Composite Fading Model Research Articles

Hybrid FSO/RF Communications in Space–Air–Ground Integrated Networks: A Reduced Overhead Link Selection Policy

Space–air–ground integrated network (SAGIN) is considered an enabler for sixth-generation (6G) networks. By integrating terrestrial and non-terrestrial (satellite, aerial) networks, SAGIN seems to be a quite promising solution to provide reliable connectivity everywhere and all the time. Its availability can be further enhanced if hybrid free space optical (FSO)/radio frequency (RF) links are adopted. In this paper, the performance of a hybrid FSO/RF communication system operating in SAGIN has been analytically evaluated. In the considered system, a high-altitude platform station (HAPS) is used to forward the satellite signal to the ground station. Moreover, the FSO channel model assumed takes into account the turbulence, pointing errors, and path losses, while for the RF links, a relatively new composite fading model has been considered. In this context, a new link selection scheme has been proposed that is designed to reduced the signaling overhead required for the switching operations between the RF and FSO links. The analytical framework that has been developed is based on the Markov chain theory. Capitalizing on this framework, the performance of the system has been investigated using the criteria of outage probability and the average number of link estimations. The numerical results presented reveal that the new selection scheme offers a good compromise between performance and complexity.

Capacity performance of uplink NOMA system with 2K+1 users over Fisher-Snedecor composite fading channels

In this paper, we study an uplink power-domain non-orthogonal multiple access (PD-NOMA) system, in which 2K+1 users are served. The user clustering process based on High-High/High-Low algorithm precedes the utilization of the data-rate based power allocation algorithm. Channels are characterized by Fisher-Snedecor composite fading model interpreted as model with a high level of generality. The influence of different fading/shadowing channel conditions, number of users and their positions is portrayed through the numerical results of data sum rate of the studied PD-NOMA system.

Relay-assisted communication over a fluctuating two-ray fading channel

ABSTRACT The intricacies of relay-aided device-to-device (D2D) communication within the novel fluctuating two-ray (FTR) model is inspected in this study. Two cases with respect to co-channel interference are considered here, in case A, co-channel interferences due to unmanned aerial vehicles affect the relay while at the D2D receiver, the co-channel interferences follow the FTR model. In case B, interferences due to unmanned aerial vehicles affect the D2D receiver and the relay now experiences interferences over the FTR channels. The channel of a co-channel interference due to unmanned aerial vehicle is assumed to be a recently proposed single-shadowing based composite fading model. Further enhancing operational efficiency, the D2D receiver incorporates a power splitting mechanism for power harvesting. In this analysis a characteristic function-based approach is applied, which serves as the foundational cornerstone for deriving expressions that govern the outage and success probabilities. These intricate expressions are connected with critical factors, such as the dynamics of path-loss phenomena, the spatial separation between the interferers and the relay, the varying distances between the interferers and the D2D receiver, and the physical gap bridging the relay and the D2D receiver. Building upon the derived expressions, an extensive numerical analysis unfurls them for both interference cases.

On the Fluctuating Beckmann Shadowed Composite Fading Model and Its Applications to Wireless Communications

In this paper, the fundamental statistics of fluctuating Beckmann shadowed (FBS) fading model which is composite of fluctuating Beckmann (FB) and inverse Nakagami- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$m$</tex-math></inline-formula> distributions, are provided. Accordingly, a wide range of composite generalized fading distributions can be obtained as special cases of the proposed distribution, such as, double shadowed <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\kappa -\mu$</tex-math></inline-formula> fading Type I. To this effect, mathematically tractable expressions of both the exact and asymptotic at high signal-to-noise (SNR) regime of the probability density function (PDF), cumulative distribution function (CDF), and generalised-moment generating function (G-MGF) are derived. In addition, the fundamental statistics for integer <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$m$</tex-math></inline-formula> and even value of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> that represent the shadowing of the dominant components and real extension of the number of the multipath clusters, respectively, are given in simple closed-from formats. These statistical characterizations are then used to evaluate the performance of the wireless communications in terms of the outage probability (OP), average bit error probability (ABEP), amount-of-fading (AF), channel quality estimation index (CQEI), error vector magnitude (EVM), average channel capacity (ACC), and effective throughput (ET). Furthermore, the area under the receiver operating characteristics (AUC) curve of the energy detection based spectrum sensing and the secure outage probability (SOP) as well as the lower bound of SOP (SOP <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{L}$</tex-math></inline-formula> ) of the physical layer are also analysed. The validation of the derived expressions is verified via comparing the numerical results with the Monte-Carlo simulations for different values of the fading parameters.

