Bit interleaver for low-density parity check codeword having length of 16200 and code rate of 2/15 and 256-symbol mapping, and bit interleaving method using same

A method of transmitting a broadcast signal, comprising:

• storing a low-density parity check (LDPC) codeword having a length of 16200 and a code rate of 2/15;
• generating an interleaved codeword by interleaving the LDPC codeword on a bit group basis, the size of the bit group corresponding to a parallel factor of the LDPC codeword;
• storing the interleaved codeword corresponding to 256-symbol mapping,
• performing 256-symbol mapping for generating a broadcast signal;
• and
• transmitting the broadcast signal over a physical channel,
• wherein the interleaving is performed using the following equation using permutation order:
• Yj=Xπ(j) 0≤j<Ngroup
• where Xπ(j) is the π(j)th bit group, Yj is an interleaved j-th bit group, and π(j) is a permutation order for bit group-based interleaving,
• wherein the permutation order corresponds to an interleaving sequence represented by the following
• interleaving sequence={31 3 38 9 34 6 4 18 15 1 21 19 42 20 12 13 30 26 14 2 10 35 28 44 23 11 22 16 29 40 27 37 25 41 5 43 39 36 7 24 32 17 33 8 0},
• wherein the interleaved codeword is generated by the interleaving using the interleaving sequence on the bit group basis before performing the 256-symbol mapping so as to distribute burst errors occurring in the transmission signal transmitted over the physical channel.