Jaewon Kim

This paper addresses two challenges faced by mm-Wave communication systems in outdoor environments. A temporary blockage of the narrow Line of Sight (LoS) beam between the base station and the mobile, e.g., by an interposed hand, face or a pedestrian, can cause an outage. It has been suggested that a dense deployment of base stations is necessary to combat blockage, which is however a capital expensive proposition. This paper presents a low cost solution. It shows that in outdoor environments with hard surfaces, such as pavements, parking lots, etc., there is generally a ground reflected beam that allows sufficient data rate for a control channel to maintain time synchronization during the blockage of the LoS beam. This makes possible a quick reversion to the LoS beam as soon as the temporary blockage ends. The design of a protocol TERRA is described, and is experimentally shown to avoid outage 84.5 % of the time during pedestrian blockages in outdoor environments. The protocol TERRA also addresses a second problem: when the blockage is permanent, or due to mobility, the user has moved away from the earlier serving base station. In such cases a handover to a neighbor base station is needed. There are several challenges of ensuring a soft handover due to the narrow mmWave beams. Since blockages are sudden, the mobile will need to be always ready to switch to a neighbor base station’s beam. This requires that it always have in hand a suitable neighbor base station, as well as continually realign its beam to that neighbor base station while it is mobile. TERRA shows how this is to be done without the neighbor base station’s active cooperation, since connection with it is not yet established. At the same time, TERRA also needs to and does continually realign the mobile’s beam with its presently serving base station to counteract its mobility. TERRA thereby enables the mobile to perform a soft handover to a neighbor base station in the event of a permanent blockage, without requiring any side information, unlike the existing works. Evaluations show that TERRA maintains received signal strength close to the optimal solution while keeping track of the neighbor base station.

A robust approach for cybersecurity of industrial control systems (ICSs) that utilize programmable logic controllers (PLCs) to control critical industrial processes is demonstrated in this paper. For example, industrial water/chemical tank-based system, the liquid level sensor measurement output data may be compromised or manipulated by attackers, this can cause tank overflow, unregulated, or even malfunction. We proposed a general-purpose method called Dynamic Watermarking (DW) to secure ICSs. The basic idea of DW is that it adds a private random signal watermark on the control signal from the controller, then this watermark signal propagates through the plant and adequately converted then comes back to the attack detector. The attack detector at the actuator side can detect Man-in-the-middle (MiTM) or Masquerade attack on the cascading system in real time. The proposed method is experimentally tested and validated with several cyber-attack scenarios on a laboratory scale water tank level control system controlled by an Allen-Bradley Micro820 PLC.

In this paper an active defense mechanism for detecting cyber-attacks on a grid-tied PV system is discussed. The proposed defense mechanism introduces a unique random signal termed as “watermark” into the control inputs of the grid-tied inverter system. The watermark signal is then shown to propagate via the switching inverter and its components and appear in all of the measurement data employed to control the system. The proposed approach employs the measured data to construct a system identification model, followed by two statistical tests (Test-1 and Test-2) that are designed to accurately flag cyber-attacks. The proposed approach is shown to rapidly detect any malicious manipulation of measurement data such as false data injection, record and replay etc. from malicious actors that would like to gain control of the the grid tied inverter and/or disturb its operation to potentially cause greater damage to the grid. The robustness of the proposed active defense mechanism is tested and validated with several attack scenarios implemented on a 3kW laboratory grid tied PV system

Grid-connected inverter systems that are important for increased utilization of renewable energy are vulnerable to cyberattacks. Malicious agents can attack a system by providing false measurements of sensed signals, such as power available/generated, or the grid current to sabotage the inverter control system. To defend against such attacks, we propose a technique of dynamic watermarking that superimposes a small secret signal onto the actuator signal and raises an alarm when the purported measurement data returned from the sensors do not contain appropriate transformations of the secret watermark. In this article, a robust attack detector is introduced, which does not require either knowledge of the variance of the ambient sensor noise or a model of the system. We develop an additional test that is not only impervious to sensor noise variance but can also be used to distinguish malicious attacks from sensor unreliability due to changing levels of sensor noise. We also show that a data-driven system identification of the switching inverter system can be employed in the dynamic watermarking tests. We present both simulation and experimental results from a grid-connected photovoltaic (PV) system, which show that the resulting robust dynamic watermarking method can detect malicious attacks on inverter control systems.

In this article, we address the cyber-security problem of industrial control systems (ICSs) when their sensor measurements may be compromised due to an attacker who has intercepted those measurements via a network. We introduce a general-purpose method “Dynamic Watermarking (DW)” to detect potential cyber-intrusions on speed sensor measurements within industrial control systems, which deploy an adjustable speed drive (ASD) to control a critical process. The DW method is injecting a random private low-amplitude signal with a zero mean Gaussian distribution, “watermark”, into one of the input phase voltages powering the ASD system. The watermark signal propagates through the system including pulse width modulation (PWM) power conversion stage and motor, then ultimately appears in the speed sensor measurements. By deploying two statistical DW tests with two proper thresholds, the system can detect potential cyber-intrusions or unobservable cyber-attacks such as replay attacks and false data injection attacks (FDIA). The DW method tested on a laboratory-scale ASD system experimentally to protect the system against cyber-intrusions. This system, powered by a commercial PWM drive operating at 208 V, 3-phase, and 3.7 kW, served as our experimental platform.

Autonomous vehicles (AVs) are rapidly proliferating. However, their future adoption is dependent on guarantees of their safety and security. Studies have shown that AVs are vulnerable to malicious cyberattacks with potentially lethal consequences. It is, therefore, imperative to deploy defensive techniques to enhance their cybersecurity. The method of dynamic watermarking (DW) has been proposed as an active technique for cyber-physical systems to detect cyberattacks. In this study, DW is implemented on an actual AV. It is shown that the DW technique is effective for timely detection of different types of attacks on the yaw rate measurement under autonomous operation, and thereby, allows recourse to measures such as stopping or pulling off to the side to prevent collisions.