Wireless base station, wireless communication method, and wireless communication system

Abstract

The present invention provides a wireless base station, a wireless communication method and a wireless communication system. The wireless base station has: a transmitting unit, which transmits a DL signal; a control unit, which controls the DL transmission by applying monitoring before transmitting the DL signal; and a receiving unit, which receives a delivery confirmation signal (ACK / NACK) for the DL transmission, wherein the control unit controls the contention window size applied for monitoring based on the number of ACKs for the DL transmission in a specified period and the number of codewords and / or the number of transmission blocks for the DL transmission.

Description

[0001] This application is a divisional application of the invention patent application with national application number 201680045980.4, international application date August 4, 2016, entry into the Chinese national phase date February 5, 2018, and invention name “Wireless Base Station, User Terminal and Wireless Communication Method”. Technical Field

[0002] The present invention relates to a wireless base station, a wireless communication method and a wireless communication system in a next generation mobile communication system. Background Art

[0003] In the UMTS (Universal Mobile Telecommunications System) network, Long Term Evolution (LTE) has become a standard for the purpose of further high-speed data rates and low latency (Non-Patent Document 1). LTE advanced (Rel. 10-12) has become a standard for the purpose of further broadband and high speed from LTE, and research is also being conducted on the successor system of LTE, such as 5G (5th generation mobile communication system).

[0004] LTE Rel. 8 to 12 are regulated based on the assumption that the system operates exclusively in a frequency band licensed to operators, namely, a licensed band. For example, 800 MHz, 2 GHz, or 1.7 GHz is used as the licensed band.

[0005] The popularity of highly functional user terminals / user devices (called UE: User Equipment) such as smartphones and tablets has led to a sharp increase in user traffic. In order to absorb this increased user traffic, it is necessary to add further frequency bands, but the spectrum in the authorized band (licensed spectrum) is limited. Therefore, in addition to the authorized band, research is being conducted to expand the frequency of the LTE system by using the band of unlicensed spectrum (called unlicensed band) that can be used (non-patent document 2).

[0006] As the unlicensed band, for example, the same 2.4 GHz or 5 GHz band as Wi-Fi (registered trademark) is used. In Rel.13 LTE, carrier aggregation (CA) between the licensed band and the unlicensed band is being studied. In this way, the communication using the unlicensed band together with the licensed band is called LAA (License-Assisted Access). In the future, dual connection (DC) of the licensed band and the unlicensed band, or stand-alone of the unlicensed band may also become the research object of LAA.

[0007] Prior art literature

[0008] Non-patent literature

[0009] Non-patent document 1: 3GPP TS 36.300 "Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2"

[0010] Non-Patent Literature 2: AT&T, Drivers, Benefits and Challenges for LTE in Unlicensed Spectrum, 3GPP TSG-RAN Meeting #62RP-131701 Summary of the invention

[0011] Problems to be solved by the invention

[0012] In the unlicensed band, in order to coexist with other operators' LTE, Wi-Fi or other systems, the introduction of interference control functions is being studied. In Wi-Fi, LBT (Listen Before Talk) based on CCA (Clear Channel Assessment) is used as an interference control function within the same frequency.

[0013] Therefore, even when an unlicensed band is set for the LTE system, monitoring (e.g., LBT) is applied as an interference control function to control UL transmission and / or DL ​​transmission. In this case, efficient and fair coexistence with other systems (e.g., Wi-Fi) or other LTE operators is required, and efficient frequency utilization is achieved.

[0014] The present invention is made in view of such problems, and one of its purposes is to provide a wireless base station, a user terminal and a wireless communication method that can achieve coexistence with other systems and improve frequency utilization efficiency in a cell (e.g., an unlicensed band) where monitoring before transmission is applied.

[0015] Means used to solve problems

[0016] The wireless base station of the present invention is characterized in that it has: a sending unit that sends a DL signal; a control unit that controls the DL sending by applying monitoring before sending the DL signal; and a receiving unit that receives a delivery confirmation signal (ACK / NACK) for the DL sending, and the control unit controls the contention window size applied for monitoring based on the number of NACKs for DL ​​sending during a specified period.

[0017] Effects of the Invention

[0018] According to the present invention, in a cell (eg, unlicensed band) to which monitoring before transmission is applied, coexistence with other systems can be achieved and frequency utilization efficiency can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG. 1A and FIG. 1B are diagrams showing an example of a wireless frame structure in LBT.

[0020] Figure 2 This is a diagram showing an example of a burst period set in transmission after DL-LBT.

[0021] Figure 3 This is a diagram showing an example of a case where random backoff is applied during monitoring.

[0022] Figure 4 This is a diagram showing an example of a method for controlling the CW dimension in this embodiment.

[0023] Figure 5A , Figure 5B It is a diagram showing another example of the method of controlling the CW dimension in the present embodiment.

[0024] Figure 6 This is a diagram showing an example of the monitoring operation procedure in this embodiment.

[0025] Figure 7 This is a schematic diagram showing an example of a wireless communication system according to the present embodiment.

[0026] Figure 8 It is a diagram for explaining the overall configuration of a wireless base station according to the present embodiment.

[0027] Fig. 9 It is a diagram for explaining the functional configuration of the wireless base station according to the present embodiment.

[0028] Fig.10 It is a diagram for explaining the overall configuration of a user terminal according to the present embodiment.

[0029] Fig.11 It is a diagram for explaining the functional configuration of a user terminal according to the present embodiment. DETAILED DESCRIPTION

[0030] As mentioned above, in the unlicensed band, in order to coexist with LTE, Wi-Fi (registered trademark) or other systems of other operators, an interference control function is required. As an interference control function at the same frequency, a function called LBT (Listen Before Talk) based on CCA is installed in Wi-Fi. In Japan and Europe, the LBT function is required in systems such as Wi-Fi operating in the 5GHz unlicensed band.

[0031] Therefore, in systems that operate LTE / LTE-A in unlicensed bands (e.g., LAA systems), research is underway to apply monitoring before sending signals to control interference within the same frequency. It is assumed that in a carrier where monitoring is set, wireless base stations or user terminals in multiple systems share the same frequency band.

[0032] By applying monitoring, interference between LAA and Wi-Fi, interference between LAA systems, etc. can be avoided. In addition, even if each operator running the LAA system independently controls the user terminals that can be connected, interference can be reduced without monitoring the control content of each operator.

[0033] Here, monitoring refers to an operation in which a certain transmission point (e.g., a wireless base station, a user terminal, etc.) detects / measures whether a signal exceeding a specified level (e.g., a specified power) is transmitted from another transmission point, etc. before transmitting a signal. In addition, monitoring performed by a wireless base station and / or a user terminal is also referred to as LBT (Listen Before Talk), CCA (Clear Channel Assessment), carrier sensing, etc.

[0034] For example, when LBT is applied in an LTE system, a transmission point (LTE-U base station and / or user terminal) performs monitoring (LBT, CCA) before transmitting a UL signal and / or a DL signal in an unlicensed band. Then, if no signal from a transmission point of another system (e.g., Wi-Fi) or other LAA is detected, communication can be performed in the unlicensed band.

