Method and apparatus for transmitting signals in a wireless communication system

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] This invention relates to a new wireless communication system. Specifically, this invention relates to a channel access method and an apparatus using the same in a wireless communication system. [Background technology]

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

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

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

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

[0006] On the other hand, the Internet is evolving into an IoT (Internet of Things) network that exchanges and processes information between distributed components such as things in a human-centered connection network where humans generate and consume information. IoE (Internet of Everything) technology, which combines big data processing technology and others through connection to cloud servers and the like, has also emerged. To realize IoT, technical elements such as sensing technology, wired and wireless communication and network infrastructure, service interface technology, and security technology are required. Recently, technologies such as sensor networks for connecting things, machine to machine (M2M), and MTC (machine type communication) have been studied. In the IoT environment, intelligent IT (internet technology) services that collect and analyze data generated from connected things to create new value for human life are provided. 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 integration and combination of conventional IT technologies and various industries.

[0007] Therefore, various attempts have been made to apply the 5G communication system to the IoT network. For example, technologies such as sensor networks, machine-to-machine, and MTC are realized by techniques such as beamforming, MIMO, and array antennas, which are 5G communication technologies. The application of cloud radio access network (cloud RAN) as the above-mentioned big data processing technology can also be regarded as an example of the integration of 5G technology and IoT technology. Generally, mobile communication systems have been developed to provide voice services while ensuring user mobility.

[0008] Sidelink (SL) refers to a communication method in which a direct link is established between terminals (User Equipment, UE) and voice or data, etc. are directly exchanged between terminals without going through a base station (Base Station, BS). SL is considered as one solution to solve the burden on the base station due to the rapidly increasing data traffic.

[0009] V2X (vehicle-to-everything) means a communication technology that exchanges information with other vehicles, pedestrians, things with built 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 the PC5 interface and / or the Uu interface.

[0010] On the other hand, as more communication devices demand larger communication capacities, the need for improved mobile broadband communication compared to existing radio access technologies (RATs) is emerging. For this reason, communication systems that consider reliability and latency-sensitive services or terminals are being discussed, and next-generation radio connectivity technologies that consider improved mobile broadband communication, massive MTC, and URLLC (Ultra-Reliable and Low Latency Communication) can be called new RATs (new radio access technology) or NRs (new radio). Vehicle-to-everything (V2X) communication may also be supported in NRs.

[0011] On the other hand, for example, in SL communications associated with services that have high reliability requirements or services that have relatively high reliability requirements, the terminal's SL HARQ feedback operation and / or mechanism may be useful. [Overview of the project] [Problems that the invention aims to solve]

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

[0013] In one aspect of the present invention, a terminal for use in a wireless communication system is provided, comprising a communication module and a processor for controlling the communication module, wherein the processor is configured to transmit a sidelink (sidelink) 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) occasion corresponding to the SL groupcast transmission to identify the received response results of the plurality of terminals to the SL groupcast transmission, and set a CWS used for channel connection of SL transmissions after the SL groupcast transmission based on the received response results of the plurality of terminals, wherein if the received 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 received response results of the plurality of terminals are considered to be ACKs, the CWS is reset to the minimum CWS value.

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

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

[0016] Preferably, the case in which the received response results of all of the multiple terminals are considered to be ACKs may include the case in which no NACKs are detected in the PSFCH opportunity.

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

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

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

[0020] Preferably, the terminal may include backing off when a channel connection is established for SL transmission, based on a counter value randomly selected within the CWS.

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

[0022] Preferably, when the CWS is reset to the minimum CWS value, the CWS for 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 connection procedure may include a Type 1 CAP (channel access procedure).

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

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

[0026] The present invention provides a method for efficiently transmitting signals in a wireless communication system and an apparatus using the same. Furthermore, the present invention provides a channel access method for efficiently transmitting signals 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 with ordinary skill in the art to which the present invention pertains from the following description. [Brief explanation of the drawing]

[0028] [Figure 1] This figure shows an example of a wireless frame structure used in wireless communication systems.

[0029] [Figure 2] This figure shows an example of a downlink (DL) / uplink (UL) slot structure in a wireless communication system.

[0030] [Figure 3] This diagram illustrates the physical channels used in 3GPP systems (e.g., NR) and a common signal transmission method utilizing those physical channels.

[0031] [Figure 4] This figure shows the SS / PBCH block for initial cell access in a 3GPP NR system.

[0032] [Figure 5] This diagram shows the procedure for transmitting control information and control channels in a 3GPP NR system.

[0033] [Figure 6] This diagram shows the CORESET to which PDCCH is transmitted in a 3GPP NR system.

[0034] [Figure 7] This diagram shows how to configure the PDCCH search space in a 3GPP NR system.

[0035] [Figure 8] Figure 8 is a conceptual diagram illustrating career integration.

[0036] [Figure 9] This diagram illustrates terminal carrier communication and multi-carrier communication.

[0037] [Figure 10]This figure shows an example where the cross-carrier scheduling technique is applied.

[0038] [Figure 11] This diagram shows the NR-U (NR-Unlicensed) service environment.

[0039] [Figure 12] This diagram shows existing communication methods that operate on unlicensed bandwidth (e.g., wireless LAN).

[0040] [Figure 13] This diagram shows the channel access process based on Category 4 LBT.

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

[0042] [Figure 15] This diagram illustrates the COT (channel occupancy time) setting and its resulting operation.

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

[0044] [Figure 17] This figure illustrates a channel connection method according to the present invention. [Figure 18] This figure illustrates a channel connection method according to the present invention. [Modes for carrying out the invention]

[0045] The terms used herein have been selected to be as widely used and general as possible, taking into account the function of the present invention; however, this may vary depending on the intent, conventions, or emergence of new technologies of the articulate. In some cases, the applicant has arbitrarily selected terms, in which case their meaning will be described in the relevant section of the invention description. Therefore, it should be made clear that the terms used herein are not merely names of terms, but should be interpreted based on their substantive meaning and the overall content of this specification.

[0046] Throughout the specification, when one configuration is said to be “connected” to another, this includes not only cases where they are “directly connected,” but also cases where they are “electrically connected” through other intermediate components. Furthermore, when a configuration is said to “include” a particular component, this means, unless otherwise stated, that it includes other components rather than excluding them. In addition, the limitations of “greater than” or “less than” a particular critical point may be appropriately replaced by “greater than” or “less than” depending on the embodiment.

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

[0048] Unless otherwise specified herein, a base station may include a gNB (next generation node B) as defined in 3GPP NR. Also, unless otherwise specified, a terminal may include a UE (user equipment). To aid understanding the explanation below, each concept will be described in separate embodiments, although these embodiments may be used in combination with each other. In this disclosure, terminal configuration may mean configuration by the base station. Specifically, the base station may transmit channels or signals to the terminal to configure the operation of the terminal or the values ​​of parameters used in the wireless communication system.

[0049] Figure 1 shows an example of a wireless frame structure used in a wireless communication system.

[0050] Referring to Figure 1, a radio frame (or radio frame) used in a 3GPP NR system has a length of 10 ms (ΔfmaxNf / 100) * Tc). A radio frame consists of 10 subframes (SF) of equal size, where Δfmax = 480 * 10³ Hz, Nf = 4096, Tc = 1 / (Δfref * Nf,ref), Δfref = 15 * 10³ Hz, and Nf,ref = 2048. Each of the 10 subframes within a single frame is assigned a number from 0 to 9. Each subframe has a length of 1 ms and consists of one or more slots determined by the subcarrier spacing. More specifically, the subcarrier spacing usable in a 3GPP NR system is 15 * 2 μkHz, where μ is the subcarrier spacing configuration, with values ​​from 0 to 4. In other words, 15kHz, 30kHz, 60kHz, 120kHz, or 240kHz are used as subcarrier intervals. A 1ms subframe consists of 2μm slots, each with a length of 2-μms. The 2μm slots within a subframe are each assigned numbers from 0 to 2μ-1. Similarly, the slots within a radio frame are each assigned numbers from 0 to 10*2μ-1. Time resources are divided by at least one of the following: radio frame number (also called radio frame index), subframe number (also called subframe index), or slot number (or slot index).

[0051] Figure 2 shows an example of a downlink (DL) / uplink (UL) slot structure in a wireless communication system. In particular, Figure 2 shows the resource grid structure of a 3GPP NR system.

