Physical channels and signal transmission / reception methods for wireless communication systems and devices utilizing the same.

Abstract

The present invention provides a method and apparatus for efficiently transmitting and receiving physical channels and signals in a wireless communication system. [Solution] Each base station 200 of the wireless communication system includes a communication module 220 and a processor 210. The processor attempts SSB transmission at candidate SSB (synchronization signal and PBCH block) transmission locations within the DRS (Discovery reference signal) transmission window. If SSB transmission fails at the first SSB transmission candidate location within the first DRS transmission window, it attempts SSB transmission at a second SSB transmission candidate location at a later time than the first SSB transmission candidate location within the first DRS transmission window. The DRS transmission window is a time interval in which the base station can transmit SSB. The SSB transmission candidate location indicates the time within the DRS transmission window in which the base station can start SSB transmission.

Description

[Technical Field]

[0001] This invention relates to a wireless communication system. More specifically, this invention relates to a physical channel for a wireless communication system, a method for transmitting and receiving signals, and an apparatus that utilizes the same. [Background technology]

[0002] Following the commercialization of 4G (4th generation) communication systems, efforts are being made 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 "beyond 4G network" systems, "post-LTE" systems, or "NR (new radio)" systems. To achieve high data transmission rates, 5G communication systems include systems operating in ultra-high frequency (mmWave) bands above 6 GHz, as well as systems operating in frequency bands below 6 GHz to ensure coverage, with implementation at base stations and terminals being considered.

[0003] The 3GPP® (3rd Generation Partnership Project) NR system improves the efficiency of the network spectrum, enabling telecommunications carriers to provide more data and voice services with the given bandwidth. Therefore, the 3GPP NR system is designed to meet the demands for high-speed data and media transmission in addition to high-capacity voice support. The advantages of the NR system include high processing power, low latency, support for FDD (frequency division duplex) and TDD (time division duplex), an improved end-user environment, and low operating costs with a simple architecture, all on the same platform.

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

[0005] To mitigate path loss in the ultra-high frequency band and increase the transmission distance of radio waves, beamforming, massive MIMO, full-dimensional MIMO (FD-MIMO), array antennas, analog beamforming, hybrid beamforming (combining analog and digital beamforming), and large-scale antenna technologies are being discussed for 5G communication systems. Furthermore, in order to improve the system network, 5G communication systems are undergoing technological development related to 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, CoMP (coordinated multi-points), and interference cancellation.In addition, 5G systems have seen the development of advanced coding modulation (ACM) methods such as FQAM (hybrid FSK and QAM modulation) and SWSC (sliding window superposition coding), as well as advanced access technologies such as FBMC (filter bank multi-carrier), NOMA (non-orthogonal multiple access), and SCMA (sparse code multiple access).

[0006] Meanwhile, the internet, a human-centered interconnected network where humans generate and consume information, is evolving into the Internet of Things (IoT) network, where distributed components such as objects exchange and process information. Internet of Everything (IoE) technology, which combines IoT technology with big data processing technologies via connections to cloud servers and other systems, is also emerging. To realize IoT, technological elements such as sensing technology, wired and wireless communication and network infrastructure, service interface technology, and security technology are required. Recently, technologies such as sensor networks for connecting objects, machine-to-machine (M2M), and machine-type communication (MTC) are being researched. In an IoT environment, intelligent IT services are provided that collect and analyze data generated from connected objects to create new value in human life. IoT, through the integration and combination of conventional IT technologies and various industries, is being applied to fields such as smart homes, smart buildings, smart cities, smart cars or connected cars, smart grids, healthcare, smart home appliances, and advanced medical services.

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

[0008] However, mobile communication systems have gradually expanded their service scope to include not only voice but also data services, and have now developed to the point where they can provide high-speed data services. However, due to resource shortages and users' demand for high-speed services, there is a need for even more advanced mobile communication systems currently in service.

[0009] The 3GPP NR system uses a dynamic Time Division Duplex (TDD) scheme, which allows the orientation of OFDM symbols constituting a slot to be freely changed by the uplink and downlink traffic of small cells. Base stations transmit information about the slot configuration to terminals to support dynamic TDD. However, there is a risk that terminals may not receive the slot configuration information, or that terminal operations may not be performed due to changes in the slot configuration, so there is a need for a way to improve this.

[0010] Recently, with the proliferation of smart devices and the resulting explosion in mobile traffic, traditional licensed frequency spectrums, or licensed frequency bands alone, are struggling to cope with the increasing data usage required to provide cellular communication services.

[0011] In this context, 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 frequency bands, where telecommunications carriers secure exclusive frequency usage rights through procedures such as auctions, unlicensed frequency bands allow numerous communication devices to be used simultaneously without restriction, provided that only a certain level of adjacent band protection regulations are observed. Therefore, if unlicensed frequency bands are used for cellular communication services, it becomes difficult to guarantee the same level of communication quality as that provided with licensed frequency bands, and there is a risk of interference problems with wireless communication devices (e.g., wireless LAN devices) that previously used unlicensed frequency bands.

[0013] In order to use LTE and NR technologies in unlicensed bands, research should be conducted in advance on coexistence strategies with conventional unlicensed band equipment and strategies for efficiently sharing radio channels with other radio channels. In other words, a robust coexistence mechanism (RCM) needs to be developed so that equipment using LTE and NR technologies in unlicensed bands does not affect conventional unlicensed band equipment. [Overview of the project] [Problems that the invention aims to solve]

[0014] One embodiment of the present invention aims to provide a method and apparatus for efficiently transmitting and receiving physical channels and signals in a wireless communication system. Another embodiment of the present invention aims to provide a method and apparatus 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 that controls the communication mode. The processor attempts SSB (synchronization signal and PBCH block) transmission candidate positions within a DRS (Discovery reference signal) transmission window. If SSB transmission fails at a first SSB transmission candidate position within a first DRS transmission window, the processor attempts SSB transmission at a second SSB transmission candidate position at a later time than the first SSB transmission candidate position within the first DRS transmission window. The DRS transmission window is a time interval during which the base station can transmit SSB. The SSB transmission candidate positions indicate the time within the DRS transmission window at which the base station can start SSB transmission.

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

[0017] The mapping relationship between the SSB transmission candidate position and the SSB within the second DRS transmission window may differ from the mapping relationship between the SSB transmission candidate position and the SSB within the first DRS transmission window. In this case, the second DRS transmission window is the DRS transmission window of the period immediately following the first DRS transmission window.

[0018] The index of the SSB mapped to each of the plurality of SSB transmission candidate positions within the second DRS transmission window is a cyclic wrap-around of the index of the SSB mapped to each of the plurality of SSB transmission candidate positions within the first DRS transmission window, and a unique index within the SSB set is assigned to each of the plurality of SSBs.

[0019] The index of the SSB mapped to each of the plurality of SSB transmission candidate positions within the second DRS transmission window is assigned in reverse order to the index of the SSB mapped to each of the plurality of SSB transmission candidate positions within the first DRS transmission window. At this time, a unique index within the SSB set is assigned to each of the plurality of SSBs. The duration of the DRS transmission window has a fixed length. The DRS transmission window is set for the terminal to be repeated at a fixed period. The subcarrier spacing used to transmit the SSB is one of 15 kHz, 30 kHz, or 60 kHz. At this time, the processor transmits a plurality of SSBs continuously in time. The value of the subcarrier spacing used to transmit the SSB is one of 15 kHz, 30 kHz, or 60 kHz. At this time, the processor ends the SSB transmission at least one or more OFDM (orthogonal frequency division multiplexing) symbols before the boundary between the slot in which the SSB transmission is performed and the next slot in which the SSB transmission is performed. The processor performs channel access at n candidate position terminals. At this time, n is a positive integer. 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 that controls the communication mode. The processor attempts to receive SSB at an SSB transmission candidate position within a DRS transmission window, and if it fails to receive SSB at the first SSB transmission candidate position within a first DRS transmission window, it attempts to receive SSB at a second SSB transmission candidate position within the first DRS transmission window at a later time than the first SSB transmission candidate position. The DRS transmission window is a time interval in which a base station can transmit SSB. The SSB transmission candidate position indicates a time within the DRS transmission window in which the terminal can start receiving SSB. The processor starts receiving the SSB transmission from the first SSB transmission candidate position, and after completing the reception of the SSB transmission, it does not attempt to receive the same SSB within the first DRS transmission window. The terminal receives an SSB set containing multiple SSBs within the DRS transmission window. Each of the multiple SSB transmission candidate locations included in the DRS transmission window is mapped to one of the multiple SSBs. At this time, the processor receives the SSB mapped to each of the at least one SSB transmission candidate locations located within the first DRS transmission window from the first SSB transmission candidate location.

[0021] The mapping relationship between the SSB transmission candidate position and the SSB within the second DRS transmission window may differ from the mapping relationship between the SSB transmission candidate position and the SSB within the first DRS transmission window. In this case, the second DRS transmission window is the DRS transmission window of the period immediately following the first DRS transmission window. The index of the SSB mapped to each of the multiple SSB transmission candidate positions in the second DRS transmission window is obtained by cyclically wrapping around the index of the SSB mapped to each of the multiple SSB transmission candidate positions in the first DRS transmission window. In this case, each of the multiple SSBs is assigned a unique index within the SSB set. The index of the SSB mapped to each of the multiple SSB transmission candidate positions in the second DRS transmission window is obtained by assigning the indices of the SSB mapped to each of the multiple SSB transmission candidate positions in the first DRS transmission window in reverse order. Each of the multiple SSBs is assigned a unique index within the SSB set. The duration of the DRS transmission window has a fixed length. Furthermore, the DRS transmission window is set at the terminal to repeat at a fixed period. The subcarrier spacing value used to transmit the SSB is one of 15kHz, 30kHz, or 60kHz. In this case, the processor receives multiple SSBs sequentially in time. The subcarrier spacing used to transmit the SSB is one of 15kHz, 30kHz, or 60kHz. In this case, the processor terminates the SSB reception before at least one OFDM symbol from the boundary between the slot in which the SSB reception takes place and the next slot in which the SSB reception takes place. [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 that utilizes the same. The effects obtained from this invention are not limited to those mentioned above. Other effects not mentioned should be clearly understood by those with ordinary skill in the art to which this invention belongs from the following description. [Brief explanation of the drawing]

[0023] [Figure 1] This figure shows an example of a wireless frame structure used in wireless communication systems. [Figure 2] This figure shows an example of a downlink (DL) / uplink (UL) slot structure in a wireless communication system. [Figure 3]This diagram illustrates the physical channels used in 3GPP systems and common signal transmission methods utilizing those physical channels. [Figure 4(a)] This figure shows the SS / PBCH block for initial cell access in a 3GPP NR system. [Figure 4(b)] This figure shows the SS / PBCH block for initial cell access in a 3GPP NR system. [Figure 5] This diagram shows the procedure for transmitting control information and control channels in a 3GPP NR system. [Figure 6] This diagram shows the CORESET (control resource set) through which the PDCCH (physical downlink control channel) is transmitted in a 3GPP NR system. [Figure 7] This diagram shows how to configure the PDCCH search space in a 3GPP NR system. [Figure 8] This is a conceptual diagram explaining career aggregation. [Figure 9] This is a diagram illustrating single-carrier and multiple-carrier communication. [Figure 10] This figure shows an example where the cross-carrier scheduling technique is applied. [Figure 11(a)] This figure shows the configuration of a code block group (CBG) and its time-frequency resource mapping according to an embodiment of the present invention. [Figure 11(b)] This figure shows the configuration of a code block group (CBG) and its time-frequency resource mapping according to an embodiment of the present invention. [Figure 12] This diagram shows the process by which a base station performs TB-based transmission or CBG-based transmission according to an embodiment of the present invention, and a terminal transmits a HARQ-ACK in response thereto. [Figure 13] This diagram shows the NR-U (NR-Unlicensed) service environment. [Figure 14] This figure shows one example of a terminal and base station deployment scenario in an NR-U service environment. [Figure 15] This diagram shows a conventional communication method that operates on unlicensed bandwidth (e.g., wireless LAN). [Figure 16] This figure shows a channel access process based on Category 4 LBT according to one embodiment of the present invention. [Figure 17] This figure shows one example of how to adjust the competition window size (CWS) based on HARQ-ACK feedback. [Figure 18] This is a block diagram showing the configuration of a terminal and a base station according to one embodiment of the present invention. [Figure 19(a)] This figure shows the position of the OFDM symbol occupied by SSB within multiple slots of the licensed bandwidth of an NR system according to one embodiment of the present invention. [Figure 19(b)] This figure shows the position of the OFDM symbol occupied by SSB within multiple slots of the licensed bandwidth of an NR system according to one embodiment of the present invention. [Figure 20] This figure shows the location of the slots occupied by SSB within a 5ms half-wireless frame of the licensed bandwidth of an NR system according to one embodiment of the present invention. [Figure 21(a)] This figure shows the position of OFDM symbols to which SSB is transmitted within a 1ms time interval when 60kHz subcarrier spacing is used according to one embodiment of the present invention and the maximum number of SSBs is 3. [Figure 21(b)] This figure shows the position of OFDM symbols to which SSB is transmitted within a 1ms time interval when 60kHz subcarrier spacing is used according to one embodiment of the present invention and the maximum number of SSBs is 3. [Figure 22(a)] This figure shows the position of OFDM symbols to which SSB is transmitted within a 1ms time interval when 60kHz subcarrier spacing is used according to one embodiment of the present invention and the maximum number of SSBs is 4. [Figure 22(b)]This figure shows the position of OFDM symbols to which SSB is transmitted within a 1ms time interval when 60kHz subcarrier spacing is used according to one embodiment of the present invention and the maximum number of SSBs is 4. [Figure 23] This figure shows the position of OFDM symbols to which SSB is transmitted within a 1ms time interval when 60kHz subcarrier spacing is used according to one embodiment of the present invention and the maximum number of SSBs is 6. [Figure 24] This figure shows the position of OFDM symbols to which SSB is transmitted within a 1ms time interval when 60kHz subcarrier spacing is used to transmit SSB according to one embodiment of the present invention, and the maximum number of SSBs is 8. [Figure 25(a)] This figure shows the positions of the slots through which SSB is transmitted in the SSB transmission window when 60 kHz subcarrier spacing is used to transmit SSB according to another embodiment of the present invention. [Figure 25(b)] This figure shows the positions of the slots through which SSB is transmitted in the SSB transmission window when 60 kHz subcarrier spacing is used to transmit SSB according to another embodiment of the present invention. [Figure 26(a)] This figure shows a case where, when 15 kHz subcarrier spacing is used to transmit SSB in an unlicensed band, there are multiple slot locations where SSB transmission can be initiated, depending on the maximum number of SSBs that the base station can transmit within the SSB transmission window according to an embodiment of the present invention. [Figure 26(b)] This figure shows a case where, when 15 kHz subcarrier spacing is used to transmit SSB in an unlicensed band, there are multiple slot locations where SSB transmission can be initiated, depending on the maximum number of SSBs that the base station can transmit within the SSB transmission window according to an embodiment of the present invention. [Figure 27(a)] This figure shows that when 30 kHz subcarrier spacing is used to transmit SSB in an unlicensed band, according to an embodiment of the present invention, there are multiple slot positions where SSB transmission can be initiated, depending on the maximum number of SSBs that the base station can transmit within the SSB transmission window. [Figure 27(b)] This figure shows that when 30 kHz subcarrier spacing is used to transmit SSB in an unlicensed band, according to an embodiment of the present invention, there are multiple slot positions where SSB transmission can be initiated, depending on the maximum number of SSBs that the base station can transmit within the SSB transmission window. [Figure 28(a)] This figure shows that when 60 kHz subcarrier spacing is used to transmit SSB in an unlicensed band, according to an embodiment of the present invention, there are multiple slot positions where SSB transmission can be initiated, depending on the maximum number of SSBs that the base station can transmit within the SSB transmission window. [Figure 28(b)] This figure shows that when 60 kHz subcarrier spacing is used to transmit SSB in an unlicensed band, according to an embodiment of the present invention, there are multiple slot positions where SSB transmission can be initiated, depending on the maximum number of SSBs that the base station can transmit within the SSB transmission window. [Figure 29(a)] This figure shows that, according to an embodiment of the present invention, when 15 kHz subcarrier spacing is used to transmit SSB in an unlicensed band, the base station has an opportunity to initiate SSB transmission for each slot within the SSB transmission window. [Figure 29(b)] This figure shows that, according to an embodiment of the present invention, when 15 kHz subcarrier spacing is used to transmit SSB in an unlicensed band, the base station has an opportunity to initiate SSB transmission for each slot within the SSB transmission window. [Figure 30(a)] This figure shows that, according to an embodiment of the present invention, when 30 kHz subcarrier spacing is used to transmit SSB in an unlicensed band, the base station has an opportunity to initiate SSB transmission for each slot within the SSB transmission window. [Figure 30(b)] This figure shows that, according to an embodiment of the present invention, when 30 kHz subcarrier spacing is used to transmit SSB in an unlicensed band, the base station has an opportunity to initiate SSB transmission for each slot within the SSB transmission window. [Figure 31(a)]This figure shows that, according to an embodiment of the present invention, when 60 kHz subcarrier spacing is used to transmit SSB in an unlicensed band, the base station has an opportunity to initiate SSB transmission for each slot within the SSB transmission window. [Figure 31(b)] This figure shows that, according to an embodiment of the present invention, when 60 kHz subcarrier spacing is used to transmit SSB in an unlicensed band, the base station has an opportunity to initiate SSB transmission for each slot within the SSB transmission window. [Figure 32] This figure shows a case in which the mapping between the SSB index and the candidate position index within the DRS transmission window is fixed according to an embodiment of the present invention. [Figure 33] This figure shows a case in which the mapping between the SSB index and the candidate position index within the DRS transmission window is not fixed according to an embodiment of the present invention. [Figure 34] This figure shows a case in which the mapping between the SSB index and the candidate position index within the DRS transmission window is not fixed according to an embodiment of the present invention. [Figure 35] This figure shows a case in which the mapping between the SSB index and the candidate position index within the DRS transmission window is not fixed, according to another embodiment of the present invention. [Figure 36] This figure shows a case in which the mapping between the SSB index and the candidate position index within the DRS transmission window is not fixed, according to another embodiment of the present invention. [Figure 37] This figure shows a case in which the mapping between the SSB index and the candidate position index within the DRS transmission window is not fixed, according to another embodiment of the present invention. [Figure 38] This figure shows a case in which the mapping between the SSB index and the candidate position index within the DRS transmission window is not fixed, according to another embodiment of the present invention. [Figure 39]This figure shows a case in which the mapping between the SSB index and the candidate position index within the DRS transmission window is not fixed, according to another embodiment of the present invention. [Figure 40] This figure shows a case in which the mapping between the SSB index and the candidate position index within the DRS transmission window is not fixed, according to another embodiment of the present invention. [Figure 41] This figure shows a case in which the mapping between the SSB index and the candidate position index within the DRS transmission window is not fixed, according to another embodiment of the present invention. [Figure 42] This figure shows a case in which the mapping between the SSB index and the candidate position index within the DRS transmission window is not fixed, according to another embodiment of the present invention. [Figure 43] This diagram shows the design of the pusher used in LTE-LAA. [Figure 44] This figure shows how multiple terminals according to an embodiment of the present invention transmit a short PUCCH using OCC within a single interlace. [Figure 45] This figure shows that, according to an embodiment of the present invention, multiple terminals transmit a long PUCCH corresponding to PUCCH format 1 using OCC within a single interlace. [Modes for carrying out the invention]

