Low-density parity-check code decoder and decoding method

A low-density parity-check (LDPC) code decoder, for de-mapping a set of initial log-likelihood ratio (LLR) outputted by a de-mapping circuit, the decoder comprising:

• a first buffer, receiving and storing the set of initial LLR from the de-mapping circuit;
• a second buffer, receiving and storing the set of initial LLR from the first buffer;
• and
• a decoding circuit, performing steps of:
• receiving the set of initial LLR from the second buffer;
• performing a decoding operation on the set of initial LLR to calculate a set of intermediate LLR, wherein a data size of the set of intermediate LLR is larger than that of the set of initial LLR;
• determining whether the set of intermediate LLR is converged;
• when it is determined that the set of intermediate LLR is not yet converged, storing the set of intermediate LLR back into the second buffer, wherein a storage space of the second buffer is greater than that of the first buffer;
• and
• when it is determined that the set of intermediate LLR is converged, outputting the set of intermediate LLR as a set of decoded LLR.