Methods for determining base station, terminal, and contention window size

Abstract

A base station includes: a transmitting unit that repeatedly performs a process of decreasing a count value randomly determined within a contention window size based on channel monitoring, and transmits a signal after the count value becomes 0; a receiving unit that receives HARQ feedback corresponding to a plurality of time slots from a terminal receiving the signal; and a control unit that determines the contention window size based on the HARQ feedback corresponding to the plurality of time slots.

Description

Technical Field

[0001] This invention relates to base stations in wireless communication systems. Background Technology

[0002] In Universal Mobile Telecommunications System (UMTS) networks, Long Term Evolution (LTE) was standardized with the goal of further increasing data rates and lower latency. Furthermore, LTE-Advanced (3GPP Rel. 10-14) was standardized with the goal of further increasing capacity and height of LTE (Third Generation Partnership Project (3GPP) Release (Rel.) 8 and 9).

[0003] They are also researching successor systems to LTE (e.g., also known as 5G, 5G plus, New Radio, 3GPPRel.15 and later).

[0004] In existing LTE systems (e.g., Rel. 8-12), the exclusive use of frequency bands (also known as licensed bands, licensed carriers, licensed component carriers, etc.) licensed by the operator has been standardized. For example, 800MHz, 1.7GHz, and 2GHz are used as licensed component carriers.

[0005] Furthermore, in existing LTE systems (e.g., Rel. 13), to extend the bandwidth, the use of frequency bands different from the aforementioned licensed bands (also known as unlicensed bands, unlicensed carriers, or unlicensed CCs) is supported. Examples of unlicensed bands include the 2.4GHz or 5GHz bands that can use Wi-Fi (trademark) or Bluetooth (trademark).

[0006] Specifically, Rel.13 supports carrier aggregation (CA), which combines carriers (CC) from licensed and unlicensed bands. Communication using both licensed and unlicensed bands simultaneously is called License-Assisted Access (LAA).

[0007] Existing technical documents

[0008] Non-patent literature

[0009] Non-patent document 1: 3GPP TS 37.213 V15.2.0 (2019-03) Summary of the Invention

[0010] The problem that the invention aims to solve

[0011] In wireless communication systems that use licensed and unlicensed bands for communication, in the downlink, the base station performs carrier sensing before transmitting data in the unlicensed band to confirm whether other devices (e.g., base stations, user terminals, Wi-Fi devices, etc.) are transmitting.

[0012] If the base station's channel is idle, the count value, randomly determined within the Contention window size (CWS), is sequentially decreased. Once the count value reaches 0, transmission to the user terminal is initiated. For example, after data transmission concludes, the base station updates the Contention window size based on HARQ feedback received from the user terminal regarding data transmission in the most recent subframe.

[0013] For example, in NR-U, it is envisioned that HARQ feedback corresponding to multiple time slots will be sent from the user terminal in aggregate. However, no method for updating the contention window size in the case of sending HARQ feedback corresponding to multiple time slots in aggregate has been proposed.

[0014] The present invention was made in view of the above-mentioned problems, and its object is to provide a technique in which a base station can appropriately determine the contention window size when HARQ feedback corresponding to multiple time slots is sent from a user terminal.

[0015] Methods for solving problems

[0016] According to publicly available technology, a base station is provided, which has:

[0017] The transmitting unit repeatedly performs the process of decreasing the count value, which is randomly determined within the contention window size, based on channel monitoring. After the count value becomes 0, it transmits the signal.

[0018] The receiving unit receives HARQ feedback corresponding to multiple time slots from the terminal that receives the signal; and

[0019] The control unit determines the contention window size based on the HARQ feedback corresponding to the multiple time slots.

[0020] A base station is provided, comprising: a transmitting unit that repeatedly performs a process of decreasing a count value randomly set within a contention window size related to channel monitoring, and transmitting a signal after the count value becomes 0; a receiving unit that receives feedback from a terminal that receives the signal; and a control unit that, when the ratio of the number of affirmative responses among the HARQ feedback corresponding to a plurality of time slots received during the most recent channel occupancy time to the number of HARQ feedback corresponding to the latest transmitted plurality of code block groups (CBGs) is greater than or equal to a threshold determined according to the channel access priority category, sets the contention window size to a predetermined minimum value, and otherwise extends or maintains the contention window size.

[0021] A terminal is provided, comprising: a transmitting unit that transmits feedback on a signal received from a base station; and a receiving unit that receives a signal transmitted from the base station after the base station has repeatedly performed a process in which a count value randomly set within a contention window size is reduced, and the count value becomes 0. Regarding the contention window size, if the ratio of the number of affirmative responses to the number of HARQ feedbacks corresponding to multiple time slots received within the most recent channel occupancy time to the number of HARQ feedbacks corresponding to the latest transmitted code block groups (CBGs) is greater than or equal to a threshold determined according to the channel access priority level, the contention window size is set to a predetermined minimum value; otherwise, the contention window size is extended or maintained.

[0022] A communication system having a base station and a terminal is provided, wherein the base station has: a transmitting unit that repeatedly performs a process of decreasing a count value randomly set within a contention window size related to channel monitoring, and transmits a signal after the count value becomes 0; a receiving unit that receives feedback from the terminal that receives the signal; and a control unit that, when the ratio of the number of affirmative responses to the number of HARQ feedback corresponding to multiple time slots received during the most recent channel occupancy time to the number of HARQ feedback corresponding to the latest transmitted multiple code block groups (CBGs) is greater than or equal to a threshold determined according to the channel access priority category, sets the contention window size to a predetermined minimum value, otherwise extends or maintains the contention window size, and the terminal has: a receiving unit that receives the signal from the base station; and a transmitting unit that transmits feedback on the signal received from the base station.

[0023] A method for determining a contention window size, performed by a base station, is provided, comprising the following steps: repeatedly performing a process that reduces a randomly set count value within a contention window size related to channel monitoring; transmitting a signal after the count value becomes 0; receiving feedback from a terminal receiving the signal; and setting the contention window size to a predetermined minimum value if, among the HARQ feedback received during the most recent channel occupancy time corresponding to multiple time slots, the ratio of the number of affirmative responses to the number of HARQ feedback corresponding to the latest transmitted multiple code block groups (CBGs) is greater than or equal to a threshold determined according to the channel access priority category; otherwise, extending or maintaining the contention window size.

[0024] Invention Effects

[0025] According to the disclosed technology, a technique is provided in which a base station can appropriately determine the contention window size when HARQ feedback corresponding to multiple time slots is sent from a user terminal. Attached Figure Description

[0026] Figure 1 This is a diagram illustrating an example of CSMA / CA with ACK.

[0027] Figure 2 This is a diagram illustrating an example of a data conflict in a hidden terminal.

[0028] Figure 3 This is a diagram illustrating an example of CSMA / CA with RTS / CTS.

[0029] Figure 4 This is a diagram illustrating an example of RTS / CTS in an NR-U system.

[0030] Figure 5 This is a diagram showing examples of selectable CWS.

[0031] Figure 6 This is a diagram showing an example of an aggregated HARQ FB.

[0032] Figure 7 This is a diagram illustrating an example of the schematic structure of a wireless communication system according to one embodiment.

[0033] Figure 8 This is a flowchart used to illustrate method 1a.

[0034] Figure 9 This is a diagram used to illustrate method 1a.

[0035] Figure 10 This is a flowchart used to illustrate method 2a.

[0036] Figure 11 This is a diagram used to illustrate method 2a.

[0037] Figure 12 This is a flowchart used to illustrate method 1b.

[0038] Figure 13 This is a flowchart used to illustrate method 2b.

[0039] Figure 14 This is a diagram illustrating an example of the structure of a base station according to one embodiment.

[0040] Figure 15 This is a diagram illustrating an example of the structure of a user terminal in one implementation.

[0041] Figure 16 This is a diagram illustrating an example of the hardware structure of a base station and a user terminal according to one embodiment. Detailed Implementation

[0042] When describing the embodiments of the present invention, an example of a conflict avoidance method in an unauthorized band domain will first be explained.

[0043] (Conflict avoidance methods in unauthorized band domains)

[0044] In unlicensed bands (e.g., the 2.4 GHz band or the 5 GHz band), it is envisioned that multiple systems, such as Wi-Fi (registered trademark) systems and LAA-enabled systems (LAA systems), will coexist. Therefore, conflict avoidance or interference control between these multiple systems is required.

[0045] NR systems using unlicensed bands (also known as 5G, 5G+, NR, 3GPP Rel.15 and later) can also be called NR-Unlicensed (U) systems, NR LAA systems, etc. Dual connectivity (DC) and stand-alone (SA) of unlicensed bands may also be adopted in NR-U.

[0046] For example, in Wi-Fi (registered trademark) systems that utilize unlicensed band domains, Carrier Sense Multiple Access / Collision Avoidance (CSMA / CA) is employed for purposes such as collision avoidance.

[0047] Figure 1 This is a diagram illustrating an example of CSMA / CA. (For example...) Figure 1As shown, wireless terminal C (data transmitting side) investigates the signal on the communication medium (carrier sensing). Even if it determines there is no signal, it does not immediately begin data transmission, but instead waits for a specified time before transmitting data. This waiting time is called the Distributed Access Interframe Space (DIFS). Access point B (data receiving side), upon receiving the data, returns an acknowledgment (ACK). To prioritize sending an ACK, it only needs to wait a shorter time than the DIFS (Short IFS) to send it. Wireless terminal C (data transmitting side) repeatedly retransmits until it receives an ACK. Therefore, Figure 1 The access method shown (access method 1) is also known as CSMA / CA with ACK.

[0048] In Wi-Fi systems, to avoid collisions, a Request to Send (RTS) is sent before transmission. If the receiving device can receive the signal, it responds with a Clear to Send (CTS) response. For example, RTS / CTS is effective in avoiding data collisions caused by hidden nodes. When a signal from a node reaches the receiving device before reaching the transmitting device, that node is called a hidden node relative to the transmitting device. Hidden nodes can also be called undetected nodes, sensed nodes, etc. Data collisions caused by hidden nodes are also known as the hidden node problem.