[0024] The terminology used herein has been selected to be as widely used and general as possible, taking into account the function of the present invention; however, this may vary depending on the intentions, conventions, or emergence of new technologies of the articulate. In some cases, the applicant has arbitrarily selected certain terms, in which case their meaning will be described in the relevant section of the invention description. Therefore, it should be made clear that the terminology used herein should not be merely names of terms, but should be analyzed based on the substantive meaning of the terms and the overall content of this specification.

[0025] Throughout the specification, when one configuration is said to be “connected” to another, this includes not only cases where they are “directly connected,” but also cases where they are “electrically connected” through other intermediate components. Furthermore, when a configuration is said to “include” a particular component, this means, unless otherwise stated, that it includes other components rather than excluding them. In addition, the limitations of “greater than” or “less than” a particular critical point may be appropriately replaced by “greater than” or “less than” depending on the embodiment.

[0026] The following technologies are used in a variety of wireless connectivity systems, including 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 using radio technology such as UTRA (Universal Terrestrial Radio Access) and CDMA2000. TDMA is implemented using radio technology such as GSM (Global System for Mobile communications) / GPRS (General Packet Radio Service) / EDGE (Enhanced Data Rates for GSM Evolution). OFDMA is implemented using radio technology such as IEEE802.11 (Wi-Fi), IEEE802.16 (WiMAX), IEEE802-20, and E-UTRA (Evolved UTRA). UTRA is part of UMTS (Universal Mobile Telecommunication System). 3GPP LTE (Long term evolution) is part of E-UMTS (Evolved UMTS) which uses E-UTRA, and LTE-A (Advanced) is an advanced version of 3GPP LTE. 3GPP NR is a system designed separately from LTE / LTE-A, and is intended to support eMBB (enhanced Mobile Broadband), URLLC (Ultra-Reliable and Low Latency Communication), and mMTC (massive Machine Type Communication) services, which are requirements of IMT-2020. While this explanation will focus on 3GPP NR for clarity, the technical concept of this invention is not limited to this.

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

[0028] Figure 1 shows an example of a wireless frame structure used in a wireless communication system. Referring to Figure 1, a radio frame (or radio frame) used in a 3GPP NR system has a length of 10 ms (ΔfmaxNf / 100) * Tc). A radio frame consists of 10 subframes (SF) of equal size, where Δfmax = 480 * 10³ Hz, Nf = 4096, Tc = 1 / (Δfref * Nf,ref), Δfref = 15 * 10³ Hz, and Nf,ref = 2048. Each of the 10 subframes within a single frame is assigned a number from 0 to 9. Each subframe has a length of 1 ms and consists of one or more slots determined by the subcarrier spacing. More specifically, the subcarrier spacing usable in a 3GPP NR system is 15 * 2 μkHz, where μ is the subcarrier spacing configuration, with values ​​from 0 to 4. In other words, 15kHz, 30kHz, 60kHz, 120kHz, or 240kHz are used as subcarrier intervals. A 1ms subframe consists of 2μm slots, each with a length of 2-μms. The 2μm slots within a subframe are each assigned numbers from 0 to 2μ-1. Similarly, the slots within a radio frame are each assigned numbers from 0 to 10*2μ-1. Time resources are divided by at least one of the following: radio frame number (also called radio frame index), subframe number (also called subframe index), or slot number (or slot index).

[0029] Figure 2 shows an example of a downlink (DL) / uplink (UL) slot structure in a wireless communication system. In particular, Figure 2 shows the resource grid structure of a 3GPP NR system. There is one resource grid per antenna port. Referring to Figure 2, a slot contains multiple OFDM symbols in the time domain and multiple resource blocks (RBs) in the frequency domain. An OFDM symbol also means a single symbol interval. Unless otherwise specified, OFDM symbols are simply referred to as symbols. Hereafter, in this specification, symbols include OFDM symbols, SC-FDMA symbols, DFTs-OFDM symbols, etc.

[0030] Referring to Figure 2, the signal transmitted from each slot is represented by a resource grid consisting of Nsize, μgrid, x*NRBSC subcarriers, and Nslotsymb OFDM symbols. Here, x=DL for a downlink resource grid and x=UL for an uplink resource grid. Nsize, μgrid, and x represent the number of resource blocks (RBs) with a subcarrier spacing component μ (x is DL or UL), and Nslotsymb represents the number of OFDM symbols in the slot. NRBSC is the number of subcarriers constituting one RB, where NRBSC=12. OFDM symbols are called CP-OFDM (cyclic prefix OFDM) symbols or DFT-S-OFDM (discrete Fourier transform spread OFDM) symbols depending on the multiplexing scheme.

[0031] The number of OFDM symbols in a single slot can vary depending on the length of the cyclic prefix (CP). For example, a normal CP may contain 14 OFDM symbols in a single slot, while an extended CP may contain 12 OFDM symbols in a single slot. In specific embodiments, extended CPs are used only with a subcarrier interval of 60 kHz. For the sake of explanation, Figure 2 illustrates a case where a single slot consists of 14 OFDM symbols, but the embodiments of the present invention can be applied in the same manner to slots with other numbers of OFDM symbols. Referring to Figure 2, each OFDM symbol contains N size, μgrid, and x*NRBSC subcarriers in the frequency domain. Subcarrier types are divided 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] A single 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, a single RB consists of Nslotsymb*NRBSC resource elements. Each resource element in the resource grid is uniquely defined by an index pair (k, l) in a single slot. k is an index given in the frequency domain from 0 to Nsize, μgrid, and x*NRBSC-1, and l is an index given in the time domain from 0 to Nslotsymb-1.

[0033] For a terminal to receive signals from a base station or transmit base station signals, the terminal's time / frequency synchronization must be synchronized with the base station's time / frequency synchronization. This is because, if the base station and the terminal are not synchronized, the terminal cannot determine the time and frequency parameters necessary to demodulate DL signals and transmit UL signals at the correct time.

[0034] Each symbol in a radio frame operating in TDD (time division duplex) or unpaired spectrum consists of at least one of the following: a downlink symbol (DL symbol), an uplink symbol (UL symbol), or a flexible symbol. In FDD (frequency division duplex) or paired spectrum, a radio frame operating on a downlink carrier consists of either a downlink symbol or a flexible symbol, while a radio frame operating on an uplink carrier consists of either an uplink symbol or a flexible symbol. Downlink symbols can be used for downlink transmission but not uplink transmission, and uplink symbols can be used for uplink transmission but not downlink transmission. The use of a flexible symbol in the downlink or uplink is determined by the signal.

[0035] Information regarding the type of each symbol, i.e., whether it is a downlink symbol, uplink symbol, or flexible symbol, consists of a cell-specific (or common) RRC signal. Additionally, information regarding the type of each symbol consists of a UE-specific (or dedicated) RRC signal. The base station uses the cell-specific RRC signal to indicate: i) the period of the cell-specific slot configuration; ii) the number of slots containing 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 downlink-only slot; iv) the number of slots containing 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 uplink-only slot. Here, a symbol that is neither an uplink nor a downlink symbol is a flexible symbol.

[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 by means of the cell-specific RRC signal. At this time, the UE-specific RRC signal cannot change a downlink symbol or an uplink symbol that consists of the cell-specific RRC signal to another symbol type. The specific UE RRC signal signals, for each slot, 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. 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, a downlink symbol or an uplink symbol consisting of the RRC signal is not changed to another symbol type. Table 1 exemplifies the dynamic SFI that the base station indicates to the UE.

[0038]

Table 1

[0039] In Table 1, D represents the downlink symbol, U represents the uplink symbol, and X represents the flexible symbol. As shown in Table 1, a maximum of two DL / UL switching operations are permitted in a single slot.

[0040] Figure 3 illustrates the physical channels used in 3GPP systems (e.g., NR) and a typical signal transmission method utilizing these physical channels. When the terminal is powered on or enters a new cell, the terminal performs the initial cell discovery process (S101). Specifically, the terminal synchronizes with the base station during the initial cell discovery. 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 the cell ID. Next, the terminal receives the physical broadcast channel from the base station and acquires broadcast information within the cell.

[0041] After completing the initial cell search, the terminal receives the physical downlink shared channel (PDSCH) via the physical downlink control channel (PDCCH) and the information carried on the PDCCH, thereby obtaining more detailed system information than the system information acquired through the initial cell search (S102).

[0042] If the terminal first accesses the base station or there are no radio resources for signal transmission, the terminal performs an arbitrary access process to the base station S103 to S106. First, the terminal transmits a preamble via a physical random access channel (PRACH) S103, and receives a response message for the preamble from the base station via PDCCH and the corresponding PDSCH S104. If the terminal receives a valid random access response message, the terminal transmits data including its identifier to the base station via a physical uplink shared channel (PUSCH) instructed by the uplink grant transmitted from the base station via PDCCH S105. Next, the terminal waits to receive PDCCH as instructed by the base station to resolve collisions S106, and the random access process ends.

[0043] After the above procedure, the terminal receives 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 terminal receives downlink control information (DCI) via PDCCH. DCI includes control information such as resource allocation information for the terminal. Also, the format of DCI may differ depending on its intended use. Uplink control information (UCI) transmitted by the terminal to the base station via the uplink includes downlink / uplink ACK / NACK signals, CQI (channel quality indicator), PMI (precoding matrix index), RI (rank indicator), etc. Here, CQI, PMI, and RI are included in CSI (channel state information). In the case of a 3GPP NR system, the terminal transmits the above-mentioned HARQ-ACK and control information such as CSI via PUSCH and / or PUCCH.

[0044] Figure 4 shows the 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 discovery process. During the cell discovery process, the terminal detects the cell's physical cell identity (NcellID). To do this, the terminal receives synchronization signals from the base station, such as the primary synchronization signal (PSS) and secondary synchronization signal (SSS), to synchronize with the base station. At this time, the terminal acquires information such as the cell identifier (identity, ID).

[0045] Refer to Figure 4(a) for a more detailed explanation of the synchronization signal (SS). The synchronization signal is divided into PSS and SSS. PSS is used to obtain time-domain synchronization and / or frequency-domain synchronization, such as OFDM symbol synchronization and slot synchronization. SSS is used to obtain frame synchronization and cell group ID. Referring to Figure 4(a) and Table 2, an SS / PBCH block consists of 20 RBs (=240 subcarriers) consecutively on the frequency axis and 4 OFDM symbols consecutively on the time axis. In this case, within the SS / PBCH block, the PSS is transmitted via subcarriers 56-182 in the first OFDM symbol, and the SSS is transmitted via subcarriers 56-182 in the third OFDM symbol. Here, the lowest subcarrier index of the SS / PBCH block is assigned starting from 0. In the first OFDM symbol on which the PSS is transmitted, the base station does not transmit signals via the remaining subcarriers, i.e., subcarriers 0-55 and 183-239. Furthermore, in the third OFDM symbol in which the SSS is transmitted, the base station does not transmit signals via subcarriers 48-55 and 183-191. In the SS / PBCH block, the base station transmits the PBCH (physical broadcast channel) via the remaining REs excluding the aforementioned signals.

[0046] [Table 2]

[0047] The SS generates a total of 1008 unique physical layer cell IDs through combinations of three PSSs and SSSs. More specifically, each physical layer cell ID is part of only one physical layer cell identifier group, and each group is grouped into 336 physical layer cell identifier groups, each containing three unique identifiers. Therefore, the physical layer cell ID NcellID = 3N(1)ID + N(2)ID is uniquely defined by an index N(1)ID ranging from 0 to 335 that represents a physical layer cell identifier group, and an index N(2)ID ranging from 0 to 2 that represents a physical layer identifier within the physical layer cell identifier group. The terminal detects the PSS and identifies one of the three unique physical layer identifiers. The terminal also detects the SSS and identifies one of the 336 physical layer cell IDs associated with the physical layer identifier. In this process, the sequence d of the PSS PSS (n) is given by the following equation 1.

[0048]

number

[0049]

number

[0050]

number

[0051]

number

[0052]

number

[0053]

number

[0054] A 10ms long wireless frame is divided into two 5ms long half-frames. Refer to Figure 4(b) to describe the slot in which the SS / PBCH block is transmitted within each half-frame. The slot in which the SS / PBCH block is transmitted is one of cases A, B, C, D, or E. In case A, the subcarrier spacing is 15kHz, and the start of the SS / PBCH block is at the {2, 8} + 14*n symbol. In this case, n=0, 1 at carrier frequencies below 3GHz. Also, n=0, 1, 2, 3 at carrier frequencies above 3GHz and below 6GHz. In case B, the subcarrier spacing is 30kHz, and the start of the SS / PBCH block is at the {4, 8, 16, 20} + 28*n symbol. In this case, n=0 at carrier frequencies below 3GHz. Also, n=0, 1 at carrier frequencies above 3GHz and below 6GHz. In Case C, the subcarrier spacing is 30 kHz, and the SS / PBCH block starts at the {2nd, 8th} + 14*nth symbol. In this case, for carrier frequencies below 3 GHz, n=0, 1. Also, 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 SS / PBCH block starts at the {4th, 8th, 16th, 20th} + 28*nth symbol. In this case, for carrier frequencies above 6 GHz, n=0, 1, 2, 3, 5, 6, 7, 8, 10, 11, 12, 13, 15, 16, 17, 18. In Case E, the subcarrier spacing is 240 kHz, and the SS / PBCH block starts at the {8th, 12th, 16th, 20th, 32nd, 36th, 40th, 44th} + 56*nth symbol. In this case, at carrier frequencies of 6 GHz or higher, n = 0, 1, 2, 3, 5, 6, 7, 8.