[0052] There is one resource grid per antenna port. Referring to Figure 2, a slot contains multiple OFDM symbols in the time domain and multiple resource blocks (RBs) in the frequency domain. An OFDM symbol also means a single symbol interval. Unless otherwise specified, OFDM symbols are simply referred to as symbols. Hereafter, in this specification, symbols include OFDM symbols, SC-FDMA symbols, DFTs-OFDM symbols, etc. Referring to Figure 2, the signal transmitted from each slot is represented by a resource grid consisting of Nsize, μgrid, x*NRBSC subcarriers and Nslotsymb OFDM symbols. Here, x=DL for a downlink resource grid and x=UL for an uplink resource grid. Nsize, μgrid, and x indicate the number of resource blocks (RBs) with a subcarrier spacing component μ (x is DL or UL), and Nslotsymb indicates the number of OFDM symbols in the slot. NRBSC is the number of subcarriers constituting one RB, where NRBSC=12. OFDM symbols are also known as CP-OFDM (cyclic prefix OFDM) symbols or DFT-S-OFDM (discrete Fourier transform spread OFDM) symbols, depending on the multiple access method.

[0053] The number of OFDM symbols in a single slot can vary depending on the length of the cyclic prefix (CP). For example, a normal CP may contain 14 OFDM symbols in a single slot, while an extended CP may contain 12 OFDM symbols in a single slot. In specific embodiments, extended CPs are used only with a subcarrier interval of 60 kHz. For the sake of explanation, Figure 2 illustrates a case where a single slot consists of 14 OFDM symbols, but the embodiments of the present invention can be applied in the same manner to slots with other numbers of OFDM symbols. Referring to Figure 2, each OFDM symbol contains N size, μgrid, and x*NRBSC subcarriers in the frequency domain. Subcarrier types are divided into data subcarriers for transmitting data, reference signal subcarriers for transmitting reference signals, and guard bands. The carrier frequency is also called the center frequency (fc).

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

[0055] For a terminal to receive signals from a base station or transmit base station signals, the terminal's time / frequency synchronization must be synchronized with the base station's time / frequency synchronization. If the base station and the terminal are not synchronized, the terminal cannot determine the time and frequency parameters necessary to demodulate DL signals and transmit UL signals at the correct time.

[0056] Each symbol in a radio frame operating in TDD (time division duplex) or unpaired spectrum consists of at least one of the following: a downlink symbol (DL symbol), an uplink symbol (UL symbol), or a flexible symbol. In FDD (frequency division duplex) or paired spectrum, a radio frame operating on a downlink carrier consists of either a downlink symbol or a flexible symbol, while a radio frame operating on an uplink carrier consists of either an uplink symbol or a flexible symbol. Downlink symbols can transmit downlink but not uplink, and uplink symbols can transmit uplink but not downlink. The use of a flexible symbol in the downlink or uplink is determined by the signal.

[0057] Information regarding the type of each symbol, i.e., whether it is a downlink symbol, uplink symbol, or flexible symbol, consists of a cell-specific (or common) RRC signal. Additionally, information regarding the type of each symbol consists of a UE-specific (or dedicated) RRC signal. The base station uses the cell-specific RRC signal to indicate: i) the period of the cell-specific slot configuration; ii) the number of slots containing only downlink symbols from the beginning of the cell-specific slot configuration period; iii) the number of downlink symbols from the first symbol in the slot immediately following the downlink-only slot; iv) the number of slots containing only uplink symbols from the end of the cell-specific slot configuration period; and v) the number of uplink symbols from the last symbol in the slot immediately preceding the uplink-only slot. Here, a symbol that is neither an uplink nor 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 that consists of the cell-specific RRC signal to another symbol type. The per-UE 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] [[ID=…]] 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 as described above, the flexible symbol may be indicated as a downlink symbol, an uplink symbol, or a flexible symbol by the dynamic SFI (slot format information) transmitted on the physical downlink control channel (PDCCH). At this time, a downlink symbol or an uplink symbol configured 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 the downlink symbol, U represents the uplink symbol, and X represents the flexible symbol. As shown in Table 1, a maximum of two DL / UL switching operations may be permitted within a single slot.

[0062] Figure 3 illustrates the physical channels used in 3GPP systems (e.g., NR) and a typical signal transmission method utilizing those physical channels.

[0063] When the terminal is powered on or enters a new cell, the terminal performs the initial cell discovery process (S101). Specifically, the terminal synchronizes with the base station during the initial cell discovery. To do this, the terminal receives a primary synchronization signal (PSS) and a secondary synchronization signal (SSS) from the base station to synchronize with the base station and acquire information such as the cell index. Next, the terminal receives the physical broadcast channel from the base station and acquires broadcast information within the cell.

[0064] After completing the initial cell search, the terminal receives the physical downlink shared channel (PDSCH) via the physical downlink control channel (PDCCH) and the information carried on the PDCCH, thereby obtaining more detailed system information than that acquired through the initial cell search (S102). Here, the system information transmitted to the terminal is the cell common system information necessary for the terminal to operate correctly in the physical layer of the RRC (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 process to the base station (steps S103 to S106). First, the terminal transmits a preamble on the physical random access channel (PRACH) (S103), and can receive a response message for the preamble from the base station on the PDCCH and the corresponding PDSCH (S104). If the terminal receives a valid random access response message, the terminal transmits data including its identifier to the base station on the physical uplink shared channel (PUSCH) indicated by the uplink grant transmitted from the base station via the PDCCH (S105). Next, the terminal waits to receive a PDCCH as an instruction from the base station for collision resolution. When the terminal successfully receives a PDCCH with its identifier (S106), the random access process ends. During the random access process, the terminal can obtain terminal-specific system information necessary for the terminal to function correctly at the physical layer of the RRC layer. Once the terminal obtains terminal-specific system information at the RRC layer, the terminal enters RRC_CONNECTED mode.

[0066] The RRC layer is used for message generation and management for control between terminals and the Radio Access Network (RAN). Furthermore, base stations and terminals can use the RRC layer to broadcast cell system information necessary for all terminals within a cell, manage the transmission of paging messages, manage mobility and handover, report and control terminal measurements, and manage terminal capabilities and storage. Generally, the update of signals transmitted in the RRC layer (hereinafter referred to as RRC signals) is longer than the transmission time interval (TTI) in the physical layer, so RRC settings can be maintained without change over long periods.

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

[0068] Figure 4 shows the SS / PBCH block 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 discovery process. During the cell discovery process, the terminal detects the cell's physical cell identity (NcellID). To do this, the terminal receives synchronization signals from the base station, such as the primary synchronization signal (PSS) and secondary synchronization signal (SSS), to synchronize with the base station. At this time, the terminal obtains information such as the cell identifier (identity, ID).

[0070] Refer to Figure 4(a) for a more detailed explanation of the synchronization signal (SS). The synchronization signal is divided into PSS and SSS. PSS is used to obtain time-domain synchronization and / or frequency-domain synchronization, such as OFDM symbol synchronization and slot synchronization. SSS is used to obtain frame synchronization and cell group ID. Referring to Figure 4(a) and Table 1, an SS / PBCH block consists of 20 RBs (=240 subcarriers) consecutively on the frequency axis and 4 OFDM symbols consecutively on the time axis. In this case, within the SS / PBCH block, the PSS is transmitted via the first OFDM symbol and the SSS via the second subcarrier (56-18) for the third OFDM symbol. Here, the lowest subcarrier index of the SS / PBCH block is assigned starting from 0. In the first OFDM symbol on which the PSS is transmitted, the base station does not transmit signals via the remaining subcarriers, i.e., subcarriers 0-55 and 183-239. Furthermore, in the third OFDM symbol on which SSS is transmitted, the base station does not transmit signals via subcarriers 48-55 and 183-19. In the SS / PBCH block, the base station transmits PBCH (physical broadcast channel) via the remaining REs excluding the aforementioned signals.

[0071] [Table 2]

[0072] The SS generates a total of 1008 unique physical layer cell IDs through combinations of three PSSs and SSSs. More specifically, each physical layer cell ID is grouped into 336 physical layer cell identifier groups, each containing three unique identifiers, such that each group is part of only one physical layer cell identifier group. Therefore, the physical layer cell ID NcellID=3N(1)ID+N(2)ID is uniquely defined by an index N(1)ID ranging from 0 to 335 that represents a physical layer cell identifier group, and an index N(2)ID ranging from 0 to 2 that represents a physical layer identifier within the physical layer cell identifier group. The terminal detects the PSS and identifies one of the three unique physical layer identifiers. The terminal also detects the SSS and identifies one of the 336 physical layer cell IDs associated with the physical layer identifier. In this case, the PSS sequence dPSS(n) is as follows:

[0073]

number

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

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

[0076] Furthermore, 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] [x0(6)x0(5)x0(4)x0(3)x0(2)x0(1) 0(0)]=[0000001] and [x1(6)x1(5)x1(4)x1(3)x1(2)x1(1)x1(0)]=[0000001] are given.

