Abstract:
A base station apparatus includes a processor. The processor executes a process including obtaining information indicating a radio status of each mobile station apparatus relevant to first communication in which radio communication is performed between the mobile station apparatuses via the base station apparatus, and second communication in which radio communication is directly performed between the mobile station apparatuses without via the base station apparatus; and notifying, based on the obtained information, the mobile station apparatuses that perform the second communication of control information for controlling the second communication.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation application of International Application PCT/JP2014/066905, filed on Jun. 25, 2014, and designating the U.S., the entire contents of which are incorporated herein by reference. 
     
    
     FIELD 
       [0002]    The present invention relates to a base station apparatus, a mobile station apparatus, a radio communication system, a communication control method of a base station apparatus, and a communication control method of a mobile station apparatus. 
       BACKGROUND 
       [0003]    In recent years, D2D (Device to Device) communication that is direct communication in which mobile stations directly perform radio communication with each other without via a base station has been known, other than cellular communication that is normal communication in which mobile stations perform radio communication with each other via a base station. The mobile station functions as a CUE (Cellular User Equipment) when being used in the cellular communication, and functions as a DUE (D2D User Equipment) when being used in the D2D communication. 
         [0004]    As a future system model, the base station (eNB: eNodeB) allocates radio resources to the CUE and the DUE so that the CUE and the DUE can coexist with each other. 
         [0005]    Patent Literature 1: US Patent Application Publication No.  2009 / 0325625   
         [0006]    Non Patent Document 1: “Dynamic Power Control Mechanism for Interference Coordination of Device-to-Device Communication in Cellular Networks”, Sungkyunkwan University, IEEE Ubiquitous and Future Networks (ICUFN), 2011 Third International Conference, 15-17 Jun. 2011. 
         [0007]    However, for example, when the CUE and the DUE share the same radio resources with each other, it is assumed that the D2D communication interferes with a UL (Up Link) signal from the CUE. That is, the effects of signal interference with the cellular communication due to the D2D communication are significant. 
       SUMMARY 
       [0008]    According to an aspect of the embodiments, a base station apparatus includes a control unit that, based on information indicating a radio status of each mobile station apparatus relevant to first communication in which radio communication is performed between the mobile station apparatuses via the base station apparatus, and second communication in which radio communication is directly performed between the mobile station apparatuses without via the base station apparatus, notifies the mobile station apparatuses that perform the second communication of control information for controlling the second communication. 
         [0009]    The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. 
         [0010]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0011]      FIG. 1  is an explanatory diagram illustrating an example of a radio system according to a first embodiment. 
           [0012]      FIG. 2  is a block diagram illustrating an example of an eNB according to the first embodiment. 
           [0013]      FIG. 3  is a block diagram illustrating an example of a UE according to the first embodiment. 
           [0014]      FIG. 4  is an explanatory diagram illustrating an example of a DCI format added with a control flag according to the first embodiment. 
           [0015]      FIG. 5  is a flowchart illustrating an example of a processing operation of a DUE associated with a communication control process according to the first embodiment. 
           [0016]      FIG. 6  is a block diagram illustrating an example of an eNB according to a second embodiment. 
           [0017]      FIG. 7  is a block diagram illustrating an example of a position determining unit. 
           [0018]      FIG. 8  is an explanatory diagram illustrating an example of a dedicated format added with a control flag according to a third embodiment. 
           [0019]      FIG. 9  is an explanatory diagram illustrating an example of a DCI format added with a control flag according to a fourth embodiment. 
           [0020]      FIG. 10  is an explanatory diagram illustrating an example of a DCI format added with a control flag according to a fifth embodiment. 
           [0021]      FIG. 11  is a flowchart illustrating an example of a processing operation of a DUE associated with a communication control process according to a sixth embodiment. 
           [0022]      FIG. 12  is a flowchart illustrating an example of a processing operation of a DUE associated with a communication control process according to a seventh embodiment. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0023]    Exemplary embodiments of a base station apparatus, a mobile station apparatus, a radio communication system, a communication control method of a base station apparatus, and a communication control method of a mobile station apparatus disclosed in the present application will be explained below in detail based on the accompanying drawings. The disclosed techniques are not limited to the embodiments. The following embodiments can be combined as appropriate without causing any contradiction. 
       First Embodiment. 
       [0024]      FIG. 1  is an explanatory diagram illustrating an example of a radio system according to a first embodiment. A radio system  1  illustrated in  FIG. 1  includes an eNB  2  and a plurality of UEs (User Equipments)  3 . The UE  3  has a function of enabling to switchably perform first communication such as cellular communication or second communication such as D2D communication. The UE  3  functions as a CUE  3 A when being used in cellular communication, and functions as a DUE  3 B when being used in D2D communication. In the radio system  1 , it is assumed that the CUE  3 A and the DUE  3 B are in an environment in which the CUE  3 A and the DUE  3 B can be used and coexist with each other. 
         [0025]      FIG. 2  is a block diagram illustrating an example of the eNB  2  according to the first embodiment. The eNB  2  illustrated in  FIG. 2  includes an antenna  11 , an RF (Radio Frequency) circuit  12 , a memory  13 , and a processor  14 . The antenna  11  transmits and receives a radio signal in the cellular communication or the D2D communication. The RF circuit  12  performs various types of signal processing with respect to a radio signal transmitted and received by the antenna  11 . The memory  13  is a region for storing various pieces of information. The processor  14  controls the entire eNB  2 . 
