Method and apparatus for transmitting uplink channel in wireless communication system

Abstract

To provide a method for transmitting an uplink channel in a wireless communication system, and an apparatus therefor.SOLUTION: A method for transmitting an uplink channel in a wireless communication system performed by a terminal comprises the steps of: receiving resource information related to transmission of an uplink channel from a base station (S2410); detecting a downlink channel transmitted from the base station (S2420); and transmitting an uplink channel to the base station based on the resource information according to a result of detecting the downlink channel (S2430), the uplink channel being transmitted within a channel occupancy time (COT) initiated by the base station or within a COT initiated by the terminal.SELECTED DRAWING: Figure 24

Description

[Technical Field]

[0001] The present specification relates to a wireless communication system, and to a method and apparatus for transmitting an uplink channel. [Background technology]

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

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

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

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

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

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

[0008] However, the mobile communication system has gradually expanded its service area to include data services in addition to voice, and has now developed to the extent that it provides high-speed data services. However, due to resource shortages in currently provided mobile communication systems and users' demands for high-speed services, a more advanced mobile communication system is required.

[0009] In recent years, the proliferation of smart devices has led to an explosive increase in mobile traffic, making it difficult for traditional licensed frequency spectrum or licensed frequency bands 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, etc.) to provide cellular communication services is being discussed as a solution to the spectrum shortage problem.

[0011] Unlike licensed bands, where telecommunications carriers secure exclusive frequency usage rights through procedures such as auctions, unlicensed bands can be used simultaneously by multiple communication devices without restrictions, as long as they comply with certain levels of adjacent band protection regulations. Therefore, when unlicensed bands are used for cellular communication services, it is difficult to guarantee the same level of communication quality as provided in licensed bands, and interference problems may occur with wireless communication devices (e.g., wireless LAN devices) that have previously used unlicensed bands.

[0012] To use LTE and NR technologies in unlicensed bands, research should be conducted in advance on coexistence methods with existing unlicensed band devices and methods for efficiently sharing radio channels with other radio channels. In other words, a robust coexistence mechanism (RCM) needs to be developed to prevent devices using LTE and NR technologies from affecting existing unlicensed band devices in unlicensed bands. Summary of the Invention [Problem to be solved by the invention]

[0013] The present specification aims to provide a method for determining whether an uplink channel is transmitted based on a channel occupied interval initiated by a base station or a channel occupied interval initiated by a terminal in a wireless communication system when a fixed frame interval is set for a base station and a terminal, respectively. [Means for solving the problem]

[0014] The present specification provides a method for transmitting an uplink channel in a wireless communication system.

[0015] Specifically, the method performed by the terminal includes the steps of receiving resource information related to transmission of an uplink channel from a base station; detecting a downlink channel transmitted from the base station; and transmitting an uplink channel to the base station based on the resource information according to the downlink channel detection result, wherein the uplink channel is transmitted based on a COT (Channel Occupancy Time) initiated and shared by the base station or based on a COT initiated by the terminal.

[0016] In addition, in the present invention, the method performed by the terminal further includes receiving, from the base station, dynamic signaling including scheduling information for transmitting the uplink channel, wherein the resource information is included in the scheduling information, and when the scheduling information includes information on a COT on which the uplink channel is transmitted, the step of sensing the downlink channel is not performed, and the uplink channel is transmitted based on the information on the COT; and when the scheduling information does not include information on a COT on which the uplink channel is transmitted, the uplink channel is transmitted based on the scheduling information according to the downlink channel sensing result, and the information on the COT is information indicating whether the uplink channel is transmitted based on a COT initiated and shared by the base station or a COT initiated by the terminal.

[0017] In addition, in the present invention, a terminal transmitting an uplink channel in a wireless communication system includes a communication module; and a processor controlling the communication module, wherein the processor receives resource information related to transmission of the uplink channel from a base station, detects a downlink channel transmitted from the base station, and transmits the uplink channel to the base station based on the resource information according to a result of the downlink channel detection, and the uplink channel is transmitted based on a channel occupancy time (COT) initiated and shared by the base station or based on a COT initiated by the terminal.

[0018] In addition, the present invention is characterized in that the uplink channel is transmitted based on a configured grant.

[0019] In addition, in the present invention, as a result of the downlink channel sensing, if the terminal senses the downlink channel, the uplink channel is transmitted based on a COT initiated and shared by the base station, and if the terminal does not sense the downlink channel, the uplink channel is transmitted based on a COT initiated by the terminal.

[0020] In addition, in the present invention, the COT initiated and shared by the base station is an interval within a Fixed Frame Period (FFP) set in the base station, and the COT initiated by the terminal is an interval within a Fixed Frame Period (FFP) set in the terminal.

[0021] In addition, in the present invention, when the uplink channel is transmitted based on a COT initiated and shared by the base station, the uplink channel is transmitted in an interval other than an idle interval in an FFP set in the base station.

[0022] In addition, in the present invention, when the uplink channel is transmitted based on a COT initiated by the terminal, the uplink channel is transmitted in an interval other than an idle interval in an FFP set in the terminal.

[0023] Furthermore, the present invention is characterized in that the FFP set in the base station and the FFP set in the terminal are different.

[0024] In addition, in the present invention, when the uplink channel is transmitted based on a COT initiated by the terminal, the uplink channel is transmitted regardless of whether the section in which the uplink channel is transmitted is included in an idle section in an FFP set in the base station.

[0025] In addition, in the present invention, when the uplink channel is transmitted based on a COT initiated and shared by the base station, the uplink channel is transmitted in an interval other than an idle interval within an FFP set in the base station, where the interval in which the uplink channel is transmitted is set.

[0026] In addition, in the present invention, the FFP set in the terminal is set in the terminal by dedicated RRC signaling information.

[0027] In addition, the present invention is characterized in that the information about the COT is included in a field for channel access that constitutes the dynamic signaling.

[0028] Also, in the present invention, there is provided a method for receiving an uplink channel in a wireless communication system, the method being performed by a base station, comprising the steps of: transmitting resource information related to transmission of the uplink channel to a terminal; and receiving an uplink channel based on the resource information from the terminal, wherein the uplink channel is transmitted based on whether the terminal senses a downlink channel transmitted from the base station, and the uplink channel is transmitted within a COT (Channel Occupancy Time) initiated by the base station or within a COT initiated by the terminal. [Effects of the Invention]

[0029] This specification provides a method for determining whether an uplink channel is transmitted based on a channel occupied interval initiated by the base station or a channel occupied interval initiated by the terminal when a fixed frame interval is set for each of a base station and a terminal in a wireless communication system, thereby enabling efficient transmission of the uplink channel. [Brief explanation of the drawings]

[0030] [Figure 1]FIG. 1 is a diagram illustrating an example of a radio frame structure used in a wireless communication system. [Figure 2] 1 is a diagram illustrating an example of a downlink (DL) / uplink (UL) slot structure in a wireless communication system. [Figure 3] 1 is a diagram illustrating physical channels used in a 3GPP system and a general signal transmission method using the channels. [Figure 4] FIG. 1 illustrates an SS / PBCH block for initial cell access in a 3GPP NR system. [Figure 5] FIG. 1 illustrates a procedure for control information and control channel transmission in a 3GPP NR system. [Figure 6] FIG. 1 is a diagram illustrating a control resource set (CORESET) in which a physical downlink control channel (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. 1 is a conceptual diagram illustrating carrier aggregation. [Figure 9] FIG. 1 is a diagram illustrating single-carrier communication and multi-carrier communication. [Figure 10] A diagram showing an example in which a cross-carrier scheduling technique is applied. [Figure 11] A diagram showing the positions of OFDM symbols occupied by SSBs within multiple slots of a licensed band in an NR system according to one embodiment of the present invention. [Figure 12] This figure shows the position of slots occupied by SSB within a half radio frame, i.e., 5 ms, of a licensed band in an NR system according to one embodiment of the present invention. [Figure 13] A diagram showing the positions of OFDM symbols occupied by SSBs in a slot containing 16 OFDM symbols according to one embodiment of the present invention. [Figure 14] 2A and 2B are block diagrams showing the configurations of a terminal and a base station according to an embodiment of the present invention. [Figure 15] A diagram showing a downlink channel access procedure according to one embodiment of the present invention. [Figure 16] FIG. 10 is a diagram illustrating a scheduled uplink transmission according to one embodiment of the present invention. [Figure 17] FIG. 1 is a diagram illustrating an LBT operation process based on FBE according to one embodiment of the present invention. [Figure 18] FIG. 1 is a diagram illustrating an FBE operation according to an embodiment of the present invention. [Figure 19] FIG. 1 is a diagram illustrating an LBE operation according to an embodiment of the present invention. [Figure 20] A diagram showing a method for performing uplink transmission and downlink transmission when different FFPs are configured in a base station and a terminal according to one embodiment of the present invention. [Figure 21] A diagram showing a method for performing uplink transmission and downlink transmission when different FFPs are configured in a base station and a terminal according to one embodiment of the present invention. [Figure 22] A diagram showing a method for performing uplink transmission and downlink transmission when different FFPs are configured in a base station and a terminal according to one embodiment of the present invention. [Figure 23] A diagram showing a method for performing uplink transmission and downlink transmission when different FFPs are configured in a base station and a terminal according to one embodiment of the present invention. [Figure 24] A diagram showing a method in which a terminal transmits an uplink channel according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0031] The terms used in this specification are generally used as widely as possible, taking into consideration the functions of the present invention. However, these may vary depending on the intentions of those skilled in the art, practice, or the emergence of new technologies. In addition, in certain cases, the applicant may arbitrarily select terms. In such cases, the meaning of the terms will be described in the relevant description of the invention. Therefore, it is clear that the terms used in this specification should be analyzed based on the substantive meaning of the terms and the overall content of this specification, rather than simply the names of the terms.

[0032] Throughout the specification, when a component is said to be "connected" to another component, this includes not only "directly connected" but also "electrically connected" through other components in between. Furthermore, when a component is said to "comprise" a specific component, this does not mean excluding the other component, but also means including the other component, unless otherwise specified. 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.

[0033] The following technologies are used in various wireless access systems, such as CDMA (code division multiple access), FDMA (frequency division multiple access), TDMA (time division multiple access), OFDMA (orthogonal frequency division multiple access), and SC-FDMA (single carrier frequency division multiple access). CDMA is implemented in radio technologies such as UTRA (Universal Terrestrial Radio Access) and CDMA2000. TDMA is implemented in radio technologies such as GSM (Global System for Mobile communications), GPRS (General Packet Radio Service), and EDGE (Enhanced Data Rates for GSM Evolution). OFDMA is implemented in radio technologies such as IEEE802.11 (Wi-Fi), IEEE802.16 (WiMAX), IEEE802-20, and E-UTRA (Evolved UTRA). UTRA is part of UMTS (Universal Mobile Telecommunications System). 3GPP LTE (Long term evolution) is a part of E-UMTS (Evolved UMTS) that uses E-UTRA, and LTE-Advanced (LTE-A) 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, the following description will focus on 3GPP NR, but the technical concept of the present invention is not limited thereto.

[0034] Unless otherwise specified herein, the base station may include a next generation node B (gNB) defined in 3GPP NR. Also, unless otherwise specified, the terminal may include a user equipment (UE). Hereinafter, for ease of understanding, each content will be described separately in an embodiment, but the embodiments may be used in combination with each other. In the present disclosure, the terminal configuration may refer to 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 values ​​of parameters used in the wireless communication system.

[0035] FIG. 1 is a diagram illustrating an example of a radio frame structure used in a radio communication system.

[0036] Referring to FIG. 1, a radio frame used in a 3GPP NR system has a length of 10 ms (ΔfmaxNf / 100)*Tc). Each radio frame consists of 10 equally sized subframes (SF). Here, Δfmax=480*103 Hz, Nf=4096, Tc=1 / (Δfref*Nf,ref), Δfref=15*103 Hz, and Nf,ref=2048. The 10 subframes in a frame are numbered 0 to 9. Each subframe has a length of 1 ms and consists of one or more slots depending on the subcarrier spacing. More specifically, the subcarrier spacing that can be used in a 3GPP NR system is 15*2 μkHz. μ is the subcarrier spacing configuration factor and has values ​​from 0 to 4. That is, 15 kHz, 30 kHz, 60 kHz, 120 kHz, or 240 kHz is used as the subcarrier spacing. A 1-ms-long subframe consists of 2μ slots. Each slot is 2-μms long. The 2μ slots in one subframe are numbered from 0 to 2μ-1. The slots in one radio frame are numbered from 0 to 10*2μ-1. Time resources are divided by at least one of a radio frame number (also called a radio frame index), a subframe number (also called a subframe index), and a slot number (or a slot index).

[0037] 2 is a diagram illustrating an example of a downlink (DL) / uplink (UL) slot structure in a wireless communication system, and in particular, a resource grid structure of a 3GPP NR system.

[0038] There is one resource grid per antenna port. Referring to FIG. 2, a slot includes multiple orthogonal frequency division multiplexing (OFDM) symbols in the time domain and multiple resource blocks (RBs) in the frequency domain. An OFDM symbol also refers to one symbol section. Unless otherwise specified, an OFDM symbol may simply be referred to as a symbol. One RB includes 12 consecutive subcarriers in the frequency domain. Referring to FIG. 2, a signal transmitted from each slot may be represented by a resource grid including Nsize,μgrid,x*NRBsc subcarriers and Nslotsymb OFDM symbols. Here, x = DL if the signal is a DL signal, and x = UL if the signal is a UL signal. Nsize,μgrid,x represents the number of resource blocks (RBs) according to the subcarrier spacing, which is a component of μ (x is DL or UL), and Nslotsymb represents 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, OFDM symbols may be referred to as cyclic shift OFDM (CP-OFDM) symbols or discrete Fourier transform spread OFDM (DFT-s-OFDM) symbols.

[0039] The number of OFDM symbols included in one slot may vary according to the length of the cyclic prefix (CP). For example, in the case of a normal CP, one slot may include 14 OFDM symbols, while in the case of an extended CP, one slot may include 12 OFDM symbols. In a particular embodiment, the extended CP may be used only with 60 kHz subcarrier spacing. In FIG. 2, for convenience of explanation, one slot is configured using 14 OFDM symbols as an example, but the embodiments of the present disclosure may be similarly applied to slots having a different number of OFDM symbols. Referring to FIG. 2, each OFDM symbol is N size,μgrid,x *N RB sc The carrier frequency includes four subcarriers. The subcarrier types can be divided into data subcarriers for data transmission, reference signal subcarriers for transmitting reference signals, and guard bands. The carrier frequency is also called the center frequency (fc).

[0040] One RB is N RB sc A resource may be defined by (e.g., 12) consecutive subcarriers. For reference, a resource configured using one OFDM symbol and one subcarrier may be referred to as a resource element (RE) or tone. Thus, one RB is defined by N slot symb *N RB sc Each resource element in the resource grid can be uniquely defined within a slot by a pair of indices (k, l), where k ranges from 0 to N in the frequency domain. size,μ grid,x *N RB sc l may be an index ranging from 0 to N in the time domain. slot symb It may be an index numbered down to -1.

[0041] In order for a UE to receive signals from or transmit signals to a base station, the time / frequency of the UE may be synchronized to the time / frequency of the base station, since when the base station and the UE are synchronized, the UE can determine the time and frequency parameters needed to demodulate DL signals and transmit UL signals at the appropriate times.

[0042] Each symbol of a radio frame used in time division duplex (TDD), i.e., unpaired spectrum, may be configured with at least one of DL symbols, UL symbols, and flexible symbols. In frequency division duplex (FDD), i.e., paired spectrum, a radio frame used as a DL carrier may be configured with DL symbols or flexible symbols, and a radio frame used as a UL carrier may be configured with UL symbols or flexible symbols. DL symbols allow DL transmission but not UL transmission. UL symbols allow UL transmission but not DL transmission. Flexible symbols may be determined to be used as DL or UL according to the signal.

[0043] Information about the type of each symbol, i.e., information indicating any one of DL symbols, UL symbols, and flexible symbols, can be configured using cell-specific or common radio resource control (RRC) signals. In addition, information about the type of each symbol can be additionally configured using UE-specific or dedicated RRC signals. The base station notifies i) the duration of the cell-specific slot configuration, ii) the number of slots with only DL symbols from the beginning of the cell-specific slot configuration period, iii) the number of DL symbols from the first symbol of the slot immediately following the slot with only DL symbols, iv) the number of slots with only UL symbols from the end of the cell-specific slot configuration period, and v) the number of UL symbols from the last symbol of the slot immediately preceding the slot with only UL symbols by using cell-specific RRC signals. Here, a symbol that is not configured using either UL symbols or DL ​​symbols is a flexible symbol.

[0044] When information about symbol types is configured using UE-specific RRC signals, the base station can signal in the cell-specific RRC signal whether the flexible symbol is a DL symbol or a UL symbol. In this case, the UE-specific RRC signal cannot change a DL symbol or a UL symbol configured using the cell-specific RRC signal to another symbol type. The UE-specific RRC signal can signal the number of DL symbols among the Nslotsymb symbols of the corresponding slot for each slot, and the number of UL symbols among the Nslotsymb symbols of the corresponding slot. In this case, the DL symbols of the slot can be continuously configured using the first symbol to the i-th symbol of the slot. In addition, the UL symbols of the slot can be continuously configured using the j-th symbol to the last symbol of the slot (where i < j). Among the slots, a symbol that is not configured using either UL symbols or DL symbols is a flexible symbol.

[0045] The type of symbol consisting of the above RRC signals is referred to as a semi-static DL / UL configuration. In the semi-static DL / UL configuration consisting of the above-described RRC signals, the flexible symbol is indicated as a downlink symbol, an uplink symbol, or a flexible symbol via the dynamic SFI (slot format information) transmitted on the physical downlink control channel (PDCCH). At this time, the downlink symbol or uplink symbol consisting of the RRC signal is not changed to another symbol type. Table 1 exemplifies the dynamic SFI indicated by the base station to the terminal.

[0046]

Table 1

[0047] In Table 1, D denotes a downlink symbol, U denotes an uplink symbol, and X denotes a flexible symbol. As shown in Table 1, up to two DL / UL switchings are allowed in one slot.

[0048] FIG. 3 is a diagram illustrating physical channels used in a 3GPP system (e.g., NR) and a general signal transmission method using the physical channels.

[0049] When a UE is powered on or camps on a new cell, the UE performs an initial cell search (S101). Specifically, the UE may synchronize with a BS during the initial cell search. To this end, the UE may receive a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) from a base station to synchronize with the base station and obtain information such as a cell ID. The UE may then receive a physical broadcast channel from the base station and obtain broadcast information in the cell.

[0050] Upon completion of the initial cell search, the UE receives a physical downlink control channel (PDCCH) and a physical downlink shared channel (PDSCH) according to information in the PDCCH, so that the UE can acquire system information that is more specific than the system information acquired through the initial cell search (S102). Here, the system information acquired by the UE is cell-common system information for the UE to operate correctly at the physical layer in Radio Resource Control (RRC), and is also referred to as remaining system information or system information block (SIB) 1.

[0051] When a UE first accesses a base station or does not have radio resources for signal transmission, the UE may perform a random access procedure with the base station (operations S103 to S106). First, the UE may transmit a preamble over a physical random access channel (PRACH) (S103) and receive a response message for the preamble from the base station over a PDCCH and a corresponding PDSCH (S104). If the UE receives a valid random access response message, the UE transmits data including the UE's identifier and the like to the base station over a physical uplink shared channel (PUSCH) indicated by a UL grant transmitted from the base station over the PDCCH (S105). Next, the UE waits for reception of a PDCCH as an indication from the base station for collision resolution. If the UE successfully receives the PDCCH via the UE's identifier (S106), the random access process is terminated. During the random access procedure, the UE may acquire UE-specific system information required for the UE to operate correctly at the physical layer in the RRC layer. Once the UE acquires UE-specific system information at the RRC layer, the UE enters the RRC connected mode (RRC_CONNECTED mode).