[0080] A 10ms long wireless frame is divided into two 5ms long half-frames. Refer to Figure 4(b) to describe the slot in which an SS / PBCH block is transmitted within each half-frame. The slot in which an SS / PBCH block is transmitted is one of cases A, B, C, D, or E. In case A, the subcarrier interval is 15kHz, and the start of the SS / PBCH block is at the {2, 8} + 14*n symbol. In this case, n=0, 1 for carrier frequencies below 3GHz. Also, n=0, 1, 2, 3 for carrier frequencies above 3GHz and below 6GHz. In case B, the subcarrier interval is 30kHz, and the start of the SS / PBCH block is at the {4, 8, 16, 20} + 28*n symbol. In this case, n=0 for carrier frequencies below 3GHz. Also, n=0, 1 for carrier frequencies above 3GHz and below 6GHz. In Case C, the subcarrier spacing is 30 kHz, and the SS / PBCH block starts at the {2nd, 8th} + 14*nth symbol. In this case, for carrier frequencies below 3 GHz, n=0, 1. Also, for carrier frequencies above 3 GHz and below 6 GHz, n=0, 1, 2, 3. In Case D, the subcarrier spacing is 120 kHz, and the SS / PBCH block starts at the {4th, 8th, 16th, 20th} + 28*nth symbol. In this case, for carrier frequencies above 6 GHz, n=0, 1, 2, 3, 5, 6, 7, 8, 10, 11, 12, 13, 15, 16, 17, 18. In Case E, the subcarrier spacing is 240 kHz, and the SS / PBCH block starts at the {8th, 12th, 16th, 20th, 32nd, 36th, 40th, 44th} + 56*nth symbol. In this case, at carrier frequencies of 6 GHz or higher, n = 0, 1, 2, 3, 5, 6, 7, 8.

[0081] Figure 5 shows the procedure for transmitting control information and control channels in a 3GPP NR system. Referring to Figure 5(a), the base station adds a CRC (cyclic redundancy check) masked (e.g., by XOR operation) with an RNTI (radio network temporary identifier) ​​to the control information (e.g., DCI) in S202. The base station scrambles the CRC with an RNTI value determined according to the purpose / target of each piece of control information. A common RNTI used by one or more terminals includes at least one of the following: SI-RNTI (system information RNTI), P-RNTI (paging RNTI), RA-RNTI (random access RNTI), and TPC-RNTI (transmit power control RNTI). Furthermore, the terminal-specific RNTI includes at least one of the following: C-RNTI (cell temporary RNTI), CS-RNTI, or MCS-C-RNTI. Next, after the base station performs channel encoding (e.g., polar coding) in S204, it performs rate-matching in S206 to match the amount of resources used for PDCCH transmission. Next, the base station multiplexes the DCIs (data elements) based on the CCE (control channel element)-based PDCCH structure in S208. The base station also applies additional processes S210 to the multiplexed DCIs (data elements), such as scrambling, modulation (e.g., QPSK), and interleaving, before mapping them to the resources to be transmitted. A CCE is the basic resource unit for PDCCH, and one CCE consists of multiple (e.g., 6) REGs (resource element groups). One REG consists of multiple (e.g., 12) REs. The number of CCEs used for one PDCCH is defined as the aggregation level. The 3GPP NR system uses 1, 2, 4, 8, or 16 integrated levels.Figure 5(b) is a diagram relating to the CCE integration level and PDCCH multiplexing, showing the types of CCE integration levels used for a single PDCCH and the CCEs transmitted in the control domain as a result.

[0082] Figure 6 shows the CORESET to which PDCCH is transmitted in a 3GPP NR system.

[0083] A CORESET is a time-frequency resource on which PDCCH, a control signal for a terminal, is transmitted. Furthermore, the search space, described later, is mapped to a single CORESET. Therefore, instead of monitoring the entire frequency band to receive PDCCH, the terminal monitors the CORESET and the designated time-frequency domain to decode the PDCCH mapped to the CORESET. A base station configures one or more CORESETs for each cell in the terminal. A CORESET consists of up to three consecutive symbols on the time axis. A CORESET also consists of six consecutive PRB units on the frequency axis. In the embodiment shown in Figure 5, CORESET#1 consists of consecutive PRBs, while CORESET#2 and CORESET#3 consist of discontinuous PRBs. A CORESET can be located at any symbol within a slot. For example, in the embodiment shown in Figure 5, CORESET#1 starts at the first symbol of the slot, CORESET#2 starts at the fifth symbol of the slot, and CORESET#9 starts at the ninth symbol of the slot.

[0084] Figure 7 shows how to configure the PDCCH search space in a 3GPP NR system.

[0085] To transmit a PDCCH to a terminal, each CORESET has at least one search space. In embodiments of the present invention, the search space is a collection of all time-frequency resources (hereinafter referred to as PDCCH candidates) from which the terminal's PDCCH is transmitted. The search space includes a common search space that all 3GPP NR terminals should search in common, and a terminal-specific or UE-specific search space that a specific terminal should search. In the common search space, all terminals in a cell belonging to the same base station monitor the PDCCH that they are set to search in common. The terminal-specific search spaces are configured terminal-specific to monitor the PDCCH assigned to each terminal at different locations in the search space depending on the terminal. In the case of terminal-specific search spaces, the search spaces between terminals may partially overlap due to the limited control area to which the PDCCH is assigned. Monitoring a PDCCH includes blind decoding of PDCCH candidates in the search space. If blind decoding is successful, it is expressed as the PDCCH being (successfully) detected / received. If blind decoding fails, it is expressed as the PDCCH not being detected / received, or not being successfully detected / received.

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

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

[0088] The base station transmits a PDCCH containing information about which terminals (one or more terminals) the PDSCH data will be sent to and how those terminals should receive and decode the PDSCH data. For example, suppose a DCI transmitted via a particular PDCCH is CRC masked with an RNTI named "A", and that DCI indicates that the PDSCH is assigned to a radio resource (e.g., frequency location) named "B", and indicates transmission format information (e.g., transmit block size, modulation scheme, coding information, etc.) named "C". Terminals monitor the PDCCH using their own RNTI information. In this case, if a terminal blind-decodes the PDCCH using the "A" RNTI, that terminal will receive the PDCCH and, through the information of the received PDCCH, receive the PDSCH indicated by "B" and "C".

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

[0090] [Table 3]

[0091] PUCCH is used to transmit the following Uplink Control Information (UCI):

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

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

[0094] -CSI: This is feedback information for the downlink channel. It is generated by the terminal based on the CSI-RS (Reference Signal) transmitted by the base station. MIMO (multiple input multiple output) related feedback information includes RI and PMI. CSI is divided into CSI Part 1 and CSI Part 2 depending on the information it indicates.

[0095] The 3GPP NR system uses five PUCCH formats to support diverse service scenarios, diverse channel environments, and frame structures.

[0096] PUCCH format 0 is a format for transmitting 1-bit or 2-bit HARQ-ACK information or SR. PUCCH format 0 is transmitted via one or two OFDM symbols on the time axis and one RB on the frequency axis. If PUCCH format 0 is transmitted with two OFDM symbols, the same sequence is transmitted for each symbol with different RBs. Through this, the terminal obtains a frequency diversity gain. More specifically, the terminal determines the cyclic shift value mcs according to the Mbit bit UCI (Mbit=1 or 2), and maps a sequence obtained by cyclic shifting a base sequence of length 12 by the determined value mcs to 12 REs (Res) consisting of one OFDM symbol and one PRB, and transmits it. If the number of cyclic shifts available to the terminal is 12 and Mbit=1, then 1-bit UCI0 and 1 are represented by sequences corresponding to two cyclic shifts with a cyclic shift value difference of 6. Furthermore, if Mbit=2, the 2-bit UCI00, 01, 11, and 10 represent a sequence of four cyclic shifts where the difference in cyclic shift values ​​is 3.

[0097] PUCCH format 1 transmits 1-bit or 2-bit HARQ-ACK information or SR. PUCCH format 1 is transmitted via a continuous sequence of OFDM symbols on the time axis and 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, a UCI with Mbit=1 is modulated with BPSK. The terminal modulates a UCI with Mbit=2 with QPSK (quadrature phase shift keying). A signal is obtained by multiplying the modulated complex valued symbol d(0) by a sequence of length 12. The terminal spreads the obtained signal with a time-axis OCC (orthogonal cover code) to the even-numbered OFDM symbols assigned to PUCCH format 1 and transmits it. The maximum number of different terminals multiplexed on the same RB in PUCCH format 1 is determined by the length of the OCC used. For odd-numbered OFDM symbols in PUCCH format 1, the DMRS (demodulation reference signal) is spread across the OCC and mapped to them.

