Patent Publication Number: US-2012034865-A1

Title: Base station, relay station, communication system, and communication method

Description:
CROSS REFERENCE TO THE RELATED APPLICATIONS 
     This application is a continuation application of International Application PCT/JP2009/059199, filed May 19, 2009, now pending, the contents of which are herein wholly incorporated by reference. 
    
    
     FIELD 
     The embodiments discussed herein are related to wireless communication. 
     BACKGROUND 
     Wireless relay as a technique for realizing high throughput over a wide area is being actively investigated. For example, at the Institute of Electrical and Electronics Engineers (IEEE), investigation related to multi-hop relay is advancing. 
     Under the 3rd Generation Partnership Project (3GPP), in the standardization toward LTE-Advanced, investigation related to relay functionality is advancing. Furthermore, technology has been proposed in which scheduling is performed such that slot collisions do not occur when one relay station relays the signals of multiple base stations (see, for example, Japanese Laid-Open Patent Publication No. 2008-60868). 
     However, with the conventional technologies above, a problem arises in that when relay stations of different cells are near the border between the cells, the wireless communication performed by each of the relay stations interferes with one another causing throughput to drop. For example, the downlink of a mobile station may be affected by interference from a base station of an adjacent cell and/or from a relay station of an adjacent cell. 
     Further, the uplink of a relay station or a base station may be affected by interference from a mobile station of an adjacent cell and from a relay station of an adjacent cell. Consequently, wireless communication of a high transmission speed is difficult to provide by the relay of a relay station that is near a cell border. Further, Patent Document 1 does not disclose a method of controlling interference that occurs near the borders of cells in a communication system in which relay stations respectively relay signals from various base stations. 
     SUMMARY 
     According to an aspect of an embodiment, a base station, by relay of a relay station provided in a cell of the base station, wirelessly communicates with a mobile station located in the cell and includes a receiver that receives from an adjacent-cell relay station provided in an adjacent cell, adjacent cell resource information related to wireless resources allocated to the adjacent-cell relay station; and a processor that preferentially allocates to a wireless path between the relay station and the mobile station, wireless resources that are different from the wireless resources indicated in the received adjacent cell resource information. 
     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. 
     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, as claimed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram of a configuration of a communication system according to a first embodiment. 
         FIG. 2  is a diagram of an example of a wireless resource in the communication system depicted in  FIG. 1 . 
         FIG. 3  is a block diagram of a base station depicted in  FIG. 1 . 
         FIG. 4  is a block diagram of a relay station depicted in  FIG. 1 . 
         FIG. 5  is a block diagram of a mobile station depicted in  FIG. 1 . 
         FIG. 6  is a sequence diagram of an example of downlink operation of the communication system depicted in  FIG. 1 . 
         FIG. 7  is a sequence diagram of uplink operation of the communication system depicted in  FIG. 1 . 
         FIG. 8  is a diagram of an example of SIR in wireless paths between the relay station and the mobile stations. 
         FIG. 9  is a diagram of an example of request information transmitted by a relay station. 
         FIG. 10  is a diagram of another example of request information. 
         FIG. 11  is a diagram of a wireless resource allocated by the base station. 
         FIG. 12  is a sequence diagram of another example of the downlink operation depicted in  FIG. 6 . 
         FIG. 13  is a sequence diagram of another example of the uplink operation depicted in  FIG. 7 . 
         FIG. 14  is a diagram of a configuration of the communication system according to a second embodiment. 
         FIG. 15  is a block diagram of the base station depicted in  FIG. 14 . 
         FIG. 16  is a block diagram of the relay station depicted in  FIG. 14 . 
         FIG. 17  is a sequence diagram of an example of downlink operation of the communication system depicted in  FIG. 14 . 
         FIG. 18  is a sequence diagram of an example of uplink operation of the communication system depicted in  FIG. 14 . 
         FIG. 19  is a diagram of an example wireless resource determination by the relay station. 
         FIG. 20  is a sequence diagram of another example of the downlink operation depicted in  FIG. 17 . 
         FIG. 21  is a sequence diagram of another example of the uplink operation depicted in  FIG. 18 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Preferred embodiments of the present invention will be explained with reference to the accompanying drawings. 
       FIG. 1  is a diagram of a configuration of the communication system according to a first embodiment. As depicted in  FIG. 1 , a communication system  100  according to the first embodiment includes a base station  111  (BS 1 ), a base station  112  (BS 2 ), a relay station  121  (relay node (RN 1 )), a relay station  122  (RN 2 ), and mobile stations  131 - 133  (MS 1 -MS 3 ). 
     The base station  111  is connected to a core network  101  and manages communication between a communication apparatus in a cell  111   a  (given cell) and the core network  101 . For example, by relay through the relay station  121 , which is in the cell  111   a  (of the base station  111 ) and near the border with (at a “cell border region”, “cell edge”, etc.) the cell  112   a  (adjacent cell), the base station  111  wirelessly communicates with mobile stations located within a range of the relay station  121 . Although not depicted, in addition to the relay station  121 , other relay stations may be provided in the cell  111   a , in which case, the base station  111  wirelessly communicates with mobile stations located within a range of the relay stations, by relay through the relay stations in the cell  111   a.    
     The base station  112  is connected to a core network  102  and manages communication between the core network  102  and a communication apparatus in the cell  112   a , which is adjacent to the cell  111   a . Here, the core network  101  and the core network  102  may be one in the same. For example, by relay through the relay station  122 , which is in the cell  112   a  (of the base station  112 ) and near the border with the cell  111   a  (adjacent cell), the base station  112  wirelessly communicates with mobile stations in the cell  112   a . Although not depicted, in addition to the relay station  122 , other relays stations may be provided in the cell  112   a , in which case, the base station  112  wirelessly communications with mobile stations within a range of the relays stations in the cell  112   a.    
     The relay station  121  relays communication between the base station  111  and the mobile stations  131 ,  132 . The relay station  121  transmits to the base station  111 , request information (reference character  141 ) requesting wireless resources for a wireless path L 1  between the relay station  121  and the mobile station  131 , and a wireless path L 2  between the relay station  121  and the mobile station  132 . 
     The relay station  121  further transmits (reference character  151 ) to the base station  112 , the request information (reference character  141 ) that is transmitted to the base station  111 . Using the wireless resources indicated by allocation information (reference character  161 ) transmitted from the base station  111  in response to the request information transmitted thereto, the relay station  121  wirelessly communicates with the mobile stations  131 ,  132 . 
     The relay station  122  relays communication between the base station  112  and the mobile station  133 . The relay station  122  transmits to the base station  112 , request information (reference character  142 ) requesting wireless resources for a wireless path L 3  between the relay station  122  and the mobile station  133 . The relay station  122  further transmits (reference character  152 ) to the base station  111 , the request information that is transmitted to the base station  112 . Using the wireless resources indicated by allocation information (reference character  162 ) transmitted from the base station  112  in response to the request information transmitted thereto, the relay station  122  wirelessly communicates with the mobile station  133 . 
     The mobile station  131  and the mobile station  132  are respectively located within a range of the relay station  121  and through relay by the relay station  121 , wirelessly communicate with the base station  111 . The mobile station  133  is located within a range of the relay station  122  and through relay by the relay station  122 , wirelessly communicates with the base station  112 . Consequently, if the wireless resources used by the relay station  121  and the relay station  122  overlap, the wireless communication between the relay station  121  and the mobile stations  131 ,  132  and the wireless communication between the relay station  122  and the mobile station  133  are mutually affected by interference. 
     The base station  111  receives the request information (reference character  152 ) transmitted from the relay station  122  (adjacent-cell relay station). The request information (reference character  152 ) indicates wireless resource candidates allocatable to the relay station  122 . The base station  111  preferentially allocates to the wireless path L 1  and the wireless path L 2 , wireless resources that are not indicated in (are different from the wireless resources indicated in) the request information (reference character  152 ) and transmits to the relay station  121 , allocation information (reference character  161 ) indicating the allocated wireless resources. 
     For example, among the wireless resources indicated in the request information (reference character  141 ), the base station  111  allocates to the wireless path L 1  and the wireless path L 2 , wireless resources that are not indicated in the request information (reference character  152 ), whereby from among the wireless resources requested by the relay station  121 , wireless resources that are not allocated to the relay station  122  are selected and allocated to the relay station  121 . 
     Configuration may be such that if another condition concerning the wireless resources is the same, the base station  111  allocates to the wireless path L 1  and the wireless path L 2 , wireless resources that are different from the wireless resources indicated in the request information (reference character  152 ). An example of a condition in such a case is communication quality, such as the signal to interference ratio (SIR). 
     Further, configuration may be such that among the wireless resources that are not indicated in the request information (reference character  152 ), the base station  111  allocates to the wireless path L 1  and the wireless path L 2 , wireless resources that satisfy another condition. An example of a condition in such a case is a condition that the wireless resource is one that is not allocated (or, not planned to be allocated) to another relay station in the cell  111   a , a condition that the wireless resource is one whose communication quality is greater than or equal to a given threshold. 
     The base station  112  receives the request information (reference character  151 ) transmitted from the relay station  121  (adjacent-cell relay station). The request information (reference character  151 ) indicates wireless resource candidates that are allocatable to the relay station  121 . The base station  112  preferentially allocates to the wireless path L 3 , wireless resources that are not indicated in the request information (reference character  151 ) and transmits to the relay station  122 , allocation information (reference character  162 ) indicating the allocated wireless resources. 
       FIG. 2  is a diagram of an example of a wireless resource in the communication system depicted in  FIG. 1 . The horizontal axis depicted in  FIG. 2  represents frequency. A wireless resource  210  is a frequency band used in the communication system  100  (refer to  FIG. 1 ). Here, an example will be described in which the wireless resource  210  is divided into wireless resources # 1 -# 10 . The wireless resources # 1 -# 10  are allocated to wireless intervals of the communication system  100 . In  FIG. 2 , although the wireless resource is described as a frequency domain, the wireless resource may be a unit of a time domain, or a combination of a frequency domain and a time domain. 
     The base station  111  and the base station  112  respectively allocate the wireless resources # 1 -# 10  such that interference between wireless paths in the respective cells does not occur. Consequently, the least number of required wireless resources are allocated to the wireless paths, enabling highly efficient frequency use. Nevertheless, while making adjustments such that interference does not occur between the cells  111   a  and  112   a , the base stations  111 ,  112  allocate wireless resources to the relay stations  121 ,  122  that are near the border between the cell  111   a  and the cell  112   a.    
