Patent Publication Number: US-10772093-B2

Title: Communication control device, communication control method, and communication device

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 15/463,967, filed Mar. 20, 2017, which is a continuation of U.S. application Ser. No. 14/758,926, filed Jul. 1, 2015 (now U.S. Pat. No. 9,642,134), which is a U.S. national stage application of International Application No. PCT/JP2013/082397, filed Dec. 2, 2013, which is based on and claims priority to Japanese Application No. 2013-045132, filed Mar. 7, 2013, the entire contents of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a communication control device, a communication control method, and a communication device. 
     BACKGROUND ART 
     Wireless communication environments of recent years are facing the problem of depletion of frequency resources, which has been caused by soaring amounts of data traffic. Thus, active discussions have been exchanged with regard to a framework for opening frequency bands that were authorized for use by specific business operators but are not being used for secondary communication. The framework for secondary communication is referred to as Licensed Shared Access (LSA). For example, the European Conference of Postal and Telecommunications Administrations (CEPT) suggests technical requirements for devices that secondarily use so-called “TV white spaces” (White Space Devices, or WSDs) that are not being used for television broadcasting in Non-Patent Literature 1 below. 
     Generally, transmission power of a transmitter that uses a frequency band secondarily is restricted from causing unfavorable interference with a receiver of a primary system. For example, Non-Patent Literature 1 below proposes deployment of a geo-location database (GLDB) which provides information on the coverage of digital terrestrial television (DTT) systems that are primary systems, positions of DTT receivers, tolerable interference levels, and the like in order to appropriately control transmission power of a WSD. Since use of frequency bands is normally authorized by country (or region), a different GLDB may be deployed for each country (or region). 
     Non-Patent Literature 3 below proposes, for example, a country or a third party installing an advanced geo-location engine (AGLE) which uses information provided from a GLDB for maximizing a system capacity of a secondary system through more advanced calculation. The frequency managing agent of the UK, the Office of Communications (OfCom), and a third party database provider have decided to employ the approach of installing an AGLE. 
     In addition, in Non-Patent Literature 4 below, a technology of coexistence of devices which use a frequency band secondarily is discussed. 
     CITATION LIST 
     Non-Patent Literature 
     
         
         Non-Patent Literature 1: Electronic Communications Committee (ECC), “TECHNICAL AND OPERATIONAL REQUIREMENTS FOR THE POSSIBLE OPERATION OF COGNITIVE RADIO SYSTEMS IN THE ‘WHITE SPACES’ OF THE FREQUENCY BAND 470 TO 790 MHz,” ECC REPORT 159, January 2011 
         Non-Patent Literature 2: Electronic Communications Committee (ECC), “Complementary Report to ECC Report 159; Further definition of technical and operational requirements for the operation of white space devices in the band 470 to 790 MHz,” ECC REPORT 185, September 2012 
         Non-Patent Literature 3: Naotaka Sato (Sony Corporation), “TV WHITE SPACE AS PART OF THE FUTURE SPECTRUM LANDSCAPE FOR WIRELESS COMMUNICATIONS,” ETSI Workshop on Reconfigurable Radio Systems, Dec. 12, 2012, Cannes (France) 
         Non-Patent Literature 4: Draft ETSI TS 102 946, Reconfigurable Radio Systems (RRS); System Requirements for Operation in UHF TV Band White Spaces 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     However, influence of wireless communication of a primary system on wireless communication of a secondary system which secondarily uses a frequency band for the primary system has not been carefully considered. That is to say, influence of transmission power of a transmitter of a primary system on a receiver of a secondary system has not been carefully considered. For this reason, transmission power of the primary system can have significant influence on wireless communication of the secondary system. As a result, a decrease of the throughput of the secondary system is a concern. In addition, the same problem can arise not only in the secondary system with respect to TV white spaces but also in the case of a mobile communication system in which a small cell that is partly or entirely overlapped by a macro cell is disposed. 
     Thus, even when there are a transmitter and a receiver both using the same or close frequency bands, it is desirable to provide a framework in which more desirable wireless communication can be performed through the receiver. 
     Solution to Problem 
     According to the present disclosure, there is provided a communication control device that controls wireless communication in compliance with a time division duplex (TDD) scheme, the communication control device including: a selection unit configured to select a link direction configuration for the wireless communication among a plurality of candidates for the link direction configuration which indicates a link direction in units of sub-frames of a radio frame which includes a plurality of sub-frames; and an application unit configured to apply the selected link direction configuration to the wireless communication. The plurality of candidates include at least one of a link direction configuration dedicated to a downlink and a link direction configuration dedicated to an uplink. 
     According to the present disclosure, there is provided a communication control method for controlling wireless communication in compliance with a time division duplex (TDD) scheme, the communication control method including: selecting a link direction configuration for the wireless communication among a plurality of candidates for the link direction configuration which indicates a link direction in units of sub-frames of a radio frame which includes a plurality of sub-frames; and applying the selected link direction configuration to the wireless communication. The plurality of candidates include at least one of a link direction configuration dedicated to a downlink and a link direction configuration dedicated to an uplink. 
     According to the present disclosure, there is provided a communication control device including: a recognition unit configured to recognize a frequency channel on which wireless communication is performed in compliance with a time division duplex (TDD) scheme; and a decision unit configured to, when the wireless communication is performed on two or more frequency channels, decide one or more candidates selectable to be applied to wireless communication of each of the frequency channels among a plurality of candidates for a link direction configuration that indicates a link direction in units of sub-frames of a radio frame that includes a plurality of sub-frames for each of the frequency channels included in the two or more frequency channels, on the basis of information relating to the distance between an interference frequency channel on which an interference signal is transmitted and each of the frequency channels in a frequency direction. The plurality of candidates include at least one of a link direction configuration dedicated to a downlink and a link direction configuration dedicated to an uplink. 
     According to the present disclosure, there is provided a communication device that controls wireless communication in compliance with a time division duplex (TDD) scheme, the communication device including: a recognition unit configured to recognize a link direction configuration to be applied to the wireless communication among a plurality of candidates for the link direction configuration that indicates a link direction in units of sub-frames of a radio frame that includes a plurality of sub-frames; and a communication control unit configured to control the wireless communication in compliance with the recognized link direction configuration. The plurality of candidates include at least one of a link direction configuration dedicated to a downlink and a link direction configuration dedicated to an uplink. 
     Advantageous Effects of Invention 
     According to the present disclosure described above, even when there are a transmitter and a receiver both using the same or close frequency bands, more desirable wireless communication can be performed through the receiver. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an illustrative diagram for describing specific examples of TDD configurations. 
         FIG. 2  is an illustrative diagram for describing an example of influence that transmission power of a primary system has on an uplink of a secondary system. 
         FIG. 3  is an illustrative diagram for describing an example of influence that transmission power of the primary system has on a downlink of the secondary system. 
         FIG. 4  is an illustrative diagram for describing an example of the comparison result of the SINR of an uplink and the SINR of a downlink of a WSD. 
         FIG. 5  is an illustrative diagram for describing an example of interference from a frequency channel of a primary system in each frequency channel used in a secondary system. 
         FIG. 6  is an illustrative diagram for describing a TDD configuration dedicated to a downlink. 
         FIG. 7  is an illustrative diagram for describing TDD configurations dedicated to uplinks. 
         FIG. 8  is an illustrative diagram illustrating an example of a schematic configuration of a communication system according to an embodiment of the present disclosure. 
         FIG. 9  is a block diagram illustrating an example of a configuration of an AGLE according to an embodiment. 
         FIG. 10  is an illustrative diagram for describing an example of available channels for a secondary system. 
         FIG. 11  is an illustrative diagram for describing an example of available channel related information to which information on selectable candidates is added. 
         FIG. 12  is a block diagram illustrating an example of a configuration of a master WBS according to an embodiment. 
         FIG. 13  is a block diagram illustrating an example of a configuration of a slave WSD according to an embodiment. 
         FIG. 14  is a sequence diagram illustrating an example of the schematic flow of a communication control process according to an embodiment. 
         FIG. 15  is a sequence diagram illustrating an example of the schematic flow of a communication control process according to a first modified example of an embodiment. 
         FIG. 16  is a sequence diagram illustrating an example of the schematic flow of a communication control process according to a second modified example of an embodiment. 
         FIG. 17  is an illustrative diagram for describing an example of disposition of each device which is a premise of a third embodiment. 
         FIG. 18A  is a first sequence diagram illustrating an example of the schematic flow of a communication control process according to a third modified example of an embodiment. 
         FIG. 18B  is a second sequence diagram illustrating an example of the schematic flow of the communication control process according to the third modified example of an embodiment. 
         FIG. 19  is an illustrative diagram for describing another example of disposition of a CRM. 
         FIG. 20  is an illustrative diagram for describing still another example of disposition of CRMs. 
         FIG. 21  is a block diagram illustrating an example of a schematic configuration of a server to which the technology according to the present disclosure can be applied. 
         FIG. 22  is a block diagram illustrating a first example of a schematic configuration of an eNB to which the technology according to the present disclosure can be applied. 
         FIG. 23  is a block diagram illustrating a second example of the schematic configuration of the eNB to which the technology according to the present disclosure can be applied. 
         FIG. 24  is a block diagram illustrating an example of a schematic configuration of a smartphone to which the technology according to the present disclosure can be applied. 
         FIG. 25  is a block diagram illustrating an example of a schematic configuration of a car navigation apparatus to which the technology according to the present disclosure can be applied. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, preferred embodiments of the present disclosure will be described in detail with reference to the appended drawings. Note that, in this specification and the drawings, elements that have substantially the same function and structure are denoted with the same reference signs, and repeated explanation is omitted. 
     Description will be provided in the following order. 
     1. Introduction
         1.1 Trend of a duplex scheme   1.2. Technical problem   1.3. New technique according to an embodiment       

     2. Schematic configuration of a communication system according to an embodiment 
     3. Configuration of each device
         3.1. Configuration of an AGLE   3.2. Configuration of a master WSD   3.3. Configuration of a slave WSD       

     4. Flow of a process 
     5. Modified examples
         5.1. First modified example   5.2. Second modified example   5.3. Third modified example       

     6. Application examples
         6.1. Application example of an AGLE and a GLDB   6.2. Application example of a master WSD   6.3. Application example of a slave WSD       

     7. Conclusion 
     1. INTRODUCTION 
     First, a trend, a technical problem, and a new technique according to an embodiment with respect to a duplex scheme will be described. 
     1.1. Trend of a Duplex Scheme 
     As duplex schemes with respect to TV white spaces, frequency division duplex (FDD) or time division duplex (TDD) can be employed. In FDD, a frequency channel for an uplink and a frequency channel for a downlink are prepared separately, but in TDD, a frequency channel can be flexibly allocated to an uplink and a downlink. 
     In addition, the more flexible TDD is considered to be desirable as a duplex scheme with respect to the TV white spaces. More flexible allocation to an uplink and a downlink is favorable because a frequency channel used in a primary system depends on the states of channels at each location. It is also because a protocol that operates in carrier sense multiple access (CSMA) or time division multiple access (TDMA) based on TDD in super Wi-Fi (defined in IEEE 802.11af and IEEE 802.22) that is a dominant radio access technology (RAT) of WSDs is employed. In addition, active movements of using frequency bands secondarily through Time Division Long Term Evolution (TD-LTE) have recently appeared in Europe. 
     It should be noted that, in TDD, a plurality of sub-frames are included in a radio frame and a link direction (for example, a downlink or an uplink) is set in units of sub-frames. To be more specific, a plurality of candidates for a link direction configuration (i.e., TDD configuration) which indicates a link direction in units of sub-frames are prepared in a radio frame in advance. In addition, any candidate among the plurality of candidates is set. Specific examples of a plurality of candidates for a TDD configuration will be described below with reference to  FIG. 1 . 
       FIG. 1  is an illustrative diagram for describing the specific examples of TDD configurations. Referring to  FIG. 1 , 7 TDD configurations (Configurations  0  to  6 ) that are defined in the technical standard of 3 rd  Generation Partnership Project (3GPP) (TS 36.211 Table 4.2-2: Uplink-downlink configuration) are shown. In the TDD configurations, each sub-frame is any of a downlink frame that is a sub-frame for a downlink, an uplink frame that is a sub-frame for an uplink, and a special sub-frame. Special sub-frames are provided at the time of switching of a downlink sub-frame and an uplink sub-frame in order to consider a propagation delay from a base station to a terminal device. 