[0052] The RRC layer is used to generate and manage messages for control between a terminal and a wireless access network (RAN). More specifically, the base station and terminal can perform storage management including broadcasting cell system information required for all terminals in a cell, transmission management of paging messages, mobility management and handover, terminal measurement reports and control thereof, terminal capability management, and device management at the RRC layer. Generally, the update of signals transmitted at the RRC layer (hereinafter referred to as RRC signals) is longer than the transmission / reception period (i.e., transmission time interval, TTI) at the physical layer, so that RRC signals can be maintained unchanged for a long period.

[0053] After the above-described procedure, the UE receives the PDCCH / PDSCH (S107) and transmits the physical uplink shared channel (PUSCH) / physical uplink control channel (PUCCH) as a general UL / DL signal transmission procedure (S108). Specifically, the UE may receive downlink control information (DCI) through the PDCCH. The DCI may include control information such as resource allocation information for the UE. The format of the DCI may vary depending on the intended use. The uplink control information (UCI) transmitted by the UE to the base station through the UL includes a DL / UL ACK / NACK signal, a channel quality indicator (CQI), a precoding matrix index (PMI), a rank indicator (RI), etc. Here, the CQI, PMI, and RI may be included in channel state information (CSI). In a 3GPP NR system, a UE may transmit control information, such as the HARQ-ACK and CSI described above, over a PUSCH and / or a PUCCH.

[0054] FIG. 4 shows the SS / PBCH block for initial cell access in a 3GPP NR system.

[0055] When a UE is powered on or wants to access a new cell, it may acquire time and frequency synchronization with the cell and perform an initial cell search procedure. The UE may detect the physical cell identity (NcellID) of the cell during the cell search procedure. To this end, the UE may receive synchronization signals, such as a primary synchronization signal (PSS) and a secondary synchronization signal (SSS), from a base station and synchronize to the base station. In this case, the UE may obtain information such as a cell identity (ID).

[0056] Referring to FIG. 4a, the synchronization signal (SS) will be described in more detail. The synchronization signal can be classified into a PSS and an SSS. The PSS can be used to obtain time-domain synchronization and / or frequency-domain synchronization, such as OFDM symbol synchronization and slot synchronization. The SSS can be used to obtain frame synchronization and a cell group ID. Referring to FIG. 4a and Table 1, an SS / PBCH block can be configured using 20 consecutive RBs (=240 subcarriers) in the frequency domain and 4 consecutive OFDM symbols in the time domain. In this case, within the SS / PBCH block, the PSS is transmitted in the first OFDM symbol, and the SSS is transmitted in the third OFDM symbol through subcarriers 56 to 182. Here, the smallest subcarrier index of the SS / PBCH block is numbered starting from 0. In the first OFDM symbol in which the PSS is transmitted, the base station does not transmit signals through the remaining subcarriers, i.e., subcarriers 0 to 55 and 183 to 239. In addition, in the third OFDM symbol in which the SSS is transmitted, the base station does not transmit signals through subcarriers 48 to 55 and 183 to 191. The base station transmits a physical broadcast channel (PBCH) through the remaining REs in the SS / PBCH block excluding the above signals.

[0057] [Table 2]

[0058] The SS allows a total of 1008 unique physical layer cell IDs to be grouped into 336 physical layer cell identifier groups, with each group specifically including three unique identifiers through the combination of three PSSs and SSSs, such that each physical layer cell ID is only part of one physical layer cell identifier group. Thus, a physical layer cell ID NcellID=3N(1)ID+N(2)ID can be 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 within the physical layer cell identifier group. A UE can detect the PSS and identify one of the three unique physical layer identifiers. In addition, the UE can detect the SSS and identify one of the 336 physical layer cell IDs associated with the physical layer identifiers. In this case, the sequence of PSSs dPSS(n) is as follows:

[0059]

number

[0060] where:

number

number

[0061] Furthermore, the SSS sequence dSSS(n) is as follows:

[0062]

number

[0063] where:

number

number

[0064] A 10-ms radio frame may be divided into two 5-ms half-frames. Referring to Figure 4b, the slots in which the SS / PBCH blocks are transmitted within each half-frame are described. The slots in which the SS / PBCH blocks are transmitted may be any one of Cases A, B, C, D, and E. In Case A, the subcarrier spacing is 15 kHz, and the start of the SS / PBCH block is the ({2, 8} + 14*n)th symbol. In this case, n = 0 or 1 for carrier frequencies below 3 GHz. Additionally, n = 0, 1, 2, or 3 may be used for carrier frequencies above 3 GHz and below 6 GHz. In Case B, the subcarrier spacing is 30 kHz, and the start of the SS / PBCH block is {4, 8, 16, 20} + 28*n. In this case, n = 0 for carrier frequencies below 3 GHz. Additionally, n = 0 or 1 may be used 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 the ({2,8}+14*n)th symbol. In this case, n=0 or 1 for carrier frequencies below 3 GHz. Additionally, n=0, 1, 2, or 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 the ({4,8,16,20}+28*n)th symbol. In this case, n=0, 1, 2, 3, 5, 6, 7, 8, 10, 11, 12, 13, 15, 16, 17, or 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 the ({8,12,16,20,32,36,40,44}+56*n)th symbol. In this case, n=0, 1, 2, 3, 5, 6, 7, 8 for carrier frequencies above 6 GHz.

[0065] Figure 5 shows a procedure for transmitting control information and control channels in a 3GPP NR system. Referring to Figure 5a, a base station may add a cyclic redundancy check (CRC) masked (e.g., XORed) with a radio network temporary identifier (RNTI) to control information (e.g., downlink control information (DCI)) (S202). The base station may scramble the CRC using an RNTI value determined according to the purpose / target of each control information. The common RNTI used by one or more UEs may include at least one of a system information RNTI (SI-RNTI), a paging RNTI (P-RNTI), a random access RNTI (RA-RNTI), and a transmit power control RNTI (TPC-RNTI). In addition, the UE-specific RNTI may include at least one of a cell temporary RNTI (C-RNTI) and a CS-RNTI. The base station may then perform channel coding (e.g., polar coding) (S204) and then perform rate matching according to the amount of resources used for PDCCH transmission (S206). The base station may then multiplex DCI based on a control channel element (CCE)-based PDCCH structure (S208). Additionally, the base station may apply additional processes, such as scrambling, modulation (e.g., QPSK), and interleaving, to the multiplexed DCI (S210), and then map the DCI to resources to be transmitted. A CCE is a basic resource unit for the PDCCH, and one CCE may include multiple (e.g., 6) resource element groups (REGs). One REG may be configured with multiple (e.g., 12) REs. The number of CCEs used for one PDCCH may be defined as an aggregation level.In a 3GPP NR system, aggregation levels of 1, 2, 4, 8, or 16 may be used. Figure 5b is a diagram relating to CCE aggregation levels and PDCCH multiplexing, showing the type of CCE aggregation level used for one PDCCH and the CCEs transmitted in the control area accordingly.

[0066] FIG. 6 illustrates a control resource set (core set) in which a physical downlink control channel (PDCCH) may be transmitted in a 3GPP NR system.

[0067] A core set is a time-frequency resource within which the PDCCH, i.e., a control signal for the UE, is transmitted. In addition, a search space, which will be described later, may be mapped to a core set. Thus, instead of monitoring all frequency bands for PDCCH reception, the UE may monitor a time-frequency region designated as a core set and decode the PDCCH mapped to the core set. A base station may configure one or more core sets per cell for a UE. A core set may be configured using up to three consecutive symbols on the time axis. Additionally, a core set may be configured in units of six consecutive PRBs on the frequency axis. In the embodiment of FIG. 6, core set #1 is configured using consecutive PRBs, and core sets #2 and #3 are configured using non-consecutive PRBs. A core set may be positioned within any symbol within a slot. For example, in the embodiment of FIG. 6, core set #1 starts in the first symbol of the slot, core set #2 starts in the fifth symbol of the slot, and core set #9 starts in the ninth symbol of the slot.

[0068] FIG. 7 illustrates a method for configuring a PDCCH search space in a 3GPP NR system.

[0069] To transmit a PDCCH to a UE, each core set may have at least one search space. In an embodiment of the present disclosure, a search space is a set of all time-frequency resources (hereinafter referred to as PDCCH candidates) through which the UE's PDCCH can be transmitted. The search space may include a common search space that 3GPP NR UEs are required to search in common, and a terminal-specific or UE-specific search space that a specific UE is required to search. In the common search space, a UE may monitor a PDCCH that all UEs in a cell belonging to the same base station are configured to search in common. In addition, a UE-specific search space may be configured for each UE so that the UE monitors the PDCCH allocated to each UE at different search space positions according to the UE. In the case of a UE-specific search space, the search spaces between UEs may be partially overlapped due to the limited control areas in which the PDCCHs are allocated. Monitoring the PDCCH includes blind decoding to find PDCCH candidates within the search space. When blind decoding is successful, it may be expressed that the PDCCH is (successfully) detected / received, and when blind decoding fails, it may be expressed that the PDCCH is not detected / received or is not successfully detected / received.

[0070] For ease of description, a PDCCH scrambled with a group common (GC) RNTI previously known to one or more UEs to transmit DL control information to one or more UEs is referred to as a group common (GC) PDCCH or a common PDCCH. In addition, a PDCCH scrambled with a terminal-specific RNTI already known by a specific UE to transmit UL scheduling information or DL ​​scheduling information to a specific UE is referred to as a UE-specific PDCCH. The common PDCCH may be included in a common search space, and the UE-specific PDCCH may be included in a common search space or a UE-specific PDCCH.

[0071] A base station may signal information related to resource allocation of the transmission channels paging channel (PCH) and downlink shared channel (DL-SCH) (i.e., DL grants), or information related to resource allocation of the uplink shared channel (UL-SCH) and hybrid automatic repeat request (HARQ) (i.e., UL grants) to each UE or a group of UEs via the PDCCH. The base station may transmit PCH transport blocks and DL-SCH transport blocks via the PDSCH. The base station may transmit data excluding specific control information or specific service data via the PDSCH. In addition, a UE may receive data excluding specific control information or specific service data via the PDSCH.

[0072] A base station may transmit a PDCCH to a UE (one or more UEs) including information about where PDSCH data is to be transmitted and how the PDSCH data will be received and decoded by the corresponding UE. For example, assume that DCI transmitted on a specific PDCCH is CRC masked using an RNTI of "A," and the DCI indicates that the PDSCH is allocated to a radio resource (e.g., a frequency location) of "B," and indicates transmission format information (e.g., transport block size, modulation scheme, coding information, etc.) of "C." The UE monitors the PDCCH using the RNTI information that the UE has. In this case, if a UE performs blind decoding of the PDCCH using the RNTI of "A," the UE receives the PDCCH and, through the received PDCCH information, receives the PDSCH indicated by "B" and "C."

[0073] Table 3 illustrates one embodiment of a physical uplink control channel (PUCCH) used in a wireless communication system.

[0074] [Table 3]

[0075] The PUCCH may be used to transmit the following UL control information (UCI):

[0076] - Scheduling Request (SR): Information used to request UL UL-SCH resources.

[0077] - HARQ-ACK: A response to the PDCCH (indicating DL SPS release) and / or a response to a DL transport block (TB) on the PDSCH. The HARQ-ACK indicates whether information transmitted on the PDCCH or PDSCH has been received. HARQ-ACK responses include a positive ACK (simply ACK), a negative ACK (hereinafter NACK), discontinuous transmission (DTX), or NACK / DTX. Here, the term HARQ-ACK is used interchangeably with HARQ-ACK / NACK and ACK / NACK. In general, an ACK may be represented by a bit value of 1, and a NACK may be represented by a bit value of 0.

[0078] - Channel State Information (CSI): Feedback information on the DL channel. The UE generates it based on the CSI reference signal (RS) transmitted by the base station. Multiple-input multiple-output (MIMO)-related feedback information includes a rank indicator (RI) and a precoding matrix indicator (PMI). The CSI may be divided into CSI part 1 and CSI part 2 according to the information indicated by the CSI.

[0079] In a 3GPP NR system, five PUCCH formats may be used to support different service scenarios, different channel environments, and frame structures.

[0080] PUCCH format 0 is a format capable of transmitting 1-bit or 2-bit HARQ-ACK information or SR. PUCCH format 0 can be transmitted using one or two OFDM symbols on the time axis and one RB on the frequency axis. When PUCCH format 0 is transmitted in two OFDM symbols, the same sequence on the two symbols may be transmitted using different RBs. In this case, the sequence may be a cyclic shift (CS) sequence of the base sequence used for PUCCH format 0. This allows the UE to obtain frequency diversity gain. Specifically, the terminal can determine a cyclic shift (CS) value mcs according to the Mbit-bit UCI (Mbit = 1 or 2). In addition, a cyclic shifted sequence of length 12 can be mapped to 12 REs of one OFDM symbol and one RB based on the determined CS value mcs and transmitted. If the number of cyclic shifts available to a terminal is 12 and Mbit=1, then 1-bit UCI 0 and 1 can be mapped to two cyclic shifted sequences with a cyclic shift value difference of 6. If Mbit=2, then 2-bit UCI 00, 01, 11, and 10 can be mapped to four cyclic shifted sequences with a cyclic shift value difference of 3.

[0081] PUCCH format 1 carries 1-bit or 2-bit HARQ-ACK information or SR. PUCCH format 1 is transmitted using consecutive OFDM symbols on the time axis and one PRB on the frequency axis. Here, the number of OFDM symbols occupied by PUCCH format 1 is one of 4 to 14. More specifically, UCI with Mbit=1 is modulated using BPSK. A UE modulates UCI with Mbit=2 using quadrature phase shift keying (QPSK). A signal is obtained by multiplying the modulated complex-valued symbol d(0) with a sequence of length 12. A UE spreads the obtained signal using an orthogonal cover code (OCC) on the even-numbered OFDM symbols to which PUCCH format 1 is assigned and transmits it. In PUCCH format 1, the maximum number of different UEs that can be multiplexed in the same RB is determined depending on the length of the OCC used. In odd-numbered OFDM symbols of PUCCH format 1, a demodulation reference signal (DMRS) is spread by OCC and mapped.

[0082] PUCCH format 2 can deliver UCI exceeding two bits. PUCCH format 2 can be transmitted over one or two OFDM symbols on the time axis and one or more RBs on the frequency axis. When PUCCH format 2 is transmitted in two OFDM symbols, the sequences transmitted in different RBs over the two OFDM symbols may be identical to each other. Here, the sequence is a set of modulated complex-valued symbols d(0),...,d(M symbol -1), where M symbol is M bit / 2. Through this, the UE may obtain frequency diversity gain. More specifically, M bit Bit UCI(M bit>2) is bit-level scrambled, QPSK modulated, and mapped to RBs of one or two OFDM symbols, where the number of RBs may be one of 1 to 16.

[0083] PUCCH format 3 or PUCCH format 4 may deliver UCI exceeding 2 bits. PUCCH format 3 or PUCCH format 4 may be transmitted over consecutive OFDM symbols on the time axis and one PRB on the frequency axis. The number of OFDM symbols occupied by PUCCH format 3 or PUCCH format 4 may be one of 4 to 14. Specifically, the UE may transmit MUCCH signals using π / 2-2 phase shift keying (BPSK) or QPSK. bit The complex-valued symbols d(0) to d(M symb -1) where, when π / 2-BPSK is used, M symb =M bit and when using QPSK, M symb =M bit / 2. The UE does not need to apply block-wise spreading to PUCCH format 3. However, the UE may apply block-wise spreading to one RB (i.e., 12 subcarriers) using PreDFT-OCC of length 12, such that PUCCH format 4 may have a multiplexing capacity of 2 or 4. The UE performs transmit precoding (or DFT precoding) on ​​the spread signal, maps it to each RE, and transmits the spread signal.

[0084] In this case, the number of RBs occupied by PUCCH format 2, PUCCH format 3, or PUCCH format 4 may be determined according to the length of the UCI transmitted by the UE and the maximum code rate. When the UE uses PUCCH format 2, the UE may transmit HARQ-ACK information and CSI information together over the PUCCH. When the number of RBs that the UE can transmit is greater than the maximum number of RBs that PUCCH format 2, PUCCH format 3, or PUCCH format 4 can use, the UE may transmit only the remaining UCI information without transmitting some of the UCI information according to the priority of the UCI information.

[0085] PUCCH Format 1, PUCCH Format 3, or PUCCH Format 4 may be configured through RRC signaling to indicate frequency hopping within a slot. When frequency hopping is configured, the index of the RB to be frequency hopped may be configured using RRC signaling. When PUCCH Format 1, PUCCH Format 3, or PUCCH Format 4 is transmitted over N OFDM symbols on the time axis, the first hop may have floor(N / 2) OFDM symbols, and the second hop may have ceil(N / 2) OFDM symbols.

[0086] PUCCH format 1, PUCCH format 3, or PUCCH format 4 may be configured to be repeatedly transmitted in multiple slots. In this case, the number K of slots in which the PUCCH is repeatedly transmitted may be configured by RRC signaling. The repeatedly transmitted PUCCH must start at a fixed OFDM symbol in each slot and must have a constant length. When one of the OFDM symbols of a slot in which the UE should transmit the PUCCH is indicated as a DL symbol by RRC signaling, the UE may not transmit the PUCCH in the corresponding slot and may delay transmission of the PUCCH until the next slot for transmitting the PUCCH.

[0087] Meanwhile, in a 3GPP NR system, a terminal can transmit and receive using a bandwidth smaller than or equal to the bandwidth of a carrier (or cell). To this end, the terminal may be configured with a bandwidth part (BWP) consisting of a contiguous portion of the carrier's bandwidth. A terminal operating according to TDD or using an unpaired spectrum may be configured with up to four DL / UL BWP pairs per carrier (or cell). The terminal can also activate one DL / UL BWP pair. A terminal operating according to FDD or using a paired spectrum may be configured with up to four DL BWPs per downlink carrier (or cell) and up to four UL BWPs per uplink carrier (or cell). The terminal can activate one DL BWP and one UL BWP per carrier (or cell). The terminal does not need to receive or transmit on time-frequency resources other than the activated BWPs. An activated BWP can be referred to as an active BWP.

[0088] A base station can indicate to a terminal which BWPs among configured BWPs are activated using downlink control information (DCI). The BWP indicated in the DCI is activated, and other configured BWPs are deactivated. In a carrier (or cell) operating in TDD, the base station can include a bandwidth part indicator (BPI) indicating the activated BWP in the DCI scheduling a PDSCH or a PUSCH to change the DL / UL BWP pair of the terminal. The terminal can receive the DCI scheduling a PDSCH or a PUSCH and identify the activated DL / UL BWP pair based on the BPI. In a downlink carrier (or cell) operating in FDD, the base station can include a BPI indicating the activated BWP in the DCI scheduling a PDSCH to change the DL BWP of the terminal. In an uplink carrier (or cell) operating in FDD, the base station can include a BPI indicating the activated BWP in the DCI scheduling a PDSCH to change the UL BWP of the terminal.

[0089] FIG. 8 is a conceptual diagram illustrating carrier aggregation.

