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

A radio communications system, a base station, a mobile station, and a wireless communication method

0001The present invention relates to a radio communications system, a base station, a mobile station, and a wireless communication method.

0002Conventionally, in LTE (Long Term Evolution) and LTE-Advanced which are next-generation mobile communication systems, examination of the heterogeneous network is performed for the purpose of expansion of system capacity or coverage. A heterogeneous network is a network where coexistence arrangement of a macro cell and the cell (it is hereafter described as a "pico cell".) which the base station of low transmission power constitutes was carried out. In such a network, when a macro cell and a pico cell are employed on the same frequency, the interference to a pico cell from a macro cell poses a problem. That is, in the mobile station (it is hereafter described as a "pico mobile station") linked to the base station (it is hereafter described as a "pico base station".) of a pico cell, the signal from a pico base station receives interference with the signal from the base station (it is hereafter described as a "macroscopic base station".) of a macro cell.

0003The above-mentioned interference between cells affects the communication quality in each physical channel (a control channel, a share channel). In particular, in the system with which the transmit timing of a subframe synchronizes between cells, the interference between cells may occur by control channels and share channels. As art of reducing such interference between cells, application of the cooperative control art between cells is possible. Art called CoMP (Coordinated Multiple Point) which is examining LTE-Advanced (Release-11) as cooperative control art between cells, There is art called ICIC (Inter-Cell Interference Coordination) in LTE (Release-8). In cooperative control art between cells, such as CoMP and ICIC, a plurality of base stations are made to cooperate mutually, and the data signal using a share channel is transmitted to a mobile station.

0004On the other hand, by LTE in recent years, when communication is simultaneously performed among many users, we are anxious about the capacity of a control channel running short, and the art to which a control channel is made to extend for example, to a share channel field etc. is examined as art which relieves the shortage of capacity of this control channel. As opposed to the resource of PDSCH (Physical Downlink Shared CHannel) which is a share channel in this art, PDCCH is extended by carrying out frequency multiplication of the PDCCH (Physical Downlink Control CHannel) which is one of the control channels. Below, suppose that extended PDCCH is called E-PDCCH (Enhanced-PDCCH).

<p num="0005"><nplcit num="1"><text>3GPP TS 36.211 V10.2.0 (2011-06)</text></nplcit><nplcit num="2"><text>3GPP TS 36.212 V10.2.0 (2011-06)</text></nplcit><nplcit num="3"><text>3GPP TS 36.213 V10.2.0 (2011-06)</text></nplcit><nplcit num="4"><text>3GPP TR 36.814 V9.0.0 (2010-03)</text></nplcit><nplcit num="5"><text>3GPP R1-111636 (2011-05)</text></nplcit></p>

<p num="0006">By the way, in conventional technology, it is not taken into consideration about reducing the interference between cells of the control channel extended to the share channel field etc.</p><p num="0007">For example, in E-PDCCH which is the control channel extended to the share channel field etc., it is possible to apply cooperative control between cells, such as CoMP and ICIC, like PDSCH which is a share channel. However, about E-PDCCH examined now, since it is distributed by the assigned whole bandwidth, application of cooperative control between cells, such as CoMP and ICIC, is difficult. There is a possibility that the control signals using E-PDCCH as a result may interfere between cells.</p><p num="0008">The art of an indication is made in view of the above, and aims at providing the radio communications system, base station and mobile station which can reduce the interference between cells of the control channel extended to the share channel field etc., and a wireless communication method.</p>

<p num="0009">The radio communications system which this application indicates performs cooperative control between cells which makes the base station of the 1st cell, and the base station of the 2nd cell cooperate mutually, and transmits a signal to the mobile station of the 1st above-mentioned cell in one mode. A radio communications system has a base station of the 1st cell, a base station of the 2nd cell, and a mobile station of the 1st cell. The base station of the 1st cell has the 1st control part and the 2nd communications department. The 1st control part carries out interleave of the resource of the control channel of the 1st cell extended to the predetermined field of the 1st above-mentioned cell corresponding to a predetermined resource unit based on the common identifier which is an identifier which is common between the base station of the 1st above-mentioned cell, and the base station of the 2nd above-mentioned cell. The 1st communications department corresponds to at least one copy of the above-mentioned predetermined resource unit, and transmits a control signal to the mobile station of the 1st above-mentioned cell using the 1st resource of the control channel of the 1st above-mentioned cell which is a candidate for decoding of the mobile station of the 1st above-mentioned cell. The base station of the 2nd cell has the 2nd control part and the 2nd communications department. The 2nd control part carries out interleave of the resource of the control channel of the 2nd above-mentioned cell extended to the predetermined field of the 2nd above-mentioned cell corresponding to the above-mentioned predetermined resource unit based on the above-mentioned common identifier. The 2nd communications department corresponds to at least one copy of the above-mentioned predetermined resource unit, and transmits a control signal to the mobile station of the 1st above-mentioned cell using the 2nd resource of the control channel of the 2nd above-mentioned cell which is a candidate for decoding of the mobile station of the 1st above-mentioned cell. The mobile station of the 1st cell has the 3rd communications department which receives the control signal transmitted from the base station of the 2nd above-mentioned cell with the 2nd above-mentioned resource while receiving the control signal transmitted from the base station of the 1st above-mentioned cell with the 1st above-mentioned resource.</p>

<p num="0010">According to one mode of the radio communications system which this application indicates, the effect that the interference between cells of the control channel extended to the share channel field etc. can be reduced is produced.</p>

0011<figref num="1">Drawing 1 is a figure showing an example of a heterogeneous network.</figref><figref num="2">Drawing 2 is a figure for explaining the mapping method of each physical channel.</figref><figref num="3">Drawing 3 is a figure for explaining the mapping method of PDCCH.</figref><figref num="4">Drawing 4 is a figure for explaining the search space of PDCCH.</figref><figref num="5">Drawing 5 is a figure showing an example of E-PDCCH by FDM approach.</figref><figref num="6">Drawing 6 is a figure for explaining the wireless communication method in the radio communications system concerning Example 1.</figref><figref num="7">Drawing 7 is a figure showing the example of arrangement of E-Control region in Example 1 (the 1).</figref><figref num="8">Drawing 8 is a figure showing the example of arrangement of E-Control region in Example 1 (the 2).</figref><figref num="9">Drawing 9 is a figure showing the composition of the radio communications system concerning Example 1.</figref><figref num="10">Drawing 10 is a figure showing the composition of the mobile station concerning Example 1.</figref><figref num="11">Drawing 11 is a figure showing operation of the radio communications system concerning Example 1.</figref><figref num="12">Drawing 12 is a figure showing an example of E-SS Type1 in Example 1.</figref><figref num="13">Drawing 13 is a figure showing an example of E-SS Type2 in Example 1.</figref><figref num="14">Drawing 14 is a figure for explaining the user scheduling algorithm of a pico base station and a macro base station concerning Example 1.</figref><figref num="15">Drawing 15 is a figure for explaining the wireless communication method in the radio communications system concerning Example 2.</figref><figref num="16">Drawing 16 is a figure showing the composition of the radio communications system concerning Example 2.</figref><figref num="17">Drawing 17 is a figure showing operation of the radio communications system concerning Example 2.</figref><figref num="18">Drawing 18 is a figure for explaining the user scheduling algorithm of a pico base station and a macro base station concerning Example 2.</figref><figref num="19">Drawing 19 is a figure for explaining the example of composition of others of E-Control region Type1.</figref>

0012Below, the example of the radio communications system which this application indicates, a base station, a mobile station, and a wireless communication method is described in detail, referring to drawings. This invention is not limited by this example.

