Investigation on Digital Fountain Codes over Erasure Channels and Additive White Gaussian Noise Channels
Weizheng Huang · OhioLink ETD Center (Ohio Library and Information Network) · 2012
As newly invented packet erasure codes, digital fountain codes (LT codes and Raptor codes) under iterative message passing decoding can work very efficiently in computer networks for large scale data distribution (e.g., greater than 6.4×10 4 bits) without knowledge of the states of individual lossy channels, regardless of the propagation modes.Some researchers have moved further and found that fountain codes can achieve near capacity performance over AWGN channels.However, little literature on the research of a fountain code's decoding overhead had been obtained, especially for short and moderate-length data (e.g., smaller than 1×10 4 bits).We are interested in the overheads of fountain codes of different kinds or designs because a harsh communication condition can hurt some decoding schemes by limiting the number of received encoded symbols.Moreover, we have only found in literature studies of Raptor codes whose precodes are rate 0.98 left-regular, right-Poisson LDPC codes, but performance with other types of pre-codes is unknown.In this dissertation, we review conventional fountain codes and describe two system models for packet erasure fountain codes and bit error correcting fountain codes under message passing decoding over binary erasure channels or AWGN channels.We assess Raptor codes with different kinds of pre-codes, introduce maximum likelihood decoding to both LT codes and Raptor codes, and propose a hybrid