     As illustrated in  FIG. 1 , each of the TDD configurations has a different ratio of the number of sub-frames for an uplink to the number of sub-frames for a downlink. For example, when the special sub-frames are considered as sub-frames for a downlink, the TDD configuration that has the maximum ratio of sub-frames for a downlink (i.e., the downlink sub-frames and the special sub-frames) to the total number of sub-frames is Configuration  5 . The ratio of the sub-frames for a downlink of this case is nine out of ten. On the other hand, the TDD configuration that has the maximum ratio of sub-frames for an uplink to the total number of sub-frames is Configuration  0 . The ratio of the sub-frames for an uplink (i.e., uplink sub-frames) in this case is six out of ten. 
     1.2. Technical Problem 
     In general, transmission power of a transmitter that uses a frequency band secondarily is restricted from causing unfavorable interference with a receiver of a primary system. However, influence of transmission power of a transmitter of a primary system on a receiver of a secondary system that secondarily uses a frequency band has not been carefully considered. For this reason, transmission power of a primary system can significantly influence a secondary system. Examples of the influence of transmission power of a primary system on a secondary system will be described below with reference to  FIGS. 2, 3, and 4 . 
       FIG. 2  is an illustrative diagram for describing an example of the influence that transmission power of a primary system has on an uplink of a secondary system. Referring to  FIG. 2 , a transmitter  10  of a broadcast system which is the primary system, and a master WSD  20  and a slave WSD  30  of the secondary system are illustrated. As illustrated in  FIG. 2 , the transmitter  10  of the broadcast system is normally installed at a very high position so that radio waves reach distant places. In addition, the master WSD  20  that serves as an access point or a base station is also installed at a higher position than the slave WSD  30 . In this case, there is a high possibility of the propagation path from the transmitter  10  to the master WSD  20  being an estimated propagation path. Furthermore, transmission power of the transmitter  10  can be very high. For these reasons, the transmission power of the transmitter  10  can significantly influence the master WSD  20 . That is to say, a transmission signal of the transmitter  10  can seriously interfere with an uplink signal that the master WSD  20  receives. In this manner, the transmission power of the primary system can have significant influence on the uplink of the secondary system. 
       FIG. 3  is an illustrative diagram for describing an example of influence that the transmission power of the primary system has on a downlink of the secondary system. Referring to  FIG. 3 , the transmitter  10  of the broadcast system which is the primary system, and the master WSD  20  and the slave WSD  30  of the secondary system are illustrated as in  FIG. 2 . The transmitter  10  of the broadcast system is normally installed at a very high position and the master WSD  20  is installed at a higher position than the slave WSD  30  as described above. In this case, there is a high possibility of the propagation path from the transmitter  10  to the slave WSD  30  not being an estimated propagation path. For this reason, influence that transmission power of the transmitter  10  has on the slave WSD  30  is smaller than the influence that the transmission power of the transmitter  10  has on the master WSD  20 . In this manner, the provision that the transmission power of the primary system gives to the downlink of the secondary system can be smaller than the influence that the transmission power of the primary system has on the uplink of the secondary system. 
       FIG. 4  is an illustrative diagram for describing an example of the comparison result of the signal-to-interference and noise power ratios (SINR) of an uplink and SINRs of a downlink of a WSD. Referring to  FIG. 4 , an uplink characteristic of the case illustrated in  FIG. 2  and a downlink characteristic of the case illustrated in  FIG. 3  are shown. To be more specific, cumulative distribution functions (CDFs) of SINRs of each of the uplink and downlink are shown. In this example, the values defined in Annex 1 of ECC Report 186 are used for operation parameters of the primary system and secondary system. As a result, the SINRs of the uplink are lower than the SINRs of the downlink as illustrated in  FIG. 4 . 
     As described above, on the premise that the transmitter of the primary system is separated from the devices of the secondary system to some extent, the influence of the primary system on the secondary system strongly appears for the master WSD  20  that is at a higher position, regardless of the planar positional relation between the master WSD  20  and the slave WSD  30 . In other words, the influence of the primary system on the secondary system strongly appears for an uplink. 
     Such influence of the primary system on the secondary system can be particularly remarkable when TDD is employed as the duplex scheme. A specific example of this subject will be described with reference to  FIG. 5  below. 
       FIG. 5  is an illustrative diagram for describing an example of interference from a frequency channel of a primary system in each frequency channel used in a secondary system. Referring to  FIG. 5 , a primary channel that is a frequency channel used in wireless communication of a primary system and three secondary channels that are frequency channels used in wireless communication of a secondary system are shown. More serious interference occurs in the secondary channel (for example, Secondary channel # 1 ) that is closer to the primary channel due to out-of-band radiation from the primary channel as illustrated in  FIG. 5 . In other words, in the secondary channel (for example, Secondary channel # 1 ) that is closer to the primary channel, the SINR of an uplink is particularly lower than the SINR of a downlink. As a result, the throughput of the secondary system can decrease. 
     Thus, even when there are the transmitter and the receiver that use the same or a close frequency band, desirable wireless communication can be performed through the receiver in the present embodiment. To be more specific, for example, more desirable wireless communication can be performed through a WSD. 
     1.3. New Technique According to an Embodiment 
     Definition of New TDD Configurations 
     As already described with reference to  FIG. 1 , for example, 7 TDD configurations are defined by the 3GPP. Particularly in the present embodiment, new TDD configurations are defined. Specifically, a new TDD configuration dedicated to a downlink and/or a new TDD configuration dedicated to an uplink are defined. Examples of the new TDD configurations will be described below with reference to  FIGS. 6 and 7 . 
       FIG. 6  is an illustrative diagram for describing a TDD configuration dedicated to a downlink. Referring to  FIG. 6 , the TDD configuration dedicated to a downlink is shown as Configuration  7 . As illustrated in  FIG. 6 , all sub-frames in the TDD configuration dedicated to a downlink are sub-frames for a downlink (i.e., downlink sub-frames). 
       FIG. 7  is an illustrative diagram for describing TDD configurations dedicated to uplinks. Referring to  FIG. 7 , the configurations dedicated to uplinks of Case  1  and Case  2  are shown as Configuration  8 . Case  1  is a case in which the final sub-frame of the previous radio frame is an uplink sub-frame, and Case  2  is a case in which the final sub-frame of the previous radio frame is a downlink sub-frame. In both Case  1  and Case  2 , the remaining sub-frames other than the first sub-frames (i.e., sub-frames # 1  to # 9 ) are uplink sub-frames. In addition, in Case  1 , the first sub-frame (i.e., sub-frame # 0 ) is also an uplink sub-frame. On the other hand, in Case  2 , uplink transmission is not performed in a part or all of the first sub-frame. This is because reception of a downlink signal can be performed in the first sub-frame due to a propagation delay as in a special sub-frame. 
     For example, sub-frames dedicated to downlinks and sub-frames dedicated to uplinks are prepared as described above. 
     By preparing such new TDD configurations as described above, more desirable wireless communication can be performed through, for example, a receiver of a WSD. 
     For example, by preparing the TDD configurations dedicated to downlinks, influence of a primary channel on a secondary channel can be further reduced even when the primary channel that is used in wireless communication of a primary system and the secondary channel that is used in wireless communication of a secondary system are close to each other in the frequency direction. To be more specific, when the secondary channel is close to the primary channel in the frequency direction, the SINR of an uplink can be particularly lowered as described with reference to  FIG. 5 . For this reason, if a TDD configuration dedicated to a downlink is prepared, the TDD configuration dedicated to a downlink can be set as a TDD configuration for wireless communication of the secondary channel. As a result, interference from the primary system can be further suppressed even when the secondary channel is adjacent to the primary channel. That is to say, even for an available channel adjacent to the primary channel, a decrease in an SINR can be further suppressed. That is to say, desirable wireless communication can be performed through a receiver of a WSD (slave WSD). 
     In addition, for example, by preparing the TDD configuration dedicated to an uplink, the throughput of the uplink can be improved even when the bandwidth of a secondary channel that is away from the primary channel in the frequency direction is narrow (or when the number of secondary channels is small). To be more specific, when the secondary channel is close to the primary channel in the frequency direction, the SINR of the uplink can be particularly lowered as described with reference to  FIG. 5 . In other words, if the secondary channel is away from the primary channel in the frequency direction, the SINR of the uplink is not lowered very much either. For this reason, if the TDD configuration dedicated to an uplink is prepared, the TDD configuration dedicated to the uplink can be set as a TDD configuration for wireless communication of the secondary channel that is away from the primary channel. As a result, even when the bandwidth of the secondary channel is narrow (or when the number of secondary channels is small), many radio resources to be used for the uplink can be secured. For this reason, the throughput of the uplink can be improved. That is to say, more desirable wireless communication can be performed through a receiver of a WSD (master WSD). 
     Furthermore, for example, both the TDD configuration dedicated to a downlink and the TDD configuration dedicated to an uplink can be prepared. In this case, even in a wireless communication system which employs TDD as a duplex scheme, the same wireless communication as when FDD is employed as a duplex scheme can be performed temporarily and/or on some frequency channels. For this reason, for example, the TDD configuration dedicated to a downlink can be set for wireless communication of the secondary channel that is closer to the primary channel, and the TDD configuration dedicated to an uplink can be set for wireless communication of the secondary channel that is away from the primary channel. As a result, the throughput of the uplink can be improved while interference from the primary channel is suppressed. 
     2. SCHEMATIC CONFIGURATION OF A COMMUNICATION SYSTEM ACCORDING TO AN EMBODIMENT 
     Next, a schematic configuration of a communication system according to an embodiment of the present disclosure will be described with reference to  FIG. 8 .  FIG. 8  is an illustrative diagram illustrating an example of the schematic configuration of the communication system  1  according to the present embodiment. Referring to  FIG. 1 , the communication system  1  includes a geo-location database (GLDB)  50 , an advanced geo-location engine (AGLE)  100 , a master white space device (WSD)  200 , and slave WSDs. It should be noted that this example is of a communication system relating to TV white spaces. 
     The GLDB  50  is a regulatory database for managing data of frequency channels that a country operates. For example, the GLDB  50  provides and monitors information and protection rules pertaining to a primary system. As an example, the GLDB  50  provides information (hereinafter referred to as “available channel related information) relating to a frequency channel that a secondary system can use (hereinafter referred to as an “available channel”). 
     The AGLE  100  is a secondary system management node operated by a frequency managing agent of a country or a third party. For example, the AGLE  100  may modify available channel related information provided by the GLDB  50  using a more advanced protection algorithm, or add new information to the available channel related information. One AGLE  100  is presented for the GLDB  50  in this example, however, a plurality of AGLEs  100  can be presented for the GLDB  50 . 
     The master WSD  200  is a device which operates the secondary system within the area of the country. Frequency channels that the master WSD  200  uses in wireless communication, transmission power in the wireless communication, and the like can be decided by the GLDB  50  and/or the AGLE  100 . 
     The slave WSDs  300  perform wireless communication with the master WSD  200 . 
     It should be noted that the AGLE  100  and the master WSD  200  are communication control devices which control wireless communication according to the time division duplex (TDD) scheme. In addition, the wireless communication is, for example, wireless communication of the secondary system that secondarily uses a frequency channel for the primary system. For example, the AGLE  100  controls wireless communication of the secondary system including each master WSD  200 . In addition, the master WSD  200  itself controls the wireless communication of the secondary system. 
     3. CONFIGURATION OF EACH DEVICE 
     Next, examples of configurations of the AGLE  100 , the master WSD  200 , and the slave WSDs  300  according to the present embodiment will be described with reference to  FIGS. 9 to 13 . 
     &lt;3.1. Configuration of an AGLE&gt; 
     An example of the configuration of the AGLE  100  according to the present embodiment will be described with reference to  FIGS. 9 to 11 .  FIG. 9  is a block diagram illustrating the example of the configuration of the AGLE  100  according to the present embodiment. Referring to  FIG. 9 , the AGLE  100  has a network communication unit  110 , a storage unit  120 , and a control unit  130 . 
     (Network Communication Unit  110 ) 
     The network communication unit  110  communicates with other communication nodes. For example, the network communication unit  110  communicates with the GLDB  50  and the master WSD  200 . 
     (Storage Unit  120 ) 
     The storage unit  120  stores programs and data for operations of the AGLE  100 . 
     In addition, the storage unit  120  stores, for example, information relating to an available channel for a secondary system (hereinafter referred to as “available channel related information). The available channel related information includes, for example, restrictions on available time, the center frequency, bandwidth, maximum transmission power, transmission spectrum mask related information, link direction, and the like of each available channel. 