0013First, with reference to Drawing 1 - Drawing 5, the art which will be the requisite for the radio communications system which this application indicates is explained. Drawing 1 is a figure showing an example of a heterogeneous network. A heterogeneous network shown in Drawing 1 is a network where coexistence arrangement of a macro cell and the pico cell was carried out. A macro base station and each pico base station are connected via cable interfaces, such as an optical fiber. In such a heterogeneous network, when the macro cell and the pico cell are employed on the same frequency, by the mobile station linked to a pico base station, it gets down from a pico base station, and signal SGof choice1 of a link receives interference signal SG2 [ big ] from a macro base station, for example. As a result, there is a possibility that the communication quality of each physical channel (a control channel, a share channel) may deteriorate.

0014Before interference between this cell explains the influence which it has on each physical channel, the mapping method to a temporal frequency resource is explained to be the composition of each physical channel with reference to Drawing 2. Drawing 2 is a figure for explaining the mapping method of each physical channel. As shown in Drawing 2, in the direction of time, merit's subframe comprises a 14OFDM (Orthogonal Frequency Division Multiplexing) symbol for 1 ms, A control channel is mapped by n (=1-3) OFDM symbols of the front. A control channel is PCFICH (Physical Control Format Indicator CHannel), for example, They are PHICH (Physical Hybrid ARQIndicator CHannel) and PDCCH (Physical Downlink Control CHannel).

0015The value of n is defined as control information called CFI (Control Format Indicator). Share channel PDSCH (Physical Downlink Shared CHannel) used for transmission of user data, etc. is mapped by the remaining OFDM symbols. In the frequency direction, as a quota unit of a frequency resource, RB (Resource Block) comprises 12 subcarriers and frequency multiplication of the each user-oriented share channel is carried out per RB. The reference signal (Cell-specific RS (Reference Signal)) peculiar to a cell used for channel estimation etc. is sparsely mapped in time and the frequency direction. RE (ResourceElement) which is a field surrounded by 1OFDM symbol and one subcarrier as the minimum unit of a temporal frequency resource is defined. REG (Resource Element Group) constituted by 4RE which continues in the frequency direction except for RS as a mapping unit of a control channel is defined.

0016Next, the mapping method of a control channel is especially explained in full detail among each above-mentioned physical channel. PCFICH is a physical channel used for transmission of CFI. In the OFDM symbol of the head in a subframe, four REG(s) for PCFICH start from the subcarrier position depending on cell ID (IDentity), and are distributed and mapped by abbreviation regular intervals in system bandwidth.

0017PHICH is a physical channel used for transmitting the ACK/NACK information about an uphill share channel. A PHICH group number can be found depending on parameter Ng notified from a higher rank layer, and three REG(s) are used for every PHICH group. With the subcarrier position as the starting point depending on cell ID, in system bandwidth, three REG(s) distribute and are mapped by abbreviation regular intervals in REG by which PCFICH is not mapped.

0018PDCCH is a physical channel used for transmitting information information and the scheduling information about user data. Drawing 3 is a figure for explaining the mapping method of PDCCH. As a unit of the resource which each PDCCH uses, CCE (Control ChannelElement) is defined and CCE corresponds to 9REG (= 36RE). An aggregation level (it is hereafter described as "AL".) is the CCE number which PDCCH uses, i.e., the parameter equivalent to a dispersion ratio. A base station sets up AL out of {1, 2, 4, 8} according to a radio channel state etc. Although mentioned below for details, each PDCCH adds suitable offset, and multiplex is carried out, and it is modulated by QPSK (Quadrature Phase Shift Keying). Each PDCCH is mapped by REG by which PCFICH and PHICH are not mapped after interleave in four abnormal-conditions symbol units is performed.

0019In interleave processing, a base station performs block interleave for PDCCH modulated by QPSK per four abnormal-conditions symbols first, and performs the round shift based on cell ID in four abnormal-conditions symbol units. Specifically, the signal after block interleave is expressed as the following formulas 1.

0020<maths num="1"><img file="WO2013046471A1_D0001.tif" /></maths>

0021The signal after a round shift is expressed as the following formulas 2.

0022<maths num="2"><img file="WO2013046471A1_D0002.tif" /></maths>

0023When formula 1 and formula 2 are referred to and the conditions of the number of abnormal-conditions symbols or cell ID differ, it turns out that it is a mechanism in which the rules of rearrangement in interleave processing also differ.

0024Since a mobile station is not told the multiplex position of PDCCH from a base station, it looks for the candidate of a possible multiplex position when decoding PDCCH, and tries decoding to each received signal. In order to restrict this number of times of decoding to the grade which can be processed by a mobile station, the concept of the search space (it is hereafter described as "SS".) is introduced. Therefore, a base station carries out multiplex [ of the PDCCH ] to the arbitrary places in the restricted search space, and a mobile station searches only for a search space and should just try decoding.

0025Drawing 4 is a figure for explaining the search space of PDCCH. An example of the search space in a certain subframe in case there are 33 usable CCE(s) is shown in Drawing 4. The common search space (Common Search Space) provided for PDCCH which transmits the scheduling information on information information is always being fixed to top 16CCE. The mobile station peculiar search space (UE (User Equipment) Specific Search Space) provided for PDCCH which transmits the scheduling information on user data differs in a head position for every mobile station, AL, and subframe. This head position is determined by the hash function. An usable CCE number may change according to system bandwidth, antenna composition, CFI, and Ng.

0026Next, interference between cells explains the influence which it has on each physical channel. In the system with which the transmit timing of a subframe synchronizes between cells, the interference between cells may occur by share channels and control channels. In LTE, in order to reduce interference between such cells, the cooperative control art between cells is prepared about the share channel. Art in which the cooperative control art between cells is called CoMP (Coordinated Multiple Point) which is examining LTE-Advanced (Release-11), for example, It is the art called ICIC (Inter-Cell Interference Coordination) in LTE (Release-8). In cooperative control art between cells, such as these CoMP(s) and ICIC, a plurality of base stations are made to cooperate mutually, and the data signal using a share channel is transmitted to a mobile station.

0027For example, in CoMP, a signal ingredient transmits the same share channel PDSCH from a pico base station and a macro base station to a specific pico mobile station. That is, in a pico mobile station, since the signal from an adjoining macro cell is received as a signal of choice, interference between cells can be reduced.

0028For example, by ICIC, specific RB is assigned to the share channel of the mobile station of a cell boundary in a pico base station about share channel PDSCH. On the other hand, in a macro base station, or it does not transmit a share channel by the RB, interference between cells can be reduced by transmitting by low transmission power.

0029However, in above-mentioned art, application of cooperative control art between cells, such as CoMP and ICIC, is difficult about control channels, such as PDCCH. In a control channel, it is because the rules of rearrangement in interleave processing differ as it already explained with reference to formula 1, since the conditions of the number of abnormal-conditions symbols or cell ID differed between the adjoining cells. Thus, about a control channel, since the mapping position of PDCCH does not become the same between the adjoining cells but the whole system bandwidth distributes, application of cooperative control art between cells, such as CoMP and ICIC, becomes difficult.

0030On the other hand, in LTE, in order to relieve the shortage of capacity of a control channel in recent years, the concept of the FDM (Frequency Division Multiplexing) approach to which a control channel is made to extend to predetermined fields, such as a share channel field, is proposed. Drawing 5 is a figure showing an example of E-PDCCH by FDM approach. As shown in Drawing 5, in FDM approach, PDCCH is extended to RB of PDSCH which is a share channel by carrying out frequency multiplication of the PDCCH which is one of the control channels. Below, suppose that PDCCH extended to predetermined fields, such as a share channel field, is called E-PDCCH.

