Method and apparatus for transmitting a signal in a wireless communication system - Patents.com

Abstract

The present invention relates to a wireless communication system, and in particular to a method and a wireless device therefor, the method including the steps of transmitting an SL groupcast transmission to a plurality of terminals, monitoring a feedback signal in a PSFCH opportunity corresponding to the SL groupcast transmission to identify reception response results of the plurality of terminals to the SL groupcast transmission, and setting a CWS to be used for channel connection of the SL transmission after the SL groupcast transmission based on the reception response results of the plurality of terminals, in which if the reception response results of the plurality of terminals include at least one NACK, the CWS is set to a value greater than the previous CWS, and if the reception response results of the plurality of terminals are all considered to be ACK, the CWS is reset to the minimum CWS value.

Description

[Technical field]

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

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

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

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

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

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

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

[0008] Sidelink (SL) is a communication method that sets up a direct link between terminals (User Equipment, UE) and transmits voice or data directly between terminals without going through a base station (Base Station, BS). SL is being considered as one solution to alleviate the burden on base stations caused by the rapidly increasing data traffic.

[0009] V2X (vehicle-to-everything) refers to a communication technology that exchanges information with other vehicles, pedestrians, infrastructure, etc., using wired / wireless communication. V2X can be classified into four types, such as V2V (vehicle-to-vehicle), V2I (vehicle-to-infrastructure), V2N (vehicle-to-network), and V2P (vehicle-to-pedestrian). V2X communication may be provided via a PC5 interface and / or a Uu interface.

[0010] Meanwhile, as more communication devices require larger communication capacity, there is an increasing need for improved mobile broadband communication compared to existing radio access technologies (RATs). For this reason, communication systems that take into account reliability and latency-sensitive services or terminals are being discussed, and next-generation wireless access technologies that take into account improved mobile broadband communication, massive MTC, and ultra-reliable and low latency communication (URLLC) can be called new radio access technology (RAT) or new radio (NR). Vehicle-to-everything (V2X) communication may also be supported in NR.

[0011] Meanwhile, for example, in SL communications associated with services having high or relatively high reliability requirements, SL HARQ feedback operations and / or mechanisms of the terminal may be useful. Summary of the Invention [Problem to be solved by the invention]

[0012] An object of the present invention is to provide a method for efficiently transmitting a signal in a wireless communication system and an apparatus using the same. More specifically, an object of the present invention is to provide a channel access method for efficiently transmitting a signal in a wireless communication system and an apparatus using the same. [Means for solving the problem]

[0013] In one aspect of the present invention, a terminal for use in a wireless communication system includes a communication module and a processor that controls the communication module, wherein the processor is configured to transmit a sidelink (SL) groupcast transmission to a plurality of terminals based on a channel connection procedure using a first contention window size (CWS), monitor a feedback signal at a physical sidelink feedback channel (PSFCH) opportunity corresponding to the SL groupcast transmission to identify reception response results of the plurality of terminals to the SL groupcast transmission, and set a CWS to be used for channel connection of the SL transmission after the SL groupcast transmission based on the reception response results of the plurality of terminals, wherein if the reception response results of the plurality of terminals include at least one negative acknowledgement (NACK), the CWS is set to a value larger than the first CWS, and if all of the reception response results of the plurality of terminals are deemed to be ACK, the CWS is reset to a minimum CWS value.

[0014] In another aspect of the present invention, there is provided a method used by a terminal in a wireless communication system, comprising: a step of transmitting a sidelink (SL) groupcast transmission to a plurality of terminals based on a channel connection procedure using a first contention window size (CWS); a step of monitoring a feedback signal at a physical sidelink feedback channel (PSFCH) opportunity corresponding to the SL groupcast transmission to identify reception response results of the plurality of terminals to the SL groupcast transmission; and a step of setting a CWS to be used for channel connection of the SL transmission after the SL groupcast transmission based on the reception response results of the plurality of terminals, wherein if the reception response results of the plurality of terminals include at least one negative acknowledgement (NACK), the CWS is set to a value larger than the first CWS, and if the reception response results of the plurality of terminals are all considered to be ACK, the CWS is reset to a minimum CWS value.

[0015] Preferably, a case where the reception response results of the multiple terminals include at least one NACK may include a case where a NACK is detected in the PSFCH opportunity.

[0016] Preferably, the case where the reception response results of the multiple terminals are all considered to be ACK may include a case where no NACK is detected in the PSFCH opportunity.

[0017] Preferably, a NACK-only feedback scheme may be configured for the SL groupcast transmission.

[0018] Preferably, the SL groupcast transmission may be transmitted on a physical sidelink shared channel (PSSCH).

[0019] Preferably, the SL transmission may be transmitted on a physical sidelink shared channel (PSSCH).

[0020] Preferably, the terminal may include performing a backoff when connecting a channel for the SL transmission based on a counter value randomly selected within the CWS.

[0021] Preferably, when the CWS is set to a value greater than the first CWS, the CWS of all priority classes may be set to the next greater value than the current CWS among the CWS values ​​allowed for each priority class.

[0022] Preferably, when the CWS is reset to the CWS minimum value, the CWS of all priority classes may be set to the minimum CWS value corresponding to each priority class.

[0023] Preferably, the wireless communication system includes a 3GPP (3rd generation partnership project) NR (new radio) based wireless communication system, and the channel access procedure may include a Type 1 CAP (channel access procedure).

[0024] In yet another aspect of the present invention, there is provided a terminal for use in a wireless communication system, comprising: a communication module; and a processor for controlling the communication module, wherein the processor is configured to transmit a first SL (sidelink) transmission based on a channel connection procedure using a first contention window size (CWS), and to perform a channel connection procedure using the second CWS to attempt a second SL transmission after the first SL transmission, wherein, when a hybrid automatic repeat request acknowledgement (HARQ-ACK) feedback is enabled for the first SL transmission, the second CWS is reset to a minimum value or set to a value larger than the first CWS based on a HARQ-ACK feedback result corresponding to the first SL transmission, and, when the HARQ-ACK feedback is disabled for the first SL transmission, the second CWS is adjusted to the same value as a CWS used for a third SL transmission that is more recent than the first SL.

[0025] Preferably, the enabling / disabling of the HARQ-ACK feedback may be indicated by a sidelink control information (SCI) corresponding to the first SL transmission. Effect of the Invention

[0026] The present invention provides a method for efficiently transmitting a signal in a wireless communication system and an apparatus using the same. The present invention also provides a channel access method for efficiently transmitting a signal in a wireless communication system and an apparatus using the same.

[0027] The effects obtained from the present invention are not limited to those mentioned above, and other effects not mentioned will be clearly understood by those having ordinary skill in the art to which the present invention pertains from the following description. [Brief description of the drawings]

[0028] [Figure 1] FIG. 2 is a diagram illustrating an example of a radio frame structure used in a wireless communication system.

[0029] [Diagram 2] FIG. 1 is a diagram illustrating an example of a downlink (DL) / uplink (UL) slot structure in a wireless communication system.

[0030] [Diagram 3] FIG. 1 is a diagram illustrating physical channels used in a 3GPP system (e.g., NR) and a general signal transmission method using the physical channels.

[0031] [Figure 4] A diagram showing SS / PBCH blocks for initial cell access in a 3GPP NR system.

[0032] [Diagram 5] FIG. 1 illustrates a procedure for control information and control channel transmission in a 3GPP NR system.

[0033] [Figure 6] A diagram showing a CORESET in which a PDCCH is transmitted in a 3GPP NR system.

[0034] [Figure 7] A diagram showing a method for setting a PDCCH search space in a 3GPP NR system.

[0035] [Figure 8] FIG. 8 is a conceptual diagram illustrating carrier aggregation.

[0036] [Figure 9] FIG. 2 is a diagram for explaining terminal carrier communication and multi-carrier communication.

[0037] [Figure 10]A diagram showing an example in which a cross-carrier scheduling technique is applied.

[0038] [Figure 11] FIG. 1 is a diagram showing an NR-U (NR-Unlicensed) service environment.

[0039] [Figure 12] FIG. 1 is a diagram showing an existing communication method (e.g., wireless LAN) that operates in an unlicensed band.

[0040] [Figure 13] A diagram showing a channel access process based on Category 4 LBT.

[0041] [Figure 14] 2 is a block diagram showing the configuration of a terminal and a base station according to an embodiment of the present invention.

[0042] [Figure 15] 1 is a diagram illustrating an example of COT (channel occupancy time) setting and operations based thereon.

[0043] [Figure 16] FIG. 1 is a diagram illustrating a sidelink (SL) communication process.

[0044] [Figure 17] FIG. 2 illustrates a channel connection method according to the present invention. [Figure 18] FIG. 2 illustrates a channel connection method according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] The terms used in this specification are selected as common terms currently widely used as much as possible in consideration of the functions in the present invention, but this may vary depending on the intentions, customs, or the emergence of new technologies of the engineers in this field. In addition, in certain cases, the applicant may arbitrarily select some terms, and in this case, the meaning will be described in the description of the relevant invention. Therefore, it is clear that the terms used in this specification should be interpreted based on the substantial meaning of the terms and the contents of the entire specification, rather than simply the names of the terms.

[0046] Throughout the specification, when a certain component is "connected" to another component, this includes not only "direct connection" but also "electrical connection" through other components in between. Furthermore, when a certain component is "included" in a certain component, this does not mean excluding other components, but further includes other components, unless otherwise specified to the contrary. In addition, limitations such as "more than" or "less than" based on a specific threshold may be appropriately replaced with "more than" or "less than", respectively, depending on the embodiment.

[0047] The following technologies are used in various wireless access systems such as code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access (SC-FDMA), etc. CDMA is implemented in radio technologies such as Universal Terrestrial Radio Access (UTRA) and CDMA2000. TDMA is implemented in radio technologies such as Global System for Mobile communications (GSM), General Packet Radio Service (GPRS), and Enhanced Data Rates for GSM Evolution (EDGE). OFDMA is implemented in radio technologies such as IEEE802.11 (Wi-Fi), IEEE802.16 (WiMAX), IEEE802-20, Evolved UTRA (E-UTRA), etc. UTRA is part of the Universal Mobile Telecommunication System (UMTS). 3GPP LTE (Long term evolution) is a part of E-UMTS (Evolved UMTS) that uses E-UTRA, and LTE-A (Advanced) is an evolved version of 3GPP LTE. 3GPP NR is a system designed separately from LTE / LTE-A, and is a system for supporting eMBB (enhanced Mobile BroadBand), URLLC (Ultra-Reliable and Low Latency Communication), and mMTC (massive Machine Type Communication) services, which are requirements of IMT-2020. For clarity of explanation, the following description will focus on 3GPP NR, but the technical idea of ​​the present invention is not limited thereto.

[0048] Unless otherwise specified in this specification, the base station may include a gNB (next generation node B) defined in 3GPP NR. Furthermore, unless otherwise specified, the terminal may include a UE (user equipment). Hereinafter, in order to facilitate understanding of the description, each content will be described as an individual embodiment, but each embodiment may be used in combination with each other. In this disclosure, the configuration of the terminal may mean the configuration by the base station. Specifically, the base station may transmit a channel or a signal to the terminal to configure the operation of the terminal or the value of a parameter used in the wireless communication system.

[0049] FIG. 1 is a diagram illustrating an example of a radio frame structure used in a wireless communication system.

