Method and apparatus for transmitting signals in a wireless communication system

Abstract

The present invention relates to a wireless communication system, and more particularly to a method and a wireless device therefor, including a step of successfully establishing a channel connection with one or more sensing beams before the start of a channel occupancy (CO), each sensing beam covering one or more transmission beams in the CO, and a step of performing a channel connection procedure for a sensing beam corresponding to a second transmission beam after transmission using a first transmission beam in the CO, in order to transmit using a second transmission beam in the CO.

Description

[Technical Field]

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

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

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

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

[0005] To mitigate the path loss of radio waves in the ultra-high frequency band and increase the transmission distance of radio waves, technologies being discussed for 5G communication systems include beamforming, massive MIMO, full dimensional MIMO (FD-MIMO), array antenna, analog beamforming, hybrid beamforming that combines analog beamforming and digital beamforming, and large scale antenna technology. In addition, to improve the system's network, technological developments are being made in the 5G communication system regarding advanced small cells, improved 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. Through the integration and convergence of traditional IT technology and various industries, the IoT is being applied to areas such as smart homes, smart buildings, smart cities, smart or connected cars, smart grids, healthcare, smart home appliances, and advanced medical services.

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

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

[0009] In recent years, as mobile traffic has increased rapidly with the proliferation of smart devices, existing licensed frequency spectrums or licensed frequency bands have become unable to withstand the increasing data usage for providing cellular communication services.

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

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

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

[0013] An object of the present invention is to provide a method for efficiently transmitting signals in a wireless communication system and an apparatus using the same. Specifically, an object of the present invention is to provide a channel access method for efficiently transmitting signals in a wireless communication system and an apparatus using the same. [Means for solving the problem]

[0014] As one aspect of the present invention, there is provided a wireless device for use in a wireless communication system, comprising: a communication module; and a processor for controlling the communication module, wherein the processor is configured to: successfully establish channel connection with one or more sensing beams before the start of a channel occupancy (CO), each sensing beam covering one or more transmission beams within the CO; and, after transmission using a first transmission beam within the CO, perform a channel connection procedure for a sensing beam corresponding to the second transmission beam in order to transmit using a second transmission beam within the CO; wherein, when the sensing beam corresponding to the second transmission beam is included in the one or more sensing beams, the channel connection procedure includes a first channel connection procedure performed without channel sensing, and when the sensing beam corresponding to the second transmission beam is not included in the one or more sensing beams, the channel connection procedure includes a second channel connection procedure based on fixed interval channel sensing.

[0015] As another aspect of the present invention, there is provided a method used by a wireless device in a wireless communication system, comprising: a step of successfully establishing a channel connection with one or more sensing beams before the start of a channel occupancy (CO), each sensing beam covering one or more transmission beams within the CO; and a step of, after transmission using a first transmission beam within the CO, performing a channel connection procedure on a sensing beam corresponding to the second transmission beam to transmit using the second transmission beam within the CO, wherein if the sensing beam corresponding to the second transmission beam is included in the one or more sensing beams, the channel connection procedure includes a first channel connection procedure performed without channel sensing, and if the sensing beam corresponding to the second transmission beam is not included in the one or more sensing beams, the channel connection procedure includes a second channel connection procedure based on fixed interval channel sensing.

[0016] Preferably, the transmission using the first transmission beam and the transmission using the second transmission beam may be multiplexed in the time domain within the CO by time division multiplexing (TDM).

[0017] Preferably, transmissions using the first transmit beam and transmissions using the second transmit beam may not overlap in the time domain within the CO.

[0018] Preferably, the CO may be initiated identically for multiple transmit beams.

[0019] Preferably, for the channel access, a back-off based third channel access procedure may be performed independently for each sensing beam before the start of the CO.

[0020] Preferably, in the third channel access procedure, the initial value of the random backoff counter may be set independently for each sensing beam.

[0021] Preferably, the wireless communication system may include a 3GPP (registered trademark) (3rd generation partnership project) based wireless communication system. [Effects of the Invention]

[0022] The present invention provides a method for efficiently transmitting signals in a wireless communication system and an apparatus using the same. The present invention also provides a channel access method for efficiently transmitting signals in a wireless communication system and an apparatus using the same.

[0023] The effects obtained from the present invention are not limited to those mentioned above, and other effects not mentioned will be clearly understood by those having ordinary skill in the art to which the present invention pertains from the following description. [Brief explanation of the drawings]

[0024] [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 (registered trademark) system (e.g., NR) and a general signal transmission method using the physical channels. [Figure 4] FIG. 1 illustrates an SS / PBCH block for initial cell access in a 3GPP NR system. [Figure 5] FIG. 1 illustrates a procedure for control information and control channel transmission in a 3GPP NR system. [Figure 6] FIG. 1 is a diagram illustrating a CORESET in which a PDCCH is transmitted in a 3GPP (registered trademark) NR system. [Figure 7] FIG. 1 illustrates a method for configuring 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 for explaining terminal carrier communication and multi-carrier communication. [Figure 10] A diagram showing an example in which a cross-carrier scheduling technique is applied. [Figure 11] FIG. 1 is a diagram illustrating an NR-U (NR-Unlicensed) service environment. [Figure 12] 1 is a diagram illustrating an existing communication system (e.g., wireless LAN) that operates in an unlicensed band. [Figure 13] A diagram showing the channel access process based on Category 4 LBT. [Figure 14] 2A and 2B are block diagrams showing the configurations of a terminal and a base station according to an embodiment of the present invention. [Figure 15] 10A and 10B are diagrams illustrating an example of COT (channel occupancy time) setting and operations based thereon. [Figure 16] and [Figure 17] A diagram illustrating multiple beams for channel sensing / transmission. [Figure 18] FIG. 1 illustrates a beam-based channel sensing / transmission method. [Figure 19] ~ [Figure 22] FIG. 1 illustrates a beam-based channel sensing / transmission method according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0025] The terms used in this specification are generally used as widely as possible, taking into consideration the functions of the present invention. However, these may vary depending on the intentions of those skilled in the art, practice, or the emergence of new technologies. In addition, in certain cases, the applicant may arbitrarily select terms. In such cases, the meaning of the terms will be described in the description of the relevant invention. Therefore, it is clear that the terms used in this specification should be interpreted based on the substantive meaning of the terms and the overall content of this specification, rather than simply the names of the terms.

[0026] Throughout this specification, when a component is said to be "connected" to another component, this includes not only "directly connected" but also "electrically connected" through other components in between. Furthermore, when a component is said to "comprise" a specific component, this does not mean excluding the other component, but also means including the other component, unless otherwise specified to the contrary. In addition, limitations such as "more than" or "less than" based on a specific threshold may be appropriately replaced with "more than" or "less than," respectively, depending on the embodiment.

