Patent Publication Number: US-2021176736-A1

Title: User terminal, radio base station, and radio communication method

Description:
TECHNICAL FIELD 
     The present invention relates to a user terminal, a radio base station, and a radio communication method in a next generation mobile communication system. 
     BACKGROUND ART 
     In Universal Mobile Telecommunications System (UMTS) networks, for the purpose of higher data rates, low latency, and the like, Long Term Evolution (LTE) has been specified (Non-Patent Literature 1). For the purpose of achieving further broadbandization and increased speed beyond LTE (in other words, LTE Rel.8 or 9), LTE-A (in other words, LTE-ADVANCED, LTE Rel.10, 11, or 12) is specified, and a succeeding system of the LTE (in other words, for example, Future Radio Access (FRA), 5th generation mobile communication system (5G), and LTE Rel.13) is also examined. 
     The LTEs Rel. 8 to 12 have been specified assuming exclusive operations in a frequency band (in other words, a licensed band) licensed to a telecommunication carrier (operator). For example, 800 MHz, 1.7 GHz, and 2 GHz are used as the licensed band. 
     Recently, a spread of sophisticated user terminals (UE: User Equipment), such as a smart phone and a tablet, has rapidly increased a user traffic. To absorb the increasing user traffic, further addition of frequency bands has been requested. However, a spectrum of the licensed band (licensed spectrum) has a limit. 
     In view of this, with the Rel.13 LTE, there has been examined an extension of a frequency in the LTE system using a band of an unlicensed spectrum (in other words, an unlicensed band) usable in addition to the licensed band (Non-Patent Literature 2). For example, a use of 2.4 GHz-band and 5 GHz-band in which Wi-Fi (registered trademark) and Bluetooth (registered trademark) are usable as the unlicensed band has been examined. 
     Specifically, performing a Carrier Aggregation (CA) between the licensed band and the unlicensed band has been examined in the Rel.13 LTE. Thus, communications using both the licensed band and the unlicensed band are referred to as a License-Assisted Access (LAA). In the future, Dual Connectivity (DC) with the licensed band and the unlicensed band and Stand-Alone (SA) with the unlicensed band are possibly a target for examination of the LAA. 
     CITATION LIST 
     Non-Patent Literature 
     Non-Patent Literature 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” 
     Non-Patent Literature 2: AT&amp;T, “Drivers, Benefits and Challenges for LTE in Unlicensed Spectrum,” 3GPP TSG RAN Meeting #62 RP-131701 
     SUMMARY OF INVENTION 
     Technical Problem 
     An Uplink (UL) transmission in a licensed band applies a clustered Single Carrier Frequency Division Multiple Access (SC-FDMA) that employs a resource block (Physical Resource Block (PRB)) as an allocation unit and allocates clusters, which are one or more consecutive PRBs, to a user terminal. Clustered SC-FDMA in the licensed band supports a single cluster allocation, which allocates a single cluster, and a dual cluster allocation, which allocates two clusters. 
     Meanwhile, it is assumed that the uplink transmission in an unlicensed band has a property different from the uplink transmission in the licensed band, for example, a minimum transmission bandwidth of the user terminal is restricted to equal to or more than a predetermined bandwidth. Accordingly, an application of an allocation method for an uplink resource in the licensed band to the unlicensed band without a change possibly fails to appropriately execute the uplink transmission in the unlicensed band. 
     The present invention has been made in consideration of this point, and an object of the present invention is to provide a user terminal, a radio base station, and a radio communication method that can execute the uplink transmission using the allocation method for the uplink resource suitable for a cell (for example, a cell in the unlicensed band) to which listening is applied before the transmission. 
     Solution to Problem 
     A user terminal according to one aspect of the present invention is a user terminal in a cell to which listening is executed before transmission. The user terminal includes a receiving section, a control section, and a transmitting section. The receiving section is configured to receive downlink control information. The downlink control information includes allocation information for an uplink resource allocated by any one of a first allocation method and a second allocation method. The first allocation method is configured to allocate a single cluster to the user terminal. The second allocation method is configured to allocate a transmission unit to the user terminal. The transmission unit is constituted of a plurality of clusters uniformly arranged in a frequency direction. The control section is configured to determine the uplink resource based on the allocation information. The transmitting section is configured to transmit an uplink shared channel using the uplink resource. 
     Advantageous Effects of Invention 
     With the present invention, an uplink transmission can be executed using an allocation method for the uplink resource suitable for a cell (for example, a cell in an unlicensed band) to which listening is applied before the transmission. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIGS. 1A and 1B  are drawings illustrating an exemplary allocation of an uplink resource. 
         FIG. 2  is a drawing illustrating an exemplary interlaced multi-cluster allocation. 
         FIG. 3  is a drawing illustrating a notification example of an allocation resource by the interlaced multi-cluster allocation according to a first aspect. 
         FIGS. 4A and 4B  are drawings illustrating restriction examples of parameters regarding a transmission bandwidth (total transmission bandwidth) of a user terminal according to a second aspect. 
         FIG. 5  is a drawing illustrating an exemplary multi sub-frame scheduling according to the second aspect. 
         FIG. 6  is a drawing illustrating an exemplary listening according to a third aspect. 
         FIG. 7  is a drawing illustrating an exemplary schematic constitution of a radio communication system according to an embodiment. 
         FIG. 8  is a drawing illustrating an exemplary overall constitution of a radio base station according to the embodiment. 
         FIG. 9  is a drawing illustrating an exemplary function constitution of the radio base station according to the embodiment. 
         FIG. 10  is a drawing illustrating an exemplary overall constitution of a user terminal according to the embodiment. 
         FIG. 11  is a drawing illustrating an exemplary function constitution of the user terminal according to the embodiment. 
         FIG. 12  is a drawing illustrating an exemplary hardware constitution of the radio base station and the user terminal according to the embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     It is considered that a system that operates LTE/LTE-A in an unlicensed band (for example, an LAA system) requires an interference control function for coexistence with the LTE, Wi-Fi, or another system of another carrier. The system that operates the LTE/LTE-A in the unlicensed band may be collectively referred to as, for example, LAA, LAA-LTE, LTE-U, and U-LTE, regardless of an operation form any of CA, DC, or SA. 
     Generally, a transmission point (for example, a radio base station (eNB) and the user terminal (UE)) that performs communications using a carrier of the unlicensed band (may be referred to as a carrier frequency or simply referred to as a frequency) is inhibited to perform a transmission in this carrier in the case where another entity (for example, another user terminal) that performs communications in the carrier of this unlicensed band is detected. 
     In view of this, the transmission point executes a listening (Listen Before Talk (LBT)) at a timing before a predetermined period from a transmission timing. Specifically, the transmission point that executes the LBT searches for a target entire carrier band (for example, one Component Carrier (CC)) at the timing before the predetermined period from the transmission timing to confirm whether other apparatuses (for example, the radio base stations, the user terminals, and Wi-Fi apparatuses) perform communications in this carrier band. 
     In this description, the listening means an operation to detect/measure whether other transmission points or similar points transmit signals exceeding a predetermined level (for example, a predetermined electric power) before a certain transmission point (for example, the radio base station and the user terminal) transmits a signal. The listening executed by the radio base station and/or the user terminal may referred to as, for example, LBT, a Clear Channel Assessment (CCA), and a carrier sense. 
     When the transmission point can confirm that the other apparatuses do not perform the communications, the transmission point executes the transmission using this carrier. For example, in the case where a received electric power measured by the LBT (a received signal electric power during the LBT period) is equal to or less than a predetermined threshold, the transmission point judges that a channel is in an idle state (LBT and executes the transmission. In other words, “a channel is in an idle state” means a state where the channel is not occupied by a specific system. This is also referred to as, for example, a channel idles, a channel is clear, and a channel is free. 
     Meanwhile, in the case where the transmission point detects that another apparatus is using even a part of the target carrier band, the transmission point cancels own transmitting process. For example, in the case where the transmission point detects that a received electric power of a signal from another apparatus related to this band exceeds a predetermined threshold, the transmission point judges that the channel is in the busy state (LBT busy ) and does not execute the transmission. In the LBT busy , this channel becomes usable only after that the LBT is executed again and it can be confirmed that the channel is in the idle state. A method of judging the idle state/busy state of the channel by the LBT is not limited to this. 
     Frame Based Equipment (FBE) and Load Based Equipment (LBE) have been examined as a mechanism (scheme) of the LBT. Differences between both are, for example, a frame structure used for transmission/reception and a channel occupancy time. The FBE is one whose constitution for transmission/reception related to the LBT has a fixed timing and is also referred to as, for example, a category 2. The LBE is one whose constitution for transmission/reception related to the LBT is not fixed in a time line direction and executes the LBT according to a demand. The LBE is also referred to as, for example, a category 4. The transmission without the LBT is also referred to as, for example, a category 1. 
     Specifically, the FBE has a fixed frame period and has the following mechanism. As a result of the carrier sense with a predetermined frame and a certain period of time (may also be referred to as, for example, an LBT duration), when the channel is usable, the FBE executes the transmission. When the channel is unusable, the FBE does not execute the transmission until a carrier sense timing of the next frame and stands by. 
     Meanwhile, the LBE has the following mechanism. As a result of executing the carrier sense (initial CCA), when the channel is unusable, the LBE extends a carrier sense time and executes an Extended CCA (ECCA) procedure that continuously executes the carrier sense until the channel becomes usable. To appropriately avoid a collision, the LBE requires a random back-off 
     The carrier sense time (may also be referred to as a carrier sense period) is a period (for example, one symbol length) during which a process such as the listening is executed to obtain one LBT result and availability of the channel is judged. 
