Distribution of the Sum of Fisher-Snedecor $\mathcal{F}$ Random Variables and Its Applications

TL;DR

This paper derives exact and approximate statistical distributions for the sum of Fisher-Snedecor  variables, enabling performance analysis of wireless systems under various adaptive strategies with high accuracy and practical insights.

Contribution

It provides the first closed-form expressions for the sum of Fisher-Snedecor  RVs and introduces a simple approximation method for system performance evaluation.

Findings

Exact PDF and CDF derived using multivariate Fox's H-function.

Approximate expressions using moment matching are highly accurate.

Numerical results confirm the effectiveness of the proposed models.

Abstract

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 $\mathcal{F}$ 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 $\mathcal{F}$ 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 strategies. 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.