Work In Progress: Improving the intermediate recovery rate of LT codes using a novel degree distribution

The belief propagation (BP) decoding of LT codes on BEC recovers only a small subset of the source symbols when the overhead is smaller than a particular value, at which point an avalanche of decoding takes place. In this paper, a degree distribution modification method is proposed to solve this problem. The encoder adopting the modified degree distribution equals to an encoder adopting the original degree distribution which produces the encoded symbols from the original source symbols and some so-called known symbols, whose values are known to both encoder and decoder. The mean degree of the modified degree distribution is always smaller than that of the original one. Theoretical analysis gives the improvement of the intermediate recovery rate. Simulation results show that the proposed modification method is effective to Robust degree distributions and the fixed degree distribution, on both BEC and AWGN channels.