[0027] The following technologies are used in various wireless access systems, such as CDMA (code division multiple access), FDMA (frequency division multiple access), TDMA (time division multiple access), OFDMA (orthogonal frequency division multiple access), and SC-FDMA (single carrier frequency division multiple access). CDMA is implemented in radio technologies such as UTRA (Universal Terrestrial Radio Access) and CDMA2000. TDMA is implemented in radio technologies such as GSM (Global System for Mobile communications), GPRS (General Packet Radio Service), and EDGE (Enhanced Data Rates for GSM Evolution). OFDMA is implemented in radio technologies such as IEEE802.11 (Wi-Fi), IEEE802.16 (WiMAX), IEEE802-20, and E-UTRA (Evolved UTRA). UTRA is part of UMTS (Universal Mobile Telecommunications System). 3GPP® LTE (Long term evolution) is a part of E-UMTS (Evolved UMTS) that uses E-UTRA, and LTE-A (Advanced) is an evolved version of 3GPP® LTE. 3GPP® NR is a system designed separately from LTE / LTE-A to support enhanced Mobile Broadband (eMBB), Ultra-Reliable and Low Latency Communication (URLLC), and massive Machine Type Communication (mMTC) services, which are requirements of IMT-2020.For clarity of explanation, the following description will be focused on 3GPP (registered trademark) NR, but the technical idea of ​​the present invention is not limited to this.

[0028] Unless otherwise specified herein, a base station may include a next generation node B (gNB) defined in 3GPP NR. Also, unless otherwise specified, a terminal may include a user equipment (UE). Hereinafter, for ease of understanding, each content will be described as a separate embodiment, but each embodiment may be used in combination with each other. In this disclosure, "configuring" a terminal may mean configuration by a base station. Specifically, a base station may transmit a channel or a signal to a terminal to configure the operation of the terminal or parameter values ​​used in a wireless communication system.

[0029] FIG. 1 is a diagram illustrating an example of a radio frame structure used in a radio communication system.

[0030] Referring to FIG. 1, a radio frame used in a 3GPP (registered trademark) NR system has a length of 10 ms (ΔfmaxNf / 100)*Tc). The radio frame also 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 (registered trademark) NR system is 15*2 μkHz. μ is the subcarrier spacing configuration factor and has values ​​from 0 to 4. That is, 15 kHz, 30 kHz, 60 kHz, 120 kHz, or 240 kHz is used as the subcarrier spacing. A 1 ms long subframe consists of 2μ slots, each of which is 2-μms long. The 2μ slots in one subframe are numbered from 0 to 2μ-1. The slots in one radio frame are numbered from 0 to 10*2μ-1. Time resources are divided by at least one of the radio frame number (also called radio frame index), subframe number (also called subframe index), and slot number (or slot index).

[0031] 2 illustrates an example of a downlink (DL) / uplink (UL) slot structure in a wireless communication system, particularly a resource grid structure in a 3GPP (registered trademark) NR system.

[0032] There is one resource grid per antenna port. Referring to FIG. 2, a slot includes multiple OFDM symbols in the time domain and multiple resource blocks (RBs) in the frequency domain. An OFDM symbol also refers to one symbol interval. Unless otherwise specified, an OFDM symbol is simply referred to as a symbol. Hereinafter, the term "symbol" includes OFDM symbols, SC-FDMA symbols, DFTs-OFDM symbols, etc. Referring to FIG. 2, a signal transmitted from each slot is represented by a resource grid consisting of Nsize, μgrid, x*NRBSC subcarriers, and Nslotsymb OFDM symbols. Here, x=DL for the downlink resource grid and x=UL for the uplink resource grid. Nsize, μgrid, and x denote the number of resource blocks (RBs) according to the subcarrier spacing factor μ (x is DL or UL), and Nslotsymb denotes the number of OFDM symbols in a slot. NRBSC is the number of subcarriers constituting one RB, and NRBSC=12. Depending on the multiple access method, the OFDM symbol is called a cyclic prefix OFDM (CP-OFDM) symbol or a discrete Fourier transform spread OFDM (DFT-S-OFDM) symbol.

[0033] The number of OFDM symbols included in one slot may vary depending on the length of the cyclic prefix (CP). For example, a normal CP includes 14 OFDM symbols, while an extended CP includes 12 OFDM symbols. In a specific embodiment, the extended CP is used only with a subcarrier spacing of 60 kHz. For convenience of explanation, FIG. 2 illustrates a case where one slot consists of 14 OFDM symbols. However, the present invention is equally applicable to slots having other numbers of OFDM symbols. Referring to FIG. 2, each OFDM symbol includes Nsize, μgrid, and x*NRBSC subcarriers in the frequency domain. Subcarriers are classified into data subcarriers for transmitting data, reference signal subcarriers for transmitting reference signals, and guard bands. The carrier frequency is also called the center frequency (fc).

[0034] One RB is defined by NRBSC (e.g., 12) consecutive subcarriers in the frequency domain. Incidentally, a resource consisting of one OFDM symbol and one subcarrier is called a resource element (RE) or tone. Therefore, one RB consists of Nslotsymb*NRBSC resource elements. Each resource element in the resource grid is uniquely defined by an index pair (k, l) within one slot. k is an index ranging from 0 to Nsize, μgrid, x*NRBSC-1 in the frequency domain, and l is an index ranging from 0 to Nslotsymb-1 in the time domain.

[0035] In order for a terminal to receive a signal from a base station or transmit a base station signal, the time / frequency synchronization of the terminal must be aligned with the time / frequency synchronization of the base station, because if the base station and the terminal are not synchronized, the terminal cannot determine the time and frequency parameters required to demodulate DL signals and transmit UL signals at the correct time.

[0036] Each symbol in a radio frame operating in time division duplex (TDD) or unpaired spectrum consists of at least one of a downlink symbol (DL symbol), an uplink symbol (UL symbol), or a flexible symbol. A radio frame operating on a downlink carrier in frequency division duplex (FDD) or paired spectrum consists of downlink symbols or flexible symbols, and a radio frame operating on an uplink carrier consists of uplink symbols or flexible symbols. A downlink symbol allows downlink transmission but not uplink transmission, and an uplink symbol allows uplink transmission but not downlink transmission. Whether a flexible symbol is used for downlink or uplink is determined depending on the signal.

