The statistical characterization of the sum of random variables (RVs) are useful for investigating the performance of wireless communication systems. We derive exact closed-form expressions for the probability density function (PDF) and cumulative distribution function (CDF) of a sum of independent but not identically distributed (i.n.i.d.)Fisher-Snedecor F RVs. Both PDF and CDF are given in terms of the multivariate Fox's H-function. Besides, a simple and accurate approximation to the sum of i.n.i.d. Fisher-Snedecor F variates is presented using the moment matching method. The obtained PDF and CDF are used to evaluate the performance of wireless communication applications including the outage probability, the effective capacity and the channel capacities under four different adaptive transmission strtegies. Moreover, the corresponding approximate expressions are obtained to provide useful insights for the design and deployment of wireless communication systems. In addition, we derive simple asymptotic expressions for the proposed mathematical analysis in the high signal-to-noise ratio regime. Finally, the numerical results demonstrate the accuracy of the derived expressions.
Index TermsChannel capacity, effective capacity, Fisher-Snedecor F -distribution, sum of random variables, Recently, the Fisher-Snedecor F distribution was proposed [1] as a tractable fading model to describe the combined effects of shadowing and multipath fading. This distribution can be reduced to some common ). 2 fading models, such as Nakagami-m and Rayleigh fading channels. Furthermore, it is found in [1] that the F distribution can provide a better fit to the experimental data obtained for device-to-device (D2D) and wearable communication links, especially at 5.8 GHz, as compared with the well established generalized-K (GK) distribution. In addition, its probability density function (PDF) consists of only elementary functions and it leads to more tractable analysis than the GK model [1]. Due to its promising properties, the performance of digital communication systems over F distributed fading channels has been analyzed in [2]-[5] and the references therein. The sum of random variables (RVs) has a wide range of important applications in the performance analysis of wireless communication systems. For example, to enhance the quality of the received signal, maximal-ratio combining (MRC) can be deployed at the receiver to maximize the combiner output signalto-noise ratio (SNR) [6]. The system with MRC receiver operating over different fading channels has been extensively studied [7]-[12]. The PDF and CDF of the sum of Fisher-Snedecor F RVs has been derived in terms of Lauricella multivariate hypergeometric function [13]. However, there results are difficult to be used in the performance analysis of MRC systems over Fisher-Snedecor F fading channels due to the complex of the Lauricella multivariate hypergeometric function. Moreover, authors in [13] obtain outage probability (OP) and outage capacity expressions involving L-fold Mellin-Barnes...