In this work, a flexible and extensive digital platform for Smart Homes is presented, exploiting the most advanced technologies of the Internet of Things, such as Radio Frequency Identification, wearable electronics, Wireless Sensor Networks, and Artificial Intelligence. Thus, the main novelty of the paper is the system-level description of the platform flexibility allowing the interoperability of different smart devices. This research was developed within the framework of the operative project HABITAT (Home Assistance Based on the Internet of Things for the Autonomy of Everybody), aiming at developing smart devices to support elderly people both in their own houses and in retirement homes, and embedding them in everyday life objects, thus reducing the expenses for healthcare due to the lower need for personal assistance, and providing a better life quality to the elderly users.

We present here a novel, fully discrete Ray Launching field prediction algorithm that takes advantage of environment preprocessing to efficiently trace rays undergoing both specular and diffuse interactions. The algorithm is “environment-driven” because rays are traced from the ray source according to the presence and distribution of obstacles in the surrounding space, therefore adapting ray density to the environment’s characteristics. The environment is discretized into simple regular shapes to facilitate faster geometric computations, to allow for visibility preprocessing and for the algorithm to be parallelized in a straightforward way. These innovative features combined together and implemented on a NVIDIA Graphical Processing Unit (GPU) are shown to speed-up computation by several orders of magnitude compared to more conventional algorithms, while retaining a similar accuracy level. The speed-up and prediction accuracy achieved in reference cases is presented in comparison to a pre-existing ray-based model and RF-coverage measurements.

Reconfigurable Intelligent Surfaces (RISs), which can be implemented using metasurface technology or reflect/ transmit antenna array technology, have garnered significant attention in research studies focused on both their technological aspects and potential applications. While various modeling approaches have been proposed - ranging from electromagnetic simulations and analytical integral formulations to simplified approaches based on scattering matrix theory - there remains a great need for efficient and electromagnetically-consistent macroscopic models that can accurately simulate scattering from RISs, particularly for realistic simulations of RIS-based wireless networks. Building on previous work based on the characterization of the RIS through a surface impedance (or ”spatial modulation”) function and a few parameters, in the present paper we propose a fully ray-based approach for the computation of the re-radiated field that can be easily embedded in efficient, forward ray tracing (also known as ”ray launching”) models. We validate the proposed model by comparison to well established methods available in the literature. Results show that, although the considered method is based on a completely different formulation and is much more efficient than integral formulation methods, results are almost indistinguishable in some benchmark cases.

Frequency bands above 6 GHz are being considered for future 5G wireless systems because of the larger bandwidth availability and of the smaller wavelength, which can ease the implementation of high-throughput massive MIMO schemes. However, great challenges are around the corner at each implementation level, including the achievement of a thorough multi-dimensional characterization of the mm-wave radio channel, which represents the base for the realization of reliable and high-performance radio interfaces and system architectures. The main properties of the indoor radio channel at 70 GHz, including angular and temporal dispersion as well as an assessment of the major interaction mechanisms, are investigated in this study by means of UWB directional measurements and ray tracing simulations in a reference, small-indoor office environment.

This study concerns the evaluation of beamforming techniques in multi-user indoor environment at the mm-wave frequency band of 70 GHz using both measurements and ray tracing simulations carried out in a furnished small-office environment. The goal of the work is twofold: (i) to evaluate ray tracing as a reliable directional channel model for beamforming assessment and for real-time assistance in the beam-searching phase, (ii) to evaluate simple beamforming schemes as means to enforce spatial division in a small-indoor environment. Results suggest that the considered ray tracing model can be reliable enough to reproduce the general performance trends of different beamforming schemes and to assist the beam-searching phase, therefore potentially reducing the related time delay and computational overhead.

A measurement setup, including millimeter-wave and ultrawideband transceivers mounted on both a customized unmanned aerial vehicle and a ground station and a measurement procedure for full 3-D wireless propagation analysis, is described in this work. The custom-made developed system represents a flexible solution for the characterization of wireless channels and especially of urban propagation, as the drone might be easily located almost anywhere from ground level to the buildings' rooftop and beyond. The double-directional properties of the channel can be achieved by rotating directive antennas at the link ends. Other possible applications in urban contexts include the study of outdoor-to-indoor penetration, line-of-sight to non-line-of-sight transition, 3-D scattering from buildings, and air-to-ground channel characterization for drone-assisted wireless communications.