Aspects concerning the structure and behaviours of individual networks have been studied intensely in the past decade, but the exploration of interdependent systems in the context of complex networks has started only recently. This article reviews a general framework for modelling the percolation properties of interacting networks and the first results drawn from its study.

/pdf/networks-formed-from-interdependent-networks-56ypv3825y.pdf

Networks formed from interdependent networks

Electromagnetic interference (EMI) affects circuits by inducing voltages on conductors. Analog sensing of signals on the order of a few millivolts is particularly sensitive to interference. This work (1) measures the susceptibility of analog sensor systems to signal injection attacks by intentional, low-power emission of chosen electromagnetic waveforms, and (2) proposes defense mechanisms to reduce the risks. Our experiments use specially crafted EMI at varying power and distance to measure susceptibility of sensors in implantable medical devices and consumer electronics. Results show that at distances of 1-2m, consumer electronic devices containing microphones are vulnerable to the injection of bogus audio signals. Our measurements show that in free air, intentional EMI under 10 W can inhibit pacing and induce defibrillation shocks at distances up to 1-2m on implantable cardiac electronic devices. However, with the sensing leads and medical devices immersed in a saline bath to better approximate the human body, the same experiment decreases to about 5 cm. Our defenses range from prevention with simple analog shielding to detection with a signal contamination metric based on the root mean square of waveform amplitudes. Our contribution to securing cardiac devices includes a novel defense mechanism that probes for forged pacing pulses inconsistent with the refractory period of cardiac tissue.

Ghost Talk: Mitigating EMI Signal Injection Attacks against Analog Sensors

Методы подавления шумов и помех в электронных системах. (Noise reduction techniques in electronic systems)

Network science has attracted much attention in recent years due to its interdisciplinary applications. We witnessed the revolution of network science in 1998 and 1999 started with small-world and scale-free networks having now thousands of high-profile publications, and it seems that since 2010 studies of ‘network of networks’ (NON), sometimes called multilayer networks or multiplex, have attracted more and more attention. The analytic framework for NON yields a novel percolation law for n interdependent networks that shows that percolation theory of single networks studied extensively in physics and mathematics in the last 50 years is a specific limit of the rich and very different general case of n coupled networks. Since then, properties and dynamics of interdependent and interconnected networks have been studied extensively, and scientists are finding many interesting results and discovering many surprising phenomena. Because most natural and engineered systems are composed of multiple subsystems and layers of connectivity, it is important to consider these features in order to improve our understanding of such complex systems. Now the study of NON has become one of the important directions in network science. In this paper, we review recent studies on the new emerging area—NON. Due to the fast growth of this field, there are many definitions of different types of NON, such as interdependent networks, interconnected networks, multilayered networks, multiplex networks and many others. There exist many datasets that can be represented as NON, such as network of different transportation networks including flight networks, railway networks and road networks, network of ecological networks including species interacting networks and food webs, network of biological networks including gene regulation network, metabolic network and protein–protein interacting network, network of social networks and so on. Among them, many interdependent networks including critical infrastructures are embedded in space, introducing spatial constraints. Thus, we also review the progress on study of spatially embedded networks. As a result of spatial constraints, such interdependent networks exhibit extreme vulnerabilities compared with their non-embedded counterparts. Such studies help us to understand, realize and hopefully mitigate the increasing risk in NON.

http://havlin.biu.ac.il/PS/From%20a%20single%20network%20to%20a%20network%20of%20networks.pdf

From a single network to a network of networks

Reverberation chambers are emerging as a test facility for testing wireless devices and for emulating different wireless multipath environments. The commonly used quantities for characterizing the chambers in wireless applications are 1) the chamber quality factor, 2) the chamber decay time (τRC), 3) the RMS delay spread of the time-domain chamber response τrm s, and 4) the coherence bandwidth BW of the frequency-domain transfer function of the chamber. Analytic expressions that relate τRC and BW and the relationship between τrms and BW are given in the literature. However, these expressions neglect the early-time behavior of the chamber (the time before a chamber reaches a reverberant condition), and hence can give inconsistent results when one is analyzing experimental data. In this paper, we discuss the relationship between BW, τRC, and τrms for realistic chamber behaviors, and we present expressions for these relationships when one takes into account the early-time behavior of the reverberation chamber. This early-time behavior is crucial when one tries to assess and compare these different quantities in experimental data, and as we will see, the relationship between these quantities can be different for different chambers (i.e., different chamber sizes and loading conditions). The model presented here illustrates how the early-time behavior can affect these chamber characteristic quantities for loaded and unloaded chambers, and it also illustrates the problems that can occur when the early-time behavior is not considered.

