Search results for: S. Avestimehr
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We consider the problem of characterizing network capacity in the presence of adversarial errors on network links, focusing in particular on the effect of low-capacity feedback links across network cuts. We give a new outer bound as well as a new achievable strategy, and show a family of networks where the inner and outer bounds coincide.
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IEEE Transactions on Information Theory > 2011 > 57 > 4 > 1872 - 1905
In a wireless network with a single source and a single destination and an arbitrary number of relay nodes, what is the maximum rate of information flow achievable? We make progress on this long standing problem through a two-step approach. First, we propose a deterministic channel model which captures the key wireless properties of signal strength, broadcast and superposition. We obtain an exact...
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IEEE Transactions on Information Theory > 2011 > 57 > 5 > 2711 - 2729
“If we know more, we can achieve more.” This adage also applies to communication networks, where more information about the network state translates into higher sum-rates. In this paper, we formalize this increase of sum-rate with increased knowledge of the network state. The knowledge of network state is measured in terms of the number of hops, h, of information available to each transmitter and...
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IEEE Transactions on Signal Processing > 2011 > 59 > 5 > 1985 - 2001
In this paper, we introduce a nonuniform sparsity model and analyze the performance of an optimized weighted ℓ1 minimization over that sparsity model. In particular, we focus on a model where the entries of the unknown vector fall into two sets, with entries of each set having a specific probability of being nonzero. We propose a weighted ℓ1 minimization recovery algorithm and analyze its performance...
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In large wireless networks, acquiring full network state information is typically infeasible. Hence, nodes need to flow the information and manage the interference based on partial information about the network. In this paper, we consider multi-hop wireless networks and assume that each source only knows the channel gains that are on the routes from itself to other destinations in the network. We...
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We study the problem of cooperative communication in the case that the assisting node (i.e. the relay) has access to correlated information about the source that needs to be reconstructed at the destination. Finding the relaying strategy that minimizes the reconstruction distortion at the destination, is one of the long standing open problems in information theory. In this paper, we propose a novel...
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In this work, we address the following question: ??When can we guarantee the optimality of linear coding at all internal nodes of a network??? While sufficient conditions for linear coding throughout the network are known, it is not clear whether relaxing the linearity constraints at the terminal nodes can result in simpler operations at the internal nodes. We present a novel method to analyze the...
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We study network error correction with unequal link capacities. Previous results on network error correction assume unit link capacities. We consider network error correction codes that can correct arbitrary errors occurring on up to z links. We find the capacity of a network consisting of parallel links, and a generalized Singleton outer bound for any arbitrary network. We show by example that linear...
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In distributed wireless networks, nodes often do not know the topology (network size, connectivity and the channel gains) of the network. Thus, they have to compute their transmission and reception parameters in a distributed fashion. In this paper, we consider that each of the transmitter know the channel gains of all the links that are at-most two-hop distant from it and the receiver knows the channel...
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2009 IEEE International Symposium on Information Theory > 1343 - 1347
In this paper, we generalize the lossless coded side information problem from the three-node network of Ahlswede and Korner to more general network scenarios. We derive inner and outer bounds on the achievable rate region in the general network scenario and show that they are tight for some families of networks. Our approach demonstrates how solutions to canonical source coding problems can be used...
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One of the distinguishing features of wireless communication is its broadcast nature. This creates complicated signal interactions when there are multiple transmitting and receiving nodes, due to superposition of signals at the receivers. In this paper, we focus on wireless relay networks where (relay) nodes facilitate communications between a source and a destination. We review some recent progress...
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Relay networks was formulated in the 1970s, but the complete characterization of the achievable rates of relay networks is open, even for the simplest three node network (single source, single destination, one relay). This is true even for the special case of Gaussian relay networks, where Gaussian broadcast and multiple access channels model the relay network interactions. Our philosophy was to simplify...
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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...
