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Overlapped Decoding for a Class of Quasi-Cyclic LDPC Codes

Sang-Min Kim, Keshab K. Parhi

In low-density parity-check (LDPC) code decoding with the iterative sum-product algorithm (SPA), due to the randomness of the parity-check matrix, H, the overlapping of the check node processing unit (CNU) and variable node processing unit (VNU) in the same clock cycle is difficult. The paper demonstrates that overlapped decoding can be exploited as long as the LDPC matrix is composed of identity matrices and their cyclic-shifted matrices, i.e., the parity-check matrix, H, belongs to a class of quasi-cyclic LDPC codes. It is shown that the number of clock cycles required for decoding can be reduced by 50% when overlapped decoding is applied to a (3,6)-regular LDPC code decoder.In low-density parity-check (LDPC) code decoding with the iterative sum-product algorithm (SPA), due to the randomness of the parity-check matrix, H, the overlapping of the check node processing unit (CNU) and variable node processing unit (VNU) in the same clock cycle is difficult. The paper demonstrates that overlapped decoding can be exploited as long as the LDPC matrix is composed of identity matrices and their cyclic-shifted matrices, i.e., the parity-check matrix, H, belongs to a class of quasi-cyclic LDPC codes. It is shown that the number of clock cycles required for decoding can be reduced by 50% when overlapped decoding is applied to a (3,6)-regular LDPC code decoder.

SiPS ... design and implementation - IEEE Workshop on Signal Processing SystemsDec 23, 200412 citations

Construction of good quasi-cyclic LDPC codes

Xiao Xiao, Lee

Jan 1, 200616 citations

On the Construction and Decoding of Cyclic LDPC Codes

Chao Chen

Jan 1, 20140 citations

Quasi-Cyclic LDPC Codes using Superposition Matrices and Their Layered Decoders for Wibro Systems

Beomkyu Shin, Hosung Park, Jong‐Seon No +1 more

Most communication systems including Wibro use quasi-cyclic LDPC codes composed of circulants. However, it is very difficult to design quasi-cyclic(QC) LDPC codes with optimal degree distribution satisfying conditions on layered decoding and girth due to the restriction of the size of its base matrix. In this paper, we propose a good solution by introducing superposition matrices to QC LDPC codes. We derive the conditions on checking girth of QC LDPC codes with superposition matrices, and propose new decoder to support layered decoding both for original QC LDPC codes and their modifications with superposition matrices. Simulation results show considerable improvements to convergence speed and error-correcting performance of proposed scheme which adopts QC LDPC codes with superposition matrices.Most communication systems including Wibro use quasi-cyclic LDPC codes composed of circulants. However, it is very difficult to design quasi-cyclic(QC) LDPC codes with optimal degree distribution satisfying conditions on layered decoding and girth due to the restriction of the size of its base matrix. In this paper, we propose a good solution by introducing superposition matrices to QC LDPC codes. We derive the conditions on checking girth of QC LDPC codes with superposition matrices, and propose new decoder to support layered decoding both for original QC LDPC codes and their modifications with superposition matrices. Simulation results show considerable improvements to convergence speed and error-correcting performance of proposed scheme which adopts QC LDPC codes with superposition matrices.

한국통신학회논문지Jan 1, 20101 citation

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

Jianing Su, Zhenghao Lu

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.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.

IEEE International Conference on ASIC (ASICON)Oct 1, 20132 citations

Quasi-Cyclic LDPC Codes Constructed Based on Row-Column Constrained Matrices

Hengzhou Xu, Baoming Bai, Hai Jiang Zhu +2 more

Communications in computer and information scienceJan 1, 20181 citation

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