[0098] PUCCH format 2 transmits UCI exceeding 2 bits. PUCCH format 2 is transmitted via one or two OFDM symbols on the time axis and one or more RBs on the frequency axis. If PUCCH format 2 is transmitted via two OFDM symbols, the same sequence is transmitted via the two OFDM symbols with different RBs. Through this, the terminal gains frequency diversity gain. More specifically, an Mbit bit UCI (Mbit > 2) is bit-level scrambled and QPSK modulated and mapped to the RBs of one or two OFDM symbols, where the number of RBs is one between 1 and 16.

[0099] PUCCH format 3 or PUCCH format 4 transmits UCI exceeding 2 bits. PUCCH format 3 or PUCCH format 4 is transmitted via continuous OFDM symbols on the time axis and one PRB on the frequency axis. The number of OFDM symbols occupied by PUCCH format 3 or PUCCH format 4 is one of 4 to 14. Specifically, the terminal modulates an Mbit bit UCI (Mbit>2) with π / 2-BPSK (Binary Phase Shift Keying) or QPSK to generate complex number symbols d(0) to d(Msymb-1). Here, with π / 2-BPSK, Msymb = Mbit, and with QPSK, Msymb = Mbit / 2. The terminal does not apply block-unit spreading to PUCCH format 3. However, the terminal may apply block-unit spreading to one RB (i.e., 12 subcarriers) using a PreDFT-OCC of length -12 so that the PUCCH format 4 has two or four multiplexing capacities. The terminal transmits the spread signal using transmit precoding (or DFT-precoding) and maps it to each RE to transmit 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 the UCI transmitted by the terminal and the maximum code rate. If the terminal uses PUCCH format 2, it transmits both HARQ-ACK information and CSI information via PUCCH. If the number of RBs that the terminal can transmit is greater than the maximum number of RBs that PUCCH format 2, PUCCH format 3, or PUCCH format 4 can use, the terminal will not transmit some of the UCI information according to the priority of the UCI information, and will transmit only the remaining UCI information.

[0101] PUCCH format 1, PUCCH format 3, or PUCCH format 4 is configured via an RRC signal to instruct frequency hopping within a slot. When frequency hopping is configured, the index of the RB to be frequency-hopped is determined by the RRC signal. If PUCCH format 1, PUCCH format 3, or PUCCH format 4 is transmitted over N OFDM symbols in the time axis, the first hop will have floor(N / 2) OFDM symbols, the second hop will have ceil(N / 2) OFDM symbols.

[0102] PUCCH format 1, PUCCH format 3, or PUCCH format 4 are configured to be repeatedly transmitted to multiple slots. In this case, the number K of slots to which the PUCCH is repeatedly transmitted is determined by the RRC signal. The repeatedly transmitted PUCCH should start with the same OFDM symbol at the same position within each slot and have the same length. If any of the OFDM symbols in a slot from which the terminal is to transmit the PUCCH is indicated as a DL symbol by the RRC signal, the terminal will not transmit the PUCCH from that slot but will postpone transmission to the next slot.

[0103] On the other hand, in the 3GPP NR system, terminals transmit and receive using a bandwidth smaller than or equal to the carrier (or cell) bandwidth. For this purpose, terminals are configured with a bandwidth part (BWP) consisting of a continuous portion of the carrier bandwidth. Terminals operating according to TDD or in the ampered spectrum have up to four DL / UL BWP pairs per carrier (or cell). The terminal also activates one DL / UL BWP pair. Terminals operating according to FDD or in the paired spectrum have up to four DL BWPs configured on the downlink carrier (or cell) and up to four UL BWPs configured on the uplink carrier (or cell). The terminal activates one DL BWP and one UL BWP for each carrier (or cell). The terminal does not have to receive or transmit from time-frequency resources other than the activated BWPs. The activated BWPs are called active BWPs.

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

[0105] Figure 8 is a conceptual diagram illustrating career integration.

[0106] Carrier aggregation refers to a method used by wireless communication systems to utilize a wider frequency band by having terminals use multiple frequency blocks, or (logical) cells, consisting of uplink resources (or component carriers) and / or downlink resources (or component carriers), within a single larger logical frequency band. For convenience of explanation, the term "component carrier" will be used consistently below.

[0107] Referring to Figure 8, as an example of a 3GPP NR system, the overall system bandwidth includes up to 16 component carriers, each component carrier having a bandwidth of up to 400 MHz. Each component carrier includes one or more physically consecutive subcarriers. Although Figure 8 shows each component carrier having the same bandwidth, this is merely illustrative, and each component carrier may have different bandwidths. Also, although each component carrier is shown as being adjacent to each other on the frequency axis, the diagram is a logical representation, and each component carrier may be physically adjacent to or far from each other.

[0108] Each component carrier uses a different center frequency. Furthermore, physically adjacent component carriers share a single common center frequency. In the embodiment shown in Figure 8, assuming all component carriers are physically adjacent, center frequency A is used for all component carriers. If we assume that the component carriers are not physically adjacent, then center frequencies A and B are used for each component carrier.

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

[0110] Figure 9 is a diagram illustrating terminal carrier communication and multiple carrier communication. Specifically, Figure 9(a) shows the subframe structure of a single carrier, and Figure 9(b) shows the subframe structure of a multiple carrier.

[0111] Referring to Figure 9(a), a typical wireless communication system, in FDD mode, transmits or receives data via one DL band and its corresponding UL band. In other specific embodiments, in TDD mode, the wireless communication system divides the wireless frame into uplink time units and downlink time units in the time domain, and transmits or receives data via the uplink / downlink time units. Referring to Figure 9(b), three 20MHz component carriers (CCs) are aggregated in both the UL and DL bands, supporting a 60MHz bandwidth. Each CC is either adjacent or non-adjacent to the others in the frequency domain. For convenience, Figure 9(b) shows a symmetrical case where the bandwidths of the UL CCs and DL CCs are the same, but the bandwidths of each CC may be determined independently. Asymmetric carrier aggregations with different numbers of UL CCs and DL CCs are also possible. A DL / UL CC assigned / configured to a specific terminal via RRC is referred to as the serving DL / UL CC of that terminal.

[0112] A base station communicates with a terminal by activating some or all of the terminal's serving CCs, or by deactivating some of the CCs. The base station may change which CCs are activated / deactivated, or change the number of CCs that are activated / deactivated. Once a base station assigns available CCs to a terminal, either cell-specific or terminal-specific, at least one of the initially assigned CCs does not need to be deactivated unless the CC assignments for the terminal are completely reconfigured or the terminal is handed over. The CC that is not deactivated by the terminal is called the primary CC (PCC) or PCell (primary cell), and the CCs that the base station can freely activate / deactivate are called secondary CCs (SCC) or SCell (secondary cell).

[0113] On the other hand, 3GPP NR uses the concept of a cell to manage radio resources. A cell is defined as a combination of downlink and uplink resources, i.e., a combination of DL CC and UL CC. A cell consists of DL resources alone, or a combination of DL and UL resources. If carrier aggregation is supported, the linkage between the carrier frequency of the DL resource (or DL ​​CC) and the carrier frequency of the UL resource (or UL CC) is indicated by system information. Carrier frequency refers to the center frequency of each cell or CC. A cell corresponding to a PCC is called a PCell, and a cell corresponding to an SCC is called a SCell. In the downlink, the carrier corresponding to a PCell is a DL PCC, and in the uplink, the carrier corresponding to a PCell is a UL PCC. Similarly, in the downlink, the carrier corresponding to a SCell is a DL SCC, and in the uplink, the carrier corresponding to a SCell is a UL SCC. Depending on the terminal capacity, a serving cell consists of one PCell and zero or more SCells. If the RRC_CONNECTED state exists but carrier aggregation is not configured, or if the UE does not support carrier aggregation, there will be only one serving cell consisting solely of PCells.

[0114] As described above, the term "cell" used in carrier aggregation is distinct from the term "cell" which refers to a specific geographical area where communication services are provided by a single base station or antenna group. However, in order to distinguish between a cell referring to a specific geographical area and a cell in carrier aggregation, in this invention, a cell in carrier aggregation is referred to as CC, and a cell referring to a geographical area is referred to as cell.

[0115] Figure 10 shows an example where the cross-carrier scheduling technique is applied. Once cross-carrier scheduling is set up, the control channel transmitted via the first CC uses the carrier indicator field (CIF) to schedule the data channel transmitted via the first or second CC. The CIF is contained within the DCI. In other words, a scheduling cell is set up, and DL grants / UL grants transmitted from the PDCCH area of ​​the scheduling cell schedule the PDSCH / PUSCH of the scheduled cell. That is, the PDCCH area of ​​the scheduling cell is a search area for multiple component carriers. A PCell is essentially a scheduling cell, and a particular SCell is designated as a scheduling cell by a higher hierarchy.

