A modified design of Raptor codes for small message length

Raptor codes are a class of fountain codes which can get capacity-achieving performance over various channels. Traditional Raptor codes can obtain perfect performance for large message length. However, small message length can cause significant performance deterioration. In this paper, a modified design of Raptor codes for small message length is proposed. The proposed Raptor codes are obtained by pre-coding the information symbols by low rate low-density parity-check codes and utilizing a low constant average degree distribution with high intermediate symbol recovery rate. Simulation results demonstrate that, although traditional Raptor codes can get good asymptotical performance, our proposed Raptor codes outperform traditional Raptor codes for small message length over binary erasure channels and binary input additive white Gaussian noise channels.