Improved systematic fountain codes in AWGN channel

Abstract

Fountain codes are typically defined solely based on the right degree distributions which are Soliton or Soliton-like in most cases. In this paper, we consider Fountain encoders for the Gaussian channel and improve their performance by shaping the resulting left degree distributions away from Poisson. The proposed Fountain encoders achieve lower left degree variance at the same average degree. This in turn improves the growth of the so-called ripple in the BP decoding. The new encoders outperform the traditional ones in terms of overhead, error rate, and decoding complexity.