[0037] Information about the type of each symbol, i.e., information indicating any one of downlink symbols, uplink symbols, and flexible symbols, is formed by a cell-specific (or common) RRC signal. The information about each symbol type is additionally formed by a UE-specific (or dedicated) RRC signal. The base station uses the cell-specific RRC signal to notify i) the period of the cell-specific slot configuration, ii) the number of slots having only downlink symbols from the beginning of the period of the cell-specific slot configuration, iii) the number of downlink symbols from the first symbol in the slot immediately following the slot having only downlink symbols, iv) the number of slots having only uplink symbols from the end of the period of the cell-specific slot configuration, and v) the number of uplink symbols from the last symbol in the slot immediately preceding the slot having only uplink symbols. Here, symbols that are not configured as either uplink or downlink symbols are flexible symbols.

[0038] If the information regarding the symbol type consists of the per-terminal RRC signal, the base station signals, via the cell-specific RRC signal, whether the flexible symbol is a downlink symbol or an uplink symbol. At this time, the per-terminal RRC signal cannot change a downlink symbol or an uplink symbol that consists of the cell-specific RRC signal to another symbol type. The per-terminal RRC signal signals, for each slot, the number of downlink symbols among the Nslotsymb symbols of the slot and the number of uplink symbols among the Nslotsymb symbols of the slot. At this time, the downlink symbols of the slot are continuously configured from the first symbol to the i-th symbol of the slot. Also, the uplink symbols of the slot are continuously configured from the j-th symbol to the last symbol of the slot (where i < j). In a slot, a symbol that is not configured as either an uplink symbol or a downlink symbol is a flexible symbol.

[0039] The type of symbol configured with the RRC signal as described above can be called a semi-static DL / UL configuration. In the semi-static DL / UL configuration configured with the RRC signal as described above, the flexible symbol may be indicated as a downlink symbol, an uplink symbol, or a flexible symbol by the dynamic SFI (slot format information) transmitted on the physical downlink control channel (PDCCH). At this time, a downlink symbol or an uplink symbol configured with the RRC signal is not changed to another symbol type. Table 1 exemplifies the dynamic SFI that the base station can indicate to the terminal.

[0040]

Table 1

[0041] In Table 1, D represents a downlink symbol, U represents an uplink symbol, and X represents a flexible symbol. As shown in Table 1, up to two DL / UL switchings may be allowed within one slot.

[0042] FIG. 3 is a diagram illustrating physical channels used in a 3GPP (registered trademark) system (e.g., NR) and a general signal transmission method using the physical channels.

[0043] When a terminal is powered on or newly enters a cell, the terminal performs an initial cell search (S101). Specifically, the terminal synchronizes with a base station during the initial cell search. To do this, the terminal receives a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) from the base station to synchronize with the base station and acquire information such as a cell index. Next, the terminal receives a physical broadcast channel from the base station to acquire broadcast information within the cell.

[0044] After completing the initial cell search, the terminal receives a physical downlink shared channel (PDSCH) via a physical downlink control channel (PDCCH) and information carried on the PDCCH to acquire more detailed system information than that acquired through the initial cell search (S102). Here, the system information transmitted to the terminal is cell-common system information for the terminal to operate correctly in a physical layer in Radio Resource Control (RRC), and is called remaining system information or system information block (SIB) 1.

[0045] When a terminal first connects to a base station or when there are no radio resources for signal transmission (when the terminal is in RRC_IDLE mode), the terminal can perform a random access procedure with the base station (steps S103 to S106). First, the terminal transmits a preamble on a physical random access channel (PRACH) (S103) and can receive a response message for the preamble from the base station on a PDCCH and a corresponding PDSCH (S104). If the terminal receives a valid random access response message, the terminal transmits data including its own identifier, etc. to the base station on a physical uplink shared channel (PUSCH) indicated by an uplink grant transmitted from the base station on the PDCCH (S105). Next, the terminal waits for reception of a PDCCH as instructed by the base station to resolve collisions. If the terminal successfully receives the PDCCH with its own identifier (S106), the random access procedure ends. During the random access procedure, the terminal can acquire terminal-specific system information required for the terminal to operate correctly in the physical layer of the RRC layer. If the terminal acquires the terminal-specific system information in the RRC layer, the terminal enters the RRC connected mode (RRC_CONNECTED mode).

[0046] The RRC layer is used to generate and manage messages for control between a terminal and a radio access network (RAN). Furthermore, the base station and terminal can broadcast cell system information required for all terminals in the cell, manage paging message transmission, manage mobility and handover, report terminal measurements and related control, and manage and store terminal capabilities at the RRC layer. Generally, the update of signals transmitted at the RRC layer (hereinafter referred to as RRC signals) is longer than the transmission / reception period (i.e., transmission time interval, TTI) at the physical layer, so that the RRC configuration can be maintained unchanged for a long period.

[0047] After the above procedures, the terminal receives a PDCCH / PDSCH (S107) and transmits a physical uplink shared channel (PUSCH) / physical uplink control channel (PUCCH) (S108) as a general uplink / downlink signal transmission procedure. In particular, the terminal receives downlink control information (DCI) via the PDCCH. The DCI includes control information such as resource allocation information for the terminal. The format of the DCI may vary depending on the purpose of use. The uplink control information (UCI) transmitted by the terminal to the base station via the uplink includes a downlink / uplink ACK / NACK signal, a channel quality indicator (CQI), a precoding matrix index (PMI), a rank indicator (RI), etc. Here, the CQI, PMI, and RI are included in channel state information (CSI). In the case of a 3GPP NR system, the terminal transmits control information such as the above-mentioned HARQ-ACK and CSI via the PUSCH and / or PUCCH.

[0048] FIG. 4 is a diagram illustrating an SS / PBCH block for initial cell access in a 3GPP NR system.

[0049] When a terminal is powered on or attempts to access a new cell, it acquires time and frequency synchronization with the cell and performs an initial cell search process. During the cell search process, the terminal detects the cell's physical cell identity (NcellID). To do this, the terminal receives synchronization signals, such as a primary synchronization signal (PSS) and a secondary synchronization signal (SSS), from the base station to synchronize with the base station. At this time, the terminal obtains information such as a cell identity (ID).

[0050] The synchronization signal (SS) will be described in more detail with reference to Figure 4(a). The synchronization signal is divided into a PSS and an SSS. The PSS is used to obtain time-domain synchronization and / or frequency-domain synchronization, such as OFDM symbol synchronization and slot synchronization. The SSS is used to obtain frame synchronization and a cell group ID. Referring to Figure 4(a) and Table 1, an SS / PBCH block consists of 20 consecutive RBs (=240 subcarriers) on the frequency axis and 4 consecutive OFDM symbols on the time axis. In this case, in the SS / PBCH block, the PSS is transmitted in the first OFDM symbol, and the SSS is transmitted in the third OFDM symbol via subcarriers 56 to 182. Here, the lowest subcarrier index in the SS / PBCH block starts from 0. In the first OFDM symbol in which the PSS is transmitted, the base station does not transmit signals via the remaining subcarriers, i.e., subcarriers 0 to 55 and 183 to 239. In addition, in the third OFDM symbol in which the SSS is transmitted, the base station does not transmit signals through subcarriers 48 to 55 and 183 to 191. The base station transmits a physical broadcast channel (PBCH) through the remaining REs in the SS / PBCH block excluding the signals.

