Patent ID: 7600173

Claim:
A retransmission control method for a communications device that transmits a codeword to another communications device using low-density parity check codes as error correcting codes, the retransmission control method comprising: generating N parity check matrices optimized at N code rates, respectively, where N is a positive integer, wherein a k-th code rate is lower than a (k−1)-th code rate, where k is a positive integer from 2 to N; converting a first parity check matrix so that the first parity check matrix contains a check symbol generator matrix; generating a generator matrix containing the check symbol generator matrix; transmitting the codeword generated by using the generator matrix to the another communications device; generating, when the communications device receives a negative acknowledgment from the another communications device in response to the codeword, a first additional parity by using a second parity check matrix; retransmitting the first additional parity to the another communications device; generating, when the communications device receives a negative acknowledgment from the another communications device in response to a (k−1)-th additional parity generated by using a k-th parity check matrix, a k-th additional parity by using the (k+1)-th parity check matrix; and retransmitting the k-th additional parity to the another communications device.