[0049] Figure 2 This diagram illustrates an example of a data conflict caused by a hidden terminal. Figure 2 In this scenario, the radio waves emitted by wireless terminal C do not reach wireless terminal A. Therefore, even if wireless terminal A performs carrier sensing before transmission, it cannot detect the transmitted signal from wireless terminal C. As a result, while wireless terminal C is transmitting to access point B, wireless terminal A is also transmitting to access point B. In this situation, the transmitted signals from wireless terminals A and C collide at access point B, potentially reducing throughput.

[0050] Figure 3 It is shown Figure 2 A diagram illustrating an example of CSMA / CA with RTS / CTS in its structure. (See diagram for example.) Figure 3As shown, when the wireless terminal C (transmitting side) confirms that there are no other transmission signals (idle) through carrier sensing during the predetermined time before transmission (DIFS), it transmits RTS (in addition, in Figure 2 In this scenario, the RTS (Receiving Message) has not reached wireless terminal A (another terminal). RTS is preferably transmitted omnidirectionally (without directionality). RTS can also be beamformed. When access point B (the receiving side) receives the RTS from wireless terminal C, it confirms through carrier sensing for a predetermined time (Short Inter Frame Space (SIFS)) that there are no other transmission signals (idle, clear), and then transmits a CTS (Confirmation Message). CTS is preferably transmitted omnidirectionally. RTS can also be called a transmit request signal. CTS can also be called a receiveable signal.

[0051] exist Figure 2 In the process, the CTS from access point B also arrives at wireless terminal A (another device). Therefore, wireless terminal A detects the communication and delays transmission. Since the RTS / CTS packets record a predetermined period (also known as a Network Allocation Vector (NAV) or a transmission prohibition period, etc.), communication is maintained during this predetermined period (NAV "NAV(RTS)" in RTS and NAV "NAV(CTS)" in CTS).

[0052] When a wireless terminal C receives data from a CTS at access point B and confirms that there are no other transmission signals (idle) during the pre-transmission scheduled period (SIFS), it transmits a data frame. Access point B, having received the data, sends an ACK after the scheduled period (SIFS).

[0053] exist Figure 3 In this scenario, when wireless terminal A, acting as a hidden terminal of wireless terminal C, detects a CTS signal from access point B, it delays its transmission, thus avoiding signal conflicts between wireless terminals A and C in access point B.

[0054] In the LAA of existing LTE systems (e.g., Rel.13), the data transmitting device performs a listening operation (also known as LBT, CCA, carrier sensing, or channel access action) to confirm the presence or absence of transmissions by other devices (e.g., base stations, user terminals, Wi-Fi devices, etc.) before transmitting data in the unlicensed band.

[0055] The transmitting device can be a base station (e.g., gNodeB, gNB, TRP, network (NW)) in the downlink (DL) and a user terminal (e.g., user equipment (UE)) in the uplink (UL). Furthermore, the receiving device that receives data from the transmitting device can be a user terminal in the DL and a base station in the UL.

[0056] In the existing LTE system's LAA (Local Area Access) mechanism, the transmitting device begins data transmission after a predetermined period (e.g., immediately following or during a fallback period) following the detection of no other device transmitting (idle state) in the listening process. When other devices are detected transmitting (busy state) in the listening process, data transmission ceases. However, even when the transmitting device transmits data based on the listening results, the aforementioned hidden terminals exist, potentially leading to data collisions in the receiving device.

[0057] Therefore, in NR-U systems, research is underway to support the aforementioned RTS / CTS in order to improve the data collision avoidance rate in the receiving device.

[0058] Figure 4 This diagram illustrates an example of RTS / CTS in an NR-U system. In an NR-U system that supports RTS / CTS, it is envisioned that the transmitting device (base station) transmits RTS via an unlicensed band carrier (also known as an unlicensed carrier, unlicensed CC, LAA SCell (Secondary Cell), etc.) before sending downlink data to the receiving device (user terminal).

[0059] When uplink unlicensed CC is supported in such an NR-U system, such as Figure 4 As shown, consider the downlink data receiving device (user terminal) using the uplink unlicensed CC to transmit CTS. Alternatively, the uplink unlicensed CC can be replaced by a TDD (Time Division Duplex, unpaired spectrum) unlicensed CC.

[0060] In NR-U, nodes (e.g., base stations (e.g., gNBs) and UEs) obtain a transmission opportunity (TxOP, Channel Occupancy) when the LBT result is idle and transmit. When the LBT result is busy, they do not transmit. The duration of the transmission opportunity is called the Channel Occupancy Time (COT).

[0061] COT is the total duration of all transmissions within a transmission opportunity and the intervals within the scheduled time, and can also be below the maximum COT (MCOT). MCOT can be determined based on the channel access priority class. The channel access priority class can be associated with the contention window size.

[0062] Base stations that have obtained MCOT through LBT can also perform scheduling for more than one user terminal during the MCOT period.

[0063] The NR-U system can perform carrier aggregation (CA) using both unlicensed and licensed CCs, dual connectivity (DC) using both unlicensed and licensed CCs, or standalone (SA) using only unlicensed CCs. CA, DC, or SA can be performed through either NR or LTE. DC can also be performed through at least two of NR, LTE, and other systems.

[0064] UL transmission in an unauthorized CC can be at least one of PUSCH, PUCCH, and SRS.

[0065] Nodes can perform LBT or receiver-assisted LBT in LTE LAA as LBTs for obtaining COT (initial LBT, I-LBT). In this case, the LTE LAA LBT can be of category 4.

[0066] User terminals can envision detecting the presence of signals (e.g., reference signals such as demodulation reference signals (DMRS)) within bursts of transmitted PDCCH or group common-PDCCH (GC-PDCCH) from the serving base station. A PDCCH can also be a PDCCH oriented towards a single UE (UE-specific PDCCH, Regular PDCCH). A GC-PDCCH can be a PDCCH shared by more than one UE (UE group common-PDCCH).

[0067] The base station may also send a specific PDCCH (PDCCH or GC-PDCCH) containing a specific DMRS notifying the start of COT at the start of COT. At least one of the specific PDCCH and specific DMRS can also be referred to as a COT start notification signal. The base station sends a COT start notification signal to one or more specific UEs, and the UE recognizes COT upon detecting the specific DMRS.

[0068] The base station can schedule the transmission of UL within the COT of a UE through a specific PDCCH. The UE whose UL transmission within the COT is scheduled is called the specific UE. The specific UE can also be the UE whose UL signal transmission within the COT is scheduled (e.g., the initial UL signal within the COT).

[0069] In NR-U, the information exchange (handshake) process between the transmitting and receiving devices is being studied. The study investigates a scenario where a UE, designated by a specific PDCCH, sends a specific UL signal (acknowledgment signal) such as SRS after LBT, thereby enabling the information exchange process between the base station and the UE.

[0070] Thus, in NR-U, by using a specific PDCCH (COT start notification signal) as in the transmit request signal (RTS) and a response signal triggered by a specific PDCCH as in the receiveable status notification signal (CTS), we study access methods close to CSMA / CA with RTS / CTS (receiver assisted access, receiver assisted access (RAA), information exchange process, access method using RTS / CTS, and second access method).

[0071] (Topic)

[0072] Here's a more detailed example of the existing LBT mechanism in a base station implementing LAA. After the previous transmission, the base station randomly generates a backoff count value within the contention window size (CWS). The base station remains idle until it confirms that the channel (e.g., a channel or carrier on a frequency in the unlicensed band) is idle for the initial delay time, performing carrier sensing during each listening slot.

[0073] If carrier sensing indicates that the channel is idle, the backoff count is decremented. If the channel is busy, the backoff count is maintained, and carrier sensing is initiated only after the initial delay time has elapsed and the channel is confirmed to be idle.

[0074] By repeatedly performing the above actions, the base station can obtain access to the channel when the backoff count reaches 0, thereby initiating signal transmission in that channel. This signal transmission can be data transmission based on PDSCH, control information transmission based on PDCCH, or control information or data transmission based on EPDCCH.

[0075] After transmission is completed, the base station updates the CWS based on the occurrence of communication errors in the most recent transmission burst. Specifically, for example, when using the existing method described in Non-Patent Document 1, the base station updates the CWS to a longer CWS if the NACK rate of the HARQ FB (feedback) corresponding to the PDSCH transmission in the most recent transmission subframe of the carrier is 80% or higher.

[0076] Figure 5 (Table 4.1.1-1 of Non-Patent Document 1: Channel Access Priority Categories) shows examples of selectable CWS.

[0077] Figure 5 Each Channel Access Priority Class indicates the MCOT (Maximum Channel Occupancy Time), selectable CWS, etc. For example, if a base station wants to transmit small data with low latency, it can shorten the LBT time instead of shortening the COT by using Channel Access Priority Class = 1 (Channel Access Priority Class = 1).

[0078] As mentioned above, in NR-U, DL and UL switching can be performed within a COT (Cross-Operation Time). However, since LBT (Long-Terminal Bit-Break) is required during switching, the possibility of losing transmission opportunities increases when switching occurs frequently. Furthermore, a timeout period for LBT needs to be set, resulting in significant switching overhead. Therefore, in NR-U, the number of DL / UL switching operations within a single COT may also be limited.

[0079] Based on the above reasons, an extended method is being studied that allows for a longer waiting time from PDSCH-based data reception to the transmission of HARQ FBs compared to the specified time, thereby enabling the aggregated transmission of HARQ FBs within the COT by terminals such as COT terminals. Here, the aggregated HARQ FBs are referred to as aggregated HARQ FBs. It is envisioned that the aggregated HARQ FB contains HARQ FBs corresponding to multiple time slots.

[0080] Figure 6 (Excerpt from R1-1906644) illustrates an example of a user terminal sending an aggregated HARQ FB. In Figure 6 In the example shown, there are 3 time slots, and the user terminal sends an aggregated HARQ FB containing the individual HARQ FBs for the data received in each of the 3 time slots through the end part of the COT.

[0081] As mentioned above, Non-Patent Document 1 discloses that the CWS is updated based on the most recently transmitted HARQ-FB corresponding to the subframe that is expected to be received by the HARQ-FB. However, no solution has been proposed so far for how to update the CWS when multiple HARQ-FBs corresponding to multiple time slots are returned from the user terminal.

[0082] The following is a detailed description of an example of a CWS update method in the case of returning HARQ FB corresponding to multiple time slots from the user terminal as an embodiment of the present invention.

[0083] Embodiments of the present invention

[0084] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The various methods described in this embodiment can be implemented individually or in combination.

