It is an object of the present invention to hold the detecting range of a timing correlator in a base station to the minimum required and to reduce the circuit scale and power requirement of the timing correlator. Before a mobile station transmits a data signal, it transmits a signal referred to as a preamble signal to measure the transmission timing to the base station. If the base station detects the preamble signal with a timing correlator having a limited circuit scale, then the base station transmits a transmission permission signal to the mobile station. If the mobile station fails to receive the transmission permission signal over a given period of time after it has transmitted the preamble signal, then the mobile station retransmits the preamble signal at a changed transmission timing based on the received electric power of a control signal transmitted continuously from the base station and information included in the control signal. The mobile station repeatedly retransmits the preamble signal until it receives the transmission permission signal. If the mobile station receives the transmission permission signal from the base station, then the mobile station transmits a data signal at the transmission timing of the preamble signal transmitted immediately prior to the reception of the transmission permission signal.