Transmitter and signal processing method thereof

A broadcast signal generating and transmitting method, the method comprising:

• generating a codeword comprising information bits, first parity bits and second parity bits by encoding the information bits based on a parity check matrix of a low density parity check (LDPC) code;
• interleaving the codeword;
• mapping bits of the interleaved codeword onto constellation points;
• generating a broadcast signal based on the constellation points using an orthogonal frequency division multiplexing (OFDM) scheme;
• and
• transmitting the broadcast signal for a receiver,
• wherein the parity check matrix comprises an information matrix part and a parity matrix part,
• wherein the information matrix part comprises a first information submatrix with a quasi-cyclic structure and a second information submatrix with the quasi-cyclic structure,
• wherein the parity matrix part comprises a first parity submatrix with a dual diagonal matrix structure and a second parity submatrix with an identity matrix structure,
• wherein the first parity bits are generated based on the first parity submatrix, and
• wherein the second parity bits are generated based on the second parity submatrix.