Multi-carrier signal transmission method, device and system

Abstract

The present invention relates to a method, apparatus, and system for transmitting a signal using multiple carriers. Specifically, the present invention provides a wireless communication device comprising: a communication module; and a processor, wherein the processor acquires a common backoff counter for a set of carriers to transmit data, wherein the set of carriers includes at least one component carrier, and performs backoff of each component carrier using the acquired common backoff counter, and simultaneously transmits data through at least one component carrier for which backoff has been completed. The invention also provides a wireless communication device and a wireless communication method using the same.

Description

Technology Field

[0001] The present invention relates to a wireless communication system. Specifically, the present invention relates to a method, apparatus, and system for transmitting a signal using multiple carriers. Background Technology

[0002] With the recent surge in mobile traffic due to the proliferation of smart devices, existing licensed frequency spectrums or LTE-Licensed frequency bands alone are becoming insufficient to handle the increasing data usage required to provide cellular communication services.

[0003] Under these circumstances, using unlicensed frequency spectrum or LTE-Unlicensed frequency bands (e.g., 2.4GHz band, 5GHz band, etc.) to provide cellular communication services is being sought as a solution to the problem of spectrum shortage.

[0004] However, unlike licensed bands where telecommunications operators secure exclusive frequency usage rights through procedures such as auctions, multiple communication facilities can be used simultaneously without restriction in unlicensed bands as long as they comply with a certain level of adjacent band protection regulations. Consequently, when unlicensed bands are used for cellular communication services, it is difficult to guarantee the same level of communication quality as provided in licensed bands, and interference issues may arise with existing wireless communication devices (e.g., wireless LAN devices) utilizing unlicensed bands.

[0005] Therefore, for LTE technology to establish itself in unlicensed bands, research on coexistence methods with existing unlicensed band devices and methods for efficiently sharing wireless channels must be conducted prior tohand. In other words, a robust coexistence mechanism (RCM) must be developed to ensure that devices using LTE technology in unlicensed bands do not affect existing unlicensed band devices. The problem to be solved

[0006] The object of the present invention is to provide a method for efficiently transmitting a signal in a wireless communication system, particularly in a cellular wireless communication system, and an apparatus for doing so. Additionally, another object of the present invention is to provide a method for efficiently transmitting a signal in a specific frequency band (e.g., an unlicensed band) and an apparatus for doing so.

[0007] The technical problems to be solved by the present invention are not limited to the above technical problems, and other technical problems not mentioned will be clearly understood by those skilled in the art to which the present invention belongs from the description below. means of solving the problem

[0008] According to an embodiment of the present invention, the following wireless communication device and wireless communication method are provided.

[0009] First, according to an embodiment of the present invention, a wireless communication device is provided that includes a communication module; and a processor, wherein the processor acquires a common backoff counter for a set of carriers to be used to transmit data, wherein the set of carriers includes at least one component carrier, and performs backoff of each component carrier using the acquired common backoff counter, and simultaneously transmits data through at least one component carrier for which backoff has been completed.

[0010] In addition, according to an embodiment of the present invention, a data communication method using multiple carriers is provided, comprising the steps of: acquiring a common backoff counter for a set of carriers to transmit data; wherein the set of carriers includes at least one component carrier; performing backoff of each component carrier using the acquired common backoff counter; and simultaneously transmitting data through at least one component carrier for which backoff has been completed.

[0011] A self-differential is performed during the backoff of at least one component carrier, which does not arbitrarily reduce the backoff counter.

[0012] The above self-differential is performed when the remaining backoff counter value of the corresponding component carrier is greater than 0.

[0013] Additional CCA is performed during a pre-set dipper period on the first component carrier after the backoff is completed, and if the first component carrier is idle during the dipper period, data is transmitted through the first component carrier.

[0014] When data is not transmitted through the first component carrier during the simultaneous transmission of the above data, the data is transmitted after an additional CCA during the dipper period.

[0015] The above-mentioned dipper section consists of at least one slot.

[0016] A competition window value is independently set for each component carrier of the above carrier set, a backoff counter is obtained within the largest competition window value among the competition window values ​​of all component carriers of the above carrier set, and the backoff counter obtained within the largest competition window value is used as the common backoff counter.

[0017] A single competition window value is set for all component carriers of the above carrier set, and a backoff counter obtained within the single competition window is used as the common backoff counter.

[0018] The energy detection threshold for the backoff is determined based on at least one of the total bandwidth of the data to be transmitted simultaneously and the total transmission power.

[0019] The lower the total transmission power value relative to the total bandwidth, the higher the energy detection threshold is set. Effects of the invention

[0020] According to an embodiment of the present invention, a method for efficiently transmitting a signal in a wireless communication system, particularly in a cellular wireless communication system, and an apparatus for the same are provided. Additionally, a method for efficiently transmitting a signal in a specific frequency band (e.g., an unlicensed band) and an apparatus for the same are provided.

[0021] According to an embodiment of the present invention, data transmission can be performed through multi-carrier transmission. In this case, the base station can efficiently utilize time and frequency resources associated with multi-carrier transmission and reduce data transmission delay.

[0022] The effects obtainable from the present invention are not limited to those mentioned above, and other unmentioned effects will be clearly understood by those skilled in the art from the description below. Brief explanation of the drawing

[0023] Figure 1 is a diagram illustrating physical channels used in 3GPP (3rd Generation Partnership Project) systems and a general signal transmission method using them. Figure 2 shows an example of a radio frame structure used in a wireless communication system. Figure 3 shows an example of a downlink (DL) / uplink (UL) slot structure in a wireless communication system. Figure 4 illustrates the structure of a downlink subframe. Figure 5 illustrates the structure of an uplink subframe. Figure 6 is a diagram illustrating single-carrier communication and multi-carrier communication. Figure 7 illustrates an example where a cross-carrier scheduling technique is applied. Figure 8 illustrates the transmission of a Discovery Reference Signal (DRS). FIGS. 9 to 11 illustrate the structure of a reference signal used as a DRS. Figure 12 illustrates a Licensed Assisted Access (LAA) service environment. Figure 13 illustrates a deployment scenario of a terminal and a base station in an LAA service environment. Figure 14 illustrates a conventional communication method operating in an unlicensed band. Figures 15 and 16 illustrate the Listen-Before-Talk (LBT) process for DL ​​transmission. Figures 17 and 18 illustrate an LBT-based data transmission method over multiple carriers. FIG. 19 is a flowchart illustrating an example of a base station performing self-deferral. FIG. 20 shows an example in which a base station determines whether to perform self-deferral according to the method of FIG. 19. FIGS. 21 and 22 illustrate embodiments of the present invention that protect a carrier on which self-differential is performed with a reserved signal. FIG. 23 shows an example of a base station canceling a self-deferral. FIGS. 24 to 26 illustrate additional embodiments of the present invention in which a base station determines whether self-deferral is continued. FIG. 27 illustrates a self-differential execution method according to another embodiment of the present invention. FIG. 28 illustrates a self-differential execution method according to another embodiment of the present invention. FIGS. 29 and FIGS. 30 illustrate embodiments of the present invention for setting an energy detection threshold when performing LBT for multi-carrier transmission. FIG. 31 illustrates the configuration of a terminal and a base station according to one embodiment of the present invention. Specific details for implementing the invention

[0024] The terms used in this specification have been selected to be as widely used as possible, taking into account their functions in the present invention; however, these may vary depending on the intent, convention, or emergence of new technologies of those skilled in the art. In addition, in certain cases, terms have been arbitrarily selected by the applicant, and in such cases, their meanings will be described in the relevant description of the invention. Therefore, it should be noted that the terms used in this specification should be interpreted based on their actual meanings and the overall content of this specification, rather than merely their names.

[0025] Throughout the specification, when a configuration is described as being "connected" to another configuration, this includes not only cases where they are "directly connected," but also cases where they are "electrically connected" with other components interposed between them. Furthermore, when a configuration is described as "including" a specific component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components. In addition, the limitation "greater than or equal to" or "less than or equal to" based on a specific threshold value may be appropriately replaced with "greater than" or "less than," respectively, depending on the embodiment.

[0026] The following technologies can be used in various wireless access systems such as CDMA (code division multiple access), FDMA (frequency division multiple access), TDMA (time division multiple access), OFDMA (orthogonal frequency division multiple access), and SC-FDMA (single carrier frequency division multiple access). CDMA can be implemented using radio technologies such as UTRA (Universal Terrestrial Radio Access) or CDMA2000. TDMA can be implemented using radio technologies such as GSM (Global System for Mobile Communications), GPRS (General Packet Radio Service), and EDGE (Enhanced Data Rates for GSM Evolution). OFDMA can be implemented using radio technologies such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, and E-UTRA (Evolved UTRA). UTRA is part of the UMTS (Universal Mobile Telecommunications System). 3GPP (3rd Generation Partnership Project) LTE (long term evolution) is part of E-UMTS (Evolved UMTS) using E-UTRA, and LTE-A (Advanced) is an evolved version of 3GPP LTE. For clarity of explanation, the description focuses on 3GPP LTE / LTE-A, but the technical concept of the present invention is not limited thereto.

[0027] Figure 1 illustrates physical channels used in a 3GPP system and a general signal transmission method using them. A terminal receives information from a base station via a downlink (DL) and transmits information to the base station via an uplink (UL). The information transmitted and received by the base station and the terminal includes data and various control information, and various physical channels exist depending on the type and purpose of the information being transmitted and received.

[0028] When the terminal is powered on or enters a new cell, it performs initial cell search operations, such as synchronizing with the base station (S101). To do this, the terminal receives a Primary Synchronization Channel (P-SCH) and a Secondary Synchronization Channel (S-SCH) from the base station to synchronize with the base station and obtain information such as a cell ID. After that, the terminal receives a Physical Broadcast Channel from the base station to obtain broadcast information within the cell. During the initial cell search phase, the terminal receives a Downlink Reference Signal (DL RS) to check the status of the downlink channel.

[0029] A terminal that has completed initial cell search can obtain more specific system information by receiving a Physical Downlink Control Channel (PDCCH) and a Physical Downlink Shared Channel (PDSCH) according to the information carried on the PDCCH (S102).

[0030] When connecting to a base station for the first time or when there are no wireless resources available for signal transmission, the terminal may perform a Random Access Procedure (RACH) with respect to the base station (S103~S106). First, the terminal transmits a preamble through a Physical Random Access Channel (PRACH) (S103), and may receive a response message for the preamble through a PDCCH and a corresponding PDSCH (S104). When a valid Random Access response message is received by the terminal, the terminal transmits data including its identifier, etc., to the base station using an uplink grant (S105). Next, the terminal waits for the reception of a PDCCH as a directive from the base station to resolve collisions. When the terminal receives a PDCCH with its identifier (S106), the Random Access Procedure is terminated.

[0031] Subsequently, the terminal may perform PDCCH / PDSCH reception (S107) and Physical Uplink Shared Channel (PUSCH) / Physical Uplink Control Channel (PUCCH) transmission (S108) as a standard procedure. The terminal receives Downlink Control Information (DCI) via PDCCH. DCI contains control information, such as resource allocation information for the terminal, and the format varies depending on the purpose of use. The control information transmitted by the terminal to the base station is referred to as Uplink Control Information (UCI). UCI includes ACK / NACK (Acknowledgement / Negative Acknowledgement), CQI (Channel Quality Indicator), PMI (Precoding Matrix Index), RI (Rank Indicator), etc. UCI can be transmitted via PUSCH and / or PUCCH.

[0032] Figure 2 shows an example of a wireless frame structure used in a wireless communication system. Figure 2(a) shows a frame structure for Frequency Division Duplex (FDD), and Figure 2(b) shows a frame structure for Time Division Duplex (TDD).

[0033] Referring to FIG. 2, a wireless frame has a length of 10 ms (307200 Ts) and can be composed of 10 subframes (SF). Ts represents the sampling time and is expressed as Ts = 1 / (2048 * 15 kHz). Each subframe has a length of 1 ms and can be composed of 2 slots. Each slot has a length of 0.5 ms. Within a single wireless frame, 20 slots can be sequentially numbered from 0 to 19. Each slot has a length of 0.5 ms. The time required to transmit a single subframe is defined as the Transmission Time Interval (TTI). Time resources can be distinguished by the wireless frame number / index, subframe number / index (#0–#9), and slot number / index (#0–#19).

