Abstract:
Some aspects of the present disclosure relate to a base station, a communication method, and a program for supporting a multiple_ABS feature of the 3rd Generation Partnership Project (3GPP). In some embodiments, an interference protection status of a communication frame is determined, based at least in part on configurations of base stations. The configurations may indicate patterns of one of more frames of a first type. The first type of frame may be an Absolute Blank Subframe type. Some of the configurations may differ, at least in part. In some embodiments, the interference protection status of a frame may be determined to be a protected status, an unprotected status, or a partially protected status.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application builds upon concepts disclosed in a prior application by one or more of the inventors and/or the assignee, including the following: Japan Patent Application No. 2011-288780, titled “BASE STATION, COMMUNICATION METHOD, AND PROGRAM,” filed Dec. 28, 2011. 
     TECHNICAL FIELD 
     The present disclosure relates to a base station, a communication method, and a program. 
     BACKGROUND ART 
     At present, in the 3rd Generation Partnership Project (3GPP), the standardization process of LTE, the next-generation wireless communication standard, is in progress so as to further improve the performance of wireless communications. In LTE, examination has been conducted to improve coverage by the introduction of base stations other than macro eNodeBs, such as Home eNodeBs (femtocell base stations, or small base stations for mobile phones), Remote Radio Heads (RRHs), pico eNodeBs, or the like. Such next generation wireless communication is disclosed in, for example, JP 2011-521512A. 
     Also, in LTE Rel-10, an interference control method called Almost Blank Subframe (ABS) has been standardized. An ABS is a subframe which limits transmission other than a reference signal from a macro eNodeB in some subframes, or a subframe in which transmission other than a reference signal from a macro eNodeB is limited. A subframe set as an ABS may reduce interference with respect to a received signal of a user equipment (UE) belonging to a pico eNodeB located within a cell a macro eNodeB provides. Also, setting the same subframe between neighboring macro eNodeBs has been proposed. 
     CITATION LIST 
     Patent Literature 
     JP 2011-521512A 
     SUMMARY 
     However, in the 3GPP, multiple_ABS technology for permitting the setting of different ABSs between macro eNodeBs has been discussed. If multiple_ABS is introduced, macro eNodeBs setting the same subframe as the ABS and macro eNodeBs not setting the same subframe as the ABS are mixed among a plurality of neighboring macro eNodeBs. As a result, even in subframes which are set as ABSs by a macro eNodeB, a received signal of a UE belonging to a pico eNodeB may receive interference from neighboring macro eNodeBs. 
     Therefore, the present disclosure proposes a new and improved base station, communication method, and program, which can appropriately determine a protection status from interference of each communication frame. Whether an ABS configuration is well-suited to a particular cell or area may depend on the number of communication terminals in that cell or area. Thus, one advantage of multiple_ABS technology is that it allows macro eNodeBs to use different ABS configurations in different cells or areas, which protects communication terminals from interference without unduly limiting the terminals&#39; communication throughput. However, as described above, the use of multiple_ABS technology gives rise to a scenario in which one or more base stations near a terminal treat a given subframe as an ABS, while one or more other base stations near the terminal do not treat the subframe as an ABS. As a result, the terminal may experience some interference associated with the subframe. Some aspects of the present disclosure relate to techniques for determining, at a base station, an interference protection status for a communication control device associated with the base station. In addition, some aspects of the present disclosure relate to transmitting information from the base station to the communication control device in a format that is backward compatible with existing techniques for transmitting information from a base station to a communication control device. 
     According to an embodiment of the present disclosure, there is provided a method which includes, with a processor of a base station, determining an interference protection status of a frame based at least in part on information indicating configurations of base stations, wherein a first of the configurations differs from at least a second of the configurations, and wherein a portion of the information indicating the second of the configurations is received from a second base station. 
     According to another embodiment of the present disclosure, there is provided a base station including an interference determination unit configured to determine an interference protection status of a frame based at least in part on information indicating configurations of two or more base stations, wherein a first of the configurations differs from at least a second of the configurations, and wherein a portion of the information indicating the second of the configurations is received from a second base station. 
     According to another embodiment of the present disclosure, there is provided a computer-readable medium having recorded thereon a computer program which, when executed by at least one processing unit, performs a method including determining an interference protection status of a frame based at least in part on information indicating configurations of base stations, wherein a first of the configurations differs from at least a second of the configurations, and wherein a portion of the information indicating the second of the configurations is received from a second base station. According to another embodiment of the present disclosure, there is provided a wireless communication system including a first base station and a second base station. The first base station includes an interference determination unit. The first base station is configured to store information indicating a first configuration. The second base station is configured to store information indicating a second configuration. The interference determination unit of the first base station is configured to determine an interference protection status of a frame based at least in part on the information indicating the first configuration of the first base station and the information indicating the second configuration of the second base station, and the first configuration differs from the second configuration. 
     Advantageous Effects of Invention 
     As described above, according to the present disclosure, a protection status from interference of each communication frame can be appropriately determined. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is an explanatory diagram illustrating a configuration of a communication system according to an embodiment of the present disclosure. 
         FIG. 2  is an explanatory diagram illustrating a 4G frame format. 
         FIG. 3  is an explanatory diagram illustrating a range expansion area of a pico eNodeB  30 . 
         FIG. 4  is an explanatory diagram illustrating a subframe set as an ABS. 
         FIG. 5  is an explanatory diagram illustrating a subframe set as an MBSFN type ABS. 
         FIG. 6  is an explanatory diagram illustrating specific examples of configurations. 
         FIG. 7  is a functional block diagram illustrating a configuration of an eNodeB according to a first embodiment of the present disclosure. 
         FIG. 8  is an explanatory diagram illustrating a specific example of a determination by an interference determination unit. 
         FIG. 9  is a flowchart illustrating an operation of an eNodeB according to a first embodiment of the present disclosure. 
         FIG. 10  is an explanatory diagram illustrating a modified example of a determination by an interference determination unit. 
         FIG. 11  is a flowchart illustrating an operation of an eNodeB according to the modified example. 
         FIG. 12  is an explanatory diagram illustrating an application example of the first embodiment. 
         FIG. 13  is a functional block diagram illustrating a configuration of an eNodeB according to a second embodiment of the present disclosure. 
         FIG. 14  is an explanatory diagram illustrating an example of an arrangement of an eNodeB and a pico eNodeB. 
         FIG. 15  is a flowchart illustrating an operation of an eNodeB according to a second embodiment of the present disclosure. 
         FIG. 16  is an explanatory diagram illustrating a configuration of a pico eNodeB according to a third embodiment of the present disclosure. 
         FIG. 17  is a functional block diagram illustrating a configuration of a UE  20  according to a third embodiment of the present disclosure. 
         FIG. 18  is an explanatory diagram illustrating a specific example of signal quality measurement according to a third embodiment of the present disclosure. 
         FIG. 19  is an explanatory diagram illustrating an application example of the signal quality measurement. 
         FIG. 20  is a sequence diagram illustrating an operation of a communication system according to a third embodiment of the present disclosure. 
     
    
    
     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 appended drawings, structural elements that have substantially the same function and structure are denoted with the same reference numerals, and repeated explanation of these structural elements is omitted. 
     Also, in this specification and the drawings, there are cases in which a plurality of elements that have substantially the same function and structure are distinguished from one another by assigning different letters after the same reference signs. For example, a plurality of configurations that have substantially the same functional configuration, if necessary, are distinguished such as in UEs  20 A,  20 B and  20 C. However, if the plurality of elements that have substantially the same functional configuration need not be especially distinguished from one another, the common reference sign alone is assigned thereto. For example, if the UEs  20 A,  20 B and  20 C need not be especially distinguished from one another, they are simply referred to as the UEs  20 . 
     Also, the present disclosure will be described in order of the following items. 
     1. Basic Configuration of Communication System 
     2. First Embodiment 
     2-1. Configuration of eNodeB According to First Embodiment 
     2-2. Operation of eNodeB According to First Embodiment 
     2-3. Application Example 
     3. Second Embodiment 
     3-1. Configuration of eNodeB According to Second Embodiment 
     3-2. Operation of eNodeB According to Second Embodiment 
     3-3. Modified Example 
     4. Third Embodiment 
     4-1. Configuration of Pico eNodeB 
     4-2. Configuration of UE 
     4-3. Signal Quality Measurement 
     4-4. Operation of Communication System 
     5. Concluding Remarks 
     1. BASIC CONFIGURATION OF COMMUNICATION SYSTEM 
       FIG. 1  is an explanatory diagram illustrating a configuration of a communication system according to an embodiment of the present disclosure. As illustrated in  FIG. 1 , a communication system according to an embodiment of the present disclosure includes a plurality of eNodeBs  10 , a plurality of user equipment devices (UEs)  20 , and a plurality of pico eNodeBs  30 . 
