Base station, radio communications system, and processing method in base station

A radio communications system comprising:

• a plurality of terminals;
• and
• a base station capable of simultaneously receiving an uplink signal from each of the terminals and transmitting a downlink signal to each of the terminals by using an identical frequency, wherein
• the base station comprises:
• a transmitting unit that transmits, for each of the terminals, a downlink signal at a frequency assigned to the terminal via an antenna having directivity in a direction of the terminal;
• a receiving unit that receives, for each of the terminals, an uplink signal at a frequency assigned to the terminal via an antenna having directivity in a direction of the terminal;
• a determining unit that determines, for each of the terminals, whether reception quality of the uplink signal from the terminal, due to reflected waves of a downlink signal, is equal to or smaller than a certain threshold;
• and
• a change unit that, when the determining unit determines that the reception quality is equal to or smaller than the certain threshold, instructs a first terminal that is a terminal of a transmission source of an uplink signal to change the frequency of the uplink signal of the first terminal to either the frequency of an uplink signal or the frequency of a downlink signal assigned to each of the terminals, or changes the frequency of a downlink signal identical to the frequency of the uplink signal from the first terminal to either the frequency of an uplink signal or the frequency of a downlink signal assigned to each of the terminals.

A processing method in a base station capable of simultaneously receiving an uplink signal from a terminal and transmitting a downlink signal to a terminal by using an identical frequency, the processing method comprising:

• transmitting, for each terminal, a downlink signal at a frequency assigned to the terminal via an antenna having directivity in a direction of the terminal;
• receiving, for each terminal, an uplink signal at a frequency assigned to the terminal via an antenna having directivity in a direction of the terminal;
• determining, for each terminal, whether reception quality of the uplink signal from the terminal, due to reflected waves of a downlink signal, is equal to or smaller than a certain threshold;
• and
• instructing a first terminal that is a terminal of a transmission source of an uplink signal to change the frequency of the uplink signal of the first terminal to either the frequency of an uplink signal or the frequency of a downlink signal assigned to each terminal or changing the frequency of a downlink signal identical to the frequency of the uplink signal from the first terminal to either the frequency of an uplink signal or the frequency of a downlink signal assigned to each terminal when it is determined that the reception quality is equal to or smaller than the certain threshold.