0031Next, the problem about E-PDCCH is explained. Also in E-PDCCH which is the control channel extended to predetermined fields, such as a share channel field, it is desirable to apply cooperative control between cells, such as CoMP and ICIC, from a viewpoint of reducing interference between cells, like PDSCH which is a share channel. However, about E-PDCCH, since the mapping position of E-PDCCH does not become the same like the conventional PDCCH between the adjoining cells but it is distributed by the assigned whole bandwidth, application of cooperative control between cells, such as CoMP and ICIC, is difficult. There is a possibility that the control signals using E-PDCCH as a result may interfere between cells.

0032So, in the radio communications system concerning this example, the above-mentioned problem in E-PDCCH is canceled by devising the transmitting technique of E-PDCCH.

<p num="0033">First, the wireless communication method in the radio communications system concerning this example is explained. Drawing 6 is a figure for explaining the wireless communication method in the radio communications system concerning Example 1. The radio communications system of this example is constituted as a heterogeneous network where coexistence arrangement of a macro cell and the pico cell was carried out as shown in Drawing 1. And the radio communications system of this example can exchange information required in order to perform cooperative control between cells, such as CoMP and ICIC. Below, suppose that the range of a cell which can perform cooperative control between cells is called cooperation area. Cooperation area ID is defined as an identifier which is common in the macro base station belonging to cooperation area, and a pico base station. This cooperation area ID is an example of a common identifier.</p><p num="0034">signs that CCE is assigned to E-PDCCH for each mobile stations (UE:User Equipment) in Drawing 6 in some two cells (cell 1 and cell 2) in cooperation area, and every -- signs that CCE is mapped by the temporal frequency resource are shown. Here, cell 1 shall be a pico cell and cell 2 shall be a macro cell, for example.</p><p num="0035">As a temporal frequency resource for E-PDCCH, E-Control region Type1 and two kinds of fields called E-Control region Type2 are provided. Among these, E-Control region Type1 is a resource used for cooperative control between cells. It is provided by several units predetermined RB. Two E-Control region Type1 of 2RB unit are provided in the example of Drawing 6. These two E-Control region Type1 is provided in a common position in each cell in cooperation area.</p><p num="0036">On the other hand, E-Control region Type2 is a resource which is not used for the cooperative control between cells. E-Control region Type2 is provided by several units RB which is different for every cell according to the number of mobile stations, etc., for example. E-Control region Type1 and E-Control region Type2 let REG be a component like Release8 Control region. The concrete example of arrangement of these E-Control region is mentioned below.</p><p num="0037">CCE for the cooperative control between cells and CCE for non-cooperative control are provided as CCE for E-PDCCH. One CCE corresponds to 9REG like Release8 PDCCH.</p><p num="0038">First, in the mobile station linked to a pico base station, the situation where the signal of choice from a pico base station receives an interference signal from a macro base station is assumed. In this situation, a pico base station and a macro base station assign common CCE in CCE for the cooperative control between cells to the mobile station linked to a pico base station in each cell in cooperation area. In the example of Drawing 6, a pico base station and a macro base station assign common CCE in CCE for the cooperative control between cells to mobile station UE1, mobile station UE2, and mobile station UE3 in cell 1 and cell 2 in cooperation area.</p><p num="0039">On the other hand, the signal of choice from a pico base station assumes the situation where the interference signal is not received from a macro base station. In this situation, a pico base station and a macro base station assign CCE for non-cooperative control to a mobile station in the connection cell of a mobile station. In the example of Drawing 6, in cell 1 which is a connection cell of mobile station UE4, a pico base station assigns CCE for non-cooperative control to mobile station UE4, and a macro base station assigns CCE for non-cooperative control to mobile station UE5 in cell 2 which is a connection cell of mobile station UE5.</p><p num="0040">Subsequently, interleave processing is carried out per four abnormal-conditions symbols after QPSK abnormal conditions, and the resource for E-PDCCH of each CCE is mapped by each REG of E-Control region. When CCE is CCE for non-cooperative control, a pico base station and a macro base station perform block interleave for E-PDCCH by which QPSK abnormal conditions were carried out per four abnormal-conditions symbols, and, specifically, perform the round shift based on cell ID in four abnormal-conditions symbol units. On the other hand, a pico base station and a macro base station perform interleave processing per RB of E-Control region Type1, when CCE is CCE for the cooperative control between cells. For example, 22REG shall be contained in one E-Control region Type1. In this case, a pico base station and a macro base station start four abnormal-conditions symbol units by 22 pieces from CCE for the cooperative control between cells, perform block interleave per four abnormal-conditions symbols, and perform the round shift based on cooperation area ID in four abnormal-conditions symbol units.</p><p num="0041">By doing in this way, common CCE is assigned in each cell about E-PDCCH for UE1 in a figure, UE2, and UE3, for example. And block interleave is performed by each cell in a common processing unit, and the round shift based on cooperation area ID which is a common identifier is performed in each cell. Then, the resource for E-PDCCH is mapped in each cell by REG in E-Control region Type1 which is common time and frequency resource. Therefore, a signal ingredient can transmit the same control channel E-PDCCH from a pico base station and a macro base station to a specific mobile station. The receiving characteristic of E-PDCCH can be improved as a result.</p><p num="0042">For example, about E-PDCCH UE4 in a figure, and for UE5, CCE is assigned in a connection cell. Since each CCE is used about and carried out between cells, E-PDCCH for many mobile stations is stored.</p><p num="0043">Here, the concrete example of arrangement of E-Control region is explained. Drawing 7 is a figure showing the example of arrangement of E-Control region in Example 1 (the 1). Drawing 8 is a figure showing the example of arrangement of E-Control region in Example 1 (the 2). The number of transmitting antennas of Drawing 7 is 4. Signs that 3OFDM symbol is used as Release 8 Control region are shown. The number of transmitting antennas of Drawing 8 is 2. Signs that 2OFDM symbol is used as Release 8 Control region are shown.</p><p num="0044">As shown in Drawing 7 and Drawing 8, the number of RE(s) used about Cell-specific RS differed according to the number of transmitting antennas, and the mapping position has shifted in the frequency direction according to cell ID. About CSI(Channel State Information)-RS which is a reference signal for channel quality measurement, RE used in RE indicated in the figure is limited in part, and patterns, such as a transmitting cycle, are set up by the higher rank layer. Therefore, REG for which a mapping position does not depend on a cell among RE(s) which other physical channels are not using exists. REG for which a mapping position does not depend on a cell is used as E-Control regionType1 and E-Control region Type2. REG for which a mapping position depends on a cell among RE(s) which other physical channels are not using also exists. REG for which a mapping position depends on a cell is used as E-Control region Type2.</p><p num="0045">As composition of E-Control region, the composition beforehand defined within the radio communications system may be adopted. The composition of E-Control region may be composition which each base station in a radio communications system changes if needed. When each base station in a radio communications system changes the composition of E-Control region, a base station notifies the E-Control region composition information that the composition of E-Control region is expressed to a mobile station. The information on the position of RB used as E-Control region and the information on the unit bandwidth (for example, unit bandwidth of 2RB) of E-Control region Type1 are included in E-Control region composition information, for example. The information showing whether a mapping position uses REG independent of a cell as E-Control region Type1 among REG(s) for E-PDCCH is included.</p><p num="0046">Next, the composition of the radio communications system concerning this example is explained. Drawing 9 is a figure showing the composition of the radio communications system concerning Example 1. As shown in Drawing 9, radio communications system 1 has pico base station 100 and macro base station 200. Pico base station 100 and macro base station 200 shall be base stations belonging to cooperation area.</p><p num="0047">Pico base station 100 has control part 100a and communications department 100b. Control part 100a has UE judgment part 101 for CoMP application, scheduler part 102, and data signal generation part 103. Control part 100a has control signal generating part 104, reference signal generating part 105, physical channel multiplex section 106, uphill control signal demodulation section 108, and IFFT (Inversed Fast Fourier Transform) section 109. Communications department 100b has receiving RF (Radio Frequency) section 107 and transmitting RF section 110. Each of these component part is connected to one way or both directions so that input and output of a signal or data may be possible. Physically, control parts 100a are a digital circuit and DSP (Digital Signal Processor), It is constituted by CPU (Central Processing Unit) etc. and communications department 100b is constituted by the analog circuitry containing amplifier and a filter.