[0035] When the received power measured by LBT is below the specified threshold, the transmission point determines that the channel is idle (LBT-idle) and transmits. "The channel is idle" means that the channel is not occupied by a specific system, which is also called the channel is idle, the channel is clear, the channel is free, etc.

[0036] On the other hand, when the received power measured by LBT exceeds the specified threshold, the transmission point determines that the channel is in a busy state (LBT-busy) and restricts transmission. For example, when it is determined to be LBT-busy as a result of monitoring, the following processing is implemented: (1) Migrate to other carriers through DFS (Dynamic Frequency Selection); (2) Perform transmit power control (TPC); (3) Do not transmit (stop transmission or wait). In the case of LBT_busy, the channel can only be used after LBT is re-performed and it is confirmed that the channel is idle. In addition, the method for determining the idle state / busy state of a channel based on LBT is not limited to this.

[0037] For example, it is assumed that when a user terminal communicating using a carrier (also referred to as a frequency) in an unlicensed band detects other entities (other user terminals, etc.) communicating through the carrier in the unlicensed band, transmission in the carrier is prohibited. In this case, the user terminal performs LBT at a timing that is a specified period ahead of the transmission timing. The user terminal performing LBT searches the entire band of the target carrier at a timing that is a specified period ahead of the transmission timing, and confirms whether other devices (wireless base stations, LAA-UEs, Wi-Fi devices, etc.) are communicating in the band of the carrier. Only when it is confirmed that no communication is being performed, the carrier is used for transmission. On the other hand, even if other devices are detected to be in use in at least part of the band, that is, when the received power of the signal related to the band from other devices is detected to exceed the threshold, the user terminal terminates its own transmission. Here, when the received signal power during the LBT period is higher than the specified threshold, the channel is regarded as a busy state (LBT-busy). When the received signal power during the LBT period is lower than the specified threshold, the channel is regarded as an idle state (LBT-idle).

[0038] In addition, there are two types of LBT mechanisms: LBE (Load-Based Equipment) and FBE (Frame-Based Equipment). In LBE, the initial CCA is implemented, and if it is LBT-idle, the transmission starts, and if it is LBT-busy, the ECCA (Extended CCA) process is implemented. That is, LBE is a mechanism that, when the channel cannot be used as a result of carrier sensing, the carrier sensing time is extended until the channel can be used and the carrier sensing is continued. In LBE, random backoff is required to appropriately avoid conflicts.

[0039] In FBE, carrier sensing is performed at a fixed timing and a fixed cycle. If it is LBT-idle, transmission starts, and if it is LBT-busy, it waits until the next carrier sensing timing. In other words, FBE is a mechanism that has a fixed frame cycle, performs carrier sensing in a specified frame, and transmits if the channel can be used, but does not transmit and waits until the carrier sensing timing in the next frame if the channel cannot be used.

[0040] FIG1A is a diagram showing an example of a wireless frame structure in LBT, which shows an example of a wireless frame structure of FBE. In the case of FBE, the LBT time (LBT duration) and the LBT period are fixed, and LBT is performed with a specified number of symbols (e.g., 1 to 3 symbols) and period (e.g., every 1 ms). On the other hand, FIG1B shows an example of a wireless frame structure of LBE. In the case of LBE, the LBT time is not fixed. For example, the LBT symbol may continue until a specified condition is met. Specifically, the wireless base station may continue to implement LBT until LBT-idle is observed. In addition, the present embodiment can be applied directly to LBE using random backoff, but is not limited thereto.

[0041] When the result of DL-LBT monitoring performed by the wireless base station is LBT-idle, the wireless base station can be allowed to transmit a signal with LBT omitted for a predetermined period (see Figure 2 ). In a cell where monitoring is applied, the period during which transmission is possible without implementing LBT after monitoring (in the case of LBT-idle) is also referred to as a burst period (burst transmission period, burst length, maximum burst length, maximum allowed burst length, maximum burst length).

[0042] Thus, it is assumed that in an LTE / LTE-A system using an unlicensed band, monitoring is also performed before UL transmission and / or DL ​​transmission. In this case, efficient and fair coexistence with other systems (e.g., Wi-Fi) or other LTE operators and efficient frequency utilization are required.

[0043] In order to achieve fair coexistence with other systems (for example, Wi-Fi), it is considered that even when using the LTE / LTE-A system in the unlicensed band, a mechanism is adopted in which random backoff is applied during monitoring and the window size in the random backoff is set to be variable. Random backoff refers to the following mechanism: even when the channel becomes idle (idle state), each sending point does not start sending immediately, but sets the sending to standby during a randomly set period, and starts sending when the channel is idle (clear). In this way, the sending opportunities can be dispersed among multiple sending points to achieve fairness. The window size (also called contention window (CW: Contention Window)) in random backoff refers to the window size used to determine the range of the randomly set backoff period.

[0044] For example, when a channel in an unlicensed band is in use (busy state), each transmission point (access point) starts transmitting data when it determines that the channel is in an idle state (idle state) through monitoring. At this time, if multiple transmission points waiting for the idle state of the channel start transmitting at the same time, the possibility of collision between transmission points becomes high. Therefore, in order to suppress collision between transmission points, even when the channel becomes idle, each transmission point does not transmit immediately, but sets the transmission to standby during a randomly set period to suppress the probability of collision between transmission points (random backoff).

[0045] The backoff period set for each transmission point can be determined based on a randomly set counter value (random value). The range of the counter value is determined based on the contention window (CW) size, for example, the counter value is randomly set from 0 to the CW size (integer value).

[0046] Figure 3 An application example of random backoff. When the sending point determines that the channel is idle through CCA, it generates a counter value for random backoff. Then, the counter value is maintained until it is confirmed that the channel is idle for a specified period of time (also called a defer period (D_eCCA)). When it is confirmed that the channel is idle for a specified period of time, the sending point monitors for a specified time unit (for example, an eCCA time slot time unit), reduces the counter value when the channel is idle, and can send when the counter value becomes zero.

[0047] In random backoff, the counter value is determined from a range associated with the CW size. Figure 3 In the example, a random value from 1 to 16 is selected as the fallback period.

[0048] In Wi-Fi, the CW size is changed based on whether or not there is an ACK from the receiving side. For example, in UL transmission and DL transmission, if there is no ACK from the receiving side after a packet is sent from the transmission point, it is determined that a conflict has occurred at the transmission point and the CW size is increased. Figure 3 , it shows the case where the CW size is increased from 16 to 32 when there is no ACK feedback for packet transmission.

[0049] Even when the LTE system is used in the unlicensed band, it is considered that, similar to Wi-Fi, the transmission point (radio base station and / or user terminal) applies random backoff and controls by changing the CW size according to the presence or absence of ACK.

