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 transmitting apparatus comprising:
a zero padder configured to fill information bits with input bits and one or more zero padding bits, if a number of the input bits is less than a number of the information bits;
an encoder configured to encode the information bits to generate parity bits based on a low density parity check (LDPC) code, a code rate of the LDPC code being 6/15 and a code length of the LDPC code being 16200 bits;
a parity permutator configured to interleave the parity bits, split a codeword into a plurality of bit groups, the codeword comprising the information bits and the interleaved parity bits, and interleave bit groups including the interleaved parity bits among the plurality of bit groups based on a permutation order to provide an interleaved codeword;
a puncturer configured to calculate a number of the parity bits to be punctured, and puncture one or more parity bits of the interleaved codeword based on the calculated number;
a mapper configured to map the input bits and remaining parity bits of the interleaved codeword after the puncturing to constellation points, wherein the constellation points are based on quadrature phase shift keying (QPSK); and
a transmitter configured to transmit a signal which is generated based on the constellation points,
wherein bits of bit groups having indices of 35, 39, 20, 18, 43, 31, 36, 38, 22, 33, 28 and 41 among the plurality of bit groups are punctured, and
wherein bit groups to be punctured are determined based on the permutation order and the calculated number.
2. The transmitting apparatus of claim 1 , wherein a number of the parity bits is 9720.
3. The transmitting apparatus of claim 1 , wherein the plurality of bit groups comprise 45 bit groups having indices of 0 to 44.
4. A receiving apparatus comprising:
a demodulator configured to demodulate a signal received from a transmitting apparatus to generate values based on quadrature phase shift keying (QPSK);
an inserter configured to insert predetermined values corresponding to parity bits punctured in the transmitting apparatus;
a parity depermutator configured to split the values and the inserted predetermined values into a plurality of groups, and deinterleave some groups from among the plurality of groups based on a permutation order to provide the plurality of groups in which the some groups are deinterleaved; and
a decoder configured to decode values of the plurality of groups in which the some groups are deinterleaved based on a low density parity check (LDPC) code, a code rate of the LDPC code being 6/15 and a code length of the LDPC code being 16200 bits,
wherein groups having indices of 35, 39, 20, 18, 43, 31, 36, 38, 22, 33, 28 and 41 from among the plurality of groups in which the some groups are deinterleaved comprise at least a part of the predetermined values.
5. The receiving apparatus of claim 4 , wherein a number of the plurality of groups is 45.
6. The receiving apparatus of claim 4 , wherein the deinterleaved some groups comprise 45 groups having indices of 0 to 44.