         [0026]    The RF circuit  12  includes a switching unit  21 , a receiving unit  22 , and a transmitting unit  23 . The switching unit  21  is a switch that switches the receiving unit  22  and the transmitting unit  23  between the antenna  11  and the eNB  2 . The receiving unit  22  is a communication interface that receives a radio signal in the cellular communication or the D2D communication. The transmitting unit  23  is a communication interface that transmits a radio signal in the cellular communication or the D2D communication. The memory  13  stores radio resources such as a usable frequency and the like associated with the cellular communication or the D2D communication, as well as allocation information for managing the radio resources such as the usable frequency and the like to be allocated, for example, to each UE  3 . 
         [0027]    The processor  14  includes an estimating unit  31 , a data-signal decoding unit  32 , a control-signal decoding unit  33 , a quality calculating unit  34 , and a scheduler  35 . The processor  14  further includes a data-signal generating unit  36 , a control-signal generating unit  37 , an RS generating unit  38 , a data-signal encoding unit  39 , a control-signal encoding unit  40 , and an allocating unit  41 . 
         [0028]    The estimating unit  31  estimates a channel estimate value of a channel to be used from a channel state of a received signal based on an RS (Reference Signal) signal inserted into the received signal. The data-signal decoding unit  32  demodulates and decodes a data signal from the received signal based on the channel estimate value. The control-signal decoding unit  33  demodulates and decodes a control signal such as a DCI (Downlink Control Information) format from the received signal based on the channel estimate value. The DCI format is a control command of a DL (Down Link). 
         [0029]    The quality calculating unit  34  calculates reception quality from the channel estimate value. The scheduler  35  generates allocation information for allocating the radio resources to be used for the cellular communication and the D2D communication to the UEs  3  accommodated in the eNB  2 , based on reception quality of the quality calculating unit, a decoding result of the data-signal decoding unit  32 , and a decoding result of the control-signal decoding unit  33 . The scheduler  35  stores the generated allocation information in the memory  13 . 
         [0030]    The data-signal generating unit  36  generates a data signal according to a request. The control-signal generating unit  37  generates a control signal based on a decoding result of the data signal, a decoding result of the control signal, and the reception quality. Further, the control-signal generating unit  37  edits the contents of the control signal according to a request. The RS generating unit  38  generates an RS signal according to a request. The data-signal encoding unit  39  encodes and modulates the data signal generated by the data-signal generating unit  36 . The control-signal encoding unit  40  encodes and modulates the generated control signal. The allocating unit  41  allocates radio resources to the data signal, the control signal, and the RS signal based on allocation information. The control-signal generating unit  37  includes the allocation information generated by the scheduler  35  in the DCI format and transmits the DCI format to the UE  3 . 
         [0031]    The scheduler  35  determines whether the DUE  3 B to be controlled is sharing the same radio resources with the CUE  3 A. When the DUE  3 B to be controlled is sharing the same radio resources with the CUE  3 A, the scheduler  35  sets a control flag of the DUE  3 B to ON. When the DUE  3 B to be controlled is not sharing the same radio resources with the CUE  3 A, the scheduler  35  sets the control flag of the DUE  3 B to be controlled to OFF. For example, the control-signal generating unit  37  generates the DCI format for storing a UL grant for each UL grant. The UL grant is, for example, a control signal when permitting communication in the D2D communication. The control-signal generating unit  37  adds a control flag of the DUE  3 B to be controlled to the DCI format, and transmits the DCI format added with the control flag from the transmitting unit  23  to the UE  3  in the UL grant. 
         [0032]      FIG. 3  is a block diagram illustrating an example of the UE  3 . The UE  3  illustrated in  FIG. 3  includes an antenna  51 , an RF circuit  52 , a memory  53 , and a processor  54 . The antenna  51  transmits and receives a radio signal in the cellular communication or the D2D communication. The RF circuit  52  performs various types of signal processing with respect to a radio signal. The memory  53  is a region for storing various pieces of information such as allocation information from the eNB  2 . The processor  54  controls the entire UE  3 . 
         [0033]    The RF circuit  52  includes a switching unit  61 , a receiving unit  62 , and a transmitting unit  63 . The switching unit  61  is a switch that switches the receiving unit  62  and the transmitting unit  63  between the antenna  51  and the UE  3 . The receiving unit  62  is a communication interface that receives a radio signal in the cellular communication or the D2D communication. The transmitting unit  63  is a communication interface that transmits a radio signal in the cellular communication or the D2D communication. 
         [0034]    The processor  54  includes an estimating unit  71 , a data-signal decoding unit  72 , a control-signal decoding unit  73 , a quality calculating unit  74 , a data-signal generating unit  75 , a control-signal generating unit  76 , and an RS generating unit  77 . Further, the processor  54  includes a data-signal encoding unit  78 , a control-signal encoding unit  79 , an allocating unit  80 , and a communication control unit  81 . The estimating unit  71  estimates a channel estimate value based on an RS signal inserted into the received signal. The data-signal decoding unit  72  demodulates and decodes a data signal from the received signal based on the channel estimate value. The control-signal decoding unit  73  demodulates and decodes a control signal from the received signal. 
         [0035]    The quality calculating unit  74  calculates reception quality from the channel estimate value. The data-signal generating unit  75  generates a data signal according to a request. The control-signal generating unit  76  generates a control signal based on a decoding result of the data signal, a decoding result of the control signal, and the reception quality. The RS generating unit  77  generates an RS signal. The data-signal encoding unit  78  encodes and modulates the data signal. The control-signal encoding unit  79  encodes and modulates the control signal. The allocating unit  80  allocates radio resources to the data signal, the control signal, and the RS signal based on allocation information from the eNB  2  and transfers the data signal, the control signal, and the RS signal to the transmitting unit  63 . 