[0050] Referring to FIG. 1, a radio frame used in a 3GPP NR system has a length of 10 ms (ΔfmaxNf / 100)*Tc). The radio frame also consists of 10 equally sized subframes (SF), where Δfmax=480*103 Hz, Nf=4096, Tc=1 / (Δfref*Nf,ref), Δfref=15*103 Hz, and Nf,ref=2048. The 10 subframes in one frame are numbered from 0 to 9. Each subframe has a length of 1 ms and consists of one or more slots depending on the subcarrier spacing. More specifically, the subcarrier spacing that can be used in a 3GPP NR system is 15*2μkHz. μ is a subcarrier spacing configuration factor, and has a value of μ=0 to 4. That is, 15 kHz, 30 kHz, 60 kHz, 120 kHz, or 240 kHz is used as the subcarrier spacing. A 1 ms long subframe consists of 2μ slots. In this case, the length of each slot is 2-μms. The 2μ slots in one subframe are numbered from 0 to 2μ-1. Also, the slots in one radio frame are numbered from 0 to 10*2μ-1. Time resources are divided by at least one of the radio frame number (also called radio frame index), subframe number (also called subframe index), and slot number (or slot index).

[0051] FIG2 illustrates an example of a downlink (DL) / uplink (UL) slot structure in a wireless communication system, and in particular, illustrates a resource grid structure in a 3GPP NR system.

[0052] There is one resource grid per antenna port. Referring to FIG. 2, a slot includes a plurality of OFDM symbols in the time domain and a plurality of resource blocks (RBs) in the frequency domain. An OFDM symbol also means one symbol period. Unless otherwise specified, an OFDM symbol is simply referred to as a symbol. In the following description, a symbol includes an OFDM symbol, an SC-FDMA symbol, a DFTs-OFDM symbol, and the like. Referring to FIG. 2, a signal transmitted from each slot is represented by a resource grid consisting of Nsize, μgrid, x*NRBSC subcarriers, and Nslotsymb OFDM symbols. Here, x=DL for a downlink resource grid, and x=UL for an uplink resource grid. Nsize, μgrid, and x indicate the number of resource blocks (RBs) according to a subcarrier spacing factor μ (x is DL or UL), and Nslotsymb indicates the number of OFDM symbols in a slot. NRBSC is the number of subcarriers constituting one RB, and NRBSC=12. Depending on the multiple access scheme, the OFDM symbol is called a cyclic prefix OFDM symbol (CP-OFDM) symbol or a discrete Fourier transform spread OFDM symbol (DFT-S-OFDM).

[0053] The number of OFDM symbols included in one slot may vary depending on the length of a cyclic prefix (CP). For example, a normal CP includes 14 OFDM symbols in one slot, while an extended CP includes 12 OFDM symbols in one slot. In a specific embodiment, the extended CP is used only at a subcarrier interval of 60 kHz. For convenience of explanation, FIG. 2 illustrates a case where one slot includes 14 OFDM symbols, but the embodiment of the present invention is also applied to slots having other numbers of OFDM symbols in the same manner. Referring to FIG. 2, each OFDM symbol includes Nsize, μgrid, and x*NRBSC subcarriers in the frequency domain. The types of subcarriers are divided into data subcarriers for transmitting data, reference signal subcarriers for transmitting a reference signal, and guard bands. The carrier frequency is also called a center frequency (fc).

[0054] One RB is defined by NRBSC (e.g., 12) consecutive subcarriers in the frequency domain. Incidentally, a resource consisting of one OFDM symbol and one subcarrier is called a resource element (RE) or tone. Thus, one RB consists of Nslotsymb*NRBSC resource elements. Each resource element in the resource grid is uniquely defined by an index pair (k, l) in one slot. k is an index ranging from 0 to Nsize,μgrid,x*NRBSC-1 in the frequency domain, and l is an index ranging from 0 to Nslotsymb-1 in the time domain.

[0055] In order for a terminal to receive a signal from a base station or transmit a base station signal, the time / frequency synchronization of the terminal should be aligned with the time / frequency synchronization of the base station, because if the base station and the terminal are not synchronized, the terminal cannot determine the time and frequency parameters required to demodulate DL signals and transmit UL signals at the correct time.

[0056] Each symbol of a radio frame operating in time division duplex (TDD) or unpaired spectrum consists of at least one of downlink symbol (DL symbol), uplink symbol (UL symbol) or flexible symbol. A radio frame operating in frequency division duplex (FDD) or paired spectrum with a downlink carrier consists of downlink symbols or flexible symbols, and a radio frame operating with an uplink carrier consists of uplink symbols or flexible symbols. A downlink symbol allows downlink transmission but not uplink transmission, and an uplink symbol allows uplink transmission but not downlink transmission. Whether a flexible symbol is used in the downlink or uplink is determined depending on the signal.

[0057] Information on the type of each symbol, i.e., information indicating any one of the downlink symbol, the uplink symbol, and the flexible symbol, is composed of a cell-specific (cell-specific or common) RRC signal. In addition, the information on the type of each symbol is additionally composed of a specific terminal (UE-specific or dedicated) RRC signal. The base station uses the cell-specific RRC signal to inform i) the period of the cell-specific slot configuration, ii) the number of slots having only downlink symbols from the beginning of the period of the cell-specific slot configuration, iii) the number of downlink symbols from the first symbol in the slot immediately after the slot having only downlink symbols, iv) the number of slots having only uplink symbols from the end of the period of the cell-specific slot configuration, and v) the number of uplink symbols from the last symbol in the slot immediately before the slot having only uplink symbols. Here, a symbol that is not configured as either an uplink symbol or a downlink symbol is a flexible symbol.

[0058] If the information regarding the symbol type consists of the UE-specific RRC signal, the base station signals, via the cell-specific RRC signal, whether the flexible symbol is a downlink symbol or an uplink symbol. At this time, the UE-specific RRC signal cannot change a downlink symbol or an uplink symbol, which consists of the cell-specific RRC signal, into another symbol type. The UE-specific RRC signal signals, for each slot, the number of downlink symbols among the Nslotsymb symbols of the slot and the number of uplink symbols among the Nslotsymb symbols of the slot. At this time, the downlink symbols of the slot are continuously configured from the first symbol to the i-th symbol of the slot. Also, the uplink symbols of the slot are continuously configured from the j-th symbol to the last symbol of the slot (where i < j). In a slot, a symbol that is not configured as either an uplink symbol or a downlink symbol is a flexible symbol.

[0059] The type of symbol configured by the RRC signal as described above can be called a semi-static DL / UL configuration. In the semi-static DL / UL configuration configured by the RRC signal previously, the flexible symbol may be indicated as a downlink symbol, an uplink symbol, or a flexible symbol by the dynamic SFI (slot format information) transmitted on the physical downlink control channel (PDCCH). At this time, a downlink symbol or an uplink symbol configured by the RRC signal is not changed to another symbol type. Table 1 exemplifies the dynamic SFI that the base station can indicate to the UE.

[0060]

Table 1

[0061] In Table 1, D represents a downlink symbol, U represents an uplink symbol, and X represents a flexible symbol. As shown in Table 1, up to two DL / UL switchings may be allowed in one slot.

[0062] FIG. 3 is a diagram illustrating physical channels used in a 3GPP system (e.g., NR) and a general signal transmission method using the physical channels.

[0063] When a terminal is powered on or enters a new cell, the terminal performs an initial cell search operation S101. More specifically, the terminal synchronizes with a base station in the initial cell search. To this end, the terminal receives a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) from the base station to synchronize with the base station and obtain information such as a cell index. Next, the terminal receives a physical broadcast channel from the base station to obtain broadcast information within the cell.

[0064] After completing the initial cell search, the terminal receives a physical downlink shared channel (PDSCH) through a physical downlink control channel (PDCCH) and information carried on the PDCCH to obtain more detailed system information than the system information obtained through the initial cell search (S102). Here, the system information transmitted to the terminal is cell-common system information for the terminal to operate correctly in a physical layer in Radio Resource Control (RRC), and is called remaining system information or system information block (SIB) 1.

[0065] When a terminal first connects to a base station or when there are no radio resources for signal transmission (when the terminal is in RRC_IDLE mode), the terminal can perform a random access procedure with respect to the base station (steps S103 to S106). First, the terminal transmits a preamble on a physical random access channel (PRACH) (S103) and can receive a response message for the preamble from the base station on a PDCCH and a corresponding PDSCH (S104). If the terminal receives a valid random access response message, the terminal transmits data including its own identifier, etc. to the base station on a physical uplink shared channel (PUSCH) indicated by an uplink grant transmitted from the base station on the PDCCH (S105). Next, the terminal waits to receive a PDCCH as an instruction from the base station to resolve collisions. If the terminal successfully receives a PDCCH with its own identifier (S106), the random access procedure ends. During the random access procedure, the terminal may obtain terminal-specific system information required for the terminal to operate correctly in the physical layer of the RRC layer. If the terminal obtains the terminal-specific system information in the RRC layer, the terminal enters the RRC connected mode (RRC_CONNECTED mode).

[0066] The RRC layer is used to generate and manage messages for control between a terminal and a radio access network (RAN). More specifically, the base station and terminal can broadcast cell system information required for all terminals in the cell, manage the delivery of paging messages, manage mobility and handover, report measurements of terminals and control related thereto, and manage and store terminal capabilities in the RRC layer. In general, the update of signals delivered in the RRC layer (hereinafter, RRC signals) is longer than the transmission and reception period (i.e., transmission time interval, TTI) in the physical layer, so that the RRC settings can be maintained unchanged for a long period.

[0067] After the above-mentioned procedure, the terminal receives PDCCH / PDSCH S107 and transmits physical uplink shared channel (PUSCH) / physical uplink control channel (PUCCH) S108 as a general uplink / downlink signal transmission procedure. In particular, the terminal receives downlink control information (DCI) via PDCCH. DCI includes control information such as resource allocation information for the terminal. In addition, the format of DCI may differ depending on the purpose of use. Uplink control information (UCI) transmitted by the terminal to the base station via uplink includes downlink / uplink ACK / NACK signals, channel quality indicator (CQI), precoding matrix index (PMI), rank indicator (RI), etc. Here, CQI, PMI, and RI are included in channel state information (CSI). In the case of a 3GPP NR system, the terminal transmits control information such as the above-mentioned HARQ-ACK and CSI via PUSCH and / or PUCCH.

[0068] FIG. 4 is a diagram illustrating SS / PBCH blocks for initial cell access in a 3GPP NR system.

[0069] When a terminal is powered on or attempts to access a new cell, it acquires time and frequency synchronization with the cell and performs an initial cell search process. The terminal detects the physical cell identity (NcellID) of the cell during the cell search process. To this end, the terminal receives synchronization signals, such as a primary synchronization signal (PSS) and a secondary synchronization signal (SSS), from the base station to synchronize with the base station. At this time, the terminal obtains information such as a cell identity (ID).

