Data decoding method using LDPC code as error correction code and data transmitting method thereof

A data transmitting method using a low-density parity check (LDPC) code as an error correction code, comprising steps:

• providing a parity check matrix of an LDPC code, wherein said parity check matrix has a size of (m1+m2)×(n1+n2);
• using an encoder to encode an input data having K bits in a sending side according to said parity check matrix to generate a first block code having a block length of (n1+n2) bits;
• transmitting n1 bits of said first block code from said sending side through a transmission channel to a receiving side, wherein n2 bits of said first block code are not transmitted;
• and
• said receiving side receiving n1 bits of said first block code, and a decoder using said parity check matrix to undertake a decoding operation of received said n1 bits of said first block code and perform iterative operations to generate a second block code having (n1+n2) bits,
• wherein K, m1, m2, n1 and n2 are positive integers and K is smaller than (n1+n2), and
• wherein said decoder uses a signed number including a sign bit and a numeral value to express reliability information of each bit of said first block code, and assigns a given sign bit and a given value to each of said n2 bits of said first block code, which are not transmitted;
• during said decoding operation, if said numeral value of said reliability information is said given value, only said given sign bit participates in said iterative operations;
• during said decoding operation, if said numeral value of said reliability information is not said given value, said sign bit and said numeral value participate in said iterative operations.