Retransmission method and apparatus using multiple mother codes in a system using HARQ

A Hybrid Automatic Repeat reQuest (HARQ) retransmission method in a communication system, the method comprising:

• defining, by a controller, multiple mother codes;
• selecting one of code rates of the mother codes as an initial transmission code rate;
• determining, by the controller, a retransmission unit for each of codeword packets coded with code rates corresponding to the mother codes;
• and
• retransmitting, by the controller, corresponding codeword packets in units of the determined retransmission units in response to a retransmission request
• wherein the determining of the retransmission unit comprises if information word symbols of the codeword packets are equal in size, dividing each of the codeword packets into sub-packets coded with an initial transmission code rate selected for each individual codeword packet, and determining each of the divided sub-packets as a retransmission unit of the corresponding codeword packet,
• wherein the retransmitting of the corresponding codeword packets comprises upon failure to receive an acknowledgement signal (ACK) after a number of transmissions for the sub-packet has reached a maximum number of transmissions, stopping the retransmission and reselecting one of code rates of the mother codes as an initial transmission code rate according to a channel condition at the stop time, dividing each of the codeword packets into sub-packets coded with the reselected initial transmission code rate, and sequentially retransmitting the divided sub-packets one by one in response to a retransmission request.