     The transmission point can transmit a predetermined signal (for example, a channel reservation signal) according to the LBT result. Here, the LBT result means information on a vacant state of the channel obtained by the LBT in the carrier to which the LBT is configured (for example, LBT idle  and LBT busy ). 
     In the case where the transmission point starts the transmission when the LBT result is the idle state (LBT the transmission point can execute the transmission omitting the LBT by a predetermined period (for example, 10 to 13 ms). Such transmission is also referred to as, for example, a burst transmission, a burst, and a transmission burst. 
     As described above, the introduction of the interference control in the identical frequency based on the LBT mechanism to the transmission point in the LAA system ensures avoiding, for example, an interference between the LAA and the Wi-Fi and an interference between the LAA systems. Even in the case where the transmission points are independently controlled by each operator who operates the LAA system, the interference can be reduced without the LBT grasping the respective control contents. 
     In the LAA system, the user terminal executes a Radio Resource Management (RRM) measurement (includes a Reference Signal Received Power (RSRP) measurement and a similar measurement) to detect a cell in the unlicensed band (Secondary Cell (SCell)). As a signal for this RRM measurement, the use of a Discovery Reference Signal (DRS) has been examined. 
     It is only necessary that the DRS used in the LAA system includes at least one of a synchronization signal (Primary Synchronization Signal (PSS)/Secondary Synchronization Signal (SSS)), a Cell-specific Reference Signal (CRS), and a Channel State Information Reference Signal (CSI-RS). The DRS is transmitted in a DMTC duration at a predetermined cycle (also referred to as a Discovery Measurement Timing Constitution Periodicity (DMTC duration)). This DRS may be referred to as, for example, a detection signal, a detection measurement signal, a Discovery Signal (DS), LAA DRS, and LAA DS. 
     In the LAA system, the user terminal executes the CSI measurement using the CRS or/and the CSI-RS (hereinafter, the CRS/CSI-RS) transmitted by cell in the unlicensed band and reports the measurement result to the radio base station (CSI reporting). This CRS may be the CRS included in respective sub-frames on which a downlink transmission is executed and may be the CRS constituting the DRS. This CSI-RS is the CSI-RS transmitted at a predetermined cycle (for example, 5 ms and 10 ms). This CSI-RS is configured separately from the CSI-RS, which constitutes the DRS. 
     When the LAA system succeeds the LBT (is in the idle state), it is assumed that the minimum transmission bandwidth used by the transmission point is restricted to be equal to or more than a predetermined bandwidth (for example, 5 MHz or 4 MHz). 
     The uplink transmission in the licensed band uses a clustered SC-FDMA that uses a resource block (Physical Resource Block (PRB), such as a PRB pair) as an allocation unit and allocates clusters, which are the one or more consecutive PRBs, to the user terminal. The clustered SC-FDMA may also be referred to as, for example, a Clustered DFT spread OFDM and a clustered DFT-S-OFDM. 
     Specifically, the uplink transmission in the licensed band supports a single cluster allocation (in other words, for example, a type 0, an uplink resource allocation type 0, and a single cluster transmission), which allocates a single cluster to the one user terminal, and a dual cluster allocation (in other words, for example, a type 1, an uplink resource allocation type 1, and a dual cluster transmission), which allocates two clusters to the one user terminal. 
       FIG. 1  is a drawing illustrating an exemplary allocation of the uplink resource in the licensed band.  FIG. 1A  illustrates an exemplary allocation resource by the single cluster allocation (hereinafter referred to as the type 0).  FIG. 1B  illustrates an exemplary allocation resource by the dual cluster allocation (Hereinafter referred to as the type 1). 
     As illustrated in  FIG. 1A , with, the type 0, the allocation resource to the user terminal is indicated by a Resource Indication Value (RIV) corresponding to a start resource block (RBSTART) and the number of resource blocks (transmission bandwidth) (L CRBs , L CRBs ≥1), which is allocated continuous with the start resource block (RBsTART). This RIV is calculated based on the number of resource blocks (N UL RB) constituting an uplink band, the RB START , and the L CRBs . The RIV is arranged to a resource allocation field in downlink control information (DCI) (in other words, for example, an uplink scheduling grant and an UL grant). For example, with the uplink system band of 20 MHz, the resource allocation field is constituted of 13 bits. 
     As illustrated in  FIG. 1B , with the type 1, the allocation resource to the user terminal includes the two clusters (in other words, a set of resource blocks and a resource block set). The respective clusters are constituted of the one or more consecutive resource blocks. The allocation resource to the user terminal is indicated by indexes S 0  and S 1  indicative of start and end positions of a first cluster and indexes S 2  and S 3  indicative of start and end positions of a second cluster. 
     An index r indicative of the indexes S 0 , S 1 , S 2 , and S 3  is arranged at the resource allocation field in the UL grant. For example, with the uplink system band of 20 MHz, the resource allocation field is constituted of 14 bits. The indexes S 0 , S 1 , S 2 , and S 3  may be the indexes for the resource block or may be indexes for a resource block group (RBG). 
     In the above-described uplink transmission in the licensed band, concentrating transmission electric powers to the narrowed transmission bandwidth by narrowing down the transmission bandwidth of the user terminal (for example, the L CRBs  in  FIG. 1A ) secures an uplink coverage. 
     Meanwhile, it is assumed that, with the uplink transmission in the unlicensed band, the minimum transmission bandwidth is restricted to be equal to or more than a predetermined bandwidth, for example, 4 MHz. Thus, there is a possibility that the allocation method of the uplink resource in the licensed band illustrated in  FIG. 1  does not fit in the unlicensed band in which the minimum transmission bandwidth is configured to be equal to or more than the predetermined bandwidth. 
     Specifically, with the type 0 illustrated in  FIG. 1A , for example, in the case where the transmission bandwidth L CRBs  of the user terminal is restricted to be equal to or more than the predetermined bandwidth (for example, 4 MHz, 20 resource blocks), dispersion of a transmission electric power to equal to or more than this predetermined bandwidth possibly results in deterioration of the uplink coverage. With the transmission bandwidth L CRBs  restricted to the predetermined bandwidth, since a kind of the assumed transmission bandwidth L CRBs  decreases, it is also assumed that this eliminates the need for use of all bit numbers of an existing resource allocation field. 
     With the type 1 illustrated in  FIG. 1B , in the case where the entire transmission bandwidth (S 3 −S 0 ) of the user terminal (in other words, a total transmission bandwidth) is restricted to be equal to or more than the predetermined bandwidth (for example, 4 MHz, 20 resource blocks), it is assumed that this eliminates the need for configuring sizes of the first and the second clusters to be changeable any more. That is, it is assumed that, this eliminates the need for specifying the first cluster size (S 1 −S 0 ) and the second cluster size (S 3 −S 2 ) using the four indexes, S 0 , S 1 , S 2 , and S 3 . 
     Accordingly, the uplink resource allocation method suitable for the unlicensed band in which the transmission bandwidth (total transmission bandwidth) is restricted to be equal to or more than the predetermined bandwidth (for example, 4 MHz, 20 resource blocks) is preferable. Specifically, the uplink resource allocation method that can secure the uplink coverage is preferable also in the case where the transmission bandwidth (total transmission bandwidth) of the user terminal is configured to be equal to or more than the predetermined bandwidth (for example, 4 MHz). 
     As such uplink resource allocation method, for example, there has been examined a multi-cluster allocation that employs a plurality of clusters uniformly dispersed in a frequency direction in a system band as a transmission unit and allocates these transmission units to the user terminal. The multi-cluster allocation does not limit the maximum number of clusters that can be allocated to the one user terminal to two, like the uplink resource allocation method in the licensed band illustrated in  FIG. 1 . This multi-cluster allocation is also be referred to as, for example, an interlaced multi-cluster allocation and an interlaced multi-cluster transmission. 
       FIG. 2  is a drawing illustrating an exemplary interlaced multi-cluster allocation. In  FIG. 2 , the transmission unit in the uplink transmission is constituted of the plurality of clusters arranged (spaced) at regular intervals in a frequency direction in the system band. This transmission unit may be referred to as an interlace. The respective clusters constituting the one interlace are constituted of one or more consecutive frequency units (for example, the resource block and a subcarrier, for example, the one resource block in  FIG. 2 ). 
     For example, in  FIG. 2 , the system band is 20 MHz (100 resource blocks), and an interlace #i is constituted of the ten resource blocks (clusters) with index values of {i, i+10, i+20, . . . , i+90}. In  FIG. 2 , numbers given to the respective resource blocks indicate the indexes of the interlaces. 
     As illustrated in  FIG. 2 , in the case where the uplink system band is constituted of 20 MHz (100 resource blocks), ten interlaces # 0  to # 9  are disposed. For example, in  FIG. 2 , the interlaces # 0  and # 6  are allocated to the user terminal # 1 . That is, the 20 clusters constituting the interlaces # 0  and # 6  are allocated to the user terminal # 1 . 
     Similarly, the 30 clusters constituting the interlaces # 1 , # 4 , and # 7  are allocated to a user terminal # 2 . The ten clusters constituting the interlace # 2  are allocated to a user terminal # 3 . The ten clusters constituting the interlace # 3  are allocated to a user terminal # 4 . The  20  clusters constituting the interlaces # 5  and # 9  are allocated to a user terminal # 5 . The ten clusters constituting the interlace # 8  are allocated to a user terminal # 6 . 