</p><p num="0048">UE judgment part 101 for CoMP application is based on the information on the received power (RSRP (Reference Signal Received Power)) of each cell notified from each mobile station, It judges whether the mobile station concerned is candidate UE for CoMP application, and determines a cooperation cell. A cooperation cell refers to the cell which can perform CoMP which is one of the cooperative control between cells. UE judgment part 101 for CoMP application notifies the information which shows whether a mobile station is candidate UE for CoMP application, and the information on a cooperation cell to scheduler part 102 as UE information for CoMP application.</p><p num="0049">Channel quality information to which it was notified from each mobile station that scheduler part 102 was UE information for CoMP application (user scheduling is performed based on CQI (Channel Quality Indicator).) For example, scheduler part 102 assigns CCE to assignment of the frequency resource to the share channel for each mobile stations, and E-PDCCH for each mobile stations based on UE information for CoMP application, and CQI notified from each mobile station. In order to perform user scheduling which cooperated between cells, scheduler part 102 exchanges the user data about candidate UE for CoMP application, control data, and scheduling information between scheduler parts 202 of macro base station 200 which store a cooperation cell. This exchange is performed via a cable interface.</p><p num="0050">Data signal generation part 103 generates data signals, such as PDSCH, based on user data, the below-mentioned search space change directions, E-Control region composition information, etc. Control signal generating part 104 generates control signals, such as E-PDCCH, based on the control information which comprises resource quota information etc. Reference signal generating part 105 generates a reference signal.</p><p num="0051">Physical channel multiplex section 106 carries out frequency multiplication of each physical channel. for example, physical channel multiplex section 106 -- the inside of a physical channel -- every -- frequency multiplication of E-PDCCH is carried out by performing block interleave for E-PDCCH of CCE per four abnormal-conditions symbols, and performing the round shift based on cooperation area ID in four abnormal-conditions symbol units.</p><p num="0052">To the received signal of an uphill link, receiving RF section 107 performs conversion to baseband from a radio frequency, and performs a rectangular recovery and A/D (Analog to Digital). Receiving RF section 107 has antenna A1, and receives an uphill signal. Uphill control signal demodulation section 108 restores to an uphill control signal, and restores CQI and RSRP of each cell which are control information. IFFT part 109 performs inverse Fourier transform (IFFT), and adds CP (Cyclic Prefix). Transmitting RF section 110 performs D/A conversion and quadrature modulation, and it performs conversion to a radio frequency from baseband, amplifies and gets down from electric power, and transmits the signal of a link. Transmitting RF section 110 has antenna A2, gets down and transmits a signal.</p><p num="0053">Similarly, macro base station 200 has control part 200a and communications department 200b. Control part 200a has UE judgment part 201 for CoMP application, scheduler part 202, and data signal generation part 203. Control part 200a has control signal generating part 204, reference signal generating part 205, physical channel multiplex section 206, uphill control signal demodulation section 208, and IFFT (Fast Fourier Transform) section 209. Communications department 200b has receiving RF section 207 and transmitting RF section 210. Each of these component part is connected to one way or both directions so that input and output of a signal or data may be possible. Physically, control part 200a is constituted by a digital circuit, DSP, CPU, etc., and communications department 200b is constituted by the analog circuitry containing amplifier and a filter.</p><p num="0054">Macro base station 200 has the same composition as pico base station 100. Therefore, while an end gives the same reference mark to the same component, the detailed explanation is omitted.</p><p num="0055">Next, the composition of mobile station 10 is explained. Drawing 10 is a figure showing the composition of the mobile station concerning Example 1. Mobile station 10 has control part 10a and communications department 10b. Control part 10a has FFT section 12, data signal demodulation section 13, control signal demodulation section 14, channel estimation part 15, CQI calculation part 16, RSRP measurement part 17, and going-up control signal generating part 18. Communications department 10b has receiving RF section 11 and transmitting RF section 19. Each of these component part is connected to one way or both directions so that input and output of a signal or data may be possible.</p><p num="0056">Receiving RF section 11 gets down, to the received signal of a link, performs conversion to baseband from a radio frequency, and performs a rectangular recovery and an A/D conversion. It gets down with antenna A5, and receiving RF section 11 receives a signal. After FFT section 12 detects the logging timing of a received signal and removes CP like a typical OFDM method, it changes this detection result into the received signal of a frequency domain by Fourier transform (FFT).</p><p num="0057">Data signal demodulation section 13 restores to the data signal extracted from the received signal based on resource quota information, and restores data information. The control information from higher rank layers, such as search space change directions and E-Control region composition information, other than user data is included in data information. Data signal demodulation section 13 notifies the restored search space (SS:Search Space) change directions to control signal demodulation section 14, when search space change directions are restored as data information.</p><p num="0058">Control signal demodulation section 14 restores to control signals, such as E-PDCCH extracted from the received signal, and restores resource quota information as control information. Control signal demodulation section 14 changes the range searched at the time of decoding of E-PDCCH, when SS change directions are notified from data signal demodulation section 13.</p><p num="0059">Channel estimation part 15 acquires a channel estimation value by taking correlation with the replica of the reference signal extracted from the received signal, and a known reference signal. This channel estimation is performed not only about the cell which mobile station 10 has connected but about the cell of the circumference of it. CQI calculation part 16 computes channel quality information (above-mentioned CQI) using the channel estimation value of the cell which has connected mobile station 10. RSRP measurement part 17 measures the received power (above-mentioned RSRP) of the reference signal of each cell using the cell which has connected mobile station 10, and the channel estimation value of the circumference cell. Going-up control signal generating part 18 generates an uphill control signal based on the control information constituted by CQI and RSRP of each cell. After transmitting RF section 19 performs D/A (Digital to Analog) conversion and quadrature modulation, it performs conversion to a radio frequency from baseband, amplifies electric power, goes up, and transmits the signal of a link. Transmitting RF section 19 goes up with antenna A6, and transmits a signal. Physically, control part 10a is constituted by a digital circuit, DSP, CPU, etc., and communications department 10b is constituted by the analog circuitry containing amplifier and a filter.</p><p num="0060">Next, operation is explained. In this example, the network environment to which a plurality of pico cells are intermingled in a macro cell as shown in Drawing 1 is assumed. Drawing 11 is a figure showing operation of radio communications system 1 concerning Example 1. Below, mobile station 10 shall have connected with pico base station 100, and it shall hold cooperation area ID with common pico base station 100 and macro base station 200 belonging to cooperation area. Below, the pico cell which mobile station 10 has connected may be called a connection cell.</p><p num="0061">In S1, pico base station 100 notifies E-Control region composition information to mobile station 10. Mobile station 10 which received E-Control region composition information specifies arrangement of E-Control region Type1 by which CCE is mapped, and E-Control region Type2.</p><p num="0062">In S2, pico base station 100 transmits CSI-RS. In S3, macro base station 200 transmits CSI-RS. In S4, mobile station 10 measures the received power of CSI-RS about the pico cell which has connected, and its circumference cell. A circumference cell contains each cell in cooperation area. By S5, mobile station 10 sets the measurement result of received power to RSRP, and reports it to pico base station 100.