[0116] In the embodiment shown in Figure 10, we assume that three DL CCs are merged. Here, DL component carrier #0 is assumed to be a DL PCC (or PCell), and DL component carriers #1 and #2 are assumed to be DL SCCs (or SCells). We also assume that the DL PCC is configured as a PDCCH monitoring CC. If cross-carrier scheduling is not configured by terminal-specific (or terminal-group-specific, or cell-specific) higher-level signaling, the CIF will be disabled, and each DL CC will send only PDCCHs that schedule their own PDSCH without a CIF according to the NR PDCCH rule (non-cross-carrier scheduling, self-carrier scheduling). In contrast, if cross-carrier scheduling is configured through terminal-specific (or terminal-group-specific, or cell-specific) higher-level signaling, CIF is enabled, and a specific CC (e.g., DL PCC) uses CIF to transmit not only PDCCHs that schedule DL CC A's PDSCH, but also PDCCHs that schedule other CCs' PDSCHs (cross-carrier scheduling). In contrast, other DL CCs do not transmit PDCCHs. Therefore, depending on whether cross-carrier scheduling is configured for the terminal, the terminal either monitors PDCCHs without CIFs to receive self-carrier scheduled PDSCHs, or monitors PDCCHs with CIFs to receive cross-carrier scheduled PDSCHs.

[0117] On the other hand, Figures 9 and 10 illustrate the subframe structure of a 3GPP LTE-A system, and the same or similar configurations are also applicable to a 3GPP NR system. However, in a 3GPP NR system, the subframes in Figures 9 and 10 may be replaced with slots.

[0118] <Communication methods in unlicensed frequency bands>

[0119] Figure 11 illustrates an NR-U (NR-Unlicensed) service environment.

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

[0121] Figure 12 shows existing communication methods that operate in unlicensed bands (e.g., wireless LANs). Since devices operating in unlicensed bands usually operate on an LBT (Listen-Before-Talk) basis, they perform Clear Channel Assessment (CCA) to sense the channel before transmitting data.

[0122] Referring to Figure 12, a wireless LAN device (e.g., AP, STA) performs carrier sensing before transmitting data to check whether the channel is busy or not. If a wireless signal of a certain strength or higher is detected from the channel from which data is to be transmitted, the channel is determined to be busy, and the wireless LAN device delays access to that channel. This process is called clear channel evaluation, and the signal level that determines whether or not a signal is detected is called the CCA threshold. On the other hand, if no wireless signal is detected from the channel, or if a wireless signal of a strength lower than the CCA threshold is detected, the channel is determined to be idle.

[0123] When a channel is determined to be idle, terminals with data to transmit perform a backoff procedure after a defer duration (e.g., AIFS (Arbitration InterFrame Space), PIFS (PCF IFS)). The defer duration is the minimum time a terminal must wait after a channel becomes idle. The backoff procedure allows a terminal to wait for any additional time after the defer duration expires. For example, a terminal may wait within a Contention Window (CW) while the channel is idle, decreasing its assigned slot time by a random number. Once a terminal has exhausted all its slot time, it can attempt to access the channel.

[0124] Upon successful access to a channel, the terminal can transmit data through the channel. If data transmission is successful, the competition window size (CWS) is reset to its initial value (CWmin). On the other hand, if data transmission fails, the CWS doubles. This causes the terminal to be assigned a new random number within twice the previous random number range and to perform a backoff procedure in the next CW. In wireless LANs, only ACK is defined as the received response information for data transmission. Therefore, if an ACK is received for data transmission, the CWS is reset to its initial value, and if no feedback information is received for data transmission, the CWS doubles.

[0125] As mentioned above, existing communications in unlicensed bands usually operate on an LBT basis, so channel access in NR-U systems also uses LBT to coexist with existing equipment. Specifically, channel access methods on unlicensed bands in NR can be classified into the following four categories depending on the presence / absence and 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] - In order to transmit, the Tx entity senses whether the channel is idle or not during the first interval without random backoff. That is, the Tx entity can transmit on the channel immediately after it is sensed as idle during the first interval. The first interval is an interval of a pre-set length immediately before the Tx entity transmits. In one embodiment, the first interval may be an interval of 25us, but the present invention is not limited thereto.

[0130] ●Category 3: LBT that performs random backoff using fixed-size CW

[0131] - The Tx entity obtains a random number within a fixed-size CW and sets it as the initial value of the backoff counter (or backoff timer) N, and performs backoff using the set backoff counter N. That is, in the backoff procedure, the Tx entity decrements the backoff counter by 1 each time the channel is sensed as idle during the already set slot period. Here, the already set slot period may be 9us, but the present invention is not limited to this. The backoff counter N decreases by 1 from its initial value, and when the value of the backoff counter N reaches 0, the Tx entity can transmit. On the other hand, in order to perform backoff, the Tx entity uses a second interval (i.e., a defer period T) dFirst, the Tx entity senses whether the channel is idle or not during the second interval. According to an embodiment of the present invention, the Tx entity can sense (or determine) whether the channel is idle or not during the second interval by determining whether the channel is idle or not 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 consists of a period of 16us and m consecutive slot periods, where m is a value set by the channel access priority class. The Tx entity performs channel sensing for backoff counter decrement if the channel is sensed as idle during the second interval. On the other hand, if the channel is sensed as occupied during the backoff procedure, the backoff procedure is interrupted. After the interruption of 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, in addition to the slot periods of the backoff counter N. At this time, the initial value of the backoff counter N is obtained within a fixed-size CW (Continuous Wave) transmission.

[0132] ●Category 4: LBT that performs random backoff using variable-size CW

[0133] - The Tx entity obtains a random number within a variable-size CW and sets it as the initial value of the backoff counter (or backoff timer) N, and then 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 previous transmissions, and the initial value of the backoff counter N is obtained within the adjusted-size CW. The specific process by which the Tx entity performs backoff is as described in Category 3. The Tx entity can transmit if the channel is idle during the second interval in addition to the slot period of the backoff counter N. In this case, the initial value of the backoff counter N is obtained within a variable-size CW.

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

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

[0136] To perform channel access, first, the Tx entity must defer period T. d Channel sensing is performed for (S302). According to an embodiment of the present invention, the defer period T in step S302 d Channel sensing for the specified differential period T d This may be done by channel sensing during at least a portion of the period within the period T. For example, during the defer period T. d Channel sensing for the specified differential period T d This may be done by channel sensing during one of the slot periods. The Tx entity is defined by the defer period T. d Channel sensing is used to determine whether the channel is idle or not (S304). dWhen sensed as an idle state for, the Tx entity proceeds to step S306. When the channel is sensed as idle for a deferral period T d When not sensed as an idle state for (i.e., when sensed as an occupied state for), the Tx entity returns to step S302. The Tx entity repeats the process of steps S302 to S304 until the channel is sensed as idle for a deferral period T d The deferral period T d may be set based on the channel access priority class of the Tx entity and is composed of a period of 16 us and m consecutive slot periods. Here, m is a value set according to the channel access priority class.

[0137] Next, the Tx entity obtains a random number within a predefined CW and sets it as the initial value of a backoff counter (or a backoff timer) N (S306) and proceeds to step S308. The initial value of the backoff counter N is randomly selected from values in the range of 0 to CW. The Tx entity performs a backoff procedure using the set backoff counter N. That is, the Tx entity repeats the process of steps S308 to S316 until the value of the backoff counter N reaches 0 to perform the backoff procedure. On the other hand, in FIG. 13, it is assumed that step S306 is performed after the channel is sensed as idle for a deferral 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, when the channel is sensed as idle for a deferral period T d by steps S302 to S304, the Tx entity proceeds to step S308.

[0138] In step S308, the Tx entity checks whether the value of the backoff counter N is 0. If the value of the backoff counter N is 0, the Tx entity proceeds to step S320 and transmits. If the value of the backoff counter N is not 0, the Tx entity proceeds to step S310. In step S310, the Tx entity decreases the value of the backoff counter N by 1. According to one embodiment, the Tx entity can selectively decrease the value of the backoff counter by 1 during the channel sensing process for each slot. In this case, step S310 may be skipped at least once by the selection of the Tx entity. Next, the Tx entity performs channel sensing for the additional slot period (S312). The Tx entity checks whether the channel is idle or not by 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 way, the Tx entity can decrement the backoff counter by 1 each time the channel is sensed as idle during an already configured slot period. Here, the already configured slot period may be 9us, but the present invention is not limited to this.

[0139] In step S314, if the channel is not sensed as idle for the additional slot period (i.e., sensed as occupied), the Tx entity proceeds to step S316. In step S316, the Tx entity determines that the channel is not sensed as idle for the additional defer period T d In this step, it is confirmed whether or not it is idle. 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 undergoes an additional defer period T. d Check whether the channel is sensed as idle throughout the entire slot period. Additional defer period T d If an occupied slot is detected within, the Tx entity immediately resumes phase S316. Additional defer period T dIf the channel is sensed as idle for the entire slot period, the Tx entity returns to stage S308.

