A method for transmitting/receiving an additional control signal without any loss of bandwidth and power in an original Tx signal is disclosed. If the additional control signal is transmitted via the Tx signal composed of at least one of data and control signals, at least one of the amplitude and phase of the Tx signal of the time- and frequency-resource domain is modulated according to the additional control signal to be transmitted. The modulated Tx signal is transmitted to the receiver, so that the additional control signal can be transmitted irrespective of the original Tx signal. According to a modulation status of at least one of an amplitude and a phase of the Rx signal contained in the time- and frequency-resource domain, the additional control signal can be acquired.