Physical channel and signal transmission / reception method for wireless communication system and device using same

Abstract

To provide a method for efficiently transmitting and receiving physical channels and signals in a wireless communication system, and an apparatus therefor.SOLUTION: A base station 200 in a wireless communication system comprising a terminal 100 and the base station 200 includes: a communication module 220; and a processor 210. When the processor attempts to transmit a synchronization signal and PBCH block (SSB) at a SSB transmission candidate position in a discovery reference signal (DRS) transmission window, and fails to transmit an SSB at a first SSB transmission candidate position in a first DRS transmission window, the processor attempts to transmit the SSB at a second SSB transmission candidate position that is later than the first SSB transmission candidate position in the first DRS transmission window. The DRS transmission window is a time interval in which the base station can transmit the SSB. The SSB transmission candidate position indicates a time point at which the base station can start SSB transmission within the DRS transmission window.SELECTED DRAWING: Figure 18

Description

[Technical Field]

[0001] The present invention relates to a wireless communication system, and more particularly to a physical channel and a signal transmission / reception method for a wireless communication system and an apparatus using the same. [Background technology]

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

[0003] The 3GPP (3rd Generation Partnership Project) NR system improves network spectrum efficiency, enabling 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 supporting high-capacity voice. 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 operating costs due to a simple architecture.

[0004] For more efficient data processing, dynamic TDD in the NR system uses a scheme that varies the number of orthogoal frequency division multiplexing (OFDM) symbols available for uplink and downlink depending on the data traffic direction of the user in the cell. For example, if the downlink traffic of a cell is greater than the uplink traffic, the base station allocates a number of downlink OFDM symbols to a slot (or subframe). Information about the slot configuration should 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 multiple input / output (massive MIMO), full dimension multiple input / output (FD-MIMO), array antenna, analog beamforming, hybrid beamforming that combines analog beamforming and digital beamforming, and large scale antenna technologies. In addition, to improve the system network, technological developments are being carried out for the 5G communication system in areas such as 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 the currently provided mobile communication systems and users' demands for high-speed services, a more advanced mobile communication system is required.

[0009] The 3GPP NR system uses a dynamic time division duplex (TDD) scheme that allows the direction of OFDM symbols constituting a slot to be freely changed depending on the uplink and downlink traffic of a small cell. To support dynamic TDD, the base station transmits slot configuration information to the terminal. However, there is a risk that the terminal may not be able to receive the slot configuration information or that the terminal's operation may be hindered due to the change in slot configuration, so a solution is needed.

[0010] Recently, as mobile traffic has exploded due to the proliferation of smart devices, it has become difficult for traditional licensed frequency spectrum or licensed frequency bands alone to withstand the increasing data usage required to provide cellular communication services.

[0011] In this situation, the use of unlicensed frequency spectrum or unlicensed frequency bands (e.g., 2.4 GHz band, 5 GHz band, etc.) to provide cellular communication services is being discussed as a solution to the spectrum shortage problem.

[0012] Unlike licensed bands, where telecommunications carriers secure exclusive frequency usage rights through procedures such as auctions, unlicensed bands allow multiple communication devices to be used simultaneously without restrictions, provided that certain levels of adjacent band protection regulations are observed. Therefore, if unlicensed bands are used for cellular communication services, it will be difficult to guarantee the same level of communication quality as that provided in licensed bands, and there is a risk of interference problems with wireless communication devices (e.g., wireless LAN devices) that have previously used unlicensed bands.

[0013] To use LTE and NR technologies in unlicensed bands, research should be conducted in advance on coexistence methods with existing unlicensed band devices and methods for efficiently sharing radio channels with other radio channels. In other words, a robust coexistence mechanism (RCM) needs to be developed to prevent devices using LTE and NR technologies in unlicensed bands from affecting existing unlicensed band devices. Summary of the Invention [Problem to be solved by the invention]

[0014] An object of one embodiment of the present invention is to provide a method and an apparatus for efficiently transmitting and receiving physical channels and signals in a wireless communication system. Another object of one embodiment of the present invention is to provide a method and an apparatus for using the method for transmitting and receiving physical channels and signals in a wireless communication system. [Means for solving the problem]

[0015] A base station of a wireless communication system according to an embodiment of the present invention includes a communication module and a processor for controlling the communication mode. The processor attempts SSB (synchronization signal and PBCH block) transmission at an SSB (discovery reference signal) transmission candidate position within a DRS (discovery reference signal) transmission window, and if SSB transmission at a first SSB transmission candidate position within a first DRS transmission window fails, attempts the SSB transmission at a second SSB transmission candidate position within the first DRS transmission window that is later than the first SSB transmission candidate position. The DRS transmission window is a time period during which the base station can transmit SSBs. The SSB transmission candidate position indicates a time within the DRS transmission window at which the base station can start SSB transmission.

[0016] The base station transmits an SSB set including a plurality of SSBs within the pre-designated DRS transmission window. Each of a plurality of SSB transmission candidate positions included in the DRS transmission window is mapped to one of the plurality of SSBs. In this case, if the base station successfully accesses the channel before the first SSB transmission candidate position, the processor transmits the SSB mapped to each of the at least one SSB transmission candidate position within the DRS transmission window from the first SSB transmission candidate position. The maximum number of SSBs that the base station can transmit in the first DRS transmission window is limited.

[0017] A mapping relationship between the SSB transmission candidate positions in the second DRS transmission window and the SSB may be different from a mapping relationship between the SSB transmission candidate positions in the first DRS transmission window and the SSB, where the second DRS transmission window is a DRS transmission window with a period immediately following the first DRS transmission window.

[0018] The indexes of the SSBs mapped to each of the multiple SSB transmission candidate positions in the second DRS transmission window are cyclically wrapped around the indexes of the SSBs mapped to each of the multiple SSB transmission candidate positions in the first DRS transmission window, and each of the multiple SSBs is assigned a unique index within the SSB set.

[0019] The indices of the SSBs mapped to each of the plurality of SSB transmission candidate positions in the second DRS transmission window are the indices of the SSBs mapped to each of the plurality of SSB transmission candidate positions in the first DRS transmission window, assigned in reverse order, where each of the plurality of SSBs is assigned a unique index within the SSB set. The duration of the DRS transmission window is fixed, and the DRS transmission window is set in the terminal so as to repeat at regular intervals. The subcarrier spacing used to transmit the SSBs is one of 15 kHz, 30 kHz, and 60 kHz, and the processor transmits a plurality of SSBs consecutively in time. The subcarrier spacing value used to transmit the SSB is one of 15 kHz, 30 kHz, and 60 kHz, and the processor terminates the SSB transmission at least one or more orthogonal frequency division multiplexing (OFDM) symbols before the boundary between the slot in which the SSB transmission is performed and the slot next to the slot in which the SSB transmission is performed. The processor performs channel access with n candidate location terminals, where n is a positive integer, and n is 1.

[0020] A terminal of a wireless communication system according to an embodiment of the present invention includes a communication module and a processor for controlling the communication mode. The processor attempts SSB reception at an SSB transmission candidate position within a DRS transmission window, and if SSB reception fails at a first SSB transmission candidate position within a first DRS transmission window, attempts SSB reception at a second SSB transmission candidate position within the first DRS transmission window that is later than the first SSB transmission candidate position. The DRS transmission window is a time period during which a base station can transmit SSB. The SSB transmission candidate position indicates a time within the DRS transmission window at which the terminal can start SSB reception. The processor starts receiving an SSB transmission from the first SSB transmission candidate location, and after completing reception of the SSB transmission, does not attempt to receive the same SSB within the first DRS transmission window. The terminal receives an SSB set including a plurality of SSBs within the DRS transmission window, and each of the plurality of SSB transmission candidate positions included in the DRS transmission window is mapped to one of the plurality of SSBs. In this case, the processor receives the SSBs mapped to the at least one SSB transmission candidate position from the first SSB transmission candidate position to each of the at least one SSB transmission candidate position located within the first DRS transmission window.

[0021] A mapping relationship between the SSB transmission candidate positions in the second DRS transmission window and the SSB may be different from a mapping relationship between the SSB transmission candidate positions in the first DRS transmission window and the SSB, where the second DRS transmission window is a DRS transmission window with a period immediately following the first DRS transmission window. The indices of the SSBs mapped to each of the plurality of SSB transmission candidate positions in the second DRS transmission window are obtained by cyclically wrapping around the indices of the SSBs mapped to each of the plurality of SSB transmission candidate positions in the first DRS transmission window, and each of the plurality of SSBs is assigned a unique index within the SSB set. The indices of the SSBs mapped to each of the plurality of SSB transmission candidate positions in the second DRS transmission window are the indices of the SSBs mapped to each of the plurality of SSB transmission candidate positions in the first DRS transmission window, assigned in reverse order. Each of the plurality of SSBs is assigned a unique index within the SSB set. The duration of the DRS transmission window has a fixed length, and the DRS transmission window is set in the terminal so that it repeats at regular intervals. The subcarrier spacing used to transmit the SSBs is one of 15 kHz, 30 kHz, and 60 kHz, and the processor receives a plurality of SSBs consecutively in time. The subcarrier spacing used to transmit the SSB is one of 15 kHz, 30 kHz, and 60 kHz, and the processor terminates the SSB reception at least one OFDM symbol before the boundary between the slot in which the SSB reception is performed and the slot next to the slot in which the SSB reception is performed. [Effects of the Invention]

[0022] One embodiment of the present invention provides a method for efficiently transmitting and receiving physical channels and signals in a wireless communication system, and an apparatus using the same. 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]

[0023] [Figure 1] FIG. 1 is a diagram illustrating an example of a radio frame structure used in a wireless communication system. [Figure 2] 1 is a diagram illustrating an example of a downlink (DL) / uplink (UL) slot structure in a wireless communication system. [Figure 3]1 is a diagram illustrating physical channels used in a 3GPP system and a general signal transmission method using the corresponding 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] 1 is a diagram illustrating a control resource set (CORESET) in which a physical downlink control channel (PDCCH) is transmitted in a 3GPP NR system. [Figure 7] A diagram showing a method for setting a PDCCH search space in a 3GPP NR system. [Figure 8] FIG. 1 is a conceptual diagram illustrating carrier aggregation. [Figure 9] FIG. 1 is a diagram for explaining single-carrier communication and multi-carrier communication. [Figure 10] A diagram showing an example in which a cross-carrier scheduling technique is applied. [Figure 11] 1 is a diagram illustrating a code block group (CBG) configuration and its time-frequency resource mapping according to an embodiment of the present invention; [Figure 12] 10 is a diagram illustrating a process in which a base station performs TB-based transmission or CBG-based transmission and a terminal transmits HARQ-ACK in response thereto according to an embodiment of the present invention. [Figure 13] FIG. 1 is a diagram illustrating an NR-U (NR-Unlicensed) service environment. [Figure 14] FIG. 1 is a diagram illustrating an example of a deployment scenario of a terminal and a base station in an NR-U service environment. [Figure 15] 1 is a diagram illustrating a conventional communication system (e.g., wireless LAN) that operates in an unlicensed band. [Figure 16]FIG. 1 illustrates a channel access process based on Category 4 LBT according to one embodiment of the present invention. [Figure 17] A diagram showing one embodiment of a method for adjusting the contention window size CWS based on HARQ-ACK feedback. [Figure 18] 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 19] FIG. 1 is a diagram showing the positions of OFDM symbols occupied by SSBs within multiple slots of a licensed band in an NR system according to one embodiment of the present invention. [Figure 20] This figure shows the positions of slots occupied by SSBs within a half radio frame, i.e., 5 ms, of a licensed band of an NR system according to one embodiment of the present invention. [Figure 21] 10 is a diagram showing the positions of OFDM symbols in which SSBs are transmitted within a 1 ms time interval when 60 KHz subcarrier spacing is used and the maximum number of SSBs is 3 according to one embodiment of the present invention. [Figure 22] 10 is a diagram showing the positions of OFDM symbols in which SSBs are transmitted within a 1 ms time interval when 60 KHz subcarrier spacing is used and the maximum number of SSBs is 4 according to one embodiment of the present invention. [Figure 23] 10 is a diagram showing the positions of OFDM symbols in which SSBs are transmitted within a 1 ms time interval when 60 KHz subcarrier spacing is used and the maximum number of SSBs is 6 according to one embodiment of the present invention. [Figure 24] This figure shows the positions of OFDM symbols in which SSBs are transmitted within a 1 ms time interval when 60 KHz subcarrier spacing is used to transmit SSBs and the maximum number of SSBs is 8 according to one embodiment of the present invention. [Figure 25] 10 is a diagram showing the position of slots in which SSBs are transmitted in an SSB transmission window when 60 KHz subcarrier spacing is used to transmit SSBs according to another embodiment of the present invention. [Figure 26]This figure shows a case where, when 15 kHz subcarrier spacing is used to transmit SSBs in an unlicensed band, there are multiple slot positions at which a base station can start transmitting SSBs depending on the maximum number of SSBs that a base station can transmit within an SSB transmission window according to an embodiment of the present invention. [Figure 27] This figure shows that when 30 KHz subcarrier spacing is used to transmit SSBs in an unlicensed band, there are multiple slot positions at which a base station can start transmitting SSBs depending on the maximum number of SSBs that a base station can transmit within an SSB transmission window according to an embodiment of the present invention. [Figure 28] This figure shows that when 60 KHz subcarrier spacing is used to transmit SSBs in an unlicensed band, there are multiple slot positions at which a base station can start transmitting an SSB, depending on the maximum number of SSBs that a base station can transmit within an SSB transmission window according to an embodiment of the present invention. [Figure 29] This figure shows that when 15 kHz subcarrier spacing is used to transmit SSB in an unlicensed band, a base station has an opportunity to start SSB transmission every slot within the SSB transmission window according to an embodiment of the present invention. [Figure 30] This figure shows that when 30 KHz subcarrier spacing is used to transmit SSB in an unlicensed band, a base station has an opportunity to start SSB transmission every slot within the SSB transmission window according to an embodiment of the present invention. [Figure 31] This figure shows that when 60 KHz subcarrier spacing is used to transmit SSB in an unlicensed band, a base station has an opportunity to start SSB transmission every slot within the SSB transmission window according to an embodiment of the present invention. [Figure 32] 10 illustrates a case where the mapping between SSB indexes and candidate position indexes within a DRS transmission window is fixed according to an embodiment of the present invention. FIG. [Figure 33] 10 illustrates a case where the mapping between SSB indexes and candidate position indexes within a DRS transmission window is not fixed according to an embodiment of the present invention. FIG. [Figure 34] 10 illustrates a case where the mapping between SSB indexes and candidate position indexes within a DRS transmission window is not fixed according to an embodiment of the present invention. FIG. [Figure 35] 10 is a diagram illustrating a case where the mapping between SSB indexes and candidate position indexes within a DRS transmission window is not fixed according to another embodiment of the present invention. FIG. [Figure 36] 10 is a diagram illustrating a case where the mapping between SSB indexes and candidate position indexes within a DRS transmission window is not fixed according to another embodiment of the present invention. FIG. [Figure 37] 10 is a diagram illustrating a case where the mapping between SSB indexes and candidate position indexes within a DRS transmission window is not fixed according to another embodiment of the present invention. FIG. [Figure 38] 10 is a diagram illustrating a case where the mapping between SSB indexes and candidate position indexes within a DRS transmission window is not fixed according to another embodiment of the present invention. [Figure 39] 10 is a diagram illustrating a case where the mapping between SSB indexes and candidate position indexes within a DRS transmission window is not fixed according to another embodiment of the present invention. [Figure 40] 10 is a diagram illustrating a case where the mapping between SSB indexes and candidate position indexes within a DRS transmission window is not fixed according to another embodiment of the present invention. [Figure 41] 10 is a diagram illustrating a case where the mapping between SSB indexes and candidate position indexes within a DRS transmission window is not fixed according to another embodiment of the present invention. [Figure 42] 10 is a diagram illustrating a case where the mapping between SSB indexes and candidate position indexes within a DRS transmission window is not fixed according to another embodiment of the present invention. [Figure 43] A diagram showing the design of a PUSCH used in LTE-LAA. [Figure 44]10 is a diagram illustrating multiple terminals transmitting short PUCCHs using OCC within one interlace according to an embodiment of the present invention. [Figure 45] 10 is a diagram illustrating a case where multiple terminals transmit a long PUCCH corresponding to PUCCH format 1 using OCC within one interlace according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0024] 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 analyzed based on the substantive meaning of the terms and the overall content of this specification, rather than simply the names of the terms.

