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We analyze a distributed M-user multiple-access problem in both the additive white Gaussian noise channel and the discrete memoryless channel. A system where each user independently chooses a transmission rate according to a probability distribution function is considered. Under the assumption of symmetric capacity regions, we show that the optimal transmission rate distribution is a point mass for...
A multi-access problem is considered where two encoders wish to communicate their messages to two decoders. The encoders can further cooperate via a conference, as introduced by Willems for multi-access channels. The capacity region of this channel is shown to be the intersection of the capacity regions of two multi-access channels with partially cooperating encoders
The cutoff rate R0(W) of a discrete memoryless channel (DMC) W is often used as a figure of merit, alongside the channel capacity C(W). Given a channel W consisting of two possibly correlated subchannels W1, W2, the capacity function always satisfies C(W1) + C(W2) les C(W), while there are examples for which R0(W1) + R0(W 2) > R0(W). This fact that the cutoff rate can be "created" by...
We consider communication over a time invariant discrete memoryless channel with noiseless and instantaneous feedback. We assume that the communicating parties are not aware of the underlying channel, however they know that it belongs to some specific family of discrete memoryless channels. Recent results (A. Tchamkerten and I.E. Telatar) show that for certain families (e.g., binary symmetric channels...
Suppose Q is a family of discrete memoryless channels. An unknown member of Q is available with perfect (causal) feedback for communication. A recent result (A. Tchamkerten and I.E. Telatar) shows the existence, for certain families of channels (e.g. binary symmetric channels and Z channels), of coding schemes that achieve Burnashev's exponent universally over these families. In other words, in certain...
It is shown that one cannot always layer, or separate, channel and network coding for multicasting in deterministic relay networks with no interference. We call such networks Aref networks. The suboptimality of such layering in Aref networks is in contrast to the optimality of a similar layering in networks of discrete memoryless channels and certain networks of two-way channels
We study the reliability of sequential codes in a two-state Markov fading AWGN channel under the assumption of noiseless feedback and an average power constraint. We present a capacity achieving scheme with a doubly exponential anytime reliability function with respect to delay for every bit. The scheme is represented by a hybrid control system at the encoder in which the discrete system dynamics...
Let {Xt} be a stationary finite-alphabet Markov chain and {Zt} denote its noisy version when corrupted by a discrete memoryless channel. We present an approach to bounding the entropy rate of {Zt} by the construction and study of a related measure-valued Markov process. To illustrate its efficacy, we specialize it to the case of a BSC-corrupted binary Markov chain. The bounds obtained are sufficiently...
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