[0051] [Table 2]

[0052] The SS groups a total of 1008 unique physical layer cell IDs (physical layer cell IDs) into 336 physical layer cell ID groups, each containing three unique identifiers, through the combination of three PSSs and SSSs. Specifically, each physical layer cell ID is part of only one physical layer cell ID group. Thus, the physical layer cell ID NcellID = 3N(1)ID + N(2)ID is uniquely defined by an index N(1)ID ranging from 0 to 335 indicating a physical layer cell ID group and an index N(2)ID ranging from 0 to 2 indicating a physical layer identifier within the physical layer cell ID group. The UE detects the PSS and identifies one of the three unique physical layer identifiers. The UE also detects the SSS and identifies one of the 336 physical layer cell IDs associated with the physical layer identifier. In this case, the PSS sequence dPSS(n) is as follows:

[0053]

number

[0054] where x(i+7)=(x(i+4)+x(i)) mod 2,

[0055] Given that [x(6)x(5)x(4)x(3)x(2)x(1)x(0)]=[1110110].

[0056] Also, the SSS sequence dSSS(n) is as follows:

[0057]

number

[0058] where x0(i+7)=(x0(i+4)+x0(i))mod 2 x1(i+7)=(x1(i+1)+x1(i))mod 2,

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

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

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

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

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

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

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

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

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

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

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

[0070] [Table 3]

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[0093] Meanwhile, 3GPP NR uses the concept of a cell to manage radio resources. A cell is defined as a combination of downlink and uplink resources, i.e., a combination of a DL CC and a UL CC. A cell may consist of only DL resources or a combination of DL and UL resources. If carrier aggregation is supported, the linkage between the carrier frequency of DL resources (or DL ​​CC) and the carrier frequency of UL resources (or UL CC) is indicated by system information. The 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 the downlink is a DL PCC, and a carrier corresponding to a PCell in the uplink is a UL PCC. Similarly, a carrier corresponding to an SCell in the downlink is a DL SCC, and a carrier corresponding to an SCell in the uplink is a UL SCC. Depending on the terminal capacity, a serving cell(s) may consist of one PCell and zero or more SCells. For a UE in RRC_CONNECTED state but not configured with carrier aggregation or not supporting carrier aggregation, there is only one serving cell consisting of only a PCell.

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

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

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

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

[0098] <Communication methods in unlicensed spectrum>

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

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

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

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

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

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

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

[0106] ●Category 1: No LBT

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

[0108] Category 2: LBT without random backoff

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

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

[0111] - The Tx entity obtains a random number within a fixed-size CW, sets it as the initial value of a backoff counter (or backoff timer) N, and performs backoff using the set backoff counter N. That is, in the backoff procedure, the Tx entity decrements the backoff counter by 1 each time the channel is sensed as idle during a pre-set slot period. Here, the pre-set slot period may be 9 us, but the present invention is not limited 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 can transmit. Meanwhile, to perform backoff, the Tx entity decrements the second interval (i.e., the defer period T d) to determine whether the channel is idle. According to an embodiment of the present invention, the Tx entity can sense (or determine) whether the channel is idle during the second interval based on whether the channel is idle during at least a portion (e.g., one slot) of the second interval. The second interval may be set based on the channel access priority class of the Tx entity and may consist of a 16 us period and m consecutive slot periods, where m is a value set by the channel access priority class. If the channel is sensed as idle during the second interval, the Tx entity performs channel sensing to decrease the backoff counter. On the other hand, if the channel is sensed as occupied during the backoff procedure, the backoff procedure is aborted. After aborting the backoff procedure, the Tx entity can resume backoff if the channel is sensed as idle during an additional second interval. In this way, the Tx entity can transmit if the channel is idle for N slot periods of the backoff counter in addition to the second interval. At this time, the initial value of the backoff counter N is obtained within a CW of fixed size.

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

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

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

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

[0116] To perform channel access, the Tx entity first waits for a defer period T d According to an embodiment of the present invention, the defer period T d The channel sensing for the defer period T d For example, the defer period T d The channel sensing for the defer period T d The Tx entity may perform channel sensing during one slot period within the defer period T d It is checked whether the channel is idle by channel sensing for the channel (S304). dIf the channel is sensed as idle for the defer period T, the Tx entity proceeds to step S306. d If the channel is not sensed as idle for the defer period T (i.e., sensed as occupied), the Tx entity returns to step S302. d The steps S302 to S304 are repeated until the device is sensed as being in an idle state. d may be set based on the channel access priority class of the Tx entity and consists of a period of 16us and m consecutive slot periods, where m is the value set by the channel access priority class.

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

[0118] In step S308, the Tx entity determines whether the value of the backoff counter N is 0. If the value of the backoff counter N is 0, the Tx entity proceeds to step S320 and transmits. If the value of the backoff counter N is not 0, the Tx entity proceeds to step S310. In step S310, the Tx entity decrements the value of the backoff counter N by 1. According to one embodiment, the Tx entity may selectively decrement the value of the backoff counter by 1 during the channel sensing process for each slot. At this time, step S310 may be skipped at least once depending on the Tx entity's selection. Next, the Tx entity performs channel sensing for an additional slot period (S312). The Tx entity determines whether the channel is idle through channel sensing for the additional slot period (S314). If the channel is sensed as idle for the additional slot period, the Tx entity returns to step S308. In this manner, the Tx entity can decrement the backoff counter by 1 each time the channel is sensed as idle during a pre-set slot period, where the pre-set slot period may be 9 us, but the present invention is not limited thereto.

[0119] If the channel is not sensed as idle (i.e., sensed as occupied) for an additional slot period in step S314, the Tx entity proceeds to step S316. In step S316, the Tx entity determines whether the channel is to be idle for an additional deferred period T d According to an embodiment of the present invention, the channel sensing in step S316 may be performed in slot units. That is, the Tx entity may check whether the channel is idle in the additional defer period T d Check whether the channel is sensed as idle for all slot periods of T d If an occupied slot is detected within the additional defer period T, the Tx entity immediately restarts step S316. dIf the channel is sensed as idle for the entire slot period, the Tx entity returns to step S308.

[0120] On the other hand, if the value of the backoff counter N is confirmed as 0 in step S308, the Tx entity performs transmission (S320). The Tx entity receives HARQ-ACK feedback corresponding to the transmission (S322). The Tx entity can determine whether the previous transmission was successful based on the received HARQ-ACK feedback. Next, the Tx entity adjusts the CW size for the next transmission based on the received HARQ-ACK feedback (S324).