     In addition, the storage unit  120  stores, for example, various kinds of control information to be provided to the GLDB  50  and the master WSD  200  and various kinds of control information to be provided from the GLDB  50  and the master WSD  200  in addition to the available channel related information described above. 
     (Control Unit  130 ) 
     The control unit  130  provides various functions of the AGLE  100 . The control unit  130  includes an information acquisition unit  131 , a channel recognition unit  132 , a selectable candidate decision unit  133 , a channel allocation unit  135 , a configuration selection unit  137 , and a configuration application unit  139 . 
     (Information Acquisition Unit  131 ) 
     The information acquisition unit  131  acquires information relating to available channels for a secondary system (i.e., available channel related information). 
     For example, the available channel related information includes available time, center frequency, bandwidth, maximum transmission power, transmission spectrum mask related information, and the like of each available channel. It should be noted that the available channel information may be information provided by the GLDB  50 , or may be information modified by the AGLE  100  (control unit  130 ) from the information provided by the GLDB  50 . 
     In addition, for example, the information acquisition unit  131  acquires various kinds of information provided from the GLDB  50  and the master WSD  200  via the network communication unit  110 , and causes the storage unit  120  to store the information. 
     In addition, for example, the information acquisition unit  131  acquires various kinds of control information to be provided to the GLDB  50  and the master WSD  200  from the storage unit  120 , and provides the various kinds of information to the GLDB  50  and the master WSD  200  via the network communication unit  110 . 
     (Channel Recognition Unit  132 ) 
     The channel recognition unit  132  recognizes a frequency channel on which wireless communication controlled by the AGLE  100  (hereinafter referred to as “target wireless communication”) is performed. 
     For example, the channel recognition unit  132  recognizes an available channel for a secondary system from acquired available channel information. A specific example of this subject will be described below with reference to  FIG. 10 . 
       FIG. 10  is an illustrative diagram for describing an example of available channels for a secondary system. Referring to  FIG. 10 , a primary channel (i.e., a frequency channel used in wireless communication of a primary system) and three available channels # 1  to # 3  (i.e., frequency channels that the secondary system can use) are shown. The available channel # 1  is the channel that is the closest to the primary channel among the available channels, and the available channel # 3  is the channel that is furthest from the primary channel among the available channels. For example, the channel recognition unit  132  recognizes the three available channels as above. 
     (Selectable Candidate Decision Unit  133 ) 
     For example, target wireless communication is performed on two or more frequency channels. In this case, the selectable candidate decision unit  133  decides one or more candidates that are selectable to be applied to wireless communication of the individual frequency channels (hereinafter referred to as “selectable candidates”) among a plurality of candidates for a TDD configuration for each frequency channel included in the two or more frequency channels. In addition, the selectable candidate decision unit  133  decides one or more selectable candidates based on information of the distance between an interference frequency channel on which an interference signal is transmitted and each of the frequency channels in the frequency direction (hereinafter referred to as “distance related information”). For example, the interference frequency channel is a frequency channel used in a different wireless communication system from the secondary system. As an example, the interference frequency channel is a frequency channel used in the primary system corresponding to the secondary system (or another primary system) (i.e., a primary channel). 
     For example, wireless communication of the secondary system (i.e., target wireless communication) is performed on two or more available channels. In this case, the selectable candidate decision unit  133  decides one or more selectable candidates (TDD configurations) for each available channel included in the two or more available channels. In addition, the selectable candidate decision unit  133  decides one or more selectable candidates based on information relating to the distance between the primary channel and each of the available channels in the frequency direction (i.e., distance related information). That is to say, a restriction on the link direction (TDD configuration) is decided for each available channel based on the distance between an available channel and the primary channel. 
     In addition, the plurality of candidates for a TDD configuration include a TDD configuration dedicated to a downlink and/or a TDD configuration dedicated to an uplink. That is to say, the plurality of candidates for a TDD configuration include Configuration  7  and/or Configuration  8  as illustrated in  FIGS. 6 and 7 . In addition, the plurality of candidates include, for example, Configurations  0  to  6  as illustrated in  FIG. 1 . 
     Technique for Deciding One or More Selectable Candidates 
     First Example 
     As a first example, when the distance between the interference frequency channel and each of the frequency channels is shorter than a distance D 1 , the one or more selectable candidates include a TDD configuration dedicated to a downlink. That is to say, when the distance between the interference frequency channel and each of the frequency channels is shorter than a first distance, the selectable candidate decision unit  133  decides a TDD configuration dedicated to a downlink as the selectable candidate. 
     For example, when the distance between the primary channel and each of the available channels is shorter than the distance D 1 , the selectable candidate decision unit  133  decides the TDD configuration dedicated to a downlink as the selectable candidate. As an example, when there are the three available channels  1  to  3  illustrated in  FIG. 10 , the selectable candidate for the available channel  1  is the TDD configuration dedicated to a downlink. 
     Accordingly, for the available channel that is close to the primary channel (interference frequency channel), the TDD configuration with only downlink sub-frames (TDD configuration with no uplink sub-frame) is selected and applied. As a result, on the available channel, only wireless communication of the downlink is performed, without performing wireless communication of an uplink. For this reason, interference in the available channel is suppressed. That is to say, a decrease in the SINR of the available channel is suppressed. 
     Second Example 
     As a second example, when the distance between the interference frequency channel and each of the frequency channels is longer than a distance D 2 , the one or more selectable candidates include a TDD configuration dedicated to an uplink. 
     For example, when the distance between the primary channel and each of the available channels is longer than the distance D 2 , the selectable candidate decision unit  133  decides the TDD configuration dedicated to an uplink as one selectable candidate. As an example, when there are the three available channels  1  to  3  as illustrated in  FIG. 10 , one or more selectable candidates for the available channel  3  includes the TDD configuration dedicated to an uplink. 
     Accordingly, for the available channel that is away from the primary channel (interference frequency channel), the TDD configuration only with uplink sub-frames can be selected. For this reason, due to the selection of the TDD configuration, the throughput of the uplink in the secondary system can be improved even when the bandwidth of the available channel (or the sum of the bandwidths of all available channels) is narrow. 
     Third Example 
     As a third example, when the distance between the interference frequency channel and each of the frequency channels in the frequency direction is even longer, the one or more selectable candidates include a TDD configuration having a larger number of uplink sub-frames. 
     For example, when the distance between the primary channel and each of the available channels in the frequency direction is even longer, the selectable candidate decision unit  133  decides a TDD configuration having a larger number of uplink sub-frames as a selectable candidate. As an example, when there are the three available channels  1  to  3  as illustrated in  FIG. 10 , the selectable candidate for the available channel  3  includes Configuration  8  (i.e., the TDD configuration dedicated to the uplink). On the other hand, a selectable candidate for the available channel  1  and a selectable candidate for the available channel  2  do not include Configuration  8 . In addition, for example, the selectable candidate for the available channel  2  includes Configurations  0  to  6 . On the other hand, the selectable candidate for the available channel  1  only includes Configuration  7  without including Configurations  0  to  6 . In this manner, as the available channel is farther from the primary channel, the selectable candidates include a TDD configuration having a larger number of uplink sub-frames. 
     Accordingly, when an available channel is farther from the primary channel (interference frequency channel), a TDD configuration having a larger number of uplink sub-frames can be selected for the available channel. On the other hand, when an available channel is closer to the primary channel (interference frequency channel), only a TDD configuration having a smaller number of uplink sub-frames can be selected for the available channel. For this reason, due to the selection of the TDD configuration, interference in the available channels is suppressed. That is to say, a decrease of the SINR of the available channels is suppressed. 
     The first to third examples of the technique for deciding one or more selectable candidates have been described as above. Information of the selectable candidates decided as above is, for example, added to the available channel related information. That is to say, restrictions on the link direction are added to the available channel related information. An example of such available channel related information will be described with reference to  FIG. 11 . 
       FIG. 11  is an illustrative diagram for describing the example of available channel related information to which information of selectable candidates is added. Referring to  FIG. 11 , the available channel related information is shown in the form of a list. For example, the available channel related information includes available duration, center frequency, bandwidth, maximum transmission power, transmission spectrum mask related information, and a restriction on the link direction of the available channels. The restriction on the link direction is the same as selectable candidates. For example, for an available channel with the center frequency of f 1 , the restriction on the link direction is only an FDD uplink. That is to say, a selectable candidate for the available channel is only the TDD configuration dedicated for the uplink. In addition, for an available channel with the center frequency of f 2 , all link directions are approved. That is to say, selectable candidates for the available channel are all TDD configurations. In addition, for an available channel with the center frequency of fn, the restriction on the link direction is only an FDD downlink. That is to say, a selectable candidate for the available channel is only the TDD configuration dedicated to the downlink. In this manner, the available channel related information that includes selectable candidates is generated. 
     Decision Based on QoS 
     In addition, the one or more selectable candidates may be decided based further on information relating to quality of service (QoS) desired for target wireless communication (hereinafter referred to as “QoS related information”). That is to say, the selectable candidate decision unit  133  may decide the one or more selectable candidates based on distance related information and QoS related information. 
     For example, the QoS related information includes throughput, latency, bandwidth, or the like. As an example, when high throughput is not demanded, the selectable candidate decision unit  133  may decide Configurations  0  to  6  as selectable candidates for an available channel that is close to the primary channel. 
     Accordingly, TDD configurations can be selected with a restriction that is necessary and sufficient for wireless communication according to QoS desired for the wireless communication. For this reason, frequency channels can be used more flexibly. 
     Distance Related Information 
     It should be noted that, as an example, the distance related information (i.e., information relating to the distance between the primary channel and each of the available channels in the frequency direction) is, for example, the distance between the center frequency of the primary channel and the center frequency of each of the available channels in the frequency direction. In this case, for example, the center frequency of the primary channel is included in the control information provided from the GLDB  50 , and the center frequency of each of the available channels is included in the available channel related information. 
     As described above, selectable candidates for a TDD configuration are decided for each of the frequency channels. Thereby, the throughput can be improved while suppressing influence of interference. 
     (Channel Allocation Unit  135 ) 
     The channel allocation unit  135  allocates a frequency channel to target wireless communication. 
     For example, the channel allocation unit  135  allocates one or more available channels to wireless communication of the secondary system. 
     Allocation of a Frequency Channel that is Away from the Primary Channel 
     In addition, the target wireless communication is performed on one or more frequency channels. Then, the one or more frequency channels include a frequency channel that is a distance D 4  or farther from the interference frequency channel on which an interference signal is transmitted in the frequency direction. 
     Specifically, for example, wireless communication of the secondary system is performed on one or more available channels. Then, the one or more available channels include an available channel that is the distance D 4  or farther from the primary channel in the frequency direction. That is to say, the channel allocation unit  135  allocates an available channel that is the distance D 4  or farther from the primary channel in the frequency direction for the wireless communication of the secondary system. 
     With such allocation, interference from the primary channel can be reduced more. For this reason, the throughput of the uplink in the secondary system can be improved. 
     Allocation Destination of a Frequency Channel 
     It should be noted that, when there are a plurality of master WSDs  200 , the channel allocation unit  135  may allocate the same available channel or allocate different available channels to each of the master WSDs  200 . As an example, according to the position of each of the master WSDs  200 , the channel allocation unit  135  may allocate available channels thereto, taking influence of the primary channel on the positions into account. 
     (Configuration Selection Unit  137 ) 
     The configuration selection unit  137  selects a TDD configuration for the target wireless communication among the plurality of candidates for a TDD configuration. 
     For example, the configuration selection unit  137  selects a TDD configuration for wireless communication (i.e., the target wireless communication) of the secondary system among the plurality of candidates for a TDD configuration. 
     For example, the plurality of candidates include at least one of the TDD configuration dedicated to the downlink and the TDD configuration dedicated to the uplink. 
     In addition, for example, the plurality of candidates include the TDD configuration dedicated to the downlink. Accordingly, even for an available channel adjacent to the primary channel, interference from the primary system can be further suppressed as described above. That is to say, even for an available channel adjacent to the primary channel, a decrease of the SINR can be further suppressed. 
     In addition, for example, the plurality of candidates include the TDD configuration dedicated to the uplink. Accordingly, even when the bandwidth of the secondary channels that are away from the primary channel is narrow (or the number of secondary channels is small), many radio resources for the uplink can be secured as described above. For this reason, the throughput of the uplink can be improved. 