     In  FIG. 2 , the one resource block in the one interlace corresponds to the one cluster; however, this should not be constructed in a limiting sense. It is only necessary that the one cluster is constituted of the one or more consecutive frequency units (for example, the resource block, the subcarrier, and the resource block group). In  FIG. 2 , the interlace (transmission unit) is constituted of the ten clusters; however, the number of clusters constituting the one interlace is not limited to ten. 
     With the interlaced multi-cluster allocation illustrated in  FIG. 2 , the interlace (transmission unit) allocated to the user terminal is constituted of the plurality of clusters dispersed in the system band. Accordingly, the total transmission bandwidth of the user terminal can be configured to be equal to or more than the predetermined bandwidth (for example, 4 MHz). Meanwhile, the respective clusters are, for example, constituted of the narrow band such as the one resource block. Accordingly, concentrating the transmission electric powers to this narrow band can prevent the deterioration of the uplink coverage. 
     The inventors have focused on effectiveness of the interlace multi-cluster allocation to prevent the deterioration of the uplink coverage in the unlicensed band in which the transmission bandwidth (total transmission bandwidth) is restricted to be equal to or more than the predetermined bandwidth (for example, 4 MHz). Thus, the inventors have arrived at the present invention. Specifically, the inventors have found that the single cluster allocation and the interlaced multi-cluster allocation can be supported as the uplink resource allocation method for cell in the unlicensed band. 
     The following describes one embodiment of the present invention in detail with reference to the drawings. The embodiment describes a carrier (cell) to which the listening is configured as the unlicensed band; however, this should not be constructed in a limiting sense. As long as a frequency carrier (cell) to which the listening is configured is used, the embodiment is applicable regardless of the licensed band or the unlicensed band. 
     The embodiment assumes the case where the CA or the DC is applied to the carrier to which the listening is not configured (for example, a primary cell (PCell) in the licensed band) and the carrier to which the listening is configured (for example, a secondary cell (SCell) in the unlicensed band); however, this should not be constructed in a limiting sense. For example, the embodiment is also applicable to the case where the Stand-Alone user terminal is connected to the carrier (cell) to which the listening is configured. 
     In the embodiment, the interlaced multi-cluster allocation is applied to the cell in the unlicensed band; however, this should not be constructed in a limiting sense. This interlaced multi-cluster allocation may be applied to the cell in the licensed band. 
     (Radio Communication Method) 
     With the radio communication method according to the embodiment, the user terminal in the cell on which the listening is executed before the transmission receives the downlink control information (DCI). The downlink control information (DCI) includes the allocation information of the uplink resource allocated by any one of the single cluster allocation or the interlaced multi-cluster allocation. Based on the allocation information, this user terminal determines the uplink resource used for the transmission of Physical Uplink Shared Channel (PUSCH). 
     Here, the single cluster allocation (type 0) is a first allocation method for the uplink resource that allocates the single cluster to this user terminal (see  FIG. 1A ). As described above, the allocation resource by the type 0 is identified by allocation information included in the DCI (for example, the RIV corresponding to the RB  S TART and the L CRBs  configured to the resource allocation field). 
     The interlaced multi-cluster allocation is a second allocation method for the uplink resource that allocates the transmission units constituted of the plurality of clusters arranged at regular intervals in the frequency direction to the user terminal. The interlaced multi-cluster allocation is also referred to as, for example, a type 2 and an uplink resource allocation type 2, and is hereinafter referred to as the type 2. The maximum number of clusters (N) allocated by the interlaced multi-cluster allocation is not limited to be two. 
     Whether the uplink resource is allocated using any of the allocation methods of the type 0 or 2 may be indicated by type information in the DCI (for example, a value in a resource allocation type field). Based on the type information in the DCI, the user terminal may interpret the allocation information (for example, the value in the resource allocation field) by any of the type 0 or the type 2. When the type information indicates the dual cluster allocation (type 1, a third allocation method) illustrated in  FIG. 1B , the user terminal may interpret that the uplink resource is allocated by the type 2. 
     &lt;First Aspect&gt; 
     The first aspect describes a notification method of the allocation resource by the interlaced multi-cluster allocation (type 2). The interlaced multi-cluster allocation is also referred to as, for example, the type 2 and the uplink resource allocation type 2 and is hereinafter referred to as the type 2. 
       FIG. 3  is a drawing illustrating the notification example of the allocation resource by the interlaced multi-cluster allocation (type 2) according to the first aspect. As illustrated in  FIG. 3 , with the type 2, the allocation resource for the user terminal includes N (N≥2) pieces of clusters constituting the one transmission unit (interlace). 
     As illustrated in  FIG. 3 , the user terminal may determine a start position of the first cluster, sizes of the respective clusters (cluster sizes), an arrangement interval between the respective clusters (cluster interval), and the total transmission bandwidth of the user terminal based on the allocation information included in the DCI to determine the allocation resource for the user terminal. 
     Here, the allocation information may indicate the first and the second index values S 0  and S 1 , which indicate the start and the end positions of the first cluster, the third index value S 2 , which indicates the start position of the second cluster, and the fourth index value S 3 , which indicates the end position of the N-th (last) cluster. The allocation information indicative of these first to fourth index values S 0 , S 1 , S 2 , and S 3  may be arranged to the resource allocation field of the DCI. 
     For example, the user terminal may determine the start position of the first cluster by the first index value (S 0 ). The user terminal may determine the cluster size based on a difference between the second index value and the first index value (S 1 −S 0 ). The user terminal may determine the cluster interval based on a difference between the third index value and the first index value (S 2 −S 0 ). The user terminal may determine the total transmission bandwidth based on a difference between the fourth index value and the first index value (S 3 −S 0 ). 
     The first to the fourth index values S 0 , S 1 , S 2 , and S 3  are, for example, the PRB indexes; however, this should not be constructed in a limiting sense. The first to the fourth index values S 0 , S 1 , S 2 , and S 3  may be the indexes for the resource block group (RBG) or similar indexes. 
     The type 2 illustrated in  FIG. 3  notifies the allocation resource by reusing parameters S 0 , S 1 , S 2 , and S 3 , which are used by the type 1 described in  FIG. 1B . In view of this, bit sizes of the resource allocation fields in the DCI are equal between the type 2 and the type 1. 
     When the type information in the DCI indicates the type 1 (for example, the value in the resource allocation type field is “1”), the user terminal may judge that the type 2 allocates the uplink resource and may interpret the allocation information (for example, the value in the resource allocation field) by the type 2. That is, the user terminal may read the interpretation of the first to the fourth index values S 0 , S 1 , S 2 , and S 3  differently. 
     Similar to the dual cluster allocation (type 1), the interlace multi-cluster allocation (type 2) may not apply a hopping of the PUSCH. 
     As described above, the first aspect specifies the allocation resource by the type 2 by reusing the first to the fourth index values, which are used for the notification of the allocation resource by the type 1. This ensures notifying the user terminal of the allocation resource by the type 2 without changing an existing DCI format (for example, a DCI format 0 or 4). 
       FIG. 3  illustrates the case where the single transmission unit (interlace) is allocated to the one user terminal as the example. However, for example, like the user terminals # 1 , # 2 , and # 5  in  FIG. 2 , the plurality of transmission units may be allocated to the one user terminal. In this case, the DCI may internally include start positions of the plurality of clusters constituting another transmission unit (interlace), the cluster sizes, the cluster interval, and the allocation information to determine the total transmission bandwidth (the existing DCI format may be extended). 
     &lt;Second Aspect&gt; 
     At the cell in the licensed band, the transmission bandwidth (total transmission bandwidth) of the user terminal is restricted to be equal to or more than the predetermined bandwidth (for example, 4 MHz). Accordingly, the restriction on the parameter regarding the transmission bandwidth (total transmission bandwidth) of the user terminal can reduce the bit numbers of the allocation information (for example, the value in the resource allocation field) of the uplink resource in the DCI, thereby ensuring notifying new information without an increase in bit numbers of the existing DCI format. 
     The following describes the second aspect on restrictions on the parameters regarding the transmission bandwidth (total transmission bandwidth) of the user terminal and the multi sub-frame scheduling with the reduced bit. The second aspect mainly describes differences from the first aspect. 
       FIG. 4  is a drawing illustrating exemplary restrictions of the parameters regarding the transmission bandwidth (total transmission bandwidth) of the user terminal.  FIG. 4A  illustrates the restriction example by the type 0, and  FIG. 4B  illustrates the restriction example by the type 2. 
     As illustrated in  FIG. 4A , in the case where the type 0 restricts the transmission bandwidth (L CRBs ) of the user terminal only to a fixed value (for example, 4 MHz), the notification of the transmission bandwidth (L CRBs ) to the user terminal becomes unnecessary. That is, it is only necessary for the allocation information in the DCI (for example, the resource allocation field value) to indicate only the start position of the single cluster (RB START ); therefore, the allocation information does not need to indicate the transmission bandwidth (L CRBs ). 
     Alternatively, in the case where the transmission bandwidth (L CRBs ) is restricted to a plurality of candidate values (for example, 4 MHz, 5 MHz, 10 MHz, 15 MHz, and 20 MHz), it is only necessary for the allocation information in the DCI (for example, the resource allocation field value) to indicate any one of these plurality of candidate values as the transmission bandwidth (L CRBs ). In view of this, compared with the case where the transmission bandwidth is not restricted to the plurality of candidate values, this allows reducing the bit numbers required to notify the transmission bandwidth (L CRBs ). 
     Thus, the restriction of the parameter (L CRBs ) regarding the transmission bandwidth in the type 0 allows reducing the bit numbers of the allocation information indicative of this parameter (L CRBs ) and the parameter indicative of the start position of the cluster (RB START ) (that is, the resource identification value (RIV), the value in the resource allocation field). 
