A new modulation/demodulation method and apparatus are described for use with RF communication. A transmitter (1001T) modulates information onto a plurality of carrier signals transmitted simultaneously over a corresponding plurality of frequencies using cepstral modulation. A receiver (1003R) receives the plurality of carrier signals and demodulates the signals utilizing cepstral demodulation. Receiver (1003R) monitors the carrier signals and in response to predetermined conditions selects a cepstral constellation to be utilized. Receiver (1003R) provides the cepstral constellation information to a transmitter (1003T) that, in turn, transmits the cepstral constellation information to a receiver (1001R), in turn, provides the cepstral constellation information to transmitter (100T). Transmitter (1001T) utilizes the selected cepstral constellation information to modulate the next transmission of the plurality of carrier signals.