In this letter we propose a unified analytical expression for the average bit error probability of dual-hop amplify- and-forward relaying systems operating in the presence of both fast fading and shadowing. In order to provide a realistic end-to- end performance of the considered system we assume that both hops are subject to independent but not necessarily identically distributed Extended Generalized-K fading. Our newly derived formula is obtained in terms of the bivariate H-Fox function. A computationally efficient algorithm to evaluate the average bit error probability is also proposed. The accuracy of the proposed method is substantiated by various numerically evaluated and computer simulation results.

In this letter, we study the performance of wireless communications empowered by Reconfigurable Intelligent Surface (RISs) over Nakagami- m fading channels. We consider two phase configuration designs for the RIS, one random and another one based on coherent phase shifting. For both phase configuration cases, we present single-integral expressions for the outage probability and the bit error rate of binary modulation schemes, which can be efficiently evaluated numerically. In addition, we propose accurate closed-form approximations for the ergodic capacity of the considered system. For all considered metrics, we have also derived simple analytical expressions that become tight for large numbers of RIS reflecting elements. Numerically evaluated results compared with Monte Carlo simulations are presented in order to verify the correctness of the proposed analysis and showcase the impact of various system settings.

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The fluctuating two-ray (FTR) fading model has been proposed to provide a much better fit than other fading for small-scale fading measurements in millimeter wave communications. Using a mixture of gamma distributions, we provide new results of exact closed-form expressions for the probability density function and cumulative distribution function of the FTR distribution with arbitrary fading parameters. Moreover, the performance of digital communication systems over the FTR fading channel is evaluated in terms of the channel capacity and the bit error rate, respectively. The interaction between channel fading parameters and system performance is investigated. Finally, Monte Carlo simulations are presented to corroborate our derived results, which extend and complement previous knowledge of the FTR fading model.

In this paper we propose the use of the so-called Fisher-Snedecor F-distribution to model atmospheric turbulence induced fading in free space optical communication systems. The proposed model is a two-parameter distribution, defined as the ratio of two independent gamma random variables. In this context, the proposed model is based on a doubly stochastic theory of turbulence induced fading, assuming that smallscale irradiance variations of the propagating wave, modeled by a gamma distribution, are subject to large-scale irradiance fluctuations, modeled by an inverse gamma distribution. It is shown that the F-distribution yields at least as good, or even better fit to experimental and computer simulation data as compared to the well known gamma-gamma distribution. Also, important statistical measures such as its cumulative distribution function (CDF) and its moment generating function (MGF) are mathematically simpler than those of the gamma-gamma distribution. Motivated by these facts, the performance of singleinput multiple output (SIMO) and multiple-input multiple output (MIMO) systems operating in the presence of F turbulence is assessed. The proposed analysis is substantiated by numerically evaluated results and Monte Carlo simulations.

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