This work presents accurate closed-form approximations for the probability density function (PDF) of the sum of independent and identically distributed (i.i.d.) fading envelopes and square fading envelopes, experienced by indoor and outdoor channels operating in the D-band. In order to provide a simple yet accurate analytical expression for these PDFs, we propose the use of the Pearson family of distributions, which are mainly characterized by their skewness and kurtosis. Our analysis has demonstrated that among the seven types of Pearson distributions, the type I Pearson distribution provides the most accurate fit to the exact PDF of envelopes and squared envelopes, for a diverse range of indoor and outdoor wireless propagation scenarios. The distribution parameters are estimated using moments-matching techniques, while the requisite moments are obtained through a measurement campaign conducted in indoor as well as outdoor environments. Specifically, with regard to the indoor scenarios, the following locations have been considered: A mall, an airport, and an entrance hall. With regard to the outdoor scenarios, the following locations have been selected: A university campus, a residential area, and a city center. Our results are further applied to analyze the average bit error rate performance and the ergodic capacity of equal-gain combining (EGC) and maximal-ratio combining (MRC) receivers, the sum rate of rate splitting multiple access (RSMA) systems with EGC diversity reception, as well as the coverage probability of wireless systems employing intelligent reflecting surfaces (IRS). Our analysis is supported by extensive numerical results and Monte Carlo simulations.

As the demands of users increase continuously over time, especially in 5G and beyond 5G era, accurate performance evaluation is essential for design and optimization of cellular networks. To this end, stochastic geometry and specifically, uniform Poisson Point Processes (PPPs) have been employed in the past for the performance analysis of such networks, due to their mathematical tractability and adequate accuracy they provide. The distribution of the distance between a user node and its tagged access point (AP) is an important metric, which is derived from the statistical properties of PPPs. However, the presence of obstacles within the network's deployment area, has not attracted much attention from the research community. In this paper, we study the distribution of the distance between a user node and its tagged AP in areas with obstacles, where network nodes are distributed according to a PPP. Numerical results accompanied with simulations, are presented to verify the proposed analysis.

In this paper, we examine the potential for a reconfigurable intelligent surface (RIS) to be powered by energy harvested from information signals. This feature might be key to reap the benefits of RIS technology’s lower power consumption compared to active relays. We first identify the main RIS power-consuming components and then propose an energy harvesting and power consumption model. Furthermore, we formulate and solve the problem of the optimal RIS placement together with the amplitude and phase response adjustment of its elements in order to maximize the signal-to-noise ratio (SNR) while harvesting sufficient energy for its operation. Finally, numerical results validate the autonomous operation potential and reveal the range of power consumption values that enables it.