[0121] Thus, the Tx entity can transmit the data for a deferred period T d After sensing the channel as idle for N additional slot periods, transmission can occur if the channel is idle. As mentioned above, the Tx entity may be a base station or a terminal, and the channel access process of FIG. 13 may be used for downlink transmission of the base station and / or uplink transmission of the terminal.

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

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

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

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

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

[0127] The cellular communication interface card 122 transmits and receives wireless signals to and from at least one of the base station 200, the external device, and the 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 a cellular communication standard or protocol for the frequency band above 6 GHz that the NIC module supports.

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

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

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

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

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

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

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

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

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

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

[0138] The terminal 100 and base station 200 shown in Figure 14 are block diagrams according to one embodiment of the present invention, and the separate blocks are used to logically distinguish between the elements of the devices. 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.

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

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

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

[0142] When the downlink channel transmitted by the wireless communication device includes data traffic, the defer duration may be set based on the channel access priority class of the traffic included in the downlink channel. f ) one or more (m p ) slot section (T sl ) can be included. In this case, the slot interval (T slThe duration of the initial interval may be 9 us. sl ) is included in the defer period. p ) may be set based on the channel access priority class as described above. Specifically, the number of slot periods included in the defer period (m p ) may be set as shown in Table 4.

[0143] [Table 4]

[0144] In addition, the wireless communication device can set the range of the CW value according to the channel access priority class. min,p <=CW<=CW max,p The CW value can be set to satisfy the following. min,p ) and maximum value (CW max,p ) may be determined by the channel access priority class. Specifically, the minimum value of CW (CW min,p ) and maximum value (CW max,p ) may be determined as shown in Table 4. The wireless communication device determines the minimum value of CW (CW min,p ) and maximum value (CW max,p ) can be set. When a wireless communication device accesses a channel, the wireless communication device can adjust the value of CW as previously described in FIG. 13. In addition, in the unlicensed band, MCOT(T mcot,p) may be determined according to the channel access priority of the data included in the transmission, as described above. Specifically, the MCOT may be determined as shown in Table 4. As a result, the wireless communication device may not be allowed to transmit continuously in the unlicensed band for a time exceeding the MCOT. This is because the unlicensed band is a frequency band that various wireless communication devices use according to certain rules. In Table 4, when the value of the channel access priority class is p=3 or p=4 and there is no wireless communication device that uses the unlicensed band for a long term according to the regulations and uses other technology, the wireless communication device mcot,p = 10 ms. Otherwise, the wireless communication device mcot,p =8ms.

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

[0146] [Table 5]

[0147] As shown in Table 5, the MCOT value of 6 ms may be increased to 8 ms if a transmission includes one or more gaps. A gap refers to the time from when transmission is interrupted on a carrier until transmission resumes on that carrier. In this case, the minimum duration of a gap is 100 us. The maximum duration of a transmission before a gap is 6 ms. The duration of a gap is not included in the channel occupancy time. When 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, other wireless access technologies may include Wi-Fi. In other cases, the MCOT value may be determined as described in Note 1 of Table 5.

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

[0149] <Sensing structure in the deferral period>

[0150] The present invention proposes a basic sensing slot structure for performing LBT in the 52.6 GHz or higher band, and also proposes a slot sensing structure for performing LBT by measuring energy in a deferred interval of a specific length that can be commonly used in the 52.6 GHz or higher band.

[0151] First, it is assumed that a base station or a terminal, i.e., a wireless device, performs sensing within a 5 us observation slot in a band above 52.6 GHz. In this case, the period during which the wireless device performs sensing within the 5 us observation slot may be defined as at least T [us], rather than being precisely defined. If the power detected during sensing by the wireless device for T [us] within the 5 us observation slot is below an energy detection threshold (EDT), the channel may be determined to be idle in the observation slot. Here, the energy detection threshold may be calculated using Equation 1 or Equation 2 below.

[0152] [Mathematical formula 1] EDT = -80 dBm + 10*log10(Pmax / Pout) + 10*log10(operating Channel BW in MHz)

[0153] Here, Pout is RF output power (effective isotropic radiated power, EIRP), and Pmax is the RF out power limit. Pout may always be set to be smaller than or equal to Pmax. Also, the operating channel BW [MHz] represents the channel BW in which the wireless device performs sensing. The operating channel BW may be set to one of the transmission BW, the basic LBT band, or the channel BW in which LBT can be performed. The operating channel BW (e.g., LBT band) is composed of a set of multiple contiguous frequency resources (e.g., PRBs).

[0154] [Mathematical formula 2] EDT = -80 dBm + Pmax - Pout + 10*log10(BW)

[0155] Here, Pout represents the maximum EIRP of transmission intended by a wireless device requesting one CO (channel occupancy) and is expressed in dBm, and Pmax is the RF out power limit, also expressed in dBm. Pout may always be set to be smaller than or equal to Pmax. The maximum EIRP used by a wireless device that initiates transmission in the CO for that transmission is limited to Pout. Also, BW [MHz] represents the channel BW in which the wireless device performs sensing. The channel BW may be set to one of the transmission BW, the basic LBT band in which LBT can be performed, or the channel BW. A channel BW (e.g., an LBT band) consists of a set of multiple contiguous frequency resources (e.g., PRBs).

[0156] The length of the defer interval commonly used for wireless device sensing may be defined as 8 us. However, it may be necessary to define a method for setting a sensing slot at 8 us and a period for wireless device sensing. It may also be necessary to define how many sensing operations, i.e., energy measurements, should be performed within the 8 us defer interval. The present invention proposes a sensing structure for such energy measurement.

[0157] First, when only one energy measurement is performed within an 8 us defer interval, the sensing structure may be considered as follows.

[0158] As a first method, to prevent missing the fact that the channel is not idle within 8 us, i.e., the channel is in use, an observation slot, i.e., 5 us, can be set within the last 5 us of the 8 us defer interval. In this case, if the channel is sensed as idle for at least the entire 5 us interval based on energy measurement in an interval that is at least smaller than the actual 5 us that occurs in the observation slot, for example, 3 us (or 4 us), the channel may be determined / set as idle within the 8 us defer interval.

[0159] As a second method, to avoid missing the fact that the channel is not idle within 8 us, i.e., the channel is in use, an observation slot, i.e., 5 us, can be set in the last 5 us of the 8 us defer interval. In this case, if the channel is sensed as idle for at least the entire 5 us interval based on energy measurement in an interval that is at least smaller than the actual 5 us occurring in the defer interval, for example, 3 us (or 4 us), the channel may be determined / set as idle within the 8 us defer interval.