       FIG. 3  is a block diagram of the base station depicted in  FIG. 1 . As depicted in  FIG. 3 , the base station  111  (refer to  FIG. 1 ) includes a receiving antenna  301 , a receiver  302 , a demultiplexer  303 , an own-cell control CH decoder  304 , a DL scheduler  305 , a control CH generator  306 , an IP receiver  307 , a DL buffer  308 , a data CH generator  309 , a pilot generator  310 , a multiplexer  311 , a transmitter  312 , a transmitting antenna  313 , and an other-cell control CH decoder  319 . 
     The base station  111  further includes an SIR measurer  314 , a UL scheduler  315 , a data CH decoder  316 , a UL buffer  317 , and an IP transmitter  318 . The receiving antenna  301  and the receiver  302  form a receiver that receives from the relay station  122  (adjacent-cell relay station) that is in the cell  112   a  (adjacent cell) and near the border with the cell  111   a  (of base station  111 ), adjacent cell resource information indicating the wireless resources allocated to the relay station  122 . 
     The DL scheduler  305  and the UL scheduler  315  form an allocating unit that preferentially allocates to wireless paths (the wireless paths L 1 , L 2  in  FIG. 1 ) between the relay station  121  and the mobile stations  131 ,  132 , wireless resources that are not indicated in the adjacent cell resource information. The DL scheduler  305  and the UL scheduler  315 , for example, are implemented by a processor such as a central processing unit (CPU), Digital Signal Processor (DSP), Field Programmable Gate Allay (FPGA), etc. 
     Processing at the base station  111  and related to downlinks (DL), which transfer data from the core network  101  to the mobile stations  131 ,  132 , will be described. Nonetheless, at the base station  112 , the processing related to downlinks that transfer data from the core network  102  to the mobile station  133  is identical. 
     The receiver  302  receives a channel quality indicator (CQI) (BS 1 -RN 1 ) and request information (RN 1 -MS) via the receiving antenna  301 . The CQI (BS 1 -RN 1 ) indicates the SIR between the base station  111  and the relay station  121 . The request information (RN 1 -MS) indicates the wireless resources requested of the base station  111 , for the wireless paths between the relay station  121  and the mobile stations  131 ,  132 . 
     The receiver  302  outputs to the demultiplexer  303 , the received CQI (BS 1 -RN 1 ) and the request information (RN 1 -MS). The receiver  302  further receives, via the receiving antenna  301 , adjacent cell resource information transmitted by the relay station  122  in the cell  112   a . The adjacent cell resource information indicates the wireless resources allocated to the relay station  122  in the cell  112   a.    
     The receiver  302  outputs the adjacent cell resource information to the demultiplexer  303 . The demultiplexer  303  outputs to the own-cell control CH decoder  304 , the CQI (BS 1 -RN 1 ) and the request information (RN 1 -MS) received from the receiver  302 . The demultiplexer  303  further outputs the adjacent cell resource information to the other-cell control CH decoder  319 . 
     The own-cell control CH decoder  304  decodes the CQI (BS 1 -RN 1 ) and the request information (RN 1 -MS) received from the demultiplexer  303  and outputs the decoded the CQI (BS 1 -RN 1 ) and the request information (RN 1 -MS) to the DL scheduler  305 . The other-cell control CH decoder  319  decodes the adjacent cell resource information received from the demultiplexer  303  and outputs the decoded adjacent cell resource information to the DL scheduler  305 . 
     The DL scheduler  305 , based on the CQI (BS 1 -RN 1 ) received from the own-cell control CH decoder  304 , allocates wireless resources to a wireless path between the base station  111  and the relay station  121 . The DL scheduler  305 , based on the request information (RN 1 -MS) received from the own-cell control CH decoder  304  and the adjacent cell resource information received from the other-cell control CH decoder  319 , allocates wireless resources to wireless paths between the relay station  121  and the mobile stations  131 ,  132 . 
     For example, among the wireless resources indicated in the request information (RN 1 -MS), the DL scheduler  305  preferentially allocates to the wireless paths between the relay station  121  and the mobile stations  131 ,  132 , wireless resources that are not indicated in the adjacent cell resource information. Further, configuration may be such that aside from CQI, the DL scheduler  305  allocates wireless resources, based on ID information concerning the relay station  121  and the mobile stations  131 ,  132 ; traffic information and/or quality of service (QoS) information concerning the mobile stations  131 ,  132 , etc. 
     The DL scheduler  305  outputs to the control CH generator  306  and the data CH generator  309 , allocation information (BS 1 -RN 1 ) that indicates the wireless resources allocated to the wireless path between the base station  111  and the relay station  121 . The DL scheduler  305  further outputs to the control CH generator  306 , allocation information (RN 1 -MS) that indicates the wireless resources allocated to the wireless paths between the relay station  121  and the mobile stations  131 ,  132 . 
     The control CH generator  306  assigns to a control channel (CH), the allocation information received from the DL scheduler  305  and outputs the control CH assigned allocation information to the multiplexer  311 . The allocation information (BS 1 -RN 1 ) and the allocation information (RN 1 -MS) output from the control CH generator  306  are transmitted to the relay station  121 , by the transmitter  312 . 
     The IP receiver  307  receives from the core network  101 , DL data (MS 1 ) addressed to the mobile station  131  and DL data (MS 2 ) addressed to the mobile station  132 . The IP receiver  307  outputs the received DL data to the DL buffer  308 . The DL buffer  308  stores the DL data output by the IP receiver  307 . 
     The data CH generator  309  assigns the DL data stored in the DL buffer  308  to the wireless resources indicated in the allocation information (BS 1 -RN 1 ) output from the DL scheduler  305 . The data CH generator  309  outputs to the multiplexer  311 , the wireless resource assigned DL data. Consequently, the DL data (MS 1 ) and the DL data (MS 2 ) are transmitted to the relay station  121  using the wireless resources indicated in the allocation information (BS 1 -RN 1 ). 
     The pilot generator  310  generates a pilot signal (BS 1 ) and outputs the generated signal to the multiplexer  311 . The multiplexer  311  multiplexes the allocation information output from the control CH generator  306 , the DL data (MS 1 ) and the DL data (MS 2 ) output from the data CH generator  309 , and the pilot signal (BS 1 ) output from the pilot generator  310 . The multiplexer  311  outputs the resulting multiplexed signal to the transmitter  312 . 
     The transmitter  312  transmits, via the transmitting antenna  313 , the multiplexed signal received from the multiplexer  311 . The relay station  121  receives the allocation information (BS 1 -RN 1 ), the allocation information (RN 1 -MS), the DL data (MS 1 ), the DL data (MS 2 ), and the pilot signal (BS 1 ) that are included in the multiplexed signal transmitted by the transmitter  312 . 
     Processing at the base station  111  and related to uplinks (UL), which transfer data from the mobile stations  131 ,  132  to the core network  101 , will be described. Nonetheless, at the base station  112 , the processing related to uplinks that transfer data from the mobile station  133  to the core network  102  is identical. 
     The receiver  302  receives, via the receiving antenna  301 , a pilot signal (RN 1 ) and the request information (RN 1 -MS) respectively transmitted by the relay station  121 . The receiver  302  further receives, from the relay station  121  and via the receiving antenna  301 , UL data (MS 1 ) and UL data (MS 2 ). The UL data (MS 1 ) is data that is transmitted to the core network  101  by the mobile station  131 . The UL data (MS 2 ) is data that is transmitted to the core network  101  by the mobile station  132 . 
     The receiver  302  outputs the received pilot signal (RN 1 ), request information (RN 1 -MS), UL data (MS 1 ), and UL data (MS 2 ) to the demultiplexer  303 . The receiver  302  further receives, via the receiving antenna  301 , adjacent cell resource information transmitted by the relay station  122 . The receiver  302  outputs the received adjacent cell resource information to the demultiplexer  303 . 
     The demultiplexer  303  outputs the pilot signal (RN 1 ) to the SIR measurer  314  and outputs the request information (RN 1 -MS) to the own-cell control CH decoder  304 . The demultiplexer  303  outputs the adjacent cell resource information to the other-cell control CH decoder  319  and outputs the UL data (MS 1 ) and the UL data (MS 2 ) to the data CH decoder  316 . 
     The SIR measurer  314 , based on the pilot signal (RN 1 ) received from the demultiplexer  303 , measures the SIR (BS 1 -RN 1 ) between the base station  111  and the relay station  121 . The SIR measurer  314  outputs to the UL scheduler  315 , the CQI (BS 1 -RN 1 ), which indicates the measured SIR (BS 1 -RN 1 ). 
     The own-cell control CH decoder  304  decodes the request information (RN 1 -MS) received from the demultiplexer  303  and outputs the decoded request information (RN 1 -MS) to the UL scheduler  315 . The other-cell control CH decoder  319  decodes the adjacent cell resource information received from the demultiplexer  303  and outputs the decoded adjacent cell resource information to the UL scheduler  315 . 
     The UL scheduler  315 , based on the CQI (BS 1 -RN 1 ) received from the SIR measurer  314 , allocates wireless resources to the wireless path between the base station  111  and the relay station  121 . The UL scheduler  315 , based on the request information (RN 1 -MS) received from the own-cell control CH decoder  304  and the adjacent cell resource information received from the other-cell control CH decoder  319 , allocates wireless resources to the wireless paths between the relay station  121  and the mobile stations  131 ,  132 . 
     For example, among the wireless resources indicated in the request information (RN 1 -MS), the UL scheduler  315  preferentially allocates to the wireless paths between the relay station  121  and the mobile stations  131 ,  132 , wireless resources that are not indicated in the adjacent cell resource information. Further, configuration may be such that aside form the CQI, the UL scheduler  315  allocates wireless resources, based on ID information concerning the relay station  121  and the mobile stations  131 ,  132 ; QoS information and/or QoS information concerning the mobile stations  131 ,  132 , etc. 
     The UL scheduler  315  outputs to the control CH generator  306 , the allocation information (BS 1 -RN 1 ), which indicates the wireless resources allocated to the wireless path between the base station  111  and the relay station  121 . The UL scheduler  315  further outputs to the control CH generator  306 , the allocation information (RN 1 -MS), which indicates the wireless resources allocated to the wireless paths between the relay station  121  and the mobile stations  131 ,  132 . 
     The control CH generator  306  assigns to a control CH, the allocation information received from the UL scheduler  315  and outputs the control CH assigned allocation information to the multiplexer  311 . The allocation information (BS 1 -RN 1 ) and the allocation information (RN 1 -MS) output from the control CH generator  306  is transmitted to the relay station  121 , by the transmitter  312 . 