[0070] With reference to FIG. 4(a), the synchronization signal (SS) will be described in more detail. The synchronization signal is divided into PSS and SSS. The PSS is used to obtain time domain synchronization and / or frequency domain synchronization such as OFDM symbol synchronization and slot synchronization. The SSS is used to obtain frame synchronization and cell group ID. With reference to FIG. 4(a) and Table 1, the SS / PBCH block consists of 20 consecutive RBs (=240 subcarriers) on the frequency axis and 4 consecutive OFDM symbols on the time axis. In this case, in the SS / PBCH block, the PSS is transmitted in the first OFDM symbol and the SSS is transmitted in the third OFDM symbol via the 56th to 18th subcarriers. Here, the lowest subcarrier index of the SS / PBCH block is numbered from 0. In the first OFDM symbol in which the PSS is transmitted, the base station does not transmit signals via the remaining subcarriers, i.e., the 0th to 55th and 183rd to 239th subcarriers. In addition, in the third OFDM symbol in which the SSS is transmitted, the base station does not transmit signals via subcarriers 48 to 55 and 183 to 19. The base station transmits a physical broadcast channel (PBCH) via the remaining REs in the SS / PBCH block excluding the above-mentioned signals.

[0071] [Table 2]

[0072] The SS is grouped into 336 physical-layer cell-identifier groups, each of which includes three unique identifiers, so that a total of 1008 unique physical layer cell IDs are obtained through a combination of three PSSs and SSSs, more specifically, each physical layer cell ID is part of only one physical-layer cell-identifier group. Thus, a physical layer cell ID NcellID=3N(1)ID+N(2)ID is uniquely defined by an index N(1)ID ranging from 0 to 335 indicating a physical-layer cell-identifier group and an index N(2)ID ranging from 0 to 2 indicating a physical-layer identifier in the physical-layer cell-identifier group. The UE detects the PSS and identifies one of the three unique physical-layer identifiers. The UE also detects the SSS and identifies one of the 336 physical layer cell IDs associated with the physical-layer identifier. In this case, the sequence dPSS(n) of the PSS is as follows:

[0073]

number

[0074] where x(i+7)=(x(i+4)+x(i)) mod 2,

[0075] Given: [x(6)x(5)x(4)x(3)x(2)x(1)x(0)]=[1110110].

[0076] Also, the SSS sequence dSSS(n) is as follows:

[0077]

number

[0078] Here, x0(i+7)=(x0(i+4)+x0(i))mod 2 x1(i+7)=(x1(i+1)+x1(i))mod 2,

[0079] Given that [x0(6)x0(5)x0(4)x0(3)x0(2)x0(1) 0(0)]=[0000001], [x1(6)x1(5)x1(4)x1(3)x1(2)x1(1)x1(0)]=[0000001].

[0080] A radio frame with a length of 10 ms is divided into two half-frames with a length of 5 ms. The slots in each half-frame in which the SS / PBCH block is transmitted will be described with reference to FIG. 4(b). The slots in which the SS / PBCH block is transmitted are any one of cases A, B, C, D, and E. In case A, the subcarrier spacing is 15 kHz, and the start point of the SS / PBCH block is the {2, 8}+14*nth symbol. In this case, n=0, 1 for carrier frequencies below 3 GHz. Also, n=0, 1, 2, 3 for carrier frequencies above 3 GHz and below 6 GHz. In case B, the subcarrier spacing is 30 kHz, and the start point of the SS / PBCH block is the {4, 8, 16, 20}+28*nth symbol. In this case, n=0 for carrier frequencies below 3 GHz. Also, n=0, 1 for carrier frequencies above 3 GHz and below 6 GHz. In case C, the subcarrier spacing is 30 kHz and the start of the SS / PBCH block is {2, 8}+14*n symbols, where n=0, 1 for carrier frequencies below 3 GHz. Also, n=0, 1, 2, 3 for carrier frequencies above 3 GHz and below 6 GHz. In case D, the subcarrier spacing is 120 kHz and the start of the SS / PBCH block is {4, 8, 16, 20}+28*n symbols, where n=0, 1, 2, 3, 5, 6, 7, 8, 10, 11, 12, 13, 15, 16, 17, 18 for carrier frequencies above 6 GHz. In case E, the subcarrier spacing is 240 kHz and the start of the SS / PBCH block is {8, 12, 16, 20, 32, 36, 40, 44}+56*n symbols. In this case, n=0, 1, 2, 3, 5, 6, 7, 8 for carrier frequencies of 6 GHz or higher.

[0081] Figure 5 is a diagram showing a procedure for transmitting control information and a control channel in a 3GPP NR system. Referring to Figure 5(a), a base station adds a cyclic redundancy check (CRC) masked (e.g., XORed) with a radio network temporary identifier (RNTI) to control information (e.g., DCI) S202. The base station scrambles the CRC with an RNTI value determined according to the purpose / target of each control information. The common RNTI used by one or more terminals includes at least one of a system information RNTI (SI-RNTI), a paging RNTI (P-RNTI), a random access RNTI (RA-RNTI), and a transmit power control RNTI (TPC-RNTI). Also, the UE-specific RNTI includes at least one of C-RNTI (cell temporary RNTI), CS-RNTI, or MCS-C-RNTI. Next, the base station performs channel encoding (e.g., polar coding) S204, and then performs rate-matching according to the amount of resource(s) used for PDCCH transmission S206. Next, the base station multiplexes DCI(s) based on a PDCCH structure based on a control channel element (CCE) S208. In addition, the base station applies additional processes such as scrambling, modulation (e.g., QPSK), and interleaving to the multiplexed DCI(s) S210, and maps them to resources to be transmitted. A CCE is a basic resource unit for a PDCCH, and one CCE consists of a plurality of (e.g., 6) resource element groups (REGs). One REG consists of a plurality of (e.g., 12) REs. The number of CCEs used for one PDCCH is defined as an aggregation level. 3GPP NR systems use aggregation levels of 1, 2, 4, 8, or 16.FIG. 5(b) is a diagram relating to CCE aggregation levels and PDCCH multiplexing, showing the types of CCE aggregation levels used for one PDCCH and the CCE(s) transmitted in the control region accordingly.

[0082] FIG. 6 is a diagram showing a CORESET in which a PDCCH is transmitted in a 3GPP NR system.

[0083] A CORESET is a time-frequency resource in which a PDCCH, which is a control signal for a terminal, is transmitted. A search space, which will be described later, is mapped to one CORESET. Thus, a terminal does not monitor all frequency bands to receive a PDCCH, but monitors a time-frequency region designated as a CORESET and decodes a PDCCH mapped to the CORESET. A base station configures one or more CORESETs for a terminal for each cell. A CORESET is made up of up to three consecutive symbols on the time axis. Also, a CORESET is made up of six units of consecutive PRBs on the frequency axis. In the embodiment of FIG. 5, CORESET#1 is made up of consecutive PRBs, and CORESET#2 and CORESET#3 are made up of discontinuous PRBs. A CORESET may be located at any symbol in a slot. For example, in the embodiment of FIG. 5, CORESET#1 starts from the first symbol of a slot, CORESET#2 starts from the fifth symbol of a slot, and CORESET#9 starts from the ninth symbol of a slot.

[0084] FIG. 7 is a diagram illustrating a method for setting a PDCCH search space in a 3GPP NR system.

[0085] In order to transmit a PDCCH to a terminal, at least one or more search spaces exist in each CORESET. In an embodiment of the present invention, the search space is a set of all time-frequency resources (hereinafter, PDCCH candidates) in which the PDCCH of the terminal is transmitted. The search space includes a common search space that 3GPP NR terminals should commonly search, and a terminal-specific or UE-specific search space that a specific terminal should search. In the common search space, all terminals in a cell belonging to the same base station monitor a PDCCH that is set to be commonly searched. In addition, the terminal-specific search space is set for each terminal so that the PDCCH allocated to each terminal is monitored at a position of the search space that differs from one another according to the terminal. In the case of the terminal-specific search space, the search spaces between terminals may be partially overlapped due to the limited control region to which the PDCCH is allocated. Monitoring the PDCCH includes blind decoding the PDCCH candidates in the search space. If blind decoding is successful, it is expressed as the PDCCH being (successfully) detected / received, and if blind decoding is unsuccessful, it is expressed as the PDCCH being undetected / not received or not successfully detected / received.

[0086] For convenience of explanation, a PDCCH scrambled with a group common (GC) RNTI already known by one or more terminals to transmit downlink control information to one or more terminals is referred to as a group common (GC) PDCCH or a common PDCCH. Also, a PDCCH scrambled with a terminal-specific RNTI already known by a specific terminal to transmit uplink scheduling information or downlink scheduling information to one specific terminal is referred to as a terminal-specific PDCCH. The common PDCCH is included in a common search space, and the terminal-specific PDCCH is included in a common search space or a terminal-specific PDCCH.

[0087] The base station notifies each terminal or terminal group of information on resource allocation of transmission channels PCH (paging channel) and DL-SCH (downlink-shared channel) (i.e., DL Grant) or information on UL-SCH resource allocation and hybrid automatic repeat request (HARQ) (i.e., UL Grant) via the PDCCH. 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. In addition, the terminal receives data excluding specific control information or specific service data via the PDSCH.

[0088] The base station transmits information on which terminal (one or more terminals) the PDSCH data is transmitted to and how the terminal should receive and decode the PDSCH data by including it in the PDCCH. For example, assume that the DCI transmitted through a specific PDCCH is CRC masked with RNTI "A", the DCI indicates that the PDSCH is allocated to radio resource "B" (e.g., frequency position) and indicates transmission format information "C" (e.g., transmission block size, modulation method, coding information, etc.). The terminal monitors the PDCCH using its own RNTI information. In this case, if there is a terminal that blind decodes the PDCCH using RNTI "A", the terminal receives the PDCCH and receives the PDSCH indicated by "B" and "C" through the received PDCCH information.

[0089] Table 3 shows one embodiment of a PUCCH used in a wireless communication system.

[0090] [Table 3]

[0091] The PUCCH is used to transmit the following uplink control information (UCI):

[0092] -SR (Scheduling Request): Information used to request uplink UL-SCH resources.

[0093] -HARQ-ACK: a response to a PDCCH (indicating DL SPS release) and / or a response to an uplink transport block (TB) on a PDSCH. HARQ-ACK indicates whether information transmitted via a PDCCH or a PDSCH has been received. HARQ-ACK responses include a positive ACK (simply, ACK), a negative ACK (hereinafter, NACK), a discontinuous transmission (DTX), or a NACK / DTX. Here, the term HARQ-ACK is used interchangeably with HARQ-ACK / NACK and ACK / NACK. In general, an ACK is represented by a bit value of 1, and a NACK is represented by a bit value of 0.

[0094] -CSI: Feedback information for a downlink channel. It is generated by a terminal based on a CSI-RS (Reference Signal) transmitted by a base station. MIMO (multiple input multiple output)-related feedback information includes RI and PMI. CSI is divided into CSI part 1 and CSI part 2 according to the information indicated by CSI.

[0095] In the 3GPP NR system, five PUCCH formats are used to support various service scenarios and various channel environments and frame structures.

[0096] PUCCH format 0 is a format that transmits 1-bit or 2-bit HARQ-ACK information or SR. PUCCH format 0 is transmitted through one or two OFDM symbols on the time axis and one RB on the frequency axis. If PUCCH format 0 is transmitted with two OFDM symbols, the same sequence is transmitted with different RBs for the two symbols. Through this, the terminal obtains frequency diversity gain. More specifically, the terminal determines a cyclic shift value mcs according to the Mbit bit UCI (Mbit=1 or 2), and transmits a sequence obtained by cyclically shifting a base sequence of length 12 by the determined value mcs, by mapping the sequence to 12 REs of one OFDM symbol and one PRB. If the number of cyclic shifts available to the terminal is 12 and Mbit=1, 1-bit UCI 0 and 1 are represented by sequences corresponding to two cyclic shifts with a cyclic shift value difference of 6. Also, if Mbit=2, then 2-bit UCI 00, 01, 11, 10 is represented by a sequence corresponding to four cyclic shifts with a difference between the cyclic shift values ​​being three.

