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139
Gaussian interference channel capacity to within one bit
 5534–5562, 2008. EURASIP Journal on Advances in Signal Processing
"... Abstract—The capacity of the twouser Gaussian interference channel has been open for 30 years. The understanding on this problem has been limited. The best known achievable region is due to Han and Kobayashi but its characterization is very complicated. It is also not known how tight the existing o ..."
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Cited by 452 (28 self)
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Abstract—The capacity of the twouser Gaussian interference channel has been open for 30 years. The understanding on this problem has been limited. The best known achievable region is due to Han and Kobayashi but its characterization is very complicated. It is also not known how tight the existing outer bounds are. In this work, we show that the existing outer bounds can in fact be arbitrarily loose in some parameter ranges, and by deriving new outer bounds, we show that a very simple and explicit Han–Kobayashi type scheme can achieve to within a single bit per second per hertz (bit/s/Hz) of the capacity for all values of the channel parameters. We also show that the scheme is asymptotically optimal at certain high signaltonoise ratio (SNR) regimes. Using our results, we provide a natural generalization of the pointtopoint classical notion of degrees of freedom to interferencelimited scenarios. Index Terms—Capacity region, Gaussian interference channel, generalized degrees of freedom.
Stochastic Geometry and Random Graphs for the Analysis and Design of Wireless Networks
"... Wireless networks are fundamentally limited by the intensity of the received signals and by their interference. Since both of these quantities depend on the spatial location of the nodes, mathematical techniques have been developed in the last decade to provide communicationtheoretic results accoun ..."
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Cited by 240 (42 self)
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Wireless networks are fundamentally limited by the intensity of the received signals and by their interference. Since both of these quantities depend on the spatial location of the nodes, mathematical techniques have been developed in the last decade to provide communicationtheoretic results accounting for the network’s geometrical configuration. Often, the location of the nodes in the network can be modeled as random, following for example a Poisson point process. In this case, different techniques based on stochastic geometry and the theory of random geometric graphs – including point process theory, percolation theory, and probabilistic combinatorics – have led to results on the connectivity, the capacity, the outage probability, and other fundamental limits of wireless networks. This tutorial article surveys some of these techniques, discusses their application to model wireless networks, and presents some of the main results that have appeared in the literature. It also serves as an introduction to the field for the other papers in this special issue.
Interference alignment on the deterministic channel and application to gaussian networks
"... Abstract—An interference alignment example is constructed for the deterministic channel model of the user interference channel. The deterministic channel example is then translated into the Gaussian setting, creating the first known example of a fully connected Gaussian user interference network w ..."
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Cited by 75 (23 self)
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Abstract—An interference alignment example is constructed for the deterministic channel model of the user interference channel. The deterministic channel example is then translated into the Gaussian setting, creating the first known example of a fully connected Gaussian user interference network with single antenna nodes, real, nonzero and constant channel coefficients, and no propagation delays where the degrees of freedom outerbound is achieved. An analogy is drawn between the propagation delay based interference alignment examples and the deterministic channel model which also allows similar constructions for the user channel as well. I.
Interference Alignment and the Degrees of Freedom of Wireless X Networks
"... We explore the degrees of freedom of M × N user wireless X networks, i.e. networks of M transmitters and N receivers where every transmitter has an independent message for every receiver. We derive a general outerbound on the degrees of freedom region of these networks. When all nodes have a single ..."
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Cited by 71 (22 self)
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We explore the degrees of freedom of M × N user wireless X networks, i.e. networks of M transmitters and N receivers where every transmitter has an independent message for every receiver. We derive a general outerbound on the degrees of freedom region of these networks. When all nodes have a single antenna and all channel coefficients vary in time or frequency, we show that the total number of degrees of freedom of the X network is equal to MN M+N−1 per orthogonal time and frequency dimension. Achievability is proved by constructing interference alignment schemes for X networks that can come arbitrarily close to the outerbound on degrees of freedom. For the case where either M = 2 or N = 2 we find that the degrees of freedom characterization also provides a capacity approximation that is accurate to within O(1). For these cases the degrees of freedom outerbound is exactly achievable. There is increasing interest in approximate capacity characterizations of wireless networks as a means to understanding their performance limits. In particular, the high SNR regime where the local additive white Gaussian noise (AWGN) at each node is deemphasized relative to signal and interference powers offers fundamental insights into optimal interference management schemes. The degreesoffreedom approach provides a capacity
Symmetric Feedback Capacity of the Gaussian Interference Channel to Within One Bit
"... We characterize the symmetric capacity of the twouser Gaussian interference channel with feedback to within 1 bit/s/Hz. The result makes use of a deterministic model to provide insights into the Gaussian channel. We derive a new outer bound to show that a proposed scheme can achieve the symmetric ..."
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Cited by 67 (5 self)
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We characterize the symmetric capacity of the twouser Gaussian interference channel with feedback to within 1 bit/s/Hz. The result makes use of a deterministic model to provide insights into the Gaussian channel. We derive a new outer bound to show that a proposed scheme can achieve the symmetric capacity to within one bit for all channel parameters. From this result, we show that feedback provides unbounded gain, i.e., the gain becomes arbitrarily large for certain channel parameters. It is a surprising result because feedback has been so far known to provide no gain in memoryless pointtopoint channels and only power gain (bounded gain) in the multiple access channels.
