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31
Retrospective interference alignment
 in Information Theory, 2011. ISIT 2011. IEEE International Symposium on, 2011
"... We explore similarities and differences in recent works on blind interference alignment under different models such as staggered block fading model and the delayed CSIT model. In particular we explore the possibility of achieving interference alignment with delayed CSIT when the transmitters are di ..."
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Cited by 40 (14 self)
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We explore similarities and differences in recent works on blind interference alignment under different models such as staggered block fading model and the delayed CSIT model. In particular we explore the possibility of achieving interference alignment with delayed CSIT when the transmitters are distributed. Our main contribution is an interference alignment scheme, called retrospective interference alignment in this work, that is specialized to settings with distributed transmitters. With this scheme we show that the 2 user X channel with only delayed channel state information at the transmitters can achieve 8/7 DoF, while the interference channel with 3 users is able to achieve 9/8 DoF. We also consider another setting where delayed channel output feedback is available to transmitters. In this setting the X channel and the 3 user interference channel are shown to achieve 4/3 and 6/5 DoF, respectively. 1
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.
The degrees of freedom region of twouser and certain threeuser MIMO broadcast channel with delayed CSI
 IEEE Trans. Inf. Theory
"... The degrees of freedom (DoF) region of the fastfading MIMO (multipleinput multipleoutput) Gaussian broadcast channel (BC) is studied when there is delayed channel state information at the transmitter (CSIT). In this setting, the channel matrices are assumed to vary independently across time and t ..."
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Cited by 20 (1 self)
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The degrees of freedom (DoF) region of the fastfading MIMO (multipleinput multipleoutput) Gaussian broadcast channel (BC) is studied when there is delayed channel state information at the transmitter (CSIT). In this setting, the channel matrices are assumed to vary independently across time and the transmitter is assumed to know the channel matrices with some arbitrary finite delay. An outerbound to the DoF region of the general Kuser MIMO BC (with an arbitrary number of antennas at each terminal) is derived. This outerbound is then shown to be tight for two classes of MIMO BCs, namely, (a) the twouser MIMO BC with arbitrary number of antennas at all terminals, and (b) for certain threeuser MIMO BCs where all three receivers have an equal number of antennas and the transmitter has no more than twice the number of antennas present at each receivers. The achievability results are obtained by developing an interference alignment scheme that optimally accounts for multiple, and possibly distinct, number of antennas at the receivers. Index Terms Broadcast channel, degrees of freedom, delayed CSIT, interference alignment, outer bound.
3Receiver Broadcast Channels with Common and Confidential Messages
, 2009
"... AbstractAchievable secrecy rate regions for the general 3receiver broadcast channel with one common and one confidential message sets are established. We consider two setups: (i) when the confidential message is to be sent to two of the receivers and the third receiver is an eavesdropper; and (ii) ..."
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Cited by 19 (4 self)
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AbstractAchievable secrecy rate regions for the general 3receiver broadcast channel with one common and one confidential message sets are established. We consider two setups: (i) when the confidential message is to be sent to two of the receivers and the third receiver is an eavesdropper; and (ii) when the confidential message is to be sent to one of the receivers and the other two receivers are eavesdroppers. We show that our secrecy rate regions are optimurn for some special cases. I.
DegreesofFreedom Region of the MISO Broadcast Channel with General MixedCSIT
"... Abstract—In the setting of the twouser broadcast channel, recent work by MaddahAli and Tse has shown that knowledge of prior channel state information at the transmitter (CSIT) can be useful, even in the absence of any knowledge of current CSIT. Very recent work by Kobayashi et al., Yang et al., a ..."
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Cited by 18 (8 self)
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Abstract—In the setting of the twouser broadcast channel, recent work by MaddahAli and Tse has shown that knowledge of prior channel state information at the transmitter (CSIT) can be useful, even in the absence of any knowledge of current CSIT. Very recent work by Kobayashi et al., Yang et al., and Gou and Jafar, extended this to the case where, instead of no current CSIT knowledge, the transmitter has partial knowledge, and where under a symmetry assumption, the quality of this knowledge is identical for the different users ’ channels. Motivated by the fact that in multiuser settings, the quality of CSIT feedback may vary across different links, we here generalize the above results to the natural setting where the current CSIT quality varies for different users ’ channels. For this setting we derive the optimal degreesoffreedom (DoF) region, and provide novel multiphase broadcast schemes that achieve this optimal region. Finally this generalization incorporates and generalizes the corresponding result in Maleki et al. which considered the broadcast channel with one user having perfect CSIT and the other only having prior CSIT. I.