[0097] PUCCH format 1 transmits 1-bit or 2-bit HARQ-ACK information or SR. PUCCH format 1 is transmitted through continuous OFDM symbols on the time axis and one PRB on the frequency axis. Here, the number of OFDM symbols occupied by PUCCH format 1 is one of 4 to 14. More specifically, UCI with Mbit=1 is modulated by BPSK. The terminal modulates UCI with Mbit=2 by quadrature phase shift keying (QPSK). A signal is obtained by multiplying the modulated complex valued symbol d(0) by a sequence of length 12. The terminal transmits the obtained signal by spreading it by a time-axis orthogonal cover code (OCC) on even-numbered OFDM symbols to which PUCCH format 1 is assigned. In PUCCH format 1, the maximum number of different terminals multiplexed in the same RB can be determined according to the length of the OCC used. In odd-numbered OFDM symbols of PUCCH format 1, a demodulation reference signal (DMRS) is spread by OCC and mapped.

[0098] PUCCH format 2 transmits UCI exceeding 2 bits. PUCCH format 2 is transmitted through one or two OFDM symbols on the time axis and one or more RBs on the frequency axis. If PUCCH format 2 is transmitted through two OFDM symbols, the same sequence is transmitted through two OFDM symbols in different RBs. In this way, the terminal obtains frequency diversity gain. More specifically, Mbit UCI (Mbit>2) is bit-level scrambled and QPSK modulated to be mapped to RBs of one or two OFDM symbol(s). Here, the number of RBs is one of 1 to 16.

[0099] PUCCH format 3 or PUCCH format 4 transmits UCI exceeding 2 bits. PUCCH format 3 or PUCCH format 4 is transmitted through continuous OFDM symbols on the time axis and one PRB on the frequency axis. The number of OFDM symbols occupied by PUCCH format 3 or PUCCH format 4 is one of 4 to 14. In particular, the terminal modulates Mbit UCI (Mbit>2) with π / 2-BPSK (Binary Phase Shift Keying) or QPSK to generate complex symbols d(0) to d(Msymb-1). Here, Msymb=Mbit when π / 2-BPSK is used, and Msymb=Mbit / 2 when QPSK is used. The terminal does not apply block-wise spreading to PUCCH format 3. However, the terminal may apply block-wise spreading to one RB (i.e., 12 subcarriers) using PreDFT-OCC of length -12 so that PUCCH format 4 has a multiplexing capacity of 2 or 4. The terminal transmit precoding (or DFT-precoding) the spread signal, maps it to each RE, and transmits the spread signal.

[0100] In this case, the number of RBs occupied by PUCCH format 2, PUCCH format 3, or PUCCH format 4 is determined according to the length of UCI transmitted by the terminal and the maximum code rate. If the terminal uses PUCCH format 2, the terminal transmits both HARQ-ACK information and CSI information via PUCCH. If the number of RBs that the terminal can transmit is greater than the maximum number of RBs that PUCCH format 2, PUCCH format 3, or PUCCH format 4 can use, the terminal does not transmit some UCI information according to the priority of the UCI information, and transmits only the remaining UCI information.

[0101] PUCCH format 1, PUCCH format 3, or PUCCH format 4 is configured via RRC signaling to indicate frequency hopping within a slot. When frequency hopping is configured, the index of the RB to be frequency hopped is configured via RRC signaling. If PUCCH format 1, PUCCH format 3, or PUCCH format 4 is transmitted across N OFDM symbols in the time axis, the first hop has floor(N / 2) OFDM symbols and the second hop has ceil(N / 2) OFDM symbols.

[0102] PUCCH format 1, PUCCH format 3, or PUCCH format 4 is configured to be repeatedly transmitted in multiple slots. In this case, the number K of slots in which the PUCCH is repeatedly transmitted is configured by an RRC signal. The repeatedly transmitted PUCCH should start from the same OFDM symbol position in each slot and have the same length. If the RRC signal indicates that any one of the OFDM symbols in a slot in which the terminal should transmit the PUCCH is a DL symbol, the terminal does not transmit the PUCCH from that slot, but postpones it to the next slot for transmission.

[0103] Meanwhile, in a 3GPP NR system, a terminal transmits and receives using a bandwidth smaller than or equal to the bandwidth of a carrier (or cell). To this end, the terminal is configured with a BWP (bandwidth part) consisting of a continuous bandwidth that is a part of the carrier bandwidth. A terminal operating according to TDD or in an unpaired spectrum is configured with up to four DL / UL BWP pairs for one carrier (or cell). The terminal also activates one DL / UL BWP pair. A terminal operating according to FDD or in a paired spectrum is configured with up to four DL BWPs for a downlink carrier (or cell) and up to four UL BWPs for an uplink carrier (or cell). The terminal activates one DL BWP and one UL BWP for each carrier (or cell). The terminal may not receive or transmit from time-frequency resources other than the activated BWP. The activated BWP is called an active BWP.

[0104] The base station refers to an activated BWP among the BWPs configured for the terminal as a DCI. The BWP indicated by the DCI is activated, and the other configured BWP(s) is deactivated. In a carrier (or cell) operating in TDD, the base station includes a BPI (bandwidth part indicator) indicating the activated BWP in the DCI for scheduling the PDSCH or PUSCH to change the DL / UL BWP pair of the terminal. The terminal receives the DCI for scheduling the PDSCH or PUSCH and identifies the activated DL / UL BWP pair based on the BPI. In the case of a downlink carrier (or cell) operating in FDD, the base station includes a BPI indicating the activated BWP in the DCI for scheduling the PDSCH to change the DL BWP of the terminal. In the case of an uplink carrier (or cell) operating in FDD, the base station includes a BPI indicating the activated BWP in the DCI for scheduling the PDSCH to change the UL BWP of the terminal.

[0105] FIG. 8 is a conceptual diagram illustrating carrier aggregation.

[0106] Carrier aggregation refers to a method in which a terminal uses multiple frequency blocks or (logical) cells consisting of uplink resources (or component carriers) and / or downlink resources (or component carriers) in one large logical frequency band in order for a wireless communication system to use a wider frequency band. For convenience of explanation, the term "component carrier" will be used hereinafter.

[0107] Referring to FIG. 8, as an example of a 3GPP NR system, the entire system band includes up to 16 component carriers, and each component carrier has a bandwidth of up to 400 MHz. The component carrier includes one or more physically contiguous subcarriers. Although each component carrier is shown to have the same bandwidth in FIG. 8, this is merely an example, and each component carrier may have a different bandwidth. Also, although each component carrier is shown to be adjacent to each other on the frequency axis, the drawing is a logical concept, and each component carrier may be physically adjacent to each other or separated from each other.

[0108] A different center frequency is used in each component carrier. Also, a common center frequency is used in physically adjacent component carriers. In the embodiment of FIG. 8, if it is assumed that all component carriers are physically adjacent, center frequency A is used in all component carriers. Also, if it is assumed that each component carrier is not physically adjacent, center frequency A and center frequency B are used in each component carrier.

[0109] When the entire system band is expanded by carrier aggregation, the frequency band used for communication with each terminal is defined in component carrier units. Terminal A uses the entire system band of 100 MHz and communicates using all five component carriers. Terminals B1 to B5 use only a 20 MHz bandwidth and communicate using one component carrier. Terminals C1 and C2 use only a 40 MHz bandwidth and communicate using two component carriers each. The two component carriers may be logically / physically adjacent or not adjacent. The embodiment of FIG. 8 shows a case where terminal C1 uses two non-adjacent component carriers and terminal C2 uses two adjacent component carriers.

[0110] 9 is a diagram for explaining terminal carrier communication and multi-carrier communication. In particular, FIG. 9(a) shows a subframe structure of a single carrier, and FIG. 9(b) shows a subframe structure of a multi-carrier.

[0111] Referring to FIG. 9(a), a general wireless communication system transmits or receives data through one DL band and one corresponding UL band in the FDD mode. In another specific embodiment, in the TDD mode, the wireless communication system divides a wireless frame into an uplink time unit and a downlink time unit in the time domain, and transmits or receives data through the uplink / downlink time unit. Referring to FIG. 9(b), three 20 MHz component carriers (CCs) are aggregated in the UL and DL, respectively, to support a bandwidth of 60 MHz. The CCs are adjacent or non-adjacent to each other in the frequency domain. Although FIG. 9(b) illustrates a case in which the bandwidth of the UL CC and the bandwidth of the DL CC are the same and symmetrical for convenience, the bandwidth of each CC may be determined independently. Also, asymmetric carrier aggregation in which the number of UL CCs and the number of DL CCs are different is possible. The DL / UL CC allocated / configured to a specific terminal through RRC is called a serving DL / UL CC of the specific terminal.

[0112] The base station activates some or all of the serving CCs of the terminal, or deactivates some of the CCs to communicate with the terminal. The base station may change the CCs to be activated / deactivated, or may change the number of CCs to be activated / deactivated. When the base station allocates CCs available to the terminal in a cell-specific or terminal-specific manner, at least one of the CCs once allocated may not be deactivated unless the CC allocation for the terminal is completely reconfigured or the terminal performs a handover. A CC that is not deactivated by the terminal is called a primary CC (PCC) or PCell (primary cell), and a CC that the base station can activate / deactivate freely is called a secondary CC (SCC) or SCell (secondary cell).

[0113] Meanwhile, 3GPP NR uses the concept of a cell to manage radio resources. A cell is defined as a combination of downlink and uplink resources, i.e., a combination of DL CC and UL CC. A cell consists of DL resources alone or a combination of DL and UL resources. If carrier aggregation is supported, the linkage between the carrier frequency of DL resources (or DL ​​CC) and the carrier frequency of UL resources (or UL CC) is indicated by system information. Carrier frequency means the center frequency of each cell or CC. A cell corresponding to a PCC is called a PCell, and a cell corresponding to a SCC is called a SCell. A carrier corresponding to a PCell in the downlink is a DL PCC, and a carrier corresponding to a PCell in the uplink is a UL PCC. Similarly, a carrier corresponding to a SCell in the downlink is a DL SCC, and a carrier corresponding to a SCell in the uplink is a UL SCC. Depending on the terminal capacity, a serving cell(s) consists of one PCell and zero or more SCells. For a UE in RRC_CONNECTED state but with no carrier aggregation configured or that does not support carrier aggregation, there is only one serving cell consisting of only a PCell.

[0114] As described above, the term cell used in carrier aggregation is different from the term cell referring to a certain geographical area to which communication services are provided by one base station or one antenna group. However, in order to distinguish between a cell referring to a certain geographical area and a cell of carrier aggregation, in the present invention, a cell of carrier aggregation is referred to as CC, and a cell of a geographical area is referred to as cell.

[0115] FIG. 10 is a diagram showing an example in which a cross-carrier scheduling technique is applied. If cross-carrier scheduling is configured, a control channel transmitted through a first CC schedules a data channel transmitted through a first CC or a second CC using a carrier indicator field (CIF). The CIF is included in the DCI. In other words, a scheduling cell is configured, and a DL grant / UL grant transmitted from a PDCCH region of the scheduling cell schedules a PDSCH / PUSCH of a scheduled cell. That is, a search region for multiple component carriers is the PDCCH region of the scheduling cell. A PCell is basically a scheduling cell, and a specific SCell is designated as a scheduling cell by a higher layer.