[0025] 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.

[0026] The following technologies are used in various wireless access systems, such as CDMA (code division multiple access), FDMA (frequency division multiple access), TDMA (time division multiple access), OFDMA (orthogonal frequency division multiple access), and SC-FDMA (single carrier frequency division multiple access). CDMA is implemented in radio technologies such as UTRA (Universal Terrestrial Radio Access) and CDMA2000. TDMA is implemented in radio technologies such as GSM (Global System for Mobile communications), GPRS (General Packet Radio Service), and EDGE (Enhanced Data Rates for GSM Evolution). OFDMA is implemented in radio technologies such as IEEE802.11 (Wi-Fi), IEEE802.16 (WiMAX), IEEE802-20, and E-UTRA (Evolved UTRA). UTRA is part of UMTS (Universal Mobile Telecommunications System). 3GPP LTE (Long term evolution) is a part of E-UMTS (Evolved UMTS) that uses E-UTRA, and LTE-Advanced (LTE-A) is an evolved version of 3GPP LTE. 3GPP NR is a system designed separately from LTE / LTE-A and is a system for supporting eMBB (enhanced Mobile Broadband), URLLC (Ultra-Reliable and Low Latency Communication), and mMTC (massive Machine Type Communication) services, which are requirements of IMT-2020. For clarity, the following description will focus on 3GPP NR, but the technical concept of the present invention is not limited thereto.

[0027] Unless otherwise specified in this specification, the base station may include a next generation node B (gNB) defined in 3GPP NR. Also, unless otherwise specified, the terminal may include a user equipment (UE).

[0028] FIG. 1 is a diagram illustrating an example of a radio frame structure used in a radio communication system. Referring to FIG. 1, a radio frame used in a 3GPP NR system has a length of 10 ms (ΔfmaxNf / 100)*Tc). Each radio frame consists of 10 equally sized subframes (SF). Here, Δfmax=480*103 Hz, Nf=4096, Tc=1 / (Δfref*Nf,ref), Δfref=15*103 Hz, and Nf,ref=2048. The 10 subframes in a frame are numbered 0 to 9. Each subframe has a length of 1 ms and consists of one or more slots depending on the subcarrier spacing. More specifically, the subcarrier spacing that can be used in a 3GPP NR system is 15*2 μkHz. μ is the subcarrier spacing configuration factor and has values ​​from 0 to 4. That is, 15 kHz, 30 kHz, 60 kHz, 120 kHz, or 240 kHz is used as the subcarrier spacing. A 1 ms long subframe consists of 2μ slots, each 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).

[0029] 2 is a diagram illustrating an example of a downlink (DL) / uplink (UL) slot structure in a wireless communication system, and in particular, a resource grid structure of a 3GPP NR system. There is one resource grid per antenna port. Referring to Figure 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, in this specification, a symbol includes an OFDM symbol, an SC-FDMA symbol, a DFTs-OFDM symbol, etc.

[0030] Referring to Figure 2, the signal transmitted from each slot is represented by a resource lattice consisting of Nsize, μgrid, x*NRBSC subcarriers, and Nslotsymb OFDM symbols. Here, x=DL for the downlink resource lattice and x=UL for the uplink resource lattice. Nsize, μgrid, and x represent the number of resource blocks (RBs) according to the subcarrier spacing factor μ (x is DL or UL), and Nslotsymb represents the number of OFDM symbols in a slot. NRBSC is the number of subcarriers constituting one RB, and NRBSC=12. Depending on the multiple access method, the OFDM symbol is called a cyclic prefix OFDM (CP-OFDM) symbol or a discrete Fourier transform spread OFDM (DFT-S-OFDM) symbol.

[0031] 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 includes 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).

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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 further 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 cell-specific slot configuration period, iii) the number of downlink symbols from the first symbol of the slot immediately following the slot having only downlink symbols, iv) the number of slots having only uplink symbols from the end of the cell-specific slot configuration period, and v) the number of uplink symbols from the last symbol of 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.

[0036] If the information regarding the symbol type consists of the UE-specific RRC signal, the base station signals whether the flexible symbol is a downlink symbol or an uplink symbol using the cell-specific RRC signal. At this time, the UE-specific RRC signal cannot change the downlink symbol or uplink symbol that consists of the cell-specific RRC signal to another symbol type. The UE-specific RRC signal signals the number of downlink symbols among the Nslotsymb symbols of the corresponding slot and the number of uplink symbols among the Nslotsymb symbols of the corresponding slot for each 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.

[0037] The type of symbol consisting of the RRC signal as described above is referred to as a semi-static DL / UL configuration. In the semi-static DL / UL configuration consisting of the RRC signal described above, the flexible symbol is indicated as a downlink symbol, an uplink symbol, or a flexible symbol via the dynamic SFI (slot format information) transmitted on the physical downlink control channel (PDCCH). At this time, the downlink symbol or uplink symbol consisting of the RRC signal is not changed to another symbol type. Table 1 exemplifies the dynamic SFI indicated by the base station to the UE.

[0038]

Table 1

[0039] In Table 1, D denotes a downlink symbol, U denotes an uplink symbol, and X denotes a flexible symbol. As shown in Table 1, up to two DL / UL switchings are allowed in one slot.

[0040] FIG. 3 is a diagram illustrating physical channels used in a 3GPP system (e.g., NR) and a general signal transmission method using the physical channels. 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 ID. Next, the terminal receives a physical broadcast channel from the base station to acquire broadcast information within the cell.

[0041] 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, thereby acquiring more detailed system information than the system information acquired through the initial cell search (S102).

[0042] When a terminal first accesses a base station or if there are no radio resources for signal transmission, the terminal performs a random access procedure with the base station (S103 to S106). First, the terminal transmits a preamble over a physical random access channel (PRACH) (S103) and receives a response message for the preamble from the base station over 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 over a physical uplink shared channel (PUSCH) indicated by an uplink grant transmitted from the base station over 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 via its own identifier (S106), the random access procedure is terminated.

[0043] After the above procedures, the UE receives the PDCCH / PDSCH (S107) and transmits the physical uplink shared channel (PUSCH) / physical uplink control channel (PUCCH) (S108) as a general uplink / downlink signal transmission procedure. In particular, the UE receives downlink control information (DCI) via the PDCCH. The DCI includes control information such as resource allocation information for the UE. The format of the DCI may vary depending on the purpose of use. The uplink control information (UCI) transmitted by the UE 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 UE transmits control information such as the above-mentioned HARQ-ACK and CSI via the PUSCH and / or PUCCH.

[0044] FIG. 4 is a diagram illustrating an SS / PBCH block for initial cell access in a 3GPP NR system. 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 acquires information such as a cell identity (ID).

[0045] The synchronization signal (SS) will be described in more detail with reference to FIG. 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 FIG. 4(a) and Table 2, 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 above signals.

[0046] [Table 2]

[0047] 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, a physical layer cell ID NcellID=3N(1)ID+N(2)ID is uniquely defined by an index N(1)ID ranging from 0 to 335 indicating a physical layer cell 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 d PSS (n) is as shown in the following formula 1.

[0048]

number

[0049]

number

[0050]

number

[0051]

number

[0052]

number

[0053]

number

[0054] A 10-ms radio frame is divided into two 5-ms half-frames. Referring to FIG. 4(b), the slot in which the SS / PBCH block is transmitted within each half-frame is described. The slot in which the SS / PBCH block is transmitted is one of Cases A, B, C, D, and E. In Case A, the subcarrier spacing is 15 kHz, and the start point of the SS / PBCH block is the {2, 8}+14*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.

[0055] 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) S202. The base station scrambles the CRC with an RNTI value determined according to the purpose / target of each control information. The common RNTI used by one or more terminals includes at least one of a system information RNTI (SI-RNTI), a paging RNTI (P-RNTI), a random access RNTI (RA-RNTI), and a transmit power control RNTI (TPC-RNTI). The UE-specific RNTI includes at least one of a cell temporary RNTI (C-RNTI), a CS-RNTI, or an MCS-C-RNTI. The base station then performs channel encoding (e.g., polar coding) S204 and rate-matching S206 according to the amount of resource(s) used for PDCCH transmission. The base station then 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.

[0056] FIG. 6 is a diagram showing a CORESET in which a PDCCH is transmitted in a 3GPP NR system. A CORESET is a time-frequency resource in 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.

[0057] FIG. 7 is a diagram illustrating a method for configuring a PDCCH search space in a 3GPP NR system. At least one search space exists in each CORESET for transmitting a PDCCH to a UE. 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 UE is transmitted. The search space includes a common search space that 3GPP NR UEs should commonly search and a terminal-specific or UE-specific search space that a specific UE should search. In the common search space, all UEs in a cell belonging to the same base station monitor a PDCCH that is configured to be commonly searched. In addition, the UE-specific search space is configured for each UE so that the UEs monitor the PDCCHs allocated to each UE at different search space positions. In the case of a UE-specific search space, the search spaces allocated to UEs 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, the PDCCH is said to be (successfully) detected / received, and if blind decoding fails, the PDCCH is said to be undetected / unreceived or not successfully detected / received.

[0058] 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.

[0059] 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.

[0060] The base station transmits information on which terminal (one or more terminals) the PDSCH data is transmitted to and how the terminal should receive and decode the PDSCH data, by including the information in the PDCCH. For example, assume that DCI transmitted over a specific PDCCH is CRC masked with RNTI "A," and the DCI 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.). The 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.

[0061] Table 3 shows an example of a PUCCH used in a wireless communication system.

[0062] [Table 3] The PUCCH is used to transmit the following uplink control information (UCI): - SR (Scheduling Request): Information used to request uplink UL-SCH resources.

[0063] 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.

[0064] 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.

[0065] In the 3GPP NR system, five PUCCH formats are used to support various service scenarios, various channel environments, and frame structures.

[0066] 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 bit Bit UCI(M bit =1 or 2), the cyclic shift value m cs Determine the base sequence of length 12 and set it to a given value m cs The sequence cyclically shifted by M is mapped to 12 REs of one OFDM symbol and one PRB and transmitted. bit If =1, 1-bit UCI0 and 1 are represented by a sequence corresponding to two cyclic shifts whose difference in cyclic shift value is 6. Also, M bit = 2, then the 2-bit UCI 00, 01, 11, 10 is represented by a sequence corresponding to four cyclic shifts with a difference of 3 between the cyclic shift values.

[0067] 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). A signal is obtained by multiplying the modulated complex-valued symbol d(0) with a length 12 sequence. The UE transmits the obtained signal by spreading it with an orthogonal cover code (OCC) on the even-numbered OFDM symbols assigned to PUCCH format 1. In PUCCH format 1, the maximum number of different UEs that can be multiplexed in the same RB is determined depending on the length of the OCC used. In odd-numbered OFDM symbols of PUCCH format 1, a demodulation reference signal (DMRS) is spread by OCC and mapped.

[0068] 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.

[0069] 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, when π / 2-BPSK is used, Msymb=Mbit, and when QPSK is used, Msymb=Mbit / 2. 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.

[0070] 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.

[0071] 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.

[0072] PUCCH format 1, PUCCH format 3, or PUCCH format 4 is configured to be repeatedly transmitted in multiple slots. In this case, the number K of slots in which the PUCCH is repeatedly transmitted is configured by an RRC signal. The repeatedly transmitted PUCCH should start from the same OFDM symbol position in each slot and have the same length. If the RRC signal indicates that any one of the OFDM symbols in a slot in which the UE should transmit the PUCCH is a DL symbol, the UE does not transmit the PUCCH from the corresponding slot but postpones its transmission to the next slot.

[0073] 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 per 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 per downlink carrier (or cell) and up to four UL BWPs per 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.

[0074] 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.

[0075] 8 is a conceptual diagram illustrating carrier aggregation. Carrier aggregation refers to a method in which a terminal uses multiple frequency blocks (logically speaking) 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.

[0076] 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 shown only as a logical concept, and each component carrier may be physically adjacent to each other or separated from each other.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] 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.

[0081] 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).

[0082] Meanwhile, 3GPP NR uses the concept of a cell to manage radio resources. A cell is defined as a combination of downlink and uplink resources, i.e., a combination of DL CC and UL CC. A cell 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. 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. The carrier corresponding to a PCell in the downlink is a DL PCC, and the carrier corresponding to a PCell in the uplink is a UL PCC. Similarly, the carrier corresponding to an SCell in the downlink is a DL SCC, and the 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.

[0083] 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.

[0084] 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. A PCell is basically a scheduling cell, and a specific SCell is designated as the scheduling cell by a higher layer.

[0085] 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 UE-specific (or UE-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 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.

[0086] 9 and 10 illustrate the subframe structure of a 3GPP LTE-A system, the same or similar structure can also be applied to a 3GPP NR system, except that in a 3GPP NR system, the subframes in FIGS. 9 and 10 are switched to slots.

[0087] In the present invention, the number of symbols contained in one slot is 14 for cells consisting of a normal CP (cyclic prefix) and 12 for cells consisting of an extended CP, but for convenience of explanation, we will assume that there are 7 symbols.

[0088] 11A and 11B illustrate a code block group (CBG) configuration and its time-frequency resource mapping according to an embodiment of the present invention. More specifically, FIG. 11A illustrates an embodiment of a CBG configuration included in one transport block (TB), and FIG. 11B illustrates the time-frequency resource mapping of the corresponding CBG configuration.

[0089] A maximum supportable length is defined for a channel code. For example, the maximum support length of the turbo code used in 3GPP LTE(-A) is 6144 bits. However, the length of the transport block (TB) transmitted on the PDSCH may be longer than 6144 bits. If the length of the TB is longer than the maximum support length, the TB is divided into code blocks (CBs) of up to 6144 bits in length. Each CB is the unit for channel coding. Furthermore, for efficient retransmission, several CBs may be bundled to form one CBG. The UE and the base station require information about how the CBG is configured.

[0090] Within a TB, CBGs and CBs are configured according to various embodiments. According to one embodiment, the number of available CBGs is determined as a fixed value or configured as RRC configuration information between a base station and a terminal. In this case, the number of CBs is determined according to the length of the TB, and the CBG is configured according to the determined number information. According to another embodiment, the number of CBs included in one CBG may be determined as a fixed value or configured as RRC configuration information between a base station and a terminal. In this case, if the number of CBs is determined according to the length of the TB, the number of CBGs is configured according to the number information of CBs per CBG.