[0055] Figure 5 shows the procedure for transmitting control information and control channels in a 3GPP NR system. Referring to Figure 5(a), the base station adds a CRC (cyclic redundancy check) masked (e.g., by XOR operation) with an RNTI (radio network temporary identifier) ​​to the control information (e.g., DCI) S202. The base station scrambles the CRC with an RNTI value determined according to the purpose / target of each piece of control information. A common RNTI used by one or more terminals includes at least one of the following: SI-RNTI (system information RNTI), P-RNTI (paging RNTI), RA-RNTI (random access RNTI), and TPC-RNTI (transmit power control RNTI). Furthermore, the terminal-specific RNTI includes at least one of the following: C-RNTI (cell temporary RNTI), CS-RNTI, or MCS-C-RNTI. Next, after the base station performs channel encoding (e.g., polar coding) in S204, it performs rate-matching in S206 to match the amount of resources used for PDCCH transmission. Next, the base station multiplexes the DCIs (etc.) based on the PDCCH structure of the CCE (control channel element) in S208. The base station also applies additional processes S210 to the multiplexed DCIs (etc.), such as scrambling, modulation (e.g., QPSK), and interleaving, before mapping them to the resources to be transmitted. A CCE is the basic resource unit for PDCCH, and one CCE consists of multiple (e.g., 6) REGs (resource element groups). One REG consists of multiple (e.g., 12) REs. The number of CCEs used for one PDCCH is defined as the aggregation level. The 3GPP NR system uses 1, 2, 4, 8, or 16 integrated levels.Figure 5(b) is a diagram relating to the CCE integration level and PDCCH multiplexing, showing the types of CCE integration levels used for a single PDCCH and the CCEs transmitted in the control domain thereunder.

[0056] Figure 6 shows the CORESET through which PDCCH is transmitted in a 3GPP NR system. A CORESET is a time-frequency resource on which PDCCH, a control signal for a terminal, is transmitted. Furthermore, the search space, described later, is mapped to a single CORESET. Therefore, instead of monitoring the entire frequency band to receive PDCCH, the terminal monitors the CORESET and the designated time-frequency domain to decode the PDCCH mapped to the CORESET. A base station configures one or more CORESETs for each cell in the terminal. A CORESET consists of up to three consecutive symbols on the time axis. A CORESET also consists of six consecutive PRB units on the frequency axis. In the embodiment shown in Figure 5, CORESET#1 consists of consecutive PRBs, while CORESET#2 and CORESET#3 consist of discontinuous PRBs. A CORESET can be located at any symbol within a slot. For example, in the embodiment shown in Figure 5, CORESET#1 starts at the first symbol in the slot, CORESET#2 starts at the fifth symbol in the slot, and CORESET#9 starts at the ninth symbol in the slot.

[0057] Figure 7 shows how to configure the PDCCH search space in a 3GPP NR system. To transmit PDCCH to a terminal, each CORESET has at least one search space. In embodiments of the present invention, the search space is a collection of all time-frequency resources (hereinafter referred to as PDCCH candidates) to which the terminal's PDCCH is transmitted. The search space includes a common search space that all 3GPP NR terminals should search in common, and a terminal-specific or UE-specific search space that a specific terminal should search. In the common search space, PDCCHs that all terminals in a cell belonging to the same base station are set to search in common are monitored. In addition, terminal-specific search spaces are set up individually for each terminal to monitor the PDCCH assigned to each terminal at different locations in the search space depending on the terminal. In the case of terminal-specific search spaces, due to the limited control area to which PDCCHs are assigned, the search spaces between terminals may be partially overlapping. Monitoring PDCCHs includes blind decoding of PDCCH candidates in the search space. If blind decoding is successful, it is expressed as the PDCCH being (successfully) detected / received. If blind decoding fails, it is expressed as the PDCCH not being detected / received, or not being successfully detected / received.

[0058] For the sake of explanation, a PDCCH scrambled with a group common (GC) RNTI already known by one or more terminals for the purpose of transmitting downlink control information to one or more terminals is referred to as a group common (GC) PDCCH or common PDCCH. Furthermore, a PDCCH scrambled with a terminal-specific RNTI already known by a specific terminal for the purpose of transmitting uplink scheduling information or downlink scheduling information to a specific terminal is referred to as a terminal-specific PDCCH. The common PDCCH is included in the common search space, and the terminal-specific PDCCH is included in either the common search space or the terminal-specific PDCCH.

[0059] The base station informs each terminal or group of terminals via the PDCCH about resource allocation information for the transmission channels PCH (paging channel) and DL-SCH (downlink-shared channel) (i.e., DL Grant), or information about UL-SCH resource allocation and HARQ (hybrid automatic repeat request) (i.e., UL Grant). The base station transmits PCH transmission blocks and DL-SCH transmission blocks via the PDSCH. The base station transmits data excluding specific control information or specific service data via the PDSCH. The terminal also receives data excluding specific control information or specific service data via the PDSCH.

[0060] The base station transmits the PDCCH containing information about which terminals (one or more terminals) the PDSCH data will be transmitted to and how those terminals should receive and decode the PDSCH data. For example, suppose a DCI transmitted via a specific PDCCH is CRC masked with an RNTI named "A", and that DCI indicates that the PDSCH is assigned to a radio resource (e.g., frequency location) named "B", and indicates transmission format information (e.g., transmission block size, modulation scheme, coding information, etc.) named "C". Terminals monitor the PDCCH using their own RNTI information. In this case, if a terminal blind-decodes the PDCCH using the "A" RNTI, that terminal will receive the PDCCH and, through the information of the received PDCCH, receive the PDSCH indicated by "B" and "C".

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

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

[0063] -HARQ-ACK: A response to a PDCCH (indicating a DL SPS release) and / or to an uplink transmission block (TB) on a PDSCH. HARQ-ACK indicates whether information transmitted via the PDCCH or PDSCH has been received. HARQ-ACK responses include positive ACK (simply ACK), negative ACK (hereinafter 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: This is 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 depending on the information it indicates.

[0065] The 3GPP NR system uses five PUCCH formats to support diverse service scenarios, diverse channel environments, and frame structures.

[0066] PUCCH format 0 is a format for transmitting 1-bit or 2-bit HARQ-ACK information or SR. PUCCH format 0 is transmitted via one or two OFDM symbols on the time axis and one RB on the frequency axis. If PUCCH format 0 is transmitted via two OFDM symbols, the same sequence is transmitted to the two symbols with different RBs. Through this, the terminal obtains a frequency diversity gain. More specifically, the terminal is M bit Bit UCI(M bit The value of the cyclic shift m depends on whether it is =1 or 2. cs Determine the base sequence of length 12 and set the value m cs The cyclically shifted sequence is mapped to 12 REs, consisting of one OFDM symbol and one PRB, and transmitted. The terminal has 12 cyclic shifts available, M bit If = 1, then 1-bit UCI0 and 1 represent a sequence of two cyclic shifts with a difference of 6 in cyclic shift values. Also, M bit If = 2, then the 2-bit UCI00, 01, 11, and 10 represent a sequence of four cyclic shifts where the difference in cyclic shift values ​​is 3.

[0067] PUCCH format 1 transmits 1-bit or 2-bit HARQ-ACK information or SR. PUCCH format 1 is transmitted via a continuous sequence of OFDM symbols on the time axis and a single PRB on the frequency axis. Here, the number of OFDM symbols occupied by PUCCH format 1 is one between 4 and 14. More specifically, a UCI with Mbit=1 is modulated with BPSK. The terminal modulates a UCI with Mbit=2 with QPSK (quadrature phase shift keying). A signal is obtained by multiplying the modulated complex valued symbol d(0) by a sequence of length 12. The terminal transmits the obtained signal by spreading it with a time-axis OCC (orthogonal cover code) to the even-numbered OFDM symbols assigned to PUCCH format 1. The maximum number of different terminals that can be multiplexed on the same RB in PUCCH format 1 is determined by the length of the OCC used. For odd-numbered OFDM symbols in PUCCH format 1, the DMRS (demodulation reference signal) is spread across the OCC and mapped to them.

[0068] PUCCH format 2 transmits UCI exceeding 2 bits. PUCCH format 2 is transmitted via one or two OFDM symbols on the time axis and one or more RBs on the frequency axis. If PUCCH format 2 is transmitted via two OFDM symbols, the same sequence is transmitted via the two OFDM symbols with different RBs. Through this, the terminal obtains frequency diversity gain. More specifically, an Mbit bit UCI (Mbit > 2) is bit-level scrambled and QPSK modulated and mapped to the RBs of one or two OFDM symbols, where the number of RBs is one between 1 and 16.

[0069] PUCCH format 3 or PUCCH format 4 transmits UCI exceeding 2 bits. PUCCH format 3 or PUCCH format 4 is transmitted via continuous OFDM symbols on the time axis and one PRB on the frequency axis. The number of OFDM symbols occupied by PUCCH format 3 or PUCCH format 4 is one of 4 to 14. Specifically, the terminal modulates an Mbit bit UCI (Mbit > 2) with π / 2-BPSK (Binary Phase Shift Keying) or QPSK to generate complex number symbols d(0) to d(Msymb-1). Here, with π / 2-BPSK, Msymb = Mbit, and with QPSK, Msymb = Mbit / 2. The terminal does not apply block-unit spreading to PUCCH format 3. However, the terminal may apply block-unit spreading to one RB (i.e., 12 subcarriers) using a PreDFT-OCC of length -12 so that the PUCCH format 4 has two or four multiplexing capacities. The terminal transmits the spread signal by transmitting precoding (or DFT-precoding) and mapping it to each RE.

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

[0071] PUCCH format 1, PUCCH format 3, or PUCCH format 4 is configured via an RRC signal to instruct frequency hopping within a slot. When frequency hopping is configured, the index of the RB to be frequency-hopped is determined by the RRC signal. If PUCCH format 1, PUCCH format 3, or PUCCH format 4 is transmitted over N OFDM symbols in the time axis, the first hop will have floor(N / 2) OFDM symbols, the second hop will have ceil(N / 2) OFDM symbols.

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

[0073] On the other hand, in the 3GPP NR system, terminals transmit and receive using a bandwidth smaller than or equal to the carrier (or cell) bandwidth. For this purpose, terminals are configured with a bandwidth part (BWP) consisting of a continuous portion of the carrier bandwidth. Terminals operating according to TDD or in the ampered spectrum have up to four DL / UL BWP pairs per carrier (or cell). The terminal also activates one DL / UL BWP pair. Terminals operating according to FDD or in the paired spectrum have up to four DL BWPs configured on the downlink carrier (or cell) and up to four UL BWPs configured on the uplink carrier (or cell). The terminal activates one DL BWP and one UL BWP for each carrier (or cell). The terminal does not have to receive or transmit from time-frequency resources other than the activated BWPs. The activated BWPs are called active BWPs.

[0074] The base station refers to the activated BWP among the configured BWPs of a terminal as the DCI. The BWP indicated by the DCI is activated, and the other configured BWPs are deactivated. In a carrier (or cell) operating in TDD mode, the base station includes a BPI (bandwidth part indicator) in the DCI that schedules the PDSCH or PUSCH to indicate which BWP to activate in order to change the terminal's DL / UL BWP pair. The terminal receives the DCI that schedules the PDSCH or PUSCH and identifies the DL / UL BWP pair to activate based on the BPI. In the case of a downlink carrier (or cell) operating in FDD mode, the base station includes a BPI informing the DCI that schedules the PDSCH which BWP to activate in order to change the terminal's DL BWP. In the case of an uplink carrier (or cell) operating in FDD mode, the base station includes a BPI informing the DCI that schedules the PUSCH which BWP to activate in order to change the terminal's UL BWP.

[0075] Figure 8 is a conceptual diagram illustrating carrier aggregation. Carrier aggregation refers to a method by which a wireless communication system uses multiple frequency blocks, or (logical) cells, consisting of uplink resources (or component carriers) and / or downlink resources (or component carriers), to utilize a wider frequency band within a single larger logical frequency band. For convenience of explanation, the term "component carrier" will be used consistently below.

[0076] Referring to Figure 8, as an example of a 3GPP NR system, the overall system bandwidth includes up to 16 component carriers, each component carrier having a bandwidth of up to 400 MHz. Each component carrier includes one or more physically consecutive subcarriers. Although Figure 8 shows each component carrier having the same bandwidth, this is merely illustrative, and each component carrier may have different bandwidths. Also, although each component carrier is shown as being adjacent to each other on the frequency axis, the diagram is a logical representation, and each component carrier may be physically adjacent to or far from each other.

[0077] Each component carrier uses a different center frequency. Furthermore, physically adjacent component carriers share a single common center frequency. In the embodiment shown in Figure 8, assuming all component carriers are physically adjacent, center frequency A is used for all component carriers. If we assume that the component carriers are not physically adjacent, then center frequencies A and B are used for each component carrier.

[0078] When the overall system bandwidth is expanded through carrier aggregation, the frequency band used for communication with each terminal is defined on a component carrier basis. Terminal A uses the overall system bandwidth of 100 MHz and communicates using all five component carriers. Terminals B1 to B5 use only a 20 MHz bandwidth and communicate using one component carrier each. Terminals C1 and C2 use only a 40 MHz bandwidth and communicate using two component carriers each. The two component carriers may be logically / physically adjacent or not. In the embodiment shown in Figure 8, terminal C1 uses two non-adjacent component carriers, and terminal C2 uses two adjacent component carriers.

[0079] Figure 9 is a diagram illustrating terminal carrier communication and multiple carrier communication. Specifically, Figure 9(a) shows the subframe structure of a single carrier, and Figure 9(b) shows the subframe structure of a multiple carrier.

[0080] Referring to Figure 9(a), a typical wireless communication system, in FDD mode, transmits or receives data via one DL band and its corresponding UL band. In other specific embodiments, in TDD mode, the wireless communication system divides the wireless frame into uplink time units and downlink time units in the time domain, and transmits or receives data via the uplink / downlink time units. Referring to Figure 9(b), three 20MHz component carriers (CCs) are aggregated in both the UL and DL bands, supporting a 60MHz bandwidth. Each CC is either adjacent or non-adjacent to the others in the frequency domain. For convenience, Figure 9(b) shows a symmetrical case where the bandwidths of the UL CCs and DL CCs are the same, but the bandwidths of each CC may be determined independently. Asymmetric carrier aggregations with different numbers of UL CCs and DL CCs are also possible. A DL / UL CC assigned / configured to a specific terminal via RRC is referred to as the serving DL / UL CC of that terminal.

[0081] A base station communicates with a terminal by activating some or all of the terminal's serving CCs, or by deactivating some of the CCs. The base station may change which CCs are activated / deactivated, or change the number of CCs that are activated / deactivated. Once a base station assigns available CCs to a terminal on a cell-specific or terminal-specific basis, at least one of the initially assigned CCs does not need to be deactivated unless the CC assignments for the terminal are completely reconfigured or the terminal is handed over. The CC that is not deactivated by the terminal is called the primary CC (PCC) or PCell (primary cell), and the CC that the base station can freely activate / deactivate is called the secondary CC (SCC) or SCell (secondary cell).

[0082] On the other hand, 3GPP NR uses the concept of a cell to manage radio resources. A cell is defined as a combination of downlink and uplink resources, i.e., a combination of DL CC and UL CC. A cell consists of DL resources alone, or a combination of DL and UL resources. If carrier aggregation is supported, the linkage between the carrier frequency of the DL resource (or DL ​​CC) and the carrier frequency of the UL resource (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 a SCell. In the downlink, the carrier corresponding to a PCell is a DL PCC, and in the uplink, the carrier corresponding to a PCell is a UL PCC. Similarly, in the downlink, the carrier corresponding to a SCell is a DL SCC, and in the uplink, the carrier corresponding to a SCell is a UL SCC. Depending on the terminal capacity, a serving cell consists of one PCell and zero or more SCells. If the RRC_CONNECTED state exists but carrier aggregation is not configured, or if the UE does not support carrier aggregation, there will be only one serving cell consisting solely of PCells.

[0083] As described above, the term "cell" used in carrier aggregation is distinct from the term "cell" which refers to a specific geographical area where communication services are provided by a single base station or antenna group. However, in order to distinguish between a cell referring to a specific geographical area and a cell in carrier aggregation, in this invention, a cell in carrier aggregation is referred to as CC, and a cell referring to a geographical area is referred to as cell.

[0084] Figure 10 shows an example where the cross-carrier scheduling technique is applied. Once cross-carrier scheduling is set up, the control channel transmitted via the first CC uses the carrier indicator field (CIF) to schedule the data channel transmitted via the first or second CC. The CIF is contained within the DCI. In other words, a scheduling cell is set up, and DL grants / UL grants transmitted from the PDCCH region of the scheduling cell schedule the PDSCH / PUSCH of the scheduled cell. That is, the PDCCH region of the scheduling cell is a search area for multiple component carriers. A PCell is essentially a scheduling cell, and a specific SCell is designated as a scheduling cell by a higher hierarchy.