[0090] Carrier aggregation is a method in which a UE uses multiple frequency blocks or cells (in a logical sense) configured using UL resources (or component carriers) and / or DL ​​resources (or component carriers) as one large logical frequency band so that a wireless communication system can use a wider frequency band. One component carrier may also be referred to as a primary cell (PCell) or a secondary cell (SCell), or a primary SCell (PScell). However, for convenience of explanation, the term "component carrier" will be used hereinafter.

[0091] Referring to Figure 8, as an example of a 3GPP NR system, the overall system band may include up to 16 component carriers, and each component carrier may have a bandwidth of up to 400 MHz. A component carrier may include one or more physically contiguous subcarriers. Although Figure 8 shows each of the component carriers having the same bandwidth, this is merely an example, and each component carrier may have a different bandwidth. Also, although the component carriers are shown as being adjacent to each other on the frequency axis, the drawing is shown in a logical concept, and the component carriers may be physically adjacent to each other or may be spaced apart.

[0092] A different center frequency may be used for each component carrier. Also, one common center frequency may be used for physically adjacent component carriers. In the embodiment of Figure 8, assuming that all component carriers are physically adjacent, center frequency A may be used for all component carriers. Furthermore, assuming that the respective component carriers are not physically adjacent to each other, center frequency A and center frequency B may be used for each of the component carriers.

[0093] When the overall system band is expanded by carrier aggregation, the frequency band used for communication with each UE may be specified in component carrier units. UE A may use the overall system band of 100 MHz and perform communication using all five component carriers. UEs B1 to B5 may use only a 20 MHz bandwidth and perform communication using one component carrier. UEs C1 and C2 may use a 40 MHz bandwidth and each perform communication using two component carriers. The example in FIG. 8 shows a case where UE C1 uses two non-adjacent component carriers and UE C2 uses two adjacent component carriers.

[0094] 9A and 9B are diagrams for explaining single-carrier communication and multi-carrier communication. Specifically, FIG. 9A shows a single-carrier subframe structure, and FIG. 9B shows a multi-carrier subframe structure.

[0095] Referring to FIG. 9(a), in FDD mode, a typical wireless communication system may transmit or receive data through one DL band and one UL band corresponding thereto. In another specific embodiment, in TDD mode, the wireless communication system may divide a radio frame into UL time units and DL time units in the time domain and transmit or receive data through the UL / DL time units. Referring to FIG. 9(b), three 20 MHz component carriers (CCs) may be aggregated into UL and DL so that a 60 MHz bandwidth can be supported. The CCs may or may not be adjacent to each other in the frequency domain. Although FIG. 9(b) illustrates a case where the bandwidth of the UL CC and the bandwidth of the DL CC are identical and symmetrical, the bandwidth of each CC may be determined independently. In addition, asymmetric carrier aggregation, in which the number of UL CCs and DL CCs differs, is possible. The DL / UL CC allocated / configured to a specific UE through RRC may be referred to as the serving DL / UL CC of the specific UE.

[0096] A base station may communicate with a UE by activating some or all of the UE's serving CCs or deactivating some CCs. The base station can change the CCs to be activated / deactivated and the number of CCs to be activated / deactivated. When a base station allocates CCs available to a UE as cell-specific or UE-specific, at least one of the allocated CCs may be deactivated unless the CC allocation for the UE is completely reconfigured or the UE is handed over. A CC that is not deactivated by the UE is called a Primary CC (PCC) or a Primary Cell (PCell), and a CC that the base station can activate / deactivate freely is called a Secondary CC (SCC) or a Secondary Cell (SCell).

[0097] On the other hand, 3GPP NR uses the concept that a cell manages radio resources. A cell is defined as a combination of DL resources and UL resources, i.e., a combination of DL CC and UL CC. A cell can be configured with only DL resources or a combination of DL resources and UL resources. When carrier aggregation is supported, the association between the carrier frequency of DL resources (i.e., DL CC) and the carrier frequency of UL resources (i.e., UL CC) may be indicated by system information. Carrier frequency refers to the center frequency of each cell or CC. A cell corresponding to a PCC is called a PCell, and a cell corresponding to an SCC is called an SCell. A carrier corresponding to a PCell in DL is a DL PCC, and a carrier corresponding to a PCell in UL is a UL PCC. Similarly, a carrier corresponding to an SCell in DL is a DL SCC, and a carrier corresponding to an SCell in UL is a UL SCC. According to UE capabilities, a serving cell can be configured with one PCell and zero or more SCells. For a UE that is in RRC_CONNECTED state but is not configured for or does not support carrier aggregation, there is only one serving cell configured with only a PCell.

[0098] As mentioned above, the term "cell" used in carrier aggregation is distinguished from the term "cell" which refers to several geographical areas for which communication services are provided by one base station or one antenna group. That is, one component carrier may also be referred to as a scheduling cell, a scheduled cell, a primary cell (PCell), a secondary cell (SCell), or a primary SCell (PScell). However, to distinguish between a cell which refers to several geographical areas and a cell of carrier aggregation, in this disclosure, a cell of carrier aggregation is referred to as a CC, and a cell of a geographical area is referred to as a cell.

[0099] 10 illustrates an example in which a cross-carrier scheduling technique is applied. When cross-carrier scheduling is configured, a control channel transmitted over a first CC may schedule a data channel transmitted over 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 in the PDCCH area of ​​the scheduling cell schedules the PDSCH / PUSCH of the scheduled cell. That is, a search area for multiple component carriers exists in the PDCCH area of ​​the scheduling cell. A PCell may essentially be the scheduling cell, and a specific SCell may be designated as the scheduling cell by higher layers.

[0100] In the embodiment of FIG. 10, it is assumed that three DL CCs are merged. Here, it is assumed that DL component carrier #0 is a DL PCC (or PCell), and DL component carrier #1 and DL component carrier #2 are DL SCCs (or SCells). In addition, it is assumed that the DL PCC is configured as a PDCCH monitoring CC. When cross-carrier scheduling is not configured by UE-specific (or UE group-specific or cell-specific) higher layer signaling, the CIF is disabled, and each DL CC can transmit only a PDCCH for scheduling its PDSCH without using the CIF according to the NR PDCCH rules (non-cross-carrier scheduling, self-carrier scheduling). On the other hand, when cross-carrier scheduling is configured by UE-specific (or UE group-specific or cell-specific) higher layer signaling, the CIF is enabled, and a specific CC (e.g., DL PCC) may transmit not only a PDCCH for scheduling the PDSCH of DL CC A using the CIF, but also a PDCCH for scheduling the PDSCH of another CC (cross-carrier scheduling). On the other hand, the PDCCH is not transmitted in another DL CC. Thus, the UE monitors either the PDCCH without a CIF to receive a self-carrier scheduled PDSCH or the PDCCH with a CIF to receive a cross-carrier scheduled PDSCH, depending on whether cross-carrier scheduling is configured for the UE.

[0101] On the other hand, Figures 9 and 10 show the subframe structure of a 3GPP LTE-A system, and the same or similar configurations may be applied to a 3GPP NR system, except that in a 3GPP NR system, the subframes in Figures 9 and 10 may be replaced with slots.

[0102] Since most communications in conventional unlicensed bands operate based on LBT, channel access in NR-U systems also uses LBT to coexist with conventional devices. Specifically, channel access methods in unlicensed bands in NR are divided into the following four categories depending on whether or not LBT is used / applied.

[0103] ● Category 1: No LBT

[0104] The Tx entity does not perform the LBT procedure for transmission.

[0105] ● Category 2: LBT without random backoff

[0106] The Tx entity senses whether the channel is idle for a first interval without random backoff in order to transmit. That is, the Tx entity transmits through the channel immediately after sensing that the channel is idle for the first interval. The first interval is an interval of a predetermined length immediately before the Tx entity transmits. According to one embodiment, the first interval may be an interval of 25 us, but the present invention is not limited thereto.

[0107] Category 3: LBT with random backoff using a fixed-size CW

[0108] - The Tx entity obtains a random number within a fixed-size CW, sets it as the initial value of a backoff counter (or backoff timer) N, and performs backoff using the set backoff counter N. That is, in the backoff procedure, the Tx entity decrements the backoff counter by 1 each time the channel is sensed as being idle during a preset slot period. Here, the preset slot period may be 9 us, but the present invention is not limited to this. The backoff counter N is decremented by 1 from its initial value, and when the value of the backoff counter N reaches 0, the Tx entity performs transmission. Meanwhile, to perform backoff, the Tx entity decrements the second interval (i.e., the defer period T d ) first senses whether the channel is idle during the second interval. According to an embodiment of the present invention, the Tx entity senses (or determines) whether the channel is idle during the second interval depending on whether the channel is idle for at least a portion of the second interval (e.g., one slot period). The second interval is set based on the channel access priority class of the Tx entity and consists of a 16 us period and m consecutive slot periods, where m is a value set by the channel access priority class. If the Tx entity senses that the channel is idle during the second interval, it performs channel sensing to decrement the backoff counter. On the other hand, if the channel is sensed as occupied during the backoff procedure, the backoff procedure is aborted. After aborting the backoff procedure, the Tx entity resumes backoff if it senses that the channel is idle for an additional second interval. In this way, the Tx entity transmits if the channel is idle for the second interval plus the N slot period of the backoff counter. At this time, the initial value of the backoff counter N is obtained within a CW of a fixed size.

[0109] Category 4: LBT with random backoff using variable-size CW

[0110] - The Tx entity obtains a random number within the variable-size 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 adjusts 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 CW of the adjusted size. The detailed process by which the Tx entity performs backoff is as described in Category 3. The Tx entity performs transmission if the channel is idle for the second interval plus the slot period of the backoff counter N. In this case, the initial value of the backoff counter N is obtained within the variable-size CW.

[0111] In the above categories 1 to 4, the Tx entity is a base station or a terminal. According to an embodiment of the present invention, the first type of channel access is referred to as Category 4 channel access, and the second type of channel access is referred to as Category 2 channel access.

[0112] FIG. 11 is a diagram showing the positions of OFDM symbols occupied by SSBs within multiple slots of a licensed band in an NR system according to an embodiment of the present invention.

[0113] An SSB can include four OFDM symbols and 20 RBs. Specifically, the PSS occupies one OFDM symbol, the SSS occupies one OFDM symbol, and the PBCH occupies two OFDM symbols and one OFDM symbol multiplexed with the SSS and FDM. The OFDM symbol position within the slot occupied by the SSB may vary depending on the subcarrier spacing (SCS). Figure 11(a) shows SSB patterns when the subcarrier spacing for SSB transmission is 15 kHz and 30 kHz. Figure 11(b) shows SSB patterns when the subcarrier spacing for SSB transmission is 120 kHz and 240 kHz. When the subcarrier spacing is 30 kHz, either the SSB pattern for eMBB transmission or an SSB pattern that takes URLLC into consideration may be used. In Figure 11, the hatched OFDM symbols indicate the OFDM symbol positions within the slot occupied by the SSB. Also, different hatching patterns indicate that they correspond to different SSB indices.

[0114] Figure 12 is a diagram showing the positions of slots occupied by SSBs within a half radio frame, i.e., 5 ms, of a licensed band in an NR system according to an embodiment of the present invention.

[0115] In Figure 12, the hatched slots indicate the positions of slots containing SSBs within a half radio frame. One slot can contain two SSBs. Two SSBs within one slot may have different SSB indices. SSBs located in different slots may also have different SSB indices. SSB indices will be described in more detail below. Also, L in Figure 12 indicates the maximum number of SSBs that a base station can transmit in a half radio frame.

[0116] The NR system specifies that one subcarrier spacing must be defined for each frequency band, reducing the complexity of SSB search for initial cell access by the UE. In particular, when a frequency band below 6 GHz is used, the NR system specifies that either 15 kHz or 30 kHz subcarrier spacing must be used for SSB. In addition, when a frequency band above 6 GHz is used, the NR system specifies that either 120 kHz or 240 kHz subcarrier spacing must be used for SSB.

[0117] In unlicensed bands, the LBT procedure is used when a wireless communication device attempts channel access. Therefore, if the channel is not idle, the wireless communication device may fail to access the channel. When a base station attempts channel access to transmit SSBs, channel access may also fail, resulting in the SSBs not being transmitted at the location set by the base station. Even if the base station configures the SSB transmission location to the terminal so that the terminal can assume the location where the SSBs will be transmitted, the terminal may not be able to receive the SSBs. Because SSBs are transmitted periodically, even if the terminal fails to receive the SSBs at any point, it can receive them one period after that point. However, if the terminal receives the SSBs in this way, delays occur in RRM measurements and measurements of neighbor cells. Ultimately, this increases latency throughout the system.

[0118] SSBs are also used to set up beam links and operate beams. Specifically, a base station transmits multiple SSBs corresponding to different SSB indexes in different time domains. A terminal uses multiple SSBs to set up multiple beam links. The base station performs beam sweeping. The terminal sets up a beam link depending on whether it receives SSBs transmitted on different beams in different time domains. If the base station fails to access the channel and is unable to transmit the SSB, a problem occurs in which the beam link cannot be set up. Ultimately, channel access failures increase the latency for beam linking. Therefore, a method is needed to reduce SSB transmission failures and increase SSB transmission opportunities.

[0119] When an NR system is used in an unlicensed band, 60 kHz subcarrier spacing is used to transmit SSBs to increase channel access opportunities. In licensed bands below 6 GHz, 15 kHz or 30 kHz subcarrier spacing is used to transmit SSBs. Furthermore, in licensed bands below 6 GHz, 15 kHz, 30 kHz, or 60 kHz subcarrier spacing is used to transmit data. Furthermore, in licensed bands above 6 GHz, 120 kHz or 240 kHz subcarrier spacing is used to transmit SSBs. Furthermore, in licensed bands above 6 GHz, 60 kHz or 120 kHz subcarrier spacing is used to transmit data. When an NR system is used in an unlicensed band below 7 GHz (e.g., below 7.125 GHz), 15 kHz or 30 kHz subcarrier spacing may be considered, similar to the subcarrier spacing used in licensed bands below 6 GHz. However, when 60 kHz subcarrier spacing is used to transmit SSB in an unlicensed band, the spacing between OFDM symbols is reduced to one-quarter of that when 15 kHz subcarrier spacing is used. Therefore, when 60 kHz subcarrier spacing is used in an NR system in an unlicensed band, symbol-by-symbol transmission opportunities for SSB and data channels can be increased after channel access. When 15 kHz and 30 kHz subcarrier spacing are used, if a base station successfully accesses a channel within one OFDM symbol, the time for transmitting a reservation signal is reduced when 60 kHz subcarrier spacing is used to prepare for the time required. The following describes SSB transmission methods that can be used in unlicensed bands, particularly when 60 kHz subcarrier spacing is used.

[0120] NR-U DRS (or DRS) configuration

[0121] In the unlicensed spectrum of the NR system, a base station can transmit a signal including at least one SSB or at least one SSB burst set. An SSB burst set is a set of SSBs transmitted continuously within a certain time interval. In this case, the signal may be a discovery signal burst (DRS burst). The base station can transmit the DRS burst according to the following principles: The base station can transmit the DRS burst so that the time interval in which the DRS burst is transmitted within the beam does not include any gaps. The base station can transmit the DRS burst so that the occupied channel bandwidth (OCB) requirement is met. However, in some cases, the base station can transmit the DRS burst so that the occupied channel bandwidth requirement is not met. Furthermore, the base station can consider a method to minimize the channel occupancy time of the DRS burst and achieve rapid channel access. For convenience of explanation, the DRS burst will be referred to as DRS.

[0122] The DRS transmitted in the unlicensed band may include a PDSCH including remaining system information (RMSI) related to the SSB, i.e., System Information Block 1 (SIB1). Furthermore, the DRS may include RMSI-CORESET, which is a time and frequency resource region for control channel transmission for transmitting scheduling information for the RMSI. In other words, it may include CORESET, which is a time and frequency resource region for transmitting a PDCCH that schedules the PDSCH including SIB1. Furthermore, the DRS may include CSI-RS. Furthermore, the DRS may include other types of signals. Specifically, the DRS may include other system information (OSI) or paging. Therefore, when a base station transmits a DRS in the unlicensed band, the base station can multiplex the DRS with a physical channel or signal. At this point, the question is how the base station performs channel access. In particular, the question is how the base station uses one of the various channel access methods described above and sets the parameters used for channel access. Furthermore, the DRS may include an SSB or an SSB burst set transmission.

[0123] In one embodiment of the present invention, when a base station multiplexes a DRS with unicast data, the base station may perform channel access for transmission of the multiplexed DRS and unicast data, in which random backoff is performed using a variable-size CW, and the size of the CW is determined by a channel access priority class. In this case, the terminal may perform channel access according to the channel access priority class of the multiplexed unicast data. Specifically, the channel access method may be the first type of channel access described above.

[0124] These embodiments describe the case where a base station multiplexes DRS with signals or information other than unicast data. Signals or information other than unicast data may represent signals or channels that are not data traffic and for which a channel access priority class cannot be established. Signals or information other than unicast data may include control messages related to initial connection, random access, mobility, or paging. Furthermore, signals or information other than unicast data may include transmissions that include only reference signals. Furthermore, signals or information other than unicast data may include transmissions that include only PDCCH. A transmission that includes only PDCCH may include at least one of a RACH message-4 under a random access procedure, a handover command, a group-common PDCCH, a short paging message, other system information (OSI), paging, and a random access response (RAR). Signals or information other than unicast data may also be transmitted via PDCCH and PDSCH. For convenience of explanation, signals or information other than unicast data are referred to as non-unicast data. Furthermore, multiplexing DRS with non-unicast data herein may indicate that the corresponding transmission does not include unicast data. In a specific embodiment, when a base station multiplexes DRS with non-unicast data, the base station may perform channel access in which only a single-time-interval-based LBT is performed for transmission of the multiplexed DRS and non-unicast data. The channel access in which only a single-time-interval-based LBT is performed may be the second type of channel access described above. In this case, the duration of the single time interval may be 25 us or 34 us.

[0125] In yet another specific embodiment, when a base station multiplexes DRS with non-unicast data, the base station may perform random backoff using a variable-sized CW for the transmission in which DRS and non-unicast data are multiplexed, and perform channel access in which the size of the CW is determined by the channel access priority class. This embodiment takes into account that single-time-interval-based LBT can be performed only if the total duration of a transmission including only DRS is 1 ms or less and the duty cycle of the DRS transmission is 1 / 20 or less. In such an embodiment, the base station may use the channel access priority class with the highest priority (e.g., channel access priority class #1). This allows the base station to prioritize non-unicast data over channel access compared to unicast data. Furthermore, while using the channel access priority class with the highest priority, the base station may use the smallest CW size allowed by the corresponding channel access priority class. In yet another specific embodiment, while using the channel access priority class with the highest priority, the base station may use the largest CW size allowed by the corresponding channel access priority class.

[0126] In yet another specific embodiment, when a base station multiplexes DRS with non-unicast data, the base station may perform channel access with random backoff using a fixed-size CW for the transmission of multiplexed DRS and non-unicast data. In this case, the channel access method may be the above-mentioned Category 3 channel access. In such an embodiment, the base station may use the channel access priority class with the highest priority (e.g., channel access priority class #1). This allows the base station to prioritize channel access for non-unicast data over unicast data. Furthermore, while using the channel access priority class with the highest priority, the base station may use the smallest CW size allowed by the corresponding channel access priority class. In yet another specific embodiment, while using the channel access priority class with the highest priority, the base station may use the largest CW size allowed by the corresponding channel access priority class.

[0127] When a base station transmits non-unicast data that is not multiplexed with a DRS, the base station may perform channel access for transmitting the non-unicast data using a channel access method used when multiplexing the non-unicast data and a DRS. Specifically, when a base station transmits non-unicast data that is not multiplexed with a DRS, the base station may use a channel access type and channel access parameters used when multiplexing the non-unicast data and a DRS.

