Transmitter and parity permutation method thereof

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

• encoding 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;
• splitting a codeword comprising the information bits and the parity bits into a plurality of bit groups;
• obtaining a permutation order of the mode from among a plurality of permutation orders;
• interleaving the plurality of bit groups using the permutation order of the mode, to provide an interleaved codeword;
• calculating a number of parity bits to be punctured based on a number of the information bits;
• puncturing one or more parity bits of the interleaved codeword based on the calculated number;
• mapping 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;
• generating a broadcast signal based on the constellation points, and
• transmitting the broadcast signal,
• wherein the plurality of bit groups are interleaved based on following equations:
• Yj=Xj,0≤j<Kldpc/360
• Yj=Xπp(j),Kldpc/360≤j<Ngroup,
• where Yj represents a j-th bit group among the interleaved plurality of bit groups, Xj represents a j-th bit group among the plurality of bit groups, Kldpc represents a number of the information bits, Ngroup represents a number of the plurality of bit groups, and π9(j) represents the pet order of the mode, and
• wherein the πp(j) is represented as follows:
• Order of Group-Wise Interleaving
• πp(f) (9 ≤ j < 45)
• πp(9)
• πp(10)
• πp(11)
• πp(12)
• πp(13)
• πp(14)
• πp(15)
• πp(21)
• πp(22)
• πp(23)
• πp(24)
• πp(25)
• πp(26)
• πp(27)
• Ngroup
• πp(33)
• πp(34)
• πp(35)
• πp(36)
• πp(37)
• πp(38)
• πp(39)
• 45
• 9
• 31
• 23
• 10
• 11
• 25
• 43
• 26
• 18
• 37
• 15
• 13
• 17
• 35
• 22
• 40
• 19
• 32
• 38
• 41
• 30
• Order of Group-Wise Interleaving
• πp(f) (9 ≤ j < 45)
• πp(16)
• πp(17)
• πp(18)
• πp(19)
• πp(20)
• πp(28)
• πp(29)
• πp(30)
• πp(31)
• πp(32)
• Ngroup
• πp(40)
• πp(41)
• πp(42)
• πp(43)
• πp(44)
• 45
• 29
• 36
• 16
• 27
• 34
• 21
• 20
• 24
• 44
• 12
• 33
• 14
• 28
• 39
• 42