A base station including at least one circuit configured to: receive a signal from a communication terminal via an array antenna; calculate a weight to be applied to the array antenna with respect to the communication terminal, based on a known signal supplied from the communication terminal and received by the circuit; transmit a signal to the communication terminal via the array antenna; determine m (m>1) communication terminals among the plurality of communication terminals, based on a first communication quality between base stations and a plurality of communication terminals, as communication-object candidates; cause to transmit control information, which is configured to cause the communication terminal to transmit the known signal, to the m communication terminals. Thus, the circuit may determine, as communication objects, l (1≦l