     The data CH decoder  316  decodes the UL data (MS 1 ) and the UL data (MS 2 ) received from the demultiplexer  303  and outputs the decoded UL data to the UL buffer  317 . The UL buffer  317  stores the UL data output by the data CH decoder  316 . The IP transmitter  318  reads out the UL data stored in the UL buffer  317  and transmits the read UL data to the core network  101 . 
       FIG. 4  is a block diagram of the relay station depicted in  FIG. 1 . As depicted in  FIG. 4 , the relay station  121  (refer to  FIG. 1 ) includes a receiving antenna  401 , a receiver  402 , a demultiplexer  403 , an own-cell control CH decoder  404 , a DL scheduler  405 , a control CH generator  406 , a receiving antenna  407 , a receiver  408 , a demultiplexer  409 , an SIR measurer  410 , a CQI generator  411 , an own-cell control CH generator  412 , a multiplexer  413 , a transmitter  414 , a transmitting antenna  415 , and a control CH decoder  416 . 
     The relay station  121  further includes a data CH decoder  417 , a data CH generator  418 , a pilot generator  419 , a multiplexer  420 , a transmitter  421 , a transmitting antenna  422 , an SIR measurer  423 , a UL scheduler  424 , a data CH decoder  425 , a data CH generator  426 , a pilot generator  427 , and an other-cell control CH generator  428 . Although the relay station  121  has been described, the relay station  122  is similarly configured. 
     Processing at the relay station  121  and related to downlinks that transfer DL data from the base station  111  to the mobile station  131  and the mobile station  132  will be described. Nonetheless, at the relay station  122 , the processing related to downlinks that transfer DL data from the base station  112  to the mobile station  133  is identical. 
     The receiver  402  receives, via the receiving antenna  401 , the CQI (RN 1 -MS 1 ) transmitted by the mobile station  131  and concerning the relay station  121  and the mobile station  131 . The receiver  402  further receives, via the receiving antenna  401 , the CQI (RN 1 -MS 2 ) transmitted by the mobile station  132  and concerning the relay station  121  and the mobile station  132 . 
     The receiver  402  outputs the received CQIs to the demultiplexer  403 . The demultiplexer  403  outputs to the own-cell control CH decoder  404 , the CQIs received from the receiver  402 . The own-cell control CH decoder  404  decodes the CQIs received from the demultiplexer  403  and outputs the decoded CQIs to the DL scheduler  405 . 
     The DL scheduler  405 , based on the CQI (RN 1 -MS 1 ) and the CQI (RN 1 -MS 2 ) received from the own-cell control CH decoder  404 , determines the wireless resources to be requested for the wireless paths between the relay station  121  and the mobile stations  131 ,  132 . For example, among the wireless resources # 1 -# 10  (refer to  FIG. 2 ), the DL scheduler  405  determines, as the wireless resources to be requested, wireless resources for which the CQI indicates a relatively high quality. 
     The DL scheduler  405  outputs to the own-cell control CH generator  412  and the other-cell control CH generator  428 , the request information (RN 1 -MS), which indicates the determined wireless resources to be requested. The DL scheduler  405 , by outputting the request information (RN 1 -MS) to the own-cell control CH generator  412 , acquires from the control CH decoder  416 , the allocation information (RN 1 -MS) transmitted by the base station  111 . The DL scheduler  405  allocates to the wireless path between the relay station  121  and the mobile station  131  and to the wireless path between the relay station  121  and the mobile station  132 , the wireless resources indicated in the acquired allocation information (RN 1 -MS). 
     The DL scheduler  405  outputs to the control CH generator  406  and the data CH generator  418 , allocation information (RN 1 -MS 1 ) that indicates the wireless resources allocated to the wireless path between the relay station  121  and the mobile station  131 . The DL scheduler  405  further outputs to the control CH generator  406  and the data CH generator  418 , allocation information (RN 1 -MS 2 ) that indicates the wireless resources allocated to the wireless path between the relay station  121  and the mobile station  132 . 
     The control CH generator  406  assigns to a control CH, the allocation information received from the DL scheduler  405  and outputs the control CH assigned allocation information to the multiplexer  420 . The allocation information (RN 1 -MS 1 ) output from the control CH generator  406  is transmitted to the mobile station  131 , by the transmitter  421 . The allocation information (RN 1 -MS 2 ) output from the control CH generator  406  is transmitted to the mobile station  132 , by the transmitter  421 . 
     The receiver  408  receives, via the receiving antenna  407 , the pilot signal (BS 1 ), the allocation information (RN 1 -MS), the DL data (MS 1 ), and the DL data (MS 2 ) transmitted by the base station  111 . The receiver  408  outputs to the demultiplexer  409 , the received pilot signal (BS 1 ), allocation information (RN 1 -MS), and DL data. 
     The demultiplexer  409  outputs the pilot signal (BS 1 ) to the SIR measurer  410  and outputs the allocation information (RN 1 -MS) to the control CH decoder  416 . The demultiplexer  409  further outputs the DL data to the data CH decoder  417 . 
     The SIR measurer  410 , based on the pilot signal (BS 1 ) received from the demultiplexer  409 , measures the SIR (BS 1 -RN 1 ) between the base station  111  and the relay station  121 . The SIR measurer  410  reports to the CQI generator  411 , the measured SIR (BS 1 -RN 1 ). The CQI generator  411  generates the CQI (BS 1 -RN 1 ), which indicates the SIR (BS 1 -RN 1 ) reported by the SIR measurer  410 . The CQI generator  411  outputs the generated CQI (BS 1 -RN 1 ) to the own-cell control CH generator  412 . 
     The own-cell control CH generator  412  assigns to a control CH, the request information (RN 1 -MS) received from the DL scheduler  405  and the CQI (BS 1 -RN 1 ) received from the CQI generator  411 . The own-cell control CH generator  412  outputs the control CH assigned request information (RN 1 -MS) and CQI (BS 1 -RN 1 ) to the multiplexer  413 . The request information (RN 1 -MS) and the CQI (BS 1 -RN 1 ) output from the own-cell control CH generator  412  is transmitted to the base station  111 , by transmitter  414 . 
     The other-cell control CH generator  428  assigns to a control CH, the request information (RN 1 -MS) received from the DL scheduler  405  and outputs the control CH assigned request information (RN 1 -MS) to the multiplexer  413 . The request information (RN 1 -MS) transmitted from the other-cell control CH generator  428  is transmitted to the base station  112 , by the transmitter  414 . 
     The multiplexer  413  multiplexes the request information (RN 1 -MS) and the CQI (BS 1 -RN 1 ) received from the own-cell control CH generator  412  and outputs the resulting multiplexed signal to the transmitter  414 . The transmitter  414  transmits the received multiplexed signal to the base station  111 , via the transmitting antenna  415 . 
     The control CH decoder  416  decodes the allocation information (RN 1 -MS) received from the demultiplexer  409  and outputs the decoded allocation information (RN 1 -MS) to the DL scheduler  405  and the data CH decoder  417 . The data CH decoder  417 , based on the allocation information (RN 1 -MS) received from the control CH decoder  416 , decodes the DL data (MS 1 ) and the DL data (MS 2 ) received from the demultiplexer  409 . 
     The decoding at the data CH decoder  417  may use ID information concerning the mobile stations  131 ,  132  to which the data is addressed, and/or information such as the bit count of the data CH. Such information is, for example, reported by the base station  111  through a downlink control CH. The data CH decoder  417  outputs the decoded DL data to the data CH generator  418 . 
     The data CH generator  418  assigns to the wireless resources indicated in the allocation information (RN 1 -MS 1 ) received from the DL scheduler  405 , the DL data (MS 1 ) received from the data CH decoder  417 . The data CH generator  418  outputs the wireless resource assigned DL data (MS 1 ) to the multiplexer  420 . Consequently, the DL data (MS 1 ) is transmitted to the mobile station  131 , by the wireless resources indicated in the allocation information (RN 1 -MS 1 ). 
     The data CH generator  418  further assigns to the wireless resources indicated in the allocation information (RN 1 -MS 2 ) received from the DL scheduler  405 , the DL data (MS 2 ) received from the data CH decoder  417 . The data CH generator  418  outputs the wireless resource assigned DL data (MS 2 ) to the multiplexer  420 . Consequently, the DL data (MS 2 ) is transmitted to the mobile station  132 , by the wireless resources indicated in the allocation information (RN 1 -MS 2 ). 
     The pilot generator  419  generates the pilot signal (RN 1 ) and outputs the generated signal to the multiplexer  420 . The multiplexer  420  multiplexes the allocation information (RN 1 -MS 1 ) and the allocation information (RN 1 -MS 2 ) received from the control CH generator  406 , the DL data (MS 1 ) and the DL data (MS 2 ) received from the data CH generator  418 , and the pilot signal (RN 1 ) received from the pilot generator  419 ; and outputs the resulting multiplexed signal to the transmitter  421 . 
     The transmitter  421  transmits the multiplexed signal to the mobile station  131 ,  132 , via the transmitting antenna  422 . The mobile station  131  and the mobile station  132  receive the pilot signal (RN 1 ) that is included in the multiplexed signal transmitted by the transmitter  421 . The mobile station  131  receives the allocation information (RN 1 -MS 1 ) and the DL data (MS 1 ) transmitted by the transmitter  421 ; and the mobile station  132  receives the allocation information (RN 1 -MS 2 ) and the DL data (MS 2 ) transmitted by the transmitter  421 . 
     Processing at the relay station  121  and related to uplinks that transfer UL data from the mobile stations  131 ,  132  to the core network  101  will be described. Nonetheless, at the relay station  122 , the processing related to uplinks that transfer UL data from the mobile station  133  to the core network  102  is identical. 
     The receiver  402  receives, via the receiving antenna  401 , a pilot signal (MS 1 ) transmitted by the mobile station  131  and a pilot signal (MS 2 ) transmitted by the mobile station  132 . The receiver  402  further receives, via the receiving antenna  401 , the UL data (MS 1 ) transmitted to the core network  101 , by the mobile station  131  and the UL data (MS 2 ) transmitted to the core network  101 , by the mobile station  132 . 
     The receiver  402  outputs the received pilot signals and UL data to the demultiplexer  403 . The demultiplexer  403  outputs to the SIR measurer  423 , the pilot signals received from the receiver  402 . The demultiplexer  403  further outputs to the data CH decoder  425 , the UL data received from the receiver  402 . 