[0034] Radio frames can be configured differently depending on the duplex mode. In FDD mode, downlink and uplink transmissions are distinguished by frequency, and a radio frame contains only one of either a downlink subframe or an uplink subframe for a specific frequency band. In TDD mode, downlink and uplink transmissions are distinguished by time, and a radio frame contains both a downlink subframe and an uplink subframe for a specific frequency band. TDD radio frames additionally include special subframes for downlink and uplink switching. The special subframe consists of a Downlink Pilot Time Slot (DwPTS), a Guard Period (GP), and an Uplink Pilot Time Slot (UpPTS).

[0035] Figure 3 shows the structure of the down / up link slot.

[0036] Referring to FIG. 3, a slot contains multiple Orthogonal Frequency Divisional Multiplexing (OFDM) symbols in the time domain and multiple Resource Blocks (RBs) in the frequency domain. An OFDM symbol also refers to a single symbol interval. Depending on the multiple access method, OFDM symbols may be referred to as OFDMA symbols, Single Carrier Frequency Division Multiple Access (SC-FDMA) symbols, etc. The number of OFDM symbols included in a single slot can vary depending on the length of the Cyclic Prefix (CP). For example, in the case of a normal CP, a single slot contains 7 OFDM symbols, whereas in the case of an extended CP, a single slot contains 6 OFDM symbols. The RB is N in the time domain. DL / UL symb 7 consecutive OFDM symbols and N in the frequency domain RB sc It is defined as 12 consecutive subcarriers. A resource consisting of one OFDM symbol and one subcarrier is called a Resource Element (RE) or tone. One RB is N DL / UL symb *N RB sc It consists of several resource elements.

[0037] The resources of the slot are N DL / UL RB *N RB sc N subcarriers and N DL / UL symb It can be represented as a resource grid consisting of OFDM symbols. Each RE within the resource grid is uniquely defined by an index pair (k, 1) per slot. k ranges from 0 to N in the frequency domain. DL / UL RB *NRB sc It is an index assigned up to -1, and l is from 0 to N in the time domain. DL / UL symb It is an index assigned up to -1. Here, N DL RB represents the number of resource blocks (RB) in the downlink slot, and N UL RB represents the number of RBs in the UL slot. N DL RB and N UL RB It depends on the DL transmission bandwidth and UL transmission bandwidth, respectively. N DL symb represents the number of symbols within the downlink slot, and N UL symb indicates the number of symbols within the UL slot. N RB sc represents the number of subcarriers constituting a single RB. There is one resource grid per antenna port.

[0038] Figure 4 illustrates the structure of a downlink subframe.

[0039] Referring to FIG. 4, a subframe can be composed of 14 OFDM symbols. Depending on the subframe configuration, the first 1 to 3 (or 2 to 4) OFDM symbols are used as the control domain, and the remaining 13 to 11 (or 12 to 10) OFDM symbols are used as the data domain. R1 to R4 represent reference signals for antenna ports 0 to 3. Control channels assigned to the control domain include PCFICH (Physical Control Format Indicator Channel), PHICH (Physical Hybrid-ARQ Indicator Channel), PDCCH (Physical Downlink Control Channel), etc. Data channels assigned to the data domain include PDSCH, etc. When EPDCCH (Enhanced PDCCH) is configured, PDSCH and EPDCCH in the data domain are multiplexed using FDM (Frequency Division Multiplexing).

[0040] The PDCCH is the physical downlink control channel and is assigned to the first n OFDM symbols of a subframe. n is an integer greater than or equal to 1 (or 2) and is indicated by the PCFICH. The PDCCH informs each terminal or group of terminals of information related to resource allocation for the transport channels, the PCH (Paging Channel) and DL-SCH (Downlink-Shared Channel), as well as uplink scheduling grants and HARQ information. Data for the PCH and DL-SCH (i.e., transport blocks) is transmitted via the PDSCH. The base station and the terminal generally transmit and receive data, respectively, via the PDSCH, except for specific control information or specific service data.

[0041] Information regarding which terminal (one or more terminals) the PDSCH data is transmitted to, and how said terminals should receive and decode the PDSCH data, etc., is included in and transmitted in the PDCCH / EPDCCH. For example, it is assumed that the PDCCH / EPDCCH is CRC masked with an RNTI (Radio Network Temporary Identity) named "A," and that information regarding the data being transmitted is transmitted through a specific subframe using a radio resource named "B" (e.g., frequency location) and a DCI format named "C," i.e., transmission format information (e.g., transmission block size, modulation method, coding information, etc.). In this case, terminals within the cell monitor the PDCCH / EPDCCH using the RNTI information they possess, and if there is one or more terminals with the "A" RNTI, said terminals receive the PDCCH / EPDCCH and receive the PDSCH indicated by "B" and "C" through the information in the received PDCCH / EPDCCH.

[0042] Figure 5 illustrates the structure of an uplink subframe.

[0043] Referring to Fig. 5, a subframe can be divided into a control area and a data area in the frequency domain. PUCCH is assigned to the control area and carries UCI. PUSCH is assigned to the data area and carries user data.

[0044] PUCCH can be used to transmit the following control information.

[0045] - SR (Scheduling Request): Information used to request UL-SCH resources. It is transmitted using the OOK (On-Off Keying) method.

[0046] - HARQ-ACK: A response to a PDCCH and / or a downlink data packet (e.g., codeword) on a PDSCH. A codeword is an encoded form of a transmission block. HARQ-ACK indicates whether the PDCCH or PDSCH has been successfully received. HARQ-ACK responses include a positive ACK (simply ACK), a negative ACK (NACK), a DTX (Discontinuous Transmission), or a NACK / DTX. A DTX indicates that the terminal has missed the PDCCH (or SPS (Semi-persistent scheduling) PDSCH), and a NACK / DTX means a NACK or a DTX. HARQ-ACK is used interchangeably with HARQ-ACK / NACK and ACK / NACK.

[0047] - CSI (Channel State Information): This is feedback information regarding the downlink channel. MIMO (Multiple Input Multiple Output) related feedback information includes RI and PMI.

[0048] Table 1 shows the relationship between the PUCCH format and UCI.

[0049]

[0050] Carrier aggregation is described below. Carrier aggregation refers to a method of using multiple frequency blocks as one large logical frequency band in order for a wireless communication system to use a wider frequency band. When the entire system band is expanded through carrier aggregation, the frequency band used for communication with each terminal is defined in units of Component Carriers (CC).

[0051] FIG. 6 is a diagram illustrating single-carrier communication and multi-carrier communication. FIG. 6(a) illustrates the subframe structure of a single carrier, and FIG. 6(b) illustrates the subframe structure of a carrier-aggregated multi-carrier.

[0052] Referring to FIG. 6(a), in a single-carrier system, the base station and the terminal perform data communication through a single DL band and a corresponding UL band. The DL / UL band is divided into multiple orthogonal subcarriers, and each frequency band operates on a single carrier frequency. In FDD, the DL / UL bands each operate on different carrier frequencies, while in TDD, the DL / UL bands operate on the same carrier frequency. The carrier frequency refers to the center frequency of the frequency band.

[0053] Referring to FIG. 6(b), carrier aggregation is distinguished from OFDM systems, which perform DL / UL communication by carrying a fundamental frequency band divided into multiple subcarriers onto a single carrier frequency, in that it performs DL / UL communication using multiple carrier frequencies. Referring to FIG. 6(b), three 20 MHz CCs can be aggregated in the UL and DL respectively to support a bandwidth of 60 MHz. The CCs can be adjacent or non-adjacent to each other in the frequency domain. For convenience, FIG. 6(b) illustrates a case where the bandwidths of the UL CCs and DL CCs are both identical and symmetrical, but the bandwidths of each CC can be determined independently. Additionally, asymmetric carrier aggregation is possible where the number of UL CCs and DL CCs are different. The DL / UL CC(s) are independently allocated / configured for each terminal, and the DL / UL CC(s) allocated / configured to a terminal are referred to as the terminal's serving UL / DL CC(s).

[0054] The base station may activate some or all of the terminal's serving CCs, or deactivate some of the CCs. When the base station assigns CC(s) to a terminal, at least one specific CC among the CC(s) configured for that terminal is not deactivated unless the CC assignment for the terminal is completely reconfigured or the terminal undergoes a handover. A specific CC that is always active is referred to as a PCC (Primary CC), and a CC that the base station can freely activate or deactivate is referred to as a SCC (Secondary CC). PCCs and SCCs may also be distinguished based on control information. For example, specific control information may be configured to be transmitted and received only through a specific CC; such a specific CC may be referred to as a PCC, and the remaining CC(s) may be referred to as SCC(s). PUCCH is transmitted only over the PCC.

[0055] 3GPP uses the concept of a cell to manage radio resources. A cell is defined as a combination of DL resources and UL resources, specifically a combination of a DL CC and a UL CC. A cell can consist of a DL resource alone or a combination of a DL resource and a UL resource. Where carrier aggregation is supported, the linkage between the carrier frequency of a DL resource (or DL ​​CC) and the carrier frequency of a UL resource (or 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) linkage. The carrier frequency refers to the center frequency of each cell or CC. The cell corresponding to a PCC is referred to as a PCell (Primary Cell), and the cell corresponding to an SCC is referred to as a SCell (Secondary Cell). In the downlink, the carrier corresponding to a PCell is a DL PCC, and in the uplink, the carrier corresponding to a PCell is a UL PCC. Similarly, the carrier corresponding to the SCell in the downlink is the DL SCC, and the carrier corresponding to the SCell in the uplink is the UL SCC. Depending on the terminal capability, the serving cell(s) may consist of one PCell and zero or more SCells. For a terminal in the RRC_CONNECTED state but where carrier aggregation is not configured or does not support carrier aggregation, there exists only one serving cell consisting solely of PCells.

[0056] FIG. 7 illustrates an example where cross-carrier scheduling is applied. When cross-carrier scheduling is configured, a control channel transmitted through the first CC can schedule a data channel transmitted through the first CC or the second CC using a Carrier Indicator Field (CIF). The CIF is included within the DCI. In other words, a scheduling cell is configured, and DL grants / UL grants transmitted in the PDCCH area of ​​the scheduling cell schedule the PDSCH / PUSCH of the scheduled cell. That is, a search area for multiple component carriers exists in the PDCCH area of ​​the scheduling cell. A PCell is basically a scheduling cell, and a specific SCell can be designated as a scheduling cell by an upper layer.

[0057] Figure 7 assumes that three DL CCs have been merged. Here, DL component carrier #0 is assumed to be a DL PCC (or PCell), and DL component carriers #1 and #2 are assumed to be DL SCCs (or SCell). Additionally, it is assumed that the DL PCC is configured as a PDCCH monitoring CC. When CIF is disabled, each DL CC can transmit only the PDCCH that schedules its own PDSCH without CIF according to LTE PDCCH rules (non-cross-carrier scheduling, self-carrier scheduling). On the other hand, when CIF is enabled by terminal-specific (or terminal-group-specific or cell-specific) upper layer signaling, a specific CC (e.g., DL PCC) can use CIF to transmit not only the PDCCH that schedules the PDSCH of DL CC A, but also the PDCCH that schedules the PDSCH of other CCs (cross-carrier scheduling). On the other hand, the PDCCH is not transmitted from other DL CCs.

[0058] Hereinafter, DRS transmission in the licensed band will be described with reference to FIGS. 8 to 11. FIG. 8 illustrates DRS transmission, and FIGS. 9 to 11 illustrate the structure of a reference signal used as DRS. For convenience, DRS in the licensed band is referred to as Rel-12 DRS. DRS supports small cell on / off, and a SCell that is not activated for any terminal can be turned off except for periodic DRS transmission. Additionally, based on DRS, the terminal can perform cell identification information acquisition, RRM (Radio Resource Management) measurement, and downlink synchronization acquisition.