Gamma-shadowed two-ray with diffuse power composite fading model

In this paper, a novel gamma-shadowed two-ray with diffuse power (GS-TWDP) composite fading model is proposed by assuming that the shadowing-caused mean power variations of the received signal, affected by TWDP multipath fading, are gamma distributed. For the proposed model, the essential statistics such as probability density function (PDF), cumulative distribution function (CDF), moment generating function (MGF) and higher order moments are obtained and used to derive the approximate general order rectangular quadrature amplitude (RQAM) average symbol error probability (ASEP). That expression enabled us to investigate the effect of shadowing on overall error probability, in case when signal is propagating in channels with TWDP multipath fading. The proposed model is verified by comparing analytically obtained results with those measured at 28 GHz and reported in literature, which makes the GS-TWDP model a promising candidate for modeling propagation at millimeter wave (mmWave) frequencies. Analytical results are validated by Monte-Carlo simulation.

Selection Combining Diversity for Fisher-Snedecor Composite Fading Model under Interference

Selection Combining Diversity for Fisher-Snedecor Composite Fading Model under Interference

The Generalized-Fisher composite fading model for the next generation of mobile communication systems

The new generation of communication systems is moving towards using a millimeter-wave spectrum. Since the shadowing effects are undeniable in this type of propagation, the proposed Generalized Fisher (GF) distribution can be useful in modeling shadowed fading channels, considering the non-linearity and the multi-cluster nature of the diffusion medium. After introducing the model, its main statistics, including Probability Density Function (PDF), Cumulative Distribution Function (CDF), Moment Generating Function (MGF), and the distribution of the sum of an arbitrary number of independent and non-identically distributed (i.n.i.d.) random variables with GF distribution are calculated. Subsequently, some wireless communication application criteria such as ergodic and outage capacities, are computed. Finally, considering the classic Wyner's wiretap model and passive eavesdropping scenario, specific security criteria, such as the probability of non-zero secrecy capacity and secrecy outage probability, are also determined. These expressions are measured in terms of either univariate or multivariate Fox's H-function.

Second Order Statistics of -Fisher-Snedecor Distribution and Their Application to Burst Error Rate Analysis of Multi-Hop Communications

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.

Composite Fading Models Based on Inverse Gamma Shadowing: Theory and Validation

We introduce a general approach to characterize composite fading models based on inverse gamma (IG) shadowing. We first determine to what extent the IG distribution is an adequate choice for modeling shadow fading, by means of a comprehensive test with field measurements and other distributions conventionally used for this purpose. Then, we prove that the probability density function and cumulative distribution function of any IG-based composite fading model are directly expressed in terms of a Laplace-domain statistic of the underlying fast fading model and, in some relevant cases, as a mixture of well-known state-of-the-art distributions. Also, exact and asymptotic expressions for the outage probability are provided, which are valid for any choice of baseline fading distribution. Finally, we exemplify our approach by presenting several application examples for IG-based composite fading models, for which their statistical characterization is directly obtained in a simple form.

Composite Fading Model for Aerial MIMO FSO Links in the Presence of Atmospheric Turbulence and Pointing Errors

In this letter, we introduce accurate approximation expressions for composite fading channel model and outage probability of multiple-input multiple-output (MIMO) free space optical (FSO) link between two unmanned aerial vehicles (UAVs) in hovering state. In our derivations, we consider the effects of weather attenuation, random fluctuations in UAVs' positions and orientations, and atmospheric turbulence. Our proposed model is unified with respect to turbulence effect, which means it is valid for different atmospheric turbulence models. We show the accuracy of the proposed model through comparisons with Monte Carlo simulations under different channel conditions.

MIMO Systems in a Composite Fading and Generalized Noise Scenario: A Review

Multiple-Input Multiple-Output (MIMO) systems have been endorsed to enable future wireless communication requirements. The efficient system designing appeals an appropriate channel model that considers all the dominating effects of the wireless environment. Therefore, some complex or less analytically acquiescent composite channel models have been proposed typically for Single-Input Single-Output (SISO) systems. These models are explicitly employed for mobile applications, though, we need a specific study of a model for the MIMO system which can deal with radar clutters and different indoor/outdoor and mobile communication environments. Subsequently, the performance enhancement of the MIMO system is also required in such a scenario. The system performance enhancement can be examined by low error rate and high capacity using spatial diversity and spatial multiplexing respectively. Furthermore, for a more feasible and practical system modeling, we require a generalized noise model along with a composite channel model. Thus, all the patents related to MIMO channel models are revised to achieve the nearoptimal system performance in a real-world scenario. This review paper offers the methods to improve MIMO system performance in less and severe fading as well as shadowing environment and focused on a composite Weibull-gamma fading model. The development is the collective effects of selecting the appropriate channel models, spatial multiplexing/detection, and spatial diversity techniques both at the transmitter and the receivers in the presence of arbitrary noise.

