On Parity-Check Collections for Iterative Erasure Decoding That Correct all Correctable Erasure Patterns of a Given Size

Recently there has been interest in the construction of small parity-check sets for iterative decoding of the Hamming code with the property that each uncorrectable (or stopping) set of size three is the support of a codeword and hence uncorrectable anyway. Here we reformulate and generalize the problem and improve on this construction. We show that a parity-check collection that corrects all correctable erasure patterns of size m for the Hamming code with codimension r provides, in fact, for all codes of codimension r a corresponding "generic" parity-check collection with this property. This leads in a natural way to a necessary and sufficient condition for such generic parity-check collections. We use this condition to construct a generic parity-check collection for codes of codimension r correcting all correctable erasure patterns of size at most m, for all r and mlesr, thus generalizing the known construction for m=3. Then we discuss optimality of our construction and show that it can be improved for mges3 and r large enough. Finally, we discuss some directions for further research