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103
On the condition number distribution of complex wishart matrices
, 2010
"... Abstract—This paper investigates the distribution of the condition number of complex Wishart matrices. Two closely related measures are considered: the standard condition number (SCN) and the Demmel condition number (DCN), both of which have important applications in the context of multipleinput m ..."
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Cited by 20 (1 self)
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Abstract—This paper investigates the distribution of the condition number of complex Wishart matrices. Two closely related measures are considered: the standard condition number (SCN) and the Demmel condition number (DCN), both of which have important applications in the context of multipleinput multipleoutput (MIMO) communication systems, as well as in various branches of mathematics. We first present a novel generic framework for the SCN distribution which accounts for both central and noncentral Wishart matrices of arbitrary dimension. This result is a simple unified expression which involves only a single scalar integral, and therefore allows for fast and efficient computation. For the case of dual Wishart matrices, we derive new exact polynomial expressions for both the SCN and DCN distributions. We also formulate a new closedform expression for the tail SCN distribution which applies for correlated central Wishart matrices of arbitrary dimension and demonstrates an interesting connection to the maximum eigenvalue moments of Wishart matrices of smaller dimension. Based on our analytical results, we gain valuable insights into the statistical behavior of the channel conditioning for various MIMO fading scenarios, such as uncorrelated/semicorrelated Rayleigh fading and Ricean fading. Index Terms—MIMO systems, complex Wishart matrices, condition number, joint eigenvalue distribution.
Cognitive femtocells: Breaking the spatial reuse barrier of cellular systems
 in Information Theory and Applications Workshop (ITA
, 2011
"... Abstract—We consider smart “cognitive ” femtocells, that can decode the base station control channel and make decision on their transmission opportunities based on the scheduling and resource allocation of the overlaying macrocell. The operation of such femtocells is somehow reminiscent of “Type II ..."
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Cited by 18 (4 self)
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Abstract—We consider smart “cognitive ” femtocells, that can decode the base station control channel and make decision on their transmission opportunities based on the scheduling and resource allocation of the overlaying macrocell. The operation of such femtocells is somehow reminiscent of “Type II ” relays, as specified in the IEEE 802.16j standard. Under certain system assumptions, we consider the tradeoff region of the macrocell versus aggregate femtocell throughput. For the basic system architecture, we evaluate the impact of open versus closed access and interference cancellation at the femtocells. As possible improvements, we consider an application of the “downlink interference alignment ” idea to our system, and the use of multiple antennas at the femtocell access points. We show that a careful combination of these techniques achieves a remarkably large aggregate femtocell throughput, at very low penalty in terms of the precious and scarce macrocell throughput. The unprecedented performance achievable by the proposed architecture advocates a system design that places femtocells at the core of future wireless networks, rather than treating them as an addon afterthought. Index Terms—Femtocells, interference coordination, cellular systems, wireless communications, interference cancelation, interference alignment, MISO/SIMO interference channel. I. BREAKING THE CELLULAR BOTTLENECK Consider a cellular system with M antennas per Base
A deterministic equivalent for the capacity analysis of correlated multiuser MIMO channels
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FiniteSNR DiversityMultiplexing Tradeoff via Asymptotic Analysis of Large MIMO Systems
, 2010
"... Diversitymultiplexing tradeoff (DMT) was characterized asymptotically (SNR> infinity) for i.i.d. Rayleigh fading channel by Zheng and Tse [1]. The SNRasymptotic DMT overestimates the finiteSNR one [2]. This paper outlines a number of additional limitations and difficulties of the DMT framewo ..."
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Cited by 15 (9 self)
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Diversitymultiplexing tradeoff (DMT) was characterized asymptotically (SNR> infinity) for i.i.d. Rayleigh fading channel by Zheng and Tse [1]. The SNRasymptotic DMT overestimates the finiteSNR one [2]. This paper outlines a number of additional limitations and difficulties of the DMT framework and discusses their implications. Using the recent results on the sizeasymptotic (in the number of antennas) outage capacity distribution, the finiteSNR, sizeasymptotic DMT is derived for a broad class of fading distributions. The SNR range over which the finiteSNR DMT is accurately approximated by the SNRasymptotic one is characterized. The multiplexing gain definition is shown to affect critically this range and thus should be carefully selected, so that the SNRasymptotic DMT is an accurate approximation at realistic SNR values and thus has operational significance to be used as a design criterion. The finiteSNR diversity gain is shown to decrease with correlation and power imbalance in a broad class of fading channels, and such an effect is described in a compact, closed form. Complete characterization of the outage probability (or outage capacity) requires not only the finiteSNR DMT, but also the SNR offset, which is introduced and investigated as well. This offset, which is not accounted for in the DMT framework, is shown to have a significant impact on the outage probability for a broad class of fading channels, especially when the multiplexing gain is small. The analytical results and conclusions are validated via extensive Monte Carlo simulations. Overall, the sizeasymptotic DMT represents a valuable alternative to the SNRasymptotic one.
Multicell MIMO downlink with cell cooperation and fair scheduling: A largesystem limit analysis
 IEEE Trans. Inform. Theory
, 2011
"... We consider the downlink of a cellular network with multiple cells and multiantenna base stations, including a realistic distancedependent pathloss model, clusters of cooperating cells, and general “fairness ” requirements. Beyond Monte Carlo simulation, no efficient computation method to evaluat ..."