     The SIR measurer  423 , based on the pilot signal (MS 1 ) received from the demultiplexer  403 , measures the SIR (RN 1 -MS 1 ) between the relay station  121  and the mobile station  131 . The SIR measurer  423  outputs to the UL scheduler  424 , the CQI (RN 1 -MS 1 ), which indicates the measured SIR (RN 1 -MS 1 ). Further, the SIR measurer  423 , based on the pilot signal (MS 2 ) received from the demultiplexer  403 , measures the SIR (RN 1 -MS 2 ) between the relay station  121  and the mobile station  132 . The SIR measurer  423  outputs to the UL scheduler  424 , the CQI (RN 1 -MS 2 ), which indicates the measured SIR (RN 1 -MS 2 ). 
     The receiver  408 , via the receiving antenna  407 , receives the allocation information (BS 1 -RN 1 ) and the allocation information (RN 1 -MS) transmitted by the base station  111 . The receiver  408  outputs the received allocation information to the demultiplexer  409 . The demultiplexer  409  outputs to the control CH decoder  416 , the allocation information received from the receiver  408 . The control CH decoder  416  decodes the allocation information received from the demultiplexer  409  and outputs the decoded allocation information to the UL scheduler  424 . 
     The UL scheduler  424 , based on the CQI (RN 1 -MS 1 ) and the CQI (RN 1 -MS 2 ) received from the SIR measurer  423 , determines the wireless resources to be requested of the base station  111 , for the wireless paths between the relay station  121  and the mobile stations  131 ,  132 . For example, from among the wireless resources # 1 -# 10  (refer to  FIG. 2 ), the UL scheduler  424  determines, as the wireless resources to be requested, wireless resources for which the CQI indicates a relatively high quality. 
     The UL scheduler  424  outputs to the own-cell control CH generator  412  and the other-cell control CH generator  428 , the request information (RN 1 -MS) which indicates the determined wireless resources to be requested. The UL scheduler  424 , by outputting the request information (RN 1 -MS) to the own-cell control CH generator  412 , acquires from the control CH decoder  416 , the allocation information (RN 1 -MS) transmitted by the base station  111 . The UL scheduler  424  allocates to the wireless path between the relay station  121  and the mobile station  131 , and to the wireless path between the relay station  121  and the mobile station  132 , the wireless resources indicated in the acquired allocation information (RN 1 -MS). 
     The UL scheduler  424  outputs to the control CH generator  406  and the data CH decoder  425 , the allocation information (RN 1 -MS 1 ), which indicates the wireless resources allocated to the wireless path between the relay station  121  and the mobile station  131 . The UL scheduler  424  further outputs to the control CH generator  406  and the data CH decoder  425 , the allocation information (RN 1 -MS 2 ), which indicates the wireless resources allocated to the wireless path between the relay station  121  and the mobile station  132 . Further, the UL scheduler  424  outputs to the data CH generator  426 , the allocation information (BS 1 -RN 1 ) received from the control CH decoder  416 . 
     The own-cell control CH generator  412  assigns to a control CH, the request information (RN 1 -MS) received from the UL scheduler  424  and outputs the control CH assigned request information (RN 1 -MS) to the multiplexer  413 . The request information (RN 1 -MS) output from the own-cell control CH generator  412  is transmitted to the base station  111 , by the transmitter  414  and the transmitting antenna  415 . 
     The other-cell control CH generator  428  assigns to a control CH, the request information (RN 1 -MS) received from the UL scheduler  424  and outputs the control CH assigned request information (RN 1 -MS) to the multiplexer  413 . The request information (RN 1 -MS) output from the other-cell control CH generator  428  is transmitted to the base station  112 , by the transmitter  414 . 
     The control CH generator  406  assigns to a control CH, the allocation information received from the UL scheduler  424  and outputs the control CH assigned allocation information to the multiplexer  420 . The allocation information (RN 1 -MS 1 ) output from the control CH generator  406  is transmitted to the mobile station  131 , by the transmitter  421 . The allocation information (RN 1 -MS 2 ) output from the control CH generator  406  is transmitted to the mobile station  132 , by the transmitter  421 . 
     The data CH decoder  425 , based on the allocation information (RN 1 -MS 1 ) received from the UL scheduler  424 , decodes the UL data (MS 1 ) and the UL data (MS 2 ) received from the demultiplexer  403 . The data CH decoder  425  outputs the decoded UL data to the data CH generator  426 . 
     The data CH generator  426  allocates to the wireless resources indicated in the allocation information (BS 1 -RN 1 ) received from the UL scheduler  424 , the UL data received from the data CH decoder  425 . The data CH generator  426  outputs the data CH assigned UL data to the multiplexer  413 . The UL data output from the data CH generator  426  is transmitted to the base station  111 , by the transmitter  414 . 
       FIG. 5  is a block diagram of the mobile station depicted in  FIG. 1 . As depicted in  FIG. 5 , the mobile station  131  (refer to  FIG. 1 ) includes a receiving antenna  501 , a receiver  502 , a demultiplexer  503 , an SIR measurer  504 , a CQI generator  505 , a control CH generator  506 , a multiplexer  507 , a transmitter  508 , a transmitting antenna  509 , a control CH decoder  510 , a data CH decoder  511 , a DL buffer  512 , and the data processor  513 . 
     The mobile station  131  further includes a pilot generator  514 , a UL buffer  515 , and a data CH generator  516 . Although configuration of the mobile station  131  will be described, the respective configurations of the mobile stations  132 ,  133  are similar. 
     Processing at the mobile station  131  and related to downlinks, which receive data from the core network  101 , will be described. Nonetheless, the processing at the mobile station  132  and related to downlinks that receive data from the core network  101 , as well as the processing at the mobile station  133  and related to downlinks that receive data from the core network  102  are identical to that at the mobile station  131 . 
     The receiver  502 , via the receiving antenna  501 , receives the pilot signal (RN 1 ), the allocation information (RN 1 -MS 1 ), and the DL data (MS 1 ) transmitted by the relay station  121 . The receiver  502  outputs the received pilot signal (RN 1 ), allocation information (RN 1 -MS 1 ), and DL data (MS 1 ) to the demultiplexer  503 . 
     The demultiplexer  503  outputs the pilot signal (RN 1 ) to the SIR measurer  504 , outputs the allocation information (RN 1 -MS 1 ) to the control CH decoder  510 , and outputs the DL data (MS 1 ) to the data CH decoder  511 . 
     The SIR measurer  504 , based on the pilot signal (RN 1 ) received from the demultiplexer  503 , measures the SIR (RN 1 -MS 1 ) in the wireless path between the relay station  121  and the mobile station  131 . The SIR measurer  504  reports to the CQI generator  505 , the measured the SIR (RN 1 -MS 1 ). The CQI generator  505  generates the CQI (RN 1 -MS 1 ), which indicates the SIR (RN 1 -MS 1 ) reported by the SIR measurer  504 , and outputs the generated the CQI (RN 1 -MS 1 ) to the control CH generator  506 . 
     The control CH generator  506  assigns to a control CH, the CQI (RN 1 -MS 1 ) received from the CQI generator  505  and outputs the control CH assigned CQI (RN 1 -MS 1 ) to the multiplexer  507 . The CQI (RN 1 -MS 1 ) output by the control CH generator  506  is transmitted to the relay station  121 , by the transmitter  508 . 
     The multiplexer  507  multiplexes the CQI (RN 1 -MS 1 ) received from the control CH generator  506 , the UL data (MS 1 ) received from the data CH generator  516 , and the pilot signal (MS 1 ) received from the pilot generator  514 . The multiplexer  507  outputs the resulting multiplexed signal to the transmitter  508 . The transmitter  508  transmits the multiplexed signal to the relay station  121 , via the transmitting antenna  509 . 
     The control CH decoder  510  decodes the allocation information (RN 1 -MS 1 ) received from the demultiplexer  503  and outputs the decoded allocation information (RN 1 -MS 1 ) to the data CH decoder  511 . The data CH decoder  511 , based on the allocation information (RN 1 -MS 1 ) received from the control CH decoder  510 , decodes the DL data (MS 1 ) received from the demultiplexer  503 . The data CH decoder  511  outputs the decoded DL data (MS 1 ) to the DL buffer  512 . 
     The DL buffer  512  stores the DL data (MS 1 ) output by the data CH decoder  511 . The data processor  513  reads out the DL data (MS 1 ) stored in the DL buffer  512  and performs various types of processing using the DL data (MS 1 ). 
     Processing at the mobile station  131  and related to uplinks that transmit data to the core network  101  will be described. Nonetheless, the process at the mobile station  132  and related to uplinks that transmit data to the core network  101  and the processing at the mobile station  133  and related to uplinks that transmit data to the core network  102  are identical to that at the mobile station  131 . The pilot generator  514  generates the pilot signal (MS 1 ) and outputs the generated pilot signal (MS 1 ) to the multiplexer  507 . 
     The data processor  513  generates the UL data (MS 1 ) addressed to the core network  101  and outputs the generated UL data (MS 1 ) to the UL buffer  515 . The UL buffer  515  stores the UL data (MS 1 ) output by the data processor  513 . The control CH decoder  510  outputs the allocation information (RN 1 -MS 1 ) to the data CH generator  516 . 
     The data CH generator  516  assigns the UL data (MS 1 ) stored in the UL buffer  515 , to the wireless resources indicated in the allocation information (RN 1 -MS 1 ) received from the control CH decoder  510 . The data CH generator  516  outputs the wireless resource assigned UL data (MS 1 ) to the multiplexer  507 . The UL data (MS 1 ) output by the data CH generator  516  is transmitted to the relay station  121 , by the transmitter  508 . 
       FIG. 6  is a sequence diagram of an example of downlink operation of the communication system depicted in  FIG. 1 . Although downlink operation at the communication system  100 , from the base station  111  to the mobile stations  131 ,  132  will be described, the downlink operation from the base station  112  to the mobile station  133  is identical. 
     The mobile station  131  measures the SIR (RN 1 -MS 1 ) in the wireless path between the relay station  121  and the mobile station  131  (step S 601 ). The mobile station  131  uses the control CH and transmits to the relay station  121 , the CQI (RN 1 -MS 1 ), which indicates the SIR (RN 1 -MS 1 ) measured at step S 601  (step S 602 ). 
     The mobile station  132  measures the SIR (RN 1 -MS 2 ) in the wireless path between the relay station  121  and the mobile station  132  (step S 603 ). The mobile station  132 , uses the control CH and transmits to the relay station  121 , the CQI (RN 1 -MS 2 ), which indicates the SIR (RN 1 -MS 2 ) measured at step S 603  (step S 604 ). 
     The relay station  121 , based on the CQIs transmitted at step S 602  and step S 604 , determines the wireless resources to be requested (step S 605 ). The relay station  121  uses the control CH and transmits to the base station  111 , the request information (RN 1 -MS), which indicates the wireless resources determined at step S 605  (step S 606 ). 