[0085] In this disclosure, frequency, band, frequency band, spectrum, carrier, component carrier (CC), cell, channel, subband domain, LBT subband domain, active bandwidth part (BWP), and active BWP part can be interchanged.

[0086] In this disclosure, listening, listening before talking (LBT), clear channel assessment (CCA), carrier listening, listening, channel listening, or channel access procedure are interchangeable.

[0087] In this disclosure, NR-U frequency, NR-U object frequency, NR-U band, shared spectrum, unlicensed band, unlicensed spectrum, LAA SCell, LAA cell, primary cell (PCell, primary secondary cell (PSCell), special cell (SpCell), secondary cell (SCell), and the frequency band used for channel monitoring can be interchanged.

[0088] In this disclosure, NR frequency, NR object frequency, licensed band, licensed spectrum, PCell, PSCell, SpCell, SCell, non-NR-U frequency, Rel.15, NR, and channel monitoring unused frequency bands can be interchanged.

[0089] Different frame structures can also be used in NR-U object frequency and NR object frequency.

[0090] Wireless communication systems (NR-U, LAA systems) can also follow the first wireless communication standard (e.g., NR, LTE, etc.) (supporting the first wireless communication standard).

[0091] Other systems (coexisting systems, coexisting devices) and other wireless communication devices (coexisting devices) that coexist with the first wireless communication standard may comply with a second wireless communication standard (supporting the second wireless communication standard), such as LTE, Wi-Fi, Bluetooth, WiGig, LAN (Local Area Network), IEEE 802.11, or Low Power Wide Area (LPWA), which are different from the first wireless communication standard. A coexisting system can be a system that receives interference from the wireless communication system, or it can be a system that causes interference to the wireless communication system.

[0092] In this disclosure, the UE (user terminal) transmit, UL transmit, UL signal, physical uplink shared channel (PUSCH), physical uplink control channel (PUCCH), sounding reference signal (SRS), uplink-reference signal (UL-RS), preamble, random access channel (RACH), and physical random access channel (PRACH) can be interchanged.

[0093] In this disclosure, the base station's transmission, DL transmission, DL signal, physical downlink shared channel (PDSCH), physical downlink control channel (PDCCH), downlink-reference signal (DL-RS), demodulation reference signal (DMRS) for PDCCH, and DMRS for PDSCH can be interchanged.

[0094] In this disclosure, nodes, UEs, base stations, transceiver points (TRPs), wireless communication devices, and devices can be interchanged.

[0095] Furthermore, the NR-U disclosed herein is not limited to LAA, but may also include cases where unlicensed band domains are used in a stand-alone manner.

[0096] Wireless Communication Systems

[0097] The structure of a wireless communication system according to one embodiment of this disclosure will now be described. In this wireless communication system, communication is performed using any one or a combination of the methods described in this disclosure embodiment. Furthermore, this wireless communication system is capable of performing at least the operations of the NR-U system described above.

[0098] Figure 7This is a diagram illustrating an example of the schematic structure of a wireless communication system according to one implementation. The wireless communication system 1 may be a system that uses Long Term Evolution (LTE), 5G New Radio (5G NR), etc., which are standardized by the Third Generation Partnership Project (3GPP) to achieve communication.

[0099] In addition, the wireless communication system 1 can also support dual connectivity between multiple radio access technologies (RATs) (Multi-RAT Dual Connectivity (MR-DC)).

[0100] MR-DC can include dual connectivity of LTE (Evolved Universal Terrestrial Radio Access (E-UTRA)) and NR (EN-DC: E-UTRA-NR Dual Connectivity), dual connectivity of NR and LTE (NE-DC: NR-E-UTRA Dual Connectivity), etc.

[0101] In EN-DC, the LTE (E-UTRA) base station (eNB) is the master node (MN), and the NR base station (gNB) is the secondary node (SN). In NE-DC, the NR base station (gNB) is the MN, and the LTE (E-UTRA) base station (eNB) is the SN.

[0102] Wireless communication system 1 can support dual connectivity between multiple base stations within the same RAT (e.g., dual connectivity between base stations (gNB) where both MN and SN are NR (NN-DC: NR-NR Dual Connectivity)).

[0103] The wireless communication system 1 may include: a base station 11, which forms a macro cell C1 with a relatively large coverage area; and base stations 12 (12a-12c), which are configured within the macro cell C1 to form a small cell C2 smaller than the macro cell C1. User terminals 20 may be located within at least one cell. The configuration and number of cells and user terminals 20 are not limited to the illustrated arrangement. Hereinafter, without distinguishing between base stations 11 and 12, they will be collectively referred to as base station 10. Furthermore, the CWS update operation of this invention can also be performed through any one of the base stations.

[0104] User terminal 20 can be connected to at least one of multiple base stations 10. User terminal 20 can also utilize at least one of carrier aggregation (CA) using multiple component carriers (CC) and dual connectivity (DC).

[0105] Each CC can be included in at least one of frequency band 1 (FR1) and frequency band 2 (FR2). Macro cell C1 can be included in FR1, and small cell C2 can be included in FR2. For example, FR1 can be a frequency band below 6 GHz (sub-6 GHz), and FR2 can be a frequency band above 24 GHz (above-24 GHz). In addition, the frequency bands, definitions, etc. of FR1 and FR2 are not limited to these; for example, FR1 can also correspond to a frequency band higher than FR2.

[0106] In addition, user terminal 20 can use at least one of time division duplex (TDD) and frequency division duplex (FDD) to communicate in each CC.

[0107] Multiple base stations 10 can be connected via wired (e.g., fiber optic, X2 interface, etc. according to the Common Public Radio Interface (CPRI)) or wireless (e.g., NR communication). For example, when NR communication is used as a backhaul between base stations 11 and 12, base station 11, which is equivalent to the host station, can be referred to as the Integrated Access Backhaul (IAB) donor, and base station 12, which is equivalent to the relay station, can be referred to as the IAB node.

[0108] Base station 10 can be connected to core network 30 via other base stations 10 or directly. Core network 30 may include at least one of the following: Evolved Packet Core (EPC), 5G Core Network (5GCN), Next Generation Core (NGC).

[0109] User terminal 20 can be a terminal corresponding to at least one of the communication methods such as LTE, LTE-A, and 5G.

[0110] In wireless communication system 1, wireless access methods based on Orthogonal Frequency Division Multiplexing (OFDM) can also be used. For example, in at least one of the downlink (DL) and uplink (UL), Cyclic Prefix OFDM (CP-OFDM), Discrete Fourier Transform Spread OFDM (DFT-s-OFDM), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier Frequency Division Multiple Access (SC-FDMA), etc.

[0111] The wireless access method can also be referred to as a waveform. In addition, other wireless access methods (e.g., other single-carrier transmission methods, other multi-carrier transmission methods) can also be used in the wireless access methods of UL and DL in wireless communication system 1.

[0112] In the wireless communication system 1, as a downlink channel, the following can be used: downlink shared channel (Physical Downlink Shared Channel (PDSCH)), broadcast channel (Physical Broadcast Channel (PBCH)), downlink control channel (Physical Downlink Control Channel (PDCCH)), etc., which are shared among the user terminals 20.

[0113] Furthermore, in the wireless communication system 1, as the uplink channel, the following can be used: the uplink shared channel (Physical Uplink Shared Channel (PUSCH)), the uplink control channel (Physical Uplink Control Channel (PUCCH)), and the random access channel (Physical Random Access Channel (PRACH)) shared by each user terminal 20.

[0114] User data, high-level control information, and System Information Blocks (SIBs) are transmitted via PDSCH. User data and high-level control information can also be transmitted via PUSCH. Additionally, Master Information Blocks (MIBs) can be transmitted via PBCH.

[0115] Lower-layer control information can also be transmitted via PDCCH. This lower-layer control information may include, for example, downlink control information (DCI), which contains scheduling information for at least one of PDSCH and PUSCH.

[0116] Additionally, the DCI for scheduling PDSCH can be called DL allocation, DL DCI, etc., and the DCI for scheduling PUSCH can be called UL authorization, UL DCI, etc. Furthermore, PDSCH can be replaced with DL data, and PUSCH can be replaced with UL data.

[0117] In PDCCH detection, a Control Resource Set (CORESET) and a search space can be used. A CORESET corresponds to the resources used to search for DCIs. The search space corresponds to the search area and search method for PDCCH candidates. One CORESET can be associated with one or more search spaces. User terminal 20 can monitor CORESETs associated with a specific search space according to the search space settings.

[0118] One search space can correspond to one or more PDCCH candidates equivalent to one or more aggregation levels. One or more search spaces can be referred to as a search space set. In addition, the terms "search space", "search space set", "search space setting", "search space set setting", "CORESET", and "CORESET setting" in this disclosure are interchangeable.

[0119] Uplink control information (UCI) containing at least one of the following can be transmitted via PUCCH: Channel State Information (CSI), Delivery Acknowledgment Information (e.g., also known as Hybrid Automatic Repeat reQuest ACK knowledge, ACK / NACK, etc.), and Scheduling Request (SR). Random access preambles used for establishing connections with cells can also be transmitted via PRACH.

[0120] In addition, in this disclosure, downlink, uplink, etc., may be described without the word "link". Furthermore, the word "physical" may be omitted from the beginning of various channels.

[0121] In wireless communication system 1, synchronization signals (SS) and downlink reference signals (DL-RS) can be transmitted from base station 10. In wireless communication system 1, the DL-RS can transmit cell-specific reference signals (CRS), channel state information reference signals (CSI-RS), demodulation reference signals (DMRS), positioning reference signals (PRS), and phase tracking reference signals (PTRS).

[0122] Synchronization signals can be, for example, at least one of the primary synchronization signal (PSS) and secondary synchronization signal (SSS). A signal block containing SS (PSS, SSS) and PBCH (and DMRS for PBCH) can also be called an SS / PBCH block, SS block (SSB), etc. Additionally, SS, SSB, etc., can also be called reference signals.

[0123] Furthermore, in the wireless communication system 1, measurement reference signals (SRS) and demodulation reference signals (DMRS) can also be transmitted from the user terminal 20 as uplink reference signals (UL-RS). In addition, DMRS can also be called user terminal-specific reference signals (UE-specific Reference Signal).

