Method and apparatus for performing uplink channel access in a wireless communication system

Abstract

The present invention relates to a method and an apparatus for performing uplink channel access in a wireless communication system. In particular, the present invention includes the following steps: receiving an uplink grant for scheduling uplink transmission in at least one subframe from a base station; and performing uplink transmission in at least one subframe by using at least one of a first type of channel access and a second type of channel access. When all of the at least one subframe is included in a predetermined interval determined based on downlink transmission from a base station via an unlicensed cell, the uplink transmission is performed by using the second type of channel access.

Description

[0001] This application is a divisional application of the patent application with the application number 201780018454.3 (PCT / KR2017 / 003084), international filing date of March 22, 2017, and invention title of "Method and apparatus for unlicensed band uplink channel access in a wireless communication system", which was filed with the Chinese Patent Office on September 19, 2018. Technical Field

[0002] The present invention relates to a wireless communication system. Specifically, the present invention relates to a method and an apparatus for accessing an uplink channel in an unlicensed band in a wireless communication system. Background Art

[0003] In recent years, with the explosive growth of mobile services due to the popularization of smart devices, it has been difficult to handle the increasing data usage for providing cellular communication services only through conventional licensed spectrum or LTE licensed bands.

[0004] In this case, a solution to the spectrum shortage problem has been designed by using unlicensed (alternatively, unauthorized, unlicensed, or license - unnecessary) spectrum or LTE unlicensed bands (e.g., 2.4 GHz band, 5 GHz band, etc.) to provide cellular communication services.

[0005] However, different from the licensed band where a communication service provider secures the exclusive frequency usage right through processes in the unlicensed band (such as auctions, etc.), when only complying with a predetermined level of adjacent band protection rules, multiple communication facilities can be used simultaneously without restrictions. Therefore, when using an unlicensed band in cellular communication services, it is difficult to guarantee the level of communication quality provided in the licensed band, and interference problems may occur with common wireless communication devices (e.g., wireless LAN devices) using the unlicensed band.

[0006] Therefore, it is necessary to prioritize research on co - existence schemes for conventional unlicensed band devices and schemes for efficiently sharing radio channels in order to solve LTE technology in the unlicensed band. That is, it is necessary to develop a robust co - existence mechanism (RCM) to prevent devices using LTE technology in the unlicensed band from affecting conventional unlicensed band devices. Summary of the Invention

[0007] Technical Problem

[0008] The present invention has been dedicated to providing a method for efficiently transmitting signals in a wireless communication system (specifically, a cellular wireless communication system and its devices). Further, the present invention has been dedicated to providing a method for efficiently transmitting signals in a specific frequency band (e.g., an unlicensed band) and its devices.

[0009] The technical objectives expected to be achieved in the present invention are not limited to the foregoing objectives, and those skilled in the art will clearly understand other technical objectives not described above from the following disclosure.

[0010] Technical solution

[0011] According to an aspect of the present invention, there is provided a method for a user equipment to perform uplink transmission to a base station through an unlicensed cell in a wireless communication system. The method includes: receiving an uplink grant for scheduling uplink transmission in at least one subframe from the base station; and performing uplink transmission in at least one subframe by using at least one of a first type of channel access or a second type of channel access. When all of the at least one subframes are included in a predetermined interval determined based on downlink transmission from the base station through the unlicensed cell, uplink transmission is performed by using the second type of channel access.

[0012] In addition, according to an aspect of the present invention, there is provided a user equipment of a wireless communication system. The user equipment includes: a wireless communication module; and a processor configured to receive an uplink grant for scheduling uplink transmission in at least one subframe from the base station, and perform uplink transmission in at least one subframe by using at least one of a first type of channel access or a second type of channel access. The processor is configured to: when all of the at least one subframes are included in a predetermined interval determined based on downlink transmission from the base station through the unlicensed cell, perform uplink transmission by using the second type of channel access.

[0013] Preferably, the uplink grant may indicate the type of channel access to be used in the uplink transmission among the first type of channel access or the second type of channel access. Preferably, when at least one subframe is not included in the predetermined interval or only a part of at least one subframe is included in the predetermined interval, uplink transmission is performed by using the type of channel access indicated in the uplink grant.

[0014] On the other hand, the predetermined interval may be determined based on a maximum channel occupancy time set through downlink transmission, and information about whether at least one subframe is the last subframe for uplink transmission is received through a common control channel.

[0015] In addition, when performing uplink transmission in the next subframe of the downlink transmission in the unlicensed cell, uplink transmission is performed by using the second type of channel access.

[0016] On the other hand, according to another aspect of the present invention, there is provided a method for a base station to receive an uplink transmission from a user equipment via an unlicensed cell in a wireless communication system. The method includes: scheduling the transmission of an uplink signal in at least one subframe, and transmitting an uplink grant indicating a type of channel access to be used by the user equipment when transmitting the uplink signal, the type of channel access being either a first type of channel access or a second type of channel access; and receiving the uplink signal in at least one subframe. The method further includes: when all of the at least one subframes are included in a predetermined interval determined based on a downlink transmission via the unlicensed cell, transmitting common downlink control information indicating that the second type of channel access is to be performed in the uplink transmission.

[0017] In addition, according to another aspect of the present invention, there is provided a base station in a wireless communication system. The base station includes: a wireless communication module; and a processor configured to schedule the transmission of an uplink signal via an unlicensed cell in at least one subframe, transmit an uplink grant indicating a type of channel access to be used by the user equipment when transmitting the uplink signal, the type of channel access being either a first type of channel access or a second type of channel access, and receive the uplink signal from the user equipment in at least one subframe. When all of the at least one subframes are included in a predetermined interval determined based on a downlink transmission via the unlicensed cell, the processor is configured to transmit common downlink control information indicating that the second type of channel access is to be performed in the uplink transmission.

[0018] In addition, when at least one subframe is not included in the predetermined interval or only a part of at least one subframe is included in the predetermined interval, the uplink grant may indicate the first type of channel access. In addition, the common downlink control information may include information about whether at least one subframe is the last subframe for uplink transmission.

[0019] Advantageous Effects

[0020] According to an exemplary embodiment of the present invention, there is provided a method for efficiently transmitting signals in a wireless communication system (specifically, a cellular wireless communication system and its devices). Further, there is provided a method and a device for efficiently accessing a channel in a specific frequency band (e.g., an unlicensed band).

[0021] The effects obtained in the present invention are not limited to the foregoing effects, and those skilled in the art will clearly understand other effects not described above from the following disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] To assist in understanding the present invention, the accompanying drawings, which are incorporated as part of the detailed description, provide embodiments of the present invention and describe the technical problems of the present invention together with the detailed description.

[0023] Figure 1 Illustrates a physical channel used in a Third Generation Partnership Project (3GPP) system and a general signal transmission method using the physical channel.

[0024] Figure 2 Illustrates an example of a radio frame structure used in a wireless communication system.

[0025] Figure 3 Illustrates an example of a downlink (DL) / uplink (UL) time slot structure used in a wireless communication system.

[0026] Figure 4 Illustrates the structure of a downlink subframe (SF).

[0027] Figure 5 Illustrates the structure of an uplink subframe.

[0028] Figure 6 Is a schematic diagram for describing single-carrier communication and multi-carrier communication.

[0029] Figure 7 Illustrates an example of applying cross-carrier scheduling technology.

[0030] Figure 8 Illustrates the ACK / NACK (A / N) transmission process in the case of a single cell.

[0031] Figure 9 Illustrates a Licensed-Assisted Access (LAA) service environment.

[0032] Figure 10 Illustrates the deployment scenarios of user equipment and a base station in an LAA service environment.

[0033] Figure 11 Illustrates a communication scheme (e.g., wireless LAN) operating in an unlicensed band in the prior art.

[0034] Figures 12 to 13 Illustrates the Listen-Before-Talk (LBT) process for downlink transmission.

[0035] Figure 14 Illustrates downlink transmission in an unlicensed band.

[0036] Figure 15 Is a schematic diagram illustrating the case of transmitting a PDCCH including only an uplink grant without PDSCH transmission as an embodiment of the present invention.

[0037] Figure 16It is a schematic diagram illustrating a case where an EPDCCH including only an uplink grant is transmitted without PDSCH transmission as an embodiment of the present invention.

[0038] Figure 17 It is a schematic diagram illustrating a case where LBT is independently performed for a subframe for transmitting only a UL grant without PDSCH transmission and a (plural) subframe for performing PDSCH transmission according to an embodiment of the present invention.

[0039] Figure 18 It is a schematic diagram illustrating a case where LBT is independently performed for a subframe for transmitting only a UL grant without PDSCH transmission and a (plural) subframe for performing PDSCH transmission according to an embodiment of the present invention.

[0040] Figure 19 It is a schematic diagram illustrating an example of switching an LBT type according to an embodiment of the present invention when DL scheduling occurs between UL grant transmission and corresponding UL service transmission.

[0041] Figure 20 It is a schematic diagram illustrating another example of switching an LBT type according to an embodiment of the present invention when DL scheduling occurs between UL grant transmission and corresponding UL service transmission.

[0042] Figure 21 It is a schematic diagram illustrating another example of switching an LBT type according to an embodiment of the present invention when DL scheduling occurs between UL grant transmission and corresponding UL service transmission.

[0043] Figure 22 It is a schematic diagram illustrating a method for performing UL channel access for consecutive UL transmissions after DL transmission in an LAA cell.

[0044] Figure 23 It shows an example in which a terminal transmits a data channel to a base station according to another embodiment of the present invention.

[0045] Figure 24 It illustrates the configurations of a user equipment and a base station according to an embodiment of the present invention. Detailed implementation

[0046] By considering the functions in the present invention, the terms used in this specification are preferably the commonly used general terms that are widely used currently. However, according to the intention, custom, and emergence of new technologies of those skilled in the art, the terms can be changed. Further, in specific cases, there are terms arbitrarily selected by the applicant, and in such cases, their meanings will be described in the corresponding description part of the present invention. Therefore, the present invention aims to show that the terms used in this specification should be analyzed, and this analysis is not only based on the name of the term but also on the substantial meaning of the term and the content throughout this specification.

