Zigzag Decodable Online Fountain Codes With High Intermediate Symbol Recovery Rates

In this paper, a new class of online fountain codes is proposed to provide high intermediate symbol recovery rates (ISRRs) with low overhead. The encoder consists of two phases. In the first phase, a zigzag decodable online fountain (ZDOF) is proposed to provide a high ISRR. We utilize the characteristics of zigzag decodable codes so that the online fountain codes start decoding in the first phase without having to wait for the receipt of symbols of degree one. In the second phase, the buffer decoding method (BDM) is proposed to utilize a buffer to hold discarded symbols so as to generate useful symbols and improve the decoding performance. In addition, we provide a theoretical analysis based on random graph theory to analyze the performance of the proposed scheme. The theoretical analysis and simulation results show that the proposed scheme outperforms conventional online fountain codes, and that the buffer size does not have to be large.