A receiving system and a method of processing broadcast signal. The receiving system includes a signal receiving unit, an equalizer, a turbo decoder, a demultiplexer, first and second error correctors, and a block interleaver. The signal receiving unit receives a broadcast signal, the broadcast signal comprising a data group, which includes mobile service data, a plurality of known data sequences, and signaling data, and demodulating the received broadcast signal. The equalizer channel-equalizes the data group using at least one of the plurality of known data sequences. The turbo decoder turbo-decodes the signaling data contained in the channel-equalized data group. The demultiplexer distinguishes transmission parameter channel (TPC) data and fast information channel (FIC) data from the turbo-decoded signaling data. The first error corrector corrects an error in the TPC data. The block deinterleaver block-deinterleaves the FIC data. The second error corrector corrects an error in the block-deinterleaved FIC data.