[0124] In the wireless communication system disclosed herein, base station 10 performs, for example, the downlink channel access procedure described above to transmit signals using a carrier (also referred to as a channel) in the unlicensed band. That is, after the previous transmission, base station 20 randomly generates a backoff count value within the range of the CWS. Base station 20 performs carrier sensing (= channel sensing) during each listening time slot until it is confirmed that the channel is idle, with an initial standby delay time.

[0125] If carrier sensing indicates the channel is idle, the backoff count is decreased. If the channel is busy, the backoff count is maintained, and carrier sensing is performed again after the initial standby delay until the channel is confirmed to be idle.

[0126] By repeating the above actions, the base station can obtain access to the channel when the backoff count value becomes 0, and thus begin transmitting.

[0127] After transmission is completed, base station 10 performs a CWS update operation, for example, at the LBT start timing, or at any timing during the period from the moment the last aggregated HARQFB is received to the LBT start timing. Details of the CWS update operation in this disclosure will be described later. Furthermore, the aforementioned "LBT start" timing can refer to the timing immediately preceding the random generation of the backoff count value.

[0128] In addition, if using Figure 6 As described, the user terminal 20 in the wireless communication system 1 of this disclosure is able to aggregate HARQ FBs corresponding to multiple time slots as an aggregated HARQ FB for transmission.

[0129] (CWS update action)

[0130] The following describes the CWS update operation performed by the base station 10 in this disclosure. The base station 10 in this disclosure is designed to support NR-U, but the operations described below are not limited to NR-U and can also be applied to other methods.

[0131] In this disclosure, the base station 10 receives HARQFBs (Aggregated HARQ FBs) corresponding to multiple time slots from the user terminal 20 via a COT terminal or the like, and uses the received HARQ FBs corresponding to multiple time slots to perform CWS update determination. Hereinafter, methods 1a, 2a, 2-1a, 1b, 2b, and 2-1b will be described as specific examples.

[0132] <Method 1a>

[0133] In method 1a, base station 10 receives all the HARQ FBs that should be received from the most recently received aggregated HARQ FBs since the LBT started, and shortens (or maintains) the CWS only if all of them are ACKs, or resets the CWS to the minimum value. Otherwise, base station 10 extends (or maintains) the CWS.

[0134] Refer to the example showing the update action of CWS. Figure 8 The flowchart below illustrates method 1a. In step S (Step 101), base station 10 determines the most recently received aggregated HARQ FB from the LBT. Additionally, base station 10 stores at least the information of the most recently received aggregated HARQ FB (e.g., the bit sequence of ACK / NACK) in a storage device such as memory, thus enabling it to read the aggregated HARQ FB from memory and use it for CWS update operations.

[0135] Figure 9 This illustrates an example of an aggregated HARQ FB received by base station 10 from user terminal 20. Figure 9 In the example shown, base station 10 receives aggregated HARQ FB-A, aggregated HARQ FB-B, and aggregated HARQ FB-C. Figure 9 In the example shown, Figure 8 In S101, base station 10 determines the aggregated HARQ FB-A.

[0136] exist Figure 8 In S102, base station 10 confirms the content of the determined aggregated HARQ FB, receives all the HARQ FBs that should be received, and determines whether they are all ACKs.

[0137] In order to transmit data (also known as signals) based on PDSCH, base station 10 sends control information (DCI) to user terminal 20 via PDCCH, thus being able to know the HARQ FB that should be received corresponding to the data transmission based on PDSCH.

[0138] As an example, consider the following scenario: Base station 10 schedules user terminal 20 to transmit 2TB (transport block) across 3 time slots, and transmits aggregated HARQ FB based on PUCCH through the end part of the 3rd time slot.

[0139] In this case, base station 10 confirms the contents of the aggregated HARQ FB in S102 and determines whether all 6 HARQ FBs are ACKs.

[0140] If the determination result in S102 is "yes", proceed to S103, and base station 10 shortens (or maintains) the CWS in the case of the minimum value. Alternatively, the CWS can be reset to the minimum value. As an example, assume that it is possible to use... Figure 5 The CWS is shown, and it is assumed that the corresponding channel access priority category is 3. In this case, if the CWS before the update was 63, then in S103, the CWS is shortened to 31. Furthermore, if the CWS before the update was 15, then in S103, the CWS is maintained.

[0141] If the decision result in S102 is "No", proceed to S104, and base station 10 extends (or maintains) the CWS in the case of the maximum value. As an example, assume that it is possible to use... Figure 5 The CWS is shown, and it is assumed that the corresponding channel access priority category is 3. In this case, if the CWS before the update was 15, then in S104, the CWS is extended to 31. Furthermore, if the CWS before the update was 63, then in S104, the CWS is maintained.

[0142] <Method 2a>

[0143] Next, method 2a will be described. In method 2a, base station 10 receives all HARQ FBs corresponding to the most recently received aggregated HARQ FBs from the LBT onwards, and shortens (or maintains) the CWS to the minimum value only if all of them are ACKs. Otherwise, base station 10 extends (or maintains) the CWS to the maximum value. N is a predetermined number. N can be determined according to the channel access priority category. Alternatively, the transmitted data such as TB and CBG that expect to receive HARQ FBs can be referred to as signals.

[0144] Reference Figure 10 The flowchart below illustrates method 2a. In S201, base station 10 determines the most recently received aggregated HARQ FB from the LBT.

[0145] In S202, base station 10 confirms the content of the determined aggregated HARQ FB, receives all HARQ FBs corresponding to the latest N TBs or CBGs, and determines whether they are all ACKs.

[0146] Figure 11 An example is shown. Figure 11 An example is shown where base station 10 transmits transport blocks A to D (TB-A to TB-D) through the illustrated time slots within the COT and returns an aggregated HARQ FB consisting of four ACKs / NACKs corresponding to TB-A to TB-D.

[0147] In this case, if N=3, then in S202, base station 10 receives the HARQ FB corresponding to TB-B, the HARQ FB corresponding to TB-C, and the HARQ FB corresponding to TB-D, and determines whether they are all ACKs.

[0148] If the determination result in S202 is "yes", proceed to S203, and base station 10 shortens (or maintains) the CWS in the case of minimum value. Alternatively, the CWS can be reset to the minimum value.

[0149] If the determination result in S202 is "no", proceed to S204, and base station 10 extends (or maintains) CWS in the case of the maximum value.

[0150] <Method 2-1a>

[0151] Next, method 2-1a will be explained. The processing procedure of method 2-1a is the same as that of method 2a. However, in method 2-1a, the number n of all HARQ FBs to be received in the aggregated HARQ FBs determined in S201 is less than N. In this case, base station 10 uses only n HARQ FBs to perform the CWS update operation. The operation in method 2-1a is the same as the operation in method 1a in terms of result.

[0152] <Method 1b>

[0153] Next, method 1b will be described. In method 1b, base station 10 shortens (or maintains) the CWS or resets the CWS to its minimum value only if the proportion of received ACKs in all HARQ FBs that should be received in the most recent aggregated HARQ FBs received since the LBT is x% or higher (x is a real number from 0 to 100). Otherwise, base station 10 extends (or maintains) the CWS. x is a predetermined amount. x can be determined according to the channel access priority category.

[0154] Reference Figure 12 The flowchart below illustrates method 1b. In S301, base station 10 determines the most recently received aggregated HARQ FB from the LBT.

[0155] In S302, base station 10 confirms the content of the determined aggregated HARQ FB and determines whether the ratio of the number of received ACKs to the total number of HARQ FBs that should be received is greater than x [%].

[0156] For example, if base station 10 intends to receive all 10 HARQ FBs using the aggregated HARQ FB determined in S301, assume that the aggregated HARQ FB contains 8 ACKs. In this case, for example, if x is 80, base station 10 determines that the proportion of the number of received ACKs to the total number of HARQ FBs to be received is x [%] or more.

[0157] If the determination result in S302 is "yes", proceed to S303, and base station 10 shortens (or maintains) the CWS in the case of minimum value. Alternatively, the CWS can be reset to the minimum value.

[0158] If the determination result in S302 is "no", proceed to S304, and base station 10 extends (or maintains) CWS in the case of the maximum value.

[0159] Alternatively, the following actions can also be performed in method 1b.

[0160] Base station 10 extends (or maintains) the Channel Access Window (CWS) only if the proportion of received NACKs in all HARQ FBs that should be received, traced back from the LBT to the most recent aggregated HARQ FB, is greater than or equal to y [%] (y is a real number from 0 to 100). Otherwise, base station 10 shortens (or maintains) the CWS. y is a predetermined amount. y can be determined based on the channel access priority category.

[0161] <Method 2b>

[0162] Next, method 2b will be described. In method 2b, base station 10 shortens (or maintains) the CWS or resets it to the minimum value only when the proportion of received ACKs in the predetermined received HARQ FBs corresponding to the most recently sent N (N is an integer greater than or equal to 0) TBs or CBGs traced back from the LBT is x% or greater (x is a real number from 0 to 100). Otherwise, base station 10 extends (or maintains) the CWS. N and x are predetermined quantities. N and x can be determined according to the channel access priority category.

[0163] Reference Figure 13 The flowchart below illustrates method 2b. In S401, base station 10 determines the most recently received aggregated HARQ FB from the LBT.

[0164] In S402, base station 10 confirms the content of the determined aggregated HARQ FB and determines whether the ratio of the number of received ACKs to the number of predetermined received HARQ FBs corresponding to the latest sent N TBs or CBGs is greater than x[%].

[0165] Using the above Figure 11 As an example, in this case, if N=3, then in S402, base station 10 investigates the ACK ratio of the three HARQ FBs: the HARQ FB corresponding to TB-B, the HARQ FB corresponding to TB-C, and the HARQ FB corresponding to TB-D. For example, if two out of the three are ACKs and x is 80, then base station 10 determines it as "No" in S402.

[0166] If the determination result in S402 is "yes", proceed to S403, and base station 10 shortens (or maintains) the CWS in the case of minimum value. Alternatively, the CWS can be reset to the minimum value.

[0167] If the determination result in S402 is "no", proceed to S404, and base station 10 extends (or maintains) CWS in the case of the maximum value.

[0168] In method 2b, the following actions can also be performed.