[0050] However, in Wi-Fi, basically one burst transmission is only directed to one terminal, whereas in LTE / LTE-A system (LAA), one burst transmission includes data directed to multiple user terminals. Thus, the inventors of the present invention have come up with the following point: In the LTE system, the difference from Wi-Fi is that for one burst transmission, a delivery confirmation signal (ACK / NACK) is fed back from multiple user terminals.

[0051] Therefore, when monitoring in the LTE system, if the CW size is changed based on the presence or absence of ACK feedback from one user terminal, as in Wi-Fi, the CW size may be unnecessarily increased. For example, even when data is properly transmitted to most user terminals, the CW size may be increased when data cannot be transmitted to a specific user terminal. If the CW size is unnecessarily increased, the standby time before signal transmission becomes longer, and there is a concern that frequency utilization efficiency is reduced or transmission opportunities are reduced.

[0052] In addition, in the LTE system, since retransmission control (HARQ) and the like are applied, the modulation / coding scheme (MCS) is usually set with a target block error rate (BLER) of 10% or the like. Therefore, NACK may be received even when there is no need to increase the CW size (such as collision). In this case, the possibility that the CW size may be unnecessarily increased is considered even when there is no collision problem.

[0053] Therefore, the present inventors have found that, when monitoring is applied in an LTE / LTE-A system (LAA), the CW size is controlled based on the number of ACKs and / or NACKs for data included in a transmission (e.g., burst transmission) after monitoring. For example, in LAA monitoring, the number of NACKs for data included in a burst transmission after monitoring is counted, and the CW size is controlled to be expanded when the counted number of NACKs exceeds a predetermined threshold.

[0054] This can suppress the loss of transmission opportunities and the reduction in frequency utilization efficiency caused by unnecessary expansion of the CW size. In addition, since the CW size can be adjusted based on appropriate conditions, fair coexistence with other systems can be achieved.

[0055] In addition, the threshold value can be determined by considering the number of users multiplexed during the period of counting the number of NACKs (or the number of ACKs), and the range of burst transmission during the period of counting the number of NACKs can be limited. Thus, the CW size can be appropriately changed according to the communication conditions. In addition, DTX can be included in the number of NACKs.

[0056] Hereinafter, the above-mentioned present embodiment is described in detail with reference to the accompanying drawings. In addition, in the present embodiment, a frequency carrier for which monitoring (LBT) is not set is described as an authorized band, and a carrier for which monitoring is set is described as an unlicensed band, but it is not limited thereto. As long as it is a frequency carrier (or cell) for which monitoring is set, the present embodiment can be applied to both the authorized band and the unlicensed band.

[0057] In addition, in the following description, the monitoring of DL transmission of a wireless base station is used as an example for description, but the present invention is not limited to this. As long as it is a transmission point (for example, a user terminal) to which monitoring is applied, the present embodiment can be applied. For example, the wireless base station in the following description can be replaced with a user terminal. In addition, in the following description, the case where monitoring is applied in an LTE / LTE-A system is described, but the present embodiment is not limited to this. As long as monitoring is applied before signal transmission and a system that feeds back multiple delivery confirmation signals (ACK / NACK) can be applied.

[0058] (First method)

[0059] In the first embodiment, the case where the CW size is controlled based on the number of NACKs for data included in the burst transmission after monitoring is described in detail. In addition, the number of NACKs may include DTX, and the CW size may be controlled based on the number of ACKs instead of the number of NACKs.

[0060] Figure 4 FIG. 1 is a diagram showing an example of DL transmission to which monitoring is applied. Figure 4In FIG. 1 , when the monitoring result is an idle state, a DL burst transmission of a maximum of 4 ms is set. The period of DL burst transmission is not limited to 4 ms and can be set appropriately.

[0061] In this embodiment, as parameters for controlling the change of CW size (counting the number of NACKs), the following can be set: (1) the number of subframes in a burst for counting the number of NACKs (L subframes); (2) the burst period for counting the number of NACKs (M bursts); and (3) the NACK number threshold (N) for determining the expansion of the CW size.

[0062] For example, suppose that the number of NACKs is counted in all subframes in a burst (here, L = 4 subframes), and the number of NACKs is counted in each burst transmission after monitoring (here, the burst period M = 1 burst). In this case, the wireless base station will count the number of NACKs for each burst transmission after LBT ( Figure 4 The number of NACKs for DL ​​data transmitted in each subframe of burst transmission #1 to #3 in the UE is counted, and when the counted number of NACKs exceeds a predetermined threshold, the CW size is extended.

[0063] When the CW size is extended, for example, it can be changed to twice the CW size before the extension. On the other hand, when the counted number of NACKs is below a predetermined threshold, the CW size is maintained. Alternatively, when the counted number of NACKs is below a predetermined threshold and the CW size is enlarged (for example, CW=16) from the initial value (for example, CW=8), the CW size can be reset and returned to the initial value.

[0064] Furthermore, the wireless base station can limit the period (target burst transmission) for counting the number of NACKs to a part of the burst transmissions instead of all the burst transmissions. Furthermore, the transmission time interval (TTI: Transmission Time Interval) (eg, subframe) within the burst transmission for which the number of NACKs is counted can be limited.

[0065] Figure 5A This indicates that the burst transmission for which the number of NACKs is counted is set to be every 2 cycles (burst cycle M=2) instead of every burst transmission. Figure 5B Indicates that it is further limited to Figure 5A In this way, by limiting the burst transmission or transmission time interval (for example, subframe) for counting the number of NACKs, the operation associated with the control of the CW size can be simplified.

[0066] in addition, Figure 5B The subframe in can be set to a transmission time interval (e.g., 1 ms) from the timing of starting transmission after LBT. Alternatively, when the user terminal is also connected to another cell (e.g., a licensed band), the subframe to be counted for the number of NACKs can be set based on the transmission time interval set synchronously with the licensed band.

[0067] In addition, the burst transmission cycle or the number of subframes for counting the number of NACKs is not limited to Figure 4 , Figure 5A , Figure 5B The following describes an example of a method for setting (1) the number of subframes in a burst for counting the number of NACKs (L subframes), (2) the burst period for counting the number of NACKs (M bursts), and (3) the NACK number threshold (N) for determining the expansion of the CW size.

[0068] (1) Number of subframes in a burst for counting the number of NACKs (L subframes)

[0069] The number of subframes for counting the number of NACKs can be set to 1 (L=1). In this case, since the period required for counting the number of NACKs is reduced, the determination operation of the CW size change can be simplified. Alternatively, the number of subframes L for counting the number of NACKs can be set to be greater than 1 (for example, all subframes in a burst transmission). In this case, the situation in which a large number of users fail to receive DL due to collisions can be more accurately understood.

[0070] The number of subframes may be set to a structure predefined according to the standard, or may be settable during communication. When the number of subframes is predefined according to the standard, it may be defined in association with (e.g., proportional to) the maximum burst length after monitoring, or may be set to a fixed value regardless of the maximum burst length.