</p><p num="0063">In S6, pico base station 100 presumes the state of the interference between cells in mobile station 10 based on RSRP of each cell reported from mobile station 10, and detects candidate UE for CoMP application based on the estimation result, and determines a cooperation cell. For example, RSRP of the pico cell which mobile station 10 has connected is made into "RSRP_S", and when RSRP of each cell in the cooperation area containing a macro cell is made into "RSRP_I", difference alpha=|RSRP_S-RSRP_I| expresses the state of the interference between cells in mobile station 10. Then, pico base station 100 determines the cell which detects mobile station 10 linked to a pico cell as candidate UE for CoMP application, and alpha becomes below in a fixed threshold as a cooperation cell, when the cell which alpha becomes among the cells in cooperation area below in a fixed threshold exists. In this example, pico base station 100 should determine the macro cell as a cooperation cell.</p><p num="0064">In S7, pico base station 100 notifies SS change directions which direct to change the search space (SS) which mobile station 10 searchs at the time of decoding of E-PDCCH to mobile station 10.</p><p num="0065">Here, the concrete processing performed in pico base station 100S7 is explained. SS which mobile station 10 searchs at the time of decoding of E-PDCCH contains E(Enhanced)-SS Type1 which is SS defined on CCE for the cooperative control between cells, and E-SS Type2 which are SS defined on CCE for non-cooperative control, as shown in Drawing 12 and Drawing 13. Pico base station 100 notifies SS change directions which direct to change the present SS to E-SS Type1 shown in Drawing 12 to mobile station 10, when mobile station 10 is candidate UE for CoMP application. On the other hand, pico base station 100 notifies SS change directions which direct to change the present SS to E-SS Type2 shown in Drawing 13 to mobile station 10, when mobile station 10 is not candidate UE for CoMP application. Drawing 12 is a figure showing an example of E-SS Type1 in Example 1. Drawing 13 is a figure showing an example of E-SS Type2 in Example 1.</p><p num="0066">Returning to Drawing 11, by S8, pico base station 100 and macro base station 200 cooperate mutually, and perform user scheduling.</p><p num="0067">Drawing 14 is a figure for explaining the user scheduling algorithm which 200 performs in pico base station 100 and macro base stationS8 concerning Example 1. Since the user scheduling which pico base station 100 and macro base station 200 perform has the same contents of processing, the contents of processing of pico base station 100 are explained as a representative here.</p><p num="0068">First, pico base station 100 selection of UE which is the target of scheduling will judge whether UE selected by S31 is candidate UE for CoMP application (S32). (S31)</p><p num="0069">When UE of S32 selected as a result of the judgment by S31 is not candidate UE for CoMP application (S32;No), it is judged whether pico base station 100 is securable of RB for data signals (S33). As a result of the judgment concerned, when reservation of RB is possible, (S33;Yes) and pico base station 100 choose AL of E-PDCCH (S34), and it is judged whether reservation of CCE for E-PDCCH is possible in the field of E-SSType2 of a connection cell (S35). As a result of the judgment concerned, when reservation of CCE is possible (S35;Yes), pico base station 100 secures RB for data signals, and CCE for E-PDCCH (S36). At this time, pico base station 100 secures RB for data signals, and CCE for E-PDCCH based on own cell ID. Then, if pico base station 100 searches for other UE(s) which are the targets of scheduling in cooperation area (S37) and other UE(s) cannot be found (S37;No), it will end user scheduling processing.</p><p num="0070">When UE of S32 selected as a result of the judgment by S31 is candidate UE for CoMP application (S32;Yes), it is judged whether pico base station 100 is securable in a connection cell and a cooperation cell of RB for data signals (S38). As a result of the judgment concerned, when reservation of RB is possible (S38;Yes), pico base station 100 chooses AL of E-PDCCH (S39), and it is judged whether reservation of CCE for E-PDCCH is possible in the field of E-SS Type1 of a connection cell and a cooperation cell (S40). As a result of the judgment concerned, when reservation of CCE is possible (S40;Yes), pico base station 100 secures RB for data signals, and CCE for E-PDCCH (S36). At this time, pico base station 100 secures CCE for E-PDCCH of a position common in the field of E-SS Type1 of RB for data signals, a connection cell, and a cooperation cell based on cooperation area ID.</p><p num="0071">When judged with reservation of RB being impossible in above S33 and S38, it returns to (S33;No, S38;No), and S31, and processing after it is performed again. When judged with reservation of CCE being impossible in above S35 and S40 (S35;No, S40;No), similarly, it returns to S31 and processing after it is performed again.</p><p num="0072">A series of processings of S31-S40 mentioned above are ended, when it performs repeatedly (S37;Yes) and scheduling processing is completed about all the UE(s) until UE used as a scheduling object is lost.</p><p num="0073">Returning to Drawing 11, by S9, pico base station 100 transmits the same E-PDCCH as macro base station 200 to mobile station 10 which is candidate UE for CoMP application using CCE for E-PDCCH of a position common in the field of E-SS Type1 of a connection cell and a cooperation cell.</p><p num="0074">In S10, macro base station 200 transmits the same E-PDCCH as pico base station 100 to mobile station 10 which is candidate UE for CoMP application using CCE for E-PDCCH of a position common in the field of E-SS Type1 of a connection cell and a cooperation cell. E-PDCCH transmitted by S9 and E-PDCCH transmitted by S10 are in the state which was compounded on the radio channel and whose SINR (Signal to Interference and Noise Ratio) improved, and it reaches the receiving antenna of mobile station 10. Thereby, the interference to E-PDCCH for [ in a pico cell / UE ] CoMP application from a macro cell is reduced.</p><p num="0075">Pico base station 100 transmits E-PDCCH to mobile station 10 which is not candidate UE for CoMP application using CCE in the field of E-SS Type2.</p><p num="0076">In S11, mobile station 10 changes SS according to SS change directions notified from pico base station 100 in S7, searchs SS after a change, and decodes E-PDCCH. Mobile station 10 which is candidate UE for CoMP application changes the present SS to E-SS Type1, searchs E-SS Type1, and, specifically, decodes E-PDCCH. On the other hand, mobile station 10 which is not candidate UE for CoMP application changes the present SS to E-SS Type2, searchs E-SS Type2, and decodes E-PDCCH. And mobile station 10 acquires the resource quota information on decoded E-PDCCH to PDSCH.</p><p num="0077">In S12, pico base station 100 transmits the same PDSCH as macro base station 200 using RB of the common position assigned to mobile station 10 which is candidate UE for CoMP application.</p><p num="0078">In S13, macro base station 200 transmits the same PDSCH as pico base station 100 using RB of the common position assigned to mobile station 10 which is candidate UE for CoMP application. PDSCH transmitted by S12 and PDSCH transmitted by S13 are in the state which was compounded on the radio channel and whose SINR improved, and it reaches the receiving antenna of mobile station 10. Thereby, the interference to PDSCH for [ in a pico cell / UE ] CoMP application from a macro cell is reduced.</p><p num="0079">Pico base station 100 transmits PDSCH using RB assigned to mobile station 10 which is not candidate UE for CoMP application.</p><p num="0080">In S14, mobile station 10 decodes PDSCH mapped by RB which the resource quota information acquired by S11 shows, and obtains user data.</p><p num="0081">As mentioned above, radio communications system 1 of Example 1 performs cooperative control between cells which makes pico base station 100 and macro base station 200 cooperate mutually, and transmits a signal to mobile station 10 of a pico cell. Radio communications system 1 has pico base station 100, macro base station 200, and mobile station 10 of a pico cell. Pico base station 100 has control part 100a and communications department 100b. Control part 100a carries out interleave of the resource of E-PDCCH of a pico cell corresponding to a predetermined resource unit based on cooperation area ID which is an identifier which is common between pico base station 100 and macro base station 200. Communications department 100b corresponds to at least one copy of the above-mentioned predetermined resource unit, and transmits a control signal to mobile station 10 of a pico cell using the 1st resource of E-PDCCH of a pico cell which is a candidate for decoding of mobile station 10 of a pico cell. Macro base station 200 has control part 200a and communications department 200b. Control part 200a carries out interleave of the resource of E-PDCCH of a macro cell corresponding to the above-mentioned predetermined resource unit based on above-mentioned cooperation area ID. Communications department 200b corresponds to at least one copy of the above-mentioned predetermined resource unit, and transmits a control signal to mobile station 10 of a pico cell using the 2nd resource of E-PDCCH of a macro cell which is a candidate for decoding of mobile station 10 of a pico cell. Mobile station 10 of a pico cell has communications department 10b which receives the control signal transmitted from macro base station 200 with the 2nd resource while receiving the control signal transmitted from pico base station 100 with the 1st resource. Here, predetermined resource units are one or more RB(s). The 1st resource contains E-SS Type1 which is a search space (SS) peculiar to mobile station 10 of a pico cell, for example, is SS defined on CCE for the cooperative control between cells, and E-SS Type2 which are SS defined on CCE for non-cooperative control. Thereby, radio communications system 1 can reduce the interference between cells of E-PDCCH.</p>

