Receiving apparatus and de-interleaving method thereof

A broadcast signal transmitting apparatus comprising:

• an encoder configured to encode input bits to generate parity bits based on a low density parity check (LDPC) code, a code rate of the LDPC code being 5/15 and a code length of the LDPC code being 16200 bits;
• an interleaver configured to split a codeword comprising the input bits and the parity bits into a plurality of bit groups, interleave the plurality of bit groups, and interleave bits of the interleaved plurality of bit groups;
• a mapper configured to map the interleaved bits to constellation points for quadrature phase shift keying (QPSK) modulation;
• and
• a transmitter configured to transmit a broadcast signal which is generated based on the constellation points,
• wherein the plurality of bit groups are interleaved based on a following equation:
• Yj=Xπ(j) for (0≤j<Ngroup),
• where Xj is a j-th bit group among the plurality of bit groups, Yj is a j-th bit group among the interleaved plurality of bit groups, Ngroup is a number of the plurality of bit groups and π(j) denotes an interleaving order for the interleaving, and
• wherein the π(j) is represented as follows:
• Order of interleaving
• π(j) (0 ≤ j < 45)
• Code
• j
• 0
• 1
• 2
• 3
• 4
• 5
• 6
• 7
• 8
• 9
• 10
• 11
• 12
• 13
• 14
• 15
• 16
• 17
• 18
• 19
• 20
• 21
• 22
• Rate
• 23
• 24
• 25
• 26
• 27
• 28
• 29
• 30
• 31
• 32
• 33
• 34
• 35
• 36
• 37
• 38
• 39
• 40
• 41
• 42
• 43
• 44
• 5/15
• π(j)
• 35
• 7
• 29
• 11
• 14
• 32
• 38
• 28
• 20
• 17
• 25
• 39
• 19
• 4
• 1
• 12
• 10
• 30
• 0
• 44
• 43
• 2
• 21
• 5
• 13
• 34
• 37
• 23
• 15
• 36
• 18
• 42
• 16
• 33
• 31
• 27
• 22
• 3
• 6
• 40
• 24
• 41
• 9
• 26
• 8