     Meanwhile, as illustrated in  FIG. 4B , with the type 2, in the case where the total transmission bandwidth of the user terminal is restricted to only the fixed value (for example, 20 MHz), the notification of the fourth index value (S 3 ) used for determining the total transmission bandwidth becomes unnecessary. That is, it is only necessary for the allocation information in the DCI (for example, the resource allocation field value) to indicate the first and the second index values (S 0  and S 1 ), which indicate the start and the end positions of the first cluster, and the third index value (S 2 ), which indicates the start position of the second cluster; therefore, the allocation information does not need to indicate the fourth index value (S 3 ). 
     Alternatively, in the case where the total transmission bandwidth is restricted to the plurality of candidate values (for example, 4 MHz, 5 MHz, 10 MHz, 15 MHz, and 20 MHz), it is only necessary for the allocation information in the DCI to specify any one of these plurality of candidate values. That is, it is only necessary to indicate the first to the third index values (S 0 , S 1 , S 2 ) and the value selected from these plurality of candidate values as the allocation information in the DCI (for example, the resource allocation field value). 
     Thus, with the type 2, restricting the parameter (S 3 ) regarding the total transmission bandwidth allows reducing the bit numbers of this allocation information compared with the case where the allocation information in the DCI (for example, the resource allocation field value) indicates the first to the third index values (S 0 , S 1 , S 2 ) and the fourth index value (S 3 ), which indicates the end position of the N-th cluster (for example, the PRB index). 
     With the second aspect, the parameter regarding the transmission bandwidth in the type 0 and the bits reduced by the restriction on the total transmission bandwidth by the type 2 may be used for the multi sub-frame scheduling. Specifically, the DCI (UL grant) that allocates the PUSCH may include sub-frame information indicative of the one or more sub-frames that transmits the PUSCH. 
     This sub-frame information is, for example, one or two bits. With the use of the one-bit sub-frame information, the transmission of the single sub-frame (for example, a sub-frame #n+ 4 ) or the transmission of the two sub-frames (for example, the sub-frames #n+ 4  and #n+ 5  or the sub-frames #n+ 4  and #n+ 3 ) may be instructed. 
     Alternatively, with the use of the two-bit sub-frame information, the transmission of the consecutive sub-frames up to four can be instructed.  FIG. 5  is a drawing illustrating an exemplary multi sub-frame scheduling according to the second aspect.  FIG. 5  assumes the case where the user terminal receives the UL grant including the two-bit sub-frame information by the sub-frame #n. 
     For example, as illustrated in  FIG. 5 , with the sub-frame information of “00”, the transmission of the single sub-frame (for example, the sub-frame #n+ 4 ) may be instructed. With the sub-frame information of “01”, the transmission of the consecutive two sub-frames (for example, the sub-frames #n+ 4  and #n+ 5 ) may be instructed. With the sub-frame information of “10”, the transmission of the consecutive three sub-frames (for example, the sub-frames #n+ 4 , #n+ 5 , and #n+ 6 ) may be instructed. With the sub-frame information of “11”, the transmission of the consecutive four sub-frames (for example, the sub-frames #n+ 4  to #n+ 7 ) may be instructed. 
       FIG. 5  illustrates the case where the sub-frame information specifies the consecutive sub-frames of the sub-frame #n+ 4  and after the sub-frame #n+ 4 ; however, this should not be constructed in a limiting sense. For example, the sub-frame information may specify the consecutive sub-frames before the sub-frame #n+ 4 . The bit values shown in  FIG. 5  are merely one example and this should not be constructed in a limiting sense. Three bits or more may be used as the sub-frame information. 
     As described above, with the second aspect, the restriction on the parameter regarding the transmission bandwidth by the type 0 and the restriction on the parameter regarding the total transmission bandwidth by the type 2 can reduce the bit numbers of the DCI. The use of the reduced bits to the sub-frame information allows supporting the multi sub-frame scheduling without the change in the entire bit number of the existing DCI format. 
     &lt;Third Aspect&gt; 
     The third aspect describes the case where the bits reduced by the restriction on the parameter regarding the transmission bandwidth (total transmission bandwidth) of the user terminal are used for the listening (LBT). Specifically, the DCI (UL grant) that allocates the PUSCH may include listening information indicative of parameters used for the listening executed by the user terminal before the transmission. The third aspect mainly describes differences from the second aspect. The third aspect may be combined with the second aspect. 
     This listening information may be at least one of: (1) a value of the random back-off (random back-off value), (2) a size of Contention Window (CW) (CW window size) used to generate this random back-off value, (3) a threshold of electric power detection in the listening, and (4) a type of the listening. 
     Here, the random back-off means a mechanism that does not immediately start the transmission even if the channel becomes the vacant state (idle state) but waits for the transmission by a randomly configured period and starts the transmission when the channel is clear. The CW window size means a window size to determine a range of the randomly configured back-off period. 
     The period of the random back-off can be determined based on the randomly configured random value (random back-off value). The range of the random back-off value is determined based on the Contention Window (CW) size and is randomly configured in a range of, for example, 0 to CW size (integer). 
     As illustrated in  FIG. 6 , when the user terminal can confirm that the channel is vacant by a predetermined defer period, the user terminal executes the sensing at intervals of predetermined times (for example, eCCA slot time). When the channel is vacant, the user terminal counts down the random back-off value (here, 7) and can execute the transmission when this random back-off value becomes zero. 
     It is assumed that, at the cell in the unlicensed band, even if the reception (decoding) of the DCI (UL grant) succeeds, if the listening fails, the transmission of PUSCH fails. When the plurality of user terminals use different random back-off values, the transmission of PUSCH from a certain user terminal possibly interrupts the listening by another user terminal, resulting in a failure of the transmission of PUSCH by the user terminals other than the user terminal that has succeeded the listening first. 
     In view of this, it is considered to include (1) the random back-off value in the DCI as the listening information. Specifically, the DCI (UL grant) including the identical random back-off value may be notified to the plurality of user terminals where the PUSCH is allocated to the identical sub-frame. This allows these plurality of user terminals to start the transmission of the PUSCH at the identical timing. This ensures avoiding the user terminals other than the user terminal that has succeeded the listening first to fail the transmission of PUSCH. 
     Alternatively, the DCI may internally include (2) the CW window size used to generate the random back-off value as the listening information. The user terminal executes the listening using the random back-off value, which is generated based on this CW window size. 
     Alternatively, the DCI may internally include (3) the threshold of electric power detection used for the judgement whether the channel is vacant (whether the listening succeeds) as the listening information. Alternatively, the DCI may internally include (4) the type of listening as the listening information. The type of listening may be, for example, the FBE (category 2), the LBE (category 4), and no-listening (category 1). 
     As described above, the third aspect uses the bits reduced by the restrictions on the parameter regarding the transmission bandwidth by the type 0 and the parameter regarding the total transmission bandwidth by the type 2 for the listening information. This allows appropriately executing the listening without the change in the bit numbers of the existing DCI format. To use the second aspect in combination with the third aspect, the existing DCI format may be extended. 
     &lt;Fourth Aspect&gt; 
     The following describes the fourth aspect that uses the bits reduced by the restriction on the parameter regarding the transmission bandwidth (total transmission bandwidth) of the user terminal for Aperiodic CSI reporting. Specifically, the DCI (UL grant) that allocates the PUSCH may include aperiodic CSI information indicating the parameter used to report the aperiodic CSI (hereinafter referred to as A-CSI). The fourth aspect mainly describes differences from the second aspect. The fourth aspect may be combined with the second aspect and/or the third aspect. 
     This aperiodic CSI information may be, for example, cell information indicative of a cell at a report destination for the A-CSI. 
     With the A-CSI reporting in the licensed band, in the case where a trigger in the DCI (UL grant) (for example, an A-CSI trigger) instructs to report the A-CSI, the A-CSI is reported to the cell where the PUSCH is scheduled by this DCI. 
     Meanwhile, it is assumed that, in the unlicensed band, the A-CSI is reported to a cell different from the cell to which this DCI is scheduled. For example, in the case where the user terminal receives the DCI including the A-CSI trigger at the cell (SCell) in the unlicensed band, it is assumed that the A-CSI is reported not to the SCell that has received this DCI but to a Primary Cell (PCell) in the licensed band, a secondary cell (SCell) in the licensed band, or a similar cell. 
     Therefore, the DCI may internally include the cell information indicative of the cell at the report destination for the A-CSI as the aperiodic CSI information. 
     As described above, the fourth aspect uses the bits reduced by the restrictions on the parameter regarding the transmission bandwidth by the type 0 and the parameter regarding the total transmission bandwidth by the type 2 for the aperiodic CSI information. This allows appropriately reporting the A-CSI without the change in the bit numbers of the existing DCI format. To use the fourth aspect in combination with the second aspect and/or third aspect, the existing DCI format may be extended. 
     (Radio Communication System) 
     The following describes a constitution of a radio communication system according to the embodiment. The above-described radio communication methods according to the respective aspects are applied to this radio communication system. The radio communication methods according to the respective aspects may be applied individually or may be applied in combination. 
       FIG. 7  is a drawing illustrating an exemplary schematic constitution of the radio communication system according to the embodiment. A radio communication system  1  can apply Carrier Aggregation (CA) and/or Dual Connectivity (DC) that integrate a plurality of basic frequency blocks (Component Carriers) with a system bandwidth of the LTE system as one unit. The radio communication system  1  includes a radio base station that can use the unlicensed band (for example, a LTE-U base station). 