[0128] In yet another specific embodiment, when a base station transmits non-unicast data that is not multiplexed with a DRS, the base station may perform channel access for the non-unicast data transmission, in which random backoff is performed using a variable-sized CW, and the size of the CW is determined according to the channel access priority class. Specifically, the channel access method may be the first type channel access described above. In such an embodiment, the base station may use a channel access priority class with the highest priority (e.g., channel access priority class #1). This allows the base station to prioritize channel access for non-unicast data over unicast data. Furthermore, while using the channel access priority class with the highest priority, the base station may use the smallest CW size among the CW sizes allowed for that channel access priority class. In yet another specific embodiment, while using the channel access priority class with the highest priority, the base station may use the largest CW size among the CW sizes allowed for that channel access priority class.

[0129] In yet another specific embodiment, when a base station transmits non-unicast data that is not multiplexed with a DRS, the base station may perform channel access with random backoff using a fixed-size CW for the non-unicast data transmission. In this case, the channel access method may be the above-mentioned Category 3 channel access. In such an embodiment, the base station may use a channel access priority class with the highest priority (e.g., channel access priority class #1). This allows the base station to prioritize channel access for non-unicast data over unicast data. Furthermore, while using the channel access priority class with the highest priority, the base station may use the smallest CW size among the CW sizes allowed for that channel access priority class. In yet another specific embodiment, the base station may use a channel access priority class with the highest priority and use the largest CW size among the CW sizes allowed for that channel access priority class.

[0130] In the above-described embodiment, the base station determines the channel access method for a transmission in which DRS and non-unicast data or unicast data are multiplexed, regardless of the duration of the transmission in which DRS and non-unicast data or unicast data are multiplexed and the duty cycle of the DRS transmission. When the base station determines the channel access method, the base station can treat a transmission including only DRS and a transmission in which DRS and non-unicast data are multiplexed in the same way. Specifically, the base station can determine the channel access method for a transmission in which DRS and non-unicast data or unicast data are multiplexed based on the duration of the transmission in which DRS and non-unicast data or unicast data are multiplexed and the duty cycle of the DRS transmission. The base station can determine the channel access method for a transmission in which DRS and non-unicast data or unicast data are multiplexed based on whether the duration of the transmission in which DRS and non-unicast data or unicast data is multiplexed is 1 ms or less and whether the duty cycle of the DRS transmission is 1 / 20 or less.

[0131] When a base station transmits a DRS and non-unicast data multiplexed transmission, the base station can select one of two channel access types depending on whether both of the following two conditions are met: the duration of the DRS and non-unicast data multiplexed transmission is 1 ms or less, and the duty cycle of the DRS transmission is 1 / 20 or less. One of the two channel access types is channel access in which only single-time-interval-based LBT is performed, and the other is channel access in which random backoff is performed using a variable-size CW, the size of which is determined by the channel access priority class. In a specific embodiment, if the duration of the DRS and non-unicast data multiplexed transmission is 1 ms or less and the duty cycle of the DRS transmission is 1 / 20 or less, the base station can perform channel access in which only single-time-interval-based LBT is performed for the DRS and non-unicast data multiplexed transmission. In this case, the duration of the single time interval may be 25 us. The single-time-interval-based LBT may be the second type of channel access described above. Furthermore, when the duration of the transmission in which DRS and non-unicast data are multiplexed is greater than 1 ms or the duty cycle of the DRS transmission is greater than 1 / 20, the base station may perform channel access for the transmission in which DRS and non-unicast data are multiplexed, in which random backoff is performed using a variable-size CW, and the size of the CW is determined by the channel access priority class. The base station may also select any channel access priority class. In this case, the base station may arbitrarily select any one of the channel access priority classes that satisfy the MCOT length condition according to the duration of the transmission in which DRS and non-unicast data are multiplexed. The base station may use the selected channel access priority class for channel access for the transmission in which DRS and non-unicast data are multiplexed.That is, the base station can use the CW size according to the selected channel access priority class for channel access. For example, the base station can use the channel access priority class with the highest priority (e.g., channel access priority class #1). This allows the base station to give higher priority to non-unicast data than to unicast data for channel access. Furthermore, while using the channel access priority class with the highest priority, the base station can use the smallest CW size among the CW sizes allowed for that channel access priority class. In yet another specific embodiment, while using the channel access priority class with the highest priority, the base station can use the largest CW size among the CW sizes allowed for that channel access priority class.

[0132] In this embodiment, when the base station can determine whether the terminal receives non-unicast data and whether the reception is successful, the base station can adjust the size of the CW based on the ratio of ACKs to NACKs. Specifically, the base station converts feedback information from the terminal regarding the non-unicast data received by the terminal into ACKs and NACKs, and can adjust the size of the CW based on the ratio of ACKs to NACKs. A channel access method in which random backoff is performed using a variable-sized CW and the size of the CW is determined according to a channel access priority class may be a first-type channel access.

[0133] As described above, the base station and the terminal can adjust the size of the CW based on HARQ feedback when accessing a channel using the CW. However, the base station and the terminal may not expect HARQ feedback for all or part of the non-unicast data. Furthermore, the base station and the terminal may not be able to determine whether the terminal or the base station has received all or part of the non-unicast data, respectively. Furthermore, when the base station and the terminal perform an initial access procedure, they may not be able to determine HARQ-ACK feedback for some of the downlink signals and channels and uplink signals and channels used during the initial access procedure. Furthermore, the base station and the terminal may not perform transmission for a specific channel access priority class and may not be able to determine HARQ-ACK feedback corresponding to the transmission for that channel access priority class. In such cases, a method for determining a CW to be used for channel access when transmitting a channel and signal including all or part of the non-unicast data for which HARQ feedback is not expected will be described. For convenience of explanation, the base station will be mainly described, but the following embodiments may also be applied to a terminal.

[0134] When the base station cannot determine HARQ-ACK feedback for a transmission associated with a channel access priority class that determines the size of the CW, the base station may perform channel access in which random backoff is performed within the CW corresponding to the channel access priority class. In this case, the base station may use the smallest CW size among the CW sizes allowed for the corresponding channel access priority class. In yet another specific embodiment, the base station may use the channel access priority class with the highest priority and use the largest CW size among the CW sizes allowed for the channel access priority class.

[0135] Furthermore, when the base station cannot determine whether the terminal has received all or part of non-unicast data for which HARQ feedback is not expected, the base station may perform channel access in which random backoff is performed within a fixed CW size for transmission in which the non-unicast data and DRS are multiplexed. Specifically, the base station may use a CW corresponding to any one of the channel access priority classes in the first type channel access described above. In a specific embodiment, the base station may use any one of the channel access priority classes that satisfy the MCOT length condition according to the duration of transmission in which non-unicast data and DRS are multiplexed in the first type channel access. The base station may use the channel access priority class with the highest priority. In a specific embodiment, the base station may use the channel access priority class with the highest priority among the channel access priority classes that satisfy the MCOT length condition according to the duration of transmission in which non-unicast data and DRS are multiplexed in the first type channel access. Furthermore, the base station may use the channel access priority class with the highest priority and use the smallest CW size among the CW sizes allowed for the channel access priority class. In yet another specific embodiment, the base station can use the channel access priority class with the highest priority and use the largest CW size among the CW sizes allowed for that channel access priority class.

[0136] In yet another specific embodiment, when the base station cannot determine whether the terminal has received all or part of non-unicast data for which HARQ feedback is not expected, the base station may perform the above-mentioned Category 3 channel access for a transmission in which the non-unicast data and DRS are multiplexed. The base station may use the channel access priority class with the highest priority. The base station may use the channel access priority class with the highest priority among the channel access priority classes that satisfy the MCOT length condition according to the duration of the transmission in which the non-unicast data and DRS are multiplexed. Furthermore, while using the channel access priority class with the highest priority, the base station may use the smallest CW size among the CW sizes allowed for that channel access priority class. In yet another specific embodiment, the base station may use the channel access priority class with the highest priority and use the largest CW size among the CW sizes allowed for that channel access priority class.

[0137] A base station may be unable to transmit an SSB due to a channel access (e.g., LBT) procedure failure. An SSB transmission window may be defined so that if a base station is unable to transmit an SSB at a configured location, it can transmit at another location. The SSB transmission window is a time period during which a base station can transmit an SSB and includes multiple SSB transmission candidate locations. If a base station is unable to start SSB transmission at one of the SSB transmission candidate locations, the base station can attempt SSB transmission at an SSB transmission candidate location later than the SSB transmission candidate location within the SSB transmission window. An SSB transmission candidate location is a time point at which a base station can start SSB transmission. If a terminal is unable to receive an SSB at one of the SSB transmission candidate locations within the SSB transmission window, the terminal can receive an SSB at an SSB transmission candidate location later than the SSB transmission candidate location within the SSB transmission window. At this time, the terminal can determine whether the base station was unable to start SSB transmission at the SSB transmission candidate location or whether the base station failed to transmit the SSB. In a specific embodiment, if a terminal fails to receive an SSB at any one SSB transmission candidate position within the SSB transmission window, the terminal can attempt SSB reception at the next SSB transmission candidate position within the SSB transmission window. After the terminal starts and completes SSB reception at any one SSB transmission candidate position, the terminal does not need to expect to receive any further SSBs within the SSB transmission window. Specifically, after the terminal starts and completes SSB reception at any one SSB transmission candidate position, the terminal does not need to attempt to receive any further SSBs within the SSB transmission window.

[0138] In yet another specific embodiment, if a terminal fails to receive a specific SSB at any one SSB transmission candidate position within an SSB transmission window, the terminal may attempt to receive the specific SSB at the next SSB transmission candidate position within the SSB transmission window. After the terminal starts receiving a specific SSB at any one SSB transmission candidate position and completes receiving the specific SSB, the terminal may no longer receive the specific SSB within the SSB transmission window. Specifically, after the terminal receives a specific SSB at any one SSB transmission candidate position, the terminal may no longer attempt to receive the specific SSB within the SSB transmission window.

[0139] In another specific embodiment, even after the terminal has completed reception of a specific SSB at any one SSB transmission candidate position, the terminal can attempt to receive the specific SSB within the corresponding SSB transmission window. In this case, the terminal can further receive the specific SSB and obtain a combining gain from the further received specific SSB. This embodiment may be applied not only to cases where multiple SSBs corresponding to different beam indexes are transmitted for beam operation, but also to cases where an omni-transmission (omni-TX) scheme is used. Specifically, it may also be applied to cases where the same SSB is repeatedly transmitted.

[0140] DRS LBT method

[0141] FIG. 13 is a diagram showing the positions of OFDM symbols occupied by SSBs according to an embodiment of the present invention within a slot containing 14 OFDM symbols.

[0142] Hereinafter, a channel access method for a DRS including one or more SSBs will be described with reference to Fig. 13. Specifically, a channel access method performed by a base station before transmitting a DRS will be described, which is a method for setting different LBTs depending on the number of SSBs included in the DRS transmitted by the base station.

[0143] Figure 13 shows the positions of OFDM symbols occupied by SSBs within a slot consisting of 14 OFDM symbols. SSB pattern A is the same as the positions of OFDM symbols occupied by SSBs in the NR system specified in 3GPP Rel. 15. In SSB pattern B, the OFDM symbols occupied by SSBs in the second half slot within one slot are located one symbol after SSB pattern A. Therefore, SSB pattern B is set so that the positions of OFDM symbols occupied by SSBs within one slot are symmetrical with each other on a half slot basis.

[0144] The base station may perform multiple transmissions and determine a channel access method for each of the multiple DRS transmissions if the total duration of the transmissions including the DRS is 1 ms or more.

[0145] When an unlicensed band in the 5 GHz band or the 6 GHz band is used, a base station can transmit up to n SSBs to the DRS. Here, the value of n may be 2, 4, or 8. The subcarrier spacing used for DRS transmission may be 15 kHz or 30 kHz. When the subcarrier spacing is 15 kHz, the duration of one slot may be 1 ms, and the number of SSBs that can be included in a 1 ms interval may be 2. When the subcarrier spacing is 30 kHz, the duration of one slot may be 0.5 ms, and the number of SSBs that can be included in a 1 ms interval may be 4. The total duration of DRS transmission, in which the duty cycle of DRS transmission is 1 / 20, may vary depending on the DRS transmission period setting.

[0146] As described above, the total duration of a transmission including DRS may be 1 ms or less, and the duty cycle of the DRS transmission may be 1 / 20 or less. In this case, when a base station performs a transmission including only DRS or a transmission in which DRS and non-unicast data are multiplexed, the base station may perform channel access in which only single-time-interval-based LBT is performed for the transmission. Channel access in which only single-time-interval-based LBT is performed may be the second type of channel access described above. The total duration of a transmission including DRS may be greater than 1 ms, or the duty cycle of the DRS transmission may be greater than 1 / 20. In this case, when a base station performs a transmission including only DRS or a transmission in which DRS and non-unicast data are multiplexed, the base station may perform channel access in which random backoff is performed using a variable-size CW for the transmission, and the size of the CW is determined according to the channel access priority class. In this case, the channel access method in which random backoff is performed using a variable-size CW, and the size of the CW is determined according to the channel access priority class may be the first type of channel access.

[0147] In one embodiment of the present invention, a method in which a base station performs single-time-interval-based LBT may be used, taking into account the characteristics of a transmission including DRS. When the total duration of transmissions including DRS is greater than 1 ms, the base station may determine a channel access method in 1-ms duration units. Specifically, when the total duration of transmissions including DRS is greater than 1 ms, the base station may perform multiple transmissions, each with a duration of 1 ms or less, and perform channel access including only single-time-interval-based LBT for each of the multiple transmissions. The base station may apply this embodiment only when the duty cycle of DRS transmission is 1 / 20 or less. This is because the ETSI regulation states that in the case of a transmission performed without LBT, a short control signal should not exceed 5% of the transmission. This embodiment allows the base station and the terminal to quickly perform initial connection and RRM measurement using SSB included in the DRS transmitted from the base station. For example, when the DRS transmission period is set to 40 ms or more and the base station transmits DRS within a 5 ms DRS transmission window at a minimum of every 40 ms period, the total duration of the transmissions including the DRS may be 2 ms or less, under the condition that the duty cycle of the DRS transmission is 1 / 20 or less. The base station may perform multiple DRS transmissions, each with a duration of 1 ms or less, under the constraint of a total duration of 2 ms or less including the DRS. In this case, the base station may perform second-type channel access before each of the multiple transmissions. This embodiment allows the base station to quickly transmit DRS to the terminal. Furthermore, when the DRS transmission period is set to 80 ms or more and the base station transmits DRS within a 5 ms DRS transmission window at a minimum of every 80 ms period, the total duration of the transmissions including the DRS may be 4 ms or less, under the constraint of a total duration of 4 ms or less including the DRS.At this time, the base station can perform second type channel access before each of the multiple transmissions.

[0148] Furthermore, when the total duration of transmissions including DRS is greater than 1 ms and the duty cycle of the DRS transmission is greater than 1 / 20, the base station may perform channel access for the transmissions including DRS, in which random backoff is performed using a variable-size CW and the size of the CW is determined by the channel access priority class. In this case, the channel access method may be the first type channel access.

[0149] In yet another specific embodiment, a portion of a transmission including a DRS may have a transmission duty cycle of 1 / 20 or less. In this case, the base station may perform channel access in which only single-time-interval-based LBT is performed for a portion of the transmission period of a transmission including a DRS with a duty cycle of 1 / 20 or less. In this embodiment, the base station may perform multiple transmissions, each having a duration of 1 ms or less, and perform channel access in which only single-time-interval-based LBT is performed for each of the multiple transmissions. In this case, the channel access in which only single-time-interval-based LBT is performed may be second-type channel access. In addition, the base station may perform channel access in which random backoff is performed using a variable-size CW, where the size of the CW is determined according to a channel access priority class, for the remaining transmission period of a transmission including a DRS. In this case, channel access in which random backoff is performed using a variable-size CW, where the size of the CW is determined according to a channel access priority class may be first-type channel access. For example, the period of the DRS transmission may be a multiple of 20 ms. Specifically, when the DRS transmission period is 20 ms, the duration of the transmission period in which the duty cycle of the DRS transmission is 1 / 20 or less is 1 ms. When the DRS transmission period is 40 ms, the duration of the transmission period in which the duty cycle of the DRS transmission is 1 / 20 or less is 2 ms. When the DRS transmission period is 60 ms, the duration of the transmission period in which the duty cycle of the DRS transmission is 1 / 20 or less is 3 ms. When the DRS transmission period is 80 ms, the duration of the transmission period in which the duty cycle of the DRS transmission is 1 / 20 or less is 4 ms. In this case, the base station may perform second type channel access for a part of the transmission period of the transmission including the DRS with a duty cycle of 1 / 20, and may perform first type channel access for the remaining transmission period of the transmission including the DRS.

[0150] The maximum number of SSBs that can be included in a DRS may be eight. In the following description, it is assumed that the number of SSBs included in a DRS is eight. When the DRS transmission period is 20 ms, the duration of a transmission period in which the DRS transmission duty cycle is 1 / 20 or less is 1 ms. Therefore, when the subcarrier spacing is 15 kHz, two SSBs may be included in a transmission period in which the DRS transmission duty cycle is 1 / 20 or less. In this case, the base station performs second-type channel access before performing the first transmission, and can transmit two SSBs if channel access is successful. Furthermore, the base station performs first-type channel access before performing the second transmission, and can transmit six SSBs if channel access is successful. Furthermore, when the DRS transmission period is 20 ms, the duration of a transmission period in which the DRS transmission duty cycle is 1 / 20 or less is 1 ms. Therefore, when the subcarrier spacing is 30 kHz, four SSBs may be included in a transmission period in which the DRS transmission duty cycle is 1 / 20 or less. In this case, the base station performs second type channel access before performing the first transmission and can transmit four SSBs if the channel access is successful.Also, the base station performs first type channel access before performing the second transmission and can transmit four SSBs if the channel access is successful.

[0151] When the DRS transmission period is 40 ms, the duration of the transmission interval in which the DRS transmission duty cycle is 1 / 20 or less is 2 ms. Therefore, when the subcarrier spacing is 15 kHz, the transmission interval in which the DRS transmission duty cycle is 1 / 20 or less may include four SSBs. In this case, the base station performs two transmissions with a duration of 1 ms, and each transmission can transmit two SSBs. The base station performs second-type channel access before the first transmission and can transmit two SSBs if channel access is successful. Also, the base station performs second-type channel access before the second transmission and can transmit two SSBs if channel access is successful. Also, the base station performs first-type channel access before the third transmission and can transmit the remaining four SSBs if channel access is successful. Furthermore, when the DRS transmission period is 40 ms, the duration of the transmission section in which the DRS transmission duty cycle is 1 / 20 or less is 2 ms, so when the subcarrier spacing is 30 kHz, the transmission section in which the DRS transmission duty cycle is 1 / 20 or less may include 8 SSBs. In this case, the base station performs second type channel access before performing the first transmission, and can transmit 4 SSBs if channel access is successful. Furthermore, the base station performs second type channel access before performing the second transmission, and can transmit 4 SSBs if channel access is successful.

[0152] In yet another specific embodiment, some intervals of a transmission including a DRS may have a duration of 1 ms or less, and the DRS transmission duty cycle may be 1 / 20 or less. In this case, the base station may perform channel access in which only single-time-interval-based LBT is performed for some intervals of a transmission including a DRS, which has a duty cycle of 1 / 20 or less and a duration of 1 ms or less. In this case, the channel access in which only single-time-interval-based LBT is performed may be second-type channel access. In addition, the base station may perform channel access in which random backoff is performed using a variable-size CW for the remaining transmission interval, and the size of the CW is determined according to a channel access priority class. In this case, channel access in which random backoff is performed using a variable-size CW, and the size of the CW is determined according to a channel access priority class may be first-type channel access.

