A transmission circuit transmits a connection request including a “signature” to a base station. The demodulator demodulates the AICH for transmitting a notification corresponding to the connection request. When requested communications are enabled, the AICH transmits the “signature”. A multiplier multiplies a demodulation signal by the “signature”. A voltage computation unit converts the output of the multiplier into a voltage value. An integrator integrates the voltage value computed by the voltage computation unit for each received symbol for the respective symbols corresponding to the “signature”. A threshold generation unit adaptively selects one of a threshold determined based on the noise of a transmission path or a threshold determined based on the receiving power. If the output of the integrator is larger than the selected threshold, it is determined that the communications have been enabled.