         [0036]    The communication control unit  81  decodes the control signal from the eNB  2  by the control-signal decoding unit  73  and determines whether the control flag for the equipment itself added to the DCI format of the control signal is ON. If the control flag is ON, the communication control unit  81  controls the transmission power of the transmitting unit  63 . 
         [0037]    The communication control unit  81  calculates a transmission power amount Pd in the D2D communication as a provisional transmission power amount by using (expression  1 ) of OL-TPC in the D2D communication (see 3GPP TS 36.213 v12.1.0). 
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         [0038]    i: sub-frame number 
         [0039]    P(i): transmission power in sub-frame i 
         [0040]    P(i): maximum transmission power defined in sub-frame i 
         [0041]    M(i): number of RBs allocated to PUSCH in sub-frame i 
         [0042]    P o : pass loss between serving cell and UE 
         [0043]    α: pass loss compensation factor 
         [0044]    Δ TF  (i): value calculated by function of f(i) based on parameter instructed from upper layer 
         [0045]    Furthermore, the communication control unit  81  calculates a pass loss PLc between the eNB  2  and the UE  3 . The pass loss PLc is calculated by subtracting an RSRP (Reference Signal Received Power) applied with a filter of an upper layer from the transmission power amount of the RS signal. The transmission power amount of the RS signal is notified in the upper layer from the eNB  2  to the UE  3 . The communication control unit  81  calculates an estimated received power amount of the DUE  3 B on the side of the eNB  2  by (Pd-PLc). The communication control unit  81  also determines whether the estimated received power amount (Pd-PLc) is equal to or less than a threshold Th. The threshold Th corresponds to a transmission power amount that does not cause signal interference with a UL signal of the CUE  3 A between the eNB  2  and the UE  3 , and is calculated in advance. 
         [0046]    If the estimated received power amount (Pd-PLc) is equal to or less than the threshold Th, the communication control unit  81  does not need to reduce the calculated transmission power amount Pd, and controls the transmission power of the transmitting unit  63  so as to set the transmission power amount in the D2D communication to Pd. Further, if the estimated received power amount (Pd-PLc) is not equal to or less than the threshold Th, the communication control unit  81  controls the transmission power of the transmitting unit  63  so as to set the transmission power amount in the D2D communication to the threshold Th. If the control flag is not ON, the communication control unit  81  controls the transmission power of the transmitting unit  63  so as to set the transmission power amount in the D2D communication to Pd. 
         [0047]      FIG. 4  is an explanatory diagram illustrating an example of a DCI format added with a control flag. The DCI format is for example a DCI format “0”. A DCI format  90  illustrated in  FIG. 4  includes a carrier indicator (0 or 3 bits)  91 , a flag for format0/format1A differentiation (1 bit)  92 , and a frequency hopping flag (1 bit)  93 . The DCI format  90  also includes a resource block assignment and hopping recourse allocation (maximum 12 bits)  94 , a modulation and coding scheme and redundancy version (5 bits)  95 , and a new data indicator (1 bit)  96 . The DCI format  90  further includes a TPC command for scheduled PUSCH (2 bits)  97 , a cyclic shift for DM RS and OCC index (3 bits)  98 , a UL index (2 bits)  99 , and a downlink assignment index (DAI) (2 bits)  100 . Further, the DCI format  90  includes CSI requests (1 or 2 bits)  101  and a resource allocation type (1 bit)  102 . The control-signal generating unit  76  generates the DCI format  90  and adds control flags  103  for the number of UEs  3  to be controlled to the DCI format  90 . 
         [0048]    An operation of the radio system  1  according to the first embodiment is described next. The scheduler  35  of the eNB  2  determines whether the DUE  3 B to be controlled is sharing the same radio resources with the CUE  3 A. If the DUE  3 B to be controlled is sharing the same radio resources with the CUE  3 A, the scheduler  35  sets the control flag of the DUE  3 B to ON. If the DUE  3 B to be controlled is not sharing the same radio resources with the CUE  3 A, the scheduler  35  sets the control flag of the DUE  3 B to OFF. The control-signal generating unit  76  generates a DCI format that stores an UL grant for each UL grant permitting the D2D communication, and adds the control flag of the DUE  3 B to be controlled to the generated DCI format. The transmitting unit  23  transmits the DCI format added with the control flag to the DUE  3 B to be controlled. 
         [0049]      FIG. 5  is a flowchart illustrating an example of a processing operation of the DUE  3 B associated with a communication control process according to the first embodiment. The communication control process illustrated in  FIG. 5  is a process on the side of the DUE  3 B that controls the transmission power in the D2D communication based on the control flag for the equipment itself. 
         [0050]    In  FIG. 5 , the communication control unit  81  of the DUE  3 B calculates the transmission power amount Pd in the D2D communication (Step S 11 ) and determines whether the control flag  103  for the equipment itself which is added to the received DCI format  90  is ON (Step S 12 ). If the control flag  103  for the equipment itself is ON (YES at Step S 12 ), the communication control unit  81  calculates the pass loss PLc between the eNB  2  and the UE  3  (Step S 13 ). 