[0140] On the other hand, if the value of the backoff counter N is confirmed to be 0 in step S308, the Tx entity performs a transmission (S320). The Tx entity receives HARQ-ACK feedback corresponding to the transmission (S322). The Tx entity can confirm whether or not a previous transmission was successful based on the received HARQ-ACK feedback. Next, the Tx entity adjusts the CW size for the next transmission based on the received HARQ-ACK feedback (S324).

[0141] Thus, the Tx entity has a deferred period T. d After sensing the channel as idle, transmission can be performed if the channel remains idle for N additional slot periods. As mentioned above, the Tx entity may be a base station or a terminal, and the channel access process in Figure 13 may be used for downlink transmissions by the base station and / or uplink transmissions by the terminal.

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

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

[0144] First, the processor 110 executes various instructions or programs to process data inside 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 units. Here, the processor 110 is configured to perform the operations described in the embodiment of the present invention. For example, the processor 110 may receive slot configuration information, determine the slot configuration based on that information, and perform communication according to the determined slot configuration.

[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. To this end, the communication module 120 incorporates multiple network interface cards (NICs), such as cellular communication interface cards 121 and 122 and an unlicensed band communication interface card 123, either internally or externally. In the drawing, the communication module 120 is shown as an integrated module, but each network interface card may be arranged independently depending on the circuit configuration or application, contrary to the drawing.

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

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

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

[0149] Next, the memory 130 stores control programs used by the terminal 100 and various data associated with them. Such control programs include predetermined programs necessary for the terminal 100 to communicate wirelessly with at least one of the following: a base station 200, an external device, or a server.

[0150] Next, the user interface 140 includes various forms of input / output means provided in the terminal 100. In other words, the user interface unit 140 receives user input using various input means, and the processor 110 controls the terminal 100 based on the received user input. The user interface 140 also outputs based on instructions from the processor 110 using various output means.

[0151] Next, the display unit 150 outputs various images to the display screen. The display unit 150 outputs various display objects, such as content generated by the processor 110 or user interfaces based on control instructions from the processor 110.

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

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

[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. To this end, the communication module 220 incorporates multiple network interface cards, such as cellular communication interface cards 221 and 222, and an unlicensed band communication interface card 223, either internally or externally. In the drawings, the communication module 220 is shown as an integrated module, but each network interface card may be arranged independently depending on the circuit configuration or application, contrary to the drawings.

[0155] The cellular communication interface card 221 transmits and receives wireless signals to and from at least one of the terminal 100, external devices, and servers described above using a mobile communication network, and provides cellular communication services in the first frequency band based on instructions from the processor 210. According to one embodiment, the cellular communication interface card 221 includes at least one NIC module that utilizes a frequency band of less than 6 GHz. At least one NIC module of the cellular communication interface card 221 independently performs cellular communication with at least one of the terminal 100, external devices, and servers, depending on the cellular communication standard or protocol of the frequency band of less than 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 cellular communication services in a second frequency band based on instructions from the processor 210. According to one embodiment, the cellular communication interface card 222 includes at least one NIC module that utilizes a frequency band of 6 GHz or higher. At least one NIC module of the cellular communication interface card 222 independently performs cellular communication with at least one of the terminal 100, an external device, and a server, according to the cellular communication standard or protocol of the 6 GHz or higher frequency band supported by the NIC module.

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

[0158] The terminal 100 and base station 200 shown in Figure 14 are block diagrams according to one embodiment of the present invention, and the separately shown blocks logically distinguish the elements of the device. Therefore, the above-mentioned elements of the device are mounted on one or more chips depending on the device design. In addition, some components of the terminal 100, such as the user interface unit 150 and the display unit 150, may be selectively provided in the terminal 100. Furthermore, the user interface 140 and the display unit 150, etc., may be additionally provided in the base station 200 as needed.

[0159] Using Figure 15, the channel access procedure performed by a wireless communication device in an unlicensed band will be explained. The LBT procedure used when a wireless communication device performs channel access in an unlicensed band will be explained. In particular, the wireless communication device may be configured to perform channel access based on the results of channel sensing within a predetermined time interval. In this case, the operation method of the wireless communication device will be explained if the channel access fails. The predetermined duration mentioned above may be 16us.

[0160] For the sake of explanation, a radio communication device that initiates channel occupancy is called an initiating node. A radio communication device that communicates 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. Alternatively, the initiating node may be a terminal and the responding node may be a base station. When an initiating node attempts to transmit data, it can perform channel access based on a channel access priority class determined by the type of data. At this time, the parameters used for channel access may be determined by the type of data. The parameters used for channel access may include at least one of the following: the minimum CW value, the maximum CW value, the maximum occupancy time (MCOT), which is the maximum duration for which a channel can be occupied in a single channel occupancy, and the number of sensing slots (mp). Specifically, the initiating node can perform the aforementioned Category 4 LBT based on the channel access priority class determined by 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 the parameter values ​​used for channel access for downlink transmission in the LTE LAA system, categorized by channel access priority class.

[0162] When a downlink channel transmitted by a wireless communication device contains data traffic, the defer duration may be set based on the channel access priority class of the traffic contained in the downlink channel. Furthermore, the defer duration may be set based on the initial interval (T f ) one or more (m p ) slot section (T sl ) can include the slot interval (T slThe duration of ) may be 9us. The initial interval is one idle slot interval (T sl ) is included. Also, the number of slot intervals included in the defer period (m p ) may be set based on the channel access priority class, as mentioned above. Specifically, the number of slot intervals included in the defer period (m p The values ​​may be set as shown in Table 4.

[0163] [Table 4]

[0164] Furthermore, the wireless communication device can set the range of CW values ​​according to the channel access priority class. Specifically, the wireless communication device can set the range of CW min,p <=CW<=CW max,p The CW value can be set to satisfy the following conditions. In this case, the minimum value of CW (CW min,p ) and maximum value (CW max,p ) may be determined by the channel access priority class. Specifically, the minimum value for CW (CW min,p ) and maximum value (CW max,p The minimum value of CW (CW) may be determined as shown in Table 4. The radio communication device sets the minimum value of CW in the counter value setting procedure. min,p ) and maximum value (CW max,p ) can be set. When a wireless communication device accesses a channel, the wireless communication device can adjust the CW value as explained earlier in Figure 13. Also, MCOT(T mcot,p) may be determined by the channel access priority of the data included in the transmission, as described above. Specifically, MCOT may be determined as shown in Table 4. This means that the radio communication device may not be permitted to transmit continuously during the time exceeding MCOT in the unlicensed band. This is because the unlicensed band is a frequency band used by various radio communication devices according to certain rules. In Table 4, if the channel access priority class value is p=3 or p=4, and the radio communication device uses the unlicensed band for a long term according to the regulations, and there are no other radio communication devices using other technology, then the radio communication device is T mcot,p It can be set to =10ms. Otherwise, the wireless communication device will T mcot,p It can be set to =8ms.

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

[0166] [Table 5]

[0167] As shown in Table 5, the MCOT value of 6ms may increase to 8ms if the transmission includes one or more gaps. A gap is the time between the interruption of transmission on a carrier and the resumption of transmission on that carrier. In this case, the minimum duration of the gap is 100us. The maximum duration of transmissions performed before the gap is 6ms. The duration of the gap is not included in the channel occupancy time. The MCOT value may be 10ms if the channel access priority class value is 3 or 4 and it is guaranteed that no other radio connectivity technology is used on the carrier where the channel access is performed. In this case, the other radio connectivity 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 a radio communication device occupies a channel. MCOT, as mentioned above, represents the maximum continuous time a starting node can occupy a channel on any one carrier in the unlicensed band. However, as mentioned above, gaps, which are periods in which no transmissions occur, may be included between multiple transmissions, and in cases where gaps are included, the value of MCOT may be applied differently.

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

[0170] Figure 16 illustrates the SL communication process. SL communication refers to a communication method that establishes a direct link between terminals, allowing for the direct exchange of voice or data without the need for a base station. In SL communication, the base station in Figure 14 may be replaced with a terminal.

[0171] Referring to Figure 16, UE-A can send SCI (sidelink control information) to UE-B (S1602). The SCI is the first SCI (1 st SCI) and the second SCI(2 ndThe SCI can be distinguished as follows: The first SCI is transmitted over the PSCCH (physical sidelink control channel). The first SCI contains some information necessary 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. The second SCI, on the other hand, is decoded by each receiving terminal and contains the remaining information necessary for PSSCH scheduling. The second SCI may be transmitted using PSSCH resources. Subsequently, UE-A can transmit the PSSCH to UE-B (S1604). Inter-terminal data may be transmitted over the PSSCH. Unicast and groupcast transmissions may also occur over the PSSCH. When HARQ-ACK is enabled for SL transmissions (e.g., PSSCH), UE-B can send HARQ-ACK feedback to PSSCH via the PSFCH (physical sidelink feedback channel) to UE-A (S1606). On the other hand, when HARQ-ACK is disabled for SL transmissions (e.g., PSSCH), UE-A does not expect explicit HARQ-ACK feedback to PSSCH from UE-B.