[0091] Referring to the embodiment of FIG. 11(a), one TB is divided into eight CBs. The eight CBs are further aggregated into four CBGs. The mapping relationship between the CBs and CBGs (or the CBG configuration) is statically configured between the base station and the UE, or semi-statically configured as RRC configuration information. According to another embodiment, the mapping relationship is configured through dynamic signaling. When the UE receives a PDCCH transmitted by the base station, the UE directly or indirectly identifies the mapping relationship between the CBs and CBGs (or the CBG configuration) through explicit information and / or implicit information. One CBG may include only one CB or all CBs constituting one TB. Note that the technique proposed in the embodiment of the present invention is applicable regardless of the CB and CBG configuration.

[0092] Referring to FIG. 11(b), the CBGs constituting one TB are mapped to the time-frequency resources on which the PDSCH is scheduled. According to one embodiment, each CBG is first allocated to the frequency axis and then extended to the time axis. If a PDSCH consisting of one TB including four CBGs is allocated to seven OFDM symbols, CBG0 is transmitted over the first and second OFDM symbols, CBG1 is transmitted over the second, third, and fourth OFDM symbols, CBG2 is transmitted over the fourth, fifth, and sixth OFDM symbols, and CBG3 is transmitted over the sixth and seventh OFDM symbols. The time-frequency mapping relationship allocated between the CBGs and the PDSCH is determined between the UEs. However, the mapping relationship shown in FIG. 11(b) is merely an example for explaining the present invention, and the technique proposed in this embodiment of the present invention may be applied regardless of the time-frequency mapping relationship of the CBGs.

[0093] FIG. 12 illustrates a process in which a base station performs TB-based transmission or CBG-based transmission and a terminal transmits a HARQ-ACK in response thereto. Referring to FIG. 12, the base station configures a transmission method suitable for the terminal, either TB-based transmission or CBG-based transmission. The terminal transmits HARQ-ACK information bit(s) according to the transmission method configured by the base station on a PUCCH or PUSCH. The base station configures a PDCCH to schedule a PDSCH to be transmitted to the terminal. The PDCCH schedules TB-based transmission and / or CBG-based transmission. For example, one TB or two TBs are scheduled in the PDCCH. If one TB is scheduled, the terminal should feed back a 1-bit HARQ-ACK. If two TBs are scheduled, the terminal should feed back a 2-bit HARQ-ACK for each of the two TBs. To eliminate ambiguity between the base station and the terminal, a predetermined order exists between each information bit of the 2-bit HARQ-ACK and the two TBs. Incidentally, if the MIMO transmission rank or layer is low, one TB is transmitted over one PDSCH, and if the MIMO transmission rank or layer is high, two TBs are transmitted over one PDSCH.

[0094] The UE transmits a 1-bit TB-based HARQ-ACK per TB to inform the base station of whether each TB was successfully received. To generate a HARQ-ACK for one TB, the UE checks whether there is a reception error for the corresponding TB via the TB-CRC. If the TB-CRC for the TB is successfully checked, the UE generates an ACK for the HARQ-ACK for the corresponding TB. However, if a TB-CRC error occurs for the TB, the UE generates a NACK for the HARQ-ACK for the corresponding TB. The UE transmits the generated TB-based HARQ-ACK(s) to the base station. The base station retransmits the TBs for which a NACK was returned from the UE among the TB-based HARQ-ACK(s) received from the UE.

[0095] The UE also transmits a 1-bit CBG-based HARQ-ACK per CBG to inform the base station of the successful reception of each CBG. To generate a HARQ-ACK for one CBG, the UE decodes all CBs included in the CBG and checks whether there is a reception error for the corresponding CB via the CB-CRC. If the UE successfully receives all CBs constituting a CBG (i.e., if all CB-CRCs are successfully checked), the UE generates an ACK for the HARQ-ACK for the corresponding CBG. However, if the UE does not successfully receive at least one of the CBs constituting a CBG (i.e., if at least one CB-CRC error occurs), the UE generates a NACK for the HARQ-ACK for the corresponding CBG. The UE transmits the generated CBG-based HARQ-ACK(s) to the base station. The base station retransmits the CBGs for which a NACK was returned from the UE among the CBG-based HARQ-ACK(s) received from the UE. According to one embodiment, the CB configuration of the retransmitted CBG is the same as the CB configuration of the previously transmitted CBG. The length of the CBG-based HARQ-ACK information bit(s) transmitted by the UE to the base station is determined based on the number of CBGs transmitted over the PDSCH or the maximum number of CBGs consisting of RRC signals.

[0096] On the other hand, even if the UE successfully receives all CBGs included in the TB, a TB-CRC error may occur for the corresponding TB. In this case, the UE performs CBG-substrate HARQ-ACK flipping to request retransmission for the corresponding TB. That is, even if the UE successfully receives all CBGs included in the TB, the UE may generate all CBG-substrate HARQ-ACK information bits as NACK. When the BS receives CBG-substrate HARQ-ACK feedback in which all HARQ-ACK information bits are NACK, it retransmits all CBGs for the corresponding TB.

[0097] According to an embodiment of the present invention, CBG-based HARQ-ACK feedback is used to successfully transmit a TB. The base station instructs the UE to transmit a CBG-based HARQ-ACK. At this time, a retransmission technique based on the CBG-based HARQ-ACK is used. The CBG-based HARQ-ACK is transmitted via a PUCCH. Also, if UCI is configured to be transmitted via a PUSCH, the CGB-based HARQ-ACK may be transmitted via the corresponding PUSCH. In the PUCCH, the configuration of HARQ-ACK resources is configured via an RRC signal. Also, the HARQ-ACK resource to be actually transmitted is indicated via a PDCCH that schedules a PDSCH transmitted based on the CBG. The UE transmits HARQ-ACK(s) indicating whether the transmitted CBG was successfully received via one or more PUCCH resources indicated via the PDCCH among the PUCCH resources configured by RRC.

[0098] The base station identifies whether the terminal has successfully received the CBG(s) transmitted to it through the CBG-based HARQ-ACK feedback of the terminal. That is, through the HARQ-ACK for each CBG received from the terminal, the base station recognizes the CBG(s) that the terminal has successfully received and the CBG(s) that the terminal has failed to receive. The base station performs CBG retransmission based on the received CBG-based HARQ-ACK. More specifically, the base station aggregates and retransmits only the CBG(s) for which unsuccessful reception of HARQ-ACK has been acknowledged in one TB. In this case, the CBG(s) for which successful reception of HARQ-ACK has been acknowledged are excluded from retransmission. The base station schedules the retransmitted CBG(s) on one PDSCH and transmits it to the terminal.

[0099] <Communication methods in unlicensed spectrum> FIG. 13 illustrates an NR-U service environment. Referring to Figure 13, a service environment is provided to users that combines NR technology 11 in licensed spectrum and NR-U, which is NR technology 12 in unlicensed spectrum. For example, in an NR-U environment, NR technology 11 in licensed spectrum and NR technology 12 in unlicensed spectrum are integrated using technologies such as carrier aggregation, which contributes to expanding network capacity. Also, in an asymmetric traffic structure where downlink data is greater than uplink data, NR-U provides NR services optimized for various requirements and environments. For convenience, NR technology in licensed spectrum will be referred to as NR-L (NR-Licensed), and NR technology in unlicensed spectrum will be referred to as NR-U.

[0100] Figure 14 shows an example of a deployment scenario for terminals and base stations in an NR-U service environment. The NR-U service environment and the target frequency band have high-frequency characteristics, so the wireless communication reach is short. Considering this, in an environment where conventional NR-L services and NR-U services coexist, the deployment scenario for terminals and base stations is an overlay model or a co-located model.

[0101] In the overlay model, a macro base station uses licensed band carriers to perform wireless communication with X and X' terminals within a macro region 32, and is connected to multiple RRHs (Radio Remote Heads) via an X2 interface. Each RRH performs wireless communication with X or X' terminals within a certain region 31 using unlicensed band carriers. The macro base station and RRH frequency bands are different and do not interfere with each other, but fast data exchange should be performed between the macro base station and RRHs via the X2 interface in order to use the NR-U service as a supplementary downlink channel for the NR-L service through carrier aggregation.

[0102] In the co-located model, the pico / femto base station simultaneously uses licensed and unlicensed band carriers to communicate wirelessly with the Y terminal. However, the pico / femto base station is limited to using both NR-L and NR-U services during downlink transmission. The coverage 33 of the NR-L service and the coverage 34 of the NR-U service may differ depending on the frequency band, transmission power, etc.

[0103] When NR communication is performed in an unlicensed band, conventional equipment communicating in the corresponding unlicensed band (e.g., wireless LAN (Wi-Fi) equipment) cannot demodulate the NR-U message or data. Therefore, the conventional equipment determines that the NR-U message or data is a type of energy and performs interference avoidance operations using energy detection techniques. In other words, if the energy corresponding to the NR-U message or data is less than -62 dBm or a specific ED (Energy Detection) threshold value, the WLAN equipment ignores the message or data and continues communication. As a result, terminals performing NR communication in an unlicensed band may be frequently interfered with by WLAN equipment.

[0104] Therefore, to effectively implement NR-U technology / services, it is necessary to allocate or reserve specific frequency bands for specific times. However, there is a problem that efficient NR-U services are difficult because peripheral devices communicating via unlicensed bands attempt access based on energy detection techniques. Therefore, in order for NR-U technology to take root, research must be conducted on methods for coexistence with conventional unlicensed band devices and methods for efficiently sharing wireless channels. In other words, a powerful mechanism must be developed to ensure that NR-U devices do not affect conventional unlicensed band devices.

[0105] 15 is a diagram illustrating a conventional communication method (e.g., wireless LAN) that operates in an unlicensed band. Most devices that operate in an unlicensed band operate based on LBT (Listen-Before-Talk), and therefore perform Clear Channel Assessment (CCA) to sense the channel before transmitting data.

[0106] Referring to Figure 15, a WLAN device (e.g., AP, STA) performs carrier sensing to check whether a channel is busy before transmitting data. If a wireless signal of a certain strength or higher is detected on 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 level used to determine whether a signal is detected is called the CCA threshold. On the other hand, if no wireless signal is detected on the channel or a wireless signal of a strength lower than the CCA threshold is detected, the channel is determined to be idle.

[0107] If the channel is determined to be in an idle state, a terminal with data to transmit performs a backoff procedure after a defer duration (e.g., Arbitration InterFrame Space (AIFS) or PCF IFS (PIFS)). The defer duration refers to the minimum time a terminal must wait after a channel becomes idle. The backoff procedure allows the terminal to wait for an arbitrary period of time after the defer deadline. For example, a terminal waits while decreasing a slot time equivalent to a random number assigned to the terminal within a contention window (CW) while the channel is in an idle state, and if all slot times are used up, the terminal attempts to access the channel.

[0108] If the terminal successfully accesses the channel, it transmits data through the channel. If the data transmission is successful, the contention window size (CWS) is reset to its initial value (CWmin). Conversely, if the data transmission fails, the CWS is doubled. As a result, the terminal is assigned a new random number within a range twice the previous random number range and performs a backoff procedure in the next CW. In WLAN, only ACK is defined as reception response information for data transmission. Therefore, if an ACK is received for data transmission, the CWS is reset to its initial value, and if no feedback information is received for data transmission, the CWS is doubled.

[0109] As mentioned above, most communications in conventional unlicensed bands operate based on LBT, so channel access in NR-U systems also uses LBT to coexist with conventional devices. Specifically, channel access methods in unlicensed bands in NR are divided into the following four categories depending on whether or not LBT is used / applied. ●Category 1: No LBT The Tx entity does not perform the LBT procedure for transmission. Category 2: LBT without random backoff

[0110] The Tx entity senses whether the channel is idle for a first interval without random backoff in order to transmit. That is, the Tx entity transmits through the channel immediately after sensing that the channel is idle for the first interval. The first interval is an interval of a predetermined length immediately before the Tx entity transmits. According to one embodiment, the first interval may be an interval of 25 us, but the present invention is not limited thereto. 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 being idle during a preset slot period. Here, the preset slot period may be 9 us, but the present invention is not limited thereto. The backoff counter N is decremented by 1 from its initial value, and when the value of the backoff counter N reaches 0, the Tx entity performs transmission. Meanwhile, to perform backoff, the Tx entity decrements the second interval (i.e., the defer period T d ) first senses whether the channel is idle during the second interval. According to an embodiment of the present invention, the Tx entity senses (or determines) whether the channel is idle during the second interval depending on whether the channel is idle for at least a portion of the second interval (e.g., one slot period). The second interval is set based on the channel access priority class of the Tx entity and consists of a 16 us period and m consecutive slot periods, where m is a value set by the channel access priority class. If the Tx entity senses that the channel is idle during the second interval, it performs channel sensing to decrement the backoff counter. On the other hand, if the channel is sensed as occupied during the backoff procedure, the backoff procedure is aborted. After aborting the backoff procedure, the Tx entity resumes backoff if it senses that the channel is idle for an additional second interval. In this way, the Tx entity transmits if the channel is idle for the second interval plus the N slot period of the backoff counter. At this time, the initial value of the backoff counter N is obtained within a fixed size CW. Category 4: LBT with random backoff using variable-size CW

[0112] The Tx entity obtains a random number within a variable-size CW, sets it as the initial value of the backoff counter (or backoff timer) N, and performs backoff using the set backoff counter N. More specifically, the Tx entity adjusts the size of the CW based on HARQ-ACK information for the previous transmission, and the initial value of the backoff counter N is obtained within the CW of the adjusted size. The detailed process by which the Tx entity performs backoff is as described in Category 3. The Tx entity transmits if the channel is idle for the second interval plus the slot period of the backoff counter N. In this case, the initial value of the backoff counter N is obtained within the variable-size CW.

[0113] In the above categories 1 to 4, the Tx entity is a base station or a terminal. According to an embodiment of the present invention, the first type of channel access is referred to as Category 4 channel access, and the second type of channel access is referred to as Category 2 channel access.

[0114] FIG. 16 is a diagram illustrating a channel access process based on Category 4 LBT according to an embodiment of the present invention. To perform channel access, the Tx entity first waits for a deferred period T d In accordance with an embodiment of the present invention, the deferred 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 performs channel sensing during one slot period within the deferred period T d S304: It is determined whether the channel is idle through channel sensing for the deferred period T d If the channel is sensed as idle for the deferred period T, the Tx entity proceeds to S306.d If the channel is not sensed as idle for the deferred period T d The steps S302 to S304 are repeated until the defer period T d is set based on the Tx entity's channel access priority class and consists of a 16us period and m consecutive slot periods, where m is the value set by the channel access priority class.

[0115] Next, the Tx entity obtains a random number from within a predetermined CW, sets it as the initial value of a backoff counter (or backoff timer) N, and proceeds to S306 and S308. The initial value of the backoff counter N is randomly selected from values ​​between 0 and CW. The Tx entity performs the backoff procedure using the set backoff counter N. That is, the Tx entity performs the backoff procedure by repeating steps S308 to S316 until the value of the backoff counter N reaches 0. Meanwhile, in FIG. 16, when the channel is in the deferred period T d Although S306 is shown to be performed after sensing that the channel is in an idle state, the present invention is not limited to this. That is, S306 may be performed independently of S302 to S304, or may be performed before S302 to S304. If S306 is performed before S302 to S304, the channel is set to the deferred period T d If the Tx entity senses that the channel is idle, the Tx entity proceeds to S308.

[0116] In 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 S320 and transmits. If the value of the backoff counter N is not 0, the Tx entity proceeds to S310. In S310, the Tx entity decrements the value of the backoff counter N by 1. According to one embodiment, the Tx entity selectively decrements the value of the backoff counter by 1 during the channel sensing process for each slot. At this time, S10 may be skipped at least once depending on the Tx entity's choice. Next, the Tx entity performs channel sensing for an additional slot period in S312. The Tx entity determines whether the channel is idle through channel sensing for the additional slot period in S314. If the channel is sensed as idle for the additional slot period, the Tx entity returns to S308. In this manner, the Tx entity decrements the backoff counter by 1 each time the channel is sensed as idle during a preset slot period. Here, the preset slot period may be 9 us, but the present invention is not limited to this.