         [0051]    The communication control unit  81  determines whether the estimated received power amount (Pd-PLc) on the side of the eNB  2  obtained by subtracting the pass loss PLc from the transmission power amount Pd in the D2D communication is equal to or less than the threshold Th (Step S 14 ). If the estimated received power amount (Pd-PLc) is equal to or less than the threshold Th (YES at Step S 14 ), the communication control unit  81  controls the transmission power in the transmitting unit  63  so as to set the transmission power amount in the D2D communication to Pd and performs the D2D communication (Step S 15 ) to end the processing operation illustrated in  FIG. 5 . 
         [0052]    If the estimated received power amount (Pd-PLc) is not equal to or less than the threshold Th (NO at Step S 14 ), the communication control unit  81  determines that there are effects of signal interference due to the D2D communication. The communication control unit  81  then controls the transmission power in the transmitting unit  63  so as to set the transmission power amount in the D2D communication to the threshold Th and performs the D2D communication (Step S 16 ) to end the processing operation illustrated in  FIG. 5 . 
         [0053]    If the control flag  103  for the equipment itself is not ON (NO at Step S 12 ), the communication control unit  81  determines that there is no effect of signal interference due to the D2D communication. The communication control unit  81  then controls the transmission power in the transmitting unit  63  so as to set the transmission power amount in the D2D communication to Pd and performs the D2D communication (Step S 17 ) to end the processing operation illustrated in  FIG. 5 . That is, the DUE  3 B executes TPC (Transmission Power Control) between the DUE  3 B facing thereto and itself, thereby realizing the D2D communication. 
         [0054]    The DUE  3 B that performs the communication control process illustrated in  FIG. 5  controls the transmission power of the transmitting unit  63  so as to set the transmission power amount to Pd, if the control flag  103  is ON and the estimated received power amount (Pd-PLc) is equal to or less than the threshold Th. As a result, signal interference with the UL signal to the CUE  3 A due to the D2D communication can be reduced. 
         [0055]    If the control flag  103  is ON and the estimated received power amount (Pd-PLc) is not equal to or less than the threshold Th, the DUE  3 B controls the transmission power of the transmitting unit  63  so as to set the transmission power amount to the threshold Th. As a result, signal interference with the UL signal to the CUE  3 A due to the D2D communication can be reduced. 
         [0056]    If the control flag  103  is OFF, the DUE  3 B controls a transmission output of the transmitting unit  63  so as to set the transmission power amount to Pd. 
         [0057]    If the DUE  3 B to be controlled is sharing the same radio resources with the CUE  3 A, the eNB  2  according to the first embodiment sets the control flag  103  of the DUE  3 B to be controlled to ON. If the DUE  3 B to be controlled is not sharing the same radio resources with the CUE  3 A, the eNB  2  sets the control flag  103  of the DUE  3 B to be controlled to OFF. The eNB  2  adds the control flags  103  for the number of DUEs  3 B to be controlled to the DCI format  90  and notifies the DUEs  3 B to be controlled of the DCI format  90 . As a result, if the control flag  103  for the equipment itself is ON, the DUE  3 B controls the transmission power in the D2D communication, thereby enabling to reduce signal interference with the cellular communication due to the D2D communication. 
         [0058]    If the control flag  103  is ON and the estimated received power amount (Pd-PLc) is equal to or less than the threshold Th, the DUE  3 B controls the transmission power of the transmitting unit  63  so as to set the transmission power amount in the D2D communication to Pd. As a result, signal interference with the UL signal of the CUE  3 A due to the D2D communication can be reduced. 
         [0059]    If the control flag  103  is ON and the estimated received power amount (Pd-PLc) is not equal to or less than the threshold Th, the DUE  3 B controls the transmission power of the transmitting unit  63  so as to set the transmission power amount in the D2D communication to the threshold Th. As a result, signal interference with the UL signal of the CUE  3 A due to the D2D communication can be reduced. 
         [0060]    According to the first embodiment, because the same radio resources can be shared by the CUE  3 A and the DUE  3 B, the efficiency of use of the radio resources can be increased. 
         [0061]    According to the first embodiment, when the DUE  3 B to be controlled is sharing the same radio resources as the CUE  3 A, transmission power control based on the estimated received power amount taking the pass loss PLc into consideration is executed. Accordingly, the frequency of unnecessary transmission power control can be reduced, as compared to a case where OL-TPC (Open Loop Transmission Power Control) is adopted. In the OL-TPC, even in an environment in which there is no signal interference with the CUE  3 A, the transmission power control is executed at all times, and thus the throughput of the D2D communication decreases. 
         [0062]    According to the first embodiment, even if the schedule status of the radio resources changes every second, signal interference with the cellular communication due to the D2D communication can be decreased depending on the status, without decreasing the transmission power in the D2D communication unnecessarily. 
         [0063]    The eNB  2  according to the first embodiment switches the control flag  103  to ON/OFF depending on whether the DUE  3 B to be controlled is sharing the same radio resources with the CUE  3 A. However, the control flag  103  can be switched to ON/OFF depending on whether the DUE  3 B is adjacent to the eNB  2 . An embodiment in this case is described below as a second embodiment. 
       Second Embodiment 
       [0064]      FIG. 6  is a block diagram illustrating an example of an eNB  2 A according to the second embodiment. Configurations identical to those of the radio system  1  according to the first embodiment are denoted by like reference signs and redundant explanations of identical configurations and operations will be omitted. A point that the eNB  2 A illustrated in  FIG. 6  is different from the eNB  2  illustrated in  FIG. 2  is that a position determining unit  42  is added thereto. The position determining unit  42  determines whether the DUE  3 B is adjacent to the eNB  2 A based on position information of the DUE  3 B and the eNB  2 A. If the DUE  3 B is adjacent to the eNB  2 A according to determination of the position determining unit  42 , the scheduler  35  sets the control flag  103  for the DUE  3 B to ON. 
