In this letter, a mathematical characterization for the cascaded double Beaulieu-Xie (BX) fading model is presented. Exact and new expressions are determined for the probability density function (PDF) and for the cumulative distribution function (CDF) of the random variable that models the envelope of the cascaded double BX fading, and for the PDF and the CDF of the instantaneous signal-to-noise ratio received. Expressions are obtained for the moment generating function, higher order moments, average channel capacity, outage capacity, outage probability, amount of fading, channel quality estimation index and symbol error probability, for different modulation schemes, of the channel model considered. Several curves, corroborated by simulations performed with Monte Carlo method, are presented for different parameters that characterize the fading model.

This work aims to study heat and mass transfer in solids with parallelepiped shape with particular reference to drying process. A transient three-dimensional mathematical model based on the Fick ́s and Fourier ́s Laws was developed to predict heat and mass transport in solids considering constant physical properties and convective boundary conditions at the surface of the solid. The analytical solution of the governing equations was obtained using the method of separation of variables. The study was applied in the drying of common ceramic bricks. Predicted results of the heating and drying kinetics and the moisture and temperature distributions inside the material during the process, are compared with experimental data and good agreement was obtained. It has been found that the vertices of the solid dry and heat first. This provokes thermal and hydric stresses inside the material, which may compromise the quality of the product after drying.

A new, exact and closed-form expression is presented for the Beaulieu-Xie (BX) phase-envelope joint distribution. In addition, bivariate statistics are also determined for the BX distribution: the bivariate probability density function (PDF) of the envelope, the bivariate PDF of the instantaneous signal to noise ratio (SNR) and the generalized joint moment of the envelope, with and without correlation between the in-phase and quadrature components. Theoretical curves are plotted for different parameter values that characterize the fading.

In this letter, new and simple expressions are presented for the outage probability (OP) of the product of two Beaulieu-Xie, -, - or - random variables. The OP expressions obtained in this work are determined using the Gauss-Laguerre quadrature and are corroborated by computational simulations performed with the Monte Carlo method. Several theoretical and simulated OP curves are shown, with a great adherence between the curves, considering different values of the parameters that characterize the fading distributions.

The cell-free (CF) systems are a key technology for future wireless networks, which exploit the scenario spatial macro-diversity to offer high channel capacity and link reliability, uniform user quality of service (QoS), and better coverage. A technique for access point selection (APS) must be applied to improve the use of the macro-diversity. This paper proposes a low-complexity APS technique based on the derived signal-to-interference-plus-noise ratio (SINR) theoretical expression. Additionally, to increase the system’s spectral efficiency (SE), an expression for the bit error probability (BEP) of the generic square M_m -ary quadrature amplitude modulation ( M_m -QAM) scheme for each user is proposed and applied to an adaptive modulation (AM) algorithm. The results revealed that the proposed APS technique outperforms techniques with similar simplicity and that the AM algorithm provides higher system SE maintaining the error rate below a given threshold.