     The eNodeB  10  is a radio base station that communicates with the UE  20  included in a cell provided by the eNodeB  10 , that is, coverage of the eNodeB  10  (in this specification, unless specifically described otherwise, the eNodeB  10  represents a macro eNodeB). The eNodeB  10  has enough high power output to form a cell of several km to about 10 km. Also, each eNodeB  10  is connected through a cable, called an X2 interface, and may communicate control data or user data with other eNodeBs  10  through the X2 interface. 
     The pico eNodeB  30  is a low-transmission-power type communication control apparatus that has a transmission power lower than that of the eNodeB  10  by, for example, about 10 dB. Therefore, the pico eNodeB  30  forms a smaller cell than the eNodeB  10  within a cell formed by the eNodeB  10 . The pico eNodeB  30  controls communication with the UE  20  belonging to the pico eNodeB  30 . Also, the pico eNodeB  30  is connected to the eNodeB  10  by the X2 interface, and may communicate control data or user data with the eNodeB  10  through the X2 interface. 
     The UE  20  is a communication terminal that performs reception processing in a resource block for downlink allocated by a base station, such as the eNodeB  10  or the pico eNodeB  30 , and performs transmission processing in a resource block for uplink. In the example illustrated in  FIG. 1 , the UE  20 A belongs to the eNodeB  10 A and performs uplink communication and downlink communication with the eNodeB  10 A. Also, the UE  20 B belongs to the pico eNodeB  30  and performs uplink communication and downlink communication with the pico eNodeB  30 . 
     The UE  20 , for example, may be a smart phone or may be an information processing device, such as a personal computer (PC), a household image processing device (DVD recorder, video deck, or the like), a personal digital assistant (PDA), a household game apparatus, a household appliance, or the like. Also, the UE  20  may be a mobile communication device, such as a portable phone, a personal handyphone system (PHS), a portable music reproduction device, a portable video processing device, a portable game apparatus, or the like. 
     (Frame Configuration) 
     Next, a radio frame shared between a base station such as the above-described eNodeB  10  and the UE  20  will be described. 
       FIG. 2  is an explanatory diagram illustrating a 4G frame format. As illustrated in  FIG. 2 , a 10-ms radio frame includes ten 1-ms subframes #0 to #9. Each subframe is a single resource block including 12 sub carriers X 14 orthogonal frequency division multiplexing (OFDM) symbols, and scheduling allocation is performed in units of resource blocks. Also, 1 OFDM symbol is a unit that is used in an OFDM modulation based communication scheme, and is a unit that outputs data processed in one Fast Fourier Transform (FFT). 
     Also, as illustrated in  FIG. 2 , each subframe includes a control area and a data area. The control area includes the leading 1 to 3 OFDM symbols ( FIG. 2  illustrates an example in which the control area is 3 OFDM symbols), and is used for transmission of a control signal, called a Phy DownLink Control Channel (PDCCH). Also, the data area following the control area is used for transmission of user data or the like, called a Phy DownLink Shared Channel (PDSCH). 
     Also, in the control area and the data area, a cell-specific reference signal (RS) is arranged. The UE  20  may perform channel estimation by receiving the reference signal, and may perform decoding processing of the PDSCH or the like, based on the result of the channel estimation. 
     (Range Expansion) 
     Incidentally, the UE  20  performs measurement of received power, and basically determines a base station having the highest received power as a connection destination. However, as described above, the pico eNodeB  30  has a transmission power lower than that of the eNodeB  10 . For this reason, in the measurement by the UE  20 , even when the UE  20  is located close to the pico eNodeB  30 , the received power of the eNodeB  10  is frequently high. As a result, the opportunity for the UE  20  to belong to the pico eNodeB  30  is reduced. 
     To solve such a problem, range expansion technology has been conceived. Range expansion is technology for expanding the cell of the pico eNodeB  30 . Specifically, range expansion is technology that considers the received power of the pico eNodeB  30  as a value greater than an actual measured value by about 20 dB when the UE  20  performs the measurement. 
       FIG. 3  is an explanatory diagram illustrating the range expansion area of the pico eNodeB  30 . Through range expansion, the cell of the pico eNodeB  30  is expanded up to the range expansion area illustrated in  FIG. 3 . By such a configuration, the opportunity for the UE  20  to belong to the pico eNodeB  30  may be increased. 
     On the other hand, in the UE  20  that belongs to the pico eNodeB  30  and is located in the range expansion area, the received power from the eNodeB  10  may be higher than that of the pico eNodeB  30  by about 20 dB. For this reason, it is important to appropriately control interference from the eNodeB  10 . Hereinafter, interference control of the data area to which the PDSCH is transmitted, and interference control of the control area to which the PDCCH is transmitted will be described. 
     (Interference Control of Data Area) 
     Inter-Cell Interference Coordination (ICIC) makes it possible to cope with the interference of the data area. Specifically, the eNodeB  10  may control the interference of the data area in units of resource blocks by exchanging information of a resource block having great interference or a resource block expected to have great interference with the neighboring eNodeBs  10  through the X2 interface. On the other hand, in ICIC, the transmission of the PDCCH is not stopped, and therefore, it has been difficult to use ICIC to avoid the interference of the control area. 
     (Interference Control of Control Area—ABS) 
     For this reason, Almost Blank Subframe (ABS) has been employed for the interference control of the control area. ABS limits transmission other than the reference signal from the macro eNodeB in some subframes. A subframe set as an ABS becomes a transmission limit frame in which transmission other than the reference signal is limited. Hereinafter, ABS will be described in more detail with reference to  FIG. 4 . 
       FIG. 4  is an explanatory diagram illustrating the subframe set as the ABS. As illustrated in  FIG. 4 , in the subframe set as the ABS, the PDCCH and the PDSCH are not transmitted, and the reference signal of the control area and the reference signal of the data area are transmitted. Therefore, in the subframe set as the ABS by the eNodeB  10 , the interference of both of the control area and the data area of the pico eNodeB  30  is suppressed. 
     Also, ABSs include Multimedia Broadcast multicast Single Frequency Network (MBSFN) type ABSs. In a subframe set as an MBSFN type ABS, as illustrated in  FIG. 5 , the reference signal of the data area is not transmitted, and only the reference signal of the control area is transmitted. For this reason, in the subframe set as the MBSFN type ABS, the interference of the pico eNodeB  30  is suppressed more than in the general ABS illustrated in  FIG. 4 . 
     (Setting Pattern of ABSs) 
     As the setting pattern of the ABSs, a plurality of configurations, the cycle of which is eight subframes, are defined. Hereinafter, specific examples of the configurations will be described with reference to  FIG. 6 . 
       FIG. 6  is an explanatory diagram illustrating specific examples of configurations. As illustrated in  FIG. 6 , in a configuration 1, a first subframe is not set as an ABS, and the ABSs are set to second to eighth subframes. Also, in a configuration 2, first and fifth subframes are not set as ABSs, and the ABSs are set to the second to fourth subframes and sixth to eighth subframes. In a similar manner, in configurations 3 to 5, the ABSs are set according to patterns having cycles of 8 ms. 
     Also, although 1 radio frame is 10 ms, since the cycle of a hybrid ACK is 8 ms, the cycle of the configuration was also determined as 8 ms in terms of consistency with the hybrid ACK. 
     (Multiple_ABS) 
     So far, in the neighboring eNodeBs  10 , setting the same configuration among the configurations has been considered. For example, in the example illustrated in  FIG. 1 , the subframe set as the ABS by the eNodeB  10 A was also considered to be set as the ABS by the eNodeBs  10 B and  10 C. For this reason, in the subframe set as the ABS by the eNodeB  10 A, the UE  20 B located near the cell boundary of the eNodeB  10 A received less interference from the neighboring eNodeBs  10 B and  10 C. 