         [0065]      FIG. 7  is an explanatory diagram illustrating an example of the position determining unit  42 . The position determining unit  42  includes a position comparing unit  42 A and a quality comparing unit  42 B. The position comparing unit  42 A compares position information of the DUE  3 B in the D2D communication with position information of the eNB  2 A. If a distance therebetween is within a predetermined distance, the position comparing unit  42 A determines that the DUE  3 B and the eNB  2 A are adjacent to each other. The quality comparing unit  42 B compares, for example, the reception quality in the D2D communication such as the pass loss and RSRP (Reference Signal Received Power) with a quality threshold. If the reception quality has exceeded the quality threshold, the quality comparing unit  42 B determines that the DUE  3 B and the eNB  2 A are adjacent to each other. 
         [0066]    When the position determining unit  42  determines that the DUE  3 B is adjacent to the eNB  2 A, the scheduler  35  sets the control flag  103  for the DUE  3 B to ON. When the position determining unit  42  determines that the DUE  3 B is not adjacent to the eNB  2 A, the scheduler  35  sets the control flag  103  for the DUE  3 B to OFF. The control-signal generating unit  76  adds the control flags  103  for the number of DUEs  3 B to be controlled to the DCI format  90 . The transmitting unit  23  transmits the DCI format  90  added with the control flags  103  to the DUEs  3 B to be controlled. 
         [0067]    If the control flag  103  is ON and the estimated received power amount (Pd-PLc) is equal to or less than the threshold Th, the DUE  3 B controls the transmission power of the transmitting unit  63  so as to set the transmission power amount in the D2D communication to Pd. As a result, signal interference with the UL signal to the CUE  3 A due to the D2D communication can be reduced. 
         [0068]    If the control flag  103  is ON and the estimated received power amount (Pd-PLc) is not equal to or less than the threshold Th, the DUE  3 B controls the transmission power of the transmitting unit  63  so as to set the transmission power amount in the D2D communication to the threshold Th. As a result, signal interference with the UL signal to the CUE  3 A due to the D2D communication can be reduced. 
         [0069]    The eNB  2 A according to the second embodiment sets the control flag  103  for the DUE  3 B to be controlled to ON if the 
         [0070]    DUE  3 B is adjacent to the eNB  2 A, and sets the control flag  103  for the DUE  3 B to be controlled to OFF if the DUE  3 B is not adjacent to the eNB  2 A. The eNB  2 A adds the control flags  103  for the number of DUEs  3 B to be controlled to the DCI format  90  and notifies the DUEs  3 B to be controlled of the DCI format  90 . As a result, the DUE  3 B controls the transmission power in the D2D communication if the control flag  103  for the equipment itself is ON, thereby enabling to reduce signal interference with the cellular communication due to the D2D communication. 
         [0071]    Furthermore, if the control flag  103  is ON and the estimated received power amount (Pd-PLc) is equal to or less than the threshold Th, the DUE  3 B controls the transmission power of the transmitting unit  63  so as to set the transmission power amount in the D2D communication to Pd. As a result, signal interference with the UL signal of the CUE  3 A due to the D2D communication can be reduced, even if the DUE  3 B is adjacent to the eNB  2 A. 
         [0072]    If the control flag  103  is ON and the estimated received power amount (Pd-PLc) is not equal to or less than the threshold Th, the DUE  3 B controls the transmission power of the transmitting unit  63  so as to set the transmission power amount in the D2D communication to the threshold Th. As a result, signal interference with the UL signal of the CUE  3 A due to the D2D communication can be reduced, even if the DUE  3 B is adjacent to the eNB  2 A. 
         [0073]    For example, even if the transmission power in the D2D communication is reduced between the DUEs  3 B, a reception level may be low at a point in time when the UL signal from the CUE  3 A near an end of a cell area reaches the eNB  2 A, and may be affected by the D2D communication. According to the second embodiment, because the transmission power in the D2D communication is reduced even if the DUE  3 B is adjacent to the eNB  2 A, signal interference with the UL signal of the CUE  3 A due to the D2D communication can be reduced. 
         [0074]    According to the second embodiment, the control flag  103  for the DUE  3 B to be controlled is set based on an adjacency relationship of whether the DUE  3 B to be controlled is adjacent to the eNB  2 A determined by the position determining unit  42 . However, other than the adjacency relationship, the control flag  103  for the DUE  3 B to be controlled may be set based on the presence of shared usage indicating whether the DUE  3 B to be controlled is sharing the same radio resources with the CUE  3 A, as in the first embodiment. 
         [0075]    In the first and second embodiments described above, the control flags  103  for the number of UEs to be controlled are added to the DCI format  90 . However, the control flag  103  can be allocated instead of the control information unnecessary in the D2D communication, for example, the new data indicator  96 . The new data indicator  96  is control information being unnecessary, for example, if it is not retransmitted at the time of broadcast transmission. 