BER and channel capacity analysis of wireless system over $${\kappa -\mu /}$$inverse gamma and $${\eta -\mu /}$$inverse gamma composite fading model

The $${\kappa -\mu /}$$ Inverse Gamma (KMIG) and $${\eta -\mu /}$$ Inverse Gamma (EMIG) are recently introduced composite fading distributions for the precise design of the wireless systems, where multipath fading and shadowing occur concomitantly. Further, these composite fading models are competent to be employed in the performance investigation of the digital communication system as their mathematical formulations are quite tractable. Average symbol error probability (SEP) and channel capacity analysis are important parameters to investigate the performance of a digital communication system. The applicability of these fading models is illustrated by analysing the performance matrices of the digital communication channels in the present work. Various performance matrices such as the average SEP, the channel capacity under different adaptive schemes namely, optimum rate adaptation (ORA), channel inversion with fixed rate (CIFR) and truncated CIFR are derived. The asymptotic analysis of KMIG and EMIG composite fading models over average SEP performance matrices with coding gain and diversity gain is also carried out in this work. The simplified high and low signal-to-noise-ratio solutions to channel capacity are also provided as a by-product. In addition, approximate analysis to ORA and CIFR capacity are provided under realistic environmental conditions. The accuracy of the derived numerical formulations is validated with the use of Monte–Carlo simulation. The results of present work will be advantageous in the modelling and designing of popular wireless services such as vehicle-to-vehicle communication, wearable communication and wireless power transfer related technologies.

Performance Analysis of Non-identical Cascaded $$\alpha$$–$$\mu$$ Fading Channels

Relying on the fact that, cascaded $$\alpha$$ – $$\mu$$ distribution provide simplified and excellent fitting to the measurement data compared to the other composite fading model. This work investigates the performance of versatile cascaded non-identical $$\alpha$$ – $$\mu$$ fading channel. The $$\alpha$$ – $$\mu$$ / $$\alpha$$ – $$\mu$$ model has emerged as a generalization of the cascaded line-of-sight multipath fading channels such as Rayleigh, Weibull, and Nakagami-m etc., by appropriately choosing the values of $$\alpha$$ and $$\mu$$ parameters. More specifically, we present novel closed-form formulations for some of the interested fundamental statistics of the wireless communication system, namely, generalized moment, moment generating function, Error rate (coherent/non-coherent), channel capacity under different transmission policy. The results are expressed in terms of easily implementable well-known Fox’s H function. Also, an asymptotic investigation of all the mentioned metrics is performed, so as to gain more insights of the impact of the key system parameters. The proposed expressions provide flexibility to satisfy different propagation scenarios.

The α-η-κ-F Composite Fading Distribution

In this letter, a new general composite fading model, namely $\alpha $ - $\eta $ - $\kappa $ - $\mathcal {F}$ model, is proposed. It considers most of the well-known propagation phenomena in wireless fading channels, such as shadowing, multi-path fading, non-linearity of the propagation medium, power of the dominant components, and power of the scattered waves. Additionally, most of the important statistical fading models are included in the $\alpha $ - $\eta $ - $\kappa $ - $\mathcal {F}$ model as special cases. The envelope probability density function (PDF) and cumulative distribution function (CDF) are derived and then employed to derive the PDF and CDF of the instantaneous signal-to-noise ratio. The performance of a wireless communication system operating under the $\alpha $ - $\eta $ - $\kappa $ - $\mathcal {F}$ composite model is evaluated in terms of outage probability and symbol error rate. Numerical results are supported by Monte-Carlo simulations to validate the analysis.

Performance analysis of uncoded and SFBC OFDM system over composite fading channels

This paper presents the performance of uncoded and space-frequency block coded (SFBC) orthogonal frequency division multiplexing (OFDM) system for two recently proposed composite fading model i.e. Fisher–Snedecor (F) and κ-μ/gamma. Both models are adequate for wearable communication system. In this paper, we derive the exact and approximate expressions of average bit error rate (ABER) for uncoded and SFBC OFDM system using fast Fourier transform (FFT) and fractional Fourier transform (FrFT). Further, these generalized expressions reduce to special cases of both composite fading models. Particularly, M-ary quadrature amplitude modulation (MQAM) and M-ary phase-shift keying (MPSK) modulation schemes are considered to derive ABER expressions. The numerical results are compared with the previous results of Rayleigh and Nakagami-m distribution. Also, the Monte Carlo simulation results are provided to crosscheck the validity of derived expressions.

