Weighted zigzag decodable fountain codes for unequal error protection

By combining bit-shift and exclusive-or operations, a weighted zigzag decodable fountain code is proposed to achieve an unequal error protection property. In the proposed scheme, the input symbols of different importance levels are first pre-coded into variable nodes using low-density parity-check codes. Then, bit-shift operations prior to exclusive-or are performed on the non-uniformly selected variable nodes to generate encoded symbols. An analysis of the erasure probabilities based on the and-or tree is further introduced. Simulation results show that by appropriately choosing the maximum bit-shift amount, the proposed weighted zigzag decodable fountain codes can successfully recover the more important input symbols prior to the less important ones.