Method of transmitting signal

A method of transmitting a signal, comprising:

• defining data to be transmitted to a mobile station through a relay station;
• creating a data block having an integrated slot by making the number of slots of the data block for forward error correction encoding an integer;
• creating an encoded signal by encoding a plurality of data blocks with a predetermined code rate;
• creating a first modulated signal by modulating the encoded signal;
• and
• transmitting the first modulated signal to the mobile station through the relay station,
• wherein the creating of a data block includes:
• selecting a code rate and a modulation method for the data to be transmitted to the relay station;
• calculating the number of slots of the data block according to the selected code rate and the modulation method;
• and
• making the number of slots the integer by multiplying the least common multiple of denominators of the number of slots according to the code rate and the modulation method by the number of slots.