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To limit the spread of COVID-19, social distancing measurements and contact tracing have become popular strategies implemented worldwide. In addition to manual contact tracing, smartphone-based applications based on proximity detection have emerged to speed up the discovery of potential infectious individuals. However, so far, their effectiveness has been limited, mainly due to privacy issues. A new tracing mechanism is represented by Online Social Networks (OSNs), which provide a successful way to track, share and exchange information in real-time. Being extremely popular and largely used by citizens, OSNs are less exposed to privacy concerns. In this paper, we present an OSN-based contact tracing platform called TraceMe to reduce the spread of the epidemic. The proposal currently targets COVID-19, but it can be used in presence of other infectious diseases, like Ebola, swine flue, etc. TraceMe implements conventional contact tracing based on physical proximity and, in addition, it leverages OSNs to identify other contacts potentially exposed to the virus. To efficiently find the targeted social community, while saving the time complexity, a clique-based method is applied. Performance evaluation based on a realistic dataset shows that TraceMe is able to analyse large-scale social networks in order to find, and then alert, the tight communities of contacts that are at high risk of infection.

The coexistence of radio frequency (RF) and visible light communications (VLC) in typical indoor environments can be leveraged to support vast user quality-of-service (QoS) needs. In this paper, we target a hybrid RF/VLC network in which data transmission is provided via either an RF access point or a VLC luminary based on a selection process. We employ the concept of effective capacity, which defines the maximum constant arrival data rate at the transmitter buffer when the QoS needs are imposed as limits on the buffer overflow and delay violation probabilities, as the main selection criteria. We initially formulate the effective capacity of both channels with respect to channel gains and user distribution. Under the assumption of uniform user distribution within the VLC cell, we then provide a closed-form approximation for the effective capacity of the VLC channel. We further investigate the effects of illumination needs and line-of-sight blockage on the VLC performance. In addition, we explore the non-asymptotic bounds regarding the buffering delay by capitalizing on the effective capacity. Through simulation results, we show the impacts of different physical aspects and datalink QoS needs on the effective capacity and delay bounds.

In this contribution, we present the analysis and design of coupled microstriplines loaded with proper epsilon negative (ENG) metamaterial slabs. The behavior of the proposed component is at first analyzed through a heuristic approach. The main result of this investigation is that, depending on the orientation of the ENG slab, it is possible to achieve either higher or very reduced coupled values. A conformal mapping technique is, then, applied in order to derive closed analytical forms for the effective permittivity and the mutual coupling as a function of the geometrical and electrical parameters for the different orientations of the ENG slab. Such formulas are used to design different components, such as power dividers, decoupled lines, coupled lines with anomalous values of coupling, etc. Finally, the electromagnetic behavior of these components expected from the analytical design has been compared to the one obtained through full-wave numerical simulations, showing a very good agreement.

A method, based on the Full Wave Analysis (FWA) is presented to treat analytically and evaluate numerically the electromagnetic field sustained by an electric source inside an electrically biaxial grounded slab embedded in an isotropic homogeneous half-space in presence of a perfectly conducting finite patch located at the interface. As a prerequisite to this approach, the electric spectral (Fourier) dyadic Green's function of the structure is first developed and fully derived via the transmission-line analogy. Then the expression of the electric.field in each region of the space in terms of the spectral electric Green's dyad is given. The use of the boundary conditions allows us to determine a Spectral Electric Integral Equation (SEIE) for the electric current density induced on the scatterer's surface. The solution of the SEIE is carried out in the general case of location of the electric sources with the patch parallel to the interface. Numerical results for the radiated far-field, for the structure without the patch, with noteworthy information about the radiation on the horizontal plane and constraints on the electromagnetic parameters, thickness of the slab, working frequency and source position are presented and discussed. Finally, a numerical solution for SEIE, in order to evaluate the electric current densities induced on the patch, is shown.

To provide advanced services to citizens, Smart City services are enabled by a massive use of Internet of Things (IoT) technologies. The envisaged huge amount of sensors, and terminals with a great variety of typologies and applications, do not allow having a unique way to manage them, requiring for example minimal packaging and presentation overhead for many of them. In general in a network providing Smart City services, both IP and non-IP devices are present. In this paper, we tackle the security issue for non-IP devices able to connect by a short-range with a mediator gateway, forming a capillary access network, which can be seen as a short range extension of conventional access network in order to efficiently capture the IoT traffic. In particular, we propose security algorithms both for uni- and bi-directional terminals, depending on the terminal capabilities. The security algorithms are based on a local key renewal (without any exchange in air), performed just considering the local clock time. Performance are obtained respect to the maximum number of terminals that can be managed by one mediator gateway and the maximum packet delay as a function of the number of terminals in the area. © 2014 IEEE.