[0153] The maximum number of SSBs that can be included in a DRS may be 8. In the following description, it is assumed that the number of SSBs included in a DRS is 8.

[0154] When the DRS transmission period is 20 ms, the duration of the transmission period in which the DRS transmission duty cycle is 1 / 20 or less is 1 ms. Therefore, when the subcarrier spacing is 15 kHz, two SSBs may be included in the transmission period in which the DRS transmission duty cycle is 1 / 20 or less. In this case, the base station performs second-type channel access before performing the first transmission, and can transmit two SSBs if channel access is successful. Also, the base station performs first-type channel access before performing the second transmission, and can transmit six SSBs if channel access is successful. Also, when the DRS transmission period is 20 ms, the duration of the transmission period in which the DRS transmission duty cycle is 1 / 20 or less is 1 ms. Therefore, when the subcarrier spacing is 30 kHz, four SSBs may be included in the transmission period in which the DRS transmission duty cycle is 1 / 20 or less. In this case, the base station performs second-type channel access before performing the first transmission, and can transmit four SSBs if channel access is successful. Furthermore, the base station performs first type channel access before performing the second transmission, and can transmit four SSBs if the channel access is successful.

[0155] When the DRS transmission period is 40 ms, the duration of the transmission period in which the DRS transmission duty cycle is 1 / 20 or less is 2 ms. When the subcarrier spacing is 15 kHz, the transmission period in which the DRS transmission duty cycle is 1 / 20 or less may include two SSBs and have a 1 ms duration. The base station performs second-type channel access before performing the first transmission, and can transmit two SSBs if channel access is successful. The base station also performs first-type channel access before performing the second transmission, and can transmit the remaining six SSBs if channel access is successful. When the DRS transmission period is 40 ms, the duration of the transmission period in which the DRS transmission duty cycle is 1 / 20 or less is 2 ms. When the subcarrier spacing is 30 kHz, the transmission period in which the DRS transmission duty cycle is 1 ms or less may include four SSBs. In this case, the base station performs second type channel access before performing the first transmission, and can transmit four SSBs if the channel access is successful.Also, the base station performs first type channel access before performing the second transmission, and can transmit four SSBs if the channel access is successful.

[0156] The DRS transmission window duration may be set to T ms, where T may be a natural number greater than or equal to 1. T may be 5 or 6. Alternatively, T may be set to a multiple of the smallest time interval in which the maximum possible number of SSBs included in the DRS can be included. If the duration of the DRS transmission window is 1 ms or greater, the base station may perform channel access in which only single-time-interval-based LBT is performed within the last 1 ms of the DRS transmission window. In this case, if the DRS transmission duty cycle for the last 1 ms of the DRS transmission window is 1 / 20 or less, the base station may perform channel access in which only single-time-interval-based LBT is performed within the last 1 ms of the DRS transmission window. The channel access in which only single-time-interval-based LBT is performed may be the above-mentioned second type channel access. Furthermore, the base station may perform first type channel access or second type channel access within the last 1 ms of the DRS transmission window. This embodiment allows the terminal to quickly perform initial access and RRM measurement.

[0157] FIG. 14 is a block diagram showing the configurations of a terminal and a base station according to an embodiment of the present invention.

[0158] In one embodiment of the present invention, the terminal may be embodied as any of various types of wireless communication devices or computing devices that ensure portability and mobility. The terminal may be referred to as a UE, a Station (STA), a Mobile Subscriber (MS), etc. In addition, in an embodiment of the present invention, a base station controls and manages cells (e.g., macrocells, femtocells, picocells, etc.) corresponding to a service area, and performs functions such as signal transmission, channel assignment, channel monitoring, self-diagnosis, and relaying. The base station may be referred to as a next generation NodeB (gNB) or an Access Point (AP), etc.

[0159] 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 .

[0160] First, the processor 110 executes various commands or programs to process data within the terminal 100. The processor 110 also controls the overall operation of the terminal 100, including each unit, and controls the transmission and reception of data between the units. Here, the processor 110 is configured to perform operations according to the embodiments described in the present invention. For example, the processor 110 may receive slot configuration information, determine the slot configuration based on the information, and perform communication according to the determined slot configuration.

[0161] Next, the communication module 120 is an integrated module that performs wireless communication using a wireless communication network and wireless LAN access using a wireless LAN. To this end, the communication module 120 includes multiple network interface cards (NICs) built in or externally mounted, such as cellular communication interface cards 121 and 122 and an unlicensed band communication interface card 123. Although the communication module 120 is shown as an integrated module in the drawings, the network interface cards may be independently arranged depending on the circuit configuration or application, unlike the drawings.

[0162] The cellular communication interface card 121 transmits and receives wireless signals to and from at least one of the base station 200, an external device, and a server via a mobile communication network, and provides cellular communication services using a first frequency band based on instructions from the processor 110. According to one embodiment, the cellular communication interface card 121 includes at least one NIC module that utilizes a frequency band below 6 GHz. The at least one NIC module of the cellular communication interface card 121 independently performs cellular communication with at least one of the base station 200, the external device, and the server in accordance with a cellular communication standard or protocol for the frequency band below 6 GHz supported by the corresponding NIC module.

[0163] The cellular communication interface card 122 transmits and receives wireless signals to and from at least one of the base station 200, an external device, and a server using a mobile communication network, and provides cellular communication services in the second frequency band based on instructions from the processor 110. According to one embodiment, the cellular communication interface card 122 includes at least one NIC module that uses a frequency band above 6 GHz. The at least one NIC module of the cellular communication interface card 122 independently performs cellular communication with at least one of the base station 200, the external device, and the server in accordance with the cellular communication standard or protocol for the frequency band above 6 GHz supported by the corresponding NIC module.

[0164] The unlicensed band communication interface card 123 transmits and receives wireless signals to and from at least one of the base station 200, an external device, and a server via the third frequency band, which is an unlicensed band, and provides unlicensed band communication services based on instructions from the processor 110. The unlicensed band communication interface card 123 includes at least one NIC module that uses the unlicensed band. For example, the unlicensed band may be 2.4 GHz, 5 GHz, 6 GHz, 7 GHz, or 52.6 GHz or higher. The at least one NIC module of the unlicensed band communication interface card 123 independently or dependently performs cellular communication with at least one of the base station 200, the external device, and the server according to the unlicensed band communication standard or protocol of the frequency band supported by the corresponding NIC module.

[0165] 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.

[0166] Next, the user interface 140 includes various types of input / output means provided in the terminal 100. That is, the user interface unit 140 receives user input using various input means, and the processor 110 controls the terminal 100 based on the received user input. Also, the user interface 140 performs output based on instructions from the processor 110 using various output means.

[0167] The display unit 150 then outputs various images to a display screen, and displays various display objects such as content or a user interface based on a control command from the processor 110.

[0168] 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 .

[0169] 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 the transmission and reception of data between the units. Here, the processor 210 is configured to perform operations according to the embodiments described herein. For example, the processor 210 may signal slot configuration information and perform communication according to the signaled slot configuration.

[0170] Next, the communication module 220 is an integrated module that performs wireless communication using a wireless communication network and wireless LAN access using a wireless LAN. To this end, the communication module 220 includes multiple network interface cards, such as cellular communication interface cards 221 and 222 and an unlicensed band communication interface card 223, either built-in or externally mounted. In the drawings, the communication module 220 is shown as an integrated module, but the network interface cards may be arranged independently depending on the circuit configuration or application, unlike in the drawings.

[0171] 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 using a first frequency band based on instructions from the processor 210. According to one embodiment, the cellular communication interface card 221 includes at least one NIC module using a frequency band below 6 GHz. The at least one NIC module of the cellular communication interface card 221 independently performs cellular communication with at least one of the terminal 100, the external device, and the server according to a cellular communication standard or protocol for the frequency band below 6 GHz supported by the corresponding NIC module.

[0172] The cellular communication interface card 222 transmits and receives wireless signals to and from at least one of the terminal 100, an external device, and a server using a mobile communication network, and provides cellular communication services using the second frequency band based on instructions from the processor 210. According to one embodiment, the cellular communication interface card 222 includes at least one NIC module that uses a frequency band above 6 GHz. The at least one NIC module of the cellular communication interface card 222 independently performs cellular communication with at least one of the terminal 100, the external device, and the server according to a cellular communication standard or protocol for the frequency band above 6 GHz that the corresponding NIC module supports.

[0173] The unlicensed band communication interface card 223 transmits and receives wireless signals to and from at least one of the terminal 100, an external device, and a server using the third frequency band, which is an unlicensed band, and provides unlicensed band communication services based on instructions from the processor 210. The unlicensed band communication interface card 223 includes at least one NIC module that uses the unlicensed band. For example, the unlicensed band may be 2.4 GHz, 5 GHz, 6 GHz, 7 GHz, or 52.6 GHz or higher. The at least one NIC module of the unlicensed band communication interface card 223 independently or dependently performs cellular communication with at least one of the terminal 100, an external device, and a server according to the unlicensed band communication standard or protocol of the frequency band supported by the corresponding NIC module.

[0174] The terminal 100 and base station 200 shown in Figure 14 are block diagrams according to one embodiment of the present invention, and the separate blocks indicate logically distinct device elements. Therefore, the above-described device elements may be mounted on one chip or multiple chips depending on the device design. In addition, some components of the terminal 100, such as the user interface 140 and the display unit 150, may be selectively provided in the terminal 100. In addition, the user interface 140 and the display unit 150 may be additionally provided in the base station 200 as needed.

[0175] In the following, this specification will describe a channel access method that a base station performs before transmitting a downlink channel in a wireless communication system using an unlicensed band. More specifically, this specification will describe what channel access priority class (CAPC) a base station should use when accessing a channel to transmit a downlink control channel (e.g., PDCCH).

[0176] When a base station performs channel access before transmitting a downlink control channel, different channel access priority classes should be applied depending on various information transmitted over the downlink control channel and the transmission time of the downlink control channel. Typically, when a PDSCH including unicast data scheduled over a PDCCH is transmitted on the same slot of the same carrier as the PDCCH, the base station can set a CAPC according to the type of traffic of the unicast data included in the PDSCH. Then, according to the set CAPC, the base station can perform channel access for transmitting the PDCCH and the PDSCH on the same slot of the same carrier. However, for transmission of PDCCHs other than the PDCCH for scheduling the PDSCH including unicast data transmitted on the same slot of the same carrier as the PDCCH, it may be unclear which CAPC the base station should select when performing channel access. Therefore, in this invention, we will explain which CAPC a base station should select to perform channel access for PDCCH transmission depending on the information transmitted via PDCCH, the scheduling time of PDCCH and PDSCH, and whether the PDSCH scheduled by PDCCH is transmitted on the same carrier as the PDCCH or on a different carrier.

[0177] When a base station transmits a downlink control channel (e.g., PDCCH) to a terminal, the information transmitted via the PDCCH may be various information as follows. In this case, the base station may transmit PDCCHs each including the various information individually, or may transmit multiple PDCCHs including each information within one control resource set (CORESET). The CORESET may refer to a resource region in which the PDCCHs are transmitted.

[0178] Various types of information transmitted via the PDCCH will be described, i.e., various DCI formats that can be transmitted via the PDCCH will be described.

[0179] 1. DCI format for downlink shared channel (PDSCH) transmission transmitted via PDCCH

[0180] 1-A. DCI format for scheduling a PDSCH containing unicast data transmitted on one or more slots including the same slot as the transmission time of the PDCCH on the same carrier as the PDCCH

[0181] 1-B. DCI format for scheduling a PDSCH containing unicast data that is transmitted on a slot different from the transmission time of the PDCCH of the same carrier as the PDCCH

[0182] 1-C. DCI format for scheduling PDSCH containing unicast data transmitted on a slot of a carrier different from that of the PDCCH

[0183] 1-D. DCI format for instructing PDSCH reception under Semi-Persistent Scheduling (SPS)

[0184] 1-E.SPS DCI format for instructing release of PDSCH reception

[0185] 2. DCI format for uplink shared channel (PUSCH) transmission transmitted via PDCCH

[0186] 2-A. DCI format for scheduling a PUSCH containing unicast data to be transmitted by a terminal on one or more slots including the same slot as the transmission time of the PDCCH of the same carrier as the PDCCH

[0187] 2-B. DCI Format for Scheduling PUSCH Including Unicast Data Transmitted by a Terminal on a Slot Different from the Transmission Time of the PDCCH of the Same Carrier as the PDCCH

[0188] 2-C. DCI format for scheduling PUSCH containing unicast data transmitted by a terminal on a slot of a carrier different from that of the PDCCH

[0189] 2-D. DCI format for indicating activation of configured grant PUSCH

[0190] 2-E. DCI format for instructing release of configured grant PUSCH

[0191] 2-F. DCI format indicating downlink feedback information for configured grant PUSCH

[0192] 3. DCI formats for other purposes (excluding those for uplink / downlink shared channel (PUSCH / PDSCH) transmission) transmitted via PDCCH

[0193] 3-A. DCI format for informing a group of UEs of slot format, available RB set, channel occupancy time (COT) duration, and search space set group switching

[0194] 3-B. DCI Format to Signal PRB and OFDM Symbols so Terminals Can Assume No Intended Transmission

[0195] 3-C. DCI format for informing a group of UEs of TPC (Transmit Power Control) command transmission for PUCCH and PUSCH

[0196] DCI format for informing one or more UEs of a TPC group (a group of TPC) command transmission for 3-D.SRS (Sounding Reference Signal) transmission

[0197] When the DCI formats transmitted via the above-mentioned PDCCHs 1 to 3 are multiplexed with a PDSCH containing unicast data, the base station can select a CAPC based on the traffic type of the unicast data included in the PDSCH.

[0198] However, in cases where the DCI format is not multiplexed with the PDSCH containing unicast data transmitted in a slot different from the slot in which the PDCCH is transmitted, as in the above-mentioned 1-B to 1-E, 2-A to 2-F, and 3-A to 3-D, but is transmitted independently in one slot via the PDCCH, or in cases where the DCI format scheduling the PUSCH containing unicast data is transmitted in one slot via the PDCCH (for example, the above-mentioned 2-A to 2-F), it is necessary to define which CAPC the base station should select to perform channel access when accessing the channel for PDCCH transmission.

[0199] When the DCI format is not multiplexed with a PDSCH including unicast data transmitted in a slot different from the slot in which the PDCCH is transmitted, the base station may select a CAPC with the highest priority to perform channel access for the transmission of the PDCCH. When the base station performs channel access using a CAPC with the highest priority, it has the effect of increasing the channel access priority for the transmission of the control channel (i.e., the PDCCH).

[0200] When the DCI format is not multiplexed with a PDSCH including unicast data transmitted in a slot different from the slot in which the PDCCH is transmitted, the base station can select the CAPC with the lowest priority to perform channel access for transmitting the PDCCH. When the base station performs channel access using the CAPC with the lowest priority, the base station can perform channel access using the longest MCOT (Maximum Channel Occupancy Time) among the CAPCs. This is because the longest MCOT is set to the CAPC with the lowest priority. Therefore, within the MCOT set by the CAPC with the lowest priority, control channels and data channels having the same CAPC as the CAPC with the lowest priority and CAPCs with higher priorities can be multiplexed and transmitted in slots after channel access.

[0201] There may be a method in which the base station selects a CAPC for each of the above-mentioned DCI formats 1 to 3. Specifically, when the DCI format transmitted over the PDCCH is multiplexed with a PDSCH including unicast data, the base station selects a CAPC according to the traffic type of the unicast data included in the PDSCH. For example, when the above-mentioned two DCI formats transmitted over the PDCCH schedule a PUSCH including unicast data, the base station may select a CAPC according to the traffic type of the unicast data included in the PUSCH.

[0202] In the above-mentioned three DCI formats transmitted via the PDCCH for a specific purpose, the base station can perform channel access using the CAPC with the highest priority to increase the channel access priority. This is because information for a specific purpose must be transmitted in the DCI. On the other hand, when the above-mentioned three DCI formats are transmitted via the PDCCH for a specific purpose, the base station can use the CAPC with the lowest priority when performing channel access. When the base station performs channel access using the CAPC with the lowest priority, the base station can perform channel access using the longest MCOT (Maximum Channel Occupancy Time) among the CAPCs. This is because the longest MCOT is set for the CAPC with the lowest priority. Therefore, there is an effect that control channels and data channels having the same CAPC as the lowest priority CAPC and CAPCs with higher priorities within the MCOT set by the CAPC with the lowest priority can be multiplexed and transmitted in slots after channel access. In other words, the above-mentioned three DCI formats may refer to DCI formats that do not include information for scheduling uplink / downlink channels (e.g., PUSCH, PDSCH).

[0203] When each of the above DCI formats 1 to 3 is transmitted via the PDCCH, the base station can select a CAPC for channel access according to each DCI format. A specific CAPC selection method is shown in Table 4.

[0204] [Table 4-1] [Table 4-2] [Table 4-3]

[0205] Each of the above-mentioned DCI formats 1 to 3 may be transmitted over one PDCCH, and one or more PDCCHs may be multiplexed within a CORESET and transmitted from a base station to a terminal. Therefore, when one or more PDCCHs are multiplexed within a CORESET, the base station needs to select which CAPC to select for channel access when accessing a channel to transmit one or more PDCCHs in the time and frequency domains including one or more PDCCHs.

[0206] When there is one or more PDCCHs multiplexed in a CORESET, the base station can perform channel access using the CAPC with the lowest priority among the CAPCs set for each PDCCH. When the base station performs channel access using the CAPC with the lowest priority, the base station can perform channel access using the longest MCOT (Maximum Channel Occupancy Time) among the CAPCs. This is because the longest MCOT is set for the CAPC with the lowest priority. Therefore, there is an effect that control channels and data channels having the same CAPC as the lowest priority CAPC and CAPCs with higher priorities within the MCOT set by the CAPC with the lowest priority can be multiplexed and transmitted in slots after channel access.

[0207] On the other hand, if there is one or more PDCCHs multiplexed within the CORESET, the base station can perform channel access using the CAPC that is set when a specific PDCCH schedules a PDSCH or PUSCH containing unicast data, or can perform channel access using the CAPC that is set when the PDCCH and PDSCH are multiplexed.

[0208] The above-mentioned highest priority CAPC and lowest priority CAPC may refer to the CAPC with the highest priority (e.g., p=1) and the lowest priority (e.g., p=4) among the multiple CAPCs already set (see Table 4).

[0209] FIG. 15 is a diagram illustrating a downlink channel access procedure according to one embodiment of the present invention.

[0210] Figure 15 shows a downlink channel access procedure used during UE initiated Channel Occupancy Time (COT) sharing. Figure 15(a) shows an example of the downlink channel access procedure when the gap is less than 16 us, Figure 15(b) shows an example of the downlink channel access procedure when the gap is 16 us, and Figure 15(c) shows an example of the downlink channel access procedure when the gap is 25 us.

[0211] For uplink (e.g., PUSCH) transmissions on scheduled or configured resources, a terminal can use a Category 4 channel access procedure to obtain terminal initiation channel occupancy, which the terminal can then share with the base station for base station transmissions.