<p num="0082">Example 2 explains the example which applied the art of ICIC to the radio communications system in Example 1. That is, scheduler part 102 of pico base station 100 of Example 1 and scheduler part 202 of macro base station 200 secured CCE for E-PDCCH of the position common in the field of E-SS Type1 of a connection cell and a cooperation cell based on cooperation area ID. This enables a signal ingredient to transmit the same E-PDCCH from a pico base station and a macro base station using all the resources of CCE for the cooperative control between cells secured as CCE for E-PDCCH, and it becomes possible to reduce the interference between cells of E-PDCCH. However, by one side, in order to exchange the control information to transmit between base stations, high-speed control is called for.</p><p num="0083">Then, the radio communications system of this example performs cooperative control between cells which reduces the interference between cells of E-PDCCH by a comparatively simple method. In order to realize cooperative control between these cells, one scheduler part of a pico base station and a macro base station sets some fields of CCE for the cooperative control between cells as transmission power zero or low transmission power, and the scheduler of another side transmits E-PDCCH in the field.</p><p num="0084">First, the wireless communication method in the radio communications system concerning this example is explained. Drawing 15 is a figure for explaining the wireless communication method in the radio communications system concerning Example 2. setting in Drawing 15 in some two cells (cell 1 and cell 2) in cooperation area -- every -- signs that CCE is assigned to E-PDCCH for UE, and every -- signs that CCE is mapped by the temporal frequency resource are shown. Here, cell 1 shall be a pico cell and cell 2 shall be a macro cell, for example. Below, the main differences between Example 2 and Example 1 are explained.</p><p num="0085">First, a pico base station and a macro base station set the transmission power of at least some fields of CCE for the cooperative control between cells as a value smaller than zero or a present value. Thus, below, transmission power presupposes that the field set as the value smaller than zero or a present value is called "an untransmitted field." A pico base station sets up four CCE(s) as an untransmitted field among CCE(s) for the cooperative control between cells in cell 1, and a macro base station sets up eight CCE(s) as an untransmitted field among CCE(s) for the cooperative control between cells in cell 2 in the example of Drawing 15.</p><p num="0086">And a pico base station and a macro base station exchange the untransmitted field information that an untransmitted field is expressed. In the example of Drawing 15, a pico base station notifies the information, including the position of four CCE(s), an identification number, etc., set up as an untransmitted field among CCE(s) for the cooperative control between cells to a macro base station as untransmitted field information. On the other hand, a macro base station notifies the information, including the position of eight CCE(s), an identification number, etc., set up as an untransmitted field among CCE(s) for the cooperative control between cells to a pico base station as untransmitted field information.</p><p num="0087">And a pico base station assigns CCE of the overlapping field to E-PDCCH for mobile stations which exists in a boundary with the macro cell used as a neighboring cell, when the untransmitted field of the macro base station which the untransmitted field information notified from the macro base station shows overlaps with CCE for the cooperative control between cells. In the example of Drawing 15, a pico base station assigns eight CCE(s) of the field where the untransmitted field of a macro base station overlaps with CCE for the cooperative control between cells to mobile stations UE1 and UE3 which exist in a boundary with cell 2 in cell 1.</p><p num="0088">And a macro base station assigns CCE of the overlapping field to E-PDCCH for mobile stations which exists in a boundary with the pico cell used as a neighboring cell, when the untransmitted field of the pico base station which the untransmitted field information notified from the pico base station shows overlaps with CCE for the cooperative control between cells. In the example of Drawing 15, a macro base station assigns four CCE(s) of the field where the untransmitted field of a pico base station overlaps with CCE for the cooperative control between cells to mobile station UE2 which exists in a boundary with cell 1 in cell 2.</p><p num="0089">By doing in this way, interference between E-PDCCH for UE1 in a figure, UE2, and UE3 and a neighboring cell can be reduced, for example.</p><p num="0090">Next, the composition of the radio communications system concerning this example is explained. Drawing 16 is a figure showing the composition of the radio communications system concerning Example 2. As shown in Drawing 16, radio communications system 2 has pico base station 300 and macro base station 400. Pico base station 300 has control part 300a and communications department 300b. Control part 300a has UE judgment part 301 for ICIC application, scheduler part 302, and data signal generation part 303. Control part 300a has control signal generating part 304, reference signal generating part 305, physical channel multiplex section 306, uphill control signal demodulation section 308, and IFFT part 309. Communications department 300b has receiving RF section 307 and transmitting RF section 310. Each of these component part is connected to one way or both directions so that input and output of a signal or data may be possible.</p><p num="0091">Similarly, macro base station 400 has control part 400a and communications department 400b. Control part 400a has UE judgment part 401 for ICIC application, scheduler part 402, and data signal generation part 403. Control part 400a has control signal generating part 404, reference signal generating part 405, physical channel multiplex section 406, uphill control signal demodulation section 408, and IFFT part 409. Communications department 400b has receiving RF section 407 and transmitting RF section 410. Each of these component part is connected to one way or both directions so that input and output of a signal or data may be possible.</p><p num="0092">Radio communications system 2 has the same composition as radio communications system 1 in Example 1. Therefore, while an end gives the same reference mark to the same component, the detailed explanation is omitted.</p><p num="0093">Specifically, pico base station 300 in Example 2 and macro base station 400 are the components respectively corresponding to pico base station 100 in Example 1, and macro base station 200. Control part 300a of pico base station 300 and communications department 300b are equivalent to control part 100a of pico base station 100, and communications department 100b, respectively. Similarly, control part 400a of macro base station 400 and communications department 400b are equivalent to control part 200a of macro base station 200, and communications department 200b, respectively.</p><p num="0094">UE judgment part 301 for ICIC application, scheduler part 302, and data signal generation part 303 of pico base station 300 correspond to UE judgment part 101 for CoMP application, scheduler part 102, and data signal generation part 103 of pico base station 100, respectively. Control signal generating part 304, reference signal generating part 305, and physical channel multiplex section 306 correspond to control signal generating part 104, reference signal generating part 105, and physical channel multiplex section 106, respectively. Uphill control signal demodulation section 308 and IFFT part 309 correspond to control signal demodulation section 108 and IFFT part 109, respectively. Receiving RF section 307 and transmitting RF section 310 correspond to receiving RF section 107 and transmitting RF section 110, respectively.