Duplicated zigzag decodable fountain codes with the unequal error protection property

A low overhead fountain code with an unequal error protection property, called duplicated-zigzag unequal-error-protection (DZ-UEP) code, is proposed. Using low-density-parity-check codes of different code rates, input symbols of different important levels are first precoded into variable nodes. Based on predefined duplication factors, these variable nodes of different important levels are then duplicated to produce a group of duplicated symbols. Defining a window as the set of duplicated symbols of the same importance level, a window is randomly selected with a probability proportional to the number of symbols it contains. Duplicated symbols in the selected window and those of the more importance levels are further repeated. Subsequently based on all the repeated symbols formed, encoded symbols are derived using exclusive-or and bit-level shift operations. Theoretical analysis on the proposed DZ-UEP scheme is performed. Simulation results have also verified that input symbols with two or three levels of importance can be provided with unequal error protection under the proposed scheme.