For decoding non-binary low-density parity check (LDPC) codes,logarithm-domain sum-product (Log-SP) algorithms were proposed for reducingquantization effects of SP algorithm in conjunction with FFT. Since FFT is notapplicable in the logarithm domain, the computations required at check nodes inthe Log-SP algorithms are computationally intensive. What is worth, check nodesusually have higher degree than variable nodes. As a result, most of the timefor decoding is used for check node computations, which leads to a bottleneckeffect. In this paper, we propose a Log-SP algorithm in the Fourier domain.With this algorithm, the role of variable nodes and check nodes are switched.The intensive computations are spread over lower-degree variable nodes, whichcan be efficiently calculated in parallel. Furthermore, we develop a fastcalculation method for the estimated bits and syndromes in the Fourier domain.
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