Fig. 9

Kullback-Leibler divergence between distributions of LLRs that correspond to bits in error and LLRs that correspond to correct bits at the output of an LDPC soft decoder, as a function of the hard-decision BER at the output of the decoder. As the BER approaches 0.5, the distributions become more alike, to the point where detecting a correct bit or a bit in error is impossible, even with soft information