A broadcast signal receiver includes a demodulator configured to perform Orthogonal Frequency Division Multiplexing (OFDM) demodulation on a received broadcast signal; a frame parser configured to derive service data by parsing a signal frame of the received broadcast signal based on a number of carriers of the signal frame; a decoder configured to perform error correction on the service data; and an output processor configured to receive the service data and output a data stream, wherein the number of carriers of the signal frame is determined by equation: NoC=NoC_max−k*Δ, the NoC being the number of carriers, the NoC_max being maximum number of carriers, the k being a reducing coefficient and the Δ being a control unit value, wherein the k ranges from 0 to 4 and the Δ is 96 for 8K Fast Fourier Transform (FFT), 192 for 16K FFT, 384 for 32K FFT.