[0117] If the channel is not sensed as idle (i.e., sensed as occupied) for an additional slot period in S314, the Tx entity proceeds to S316. In S316, the Tx entity determines whether the channel is sensed as idle for an additional deferred period T d According to an embodiment of the present invention, the channel sensing in S316 is performed in slot units. That is, the Tx entity checks whether the Tx is idle for an additional deferred period T d It is checked whether the channel is sensed as idle during all slot periods of the additional defer period T d If an occupied slot is detected within the additional defer period T, the Tx entity immediately restarts S316. d If the channel is sensed idle for all slot periods, the Tx entity returns to S308.

[0118] On the other hand, if the value of the backoff counter N is determined to be 0 in S308, the Tx entity performs transmission S320. The Tx entity receives HARQ-ACK feedback corresponding to the transmission S322. The Tx entity determines whether the previous transmission was successful through the received HARQ-ACK feedback. Next, the Tx entity adjusts the CW size for the next transmission based on the received HARQ-ACK feedback S324.

[0119] In this way, the Tx entity d After sensing the channel as idle for N additional slot periods, transmission is performed if the channel is idle. As described above, the Tx entity may be a base station or a terminal, and the channel access procedure of FIG. 16 is used for downlink transmission of the base station and / or uplink transmission of the terminal.

[0120] Hereinafter, a method for adaptively adjusting CWS when accessing a channel in an unlicensed band is proposed. CWS is adjusted based on UE (User Equipment) feedback, and the UE feedback used for CWS adjustment includes HARQ-ACK feedback, CQI / PMI / RI. In this invention, a method for adaptively adjusting CWS based on HARQ-ACK feedback is proposed. HARQ-ACK feedback includes at least one of ACK, NACK, DTX, and NACK / DTX.

[0121] As mentioned above, in WLAN systems, CWS is also adjusted based on ACK. If ACK feedback is received, CWS is reset to the minimum value (CWmin), and if ACK feedback is not received, CWS increases. However, in cellular systems, a CWS adjustment method that takes multiple access into account is required. First, in order to explain the present invention, the following terms are defined.

[0122] Set of HARQ-ACK feedback values ​​(i.e., HARQ-ACK feedback set): refers to HARQ-ACK feedback value(s) used to update / adjust CWS. The HARQ-ACK feedback set corresponds to the HARQ-ACK feedback value(s) that are decoded and available at the time the CWS is determined. The HARQ-ACK feedback set includes HARQ-ACK feedback value(s) for one or more DL (channel) transmissions (e.g., PDSCH) on an unlicensed band carrier (e.g., Scell, NR-U cell). The HARQ-ACK feedback set includes HARQ-ACK feedback value(s) for DL ​​(channel) transmissions (e.g., PDSCH), for example, multiple HARQ-ACK feedback values ​​fed back from multiple UEs. The HARQ-ACK feedback value indicates acknowledgement information for a code block group (CBG) or a transport block (TB) and indicates any one of ACK, NACK, DTX, or NACK / DTX. Depending on the context, the HARQ-ACK feedback value may be mixed with terms such as HARQ-ACK value, HARQ-ACK information bit, and HARQ-ACK response.

[0123] Reference window: A time interval during which DL transmission (e.g., PDSCH) corresponding to a HARQ-ACK feedback set is performed in an unlicensed band carrier (e.g., an Scell, an NR-U cell). The reference window is defined in slot or subframe units depending on the embodiment. The reference window refers to one or more specific slots (or subframes). According to an embodiment of the present invention, the specific slot (or reference slot) includes the start slot of the most recent DL transmission burst that is expected to use at least some HARQ-ACK feedback.

[0124] 17 illustrates an embodiment of a method for adjusting a contention window size (CWS) based on HARQ-ACK feedback. In the embodiment of FIG. 17, the Tx entity may be a base station and the Rx entity may be a terminal, but the present invention is not limited thereto. Also, the embodiment of FIG. 17 assumes a channel access procedure for DL ​​transmission of the base station, but at least some of the configuration may be applied to a channel access procedure for UL transmission of the terminal.

[0125] Referring to Figure 17, after a Tx entity transmits an nth DL transmission burst on an unlicensed band carrier (e.g., an S cell, an NR-U cell) S402, if an additional DL transmission is required, the Tx entity transmits an (n+1)th DL transmission burst based on LBT channel access S412. Here, a transmission burst refers to a transmission via one or more adjacent slots (or subframes). Figure 17 illustrates a channel access procedure and a CWS coordination method based on the first type of channel access (i.e., Category 4 channel access) described above.

[0126] First, the Tx entity receives HARQ-ACK feedback corresponding to PDSCH transmission(s) on an unlicensed spectrum carrier (e.g., an S cell, an NR-U cell) S404. The HARQ-ACK feedback used for CWS adjustment includes HARQ-ACK feedback corresponding to the most recent DL transmission burst (i.e., the nth DL transmission burst) on the unlicensed spectrum carrier. More specifically, the HARQ-ACK feedback used for CWS adjustment includes HARQ-ACK feedback corresponding to PDSCH transmission on a reference window within the most recent DL transmission burst. The reference window refers to one or more specific slots (or subframes). According to an embodiment of the present invention, the specific slot (or reference slot) includes the starting slot of the most recent DL transmission burst for which at least a portion of the HARQ-ACK feedback is expected to be available.

[0127] When HARQ-ACK feedback is received, a HARQ-ACK value is obtained for each transport block (TB). The HARQ-ACK feedback includes at least one of a TB-based HARQ-ACK bit sequence and a CBG-based HARQ-ACK. If the HARQ-ACK feedback is a TB-based HARQ-ACK bit sequence, one HARQ-ACK information bit is obtained for each TB. On the other hand, if the HARQ-ACK feedback is a CBG-based HARQ-ACK bit sequence, N HARQ-ACK information bit(s) are obtained for each TB. Here, N is the maximum number of CBGs per TB configured in the Rx entity for PDSCH transmission. According to an embodiment of the present invention, to determine the CWS, HARQ-ACK value(s) for each TB are determined according to the HARQ-ACK information bit(s) for each TB in the HARQ-ACK feedback. More specifically, if the HARQ-ACK feedback is a TB-based HARQ-ACK bit sequence, one HARQ-ACK information bit of the corresponding TB is determined as the HARQ-ACK value, whereas if the HARQ-ACK feedback is a CBG-based HARQ-ACK bit sequence, one HARQ-ACK value is determined based on N HARQ-ACK information bit(s) corresponding to the CBG included in the corresponding TB.

[0128] Next, the Tx entity adjusts the CWS based on the HARQ-ACK value determined in S404 (S406). That is, the Tx entity determines the CWS based on the HARQ-ACK value(s) determined by the HARQ-ACK information bit(s) for each TB in the HARQ-ACK feedback. More specifically, the CWS is adjusted based on the ratio of NACKs in the HARQ-ACK value(s). First, the following variables are defined: -p:Priority class value - CW_min_p: preset CWS minimum value for priority class p - CW_max_p: preset CWS maximum value of priority class p CW_p: CWS for transmitting priority class p. CW_p is set to one of a plurality of CWS values ​​between CW_min_p and CW_max_p included in the allowed CWS set of priority class p.

[0129] According to an embodiment of the present invention, the CWS is determined by the following steps. Step A-1) First, for priority class p, CW_p is set to CW_min_p, where priority class p includes {1, 2, 3, 4}. Step A-2) If the ratio of NACKs among HARQ-ACK values ​​for PDSCH transmission(s) in reference window k is greater than or equal to Z%, CW_p is increased to the next highest allowed value for all priority classes p (and remain at step A-2). Otherwise, proceed to step A-1, where Z is a pre-set integer in the range 0≦Z≦100, and in one embodiment is set to one of {30, 50, 70, 80, 100}. Here, reference window k includes the most recent start slot (or subframe) of transmission by the Tx entity, and is the slot (or subframe) in which at least some HARQ-ACK feedback is expected to be possible. If CW_p=CW_max_p, then the next highest allowable value for adjusting CW_p is CW_max_p.

[0130] Next, the Tx entity selects a random number from the CWS determined in S406 and sets it as the initial value of the backoff counter N in S408. The Tx entity performs backoff using the set backoff counter N in S410. That is, the Tx entity decrements the backoff counter by 1 for each slot period in which the channel is sensed as idle. When the backoff counter value reaches 0, the Tx entity transmits the (n+1)th DL transmission burst on the corresponding channel in S412.

[0131] Meanwhile, in the above-mentioned CWS adjustment process, it should be determined whether to consider not only ACK and NACK but also DTX or NACK / DTX in the HARQ-ACK feedback. According to an embodiment of the present invention, whether to consider DTX or NACK / DTX in the CWS adjustment process is determined depending on whether transmission in the unlicensed band is based on self-carrier scheduling or cross-carrier scheduling.

[0132] In self-carrier scheduling, DL transmission (e.g., PDSCH) on an unlicensed band carrier is scheduled via a control channel (e.g., (E)PDCCH) transmitted on the same unlicensed band carrier. Here, DTX is used for CWS adjustment together with NACK since DTX indicates a case where DL transmission fails due to a hidden node on the unlicensed band carrier. DTX is also one of the methods by which a terminal notifies a base station when the terminal fails to decode a control channel (e.g., (E)PDCCH) containing scheduling information transmitted from the base station to the terminal. DTX is determined only by the HARQ-ACK feedback value or is determined by considering the HARQ-ACK feedback value and the actual scheduling situation. According to an embodiment of the present invention, in a self-carrier scheduling situation, DTX and NACK / DTX are counted as NACKs for CWS adjustment. That is, if the combined ratio of NACK, DTX, and NACK / DTX among the HARQ-ACK values ​​for PDSCH transmission(s) in reference window k is equal to or greater than Z%, CWS is increased to the next highest allowed value. Otherwise, CWS is reset to its minimum value.

[0133] In cross-carrier scheduling, DL transmission (e.g., PDSCH) on an unlicensed band carrier is scheduled via a control channel (e.g., (E)PDCCH) transmitted on a licensed band carrier. In this case, DTX feedback is used to determine the UE's decoding status for the control channel transmitted on the licensed band carrier, and is therefore not useful for adaptively adjusting CWS for channel access in the unlicensed band. Therefore, according to an embodiment of the present invention, in a cross-carrier scheduling situation from a licensed band, DTX may be ignored to determine CWS. That is, to adjust CWS, the NACK ratio may be calculated by considering only ACK and NACK among the HARQ-ACK value(s), or the NACK ratio may be calculated by considering only ACK, NACK, and NACK / DTX. Therefore, DTX is excluded when calculating the NACK ratio.

[0134] 18 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.

[0135] 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 .

[0136] First, the processor 110 executes various commands or programs to process data within the terminal 100. The processor 100 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.

[0137] 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.

[0138] The cellular communication interface card 121 transmits and receives wireless signals to and from at least one of the base station 200, an external device, and a server via a mobile communication network, and provides cellular communication services using a first frequency band based on instructions from the processor 110. According to one embodiment, the cellular communication interface card 121 includes at least one NIC module that utilizes a frequency band below 6 GHz. The at least one NIC module of the cellular communication interface card 121 independently performs cellular communication with at least one of the base station 200, the external device, and the server in accordance with a cellular communication standard or protocol for the frequency band below 6 GHz supported by the corresponding NIC module.

[0139] The cellular communication interface card 122 transmits and receives wireless signals to and from at least one of the base station 200, an external device, and a server using a mobile communication network, and provides cellular communication services in the second frequency band based on instructions from the processor 110. According to one embodiment, the cellular communication interface card 122 includes at least one NIC module that uses a frequency band above 6 GHz. The at least one NIC module of the cellular communication interface card 122 independently performs cellular communication with at least one of the base station 200, the external device, and the server in accordance with the cellular communication standard or protocol for the frequency band above 6 GHz that the corresponding NIC module supports.

[0140] The unlicensed band communication interface card 123 transmits and receives wireless signals to and from at least one of the base station 200, an external device, and a server via the third frequency band, which is an unlicensed band, and provides unlicensed band communication services based on instructions from the processor 110. The unlicensed band communication interface card 123 includes at least one NIC module that uses the unlicensed band. For example, the unlicensed band may be 2.4 GHz, 5 GHz, 6 GHz, 7 GHz, or a band above 52.6 GHz. The at least one NIC module of the unlicensed band communication interface card 123 independently or dependently performs cellular communication with at least one of the base station 200, the external device, and the server according to the unlicensed band communication standard or protocol of the frequency band supported by the corresponding NIC module.

[0141] 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.

[0142] 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.

[0143] 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. 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 .

[0144] 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.

[0145] 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.

[0146] The cellular communication interface card 221 transmits and receives wireless signals to and from at least one of the terminal 100, the external device, and the server using a mobile communication network, and provides a cellular communication service using a first frequency band based on instructions from the processor 210. According to one embodiment, the cellular communication interface card 221 includes at least one NIC module using a frequency band below 6 GHz. The at least one NIC module of the cellular communication interface card 221 independently performs cellular communication with at least one of the terminal 100, the external device, and the server according to a cellular communication standard or protocol for the frequency band below 6 GHz supported by the corresponding NIC module.

[0147] 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 according to a cellular communication standard or protocol for the frequency band above 6 GHz that the corresponding NIC module supports.

[0148] The unlicensed band communication interface card 223 transmits and receives wireless signals to and from at least one of the terminal 100, an external device, and a server using the third frequency band, which is an unlicensed band, and provides unlicensed band communication services based on instructions from the processor 210. The unlicensed band communication interface card 223 includes at least one NIC module that uses the unlicensed band. For example, the unlicensed band may be 2.4 GHz, 5 GHz, 6 GHz, 7 GHz, or 52.6 GHz or higher. The at least one NIC module of the unlicensed band communication interface card 223 independently or dependently performs cellular communication with at least one of the terminal 100, an external device, and a server according to the unlicensed band communication standard or protocol of the frequency band supported by the corresponding NIC module.

[0149] The terminal 100 and base station 200 shown in Figure 18 are block diagrams according to one embodiment of the present invention, and the separate blocks indicate logically distinct device elements. Therefore, the above-described device elements may be mounted on one chip or multiple chips depending on the device design. In addition, some components of the terminal 100, such as the user interface 140 and display unit 150, may be selectively provided in the terminal 100. In addition, the user interface 140 and display unit 150 may be additionally provided in the base station 200 as needed.

[0150] In an NR system, a synchronization signal (SS) and a physical broadcast channel (PBCH) are received, and at least one of initial cell access, RRM measurements, and mobility management is performed based on the synchronization signal and the PBCH. As described above, the synchronization signal includes a PSS and an SSS. The synchronization signal and the PBCH are also referred to as an SS / PBCH block or SSB. Examples of transmission and reception of SSBs are described below with reference to Figures 19 to 42. Figure 19 is a diagram showing the positions of OFDM symbols occupied by SSBs within multiple slots of a licensed band in an NR system according to one embodiment of the present invention.