[0172] The present invention relates to a channel access method / procedure for performing SL transmission (e.g., PSSCH) over an unlicensed spectrum. Specifically, the present invention proposes a method for adjusting the CWS for channel access on an unlicensed spectrum, in which the CWS is adjusted according to the (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). Here, the channel access procedure using the CWS includes, for example, a Type 1 channel access procedure (CAP) (or Cat-4 (category 4) LBT, a random backoff-based channel access procedure with variable CW). For example, when a Type 1 channel access is performed for SL transmission, the radio equipment (e.g., a terminal) can adjust the CWS based on the type of SL transmission before performing the Type 1 channel access.

[0173] Transmission types may be classified based on (i) the type of transmission (e.g., unicast, groupcast, broadcast) and (ii) the HARQ-ACK feedback scheme / mode set for the transmission (HARQ-ACK, NACK only, no HARQ-ACK). In this specification, transmission types include, but are not limited to, the following:

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

[0175] - transmission w / NACK only: This means a transmission in which only NACK is allowed as HARQ-ACK feedback. Therefore, after a terminal sends a transmission to a receiving terminal, it 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 (i.e., implicit ACK) by the fact that no NACK is detected / received for that transmission. Here, the transmission includes groupcast transmissions.

[0176] - transmission w / o HARQ-ACK: This means a transmission in which HARQ-ACK feedback is not permitted. In other words, it means that the HARQ-ACK scheme / mode is not set for the transmission. Therefore, after the terminal sends the transmission to the receiving terminal, it does not expect any HARQ-ACK feedback from the receiving terminal for that transmission. Here, the transmission includes groupcast transmissions or broadcast transmissions.

[0177] Unicast / group transmission with HARQ-ACK

[0178] This is a unicast or groupcast transmission with HARQ-ACK, and the radio equipment (e.g., terminal) can transmit PSSCH. In this case, when transmitting on an unlicensed spectrum, the terminal can establish a Type 1 channel connection. When establishing a Type 1 channel connection, the terminal can adjust the CWS to determine the time window (i.e., CW) for random backoff. A method for doing this is proposed below.

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

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

[0181] Specifically, when a PSFCH resource is set in the resource pool and the second SCI indicates the value of the HARQ-ACK enabled / disabled indicator to "1" (meaning enabled), UE-A can expect that HARQ-ACK feedback for the PSFCH sent from UE-A to UE-B will be sent from UE-B to UE-A. At this time, if the HARQ-ACK sent from UE-B is available and contains at least one ACK, UE-A will determine the current CW for all priority classes. p The values ​​can be reset to the minimum / initial value for each priority class (see, for example, Table 5). On the other hand, if not (for example, if there are no ACKs in HARQ-ACK; All NACK), UE-A will reset to the current CW p This can be increased for all priority classes to the next highest possible value for each priority class (see, for example, Table 5). Then, the set / adjusted CW p Using this value, UE-A can establish a Type 1 channel connection when transmitting the PSSCH that it is currently attempting to transmit. Here, the subscript 'p' represents the priority class.

[0182] Furthermore, a terminal transmitting a PSSCH can use the HARQ-ACK enabled / disabled indicator on the second SCI to indicate a value of "0" (meaning disabled). In this case, the terminal does not expect an explicit HARQ-ACK from the receiving terminal and does not use the CW that was most recently used to transmit the PSSCH. p The value can be used directly for the Type 1 channel connection made when transmitting the PSSCH that is currently being sent.

[0183] Case 2) When a single resource pool is configured, there may be no PSFCH resources available if the PSFCH resource period and minimum time gap are not set. In this case, the terminal transmitting the PSSCH will set the HARQ-ACK enabled / disabled indicator on the second SCI to a value of "0" (meaning disabled). The receiving terminal, after receiving the PSSCH, will not be able to transmit HARQ-ACK information because there are no configured PSFCH resources. At this time, the terminal that transmitted the PSSCH cannot expect an explicit HARQ-ACK from the receiving terminal, and will therefore rely on the HARQ-ACK information to transmit CW p Adjustment is not possible. Therefore, the terminal that sent the PSSCH will be in CW when sending the next PSSCH. p It can be ambiguous what value to set it to. To resolve this, if the channel connection priority class of the PSSCH currently attempting to transmit has been used previously, the terminal will now use CW. p The CW that corresponds to the same priority class used most recently (for the PSSCH transmission) (before the PSSCH transmission) p You can set a value to establish a Type 1 channel connection.

[0184] Figure 17 illustrates a channel connection process according to an example of the present invention. Figure 17 corresponds to Case 1). Case 2) may be carried out similarly.

[0185] Referring to Figure 17, UE-A can set HARQ-feedback enabling / disabling for SL transmissions (e.g., PSSCH) (S1702). For example, UE-A can send an SCI to schedule a PSSCH, where the SCI (e.g., the second SCI) may include a HARQ-feedback enabled / disabled indicator. Subsequently, UE-A can establish a channel connection using the first CWS to transmit the PSSCH (S1704). Here, the PSSCH may be used for unicast or groupcast transmissions. The channel connection includes a Type 1 channel connection. If the value of the HARQ-ACK enabled / disabled indicator is set to "1" (enabled), UE-B, after receiving the PSSCH, can transmit a PSFCH in an available slot after a minimum time gap from the PSSCH. At this time, if the HARQ-ACK transmitted from UE-B contains at least one ACK, UE-A will transmit the current CW for all priority classes. p The values ​​can be reset to the minimum / initial value for each priority class (see, for example, Table 5). On the other hand, if not (for example, if there are no ACKs in HARQ-ACK; All NACK), UE-A will reset to the current CW p This can be increased for all priority classes 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), the UE-A will use the current CW p For example, the CW used in the most recent PSSCH transmission. p Either use the value as is, or if the channel connection priority class of the PSSCH you are currently trying to transmit to has been used previously, the current CW p For example, the CW used for PSSCH transmissions that belong to the same priority class. p The values ​​can be used as is. Then, the set / adjusted CW pUsing the value, UE-A can establish a channel connection (e.g., a Type 1 channel connection) when transmitting the PSSCH that it is currently about to transmit (S1708).

[0186] Groupcast transmission w / NACK only

[0187] This is a groupcast transmission with NACK-only feedback, where the radio equipment (e.g., a terminal) can transmit PSSCH. When transmitting on an unlicensed spectrum, the terminal can establish a Type 1 channel connection. When establishing a Type 1 channel connection, the terminal can adjust the CWS to determine a time window for random backoff. A method for this is proposed below. The following description may be extended to groupcast transmission with HARQ-ACK, in which case implicit ACK may be replaced with tacit ACK.

[0188] When a terminal transmits a PSSCH as a groupcast transmission with NACK-only feedback enabled, the terminal can monitor (e.g., detect) a PSFCH opportunity corresponding to the groupcast transmission to determine / confirm HARQ-ACK feedback for the groupcast transmission. Here, a PSFCH opportunity includes one or more PSFCH resources assigned to a group of terminals that received the groupcast transmission. If, as a result of monitoring the PSFCH opportunity, no HARQ-ACK feedback is received from the group of terminals that received the groupcast transmission (i.e., All implicit ACK), the terminal that transmitted the PSSCH considers the received response to the PSSCH as (All)ACK and does not retransmit the groupcast transmission. Therefore, if a terminal that transmitted a PSSCH in a groupcast transmission does not receive any HARQ-ACK feedback from the group of terminals at the PSFCH opportunity the terminal expects, it will need to perform CW for Type 1 channel connection when transmitting the next SL transmission (e.g., a PSSCH; it does not have to be a groupcast transmission). p Currently, CW is available for all priority classes. p The values ​​can be reset to the minimum / initial value for each priority class (see, for example, Table 5). That is, if the received response results from multiple terminals corresponding to a groupcast transmission are considered (All)ACK (for example, no NACKs are detected on a PSFCH opportunity), then the current CW value is set for all priority classes. p The priority class can be reset to the minimum / initial value (see, for example, Table 5). When a group of terminals attempts to send a NACK feedback on a PSFCH opportunity, the terminal that sent the PSSCH in the groupcast transmission does not know whether the transmission failed due to a channel connection failure or whether the group of terminals received a previously sent PSSCH and therefore did not send a NACK feedback. Regardless of this, the current CW is set for all priority classes. pThe settings can be reset to the minimum / initial value for each priority class (see, for example, Table 5), and a Type 1 channel connection can be established when transmitting the next SL transmission (e.g., PSSCH).

