A Low-complexity LDPC Decoder for NAND Flash Applications

This paper presents an efficient mm-sum-based decoder for high-rate low-density parity-check (LDPC) codes, where the first minimum and second minimum values are stored in registers. In order to meet a strict cost requirement imposed by NAND flash applications, we provide different upper limits for the first and second minimum values. Furthermore, we use non-uniform quantization for the second minimum value so as to reduce storage complexity. In order to enhance the error-rate performance, the normalization factor is determined based on the difference between the first two minimum values. Using the proposed techniques, a reduction in gate count of 13.36% can be achieved without suffering any degradation in error-rate performance. The implementation results for a rate-0.896 length-18624 layered decoder show that this decoder can achieve a throughput of 765.24 Mb/s at a clock frequency of 166 MHz with a gate count of 620K.