         [0076]    In the first embodiment described above, the control flags  103  for the number of UEs to be controlled are added to the DCI format  90 . However, if the number of UEs to be controlled increases, the number of control flags to be added to the DCI format also increases. Therefore, a control flag may be arranged in a dedicated format for each of the DUEs  3 B to be controlled so that the DUE  3 B can identify the control flag for the equipment itself by using CRC (Cyclic Redundancy Check) in the dedicated format. An embodiment in this case is described below as a third embodiment. Configurations identical to those of the radio system  1  according to the first embodiment are denoted by like reference signs and redundant explanations of identical configurations and operations will be omitted. 
       Third Embodiment 
       [0077]      FIG. 8  is an explanatory diagram illustrating an example of a dedicated format added with a control flag according to the third embodiment. A dedicated format  110  illustrated in  FIG. 8  has a control flag  111  in a unit of bit set for each of the DUEs  3 B to be controlled, and a CRC  112  set so as to be able to identify the control flag  111  for the equipment itself. 
         [0078]    The scheduler  35  sequentially sets the control flags  111  of the DUEs  3 B to be controlled in the dedicated format  110 . The control-signal generating unit  37  sets the CRC  112  that enables to identify the control flags  111  of the DUEs  3 B to be controlled in the dedicated format  110 . Because the CRC  112  is scrambled by C-RNTI (Cell-Radio Network Temporary Identifier) allocated to each of the DUEs  3 B, the control flag  111  for the equipment itself can be identified. Upon detection of a state change of the DUE  3 B to be controlled, the control-signal generating unit  37  dynamically sets the control flag  111  of the DUE  3 B to be controlled in the dedicated format  110  each time. The transmitting unit  23  transmits the dedicated format  110  to each of the DUEs  3 B to be controlled. 
         [0079]    When receiving the dedicated format  110 , the DUE  3 B acquires the control flag  111  for the equipment itself from the dedicated format  110  based on the CRC  112  in the dedicated format  110 . If the control flag  111  for the equipment itself is ON and the estimated received power amount (Pd-PLc) is equal to or less than the threshold Th, the DUE  3 B controls the transmission power of the transmitting unit  63  so as to set the transmission power amount in the D2D communication to Pd. As a result, signal interference with the UL signal of the CUE  3 A due to the D2D communication can be reduced. 
         [0080]    If the control flag for the equipment itself is ON and the estimated received power amount (Pd-PLc) is not equal to or less than the threshold Th, the DUE  3 B controls the transmission power of the transmitting unit  63  so as to set the transmission power amount in the D2D communication to the threshold Th. As a result, signal interference with the UL signal of the CUE  3 A due to the D2D communication can be reduced. 
         [0081]    Furthermore, the eNB  2  dynamically transmits the control flag  111  to the DUE  3 B to be controlled in the dedicated format  110 . As a result, the control flag  111  can be transmitted to each of the DUEs  3 B to be controlled depending on the change in the schedule status, as compared to a case where the control flag is transmitted to the DUE  3 B to be controlled statically by adding the control flag  111  to the DCI format for each UL grant. 
         [0082]    According to the first embodiment described above, the control flags  103  for the number of DUEs  3 B to be controlled are added to the DCI format  90 . However, the control flag can be set in a unit of sub-frame to be allocated to each DUE  3 B, without setting the control flag  103  for each DUE  3 B. An embodiment in this case is described below as a fourth embodiment. Configurations identical to those of the radio system  1  according to the first embodiment are denoted by like reference signs and redundant explanations of identical configurations and operations will be omitted. 
       Fourth Embodiment 
       [0083]      FIG. 9  is an explanatory diagram illustrating an example of a DCI format added with a control flag according to the fourth embodiment. A control flag  103 A in a unit of sub-frame is added to a DCI format  90 A illustrated in  FIG. 9 . The scheduler  35  determines whether any one of the DUEs  3 B to be controlled is sharing the same radio resources with the CUE  3 A, of a plurality of UEs  3  allocated with a sub-frame. If the DUE  3 B to be controlled is sharing the same radio resources with the CUE  3 A, the scheduler  35  sets the control flag  103 A in a unit of sub-frame to ON. If any one of the DUEs  3 B to be controlled is not sharing the same radio resources with the CUE  3 A, of the plurality of UEs  3  allocated with the sub-frame, the scheduler  35  sets the control flag  103 A in a unit of sub-frame to OFF. 
         [0084]    The control-signal generating unit  76  adds the control flag  103 A in a unit of sub-frame to the DCI format  90 A. The transmitting unit  23  transmits the DCI format  90 A added with the control flag  103 A to each of the DUEs  3 B to be controlled. 
         [0085]    If the control flag  103 A is ON and the estimated received power amount (Pd-PLc) is equal to or less than the threshold Th, each of the DUEs  3 B to be controlled controls the transmission power of the transmitting unit  63  so as to set the transmission power amount in the D2D communication to Pd. As a result, signal interference with the UL signal to the CUE  3 A due to the D2D communication can be reduced. 
         [0086]    If the control flag  103 A is ON and the estimated received power amount (Pd-PLc) is not equal to or less than the threshold Th, each of the DUEs  3 B to be controlled controls the transmission power of the transmitting unit  63  so as to set the transmission power amount in the D2D communication to the threshold Th. As a result, signal interference with the UL signal to the CUE  3 A due to the D2D communication can be reduced. 
         [0087]    Because the eNB  2  according to the fourth embodiment sets the control flag  103 A in a unit of sub-frame, the eNB  2  can reduce the processing load in the process of setting the control flag  103 A to the DCI format  90 A, as compared to a case where the control flag  103  is set in a unit of UE  3 . Further, because the control flag  103 A needs only one bit, the DCI format  90 A has a format configuration same as the DCI format “3”, and thus the process of detecting the DCI format by the DUE  3 B is unnecessary. 
