Base Station for Allocating Downlink Radio Resource for Directivity Transmission

1. A base station for communicating with a communication terminal, the base station comprising: a communication section for communicating with the communication terminal using a plurality of antennas and controlling transmission directivity in the plurality of antennas when downlink communication with the communication terminal is performed; and a scheduling executing section for determining the communication terminal for downlink communication and allocating, to the communication terminal, a use downlink radio resource to be used by the communication section for the downlink communication with the communication terminal, wherein an uplink radio resource for known signal which is capable of being used when the communication terminal transmits a known signal, and the downlink radio resource, which is associated with the uplink radio resource for known signal and is capable of being used when the communication section performs downlink communication with the communication terminal are determined, when the scheduling executing section allocates the use downlink radio resource including a frequency band included in a transmission frequency band of the known signal in a frequency direction to the communication terminal that transmits the known signal using at least a part of the uplink radio resource for known signal, the scheduling executing section executes the allocating process for allocating the use downlink radio resource from the downlink radio resource associated with the uplink radio resource for known signal to the communication terminal, when the scheduling executing section executes the allocating process on the communication terminal transmitting the known signal using at least a part of the uplink radio resource for known signal, the communication section controls the transmission directivity in the plurality of antennas based on a reception signal including the known signal as a desired wave component received by at least part of the uplink radio resource for known signal when the downlink communication with the communication terminal is performed by using the use downlink radio resource, when the scheduling executing section allocates the use downlink radio resources including in the frequency direction the frequency band, in which the known signal is not received by the uplink radio resource for known signal, from the downlink radio resource associated with the uplink radio resource for known signal to the communication terminal, the communication section controls the transmission directivity in the plurality of antennas based on a new reception signal obtained by generating a known signal received from the communication terminal in the frequency band of the use downlink radio resource in a pseudo manner when performing the downlink communication with the communication terminal using the use downlink radio resource and by adding the pseudo known signal as the desired wave component to the reception signal received in the frequency band of the use downlink radio resource in the uplink radio resource for known signal.

2. The base station according to claim 1 , wherein when the scheduling executing section allocates the use downlink radio resource including in the frequency direction the frequency band, in which the known signal is not received by the uplink radio resource for known signal, from the downlink radio resource associated with the uplink radio resource for known signal to the communication terminal, the scheduling executing section determines the communication terminal to which the use downlink radio resource is allocated based on a communication state of the downlink communication between the base station and the communication terminal.

3. The base station according to claim 2 , wherein when the scheduling executing section allocates the use downlink radio resource including in the frequency direction the frequency band, in which the known signal is not received by the uplink radio resource for known signal, from the downlink radio resource associated with the uplink radio resource for known signal to the communication terminal, the scheduling executing section determines the communication terminal to which the use downlink radio resource is allocated based on proportional fairness of the downlink communication between the base station and the communication terminal.