[0151] An SSB includes four OFDM symbols and 20 RBs. Specifically, the PSS occupies one OFDM symbol, the SSS occupies one OFDM symbol, and the PBCH occupies two OFDM symbols and one OFDM symbol multiplexed with the SSS and FDM. The location of the OFDM symbol within the slot occupied by the SSB may vary depending on the subcarrier spacing (SCS). Figure 19(a) shows SSB patterns when the subcarrier spacing for transmitting the SSB is 15 kHz and 30 kHz. Figure 19(b) shows SSB patterns when the subcarrier spacing for transmitting the SSB is 120 kHz and 240 kHz. When the subcarrier spacing is 30 kHz, either the SSB pattern for transmitting eMBB or the SSB pattern considering URLLC is used. In Figure 19, the hatched OFDM symbols indicate the positions of the OFDM symbols within the slots occupied by the SSBs. Different hatched patterns indicate different SSB indices. SSB indices will be described later.

[0152] Figure 20 is a diagram showing the positions of slots occupied by SSBs within a half radio frame, i.e., 5 ms, of the licensed band of an NR system according to one embodiment of the present invention. In Figure 20, hatched slots indicate the positions of slots containing SSBs within the half radio frame. One slot contains two SSBs. Two SSBs within one slot have different SSB indices. SSBs located in different slots also have different SSB indices. The SSB index will be described later. Also, L in Figure 20 indicates the maximum number of SSBs that a base station can transmit in a half radio frame.

[0153] The NR system specifies that one subcarrier spacing must be defined for each frequency band, reducing the complexity of SSB search for initial cell access by the UE. In particular, when a frequency band below 6 GHz is used, the NR system specifies that either 15 kHz or 30 kHz subcarrier spacing must be used for SSB. In addition, when a frequency band above 6 GHz is used, the NR system specifies that either 120 kHz or 240 kHz subcarrier spacing must be used for SSB.

[0154] In unlicensed bands, the LBT procedure is used when a wireless communication device attempts channel access. Therefore, if the channel is not idle, the wireless communication device may fail to access the channel. When a base station attempts channel access to transmit SSBs, channel access may also fail, resulting in the SSBs not being transmitted at the location set by the base station. Even if the base station configures the SSB transmission location to the terminal so that the terminal can assume the location where the SSBs will be transmitted, the terminal may not be able to receive the SSBs. Because SSBs are transmitted periodically, even if the terminal fails to receive the SSBs at any point, it can receive them one period after that point. However, if the terminal receives the SSBs in this way, delays occur in RRM measurements and measurements of neighbor cells. Ultimately, this increases latency throughout the system.

[0155] SSBs are also used to set up beam links and operate beams. Specifically, a base station transmits multiple SSBs corresponding to different SSB indexes in different time domains. A terminal uses multiple SSBs to set up multiple beam links. The base station performs beam sweeping. The terminal sets up a beam link depending on whether it receives SSBs transmitted on different beams in different time domains. If the base station fails to access the channel and is unable to transmit the SSB, a problem occurs in which the beam link cannot be set up. Ultimately, channel access failures increase the latency for beam linking. Therefore, a method is needed to reduce SSB transmission failures and increase SSB transmission opportunities.

[0156] When an NR system is used in an unlicensed band, 60 kHz subcarrier spacing is used to transmit SSBs to increase channel access opportunities. In licensed bands below 6 GHz, 15 kHz or 30 kHz subcarrier spacing is used to transmit SSBs. In licensed bands below 6 GHz, 15 kHz, 30 kHz, or 60 kHz subcarrier spacing is used to transmit data. In licensed bands above 6 GHz, 120 kHz or 240 kHz subcarrier spacing is used to transmit SSBs. In licensed bands above 6 GHz, 60 kHz or 120 kHz subcarrier spacing is used to transmit data. When an NR system is used in an unlicensed band below 7 GHz (e.g., below 7.125 GHz), 15 kHz or 30 kHz subcarrier spacing may be considered, similar to the subcarrier spacing used in licensed bands below 6 GHz. However, when 60 kHz subcarrier spacing is used to transmit SSB in an unlicensed band, the spacing between OFDM symbols is reduced to one-quarter of that when 15 kHz subcarrier spacing is used. Therefore, when 60 kHz subcarrier spacing is used in an NR system in an unlicensed band, symbol-by-symbol transmission opportunities for SSB and data channels can be increased after channel access. When 15 kHz and 30 kHz subcarrier spacing are used, if a base station successfully accesses a channel within one OFDM symbol, the time for transmitting a reservation signal is reduced when 60 kHz subcarrier spacing is used to prepare for the time required. The following describes SSB transmission methods that can be used in unlicensed bands, particularly when 60 kHz subcarrier spacing is used.

[0157] When SSBs are transmitted in an unlicensed band and a subcarrier spacing (SCS) of 15 kHz or 30 kHz is used, the SSB patterns described in Figures 19 and 20 can be used as is or with some modifications. The SSB patterns for transmitting SSBs in an unlicensed band when the subcarrier spacing value is 60 kHz are described in Figures 21 to 23.

[0158] An SSB pattern that allows for continuous transmission within a slot is used. This allows the base station to improve transmission efficiency. In this embodiment, after successfully accessing a channel, the base station continuously occupies the channel by transmitting the same beam or different beams. This prevents other wireless communication devices from occupying the channel. As a result, the base station transmits multiple SSBs after successfully accessing the channel once, thereby increasing the probability of subsequent transmissions. The base station transmits SSBs consecutively within a slot. The base station also transmits multiple SSBs consecutively within a slot. More specifically, the base station transmits SSBs as DL burst transmissions. If an SSB pattern that allows continuous transmission is used, the base station continuously uses a specific channel to prevent other wireless communication devices from accessing the channel. In this embodiment, the subcarrier spacing for transmitting SSBs in the unlicensed band is 60 kHz.

[0159] In addition, an SSB pattern is used in which transmission is terminated before the boundary between the slot in which the SSB is transmitted and the slot following the slot in which the SSB is transmitted. That is, a gap for the LBT procedure is set after SSB transmission before the start of the next slot. Specifically, the base station terminates SSB transmission a predetermined time before the boundary between the slot in which the SSB is transmitted and the slot following the slot in which the SSB is transmitted. More specifically, the base station terminates SSB transmission at least one OFDM symbol before the boundary between the slot in which the SSB is transmitted and the slot following the slot in which the SSB is transmitted. If such an SSB pattern is used, the base station starts the LBT procedure after transmitting the SSB, thereby increasing the possibility of transmitting a PDCCH or PDSCH from the start of the slot following the slot in which the SSB is transmitted. In this embodiment, the subcarrier spacing value for transmitting SSBs in the unlicensed band is 60 kHz.

[0160] FIG. 21 illustrates the location of OFDM symbols in which SSBs are transmitted within a 1 ms time interval when 60 kHz subcarrier spacing is used and the maximum number of SSBs is three, according to an embodiment of the present invention. FIG. 22 illustrates the location of OFDM symbols in which SSBs are transmitted within a 1 ms time interval when 60 kHz subcarrier spacing is used and the maximum number of SSBs is four, according to an embodiment of the present invention. FIG. 23 illustrates the location of OFDM symbols in which SSBs are transmitted within a 1 ms time interval when 60 kHz subcarrier spacing is used and the maximum number of SSBs is six, according to an embodiment of the present invention. In FIGS. 21 to 23, hatched OFDM symbols indicate OFDM symbols occupied by SSBs. Different hatching patterns indicate different SSB indexes. In FIGS. 21 to 23, the base station transmits SSBs continuously within one slot. In this way, after the base station has successfully accessed a channel to transmit an SSB within one slot, it prevents a subsequent wireless communication device from accessing the channel within that slot. 21 to 23, the base station is terminated before the boundary between the slot in which the SSB is transmitted and the slot following the slot in which the SSB is transmitted. This increases the possibility that the base station will transmit a PDCCH or PDSCH from the start of the slot following the slot in which the SSB is transmitted after transmitting the SSB. As a result, the base station prevents delays in initial cell access, radio resource management (RRM) measurement, and radio link monitoring (RLM) measurement due to LBT failure through the embodiments described with reference to FIGS. 21 to 23.

[0161] The base station transmits multiple SSBs via SSB transmission within a pre-designated time interval for transmitting the SSBs. The duration of the pre-designated time interval for transmitting the SSBs is 5 ms. The multiple SSBs transmitted via SSB transmission are referred to as an SSB set. A unique SSB index is assigned to each of the multiple SSBs included in the SSB set. The SSB index starts from 0 and increases by 1. In Figures 21 to 23, SSBs with different hatching correspond to different SSB indices. Figures 21(a), 22(a), and 23 illustrate cases where the position of an OFDM symbol within a slot in which an SSB is transmitted is fixed for each SSB index. Figures 20(b) and 21(b) illustrate cases where the position of an OFDM symbol within a slot in which an SSB is transmitted for each SSB index is not fixed. Specifically, the base station rotates the SSB index corresponding to the SSB transmission position each time an SSB is transmitted. This embodiment allows the probability of successful SSB transmission for each SSB index to be uniformly set. This will be explained in detail with reference to FIGS.

[0162] Figure 24 illustrates the positions of OFDM symbols in which SSBs are transmitted within a 1 ms time interval when 60 kHz subcarrier spacing is used to transmit SSBs and the maximum number of SSBs is 8, according to one embodiment of the present invention. In Figure 24, hatched OFDM symbols indicate OFDM symbols occupied by SSBs. Different hatching patterns indicate different SSB indexes. Figure 24 illustrates two SSB patterns applicable when 60 kHz subcarrier spacing is used. The second SSB pattern (pattern #2) starts SSB transmission in an OFDM symbol prior to the first SSB pattern (pattern #1). The base station uses the second SSB pattern (pattern #2) to increase the probability of success of the LBT procedure for PDSCH or PDCCH transmission after SSB transmission compared to when the first SSB pattern (pattern #1) is used. When the first SSB pattern (pattern #1) and the second SSB pattern (pattern #2) are used, a gap for LBT before the slot boundary is secured for PDCCH or PDSCH transmission at the slot boundary after the slot in which the SSB is transmitted. If data channel transmission is performed, a Cat-4 LBT, i.e., a channel access procedure with random backoff, is required. Therefore, the SSB pattern of FIG. 24 can increase the possibility of data channel transmission if data channel transmission is performed after SSB transmission. From this perspective, if the base station uses the first SSB pattern (pattern #1), transmission efficiency can be improved compared to when the second SSB pattern (pattern #2) is used.

[0163] In an unlicensed band, a base station attempts to transmit an SSB from the earliest slot in the time domain of the time interval during which the SSB is transmitted. This prevents the base station from losing an SSB transmission opportunity or delaying the SSB transmission due to a failure of the LBT procedure. This will be described with reference to Figures 25 to 29. For convenience of explanation, the time interval during which the SSB is transmitted is referred to as the SSB transmission window.

[0164] 25A and 25B are diagrams illustrating the positions of slots in an SSB transmission window in which SSBs are transmitted when 60 kHz subcarrier spacing is used to transmit SSBs according to another embodiment of the present invention. Specifically, FIG. 25A illustrates the positions of slots in which SSBs are transmitted in an SSB transmission window in which the maximum number of SSBs that can be transmitted in the SSB transmission window is 4. Also, FIG. 25B illustrates the positions of slots in which SSBs are transmitted in an SSB transmission window in which the maximum number of SSBs that can be transmitted in the SSB transmission window is 8. In one embodiment, the SSB transmission window has a duration of 5 ms.

[0165] In a specific embodiment, the base station transmits the maximum number of SSBs that can be transmitted within the SSB transmission window at each transmission opportunity. For example, if the base station acquires a transmission opportunity through the LBT procedure, the base station transmits the maximum number of SSBs that can be transmitted within the SSB transmission window. In this embodiment, the time interval during which the SSB set is transmitted is set based on the maximum number of SSBs that can be transmitted within the SSB transmission window. More specifically, the time interval during which the SSB set is transmitted is set in slots corresponding to the maximum number of SSBs that can be transmitted within the SSB transmission window.

[0166] 26 to 28 show cases in which, for SSB transmission in an unlicensed band, there are multiple slot positions at which a base station can start SSB transmission in accordance with a preset maximum number of SSBs within the SSB transmission window. The base station sets the slot positions at which SSB transmission can start in the SSB transmission window in accordance with the maximum number of SSBs and performs SSB transmission, and the terminal receives SSBs from the slot positions at which SSB transmission can start set by the base station within the SSB transmission window. If the base station fails the LBT in a slot at which SSB transmission can start, it performs an LBT to start transmission in the next slot at which SSB transmission can start, and then performs SSB transmission in that slot.

[0167] Figure 26 illustrates a case where, when 15 kHz subcarrier spacing is used to transmit SSBs in an unlicensed band, a base station can start SSB transmission at multiple slot positions depending on the maximum number of SSBs that can be transmitted within the SSB transmission window, according to an embodiment of the present invention. In Figure 26(a), if the duration of the SSB transmission window is set to 5 ms and the maximum number of SSBs that can be transmitted within the SSB transmission window is set to 4, the base station sets the first, third, and fifth slots within the SSB transmission window as slot positions from which SSB transmission can be started. The terminal receives SSBs from the slot positions from which SSB transmission can be started set by the base station. In Figure 26(b), if the duration of the SSB transmission window is set to 5 ms and the maximum number of SSBs that can be transmitted within the SSB transmission window is set to 8, the base station sets the first and fifth slots within the SSB transmission window as slot positions from which SSB transmission can be started. The terminal receives SSBs from the slot positions from which SSB transmission can be started set by the base station.

[0168] Figure 27 shows multiple slot positions at which a base station can start transmitting SSBs depending on the maximum number of SSBs that can be transmitted within an SSB transmission window when 30 kHz subcarrier spacing is used to transmit SSBs in an unlicensed band according to an embodiment of the present invention. Figure 27(a) shows a case where the duration of the SSB transmission window is 5 ms and the maximum number of SSBs that can be transmitted within the SSB transmission window is 4. Figure 27(b) shows a case where the duration of the SSB transmission window is 5 ms and the maximum number of SSBs that can be transmitted within the SSB transmission window is 8.

[0169] Figure 28 shows multiple slot positions at which a base station can start transmitting SSBs depending on the maximum number of SSBs that can be transmitted within an SSB transmission window when 60 kHz subcarrier spacing is used to transmit SSBs in an unlicensed band according to an embodiment of the present invention. Figure 28(a) shows a case where the duration of the SSB transmission window is 5 ms and the maximum number of SSBs that can be transmitted within the SSB transmission window is 4. Figure 28(b) shows a case where the duration of the SSB transmission window is 5 ms and the maximum number of SSBs that can be transmitted within the SSB transmission window is 8.

[0170] In another specific embodiment, the base station configures the SSB transmission window to start for each slot. Depending on the channel access result, the position of the slot where the SSB transmission starts within the SSB transmission window may differ for each SSB transmission window. Therefore, due to channel access failure, an imbalance in transmission opportunities may occur for multiple SSBs transmitted using different beams with different SSB indices. Through this embodiment, the base station can reduce the imbalance in transmission opportunities for each SSB. In this case, the base station transmits SSBs corresponding to different SSB indices for each SSB transmission available position included in each slot. As a result, SSBs corresponding to different SSB indices can have equal transmission opportunities.

[0171] 29A and 29B are diagrams illustrating how a base station has an opportunity to start SSB transmission for each slot within an SSB transmission window according to an embodiment of the present invention when 15 kHz subcarrier spacing is used to transmit SSBs in an unlicensed band. In Fig. 29A, the duration of the SSB transmission window is set to 5 ms, and the maximum number of SSBs that can be transmitted within the SSB transmission window is set to 4. In Fig. 29B, the duration of the SSB transmission window is set to 5 ms, and the maximum number of SSBs that can be transmitted within the SSB transmission window is set to 8.