/pdf/early-time-behavior-in-reverberation-chambers-and-its-effect-2c1dbqx0mj.pdf

Early Time Behavior in Reverberation Chambers and Its Effect on the Relationships Between Coherence Bandwidth, Chamber Decay Time, RMS Delay Spread, and the Chamber Buildup Time

In this paper, the vulnerability of the future electrified railway system in Europe from a high-power microwave (HPM) source is investigated. The scenario of in-band disturbances radiated toward a GSM-R antenna and damaging the connected communications system is evaluated for different classes of HPM sources and situations. The minimum realistic distances for the different HPM sources from the antenna to cause permanent damage is shown, and the severity of threat from the different sources is discussed.

Vulnerability of European Rail Traffic Management System to Radiated Intentional EMI

It is argued that it is the intent behind the electromagnetic interference in intentional electromagnetic interference (IEMI) that causes problems to large distributed systems and facilities even if they are designed by traditional zoning concept rules. Hardening such facilities against IEMI requires a correspondence between the electromagnetic zone boundary and the physical access control boundary. The three characteristics of a facility, the accessibility, susceptibility , and consequence, are discussed in the context of vulnerability to IEMI. A methodology for classification of facilities with respect to IEMI is presented.

Methodology for Classifying Facilities With Respect to Intentional EMI

In this paper, the propagation of ultra-wideband (UWB) transients through different types of junctions of low-voltage power cables and one real power network of a building were investigated. For the laboratory test, it was seen that the main mode of propagation in the cables and through the junctions tested is transverse electromagnetic (TEM). The received voltage could thus be, within a small error, estimated from transmission-line theory. The main cause for decreased voltage received at the loads of the branches of the junctions is reflections due to impedance mismatch of the junctions. Large voltages can be delivered to many unprotected loads connected to the junctions. UWB transients were also injected into a residential house using a power outlet available on the outside wall of the house. It was seen that the complexity of this network creates deviation from the TEM mode. However, relatively large voltages were still received at the various outlets inside the house. It is recommended that power outlets or lamp sockets outside buildings are controlled from inside using two-pole switches that reduce the received voltage to reduce the risk of conducted intentional electromagnetic interference.

Propagation of UWB Transients in Low-Voltage Power Installation Networks

This paper investigates the propagation of subnanosecond rise time (ultra wideband) voltage transients in low-voltage installation power cables. Experimental results are compared to simulations. It is concluded that the main mode of propagation of differentially injected transients in low-voltage installation power cables is transverse electromagnetic mode. Also, such transients would spread relatively unattenuated to any load or junction in the power system, received power primarily only limited by the impedance mismatches causing reflections. The effects of different types of bends in the cable have been studied. The study was conducted as a part of an assessment of the susceptibility of civilian facilities to intentional electromagnetic interference.

Propagation of UWB Transients in Low-Voltage Installation Power Cables

A feasibility study was conducted to gain better understanding of the influence of different Q-values of a 36.7 m3 reverberation chamber. The chamber was loaded with different types and numbers of microwave absorbers. For different chamber Q-values, the lowest usable frequency for 200 uncorrelated stirrer positions the agreement with the expected exponential power distribution, the chamber time constant and field build up process, has been studied.

M. Backstrom

Papers

Vulnerability of European Rail Traffic Management System to Radiated Intentional EMI

Methodology for Classifying Facilities With Respect to Intentional EMI

Propagation of UWB Transients in Low-Voltage Power Installation Networks

Propagation of UWB Transients in Low-Voltage Installation Power Cables

Absorber loading study in FOI 36.7 m 3 mode stirred reverberation chamber for pulsed power measurements