2,332 research outputs found
Exact MIMO Zero-Forcing Detection Analysis for Transmit-Correlated Rician Fading
We analyze the performance of multiple input/multiple output (MIMO)
communications systems employing spatial multiplexing and zero-forcing
detection (ZF). The distribution of the ZF signal-to-noise ratio (SNR) is
characterized when either the intended stream or interfering streams experience
Rician fading, and when the fading may be correlated on the transmit side.
Previously, exact ZF analysis based on a well-known SNR expression has been
hindered by the noncentrality of the Wishart distribution involved. In
addition, approximation with a central-Wishart distribution has not proved
consistently accurate. In contrast, the following exact ZF study proceeds from
a lesser-known SNR expression that separates the intended and interfering
channel-gain vectors. By first conditioning on, and then averaging over the
interference, the ZF SNR distribution for Rician-Rayleigh fading is shown to be
an infinite linear combination of gamma distributions. On the other hand, for
Rayleigh-Rician fading, the ZF SNR is shown to be gamma-distributed. Based on
the SNR distribution, we derive new series expressions for the ZF average error
probability, outage probability, and ergodic capacity. Numerical results
confirm the accuracy of our new expressions, and reveal effects of interference
and channel statistics on performance.Comment: 14 pages, two-colum, 1 table, 10 figure
Phase transitions in the condition number distribution of Gaussian random matrices
We study the statistics of the condition number
(the ratio between
largest and smallest squared singular values) of Gaussian random
matrices. Using a Coulomb fluid technique, we derive analytically and for large
the cumulative and tail-cumulative
distributions of . We find that these
distributions decay as and , where is the Dyson index of the ensemble. The left
and right rate functions are independent of and
calculated exactly for any choice of the rectangularity parameter
. Interestingly, they show a weak non-analytic behavior at
their minimum (corresponding to the average condition
number), a direct consequence of a phase transition in the associated Coulomb
fluid problem. Matching the behavior of the rate functions around
, we determine exactly the scale of typical fluctuations
and the tails of the limiting distribution of
. The analytical results are in excellent agreement with numerical
simulations.Comment: 5 pag. + 7 pag. Suppl. Material. 3 Figure
Eigenvalue Dynamics of a Central Wishart Matrix with Application to MIMO Systems
We investigate the dynamic behavior of the stationary random process defined
by a central complex Wishart (CW) matrix as it varies along a
certain dimension . We characterize the second-order joint cdf of the
largest eigenvalue, and the second-order joint cdf of the smallest eigenvalue
of this matrix. We show that both cdfs can be expressed in exact closed-form in
terms of a finite number of well-known special functions in the context of
communication theory. As a direct application, we investigate the dynamic
behavior of the parallel channels associated with multiple-input
multiple-output (MIMO) systems in the presence of Rayleigh fading. Studying the
complex random matrix that defines the MIMO channel, we characterize the
second-order joint cdf of the signal-to-noise ratio (SNR) for the best and
worst channels. We use these results to study the rate of change of MIMO
parallel channels, using different performance metrics. For a given value of
the MIMO channel correlation coefficient, we observe how the SNR associated
with the best parallel channel changes slower than the SNR of the worst
channel. This different dynamic behavior is much more appreciable when the
number of transmit () and receive () antennas is similar. However, as
is increased while keeping fixed, we see how the best and worst
channels tend to have a similar rate of change.Comment: 15 pages, 9 figures and 1 table. This work has been accepted for
publication at IEEE Trans. Inf. Theory. Copyright (c) 2014 IEEE. Personal use
of this material is permitted. However, permission to use this material for
any other purposes must be obtained from the IEEE by sending a request to
[email protected]
A Random Matrix Approach to Dynamic Factors in macroeconomic data
We show how random matrix theory can be applied to develop new algorithms to
extract dynamic factors from macroeconomic time series. In particular, we
consider a limit where the number of random variables N and the number of
consecutive time measurements T are large but the ratio N / T is fixed. In this
regime the underlying random matrices are asymptotically equivalent to Free
Random Variables (FRV).Application of these methods for macroeconomic
indicators for Poland economy is also presented.Comment: arXiv admin note: text overlap with arXiv:physics/0512090 by other
author
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