[0212] When information about the Energy Detection (ED) threshold is set

[0213] The UE may receive an energy detection (ED) threshold to be applied when acquiring channel occupancy from the base station. For example, the base station may transmit 'ULtoDL-CO-SharingED-Threshold-r16' to the UE as an RRC parameter for the ED threshold, thereby configuring the ED threshold. When the UE shares channel occupancy with the base station, the base station may transmit a specific channel or a specific signal. In this case, the uplink transmission may be a configured grant (CG)-PUSCH or a scheduled uplink (e.g., scheduled grant PUSCH) transmission. The downlink transmission of the base station may be performed after the uplink transmission of the UE. In this specification, the CG uplink transmission (e.g., CG-PUSCH) may refer to uplink transmission (e.g., CG-PUSCH) performed by the UE on the pre-configured resources after the base station semi-statically configures resources for uplink transmission in the UE.

[0214] When the uplink transmission performed by the terminal is CG-PUSCH, the terminal may receive a table for sharing channel occupancy from the base station. Specifically, a table for sharing information related to channel occupancy between the base station and the terminal (e.g., channel occupancy time (COT)) may be configured by an RRC parameter 'COT-SharingList-r16' from the base station. In addition, the terminal may receive channel occupancy information corresponding to each row of the table from the base station. For example, the channel occupancy information corresponding to each row of the table may be provided by an RRC parameter 'cg-COT-Sharing-r16'. In this case, one of the rows of the table may be configured to indicate that channel occupancy is not shared. When a terminal shares its initiated channel occupation with a base station to perform CG-PUSCH transmission, the terminal can indicate a row index corresponding to a row of a table set by the base station according to 'COT sharing information' included in the uplink control information (CG-UCI) of the CG-PUSCH. That is, when the terminal indicates an index corresponding to a row providing channel occupation information, the base station can perform downlink transmission by assuming one or more values ​​corresponding to the channel occupation information indicated by the table row indicated by the index. Specifically, the channel occupation information may include duration, offset, CAPC, etc. The duration may refer to the number of slots available (assumable) for downlink transmission within the channel occupation time initiated by the terminal. The offset refers to the time interval (difference) from the end of the slot where the base station detects CG-UCI to the slot where the downlink transmission performed by the base station begins. CAPC refers to the CAPC assumed when the terminal shares its initiated channel occupation with the base station.

[0215] If the Energy Detection (ED) threshold information is not set

[0216] The base station may not set the ED threshold in the terminal. In other words, the terminal may not receive the ED threshold from the base station. That is, the base station may not configure the terminal with 'ULtoDL-CO-SharingED-Threshold-r16' as an RRC parameter for the ED threshold, and may not configure the ED threshold in the terminal. In this case, if the uplink transmission performed by the terminal is a CG-PUSCH, the CG-UCI of the CG-PUSCH may include 'COT sharing information' indicating whether channel occupation is shared. If the terminal indicates that channel occupation is shared using the CG-UCI (e.g., if the value of the COT sharing information is 1), the terminal may accept X symbols set by the base station as symbols for downlink transmission performed by the base station. Specifically, the terminal may receive an RRC parameter 'cg-COT-SharingOffset-r16' indicating X symbols for downlink transmission from the base station, and the base station may accept X symbols as shared channel occupation initiated by the terminal for downlink transmission. In this case, X symbols refer to the last X symbols of slot n (slot #n) in which the base station detects CG-UCI.

[0217] In this case, the downlink transmission of the base station may be performed after the uplink transmission of the terminal, and the length of the downlink transmission may be limited to a maximum of 2 symbols, 4 symbols, or 8 symbols depending on the subcarrier spacing. When the subcarrier spacing is 15 kHz, the downlink transmission may be limited to a maximum of 2 symbols, when the subcarrier spacing is 30 kHz, the downlink transmission may be limited to a maximum of 4 symbols, and when the subcarrier spacing is 60 kHz, the downlink transmission may be limited to a maximum of 8 symbols.

[0218] The following describes downlink transmission performed by the base station after uplink transmission by the terminal. At this time, the downlink transmission performed by the base station may be transmission that corresponds to whether the base station has transmitted (configured) RRC parameters for the ED threshold to the terminal or has not transmitted (configured) them.

[0219] i) When the base station configures 'ULtoDL-CO-SharingED-Threshold-r16' as an RRC parameter for the ED threshold in the UE and the ED threshold is configured, after the UE performs uplink (e.g., PUSCH) transmission on scheduled resources or configured resources, the base station can perform downlink transmission including only the DRS. The DRS in this specification may include a primary synchronization signal (PSS), a secondary synchronization signal (SSS), a physical broadcast channel (PBCH), and at least one SSB including a DM-RS for the PBCH. The DRS may also include a PDSCH carrying system information block 1 (SIB1) and a CORESET for a PDCCH scheduling the PDSCH. The DRS may also include non-zero power CSI reference signals.

[0220] Meanwhile, if the ED threshold is not configured because the base station does not configure 'ULtoDL-CO-SharingED-Threshold-r16' as an RRC parameter for the ED threshold in the terminal, downlink transmission including only DRS may be performed only when the subcarrier spacing is 30 KHz or more, because the number of symbols occupied by SSBs included in the DRS is a minimum of four.

[0221] ii) After a terminal performs uplink (e.g., PUSCH) transmission on a scheduled or configured resource, the base station may perform downlink transmission including a DRS, in which non-unicast transmission for any terminal may be multiplexed.

[0222] iii) After the terminal performs uplink (e.g., PUSCH) transmission on a scheduled or configured resource, the base station may perform downlink transmission, which may include a reference signal (e.g., CSI-RS, Tracking RS, etc.) for the terminal that has started channel occupation and a non-unicast transmission for any terminal.

[0223] iv) After a terminal performs uplink (e.g., PUSCH) transmission on a scheduled resource or a configured resource, the base station may perform downlink transmission. In this case, the downlink transmission performed by the base station does not include user plane data for the terminal that has started channel occupation, but may include unicast transmission including control plane data (e.g., data for RRC configuration) and non-unicast transmission for any terminal.

[0224] When the channel occupation initiated by the terminal is shared with the base station, after the uplink transmission performed by the terminal, the base station can perform channel access based on a gap smaller than the specific gap or the specific gap, and can perform the downlink transmissions i) to iv) described above. The channel access procedure of the base station will be described below.

[0225] If the gap is less than 16 us, the base station can perform downlink transmission after performing a Type 2C downlink channel access procedure. The Type 2C downlink channel access procedure means that the base station performs downlink transmission without performing channel sensing before downlink transmission. The duration for downlink transmission may be limited to a maximum of 584 us (see 3GPP TS 37.213).

[0226] [Table 5]

[0227] If the gap is 16 us, the base station can perform downlink transmission after performing a Type 2B downlink channel access procedure. The Type 2B downlink channel access procedure means that the base station senses whether the channel is idle within a 16 us (T_f) interval before performing downlink transmission and then immediately performs downlink transmission. 16 us (T_f) can include one sensing slot within the last 9 us of the 16 us. If the channel is sensed as idle during the entire interval (e.g., at least 5 us), including the interval during which sensing is performed (e.g., at least 4 us), the channel can be considered to be idle. (See 3GPP TS 37.213)

[0228] [Table 6]

[0229] If the gap is 25 us, the base station can perform downlink transmission after performing a Type 2A downlink channel access procedure. The Type 2A downlink channel access procedure means that the base station senses whether the channel is idle during a 25 us (T_short_dl) sensing period before performing downlink transmission and then immediately performs downlink transmission. The 25 us (T_short_dl) sensing period may consist of a 16 us (T_f) period and one sensing slot (9 us) immediately following the 16 us (T_f) period. The 16 us (T_f) period may include one sensing slot (9 us). If the 25 us (T_short_dl) sensing period (i.e., all sensing slots) are sensed as idle, the channel may be considered to be idle for the 25 us (T_short_dl) period. (See 3GPP TS 37.213.)

[0230] [Table 7]

[0231] FIG. 16 is a diagram illustrating scheduled uplink transmission according to one embodiment of the present invention.

[0232] Specifically, FIG. 16 shows scheduled uplink (UL) transmissions that a terminal performs when the terminal is scheduled by a base station to perform autonomous transmission or continuous uplink transmissions without gaps after resources configured for CG-PUSCH.

[0233] When the terminal is configured to perform the scheduled uplink transmission, the terminal may perform the scheduled uplink transmission without channel access when the following condition is met: An uplink transmission on a resource configured for autonomous transmission or CG-PUSCH may be dropped at the last symbol of a slot (e.g., the (n-1)th slot) before the start of a slot (e.g., the nth slot) for the scheduled uplink transmission.

[0234] The following describes the conditions under which a terminal can perform scheduled uplink transmission without channel access.

[0235] a) The terminal shall perform Category 4 channel access (e.g., Type 1 uplink channel access) for autonomous transmission or uplink transmission on resources configured for CG-PUSCH, and the terminal shall perform autonomous transmission or uplink transmission on resources configured for CG-PUSCH before the start of the slot for scheduled uplink transmission.

[0236] b) As for frequency domain resources for scheduled uplink transmission, all resource blocks (RBs) of an LBT bandwidth (e.g., 20 MHz) that can be occupied by the first scheduled slot among the time domain resources configured for the scheduled uplink transmission should be scheduled. Alternatively, all RBs of an uplink bandwidth part (Band Width Part, BWP) configured for the UE should be scheduled. In this case, the starting symbol index of the first scheduled slot among the time domain resources configured for the CG-PUSCH may be 0. Alternatively, multiple LBT bandwidths may exist within one BWP. In this case, if resources for autonomous transmission or resources configured for the CG-PUSCH are assigned to one or more LBT bandwidths within one BWP, the frequency domain resources for scheduled uplink transmission may occupy all RBs of one subset of the one or more LBT bandwidths, or all RBs of all LBT bandwidths including the resources for autonomous transmission or resources configured for the CG-PUSCH.

[0237] c) The CAPC used when the terminal performs Category 4 channel access (e.g., Type 1 uplink channel access) for autonomous transmission or uplink transmission on resources configured for CG-PUSCH must be greater than or equal to the CAPC indicated by the base station for scheduled uplink transmission.

[0238] d) The sum of the length of an uplink transmission on resources configured for autonomous transmission or CG-PUSCH and the length of a scheduled uplink transmission shall not exceed the Maximum Channel Occupancy Time (MCOT), where MCOT is the MCOT configured when the terminal performs Category 4 channel access (e.g., Type 1 uplink channel access) for uplink transmission on resources configured for autonomous transmission or CG-PUSCH.

[0239] If all of the above conditions a) to d) are not satisfied, the terminal may suspend uplink transmission on resources configured for autonomous transmission or CG-PUSCH at the last symbol of a slot (e.g., the (n-1)th slot) before the start of a slot for scheduled uplink transmission (e.g., the (n-1)th slot). Alternatively, the terminal may suspend uplink transmission on resources configured for autonomous transmission or CG-PUSCH at least one slot (e.g., the (n-1)th slot) before the start of a slot for scheduled uplink transmission (e.g., the (n-1)th slot). On the other hand, if the time during which uplink transmission can be suspended (the time during which cancellation is guaranteed) has not elapsed, the terminal may suspend uplink transmission on resources configured for autonomous transmission or CG-PUSCH at least one slot (e.g., the (n-1)th slot) before the start of a slot for scheduled uplink transmission (e.g., the (n-1)th slot). However, if the time during which uplink transmission can be interrupted has elapsed, the terminal may perform the scheduled uplink transmission in the next slot (e.g., the (n+1)th slot) after the start of the slot for the scheduled uplink transmission (e.g., the (n+1)th slot). In this case, Category 4 channel access (e.g., Type 1 uplink channel access) may be used as the channel access procedure for performing the scheduled uplink transmission in the next slot (e.g., the (n+1)th slot). Alternatively, if the resources for the scheduled uplink transmission are included in the MCOT configured when the terminal performs Category 4 channel access (e.g., Type 1 uplink channel access) for uplink transmission on resources configured for autonomous transmission or CG-PUSCH, the terminal may perform the scheduled uplink transmission based on the Category 2 channel access (e.g., Type 2A uplink channel access) procedure.

[0240] When an uplink transmission is scheduled for a UE by a base station consecutively without a gap after a resource configured for autonomous transmission or CG-PUSCH, the UE can perform the scheduled uplink transmission without channel access according to the type of scheduled uplink transmission. The types of scheduled uplink transmission may include a PUSCH including an uplink-shared channel (UL-SCH), a PUSCH not including an UL-SCH, a PUCCH transmitting uplink control information, an uplink transmission related to a random access procedure (e.g., a PRACH preamble, Msg3), and a Sounding Reference Signal (SRS). In this case, the PUCCH may include a HARQ-ACK, a Scheduling Request (SR), a Beam-failure recovery request (BFR), or Channel State Information (CSI).

[0241] When the above conditions a) to d) are met, the terminal can perform scheduled uplink transmission without performing channel access (e.g., LBT), regardless of the type of scheduled uplink transmission.

[0242] If the scheduled uplink transmission is an uplink transmission other than a PUSCH and satisfies the above-mentioned conditions a), c), and d), the terminal can perform the scheduled uplink transmission without performing channel access.

[0243] If the scheduled uplink transmission is an uplink transmission other than a PUSCH including an UL-SCH and satisfies the above-mentioned conditions a), c), and d), the terminal can perform the scheduled uplink transmission without performing channel access.

[0244] The scheduled uplink transmission may be a PUCCH including at least one of HARQ-ACK, SR, and BFR. In this case, when interlaced-PUCCH transmission for PUCCH transmission is configured by RRC and the PUCCH transmission is scheduled by spreading it over the LBT bandwidth, if the above-mentioned conditions a), c), and d) are satisfied, the terminal can perform the scheduled PUCCH transmission without performing channel access. This is because a PUCCH including at least one of HARQ-ACK, SR, and BFR can ensure transmission on the scheduled resource as much as possible, since a failure in the channel access procedure can reduce the data transmission rate of uplink / downlink transmission or significantly increase latency due to link failure. In addition, the CAPC used for PUCCH transmission may generally be set to 1. Therefore, the CAPC used for PUCCH transmission can always be smaller or the same as the CAPC used when the terminal performs autonomous transmission or Category 4 channel access (e.g., Type 1 uplink channel access) for uplink transmission on resources configured for CG-PUSCH, thereby satisfying the above-mentioned condition c).

[0245] If the scheduled uplink transmission is a transmission of an SRS without a PUSCH, a PUCCH, a PUSCH without a UL-SCH, and a transmission associated with a random access procedure (e.g., a PRACH preamble, Msg3), and satisfies the above conditions a), c), and d), the UE may perform the scheduled uplink transmission without performing a channel access procedure. In this case, for a transmission of an SRS without a PUSCH, a PUCCH, a PUSCH without a UL-SCH, and a transmission associated with a random access procedure (e.g., a PRACH preamble, Msg3), a Category 4 channel access (e.g., Type 1 uplink channel access) procedure may be performed, and CAPC may be set to 1.

[0246] This paper describes a channel access method and procedure for semi-static channel occupancy when Frame Based Equipment (FBE)-based LBT operation in an unlicensed band, i.e., when semi-static is used as a channel access mode. Specifically, a base station and a terminal can use UE-initiated channel occupancy to perform FBE operation. This paper describes a method for a base station and a terminal to transmit and receive a channel using UE-initiated channel occupancy.

[0247] Most devices operating in unlicensed bands operate on a Listen-Before-Talk (LBT) basis, performing Clear Channel Assessment (CCA) to sense the channel before transmitting data. A communication device (e.g., AP, STA) performs carrier sensing to check whether the channel is busy before transmitting data. If a wireless signal of a certain strength or higher is detected on a channel to transmit data, the channel is determined to be busy, and the communication device delays access to the channel. This process is called Clear Channel Assessment, and the signal level that determines whether a signal is detected is called a CCA threshold. On the other hand, if no wireless signal is detected on the channel or a wireless signal of a strength lower than the CCA threshold is detected, the channel is determined to be idle. If the channel is determined to be idle, a terminal having data to transmit performs a backoff procedure after a defer period (e.g., Arbitration InterFrame Space (AIFS), PCF IFS (PIFS), etc.). The defer period refers to the minimum time a terminal must wait after a channel becomes idle. The backoff procedure allows a terminal to wait any additional time after the defer deadline. For example, a terminal waits for a random number of slot times assigned to the terminal within a contention window (CW) while the channel is idle, and when the slot time runs out, the terminal can attempt to access the channel.

[0248] FIG. 17 illustrates an LBT operation process based on FBE according to an embodiment of the present invention.

[0249] LBT can be divided into FBE-based LBT and Load Based Equipment (LBE)-based LBT depending on the operating state of the terminal (see ETSI). In the FBE method, if the channel is occupied by another communication device, the base station and terminal cannot transmit data during a fixed frame period (FFP). The fixed frame period may consist of a channel occupancy time (COT) and an idle period. Here, the channel occupancy time refers to the time during which a communication node can continue data transmission if it has successfully accessed the channel, and may be a period of 1 ms to 10 ms. The idle period may be a period of 5% or more of the channel occupancy time. A CCA process for monitoring the channel may be performed during a CCA slot (at least 20 μs) located at the end of the idle period. The communication node can perform CCA in fixed frame units. For example, when the channel is unoccupied, the communication node can transmit data during the channel occupation time, and when the channel is occupied, the communication node can suspend data transmission and wait for transmission until the CCA slot of the next period. The communication node described in this specification is a communication device, and can mean a base station or a terminal.

[0250] FIG. 18 illustrates an FBE operation according to one embodiment of the present invention.

[0251] Referring to FIG. 18, a communication node can perform a CCA procedure in a CCA slot before transmitting data on a channel of one carrier. If the channel is idle as a result of performing CCA, the communication node can transmit data. If the channel is busy as a result of performing CCA, the communication node can wait for a time equal to the fixed frame period minus the CCA slot and then perform the CCA procedure again. The communication node transmits data during the channel occupation time, and upon completion of the data transmission, can wait for a time equal to the idle period minus the CCA slot and then perform the CCA procedure again. On the other hand, if the channel is idle but the communication node does not have data to transmit, the communication node can wait for a time equal to the fixed frame period minus the CCA slot and then perform the CCA procedure again.

[0252] In a scenario where an LBE node is absent for a long period of time at a level determined by a regulation level and a base station (eNB or gNB) capable of performing FBE is synchronized, the FBE scheme can use a frequency reuse factor of 1. Therefore, random backoff is not required, reducing the complexity of channel access. The operations of the LBE mode and the FBE mode may differ in terms of channel access. In the FBE mode, a communication node can acquire channel occupation time by LBT Category 2 channel access immediately before a fixed frame period. If the gap in the acquired channel occupation time initiated by the base station is 16 us or less, the base station and the terminal can use the Category 1 channel access scheme. If the gap in the acquired channel occupation time exceeds 16 us, the base station and the terminal can use the Category 2 channel access scheme. The channel access operation may be configured to correspond to the operation for FBE so that related restriction conditions are consistent.

[0253] FIG. 19 shows an LBE operation according to one embodiment of the present invention.

[0254] Referring to FIG. 19(a), a communication node can perform CCA for each CCA slot at a certain interval to perform an LBE operation.

[0255] Referring to FIG. 19(b), a communication node can perform a CCA process in a CCA slot. If the channel is unoccupied in the first CCA slot, the communication node can transmit data for a period of time based on the maximum channel occupancy time. However, if the channel is occupied in the first CCA slot, the communication node can randomly select a value N and store it as the initial value of the counter value. N may be one of the values ​​1, 2, ..., q. The communication node can sense the channel state in units of CCA slots and decrement the set counter value by 1 if the channel is unoccupied in a specific CCA slot. When the counter value reaches 0, the communication node can transmit data for a period of time equal to the maximum channel occupancy time.