Unified performance analysis over Mckay–Meijer G shadowed fading channel

ABSTRACT Composite fading models have been considered as the suitable fading models for scenarios such as indoor communication and free space optical. Most of the composite fading models are based on Nakagami-m fading distribution in which amount of fading parameter ranges from 0.5 (most severe fading) to infinity (no fading). However, using the McKay–Meijer G function, one of the recent article presents McKay shadowed fading distribution which shows that the fading severity may have values more than that of the most severe case of Nakagami-m fading. In this paper, using the conditional unified expression for conditional bit error rate (BER), a unified expression of the average bit error rate (ABER) over McKay–Meijer G shadowed fading model has been proposed. The proposed unified expression includes the ABER of almost all the modulation schemes. In addition, expression for ABER of binary phase shift keying modulation over McKay fading channel under generalised Gaussian distribution has been derived. Finally, analytical expressions of adaptive capacity under different adaptive schemes namely, COPRA, CORA, CCIFR and truncated CIFR have been presented. Through numerical analysis, different results have been compared with similar results available in the literature.

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

The Fisher-Snedecor $\mathcal {F}$ distribution has been recently proposed as a more accurate and mathematically tractable composite fading model than traditional established models in some practical cases. In this paper, we firstly derive exact closed-form expressions for the main statistical characterizations of the ratio of products of $\mathcal {F}$ -distributed random variables, including the probability density function, the cumulative distribution function and the moment generating function. Secondly, simple and tight approximations to the distribution of products and ratio of products of $\mathcal {F}$ -distributed random variables are presented. These analytical results can be readily employed to evaluate the performance of several emerging system configurations, including full-duplex relaying systems operating in the presence of co-channel interference and wireless communication systems enhanced with physical-layer security. The proposed mathematical analysis is substantiated by numerically evaluated results, accompanied by equivalent ones obtained using Monte Carlo simulations.

A New Statistical Channel Model for Emerging Wireless Communication Systems

A new composite fading model is introduced. This shadowed Beaulieu-Xie model is developed to characterize wireless communication in an environment with an arbitrary number of line-of-sight and non-line-of-sight signals, in contrast to the existing Rayleigh, Ricean, generalized Ricean (i.e., κ - μ), and Nakagami-m models. The proposed model benefits from four parameters that characterize a wide range of fading conditions, unlike existing composite models such as the shadowed Ricean model, the two-wave with diffuse power model, and the fluctuating two-ray model. The proposed shadowed Beaulieu-Xie model is used here to characterize experimental data obtained from fading measurements in 28 GHz outdoor millimeter-wave channels, and it is found to describe the communication environment accurately. We conclude that the proposed composite fading model is particularly useful for characterizing emerging (millimeter-wave and terahertz) wireless communication systems.

Bivariate Fisher–Snedecor F Distribution and its Applications in Wireless Communication Systems

Recently, a Fisher-Snedecor .T composite fading model has gained great attention due to its mathematical tractability and modeling accuracy. However, its bivariate statistical characteristics have not been considered yet in the previous technical literature. In this paper, we present a bivariate Fisher-Snedecor .T distribution with identical shaping parameters and study its applications in the wireless communication systems. We first derive novel theoretical formulations of the statistical characteristics for the bivariate Fisher-Snedecor .T distribution model, which include the joint probability density function (PDF), the joint cumulative distribution function (CDF), the joint moment generating function (MGF) and the joint moments. Then, capitalizing on the above statistical expressions, some exact and asymptotic expressions of performance criteria, such as the outage probability, the average bit/symbol error probability (ABEP/ASEP), and the average channel capacity, for dual-branch selection combing and maximal ratio combing diversity systems are derived, respectively. Especially, the exact expressions of the ABEP/ASEP for several classical modulation schemes are obtained in terms of the multivariate Fox's H-function by applying the Mellin-Barnes type contour integral. Furthermore, we investigate the second-order statistics of a sampled Fisher-Snedecor .T composited fading envelope by utilizing the joint CDF, and obtain the mathematical expressions of the level crossing rate (LCR) and the average fade duration (AFD). Finally, we employ numerical and simulation results to demonstrate the validity of the theoretical analysis under various correlated fading and shadowing scenarios.

Higher Order Statistics for Composite Fading Models

This letter presents a novel, general second-order statistics framework for composite fading models. The aim is to obtain expressions for the level crossing rate and average fade duration statistics in any fading scenario. Two formulations are presented: 1) one that leads to exact expressions and 2) another that leads to approximate ones. By using the former, even for very simple fading scenarios, no closed-form formula can be found. By using the latter, as proposed here, closed-form formulations may be found. Interestingly, it is shown that, in practical terms, the results in 1) and 2) yield results that are almost indistinguishable from each other when applied to multipath-shadowing environments. As an application example, the $\alpha -\mu $ scenario for both multipath and shadowing has been exercised.