[0047] Throughout this specification and the following claims, when an element is described as "coupled" to another element, the element can be "directly coupled" to the other element or "electrically coupled" to the other element through a third element. Further, unless explicitly described to the contrary, the words "comprises" and variations (such as "comprises" or "comprising") will be understood to mean including the stated element but not excluding any other element. Also, in some exemplary embodiments, the limitations such as "equal to or greater than" or "equal to or less than" based on a specific threshold can be appropriately replaced by "greater than" or "less than" respectively.

[0048] The following technologies can be used in various wireless access systems, such as code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier FDMA (SC-FDMA), etc. CDMA can be implemented by radio technologies such as universal terrestrial radio access (UTRA) or CDMA 2000. TDMA can be implemented by radio technologies such as global system for mobile communications (GSM) / general packet radio service (GPRS) / enhanced data rates for GSM evolution (EDGE). OFDMA can be implemented by radio technologies such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, evolved UTRA (E-UTRA), etc. UTRA is part of the universal mobile telecommunications system (UMTS). The 3rd Generation Partnership Project (3GPP) long term evolution (LTE) is part of the evolved UMTS (E-UMTS) that uses evolved UMTS terrestrial radio access (E-UTRA), and LTE-Advanced (LTE-A) is an evolved version of 3GPP LTE. 3GPP LTE / LTE-A is mainly described for clear description, but the technical spirit of the present invention is not limited thereto.

[0049] Figure 1It illustrates the physical channels used in the 3GPP system and the general signal transmission method using the physical channels. The user equipment receives information from the base station via the downlink (DL), and the user equipment transmits information to the base station via the uplink (UL). The information transmitted / received between the base station and the user equipment includes data and various control information, and various physical channels exist according to the type / purpose of the information transmitted / received between the base station and the user equipment.

[0050] When the power of the user equipment is turned on or the user equipment enters the cell in a new manner, the user equipment performs an initial cell search operation (S301) including synchronizing with the base station. For this purpose, the user equipment receives the primary synchronization channel (P-SCH) and the secondary synchronization channel (S-SCH) from the base station to synchronize with the base station and obtain information including the cell ID, etc. Thereafter, the user equipment receives the physical broadcast channel from the base station to obtain the in-cell broadcast information. The user equipment receives the downlink reference signal (DL RS) in the initial cell search step to verify the downlink channel state.

[0051] The user equipment that has completed the initial cell search receives the physical downlink control channel (PDCCH) and the physical downlink shared channel (PDSCH) according to the information loaded on the PDCCH to obtain more detailed system information (S302).

[0052] When there is no radio resource for initial access to the base station or signal transmission, the user equipment can perform a random access procedure for the base station (RACH procedure) (S303 to S306). For this purpose, the user equipment can transmit a preamble via the physical random access channel (PRACH) (S303), and receive a response message for the preamble via the PDCCH and the corresponding PDSCH (S304). In the case of contention-based RACH, a contention resolution process can also be performed.

[0053] Thereafter, the user equipment can receive the PDCCH / PDSCH (S307), and transmit the physical uplink shared channel (PUSCH) / physical uplink control channel (PUCCH) (S308) as a general procedure. The user equipment receives the downlink control information (DCI) via the PDCCH. The DCI includes control information for the user equipment (such as resource allocation information), and the format varies according to the usage purpose. The control information transmitted by the user equipment to the base station is designated as the uplink control information (UCI). The UCI includes positive / negative acknowledgment (ACK / NACK), channel quality indicator (CQI), precoding matrix index (PMI), rank indicator (RI), etc. The UCI can be transmitted via the PUSCH and / or PUCCH.

[0054] Figure 2An example of a radio frame structure used in a wireless communication system is illustrated. Figure 2 Figure (a) of Figure 2 illustrates a frame structure for frequency division duplexing (FDD), and

[0055] Referring to Figure 2 , the frame structure may have a length of 10 ms (307200 Ts) and may be composed of 10 subframes (SF). Ts represents the sampling time and is expressed as Ts = 1 / (2048 * 15 kHz). Each subframe may have a length of 1 ms and may be composed of 2 time slots. Each time slot has a length of 0.5 ms. The time used to transmit one subframe is defined as the transmission time interval (TTI). Time resources can be distinguished by radio frame number / index, subframe number / index #0 to #9, and time slot number / index #0 to #19.

[0056] The radio frame can be configured in different ways according to the duplex mode. In the FDD mode, the downlink transmission and the uplink transmission are distinguished by frequency, and the radio frame includes only one of the downlink subframe and the uplink subframe for a specific frequency band. In the TDD mode, the downlink transmission and the uplink transmission are distinguished by time, and the radio frame includes both the downlink subframe and the uplink subframe for a specific frequency band.

[0057] Figure 3 The structure of the downlink / uplink time slot is illustrated.

[0058] Referring to Figure 3 , a time slot includes a plurality of orthogonal frequency division multiplexing (OFDM) symbols in the time domain and a plurality of resource blocks (RB) in the frequency domain. An OFDM symbol also means a symbol period. According to the multiple access scheme, the OFDM symbol can be called an OFDMA symbol, a single carrier frequency division multiple access (SC-FDMA) symbol, etc. The number of OFDM symbols included in one time slot can be variously modified according to the length of the cyclic prefix (CP). For example, in the case of the standard CP, one time slot includes 7 OFDM symbols, and in the case of the extended CP, one time slot includes 6 OFDM symbols. An RB is defined as N DL / UL symb (e.g., 7) consecutive OFDM symbols in the time domain and N RB sc (e.g., 12) consecutive subcarriers in the frequency domain. The resource composed of one OFDM symbol and one subcarrier is called a resource element (RE) or a tone. One RB is composed of N DL / UL symb *N RB scResource element composition.

[0059] The resources of a time slot can be represented as a resource grid composed of N DL / UL RB *N RB sc sub - carriers and N DL / UL symb OFDM symbols. Each resource element (RE) in the resource grid is uniquely defined by the index pair (k, l) of each time sequence. K represents the index given by 0 to N DL / UL RB *N RB sc - 1, and l represents the index given by 0 to N DL / UL symb - 1. Here, N DL RB represents the number of resource blocks (RBs) in a downlink time slot, and N UL RB represents the number of RBs in a UL time slot. N DL RB and N UL RB depend on the DL transmission bandwidth and the UL transmission bandwidth respectively. N DL symb represents the number of symbols in a downlink time slot, and N UL symb represents the number of symbols in a UL time slot. N RB sc represents the number of sub - carriers that make up one RB. A resource grid is set for each antenna port.

[0060] Figure 4 The figure illustrates the structure of a downlink sub - frame.

[0061] Referring to Figure 4 , a sub - frame can be composed of 14 OFDM symbols. According to the sub - frame setting, the first 1 to 3 (alternatively, 2 to 4) OFDM symbols are used as the control region, and the remaining 13 to 11 (alternatively, 12 to 10) OFDM symbols are used as the data region. R1 to R4 represent the reference signals for antenna ports 0 to 3. The control channels assigned to the control region include the Physical Control Format Indicator Channel (PCFICH), the Physical Hybrid ARQ Indicator Channel (PHICH), the Physical Downlink Control Channel (PDCCH), etc. The data channels assigned to the data region include the PDSCH, etc. When the Enhanced PDCCH (EPDCCH) is set, the PDSCH and the EPDCCH are multiplexed by Frequency Division Multiplexing (FDM) in the data region.

[0062] The PDCCH, which is a physical downlink control channel, is allocated to the first n OFDM symbols of a subframe, where n is represented by PCFICH as 1 (alternatively, 2) or a larger integer. The PDCCH announces information related to resource allocation of the paging channel (PCH) and the downlink shared channel (DL-SCH), which are transport channels, uplink scheduling grants, HARQ information, etc., to each user equipment or group of user equipments. The data (i.e., transport blocks) of the PCH and DL-SCH are transmitted via the PDSCH. Except for specific control information or specific service data, each of the base station and the user equipment generally transmits and receives data via the PDSCH.

[0063] Information indicating to which user equipment (one or more user equipments) the data of the PDSCH is to be transmitted, information indicating how the user equipment receives and decodes the PDSCH data, etc. are transmitted, and these information are included in the PDCCH / EPDCCH. For example, assume that the PDCCH / EPDCCH is CRC masked by using a radio network temporary identifier (RNTI) called "A" and information about data transmitted by using a radio resource called "B" (e.g., frequency position) and a DCI format called "C" (i.e., transmission format information (e.g., transport block size, modulation scheme, coding information, etc.) is transmitted via a specific subframe). In this case, the user equipments in the cell monitor the PDCCH / EPDCCH by using their RNTI information, and when one or more user equipments with the "A" RNTI are provided, the user equipments receive the PDCCH / EPDCCH and receive the PDSCH represented by "B" and "C" based on the information about the received PDCCH / EPDCCH.

[0064] Figure 5 The structure of an uplink subframe is illustrated.

[0065] Refer to Figure 5 , a subframe can be divided into a control region and a data region in the frequency domain. The PUCCH is allocated to the control region, and the PUCCH carries UCI. The PUSCH is allocated to the data region, and the PUSCH carries user data.

[0066] The following control information can be transmitted by using the PUCCH.

[0067] - Scheduling Request (SR): Information for requesting UL-SCH resources. The SR is transmitted by using an on-off keying (OOK) scheme.

[0068] - HARQ-ACK: Response to PDCCH and / or response to downlink data packets (e.g., codewords) on PDSCH. A codeword is an encoded format of a transport block. HARQ-ACK indicates whether PDCCH and PDSCH are successfully received. HARQ-ACK responses include positive ACK (simply, ACK), negative ACK (NACK), discontinuous transmission (DTX), or NACK / DTX. DTX means that the user equipment loses PDCCH (alternatively, semi-persistent scheduling (SPS) PDSCH) and NACK / DTX refers to the case of NACK or DTX. HARQ-ACK is used interchangeably with HARQ-ACK / NACK and ACK / NACK.