     The relay station  121  uses the control CH and transmits to the base station  112 , the request information (RN 1 -MS) that indicates the wireless resources determined at step S 605  (step S 607 ). The request information (RN 1 -MS) transmitted at step S 607 , from the perspective of the base station  112 , is adjacent cell resource information transmitted by the relay station  121 , which is the relay station of an adjacent cell. 
     The relay station  121  measures the SIR (BS 1 -RN 1 ) in the wireless path between the base station  111  and the relay station  121  (step S 608 ). The relay station  121  uses the control CH and transmits to the base station  111 , the CQI (BS 1 -RN 1 ), which indicates the SIR (BS 1 -RN 1 ) measured at step S 608  (step S 609 ). 
     The base station  111  receives by the control CH, the adjacent cell resource information transmitted by the relay station  122  (step S 610 ). The adjacent cell resource information received at step S 610  is the request information also transmitted to the base station  111  and indicating the wireless resources that the relay station  122  requests the base station  112  to allocate. 
     The base station  111  performs wireless resource allocation (step S 611 ). At step S 611 , based on the CQI (BS 1 -RN 1 ) transmitted at step S 609 , wireless resources are allocated to the wireless path between the base station  111  and the relay station  121 . Further, at step S 611 , among the wireless resources indicated in the request information (RN 1 -MS) transmitted at step S 606 , wireless resources that are not indicated in the adjacent cell resource information transmitted at step S 610 , are preferentially allocated to the wireless paths between the relay station  121  and the mobile stations  131 ,  132 . 
     The base station  111  transmits to the relay station  121 , the DL data (MS 1 ) addressed to the mobile station  131  (step S 612 ). The base station  111  transmits to the relay station  121 , the DL data (MS 2 ) addressed to the mobile station  132  (step S 613 ). At steps S 612 , S 613 , the DL data is transmitted using the wireless resources allocated, at step S 611 , to the wireless path between the base station  111  and the relay station  121 . 
     The base station  111  uses the control CH and transmits the allocation information (RN 1 -MS) to the relay station  121  (step S 614 ). The allocation information (RN 1 -MS) transmitted at step S 614  is allocation information that indicates the wireless resources allocated to the wireless paths between the relay station  121  and the mobile stations  131 ,  132  at step S 611 . 
     The relay station  121  allocates to the wireless path between the relay station  121  and the mobile station  131  and to the wireless path between the relay station  121  and the mobile station  132 , the wireless resources indicated in the allocation information (RN 1 -MS) transmitted at step S 614  (step S 615 ). At step S 615 , for example, the wireless resource allocation is performed based on the CQIs transmitted at step S 602  and step S 604 . 
     The relay station  121  transmits to the mobile station  131 , the DL data (MS 1 ) transmitted at step S 612  (step S 616 ). At step S 616 , the DL data (MS 1 ) is transmitted using the wireless resources allocated, at step S 615 , to the wireless path between the relay station  121  and the mobile station  131 . 
     The relay station  121  transmits to the mobile station  132 , the DL data (MS 2 ) transmitted at step S 613  (step S 617 ), ending the series of operations. At step S 617 , the DL data (MS 2 ) is transmitted using the wireless resources allocated, at step S 615 , to the wireless path between the relay station  121  and the mobile station  132 . 
       FIG. 7  is a sequence diagram of uplink operation of the communication system depicted in  FIG. 1 . Although uplink operation in the communication system  100 , from the mobile stations  131 ,  132  to the base station  111  will be described, the uplink operation from the mobile station  133  to the base station  112  is identical. 
     The mobile station  131  transmits the pilot signal (MS 1 ) to the relay station  121  (step S 701 ). The relay station  121 , based on the pilot signal (MS 1 ) transmitted at step S 701 , measures the SIR (RN 1 -MS 1 ) in the wireless path between the relay station  121  and the mobile station  131  (step S 702 ). 
     The mobile station  132  transmits the pilot signal (MS 2 ) to the relay station  121  (step S 703 ). The relay station  121 , based on the pilot signal (MS 2 ) transmitted at step S 703 , measures the SIR (RN 1 -MS 2 ) in the wireless path between the relay station  121  and the mobile station  132  (step S 704 ). 
     The relay station  121 , based on the SIRs measured at step S 702  and step S 704 , determines the wireless resources to be requested (step S 705 ). The relay station  121  uses the control CH and transmits to the base station  111 , the request information (RN 1 -MS) indicating the wireless resources determined at step S 705  (step S 706 ). 
     The relay station  121  uses the control CH and transmits to the base station  112 , the request information (RN 1 -MS) indicating the wireless resources determined at step S 705  (step S 707 ). The request information (RN 1 -MS) transmitted at step S 707 , from the perspective of the base station  112 , is adjacent cell resource information transmitted from the relay station  121 , which is the relay station of an adjacent cell. 
     The relay station  121  transmits the pilot signal (RN 1 ) to the base station  111  (step S 708 ). The base station  111 , based on the pilot signal (RN 1 ) transmitted at step S 708 , measures the SIR (BS 1 -RN 1 ) in the wireless path between the base station  111  and the relay station  121  (step S 709 ). 
     The base station  111  receives by the control CH, the adjacent cell resource information transmitted by the relay station  122  (step S 710 ). The adjacent cell resource information received at step S 710  is the request information also transmitted to the base station  111  and indicating the wireless resources that the relay station  122  requests the base station  112  to allocate. 
     The base station  111  performs wireless resource allocation (step S 711 ). At step S 711 , wireless resources are allocated to the wireless path between the base station  111  and the relay station  121 , based on the SIR (BS 1 -RN 1 ) measured at step S 709 . At step S 711 , among the wireless resources indicated in the request information (RN 1 -MS) transmitted at step S 706 , wireless resources that are not indicated in the adjacent cell resource information transmitted at step S 710  are preferentially allocated to the wireless paths between the relay station  121  and the mobile stations  131 ,  132 . 
     The base station  111  uses the control CH and transmits the allocation information (BS 1 -RN 1 ) and the allocation information (RN 1 -MS) to the relay station  121  (step S 712 ). The allocation information (BS 1 -RN 1 ) is allocation information that indicates the wireless resources allocated to the wireless path between the base station  111  and the relay station  121  at step S 711 . The allocation information (RN 1 -MS) is allocation information that indicates the wireless resources allocated to the wireless paths between the relay station  121  and the mobile stations  131 ,  132  at step S 711 . 
     The relay station  121  allocates to the wireless path between the relay station  121  and the mobile station  131 , and to the wireless path between the relay station  121  and the mobile station  132 , the wireless resources indicated in the allocation information (RN 1 -MS) transmitted at step S 712  (step S 713 ). At step S 713 , for example, the wireless resource allocation is performed based on the SIRs measured at step S 702  and step S 704 . 
     The relay station  121  transmits to the mobile station  131 , the allocation information (RN 1 -MS 1 ) indicating the wireless resources allocated to the wireless path between the relay station  121  and the mobile station  131 , at step S 713  (step S 714 ). The relay station  121  transmits to the mobile station  132 , the allocation information (RN 1 -MS 2 ) indicating the wireless resources allocated to the wireless path between the relay station  121  and the mobile station  132 , at step S 713  (step S 715 ). 
     The mobile station  131  transmits the UL data (MS 1 ) to the relay station  121 , by the wireless resources indicated in the allocation information (RN 1 -MS 1 ) transmitted at step S 714  (step S 716 ). The relay station  121  uses the wireless resources indicated in the allocation information (BS 1 -RN 1 ) transmitted at step S 712  and transmits to the base station  111 , the UL data (MS 1 ) transmitted at step S 716  (step S 717 ). 
     The mobile station  132  uses the wireless resources indicated in the allocation information (RN 1 -MS 2 ) transmitted at step S 715  and transmits the UL data (MS 2 ) to the relay station  121  (step S 718 ). The relay station  121  uses the wireless resources indicated in the allocation information (BS 1 -RN 1 ) transmitted at step S 712  and transmits to the base station  111 , the UL data (MS 2 ) transmitted at step S 718  (step S 719 ), ending the series of operations. 
     As depicted in  FIGS. 6 and 7 , the base station  111  receives, as adjacent cell resource information, the request information indicating the wireless resources that the relay station  122  requests the base station  112  of the cell  112   a  to allocate. The base station  111  preferentially allocates to the wireless paths between the relay station  121  and the mobile stations  131 ,  132 , wireless resources that are not indicated in the adjacent cell resource information, whereby wireless resources having a low potential of being affected by communication interference by the relay station  122  can be allocated to the relay station  121  located near the cell border. 
       FIG. 8  is a diagram of an example of SIR in wireless paths between the relay station and the mobile stations. SIR  810  depicted in  FIG. 8  is the SIR (RN 1 -MS 1 ) in the wireless path between the relay station  121  and the mobile station  131 . SIR  820  is the SIR (RN 1 -MS 2 ) in the wireless path between the relay station  121  and the mobile station  132 . 
     In downlinks (for example, refer to  FIG. 6 ), the relay station  121  acquires the SIR  810  by receiving the CQI (RN 1 -MS 1 ) from the mobile station  131  and further acquires the SIR  820  by receiving the CQI (RN 1 -MS 2 ) from the mobile station  132 . In uplinks (for example, refer to  FIG. 7 ), the relay station  121  measures the SIR  810 , based on the pilot signal (MS 1 ) transmitted by the mobile station  131 , and further measures the SIR  820 , based on the pilot signal (MS 2 ) transmitted by the mobile station  132 . 
     The values indicated by the SIR  810  and the SIR  820  indicate the SIR at each of the wireless resources # 1 -# 10 . In this manner, the relay station  121  acquires each SIR for multiple wireless resources. Here, the SIR values are depicted simplified as “1” to “7”, where the greater the value is, the better the communication quality is. 
       FIG. 9  is a diagram of an example of request information transmitted by a relay station. In  FIG. 9 , parts identical to those depicted in  FIG. 8  are given the same reference numerals used in  FIG. 8  and description thereof is omitted. Request information  910  is the request information (RN 1 -MS) indicating the wireless resources determined by the relay station. In the request information  910 , “1” indicates a wireless resource to be requested of the base station  111  and “0” indicates a wireless resource that is not to be requested of the base station  111 . 
     The relay station  121 , for example, among the wireless resources # 1 -# 10 , preferentially determines, as wireless resources to be requested, wireless resources for which the SIR  810  and SIR  820  values are high. For example, the relay station  121  determines wireless resources whose combined SIR  810  and SIR  820  is 10 or greater. In this example, as depicted in the request information  910 , the wireless resources to be requested are the wireless resources # 2 -# 6 . The request information  910  is transmitted to the base station  111 . 
