is in RRC_IDLE mode), the terminal can perform a random access procedure with respect to the base station (steps S103 to S106). First, the terminal transmits a preamble on a physical random access channel (PRACH) (S103) and can receive a response message for the preamble from the base station on a PDCCH and a corresponding PDSCH (S104). If the terminal receives a valid random access response message, the terminal transmits data including its own identifier, etc. to the base station on a physical uplink shared channel (PUSCH) indicated by an uplink grant transmitted from the base station on the PDCCH (S105). Next, the terminal waits to receive a PDCCH as an instruction from the base station to resolve collisions. If the terminal successfully receives a PDCCH with its own identifier (S106), the random access procedure ends. During the random access procedure, the terminal may obtain terminal-specific system information required for the terminal to operate correctly in the physical layer of the RRC layer. If the terminal obtains the terminal-specific system information in the RRC layer, the terminal enters the RRC connected mode (RRC_CONNECTED mode).

[0062] The RRC layer is used to generate and manage messages for control between a terminal and a radio access network (RAN). More specifically, the base station and terminal can broadcast cell system information required for all terminals in the cell, manage the delivery of paging messages, manage mobility and handover, report measurements of terminals and control related thereto, and manage and store terminal capabilities in the RRC layer. In general, the update of signals delivered in the RRC layer (hereinafter, RRC signals) is longer than the transmission and reception period (i.e., transmission time interval, TTI) in the physical layer, so that the RRC settings can be maintained unchanged for a long period.

[0063] After the above-mentioned procedure, the terminal receives PDCCH / PDSCH S107 and transmits physical uplink shared channel (PUSCH) / physical uplink control channel (PUCCH) S108 as a general uplink / downlink signal transmission procedure. In particular, the terminal receives downlink control information (DCI) via the PDCCH. The DCI includes control information such as resource allocation information for the terminal. The format of the DCI may differ depending on the purpose of use. The uplink control information (UCI) transmitted by the terminal to the base station via the uplink includes downlink / uplink ACK / NACK signals, a channel quality indicator (CQI), a precoding matrix index (PMI), a rank indicator (RI), etc. Here, the CQI, PMI, and RI are included in channel state information (CSI). In the case of a 3GPP NR system, the terminal transmits control information such as the above-mentioned HARQ-ACK and CSI via the PUSCH and / or PUCCH.

[0064] FIG. 4 is a diagram illustrating SS / PBCH blocks for initial cell access in a 3GPP NR system.

[0065] When a terminal is powered on or attempts to access a new cell, it acquires time and frequency synchronization with the cell and performs an initial cell search process. The terminal detects the physical cell identity (NcellID) of the cell during the cell search process. To this end, the terminal receives synchronization signals, such as a primary synchronization signal (PSS) and a secondary synchronization signal (SSS), from the base station to synchronize with the base station. At this time, the terminal obtains information such as a cell identity (ID).

[0066] With reference to FIG. 4(a), the synchronization signal (SS) will be described in more detail. The synchronization signal is divided into PSS and SSS. The PSS is used to obtain time domain synchronization and / or frequency domain synchronization such as OFDM symbol synchronization and slot synchronization. The SSS is used to obtain frame synchronization and cell group ID. With reference to FIG. 4(a) and Table 1, the SS / PBCH block consists of 20 consecutive RBs (=240 subcarriers) on the frequency axis and 4 consecutive OFDM symbols on the time axis. In this case, in the SS / PBCH block, the PSS is transmitted in the first OFDM symbol and the SSS is transmitted in the third OFDM symbol via the 56th to 18th subcarriers. Here, the lowest subcarrier index of the SS / PBCH block is numbered from 0. In the first OFDM symbol in which the PSS is transmitted, the base station does not transmit signals via the remaining subcarriers, i.e., the 0th to 55th and 183rd to 239th subcarriers. In addition, in the third OFDM symbol in which the SSS is transmitted, the base station does not transmit signals via subcarriers 48 to 55 and 183 to 19. The base station transmits a physical broadcast channel (PBCH) via the remaining REs in the SS / PBCH block excluding the above-mentioned signals.

[0067] [Table 2]

[0068] The SS is grouped into 336 physical-layer cell-identifier groups, each of which includes three unique identifiers, so that a total of 1008 unique physical layer cell IDs are obtained through a combination of three PSSs and SSSs, more specifically, each physical layer cell ID is part of only one physical-layer cell-identifier group. Thus, a physical layer cell ID NcellID=3N(1)ID+N(2)ID is uniquely defined by an index N(1)ID ranging from 0 to 335 indicating a physical-layer cell-identifier group and an index N(2)ID ranging from 0 to 2 indicating a physical-layer identifier in the physical-layer cell-identifier group. The UE detects the PSS and identifies one of the three unique physical-layer identifiers. The UE also detects the SSS and identifies one of the 336 physical layer cell IDs associated with the physical-layer identifier. In this case, the sequence dPSS(n) of the PSS is as follows:

[0069]

number

[0070] where x(i+7)=(x(i+4)+x(i)) mod 2,

[0071] Given: [x(6)x(5)x(4)x(3)x(2)x(1)x(0)]=[1110110].

[0072] Also, the SSS sequence dSSS(n) is as follows:

[0073]

number

[0074] Here, x0(i+7)=(x0(i+4)+x0(i))mod 2 x1(i+7)=(x1(i+1)+x1(i))mod 2,

[0075] Given that [x0(6)x0(5)x0(4)x0(3)x0(2)x0(1) 0(0)]=[0000001], [x1(6)x1(5)x1(4)x1(3)x1(2)x1(1)x1(0)]=[0000001].

[0076] A radio frame with a length of 10 ms is divided into two half-frames with a length of 5 ms. The slots in each half-frame in which the SS / PBCH block is transmitted will be described with reference to FIG. 4(b). The slots in which the SS / PBCH block is transmitted are any one of cases A, B, C, D, and E. In case A, the subcarrier spacing is 15 kHz, and the start point of the SS / PBCH block is the {2, 8}+14*nth symbol. In this case, n=0, 1 for carrier frequencies below 3 GHz. Also, n=0, 1, 2, 3 for carrier frequencies above 3 GHz and below 6 GHz. In case B, the subcarrier spacing is 30 kHz, and the start point of the SS / PBCH block is the {4, 8, 16, 20}+28*nth symbol. In this case, n=0 for carrier frequencies below 3 GHz. Also, n=0, 1 for carrier frequencies above 3 GHz and below 6 GHz. In case C, the subcarrier spacing is 30 kHz and the start of the SS / PBCH block is {2, 8}+14*n symbols, where n=0, 1 for carrier frequencies below 3 GHz. Also, n=0, 1, 2, 3 for carrier frequencies above 3 GHz and below 6 GHz. In case D, the subcarrier spacing is 120 kHz and the start of the SS / PBCH block is {4, 8, 16, 20}+28*n symbols, where n=0, 1, 2, 3, 5, 6, 7, 8, 10, 11, 12, 13, 15, 16, 17, 18 for carrier frequencies above 6 GHz. In case E, the subcarrier spacing is 240 kHz and the start of the SS / PBCH block is {8, 12, 16, 20, 32, 36, 40, 44}+56*n symbols. In this case, n=0, 1, 2, 3, 5, 6, 7, 8 for carrier frequencies of 6 GHz or higher.

[0077] Figure 5 is a diagram showing a procedure for transmitting control information and a control channel in a 3GPP NR system. Referring to Figure 5(a), a base station adds a cyclic redundancy check (CRC) masked (e.g., XORed) with a radio network temporary identifier (RNTI) to control information (e.g., DCI) S202. The base station scrambles the CRC with an RNTI value determined according to the purpose / target of each control information. The common RNTI used by one or more terminals includes at least one of a system information RNTI (SI-RNTI), a paging RNTI (P-RNTI), a random access RNTI (RA-RNTI), and a transmit power control RNTI (TPC-RNTI). Also, the UE-specific RNTI includes at least one of C-RNTI (cell temporary RNTI), CS-RNTI, or MCS-C-RNTI. Next, the base station performs channel encoding (e.g., polar coding) S204, and then performs rate-matching according to the amount of resource(s) used for PDCCH transmission S206. Next, the base station multiplexes DCI(s) based on a PDCCH structure based on a control channel element (CCE) S208. In addition, the base station applies additional processes such as scrambling, modulation (e.g., QPSK), and interleaving to the multiplexed DCI(s) S210, and maps them to resources to be transmitted. A CCE is a basic resource unit for a PDCCH, and one CCE consists of a plurality of (e.g., 6) resource element groups (REGs). One REG consists of a plurality of (e.g., 12) REs. The number of CCEs used for one PDCCH is defined as an aggregation level. 3GPP NR systems use aggregation levels of 1, 2, 4, 8, or 16.FIG. 5(b) is a diagram relating to CCE aggregation levels and PDCCH multiplexing, showing the types of CCE aggregation levels used for one PDCCH and the CCE(s) transmitted in the control region accordingly.

[0078] FIG. 6 is a diagram showing a CORESET in which a PDCCH is transmitted in a 3GPP NR system.

[0079] A CORESET is a time-frequency resource in which a PDCCH, which is a control signal for a terminal, is transmitted. A search space, which will be described later, is mapped to one CORESET. Thus, a terminal does not monitor all frequency bands to receive a PDCCH, but monitors a time-frequency region designated as a CORESET and decodes a PDCCH mapped to the CORESET. A base station configures one or more CORESETs for each cell in a terminal. A CORESET is made up of up to three consecutive symbols on the time axis. Also, a CORESET is made up of six units of consecutive PRBs on the frequency axis. In the embodiment of FIG. 5, CORESET#1 is made up of consecutive PRBs, and CORESET#2 and CORESET#3 are made up of discontinuous PRBs. A CORESET may be located at any symbol in a slot. For example, in the embodiment of FIG. 5, CORESET#1 starts from the first symbol of a slot, CORESET#2 starts from the fifth symbol of a slot, and CORESET#9 starts from the ninth symbol of a slot.

[0080] FIG. 7 is a diagram illustrating a method for setting a PDCCH search space in a 3GPP NR system.

[0081] In order to transmit a PDCCH to a terminal, at least one or more search spaces exist in each CORESET. In an embodiment of the present invention, the search space is a set of all time-frequency resources (hereinafter, PDCCH candidates) in which the PDCCH of the terminal is transmitted. The search space includes a common search space that 3GPP NR terminals should commonly search, and a terminal-specific or UE-specific search space that a specific terminal should search. In the common search space, all terminals in a cell belonging to the same base station monitor a PDCCH that is set to be commonly searched. In addition, the terminal-specific search space is set for each terminal so that the PDCCH allocated to each terminal is monitored at a position of the search space that differs from one another according to the terminal. In the case of the terminal-specific search space, the search spaces between terminals may be partially overlapped due to the limited control region to which the PDCCH is allocated. Monitoring the PDCCH includes blind decoding the PDCCH candidates in the search space. If blind decoding is successful, it is expressed as the PDCCH being (successfully) detected / received, and if blind decoding is unsuccessful, it is expressed as the PDCCH being undetected / not received or not successfully detected / received.