     The radio communication system  1  may be referred to as, for example, SUPER LTE-A (LTE-Advanced), IMT-Advanced, a 4th generation mobile communication system (4G), a 5th generation mobile communication system (5G), and Future Radio Access (FRA). 
     The radio communication system  1  illustrated in  FIG. 7  includes a radio base station  11  that forms a macrocell C 1 , and radio base stations  12  ( 12   a  to  12   c ) disposed within the macrocell C 1  to form small cells C 2  narrower than the macrocell C 1 . User terminals  20  are disposed in the macrocell C 1  and the respective small cells C 2 . For example, an embodiment that uses the macrocell C 1  in the licensed band and uses the small cells C 2  in the unlicensed band (LTE-U) is considered. An embodiment that uses some of the small cells in the licensed band and uses the other small cells in the unlicensed band is considered. 
     The user terminal  20  can be coupled to both of the radio base station  11  and the radio base station  12 . It is assumed that the user terminal  20  simultaneously uses the macrocell C 1  and the small cell C 2  that use different frequencies by the CA or the DC. For example, the radio base station  11  that uses the licensed band can transmit assistance information (for example, a downlink signal constitution) regarding the radio base station  12  that uses the unlicensed band (for example, the LTE-U base station) to the user terminal  20 . When the CA is executed in the licensed band and the unlicensed band, it is also possible for the one radio base station (for example, the radio base station  11 ) to control schedules of the licensed band cells and the unlicensed band cells. 
     The user terminal  20  may not be coupled to the radio base station  11  but coupled to the radio base station  12 . For example, the radio base station  12  using the unlicensed band may be coupled to the user terminal  20  in a Stand-Alone manner. In this case, the radio base station  12  controls the schedule of the unlicensed band cells. 
     Between the user terminal  20  and the radio base station  11 , communications are possible using a carrier (referred to as, for example, an existing carrier and a Legacy carrier) whose bandwidth is narrow in a relatively low frequency band (for example, 2 GHz). On the other hand, between the user terminal  20  and the radio base station  12 , a carrier whose bandwidth is wide in a relatively high frequency band (for example, 3.5 GHz and 5 GHz) may be used, and a carrier identical to that with the radio base station  11  may be used. The constitutions of the frequency bands used by the respective radio base stations are not limited to these. 
     Between the radio base station  11  and the radio base station  12  (alternatively, between two radio base stations  12 ), a wired connection (for example, optical fiber and X2 interface compliant to Common Public Radio Interface (CPRI)) or a wireless (radio) connection can be constituted. 
     The radio base station  11  and the respective radio base stations  12  are each coupled to a higher station apparatus  30 , and coupled to a core network  40  via the higher station apparatus  30 . The higher station apparatus  30 , for example, includes an access gateway apparatus, a radio network controller (RNC), and a mobility management entity (MME), but is not limited to these. The respective radio base stations  12  may be coupled to the higher station apparatus  30  via the radio base station  11 . 
     The radio base station  11 , which is a radio base station having relatively wide coverage, may be referred to as, for example, a macro base station, an aggregation node, an eNodeB (eNB), and a transmission/reception point. The radio base station  12 , which is a radio base station having local coverage, may be referred to as, for example, a small base station, a micro base station, a pico base station, a femto base station, a Home eNodeB (HeNB), a Remote Radio Head (RRH), and a transmission/reception point. Hereinafter, when the radio base stations  11  and  12  are not discriminated, they are collectively referred to as a radio base station  10 . It is preferable that the respective radio base stations  10  that share and use the identical unlicensed band are constructed to be temporally synchronized. 
     Each user terminal  20 , which is a terminal corresponding to various communication systems such as the LTE and the LTE-A, may include not only a mobile communication terminal but also a fixed communication terminal. 
     In the radio communication system  1 , as a radio access system, an Orthogonal Frequency Division Multiple Access (OFDMA) is applied to the downlink, and the Single-Carrier Frequency Division Multiple Access (SC-FDMA) is applied to the uplink. The OFDMA is a multiple carrier transmission system that divides the frequency band into a plurality of narrow frequency bands (subcarriers) to communicate such that data is mapped to the respective subcarriers. The SC-FDMA is a single carrier transmission system that divides the system bandwidth into bands constituted of one or consecutive resource blocks for each terminal and uses a plurality of terminals with bands different from one another to reduce interference between the terminals. The uplink and downlink radio access systems are not limited to these combinations. 
     In the radio communication system  1 , as a downlink channel, for example, the Physical Downlink Shared Channel (PDSCH), a Physical Broadcast Channel (PBCH), and a downlink L1/L2 control channel, which are shared by the respective user terminals  20 , are used. The PDSCH may be referred to as a downlink data channel. The PDSCH transmits, for example, user data, upper layer control information, and a System Information Block (SIB). The PBCH transmits a Master Information Block (MIB). 
     The downlink L1/L2 control channel includes, for example, the Physical Downlink Control Channel (PDCCH), the Enhanced Physical Downlink Control Channel (EPDCCH), Physical Control Format Indicator Channel (PCFICH), and the Physical Hybrid-ARQ Indicator Channel (PHICH). The PDCCH transmits, for example, the Downlink Control Information (DCI) including scheduling information of the PDSCH and the PUSCH. The PCFICH transmits Control Format Indicator (CFI), which is the number of the OFDM symbols used for the PDCCH. The PHICH transmits delivery confirmation information (ACK/NACK) of the HARQ with respect to the PUSCH. The EPDCCH is frequency-division-multiplexed with the PDSCH to be used for transmission of, for example, the DCI similar to the PDCCH. 
     In the radio communication system  1 , as the uplink channel, for example, the Physical Uplink Shared Channel (PUSCH), an uplink L1/L2 control channel (Physical Uplink Control Channel (PUCCH)), and a Physical Random Access Channel (PRACH), which are shared by the respective user terminals  20 , are used. The PUSCH may be referred to as an uplink data channel. The PUSCH transmits the user data and the upper layer control information. The PUCCH transmits, for example, the downlink Channel Quality Indicator (CQI) and delivery confirmation information (ACK/NACK). The PRACH transmits a random access preamble for connection establishment with the cell. 
     The radio communication system  1  transmits, for example, a Cell-specific Reference Signal (CRS), a Channel State Information-Reference Signal (CSI-RS), a DeModulation Reference Signal (DMRS), and a detection and/or measurement reference signal (Discovery Reference Signal (DRS)) as the downlink reference signals. The radio communication system  1  transmits, for example, a measurement reference signal (Sounding Reference Signal (SRS)) and the DeModulation Reference Signal (DMRS) as the uplink reference signals. The DMRS may also be referred to as a UE-specific Reference Signal. The transmitted reference signals are not limited to these signals. 
     &lt;Radio Base Station&gt; 
       FIG. 8  is a drawing illustrating an exemplary overall constitution of the radio base station according to the embodiment. The radio base station  10  includes a plurality of transmitting/receiving antennas  101 , an amplifying section  102 , a transmitting/receiving section  103 , a baseband signal processing section  104 , a call processing section  105 , and a transmission path interface  106 . It is only necessary to include one or more of the respective transmitting/receiving antenna  101 , amplifying section  102 , and transmitting/receiving section  103 . 
     The user data transmitted from the radio base station  10  to the user terminal  20  by the downlink is input to the baseband signal processing section  104  from the higher station apparatus  30  via the transmission path interface  106 . 
     The baseband signal processing section  104 , performs transmitting processes such as a process of a Packet Data Convergence Protocol (PDCP) layer, dividing and coupling of the user data, a transmitting process of the RLC layer such as a Radio Link Control (RLC) retransmission control, Medium Access Control (MAC) retransmission control (for example, a Hybrid Automatic Repeat reQuest (HARQ) transmitting process), scheduling, transmitting format selection, channel coding, an Inverse Fast Fourier Transform (IFFT) process, and a precoding process on the user data to forward the user data to the transmitting/receiving section  103 . The baseband signal processing section  104  also performs the transmitting processes such as the channel coding and the Inverse Fast Fourier Transform on the downlink control signal to forward the downlink control signal to the transmitting/receiving section  103 . 
     The transmitting/receiving section  103  converts a baseband signal precoded to be output by antennas from the baseband signal processing section  104 , into a radio frequency band to transmit. A radio frequency signal frequency-converted at the transmitting/receiving section  103  is amplified by the amplifying section  102  to be transmitted from the transmitting/receiving antenna  101 . 
     The transmitting/receiving section  103  can transmit/receive the uplink and/or downlink (hereinafter, the uplink/downlink) signals in the unlicensed band. The transmitting/receiving section  103  may be able to transmit/receive the uplink/downlink signals in the licensed band. The transmitting/receiving section  103  can be constituted of a transmitter/receiver, a transmitting/receiving circuit, or a transmitting/receiving apparatus described based on a common view in the technical field according to the present invention. The transmitting/receiving section  103  may be constituted as an integrated transmitting/receiving section, and may be constituted of the transmitting section and the receiving section. 
     On the other hand, for the uplink signal, the radio frequency signal received at the transmitting/receiving antenna  101  is amplified at the amplifying section  102 . The transmitting/receiving section  103  receives the uplink signal amplified at the amplifying section  102 . The transmitting/receiving section  103  frequency-converts the received signal into the baseband signal to output the baseband signal to the baseband signal processing section  104 . 
     The baseband signal processing section  104  performs the Fast Fourier Transform (FFT) process, an Inverse Discrete Fourier Transform (IDFT) process, error correction decoding, the receiving process of the MAC retransmission control, and the receiving process of the RLC layer and the PDCP layer on the user data included in the input uplink signal to forward the user data to the higher station apparatus  30  via the transmission path interface  106 . The call processing section  105  performs call processes of, for example, configuration and release of a communication channel, state management of the radio base station  10 , and management of the radio resource. 
