Strong Data Processing Constant Is Achieved by Binary Inputs

Or Ordentlich, Yury Polyanskiy*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


For any channel P Y|X the strong data processing constant is defined as the smallest number η KL\in [0,1] such that I(U;Y)\≤ η KL I(U;X) holds for any Markov chain U-X-Y. It is shown that the value of η KL is given by that of the best binary-input subchannel of P Y|X. The same result holds for any f-divergence, verifying a conjecture of Cohen, Kemperman and Zbaganu (1998).

Original languageAmerican English
Pages (from-to)1480-1481
Number of pages2
JournalIEEE Transactions on Information Theory
Issue number3
StatePublished - 1 Mar 2022

Bibliographical note

Publisher Copyright:
© 1963-2012 IEEE.


  • Contraction coefficient
  • F-divergence
  • Strong data processing inequality (SDPI)


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