[0059] Referring to FIG. 8, the Discovery Measurement Timing Configuration (DMTC) represents the time window in which the terminal expects to receive DRS. The DMTC is fixed at 6ms. The DMTC period is the transmission period of the DMTC and can be 40ms, 80ms, or 160ms. The location of the DMTC is determined by the DMTC transmission period and the DMTC offset (in subframe units), and this information is conveyed to the terminal via upper-layer signaling (e.g., RRC signaling). DRS transmission occurs at a DRS occasion within the DMTC. A DRS occasion has a transmission period of 40ms, 80ms, or 160ms, and the terminal can assume that there is one DRS occasion per DMTC period. A DRS occasion consists of 1 to 5 consecutive subframes in an FDD radio frame and 2 to 5 consecutive subframes in a TDD radio frame. The length of the DRS opportunity is conveyed to the terminal via upper-layer signaling (e.g., RRC signaling). The terminal may assume the presence of DRS within a downlink subframe in a DRS opportunity. Although a DRS opportunity may exist anywhere within the DMTC, the terminal expects the transmission interval of DRSs transmitted from the cell to be fixed (i.e., 40ms, 80ms, or 160ms). In other words, the location of a DRS opportunity within the DMTC is fixed per cell. The DRS is configured as follows.

[0060] - Cell-specific Reference Signal (CRS) of antenna port 0 (see Fig. 9): It exists within every downlink subframe within the DRS opportunity, and within the DwPTS of every special subframe. The CRS is transmitted across the entire band of the subframe.

[0061] - PSS (Primary Synchronization Signal) (see Fig. 10): In the case of an FDD radio frame, it is located in the first subframe within the DRS opportunity, or in the case of a TDD radio frame, in the second subframe within the DRS opportunity. The PSS is transmitted at the 7th (or 6th) OFMDA symbol of the subframe and is mapped to 6 RBs (= 72 subcarriers) close to the center frequency.

[0062] - SSS (Secondary Synchronization Signal) (see Fig. 10): It exists within the first subframe of the DRS opportunity. The SSS is transmitted at the 6th (or 5th) OFMDA symbol of the subframe and is mapped to 6 RBs (= 72 subcarriers) close to the center frequency.

[0063] - Non-zero-power CSI (Channel State Information)-RS (see Fig. 11): Exists within zero or more subframes within the DRS opportunity. The location of the non-zero-power CSI-RS varies depending on the number of CSI-RS ports and upper-layer configuration information.

[0064] FIG. 8 illustrates a case where the DRS reception time for each frequency is set as a separate DMTC from the perspective of the terminal. Referring to FIG. 8, for frequency F1, a DRS opportunity of 2ms in length is transmitted every 40ms, for frequency F2, a DRS opportunity of 3ms in length is transmitted every 80ms, and for frequency F3, a DRS opportunity of 4ms in length is transmitted every 80ms. The terminal can determine the starting position of the DRS opportunity from the DMTC from a subframe containing the SSS. Here, frequencies F1 to F3 can each be replaced with a corresponding cell.

[0065] Example: DRS transmission method in unlicensed band

[0066] Figure 12 illustrates a Licensed Assisted Access (LAA) service environment.

[0067] Referring to FIG. 12, a service environment incorporating LTE technology (11) in the existing licensed band and LTE technology (12) in the unlicensed band, such as LTE-U (LTE-Unlicensed) or LAA, which has recently been actively discussed, can be provided to the user. For example, in an LAA environment, LTE technology (11) in the licensed band and LTE technology (12) in the unlicensed band can be integrated using technologies such as carrier aggregation, which can contribute to expanding network capacity. In addition, in an asymmetric traffic structure where downlink data is more abundant than uplink data, LAA can provide optimized LTE services tailored to various requirements or environments. For convenience, LTE technology in the licensed band is referred to as LTE-L (LTE-Licensed), and LTE technology in the unlicensed band is referred to as LTE-U (LTE-Unlicensed) or LAA.

[0068] Figure 13 illustrates a deployment scenario for terminals and base stations in an LAA service environment. The frequency band targeted by the LAA service environment does not have a long wireless communication reach due to its high frequency characteristics. Considering this, the deployment scenario for terminals and base stations in an environment where existing LTE-L services and LAA services coexist can be an overlay model or a co-located model.

[0069] In the overlay model, the macro base station performs wireless communication with X terminals and X' terminals within the macro area (32) using a licensed band carrier and can be connected to multiple RRHs (Radio Remote Heads) via an X2 interface. Each RRH can perform wireless communication with X terminals or X' terminals within a certain area (31) using an unlicensed band carrier. Although the frequency bands of the macro base station and the RRHs are different and thus there is no mutual interference, fast data exchange must be performed between the macro base station and the RRH via the X2 interface in order to use LAA services as auxiliary downlink channels for LTE-L services through carrier aggregation.

[0070] In the co-located model, the pico / femto base station can perform wireless communication with the Y terminal by simultaneously using a licensed band carrier and an unlicensed band carrier. However, the pico / femto base station may be limited to using both LTE-L service and LAA service together during downlink transmission. The coverage (33) of the LTE-L service and the coverage (34) of the LAA service may differ depending on the frequency band, transmission power, etc.

[0071] When LTE communication is performed in an unlicensed band, existing equipment communicating in that unlicensed band (e.g., wireless LAN (Wi-Fi) equipment) cannot demodulate LAA messages or data. Therefore, existing equipment may treat LAA messages or data as a form of energy and perform interference avoidance operations using energy detection (or detection) techniques. That is, if the energy corresponding to the LAA message or data is less than -62 dBm or a specific ED (Energy Detection) threshold, wireless LAN equipment can ignore the message or data and continue communication. As a result, terminals communicating via LTE in an unlicensed band may frequently experience interference from wireless LAN equipment.

[0072] Therefore, to effectively implement LAA technology / services, it is necessary to allocate or reserve specific frequency bands for a specific period. However, there is a problem in that efficient LAA services are difficult because peripheral equipment communicating via unlicensed bands attempts to connect based on energy detection techniques. Consequently, for LAA technology to become established, research on coexistence methods with existing unlicensed band devices and methods for efficiently sharing wireless channels must be conducted first. In other words, a robust coexistence mechanism must be developed that ensures LAA devices do not affect existing unlicensed band devices.

[0073] Figure 14 illustrates a conventional communication method (e.g., wireless LAN) operating in an unlicensed band. Since most devices operating in an unlicensed band operate based on Listen-Before-Talk (LBT), they perform Clear Channel Assessment (CCA) to sense the channel before data transmission.

[0074] Referring to FIG. 14, a wireless LAN device (e.g., AP, STA) performs carrier sensing before transmitting data to check whether the channel is busy. If a wireless signal of a certain strength or higher is detected on the channel intended for data transmission, the channel is determined to be busy, and the wireless LAN device delays access to the channel. This process is called Clear Channel Evaluation, and the signal level determining whether a signal is detected is called the CCA threshold. Meanwhile, if no wireless signal is detected on the channel, or if a wireless signal of a strength lower than the CCA threshold is detected, the channel is determined to be idle.

[0075] When a channel is determined to be idle, a terminal with data to transmit performs a backoff procedure after a defer period (e.g., AIFS (Arbitration InterFrame Space), PIFS (PCF IFS), etc.). The defer period refers to the minimum time a terminal must wait after the channel becomes idle. The backoff procedure causes the terminal to wait for an arbitrary amount of time after the defer period. For example, a terminal waits within a contention window (CW) while the channel is idle, decreasing the slot time allocated to the terminal by a random number, and once the slot time is exhausted, the terminal may attempt to access the channel.

[0076] When the channel is successfully accessed, the terminal can transmit data through the channel. If data transmission is successful, the CW size (CWS) is reset to its initial value (CWmin). Conversely, if data transmission fails, the CWS is doubled. Accordingly, the terminal is assigned a new random number within twice the range of the previous random number range and performs a backoff procedure in the next CW. In wireless LANs, only ACK is defined as reception acknowledgment information for data transmission. Therefore, if an ACK is received for data transmission, the CWS is reset to its initial value, and if no feedback information is received for data transmission, the CWS is doubled.

[0077] As mentioned above, since communication in the unlicensed band generally operates based on LBT, LTE is also considering LBT in LAA to coexist with existing devices. Specifically, channel access methods in the unlicensed band in LTE can be classified into the following four categories depending on the presence or absence of LBT and the method of application.

[0078] ● Category 1: No LBT

[0079] - The LBT procedure by the Tx entity is not performed.

[0080] ● Category 2: LBT without random back-off

[0081] - A time interval is determined during which the channel must be sensed as idle before the Tx entity transmits on the channel. Random back-off is not performed.

[0082] ● Category 3: LBT with random back-off with a CW of fixed size

[0083] - This is an LBT method that performs random back-off using a fixed-size CW. The Tx entity has a random number N within the CW, and the CW size is defined by the minimum and maximum values ​​of N. The CW size is fixed. The random number N is used to determine the time interval during which the channel must be sensed as idle before the Tx entity transmits on the channel.

[0084] ● Category 4: LBT with random back-off with a CW of variable size

[0085] - This is an LBT method that performs random backoff using a variable-size CW. The Tx entity holds a random number N within the CW, and the CW size is defined by the minimum and maximum values ​​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 during which the channel must be sensed as idle before the Tx entity transmits on the channel.

[0086] FIGS. 15 and 16 illustrate a DL transmission process based on category 4 LBT. Category 4 LBT can be used to ensure fair channel access with Wi-Fi. Referring to FIGS. 15 and 16, the LBT process includes ICCA (Initial CCA) and ECCA (Extended CCA). In ICCA, random back-off is not performed, while in ECCA, random back-off is performed using a variable-size CW. ICCA is applied when the channel is idle at the time signal transmission is required, and ECCA is applied when the channel is in use or there was a DL transmission immediately prior to the time signal transmission is required. That is, ICCA determines whether the channel is idle, and data transmission is performed after the ICCA period. If data transmission is not possible due to interference signals being detected, a random back-off counter is set, and the time for data transmission can be obtained through the defer period + back-off counter.

[0087] Referring to Fig. 15, the signal transmission process can be performed as follows.

[0088] Initial CCA

[0089] - S202: The base station checks that the channel is idle.

[0090] - S204: The base station checks if signal transmission is required. If signal transmission is not required, it returns to S202; if signal transmission is required, it proceeds to S206.

[0091] - S206: The base station is in the ICCA differential period (B CCAIt checks whether the channel is idle during the period. The ICCA diff period is configurable. As an example of implementation, the ICCA diff period can consist of a 16 µs interval and n consecutive CCA slots. Here, n is a positive integer, and one CCA slot interval can be 9 µs. The number of CCA slots can be set differently depending on the QoS class. The ICCA diff period can be set to an appropriate value considering the Wi-Fi diff period (e.g., DIFS, AIFS). For example, the ICCA diff period can be 34 µs. If the channel is idle during the ICCA diff period, the base station can perform the signal transmission process (S208). If the channel is determined to be in use during the ICCA diff period, proceed to S212 (ECCA).

[0092] - S208: The base station may perform the signal transmission process. If there is no signal transmission, proceed to S202 (ICCA), and if there is a signal transmission, proceed to S210. Even if S208 is performed because the back-off counter N reaches 0 in S218, if there is no signal transmission, proceed to S202 (ICCA), and if there is a signal transmission, proceed to S210.

[0093] - S210: If no additional signal transmission is required, proceed to S202 (ICCA), and if additional signal transmission is required, proceed to S212 (ECCA).

[0094] Extended CCA

[0095] - S212: The base station generates a random number N within the CW. N is used as a counter during the back-off process and is generated from [0, q-1]. The CW consists of q ECCA slots, and the ECCA slot size can be 9 µs or 10 µs. The CW size (CWS) is defined as q and can be varied in S214. Afterwards, the base station proceeds to S216.

