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129
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 451 (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.
A Network Information Theory for Wireless Communication: Scaling Laws and Optimal Operation
 IEEE Transactions on Information Theory
, 2002
"... How much information can be carried over a wireless network with a multiplicity of nodes? What are the optimal strategies for information transmission and cooperation among the nodes? We obtain sharp information theoretic scaling laws under some conditions. ..."
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Cited by 369 (18 self)
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How much information can be carried over a wireless network with a multiplicity of nodes? What are the optimal strategies for information transmission and cooperation among the nodes? We obtain sharp information theoretic scaling laws under some conditions.
On interference channels with generalized feedback
 In Proceedings of IEEE Int. Symp. on Inform. Theory, ISIT2007
, 2007
"... An Interference Channel with Generalized Feedback (IFCGF) is a model for a wireless network where several sourcedestination pairs compete for the same channel resources, and where the sources have the ability to sense the current channel activity. The signal overheard from the channel provides inf ..."
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Cited by 48 (9 self)
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An Interference Channel with Generalized Feedback (IFCGF) is a model for a wireless network where several sourcedestination pairs compete for the same channel resources, and where the sources have the ability to sense the current channel activity. The signal overheard from the channel provides information about the activity of the other users, and thus furnishes the basis for cooperation. In this twopart paper we study achievable strategies and outer bounds for a general IFCGF with two sourcedestination pairs. We then evaluate the proposed regions for the Gaussian channel. Part I: Achievable Region. We propose that the generalized feedback is used to gain knowledge about the message sent by the other user and then exploited in two ways: (a) to relay the messages that can be decoded at both destinations–thus realizing the gains of beamforming of a distributed multiantenna system–and (b) to hide the messages that can not be decoded at the nonintended destination–thus leveraging the interference “precancellation” property of dirtypapertype coding. We show that our achievable region generalizes several known achievable regions for IFCGF and that it reduces
A Layered Lattice Coding Scheme for a Class of Three User Gaussian Interference Channels
 Allerton Conf. on Communication, Control, and Computing
, 2008
"... Abstract—The paper studies a class of three user Gaussian interference channels. A new layered lattice coding scheme is introduced as a transmission strategy. The use of lattice codes allows for an “alignment ” of the interference observed at each receiver. The layered lattice coding is shown to ach ..."
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Cited by 45 (4 self)
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Abstract—The paper studies a class of three user Gaussian interference channels. A new layered lattice coding scheme is introduced as a transmission strategy. The use of lattice codes allows for an “alignment ” of the interference observed at each receiver. The layered lattice coding is shown to achieve more than one degree of freedom for a class of interference channels and also achieves rates which are better than the rates obtained using the HanKobayashi coding scheme. I.
The degrees of freedom region and interference alignment for the MIMO interference channel with delayed CSI,” 2011. [Online]. Available: http://arxiv.org/abs/1101.5809
"... The degrees of freedom (DoF) region of the 2user multipleantenna or MIMO (multipleinput, multipleoutput) interference channel (IC) is studied under fast fading and the assumption of delayed channel state information (CSI) wherein all terminals know all (or certain) channel matrices perfectly, bu ..."
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Cited by 39 (5 self)
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The degrees of freedom (DoF) region of the 2user multipleantenna or MIMO (multipleinput, multipleoutput) interference channel (IC) is studied under fast fading and the assumption of delayed channel state information (CSI) wherein all terminals know all (or certain) channel matrices perfectly, but with a delay, and each receiver in addition knows its own incoming channels instantaneously. The general MIMO IC is considered with an arbitrary number of antennas at each of the four terminals. Dividing it into several classes depending on the relation between the numbers of antennas at the four terminals, the fundamental DoF regions are characterized under the delayed CSI assumption for all possible values of number of antennas at the four terminals. In particular, an outer bound on the DoF region of the general MIMO IC is derived. This bound is then shown to be tight for all MIMO ICs by developing interference alignment based achievability schemes for each class. A comparison of these DoF regions under the delayed CSI assumption is made with those of the idealistic ‘perfect CSI’ assumption where perfect and instantaneous CSI is available at all terminals on the one hand and with the DoF regions of the conservative ‘no CSI ’ assumption on the other, where CSI is available at the receivers but not at all at the transmitters.
TwoUnicast Wireless Networks: Characterizing the DegreesofFreedom
, 2012
"... We consider twosource twodestination (i.e., twounicast) multihop wireless networks that have a layered structure with arbitrary connectivity. We show that, if the channel gains are chosen independently according to continuous distributions, then, with probability 1, twounicast layered Gaussi ..."
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Cited by 34 (9 self)
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We consider twosource twodestination (i.e., twounicast) multihop wireless networks that have a layered structure with arbitrary connectivity. We show that, if the channel gains are chosen independently according to continuous distributions, then, with probability 1, twounicast layered Gaussian networks can only have 1, 3/2 or 2 sum degreesoffreedom (unless both sourcedestination pairs are disconnected, in which case no degreesoffreedom can be achieved). We provide sufficient and necessary conditions for each case based on network connectivity and a new notion of sourcedestination paths with manageable interference. Our achievability scheme is based on forwarding the received signals at all nodes, except for a small fraction of them in at most two key layers. Hence, we effectively create a “condensed network” that has at most four layers (including the sources layer and the destinations layer). We design the transmission strategies based on the structure of this condensed network. The converse results are obtained by developing informationtheoretic inequalities that capture the structures of the network connectivity. Finally, we extend this result and characterize the full degreesoffreedom region of twounicast layered wireless networks.
Linear Transceiver Design for Interference Alignment: Complexity and Computation,” Available on arxiv:1009.3481
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The capacity region of a class of discrete degraded interference channels
 In 44th Annual Allerton Conference on Communications, Control and Computing
, 2006
"... Abstract — We provide a singleletter characterization for the capacity region of a class of discrete degraded interference channels (DDICs). The class of DDICs considered includes the discrete additive degraded interference channel (DADIC) studied by Benzel [1]. We show that for the class of DDICs ..."
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Cited by 27 (8 self)
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Abstract — We provide a singleletter characterization for the capacity region of a class of discrete degraded interference channels (DDICs). The class of DDICs considered includes the discrete additive degraded interference channel (DADIC) studied by Benzel [1]. We show that for the class of DDICs studied, encoder cooperation does not increase the capacity region, and therefore, the capacity region of the class of DDICs is the same as the capacity region of the corresponding degraded broadcast channel. I.
Interference alignment and the generalized degrees of freedom of the X channel
 IEEE Transactions on Information Theory
, 2012
"... Abstract—We study the sum capacity of the X channel generalization of the symmetric 2user interference channel. In this X channel, there are 4 independent messages, one from each transmitter to each receiver. We characterize the sum capacity of a deterministic version of this channel, and obtain th ..."
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Cited by 21 (6 self)
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Abstract—We study the sum capacity of the X channel generalization of the symmetric 2user interference channel. In this X channel, there are 4 independent messages, one from each transmitter to each receiver. We characterize the sum capacity of a deterministic version of this channel, and obtain the generalized degrees of freedom characterization for the Gaussian version. The regime where the X channel outperforms the underlying interference channel is explicitly identified, and an interesting interference alignment scheme based on a cyclic decomposition of the signal space is shown to be optimal in this regime. I.