[0071] When the user terminal controls the CW size in the monitoring before UL transmission, the wireless base station can notify the user terminal of the information related to the number of subframes as an LBT parameter. At this time, the wireless base station can set the information related to the number of subframes in the burst for counting the number of NACKs to the user terminal through high-layer signaling (for example, RRC signaling, broadcast signal, etc.). In addition, when the user terminal is also connected to the authorized band, the wireless base station can also notify the user terminal of the information related to the number of subframes via the authorized band.

[0072] (2) Burst cycle for counting the number of NACKs (M burst)

[0073] The burst period for counting the number of NACKs can be set to 1 (M=1). In this case, since the change of the CW size is determined based on the burst transmission after each monitoring, the change of the CW size can be flexibly performed. In addition, the burst period for counting the number of NACKs can also be set to a value greater than 1. In this case, since the burst transmission that becomes the object of the NACK number counting is reduced, the judgment operation of the CW size change can be simplified.

[0074] The burst period may be a structure predefined by the standard or settable during communication. When the burst period is predefined by the standard, it may be defined in association with the maximum burst length after monitoring or may be a fixed value regardless of the maximum burst length.

[0075] When the user terminal controls the CW size in the monitoring before UL transmission, the wireless base station can notify the user terminal of the information related to the burst period as an LBT parameter. At this time, the wireless base station can set the information related to the burst period for counting the number of NACKs to the user terminal through high-layer signaling (for example, RRC signaling, broadcast signal, etc.). In addition, when the user terminal is also connected to the authorized band, the wireless base station can also notify the user terminal of the information related to the burst period via the authorized band.

[0076] (3) Increase the NACK threshold (N) for the CW size

[0077] The threshold of the number of NACKs used to determine the expansion of the CW size can be set to 1 (N=1) or a value greater than 1. In addition, the threshold of the number of NACKs can be set to a structure predefined according to the standard or settable during communication. In the case where the threshold of the number of NACKs is predefined according to the standard, it can be defined in association with (for example, proportionally to) at least one of the number of transport blocks (TBs), the number of codewords (CWs), the number of user terminals, and the number of HARQ processes multiplexed during the period that becomes the object of the NACK number counting (burst transmission period). Thus, since the prescribed threshold (NACK number threshold) can be set according to the communication conditions, it is possible to suppress the CW size from being expanded unnecessarily.

[0078] Alternatively, it may be set to a fixed value regardless of the number of transport blocks (TBs), the number of code words (CWs), the number of user terminals, and the number of HARQ processes multiplexed in the period (burst transmission period) subject to NACK number counting.

[0079] When the user terminal controls the CW size in monitoring before UL transmission, the wireless base station can notify the user terminal of information related to the threshold value of the NACK number used to determine the expansion of the CW size as an LBT parameter. At this time, the wireless base station can set the information related to the threshold value of the NACK number to the user terminal through high-layer signaling (for example, RRC signaling, broadcast signal, etc.). In addition, when the user terminal is also connected to the authorized band, the wireless base station can also notify the user terminal of information related to the threshold value of the NACK number via the authorized band.

[0080] Alternatively, when the user terminal controls the CW size in monitoring before UL transmission, the wireless base station can directly specify the CW size. In this case, the wireless base station can set the information related to the CW size applied to the UL LBT to the user terminal through high-layer signaling (e.g., RRC signaling, broadcast signal, etc.). In addition, when the user terminal is also connected to the authorized band, the wireless base station can also notify the user terminal of the information related to the CW size via the authorized band.

[0081] (Second method)

[0082] In the second aspect, an example of a method of controlling the CW size in monitoring before DL transmission will be described. Figure 6 An example of monitoring operation in the second embodiment is shown. In addition, the following CW size control method can also be applied to UL LBT (user terminal).

[0083] When starting transmission from an idle state (for example, a state where the buffer of the wireless base station is empty) (ST101, ST102-Yes), an initial LBT (CCA) period B is performed. iCCA As the initial LBT (CCA) period B iCCA , for example, can be set to 34 μs. When the channel is empty (idle) as a result of sensing (ST103-Yes), DL transmission is performed (ST104).

[0084] When the channel is not empty (busy) in the initial CCA sensing (ST103-No), or when you want to start sending outside the idle state (for example, when there is other data to be sent after the data sending of ST104 (ST105-Yes), random backoff is applied in monitoring. Specifically, the wireless base station generates a random counter value (N) (ST106) in order to utilize the random backoff. The range of the random counter value (N) can be set to an integer value selected from 0 to CW size (q-1).

[0085] In addition, as shown in the first embodiment, the CW size (q) is changed (updated) based on the number of ACKs and / or NACKs for DL ​​transmission (DL burst transmission) in a predetermined period (ST107). After generating the counter value, the wireless base station confirms that the CW size (q) is changed (updated) based on the number of ACKs and / or NACKs for DL ​​transmission (DL burst transmission) in a predetermined period (ST107). eCCA )) When the channel is empty (ST108). As a predetermined period (delay period (defer period) (D eCCA )), for example, it can be set to 34μs. When it is confirmed that the channel is empty during the specified period (ST108-Yes), the wireless base station confirms whether the counter value is zero (ST109), and when the counter value (N) is zero (ST109-Yes), DL burst transmission is performed (ST104).

[0086] When the counter value (N) is not zero (ST109-No), the wireless base station performs sensing in extended CCA (eCCA) time slot period (T) units (ST110) and confirms the channel status (ST111). The extended CCA (eCCA) time slot period (T) can be set to 9μs or 10μs, for example. When the channel status is busy (ST111-Yes), the wireless base station confirms again that the channel status is busy within a specified period (delay period (defer period) (D eCCA ))The channel is empty (ST108).

[0087] When the channel state is idle (ST111-No), the counter value (N) is reduced by 1 (ST112). Until the counter value reaches zero, the sensing of the extended CCA (eCCA) time slot time (T) unit is continued (ST109-ST112), and when the counter value reaches zero (ST109-Yes), DL burst transmission is performed (ST104).

[0088] Thus, in the second method, the CW size used in the random backoff of monitoring is determined based on the number of ACKs and / or NACKs for DL ​​transmissions in a predetermined period. This can suppress the loss of transmission opportunities or the reduction of frequency utilization efficiency caused by unnecessary expansion of the CW size. In addition, since the CW size can be adjusted based on appropriate conditions, fair coexistence with other systems can be achieved.

[0089] (Structure of wireless communication system)

[0090] The following describes the structure of a wireless communication system according to an embodiment of the present invention. In this wireless communication system, a wireless communication method according to an embodiment of the present invention is applied. In addition, the wireless communication methods according to the above-mentioned embodiments can be applied individually or in combination.

[0091] Figure 7 1 is a diagram showing an example of a schematic configuration of a wireless communication system according to an embodiment of the present invention. Figure 7 The wireless communication system shown is, for example, a system including an LTE system, a super (SUPER) 3G, an LTE-A system, and the like. In the wireless communication system, carrier aggregation (CA) and / or dual connectivity (DC) that integrates multiple component carriers (CCs) can be applied. In addition, among the multiple CCs, there are licensed band CCs that utilize a licensed band and unlicensed band CCs that utilize an unlicensed band. In addition, the wireless communication system may be referred to as IMT-Advanced, or may be referred to as 4G, 5G, FRA (Future Radio Access), and the like.

