  Fountain codes are erasure correcting codes realizing reliable communication
systems for the multicast on the Internet. The zigzag decodable fountain (ZDF)
code is one of generalization of the Raptor code, i.e, applying shift operation
to generate the output packets. The ZDF code is decoded by a two-stage
iterative decoding algorithm, which combines the packet-wise peeling algorithm
and the bit-wise peeling algorithm. By the bit-wise peeling algorithm and shift
operation, ZDF codes outperform Raptor codes under iterative decoding in terms
of decoding erasure rate and overhead. However, the bit-wise peeling algorithm
spends long decoding time. This paper proposes a fast bit-wise decoding
algorithm for the ZDF codes. Simulation results show that the proposed
algorithm drastically reduces the decoding time compared with the existing
algorithm.
