Transmitter and method for generating additional parity thereof

A broadcasting signal transmitting apparatus which is operable in a mode among a plurality of modes, the broadcasting signal transmitting apparatus comprising:

• an encoder configured to encode information bits comprising input bits to generate parity bits based on a low density parity check (LDPC) code having a code rate of the mode being 3/15 and a code length of the mode being 16200 bits, wherein the input bits are based on signalling information about a broadcasting data;
• a parity permutator configured to split a codeword into a plurality of bit groups, the codeword comprising the information bits and the parity bits, and interleave bit groups including the parity bits among the plurality of bit groups based on a permutation order of the mode, to provide an interleaved codeword;
• a puncturer configured to calculate a number of parity bits to be punctured based on a number of the information bits, and puncture bits of the interleaved codeword based on the calculated number;
• a mapper configured to map the input bits and parity bits of the interleaved codeword remaining after the puncturing onto constellation points, wherein the constellation points are generated based on a quadrature phase shift keying (QPSK) of the mode;
• a signal generator configured to generate a broadcast signal based on the constellation points using an orthogonal frequency division multiplexing(OFDM) scheme;
• and
• a transmitter configured to transmit the broadcast signal,
• wherein bits of 20th, 24th, 44th, 12th, 22th, 40th, 19th, 32th, 38th, 41th, 30th, 33th, 14th, 28th, 39th and 42th bit groups among the plurality of bit groups are punctured, and
• wherein the bit groups to be punctured are determined based on the permutation order of the mode and the calculated number.