[0085] In the embodiment shown in Figure 10, we assume that three DL CCs are merged. Here, DL component carrier #0 is assumed to be a DL PCC (or PCell), and DL component carriers #1 and #2 are assumed to be DL SCCs (or SCells). We also assume that the DL PCC is configured as a PDCCH monitoring CC. If cross-carrier scheduling is not configured by terminal-specific (or terminal-group-specific, or cell-specific) higher-level signaling, the CIF will be disabled, and each DL CC will transmit only PDCCHs that schedule their own PDSCH without a CIF according to the NR PDCCH rules (non-cross-carrier scheduling, self-carrier scheduling). In contrast, if cross-carrier scheduling is configured through terminal-specific (or terminal-group-specific, or cell-specific) higher-level signaling, CIF becomes enabled, and a specific CC (e.g., DL PCC) uses CIF to transmit not only PDCCHs that schedule PDSCHs of DL CC A, but also PDCCHs that schedule PDSCHs of other CCs (cross-carrier scheduling). In contrast, other DL CCs do not transmit PDCCHs. Therefore, depending on whether cross-carrier scheduling is configured for the terminal, the terminal either monitors PDCCHs without CIFs and receives self-carrier scheduled PDSCHs, or monitors PDCCHs with CIFs and receives cross-carrier scheduled PDSCHs.

[0086] On the other hand, Figures 9 and 10 illustrate the subframe structure of a 3GPP LTE-A system, and the same or similar configurations are applicable to a 3GPP NR system. However, in a 3GPP NR system, the subframes in Figures 9 and 10 are switched to slots.

[0087] In this invention, the number of symbols contained in one slot is 14 if the cell consists of normal CPs (cyclic prefixes), and 12 if the cell consists of extended CPs. However, for the sake of explanation, we will assume that there are 7 symbols.

[0088] Figure 11 shows the configuration of a code block group (CBG) according to an embodiment of the present invention and its time-frequency resource mapping. More specifically, Figure 11(a) shows one embodiment of the CBG configuration included in a single transmission block (TB), and Figure 11(b) shows the time-frequency resource mapping of the said CBG configuration.

[0089] Channel codes have a defined maximum supported length. For example, the maximum supported length of Turbo Code used in 3GPP LTE(-A) is 6144 bits. However, the length of a transmission block (TB) transmitted in a PDSCH may be longer than 6144 bits. If the length of a TB is longer than the maximum supported length, the TB is divided into code blocks (CBs) of up to 6144 bits in length. Each CB is the unit in which channel coding is performed. Furthermore, for efficient retransmission, several CBs may be bundled together to form a CBG. Terminals and base stations need information on how the CBG is configured.

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

[0091] Referring to the embodiment in Figure 11(a), one TB is divided into eight CBs. The eight CBs are further bundled into four CBGs. Such a mapping relationship between CBs and CBGs (or CBG configuration) is set statically between the base station and the terminal, or semi-statically as RRC configuration information. According to other embodiments, the mapping relationship is set via dynamic signaling. When the terminal receives the PDCCH transmitted by the base station, the terminal directly or indirectly identifies the mapping relationship between CBs and CBGs (or CBG configuration) through explicit and / or implicit information. A single CBG may contain only one CB, or it may contain all the CBs that constitute a single TB. Incidentally, the technique proposed in the embodiments of the present invention is applicable regardless of the configuration of CBs and CBGs.

[0092] Referring to Figure 11(b), the CBGs constituting a single TB are mapped to the time-frequency resources scheduled by the PDSCH. In one embodiment, each CBG is first assigned to the frequency axis and then extended to the time axis. If a PDSCH consisting of one TB containing four CBGs is assigned to seven OFDM symbols, then 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. Such time-frequency mapping relationships assigned between CBGs and PDSCHs are determined between the terminals. However, the mapping relationships shown in Figure 11(b) are one embodiment for illustrating the present invention, and the techniques proposed in the embodiments of the present invention may be applied independently of the time-frequency mapping relationships of the CBGs.

[0093] Figure 12 illustrates the process by which a base station performs TB-based transmission or CBG-based transmission, and a terminal transmits a HARQ-ACK in response. Referring to Figure 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 bits(s) according to the transmission method configured by the base station via PUCCH or PUSCH. The base station configures a PDCCH to schedule the 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, there is a predetermined order 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 through one PDSCH, and if the MIMO transmission rank or layer is high, two TBs are transmitted through one PDSCH.

[0094] The terminal transmits a 1-bit TB-based HARQ-ACK per TB to inform the base station whether each TB was successfully received. To generate a HARQ-ACK for a TB, the terminal checks for reception errors for that TB via TB-CRC. If the TB-CRC check for a TB is successful, the terminal generates an ACK for the HARQ-ACK of that TB. However, if a TB-CRC error occurs for a TB, the terminal generates a NACK for the HARQ-ACK of that TB. The terminal transmits these generated TB-based HARQ-ACKs to the base station. The base station retransmits the TBs for which a NACK was responded from the TB-based HARQ-ACKs received from the terminal.

[0095] Furthermore, the terminal transmits a 1-bit CBG-based HARQ-ACK for each CBG to inform the base station whether each CBG was successfully received. To generate a HARQ-ACK for a single CBG, the terminal decodes all CBs included in the CBG and checks for reception errors for the relevant CBs via CB-CRC. If the terminal successfully receives all CBs constituting a single CBG (i.e., all CB-CRC checks are successful), the terminal generates an ACK for the HARQ-ACK of that CBG. However, if the terminal fails to successfully receive at least one of the CBs constituting a single CBG (i.e., at least one CB-CRC error occurs), the terminal generates a NACK for the HARQ-ACK of that CBG. The terminal transmits these generated CBG-based HARQ-ACKs to the base station. The base station retransmits the CBGs for which a NACK was responded from the CBG-based HARQ-ACKs received from the terminal. According to one embodiment, the CB configuration of the retransmitted CBG is the same as the CB configuration of the conventionally transmitted CBG. The length of the CBG-underlying HARQ-ACK information bits transmitted by the terminal to the base station is determined based on the number of CBGs transmitted via the PDSCH, or the maximum number of CBGs consisting of RRC signals.

[0096] On the other hand, even if a terminal successfully receives all CBGs contained in a TB, a TB-CRC error may still occur for that TB. In this case, the terminal performs CBG-board HARQ-ACK flipping to request retransmission for the TB. In other words, even though the terminal successfully received all CBGs contained in the TB, it may generate NACKs for all CBG-board HARQ-ACK information bits. A base station that receives a CBG-board HARQ-ACK feedback in which all HARQ-ACK information bits are NACKs will retransmit all of the TB and CBGs.

[0097] According to an embodiment of the present invention, CBG-based HARQ-ACK feedback is used to ensure successful transmission of TB. The base station instructs the terminal to transmit CBG-based HARQ-ACK. In this case, a retransmission technique using CBG-based HARQ-ACK is used. CBG-based HARQ-ACK is transmitted via PUCCH. Alternatively, if UCI is configured to be transmitted via PUCCH, CBG-based HARQ-ACK may be transmitted via the corresponding PUCCH. In PUCCH, the setting of HARQ-ACK resources is configured via RRC signals. Furthermore, the HARQ-ACK resources to be actually transmitted are indicated via PDCCH, which schedules PDSCH transmitted in the CBG-based system. The terminal transmits HARQ-ACK(etc.) regarding the success or failure of receiving the transmitted CBG via one or more PUCCH resources indicated via PDCCH from among the PUCCH resources consisting of RRC.

[0098] The base station identifies whether the terminal successfully received the CBG(etc.) transmitted to the terminal via the terminal's CBG-based HARQ-ACK feedback. In other words, the base station recognizes which CBG(etc.) the terminal successfully received and which it failed to receive via the HARQ-ACK received for each CBG from the terminal. The base station then performs CBG retransmission based on the received CBG-based HARQ-ACK. More specifically, the base station bundles and retransmits only the CBG(etc.) that received a failed HARQ-ACK in a single TB. At this time, CBG(etc.) that received a successful HARQ-ACK are excluded from retransmission. The base station then schedules the retransmitted CBG(etc.) into a single PDSCH and transmits them to the terminal.

[0099] <Communication methods in unlicensed frequency bands> Figure 13 illustrates an NR-U service environment. Referring to Figure 13, a service environment is provided to the user that combines NR technology 11 in the licensed band and NR technology 12 in the unlicensed band, which is NR-U. For example, in an NR-U environment, NR technology 11 in the licensed band and NR technology 12 in the unlicensed band are integrated using technologies such as carrier aggregation, which contributes to expanding network capacity. Furthermore, in an asymmetric traffic structure where there is more downlink data than uplink data, NR-U provides NR services optimized to diverse requirements and environments. For convenience, NR technology in the licensed band is referred to as NR-L (NR-Licensed), and NR technology in the unlicensed band is referred to as NR-U.

[0100] Figure 14 shows one example of a terminal and base station placement scenario in an NR-U service environment. Due to the high-frequency characteristics of the NR-U service environment and its target frequency band, the wireless communication range is not long. Considering this, in an environment where conventional NR-L services and NR-U services coexist, the terminal and base station placement scenario is either an overlay model or a co-located model.

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

[0102] In the co-located model, pico / femtobase stations use both licensed and unlicensed band carriers simultaneously to communicate wirelessly with Y terminals. However, the use of both NR-L and NR-U services by pico / femtobase stations is limited to downlink transmission. The coverage 33 of NR-L services and the coverage 34 of NR-U services may vary depending on the frequency band, transmission power, etc.

[0103] When NR communication is performed in an unlicensed band, conventional equipment communicating in that band (for example, wireless LAN (Wi-Fi equipment)) cannot demodulate NR-U messages or data. Therefore, conventional equipment treats NR-U messages or data as a type of energy and performs interference avoidance operations using energy detection techniques. In other words, if the energy corresponding to an NR-U message or data is less than -62 dBm or a specific ED (Energy Detection) critical value, wireless LAN equipment will ignore the message or data and communicate. As a result, terminals performing NR communication in an unlicensed band may frequently experience interference from wireless LAN equipment.

[0104] Therefore, in order to effectively implement NR-U technology / service, it is necessary to allocate or reserve a specific frequency band during a specific period of time. However, there is a problem in that efficient NR-U service is difficult because peripheral equipment communicating via unlicensed bands attempts to access them based on energy detection techniques. Therefore, in order for NR-U technology to take root, research should be prioritized on coexistence methods with conventional unlicensed band equipment and methods for efficiently sharing radio channels. In other words, a robust mechanism should be developed so that NR-U equipment does not affect conventional unlicensed band equipment.

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

[0106] Referring to Figure 15, wireless LAN devices (e.g., APs, STAs) perform carrier sensing before transmitting data to check if a channel is busy. If a wireless signal of a certain strength or higher is detected on the channel to which data is to be transmitted, the channel is determined to be busy, and the wireless LAN device delays access to that channel. This process is called clear channel evaluation, and the level at which a signal is detected is called the CCA threshold. On the other hand, if no wireless signal is detected on the channel, or if a wireless signal with an intensity lower than the CCA threshold is detected, the channel is determined to be idle.

[0107] If a channel is determined to be idle, terminals with data to transmit will perform a defer duration (e.g., AIFS (Arbitration InterFrame Space), PIFS (PCF IFS)) followed by a backoff procedure. The defer duration is the minimum time a terminal must wait after a channel becomes idle. The backoff procedure causes terminals to wait for an arbitrary amount of time after the defer duration expires. For example, a terminal waits within a Contention Window (CW) while the channel is idle, decreasing its slot time by a random number assigned to it. Once a terminal has exhausted all its slot time, it attempts to access the channel.

[0108] If channel access is successful, the terminal transmits data through the channel. If data transmission is successful, the competition window size (CWS) is reset to its initial value (CWmin). Conversely, if data transmission fails, the CWS doubles. As a result, the terminal is assigned a new random number within twice the previous random number range and performs the backoff procedure in the next CW. In wireless LANs, only ACK is defined as the received 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 doubles.

[0109] As mentioned above, since most communications in conventional unlicensed bands operate on an LBT (Low-Block Test) basis, channel access in NR-U systems also uses LBT to coexist with conventional equipment. In detail, channel access methods on unlicensed bands in NR are classified into the following four categories depending on the presence / absence and application method of LBT. ●Category 1: No LBT -Tx entities do not perform LBT procedures for transmission. ●Category 2: LBT without random backoff

[0110] -The Tx entity senses whether the channel is idle during the first interval without random backoff in order to perform a transmission. That is, immediately after the Tx entity senses that the channel is idle during the first interval, it performs a transmission through that channel. The first interval is a preset interval of length immediately before the Tx entity performs a transmission. In one embodiment, the first interval may be an interval of length 25us, but the present invention is not limited thereto. ●Category 3: LBT that uses a fixed-size CW to perform random backoff

[0111] - The Tx entity obtains a random number within a fixed-size CW and sets it as the initial value of the backoff counter (or backoff timer) N, and uses the set backoff counter N to perform backoff. In other words, in the backoff procedure, the Tx entity decrements the backoff counter by 1 each time the channel is sensed to be idle during a preset slot period. Here, the preset slot period may be 9us, but the present invention is not limited to this. The backoff counter N is decremented by 1 from its initial value, and when the value of the backoff counter N reaches 0, the Tx entity transmits. On the other hand, in order to perform backoff, the Tx entity uses a second interval (i.e., a differ period T) d The Tx entity 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 during 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 period of 16us 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 to be occupied during the backoff procedure, the backoff procedure is interrupted. After interrupting the backoff procedure, the Tx entity resumes backoff if the channel is sensed to be idle during an additional second interval. In this way, the Tx entity transmits if the channel is idle during the second interval plus the slot periods of the backoff counter N. In this case, the initial value of the backoff counter N is obtained within a fixed-size CW (Continuous Wave) transmission. ●Category 4: LBT that uses variable-size CW to perform random backoff

[0112] - The Tx entity obtains a random number within a CW of variable size and sets it as the initial value of a backoff counter (or a 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 the HARQ-ACK information for the previous transmission, but the initial value of the backoff counter N is obtained within the CW of the adjusted size. The detailed process of the Tx entity performing backoff is as described in Category 3. The Tx entity performs transmission if the channel is idle during the slot period of the backoff counter N in addition to the second interval. At this time, the initial value of the backoff counter N is obtained within the CW of variable size.

[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 the channel access of Category 4, and the second type of channel access is referred to as the channel access of Category 2.

[0114] FIG. 16 is a diagram showing a channel access process based on Category 4 LBT according to an embodiment of the present invention. To perform channel access, first, the Tx entity performs channel sensing S302 for the defer period T d According to an embodiment of the present invention, the channel sensing for the defer period T d in S302 is performed through channel sensing during at least a part of the defer period T d For example, the channel sensing for the defer period T d is performed through channel sensing during one slot period within the defer period T d The Tx entity confirms whether the channel is idle through channel sensing for the defer period T d In S304. If the channel is sensed to be idle for the defer period T d the Tx entity proceeds to S306. If the channel is sensed to be idle for the defer period Td If the channel is not sensed as idle (i.e., sensed as occupied), the Tx entity returns to S302. The Tx entity is considered to have a channel with a defer period of T d The process described in S302 to S304 is repeated until the system is sensed to be in an idle state. Difference period T d This is set based on the channel access priority class of the Tx entity and consists of a 16us period followed by 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 a predetermined set of CW values ​​and sets it as the initial value of the backoff counter (or backoff timer) N, then proceeds to S306 and S308. The initial value of the backoff counter N is randomly selected from a value between 0 and CW. The Tx entity performs the backoff procedure using the set backoff counter N. In other words, the Tx entity repeats the process from S308 to S316 until the value of the backoff counter N reaches 0, thus performing the backoff procedure. Meanwhile, in Figure 16, the channel has a differ period T d Although it is indicated that S306 is performed after the channel is sensed to be idle, the present invention is not limited to this. In other words, S306 may be performed independently of S302 to S304, or before S302 to S304. If S306 is performed before S302 to S304, S302 to S304 will cause the channel to undergo a differ period T. d If it is sensed to be idle, the Tx entity proceeds to S308.

[0116] In S308, the Tx entity checks if 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 to perform transmission. If the value of the backoff counter N is not 0, the Tx entity proceeds to S310. In S310, the Tx entity decreases the value of the backoff counter N by 1. According to one embodiment, the Tx entity selectively decreases the value of the backoff counter by 1 during the channel sensing process for each slot. In this case, S10 may be skipped at least once at the Tx entity's discretion. Next, the Tx entity performs channel sensing for an additional slot period in S312. The Tx entity checks in S314 whether the channel is idle through channel sensing for the additional slot period. If the channel is sensed to be idle for the additional slot period, the Tx entity returns to S308. In this way, the Tx entity decreases the backoff counter by 1 each time the channel is sensed to be idle during a predetermined slot period. Here, the preset slot period may be 9us, but the present invention is not limited to this.