[0172] 30A and 30B illustrate how a base station has an opportunity to start SSB transmission for each slot within an SSB transmission window according to an embodiment of the present invention when 30 kHz subcarrier spacing is used to transmit SSBs in an unlicensed band. In Fig. 30A, the duration of the SSB transmission window is set to 5 ms, and the maximum number of SSBs that can be transmitted within the SSB transmission window is set to 4. In Fig. 30B, the duration of the SSB transmission window is set to 5 ms, and the maximum number of SSBs that can be transmitted within the SSB transmission window is set to 8.

[0173] 31A and 31B illustrate how a base station has an opportunity to start SSB transmission for each slot within an SSB transmission window according to an embodiment of the present invention when 60 kHz subcarrier spacing is used to transmit SSBs in an unlicensed band. In Fig. 31A, the duration of the SSB transmission window is set to 5 ms, and the maximum number of SSBs that can be transmitted within the SSB transmission window is set to 4. In Fig. 31B, the duration of the SSB transmission window is set to 5 ms, and the maximum number of SSBs that can be transmitted within the SSB transmission window is set to 8.

[0174] In another specific embodiment, the base station sets an SSB transmission start opportunity for each specific time interval within the SSB transmission window and transmits the SSB. Specifically, the base station attempts SSB transmission for each specific time interval. In this case, the specific time interval has a duration that is an integer multiple of the slot. The specific time interval is set in the RRC configuration of the base station from a preset candidate set. The specific time interval is a fixed value agreed upon between the terminal and the base station.

[0175] A base station may be unable to transmit SSB due to a channel access (e.g., LBT) procedure failure. An SSB transmission window is defined so that if the base station is unable to transmit SSB at a configured location, it can transmit at another location. The SSB transmission window is the period during which the base station can transmit SSB and includes multiple SSB transmission candidate locations. If the base station is unable to start SSB transmission at one of the SSB transmission candidate locations, the base station attempts SSB transmission at an SSB transmission candidate location later than the corresponding SSB transmission candidate location within the SSB transmission window. An SSB transmission candidate location is a point in time at which the base station can start SSB transmission. If the terminal is unable to receive SSB at one of the SSB transmission candidate locations within the SSB transmission window, the terminal receives SSB at an SSB transmission candidate location later than the corresponding SSB transmission candidate location within the corresponding SSB transmission window. At this time, the terminal determines whether the base station was unable to start SSB transmission at the SSB transmission candidate location or whether the base station's SSB transmission failed. In a specific embodiment, if a terminal is unable to receive an SSB at any one SSB transmission candidate position within an SSB transmission window, the terminal attempts to receive an SSB at the SSB transmission candidate position next to the corresponding SSB transmission candidate position within the corresponding SSB transmission window. After the terminal starts receiving an SSB at any one SSB transmission candidate position and completes SSB reception, the terminal does not expect to receive any additional SSBs within the corresponding SSB transmission window. Specifically, after the terminal starts receiving an SSB at any one SSB transmission candidate position and completes SSB reception, the terminal does not attempt to receive any additional SSBs within the corresponding SSB transmission window.

[0176] In another specific embodiment, if the terminal is unable to receive a specific SSB at any one SSB transmission candidate position within the SSB transmission window, the terminal attempts to receive the specific SSB at the SSB transmission candidate position next to the corresponding SSB transmission candidate position within the corresponding SSB transmission window. After the terminal starts receiving a specific SSB at any one SSB transmission candidate position and completes reception of the specific SSB, the terminal does not receive the specific SSB within the corresponding SSB transmission window. Specifically, after the terminal receives a specific SSB at any one SSB transmission candidate position, the terminal does not make any further attempts to receive the specific SSB within the corresponding SSB transmission window.

[0177] In another specific embodiment, even after a terminal has completed reception of a specific SSB at one SSB transmission candidate position, the terminal may additionally attempt to receive the specific SSB within the corresponding SSB transmission window. In this case, the terminal can receive the specific SSB and obtain combining gain through the additionally received specific SSB. This embodiment applies not only to cases in which multiple SSBs corresponding to different beam indices are transmitted for beam operation, but also to cases in which an omni-transmission (omni-TX) scheme is used. More specifically, it also applies to cases in which the same SSB is repeatedly transmitted. A base station may transmit an SSB after the LBT procedure, and a failure of the LBT procedure may prevent transmission of all SSBs in the SSB block set within the DRS transmission window. Therefore, the SSB transmission probability may vary for each SSB index depending on the SSB transmission order. An embodiment is needed that ensures uniform transmission probabilities for SSBs corresponding to different SSB indices. This will be described with reference to Figures 32 to 42.

[0178] Each SSB transmission candidate position within the SSB transmission window is mapped to one SSB in the SSB set, and the base station transmits the SSBs based on the mapping between the SSB transmission candidate positions and the SSBs. In this case, the multiple SSBs in the SSB set are identified by an SSB index, which is a unique value within the SSB set. Furthermore, within the SSB transmission window, the multiple SSB transmission candidate positions are identified by an SSB transmission candidate position index. Specifically, when the base station successfully accesses a channel at a specific SSB transmission candidate position, the base station starts transmitting the SSB from the corresponding SSB transmission candidate position. At this time, the base station transmits the SSBs mapped to each SSB transmission candidate position. In a specific embodiment, the base station transmits the SSBs mapped to at least one SSB transmission candidate position from each of at least one SSB transmission candidate positions located in the time interval from the SSB transmission candidate position where channel access was successful to the end of transmission of the SSB set. Furthermore, the base station transmits the SSBs within the SSB transmission window, transmitting the SSBs within the maximum number of SSBs that can be transmitted within the SSB transmission window.

[0179] The base station transmits SSBs based on the DRS transmission periodicity. Specifically, the DRS transmission of the base station includes SSB transmission. In this regard, in the above description, the window for transmitting SSBs or the SSB transmission window is replaced with the DRS transmission window. The DRS transmission window indicates a time period during which DRS can be transmitted. The duration of the DRS transmission window is fixed. The DRS transmission window is set to repeat at a fixed period. The DRS transmission window is set for each terminal.

[0180] FIG. 32 illustrates a case where the mapping between SSB indices and SSB transmission candidate position indexes within the DRS transmission window is fixed according to an embodiment of the present invention.

[0181] FIG. 32 shows that when a 30 kHz subcarrier spacing is used and the duration of the DRS transmission window is set to 5 ms, there are 20 SSB transmission candidate positions within the DRS transmission window, and each of the 20 SSB transmission candidate positions corresponds to one SSB index. In this case, the SSB index corresponding to each of the 20 SSB transmission candidate positions is static. That is, once the SSB index corresponding to each of the 20 SSB transmission candidate positions is set, it remains unchanged. For example, if the maximum number of transmittable SSBs is 8, the SSB transmission candidate position indexes and SSB indexes are mapped as follows: Because a 30 kHz subcarrier spacing is used, the DRS transmission window with a duration of 5 ms contains a total of 20 SSB transmission candidate positions. For convenience of explanation, each SSB transmission candidate position index is denoted by i, and the SSB index corresponding to SSB transmission candidate position i is denoted by i_SSB. If the SSB transmission candidate position index is 0 to 7, i_SSB = i. Also, if the SSB transmission candidate location index is 8 to 15, i_SSB = (i-8). If the SSB transmission candidate location index is 16 to 19, i_SSB = (i-16). This mapping between the SSB transmission candidate location index and the SSB index is maintained in the DRS transmission window of the next period. FIG. 32 shows a case where such an embodiment is applied. In this embodiment, assuming that the LBT success probability is the same for each SSB transmission candidate location index, the probability of a transmission opportunity for SSBs with SSB index values ​​of 0 to 3 is 3 / 20, and the probability of a transmission opportunity for SSBs with SSB index values ​​of 4 to 7 is 1 / 10. In order to ensure uniform transmission probabilities for SSBs corresponding to different SSB indices, the mapping between the SSB transmission candidate location index and the SSB index may be further configured for each DRS transmission window. In particular, the mapping relationship between the SSB transmission candidate positions and the SSB in the second DRS transmission window may be different from the mapping relationship between the SSB transmission candidate positions and the SSB in the first DRS transmission window.

[0182] 33 and 34 are diagrams illustrating a case where the mapping between SSB indices and SSB transmission candidate position indexes in the DRS transmission window is not fixed according to an embodiment of the present invention.

[0183] The base station cyclically wraps around the SSB indices that were mapped to SSB transmission candidate position indices in the previous DRS transmission window and maps them to SSB transmission candidate position indices. Specifically, the SSB indices are mapped to the SSB transmission candidate position indices in the DRS transmission window in the reverse order of the SSB indices that were mapped to the SSB transmission candidate position indices in the immediately previous DRS transmission window. The base station maps the SSB indices to the SSB transmission candidate position indices in the DRS transmission window in the reverse order of the SSB indices that were mapped to the SSB transmission candidate position indices in the immediately previous DRS transmission window, and transmits the SSBs based on the mapping between the SSB transmission candidate position indices and the SSB indices. In a specific embodiment, in even-numbered DRS transmission windows, the SSB indices are mapped to the SSB transmission candidate position indices according to the following equation: i_SSB=i mod L In this case, x mod y means the remainder when x is divided by y, and L is the maximum number of SSBs that the base station can transmit within the DRS transmission window. In addition, in odd-numbered DRS transmission windows, the SSB index is mapped to the SSB transmission candidate position index as shown in the following formula. i_SSB=(L-1)-(i mod L)

[0184] For example, if the maximum number of SSBs that can be transmitted within a DRS transmission window is 8, the duration of the DRS transmission window is 5 ms, and 30 kHz subcarrier spacing is used for SSB transmission, the SSB transmission candidate position indexes and SSB indices are mapped as follows: Because 30 kHz subcarrier spacing is used, a DRS transmission window with a 5 ms duration contains a total of 20 SSB transmission candidate positions for SSB transmission. X is an even number. If the Xth SSB transmission candidate position index is 0 to 7, i_SSB = i mod 8. Also, if the SSB transmission candidate position index is 8 to 15, i_SSB = i mod 8. Also, if the SSB transmission candidate position index is 16 to 19, i_SSB = i mod 8. For the Xth DRS transmission window, if the SSB transmission candidate position index is 0 to 7, i_SSB = 7 - (i mod 8). Also, if the SSB transmission candidate position index is 8 to 15, then i_SSB=7-(i mod 8). Also, if the SSB transmission candidate position index is 16 to 19, then i_SSB=7-(i mod 8). Figure 33 shows SSB transmission to which this embodiment is applied.

[0185] In FIG. 33, the base station performs the LBT procedure for one slot for transmitting SSBs, i.e., in units of two SSB transmission candidate positions (granularity). In this way, the base station performs channel access for one slot, i.e., in units of two SSB transmission candidate positions for transmitting SSBs. More specifically, the base station performs the LBT procedure for one slot for transmitting SSBs, i.e., in units of SSB transmission candidate positions for transmitting two SSBs. In this case, if the base station fails the LBT procedure for starting SSB transmission at the SSB transmission candidate position with index i, the base station performs the LBT procedure for starting SSB transmission at the SSB transmission candidate position with index i+2, and the base station cannot perform the LBT procedure for starting SSB transmission at the SSB transmission candidate position with index i+1. However, this embodiment is not limited to this, and the base station may perform channel access for SSB transmission in units of n SSB transmission candidate positions, where n is a positive integer. More specifically, the base station performs the LBT procedure for SSB transmission in units of n SSB transmission candidate positions. In particular, if the LBT procedure for initiating SSB transmission at an SSB transmission candidate location with index i fails, the base station can perform the LBT procedure for initiating SSB transmission at an SSB transmission candidate location with index i+n, but cannot perform the LBT procedure for initiating SSB transmission at an SSB transmission candidate location that precedes the SSB transmission candidate location with index i+n. In a specific embodiment, n is 1.

[0186] FIG. 34 is a diagram showing how a base station performs an LBT procedure for transmitting an SSB for each SSB transmission candidate position. In the above description, an example is given in which there are 20 SSB transmission candidate positions within the DRS transmission window and the maximum number of positions that can be transmitted within 5 ms is 8, but the above embodiment is not limited to this number. It also applies to a case in which there are P SSB transmission candidate positions within the DRS transmission window and the maximum number of positions that can be transmitted within 5 ms is Q. In this case, P is a natural number greater than Q, and Q is a natural number greater than 0.

[0187] In the embodiment described with reference to Figures 33 and 34, two types of mapping between SSB transmission candidate positions and SSB indices are alternately applied to the DRS transmission window. Four types of mapping between SSB transmission candidate positions and SSB indices may also be alternately applied to the DRS transmission window, as will be described with reference to Figures 35 and 36.

[0188] 35 to 37 are diagrams illustrating a case where the mapping between SSB indices in the DRS transmission window and SSB transmission candidate position indexes is not fixed according to another embodiment of the present invention.

[0189] In a specific embodiment, in the (x+N)th DRS transmission window, if the remainder when N is divided by 4 is 0, the SSB index is mapped to the SSB transmission candidate position index according to the following formula: i_SSB=i mod L In this case, x mod y means the remainder when x is divided by y, and L is the maximum number of SSBs that the base station can transmit within the DRS transmission window.

[0190] Also, in the (x+N)th DRS transmission window, if the remainder when N is divided by 4 is 1, the SSB index is mapped to the SSB transmission candidate position index as shown in the following formula. i_SSB=(L-1)-(i mod L)

[0191] Also, in the (x+N)th DRS transmission window, if the remainder when N is divided by 4 is 2, the SSB index is mapped to the SSB transmission candidate position index as shown in the following formula. i_SSB=(i+2) mod L

[0192] Also, in the (x+N)th DRS transmission window, if the remainder when N is divided by 4 is 3, the SSB index is mapped to the SSB transmission candidate position index as shown in the following formula. i_SSB=(L-1)-{(i+2) mod L}

[0193] For example, if the maximum number of SSBs that can be transmitted within a DRS transmission window is 8, the duration of the DRS transmission window is 5 ms, and 15 kHz subcarrier spacing is used for SSB transmission, the SSB transmission candidate location indexes and SSB indices are mapped as follows: Because 15 kHz subcarrier spacing is used, a DRS transmission window with a 5 ms duration contains a total of 10 SSB transmission candidate locations for SSB transmission. X is a multiple of 4. If the Xth SSB transmission candidate location index is 0 to 7, i_SSB = i mod 8. If the SSB transmission candidate location index is 8 to 9, i_SSB = i mod 8. If the X+1th transmission candidate location index is 0 to 7, i_SSB = 7 - (i mod 8). If the SSB transmission candidate location index is 8 to 9, i_SSB = 7 - (i mod 8). If the X+2th transmission candidate location index is 0 to 5, i_SSB = (i+2) mod 8. Also, if the SSB transmission candidate position index is 6 to 9, then i_SSB = (i+2) mod 8. If the (X+3)th transmission candidate position index is 0 to 5, then i_SSB = 7 - {(i+2) mod 8)}. Also, if the SSB transmission candidate position index is 6 to 9, then i_SSB = 7 - {(i+2) mod 8)}.