[0116] In the embodiment of Figure 10, it is assumed that three DL CCs are merged. Here, it is assumed that DL component carrier #0 is DL PCC (or PCell), and DL component carrier #1 and DL component carrier #2 are DL SCC (or SCell). It is also assumed that DL PCC is configured as PDCCH monitoring CC. If cross-carrier scheduling is not configured by terminal-specific (or terminal-group-specific, or cell-specific) higher layer signaling, CIF is disabled, and each DL CC transmits only PDCCH that schedules its own PDSCH without CIF according to NR PDCCH rules (non-cross-carrier scheduling, self-carrier scheduling). On the other hand, if cross-carrier scheduling is configured by terminal-specific (or terminal-group-specific, or cell-specific) higher layer signaling, the CIF is enabled, and a specific CC (e.g., DL PCC) transmits not only a PDCCH for scheduling the PDSCH of DL CC A but also a PDCCH for scheduling the PDSCH of other CCs using the CIF (cross-carrier scheduling). On the other hand, no PDCCH is transmitted in other DL CCs. Thus, depending on whether cross-carrier scheduling is configured in the terminal, the terminal monitors a PDCCH that does not include a CIF to receive a self-carrier scheduled PDSCH, or monitors a PDCCH that includes a CIF to receive a cross-carrier scheduled PDSCH.

[0117] 9 and 10 illustrate the subframe structure of the 3GPP LTE-A system, the same or similar configuration can be applied to the 3GPP NR system, however, in the 3GPP NR system, the subframes in FIG. 9 and 10 may be replaced with slots.

[0118] <Communication methods in unlicensed bands>

[0119] FIG. 11 illustrates an example of an NR-U (NR-Unlicensed) service environment.

[0120] Referring to FIG. 11, a service environment in which NR technology 11 in a licensed band and NR-U, which is NR technology 12 in an unlicensed band, are integrated may be provided to a user. For example, in an NR-U environment, NR technology 11 in a licensed band and NR technology 12 in an unlicensed band may be integrated using a technique such as carrier aggregation, which can contribute to network capacity expansion. In addition, in an asymmetric traffic structure in which downlink data is relatively more than uplink data, NR-U can provide NR services optimized according to various requirements or environments. For convenience, NR technology in a licensed band is called NR-L (NR-Licensed), and NR technology in an unlicensed band is called NR-U (NR-Unlicensed).

[0121] Fig. 12 shows an existing communication method (e.g., wireless LAN) that operates in an unlicensed band. Devices that operate in an unlicensed band usually operate on a Listen-Before-Talk (LBT) basis, and therefore perform Clear Channel Assessment (CCA) to sense the channel before transmitting data.

[0122] Referring to FIG. 12, a WLAN device (e.g., AP, STA) performs carrier sensing before transmitting data to check whether a channel is busy. If a wireless signal of a certain strength or more is detected from a channel to which data is to be transmitted, the channel is determined to be busy and the WLAN device delays access to the channel. This process is called clear channel evaluation, and the signal level that determines whether a signal is detected is called a CCA threshold. On the other hand, if no wireless signal is detected from the channel or a wireless signal of a strength lower than the CCA threshold is detected, the channel is determined to be in an idle state.

[0123] When a channel is determined to be idle, a terminal that has data to transmit performs a backoff procedure after a defer duration (e.g., Arbitration InterFrame Space (AIFS), PCF IFS (PIFS), etc.). The defer duration refers to the minimum time that a terminal must wait after a channel becomes idle. The backoff procedure allows a terminal to wait any amount of time after the defer deadline. For example, a terminal waits while decreasing a slot time of a random number assigned to the terminal within a contention window (CW) while the channel is idle, and a terminal that has exhausted all the slot times can attempt to access the channel.

[0124] When the terminal successfully accesses a channel, the terminal can transmit data through the channel. If the data transmission is successful, the contention window size (CWS) is reset to an initial value (CWmin). On the other hand, if the data transmission fails, the CWS is doubled. As a result, the terminal is assigned a new random number within a range twice the previous random number range and performs a backoff procedure in the next CW. In WLAN, only ACK is defined as reception response information for data transmission. Therefore, if an ACK is received for data transmission, the CWS is reset to the initial value, and if no feedback information is received for data transmission, the CWS is doubled.

[0125] As described above, since existing communications in unlicensed bands mostly operate on the basis of LBT, channel access in the NR-U system also performs LBT for coexistence with existing devices. Specifically, channel access methods on unlicensed bands in NR may be classified into the following four categories depending on the presence / absence / application method of LBT.

[0126] ●Category 1: No LBT

[0127] - The Tx entity does not perform the LBT procedure for transmission.

[0128] Category 2: LBT without random backoff

[0129] - The Tx entity senses whether the channel is idle in a first interval without random backoff in order to transmit, i.e., the Tx entity can transmit on the channel immediately after sensing the channel as idle during the first interval, the first interval being an interval of a pre-configured length immediately prior to the Tx entity transmitting. According to one embodiment, the first interval may be an interval of 25us length, but the invention is not limited thereto.

[0130] Category 3: LBT with random backoff using a fixed-size CW

[0131] - The Tx entity obtains a random number within the fixed size CW, sets it as the initial value of a backoff counter (or backoff timer) N, and performs backoff using the set backoff counter N. That is, in the backoff procedure, the Tx entity decrements the backoff counter by 1 every time the channel is sensed as being idle in a previously set slot period. Here, the previously set slot period may be 9 us, but the present invention is not limited to this. The backoff counter N is decremented by 1 from the initial value, and when the value of the backoff counter N reaches 0, the Tx entity can transmit. Meanwhile, to perform backoff, the Tx entity decrements the backoff counter by 1 in the second interval (i.e., the defer period T d) whether the channel is idle. According to an embodiment of the present invention, the Tx entity can sense (or determine) whether the channel is idle during the second interval depending on whether the channel is idle during at least a portion of the second interval (e.g., one slot period). The second interval may be set based on the channel access priority class of the Tx entity, and is composed of a period of 16us and m consecutive slot periods, where m is a value set by the channel access priority class. If the channel is sensed as idle during the second interval, the Tx entity performs channel sensing for decreasing the backoff counter. On the other hand, if the channel is sensed as occupied during the backoff procedure, the backoff procedure is interrupted. After interrupting the backoff procedure, the Tx entity can resume backoff if the channel is sensed as idle during an additional second interval. In this way, the Tx entity can transmit if the channel is idle during the second interval plus the slot period of the backoff counter N. At this time, the initial value of the backoff counter N is obtained within a CW of a fixed size.

[0132] Category 4: LBT with random backoff using variable-size CW

[0133] - The Tx entity obtains a random number within the variable-sized CW, sets it as the initial value of the backoff counter (or backoff timer) N, and performs backoff using the set backoff counter N. More specifically, the Tx entity can adjust the size of the CW based on HARQ-ACK information for the previous transmission, and the initial value of the backoff counter N is obtained within the adjusted size of the CW. The specific process of the Tx entity performing backoff is as described in Category 3. The Tx entity can transmit if the channel is idle during the second interval plus the slot period of the backoff counter N. In this case, the initial value of the backoff counter N is obtained within the variable-sized CW.

[0134] In the above categories 1 to 4, the Tx entity may be a base station or a terminal. According to the embodiment of the present invention, the first type channel access may refer to the channel access of category 4, and the second type channel access may refer to the channel access of category 2, respectively.

[0135] FIG. 13 illustrates a channel access process based on Category 4 LBT according to an embodiment of the present invention.

[0136] To access the channel, the Tx entity first waits for a defer period T d According to an embodiment of the present invention, the defer period T d The channel sensing for the defer period T d For example, the defer period T d The channel sensing for the defer period T d The Tx entity may perform channel sensing during one slot period in the defer period T d It is checked whether the channel is idle by channel sensing for the channel (S304). dIf the channel is sensed as idle for the defer period T, the Tx entity proceeds to step S306. d If the channel is not sensed as idle for the defer period T (i.e., sensed as occupied), the Tx entity returns to step S302. d The process of steps S302 to S304 is repeated until the device is sensed as being in an idle state for the defer period T d may be set based on the channel access priority class of the Tx entity and consists of a period of 16us and m consecutive slot periods, where m is the value set by the channel access priority class.

[0137] Next, the Tx entity obtains a random number within a predetermined CW, sets it as the initial value of a backoff counter (or backoff timer) N (S306), and proceeds to step S308. The initial value of the backoff counter N is randomly selected from a range of values ​​from 0 to CW. The Tx entity performs a backoff procedure using the set backoff counter N. That is, the Tx entity performs the backoff procedure by repeating steps S308 to S316 until the value of the backoff counter N reaches 0. Meanwhile, in FIG. 13, the channel is in a deferred period T d However, the present invention is not limited to this. That is, step S306 may be performed independently of steps S302 to S304, or may be performed prior to steps S302 to S304. When step S306 is performed prior to steps S302 to S304, the channel is set to the defer period T by steps S302 to S304. d If the Tx entity senses the ACK state as idle, the Tx entity proceeds to step S308.

[0138] In step S308, the Tx entity checks whether the value of the back-off counter N is 0. If the value of the back-off counter N is 0, the Tx entity proceeds to step S320 to transmit. If the value of the back-off counter N is not 0, the Tx entity proceeds to step S310. In step S310, the Tx entity decrements the value of the back-off counter N by 1. According to an embodiment, the Tx entity can selectively decrement the value of the back-off counter by 1 in the channel sensing process for each slot. At this time, step S310 can be skipped at least once depending on the selection of the Tx entity. Next, the Tx entity performs channel sensing for an additional slot period (S312). The Tx entity checks whether the channel is idle through the channel sensing for the additional slot period (S314). If the channel is sensed as idle for the additional slot period, the Tx entity returns to step S308. In this manner, the Tx entity may decrement the backoff counter by 1 each time the channel is sensed as being idle during a pre-configured slot period, where the pre-configured slot period may be 9 us, although the present invention is not limited thereto.

[0139] If the channel is not sensed as idle (i.e., sensed as occupied) for an additional slot period in step S314, the Tx entity proceeds to step S316. In step S316, the Tx entity determines whether the channel is to be idle for an additional deferred period T d According to an embodiment of the present invention, the channel sensing in step S316 may be performed on a slot-by-slot basis. That is, the Tx entity checks whether the channel is idle for an additional defer period T d Check whether the channel is sensed as idle for all slots of the additional defer period T d If an occupied slot is detected within the additional defer period T, the Tx entity immediately restarts step S316. dIf the channel is sensed as idle for the entire slot period, the Tx entity returns to step S308.

[0140] On the other hand, if the value of the backoff counter N is confirmed as 0 in step S308, the Tx entity performs transmission (S320). The Tx entity receives HARQ-ACK feedback corresponding to the transmission (S322). The Tx entity can determine whether the previous transmission was successful based on the received HARQ-ACK feedback. The Tx entity then adjusts the CW size for the next transmission based on the received HARQ-ACK feedback (S324).

[0141] In this way, the Tx entity can d After sensing the channel as idle for N additional slot periods, transmission may occur if the channel is idle. As mentioned above, the Tx entity may be a base station or a terminal, and the channel access process of FIG. 13 may be used for downlink transmission of the base station and / or uplink transmission of the terminal.

