A mobile station (14) transmits a signal after connection is established, by using the same number of subcarriers as the number of subcarriers equal to or smaller than a predetermined number used for transmitting a connection request signal (TCCH). A base station (12) detects the number of subcarriers used for transmitting the connection request signal (TCCH) (S106), and controls in accordance with the detected number of subcarriers the passband width of a bandpass filter having a passband with a variable width accommodating the predetected number of subcarriers, for separating a signal of the mobile station (14) falling within the passband from a received signal (S108).