[0256] When FBE (Frame based equipment) based LBT operation in an unlicensed band, i.e., when semi-static is used in channel access mode, the terminal may be allowed to transmit data within one channel occupation period initiated by the base station, and the channel access procedure for this is defined in the 3GPP standard and is as shown in Table 5.

[0257] [Table 8]

[0258] The base station can instruct the terminal that the channel access mode is semi-static using higher layer parameters. For example, the base station can instruct the terminal that the channel access mode is semi-static using SIB1 or a dedicated RRC configuration with a higher layer parameter called "channelaccessmode-r16." In this case, the periodic channel occupancy has a maximum channel occupancy time (T_y) and may be initiated every T_x within every two consecutive radio frames starting from the even-indexed radio frame in x*T_x. In this case, T_y is 0.95*T_x, where T_x is the channel occupancy period in ms, and x is a value instructed by the base station using the higher layer parameter (semiStaticChannelAccessConfig-r16) and may have values ​​of 0, 1, ..., 20 / T_x-1. The sensing slot duration (T_sl) described in this specification may be 9 us. The dedicated RRC described in this specification is an RRC dedicated for a specific terminal, and the dedicated RRC configuration may be configuration information that a base station configures in a terminal using the dedicated RRC for a specific terminal.

[0259] A channel occupation initiated by a base station and shared with a terminal must satisfy the following conditions:

[0260] i) The base station may transmit a downlink transmission burst starting at the beginning of the channel occupation time immediately after sensing that the channel is idle for at least the sensing slot period (T_sl). If the channel is sensed to be in use, the base station does not need to transmit anything during the current channel occupation time.

[0261] ii) If there is a gap of more than 16 us between a downlink burst and the previous transmission, the base station may transmit the downlink transmission burst within the channel occupancy time immediately after sensing that the channel is idle for at least T_sl.

[0262] iii) If the interval between the downlink transmission burst and the uplink transmission burst is at most 16 us, the base station can transmit the downlink transmission burst after the uplink transmission burst during the channel occupation time without sensing the channel.

[0263] iv) The terminal can transmit an uplink transmission burst after detecting a downlink transmission burst within the channel occupancy time, such as iv-1 and iv-2.

[0264] iv-1) If the gap between an uplink transmission burst and a downlink transmission burst is at most 16 us, the terminal can transmit an uplink transmission burst after a downlink transmission burst during the channel occupation time without sensing the channel.

[0265] iv-2) If the gap between the uplink transmission burst and the downlink transmission burst exceeds 16 us, the terminal can sense that the channel is idle in at least one sensing slot period (T_sl) within the 25 us interval that ends immediately before transmission, and then transmit the uplink transmission burst after the downlink transmission burst during the channel occupation time.

[0266] v) The base station and terminal cannot transmit any consecutive symbol sets for at least T_z intervals before the next channel occupancy period begins, where T_z is max(0.05T_x,100us) and max(a,b) is a function that returns the larger of a and b.

[0267] Conventionally, in an unlicensed band, when a channel access mode is semi-static, a channel occupation is initiated by a terminal or a base station and a terminal share a channel occupation time during the channel occupation initiated by the terminal, and the terminal and the base station cannot transmit data. Hereinafter, a method for transmitting data by a base station and a terminal when a channel occupation is initiated by a terminal or a channel occupation initiated by the terminal and the base station shares a channel occupation time will be described.

[0268] When the terminal operates as a channel occupation initiating device, the signaling method for performing FBE operation is as follows.

[0269] Similar to when a base station operates as a channel occupation initiator, the base station can instruct the terminal to operate as a channel occupation initiator in the current network using higher layer signaling such as SIB1 or dedicated RRC configuration. The base station can determine whether the current network situation is a controlled environment, a single network environment as referred to in regulations, or a communication node operating in LBE has not existed for a long period of time at a level determined by the regulation level. The base station can also determine whether multiple FBE-capable base stations are synchronized. In other words, since the base station is aware of a scenario in which the terminal can perform FBE operation, the base station can instruct the terminal to become a channel occupation initiator and transmit uplink bursts in FBE operation by RRC configuration or MAC CE.

[0270] Alternatively, when the base station instructs the terminal to transmit an uplink channel or signal through scheduling, the base station may instruct the terminal through dynamic L1 signaling to start a channel occupation time (COT) as a channel occupation initiator and transmit the COT, and share the COT with the base station to use for transmission between the terminal and the base station. Specifically, the base station may instruct the terminal through dynamic L1 signaling by instructing the terminal through an uplink (UL) grant or a downlink (DL) grant including scheduling information for transmitting an uplink channel or signal. Alternatively, the base station may instruct grouped terminals in the network through group common signaling.

[0271] The base station can instruct the terminal, via dynamic L1 signaling, to determine whether to transmit an uplink channel or signal based on a channel occupation time initiated by the terminal as a channel occupation initiator (UE-initiated COT) or a shared channel occupation time initiated by the base station (shared gNB-initiated COT) when transmitting the uplink channel or signal. Furthermore, when receiving a downlink channel or signal scheduled by the base station, the terminal can determine, via dynamic L1 signaling, whether to receive based on a shared channel occupation time initiated by the terminal or a channel occupation time initiated by the base station. The base station instructing the terminal via dynamic L1 signaling may be instructing via an uplink grant or downlink grant including scheduling information for transmitting the uplink channel or signal. Alternatively, the base station can instruct a group of terminals in the network via group common signaling.

[0272] Meanwhile, when the UE does not transmit / receive an uplink / downlink channel or signal using an uplink grant or downlink grant according to scheduling using dynamic L1 signaling from the base station, i.e., when the UE performs uplink transmission according to a configured uplink grant, the base station cannot instruct the UE to determine whether to transmit according to a channel occupation time initiated by the UE as an occupation initiator or a channel occupation time initiated by the base station through dynamic L1 signaling.

[0273] When the UE receives downlink transmission through downlink detection and recognizes the channel occupation time initiated and shared by the base station and the FFP-g, the UE can perform uplink transmission according to the configured uplink grant in an interval other than the idle interval in the FFP-g by assuming the channel occupation time initiated and shared by the base station. In this case, the FFP-g may be a fixed frame period configured by the base station.

[0274] The UE may not be able to receive downlink transmission due to downlink sensing, and therefore may not be able to assume the channel occupation time and FFP-g initiated and shared by the base station, or the UE may set the channel occupation time initiated by the UE in the FFP-u interval. In this case, if resources for uplink transmission according to the uplink grant established within the channel occupation time initiated by the UE are established, the UE may consider that the uplink transmission according to the established uplink grant is performed within the channel occupation time initiated by the UE. Therefore, the UE may perform uplink transmission according to the established uplink grant in the channel occupation period initiated by the UE in a period other than the idle period in FFP-u. In this case, FFP-u may be a fixed frame period established in the UE.

[0275] The base station may schedule an uplink channel or signal to the terminal through an uplink grant or a downlink grant. In this case, the base station may configure information about a field related to channel access included in the uplink grant or the downlink grant to the terminal through RRC signaling. When information about the field related to channel access is configured through RRC signaling, the terminal can instruct the terminal to determine whether to transmit according to a channel occupation time initiated by the base station or a channel occupation time initiated by the terminal through the field related to channel access included in the uplink grant or the downlink grant. However, if the base station does not configure information about the field related to channel access included in the uplink grant or the downlink grant to the terminal through RRC signaling, or if the information about the field related to channel access is set to 0 bits through RRC signaling, i.e., the information about the field related to channel access may be 0 bits. In other words, the base station cannot instruct the terminal whether to transmit according to a channel occupation time initiated by the terminal or a channel occupation time initiated by the base station. In this case, the UE can perform uplink transmission in the same manner as performing uplink transmission according to the configured uplink grant. That is, the UE receives a downlink channel through downlink sensing, recognizes the channel occupation time and FFP-g initiated and shared by the base station, and can perform uplink transmission in a section other than the idle section in the FFP-g section. However, if the UE cannot receive a downlink channel through downlink sensing and therefore cannot assume the channel occupation time and FFP-g initiated and shared by the base station, the UE can assume the channel occupation time initiated by the UE in the FFP-u section and perform uplink transmission in a section other than the idle section in the FFP-u section configured for the UE.

[0276] When uplink channel transmission is scheduled and there is an uplink burst to be transmitted by the terminal, the terminal can transmit the uplink burst during a channel occupation time initiated by the terminal. Also, during the channel occupation time initiated by the terminal, the terminal can share channel occupation with the base station, and the terminal's uplink burst transmission and the base station's downlink burst transmission may be performed during the channel occupation time initiated and shared by the terminal. In this case, the channel occupation shared with the base station during the channel occupation time initiated and shared by the terminal must satisfy the following conditions:

[0277] i) The UE can transmit an uplink transmission burst starting at the start of the channel occupation time immediately after sensing that the channel is idle for at least the sensing slot period (T_sl). If the channel is sensed as being in use, the UE does not need to perform any transmission during the current channel occupation time. However, if the BS performs downlink transmission during the channel occupation time started by the BS, and the UE senses the downlink transmission burst during the channel occupation time, the UE can transmit data according to the following i-1 and i-2 methods.

[0278] i-1) If the gap between an uplink transmission burst and a downlink transmission burst is at most 16 us, the terminal can transmit an uplink transmission burst after a downlink transmission burst within the channel occupancy time without sensing the channel.

[0279] i-2) If the gap between the uplink transmission burst and the downlink transmission burst exceeds 16 us, the terminal can sense that the channel is idle in at least one sensing slot period (T_sl) within a 25 us interval that ends immediately before transmission, and then transmit the uplink transmission burst after the downlink transmission burst within the channel occupancy time.

[0280] ii) If there is a gap of more than 16 us between an uplink transmission burst and the previous transmission, the base station may transmit the uplink transmission burst within the channel occupancy time immediately after sensing that the channel is idle for at least T_sl.

[0281] iii) When the interval between an uplink transmission burst and a downlink transmission burst is at most 16 us, the terminal does not sense the channel and can transmit an uplink transmission burst after a downlink transmission burst within the channel occupancy time.

[0282] iv) The base station can transmit a DL transmission burst after detecting an uplink transmission burst within the channel occupancy time, as in iv-1 and iv-2.

[0283] iv-1) When the gap between an uplink transmission burst and a downlink transmission burst is at most 16 us, the base station can transmit a downlink transmission burst after an uplink transmission burst within the channel occupancy time without sensing the channel.

[0284] iv-2) If the gap between an uplink transmission burst and a downlink transmission burst exceeds 16 us, the base station can transmit a downlink transmission burst after the uplink transmission burst within the channel occupancy time after sensing that the channel is idle for at least one sensing slot period (T_sl) within a 25 us interval ending immediately before transmission.

[0285] v) The base station and the terminal cannot transmit any consecutive symbol sets for at least T_z intervals before the next channel occupancy period begins, where T_z is max(0.05T_x, 100 us).

[0286] When a base station operates as a channel occupation initiator, one base station can manage and schedule uplink transmissions for individual terminals, thereby enabling flexible multiplexing between different terminals in one channel occupation. However, when a terminal operates as a channel occupation initiator, collisions may occur in transmissions between terminals due to channel occupation times that start at different times or with different lengths (number of symbols). Specifically, when a terminal shares a channel occupation time that it started with a base station and the base station performs downlink transmission, channel occupation times that multiple terminals started at different times or with different lengths may exist. In this case, ambiguity may occur in channel access for downlink transmissions of the base station depending on whether the base station detects uplink transmissions performed by different terminals. Therefore, this specification proposes a method for solving the collision problem that occurs due to channel occupation times that different terminals start at different times or with different lengths. Furthermore, a method for resolving ambiguity in channel access for downlink transmissions when the base station performs downlink transmissions by sharing channel occupation time between a terminal and a base station is proposed.

[0287] When the channel access mode operates in the LBE mode rather than the semi-static mode, a terminal may transmit a PUSCH via autonomous transmission or a configured grant in an existing unlicensed band. In this case, the PUSCH transmitted by the terminal may include UCI. The UCI may include HARQ-ID, New Data Indication (NDI), RV (CAPC), and channel occupation time sharing (COT sharing) information. The base station can confirm the channel occupation time with the base station within the channel occupation time initiated by the terminal based on the CAPC and channel occupation time sharing information included in the UCI transmitted by the terminal. Then, the base station can perform downlink transmission within the channel occupation time initiated by the terminal.

[0288] In the semi-static channel access mode, the terminal can share the channel occupation time started by the terminal with the base station and transmit the set grant PUSCH. At this time, the UCI included in the PUSCH can include channel occupation time sharing information. The base station can confirm the channel occupation time started by the terminal based on the channel occupation time sharing information included in the UCI transmitted by the terminal. Then, the base station can perform channel access within the channel occupation time started by the terminal and transmit a downlink burst. At this time, the channel access can be performed according to a gap length. For example,

[0289] i) When a downlink burst transmission starts and ends within a channel occupation time initiated by the terminal, the base station can perform channel access according to the respective gap lengths and transmit the downlink burst. As another example, when a downlink burst transmission starts within a channel occupation time initiated by the terminal but the end point of the downlink burst is not included in the channel occupation time initiated by the terminal, the base station can suspend the downlink burst transmission outside the channel occupation time initiated by the terminal on a slot or symbol basis. This is to ensure that the downlink burst is transmitted only within the channel occupation time initiated by the terminal.

[0290] ii) If the transmission of a downlink burst starts within the channel occupation time started by the terminal but the end point of the downlink burst is not included in the channel occupation time started by the terminal, the base station can perform channel sensing again for the transmission of the downlink burst that is not included in the channel occupation time started by the terminal. Specifically, for the transmission of a downlink burst that is not included in the channel occupation time started by the terminal, the base station can perform channel sensing within a radio frame of x*T_x duration after the channel occupation time started by the terminal, set up channel occupation, and transmit the downlink burst.

[0291] iii) There may be cases where the transmission of a downlink burst starts within the channel occupation time initiated by the terminal, but the end point of the downlink burst is not included in the channel occupation time initiated by the terminal. In this case, if the length of the downlink burst that is not included in the channel occupation time initiated by the terminal is included in the x*T_x period of FBE operation in which the channel occupation time initiated by the terminal exists, the base station senses the channel in one sensing slot period (T_sl) and can transmit the downlink burst if it is in an idle state.

[0292] Unlike the configured grant PUSCH, a terminal transmitting a channel configured by scheduling from a base station, a signal, and a channel used in a random access procedure may become a channel occupation initiator, and in this case, the channel occupation time initiated by the terminal may be shared with the base station. For channels configured by scheduling, a signal, and a channel used in a random access procedure, there is no mechanism for the terminal to provide channel occupation time sharing information to the base station via the PUSCH. Therefore, the base station does not know information related to the channel occupation initiated and shared by the terminal as a channel occupation initiator. In this case, ambiguity may occur in the channel access method used by the base station to transmit downlink bursts. A method for resolving ambiguity regarding the channel access method will be described below.

[0293] Channels and signals configured by scheduling from the base station and channels used for the random access procedure may be transmitted on resources scheduled based on resource allocation information regarding time and frequency resources transmitted by the base station. Specifically, when the base station transmits downlink control information over a PDCCH and the terminal successfully receives the PDCCH, the base station may transmit resource allocation information to the terminal, and the terminal may perform uplink transmission based on the resource allocation information. In this case, the channel used for the random access procedure may be a PRACH for non-contention-based random access other than a PRACH for a contention-based random access procedure, and a PRACH for a 2-step random access procedure. Therefore, the terminal may transmit channels and signals scheduled by the base station to the base station, and the base station may detect channels and signals transmitted from the terminal. In this case, the base station may determine the length of channel occupancy time that the terminal starts and shares based on the resource allocation information configured in the terminal. In this case, the resource allocation information may be time domain resource allocation (TDRA) information.

[0294] When the UE and the BS are synchronized in FBE mode, the BS can transmit a downlink burst within the T_y interval, taking into account the length of the channel occupancy time started by the UE and the T_x interval. T_y is an interval other than the interval in which the BS performs channel sensing within the T_x interval, and may be 0.95*T_x [0 ms]. In this case, if there is a gap exceeding 16 us, the BS senses the channel in one sensing slot interval (T_sl) and can transmit a downlink burst if the channel is idle.

[0295] Since LBT is performed when operating in LBE mode, a channel access priority class may be set for the scheduled channels, signals, and channels used during the random access procedure. The base station and the terminal can determine the length of the channel occupation time that the terminal starts based on the maximum channel occupation time corresponding to the channel access priority class used by each channel and signal. The length of the channel occupation time assumed by the base station and the terminal for the scheduled channels, signals, and channels used during the random access procedure is as follows:

[0296] i) When only PUSCH is transmitted without PUCCH or UL-SCH, the LBT priority class or channel access priority may be 1. The length of the available channel occupancy time may be set to 2 ms, which is the MCOT value, as shown in Table 6.

[0297] ii) The priority class or channel access priority class of the PUSCH associated with the random access procedure without PRACH and user plane data may be 1. In this case, the length of the channel occupancy time initiated by the terminal may be set to 2 ms, which is the MCOT value, as shown in Table 6.

[0298] iii) An SRS that does not include a PUSCH may have an LBT priority class or a channel access priority class of 1. In this case, the length of the channel occupation time initiated by the terminal may be set to 2 ms, which is the MCOT value, as shown in Table 6.

[0299] iv) For PUSCHs other than i) to iii), the length of the channel occupation time may be set based on the traffic transmitted by the terminal or the channel access priority class instructed by the base station to the terminal. Specifically, the MCOT value disclosed in Table 6 may be set as the length of the channel occupation time.

[0300] v) When various types of uplink channels and signals are mixed and configured as one uplink burst, the length of the channel occupation time may be set to the longest MCOT length among the MCOT lengths that can be set for each channel and signal, or the length of the channel occupation time may be set to the longest length in time based on the resources configured to transmit the mixed uplink burst.

[0301] Table 6 shows parameter values ​​used for channel access by channel access priority class for uplink transmission used in the LTE LAA system.

[0302] [Table 9]

[0303] Referring to Table 6, the MCOT value of 6 ms may be increased to 8 ms if the transmission contains one or more gaps. A gap refers to the time from when transmission is interrupted to when it is restarted on a certain carrier. In this case, the minimum duration of the gap may be 100 us. Also, the maximum duration of the transmission before the gap is included may be 6 ms. The duration of the gap may not be included in the channel occupancy time.

[0304] If the channel access priority class value is 3 or 4 and it is guaranteed that no other wireless access technologies are used on the carrier where channel access is performed, the MCOT value may be 10 ms. In this case, the other wireless access technologies may include Wi-Fi. In other cases, the MCOT value may be determined as in NOTE 1 of Table 6.

[0305] MCOT refers to the maximum time that an initiating node can continuously occupy a channel of any one carrier in an unlicensed band. Gaps, which are periods when no transmission is performed, may be included between multiple transmissions, and when gaps are included, the MCOT value may be applied differently.

[0306] Hereinafter, this specification describes a method in which a base station and a terminal transmit within a channel occupation time initiated by the base station shared between the base station and the terminal when the base station and the terminal operate in FBE, i.e., when the channel access mode is semi-static.

[0307] First, a signaling method for performing FBE operation when a terminal operates as a channel occupation initiator will be described. The base station can instruct the terminal that the terminal can operate as a channel occupation initiator by higher layer signaling such as SIB1 or dedicated RRC configuration. In addition, the base station provides information about FFP to the terminal by higher layer signaling such as SIB1 or dedicated RRC configuration, and the terminal that receives this information can configure FFP.

