Transmitting apparatus and receiving apparatus for communication systems use coded orthogonal frequency-division multiplexed (COFDM) dual-subcarrier-modulation (DCM) signals. The same coded data is mapped both to COFDM subcarriers located in the lower-frequency half spectrum of the DCM signal and to COFDM subcarriers located in its upper-frequency half spectrum. Symbol constellation mappings of COFDM subcarriers in those half spectra preferably employ labeling diversity providing peak-to-average power ratio (PAPR) of the COFDM DCM signals substantially reduced from PAPR of double-sideband COFDM signals.