[0117] In S314, if the channel is not sensed as idle for the additional slot period (i.e., if it is sensed as occupied), the Tx entity proceeds to S316. In S316, the Tx entity proceeds to S316 if the channel is not sensed as idle for the additional defer period T d It is checked whether it is idle during this period. According to the embodiment of the present invention, channel sensing in S316 is performed on a slot-by-slot basis. In other words, the Tx entity is checked for an additional defer period T d Check whether the channel is sensed as idle for the entire duration of the slot. Additional defer period T d If an occupied slot is detected within, the Tx entity immediately restarts S316. Additional defer period T d If the channel is sensed to be idle for the entire duration of the slot, the Tx entity returns to S308.

[0118] On the other hand, if the value of the backoff counter N is confirmed to be 0 in S308, the Tx entity performs the transmission in S320. The Tx entity receives HARQ-ACK feedback corresponding to the transmission in S322. The Tx entity checks whether the previous transmission was successful or not via the received HARQ-ACK feedback. Next, the Tx entity adjusts the CW size for the next transmission in S324 based on the received HARQ-ACK feedback.

[0119] Thus, the Tx entity has a deferred period T. d After sensing that the channel is idle, transmission is performed if the channel remains idle for N additional slot periods. As described above, the Tx entity may be a base station or a terminal, and the channel access process in Figure 16 is used for downlink transmission at a base station and / or uplink transmission at a terminal.

[0120] The following proposes a method for adaptively adjusting the CWS during channel access in unlicensed bandwidth. The CWS is adjusted based on UE (User Equipment) feedback, and the UE feedback used for CWS adjustment includes HARQ-ACK feedback and CQI / PMI / RI. This invention proposes a method for adaptively adjusting the CWS based on HARQ-ACK feedback. HARQ-ACK feedback includes at least one of ACK, NACK, DTX, and NACK / DTX.

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

[0122] - A set of HARQ-ACK feedback values ​​(i.e., a HARQ-ACK feedback set): This refers to the HARQ-ACK feedback values ​​used for CWS updates / adjustments. The HARQ-ACK feedback set is decoded at the time the CWS is determined and corresponds to the available HARQ-ACK feedback values. The HARQ-ACK feedback set includes HARQ-ACK feedback values ​​for one or more DL (channel) transmissions (e.g., PDSCH) on an unlicensed bandwidth carrier (e.g., Scell, NR-U cell). The HARQ-ACK feedback set includes HARQ-ACK feedback values ​​for DL ​​(channel) transmissions (e.g., PDSCH), e.g., multiple HARQ-ACK feedback values ​​fed back from multiple terminals. The HARQ-ACK feedback value indicates received response information for a code block group (CBG) or transmission block (TB) and represents one of the following: ACK, NACK, DTX, or NACK / DTX. Depending on the context, the HARQ-ACK feedback value may be used interchangeably with terms such as HARQ-ACK value, HARQ-ACK information bits, and HARQ-ACK response.

[0123] -Reference window: This refers to a time interval in an unlicensed bandwidth carrier (e.g., Scell, NR-U cell) where DL transmissions (e.g., PDSCH) corresponding to a set of HARQ-ACK feedback occur. The reference window is defined by the embodiment on a slot or subframe basis. The reference window refers to one or more specific slots (or subframes). According to embodiments of the present invention, a specific slot (or reference slot) includes the start slot of the most recent DL transmission burst that is expected to be able to utilize at least some of the HARQ-ACK feedback.

[0124] Figure 17 shows an example of a method for adjusting the competition window size (CWS) based on HARQ-ACK feedback. In the example in Figure 17, the Tx entity may be a base station and the Rx entity may be a terminal, but the present invention is not limited to this. Also, the example in Figure 17 assumes a channel access process for DL ​​transmission at a base station, but at least some of the configurations may be applied to a channel access process for UL transmission at a terminal.

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

[0126] First, the Tx entity receives HARQ-ACK feedback corresponding to PDSCH transmissions(etc.) on an unlicensed bandwidth carrier (e.g., Scell, NR-U cell) in S404. The HARQ-ACK feedback used for CWS tuning includes HARQ-ACK feedback corresponding to the most recent DL transmission burst (i.e., the nth DL transmission burst) on the unlicensed bandwidth carrier. More specifically, the HARQ-ACK feedback used for CWS tuning includes HARQ-ACK feedback corresponding to PDSCH transmissions 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 embodiments of the present invention, the specific slots (or reference slots) include the starting slot of the most recent DL transmission burst from which at least some HARQ-ACK feedback is expected to be available.

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

[0128] Next, the Tx entity adjusts the CWS based on the HARQ-ACK value determined in S404 in S406. In other words, the Tx entity determines the CWS based on the HARQ-ACK value(s) determined by the HARQ-ACK information bits(s) for each TB in the HARQ-ACK feedback. More specifically, the CWS is adjusted based on the proportion of NACKs in the HARQ-ACK value(s). First, the variables are defined as follows: -p: Priority class value -CW_min_p: Pre-configured minimum CWS value for priority class p -CW_max_p: Pre-configured maximum CWS value for priority class p -CW_p: CWS for transmitting priority class p. CW_p is set to one of several CWS values ​​between CW_min_p and CW_max_p that are included in the allowed CWS set for 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. In this case, priority class p includes {1, 2, 3, 4}. Step A-2) If the proportion of NACKs among the HARQ-ACK values ​​for PDSCH transmissions (and) in the reference window k is Z% or greater, then CW_p is increased to the next highest tolerance for all priority classes p (and the process remains in Step A-2). Otherwise, the process proceeds to Step A-1. Here, Z is a preset integer in the range 0 ≤ Z ≤ 100, and according to one embodiment, it is set to one of {30, 50, 70, 80, 100}. Here, the reference window k includes the most recent transmission start slot (or subframe) by the Tx entity. The reference window k is also the slot (or subframe) where at least some HARQ-ACK feedback is expected to be possible. If CW_p = CW_max_p, then the next highest tolerance for adjusting CW_p is CW_max_p.

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

[0131] On the other hand, in the CWS adjustment process described above, it should be determined whether or not DTX or NACK / DTX are considered together in addition to ACK and NACK in the HARQ-ACK feedback. According to an embodiment of the present invention, whether or not DTX or NACK / DTX are considered together in the CWS adjustment process is determined by whether the transmission in the unlicensed band is based on self-carrier scheduling or cross-carrier scheduling.

[0132] During self-carrier scheduling, DL transmissions (e.g., PDSCH) on an unlicensed bandwidth carrier are scheduled via a control channel (e.g., (E)PDCCH) transmitted on the same unlicensed bandwidth carrier. Here, DTX occurs when DL transmission fails on an unlicensed bandwidth carrier due to a hidden node or the like, and is used together with NACK for CWS adjustment. DTX is also one way for a terminal to notify a base station if it was unable to decode a control channel (e.g., (E)PDCCH) containing scheduling information, even though the base station transmitted it to the terminal. DTX is determined either solely by the HARQ-ACK feedback value or by considering the HARQ-ACK feedback value and the actual scheduling status. According to an embodiment of the present invention, in a self-carrier scheduling situation, DTX and NACK / DTX are counted by NACK to adjust the CWS. That is, if the sum of NACK, DTX, and NACK / DTX among the HARQ-ACK values ​​for PDSCH transmissions (etc.) in the reference window k is Z% or greater, the CWS is increased to the next highest tolerance value. Otherwise, CWS will be reset to its minimum value.

[0133] During cross-carrier scheduling, DL transmissions on unlicensed band carriers (e.g., PDSCH) are scheduled via control channels (e.g., (E)PDCCH) transmitted on licensed band carriers. In this case, DTX feedback is used to determine the terminal's decoding status for the control channel transmitted on the licensed band carrier, and is therefore not useful for adaptively adjusting the CWS for channel access in the unlicensed band. Thus, according to embodiments of the present invention, DTX may be ignored to determine the CWS in cross-carrier scheduling situations from licensed bands. That is, to adjust the CWS, the proportion of NACK may be calculated by considering only ACK and NACK among the HARQ-ACK values, or the proportion of NACK may be calculated by considering only ACK, NACK, and NACK / DTX. Thus, when calculating the proportion of NACK, DTX is excluded.

[0134] Figure 18 is a block diagram showing the configuration of a terminal and a base station according to one embodiment of the present invention. In one embodiment of the present invention, the terminal is embodied in various types of wireless communication devices or computing devices that ensure portability and mobility. The terminal is referred to as UE, STA (Station), MS (Mobile Subscriber), etc. In the embodiment of the present invention, the base station controls and manages the cells (e.g., macrocells, femtocells, picocells, etc.) in the service area and performs functions such as signal transmission, channel assignment, channel monitoring, self-diagnosis, and relaying. The base station is referred to as gNB (next Generation NodeB) or AP (Access Point), etc.

[0135] As shown in the figure, 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 instructions or programs to process data inside 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 units. Here, the processor 110 is configured to perform the operations described in the embodiment of the present invention. For example, the processor 110 may receive slot configuration information, determine the slot configuration based on that 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 incorporates multiple network interface cards (NICs), such as cellular communication interface cards 121 and 122 and an unlicensed band communication interface card 123, either internally or externally. In the drawing, the communication module 120 is shown as an integrated module, but each network interface card may be arranged independently depending on the circuit configuration or application, contrary to the drawing.

[0138] The cellular communication interface card 121 transmits and receives radio 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 in a first frequency band based on instructions from the processor 110. According to one embodiment, the cellular communication interface card 121 includes at least one NIC module that utilizes a frequency band of less than 6 GHz. 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, an external device, and a server, depending on the cellular communication standard or protocol of the sub-6 GHz frequency band supported by the NIC module.

[0139] The cellular communication interface card 122 uses a mobile communication network to send and receive radio signals with at least one of the base station 200, an external device, or a server, and provides cellular communication services in the second frequency band based on instructions from the processor 110. In one embodiment, the cellular communication interface card 122 includes at least one NIC module that utilizes a frequency band of 6 GHz or higher. 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, an external device, or a server, according to the cellular communication standard or protocol of the 6 GHz or higher frequency band supported by the NIC module.

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

[0141] Next, the memory 130 stores control programs used by the terminal 100 and various data associated with them. Such control programs include predetermined programs necessary for the terminal 100 to communicate wirelessly with at least one of the following: a base station 200, an external device, or a server.

[0142] Next, the user interface 140 includes various forms of input / output means provided in the terminal 100. In other words, 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. The user interface 140 also outputs based on instructions from the processor 110 using various output means.

[0143] Next, the display unit 150 outputs various images to the display screen. The display unit 150 outputs various display objects, such as content generated by the processor 110 or user interfaces based on control instructions from the processor 110. Furthermore, the base station 200 according to the embodiment of the present invention 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 units. Here, the processor 210 is configured to perform the operations described in the embodiment of the present invention. 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 incorporates multiple network interface cards, such as cellular communication interface cards 221 and 222, and an unlicensed band communication interface card 223, either internally or externally. In the drawings, the communication module 220 is shown as an integrated module, but each network interface card may be arranged independently depending on the circuit configuration or application, contrary to the drawings.

[0146] The cellular communication interface card 221 transmits and receives wireless signals to and from at least one of the terminal 100, external devices, and servers described above using a mobile communication network, and provides cellular communication services in the first frequency band based on instructions from the processor 210. According to one embodiment, the cellular communication interface card 221 includes at least one NIC module that utilizes a frequency band of less than 6 GHz. At least one NIC module of the cellular communication interface card 221 independently performs cellular communication with at least one of the terminal 100, external devices, and servers, according to the cellular communication standard or protocol of the frequency band of less than 6 GHz supported by the NIC module.

[0147] The cellular communication interface card 222 uses a mobile communication network to send and receive wireless signals to and from at least one of the terminal 100, an external device, and a server, and provides cellular communication services in the second frequency band based on instructions from the processor 210. In one embodiment, the cellular communication interface card 222 includes at least one NIC module that utilizes a frequency band of 6 GHz or higher. At least one NIC module of the cellular communication interface card 222 independently performs cellular communication with at least one of the terminal 100, an external device, and a server, according to the cellular communication standard or protocol of the 6 GHz or higher frequency band supported by the NIC module.

[0148] The unlicensed band communication interface card 223 uses the third frequency band, which is an unlicensed band, to send and receive wireless signals with at least one of the terminal 100, an external device, or a server, and provides communication services in the unlicensed band based on instructions from the processor 210. The unlicensed band communication interface card 223 includes at least one NIC module that utilizes the unlicensed band. For example, the unlicensed band may be 2.4GHz, 5GHz, 6GHz, 7GHz, or a band of 52.6GHz or higher. 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, or a server, depending on the unlicensed band communication standard or protocol of the frequency band supported by the 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 separately shown blocks represent logically distinguished elements of the device. Therefore, the above-mentioned elements of the device are mounted on one or more chips depending on the device design. Furthermore, some components of the terminal 100, such as the user interface unit 150 and the display unit 150, may be selectively provided in the terminal 100. In addition, the user interface 140 and the display unit 150 may be additionally provided in the base station 200 as needed.

[0150] The NR system receives a synchronization signal (SS) and a physical broadcast channel (PBCH), and performs at least one of the following based on the synchronization signal and PBCH: initial cell access, RRM measurement, and mobility management. The synchronization signal includes PSS and SSS as described above. The synchronization signal and PBCH are referred to as the SS / PBCH block or SSB. Examples of SSB transmission and reception will be described with reference to Figures 19 to 42. Figure 19 shows the position of OFDM symbols occupied by SSB within multiple slots of the licensed bandwidth of an NR system according to one embodiment of the present invention.

[0151] SSB includes four OFDM symbols and 20RBs. More specifically, PSS occupies one OFDM symbol, SSS occupies one OFDM symbol, and PBCH occupies two OFDM symbols and one OFDM symbol multiplexed with SSS and FDM. The position of OFDM symbols within the slots occupied by SSB can differ depending on the subcarrier spacing (SCS). Figure 19(a) shows the SSB patterns when the subcarrier spacing values ​​for transmitting SSB are 15kHz and 30kHz, respectively. Figure 19(b) shows the SSB patterns when the subcarrier spacing values ​​for transmitting SSB are 120kHz and 240kHz, respectively. When the subcarrier spacing is 30kHz, either the SSB pattern for transmitting eMBB or the SSB pattern considering URLLC is used. In Figure 19, the hatched OFDM symbols indicate the position of the OFDM symbol within the slot occupied by the SSB. Different hatching patterns indicate different SSB indices. The SSB index will be discussed again later.

[0152] Figure 20 shows the location of slots occupied by SSB within a 5ms half-radio frame of the licensed band of an NR system according to one embodiment of the present invention. In Figure 20, hatched slots indicate the location of slots containing SSB within a half-radio frame. One slot contains two SSBs. The two SSBs within a single slot have different SSB indices. Also, SSBs located in different slots have different SSB indices. SSB indices will be discussed again later. In Figure 20, L 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 should be defined for each frequency band, reducing the complexity for terminals to search for SSB for initial cell access. Specifically, if a frequency band below 6 GHz is used, the NR system specifies that either a 15 kHz or 30 kHz subcarrier spacing should be used for SSB. If a frequency band above 6 GHz is used, the NR system specifies that either a 120 kHz or 240 kHz subcarrier spacing should be used for SSB.

[0154] In unlicensed bands, the LBT procedure is used when a radio communication device accesses a channel. Therefore, if the channel is not idle, the radio communication device may fail to access the channel. Similarly, when a base station accesses a channel to transmit SSB, it may fail to access the channel, meaning that SSB transmission may not occur at the location set by the base station. Ultimately, even if the base station configures the terminal to assume the location where SSB is transmitted, the terminal may still not receive the SSB. Since SSB is transmitted periodically, even if the terminal fails to receive the SSB at any given time, it can receive it one cycle later. However, if the terminal receives the SSB in this way, a delay occurs in RRM measurement and measurement to neighboring cells. Ultimately, this increases latency across the entire system.

[0155] Furthermore, SSB is used for beamlink configuration and beam operation. Specifically, the base station transmits multiple SSBs corresponding to different SSB indices in different time domains. The terminal uses multiple SSBs to configure multiple beamlinks. The base station performs beam sweeping. The terminal configures the beamlinks depending on whether it received SSBs transmitted in different time domains and on different beams. If the base station fails to access the channel and cannot transmit the SSB, a problem occurs where the beamlink cannot be configured. Ultimately, the latency for beamlinks increases due to the failure of channel access. Therefore, a method is needed to reduce SSB transmission failures and increase the opportunities for SSB transmission.

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

[0157] When SSB is 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 to 20 can be used as is or with some modifications. The SSB patterns when the subcarrier spacing value for transmitting SSB in an unlicensed band is 60 kHz are described in Figures 21 to 23.