       FIG. 10  is a diagram of another example of request information. In  FIG. 10 , parts identical to those depicted in  FIG. 9  are given the same reference numerals used in  FIG. 9  and description thereof is omitted. The request information (RN 1 -MS) transmitted to the base station  111  by the relay station  121  may be configured like request information  1010  depicted in  FIG. 10 . 
     The values of the request information  1010  indicate priority levels of the wireless resources to be requested of the base station  111 , where the greater the value is, the higher the priority is. The relay station  121 , for example, respectively compares the SIR  810  and the SIR  820  among the wireless resources # 1 -# 10  and determines those with large SIRs as the request information  1010 . The request information  1010  is transmitted to the base station  111 . 
       FIG. 11  is a diagram of a wireless resource allocated by the base station. In  FIG. 11 , parts identical to those depicted in  FIG. 9  are given the same reference numerals used in  FIG. 9  and description thereof is omitted. Here, an example will be described where the request information (RN 1 -MS) transmitted to the base station  111  by the relay station  121  is the request information  910  depicted in  FIG. 9 . 
     Adjacent cell resource information  1110  is the adjacent cell resource information transmitted to the base station  111  by the relay station  122 . In the adjacent cell resource information  1110 , “1” indicates a wireless resource that is requested of the base station  111 , by the relay station  122  and “0” indicates a wireless resource that is not requested of the base station  111 , by the relay station  122 . 
     In this example, the adjacent cell resource information  1110  indicates the wireless resources # 1 , # 2 , # 6 -# 8  to be wireless resources requested of the base station  111  by the relay station  122 . The base station  111 , among the wireless resources # 2 -# 6  indicated in the request information  910 , preferentially allocates to the wireless paths between the relay station and the respective mobile stations, the wireless resources that are not the wireless resources # 1 , # 2 , # 6 -# 8  indicated in the adjacent cell resource information  1110 . Here, the base station  111  allocates the wireless resources # 3 -# 5  to the wireless paths between the relay station  121  and the respective mobile stations. 
     Allocation information  1120  is the allocation information (RN 1 -MS) transmitted to the relay station  121  by the base station  111 . In the allocation information  1120 , “1” indicates a wireless resource allocated to the wireless paths between the relay station  121  and the respective mobile stations and “0” indicates a wireless resource not allocated to the wireless paths between the relay station  121  and the respective mobile stations. 
     The allocation information  1120  is transmitted to the relay station  121 . The relay station  121  allocates the wireless resources # 3 -# 5  indicated in the allocation information  1120  to the wireless path between the relay station  121  and the mobile station  131  and the wireless path between the relay station  121  and the mobile station  132 . For example, the relay station  121  allocates the wireless resources # 3 , # 4  to the wireless path between the relay station  121  and the mobile station  131  and allocates the wireless resource # 5  to the wireless path between the relay station  121  and the mobile station  132 . 
     Although the request information (RN 1 -MS) transmitted to the base station  111  by the relay station  121  has been described as the request information  910  depicted in  FIG. 9 , the request information (RN 1 -MS) may be the request information  1010  depicted in  FIG. 10 . In this case, configuration may be such that among the wireless resources that are not the wireless resources # 1 , # 2 , # 6 -# 8  indicated in the adjacent cell resource information  1110 , the base station  111  preferentially allocates to the wireless paths between the relay station  121  and the respective mobile stations, wireless resources whose priority level indicated in the request information  1010  is high. 
     For example, among the wireless resources that are not the wireless resources # 1 , # 2 , # 6 -# 8  indicated in the adjacent cell resource information  1110 , the base station  111  allocates to the wireless paths between the relay station  121  and the respective mobile stations, wireless resources whose priority level indicated in the request information  1010  is 6 or greater. In this case, the allocation information (RN 1 -MS), which indicates the wireless resources allocated to the wireless path between the relay station  121  and the respective mobile stations becomes like the allocation information  1120 . 
       FIG. 12  is a sequence diagram of another example of the downlink operation depicted in  FIG. 6 . Steps S 1201 -S 1213  depicted in  FIG. 12  are identical to steps S 601 -S 606 , and steps S 608 -S 614  depicted in  FIG. 6  and description thereof is omitted. However, the adjacent cell resource information received at step S 1209  is the allocation information that is transmitted to the relay station  122  by the base station  112  and transmitted by the relay station  122  to the base station  111 . 
     After step S 1213 , the relay station  121  uses the control CH and transmits to the base station  112 , the allocation information (RN 1 -MS) transmitted at step S 1213  (step S 1214 ). The allocation information (RN 1 -MS) transmitted at step S 1214 , from the perspective of the base station  112 , is the adjacent cell resource information from the relay station  121 , which is a relay station of an adjacent cell. Steps S 1215 -S 1217  depicted in  FIG. 12  are identical to steps S 615 -S 617  depicted in  FIG. 6  and description therefor is omitted. 
     At step S 1214 , the DL scheduler  405  depicted in  FIG. 4  outputs to the other-cell control CH generator  428 , the allocation information (RN 1 -MS) output by the control CH decoder  416 . The other-cell control CH generator  428  assigns to a control CH, the allocation information (RN 1 -MS) received from the DL scheduler  405  and outputs the control CH assigned allocation information (RN 1 -MS) to the multiplexer  413 . The allocation information (RN 1 -MS) output from the other-cell control CH generator  428  is transmitted to the base station  112 , by the transmitter  414 . 
       FIG. 13  is a sequence diagram of another example of the uplink operation depicted in  FIG. 7 . Steps S 1301 -S 1311  depicted in  FIG. 13  are identical to steps S 701 -S 706  and steps S 708 -S 712  depicted in  FIG. 7  and description thereof is omitted. However, the adjacent cell resource information received at step S 1309  is the allocation information transmitted by the base station  112  to the relay station  122  and transmitted by the relay station  122  to the base station  111 . 
     After step S 1311 , the relay station  121  uses the control CH and transmits to the base station  112 , the allocation information (RN 1 -MS) transmitted at step S 1311  (step S 1312 ). The allocation information (RN 1 -MS) transmitted at step S 1312 , from the perspective of the base station  112 , is the adjacent cell resource information from the relay station  121 , which is a relay station of an adjacent cell. Steps S 1313 -S 1319  depicted in  FIG. 13  are identical to steps S 713 -S 719  depicted in  FIG. 7  and description thereof is omitted. 
     At step S 1312 , the UL scheduler  424  depicted in  FIG. 4  outputs to the other-cell control CH generator  428 , the allocation information (RN 1 -MS) output by the control CH decoder  416 . The other-cell control CH generator  428  assigns to a control CH, the allocation information (RN 1 -MS) received from the UL scheduler  424  and outputs the control CH assigned allocation information (RN 1 -MS) to the multiplexer  413 . The allocation information (RN 1 -MS) output by the other-cell control CH generator  428  is transmitted to the base station  112 , by the transmitter  414 . 
     As depicted in  FIGS. 12 and 13 , the base station  111  receives, as adjacent cell resource information, the allocation information indicating the wireless resources allocated to the relay station  122  by the base station of the cell  112   a  (adjacent cell). The base station  111  preferentially allocates to the wireless paths between the relay station  121  and the mobile stations  131 ,  132 , wireless resources that are not indicated in the adjacent cell resource information, whereby wireless resources having a potential of being affected by communication interference by the relay station  122  can be allocated to the relay station  121  located near the border of the cell  122   a.    
     In this manner, according to the base station  111  of the first embodiment, wireless resources having a low potential of being affected by communication interference by the relay station  122  (adjacent-cell relay station) can be allocated to wireless paths of the relay station  121  located near the border between the cell  111   a  and the cell  112   a . Consequently, throughput in a vicinity of the border between the cell  111   a  and the cell  112   a  can be improved, whereby, for example, the overall throughput of the cell  111   a  can be equalized. 
     Further, request information (or allocation information) from the relay station  122 , which is provided in the cell  112   a  and near the border with the cell  111   a , to the base station  111  is transmitted as adjacent cell resource information, enabling the above effects to be achieved. In general, since the number of relay stations (e.g., the relay station  122 ) near a border relative to the total number of relay stations in the cell  112   a  is small, the adjacent cell resource information can be transmitted by newly setting few control CHs. Therefore, the above effects can be achieved without large changes to the communication system. 
     In the first embodiment, a configuration is assumed in which adjacent cell resource information is exchanged between the cell  111   a  and the cell  112   a ; and at the base station  111  and the base station  112 , respectively, wireless resource allocation is performed that takes into consideration the adjacent cell resource information. Therefore, at the cell  112   a , the above effects described with respect to the cell  111   a  can also be achieved. 
     However, any one among the configuration of transmitting adjacent cell resource information from the cell  111   a  to the cell  112   a  and the configuration of transmitting adjacent cell resource information from the cell  112   a  to the cell  111   a  can be omitted. For example, the configuration of transmitting adjacent cell resource information from the relay station  121  to the base station  112  can be omitted. In this case, at the base station  112 , wireless resource allocation is performed that does not take into consideration the adjacent cell resource information. Nonetheless, at cell  111   a , the above effects can be achieved. 
       FIG. 14  is a diagram of a configuration of the communication system according to a second embodiment. In  FIG. 14 , components identical to those depicted in  FIG. 1  are given the same reference numerals used in  FIG. 1  and description thereof is omitted. In the second embodiment, the relay station  121  further transmits (reference character  1411 ) to the relay station  122 , the request information transmitted (reference character  141 ) to the base station  111 . In this case, the relay station  121  can omit transmitting request information to the base station  112 . 
     The relay station  121  receives from the relay station  122  (adjacent-cell relay station), which is in the cell  112   a  (adjacent cell) and near the border with the cell  111   a  (of the relay station  121 ), adjacent cell resource information (reference character  1412 ) indicating the wireless resources allocated to the relay station  122 . The relay station  121  preferentially uses wireless resources that are not indicated in the received adjacent cell resource information and wirelessly communicates with the mobile stations  131 ,  132 , respectively. 
     For example, as wireless resources to be requested for allocation, the relay station  121  preferentially determines wireless resources that are not indicated in the received adjacent cell resource information and transmits to the base station  111 , request information (reference character  141 ) indicating the determined wireless resources. The relay station  121  wirelessly communicates with the mobile stations  131 ,  132 , respectively, using the wireless resources indicated in the allocation information (reference character  161 ) transmitted by the base station  111  in response to the request information. 
