Optimized irregular Gallager codes for OFDM transmission

We present an optimized channel coding scheme for OFDM transmitter. Traditional coding methods use regular codes, in the sense that each bit participates in the same way to the channel encoding. Our approach consists in using a priory assumption on the channel available at the transmitter in order to optimize the coding scheme. We have considered the irregular Gallager block codes in our study. Simulations provide evidence of the usefulness of our approach with a gain of 2 dB at a bit error rate equal to 10/sup -5/ for optimized irregular coding scheme compared to regular one.