[0142] FIG. 14 is a block diagram showing the configuration of a terminal and a base station according to an embodiment of the present invention. In an embodiment of the present invention, the terminal is embodied as various types of wireless communication devices or computing devices that ensure portability and mobility. The terminal is referred to as a UE, a Station (STA), a Mobile Subscriber (MS), etc. In addition, in an embodiment of the present invention, the base station controls and manages cells (e.g., macrocells, femtocells, picocells, etc.) corresponding to a service area, and performs functions such as signal transmission, channel assignment, channel monitoring, self-diagnosis, and relaying. The base station is referred to as a next generation NodeB (gNB) or an Access Point (AP), etc.

[0143] As shown, a terminal 100 according to one embodiment of the present invention includes a processor 110 , a communication module 120 , a memory 130 , a user interface unit 140 , and a display unit 150 .

[0144] First, the processor 110 executes various commands or programs to process data within the terminal 100. The processor 110 also controls the overall operation of the terminal 100 including each unit, and controls the transmission and reception of data between the units. Here, the processor 110 is configured to perform operations according to the embodiments described in the present invention. For example, the processor 110 may receive slot configuration information, determine the slot configuration based thereon, and perform communication according to the determined slot configuration.

[0145] Next, the communication module 120 is an integrated module that performs wireless communication using a wireless communication network and wireless LAN access using a wireless LAN. For this purpose, the communication module 120 includes a plurality of network interface cards (NICs) such as cellular communication interface cards 121 and 122 and an unlicensed band communication interface card 123, either built-in or external. In the drawings, the communication module 120 is shown as an integrated module, but the network interface cards may be arranged independently depending on the circuit configuration or application, unlike the drawings.

[0146] The cellular communication interface card 121 transmits and receives wireless signals to and from at least one of the base station 200, the external device, and the server via the mobile communication network, and provides a cellular communication service in a first frequency band based on instructions from the processor 110. According to an embodiment, the cellular communication interface card 121 includes at least one NIC module that utilizes a frequency band below 6 GHz. The at least one NIC module of the cellular communication interface card 121 independently performs cellular communication with at least one of the base station 200, the external device, and the server according to a cellular communication standard or protocol of the frequency band below 6 GHz supported by the NIC module.

[0147] The cellular communication interface card 122 transmits and receives wireless signals to and from at least one of the base station 200, the external device, and the server using a mobile communication network, and provides a cellular communication service in the second frequency band based on instructions from the processor 110. According to an embodiment, the cellular communication interface card 122 includes at least one NIC module that utilizes a frequency band of 6 GHz or higher. The at least one NIC module of the cellular communication interface card 122 independently performs cellular communication with at least one of the base station 200, the external device, and the server according to a cellular communication standard or protocol of the 6 GHz or higher frequency band supported by the NIC module.

[0148] The unlicensed band communication interface card 123 transmits and receives wireless signals to and from at least one of the base station 200, the external device, and the server through the third frequency band, which is an unlicensed band, and provides communication services in the unlicensed band based on instructions from the processor 110. The unlicensed band communication interface card 123 includes at least one NIC module that utilizes the unlicensed band. For example, the unlicensed band may be a band of 2.4 GHz, 5 GHz, 6 GHz, 7 GHz, or 52.6 GHz or higher. The at least one NIC module of the unlicensed band communication interface card 123 performs cellular communication with at least one of the base station 200, the external device, and the server, independently or dependently, according to the unlicensed band communication standard or protocol of the frequency band supported by the NIC module.

[0149] Next, the memory 130 stores a control program and various data associated therewith used by the terminal 100. Such a control program includes a predetermined program required for the terminal 100 to perform wireless communication with at least one of the base station 200, an external device, and a server.

[0150] Next, the user interface 140 includes various types of input / output means provided in the terminal 100. That is, the user interface unit 140 receives user input using various input means, and the processor 110 controls the terminal 100 based on the received user input. Also, the user interface 140 performs output based on a command from the processor 110 using various output means.

[0151] Then, the display unit 150 outputs various images on a display screen. The display unit 150 outputs various display objects, such as a user interface, based on the contents performed by the processor 110 or a control command of the processor 110.

[0152] The base station 200 according to the embodiment of the present invention also includes a processor 210 , a communication module 220 , and a memory 230 .

[0153] First, the processor 210 executes various commands or programs to process data within the base station 200. The processor 210 also controls the overall operation of the base station 200 including each unit, and controls transmission and reception of data between the units. Here, the processor 210 is configured to perform operations according to the embodiments described in the present invention. For example, the processor 210 may signal slot configuration information and perform communication according to the signaled slot configuration.

[0154] Next, the communication module 220 is an integrated module that performs wireless communication using a wireless communication network and wireless LAN access using a wireless LAN. For this purpose, the communication module 220 includes a plurality of network interface cards, such as cellular communication interface cards 221 and 222 and an unlicensed band communication interface card 223, either built-in or external. In the drawings, the communication module 220 is shown as an integrated module, but the respective network interface cards may be arranged independently depending on the circuit configuration or application, unlike the drawings.

[0155] The cellular communication interface card 221 transmits and receives wireless signals to and from at least one of the terminal 100, the external device, and the server using a mobile communication network, and provides a cellular communication service in a first frequency band according to an instruction of the processor 210. According to an embodiment, the cellular communication interface card 221 includes at least one NIC module that uses a frequency band below 6 GHz. The at least one NIC module of the cellular communication interface card 221 independently performs cellular communication with at least one of the terminal 100, the external device, and the server according to a cellular communication standard or protocol of the frequency band below 6 GHz supported by the NIC module.

[0156] The cellular communication interface card 222 transmits and receives wireless signals to and from at least one of the terminal 100, an external device, and a server using a mobile communication network, and provides a cellular communication service in the second frequency band based on instructions from the processor 210. According to an embodiment, the cellular communication interface card 222 includes at least one NIC module that uses a frequency band of 6 GHz or higher. The at least one NIC module of the cellular communication interface card 222 independently performs cellular communication with at least one of the terminal 100, an external device, and a server according to a cellular communication standard or protocol of the 6 GHz or higher frequency band supported by the NIC module.

[0157] The unlicensed band communication interface card 223 transmits and receives wireless signals to and from at least one of the terminal 100, the external device, and the server using the third frequency band, which is an unlicensed band, and provides communication services in the unlicensed band based on instructions from the processor 210. The unlicensed band communication interface card 223 includes at least one NIC module that uses the unlicensed band. For example, the unlicensed band may be a band of 2.4 GHz, 5 GHz, 6 GHz, 7 GHz, or 52.6 GHz or higher. The at least one NIC module of the unlicensed band communication interface card 223 performs cellular communication with at least one of the terminal 100, the external device, and the server, independently or dependently, according to the unlicensed band communication standard or protocol of the frequency band supported by the NIC module.

[0158] The terminal 100 and base station 200 shown in FIG. 14 are block diagrams according to an embodiment of the present invention, and the separated blocks are used to logically distinguish the elements of the devices. Thus, the above-mentioned device elements may be mounted on one chip or multiple chips depending on the design of the device. Also, some components of the terminal 100, such as the user interface 150 and the display unit 150, may be selectively provided in the terminal 100. Also, the user interface 140 and the display unit 150 may be additionally provided in the base station 200 as necessary.

[0159] A channel access procedure performed by a wireless communication device in an unlicensed band will be described with reference to FIG. 15. An LBT procedure used when a wireless communication device performs channel access in an unlicensed band will be described. In particular, a channel access in which the wireless communication device transmits according to a result of channel sensing within a time interval of a pre-specified duration may be set in the wireless communication device. At this time, if the wireless communication device fails to access the channel, an operation method of the wireless communication device will be described. The pre-specified duration mentioned above may be 16 us.

[0160] For convenience of explanation, a wireless communication device that is a wireless endpoint initiating channel occupancy is called an initiating node. Also, a wireless communication device that is a wireless endpoint communicating with the initiating node is called a responding node. The initiating node may be a base station, and the responding node may be a terminal. Also, the initiating node may be a terminal, and the responding node may be a base station. When the initiating node is about to transmit data, the initiating node may perform channel access based on a channel access priority class determined according to the type of data. At this time, parameters used for channel access may be determined according to the type of data. The parameters used for channel access may include at least one of a minimum value of CW, a maximum value of CW, a maximum channel occupancy time (MCOT) that is the maximum duration that a channel can be occupied in one channel occupancy, and the number of sensing slots (mp). Specifically, the initiating node may perform the above-mentioned Category 4 LBT based on a channel access priority class determined according to the type of data.

[0161] Table 4 below shows an example of parameter values ​​used for channel access based on the channel access priority class. Specifically, Table 4 shows parameter values ​​used for channel access for each channel access priority class for downlink transmission in the LTE LAA system.

[0162] When the downlink channel transmitted by the wireless communication device includes data traffic, the defer duration may be set based on the channel access priority class of the traffic included in the downlink channel. f ) or more (m p ) slot section (T sl ) can be included. In this case, the slot period (T slThe duration of the initial interval may be 9us. The initial interval is one idle slot interval (T sl ) is included in the defer period. p ) may be set based on the channel access priority class as described above. Specifically, the number of slot periods included in the defer period (m p ) may be set as shown in Table 4.

[0163] [Table 4]

[0164] In addition, the wireless communication device can set the range of the CW value according to the channel access priority class. min,p <=CW<=CW max,p The CW value can be set to satisfy the following. In this case, the minimum CW value (CW min,p ) and maximum value (CW max,p ) may be determined by the channel access priority class. Specifically, the minimum value of CW (CW min,p ) and maximum value (CW max,p ) may be determined as shown in Table 4. In the counter value setting procedure, the wireless communication device sets the minimum value of CW (CW min,p ) and maximum value (CW max,p ) can be set. When the wireless communication device accesses the channel, the wireless communication device can adjust the value of CW as described above with reference to FIG. 13. In addition, in the unlicensed band, MCOT (T mcot,p) may be determined according to the channel access priority of the data included in the transmission, as described above. Specifically, the MCOT may be determined as shown in Table 4. Thus, the wireless communication device may not be allowed to transmit continuously in the unlicensed band for a time exceeding the MCOT. This is because the unlicensed band is a frequency band that various wireless communication devices use according to certain rules. In Table 4, when the value of the channel access priority class is p=3 or p=4 and there is no wireless communication device that uses the unlicensed band for a long term according to the regulations and uses other technology, the wireless communication device may determine T mcot,p = 10 ms. Otherwise, the wireless communication device mcot,p =8ms can be set.

[0165] Table 5 shows parameter values ​​used for channel access according to channel access priority class for uplink transmission used in the LTE LAA system.

[0166] [Table 5]

[0167] As described in Table 5, the MCOT value of 6 ms may be increased to 8 ms when the transmission includes one or more gaps. A gap refers to the time from when a transmission is interrupted on a carrier until the transmission resumes on the carrier. In this case, the minimum duration of the gap is 100 us. The maximum duration of the transmission before the gap is included is 6 ms. The duration of the gap is not included in the channel occupancy time. When the value of the channel access priority class is 3 or 4 and it is guaranteed that no other wireless access technology is used on the carrier where the channel access is performed, the MCOT value may be 10 ms. In this case, the other wireless access technology may include Wi-Fi. In other cases, the MCOT value may be determined as described in Note 1 of Table 5.

