Decoding method and decoding apparatus as well as program

A decoding apparatus which sorts received words in the order of the magnitude of the reliability of the received words, performs belief propagation using a parity check matrix diagonalized in the order to update the reliabilities, and repetitively performs the sorting and the belief propagation for the updated values, comprising

• a processing section for performing, when belief propagation is performed using a parity check matrix diagonalized in an order of columns corresponding to symbols having comparatively low reliability values of the received words to update the reliability and the belief propagation is repetitively performed based on the updated reliability, in the second or later cycle of repetition, diagonalization of the parity check matrix for restricted ones of the columns of the parity check matrix.

A program for causing a computer to execute a decoding process for sorting received words in the order of the magnitude of the reliability of the received words, performing belief propagation using a parity check matrix diagonalized in the order to update the reliabilities, and repetitively performing the sorting and the belief propagation for the updated values, comprising

• an inner repeated decoding process step of performing belief propagation using a parity check matrix diagonalized in an order of columns corresponding to symbols having comparatively low reliability values of the received words to update the reliability and repetitively performing the belief propagation based on the updated reliability;
• the inner repeated decoding process step in the second or later cycle of repetition thereof including diagonalization of the parity check matrix for restricted ones of the columns of the parity check matrix.

A decoding method for sorting received words in the order of the magnitude of the reliability of the received words, performing belief propagation using a parity check matrix diagonalized in the order to update the reliabilities, and repetitively performing the sorting and the belief propagation for the updated values, comprising

• a belief propagation step of performing belief propagation of the reliability of the received words;
• the belief propagation at the belief propagation step being performed only using indexes of columns to be updated, pivot columns of the parity check matrix corresponding to the columns and reliability values of all columns.

A decoding apparatus which sorts received words in the order of the magnitude of the reliability of the received words, performs belief propagation using a parity check matrix diagonalized in the order to update the reliabilities, and repetitively performs the sorting and the belief propagation for the updated values, comprising

• a belief propagation section performing belief propagation of the reliability of the received words;
• said belief propagation section performing the belief propagation only using indexes of columns to be updated, pivot columns of the parity check matrix corresponding to the columns and reliability values of all columns.

A program for causing a computer to execute a decoding process for sorting received words in the order of the magnitude of the reliability of the received words, performing belief propagation using a parity check matrix diagonalized in the order to update the reliabilities, and repetitively performing the sorting and the belief propagation for the updated values, comprising:

• a belief propagation step of performing belief propagation of the reliability of the received words;
• the belief propagation at the belief propagation step being performed only using indexes of columns to be updated, pivot columns of the parity check matrix corresponding to the columns and reliability values of all columns.

A decoding apparatus which sorts received words in the order of the magnitude of the reliability of the received words, performs belief propagation using a parity check matrix diagonalized in the order to update the reliabilities, and repetitively performs the sorting and the belief propagation for the updated values, comprising

• processing means for performing, when belief propagation is performed using a parity check matrix diagonalized in an order of columns corresponding to symbols having comparatively low reliability values of the received words to update the reliability and the belief propagation is repetitively performed based on the updated reliability, in the second or later cycle of repetition, diagonalization of the parity check matrix for restricted ones of the columns of the parity check matrix.

A decoding apparatus which sorts received words in the order of the magnitude of the reliability of the received words, performs belief propagation using a parity check matrix diagonalized in the order to update the reliabilities, and repetitively performs the sorting and the belief propagation for the updated values, comprising

• belief propagation means performing belief propagation of the reliability of the received words;
• said belief propagation means performing the belief propagation only using indexes of columns to be updated, pivot columns of the parity check matrix corresponding to the columns and reliability values of all columns.