     The base station  111  receives request information (reference character  141 ) transmitted by the relay station  121 . The base station  111 , from among the wireless resources indicated in the request information (reference character  141 ), determines the wireless resources to be allocated to the wireless path L 1  and the wireless path L 2 . The base station  111  transmits to the relay station  121 , the allocation information (reference character  161 ) indicating the determined wireless resources. 
     The base station  112  and the relay station  122  will be described. The relay station  122  further transmits (reference character  1412 ) to the relay station  121 , the request information transmitted (reference character  142 ) to the base station  112 . In this case, the relay station  122  can omit transmitting request information to the base station  111 . 
     The relay station  122  receives from the relay station  121  (adjacent-cell relay station), which is in the cell  111   a  (adjacent cell) and near the border with the cell  112   a  (of the relay station  122 ), adjacent cell resource information (reference character  1411 ) indicating the wireless resources allocated to the relay station  121 . The relay station  122  preferentially uses wireless resources that are not indicated in the received adjacent cell resource information and wirelessly communicates with the mobile station  133 . 
     For example, as wireless resources to be requested for allocation, the relay station  122  preferentially determines wireless resources that are not indicated in the received adjacent cell resource information and transmits to the base station  112 , request information (reference character  142 ) indicating the determined wireless resources. The relay station  122  wirelessly communicates with the mobile station  133 , using the wireless resources indicated in the allocation information (reference character  162 ) transmitted by the base station  112  in response to the request information. 
     For example, if another condition concerning the wireless resource is the same, the relay station  122 , as wireless resources to be requested, determines wireless resources that are not indicated in the received adjacent cell resource information. An example of a condition in such a case is communication quality, such as SIR. Configuration may be such that among the wireless resources that are not indicated in the received adjacent cell resource information, the relay station  122 , as the wireless resources to be requested, determines wireless resources that satisfy another condition, such as SIR communication quality that is greater than or equal to a threshold, communication quality that is higher than a given level, etc. 
     In this manner, configuration may be such that the relay station  122  acquires the communication quality for a wireless path between the relay station  122  and the mobile station  133  and based on the acquired communication quality, determines the wireless resources to be requested, from among wireless resource not indicated in the adjacent cell resource information. 
     The base station  112  receives request information (reference character  142 ) transmitted by the relay station  122 . The base station  112  determines the wireless resources to be allocated to the wireless path L 3 , from among the wireless resources indicated in the request information (reference character  142 ). The base station  112  transmits to the relay station  122 , allocation information (reference character  162 ) indicating the determined wireless resources. The wireless resources in the communication system depicted in  FIG. 14  are identical to the wireless resources depicted in  FIG. 2  and description thereof is omitted. 
       FIG. 15  is a block diagram of the base station depicted in  FIG. 14 . In  FIG. 15 , components identical to those depicted in  FIG. 3  are given the same reference numerals used in  FIG. 3  and description thereof is omitted. As depicted in  FIG. 15 , the base station  111  (refer to  FIG. 14 ) according to the second embodiment may be of the configuration depicted in  FIG. 3 , less the other-cell control CH decoder  319 . 
     Processing at the base station  111  and related to downlinks that transfer DL data from the core network  101  to the mobile station  131  and the mobile station  132  will be described. Nonetheless, at the base station  112 , the processing related to downlinks that transfer DL data from the core network  102  to the mobile station  133  is identical. The receiver  302  may omit receiving the adjacent cell resource information (refer to  FIG. 3 ) transmitted by the relay station  122  of the cell  112   a . In this case, the adjacent cell resource information is not input to the DL scheduler  305 . 
     The DL scheduler  305 , based on the request information (RN 1 -MS) received from the own-cell control CH decoder  304 , allocates wireless resources to the wireless paths between the relay station  121  and the mobile stations  131 ,  132 . 
     Processing at the base station  111  and related to uplinks that transfer UL data from the mobile stations  131 ,  132  to the core network  101  will be described. Nonetheless, at the base station  112 , the processing related to uplinks that transfer UL data from the mobile station  133  to the core network  102  is identical. The receiver  302  may omit receiving the adjacent cell resource information (refer to  FIG. 3 ) transmitted by the relay station  122  of the cell  112   a . In this case, the adjacent cell resource information is not input to the UL scheduler  315 . 
     The UL scheduler  315 , based on the request information (RN 1 -MS) received from the own-cell control CH decoder  304 , allocates wireless resources to the wireless paths between the relay station  121  and the mobile stations  131 ,  132 . 
       FIG. 16  is a block diagram of the relay station depicted in  FIG. 14 . In  FIG. 16 , components identical to those depicted in  FIG. 4  are given the same reference numerals used in  FIG. 4  and description thereof is omitted. As depicted in  FIG. 16 , the relay station  121  (refer to  FIG. 14 ) according to the second embodiment, includes an other-cell control CH decoder  1611  in addition to the configuration depicted in  FIG. 4 . Although configuration of the relay station  121  will be described, the configuration of the relay station  122  is identical. 
     The receiving antenna  401  and the receiver  402  form a receiver that receives from the relay station  122  (adjacent-cell relay station) in the cell  112   a  (adjacent cell) and near the border with the cell  111   a  (of the relay station  121 ), adjacent cell resource information indicating the wireless resources allocated to the relay station  122 . The receiving antenna  401 , the receiver  402 , the transmitter  421 , and the transmitting antenna  422  form a communications unit that uses wireless resources that are not indicated in the adjacent cell resource information received by the receiver and wirelessly communicates with the mobile stations  131 ,  132 . 
     The DL scheduler  405  and the UL scheduler  424  form a determining unit that as wireless resources to be requested for allocation to the wireless paths between the relay station  121  and the mobile stations  131 ,  132 , preferentially determines wireless resources that are not indicated in the adjacent cell resource information. The DL scheduler  405  and the UL scheduler  424 , for example, are implemented by a processor such as a CPU, DSP, FPGA, etc. 
     The transmitter  414  and the transmitting antenna  415  form a transmitting unit that transmits to the base station  111 , request information indicating the wireless resources determined by determining unit. The receiving antenna  407  and the receiver  408  form a second receiver that receives allocation information indicating the wireless resources allocated by the base station  111  according to the request information transmitted by the transmitting unit. 
     Processing at the relay station  121  and related to downlinks that transfer DL data from the core network  101  to the mobile station  131  and the mobile station  132  will be described. Nonetheless, at the relay station  122 , the processing related to downlinks that transfer DL data from the core network  102  to the mobile station  133  is identical. 
     The receiver  402  receives, via the receiving antenna  401 , the adjacent cell resource information transmitted by the relay station  122 . The receiver  402  outputs the received adjacent cell resource information to the demultiplexer  403 . The demultiplexer  403  outputs to the other-cell control CH decoder  1611 , the adjacent cell resource information received from the receiver  402 . The other-cell control CH decoder  1611  decodes the adjacent cell resource information received from the demultiplexer  403 . The other-cell control CH decoder  1611  outputs the decoded adjacent cell resource information to the DL scheduler  405 . 
     The DL scheduler  405 , based on the adjacent cell resource information received from the other-cell control CH decoder  1611 , determines the wireless resources to be requested of the base station  111 , for the wireless paths between the relay station  121  and the mobile stations  131 ,  132 . For example, as wireless resources to be requested, the DL scheduler  405  preferentially determines wireless resources that are not indicated in the adjacent cell resource information. For example, among the wireless resources # 1 -# 10  (refer to  FIG. 2 ), the DL scheduler  405 , determines, as the wireless resources to be requested, wireless resources that are not indicated in the adjacent cell resource information and for which the CQI indicates relatively high quality. 
     Processing at the relay station  121  and related to uplinks that transfer data from the mobile stations  131 ,  132  to the core network  101  will be described. Nonetheless, at the relay station  122 , the processing related to uplinks that transfer data from the mobile station  133  to the core network  102  is identical. The other-cell control CH decoder  1611  outputs the decoded adjacent cell resource information to the UL scheduler  424 . 
     The UL scheduler  424 , based on the adjacent cell resource information received from the other-cell control CH decoder  1611 , determines the wireless resources to be requested of the base station  111 , for the wireless paths between the relay station  121  and the mobile stations  131 ,  132 . For example, as wireless resources to be requested, the UL scheduler  424  preferentially determines wireless resources that are not indicated in the adjacent cell resource information. For example, from among the wireless resources # 1 -# 10  (refer to  FIG. 2 ), the UL scheduler  424  determines as wireless resources to be requested, wireless resources that are not indicated in the adjacent cell resource information and for which the CQI indicates a relatively high quality. 
       FIG. 17  is a sequence diagram of an example of downlink operation of the communication system depicted in FIG.  14 . Although downlink operation at the communication system  100 , from the base station  111  to the mobile stations  131 ,  132  will be described, the downlink operation from the base station  112  to the mobile station  133  is identical. Steps S 1701 -S 1704  depicted in  FIG. 17  are identical to steps S 601 -S 604  depicted in  FIG. 6  and description thereof is omitted. 
     After step S 1704 , the relay station  121 , based on the CQIs transmitted at step S 1702  and step S 1704 , tentatively determines the wireless resource to be requested (step S 1705 ). The relay station  121  uses the control CH to transmit to the relay station  122 , the request information (RN 1 -MS) indicating wireless resources tentatively determined at the step S 1705  (step S 1706 ). The request information (RN 1 -MS) transmitted at step S 1706 , from the perspective of the relay station  122 , is adjacent cell resource information transmitted from the relay station  121 , which is the relay station of an adjacent cell. 
     The relay station  121  receives, by the control CH, the adjacent cell resource information transmitted by the relay station  122  (step S 1707 ). The adjacent cell resource information transmitted at step S 1707  is the request information also transmitted to the relay station  121  and indicating the wireless resources that the relay station  122  requests the base station  112  to allocate. 
     Further, the adjacent cell resource information received at step S 1707  may be the request information also transmitted to the relay station  121  and indicating the wireless resources tentatively determined to be requested by the relay station  122 . The relay station  121 , based on the wireless resources tentatively determined at step S 1705  and on the adjacent cell resource information received at step S 1707 , determines the wireless resources to be requested (step S 1708 ). 
     The relay station  121  uses the control CH to transmit to the base station  111 , the request information (RN 1 -MS) indicating the wireless resources determined at step S 1708  (step S 1709 ). The relay station  121  measures the SIR (BS 1 -RN 1 ) in the wireless path between the base station  111  and the relay station  121  (step S 1710 ). The relay station  121  uses the control CH to transmit to the base station  111 , the CQI (BS 1 -RN 1 ) indicating the SIR (BS 1 -RN 1 ) measured at step S 1710  (step S 1711 ). 