[0168] COT represents the time that the wireless communication device occupies the channel. MCOT represents the maximum time that the initiating node can continuously occupy the channel in any one carrier of the unlicensed band, as described above. However, as described above, a gap, which is a period during which no transmission is performed, may be included between multiple transmissions, and when a gap is included, the value of MCOT may be applied differently.

[0169] <Example: Channel access for SL (sidelink) transmission>

[0170] Figure 16 illustrates an example of a SL communication process. SL communication refers to a communication method in which a direct link is set between terminals and voice or data is directly transmitted between the terminals without going through a base station. In SL communication, the base station in Figure 14 may be replaced by a terminal.

[0171] Referring to FIG. 16, UE-A can transmit sidelink control information (SCI) to UE-B (S1602). st SCI) and the second SCI (2 ndSCI) may be distinguished from the first SCI. The first SCI is transmitted on a physical sidelink control channel (PSCCH). The first SCI includes some information required for PSSCH (physical sidelink shared channel) scheduling (e.g., resources / information for decoding the second SCI, DMRS pattern, antenna port, etc.) and may be decoded by all terminals in the cell for channel sensing. Meanwhile, the second SCI is decoded by each receiving terminal and includes the remaining information required for PSSCH scheduling. The second SCI may be transmitted using PSSCH resources. Then, UE-A can transmit the PSSCH to UE-B (S1604). Terminal-to-terminal data may be transmitted on the PSSCH. Unicast transmission and groupcast transmission may also be performed on the PSSCH. When HARQ feedback operation is supported / configured for SL transmission (e.g., PSSCH) (HARQ-ACK enabled), UE-B can transmit HARQ-ACK feedback for PSSCH to UE-A on a physical sidelink feedback channel (PSFCH) (S1606). On the other hand, when HARQ feedback operation is not supported / configured for SL transmission (e.g., PSSCH) (HARQ-ACK disabled), UE-A does not expect explicit HARQ-ACK feedback for PSSCH from UE-B.

[0172] The present invention relates to a channel access method / procedure when performing SL transmission (e.g., PSSCH) on an unlicensed spectrum. Specifically, the present invention proposes a method of adjusting a CWS according to a (SL) transmission type (e.g., unicast / group transmission with HARQ-ACK, groupcast transmission w / NACK only, groupcast transmission w / o HARQ-ACK, and broadcast transmission) when adjusting a CWS for channel access on an unlicensed spectrum. Here, the channel access procedure using a CWS includes, for example, a Type 1 channel access procedure (CAP) (or a Cat-4 (category 4) LBT, a random backoff-based channel access procedure with a variable CW). For example, when a Type 1 channel access is performed for SL transmission, a wireless device (e.g., a terminal) can adjust a CWS based on the type of the SL transmission before performing a Type 1 channel access.

[0173] The transmission type may be classified based on (i) the type of the transmission (e.g., unicast, groupcast, broadcast) and (ii) the HARQ-ACK feedback scheme / mode (HARQ-ACK, NACK only, no HARQ-ACK) configured for the transmission.

[0174] - transmission with HARQ-ACK: refers to a transmission that requires HARQ-ACK feedback (e.g., ACK, NACK). Thus, after a terminal sends a transmission to a receiving terminal, the terminal expects a HARQ-ACK feedback (e.g., ACK or NACK) for the transmission from the receiving terminal (i.e., explicit ACK / NACK). Here, the transmission includes a unicast transmission or a groupcast transmission.

[0175] - transmission w / NACK only: refers to a transmission where only NACK is allowed as HARQ-ACK feedback. Thus, after sending a transmission to a receiving terminal, a terminal can explicitly expect only NACK as HARQ-ACK feedback for that transmission from the receiving terminal. In this case, the ACK is indirectly fed back by not detecting / receiving a NACK for that transmission (i.e., implicit ACK). Here, the transmission includes a groupcast transmission.

[0176] - transmission w / o HARQ-ACK: refers to a transmission for which HARQ-ACK feedback is not permitted. That is, it refers to a case where the HARQ-ACK method / mode is not configured for the transmission. Therefore, after sending a transmission to a receiving terminal, the terminal does not expect HARQ-ACK feedback for the transmission from the receiving terminal. Here, the transmission includes a groupcast transmission or a broadcast transmission.

[0177] Unicast / group transmission with HARQ-ACK

[0178] A wireless device (e.g., a terminal) can transmit a PSSCH, which is a unicast or groupcast transmission with HARQ-ACK. In this case, when transmitting in an unlicensed spectrum, the terminal can perform a Type 1 channel access. When performing a Type 1 channel access, the terminal can adjust the CWS to determine a time window (i.e., CW) for performing a random backoff. A method for this is proposed below.

[0179] First, when transmitting the PSSCH, the PSSCH transmission may be performed using (a) a sidelink resource allocation mode 1 scheme in which the base station informs the terminal of time and frequency resources for PSSCH transmission, or (b) a sidelink resource allocation mode 2 scheme in which (one) resource pool is configured, the terminal senses the resource pool to select resources, and then allocates actually transmittable resources. Here, the PSSCH may be transmitted using a PC-5 link. The PC-5 link refers to a link for direct communication between devices.

[0180] Case 1) When (one) resource pool is configured, (a) a PSFCH resource period and (b) a minimum time gap in which PSFCH can be received after PSSCH may be configured. In this case, HARQ-ACK enabling / disabling may be configured for SL transmission (e.g., PSSCH). For example, a terminal transmitting a PSSCH may set a HARQ-ACK enabled / disabled indicator in the second SCI to a specific value. For example, when the value of the HARQ-ACK enabled / disabled indicator is indicated as "1" (meaning enabled), a receiving terminal may transmit a PSFCH in an available slot after a minimum time gap from PSSCH according to the PSFCH resource period after receiving a PSSCH. This allows a terminal that transmitted a PSSCH to receive (e.g., detect / monitor) a PSFCH and receive HARQ-ACK information.

[0181] Specifically, when a PSFCH resource is configured in the resource pool and the value of the HARQ-ACK enabled / disabled indicator is instructed by the second SCI to be "1" (meaning enabled), UE-A can expect that UE-B will transmit HARQ-ACK feedback for the PSSCH transmitted from UE-A to UE-B to UE-A. At this time, if the HARQ-ACK transmitted from UE-B is available and contains at least one ACK, UE-A can check the current CW for all priority classes. p To the minimum / initial value for each priority class (see Table 5 for example), UE-A can reset the current CW p can be increased for all priority classes to the next higher possible value for each priority class (see, for example, Table 5). Then, the set / adjusted CW p Using the value, UE-A can perform Type 1 channel connection when transmitting the currently intended PSSCH, where the subscript p represents the priority class.

[0182] Also, the terminal transmitting the PSSCH can specify the value "0" (meaning disabled) using the HARQ-ACK enabled / disabled indicator in the second SCI. In this case, the terminal does not expect an explicit HARQ-ACK from the receiving terminal, and does not use the CW used most recently to transmit the PSSCH. p The value can be used as is for Type 1 channel connection when transmitting the PSSCH currently being transmitted.

[0183] Case 2) When (one) resource pool is configured, there may be cases where there are no PSFCH resources because the PSFCH resource period and minimum time gap are not configured. In this case, the terminal transmitting the PSSCH indicates the value "0" (meaning disabled) in the HARQ-ACK enabled / disabled indicator in the second SCI, and the terminal receiving this cannot transmit HARQ-ACK information after receiving the PSSCH because there are no configured PSFCH resources. In this case, the terminal transmitting the PSSCH cannot expect an explicit HARQ-ACK from the receiving terminal, so it does not transmit CW information based on the HARQ-ACK information. p Therefore, the terminal that has transmitted the PSSCH cannot adjust the current CW when transmitting the next PSSCH. p To resolve this, if the channel access priority class of the PSSCH to be currently transmitted has been used before, the terminal may set the current CW p The CW corresponding to the same priority class used most recently (before PSSCH transmission) p value to make a Type 1 channel connection.

[0184] 17 illustrates a channel connection process according to an embodiment of the present invention. FIG. 17 corresponds to Case 1). Case 2) may be performed similarly.

[0185] Referring to FIG. 17, UE-A may set HARQ-feedback enabling / disabling for SL transmission (e.g., PSSCH) (S1702). For example, UE-A may transmit an SCI for scheduling PSSCH. Here, the SCI (e.g., the second SCI) may include a HARQ-feedback enabled / disabled indicator. Then, UE-A may perform channel connection using a first CWS to transmit PSSCH (S1704). Here, PSSCH may be used for unicast transmission or groupcast transmission. In addition, the channel connection includes Type 1 channel connection. When the value of the HARQ-ACK enabled / disabled indicator is set to "1" (enabled), UE-B may transmit PSFCH in an available slot after a minimum time gap from PSSCH after receiving PSSCH. At this time, if there is at least one ACK in the HARQ-ACK transmitted from UE-B, UE-A may perform channel connection using the current CWS for all priority classes (S1705). p To the minimum / initial value for each priority class (see Table 5 for example), UE-A can reset the current CW p For all priority classes, the HARQ-ACK enabled / disabled indicator may be increased to the next highest possible value for each priority class (see, for example, Table 5) (S1706a). On the other hand, if the value of the HARQ-ACK enabled / disabled indicator is set to '0' (disabled), UE-A may increase the current CW p , the CW used for the most recent PSSCH transmission p Use the value as is, or if the channel access priority class of the PSSCH you are currently trying to transmit was used previously, use the current CW p As a result, the CW used for PSSCH transmission that belongs to the same priority class is p The value can be used as is. After that, the set / adjusted CW pUsing the value, UE-A can perform channel access (eg, Type 1 channel access) when transmitting the PSSCH that it is currently attempting to transmit (S1708).

[0186] Groupcast transmission w / NACK only

[0187] Groupcast transmission with NACK only feedback, where the wireless device (e.g., terminal) can transmit PSSCH. In this case, when transmitting in an unlicensed spectrum, the terminal can perform Type 1 channel access. When performing Type 1 channel access, the terminal can adjust the CWS to determine the time window for random backoff. A method for this is proposed below. The following description may also be extended to groupcast transmission with HARQ-ACK, where the implicit ACK may be replaced with an implicit ACK.

[0188] When a terminal transmits a PSSCH as a groupcast transmission configured with NACK only feedback, the terminal can monitor (e.g., detect) a PSFCH occasion corresponding to the groupcast transmission to determine / confirm HARQ-ACK feedback for the groupcast transmission. Here, the PSFCH opportunity includes one or more PSFCH resources allocated to a group of terminals that receive the groupcast transmission. If, as a result of monitoring the PSFCH opportunity, no HARQ-ACK feedback is received from a group of terminals that are targets of receiving the groupcast transmission (i.e., All implicit ACK), the terminal that transmitted the PSSCH regards the reception response to the PSSCH as (All) ACK and does not perform retransmission of the groupcast transmission. Therefore, if a terminal that transmitted a PSSCH in a groupcast transmission does not receive any HARQ-ACK feedback from a group of terminals in a PSFCH opportunity expected by the terminal, the terminal may determine whether to perform a CW for a Type 1 channel connection to be performed when transmitting a next SL transmission (e.g., PSSCH; not necessarily a groupcast transmission) to be transmitted. p As a result, the current CW for all priority classes p can be reset to the minimum / initial value for each priority class (see Table 5 for example). That is, when the reception response results from multiple terminals corresponding to groupcast transmission are considered as (All) ACK (for example, no NACK is detected in the PSFCH opportunity), the current CW p can be reset to the minimum / initial value for each priority class (see Table 5 for example). When a group of terminals attempts to transmit a NACK feedback on a PSFCH opportunity, the terminals that transmitted the PSSCH in the groupcast transmission do not know whether the channel connection was unsuccessful and the transmission was not possible, or whether the terminals in the group received the previously transmitted PSSCH well and did not transmit a NACK feedback. Therefore, regardless of this, the current CW pto the minimum / initial value for each priority class (see, for example, Table 5), and a Type 1 channel connection can be performed when transmitting the next SL transmission (eg, PSSCH).

