A method of transmitting an ACK/NACK signal via an ACK/NACK channel including one or more tiles comprised of a plurality of OFDM symbols in a time domain and a plurality of subcarriers in a frequency domain in a wireless communication system includes generating a first codeword by applying a first spreading code to data symbols and pilot symbols, wherein the tile includes a plurality of data subcarriers and a plurality of pilot subcarriers, the data symbols are allocated to the plurality of data subcarriers and the pilot symbols are allocated to the plurality of pilot subcarriers, generating a second codeword by allocating data symbols applied a second spreading code to the plurality of data subcarriers, and transmitting the first and second codewords.