     The base station  111  performs wireless resource allocation (step S 1712 ). At step S 1712 , wireless resources are allocated to the wireless path between the base station  111  and the relay station  121 , based on the CQI (BS 1 -RN 1 ) transmitted at step S 1711 . Wireless resources included among the wireless resources indicated in the request information (RN 1 -MS) transmitted at step S 1709  are allocated to the wireless paths between the relay station  121  and the mobile stations  131 ,  132 . Steps S 1713 -S 1718  depicted in  FIG. 17  are identical to steps S 612 -S 617  depicted in  FIG. 6  and description thereof is omitted. 
       FIG. 18  is a sequence diagram of an example of uplink operation of the communication system depicted in  FIG. 14 . Although uplink operation in the communication system  100 , from the mobile stations  131 ,  132  to the base station  111  will be described, the uplink operation from the mobile station  133  to the base station  112  is identical. Steps S 1801 -S 1804  depicted in  FIG. 18  are identical to steps S 701 -S 704  depicted in  FIG. 7  and description thereof is omitted. 
     After step S 1804 , the relay station  121 , based on the SIRs measured at step S 1802  and step S 1804 , tentatively determines the wireless resources to be requested (step S 1805 ). The relay station  121  uses the control CH to transmit to the relay station  122 , the request information (RN 1 -MS) indicating the wireless resources tentatively determined at step S 1805  (step S 1806 ). The request information (RN 1 -MS) transmitted at step S 1806 , from the perspective of the relay station  122 , is adjacent cell resource information transmitted by the relay station  121 , which is the relay station of an adjacent cell. 
     The relay station  121  receives, by the control CH, the adjacent cell resource information transmitted by the relay station  122  (step S 1807 ). The adjacent cell resource information received at step S 1807  is the request information also transmitted to the relay station  121  and indicating the wireless resources that the relay station  122  requests the base station  112  to allocate. 
     The adjacent cell resource information received at step S 1807  may be the request information also transmitted to the base station  111  and indicating the wireless resources tentatively determined to be requested by the relay station  122 . The relay station  121 , based on the wireless resources tentatively determined at step S 1805  and on the adjacent cell resource information received at step S 1807 , determines the wireless resources to be requested (step S 1808 ). 
     The relay station  121  transmits to the base station  111 , the request information (RN 1 -MS) indicating wireless resources determined at the step S 1808  (step S 1809 ). The relay station  121  transmits the pilot signal (RN 1 ) to the base station  111  (step S 1810 ). The base station  111 , based on the pilot signal (RN 1 ) transmitted at step S 1808 , measures the SIR (BS 1 -RN 1 ) in the wireless path between the base station  111  and the relay station  121  (step S 1811 ). 
     The base station  111  performs wireless resource allocation (step S 1812 ). At step S 1812 , wireless resources are allocated to the wireless path between the base station  111  and the relay station  121 , based on the SIR (BS 1 -RN 1 ) measured at step S 1811 . Wireless resources included among the wireless resources indicated by the request information (RN 1 -MS) received at step S 1809  are allocated to the wireless paths between the relay station  121  and the mobile stations  131 ,  132 . Steps S 1813 -S 1820  depicted in  FIG. 18  are identical to steps S 712 -S 719  depicted in  FIG. 7  and description thereof is omitted. 
       FIG. 19  is a diagram of an example wireless resource determination by the relay station. In  FIG. 19 , parts identical to those depicted in  FIG. 11  are given the same reference numerals and description thereof is omitted. In this example, it is assumed that the SIR in the wireless paths between the relay station  121  and the mobile stations  131 ,  132  is the SIR  810  and the SIR  820  values depicted in  FIG. 8 . Tentative-determination information  1910  depicted in  FIG. 19  indicates the wireless resources tentatively determined to be requested by the relay station  121 . 
     In the tentative-determination information  1910 , “1” indicates a wireless resource to be requested of the base station  111 , and “0” a wireless resource that is not to be requested of the base station  111 . For example, as wireless resources to be requested, the relay station  121  determines wireless resources for which the SIR  810  and the SIR  820  are relatively high among the wireless resources # 1 -# 10 . In this example, it is assumed that the relay station  121  tentatively determines the wireless resources # 2 -# 6  as wireless resources to be requested. 
     The relay station  121 , among the wireless resources # 2 -# 6  indicated in the tentative-determination information  1910 , preferentially determines, as the wireless resources to be requested, the wireless resources that are not the wireless resources # 1 , # 2 , # 6 -# 8  indicated in the adjacent cell resource information  1110 . In this example, as depicted in the request information  910 , the relay station  121  determines the wireless resources # 3 -# 5  as the wireless resources to be requested. 
     The request information  910  is transmitted to the base station  111 . The base station  111  allocates to the wireless paths between the relay station  121  and the mobile stations  131 ,  132 , wireless resources included among the wireless resources # 3 -# 5  indicated in the request information  910 . For example, if none of the wireless resources # 3 -# 5  have been allocated to a relay station, excluding the relay station  121  in the cell  111   a , the base station  111  allocates the wireless resources # 3 -# 5  to the wireless paths between the relay station  121  and the mobile stations  131 ,  132 . 
       FIG. 20  is a sequence diagram of another example of the downlink operation depicted in  FIG. 17 . Steps S 2001 -S 2014  depicted in  FIG. 20  are identical to steps S 1701 -S 1705 , S 1707 -S 1715  depicted in  FIG. 17  and description thereof is omitted. Nonetheless, the adjacent cell resource information received at step S 2006  is the allocation information transmitted by the base station  112  to the relay station  122 , and by the relay station  122  to the relay station  121 . 
     After step S 2014 , the relay station  121  uses the control CH and transmits to the relay station  122 , the allocation information (RN 1 -MS) transmitted at step S 2014  (step S 2015 ). The allocation information (RN 1 -MS) transmitted at step S 2015  is, from the perspective of the relay station  122 , adjacent cell resource information transmitted by the relay station  121 , which is the relay station of an adjacent cell. Steps S 2016 -S 2018  depicted in  FIG. 20  are identical to steps S 1716 -S 1718  depicted in  FIG. 17  and description thereof is omitted. 
     At step S 2015 , the DL scheduler  405  depicted in  FIG. 16  outputs to the other-cell control CH generator  428 , the allocation information (RN 1 -MS) output by the control CH decoder  416 . The other-cell control CH generator  428  assigns to a control CH, the allocation information (RN 1 -MS) received from the DL scheduler  405  and outputs the control CH assigned allocation information (RN 1 -MS) to the multiplexer  413 . The allocation information (RN 1 -MS) output by the other-cell control CH generator  428  is transmitted to the relay station  122 , by the transmitter  414 . 
       FIG. 21  is a sequence diagram of another example of the uplink operation depicted in  FIG. 18 . Steps S 2101 -S 2112  depicted in  FIG. 21  are identical to steps S 1801 -S 1805 , S 1807 -S 1813  depicted in  FIG. 18  and description thereof is omitted. Nonetheless, the adjacent cell resource information transmitted at step S 2106  is the allocation information transmitted by the base station  112  to the relay station  122 , and transmitted by the relay station  122  to the relay station  121 . 
     After step S 2112 , the relay station  121  uses the control CH and transmits to the relay station  122 , the allocation information (RN 1 -MS) transmitted at step S 2112  (step S 2113 ). The request information (RN 1 -MS) transmitted at step S 2113  is, from the perspective of the relay station  122 , adjacent cell resource information transmitted by the relay station  121 , which is the relay station of an adjacent cell. Steps S 2114 -S 2120  depicted in  FIG. 21  are identical to steps S 1814 -S 1820  depicted in  FIG. 18  and description thereof is omitted. 
     At step S 2113 , the UL scheduler  424  depicted in  FIG. 16  outputs to the other-cell control CH generator  428 , the allocation information (RN 1 -MS) output by the control CH decoder  416 . The other-cell control CH generator  428  assigns to a control CH the allocation information (RN 1 -MS) received from the UL scheduler  424  and outputs the control CH assigned allocation information (RN 1 -MS) to the multiplexer  413 . The allocation information (RN 1 -MS) output by the other-cell control CH generator  428  is transmitted to the relay station  122 , by the transmitter  414 . 
     As depicted in  FIGS. 20 and 21 , the relay station  121  receives, as adjacent cell resource information, allocation information that indicates the wireless resources allocated to the relay station  122 , by the base station  112  of the cell  112   a  (adjacent cell). The relay station  121  preferentially determines, as wireless resources to be requested, wireless resources that are not indicated in the adjacent cell resource information. Consequently, the base station  111  is able to allocate to the relay station  121  near the border with the cell  112   a , wireless resource that have a low potential of being affected by wireless communication interference consequent to the relay station  122 . 
     In this manner, according to the relay station  121  of second embodiment, the base station  111  is able to allocate wireless resources having a low potential of being affected by wireless communication interference consequent to the relay station  122  (adjacent-cell relay station). Consequently, throughput in a vicinity of the border between the cell  111   a  and the cell  112   a  can be improved, whereby, for example, the overall throughput of the cell  111   a  can be equalized. 
     Further, request information (or allocation information) from the relay station  122 , which is in the cell  112   a  and near the border with the cell  111   a , to the relay station  121  is transmitted as adjacent cell resource information, enabling the above effects to be achieved. In general, since the number of relay stations (e.g., the relay station  122 ) near a border relative to the total number of relay station in the cell  112   a  is small, the adjacent cell resource information can be transmitted by newly setting few control CHs. Therefore, the above effects can be achieved without large changes to the communication system. 
     In the second embodiment, a configuration is assumed in which adjacent cell resource information is exchanged between the relay station  121  and the relay station  122 ; and at the relay station  121  and the relay station  122 , respectively, wireless resources to be requested, are determined taking the adjacent cell resource information into consideration. Therefore, at the cell  112   a , the above effects described with respect to cell  111   a  can also be achieved. 
     However, any one among the configuration of transmitted adjacent cell resource information from the relay station  121  to the relay station  122  and the configuration of transmitting adjacent cell resource information from the relay station  122  to the relay station  121  can be omitted. For example, the configuration of transmitting adjacent cell resource information from the relay station  121  to the relay station  122  can be omitted. In this case, at the relay station  122 , wireless resources to be requested are determined without taking the adjacent cell resource information into consideration. Nonetheless, at cell  111   a , the above effects can be achieved. 
     As described, according to the disclosed base station, relay station, communication system, and communication method, throughput near cell boundaries can be improved. 
     All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation 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 the 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.