[0082] For convenience of explanation, a PDCCH scrambled with a group common (GC) RNTI already known by one or more terminals to transmit downlink control information to one or more terminals is referred to as a group common (GC) PDCCH or a common PDCCH. Also, a PDCCH scrambled with a terminal-specific RNTI already known by a specific terminal to transmit uplink scheduling information or downlink scheduling information to one specific terminal is referred to as a terminal-specific PDCCH. The common PDCCH is included in a common search space, and the terminal-specific PDCCH is included in a common search space or a terminal-specific PDCCH.

[0083] The base station notifies each terminal or terminal group of information on resource allocation of the transmission channels PCH (paging channel) and DL-SCH (downlink-shared channel) (i.e., DL Grant) or information on resource allocation of the UL-SCH and hybrid automatic repeat request (HARQ) (i.e., UL Grant) via the PDCCH. The base station transmits a PCH transport block and a DL-SCH transport block via the PDSCH. The base station transmits data excluding specific control information or specific service data via the PDSCH. Also, the terminal receives data excluding specific control information or specific service data via the PDSCH.

[0084] The base station transmits information on which terminal (one or more terminals) the PDSCH data is transmitted to and how the terminal should receive and decode the PDSCH data by including it in the PDCCH. For example, assume that the DCI transmitted through a specific PDCCH is CRC masked with RNTI "A", the DCI indicates that the PDSCH is allocated to radio resource "B" (e.g., frequency position) and indicates transmission format information "C" (e.g., transmission block size, modulation method, coding information, etc.). The terminal monitors the PDCCH using its own RNTI information. In this case, if there is a terminal that blindly decodes the PDCCH using RNTI "A", the terminal receives the PDCCH and receives the PDSCH indicated by "B" and "C" through the received PDCCH information.

[0085] Table 3 shows one embodiment of a PUCCH used in a wireless communication system.

[0086] [Table 3]

[0087] The PUCCH is used to transmit the following uplink control information (UCI):

[0088] -SR (Scheduling Request): Information used to request uplink UL-SCH resources.

[0089] -HARQ-ACK: a response to a PDCCH (indicating DL SPS release) and / or a response to an uplink transport block (TB) on a PDSCH. HARQ-ACK indicates whether information transmitted via a PDCCH or a PDSCH has been received. HARQ-ACK responses include a positive ACK (simply, ACK), a negative ACK (hereinafter, NACK), a discontinuous transmission (DTX), or a NACK / DTX. Here, the term HARQ-ACK is used interchangeably with HARQ-ACK / NACK and ACK / NACK. In general, an ACK is represented by a bit value of 1, and a NACK is represented by a bit value of 0.

[0090] -CSI: Feedback information for a downlink channel. It is generated by a terminal based on a CSI-RS (Reference Signal) transmitted by a base station. MIMO (multiple input multiple output)-related feedback information includes RI and PMI. CSI is divided into CSI part 1 and CSI part 2 according to the information indicated by CSI.

[0091] In the 3GPP NR system, five PUCCH formats are used to support various service scenarios and various channel environments and frame structures.

[0092] PUCCH format 0 is a format that transmits 1-bit or 2-bit HARQ-ACK information or SR. PUCCH format 0 is transmitted through one or two OFDM symbols on the time axis and one RB on the frequency axis. If PUCCH format 0 is transmitted with two OFDM symbols, the same sequence is transmitted with different RBs for the two symbols. Through this, the terminal obtains frequency diversity gain. More specifically, the terminal determines a cyclic shift value mcs according to the Mbit bit UCI (Mbit=1 or 2), and transmits a sequence obtained by cyclically shifting a base sequence of length 12 by the determined value mcs, by mapping the sequence to 12 REs of one OFDM symbol and one PRB. If the number of cyclic shifts available to the terminal is 12 and Mbit=1, 1-bit UCI 0 and 1 are represented by sequences corresponding to two cyclic shifts with a cyclic shift value difference of 6. Also, if Mbit=2, then 2-bit UCI 00, 01, 11, 10 is represented by a sequence corresponding to four cyclic shifts with a difference between the cyclic shift values ​​being three.

[0093] PUCCH format 1 transmits 1-bit or 2-bit HARQ-ACK information or SR. PUCCH format 1 is transmitted through continuous OFDM symbols on the time axis and one PRB on the frequency axis. Here, the number of OFDM symbols occupied by PUCCH format 1 is one of 4 to 14. More specifically, UCI with Mbit=1 is modulated by BPSK. The terminal modulates UCI with Mbit=2 by quadrature phase shift keying (QPSK). A signal is obtained by multiplying the modulated complex valued symbol d(0) by a sequence of length 12. The terminal transmits the obtained signal by spreading it by a time-axis orthogonal cover code (OCC) on even-numbered OFDM symbols to which PUCCH format 1 is assigned. In PUCCH format 1, the maximum number of different terminals multiplexed in the same RB can be determined according to the length of the OCC used. In odd-numbered OFDM symbols of PUCCH format 1, a demodulation reference signal (DMRS) is spread by OCC and mapped.

[0094] PUCCH format 2 transmits UCI exceeding 2 bits. PUCCH format 2 is transmitted through one or two OFDM symbols on the time axis and one or more RBs on the frequency axis. If PUCCH format 2 is transmitted through two OFDM symbols, the same sequence is transmitted through two OFDM symbols in different RBs. In this way, the terminal obtains frequency diversity gain. More specifically, Mbit UCI (Mbit>2) is bit-level scrambled and QPSK modulated to be mapped to RBs of one or two OFDM symbol(s). Here, the number of RBs is one of 1 to 16.

[0095] PUCCH format 3 or PUCCH format 4 transmits UCI exceeding 2 bits. PUCCH format 3 or PUCCH format 4 is transmitted through continuous OFDM symbols on the time axis and one PRB on the frequency axis. The number of OFDM symbols occupied by PUCCH format 3 or PUCCH format 4 is one of 4 to 14. In particular, the terminal modulates Mbit UCI (Mbit>2) with π / 2-BPSK (Binary Phase Shift Keying) or QPSK to generate complex symbols d(0) to d(Msymb-1). Here, Msymb=Mbit when π / 2-BPSK is used, and Msymb=Mbit / 2 when QPSK is used. The terminal does not apply block-wise spreading to PUCCH format 3. However, the terminal may apply block-wise spreading to one RB (i.e., 12 subcarriers) using PreDFT-OCC of length -12 so that PUCCH format 4 has a multiplexing capacity of 2 or 4. The terminal transmit precoding (or DFT-precoding) the spread signal, maps it to each RE, and transmits the spread signal.

[0096] In this case, the number of RBs occupied by PUCCH format 2, PUCCH format 3, or PUCCH format 4 is determined according to the length of UCI transmitted by the terminal and the maximum code rate. If the terminal uses PUCCH format 2, the terminal transmits both HARQ-ACK information and CSI information via PUCCH. If the number of RBs that the terminal can transmit is greater than the maximum number of RBs that PUCCH format 2, PUCCH format 3, or PUCCH format 4 can use, the terminal does not transmit some UCI information according to the priority of the UCI information and transmits only the remaining UCI information.

[0097] PUCCH format 1, PUCCH format 3, or PUCCH format 4 is configured via RRC signaling to indicate frequency hopping within a slot. When frequency hopping is configured, the index of the RB to be frequency hopped is configured via RRC signaling. If PUCCH format 1, PUCCH format 3, or PUCCH format 4 is transmitted across N OFDM symbols in the time axis, the first hop has floor(N / 2) OFDM symbols and the second hop has ceil(N / 2) OFDM symbols.

[0098] PUCCH format 1, PUCCH format 3, or PUCCH format 4 is configured to be repeatedly transmitted in multiple slots. In this case, the number K of slots in which the PUCCH is repeatedly transmitted is configured by an RRC signal. The repeatedly transmitted PUCCH should start from the same OFDM symbol position in each slot and have the same length. If the RRC signal indicates that any one of the OFDM symbols in a slot in which the UE should transmit the PUCCH is a DL symbol, the UE does not transmit the PUCCH from the slot, but postpones it to the next slot for transmission.

[0099] Meanwhile, in a 3GPP NR system, a terminal transmits and receives using a bandwidth smaller than or equal to the bandwidth of a carrier (or cell). To this end, the terminal is configured with a BWP (bandwidth part) consisting of a continuous bandwidth that is a part of the carrier bandwidth. A terminal operating according to TDD or in an unpaired spectrum is configured with up to four DL / UL BWP pairs for one carrier (or cell). The terminal also activates one DL / UL BWP pair. A terminal operating according to FDD or in a paired spectrum is configured with up to four DL BWPs for a downlink carrier (or cell) and up to four UL BWPs for an uplink carrier (or cell). The terminal activates one DL BWP and one UL BWP for each carrier (or cell). The terminal may not receive or transmit from time-frequency resources other than the activated BWP. The activated BWP is called an active BWP.

[0100] The base station refers to an activated BWP among the BWPs configured for the terminal as a DCI. The BWP indicated by the DCI is activated, and the other configured BWP(s) is deactivated. In a carrier (or cell) operating in TDD, the base station includes a BPI (bandwidth part indicator) indicating the activated BWP in the DCI for scheduling the PDSCH or PUSCH to change the DL / UL BWP pair of the terminal. The terminal receives the DCI for scheduling the PDSCH or PUSCH and identifies the activated DL / UL BWP pair based on the BPI. In the case of a downlink carrier (or cell) operating in FDD, the base station includes a BPI indicating the activated BWP in the DCI for scheduling the PDSCH to change the DL BWP of the terminal. In the case of an uplink carrier (or cell) operating in FDD, the base station includes a BPI indicating the activated BWP in the DCI for scheduling the PDSCH to change the UL BWP of the terminal.

[0101] FIG. 8 is a conceptual diagram illustrating carrier aggregation.

[0102] Carrier aggregation refers to a method in which a terminal uses multiple frequency blocks or (logical) cells consisting of uplink resources (or component carriers) and / or downlink resources (or component carriers) in one large logical frequency band in order for a wireless communication system to use a wider frequency band. For convenience of explanation, the term "component carrier" will be used hereinafter.

[0103] Referring to FIG. 8, as an example of a 3GPP NR system, the entire system band includes up to 16 component carriers, and each component carrier has a bandwidth of up to 400 MHz. The component carrier includes one or more physically contiguous subcarriers. Although each component carrier is shown to have the same bandwidth in FIG. 8, this is merely an example, and each component carrier may have a different bandwidth. Also, although each component carrier is shown to be adjacent to each other on the frequency axis, the drawing is a logical concept, and each component carrier may be physically adjacent to each other or separated from each other.

[0104] A different center frequency is used in each component carrier. Also, a common center frequency is used in physically adjacent component carriers. In the embodiment of FIG. 8, if it is assumed that all component carriers are physically adjacent, center frequency A is used in all component carriers. Also, if it is assumed that each component carrier is not physically adjacent, center frequency A and center frequency B are used in each component carrier.