In this contribution we will present our research activities recently developed at Roma Tre University in the field of plasmonic nanoparticles for biosensing applications. We show several innovative sensing platforms, operating in the visible and near-infrared frequency regime. The contribution of our group regards to the electromagnetic modeling of such nanoparticles and their applications for the analysis and recognition of organic compounds. Numerical results, performed by full-wave simulations, show as the sensors can be used for the recognition of different organic compounds and their concentrations in a highly accurate and sensitive way.

Metamaterials Congress was initiated in 2007 by the FP6 Network of Excellence Metamorphose as the fusion between the series of conferences Bianisotropics and the series of the international workshops Metamaterials and Special Materials for Electromagnetic Applications and TLC. This year we celebrate the 20th anniversary of the Bianisotropics (previously called Bi-isotropics) conference and the 10th anniversary of the meta-workshops. In this contribution, we present a brief history of the meta-workshops and how they merged with Bianisotropics to originate the Metamaterials Congress. In particular, by using the paradigmatic example of the artificial chiral materials, we would also like to reflect the status of the research on complex media in the late 90s and in the beginning of the new century, in order to highlight the reasons behind the contemporary origin of the meta-workshops and of the network Metamorphose.

Date of Conference: 12-13 Nov. 2012 In this contribution, we review our recent work on the extraction of the electromagnetic power from electrically small apertures by using metamaterial-inspired resonators. First, we present an antenna interpretation of the power transmission through sub-wavelength apertures and discuss the questioned concept of 'enhanced transmission'. Then, we present the so-called 'connected bi-omega particle' and the related analytical model. After that, exploiting proper numerical and experimental examples, we also show that the electromagnetic response of such a particle is not influenced by the surrounding environment. This unique property makes the particle a suitable candidate for the implementation of microwave components based on the selective power extraction from electrically small apertures. Finally, the application of the proposed concepts to the design of innovative microwave components, such as waveguide filters, diplexers, power-splitters, modal filters, horn antennas, etc. will be considered and demonstrated through proper numerical and experimental results. © 2012 IEEE.

This contribution focuses on securing end-to-end unicast communications in heterogeneous wireless sensor networks comprising satellite links, while maintaining effective network performance. The proposed protocol extends the LOCKSAT key management procedure, and is able to guarantee a frequent key renewal while overcoming limitations of each subnetwork (e.g., sensor and satellite). The effectiveness of the proposed solution is assessed through the design of the system supporting the algorithm even through a frame format definition and a test bed including satellite link delays.

In this study a low-cost, compact, and high-performing metamaterial-based biosensor operating in the GHz regime is presented. The sensor is designed to detect the presence of a tumor by means of permittivity and absorption measurements. A shift in the position of the sensor response and in the amplitude width is related to the different permittivity and absorption values of the malignant and normal tissues, respectively.

In this paper we investigate the time delay propagation rates in a Vehicular Ad-Hoc Network, where vehicular connectivity is supported by both Vehicle-to-Vehicle (V2V) and Vehicle-to-Infrastructure (V2I) protocols. In our vision, seamless connectivity issues in a VANET with nearby network infrastructure, can be fixed by an opportunistic choice of a vehicular protocol between V2V and V2I. Such a decision is taken by each vehicle whenever it needs to transmit messages. Our technique — called as Vehicle-to-X — represents a handoff procedure between V2V and V2I, and vice versa, in order to keep vehicles connected independent of mobility issues and traffic scenarios. We investigate the time delay as a performance metric for protocol switching, and present the time propagation rates which occur when vehicles are transmitting warning messages, via V2V or V2I. Simulation results show how the simultaneous usage of pre-existing network infrastructure, together with inter-vehicular communications, provides low delays; while traditional opportunistic vehicular communications increases the transmission time delays and does not guarantee seamless connectivity to vehicles.

In this paper we propose a data dissemination technique based on Fountain codes, that is particularly suitable for vehicular environments, where mobility and connectivity issues often occur. We investigate the reliability of a real-time service and data delivery for multicast transmission over lossy Vehicular Ad-hoc NETworks (VANETs). The proposed technique represents the next work of a previous approach initially applied to traditional Mobile Ad-Hoc NETworks (MANETs). This technique combines application layer channel coding based on Luby Transform (LT) codes with multicast delivery in a wireless network exploiting PUMA (Protocol for Unified Multicasting through Announcements). The main goal is to achieve a real-time service with an high quality level in a lossy vehicular network environment. The rateless property, the ability of adapt the code on-the-fly, makes Fountain codes an attractive solution for data broadcast/multicast applications, like the well-known comfort applications. In a VANET scenario characterized by dynamic topology conditions, packet losses and disconnections, the proposed approach leads to an improvement on arrival times of packets towards destination vehicles. Simulation results provide the effectiveness of our technique compared with traditional data dissemination approach.

