Transmission apparatus and method, and reception apparatus and method

1. A reception apparatus comprising:

a reception circuit configured to receive a modulated signal from a transmission apparatus;

a demodulating circuit configured to demodulate the modulated signal to generate second coded data blocks; and

a decoding circuit configured to low-density parity-check decode the second coded data blocks,

wherein the modulated signal has been generated by the transmission apparatus performing an encoding process, the encoding process including:

adding known information data bits to information data bits to generate first data blocks;

performing low-density parity-check encoding on the first data blocks to generate first coded data blocks including parity data blocks such that the first coded data blocks satisfy a first code rate;

removing the known information data bits from the first coded data blocks to generate the second coded data blocks, the second coded data blocks satisfying a second code rate different from the first code rate; and

modulating the second coded data blocks using a modulation scheme to generate the modulated signal, wherein

a number of the known information data bits depends on a number of the information data bits such that the first code rate is fixed regardless of the number of the information data bits.

2. The reception apparatus according to claim 1 , wherein the low-density parity-check decoding comprises:

performing a row processing computing using a check matrix corresponding to parity check polynomials used for the low-density parity-check encoding;

performing a column processing computing using the check matrix; and

estimating a codeword using computation results in the row processing computing and the column processing computing.

3. The reception apparatus according to claim 1 , wherein

the first code rate is ½ and the second code rate is ⅓,

low-density parity check convolutional code of the first code rate and low-density parity check convolutional code of the second code rate have a time varying period of 3,

the low-density parity check convolutional code of the first code rate is defined based on:

a first parity check polynomial in which (a1%3, a2%3, a3%3) and (b1%3, b2%3, b3%3) are any of (0, 1, 2), (0, 2, 1), (1, 0, 2), (1, 2, 0), (2, 0, 1) and (2, 1, 0) of a parity check polynomial represented by equation 1-1;

a second parity check polynomial in which (A1%3, A2%3, A3%3) and (B1%3, B2%3, B3%3) are any of (0, 1, 2), (0, 2, 1), (1, 0, 2), (1, 2, 0) and (2, 0, 1), (2, 1, 0) of a parity check polynomial represented by equation 1-2; and

a third parity check polynomial in which (a1%3, a2%3, a3%3) and (01%3, 02%3, 03%3) are any of (0, 1, 2), (0, 2, 1), (1, 0, 2), (1, 2, 0), (2, 0, 1) and (2, 1, 0) of a parity check polynomial represented by equation 1-3, wherein c % d (where c and d are any integers) represents a remainder after dividing c by d, the low-density parity-check encoding on the first data blocks is performed by:

inserting, using an encode circuit, the known information data bits into 3k pieces of information Xj (where j's are any indexes of 6i, 6i+1, 6i+2, . . . ,6(i+k−1)+3, 6(i+k−1)+4, 6(i+k−1)+5, and j's are different from each other) of 6k bits of information X 6i , X 6i+1 , X 6i+2 , X 6i+3 , X 6i+4 , X 6i+5 , . . . , X 6(i+k−1) , X 6(i+k−1)+1 , X 6(i+k−1)+2 , X 6(i+k−1)+3 , X 6(i+k−1)+4 , X 6(i+k−1)+5 such that, of remainders after dividing values of the 3k different indexes j's by 3, a number of remainders which become 0 is k, a number of remainders which become 1 is k and a number of remainders which become 2 is k, the 6k bits of information made by extracting information from information part of one period of encoded outputs including the information part and parity part, and by arranging the extracted information in output order of the encoded outputs, the one period of the encoded outputs composed of 12k (k is a natural number) bits of the information part and the parity part which are the encoded outputs using low-density parity check convolutional code of a coding rate of ½; and

obtaining, using the encode circuit, the parity part from the information including the known information data bits,

wherein:

the equation 1-1 is

D a1 +D a2 +D a3 ) X ( D )+( D b1 +D b2 +D b3 ) P ( D )=0;

the equation 1-2 is

( D A1 +D A2 +D A3 ) X ( D )+( D B1 +D B2 +D B3 ) P ( D )=0;

the equation 1-3 is

( D α1 +D α2 +D α3 ) X ( D )+( D β1 +D β2 +D β3 ) P ( D )=0;

where:

X(D) is a polynomial representation of information X and P(D) is a parity polynomial representation;

a1, a2 and a3 are integers (where a1≠a2≠a3) and b1, b2 and b3 are integers (where b1≠b2≠b3);

A1, A2 and A3 are integers (where A1≠A2≠A3) and B1, B2 and B3 are integers (where B1≠B2≠B3); and

α1, α2 and α3 are integers (where α1≠α2≠α3) and β1, β2 and β3 are integers (where β1≠β2≠β3).

4. The reception apparatus according to claim 1 , wherein the known information data bits are zeroed bits.