Variable block length coding for channels with feedback and cost constraints

Abstract

Variable-decoding-time/generalized block-coding schemes are investigated for discrete memoryless channels (DMC) with perfect feedback (error free, delay free, infinite capacity) under cost constraints. For a given number of messages and average error probability, upper and lower bounds are found for expected decoding time. These coincide with each other up to a proportionality constant which approaches one in a certain asymptotic sense. A resulting reliability function is found for variable decoding time DMC's with perfect feedback under a cost constraint. The results in this work generalize Burnashev's results, to the cost constrained case.