[0092] Figure 7 The wireless communication system 1 shown includes a wireless base station 11 forming a macro cell C1 and wireless base stations 12 (12a-12c) arranged in the macro cell C1 and forming small cells C2 narrower than the macro cell C1. In addition, user terminals 20 are arranged in the macro cell C1 and each small cell C2.

[0093] The user terminal 20 can connect to both the radio base station 11 and the radio base station 12. It is assumed that the user terminal 20 uses the macro cell C1 and the small cell C2 using different frequencies simultaneously through CA or DC. In addition, the user terminal 20 can apply CA using at least two CCs (cells) and can also use six or more CCs.

[0094] Between the user terminal 20 and the wireless base station 11, a carrier with a narrow bandwidth (referred to as an existing carrier, a legacy carrier, etc.) can be used for communication in a relatively low frequency band (e.g., 2 GHz). On the other hand, between the user terminal 20 and the wireless base station 12, a carrier with a wide bandwidth can be used in a relatively high frequency band (e.g., 3.5 GHz, 5 GHz, etc.), or the same carrier as that between the wireless base station 11 can be used. Between the wireless base station 11 and the wireless base station 12 (or between two wireless base stations 12), a wired connection (optical fiber, X2 interface, etc.) or a wireless connection can be set.

[0095] The wireless base station 11 and each wireless base station 12 are respectively connected to the upper station device 30, and connected to the core network 40 via the upper station device 30. In addition, the upper station device 30 includes, for example, an access gateway device, a radio network controller (RNC), a mobility management entity (MME), etc., but is not limited thereto. In addition, each wireless base station 12 can also be connected to the upper station device 30 via the wireless base station 11.

[0096] In addition, the wireless base station 11 is a wireless base station with a relatively wide coverage range, and may also be referred to as a macro base station, a convergence node, an eNB (eNodeB), a transmission and reception point, etc. In addition, the wireless base station 12 is a wireless base station with a local coverage range, and may also be referred to as a small base station, a micro base station, a pico base station, a femto base station, HeNB (Home eNodeB), RRH (Remote Radio Head), a transmission and reception point, etc. Hereinafter, when the wireless base stations 11 and 12 are not distinguished, they are collectively referred to as wireless base stations 10. Each user terminal 20 is a terminal that supports various communication methods such as LTE and LTE-A, and may include not only mobile communication terminals but also fixed communication terminals.

[0097] In a wireless communication system, OFDMA (Orthogonal Frequency Division Multiple Access) is applied to the downlink and SC-FDMA (Single Carrier Frequency Division Multiple Access) is applied to the uplink as a wireless access method. OFDMA is a multi-carrier transmission method that divides the frequency band into multiple narrow frequency bands (subcarriers) and maps data to each subcarrier for communication. SC-FDMA is a single-carrier transmission method that divides the system bandwidth into bands consisting of one or continuous resource blocks for each terminal, and multiple terminals use different bands to reduce interference between terminals. In addition, the wireless access methods for uplink and downlink are not limited to these combinations.

[0098] In the wireless communication system 1, as downlink channels, a downlink shared channel (physical downlink shared channel (PDSCH: Physical Downlink Shared Channel)), a broadcast channel (physical broadcast channel (PBCH: Physical Broadcast Channel)), a downlink L1 / L2 control channel, etc., which are shared by each user terminal 20, are used. User data or high-layer control information, and a specified SIB (System Information Block) are transmitted through the PDSCH. In addition, the MIB (Master Information Block) and the like are transmitted through the PBCH.

[0099] Downlink L1 / L2 control channels include PDCCH (Physical Downlink Control Channel), EPDCCH (Enhanced Physical Downlink Control Channel), PCFICH (Physical Control Format Indicator Channel), PHICH (Physical Hybrid-ARQ Indicator Channel), etc. Downlink control information (DCI: Downlink Control Information) including scheduling information of PDSCH and PUSCH is transmitted through PDCCH. The number of OFDM codewords used for PDCCH is transmitted through PCFICH. The delivery confirmation signal (ACK / NACK) for HARQ of PUSCH is transmitted through PHICH. EPDCCH is frequency-division multiplexed with PDSCH (downlink shared data channel) and is used to transmit DCI, etc. in the same way as PDCCH.

[0100] In addition, the downlink reference signals include a cell-specific reference signal (CRS), a reference signal for channel state measurement (Channel State Information-Reference Signal (CSI-RS)), a user-specific reference signal used for demodulation (Demodulation Reference Signal (DM-RS)), etc.

[0101] In the wireless communication system 1, as uplink channels, an uplink shared channel (physical uplink shared channel (PUSCH: Physical Uplink Shared Channel)), an uplink control channel (physical uplink control channel (PUCCH: Physical Uplink Control Channel)), a random access channel (physical random access channel (PRACH: Physical Random Access Channel)), etc., which are shared by each user terminal 20, are used. User data or high-layer control information is transmitted through the PUSCH. In addition, downlink wireless quality information (channel quality indicator (CQI: Channel Quality Indicator)), a delivery confirmation signal (HARQ-ACK), etc. are transmitted through the PUCCH. A random access preamble (RA preamble) for establishing a connection with a cell is transmitted through the PRACH.

[0102] <Wireless base station>

[0103] Figure 8 1 is a diagram showing an example of the overall structure of a wireless base station according to an embodiment of the present invention. The wireless base station 10 includes a plurality of transmitting and receiving antennas 101, an amplifier unit 102, a transmitting and receiving unit 103, a baseband signal processing unit 104, a call processing unit 105, and a transmission path interface 106. In addition, the transmitting and receiving unit 103 is composed of a transmitting unit and a receiving unit.

[0104] User data transmitted from the radio base station 10 to the user terminal 20 via the downlink is input from the upper station apparatus 30 to the baseband signal processing unit 104 via the transmission path interface 106 .

[0105] In the baseband signal processing unit 104, for user data, transmission processing such as PDCP (Packet Data Convergence Protocol) layer processing, user data segmentation / combination, RLC (Radio Link Control) retransmission control and other RLC layer transmission processing, MAC (Medium Access Control) retransmission control (for example, HARQ (Hybrid Automatic Repeat reQuest) transmission processing), scheduling, transmission format selection, channel coding, inverse fast Fourier transform (IFFT: Inverse Fast Fourier Transform) processing, precoding processing, etc. are performed, and the data is transferred to the transmission and reception unit 103. In addition, for downlink control signals, transmission processing such as channel coding and inverse fast Fourier transform is also performed, and the data is transferred to each transmission and reception unit 103.

[0106] Each transmitting / receiving unit 103 converts the baseband signal pre-coded and outputted from the baseband signal processing unit 104 for each antenna into a radio frequency band and transmits it. The radio frequency signal frequency-converted in the transmitting / receiving unit 103 is amplified by the amplifier unit 102 and transmitted from the transmitting / receiving antenna 101.

