Sum Statistics of Squared FTR-Based Variates

Two generalizations of the fluctuating two-ray (FTR) fading model have recently appeared in the literature. In particular, in these FTR-based models, the specular components of the complex baseband signal are modulated by the square root of either (i) the product (Cascade FTR) or (ii) the ratio of products (Ratio-Product FTR) of Gamma random variables (RVs). Leveraging the applicability of the sum of RVs in performance analysis of communications systems, this paper explores the sum statistics of these two newly introduced FTR-based RVs. More precisely, we obtain novel exact formulations for the probability density function (PDF), the cumulative distribution function (CDF), and the raw moments of the sum of independent and identically distributed (i.i.d.) squared FTR-based RVs. Moreover, we carry out a truncation error analysis for the derived PDFs and CDFs. Finally, we obtain in an exact and asymptotic manner essential performance metrics such as outage probability (OP) and symbol error probability (SEP) for a maximal-ratio combining (MRC) receiver.