[0069] - Channel State Information (CSI): Feedback information about the downlink channel. Feedback information related to Multiple-Input Multiple-Output (MIMO) includes RI and PMI.

[0070] In the following, carrier aggregation will be described. Carrier aggregation means that a wireless communication system uses multiple frequency blocks as one larger logical frequency band in order to use a wider frequency band method. When the entire system band is extended by carrier aggregation, the frequency bands used for communication with each user equipment are defined by component carrier (CC) units.

[0071] Figure 6 is a schematic diagram for describing single-carrier communication and multi-carrier communication. Figure 6 The (a) of illustrates the subframe structure of a single carrier, and Figure 6 the (b) of illustrates the subframe structure of multi-carriers of carrier aggregation.

[0072] Figure 6 The (b) of illustrates the subframe structure of multi-carriers of carrier aggregation.

[0073] Referring to Figure 6 In the (a) of , in a single-carrier system, the base station and the user equipment perform data communication through one corresponding DL band and one UL band. The DL / UL band is divided into multiple orthogonal subcarriers, and each frequency band operates at one carrier frequency. In FDD, the DL and UL bands operate at different carrier frequencies respectively, and in TDD, the DL and UL bands operate at the same carrier frequency. The carrier frequency refers to the center frequency of the frequency band.

[0074] Referring to Figure 6 In the (b) of , carrier aggregation is distinguished from an OFDM system that performs DL / UL communication in a baseband divided into multiple subcarriers by using one carrier frequency, because carrier aggregation performs DL / UL communication by using multiple carrier frequencies. Referring to Figure 6In (b), three 20 MHz CCs are aggregated in each of UL and DL to support a bandwidth of 60 MHz. The CCs can be adjacent to each other or non - adjacent to each other in the frequency domain. For convenience, Figure 6 Figure (b) illustrates the case where the bandwidths of the UL CC and the DL CC are the same and symmetric to each other, but the bandwidths of the corresponding CCs can be determined independently. Further, asymmetric carrier aggregation where the number of UL CCs and the number of DL CCs are different from each other is also available. (Multiple) DL / UL CCs are allocated / configured independently for each user equipment, and the (multiple) DL / UL CCs allocated / configured for the user equipment are designated as the (multiple) serving UL / DL CCs of the corresponding user equipment.

[0075] The base station can activate some or all of the serving CCs of the user equipment or deactivate some CCs. When the base station allocates (multiple) CCs to the user equipment, at least one specific CC among the (multiple) CCs configured for the corresponding user equipment is not deactivated if there is a complete re - configuration of the CC allocation to the user equipment or if the user equipment does not perform a handover. The specific CC that is always activated is called the primary CC (PCC), and the CCs that the base station can activate / deactivate arbitrarily are called secondary CCs (SCCs). The PCC and SCCs can be distinguished based on control information. For example, specific control information can be set to be sent / received only through a specific CC, and the specific CC can be called the PCC, and the remaining (multiple) CCs can be called the (multiple) SCCs. The PUCCH is transmitted only on the PCC.

[0076] In 3GPP, the concept of a cell is used to manage radio resources. A cell is defined as a combination of DL resources and UL resources, i.e., a combination of DL CC and UL CC. A cell can be configured with only DL resources or a combination of DL resources and DL resources. When carrier aggregation is supported, the link between the carrier frequency of the DL resources (alternatively, DL CC) and the carrier frequency of the UL resources (alternatively, UL CC) can be indicated by system information. For example, the combination of DL resources and UL resources can be indicated by a System Information Block type 2 (SIB2) link. The carrier frequency refers to the center frequency of each cell or CC. The cell corresponding to the PCC is called the primary cell (PCell), and the cell corresponding to the SCC is called the secondary cell (SCell). The carrier corresponding to the PCell is the DL PCC in the downlink, and the carrier corresponding to the PCell is the UL PCC in the uplink. Similarly, the carrier corresponding to the SCell is the DL SCC in the downlink, and the carrier corresponding to the SCell is the UL SCC in the uplink. Depending on the user equipment capabilities, the (multiple) serving cells can consist of the PCell and zero or more SCells. For a user equipment in the RRC_CONNECTED state that does not have any configuration for carrier aggregation or does not support carrier aggregation, there is a single serving cell consisting only of the PCell.

[0077] Figure 7 An example of applying cross-carrier scheduling is illustrated. When cross-carrier scheduling is configured, the control channel transmitted through the first CC can schedule the data channel transmitted through the first CC or the second CC by using the Carrier Indicator Field (CIF). The CIF is included in the DCI. In other words, a scheduling cell is configured, and the DL grant / UL grant transmitted in the PDCCH region of the scheduling cell schedules the PDSCH / PUSCH of the scheduled cell. That is, the search space for multiple component carriers exists in the PDCCH region of the scheduling cell. The PCell can basically be the scheduling cell, and a specific SCell can be designated as the scheduling cell by the upper layer.

[0078] In Figure 7In this case, it is assumed that three DL CCs are aggregated. In this document, DL component carrier #0 is assumed to be the DL PCC (alternatively, the PCell), and DL component carriers #1 and #2 are assumed to be DL SCCs (alternatively, SCell). Further, it is assumed that the DL PCC is set to monitor the PDCCH of the CCs. When CIF is disabled, according to the LTE PDCCH rules (non-cross-carrier scheduling and self-carrier scheduling), the corresponding DL CC can transmit only the PDCCH scheduling its PDSCH without CIF. Conversely, when CIF is enabled by UL-specific (alternatively, UL-group-specific or cell-specific) upper-layer signaling, a specific CC (e.g., the DLPCC) can transmit the PDCCH scheduling the PDSCH of DL CC A and the PDCCH scheduling the PDSCH of another CC by using CIF (cross-carrier scheduling). Conversely, in another DL CC, no PDCCH is transmitted.

[0079] Figure 8 The figure illustrates the ACK / NACK (A / N) transmission process in the case of a single cell. (i) The PDSCH scheduled by the PDCCH, (ii) the PDSCH without a corresponding PDCCH (i.e., the SPS PDSCH), and (iii) the PDCCH indicating the SPS release. The figure illustrates the process of transmitting the ACK / NACK for the PDSCH in (i). The PDCCH includes the EPDCCH.

[0080] Referring to Figure 8 , the user equipment receives the PDCCH (or EPDCCH) in subframe #n-k (S802), and receives the PDSCH indicated by the PDCCH in the same subframe (S804). The PDCCH transmits scheduling information (i.e., DL grant), and the PDSCH transmits one or more (e.g., two) transport blocks TB (or codewords CW) according to the transmission mode. Thereafter, the user equipment can transmit the ACK / NACK for the PDSCH (i.e., the transport block) in subframe #n (S806). In response to a single transport block, one bit of the ACK / NACK can be transmitted, and in response to two transport blocks, two bits of the ACK / NACK can be transmitted. The ACK / NACK is basically transmitted via the PUCCH, but when there is a PUSCH transmission in subframe #n, the ACK / NACK is transmitted via the PUSCH. k represents the time interval between the DL subframe and the UL subframe. In FDD, K = 4, and k in TDD can be given by the downlink association set index (DASI). The ACK / NACK represents the HARQ-ACK. The HARQ-ACK response includes ACK, NACK, DTX, and NACK / DTX.

[0081] When multiple cells are configured for a user equipment, ACK / NACK information can be transmitted by using PUCCH format 3, or ACK / NACK information can be transmitted by using a channel selection scheme based on PUCCH format 1b.

[0082] Each cell is configured with an ACK / NACK payload of PUCCH format 3, and the concatenated ACK / NACK payloads are in the order of cell indices. The ACK / NACK payloads are configured for all cells configured for the user equipment, regardless of whether actual data is transmitted in each cell. Each bit in the ACK / NACK payload represents the HARQ-ACK feedback for that transport block (or codeword). The HARQ-ACK feedback indicates ACK or NACK, and DTX is treated as NACK. NACK and DTX have the same HARQ-ACK feedback value. If necessary, the base station can distinguish NACK from DTX by using the information about the control channels that the base station has transmitted to the user equipment.

[0083] When two cells are aggregated, a channel selection scheme based on PUCCH format 1b can be configured for ACK / NACK transmission. In the channel selection scheme based on PUCCH format 1b, the ACK / NACK responses for multiple transport blocks (or codewords) are identified by combining the PUCCH resource index and the bit value.

[0084] Figure 9 FIG. illustrates a Licensed-Assisted Access (LAA) service environment.

[0085] Referring to Figure 9 , a service environment can be provided to a user in which the LTE technology (11) in a conventional licensed band that has been actively discussed and LTE Unlicensed (LTE-U) or LAA as the LTE technology (12) in an unlicensed band can be connected to each other. For example, the LTE technology (11) in the licensed band and the LTE technology (12) in the unlicensed band in the LAA environment can be integrated by using techniques (such as, carrier aggregation, etc.), which can help to expand the network capacity. Further, in an asymmetric traffic structure where the downlink data volume is greater than the uplink data volume, LAA can provide optimized LTE services according to various requirements or environments. For convenience, the LTE technology in the licensed (alternatively, authorized or permitted) band is referred to as LTE Licensed (LTE-L), and the LTE technology in the unlicensed (alternatively, unauthorized, unlicensed, not necessarily authorized) band is referred to as LTE Unlicensed (LTE-U) or LAA.

[0086] Figure 10The figure illustrates the layout scenarios of user equipment and base stations in an LAA service environment. The frequency band targeted by the LAA service environment has a short radio communication reach due to its high-frequency characteristics. Considering this, the layout scenarios of user equipment and base stations in an environment where conventional LTE-L services and LAA services coexist can be an overlapping model and a co-location model.

