Bit interleaver for low-density parity check codeword having length of 16200 and code rate of 2/15 and 64-symbol mapping, and bit interleaving method using same
A bit interleaver, a bit-interleaved coded modulation (BICM) device and a bit interleaving method are disclosed herein. The bit interleaver includes a first memory, a processor, and a second memory. The first memory stores a low-density parity check (LDPC) codeword having a length of 16200 and a code rate of 2/15. The processor generates an interleaved codeword by interleaving the LDPC codeword on a bit group basis. The size of the bit group corresponds to a parallel factor of the LDPC codeword. The second memory provides the interleaved codeword to a modulator for 64-symbol mapping.
1. A bit group-unit interleaver, comprising:
a first memory configured to store a low-density parity check (LDPC) codeword having a length of 16200 and a code rate of 2/15;
a processor configured to generate 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; and
a second memory configured to transmit the interleaved codeword corresponding to a modulator for 64-symbol mapping for generating a transmission signal, the transmission signal being transmitted over a wireless channel,
wherein the interleaving is performed using the following equation using permutation order:
Y j =X π(j) 0≦ j≦N group
where X π(j) is a π(j)th bit group, Y j is an interleaved j-th bit group, N group is the number of bit groups obtained by dividing the LDPC codeword into the bit groups, 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 equation:
interleaving sequence={7 11 4 38 19 25 2 43 15 26 18 14 9 29 44 32 0 5 35 10 1 12 6 36 21 33 37 34 3 31 20 16 40 23 41 22 30 39 13 24 17 42 28 8 27}, and
wherein the interleaving sequence is for a case where the 64-symbol mapping is employed and the interleaved codeword interleaved by the interleaving sequence distributes burst errors occurring in the wireless channel for the transmission signal, and a modulated signal output from the modulator corresponds to the transmission signal, the transmission signal being transmitted to a reception device.
2. The bit group-unit interleaver of claim 1 , wherein the 64-symbol mapping is a Non-Uniform Constellation (NUC) symbol mapping which corresponds to 64 constellations.
3. The bit group-unit interleaver of claim 2 , wherein the parallel factor is 360, and the bit group includes 360 bits.
4. The bit group-unit interleaver of claim 3 , wherein the LDPC codeword is represented by (u 0 , u 1 , . . . , u N ldpc −1 ) (where N ldpc is 16200), and is divided into 45 bit groups each including 360 bits, as in the following equation:
X j ={u k |360× j≦k< 360×( j+ 1),0≦ k<N ldpc } for 0≦ j<N group
where X j is an j-th bit group, N ldpc is 16200, and N group is 45.