Accurate closed-form approximations to the sum of generalized random variables and applications

Accurate closed-form approximations to the sum of independent identically distributed eta-mu and kappa-mu random variables are provided. The proposed approximations turn out to be simple, precise and find applicability in obtaining important performance metrics of communications systems where sums of variates arise. In particular, outage probability and average bit error rate of some modulation schemes of multibranch equal-gain combining receivers are attained to illustrate the usefulness of the approximations. In passing, based on the fading models of the corresponding fading scenarios, exact expressions for these metrics for multibranch maximal-ratio combining receivers are attained that present the same functional form of the corresponding expressions for a single branch.