[0169] Base station 10 extends (or maintains) the number of received NACKs in the expected received HARQ FBs corresponding to the most recently received aggregated HARQ FBs (where N is an integer greater than or equal to 0) TBs or CBGs, only if the ratio of NACKs received to the most recently received aggregated HARQ FBs (where N is a real number from 0 to 100) is greater than or equal to y[%] (y is a real number from 0 to 100). Otherwise, base station 10 shortens (or maintains) the CWS (Channel Wire Side Width). N and y are predetermined values. N and y can be determined separately based on the channel access priority category.

[0170] <Method 2-1b>

[0171] Next, method 2-1b will be explained. The processing procedure of method 2-1b is the same as that of method 2b. However, in method 2-1b, the number n of all HARQ FBs to be received in the aggregated HARQ FBs determined in S401 is less than N. In this case, base station 10 uses only n HARQ FBs to perform the CWS update operation. The operation in method 2-1b is the same as the operation in method 1b in terms of result.

[0172] In addition, the CWS when the user terminal 20 transmits a signal can be obtained by means of one or more HARQ FBs for the uplink signal or by aggregated HARQ FBs for the uplink signal, using the same method as the base station of this disclosure. Alternatively, the value can be obtained from the base station 10 using RRC signaling or MAC CE.

[0173] That is, in methods 1a, 2a, 2-1a, 1b, 2b, and 2-1b, base station 10 and user terminal 20 can be replaced with user terminal 20 and base station 10, respectively. Transmissions from base station 10 (which becomes user terminal 20 after replacement) are considered uplink signal transmissions, and receptions based on base station 10 (which becomes user terminal 20 after replacement) are considered downlink signal receptions. In this case, the replaced user terminal 20 performs the actions of base station 10 in methods 1a, 2a, 2-1a, 1b, 2b, and 2-1b, and the replaced base station 10 performs the actions of user terminal 20 in methods 1a, 2a, 2-1a, 1b, 2b, and 2-1b. Furthermore, as described above, the CWS when user terminal 20 transmits signals can use the value notified from base station 10 using RRC signaling or MAC CE, etc.

[0174] (Device structure)

[0175] Next, an example of the structure of the base station 10 and the user terminal 20 in this disclosure will be described.

[0176] <base station>

[0177] Figure 14 This diagram illustrates an example of the structure of a base station 10 according to one embodiment. The base station 10 includes a control unit 110, a transceiver unit 120, a transceiver antenna 130, and a transmission line interface 140. Alternatively, more than one control unit 110, transceiver unit 120, transceiver antenna 130, and transmission line interface 140 may be included.

[0178] Furthermore, in this example, only the functional blocks of the characteristic parts of this embodiment are shown. The base station 10 can be envisioned as also having other functional blocks required for wireless communication. Some of the processing of the various components described below may also be omitted.

[0179] The control unit 110 implements overall control of the base station 10. The control unit 110 may be composed of a controller, control circuit, etc., which are described based on common knowledge in the art of this disclosure.

[0180] The control unit 110 can control signal generation and scheduling (e.g., resource allocation, mapping). The control unit 110 can control transmission, reception, and measurement using the transceiver unit 120, transceiver antenna 130, and propagation line interface 140. The control unit 110 generates data, control information, and sequences for signal transmission and forwards them to the transceiver unit 120. The control unit 110 can perform call processing (setting, releasing, etc.) of the communication channel, status management of the base station 10, and management of radio resources.

[0181] The transceiver unit 120 may include a baseband unit 121, a radio frequency (RF) unit 122, and a measurement unit 123. The baseband unit 121 may include a transmission processing unit 1211 and a reception processing unit 1212. The transceiver unit 120 may be composed of a transmitter / receiver, RF circuitry, baseband circuitry, filters, phase shifters, measurement circuitry, and transceiver circuitry, as described based on common knowledge in the art of this disclosure.

[0182] The transceiver unit 120 can be configured as a single unit, or it can be composed of a transmitting unit and a receiving unit. The transmitting unit can be composed of a transmitting processing unit 1211 and an RF unit 122. The receiving unit can be composed of a receiving processing unit 1212, an RF unit 122, and a measurement unit 123.

[0183] The transceiver antenna 130 may be composed of an antenna, such as an array antenna, as described in the art based on common knowledge in the field of this disclosure.

[0184] The transceiver unit 120 can transmit the aforementioned downlink channel, synchronization signal, downlink reference signal, etc. The transceiver unit 120 can also receive the aforementioned uplink channel, uplink reference signal, etc.

[0185] The transceiver unit 120 may use digital beamforming (e.g., precoding), analog beamforming (e.g., phase rotation), etc., to form at least one of the transmit beam and the receive beam.

[0186] The transceiver unit 120 (transmission processing unit 1211) can process data and control information obtained from the control unit 110, such as data at the Packet Data Convergence Protocol (PDCP) layer, at the Radio Link Control (RLC) layer (e.g., RLC retransmission control), at the Medium Access Control (MAC) layer (e.g., HARQ retransmission control), and generate a bit sequence to be transmitted.

[0187] The transceiver unit 120 (transmission processing unit 1211) can perform channel coding (which may also include error correction coding), modulation, mapping, filtering, Discrete Fourier Transform (DFT) processing (as needed), Inverse Fast Fourier Transform (IFFT) processing, precoding, digital-to-analog conversion, and other transmission processing on the bit sequence to be transmitted, and output the baseband signal.

[0188] The transceiver unit 120 (RF unit 122) can also modulate, filter, amplify, etc., the baseband signal to the wireless frequency band, and transmit the wireless frequency band signal via the transceiver antenna 130.

[0189] On the other hand, the transceiver unit 120 (RF unit 122) can also amplify, filter, and demodulate the signals in the wireless frequency band received by the transceiver antenna 130 into baseband signals.

[0190] The transceiver unit 120 (receiver processing unit 1212) can also perform receiving processing on the acquired baseband signal, including analog-to-digital conversion, Fast Fourier Transform (FFT), Inverse Discrete Fourier Transform (IDFT) (as needed), filtering, demapping, demodulation, decoding (which may also include error correction decoding), MAC layer processing, RLC layer processing, and PDCP layer processing, and acquire user data, etc.

[0191] The transceiver unit 120 (measurement unit 123) can perform measurements related to the received signal. For example, the measurement unit 123 can perform radio resource management (RRM) measurements, channel state information (CSI) measurements, etc., based on the received signal. The measurement unit 123 can also measure received power (e.g., reference signal received power (RSRP), received quality (e.g., reference signal received quality (RSRQ), signal to interference plus noise ratio (SINR), signal to noise ratio (SNR)), signal strength (e.g., received signal strength indicator (RSSI)), propagation line information (e.g., CSI). The measurement results can be output to the control unit 110.

[0192] The transmission line interface 140 can send and receive signals (backhaul signaling) with devices included in the core network 30 and other base stations 10, and can acquire and transmit user data (user plane data), control plane data, etc. used by the user terminal 20. The transmitting and receiving units of the base station 10 in this disclosure can be composed of at least one of a transceiver unit 120 and a transceiver antenna 130.

[0193] The transmitting unit of base station 10, for example, repeatedly performs a process of decreasing a count value randomly determined within the contention window size based on channel monitoring. After the count value becomes 0, it transmits a signal through the aforementioned channel. The receiving unit receives HARQ feedback corresponding to multiple time slots from the terminal receiving the signal. The control unit determines the contention window size based on the HARQ feedback corresponding to the multiple time slots. Alternatively, the process of decreasing the count value randomly determined within the contention window size based on channel monitoring can also be performed by the receiving unit.

[0194] The control unit can shorten or maintain the contention window size if all the HARQ feedbacks to be received corresponding to the multiple time slots are ACK, and otherwise extend or maintain the contention window size.

[0195] The control unit can shorten or maintain the contention window size if all the HARQ feedbacks corresponding to the latest N (N is an integer greater than or equal to 0) signals in the HARQ feedback corresponding to the multiple time slots are ACK, and otherwise extend or maintain the contention window size.

[0196] The control unit may shorten or maintain the contention window size if the ratio of the number of received ACKs to the number of HARQ feedbacks that should be received corresponding to the multiple time slots is above a threshold, and otherwise extend or maintain the contention window size.

[0197] The control unit may shorten or maintain the contention window size if the ratio of the number of received ACKs to the number of HARQ feedbacks that should be received corresponding to the latest N (N is an integer greater than or equal to 0) signals in the HARQ feedbacks corresponding to the multiple time slots is greater than or equal to a threshold; otherwise, it may extend or maintain the contention window size.

[0198] <User Terminal>

[0199] Figure 15 This diagram illustrates an example of the structure of a user terminal 20 according to one embodiment. The user terminal 20 includes a control unit 210, a transceiver unit 220, and a transceiver antenna 230. Alternatively, more than one control unit 210, transceiver unit 220, and transceiver antenna 230 may be included.

[0200] Furthermore, in this example, only the functional blocks of the characteristic parts of this embodiment are shown. The user terminal 20 can be envisioned to also have other functional blocks required for wireless communication. Parts of the processing of the components described below may also be omitted.

[0201] The control unit 210 implements overall control of the user terminal 20. The control unit 210 may be composed of a controller, control circuit, etc., which are described based on common knowledge in the art of this disclosure.

[0202] The control unit 210 can control signal generation, mapping, etc. The control unit 210 can also control transmission, reception, and measurement using the transceiver unit 220 and transceiver antenna 230. The control unit 210 generates data, control information, sequences, etc., for signal transmission and forwards them to the transceiver unit 220.

[0203] The transceiver unit 220 may include a baseband unit 221, an RF unit 222, and a measurement unit 223. The baseband unit 221 may include a transmission processing unit 2211 and a reception processing unit 2212. The transceiver unit 220 may be composed of a transmitter / receiver, RF circuit, baseband circuit, filter, phase shifter, measurement circuit, transceiver circuit, etc., as described based on common knowledge in the art of this disclosure.

[0204] The transceiver unit 220 can be configured as a single unit, or it can be composed of a transmitting unit and a receiving unit. The transmitting unit can be composed of a transmitting processing unit 2211 and an RF unit 222. The receiving unit can be composed of a receiving processing unit 2212, an RF unit 222, and a measurement unit 223.

[0205] The transceiver antenna 230 may be composed of an antenna, such as an array antenna, as described in the art based on common knowledge in the field of this disclosure.

[0206] The transceiver unit 220 can receive the downlink channel, synchronization signal, downlink reference signal, etc., mentioned above. The transceiver unit 220 can also transmit the uplink channel, uplink reference signal, etc., mentioned above.

