Mostafa Abedi PhD Proposal Review

Title: Power-Efficient and Security-Enhancing Techniques for Ultra-low Power IoT  Devices

Committee Members:

Prof. Aatmesh Shrivastava (Advisor)
Prof. Marvin Onabajo
Prof. Nian X. Sun

Abstract:
Internet-of-things (IoT) devices often rely on ambient energy sources such as photovoltaic (PV) cells and thermoelectric generators (TEGs) for their operation. Minimizing power loss through ambient energy harvesting optimization can significantly extend the battery life or support battery-free sensor nodes in IoT devices. A maximum power point tracking (MPPT) circuit is often used for impedance matching to maximize energy transfer efficiency. This research proposes an ultra-low power, high-tracking efficiency MPPT circuit based on Hill-Climbing (HC) algorithm suitable for micro-power DC harvesters. The proposed system employs a modified version of the hill-climbing algorithm. In case of input power changes and consequent deviation of the harvester from the MPP, an integrated Power Change Detector (PCD) is proposed to reactivate the MPPT circuit. The PCD detects changes in input power and activates the MPPT circuit, enabling automatic activation and resulting in substantial power savings. Furthermore, due to the proposed power estimation technique, the MPPT is not dependent on the internal structure of the energy source, and its tracking efficiency is unrelated to the conversion ratio of the converter. This approach enables us to achieve a peak tracking efficiency of over 99.9\%. To adjust the input power of the harvester to track the maximum power point, we propose a new, efficient Pulse Width Modulation (PWM) circuit. This circuit exhibits a wide duty cycle range, low power consumption, linearity, and robustness against variations.

This research also focuses on increasing the security of IoT devices. In the past, chip fabrication was mostly done internally by semiconductor firms. Now, it is more collaborative, pulling in designs from various sources and having a few factories produce them. This new way of working means that companies that only handle design might face more challenges like the threat of hardware Trojans (HT) being added either during the design phase or production. With that in mind, we introduce a different circuit design approach. We aim to find these Trojans, particularly the newer analog Trojans. The idea is to boost the security of IoT devices by detecting these issues early. In addition, to improve the security of IoT systems, we propose an ultra-low power energy monitoring system (EMS) to detect and mitigate denial-of-sleep (DoSL) attacks. In this project, we explore a new method of defense against DoSL attacks by monitoring energy consumption. We will implement a low-power system to monitor the lifetime of the IoT node by continuously evaluating the harvested, stored, and consumed energy in the node.