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Survey of channel and radio propagation models for wireless MIMO systems
 EURASIP Journal on Wireless Communications and Networking
"... This paper provides an overview of stateoftheart radio propagation and channel models for wireless multipleinput multipleoutput (MIMO) systems. We distinguish between physical models and analytical models and discuss popular examples from both model types. Physical models focus on the doubledi ..."
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Cited by 24 (4 self)
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This paper provides an overview of stateoftheart radio propagation and channel models for wireless multipleinput multipleoutput (MIMO) systems. We distinguish between physical models and analytical models and discuss popular examples from both model types. Physical models focus on the doubledirectional propagation mechanisms between the location of transmitter and receiver without taking the antenna configuration into account. Analytical models capture physical wave propagation and antenna configuration simultaneously by describing the impulse response (equivalently, the transfer function) between the antenna arrays at both link ends. We also review some MIMO models that are included in current standardization activities for the purpose of reproducible and comparable MIMO system evaluations. Finally, we describe a couple of key features of channels and radio propagation which are not sufficiently included in current MIMO models. I. INTRODUCTION AND OVERVIEW Within roughly ten years, multipleinput multipleoutput (MIMO) technology has made its way from purely theoretical performance analyses that promised enormous capacity gains [1], [2] to actual products for the wireless market (e.g., [3], [4], [5]). However, numerous MIMO techniques still have not been sufficiently tested under realistic propagation conditions and hence their integration into real applications can be considered to
Informationtheoretic multihopping for relay networks
 in Proc. 2004 Int. Zurich Seminar on Communications
, 2004
"... Abstract — Recent advances in multihopping are extended to relay networks having multiple antennas and multiple sources. As for the singleantenna and singlesource case, one can achieve the ergodic capacity of wireless relay networks with phase fading if the relays are in a region near the source ..."
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Cited by 15 (2 self)
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Abstract — Recent advances in multihopping are extended to relay networks having multiple antennas and multiple sources. As for the singleantenna and singlesource case, one can achieve the ergodic capacity of wireless relay networks with phase fading if the relays are in a region near the source terminal, and if phase information is available only locally. The capacity results further generalize to Rayleigh fading, singlebounce fading, certain quasistatic fading problems, cases where partial channel knowledge is available at the transmitters, and cases where local user cooperation is permitted. The multisource networks considered are the multiaccess and broadcast relay channels. I.
MOBILE FLEXIBLE NETWORKS: THE CHALLENGES AHEAD
 INTERNATIONAL CONFERENCE ON ADVANCED TECHNOLOGIES FOR COMMUNICATIONS, VIET NAM
, 2008
"... The general framework of Mobile Flexible Networks is to design selforganizing secure networks where terminals and base stations interact and selfadapt in an intelligent manner without the need of a central controller (or with the right amount of regulation...just enough to let the agents in the ne ..."
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Cited by 13 (10 self)
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The general framework of Mobile Flexible Networks is to design selforganizing secure networks where terminals and base stations interact and selfadapt in an intelligent manner without the need of a central controller (or with the right amount of regulation...just enough to let the agents in the network exploit fully the degrees of freedom). Of course, the design depends on the mobility pattern and delay tolerance as in highly mobile environments, exchange of control signaling bears a huge cost whereas for fixed (nonmobile) networks, the designer can dedicate a fraction of the rate (which is negligible in terms of overhead) to optimize the system. One of the big challenges is to find how to optimally split the intelligence between cognitive terminals and cognitive networks. In this paper, we discuss the challenges ahead and provide some research directions to develop the theoretical foundations of these networks.
MIMO diversity in the presence of double scattering
 IEEE Trans. Inform. Theory
, 2008
"... The potential benefits of multipleantenna systems may be limited by two types of channel degradations—rank deficiency and spatial fading correlation of the channel. In this paper, we assess the effects of these degradations on the diversity performance of multipleinput multipleoutput (MIMO) syste ..."
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Cited by 10 (3 self)
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The potential benefits of multipleantenna systems may be limited by two types of channel degradations—rank deficiency and spatial fading correlation of the channel. In this paper, we assess the effects of these degradations on the diversity performance of multipleinput multipleoutput (MIMO) systems, with an emphasis on orthogonal space–time block codes, in terms of the symbol error probability, the effective fading figure (EFF), and the capacity at low signaltonoise ratio (SNR). In particular, we consider a general family of MIMO channels known as doublescattering channels, which encompasses a variety of propagation environments from independent and identically distributed Rayleigh to degenerate keyhole or pinhole cases by embracing both rankdeficient and spatial correlation effects. It is shown that a MIMO system with nT transmit and nR receive antennas achieves the diversity of order nTnSnR max(nT,nS,nR) in a doublescattering channel with nS effective scatterers. We also quantify the combined effect of the spatial correlation and the lack of scattering richness on the EFF and the lowSNR capacity in terms of the correlation figures of transmit, receive, and scatterer correlation matrices. We further show the
Maximum Entropy MIMO Wireless Channel Models with Limited Information
 in Proc. MATHMOD Conference on Mathematical Modeling
, 2006
"... In this contribution, models of wireless channels are derived from the maximum entropy principle, for several cases where only limited information about the propagation environment is available. First, analytical models are derived for the cases where certain parameters (channel energy, average ener ..."