[0207] The transceiver unit 220 may use digital beamforming (e.g., precoding), analog beamforming (e.g., phase rotation), etc., to form at least one of the transmit beam and the receive beam.

[0208] The transceiver unit 220 (transmission processing unit 2211) can process data and control information obtained from the control unit 210 at the PDCP layer, the RLC layer (e.g., RLC retransmission control), and the MAC layer (e.g., HARQ retransmission control), and generate a bit sequence to be transmitted.

[0209] The transceiver unit 220 (transmission processing unit 2211) can perform channel coding (which may also include error correction coding), modulation, mapping, filtering, DFT processing (as needed), IFFT processing, precoding, digital-to-analog conversion and other transmission processing on the bit sequence to be transmitted, and output the baseband signal.

[0210] Furthermore, whether or not to apply DFT processing can be based on the setting of transform precoding. For a certain channel (e.g., PUSCH), the transceiver unit 220 (transmission processing unit 2211) may perform DFT processing as the aforementioned transmission processing in order to transmit the channel using a DFT-s-OFDM waveform when transform precoding is enabled, or it may not perform DFT processing as the aforementioned transmission processing in other cases.

[0211] The transceiver unit 220 (RF unit 222) can also modulate, filter, amplify, etc., the baseband signal to the wireless frequency band, and transmit the wireless frequency band signal via the transceiver antenna 230.

[0212] On the other hand, the transceiver unit 220 (RF unit 222) can also amplify, filter, and demodulate the signals in the wireless frequency band received by the transceiver antenna 230 into baseband signals.

[0213] The transceiver unit 220 (receiver processing unit 2212) can perform receiving processing on the acquired baseband signal, including analog-to-digital conversion, FFT processing, IDFT processing (as needed), filtering processing, demapping, demodulation, decoding (which may also include error correction decoding), MAC layer processing, RLC layer processing, and PDCP layer processing, and acquire user data, etc.

[0214] The transceiver unit 220 (measurement unit 223) can perform measurements related to the received signal. For example, the measurement unit 223 can perform RRM measurements, CSI measurements, etc., based on the received signal. The measurement unit 223 can also measure received power (e.g., RSRP), received quality (e.g., RSRQ, SINR, SNR), signal strength (e.g., RSSI), propagation line information (e.g., CSI), etc. The measurement results can be output to the control unit 210.

[0215] In addition, the transmitting and receiving units of the user terminal 20 in this disclosure may be composed of at least one of the transceiver unit 220, the transceiver antenna 230, and the propagation line interface 240.

[0216] Furthermore, the transmitting unit of user terminal 20, for example, repeatedly performs a process of decreasing the count value randomly determined within the contention window size based on channel monitoring. After the count value becomes 0, it transmits a signal through the aforementioned channel, and the receiving unit receives HARQ feedback corresponding to multiple time slots from the base station that received the signal. The control unit determines the contention window size based on the HARQ feedback corresponding to the multiple time slots. Alternatively, the process of decreasing the count value randomly determined within the contention window size based on channel monitoring can also be performed by the receiving unit.

[0217] The control unit can shorten or maintain the contention window size if all the HARQ feedbacks to be received corresponding to the multiple time slots are ACK, and otherwise extend or maintain the contention window size.

[0218] The control unit can shorten or maintain the contention window size if all the HARQ feedbacks corresponding to the latest N (N is an integer greater than or equal to 0) signals in the HARQ feedback corresponding to the multiple time slots are ACK, and otherwise extend or maintain the contention window size.

[0219] The control unit may shorten or maintain the contention window size if the ratio of the number of received ACKs to the number of HARQ feedbacks that should be received corresponding to the multiple time slots is above a threshold, and otherwise extend or maintain the contention window size.

[0220] The control unit may shorten or maintain the contention window size if the ratio of the number of received ACKs to the number of HARQ feedbacks that should be received corresponding to the latest N (N is an integer greater than or equal to 0) signals in the HARQ feedbacks corresponding to the multiple time slots is greater than or equal to a threshold; otherwise, it may extend or maintain the contention window size.

[0221] Furthermore, the receiving unit of user terminal 20 receives the value of the contention window size from the base station, for example, using RRC signaling or MAC CE. The transmitting unit, for example, repeatedly performs the process of decreasing the count value randomly determined within the aforementioned contention window size based on channel monitoring, and transmits the signal through the aforementioned channel after the count value becomes 0.

[0222] (Hardware structure)

[0223] Furthermore, the block diagrams used in the above description of the embodiments illustrate blocks based on function. These functional blocks (structural units) are implemented through any combination of at least one of hardware and software. Moreover, the implementation method of each functional block is not particularly limited. That is, each functional block can be implemented using a single device that is physically or logically combined, or by directly or indirectly (e.g., using wired, wireless, etc.) connecting two or more physically or logically separate devices, and implementing it using these multiple devices. Functional blocks can also be implemented by combining software with the aforementioned single device or multiple devices.

[0224] Here, the functionalities include judgment, decision, determination, calculation, calculation, processing, derivation, investigation, search, confirmation, receiving, sending, output, access, resolution, selection, selection, establishment, comparison, assumption, expectation, consideration, broadcasting, notifying, communicating, forwarding, configuring, reconfiguring, allocating, mapping, and assigning, but are not limited to these. For example, a functional block (structural unit) that performs the function of sending can also be called a transmitting unit or a transmitter. In short, as mentioned above, the implementation method is not particularly limited.

[0225] For example, in one embodiment of this disclosure, the base station, user terminal, etc., can also function as a computer for processing the wireless communication method of this disclosure. Figure 16 This is a diagram illustrating an example of the hardware structure of a base station and a user terminal according to one embodiment. The base station 10 and the user terminal 20 described above can be configured as a computer device that physically includes a processor 1001, a memory 1002, a storage device 1003, a communication device 1004, an input device 1005, an output device 1006, and a bus 1007, etc.

[0226] Furthermore, in this disclosure, terms such as apparatus, circuit, device, section, and unit are interchangeable. The hardware structure of base station 10 and user terminal 20 can be configured to include one or more of the apparatuses shown in the figures, or it can be configured to not include any of the parts.

[0227] For example, only one processor 1001 is shown, but multiple processors are also possible. Furthermore, processing can be performed by one processor, or by two or more processors simultaneously, sequentially, or using other methods. Additionally, processor 1001 can be mounted on more than one chip.

[0228] The functions in base station 10 and user terminal 20 are implemented, for example, by reading predetermined software (programs) into hardware such as processor 1001 and memory 1002, so that processor 1001 performs calculations and controls communication via communication device 1004, or controls at least one of reading out and writing data in memory 1002 and storage 1003.

[0229] The processor 1001 controls the computer as a whole, for example, by enabling the operating system to operate. The processor 1001 may also be a central processing unit (CPU) that includes interfaces with peripheral devices, control devices, arithmetic devices, registers, etc. For example, at least some of the control unit 110 (210), transceiver unit 120 (220), etc. described above can be implemented by the processor 1001.

[0230] Furthermore, the processor 1001 reads programs (program code), software modules, or data from at least one direction of the memory 1002 in the memory 1003 and the communication device 1004, and performs various processes accordingly. As a program, a program is used that causes the computer to perform at least a portion of the actions described in the above embodiments. For example, the control unit 110 (210) can be implemented by a control program stored in the memory 1002 and operating in the processor 1001, and other functional blocks can also be implemented similarly.

[0231] Memory 1002 is a computer-readable recording medium, which may be composed of at least one of read-only memory (ROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), random access memory (RAM), or other suitable storage media. Memory 1002 may also be referred to as a register, cache, main memory (main storage device), etc. Memory 1002 can store programs (program code), software modules, etc., that are executable for implementing a wireless communication method according to one embodiment of the present disclosure.

[0232] The memory 1003 is a computer-readable recording medium, and may also be composed of at least one of the following: floppy disk, floppy disk, magneto-optical disk (e.g., compact disc (CD-ROM, etc.), digital multipurpose disk, Blu-ray disk), removable disk, hard disk, smart card, flash memory device (e.g., card, stick, key drive), magnetic stripe, database, server, and other suitable storage media. The memory 1003 may also be referred to as an auxiliary storage device.

[0233] The communication device 1004 is hardware (transceiver) used for communication between computers via at least one of a wired network and a wireless network. It may also be referred to as a network device, network controller, network interface card (NIC), communication module, etc. The communication device 1004 may also be configured to include a high-frequency switch, duplexer, filter, frequency synthesizer, etc., to implement at least one of Frequency Division Duplex (FDD) and Time Division Duplex (TDD). For example, the aforementioned transceiver unit 120 (220) and transceiver antenna 130 (230) can be implemented using the communication device 1004. The transceiver unit 120 (220) may also be physically or logically separated by a transmitting unit 120a (220a) and a receiving unit 120b (220b).

[0234] Input device 1005 is an input device that receives input from external sources (e.g., keyboard, mouse, microphone, switch, button, sensor, etc.). Output device 1006 is an output device that performs output to external sources (e.g., display, speaker, LED (Light Emitting Diode) lamp, etc.). Alternatively, input device 1005 and output device 1006 can also be integrated (e.g., a touch panel).

[0235] Furthermore, the processor 1001, memory 1002, and other devices are connected via a bus 1007 for communication. The bus 1007 can be configured as a single bus or as different buses used between each device.

[0236] Furthermore, the base station 10 and the user terminal 20 can be configured to include hardware such as a microprocessor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a programmable logic device (PLD), and a field-programmable gate array (FPGA), and can also use this hardware to implement part or all of the functional blocks. For example, the processor 1001 can also be installed using at least one of these hardware components.

[0237] (Effects of the implementation method)

[0238] According to the techniques described in the embodiments, a technique is provided in which the base station can appropriately determine the contention window size when HARQ feedback corresponding to multiple time slots is sent from the user terminal.

[0239] More specifically, according to method 1a, the CWS can be updated based on as much FB information as possible that can be efficiently collected. This enables high-precision detection of signal collisions and appropriate CWS selection.

[0240] According to method 2a, the CWS can also be updated based on as much FB information as possible that can be efficiently collected. This allows for high-precision detection of signal collisions and appropriate CWS selection. Furthermore, by uniformly distributing the amount of information used in each implementation, more stable operation can be achieved.