[0158] A temporally continuous SSB pattern is used within a single slot. Through this, the base station can increase its transmission efficiency. In such an embodiment, if the base station transmits the same beam continuously or different beams after successfully accessing a channel, the base station will continuously occupy the channel. This prevents other radio communication devices attempting to use the channel from occupying it. Ultimately, by successfully accessing a channel once, the base station can transmit multiple SSBs, increasing the probability of being able to perform other transmissions after the SSB transmission. The base station transmits SSBs consecutively within a single slot. Furthermore, the base station transmits multiple SSBs temporally consecutively within a single slot. More specifically, the base station transmits SSBs as DL burst transmissions. If a continuously transmittable SSB pattern is used, the base station can continuously use a specific channel to prevent other radio communication devices from accessing that channel. In such an embodiment, the subcarrier spacing value for transmitting SSB in an unlicensed band is 60 kHz.

[0159] Furthermore, an SSB pattern is used in which the transmission ends before the boundary between the slot in which the SSB is transmitted and the next slot in which the SSB is transmitted. In other words, after the SSB transmission, a gap is set for the LBT procedure before the next slot begins. Specifically, the base station terminates the SSB transmission at a predetermined time prior to the boundary between the slot in which the SSB is transmitted and the next slot in which the SSB is transmitted. Specifically, the base station terminates the SSB transmission at least one OFDM symbol prior to the boundary between the slot in which the SSB is transmitted and the next slot in which the SSB is transmitted. When such an SSB pattern is used, the base station increases the likelihood of initiating the LBT procedure after transmitting the SSB and transmitting a PDCCH or PDSCH from the start of the next slot in which the SSB is transmitted. In such an embodiment, the subcarrier spacing value for transmitting SSB in the unlicensed band is 60 kHz.

[0160] Figure 21 shows the position of OFDM symbols to which SSB is transmitted within a 1ms time interval when 60KHz subcarrier spacing is used and the maximum number of SSBs is 3 according to one embodiment of the present invention. Figure 22 shows the position of OFDM symbols to which SSB is transmitted within a 1ms time interval when 60KHz subcarrier spacing is used and the maximum number of SSBs is 4 according to one embodiment of the present invention. Figure 23 shows the position of OFDM symbols to which SSB is transmitted within a 1ms time interval when 60KHz subcarrier spacing is used and the maximum number of SSBs is 6 according to one embodiment of the present invention. In Figures 21 to 23, OFDM symbols shown in hatching indicate OFDM symbols occupied by SSB. Different hatching patterns indicate that they correspond to different SSB indices. In Figures 21 to 23, the base station continuously transmits SSB within a single slot. Through this, after the base station successfully accesses the channel to transmit SSB within a single slot, it prevents the next wireless communication device from accessing the channel within that slot. Furthermore, in Figures 21 to 23, the base station terminates before the boundary between the slot in which the SSB is transmitted and the next slot in which the SSB is transmitted. Through this, the base station increases the likelihood of transmitting PDCCH or PDSCH from the start of the next slot in which the SSB is transmitted after transmitting the SSB. In short, the base station prevents delays in initial cell access, RRM (radio resource management) measurement, and RLM (radio link monitoring) measurement due to LBT failure through the embodiments described in Figures 21 to 23.

[0161] The base station transmits multiple SSBs via SSB transmission within a predetermined time interval for transmitting SSBs. The duration of this predetermined time interval is 5ms. Multiple SSBs transmitted via SSB transmission are referred to as an SSB set. Each SSB in an SSB set is assigned a unique SSB index. The SSB index starts at 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 show cases where the position of the OFDM symbol within the SSB transmission slot is fixed for each SSB index. Figures 20(b) and 21(b) show cases where the position of the OFDM symbol within the SSB transmission slot is not fixed for each SSB index. Specifically, the base station cycles the SSB index corresponding to the SSB transmission position each time an SSB is transmitted. This implementation allows for a uniform setting of the success probability of SSB transmission for each SSB index. This will be explained in detail through Figures 32 to 42.

[0162] Figure 24 shows the position of OFDM symbols to which SSB is transmitted within a 1ms time interval when 60kHz subcarrier spacing is used to transmit SSB according to one embodiment of the present invention, and the maximum number of SSBs is 8. In Figure 24, OFDM symbols shown in hatching indicate OFDM symbols occupied by SSB. Different hatching patterns indicate that they correspond to different SSB indices. Figure 24 shows two examples of SSB patterns applicable when 60kHz subcarrier spacing is used. The second SSB pattern (pattern #2) initiates SSB transmission at an OFDM symbol further ahead than the first SSB pattern (pattern #1). The base station uses the second SSB pattern (pattern #2) to increase the success rate of the LBT procedure for PDSCH transmission or PDCCH transmission after SSB transmission compared to when the first SSB pattern (pattern #1) is used. If 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 at the slot boundary after the slot in which SSB is transmitted for PDCCH or PDSCH transmission. If data channel transmission is performed, a channel access procedure with Cat-4 LBT, i.e., random backoff, is required. Therefore, the SSB pattern in Figure 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), it can increase transmission efficiency compared to when using the second SSB pattern (pattern #2).

[0163] In the unlicensed band, the base station attempts to transmit SSB from the earliest slot in the time domain of the time interval in which SSB is transmitted. Through this, the base station prevents the loss of SSB transmission opportunities or delays in SSB transmission due to LBT procedure failures. This will be explained with reference to Figures 25 to 29. For the sake of explanation, the time interval in which SSB is transmitted will be referred to as the SSB transmission window.

[0164] Figure 25 shows the positions of the slots through which SSB is transmitted in the SSB transmission window when 60 kHz subcarrier spacing is used to transmit SSB according to another embodiment of the present invention. Specifically, Figure 25(a) shows the positions of the slots through which SSB is transmitted in the SSB transmission window when the maximum number of SSBs that can be transmitted within the SSB transmission window is 4. Also, Figure 25(b) shows the positions of the slots through which SSB is transmitted in the SSB transmission window when the maximum number of SSBs that can be transmitted within 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 an SSB transmission window for each transmission opportunity. For example, when the base station acquires a transmission opportunity via the LBT procedure, it transmits the maximum number of SSBs that can be transmitted within an SSB transmission window. In such an embodiment, the time interval in which an SSB set is transmitted is set based on the maximum number of SSBs that can be transmitted within an SSB transmission window. More specifically, the time interval in which an SSB set is transmitted is set in slots equal to the maximum number of SSBs that can be transmitted within an SSB transmission window.

[0166] Figures 26 to 28 show a case in an unlicensed band where, for SSB transmission, there are multiple slot locations where a base station can initiate SSB transmission within an SSB transmission window, depending on the maximum number of SSBs pre-set. The base station sets the location of a slot where SSB transmission can be initiated within the SSB transmission window according to the maximum number of SSBs and performs SSB transmission, and the terminal receives SSB from the slot location where SSB transmission is possible, as set by the base station within the SSB transmission window. If the LBT fails in a slot where SSB transmission can be initiated, the base station performs an LBT to initiate transmission in the next slot where SSB transmission can be initiated and performs SSB transmission in that slot.

[0167] Figure 26 shows a case where, when 15 kHz subcarrier spacing is used to transmit SSB in an unlicensed band, there are multiple slot locations where SSB transmission can be initiated, depending on the maximum number of SSBs that the base station can transmit 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 slot, the third slot, and the fifth slot within the SSB transmission window as slot locations where SSB transmission can be initiated. The terminal receives SSB from the slot locations where SSB transmission can be initiated 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 slot and the fifth slot within the SSB transmission window as slot locations where SSB transmission can be initiated. The terminal receives SSB from the slot locations where SSB transmission can be initiated set by the base station.

[0168] Figure 27 shows that when 30 kHz subcarrier spacing is used to transmit SSB in an unlicensed band, according to an embodiment of the present invention, there are multiple slot positions where SSB transmission can be initiated, depending on the maximum number of SSBs that the base station can transmit within the SSB transmission window. Figure 27(a) shows the 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 the 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 that when 60 kHz subcarrier spacing is used to transmit SSB in an unlicensed band, according to an embodiment of the present invention, there are multiple slot positions where SSB transmission can be initiated, depending on the maximum number of SSBs that the base station can transmit within the SSB transmission window. Figure 28(a) shows the 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 the 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 other specific embodiments, the base station configures itself to initiate SSB transmission for each slot within an SSB transmission window. Within an SSB transmission window, the location of the slot where SSB transmission begins may differ from window to window depending on the channel access result. Therefore, channel access failures may lead to an imbalance in transmission opportunities for multiple SSBs that transmit using different beams and different SSB indices. Through such embodiments, 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-enabled location included in each slot. Through this, SSBs corresponding to different SSB indices can have a uniform transmission opportunity.

[0171] Figure 29 shows that, according to an embodiment of the present invention, when 15 kHz subcarrier spacing is used to transmit SSB in an unlicensed band, the base station has an opportunity to initiate SSB transmission for each slot within the SSB transmission window. In Figure 29(a), 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 Figure 29(b), 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] Figure 30 shows that, according to an embodiment of the present invention, when 30 kHz subcarrier spacing is used to transmit SSB in an unlicensed band, the base station has an opportunity to initiate SSB transmission for each slot within the SSB transmission window. In Figure 30(a), 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 Figure 30(b), 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] Figure 31 shows that, according to an embodiment of the present invention, when 60 kHz subcarrier spacing is used to transmit SSB in an unlicensed band, the base station has an opportunity to initiate SSB transmission for each slot within the SSB transmission window. In Figure 31(a), 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 Figure 31(b), 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 other specific embodiments, the base station transmits SSB by setting an opportunity to initiate SSB transmission at specific time intervals within the SSB transmission window. More specifically, the base station attempts SSB transmission at 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 base station's RRC configuration within a pre-configured group of candidates. Furthermore, the specific time interval is a fixed value agreed upon by the terminal and the base station.

[0175] A failure in the channel access procedure (e.g., LBT) may prevent the base station from transmitting SSB. If the base station cannot transmit SSB at a configured location, an SSB transmission window is defined to allow transmission at other locations. The SSB transmission window is the period in which the base station can transmit SSB, and includes multiple candidate SSB transmission locations. If the base station fails to initiate SSB transmission at any one candidate SSB transmission location, the base station attempts SSB transmission at a later SSB transmission location within the SSB transmission window. An SSB transmission location is a point in time when the base station can initiate SSB transmission. If a terminal fails to receive SSB at any one candidate SSB transmission location within the SSB transmission window, the terminal receives SSB at a later SSB transmission location within the SSB transmission window. At this point, the terminal determines whether the base station failed to initiate SSB transmission at the candidate SSB transmission location or whether the base station's SSB transmission failed. In a specific embodiment, if a terminal fails to receive an SSB at any of the SSB transmission candidate locations within an SSB transmission window, the terminal attempts to receive an SSB at the next SSB transmission candidate location within that SSB transmission window. After the terminal starts receiving an SSB at any of the SSB transmission candidate locations and completes the reception, the terminal does not expect to receive any additional SSBs within that SSB transmission window. More specifically, after the terminal starts receiving an SSB at any of the SSB transmission candidate locations and completes the reception, the terminal does not attempt to receive any additional SSBs within that SSB transmission window.

[0176] In other specific embodiments, if a terminal fails to receive a specific SSB at any of the candidate SSB transmission locations within an SSB transmission window, the terminal attempts to receive the specific SSB at the next candidate SSB transmission location within that SSB transmission window. After the terminal starts receiving a specific SSB at any of the candidate SSB transmission locations and completes the reception of the specific SSB, the terminal does not attempt to receive the specific SSB again within that SSB transmission window. More specifically, after the terminal receives a specific SSB at any of the candidate SSB transmission locations, the terminal does not attempt to receive any additional specific SSBs within that SSB transmission window.

[0177] In other specific embodiments, even after a terminal has completed receiving a specific SSB at any one SSB transmission candidate location, the terminal may attempt to receive an additional specific SSB within the relevant SSB transmission window. This is because the terminal can receive an additional specific SSB and obtain a combining gain through the additionally received specific SSB. Such embodiments apply not only when multiple SSBs corresponding to different beam indices are transmitted for beam operation, but also when using an omni-TX transmission method. More specifically, it also applies when the same SSB is transmitted repeatedly. A base station may transmit an SSB after the LBT procedure, and a failure of the LBT procedure may prevent the transmission of all SSBs in the SSB block set within the DRS transmission window. Therefore, the transmission probability of an SSB may differ depending on the transmission order of the SSBs, depending on the SSB index. An embodiment is needed to ensure uniform transmission probabilities for SSBs corresponding to different SSB indices. This will be explained with reference to Figures 32 to 42.

[0178] Each SSB transmission candidate location within an SSB transmission window is mapped to one of the SSBs in the SSB set, and the base station transmits the SSB based on the mapping between the SSB transmission candidate location and the SSB. In this case, multiple SSBs in the SSB set are identified by an SSB index, which is a unique value within the SSB set. Also, within an SSB transmission window, multiple SSB transmission candidate locations are identified by an SSB transmission candidate location index. Specifically, once the base station successfully accesses a channel at a particular SSB transmission candidate location, the base station begins transmitting the SSB from that SSB transmission candidate location. In this case, the base station transmits the SSB mapped to each SSB transmission candidate location. In a specific embodiment, the base station transmits the SSB mapped to at least one SSB from each of the at least one SSB transmission candidate locations located within the time interval from the SSB transmission candidate location that successfully accessed the channel until the end of transmission of the SSB set. The base station also transmits SSBs within an SSB transmission window, and transmits SSBs within the maximum number of SSBs that can be transmitted within the SSB transmission window.

[0179] Base stations transmit SSB based on the DRS transmission period (periodicity). More specifically, base station DRS transmission includes SSB transmission. In this context, the window for transmitting SSB or SSB transmission window is replaced by the DRS transmission window in the above explanation. The DRS transmission window indicates the time interval during which DRS can be transmitted. The duration size 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 individually for each terminal.

[0180] Figure 32 shows a case in which the mapping between the SSB index and the SSB transmission candidate position index within the DRS transmission window is fixed according to an embodiment of the present invention.

[0181] Figure 32 shows that when 30kHz subcarrier spacing is used and the DRS transmission window duration is set to 5ms, 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 and is maintained. For example, if the maximum number of transmittable SSBs is 8, the SSB transmission candidate position index and SSB index are mapped as follows. Because 30kHz subcarrier spacing is used, a DRS transmission window with a duration of 5ms contains a total of 20 SSB transmission candidate positions for SSB transmission. For convenience of explanation, each SSB transmission candidate position index is denoted as i, and the SSB index corresponding to SSB transmission candidate position i is denoted as i_SSB. If the SSB transmission candidate position index is between 0 and 7, then i_SSB = i. Furthermore, if the SSB transmission candidate position index is between 8 and 15, then i_SSB = (i-8). Similarly, if the SSB transmission candidate position index is between 16 and 19, then i_SSB = (i-16). This mapping between the SSB transmission candidate position index and the SSB index is maintained in the next DRS transmission window. Figure 32 shows an example where such an embodiment is applied. In this embodiment, assuming that the LBT success probability is the same for each SSB transmission candidate position index, SSBs with SSB index values ​​between 0 and 3 have a transmission opportunity probability of 3 / 20, and SSBs with SSB index values ​​between 4 and 7 have a transmission opportunity probability of 1 / 10. To ensure uniform transmission probabilities for SSBs with different SSB indices, the mapping between the SSB transmission candidate position index and the SSB index may be further set for each DRS transmission window. More specifically, the mapping relationship between SSB transmission candidate locations and SSBs within the second DRS transmission window may differ from the mapping relationship between SSB transmission candidate locations and SSBs within the first DRS transmission window.

[0182] Figures 33 to 34 show the case in which the mapping between the SSB index and the SSB transmission candidate position index within 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 mapped to SSB transmission candidate location indices in the previous DRS transmission window and maps them to the SSB transmission candidate location indices. More specifically, the SSB indices are mapped to the SSB transmission candidate location indices in the DRS transmission window in reverse order of the SSB indices mapped to the SSB transmission candidate location indices in the immediately preceding DRS transmission window. The base station maps the SSB indices to the SSB transmission candidate location indices in the DRS transmission window in reverse order of the SSB indices mapped to the SSB transmission candidate location indices in the immediately preceding DRS transmission window, and transmits SSB based on the mapping between the SSB transmission candidate location indices and the SSB indices. In a specific example, in an even-numbered DRS transmission window, the SSB indices are mapped to the SSB transmission candidate location indices as shown in the following formula. i_SSB=i mod L In this case, x mod y represents the remainder when x is divided by y. Also, L is the maximum number of SSBs that the base station can transmit within the DRS transmission window. Furthermore, 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 5ms, and a 30kHz subcarrier spacing is used for SSB transmission, then the SSB transmission candidate position index and the SSB index are mapped as follows: Because a 30kHz subcarrier spacing is used, a DRS transmission window with a duration of 5ms contains a total of 20 SSB transmission candidate positions. X is an even number. If the Xth SSB transmission candidate position index is between 0 and 7, then i_SSB = i mod 8. Also, if the SSB transmission candidate position index is between 8 and 15, then i_SSB = i mod 8. Also, if the SSB transmission candidate position index is between 16 and 19, then i_SSB = i mod 8. For the Xth DRS transmission window, if the SSB transmission candidate position index is between 0 and 7, then i_SSB = 7 - (i mod 8). Furthermore, if the SSB transmission candidate position index is between 8 and 15, then i_SSB = 7 - (i mod 8). Also, if the SSB transmission candidate position index is between 16 and 19, then i_SSB = 7 - (i mod 8). Figure 33 shows an SSB transmission to which such an embodiment is applied.