     However, multiple_ABS technology for permitting the setting of different configurations between the neighboring eNodeBs  10  has recently been discussed. Taking this into consideration, an appropriate number of subframes set as the ABSs by the eNodeB  10  will be different. In other words, while the eNodeB  10 , to which a large number of pico eNodeBs  30  belong, has to set a large number of subframes as the ABSs, the eNodeB  10 , to which a small number of pico eNodeBs  30  belong, will have less of a need to set a large number of subframes as the ABSs. 
     Due to this introduction of the multiple_ABS, macro eNodeBs setting the same subframe as the ABS and macro eNodeBs not setting the same subframe as the ABS are mixed among a plurality of neighboring macro eNodeBs. For example, in a case in which the eNodeB  10 A illustrated in  FIG. 1  sets the configuration 2 and the eNodeB  10 B sets the configuration 5, the subframe #3 in the eNodeB  10 A is an ABS, but the subframe #3 in the eNodeB  10 B is not an ABS. For this reason, the UE  20 B located near the cell boundary of the eNodeB  10 A may receive interference from the eNodeB  10 B in the subframe #3. 
     Second Embodiment 
     Background of First Embodiment 
     As described above, when only the configuration of the eNodeB  10 , to which the pico eNodeB  30  belongs, is considered by the introduction of the multiple_ABS, it is difficult for the pico eNodeB  30  to avoid the interference. 
     For this reason, while a plurality of eNodeBs  10  notifying the pico eNodeB  30  of each configuration may be considered, such notification leads to an increase in the load of the X2 interface to the pico eNodeB  30 . Also, since the pico eNodeB  30  basically has the X2 interface with one eNodeB  10 , it is appropriate for one eNodeB  10  to notify of the configuration. 
     Also, in the discussions so far, sharing one configuration between the eNodeB  10  and the pico eNodeB  30  through the X2 interface has been considered. Therefore, in terms of backward compatibility, it is undesirable to notify the pico eNodeB  30  of a plurality of configurations of a plurality of eNodeBs  10 . 
     Therefore, based on the above circumstances, the first embodiment of the present disclosure was created. According to the first embodiment of the present disclosure, even when the multiple_ABS is introduced, a protection status from the interference of each subframe may be appropriately determined. Hereinafter, the first embodiment of the present disclosure will be described in detail. 
     2-1. Configuration of eNodeB According to First Embodiment 
       FIG. 7  is a functional block diagram illustrating the configuration of the eNodeB  10  according to the first embodiment of the present disclosure. As illustrated in  FIG. 7 , the eNodeB  10  according to the first embodiment of the present disclosure includes an antenna group  104 , a radio processing unit  110 , a DA/AD conversion unit  120 , a digital processing unit  130 , an ABS setting unit  140 , an X2 communication unit  150 , a configuration retention unit  160 , and an interference determination unit  170 . 
     (Antenna Group) 
     The antenna group  104  acquires an electrical radio-frequency signal by receiving a radio signal from the UE  20 , and provides the radio-frequency signal to the radio processing unit  110 . Also, the antenna group  104  transmits the radio signal to the UE  20  based on the radio-frequency signal provided from the radio processing unit  110 . Since the eNodeB  10  includes the antenna group  104  having a plurality of antennas, the eNodeB  10  may perform MIMO communication or diversity communication. 
     (Radio Processing Unit) 
     The radio processing unit  110  converts the radio-frequency signal, which is provided from the antenna group  104 , into a baseband signal (uplink signal) by performing analog processing, such as amplification, filtering, and down-conversion. Also, the radio processing unit  110  converts a baseband signal (downlink signal), which is provided from the DA/AD conversion unit  120 , into a radio-frequency signal. 
     (DA/AD Conversion Unit) 
     The DA/AD conversion unit  120  converts the analog-format uplink signal, which is provided from the radio processing unit  110 , into a digital format, and provides the digital-format uplink signal to the digital processing unit  130 . Also, the DA/AD conversion unit  120  converts the digital-format downlink signal, which is provided from the digital processing unit  130 , into an analog format, and provides the analog-format downlink signal to the radio processing unit  110 . 
     (Digital Processing Unit) 
     The digital processing unit  130  performs digital processing on the uplink signal provided from the DA/AD conversion unit  120 , and detects control signal such as PUCCH, or user data such as PUSCH. Also, the digital processing unit  130  generates a digital-format downlink signal for transmission from the eNodeB  10 , and provides the downlink signal to the DA/AD conversion unit  120 . 
     (ABS Setting Unit) 
     The ABS setting unit  140  sets the ABS by the selection and setting of the configuration described with reference to  FIG. 6 . 
     (X2 Communication Unit) 
     The X2 communication unit  150  is configured to perform communication with another eNodeB  10  or the pico eNodeB  30  through the X2 interface. For example, the X2 communication unit  150  has a function as a setting information reception unit that receives setting information, that is, a configuration, of the ABS of the neighboring eNodeB  10 . Also, the X2 communication unit  150  has a function as a notification unit that notifies the pico eNodeB  30  of information indicating a determination result of an interference protection status for each subframe by the interference determination unit  170 . 
     (Configuration Retention Unit) 
     The configuration retention unit  160  retains the configurations of the neighboring eNodeBs  10  which are received by the X2 communication unit  150 . 
     (Interference Determination Unit) 
     The interference determination unit  170  determines the interference protection status of the UE  20 , which belongs to the pico eNodeB  30  within the cell of the eNodeB  10 , at each subframe. Specifically, the interference determination unit  170  determines the interference protection status, based on the configuration which is set by the ABS setting unit  140  and the configuration of the neighboring eNodeB  10  which is retained in the configuration retention unit  160 . 
     For example, in the subframe which is set as the ABS by both the eNodeB  10  including the target pico eNodeB  30  within the cell (hereinafter, when necessary, referred to as a serving eNodeB  10 ) and the neighboring eNodeBs  10 , the communication of the UE  20  belonging to the pico eNodeB  30  is considered to receive less interference. Therefore, the interference determination unit  170  determines that the subframe set as the ABS by the serving eNodeB  10  and the neighboring eNodeBs  10  is a protected frame. 
     Also, in the subframe which is set as the ABS by neither the serving eNodeB  10  nor the neighboring eNodeBs  10 , it is considered that the communication of the UE  20  belonging to the pico eNodeB  30  will receive interference from the plurality of eNodeBs  10 . Therefore, the interference determination unit  170  determines that the subframe set as the ABS by neither the serving eNodeB  10  nor the neighboring eNodeBs  10  is an unprotected (Not Protected) frame. 
     Also, in the subframe which is set as the ABS by the neighboring eNodeBs  10  but is not set as the ABS by the serving eNodeB  10 , it is highly likely that the communication of the UE  20  belonging to the pico eNodeB  30  will receive interference from the serving eNodeB  10 . Therefore, the interference determination unit  170  may determine that the subframe which is set as the ABS by the neighboring eNodeBs  10  and is not set as the ABS by the serving eNodeB  10  is an unprotected frame. 
     Also, in the subframe which is set as the ABS by the serving eNodeB  10  but is not set as the ABS by the neighboring eNodeBs  10 , it is likely that the communication of the UE  20  belonging to the pico eNodeB  30  will receive interference from the neighboring eNodeBs  10 . In other words, the communication of the UE  20  belonging to the pico eNodeB  30  may receive strong or weak interference. Therefore, the interference determination unit  170  determines that the subframe which is set as the ABS by the serving eNodeB  10  and is not set as the ABS by the neighboring eNodeBs  10  is a partially protected (Partial Protected) frame, the interference status of which is uncertain. 
     Hereinafter, a specific example of the determination by the above-mentioned interference determination unit  170  will be described with reference to  FIG. 8 . 
       FIG. 8  is an explanatory diagram illustrating a specific example of the determination by the interference determination unit  170 . More specifically,  FIG. 8  illustrates an example in which the serving eNodeB  10 A sets configuration 2, and the neighboring eNodeBs  10 B and  10 C set configurations 3 and 4, respectively. 
     In this case, since the subframes #2 and #6 are set as ABSs by all of the eNodeBs  10 , the interference determination unit  170  determines that the subframes #2 and #6 are protected frames. 
     Also, since the subframes #1 and #5 are not set as ABSs by any of the eNodeBs  10 , the interference determination unit  170  determines that the subframes #1 and #5 are unprotected frames. 