     Then, for example, the plurality of candidates include both the TDD configuration dedicated to the downlink and the TDD configuration dedicated to the uplink as above. In this case, even in a wireless communication system which employs TDD as a duplex scheme, the same wireless communication as when FDD is employed as a duplex scheme can be performed temporarily and/or on some frequency channels. As a result, the throughput of the uplink can be improved while suppressing interference from the primary channel. 
     In addition, for example, a link direction configuration dedicated to an uplink includes a TDD configuration in which uplink transmission is not performed in a part or all of the first sub-frame among a plurality of sub-frames included in radio frames as described above. This subject is as described in Case  2  with reference to  FIG. 7 . Accordingly, even when the final sub-frame of the previous radio frame is a downlink sub-frame, interference in a downlink signal of the downlink sub-frame can be avoided. 
     When the Target Wireless Communication is Performed on Two or More Frequency Channels 
     When the target wireless communication is performed on two or more frequency channels, the configuration selection unit  137  selects a TDD configuration for the wireless communication of the individual frequency channels among the plurality of candidates for each of the frequency channels included in the two or more frequency channels. 
     For example, when the wireless communication of the secondary system is performed on two or more available channels, the configuration selection unit  137  selects a TDD configuration for the individual available channels included in the two or more available channels. 
     Technique of Selecting a TDD Configuration 
     Selection from Selectable Candidates 
     For example, the configuration selection unit  137  selects a TDD configuration for the wireless communication of the individual frequency channels from one or more selectable candidates among the plurality of candidates. 
     For example, the configuration selection unit  137  selects a TDD configuration from one or more selectable candidates decided by the selectable candidate decision unit  133  for each of available channels included in the two or more available channels. 
     Selection According to the Distance from the Primary Channel 
     First Example 
     As a first example, the two or more frequency channels on which the target wireless communication is performed include a first frequency channel that is closer to the interference frequency channel on which an interference signal is transmitted and a second frequency channel that is away from the interference frequency channel. Then, the configuration selection unit  137  selects a first TDD configuration in which the number of downlink sub-frames is a first number as a TDD configuration for wireless communication of the first frequency channel. In addition, the configuration selection unit  137  selects a second link direction configuration in which the number of downlink sub-frames is a second number that is smaller than the first number as a TDD configuration for wireless communication of the second frequency channel. 
     Specifically, for example, the two or more available channels on which the wireless communication of the secondary system is performed include a first available channel that is close to the primary channel and a second available channel that is away from the primary channel. Then, the configuration selection unit  137  selects a first TDD configuration in which the number of downlink sub-frames is N 1  as a TDD configuration for wireless communication of the first available channel. In addition, the configuration selection unit  137  selects a second TDD configuration in which the number of downlink sub-frames is N 2  (N 2 &lt;N 1 ) as a TDD configuration for wireless communication of the second available channel. That is to say, for the available channel that is closer to the primary channel, the TDD configuration having a larger number of downlink sub-frames is selected, and for the available channel that is away from the primary channel, the TDD configuration having a smaller number of downlink sub-frames is selected. 
     With the selection of the TDD configuration described above, interference in the available channels is suppressed. That is to say, a decrease in the SINR of the available channels is suppressed. 
     It should be noted that, when the selectable candidates are decided as in the “third example” of the “technique for deciding one or more selectable candidates” described above, the selection of the TDD configuration can be automatically realized by selecting the TDD configuration from the selectable candidates. 
     Second Example 
     As a second example, when the distance between the interference frequency channel and each of the frequency channels in the frequency direction is shorter than a distance D 3 , the configuration selection unit  137  selects a TDD configuration dedicated to a downlink as a TDD configuration for wireless communication of each of the frequency channels. 
     Specifically, when the distance between the primary channel and each of the available channels is shorter than D 3 , for example, the configuration selection unit  137  selects a TDD configuration dedicated to a downlink as a TDD configuration for the wireless communication of each of the available channels. 
     With the selection of the TDD configuration as above, interference in the available channel that is close to the primary channel is suppressed. That is to say, a decrease in the SINR of the available channel is suppressed. 
     It should be noted that, when the selectable candidate is decided as in the “first example” of the “technique for deciding one or more selectable candidates” described above, the selection of the TDD configuration can be automatically realized by selecting the TDD configuration from the selectable candidates. 
     When the Target Wireless Communication is Performed on One Frequency Channel 
     When the target wireless communication is performed on one frequency channel, for example, the configuration selection unit  137  selects a TDD configuration for the wireless communication of the one frequency channel among the plurality of candidates. 
     For example, when the wireless communication of the secondary system is performed on one available channel, the configuration selection unit  137  selects a TDD configuration for the wireless communication of the one available channel. 
     As an example, when the wireless communication of the secondary system needs both an uplink and a downlink, the configuration selection unit  137  selects any one of Configurations  0  to  6  as the TDD configuration for the wireless communication of the one available channel. 
     When a Predetermined Type of Wireless Communication is Performed 
     As described above, the target wireless communication is performed, for example, on one or more frequency channels, and the one or more frequency channels include a frequency channel that is the distance D 4  or farther from the interference frequency channel on which an interference signal is transmitted in the frequency direction. In addition, when the target wireless communication is a predetermined type of wireless communication, the configuration selection unit  137  selects a TDD configuration in which the number of uplink sub-frames is greater than a predetermined number as a TDD configuration for the frequency channel that is the distance D 4  or farther from the interference channel. For example, the predetermined type of wireless communication is machine-to-machine (M2M) communication. 
     For example, the wireless communication of the secondary system is performed on one or more available channels, and the one or more available channels include a frequency channel that is the distance D 4  or farther from the primary channel in the frequency direction. In addition, when the line communication of the secondary system is M2M communication, the configuration selection unit  137  selects a TDD configuration in which the number of uplink sub-frames is greater than a predetermined number as a TDD configuration for the frequency channel that is the distance D 4  or farther from the interference channel. 
     With the selection of the TDD configuration as above, interference from the primary channel can be reduced more and the throughput of the uplink can be improved in the wireless communication in which traffic of the uplink is heavy (for example, M2M communication). 
     (Configuration Application Unit  139 ) 
     The configuration application unit  139  applies a selected TDD configuration to the target wireless communication. 
     Specifically, the configuration application unit  139  applies a selected TDD configuration to, for example, wireless communication of the secondary system. 
     When the Target Wireless Communication is Performed on Two or More Frequency Channels 
     For example, the target wireless communication is performed on two or more frequency channels. In this case, the configuration application unit  139  applies a TDD configuration selected for each of frequency channels included in the two or more frequency channels to the wireless communication of each of the frequency channels. 
     Specifically, for example, wireless communication of the secondary system is performed on two or more available channels. In this case, the configuration application unit  139  applies a TDD configuration selected for each of available channels included in the two or more available channels to the wireless communication of each of the available channels. 
     Specific Application Technique 
     For example, the configuration application unit  139  applies a selected TDD configuration to the target wireless communication (for example, wireless communication of the secondary system) by setting the selected TDD configuration in the master WSD  200 . 
     Specifically, for example, the configuration application unit  139  notifies the master WSD  200  of available channel related information, an available channel allocation result, and a TDD configuration selection result via the network communication unit  110 . Then, the master WSD  200  that has received the notification sets the selected TDD configuration for wireless communication of the allocated available channel. Then, the wireless communication in compliance with the selected TDD configuration is performed. 
     &lt;3.2. Configuration of a Master WSD&gt; 
     Next, an example of a configuration of the master WSD  200  according to the present embodiment will be described with reference to  FIG. 12 .  FIG. 12  is a block diagram illustrating the example of the configuration of the master WSD  200  according to the present embodiment. Referring to  FIG. 12 , the master WSD  200  has an antenna unit  210 , a wireless communication unit  220 , a network communication unit  230 , a storage unit  240 , and a control unit  250 . 
     (Antenna Unit  210 ) 
     The antenna unit  210  receives a radio signal, and outputs the received radio signal to the wireless communication unit  220 . In addition, the antenna unit  210  transmits a transmission signal output from the wireless communication unit  220 . 
     (Wireless Communication Unit  220 ) 
     The wireless communication unit  220  performs wireless communication with the slave WSDs  300  when the slave WSDs  300  are positioned within the communication range of the master WSD  200 . 
     (Network Communication Unit  230 ) 
     The network communication unit  230  communicates with other communication nodes. For example, the network communication unit  230  communicates with the AGLE  100 . 
     (Storage Unit  240 ) 
     The storage unit  240  stores programs and data for operations of the master WSD  200 . 
     In addition, for example, the storage unit  240  stores the available channel related information, available channel allocation result, and TDD configuration selection result. 
     In addition, for example, the storage unit  240  stores various kinds of control information provided from the AGLE  100  in addition to the above information. In addition, the storage unit  240  stores various kinds of control information to be provided to the AGLE  100 . 
     (Control Unit  250 ) 
     The control unit  250  provides various functions to the master WSD  200 . The control unit  250  includes an information acquisition unit  251 , a configuration selection unit  253 , a configuration application unit  255 , and a communication control unit  257 . 
     (Information Acquisition Unit  251 ) 
     The information acquisition unit  251  acquires information necessary for the target wireless communication. 
     For example, the information acquisition unit  251  acquires the available channel related information, available channel allocation result, and TDD configuration selection result from the AGLE  100  via the network communication unit  230 . In addition, the information acquisition unit  251  causes the storage unit  240  to store the information. 
     In addition, for example, the information acquisition unit  251  acquires various other kinds of information provided from the AGLE  100  via the network communication unit  230 , and causes the storage unit  240  to store the information. 
     In addition, for example, the information acquisition unit  251  acquires various kinds of control information to be provided to the AGLE  100  from the storage unit  240 , and provides the various kinds of information to the AGLE  100  via the network communication unit  230 . 
     (Configuration Selection Unit  253 ) 
     The configuration selection unit  253  selects a TDD configuration for the target wireless communication among a plurality of candidates for a TDD configuration. 
     For example, the configuration selection unit  253  selects a TDD configuration for the wireless communication of the secondary system (i.e., target wireless communication) among the plurality of candidates for the TDD configuration. 
     In addition, for example, when the target wireless communication is performed on two or more frequency channels, the configuration selection unit  253  selects a TDD configuration for the wireless communication of each of the frequency channels among the plurality of candidates for each of the frequency channels included in the two or more frequency channels. 
     For example, when the wireless communication of the secondary system is performed on two or more available channels, the configuration selection unit  253  selects a TDD configuration for each of the available channels included in the two or more available channels. 
     Specific Selection Technique 
     For example, the configuration selection unit  253  selects a TDD configuration based on the result of selection of the TDD configuration provided from the AGLE  100 . 
     (Configuration Application Unit  255 ) 
     The configuration application unit  255  applies the selected TDD configuration to the target wireless communication. 
     Specifically, for example, the configuration application unit  255  applies the selected TDD configuration to the wireless communication of the secondary system. 
     When the Target Wireless Communication is Performed on Two or More Frequency Channels 
     For example, the target wireless communication is performed on two or more frequency channels. In this case, the configuration application unit  255  applies a TDD configuration selected for each of the frequency channels included in the two or more frequency channels to the wireless communication of each of the frequency channels. 
     Specifically, for example, the wireless communication of the secondary system is performed on two or more available channels. In this case, the configuration application unit  255  applies the TDD configuration selected for each of the available channels included in the two or more available channels to the wireless communication of each of the available channels. 
     Specific Application Technique 
     For example, the configuration application unit  255  applies the selected TDD configuration to the target wireless communication (for example, the wireless communication of the secondary system) by setting the selected TDD configuration in the master WSD  200 . In addition, the configuration application unit  255  notifies the slave WSDs  300  of the set TDD configuration via the wireless communication unit  220 . 
     (Communication Control Unit  257 ) 
     The communication control unit  257  controls wireless communication in compliance with the time division duplex (TDD) scheme. For example, the wireless communication is wireless communication of the secondary system which secondarily uses a frequency channel for the primary system. 
     Specifically, for example, the communication control unit  257  controls the wireless communication of the secondary system based on the TDD scheme according to the set TDD configuration. That is to say, the communication control unit  257  causes the wireless communication unit  220  to transmit a downlink signal using downlink sub-frames and to receive an uplink signal using uplink sub-frames. 
     &lt;3.3. Configuration of a Slave WSD&gt; 
     Next, an example of a configuration of the slave WSD  300  according to the present embodiment will be described with reference to  FIG. 13 .  FIG. 13  is a block diagram illustrating the example of the configuration of the slave WSD  300  according to the present embodiment. Referring to  FIG. 13 , the slave WSD  300  has an antenna unit  310 , a wireless communication unit  320 , a storage unit  330 , and a control unit  340 . 