         [0088]    According to the fourth embodiment described above, the control flag  103 A in a unit of sub-frame is added to the DCI format  90 A. However, as described above, the control flag  103 A in a unit of sub-frame can be allocated instead of the control information unnecessary in the D2D communication, for example, the new data indicator  96 . 
         [0089]    According to the fourth embodiment described above, the control flag  103 A in a unit of sub-frame is added to the DCI format  90 A. However, the present invention is not limited thereto, and an embodiment in this case is described below as a fifth embodiment. Configurations identical to those of the radio system  1  according to the first embodiment are denoted by like reference signs and redundant explanations of identical configurations and operations will be omitted. 
       Fifth Embodiment 
       [0090]      FIG. 10  is an explanatory diagram illustrating an example of a DCI format added with a control flag according to the fifth embodiment. A control flag  103 B is added to a DCI format  90 B illustrated in  FIG. 10  for each sub-frame. The scheduler  35  determines the presence of shared usage of the radio resources for each specified sub-frame. The scheduler  35  sets the control flag  103 B respectively based on a determination result for each sub-frame. The control-signal generating unit  76  adds the control flag  103 B to the DCI format  90 B for each sub-frame. That is, the control-signal generating unit  76  adds the control flags  103 B for the number of specified sub-frames to the DCI format  90 B. The transmitting unit  23  transmits the DCI format  90 B added with the control flag  103 B for each sub-frame to the DUE  3 B to be controlled. 
         [0091]    If the control flag  103 B for the sub-frame used by itself is ON and the estimated received power amount (Pd-PLc) is equal to or less than the threshold Th, each of the DUEs  3 B to be controlled controls the transmission power of the transmitting unit  63  so as to set the transmission power amount in the D2D communication to Pd. As a result, signal interference with the UL signal to the CUE  3 A due to the D2D communication can be reduced. 
         [0092]    If the control flag  103 B for the sub-frame used by itself is ON and the estimated received power amount (Pd-PLc) is not equal to or less than the threshold Th, each of the DUEs  3 B to be controlled controls the transmission power of the transmitting unit  63  so as to set the transmission power amount in the D2D communication to the threshold Th. As a result, signal interference with the UL signal to the CUE  3 A due to the D2D communication can be reduced. 
         [0093]    The eNB  2  according to the fifth embodiment determines the presence of shared usage of the radio resources for each sub-frame and sets the control flag  103 B for each determination result. The eNB  2  adds the control flag  103 B for each sub-frame to the DCI format  90 B, and notifies the DUEs  3 B to be controlled of the DCI format  90 B. As a result, the DUEs  3 B to be controlled can recognize the control flag  103 B for the future sub-frame beforehand. If the control flag  103 B for the sub-frame used by itself, of the control flags  103 B for the respective sub-frames, is ON and the estimated received power amount (Pd-PLc) is equal to or less than the threshold Th, the DUE  3 B to be controlled controls the transmission power of the transmitting unit  63  so as to set the transmission power amount to Pd. As a result, signal interference with the UL signal to the CUE  3 A due to the D2D communication can be reduced. 
         [0094]    If the control flag  103 B for the sub-frame used by itself, of the control flags for the respective sub-frames, is ON and the estimated received power amount (Pd-PLc) is not equal to or less than the threshold Th, the DUE  3 B to be controlled controls the transmission power of the transmitting unit  63  so as to set the transmission power amount to the threshold Th. As a result, signal interference with the UL signal to the CUE  3 A due to the D2D communication can be reduced. 
         [0095]    According to the first embodiment described above, if the control flag is ON and the estimated received power amount (Pd-PLc) is equal to or less than the threshold Th, the DUE  3 B controls the transmission power of the transmitting unit  63  so as to set the transmission power amount in the D2D communication to Pd. However, the present invention is not limited thereto, and an embodiment in this case is described as a sixth embodiment. Configurations identical to those of the radio system  1  according to the first embodiment are denoted by like reference signs and redundant explanations of identical configurations and operations will be omitted. 
       Sixth Embodiment 
       [0096]      FIG. 11  is a flowchart illustrating an example of a processing operation of the DUE  3 B associated with the communication control process according to the sixth embodiment. In  FIG. 11 , the communication control unit  81  of the DUE  3 B calculates the transmission power amount Pd in the D2D communication (Step S 21 ), and determines whether the control flag  103  is ON (Step S 22 ). If the control flag  103  is ON (YES at Step S 22 ), the communication control unit  81  stops the D2D communication (Step S 23 ) to end the processing operation illustrated in  FIG. 11 . The communication control unit  81  de-actuates the data-signal generating unit  75 , the control-signal generating unit  76 , and the RS generating unit  77  in the D2D communication to stop the D2D communication. 
         [0097]    If the control flag  103  is not ON (NO at Step S 22 ), the communication control unit  81  controls the transmission power of the transmitting unit  63  so as to set the transmission power amount in the D2D communication to Pd and performs the D2D communication (Step S 24 ) to end the processing operation illustrated in  FIG. 11 . 
         [0098]    If the control flag  103  is ON, the DUE  3 B that performs the communication control process illustrated in  FIG. 11  stops the D2D communication without controlling the transmission power. As a result, signal interference with the UL signal to the CUE  3 A due to the D2D communication can be reduced. 
