Coding device, decoding device, coding method, decoding method, and communication system

A decoding device comprising:

• a decoding unit operable to generate a decoded bit sequence by performing decode processing on a pre-decoding bit sequence input thereto, the decode processing complying with an applied coding method that utilizes a quasi-cyclic code;
• a checking unit operable to check whether the decoded bit sequence is judged as an error-free code word by a parity check of the coding method;
• a judging unit operable to judge whether at least one insertion position in the decoded bit sequence holds at least one predetermined bit value, wherein according to the coding method, a bit position in a first code word which corresponds to the insertion position is predetermined to hold a different bit value from a bit position in a second code word which corresponds to the insertion position, the first code word being generated by a transmitter device according to the coding method, and the second code word being judged as an error-free code word by the parity check but being different from the first code word by the minimum Hamming distance;
• and
• an error detecting unit operable to, in a case where the judging unit judges in the negative, judge that the decoded bit sequent is erroneous even when a result of the checking by the checking unit shows that the decoded bit sequence has been judged as the error-free code word by the parity check.

A coding method for coding an information bit sequence, comprising the steps of:

• (A) determining, in accordance with an applied coding method that utilizes a quasi-cyclic code, at least one bit position in the information bit sequence as an insertion position into which a predetermined bit value is to be inserted, wherein a bit position in a first code word which corresponds to the insertion position holds a different bit value from a bit position in at least one second code word which corresponds to the insertion position, the first code word being obtained by coding the information bit sequence in accordance with the coding method, the second code word being judged as an error-free code word by a parity check of the coding method but being different from the first code word by the minimum Hamming distance;
• (B) generating a pre-coding bit sequence by inserting the predetermined bit value into the insertion position of the information bit sequence;
• and
• (C) generating a third code word by coding the pre-coding bit sequence in accordance with the coding method.

A decoding method comprising the steps of:

• (A) generating a code word by decoding a received signal in accordance with an applied coding method that utilizes a quasi-cyclic code;
• (B) checking whether the code word generated in the step (A) is an error-free code word by a parity check of the coding method;
• (C) judging whether at least one insertion position in the generated code word holds at least one predetermined bit value, wherein according to the coding method, a bit position in a first code word which corresponds to the insertion position is predetermined to hold a different bit value from a bit position in a second code word which corresponds to the insertion position, the first code word being generated by a transmitter device according to the coding method, and the second code word being judged as an error-free code word by the parity check but being different from the first code word by the minimum Hamming distance;
• and
• (D) in a case where the judgment in the step (C) is in the negative, judging that the generated code word is erroneous even when a result of the checking by the step (B) shows that the generated code word has been judged as the error-free code word by the parity check.

A communication system including a transmitter device and a receiver device,

• the transmitter device, which codes an information bit sequence and transmits the coded information bit sequence, comprising:
• a determining unit operable to, in accordance with an applied coding method that utilizes a quasi-cyclic code, determine at least one bit position in the information bit sequence as an insertion position into which a predetermined bit value is to be inserted, wherein a bit position in a first code word which corresponds to the insertion position holds a different bit value from a bit position in at least one second code word which corresponds to the insertion position, the first code word being obtained by coding the information bit sequence in accordance with the coding method, the second code word being judged as an error-free code word by a parity check of the coding method but being different from the first code word by the minimum Hamming distance;
• an inserting unit operable to generate a pre-coding bit sequence by inserting the predetermined bit value into the insertion position of the information bit sequence;
• a coding unit operable to generate a third code word by coding the pre-coding bit sequence in accordance with the coding method;
• and
• a transmitting unit operable to transmit a wireless signal containing the third code word,
• the receiver device comprising:
• a receiving unit operable to receive the wireless signal;
• a decoding unit operable to generate a code word by decoding the received signal in accordance with the coding method;
• a checking unit operable to check whether the code word generated by the decoding unit is judged as an error-free code word by the parity check of the coding method;
• a judging unit operable to judge whether at least one insertion position in the generated code word holds at least one predetermined bit value, wherein according to the coding method, a bit position in a first code word which corresponds to the insertion position is predetermined to hold a different bit value from a bit position in a second code word which corresponds to the insertion position, the first code word being generated by the transmitter device according to the coding method, and the second code word being judged as an error-free code word by the parity check but being different from the first code word by the minimum Hamming distance;
• and
• an error detecting unit operable to, in a case where the judging unit judges in the negative, judge that the generated code word is erroneous even when a result of the checking by the checking unit shows that the generated code word has been judged as the error-free code word by the parity check.