[0105] When the entire system band is expanded by carrier aggregation, the frequency band used for communication with each terminal is defined in component carrier units. Terminal A uses the entire system band of 100 MHz and communicates using all five component carriers. Terminals B1 to B5 use only a 20 MHz bandwidth and communicate using one component carrier. Terminals C1 and C2 use only a 40 MHz bandwidth and communicate using two component carriers each. The two component carriers may be logically / physically adjacent or not adjacent. The embodiment of FIG. 8 shows a case where terminal C1 uses two non-adjacent component carriers and terminal C2 uses two adjacent component carriers.

[0106] 9 is a diagram for explaining terminal carrier communication and multi-carrier communication. In particular, FIG. 9(a) shows a subframe structure of a single carrier, and FIG. 9(b) shows a subframe structure of a multi-carrier.

[0107] Referring to FIG. 9(a), a general wireless communication system transmits or receives data through one DL band and one corresponding UL band in the FDD mode. In another specific embodiment, in the TDD mode, the wireless communication system divides a wireless frame into an uplink time unit and a downlink time unit in the time domain, and transmits or receives data through the uplink / downlink time unit. Referring to FIG. 9(b), three 20 MHz component carriers (CCs) are aggregated in the UL and DL, respectively, to support a bandwidth of 60 MHz. The CCs are adjacent or non-adjacent to each other in the frequency domain. Although FIG. 9(b) illustrates a case in which the bandwidth of the UL CC and the bandwidth of the DL CC are the same and symmetrical for convenience, the bandwidth of each CC may be determined independently. Also, asymmetric carrier aggregation in which the number of UL CCs and the number of DL CCs are different is possible. The DL / UL CC allocated / configured to a specific terminal through RRC is called a serving DL / UL CC of the specific terminal.

[0108] The base station activates some or all of the serving CCs of the terminal, or deactivates some of the CCs to communicate with the terminal. The base station may change the CCs to be activated / deactivated, or may change the number of CCs to be activated / deactivated. When the base station allocates CCs available to the terminal in a cell-specific or terminal-specific manner, at least one of the CCs once allocated may not be deactivated unless the CC allocation for the terminal is completely reconfigured or the terminal performs a handover. A CC that is not deactivated by the terminal is called a primary CC (PCC) or PCell (primary cell), and a CC that the base station can activate / deactivate freely is called a secondary CC (SCC) or SCell (secondary cell).

[0109] Meanwhile, 3GPP NR uses the concept of a cell to manage radio resources. A cell is defined as a combination of downlink and uplink resources, i.e., a combination of DL CC and UL CC. A cell consists of DL resources alone or a combination of DL and UL resources. If carrier aggregation is supported, the linkage between the carrier frequency of DL resources (or DL ​​CC) and the carrier frequency of UL resources (or UL CC) is indicated by system information. Carrier frequency means the center frequency of each cell or CC. A cell corresponding to a PCC is called a PCell, and a cell corresponding to a SCC is called a SCell. A carrier corresponding to a PCell in the downlink is a DL PCC, and a carrier corresponding to a PCell in the uplink is a UL PCC. Similarly, a carrier corresponding to a SCell in the downlink is a DL SCC, and a carrier corresponding to a SCell in the uplink is a UL SCC. Depending on the terminal capacity, a serving cell(s) consists of one PCell and zero or more SCells. For a UE in RRC_CONNECTED state but with no carrier aggregation configured or that does not support carrier aggregation, there is only one serving cell consisting of only a PCell.

[0110] As described above, the term cell used in carrier aggregation is different from the term cell referring to a certain geographical area to which communication services are provided by one base station or one antenna group. However, in order to distinguish between a cell referring to a certain geographical area and a cell of carrier aggregation, in the present invention, a cell of carrier aggregation is referred to as CC, and a cell of a geographical area is referred to as cell.

[0111] FIG. 10 is a diagram showing an example in which a cross-carrier scheduling technique is applied. If cross-carrier scheduling is configured, a control channel transmitted through a first CC schedules a data channel transmitted through a first CC or a second CC using a carrier indicator field (CIF). The CIF is included in the DCI. In other words, a scheduling cell is configured, and a DL grant / UL grant transmitted from a PDCCH region of the scheduling cell schedules a PDSCH / PUSCH of a scheduled cell. That is, a search region for multiple component carriers is the PDCCH region of the scheduling cell. A PCell is basically a scheduling cell, and a specific SCell is designated as a scheduling cell by a higher layer.

[0112] In the embodiment of Figure 10, it is assumed that three DL CCs are merged. Here, it is assumed that DL component carrier #0 is DL PCC (or PCell), and DL component carrier #1 and DL component carrier #2 are DL SCC (or SCell). It is also assumed that DL PCC is configured as PDCCH monitoring CC. If cross-carrier scheduling is not configured by terminal-specific (or terminal-group-specific, or cell-specific) higher layer signaling, CIF is disabled, and each DL CC transmits only PDCCH that schedules its own PDSCH without CIF according to NR PDCCH rules (non-cross-carrier scheduling, self-carrier scheduling). On the other hand, if cross-carrier scheduling is configured by terminal-specific (or terminal-group-specific, or cell-specific) higher layer signaling, the CIF is enabled, and a specific CC (e.g., DL PCC) transmits not only a PDCCH for scheduling the PDSCH of DL CC A but also a PDCCH for scheduling the PDSCH of other CCs using the CIF (cross-carrier scheduling). On the other hand, no PDCCH is transmitted in other DL CCs. Thus, depending on whether cross-carrier scheduling is configured in the terminal, the terminal monitors a PDCCH that does not include a CIF to receive a self-carrier scheduled PDSCH, or monitors a PDCCH that includes a CIF to receive a cross-carrier scheduled PDSCH.

[0113] 9 and 10 illustrate the subframe structure of the 3GPP LTE-A system, the same or similar configuration can be applied to the 3GPP NR system, however, in the 3GPP NR system, the subframes in FIG. 9 and 10 may be replaced with slots.

[0114] 11 shows a code block group (CBG) configuration and its time-frequency resource mapping according to an embodiment of the present invention. More specifically, FIG. 11(a) shows an embodiment of a CBG configuration included in one transport block (TB), and FIG. 11(b) shows time-frequency resource mapping of the CBG configuration.

[0115] The maximum supportable length of the channel code is defined. For example, the maximum supportable length of the turbo code used in 3GPP LTE(-A) is 6144 bits. However, the length of a transport block (TB) transmitted in the PDSCH may be longer than 6144 bits. If the length of the TB is longer than the maximum supportable length, the TB may be divided into code blocks (CB) of a maximum length of 6144 bits. Each CB is a unit for performing channel coding. Furthermore, for efficient retransmission, several CBs may be grouped together to form one CBG. The terminal and the base station require information on how the CBG is configured.

[0116] The CBG and CB in the TB may be configured according to various embodiments. According to one embodiment, the number of available CBGs may be determined to a fixed value or may be configured by RRC configuration information between the base station and the terminal. In this case, the number of CBs may be determined according to the length of the TB, and the CBG may be set according to the determined number information. According to another embodiment, the number of CBs that may be included in one CBG may be determined to a fixed value or may be configured according to RRC configuration information between the base station and the terminal. In this case, when the number of CBs is determined according to the length of the TB, the number of CBGs may be set according to the CB number information per CBG.

[0117] Referring to the embodiment of FIG. 11(a), one TB may be divided into eight CBs. The eight CBs may be further grouped into four CBGs. Such a mapping relationship between the CBs and the CBGs (or the CBG configuration) may be statically set between the base station and the terminal, or may be semi-statically set by RRC configuration information. According to another embodiment, the mapping relationship may be set by dynamic signaling. When the terminal receives the PDCCH transmitted by the base station, the terminal may directly or indirectly identify the CB and the CBG mapping relationship (or the CBG configuration) by using explicit information and / or implicit information. One CBG may include only one CB or may include all CBs constituting one TB. For reference, the method proposed in the embodiment of the present invention is applicable regardless of the CB and the CBG configuration.

[0118] Referring to FIG. 11(b), the CBGs constituting one TB are mapped to the scheduled time-frequency resources of the PDSCH. According to an embodiment, each CBG may be first allocated to the frequency axis and then extended to the time axis. When the PDSCH composed of one TB including four CBGs is allocated to seven OFDM symbols, CBG0 may be transmitted over the first and second OFDM symbols, CBG1 may be transmitted over the second, third and fourth OFDM symbols, CBG2 may be transmitted over the fourth, fifth and sixth OFDM symbols, and CBG3 may be transmitted over the sixth and seventh OFDM symbols. Such a time-frequency mapping relationship allocated to the CBGs and the PDSCH may be determined between the base station and the terminal. However, the mapping relationship shown in FIG. 11(b) is an embodiment for explaining the present invention, and the method proposed in the embodiment of the present invention is applicable regardless of the time-frequency mapping relationship of the CBGs.

[0119] FIG. 12 illustrates a process in which a base station performs TB-based transmission or CBG-based transmission, and a terminal transmits a HARQ-ACK in response thereto. Referring to FIG. 12, a base station may configure a transmission scheme suitable for a terminal, among TB-based transmission and CBG-based transmission. The terminal may transmit HARQ-ACK information bits according to the transmission scheme configured by the base station on a PUCCH or a PUSCH. The base station may configure a PDCCH to schedule a PDSCH to be transmitted to the terminal. The PDCCH may schedule TB-based transmission and / or CBG-based transmission. For example, one TB or two TBs may be scheduled in the PDCCH. If one TB is scheduled, the terminal must feed back a one-bit HARQ-ACK. If two TBs are scheduled, the terminal must feed back a two-bit HARQ-ACK for each of the two TBs. In order to eliminate ambiguity between the base station and the terminal, a predetermined order may exist between each information bit of the two-bit HARQ-ACK and the two TBs. For reference, when the MIMO transmission rank or layer is low, one TB may be transmitted in one PDSCH, and when the MIMO transmission rank or layer is high, two TBs may be transmitted in one PDSCH.

[0120] The terminal may transmit a 1-bit TB-based HARQ-ACK for each TB to inform the base station of whether each TB has been successfully received. To generate a HARQ-ACK for one TB, the terminal may check whether there is a reception error for the TB using the TB-CRC. If the TB-CRC for the TB is successfully checked, the terminal generates an ACK for the HARQ-ACK for the TB. However, if a TB-CRC error occurs for the TB, the terminal generates a NACK for the HARQ-ACK for the TB. The terminal transmits the TB-based HARQ-ACK thus generated to the base station. The base station retransmits the TB for which a NACK has been responded to among the TB-based HARQ-ACKs received from the terminal.

[0121] Also, the terminal may transmit a 1-bit CBG-based HARQ-ACK for each CBG to inform the base station of whether each CBG has been successfully received. To generate a HARQ-ACK for one CBG, the terminal may decode all CBs included in the CBG and check whether there is a reception error for each CB using the CB-CRC. If the terminal successfully receives all CBs constituting one CBG (i.e., all CB-CRCs are successfully checked), the terminal generates an ACK for the HARQ-ACK of the CBG. However, if the terminal does not successfully receive at least one of the CBs constituting one CBG (i.e., at least one CB-CRC error occurs), the terminal generates a NACK for the HARQ-ACK of the CBG. The terminal transmits the CBG-based HARQ-ACK thus generated to the base station. The base station retransmits the CBG for which a NACK has been responded to among the CBG-based HARQ-ACKs received from the terminal. 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 transmitted by the terminal to the base station may be determined based on the number of CBGs transmitted in the PDSCH or the maximum number of CBGs configured in the RRC signal.