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Cited by 9 (6 self)
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In this contribution, models of wireless channels are derived from the maximum entropy principle, for several cases where only limited information about the propagation environment is available. First, analytical models are derived for the cases where certain parameters (channel energy, average energy, spatial correlation matrix) are known deterministically. Frequently, these parameters are unknown (typically because the received energy or the spatial correlation varies with the user position), but still known to represent meaningful system characteristics. In these cases, analytical channel models are derived by assigning entropymaximizing distributions to these parameters, and marginalizing them out. For the MIMO case with spatial correlation, we show that the distribution of the covariance matrices is conveniently handled through its eigenvalues. The entropymaximizing distribution of the covariance matrix is shown to be a Wishart distribution. Furthermore, the corresponding probability density function of the channel matrix is shown to be described analytically by a function of the channel Frobenius norm. This technique can provide channel models incorporating the effect of shadow fading and spatial correlation between antennas without the need to assume explicit values for these parameters. The results are compared in terms of mutual information to the classical i.i.d. Gaussian model.
Spectral Efficiency of CDMA Downlink Cellular Networks with Matched Filter
, 2006
"... In this contribution, the performance of a downlink code division multiple access (CDMA) system with orthogonal spreading and multicell interference is analyzed. A useful framework is provided in order to determine the optimal base station coverage for wireless frequency selective channels with dens ..."
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Cited by 7 (2 self)
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In this contribution, the performance of a downlink code division multiple access (CDMA) system with orthogonal spreading and multicell interference is analyzed. A useful framework is provided in order to determine the optimal base station coverage for wireless frequency selective channels with dense networks where each user is equipped with a matched filter. Using asymptotic arguments, explicit expressions of the spectral efficiency are obtained and provide a simple expression of the network spectral efficiency based only on a few meaningful parameters. Contrarily to a common misconception which asserts that to increase spectral efficiency in a CDMA network, one has to increase the number of cells, we show that, depending on the path loss and the fading channel statistics, the code orthogonal gain (due to the synchronization of all the users at the base station) can compensate and even compete in some cases with the drawbacks due to intercell interference. The results are especially realistic and useful for the design of dense networks.
Impact of scattering on the capacity, diversity and propagation range of multiple antenna channels
 IEEE Trans. on Information Theory
, 2004
"... Abstract — The impact of scattering condition and array configuration on performances are inseparable in early analyses of multipleantenna systems. An arrayindependent scattering model is introduced where three basic scattering mechanisms are modeled. Performance results become more intrinsic prop ..."
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Cited by 6 (1 self)
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Abstract — The impact of scattering condition and array configuration on performances are inseparable in early analyses of multipleantenna systems. An arrayindependent scattering model is introduced where three basic scattering mechanisms are modeled. Performance results become more intrinsic property of the scattering channel itself. For linear arrays of length L in an environment of total angle spread Ω, the ergodic capacity is shown to increase linearly with LΩ  for large arrays. When antenna arrays reduce to practical sizes, the capacity scaling depends on the SNR as well. This implies that the number of antennas used should also depend on the SNR. In terms of outage capacity, the tradeoff between spatial multiplexing gain and diversity gain is shown to be very sensitive to the underlying scattering mechanisms. Finally, as Ω  varies with the propagation range, the tradeoff among multiplexing gain, diversity gain, and propagation range is studied. Index Terms — Multiple antennas, multipleinput multipleoutput (MIMO) systems, physical channel modeling, antenna
EnergyEfficient Precoding for MultipleAntenna Terminals
, 2011
"... The problem of energyefficient precoding is investigated when the terminals in the system are equipped with multiple antennas. Considering static and fastfading multipleinput multipleoutput (MIMO) channels, the energyefficiency is defined as the transmission rate to power ratio and shown to be ..."
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Cited by 5 (3 self)
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The problem of energyefficient precoding is investigated when the terminals in the system are equipped with multiple antennas. Considering static and fastfading multipleinput multipleoutput (MIMO) channels, the energyefficiency is defined as the transmission rate to power ratio and shown to be maximized at low transmit power. The most interesting case is the one of slow fading MIMO channels. For this type of channels, the optimal precoding scheme is generally not trivial. Furthermore, using all the available transmit power is not always optimal in the sense of energyefficiency [which, in this case, corresponds to the communicationtheoretic definition of the goodputtopower (GPR) ratio]. Finding the optimal precoding matrices is shown to be a new open problem and is solved in several special cases: 1. when there is only one receive antenna; 2. in the low or high signaltonoise ratio regime; 3. when uniform power allocation and the regime of large numbers of antennas are assumed. A complete numerical analysis is provided to illustrate the derived results and stated conjectures. In particular, the impact of the number of antennas on the energyefficiency is assessed and shown to be significant.
Vector precoding for wireless MIMO systems and its replica analysis
 IEEE J. Sel. Areas Commun
"... We apply the replica method to analyze vector precoding, a method to reduce transmit power in antenna array communications. The analysis applies to a very general class of channel matrices. The statistics of the channel matrix enter the transmitted energy per symbol via its Rtransform. We find that ..."
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Cited by 3 (1 self)
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We apply the replica method to analyze vector precoding, a method to reduce transmit power in antenna array communications. The analysis applies to a very general class of channel matrices. The statistics of the channel matrix enter the transmitted energy per symbol via its Rtransform. We find that vector precoding performs much better for complex than for real alphabets. As a byproduct, we find a nonlinear precoding method with polynomial complexity that outperforms NPhard TomlinsonHarashima precoding for binary modulation on complex channels if the number of transmit antennas is slightly larger than twice the number of receive antennas. Index Terms Multipleantenna wireless, multipleinput multipleoutput (MIMO), spatial equalization, TomlinsonHarashima precoding, replica method, random matrices, Rtransform. I.