Tightness conjecture for the MAP conditional-entropy bound
Tightness conjecture for the MAP conditional-entropy bound
Let denote the normalized conditional entropy in the code ensemble, and let and be the degree sequences appearing in Theorem 1. For each admissible random variable , let be the corresponding trial-entropy functional. Under the hypotheses of Theorem 1, tightness conjecture.
where the supremum is taken over the space of admissible random variables, with the degree sequences used as arguments of fixed to be those of Theorem 1. The conjecture asserts that the upper bound from Theorem 1 is asymptotically tight; establishing equality requires optimizing the trial entropy over all admissible random variables.
Sources & referencesView supporting material
Primary source
Andrea Montanari, “Tight bounds for LDPC and LDGM codes under MAP decoding”, arXiv:cs/0407060 (2005).
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