A method in a communication system, where a systematic code obtained by systematic encoding of information bits having dummy bits inserted and by deletion of the dummy bits from results of the systematic encoding is transmitted. On a receiving side, the deleted dummy bits are inserted into the received systematic code and then decoded. The method includes: deciding a size of dummy bits for insertion into information bits; segmenting the information bits into a number of code blocks when a bit size of the information bits is greater than a stipulated size; inserting dummy bits into each block of the segmented information bits in conformity with a dummy bit insertion pattern; performing systematic encoding of each block of the information bits into which the dummy bits are inserted, and deleting the dummy bits from the results of the systematic encoding to generate a systematic code.