615 research outputs found
An efficient approximation to the correlated Nakagami-m sums and its application in equal gain diversity receivers
There are several cases in wireless communications theory where the
statistics of the sum of independent or correlated Nakagami-m random variables
(RVs) is necessary to be known. However, a closed-form solution to the
distribution of this sum does not exist when the number of constituent RVs
exceeds two, even for the special case of Rayleigh fading. In this paper, we
present an efficient closed-form approximation for the distribution of the sum
of arbitrary correlated Nakagami-m envelopes with identical and integer fading
parameters. The distribution becomes exact for maximal correlation, while the
tightness of the proposed approximation is validated statistically by using the
Chi-square and the Kolmogorov-Smirnov goodness-of-fit tests. As an application,
the approximation is used to study the performance of equal-gain combining
(EGC) systems operating over arbitrary correlated Nakagami-m fading channels,
by utilizing the available analytical results for the error-rate performance of
an equivalent maximal-ratio combining (MRC) system
BER of MRC for M-QAM with imperfect channel estimation over correlated Nakagami-m fading
In this contribution, we provide an exact BER analysis for M-QAM transmission over arbitrarily correlated Nakagami-m fading channels with maximal-ratio combining (MRC) and imperfect channel estimation at the receiver. Assuming an arbitrary joint fading distribution and a generic pilot-based channel estimation method, we derive an exact BER expression that involves an expectation over (at most) 4 variables, irrespective of the number of receive antennas. The resulting BER expression includes well-known PDFs and the PDF of only the norm of the channel vector. In order to obtain the latter PDF for arbitrarily correlated Nakagami-m fading, several approaches from the literature are discussed. For identically distributed and arbitrarily correlated Nakagami-m channels with integer m, we present several BER performance results, which are obtained from numerical evaluation and confirmed by straightforward computer simulations. The numerical evaluation of the exact BER expression turns out to be much less time-consuming than the computer simulations
On the Sum of Fisher-Snedecor F Variates and its Application to Maximal-Ratio Combining
Capitalizing on the recently proposed Fisher-Snedecor F composite fading
model, in this letter, we investigate the sum of independent but not
identically distributed (i.n.i.d.) Fisher-Snedecor F variates. First, a novel
closed-form expression is derived for the moment generating function of the
instantaneous signal-to-noise ratio. Based on this, the corresponding
probability density function and cumulative distribution function of the sum of
i.n.i.d. Fisher- Snedecor F variates are derived, which are subsequently
employed in the analysis of multiple branch maximal-ratio combining (MRC).
Specifically, we investigate the impact of multipath and shadowed fading on the
outage probability and outage capacity of MRC based receivers. In addition, we
derive exact closed-form expressions for the average bit error rate of coherent
binary modulation schemes followed by an asymptotic analysis which provides
further insights into the effect of the system parameters on the overall
performance. Importantly, it is shown that the effect of multipath fading on
the system performance is more pronounced than that of shadowing.Comment: 5 pages, 3 figure
On the Multivariate Gamma-Gamma () Distribution with Arbitrary Correlation and Applications in Wireless Communications
The statistical properties of the multivariate Gamma-Gamma ()
distribution with arbitrary correlation have remained unknown. In this paper,
we provide analytical expressions for the joint probability density function
(PDF), cumulative distribution function (CDF) and moment generation function of
the multivariate distribution with arbitrary correlation.
Furthermore, we present novel approximating expressions for the PDF and CDF of
the sum of random variables with arbitrary correlation. Based
on this statistical analysis, we investigate the performance of radio frequency
and optical wireless communication systems. It is noteworthy that the presented
expressions include several previous results in the literature as special
cases.Comment: 7 pages, 6 figures, accepted by IEEE Transactions on Vehicular
Technolog
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