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17
Topological interference management through index coding
, 2013
"... While much recent progress on interference networks has come about under the assumption of abundant channel state information at the transmitters (CSIT), a complementary perspective is sought in this work through the study of interference networks with no CSIT except a coarse knowledge of the topolo ..."
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Cited by 30 (14 self)
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While much recent progress on interference networks has come about under the assumption of abundant channel state information at the transmitters (CSIT), a complementary perspective is sought in this work through the study of interference networks with no CSIT except a coarse knowledge of the topology of the network that only allows a distinction between weak and significant channels and no further knowledge of the channel coefficients ’ realizations. Modeled as a degreesoffreedom (DoF) study of a partially connected interference network with no CSIT, the problem is found to have a counterpart in the capacity analysis of wired networks with arbitrary linear network coding at intermediate nodes, under the assumption that the sources are aware only of the end to end topology of the network. The wireless (wired) network DoF (capacity) region, expressed in dimensionless units as a multiple of the DoF (capacity) of a single point to point channel (link), is found to be bounded above by the capacity of an index coding problem where the antidotes graph is the complement of the interference graph of the original network and the bottleneck link capacity is normalized to unity. The problems are shown to be equivalent under linear solutions over the same field. An interference alignment
Geometry of the 3User MIMO interference channel
 in Proc. Allerton Conference on Communication, Control, and Computing (Allerton
, 2011
"... Abstract—This paper studies vector space interference alignment for the threeuser MIMO interference channel with no time or frequency diversity. The main result is a characterization of the feasibility of interference alignment in the symmetric case where all transmitters have M antennas and all ..."
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Abstract—This paper studies vector space interference alignment for the threeuser MIMO interference channel with no time or frequency diversity. The main result is a characterization of the feasibility of interference alignment in the symmetric case where all transmitters have M antennas and all receivers have N antennas. If N ≥M and all users desire d transmit dimensions, then alignment is feasible if and only if (2r+1)d ≤ max(rN, (r+1)M) for all nonnegative integers r. The analogous result holds with M and N switched if M ≥ N. It turns out that, just as for the 3user parallel interference channel [1], the length of alignment paths captures the essence of the problem. In fact, for each feasible value of M and N the maximum alignment path length dictates both the converse and achievability arguments. One of the implications of our feasibility criterion is that simply counting equations and comparing to the number of variables does not predict feasibility. Instead, a more careful investigation of the geometry of the alignment problem is required. The necessary condition obtained by counting equations is implied by our new feasibility criterion. I.
Approximate sumcapacity of Kuser cognitive interference channels with cumulative message sharing
 IEEE J. Select. Areas Commun
, 2014
"... Abstract—This paper considers the Kuser cognitive interference channel with one primary and K − 1 secondary/cognitive transmitters with a cumulative message sharing structure, i.e., cognitive transmitter i ∈ [2: K] has noncausal knowledge of the messages of users with index less than i. A computa ..."
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Cited by 6 (4 self)
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Abstract—This paper considers the Kuser cognitive interference channel with one primary and K − 1 secondary/cognitive transmitters with a cumulative message sharing structure, i.e., cognitive transmitter i ∈ [2: K] has noncausal knowledge of the messages of users with index less than i. A computable outer bound valid for any memoryless channel is proposed. The sumrate outer bound is evaluated first for the highSNR linear deterministic approximation of the Gaussian noise channel. This is shown to be both the sum capacity for the 3user channel with arbitrary channel gains, and the sumcapacity for the symmetric Kuser channel. Interestingly, for the K user channel, cognition at transmitters 2 to K − 1 is not needed, and knowledge of all messages at the Kth transmitter only is sufficient to achieve the sumcapacity. Next, the sumcapacity of the symmetric Gaussian noise channel is characterized to within a constant additive and multiplicative gap, both of which are functions of K. As opposed to other multiuser interference channel models, a single scheme (in this case based on dirtypaper coding) suffices for both the weak and strong interference regimes. The generalized degrees of freedom (gDoF) are then derived and are shown, unlike interference and broadcast channels, to be a function of K. Interestingly, it is shown that as the number of users grows to infinity the gDoF of the Kuser cognitive interference channel with cumulative message sharing tends to the gDoF of a broadcast channel with a Kantenna transmitter and K singleantenna receivers. Finally, numerical evaluations show that the actual gaps between the presented inner and outer bounds are significantly smaller than the analytically derived gaps. Index Terms—Cognitive interference channel, generalized degreesoffreedom, sumcapacity, linear deterministic channel, symmetric Gaussian channel, MIMO broadcast channel, multiplicative gap, additive gap. I.