[0087] In the overlapping model, the macro base station can perform radio communication with X UEs and X' UEs in the macro area (32) by using an authorized carrier and is connected to multiple remote radio heads (RRHs) through the X2 interface. Each RRH can perform radio communication with X UEs or X' UEs in a predetermined area (31) by using an unlicensed carrier. The frequency bands of the macro base station and the RRHs are different from each other and do not interfere with each other, but it is necessary to quickly exchange data between the macro base station and the RRHs through the X2 interface in order to use the LAA service as an auxiliary downlink channel for the LTE-L service through carrier aggregation.

[0088] In the co-location model, the pico / femto base station can perform radio communication with Y UEs by using an authorized carrier and an unlicensed carrier. However, it may be limited for the pico / femto base station to use LTE-L services and LAA services for downlink transmission. Depending on the frequency band, transmission power, etc., the coverage area (33) of the LTE-L service and the coverage area (34) of the LAA service may be different.

[0089] When performing LTE communication in the unlicensed band, a conventional device (e.g., a wireless LAN (Wi-Fi) device) performing communication in the corresponding unlicensed band may not demodulate the LTE-U message or data and determines the LTE-U message or data as a kind of energy for performing interference avoidance operations through energy detection technology. That is, when the energy corresponding to the LTE-U message or data is less than -62 dBm, the wireless LAN device can perform communication by ignoring the corresponding message or data. Therefore, the user equipment performing LTE communication in the unlicensed band may be frequently interfered with by wireless LAN devices.

[0090] Therefore, it is necessary to allocate or reserve a specific frequency band within a specific time in order to effectively implement the LTE-U technology / service. However, since peripheral devices performing communication through the unlicensed band attempt to access based on energy detection technology, there is a problem of difficulty in performing efficient LTE-U services. Therefore, it is necessary to prioritize research on coexistence schemes for conventional unlicensed band devices and schemes for efficient sharing of radio channels in order to solve the LTE-U technology. That is, it is necessary to develop a robust coexistence mechanism in which LTE-U devices do not affect conventional unlicensed band devices.

[0091] Figure 11Illustrated is a communication scheme (e.g., wireless LAN) operating in an unlicensed band in the prior art. Since most devices operating in the unlicensed band operate based on listen-before-talk (LBT), a clear channel assessment (CCA) technique that senses the channel before data transmission is performed.

[0092] Referring Figure 11 , a wireless LAN device (e.g., AP or STA) checks whether the channel is busy by performing carrier sensing before transmitting data. When a radio signal with a predetermined intensity or greater intensity is sensed in the channel for transmitting data, it is determined that the corresponding channel is busy, and the wireless LAN device delays accessing the corresponding channel. This process is called clear channel assessment, and the signal level used to determine whether a signal is sensed is called the CCA threshold. Meanwhile, when no radio signal is sensed in the corresponding channel or a radio signal with an intensity less than the CCA threshold is sensed, it is determined that the channel is idle.

[0093] When it is determined that the channel is idle, a terminal having data to transmit performs a backoff process after a delay period (e.g., arbitration interframe space (AIFS), PCF interframe space (PIFS), etc.). The delay period refers to the minimum time that the terminal needs to wait after the channel becomes idle. The backoff process allows the terminal to standby further for a predetermined time after the delay period. For example, during the period when the channel is in an idle state, the terminal stands by while reducing the slot time for the slot time corresponding to the random number assigned to the terminal in the contention window (CW), and the terminal that has completely exhausted the slot time can attempt to access the corresponding channel.

[0094] When the terminal successfully accesses the channel, the terminal can transmit data through the channel. When the data is successfully transmitted, the CW size (CWS) is reset to the initial value (CWmin). On the contrary, when the data is not successfully transmitted, the CWS is doubled. Therefore, the terminal is assigned a new random number within a range twice as large as the previous random number range to perform the backoff process in the next CW. In a wireless LAN, only ACK is defined as the response information received for data transmission. Therefore, when ACK is received for data transmission, the CWS is reset to the initial value, and when no feedback information is received for data transmission, the CWS is doubled.

[0095] As described above, since most communications in the unlicensed band in the prior art operate based on LBT, LTE also considers LBT in LAA to coexist with conventional devices. Specifically, in LTE, the channel access method on the unlicensed band can be classified into the following 4 categories according to the presence / application scheme of LBT.

[0096] (1) Category 1: No LBT

[0097] - The LBT process performed by the Tx entity is not executed.

[0098] (2) Category 2: LBT without random backoff

[0099] - Determine the time interval for which the Tx entity needs to sense the channel in the idle state before performing a transmission on the channel. No random backoff is performed. This can be referred to as type 2 channel access.

[0100] (3) Category 3: LBT with random backoff with a fixed-size CW

[0101] - An LBT method that performs random backoff by using a fixed-size CW. The Tx entity has a random number N in the CW, and the CW size is defined by the minimum / maximum value. The CW size is fixed. The random number N is used to determine the time interval for which the Tx entity needs to sense the channel in the idle state before performing a transmission on the channel.

[0102] (4) Category 4: LBT with random backoff with a variable-size CW

[0103] - An LBT method that performs random backoff by using a variable-size CW. The Tx entity has a random number N in the CW, and the CW size is defined by the minimum / maximum value of N. The Tx entity can change the CW size when generating the random number N. The random number N is used to determine the time interval for which the Tx entity needs to sense the channel in the idle state before performing a transmission on the channel. This can be referred to as type 1 channel access.

[0104] Figure 12 and Figure 13 illustrates the downlink transmission process based on category 4 LBT. Category 4 LBT can be used to ensure fair channel access using Wi-Fi. Refer to Figure 12 and Figure 13 , the LBT process includes an initial CCA (ICCA) and an extended CCA (ECCA). In ICCA, no random backoff is performed, and in ECCA, random backoff is performed by using a variable-size CW. ICCA is applicable when the channel is idle when signal transmission is required, and ECCA is applicable when the channel was busy just before performing a downlink transmission.

[0105] Refer to Figure 12 , the downlink transmission process based on category 4 LBT, type 1 channel access can be performed as follows.

[0106] Initial CCA

[0107] - S1202: The base station verifies that the channel is idle.

[0108] -S1204: The base station verifies whether signal transmission is required. When signal transmission is not required, the process returns to S1202, and when signal transmission is required, the process continues to S1206.

[0109] -S1206: The base station verifies whether the channel is idle within the ICCA delay period (BCCA). The ICCA delay period is configurable. As an example of an implementation, the ICCA delay period can consist of an interval of 16 μs and n consecutive CCA time slots. Here, n can be a positive integer, and one CCA time slot interval can be 9 μs. Depending on the QoS level, the number of CCA time slots can be configured in different ways. By considering the delay period of Wi-Fi (e.g., DIFS or AIFS), the ICCA delay period can be set to an appropriate value. For example, the ICCA delay period can be 34 μs. When the channel is idle within the ICCA delay period, the base station can perform the signal transmission process (S1208). When it is determined that the channel is busy during the ICCA delay period, the process continues to S1212 (ECCA).

[0110] -S1208: The base station can perform the signal transmission process. When signal transmission is not performed, the process continues to S1202 (ICCA), and when signal transmission is performed, the process continues to S1210. Even when the backoff count N reaches 0 in S1218 and S1208 is executed, when signal transmission is not performed, the process continues to S1202 (ICCA), and when signal transmission is performed, the process continues to S1210.

[0111] -S1210: When additional signal transmission is not required, the process continues to S1202 (ICCA), and when additional signal transmission is required, the process continues to S1212 (ECCA).

[0112] Extended CCA

[0113] -S1212: The base station generates a random number N in the CW. N is used as a count during the backoff process and is generated from [0, q - 1]. The CW can consist of q ECCA time slots, and the ECCA time slot size can be 9 μs or 10 μs. In S1214, the CW size (CWS) can be defined as q and can be variable. Subsequently, the base station continues to S1216.

[0114] -S1214: The base station can update the CWS. The CWS q can be updated to a value between X and Y. The X and Y values are configurable parameters. The CWS update / adjustment (dynamic backoff) can be performed whenever N is generated, and the CWS update / adjustment (semi-static backoff) can be performed semi-statically at a predetermined time interval. The CWS can be updated / adjusted based on exponential backoff or binary backoff. That is, the CWS can be updated / adjusted in the form of the square of 2 or a multiple of 2. In combination with PDSCH transmission, the CWS can be updated / adjusted based on the feedback / report of the user equipment (e.g., HARQ ACK / NACK) or based on base station sensing.

[0115] -S1216: The base station verifies whether the channel is idle within the ECCA delay period (DeCCA). The ECCA delay period is configurable. As an example of an implementation, the ECCA delay period can consist of an interval of 16 μs and n consecutive CCA time slots. Here, n can be a positive integer, and one CCA time slot interval can be 9 μs. According to the QoS level, the number of CCA time slots can be configured in different ways. By considering the delay period of Wi-Fi (e.g., DIFS or AIFS), the ECCA delay period can be set to an appropriate value. For example, the ECCA delay period can be 34 μs. When the channel is idle within the ECCA delay period, the base station continues to S1218. When it is determined that the channel is busy during the ECCA delay period, the base station repeats S1216.

[0116] -S1218: The base station verifies whether N is 0. When N is 0, the base station can perform the signal transmission process (S1208). In this case, (N = 0), the base station may not perform transmission immediately and performs a CCA check within at least one time slot to continue the ECCA process. When N is not 0 (i.e., N > 0), the process continues to S1220.

[0117] -S1220: The base station senses the channel during one ECCA time slot interval (T). The ECCA time slot size can be 9 μs or 10 μs, and the actual sensing time can be at least 4 μs.

[0118] -S1222: When it is determined that the channel is idle, the process continues to S1224. When it is determined that the channel is busy, the process returns to S1216. That is, after the channel becomes idle, an ECCA delay period is applied again, and N is not counted during the ECCA delay period.