[0096] - S214: The base station can update the CWS. The CWS q can be updated with a value between X and Y. The values ​​of X and Y are configurable parameters. The CWS update / adjustment can be performed every time N is generated (dynamic back-off) or semi-statically at regular intervals (semi-static back-off). The CWS can be updated / adjusted based on exponential back-off or binary back-off. That is, the CWS can be updated / adjusted in the form of powers of 2 or multiples of 2. In relation to PDSCH transmission, the CWS can be updated / adjusted based on terminal feedback / reports (e.g., HARQ ACK / NACK) or based on base station sensing.

[0097] - S216: The base station checks if the channel is idle during the ECCA deCCA period. The ECCA deCCA period is configurable. As an example of implementation, the ECCA deCCA period may consist of a 16 µs interval and n consecutive CCA slots. Here, n is a positive integer, and one CCA slot interval may be 9 µs. The number of CCA slots may be set differently depending on the QoS class. The ECCA deCCA period may be set to an appropriate value considering the Wi-Fi deCCA period (e.g., DIFS, AIFS). For example, the ECCA deCCA period may be 34 µs. If the channel is idle during the ECCA deCCA period, the base station proceeds to S218. If the channel is determined to be in use during the ECCA deCCA period, the base station repeats S216.

[0098] - S218: The base station checks if N is 0. If N is 0, the base station can perform the signal transmission process (S208). In this case (i.e., N=0), the base station does not perform transmission immediately, but can continue the ECCA process by performing a CCA check for at least one slot. If N is not 0 (i.e., N>0), proceed to S220.

[0099] - S220: The base station senses the channel during one ECCA slot interval (T). The ECCA slot size is 9 µs or 10 µs, and the actual sensing time may be at least 4 µs.

[0100] - S222: If the channel is determined to be idle, proceed to S224. If the channel is determined to be in use, return to S216. In other words, one ECCA diff period is applied again after the channel is idle, and N is not counted down during the ECCA diff period.

[0101] - S224: Decrease N by 1 (ECCA countdown).

[0102] FIG. 16 is substantially identical or similar to the transmission process of FIG. 15, with differences depending on the implementation method. Therefore, for details, refer to FIG. 15.

[0103] Initial CCA

[0104] - S302: The base station checks if signal transmission is required. If signal transmission is not required, S302 is repeated; if signal transmission is required, the process proceeds to S304.

[0105] - S304: The base station checks if the slot is idle. If the slot is idle, proceed to S306, and if the slot is in use, proceed to S312 (ECCA). The slot may correspond to the CCA slot in FIG. 15.

[0106] - S306: The base station checks whether the channel is idle during the dipping period (D). D may correspond to the ICCA dipping period in FIG. 15. If the channel is idle during the dipping period, the base station can perform the signal transmission process (S308). If the channel is determined to be in use during the dipping period, proceed to S304.

[0107] - S308: The base station can perform the signal transmission process if necessary.

[0108] - S310: If there is no signal transmission, proceed to S302 (ICCA); if there is a signal transmission, proceed to S312 (ECCA). Even if S308 is executed because the back-off counter N reaches 0 in S318, if there is no signal transmission, proceed to S302 (ICCA); if there is a signal transmission, proceed to S312 (ECCA).

[0109] Extended CCA

[0110] - S312: The base station generates a random number N within the CW. N is used as a counter during the back-off process and is generated from [0, q-1]. The CW size (CWS) is defined as q and can be varied in S314. Afterwards, the base station proceeds to S316.

[0111] - S314: The base station may update the CWS. The CWS q may be updated with a value between X and Y. The values ​​of X and Y are configurable parameters. The CWS update / adjustment may be performed every time N is generated (dynamic back-off) or semi-statically at regular intervals (semi-static back-off). The CWS may be updated / adjusted based on exponential back-off or binary back-off. That is, the CWS may be updated / adjusted in the form of powers of 2 or multiples of 2. In relation to PDSCH transmission, the CWS may be updated / adjusted based on terminal feedback / reports (e.g., HARQ ACK / NACK) or based on base station sensing.

[0112] - S316: The base station checks whether the channel is idle during the dipping period (D). D may correspond to the ECCA dipping period of FIG. 15. D may be the same in S306 and S316. If the channel is idle during the dipping period, the base station proceeds to S318. If the channel is determined to be in use during the dipping period, the base station repeats S316.

[0113] - S318: The base station checks if N is 0. If N is 0, the base station can perform the signal transmission process (S308). In this case (N=0), the base station does not perform transmission immediately, but can continue the ECCA process by performing a CCA check for at least one slot. If N is not 0 (i.e., N>0), proceed to S320.

[0114] - S320: The base station chooses one of the following actions: decreasing N by 1 (ECCA countdown) or not decreasing N (self-deferral). The self-deferral action may be performed according to the implementation / selection of the base station. During self-deferral, the base station does not perform sensing for energy detection and does not perform the ECCA countdown.

[0115] - S322: The base station may choose between an operation that does not perform sensing for energy detection and an energy detection operation. If sensing for energy detection is not performed, proceed to S324. If the energy detection operation is performed, proceed to S324 if the energy level is below the energy detection threshold (i.e., idle). If the energy level exceeds the energy detection threshold (i.e., busy), return to S316. In other words, a single diff period is applied again after the channel is idle, and N is not counted down during the diff period.

[0116] - S324: Proceed with S318.

[0117] FIGS. 17 and 18 illustrate an LBT-based data transmission method over multiple carriers. In the embodiments of FIGS. 17 and 18, multiple carriers are used that include at least one of a first component carrier (hereinafter, the first CC), a second component carrier (hereinafter, the second CC), a third component carrier (hereinafter, the third CC), and a fourth component carrier (hereinafter, the fourth CC). According to one embodiment of the present invention, the multiple carriers may be composed of contiguous component carriers. However, according to another embodiment of the present invention, the multiple carriers may be composed of non-contiguous component carriers. As described above, in the embodiments of the present invention, the data transmitted by the base station through each component carrier includes at least one of PDCCH and PDSCH. Additionally, the component carrier may represent a channel of 20 MHz or a subchannel of less. According to one embodiment of the present invention, the multiple carriers on which data transmission is performed may include at least one licensed band component carrier and at least one unlicensed band component carrier.

[0118] FIG. 17 illustrates an LBT-based multi-carrier data transmission method according to an embodiment of the present invention. In the embodiment of FIG. 17, a base station attempts to transmit data through multiple carriers including a first CC, a second CC, and a fourth CC. The base station may perform independent backoff for each 20 MHz carrier. The base station performs data transmission based on the backoff procedure performed independently for each carrier. In the embodiment of FIG. 17, it is assumed that the same backoff counter is assigned for the backoff procedure of each carrier. Additionally, in FIG. 17, B1 indicates the time when backoff is completed without interference, and B2 indicates the time when backoff is completed delayed due to interference during backoff.

[0119] First, referring to FIG. 17(a), no interference occurred in all carriers where backoff was performed. Therefore, backoff of the first CC, second CC, and fourth CC is completed simultaneously at B1. At time B1, the base station transmits data simultaneously through the first CC, second CC, and fourth CC.

[0120] Referring to FIG. 17(b), interference occurred in the first CC and the fourth CC during the backoff of each carrier. Therefore, the backoff of the second CC is completed at B1, but the backoff of the first CC and the fourth CC is not completed at B1. According to the embodiment of FIG. 17(b), the base station can transmit data only through the carrier for which backoff was completed without interference. That is, the base station can transmit data to B1 only through the second CC for which no interference occurred. Meanwhile, the base station determines that the backoff of the first CC and the fourth CC has failed and can resume the backoff of the first CC and the fourth CC at the next transmission opportunity.

[0121] Next, referring to FIG. 17(c), interference occurred in the 4th CC during the backoff of each carrier. Therefore, the backoff of the 1st CC and 2nd CC is completed at B1, but the backoff of the 4th CC is not completed at B1. The completion time of the backoff of the 4th CC is delayed to B2. According to the embodiment of FIG. 17(c), the base station may delay data transmission until the backoff of some or all of the carriers where interference occurred is completed. That is, the base station may transmit data simultaneously at the time when the backoff of some or all of the carriers where interference occurred is completed. To this end, the base station performs additional backoff in the 1st CC and 2nd CC until B2, when the backoff of the 4th CC is completed. At time B2, the base station transmits data simultaneously through the 1st CC, 2nd CC, and 4th CC. In this way, by performing additional backoff, the base station can transmit data over a wider bandwidth.

[0122] FIG. 18 illustrates a method for synchronizing LBT-based multi-carrier data transmission using self-deferral. In the embodiment of FIG. 18, a base station attempts to transmit data through multiple carriers including a first CC, a second CC, a third CC, and a fourth CC. The base station can perform independent backoff for each 20 MHz carrier.

[0123] According to an embodiment of the present invention, a base station (hereinafter, a terminal is also included) may perform self-differential for multi-carrier data transmission. Self-differential refers to an operation in which the base station does not arbitrarily decrease the backoff counter while performing backoff. That is, even if the carrier is in an idle state, the base station may not arbitrarily decrease the backoff counter. The base station may synchronize the completion time of the multi-carrier backoff by delaying the backoff of at least one component carrier during the multi-carrier CCA process. The base station may transmit data simultaneously through the multi-carriers after the backoff of the multi-carriers is completed and a preset time has passed. In FIG. 18, B3 represents the completion time of the multi-carrier backoff synchronized based on self-differential, and B4 represents the time of the base station's synchronized multi-carrier transmission. According to one embodiment, B4 represents a time after a preset dividing interval (P_d) from B3. According to another embodiment, B4 may be set to the same time as B3.

[0124] First, referring to FIG. 18(a), interference occurred in the third CC and the fourth CC during the backoff process for the first to fourth CCs. Therefore, if a standard backoff procedure is performed, the backoff of the third CC and the fourth CC may not be completed at the time when the backoff of the first CC and the second CC is completed. The base station performs self-differential to synchronize the completion time of the backoff of the multiple carriers. According to one embodiment, the duration of the self-differential may be determined within a preset time range. Various embodiments for setting the self-differential duration will be described later. FIG. 18(a) illustrates an embodiment in which self-differential is performed on all component carriers constituting the multiple carriers. However, the specific method of performing self-differential is not limited thereto and can be extended to various embodiments described later. In this way, by performing self-differential on at least one component carrier, the completion time of the backoff of the multiple carriers can be synchronized to B3.

[0125] When the multi-carrier backoff procedure is completed, the base station may perform additional CCA during a pre-configured diff interval (P_d). In an embodiment of the present invention, the diff interval (P_d) may be defined in various ways. The diff interval (P_d) consists of at least one slot. According to one embodiment, the diff interval (P_d) may be configured to be the same as the aforementioned ICCA diff period. That is, the diff interval (P_d) may consist of a period of 16 μs and n consecutive slots. Here, n is a positive integer and one slot has a length of 9 μs. n may be configured based on the QoS class of the data to be transmitted.

[0126] The base station performs multi-carrier data transmission at B4, which is after the dividing period (P_d) from B3, the time when the synchronized multi-carrier backoff is completed. At this time, data can be transmitted only through component carriers that are idle during the dividing period (P_d) after the backoff is completed. In the embodiment of FIG. 18(a), the backoff of the component carriers that experienced interference, namely the third CC and the fourth CC, is completed before B3, and the first CC to the fourth CC are determined to be idle during the dividing period (P_d). Therefore, the base station transmits data simultaneously through the first CC to the fourth CC. In this way, by performing self-diverral, the base station can transmit data over a wider bandwidth.

[0127] Meanwhile, according to an embodiment of the present invention, additional CCA during the dividing period (P_d) may be omitted depending on the transmission situation of the base station. For example, the base station may perform additional CCA during the dividing period (P_d) only for carriers that did not participate in data transmission through multiple carriers. More specifically, the backoff of the first component carrier may be completed before the simultaneous transmission of data through multiple carriers, but data transmission through the first component carrier may not be performed during the simultaneous transmission. When data transmission through the first component carrier is prepared later, the base station may transmit data after performing only additional CCA during the dividing period (P_d). That is, if the first component carrier is idle during the dividing period (P_d), the base station may immediately transmit data through the first component carrier.

