A broadcast signal transmitter is provided that includes an input formatter, a Forward Error Correction (FEC) encoder, a constellation mapper, a time interleaver, a framer and a waveform generator. The input formatter input processes input data to output Physical Layer Pipe (PLP) data. The FEC encoder performs FEC encoding on the PLP data. The constellation mapper performs constellation mapping on the PLP data. The time interleaver is configured to time interleave the PLP data. The framer is configured to generate a signal frame comprising the PLP data. The waveform generator is configured to generate a transmission broadcast signal comprising the signal frame. A number of carriers of the signal frame is determined by the equation: NoC=NoC_max−k*Δ, wherein NoC is the number of carriers, NoC_max is a maximum number of carriers, k is a reducing coefficient, and Δ is a control unit value.