     (Antenna Unit  310 ) 
     The antenna unit  310  receives a radio signal, and outputs the received radio signal to the wireless communication unit  320 . In addition, the antenna unit  310  transmits a transmission signal output by the wireless communication unit  320 . 
     (Wireless Communication Unit  320 ) 
     The wireless communication unit  320  performs wireless communication with the master WSD  200  when the slave WSD  300  is positioned within the communication range of the master WSD  200 . 
     (Storage Unit  330 ) 
     The storage unit  330  stores programs and data for operations of the slave WSD  300 . 
     In addition, for example, the storage unit  330  stores a TDD configuration set by the master WSD  200 . 
     In addition, for example, the storage unit  330  stores information provided from the master WSD  200  in addition to the above-mentioned information. In addition, the storage unit  330  stores various kinds of control information to be provided to the master WSD  200 . 
     (Control Unit  340 ) 
     The control unit  340  provides various functions of the slave WSD  300 . The control unit  340  includes an information acquisition unit  341 , a configuration recognition unit  343 , and a communication control unit  345 . 
     (Information Acquisition Unit  341 ) 
     The information acquisition unit  341  acquires information necessary for the target wireless communication. 
     For example, the information acquisition unit  341  acquires the set TDD configuration from the master WSD  200  via the wireless communication unit  320 . Then, the information acquisition unit  34  causes the storage unit  330  to store the set TDD configuration. 
     In addition, for example, the information acquisition unit  341  acquires various other kinds of information provided from the master WSD  200  via the wireless communication unit  320 , and causes the storage unit  330  to store the information. 
     In addition, for example, the information acquisition unit  341  acquires various kinds of control information to be provided to the master WSD  200  from the storage unit  330 , and provides the various kinds of information to the master WSD  200  via the wireless communication unit  320 . 
     (Configuration Recognition Unit  343 ) 
     The configuration recognition unit  343  recognizes a TDD configuration to be applied to the target wireless communication among a plurality of candidates for the TDD configuration. 
     For example, the information acquisition unit  341  acquires the set TDD configuration from the master WSD  200  as described above. Then, the configuration recognition unit  343  recognizes the set TDD configuration. 
     (Communication Control Unit  345 ) 
     The communication control unit  345  controls wireless communication in compliance with the time division duplex (TDD) scheme. For example, the wireless communication is wireless communication of the secondary system which secondarily uses a frequency channel for the primary system. 
     Specifically, for example, the communication control unit  345  controls the wireless communication of the secondary system based on the TDD scheme according to the set TDD configuration. That is to say, the communication control unit  345  causes the wireless communication unit  320  to transmit a downlink signal using downlink sub-frames and to receive an uplink signal using uplink sub-frames. 
     4. FLOW OF A PROCESS 
     Next, an example of a communication control process according to the present embodiment will be described with reference to  FIG. 14 .  FIG. 14  is a sequence diagram illustrating the example of the schematic flow of the communication control process according to the present embodiment. 
     First, the GLDB  50  and the AGLE  100  exchange information in a cyclic manner or according to a predetermined trigger (Step S 401 ). The exchanged information herein includes for example, synchronization information (NTP information, Global Positioning System (GPS), IEEE 1588 (a protocol for causing clocks of base stations distributed on a network to synchronize with each other), time correction information, and the like), ID information, managed area information (country, region, latitude, longitude, altitude, and the like), security information (security keys for mutual authentication and the like), information updating cycle information, backup related information, and primary system transmitter information (height of an antenna, position (latitude and longitude), transmission spectrum mask information, use frequency related information (center frequency and bandwidth), gain of an antenna, directivity of an antenna, and the like). 
     In addition, the AGLE  100  and the master WSD  200  exchange information in a cyclic manner or according to a predetermined trigger (Step S 403 ). The exchanged information herein includes, for example, synchronization information, ID information, managed area information, security information, information updating cycle information, backup related information, and transmitter and receiver information of the master WSD  200  and the slave WSD  300  (height of an antenna, position (latitude and longitude), transmission spectrum mask information, use frequency related information (center frequency and bandwidth), gain of an antenna, directivity of an antenna, and the like). 
     In addition, the AGLE  100  decides information relating to an available channel for the secondary system (i.e., available channel related information) (Step S 405 ). The available channel related information includes available time, center frequency, bandwidth, maximum transmission power, and transmission spectrum mask related information of each available channel. In addition, the AGLE  100  (selectable candidate decision unit  133 ) decides one or more selectable candidates (TDD configurations) among a plurality of candidates for a TDD configuration for each of available channels. The one or more selectable candidates are decided based on information relating to the distance between the primary channel and each of the available channels in the frequency direction (i.e., distance related information). Then, the information of the one or more selectable candidates decided as described above is added to the available channel related information. 
     Then, the AGLE  100  (channel allocation unit  135 ) allocates the one or more available channels to wireless communication of the secondary system (Step S 407 ). 
     In addition, the AGLE  100  (configuration selection unit  137 ) selects a TDD configuration for wireless communication of the individual available channels among the plurality of candidates for the TDD configuration for each of the allocated available channels (Step S 409 ). Specifically, the AGLE  100  selects a TDD configuration for wireless communication of the individual available channels from one or more selectable candidates (TDD configurations) for each of the allocated available channels. 
     Then, AGLE  100  (configuration application unit  139 ) notifies the master WSD  200  of the TDD configuration selection result (Step S 411 ). In addition, the AGLE  100  also notifies the master WSD  200  of the available channel related information and the available channel allocation result. 
     After that, the master WDS  200  (configuration application unit  255 ) sets the TDD configuration selected for each of the available channels in the master WSD  200  (S 413 ). 
     Then, the master WSD  200  (communication control unit  257 ) starts wireless communication of the secondary system based on the TDD scheme in compliance with the set TDD configuration. 
     5. MODIFIED EXAMPLES 
     Next, first to fourth modified examples of the present embodiment will be described. 
     5.1. First Modified Example 
     In the examples of the present embodiment described above, the AGLE  100  performs decision of selectable candidates, allocation of available channels, and selection of a TDD configuration. On the other hand, in the first modified example, the GLDB  50  performs decision of selectable candidates, allocation of available channels, and selection of a TDD configuration. That is to say, in the first modified example, the functions of the selectable candidate decision unit  133 , the channel allocation unit  135 , and the configuration selection unit  137  of the AGLE  100  are provided in the GLDB  50  instead of the AGLE  100 . An example of the communication control process according to the first modified example will be described below with reference to  FIG. 15 . 
       FIG. 15  is a sequence diagram illustrating an example of the schematic flow of a communication control process according to the first modified example of the embodiment. It should be noted that Steps S 501 , S 503 , S 513 , S 515 , and S 517  are the same as Steps S 401 , S 403 , S 411 , S 413 , and S 415  of the communication control process described with reference to  FIG. 14 . Thus, only Steps S 505 , S 507 , S 509 , and S 511  will be described here. 
     The GLDB  50  decides information relating to available channels for the secondary system (i.e., available channel related information) (Step S 505 ). The available channel related information includes available time, center frequency, bandwidth, maximum transmission power, and transmission spectrum mask related information of each of the available channels. In addition, the GLDB  50  decides one or more selectable candidates (TDD configurations) among a plurality of candidates for a TDD configuration for each of the available channels. The one or more selectable candidates are decided based on information relating to the distance between the primary channel and each of the available channels in the frequency direction (i.e., distance related information). Then, the information of the one or more selectable candidates decided in this manner is added to the available channel related information. 
     Then, the GLDB  50  allocates the one or more available channels to wireless communication of the secondary system (Step S 507 ). 
     In addition, the GLDB  50  selects a TDD configuration for the wireless communication of the individual available channels among the plurality of candidates for the TDD configuration for each of the allocated available channels (Step S 509 ). 
     Then, the GLDB  50  notifies the AGLE  100  of the TDD configuration selection result (Step S 511 ). In addition, the GLDB  50  also notifies the AGLE  100  of the available channel related information and the available channel allocation result. 
     As described above, according to the first modified example, the decision of selectable candidates, allocation of available channels, and selection of a TDD configuration are performed by the GLDB  50 . It should be noted that some of the decision of selectable candidates, allocation of available channels, and selection of a TDD configuration may be performed by the GLDB  50  and the rest may be performed by the AGLE  100 . 
     5.2. Second Modified Example 
     In the example of the embodiment described above, the AGLE  100  performs selection of a TDD configuration. On the other hand, in the second modified example of the embodiment, the macro WSD  200  performs selection of a TDD configuration. That is to say, in the second modified example, among the functions of the AGLE  100 , the function of the configuration selection unit  137  is provided in the master WSD  200  instead of the AGLE  100 . An example of a communication control process according to the second modified example will be described below with reference to  FIG. 16 . 
       FIG. 16  is a sequence diagram illustrating an example of the schematic flow of the communication control process according to the second modified example of the embodiment. It should be noted that Steps S 601  to S 607 , S 613 , and S 615  are the same as Steps S 401  to S 407 , S 413 , and S 415  of the communication control process described with reference to  FIG. 14 . Thus, only Steps S 609  and S 611  will be described herein. 
     The AGLE  100  notifies the master WSD  200  of the available channel related information and the available channel allocation result (Step S 609 ). 
     After that, the master WSD  200  selects a TDD configuration for wireless communication of the individual available channels among the plurality of candidates for the TDD configuration for each of the allocated available channels (Step S 611 ). 
     As described above, according to the second modified example, the selection of a TDD configuration is performed by the macro WSD  200 . It should be noted that, in such a case, decision of selectable candidates and/or allocation of available channels may be further performed by the GLDB  50 . 
     5.3. Third Modified Example 
     In the examples of the embodiment described above, the techniques for suppressing or avoiding interference of the primary system in the secondary system under management of one GLDB  50  that corresponds to one country have been described. However, when the secondary system (for example, the master WSD  200 ) is positioned near a boundary between countries, there is a possibility of the secondary system being affected by primary systems of the different countries. That is to say, there is a possibility of a primary system of a certain country interfering with a secondary system of another country. 
     Thus, in the third modified example of the present embodiment, not only a primary system under management of one GLDB  50  that corresponds to one country but also a primary system under management of a GLDB  50  that corresponds to another country is taken into account. That is to say, a technique for suppressing or avoiding interference from the primary system under management of the GLDB  50  that corresponds to the other country in a secondary system is provided. 
     Example of Disposition of Each Device According to the Third Modified Example 
     First, an example of disposition of each device that is a premise of a third embodiment will be described with reference to  FIG. 17 .  FIG. 17  is an illustrative diagram for describing the example of disposition of each device that is the premise of the third embodiment. Referring to  FIG. 17 , a boundary  60  between a country A and a country B is shown. The boundary  60  may not necessarily coincide with a border, and may be flexibly set from the perspective of management of frequency bands. In addition, the third modified example can be widely applied to control of secondary use not only at a boundary between countries but also at a boundary between other types of regions that can include communities, states, prefectures, or the like. 
     A GLDB  50 A is a regulatory database that manages data of frequency channels managed by the country A. In addition, an AGLE  100 A is a secondary system management node operated by a frequency managing agent or a third party in the country A. On the other hand, a GLDB  50 B is a regulatory database that manages data of frequency channels managed by the country B. In addition, an AGLE  50 B is a secondary system management node operated by a frequency managing agent or a third party in the country B. 
     A master WSD  200 A is a device that operates a secondary system near the boundary  60  in a region of the country A. A master WSD  200 B is a device that operates a secondary system near the boundary  60  in a region of the country B. There is a possibility of the master WSD  200 A of the country A being influenced not only by a primary system of the country A but also by a primary system of the country B. In addition, similarly, there is a possibility of the master WSD  200 B of the country B being influenced not only by the primary system of the country B but also by the primary system of the country A. 
     For this reason, in the third embodiment, as a control entity for suppressing or avoiding such influence, a Coordinated Resource Management (CRM) is provided. The CRM verifies whether a primary system of a country influences a secondary system of another country, and performs adjustment relating to available channels when necessary. In the example illustrated in  FIG. 17 , the CRM is installed as a part of each AGLE  100 . 
     Flow of a Process 
     Next, an example of a communication control process according to the third modified example of the embodiment will be described with reference to  FIGS. 18A and 18B .  FIGS. 18A and 18B  are sequence diagrams illustrating an example of the schematic flow of the communication control process according to the third modified example of the embodiment. 