[0119] -S1224: Subtract 1 from N (ECCA decrement count)

[0120] Figure 13 Substantially the same asFigure 12 The transmission process is the same / similar and, according to the implementation solution, is different from Figure 12 Therefore, the detailed problem can be described by referring to the content of Figure 12 .

[0121] -S1302: The base station verifies whether signal transmission is required. When signal transmission is not required, S1302 is repeated, and when signal transmission is required, the process continues to S1304.

[0122] -S1304: The base station verifies whether the time slot is idle. When the time slot is idle, the process continues to S1306, and when the time slot is busy, the process continues to S1312 (ECCA). The time slot can correspond to the Figure 12 CCA time slot in

[0123] -S1306: The base station verifies whether the channel is idle within the delay period (D). D can correspond to the Figure 12 ICCA delay period in . When the channel is idle within the delay period, the base station can perform the signal transmission process (S1308). When it is determined that the channel is busy during the delay period, the process continues to S1304.

[0124] -S1308: If necessary, the base station can perform the signal transmission process.

[0125] -S1310: When signal transmission is not performed, the process continues to S1302 (ICCA), and when signal transmission is performed, the process continues to S1312 (ECCA). Even when the backoff count N reaches 0 in S1318 and S1308 is performed, when signal transmission is not performed, the process continues to S1302 (ICCA), and when signal transmission is performed, the process continues to S1312 (ECCA).

[0126] Extended CCA

[0127] -S1312: The base station generates a random number N in the CW. N is used as a count during the backoff process, and N is generated from [0, q - 1]. In S1314, the CW size (CWS) can be defined as q and can be variable. Thereafter, the base station continues to S1316.

[0128] -S1314: The base station can update the CWS. The CWS q can be updated to a value between X and Y. The X and Y values are configurable parameters. The CWS update / adjustment (dynamic backoff) can be performed whenever N is generated, and the CWS update / adjustment (semi-static backoff) can be performed semi-statically at a predetermined time interval. The CWS can be updated / adjusted based on exponential backoff or binary backoff. That is, the CWS can be updated / adjusted in the form of the square of 2 or a multiple of 2. In combination with PDSCH transmission, the CWS can be updated / adjusted based on the feedback / report of the user equipment (e.g., HARQ ACK / NACK) or based on base station sensing.

[0129] -S1316: The base station verifies whether the channel is idle within a delay period (D). D can correspond to the ECCA delay period in Figure 12 . D in S1306 and D in S1316 can be the same as each other. When the channel is idle within the delay period, the base station continues to S1318. When it is determined that the channel is busy during the delay period, the base station repeats S1316.

[0130] -S1318: The base station verifies whether N is 0. When N is 0, the base station can perform the signal transmission process (S1308). In this case, (N = 0), the base station may not perform the transmission immediately and perform a CCA check during at least one time slot to continue the ECCA process. When N is not 0 (i.e., N > 0), the process continues to S1320.

[0131] -S1320: The base station selects one of the operations of subtracting 1 from N and the operation of not decreasing N (self-delay). The self-delay operation can be performed according to the implementation / selection of the base station, and in self-delay, the base station does not perform energy detection sensing and does not even perform the ECCA decrement count.

[0132] -S1322: The base station can select one of the operation of not performing energy detection sensing and the energy detection operation. When energy detection sensing is not performed, the process continues to S1324. When the energy detection operation is performed, if the energy level is equal to or less than the energy detection threshold (i.e., idle), the process continues to S1324. If the energy level is greater than the energy detection threshold (i.e., busy), the process returns to S1316. That is, after the channel is idle, a delay period is applied again, and N is not counted within the delay period.

[0133] -S1324: The process continues to S1318.

[0134] Figure 14Illustrates an example of a base station performing downlink transmission in an unlicensed band. The base station may aggregate one or more cells in a licensed band (for convenience, LTE-L cells) and one or more cells in an unlicensed band (for convenience, LTE-U cells). In Figure 14 , it is assumed that one LTE-L cell and one LTE-U cell are aggregated for communication with a user equipment. The LTE-L cell may be a PCell, and the LTE-U cell may be an SCell. In the LTE-L cell, the base station may only use frequency resources and perform operations according to LTE in the prior art. Therefore, all radio frames may be composed of regular subframes (rSFs) with a length of 1 ms (see Figure 2 ), and DL transmission (e.g., PDCCH and PDSCH) may be performed in each subframe (see Figure 1 ). Meanwhile, in the LTE-U cell, downlink transmission is performed based on LBT for coexistence with conventional devices (e.g., Wi-Fi devices). Further, it is necessary to allocate or reserve a specific frequency band within a specific time to effectively implement LTE-U technology / services. Therefore, in the LTE-U cell, downlink transmission may be performed through a set of one or more consecutive subframes (DL transmission bursts) after LBT. According to the LBT situation, the DL transmission burst may start with a regular subframe (rSF) or a partial subframe (pSF). The pSF may be a part of a subframe and may include the second time slot of the subframe. Further, the downlink transmission burst may end with an rSF or a pSF.

[0135] <Method for Performing LBT in Uplink-Only Grant Transmission>

[0136] Hereinafter, a channel access method for performing transmission of a downlink control channel (e.g., PDCCH or EPDCCH) will be described when performing channel access for uplink signal and uplink data transmission through an unlicensed band, considering uplink-only grant (UL-only grant) transmission, as well as transmission of an uplink grant and uplink traffic scheduled by the uplink grant.

[0137] In particular, the present invention focuses on illustrating an LBT method for performing transmission of a downlink control channel considering uplink-only grant transmission and uplink traffic transmission scheduled by a corresponding uplink grant.

[0138] Figure 15 Is a schematic diagram illustrating a case of transmitting a PDCCH including only an uplink grant without PDSCH transmission as an embodiment of the present invention.

[0139] Refer to Figure 15, when performing self-carrier scheduling on uplink data traffic transmitted in the LAA SCell through a control channel transmitted in the corresponding LAA SCell, a control channel that transmits only uplink grants can be transmitted in the PDCCH of the DL subframe, that is, in the case where there is no PDSCH transmission in a subframe, only uplink grant transmission can be performed in the PDCCH. In this case, the OFDM symbols that the PDSCH region can have in the subframe can be made invalid without transmitting any signal, and channel access from other nodes or Wi-Fi nodes can be allowed in the corresponding invalidated OFDM symbols of the unlicensed carrier.

[0140] Therefore, although the base station attempts to ensure the transmission of the base station by configuring the maximum channel occupancy time (MCOT) configuration differently according to the channel access priority level and the LBT performed for only uplink grant transmission is also successful, for the transmission of the PDSCH and the scheduled PUSCH in the next subframe, as shown in Figure 15 , it may be impossible to transmit the PDSCH and the scheduled PUSCH.

[0141] In Figure 15 , the case where the starting subframe of the LAA burst on the unlicensed carrier is configured as a partial subframe that performs only uplink grant transmission is described as an embodiment, but the present invention is not limited thereto. As another embodiment, there may be a case where the last subframe of the LAA burst is configured as a partial subframe that performs only uplink grant transmission. In another embodiment, even in the starting subframe of the LAA burst in the unlicensed carrier or in a subframe that is not the last subframe of the LAA burst, invalidated OFDM symbols can be generated in the subframe that performs only UL grant transmission, and thus, the above-mentioned problem may occur. Hereinafter, a method for solving the above-mentioned problem will be described.

[0142] Method A)

[0143] Figure 16 Illustrates the case of transmitting an EPDCCH that includes only UL grants without PDSCH transmission. Accordingly, since the EPDCCH is allocated in the PDSCH region in the FDM scheme of the PDSCH, even for only UL grant transmission without PDSCH, it is possible to prevent (multiple) invalidated OFDM symbols from appearing in the PDSCH region and to prevent other nodes from accessing the channel through LBT.

[0144] Moreover, as a method for performing LBT used by a (multi - ) UE when transmitting UL traffic corresponding to a corresponding UL grant, by executing the LBT scheme performed during the transmission of the UL grant, or when transmitting UL traffic in the MCOT ensured in the UL grant transmission, performing a single - interval LBT such as 16 us, 25 us, 34 us, or 43 us, etc. (hereinafter referred to as type 2 channel access for ease of explanation), fast channel access for UL data transmission can be achieved.

[0145] Alternatively, as a method for LBT used in a (multi - ) UE when transmitting UL traffic corresponding to a UL grant, execute the LBT scheme performed during the transmission of the UL grant, or perform cat - 4 LBT when transmitting UL traffic outside the MCOT obtained during the UL grant transmission (hereinafter referred to as type 1 channel access for ease of explanation).

[0146] Alternatively, in this case, the following method can be considered: By this method, the base station signals whether to perform type 2 channel access to allow the user equipment to have fast channel access as LBT for UL traffic, or whether to perform type 1 channel access to perform back - off. The type of channel access that the base station can notify the user equipment can be transmitted through the UL grant, and the base station can notify type 1 channel access or type 2 channel access in the corresponding UL grant. Here, type 1 channel access refers to Cat - 4 LBT, and type 2 channel access refers to 25 - us LBT.

[0147] Method B)

[0148] Figure 17 is a schematic diagram illustrating the case of independently performing LBT for sub - frames for transmitting only UL grants without PDSCH transmission and (multi - ) sub - frames for performing PDSCH transmission according to an embodiment of the present invention.

[0149] As shown in Figure 17 even when transmitting PDCCH or EPDCCH for only UL grant transmission in one sub - frame, in the next sub - frame for transmitting PDSCH, independent of the LBT in the sub - frame for only UL grant transmission, a method of configuring the LBT to be performed according to the channel access priority level of the PDSCH can be considered.

[0150] In this case, when the LBT in the sub - frame for transmitting PDSCH is successful, configure the MCOT from the corresponding sub - frame. When there is a UL sub - frame for transmitting UL traffic corresponding to a previously scheduled UL grant in the corresponding MCOT, type 2 channel access can be performed to achieve fast channel access for UL data transmission.