[0122] Meanwhile, even if the UE successfully receives all CBGs included in the TB, a TB-CRC error may occur for the TB. In this case, the UE may perform flipping of the CBG-based HARQ-ACK to request retransmission for the TB. That is, even if all CBGs included in the TB are successfully received, the UE may generate all CBG-based HARQ-ACK information bits as NACK. The base station that receives the CBG-based HARQ-ACK feedback in which all HARQ-ACK information bits are NACK retransmits all CBGs of the TB.

[0123] According to an embodiment of the present invention, CBG-based HARQ-ACK feedback may be used for successful transmission of TB. The base station may instruct the terminal to transmit the CBG-based HARQ-ACK. At this time, a retransmission method using the CBG-based HARQ-ACK may be used. The CBG-based HARQ-ACK may be transmitted on a PUCCH. Also, when UCI is configured to be transmitted on a PUSCH, the CBG-based HARQ-ACK may be transmitted on the PUSCH. The configuration of the HARQ-ACK resource in the PUCCH may be configured by an RRC signal. Also, the HARQ-ACK resource to be actually transmitted may be indicated via a PDCCH that schedules a PDSCH to be transmitted on a CBG basis. The terminal may transmit a HARQ-ACK regarding whether or not the transmitted CBG has been successfully received via one PUCCH resource indicated by the PDCCH among the PUCCH resources configured by the RRC signal.

[0124] The base station can identify whether the terminal successfully receives the CBG transmitted to the terminal by using the CBG-based HARQ-ACK feedback of the terminal. That is, the base station can recognize the CBG that the terminal successfully receives and the CBG that the terminal fails to receive by using the HARQ-ACK for each CBG received from the terminal. The base station can perform CBG retransmission based on the received CBG-based HARQ-ACK. More specifically, the base station can collectively retransmit only the CBGs for which the reception failure HARQ-ACK is responded in one TB. At this time, the CBGs for which the reception success HARQ-ACK is responded are excluded from the retransmission. The base station can schedule the CBG to be retransmitted in one PDSCH and transmit it to the terminal.

[0125] <Communication methods in unlicensed bands>

[0126] FIG. 13 illustrates an NR-U (NR-Unlicensed) service environment.

[0127] Referring to FIG. 13, a service environment in which NR technology 11 in a licensed band and NR-U, which is NR technology 12 in an unlicensed band, are integrated may be provided to a user. For example, in an NR-U environment, NR technology 11 in a licensed band and NR technology 12 in an unlicensed band may be integrated using a technique such as carrier aggregation, which can contribute to network capacity expansion. In addition, in an asymmetric traffic structure in which downlink data is relatively more than uplink data, NR-U can provide NR services optimized according to various requirements or environments. For convenience, NR technology in a licensed band is called NR-L (NR-Licensed), and NR technology in an unlicensed band is called NR-U (NR-Unlicensed).

[0128] FIG. 14 shows an example of a deployment scenario of a terminal and a base station in an NR-U service environment. The frequency band targeted by the NR-U service environment has high frequency characteristics, and therefore the wireless communication reach is not long. Considering this, in an environment where the existing NR-L service and the NR-U service coexist, the deployment scenario of the terminal and the base station may be an overlay model or a co-located model.

[0129] In the overlay model, a macro base station may perform wireless communication with X and X' terminals in a macro region 32 using a licensed band carrier, and may be connected to a plurality of RRHs (Radio Remote Heads) via an X2 interface. Each RRH may perform wireless communication with X or X' terminals in a certain region 31 using an unlicensed band carrier. Since the frequency bands of the macro base station and the RRH are different from each other, there is no mutual interference, but in order to use the NR-U service as a supplementary downlink channel for the NR-L service using carrier aggregation, fast data exchange is required between the macro base station and the RRH via the X2 interface.

[0130] In the co-located model, the pico / femto base station can perform wireless communication with the Y terminal using the licensed band carrier and the unlicensed band carrier at the same time. However, the pico / femto base station may use both the NR-L service and the NR-U service only during downlink transmission. The coverage 33 of the NR-L service and the coverage 34 of the NR-U service may differ from each other depending on the frequency band, transmission power, etc.

[0131] When NR communication is performed in an unlicensed band, existing equipment (e.g., wireless LAN (Wi-Fi) equipment) that communicates in the unlicensed band cannot demodulate the NR-U message or data. Therefore, the existing equipment can determine that the NR-U message or data is a type of energy and perform interference avoidance operations using an energy detection (or detection) method. In other words, if the energy corresponding to the NR-U message or data is less than -62 dBm or a specific ED (Energy Detection) threshold value, the wireless LAN equipment can ignore the message or data and communicate. Therefore, terminals that perform NR communication in an unlicensed band may frequently be interfered with by wireless LAN equipment.

[0132] Therefore, in order to effectively implement NR-U technology / services, it is necessary to allocate or reserve specific frequency bands at specific times. However, there is a problem that efficient NR-U services are difficult because peripheral devices communicating in unlicensed bands attempt to connect based on an energy detection method. Therefore, in order for NR-U technology to settle, research on coexistence methods with existing unlicensed band devices and methods for efficiently sharing radio channels needs to be conducted in advance. In other words, a strong coexistence mechanism needs to be developed that does not affect NR-U devices in existing unlicensed band devices.

[0133] Fig. 15 shows an existing communication method (e.g., wireless LAN) that operates in an unlicensed band. Devices that operate in an unlicensed band usually operate on a Listen-Before-Talk (LBT) basis, and therefore perform Clear Channel Assessment (CCA) to sense the channel before transmitting data.

[0134] Referring to FIG. 15, a WLAN device (e.g., AP, STA) performs carrier sensing before transmitting data to check whether a channel is busy. If a wireless signal of a certain strength or more is detected from a channel to which data is to be transmitted, the channel is determined to be busy and the WLAN device delays access to the channel. This process is called clear channel evaluation, and the signal level that determines whether a signal is detected is called a CCA threshold. On the other hand, if no wireless signal is detected from the channel or a wireless signal of a strength lower than the CCA threshold is detected, the channel is determined to be in an idle state.

[0135] When a channel is determined to be idle, a terminal that has data to transmit performs a backoff procedure after a defer duration (e.g., Arbitration InterFrame Space (AIFS), PCF IFS (PIFS), etc.). The defer duration refers to the minimum time that a terminal must wait after a channel becomes idle. The backoff procedure allows a terminal to wait any amount of time after the defer deadline. For example, a terminal waits while decreasing a slot time of a random number assigned to the terminal within a contention window (CW) while the channel is idle, and a terminal that has exhausted all the slot times can attempt to access the channel.

[0136] When the terminal successfully accesses a channel, the terminal can transmit data through the channel. If the data transmission is successful, the contention window size (CWS) is reset to an initial value (CWmin). On the other hand, if the data transmission fails, the CWS is doubled. As a result, the terminal is assigned a new random number within a range twice the previous random number range and performs a backoff procedure in the next CW. In WLAN, only ACK is defined as reception response information for data transmission. Therefore, if an ACK is received for data transmission, the CWS is reset to the initial value, and if no feedback information is received for data transmission, the CWS is doubled.

[0137] As described above, since existing communications in unlicensed bands mostly operate on the basis of LBT, channel access in the NR-U system also performs LBT for coexistence with existing devices. Specifically, channel access methods on unlicensed bands in NR may be classified into the following four categories depending on the presence / absence / application method of LBT.

[0138] ●Category 1: No LBT

[0139] - The Tx entity does not perform the LBT procedure for transmission.

[0140] Category 2: LBT without random backoff

[0141] - The Tx entity senses whether the channel is idle in a first interval without random backoff in order to transmit, i.e., the Tx entity can transmit on the channel immediately after sensing the channel as idle during the first interval, the first interval being an interval of a pre-configured length immediately prior to the Tx entity transmitting. According to one embodiment, the first interval may be an interval of 25us length, but the invention is not limited thereto.

[0142] Category 3: LBT with random backoff using a fixed-size CW

[0143] - The Tx entity obtains a random number within the fixed size CW, sets it as the initial value of a backoff counter (or backoff timer) N, and performs backoff using the set backoff counter N. That is, in the backoff procedure, the Tx entity decrements the backoff counter by 1 every time the channel is sensed as being idle in a previously set slot period. Here, the previously set slot period may be 9 us, but the present invention is not limited to this. 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 transmit. Meanwhile, to perform backoff, the Tx entity decrements the backoff counter by 1 in the second interval (i.e., the defer period T d ) whether the channel is idle. According to an embodiment of the present invention, the Tx entity can sense (or determine) whether the channel is idle during the second interval depending on whether the channel is idle during at least a portion of the second interval (e.g., one slot period). The second interval may be set based on the channel access priority class of the Tx entity, and is composed of a period of 16us and m consecutive slot periods, where m is a value set by the channel access priority class. If the channel is sensed as idle during the second interval, the Tx entity performs channel sensing for decreasing the backoff counter. On the other hand, if the channel is sensed as occupied during the backoff procedure, the backoff procedure is interrupted. After interruption of the backoff procedure, the Tx entity can resume backoff if the channel is sensed as idle during an additional second interval. In this way, the Tx entity can transmit if the channel is idle during the second interval plus the slot period of the backoff counter N. At this time, the initial value of the backoff counter N is obtained within a CW of a fixed size.

[0144] Category 4: LBT with random backoff using variable-size CW

[0145] - The Tx entity obtains a random number within the variable-sized CW, sets it as the initial value of the backoff counter (or backoff timer) N, and performs backoff using the set backoff counter N. More specifically, the Tx entity can adjust the size of the CW based on HARQ-ACK information for the previous transmission, and the initial value of the backoff counter N is obtained within the adjusted size of the CW. The specific process of the Tx entity performing backoff is as described in Category 3. The Tx entity can transmit if the channel is idle during the second interval plus the slot period of the backoff counter N. In this case, the initial value of the backoff counter N is obtained within the variable-sized CW.

[0146] In the above categories 1 to 4, the Tx entity may be a base station or a terminal. According to the embodiment of the present invention, the first type channel access may refer to the channel access of category 4, and the second type channel access may refer to the channel access of category 2, respectively.

[0147] FIG. 16 illustrates a channel access process based on Category 4 LBT according to an embodiment of the present invention.