     Also, since the subframes #3 and #7 are subframes that are set as ABSs by the neighboring eNodeB  10 B and are not set as ABSs by the serving eNodeB  10 A, the interference determination unit  170  determines that the subframes #3 and #7 are unprotected frames. 
     Also, since the subframes #4 and #8 are subframes that are set as ABSs by the serving eNodeB  10  and are not set as ABSs by the neighboring eNodeBs  10 , the interference determination unit  170  determines that the subframes #4 and #8 are partially protected frames. 
     When the interference determination unit  170  determines the interference protection status of each subframe as described above, the interference determination unit  170  specifies configuration X corresponding to the determination result. Herein, in the embodiment, the configuration defining a combination including the partially protected frames in the configurations 1 to 5 described with reference to  FIG. 6  is added, and the interference determination unit  170  specifies the configuration X corresponding to the determination result from these configurations. The X2 communication unit  150  notifies the pico eNodeB  30  of the configuration X specified by the interference determination unit  170 . 
     By this configuration, the pico eNodeB  30  may appropriately check the interference protection status of each subframe based on one configuration received from the serving eNodeB  10 , without notifying the pico eNodeB  30  of the plurality of configurations of the plurality of eNodeBs  10 . 
     2-2. Operation of eNodeB According to First Embodiment 
     The configuration of the eNodeB  10  according to the first embodiment of the present disclosure has been described above. Next, the operation of the eNodeB  10  according to the first embodiment of the present disclosure will be described with reference to  FIG. 9 . 
       FIG. 9  is a flowchart illustrating the operation of the eNodeB  10  according to the first embodiment of the present disclosure. As illustrated in  FIG. 9 , first, the ABS setting unit  140  of the serving eNodeB  10  selects a configuration and sets an ABS (S 404 ), and the X2 communication unit  150  receives a configuration of the neighboring eNodeB  10  (S 408 ). After that, the interference determination unit  170  performs determinations indicated in S 412  to S 428  at each subframe. 
     Specifically, the interference determination unit  170  determines whether a target subframe is set as an ABS by the serving eNodeB  10  (S 412 ). When the target subframe is not set as an ABS by the serving eNodeB  10 , the interference determination unit  170  determines that the corresponding subframe is an unprotected frame (S 416 ). 
     On the other hand, when the target subframe is set as an ABS by the serving eNodeB  10 , the interference determination unit  170  determines whether the corresponding subframe is set as an ABS by all of the neighboring eNodeBs  10  (S 420 ). When all of the neighboring eNodeBs  10  have set the corresponding subframe as an ABS, the interference determination unit  170  determines that the corresponding subframe is a protected frame (S 424 ). On the other hand, when some of the neighboring eNodeBs  10  have not set the corresponding subframe as an ABS (S 420 ), the interference determination unit  170  determines that the corresponding subframe is a partially protected frame (S 428 ). 
     After that, the interference determination unit  170  specifies the configuration corresponding to the determination result of each subframe, and the X2 communication unit  150  notifies the pico eNodeB  30  of the specified configuration (S 432 ). 
     Modified Example 
     Also, although the above description has been given of the example in which the subframe that is set as the ABS by the neighboring eNodeB  10  and is not set as the ABS by the serving eNodeB  10  is handled as the unprotected frame, the embodiment is not limited to this example. For example, the interference determination unit  170  may determine that the subframe which is set as the ABS by the neighboring eNodeB  10  and is not set as the ABS by the serving eNodeB  10  is a partially protected frame. Hereinafter, such a modified example will be described with reference to  FIGS. 10 and 11 . 
       FIG. 10  is an explanatory diagram illustrating the modified example of the determination by the interference determination unit  170 . More specifically, like in  FIG. 8 ,  FIG. 10  illustrates an example in which the serving eNodeB  10 A sets configuration 2, and the neighboring eNodeBs  10 B and  10 C set configurations 3 and 4, respectively. 
     In this case, since the subframes #3 and #7 are subframes that are set as ABSs by the neighboring eNodeB  10 B and are not set as ABSs by the serving eNodeB  10 A, the interference determination unit  170  according to the modified example, as illustrated in  FIG. 10 , determines that the subframes #3 and #7 are partially protected frames. Also, since the determination results regarding the subframes #1, #2, #4-6, and #8 are the same as those described with reference to  FIG. 8 , a detailed description thereof will be omitted herein. 
       FIG. 11  is a flowchart illustrating the operation according to the modified example. As illustrated in  FIG. 11 , first, the ABS setting unit  140  of the serving eNodeB  10  selects a configuration and sets an ABS (S 404 ), and the X2 communication unit  150  receives a configuration of the neighboring eNodeB  10  (S 408 ). After that, the interference determination unit  170  performs determinations indicated in S 414  to S 430  at each subframe. 
     Specifically, the interference determination unit  170  determines whether a target subframe is set as an ABS by all of the eNodeBs  10  including the serving eNodeB  10  and the neighboring eNodeB  10  (S 414 ). When the target subframe is set as an ABS by all of the eNodeBs, the interference determination unit  170  determines that the corresponding subframe is a protected frame (S 418 ). 
     On the other hand, the interference determination unit  170  determines whether the target subframe is set as an ABS by not all but some of the eNodeBs  10  (S 422 ). When the target subframe is not set as an ABS by any of the eNodeBs  10 , the interference determination unit  170  determines that the corresponding subframe is an unprotected frame (S 426 ). On the other hand, when the target subframe is set as an ABS by some of the eNodeBs  10 , the interference determination unit  170  determines that the corresponding subframe is a partially protected frame (S 430 ). 
     After that, the interference determination unit  170  specifies the configuration corresponding to the determination result of each subframe, and the X2 communication unit  150  notifies the pico eNodeB  30  of the specified configuration (S 432 ). 
     2-3. Application Example 
     As described above, according to the embodiment, since the pico eNodeB  30  is notified of the configuration indicating the partially protected frame having the probability of interference, the pico eNodeB  30 , for example, may perform scheduling on the UE  20  located within the range expansion area, while avoiding the partially protected frame, in addition to the unprotected frame. 
     However, if the number of the partially protected frames increases, an amount of resources allocable by the pico eNodeB  30  is adversely affected. Therefore, a case in which the throughput of the pico eNodeB  30  is reduced may be presumed. Therefore, as the application example of the embodiment, a configuration for suppressing the number of partially protected frames will be described below. 
     The ABS setting unit  140  according to the application example sets the configuration at each sector of the eNodeB  10  in cooperation with the neighboring eNodeBs  10 . Specifically, the ABS setting unit  140  of each of the plurality of neighboring eNodeBs  10  sets the same configuration to the sector directed to the central direction of the plurality of corresponding eNodeBs  10 . Hereinafter, a further detailed description will be given with reference to  FIG. 12 . 
       FIG. 12  is an explanatory diagram illustrating the application example of the first embodiment. As illustrated in  FIG. 12 , a sector of the eNodeB  10 A that is directed in the central direction of the eNodeBs  10 A to  10 D is a first sector S1A. Also, a sector of the eNodeB  10 B that is directed in the central direction of the eNodeBs  10 A to  10 D is a first sector S1B. Also, a sector of the eNodeB  10 C that is directed in the central direction of the eNodeBs  10 A to  10 D is a first sector S1C. Likewise, a sector of the eNodeB  10 D that is directed in the central direction of the eNodeBs  10 A to  10 D is a first sector S1D. 
     Therefore, the ABS setting units  140  of the eNodeBs  10 A to  10 D set the same configuration 2 for the first sector S1A of the eNodeB  10 A, the first sector S1B of the eNodeB  10 B, the first sector S1C of the eNodeB  10 C, and the first sector S1D of the eNodeB  10 D. 
     Likewise, the ABS setting units  140  of the eNodeBs  10 A and  10 D to  10 F set the same configuration 3 for the first sector S2A of the eNodeB  10 A, the first sector S2D of the eNodeB  10 D, the first sector S1E of the eNodeB  10 E, and the first sector S1F of the eNodeB  10 F. 
     Herein, the interference determination unit  170  according to the application example determines interference based on the configuration set to the sector of each of the plurality of neighboring eNodeBs  10  which is directed in the central direction of the plurality of eNodeBs  10 . For this reason, according to the application example in which the same configuration is set to these sectors, the mixture of the eNodeBs  10  setting the same subframe as an ABS and the eNodeBs  10  not setting the same subframe as an ABS may be avoided. Therefore, the number of partially protected frames may be suppressed. As a result, the throughput of the pico eNodeB  30  may be improved. 