[0128] According to the embodiment of FIG. 18(b), interference occurring in a specific carrier constituting a multi-carrier may be prolonged beyond a certain level. The base station performs self-differential to synchronize the backoff completion times of the first to fourth CCs, but due to interference, the third CC remains busy until B3 and the subsequent dividing period (P_d). Additionally, the backoff of the fourth CC may not be completed by time B3. Thus, if backoff is not completed by the synchronized backoff completion time B3, or if there is a carrier in a busy state during the pre-set dividing period (P_d), the base station performs multi-carrier data transmission by excluding the carrier. That is, the base station can transmit data through some component carriers that are backoff completed by the synchronized backoff completion time B3 and remain idle during the pre-set dividing period (P_d).

[0129] According to an embodiment of the present invention, the self-differential period can be set according to various embodiments. A base station can adjust the self-differential period of each component carrier based on at least one variable within the maximum self-differential period.

[0130] According to an embodiment of the present invention, a base station may set or modify the self-differential period when a specific carrier is in an occupied state during backoff. According to one embodiment of the present invention, a base station may set, modify, and / or cancel the self-differential based on the length of the interference. If the length of the interference occurring during backoff exceeds a preset first threshold, the base station may set the self-differential period longer, anticipating that the completion time of backoff will be delayed. However, if the length of the interference occurring during backoff exceeds a preset second threshold, the base station may reduce the self-differential period or cancel the self-differential. The base station may perform data transmission through the corresponding component carrier when the backoff of a specific component carrier is completed. In this case, the second threshold is a value greater than the first threshold. According to an additional embodiment of the present invention, the self-differential period may be variable based on the bandwidth of the interference. The wider the bandwidth of the interference, the shorter the length of the interference may be. Therefore, the base station may shorten the self-differential period as the bandwidth of the interference increases. When a base station acquires interference bandwidth information, it may set, modify, and / or cancel the self-differential based on the information.

[0131] A base station may set or modify the self-differential period of a first carrier based on the length of interference in a second carrier. Here, the first carrier and the second carrier represent different carriers. Additionally, the first carrier and the second carrier each include at least one component carrier. If the interference in the second carrier is prolonged, the time at which the backoff of the first carrier performing self-differential is completed may be delayed. Accordingly, the base station may gradually reduce or stop the self-differential period of the first carrier based on the length of interference in the second carrier. When the self-differential and backoff of the first carrier are completed, the base station may immediately transmit data through the first carrier. Alternatively, the base station may transmit data after performing CCA of the carrier during the defer period following the completion of self-differential and backoff.

[0132] The base station can predict the length of interference in the second carrier in various ways. According to one embodiment, the base station may determine that the length of interference is greater than or equal to the second threshold value if the second carrier maintains an occupied state for more than a preset number of slots. In this way, when the second carrier is continuously occupied, the base station may gradually reduce or stop the self-deferral period of the first carrier. When the self-deferral period and backoff of the first carrier are completed, the base station may immediately transmit data through the first carrier or transmit data after the deferral period. In this way, the base station can prevent the data transmission of another carrier from being unnecessarily delayed due to interference occurring in a specific carrier.

[0133] According to another embodiment of the present invention, a base station can adjust the self-differential period based on the number of active carriers in a configurable unlicensed band. As the number of active carriers increases, the probability of interference increases. Therefore, the base station can set the self-differential period shorter as the number of active carriers increases.

[0134] According to another embodiment of the present invention, a base station may adjust the self-deferral period based on the number of carriers for which self-deferral is performed. For example, the base station may set the self-deferral period shorter as the number of carriers for which self-deferral is performed increases. Alternatively, the base station may set the self-deferral period shorter as the value of 'number of carriers for which self-deferral is performed' / 'number of active carriers' increases. In this way, by adjusting the self-deferral period based on the number of carriers for which self-deferral is performed, the base station can save resources.

[0135] The base station may reduce or expand the self-deferral period in stages based on the length of the interference. Additionally, if the self-deferral period expanded in stages exceeds a certain level, the base station may cancel the self-deferral. According to one embodiment, the self-deferral period may be divided into X segments. For example, the self-deferral period may be divided into X segments of equal length. Alternatively, the self-deferral period may be divided into X segments that increase or decrease exponentially. Alternatively, the self-deferral period may be divided into X segments that increase or decrease by a certain multiple. The base station may cancel the self-deferral if interference occurs continuously in Y segments among the divided X segments. In this case, Y is a value less than or equal to X. The base station may resume backoff of the carrier whose self-deferral has been canceled. When the self-deferral and backoff of the carrier are completed, the base station may immediately transmit data through the carrier. According to another embodiment, the base station can transmit data after performing the carrier's CCA during the dividing period after self-diverral and backoff are completed.

[0136] FIG. 19 is a flowchart illustrating an embodiment in which a base station performs self-differential. When the transmission of previous data is finished (S402), the base station initializes the backoff counter (S404). The base station performs multi-carrier backoff based on the initialized backoff counter. According to one embodiment, the base station may perform independent backoff for each carrier.

[0137] When the backoff of a specific carrier is completed (S406), the base station checks whether there are any other carriers remaining backoff (S408). If there are no carriers with remaining backoff counters at the time the backoff of the specific carrier is completed, the base station can perform data transmission through all carriers without self-differential (S412). However, if there are carriers with remaining backoff counters at the time the backoff of the specific carrier is completed, the base station checks whether the carrier with remaining backoff is in a occupied state (S410). That is, the base station can decide whether to perform self-differential based on whether the carrier that has not completed backoff is in a occupied state. If the carrier that has not completed backoff is in a occupied state, the base station does not perform self-differential and immediately transmits data only to the carrier that has completed backoff (S412). However, if the carrier that has not completed backoff is in an idle state, the base station can perform self-differential (S414). When self-differential and backoff are completed, the base station can perform multi-carrier data transmission (S416). As described above, depending on the situation, the base station may additionally perform carrier CCA during the dividing period (P_d) before data transmission.

[0138] A base station may determine whether to perform self-deferral based on at least one variable. In one embodiment, the base station may determine whether to perform self-deferral based on at least one of the remaining backoff counter value (bo_remaining) of a carrier that has not completed backoff and the number of carriers that have not completed backoff (n_remaining). The base station may perform self-deferral when backoff in the first carrier is completed and the bo_remaining value of the second carrier is less than or equal to a preset value (bo_threshold). Additionally, the base station may perform self-deferral only when backoff in the first carrier is completed and the n_remaining value is greater than or equal to a preset value. This is because, when the number of carriers that have not completed backoff is small, the bandwidth gain relative to the channel occupancy delay caused by performing self-deferral may not be significant. If it is decided not to perform self-deferral, the base station may immediately perform data transmission through the carrier that has completed backoff.

[0139] Meanwhile, the bo_threshold value can be set smaller as the backoff stage of the corresponding carrier increases. When a specific carrier becomes occupied and its backoff stage increases, it is assigned a backoff counter within an increased CW. If a high backoff counter is assigned within an increased CW, the probability of that carrier becoming occupied again increases. Additionally, a high backoff stage may indicate a high traffic load for that carrier. Therefore, the base station can perform fast carrier access by setting the bo_threshold value of the corresponding component carrier to a low level.

[0140] Meanwhile, FIG. 19 illustrates an embodiment in which a base station performs self-deferral, but the present invention is not limited thereto. That is, individual conditions for a base station to perform self-deferral can be varied.

[0141] FIG. 20 illustrates an embodiment in which a base station determines whether to perform self-differential according to the method of FIG. 19. The base station attempts to transmit data through multiple carriers including the first CC to the fourth CC. The base station performs independent backoff for each component carrier. As illustrated, interference occurs in the third CC and the fourth CC during the backoff performance for the first CC to the fourth CC. Therefore, the backoff of the third CC and the fourth CC may not be completed at the time when the backoff of the first CC and the second CC is completed. In the embodiment of FIG. 20, the third CC and the fourth CC remain in an occupied state even at the time when the backoff of the first CC and the second CC is completed. Therefore, the base station can immediately transmit data only to the first CC and the second CC, for which backoff has been completed, without performing self-differential.

[0142] FIGS. 21 and 22 illustrate embodiments of the present invention that protect a carrier on which self-differential is performed with a reserved signal.

[0143] As mentioned above, if the backoff completion times of carriers are not identical due to interference, the base station can perform self-differential to increase the number of carriers completing backoff and transmit data over a wider bandwidth. However, if a carrier is not used while self-differential is being performed, another device may perceive that carrier as idle and use it. If signal transmission by another device continues until the end of self-differential, the base station cannot perform data transmission using that carrier.

[0144] Accordingly, according to an embodiment of the present invention, a base station can prevent another device from occupying the carrier by transmitting a reserved signal while self-differential is being performed. In an embodiment of the present invention, the reserved signal includes a dummy signal with a power greater than a certain level, a signal having specific information, etc.

[0145] First, FIG. 21 illustrates an embodiment in which a base station transmits a signal reserved during the self-differential period. According to an embodiment of the present invention, the base station may transmit a signal reserved during the entire period in which self-differential is performed on each carrier. As illustrated in FIG. 21, the time for self-differential to be performed may differ for each component carrier constituting multiple carriers. The base station transmits a signal reserved independently during the self-differential period of each component carrier.

[0146] Meanwhile, due to the transmission of a reserved signal by the base station, the carrier undergoing self-deferral may become unnecessarily occupied. Therefore, the base station may determine whether to perform self-deferral based on at least one variable as described above. For example, the base station may not perform self-deferral if the number of carriers with completed backoff (n_complete) is greater than or equal to a preset value (or if the number of carriers with incomplete backoff (n_remaining) is less than a preset value). If self-deferral is being performed on a specific carrier, the base station may cancel the self-deferral for that carrier. If it is decided not to perform self-deferral, the base station may immediately perform data transmission through the carrier that has completed backoff.

[0147] Next, FIG. 22 illustrates another embodiment in which a base station transmits a reserved signal during the self-differential period. When the reserved signal is transmitted, power leakage to an adjacent carrier may occur. If the reserved signal is transmitted during the entire period in which self-differential is performed at each carrier, as in the embodiment of FIG. 21, it may affect the backoff of the adjacent carrier. That is, power leakage of the reserved signal transmitted through the first carrier may cause the second carrier to be occupied, and as a result, the backoff of the second carrier may be interrupted.

[0148] Accordingly, according to another embodiment of the present invention, a base station can transmit a reserved signal through each component carrier only when self-differential is performed on all component carriers constituting multiple carriers. In FIG. 22, since self-differential of the third CC and fourth CC is not performed at the start of self-differential of the first CC and second CC, the base station does not transmit the reserved signal. When self-differential of the third CC and fourth CC is started and self-differential is performed on all component carriers, the base station can transmit the reserved signal through the first CC to the fourth CC.

[0149] According to another embodiment of the present invention, a base station may transmit a reserved signal based on whether backoff is performed on an adjacent carrier. Power leakage resulting from the transmission of the signal may primarily affect only the adjacent channel. Therefore, even if self-differential is not performed on all carriers, if backoff is not performed on an adjacent carrier, the base station may transmit the reserved signal to the carrier where self-differential is performed.

[0150] FIG. 23 illustrates an embodiment in which a base station cancels self-differential. As previously described, a base station can perform self-differential for multi-carrier data transmission. However, if interference occurs in at least some carriers during the self-differential period, the base station may cancel the self-differential. That is, if interference occurs during the self-differential period, the base station cancels the self-differential of all carriers to reduce the data transmission waiting time caused by the interference. After the self-differential is canceled, the base station can immediately perform data transmission through the carriers for which backoff is completed. According to the embodiment, the base station may transmit data after performing additional CCA of the carriers during the dividing period (P_d). In FIG. 23, interference occurred in the third CC and the fourth CC while the self-differential of the first CC to the fourth CC was being performed. Therefore, the base station cancels the self-differential of the first CC to the fourth CC and transmits data through the first CC and the second CC for which backoff is completed.

[0151] FIGS. 24 to 26 illustrate additional embodiments of the present invention in which a base station determines whether to continue self-deferral. According to an embodiment of the present invention, a base station may set a reference point (R_s) for determining whether to continue self-deferral. A base station performing self-deferral may determine whether to continue self-deferral based on at least one piece of information at the reference point (R_s). The reference point (R_s) may be set to a specific point in time within the self-deferral period.