[0148] To access the channel, the Tx entity first waits for a defer period T d According to an embodiment of the present invention, the defer period T d The channel sensing for the defer period T d For example, the defer period T d The channel sensing for the defer period T dThe Tx entity may perform channel sensing during one slot period in the defer period T d It is checked whether the channel is idle by channel sensing for the channel (S304). d If the channel is sensed as idle for the defer period T, the Tx entity proceeds to step S306. d If the channel is not sensed as idle for the defer period T (i.e., sensed as occupied), the Tx entity returns to step S302. d The process of steps S302 to S304 is repeated until the device is sensed as being in an idle state for the defer period T d may be set based on the channel access priority class of the Tx entity and consists of a period of 16us and m consecutive slot periods, where m is the value set by the channel access priority class.

[0149] Next, the Tx entity obtains a random number within a predetermined CW, sets it as the initial value of a backoff counter (or backoff timer) N (S306), and proceeds to step S308. The initial value of the backoff counter N is randomly selected from a range of values ​​from 0 to CW. The Tx entity performs a backoff procedure using the set backoff counter N. That is, the Tx entity performs the backoff procedure by repeating steps S308 to S316 until the value of the backoff counter N reaches 0. Meanwhile, in FIG. 16, the channel is in a deferred period T d However, the present invention is not limited to this. That is, step S306 may be performed independently of steps S302 to S304, or may be performed prior to steps S302 to S304. When step S306 is performed prior to steps S302 to S304, the channel is set to the defer period T by steps S302 to S304. d If the Tx entity senses the ACK state as idle, the Tx entity proceeds to step S308.

[0150] In step S308, the Tx entity checks whether the value of the back-off counter N is 0. If the value of the back-off counter N is 0, the Tx entity proceeds to step S320 to transmit. If the value of the back-off counter N is not 0, the Tx entity proceeds to step S310. In step S310, the Tx entity decrements the value of the back-off counter N by 1. According to an embodiment, the Tx entity may selectively decrement the value of the back-off counter by 1 in the channel sensing process for each slot. At this time, step S310 may be skipped at least once depending on the selection of the Tx entity. Next, the Tx entity performs channel sensing for an additional slot period (S312). The Tx entity checks whether the channel is idle through the channel sensing for the additional slot period (S314). If the channel is sensed as idle for the additional slot period, the Tx entity returns to step S308. In this manner, the Tx entity may decrement the backoff counter by 1 each time the channel is sensed as being idle during a pre-configured slot period, where the pre-configured slot period may be 9 us, although the present invention is not limited thereto.

[0151] If the channel is not sensed as idle (i.e., sensed as occupied) for an additional slot period in step S314, the Tx entity proceeds to step S316. In step S316, the Tx entity determines whether the channel is to be idle for an additional deferred period T d According to an embodiment of the present invention, the channel sensing in step S316 may be performed on a slot-by-slot basis. That is, the Tx entity checks whether the channel is idle for an additional defer period T d Check whether the channel is sensed as idle for all slots of the additional defer period T d If an occupied slot is detected within the additional defer period T, the Tx entity immediately restarts step S316. dIf the channel is sensed as idle for the entire slot period, the Tx entity returns to step S308.

[0152] On the other hand, if the value of the backoff counter N is confirmed as 0 in step S308, the Tx entity performs transmission (S320). The Tx entity receives HARQ-ACK feedback corresponding to the transmission (S322). The Tx entity can determine whether the previous transmission was successful based on the received HARQ-ACK feedback. The Tx entity then adjusts the CW size for the next transmission based on the received HARQ-ACK feedback (S324).

[0153] In this way, the Tx entity can d After sensing the channel as idle for N additional slot periods, transmission may occur if the channel is idle. As mentioned above, the Tx entity may be a base station or a terminal, and the channel access process of FIG. 16 may be used for downlink transmission of the base station and / or uplink transmission of the terminal.

[0154] Hereinafter, a method for adaptively adjusting CWS during channel access in unlicensed band is proposed. CWS may be adjusted based on UE (User Equipment) feedback, and UE feedback used for CWS adjustment may include HARQ-ACK feedback, CQI / PMI / RI. In the present invention, a method for adaptively adjusting CWS based on HARQ-ACK feedback is proposed. HARQ-ACK feedback includes at least one of ACK, NACK, DTX, and NACK / DTX.

[0155] As mentioned above, in WLAN systems, CWS is also adjusted based on ACK. When ACK feedback is received, CWS is reset to the minimum value (CWmin), and when ACK feedback is not received, CWS is increased. However, in cellular systems, a CWS adjustment method that takes multiple connections into account is required.

[0156] First, in order to explain the present invention, the following terms are defined:

[0157] - Set of HARQ-ACK feedback values ​​(i.e., HARQ-ACK feedback set): refers to HARQ-ACK feedback values ​​used for CWS update / adjustment. The HARQ-ACK feedback set corresponds to the HARQ-ACK feedback value that is decoded and available at the time when the CWS is determined. 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 terminals. The HARQ-ACK feedback value indicates reception response information for a code block group (CBG) or a transmission block (TB), and may indicate any one of ACK, NACK, DTX, or NACK / DTX. In this context, the HARQ-ACK feedback value may be used interchangeably with terms such as HARQ-ACK value, HARQ-ACK information bit, and HARQ-ACK response.

[0158] Reference window: A time interval during which DL transmission (e.g., PDSCH) corresponding to a HARQ-ACK feedback set is performed in an unlicensed band carrier (e.g., Scell, NR-U cell). The reference window may be defined in slot or subframe units depending on the embodiment. The reference window may refer to one or more specific slots (or subframes). According to an embodiment of the present invention, the specific slot (or reference slot) may include the starting slot of the last DL transmission burst in which at least a portion of the HARQ-ACK feedback is expected to be available.

[0159] FIG. 17 illustrates an embodiment of a method for adjusting a contention window size (CWS) based on HARQ-ACK feedback. In the embodiment of FIG. 17, the Tx entity may be a base station and the Rx entity may be a terminal, but the present invention is not limited thereto. In addition, the embodiment of FIG. 17 assumes a channel access process for DL ​​transmission of the base station, but at least a part of the configuration may be applied to a channel access process for UL transmission of the terminal.

[0160] Referring to Figure 17, after a Tx entity transmits an n-th DL transmission burst on an unlicensed band carrier (e.g., Scell, NR-U cell) (S402), if an additional DL transmission is required, the Tx entity can transmit an (n+1)-th DL transmission burst based on LBT channel access (S412). Here, a transmission burst represents a transmission using one or more adjacent slots (or subframes). Figure 17 illustrates a channel access procedure and a CWS coordination method based on the first type channel access (i.e., Category 4 channel access) described above.

[0161] First, the Tx entity receives HARQ-ACK feedback corresponding to a PDSCH transmission on an unlicensed band carrier (e.g., Scell, NR-U cell) (S404). The HARQ-ACK feedback used for CWS adjustment includes HARQ-ACK feedback corresponding to a last DL transmission burst (i.e., n-th DL transmission burst) on the unlicensed band carrier. More specifically, the HARQ-ACK feedback used for CWS adjustment includes HARQ-ACK feedback corresponding to a PDSCH transmission on a reference window within the last DL transmission burst. The reference window may represent one or more specific slots (or subframes). According to an embodiment of the present invention, the specific slot (or reference slot) includes a starting slot of the last DL transmission burst where at least a portion of the HARQ-ACK feedback is expected to be available.

[0162] When the HARQ-ACK feedback is received, a HARQ-ACK value is obtained for each transmission block (TB). The HARQ-ACK feedback includes at least one of a TB-based HARQ-ACK bit sequence and a CBG-based HARQ-ACK. If the HARQ-ACK feedback is a TB-based HARQ-ACK bit sequence, one HARQ-ACK information bit is obtained for each TB. Meanwhile, if the HARQ-ACK feedback is a CBG-based HARQ-ACK bit sequence, N HARQ-ACK information bits are obtained for each TB. Here, N is the maximum number of CBGs per TB configured in the Rx entity of the PDSCH transmission. According to an embodiment of the present invention, for CWS determination, a HARQ-ACK value for each TB may be determined according to a HARQ-ACK information bit for each TB in the HARQ-ACK feedback. More specifically, if the HARQ-ACK feedback is a TB-based HARQ-ACK bit sequence, one HARQ-ACK information bit for the TB is determined as the HARQ-ACK value. However, if the HARQ-ACK feedback is a CBG-based HARQ-ACK bit sequence, one HARQ-ACK value may be determined based on the N HARQ-ACK information bits corresponding to the CBG included in the TB.

[0163] 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 by the HARQ-ACK information bit for each TB in the HARQ-ACK feedback. More specifically, the CWS may be adjusted based on the ratio of NACKs in the HARQ-ACK value. First, variables may be defined as follows:

[0164] - p: Priority class value

[0165] - CW_min_p: already configured CWS minimum value for priority class p

[0166] - CW_max_p: Maximum already configured CWS value for priority class p

[0167] - CW_p: CWS for transmission of priority class p. CW_p is set to one of multiple CWS values ​​between CW_min_p and CW_max_p included in the allowed CWS set of priority class p.

[0168] According to an embodiment of the present invention, the CWS may be determined by the following steps:

[0169] Step A-1) For all priority classes p, CW_p is set to CW_min_p, where p includes {1, 2, 3, 4}.

[0170] Step A-2) If the ratio of NACKs in the HARQ-ACK values ​​for PDSCH transmissions of reference window k is equal to or greater than Z%, then increase CW_p for all priority classes p to the next highest allowed value (and remain in step A-2). Otherwise, go to step A-1, where Z is a pre-configured integer in the range 0<=Z<=100, and according to one embodiment, may be set to any one of the values ​​{30, 50, 70, 80, 100}.

[0171] Here, reference window k includes the starting slot (or subframe) of the last transmission by the Tx entity, and is the slot (or subframe) in which at least some HARQ-ACK feedback is expected to be possible. If CW_p=CW_max_p, then the next highest allowed value for CW_p adjustment is CW_max_p.

[0172] Next, the Tx entity selects a random number within the CWS determined in step S406 and sets it as the initial value of a backoff counter N (S408). The Tx entity performs backoff using the set backoff counter N (S410). That is, the Tx entity may decrement the backoff counter by 1 for each slot period during which the channel is sensed as being idle. When the value of the backoff counter reaches 0, the Tx entity may transmit the (n+1)th DL transmission burst on the channel (S412).

[0173] Meanwhile, in the above-mentioned CWS adjustment process, it is necessary to determine whether DTX or NACK / DTX is also considered in addition to ACK and NACK in the 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 may be determined whether DTX or NACK / DTX is also considered in the CWS adjustment process.

[0174] In self-carrier scheduling, DL transmission (e.g., PDSCH) on an unlicensed band carrier is scheduled by a control channel (e.g., (E)PDCCH) transmitted on the same unlicensed band carrier. Here, DTX is a case where DL transmission fails due to a hidden node in the unlicensed band carrier, and may be used for CWS adjustment together with NACK. Also, DTX is one of the methods by which a terminal informs a base station of a case where the terminal cannot decode a control channel (e.g., (E)PDCCH) including scheduling information transmitted from the base station to the terminal. DTX may be determined only by the HARQ-ACK feedback value, or may be determined by considering the HARQ-ACK feedback value and the actual scheduling situation. According to an embodiment of the present invention, DTX and NACK / DTX may be counted as NACK for CWS adjustment in a self-carrier scheduling situation. That is, if the combined ratio of NACK, DTX and NACK / DTX in the HARQ-ACK values ​​for PDSCH transmissions of reference window k is equal to or greater than Z%, CWS is increased to the next highest allowed value, otherwise CWS is reset to its minimum value.

