Optical Wireless Networks on-Chip have been recently proposed as alternative paradigm to overcome the communication bottleneck in computing architectures based on electrical networks. In this paper, we propose the design of a 3×3 switching matrix for optical wireless on-chip interconnection. The design exploits integrated optical phased arrays to guarantee the communication among three transmitters and three receivers. In this work, the effect of multipath propagation in the on-chip multi-layer structure is taken into account, and the impact of the cladding layer thickness is evaluated. The proposed device is intended to interconnect multiple nodes assuring reconfigurability and high bandwidth.
During the past years, the number of antenna installations has considerably increased mainly as a consequence of the great diffusion of cellular systems. While the emissions of mobile terminals principally concern cellular system users, the exposure due to base stations (BSs) is permanent and spread over the entire territory. In this paper, a flexible approach for the evaluation of exposure levels generated by cellular systems BSs is proposed. Both a conceptual method for the evaluation of the overall exposure level and a site specific method for the computation of the field in the surroundings of BS antennas are proposed. This last method is based on a combination of three different propagation models which enable an accurate evaluation of the field both close to the antenna and farther off. The validity of the approach is checked by comparison with measurements in single-antenna and multiantenna cases.
mm-waves are envisaged as a key enabler for 5G and 6G wireless communications, thanks to the wide bandwidth and to the possibility of implementing large-scale antenna arrays and advanced transmission techniques, such as massive MIMO and beamforming, that can take advantage of the multidimensional properties of the wireless channel. In order to analyze in depth the peculiar characteristics of mm-wave propagation, joint measurement and simulation campaigns in indoor and outdoor microcellular environments have been carried out. The investigation highlights that the assumption that mm-wave NLoS connectivity is hardly feasible is not necessarily true as significant reflections, scattering and even transmission mechanisms can provide good NLoS coverage in the considered indoor and outdoor scenarios. This is also reflected in the limited angle-spread differences between LoS and NLoS locations in some cases. Finally, the contribution of different propagation mechanisms (reflection, diffraction, scattering and combination of them) to the received signal is analyzed in the paper with the help of ray tracing simulations. These outcomes can be helpful to predict the performance of mm-wave wireless systems and for the development of deterministic and geometric-stochastic mm-wave channel models.
Unmanned Aerial Vehicles (UAV), also known as "drones", are attracting increasing attention as enablers for many technical applications and services, and this trend is likely to continue in the next future. When compared to conventional terrestrial communications, those making use of UAVs as base- or relay-stations can definitely be more useful and flexible in reaction to specific events, like natural disasters and terrorist attacks. Among the many and different fields, UAV enabled communications emerge as one of the most promising solutions for next-generation mobile networks, with a special focus on the extension of coverage and capacity of mobile radio networks. Motivated by the air-to-ground (A2G) propagation conditions which are likely to be different than those experienced by traditional ground communication systems, this paper aims at investigating the narrowband properties of the air-to-ground channel for 5G communications and beyond by means of GPU accelerated ray launching simulations. Line of sight probability as well as path loss exponent and shadowing standard deviations are analysed for different UAV flight levels, frequencies and dense urban scenarios, and for different types of on board antennas. Thanks to the flexibility of the ray approach, the role played by the different electromagnetic interactions, namely reflection, diffraction and diffuse scattering, in the air-to-ground propagation process is also investigated. Computation time is reported as well to show that designing UAV communication networks and optimising their performances in a fast and reliable manner, might avoid exhausting – multiple - measurement campaigns.
Outdoor-to-indoor propagation path-loss measurements have been carried out at 27 and 38 GHz, two of the frequencies allocated for 5G networks, for two different buildings: an office glass, steel and concrete building and a brick-wall residential house. The outdoor station has been mounted on a drone in order to have more placement flexibility and reach the desired height above ground without the use of a crane truck. Overall outdoor-to-indoor loss seems to depend primarily on the window surface and on the construction material. While loss is higher at 38GHz with respect to 27 GHz for the office building, brick-walls of the residential house appear to be less frequency selective.