     The transmission path interface  106  transmits and receives the signal to/from the higher station apparatus  30  via a predetermined interface. The transmission path interface  106  may transmit and receive (backhaul signaling) the signal to/from another radio base station  10  via the interface between the base stations (for example, the optical fiber and the X2 interface compliant to the Common Public Radio Interface (CPRI)). 
     The transmitting/receiving section  103  transmits the downlink signals to the user terminal  20  using at least the unlicensed band. For example, the transmitting/receiving section  103  transmits the DCI (UL grant) that allocates the PUSCH to the user terminal  20  and the DCI (DL assignment) to allocate the PDSCH to the user terminal  20 . 
     The transmitting/receiving section  103  receives the uplink signals from the user terminal  20  using at least the unlicensed band. For example, the transmitting/receiving section  103  receives the PUSCH allocated by the DCI (UL grant) from the user terminal  20 . The transmitting/receiving section  103  may receive results of the RRM measurement and/or the CSI measurement (for example, the A-CSI) from the user terminal  20  in the licensed band and/or the unlicensed band. 
       FIG. 9  is a drawing illustrating an exemplary function constitution of the radio base station according to the embodiment.  FIG. 9  mainly illustrates a function block of a characterizing portion according to the embodiment, and it is assumed that the radio base station  10  also has other function blocks required for the radio communication. As illustrated in  FIG. 9 , the baseband signal processing section  104  at least includes a control section (scheduler)  301 , a transmission signal generating section  302 , a mapping section  303 , a reception signal processing section  304 , and a measurement section  305 . 
     The control section (scheduler)  301  controls the entire radio base station  10 . To execute the scheduling on the licensed band and the unlicensed band by the one control section (scheduler)  301 , the control section  301  controls communications of the licensed band cells and the unlicensed band cells. The control section  301  may be a controller, a control circuit, or a control apparatus described based on the common view in the technical field according to the present invention. 
     The control section  301 , for example, controls the generation of the downlink signals by the transmission signal generating section  302  and the allocation of the downlink signals by the mapping section  303 . The control section  301  controls the receiving process of the signals by the reception signal processing section  304  and the measurement of the signals by the measurement section  305 . 
     The control section  301  controls, for example, the scheduling, the generation, the mapping, and the transmission of the downlink signals (for example, the PDCCH/EPDCCH to transmit the system information and the DCI, the PDSCH, the downlink reference signal, and the synchronization signal). The control section  301  controls the LBT (listening) by the measurement section  305  and controls the transmission of the downlink signals to the transmission signal generating section  302  and the mapping section  303  in accordance with the LBT result. 
     The control section  301  controls, for example, the scheduling and reception of the uplink signals (PUSCH, PUCCH, PRACH, the uplink reference signal, and a similar signal). 
     Specifically, the control section  301  allocates the uplink resource used for the transmission of the PUSCH from the user terminal  20  by any one of the single cluster allocation (the type 0, the first allocation method) or the interlaced multi-cluster allocation (the type 2, the second allocation method) (first aspect). 
     The control section  301  controls the transmission signal generating section  302  and the mapping section  303  so as to transmit the DCI including the allocation information of the uplink resource (for example, the resource allocation field value). This DCI may include the type information (for example, a resource allocation type field value) indicative of the allocation type of the uplink resource. In the case where the uplink resource is allocated by the interlaced multi-cluster allocation, the control section  301  may set a value indicative of the dual cluster allocation as the type information. 
     The control section  301  may control the transmission signal generating section  302  such that this DCI includes the sub-frame information (second aspect), the listening information (third aspect), and the aperiodic CSI information (fourth aspect). 
     The transmission signal generating section  302  generates the downlink signals based on an instruction from the control section  301  to output the downlink signals to the mapping section  303 . The transmission signal generating section  302  can be constituted of a signal generator, a signal generation circuit, or a signal generation apparatus described based on the common view in the technical field according to the present invention. 
     The transmission signal generating section  302 , for example, generates the allocation information of the downlink resource (DL assignment) and the allocation information of the uplink resource (UL grant) based on the instruction from the control section  301 . A coding process and a modulation process are executed on the downlink data signals in accordance with, for example, a code rate and a modulation scheme determined based on the result of the CSI measurement in the respective user terminals  20  and a similar result. The transmission signal generating section  302  generates the DRS including, for example, the PSS, the SSS, the CRS, and the CSI-RS. 
     The mapping section  303  maps the downlink signal generated at the transmission signal generating section  302  to a predetermined radio resource to output the downlink signal to the transmitting/receiving section  103 , based on the instruction from the control section  301 . The mapping section  303  can be constituted of a mapper, a mapping circuit, or a mapping apparatus described based on the common view in the technical field according to the present invention. 
     The reception signal processing section  304  executes the receiving process (for example, a demapping, the demodulation, and the decoding) on the received signal input from the transmitting/receiving section  103 . Here, the received signal is, for example, the uplink signal transmitted from the user terminal  20 . The reception signal processing section  304  can be constituted of a signal processor, a signal processing circuit, or a signal processing apparatus described based on the common view in the technical field according to the present invention. 
     The reception signal processing section  304  outputs the information decoded by the receiving process to the control section  301 . For example, when the reception signal processing section  304  receives the PUCCH including the HARQ-ACK, the reception signal processing section  304  outputs the HARQ-ACK to the control section  301 . The reception signal processing section  304  outputs the received signal and the signal after the receiving process to the measurement section  305 . 
     The measurement section  305  executes the measurement regarding the received signal. The measurement section  305  can be constituted of a measuring instrument, a measuring circuit, or a measuring apparatus described based on the common view in the technical field according to the present invention. 
     The measurement section  305  executes the LBT (listening) in the carrier (for example, the unlicensed band) where the LBT is configured based on the instruction from the control section  301  and outputs the LBT result (for example, a judgment result whether the channel state is idle or busy) to the control section  301 . 
     The measurement section  305  may measure, for example, the received electric power of the received signal (for example, a Reference Signal Received Power (RSRP)), a reception quality (for example, a Reference Signal Received Quality (RSRQ)), and the channel state. The measurement result may be output to the control section  301 . 
     &lt;User Terminal&gt; 
       FIG. 10  is a drawing illustrating an exemplary overall constitution of the user terminal according to the embodiment. The user terminal  20  includes a plurality of transmitting/receiving antennas  201 , amplifying sections  202 , and transmitting/receiving sections  203 , a baseband signal processing section  204 , and an application section  205 . It is only necessary to include one or more of the respective transmitting/receiving antenna  201 , amplifying section  202 , and transmitting/receiving section  203 . 
     The radio frequency signals received at the transmitting/receiving antenna  201  are amplified at the amplifying sections  202 . The transmitting/receiving sections  203  receive the downlink signals amplified at the amplifying sections  202 . The transmitting/receiving section  203  frequency-converts the received signal into the baseband signal to output the baseband signal to the baseband signal processing section  204 . The transmitting/receiving section  203  can transmit/receive the uplink/downlink signals in the unlicensed band. The transmitting/receiving section  203  may be able to transmit/receive the uplink/downlink signals in the licensed band. 
     The transmitting/receiving section  203  can be constituted of a transmitter/receiver, a transmitting/receiving circuit, or a transmitting/receiving apparatus described based on the common view in the technical field according to the present invention. The transmitting/receiving section  203  may be constituted as an integrated transmitting/receiving section, and may be constituted of the transmitting section and the receiving section. 
     The baseband signal processing section  204  performs, for example, an FFT process, the error correction decoding, and the receiving process of the retransmission control, with respect to the input baseband signal. The user data in the downlink is forwarded to the application section  205 . The application section  205  performs, for example, a process regarding a layer upper than a physical layer and a MAC layer. Among the data in the downlink, the notification information is also forwarded to the application section  205 . 
     On the other hand, the user data in the uplink is input to the baseband signal processing section  204  from the application section  205 . At the baseband signal processing section  204 , for example, the transmitting process of the retransmission control (for example, the transmitting process of the HARQ), the channel coding, the precoding, a Discrete Fourier Transform (DFT) process, and an IFFT process are performed to forward the user data to the transmitting/receiving sections  203 . The transmitting/receiving section  203  converts the baseband signal output from the baseband signal processing section  204  into the radio frequency band to transmit. The radio frequency signal frequency-converted at the transmitting/receiving section  203  is amplified at the amplifying section  202  to be transmitted from the transmitting/receiving antenna  201 . 
     The transmitting/receiving section  203  receives the downlink signal transmitted from the radio base station  10  using at least the unlicensed band. For example, the transmitting/receiving section  203  receives the measurement reference signal in the unlicensed band. 
     The transmitting/receiving section  203  transmits the uplink signal to the radio base station  10  using at least the unlicensed band. For example, the transmitting/receiving section  203  may transmit the PUSCH using the uplink resource allocated by the DCI (UL grant). The transmitting/receiving section  203  may transmit the CSI instructed by the A-CSI trigger in the DCI (UL grant). 
       FIG. 11  is a drawing illustrating an exemplary function constitution of the user terminal according to the embodiment.  FIG. 11  mainly illustrates a function block of a characterizing portion according to the embodiment, and it is assumed that the user terminal  20  also has other function blocks required for the radio communication. As illustrated in  FIG. 11 , the baseband signal processing section  204  included in the user terminal  20  at least includes a control section  401 , a transmission signal generating section  402 , a mapping section  403 , a reception signal processing section  404 , and a measurement section  405 . 
