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14
HighSNR power offset in multiantenna communication
 IEEE Transactions on Information Theory
, 2005
"... Abstract—The analysis of the multipleantenna capacity in the high regime has hitherto focused on the high slope (or maximum multiplexing gain), which quantifies the multiplicative increase as a function of the number of antennas. This traditional characterization is unable to assess the impact of ..."
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Cited by 68 (14 self)
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Abstract—The analysis of the multipleantenna capacity in the high regime has hitherto focused on the high slope (or maximum multiplexing gain), which quantifies the multiplicative increase as a function of the number of antennas. This traditional characterization is unable to assess the impact of prominent channel features since, for a majority of channels, the slope equals the minimum of the number of transmit and receive antennas. Furthermore, a characterization based solely on the slope captures only the scaling but it has no notion of the power required for a certain capacity. This paper advocates a more refined characterization whereby, as a function of �f, the high capacity is expanded as an affine function where the impact of channel features such as antenna correlation, unfaded components, etc., resides in the zeroorder term or power offset. The power offset, for which we find insightful closedform expressions, is shown to play a chief role for levels of practical interest. Index Terms—Antenna correlation, channel capacity, coherent communication, fading channels, high analysis, multiantenna arrays, Ricean channels.
On the Outage Capacity of Correlated MultiplePath MIMO Channels
, 2005
"... The use of multiantenna arrays in both transmission and reception has been shown to dramatically increase the throughput of wireless communication systems. As a result there has been considerable interest in characterizing the ergodic average of the mutual information for realistic correlated chan ..."
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Cited by 14 (0 self)
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The use of multiantenna arrays in both transmission and reception has been shown to dramatically increase the throughput of wireless communication systems. As a result there has been considerable interest in characterizing the ergodic average of the mutual information for realistic correlated channels. Here, an approach is presented that provides analytic expressions not only for the average, but also the higher cumulant moments of the distribution of the mutual information for zeromean Gaussian MIMO channels with the most general multipath covariance matrices when the channel is known at the receiver. These channels include multitap delay paths, as well as general channels with covariance matrices that cannot be written as a Kronecker product, such as dualpolarized antenna arrays with general correlations at both transmitter and receiver ends. The mathematical methods are formally valid for large antenna numbers, in which limit it is shown that all higher cumulant moments of the distribution, other than the first two scale to zero. Thus, it is confirmed that the distribution of the mutual information tends to a Gaussian, which enables one to calculate the outage capacity. These results are quite accurate even in the case of a few antennas, which makes this approach applicable to realistic situations.
Spectral efficiency of multicarrier CDMA
 IEEE Trans. Inf. Theory
, 2005
"... Abstract—We analyze the spectral efficiency (sumrate per subcarrier) of randomly spread synchronous multicarrier codedivision multiple access (MCCDMA) subject to frequencyselective fading in the asymptotic regime of number of users and bandwidth going to infinity with a constant ratio. Both upli ..."
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Cited by 13 (1 self)
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Abstract—We analyze the spectral efficiency (sumrate per subcarrier) of randomly spread synchronous multicarrier codedivision multiple access (MCCDMA) subject to frequencyselective fading in the asymptotic regime of number of users and bandwidth going to infinity with a constant ratio. Both uplink and downlink are considered, either conditioned on the subcarrier fading coefficients (for nonergodic channels) or unconditioned thereon (for ergodic channels). The following receivers are analyzed: a) jointly optimum receiver, b) linear minimum meansquare error (MMSE) receiver, c) decorrelator, and d) singleuser matched filter. Index Terms—Channel capacity, multicarrier codedivision multiple access (MCCDMA), random matrix theory, multiuser
When is limited feedback for transmit beamforming beneficial
 In Proc. IEEE International Symposium on Information Theory
, 2005
"... Multiantenna systems have been shown to offer tremendous capacity increase in ideal rich scattering conditions. Transmit beamforming and receive combining are low complexity techniques that help in achieving the full diversity afforded by the multiantenna channel. Even if complete channel knowledge ..."
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Cited by 4 (2 self)
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Multiantenna systems have been shown to offer tremendous capacity increase in ideal rich scattering conditions. Transmit beamforming and receive combining are low complexity techniques that help in achieving the full diversity afforded by the multiantenna channel. Even if complete channel knowledge at the receiver maybe a realistic assumption in these systems, the same may not be true at the transmitter side. Thus, quantized beamforming with limited feedback on a reverse link has been a topic that has attracted great attention recently. But almost all of the work to date has focussed on modeling the channel with independent, identically distributed (i.i.d.) Rayleigh fading between antenna pairs. In this report, we first review the earlier works which focus on Grassmannian line packing. We then consider the correlated channel case, and show that Grassmannian line packing is an artificial artifact of the i.i.d. assumption. We show that there are dominant peaks in the eigendomain when correlation is imposed and the codebook construction should be matched to the correlation in the channel, which renders the problem in this case easier than for the i.i.d. channels. 1
Transmit Diversity v. Spatial Multiplexing in Modern MIMO Systems
, 2008
"... A contemporary perspective on the tradeoff between transmit antenna diversity and spatial multiplexing is provided. It is argued that, in the context of most modern wireless systems and for the operating points of interest, transmission techniques that utilize all available spatial degrees of freedo ..."