[0185] In Figure 33, the base station performs the LBT procedure for one slot for SSB transmission, that is, for two SSB transmission candidate location units (granualities). In this way, the base station performs channel access for one slot, that is, for two SSB transmission candidate location units for SSB transmission. More specifically, the base station performs the LBT procedure for one slot for SSB transmission, that is, for two SSB transmission candidate location units for SSB transmission. In this case, if the base station fails to perform the LBT procedure to start SSB transmission at the SSB transmission candidate location with index i, the base station will perform the LBT procedure to start SSB transmission at the SSB transmission candidate location with index i+2, and the base station will not be able to perform the LBT procedure to start SSB transmission at the SSB transmission candidate location with index i+1. However, this embodiment is not limited to this, and the base station may perform channel access for n SSB transmission candidate location units, where n is a positive integer. More specifically, the base station performs the LBT procedure for n SSB transmission candidate location units. More specifically, 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 a previous SSB transmission candidate location prior to the SSB transmission candidate location with index i+n. In a specific embodiment, n is 1.

[0186] Figure 34 shows that the base station performs the LBT procedure for transmitting SSB at each SSB transmission candidate location. In the explanation above, we used the example where there are 20 SSB transmission candidate positions within the DRS transmission window and the maximum number that can be transmitted within 5ms is 8. However, the above embodiment is not limited to such numbers. It also applies when there are P SSB transmission candidate positions within the DRS transmission window and the maximum number that can be transmitted within 5ms 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 mappings between SSB transmission candidate locations and SSB indices are alternately applied to the DRS transmission window. Alternatively, four types of mappings between SSB transmission candidate locations and SSB indices may be alternately applied to the DRS transmission window. This will be explained with reference to Figures 35 and 36.

[0188] Figures 35 to 37 show cases in which the mapping between the SSB index and the SSB transmission candidate position index in the DRS transmission window is not fixed, according to other embodiments of the present invention.

[0189] In a specific example, if the remainder when N is divided by 4 is 0 in the (x+N)th DRS transmission window, 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 represents the remainder when x is divided by y. Also, L is the maximum number of SSBs that the base station can transmit within the DRS transmission window.

[0190] Furthermore, 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] Furthermore, 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] Furthermore, 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 5ms, and a 15kHz subcarrier spacing is used for SSB transmission, then the SSB transmission candidate position index and the SSB index are mapped as follows: Because a 15kHz subcarrier spacing is used, a DRS transmission window with a duration of 5ms contains a total of 10 SSB transmission candidate positions. X is a multiple of 4. If the Xth SSB transmission candidate position index is between 0 and 7, then i_SSB = i mod 8. Also, if the SSB transmission candidate position index is between 8 and 9, then i_SSB = i mod 8. If the (X+1)th transmission candidate position index is between 0 and 7, then i_SSB = 7 - (i mod 8). Also, if the SSB transmission candidate position index is between 8 and 9, then i_SSB = 7 - (i mod 8). If the (X+2)th transmission candidate position index is between 0 and 5, then i_SSB = (i+2) mod 8. Furthermore, if the SSB transmission candidate position index is between 6 and 9, then i_SSB = (i+2) mod 8. If the (x+3)th transmission candidate position index is between 0 and 5, then i_SSB = 7 - {(i+2) mod 8)}. Furthermore, if the SSB transmission candidate position index is between 6 and 9, then i_SSB = 7 - {(i+2) mod 8)}.

[0194] In Figure 35, the base station performs the LBT procedure for one slot for SSB transmission, that is, for each of two SSB transmission candidate locations. In this way, the base station performs the LBT procedure for one slot, that is, for each of two SSB transmission candidate locations for SSB transmission. If the base station fails to perform the LBT procedure to start SSB transmission at the SSB transmission candidate location with index i, the base station will perform the LBT procedure to start SSB transmission at the SSB transmission candidate location with index i+2, and the base station will not be able to perform the LBT procedure to start SSB transmission at the SSB transmission candidate location with index i+1. However, this embodiment is not limited to this, and the base station may perform the LBT procedure for SSB transmission for each of n SSB transmission candidate locations, where n is a positive integer. More specifically, if the LBT procedure to initiate SSB transmission at an SSB transmission candidate location with index i fails, the base station can perform the LBT procedure to initiate SSB transmission at an SSB transmission candidate location with index i+n, but cannot perform the LBT procedure to initiate SSB transmission at a previous SSB transmission candidate location prior to the SSB transmission candidate location with index i+n.

[0195] Figure 36 shows that the base station performs the LBT procedure for transmitting SSB at each SSB transmission candidate location. In the explanation above, we used the example where there are 10 SSB transmission candidate positions within the DRS transmission window and the maximum number that can be transmitted within 5ms is 8. However, the above embodiment is not limited to such numbers. It also applies when there are P SSB transmission candidate positions within the DRS transmission window and the maximum number that can be transmitted within 5ms 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 example, if the remainder when N is divided by 4 is 0 in the (x+N)th DRS transmission window, 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 represents the remainder when x is divided by y. Also, L is the maximum number of SSBs that the base station can transmit within a half-wireless frame.

[0197] Furthermore, 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] Furthermore, 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] Figure 37 shows that the embodiment described via Figure 35 applies when the maximum number of SSBs that can be transmitted within the DRS transmission window is 4. Figures 38 to 42 show cases in which the mapping between the SSB index and the SSB transmission candidate position index within the DRS transmission window is not fixed, according to other embodiments of the present invention.

[0201] The base station sets the mapping between SSB transmission candidate location indices and SSB indices to be different 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 mapped to the SSB transmission candidate location indices using cyclic wraparound. If the maximum number of SSBs that the base station can transmit in a half-radio frame is 8, the base station applies cyclic wraparound to the SSB transmission candidate location and SSB index mapping in units of 4, 2, or 1. If the maximum number of SSBs that the base station can transmit in a half-radio frame is 4, the base station applies cyclic wraparound to the SSB transmission candidate location and SSB index mapping in units of 2 or 1.

[0202] The base station applies cyclic wrap-around to the SSB transmission candidate locations and SSB index mapping in units of the maximum number of SSBs the base station can transmit divided by 4 within the DRS transmission window. Figures 38 and 39 show, in an embodiment, that cyclic extension is applied to the SSB transmission candidate locations and SSB index mapping in units of the maximum number of SSBs the base station can transmit divided by 4 within a half-radio frame. For more details, the SSB transmission candidate location 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 represents the remainder when x is divided by y. Also, L is the maximum number of SSBs that the base station can transmit within the DRS transmission window.

[0204] Furthermore, 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 indices and SSB indices when the maximum number of SSBs that can be transmitted within the DRS transmission window is 8 and a 30kHz subcarrier spacing is used to transmit the SSBs. Therefore, the DRS transmission window contains 20 SSB transmission candidate positions. In Figure 38, an example is given where there are 20 SSB transmission candidate positions in the DRS transmission window, the maximum number that can be transmitted within the DRS transmission window is 8, and the duration of the DRS transmission window is 5ms, but the above embodiment is not limited to such numbers. It also applies when there are P SSB transmission candidate positions in the DRS transmission window and the maximum number 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 Figure 38, the base station performs the LBT procedure for transmitting SSB in units of one slot, i.e., two SSB transmission candidate locations. In this way, the base station performs the LBT procedure for transmitting SSB in units of one slot, i.e., two SSBs per transmission candidate location. If the base station fails to perform the LBT procedure to start SSB transmission at the SSB transmission candidate location with index i, the base station will perform the LBT procedure to start SSB transmission at the SSB transmission candidate location with index i+2, and will not be able to perform the LBT procedure to start SSB transmission at the SSB transmission candidate location 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 locations, where n is a positive integer. More specifically, if the LBT procedure to initiate SSB transmission at an SSB transmission candidate location with index i fails, the base station can perform the LBT procedure to initiate SSB transmission at an SSB transmission candidate location with index i+n, but cannot perform the LBT procedure to initiate SSB transmission at a previous SSB transmission candidate location prior to the SSB transmission candidate location with index i+n. Figure 39 shows that the base station performs the LBT procedure for transmitting SSB at each SSB transmission candidate location.

[0207] The base station applies cyclic extensions to the SSB transmission candidate locations and SSB index mappings in units of half the maximum number of SSBs the base station can transmit within a half-radio frame, divided by two. Figures 40 to 42 illustrate, in an embodiment, how cyclic extensions are applied to the SSB transmission candidate locations and SSB index mappings in units of half the maximum number of SSBs the base station can transmit within a half-radio frame, divided by two.

[0208] The base station applies cyclic extensions in units of half the maximum number of SSBs it can transmit within a half-wireless frame, divided by two. Specifically, the SSB transmission candidate location 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 represents the remainder when x is divided by y. Also, L is the maximum number of SSBs that the base station can transmit within a half-wireless frame.

[0210] Furthermore, 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] Furthermore, 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] Furthermore, 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 indices and SSB indices when the maximum number of SSBs that can be transmitted within the DRS transmission window is 8, and a 15kHz subcarrier spacing is used to transmit the SSBs. Therefore, the DRS transmission window contains 10 SSB transmission candidate positions. In Figure 40, an example is given where there are 10 SSB transmission candidate positions in the DRS transmission window, the maximum number of transmittable signals within the DRS transmission window is 8, and the duration of the DRS transmission window is 5ms, but the above embodiment is not limited to such numbers. It also applies when there are P SSB transmission candidate positions in the DRS transmission window and the maximum number of transmittable signals 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 transmitting SSB in units of one slot, i.e., two SSB transmission candidate locations. In this way, the base station performs the LBT procedure for transmitting SSB in units of one slot, i.e., two SSBs per transmission candidate location. If the base station fails to perform the LBT procedure to start SSB transmission at the SSB transmission candidate location with index i, the base station will perform the LBT procedure to start SSB transmission at the SSB transmission candidate location with index i+2, and will not be able to perform the LBT procedure to start SSB transmission at the SSB transmission candidate location 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 locations, where n is a positive integer. More specifically, if the LBT procedure to initiate SSB transmission at an SSB transmission candidate location with index i fails, the base station can perform the LBT procedure to initiate SSB transmission at an SSB transmission candidate location with index i+n, but cannot perform the LBT procedure to initiate SSB transmission at a previous SSB transmission candidate location prior to the SSB transmission candidate location with index i+n.

[0215] Figure 41 shows that the base station performs the LBT procedure for transmitting SSB at each SSB transmission candidate location. Figure 42 shows the case where the maximum number of SSBs that can be transmitted by the base station within the 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 other specific embodiments, the SSB transmission candidate position 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 At this time, x mod y means the remainder when x is divided by y. Also, L is the maximum number of SSBs that can be transmitted by the base station 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] Furthermore, 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, excluding the SSB transmission candidate position index and SSB index mapping, are the same as those described in the embodiments shown in Figures 40 to 42.

[0222] The base station transmits SSBs based on the mapping between SSB transmission candidate locations and SSBs to which the embodiments described in Figures 32 to 42 are applied. Specifically, once the base station successfully accesses a channel at a particular SSB transmission candidate location, it begins transmitting SSBs from that SSB transmission candidate location. At this time, the base station transmits the SSB mapped to each SSB transmission candidate location. In a specific embodiment, the base station transmits the SSB mapped to at least one SSB transmission candidate location at each of the at least one SSB transmission candidate locations located within the time interval from the SSB transmission candidate location where channel access was successfully achieved until the end of SSB transmission. The base station also transmits SSBs within the DRS transmission window and transmits 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 the following based on the DRS: initial access, cell detection, RRM, RLM, and RSSI measurement.

[0223] Through the embodiments described in Figures 33 to 42, the base station can ensure the most uniform probability of transmission for each SSB index. As illustrated in the embodiments shown in Figures 33 to 42, after receiving an SSB, the terminal needs to receive additional timing information. In other words, the same SSB is transmitted at multiple SSB transmission candidate locations within a single DRS transmission window. For example, in Figure 33, the transmission of an SSB with the first SSB index (SSB index #0) is transmitted at an SSB transmission candidate location within the x-th DRS transmission window where the SSB transmission candidate location index value is one of 0, 8, or 16. When a terminal receives an SSB with the first SSB index (SSB index #0), it cannot know whether it was received at the first SSB transmission candidate location index (#0), the ninth SSB transmission candidate location index (#8), or the seventeenth SSB transmission candidate location index (#16). Furthermore, in Figure 42, an SSB with the first SSB index (SSB index #0) is transmitted within the x-th DRS transmission window at either the first SSB transmission candidate position index (#0) or the fifth SSB transmission candidate position index (#4). When a terminal receives an SSB with the first SSB index (SSB index #0), it cannot know whether it was received at the first SSB transmission candidate position index (#0) or the fifth SSB transmission candidate position index (#4). Therefore, without additional timing information, the terminal cannot know at which SSB transmission candidate position the SSB was received. In short, without additional timing information, the terminal cannot set the SSB reception timing based on the SSB transmission candidate position. Therefore, during initial access, the base station instructs the terminal with additional timing information via the PBCH. At this time, the base station transmits a timing offset to the SSB transmission candidate position mapped to the same SSB index to the terminal via the PBCH. Specifically, the base station instructs the timing information with the value offset_SSB=floor(i / L). In this case, i is the index of the SSB transmission candidate location, 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 locations 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 locations 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. The above explanation assumed 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 in one slot, but the embodiments of the present invention are not limited to this.

[0224] Furthermore, in unlicensed bands, terminals and base stations perform channel access in 20MHz units. This is to allow coexistence with other RATs (radio access technologies) that use unlicensed bands, such as Wi-Fi. Specifically, in unlicensed bands, terminals and base stations perform LBT procedures in 20MHz units, and channel transmission is performed according to the results of the LBT procedure. In the case of terminals, random access should be performed to synchronize the uplink with the base station. Specifically, random access is necessary not only when the terminal operates standalone in an unlicensed band, but also when using both unlicensed and licensed carriers. Terminals are either non-collocated with the base station or use a non-ideal backhaul in indoor or low-coverage outdoor environments, and in such cases, a random access procedure is necessary to synchronize the uplink. If a terminal is configured with a bandwidth consisting of multiple 20MHz bandwidths for uplink transmission, the terminal attempts random access preamble transmission using a 20MHz bandwidth that is part of the relevant frequency bandwidth. If the frequency band used for attempting to transmit a random access preamble is busy, the terminal cannot transmit the random access preamble, even if other frequency bands besides the 20MHz band used for transmission are idle. This problem may reduce spectral efficiency. Therefore, a solution is needed to address this issue.

[0225] The base station configures the unlicensed bandwidth part (BWP) to have a 20MHz bandwidth. Specifically, the base station is not permitted to set the bandwidth of the unlicensed bandwidth BWP to a value other than 20MHz. If a frequency bandwidth of 20MHz or more is used, multiple BWPs are configured on the terminal. The base station also configures a PRACH transmission occasion for each BWP. The terminal attempts to transmit PRACH for each BWP. In this case, if the terminal successfully accesses a channel with any one of the BWPs, the terminal transmits PRACH with that BWP. Therefore, in such an embodiment, the terminal can secure a higher PRACH transmission probability than when it attempts to transmit PRACH with any one frequency bandwidth having a 20MHz bandwidth. The base station also configures a PRACH transmission occasion for each 20MHz bandwidth on the terminal. The terminal attempts to transmit PRACH for each 20MHz bandwidth. In this case, if the terminal successfully accesses a channel with any one of the 20MHz bandwidths, the terminal transmits PRACH with that 20MHz bandwidth. Therefore, in such an embodiment, the terminal can secure a higher PRACH transmission probability than when attempting PRACH transmission in any one of the frequency bandwidths having a 20MHz bandwidth.

