Average Coset Weight Distribution of Combined LDPC Matrix Ensembles

In this paper, the average coset weight distribution (ACWD) of structured ensembles of low-density parity-check (LDPC) matrices, which are called combined ensembles, is discussed. A combined ensemble is composed of a set of simpler ensembles such as a regular bipartite ensemble. Two classes of combined ensembles have prime importance; a stacked ensemble and a concatenated ensemble. The ACWD formulas of these ensembles are shown in this paper. Such formulas play a key role to evaluate the average weight distribution of some classes of combined ensembles