[0189] Meanwhile, when a PSSCH is transmitted as a groupcast transmission configured with NACK only feedback, and HARQ-ACK feedback with all NACKs or HARQ-ACK feedback with at least one NACK is received from a group of terminals that have received the PSSCH, the terminal that transmitted the PSSCH may perform retransmission for the groupcast transmission. That is, when all NACKs or at least one NACK is detected in the PSFCH opportunity corresponding to the groupcast as a result of monitoring the PSFCH opportunity, the terminal that transmitted the PSSCH may perform retransmission for the groupcast transmission. In this case, a terminal that intends to retransmit the PSSCH in the groupcast transmission may perform a CW for Type 1 channel connection to be performed at the time of PSSCH retransmission. p It may be ambiguous what value to set as

[0190] 1. As an example, considering that a terminal transmits a PSSCH as a retransmission of a groupcast transmission, a method of performing CW adjustment when a NACK is received can be used in which all terminals in a group transmit HARQ-ACK feedback with NACK, and the terminal that transmitted the PSSCH receives this, or in which a HARQ-ACK feedback with at least one NACK is received from a terminal in a group. For example, a terminal that transmitted a PSSCH as a groupcast transmission can use a method of performing CW adjustment when a NACK is received. p to the next highest possible value for each priority class, and a Type 1 channel connection can be performed when transmitting the next PSSCH to be transmitted. That is, when the reception response results from multiple terminals corresponding to groupcast transmission are considered to be Not (All) ACK (for example, at least one NACK is detected during the PSFCH opportunity), the current CW for all priority classes isp to the next highest possible value for each priority class (see, for example, Table 5).

[0191] 2. As another example, except when all terminals in a group transmit HARQ-ACK feedback with NACK, if HARQ-ACK feedback with at least one NACK is received from terminals in a group, the terminal that transmitted the PSSCH can determine that at least one terminal in the group has received the PSSCH well. In this case, it can be determined that there is no channel congestion from the perspective of channel connection, and a method of performing CW adjustment when receiving ACK feedback can be used. For example, the terminal that transmitted the PSSCH can adjust the current CW for all priority classes. p to the minimum / initial value for each priority class, and a Type 1 channel connection can be performed when transmitting the next PSSCH (see, for example, Table 5).

[0192] FIG. 18 illustrates a channel connection process according to an embodiment of the present invention. Referring to FIG. 18, UE-A may perform channel connection using a first CWS to transmit a groupcast transmission (S1802). Here, the groupcast transmission may be performed on a PSSCH. The channel connection includes a Type 1 channel connection. Then, UE-A may monitor a PSFCH (opportunity / resource) corresponding to the groupcast transmission (S1804). As a result of the monitoring, if the HARQ feedback result is considered as All ACKs (e.g., no NACK is detected on the PSFCH opportunity / resource), UE-A may monitor the current CWS for all priority classes. p can be reset to the minimum / initial value for each priority class (see, for example, Table 5) (S1806a). On the other hand, if the HARQ feedback result is not considered as All ACKs (e.g., at least one NACK is detected in the PSFCH opportunity / resource), UE-A can reset the current CW pcan be increased to the next highest possible value for each priority class for all priority classes (see, for example, Table 5) (S1806b). Then, the set / adjusted CW p Using the value, UE-A can perform channel access (e.g., Type 1 channel access) when transmitting a currently intended SL transmission (e.g., PSSCH) (after groupcast transmission) (S1808). Here, the HARQ-feedback method set for groupcast transmission includes a NACK only feedback method.

[0193] When transmitting PSSCH as groupcast transmission configured with NACK only feedback, the base station may perform a sidelink resource allocation mode 1 method in which the base station informs the terminal of time / frequency resources for PSSCH transmission, or may perform a sidelink resource allocation mode 2 operation in which one resource pool is configured, the base station senses the resource pool to select resources, and then allocates resources that can actually be transmitted. Meanwhile, when (one) resource pool is configured, there may be cases where there are no PSFCH resources because the PSFCH resource period and minimum time gap are not configured. In this case, the terminal transmitting PSSCH indicates a value of "0" (meaning disabled) by the HARQ-ACK enabled / disabled indicator in the second SCI, and the terminal receiving this indicates that there are no configured PSFCH resources after receiving PSSCH, and therefore cannot transmit HARQ-ACK information, which is feedback information for NACK only. In this case, the terminal transmitting PSSCH cannot expect an explicit HARQ-ACK from the receiving terminal, and therefore may perform a CW based on the HARQ-ACK information. p Therefore, when a terminal that has transmitted a PSSCH transmits the next PSSCH, the terminal cannot adjust the current CW p To resolve this, if the channel access priority class of the PSSCH to be currently transmitted has been used before, the terminal may set the value of the current CW pis the CW that corresponds to the same priority class that was used most recently (before PSSCH transmission) (for PSSCH transmission). p value to make a Type 1 channel connection.

[0194] Alternatively, the terminal transmitting the PSSCH can specify the value "0" (meaning disabled) by the HARQ-ACK enabled / disabled indicator in the second SCI. In this case, the terminal does not expect an explicit HARQ-ACK from the receiving terminal and does not use the CW used for the most recent PSSCH transmission. p The value can be used as is for Type 1 channel connection when transmitting the current PSSCH.

[0195] Although the method and system of the present invention have been described in conjunction with specific embodiments, some or all of its components or operations may be implemented using a computing system having a general-purpose hardware architecture.

[0196] The above description of the present invention is for illustrative purposes only, and those skilled in the art will understand that the present invention can be easily modified into other specific forms without changing the technical idea or essential features of the present invention. Therefore, the above-described embodiments should be understood to be illustrative in all respects and not restrictive. For example, each component described as a single type may be implemented in a distributed form, and similarly, each component described as a distributed type may be implemented in a combined form.

[0197] The scope of the present invention is indicated by the claims set forth below rather than by the above detailed description, and any modifications or variations derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included within the scope of the present invention.

Claims

1. A terminal for use in a wireless communication system, A communication module; a processor for controlling the communication module; The processor, Transmitting a sidelink (SL) groupcast transmission to a plurality of terminals based on a channel access procedure using a first contention window size (CWS); monitoring a feedback signal at a physical sidelink feedback channel (PSFCH) opportunity corresponding to the SL groupcast transmission to identify reception response results of the terminals for the SL groupcast transmission; and Based on the reception response results of the plurality of terminals, a CWS to be used for channel connection of the SL transmission after the SL groupcast transmission is set; If the reception response results of the plurality of terminals include at least one NACK (negative acknowledgment), the CWS is set to a value greater than the first CWS; When the reception response results of the multiple terminals are all regarded as ACK, the CWS is reset to a CWS minimum value.

2. The terminal according to claim 1 , wherein a case where the reception response results of the plurality of terminals include at least one NACK includes a case where a NACK is detected in the PSFCH opportunity.

3. The terminal of claim 1, wherein the cases where the reception response results of the plurality of terminals are all considered to be ACKs include a case where no NACK is detected in the PSFCH opportunity.

4. The terminal of claim 1 , wherein a NACK-only feedback method is configured for the SL groupcast transmission.

5. The terminal of claim 1 , wherein at least one of the SL groupcast transmission and the SL transmission is transmitted on a physical sidelink shared channel (PSSCH).

6. The terminal of claim 1 , further comprising: performing a backoff upon channel connection for the SL transmission based on a randomly selected counter value within the CWS.

7. 2. The terminal of claim 1, wherein when the CWS is set to a value greater than the first CWS, the CWS of all priority classes are set to the next greater value than the current CWS among the CWS values ​​allowed for each priority class.

8. 2. The terminal of claim 1, wherein when the CWS is reset to a CWS minimum value, the CWS of all priority classes is set to the minimum of the CWS corresponding to the respective priority class.

9. The terminal of claim 1 , wherein the wireless communication system includes a 3rd generation partnership project (3GPP) new radio (NR)-based wireless communication system, and the channel access procedure includes a Type 1 channel access procedure (CAP).

10. 1. A method for use by a terminal in a wireless communication system, comprising: transmitting a sidelink (SL) groupcast transmission to a plurality of terminals based on a channel access procedure using a first contention window size (CWS); monitoring a feedback signal at a physical sidelink feedback channel (PSFCH) opportunity corresponding to the SL groupcast transmission to identify reception response results of the plurality of terminals for the SL groupcast transmission; and setting a CWS to be used for channel connection of SL transmission after the SL groupcast transmission based on the reception response results of the plurality of terminals; If the reception response results of the plurality of terminals include at least one NACK (negative acknowledgment), the CWS is set to a value greater than the first CWS; A method according to claim 1, wherein the CWS is reset to a minimum CWS value when the reception response results of the multiple terminals are all deemed to be ACK.

11. The method according to claim 10, wherein the reception response results of the plurality of terminals include at least one NACK, and further includes a case where a NACK is detected in the PSFCH opportunity.

12. The method according to claim 10, wherein the case where the reception response results of the plurality of terminals are all regarded as ACK includes a case where no NACK is detected in the PSFCH opportunity.

13. The terminal of claim 10, wherein a NACK-only feedback scheme is configured for the SL groupcast transmission.

14. The method of claim 10, wherein at least one of the SL groupcast transmission and the SL transmission is transmitted on a physical sidelink shared channel (PSSCH).

15. The method of claim 10, further comprising: the terminal backing off upon channel connection for the SL transmission based on a randomly selected counter value in the CWS.

16. 11. The method of claim 10, wherein when the CWS is set to a value greater than the first CWS, the CWS of all priority classes are set to the next higher value than the current CWS among the CWS values ​​allowed for each priority class.

17. 11. The method of claim 10, wherein when the CWS is reset to a CWS minimum, the CWS of all priority classes is set to the minimum of the CWS applicable to the respective priority classes.

18. 11. The method of claim 10, wherein the wireless communication system comprises a 3rd generation partnership project (3GPP) new radio (NR) based wireless communication system, and the channel access procedure comprises a Type 1 channel access procedure (CAP).

19. A terminal for use in a wireless communication system, A communication module; a processor for controlling the communication module; The processor, Transmitting a first sidelink (SL) transmission based on a channel access procedure using a first contention window size (CWS); and performing a channel access procedure using the second CWS to attempt a second SL transmission after the first SL transmission; If a hybrid automatic repeat request acknowledgment (HARQ-ACK) feedback is enabled for the first SL transmission, the second CWS is reset to a minimum value based on a HARQ-ACK feedback result corresponding to the first SL transmission or is set to a value greater than the first CWS; A terminal, wherein when the HARQ-ACK feedback is disabled for the first SL transmission, the second CWS is adjusted to the same value as the CWS used for the third SL transmission that is more recent than the first SL.

20. The terminal of claim 19, wherein the enabling / disabling of the HARQ-ACK feedback is indicated by sidelink control information (SCI) corresponding to the first SL transmission.

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