[0151] Alternatively, as a method for performing LBT used in a (plural) UE during transmission of UL traffic corresponding to a UL grant, the method may be configured to perform an LBT scheme executed during transmission of the UL grant, or perform type 1 channel access when transmitting UL traffic outside the MCOT obtained by LBT in a subframe transmitting a PDSCH.

[0152] Alternatively, in this case, the following method may be considered: By this method, the base station signals whether to perform type 2 channel access to allow the user equipment to have fast channel access as LBT for UL traffic, or whether to perform type 1 channel access to perform backoff. The type of channel access that the base station can notify the terminal may be transmitted through a UL grant, and the base station may notify type 1 channel access or type 2 channel access in the corresponding UL grant. Here, type 1 channel access may refer to Cat-4 LBT, and type 2 channel access may refer to 25us LBT.

[0153] Method C)

[0154] Figure 18 is a schematic diagram illustrating a case of independently performing LBT for a subframe that only transmits a UL grant without PDSCH transmission and a (plural) subframe for performing PDSCH transmission according to an embodiment of the present invention. (Plural) invalid OFDM symbols in the PDSCH region can be prevented from appearing by transmitting a reservation signal, and other nodes can be prevented from accessing the channel through LBT. Moreover, because of this, a PDSCH transmitted in the next subframe can be transmitted in the MCOT without additional LBT.

[0155] As an example of the reservation signal, there may be one EPDCCH transmission common to all UEs, and as another example, a method of extending CRS ports 0 and 1 to extend the transmission in OFDM symbol indices #0, #4, #5, and #7 to the remaining symbols may be considered. In addition, a form of extending and transmitting CRS ports 0 to 4 may be considered, and a method of transmitting dummy data to an RB in a specific frequency region as a reservation signal may be considered.

[0156] Moreover, as a method for performing LBT used in a (plural) UE when transmitting UL traffic corresponding to a UL grant, type 2 channel access may be performed when transmitting UL traffic in the MCOT ensured in the transmission of the UL grant, thereby achieving fast channel access for UL data transmission.

[0157] Alternatively, as a method for performing LBT used in a (plural) UE during transmission of UL traffic corresponding to a UL grant, the method may be configured to perform a scheme of LBT performed during transmission of the UL grant, or perform type 1 channel access when transmitting UL traffic outside the MCOT obtained in the UL grant transmission.

[0158] Alternatively, in this case, the following method may be considered: By this method, the base station signals whether to perform type 2 channel access to allow the user equipment to have fast channel access as LBT for UL traffic, or whether to perform type 1 channel access to perform backoff. The type of channel access that the base station can notify the user equipment may be transmitted by the UL grant, and the base station may notify type 1 channel access or type 2 channel access in the corresponding UL grant. Here, type 1 channel access refers to Cat-4 LBT, and type 2 channel access refers to 25 us LBT.

[0159] In Figures 16 to 18 there is a case where the start subframe of the LAA burst based on the unlicensed carrier is set to a partial subframe that performs only UL grant transmission, but the present invention is not limited thereto. As another embodiment, there may be a case where the last subframe of the LAA burst is set to a partial subframe that performs only UL grant transmission. In another embodiment, even in the start subframe of the LAA burst in the unlicensed carrier or in a subframe that is not the last subframe of the LAA burst, an invalid OFDM symbol may be generated in the subframe that performs only UL grant transmission, and thus, the above problem may occur.

[0160] Moreover, although Figures 15 to 18 has been described with reference to a conventional subframe, Figures 15 to 18 it can be equivalently applied to the case where the start subframe is a partial subframe (for example, a subframe composed of less than 14 OFDM symbols) and the case where the last subframe is a partial subframe.

[0161] Next, during only UL grant transmission, considering the channel access priority level of UL traffic corresponding to the UL grant, a DL control channel (e.g., PDCCH, EPDCCH) including the UL grant, an LBT method, and an LBT scheme for UL traffic transmission corresponding to the UL grant will be described. In addition, an LBT scheme for UL traffic transmission corresponding to the UL grant when transmitting the UL grant together with PDSCH transmission will be described.

[0162] First, when transmitting a UL grant together with PDSCH transmission, the LBT for the PDCCH and EPDCCH, which are the control channels through which the UL grant is transmitted, includes: performing channel access by using LBT parameters according to the channel access priority class of the PDSCH (hereinafter referred to as CAPC for convenience).

[0163] Table 1 below shows the LBT parameters according to the channel access priority classes for transmitting the PDSCH as a downlink transmission.

[0164] [Table 1] Channel Access Priority Categories

[0165]

[0166]

[0167] As an example, when the CAPC of the PDSCH is 1 or 2, since the MCOT is 2 ms or 3 ms, assuming that the minimum time delay for UL grant and UL service transmission is 4 ms, the UL service transmission corresponding to the UL grant is performed outside the MCOT of the downlink burst to which the UL grant is transmitted. Therefore, the LBT for the UL service transmission corresponding to the UL grant can be configured to perform LBT according to the CAPC of the UL service to be transmitted by the user equipment. When there are multiple CAPCs of the UL service to be transmitted instead of one CAPC, the user equipment is configured to perform type 1 channel access based on the CAPC with the lowest priority among the multiple CAPCs.

[0168] As another example, when the CAPC of the PDSCH transmitted using the UL grant is 3 or 4, since the MCOT is 8 ms or 10 ms, it is possible to transmit the UL service transmission corresponding to the UL grant within the MCOT, but it is also possible to transmit the UL service transmission corresponding to the UL grant outside the MCOT. Therefore, when the downlink transmission, UL LBT, and UL service transmission can occur within the MCOT, a single interval (e.g., 16 us, 25 us, 34 us, 43 us, or 16 + 9*N, where N can be 1 or a larger value) LBT is performed regardless of the CAPC of the UL service. That is, the UL service transmission is performed through type 2 channel access. On the other hand, in the case where the DL transmission, UL LBT, and UL service transmission do not occur within the MCOT, type 2 channel access is performed for the UL transmission that may occur within the MCOT regardless of the CAPC of the UL service. However, for the UL service transmission scheduled to be transmitted outside the MCOT, the user equipment can be configured to perform LBT according to the CAPC of the UL service to be transmitted by the user equipment. When there are multiple CAPCs of the UL service to be transmitted by the corresponding user equipment, the corresponding user equipment can perform type 1 channel access based on the CAPC with the lowest priority among the multiple CAPCs.

[0169] As another example, when the CAPC of the PDSCH transmitted using the UL grant is set to 3 and the UL grant is also executed according to CAPC 3, if the CAPC of the UL service that the user equipment actually wants to transmit is set to 3 or less, the UL service is transmitted through type 2 channel access regardless of the CAPC of the UL service. However, if the CAPC of the UL service is 4, the user equipment can be set to perform type 1 channel access using the LBT parameters according to the CAPC 4 of the UL service to perform the UL transmission regardless of whether the corresponding UL service transmission has occurred within the MCOT. Moreover, when the CAPC of the PDSCH transmitted using the UL grant is configured to 4 and the transmission of the UL grant is also executed according to CAPC 4, the user equipment can perform the UL service transmission through type 2 channel access regardless of the CAPC of the UL service that the user equipment actually wants to transmit.

[0170] As another example, when performing LBT by using the CAPC value X of the PDSCH transmitted with a UL license, for the CAPC values of UL services that are less than or equal to X, UL service transmission through type 2 channel access can be performed. In other cases, the user equipment can be configured to perform LBT according to the CAPC of the UL service to be transmitted by the user equipment. When there are multiple CAPCs of the UL service to be transmitted by the corresponding user equipment, the corresponding user equipment can be configured to perform type 1 channel access based on the CAPC with the lowest priority among the multiple CAPCs.

[0171] <ul lbt类型切换>

[0172] In the following, a method of switching the type of UL LBT during the execution of UL channel access will be described.

[0173] The base station notifies the user equipment of the LBT type and the parameters for the LBT that the user equipment should perform. The base station can specify the LBT type through the UL grant, and notify type 1 channel access, type 2 channel access, or no LBT as the LBT type.

[0174] Figure 19 is a schematic diagram illustrating a method of switching the LBT type according to an embodiment of the present invention when DL scheduling occurs between UL grant transmission and the corresponding UL service transmission. Specifically, in Figure 19 , the base station notifies the user equipment of the LBT type through the UL grant, but it is assumed that DL scheduling occurs between the UL grant transmission and the corresponding UL transmission.

[0175] Figure 19 (a) of notifies that type 1 channel access is performed through the UL grant in the sixth or tenth subframe starting from the first DL subframe for UL service transmission. In this case, the user equipment can perform type 1 channel access and perform UL transmission. In Figure 19 (a) of , since the MCOT is set to 3 ms through the first DL subframe, the UL service transmission scheduled in the sixth or tenth subframe does not exist within the MCOT set in the DL. Therefore, the base station can instruct the user equipment to perform type 1 channel access for the UL transmission.

[0176] In contrast, when the UL service transmission exists within the MCOT set in the DL, for example, when the configured MCOT from the first DL subframe is 8 ms, the base station can instruct the user equipment to perform type 2 channel access through the UL grant, and the instructed user equipment can perform type 2 channel access to transmit the UL service.

[0177] In Figure 19 (b) of , assuming that type 1 channel access is instructed through the UL grant for the transmission of UL service configured in the sixth or tenth subframe starting from the first DL subframe, when DL scheduling is performed in the fifth subframe as in Figure 19 (b) of before the scheduled UL service transmission, the following method can be considered, in which the user equipment that has performed DL reception can change the channel access type indicated in the UL grant received by the user equipment from the first DL subframe.