An achievable rate region for a multiuser halfduplex twoway channel
 in Annual Conference on Signal, Systems, and Computers, Asilomar, OctNov
, 2006
"... Abstract — Feedback is known to enlarge the capacity region of a multiuser channel. However, none of the information theoretic analysis account for resource usage of the feedback link. In this paper, we adopt a novel twoway formulation for multiuser systems, which jointly designs the uplink and dow ..."
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Cited by 6 (2 self)
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Abstract — Feedback is known to enlarge the capacity region of a multiuser channel. However, none of the information theoretic analysis account for resource usage of the feedback link. In this paper, we adopt a novel twoway formulation for multiuser systems, which jointly designs the uplink and downlink communication. By assuming that nodes are halfduplex (in time) and feedback shares resources with data, all resource usage is accurately accounted in the system. Our achievable rate region shows that feedback is beneficial only if the the channel is twoway, i.e, there is data to be sent in both directions. I.
Coding Schemes and Asymptotic Capacity for the Gaussian Broadcast and Interference Channels With Feedback
"... Abstract — A coding scheme is proposed for the memoryless Gaussian broadcast channel with correlated noises and feedback. For all noise correlations other than ±1, the gap between the sumrate that the scheme achieves and the fullcooperation bound vanishes as the signaltonoise ratio tends to infin ..."
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Cited by 5 (0 self)
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Abstract — A coding scheme is proposed for the memoryless Gaussian broadcast channel with correlated noises and feedback. For all noise correlations other than ±1, the gap between the sumrate that the scheme achieves and the fullcooperation bound vanishes as the signaltonoise ratio tends to infinity. When the correlation coefficient is −1, the gains afforded by feedback are unbounded and the prelog is doubled. When the correlation coefficient is +1, we demonstrate a dichotomy that if the noise variances are equal, then feedback is useless, and otherwise, feedback affords unbounded rate gains and doubles the prelog. The unbounded feedback gains, however, require perfect (noiseless) feedback. When the feedback links are noisy, the feedback gains are bounded, unless the feedback noise decays to zero sufficiently fast with the signaltonoise ratio. Extensions to more receivers are also discussed as is the memoryless Gaussian interference channel with feedback. Index Terms — Broadcast channel, capacity, feedback, high SNR, interference channel, prelog.
Optimal Rate Delay Tradeoffs and Delay Mitigating Codes for Multipath Routed and Network Coded Networks
, 2009
"... Via multiterminal information theory, a framework is presented for deriving fundamental rate delay tradeoffs that delay mitigating codes must have when utilized over multipath routed and random linear network coded networks. The rate delay tradeoff is formulated as a calculus problem on a capacity ..."
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Cited by 5 (1 self)
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Via multiterminal information theory, a framework is presented for deriving fundamental rate delay tradeoffs that delay mitigating codes must have when utilized over multipath routed and random linear network coded networks. The rate delay tradeoff is formulated as a calculus problem on a capacity region of a related abstracted broadcast channel. Given this general framework for studying such rate delay tradeoffs, the extreme case of uniform networks, in which each possible received packet arrival order is equally likely, is considered. For these networks, the rate delay calculus problem is simplified to an integer programming problem, which for small numbers of packets may be solved explicitly, or for larger numbers of packets, may be accurately approximated through the calculus of variations by appropriate relaxation of an integer constraint. Explicit expressions for the rate delay tradeoff in uniform networks are presented in the special cases of i) constant packet interarrival times, and ii) exponential i.i.d. packet arrival times. Finally, the delay mitigating codes achieving these rate delay tradeoffs are discussed.
1Layered Interference Networks with Delayed CSI: DoF Scaling with Distributed Transmitters
"... The layered interference network is investigated with delayed channel state information (CSI) at all nodes. It is demonstrated how multihopping can be utilized to increase the achievable degrees of freedom (DoF). In particular, a multiphase transmission scheme is proposed for the Kuser 2Khop int ..."
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Cited by 5 (4 self)
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The layered interference network is investigated with delayed channel state information (CSI) at all nodes. It is demonstrated how multihopping can be utilized to increase the achievable degrees of freedom (DoF). In particular, a multiphase transmission scheme is proposed for the Kuser 2Khop interference network in order to systematically exploit the layered structure of the network and delayed CSI to achieve DoF values that scale with K. This result provides the first example of a network with distributed transmitters and delayed CSI whose DoF scales with the number of users. I.