Communications in Information and Systems

Volume 14 (2014)

Number 2

Generalization of Mrs. Gerber’s lemma

Pages: 79 – 86



Fan Cheng (Institute of Network Coding, The Chinese University of Hong)


Mrs. Gerber’s Lemma (MGL) hinges on the convexity of $H(p*H^{-1}(u))$, where $H(u)$ is the binary entropy function. In this work, we prove that $H(p*f(u))$ is convex in $u$ for every $p \in [0, 1]$ provided $H(f(u))$ is convex in $u$, where $f(u) \colon (a, b) \to [0, \frac{1}{2}]$. Moreover, our result subsumes MGL and simplifies the original proof. We show that the generalized MGL can be applied in binary broadcast channel to simplify some discussion.


Mrs. Gerber’s lemma, binary channel

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