532 research outputs found
Impact of Spatial Correlation on the Finite-SNR Diversity-Multiplexing Tradeoff
The impact of spatial correlation on the performance limits of multielement
antenna (MEA) channels is analyzed in terms of the diversity-multiplexing
tradeoff (DMT) at finite signal-to-noise ratio (SNR) values. A lower bound on
the outage probability is first derived. Using this bound accurate finite-SNR
estimate of the DMT is then derived. This estimate allows to gain insight on
the impact of spatial correlation on the DMT at finite SNR. As expected, the
DMT is severely degraded as the spatial correlation increases. Moreover, using
asymptotic analysis, we show that our framework encompasses well-known results
concerning the asymptotic behavior of the DMT.Comment: Accepted for publication to IEEE Transaction on Wireless
Communication on June 4th 200
A Generalized Spatial Correlation Model for 3D MIMO Channels based on the Fourier Coefficients of Power Spectrums
Previous studies have confirmed the adverse impact of fading correlation on
the mutual information (MI) of two-dimensional (2D) multiple-input
multiple-output (MIMO) systems. More recently, the trend is to enhance the
system performance by exploiting the channel's degrees of freedom in the
elevation, which necessitates the derivation and characterization of
three-dimensional (3D) channels in the presence of spatial correlation. In this
paper, an exact closed-form expression for the Spatial Correlation Function
(SCF) is derived for 3D MIMO channels. This novel SCF is developed for a
uniform linear array of antennas with nonisotropic antenna patterns. The
proposed method resorts to the spherical harmonic expansion (SHE) of plane
waves and the trigonometric expansion of Legendre and associated Legendre
polynomials. The resulting expression depends on the underlying arbitrary
angular distributions and antenna patterns through the Fourier Series (FS)
coefficients of power azimuth and elevation spectrums. The novelty of the
proposed method lies in the SCF being valid for any 3D propagation environment.
The developed SCF determines the covariance matrices at the transmitter and the
receiver that form the Kronecker channel model. In order to quantify the
effects of correlation on the system performance, the information-theoretic
deterministic equivalents of the MI for the Kronecker model are utilized in
both mono-user and multi-user cases. Numerical results validate the proposed
analytical expressions and elucidate the dependence of the system performance
on azimuth and elevation angular spreads and antenna patterns. Some useful
insights into the behaviour of MI as a function of downtilt angles are
provided. The derived model will help evaluate the performance of correlated 3D
MIMO channels in the future.Comment: Accepted in IEEE Transactions on signal processin
Asymptotic SER and Outage Probability of MIMO MRC in Correlated Fading
This letter derives the asymptotic symbol error rate (SER) and outage
probability of multiple-input multiple-output (MIMO) maximum ratio combining
(MRC) systems. We consider Rayleigh fading channels with both transmit and
receive spatial correlation. Our results are based on new asymptotic
expressions which we derive for the p.d.f. and c.d.f. of the maximum eigenvalue
of positive-definite quadratic forms in complex Gaussian matrices. We prove
that spatial correlation does not affect the diversity order, but that it
reduces the array gain and hence increases the SER in the high SNR regime.Comment: 10 pages, 2 figures, to appear in IEEE Signal Processing Letter
Optimization of linear multielement antennas for selection combining by means of a Butler matrix in different MIMO environments
An optimized linear multielement antenna (MEA)
is presented for selection combining schemes that improves the
selection diversity gain and selection diversity capacity in medium
and low multipath environments, with respect to the performance
achieved with a simple uniform linear array (ULA) using omnidirectional
antennas, while it performs equally as well as a
ULA in highly scattered environments. An analytical investigation
based on the analysis of the correlation coefficients, together with
simulations and extensive measurements, have been carried out
for different fading multiple-input multiple-output environments
ranging from line of sight (LOS) to non-LOS. Two MEAs are
compared: a simple ULA with omnidirectional antennas and a
MEA combining a ULA and a Butler matrix. The measurement
results show that the nature of the proposed MEA is such that it
is adaptive to any propagation scenario by simultaneously taking
advantage of beamforming gain and signal diversity gain.Peer Reviewe
- âŠ