     First, the GLDB  50 A and the AGLE  100 A exchange information in a cyclic manner or according to a predetermined trigger (Step S 701 ). Similarly, the GLDB  50 B and the AGLE  100 B also exchange information in a cyclic manner or according to a predetermined trigger. The exchanged information here is as described relating to Step S 401  shown in  FIG. 14 . 
     In addition, the AGLE  100 A and the master WSD  200 A exchange information in a cyclic manner or according to a predetermined trigger (Step S 703 ). Similarly, the AGLE  100 B and the master WSD  200 B also exchange information in a cyclic manner or according to a predetermined trigger. The exchanged information here is as described relating to Step S 403  shown in  FIG. 14 . 
     In addition, the AGLE  100 A decides information relating to available channels (i.e., available channel related information) for the secondary system in the country A (Step S 705 ). Similarly, the AGLE  100 B also decides information relating to available channels (i.e., available channel related information) for the secondary system in the country B. The decided available channel related information includes information of one or more selectable candidates (TDD configurations). 
     Particularly, in the third modified example, the AGLE  100 A and the AGLE  100 B exchange information (Step S 707 ). The exchanged information here includes part or all of the information exchanged in Steps S 701  and S 703 . 
     Then, each of the AGLE  100 A and the AGLE  100 B checks whether there is a primary system that is a primary system of another country whose presence is not known and has influence on the secondary system of its own country. Then, when there is such a primary system, the AGLE  100  estimates influence from the primary system on the secondary system (for example, a level of interference). When the influence is equal to or greater than a predetermined level, the AGLE  100  modifies the available channel information, and makes a decision again (Step S 709 ). The fixing of the available channel information may be, for example, a change of selectable candidates for a TDD configuration, a reduction in the bandwidth of the available channels that receive the influence, or deletion of the available channels. 
     After that, the AGLE  100 A and the AGLE  100 B exchange information again (Step S 711 ). The exchanged information here includes, for example, the re-decided available channel related information. Then, the AGLE  100 A and the AGLE  100 B each confirm the re-decision of the available channel related information and reach an agreement. 
     Then, in Step S 721  to Step S 729 , the same processes as Steps S 407  to S 415  described with reference to  FIG. 14  are performed. 
     It should be noted that the process of Step S 713  may be performed by only one of the AGLE  100 A and the AGLE  100 B rather than both. In this case, which of the AGLE  100 A and the AGLE  100 B will perform the process may be decided based on a load of the process on each of the devices, or may be randomly decided. In addition, the process may be performed alternately by the AGLE  100 A and the AGLE  100 B. 
     In addition, a frequency channel that is dedicated to avoiding the problem of interference near the boundary  60  may be secured. In this case, when influence of the primary system on the secondary system reaches a predetermined level or higher in Step S 713 , use of the dedicated frequency channel may be permitted. 
     Example of Disposition of Other CRMs 
     In the example described above, the CRM is disposed in the AGLEs  100 . However, disposition of the CRM according to the third embodiment is not limited to the example. A specific example of this subject will be described below with reference to  FIGS. 19 and 20 . 
       FIG. 19  is an illustrative diagram for describing another example of disposition of a CRM. Referring to  FIG. 19 , the GLDB  50 A and AGLE  100 A, and the GLDB  50 B and AGLE  100 B are as illustrated in  FIG. 17 . A CRM  300  is installed as a physically independent device from the GLDBs  50  and AGLEs  100  as illustrated in  FIG. 19 , and it may be communicably connected to the GLDBs  50  and AGLEs  100 . 
     This CRM  300 , for example, exchanges information with the AGLE  100 A and AGLE  100 B (and the GLDB  50 A and GLDB  50 B), and checks whether there is a primary system of another country that has influence on a secondary system of one country. Then, when there is such a primary system, the CRM  300  estimates the influence of the primary system on the secondary system (for example, a level of interference). When the influence is equal to or greater than a predetermined level, the CRM  300  modifies the available channel information and makes a decision again. 
       FIG. 20  is an illustrative diagram for describing still another example of disposition of CRMs. Referring to  FIG. 20 , the GLDB  50 A and AGLE  100 A, and the GLDB  50 B and AGLE  100 B are as illustrated in  FIG. 17 . As illustrated in  FIG. 20 , the CRMs may be installed as a part of each GLDB  50 . 
     The GLDB  50  that includes such a CRM in a part thereof checks, for example, whether there is a primary system of another country that has influence on a secondary system of one country. Then, when there is such a primary system, the GLDB  50  estimates the influence of the primary system on the secondary system (for example, a level of interference). When the influence is equal to or greater than a predetermined level, the GLDB  50  modifies the available channel information and makes a decision again. 
     The third modified example of the embodiment has been described above. According to the third modified example of the embodiment, not only interference of a primary system of a country but also interference of a primary system of another country is suppressed or avoided. 
     5.4. Fourth Modified Example 
     The embodiments have mainly been described in the context of TV white spaces so far. However, the technology according to the embodiments is not limited thereto. 
     For example, in review of a fifth generation (5G) wireless communication scheme since 3GPP Release 12, overlapping a macro cell and a small cell has been proposed in order to improve communication capacities (NTT DOCOMO, INC., “Requirements, Candidate Solutions &amp; Technology Roadmap for LTE Rel-12 Onward,” 3GPP Workshop on Release 12 and onwards, Ljubljana, Slovenia, Jun. 11 to 12, 2012). The technology of the embodiments can also be applied to a case in which interference between a macro cell and a small cell can occur. That is to say, the target wireless communication may be wireless communication of a small cell that is partly or entirely overlapped by a macro cell, and an interference frequency channel may be a frequency channel used in the macro cell. 
     In addition, the technology according to the embodiments can also be applied to a case of LSA that is based on the premise of infrastructure sharing. In addition, the technology according to the embodiments can also be applied to a cell case in which interference between a system operated by a mobile virtual network operator (MVNO) and/or a mobile virtual network enabler (MVNE) and a system operated by a mobile network operator (MNO) can occur. In addition, the technology according to the embodiments can also be applied to a case to which Multimedia Broadcast Multicast Service (MBMS) is applied. Specifically, for example, when the same signal is transmitted from a plurality of base stations at once in a synchronized manner using an MBMS single frequency network (MBSFN) transmission scheme, a TDD configuration dedicated to a downlink may be applied to wireless communication of (a plurality of) frequency channels. In this case, a process relating to allocation of uplink channels may be omitted. 
     It should be noted that which system or cell is to be set as an interfering side and which system or cell is to be set to receive interference may be decided according to the priority of each communication link. The priority can be specified based on a QoS requirement or defined in advance. 
     6. APPLICATION EXAMPLES 
     The technology of the present disclosure is applicable to various products. For example, each of the AGLE  100  and the GLDB  50  may be realized as any type of server such as a tower server, a rack server, and a blade server. Each of the AGLE  100  and the GLDB  50  may be a control module (such as an integrated circuit module including a single die, and a card or a blade that is inserted into a slot of a blade server) mounted on a server. 
     For example, the master WSD  200  may be realized as any type of evolved Node B (eNB) such as a macro eNB, and a small eNB. A small eNB may be an eNB that covers a cell smaller than a macro cell, such as a pico eNB, micro eNB, or home (femto) eNB. Instead, the master WSD  200  may be realized as any other types of base stations such as a NodeB and a base transceiver station (BTS). The master WSD  200  may include a main body (that is also referred to as a base station apparatus) configured to control wireless communication, and one or more remote radio heads (RRH) disposed in a different place from the main body. Additionally, various types of terminals to be described below may also operate as the master WSD  200  by temporarily or semi-permanently executing a base station function. 
     For example, the slave WSD  300  may be realized as a mobile terminal such as a smartphone, a tablet personal computer (PC), a notebook PC, a portable game terminal, a portable/dongle type mobile router, and a digital camera, or an in-vehicle terminal such as a car navigation apparatus. The slave WSD  300  may also be realized as a terminal that performs machine-to-machine (M2M) communication (that is also referred to as a machine type communication (MTC) terminal). Furthermore, the slave WSD  300  may be a wireless communication module (such as an integrated circuit module configured with a single die) mounted on each of the terminals. 
     &lt;6.1. Application Example of an AGLE and a GLDB&gt; 
       FIG. 21  is a block diagram illustrating an example of a schematic configuration of a server  750  to which the technology of the present disclosure may be applied. The server  750  includes a processor  751 , a memory  752 , a storage  753 , a network interface  754 , and a bus  756 . 
     The processor  751  may be, for example, a central processing unit (CPU) or a digital signal processor (DSP), and controls functions of the server  750 . The memory  752  includes a random access memory (RAM) and a read only memory (ROM), and stores a program that is executed by the processor  751  and data. The storage  753  may include a storage medium such as a semiconductor memory and a hard disk. 
     The network interface  754  is a wired communication interface for connecting the server  750  to a wired communication network  755 . The wired communication network  755  may be a core network such as an Evolved Packet Core (EPC), or a packet data network (PDN) such as the Internet. 
     The bus  756  connects the processor  751 , the memory  752 , the storage  753 , and the network interface  754  to each other. The bus  756  may include two or more buses (such as a high speed bus and a low speed bus) each of which has different speed. 
     In the server  750  illustrated in  FIG. 21 , the configuration selection unit  137  and the configuration application unit  139  described referring to  FIG. 9  may be implemented by the processor  751 . In addition, the channel recognition unit  132  and the selectable candidate decision unit  133  described referring to  FIG. 9  may be implemented by the processor  751 . 
     &lt;6.2. Application Example of a Master WSD&gt; 
     First Application Example 
       FIG. 22  is a block diagram illustrating a first example of a schematic configuration of an eNB to which the technology of the present disclosure may be applied. An eNB  800  includes one or more antennas  810  and a base station apparatus  820 . Each antenna  810  and the base station apparatus  820  may be connected to each other via an RF cable. 
     Each of the antennas  810  includes a single or a plurality of antenna elements (such as a plurality of antenna elements included in an MIMO antenna), and is used for the base station apparatus  820  to transmit and receive radio signals. The eNB  800  may include the plurality of antennas  810 , as illustrated in  FIG. 22 . For example, the plurality of antennas  810  may each correspond to a plurality of frequency bands used by the eNB  800 . Although  FIG. 22  illustrates the example in which the eNB  800  includes the plurality of antennas  810 , the eNB  800  may also include a single antenna  810 . 
     The base station apparatus  820  includes a controller  821 , a memory  822 , a network interface  823 , and a wireless communication interface  825 . 
     The controller  821  may be, for example, a CPU or a DSP, and operates various functions of a higher layer of the base station apparatus  820 . For example, the controller  821  generates a data packet from data in signals processed by the wireless communication interface  825 , and transfers the generated packet via the network interface  823 . The controller  821  may bundle data from a plurality of base band processors to generate the bundled packet, and transfer the generated bundled packet. The controller  821  may have logical functions of performing control such as radio resource control, radio bearer control, mobility management, admission control, and scheduling. The control may be performed in corporation with an eNB or a core network node in the vicinity. The memory  822  includes a RAM and a ROM, and stores a program that is executed by the controller  821 , and various types of control data (such as a terminal list, transmission power data, and scheduling data). 
     The network interface  823  is a communication interface for connecting the base station apparatus  820  to a core network  824 . The controller  821  may communicate with a core network node or another eNB via the network interface  823 . In that case, the eNB  800 , and the core network node or the other eNB may be connected to each other through a logical interface (such as an Si interface and an X2 interface). The network interface  823  may also be a wired communication interface or a wireless communication interface for wireless backhaul. If the network interface  823  is a wireless communication interface, the network interface  823  may use a higher frequency band for wireless communication than a frequency band used by the wireless communication interface  825 . 
     The wireless communication interface  825  supports any cellular communication scheme such as Long Term Evolution (LTE) and LTE-Advanced, and provides radio connection to a terminal positioned in a cell of the eNB  800  via the antenna  810 . The wireless communication interface  825  may typically include, for example, a baseband (BB) processor  826  and an RF circuit  827 . The BB processor  826  may perform, for example, encoding/decoding, modulating/demodulating, and multiplexing/demultiplexing, and performs various types of signal processing of layers (such as L1, medium access control (MAC), radio link control (RLC), and a packet data convergence protocol (PDCP)). The BB processor  826  may have a part or all of the above-described logical functions instead of the controller  821 . The BB processor  826  may be a memory that stores a communication control program, or a module that includes a processor and a related circuit configured to execute the program. Updating the program may allow the functions of the BB processor  826  to be changed. The module may be a card or a blade that is inserted into a slot of the base station apparatus  820 . Alternatively, the module may also be a chip that is mounted on the card or the blade. Meanwhile, the RF circuit  827  may include, for example, a mixer, a filter, and an amplifier, and transmits and receives radio signals via the antenna  810 . 