     3. SECOND EMBODIMENT 
     The first embodiment of the present disclosure has been described above. Next, the second embodiment of the present disclosure will be described. According to the second embodiment, a configuration suitable for each pico eNodeB  30  may be obtained by determining configurations at each pico eNodeB  30  within an eNodeB  10 - 2 . 
     3-1. Configuration of eNodeB According to Second Embodiment 
       FIG. 13  is a functional block diagram illustrating a configuration of an eNodeB  10 - 2  according to a second embodiment of the present disclosure. As illustrated in  FIG. 13 , an eNodeB  10 - 2  according to a second embodiment of the present disclosure includes an antenna group  104 , a radio processing unit  110 , a DA/AD conversion unit  120 , a digital processing unit  130 , an ABS setting unit  140 , an X2 communication unit  150 , a configuration retention unit  160 , an interference determination unit  172 , and a position information retention unit  180 . Since the configurations of the antenna group  104 , the radio processing unit  110 , the DA/AD conversion unit  120 , the digital processing unit  130 , and the ABS setting unit  140  are the same as those described in the first embodiment, a detailed description thereof will be omitted herein. 
     (Position Information Retention Unit) 
     The position information retention unit  180  retains position information of the pico eNodeB  30  within the eNodeB  10 - 2 . Also, the position information of each pico eNodeB  30  may be manually set and may be reported from the pico eNodeB  30 . 
     (Interference Determination Unit) 
     The interference determination unit  172  determines configuration for notification at each pico eNodeB  30  based on the position information of each pico eNodeB  30  which is retained in the position information retention unit  180 , in addition to configurations of a plurality of eNodeBs  10 - 2 . Hereinafter, this point will be described in more detail with reference to  FIG. 14 . 
       FIG. 14  is an explanatory diagram illustrating an example of an arrangement of the eNodeB  10 - 2  and the pico eNodeB  30 . In the example illustrated in  FIG. 14 , the pico eNodeB  30 A is located relatively near the eNodeB  10 - 2 A, and the pico eNodeB  30 B is located near the cell edge of the eNodeB  10 - 2 A. 
     As such, if the position of each pico eNodeB  30  is different, the interference protection status of each pico eNodeB  30  is different even though the combination of the configurations of the respective eNodeBs  10 - 2  is identical. For example, the pico eNodeB  30 A located relatively near the eNodeB  10 - 2 A receives less interference from the neighboring eNodeBs  10 - 2 B and  10 - 2 C. On the other hand, the pico eNodeB  30 B located near the cell edge of the eNodeB  10 - 2 A is expected to receive a relatively large amount of interference from the neighboring eNodeBs  10 - 2 B and  10 - 2 C. 
     Therefore, when there is a non-uniform subframe that is set as an ABS by the serving eNodeB  10 - 2  and is not set as an ABS by the neighboring eNodeB  10 - 2 , the interference determination unit  172  according to the second embodiment determines the interference protection status of the corresponding subframe based on the position information of each pico eNodeB  30 . 
     Specifically, when the pico eNodeB  30  is within a predetermined range from the serving eNodeB  10 - 2 , the interference determination unit  172  may determine that the non-uniform subframe is a protected frame. On the other hand, when the pico eNodeB  30  exists out of the predetermined range from the serving eNodeB  10 - 2 , the interference determination unit  172  may determine that the non-uniform subframe is an unprotected frame. 
     According to this configuration, there is a merit in that it is unnecessary to add a configuration defining a combination including the partially protected frame. However, when the pico eNodeB  30  is within the predetermined range from the serving eNodeB  10 - 2  or outside of the predetermined range, the interference determination unit  172  may determine that the non-uniform subframe is a partially protected frame. 
     3-2. Operation of eNodeB According to Second Embodiment 
     The configuration of the eNodeB  10 - 2  according to the second embodiment of the present disclosure has been described above. Next, the operation of the eNodeB  10 - 2  according to the second embodiment of the present disclosure will be described with reference to  FIG. 15 . 
       FIG. 15  is a flowchart illustrating the operation of the eNodeB  10 - 2  according to the second embodiment of the present disclosure. As illustrated in  FIG. 15 , first, the ABS setting unit  140  of the serving eNodeB  10 - 2  selects a configuration and sets an ABS (S 404 ), and the X2 communication unit  150  receives a configuration of the neighboring eNodeB  10 - 2  (S 408 ). After that, the interference determination unit  170  performs determinations indicated in S 436  to S 456  at each subframe. 
     Specifically, the interference determination unit  172  determines whether a target subframe is set as an ABS by the serving eNodeB  10 - 2  (S 436 ). When the target subframe is not set as an ABS by the serving eNodeB  10 - 2 , the interference determination unit  172  determines that the corresponding subframe is an unprotected frame (S 440 ). 
     On the other hand, when the target subframe is set as an ABS by the serving eNodeB  10 - 2 , the interference determination unit  172  determines whether the corresponding subframe is set as an ABS by all of the neighboring eNodeBs  10 - 2  (S 444 ). When all of the neighboring eNodeBs  10 - 2  have set the corresponding subframe as an ABS, the interference determination unit  172  determines that the corresponding subframe is a protected frame (S 448 ). 
     Herein, when some of the neighboring eNodeBs  10 - 2  have not set the corresponding subframe as an ABS (S 444 ), the interference determination unit  172  determines whether the target pico eNodeB  30  is within a predetermined range from the serving eNodeB  10 - 2  (S 452 ). When the target pico eNodeB  30  is within the predetermined range from the serving eNodeB  10 - 2 , the interference determination unit  172  determines that the corresponding subframe is a protected frame (S 448 ), and when outside of the predetermined range, the interference determination unit  172  determines that the corresponding subframe is an unprotected frame (S 456 ). 
     After that, the interference determination unit  172  specifies the configuration corresponding to the determination result of each subframe, and the X2 communication unit  150  notifies the pico eNodeB  30  of the specified configuration (S 460 ). 
     As described above, according to the second embodiment of the present disclosure, a configuration suitable for each pico eNodeB  30  may be obtained by determining configurations at each pico eNodeB  30  based on the position information of each pico eNodeB  30 . 
     3-3. Modified Example 
     Also, although the above description has been given of the example in which the interference protection status is determined according to whether the pico eNodeB  30  is within the predetermined range from the serving eNodeB  10 - 2 , the embodiment is not limited to this example. As the modified example, the interference determination unit  172  may determine the interference protection status based on the distance between the pico eNodeB  30  and the neighboring eNodeB  10 - 2 . 
     As one example, the non-uniform subframe which is set as the ABS by the serving eNodeB  10 - 2  and is not set as the ABS by the neighboring eNodeB  10 - 2  is considered. In this case, as the distance between the pico eNodeB  30  and the neighboring eNodeB  10 - 2  is shorter, the pico eNodeB  30  receives more interference from the eNodeB  10 - 2  in the corresponding subframe. 
     Therefore, when the distance between the pico eNodeB  30  and the neighboring eNodeB  10 - 2  is less than a predetermined distance, the interference determination unit  172  may determine that the non-uniform subframe is an unprotected frame. On the other hand, when the distance between the pico eNodeB  30  and the neighboring eNodeB  10 - 2  is equal to or greater than the predetermined distance, the interference determination unit  172  may determine that the non-uniform subframe is a protected frame. 
     4. THIRD EMBODIMENT 
     The second embodiment of the present disclosure has been described above. Next, the third embodiment of the present disclosure will be described. According to the third embodiment of the present disclosure, when macro eNodeBs setting the same subframe as an ABS and macro eNodeBs not setting the same subframe as an ABS are mixed, the interference protection status of the corresponding subframe may be determined not on an eNodeB  10  side but on a pico eNodeB  30  side. 
     4-1. Configuration of Pico eNodeB 
       FIG. 16  is an explanatory diagram illustrating a configuration of a pico eNodeB  30  according to a third embodiment of the present disclosure. As illustrated in  FIG. 16 , a pico eNodeB  30  according to a third embodiment of the present disclosure includes an antenna group  304 , a radio processing unit  310 , a DA/AD conversion unit  320 , a digital processing unit  330 , an X2 communication unit  350 , a configuration retention unit  360 , an interference determination unit  370 , a scheduler  380 , and a measurement result retention unit  390 . 