In this paper we present a localization technique for tracking and positioning services in self-organizing hybrid networks, where both indoor and outdoor scenarios coexist. In the proposed framework, outdoor anchor nodes act as reference nodes for estimating the position of mobile nodes, which are moving in a neighboring indoor region. The mobile nodes share some location information for estimating their own position by using flooding communication scheme. Communications between mobile nodes are allowed by IEEE 802.16e technology. The outdoor reference nodes are equipped with Global Positioning Service network interface card. The cooperation among mobile and reference nodes, and the self-organizing network behavior guarantee fast positioning estimate. The accuracy of localization measurement - in terms of position and speed uncertainty - is assessed through the Dilution of Precision factor. Moreover, to minimize position and speed estimation errors of each node, an Extended Kalman Filtering technique is adopted. Simulation results demonstrate the effectiveness of the proposed approach.

Vertical handover (VHO) techniques are applied when mobile users require service continuity and a seamless roaming between heterogeneous networks. A VHO decision can be taken on the basis of physical parameters, such as the received signal strength (RSS), data rate and signal-to-interference and noise ratio (SINR). In this paper, we compare three VHO decision criterions, each of them based on different physical metrics. A smart combination of several VHO criterions is the core of our proposed approach, which uses not only RSS or SINR parameters, but also a hybrid mixture from different wireless access networks. To improve quality of service for mobile users, a data rate gain parameter is introduced that lets an efficient VHO be executed. Simulation results of the proposed VHO approach are in terms of both end-users efficiency, i.e. cumulative received bits, and network performances, i.e. VHO frequency.

Vertical handover is a new trend for heterogeneous next generation networks, in order to assure ubiquitous and seamless connectivity to mobile users. This paper presents a novel vertical handover algorithm based on a probabilistic approach for decision strategy. The proposed technique deals with the assessment of a Wrong Decision Probability (WDP), which assures a trade-off between network performance maximization and mitigation of the ping-pong effect. The WDP is evaluated using network parameters, such as instantaneous estimated goodput. Analytical and simulation sections are presented in order to validate the VHO assessment. Basically, a simulated network scenario has been considered, where a mobile device moves at low speed. Specifically, simulated results have been evaluated for typical wireless access technologies (i.e. with small and medium transmission ranges). Results depict the effectiveness of the proposed vertical handover algorithm in terms of maximization of cumulative received bits, and minimization of unwanted and unnecessary vertical handovers.

In this contribution, we practically show the use of “antiphase” plasmonic scatterers to effectively reduce the scattering cross-section of a cylindrical dielectric object in the visible regime. By properly distributing a set of silver rods around a cylindrical inner core of silica, we demonstrate through a set of full-wave simulations the possibility to obtain a sensible reduction of the scattering phenomenon, achieving a condition of transparency for the structure.

In this contribution, we propose the design of innovative microwave components based on metamaterials, such as patch and leaky wave radiators, absorbers, and directional couplers. The employment of metamaterials aims to overcome the intrinsic limitations of the standard components, based on the diffraction limit. In this way, patch antennas can be miniaturized compared to their traditional counterparts, leaky wave radiators can achieve improved directivity performances, resonant microwave absorbers can be miniaturized beyond 1/100 of the operating wavelength in terms of thickness, microstrip directional couplers can be made very short and with very high coupling values. The physical mechanisms behind the operation of such components, the analysis and design steps, and the experiments conducted in cooperation with other universities will be presented. Part of this work has been performed in the frame of the Network of Excellence Metamorphose and in the national project PRIN 2006 leaded by Roma Tre.

In this contribution we study the polarizing capabilities of multilayer structures loaded with birefringent negative indexed materials (BNIM), naturally occurring at optical frequencies. To this end, we have developed a general formulation valid for any characteristic property of birefringent media. Numerical results together with some remarks about possible practical implementations of the proposed components are also given.

In this work we describe a reactive algorithm for management of mobile controlled vertical handover (VHO) in dual-mode terminals provided with UMTS and IEEE 802.11 network interface cards (NICs). The VHO aims at providing service continuity and maximize throughput while limiting the so called ldquoping-pong effectldquo. We collected experimental results and provided an assessment of its performance. Namely, in the presented statistics is discussed how channel bandwidth estimation and limitation of handover frequency can affect maximization of throughput.