[0107] On the other hand, regarding uplink signals, the radio frequency signals received by the respective transmitting / receiving antennas 101 are amplified by the amplifier units 102. Each transmitting / receiving unit 103 receives the uplink signals amplified by the amplifier units 102. The transmitting / receiving unit 103 converts the frequency of the received signals into baseband signals, and outputs the signals to the baseband signal processing unit 104.

[0108] For example, the transmitting and receiving unit (receiving unit) 103 receives a delivery confirmation signal (ACK / NACK) for DL ​​transmission. In addition, the transmitting and receiving unit (transmitting unit) 103 can notify the user terminal of at least any one of information related to the number of subframes in the UL burst transmission for counting the number of NACKs for UL transmission, information related to the UL burst transmission period for counting the number of NACKs for UL transmission, information related to a prescribed threshold for comparison with the count number of NACKs for UL transmission, and information related to the contention window size applied in monitoring before UL transmission. In addition, when the result of DL-LBT implemented before sending the DL signal is LBT-idle, the transmitting and receiving unit 103 can send the DL signal in the unlicensed band. In addition, the transmitting and receiving unit 103 can be set to a transmitter / receiver, a transmitting and receiving circuit, or a transmitting and receiving device described based on the common understanding in the technical field of the present invention.

[0109] In the baseband signal processing unit 104, the user data included in the input uplink signal is subjected to fast Fourier transform (FFT) processing, inverse discrete Fourier transform (IDFT) processing, error correction decoding, MAC retransmission control reception processing, RLC layer, and PDCP layer reception processing, and is forwarded to the upper station device 30 via the transmission path interface 106. The call processing unit 105 performs call processing such as setting or releasing a communication channel, state management of the wireless base station 10, and management of wireless resources.

[0110] The transmission path interface 106 transmits and receives signals via a predetermined interface with the host station device 30. In addition, the transmission path interface 106 may transmit and receive (backhaul signaling) signals with the adjacent wireless base station 10 via an inter-base station interface (eg, optical fiber, X2 interface).

[0111] Fig. 9 is a diagram showing an example of a functional configuration of a wireless base station according to this embodiment. Fig. 9 The functional blocks of the characteristic parts of this embodiment are mainly shown, and it is assumed that the wireless base station 10 also has other functional blocks required for wireless communication. Fig. 9 As shown, the baseband signal processing unit 104 includes a control unit (scheduler) 301 , a transmission signal generating unit (generating unit) 302 , a mapping unit 303 , a reception signal processing unit 304 , and a measuring unit 305 .

[0112] The control unit (scheduler) 301 controls the scheduling (e.g., resource allocation) of downlink data sent in PDSCH and downlink control information transmitted in PDCCH and / or EPDCCH. In addition, it also controls the scheduling of system information, synchronization signal, paging information, CRS, CSI-RS, etc.

[0113] The control unit 301 controls scheduling of uplink reference signals, uplink data signals transmitted in PUSCH, uplink control signals transmitted in PUCCH and / or PUSCH, random access preambles transmitted in PRACH, etc. In addition, the control unit 301 controls transmission of DL signals based on monitoring (DL LBT) results.

[0114] When DL LBT is performed, the control unit 301 can control the CW size applied to monitoring based on the number of ACKs and / or NACKs for DL ​​transmission (e.g., DL burst transmission) during a specified period. For example, when the number of NACKs for DL ​​transmission included in the entire period or a portion of a burst transmission after monitoring is greater than a specified threshold, the control unit 301 can change the CW size. A portion of the period in the burst transmission can be set to a specified transmission time interval (e.g., a subframe).

[0115] In addition, when the number of NACKs of DL transmission included in a part of the burst transmissions sent after each monitoring is greater than a predetermined threshold, the control unit 301 can change the CW size. In addition, the control unit 301 can set the predetermined threshold based on the value of at least one of the number of transport blocks, the number of codewords, the number of user terminals, and the number of HARQ processes multiplexed during the DL transmission period for counting the number of NACKs.

[0116] Furthermore, when the number of NACKs transmitted for a predetermined period of DL is less than a predetermined threshold, control unit 301 can maintain or reset the CW size to an initial value. Control unit 301 can be a controller, control circuit, or control device described based on common knowledge in the technical field of the present invention.

[0117] The transmission signal generating unit 302 generates a DL signal based on an instruction from the control unit 301, and outputs it to the mapping unit 303. For example, the transmission signal generating unit 302 generates a DL allocation for notifying allocation information of a downlink signal and a UL grant for notifying allocation information of an uplink signal based on an instruction from the control unit 301. In addition, the transmission signal generating unit 302 can include information related to LBT for UL transmission in the DL signal transmitted in the unlicensed band. In addition, the transmission signal generating unit 302 can include information related to whether UL-LBT is applied in the UL grant. In addition, the transmission signal generating unit 302 can be set to a signal generator, a signal generating circuit, or a signal generating device explained based on the common understanding in the technical field of the present invention.

[0118] Based on the instruction from the control unit 301, the mapping unit 303 maps the downlink signal generated in the transmission signal generation unit 302 to a predetermined wireless resource and outputs it to the transmission and reception unit 103. In addition, the mapping unit 303 can be set to a mapper, a mapping circuit or a mapping device explained based on the common knowledge in the technical field of the present invention.

[0119] The reception signal processing unit 304 performs reception processing (e.g., demapping, demodulation, decoding, etc.) on the UL signal (e.g., a delivery confirmation signal (HARQ-ACK), a data signal transmitted in the PUSCH, etc.) transmitted from the user terminal. The processing result is output to the control unit 301. The reception signal processing unit 304 can be composed of a signal processor, a signal processing circuit, or a signal processing device explained based on the common knowledge in the technical field of the present invention.

[0120] The measurement unit 305 can use the received signal to measure the received power (for example, RSRP (Reference Signal Received Power)), the received quality (RSRQ (Reference Signal Received Quality)) or the channel state, etc. In addition, the measurement unit 305 can measure the received power of the signal transmitted from other systems, etc. in the monitoring performed before the transmission of the DL signal in the unlicensed band. The result measured in the measurement unit 305 is output to the control unit 301. The control unit 301 can control the transmission of the DL signal based on the measurement result (monitoring result) of the measurement unit 305.

[0121] The measuring unit 305 can be formed of a measuring device, a measuring circuit, or a measuring apparatus that will be described based on common knowledge in the technical field of the present invention.

[0122] <User terminal>

[0123] Fig.10 2 is a diagram showing an example of the overall structure of a user terminal according to the present embodiment. The user terminal 20 includes a plurality of transmitting and receiving antennas 201 for MIMO transmission, an amplifier unit 202, a transmitting and receiving unit 203, a baseband signal processing unit 204, and an application unit 205. In addition, the transmitting and receiving unit 203 may be composed of a transmitting unit and a receiving unit.

