Transmitting apparatus and interleaving method thereof

An interleaving method comprising:

• encoding input bits to generate parity bits based on a low density parity check (LDPC) code according to a code rate of 10/15 and a code length of 64800 bits;
• interleaving the parity bits;
• splitting a codeword into a plurality of bit groups, the codeword comprising the input bits and the interleaved parity bits;
• interleaving the plurality of bit groups to provide an interleaved codeword;
• generating modulation symbols by modulating the interleaved codeword according to 16-quadrature amplitude modulation (QAM);
• and
• transmitting a signal based on the modulation symbols generated by the modulating to a receiving device,
• wherein the plurality of bit groups comprise 180 bit groups,
• wherein each of the plurality of bit groups comprises 360 bits,
• wherein the plurality of bit groups are interleaved based on a following equation:
• Yj=Xπ(j) for (0≦j<Ngroup),
• where Xπ(j) is a π(j)th bit group among the plurality of bit groups, Yj is a jth bit group among the interleaved plurality of bit groups, Ngroup is a total number of the plurality of bit groups, and π(j) denotes a permutation order for the interleaving, and
• wherein the π(j) is represented as follows: