Computational complexity and quantization effects of decoding algorithms for non-binary LDPC codes

This contribution deals with the comparison of the sum-product algorithm (SPA) and its log-domain version (log-SPA) for decoding LDPC (low density parity check) codes over general binary extension fields. For both algorithms, we determine their computational complexity based on the number of real-valued operations and investigate their sensitivity to quantization effects. Whereas the log-SPA yields the shorter decoding time in the case of binary LDPC codes, we point out that increasing the field size tends to favor the SPA, especially when a multiplication takes only slightly more time than an addition. Further, we show that log-SPA requires fewer quantization levels and suffers less from a quantization induced error-floor.