On the achievable degrees of freedom for the 3user rankdeficient MIMO interference channel,” [Online]. Available: http://arxiv.org/abs/1211.4198
, 2012
"... ar ..."
Approximate ergodic capacity of a class of fading 2user 2hop networks
, 2012
"... We consider a fading AWGN 2user 2hop network in which the channel coefficients are independently and identically distributed (i.i.d.) drawn from a continuous distribution and vary over time. For a broad class of channel distributions, we characterize the ergodic sum capacity within a constant num ..."
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Cited by 5 (2 self)
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We consider a fading AWGN 2user 2hop network in which the channel coefficients are independently and identically distributed (i.i.d.) drawn from a continuous distribution and vary over time. For a broad class of channel distributions, we characterize the ergodic sum capacity within a constant number of bits/sec/Hz, independent of signaltonoise ratio. The achievability follows from the analysis of an interference neutralization scheme where the relays are partitioned into K pairs, and interference is neutralized separately by each pair of relays. For K =1, we previously proved a gap of 4 bits/sec/Hz for i.i.d. uniform phase fading and approximately 4.7 bits/sec/Hz for i.i.d. Rayleigh fading. In this paper, we give a result for general K. In the limit of large K, we characterize the ergodic sum capacity within 4((log π) − 1) ≃ 2.6 bits/sec/Hz for i.i.d. uniform phase fading and 4(4 − log 3π) ≃ 3.1 bits/sec/Hz for i.i.d. Rayleigh fading.
Degrees of Freedom of RankDeficient MIMO Interference Channels
"... Abstract — We characterize the degrees of freedom (DoF) of multipleinput and multipleoutput (MIMO) interference channels with rankdeficient channel matrices. For the twouser rankdeficient MIMO interference channel, we provide a tight outer bound to show that the previously known achievable DoF ..."
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Cited by 5 (4 self)
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Abstract — We characterize the degrees of freedom (DoF) of multipleinput and multipleoutput (MIMO) interference channels with rankdeficient channel matrices. For the twouser rankdeficient MIMO interference channel, we provide a tight outer bound to show that the previously known achievable DoF in the symmetric case is optimal and generalize the result to fully asymmetric settings. For the Kuser rankdeficient interference channel, we improve the previously known achievable DoF and provide a tight outer bound to establish optimality in symmetric settings. In particular, we show that for the Kuser rankdeficient interference channel, when all nodes have M antennas, all direct channels have rank D0, all cross channels are of rank D, and the channels are otherwise generic, the optimal DoF value per user is min(D0, M − (min(M, (K − 1)D)/2)). Notably for interference channels, the rankdeficiency of direct channels does not help and the rank deficiency of crosschannels does not hurt. The main technical challenge is to account for the spatial dependences introduced by rank deficiencies in the interference alignment schemes that typically rely on the independence of channel coefficients. Index Terms — Channel capacity, degrees of freedom, interference channel, multipleinput multipleoutput (MIMO), rank deficient channels, interference alignment I.
Genie Chains: Exploring Outer Bounds on the Degrees of Freedom of MIMO Interference Networks,” ArXiv eprints, vol. arXiv:1404.2258v1 [cs.IT
, 2014
"... All intext references underlined in blue are linked to publications on ResearchGate, letting you access and read them immediately. ..."
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Cited by 4 (2 self)
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All intext references underlined in blue are linked to publications on ResearchGate, letting you access and read them immediately.