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An information-theoretic framework for unequal error protection is developed in terms of the exponential error bounds. The fundamental difference between the <i>bit-wise</i> and <i>message-wise</i> unequal error protection ( <i>UEP</i>) is demonstrated, for fixed-length block codes on discrete memoryless channels (DMCs) without feedback. Effect of feedback(More)
Feedback coupled with variable-length codes can substantially increase the reliability of a discrete memoryless channel (DMC). Burnashev, in a remarkable paper published in 1976, derived an asymptotically achievable lower bound to the average blocklength needed for a system that communicates at a specified rate and achieves a given error probability. We(More)
A lower bound bound is established on the error probability of fixed-length block-coding systems with finite memory feedback, which can be described in terms of a time dependent finite state machine. It is shown that the reliability function of such coding systems over discrete memoryless channels is upper-bounded by the sphere-packing exponent.
Variable-length block-coding schemes are investigated for discrete memoryless channels with ideal feedback under cost constraints. Upper and lower bounds are found for the minimum achievable probability of decoding error Pe,min as a function of constraints R, P, and tau on the transmission rate, average cost, and average block length, respectively. For(More)
Schalkwijk and Kailath (1966) developed a class of block codes for Gaussian channels with ideal feedback for which the probability of decoding error decreases as a second-order exponent in block length for rates below capacity. This well-known but surprising result is explained and simply derived here in terms of a result by Elias (1956) concerning the(More)
In a remarkable paper published in 1976, Burnashev determined the reliability function of variable-length block codes over discrete memoryless channels (DMCs) with feedback. Subsequently, an alternative <i>achievability</i> proof was obtained by Yamamoto and Itoh via a particularly simple and instructive scheme. Their idea is to alternate between a(More)
Inner and outer bounds are derived on the optimal performance of fixed-length block codes on discrete memoryless channels with feedback and errors-and-erasures decoding. First, an inner bound is derived using a two-phase encoding scheme with communication and control phases together with the optimal decoding rule for the given encoding scheme, among(More)
A new technique is proposed for upper bounding the error probability of fixed length block codes with feedback. Error analysis is inspired by Gallager's error analysis for block codes without feedback. Zigangirov-D'yachkov (Z-D ) encoding scheme is analyzed with the technique on binary input channels and k-ary symmetric channels. A strict improvement is(More)
The bit-wise unequal error protection problem, for the case when the number of groups of bits <i>l</i> is fixed, is considered for variable-length block codes with feedback. An encoding scheme based on fixed-length block codes with erasures is used to establish inner bounds to the achievable performance for finite expected decoding time. A new technique for(More)
Various formulations are considered where some information is more important than other and needs better protection. Our information theoretic framework in terms of exponential error bounds provides some fundamental limits and optimal strategies for such problems of unequal error protection. Even for data-rates approaching the channel capacity, it shows how(More)