[0241] According to method 1b, in addition to the features of method 1a, it is also possible to exclude ACK undetected states caused by reasons other than signal collisions when updating the CWS. Furthermore, according to method 2b, in addition to the features of method 2a, it is also possible to exclude ACK undetected states caused by reasons other than signal collisions when updating the CWS.

[0242] (Modified example)

[0243] Furthermore, the terms used in this disclosure and those necessary for understanding this disclosure may be replaced with terms that have the same or similar meanings. For example, channel, symbol, and signal (signal or signaling) can be used interchangeably. Additionally, a signal can also be a message. A reference signal can also be abbreviated as RS, and may also be called a pilot, pilot signal, etc., depending on the applied standard. Furthermore, a component carrier (CC) can also be called a cell, frequency carrier, carrier frequency, etc.

[0244] A radio frame can also consist of one or more periods (frames) in the time domain. Each of these periods (frames) constituting a radio frame can also be called a subframe. Furthermore, a subframe can also consist of one or more time slots in the time domain. A subframe can be a fixed time length (e.g., 1 ms) independent of parameters (numerology).

[0245] Here, the parameter set can also be communication parameters applied to at least one of the transmission and reception of a signal or channel. The parameter set can also represent at least one of the following: subcarrier spacing (SCS), bandwidth, symbol length, cyclic prefix length, transmission time interval (TTI), number of symbols per TTI, radio frame structure, specific filtering processing performed by the transceiver in the frequency domain, specific windowing processing performed by the transceiver in the time domain, etc.

[0246] A time slot can also be composed of one or more symbols in the time domain (such as Orthogonal Frequency Division Multiplexing (OFDM) symbols, Single Carrier Frequency Division Multiple Access (SC-FDMA) symbols, etc.). Furthermore, a time slot can also be a time unit based on a set of parameters.

[0247] A time slot can also contain multiple mini-time slots. Each mini-time slot can also consist of one or more symbols in the time domain. Furthermore, a mini-time slot can also be called a sub-time slot. A mini-time slot can also consist of fewer symbols than a time slot. PDSCH (or PUSCH) transmitted in time units larger than mini-time slots can also be called PDSCH (PUSCH) mapping type A. PDSCH (or PUSCH) transmitted using mini-time slots can also be called PDSCH (PUSCH) mapping type B.

[0248] Radio frames, subframes, time slots, mini-time slots, and symbols all refer to units of time for transmitting signals. Other corresponding names may also be used for radio frames, subframes, time slots, mini-time slots, and symbols. Furthermore, the time units such as frames, subframes, time slots, mini-time slots, and symbols used in this disclosure are interchangeable.

[0249] For example, one subframe can also be called a TTI, multiple consecutive subframes can also be called a TTI, and one time slot or one mini-time slot can also be called a TTI. That is, at least one of the subframe and TTI can be an existing LTE subframe (1ms), a period shorter than 1ms (e.g., symbols 1-13), or a period longer than 1ms. In addition, the unit representing TTI can also be called a time slot, mini-time slot, etc., instead of a subframe.

[0250] Here, TTI refers, for example, to the smallest unit of time for scheduling in wireless communication. For instance, in an LTE system, the base station schedules radio resources (bandwidth, transmit power, etc., available to each user terminal) on a TTI basis. However, the definition of TTI is not limited to this.

[0251] TTI can be a transmission time unit for channel-coded data packets (transmission blocks), code blocks, codewords, etc., or it can be a processing unit such as scheduling or link adaptation. In addition, when a TTI is assigned, the actual time interval (e.g., the number of symbols) mapping the transmission block, code block, codeword, etc., can be shorter than the TTI.

[0252] In addition, when one time slot or one mini time slot is referred to as a TTI, more than one TTI (i.e., more than one time slot or more than one mini time slot) can also be used as the minimum time unit for scheduling. Furthermore, the number of time slots (number of mini time slots) constituting the minimum time unit of the schedule can also be controlled.

[0253] A TTI with a duration of 1ms can also be called a normal TTI (TTI in 3GPP Rel.8-12), a regular TTI, a long TTI, a normal subframe, a regular subframe, a long subframe, a time slot, etc. A TTI shorter than a normal TTI can also be called a shortened TTI, a short TTI, a partial TTI (partial or fractional TTI), a shortened subframe, a short subframe, a mini time slot, a sub-time slot, a time slot, etc.

[0254] In addition, long TTIs (e.g., normal TTIs, subframes, etc.) can be replaced with TTIs with a duration of more than 1ms, and short TTIs (e.g., shortened TTIs, etc.) can be replaced with TTIs with a duration of less than long TTIs but more than 1ms.

[0255] A resource block (RB) can be a unit of resource allocation in both the time and frequency domains. In the frequency domain, it contains one or more consecutive subcarriers. The number of subcarriers in an RB can be the same regardless of the parameter set, for example, it can be 12. The number of subcarriers in an RB can be determined based on the parameter set.

[0256] Furthermore, an RB can contain one or more symbols in the time domain, and can also be 1 time slot, 1 mini-time slot, 1 subframe, or 1 TTI in length. 1 TTI, 1 subframe, etc., can also be composed of one or more resource blocks.

[0257] In addition, one or more RBs can also be called Physical Resource Block (PRB), Sub-Carrier Group (SCG), Resource Element Group (REG), PRB pair, RB pair, etc.

[0258] Furthermore, a resource block can also consist of one or more resource elements (REs). For example, 1 RE can also be a radio resource area with 1 subcarrier and 1 symbol.

[0259] The Bandwidth Part (BWP) (also known as partial bandwidth, etc.) can also represent a subset of contiguous common resource blocks (RBs) used by a certain parameter set in a given carrier. Here, common RBs can also be determined by the index of RBs based on a common reference point of that carrier. A PRB can be defined by a BWP or numbered within that BWP.

[0260] A BWP can also include a UL BWP (the BWP used by UL) and a DL BWP (the BWP used by DL). Alternatively, one or more BWPs can be configured within a single carrier for the UE.

[0261] At least one of the configured BWPs can be active, or it may be assumed that the UE will transmit or receive predetermined signals / channels outside of the active BWP. In addition, "cell", "carrier", etc. in this disclosure can also be replaced with "BWP".

[0262] Furthermore, the structures of radio frames, subframes, time slots, mini-time slots, and symbols described above are merely illustrative. For example, the number of subframes contained in a radio frame, the number of time slots in each subframe or radio frame, the number of mini-time slots contained within a time slot, the number of symbols and RBs contained in a time slot or mini-time slot, the number of subcarriers contained in an RB, and the number of symbols in a TTI, symbol length, and cyclic prefix (CP) length can be varied in many ways.

[0263] Furthermore, the information, parameters, etc., described in this disclosure may be represented using absolute values, relative values ​​to predetermined values, or other corresponding information. For example, wireless resources may also be indicated by predetermined indexes.

[0264] The names used for the parameters in this disclosure are not limited in any way. Furthermore, the formulas, etc., using these parameters may differ from those explicitly disclosed in this disclosure. Since a wide variety of channels (PUCCH, PDCCH, etc.) and information elements can be identified by all appropriate names, the various names assigned to these diverse channels and information elements are not limited in any way.

[0265] The information, signals, etc., described in this disclosure can also be represented using any of a variety of different technologies. For example, the data, instructions, commands, information, signals, bits, symbols, chips, etc., that may be involved in the above description can be represented by voltage, current, electromagnetic waves, magnetic fields or magnetic particles, light fields or photons, or any combination thereof.

[0266] Furthermore, information and signals can be output from higher to lower levels and from lower to higher levels, at least in one direction. Information and signals can be input or output via multiple network nodes.

[0267] Input or output information, signals, etc., can be stored in a specific location (e.g., memory) or managed using a management table. Input or output information, signals, etc., can be rewritten, updated, or recorded. Output information, signals, etc., can also be deleted. Input information, signals, etc., can also be sent to other devices.

[0268] The notification of information is not limited to the forms / implementations described in this disclosure, and other methods may also be used. For example, the notification of information in this disclosure may be implemented through physical layer signaling (e.g., downlink control information (DCI), uplink control information (UCI)), higher layer signaling (e.g., radio resource control (RRC) signaling, broadcast information (master information block (MIB), system information block (SIB) etc.), medium access control (MAC) signaling), other signals, or combinations thereof.

[0269] In addition, physical layer signaling can also be called Layer 1 / Layer 2 (L1 / L2) control information (L1 / L2 control signals), L1 control information (L1 control signals), etc. Furthermore, RRC signaling can also be called RRC messages, for example, RRC connection setup messages, RRC connection reconfiguration messages, etc. Additionally, MAC signaling can be communicated using, for example, MAC control elements (CE).

[0270] Furthermore, notification of reservation information (e.g., notification of "is X") is not limited to explicit notification, but can also be implicit (e.g., not to notify of the reservation information or through other information).

[0271] The determination can be made by the value represented by 1 bit (0 or 1), by the boolean value represented as true or false, or by comparison of numerical values ​​(e.g., comparison with a predetermined value).

[0272] Software, whether called software, firmware, middleware, microcode, hardware description language, or by other names, should be broadly interpreted as referring to commands, command sets, code, code segments, program code, programs, subroutines, software modules, applications, software applications, software packages, routines, subroutines, objects, executable files, execution threads, procedures, functions, etc.

[0273] Furthermore, software, commands, information, etc., can be sent and received via a transmission medium. For example, when using at least one of wired technologies (coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL) etc.) and wireless technologies (infrared, microwave, etc.) to send software from a webpage, server, or other remote source, at least one of these wired and wireless technologies is included within the definition of a transmission medium.

[0274] The terms “system” and “network” as used in this disclosure are used interchangeably. “Network” can refer to devices included in a network (e.g., a base station).

[0275] In this disclosure, the terms "precoding", "precoder", "weight (precoding weight)", "quasi-co-location (QCL)", "transmission configuration indication state (TCI state)", "spatial relation", "spatial domain filter", "transmit power", "phase rotation", "antenna port", "antenna port group", "layer", "number of layers", "rank", "resource", "resource set", "resource group", "beam", "beamwidth", "beam angle", "antenna", "antenna element", and "panel" are used interchangeably.