     The control section  401  controls the entire user terminal  20 . The control section  401  can be constituted of a controller, a control circuit, or a control apparatus described based on the common view in the technical field according to the present invention. 
     The control section  401 , for example, controls the generation of the uplink signal by the transmission signal generating section  402  and the allocation of the uplink signals by the mapping section  403 . The control section  401  controls the receiving process of the downlink signal by the reception signal processing section  404  and the measurement of the signal by the measurement section  405 . 
     The control section  401  obtains the downlink signals (the PDCCH/EPDCCH, the PDSCH, the downlink reference signal, the synchronization signal, and a similar signal) transmitted from the radio base station  10  from the reception signal processing section  404 . The control section  401  controls generation of the uplink control signal (for example, the PUCCH and the PUSCH) based on the decoding results of the DCI included in the PDCCH/EPDCCH (downlink control signal) and the PDSCH (downlink data signal). 
     The control section  401  may control the transmission of the uplink signal on the transmission signal generating section  402  and the mapping section  403  in accordance with the LBT result obtained by the measurement section  405 . 
     Specifically, the control section  401  determines the uplink resource allocated by any one of the single cluster allocation (the type 0, the first allocation method) or the interlaced multi-cluster allocation (the type 2, the second allocation method) based on the allocation information in the DCI (for example, the resource allocation field value) (first aspect). 
     The control section  401  may judge whether the uplink resource is allocated by any one of allocation methods, the type 0 or 2, based on the type information in the DCI (for example, the resource allocation type field value) to interpret the allocation information in the DCI based on the judgement result. For example, when the type information in the DCI indicates the dual cluster allocation (the type 1, the third allocation method), the control section  401  may determine that the uplink resource is allocated by the type 2. 
     When the uplink resource is allocated by the type 2, the control section  401  may determine the start position of the first cluster, the sizes of the respective clusters, the arrangement interval between the respective clusters, and the total transmission bandwidth used for the transmission of the PUSCH based on the allocation information in the DCI (for example, the resource allocation field value). 
     Here, the allocation information of the type 2 may indicate the first and the second index values (S 0 , S 1 ), which indicate the start and the end positions of the first cluster, the third index value (S 2 ), which indicates the start position of the second cluster, and the fourth index value (S 3 ), which indicates the end position of the last cluster ( FIG. 3 ). In this case, the control section  401  may determine the start position of the first cluster by the first index value (S 0 ), may determine the cluster size based on the difference between the second index value and the first index value (S 1 −S 0 ), may determine the cluster interval based on the difference between the third index value and the first index value (S 2 −S 0 ), and may determine the total transmission bandwidth based on the difference between the fourth index value and the first index value (S 3 −S 0 ). 
     Alternatively, the allocation information of the type 2 may indicate the first and the second index values (S 0 , S 1 ), which indicate the start and the end positions of the first cluster, and the third index value (S 2 ), which indicates the start position of the second cluster ( FIG. 4B ). In this case, the control section  401  may determine the predetermined fixed value to the total transmission bandwidth (for example, 20 MHz). 
     Alternatively, the allocation information of the type 2 may indicate the first and the second index values (S 0 , S 1 ), which indicate the start and the end positions of the first cluster, the third index value (S 2 ), which indicates the start position of the second cluster, and a value selected from the plurality of candidate values of the total transmission bandwidth (for example, 4 MHz, 5 MHz, 10 MHz, 15 MHz, and 20 MHz) ( FIG. 4B ). In this case, the control section  401  may determine this selected value as the total transmission bandwidth. 
     When the uplink resource is allocated by the type 0, the control section  401  may determine the start position of the single cluster and the transmission bandwidth based on the allocation information in the DCI (for example, the resource allocation field value). 
     Here, the allocation information of the type 0 may indicate the index value (RB START ), which indicates the start position of the single cluster, and the length of this single cluster (cluster length) (L CRBs ) ( FIG. 1A ). In this case, the control section  401  may determine the start position of the single cluster by the index value (RB START ) and may determine the transmission bandwidth by the cluster length (L CRBs ). 
     Alternatively, the allocation information of the type 0 may indicate the index value (RB START ), which indicates the start position of the single cluster ( FIG. 4A ). In this case, the control section  401  may determine the predetermined fixed value as the total transmission bandwidth (for example, 4 MHz). 
     Alternatively, the allocation information of the type 0 may indicate the index value (RB START ), which indicates the start position of the single cluster, and the value selected from the plurality of candidate values of the total transmission bandwidth (for example, 4 MHz, 5 MHz, 10 MHz, 15 MHz, and 20 MHz) ( FIG. 4A ). In this case, the control section  401  may determine this selected value as the total transmission bandwidth. 
     The control section  401  may control the transmission of the PUSCH in the one or more consecutive sub-frames indicated by the sub-frame information in the DCI (second aspect). In this case, the control section  401  may control the transmission signal generating section  402  and the mapping section  403  such that the PUSCH is transmitted using the identical uplink resource determined as described above in these one or more consecutive sub-frames. 
     The control section  401  may control the listening based on the listening information in the DCI (third aspect). Specifically, the control section  401  may control the listening by the measurement section  305  based on at least one of the random back-off value, the CW window size, the threshold of the electric power detection, and the type information of listening. 
     The control section  401  may control the aperiodic CSI reporting based on the aperiodic CSI information in the DCI (fourth aspect). Specifically, the control section  401  may control the transmission signal generating section  402  and the mapping section  403  such that the CSI is reported to the cell indicated by the aperiodic CSI information. 
     The control section  401  controls the reception signal processing section  404  and the measurement section  405  such that the RRM is measured and/or the CSI is measured using the measurement reference signal in the unlicensed band. The RRM may be measured using the DRS. This measurement reference signal may be any one of the CSI or the CSI-RS included in the CRS, the CSI-RS, and the DRS. 
     The transmission signal generating section  402  generates the uplink signal (for example, the PUSCH, the PUCCH, and the uplink reference signal) based on the instruction from the control section  401  and outputs the uplink signal to the mapping section  403 . The transmission signal generating section  402  can be constituted of a signal generator, a signal generation circuit, or a signal generation apparatus described based on the common view in the technical field according to the present invention. For example, when the downlink control signal from the radio base station  10  includes the DCI (UL grant) addressed to the user terminal  20 , the control section  401  instructs the generation of the PUSCH to the transmission signal generating section  402 . 
     The mapping section  403  maps the uplink signal generated by the transmission signal generating section  402  to a radio resource and outputs the uplink signal to the transmitting/receiving section  203  based on the instruction from the control section  401 . The mapping section  403  can be constituted of a mapper, a mapping circuit, or a mapping apparatus described based on the common view in the technical field according to the present invention. 
     The reception signal processing section  404  executes the receiving process (for example, the demapping, the demodulation, and the decoding) on the received signal input from the transmitting/receiving section  203 . Here, the received signal is, for example, the downlink signal transmitted from the radio base station  10 . The reception signal processing section  404  can be constituted of a signal processor, a signal processing circuit, or a signal processing apparatus described based on the common view in the technical field according to the present invention. The reception signal processing section  404  can constitute the receiving section according to the present invention. 
     The reception signal processing section  404  outputs the information decoded by the receiving process to the control section  401 . The reception signal processing section  404  outputs, for example, the notification information, the system information, the RRC signaling, and the DCI to the control section  401 . The reception signal processing section  404  outputs the received signal and the signal after the receiving process to the measurement section  405 . 
     The measurement section  405  executes the measurement regarding the received signal. The measurement section  405  can be constituted of a measuring instrument, a measuring circuit, or a measuring apparatus described based on the common view in the technical field according to the present invention. 
     The measurement section  405  may execute the LBT in the carrier (for example, the unlicensed band) where the LBT is configured based on the instruction from the control section  401 . The measurement section  405  may output the LBT result (for example, a judgment result whether the channel state is idle or busy) to the control section  401 . 
     The measurement section  405  executes the RRM measurement and the CSI measurement in accordance with the instruction from the control section  401 . For example, the measurement section  405  measures the CSI using the measurement reference signal (any one of the CRS, CSI-RS, CRS included in DRS, or CSI-RS for CSI measurement arranged in the transmission sub-frame for DRS). The measurement result is output to the control section  401  and is transmitted from the transmitting/receiving section  103  using PUSCH or PUCCH. 
     &lt;Hardware Constitution&gt; 
     The block diagrams used for the description of the above-described embodiment illustrate blocks by functions. These function blocks (constitution sections) are implemented with an optional combination of hardware and/or software. An implementation means of each function block is not specifically limited. That is, each function block may be implemented with physically-bounded one apparatus, and by coupling physically-separate two or more apparatuses with wire or without wire, each function block may be implemented with these plurality of apparatuses. 
     For example, the radio base station, the user terminal, and the like in the one embodiment of the present invention may function as computers that perform the processes of the radio communication method of the present invention.  FIG. 12  is a drawing illustrating an exemplary hardware constitution of the radio base station and the user terminal according to the one embodiment of the present invention. The above-described radio base station  10  and user terminal  20  may be physically constituted as a computer apparatus including, for example, a processor  1001 , a memory  1002 , a storage  1003 , a communication apparatus  1004 , an input apparatus  1005 , an output apparatus  1006 , and a bus  1007 . 
     In the following description, the word “an apparatus” can be reworded to, for example, a circuit, a device, and a unit. The hardware constitution of the radio base station  10  and the user terminal  20  may include one or more of each apparatus illustrated in the drawing, and may be constituted without a part of the apparatuses. 