</p><p num="0095">Macro base station 400 has the same composition as pico base station 300. Therefore, while an end gives the same reference mark to the same component, the detailed explanation is omitted. Since the composition of a mobile station is the same as that of Example 1, the explanation is omitted.</p><p num="0096">Hereinafter, the main differences between Example 2 and Example 1 are explained. Based on the information on RSRP of each cell notified from each mobile station, UE judgment part 301 for ICIC application of pico base station 300 judges whether the mobile station concerned is candidate UE for ICIC application, and determines a cooperation cell. A cooperation cell points out the cell which can perform ICIC which is one of the cooperative control between cells. UE judgment part 301 for ICIC application notifies the information which shows whether a mobile station is candidate UE for ICIC application, and the information on a cooperation cell to scheduler part 302 as UE information for ICIC application.</p><p num="0097">Scheduler part 302 performs user scheduling based on CQI it was notified from each mobile station that was UE information for ICIC application. For example, scheduler part 302 is based with UE information for ICIC application, and CQI notified from each mobile station, and assigns CCE to assignment of the frequency resource to the share channel for each mobile stations, and E-PDCCH for each mobile stations. In order to perform user scheduling using the untransmitted field of the cell, scheduler part 302 exchanges the untransmitted field information on PDSCH, and the untransmitted field information on E-PDCCH between scheduler parts 402 of macro base station 400 which store a cooperation cell. This exchange is performed via a cable interface.</p><p num="0098">Next, operation is explained. In this example, the network environment to which a plurality of pico cells are intermingled in a macro cell as shown in Drawing 1 is assumed. Drawing 17 is a figure showing operation of radio communications system 2 concerning Example 2. Below, mobile station 10 shall have connected with pico base station 300, and it shall hold cooperation area ID with common pico base station 300 and macro base station 400 belonging to cooperation area. Below, the pico cell which mobile station 10 has connected may be called a connection cell.</p><p num="0099">In S51, pico base station 300 notifies E-Control region composition information to mobile station 10. Mobile station 10 which received E-Control region composition information specifies arrangement of E-Control region Type1 by which CCE is mapped, and E-Control region Type2.</p><p num="0100">In S52, pico base station 300 transmits CSI-RS. In S53, macro base station 400 transmits CSI-RS. In S54, mobile station 10 measures the received power of CSI-RS about the pico cell which has connected, and its circumference cell. A circumference cell contains each cell in cooperation area. By S55, mobile station 10 sets the measurement result of received power to RSRP, and reports it to pico base station 300.</p><p num="0101">In S56, pico base station 300 sets up the untransmitted field of PDSCH, and the untransmitted field of E-PDCCH, and notifies the untransmitted field information on PDSCH, and the untransmitted field information on E-PDCCH to macro base station 400. In S57, macro base station 400 sets up the untransmitted field of PDSCH, and the untransmitted field of E-PDCCH, and notifies the untransmitted field information on PDSCH, and the untransmitted field information on E-PDCCH to pico base station 300.</p><p num="0102">In S58, pico base station 300 presumes the state of the interference between cells in mobile station 10 based on RSRP of each cell reported from mobile station 10, and detects candidate UE for ICIC application based on the estimation result, and determines a cooperation cell. Specifically, pico base station 300 detects mobile station 10 linked to a pico cell as candidate UE for ICIC application, when the cell which alpha which expresses the state of the interference between cells in mobile station 10 among the cells in cooperation area becomes below in a fixed threshold exists. Pico base station 300 determines the cell of the maximum [ RSRP ] as a cooperation cell in the cell which alpha becomes below in a fixed threshold. In this example, pico base station 300 should determine the macro cell as a cooperation cell.</p><p num="0103">In S59, pico base station 300 notifies SS change directions which direct to change SS which mobile station 10 searchs at the time of decoding of E-PDCCH to mobile station 10. Specifically, pico base station 300 notifies SS change directions which direct to change the present SS to E-SS Type1 shown in above-mentioned Drawing 12 to mobile station 10, when mobile station 10 is candidate UE for ICIC application. On the other hand, pico base station 300 notifies SS change directions which direct to change the present SS to E-SS Type2 shown in above-mentioned Drawing 13 to mobile station 10, when mobile station 10 is not candidate UE for ICIC application.</p><p num="0104">In S60, pico base station 300 and macro base station 400 perform user scheduling based on the uncommunicated field which the untransmitted field information exchanged by S56 and S57 shows.</p><p num="0105">Drawing 18 is a figure for explaining the user scheduling algorithm which 400 performs in pico base station 300 and macro base stationS60 concerning Example 2. Since the user scheduling which pico base station 300 and macro base station 400 perform has the same contents of processing, the contents of processing of pico base station 300 are explained as a representative here. Drawing 18 is replaced with Steps S32, S38, and S40 of Drawing 14, and except for the point of having Steps S72, S78, and S80, since it is the same as that of Drawing 14, detailed explanation of Drawing 18 is omitted. Steps S71, S73-S77, and S79 of Drawing 18 are equivalent to Steps S31, S33-S37, and S39 of Drawing 14, respectively.</p><p num="0106">First, pico base station 300 selection of UE which is the target of scheduling will judge whether UE selected by S71 is candidate UE for ICIC application (S72). (S71) When UE of S72 selected as a result of the judgment by S71 is not candidate UE for ICIC application (S72;No), pico base station 300 shifts to the processing after S73.</p><p num="0107">On the other hand, when UE selected by S71 is candidate UE for ICIC application (S72;Yes), in the field to which the untransmitted field of a cooperation cell and RB of a connection cell overlap, pico base station 300 judges whether reservation of RB for data signals is possible (S78). As a result of the judgment concerned, when reservation of RB is possible (S78;Yes), pico base station 300 shifts to processing of S79. In the field to which the untransmitted field of a cooperation cell and E-SS Type1 of a connection cell overlap, pico base station 300 judges whether reservation of CCE for E-PDCCH is possible after processing of S79 (S80). As a result of the judgment concerned, when reservation of CCE is possible (S80;Yes), pico base station 300 shifts to processing of S76 shift.</p><p num="0108">When judged with reservation of RB being impossible in above S78 (S78;No), and when it is judged with reservation of CCE being impossible in above S80 (S80;No), it returns to S71 and processing after it is performed again.</p><p num="0109">Returning to Drawing 17, by S61, pico base station 300 transmits E-PDCCH using CCE for E-PDCCH with which the untransmitted field of a cooperation cell and E-SS Type1 of a connection cell overlap to mobile station 10 which is candidate UE for ICIC application. In order that E-PDCCH transmitted from pico base station 300 by S61 may not receive interference by the signal from a cooperation cell, it is in the state whose SINR improved and reaches the receiving antenna of mobile station 10. Thereby, the interference to E-PDCCH for [ in a pico cell / UE ] ICIC application from a macro cell is reduced.</p><p num="0110">Pico base station 100 transmits E-PDCCH to mobile station 10 which is not a candidate for ICIC application using CCE in the field of E-SSType2.