Autonomous Underwater Vehicles (AUVs) are assuming an important role in the monitoring and mapping of marine ecosystems, especially for their ability to explore harsh environments. AUV swarm can collect data operating autonomously for long periods enabling new applications in this field. However, the mission duration is usually limited also by the high power consumption required for acoustic transmissions. A new generation of devices complements the acoustic modem with an optical modem that can provide a communication channel with higher capacity and lower power consumption with respect to the acoustic channel. However, the optical link that uses the visible light is very sensitive to the water turbidity that can strongly limit the link coverage. In this paper, we evaluate the networking performances of the Venus vessel, a real AUV prototype equipped with an acoustical modem and an optical modem. The presented analysis aims to evaluate key system parameters allowing to select the best way to set up network communications according to the surrounding conditions (e.g., quality of water) and to the application requirements. Simulation results account for the case of ports or basins, where the water quality is poor and the use of the optical modem is strongly limited by distance. We evaluate system performance in terms of transmission delay in the network and we also provide a power–capacity trade-off.

Exposure from radio base stations is often only monitored over short periods, typically during the daily hours of working days. However, base station exposure can vary throughout the day and even between working days and weekends or holidays. The objective of this study is to determine to what extent short-term exposure measurements taken during daily hours are representative of daily average exposure levels. To achieve this goal, we analyzed a set of long-term measurements taken by monitoring units located in sensitive areas, which are characterized by a homogeneous distribution of users over working hours, such as hospitals, train stations, and university centers. Our results reveal that 6-minute measurements taken on working days can overestimate the average exposure level over 24 hours if taken over a wider time interval than that commonly considered for peak traffic and, therefore, higher exposure. Based on the common pattern of exposure over time in various locations, an extrapolation factor is proposed to predict daily exposure levels from short-time measurements.

5G service is already available in many countries, including Italy. Currently, 5G networks are run in parallel to the already deployed pre-5G ones (including 4G). In this work, we face the problem of continuously monitoring the exposure from a vantage point over a very long period of time (i.e., several months). After designing and validating a measurement setup suitable for our aims, we extensively collected 5G and pre-5G exposure data from the considered location. Results show that, although the share of 5G exposure is in general lower than pre-5G one, both intensity and occurrence of 5G exposure peaks are rapidly increasing over the months, suggesting a growth of 5G exposure levels in the near future.

Despite the broad adoption of 5G terminals, public concerns regarding ElectroMagnetic Field (EMF) exposure are primarily focused on the nearby presence of Radio Base Stations (RBSs), which are currently considered the strongest source of EMF radiation. However, is the RBS exposure really higher than that generated by multiple terminals in the same location? To address this question, we design and evaluate an innovative narrow-band measurement methodology, called Electromagnetic field Measurement for Fixed Wireless Access (EM-FWA), tailored to the evaluation of the exposure from multiple terminals vs. the one radiated by the RBS in a operative 5G StandAlone (SA) Fixed Wireless Access (FWA) network. Our approach, which includes a new narrow-band measurement algorithm, involves exposure assessments upon the generation of Downlink (DL), Uplink (UL) and combined DL/UL data transfers from the pool of terminals. Results, obtained from multiple locations subject to variegate propagation conditions, indicate that almost 100% saturation of the radio link resources in the DL direction is only achieved when three distinct terminals generate traffic in proximity to the RBS, thus justifying the adoption of our methodology. Conversely, terminal exposure significantly exceeds the RBS one at the cell edge, even when a single terminal is employed, with more than 1.4 V/m from CPE and less than 0.2 V/m from RBS. Furthermore, the RBS output power is influenced more by the volume of DL traffic than by the terminal propagation condition. Finally, we demonstrate that the overall exposure cost is minimized when the pool of terminals is placed close to the RBS. We believe that our work can pave the way to a new family of EMF compliance assessment procedures for 5G networks, adopting multiple terminals that generate traffic during the exposure measurements.

Interest in underwater optical communications has grown in recent years. A key aspect for the development of such systems is the modeling of light signal propagation in turbid water. In this paper, we present an experimental estimation of the light beam attenuation coefficient by varying the turbid water conditions with pollutants and also considering sea and lake water. The estimation of the beam attenuation coefficient c is based on laboratory measurements of the optical signal-to-noise ratio (SNR) for underwater transmissions and an analytical model of c as a function of SNR. To assess the reliability of the estimation procedure, c has been estimated in the case of clear water and the value obtained is very close to that reported in many studies. Next, c has been estimated for different water conditions. In particular, the results show that the value of c for polluted waters varies between 2.875m⁻¹ and 15.675m⁻¹. In addition, the values of c for lake and clear sea water are 0.6m⁻¹ and 0.9m⁻¹, respectively.

We present an application scenario of a Passive Optical Metropolitan Area Network (PO-MAN). Multilevel Polarization Shift Keying (M-PolSK) is used to obtain 40 and 100 Gbps per single channel. Moreover, M-PolSKs allow to implement advanced protection techniques based on birefringence, an intrinsic electro-optical effect of optical fiber usually considered a constraint [1]. Nevertheless, we can exploit this effect to our advantage to protect the information. Unlike spread-spectrum technique in which information is protected by exploiting noise, this new paradigm exploits the birefringence effects specific of the optical fibers. These technological solutions are able to replace or coexist with the current ones and those under development, ensuring backward compatibility and flexibility of the networks.