1. A transmission device in a wireless communication system, comprising: a spreading unit configured to generate two data flows by applying a conjugate symmetric discrete fourier transform (CS-DFT) spreading operation to a first complex-value data flow input thereto, the CS-DFT spreading operation comprising a conjugate symmetric operation and a subsequent discrete fourier transform (DFT) spreading operation; a sub-carrier mapping unit configured to map each of the two data flows to sub-carriers; and a modulator configured to generate offset quadrature amplitude modulation (OQAM) signals by applying a quadrature amplitude modulation operation to the data flows mapped on sub-carriers.