[0160] As a third method, when the channel is found to be idle after sensing and transmission is actually performed, in order to guarantee the Rx-to-Tx switching interval, at least Y [us] at the end of the defer interval can be preset as the Rx-to-Tx switching interval, and the last 5 [us] of the remaining (8-Y) [us] interval can be set as an observation slot. In this case, if the channel is sensed as idle by one channel sensing within the 5 us observation slot, the channel can be determined / set as idle within the 8 us defer interval.

[0161] As a fourth method, when the channel is found to be idle after sensing and transmission is actually performed, to guarantee an Rx-to-Tx switching interval, at least Y [us] at the end of the defer interval can be preset as the Rx-to-Tx switching interval, and the last 5 [us] of the remaining (8-Y) [us] interval can be set as an observation slot. In this case, if the channel is sensed as idle for at least the entire 5 us interval based on energy measurement in an interval that is at least 3 us (or 4 us) shorter than the actual 5 us that occurs in the observation slot, the channel may be determined / set as idle within the 8 us defer interval.

[0162] As a fifth method, when the channel is found to be idle after sensing and transmission is actually performed, at least Y [us] at the end of the defer interval may be preset as the Rx-to-Tx switching interval to guarantee an Rx-to-Tx switching interval. In this case, if the channel is sensed as idle for at least the entire 5 us interval based on energy measurement in at least a 3 us (or 4 us) interval, which is actually less than 5 us within the remaining (8-Y) [us] interval, the channel may be determined / set as idle within the 8 us defer interval.

[0163] Next, when two energy measurements are performed within an 8 us defer interval, the sensing structure may be considered as follows.

[0164] As a first method, to ensure that the channel is not idle within the 8 usb period, i.e., that the channel is in use, the 8 usb defer interval can be set as a 3 usb period before and a 5 usb period after. That is, the last 5 usb of the 8 usb defer interval can be set as one observation slot. In this case, energy measurement can be performed once within the first 3 usb period and again within the last 5 usb observation slot. If the channel is sensed as idle from both energy measurement results, the channel can be determined / set as idle within the 8 usb defer interval.

[0165] As a second method, to ensure that the channel is not idle within the 8 usb period, i.e., the channel is in use, the 8 usb defer interval can be set as a 3 usb period before and a 5 usb period after. That is, the last 5 usb of the 8 usb defer interval can be set as one observation slot. Energy measurement can be performed once within the 3 usb period, and then again within the last 3 usb period of the last 5 usb observation slot. If both energy measurement results indicate that the channel is idle, the channel can be determined / set as idle within the 8 usb defer interval.

[0166] As a third method, to guarantee an Rx-to-Tx switching interval when the channel is idle after sensing and transmission is actually performed, at least Y us at the end of the defer interval can be preset as the Rx-to-Tx switching interval, and the remaining (8-Y) us interval can be set to a first 3 us interval and a second (8-Y-3) us interval. In this case, energy measurement can be performed once in the first 3 us interval and again in the last (8-Y-3) us interval. If the channel is sensed as idle in both energy measurements, the channel can be determined / set as idle within the 8 us defer interval. However, if the (8-Y-3) us interval is set to be at least Z us, the minimum setting interval for energy measurement, energy measurement can be set to be performed again within the last (8-Y-3) us interval. If the (8-Y-3) [us] interval is less than Z [us], the channel may be determined / set to be idle within that 8us defer interval based solely on energy measurements within the previous 3us interval.

[0167] The Type 1 / 2 / 3 channel access procedure (CAP) proposed in the present invention can be defined as follows: In the description of the present invention, performing a Type X channel access procedure may be expressed as performing a Type X channel access.

[0168] - Type 1 Channel Access Procedure (CAP)

[0169] * A channel access method with a fixed CW (contention window) and random backoff without CW adjustment.

[0170] - Type 2 Channel Connection Procedure (CAP)

[0171] * A channel access method that performs sensing without backoff during a single interval time period. The time period during which sensing should be performed before UL or DL ​​transmission is deterministically set. The single interval time period spans at least one sensing slot that should be sensed as idle before transmission.

[0172] *As an example, a single interval (T_d) may include a sensing slot for performing at least one single measurement to determine whether a channel is sensed as idle, and if the channel is sensed as idle, transmission may occur on that channel immediately after T_d.

[0173] - Type 3 Channel Access Procedure (CAP)

[0174] * A channel connection method that transmits on the channel without channel sensing.

[0175] <Multiple beam-based channel sensing / transmission>

[0176] The present invention relates to a sensing method performed before the start of CO and a transmission method after CO is set (e.g., within CO) when one node (e.g., a base station, a terminal) senses a channel based on multiple beam operation, sets COT (channel occupancy time) (or channel occupancy, CO) based on the sensing results, and attempts to transmit.

[0177] 16 and 17 illustrate multiple beams for channel sensing / transmission. Referring to FIG. 16 and FIG. 17, in the frequency domain, a BW includes multiple channel BWs (e.g., LBT BWs), and channel sensing / transmission may be performed on a channel BW basis. A channel BW may be composed of multiple consecutive PRBs (i.e., a PRB set) in the frequency domain. In the spatial domain, one channel BW may be divided into multiple beams. Multiple beams within a channel BW share time-frequency resources, and channel sensing / transmission may be performed on a beam-by-beam basis.

[0178] FIG. 18 illustrates a beam-based channel sensing / transmission method. Referring to FIG. 18, channel sensing / transmission may be performed on a beam basis. In FIG. 18, s, f, and t represent the spatial axis, the frequency axis, and the time axis, respectively. Meanwhile, a beam on which channel sensing is performed (hereinafter, a sensing beam) and a beam on which channel transmission is performed (hereinafter, a transmission beam) may be configured independently. The association / correspondence relationship between a sensing beam and a transmission beam may be defined as one-to-one or one-to-many. For example, one sensing beam may cover all transmission beams (Case A), or one sensing beam may cover one or more transmission beams (Case B). Therefore, a channel access procedure for a transmission beam includes performing a channel access procedure for a sensing beam corresponding to the transmission beam. For example, if channel transmission (on a transmission beam) is required, channel sensing is performed on a sensing beam before CO (or COT), and once the CO is configured based on the channel sensing result, channel transmission may be performed on (or using) a transmission beam corresponding to the CO. CO may be initiated at the same time for multiple transmit beams.

[0179] When a CO includes transmissions that are spatial domain multiplexed (SDM) among different beams, the following methods may be used as sensing methods before the CO is started and transmission methods after the CO is set up (e.g., within the CO): Figure 19 illustrates channel sensing / transmission operations when transmissions included in the CO are spatial domain multiplexed among multiple beams.

[0180] 1. A single sensing beam covers all transmitting beams within one CO (Fig. 18, Case A).