[0124] The radio frequency signals received by the plurality of transmitting and receiving antennas 201 are amplified by amplifier units 202. Each transmitting and receiving unit 203 receives the downlink signal amplified by amplifier unit 202. Transmitting and receiving unit 203 converts the received signal into a baseband signal and outputs it to baseband signal processing unit 204.

[0125] The transmitting and receiving unit (receiving unit) 203 is capable of receiving a DL signal (e.g., UL grant) indicating UL transmission in an unlicensed band, or a delivery confirmation signal (ACK / NACK) for UL transmission. In addition, the transmitting and receiving unit (receiving unit) 203 is capable of receiving at least one of information related to the number of subframes in a UL burst transmission for counting the number of NACKs for UL transmission, information related to a UL burst transmission period for counting the number of NACKs for UL transmission, information related to a predetermined threshold for comparison with the count number of NACKs for UL transmission, and information related to a contention window size applied in monitoring before UL transmission. In addition, the transmitting and receiving unit 203 can be set to a transmitter / receiver, a transmitting and receiving circuit, or a transmitting and receiving device explained based on the common understanding in the technical field of the present invention.

[0126] The baseband signal processing unit 204 performs FFT processing, error correction decoding, reception processing of retransmission control, etc. on the input baseband signal. The downlink user data is forwarded to the application unit 205. The application unit 205 performs processing related to a layer higher than the physical layer or the MAC layer, etc. In addition, in the downlink data, broadcast information is also forwarded to the application unit 205.

[0127] On the other hand, uplink user data is input from the application unit 205 to the baseband signal processing unit 204. In the baseband signal processing unit 204, transmission processing of retransmission control (for example, transmission processing of HARQ), channel coding, precoding, discrete Fourier transform (DFT: Discrete Fourier Transform) processing, IFFT processing, etc. are performed, and the baseband signal is forwarded to each transmission and reception unit 203. The transmission and reception unit 203 converts the baseband signal output from the baseband signal processing unit 204 into a radio frequency band and transmits it. The radio frequency signal subjected to frequency conversion in the transmission and reception unit 203 is amplified in the amplifier unit 202 and transmitted from the transmission and reception antenna 201.

[0128] Fig.11 is a diagram showing an example of a functional configuration of a user terminal according to the present embodiment. Fig.11 In FIG. 1 , the functional blocks of the characteristic parts of the present embodiment are mainly shown, and it is assumed that the user terminal 20 also has other functional blocks required for wireless communication. Fig.11 As shown, the baseband signal processing unit 204 of the user terminal 20 includes a control unit 401 , a transmission signal generating unit 402 , a mapping unit 403 , a reception signal processing unit 404 , and a measuring unit 405 .

[0129] The control unit 401 can control the transmission signal generating unit 402, the mapping unit 403, and the reception signal processing unit 404. For example, the control unit 401 obtains the downlink control signal (signal transmitted in the PDCCH / EPDCCH) and the downlink data signal (signal transmitted in the PDSCH) transmitted from the wireless base station 10 from the reception signal processing unit 404. The control unit 401 controls the generation / transmission (UL transmission) of the uplink control signal (for example, HARQ-ACK, etc.) or the uplink data based on the downlink control information (UL grant) or the result of determining whether the retransmission control of the downlink data is required. In addition, the control unit 401 controls the transmission of the UL signal based on the monitoring (UL LBT) result.

[0130] When UL LBT is performed, the control unit 401 can control the CW size applied to monitoring based on the number of ACKs and / or NACKs for UL transmission (e.g., UL burst transmission) during a specified period. For example, when the number of NACKs for UL transmission included in the entire period or a portion of a burst transmission after monitoring is greater than a specified threshold, the control unit 401 can change the CW size. A portion of the period in the burst transmission can be set to a specified transmission time interval (e.g., a subframe).

[0131] In addition, when the number of NACKs for UL transmissions included in a portion of burst transmissions sent after each monitoring is greater than a predetermined threshold, the control unit 401 can change the CW size. In addition, when the number of NACKs for UL transmissions during a predetermined period is less than a predetermined threshold, the control unit 301 can maintain or reset the CW size and change it to an initial value. In addition, the control unit 401 can be a controller, a control circuit, or a control device described based on the common knowledge in the technical field of the present invention.

[0132] The transmission signal generating unit 402 generates a UL signal based on the instruction from the control unit 401, and outputs it to the mapping unit 403. For example, the transmission signal generating unit 402 generates an uplink control signal such as a delivery confirmation signal (HARQ-ACK) or channel state information (CSI) corresponding to the DL signal based on the instruction from the control unit 401.

[0133] In addition, the transmission signal generating unit 402 generates an uplink data signal based on an instruction from the control unit 401. For example, when the downlink control signal notified from the wireless base station 10 includes a UL grant, the transmission signal generating unit 402 is instructed by the control unit 401 to generate an uplink data signal. The transmission signal generating unit 402 can be a signal generator, a signal generating circuit, or a signal generating device explained based on the common knowledge in the technical field of the present invention.

[0134] Based on the instruction from the control unit 401, the mapping unit 403 maps the uplink signal (uplink control signal and / or uplink data) generated in the transmission signal generation unit 402 to the wireless resource, and outputs it to the transmission and reception unit 203. The mapping unit 403 can be set to a mapper, a mapping circuit or a mapping device explained based on the common understanding in the technical field of the present invention.

[0135] The reception signal processing unit 404 performs reception processing (e.g., demapping, demodulation, decoding, etc.) on DL signals (e.g., downlink control signals sent from the wireless base station in PDCCH / EPDCCH, downlink data signals sent in PDSCH, etc.). The reception signal processing unit 404 outputs the information received from the wireless base station 10 to the control unit 401 and the measurement unit 405. In addition, the reception signal processing unit 404 can be composed of a signal processor, a signal processing circuit, or a signal processing device explained based on the common understanding in the technical field of the present invention. In addition, the reception signal processing unit 404 can constitute the receiving unit of the present invention.

[0136] In addition, the measurement unit 405 can use the received signal to measure the received power (e.g., RSRP (Reference Signal Received Power)), the received quality (RSRQ (Reference Signal Received Quality)) or the channel state, etc. In addition, in the monitoring performed before the transmission of the UL signal in the unlicensed band, the measurement unit 405 can measure the received power of the signal transmitted from other systems, etc. The result measured in the measurement unit 405 is output to the control unit 401. The control unit 401 can control the transmission of the UL signal based on the measurement result (monitoring result) of the measurement unit 405.

[0137] The measuring unit 405 can be formed of a measuring device, a measuring circuit, or a measuring apparatus that will be described based on common knowledge in the technical field of the present invention.

[0138] In addition, the block diagram used in the description of the above-mentioned embodiment represents a block of a functional unit. These functional blocks (structural units) are implemented by any combination of hardware and software. In addition, the implementation means of each functional block is not particularly limited. That is, each functional block can be implemented by a physically combined device, or two or more physically separated devices can be connected using wired or wireless, and implemented by these multiple devices.