     Each function in the radio base station  10  and the user terminal  20  is achieved such that the processor  1001  performs arithmetic operation such that predetermined software (program) is read into the hardware such as the processor  1001  and the memory  1002 , to control communication by the communication apparatus  1004  and reading and/or writing of data in the memory  1002  and the storage  1003 . 
     The processor  1001 , for example, operates an operating system to control the computer as a whole. The processor  1001  may be constituted of a Central Processing Unit (CPU) including, for example, an interface with peripheral apparatuses, a control apparatus, an arithmetic apparatus, and a register. For example, the above-described baseband signal processing section  104  ( 204 ), call processing section  105 , and the like may be implemented with the processor  1001 . 
     The processor  1001  reads out a program (program code), a software module, and data from the storage  1003  and/or the communication apparatus  1004  to the memory  1002 , and then performs various processes in accordance with them. As the program, a program that causes the computer to execute at least a part of the operation described in the above-described embodiment is used. For example, the control section  401  of the user terminal  20  may be stored in the memory  1002  to be achieved by a control program that operates in the processor  1001 . Other function blocks may be similarly achieved. 
     The memory  1002 , which is a computer readable recording medium, may be constituted of, for example, at least one of a Read Only Memory (ROM), an Erasable Programmable ROM (EPROM), and a Random Access Memory (RAM). The memory  1002  may be also referred to as, for example, a register, a cache, and a main memory (main storage unit). The memory  1002  can store, for example, a program (program code) and a software module executable for performing the radio communication method according to the one embodiment of the present invention. 
     The storage  1003 , which is a computer readable recording medium, may be constituted of, for example, at least one of an optical disk such as a Compact Disc ROM (CD-ROM), a hard disk drive, a flexible disk, a magneto-optic disk, and a flash memory. The storage  1003  may be referred to as an auxiliary storage unit. 
     The communication apparatus  1004 , which is hardware (transmitting/receiving device) for communicating between the computers via wired and/or wireless network, is in other words, for example, a network device, a network controller, a network card, and a communication module. For example, the above-described transmitting/receiving antenna  101  ( 201 ), amplifying section  102  ( 202 ), transmitting/receiving section  103  ( 203 ), and transmission path interface  106 , may be implemented with the communication apparatus  1004 . 
     The input apparatus  1005  is an input device (for example, a keyboard and a computer mouse) that accepts input from outside. The output apparatus  1006  is an output device (for example, a display and a speaker) that performs an output to the outside. The input apparatus  1005  and the output apparatus  1006  may have an integral constitution (for example, a touch panel). 
     The respective apparatuses such as the processor  1001  and the memory  1002  are coupled by the bus  1007  for communicating information. The bus  1007  may be constituted of a single bus, and may be constituted of different buses between the apparatuses. 
     The radio base station  10  and the user terminal  20  may be constituted including the hardware such as a microprocessor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Programmable Logic Device (PLD), and a Field Programmable Gate Array (FPGA). This hardware may implement a part of or all the respective function blocks. For example, the processor  1001  may be implemented with at least one of this hardware. 
     The terms described in this description and/or the terms required for understanding this description may be replaced by terms having identical or similar meaning. For example, the channel and/or the symbol may be a signal (signaling). The signal may be a message. The Component Carrier (CC) may be also referred to as, for example, a cell, a frequency carrier, and a carrier frequency. 
     The radio frame may be constituted of one or more periods (frames) in the time domain. Each of this one or more periods (frames) that constitute the radio frame may be referred to as a sub-frame. Furthermore, the sub-frame may be constituted of one or more slots in the time domain. Furthermore, the slot may be constituted of one or more symbols (for example, OFDM symbols and SC-FDMA symbols) in the time domain. 
     The radio frame, the sub-frame, the slot, and the symbol each represent a time unit to transmit the signal. For the radio frame, the sub-frame, the slot, and the symbol, another name corresponding to each of them may be used. For example, one sub-frame may be referred to as a Transmission Time Interval (TTI), a plurality of consecutive sub-frames may be referred to as a TTI, and one slot may be referred to as a TTI. That is, the sub-frame or the TTI may be a sub-frame (1 ms) in the existing LTE, may be a period shorter than 1 ms (for example, one to 13 symbols), and may be a period longer than 1 ms. 
     Here, the TTI is, for example, a minimum time unit of scheduling in the radio communication. For example, in the LTE system, the radio base station performs scheduling that allocates the radio resource (for example, a frequency bandwidth and transmission power available for each user terminal) in a unit of TTI, with respect to each user terminal. The definition of the TTI is not limited to this. 
     The TTI with a time length of  1  ms may be referred to as, for example, a basic TTI (TTI in LTE Rel.8 to 12), a normal TTI, a long TTI, a basic sub-frame, a normal sub-frame, or a long sub-frame. The TTI shorter than the basic TTI may also be referred to as, for example, a reduced TTI, a short TTI, a reduced sub-frame, or a short sub-frame. 
     The Resource Block (RB), which is a resource allocation unit in the time domain and the frequency domain, may include one or more consecutive subcarriers in the frequency domain. The RB may include one or more symbols in the time domain, and may be a length of one slot, one sub-frame, or one TTI. One TTI and one sub-frame each may be constituted of one or more resource blocks. The RB may be referred to as, for example, a Physical Resource Block (Physical RB (PRB)), a PRB pair, and a RB pair. 
     The resource block may be constituted of one or more Resource Elements (REs). For example, one RE may be a radio resource region of one subcarrier and one symbol. 
     The above-described structures of the radio frame, the sub-frame, the slot, the symbol, and the like are only illustrative. For example, the number of the sub-frames included in the radio frame, the number of the slots included in the sub-frame, the number of the symbols and the RBs included in the slot, the number of the subcarriers included in the RB, and the constitution such as the number of the symbols, the symbol length, and the Cyclic Prefix (CP) length within the TTI can be variously changed. 
     For example, the information and the parameter described in this description may be represented by absolute values, may be represented by relative values from predetermined values, and may be represented by corresponding other information. For example, the radio resource may be instructed by a predetermined index. 
     For example, the information and the signal described in this description may be represented using any of various different techniques. For example, the data, the order, the command, the information, the signal, the bit, the symbol, and the chip mentionable over the above-described entire description may be represented by voltage, current, electromagnetic wave, magnetic field or magnetic particle, optical field or photon, or an optional combination of them. 
     For example, the software, the order, and the information may be transmitted and received via a transmission medium. For example, when the software is transmitted from a website, a server, or another remote source using wired techniques (for example, a coaxial cable, an optical fiber cable, a twisted pair, and a digital subscriber line (DSL)) and/or wireless techniques (for example, infrared and microwave), these wired techniques and/or wireless techniques are included in the definition of the transmission medium. 
     The radio base station in this description may be reworded to the user terminal. For example, the respective aspects/embodiments of the present invention may be applied to a constitution where the communication between the radio base station and the user terminal is replaced by communication between a plurality of user terminals (Device-to-Device (D2D)). In this case, the user terminal  20  may have the above-described functions that the radio base station  10  has. The words such as “uplink” and “downlink” may be reworded to “side.” For example, the uplink channel may be reworded to the side channel. 
     Similarly, the user terminal in this description may be reworded to the radio base station. In this case, the radio base station  10  may have the above-described functions that the user terminal  20  has. 
     The respective aspects/embodiments described in this description may be used alone, may be used in combination, and may be used by switching in accordance with execution. The notification of the predetermined information (for example, the notification “being X”) is not limited to explicit execution, and may be implicit execution (for example, by not performing the notification of this predetermined information). 
     The notification of the information is not limited to the aspects/embodiments described in this description, and may be performed by another method. For example, the notification of the information may be performed by physical layer signaling (for example, Downlink Control Information (DCI) and Uplink Control Information (UCI)), the upper layer signaling (for example, Radio Resource Control (RRC) signaling, the notification information (for example, Master Information Block (MIB) and System Information Block (SIB)), and Medium Access Control (MAC) signaling), another signal, or these combination. The RRC signaling may be referred to as a RRC message, for example, and may be RRCConnectionSetup message and RRCConnectionReconfiguration message. The MAC signaling may be notified by, for example, a MAC Control Element (CE). 
     The respective aspects/embodiments described in this description may be applied to a system that uses Long Term Evolution (LTE), LTE-Advanced (LTE-A), LTE-Beyond (LTE-B), SUPER 3CG, IMT-Advanced, 4th generation mobile communication system (4G), 5th generation mobile communication system (5G), Future Radio Access (FRA), Radio Access Technology (New-RAT), CDMA2000, Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi (registered trademark)), IEEE 802.16 (WiMAX (registered trademark)), IEEE 802.20, Ultra-WideBand (UWB), Bluetooth (registered trademark), and another appropriate radio communication method, and/or a next generation system extended based on them. 
     For, for example, the process procedure, the sequence, and the flowchart of the respective aspects/embodiments described in this description, the order may be interchanged without inconsistencies. For example, for the method described in this description, various step elements are presented in an exemplary order. The order is not limited to the presented specific order. 
     Now, although the present invention has been described in detail, it should be obvious to a person skilled in the art that the present invention is by no means limited to the embodiments described herein. For example, the above-described respective embodiments may be used alone, and may be used in combination. The present invention can be implemented with various corrections and in various modifications, without departing from the spirit and scope of the present invention defined by the recitations of claims. Consequently, the description herein is provided only for the purpose of explaining examples, and should by no means be construed to limit the present invention in any way. 
     This application is based on Japanese Patent Application No. 2016-009115 filed on Jan. 20, 2016, and the disclosure of which is incorporated herein.