[0152] More specifically, while performing self-deferral on the first carrier, the base station checks the time of completion of backoff of the second carrier at a reference time (R_s). The base station determines whether the backoff of the second carrier is completed before the time of completion of self-deferral and backoff of the first carrier. If the backoff of the second carrier is completed before the time of completion of self-deferral and backoff of the first carrier, the base station continues the self-deferral of the first carrier. The base station can transmit data simultaneously through the first carrier and the second carrier after both the backoff of the first carrier and the backoff of the second carrier are completed. According to an embodiment, the base station can transmit data after performing additional CCA of the first carrier and the second carrier during a diff interval (P_d).

[0153] However, if the backoff of the second carrier is completed after the completion of the self-differential and backoff of the first carrier, the base station cancels the self-differential of the first carrier. When the self-differential is canceled, the base station can immediately transmit data through the carrier after the completion of the backoff of the first carrier. According to an embodiment, the base station can transmit data after performing additional CCA of the first carrier during the dividing period (P_d).

[0154] FIG. 24 illustrates an embodiment in which a base station decides to continue self-differential based on the above method. FIG. 24(a) shows a situation in which the backoff counters of each component carrier constituting the multiple carriers are set identically, and FIG. 24(b) shows a situation in which the backoff counters of each component carrier are set independently. Referring to FIG. 24, interference occurred in the third CC and the fourth CC during the backoff execution for the first CC to the fourth CC. Therefore, when a normal backoff procedure is performed, the backoff of the third CC and the fourth CC may be completed later than the backoff of the first CC and the second CC.

[0155] According to an embodiment of the present invention, a base station first performs self-deferral for the first CC and the second CC. During the performance of self-deferral for the first CC and the second CC, the base station checks the backoff completion time of the third CC and the fourth CC at a reference time (R_s). The base station can check the respective backoff completion time based on the remaining backoff counter value (bo_remaining) of the third CC and the fourth CC. In the embodiment of FIG. 24, since the backoff of the third CC and the fourth CC is completed before the self-deferral and backoff completion time of the first CC and the second CC, the base station continues the self-deferral for the first CC and the second CC. According to one embodiment, the base station may also perform self-deferral for the third CC and / or the fourth CC to synchronize the backoff completion time of the entire component carrier. When the backoff procedure for the first CC to the fourth CC is all completed, the base station may perform additional CCA during a pre-set dividing interval (P_d) according to the embodiment. In the above process, if the component carriers are idle, the base station transmits data through the corresponding component carriers.

[0156] A reference point (R_s) for determining whether self-deferral persists can be set according to various embodiments. First, according to one embodiment of the present invention, the self-deferral period may be divided into n intervals (where n is a natural number greater than or equal to 2), and the reference point (R_s) may be set as at least one of the end points of each divided interval. If the self-deferral period is divided into two intervals as shown in FIG. 24, the reference point (R_s) may be set at the halfway point of the self-deferral period. The reference point (R_s) may be set independently for each carrier, but the present invention is not limited thereto, and a reference point (R_s) common to all carriers may be applied.

[0157] According to an embodiment of the present invention, the self-differential period can be set independently for each carrier. As described above, the base station can adjust the self-differential period of each carrier based on at least one variable within the maximum self-differential period. Since the backoff counter and interference conditions may differ for each carrier, the base station can perform simultaneous data transmission through multiple carriers by setting the self-differential period independently for each carrier.

[0158] According to one embodiment of the present invention, a base station may set up a carrier set including at least one component carrier to transmit data, and acquire a common backoff counter for the carrier set. In the embodiment of FIG. 24(b), the first CC and the second CC are set up as the same carrier set and assigned a common backoff counter 5. The base station performs backoff for each component carrier of the carrier set using the acquired common backoff counter. That is, the base station can synchronize multi-carrier transmission by assigning the same backoff counter to each component carrier within the same carrier set and performing backoff.

[0159] According to an embodiment of the present invention, a shared backoff counter can be set by various methods. According to one embodiment, a base station sets a single contention window value for all component carriers of a carrier set and can use a backoff counter obtained within the single contention window as a shared backoff counter. That is, in the embodiment of FIG. 24(b), a single contention window for the first CC and the second CC of the same carrier set can be maintained. According to another embodiment, a base station can set a contention window value independently for each component carrier of the carrier set. That is, in the embodiment of FIG. 24(b), separate contention windows for the first CC and the second CC of the same carrier set can be maintained. The base station obtains a backoff counter within the largest contention window value among the contention window values ​​of all component carriers of the carrier set and can use the obtained backoff counter as a shared backoff counter. If the contention window value of the first CC is greater than or equal to the contention window value of the second CC, the base station obtains a shared backoff counter within the contention window value of the first CC. However, if the contention window value of the second CC is greater than or equal to the contention window value of the first CC, the base station acquires a shared backoff counter within the contention window value of the second CC. Backoff for each of the first CC and the second CC is performed using the acquired shared backoff counter.

[0160] The base station simultaneously transmits data through at least one component carrier for which backoff has been completed. According to one embodiment, multi-carrier data transmission can be performed in units of carrier sets. For example, the aforementioned self-differential can be performed to synchronize the backoff completion times between component carriers of the same carrier set. That is, through the self-differential, the backoff completion times between each component carrier of the first carrier set can be synchronized with each other, and the backoff completion times between each component carrier of the second carrier set can be synchronized with each other. If the backoff of the second carrier set is also completed and idle at the time the backoff of the first carrier set is completed, the base station can perform synchronized transmission using both the first carrier set and the second carrier set. However, if there are no other carriers that have already completed backoff and are idle at the time the backoff of the first carrier set is completed, the base station can perform synchronized transmission using only the first carrier set. According to one embodiment, a base station can perform data transmission by performing carrier aggregation in units of carrier sets.

[0161] According to an additional embodiment of the present invention, synchronized transmission can be performed using only component carriers of the same carrier set depending on the configuration of the base station. When all component carriers of the same carrier set complete backoff at the same time, the base station can immediately perform data transmission without self-differential of the carrier set. Through this, the base station can efficiently use time and frequency resources associated with multi-carrier transmission and reduce data transmission delay.

[0162] According to another embodiment of the present invention, a reference time point (R_s) for determining whether to continue the self-deferral can be set as the time point at which the self-deferral of the carrier whose backoff is completed first begins. If the backoff of the first carrier is completed first, the self-deferral of the first carrier can be modified in the following way according to the CCA result at the reference time point (R_s) of the remaining carrier(s) excluding the carrier(s).

[0163] First, among the remaining carrier(s), carriers that are in an occupied state at the reference time (R_s) may be excluded from multi-carrier simultaneous transmission regardless of the remaining backoff counter value of the first carrier. This is because, considering the length of typical wireless LAN or LTE data and the self-deferral length, it is unlikely that an occupied carrier will change back to an idle state within the self-deferral period. In this case, the occupied carriers do not affect the setting of the first carrier's self-deferral period.

[0164] Secondly, among the remaining carrier(s), carriers that are in an idle state at the reference time (R_s) may be used for multi-carrier simultaneous transmission only if backoff can be completed within the maximum self-differential period of the first carrier. That is, even if a carrier is in an idle state at the reference time (R_s), if the remaining backoff counter value is greater than a preset value and backoff cannot be completed within the maximum self-differential period of the first carrier, the carrier may be excluded from multi-carrier simultaneous transmission. At this time, the base station determines the self-differential period based on the backoff counter of the carrier with the largest backoff counter value among the remaining carriers to be used for multi-carrier simultaneous transmission. By setting the self-differential period by considering the carrier that completes backoff the latest among the carriers that can participate in simultaneous transmission, the base station can include as many carriers as possible in multi-carrier simultaneous transmission.

[0165] The self-differential period determined by the above method may be adjusted based on channel changes of the remaining carriers. A carrier that changes to an occupied state within the set self-differential period may be excluded from the corresponding multi-carrier simultaneous transmission. If the excluded carrier is the carrier with the largest backoff value, the base station may reduce the self-differential period of the first carrier. In this case, the self-differential period may be changed based on the backoff counter of the carrier having the next largest backoff counter value among the remaining carriers to be used for simultaneous transmission, after the excluded carrier.

[0166] FIGS. 25 and 26 illustrate embodiments in which a base station decides to cancel self-differential based on the method for determining whether to continue self-differential described above. FIG. 25 illustrates a situation in which the backoff counters of each component carrier constituting a multi-carrier are set identically, and FIG. 26 illustrates a situation in which the backoff counters of each component carrier are set independently. In the embodiments of FIGS. 25 and 26, parts that are identical or corresponding to the embodiment of FIG. 24 described above are omitted from redundant description.

[0167] First, FIG. 25 illustrates an example of a base station canceling self-differential. FIG. 25(a) shows time (t_w) wasted due to interference from another carrier within the self-differential period, and FIG. 25(b) shows a situation in which the base station cancels self-differential to prevent wasted time (t_w).

[0168] Referring to FIG. 25, interference occurred in the third CC and the fourth CC during the backoff process for the first CC to the fourth CC. The base station first performs self-differential for the first CC and the second CC. However, as shown in FIG. 25(a), the backoff for the third CC and the fourth CC may not be completed before the completion of the self-differential and backoff for the first CC and the second CC. In this case, time resources may be unnecessarily wasted when self-differential is performed on the first CC and the second CC.

[0169] Accordingly, during the execution of the self-differential of the first CC and the second CC, the base station checks the backoff completion time of the third CC and the fourth CC at a reference time (R_s). The base station can check the respective backoff completion time based on the remaining backoff counter value (bo_remaining) of the third CC and the fourth CC. Since the backoff of the third CC and the fourth CC is completed after the self-differential and backoff completion time of the first CC and the second CC, the base station cancels the self-differential of the first CC and the second CC as illustrated in FIG. 25(b). The base station can immediately transmit data through the corresponding component carrier after the backoff of the first CC and the second CC is completed. According to an embodiment, the base station can transmit data after performing additional CCA of the first CC and the second CC during the dividing period (P_d).

[0170] Next, FIG. 26 illustrates another embodiment in which a base station cancels self-differential. FIG. 26(a) shows time (t_w) wasted due to interference from another carrier within the self-differential period, and FIG. 26(b) shows a situation in which a base station cancels self-differential to prevent wasted time (t_w).

[0171] In FIG. 26, the backoff counter for each component carrier is set independently. As previously described, a base station may set up a carrier set including at least one component carrier to transmit data and obtain a common backoff counter for said carrier set. In the embodiment of FIG. 26, the first CC and the second CC are set up as the same carrier set and assigned a common backoff counter 5. The base station performs backoff for each component carrier of the carrier set using the obtained common backoff counter.

[0172] As described in FIG. 25, interference occurred in the third CC and the fourth CC during the backoff process for the first CC through the fourth CC. The base station first performs the self-differential of the first CC and the second CC. However, as shown in FIG. 26(a), the backoff of the third CC and the fourth CC may not be completed before the completion of the self-differential and backoff of the first CC and the second CC.

[0173] Accordingly, during the execution of the self-deferral of the first CC and the second CC, the base station checks the time of completion of the backoff of the third CC and the fourth CC at the reference time (R_s). Since the backoff of the third CC and the fourth CC is completed after the time of completion of the self-deferral and backoff of the first CC and the second CC, the base station cancels the self-deferral of the first CC and the second CC as shown in FIG. 26(b).

[0174] Hereinafter, an embodiment of the LBT operation in the aforementioned LAA is summarized and explained again. When performing LBT operation in the LAA, the slot size of the ECCA is 9 μs, and the actual sensing time within the slot is at least 4 μs. In the case of the LBT Category-4 method for PDSCH, one dipper interval consists of a 16 μs period and n consecutive CCA slots. Here, n is a positive integer, the CCA slot period is 9 μs, and the number of slots n in the dipper interval can be set differently depending on the QoS class. During the initial 16 μs period of the dipper interval, the backoff counter countdown is not performed. When all n slots of the backoff counter are observed to be idle, the backoff counter may be decremented to 1 at the end of the dipper interval. If the backoff counter reaches 0 after decrement, the node does not immediately transmit data but continues the ECCA process by performing a CCA check for at least one slot. If a channel is observed to be occupied within a dipper interval, that dipper interval may be suspended.