[0178] In other words, when there is UL transmission in the MCOT configured in the DL, since the base station can transmit UL services through type 2 channel access, the base station can be configured to transmit UL services through type 2 channel access instead of the indicated type 1 channel access. Therefore, the base station can provide a trigger message to enable the user equipment to perform type 2 channel access, so that the user equipment receiving the trigger message can perform type 2 channel access to transmit UL services.

[0179] However, when the UL grant indicated by the base station is configured to perform continuous multiple subframe scheduling via one UL grant as in Figure 19 (a) of Figure 19 and Figure 19 (b) of Figure 19 , that is, it is necessary to consider the case of configuring the first DL subframe to perform the scheduling of the sixth UL subframe and the seventh UL subframe in

[0180] (a) of Figure 19 and

[0181] (b) of Figure 19 . In particular, when there is DL service to be transmitted by the base station, DL scheduling is performed in the 5th subframe, and the MCOT is set to 2 ms in the DL transmission, for the UE that schedules the sixth and seventh consecutive UL subframes in the first DL subframe, the ULLBT configured for the UL transmission in the sixth and seventh consecutive subframes is within the newly set MCOT (2 ms). Therefore, it may be possible to transmit UL services by switching from type 1 channel access to type 2 channel access. However, since although the LBT for the seventh subframe is outside the 2 - ms MCOT, the LBT time point for the sixth subframe is within the 2 - ms MCOT, it is possible to benefit from performing fast channel access, which may cause fairness problems among systems using other unlicensed bands. To improve this, according to an embodiment of the present invention, the user equipment that schedules the UL transmission of multiple subframes in the sixth subframe can consider a method of performing type 1 channel access for the UL transmission of the seventh subframe. Figure 19 On the other hand, when the length of the entire UL burst (i.e., the sixth and seventh subframes) is not included in the newly set DL MCOT, in

[0182] Figure 20 (b) of

[0181] , a method of performing the channel access type configured by the previous UL grant (i.e., type 1 channel access configured by the UL grant from the first DL subframe) can be considered. Figure 19 Although the UL burst in the sixth and seventh subframes is described with reference to Figure 19 , it can be equivalently applied to the UL burst in the tenth and eleventh subframes.

[0182] Figure 20 FIG. is a schematic diagram showing another example of switching the channel access type according to another embodiment of the present invention when DL scheduling occurs between UL licensed transmission and the corresponding UL service transmission. In the same way, in particular, in Figure 20 , the base station notifies the user equipment of the channel access type through UL license, but it is assumed that DL scheduling occurs between UL licensed transmission and the corresponding UL transmission. In addition, in Figure 20 , it is assumed that the channel access type for UL bursts is notified when scheduling multiple subframes, and the user equipment performs the corresponding LBT.

[0183] In Figure 20 (a), the base station schedules the tenth UL subframe and the eleventh UL subframe in the first, second, or third DL subframe, that is, through the UL license on the previous DL burst, and instructs to perform type 1 channel access as the associated channel access type and transmit UL service.

[0184] By the way, as shown in Figure 20 (b), when DL scheduling (e.g., the eighth subframe and the ninth subframe) occurs between UL licensed transmission and the corresponding UL service transmission, and the MCOT of the DL burst includes the tenth and eleventh UL subframes as UL bursts, the UL service transmission exists in the MCOT of the DL. Therefore, the channel access type for the tenth UL subframe and the eleventh UL subframe is switched to type 2 channel access to transmit UL service.

[0185] On the other hand, as shown in Figure 20 (c), if the MCOT of the DL burst that occurs between UL licensed transmission and the corresponding UL service transmission does not include UL bursts (i.e., the tenth UL subframe and the eleventh UL subframe), then only type 2 channel access is allowed for the UL subframes included in the MCOT among the UL bursts, and if not, UL service is transmitted by performing type 1 channel access on the eleventh subframe.

[0186] Moreover, as shown in Figure 20 (d), when the length of the entire UL burst for scheduling multiple subframes is not included in the newly formed MCOT, UL burst LBT is performed using the channel access type previously indicated by the base station through UL license to transmit UL service.

[0187] Finally, in Figure 20 (e), when DL scheduling (the eighth subframe and the ninth subframe) occurs between UL licensed transmission and the corresponding UL service transmission, if the MCOT of the DL burst does not include any part of the UL burst, then UL burst LBT is performed using the channel access type previously indicated by the base station through UL license to transmit UL service.

[0188] Figure 21 is a schematic diagram showing another example of switching the channel access type according to an embodiment of the present invention when DL scheduling occurs between UL licensed transmission and the corresponding UL service transmission. In particular, in Figure 21 , the base station notifies the user equipment of the channel access type through UL license, but it is assumed that DL scheduling occurs between UL licensed transmission and the corresponding UL transmission. Moreover, in Figure 21 , it is assumed that the channel access type of each UL subframe constituting the UL burst is notified when scheduling multiple subframes or a single subframe, and the user equipment performs the corresponding LBT.

[0189] In Figure 21 's (a), the base station schedules the tenth UL subframe and the eleventh UL subframe in the first, second, or third DL subframe, that is, through UL license on the previous DL burst, and instructs to perform type 1 channel access and transmit UL service for each UL subframe.

[0190] However, as shown in Figure 21 's (b), if the MCOT of the DL burst occurring between UL licensed transmission and the corresponding UL service transmission does not include the UL burst (i.e., the tenth UL subframe and the eleventh UL subframe), then the UL service is transmitted by allowing type 2 channel access to the UL subframes included in the MCOT among the UL bursts and not performing type 1 channel access to the eleventh subframe not included in the MCOT.

[0191] Moreover, as shown in Figure 21 's (c), when the length of the entire UL burst for which multiple subframes are scheduled is not included in the newly formed MCOT, LBT is performed using the channel access type previously indicated by the base station through UL license to transmit the UL service.

[0192] Implicit or explicit signaling methods for switching the LBT type from the base station can be considered, and as an implicit signaling method, by determining whether there is a transmission of the UL burst in the newly formed MCOT by receiving the first DL subframe on the DL burst, the channel access type for UL transmission can be changed, and LBT is performed to transmit the UL service. Figures 19 to 21 described above, and as an implicit signaling method, by determining whether there is a transmission of the UL burst in the newly formed MCOT by receiving the first DL subframe on the DL burst, the channel access type for UL transmission can be changed, and LBT is performed to transmit the UL service.

[0193] Alternatively, as explicit signaling, if DL scheduling occurs between UL grant transmission and the corresponding UL service transmission, the base station may transmit signaling for changing the channel access type to the user equipment, and the user equipment may change the channel access type to transmit the UL service by receiving the corresponding signaling. Alternatively, the base station notifies the user equipment of the MCOT for each DL burst, and if the UL burst is configured to be completed within the MCOT configured by the base station, the user equipment may change the channel access type to perform LBT through type 2 channel access and transmit the UL service.

[0194]

[0195] Meanwhile, if the base station schedules UL transmissions for multiple user equipments, the base station may know whether the UL subframe to be scheduled is the last UL subframe for the UE in the cell when transmitting the UL grant. Therefore, preferably, the base station signals whether the subframe to be scheduled for the UE is the last subframe. As a signaling method, when transmitting the UL grant, there may be a notification method through the DL common control signal for DL or a notification method through the UL common control signal.

[0196] As an example of the above common control signal, it may represent a PDCCH with DCI scrambled by CC-RNTI. The base station may notify the UE of the last subframe in the UL subframe through the common control signal. If the (multiple) scheduled UL subframes are all included before the last subframe indicated by the common control signal in the cell, the user equipment may perform type 2 channel access to perform UL transmission in the (multiple) scheduled UL subframes, regardless of the channel access type indicated by the base station for the (multiple) scheduled UL subframes.

[0197] On the other hand, when the (multiple) scheduled UL subframes are only partially included or not fully included before the last subframe indicated by the common control signal in the cell, the user equipment may perform channel access according to the channel access type indicated for the (multiple) UL subframes scheduled by the base station and perform UL transmission in the (multiple) scheduled UL subframes.

[0198] <Method for Performing LBT for Continuous UL Transmission after DL Transmission>

[0199] Hereinafter, a UL channel access method for continuous UL transmission after DL transmission in an LAA cell will be described.

[0200] Figure 22 is a schematic diagram illustrating a method for performing UL channel access for continuous UL transmission after DL transmission in an LAA cell.

[0201] As Figure 22 As in the case where the base station transmits a UL grant to the user equipment in subframe #n and schedules a UL transmission in subframe #(n + 4), any user equipment can identify that the PDSCH for the user equipment itself is included in the DL transmission from the base station in subframe #(n + 3) through the PDCCH / EPDCCH, or can identify its DL scheduling through the PDCCH / EPDCCH and successful decoding of the PDSCH.

[0202] In this case, DL reception is completed, and the UL service transmission of the user equipment can be performed immediately without performing UL LBT after a certain interval (e.g., 16 us, 20 us, or 25 us, or any other value) starting from the time when DL reception is completed, or only perform type 2 channel access. Since LBT is performed once in the DL during the UL grant transmission, for the UL transmission expected by the UL grant, the user equipment can either not perform UL LBT additionally or perform a simple LBT operation without backoff to transmit the UL service.

[0203] Here, when transmitting the UL service after a certain interval, the transmission after a specific period can be considered regardless of the subframe boundary, or the transmission can be performed corresponding to the OFDM symbol (or SC - FDMA symbol) boundary. Alternatively, there may be a method of transmitting the UL service corresponding to the UL subframe boundary. However, when setting a certain interval, it may be preferable to consider the switching time from DL to UL.

[0204] Figure 23 An example of a user equipment transmitting a data channel to a base station according to another embodiment of the present invention is shown.

[0205] Referring to Figure 23 , when UL transmission is scheduled after a DL subframe in the same carrier, the user equipment can start UL transmission according to a channel access procedure not based on a backoff process. Specifically, the user equipment can perform type 2 channel access and start UL transmission based on whether the channel is idle during a single sensing interval.

