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ABSTRACT: Let X and Y be finite alphabets and P<sub>XY</sub> a joint distribution over them, with P<sub>X</sub> and P<sub>Y</sub> representing the marginals. For any ϵ > 0, the set of n-length sequences x<sup>n</sup> and y<sup>n</sup> that are jointly typical according to P<sub>XY</sub> can be represented on a bipartite graph. We present a formal definition of such a graph, known as a typicality graph, and study some of its properties. These properties arise in the study of several multiuser communication problems.
Information Theory Proceedings (ISIT), 2010 IEEE International Symposium on; 07/2010
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ABSTRACT: In this work, a new upper bound for average error probability of a two-user discrete memoryless (DM) multiple-access channel (MAC) is derived. This bound can be universally obtained for all discrete memoryless MACs with given input and output alphabets. This is the first bound of this type that explicitly uses the method of expurgation. It is shown that the exponent of this bound is greater than or equal to those of previously known bounds.
Information Sciences and Systems, 2009. CISS 2009. 43rd Annual Conference on; 04/2009
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ABSTRACT: In this work, a new lower bound for the maximal error probability of a two-user discrete memoryless (DM) multiple-access channel (MAC) is derived. This is the first bound of this type that explicitly imposes independence of the userspsila input distributions (conditioned on the time-sharing auxiliary variable) and thus results in a tighter sphere-packing exponent when compared to the tightest known exponent derived by Haroutunian.
Information Theory, 2008. ISIT 2008. IEEE International Symposium on; 08/2008