         [0099]    If the control flag  103  is ON, the DUE  3 B according to the fifth embodiment stops the D2D communication without controlling the transmission power. As a result, signal interference with the UL signal to the CUE  3 A due to the D2D communication can be reduced. 
         [0100]    According to the first embodiment described above, if the control flag  103  is ON and the estimated received power amount (Pd-PLc) is equal to or less than the threshold Th, the DUE  3 B controls the transmission power of the transmitting unit  63  so as to set the transmission power amount in the D2D communication to Pd. However, the present invention is not limited thereto, and an embodiment in this case is described as a seventh embodiment. Configurations identical to those of the radio system  1  according to the first embodiment are denoted by like reference signs and redundant explanations of identical configurations and operations will be omitted. 
       Seventh Embodiment 
       [0101]      FIG. 12  is a flowchart illustrating an example of a processing operation of the DUE  3 B associated with the communication control process according to the seventh embodiment. In  FIG. 12 , the communication control unit  81  in the DUE  3 B calculates the transmission power amount Pd in the D2D communication (Step S 31 ) and determines whether the control flag  103  is ON (Step S 32 ). If the control flag  103  is ON (YES at Step S 32 ), the communication control unit  81  calculates the pass loss PLc between the eNB  2 A and the UE  3  (Step S 33 ). 
         [0102]    The communication control unit  81  determines whether the estimated received power amount (Pd-PLc) is equal to or less than the threshold Th (Step S 34 ). If the estimated received power amount (Pd-PLc) is equal to or less than the threshold Th (YES at Step S 34 ), the communication control unit  81  controls the transmission power in the transmitting unit  63  so as to set the transmission power amount in the D2D communication to Pd and performs the D2D communication (Step S 35 ) to end the processing operation illustrated in  FIG. 12 . 
         [0103]    If the estimated received power amount (Pd-PLc) is not equal to or less than the threshold Th (NO at Step S 34 ), the communication control unit  81  stops the D2D communication (Step S 36 ) to end the processing operation illustrated in  FIG. 12 . The communication control unit  81  de-actuates the data-signal generating unit  75 , the control-signal generating unit  76 , and the RS generating unit  77  to stop the D2D communication. 
         [0104]    If the control flag  103  is not ON (NO at Step S 32 ), the communication control unit  81  controls the transmission power in the transmitting unit  63  so as to set the transmission power amount in the D2D communication to Pd and performs the D2D communication (Step S 37 ) to end the processing operation illustrated in  FIG. 12 . 
         [0105]    If the control flag  103  is ON and the estimated received power amount (Pd-PLc) is equal to or less than the threshold Th, the DUE  3 B that performs the communication control process illustrated in  FIG. 12  controls the transmission power in the transmitting unit  63  so as to set the transmission power amount in the D2D communication to Pd. As a result, signal interference with the UL signal of the CUE  3 A due to the D2D communication can be reduced. 
         [0106]    If the control flag  103  is ON and the estimated received power amount (Pd-PLc) is not equal to or less than the threshold Th, the DUE  3 B stops the D2D communication. As a result, signal interference with the UL signal of the CUE  3 A due to the D2D communication can be reduced. 
         [0107]    If the control flag  103  is ON and the estimated received power amount (Pd-PLc) is equal to or less than the threshold Th, the DUE  3 B according to the seventh embodiment controls the transmission power in the transmitting unit  63  so as to set the transmission power amount in the D2D communication to Pd. As a result, signal interference with the UL signal of the CUE  3 A due to the D2D communication can be reduced. 
         [0108]    If the control flag  103  is ON and the estimated received power amount (Pd-PLc) is not equal to or less than the threshold Th, the DUE  3 B stops the D2D communication. As a result, signal interference with the UL signal of the CUE  3 A due to the D2D communication can be reduced. 
         [0109]    In the embodiments described above, for convenience sake of explanation, it has been described that the UE  3  is a mobile station that can switch the functions of the CUE  3 A and the DUE  3 B. However, for example, the embodiments described above are applicable to a mobile station having only the function as the DUE  3 B. 
         [0110]    The eNB  2  according to the present embodiments has been described as an integrated apparatus having a radio function and a control function. However, the eNB  2  is not limited thereto, and a radio device and a control device can be individually formed to configure the eNB. In this case, the radio device incorporates the antenna  11  and the RF circuit  12  therein, and the control device incorporates the memory  13  and the processor  14  therein. 
         [0111]    Respective constituent elements of respective units illustrated in the drawings do not necessarily have to be physically configured in the way as illustrated in these drawings. That is, the specific mode of distribution and integration of respective units is not limited to the illustrated ones and all or a part of these units can be functionally or physically distributed or integrated in an arbitrary unit, according to various kinds of load and the status of use. 
         [0112]    Furthermore, all or an arbitrary part of each processing function performed by respective devices can be realized by a CPU (Central Processing Unit) (or a microcomputer such as an MPU (Micro Processing Unit) and an MCU (Micro Controller Unit)). Further, all or an arbitrary part of the respective processing function can be realized by a program analyzed and executed in the CPU (or a microcomputer such as an MPU and an MCU), or realized as hardware by a wired logic. 
         [0113]    In one mode, it is possible to reduce the effects of signal interference with first communication due to second communication. 
         [0114]    All examples and conditional language provided herein are intended for the pedagogical purposes of aiding the reader in understanding the invention and the concepts contributed by the inventors to further the art, and are not to be construed as limitations to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although one or more embodiments of the present invention have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.