Avoiding trapping sets in SC-LDPC codes under windowed decoding

Spatially coupled low-density parity-check (SC-LDPC) codes are sparse graph codes that have recently become of interest due to their capacity-approaching performance on memoryless binary input channels. Moreover, protograph SC-LDPC codes have been shown to be asymptotically good under certain conditions. SC-LDPC codes are amenable to a windowed decoder that allows decoding of blocks of bits to be done serially, making them good candidates for applications such as streaming. Depending on how they are constructed, however, the codes may still be prone to error floors. One key element in protograph SC-LDPC code design is the edge-spreading method used to couple copies of the base protograph in the construction of the SC-protograph. In this paper, we present an edge-spreading algorithm that is designed to remove trapping sets from the resulting SC-protograph that are harmful with respect to the windowed decoder, and we examine how to determine which trapping sets should be removed in the construction.