[0175] The LBT procedure and multi-carrier LBT are described below. During the ECCA process of LBT, the backoff counter does not need to be decremented when a slot is idle. That is, the backoff counter may be decremented optionally when a slot is idle. If a slot is not observed, it should be considered occupied.

[0176] For LBT on multiple carriers, the following two methods may be considered. First, the base station may perform Category-4 LBT on only one unlicensed band carrier. That is, when the base station completes LBT on one carrier, the base station may sense other carriers during a pre-configured interval, such as PIFS (25 μs), immediately before completing LBT on that carrier. In the above procedure, the base station may transmit DL data bursts through the other carrier(s) sensed as idle. How quickly the base station can change the carrier performing Category-4 based LBT may be determined at the subframe, multiple subframe, or RRC (Radio Resource Control) level.

[0177] Next, the base station may perform Category-4 based LBT on one or more unlicensed band carriers. That is, the base station may transmit DL data bursts through carriers that have completed Category-4 based LBT. In this case, the base station may perform self-differential to align the transmission times among multiple carriers. If the base station can receive through one carrier while simultaneously transmitting through another carrier, the base station may freeze the backoff counter for the carrier that is not transmitting while transmission is being performed through the other carrier. In this case, the base station may perform the backoff counter freezing if the carriers are separated within a preset frequency range.

[0178] When multi-carrier LBT is performed within a single carrier set, at least one of the two methods presented above may be applied. Alternatively, multi-carrier LBT using different methods may be performed for each carrier set.

[0179] FIG. 27 illustrates a self-differential execution method according to another embodiment of the present invention. In the embodiment of FIG. 27, parts identical or corresponding to the embodiments of the aforementioned drawings are omitted from redundant description.

[0180] As described above, a base station can synchronize multi-carrier data transmission by performing self-differential. According to an embodiment of the present invention, self-differential may be performed when the remaining backoff counter value of the corresponding carrier is greater than 0. In the embodiment of FIG. 27, the base station performs self-differential when the remaining backoff counter values ​​of the first CC and the second CC are 1. For a carrier that becomes occupied during backoff, the base station operates according to existing CCA rules. The base station may apply CCA during a pre-set dividing interval (P_d) in the LBT process.

[0181] More specifically, as shown in FIG. 27, the base station can perform self-deferral on the carrier when the remaining backoff counter value of the first CC and the second CC is 1. When the self-deferral is terminated and the carrier remains idle during a preset dividing period (P_d) until the backoff counter is completed, the base station can transmit data through the carrier. The dividing period (P_d) consists of a 16 µs period that does not decrease the backoff counter and subsequent n additional CCA slots. The CCA slot period can be set to 9 µs, the same as Wi-Fi, or a similar length, and the number of slots n can be set differently depending on the QoS class.

[0182] According to one embodiment, the base station may decrease the backoff counter in the n additional CCA slots. The base station performs data transmission simultaneously through a plurality of carriers whose backoff counter values ​​have become 0. Although the embodiment of FIG. 27 illustrates an embodiment in which self-deferral is performed when the remaining backoff counter value is 1, the present invention is not limited thereto. That is, the base station may perform self-deferral even when any backoff counter value remains. According to one embodiment, fast data transmission is possible if the backoff counter is decreased through the deferral interval (P_d) and data is transmitted immediately. Accordingly, the base station may set a maximum and / or minimum backoff counter as a condition for performing self-deferral, and may perform self-deferral if the remaining backoff counter is within the set backoff counter range. If the backoff counter at the time when self-deferral is performed differs for each carrier, the deferral interval (P_d) may start at different times for each carrier.

[0183] FIG. 28 illustrates a self-differential execution method according to another embodiment of the present invention. In the embodiment of FIG. 28, parts identical or corresponding to the embodiments of the aforementioned drawings are omitted from redundant description.

[0184] According to the embodiment of FIG. 28, the dividing interval (P_d) can be set differently for each carrier. For example, due to the transmission of different QoS data, the number of slots n of the dividing interval (P_d) can be determined differently for each carrier. Accordingly, if the backoff counter can be reduced in the slot of the dividing interval (P_d), the base station can determine the start time of the dividing interval (P_d) based on the length of the dividing interval (P_d). Accordingly, in the embodiment of FIG. 28, the dividing interval (P_d) of the first CC, second CC, and fourth CC, which have 2 slots, can start when the remaining backoff counter value of the corresponding carrier is 2, and the dividing interval (P_d) of the third CC, which has 1 slot, can start when the remaining backoff counter value of the corresponding carrier is 1.

[0185] The base station sets a maximum and / or minimum backoff counter as a condition for the start of the dividing period (P_d), and can start the dividing period (P_d) for each carrier at the same time within the set backoff counter range. Meanwhile, the remaining backoff counter value for starting self-diverral can be set identically for each carrier, but may also be set differently for transmission synchronization.

[0186] The following describes a method for setting an adaptive energy detection threshold according to a region-specific protocol when performing energy detection for channel access in an LAA Scell. The maximum allowable energy detection threshold in an LAA Scell ​​can be selected from two values ​​in the set {X, Y} (where Y <X). 여기서 최대 허용 에너지 검출 임계값으로 X, Y를 설정하는 아래 수학식 1 또는 수학식 2의 두 가지 방법이 고려될 수 있다.

[0187]

[0188]

[0189] Here, A is -75 dBm / MHz, and W represents the bandwidth (in MHz) to which the energy detection process is applied. Ph is the data transmission power value and can be determined according to the following two options. In the first option, Ph can be the maximum transmission power class of the LAA transmission point within the unlicensed band. In the second option, Ph can be the maximum transmission power within a transmission burst following the LBT procedure.

[0190] In addition, a method such as Equation 3 below can be considered as a threshold for detecting the maximum allowable energy.

[0191]

[0192] Here, T A It is set to 10dB for transmissions including PDSCH, and to 5dB for transmissions including discovery signal transmissions without PDSCH. In addition, P H is 23dBm, and T max The value is set to -75dB / MHz + 10*log10(BWMHz). T max When converted to dBm units, it is set as shown in mathematical formula 4 below.

[0193]

[0194] Also P TX represents the dB value as the maximum output power value that can be set for each carrier. Here, the base station P regardless of single-carrier transmission or multi-carrier transmission TX can be used as a fixed value. According to another embodiment, in the case of multi-carrier transmission, the base station has a sum of the maximum power in each transmittable carrier equal to P TX The maximum transmission power values ​​in each carrier can be distributed and applied so as to be. And BWMHz refers to the bandwidth in MHz units in a single carrier.

[0195] FIGS. 29 and 30 illustrate embodiments of the present invention for setting an energy detection threshold when performing LBT for multi-carrier transmission. A base station and a terminal can determine whether a carrier is in an occupied state based on an energy detection threshold (i.e., an energy detection reference value) when performing CCA. That is, if no radio signal is detected from the carrier or if a signal having a level below the energy detection threshold is detected, the carrier is determined to be in an idle state. However, if a signal having a level exceeding the energy detection threshold is detected from the carrier, the carrier is determined to be in an occupied state.

[0196] According to an embodiment of the present invention, an energy detection threshold can be determined based on at least one of the total transmission power and the total bandwidth of the data to be simultaneously transmitted by a base station. When the transmission power is set low, the base station may attempt more aggressive channel occupancy by applying a relatively high energy detection threshold. Additionally, when data is transmitted over a wide bandwidth, the predetermined total transmission power is distributed, thereby reducing power interference within a unit band. Therefore, the base station may increase the energy detection threshold as data is transmitted over a wide bandwidth.

[0197] FIG. 29 illustrates a method for setting an energy detection threshold according to an embodiment of the present invention. According to an embodiment of the present invention, a base station may determine an energy detection threshold based on at least one of the total transmission power and the total bandwidth of data to be transmitted simultaneously. However, whether actual data transmission will be performed through which component carriers may be determined when the backoff process is completed.

[0198] Accordingly, according to an embodiment of the present invention, a base station may determine an energy detection threshold X0 in an LBT operation in a situation where the data transmission power and total bandwidth are not determined (hereinafter, the first LBT operation) and an energy detection threshold X1 in an LBT operation in a situation where the parameters are determined (hereinafter, the second LBT operation) in different ways. The first LBT operation may refer to a CCA in a backoff and self-differential interval, and the second LBT operation may refer to a CCA in at least one pre-set slot immediately before the data transmission time.

[0199] According to one embodiment, the energy detection threshold X0 in the first LBT operation can be determined independently for each carrier. When the energy detection threshold is determined based on Equation 1, Ph can be set to a fixed power value and W can be set to the bandwidth of the carrier on which energy detection is performed. For example, if Ph is set to 23 dBm and W to 20 MHz, the energy detection threshold X0 can be determined to be -62 dBm. According to one embodiment, Ph can be set considering the maximum transmission power class value. In addition, when the energy detection threshold is determined based on Equation 3, P H is set to a fixed power value, and the BWMHz can be set as the bandwidth of the carrier where energy detection is performed. For example, P H When =23dBm and BWMHz=20MHz are set, the energy detection threshold X0 can be determined to be -72dBm. According to one embodiment, P H It can be set by considering the maximum transmission power class value.

[0200] According to another embodiment, the energy detection threshold X0 in the first LBT operation can be determined by considering the total bandwidth and transmission power where the LBT operation is performed. For example, Ph can be set by distributing the transmittable power value over the total bandwidth where energy detection is performed. That is, in the first LBT operation, Ph can be set as 'total transmission power' * 'bandwidth of the carrier where energy detection is performed' / 'total bandwidth where energy detection is performed'. For example, as in the embodiment of FIG. 29, when the transmittable power value is 23 dBm, the bandwidth of the carrier where energy detection is performed is 20 MHz, and the total bandwidth where energy detection is performed is 80 MHz, Ph is set as 23 * 20 / 80 dBm. Therefore, the lower the transmittable power value relative to the total bandwidth where energy detection is performed, the higher the energy detection threshold X0 is set. According to an additional embodiment of the present invention, the Ph value may be set differently for each carrier.

[0201] Meanwhile, the energy detection threshold X1 in the second LBT operation can be determined by considering the total transmission power and total bandwidth of the data to be actually transmitted. As described above, the second LBT operation represents an LBT operation in a situation where the data transmission power and total bandwidth are determined, and refers to the CCA in at least one pre-set slot immediately before the data transmission time. According to one embodiment, the second LBT operation may refer to the CCA in the dipper interval (P_d), but the present invention is not limited thereto. In the second LBT operation, Ph can be set as 'total transmission power' * 'bandwidth of the carrier where energy detection is performed' / 'total bandwidth of the data to be transmitted simultaneously'. For example, in the embodiment of FIG. 29, as a result of the LBT operation, data is transmitted simultaneously in a 60 MHz band including the first CC, the second CC, and the fourth CC. Accordingly, the total transmission power value is 23 dBm, the bandwidth of the carrier where energy detection is performed is 20 MHz, and the total bandwidth of the data to be transmitted simultaneously is 60 MHz, and Ph is set as 23 * 20 / 60 dBm. Therefore, the lower the total transmission power value relative to the bandwidth where data is transmitted simultaneously, the higher the energy detection threshold X1 is set.

[0202] In the above-described embodiment, the bandwidth of the carrier on which energy detection is performed is described as 20 MHz, but the present invention is not limited thereto. That is, the bandwidth of the carrier on which energy detection is performed may be set to a specific value of 20 MHz or less, such as 10 MHz, 5 MHz, etc.

[0203] FIG. 30 illustrates a method for setting an energy detection threshold according to another embodiment of the present invention. In the embodiment of FIG. 30, parts identical or corresponding to the embodiment of FIG. 29 are omitted from redundant description.