Interference alignment with asymmetric complex signaling  settling the HostMadsenNosratinia conjecture
 IEEE TRANSACTION ON INFORMATION THEORY
, 2009
"... It has been conjectured by HøstMadsen and Nosratinia that complex Gaussian interference channels with constant channel coefficients have only one degreeoffreedom regardless of the number of users. While several examples are known of constant channels that achieve more than 1 degree of freedom, th ..."
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Cited by 65 (17 self)
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It has been conjectured by HøstMadsen and Nosratinia that complex Gaussian interference channels with constant channel coefficients have only one degreeoffreedom regardless of the number of users. While several examples are known of constant channels that achieve more than 1 degree of freedom, these special cases only span a subset of measure zero. In other words, for almost all channel coefficient values, it is not known if more than 1 degreeoffreedom is achievable. In this paper, we settle the HøstMadsenNosratinia conjecture in the negative. We show that at least 1.2 degreesoffreedom are achievable for all values of complex channel coefficients except for a subset of measure zero. For the class of linear beamforming and interference alignment schemes considered in this paper, it is also shown that 1.2 is the maximum number of degrees of freedom achievable on the complex Gaussian 3 user interference channel with constant channel coefficients, for almost all values of channel coefficients. To establish the achievability of 1.2 degrees of freedom we introduce the novel idea of asymmetric complex signaling i.e., the inputs are chosen to be complex but not circularly symmetric. It is shown that unlike Gaussian pointtopoint, multipleaccess and broadcast channels where circularly
Wireless Network Information Flow
, 710
"... Abstract — We present an achievable rate for general deterministic relay networks, with broadcasting at the transmitters and interference at the receivers. In particular we show that if the optimizing distribution for the informationtheoretic cutset bound is a product distribution, then we have a ..."
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Cited by 55 (15 self)
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Abstract — We present an achievable rate for general deterministic relay networks, with broadcasting at the transmitters and interference at the receivers. In particular we show that if the optimizing distribution for the informationtheoretic cutset bound is a product distribution, then we have a complete characterization of the achievable rates for such networks. For linear deterministic finitefield models discussed in a companion paper [3], this is indeed the case, and we have a generalization of the celebrated maxflow mincut theorem for such a network. I.
Aligned interference neutralization and the degrees of freedom of the 2×2×2 interference channel with . . .
, 2010
"... Previous work showed that the 2×2×2 interference channel, i.e., the multihop interference network formed by concatenation of two 2user interference channels, achieves the mincut outer bound value of 2 DoF. This work studies the 2×2×2 interference channel with one additional assumption that two re ..."
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Cited by 52 (14 self)
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Previous work showed that the 2×2×2 interference channel, i.e., the multihop interference network formed by concatenation of two 2user interference channels, achieves the mincut outer bound value of 2 DoF. This work studies the 2×2×2 interference channel with one additional assumption that two relays interfere with each other. It is shown that even in the presence of the interfering links between two relays, the mincut outer bound of 2 DoF can still be achieved for almost all values of channel coefficients, for both fixed or timevarying channel coefficients. The achievable scheme relies on the idea of aligned interference neutralization as well as exploiting memory at source and relay nodes.
Approximate capacity of Gaussian relay networks
, 2008
"... We present an achievable rate for general Gaussian relay networks. We show that the achievable rate is within a constant number of bits from the informationtheoretic cutset upper bound on the capacity of these networks. This constant depends on the topology of the network, but not the values of th ..."
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Cited by 44 (11 self)
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We present an achievable rate for general Gaussian relay networks. We show that the achievable rate is within a constant number of bits from the informationtheoretic cutset upper bound on the capacity of these networks. This constant depends on the topology of the network, but not the values of the channel gains. Therefore, we uniformly characterize the capacity of Gaussian relay networks within a constant number of bits, for all channel parameters.
Rethinking information theory for mobile ad hoc networks
 IEEE Communications Magazine, Submitted
, 2007
"... The subject of this paper is the longstanding open problem of developing a general capacity theory for wireless networks, particularly a theory capable of describing the fundamental performance limits of mobile ad hoc networks (MANETs). A MANET is a peertopeer network with no preexisting infrast ..."
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Cited by 38 (6 self)
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The subject of this paper is the longstanding open problem of developing a general capacity theory for wireless networks, particularly a theory capable of describing the fundamental performance limits of mobile ad hoc networks (MANETs). A MANET is a peertopeer network with no preexisting infrastructure. MANETs are the most general wireless networks, with singlehop, relay, interference, mesh, and star networks comprising special cases. The lack of a MANET capacity theory has stunted the development and commercialization of many types of wireless networks, including emergency, military, sensor, and community mesh networks. Information theory, which has been vital for links and centralized networks, has not been successfully applied to decentralized wireless networks. Even if this was accomplished, for such a theory to truly characterize the limits of deployed MANETs it must overcome three key roadblocks. First, most current capacity results rely on the allowance of unbounded delay and reliability. Second, spatial and timescale decompositions have not yet been developed for optimally modeling the spatial and temporal dynamics of wireless networks. Third, a useful network capacity theory must integrate rather than ignore the important role of overhead messaging and feedback. This paper describes some of the shifts in thinking that may be needed to overcome these roadblocks and