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29
Jr., “User partitioning for less overhead in MIMO interference channels
 IEEE Trans. Wireless Communications
, 2012
"... This paper presents a study on multipleantenna interference channels, accounting for general overhead as a function of the number of users and antennas in the network. The model includes both perfect and imperfect channel state information based on channel estimation in the presence of noise. Thre ..."
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Cited by 12 (6 self)
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This paper presents a study on multipleantenna interference channels, accounting for general overhead as a function of the number of users and antennas in the network. The model includes both perfect and imperfect channel state information based on channel estimation in the presence of noise. Three lowcomplexity methods are proposed for reducing the impact of overhead in the sum network throughput by partitioning users into orthogonal groups. The first method allocates spectrum to the groups equally, creating an imbalance in the sum rate of each group. The second proposed method allocates spectrum unequally among the groups to provide rate fairness. Finally, geographic grouping is proposed for cases where some receivers do not observe significant interference from other transmitters. For each partitioning method, the optimal solution not only requires a brute force search over all possible partitions, but also requires full channel state information, thereby defeating the purpose of partitioning. We therefore propose greedy methods to solve the problems, requiring no instantaneous channel knowledge. Simulations show that the proposed greedy methods switch from timedivision to interference alignment as the coherence time of the channel increases, and have a small loss relative to optimal partitioning only at moderate coherence times. I.
The practical challenges of interference alignment
 IEEE Wireless Communications
, 2013
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Time interference alignment via delay offset for long delay networks,” Arxiv preprint arXiv:1111.3204
, 2011
"... Abstract — Time Interference Alignment is a flavor of Interference Alignment that increases the network capacity by suitably staggering the transmission delays of the senders. In this work the analysis of the existing literature is generalized and the focus is on the computation of the degrees of f ..."
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Cited by 3 (0 self)
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Abstract — Time Interference Alignment is a flavor of Interference Alignment that increases the network capacity by suitably staggering the transmission delays of the senders. In this work the analysis of the existing literature is generalized and the focus is on the computation of the degrees of freedom for networks with randomly placed users in a ndimensional Euclidean space. In the basic case without coordination among the transmitters analytical expressions of the sum degrees of freedom (dof) can be derived. If the transmit delays are coordinated, in 20 % of the cases time Interference Alignment yields additional dof with respect to orthogonal access schemes. The potential capacity improvements for satellite networks are also investigated. I.
Asymptotic SumCapacity of Random Gaussian Interference Networks using Interference Alignment
, 1002
"... Abstract—We consider a dense nuser Gaussian interference network formed by paired transmitters and receivers placed independently at random in Euclidean space. Under natural conditions on the node position distributions and signal attenuation, we prove convergence in probability of the average per ..."
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Cited by 3 (2 self)
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Abstract—We consider a dense nuser Gaussian interference network formed by paired transmitters and receivers placed independently at random in Euclidean space. Under natural conditions on the node position distributions and signal attenuation, we prove convergence in probability of the average peruser capacity CΣ/n to 1 2 Elog(1+2SNR). The achievability result follows directly from results based on an interference alignment scheme presented in recent work of Nazer et al. Our main contribution comes through the converse result, motivated by ideas of ‘bottleneck links ’ developed in recent work of Jafar. An information theoretic argument gives a capacity bound on such bottleneck links, and probabilistic counting arguments show there are sufficiently many such links to tightly bound the sumcapacity of the whole network. Index Terms—Networks, capacity, sumcapacity, interference alignment, interference network. I.
User scheduling for heterogeneous multiuser mimo systems: A subspace viewpoint,” Vehicular Technology
 IEEE Transactions on
, 2011
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Interference alignment (IA) and coordinated multipoint (CoMP) with IEEE802.11ac feedback compression: testbed results
 in IEEE Vehicular Technology Conference
, 2014
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1A Feasibility Test for Linear Interference Alignment in MIMO Channels with Constant Coefficients
"... Abstract—In this paper, we consider the feasibility of linear interference alignment (IA) for multipleinput multipleoutput (MIMO) channels with constant coefficients for any number of users, antennas and streams per user; and propose a polynomialtime test for this problem. Combining algebraic geo ..."
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Abstract—In this paper, we consider the feasibility of linear interference alignment (IA) for multipleinput multipleoutput (MIMO) channels with constant coefficients for any number of users, antennas and streams per user; and propose a polynomialtime test for this problem. Combining algebraic geometry techniques with differential topology ones, we first prove a result that generalizes those previously published on this topic. Specifically, we consider the input set (complex projective space of MIMO interference channels), the output set (precoder and decoder Grassmannians) and the solution set (channels, decoders and precoders satisfying the IA polynomial equations), not only as algebraic sets but also as smooth compact manifolds. Using this mathematical framework, we prove that the linear alignment problem is feasible when the algebraic dimension of the solution variety is larger than or equal to the dimension of the input space and the linear mapping between the tangent spaces of both smooth manifolds given by the first projection is generically surjective. If that mapping is not surjective, then the solution variety projects into the input space in a singular way and the projection is a zeromeasure set. This result naturally yields a simple feasibility test, which amounts to checking the rank of a matrix. We also provide an exact arithmetic version of the test, which proves that testing the feasibility of IA for generic MIMO channels belongs to the boundederror probabilistic polynomial (BPP) complexity class. Index Terms—Interference alignment, MIMO interference channel, polynomial equations, algebraic geometry, differential topology. I.
On the Region of Feasibility of Interference Alignment in Underwater Sensor Networks
"... Abstract—To enable underwater applications such as coastal and tactical surveillance, undersea explorations, and picture/video acquisition, there is a need to achieve high datarate underwater acoustic communications, which translates into attaining high acoustic channel spectral efficiencies. Interf ..."
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Abstract—To enable underwater applications such as coastal and tactical surveillance, undersea explorations, and picture/video acquisition, there is a need to achieve high datarate underwater acoustic communications, which translates into attaining high acoustic channel spectral efficiencies. Interference Alignment (IA) technique, which has recently been proposed for radiofrequency MIMO terrestrial communication systems, aims at improving the spectral efficiency by enabling nodes to transmit data simultaneously at a rate equal to half of the interferencefree channel capacity. While promising, there are challenges to be solved for the use of IA underwater, i.e., imperfect acoustic channel knowledge, high computational complexity, and high communication delay. In this paper, a feasibility study on the practical employment of IA underwater is presented, and a novel distributed computing framework for sharing processing resources in the network so to parallelize an iterative IA algorithm is proposed. Index Terms—Underwater acoustic networks, MIMO technology, interference alignment, channel estimation.
On Interference Alignment for Multihop MIMO Networks
"... Abstract—Interference alignment (IA) is a major advance in information theory. Despite its rapid advance in the information theory community, most results on IA remain pointtopoint or singlehop and there is a lack of advance of IA in the context of multihop wireless networks. The goal of this pa ..."
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Abstract—Interference alignment (IA) is a major advance in information theory. Despite its rapid advance in the information theory community, most results on IA remain pointtopoint or singlehop and there is a lack of advance of IA in the context of multihop wireless networks. The goal of this paper is to make a concrete step toward advancing IA technique in multihop MIMO networks. We present an IA model consisting of a set of constraints at a transmitter and a receiver that can be used to determine a subset of interfering streams for IA. Based on this IA model, we develop an IA optimization framework for a multihop MIMO network. For performance evaluation, we compare the performance of a network throughput optimization problem under our proposed IA framework and the same problem when IA is not employed. Simulation results show that the use of IA can significantly decrease the DoF consumption for IC, thereby improving network throughput. I.