     The wireless communication interface  825  may include the plurality of BB processors  826  as illustrated in  FIG. 22 . For example, the plurality of BB processors  826  may each correspond to a plurality of frequency bands used by the eNB  800 . The wireless communication interface  825  may include the plurality of RF circuits  827  as illustrated in  FIG. 22 . For example, the plurality of RF circuits  827  may each correspond to a plurality of antenna elements. Although  FIG. 22  illustrates the example in which the wireless communication interface  825  includes the plurality of BB processors  826  and the plurality of RF circuits  827 , the wireless communication interface  825  may also include a single BB processor  826  or a single RF circuit  827 . 
     Second Application Example 
       FIG. 23  is a block diagram illustrating a second example of a schematic configuration of an eNB to which the technology of the present disclosure may be applied. An eNB  830  includes one or more antennas  840 , a base station apparatus  850 , and an RRH  860 . Each antenna  840  and the RRH  860  may be connected to each other via an RF cable. The base station apparatus  850  and the RRH  860  may be connected to each other via a high speed line such as an optical fiber cable. 
     Each of the antennas  840  includes a single or a plurality of antenna elements (such as a plurality of antenna elements included in an MIMO antenna), and is used for the RRH  860  to transmit and receive radio signals. The eNB  830  may include the plurality of antennas  840  as illustrated in  FIG. 23 . For example, the plurality of antennas  840  may each correspond to a plurality of frequency bands used by the eNB  830 . Although  FIG. 23  illustrates the example in which the eNB  830  includes the plurality of antennas  840 , the eNB  830  may also include a single antenna  840 . 
     The base station apparatus  850  includes a controller  851 , a memory  852 , a network interface  853 , a wireless communication interface  855 , and a connection interface  857 . The controller  851 , the memory  852 , and the network interface  853  are the same as the controller  821 , the memory  822 , and the network interface  823  described with reference to  FIG. 22 . 
     The wireless communication interface  855  supports any cellular communication scheme such as LTE and LTE-Advanced, and provides wireless communication to a terminal positioned in a sector corresponding to the RRH  860  via the RRH  860  and the antenna  840 . The wireless communication interface  855  may typically include, for example, a BB processor  856 . The BB processor  856  is the same as the BB processor  826  described with reference to  FIG. 22 , except that the BB processor  856  is connected to the RF circuit  864  of the RRH  860  via the connection interface  857 . The wireless communication interface  855  may include the plurality of BB processors  856 , as illustrated in  FIG. 23 . For example, the plurality of BB processors  856  may each correspond to a plurality of frequency bands used by the eNB  830 . Although  FIG. 23  illustrates the example in which the wireless communication interface  855  includes the plurality of BB processors  856 , the wireless communication interface  855  may also include a single BB processor  856 . 
     The connection interface  857  is an interface for connecting the base station apparatus  850  (wireless communication interface  855 ) to the RRH  860 . The connection interface  857  may also be a communication module for communication in the above-described high speed line that connects the base station apparatus  850  (wireless communication interface  855 ) to the RRH  860 . 
     The RRH  860  includes a connection interface  861  and a wireless communication interface  863 . 
     The connection interface  861  is an interface for connecting the RRH  860  (wireless communication interface  863 ) to the base station apparatus  850 . The connection interface  861  may also be a communication module for communication in the above-described high speed line. 
     The wireless communication interface  863  transmits and receives radio signals via the antenna  840 . The wireless communication interface  863  may typically include, for example, the RF circuit  864 . The RF circuit  864  may include, for example, a mixer, a filter, and an amplifier, and transmits and receives radio signals via the antenna  840 . The wireless communication interface  863  may include a plurality of RF circuits  864 , as illustrated in  FIG. 23 . For example, the plurality of RF circuits  864  may each correspond to a plurality of antenna elements. Although  FIG. 23  illustrates the example in which the wireless communication interface  863  includes the plurality of RF circuits  864 , the wireless communication interface  863  may also include a single RF circuit  864 . 
     In the eNB  800  and the eNB  830  illustrated in  FIGS. 22 and 23 , the configuration selection unit  253  and the configuration application unit  255  described by using  FIG. 12  may be implemented by the wireless communication interface  825  and the wireless communication interface  855 , and/or the wireless communication interface  863 . At least a part of the functions may also be implemented by the controller  821  and the controller  851 . 
     &lt;6.3. Application Example of a Slave WSD&gt; 
     First Application Example 
       FIG. 24  is a block diagram illustrating an example of a schematic configuration of a smartphone  900  to which the technology of the present disclosure may be applied. The smartphone  900  includes a processor  901 , a memory  902 , a storage  903 , an external connection interface  904 , a camera  906 , a sensor  907 , a microphone  908 , an input device  909 , a display device  910 , a speaker  911 , a wireless communication interface  912 , one or more antenna switches  915 , one or more antennas  916 , a bus  917 , a battery  918 , and an auxiliary controller  919 . 
     The processor  901  may be, for example, a CPU or a system-on-chip (SoC), and controls functions of an application layer and another layer of the smartphone  900 . The memory  902  includes a RAM and a ROM, and stores a program that is executed by the processor  901 , and data. The storage  903  may include a storage medium such as a semiconductor memory and a hard disk. The external connection interface  904  is an interface for connecting an external device such as a memory card or a universal serial bus (USB) device to the smartphone  900 . 
     The camera  906  includes an image sensor such as a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS), and generates a captured image. The sensor  907  may include a group of sensors such as a measurement sensor, a gyro sensor, a geomagnetic sensor, and an acceleration sensor. The microphone  908  converts sounds that are input to the smartphone  900  to audio signals. The input device  909  includes, for example, a touch sensor configured to detect touch onto a screen of the display device  910 , a keypad, a keyboard, a button, or a switch, and receives an operation or an information input from a user. The display device  910  includes a screen such as a liquid crystal display (LCD) and an organic light-emitting diode (OLED) display, and displays an output image of the smartphone  900 . The speaker  911  converts audio signals that are output from the smartphone  900  to sounds. 
     The wireless communication interface  912  supports any cellular communication scheme such as LTE and LTE-Advanced, and performs wireless communication. The wireless communication interface  912  may typically include, for example, a BB processor  913  and an RF circuit  914 . The BB processor  913  may perform, for example, encoding/decoding, modulating/demodulating, and multiplexing/demultiplexing, and performs various types of signal processing for wireless communication. Meanwhile, the RF circuit  914  may include, for example, a mixer, a filter, and an amplifier, and transmits and receives radio signals via the antenna  916 . The wireless communication interface  912  may also be a one-chip module that has the BB processor  913  and the RF circuit  914  integrated thereon. The wireless communication interface  912  may include a plurality of BB processors  913  and a plurality of RF circuits  914 , as illustrated in  FIG. 24 . Although  FIG. 24  illustrates the example in which the wireless communication interface  912  includes the plurality of BB processors  913  and the plurality of RF circuits  914 , the wireless communication interface  912  may also include a single BB processor  913  or a single RF circuit  914 . 
     Furthermore, in addition to a cellular communication scheme, the wireless communication interface  912  may support another type of wireless communication scheme such as a short-distance wireless communication scheme, a near field communication scheme, or a wireless local area network (LAN) scheme. In that case, the wireless communication interface may include the BB processor  913  and the RF circuit  914  for each wireless communication scheme. 
     Each of the antenna switches  915  switches connection destinations of the antennas  916  among a plurality of circuits (such as circuits for different wireless communication schemes) included in the wireless communication interface  912 . 
     Each of the antennas  916  includes a single or a plurality of antenna elements (such as a plurality of antenna elements included in an MIMO antenna), and is used for the wireless communication interface  912  to transmit and receive radio signals. The smartphone  900  may include the plurality of antennas  916 , as illustrated in  FIG. 24 . Although  FIG. 24  illustrates the example in which the smartphone  900  includes the plurality of antennas  916 , the smartphone  900  may also include a single antenna  916 . 
     Furthermore, the smartphone  900  may include the antenna  916  for each wireless communication scheme. In that case, the antenna switches  915  may be omitted from the configuration of the smartphone  900 . 
     The bus  917  connects the processor  901 , the memory  902 , the storage  903 , the external connection interface  904 , the camera  906 , the sensor  907 , the microphone  908 , the input device  909 , the display device  910 , the speaker  911 , the wireless communication interface  912 , and the auxiliary controller  919  to each other. The battery  918  supplies power to each of the blocks of the smartphone  900  illustrated in  FIG. 24  via feeder lines, which are partially shown as dashed lines in the figure. The auxiliary controller  919  operates minimum necessary functions of the smartphone  900 , for example, in a sleep mode. 
     In the smartphone  900  illustrated in  FIG. 24 , the configuration recognition unit  343  and the communication control unit  345  described by using  FIG. 13  may be implemented by the wireless communication interface  912 . At least a part of the functions may also be implemented by the processor  901  and the auxiliary controller  919 . 
     Second Application Example 
       FIG. 25  is a block diagram illustrating an example of a schematic configuration of a car navigation apparatus  920  to which the technology of the present disclosure may be applied. The car navigation apparatus  920  includes a processor  921 , a memory  922 , a global positioning system (GPS) module  924 , a sensor  925 , a data interface  926 , a content player  927 , a storage medium interface  928 , an input device  929 , a display device  930 , a speaker  931 , a wireless communication interface  933 , one or more antenna switches  936 , one or more antennas  937 , and a battery  938 . 
     The processor  921  may be, for example, a CPU or a SoC, and controls a navigation function and another function of the car navigation apparatus  920 . The memory  922  includes a RAM and a ROM, and stores a program that is executed by the processor  921 , and data. 
     The GPS module  924  uses GPS signals received from a GPS satellite to measure a position (such as latitude, longitude, and altitude) of the car navigation apparatus  920 . The sensor  925  may include a group of sensors such as a gyro sensor, a geomagnetic sensor, and an air pressure sensor. The data interface  926  is connected to, for example, an in-vehicle network  941  via a terminal that is not shown, and acquires data generated by the vehicle, such as vehicle speed data. 
     The content player  927  reproduces content stored in a storage medium (such as a CD or a DVD) that is inserted into the storage medium interface  928 . The input device  929  includes, for example, a touch sensor configured to detect touch onto a screen of the display device  930 , a button, or a switch, and receives an operation or an information input from a user. The display device  930  includes a screen such as an LCD or an OLED display, and displays an image of the navigation function or reproduced content. The speaker  931  outputs sounds of the navigation function or the reproduced content. 
     The wireless communication interface  933  supports any cellular communication scheme such as LTE and LTE-Advanced, and performs wireless communication. The wireless communication interface  933  may typically include, for example, a BB processor  934  and an RF circuit  935 . The BB processor  934  may perform, for example, encoding/decoding, modulating/demodulating, and multiplexing/demultiplexing, and performs various types of signal processing for wireless communication. Meanwhile, the RF circuit  935  may include, for example, a mixer, a filter, and an amplifier, and transmits and receives radio signals via the antenna  937 . The wireless communication interface  933  may be a one chip module having the BB processor  934  and the RF circuit  935  integrated thereon. The wireless communication interface  933  may include a plurality of BB processors  934  and a plurality of RF circuits  935 , as illustrated in  FIG. 25 . Although  FIG. 25  illustrates the example in which the wireless communication interface  933  includes the plurality of BB processors  934  and the plurality of RF circuits  935 , the wireless communication interface  933  may also include a single BB processor  934  or a single RF circuit  935 . 
     Furthermore, in addition to a cellular communication scheme, the wireless communication interface  933  may support another type of wireless communication scheme such as a short-distance wireless communication scheme, a near field communication scheme, or a wireless LAN scheme. In that case, the wireless communication interface may include the BB processor  934  and the RF circuit  935  for each wireless communication scheme. 
     Each of the antenna switches  936  switches connection destinations of the antennas  937  among a plurality of circuits (such as circuits for different wireless communication schemes) included in the wireless communication interface  933 . 
     Each of the antennas  937  includes a single or a plurality of antenna elements (such as a plurality of antenna elements included in an MIMO antenna), and is used for the wireless communication interface  933  to transmit and receive radio signals. The car navigation apparatus  920  may include the plurality of antennas  937 , as illustrated in  FIG. 25 . Although  FIG. 25  illustrates the example in which the car navigation apparatus  920  includes the plurality of antennas  937 , the car navigation apparatus  920  may also include a single antenna  937 . 
