Apparatus and method for transmitting and receiving a signal in a communication system

An apparatus for transmitting a signal in a communication system, the apparatus comprising:

• an encoder for encoding an information vector using a structured low density parity check (LDPC) coding scheme supporting a first coding rate to generate a first structured LDPC codeword vector including a first part mapped to the information vector and a second part mapped to a parity vector, and encoding the information vector using a structured LDPC coding scheme supporting a second coding rate to generate a second structured LDPC codeword vector including the first part, the second part, and a third part mapped to an additional parity vector;
• a transmitter for transmitting the first structured LDPC codeword vector to a signal reception apparatus and transmitting the third part of the second structured LDPC codeword vector to the signal reception apparatus, when an error is detected by the signal reception apparatus in the first structured LDPC codeword vector;
• and
• a controller for, at initial transmission, performing a control operation of encoding the information vector using a structured LDPC coding scheme supporting the first coding rate to transmit the first structured LDPC codeword vector to the signal reception apparatus, and detecting the error occurred upon reception of the first structured LDPC codeword vector, encoding the information vector using a structured LDPC coding scheme supporting the second coding rate to transmit the third part of the second structured LDPC codeword vector to the signal reception apparatus.