[0189] On the other hand, if a terminal sends a PSSCH as a group cast transmission set to NACK only feedback, and receives HARQ-ACK feedback with all NACKs, or at least one NACK, from a group of terminals that received the PSSCH, the terminal that sent the PSSCH may retransmit the group cast transmission. In other words, if monitoring a PSFCH opportunity corresponding to a group cast reveals that all NACKs, or at least one NACK, is detected in that PSFCH opportunity, the terminal that sent the PSSCH may retransmit the group cast transmission. At this time, the terminal attempting to retransmit the PSSCH in the group cast transmission should perform the CW for Type 1 channel connection that should be done when retransmitting the PSSCH. p It can be ambiguous which value to set.

[0190] 1. As an example, considering that a terminal sends a PSSCH as a retransmission of a groupcast transmission, a method can be used in which CW adjustment is performed when a NACK is received if all terminals in a group send a NACK HARQ-ACK feedback, and this is received by the terminal that sent the PSSCH, or if at least one NACK HARQ-ACK feedback is received from the terminals in a group. For example, a terminal that sent a PSSCH as a groupcast transmission is currently in CW for all priority classes. p The value is increased to the next highest possible value for each priority class, and a Type 1 channel connection can be established when transmitting the next PSSCH. That is, if the received response results from multiple terminals corresponding to the groupcast transmission are considered Not(All) ACK (for example, if at least one NACK is detected during a PSFCH opportunity), then CW is currently available for all priority classes.p This can be increased to the next highest possible value for each priority class (see, for example, Table 5).

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

[0192] Figure 18 illustrates a channel connection process according to an example of the present invention. Referring to Figure 18, UE-A can establish a channel connection using the first CWS to transmit a group cast transmission (S1802). Here, the group cast transmission may be performed on a PSSCH. The channel connection also includes a Type 1 channel connection. Subsequently, UE-A can monitor the PSFCH (opportunity / resource) corresponding to the group cast transmission (S1804). If the monitoring results indicate that the HARQ feedback result is All ACKs (for example, no NACKs are detected in the PSFCH opportunity / resource), UE-A will perform the current CW for all priority classes. p The values ​​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 All ACKs (for example, if at least one NACK is detected in the PSFCH opportunity / resource), UE-A will reset the current CW pThis can be increased for all priority classes to the next highest possible value for each priority class (see, for example, Table 5) (S1806b). Then the set / adjusted CW p Using the value, UE-A can establish a channel connection (e.g., a Type 1 channel connection) when transmitting the SL transmission (e.g., PSSCH) that it is currently attempting to transmit (after sending a groupcast) (S1808). Here, the HARQ-feedback scheme set for the groupcast transmission includes the NACK-only feedback scheme.

[0193] When transmitting a PSSCH as a groupcast transmission configured with NACK-only feedback, either the base station can use sidelink resource allocation mode 1, where it informs the terminal of the time / frequency resources available for PSSCH transmission, or sidelink resource allocation mode 2, where a single resource pool is configured, the base station senses the pool to select resources, and then allocates the resources that are actually available for transmission. On the other hand, when a (single) resource pool is configured, there may be cases where no PSFCH resources are available if the PSFCH resource period and minimum time gap are not configured. In this case, the terminal transmitting the PSSCH will indicate a value of "0" (meaning disabled) using the HARQ-ACK enabled / disabled indicator in the second SCI, and the receiving terminal, after receiving the PSSCH, will not be able to transmit the HARQ-ACK information, which is NACK-only feedback information, because there are no configured PSFCH resources. At this time, the terminal that transmitted the PSSCH cannot expect an explicit HARQ-ACK from the receiving terminal, and therefore will not be able to transmit CW based on the HARQ-ACK information. p Adjustment is not possible. Therefore, when the terminal that sent PSSCH sends the next PSSCH, it will currently be in CW mode. p It can be ambiguous which value to set it to. To resolve this, if the channel connection priority class of the PSSCH currently attempting to transmit has been used previously, the terminal will now use CW. pThis corresponds to the CW of the same priority class that was most recently used (for the PSSCH transmission) (before the PSSCH transmission). p You can set a value to establish a Type 1 channel connection.

[0194] Alternatively, the terminal transmitting the PSSCH can indicate a value of "0" (meaning disabled) using the HARQ-ACK enabled / disabled indicator on 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 that was most recently used to transmit the PSSCH. p The value can be used directly for the Type 1 channel connection made when transmitting the PSSCH that is currently being sent.

[0195] Although the methods and systems of the present invention have been described in relation to specific embodiments, some or all of their components or operations may be embodied using a computing system having a general-purpose hardware architecture.

[0196] The foregoing description of the present invention is illustrative, and a person with ordinary skill in the art to which the invention pertains will understand that it can be readily modified into other specific forms without altering the technical idea or essential features of the invention. Therefore, the embodiments described above should be understood to be illustrative and not limiting in all respects. For example, each component described as a single type may be implemented in a distributed manner, and similarly, components described as distributed may be implemented in a combined manner.

[0197] The scope of the present invention is defined more by the claims described below than by the detailed description above, and any modified or altered forms derived from the meaning and scope of the claims and the concept of equivalents thereof should be interpreted as being included within the scope of the present invention.

Claims

1. A terminal configured to operate in a wireless communication system, Communication module and A processor that controls the communication module, The aforementioned processor, It is configured to attempt to send a sidelink (SL) transmission according to a channel access procedure (CAP) using a randomly selected backoff counter within a competition window (CW), When HARQ-ACK (hybrid automatic repeat request acknowledgedgement) feedback is enabled for the SL transmission, and the HARQ-ACK feedback result for the groupcast SL transmission is available before the SL transmission, the CW value is reset to a minimum or increased to the next highest possible value, based on whether the HARQ-ACK feedback result for the groupcast SL transmission contains at least one NACK (negative ACK), before the CAP for the SL transmission is executed. A terminal in which, when the HARQ-ACK feedback is disabled for the SL transmission, the CW value is adjusted to the same value as the CW used for the most recent SL transmission before executing the CAP for the SL transmission.

2. The terminal according to claim 1, wherein the enabling / disabling of the HARQ-ACK feedback is instructed by SCI (sidelink control information) corresponding to the SL transmission.

3. The terminal according to claim 1, wherein the CW value is reset to a minimum value when the HARQ-ACK feedback result for the groupcast SL transmission does not include at least one NACK.

4. The terminal according to claim 1, wherein the value of CW is increased to the next highest possible value when the HARQ-ACK feedback result for the groupcast SL transmission includes the at least one NACK.

5. The terminal according to claim 1, wherein the SL transmission includes PSSCH (physical sidelink shared channel).

6. The terminal according to claim 1, wherein the CW value is reset to the minimum value or increased to the next highest possible value for each priority class.

7. The terminal according to claim 1, wherein the wireless communication system includes a 3GPP® (3rd generation partnership project) based wireless communication system, and the CAP includes a Type 1 CAP.

8. A method performed by a terminal configured to operate in a wireless communication system, The process includes the step of attempting to send a sidelink (SL) transmission according to a channel access procedure (CAP) using a randomly selected backoff counter within a competition window (CW), When HARQ-ACK (hybrid automatic repeat request acknowledgedgement) feedback is enabled for the SL transmission, and the HARQ-ACK feedback result for the groupcast SL transmission is available before the SL transmission, the CW value is reset to a minimum or increased to the next highest possible value, based on whether the HARQ-ACK feedback result for the groupcast SL transmission contains at least one NACK (negative ACK), before the CAP for the SL transmission is executed. A method in which, when the HARQ-ACK feedback is disabled for the SL transmission, the CW value is adjusted to the same value as the CW used for the most recent SL transmission before the CAP is executed for the SL transmission.

9. The method according to claim 8, wherein the enabling / disabling ring of the HARQ-ACK feedback is indicated by SCI (sidelink control information) corresponding to the SL transmission.

10. The method according to claim 8, wherein the value of CW is reset to a minimum value when the HARQ-ACK feedback result for the groupcast SL transmission does not include the at least one NACK.

11. The method according to claim 8, wherein the value of CW is increased to the next highest possible value when the HARQ-ACK feedback result for the groupcast SL transmission includes the at least one NACK.

12. The method according to claim 8, wherein the SL transmission includes PSSCH (physical sidelink shared channel).

13. The method according to claim 8, wherein the value of CW is reset to the minimum value or increased to the next highest possible value for each priority class.

14. The method according to claim 8, wherein the wireless communication system includes a 3GPP® (3rd generation partnership project) based wireless communication system, and the CAP includes a Type 1 CAP.

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