</p><p num="0111">In S62, mobile station 10 changes SS according to SS change directions notified from pico base station 300 in S59, searchs SS after a change, and decodes E-PDCCH. Mobile station 10 which is candidate UE for ICIC application changes the present SS to E-SS Type1, searchs E-SS Type1, and, specifically, decodes E-PDCCH. On the other hand, mobile station 10 which is not candidate UE for ICIC application changes the present SS to E-SS Type2, searchs E-SS Type2, and decodes E-PDCCH. And mobile station 10 acquires the resource quota information on decoded E-PDCCH to PDSCH.</p><p num="0112">In S63, pico base station 300 transmits PDSCH using RB of the connection cell which overlaps with the untransmitted field of a cooperation cell to mobile station 10 which is candidate UE for ICIC application. In order that PDSCH transmitted from pico base station 300 by S63 may not receive interference by the signal from a cooperation cell, it is in the state whose SINR improved and reaches the receiving antenna of mobile station 10. Thereby, the interference to PDSCH for [ in a pico cell / UE ] ICIC application from a macro cell is reduced.</p><p num="0113">Pico base station 300 transmits PDSCH using RB assigned to mobile station 10 which is not a candidate for ICIC application.</p><p num="0114">In S64, mobile station 10 decodes PDSCH mapped by RB which the resource quota information acquired by S62 shows, and obtains user data.</p><p num="0115">As mentioned above, in radio communications system 2 of Example 2, control part 400a of macro base station 400 sets up at least some fields of CCE for the cooperative control between cells as an untransmitted field, and exchanges for pico base station 300 the untransmitted field information that an untransmitted field is expressed. The case where the untransmitted field in macro base station 400 which the untransmitted field information notified from macro base station 400 shows overlaps with CCE for the cooperative control between cells is assumed. In this case, communications department 300b of pico base station 300 transmits a control signal to mobile station 10 of a pico cell which exists in a boundary with the macro cell used as a neighboring cell using CCE in the overlapping field. Interference between E-PDCCH and a neighboring cell can be reduced by a thereby comparatively simple method.</p><p num="0116">By the way, in the above-mentioned Examples 1 and 2, E-Control region Type1 used for the cooperative control between cells explained the case where it was provided in the temporal frequency position which is common in two cells in cooperation area. However, E-Control region Type1 should just be provided in the temporal frequency position which is common in at least two cells among all the cells in cooperation area. Below, the example of composition of others of E-Control region Type1 is explained.</p><p num="0117">Drawing 19 is a figure for explaining the example of composition of others of E-Control region Type1. As shown in Drawing 19, E-Control region Type1 is provided in the position of RB0 and RB1 which are common in two cells 1 and cell 3 among all the 3 pieces cells 1-3 in cooperation area. For example, E-Control region Type1 is provided in the position of RB2 and RB3 which are common in two cells 2 and cell 3 among all the 3 pieces cells 1-3 in cooperation area. For example, E-Control region Type1 is provided in the position of RB4 and RB5 which are common in two cells 1 and cell 2 among all the 3 pieces cells 1-3 in cooperation area. In short, E-Control region Type1 should just be provided in the temporal frequency position which is common in at least two cells among all the cells in cooperation area.</p><p num="0118">Here, E-Control region Type1 assumes the case where it is provided in the temporal frequency position which is common in at least two cells among all the cells in cooperation area. In this case, a pico base station and a macro base station transmit E-PDCCH in E-Control region Type1 provided in the temporal frequency position which is common in at least two cells.</p><p num="0119">It explains using the example shown in Drawing 19. That is, in E-Control region Type1 provided in the position of RB0 and RB1 which are common in cell 1 and cell 3, a pico base station and a macro base station transmit E-PDCCH for UE(s) which apply CoMP or ICIC between cell 1 and cell 3. In E-Control region Type1 provided in the position of RB2 and RB3 which are common in cell 2 and cell 3, a pico base station and a macro base station transmit E-PDCCH for UE(s) which apply CoMP or ICIC between cell 2 and cell 3. In E-Control region Type1 provided in the position of RB4 and RB5 which are common in cell 1 and cell 2, a pico base station and a macro base station transmit E-PDCCH for UE(s) which apply CoMP or ICIC between cell 1 and cell 2. E-Control region of all the cells in common area In Type1, correspondence with the position of CCE for the cooperative control between cells and the position of the temporal frequency resource with which CCE is mapped is common. Therefore, when the base station of a different cell transmits the same E-PDCCH on CCE for the cooperative control between cells, it becomes possible to apply the art of CoMP to the base station of a different cell. When the base station of a different cell transmits E-PDCCH so that it may intersect perpendicularly on CCE for the cooperative control between cells, it becomes possible to apply the art of ICIC to the base station of a different cell.</p><p num="0120">Thereby, the base station of a different cell can hold down to the minimum the amount of resources of E-Control region Type1 used for the cooperative control between cells. As a result, the base station of a different cell can increase the ratio of the amount of resources for PDSCH, or the amount of resources of E-Control region Type2 usable between cells. That is, it becomes possible to use the limited radio resource efficiently.</p><p num="0121">It is although a control channel is made to extend to a share channel field in the above-mentioned Examples 1 and 2, For example, when making it extend to the arbitrary fields which can be set as the same size between cells, and making it extend to the predetermined field of each cell, it can apply [ when making a control channel extend to the surplus field which changes the bandwidth of a control channel field and produces, or ].<br />In the above-mentioned Examples 1 and 2, the radio communications system which this application indicates shall reduce interference between a macro cell and a pico cell. However, radio communications systems 1 and 2 are also applicable as art of reducing the interference between not only this but a macro cell, interference between femtocells and a pico cell, and a femtocell, or interference between a pico cell and a pico cell.</p>

01221 and 2 Radio communications system<br />10 Mobile Station<br />10a Control part<br />10b Communications department<br />11 Receiving RF Section<br />12 FFT Section<br />13 Data Signal Demodulation Section<br />14 Control Signal Demodulation Section<br />15 Channel Estimation Part<br />16 CQI Calculation Part<br />17 RSRP Measurement Part<br />18 Uphill Control Signal Generating Part<br />19 Transmitting RF Section<br />100 and 300 Pico base station<br />100a and 300a Control part<br />100b and 300b Communications department<br />101, UE judgment part for 201 CoMP application<br />102, 202, 302, and 402 Scheduler part<br />103, 203, 303, and 403 Data signal generation part<br />104, 204, 304, and 404 Control signal generating part<br />105, 205, 305, and 405 Reference signal generating part<br />106, 206, 306, and 406 Physical channel multiplex section<br />107, 207, 307, and 407 Receiving RF section<br />108, 208, 308, and 408 Uphill control signal demodulation section<br />109, 209, 309, and 409 IFFT part<br />110, 210, 310, and 410 Transmitting RF section<br />200 and 400 Macro base station<br />200a and 400a Control part<br />200b and 400b Communications department<br />301, UE judgment part for 401 ICIC application