[0206] Specifically, the user equipment senses whether the channel is idle during a single sensing interval. If the channel is idle, the user equipment can start UL transmission through the corresponding channel. At this time, the single sensing interval can represent the minimum time interval of the idle time interval required for the user equipment to access the channel. At this time, the user equipment can determine whether the corresponding channel is idle through a Clear Channel Assessment (CCA) operation. In addition, the user equipment can start UL transmission at the subframe boundary. At this time, the user equipment can sense whether the channel corresponding to the UL transmission is idle during a single sensing interval (for example, a 25 us interval), and can start UL transmission when the corresponding channel is idle. At this time, the specific operation of the user equipment can be the same as the method of transmitting UL by performing the above type 2 channel access.

[0207] Figure 24 The configuration of a user equipment and a base station according to an embodiment of the present invention is illustrated. In an embodiment of the present invention, the user equipment can be implemented by various types of wireless communication devices or computing devices that are guaranteed to be portable and have mobility. The user equipment can be referred to as a Station (STA), a Mobile Subscriber (MS), etc. In an embodiment of the present invention, the base station can control and manage a cell corresponding to a service area (for example, a macro cell, a femto cell, a pico cell, etc.), and perform functions such as transmitting signals, designating channels, monitoring channels, self-diagnosis, and relaying. The base station can be referred to as an evolved Node B (eNB), an Access Point (AP), etc.

[0208] Referring to Figure 24 , the user equipment 100 may include a processor 110, a communication module 120, a memory 130, a user interface unit 140, and a display unit 150.

[0209] The processor 110 can execute various commands or programs according to the present invention and process data in the user equipment 100. Further, the processor 100 can control all operations of the corresponding units of the user equipment 100 and control data transmission / reception between these units. For example, the processor 110 can receive a DL signal in an LTE-U cell in the LAA environment and can send a HARQ-ACK response for the DL signal to the base station.

[0210] The communication module 120 can be an integrated module that performs mobile communication by using a mobile communication network and performs wireless LAN access by using a wireless LAN. For this purpose, the communication module 120 can include multiple network interface cards, such as cellular communication interface cards 121 and 122 and internal or external type wireless LAN interface cards 123. In Figure 24 it, the communication module 120 is illustrated as an integrated module, but can be based on a circuit configuration or different from Figure 24 The use independently sets the corresponding network interface card.

[0211] The cellular communication interface card 121 transmits / receives radio signals to / from at least one of the base station 200, an external device, and a server through the use of a mobile communication network, and provides cellular communication services at a first frequency band based on a command of the processor 110. The cellular communication interface card 121 may include at least one NIC module that uses an LTE licensed band. The cellular communication interface card 122 transmits / receives radio signals to / from at least one of the base station 200, an external device, and a server through the use of a mobile communication network, and provides cellular communication services at a second frequency band based on a command of the processor 110. The cellular communication interface card 122 may include at least one NIC module that uses an LTE unlicensed band. For example, the LTE unlicensed band may be a band of 2.4 GHz or 5 GHz.

[0212] The wireless LAN interface card 123 transmits / receives radio signals to / from at least one of the base station 200, an external device, and a server through wireless LAN access, and provides wireless LAN services at a second frequency band based on a command of the processor 110. The wireless LAN interface card 123 may include at least one NIC module that uses a wireless LAN band. For example, the wireless LAN band may be an unlicensed radio band, such as a band of 2.4 GHz or 5 GHz.

[0213] The memory 130 stores control programs and various result data used in the user equipment 100. The control programs may include programs required for the user equipment 100 to perform wireless communication with at least one of the base station 200, an external device, and a server. The user interface 140 includes various types of input / output devices provided in the user equipment 100. The display unit 150 outputs various images on a display screen.

[0214] Furthermore, the base station 200 according to an exemplary embodiment of the present invention may include a processor 210, a communication module 220, and a memory 230.

[0215] The processor 210 may execute various commands or programs according to the present invention and process data in the base station 200. Furthermore, the processor 210 may control all operations of corresponding units of the base station 200 and control data transmission / reception between these units. For example, the processor 210 may perform downlink transmission. Specifically, the processor 210 may perform downlink transmission, HARQ-ACK feedback set check, and CWS adjustment, etc. according to cases 1, 2-1, and 2-2.

[0216] The communication module 220 may be an integrated module that performs mobile communication by using a mobile communication network and performs wireless LAN access by using a wireless LAN, such as the communication module 120 of the user equipment 100. To this end, the communication module 120 may include multiple network interface cards, such as cellular communication interface cards 221 and 222 and an internal or external type of wireless LAN interface card 223. In Figure 18 , the communication module 220 is illustrated as an integrated module, but the corresponding network interface cards may be independently provided according to the circuit configuration or for uses different from Figure 18 .

[0217] The cellular communication interface card 221 transmits / receives radio signals to / from at least one of the user equipment 100, an external device, and a server by using a mobile communication network, and provides cellular communication services at a first frequency band based on a command of the processor 210. The cellular communication interface card 221 may include at least one NIC module that uses an LTE licensed band. The cellular communication interface card 222 transmits / receives radio signals to / from at least one of the user equipment 100, an external device, and a server by using a mobile communication network, and provides cellular communication services at a second frequency band based on a command of the processor 210. The cellular communication interface card 222 may include at least one NIC module that uses an LTE unlicensed band. The LTE unlicensed band may be a band of 2.4 GHz or 5 GHz.

[0218] The wireless LAN interface card 223 transmits / receives radio signals to / from at least one of the user equipment 100, an external device, and a server through wireless LAN access, and provides wireless LAN services at a second frequency band based on a command of the processor 210. The wireless LAN interface card 223 may include at least one NIC module that uses a wireless LAN band. For example, the wireless LAN band may be an unlicensed radio band, such as a band of 2.4 GHz or 5 GHz.

[0219] In Figure 24 , the blocks of the user equipment and the base station are logically divided and the elements of the device are illustrated. According to the design of the device, the elements of the device may be installed as one chip or multiple chips. Further, some components of the user equipment 100 (that is, the user interface 140 and the display unit 150) may be selectively provided in the user equipment 100. Further, some components of the base station 200 (that is, the wireless LAN interface 223, etc.) may be selectively provided in the base station 200. If necessary, the user interface 140 and the display unit 150 may also be provided in the base station 200.

[0220] The methods and systems of the present invention are described with reference to specific embodiments, but some or all of the components and operations of the present invention can be implemented using a computer system having a general hardware architecture.

[0221] The description of the present invention is for illustrative purposes, and those skilled in the art will understand that the present invention can be easily modified into other detailed forms without changing the technical spirit or essential features of the present invention. Therefore, the foregoing exemplary embodiments are illustrative in all respects and not restrictive. For example, each component described as a single type can be implemented as a distributed component, and similarly, components described as distributed components can also be implemented in a combined form.

[0222] The scope of the present invention is represented by the claims (rather than the detailed description) to be described below, but the scope of the present invention should be construed as including all variations or modifications from the meaning and scope of the claims and their equivalents.

[0223] Industrial Applicability

[0224] The present invention can be applied to various communication devices used in a wireless communication system (e.g., stations using unlicensed band communication, stations using cellular communication, base stations, etc.).

Claims

1. A method for a user equipment to perform uplink transmission to a base station via an unlicensed cell in a wireless communication system, the method comprising: Receiving an uplink grant for scheduling the uplink transmission in at least one subframe from the base station, wherein the uplink grant indicates a channel access type to be used among a first type of channel access or a second type of channel access for the uplink transmission; and Performing the uplink transmission in the at least one subframe using at least one of the first type of channel access or the second type of channel access, wherein the first type of channel access is based on channel sensing with a random backoff using a contention window CW of variable size before data transmission, and wherein the second type of channel access is based on channel sensing with a single interval before data transmission, wherein when all of the uplink transmission in the at least one subframe is included in a predetermined interval determined based on a downlink transmission from the base station via the unlicensed cell, the second type of channel access is used to perform the uplink transmission, wherein when the uplink transmission is not included in the predetermined interval or only a part of the uplink transmission is included in the predetermined interval, the channel access type indicated in the uplink grant is used to perform the uplink transmission.

2. The method according to claim 1, wherein, Determining the predetermined interval based on a maximum channel occupancy time set by the downlink transmission.

3. The method according to claim 1, wherein Receiving, via a common control channel, information about whether the at least one subframe is the last subframe for the uplink transmission.

4. The method according to claim 1, wherein When performing the uplink transmission in the next subframe of the downlink transmission via the unlicensed cell, using the second type of channel access to perform the uplink transmission.

5. A user equipment in a wireless communication system, the user equipment comprising: A wireless communication module; and A processor configured to receive, via the wireless communication module, an uplink grant for scheduling an uplink transmission in at least one subframe from a base station, and to perform the uplink transmission in the at least one subframe using at least one of a first type of channel access or a second type of channel access via the wireless communication module, wherein the first type of channel access is based on channel sensing with a random backoff using a contention window CW of variable size before data transmission, wherein the second type of channel access is based on channel sensing with a single interval before data transmission, and wherein the uplink grant indicates the channel access type to be used among the first type of channel access or the second type of channel access for the uplink transmission; Wherein, when all of the uplink transmissions in the at least one subframe are included in a predetermined interval determined based on the downlink transmission via an unlicensed cell from the base station, the processor uses the second type of channel access to perform the uplink transmission, and when the uplink transmission is not included in the predetermined interval or only a part of the uplink transmission is included in the predetermined interval, the processor uses the channel access type indicated in the uplink grant to perform the uplink transmission.

6. The user equipment according to claim 5, wherein, The predetermined interval is determined based on a maximum channel occupancy time set by the downlink transmission.

7. The user equipment according to claim 5, wherein, Information regarding whether the at least one subframe is the last subframe for the uplink transmission is received via a common control channel.

8. The user equipment according to claim 5, wherein, When performing the uplink transmission in the next subframe of the downlink transmission via the unlicensed cell, the processor is configured to use the second type of channel access to perform the uplink transmission.

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