[0175] During cross-carrier scheduling, DL transmission (e.g., PDSCH) on an unlicensed band carrier may be scheduled on a control channel (e.g., (E)PDCCH) transmitted on a licensed band carrier. In this case, DTX feedback is used to determine the terminal's decoding status for the control channel transmitted on the licensed band carrier, and is therefore not useful for adaptively adjusting CWS for channel access in an unlicensed band. Therefore, according to an embodiment of the present invention, DTX may be ignored for CWS determination in a cross-carrier scheduling situation from a licensed band. That is, for CWS adjustment, the ratio of NACK may be calculated by considering only ACK and NACK among HARQ-ACK values, or the ratio of NACK may be calculated by considering only ACK, NACK, and NACK / DTX. Therefore, DTX may be excluded when calculating the ratio of NACK.

[0176] FIG. 18 is a block diagram showing the configuration of a terminal and a base station according to an embodiment of the present invention. In an embodiment of the present invention, the terminal is embodied as various types of wireless communication devices or computing devices that ensure portability and mobility. The terminal is referred to as a UE, a Station (STA), a Mobile Subscriber (MS), etc. In addition, in an embodiment of the present invention, the base station controls and manages cells (e.g., macrocells, femtocells, picocells, etc.) corresponding to a service area, and performs functions such as signal transmission, channel assignment, channel monitoring, self-diagnosis, and relaying. The base station is referred to as a next generation NodeB (gNB) or an Access Point (AP), etc.

[0177] As shown, a terminal 100 according to one embodiment of the present invention includes a processor 110 , a communication module 120 , a memory 130 , a user interface unit 140 , and a display unit 150 .

[0178] First, the processor 110 executes various commands or programs to process data within the terminal 100. The processor 110 also controls the overall operation of the terminal 100 including each unit, and controls the transmission and reception of data between the units. Here, the processor 110 is configured to perform operations according to the embodiments described in the present invention. For example, the processor 110 may receive slot configuration information, determine the slot configuration based thereon, and perform communication according to the determined slot configuration.

[0179] Next, the communication module 120 is an integrated module that performs wireless communication using a wireless communication network and wireless LAN access using a wireless LAN. For this purpose, the communication module 120 includes a plurality of network interface cards (NICs) such as cellular communication interface cards 121 and 122 and an unlicensed band communication interface card 123, either built-in or external. In the drawings, the communication module 120 is shown as an integrated module, but the network interface cards may be arranged independently depending on the circuit configuration or application, unlike the drawings.

[0180] The cellular communication interface card 121 transmits and receives wireless signals to and from at least one of the base station 200, the external device, and the server via the mobile communication network, and provides a cellular communication service in a first frequency band based on instructions from the processor 110. According to an embodiment, the cellular communication interface card 121 includes at least one NIC module that utilizes a frequency band below 6 GHz. The at least one NIC module of the cellular communication interface card 121 independently performs cellular communication with at least one of the base station 200, the external device, and the server according to a cellular communication standard or protocol of the frequency band below 6 GHz supported by the NIC module.

[0181] The cellular communication interface card 122 transmits and receives wireless signals to and from at least one of the base station 200, the external device, and the server using a mobile communication network, and provides a cellular communication service in the second frequency band based on instructions from the processor 110. According to an embodiment, the cellular communication interface card 122 includes at least one NIC module that utilizes a frequency band of 6 GHz or higher. The at least one NIC module of the cellular communication interface card 122 independently performs cellular communication with at least one of the base station 200, the external device, and the server according to a cellular communication standard or protocol of the 6 GHz or higher frequency band supported by the NIC module.

[0182] The unlicensed band communication interface card 123 transmits and receives wireless signals to and from at least one of the base station 200, the external device, and the server through the third frequency band, which is an unlicensed band, and provides communication services in the unlicensed band based on instructions from the processor 110. The unlicensed band communication interface card 123 includes at least one NIC module that utilizes the unlicensed band. For example, the unlicensed band may be a band of 2.4 GHz, 5 GHz, 6 GHz, 7 GHz, or 52.6 GHz or higher. The at least one NIC module of the unlicensed band communication interface card 123 performs cellular communication with at least one of the base station 200, the external device, and the server, independently or dependently, according to the unlicensed band communication standard or protocol of the frequency band supported by the NIC module.

[0183] The memory 130 stores control programs and various data used by the terminal 100. The control programs include predetermined programs required for the terminal 100 to perform wireless communication with at least one of the base station 200, an external device, and a server.

[0184] Next, the user interface 140 includes various types of input / output means provided in the terminal 100. That is, the user interface unit 140 receives user input using various input means, and the processor 110 controls the terminal 100 based on the received user input. Also, the user interface 140 performs output based on a command from the processor 110 using various output means.

[0185] Then, the display unit 150 outputs various images on a display screen. The display unit 150 outputs various display objects, such as a user interface, based on the contents performed by the processor 110 or a control command of the processor 110.

[0186] The base station 200 according to the embodiment of the present invention also includes a processor 210 , a communication module 220 , and a memory 230 .

[0187] First, the processor 210 executes various commands or programs to process data within the base station 200. The processor 210 also controls the overall operation of the base station 200 including each unit, and controls transmission and reception of data between the units. Here, the processor 210 is configured to perform operations according to the embodiments described in the present invention. For example, the processor 210 may signal slot configuration information and perform communication according to the signaled slot configuration.

[0188] Next, the communication module 220 is an integrated module that performs wireless communication using a wireless communication network and wireless LAN access using a wireless LAN. For this purpose, the communication module 220 includes a plurality of network interface cards, such as cellular communication interface cards 221 and 222 and an unlicensed band communication interface card 223, either built-in or external. In the drawings, the communication module 220 is shown as an integrated module, but the respective network interface cards may be arranged independently depending on the circuit configuration or application, unlike the drawings.

[0189] The cellular communication interface card 221 transmits and receives wireless signals to and from at least one of the terminal 100, the external device, and the server using a mobile communication network, and provides a cellular communication service in a first frequency band according to an instruction of the processor 210. According to an embodiment, the cellular communication interface card 221 includes at least one NIC module that uses a frequency band below 6 GHz. The at least one NIC module of the cellular communication interface card 221 independently performs cellular communication with at least one of the terminal 100, the external device, and the server according to a cellular communication standard or protocol of the frequency band below 6 GHz supported by the NIC module.

[0190] The cellular communication interface card 222 transmits and receives wireless signals to and from at least one of the terminal 100, an external device, and a server using a mobile communication network, and provides a cellular communication service in the second frequency band based on instructions from the processor 210. According to an embodiment, the cellular communication interface card 222 includes at least one NIC module that uses a frequency band of 6 GHz or higher. The at least one NIC module of the cellular communication interface card 222 independently performs cellular communication with at least one of the terminal 100, an external device, and a server according to a cellular communication standard or protocol of the 6 GHz or higher frequency band supported by the NIC module.

[0191] The unlicensed band communication interface card 223 transmits and receives wireless signals to and from at least one of the terminal 100, the external device, and the server using the third frequency band, which is an unlicensed band, and provides communication services in the unlicensed band based on instructions from the processor 210. The unlicensed band communication interface card 223 includes at least one NIC module that uses the unlicensed band. For example, the unlicensed band may be a band of 2.4 GHz, 5 GHz, 6 GHz, 7 GHz, or 52.6 GHz or higher. The at least one NIC module of the unlicensed band communication interface card 223 performs cellular communication with at least one of the terminal 100, the external device, and the server, independently or dependently, according to the unlicensed band communication standard or protocol of the frequency band supported by the NIC module.

[0192] The terminal 100 and base station 200 shown in FIG. 18 are block diagrams according to an embodiment of the present invention, and the separated blocks are used to logically distinguish the elements of the devices. Thus, the above-mentioned device elements may be mounted on one chip or multiple chips depending on the design of the device. Also, some components of the terminal 100, such as the user interface 150 and the display unit 150, may be selectively provided in the terminal 100. Also, the user interface 140 and the display unit 150 may be additionally provided in the base station 200 as necessary.

[0193] A channel access procedure performed in an unlicensed band by a wireless communication device according to an embodiment of the present invention will be described with reference to FIG. 19. Specifically, an LBT procedure used when a wireless communication device according to an embodiment of the present invention performs channel access in an unlicensed band will be described. In particular, a channel access in which the wireless communication device performs transmission according to a result of channel sensing within a time interval of a pre-specified duration may be set in the wireless communication device. At this time, if the wireless communication device fails to access the channel, an operation method of the wireless communication device will be described. The pre-specified duration mentioned above may be 16us.

[0194] For convenience of explanation, a wireless communication device that is a wireless endpoint initiating channel occupancy is called an initiating node. Also, a wireless communication device that is a wireless endpoint communicating with the initiating node is called a responding node. The initiating node may be a base station, and the responding node may be a terminal. Also, the initiating node may be a terminal, and the responding node may be a base station. When the initiating node is about to transmit data, the initiating node may perform channel access based on a channel access priority class determined according to the type of data. At this time, parameters used for channel access may be determined according to the type of data. The parameters used for channel access may include at least one of a minimum value of CW, a maximum value of CW, a maximum channel occupancy time (MCOT) that is the maximum duration that the channel can be occupied in one channel occupancy, and the number of sensing slots (mp). Specifically, the initiating node may perform the above-mentioned Category 4 LBT based on a channel access priority class determined according to the type of data.

[0195] Table 4 below shows an example of parameter values ​​used for channel access based on the channel access priority class. Specifically, Table 4 shows parameter values ​​used for channel access for each channel access priority class for downlink transmission in the LTE LAA system.

[0196] When the downlink channel transmitted by the wireless communication device includes data traffic, the defer duration may be set based on the channel access priority class of the traffic included in the downlink channel. f ) or more (m p ) slot section (T sl ) can be included. In this case, the slot period (T slThe duration of the initial interval may be 9us. The initial interval is one idle slot interval (T sl ) is included in the defer period. p ) may be set based on the channel access priority class as described above. Specifically, the number of slot periods included in the defer period (m p ) may be set as shown in Table 4.

[0197] [Table 4]

[0198] In addition, the wireless communication device can set the range of the CW value according to the channel access priority class. min,p <=CW<=CW max,p The CW value can be set to satisfy the following. In this case, the minimum CW value (CW min,p ) and maximum value (CW max,p ) may be determined by the channel access priority class. Specifically, the minimum value of CW (CW min,p ) and maximum value (CW max,p ) may be determined as shown in Table 4. In the counter value setting procedure, the wireless communication device sets the minimum value of CW (CW min,p ) and maximum value (CW max,p ) can be set. When the wireless communication device accesses a channel, the wireless communication device can adjust the value of CW as described above with reference to Figs. 15 to 17. In addition, in the unlicensed band, MCOT (T mcot,p) may be determined according to the channel access priority of the data included in the transmission, as described above. Specifically, the MCOT may be determined as shown in Table 4. Thus, the wireless communication device may not be allowed to transmit continuously in the unlicensed band for a time exceeding the MCOT. This is because the unlicensed band is a frequency band that various wireless communication devices use according to certain rules. In Table 4, when the value of the channel access priority class is p=3 or p=4 and there is no wireless communication device that uses the unlicensed band for a long term according to the regulations and uses other technology, the wireless communication device may determine T mcot,p = 10 ms. Otherwise, the wireless communication device mcot,p =8ms can be set.