[0308] However, the base station may not configure a signaling configuration indicating information about a semi-static channel access mode or information about an FFP through SIB1 that the UE can receive before RRC connection, but may configure a signaling configuration indicating information about a semi-static channel access mode or information about an FFP through dedicated RRC configuration information that the UE can receive after RRC connection. In this case, the UE needs to assume the FFP configured in the UE for transmitting the PRACH preamble and Msg3 transmitted during a random access procedure in which the UE should transmit before RRC connection. This is because the PRACH preamble and Msg3 must be transmitted before RRC connection. That is, when operating in FBE mode, transmission is not permitted in idle intervals, but is permitted in intervals other than the idle interval within the FFP interval. Therefore, when the UE cannot receive information about the channel access mode or information about the FFP from the base station, the UE may perform uplink transmission by assuming the FFP configured in the base station as the UE's FFP. In this case, the terminal can perform uplink transmission in a section other than the idle section of the FFP section set in the base station. The base station can perform downlink transmission in a section other than the idle section in the FFP set in the base station. If the FFP assumed by the terminal is different from the FFP set in the base station, downlink transmission does not have to be performed in a section other than the idle section in the FFP set in the base station. However, since the FFP assumed by the terminal is the same as the FFP set in the base station, the base station can perform downlink transmission in a section other than the idle section in the FFP set in the base station. In other words, if the FFP differs between the base station and the terminal, the section in which the base station performs downlink transmission may be a section other than the idle section in the FFP set in the base station, but may also be an idle section in the FFP set in the terminal.

[0309] Even before RRC connection, the UE can receive a PRACH opportunity (occasion) on which it can transmit a PRACH from the base station. The base station can configure the UE with a PRACH opportunity (occasion) within an interval other than an idle interval within the FFP configured in the base station. If the UE cannot receive information on the channel access mode or information on the FFP from the base station, the UE can perform uplink transmission by assuming that the FFP configured in the base station is the FFP of the UE. In this case, it needs to be defined whether the UE performs uplink transmission without channel sensing or after channel sensing.

[0310] The base station can configure PRACH opportunities for the terminal regardless of idle intervals in the FFP configured in the base station. In other words, some / all of the PRACH opportunities may be included in the idle intervals in the FFP configured in the base station. In this case, the terminal can transmit PRACH on PRACH opportunities configured in intervals other than the idle intervals in the FFP configured in the base station. The terminal cannot receive downlink transmission from the base station and can perform uplink transmission in intervals other than the idle intervals in the FFP. A method for the terminal to perform uplink transmission is as follows. In this specification, uplink / downlink bursts may include uplink / downlink channels and signals.

[0311] i) Immediately after sensing that the channel is idle for at least the sensing slot duration (T_sl), the terminal can transmit an uplink burst including a channel or signal to be transmitted in the uplink before RRC connection starting at the start of the channel occupation time. If the channel is sensed as being in use as a result of channel sensing, the terminal does not need to perform any transmission during the current channel occupation time. However, if the terminal senses a downlink burst transmitted during the channel occupation initiated by the base station, the terminal can transmit the uplink burst according to methods i-1 and i-2 during the channel occupation time initiated by the base station.

[0312] i-1) If the gap between an uplink burst and a downlink burst before RRC connection is a maximum of 16 us, the terminal can transmit the uplink burst after the downlink burst without sensing the channel.

[0313] i-2) If the gap between the uplink burst and the downlink burst exceeds 16 us before RRC connection, the terminal can sense that the channel is idle in at least one sensing slot period (T_sl) within a 25 us interval ending just before transmitting the uplink burst, and then transmit the uplink burst after the downlink burst within the channel occupancy time.

[0314] ii) If there is a gap of more than 16 us between the uplink burst and the previous transmission before the RRC connection, the terminal can transmit the uplink burst within the channel occupancy time immediately after sensing that the channel is idle in at least one sensing slot period (T_sl).

[0315] iii) If the gap between the uplink burst and the downlink burst is at most 16 us, the terminal can transmit an uplink transmission burst after a downlink transmission burst within the channel occupancy time without sensing the channel.

[0316] iv) The base station can transmit a downlink burst after detecting an uplink burst transmitted within the channel occupancy time before the RRC connection.

[0317] iv-1) If the gap between the uplink burst and the downlink burst is a maximum of 16us, the base station can transmit the downlink burst after the uplink burst transmitted within the channel occupancy time before RRC connection without sensing the channel.

[0318] iv-2) If the gap between the uplink burst and the downlink burst exceeds 16 us, the base station can sense that the channel is idle in at least one sensing slot period (T_sl) within a 25 us interval ending just before the downlink burst transmission. Thereafter, the base station can transmit the downlink burst after the uplink burst transmitted within the channel occupancy time before the RRC connection.

[0319] v) The base station and the terminal cannot transmit any data on consecutive symbol sets for at least T_z intervals before the next channel occupancy period begins, where T_z may be max(0.05T_x, 100 us).

[0320] There may be cases where different FFPs are set between a terminal and a base station to perform uplink transmission and downlink transmission. Hereinafter, a method for a terminal to perform uplink transmission and a method for a base station to perform downlink transmission will be described.

[0321] 20 to 23 show a method for performing uplink transmission and downlink transmission when different FFPs are configured for a base station and a terminal according to an embodiment of the present invention. In Fig. 20 to 23, FFP-u is an FFP configured for the terminal, and FFP-g is an FFP configured for the base station. idle-u is an idle period configured for the terminal, and idle-g is an idle period configured for the base station.

[0322] Referring to FIG. 20, different FFPs may be configured for the base station and the terminal. In this case, the base station does not perform downlink transmission in the idle section of the FFP configured for the base station, but can perform downlink transmission in the idle section of the FFP configured for the terminal. In other words, the terminal can receive downlink transmission performed by the base station in the idle section of the FFP configured for the terminal. Similarly, the terminal does not perform uplink transmission in the idle section of the FFP configured for the terminal, but can perform uplink transmission in the idle section of the FFP configured for the base station. In other words, the base station can receive uplink transmission performed by the terminal in the idle section of the FFP configured for the base station.

[0323] Referring to FIG. 21, different FFPs may be configured for the base station and the terminal. In this case, the base station and the terminal may assume that no uplink transmission or downlink transmission is performed in any idle interval. In other words, the base station and the terminal may assume that no uplink transmission or downlink transmission is performed in the idle interval of the FFP configured for the base station and the idle interval of the FFP configured for the terminal. That is, the base station may assume that no downlink transmission is performed in the idle interval of the FFP configured for the base station, and that no uplink transmission is transmitted by the terminal. Similarly, the terminal may assume that no downlink transmission is performed in the idle interval of the FFP configured for the terminal, and that no uplink transmission is transmitted by the base station.

[0324] Referring to FIG. 22, different FFPs may be configured for the base station and the terminal. In this case, the base station does not perform downlink transmission only in the idle section of the FFP configured for the base station, but can perform downlink transmission in the idle section of the FFP configured for the terminal. In other words, the terminal can receive downlink transmission performed by the base station in the idle section of the FFP configured for the terminal. The terminal does not perform uplink transmission in the idle section of the FFP configured for the terminal, but can perform uplink transmission in the idle section of the FFP configured for the base station. In other words, the base station can receive uplink transmission performed by the terminal in the idle section of the FFP configured for the base station.

[0325] Referring to FIG. 23, different FFPs may be configured for the base station and the terminal. In this case, the base station and the terminal may assume that no uplink transmission or downlink transmission is performed in any idle interval. In other words, the base station and the terminal may assume that no uplink transmission or downlink transmission is performed in the idle interval of the FFP configured for the base station and the idle interval of the FFP configured for the terminal. That is, the base station may assume that no downlink transmission is performed in the idle interval of the FFP configured for the base station, and no uplink transmission is transmitted by the terminal. Similarly, the terminal may assume that no downlink transmission is performed in the idle interval of the FFP configured for the terminal, and no uplink transmission is transmitted by the base station. Uplink transmission from the terminal to the base station may be scheduled by the base station. In addition, intervals for downlink transmission or uplink transmission may be configured in intervals other than the idle intervals in the FFP configured for the base station and the FFP configured for the terminal. Therefore, intervals for downlink transmission and intervals for uplink reception may be configured in intervals other than the idle intervals in the FFP configured for the base station. The base station can perform downlink transmission in a section where downlink transmission is set in a section other than an idle section in the FFP set in the base station, and can receive uplink transmissions made by the terminal in a section where uplink transmission is set. Similarly, the terminal can perform uplink transmission in a section other than an idle section in the FFP set in the terminal when uplink transmission is set, and can receive downlink transmissions transmitted by the base station when downlink transmission is set.

[0326] The methods described in FIGS. 20 to 23 may be applied when the base station and the terminal recognize their respective FFPs. However, the base station can notify the terminal of the FFP set in the base station by SIB1 or dedicated signaling. Therefore, there is no ambiguity between the base station and the terminal regarding the FFP set in the base station. However, when the channel occupation time started by the terminal in the FFP set in the terminal is shared with the base station, the base station may not be able to grasp the channel occupation time started by the terminal. When the base station detects uplink transmission performed by the terminal within the FFP set in the terminal, the base station can determine the channel occupation time within the FFP set in the terminal. Then, the base station can perform downlink transmission before the idle interval within the determined channel occupation time. At this time, the conditions and channel sensing method for the base station to perform downlink transmission will be described.

[0327] If there is a gap of more than 16 us between a downlink transmission burst and the previous transmission, the base station can sense an idle channel in one sensing slot period (T_sl) and transmit a downlink burst within the channel occupation time immediately after sensing.If the gap between a downlink burst and an uplink burst is up to 16 us, the base station can transmit a downlink transmission burst after an uplink transmission burst within the channel occupation time without sensing the channel.

[0328] However, if the base station cannot sense uplink transmission within the FFP set for the UE, the base station cannot recognize the channel occupation time initiated by the UE. Therefore, the base station can perform downlink transmission only in sections other than the idle section of the FFP set for the base station. The base station performs channel sensing in at least one sensing slot section (T_sl) to detect that the channel is idle and can transmit a downlink burst starting from the start position of the channel occupation time immediately after the detection. If the channel is detected as being in use as a result of channel sensing, the base station does not need to perform any transmission in the FFP section set for the base station. If there is a gap of more than 16 us between a downlink burst and the previous transmission, the base station can perform channel sensing in at least one sensing slot section to sense an idle channel and can transmit a downlink burst within the FFP set for the base station immediately after the detection.

[0329] A method in which different FFPs are set for multiple terminals and the terminals perform uplink transmission will be described.

[0330] When a base station configures different FFPs for different terminals through UE-specific dedicated signaling, one terminal cannot determine whether the same FFP or different FFPs are configured for other terminals. In this case, one terminal may not perform uplink transmission in the idle interval of the configured FFP, but may perform uplink transmission in an interval other than the idle interval. In addition, when a terminal shares a channel occupation time initiated by a base station in an FFP configured by the base station, the terminal may not perform uplink transmission in the idle interval of the shared channel occupation time.

[0331] FIG. 24 illustrates a method for a terminal to transmit an uplink channel according to an embodiment of the present invention.

[0332] With reference to FIG. 24, a method of transmitting the uplink channel (signal) described above with reference to FIGS. 1 to 23 will be described.

[0333] The terminal may receive resource information related to transmission of an uplink channel from the base station (S2410).

[0334] The terminal can detect a downlink channel transmitted from the base station (S2420).

[0335] The base station can transmit an uplink channel based on the resource information according to the downlink channel sensing result (S2430).

[0336] In this case, the uplink channel may be transmitted based on a COT initiated and shared by the base station or based on a COT initiated by the terminal.

[0337] An uplink channel transmitted by the terminal may be transmitted based on a configured grant. As a result of downlink channel sensing performed by the terminal in step S2420, if the terminal senses the downlink channel, the uplink channel may be transmitted based on a COT initiated and shared by the base station. On the other hand, if the terminal does not sense the downlink channel, the uplink channel may be transmitted based on a COT initiated by the terminal. In this case, the COT initiated and shared by the base station may be a period within a Fixed Frame Period (FFP) configured in the base station, and the COT initiated by the terminal may be a period within an FFP configured in the terminal. The FFP configured in the base station and the FFP configured in the terminal may be different from each other. When the uplink channel is transmitted based on a COT initiated and shared by the base station, the uplink channel may be transmitted in a period other than an idle period within the FFP configured in the base station. On the other hand, when the uplink channel is transmitted based on a COT initiated by the terminal, the uplink channel may be transmitted in an interval other than an idle interval in an FFP established for the terminal. When the uplink channel is transmitted based on a COT initiated by the terminal, the uplink channel may be transmitted regardless of whether the interval in which the uplink channel is transmitted is included in an idle interval in an FFP established for the base station. On the other hand, when the uplink channel is transmitted based on a COT initiated and shared by the base station, the interval in which the uplink channel is transmitted may be transmitted in an interval other than an idle interval in an FFP established for the base station. In this case, the FFP established for the terminal may be configured for the terminal by dedicated RRC signaling information.

[0338] Meanwhile, the uplink channel may be scheduled by dynamic signaling from a base station. In this case, the terminal may receive dynamic signaling including scheduling information for transmitting the uplink channel from the base station. The resource information may be included in the scheduling information. If the scheduling information includes information on a COT on which the uplink channel is transmitted, the sensing of the downlink channel may be omitted, and the uplink channel may be transmitted based on the information on the COT. However, if the scheduling information does not include information on a COT on which the uplink channel is transmitted, the uplink channel may be transmitted based on the scheduling information according to the downlink channel sensing result. The information on the COT may be information indicating whether the uplink channel is transmitted based on a COT initiated and shared by the base station or a COT initiated by the terminal. The information on the COT may be included in a field for channel access constituting the dynamic signaling.

[0339] The terminal performing the method for transmitting an uplink channel described in FIG. 24 may be the terminal described in FIG. 14. Specifically, the terminal may be configured to include a communication module for transmitting and receiving radio signals and a processor for controlling the communication module. At this time, the method for transmitting an uplink channel (signal) described in FIG. 24 may be performed by the processor. Similarly, at this time, the base station may be the base station described in FIG. 14. The base station may also be configured to include a communication module for transmitting and receiving radio signals and a processor for controlling the communication module. That is, the base station can receive the uplink channel (signal) described in FIG. 24 from the terminal. At this time, the method for receiving an uplink channel (signal) may be performed by the processor of the base station.

[0340] Although the method and system of the present invention have been described in connection with particular embodiments, some or all of the components or operations thereof may be implemented using a computer system having a general-purpose hardware architecture.

[0341] The above description of the present invention is for illustrative purposes only, and those skilled in the art will understand that the present invention can be easily modified into other specific forms without changing the technical spirit or essential features of the present invention. Therefore, the above-described embodiments should be understood to be illustrative in all respects and not restrictive. For example, each component described as a single component may be implemented in a distributed form, and similarly, each component described as a distributed component may be implemented in a combined form.

[0342] The scope of the present invention is indicated by the claims that follow rather than by the above detailed description, and all modifications and variations that fall within the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

Claims

1. A method for transmitting an uplink channel in a wireless communication system, the method being performed by a terminal, comprising: receiving, from a base station, resource information related to transmission of an uplink channel; detecting a downlink channel transmitted from the base station; transmitting an uplink channel based on the resource information in accordance with the downlink channel sensing result to the base station; The method, wherein the uplink channel is transmitted based on a COT (Channel Occupancy Time) initiated and shared by the base station, or based on a COT initiated by the terminal.

2. The method of claim 1, wherein the uplink channel is transmitted based on a configured grant.

3. As a result of the downlink channel sensing, When the terminal senses the downlink channel, the uplink channel is transmitted based on a COT initiated and shared by the base station; The method of claim 2, wherein if the terminal does not sense the downlink channel, the uplink channel is transmitted based on a COT initiated by the terminal.

4. The COT initiated and shared by the base station is a period within a fixed frame period (FFP) set in the base station, The method of claim 3, wherein the COT initiated by the terminal is an interval within an FFP set for the terminal.

5. When the uplink channel is transmitted based on a base station-initiated shared COT, The method of claim 4, wherein the uplink channel is transmitted in an interval other than an idle interval in an FFP set in the base station.

6. When the uplink channel is transmitted based on a COT initiated by the terminal, The method of claim 4, wherein the uplink channel is transmitted in an interval other than an idle interval in an FFP set for the terminal.

7. The method according to claim 4, wherein the FFP set in the base station is different from the FFP set in the terminal.

8. When the uplink channel is transmitted based on a COT initiated by the terminal, The method of claim 4, wherein the uplink channel is transmitted regardless of whether the transmission interval of the uplink channel is included in an idle interval within an FFP set in the base station.

9. When the uplink channel is transmitted based on a shared COT initiated by the base station, The method of claim 4, wherein the uplink channel is transmitted in an interval other than an idle interval within an FFP set in the base station.

10. The method according to claim 4, wherein the FFP configured in the terminal is configured in the terminal by dedicated RRC signaling information.

11. receiving dynamic signaling from the base station, the dynamic signaling including scheduling information for the uplink channel transmission; the resource information is included in the scheduling information; If the scheduling information includes information about a COT during which the uplink channel is transmitted, the step of sensing the downlink channel is not performed, and the uplink channel is transmitted based on the information about the COT; When the scheduling information does not include information about a COT on which the uplink channel is transmitted, the uplink channel is transmitted based on the scheduling information according to the downlink channel sensing result; 2. The method of claim 1, wherein the information regarding the COT is information indicating whether the uplink channel is transmitted based on a COT initiated and shared by the base station or a COT initiated by the terminal.

12. 12. The method of claim 11, wherein the information about the COT is included in a field for channel access that configures the dynamic signaling.

13. A terminal that transmits an uplink channel in a wireless communication system includes: a communication module; and a processor for controlling the communication module; The processor: receiving, from a base station, resource information related to transmission of an uplink channel; Detecting a downlink channel transmitted from the base station; transmitting an uplink channel based on the resource information to the base station according to the downlink channel sensing result; The terminal is characterized in that the uplink channel is transmitted based on a COT (Channel Occupancy Time) initiated and shared by the base station, or is transmitted based on a COT initiated by the terminal.

14. The terminal of claim 13, wherein the uplink channel is transmitted based on a configured grant.

15. As a result of the downlink channel sensing, When the terminal senses the downlink channel, the uplink channel is transmitted based on a COT initiated and shared by the base station; The terminal of claim 14, wherein when the terminal does not sense the downlink channel, the uplink channel is transmitted based on a COT initiated by the terminal.

16. The COT initiated and shared by the base station is a period within a fixed frame period (FFP) set in the base station, The terminal of claim 15, wherein the COT initiated by the terminal is an interval within an FFP set in the terminal.

17. When the uplink channel is transmitted based on a base station-initiated shared COT, The terminal of claim 16, wherein the uplink channel is transmitted in an interval other than an idle interval in an FFP set in the base station.

18. When the uplink channel is transmitted based on a COT initiated by the terminal, The terminal of claim 17, wherein the uplink channel is transmitted in an interval other than an idle interval in an FFP set for the terminal.

19. When the uplink channel is transmitted based on a COT initiated by the terminal, The terminal of claim 17, wherein the uplink channel is transmitted in an interval other than an idle interval in an FFP set for the terminal.

20. 1. A method for receiving an uplink channel in a wireless communication system, the method being performed by a base station, comprising: transmitting, to the terminal, resource information related to transmission of the uplink channel; receiving an uplink channel based on the resource information from the terminal; The uplink channel is transmitted based on whether the terminal senses a downlink channel transmitted from a base station; The method, wherein the uplink channel is transmitted within a COT (Channel Occupancy Time) initiated by the base station or within a COT initiated by the terminal.

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