Erasure/list random coding error exponents are not universally achievable

Nir Weinberger, Wasim Huleihel, Neri Merhav

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review


We study the problem of universal decoding for unknown discrete memoryless channels in the presence of erasure/list option at the decoder, in the random coding regime. Specifically, we harness a universal version of Forney's classical erasure/list decoder developed in earlier studies, which is based on the competitive minimax methodology, and guarantees universal achievability of a certain fraction of the optimum random coding error exponents. In this paper, we derive an exact single-letter expression for the maximum achievable fraction. Examples are given in which the maximal achievable fraction is strictly less than unity, which imply that, in general, there is no universal erasure/list decoder which achieves the same random coding error exponents as the optimal decoder for a known channel. This is in contrast to the situation in ordinary decoding (without the erasure/list option), where optimum exponents are universally achievable, as is well known. It is also demonstrated that previous lower bounds derived for the maximal achievable fraction are not tight in general.

Original languageEnglish
Title of host publication2015 IEEE Information Theory Workshop, ITW 2015
PublisherInstitute of Electrical and Electronics Engineers Inc.
ISBN (Electronic)9781479955268
StatePublished - 24 Jun 2015
Externally publishedYes
Event2015 IEEE Information Theory Workshop, ITW 2015 - Jerusalem, Israel
Duration: 26 Apr 20151 May 2015

Publication series

Name2015 IEEE Information Theory Workshop, ITW 2015


Conference2015 IEEE Information Theory Workshop, ITW 2015


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