[0139] For example, part or all of the functions of the wireless base station 10 or the user terminal 20 can be implemented using hardware such as ASIC (Application Specific Integrated Circuit), PLD (Programmable Logic Device), FPGA (Field Programmable Gate Array), etc. In addition, the wireless base station 10 or the user terminal 20 can be implemented by a computer device including a processor (central processing unit (CPU: Central Processing Unit)), a communication interface for network connection, a memory, and a computer-readable storage medium that stores a program. That is, the wireless base station, user terminal, etc. of one embodiment of the present invention can function as a computer that performs processing of the wireless communication method of the present invention.

[0140] Here, the processor or memory is connected via a bus for information communication. In addition, computer-readable recording media include storage media such as floppy disks, optical magnetic disks, ROM (Read Only Memory), EPROM (Erasable Programmable ROM), CD-ROM (Compact Disc ROM), RAM (Random Access Memory), and hard disks. In addition, the program can be sent from the network via an electrical communication line. In addition, the wireless base station 10 or the user terminal 20 may include an input device such as an input key, or an output device such as a display.

[0141] The functional configuration of the wireless base station 10 and the user terminal 20 may be implemented by the above-mentioned hardware, by a software module executed by a processor, or by a combination of the two. The processor controls the entire user terminal by operating an operating system. In addition, the processor reads a program, a software module, or data from a storage medium to a memory, and performs various processes based on the program, the software module, or the data.

[0142] Here, the program may be any program that causes a computer to execute each operation described in each of the above embodiments. For example, the control unit 401 of the user terminal 20 may be implemented by a control program stored in a memory and executed in a processor, and other functional blocks may be implemented similarly.

[0143] In addition, software, commands, etc. may be sent and received via a transmission medium. For example, where the software is sent from a website, server, or other remote source using wired technologies such as coaxial cable, fiber optic cable, twisted pair, and digital subscriber line (DSL) and / or wireless technologies such as infrared, wireless, and microwave, these wired technologies and / or wireless technologies are included in the definition of transmission medium.

[0144] In addition, the terms described in this specification and / or the terms required for understanding of this specification can be replaced with terms having the same or similar meanings. For example, a channel and / or a code element can be a signal (signaling). In addition, a signal can be a message. In addition, a component carrier (CC) can also be referred to as a carrier frequency, a cell, etc.

[0145] In addition, the information, parameters, etc. described in this specification may be represented by absolute values, relative values ​​relative to a specified value, or other corresponding information. For example, wireless resources may also be indicated by indexes.

[0146] Information, signals, etc. described in this specification may be represented using any of a variety of different techniques. For example, data, commands, instructions, information, signals, bits, symbols, chips, etc. mentioned throughout the above description may be represented by voltage, current, electromagnetic waves, magnetic fields or magnetic particles, light fields or photons, or any combination thereof.

[0147] Each method / implementation method described in this specification may be used alone or in combination, or may be switched during execution. In addition, notification of specified information (e.g., notification of "is X") is not limited to being performed explicitly, but may also be performed implicitly (e.g., by not notifying the specified information).

[0148] The notification of information is not limited to the method / implementation method described in this specification, and may be performed by other methods. For example, the notification of information may be implemented through physical layer signaling (e.g., DCI (Downlink Control Information), UCI (Uplink Control Information)), high-layer signaling (e.g., RRC (Radio Resource Control) signaling, MAC (Medium Access Control) signaling, broadcast information (MIB (Master Information Block), SIB (System Information Block)), other signals or a combination thereof. In addition, RRC signaling may be referred to as an RRC message, for example, an RRC Connection Setup message, an RRC Connection Reconfiguration message, and the like.

[0149] The various methods / implementations described in this specification can be applied to systems utilizing LTE (Long Term Evolution), LTE-A (LTE-Advanced), Super 3G, IMT-Advanced, 4G, 5G, FRA (Future Radio Access), CDMA2000, UMB (Ultra Mobile Broadband), IEEE802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, UWB (Ultra-WideBand), Bluetooth (registered trademark), and other suitable systems and / or next-generation systems expanded upon them.

[0150] The processing procedures, timings, flow charts, etc. of each method / implementation described in this specification may be interchanged as long as they are not contradictory. For example, regarding the method described in this specification, the elements of various steps are presented in the order of illustration and are not limited to the specific order presented.

[0151] The present invention has been described in detail above, but it is obvious to those skilled in the art that the present invention is not limited to the embodiments described in this specification. The present invention can be implemented as a modification and variation without departing from the purpose and scope of the present invention as determined by the description of the claims. Therefore, the description of this specification is for the purpose of illustration and does not have any restrictive meaning to the present invention.

[0152] This application is based on Japanese Patent Application No. 2015-155361 filed on August 5, 2015, the entire contents of which are expressly incorporated herein by reference.

Claims

1. A wireless base station, characterized in that: have: A sending unit, sending a DL signal; a control unit for controlling DL transmission by applying monitoring before transmitting a DL signal; and The receiving unit receives a delivery confirmation signal, i.e., ACK / NACK, for DL ​​transmission. The control unit controls a contention window size used for monitoring based on the number of ACKs for DL ​​transmission in a predetermined period and the number of codewords and transport blocks for performing the DL transmission, The control unit increases the contention window size when the number of ACKs for DL ​​transmission in the predetermined period is smaller than a predetermined threshold value set according to the number of codewords and the number of transport blocks.

2. The wireless base station according to claim 1, wherein: The predetermined period is a predetermined subframe.

3. The wireless base station according to claim 1, wherein: When the number of ACKs for DL ​​transmission in the predetermined period is equal to or larger than a predetermined threshold, the control unit maintains the contention window size or changes the contention window size to an initial value.

4. A wireless communication method, characterized in that: have: Applying monitoring before sending a signal to control the sending step; The step of sending when the monitoring result meets the specified conditions; as well as The step of receiving a transmission confirmation signal, i.e., ACK / NACK, controlling a contention window size applied to the monitoring based on the number of ACKs for transmissions during a predetermined period and the number of codewords and transport blocks used for the transmissions, When the number of ACKs for DL ​​transmission in the predetermined period is less than a predetermined threshold value set according to the number of codewords and the number of transport blocks, the contention window size is increased.

5. A wireless communication system comprising a wireless base station and a terminal, characterized in that: The wireless base station has: A sending unit, sending a DL signal; a control unit for controlling DL transmission by applying monitoring before transmitting a DL signal; and The receiving unit receives a delivery confirmation signal, i.e., ACK / NACK, for DL ​​transmission. The control unit controls a contention window size used for monitoring based on the number of ACKs for DL ​​transmission in a predetermined period and the number of codewords and transport blocks for performing the DL transmission, When the number of ACKs transmitted for the DL in the predetermined period is less than a predetermined threshold value set according to the number of codewords and the number of transport blocks, the control unit increases the contention window size, The terminal has: a receiving unit, receiving the DL signal; and The sending unit sends the ACK / NACK.

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