     (Antenna Group) 
     The antenna group  304  acquires an electrical radio-frequency signal by receiving a radio signal from the UE  20 , and provides the radio-frequency signal to the radio processing unit  310 . Also, the antenna group  304  transmits the radio signal to the UE  20 , based on the radio-frequency signal provided from the radio processing unit  110 . Since the pico eNodeB  30  includes the antenna group  304  having a plurality of antennas, the pico eNodeB  30  may perform MIMO communication or diversity communication. 
     (Radio Processing Unit) 
     The radio processing unit  310  converts the radio-frequency signal, which is provided from the antenna group  304 , into a baseband signal (uplink signal) by performing analog processing, such as amplification, filtering, and down-conversion. Also, the radio processing unit  310  converts a baseband signal (downlink signal), which is provided from the DA/AD conversion unit  320 , into a radio-frequency signal. 
     (DA/AD Conversion Unit) 
     The DA/AD conversion unit  320  converts the analog-format uplink signal, which is provided from the radio processing unit  310 , into a digital format, and provides the digital-format uplink signal to the digital processing unit  330 . Also, the DA/AD conversion unit  320  converts the digital-format downlink signal, which is provided from the digital processing unit  330 , into an analog format, and provides the analog-format downlink signal to the radio processing unit  310 . 
     (Digital Processing Unit) 
     The digital processing unit  330  performs digital processing on the uplink signal provided from the DA/AD conversion unit  320 , and detects control signal such as PUCCH, or user data such as PUSCH. Also, the digital processing unit  330  generates a digital-format downlink signal for transmission from the pico eNodeB  30 , and provides the downlink signal to the DA/AD conversion unit  320 . The digital processing unit  330  operates as a communication unit together with the DA/AD conversion unit  320 , the radio processing unit  310 , and the antenna group  304 . 
     (X2 Communication Unit) 
     The X2 communication unit  350  is configured to perform communication with the eNodeB  10  through the X2 interface. For example, the X2 communication unit  350  receives the notification of configuration information, which defines the combination of partially protected frames, from the eNodeB  10 , as described in the first embodiment. 
     (Configuration Retention Unit) 
     The configuration retention unit  360  retains the configuration received from the pico eNodeB  30  by the X2 communication unit  350 . The UE  20  receives the configuration transmitted through the antenna group  304 , performs signal quality measurement according to the received configuration, and reports the measurement result to the pico eNodeB  30 . 
     (Measurement Result Retention Unit) 
     The measurement result retention unit  390  retains the measurement result reported from the UE  20  as described below. Also, the UE  20  performing the measurement may be any one of UEs  20  belonging to the pico eNodeB  30  and may be a UE  20  located within the range expansion area. 
     (Interference Determination Unit) 
     The interference determination unit  370  determines, based on the measurement result of the UE  20 , whether each partially protected frame is handled as a protected frame which is protected from interference or an unprotected frame which receives interference. This point will be described later with reference to  FIGS. 18 and 19 . 
     (Scheduler) 
     The scheduler  380  performs scheduling of the UE  20 , which belongs to the pico eNodeB  30 , according to the determination result by the interference determination unit  370  and the configuration retained by the configuration retention unit  360 . For example, the scheduler  380  allocates only communication resources of protected frames to the UE  20  located within the range expansion area. By such a configuration, it is possible to prevent the UE  20  located within the range expansion area from receiving interference from the eNodeB  10 . 
     4-2. Configuration of UE 
     The configuration of the pico eNodeB  30  according to the third embodiment of the present disclosure has been described above. Next, the configuration of the UE  20  according to the third embodiment of the present disclosure will be described. 
       FIG. 17  is a functional block diagram illustrating the configuration of the UE  20  according to a third embodiment of the present disclosure. As illustrated in  FIG. 17 , the UE  20  according to the third embodiment of the present disclosure includes an antenna group  204 , a radio processing unit  210 , a DA/AD conversion unit  220 , a digital processing unit  230 , a configuration retention unit  260 , and a measurement management unit  270 . 
     (Antenna Group) 
     The antenna group  204  acquires an electrical radio-frequency signal by receiving a radio signal from the eNodeB  10  or the pico eNodeB  30 , and provides the radio-frequency signal to the radio processing unit  210 . Also, the antenna group  204  transmits the radio signal to the eNodeB  10  or the pico eNodeB  30 , based on the radio-frequency signal provided from the radio processing unit  210 . Since the UE  20  includes the antenna group  204  having a plurality of antennas, the UE  20  may perform MIMO communication or diversity communication. 
     (Radio Processing Unit) 
     The radio processing unit  210  converts the radio-frequency signal, which is provided from the antenna group  204 , into a baseband signal (downlink signal) by performing analog processing, such as amplification, filtering, and down-conversion. Also, the radio processing unit  210  converts a baseband signal (uplink signal), which is provided from the DA/AD conversion unit  220 , into a radio-frequency signal. 
     (DA/AD Conversion Unit) 
     The DA/AD conversion unit  220  converts the analog-format downlink signal, which is provided from the radio processing unit  210 , into a digital format, and provides the digital-format downlink signal to the digital processing unit  230 . Also, the DA/AD conversion unit  220  converts the digital-format uplink signal, which is provided from the digital processing unit  230 , into an analog format, and provides the analog-format uplink signal to the radio processing unit  210 . 
     (Digital Processing Unit) 
     The digital processing unit  230  performs digital processing on the downlink signal provided from the DA/AD conversion unit  220 , and detects control signal such as PDCCH, or user data such as PDSCH. Also, the digital processing unit  230  generates a digital-format uplink signal for transmission from the UE  20 , and provides the uplink signal to the DA/AD conversion unit  220 . The digital processing unit  230  operates as a communication unit together with the DA/AD conversion unit  220 , the radio processing unit  210 , and the antenna group  204 . 
     (Configuration Retention Unit) 
     The configuration retention unit  260  retains the configuration received from the pico eNodeB  30 . Also, the configuration represents whether each subframe is a protected frame (ABS), an unprotected frame (not ABS), or a partially protected frame. 
     (Measurement Management Unit) 
     The measurement management unit  270  manages the signal quality measurement according to the configuration retained in the configuration retention unit  260 , and controls the report of the measurement result to the pico eNodeB  30 . Hereinafter, the signal quality measurement will be described in more detail. 
     4-3. Signal Quality Measurement 
     When the subframe defined by the configuration is either of two types, the protected frame or the unprotected frame, the UE  20  performs two types of measurement. In other words, the measurement management unit  270  averages the measurement results of the plurality of protected frames, averages the measurement results of the plurality of unprotected frames, and reports the average value of the protected frames and the average value of the unprotected frames to the pico eNodeB  30  as the measurement result. 
     On the other hand, since each of the partially protected frames is considered to be different in the degree of interference by the combination of the eNodeBs  10  setting ABSs, averaging the measurement results of all partially protected frames is not optimal. Therefore, the measurement management unit  270  may independently perform the measurement of each partially protected frame. In other words, the measurement management unit  270  may report the measurement result of each partially protected frame to the pico eNodeB  30  without averaging the measurement result of each partially protected frame. Hereinafter, this point will be described in more detail with reference to  FIG. 18 . 
       FIG. 18  is an explanatory diagram illustrating a specific example of the signal quality measurement by the third embodiment of the present disclosure. As illustrated in  FIG. 18 , the UE  20  performs measurement in subframes #2, #6 and #10 which are the protected frames (A-1 to A-3), and reports an average value of the measurement result as the measurement result of the protected frames. Also, the UE  20  performs measurement in subframes #1, #5 and #9 which are the unprotected frames (B-1 to B-3), and reports an average value of the measurement result as the measurement result of the unprotected frames. 
     On the other hand, the subframes #3, #4 and #7, which are the partially protected frames, are independently measured. In other words, the UE  20  performs measurement in the subframe #3 which is the partially protected frame (C), and reports the measurement result, without averaging the measurement results of other partially protected frames. Also, the UE  20  may average the measurement result of the subframe #3 with the measurement result of other subframes having different cycles from the subframe #3 (for example, a subframe #1 of a next radio frame), even if the subframe is another partially protected frame. 