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Cited by 3 (3 self)
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A contemporary perspective on the tradeoff between transmit antenna diversity and spatial multiplexing is provided. It is argued that, in the context of most modern wireless systems and for the operating points of interest, transmission techniques that utilize all available spatial degrees of freedom for multiplexing outperform techniques that explicitly sacrifice spatial multiplexing for diversity. In the context of such systems, therefore, there essentially is no decision to be made between transmit antenna diversity and spatial multiplexing in MIMO communication. Reaching this conclusion, however, requires that the channel and some key system features be adequately modeled and that suitable performance metrics be adopted; failure to do so may bring about starkly different conclusions. As a specific example, this contrast is illustrated using the 3GPP LongTerm Evolution system design.
Transmit Diversity vs. Spatial Multiplexing in Modern MIMO Systems
, 2010
"... A contemporary perspective on transmit antenna diversity and spatial multiplexing is provided. It is argued that, in the context of most modern wireless systems and for the operating points of interest, transmission techniques that utilize all available spatial degrees of freedom for multiplexing o ..."
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Cited by 3 (1 self)
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A contemporary perspective on transmit antenna diversity and spatial multiplexing is provided. It is argued that, in the context of most modern wireless systems and for the operating points of interest, transmission techniques that utilize all available spatial degrees of freedom for multiplexing outperform techniques that explicitly sacrifice spatial multiplexing for diversity. Reaching this conclusion, however, requires that the channel and some key system features be adequately modeled and that suitable performance metrics be adopted; failure to do so may bring about starkly different conclusions. As a specific example, this contrast is illustrated using the 3GPP LongTerm Evolution system design.
The Space Frontier: Physical Limits of Multiple Antenna Information Transfer
 in "Proc. of 3rd Workshop on Interdisciplinary Systems Approach in Performance Evaluation and Design of Computer and Communication Systems (InterPerf 2008
"... In this paper, we study the capacity limits of dense multiantenna systems. We derive asymptotic capacity expressions for pointtopoint and broadcast channels by applying recent tools from random matrix theory. In the case of broadcast channels, we focus on linear precoding techniques. We found that ..."
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In this paper, we study the capacity limits of dense multiantenna systems. We derive asymptotic capacity expressions for pointtopoint and broadcast channels by applying recent tools from random matrix theory. In the case of broadcast channels, we focus on linear precoding techniques. We found that the asymptotic capacity depends only on the ratio between the size of the antenna array and the wavelength. This provides useful guidelines on the achievable limits of information transfer. In particular, it is shown that the total capacity grows unbounded if the transmitter has perfect knowledge on the channel, while the capacity saturates in the absence of channel knowledge at the transmitter. We provide numerical results supporting the theoretical derivations. 1.
2006 IEEE Ninth International Symposium on Spread Spectrum Techniques and Applications Theory of Large Dimensional Random Matrices for Engineers
"... Abstract — In the last few years, the asymptotic distribution of the singular values of certain random matrices has emerged as a key tool in the analysis and design of wireless communication channels. These channels are characterized by random matrices that admit various statistical descriptions dep ..."
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Abstract — In the last few years, the asymptotic distribution of the singular values of certain random matrices has emerged as a key tool in the analysis and design of wireless communication channels. These channels are characterized by random matrices that admit various statistical descriptions depending on the actual application. The goal of this paper is the investigation and application of random matrix theory with particular emphasis on the asymptotic theorems on the distribution of the squared singular values under various assumption on the joint distribution of the random matrix entries. I.
PerAntenna Rate and Power Control for MIMO Layered Architectures in the Low and HighPower Regimes
, 2009
"... In a MIMO layered architecture, several codewords are transmitted from a multiplicity of antennas. Although the spectral efficiency is maximized if the rates of these codewords are separately controlled, the feedback rate within the link adaptation loop is reduced if they are constrained to be ident ..."
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In a MIMO layered architecture, several codewords are transmitted from a multiplicity of antennas. Although the spectral efficiency is maximized if the rates of these codewords are separately controlled, the feedback rate within the link adaptation loop is reduced if they are constrained to be identical. This poses a direct tradeoff between performance and feedback overhead. This paper provides analytical expressions that quantify the difference in spectral efficiency between both approaches for arbitrary numbers of antennas. Specifically, the characterization takes place in the realm of the low and highpower regimes via expansions that are shown to have a wide range of validity. In addition, the possibility of adjusting the transmit power of each codeword individually is considered as an alternative to the separate control of their rates. Power allocation, however, turns out to be inferior to rate control within the context of this problem.