[0199] Table 5 shows parameter values ​​used for channel access according to channel access priority class for uplink transmission used in the LTE LAA system.

[0200] [Table 5]

[0201] As described in Table 5, the MCOT value of 6 ms may be increased to 8 ms when the transmission includes one or more gaps. A gap refers to the time from when a transmission is interrupted on a carrier until the transmission resumes on the carrier. In this case, the minimum duration of the gap is 100 us. The maximum duration of the transmission before the gap is included is 6 ms. The duration of the gap is not included in the channel occupancy time. When the value of the channel access priority class is 3 or 4 and it is guaranteed that no other wireless access technology is used on the carrier where the channel access is performed, the MCOT value may be 10 ms. In this case, the other wireless access technology may include Wi-Fi. In other cases, the MCOT value may be determined as described in Note 1 of Table 5.

[0202] COT represents the time that the wireless communication device occupies the channel. MCOT represents the maximum time that the initiating node can continuously occupy the channel in any one carrier of the unlicensed band, as described above. However, as described above, a gap, which is a period during which no transmission is performed, may be included between multiple transmissions, and when a gap is included, the value of MCOT may be applied differently.

[0203] 19 shows that in an embodiment of the present invention, when the duration of the initiating node's transmission during the channel occupation initiated by the initiating node does not exceed the MCOT of the channel occupation, the responding node transmits during the channel occupation initiated by the initiating node. In other words, after the initiating node completes transmission during one of the channels, the responding node transmits during the channel. This transmission during which the initiating node and the responding node transmit during one channel can be expressed as sharing the channel occupation.

[0204] If the duration of the initiating node's transmission is less than the duration of the MCOT, the responding node can transmit within the channel occupancy initiated by the initiating node. Such a case is shown in Figure 19, where the gap between the initiating node's transmission and the responding node's transmission is assumed to be 16us. How the responding node performs channel access can then be problematic.

[0205] In an embodiment of the present invention, if the duration of the gap is not greater than the first duration, the responding node may transmit immediately after the gap without sensing. Specifically, the responding node may perform the above-mentioned Category 1 channel access. The first duration may be 16us, which is also applicable to the embodiments described below. In such an embodiment, a further constraint may be applied to the duration of the transmission of the responding node in addition to the MCOT. In a specific embodiment, the responding node may transmit within a pre-specified duration. In this case, the pre-specified duration may be a constraint applied to the transmission of the responding node apart from the MCOT. Specifically, the pre-specified duration may be 584us.

[0206] 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 transmission following the gap. The first fixed duration based channel access is a channel access in which, when the channel is sensed to be idle within the first fixed duration, the wireless communication device performing the first fixed duration based channel access is allowed to perform transmission immediately after 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 when the channel is sensed to be idle within the fixed duration, performs transmission on the channel. The first fixed duration based channel access may be the above-mentioned Category 2 LBT. In such an embodiment, the initiating node may implicitly or explicitly instruct the responding node to perform the first fixed duration based channel access. For example, the base station, which is the initiating node, may use a grant to instruct the responding node to perform the first fixed duration based channel access.

[0207] In an embodiment of the present invention, if the gap between consecutively scheduled or granted transmissions within the channel occupation initiated by the initiating node is not greater than the second fixed duration, the node performing the second transmission may perform a second fixed duration based channel access. The second fixed duration based channel access is a channel access in which, if the channel is idle during the second fixed duration, the wireless communication device performing the second fixed duration based channel access is allowed to perform transmission immediately after the second fixed duration. Specifically, in the second fixed duration based channel access, the wireless communication device performs channel sensing during the second fixed duration, and transmits on the channel when it senses that the channel is idle during the fixed duration. The second fixed duration may be greater than the first fixed duration described above. Specifically, the second fixed duration may be 25us, which is also applicable to the embodiments described below. Also, when an uplink transmission is not followed by a downlink transmission in the same channel occupation, the terminal can perform the second fixed duration based channel access for the uplink transmission after the uplink transmission. Also, when a downlink transmission is not followed by an uplink transmission in the same channel occupation, the terminal can perform the second fixed duration based channel access for the uplink transmission. Also, when a gap between an uplink transmission and a downlink transmission following a subsequent uplink transmission in the same channel occupation is larger than 16 us and not larger than 25 us, the base station can perform the second fixed duration based channel access for the downlink transmission.

[0208] An embodiment will be described that is applied to the case where the gap is not larger than the first fixed duration, in which case the first fixed duration may be 16 us as described above.

[0209] When the gap is not greater than the first fixed duration, a responding node performing a transmission following the gap may perform the transmission immediately without sensing or may perform the transmission by performing the first fixed duration based channel access. In this case, the responding node may perform the transmission immediately without sensing or may perform the transmission by performing the first fixed duration based channel access depending on whether the transmission following the gap includes data traffic that can be classified as traffic or data traffic that determines a channel access priority class. Specifically, when the responding node transmits HARQ-ACK feedback for the data traffic transmitted from the initiating node, the responding node may perform the transmission immediately without sensing.

[0210] In yet another specific embodiment, when the responding node transmits uplink control information (UCI) for the data traffic transmitted from the initiating node, the responding node can transmit immediately without sensing.

[0211] In yet another specific embodiment, when the responding node transmits an SRS, the responding node can transmit immediately without sensing.

[0212] In yet another specific embodiment, when the responding node transmits a physical random access channel (PRACH), the responding node can transmit immediately without sensing.

[0213] In the above embodiment, if the responding node performs a transmission including data traffic immediately after the gap, the responding node may perform the first fixed duration based channel access. Specifically, if the data traffic is scheduled or set by the initiating node, the responding node may perform the first fixed duration based channel access. If the data traffic can be classified as traffic or the channel access priority class of the data traffic can be determined, the responding node may perform the first fixed duration based channel access.

[0214] In the above embodiment, the responding node immediately transmits without sensing, which may mean that the initiating node performs the above-mentioned Category 4 channel access. As described above, the first fixed duration-based channel access may be Category 2 LBT.

[0215] Within the initiating node initiated COT, the initiating node may transmit after the responding node transmits. In this case, within the initiating node initiated COT, the gap between the initiating node's transmission following the responding node's transmission may not be greater than the first fixed duration. Depending on whether the transmission after the gap includes data traffic that can be classified as traffic or data traffic that determines a channel access priority class, the initiating node may transmit immediately without sensing or may perform the first fixed duration based channel access to transmit.

[0216] Specifically, when the initiating node transmits only control information for scheduling data to be transmitted by the responding node, the initiating node can immediately transmit without sensing. In this case, the control information may be at least one of PDCCH only, group common signaling, paging, reference signal only, tracking reference signal (TRS), RACH message 4, or handover command.

[0217] In yet another specific embodiment, when the initiating node transmits only broadcasting information, the initiating node may immediately transmit without sensing. In this case, the broadcasting information may be at least one of a discovery reference signal (DRS), an SS / PBCH block, a Type0-PDCCH, or remaining system information (RMSI).

[0218] In the above embodiment, when the initiating node performs a transmission including data traffic immediately after the gap, the initiating node may perform the first fixed duration-based channel access. Specifically, when the data traffic is scheduled for or configured for the responding node, the initiating node may perform the first fixed duration-based channel access. When the data traffic can be classified into traffic or the channel access priority class of the data traffic can be determined, the initiating node may perform the first fixed duration-based channel access.

[0219] In the above embodiment, the initiating node immediately transmits without sensing, which may mean that the initiating node performs the above-mentioned Category 4 channel access. As described above, the first fixed duration-based channel access may be Category 2 LBT.

[0220] In the above-mentioned embodiment, the initiating node may be a base station and the responding node may be a terminal. That is, in the above-mentioned embodiment, the channel occupation may be initiated by the base station. The initiating node may be a terminal and the responding node may be a base station. That is, in the above-mentioned embodiment, the channel occupation may be initiated by the terminal.

[0221] In the above embodiment, nodes transmitting after the gap can transmit within the MCOT.

[0222] FIG. 20 illustrates the operation of a terminal in an embodiment of the present invention when downlink transmission cannot occupy an MCOT in a COT initiated by a base station and the terminal's transmission is scheduled or configured by the base station.

[0223] In FIG. 20, the gap between the downlink transmission of the base station and the uplink transmission of the terminal is 16 us. In FIG. 20(a), the downlink transmission includes multiple UL grants for scheduling the PUSCH transmission on a slot-by-slot basis. The terminal transmits the PUSCH in multiple slots based on the multiple UL grants. In FIG. 20(b), the downlink transmission includes one UL grant for scheduling the PUSCH transmission in multiple slots. The terminal transmits the PUSCH in multiple slots based on the UL grant. In FIG. 20, the scheduling for the uplink transmission may be performed within the channel occupancy acquired by the base station as the initiating node, or the configuration or scheduling of the uplink transmission may be performed before the channel occupancy. In such a case, the embodiment described later may be applied.

[0224] The initiating node may be a base station, and the responding node may be a terminal. 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 may implicitly or explicitly instruct the first fixed duration based channel access. For example, the base station, which is the initiating node, may use an UL grant to instruct the responding node to the first fixed duration based channel access. In this case, the terminal senses the channel within the first fixed duration. If the channel is sensed to be idle within the first duration, the terminal transmits immediately after the first fixed duration. If the channel is sensed to be busy within the first duration, the operation method of the terminal becomes an issue. Specifically, as described above, uplink transmissions on multiple slots of the terminal may be scheduled or configured. In this case, even if the terminal fails to access the channel in the first slot of the multiple slots, channel access for uplink transmission may be required in slots other than the first slot of the multiple slots. The operation method of the terminal in this case will be described. For ease of explanation, the multiple slots in which the UE's uplink transmission is scheduled or configured are denoted as {slot(n), slot(n+1), slot(n+2), ..., slot(n+k-1)}, and the number of the multiple slots is denoted as k.

[0225] A plurality of uplink transmissions may be scheduled or configured for the terminal. The plurality of uplink transmissions may be consecutive without gaps. Specifically, the terminal may receive a grant for scheduling the plurality of uplink transmissions from the base station. The grant means Downlink control information (DCI) and may include a DL grant or a UL grant for scheduling the uplink transmission. In a specific embodiment, the DL grant or the UL grant may indicate a fixed duration-based channel access as a channel access type and indicate a channel access priority used to access a channel on which the plurality of uplink transmissions are performed. In this case, the DL grant or the UL grant may indicate the first fixed duration-based channel access as a channel access type.