[0181] A. If one sensing beam covers all transmit beams within a CO, Type 1 channel access (procedure) can be performed using one single sensing beam before the start of the CO. Then, if channel access is successful using the single sensing beam, transmission can begin in the CO using a specific transmit beam (Figure 19, Tx beam #0 / 1). In this case, Type 3 channel access (procedure) can be performed within the same CO for transmissions using different transmit beams, and transmissions intended to be transmitted using the corresponding transmit beam can be transmitted (Figure 19, Tx beam #2). In other words, transmissions included in the CO using spatial domain multiplexing can be transmitted without sensing (for the corresponding sensing beam) between transmit beams. On the other hand, if Type 1 channel access fails before the start of the CO, transmissions intended to be transmitted using the corresponding transmit beam can be dropped.

[0182] 2. Each sensing beam covers at least one transmitting beam within one CO (Figure 18, Case B).

[0183] A. When using multiple sensing beams and performing Type 1 channel connection before the start of CO simultaneously (i.e., CO starts at the same time between transmit beams),

[0184] i. An independent Ninit value can be set for each sensing beam (see FIG. 13), and a backoff-based Type 1 channel connection (procedure) can be performed for each sensing beam. Since the channel conditions for each sensing beam may differ, if channel connection for at least one sensing beam is successful, transmission is performed using a transmission beam corresponding to the sensing beam. This has the advantage of reducing latency due to an LBT failure for a transmission intended by a node (e.g., a base station or a terminal). Even if channel connection for one of the sensing beams fails, if channel connection for at least one of the sensing beams is successful, the intended transmission may be performed based on the transmission beam corresponding to the successful sensing beam. However, for a transmission intended to be transmitted using a transmission beam corresponding to a sensing beam for which channel connection failed, the transmission may be dropped.

[0185] ii. Backoff is performed for each sensing beam. An Ninit value is extracted for each sensing beam, and the maximum value of the independent Ninit values ​​for each sensing beam is set as a common Ninit value, allowing Type 1 channel access (procedure) to be performed for each sensing beam. This is a method of setting the maximum length of backoff that can be performed for each sensing beam, even though the channel conditions may differ for each sensing beam. Backoff is performed for each sensing beam within the maximum backoff length, and if channel access for at least one sensing beam is successful within the maximum length, transmission is performed using the transmission beam corresponding to that sensing beam. This has the advantage of reducing latency due to LBT failure for intended transmission at a single node (e.g., base station or terminal). Furthermore, even if channel access for one of the sensing beams fails, if channel access for at least one of the sensing beams is successful, the intended transmission can be performed using the transmission beam corresponding to the successful sensing beam. However, for a transmission intended to be transmitted using a transmission beam corresponding to a sensing beam that has failed to achieve channel connection among the sensing beams, the transmission may be dropped.

[0186] When a CO includes transmissions that are time domain multiplexed (TDM) among different beams, the following methods may be used as the sensing method performed before the CO is started and the transmission method after the CO is set up (e.g., within the CO): Figures 20 to 22 illustrate examples of channel sensing / transmission operations when the transmissions included in the CO are time domain multiplexed among multiple beams.

[0187] Referring to FIG. 20 , a node (e.g., a base station or a terminal) can perform a channel access (procedure) (e.g., a Type 1 channel access procedure) for one or more sensing beams before initiating CO. If the channel access is successful, the node can transmit within the CO using a first transmit beam (e.g., Tx beam #0 in FIG. 20). On the other hand, if transmission within the CO is to be performed using a second transmit beam in a time-domain multiplexing manner (e.g., Tx beam #2 in FIG. 20), the node can perform a channel access (procedure) for a sensing beam corresponding to the second transmit beam to transmit on the second transmit beam. Here, the channel access procedure may include a Type 2 or Type 3 channel access (procedure). When transmissions using the first transmit beam and the second transmit beam are multiplexed in the time domain, the transmissions on the first transmit beam and the second transmit beam do not overlap in the time domain. CO may be initiated at the same time for multiple transmit beams.

[0188] 1. When a single sensing beam covers all transmitting beams within one CO

[0189] A. When one sensing beam covers all transmit beams, Type 1 channel connection can be performed using one single sensing beam before the start of CO. Then, if channel connection is successful using the single sensing beam, transmission can be started in the CO using a specific transmit beam (e.g., Tx beam #0 in Figure 20). In this case, for transmissions using different transmit beams (e.g., Tx beam #1 / 2 in Figure 20), Type 3 channel connection can be performed (for the sensing beam) within the same CO, and transmissions intended to be transmitted using the corresponding transmit beam can be transmitted (e.g., Tx beam #2 in Figure 20). However, if Type 1 channel connection (using the sensing beam) fails before the start of CO, transmissions intended to be transmitted using the corresponding transmit beam may be dropped.

[0190] 2. Each sensing beam covers at least one transmitting beam within one CO.

[0191] A. When using multiple sensing beams and performing Type 1 channel connection before the start of CO simultaneously (i.e., CO starts at the same time between transmit beams),

[0192] i. An independent Ninit value can be set for each sensing beam (see FIG. 13), and backoff-based Type 1 channel access can be performed for each sensing beam. This is because, since the channel conditions for each sensing beam may differ, if channel access for at least one sensing beam is successful, transmission is performed using a transmission beam corresponding to the sensing beam. This has the advantage of reducing latency due to LBT failure for transmission intended by a single node (e.g., a base station or a terminal). Even if channel access for one of the sensing beams fails, if channel access for at least one of the sensing beams is successful, the intended transmission can be performed using a transmission beam corresponding to the successful sensing beam. However, transmissions intended to be transmitted using a transmission beam corresponding to a sensing beam that failed to be channel accessed may be dropped.

[0193] Also, if channel connection is successful (all) for the first sensing beam, the intended transmission can be first performed by TDM multiplexing (using a transmit beam corresponding to the sensing beam for which channel connection was successful) (e.g., Tx beam #0 in Figures 21 and 22). Meanwhile, for subsequent transmissions within the CO, i.e., for transmissions using a different transmit beam (Tx beam #1 in Figure 21) (corresponding to the sensing beam for which channel connection was successful), Type 3 channel connection can be performed (for the sensing beam) within the same CO, and the intended transmission can be performed using the corresponding transmit beam.

