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The sum of lognormal variables has been a topic of interest in several fields of research such as engineering, biology and finance, among others. For example, in the field of telecommunications, the aggregate interference of radio frequency signals is modeled as a sum of lognormal variables. To date, there is no closed expression for the probability distribution function (PDF) of this sum. Several authors have proposed approximations for this PDF, with which they calculate the mean and variance. However, each method has limitations in its range of parameters for mean, variance and number of random variables to be added. In other cases, long approximations as power series are used, which makes the analytical treatment impractical and reduces the computational performance of numerical operations.  This paper shows an alternative method for calculating the mean and variance of the sum of lognormal random variables from a computational performance approach. Our method has been evaluated extensively by Monte Carlo simulations. As a result, this method is computationally efficient and yields a low approximation error computation for a wide range of mean values, variances and number of random variables.

Nowadays, there are a lot of misinformation and myths related to both the deployment of antennas for 5G and the frequency bands used in such technology. Many of these myths arise from the lack of serious research documents released in common language to be understood by different knowledge areas. This work makes a small contribution in this regard and shows a bibliographic review of the most relevant characteristics related to the problem of deployment of transmitters (a.k.a. base stations), and also takes into account a spectrum sharing scheme. As a case study, we will analyze the CBRS regulation used in the United States for the deployment of 5G, it will provide an overview of engineering problems and also, the areas of research that still need to be explored.

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