[0276] In this disclosure, the terms "base station (BS)," "wireless base station," "fixed station," "NodeB," "eNB (eNodeB)," "gNB (gNodeB)," "access point," "transmission point (TP)," "reception point (RP)," "transmission / reception point (TRP)," "panel," "cell," "sector," "cell group," "carrier," and "component carrier" are used interchangeably. Sometimes, terms such as macro cell, small cell, femtocell, and picocell are also used to refer to base stations.

[0277] A base station can accommodate one or more (e.g., three) cells. When a base station accommodates multiple cells, its coverage area can be divided into several smaller areas, each of which can provide communication services through a base station subsystem (e.g., a small indoor base station (Remote Radio Head (RRH)). Terms such as "cell" or "sector" refer to a portion or all of the coverage area of ​​at least one of the base station and base station subsystem providing communication services within its coverage area.

[0278] In this disclosure, the terms "Mobile Station (MS)," "user terminal," "User Equipment (UE)," and "terminal" can be used interchangeably.

[0279] User terminals are sometimes referred to as mobile stations, subscriber stations, mobile units, wireless units, remote units, mobile devices, wireless devices, wireless communication devices, remote devices, mobile subscriber stations, access terminals, mobile terminals, wireless terminals, remote terminals, terminals, handheld devices, user agents, mobile clients, clients, or other appropriate terms.

[0280] At least one of the base station and the mobile station can also be referred to as a transmitting device, a receiving device, a wireless communication device, etc. Additionally, at least one of the base station and the mobile station can also be a device mounted on a mobile body, or the mobile body itself. This mobile body can be a vehicle (e.g., a car, an airplane, etc.), a mobile body moving unmanned (e.g., a drone, an autonomous vehicle, etc.), or a robot (humanized or unmanned). Furthermore, at least one of the base station and the mobile station also includes devices that do not necessarily move during communication. For example, at least one of the base station and the mobile station can also be an Internet of Things (IoT) device such as a sensor.

[0281] Furthermore, the base station in this disclosure can also be replaced by a user terminal. For example, various forms / implementations of this disclosure can be applied to a structure that replaces the communication between the base station and the user terminal with communication between multiple user terminals (e.g., also referred to as D2D (Device-to-Device), V2X (Vehicle-to-Everything), etc.). In this case, the user terminal 20 can also be configured to have the functions of the base station 10 described above. In addition, terms such as "uplink" and "downlink" can be replaced with terms corresponding to inter-terminal communication (e.g., "side"). For example, uplink channel, downlink channel, etc., can also be replaced with side channel.

[0282] Similarly, the user terminal in this disclosure can also be replaced by a base station. In this case, the base station 10 can also be configured to have the functions of the user terminal 20 described above.

[0283] Actions described in this disclosure as being performed by a base station may sometimes be performed by its upper node, depending on the circumstances. It should be understood that in a network containing one or more network nodes having a base station, various actions performed for communication with a terminal can be performed by the base station, one or more network nodes other than the base station (e.g., considering a Mobility Management Entity (MME), a Serving Gateway (S-GW), etc., but not limited to these), or a combination thereof.

[0284] The various forms / implementations described in this disclosure can be used individually or in combination, and their use can be switched depending on the execution. Furthermore, the processing procedures, timing, and flow of the various forms / implementations described in this disclosure can be changed in order, provided there is no contradiction. For example, in the methods described in this disclosure, various elements of the steps are indicated using an illustrative order, and are not limited to the specific order indicated.

[0285] The various forms / implementations described in this disclosure can also be applied to Long Term Evolution (LTE), LTE-Advanced (LTE-A), LTE-Beyond (LTE-B), SUPER 3G, IMT-Advanced, 4th generation mobile communication system (4G), 5th generation mobile communication system (5G), Future Radio Access (FRA), New-Radio Access Technology (RAT), New Radio (NR), New Radio Access (NX), Future Generation Radio Access (FX), Global System for Mobile Communications (GSM), CDMA 2000, Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Ultra-Wideband (UWB), Bluetooth (registered trademark), systems using other suitable wireless communication methods, and next-generation systems extended therefrom. Furthermore, multiple systems can be combined (e.g., a combination of LTE or LTE-A with 5G).

[0286] As used in this disclosure, the word "based on" does not mean "based on only" unless otherwise expressly stated. In other words, the word "based on" implies both "based on only" and "based on at least".

[0287] Any reference to elements using the designations "first," "second," etc., as used in this disclosure does not necessarily limit the number or order of these elements. These designations may be used in this disclosure as a convenient way to distinguish between two or more elements. Therefore, reference to a first element and a second element does not imply that only two elements can be used, or that in any form the first element must precede the second element.

[0288] As used in this disclosure, the term "determining" sometimes encompasses a variety of actions. For example, "determining" can be interpreted as judging, calculating, computing, processing, deriving, investigating, looking up, searching, inquiring (e.g., searching in a table, database, or other data structure), ascertaining, etc.

[0289] In addition, "judgment (decision)" can also be regarded as judging (decision) receiving (e.g., receiving information), transmitting (e.g., sending information), inputting, outputting, accessing (e.g., accessing data in memory), etc.

[0290] Furthermore, "judgment (decision)" can also be viewed as resolving, selecting, choosing, establishing, comparing, etc. That is, "judgment (decision)" can also be viewed as judging (decising) any action.

[0291] In addition, "judgment (decision)" can be replaced by "assuming", "expecting", "considering", etc.

[0292] The term "maximum transmit power" as used in this disclosure can refer to the maximum value of the transmit power, the nominal maximum transmit power, or the rated maximum transmit power.

[0293] As used in this disclosure, the terms "connected," "coupled," or any variations thereof are intended to indicate any direct or indirect connection or combination between two or more elements, including cases where there is one or more intermediate elements between the two elements that are "connected" or "coupled." The combination or connection between elements can be physical, logical, or a combination thereof. For example, "connected" can also be replaced with "access."

[0294] In this disclosure, when connected to two elements, it can be considered that mutual “connection” or “combination” can be achieved by using one or more wires, cables, and printed electrical connections, as well as by using electromagnetic energy with wavelengths having wireless frequency domains, microwave regions, and light (including both visible and invisible regions) regions, as some non-limiting and non-inclusive examples.

[0295] In this disclosure, the phrase "A and B are different" can also mean "A and B are different from each other." Furthermore, this phrase can also mean "A and B are different from C respectively." Terms such as "separate" and "combined" can also be interpreted as "different."

[0296] In this disclosure, the terms “include,” “including,” and variations thereof are used in the same way as the term “comprising,” implying inclusion. Furthermore, the term “or” as used in this disclosure means not XOR.

[0297] In this disclosure, for example, in cases where articles such as a, an, and the in English are added due to translation, this disclosure may also include cases where the noun following these articles is in a plural form.

[0298] The invention disclosed herein has been described in detail above. However, those skilled in the art will recognize that the invention is not limited to the embodiments described herein. The invention can be implemented as modifications and variations without departing from the spirit and scope of the invention as defined by the claims. Therefore, the purpose of this disclosure is illustrative and it does not constitute any limitation on the invention.

[0299] Label Explanation

[0300] 10: Base station

[0301] 20: User Terminal

[0302] 1001: Processor;

[0303] 1002: Storage device;

[0304] 1003: Auxiliary storage device;

[0305] 1004: Communication devices;

[0306] 1005: Input device;

[0307] 1006: Output device

Claims

1. A base station having: a transmission section that repeatedly performs a process of reducing a count value that is randomly set within a contention window size related to monitoring of a channel, and transmits a signal after the count value becomes 0; a reception section that receives feedback from a terminal that has received the signal; and a control section that, in a case where a proportion of the number of acknowledgement in the number of HARQ feedbacks corresponding to a plurality of code block groups (CBGs) that are transmitted last among a quantity of HARQ feedbacks corresponding to a plurality of slots that are received within a latest channel occupancy time is equal to or greater than a threshold value that is decided in accordance with a channel access priority class, sets the contention window size to a predetermined minimum value, and in other cases, extends or maintains the contention window size.

2. A terminal having: a transmission section that transmits feedback for a signal received from a base station; a reception section that receives a signal that is transmitted from the base station after a process of reducing a count value that is randomly set within a contention window size is repeatedly performed in the base station, and in a case where a proportion of the number of acknowledgement in the number of HARQ feedbacks corresponding to a plurality of code block groups (CBGs) that are transmitted last among a quantity of HARQ feedbacks corresponding to a plurality of slots that are received within a latest channel occupancy time is equal to or greater than a threshold value that is decided in accordance with a channel access priority class, the contention window size is set to a predetermined minimum value, and in other cases, the contention window size is extended or maintained.

3. A communication system having a base station and a terminal, wherein the base station has: a transmission section that repeatedly performs a process of reducing a count value that is randomly set within a contention window size related to monitoring of a channel, and transmits a signal after the count value becomes 0; a reception section that receives feedback from a terminal that has received the signal; and a control section that, in a case where a proportion of the number of acknowledgement in the number of HARQ feedbacks corresponding to a plurality of code block groups (CBGs) that are transmitted last among a quantity of HARQ feedbacks corresponding to a plurality of slots that are received within a latest channel occupancy time is equal to or greater than a threshold value that is decided in accordance with a channel access priority class, sets the contention window size to a predetermined minimum value, and in other cases, extends or maintains the contention window size, the terminal has: a reception section that receives the signal from the base station; and a transmission section that transmits feedback for the signal received from the base station. The contention window size decision method has the following steps: repeatedly performing a process of reducing a count value that is randomly set within a contention window size related to monitoring of a channel, and transmitting a signal after the count value becomes 0; receiving feedback from a terminal that has received the signal; and in a case where a proportion of the number of acknowledgement in the number of HARQ feedbacks corresponding to a plurality of code block groups (CBGs) that are transmitted last among a quantity of HARQ feedbacks corresponding to a plurality of slots that are received within a latest channel occupancy time is equal to or greater than a threshold value that is decided in accordance with a channel access priority class, setting the contention window size to a predetermined minimum value, and in other cases, extending or maintaining the contention window size. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 4. A contention window size determination method performed by a base station, wherein, ​ ​ ​ In a case where a proportion of the number of acknowledgements in the number of HARQ feedbacks corresponding to the latest transmitted plurality of code block groups (CBGs) among the amount of HARQ feedbacks received in the recent channel occupancy time corresponding to the plurality of slots is equal to or higher than a threshold value determined in accordance with the channel access priority class, the contention window size is set to a predetermined minimum value, and in other cases, the contention window size is extended or maintained.

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