[0226] However, if a terminal successfully accesses a channel using multiple BWPs or multiple 20MHz bandwidths, the question arises as to whether the terminal can transmit PRACH on all of these BWPs or bandwidths. If a terminal successfully accesses a channel using multiple BWPs or multiple 20MHz bandwidths and transmits PRACH on all of them, transmission collisions between terminals may occur frequently during PRACH occasions. This could lead to contention resolution procedures being performed, potentially increasing system latency. Therefore, even if a terminal has successfully accessed multiple BWPs or 20MHz bandwidths, it will only transmit PRACH on one of them. In this case, the single BWP or 20MHz bandwidth on which PRACH transmission takes place is determined by agreement between the terminal and the base station. Specifically, after channel access, the terminal and base station discuss the priority of the BWP or 20MHz bandwidth to be used for transmission. If a terminal has successfully accessed multiple BWPs or 20MHz bandwidths, the terminal selects one of them according to priority. The terminal transmits the PRACH through the selected BWP. The base station detects the PRACH according to priority. Once the base station has completed PRACH detection for one or more BWPs or one or more 20MHz bandwidths according to priority, the base station does not perform additional PRACH detection. The number of BWPs or 20MHz bandwidths is determined by consultation between the terminal and the base station. Priority is set based on the serving cell index. Specifically, priority is set so that BWPs or 20MHz bandwidths with a large serving cell index have higher priority. In other specific embodiments, priority may be set so that BWPs or 20MHz bandwidths with a low serving cell index have higher priority. Priority is set based on the BWP index or the channel number occupied by the 20MHz bandwidth.In more detail, the priority is set so that BWPs with a larger BWP index have a higher priority. In other specific embodiments, the priority may be set so that BWPs with a lower BWP index have a higher priority.

[0227] In the random access procedure for synchronizing the uplink, the terminal and base station should perform at least four steps. Specifically, the terminal should transmit PRACH to the base station, and the base station should transmit PAR (RACH response) to the terminal. The terminal should transmit PUSCH, i.e., message-3, in response to PAR. The base station should also transmit message-4 to the terminal. In this transmission between the base station and the terminal, both the base station and the terminal should perform channel access procedures. Therefore, there is a high probability of excessive delay occurring in the random access procedure. Consequently, a method is needed to prevent excessive delay in the random access procedure. In particular, a method is needed to prevent excessive delay in RACH transmission.

[0228] The terminal attempts to transmit a PRACH within a PRACH transmission window. Specifically, if the terminal fails to transmit a PRACH in a PRACH occasion set by the base station, the terminal attempts to transmit a PRACH within a PRACH transmission window. In a specific example, if the terminal fails to transmit a PRACH in a PRACH occasion set by the base station, the terminal attempts to access the channel within a PRACH transmission window. If the terminal successfully accesses the channel, the terminal transmits a PRACH to the base station. At this time, the PRACH transmission window is set by the base station. Specifically, the PRACH transmission window is set by the base station via RRC settings. Also, before setting the RRC, the base station provides 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 setting information set via RMSI. In the above explanation, successful channel access is indicated by the success of the LBT procedure.

[0229] When a terminal operates standalone in an unlicensed band, it needs to transmit a physical uplink control channel (PUCCH) to the base station via the unlicensed band. Furthermore, even when a terminal is not co-located with a base station in an indoor or low-coverage outdoor environment, or when using an unideal backhaul, it still needs to transmit the PUCCH. Therefore, a PUCCH transmission method and design for unlicensed bands are necessary. These will be explained with reference to Figures 43 to 45.

[0230] In the case of unlicensed bands, unlike licensed bands, multiple wireless communication devices use them, and therefore regulations on their use apply on a regional or national basis. For example, regulations on fairness, power spectral density (PSD), and occupied channel bandwidth (OCB) apply. Specifically, regulations may apply that PSD should be limited to 10 dBm / MHz or less, and that the transmitting carrier should occupy 80% or more of the nominal bandwidth. In the case of downlink transmission, since the base station transmits to many terminals, occupying 80% of the nominal bandwidth may not be a problem. However, in the case of uplink transmission, since the terminal transmits to the base station, using 80% of the nominal bandwidth can be a problem. Also, since the transmission power should be 10 dBm / MHz or less in unlicensed bands, terminals must use a distributed manner for uplink transmission. Specifically, the PSD limits for each frequency band are stipulated as follows.

[0231] In the -5150-5350MHz range, when transmit power control (TPC) is applied (with TPC): 10 dBM / MHz - When transmission power control is not applied (without TPC) at 5250 - 5350 MHz: 7 dBm / MHz - When transmission power control is not applied (without TPC) at 5150 - 5350 MHz: 10 dBm / MHz - When transmission power control is applied (with TPC) at 5150 - 5250 MHz: 17 dBm / MHz - When transmission power control is applied (with TPC) at 5470 - 5725 MHz: 17 dBm / MHz - When transmission power control is not applied (without TPC) at 5470 - 5725 MHz: 14 dBm / MHz - When 40 dBm ERIP (effective isotropic radiated power) is used at 60 GHz: 13 dBm / MHz ERIP

[0232] Figure 43 is a diagram showing the design of PUSCH used in LTE - LAA. In the LTE - LAA system, an interlaced PUSCH structure with RBs as shown in Figure 43 is used. Through this, the terminal can perform PUSCH transmission while satisfying the regulations regarding PSD and OCB. In the NR system as well, an interlaced RB structure as shown in Figure 43 is used for PUSCH transmission and PUCCH transmission. However, in order to satisfy the above - mentioned regulations, when applying a 15 kHz sub - carrier spacing to a channel with 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. At this time, an interlace is a resource allocation unit, indicating that multiple RBs are located at the same interval in the frequency band.

[0233] PUCCH transmission used in unlicensed bandwidth requires a minimum of 10 RBs per terminal to satisfy PSD and OCB regulations. This limits the number of terminals that can transmit simultaneously compared to licensed bandwidth PUCCH, which uses one RB to multiplex different terminals. In other words, there is a risk of insufficient multiplexing capacity. A PUCCH transmission method and design are needed to address this issue.

[0234] If PUCCH uses an interlaced structure composed of a single RB unit, an orthogonal cover code (OCC) of length N is applied to N consecutive RBs within a single interlace in the frequency domain. If PUCCH uses an interlaced structure composed of RB groups, an OCC of length N is applied between N RB groups. In this case, an RB group represents multiple consecutive RBs in the frequency domain. Through such embodiments, the multiplexing capacity is increased by a factor of N. The base station indicates to the terminal the index of the interlace to be used for PUCCH transmission. In this case, the base station indicates to the terminal the index of the OCC that the terminal will use for PUCCH transmission. Through this, multiple terminals can simultaneously perform PUCCH transmission within an interlace of a single RB unit or RB group unit. Such embodiments are applied to PUCCH formats transmitted on a sequence-based system. Specifically, they are applied to the transmission of PUCCH format 0, PUCCH format 1, PUCCH format 3, and PUCCH format 4 as defined in the NR system. However, this does not apply to the transmission of PUCCH format 2 as defined in the NR system.

[0235] Figure 44 shows an embodiment of the present invention in which multiple terminals transmit a short PUCCH corresponding to PUCCH format 0 using OCC within a single interlace. In Figure 44(a), two terminals transmit a PUCCH through two consecutive RBs within a single interlace using OCC with an OCC length of 2. In Figure 44(b), four terminals transmit a PUCCH through four consecutive RBs within a single interlace using OCC with an OCC length of 4. Although Figure 44 illustrates the transmission of a short PUCCH through a single symbol, the embodiment of the present invention may also be applied to the transmission of a short PUCCH through two symbols.

[0236] Figure 45 shows an embodiment of the present invention in which multiple terminals transmit a long PUCCH corresponding to PUCCH format 1 using OCC within a single interlace. In Figure 45(a), two terminals transmit a PUCCH through two consecutive RBs within a single interlace using OCC with an OCC length of 2. In Figure 45(b), four terminals transmit a PUCCH through four consecutive RBs within a single interlace using OCC with an OCC length of 4. Although Figure 45 illustrates the transmission of a long PUCCH through a single symbol, the embodiment of the present invention may also be applied to the transmission of a long PUCCH through any one of 14 symbols from five symbols.

[0237] When a terminal operates in a transmission environment where a large channel delay spread is not formed and a line of sight is established, significant channel fluctuations may not occur in the frequency domain. In this case, the length of the OCC increases. Therefore, the length of the OCC can be changed depending on the transmission environment.

[0238] In other specific embodiments, when interlacing occurs in units of one or more RB groups, PUCCHs are transmitted between terminals using different patterns within the interlaced PUCCH composed of one or more RB groups. Multiple terminals transmit PUCCHs using different patterns, corresponding to the number of RB groups that make up one interlace. In this case, the sequence used for each of the one or more RB groups within one interlace is a CGS (computer generated sequence). Also, the sequence used for each of the one or more RB groups within one interlace is a ZC (Zadoff-Chu) sequence. Different patterns are applied to each RB group occupied by a single interlace. Different terminals are also assigned to each pattern. 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 receives PUCCHs transmitted by different terminals that have been multiplexed with different patterns within a single interlace.

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

[0240] As an example of how to apply different cyclic shifts to each terminal for each sequence mapped to one or more RB groups within a single interlace, we will explain the case where a single interlace contains 5 RBs. Different patterns are applied to each of the 5 RBs. Different terminals are assigned to each of the 5 patterns. The first terminal uses the CS (cyclic shift) pattern {0, 1, 2, 3, 4} which shifts the CS interval by 1 frame, the second terminal uses the CS pattern {0, 2, 4, 6, 8} which shifts the CS interval by 2 frames, and the third terminal uses the CS pattern {0, 3, 6, 9, 12} which shifts the CS interval by 3 frames. However, if different RBs within a single interlace are set with the same pattern, the PARP (peak-to-average power ratio) / CM (cubic matric) characteristics may deteriorate in an interlace structure where the intervals between RBs and RB groups are constant. In other words, because the same phase is repeatedly assigned to each RB and RB group, the PARP / CM value increases, potentially leading to reduced transmission coverage. Therefore, basically, different CS values ​​are assigned to different RBs within a single interlace. If PUCCH and PUSCH have an interlaced structure, then PRACH also has an interlaced structure for FDM (frequency division multiplexing) with PUCCH or PUSCH. In particular, in the case of PRACH transmission, it is often necessary for multiple terminals to transmit PRACH simultaneously. Therefore, the embodiment described above for PUCCH transmission can also be applied to PRACH transmission.

[0241] Although the methods and systems of the present invention have been described with reference to specific embodiments, some or all of their components or operations can be embodied using a computing system having a general-purpose hardware architecture.

[0242] The above description of the present invention is illustrative, and a person with ordinary skill in the art to which the invention pertains should understand that it can be easily modified into other specific forms without altering the technical idea or essential features of the invention. Therefore, the above-described embodiments should be understood to be illustrative and not limiting in all respects. For example, each component described as a single form may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined manner.

[0243] The scope of the present invention is indicated by the claims described below rather than by the detailed description above, and all modifications or altered forms derived from the meaning and scope of the claims and the concept of equivalents thereto should be interpreted as being included within the scope of the present invention. [Explanation of Symbols]

[0244] 31 Fixed area 32 Macro region 33 coverage 34 coverage 100 devices 110 processors 120 Communication Modules 121 Cellular Communication Interface Card 122 Cellular Communication Interface Card 123 Unlicensed Bandwidth Communication Interface Card 130 memory 140 User Interfaces 150 display units 200 base stations 210 processors 220 Communication Module 221 Cellular Communication Interface Card 222 Cellular Communication Interface Card 223 Unlicensed Bandwidth Communication Interface Card 230 memory

Claims

1. In a base station of a wireless communication system, Communication module and A processor that controls the communication mode, The aforementioned processor, Attempting SSB transmission at candidate SSB (synchronization signal and PBCH block) transmission locations within the DRS (Discovery reference signal) transmission window, If SSB transmission fails at the first SSB transmission candidate position within the first DRS transmission window, the system attempts to perform SSB transmission again at the second SSB transmission candidate position, which is at a later time than the first SSB transmission candidate position within the first DRS transmission window. The DRS transmission window is a time interval during which the base station can transmit SSB. The SSB transmission candidate location indicates the point in time within the DRS transmission window when the base station can start SSB transmission. Base station.

2. The base station transmits an SSB set containing multiple SSBs within a predetermined DRS transmission window. Each of the multiple SSB transmission candidate locations included within the DRS transmission window is mapped to one of the multiple SSBs. The aforementioned processor, If the base station successfully accesses the channel before the first SSB transmission candidate location, it transmits an SSB mapped from the first SSB transmission candidate location to each of the at least one SSB transmission candidate locations within the DRS transmission window, The maximum number of SSBs that the base station can transmit in the first DRS transmission window is limited. The base station according to claim 1.

3. The mapping relationship between the SSB transmission candidate position in the second DRS transmission window and the SSB is different from the mapping relationship between the SSB transmission candidate position in the first DRS transmission window and the SSB. The second DRS transmission window is the DRS transmission window of the period immediately following the first DRS transmission window. The base station according to claim 2.

4. The index of the SSB mapped to each of the multiple SSB transmission candidate positions in the second DRS transmission window is obtained by cyclically wrapping around the index of the SSB mapped to each of the multiple SSB transmission candidate positions in the first DRS transmission window. Each of the aforementioned multiple SSBs is assigned a unique index within the SSB set. The base station according to claim 3.

5. The index of the SSB mapped to each of the multiple SSB transmission candidate positions in the second DRS transmission window is obtained by assigning the indices of the SSB mapped to each of the multiple SSB transmission candidate positions in the first DRS transmission window in reverse order. Each of the aforementioned multiple SSBs is assigned a unique index within the SSB set. The base station according to claim 3.

6. The duration of the DRS transmission window has a fixed length. The aforementioned DRS transmission window is set on the terminal to repeat at regular intervals. The base station according to claim 1.

7. The subcarrier spacing used to transmit the aforementioned SSB is one of 15 kHz, 30 kHz, or 60 kHz. The aforementioned processor, Transmitting multiple SSB signals sequentially over time. The base station according to claim 1.

8. The subcarrier spacing value used to transmit the aforementioned SSB is one of 15 kHz, 30 kHz, or 60 kHz. The aforementioned processor, The SSB transmission terminates before at least one OFDM (orthogonal frequency division multiplicing) symbol at the boundary between the slot where the SSB transmission is performed and the next slot where the SSB transmission is performed. The base station according to claim 1.

9. The aforementioned processor, Channel access is performed for each of the n candidate positions. The aforementioned n is a positive integer. The base station according to claim 1.

10. The above n is 1. The base station according to claim 9.

11. In a wireless communication system terminal, Communication module and A processor that controls the communication mode, The aforementioned processor, Attempting SSB reception within a candidate SSB transmission location within the DRS transmission window, If SSB reception fails at the first SSB transmission candidate position within the first DRS transmission window, an attempt is made to receive SSB at the second SSB transmission candidate position within the first DRS transmission window at a later time than the first SSB transmission candidate position. The DRS transmission window is a time interval during which the base station can transmit SSB. The SSB transmission candidate position indicates the point in time within the DRS transmission window when the terminal can begin receiving SSB signals. Terminal.

12. The aforementioned processor, The system starts receiving the SSB transmission from the first SSB transmission candidate position, and after completing the reception of the SSB transmission, it does not attempt to receive the same SSB within the first DRS transmission window. The terminal according to claim 11.

13. The terminal receives an SSB set containing multiple SSBs within the DRS transmission window. Each of the multiple SSB transmission candidate locations included within the DRS transmission window is mapped to one of the multiple SSBs. The aforementioned processor, At each of the at least one SSB transmission candidate position located within the first DRS transmission window from the first SSB transmission candidate position, the SSB mapped to each of the at least one SSB transmission candidate position is received. The terminal according to claim 11.

14. The mapping relationship between the SSB transmission candidate position in the second DRS transmission window and the SSB is different from the mapping relationship between the SSB transmission candidate position in the first DRS transmission window and the SSB. The second DRS transmission window is the DRS transmission window of the period immediately following the first DRS transmission window. The terminal according to claim 13.

15. The index of the SSB mapped to each of the multiple SSB transmission candidate positions in the second DRS transmission window is obtained by cyclically wrapping around the index of the SSB mapped to each of the multiple SSB transmission candidate positions in the first DRS transmission window. Each of the aforementioned multiple SSBs is assigned a unique index within the SSB set. The terminal according to claim 14.

16. The index of the SSB mapped to each of the multiple SSB transmission candidate positions in the second DRS transmission window is obtained by assigning the indices of the SSB mapped to each of the multiple SSB transmission candidate positions in the first DRS transmission window in reverse order. Each of the aforementioned multiple SSBs is assigned a unique index within the SSB set. The terminal according to claim 14.

17. The duration of the DRS transmission window has a fixed length. The DRS transmission window is set on the terminal so as to repeat at regular intervals. The terminal according to claim 11.

18. The subcarrier spacing value used to transmit the aforementioned SSB is one of 15 kHz, 30 kHz, or 60 kHz. The aforementioned processor, Receive multiple SSB signals sequentially over time. The terminal according to claim 11.

19. The subcarrier spacing used to transmit the aforementioned SSB is one of 15 kHz, 30 kHz, or 60 kHz. The aforementioned processor, The SSB reception ends before at least one OFDM symbol at the boundary between the slot where the SSB reception takes place and the next slot where the SSB reception takes place. The terminal according to claim 11.

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