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Cited by 13 (1 self)
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We consider the downlink of a cellular network with multiple cells and multiantenna base stations, including a realistic distancedependent pathloss model, clusters of cooperating cells, and general “fairness ” requirements. Beyond Monte Carlo simulation, no efficient computation method to evaluate the ergodic throughput of such systems has been presented so far. We propose an analytic solution based on the combination of large random matrix results and convex optimization. The proposed method is computationally much more efficient than Monte Carlo simulation and provides surprisingly accurate approximations for the actual finitedimensional systems, even for a small number of users and base station antennas. Numerical examples include 2cell linear and threesectored 7cell planar layouts, with no intercell cooperation, sector cooperation, or full intercell cooperation. Index Terms Asymptotic analysis, fairness scheduling, intercell cooperation, largesystem limit, multicell MIMO downlink, weighted sum rate maximization.
Achievable Sum Rate of MIMO MMSE Receivers: A General Analytic Framework 1
, 903
"... This paper investigates the achievable sum rate of multipleinput multipleoutput (MIMO) wireless systems employing linear minimum meansquared error (MMSE) receivers. We present a new analytic framework which unveils an interesting connection between the achievable sum rate with MMSE receivers and ..."
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Cited by 12 (0 self)
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This paper investigates the achievable sum rate of multipleinput multipleoutput (MIMO) wireless systems employing linear minimum meansquared error (MMSE) receivers. We present a new analytic framework which unveils an interesting connection between the achievable sum rate with MMSE receivers and the ergodic mutual information achieved with optimal receivers. This simple but powerful result enables the vast prior literature on ergodic MIMO mutual information to be directly applied to the analysis of MMSE receivers. The framework is particularized to various Rayleigh and Rician channel scenarios to yield new exact closedform expressions for the achievable sum rate, as well as simplified expressions in the asymptotic regimes of high and low signal to noise ratios. These expressions lead to the discovery of key insights into the performance of MIMO MMSE receivers under practical channel conditions.
On the multicell processing capacity of the cellular MIMO uplink channel in correlated Rayleigh fading environment
 IEEE Trans. Wireless Commun
, 2009
"... Abstract—In the informationtheoretic literature, it has been widely shown that multicell processing is able to provide high capacity gains in the context of cellular systems and that the percell sumrate capacity of multicell processing systems grows linearly with the number of Base Station (BS) r ..."
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Cited by 11 (7 self)
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Abstract—In the informationtheoretic literature, it has been widely shown that multicell processing is able to provide high capacity gains in the context of cellular systems and that the percell sumrate capacity of multicell processing systems grows linearly with the number of Base Station (BS) receive antennas. However, the majority of results in this area has been produced assuming that the fading coefficients of the MIMO subchannels are totally uncorrelated. In this direction, this paper investigates the ergodic percell sumrate capacity of the MIMO Cellular MultipleAccess Channel under correlated fading and multicell processing. More specifically, the current channel model considers Rayleigh fading, uniformly distributed User Terminals (UTs) over a planar cellular system and powerlaw path loss. Furthermore, both BSs and Uts are equipped with correlated multiple antennas, which are modelled according to the Kronecker model. The percell sumrate capacity closed form is derived using a Free Probability approach and numerical results are produced by varying the cell density of the system, as well as the level of correlation. I.
Jr., “Benefit of pattern diversity via twoelement array of circular patch antennas in indoor clustered MIMO channels
 IEEE Transactions on Communications
, 2006
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Pilot beam pattern design for channel estimation in massive MIMO systems
 IEEE J. Sel. Topics Signal Process
, 2014
"... Abstract—In this paper, the problem of pilot beam pattern design for channel estimation in massive multipleinput multipleoutput systems with a large number of transmit antennas at the base station is considered, and a new algorithm for pilot beam pattern design for optimal channel estimation is p ..."
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Cited by 11 (8 self)
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Abstract—In this paper, the problem of pilot beam pattern design for channel estimation in massive multipleinput multipleoutput systems with a large number of transmit antennas at the base station is considered, and a new algorithm for pilot beam pattern design for optimal channel estimation is proposed under the assumption that the channel is a stationary GaussMarkov random process. The proposed algorithm designs the pilot beam pattern sequentially by exploiting the properties of Kalman filtering and the associated prediction error covariance matrices and also the channel statistics such as spatial and temporal channel correlation. The resulting design generates a sequentiallyoptimal sequence of pilot beam patterns with low complexity for a given set of system parameters. Numerical results show the effectiveness of the proposed algorithm. Index Terms—Channel estimation, massive MIMO systems, spatiotemporal correlation, training signal design. I.
Optimal transmit covariance for MIMO channels with statistical transmitter side information
 IEEE Intern. Symp. Inf. Theory
, 2005
"... Abstract — We give an optimality condition for the input covariance for arbitrary ergodic Gaussian vector channels under the condition that the channel gains are independent of the transmit signal, the transmitter has knowledge of the channel gain probability law and the receiver has knowledge of ea ..."
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Cited by 9 (2 self)
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Abstract — We give an optimality condition for the input covariance for arbitrary ergodic Gaussian vector channels under the condition that the channel gains are independent of the transmit signal, the transmitter has knowledge of the channel gain probability law and the receiver has knowledge of each channel realization. Using this optimality condition, we find an iterative algorithm for numerical computation of optimal input covariance matrices. I.