[0194] Furthermore, even if all channel connections corresponding to the first sensing beam (among the sensing beams) are successful, beam switching to a transmit beam (e.g., Tx beam #2 in Figure 22) that does not correspond to a previously sensed beam (beam that has already been sensed; first sensing beam) can be performed (e.g., Tx beam #0 => #2 in Figure 22). In this case, Type 2 channel connection can be performed (for the sensing beam corresponding to the transmit beam) within the CO (e.g., Tx beam #2 in Figure 22). If Type 2 channel connection within the CO is successful, the node (e.g., a base station or a terminal) can perform beam switching to the intended transmit beam and transmit. On the other hand, if Type 2 channel connection within the CO (for the sensing beam corresponding to the transmit beam) fails, the node (e.g., a base station or a terminal) can perform Type 1 channel connection (within the CO) to a sensing beam corresponding to a transmit beam (e.g., Tx beam #2 in Figure 22) that is not included in the previously sensed beam (e.g., the first sensing beam) and transmit. However, if the Type 1 channel connection fails, the transmission intended to be transmitted using the corresponding transmit beam may be dropped.

[0195] ii. Backoff is performed for each sensing beam. An Ninit value is extracted for each sensing beam, and the maximum value of the independent Ninit values ​​for each sensing beam is set as a common Ninit value, thereby performing Type 1 channel access for each sensing beam. This is a method of setting the maximum length of backoff that can be performed for each sensing beam, even though the channel conditions may differ depending on the sensing beam. This is to perform backoff for each sensing beam within the maximum backoff length, and if channel access for at least one sensing beam is successful within the maximum backoff length, transmission is performed using a transmission beam corresponding to the sensing beam. This can also have the advantage of reducing latency due to LBT failure for an intended transmission at a single node (e.g., a base station or a terminal). Even if channel access for one of the sensing beams fails, if channel access for at least one of the sensing beams is successful, the intended transmission can be performed using a transmission beam corresponding to the successful sensing beam. However, for a transmission intended to be transmitted using a transmission beam corresponding to a sensing beam that has failed to achieve channel connection among the sensing beams, the transmission may be dropped.

[0196] Also, if channel connection is successful (all) for the first sensing beam, the intended transmission can be first performed by TDM multiplexing (using a transmit beam corresponding to the sensing beam for which channel connection was successful) (e.g., Tx beam #0 in Figures 21 and 22). Meanwhile, for subsequent transmissions within the CO, i.e., for transmissions using a different transmit beam (Tx beam #1 in Figure 21) (corresponding to the sensing beam for which channel connection was successful), Type 3 channel connection can be performed (for the sensing beam) within the same CO, and the intended transmission can be performed using the corresponding transmit beam.

[0197] Furthermore, even if all channel connections corresponding to the first sensing beam (among the sensing beams) are successful, beam switching to a transmit beam (e.g., Tx beam #2 in Figure 22) that does not correspond to a previously sensed beam (beam that has already been sensed; first sensing beam) can be performed (e.g., Tx beam #0 => #2 in Figure 22). In this case, Type 2 channel connection can be performed (for the sensing beam corresponding to the transmit beam) within the CO (e.g., Tx beam #2 in Figure 22). If Type 2 channel connection within the CO is successful, the node (e.g., a base station or a terminal) can perform beam switching to the intended transmit beam and transmit. On the other hand, if Type 2 channel connection within the CO (for the sensing beam corresponding to the transmit beam) fails, the node (e.g., a base station or a terminal) can perform Type 1 channel connection (within the CO) to a sensing beam corresponding to a transmit beam (e.g., Tx beam #2 in Figure 22) that is not included in the previously sensed beam (e.g., the first sensing beam) and transmit. However, if the Type 1 channel connection fails, the transmission intended to be transmitted using the corresponding transmit beam may be dropped.

[0198] Although the methods and systems of the present invention have been described in connection with particular embodiments, some or all of their components or operations may be implemented using a computing system having a general-purpose hardware architecture.

[0199] 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.

[0200] The scope of the present invention is indicated by the claims set forth below rather than by the above detailed description, and any modifications or variations derived from the meaning and scope of the claims and their equivalents should be construed as being within the scope of the present invention.

Claims

1. 1. A wireless device configured to operate in a wireless communication system, comprising: a communication module; a processor for controlling the communication module; The processor: Before a channel occupancy (CO) begins, simultaneous sensing is performed for a plurality of transmit (Tx) beams by applying a first channel connection for each sensing beam, and the sensing beam covers at least one Tx beam of the plurality of Tx beams; transmitting on a first Tx beam of the plurality of Tx beams within the CO if the first channel connection is successful for the plurality of Tx beams; configured to perform a second channel connection within the CO prior to beam switching from the first Tx beam to a second Tx beam for time-domain multiplexed transmission within the CO; a type of the second channel connection is determined based on whether the second Tx beam is included in the plurality of Tx beams as follows: - if the second Tx beam is not included in the plurality of Tx beams, it is a Type 2 channel connection; - A wireless device that is a Type 3 channel connection when the second Tx beam is included in the plurality of Tx beams.

2. The wireless device of claim 1 , wherein the Type 2 channel connection is based on sensing the channel only within a fixed interval, and the Type 3 channel connection is made without sensing the channel.

3. The wireless device of claim 1 , wherein the CO is initiated identically for the multiple Tx beams.

4. The wireless device of claim 1 , wherein the first channel connection is performed independently for each sensing beam based on a random backoff.

5. The wireless device of claim 4 , wherein an initial value of a random backoff counter in the first channel connection is determined independently for each sensing beam.

6. 10. The wireless device of claim 1, wherein the wireless communication system comprises a 3rd generation partnership project (3GPP) based wireless communication system.

7. 1. A method performed by a wireless device in a wireless communication system, comprising: performing simultaneous sensing for a plurality of transmit (Tx) beams by applying a first channel connection for each sensing beam before a channel occupancy (CO) begins, wherein the sensing beam covers at least one Tx beam of the plurality of Tx beams; transmitting within the CO on a first Tx beam of the plurality of Tx beams if the first channel connection is successful for the plurality of Tx beams; performing a second channel connection within the CO prior to beam switching from the first Tx beam to a second Tx beam for time-domain multiplexed transmission within the CO; a type of the second channel connection is determined based on whether the second Tx beam is included in the plurality of Tx beams as follows: - if the second Tx beam is not included in the plurality of Tx beams, it is a Type 2 channel connection; - The method, wherein the second Tx beam is a Type 3 channel connection when included in the plurality of Tx beams.

8. 8. The method of claim 7, wherein the Type 2 channel connection is made based on sensing the channel only within a fixed interval, and the Type 3 channel connection is made without sensing the channel.

9. The method of claim 7 , wherein the CO is initiated identically for the multiple Tx beams.

10. The method of claim 7 , wherein the first channel connection is performed independently for each sensing beam based on a random backoff.

11. The method of claim 10 , wherein the initial value of the random backoff counter in the first channel connection is determined independently for each sensing beam.

12. 8. The method of claim 7, wherein the wireless communication system comprises a 3rd generation partnership project (3GPP) based wireless communication system.

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