     Furthermore, the car navigation apparatus  920  may include the antenna  937  for each wireless communication scheme. In that case, the antenna switches  936  may be omitted from the configuration of the car navigation apparatus  920 . 
     The battery  938  supplies power to each of the blocks of the car navigation apparatus  920  illustrated in  FIG. 25  via feeder lines that are partially shown as dashed lines in the figure. The battery  938  accumulates power supplied form the vehicle. 
     In the car navigation apparatus  920  illustrated in  FIG. 25 , the configuration recognition unit  343  and the communication control unit  345  described by using  FIG. 13  may be implemented by the wireless communication interface  933 . At least a part of the functions may also be implemented by the processor  921 . 
     The technology of the present disclosure may also be realized as an in-vehicle system (or a vehicle)  940  including one or more blocks of the car navigation apparatus  920 , the in-vehicle network  941 , and a vehicle module  942 . The vehicle module  942  generates vehicle data such as vehicle speed, engine RPM, or trouble information, and outputs the generated data to the in-vehicle network  941 . 
     7. CONCLUSION 
     The communication devices and each process according to the embodiments of the present disclosure have been described above using  FIGS. 1 to 20 . According to the embodiments of the present disclosure, a TDD configuration for wireless communication is selected among a plurality of candidates for the TDD configuration. Then, the selected TDD configuration is applied to the wireless communication. In addition, the plurality of candidates include at least one of a TDD configuration dedicated to a downlink and a TDD configuration dedicated to an uplink. 
     Accordingly, even when there are a transmitter and a receiver which use the same or close frequency bands, more desirable wireless communication can be performed through the receiver. 
     In addition, for example, the plurality of candidates include a TDD configuration dedicated to a downlink. 
     Accordingly, even for an available channel adjacent to the primary channel, interference of the primary system can be further suppressed. That is to say, even for an available channel adjacent to the primary channel, a decrease of the SINR can be further suppressed. 
     In addition, for example, the plurality of candidates include a TDD configuration dedicated to an uplink. 
     Accordingly, even when the bandwidth of secondary channels that are away from the primary channel is narrow (or the number of secondary channels is small), many radio resources for the uplink can be secured. For this reason, the throughput of the uplink can be improved. 
     In addition, for example, the plurality of candidates include both a TDD configuration dedicated to a downlink and a TDD configuration dedicated to an uplink. 
     In this case, even in a wireless communication system that employs TDD as a duplex scheme, the same wireless communication as when FDD is employed as a duplex scheme can be performed temporarily and/or on some frequency channels. As a result, the throughput of the uplink can be improved while suppressing interference of the primary channel. 
     In addition, for example, for each frequency channel included in the two or more frequency channels, one or more candidates selectable to be applied to wireless communication of each of the frequency channels (i.e., selectable candidates) are decided among a plurality of candidates for a TDD configuration. In addition, the one or more selectable candidates are decided based on information relating to the distance between an interference frequency channel on which an interference signal is transmitted and each of the frequency channels in the frequency direction (i.e., distance related information). 
     Accordingly, the throughput can be improved while suppressing the influence of interference. 
     In addition, for example, when the distance between the interference frequency channel and each of the frequency channels is shorter than the distance D 1 , the one or more selectable candidates include a TDD configuration dedicated to a downlink. 
     Accordingly, for an available channel that is close to the primary channel (interference frequency channel), a TDD configuration having only downlink sub-frames (a TDD configuration with no uplink sub-frames) is selected and applied. As a result, only downlink wireless communication is performed on the available channel, without performing uplink wireless communication. For this reason, interference in the available channel is suppressed. That is to say, a decrease of the SINR of the available channel is suppressed. 
     In addition, for example, when the distance between the interference frequency channel and each of the frequency channels is longer than the distance D 2 , the one or more selectable candidates include a TDD configuration dedicated to an uplink. 
     Accordingly, for an available channel that is away from the primary channel (interference frequency channel), a TDD configuration having only uplink sub-frames is selectable. For this reason, with the selection of the TDD configuration, even when the bandwidth of the available channel (or the sum of the bandwidths of all available channels) is narrow, the throughput of the uplink in the secondary system can be improved. 
     In addition, for example, when the distance between the interference frequency channel and each of the frequency channels in the frequency direction is even longer, the one or more selectable candidates include a TDD configuration having a larger number of uplink sub-frames. 
     Accordingly, when an available channel is farther from the primary channel (interference frequency channel), the TDD configuration having a larger number of uplink sub-frames can be selected for the available channel. On the other hand, when an available channel is closer to the primary channel (interference frequency channel), only a TDD configuration having a smaller number of uplink sub-frames can be selected for the available channel. For this reason, with the selection of the TDD configurations, interference in the available channel is suppressed. That is to say, a decrease of the SINR of the available channel is suppressed. 
     The preferred embodiments of the present disclosure have been described above with reference to the accompanying drawings, whilst the present disclosure is not limited to the above examples, of course. A person skilled in the art may find various alterations and modifications within the scope of the appended claims, and it should be understood that they will naturally come under the technical scope of the present disclosure. 
     Processing steps in the communication control process in the present specification do not necessarily have to be performed in the chronological order described in the flowcharts. For example, the processing steps in the communication control process may be performed in order different from the order described as the flowcharts, or may be performed in parallel. 
     It is also possible to create a computer program for causing hardware such as a CPU, ROM, and RAM built in a communication control device (such as the GLDB, the AGLE, and the master MSD) and a communication device (such as a the slave WSD) to exhibit functions similar to each structural element of the communication control device and the communication device. There is also provided a storage medium having the computer program stored therein. 
     Additionally, the present technology may also be configured as below. 
     (1) 
     A communication control device that controls wireless communication in compliance with a time division duplex (TDD) scheme, the communication control device including: 
     a selection unit configured to select a link direction configuration for the wireless communication among a plurality of candidates for the link direction configuration which indicates a link direction in units of sub-frames of a radio frame which includes a plurality of sub-frames; and 
     an application unit configured to apply the selected link direction configuration to the wireless communication, 
     wherein the plurality of candidates include at least one of a link direction configuration dedicated to a downlink and a link direction configuration dedicated to an uplink. 
     (2) 
     The communication control device according to (1), wherein the plurality of candidates include the link direction configuration dedicated to a downlink. 
     (3) 
     The communication control device according to (1) or (2), wherein the plurality of candidates include the link direction configuration dedicated to an uplink. 
     (4) 
     The communication control device according to (3), wherein the link direction configuration dedicated to an uplink includes a link direction configuration in which uplink transmission is not performed in a part or all of a first sub-frame among the plurality of sub-frames. 
     (5) 
     The communication control device according to any one of (1) to (4), 
     wherein, when the wireless communication is performed on two or more frequency channels, the selection unit selects a link direction configuration for wireless communication of each of the frequency channels from the plurality of candidates for each of the frequency channels that are included in the two or more frequency channels, and 
     wherein the application unit applies the link direction configuration selected for each of the frequency channels to wireless communication of each of the frequency channels. 
     (6) 
     The communication control device according to (5), 
     wherein the selection unit selects the link direction configuration for the wireless communication of each of the frequency channels from one or more selectable candidates among the plurality of candidates, and 
     wherein the one or more selectable candidates are decided based on information relating to the distance between an interference frequency channel on which an interference signal is transmitted and each of the frequency channels in a frequency direction. 
     (7) 
     The communication control device according to (6), wherein the one or more selectable candidates are decided based further on information relating to service quality desired for the wireless communication. 
     (8) 
     The communication control device according to (6) or (7), wherein, when the distance between the interference frequency channel and each of the frequency channels is shorter than a first distance, the one or more selectable candidates are the link direction configuration dedicated to a downlink. 
     (9) 
     The communication control device according to any one of (6) to (8), wherein, when the distance between the interference frequency channel and each of the frequency channels is longer than a second distance, the one or more selectable candidates include the link direction configuration dedicated to an uplink. 
     (10) 
     The communication control device according to any one of (6) to (9), wherein, when the distance between the interference frequency channel and each of the frequency channels is even longer, the one or more selectable candidates include a link direction configuration having the larger number of uplink sub-frames. 
     (11) 
     The communication control device according to any one of (5) to (10), 
     wherein the two or more frequency channels include a first frequency channel that is closer to an interference frequency channel on which an interference signal is transmitted and a second frequency channel that is farther from the interference frequency channel, and 
     wherein the selection unit selects a first link direction configuration of which the number of downlink sub-frames is a first number as a link direction configuration for wireless communication of the first frequency channel, and selects a second link direction configuration of which the number of downlink sub-frames is a second number that is smaller than the first number as a link direction configuration for wireless communication of the second frequency channel. 
     (12) 
     The communication control device according to any one of (5) to (11), wherein, when the distance between an interference frequency channel on which an interference signal is transmitted and each of the frequency channels in a frequency direction is shorter than a third distance, the selection unit selects the link direction configuration dedicated to a downlink as a link direction configuration for wireless communication of each of the frequency channels. 
     (13) 
     The communication control device according to any one of (1) to (12), 
     wherein the wireless communication is performed on one or more frequency channels, and 
     wherein the one or more frequency channels include a frequency channel that is a fourth distance or more apart from an interference frequency channel on which an interference signal is transmitted in a frequency direction. 
     (14) 
     The communication control device according to (13), wherein, when the wireless communication is a predetermined type of wireless communication, the selection unit selects a link direction configuration of which the number of uplink sub-frames is greater than a predetermined number as a link direction configuration for the frequency channel that is the fourth distance or more apart from the interference frequency channel. 
     (15) 
     The communication control device according to (14), wherein the predetermined type of wireless communication is machine-to-machine communication. 
     (16) 
     The communication control device according to any one of (6) to (15), 
     wherein the wireless communication is wireless communication of a secondary system that secondarily uses a frequency channel for a primary system, and 
     wherein the interference frequency channel is a frequency channel that is used in another wireless communication system different from the secondary system. 
     (17) 
     The communication control device according to any one of (6) to (15), 
     wherein the wireless communication is wireless communication of a small cell which is partly or entirely overlapped by a macro cell, and 
     wherein the interference frequency channel is a frequency channel that is used in the macro cell. 
     (18) 
     A communication control method for controlling wireless communication in compliance with a time division duplex (TDD) scheme, the communication control method including: 
     selecting a link direction configuration for the wireless communication among a plurality of candidates for the link direction configuration which indicates a link direction in units of sub-frames of a radio frame which includes a plurality of sub-frames; and 
     applying the selected link direction configuration to the wireless communication, 
     wherein the plurality of candidates include at least one of a link direction configuration dedicated to a downlink and a link direction configuration dedicated to an uplink. 
     (19) 
     A communication control device including: 
     a recognition unit configured to recognize a frequency channel on which wireless communication is performed in compliance with a time division duplex (TDD) scheme; and 
     a decision unit configured to, when the wireless communication is performed on two or more frequency channels, decide one or more candidates selectable to be applied to wireless communication of each of the frequency channels among a plurality of candidates for a link direction configuration that indicates a link direction in units of sub-frames of a radio frame that includes a plurality of sub-frames for each of the frequency channels included in the two or more frequency channels, on the basis of information relating to the distance between an interference frequency channel on which an interference signal is transmitted and each of the frequency channels in a frequency direction, 
     wherein the plurality of candidates include at least one of a link direction configuration dedicated to a downlink and a link direction configuration dedicated to an uplink. 
     (20) 
     A communication device that controls wireless communication in compliance with a time division duplex (TDD) scheme, the communication device including: 
     a recognition unit configured to recognize a link direction configuration to be applied to the wireless communication among a plurality of candidates for the link direction configuration that indicates a link direction in units of sub-frames of a radio frame that includes a plurality of sub-frames; and 
     a communication control unit configured to control the wireless communication in compliance with the recognized link direction configuration, 
     wherein the plurality of candidates include at least one of a link direction configuration dedicated to a downlink and a link direction configuration dedicated to an uplink. 
     REFERENCE SIGNS LIST 
     
         
           50  GLDB (Geo-Location Database) 
           60  boundary 
           100  AGLE (Advanced Geo-Location Engine) 
           132  channel recognition unit 
           133  selectable candidate decision unit 
           137  configuration selection unit 
           139  configuration application unit 
           200  master WSD (White Space Device) 
           253  configuration selection unit 
           255  configuration application unit 
           300  slave WSD (White Space Device) 
           343  configuration recognition unit 
           345  communication control unit