[0194] In Figure 35, the base station performs the LBT procedure for one slot for transmitting SSB, i.e., for two SSB transmission candidate positions. In this manner, the base station performs the LBT procedure for one slot, i.e., for two SSB transmission candidate positions for transmitting SSB. In this case, if the base station fails the LBT procedure for starting SSB transmission at the SSB transmission candidate position with index i, the base station performs the LBT procedure for starting SSB transmission at the SSB transmission candidate position with index i+2, and the base station cannot perform the LBT procedure for starting SSB transmission at the SSB transmission candidate position with index i+1. However, this embodiment is not limited to this, and the base station may perform the LBT procedure for SSB transmission in units of n SSB transmission candidate positions, where n is a positive integer. In particular, if the LBT procedure for initiating SSB transmission at an SSB transmission candidate position with index i fails, the base station can perform the LBT procedure for initiating SSB transmission at an SSB transmission candidate position with index i+n, but cannot perform the LBT procedure for initiating SSB transmission at an SSB transmission candidate position that precedes the SSB transmission candidate position with index i+n.

[0195] FIG. 36 is a diagram showing how a base station performs an LBT procedure for transmitting an SSB for each SSB transmission candidate position. In the above description, an example is given in which there are 10 SSB transmission candidate positions within the DRS transmission window and the maximum number of positions that can be transmitted within 5 ms is 8, but the above embodiment is not limited to this number. It also applies to a case in which there are P SSB transmission candidate positions within the DRS transmission window and the maximum number of positions that can be transmitted within 5 ms is Q. In this case, P is a natural number greater than Q, and Q is a natural number greater than 0.

[0196] In another specific embodiment, in the (x+N)th DRS transmission window, if the remainder when N is divided by 4 is 0, the SSB index is mapped to the SSB transmission candidate position index according to the following formula: i_SSB=i mod L In this case, x mod y means the remainder when x is divided by y, and L is the maximum number of SSBs that the base station can transmit within a half radio frame.

[0197] Also, in the (x+N)th DRS transmission window, if the remainder when N is divided by 4 is 1, the SSB index is mapped to the SSB transmission candidate position index as shown in the following formula.

[0198] i_SSB=(L-1)-{(i+2) mod L} Also, in the (x+N)th DRS transmission window, if the remainder when N is divided by 4 is 2, the SSB index is mapped to the SSB transmission candidate position index as shown in the following formula. i_SSB=(i+2) mod L

[0199] Also, in the (X+N)th DRS transmission window, if the remainder when N is divided by 4 is 3, the SSB index is mapped to the SSB transmission candidate position index as shown in the following formula. i_SSB=(L-1)-(i mod L)

[0200] FIG. 37 shows that the embodiment described with reference to FIG. 35 is applied to the case where the maximum number of SSBs that can be transmitted within the DRS transmission window is four. 38 to 42 are diagrams illustrating a case where the mapping between SSB indices in the DRS transmission window and SSB transmission candidate position indexes is not fixed according to another embodiment of the present invention.

[0201] The base station sets a different mapping between SSB transmission candidate position indexes and SSB indices for each transmission window from the xth DRS transmission window to the (x+N)th DRS transmission window. Specifically, each time the DRS transmission window changes, the base station sets the value of the SSB index to be mapped to the SSB transmission candidate position index by cyclic wraparound. If the maximum number of SSBs that the base station can transmit within a half radio frame is 8, the base station applies cyclic wraparound to the SSB transmission candidate position and SSB index mapping in units of 4, 2, or 1. If the maximum number of SSBs that the base station can transmit within a half radio frame is 4, the base station applies cyclic wraparound to the SSB transmission candidate position and SSB index mapping in units of 2 or 1.

[0202] The base station applies cyclic wraparound to the SSB transmission candidate locations and SSB index mapping in units of the maximum number of SSBs that the base station can transmit within the DRS transmission window divided by 4. Figures 38 and 39 show that cyclic extension is applied to the SSB transmission candidate locations and SSB index mapping in units of the maximum number of SSBs that the base station can transmit within a half radio frame divided by 4 according to an embodiment. In detail, the SSB transmission candidate position index and the SSB index are mapped as follows:

[0203] In the (x+N)th DRS transmission window, if the remainder when N is divided by 2 is 0, the SSB index is mapped to the SSB transmission candidate position index as shown in the following formula. i_SSB=i mod L In this case, x mod y means the remainder when x is divided by y, and L is the maximum number of SSBs that the base station can transmit within the DRS transmission window.

[0204] Also, in the (x+N)th DRS transmission window, if the remainder when N is divided by 2 is 1, the SSB index is mapped to the SSB transmission candidate position index as shown in the following formula. i_SSB=(i+L / 2) mod L

[0205] Figure 38 shows the mapping between SSB transmission candidate position indexes and SSB indices when the maximum number of SSBs that can be transmitted within the DRS transmission window is 8 and a subcarrier spacing of 30 kHz is used to transmit the SSBs. Therefore, the DRS transmission window includes 20 SSB transmission candidate positions. Figure 38 illustrates an example in which there are 20 SSB transmission candidate positions within the DRS transmission window, the maximum number of SSBs that can be transmitted within the DRS transmission window is 8, and the duration of the DRS transmission window is 5 ms. However, the above-described embodiment is not limited to these numbers. This also applies to a case in which there are P SSB transmission candidate positions within the DRS transmission window and the maximum number of SSBs that can be transmitted within the DRS transmission window is Q. In this case, P is a natural number greater than Q, and Q is a natural number greater than 0.

[0206] In FIG. 38, the base station performs the LBT procedure for SSB transmission in units of one slot, i.e., two SSB transmission candidate positions. In this manner, the base station performs the LBT procedure for SSB transmission in units of one slot, i.e., two SSB transmission candidate positions. If the base station fails the LBT procedure for starting SSB transmission at the SSB transmission candidate position with index i, the base station performs the LBT procedure for starting SSB transmission at the SSB transmission candidate position with index i+2, but fails to perform the LBT procedure for starting SSB transmission at the SSB transmission candidate position with index i+1. However, this embodiment is not limited to this, and the base station may perform the LBT procedure for SSB transmission in units of n SSB transmission candidate positions, where n is a positive integer. In particular, if the LBT procedure for initiating SSB transmission at an SSB transmission candidate position with index i fails, the base station can perform the LBT procedure for initiating SSB transmission at an SSB transmission candidate position with index i+n, but cannot perform the LBT procedure for initiating SSB transmission at an SSB transmission candidate position that precedes the SSB transmission candidate position with index i+n. FIG. 39 is a diagram showing how a base station performs an LBT procedure for transmitting an SSB for each SSB transmission candidate position.

[0207] The base station applies cyclic extension to the SSB transmission candidate positions and SSB index mapping in units of the maximum number of SSBs that the base station can transmit within a half radio frame divided by 2. Figures 40 to 42 show that cyclic extension is applied to the SSB transmission candidate positions and SSB index mapping in units of the maximum number of SSBs that the base station can transmit within a half radio frame divided by 2 according to an embodiment.

[0208] The base station applies cyclic extension in units of the maximum number of SSBs that the base station can transmit within a half radio frame divided by 2. In detail, the SSB transmission candidate position index and the SSB index are mapped as follows:

[0209] In the (x+N)th DRS transmission window, if the remainder when N is divided by 4 is 0, the SSB index is mapped to the SSB transmission candidate position index as shown in the following formula. i_SSB=i mod L In this case, x mod y means the remainder when x is divided by y, and L is the maximum number of SSBs that the base station can transmit within a half radio frame.

[0210] Also, in the (x+N)th DRS transmission window, if the remainder when N is divided by 4 is 1, the SSB index is mapped to the SSB transmission candidate position index as shown in the following formula. i_SSB=(i+L / 2) mod L

[0211] Also, in the (x+N)th DRS transmission window, if the remainder when N is divided by 4 is 2, the SSB index is mapped to the SSB transmission candidate position index as shown in the following formula. i_SSB=(i+L / 4) mod L

[0212] Also, in the (x+N)th DRS transmission window, if the remainder when N is divided by 4 is 3, the SSB index is mapped to the SSB transmission candidate position index as shown in the following formula. i_SSB=(i+3*L / 4) mod L

[0213] Figure 40 shows the mapping between SSB transmission candidate position indexes and SSB indices when the maximum number of SSBs that can be transmitted within the DRS transmission window is 8 and a subcarrier spacing of 15 kHz is used to transmit the SSBs. Therefore, the DRS transmission window includes 10 SSB transmission candidate positions. Figure 40 illustrates an example in which there are 10 SSB transmission candidate positions within the DRS transmission window, the maximum number of SSBs that can be transmitted within the DRS transmission window is 8, and the duration of the DRS transmission window is 5 ms. However, the above-described embodiment is not limited to these numbers. This also applies to a case in which there are P SSB transmission candidate positions within the DRS transmission window and the maximum number of SSBs that can be transmitted within the DRS transmission window is Q. In this case, P is a natural number greater than Q, and Q is a natural number greater than 0.

[0214] In Figure 40, the base station performs the LBT procedure for SSB transmission in one slot, i.e., in units of two SSB transmission candidate positions. In this manner, the base station performs the LBT procedure for SSB transmission in one slot, i.e., in units of two SSB transmission candidate positions. In this case, if the base station fails the LBT procedure for starting SSB transmission at the SSB transmission candidate position with index i, the base station performs the LBT procedure for starting SSB transmission at the SSB transmission candidate position with index i+2, and the base station cannot perform the LBT procedure for starting SSB transmission at the SSB transmission candidate position with index i+1. However, this embodiment is not limited to this, and the base station may perform the LBT procedure for SSB transmission in units of n SSB transmission candidate positions, where n is a positive integer. In particular, if the LBT procedure for initiating SSB transmission at an SSB transmission candidate position with index i fails, the base station can perform the LBT procedure for initiating SSB transmission at an SSB transmission candidate position with index i+n, but cannot perform the LBT procedure for initiating SSB transmission at an SSB transmission candidate position that precedes the SSB transmission candidate position with index i+n.

[0215] FIG. 41 is a diagram showing how a base station performs an LBT procedure for transmitting an SSB for each SSB transmission candidate position. Figure 42 shows a case where the maximum number of SSBs that a base station can transmit within a DRS transmission window is 4. That is, in the (x+N)th DRS transmission window, if the remainder when N is divided by 2 is 0, the SSB index is mapped to the SSB transmission candidate position index as shown in the following formula. i_SSB=i mod L

[0216] Also, in the (x+N)th DRS transmission window, if the remainder when N is divided by 2 is 1, the SSB index is mapped to the SSB transmission candidate position index as shown in the following formula. i_SSB=(i+L / 2) mod L In another specific embodiment, the SSB transmission candidate location index and the SSB index are mapped as follows:

[0217] In the (x+N)th DRS transmission window, if the remainder when N is divided by 4 is 0, the SSB index is mapped to the SSB transmission candidate position index as shown in the following formula. i_SSB=i mod L In this case, x mod y means the remainder when x is divided by y, and L is the maximum number of SSBs that the base station can transmit within a half radio frame.

[0218] Also, in the (x+N)th DRS transmission window, if the remainder when N is divided by 4 is 1, the SSB index is mapped to the SSB transmission candidate position index as shown in the following formula. i_SSB=(i+L / 4) mod L

[0219] Also, in the (x+N)th DRS transmission window, if the remainder when N is divided by 4 is 2, the SSB index is mapped to the SSB transmission candidate position index as shown in the following formula. i_SSB=(i+L / 2) mod L

[0220] Also, in the (x+N)th DRS transmission window, if the remainder when N is divided by 4 is 3, the SSB index is mapped to the SSB transmission candidate position index as shown in the following formula. i_SSB=(i+3*L / 4) mod L

[0221] In this case, the remaining operations except for the SSB transmission candidate position index and SSB index mapping are the same as those of the embodiments described with reference to Figures 40 to 42.

[0222] The base station transmits SSBs based on the mapping between SSB transmission candidate positions and SSBs to which the embodiments described with reference to Figures 32 to 42 are applied. Specifically, when the base station successfully accesses a channel at a specific SSB transmission candidate position, the base station starts transmitting SSBs from the corresponding SSB transmission candidate position. At this time, the base station transmits SSBs mapped to each SSB transmission candidate position at each SSB transmission candidate position. In a specific embodiment, the base station transmits SSBs mapped to at least one SSB transmission candidate position at at least one SSB transmission candidate position located in a time interval from the SSB transmission candidate position where channel access was successful to the end of SSB transmission. In addition, the base station transmits SSBs within a DRS transmission window, transmitting the SSBs within the maximum number of SSBs that can be transmitted within the duration of the DRS transmission window. The terminal receives the SSBs included in the DRS and performs at least one of initial access, cell detection, RRM, RLM, and RSSI measurement based on the DRS.

[0223] Through the embodiments described with reference to Figures 33 to 42, the base station can ensure that the probability of an SSB corresponding to each SSB index being transmitted is as uniform as possible. In the embodiments described with reference to Figures 33 to 42, the terminal needs to receive additional timing information after receiving an SSB. That is, the same SSB is transmitted at multiple SSB transmission candidate positions within one DRS transmission window. For example, in Figure 33, an SSB transmission having a first SSB index (SSB index #0) is transmitted within the x-th DRS transmission window at an SSB transmission candidate position where the SSB transmission candidate position index value is one of 0, 8, and 16. When the terminal receives an SSB having a first SSB index (SSB index #0), it cannot know whether it was received at the first SSB transmission candidate position index (#0), the ninth SSB transmission candidate position index (#8), or the 17th SSB transmission candidate position index (#16). Also, in FIG. 42, an SSB having a first SSB index (SSB index #0) is transmitted at the first SSB transmission candidate position index (#0) or the fifth SSB transmission candidate position index (#4) within the x-th DRS transmission window. When a terminal receives an SSB having a first SSB index (SSB index #0), the terminal cannot determine whether it received the SSB at the first SSB transmission candidate position index (#0) or the fifth SSB transmission candidate position index (#4). Therefore, without knowing additional timing information, the terminal cannot determine at which SSB transmission candidate position the SSB was received. Ultimately, without knowing the additional timing information, the terminal cannot set the SSB reception timing according to the SSB transmission candidate position. Therefore, the base station indicates additional timing information to the terminal via the PBCH during initial access. In this case, the base station transmits to the terminal the timing offset for the SSB transmission candidate position mapped to the same SSB index via the PBCH. Specifically, the base station indicates timing information using the value of offset_SSB=floor(i / L). Here, i is the index of the SSB transmission candidate position, and L is the maximum number of SSBs that the base station can transmit within the DRS transmission window.The number of SSB transmission candidate positions included in the DRS transmission window and the maximum number of SSBs that can be transmitted within the DRS transmission window may vary depending on the unlicensed band carrier frequency and subcarrier spacing. Furthermore, the number of SSB transmission candidate positions included in the DRS transmission window and the maximum number of SSBs that can be transmitted within the DRS transmission window may vary depending on the length of the DRS transmission window and the DRS transmission duration. While the above description assumes that the length of the DRS transmission window is the same as the length of the SSB transmission window, the length of the SSB transmission window is 5 ms, and a maximum of two SSBs can be transmitted per slot, embodiments of the present invention are not limited to this.

[0224] In unlicensed bands, a terminal and a base station access a channel in 20 MHz increments. This is to allow for coexistence with other radio access technologies (RATs), such as Wi-Fi, that use unlicensed bands. Specifically, in unlicensed bands, the terminal and a base station perform an LBT procedure in 20 MHz increments and transmit on the channel depending on the result of the LBT procedure. A terminal should perform random access for uplink synchronization with a base station. Specifically, random access is required not only when the terminal operates standalone in an unlicensed band but also when it uses both an unlicensed band carrier and a licensed band carrier. In indoor or outdoor environments with limited coverage, a terminal is not collocated with a base station or uses a non-ideal backhaul. In such cases, a random access procedure is required to synchronize the uplink. If a bandwidth consisting of multiple 20 MHz bandwidths is configured for uplink transmission in a terminal, the terminal attempts to transmit a random access preamble using a 20 MHz bandwidth that is a portion of the corresponding frequency bandwidth. If the frequency band corresponding to the frequency bandwidth where the random access preamble transmission is attempted is busy, the terminal cannot transmit the random access preamble even if the frequency bandwidth other than the 20 MHz bandwidth where the random access preamble transmission is attempted is idle among the bandwidths configured for the terminal. This problem can result in a decrease in spectral efficiency. Therefore, a method to solve this problem is needed.