[0226] When the terminal attempts a first fixed duration based channel access for a first transmission, which is one of a plurality of uplink transmissions, and the first fixed duration based channel access fails, the terminal may attempt the first fixed duration based channel access for a second transmission, which is a transmission following the first transmission. When the terminal succeeds in the first fixed duration based channel access, the terminal may perform the second transmission. In a specific embodiment, the terminal may perform the first fixed duration based channel access for uplink transmission for each of the remaining slots (slot(n+1), slot(n+2), ..., slot(n+k-1)) following a first slot (slot(n)) among the plurality of slots.

[0227] In yet another specific embodiment, the terminal may perform a first fixed duration based channel access for uplink transmission a pre-specified number of times in the remaining slots (slot(n+1), slot(n+2), ..., slot(n+k-1)) following the first slot (slot(n)) among the plurality of slots. In this case, the pre-specified number of times may be limited to k-1.

[0228] In yet another specific embodiment, when a terminal attempts a first fixed duration based channel access for a first transmission, which is one of a plurality of uplink transmissions, and the first fixed duration based channel access fails, the terminal may attempt the first fixed duration based channel access or the random backoff based channel access depending on whether the channel is sensed to be idle continuously for a second transmission, which is a transmission following the first transmission. When the terminal fails the first fixed duration based channel access in the first slot (slot(n)) and the channel is sensed to be idle continuously after the terminal fails to access the channel, the terminal may attempt the first fixed duration based channel access for the second transmission. In this case, when the terminal succeeds in the first fixed duration based channel access, the terminal may perform the second transmission. In addition, if the terminal fails in the first fixed duration based channel access in the first slot (slot(n)) and the channel is not sensed as idle continuously after the terminal fails to access the channel, the terminal may perform random backoff based channel access for uplink transmission in the remaining slots (slot(n+1), slot(n+2), ..., slot(n+k-1)) after the first slot (slot(n)) among the plurality of slots. If the terminal succeeds in the random backoff based channel access, the terminal may perform the second transmission. In this case, if the random backoff based channel access is instructed to the terminal by DCI as a channel access method in the first slot (slot(n)) or the remaining slots (slot(n+1), slot(n+2), ..., slot(n+k-1)) after the first slot among the plurality of slots, the terminal may perform random backoff based channel access using the channel access priority class instructed by DCI.In the case where a channel access method other than the random backoff-based channel access is instructed to the terminal in the DCI as a channel access method in all of a plurality of slots (slot(n), slot(n+1), slot(n+2), ..., slot(n+k-1)), the terminal can perform random backoff-based channel access for uplink transmission using the channel access priority class instructed in the scheduling DCI. To this end, when the base station instructs fixed duration-based channel access in the DCI, the base station can instruct a channel access priority class used to obtain access to a channel in the DCI. Specifically, when the base station instructs a first fixed duration-based channel access in the DCI, the base station can instruct a channel access priority class used to obtain access to a channel in the DCI.

[0229] In yet another specific embodiment, when a terminal attempts a first fixed duration based channel access for a first transmission, which is one of a plurality of uplink transmissions, and the first fixed duration based channel access fails, the terminal may attempt a second fixed duration based channel access for a second transmission, which is a transmission following the first transmission. When the terminal succeeds in the second fixed duration based channel access, the terminal may perform the second transmission. Specifically, after the terminal fails to access the first fixed duration based channel in the first slot (slot(n)), the terminal may attempt a second fixed duration based channel access in every sensing slot (T sl) can sense whether the channel is idle. If the terminal fails the first fixed duration based channel access in the first slot (slot(n)) and the channel is continuously sensed as idle after the terminal fails the channel access, the terminal can perform the second fixed duration based channel access for uplink transmission in the remaining slots (slot(n+1), slot(n+2), ..., slot(n+k-1)) after the first slot (slot(n)) among the plurality of slots. This is in consideration of the fact that the first fixed duration based channel access may be performed when the gap is the first fixed duration period, and the gap between transmissions becomes large due to the failure of channel access in the first slot (slot(n)). If the terminal fails in the first fixed duration based channel access in the first slot (slot(n)) and the terminal does not continuously sense that the channel is idle after the channel access failure, the terminal may perform random backoff based channel access for uplink transmission in the remaining slots (slot(n+1), slot(n+2), ..., slot(n+k-1)) after the first slot (slot(n)) among the plurality of slots. If the terminal succeeds in the random backoff based channel access, the terminal may perform a second transmission. In this case, if the random backoff based channel access is instructed to the terminal by DCI as a channel access method in the first slot (slot(n)) among the plurality of slots or in the remaining slots ((n+1), slot(n+2), ..., slot(n+k-1)) after the first slot, the terminal may perform random backoff based channel access using a channel access priority class instructed by DCI.In all of a plurality of slots (slot(n), slot(n+1), slot(n+2), ..., slot(n+k-1)), when a channel access method other than the random backoff-based channel access is instructed to the terminal by DCI as a channel access method, the terminal can perform random backoff-based channel access for uplink transmission using the channel access priority class instructed by the scheduling DCI. To this end, when the base station instructs fixed duration-based channel access by DCI, the base station can instruct a channel access priority class to be used for obtaining access to a channel by the DCI. Specifically, when the base station instructs a first fixed duration-based channel access by DCI, the base station can instruct a channel access priority class to be used for obtaining access to a channel by the DCI.

[0230] In yet another specific embodiment, a first fixed duration gap is set between a transmission from the base station and an uplink transmission to be transmitted by the terminal, and the terminal may switch a channel access type to a first fixed duration based channel access for a first transmission, which is one of a plurality of uplink transmissions. In this case, if the first fixed duration based channel access fails, the terminal may attempt channel access according to a channel access type indicated by the DCI for a second transmission, which is a transmission following the first transmission. If the terminal succeeds in the channel access, the terminal may perform a second transmission. Specifically, if the terminal fails the first fixed duration based channel access in a first slot (slot(n)), the terminal may perform channel access for uplink transmission according to a channel access type indicated by the DCI in the remaining slots (slot(n+1), slot(n+2), ..., slot(n+k-1)) following the first slot (slot(n)) among the plurality of slots. In addition, when a plurality of grants schedule uplink transmissions on a plurality of slots, a channel access type for uplink transmission may be indicated for each slot. The terminal may perform channel access for uplink transmission according to a channel access type indicated for each slot in the remaining slots (slot(n+1), slot(n+2), ..., slot(n+k-1)) following the first slot (slot(n)) among the plurality of slots. In such an embodiment, when the channel access type indicated by the DCI is the first fixed duration based channel access, the operation of the terminal may be the same as the first and second described embodiments. However, when the channel access type indicated by the DCI is not the first fixed duration based channel access, the operation of the terminal has differences from the first and second described embodiments.

[0231] In yet another specific embodiment, when the terminal fails in the first fixed duration based channel access in the first slot (slot(n)), the terminal may perform random backoff based channel access for uplink transmission in the remaining slots (slot(n+1), slot(n+2), ..., slot(n+k-1)) following the first slot (slot(n)) among the plurality of slots. This is in consideration of the high possibility that the channel is not idle but is being used by other nodes using the unlicensed band. Specifically, in this embodiment, when the channel is sensed as being not idle but busy by 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 subsequently performed, the channel is likely to be not idle but being busy because it is being used by other nodes. Therefore, this is a method in which the terminal performs random backoff based channel access for slot(n+1) and subsequent slot transmissions before performing uplink transmission.

[0232] In the above embodiment, the random backoff based channel access may be a Category 4 LBT.

[0233] In the case where uplink transmission is scheduled first, the embodiment of the present invention has been described mainly on the case where uplink transmission is scheduled by a scheduling grant. The above-mentioned embodiment can also be applied to the case where resources in time and frequency units are configured by RRC configuration, and the terminal performs uplink transmission using the configured resources.

[0234] Although the method and system of the present invention have been described in conjunction with specific embodiments, some or all of its components or operations may be implemented using a computing system having a general-purpose hardware architecture.

[0235] The above description of the present invention is for illustrative purposes only, and those skilled in the art will understand that the present invention can be easily modified into other specific forms without changing the technical idea or essential features of the present invention. Therefore, the above-described embodiments should be understood to be illustrative in all respects and not restrictive. For example, each component described as a single type may be implemented in a distributed manner, and similarly, each component described as a distributed type may be implemented in a combined form.

[0236] The scope of the present invention is indicated by the claims set forth below rather than by the above detailed description, and any modifications or variations derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included within the scope of the present invention. [Explanation of symbols]

[0237] 110 Processor 121 Cellular communication interface card (first frequency band) 122 Cellular communication interface card (second frequency band) 123 Unlicensed spectrum communications interface card (third frequency band) 130 Memory 140 User Interface 150 display units 210 Processor 221 Cellular communication interface card (first frequency band) 222 Cellular communication interface card (second frequency band) 223 Unlicensed spectrum communications interface card (third frequency band) 230 Memory

Claims

1. 1. A user equipment (UE) for use in a Third Generation Partnership Project (3GPP) based wireless communication system, comprising: A communication module; and a processor for controlling the communication module; The processor, configured to perform a channel access procedure for a set of consecutive transmissions; If channel access is unsuccessful for an nth transmission in the set of consecutive transmissions according to a first channel access procedure, the first channel access procedure includes sensing the channel within 16 μs prior to the nth transmission, and the processor is configured to attempt transmission of an (n+1)th transmission in the set of consecutive transmissions according to a second channel access procedure, the second channel access procedure including sensing the channel for a fixed time duration greater than 16 μs prior to the (n+1)th transmission. U.E.

2. The UE of claim 1 , wherein the fixed time duration greater than 16 μs comprises 25 μs.

3. The UE of claim 1 or 2, wherein the set of consecutive transmissions comprises consecutive physical shared channel transmissions.

4. The UE of claim 1 , wherein the set of consecutive transmissions is within a channel occupancy time (COT).

5. The UE of claim 1 , wherein the set of consecutive transmissions is associated with one or more grants.

6. The UE of claim 1 , wherein the first and second channel access procedures do not include a backoff operation.

7. 1. A method for use by a user equipment (UE) in a Third Generation Partnership Project (3GPP) based wireless communication system, comprising: performing a channel access procedure for a set of consecutive transmissions; If channel access is unsuccessful for an nth transmission in the set of consecutive transmissions according to a first channel access procedure, the first channel access procedure includes sensing a channel within 16 μs prior to the nth transmission, and the UE attempts to transmit an (n+1)th transmission in the set of consecutive transmissions according to a second channel access procedure, the second channel access procedure including sensing the channel for a fixed time duration greater than 16 μs prior to the (n+1)th transmission. method.

8. The method of claim 7 , wherein the fixed time duration greater than 16 μs comprises 25 μs.

9. The method of claim 7 or 8, wherein the set of consecutive transmissions comprises consecutive physical shared channel transmissions.

10. The method of claim 7 , wherein the set of consecutive transmissions is within a channel occupancy time (COT).

11. The method of claim 7 , wherein the set of consecutive transmissions is associated with one or more grants.

12. The method according to claim 7 , wherein the first and second channel access procedures do not include a back-off operation.

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