     Also, the UE  20  performs measurement in the subframe #4 which is the partially protected frame (D), and reports the measurement result without averaging the measurement results of other partially protected frames. Also, the UE  20  performs measurement in the subframe #7 which is the partially protected frame (E), and reports the measurement result without averaging with the measurement results of other partially protected frames. Likewise, the UE  20  performs measurement in the subframe #8 which is the partially protected frame (F), and reports the measurement result without averaging with the measurement results of other partially protected frames. 
     Since the pico eNodeB  30  receives the report of the measurement result from the UE  20  at each partially protected frame as described above, the pico eNodeB  30  may appropriately determine whether to handle the partially protected frame as the protected frame or the unprotected frame. 
     Application Example 
     Although the example of independently measuring all partially protected frames has been described above, as an application example, even when subframes are other partially protected frames, these partially protected frames may be handled as a group when the combination of the eNodeBs  10  setting the ABSs are identical. Hereinafter, the application example will be described with reference to  FIG. 19 . 
       FIG. 19  is an explanatory diagram illustrating an application example of the signal quality measurement. More specifically,  FIG. 19  illustrates an example in which the serving eNodeB  10 A sets configuration 2, the neighboring eNodeBs  10 B and  10 C set configurations 3 and 4, respectively, and, as a result, the pico eNodeB  30  is notified of configuration Y by the serving eNodeB  10 A. 
     Herein, in the configuration Y, although subframes #3, #4, #7 and #8 are the partially protected frames, the same eNodeB  10 B sets the subframes #3 and #7 as ABSs, and the same eNodeBs  10 A and  10 B set the subframes #4 and #8 as ABSs. For this reason, the interference protection statuses of the subframes #3 and #7 are considered to be similar, and the interference protection statuses of the subframes #4 and #8 are also considered to be similar. 
     Therefore, the UE  20  may perform measurement in the subframes #3 and #7 (C-1, C-2), and report an average value of the measurement result as a measurement result of a group including the subframes #3 and #7. Likewise, the UE  20  may perform measurement in the subframes #4 and #8 (D-1, D-2), and report an average value of the measurement result as a measurement result of a group including the subframes #4 and #8. 
     Also, the serving eNodeB  10  may group the partially protected frames such that the partially protected frames set as ABSs by the eNodeB  10  of the same pattern constitute the same group, and report the grouping result to the pico eNodeB  30  by, for example, RRC signaling. By reporting the grouping result of the partially protected frames to the UE  20 , the pico eNodeB  30  may acquire and report the measurement result of each group as described above. 
     4-4. Operation of Communication System 
     Next, the operation of the communication system according to the third embodiment of the present disclosure will be summarized with reference to  FIG. 20 . 
       FIG. 20  is a sequence diagram illustrating the operation of the communication system according to the third embodiment of the present disclosure. As illustrated in  FIG. 20 , first, when the eNodeB  10 , for example, specifies a configuration by the interference determination unit  170  described in the first embodiment, the eNodeB  10  notifies the pico eNodeB  30  of the specified configuration (S 510 ). The pico eNodeB  30  notifies the UE  20  of the configuration received from the eNodeB  10  (S 520 ). 
     After that, the UE  20  acquires the signal quality measurement result of each partially protected frame defined by the configuration (S 530 ), and reports the measurement result to the pico eNodeB  30  (S 540 ). 
     Subsequently, the interference determination unit  370  of the pico eNodeB  30  determines whether to handle each partially protected frame as a protected frame or an unprotected frame based on the reported measurement result (S 550 ). The scheduler  380  of the pico eNodeB  30  performs scheduling on the UE  20 , which belongs to the pico eNodeB  30 , according to the determination result by the interference determination unit  370  (S 560 ). 
     5. CONCLUDING REMARKS 
     As described above, according to the first embodiment of the present disclosure, the eNodeB  30  may appropriately check the interference protection status of each subframe based on one configuration notified from the serving eNodeB  10 , without notifying the pico eNodeB  30  of the plurality of configurations of the plurality of eNodeBs  10 . Also, the ABS setting unit  140  of each of the plurality of neighboring eNodeBs  10  sets the same configuration to the sector directed in the central direction of the plurality of corresponding eNodeBs  10 . In this way, the throughput of the pico eNodeB  30  may be improved. 
     Also, according to the second embodiment of the present disclosure, the configuration suitable for each pico eNodeB  30  may be obtained by determining configurations at each pico eNodeB  30  located within the eNodeB  10 - 2 . 
     Also, according to the third embodiment of the present disclosure, when macro eNodeBs setting the same subframe as an ABS and macro eNodeBs not setting the same subframe as an ABS are mixed, the interference protection status of the corresponding subframe may be determined not on an eNodeB  10  side but on a pico eNodeB  30  side. 
     It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof. 
     For example, in this specification, each step in the processing of the eNodeB  10  and the pico eNodeB  30  need not necessarily be processed in time series in order as described in the sequence diagram or the flowchart. For example, each step in the processing of the eNodeB  10  and the pico eNodeB  30  may be processed in a different order from that described in the flowchart, or may be processed in parallel. 
     Also, using embedded hardware such as CPU, ROM, and RAM, the eNodeB  10 , the UE  20 , and the pico eNodeB  30  can be implemented with a computer program capable of executing the same functions as the respective configurations of the eNodeB  10 , the UE  20 , and the pico eNodeB  30 . Also, a recording medium storing the computer program is provided. 
     Additionally, the present technology may also be configured as below. 
     (1) 
     A base station including: 
     a setting unit configured to set a transmission limit frame, in which transmission other than a reference signal is limited, among communication frames; 
     a setting information reception unit configured to receive setting information of a transmission limit frame of a neighboring base station; and 
     a determination unit configured to determine an interference protection status of each communication frame in a cell provided by the base station based on the transmission limit frame set by the setting unit and the transmission limit frame of the neighboring base station. 
     (2) 
     The base station according to (1), wherein the determination unit determines that a communication frame set as the transmission limit frame by any of the base station and the neighboring base station is a protected frame, and determines that a communication frame set as the transmission limit frame by neither the base station nor the neighboring base station is an unprotected frame. 
     (3) 
     The base station according to (1) or (2), wherein the determination unit determines that a communication frame set as the transmission limit frame by the base station is a partially protected frame when there is a neighboring base station that has not set the communication frame as the transmission limit frame. 
     (4) 
     The base station according to (1) or (2), wherein the determination unit determines that a communication frame set as the transmission limit frame by the base station or the neighboring base station is a partially protected frame when one of the base station and the neighboring base station has not set the communication frame as the transmission limit frame. 
     (5) 
     The base station according to (1) or (2), wherein the determination unit determines an interference protection status of a non-uniform communication frame, which is set as the transmission limit frame by the base station and is not set as the transmission limit frame by the neighboring base station, based on position information of a low-transmission-power type base station which has a transmission power lower than that of the base station and is disposed within the cell. 
     (6) 
     The base station according to (5), wherein the determination unit determines that the non-uniform communication frame is a protected frame when the low-transmission-power type base station is within a predetermined range from the base station. 
     (7) 
     The base station according to (5) or (6), wherein the determination unit determines that the non-uniform communication frame is an unprotected frame or a partially protected frame when the low-transmission-power type base station is outside of the predetermined range from the base station. 
     (8) 
     The base station according to any one of (1) to (7), further including a notification unit configured to notify a low-transmission-power type base station which has a transmission power lower than that of the base station and is disposed within the cell of the determination result of the determination unit. 
     (9) 
     A communication method including: 
     setting a transmission limit frame, in which transmission other than a reference signal from a base station is limited, among communication frames; 
     receiving setting information of a transmission limit frame of a neighboring base station; and 
     determining an interference protection status of each communication frame in a cell provided by the base station based on the transmission limit frame set to the base station and the transmission limit frame of the neighboring base station. 
     (10) 
     A program for causing a computer to function as: 
     a setting unit configured to set a transmission limit frame, in which transmission other than a reference signal from a base station is limited, among communication frames; 
     a setting information reception unit configured to receive setting information of a transmission limit frame of a neighboring base station; and 
     a determination unit configured to determine an interference protection status of each communication frame in a cell provided by the base station based on the transmission limit frame set by the setting unit and the transmission limit frame of the neighboring base station. 
     (A1) A method comprising: 
     with a processor of a base station, determining an interference protection status of a frame based at least in part on information indicating configurations of base stations, wherein a first of the configurations differs from at least a second of the configurations, and wherein a portion of the information indicating the second of the configurations is received from a second base station. 
