Transmitter and method for generating additional parity thereof
A transmitter is provided. The transmitter includes: a Low Density Parity Check (LDPC) encoder configured to encode input bits to generate an LDPC codeword including the input bits and parity bits to be transmitted in a current frame; a parity permutator configured to interleave the parity bits and group-wise interleave a plurality of parity bit groups configuring the interleaved parity bits based on a group-wise interleaving pattern including a first pattern and a second pattern to perform parity permutation; a puncturer configured to puncture at least some of the group-wise interleaved parity bit groups; and an additional parity generator configured to select at least some of the punctured parity bit groups to generate additional parity bits to be transmitted in a previous frame of the current frame, based on the first pattern and the second pattern.
1. A television (TV) broadcasting signal transmitting method of a TV broadcasting signal transmitting apparatus for transmitting layer 1 (L 1 ) signaling information and TV broadcasting data, the TV broadcasting transmitting apparatus being operable in a mode among a plurality of modes, the 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 6/15 and a code length of the mode being 16200 bits, wherein the input bits are based on the L 1 signalling information for the TV broadcasting data;
interleaving the parity bits;
splitting a codeword into a plurality of bit groups, the codeword comprising the information bits and the interleaved parity bits;
interleaving bit groups including the interleaved parity bits among the plurality of bit groups based on a 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 bits of the interleaved codeword based on the calculated number;
mapping the input bits and remaining parity bits of the interleaved codeword after the puncturing onto constellation points, wherein the constellation points are based on a quadrature phase shift keying (QPSK) of the mode;
generating a TV broadcast signal based on the constellation points; and
transmitting the TV broadcast signal,
wherein bits of 35 th , 39 th , 20 th , 18 th , 43 rd , 31 st ,36 th , 38 th ,22 nd , 33 rd , 28 th , and 41 st bit groups among the plurality of bit groups are punctured, and
wherein bit groups to be punctured are determined based on the permutation order of the mode and the calculated number.
2. The method of claim 1 , wherein the encoding encodes 6480 input bits to generate 9720 parity bits according to a code rate of 6/15.
3. The method of claim 1 , further comprising:
generating additional parity bits by selecting one or more bits from among the punctured parity bits,
wherein the additional parity bits are transmitted in a first frame,
wherein non-punctured parity bits of the interleaved codeword are transmitted in a second frame, and
wherein the first frame is transmitted prior to the second frame.