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A reconfigurable intelligent surface (RIS)-aided wireless communication system is considered in this paper, where the transmitter sends data to the receiver via a direct link and the RIS. The phases of the reflecting elements of the RIS are selected considering the phases of all the fading channels to maximize the performance of the system. Series-form expressions for the probability density function (p.d.f.) and cumulative distribution function (c.d.f.) are derived for the composite channel of the communication system by considering the RIS channels to follow independent Nakagami-m distributions and the envelope of the direct channel to follow a Rayleigh distribution. Furthermore, the expressions for the statistics of the composite channel in terms of its p.d.f. and c.d.f. are also derived by considering the approximation of the central limit theorem (CLT) and the square of the channel envelope without the direct channel to approximately follow a Gamma distribution. Utilizing the derived statistics, the performance of the RIS-assisted system is studied by deriving series-form expressions for the symbol error probability (SEP) and outage probability. Numerical results are presented to corroborate the analytical framework. It is observed that a decreasing number of reflecting elements of the RIS and an increasing shape parameter of the fading channels increase the randomness of the overall channel of the RIS-assisted wireless system. Moreover, the inefficacy of both the approximate statistics is demonstrated via simulation studies of the p.d.f., c.d.f., SEP, and outage probability.

Unnamed aerial vehicles (UAVs) are of great importance on various platforms because of its rapid and easy deployment. In order to get an insight of UAV aided communication systems, an accurate channel model of UAV channels is needed. We propose a general channel model for UAV link based on alpha-beta model, which is extensively used in the literature. Specifically, we derive the normalized expression of probability density function (PDF), cumulative distribution function (CDF), and moments of the proposed model. Shadowing component is assumed to follow log-normal distribution and multipath component is characterized with the help of Nakagami-m distribution. The outage probability of a UAV based communication system is also obtained by using CDF expression. [ABSTRACT FROM AUTHOR]

In this paper, we discuss physical model based method to generate channel coefficients for Nakagami-m distribution. We consider the phase envelope joint distribution so that the phase of the faded signal is also considered. Mainly, the coefficients are generated by exploring the physical model that relates the Nakagami-m fading distribution with Gaussian and gamma distributions for which generation of coefficients is available in commonly used simulation tools. The empirical probability density function (PDF) of generated coefficients are compared with the theoretical values and they are found in excellent agreements. The empirical PDFs for envelope and phase of the generated coefficients are validated using the Kolmogorov–Smirnov test. [ABSTRACT FROM AUTHOR]

The Nakagami-m distribution plays an important role in problems related to communication engineering. This distribution can also be used for modeling reliability data as its hazard rate (mean residual life) function presents increasing (decreasing) or bathtub (unimodal) shapes. In this study, a Bayesian inference considering objective priors for the Nakagami-m distribution parameters is presented. We propose a theorem with sufficient and necessary conditions so that a general class of posteriors are proper. The impropriety of these posteriors can be observed by the behavior of the objective priors. This theorem is applied to different objective priors such as Jeffreys’ rule, Jeffreys prior, maximal data information prior, and reference priors. Simulation studies were conducted to investigate the performance of the Bayes estimators. Finally, our methodology is illustrated using two real lifetime datasets showing that the Nakagami-m distribution can be used to describe lifetime data. [ABSTRACT FROM PUBLISHER]

This letter studies the diversity advantage of single and multiuser systems utilizing multiple-input multiple-output (MIMO) antennas for known channels at the transmitter and receiver(s) by investigating the overall distribution of the resulting channel. For the single-user case, the resultant channel is taken as the largest singular value of the MIMO channel whereas for the multiuser scenario, the resultant channel is obtained by a recently proposed joint-channel diagonalization. The channel distribution is studied using hypothesis testing with the hypothesis that the distribution follows a Nakagami-m distribution with given parameters. It is concluded from the chi-square goodness-of-fit test that the distribution of the resultant channel for single or multiuser MIMO channel is well matched with a Nakagami-m distribution. [ABSTRACT FROM PUBLISHER]