     (A2) The method of (A2), wherein the first configuration indicates a first pattern of one or more frames of a first type, and/or the second configuration indicates a second pattern of one or more frames of the first type. 
     (A3) The method of (A2), wherein the first type of frame is a transmission limit frame type, which indicates that transmission is limited other than a reference signal. 
     (A4) The method of (A2), wherein the first type comprises an Almost Blank Subframe (ABS) type. 
     (A5) The method of (A2), further comprising: 
     with a communication unit, sending the interference protection status of the frame to a communication control device. 
     (A6) The method of (A5), wherein determining the interference protection status of the frame comprises: 
     determining the frame&#39;s interference protection status to be an unprotected status if the first configuration does not associate the frame with a frame of the first type; 
     determining the frame&#39;s interference protection status to be a protected status if each of the configurations associates the frame with a frame of the first type; and 
     determining the frame&#39;s interference protection status to be a partially protected status if the first configuration associates the frame with a frame of the first type and at least another of the configurations does not associate the frame with a frame of the first type. 
     (A7) The method of (A5), wherein determining the interference protection status of the frame comprises: 
     determining the frame&#39;s interference protection status to be a protected status if each of the configurations associates the frame with a frame of the first type; 
     determining the frame&#39;s interference protection status to be a partially protected status if at least one of the configurations associates the frame with a frame of the first type and at least another of the configurations does not associate the frame with a frame of the first type; and 
     determining the frame&#39;s interference protection status to be an unprotected status if the none of the configurations associates the frame with a frame of the first type. 
     (A8) The method of (A5), wherein the determining of the interference protection status of the frame for the communication control device is further based at least in part on a position of the communication control device. 
     (A9) The method of (A8), wherein determining the interference protection status of the frame for the communication control device based at least in part on the position of the communication control device comprises determining the interference protection status of the frame based at least in part on whether the communication control device is within a predetermined distance of the base station. 
     (A10) The method of (A9), wherein the communication control device is positioned within a cell of the base station. 
     (A11) The method of (A8), wherein determining the interference protection status of the frame comprises: 
     determining the frame&#39;s interference protection status to be an unprotected status if the first configuration does not associate the frame with a frame of the first type; 
     determining the frame&#39;s interference protection status to be a protected status if each of the configurations associates the frame with a frame of the first type, or if the first configuration associates the frame with a frame of the first type and the communication control device is positioned within a range of a first of the base stations; and 
     determining the frame&#39;s interference protection status to be an unprotected status if the first configuration associates the frame with a frame of the first type and at least another of the configurations does not associate the frame with a frame of the first type and the communication control device is not positioned within the range of the first base station, 
     wherein the first configuration is a configuration of the first base station. 
     (A12) The method of (A5), wherein: 
     the first configuration is a configuration of the base station, 
     the second configuration is a configuration of the second base station, and 
     the portion of the information indicating the second configuration is received by the base station. 
     (A13) The method of (A5), wherein a plurality of the configurations of a plurality of the base stations do not differ from each other, the plurality of the configurations corresponding to one or more cells that are centrally located with respect to the plurality of the base stations. 
     (A14) The method of (A1), further comprising associating the interference protection status with the frame. 
     (A15) The method of (A1), wherein the frame is a subframe of a radio frame. 
     (A16) A base station comprising: 
     an interference determination unit configured to determine an interference protection status of a frame based at least in part on information indicating configurations of two or more base stations, wherein a first of the configurations differs from at least a second of the configurations, and wherein a portion of the information indicating the second of the configurations is received from a second base station. 
     (A17) The base station of (A16), wherein the interference determination unit is configured to determine the interference protection status of the frame by: 
     determining the frame&#39;s interference protection status to be an unprotected status if the first configuration does not associate the frame with a frame of a first type; 
     determining the frame&#39;s interference protection status to be a protected status if each of the configurations associates the frame with a frame of the first type; and 
     determining the frame&#39;s interference protection status to be a partially protected status if the first configuration associates the frame with a frame of the first type and at least another of the configurations does not associate the frame with a frame of the first type. 
     (A18) The base station of (A17), further comprising: 
     a communication unit configured to send the interference protection status of the frame to a communication control device; and 
     an associating unit configured to associate the interference protection status with the frame, 
     wherein the first configuration indicates a first pattern of one or more frames of a first type, and/or the second configuration indicates a second pattern of one or more frames of the first type, and 
     wherein the first type comprises an Almost Blank Subframe (ABS) type. 
     (A19) The base station of (A16), wherein the interference determination unit is configured to determine the interference protection status of the frame by: 
     determining the frame&#39;s interference protection status to be a protected status if each of the configurations associates the frame with a frame of a first type; 
     determining the frame&#39;s interference protection status to be a partially protected status if at least one of the configurations associates the frame with a frame of the first type and at least another of the configurations does not associate the frame with a frame of the first type; and 
     determining the frame&#39;s interference protection status to be an unprotected status if none of the configurations associates the frame with a frame of the first type. 
     (A20) The base station of (A19), further comprising: 
     a communication unit configured to send the interference protection status of the frame to a communication control device; and 
     an associating unit configured to associate the interference protection status with the frame, 
     wherein the first configuration indicates a first pattern of one or more frames of a first type, and/or the second configuration indicates a second pattern of one or more frames of the first type, and 
     wherein the first type comprises an Almost Blank Subframe (ABS) type. 
     (A21) The base station of (A16), wherein the interference determination unit is further configured to determine the interference protection status of the frame based at least in part on a position of a communication control device. 
     (A22) The base station of (A21), further comprising: 
     a communication unit configured to send the interference protection status of the frame to a communication control device; and 
     an associating unit configured to associate the interference protection status with the frame, 
     wherein the first configuration indicates a first pattern of one or more frames of a first type, and/or the second configuration indicates a second pattern of one or more frames of the first type, and 
     wherein the first type comprises an Almost Blank Subframe (ABS) type. 
     (A23) The base station of (A16), wherein: 
     the first configuration is a configuration of the base station, 
     the second configuration is a configuration of the second base station, and 
     the portion of the information indicating the second configuration is received by the base station. 
     (A24) A computer-readable medium having recorded thereon a computer program which, when executed by at least one processing unit, performs a method comprising: 
     determining an interference protection status of a frame based at least in part on information indicating configurations of base stations, wherein a first of the configurations differs from at least a second of the configurations, and wherein a portion of the information indicating the second of the configurations is received from a second base station. 
     (A25) The computer-readable medium of (A24), wherein the first configuration indicates a first pattern of one or more frames of a first type, and/or the second configuration indicates a second pattern of one or more frames of the first type. 
     (A26) The computer-readable medium of (A25), wherein the method further comprises: with a communication unit, sending the interference protection status of the frame to a communication control device. 
     (A27) A wireless communication system comprising: 
     a first base station including an interference determination unit; and 
     a second base station, 
     wherein: 
     the first base station is configured to store information indicating a first configuration, the second base station is configured to store information indicating a second configuration, 
     the interference determination unit of the first base station is configured to determine an interference protection status of a frame based at least in part on the information indicating the first configuration of the first base station and the information indicating the second configuration of the second base station, and 
     the first configuration differs from the second configuration. 
     (A28) The system of (A27), wherein the first configuration indicates a first pattern of one or more frames of a first type, and/or the second configuration indicates a second pattern of one or more frames of the first type. 
     (A29) The system of (A27), further comprising a third base station, wherein: 
     the first, second, and third base stations are configured to store information indicating a third configuration, 
     the third configuration corresponds to a cell that is centrally located with respect to the first, second, and third base stations, and 
     the first, second, and third base stations each transmit signals in the cell according to the third configuration. 
     REFERENCE SIGNS LIST 
     
         
         
           
               20  UE 
               104 ,  204 ,  304  Antenna group 
               110 ,  210 ,  310  Radio processing unit 
               120 ,  220 ,  320  DA conversion unit 
               130 ,  230 ,  330  Digital processing unit 
               140  ABS setting unit 
               150 ,  350  X2 communication unit 
               160 ,  260 ,  360  Configuration retention unit 
               170 ,  172 ,  370  Interference determination unit 
               180  Position information retention unit 
               270  Measurement management unit 
               380  Scheduler 
               390  Measurement result retention unit