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

On the Multivariate Gamma-Gamma (ΓΓ\Gamma \Gamma) Distribution with Arbitrary Correlation and Applications in Wireless Communications

The statistical properties of the multivariate Gamma-Gamma ($\Gamma \Gamma$) 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 $\Gamma \Gamma$ distribution with arbitrary correlation. Furthermore, we present novel approximating expressions for the PDF and CDF of the sum of $\Gamma \Gamma$ 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

PERFORMANCE ANALYSIS OF MRC-SC MACRODIVERSITY RECEPTION OVER GENERALIZED FADING CHANNELS

This paper shows a detailed statistical characterization of a specific system configuration consisting of one multibranch maximal-ratio-combining (MRC) and one selection-combining (SC) micro-level base station, and SC back processing unit at macro level. Primarily, the scenario of the independent and identically distributed generalized-K fading channels is investigated. After that, the correlated branches at SC-based micro-level are assumed. The outage probability and the error probability performance for both cases are defined. According to the presented analytical analysis, numerical results are obtained. Also, the impact of the number of MRC and SC input branches, the impact of the fading/shadowing factor, the predefined outage threshold, the average signal-to-noise ratios and the correlation coefficient on the specified system performance is shown. Simulations validate the accuracy of the proposed analytical analysis