Patent ID: 7519895

Claim:
A channel encoding apparatus comprising: a first low density parity check (LDPC) encoder of generating a first component LDPC code according to information bits; an interleaver for interleaving the information bits according to an interleaving rule; a second LDPC encoder for generating a second component LDPC code according to the interleaved information bits; and a controller for performing a control operation so the information bits, the first component LDPC code, and the second component LDPC code are combined according to a code rate, wherein the interleaving rule is one of a plurality of interleaving rules comprising: a first interleaving rule set so variable nodes with a low degree in a factor graph of the first component LDPC code are mapped to variable nodes with a high degree in a factor graph of the second component LDPC code; a second interleaving rule set so variable nodes with a low degree in a factor graph of the second component LDPC code are mapped to variable nodes with a high degree in a factor graph of the first component LDPC code; a third interleaving rule set so variable nodes with a short mean cycle in a factor graph of the first component LDPC code are mapped to variable nodes with a long mean cycle in a factor graph of the second component LDPC code; a fourth interleaving rule set so variable nodes with a short mean cycle in a factor graph of the second component LDPC code are mapped to variable nodes with a long mean cycle in a factor graph of the first component LDPC code; a fifth interleaving rule set so variable nodes constituting a cycle with a short length in a factor graph of the first component LDPC code are mapped to variable nodes in a factor graph of the second component LDPC code so the variable nodes are included in different cycles in the factor graph of the second component LDPC code; and a sixth interleaving rule set so variable nodes constituting a cycle with a short length in a factor graph of the second component LDPC code are mapped to variable nodes in a factor graph of the first component LDPC code so the variable nodes are included in different cycles in the factor graph of the first component LDPC code, wherein a mean cycle is a value determined by dividing a sum of lengths of all cycles to which the variable nodes belong by a degree thereof, the short mean cycle is a mean cycle length less than or equal to a threshold mean cycle length, the long mean cycle is a mean cycle greater than the threshold mean cycle length, the short length is a cycle length less than or equal to a threshold cycle length, the low degree is a degree less than or equal to a threshold degree, and the high degree is a degree greater that the threshold degree.