Reduced complexity implementation of quasi-cyclic LDPC decoders by parity-check matrix reordering

The layered scheme is famous for its efficiency and high throughput structure in decoding of LDPC codes, especially the quasi-cyclic LDPC codes, whose parity check matrices are made of cyclically-shifted identity matrices, which can be used as natural partitions of decoding layers. However, for many QC-LDPC codes, it leads to serious routing congestion if the cyclically shifted identity matrix size is taken directly as the layer partition and parallel factor in decoding. In this paper, a parity-check matrix reordering method is introduced, which can lower the decoding parallelism while keeping the layered decoding structure at the same time. The LDPC codes in DVB-S2/T2 standards are taken as an example to illustrate the proposed method, simulation and FPGA implementation shows that the method is effective in reducing the total decoder cost.