[0204] According to another embodiment of the present invention, a base station may set different energy detection thresholds based on whether each carrier is in an occupied state during the LBT process. In the backoff procedure, energy detection may be performed based on different bandwidths depending on whether each carrier is in an occupied state. At this time, when transmission power is distributed and applied to the idle state bandwidth, the transmission power value for each carrier will differ. Therefore, in the formula of the embodiment of FIG. 29 for setting the energy detection threshold, 'the total bandwidth where energy detection is performed' may be modified to 'the total bandwidth of the idle state where energy detection is performed'. Specifically, in the embodiment of FIG. 30, in the section where the 80 MHz band including the first CC to the fourth CC is in an idle state, the total bandwidth value may be set to 80 MHz to calculate the energy detection threshold X0_1. However, in the section where the third CC and the fourth CC are in an occupied state and the 40 MHz band including the first CC and the second CC is in an idle state, the total bandwidth value may be set to 40 MHz to calculate the energy detection threshold X0_2.

[0205] Meanwhile, when attempting to perform simultaneous data transmission using multiple carriers through self-differential, etc., it may be determined that transmission using a specific carrier is impossible when considering the remaining backoff counter of that carrier. In this case, the base station may set the total bandwidth and / or total transmission power values ​​of the aforementioned formula by considering the number of carriers capable of simultaneous transmission, and determine an energy detection threshold. For example, in the embodiment of FIG. 30, it may be determined that the backoff of the third CC is not completed based on the time of simultaneous multi-carrier transmission. In this case, the base station may calculate the energy detection threshold X0_3 of the fourth CC by setting the total bandwidth value to 60 MHz.

[0206] According to another embodiment of the present invention, if there is a carrier for which a separate CCA is not performed, such as a self-differential, the energy detection threshold can be determined by considering only the carrier for which energy detection is actually performed, excluding the carrier. That is, in the embodiment of FIG. 30, the base station can calculate the energy detection threshold X0_3 of the fourth CC by setting the total bandwidth to 20 MHz, excluding the first CC and second CC for which self-differential is performed, and the third CC for which it is determined to be unavailable.

[0207] FIG. 31 illustrates the configuration of a terminal and a base station according to an embodiment of the present invention. In the present invention, the terminal may be implemented as various types of wireless communication devices or computing devices that ensure portability and mobility. The terminal may be referred to as a UE (User Equipment), STA (Station), MS (Mobile Subscriber), etc. In the present invention, the base station controls and manages cells (e.g., macro cells, femto cells, pico cells, etc.) corresponding to a service area and can perform functions such as signal transmission, channel assignment, channel monitoring, self-diagnosis, and relay. The base station may be referred to as an eNB (evolved NodeB), AP (Access Point), etc.

[0208] Referring to FIG. 31, the terminal (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 within the terminal (100). Additionally, the processor (100) can control the overall operation including each unit of the terminal (100) and control the transmission and reception of data between the units. For example, the processor (110) can receive / process downlink signals according to the proposal of the present invention.

[0210] The communication module (120) may be an integrated module that performs mobile communication using a mobile communication network and wireless LAN access using a wireless LAN. To this end, the communication module (120) may be equipped with a plurality of network interface cards, such as cellular communication interface cards (121, 122) and wireless LAN interface cards (123), in an internal or external form. Although the communication module (120) is shown as an integrated module in FIG. 31, each network interface card may be arranged independently according to circuit configuration or purpose, unlike FIG. 31.

[0211] A cellular communication interface card (121) transmits and receives wireless signals with at least one of a base station (200), an external device, and a server using a mobile communication network, and provides cellular communication services in a first frequency band based on instructions from a processor (110). The cellular communication interface card (121) may include at least one NIC module using an LTE-Licensed frequency band. A cellular communication interface card (122) transmits and receives wireless signals with at least one of a base station (200), an external device, and a server using a mobile communication network, and provides cellular communication services in a second frequency band based on instructions from a processor (110). The cellular communication interface card (122) may include at least one NIC module using an LTE-Unlicensed frequency band. For example, the LTE-Unlicensed frequency band may be a band of 2.4 GHz or 5 GHz.

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

[0213] The memory (130) stores a control program used in the terminal (100) and various data associated therewith. The control program may include a program necessary for the terminal (100) to perform wireless communication with at least one of a base station (200), an external device, and a server. The user interface (140) includes various types of input / output means provided in the terminal (100). The display unit (150) outputs various images to the display screen.

[0214] In addition, a base station (200) according to one embodiment of the present invention may include a processor (210), a communication module (220), and a memory (230).

[0215] The processor (210) can execute various commands or programs according to the present invention and process data within the base station (200). Additionally, the processor (210) can control the overall operation including each unit of the base station (200) and control data transmission and reception between the units. For example, the processor (210) can transmit / process downlink signals according to the proposal of the present invention. For example, simultaneous data transmission using multiple carriers can be performed according to the embodiments of FIGS. 17 to 30.

[0216] The communication module (220) may be an integrated module that performs mobile communication using a mobile communication network and wireless LAN access using a wireless LAN, such as the communication module (120) of the terminal (100). To this end, the communication module (120) may be equipped with a plurality of network interface cards, such as cellular communication interface cards (221, 222) and wireless LAN interface cards (223), in an internal or external form. Although the communication module (220) is shown as an integrated module in FIG. 31, each network interface card may be arranged independently according to circuit configuration or purpose, unlike FIG. 31.

[0217] A cellular communication interface card (221) transmits and receives wireless signals to and from at least one of a terminal (100), an external device, and a server using a mobile communication network, and provides cellular communication services in a first frequency band based on instructions from a processor (210). The cellular communication interface card (221) may include at least one NIC module using an LTE-Licensed frequency band. A cellular communication interface card (222) transmits and receives wireless signals to and from at least one of a terminal (100), an external device, and a server using a mobile communication network, and provides cellular communication services in a second frequency band based on instructions from a processor (210). The cellular communication interface card (222) may include at least one NIC module using an LTE-Unlicensed frequency band. The LTE-Unlicensed frequency band may be a band of 2.4 GHz or 5 GHz.

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

[0219] In FIG. 31, the blocks of the terminal and the base station are illustrated by logically distinguishing the elements of the device. The elements of the device may be mounted as a single chip or multiple chips depending on the design of the device. Additionally, some components of the terminal (100), such as a user interface (140) and a display unit (150), etc., may be optionally provided in the terminal (100). Additionally, some components of the base station (200), such as a wireless LAN interface card (223), etc., may be optionally provided in the base station (200). The user interface (140) and the display unit (150), etc., may be additionally provided in the base station (200) as needed.

[0220] Although the method and system of the present invention have been described in relation to specific embodiments, some or all of their components or operations may be implemented using a computer system having a general-purpose hardware architecture.

[0221] The foregoing description of the present invention is for illustrative purposes only, and those skilled in the art will understand that other specific forms can be easily modified without altering the technical spirit or essential features of the present invention. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. For example, each component described as a single unit may be implemented in a distributed manner, and components described as distributed may likewise be implemented in a combined form.

[0222] The scope of the present invention is defined by the claims set forth below rather than by the detailed description above, and all modifications or variations derived from the meaning and scope of the claims and equivalent concepts thereof should be interpreted as being included within the scope of the present invention. Industrial applicability

[0223] The present invention can be used in various communication devices used in wireless communication systems (e.g., stations using unlicensed band communication, access points, or stations using cellular communication, base stations, etc.).

Claims

Claim 1 In a wireless communication device, a communication module; A wireless communication device comprising a processor controlling the communication module, wherein the processor receives data transmitted from a base station and transmits a HARQ-ACK for the data to the base station, wherein the data is transmitted on one component carrier within a carrier set, wherein the one component carrier transmitting the data is a component carrier that has completed backoff, wherein the data is transmitted based on the largest contention window interval among the contention window intervals of each component carrier within the carrier set, wherein the contention window intervals are independently set for each component carrier within the carrier set, wherein a self-differential is performed on a specific component carrier within the carrier set without arbitrarily reducing the backoff counter, and wherein the energy detection threshold value for the backoff is determined based on a value (X) according to the following mathematical formula: [Mathematical Formula] X(dBm) = (23 - P) + 10log(W), wherein W is a value related to the bandwidth in which the data is transmitted, and P is a value related to the maximum power for transmitting the data. Meaning. Claim 2 A wireless communication device according to claim 1, wherein the self-differential is performed when the remaining backoff counter value of the specific component carrier is greater than 0. Claim 3 A wireless communication device according to claim 1, wherein the data transmission is performed when an additional Clear Channel Assessment (CCA) is performed for the component carrier for which the backoff is completed during a preset dipper period, and the component carrier for which the backoff is completed is idle during the dipper period. Claim 4 A wireless communication device according to claim 3, wherein the additional CCA is performed when the data transmission is not performed immediately after the backoff is completed on the component carrier where the backoff is completed. Claim 5 A wireless communication device according to claim 3, wherein the dipper section is a section obtained by adding 16 us to a section corresponding to n slots, and the slot is a section of 9 us. Claim 6 In a wireless communication method using multiple carriers, a method performed by a terminal comprises the step of receiving data transmitted from a base station; A method comprising the step of transmitting a HARQ-ACK for the data to the base station, wherein the data is transmitted on one component carrier within a carrier set, the component carrier transmitting the data is a component carrier that has completed backoff, the data is transmitted based on the largest contention window interval among the contention window intervals of each component carrier within the carrier set, the contention window intervals are independently set for each component carrier within the carrier set, a self-differential is performed on a specific component carrier within the carrier set without arbitrarily reducing the backoff counter, and the energy detection threshold value for the backoff is determined based on a value (X) according to the following mathematical formula, [Mathematical Formula] X(dBm) = (23 - P) + 10log(W), wherein W is a value related to the bandwidth in which the data is transmitted, and P is a value related to the maximum power for transmitting the data. Claim 7 A method according to claim 6, characterized in that the self-differential is performed when the remaining backoff counter value of the specific component carrier is greater than 0. Claim 8 A method according to claim 6, wherein the data transmission is performed when an additional Clear Channel Assessment (CCA) is performed during a preset dipper interval for the component carrier for which the backoff is completed, and the component carrier for which the backoff is completed is idle during the dipper interval. Claim 9 A method according to claim 8, wherein the additional CCA is performed when the data transmission is not performed immediately after the backoff is completed on the component carrier where the backoff is completed. Claim 10 A method according to claim 8, wherein the above-mentioned dipper interval is a interval obtained by adding 16 us to the interval corresponding to n slots, and the above-mentioned slot is a interval of 9 us. Claim 11 In a wireless communication device, a communication module; A wireless communication device comprising a processor that controls the communication module, wherein the processor transmits data to a terminal and receives a HARQ-ACK for the data from the terminal, wherein the data is transmitted on one component carrier within a carrier set, wherein the one component carrier transmitting the data is a component carrier that has completed backoff, wherein the data is transmitted based on the largest contention window interval among the contention window intervals of each component carrier within the carrier set, wherein the contention window intervals are independently set for each component carrier within the carrier set, wherein a self-differential is performed on a specific component carrier within the carrier set without arbitrarily reducing the backoff counter, and wherein the energy detection threshold value for the backoff is determined based on a value (X) according to the following mathematical formula, [Mathematical Formula] X(dBm) = (23 - P) + 10log(W), wherein W is a value related to the bandwidth in which the data is transmitted, and P is a value related to the maximum power for transmitting the data. Claim 12 A wireless communication method using multiple carriers, wherein the method performed by a base station comprises: a step of transmitting data to a terminal; and receiving a HARQ-ACK for the data from the terminal, wherein the data is transmitted over one component carrier within a carrier set, wherein the one component carrier transmitting the data is a component carrier that has completed backoff, wherein the data is transmitted based on the largest contention window interval among the contention window intervals of each component carrier within the carrier set, wherein the contention window intervals are independently set for each component carrier within the carrier set, wherein a self-differential is performed on a specific component carrier within the carrier set without arbitrarily reducing the backoff counter, and wherein the energy detection threshold value for the backoff is determined based on a value (X) according to the following mathematical formula. [Mathematical Formula] X(dBm) = (23 - P) + 10log(W) wherein W represents a value related to the bandwidth over which the data is transmitted, and P represents a value related to the maximum power for transmitting the data.

Images