In this paper, we derive an average symbol error rate (ASER) expression of rectangular quadrature amplitude modulation (RQAM) scheme for unmanned aerial vehicle-enabled communication systems operating over double-shadowing and double-scattering composite fading channel. A moment generating function for the receiver output signal-to-noise ratio is obtained to analyze the ASER expression of non-coherent modulation schemes. An asymptotic expression of ASER for RQAM scheme is also derived to examine diversity order of the considered system. Further, the impact of composite fading parameters and path loss on ASER performance is highlighted. Finally, we validate all the theoretical results through Monte Carlo simulations.

Unmanned-aerial-vehicles (UAVs) are intended to be a vital part of beyond 5G (B5G) and 6G communication networks. UAV-to-ground communications in urban and populated areas are usually exposed to highly variable propagation conditions that can be often characterized by composite fading channels. This paper provides mathematical framework for the performance evaluation of UAV-to-ground communications over double-scattered single-shadowed (DS-SS), and double scattered double shadowed (DS-DS) fading channels. To analyse in details we provide probability density function (PDF), cumulative distribution function (CDF), average fade duration (AFD) and level crossing rate (LCR) of the product of double Nakagami-m (DN) and single inverse Gamma (SIG) random processes (RPs), as well as the product of DN and double inverse Gamma (DIG) RPs. Furthermore, the derived integral-form formulas for the second order (SO) statistical measures are approximated by Laplace integration (LI) and exponential LI in order to provide closed-form expressions. The impact of DS-SS and DS-DS fading types on the SO statistics of UAV-to-ground propagation scenario are thoroughly examined. Moreover, the impact of different values of DS-SS and DS-DS fading severities on the SO statistics are also taken into investigation. Lastly, the proposed UAV-to-ground model is extended to include the SO performance analysis of L-number of UAVs. All the analytical results for the SO statistics are confirmed by Monte-Carlo simulations.

An advantage of using the composite fading models (CFMs) is their ability to concurrently address the impact of multi-path and shadowing phenomena on the system performance in wireless communications. A Fisher-Snedecor (FS) F CFM has been recently proposed as an experimentally verified and tractable fading model that can be efficiently applied for 5G and beyond 5G wireless communication systems. This paper provides second-order (s-order) performance analysis of the product of N independent but not identically distributed (i.n.i.d) FS F random variables (RVs). In particular, accurate and closed-form approximations for level crossing rate (LCR) and average fade duration (AFD) of the product of N i.n.i.d FS F ( N-FS F) RVs are successfully derived by exploiting a general property of a Laplace approximation method for evaluation of the N-folded integral-form LCR expression. Based on the obtained s-order statistical results, the burst error rate and maximum symbol rate of the N-FS F distribution are addressed and thoroughly examined. The numerical results of the considered performance measures are discussed in relation to the N-FS F multi-path and shadowing severity parameters. Moreover, the impact of the number of hops ( N) of the N-FS F CFM on the s-order metrics, the burst error rate and maximum symbol rate are numerically evaluated and investigated. The derived s-order statistical results can be used to address the cooperative relay-assisted (RA) communications for vehicular systems. Monte-Carlo (M-C) simulations for the addressed statistical measures are developed in order to confirm the provided theoretical results.

In this paper, performance analysis of wireless communication over α−η−μ fading channels has been investigated. First, analysis has been carried out for the case when communication is subjected to the influence of co-channel interference. Closed-form expressions have been derived for the probability density function and cumulative distribution function of the received signal-to-interference ratio. Outage probability has been obtained for this case, in the function of various values of system parameters, and also for the case when selection diversity has been presented at the reception. Further, simultaneous multipath fading and shadowing occurrence has been analyzed, through deriving novel composite Gamma long-time faded α−η−μ fading distribution. First-order statistical parameters have been obtained in closed form, for this novel composite distribution, and capitalizing on them, standard performance measures have been efficiently evaluated, graphically presented and discussed in the function of system parameters.

The Fisher–Snedecor (F-S) $\mathcal{F}$ distribution has recently been introduced as a tractable turbulence-induced (TI) fading model that fits well with the experimental data. This paper provides a performance evaluation of a free-space optical (FSO) re-configurable intelligent surface (RIS)-assisted communications (ACs) link over the F-S $\mathcal{F}$ TI fading channels, assuming the intensity modulation–direct detection (IM–DD) technique. In particular, novel and closed-form (C-F) analytical expressions for the probability density function (PDF) and cumulative distribution function (CDF) of the end-to-end signal-to-noise ratio (SNR) in terms of Gaussian hyper-geometric functions are efficiently derived. Capitalizing on the obtained results, novel C-F analytical expressions for the moment generating function (${\mathcal{M}}_{MGF}$), outage probability (OP), average bit error rate (BER) and ergodic channel capacity $(C_{\gamma })$ of the FSO RIS-ACs system over the F-S $\mathcal{F}$ TI fading channels are provided and numerically evaluated under the various TI fading severity conditions. Furthermore, the second-order (S-O) statistical expressions for the level crossing rate (LCR) and average fade duration (AFD) are obtained and thoroughly examined for various FSO RIS-ACs system model parameters.

The paper analyses second order statistics of macro selection combining (SC) diversity system for radio-frequency (RF) vehicle-to-infrastructure (V2I) communications over interference limited fading channels. In particular, the macro diversity (mac-div) reception is proposed in order to diminish the impact of the composite fading(multipath and shadowing). Novel, second order statistical infinite series expressions with fast convergence,such as level crossing rate, lcrand average duration of fades, afdareobtained, analyzed and graphically presented for different RFV2I sets of parameters.