[0225] The base station configures the bandwidth part (BWP) of the unlicensed band to have a 20 MHz bandwidth. Specifically, the base station is not allowed to configure the bandwidth of the BWP of the unlicensed band to a value other than 20 MHz. If a frequency bandwidth having a bandwidth of 20 MHz or more is used, multiple BWPs are configured for the terminal. The base station also configures a PRACH transmission occasion for each BWP. The terminal attempts PRACH transmission for each BWP. If the terminal successfully accesses the channel in any one of the BWPs, the terminal transmits the PRACH in the corresponding BWP. Therefore, in this embodiment, the terminal can ensure a higher PRACH transmission probability than if the terminal attempts PRACH transmission in any one of the frequency bandwidths having a 20 MHz bandwidth. The base station also configures a PRACH transmission occasion for each 20 MHz bandwidth for the terminal. The terminal attempts PRACH transmission for each 20 MHz bandwidth. If the terminal successfully accesses the channel in any one of the 20 MHz bandwidths, the terminal transmits the PRACH in the corresponding 20 MHz bandwidth. Therefore, in this embodiment, the terminal can ensure a higher PRACH transmission probability than when attempting PRACH transmission in any one frequency bandwidth having a 20 MHz bandwidth.

[0226] However, if a terminal successfully accesses a channel using multiple BWPs or multiple 20 MHz bandwidths, the question arises as to whether the terminal can transmit the PRACH in all of the BWPs or multiple 20 MHz bandwidths. If the terminal successfully accesses a channel using multiple BWPs or multiple 20 MHz bandwidths and transmits the PRACH in multiple BWPs or multiple 20 MHz bandwidths, transmission collisions between terminals may occur frequently during the PRACH occasion. As a result, a contention resolution procedure may be performed, which may increase system latency. Therefore, even if multiple BWPs or multiple 20 MHz bandwidths have successfully accessed the channel, the terminal transmits the PRACH in only one of the BWPs or 20 MHz bandwidths. In this case, the BWP or 20 MHz bandwidth in which the PRACH is transmitted is determined by agreement between the terminal and the base station. Specifically, after channel access, the terminal and the base station negotiate the priority of the BWPs or 20 MHz bandwidths to be used for transmission. If the UE has successfully accessed a channel for multiple BWPs or 20 MHz bandwidths, the UE selects one of the multiple BWPs or multiple 20 MHz bandwidths according to a priority. The UE transmits a PRACH through the selected BWP. The base station performs PRACH detection according to a priority. Once the base station has completed PRACH detection for one or more BWPs or one or more 20 MHz bandwidths according to the priority, the base station does not perform additional PRACH detection. The number of one or more BWPs or one or more 20 MHz bandwidths is determined by negotiation between the UE and the base station. The priority is set based on the serving cell index. Specifically, the priority is set so that a BWP with a larger serving cell index or a 20 MHz bandwidth with a larger serving cell index has a higher priority. In another specific embodiment, the priority may be set so that a BWP with a lower serving cell index or a 20 MHz bandwidth with a lower serving cell index has a higher priority. The priority is set based on the BWP index or the channel number occupied by the 20 MHz bandwidth.In particular, the priority is set such that a BWP with a larger BWP index has a higher priority. In another specific embodiment, the priority may be set such that a BWP with a lower BWP index has a higher priority.

[0227] In a random access procedure for uplink synchronization, the UE and the base station should perform at least a four-step procedure. Specifically, the UE should transmit a PRACH to the base station, and the base station should transmit a PAR (RACH response) to the UE. The UE should transmit a PUSCH, i.e., message-3, in response to the PAR. The base station should also transmit message-4 to the UE. In this transmission between the BS and the UE, the BS and the UE should each perform a channel access procedure. Therefore, there is a high probability that excessive delays will occur in the random access procedure. Therefore, a method for preventing excessive delays in the random access procedure is needed. In particular, a method for preventing excessive delays in RACH transmission is needed.

[0228] The terminal attempts PRACH transmission within the PRACH transmission window. Specifically, if the terminal fails to transmit PRACH in the PRACH occasion configured by the base station, the terminal attempts PRACH transmission within the PRACH transmission window. In a specific embodiment, if the terminal fails to transmit PRACH in the PRACH occasion configured by the base station, the terminal attempts channel access within the PRACH transmission window. If the terminal successfully accesses the channel, the terminal transmits PRACH to the base station. In this case, the PRACH transmission window is configured by the base station. Specifically, the PRACH transmission window is configured by the base station through RRC configuration. Furthermore, before RRC configuration, the base station indicates information about the PRACH transmission window via RMSI. If the terminal cannot receive information about the PRACH transmission window via RMSI, the terminal uses default parameters as information about the PRACH transmission window based on the PRACH configuration information configured via RMSI. In the above description, successful channel access is indicated by a successful LBT procedure.

[0229] When a UE operates standalone in an unlicensed band, the UE needs to transmit a physical uplink control channel (PUCCH) to a base station via the unlicensed band. In addition, a UE may not be co-located with a base station indoors or in an outdoor environment with limited coverage, or may use a non-ideal backhaul. In such cases, the UE also needs to transmit a PUCCH. Therefore, a PUCCH transmission method and PUCCH design for an unlicensed band are required. This will be described with reference to Figures 43 to 45.

[0230] Unlike licensed bands, unlicensed bands are used by multiple wireless communication devices, and therefore regional or national usage restrictions apply. For example, restrictions on fairness, power spectral density (PSD), and occupied channel bandwidth (OCB) apply. Specifically, restrictions may apply that PSD should be limited to 10 dBm / MHz or less, and that transmitting carriers should occupy 80% or more of the nominal bandwidth. In the case of downlink transmission, since a base station transmits to multiple terminals, occupying 80% of the nominal bandwidth may not be an issue. However, in the case of uplink transmission, since a terminal transmits to a base station, using 80% of the nominal bandwidth may be an issue. Furthermore, since transmission power of 10 dBm / MHz or less should be used in unlicensed bands, terminals must perform uplink transmission using a distributed manner. Specifically, PSD restrictions for each frequency band are specified as follows:

[0231] - 5150-5350MHz, with transmit power control (TPC): 10dBM / MHz - 5250-5350MHz, without TPC: 7dBM / MHz - 5150-5350MHz, without TPC: 10dBM / MHz - 5150-5250MHz, when transmit power control is applied (with TPC): 17dBM / MHz - 5470-5725MHz, when transmit power control is applied (with TPC): 17dBM / MHz - 5470-5725MHz, without TPC: 14dBM / MHz - At 60 GHz, if 40 dBM ERIP (effective isotropic radiated power) is used: 13 dBM / MHz ERIP

[0232] FIG. 43 shows a design of a PUSCH used in LTE-LAA. In the LTE-LAA system, a PUSCH structure in which RBs are interlaced as shown in Figure 43 is used. This allows a terminal to transmit a PUSCH while satisfying the PSD and OCB regulations. In the NR system, the interlaced RB structure as shown in Figure 43 is also used for PUSCH transmission and PUCCH transmission. However, to satisfy the above-mentioned regulations, when 15 kHz subcarrier spacing is applied to a channel having a 20 MHz bandwidth, one interlace occupies a minimum of 10 RBs. Since one interlace occupies a minimum of 10 RBs, a maximum of 10 interlaces are used. Here, an interlace is a resource allocation unit, and indicates that multiple RBs are located at equal intervals in the frequency band.

[0233] In PUCCH transmission used in unlicensed bands, one terminal must use at least 10 RBs to satisfy the PSD and OCB regulations, so the number of terminals that can simultaneously transmit is limited compared to PUCCH in licensed bands, which multiplexes different terminals using one RB. In other words, there is a risk of insufficient multiplexing capacity. To solve this problem, a PUCCH transmission method and PUCCH design are needed.

[0234] If the PUSCH uses an interlace structure configured in units of RB, an orthogonal cover code (OCC) of length N is applied to N consecutive RBs within one interlace in the frequency domain. If the PUCCH uses an interlace structure configured in units of RB groups, an OCC of length N is applied to N RB groups. In this case, an RB group indicates multiple consecutive RBs in the frequency domain. Through this embodiment, the multiplexing capacity is increased by N times. A base station indicates an index of an interlace to be used for PUCCH transmission to a terminal. In this case, the base station indicates an index of an OCC to be used for PUCCH transmission to a terminal. This allows multiple terminals to simultaneously transmit PUCCHs within an interlace configured in units of RB or RB group. This embodiment is applicable to a PUCCH format that is transmitted based on a sequence. In particular, this embodiment is applicable to transmission of PUCCH format 0, PUCCH format 1, PUCCH format 3, and PUCCH format 4 defined in the NR system. However, this does not apply to the transmission of PUCCH format 2 defined in the NR system.

[0235] Figure 44 is a diagram showing multiple terminals transmitting a short PUCCH corresponding to PUCCH format 0 using an OCC in one interlace according to an embodiment of the present invention. In Figure 44(a), two terminals transmit PUCCHs over two consecutive RBs in one interlace using an OCC with an OCC length of 2. In Figure 44(b), four terminals transmit PUCCHs over four consecutive RBs in one interlace using an OCC with an OCC length of 4. Although Figure 44 illustrates an example in which a short PUCCH is transmitted over one symbol, the embodiment of the present invention may also be applied to a case in which a short PUCCH is transmitted over two symbols.

[0236] Figure 45 is a diagram showing multiple terminals transmitting a long PUCCH corresponding to PUCCH format 1 using an OCC in one interlace according to an embodiment of the present invention. In Figure 45(a), two terminals transmit PUCCHs over two consecutive RBs in one interlace using an OCC with an OCC length of 2. In Figure 45(b), four terminals transmit PUCCHs over four consecutive RBs in one interlace using an OCC with an OCC length of 4. Although Figure 45 illustrates an example in which the long PUCCH is transmitted over one symbol, the embodiment of the present invention may also be applied to a case in which the long PUCCH is transmitted over any one of 5 to 14 symbols.

[0237] When a terminal operates in a transmission environment where the channel delay spread is not large and line of sight is formed, there is a possibility that channel fluctuation in the frequency domain will not occur significantly. In this case, the length of the OCC is increased. Therefore, the length of the OCC can be changed depending on the transmission environment.

[0238] In another specific embodiment, when interlacing is performed in units of one or more RB groups, PUCCHs are transmitted between terminals using different patterns in the interlaced PUCCHs configured in units of one or more RB groups. A plurality of terminals transmit PUCCHs using different patterns equal to the number of one or more RB groups configuring one interlace. In this case, the sequence used for each of the one or more RB groups in one interlace is a computer generated sequence (CGS). Also, the sequence used for each of the one or more RB groups in one interlace is a Zadoff-Chu (ZC) sequence. Different patterns are applied to the RB groups occupying one interlace. Also, different terminals are assigned to different patterns. The base station receives PUCCHs transmitted to one or more RB groups based on the patterns corresponding to each of the one or more RB groups, and separately receives PUCCHs transmitted by different terminals multiplexed in different patterns within one interlace.

[0239] A method of rotating the phase of a sequence used for one or more RB groups within one interlace in different patterns is used. There are various methods of rotating the phase of a sequence used for one or more RB groups within one interlace in different patterns. A different cyclic shift is applied to each sequence mapped to one or more RB groups within one interlace for each terminal. Multiple terminals generate different scrambling sequences for each terminal and apply the corresponding scrambling sequences to one or more RB groups within one interlace.

[0240] As an example of a method of applying different cyclic shifts to each sequence mapped to one or more RB groups within one interlace for each terminal, a case where one interlace occupies five RBs will be described. Different patterns are applied to each of the five RBs. Different terminals are assigned to the five patterns. A first terminal uses a cyclic shift (CS) pattern of {0, 1, 2, 3, 4}, which shifts the CS interval by one frame, a second terminal uses a CS pattern of {0, 2, 4, 6, 8}, which shifts the CS interval by two frames, and a third terminal uses a CS pattern of {0, 3, 6, 9, 12}, which shifts the CS interval by three frames. However, if different RBs within one interlace are configured with the same pattern, the peak-to-average power ratio (PARP) / cubic matric (CM) characteristics may deteriorate in an interlace structure where the spacing between RBs and RB groups is constant. That is, since the same phase is repeatedly assigned to each RB and RB group, the PARP / CM value may increase and the transmission coverage may become smaller. Therefore, basically, different CS values ​​are assigned to different RBs within one interlace. If the PUCCH and PUSCH have an interlaced structure, the PRACH also has an interlaced structure due to frequency division multiplexing (FDM) with the PUCCH or PUSCH. In particular, in the case of PRACH transmission, it is highly likely that multiple UEs will simultaneously transmit the PRACH. Therefore, the above-described embodiments regarding PUCCH transmission also apply to PRACH transmission.

[0241] Although the method and system of the present invention have been described with reference to particular embodiments, some or all of the components or operations thereof may be implemented using a computing system having a general-purpose hardware architecture.

[0242] 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, it should be understood that the above-described embodiments are illustrative in all respects and are not limiting. For example, each component described as a single component may be implemented in a distributed form, and components described as distributed may also be implemented in a combined form.

[0243] The scope of the present invention is indicated by the claims that follow rather than by the above detailed description, and all modifications and variations that fall within the meaning and scope of the claims and their equivalents should be interpreted as being included within the scope of the present invention. [Explanation of symbols]

[0244] 31 Fixed area 32 Macro Area 33 Coverage 34 Coverage 100 devices 110 processors 120 Communication Module 121 Cellular communication interface card 122 Cellular communication interface card 123 Unlicensed Spectrum Communication Interface Card 130 memory 140 User Interface 150 display units 200 base stations 210 processors 220 Communication Module 221 Cellular communication interface card 222 Cellular communication interface card 223 Unlicensed Spectrum Communication Interface Card 230 memory

Claims

1. A terminal of a wireless communication system, the terminal comprising: receiving a synchronization signal and physical broadcast channel (PBCH) block (SSB) at a candidate SSB transmission location within a discovery reference signal (DRS) transmission window within the unlicensed spectrum; If the terminal fails to receive a first SSB at a first SSB transmission candidate position within the DRS transmission window, the terminal attempts to receive a second SSB at a second SSB transmission candidate position within the DRS transmission window that is later than the first SSB transmission candidate position within the DRS transmission window, wherein the first SSB is the same as the second SSB; If the terminal successfully receives the first SSB at the first SSB transmission candidate position, it does not expect to receive the second SSB within the DRS transmission window; The reception of the SSB occurs at least one orthogonal frequency division multiplexing (OFDM) symbol before a boundary between a slot in which the reception of the SSB occurs and a slot next to the slot in which the reception of the SSB occurs. a processor configured to: The DRS transmission window is a time period during which the base station can transmit the SSB, Each of the SSB transmission candidate positions indicates a time within the DRS transmission window at which the terminal can start receiving the SSB; The subcarrier spacing used for the SSB transmission is 15 kHz or 30 kHz. Terminal.

2. the duration of the DRS transmission window has a fixed length; The DRS transmission window is set in the terminal so as to be repeated at regular intervals. The terminal according to claim 1 .

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